Energy Transfer from Individual Semiconductor Nanocrystals to Graphene

TL;DR

This study investigates how energy transfer from photoexcited nanocrystals to graphene affects fluorescence, revealing layer-dependent transfer rates crucial for applications in photovoltaics and molecular sensing.

Contribution

It provides the first quantitative analysis of energy transfer rates from individual nanocrystals to graphene layers, validating a dipole approximation model.

Findings

Energy transfer rate to single-layer graphene is ~4 ns^-1.

Transfer rate increases with more graphene layers.

Quantifies fluorescence quenching by graphene.

Abstract

Energy transfer from photoexcited zero-dimensional systems to metallic systems plays a prominent role in modern day materials science. A situation of particular interest concerns the interaction between a photoexcited dipole and an atomically thin metal. The recent discovery of graphene layers permits investigation of this phenomenon. Here we report a study of fluorescence from individual CdSe/ZnS nanocrystals in contact with single- and few-layer graphene sheets. The rate of energy transfer is determined from the strong quenching of the nanocrystal fluorescence. For single-layer graphene, we find a rate of ~ 4ns-1, in agreement with a model based on the dipole approximation and a tight-binding description of graphene. This rate increases significantly with the number of graphene layers, before approaching the bulk limit. Our study quantifies energy transfer to and fluorescence quenching by graphene, critical properties for novel applications in photovoltaic devices and as a molecular ruler.