Nanomaterials, Properties, And Applications: Zno And Tio

Nanomaterials, Properties and Applications ——ZnO and TiO2

Yichun Liu Center for Advanced Optoelectronic Functional Materials Research, Northeast Normal University, Changchun, China [email protected]; [email protected]

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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 M F to this topic are given: O A

Part I ZnO (core)/Au (Ag) (shell) with Raman spectroscopic fingerprints for DNA detection ZnO: Environmentally friendly material; Strong resonant Raman scattering; Photostability

ZnO (core)/Au (shell): Photostability; Strong resonant Raman Spectroscopy; Water-soluble; Biocompatible

TEM of ZnO (core)/Au (shell) nanocomposites

J. PHYS. CHEM. C 111 (2007) 3290-3293

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4LO

1LO

2LO

5LO

3LO

Raman Scattering (cm-1 ) A

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3.DNA detection (target=part1 （ unknown ） +Part2 (DNA1 known vs PCR )

target A probe

B -S-A14 -ATC-CTT-ATC-AAT-ATT TAA-CAA-TAA-TCC-CTC-A14-S-

TAG-GAA-TAG-TTA-TAA-ATT-GTT-ATT-AGG-GAG

Nano-ZnO(core)/Au(shell)

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Au Φ = 5.1 eV

E0

ZnO Φ = 5.2 eV

Ec EF

EF ZnO Au

SERS

Ev

J.Phys.Chem.B, 2008,112,6484–6489

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Luminescence signal is stronger than Raman signal 30

Energy (103 cm-1 )

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Suggestions:

Up-conversion emission

ZnO:Er:Yb/Au

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(core/shell)

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up-conversion Emission/

10 5 0

Visible Emission

detecting/Mapping/ optical fiber

1040 nm Pump

Er3+

Yb3+

Infrared 1.04μm, penetrate skin, Visible emission could M be detected easily AOF

Environmental issues 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?

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Our Strategy for Highly Efficient Semiconductor Photocatalysis ZnO: a direct wide band-gap semiconductor 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 TiO2/shell as reaction site

-2 -4

ZnO/nanorode core as antenna for UV light

e-

e-

O2 O2-

-5 -6

In such a array structure, UVabsorption and photoreaction can be site-separately carried out, which may favor the efficiency of photocatalytic process.

RH

-7 -8

+

h+

ZnO

TiO2

h

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, sideeffect

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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 A

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