Stable Semi-Hollow Gold-Silver Nanostars with Tunable Plasmonic Resonances Ranging from Ultraviolet–Visible to Near-Infrared Wavelengths: Implications for Photocatalysis, Biosensing, and Theranostics

This paper reports the fabrication of highly stable semi-hollow gold-silver nanostars (hAuAgNSts). Galvanic replacement between silver nanostars (AgNSts) and chloroauric acid afforded optically tunable hAuAgNSts with plasmonic resonances ranging from UV to visible to near-infrared wavelengths. Moreover, the compositionally unique bimetallic hAuAgNSts exhibited strong extinction maxima in the UV–vis range, which contrasts AgNSts (centered in the UV) and the more common gold nanostars (AuNSts; centered largely in the near infrared). Notably, the hAuAgNSts exhibited enhanced thermal and colloidal stability without the need for surface modification when compared to AgNSts and AuNSts. This latter feature offers additional opportunities in the fields of photocatalysis and photovoltaics as well as alternative strategies for post-synthetic modification that enable applications in biosensing and theranostics.