Enhanced thermal stability of silica-encapsulated metal nanoshells

A silica-encapsulating layer of a 60-70 nm thickness is fabricated around composite nanoparticles consisting of a silica core and a gold shell (metal nanoshells). The outer silica layer provides greatly enhanced thermal stability to the nanoparticle, effectively raising its melting temperature by 300 degrees relative to uncoated nanoshells. Both spectroscopic and microscopic structural evaluations are used to assess changes in the nanostructure when subjected to potentially destructive heating cycles. This encapsulation method may prove valuable in enhancing the thermal stability of other types of assembled nanostructures and nanoscale photonic materials. (C) 2001 American Institute of Physics.