Upload
materials-research-institute
View
879
Download
6
Embed Size (px)
DESCRIPTION
Yichun Liu, Professor of Physics at Northeast Normal University (China), Materials World Network, US-China Workshop 2008
Citation preview
CAOFM
R
Center for Advanced Optoelectronic Functional Materials Research, Northeast Normal University, Changchun, China
[email protected]; [email protected]
Nanomaterials, Properties and Applications Nanomaterials, Properties and Applications
————ZnO and TiOZnO and TiO22
Yichun Liu
CAOFM
R
Recent years, my research interesting is concentrated on wide gap-band ZnO material,
GaN/i-ZnO/p-ZnO UV EL devices, in particular, on the growth of p-ZnO films and nano-ZnO with different structures, core/shell, rod, et al.
Up to now, more than 120 scientific papers had been published for scientific exchange and cited over 1000 times.
From 2007, my part interesting transfer to the application of ZnO QDs in biology molecule detection, and photocatalysis. Because the topic of this workshop is Nanostructure Materials for Global Energy and Environmental challenges.
In the following, only two suggestions related to this topic are given:
CAOFM
R
ZnO (core)/Au (Ag) (shell) with Raman spectroscopic fingerprints for DNA detection
TEM of ZnO (core)/Au (shell) nanocomposites
J. PHYS. CHEM. C 111 (2007) 3290-3293
ZnO: Environmentally friendly material;Strong resonant Raman scattering; Photostability
ZnO (core)/Au (shell):Photostability; Strong resonant Raman Spectroscopy; Water-soluble; Biocompatible
Part I
CAOFM
R
Raman Scattering (cm-1)
1LO
5LO4LO
3LO2LO
CAOFM
R
A
target
B
probe
3.DNA detection (target=part1 ( unknown ) +Part2 (DNA1 known vs PCR )
-S-A14-ATC-CTT-ATC-AAT-ATT
TAG-GAA-TAG-TTA-TAA-ATT-GTT-ATT-AGG-GAG
Nano-ZnO(core)/Au(shell)
TAA-CAA-TAA-TCC-CTC-A14-S-
CAOFM
R
EcEF
Ev
= 5.2 eV
ZnO
EF
= 5.1 eV
AuE0
ZnO
Au SERS
J.Phys.Chem.B, 2008,112,6484–6489
CAOFM
R
CAOFM
R
Yb3+
En
erg
y (1
03 cm
-1)
30
25
20
15
10
5
0
1040 nmPump
VisibleEmission
Up-conversionemission
Er3+
Suggestions:
ZnO:Er:Yb/Au
(core/shell)
up-conversion Emission/
detecting/Mapping/
optical fiber
Infrared 1.04μm,
penetrate skin,
Visible emission could be detected easily
Luminescence signal is stronger than Raman signal
CAOFM
R
TiO2 Photocatalysis: Advantages and Shortcomings
Advantages: 1) Cheap material
2) Nontoxic and stable
3) Suitable valence and conduction band positions
Shortcomings: 1) Charge recombination problem
Resolution: “Photochemical diode” type photocatalysts such as TiO2/SnO2, TiO2/Pt 2) Transparent for visible light
Resolution: non-metal doping, such as N, C, S-doped TiO2
3) Low extinction coefficient in UVA range due to its nature of indirect bandgap semiconductor
How to resolve this problem?
Environmental issues
Our Strategy for Highly Efficient Semiconductor Photocatalysis
ZnO: a direct wide band-gap semi-conductor with intense absorption in UVA; a chemically unstable oxide material, easy to be dissolved in acidic or alkaline medium
TiO2: a indirect band-gap semi-conductor with weak absorption in UVA; a chemically stable oxide material, stable in acidic or alkaline medium either in dark or under excitation.
E vs vacuum level
ZnO TiO2
e- e-
h+ h+
O2
O2-
RH
R
-2
-5
-6
-7
-8
-4
In such a array structure, UV-absorption and photoreaction can be site-separately carried out, which may favor the efficiency of photocatalytic process.
ZnO/nano-rode coreas antenna for UV light
TiO2/shell as reaction site
CAOFM
R
Nanomaterials education:
1.Nanomaterials interesting properties, quantum confine effect, optical properties, in particular, in the applications of Optoelectronic, energy, environment and biology;
2. High grade student, the course of Solid state physics, included nano-materials or low-dimensional materials.
3. It is need to enhanced the course of nanomaterials: Positive effect of nanomaterials, negative effect, side-effect
CAOFM
R
Nanomaterials education:4. Based on the experience, the physical knowledge is very important for the major of materials/deep thinking/new idea
5.Different level lectures for different grade;
6.Treating for students due to new technique and development;
7. Academic organization hold course lectures for new development in materials;
Thanks for NNSF and NSF