technologyletters.orgICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 PROCEEDINGS OF I NTERNATIONAL C ONFERENCE

ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018

PROCEEDINGS OF

INTERNATIONAL CONFERENCE ON ADVANCED NANOSTRUCTURES

(ICAN-2018) 12-14th March 2018

Editors:

Dr. Raneesh B. Dr. George Thomas (HoD)

Dr. Soosen Samuel M. PG & Research Department of Physics

Catholicate College, Pathanamthitta, kerala, India

Supported By

Organized by

Post Graduate and Research Department of Physics Catholicate College, Pathanamthitta, Kerala, 689645

In association with IIUCNN, Mahatma Gandhi University, Kerala, INDIA

& International Society for Optics and Photonics (SPIE), Washington, USA

http://www.ican18.com/




Patrons : Prof. Sabu Thomas

(Pro-Vice Chancellor, Mahatma Gandhi University, Kottayam, Kerala)

H. H Baselios Marthoma Paulose II (Catholicos and Malakara Metropolitan) Co- patrons : H. G (Dr) Thomas Mar Athanasius Metropolitan (Manger, MOC Colleges)

H.G Kuriakose MarClemis Metropolitan (Local Manger, Catholicate College) Dr. M E Kuriakose (Secretary, MOC Colleges) Dr. Mathew P Joseph (Principal, Catholicate College) Convener : Dr. Raneesh B. (Department of Physics, Catholicate

College, Pathanamthitta) Co-Conveners : Dr. George Thomas

(HOD, Department of Physics, Catholicate College, Pathanamthitta) Prof. Dr.Nandakumar Kalarikkal

(Director, IIUCNN, Mahatma Gandhi University, Kottayam, Kerala)

National Advisory Committee

Prof. Abhijit Saha, UGC-DAE-CSR, Kolkata Prof.P. S Anil Kumar, IISC, Bangalore Prof. Jacob Philip, AJC, Kottayam Prof. P.M.G. Nambissan, SINP, Kolkata Prof. M.K Jayaraj, CUSAT, Cochin Prof. P. Preedep, NIT, Calicut Prof. P.S Anil kumar, IISC, Bangalore Dr. M.M Shijumon, IISER, Trivandrum Prof. Sudhakar Yarlagadda, SINP, Kolkata Dr. Swapna S. Nair, CUK, Kasaragod Dr. Pramod P.Pillai, IISER, Pune Prof. Arul Manual Stephen, CECRI, Karaikudi Dr. V.G. Geethamma, UCE, Thodupuzha Prof. Ranjith Ramadurai, IIT, Hyderabad Prof. Kuruvilla Joseph, IIST, Trivandrum Dr. P.V Rajeesh, UGC-DAE-CSR, Kolkata Dr. M.S Latha, SNC, Kollam Dr. George Varughese (Former Principal) Dr. Achamma Kurian (Former HOD) Dr. M.J Kurien (Former HOD

International Advisory Committee

Prof. Didier Rouxel, France Prof. Sasa Lazovic, Serbia Prof. Murukeshan Vadakke Matham, Singapore Prof. Tesfakiros Woldu, Ethiopia Prof. Oluwafemi oluwatobi, South Africa Prof. Ichiro Terasaki, Japan Prof. Andrey Aleshin, Russia Prof. Hafedh Kochkar, Tunisia Prof. Gideon Grader, ISRAEL Prof. Sajid Alavi, USA Prof. Yves Grohens, France Prof. Józef T. Haponiuk, Poland Prof. Alexey Goncharov, Ukraine Prof. Manfred Stamm, Germany Prof. Maya Jacob John, South Africa Prof. Paula Moldenaers, Belgium Prof. Minn-Tsong Lin, Taiwan Prof. Harald Brune, Switzerland

Local Organizing committee

Dr. Soosan Samuel M Dr. Raji Koshi Dr. Dhanya I Dr. Anoop P D. Ms. Jini K. Jose Ms. Asitha C. Nair Mr. Sajith Babu S Dr. Achamma George Dr. Karthika S Mr. Sibi Chandran C.S Ms. Reshmi.P. Ms. Priya Elizabeth Thomas Ms. Keerthana C S Mr. Rahul M T


Contents

SI No

Title Authors name Page no

1 Urban Heat Island Mitigation using Nano Modified Surfaces

George Thomas, Reshma Mariam Reji, Parvathy S

4

2 Thermodynamic description of neutral silicon cluster formation based on van der Waals-London interaction

Srećko Botrić , Ivan Zulim , Isaac Balberg

8

3 Synthesis and characterization of Copper tin sulphide quantum dots For optoelectronic applications

Maya Mathew , K.C. Preetha

15

4 An indepth review on the emerging biopolymer: Poly lactic acid

Kalyani Sreekumar, Renjini M Nair, B Bindhu

18

5 Emerging Advances in Development New Plasma Tools for Deposition Nanostructure Coatings and Thin Films (Fundamentals, Synthesis and Characterization)

Alexey Goncharov, Andrii Dobrovolsky, Vladimir Bazhenov , Evgeniy Kostin

24

6 Synthesis and characterization of zirconium based nanocomposites

Rakhi C, K.C.Preetha 28

7 Hybrid Multiferroic Fibers of Al3Fe5O12 Nanoparticles Loaded PVDF with Excellent Flexibility and Superior Magnetoelectric Response via an Electrospinning Technique with a Rotating Collector

M T Rahul, R Sree Raj, B Raneesh

32

8 Synthesis and Characterisation of Cerium Oxide

Nanoparticles

Prabha Jyothi P S, Smitha S, Anu Krishna, Nisha J Tharayil

35

9 Optical and Morphological Properties of SnO Nanocrystals

Aiswaraya Nair, Neethu K, Aswathy Nair , Bestin Babu, Vishnu S. Kumar, Achamma George

39

10 Nanoparticles based Solar Reflective Coating to Mitigate Urban Heat Island Effect

George Thomas, Soosen Samuel M, Karthik Vinodan, Anvar Shareef Pattathodika, Sajith Babu S

44

11 Synthesis of Luminescent ZIF-8 Nanoparticles for Targeted Drug Delivery

U Arun, R Sreeja, Annie Abraham

48

ICAN2018: Technology Letters Conference Proceedings of the International Conference on advanced nanostructures, March 2018

Urban Heat Island Mitigation using Nano Modified Surfaces George Thomas*, Reshma Mariam Reji, Parvathy S Catholicate College, Pathanamthitta, Kerala, India *Corresponding author Email: [email protected] Abstract: Global climatic change contributes to increased urban temperatures and caused extreme climatic phenomena. Heat accumulated and released in the urban environment results in a positive thermal balance and increased urban ambient temperatures composed to the surrounding environment. Such a phenomenon is known as the Urban Heat Island (UHI) and it is the most documented phenomenon of climate change. This study has investigated the development of the Urban Heat Island in Kochi, a tropical coastal city during winter. Mobile surveys were conducted during winter seasons, covering pre-dawn and early evening periods to find the UHI intensity. Highest observed urban heat island intensity in Kochi is 4.0oC during winter morning. Most intense heat island is observed in the city centre. Low albedo material attains higher temperature when exposed to solar radiation. High albedo materials in the urban area reduces the amount of solar radiation absorbed through building envelop and urban structures and keep their surface cooler. Nano modified surfaces for the mitigation of UHI is studied here. Nano-modified surfaces improve its thermal performance by increasing its anti-high temperature capacity. The solar reflectance and emissive power of the nano-modified surfaces make the urban region ‘cool’ by improving its solar reflectance and emissivity. Reflectivity of the nano coated surfaces is found to have increased thereby reducing solar absorbance. Hence by

controlling the solar absorption and emissivity of the modified urban surfaces results in much lower surface temperature and a reduced sensible heat to the atmosphere.

Key words: Urban Heat Island Effect, Nanotechnology, Nanocoating 1. Introduction The Urban Heat Island is refers as the warm urban temperatures compared to those over surrounding, non-urban areas. Differences in the surface materials between a city and the surrounding rural area lead to different climates within a city and its adjoining rural areas. Heat accumulated and released in the urban environment results in a positive thermal balance and increased urban ambient temperatures. The contributing factors leading to the urban and rural temperature difference include reduction in evaporative cooling, the heat storage of the building and pavement [1],[2],[3]. The heat accumulation capacity of the building mass and the ground cover is large. The storage of solar energy in the urban fabric during the day and release of this energy into the atmosphere at night boost UHI [6],[7]. UHI mitigation efforts could depend on the relative sensitivity of the different parameters that influence the UHI at the location. Improvements in urban radiative characteristics through high albedo surfaces and surfaces with engineered reflectance spectra can reduce UHI. 2. Methodology 2.1. Mobile Traverse to quantity UHI Intensity Mobile Survey was carried out during winter in 2018 to quantify UHI intensity. Measurements were carried out at predawn from 4:30 to 6:30 am before sunrise. Observational points were so chosen as to ensure adequate representation of urban, semi urban and rural area. Air temperature

4

ICAN2018: Technology Letters Conference Proceedings of the International Conference on advanced nanostructures, March 2018 was recorded with high resolution RTD probe (MadgTech USA, Model: RTD Temp 101). The vehicle was stopped for 1 minute at each observational point along the route to eliminate the error in measurements of RTD probe before reaching the steady state. The reference temperature was taken from a temperature recorder installed at Thripunithura [5]. The instantaneous temperature difference between all observational points and the reference site was calculated in order to determine UHI intensity [4]. Surface temperature variation of different materials when exposed to solar radiation was measured in a clear days during winter season. 2.2. Nano coated surface to mitigate UHI TiO2 is prepared by chemical method. The structure and morphology of the samples were investigated by X-ray diffraction and Scanning electron microscopy. The optical property of the material was also studied. 2.3. Study area

Kochi is one of the fast growing urban centre located on the southwest coast of India, between 090 45’ N and 100 20’ N latitude and between 760 10’ E and 760 35’ E longitude, has a coastline stretching up to a length of about 48 kilometres. It hosts a number of industries, and a population of 2.2 million. The city is interlaced by estuaries fed by perennial rivers. Much of Kochi lies at sea level. Kochi features a tropical monsoon climate. Its proximity to the equator along with its coastal location results in little seasonal temperature variation, with moderate to high levels of humidity. The average annual rainfall is about 3500 mm with an average 132 rainy days annually; the bulk of the rainfall is from the South-West monsoon. The winds are moderate, with slight increase during summer and the monsoon seasons. A sketch map of the study area is shown in the Figure1

Fig.1. Map of the study area. 3. Results and Discussion 3.1. UHI Intensity The Urban Heat Island intensity at Kochi was moderate to high during winter season and is seen to relate well with urbanisation. The highest observed urban heat island intensity in Kochi is 4.0oC during winter morning. Maximum intensity was seen in the central part of the city. Surface temperature variation of the different materials when exposed to solar radiation is shown in the Figure 2. It is observed that material with low albedo and emittance retain the higher surface temperature when expose to solar radiation. Materials which usually found in the urban areas like asphalt, brick etc., showed higher value of surface temperature when exposed to solar radiation and retained it for a long time. However leaf showed low value of surface temperature throughout the measurement. Lower surface temperature also reduces the emission of long wave radiation and air temperature. Similarly materials with less thermal emittance, refers to the surface’s ability to shed heat or emit long wave radiation also influences heat island developments [8].

5

ICAN2018: Technology Letters Conference Proceedings of the International Conference on advanced nanostructures, March 2018

Fig.2. Surface temperature variation of the different materials.

3.2. Mitigation using TiO2 Photoluminescence spectrum of TiO2 nano particles shows a high reflectance in the infrared region. The use of high reflective TiO2 nanoparticles based paints on the visible solar applied on the surface of pavement can reduce the surface temperature. This will reduce the sensible heat released to the atmosphere Most of the materials used in the construction provide a low albedo surface, resulting in increased absorption of solar radiation in day time. Low albedo material attains higher temperature when exposed to solar radiation. High albedo materials in the urban area reduces the amount of solar radiation absorbed through building envelop and urban structures and keep their surface cooler. Nanoparticles based coating is an effective method used to mitigate urban heat island. Reflectivity of the pavement can be increased by covering the surfaces of the pavement with a nano coating. These coating have reflectance in wide range especially in visible and infrared region of solar spectrum. They have high emissive power and hence possess a large potential for mitigation. 4. Conclusions Highest observed urban heat island intensity in Kochi is 4.0oC during winter morning. Nano-

modified surfaces store less heat and may have lower surface temperature compared to normal surfaces. Nano-modified surfaces improve its thermal performance by increasing its anti-high temperature capacity. The solar reflectance and emissive power of the nano-modified surfaces make the urban region ‘cool’ by improving its solar reflectance and emissivity. Reflectivity of the nano coated surfaces is found to have increased thereby reducing solar absorbance. Hence by controlling the solar absorption and emissivity of the modified urban surfaces results in much lower surface temperature and a reduced sensible heat to the atmosphere. Nanoparticles based coating is an effective method used to mitigate urban heat island. These coating have reflectance in wide range especially in visible and infrared region of solar spectrum. References [1] Nunez, M.; Oke, T.R. The Energy Balance of an Urban Canyon, Journal of Applied Meteorology, 1977, 16,11-19. [2] Oke, T.R. Review of Urban Climatology 1973–1976. WMO Technical Note No. 169, WMO No. 539. World Meteorological Organization: Geneva, 1979. [3] Oke, T.R. The energetic process of the urban heat island. Quarterly journal of the Royal Meteorological Society, 1982, 108,1-24. [4] Thomas, G.; Sherin, A.P.; Ansar, S.; Zachariah, E.J. Analysis of urban heat island in Kochi, India, using a modified local climate zone classification. Procedia Environmental Sciences, 2014, 21, 3-13. [5] World Meteorological Organization, Guide to Meteorological Instruments and Methods of Observation. 7th ed., WMO-No. 8, Geneva, 2008. [6] Ackerman, B.Moisture content of city and country air, Preprints conference Air Pollution Meteorology, American Meteorological Society, 1971, 154-158.

6

ICAN2018: Technology Letters Conference Proceedings of the International Conference on advanced nanostructures, March 2018 [7] Taniguchi, M., Burnett, W.C., Ness, G.D. Integrated research on subsurface environments in Asian urban areas. Science of the Total Environment, 2009, 404, 377–392. [8] Van Hove, L. W. A., Jacobs, C. M. J., Heusinkveld, B. G., Elbers, J. A., Van Driel, B. L., Holtslag, A. A. M., Temporal and spatial variability of urban heat island and thermal comfort within the Rotterdam agglomeration. Building and Environment, 2015, 83, 91-103. Acknowledgements The authors are grateful to UGC for the encouragement and financial support extended for this study. The authors are also thankful to Dr. Raneesh B for the co-operation and support extended for this study.

7


Thermodynamic description of neutral

silicon cluster formation based on van der Waals-

London interaction Srećko Botrić *1, Ivan Zulim 1, Isaac Balberg 2 1Faculty of Electrical Engineering, Mechanical

Engineering and Naval Architecture, University of Split, Ruđera Boškovića 32, HR-21000 Split,

Croatia

2 The Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel

*Corresponding Author: [email protected]

Abstract: A model of the classic ideal gas is applied to analyze the clustering of 100 silicon atoms as an isothermal process in a volume of the order of 10-23 m3 in which the van der Waals-London interaction between neutral silicon atoms is assumed to bring about a nucleation of clusters. For the small-scale system of identical freely moving clusters the thermodynamic temperature concept is taken as valid. By combining the analysis of the nucleation process from the microscopic point of view with the laws of thermodynamics the nucleation temperature is estimated to be 734.5 K at the pressure 105 Pa. Key words: thermodynamic states, van der Waals-London interaction, Sackur-Tetrode equation, nucleation temperature.

