Single-step generation of fluorophore-encapsulated gold nanoparticle core–shellmaterials

Abstract

We report a simple route to produce fluorophore-encapsulated gold nanoparticles (AuNPs)in a single step under aqueous conditions using the fluorophore 1-pyrenemethylamine(PMA). Different amounts of PMA were used and the resulting core–shell goldnanoparticles were analyzed using UV–visible absorption spectroscopy, fluorescencespectroscopy, and transmission and scanning electron microscopy. Electron microscopyanalysis shows nanoparticles consisting of a gold nanoparticle core which is encapsulatedwith a lower contrast shell. In the UV–visible spectra, we observed a significant red shift(37 nm) of the localized surface plasmon resonance (LSPR) absorption maximum (λmax) compared to citrate-stabilized AuNPs of a similar size. We attribute the prominent LSPRwavelength shift for PMA–AuNP conjugates to the increase in the local dielectricenvironment near the gold nanoparticles due to the shell formation. This simple,aqueous-based synthesis is a new approach to the production of fluorophore-encapsulatedAuNPs that could be applicable in biological sensing systems and photonic devicefabrication.