Suparna Sadhu

Surface energy transfer from rhodamine 6G to gold nanoparticles: A spectroscopic ruler

Here, the authors report the energy transfer from rhodamine 6G dyes to gold nanoparticles. There is a pronounced effect on the photoluminescence and a shortening of the lifetime of the dye when interacting with the Au nanoparticles. The calculated distance (d) between the donor and acceptor varies from 86.06to102.47A with changing the concentrations of Au and dye. Analysis suggests that the energy transfer from dye to the Au nanoparticles is a surface energy transfer process and follows a 1∕d4 distance dependence.

Donor-Acceptor Systems : Energy Transfer from CdS Quantum Dots/Rods to Nile Red Dye

We demonstrate strong evidence of shape-dependent efficient resonance energy transfer between CdS quantum dots (QDs) and quantum rods (QRs) (donor) to Nile Red dye (acceptor). We also report a simple solution-based method for the preparation of high quality CdS QDs and CdS QRs at relatively low temperature. The observed quenching of PL intensities are 78.8 % and 63.8 % for CdS QDs and QRs, respectively in the presence of Nile Red dye. The calculated energy-transfer efficiencies are 45 % and 19 % from QDs and QRs to dyes, respectively. The energy transfer varies with changing the shape of the nanoparticles. The estimated Förster distances (R(0)) are 37.8 and 33.8 A for CdS QDs and QRs, respectively. In the present study, the estimated distances (r) between one donor and one acceptor are 39.1 and 43.1 A for QDs and QRs, respectively, using the efficiency of Förster resonance energy transfer (FRET) which depends on the inverse sixth power of the distance of separations between one nanocrystal and one dye molecule. Considering single donor and multiple acceptors interactions, the calculated average distances (r(n)) between the donor and acceptor are 47.7 and 53.9 A for QDs and QRs, respectively. The steady-state and time-resolved spectroscopic analysis of nanoassemblies confirm the formation of one donor and multiple acceptors.

A brief overview of some physical studies on the relaxation dynamics and Förster resonance energy transfer of semiconductor quantum dots.

This article highlights some physical studies on the relaxation dynamics and Förster resonance energy transfer (FRET) of semiconductor quantum dots (QDs) and the way these phenomena change with size, shape, and composition of the QDs. The understanding of the excited-state dynamics of photoexcited QDs is essential for technological applications such as efficient solar energy conversion, light-emitting diodes, and photovoltaic cells. Here, our emphasis is directed at describing the influence of size, shape, and composition of the QDs on their different relaxation processes, that is, radiative relaxation rate, nonradiative relaxation rate, and number of trap states. A stochastic model of carrier relaxation dynamics in semiconductor QDs was proposed to correlate with the experimental results. Many recent studies reveal that the energy transfer between the QDs and a dye is a FRET process, as established from 1/d(6) distance dependence. QD-based energy-transfer processes have been used in applications such as luminescence tagging, imaging, sensors, and light harvesting. Thus, the understanding of the interaction between the excited state of the QD and the dye molecule and quantitative estimation of the number of dye molecules attached to the surface of the QD by using a kinetic model is important. Here, we highlight the influence of size, shape, and composition of QDs on the kinetics of energy transfer. Interesting findings reveal that QD-based energy-transfer processes offer exciting opportunities for future applications. Finally, a tentative outlook on future developments in this research field is given.

Composition effects on quantum dot-based resonance energy transfer

The effect of composition on resonance energy transfer between CdxZn1−xS quantum dot (donor) and Nile red dye (acceptor) is studied by steady state and time-resolved spectroscopy. The energy transfer efficiency varies from 14% to 47% with change in the composition from Cd0.31Zn0.69S to Cd0.62Zn0.38S nanocrystals which follows the Forster resonance energy transfer process. Considering single donor and multiple acceptors interactions, the calculated average distances (rn) between donor and acceptor are 25.8, 31.6, and 39.9A for Cd0.62Zn0.38S, Cd0.52Zn0.48S, and Cd0.31Zn0.69S nanocrystals, respectively.