1. Introduction It is well known that the process preceding the formation of silicon quantum dots (clustering) is not yet fully understood. In the study of this and related phenomena the computer simulations are commonly applied using various models and methods amongst which those taking into account a physical microscopic interaction [1]. As a rigorous physical theory the density-functional theory (DFT) is suitable for investigating both intramolecular and intermolecular interactions [2]. But it appears that the results of the DFA with local density approximation (LDA), even with the generalized gradient approximation (GGA) for systems bonded by the van der Waals-London force, have limited accuracy [3,4]. Hence, we propose that in addition to the electronic-structure approach of the DFT-based description, an approach based on a thermodynamic description can provide estimation for the clustering energies in systems of neutral atoms. In particular we consider the nucleation process in terms of the thermodynamics of quasi-equilibrium populations of neutral gas-phase silicon clusters with a van der Waals-London interaction [5]. From the microscopic viewpoint it is possible to assume that this interaction governs the clustering process. In this paper we use two different approaches which make it possible to estimate the temperature of nucleation process:

a) applying the laws of thermodynamics to a system of a small number of freely moving neutral atoms,

b) analyzing the process from the microscopic point of view according to which the clustering of neutral silicon atoms is a sequence of continuous changes from the van der Waals-London bonding to the covalent bonding.

8

ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 2. Thermodynamic description The recently developed formalism of kinetic equations is a possible approach for studying the time evolution of the nucleation process [6]. In this paper we present another approach which is focused on the nucleation energy of the clusters. The clustering of a small number of neutral atoms is considered here without taking into account the time evolution, in spite of the fact that fluctuations are present in the course of the process. In this tentative model we consider then the isothermal cluster formation in a constant volume V. The process is supposed to be reversible; the system of non-interacting clusters is in fact an ideal Bose gas; yet the laws of classical thermodynamics are assumed to be applicable. Applying the first law of thermodynamics (thermodynamic temperature T=const., volume V=const.) one has that: UQ dd = , (1) where dQ is the infinitesimal amount of heat, U=U(T, V, N) is the internal energy of the system, T is thermodynamic temperature measured in degrees kelvin, and N is the number of particles/clusters. According to Eq. (1) the change of the internal energy in the process that is being considered, as well as the change of entropy S=S(T, V, N),

TQS dd =

, (2) occur solely due to the change of the number of particles/clusters. In our approach we assume that at the beginning of the nucleation process the system consists of N (taken below as100) neutral silicon atoms in the volume V, while the ratio V/N is supposed to be large in comparison with volume of silicon atom. Being an isothermal process the cluster formation is accompanied by the decrease of entropy and the heat release is in accordance with Eqs. (1) and (2). 2.1. A Gas-phase model Our approach to the cluster definition and to the definition of population of clusters [5] is based on the following physical picture:

- Each thermodynamic state of the system is a quasi-equilibrium one and it corresponds to a definite quasi-equilibrium population of particles/clusters.

- For simplicity, each successively appearing quasi-equilibrium population in the course of nucleation is composed of a given number Nν (< N) of identical non-interacting clusters.

- Although any population of clusters being considered is a small-scale system the thermodynamic temperature concept is taken as valid [7].

- In spite of the fact that each cluster is a composite boson any population of them is treated as a classical system obeying the Boltzmann statistics [1].

Correspondingly, the classic ideal gas law can be applied:

TkNpV Bν= , (3) where the pressure p is measured in pascals (1 Pa = kg/(ms2)), and kB = 1.38×10-23 J/K is the Boltzmann constant. In our calculation we will focus on five possible (quasi-equilibrium) populations which can be considered in defining the thermodynamic states of the system. For illustration we describe these five states as enumerated in Table 1 for the case of N = 100. Here, m is the mass of the Si atom matom and mcluster is the mass of the corresponding cluster.

Table 1 Five quasi-equilibrium populations of particle/clusters.

Thermodynamic

state / Population of

identical clusters

Mass of silicon clusters (matom=

4.662×10-26 kg)

Number of identical

particles/clusters Nν

α no cluster matom Nα = 100 β cluster

composed of two atoms

mcluster = 2matom Nβ = 50

9


γ cluster composed of three atoms

mcluster = 3matom Nγ = 33

δ cluster composed of four

atoms mcluster = 4matom Nδ = 25

ε cluster composed of five

atoms mcluster = 5matom Nε = 20

In passing we note that recently clusters composed of six or more atoms have been considered by the different theoretical approach of the DFT [8]. It is obvious that the entropy of these quasi-equilibrium states satisfies the inequalities:

εδγβα SSSSS >>>> . Following these expected thermodynamic states of nucleation process the entropy can be calculated by the application of the Sackur-Tetrode equation [9]:

Nk

NVNkS B3B 2

5ln +

Λ=

, (4) where the thermal de Broglie wavelength Λ is defined by:

( )21

Bπ2 Tkm

h=Λ

, (5) where m is the mass of gas particle/cluster and h = 6.626×10-34 Js is Planck's constant. Equation (4) is physically meaningful and applicable even to quasi-equilibrium states of a gas-phase provided that:

13 >>ΛN

V. (6)

The question that arises then is whether one can estimate theoretically the temperature of the cluster formation process within the framework of this gas-phase model. To get a physically plausible answer to this question we suggest that the analogy with the relationship between cohesive energy of a given crystal and its temperature of crystallization may be instructive. Correspondingly, it is sufficient to

consider the binding energy in the cluster formation process as the result of an attractive force between neutral (non-ionized) atoms. Since the Lennard-Jones potential approximates the interaction between a pair of neutral atoms (van der Waals-London interaction) it can be assumed to be the cause of nucleation and thus its expression can be applied for the determination of the temperature of the process. In what follows we consider then the Lennard-Jones potential as given by [10,11]

( )

−

=

6m

12m

p 2rr

rrErE

, (7)

where I

rE 6

m

2e

83α

=. For silicon the ionization energy

I = 8.1517 eV = 1.304×10-18 J, αe = 3.733×10-30 m3, rm = 2.1×10-10 m and one obtains that: E = 0.4968 eV = 7.949×10-20 J. (8) We also recall here that the atomic radius of silicon is ratom = 1.1×10-10 m. 2.2. The heat released due to the decrease of entropy The entropy decrease ∆S during the cluster formation process, with α and ε being the initial and final states respectively, is given by

αε SSS −=∆ , where:

αB3

αααBα 2

5ln NkN

VNkS +

Λ

=,

εB3

εεεBε 2

5ln NkN

VNkS +

Λ

=,

𝛬𝛼 =ℎ

(2𝜋𝑚𝛼𝑘𝐵𝑇)12

=

=ℎ

(2𝜋𝑚𝑎𝑡𝑜𝑚𝑘𝐵𝑇0)12

× 𝑇0𝑇

12

= 𝛬(𝑇0)𝑥−12

10


𝛬𝜀 = ℎ

(2𝜋𝑚𝜀𝑘𝐵𝑇)12

= ℎ

(2𝜋×5𝑚𝑎𝑡𝑜𝑚𝑘𝐵𝑇0)12

× 𝑇0𝑇12 =

= 𝛬(𝑇0)(5𝑥)−12 = 5−

12𝛬𝛼

0TTx =

and

( )( )

021

0Batom

0

π2Λ≡=Λ

Tkm

hT

. For T0 = 300 K, which is taken here as a referent temperature, one gets that:

( )m10902.1

π2

11

21

0Bα

0−×==Λ

Tkm

h

. By virtue of (3), instead of Nα = 100 and Nε = 20, it is convenient to introduce into the calculations the pressures pα and pε = pα/5 = (y/5)×105 Pa, where the dimensionless variable y is known to be limited to the interval [12]: 0.5 < y < 1.2 Thus we have:

yx

TT

yTk

NV

Ω=×

=0

50B

α Pa10 ,

23

30

23

030α

3αα

xyx

TT

NV

NV

ΛΩ

=

Λ

=Λ ,

yx

TT

yTk

NV

Ω=×

= 5Pa10

50

50B

ε ,

( ) ( ) 2

3

30

252

3

0

23

30ε

3εε

55 xyx

TT

NV

NV

ΛΩ

=

Λ

=Λ ,

where Ω = (kBT0)/(105 Pa) = 4.14×10-26 m3. Since 63

0 10017.6 ×=ΛΩ , one can express the entropies Sα and Sε by:

𝑆𝛼 = 𝑘𝐵𝑁𝛼𝑙𝑛 𝑉

𝑁𝛼𝛬𝛼3 +

52𝑘𝐵𝑁𝛼 =

= 𝑘𝐵𝑁𝛼𝑙𝑛 6.017 × 106𝑥52

𝑦 +

52𝑘𝐵𝑁𝛼

and

𝑆𝜀 = 𝑘𝐵𝑁𝜀𝑙𝑛 𝑉

𝑁𝜀𝛬𝜀3 +

52𝑘𝐵𝑁𝜀 =

= 𝑘𝐵𝑁𝜀𝑙𝑛 6.017 × 106(5𝑥)

52

𝑦 +52𝑘𝐵𝑁𝜀

According to Eq. (2) the heat released in the process of forming 20 identical clusters, each composed of 5 silicon atoms, ∆Q, is given by:

∆𝑄 = 𝑇(𝑆𝜀 − 𝑆𝛼) =

=(𝑘𝐵𝑇0) 52

(𝑁𝜀 − 𝑁𝛼)𝑥 + 52𝑁𝜀𝑥𝑙𝑛5 +

(𝑁𝜀−𝑁𝛼)𝑥𝑙𝑛 6.017 × 106 𝑥52

𝑦 (9)

For the clusters composed of five atoms (double tetrahedron) we assume that the rotational and vibrational degrees of freedom are not excited at the temperature of the process. 2.3. The heat released according to cluster configurations From the microscopic point of view, the internal energy is given by the sum of the kinetic energy of translational motion of freely moving particles/clusters and the potential energy (energy of configuration) due to the short range interaction that yields the cluster formation. Hence, for the states α and ε we have respectively:

pαBαα 2

3 ETkNU +=,

pεBεε 2

3 ETkNU +=,

where each of Epν (ν = 3, 4, 5) is calculated as a sum over all pairs of atoms belonging to the corresponding cluster. Because the initial state α is characterized by a configuration in which the interatomic distances are large it is reasonable to assume that Epα = 0.

11


Fig. 1. The identical atoms in the clusters are represented by spheres which touch in one surface point. The centers of spheres are the vertices of (a) tetrahedron, (b) double tetrahedron having mirror symmetry. Assuming that the atoms in a cluster touch approximately at one surface point, all the distances between the centers of any pair of silicon atoms in the clusters that belong to the states β, γ, and δ are equal to rm = 2ratom ≈ 2.1x10-10 m, see Fig. 1(a). This yields that the values of the energy of the configurations that we consider, following Eq. (7), are: β : Epβ = Nβ × (−E) = −50E, γ : Epγ = Nγ × (−3E) = −99E, δ : Epδ = Nδ × (−6E) = −150E. These values and their corresponding configurations are listed in Table 2. Table 2 Values of the binding energy of clusters of neutral Si atoms Thermodynamic

state / Population of

identical clusters

Shape of a cluster Energy of configuration

α no cluster

mutual distances between atoms

much greater than ratom

Epα = 0

β cluster composed of two

atoms

two spheres touching in one

surface point Epβ = −50 E

γ cluster composed of three atoms

equilateral triangle:

length of side = rm Epγ = −99 E

δ cluster composed of four

atoms

tetrahedron: length of edge =

rm Epδ = −150 E

ε cluster composed of five

atoms

double tetrahedron:

length of edge = rm

Epε = −182.054 E

A case of special interest is the cluster composed of five silicon atoms that is shaped as a double tetrahedron, see Fig. 1(b). There again all the distances between centers of any pair of silicon atoms in the cluster are equal to rm = 2.1 × 10-10 m, except for the distance between two atoms (atom 1 and atom 2) that are located on the opposite sides of the base plane of the double tetrahedron. For these

the distance is given by 𝑟12 = 8312 𝑟𝑚.

A straightforward calculation of the energy of configuration for the above double tetrahedron cluster gives then that:

𝐸𝑝12 + 𝐸𝑝1𝑘

5

𝑘=3

+ 𝐸𝑝2𝑘

5

𝑘=3

+ 𝐸𝑝3𝑘

5

𝑘=4

+ 𝐸𝑝45

= 𝐸𝑝12 + 9 × (−𝐸) = −9.1027𝐸, so that the energy of the configuration of the state ε is given by

EENE 054.182)1027.9(εpε −=−×= (where E is given by (8)). According to Eq. (1), the heat released in the process when calculated in terms of the change of internal energy ∆U = Uε - Uα is given then by: ∆𝑄 = ∆𝑈 = 3

2𝑘𝐵𝑇(𝑁𝜀 − 𝑁𝛼) + 𝐸𝑝𝜀 − 𝐸𝑝𝛼 =

32𝑘𝐵𝑇0(𝑁𝜀 − 𝑁𝛼)𝑥 + 𝐸𝑝𝜀 − 𝐸𝑝𝛼. (10)

12

ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 2.4. Estimation of the temperature of the cluster formation process Let us estimate now the temperature of the cluster formation process by equating the results of the two different approaches, i.e. the heat being determined by the entropy change and the heat calculated from the energy of the configurations:

( ) pε pαB 0 ε α

B 0

( )3 22 3

E EQ k T N N x

k T−

∆ = − + =

( ) ( )

×−++−=

yxxNNxNxNNTk

25

6αεεαε0B 10017.6ln5ln

25

25

(11)

where (due to (8))

a3.34950536.182

0B0B

pαpε =−=−=−

TkE

TkEE

. After a straightforward calculation one gets from (11) a transcendental equation from which the temperature of the process can be calculated. This equation reads:

25bexpB x

xy =

××

, (12) where 𝑏 = 𝑎

𝑁𝜀−𝑁𝛼= 43.69 and B = 1.672 × 10-7.

By simple numerical method one can find the roots of equation (12) for y=1 and y=1.2 respectively: for y=1, T = 734.5 K, pα = 105 Pa, for y=1.2, T = 741 K, pα = 1.2 × 105 Pa. The heat released for the y = 1 case with T = 734.5 K and pα = 105 Pa is 15.686 × 10-18 J. Thus according to our gas-phase model the estimated temperature of neutral silicon cluster formation equals 734.5 K at the pressure 105 Pa. 3. Conclusions We propose here an alternative model for the clustering process of neutral silicon atoms. We calculated the binding energy of small clusters

solely in terms of the van der Waals-London interaction. In this model the thermodynamic states are defined only by the number of identical clusters (clusters of the same shape) which is a measure of the population. Of course, we note that in the course of formation, clusters of different size and shape appear, but they can be considered as fluctuations with respect to the simple states β, γ, δ, ε, and as such are not discussed here. In estimating the temperature of the clustering process we have considered the system of such small scale weakly bound clusters as a thermodynamic one. Our calculations show that there is some discrepancy between the temperature obtained by making use of our model and the temperatures given in Ref. [12], but the magnitude of the temperature obtained (734.5 K at the pressure105 Pa) seems to justify the physical picture that we suggest. References [1] Drory, A; Balberg, I; Berkowitz, B., Random-adding determination of percolation thresholds in interacting systems. Phys. Rev. E. 49, R949, 1994. [2] Becke, A. D., Perspective: Fifty years of density-functional theory in chemical physics. J. Chem. Phys. 140, 18A301, 2014. [3] Klimeš, J.; Michaelides, A., Perspective: Advances and challenges in treating van der Waals dispersion forces in density functional theory. J. Chem. Phys. 137, 120901, 2012. [4] van Mourik, T; Gdanitz, R. J., A critical note on density functional theory studies on rare-gas dimers. J. Chem. Phys. 116, 9620, 2002. [5] Ford, I. J., Virial/Fisher models of molecular cluster populations. J. Chem. Phys. 106, 9734, 1997. [6] Ruby, J. M., Mesoscopic thermodynamics. Phys. Scr. 2012, 014027, 2012. [7] Simon, J. M.; Ruby, J. M., Temperature at Small Scales: A Lower Limit for a Thermodynamic Description. J. Phys. Chem. B. 115, 1422, 2011.

