Oriented crystallization of ultra-thin (2 nm) gold nanoplatelets inside a reactive hydrophobic polymeric matrix

The synthesis of an amphiphilic polymer based on a polysiloxane backbone with grafted propyloxy-citrate moieties is described. Aqueous solutions of this polymer are able to spontaneously reduce gold cations and direct gold metal crystal growth, yielding ultrathin (2 nm) crystalline nanoplatelets that have an exceptionally high aspect ratio: they are in excess of hundreds of nm in width. The growth process is accelerated by light and significantly controlled by pH: at pHs above 7, particles instead of platelets are formed.