Using elemental Se and Ag to grow pure Ag2Se dendrites/dendritie-films of highly oriented (001) nanocrystals

A clean, facile route of using only common bulk selenium (Se) powder and silver (Ag) foil in a simple solvothermal process is developed to synthesize a film of silver selenide (Ag2Se) dendrites of highly oriented (001) nanocrystals. The simple process takes similar to 10 h at 160 degrees C in a common alcohol such as methanol or ethanol in an autoclave, and the reaction time is shorter than in many prevalent methods. The adoption of elemental Se and Ag (foil) in the synthesis eases the control of the purity of the product, simplifies the reaction steps, and reduces the costs, as the synthesis does not require Se and Ag compounds, and also requires no chemical additives other than an alcohol as solvent. The results support a mechanism of dissolution of the bulk-like Se powder in the solvothermal process, transport of solvated Se to react with Ag, nucleation of Ag2Se nanocrystals, surface-mediated, solvation-assisted surface diffusion of Ag2Se nanocrystals, and diffusion-limited aggregation of the Ag2Se nanocrystals through oriented attachment for the growth of dendrites having highly oriented (001) nanocrystals. The clean, relative facile route is practical for the fabrication of Ag2Se crystals/films with hierarchically ordered nanostructures for future applications in solar cell devices. More importantly, the same concept can be adopted for the synthesis of other nanomaterials with bulk elemental reactants with no reliance on chemical compounds or additives.