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ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 [8] Haertelt M.; Lyon, J. T.; Claes, P.; de Haeck, J.; Lievens, P.; Fielicke, A., Gas-phase structures of neutral silicon clusters. J. Chem. Phys. 136, 064301, 2012. [9] Lindsay R. B., Introduction to physical statistics. Dover, New York, 1968. [10] Kittel, C., Introduction to solid state physics. Wiley, 1971. [11] Chang, R., Physical Chemistry for the Biosciences. 1 edition, University Science Books, Sansalito, California, 2005. [12] Huelser, T; Schnurre, S. M.; Wiggers, H.; Schulz, C., Gas-phase synthesis of highly-specific nanoparticles on the pilot-plant scale. in: NSTI-Nanotech 2010 Proc., NSTI-Nanotech 2010; Anaheim, CA, USA, Nuremberg, 2010: pp. 330–333, 2010.

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SYNTHESIS AND CHARACTERIZATION OF COPPER TIN SULPHIDE QUANTUM DOTS FOR OPTOELECTRONIC APPLICATIONS Maya Mathew 1, K.C. Preetha *2

1Payyannur College, Payyannur, India PIN 670327, 2Sree Narayana College, Kannur, India PIN 670007

*Corresponding Author: [email protected] Abstract: In this paper we discuss the colloidal synthesis and characterization of copper tin sulphide (CTS) quantum dots. The precursors used are copper chloride (CuCl2), tin chloride (SnCl2), and sodium sulphide (Na2S). Trisodium citrate is used as the capping agent. The as-prepared quantum dots were characterized by X-ray diffraction and Uv-Vis spectroscopy. The X-ray diffraction data of the samples matched well with the tetragonal structure of CTS (JCPDS 089-4714). The absorption of as-prepared CTS sample shows a blue shift which is an evidence of formation of smaller sized particles. The bandgap of the quantum dots have been found to be 1.65 eV, higher than the bulk bandgap thus confirming quantum confinement of the CTS quantum dots. A study was made on the influence of Triethanolamine (TEA) on the nature of CTS quantum dots. The crystallinity of the quantum dots formed increased with the addition of TEA. Key words: Copper tin sulphide, quantum dots, exciton, photovoltaics, photodetection 1. Introduction The interest in nanostructures began to arise with the discovery of fascinating properties of materials at nanoscale. The charge carriers can be confined by reducing the dimensions of the material below its de-Broglie wavelength. In doing so, the behavior of the material can be tuned according to the application of interest. On decreasing the size of the particle to the order of or below the de-Broglie wavelength of the electron, it gets confined. The charge carriers get strongly confined by decreasing the size of the particle below the Bohr radius of the charge carriers of the material. Once the particle is in the strong confinement regime, the bandgap of the particle can be varied with its size [1-3]. Quantum dots, being in the strong confinement regime, are the nanostructures of interest as the bandgap can be tuned according to the application desired. Apart from binary

quantum dots, the advantage of ternary quantum dots is that the bandgap can be tuned by changing the molar ratio of the precursors [4]. In this paper, we focus on the photovoltaic applications of ternary quantum dots. Inorder to reduce the cost of production, we have used earth- abundant elements. This paper deals with the synthesis and characterization of copper tin sulphide quantum dots for photovoltaic applications. Copper tin sulphide (CTS) is a p- type semiconductor having a high absorption coefficient of 104 cm-1

and a band gap lying in the near IR range which makes it an ideal material for IR photodetection and in photovoltaics [5]. The bandgap of CTS thin films is 1.35 eV. The exciton Bohr radius is estimated to be in the range of 2.5 - 4.6 nm. Archana Kamble et.al. have prepared Cu2SnS3 nanocrystals by heat-up synthesis technique [6]. The nanocrystals were of wurtzite structure. The solvent used was octadecene in place of toxic oleylamine. Sandra Dias et.al. have synthesized Cu2SnS3 quantum dots using a heat up technique for near infrared photodetection. Here dodecanethiol (DDT) was used as the solvent, sulphur source and capping agent [7]. Again Sandra et.al. synthesized Cu2SnS3 quantum dots using a solvothermal process [8] with poly(vinylpyrolidone) as the capping agent and ethylene glycol as the solvent. In this work, we have synthesized Cu2SnS3 quantum dots using colloidal synthesis technique. Expensive solvents were replaced with water and easily available chemicals were used as the precursors. Stable quantum dots of bandgap 1.65 eV were synthesized which has promising applications in photovoltaics and photodetection. 2. Experimental 2.1. Materials The chemicals used for the synthesis of CTS quantum dots were copper chloride (CuCl2), tin chloride (SnCl2) and sodium sulphide (Na2S). Trisodium citrate was used as the capping agent. 2.2. Methods 2.2.1. Preparation of Samples The reaction bath contains 0.001M of SnCl2, 0.001M of CuCl2, 2.2M of trisodium citrate and 0.001M of Na2S. The solution turned brown with the addition of sulphur source. After stirring for about half an hour, scores of particles, black in colour, were found suspended in solution. The suspended particles were separated from the solution by centrifugation and then dried.

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Two sets of samples were prepared. In the second sample, a few drops of triethylamine (TEA) were also added to the reaction bath. 2.2.2. Characterization of samples Structural characterization of as-prepared samples was done by X-ray diffraction. The XRD data of the sample treated with TEA showed better crystallinity than the one without TEA. The XRD data of both the samples gave the same set of peaks. The peak positions agreed well with the standard data of CTS (JCPDS 89-4714). Optical characterization of the samples was made by Uv-Vis spectroscopy. The absorption edge is in the blue region (400nm) which is due to excitonic absorption. From the Tauc plots, the bandgap is found to be 1.65 nm i.e., in the IR region. 3. Results and Discussion 3.1. Structural Characterization Figure1 shows the XRD pattern of CTS without treating with (TEA). The peaks agree well with the standard XRD pattern of CTS quantum dots (JCPDS 089-4714). The peaks marked with asterisk are the elemental peaks of unreacted copper and tin. The CTS quantum dots have a crystalline structure with tetragonal symmetry. From the XRD data, the d-spacing and the lattice constant were calculated. Figure 2 shows the XRD pattern of CTS quantum dots treated with a few drops of (TEA). On comparing the two graphs, it can be well said that the crystallinity of CTS quantum dots increases with the addition of TEA. The absence of peaks of elemental copper and tin is the major advantage. So the role of TEA is to free the cations (of precursors) from their salts, as a result of which the yield of CTS quantum dots increases. Further studies were made using the sample treated with TEA.

Fig. 1. XRD pattern of CTS (Without treating with TEA)

3.2. Optical Characterization Figure 3 shows the absorption spectrum of the CTS quantum dots and its Tauc plot. The reflectance and transmittance curves are shown in figure 4. The formed nanoparticles are of very small size as the absorption edge is in the blue region. The two peaks at 350 nm and 400 nm correspond to the excitonic transitions from the discrete energy levels of valence band to those of conduction band. The presence of excitonic peaks confirms that the synthesized nanoparticles are quantum dots. The bandgap of the CTS quantum dots, found from the Tauc plot is 1.65 eV. This value is much higher than the bandgap of CTS thin films which is 1.35 eV [8]. Thus as the size of the nanoparticle is decreased below the Bohr radius, quantum confinement effects begin to play and the bandgap can be tuned with the change in size of the particle.

Fig. 2. XRD pattern of CTS (Treating with TEA)

Figure 3: Left: Absorption spectrum of CTS quantum dots, Right: Tauc plot of CTS quantum dots

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Figure 4: Left: Reflectance spectrum of CTS quantum dots, Right: Transmittance spectrum of CTS quantum dots 3.3. Structural Parameters The XRD of CTS quantum dots of both the samples were studied. The crystal planes of CTS quantum dots are (112), (200), (102), (220), (103) and (112). From these data, the crystal structure was determined. Also the d-spacing and lattice constant were also calculated and tabulated below (Table1). Sample Crystal

Structure d-spacing Lattice

constant CTS Tetragonal 2.248 Å 5.412 Å

Table 1 The absorption spectrum was studied for its bandgap by drawing its Tauc plot. The reflectance spectrum was also studied and the refractive index and dielectric constant was calculated and tabulated below (Table2). Sample Bandgap Refractive

index Dielectric constant

CTS 1.65eV 1.67 2.789 Table 2

4. Conclusion In summary, we have synthesized copper tin sulphide (CTS) quantum dots by simple colloidal technique. The chemicals used were economical and the solvent used is water. The synthesized quantum dots are crystalline with tetragonal symmetry. The crystallinity of the quantum dots increases with the addition of triethanolamine. The absorption is in the blue region, signifying smaller sized particles. The bandgap calculated from the Tauc plot is found to be 1.65 eV, much higher than 1.35 eV (Bandgap of CTS thin films) which is due to strong quantum confinement of the quantum dots. The dielectric constant of CTS is comparable to that of polystyrene and hence can be used in capacitors as dielectric material to increase its capacitance. Thus through this work we have achieved in synthesizing strongly confined CTS quantum dots

with a bandgap of 1.65 eV which can have potential applications in photovoltaics and also in photodetection. References 1. Klimov, Victor I., ed. Nanocrystal quantum dots. CRC Press, 2010. [2] Gaponenko, Sergey V. Optical properties of semiconductor nanocrystals. Vol. 23. Cambridge university press, 1998. [3] Harrison, Paul, and Alex Valavanis. Quantum wells, wires and dots: theoretical and computational physics of semiconductor nanostructures. John Wiley & Sons, 2016. [4] Wang, Jian-Jun, Pai Liu, and Kevin M. Ryan. Chemical Communications, 2015, 51.72, 13810-13813. [5] Dias, Sandra, et al. Inorganic Chemistry, 2017, 56.4, 2198-2203. [6]. Kamble, Archana, et al. CrystEngComm , 2016, 18.16, 2885-2893. [7]. Dias, Sandra, et al. RSC Advances, 2017, 7.38, 23301-23308. [8]. Dias, Sandra, et al. Inorganic Chemistry, 2017, 56.4, 2198-2203. Acnowledgements The authors acknowledge Department of Physics, Central University of Kerala, Kasargod for providing us the necessary characterization facilities.

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An indepth review on the emerging

biopolymer: Poly lactic acid

Kalyani Sreekumar, Renjini M Nair, B Bindhu* Department of Physics, Noorul Islam Centre for

Higher Education, Kumaracoil, Thuckalay-629180 *[email protected]

Abstarct: The environmental impact associated with synthetic polymers made the researchers and industrialists to depend on sustainable polymers derived from renewable sources rather than the definitely available non-renewable sources. Being the crucial element in almost all industries, polymers pioneer in the list of sources needed for various applications. Because of the same reason, polymers from natural sources are gaining more importance and are expected to bring out revolution in the field of packaging industry, medical applications, automobile industry etc. Among the various biopolymers used, polylactid acid (PLA) is one of the most relevant one because of its significant properties that can be utilized in different industries. It is an aliphatic polyester derived from lactic acid (2-hydroxypropionic acid). It is a biodegradable polymer that can be recycled after use either by remelting and processing the material a second time or by hydrolyzing to lactic acid, the basic chemical. In this paper we focus on an indepth review on polylactic acid based blends and composites. The various applications and properties of these composites are also studied.

Key words: Polylactic acid, mechanical properties, thermal properties, polymer blends and composites

1. Introduction The enormous use of non degradable plastic materials causes many environmental hazards as they remain there as such for long. There arises the demand for cost effective degradable materials. Biopolymers are the best solution for this problem. These are polymers that are derived from natural sources. Different biopolymers find applications in many fields such as medical, packaging, automobile, and food industry. Polylactic acid (PLA) is one of the most relevant biopolymers, that is being researched widely. PLA is a highly versatile, biodegradable, aliphatic polyester derived from 100% renewable resources, such as corn and sugar beets[1]. Lactic acid (2-hydroxy propionic acid) is the building block of PLA. Since PLA is compostable and derived from sustainable sources, it has been viewed as a promising material to reduce the societal solid waste disposal problem. Different Polylactic Acid categories include Racemic PLLA (Poly-L-lactic Acid), Regular PLLA (Poly-L-lactic Acid), PDLA (Poly-D-lactic Acid), and PDLLA (Poly-DL-lactic Acid). PLA is classified as a “thermoplastic” polyester . Thermoplastic materials become liquid at their melting point. A major useful attribute about thermoplastics is that they can be heated to their melting point, cooled, and reheated again without significant degradation. Instead of burning, thermoplastics like Polylactic Acid liquefy, which allows them to be easily injection molded and then subsequently recycled. Until the last decade, the main uses of PLA have been limited to medical applications. Recently, new techniques which allow economical production of high molecular weight PLA polymer have broadened its uses [3]. Through this paper we go through an in-depth literature review on PLA, its production and various properties, details about blends, and applications.

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ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 2. Synthesis of PLA Condensation and polymerization are the two basic principle methods through which PLA is being produced. The basic building block of PLA namely lactic acid can be produced by carbohydrate fermentation or chemical synthesis. Currently, the majority of lactic acid production is based on the fermentation route[4]. Lactic acid (2-hydroxy propionic acid) is the simplest hydroxyl acid with an asymmetric carbon atom and it exists in two optically active configurations, the L(+) and D(-) isomers. The L(+) and D(-) isomers are produced in bacterial systems [5]. The chemical structure of L and D lactic acid is shown in the fig.(1).

Fig.1. Chemical structure of L and D- lactic acid[5] Hartmann et.al[6]. had discussed about various synthesis methods for the production of high molecular weight PLA. The main three methods include direct condensation polymerization; azeotropic dehydrative condensation and polymerization through lactide formation. These routes are picturized in the fig.2.

Fig.2. Synthesis methods for obtaining high molecular weight PLA, adapted from Hartmann[6]

Among the three routes, the least expensensive one is direct condensation. Polymerization through lactide formation is the commonly used method to obtain polylactide polymers of high molecular weight for commercial applications. Gruber et.al had described about this method and it is represented in fig.3[7].

Fig. 3. Current production process for PLA, adapted from Gruber[7] 3. Properties of PLA Along with the benefit of bio compatibility and producton from renewable sources, PLA has got many other properties that make it suitable for various applications. 3.1 Mechanical Properties In the biomedical field, PLA is highly accepted because of its good mechanical properties combined with its biocompatibility and its ability to degrade both in vivo and in vitro[8]. The mechanical data sheet of PLA is shown in table 1. PLA is normally a stiff and brittle polymer. Use of plasticizers such as glycerin, enthylene glycol, sorbitol, etc. in the film formulations or composites is advantageous to enhance its mechanical properties [21] Jacobsen et al.[11] had reported that the mechanical properties of PLA makes it a good substitute for petroleum based polymers. Commercial PLA, such as poly (92% L-lactide, 8%

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ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 meso-lactide), has a modulus of 2.1 GPa and an elongation at break of 9%. After plasticization, its Young’s modulus decreases to 0.7 MPa and the elongation at break rises to 200%, with a corresponding Tg shift from 58 to 1880C. This example indicates that mechanical properties can be readily tuned to satisfy different applications [12].

