ISSN 2320 -5083 Journal of International · Bidar Institute of Medical Sciences, rnataka, India. Dr Asifa Nazir, M.B.B.S, MD, Assistant Professor, Dept of Microbiology ... 11800 Penang,

Journal of International Academic Research for Multidisciplinary

ISSN 2320 -5083

A Scholarly, Peer Reviewed, Monthly, Open Access, Online Research Journal

Impact Factor – 1.393

VOLUME 1 ISSUE 10 NOVEMBER 2013

A GLOBAL SOCIETY FOR MULTIDISCIPLINARY RESEARCH

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A GREEN PUBLISHING HOUSE

Editorial Board

Dr. Kari Jabbour, Ph.D Curriculum Developer, American College of Technology, Missouri, USA.

Er.Chandramohan, M.S System Specialist - OGP ABB Australia Pvt. Ltd., Australia.

Dr. S.K. Singh Chief Scientist Advanced Materials Technology Department Institute of Minerals & Materials Technology Bhubaneswar, India

Dr. Jake M. Laguador Director, Research and Statistics Center, Lyceum of the Philippines University, Philippines.

Prof. Dr. Sharath Babu, LLM Ph.D Dean. Faculty of Law, Karnatak University Dharwad, Karnataka, India

Dr.S.M Kadri, MBBS, MPH/ICHD, FFP Fellow, Public Health Foundation of India Epidemiologist Division of Epidemiology and Public Health, Kashmir, India

Dr.Bhumika Talwar, BDS Research Officer State Institute of Health & Family Welfare Jaipur, India

Dr. Tej Pratap Mall Ph.D Head, Postgraduate Department of Botany, Kisan P.G. College, Bahraich, India.

Dr. Arup Kanti Konar, Ph.D Associate Professor of Economics Achhruram, Memorial College, SKB University, Jhalda,Purulia, West Bengal. India

Dr. S.Raja Ph.D Research Associate, Madras Research Center of CMFR , Indian Council of Agricultural Research, Chennai, India

Dr. Vijay Pithadia, Ph.D, Director - Sri Aurobindo Institute of Management Rajkot, India.

Er. R. Bhuvanewari Devi M. Tech, MCIHT Highway Engineer, Infrastructure, Ramboll, Abu Dhabi, UAE Sanda Maican, Ph.D. Senior Researcher, Department of Ecology, Taxonomy and Nature Conservation Institute of Biology of the Romanian Academy, Bucharest, Romania Dr. Reynalda B. Garcia Professor, Graduate School & College of Education, Arts and Sciences Lyceum of the Philippines University Philippines Dr.Damarla Bala Venkata Ramana Senior Scientist Central Research Institute for Dryland Agriculture (CRIDA) Hyderabad, A.P, India PROF. Dr.S.V.Kshirsagar, M.B.B.S,M.S Head - Department of Anatomy, Bidar Institute of Medical Sciences, Karnataka, India. Dr Asifa Nazir, M.B.B.S, MD, Assistant Professor, Dept of Microbiology Government Medical College, Srinagar, India. Dr.AmitaPuri, Ph.D Officiating Principal Army Inst. Of Education New Delhi, India Dr. Shobana Nelasco Ph.D Associate Professor, Fellow of Indian Council of Social Science Research (On Deputation}, Department of Economics, Bharathidasan University, Trichirappalli. India M. Suresh Kumar, PHD Assistant Manager, Godrej Security Solution, India. Dr.T.Chandrasekarayya,Ph.D Assistant Professor, Dept Of Population Studies & Social Work, S.V.University, Tirupati, India.

JOURNAL OF INTERNATIONAL ACADEMIC RESEARCH FOR MULTIDISCIPLINARY Impact Factor 1.393, ISSN: 2320-5083, Volume 1, Issue 10, November 2013

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THE PRODUCTION OF SILICA NANOPARTICLES BY INCORPORATING SIMPLE CARBONYL LIGANDS IN A ONE-POT SYNTHESIS

KASIM MOHAMMED HELLO*

FAROOK ADAM**

* Dept. of Chemistry, Collage of Science, Al-Muthanna University, Iraq **School of Chemical Sciences, University Sains Malaysia, 11800 Penang, Malaysia

ABSTRACT

The silica from rice husk ash was reacted in one pot synthesis with several organic

acids and esters, i.e. chloroacetic acid, chloroethylacetate, acetic acid, 1–chlorohexane, and

ethylpalmtate at room temperature and pressure to produce spherical shaped nanoparticles.

