Simple synthesis of gold-decorated silica nanoparticles by in situ precipitation method with new plasmonic properties

We describe a simple method for the preparation of gold-decorated silica (SiO 2 ) nanoparticles (NPs) by the in situ precipitation method using simple BH 4 − ions reduction as a procedure, where BH 4 − ions are adsorbed onto PEI-functionalized SiO 2 NPs for stabilizing and reducing gold ions onto PEI-SiO 2 surface in water under ambient conditions. The result was 3-nm gold nanoshell NPs attached to SiO 2 core (~ 75 nm) with a surface plasmon resonance (SPR) at ~ 680 nm. SPR band is associated with Au NP aggregates that arise from strong interparticle interaction. This is an alternative to the gold-seeding methods and the use of anionic gold species for the obtention of gold-decorated SiO 2 NPs with an important red-shift in UV–Vis absorption and with potential applications in biosensors and photothermal therapy.