Table 1. Mechanical properties of PLA (Material datasheet by Biomer for L9000)

Mechanical Properties Values Young’s Modulus (MPa) 3600 Tensile Strength (MPa) 70 Elongation at break (%) 2.4

Flexural Strength (N/mm²) 98 Impact strength (kJ/m²) 16.5

Notched impact strength (kJ/m²) 3.3

MFI (g/10 min) 3 to 6 Density (g/cm³) 1.25

Moisture absorption (%) 0.3 Lesser the elongation at break, more brittle the material is [13]. Balakrishnan et al.[19] had reported that, when compared with high density polyethylene (HDPE), polystyrene (PS), PLA has lower elongation at break. This brittleness can be reduced by the modification of PLA with other composites. T. Kasuga et al.[14] had reported the influence of hydroxyapaetite fibres (HAF) on PLA. With increasing HAF content, the maximum strain decreases and the specimen is apt to show a brittle fracture; this result implies that HAF in the composites can share the applied load effiently due to the formation of a bond between HAF and PLA. M. Jonoobi et al[15] reinforced PLA using cellulose nanofibers (CNF), the tensile strength and modulus were improved with increased nanofiber content. K osman et al[2] had also reported the composite with PLA and flax fibers, also showed better mechanical properties along with the addition of triacetin as a

plasticizer. The composite strength is about 50% better compared to similar PP/flax fibre composites, which are used today in many automotive panels. Also there are reports where PLA has been blended with a number of polymers, such as polycapralactone (PCL), polyhydroxyalkanoate (PHA), and polyethylene (PE). These all inferred some increase in mechanical property with the addition of other polymers. The flexibility and ductility of PLA can also be improved by blending PLA with a plasticiser. 3.2. Crystalllinity Properties The other property of polymers as important as mechanical property is their crystallinity. Crystallinity is the indication of amount of crystalline region in the polymer with respect to amorphous content[16]. Many rsearchers had studied about the crystalline behaviour of PLA. Amorphous or semicrystalline nature of PLA mainly depends on its stereochemistry and the thermal history[11]. PLA resins containing more than 93% of L-lactic acid are semicrystalline, but when with 50–93% is entirely amorphous[22]. PLA crystals can grow in 3 structural positions called α, β, and γ forms. They are characterized by different helix conformations and cell symmetries, which develop upon different thermal and/or mechanical treatments[16][17]. The rate of crystallisation of PLA is inversely related to the molecular weight and and directly related to the copolymer composition. The crystallinity of PLA is most commonly determined using the differential scanning calorimetry (DSC) technique. By measuring the heat of fusion _Hm and heat of crystallization _Hc, the crystallinity can be determined based on the following equation:

𝐶𝑟𝑦𝑠𝑡𝑎𝑙𝑙𝑖𝑛𝑖𝑡𝑦 (%) = ∆𝐻𝑚 − ∆𝐻𝑐

93.1× 100 → (1)

where the constant 93.1 J/g is the ΔHm for 100% crystalline PLLA or PDLA homopolymers. Increased crystallinity will be desirable for injection

20

ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 molded articles for which good thermal stability is important. 3.3. Thermal Properties Most of the thermoplastic polymers exhibit glass transition temperature (Tg) and possess a melting point (Tm). The glass transition temperature of PLA is 550C and the melting temperature is around 1700C[10]. A rubbery behaviour is seen for PLA above its Tg, and below this temperature, it becomes a glass which is still capable to creep until it is cooled to its β transition temperature at approximately~450C, below which it behaves as a brittle polymer[18]. The glass transition temperature and melting point of different polymers are tabulated below in table.2. Table 2. Thermal properties of different polymers Polymer Tg (0C) Tm (0C) Polylactic Acid(PLA) 55 170 Plyglycolide(PGA) 35-40 220-225 Polycarpolactone (PCL) -60 60-65 Poly(butylene succinate) (PBS)

-35 90-120

High Density Polyetrhylene(HDPE)

-125 135

Polypropylene (PP) -10 75 Poly styrene (PS) 100 No true

Tm; Gradually softens until melt

Polyamide 6 (PA6) 50 215 Acrylonitrile Butadiene Styrene (ABS)

110 No true Tm; Gradually softens until melt

As shown in the table, PLA has got relativley low Tm and high Tg than other thermoplasts. The molecular weight and the optical purity of the

polymer are reported to have effect on Tg of PLA[11]. Optical purity is found to have an effect on Tm also. The Tg is diretly proportional to molecular weight. In general, the relationship between Tg and molecular weight can be represented by the Flory Fox equation:

𝑇𝑔 =𝑇𝑔∞ − 𝐾𝑀𝑛

→ (2)

where 𝑇𝑔∞ is the Tg at the infinite molecular weight, K is a constant representing the excess free volume of the end groups for polymer chains, and 𝑀𝑛 is the number average molecular weight. The values of 𝑇𝑔∞ and K are around 57–58 C and (5.5–7.3) 104 as reported in the literature for PLLA and PDLLA, respectively[19] 4. PLA Blends and Composites Inorder to enhance the properties of PLA, it has been blended with different other materials, by different researchers. These polylactic acid blends and composites have occupied major applications in different fields such as , green packaging, medical device packaging, and as bioimedical devices. T. Kasuga et al[14]. had reported successful formation of a blend of PLA with fibrous hydroxyapetite. The modulus of elasticity was found to be strengthened with the addition of fibre content, along with almost no degradation. It is very important for practical applications that the materials have a large surface fracture energy. A composite of PLA with Polyglcolic acid had been characterized by J Moran et al.[20] for cartilage tissue engineering. The other major material being blended with PLA is starch. Many researchers had worked out on this, and better results were reported. The characteristics of PLA and star-PLA were studied by Park et al[22]. Starch plays a role as a nucleating agent in PLA.They found an increase in the crystallization rate and in the enthalpies of crystallization and melting for PLA with starch contents above 5%. Kim et al.[23] showed that PLA is incompatible with starch granules. PLA/Acrylonitile Butadiene

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ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 Styrene (ABS) blend was reported by Shimizu et al.[24]. When compared to the pristine values, elongation and impact strength was improved while as modulus and tensile strength was slightly reduced. Jaratrotkamjorn et al. [25] toughened PLA by blending with natural rubber, epoxidized natural rubber (ENR) and natural rubber grafted with poly(methyl methacrylate). NR became the best toughening agent compared with NR-g-PMMA and ENR. C.-Y. Hung et al.[26] reported enhanced thermal stability and crystallinity of PLA with the addition of reactive block copolymers poly(styrene-b-methyl methacrylate-b-glycidyl methacrylate) (PS-b-PMMA-b-PGMA, PSMG) and poly(styrene-b-glycidyl methacrylate) (PS-b-PGMA, PSG). Homogeneous nanocomposites composed of hydroxyapatite and chitosan in the presence of polylactic acid were synthesized by a novel in situ precipitation method by Xuan Cai et al.[27]. The addition of PLA in the CS matrix greatly influenced the nucleation and the growth of HA crystalline. The mechanical property study results indicated that the addition of polylactic acid can make homogeneous composites scaffold resist significantly higher stress. The elastic modulus of the composites was also improved by the addition of polylactic acid, which can make them more beneficial for surgical applications. 5. Applications Polymers made of lactic acid achieved their first commercial success as fiber materials for resorbable sutures. After this, a number of different prosthetic devices were developed [12]. Biocompatibility, bioresorbablity,. biodegradability, mechanical properties and light weight properties had made PLA to be used in, many aspects, such as medical and automotive interiors[47-50]. Many studies had reported that PLA is an economically feasible material to use as a packaging polymer[27]. Due to their good mechanical properties, PGA and

PLLA have been used as bone internal fixation devices. The fiber forming properties of PLA, had made it suitable for replacing ligament and non-degradable fibers. The fiber is also resistant to UV radiation. PLA fiber is also being used in sports clothes[28]. 5. Conclusions Biodegradable polymers have received much more attention in the last decades due to their potential applications in the fields related to environmental protection and the maintenance of physical health. These categories make a good substitute to the finitely available petroleum products, on which most of the industries are highly dependent. Among the biopolymers, Polylactic acid (PLA) is a prominent one, that can be utilized in various appications. It has got good mechanical, thermal, and barrier properties, which can further be enhanced with the addition of plasticiers, or blending with other polymers. Undoubtdly, these composites and blend of PLA will nourish the industries both economically and ecologically. References

1) Ray E; Drumright; Patrick R. Gruber; David E.

Henton. Polylactic Acid Technology; Adv. Mater. 2000, 12, No. 23, December

2) K. Oksman; M. Skrifvarsb; J.-F. Selinc. Natural fibres as reinforcement in polylactic acid (PLA) composites; Composites Science and Technology 63 (2003) 1317–1324.

3) Datta R, Henry M. Lactic acid: recent advances in products, processes and technologies—a review. J Chem Technol Biotechnol 2006;81:1119–29.

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5) Auras R, Harte B, Selke S. An overview of polylactides as packaging materials. Macromol Biosci 2004;4:835–64.

6) M. H. Hartmann, ‘‘High Molecular Weight Polylactic Acid Polymers’’, in: Biopolymers

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from Renewable Resources, 1st edition, D. L. Kaplan, Ed., Springer-Verlag Berlin Heidelberg, Berlin 1998, p. 367–411.

7) US 5142023 (1992), invs.: P. R. Gruber, E. S. Hall, J. H. Kolstad, M. L. Iwen, R. D. Benson, R. L. Borchardt

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23


Emerging Advances in Development New Plasma Tools for

Deposition Nanostructure Coatings and Thin Films (Fundamentals, Synthesis

and Characterization) Alexey Goncharov *1, Andrii Dobrovolsky 1,

Vladimir Bazhenov 1, Evgeniy Kostin 2 1Institute of Physics of NAS Ukraine, pr. Nauku 46,

Kyiv, Ukraine 2 Institute of Nuclear researches of NAS Ukraine,

pr. Nauku 47, Kyiv, Ukraine *Corresponding Author: [email protected]

Abstarct: The present paper is a brief review of researches carried out by the authors for a recent years dealing with comprehensive studies of physical parameters of the new generation plasma-optical DC magnetron sputtering systems. Applications of these original plasma tools for optimal and controlled synthesis of nanosized films of titania having various phase compositions with different optical, morphological, and photo catalytic properties are carried out. Key words: Plasma-optical DC magnetron, titania, TiO2 films, nanosized films, optical emission spectroscopy 1. Introduction At the beginning of current century there appeared heightened interest in experimental synthesis and researches of exotic nano-structured multi-functional coatings for state-of-the-art applications

in modern technologies. The state-of-art applications require modern functional materials and techniques. The physical methods based on reactive magnetron sputtering deposition are undoubtedly among the most promising ones. They provide high efficiency and productivity in deposition multi-functional resource and energy saving coatings for industrial, decorative, medical and optical applications. However, in traditional planar magnetron the plasma discharge parameters strongly depend on degree of cathode erosion during operation that decrease considerably target utilization factor (TUF). It is known, the axi- symmetric cylindrical electrostatic PL, based on the fundamental plasma optical principles of magnetic electron isolation and equipotentialization along magnetic field lines, is a well-explored plasma-optical tool for ion beam focusing, especially where the concern of beam space charge compensation is critical [1]. These fundamental principles serve as a base for elaboration the next generation plasmaoptical devices [2]. There are many theoretical models describing traditional magnetron systems [3,4]. Our advanced approach is based on application of the discharge current conservation law in frame of two-fluid magneto hydrodynamic model. On a basis of this model and cylindrical plasma lens (PL) configuration new generation DC magnetron with attractive advantages of up to 100% TUF, high uniformity coatings and stability of the operation parameters during the deposition process was elaborated and tested [2]. In this work, we study the influence of discharge parameters in a cylindrical plasma optical DC magnetron on optical properties, morphology and photo catalytic ability of titania nanosized films. It enables to determine the conditions of optimal and controlled synthesis of thin nanostructured films having various phase compositions with given properties.

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ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 2. Setup and methods Usually a magnetron sputtering device has a non-uniform cathode erosion profile due to arched magnetic field configuration and resulted localization of work gas ionization zone. In order to eliminate this drawback the virtual anode parallel to cathode surface by means of plasmaoptics principles of magnetic field equipotentialization is formed (see Fig.1). This device is suitable for basic physical researches. For technological applications in plasma processes of synthesis thin films, the related to mentioned physical principles cylindrical DC magnetron sputtering system was designed and fabricated [5] with Ar (working gas) and O2 (reactive spice) use.

Fig. 1. Scheme of the plasmaoptical DC cylindrical magnetron: 1 – magnetic system, 2 – titanium cathode (target), 3 – anode system providing virtual anode surface formation. The relative amounts of Ti, O, Ar were monitored using optical emission spectra analysis by means of CCD spectrometer in the wavelength range 350–820 nm and selection of 4 characteristic spectrum lines. Current-voltage (I-V) characteristics of the plasma discharge were measured by common elctrophysical methods. Optical monitoring of the plasma radiation of the cylindrical magnetron discharge enabled us to measure a hysteresis of the radiation intensities of the Ti, O, and Ar lines for a

discharge current variation in the presence of oxygen additions and a hysteresis of the discharge voltage for a discharge current variation in the different experimental conditions. The formation of particular polymorphic modification of titania at magnetron-based deposition of the nanosized films was verified by Raman spectroscopy. The photo catalytic abilities of deposited films were evaluated in the processes of toxic Cr(VI) to non-toxic Cr(III) ions reduction in water solution of K2Cr2O7. The surface morphology and the roughness of the films we explored with atomic force microscope (AFM). 3. Results and Discussion In Fig. 2 we show an example of the hysteresis of the I–V characteristic of the plasmaoptical cylindrical magnetron and the hysteresis of the radiation intensities of the Ti, O, and Ar lines as a function of the discharge current for fixed oxygen flow. The arrows indicate the direction of the discharge current variation. Steady-state values of the discharge voltage and emission lines intensities are plotted on Fig. 2. One can see at Ud maximum (filled symbols near the 7 amperes) in Fig. 2 radiation intensity of the O line (777.2 nm) abruptly increases, but the Ti line intensity at this part of the I–V characteristic abruptly decreases. O line increase indicates the termination of pumping–out of oxygen by the film and, in other words, the end of oxygen saturation process of the deposited film.

Fig. 2. Hysteresis of the intensities of the lines of Ti at 465.6 nm, O at 777.2 nm, Ar(1) at 812.9 nm, Ar(2) at 753.7 nm and the discharge voltage Vd vs

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ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 the discharge current Id variations for fixed oxygen flow 56 a.u. The finalization of the titanium film saturation by oxygen means the formation of the highest titanium oxide, namely compound TiO2 in the film. Changes in the Vd, and Ti and O lines emission intensity dependencies on the flow of reactive gas (Fig.3) can be compared with each other and with the composition of the obtained films. This gives us operating point of stoichiometric titania deposition.

Fig. 3. Dependencies of intensity of Ti (468,2 nm), and O (777.19 nm) lines, and the discharge voltage on the oxygen flow. Discharge current is 15 A, Ar pressure 5×10–3 Torr. Operating point for TiO2 film deposition is shown by the arrow. After the TiO2 film synthesis and its structure test by means of Raman spectroscopy, it was found that the structure of films deposited under the conditions indicated by the arrow in Fig. 3 corresponds to the compound TiO2. Thus, the operating point can be determined by the discharge characteristics and by the optical monitoring. The processes, similar to those illustrated in Fig. 3, take place during the formation of titanium nitride [5] where we have used the optical monitoring, as well as the discharge characteristics. We explored the influence of discharge and substrate characteristics on the growth of the layer at the operating point. The Raman spectroscopy shows the titania films are deposited on cold substrate is in amorphous state. As for AFM and chemical analysis, the amorphous titania film has a

smooth surface and does not have photo catalytic properties [6,7]. At the substrate heating over 380° C deposited film is in anatase phase. All results shown in Fig.4 are obtained for samples synthesized on hot substrates. Optical, morphological, and photocatalytic properties of these samples vs deposition conditions were verified. The structure of the deposited film depends on temperature of substrate and pressure of the work gas mixture [7]. The crystallite size in the film increases with a temperature rise. The variation of working gas pressure and substrate temperature allows to change crystallite size, porosity and morphology of film surface. Pressure lower 5x10-3 Тоrr allows obtaining dense films with low percent of amorphous phase, higher refractive index and larger crystallites size. The increasing of pressure up to 10-2 Тоrr leads to forming porous films with developed surface relief and large conglomerates. The substrate material influences formation of a particular polymorphic modification of titania at reactive magnetron sputtering deposition.

