Thermosensitive Au-PNIPA yolk-shell particles as “nanoreactors” with tunable optical properties

We demonstrate that Au-silica-poly(N-isopropylacrylamide) (PNIPA) trilayer composite particles with controllable thickness of PNIPA out-layer can be developed via free radical polymerization using Au-silica core-shell particles as seed. The presence of Au-silica particles does not influence of thermosensitivity of PNIPA shell, which exhibits a similar swelling behavior as pure PNIPA microgels. The etching of silica midlayer by NaOH treatment leads to Au-PNIPA particles with yolk-shell structure. The obtained yolk-shell particles can work as “nanoreactors” for the further growth of Au core within the PNIPA shell via seeded growth approach, which is followed with interesting optical properties. In addition, the optical properties of the Au cores can be modulated by the volume transition of the PNIPA shell.