The spectroscopic evidence obtained in this study showed that the silanol groups on the silica

reacted with the carbonyl functional group and not with the C–Halogen bond. The BET

results show that the modification leads to form microporous materials with very high

specific surface area. The procedure used in this study was simple, environmental friendly

and lead to the formation of silica with chloride or alkyl end groups.

KEYWORDS: Surface Modification, One Pot Synthesis, Rice Husk Ash, Silica, Sol-Gel

1. INTRODUCTION

Silica nanoparticles are useful fillers for rubber, plastics, adhesives, paint polishing

material, pigment, catalyst, reinforcement material, and other processes as it has special

physical and chemical properties [1, 2]. Several types of silica nanoparticles are now available

commercially in the market for different applications [3]. In order to create new materials or,

improve current synthetic methods, the best way is by replacing the hydrogen atom of the

surface silanol groups with silylating agents containing hydrophobic functional groups [4],

which will impart hydrophobic character to the silica surface. Tetraethylorthosilicate or

organo–silane monomer (halo or amino or marcaptoalkyltrialkoxysailine) were often used as

a modifier for silica [5]. However, surface modification of silica for the preparation of

organically modified silica needed long reaction times, non–environmental friendly organic

solvents, harsh refluxing condition and multiple steps [6][7][8]. Moreover, the vast majority of

these protocols call for expensive chemicals and techniques and cause environmental

pollution. A more direct and simple method was introduced by us to immobilize organo–

silane monomer onto silica to give functionality on the silica surface [9] [10].


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Rice husk (RH) is a cellulose–based fiber, which contains a high composition of

silica. Since it is available free it is economically viable to use it as a raw material [11] for

silica extraction. The controlled burning of RH in air leads to the formation of rice husk ash

(RHA) which contains ca. 95% silica [12]. Since the silica surface contains an abundance of

silanol (Si–OH) groups, the terminal hydrogen can be exchanged with organic ligands to give

greater functionality to the silica surface. To the best of our knowledge, the direct

modification of silica without using silylating agents has not been published.

In the present report we describe the synthesis and characterization of silica extracted

from rice husk ash with different bi–functional groups, i.e. carboxylic acid derivatives to

produce organo–silica nanoparticles. A new approach has been followed involving less

processing time, low production cost and ease of production without using

tetraethylorthosilicate or organo–silane monomers. As the products have free organic end

groups, it can be used in various academic and industrial applications including selective

binding, preparation of catalysts and hetero-biological materials, in an easier and more

flexible way than those involving the use of tetraethylorthosilicate or organo–silane

monomers.

2. Experimental

2.1 Raw materials

The chemicals used in this work include sodium hydroxide (Systerm, 99%), nitric

acid (Systerm, 65%), acetic acid (Systerm, 99.5%), chloroacetic acid (Sigma – Aldrich,

99%), chloroethylacetate (Sigma–Aldrich, 99%), acetic acid (Sigma – Aldrich, 99%),

ethylpalmtate (Sigma–Aldrich, 99%) and 1–chlorohexane (Sigma – Aldrich, 99%). The RH

was collected from a rice mill in Penang, Malaysia. All other chemicals used were AR grade

or of high purity and were used directly without further purification.

2.2. Extraction and modification of silica from RHA

2.2.1 Sources of silica

The RHA was chosen as the source of amorphous silica as it was available in

abundance. The silica was extracted from rice husk using a previously reported method

(Adam and Chua, 2004; Ahmed and Adam, 2007).

2.2.2 Preparation of silica organic complexes.

RHA silica was functionalized with chloroacetic acid, chloroethylacetate, acetic acid,

ethylpalmitate and 1–chlorohexane using sol–gel technique. The syntheses of these silica-


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organic complexes were carried out as follows: about 1.5 g of RHA was added to 100 mL of

1.0 M NaOH in a plastic container and stirred for 1 h at room temperature to convert the

silica into sodium silicate. Chloroacetic acid (1.5 g, 0.015 mol) was added to this sodium

silicate solution. The solution was titrated slowly with 3.0 M nitric acid with constant stirring.

The change in pH was monitored by using a pH meter. A gel started to form when the pH

decreased to less than 10. The titration was continued until the pH of the solution reached 3.0.