(a)

26


(b)

Fig. 4. Raman spectrum of TiO2 film deposited on CaF2 substrate at 560°C and 3•10–3 Torr Ar pressure before (a) and after annealing in air at 700°C for 3 hours (b). Spectral lines were fitted by a Lorentzian function. Frequency positions of the lines are: 154 cm–1 —anatase line Eg(1), 238 cm–1 — rutile line, 235 cm–1, 395 cm-1 — anatase line B1g, 649 cm–1 — anatase line Eg(3,) 592.3 cm–1 – rutile line A1g. Line at 321 cm–1 belongs to fluorite.

Fig. 5. The 3D view reconstruction of film surface for nano layer of anatase, pressure is 5x10-3 Torr, the substrate temperature is 520оC. The deposited films on heated substrate shows the photo catalytic activity which depends on the film thickness and Ar pressure [7]. Morphology study of deposited films by means of AFM has demonstrated

stochastic surface without peculiarities for all tested samples. The example of 3D view of surface are shown in Fig. 5

4. Conclusions We described some emerging advances in creation new generation plasma optical DC cylindrical magnetron sputtering systems for synthesis nanostructure films compounds of chemically active metals. The efficiency of elaborated system was studied at synthesis of nanosized titania films with the use of optical and Raman spectroscopy, electrothysical, chemical and AFM methods for their characterization. Use of the original plasma tools for optimal and controlled synthesis of nanosized films with given properties opens up new prospects for practical applications References [1] Goncharov. A. Rev. Sci. Instrum., 2013, 84, 021101. [2] Goncharov, A.A., Brown, I.G. IEEE TPS, 2007, 35, 986. [3] Glocker, D.A., Romach, M.M. and Lindberg, V.W. Surf. Coat. Technol., 2001, 146-147, 457. [4] Thornton, J.A. J. Vac. Sci. Technol. A, 1986, 4(6), 3059. [5] Blonskii, I.V., Goncharov, A.A., Demchishin, A.V., Kostin, E.G. et al. Technical Physics, 2009, 54 (7), 1052. [6] Goncharov, A., Dobrovolskii, A., Kostin, E. et al. Advances in Appl. Plasma Sci., 2013, 9, 9. [7] Goncharov, A.A., Dobrovol’skii, A.N., Kostin, E.G., Petrik, I.S., Frolova, E.K. Technical Physics, 2014, 59(6), 884. Acknowledgements This work was supported in part by project # PL-18-32 and P13/18-32 of NAS of Ukraine.

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ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 SYNTHESIS AND CHARACTERISATION OF ZIRCONIUM BASED NANOCOMPOSITES Rakhi C 1 and K.C.Preetha*2

1Payyannur College, Payyannur, PIN 670327, Kerala, India. 2 Sree Narayana College, Kannur, PIN 670007, Kerala, India. E-mail:[email protected] E-mail:[email protected] Abstract: In this work, Zirconium Bismuth Molybdate nanocomposites were synthesized by co-precipitation method. Zirconium Oxy Chloride (ZrOCl2.8H2O), Bismuth Nitrate (Bi(NO2)2.5H2O) and Sodium Molybdate (Na2MoO4.2H2O) were used as precursors. The influence of complexing agent triethanolamine on properties of nanocomposite is highlighted in this work. As-prepared samples were characterized by using UV-VIS NIR spectroscopy, X-Ray Diffraction spectroscopy (XRD) etc. XRD pattern reveals that the as-prepared samples are poly-crystalline. The average crystallite size calculated by Debye Scherrer formula is in the range 11nm to 18nm. The presence of complexing agent enhance crystallinity and crystallite size. Keywords: Nanocomposites, co-precipitation, complexing agent 1 Introduction

World Technology Evolution Centre studies show that nanotechnology [1] has many potential which contribute to significant advances over a wide and diverse range of technological areas [2]. Nanocomposites assure new applications in fields such as mechanically reinforced lightweight components, non-linear optics, storage devices, sensors and other systems [3]. Different ranges of nano-materials with various properties have been synthesised recently. Nowadays researchers have interest in the synthesis of metallic nanoparticles especially transition metals due to their intense mechanical and electrical strength. Transition metals find applications in many areas because of their

electrical, magnetic, optical and thermal properties. Thus, the synthesis of nanocomposites composed of these material is of prime interest.

Zirconium, mostly found as oxides and in mineral form, was ranked 18th in abundance on earth’s crust [4]. Zirconium oxide nanoparticles and their composite materials have properties including photoluminescence, Ion exchange etc. [5, 6]. It shows resistance to corrosion, aberration and heat [7, 8]. They can be used in metal oxide semiconductor materials due to high dielectric constant, good thermal stability and large band gap [9]. Zirconium molybdate and bismuth molybdate are used for catalytic activity [10, 11]. Minh Thang Le et.al, in 2016 studied the effect of highly conductive ZrO2 on the catalytic activity of beta bismuth molybdate (β- Bi2Mo2O9) [12]. They showed that the mechanical mixing of electrically conducting materials such as ZrO2 increases the catalytic effect of bismuth molybdate. Bismuth molybdate has a narrow band gap (≈2.66eV) and has high absorption coefficient in the visible region and so it exhibits photocatalytic activity. The photocatalytic property of bismuth molybdate can be enhanced by using various methods such as doping, photo-sensitization, heterojunction etc. [13, 14]. Ji Chul Jung et.al, in 2007 prepared

α-Bi2Mo3O12 and ᵧ-Bi2MoO6 catalyst by co-precipitation method and studied the catalytic activity for oxidative dehydrogenation of n-Butene into 1, 3-Butadiene [15].

This paper focuses on a facile method of preparation of zirconium bismuth molybdate nanocomposite by wet chemical synthesis. Preparation of binary and ternary nanocomposite can easily be done by using chemical methods. Among various chemical methods, co-precipitation method provides a simple and cost effective technique [16]. This paper focuses on the effect of complexing agent, triethanolamine (TEA) on the crystallinity and crystallite size of the nanoparticles [17].

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mailto:[email protected]


ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 2 Experimental

2.1 Materials

The precursors are of analytical grade and were used without further purification. 99.5% purified Zirconium oxy chloride octahydrate (ZrOCl2.8H2O), purchased from LOBA chemie laboratory reagents and fine chemicals, 98% purified bismuth (II) nitrate pentahydrate (Bi(NO2)2.5H2O) and 99.102% purified sodium molybdate dihydrate (Na2MoO42H2O) both purchased from merck specialities Pvt. Ltd., were used as precursors.

2.2 Methods

Solutions of zirconium oxy chloride, Bismuth nitrate and sodium molybdate are prepared in the ratio 1:1:3 in which distilled water is used as solvent. Sample which is not treated with TEA was labelled as ZBM 1. The second sample, ZBM 2 has been prepared by adding 2ml of TEA in the reaction bath. A white precipitate of zirconium bismuth molybdate was formed in both the cases and PH of the two samples was noted as 1. The reagents were kept without disturbing for 12 hours to settle down the particles. The precipitates are then filtered, washed with water several times and kept for drying under room temperature and pressure. The dried samples were crushed and well powdered by using a pestle and mortar arrangement.

2.3 Characterization

The as-prepared samples were characterized by using X-Ray diffraction spectroscopy (XRD) and optical studies are made by using UV-VIS spectroscopy.

Results and discussions

The X-RD patterns [Fig.1 and Fig.2] of zirconium bismuth nanocomposite, shows that the both samples are poly-crystalline. The crystallite size for each sample is calculated by using Debye Schrerrer formula [18]. The calculated value of Full Width at Half Maximum (FWHM) and crystalline size are tabulated for each samples and is given in table 1 and 2. Average crystallite size for ZBM 1 is around 14.3nm and that for ZBM 2 is 12.9nm.

The peaks at 420, 560 and 670 corresponds to (002), (102) and (110) planes of Zr and that at 40 0, 470, 500, 560, 600 and 680 corresponds to (110), (113), (202), (024), (107) and (018) planes of Bi. Peaks at 14 0, 270, 350 and 370 corresponds to (020), (040), (140) and (210) of Mo and peaks at 260 and 680 with (hkl) values (111) and (202) for MoO2. These values confirm the formation of zirconium bismuth molybdate.

Fig 1 XRD pattern of ZBM 1

Table 1 Structural parameters of ZBM 1

Sl. No 2θ FWHM Size (nm)

1 25.6739 0.6527 12.4786 2 32.3090 0.5126 16.1299 3 33.2086 0.5894 14.0607 4 40.6797 0.5675 14.9239 5 46.4746 0.5397 16.0168 6 49.4868 0.6176 14.1589 7 53.9409 0.5147 17.3120 8 58.4504 0.5756 15.8087 9 60.3546 0.7293 12.5960 10 67.9159 0.6530 14.6626

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Fig 2 XRD pattern of ZBM 2

Table 2 Structural parameters of ZBM 2

Sl. No. 2θ FWHM Size (nm)

1 26.0151 0.5905 13.8034 2 41.02792 0.6920 13.7209 3 46.8581 0.5996 14.4354 4 49.7300 0.7666 11.4181 5 58.7681 0.7306 12.4738

Optical absorption spectra (Fig 3), has absorption peak around 300nm which is in the UV region. The direct band gap of ZBM 1 obtained is 3.385ev and that for ZBM 2 is 3.509ev. Steep absorption in the UV region and uniform transparency in the VIS region is of great interest and can be utilised for many applications which includes the synthesis of UV protective materials. Static behaviour of low transmittance over the region 850nm to 1300 nm have been observed with each samples (Fig 4).

(a)

(b)

Fig 3 Wavelength vs absorbance graph of

a. ZBM 1 b. ZBM 2

(a)

(b)

Fig 4 Wavelength vs transmittance graph of a. ZBM 1 b. ZBM 2

30


(a)

(b)

Fig 5 Wavelength vs reflectance graph of a. ZBM 1 b. ZBM 2

Static behaviour of high reflectance over the region 850nm to 1300 nm have been observed with each samples (Fig 5).

Conclusion

In this study we presented a facile method of preparation of zirconium bismuth molybdate by co-precipitation method. This study includes the effect of complexing agent TEA in the synthesis of zirconium bismuth molybdate nanocomposite. Band gap seem to be slightly increased and crystallite size decreases by the addition of complexing agent. References

1. Bhatia, Saurabh., Natural Polymer Drug Delivery Systems. Springer, Cham, 2016. 33-93.

2. Poole Jr, Charles P., and Frank J. Owens. Introduction to nanotechnology. 2003.

3. Parag Diwan, Ashish Bharadwaj., Nanocomposites, 2006.

4. Vagkopoulou T, Koutayas S.O, et al., European Journal of Esthetic Dentistry, 2009, 4, 131-151.

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6. Clearfield A, Blessing R.H., Journal of Inorganic and nuclear Chemistry 1972, 34, 2643-63.

7. Behzadnasab M, Mirabedini S.M, Kabiri K, Jamali S., Corrosion Science. 2011, 53, 89-98.

8. Bai Y, Han Z.H, Li H.Q, Xu C, Xu Y.L, Wang Z, Ding C.H, Yang J.F., Applied Surface Science. 2011, 257, 7210-6.

9. Chang J.P, Lin Y.S, Chu K. Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena. 2001, 19, 1782-7

10. Le M.T, Bac L.H, Van Driessche I, Hoste S, Van Well W.J., Catalysis Today. 2008,131566-71

11. Chen K, Xie S, Iglesia E, Bell A.T., Journal of Catalysis. 2000,189, 421-30

12. Le M.T, Do V.H, Truong D.D, Bruneel E, Van Driessche I, Riisager A, Fehrmann R, Trinh QT., Industrial & Engineering Chemistry research. 2016, 55, 4846–55.

13. Jin M, Lu S, Ma L, Gan M., Applied surface Science. 2017, 396, 438-43.

14. Wen Ting L.i, Yi Fan Zheng, Hao Yong Yin, et al., Journal of nanoparticle research. 2015, 17, 271.

15. Jung J.C, Kim H, Choi A.S, Chung Y.M, Kim T.J, Lee S.J, Oh S.H, Song I.K., Journal of Molecular Catalysis A: Chemical. 2006, 259, 166-70

16. Zhang M, Sheng G, Fu J, An T, Wang X, HU X., Materials letters. 2005, 59, 3641-4.

17. Preetha K.C, Deepa K, Dhanya A.C, Ramadevi T.L., Material Science and Engineering. 2015, 73, 012086

18. T.L Ramadevi, K.C Preetha., Journal of Material Science: Materials in Electronics. 2017, 23, 2017-2023.

Acknowledgement The authors wish to acknowledge SAIF-STIC, CUSAT, Kochi for the technical support.

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ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 Hybrid Multiferroic Fibers of Al3Fe5O12 Nanoparticles Loaded PVDF with Excellent Flexibility and Superior Magnetoelectric Response via an Electrospinning Technique with a Rotating Collector

M T Rahul, R Sree Raj, B Raneesh*

Department of Physics Catholicate College, Pathanamthitta- 689645

*Corresponding Author: [email protected] Abstract: PVDF-Al3Fe5O12 composite material is prepared using an electrospinning method. Various phases in the composite were identified using X-ray diffraction analysis. Fourier transform infrared spectroscopy has been carried out to further confirm the ferroelectric β phase in the PVDF. Keywords: Multiferroic, ceramic, polymer. 1. Introduction Multiferroic is a class of materials which exhibits two or more ferroic properties simultaneously [1]. Due to this multifuctionality, multiferroics materials are promising for various applications such as data storage, sensing, actuators and more [2,3]. However, the number of materials showing the multiferroics nature is less and many of them exhibit the properties below the room temperature [4,5]. So the recent research focused on the development of new materials for the room temperature multiferroic property. Various composites including ceramic-ceramic and polymer-ceramic materials have been reported. Doped BiFeO3–BaTiO3 [6], (1-x)Ba0.95Sr0.05TiO3 - (x)Ni0.7Zn0.2Co0.1Fe2O4 [7], Sr3CuNb2O9–CoFe2O4 [8], 0.65BaTiO3–0.35Bi0.5Na0.5TiO3–BiFeO3 [9], core-shell CoFe2O4@BaTiO3 particles loaded P(VDF-HFP)[10], BiFeO3-CoFe2O4-poly(vinylidene-flouride)[11], PVDF-GO-Fe3O4 [12] are some of the reports. Nowadays, polymer-ceramic multiferroic materials are getting

substantial research attention[13]. Poly(vinylidene fluoride) (PVDF) and its co-polymers such as poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and poly(vinylidene fluoride-co- trifluoroethylene) (P(VDF-TrFE)) are the ferroelectric polymers commonly used for the development of polymer based muliferroic [14–16]. In this work, we report the fabrication and characterization of PVDF-Al3Fe5O12 polymer-ceramic multiferroic material developed using an electrospinning technique. 2. Experimental 2.1. Materials Aluminium nitrate nonahydrate (loba chemie) and iron (iii) nitrate nonahydrate (Merck) were used as the starting materials for the preparation of Al3Fe5O12 nanoparticles. PVDF with Mw ~ 400,000 (Sigma-Aldrich,) was used for the electrospinning. 2.2. Methods 2.2.1. Preparation of Samples Al3Fe5O12 nanoparticles prepared using a sol-gel method. PVDF-Al3Fe5O12 polymer-ceramic multiferroic material is developed using an electrospinning technique. 3. Results and Discussion 3.1. X-ray diffraction (XRD) Fig. 1 X-ray diffraction pattern of PVDF-Al3Fe5O12 polymer-ceramic multiferroic material. It shows the diffraction peaks of both PVDF and Al3Fe5O12 phases. The peak of the PVDF at 20.70 corresponds to the β phase of the PVDF [17]. The peaks at 24.290, 33.410 and 35.870 from the Al3Fe5O12 phase. 3.2. Fourier transform infrared spectroscopy (FTIR) Fig. 2 shows the FTIR spectra of the pure PVDF and PVDF-Al3Fe5O12 multiferroic material. The bands at 840 and 1275 cm−1 correspond to the β-

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ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 phase of the PVDF [18]. In pure PVDF peaks at 1275 cm−1 is not considerable whereas the PVDF-Al3Fe5O12 multiferroic material exhibited both the β-phase peaks, indicating more percentage of

ferroelectric phase in the composite material. Fig. 1 X-ray diffraction pattern of the PVDF-

Al3Fe5O12 polymer-ceramic multiferroic material.

