Preparation And Properties Of Multi-asymmetric Particles

In recent years, asymmetric particles have been widely investigated both theoretically and technologically. Because of its unique properties, asymmetric particles can be widely used in many fields. Such as, surfactants, chemical and biological sensors, electronic paper display materials, drug delivery and controlled release system. There are many simple methods can be used for the preparation of asymmetric particles, typically including phase separation-, immobilization-, microfluid-based strategies and micro-contact printing. In this paper, we use polymer (PS) masking method, combining with the reactive ion etching, controllable physical deposition, and chemical depositing reaction. The controllable multi-asymmetric particles can be obtained.In the second chapter, we use polymer (PS) masking method, combined with physical controllable deposition and chemical deposition reaction, multi-regional asymmetric particles were prepared. First of all, we process the surface of silica microspheres via two methods. The hydrophobic silica microspheres can be obtained. Through gas-liquid interface method, we fabricate monolayer of close-packed silica microspheres array on polymer film. Then, silica microspheres were sank into polymer to obtain partially masked silica array through heat treating due to their own gravity. Here, it allows control the masked area of silica by adjusting the thickness of PS film. These silver nanoparticles (Ag-NPs) grow on the exposed parts of silica after silver mirror reaction. It reveals the controllability of modification area. The distribution density and size of silver nanoparticles on silica can be by adjusted through changing the concentration of Tollens’reagent and the temperature of silver mirror reaction. Finally, we deposited metal on silica arrays partially modified with silver nanoparticles via the controllable deposition. Au/Ag-NPs/SiO2and Ni/Ag-NPs/SiO2can be obtained. Because of the unique optical properties of rough Au film and silver nanoparticle, the Au/Ag-NPs/SiO2particles have the potential for many areas, such as sensor. Through the magnetic testing, we found the Ni/Ag-NPs/SiO2maintain magnetic of nickel.In the third chapter, we use a combination of polymer masking, anisotropic plasma etching and physical deposition and chemical deposition reaction to prepare triblock multi-asymmetric particles. First of all, we process the surface of silica microspheres via two methods. The hydrophobic silica microspheres can be obtained. Through gas-liquid interface method, we fabricate monolayer of close-packed silica microspheres array on substrate. Then through two means of heat treatment and masking/unmasking, the partially masked silica arrays are obtained. It should be pointed that we can control the area of modified region of silica by adjusting the etching duration and thickness of PS film. Comparison of two methods, we found the heat treatment method is more suitable for larger modified areas. While masking/unmasking can more accurately control the size of modified areas. We turn the metal-silica array and then etch polymer. It can control the area of modified region of silica by adjusting the etching duration as well. The two poles of silica are modified with metal or Ag-NPs. Various multi-asymmetric particles can be obtained. We found that multi-asymmetric particles modified with nickel have maintained the magnetic of Ni. At the same time, the PS film is a good masking material. Even if the modifying reaction occurred into solution, the masking effect of PS film is quite well. In addition, materials used in the whole process of experiment are inexpensive and easy to obtain, the operation of experiment is simple and easy. Asymmetric particles obtained have multifunctional nature. Such as, magnetic, optical properties, and used as building blocks for complex structure.