Rate of Excitation Energy Transfer between Fluorescent Dyes and Nanoparticles

TL;DR

This study investigates how resonance energy transfer rates depend on distance and orientation in systems involving fluorescent dyes and nanoparticles, revealing deviations from classical F"orster theory at short ranges.

Contribution

It provides new insights into the distance dependence of RET involving nanoparticles, showing a transition from F"orster-like to different power-law behaviors.

Findings

RET rate follows a d^(-sigma) dependence with sigma approaching 6 at large distances

At short distances, the RET rate is significantly lower than F"orster theory predicts

The exponent sigma varies from 3 to 4 at intermediate distances

Abstract

Long range resonance energy transfer (RET) between a donor and an acceptor molecule is increasingly being used in many areas of biological and material science. The phenomenon is used to monitor the in vivo separation between different (bio) polymers/units of (bio) polymers and hence the dynamics of various biomolecular processes. Because of the sensitivity of the rate on to the distance between the donor (D) and the acceptor (A), the technique is popularly termed as "spectroscopic ruler". In this work we examine the distance and orientation dependence of RET in three different systems: (i) between a conjugated polymer and a fluorescent dye, (ii) between a nanometal particle (NMP) and a fluorescent dye and (iii) between two NMP. We show that in all the three cases, the rate of RET follows a distance dependence of d^(- sigma) where exponent sigma approaches 6 at large d (F"orster type dependence) but has a value varying from 3-4 at short to intermediate distance. At short separation, the amplitude of rate is considerably smaller than predicted by the F"orster theory.