Fig. 2 FTIR spectra of the PVDF-Al3Fe5O12

polymer-ceramic multiferroic material.

4. Conclusions PVDF-Al3Fe5O12 polymer-ceramic multiferroic

material is prepared by an electrospinning method.

The successful formation of the β phase of the

PVDF is confirmed in the XRD pattern and the

peaks form the Al3Fe5O12 phase were also

identified in the XRD pattern. Ferroelectric phase

of the PVDF is further validated using FTIR

spectrum. The improved electroactive nature of in

the PVDF-Al3Fe5O12 shows it as a possible

multiferroics material for various flexible device

applications.

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[8] P. Zachariasz, J. Kulawik, P. Guzdek, Preparation and characterization of the microstructure, dielectric and magnetoelectric properties of multiferroic Sr3CuNb2O9–CoFe2O4 ceramics, Mater. Des. 86 (2015) 627–632. doi:10.1016/j.matdes.2015.07.062.

[9] M. Rawat, K.L. Yadav, Study of structural, electrical, magnetic and optical properties of 0.65BaTiO3–0.35Bi0.5Na0.5TiO3–BiFeO3 multiferroic composite, J. Alloys Compd. 597 (2014) 188–199. doi:10.1016/j.jallcom.2014.01.059.

[10] L. Zhou, Q. Fu, D. Zhou, Z. Zheng, Y. Hu, W. Luo, Y. Tian, C. Wang, F. Xue, X. Tang, Self-assembled core-shell CoFe 2 O 4 @BaTiO 3 particles loaded P(VDF-HFP) flexible films with excellent magneto-electric effects, Appl. Phys. Lett. 111 (2017) 032903. doi:10.1063/1.4993161.

[11] N. Adhlakha, K.L. Yadav, M. Truccato, Manjusha, P. Rajak, A. Battiato, E. Vittone, Multiferroic and magnetoelectric properties of BiFeO 3 -CoFe 2 O 4 -poly(vinylidene-flouride) composite films, Eur. Polym. J. 91 (2017) 100–110. doi:10.1016/j.eurpolymj.2017.03.026.

[12] O.D. Jayakumar, E.H. Abdelhamid, V. Kotari, B.P. Mandal, R. Rao, J. Jagannath, V.M. Naik, R. Naik, A.K. Tyagi, Fabrication of flexible and self-standing inorganic–organic three phase magneto-dielectric PVDF based multiferroic nanocomposite films through a small loading of graphene oxide (GO) and Fe 3 O 4 nanoparticles, Dalt. Trans. 44 (2015) 15872–15881. doi:10.1039/C5DT01509J.

[13] P. Martins, S. Lanceros-Méndez, Polymer-Based Magnetoelectric Materials, Adv. Funct. Mater. 23 (2013) 3371–3385. doi:10.1002/adfm.201202780.

[14] X. Liu, S. Liu, M. Han, L. Zhao, H. Deng, J. Li, Y. Zhu, L. Krusin-Elbaum, S. O’Brien, Magnetoelectricity in CoFe 2 O 4 nanocrystal-P ( VDF-HFP ) thin films,

Nanoscale Res. Lett. 8 (2013) 1–10. doi:10.1186/1556-276X-8-374.

[15] R. Gonçalves, A. Larrea, M.S. Sebastian, V. Sebastian, P. Martins, S. Lanceros-Mendez, Synthesis and size dependent magnetostrictive response of ferrite nanoparticles and their application in magnetoelectric polymer-based multiferroic sensors, J. Mater. Chem. C. 4 (2016) 10701–10706. doi:10.1039/c6tc04188d.

[16] T. Prabhakaran, J. Hemalatha, Ferroelectric and magnetic studies on unpoled Poly (vinylidine Fluoride)/Fe3O4 magnetoelectric nanocomposite structures, Mater. Chem. Phys. 137 (2013) 781–787. doi:10.1016/j.matchemphys.2012.09.064.

[17] P. Thakur, A. Kool, B. Bagchi, S. Das, P. Nandy, Effect of in situ synthesized Fe 2 O 3 and Co 3 O 4 nanoparticles on electroactive β phase crystallization and dielectric properties of poly(vinylidene fluoride) thin films, Phys. Chem. Chem. Phys. 17 (2015) 1368–1378. doi:10.1039/C4CP04006F.

Acknowledgments We are grateful to the Science and Engineering Research Board (SERB), India, (ECR/2015/000536) for the financial assistance.

34


Synthesis and Characterisation of

Cerium Oxide Nanoparticles Prabha Jyothi P S1, Smitha S1, Anu Krishna1, Nisha

J Tharayil*2 1Department of Physics, SN College, Kollam, Kerala, India-- 691001 2 Department of Physics, SN College for women, Kollam, Kerala, India-- 691001 *Corresponding Author: nishajohntharayil at gmail dot com Abstract: Cerium oxide is a technologically important rare earth oxide material. It is unique in that it can exist in both +3 and +4 oxidation states. Nanoceria or cerium oxide nano particles have shown promising applications due to its ability to adjust or switch over its oxidation states easily. In the present work, we have synthesized nano ceria via chemical co precipitation method using DNA as the capping agent and compared it with Ethylene Diamine Tetra Acetic acid (EDTA). The carbonate precursor obtained is calcined on the basis of thermo gravimetric analysis to get the oxide nanoparticle. The synthesized samples are characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) and UV-Visible spectroscopy. The Energy dispersive x-ray analysis shows the chemical composition of nanoparticles. The average crystallite size increases with increase in temperature. The antimicrobial activities of nano ceria is also studied in microorganisms like Salmonella typhimurium, Escherichia Coli and Candida albicans.

Keywords: Nanoceria, DNA, Antimicrobial activity. 1. Introduction Cerium (Ce) is the most abundant rare earth element (atomic number 58) in the lanthanide series of the periodic table. Cerium with electronic configuration [Xe] 4f15d16s2 is unique in that it can

exist in both the +3 [Xe] 4f1 and +4[Xe] oxidation states. Cerium oxide is a promising material which has multiple applications like gas sensors, catalysis, electrolyte material for solid oxide fuel cell, sunscreen for ultraviolet absorbents, etc. However to enhance the properties of nano materials to meet the need for different applications, it is very essential to decrease the size and thus to increase the active surface area of nanoparticles. In recent years much effort has been focused on the development of environmental friendly routes for preparing nano cerium oxide to decrease the hazardous and toxic effect of chemicals. As a better choice, DNA has been used as the biological capping agent for the present study. The aim of this study is to synthesis and characterize nano ceria and to study its antimicrobial activities. Among the processes of synthesis, chemical co precipitation is simple and low cost in comparison with other techniques and moreover it can be realized in our own lab set up. The properties were characterised by x-ray diffraction analysis, fourier transform infrared spectroscopy, energy dispersive x ray analysis and uv visible spectroscopy. The antimicrobial study was carried out by disc diffusion method. 2. Experimental Details 2.1. Materials Cerium (III) nitrate hexa hydrate, ammonium carbonate and DNA were purchased from Merck and were of analytical grade. These chemicals were used without further purification. 2.2. Methods 2.2.1. Preparation of Cerium Oxide Nanoparticles Cerium oxide nano particles were synthesized by chemical co precipitation method by taking aqueous solution of cerium nitrate hexa hydrate and ammonium carbonate under constant stirring. Upon adding the solutions, precipitation of cerium carbonate occurred. The capping agents were used

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ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 to control the size of the nanoparticles. The whole mixture was then stirred for five hours. After stirring, it was filtered and washed several times with deionized water. Then the dried precipitate (the carbonate precursor) were calcined at 4000,5000 and 6000 C in a porcelain crucible for three hours and were denoted as CD1,CD2 and CD3 respectively. The synthesized nanoceria were pale yellow in color. 2.2.2. Characterization Techniques The crystalline structure of the as prepared nano ceria was carried out by Rigaku Miniflex600 diffraction system using CuKα radiation of wavelength 1.5406 A0. The purity of the sample were identified from EDAX. The optical absorbance of the cerium oxide nano particles were recorded using UV-Vis NIR Spectrophotometer- Agilent Technologies Cary 5000 in the wavelength range 200-800nm. FTIR spectra of the specimen was recorded on a Thermo Fisher Scientific iS50 FT-IR Spectrophotometer in transmittance mode. 3. Results and Discussion 3.1. XRD Analysis The structural charactization of the nano ceria were carried out by x-ray diffraction method. The diffraction pattern reveals all the major peaks of CeO2 corresponds to the(1,1,1), (2,0,0), (2,2,0) and (3,1,1), (3,3,1) crystallographic planes. Cubic fluorite structure is identified using standard data JCPDS Card No. 81-0792. No other peak of any other phase is detected indicating the high purity of the product. The broadening of the peaks in the diffraction pattern indicates the formation of nano dimensional crystals. The average crystallite size was calculated from the Debye Scherrer equation Where is the wavelength of the CuKα radiation and is the full width at half maximum and θ is Bragg’s angle of the peak. Average crystallite size

for CD1, CD2 and CD3 are found out to be 8.08nm, 10.57nm and 16.45nm which is found to be less compared to average crystalline size obtained for nanoceria synthesized using EDTA as capping agent. [22]

Fig 1. XRD pattern of pure cerium oxide

nanoparticles

3.2. EDAX Spectrum The energy dispersive x-ray analysis of the nano ceria shows the presence of cerium and oxygen elements. No other impurity peak is seen in the EDAX spectrum which confirms the purity of the as prepared sample.

Fig 2. EDAX Spectrum

3.3. FTIR Studies The infrared spectrum of the synthesized cerium oxide nanoparticles was in the range of 300-4000cm-1 wavenumber which identify the chemical

36

https://kusicc.wordpress.com/thermo-fisher-scientific-is50-ftir-spectrophotometer/

https://kusicc.wordpress.com/thermo-fisher-scientific-is50-ftir-spectrophotometer/

ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 bonds as well as functional groups in the compound. The FTIR spectrum of samples calcined at different temperatures are shown in figure. The absorption band at 1016 cm-1corresponds to carbonate species and broad peak at 3350 cm-1corresponds to O-H stretching vibration present in the water molecules and are clearly attenuated as the calcination temperature increases. The sharp peak at 366 cm-

1 corresponds to Ce-O stretching vibrations of CeO2 molecule.

Fig.3 FTIR Spectrum of CeO2

3.4. UV-Visible Studies Absorption spectra of particles were recorded using UV- Visible spectrophotometer. Absorption of UV-Visible light may result the excitation of electrons to higher energy states. The spectrum of nanoceria shows a broad absorption band. It exhibits a strong absorption band below 400nm at the UV region due to charge transfer transition from oxygen 2p to cerium 4f in CeO2 [11, 12]. From the spectrum it is clear that most of the UV light (200nm-350nm) is blocked. It shows that ceria nanoparticles can be used as a UV blocker.

Fig 4. Absorption spectra of CeO2

3.4. Antimicrobial Activity The antimicrobial activity of the synthesized nano ceria were examined by disc diffusion method. It was performed against water pathogens like Salmonella typhimurium, Escherichia Coli and antifungal activity against Candida albicans. All the pathogens exhibited a moderate inhibition of 6mm with nanoceria. Generally the antibacterial activity is due to the interaction of nanoparticles on to the bacterial cell wall by the electrostatic interaction [24].

Fig 5. Antibacterial activity of nanoceria

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ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 4. Conclusions Cerium oxide nano particles were synthesized by chemical co precipitation method using DNA as the capping agent. The structural properties were studied using XRD. The average crystallite size increases with increase in temperature. EDAX spectrum confirms the purity of the prepared sample. UV absorption spectrum shows that most of the UV light were blocked by the particles and this it can be used as a UV filter. The nanoceria exhibited inhibition to bacteria as well as fungus. Acknowledgments The authors are thankful to SICC, University of Kerala and TKM College of arts and science. Kollam for providing facility for characterization. References [1] Richard Booker and Eaul Boysen, (2005), Nanotechnology, Wiley publishing Inc., USA. [2] M.BalakrishnaRao, K.Krishna Reddy, (2007), Introduction to nanotechnology, Campus Books International. [3] B.k.Parthasarathy, (2007), Nanoscience and nanotechnology, Isha Books. [4] Sung Hun Wee, Amit Goyal, Karren L more and Eliot Specht, (2009), Nanotechnology. [5] X. zhao1, Y. liu, S. Inoue, T. Suzuki, R. O. Jones, and Y. Ando, Phys. Rev. Lett. 92, 125502, (2004). [6]B.D Cullity, Elements of x-ray diffraction(1956), Addison Wesley Publishing Company, Inc. [7] Miao, J.J. Wang, H. Li, Y.R. Zhu, J.M. Zhu, J.J. J. Cryst. Growth, No. 281 pp. 525-529,2005 [8]. Yahiro, H., Baba, Y.,. Eguchi ,K.,. Hiromich,i A., J. Electrochem. Soc.No. 135 pp. 2077-2080,1998 [9] Khan, S.B., Faisal, M.,. Rahman ,M.M., and. Jamal , Sci. Total Environ.No. 409 pp.2987-2992, 2011. [10] Patil, S., Sandberg A., Heckert E. Self., W S., Seal, BiomaterialsNo. 28 pp. 4600-4607,2007 [11] Khan, S.B., Faisal, M.,. Rahman ,M.M., and. Jamal , Sci. Total Environ.No. 409 pp.2987-2992, 2011. [12] Maensiri, S. Masingboon,C, Laokul, W. Jareonboon, V. Cryst. Growth Des. No. 7 (2007) pp.950-955.

[13] Czerwinski, F.,. Szpunar, J.A., J. Sol-Gel Sci. Technol. No.9 (1997) pp.103-114. [14] Yao, S.Y. Xie, Z.H. J. Mater. Process. Tech.No. 186 pp.54-59,2007 [15] Darroudi, M. Hoseini, S.J. Oskuee ,R.K. Hosseini, H.A. Gholami, L. Gerayli, Ceram. Int. No.40 pp.7425 ,2014 [16] Zhang P.,Ma .Y,,. Zhang, Z., He, X.,. Zhang, J., Guo, Z,.. Tai, R.,. Zhao, Y.,. Chai, Z., ACS Nano No. 11 pp.9943-9950. 2012 [17] O Thill., Zeyons Spalla, O., Chauvat,,,F., Rose, J. Auffan,M., . Flank ,A. M., Environ. Sci Technol. No.40 pp.6151-6156. 2006 [18]. Zhang, F.,. Chan ,S. W.,. Spanier, J.E,. Apak, E., Q. Jin, R.D. Robinson, I.P. Herman, Appl. Phys. Lett. No.80 pp.127-129, 2002 [19] Hu, J, Li, Y. Zhou ,X.. Cai ,M., Mater. Lett. No.61 (2007) pp.4989-4992. [20]H. Wang, J.J. Zhu, J.M. Zhu, X.H. Liao, S. Xu, T. Ding, H.Y. Chen, Phys. Chem. Chem. Phys,No.4 pp. 3794-3799,2002 [21]. Liao, X.H.,. Zhu .J.M.,. Zhu ,J.J.,. Xu .J.Z.,, Chem. Commun, pp. 937-938,2001 [22] Babitha et al, Indian Journal of pure and applied Physics.pp. 596-603,2015 [23] Sr. S Sebastiammal , V. Shally, M. Priyadharshini , Sr. Gerardin Jayam, International Journal of Engineering Trends and Technology (IJETT) – Volume 49 Number 2 July 2017 [24]Kumar A, Das S, Munusamy P, et al. Behavior of nanoceria in biologicallyrelevant environments. Environ Sci Nano. 2014;1:516–532 [25] Munusamy S, Bhakyaraj K, Vijayalakshmi L, Stephen A, Narayanan V. Synthesis and characterization of cerium oxide nanoparticles using Curvularia lunata and their antibacterial properties. Int J Innovative Res Sci Eng. 2014;2(1):318–323. [26]. Thill A, Zeyons O, Spalla O, et al. Cytotoxicity of CeO2 nanoparticles for Escherichia coli. Physico-chemical insight of the cytotoxicity mechanism. Environ Sci Technol. 2006;40(19):6151–615 [27]. Zeyons O, Thill A, Chauvat F, et al. Direct and indirect CeO2 nanoparticles toxicity for Escherichia coli and Synechocystis. Nanotoxicology. 2009;3(4):284–295.

