Preparation And Photoluminescence Study Of CdS Nanowires And Theirs Composite Structures

This article choosen CdS nanowires, CdS nanowires coated with thin layer of silicon dioxide(SiO2) and CdS-SiO2-Au hybird structure composed of CdS-SiO2 core-shell nanowires which decorated with dispersive colloidal gold (Au) particles as research objects. The band gap Eg of CdS is 2.42eV, as an important II-VI semiconductor, it has been widely used in virous opto-electric devices. But chemical synthesized CdS nanowires are usually not stable in air, to solve this problem, a thin layer of transparent SiO2 has been coated on the nanowires via a sol-gel method, which can further improve its optical properties. In addition, the surface plasman resonance properties of the colloidal gold particles has been widely studied for many years. The plasma enhanced photoluminescene emission in metal-semiconductor combined structure is seen as a feasible way to construct the high-powered light emission devices, because the emission efficiency is usually tunable by controlling the dielectric layer between the semiconductor and the metal, which have shown attractive application prospect in the bio-labeling, nonlinear optics, electricity as well as laser-emitting devices. The detailed contents of this dissertation can be summarized as follows:(1) 1D CdS nanowires which have big aspect ratio and uniform size were synthesized via a solvothermal method with cysteine as assistant agent. It was found that the molar ratio of CdO, S and cysteine used in the process play a crucial rule in the formation of such big aspect ratio CdS nanowires and only when the molar ratio satisfly the 1:1:1 give the expect products. Further more, the possible growth mechanism of CdS nanowire was discussed and the optical properties of nanowires were characterrized.(2) By using a sol-gel method, CdS nanowires were coated with a layer of SiO2 to form CdS-SiO2 core-shell structure. Various factors affecting coating thickness, and its corresponding UV-absorption and PL spectra of the coated CdS nanowires were analysized.(3) Uniform colloidal gold particles with size of about 15nm were synthesized via sodium citrate reduction of gold chloride acid. The absorption peak of the as obtained colloidal Au particles is around 520nm. Further more, gold nanoparticles supported core-shell CdS-SiO2 hybrid structures were facilely obtained by using amino-functionalized silica as interlinkers. The Au-nanoparticles plasma related photoluminescene properties of the Au-SiO2-CdS nanohybrids with different SiO2 thickness were studied by the nearfield scanning optical microscopy (NSOM).