Zinc oxide (ZnO) is a new inorganic material that has been used in a wide range of applications in rubber, dyes, inks, coatings, glass, ceramics and optoelectronics. ZnO nanoparticles are a new type of multifunctional metal oxide semiconductor material with a particle size between 1-100 nm and specific physicochemical properties. Due to the miniaturization of its particle size, the specific surface area increases dramatically compared to conventional ZnO used as an inorganic chemical material, and the surface molecular arrangement, electronic structure and crystal structure all change significantly, which has surface effect, small size effect, quantum size effect, macroscopic quantum tunneling effect, etc. It has special properties and applications in magnetic, optical, electric and catalytic fields that are incomparable to conventional ZnO. As a result, it has received extensive attention in recent years.
Fig. 1 ZnO crystal structures (Özgür, Ü.; et al. 2005).
Preparation Method of Zinc Oxide Nanoparticles
ZnO nanoparticles were first prepared by Japanese scientist Kanata et al. in the 1980s by gas-phase synthesis, and then more in-depth research was carried out on the preparation of ZnO nanoparticles in the world. At present, there are many preparation methods. The morphology and properties of ZnO nanoparticles vary from one preparation process to another, usually in the form of rods, flakes and spheres. ZnO nanoparticles are usually prepared by vapor-phase deposition, precipitation, sol-gel and solid-phase methods. The liquid-phase precipitation method, which is characterized by low production costs and high efficiency, is widely used in industry and is the main method for the preparation of zinc oxide nanoparticles.
| Methods |
Description |
| Vapor deposition |
Vapor phase deposition is the use of gas as a carrier to bring zinc-containing substances (often zinc salts or monomeric zinc) into a high temperature reaction environment, where they are transformed into a gas and reacted, and finally nuclei are created, grown and developed during cooling to form zinc oxide nanoparticles. These are generally classified as chemical vapor deposition, laser induced chemical vapor deposition and spray pyrolysis. The vapor phase deposition method has the problem of high energy consumption and high costs for industrial production. |
| Solid phase method |
The solid phase method involves mixing and grinding zinc salts or zinc oxides in a certain ratio, then heat treating the two to cause a solid phase reaction and grinding the product to obtain zinc oxide nanoparticles. The room temperature solid phase reaction method is characterized by low cost, simple experimental equipment, short process flow, easy operation and uniform particle size distribution. |
| Sol-gel method |
Sol-gel method, also known as the phase transition method, zinc oxide nanoparticles are produced by using zinc salts or alcohol salts as the zinc source, firstly by hydrolysis and condensation reactions to obtain a stable and transparent sol-gel, then by polymerization into a gel with a solvent inside, and dried and heat-treated to produce zinc oxide nanoparticles. |
| Liquid precipitation method |
Liquid phase precipitation is a method of adding a suitable precipitant to a solution of soluble zinc salts to form precipitated precursors of zinc cations, which are then filtered, washed, dried and calcined to obtain ZnO nanoparticles. |
Due to the small particle size of ZnO nanoparticles, large specific surface area and surface energy, it is easy to agglomerate, so the key to the preparation of ZnO nanoparticles is to control the particle size and reduce the agglomeration of powder.
Reference
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Özgür, Ü.; et al. A comprehensive review of ZnO materials and devices. Journal of Applied physics. 2005, 98(4).
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