The gel obtained was aged for 2 days in a covered plastic container using a water bath at 60 °C. After 2 days of aging, the gel was separated by centrifuge at 4000 rpm for 10 min. The

separation process was repeated 6 times with fresh amount of distilled water. The final

washing was done with acetone. The sample was dried at 110 °C for 24 h. Finally, it was

ground to produce a fine powder. This sample was labelled as RHACA. About 1.25 g of

RHACA was collected. Similar procedure was repeated using (1.64 mL, 0.015 mol) of

chloroethylacetate, (0.84 mL, 0.015 mol) of acetic acid, (4.93 mL, 0.015 mol) of

ethylpalmitate, and (2.08 g, 0.015 mol) of 1–chlorohexane. The resulting solid catalysts were

labelled as RHACEA, RHAA, RHAEP and RHACH respectively. About 1.4 g of RHACEA,

1.2 g of RHAA, 1.3 g of RHACH, and 1.22 g of RHAEP were collected.

2.3 Sample characterization

The RHACA, RHAA, RHAEP, RHACEA and RHACH ware characterized by Powder

X-ray diffraction (Siemens diffractometer, D5000, Kristalloflex). The nitrogen adsorption

porosimetry was carried out on an automatic physisorption porosimeter (Autosorb–1 CLP,

Quantachrom, USA). The FT–IR spectra were recorded on a PerkinElmer spectrometer

(System 2000). The scanning electron microscopy (SEM) (Leica Cambridge S360) and

energy dispersive spectrometry (EDX) (Edax Falcon System) was used to study the

morphology of the catalysts. The TEM micrographs were obtained using Philips CM12

equipment.

3. Results and Discussion

The schematic representation for the synthesis of RHACA, RHAA, RHAEP, RHACEA and

RHACH are shown in Scheme 1. The following chemical and physical analyses were used to

support the successful formation of RHACA, RHAA, RHAEP, RHACEA and RHACH.


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Scheme 1: The treatment of silica with different halide acid derivatives, acetic acid, ester and

alkyl halide. The reaction time is also shown.

3.1 Elemental analysis

Table 1 shows the chemical analysis, of RHACA, RHAA, RHAEP, RHACEA and

RHACH. The analysis was carried out by a combination of elemental and EDX methods. The

combined analysis shows that the carbon and chlorine (in RHACA and RHACEA) is present

in the samples, while both these elements were not present in RHA as was expected. The

elemental analysis showed that the RHACA and RHACEA have a similar value of carbon

and chlorine which may indicate that both samples have a similar formula. It is also observed

that the RHACH has a same elemental data with the RHA. This indicates that the reaction of

chlorohexane with sodium silicate did not take place. The presences of Si in all samples were

similar which was as expected. Apart from RHACH, the silicon content for all samples was

much less than that of RHA, which shows the successful incorporation of new elements

within the silica matrix.

Table 1: The chemical analysis of RHACA, RHACEA, RHAA, RHAEP and RHACH using a combination of elemental and EDX analysis (between bracts).

Sample

Elemental analysis (%) C H Cl Si

RHA 0.42 (6.76) 1.76 - (29.09)

RHACA 1.4 (6.6) 1.68 (0.1) (23.48)

RHACEA 1.53(7.2) 1.47 (0.13) (24.88)

RHAA 1.0 (9.5) 1.70 - (27.2)

RHAEP 4.3(14.6) 1.0 - (22.3)

RHACH 0.47(6.8) 1.62 - (29.12)

HNO3 / RT

pH = 3 / (35 min)RHA + NaOH Sodium silicateRT

SiO2(60 min)

SiO2

SiO2

ClCH2COOH

ClCH2COOEt

CH3COOH

ClCH2(CH)4CH3

OCOCH2Cl

OCOCH3

CH3(CH)12COOEt OCO(CH2)12CH3

No reaction


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3.2 Infrared spectroscopy analysis

Fig. 1 shows the FT–IR spectra of RHA, RHAEP and its differential spectrum. The

strong and broad band in the range of 3500 – 3400 cm-1 region corresponds to the hydrogen

bonded SiO–H vibrations. The RHAEP and the differential spectra show bands at 2924–2933

cm-1 corresponding to the aliphatic C–H stretching vibrations. The strong band at 1461 cm-1 is

due to the –CH2– bending group. The week band at 1750 cm-1 corresponding to the aliphatic

C=O stretching. In RHA the Si–O–Si vibration appear at 1082 cm-1. This band was observed

to shift to 1103 cm-1 in RHAEP spectrum. The RHA spectrum does not show these bands.

These results show that the ethyl palmitate was successfully immobilized onto RHA.

The FT–IR spectra of RHACA, RHAA, and RHACEA (see supplementary data, Sup.1)

did not show too much differences comparing with FT–IR of RHAEP. The main peaks of Si–

OH, C–H, C=O, –CH2– and Si–O–Si groups were observed with small shifting. These facts

were indicated that the chloroacetic acid, acetic acid and chloroethylacetate were successfully

immobilized onto RHA.