38


Optical and

Morphological Properties

of SnO Nanocrystals Aiswaraya Nair, Neethu K, Aswathy Nair , Bestin

Babu, Vishnu S. Kumar, Achamma George*

Department of Physics, Catholicate College, Pathanamthitta Kerala, India *Corresponding Author: [email protected]

Abstarct: The simple hydrothermal synthesis technique was carried out to synthesize nanocrystals of stannous oxide. X Ray Diffraction studies showed meta-stable state of the stannous oxide (SnO) nanocrystals. Transmission Electron Microscopy (TEM) studies showed 2nm size of SnO nano particles. The as-prepared SnO nanoparticles exhibit the type IV isotherm revealing the characteristic of meso porous material. The specific surface area estimated by Brunauer-Emmett-Teller (BET) method is about 225.94m2/g. Optical absorption wavelength was measured to be 272nm Photo-luminescence (PL) studies showed the emission at around 395 nm, 437 nm, 450 nm and 468nm. Key words: metastable, mesoporous, SnO, nanocrystals. 1. Introduction

Nano crystal tin oxides and semiconductor materials have been attracted since last two decades owing to their good mechanical, magnetic optical electrical and other physical properties which have

varied wide applicability ranging from gas sensors [1,2] photo catalysis and photochemistry [3] , Oxide based Magnetic semiconductors[4], Ferro Electric Field Effect memory device[5], Li ion Batteries [6]electro chemical splitting [7]transistors[8].Tin monooxide also known as stannous oxide (SnO) is an important p-type semiconductor material and can be synthesized easily by hydrothermal, solvothermal, chemical vapor deposition, and sputtering methods [9,10,11]etc It has a wide band gap of Eg=2.5-3.5eV [12], has obtained a remarkable interest due to its perfect physical, chemical and morpho-logical properties. SnO is blue-black and has the tetragonal litharge type structure (α-PbO, tP4, P4/nmm, SG No. 129, Z = 2), while the colourless SnO2 has rutile type structure (TiO2, tP6, P42/mnm, SG No. 136, Z = 2 [14]Also. SnO is metastable at ambient conditions and decomposes above a certain temperature with a noticeable rate into Sn and SnO2. Depending on the preparation method of the SnO and on the decomposition temperature, an intermediate oxide is found in various amounts. The crystal structure of this oxide is unknown and the disproportionation of SnO is the only known preparation method for this oxide.[15-17] The rich defect structure of SnO systems bear potential in effective energy storage, hence demand a systematic characterization related to the identification of defects and charge carrier concentration. An optical and morphological characterization is required. 2. Experimental 2.1. Materials AR grade (purity> 99% Tin metal, Hydrochloric acid (HCl), urea (CH2NH2COOH), and ethylene glycol (C2H6O2), were procured from Merck India. No further purification of precursors was carried out. . 2.2. Methods 2.2.1. Preparation of Samples

In a typical experiment, 0.5 g of Tin metal was dissolved in 10 ml of HCl and 40 ml of ethylene glycol. Around 3 g of urea was added into this solution and the temperature is raised to 100°Cand maintained at this value for 2 hr. The

39

ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 precipitate of SnO was obtained which was finally separated by centrifugation and washed several times with quadruple distilled water and methanol (to remove trace impurities). The samples were thereafter dried at room temperature for obtaining SnO nanocrystals.

2.2.2. Characterization

The phase identification of as-synthesized

SnO nanopowder was performed on instrument Bruker AXS D8 Advance with Cu-Kα target (λ=1.5406 A°) at room temperature. The X-ray generator was operated at 40kV with step size 0.020 degree a scan speed of 2degree/min. TEM measurements were carried out on Jeol JEM 2100 200kV with a high resolution of 2.4A°. Normalized photoluminescence spectra have been measured using Horiba Fluorolog Fluoroscence spectrometer. Quantachrome ASiQWin v6.0 was used for surface studies. 3. Results and Discussion 3.1 XRD Results

To confirm the crystalline nature of undoped SnO nanocrystalline powders, X-Ray diffraction studies were performed. SnO is metastable at ambient conditions and decomposes above a certain temperature with a noticeable rate into Sn and SnO2 .The pattern for the same is shown in (Figure 1) along with pattern standard from Joint committee powder diffraction standards (JCPDS 06-0395) file No. [5,12,13] for SnO and as it is metastable [16] here we see some peaks of Sn (JCPDS card No. 04-0673) [5]may have overlapped. Depending on the preparation method of the SnO and on the decomposition temperature, an intermediate oxide is found in various amounts. The disproportionation of SnO is reported [15-17]. SnO has tetragonal crystal structure. Assuming it to be tetragonal structure the lattice parameters was found. The lattice parameter by XRD and unit cell utilities was calculated to be a = b = 3.83 and c = 4.5026 compared to reported as a= b =3.8020, c = 4.8360. [12]

20 30 40 50 600

3000

6000

301

101

JCPDS 06-0395 SnO

2 Theta(deg)

211

112

20000

2

110

Inte

nsity

(a.u

.)

0

50

100 SnO-

Sn-

Fig. 1 XRD result showing crystalline nature of

SnO

3.2. Morphology & TEM Results for SnO Nanocrystals

The TEM pattern for pristine SnO nanocrystals is shown in (Figure 2).The crystallites have spherical morphology.

Fig.2 TEM images of undoped SnO about 2 nm

Fig 3 EDX pattern Table1 Element present with weight and atomic percent The particle size of the SnO powders, by TEM experiment is about 2nm. EDX spectrum of SnO nanoparticles and summary of analysis results is shown in the Table 1 showing the element Sn, O

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ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 and Cu (grid).The table shows weight and atomic percentage of the element present. . 3.3Surface Studies SnO nanoparticles were investigated by nitrogen adsorption-desorption isotherm at 77K. The as-prepared SnO nanoparticles exhibit the type IV isotherm Figure 4 and by the method of Barrett- Joyner-Helena (BJH) pore size radius(Adsorption) found to be 1.53969nm and pore diameter d 3.07938nm>2nm revealing the characteristic of meso porous material. The specific surface area estimated by Brunauer-Emmett-Teller (BET) method is about 225.94m2/g and Barrett- Joyner-Halenda method adsorption (BJH) is 18.1469m2/g. Here we also see the fillings during adsorption is very fast process as depth of pore size is less The more pronounced at high P/P0, being associated with the filling of micro pores in mixed micro-mesoporous systems.

0.0 0.5 1.040

60

80

100

Volum

e Ad

sorb

ed S

TP(c

c/g)

Relative pressure P/P0

Adsorption/Desorption

Fig.4. Nitrogen adsorption-desorption isotherms at 77 K (P and P0 are the equilibrium and the saturation pressures of N2 at the temperatureof adsorption)for SnO nanocrystals 3.4 Absorbance and tauc plot This absorption at UV region is considered to result from the absorption of the intrinsic band gap. Here optical absorption wavelength was measured to be 272nm shown in Fig.5. The existence of sharp absorption edge is the characteristics of crystalline state material of the which corroborates the other analysis. Tauc’s plot of nanocrystalline SnO for direct allowed transition is shown in inset Fig 5 the optical

band gap values, Eg, of the synthesized SnO nanoparticles have been calculated from the plot between hν and (αhν)2 as shown in Figure. And the band gap of the material was found to be 2.75eV. The optical band gap values of the synthesized SnO nanoparticles are in good agreement with the Eg values (2.5–3.5 eV) of SnO nanoparticles which was previously reported [7,11, 12].

500 1000 1500 2000 2500-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Wavelength(nm)

Abs

Absorbance

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.00

600

1200

( eV)

(αhν

)2 (eV

cm-1

)2

(hν )

Fig 5 Absorption spectra of SnO nanoparticles and (inset) tauc plot for finding the energy band gap 3.5 Photoluminescence Results The emission spectra of undoped SnO obtained after 250nm excitation is characterized by a peak around 395 nm, 437 nm, 450 nm and 468nm. Emission at 450nm is due to band edge emission by which the energy band gap may be about .Based on the previous luminescence studies of SnO the peak around 468 nm where the excitation was at 300nm has been attributed to the oxygen vacancies present in the nanoparticles earlier[9,18].

300 350 400 4500

100000

200000

300000

400000

500000

Inte

nsity

(CP

S)

Wavelength (nm)

Tin oxide

Fig. 6 Photoluminescence spectra

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ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 4. Conclusions The simple precipitation synthesis was carried out. X Ray Diffraction studies showed metastable state of the Tinoxide (SnO) nanocrystals. Transmission Electron Microscopy (TEM) studies showed 2nm size of SnO nano particles. Surface studies show the material to be mesoporous. The energy band gap may be about 2.75 eV. Photoluminescence PL studies showed the emission at around 395 nm, 437 nm, 450 nm and 468nm. References

[1]. Matthias Batzil and Ulrike Diebold Surface and Material Science of Tin Oxide Progress in Surface Science 79 (2005) 47–154

[2]. Adawiya J. Haider , Suaad .S.Shaker , Asma H.Mohammed A study of morphological, optical and gas sensing properties for pure and Ag doped SnO2 prepared by pulsed laser deposition (PLD) Energy Procedia 36 ( 2013 ) 776 – 787

[3]. Cui, Y., Wang, F., Iqbal, M.Z., Wang, Z., Li, Y., Tu, J.Synthesis of novel 3D SnO flower-like hierarchical architectures self-assembled by nano-leaves and its photo catalysis. Mater. Res.Bull. 70, 784–788. 2015

[4]. Chang wen Zhang shi-shen yan First-principles study on ferromagnetism in Mg-doped SnO2 Applied Physics Letters 95(23):232108-232108-3 · December 2009

[5]. J. A. Caraveo-Frescas, M. A. Khan& H. N. Alshareef Polymer ferroelectric field-effect memory device with SnO channel layer exhibits record hole mobility Scientific Reports 4 5243|DOI:10.1038/srep05243

[6]. Das, B., Reddy, M.V., Chowdari, B.V.R., SnO and SnO_CoO nanocomposite as high capacity anode materials for lithium ion batteries. Mater. Res. Bull. 74, 291–298. 2016

[7]. Liang, L., Sun, Y., Lei, F., GAO, S., Xie, Y., Free-floating ultrathin tin monoxide

sheets for solar-driven photo electrochemical water splitting. J. Mater. Chem. A 2 (27), 10647. 2014.

[8]. Chu, H., Shen, Y., Hsieh, C., Huang, J., Wu, Y., Low-voltage operation of ZrO2-gated n-type thin-film transistors based on a channel formed by hybrid phases of SnO and SnO2. ACS Appl.Mater. Interface 7 (28), 15129–15137 ,2015

[9]. P. Boroojerdian Structural and Optical Study of SnO Nanoparticles Synthesized Using Microwave–Assisted Hydrothermal Route Int. J. Nanosci. Nanotechnol., Vol. 9, No. 2, June 2013, pp. 95-100

[10]. Sun, G., Wu, N., Li, Y., Cao, J., Qi, F., Bala, H., Zhang, Z.,.Hydrothermal synthesis of honeycomb-like SnO hierarchical microstructures assembled with nanosheets. Mater. Lett. 98, 2013234–237

[11]. Hsu, P., Hsu, C., Chang, C., Tsai, S., Chen, W., Hsieh, H., Wu, C.,. Sputtering deposition of P-type SnO films with SnO2 target in hydrogen-containing atmosphere. Appl. Mater. Interface 6,13724–137292014

[12]. Bircan Haspulat , Muhammet Sarıbel, Handan Kamıs_Surfactant assisted hydrothermal synthesis of SnO nanoparticles with enhanced photocatalytic activity Arabian Journal of Chemistry http://dx.doi.org/10.1016/j.arabjc.2017.02.004 2017

[13]. † Supriya A. Patil,a Dipak V. Shinde, a Do Young Ahn,a Dilip V. Patil,a Kailas K.Tehare,b Vijaykumar V. Jadhav,bJoong K. Lee,c Rajaram S. Mane,b Nabeen K. Shrestha,a Sung-Hwan Han,a * A simple, room temperature, solid-state synthesis route for metal oxide nanostructures Journal of Materials Chemistry A DOI: 10.1039/c0xx00000x

[14]. H. Giefers, F. Porsch, G. Wortmann Structural study of SnO at high Pressure Physica B(2006)79-81

[15]. M. Sergio Moreno a,1, Graciela Punte a,1, Graciela Rigotti a,1, Roberto C. Mercader

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http://dx.doi.org/10.1016/j.arabjc.2017.02.004%202017

http://dx.doi.org/10.1016/j.arabjc.2017.02.004%202017


a,1, Ariel D. Weisz b, Miguel A. Blesa b,c,) Kinetic study of the disproportionation of tin monoxide Solid State Ionics 144 2001 81–86

[16]. F. Gauzzi, B. Verdini X-ray Diffraction and Miissbauer Analyses of SnO Disproportionation Products Inorganica Chimica Acta, IO4 (1985) 1-7

[17]. H. Giefers, F. Porsch, G. Wortmann Kinetics of the disproportionation of SnO Solid State Ionics 176 2005 199–207

[18]. F. Gu, S.F. Wang, C.F. Song, M.K. Lu, Y.X. Qi, G.J.Zhou, X. UD, D.R. Yuan: Synthesis and luminescence properties of SnO2nanoparticlesChemical Physics Letters,Vol. 372, 2003, pp. 451-54.

Acknowledgements Author owe a sincere thanks to Mahatma Gandhi University, Kottayam for TEM and PL characterization and to STIC, Kochi University, Kochi for XRD & UV characterization.

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Nanoparticles based Solar Reflective Coating to Mitigate Urban Heat Island Effect George Thomas*, Soosen Samuel M, Karthik Vinodan, Anvar Shareef Pattathodika, Sajith Babu S Catholicate College, Pathanamthitta, Kerala, India *Corresponding author Email: [email protected] Abstract: The rapid urbanization and industrialization bring about microclimatic changes particularly with regard to thermal structure of the cities. Difference in the surface material and the structure between a city and the surrounding rural area lead to the difference in the climate between two regions and create the “urban climate”. Urban Heat Island (UHI) occurs when cities replace natural land cover with dense concentrations of pavement, buildings, and other surfaces that absorb and retain heat. The transference of heat to the atmosphere is highly influenced by the albedo and emittance of surface material. Urban Heat Island intensity in Kochi, a tropical coastal city during winter 2017 was investigated. Mobile surveys were conducted during winter seasons, covering pre-dawn and early evening periods to find the UHI intensity. Urban Heat Island intensity in Kochi is 3.9oC during winter morning. Proper planning of the built environment and selection of raw materials is necessary to reduce the problem of excessive nocturnal heat loads within the built environment. Nanoparticles based coating is an effective method used to mitigate urban heat island. Reflectivity of the pavement can be increased by covering the surfaces of the pavement with a nano coating. These coating have reflectance in wide range especially in visible and infrared region of solar spectrum. Also they have high emissive power and hence possess a large potential for mitigation. Key words: Urban heat island effect, UHI Mitigation, Nanocoating.

