Life-time and line-width of individual quantum dots interfaced with graphene

TL;DR

This study investigates how interfacing quantum dots with graphene or metal surfaces affects their luminescence properties, revealing that conductive interfaces influence lifetime and spectral width without always causing quenching.

Contribution

It provides new insights into the effects of conductive surfaces on quantum dot luminescence, emphasizing the roles of screening and local density-of-states.

Findings

Quantum dots on conductive surfaces show shorter lifetime and broader line-width.

Fluorescence quenching is not always observed with conductive interfaces.

Local density-of-states influences lifetime measurements.

Abstract

We report on the luminescence's life-time and line-width from an array of individual quantum dots; these were interfaced with graphene surface guides or dispersed on a metal film. Our results are consistent with screening by charge carriers. Fluorescence quenching is typically mentioned as a sign that chromophores are interfacing a conductive surface; we found that QD interfaced with conductive layers exhibited shorter life-time and line-broadening but not necessarily fluorescence quenching as the latter may be impacted by molecular concentration, reflectivity and conductor imperfections. We also comment on selective life-time measurements, which, we postulate depend on the specifics of the local density-of-states involved.