Preparation, Characterization Of Metal-Semiconductor Composite Nano-materials

(1) CdS nanoparticles protected by surfactant AOT were prepared by reverse-micelle method. The surfactant AOT was washed away by water. By adding enthanol of different quantity, the polarity of dispersed medium was regulated and the CdS nanoparticles of different sizes were separated. The effect of CdS nanoparticles in different alkyl solvents was studied. The results identified that CdS nanoparticles synthesized with reverse-micelle method distributed uniformly; When the surfactant AOT was washed away, the fluorescence of CdS nanoparticles increased; When the CdS nanoparticles were refluxed, the diameter became larger and the intensity of the fluorescence weakened; CdS nanoparticles were separated by adjusting the polarity of dispersed medium via enthanol; The longer chains of the alkyl solvents, the larger diameter of CdS nanoparticles were formed. Physical properties and EO characteristics of CdS nanoparticles doped and pure 5CB liquid crystal cells were studied.(2)The mixture of Au@CdS and CdS nanoparticles was obtained by reverse-micelle method with dioctylsulfosuccinate sodium salt (AOT) as surfactant, which was replaced by n-dodecanethiol. The Au@CdS and CdS nanoparticles were efficiently separated by adjusting the polarity of dispersed medium via enthanol. The results showed that the smaller size of CdS nanoparticles, the easier to grow on Au nanoparticles. However, CdS nanoparticles of big sizes only could be partly coated or could not. We found that Au@CdS nanoparticles of different sizes were obtained from the first separation to the third separation, pure CdS nanoparticles could be obtained from the fourth separation, they all showed good photoluminescence properties(3) CdS/Au nanoparticles were synthesized in reverse micelle solution and aqueous phase, respectively. The size distribution of CdS/Au nanoparticles prepared in reverse micelle solutions was very asymmetric.The CdS/Au nanoparticles of different sizes could be obtained after centrifugation. The fluorescence disappeared when Au nanoparticles were coated on the surface of the CdS nanoparticles. The CdS/Au nanoparticles prepared in aquous solution distributed asymmetrically and the diameter was not uniform. When the CdS/Au nanoparticles were refluxed 3 h under the temperature of 80℃, we found that the nanoparticles distributed symmetrically and the diameter was almost uniform. When the CdS/Au nanoparticles dissloved in 0.1 M HCl, the nanoparticles would congregate. The fluorescence also disappeared when Au nanoparticles were coated on the surface of the CdS nanoparticles.(4) Pt nanoparticles separately surface-modified by Au and Ag atoms were syntheized by the reduction of HAuCl4 by hydrogen absorded on the Pt nanoparticles with the protection of PVP. The effects of the amount of Au and Ag to the catalytic activities were studied.The results showed that when the molar of Au to Pt was 0.01 and the molar of Ag to Pt was 0.005, Pt nanoparticles all showed high catalytic activity.