Ternary silver chlorobromide nanocrystals: intrinsic influence of size and morphology on photocatalytic activity

It is found that magnetic stirring can significantly influence diffusion of reaction species in high-viscosity solutions and thus the nucleation process of forming nanocrystals. This simple strategy, for the first time, has been successfully used to control the synthesis of phase-pure ternary silver chlorobromide (AgClxBr1-x) nanoparticles with varying sizes and morphologies while maintaining constant composition through co-precipitation reaction of Ag+ cations with both Cl- and Br- anions at different stirring rates. The as-synthesized AgClxBr1-x nanoparticles offer the unique opportunity to accurately study the dependence of their photocatalytic activity on particle size and morphology by taking photocatalytic decomposition of MB as an example: (1) in a solution with a high concentration of dissolved O-2, particle size represents the dominating parameter and larger particles are more active than small particles; (2) with low concentrations of dissolved O2, particle morphology becomes more dominating and nanocubes (mainly bound by {100} surface facets) are more efficient than nanospheres (mainly bound by {111} surface facets) towards decomposition of MB molecules. The results provide an unprecedented insight into the rational design and synthesis of efficient photocatalysts.