Development\nof Hybrid Silver-Coated Gold Nanostars for Nonaggregated Surface-Enhanced\nRaman Scattering

Abstract

In\nthe ongoing search for ever-brighter surface-enhanced Raman scattering\n(SERS) nanoprobes, gold nanostars (AuNSs) have emerged as one of the\nbest geometries for producing SERS in a nonaggregated state. Despite\ntheir high enhancement factor, optical extinction from plasmon-matched\nnanoparticles can greatly attenuate the overall SERS intensity. Herein,\nwe report the development of a new hybrid bimetallic NS-based platform\nthat exhibits superior resonant SERS (SERRS) properties. In this new\nnanoplatform, coating AuNSs with a subtotal layer of silver (AuNS@Ag)\ncan further increase their SERRS brightness by an order of magnitude\nwhen being interrogated by an off-resonant excitation source. Silica-encapsulated\nAuNS@Ag nanoprobes were injected intradermally into a rat pelt, where\nSERRS was readily detected with higher signal-to-noise than nanoprobes\nprepared from AuNS. Moreover, these off-resonance AuNS@Ag nanoprobes\ndid not cause any gross photothermal damage to tissue, which was observed\nwith the plasmon-matched AuNSs. This novel SERRS-active hybrid nanoprobe\nexhibits high SERRS brightness and offers promising properties for\nfuture applications in sensing and molecular imaging.