Optimized colloidal growth of hexagonal close-packed Ag microparticles and their stability under catalytic conditions

Crystal phase engineering of metal nano and microparticles is a new and promising route to tune their properties, complementary to their often exploited optimization via size and shape control. Ag microparticles have attracted much attention over the last decades due to their unique properties and their scalability. The colloidal synthesis of allotropic Ag microparticles has already been reported, but detailed knowledge of the synthesis and properties of allotropic Ag microparticles remains limited. In this work, we optimize the formation of hcp Ag via colloidal growth by tuning the chemical reduction kinetics and the surface stabilization through surfactants. The stability of allotropic Ag microparticles was investigated under catalytic conditions. It was shown that hcp Ag microparticles are stable under high pressures of N-2, O-2 and H-2 and in various solvents, but that their thermal stability is limited to 70 degrees C. These new insights on the stability of allotropic Ag microparticles will serve as a starting point to study the catalytic properties of allotropic Ag microparticles.