A new twist: controlled shape-shifting of silver nanoparticles from prisms to discs

A simple photoreduction method has been demonstrated for the preparation of prismatic silver nanoparticles (AgNPs) that reversibly transform into discs when placed in the dark. The photodevelopment and switchability of these particles were characterised by transmission electron microscopy (TEM) and optical absorption spectroscopy (UV-vis). The observed photomorphic particle transformations were attributed to the initial seeding concentrations that affect the morphological stability between the light- and dark-form shapes. The photomorphic effect was attributed to a competitive reaction that occurred between photochemical reduction of Ag⁺ onto the surface of AgNPs and the slower oxidation of AgNPs by 4,4′-(phenylphosphinidene)bis(benzenesulfonic acid)dipotassium salt (BSPP). The BSPP also acts as a limiting reagent by gradually oxidising to triphenylphosphine oxide (TPPO) which diminishes the reversibility of the photomorphic effect. Significantly, the light- and dark-state photomorphic capability of these AgNPs was successfully restored by the addition of BSPP.