Nanomaterials, Properties, and Applications: ZnO and TiO

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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

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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:

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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

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Raman Scattering (cm-1)

1LO

5LO4LO

3LO2LO

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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-

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EcEF

Ev

= 5.2 eV

ZnO

EF

= 5.1 eV

AuE0

ZnO

Au SERS

J.Phys.Chem.B, 2008,112,6484–6489

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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

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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

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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

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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