Synthesis and Surface Coatings of Anisotropic Au Nanoparticles

Gold nanoparticles of anisotropic shapes have diverse structures and functions. Single nanoparticles with anisotropic shapes can be potentially used for optical contrast enhancements and photothermal treatment, and when in the assembled form, they can offer additional photonic properties and even chiroptical responses. In particular, anisotropy in the surface chemistry of nanoparticles can bring in additional functionalities in controlling interparticle interactions during assembly processes as well as determine how nanoparticles interact with the surrounding environment in drug delivery applications. Here we report our efforts on inducing anisotropic surface coating of Au nanoparticles by post-synthesis surface functionalization of thermal responsive polymers. We first synthesize Au nanocages by conducting a galvanic replacement reaction with Ag nanocubes, and then decorate specific sites of the Au nanocages with poly(N-isopropylacrylamide) (PNIPAM) to encapsulate cargoes inside nanocages. We foresee this design of anisotropic coating of polymer on Au nanocages can offer a controlled way to release cargoes only when the system is triggered by infrared light and when heat is produced by the photothermal effects of the nanocages, which will be important for their use in drug delivery applications.