OVERVIEWS OF INDEPENDENT STUDY:

SYNTHESIS OF ZnO-TiO2 CORESHELL NANOSTRUCTURES BY HYDROTHERMAL METHOD

HA NOI UNIVERSITY OF SCIENCE AND TECHNOLOGY**** ADVANCED TRAINING PROGRAM ****

Name : Hoàng Văn Ti n ếClass : MSE-K54ID Student : 20092697Instructor : Dr. Nguy n Duy Hùng-AISTễ

OUTLINE :

• Why i choose this topic?

• ZnO-TiO2 overviews

• Hydrothermal methods

• Process of researching

• Analysis method

• Results and discussions

• Summary

WHY I CHOOSE THIS TOPIC ?

- Buried contact solar cell

• Cadmium telluride solar cell

• Copper indium gallium selenide solar cells

• Dye-sensitized solar cell

• Gallium arsenide germanium solar cell

• Hybrid solar cell

• - Organic solar cell

- Nanocrystal solar cell- Plasmonic solar cell- Plastic solar cell- Polycrystalline solar cell- Polymer solar cell- Quantum dot solar cell- Solid-state solar cell- Thin film solar cell- Monocrystalline solar cell- Multijunction solar cell- ……………………….

Types of solar cell :

WHY I CHOOSE THIS TOPIC ?

• Harmful organic compounds in the ecological unit are the main concern for the scientific society, which is causative agent of water pollution and severe contamination of the environment. Waste-water containing organic dyes (organicpollutants) inhibit sunlight penetration which suppressesphotosynthetic reaction.

• Metal oxide semi-conducting nano materials have been proven to be very efficient photocatalysts for the degradation of organic dye pollutants with the help of solar light. In particular, TiO2 and ZnO are the most versatile semiconductor oxides with applications across a wide range from cosmetics to air purification.

• However, the poor consumption of solar energy and the short diffusion length of photogenerated exciton are the two key factors restrictive to further improvement of photocatalytic efficiency

• develop new and efficient sunlight-sensitive photocatalysts.

FTO :Fluorine doped Tin Oxide

Rutile-tetragonal Brookite-orthorhombic Anatise-tetragonal

TiO2 (rutile )

Lattice Constants, Е a = 4.593c = 2.958

- Pure titanium dioxide is colorless in the massive state, non-toxic, thermally stable, inert versus acids, alkalis and solvents, and insoluble. - Rutile is the most stable and the most abundant form- Nanocrystalline TiO2 usually exhibits a wider band gapthan that of the bulk (3.03 eV for rutile and 3.20 eV for anatise)

Refractive index n=2.54 for anatiseor 2.75 for rutile at λ = 550 nm)

HYDROTHERMAL METHODS

• The term “hydrothermal” usually refers to any heterogeneous reaction in the presence of aqueous solvents or mineralizers under high pressure and temperature conditions to dissolve and recrystallize materials that are relatively insoluble under ordinary conditions.

• Uses : A large number of compounds belonging to practically all classes have been synthesized under hydrothermal conditions: elements, simple and complex oxides , tungstates , molybdates , carbonates, silicates , germanates etc. Hydrothermal synthesis is commonly used to grow synthetic quartz , gems and other single crystals with commercial value.

EXPERIMENTALPROCEDURE

• Growth of ZnO nanorods array

• Deposition of TiO2 shells on ZnO nanorods

• Materials characterization

• X‐ray diffraction (XRD) used to phase characterization and crystalline size,

• Scanning electron microscopy (SEM) to morphology and microstructure investigations.

• Diffusive UV‐visible‐NIR spectrometry to band gap calculations

• Solar cell fabrication and testing

GROWTH OF ZNO NANORODS ARRAY

• Process :- Substrate preparation- Growth ZnO nanorod

• Prepare :-Zn(COOCH3)2.2H2O- Zn(NO3)2 .6H2O - DI water-Dimethylformamide (DMF):

(CH3)2NC(O)H-hexamethylenetetramine C6H12N4

-FTO substrate-Powder coating gun

SUBSTRATE PREPARATION

• Clean substrate

• 0.44g Zn(COOCH3)2.2H2O + 20ml DMF

• Dry substrate to150oC

• Coating

• Drying

GROWTH ZNO NANOROD

- temperatures : 800C

- Times : 1h -2h-3h

- Concentrations :

• 2 (Zn(NO3)2 .6H2O) :1 HTMA - 0.75 g Zn(NO3)2 .6H2O +150ml DI

• 0.35 g hexamethylenetetramine +100ml D

• 1 (Zn(NO3)2 .6H2O) :1 HTMA - 0.45 g Zn(NO3)2 .6H2O +150ml DI

• 0.42 g hexamethylenetetramine +100ml D

• 2 (Zn(NO3)2 .6H2O) :1 HTMA - 0.75 g Zn(NO3)2 .6H2O +150ml DI

• 0.35 g hexamethylenetetramine +100ml DI

Heat controllers

∆t < 1 0C

PHOTOLUMINESCENCE

381 nm

SEM ANALYSIS

DEPOSITION OF TIO2 SHELLS ON ZNO NANORODS

• Preparations :

• ZnO nanorods on FTO substrate