Highly controlled bifunctional Ag@rubrene core–shell nanostructures: surface-enhanced fluorescence and Raman scattering

Abstract

Well-dispersed Ag@rubrene core–shell nanostructures have been fabricated by an in situ chemical reaction route. The reduction in cationic precursors of rubrene˙⁺ by Ag atoms generated neutral rubrene molecules which had a local high concentration to realize the site-specific nucleation, and followed by the in situ growth of rubrene shell. The rubrene shell thickness can be highly tuned from 2 to 16 nm by adjusting the amount of rubrene˙⁺ radical cations. Such core–shell nanostructures have significant integrated multiple enhanced optical signal outputs: thickness-dependent fluorescence and SERS signals. The results show that the shell thickness and the match of local surface plasmon resonance and the excitation band of rubrene played dominant roles in fluorescence enhancement. Additionally, these nanostructures integrating the Raman-active substrate with Ag colloidal nanoparticles could obtain an enhancement factor (EF) of ∼10³.