Laser Activating Gold Catalyst For Liquid-phase Growth Of Nanostructures

In this thesis, we investigate the LAC synthesis of CdSe nanowires in liquid via pulsed laser irradiation of Au nanoparticles at room temperature. A possible mechanism of nanowire growth in LAC process was proposed. We also research on laser heating synthesis of Au@CdS core-shell nanostructure in solution. The main research results are as follows:We have demonstrated a laser-activating-catalyst growth of CdSe nanowires in solution. The pulsed laser can heat Au nanoparticles to a molten state, which decomposes the precursors and capture Se and Cd atoms for the catalytic growth of nanowires. The irradiation time, precursor ratio and laser intensity are identified as the crucial factors determining the formation of nanowires. Our strategy possesses several advantages over the traditional solution techniques, namely, great variety of catalysts(expanded to noble metals with high melting points), simple experimental set-up(without any protective gas), and easy positioning and patterning(by controlling laser path). Thus this LAC technique shows promise for extending to a wide range of semiconductor systems, breaking the limit of traditional catalytic growth and integrating nanowires into devices.We have demonstrated a laser heating synthesis of Au@CdS core-shell nanostructure in solution. Millisecond laser can heat dispersed Au nanoparticles in solution to a higher temperature by its selective heating property, thus the surface active sites increase, which can reduce the interface energy. The heat radiation of Au particles heating the surrounding solution, making the generation of CdS clusters by active precursors. Then the clusters gradually gathered on the surface of Au nanoparticles to fabricate Au@CdS sore-shell nanostructure. The activity of precursors, the irradiation time are the crucial factors determining the formation of the core-shell particles. Our strategy possesses several advantages over the traditional techniques. Laser selective heating will make the overall solution keep a low temperature, thus less by-products; and it is a “one-pot” method, simplifying the experimental set-up, and environmental friendly.