Ultrathin Gold-Shell Coated Silver Nanoparticles onto a Glass Platform for Improvement of Plasmonic Sensors

A facile and effective approach for the improvement of localized surface plasmon resonance (LSPR) biosensors based on silver-core and gold-shell nanoparticles (Ag@AuNPs) on a glass substrate was investigated. Silver nanoparticles (core) with thin gold shells on a transparent indium tin oxide (ITO) coated glass surface were prepared by sequential electrodeposition, and the influence of the thickness of the gold shell was systematically investigated. The experimental results indicate that the properties of an LSPR band of ultrathin (similar to 1.3 nm) gold-shell coated silver nanoparticles are very similar to those of silver nanoparticles alone. The refractive index (RI) sensitivities of the metal nanostructures are calculated as 123 and 220 nm/RIU for the silver cores (similar to 480 nm of LSPR peak) and Ag@AuNPs (similar to 503 nm of LSPR peak), respectively, on the ITO substrate. The RI sensitivity of Ag@AuNPs was significantly enhanced by coating the silver nanoparticles with an ultrathin gold shell. This core-shell platform was also applied to the fabrication of biosensors. Thus, this strategy can be used to construct inexpensive, stable, versatile, and sensitive LSPR biosensors.