Purcell radiative rate enhancement of label-free proteins with ultraviolet aluminum plasmonics

TL;DR

This study demonstrates the enhancement of ultraviolet fluorescence emission of label-free proteins using aluminum plasmonic nanoapertures, enabling improved detection and analysis of proteins through the Purcell effect.

Contribution

First complete characterization of UV Purcell effect and radiative rate enhancement in proteins using aluminum plasmonic nanoapertures, bridging a gap in nanophotonics research.

Findings

Significant radiative rate enhancement observed in proteins within aluminum nanoapertures.

Excellent agreement with calibration using UV fluorescent dye.

Potential for label-free single protein detection applications.

Abstract

The vast majority of proteins are intrinsically fluorescent in the ultraviolet, thanks to the emission from their tryptophan and tyrosine amino-acid constituents. However, the protein autofluorescence quantum yields are generally very low due to the prevailing quenching mechanisms by other amino acids inside the protein. This motivates the interest to enhance the radiative emission rate of proteins using nanophotonic structures. Although there have been numerous reports of Purcell effect and local density of optical states (LDOS) control in the visible range using single dipole quantum emitters, the question remains open to apply these concepts in the UV on real proteins containing several tryptophan and tyrosine amino acids arranged in a highly complex manner. Here, we report the first complete characterization of the Purcell effect and radiative rate enhancement for the UV intrinsic fluorescence of label-free \b{eta}-galactosidase and streptavidin proteins in plasmonic aluminum nanoapertures. We find an excellent agreement with a calibration performed using a high quantum yield UV fluorescent dye. Demonstrating and intensifying the Purcell effect is essential for the applications of UV plasmonics and the label-free detection of single proteins.