Narrowing of Plasmon Resonance Peaks as an Ensemble Effect

Abstract

The frequency of localized surface plasmon resonance (LSPR) displayed by gold nanoparticles (AuNPs) redshifts as a function of their local refractive index, which renders them valuable transducers for sensing applications. An ensemble hypothesis is presented herein, along with spectroscopic evidence, using the biotin-streptavidin system on immobilized AuNPs to interpret the decrease in ensemble linewidth (ELW) consistently observed upon functionalization of plasmonic nanoparticles and the subsequent analyte binding. These results demonstrate that ELW can be used to monitor recognition reactions, providing spectral details and a possible sensitivity enhancement to the conventional wavelength sensing. A novel sensing platform allowing the simultaneous measurement of both LSPR wavelength and ELW is proposed, which not only combines the advantages of both parameters but also permits real-time measurement and miniaturization.