Hierarchical Au Nanoisland Arrays for Anticounterfeiting Surface-Enhanced Raman Scattering Stamps

Abstract

Plasmonic nanostructures of hierarchy allow for the integration of the functions of different domains and, importantly, provide built-in nanogaps and hotspots due to the intrinsic coupling effect. Although they are badly needed for a range of applications, including surface-enhanced spectroscopies, chem/biosensing, and others, simple and fast preparation of plasmonic hierarchical nanostructures remains a challenging goal. Here, the growth of hierarchical Au nanoisland arrays in a reactant in/target produced fashion is communicated. By a single-step quick injection, uniform Au nanoisland arrays with intense built-in hotspots could be produced within minutes through competitive balance between the reaction rate and seed surface passivation using a strong binding ligand. The experimental results and theoretical simulations revealed a strong electromagnetic enhancement effect of the Au nanoisland arrays. Stable anticounterfeiting SERS labels were realized by stamping the nanoisland array-based ink on an ordinary paper, by which dyes of similar appearance can be easily discriminated.