Plasmonic engineering of metal nanoparticles for enhanced fluorescence and Raman scattering

TL;DR

This study demonstrates how tuning the localized surface plasmon resonances of silver nanoparticles can significantly enhance fluorescence and Raman signals, with potential applications in sensing and spectroscopy.

Contribution

It provides a detailed analysis of how adjusting nanoparticle plasmon resonances affects fluorescence and Raman scattering, revealing optimal conditions for maximum enhancement.

Findings

Four-fold increase in fluorescence enhancement

Almost 30-fold increase in decay rate

Maximum SERS enhancement near plasmon resonance

Abstract

We have investigated the effects of tuning the localized surface plasmon resonances (LSPRs) of silver nanoparticles on the fluorescence intensity, lifetime, and Raman signal from nearby fluorophores. The presence of a metallic structure can alter the optical properties of a molecule by increasing the excitation field, and by modifying radiative and non-radiative decay mechanisms. By careful choice of experimental parameters we have been able to decouple these effects. We observe a four-fold increase in fluorescence enhancement and an almost 30-fold increase in decay rate from arrays of Ag nanoparticles, when the LSPR is tuned to the emission wavelength of a locally situated fluorophore. This is consistent with a greatly increased efficiency for energy transfer from fluorescence to surface plasmons. Additionally, surface enhanced Raman scattering (SERS) measurements show a maximum enhancement occurs when both the incident laser light and the Raman signal are near resonance with the plasmon energy. Spatial mapping of the SERS signal from a nanoparticle array reveals highly localized differences in the excitation field resulting from small differences in the LSPR energy.