The FT–IR spectra of RHACH (not shown) did not show the peaks of C–H and –CH2–

functional groups. These indicate that the reaction could not happen due to the fact that alkyl

halide is a weak nucleophile as compared with the other molecules which have a carboxyl

group beside the chloride atoms and leads to increase in the nucleophilisity. It is also

established that the reaction with the silanol groups occurred between the carboxyl side and

not from the halogen side.

Fig. 1: shows the FT–IR spectra of RHA, RHAEP and its differential spectrum.

4000.0 3000 2000 1500 1000 400.0cm-1

%T

RHA

RHAC16OEt

Differeential

3459

2924

1637

1103

971

800

470

1461

3458

1646961

798

4631082

3458

29331647

13841215

1059950

787

4201402

1745 RHAEP


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3.3 Powder X–ray Diffraction (XRD) and Nitrogen adsorption analysis

The XRD spectra (see supplementary data, Sup.2) did not show sharp diffraction

patterns. A broad diffraction band at 2θ angle of ca. 22° was observed which was typical for

amorphous silica.

Fig. 2(a, b) shows the nitrogen adsorption isotherm obtained for RHACA and

RHACEA. Inset are shown the pore size distribution graph. Both RHACA and RHACEA

gave similar hysteresis loops which were observed in the range 0.4 < P/Pο <1.0. This range is

associated with capillary condensation within the mesopores. The isotherm shown is of type

IV and exhibiting H2 hystereis loop [13].

The BET analysis (Table 2) showed the specific surface area of RHACA and

RHACEA were 655 and 654 m2g-1 respectively, while the specific surface area of RHA was

reported to be 347 m2g-1. Thus, the higher specific surface area of RHACA and RHACEA

can be assumed to be due to the presence of the chloracetic acid and chloroethylacetate acting

as a template directing agent during the preparation stage. Similar result was observed by

Adam et al. [14] when organic ligands are incorporated within the silica matrix. The RHACA

and RHACEA (Fig. 2 (a, b)) showed a broad pore size range from 4 to 8 nm with average

pore volume was 4.5–4.2 cm3 g-1 which is in the mesoporous range (Table 2). The results of

BET clearly indicated that the reaction of chloracetic acid and chloroethylacetate with sodium

silicate leads to form a product with similar surface area.

Fig. 2 (c, d) shows the nitrogen adsorption isotherm obtained for RHAA and RHAEP

respectively. Inset is shown the pore size distribution graph. The isotherm shown is of type

IV and exhibited an H2 hystereis loop. The BET analysis (Table 2) showed the specific

surface area of RHAA and RHAEP were 539 and 399 m2g-1 respectively. The RHAA and

RHAEP (Fig. 2 (c, d)) showed a broad pore size range from 4 to 8 nm with average pore

volume was 7.2–3.9 cm3 g-1 which is in the mesoporous range (Table 2). The RHAEP show

lowest specific surface area compare with other samples. This could be due to the

immobilization of a large molecule into the silica matrix which leads to a decrease in the

specific surface area

The nitrogen adsorption data of RHACH (not shown) was very much similar to that of

RHA. Both RHA and RHACH had the same specific surface area which further enhanced the

fact that no reaction took place between 1–chlorohexane and sodium silicate.


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Fig. 2: The N2 adsorption/desorption isotherms with the corresponding pore size distribution inset. (a) RHACA, (b) RHACEA, (c) RHAA and (d) RHAEP. Table 2: The results of BET analysis for RHA, RHACA, RHACEA, RHAA, RHAEP and RHACH. Sample Specific Surface area

(m2 g-1)

Average pore volume

(cc g-1)

Average pore

diameter (nm)

RHA [10] 347 0.872 10.4 RHACA 654.5 0.69 4.2

RHACEA 655 0.737 4.5

RHAA 539 0.524 3. 9

RHAEP 399.3 0.709 7.2

RHACH 345 0.885 10.3

P/Po

Vol

ume

(cc/

g at

ST

P)

1.00.80.60.40.20.0

500

400

300

200

100

Pore Diameter (nm)

dV(lo

g d)

[cc/

g]

161412108642

2.5

2.0

1.5

1.0

0.5

0.0

(b)

P/Po

Vol

ume

(cc/

g at

ST

P)

1.00.80.60.40.20.0

500

400

300

200

100 (a)

Pore diamete r (nm)

dv (l

ogd)

[cc

/g]

18161412108642

2.0

1.5

1.0

0.5

0.0

P/Po

Vol

ume

(cc/

g at

STP

)

1.00.80.60.40.20.0

350

300

250

200

150

100

50Pore diameter (nm)

dv (l

ogd)

[cc/

g]

161412108642

2.5

2.0

1.5

1.0

0.5

0.0

P/Po

Vol

ume

(cc/

g at

STP

)

1.00.80.60.40.20.0

500

400

300

200

100

0

Pore diamete r (nm)

dv (l

ogd)

[cc/

g]

18161412108642

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

(c) (d)


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3.4 The electron microscopy

The morphology of the samples was studied by SEM and TEM images. The SEM of

RHAA and RHACA are shown in Fig. 3(a, b) respectively. The SEM of RHAA in Fig. 3(a)

show very rough surface with white particles. Similar observation was noted on the SEM of

RHACA in Fig. 3(b).

