Modify Ag₂Se Nanostructures Via Laser Ablation--process And Mechanism

In this thesis, we developed a new technique of pulsed laser irradiation to modify the morphology of Ag2Se nanostructures and investigated the mechanism of shape transformation in detail. On the other hand, we successfully dissolved Se powder in ethanol with the help of high temperature and high pressure created by laser ablation.Ag2Se nanochains, nanopaticles with facts, and nanospheres were obtained via a chemical route. By using nanochains as the raw material, we successfully executed the shape modification in solution by pulsed-laser-induced decomposition or phase transformation. The power density of pulsed laser is found critical on the temperature rise of the nanoparticles and then the final morphology of the product. Correspondingly, nanorods and nanospheres can be obtained via solid phase transformation at a low power density and via pyrolysis at a high power density. The Ag2Se hexahedronal nanoplates and nanocubes can also be obtained at different irradiation doses, and particularly, the hexahedronal nanoplates are synthesized for the first time. The structural change can be well explained by employing Ag-Se diagram.Further, we successfully dissolved Se powder in ethanol through high temperature and high pressure created by laser ablation, as a sequence, Se nanosphere and nanowire were formed. Our work demonstrates that laser ablation is a new method to prepare selenium source.