Light-Mediated Growth of Gold Nanoplates Carried Out in Total Darkness.

The plasmon-mediated growth of noble metal nanoplates through the reduction of metal precursors onto resonantly excited seeds lined with planar defects stands out as one of the triumphs of photochemistry and nanometal synthesis. Such growth modes are, however, not without their drawbacks and, with a lack of suitable alternatives, limitations remain on the use of light as a synthetic control. Herein, a two-reagent seed-mediated gold nanoplate synthesis is demonstrated as a photochemical pathway where the illumination of the growth solution, as opposed to the emerging nanoplates, is the key requirement for growth. With long-lived reaction products, it becomes possible to optically prime the growth solution prior to the insertion of substrate-immobilized seeds and then carry out a seemingly paradoxical synthesis in which light-mediated growth occurs in total darkness. The redox chemistry responsible for nanoplate growth can be induced either through the direct optical excitation of the growth solution using short-wavelength visible light or at longer wavelengths through the plasmonic excitation of spherical colloidal gold nanoparticles added to the growth solution. With the former acting as a high-level wavelength-dependent control over nanoplate synthesis and the latter demonstrating plasmon-mediated metal deposition that is spatially and temporally isolated from the resonant excitation, the study forwards the use of light as an external driver for nanostructure synthesis.