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

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Abstract
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 (R0) are 37.8 and 33.8 Å 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 Å 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 (rn) between the donor and acceptor are 47.7 and 53.9 Å for QD’s and QR’s, respectively. The steady-state and time-resolved spectroscopic analysis of nanoassemblies confirm the formation of one donor and multiple acceptors.