Bimetallic alloy Ag@Au nanorings with hollow dual-rims focus near-field on circular intra-nanogaps

Here, we report a highly sensitive and reliable surface enhanced Raman scattering (SERS)-based immunoassay using bimetallic alloy Ag@Au hollow dual-rim nanorings (DRNs) where two hollow nanorings with different diameters are concentrically overlapped and connected by thin metal ligaments, forming circular hot-zones in the intra-nanogaps between the inner and outer rims. Pt DRNs were first prepared, and then Ag was deposited on the surface of the Pt skeleton, followed by Au coating, resulting in alloy Ag@Au hollow DRNs. The chemical stability of Au and the high optical properties of Ag are incorporated into a single entity, Ag@Au hollow DRNs, enabling strong single-particle SERS activity and biocompatibility through surface modification with thiol-containing functionalities. When Ag@Au hollow DRNs were utilized as nanoprobes for detecting human chorionic gonadotropin (HCG) hormone through a SERS-based immunoassay, a very low limit of detection of 10 pM with high reliability was achieved, strongly indicating their advantage as ultrasensitive SERS nanoprobes.

Automated summary

We developed a highly sensitive and reliable immunoassay based on surface enhanced Raman scattering (SERS) using bimetallic alloy Ag@Au hollow dual-rim nanorings (DRNs). The Ag@Au hollow DRNs, consisting of concentrically overlapped hollow nanorings with different diameters connected by thin metal ligaments, exhibited strong single-particle SERS activity and biocompatibility. By using Ag@Au hollow DRNs as nanoprobes, a low limit of detection of 10 pM for human chorionic gonadotropin (HCG) hormone was achieved, highlighting their potential as ultrasensitive SERS nanoprobes.