Fig. 3: The SEM micrographs of the (a) RHAA and (b) RHACA. Fig. 4 shows the TEM micrograph of RHAA and RHAEA. Very regular and spherical

shaped particles of RHAA and RHAEA were observed. It can be seen that the RHAA and

RHAEA consists of spherical particles with an estimated particle size of ca. 5 nm. The

measured sizes are in the nano range which could be used for important applications, for

example in nano medicine where active research are currently being pursued by researchers,

especially if these particles have hollow structure.

Fig. 4: The TEM micrographs of the (a, b) RHAA and (c, d) RHACA. Spherical shaped particles of RHAA and RHAEA were observed

(a) (b)

(a) (b)

(c) (d)


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4. Conclusion

The silica obtained from rice husk ash has been modified in a one pot synthesis with

different carboxyl derivatives at room temperature and pressure to produce spherical shaped

nanoparticles. The spectroscopic evidence obtained in this study showed the silanol groups

on the silica were successfully reacted with chloroacetic acid, chloroethylacetate, acetic acid,

and ethylpalmtate. However, 1–chlorohexane did not react with sodium silicate. The BET

results show that all the samples have very high specific surface area. This study shows a

very simple procedure to obtain nanoparticles. These nanoparticles could be used in many

important applications.

Sup. 1: shows the FT–IR spectra of RHA, RHACEA and its differential spectrum.

Sup.

2: The X–ray diffraction pattern shows amorphous nature of RHACEA.

4000.0 3000 2000 1500 1000 400.0cm-1

%T

RHA

RHACOEtCL

Differential

3467

1642

1090

969799

465

3458

1646961

798

4631085

3476

1641

1467

1100

976 799

470

2966

1185

Lin

(Cou

nts)

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

2-Theta - Scale10 20 30 40 50 60 70 80 90


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References

[1] Xiao-kun, M., L. Nam-Hee, O. Hyo-Jin, K. Jae-Woo, R. Chang-Kyu, P. Kyoung- Soon, K. Sun-Jae, Colloids Surf. A, 358 (2010) 172–176. [2 ] Wang, L., A. Lu, Z. Xiao, J. Ma, Y. Li. Appl. Sur. Sci. 255, (2009) 7542–7546. [3 ] Effati, E., B. Pourabbas. Powder Technology. 219 (2012) 276–283. [4 ] Kartal, A. M., C. Erkey. J. Sup. Flu., 53, (2010) 115–120. [5 ] Jung, C.Y., J. S. Kim, H. Y. Kim, J. M. Ha, Y. H. Kim, S. M. Koo. J. Colloid Interface Sci., 367 (2012) 67–73. [6 ] Hoegaerts, D., B.F. Sels, D.E. de Vos, F.Verpoort, P.A. Jacobs, Catal. Today, 6 (2000) 209–218. [7 ] Macquarrie, D.J., Chem. Commun., (1996) 1961–1962. [8 ] Brunel, D., Microporous Mesoporous Mater., 27 (1999) 329–344. [9 ] Adam, F., K. M. Hello, H. Osman, Chin. J. Chem., 28 (2010)2383—2388. [10 ] Hello, K.M., PhD thesis, University Sains Malaysia (2010) 27. [11 ] Adam, F., K.M. Hello, M.R. Ben Aisha, J. Taiw. Inst. Chem. Eng. 42 (2011) 843–851. [12 ] Adam, F., K.M. Hello, T.H. Ali, Appl. Catal. A . 399 (2011) 42–49. [13 ] Thommes, M., Chemie Ingenieur Technik, 82 (2010) 1059–1073. [14 ] Adam, F., K.M. Hello, H. Osman, J. Colloid Interface Sci. 313 (2009) 143–147.

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ISSN 2320 -5083 Journal of International · Bidar Institute of Medical Sciences, rnataka, India. Dr Asifa Nazir, M.B.B.S, MD, Assistant Professor, Dept of Microbiology ... 11800 Penang,