A general LbL strategy for the growth of pNIPAM microgels on Au nanoparticles with arbitrary shapes

A general method to encapsulate gold nanoparticles within thermoresponsive poly(N-isopropylacrylamide) (pNIPAM) shells is presented and demonstrated. The layer-by-layer (LbL) strategy was used to provide the metal nanoparticles surface with vinyl functional groups, from which pNIPAM can be readily grown. This method can be applied to the encapsulation of gold nanoparticles within a wide range of sizes, shapes and capping agents. We demonstrate here the encapsulation of cetyltrimethyl ammonium bromide (CTAB) stabilized Au spheres and poly(vinylpyrrolidone) (PVP) stabilized Au decahedra and nanostars, thereby exemplifying the fabrication of nanocomposites with tailored localized surface plasmon resonances (LSPR). Additionally, the total diameter of the Au@pNIPAM microgels, as well as the number of encapsulated metal cores, was varied through controlled addition of sodium dodecyl sulfate (SDS). The optical response could be thus modulated through temperature-induced local changes of the refractive index around the gold cores, as well as by plasmon coupling between metal nanoparticles located within the same microgel.