1. Introduction The high rate of urbanization has resulted in drastic demographic, economic, land use and climate modifications in the urban regions [1], [2], [4]. Buildings, roads, and other infrastructure replace open land and vegetation. Surfaces that were once permeable and moist generally become impermeable and dry. This development leads to the formation of urban heat islands—the phenomenon whereby urban regions experience warmer temperatures than their rural surroundings [6], [7]. The phenomenon was first investigated and described by Luke Howard the 1810s, although he was not the one to name the phenomenon. Many urban and suburban areas experience elevated temperatures compared to their outlying rural surroundings; this difference in temperature is what constitutes an urban heat island. The annual mean air temperature of a city with one million or more people can be 1.8 to 5.4°F (1 to 3°C) warmer than its surroundings, and on a clear, calm night, this temperature difference can be as much as 22°F (12°C). Even smaller cities and towns will produce heat islands, though the effect often decreases as city size decreases.

2. Methodology 2.1. Study area Kochi is one of the metropolitan cities in India which hosts a number of industries and a population of about 2.2 million [9]. It is a fast growing urban centre located on the southwest coast of India, between 09º 45’ N and 10º20’ N latitude and between 76º 10’ E and 76º 45’ E longitude has a coastline stretching up to a length of about 48km. The map of the study area is shown in figure 1. 2.2. Mobile Traverse to quantity UHI Intensity Mobile Surveys were carried out from 4:30 to 6:30 am before sunrise during winter to quantify UHI

44

ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 intensity measurements. The reference temperature was taken from a temperature recorder installed at Thripunithura (76:21: 28.8 E & 09:55: 33.6N) in the study area [10]. Air temperature was recorded with high resolution RTD probe (MadgTech USA, Model: RTD Temp 101).

Fig.1. Map of the study area. Automatic temperature recorders with 0.01 K resolutions and 0.1 K accuracy were used for reading air temperature. The vehicle was stopped for 1 minute at each observational point along the route to eliminate the error in measurements of RTD probe before reaching the steady state. Temperature and RH were automatically logged along with time stamp at 5 second interval. The coordinates were taken from a hand held GPS and time of observation was noted with a chronometer synchronized with the temperature recorder and GPS, at each point of observation. The instantaneous temperature difference between all observational points and the reference site was calculated in order to determine UHI intensity. A comparative study of the predominant materials used in the roof and walls of the houses of urban and rural areas in Ernakulam is done.

2.3. Nanocoating to mitigate UHI

Nanotechnology is used to mitigate UHI. Here we studied the reflectance spectrum of ZnO in glass. ZnO nanorods and nanotubes were synthesized by hydrothermal method [3], [5]. The structure and morphology of the samples were investigated by X-ray diffraction and Scanning electron microscopy. UV-Visible spectrum was taken to study the optical property of the material. 3. Results and Discussion 3.1 UHI Intensity Highest Urban Heat Island intensity in Kochi is 3.9oC during winter morning. Maximum intensity is found in the city centre followed by sub urban regions. 3.2. Materials used in urban and rural areas. Proper planning of the built environment and selection of raw materials is necessary to reduce the problem of excessive nocturnal heat loads within the built environment. A comparative study of the predominant material of roof in the urban and rural area of Ernakulum district is shown in the figure 2.

45


Fig.2. Percentage of Houses by predominant material of Roof in Ernakulam District. Wood construction has been the primary choice of Indian construction, especially in rural areas. In modern times, wood as a building material is also making headway into urban spaces. Bricks and blocks made up of clay or mud, bricks come in several shapes and offer high strength to the construction. They have long been used to construct homes and offices across India. Concrete, as in cement brings in the same set of advantages and disadvantages. They are long lasting building materials and have become the foundation for India’s bridges, highways, reservoirs, dams, parking structures, and everything big. However heat capacity and thermal emittance of these materials also play a vital role in the growth of heat island [8]. Concrete, bricks, steel and stone used in the urban area have higher heat capacity than the dry soil, wood and sand in the rural environment. Similarly materials with less thermal emittance, refers to the surface’s ability to shed heat or emit long wave radiation also influences heat island developments.

3.3 Nanoparticle based Mitigation TEM image of ZnO nano tubes is shown in figure 3. X-ray diffraction revealed the wurtzite structure of ZnO.

Fig.3. TEM image of ZnO nanotubes. Reflectance spectrum of both ZnO nanorods and nanotubes in the figure 4 showed a high reflectance in the infrared region. The use of ZnO nanoparticles based infrared reflective coating on the surface of the pavements can be used as an effective method to mitigate the UHI effect.

Fig.4. Reflectance spectrum of both ZnO nanorods and nanotubes.

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ICAN2018: Technology Letters Conference Proceedings of the International Conference on Advanced Nanostructures, March 2018 4. Conclusions Highest observed urban heat island intensity in Kochi is 3.9 oC during winter morning. Proper planning of the built environment and selection of raw materials is necessary to reduce the problem of excessive nocturnal heat loads within the built environment. Nanoparticles based coating is an effective method used to mitigate urban heat island. These coating have reflectance in wide range especially in visible and infrared region of solar spectrum. Also they have high emissive power and hence possess a large potential for mitigation. References [1] Akhtar, R.; Gupta, P.T.; Srivastava, A. K. Urbanization, Urban Heat Island Effects and Dengue Outbreak in Delhi, In: Rais Akhtar Climate Change and Human Health Scenario in South and Southeast Asia, Springer International Publishing, Switzerland, 2016, 99-111. [2] Han,Y.; Taylor, J.E.; Pisello, A.L. Toward mitigating urban heat island effects: Investigating the thermal-energy impact of bio-inspired retro-reflective building envelopes in dense urban settings, Energy and Buildings, 2015, 102,380–389. [3] Hui, Z.; Deren, Y.; Xiangyang, M.; Yujie, J.; Jin, X.; Duanlin, Q. Synthesis of flower-like ZnO nanostructures by an organic-free hydrothermal process, Nanotechnology, 2004, 15, 622. [4] Lemonsu, A.; Viguie, V.; Daniel, M.; Masson, V. Vulnerability to heat waves: Impact of urban expansion scenarios on urban heat island and heat stress in Paris (France), Urban Climate, 2015, 14, 4, 586–605. [5] Li, W.; J.; Shi, E. W.; Zheng, Y. Q.; Yin, Z. W. Hydrothermal preparation of nanometer ZnO powders”, J. Mater. Sci. Lett, 2001, 20, 1381. [6] Oke, T.R. The Energetic Basis of the Urban Heat Island, Quarterly Journal of the Royal Meteorological Society, 108, 1-24, 1982.

[7] Oke, T.R. Urban Climates and Global Environmental Change. In: Thompson, R.D. and A. Perry (eds.) Applied Climatology: Principles & Practices, NY: Routledge, New York, 1997, 273-287. [8] Oke. T.R. Boundary Layer Climates, New York, Routledge, 1987. [9] Thomas, G.; Sherin, A.P.; Ansar, S.; Zachariah, E.J. Analysis of urban heat island in Kochi, India, using a modified local climate zone classification. Procedia Environmental Sciences, 2014, 21, 3-13. [10] World Meteorological Organization, Guide to Meteorological Instruments and Methods of Observation. 7th ed., WMO-No. 8, Geneva, 2008. [11] Zhang, J.; Sun, L. D.; Yin, J. L.; Su, H. L.; Liao, C. S.; Yan, C. H. Control of ZnO Morphology via a Simple Solution Route”, Chem. Mater, 2002, 14, 4172.

Acknowledgements The authors are grateful to UGC for the encouragement and financial support extended for this study.

47


Synthesis of Luminescent ZIF-8

Nanoparticles for Targeted Drug

Delivery

U Arun1*, R Sreeja 2 and Annie Abraham3

1Department of Biochemistry and

Microbiology, Government College for

Women, Thiruvananthapuram,Kerala

2Assistant Professor, Department of

Physics, St John’s College, Anchal, Kerala

3Department of Biochemistry, University

of Kerala,Kariavattom,

Thiruvananthapuram, Kerala

*Email: [email protected]

Abstract

Metal–organic frameworks

(MOFs) are an emerging class of

nanoporous materials comprising metal

centers connected by organic linkers.

Zeolitic imidazolate frameworks (ZIFs) are

a sub-category of MOFs which have

tuneable pore sizes and chemical

functionality coupled with exceptional

chemical stability. ZIFs of appropriate size

range can be used for targeted drug

delivery in anticancer applications. The

present work reports the synthesis of

Fluorescein Isothiocyanate (FITC)

attached ZIF-8 NPs using a simple

solvothermal route. The NP size was found

to be around 60-70nm as confirmed by

XRD, SEM and TEM. Photoluminescence

(PL) studies proved the presence of FITC

molecules within the ZIF-8 framework.

The cell toxicity studies showed that the

ZIF-8 NPs can be effectively used for

biomedical applications.

1. Introduction

Metal–organic frameworks

(MOFs) are an emerging class of

nanoporous materials comprising metal

centers connected by various organic

linkers to create one, two, and three

dimensional porous structures. Zeolitic

imidazolate frameworks (ZIFs) are a sub-

class of MOFs that have tuneable pore

sizes and chemical functionality, coupled

with exceptional thermal and chemical

stability [1]. ZIFs form versatile structures

analogous to that of inorganic zeolites [2].

ZIF-8 (Zeolitic imidazolate framework-8)

is made of Zinc ions coordinated by four

immidazole (C3H4N2) rings. ZIF-8 is an

attractive MOF for application of targeted

drug delivery in cancer cells. The porous

structure of ZIF-8 enables its use as an

effective drug carrier. In the present work

we report the synthesis of fluorescein

isothiocyanate (FITC) molecule

encapsulated ZIF-8 NPs. The present work

is designed to investigate the cytotoxic

effect of ZIF-8/FITC NPs on human

malignant melanoma (A375) cells.

Cytotoxic potentials of ZIF-8/FITC NPs

48



are investigated by MTT Assay in A375

cells.

2. Experimental

The ZIF-8 NPs were prepared

using solvothermal synthesis [3]. We used

Zn(NO3)2.6H2O as the metal source, 2-

Methyl imidazole (HMIM) as the linkers,

and methanol as the solvent. Prepare

separate solutions of Zinc nitrate and

HMIM in methanol media (3.34 gms

HMIM in 50 ml methanol and 1.5gms zinc

nitrate in 50 ml methanol). Also prepare

separate solution of FITC (2mg/ml) in

Dimethyl sulphoxide (DMSO). Initially

add 2ml of FITC solution slowly into the

Zinc nitrate solution under vigorous

stirring (1000 rpm). Allow both solutions

to mix well for 5 minutes. Then add the

HMIM solution drop wise under vigorous

stirring for 2 hours. Centrifuge the

colloidal solution at 12000 rpm for 30

minutes to get yellow precipitate. Wash

the precipitate with methanol twice and

kept in the oven overnight to get yellow

crystalline powder.

Powder X-ray diffraction patterns

were collected using Philips Expert Pro

Diffractometer with Cu Kα radiation. The

size and morphology of the ZIF-8/FITC

NPs were studied by scanning electron

microscopy (SEM) and transmission

electron microscopy (TEM). The SEM and

TEM images were taken using FE-SEM,

NOVA Nano SEM NPEP252 and

Jeol/JEM 2100. Thermo gravimetric

analysis (TGA) was performed using SDT

Q600 TA Instruments USA. Cytotoxic

studies were performed using MTT assay

as described by Mossman [4].

2.1. Cell culture

Human malignant melanoma A375

cells were purchased from National Centre

for Cell Science, Pune and maintained in

DMEM with 10% fetal bovine serum

(FBS) and 5% CO2 incubator at 370C. The

NPs treated cancer cells were assessed for

growth inhibition by MTT assay [4].

Absorbance was measured at 570nm and

the data were quantified.

3. Results and discussions

Fig 1 shows the XRD pattern of the

ZIF-8/FITC NPs. The peaks corresponding

to (011), (002), (112), (022), (013), (222),

(114), (233), (131) confirms the sodalite

structure of ZIF-8 [5]. The XRD shows

that the addition of FITC didn’t alter the

structure of ZIF-8.The average particle

size of the NPs is found to be 65 nm as

obtained from Scherrer’s formula [6]. Fig

2 shows the SEM and TEM images of the

ZIF-8 NPs which show an average particle

size of 60nm. TEM clearly confirms the

typical hexagonal structure of ZIF-8.

49


Fig.1. XRD of ZIF-8/FITC NPs

Fig.2.(a) SEM and (b) TEM images of

the ZIF-8 /FITC NPs

The TGA (fig 3) clearly indicates

the high thermal stability of ZIF-

8/FITC NPs up to 600oC. These NPs

can be used for high temperature

applications without the loss of

structure and performance.

Fig.3. TGA curve of ZIF-8/FITC NPs

Fig.4.PL emission spectra of ZIF-8/FITC

NPs

The PL spectra (figure 4) show

that the NPs exhibit a strong emission

around the green (520nm) region. This is

attributed to the encapsulated FITC

molecules in ZIF-8. It confirms the

encapsulation of FITC molecules inside

the ZIF-8 structure.

Fig 5 shows the MTT assay of

NPs treated with the A375 cancer cells.

MTT assay shows that the NPs induced a

significant cytotoxic effect in A375 cells.

It is also observed that the cellular

inhibition rate is increased with increase in

the concentration of the NPs. Also the

percentage of inhibition is increasing with

time of treatment. The NPs diffuse

passively into the cytoplasm and other cell

organelles by endocytosis which forms NP

agglomerates inside the cell. The

interaction between aggregates of NPs

containing metals and live cells lead to cell

death. The morphological changes will be

50


more significant with increase in exposure

time and NPs concentration.

Fig.5. MTT assay of ZIF-8/FITC NPs

4. Conclusion

We have synthesised luminescent

ZIF-8/FITC NPs by solvothermal route for

anticancer applications. Sodalite structure

of the ZIF-8 was confirmed by XRD.

XRD, SEM and TEM confirmed the NPs

size to be around 60-70nm. TEM

confirmed the Hexagonal structure of the

NPs. TGA showed the high temperature

stability of the NPs. Green luminescence

emission at 520nm confirmed the

encapsulation of FITC molecules within

the ZIF-8 structure. The cytotoxicity of

ZIF-8/FITC NPs on human malignant

melanoma (A375) cells was analysed. The

percentage of cellular inhibition was found

to be increased with increase exposure

time and the concentration of the NPs.

References

[1]. Chen, B; Yang, Z; Zhu, Y and Xia, Y;

J. Mater. Chem. A, 2014, 2, 16811.

[2] Hayashi, H; Cote, A,P; Furukawa,H;

OKeeffe, M; and Yaghi,O,M. Nat. Mater.,

2007, 6, 501.

[3].Cravillon,J;Munzer,S;Lohmeier,S,J;Fel

dhoff,A; Huber,K; and Wiebcke,M;Chem.

Mater. 2009, 21,1410.

[4].Mossman,T. Journal of Immunological

Methods. 1983, 65, 55.

[5].Kida, K; Okita, M; Fujita,K;

Tanakaab,S; and Miyake,Y. Cryst. Eng.

Comm. 2013, 15, 1794.

[6]. Cullity, B. D and Stock, S. R;

Elements of X-ray diffraction, Third

Edition, Prentice Hall, New Jersey (2001)

51

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