The Study Of Controllable Synthesis Of Homogeneous Trigonal Te/Se Alloy Nanocrystals

Semiconductor nanomaterials have many unique structure/shape dependent optical, electrical, chemical and magnetic characters, which leads to controllable synthesis nanostructures has been extensively studied for many years. Te, Se and Te/Se alloys exhibits interesting properties in photoconductivity, thermoelectric, low melting point and high redox acitivity, which provide a great potential to fabricate functional nano-devices. However, the studies of Te/Se alloys in the early works are not sufficient, and the diversity and synthesis method of Te/Se alloys need to be expanded. A convenient method has been developed for controllable synthesis of homogeneous trigonal Te/Se alloy nanocrystals(t-Te/Se ANCs) with diverse morphologies, aspect ratios and compositions at room temperature within aqueous solution.1. The evolution of t-Te/Se ANCs’ morphology was primarily in two paths by tuning the initial molar ratio of Te O2 to H2 Se O3(x(Te:Se)) in the precursors: the generation of trigonal Te/Se alloy tri-fold nanorods(t-Te/Se ATNRs) when the value of x(Te:Se) is from 30:1 to 10:1; trigonal Te/Se alloy single nanorods(t-Te/Se ASNRs) were formed when x(Te:Se) ranging from 200:1 to 100:1 or 2:1 to 1:1. These alloy nanorods were generated in a self-seeding process, and the nanocrystal was homogeneous alloy nanocrystal which grew alone the [001] direction.2. The UV-Vis spectra, crystal structures, compositions and Raman spectra of these nanorods have also been analyzed in detail. The characteristics of those respects were changed according to the change of t-Te/Se ANCs morphologies. With longer length of t-Te/Se ANCs the UV-Vis spectra showed a blue shift. The crystal structures, compositions and Raman spectra got closer to trigonal Se(t-Se) as the value of x(Te:Se) became bigger.3. The growth mechanisms of t-Te/Se ANCs has been studied. The TEM(Transmission Electron Microscopy) of t-Te/Se ANCs at different stages depicted that the formation of t-Te/Se ATNRs and t-Te/Se ASNRs had different nucleation process. The generation of t-Te/Se ASNRs just grew bigger from the initial hexagonal nuclei(seeds), while t-Te/Se ATNRs had a separate nucleation which had another three nucleation on the edges of the seeds. This specific morphology evolution may be caused by the different chemical and crystallinity between Te and Se, so the different mole ratio has resulted in different growth paths.