Composition-dependent energy transfer from alloyed ternary CdSeS/ZnS quantum dots to Rhodamine 640 dye

Quantum dots (QDs), highly luminescent semiconductor nanocrystals, have found extensive applications spanning from optoelectronics to chemo- and biosensors to bioimaging. In addition to these QDs, semiconductor alloy nanostructures with tunable composition provide excellent material platform for biological applications. This paper reports the effect of composition of alloyed QDs on resonance energy transfer between hydrophilic ternary alloyed CdSeS/ZnS QDs (donor) and Rhodamine 640 dye (acceptor) employing steady state and time-resolved fluorescence spectroscopic techniques. Time-resolved decay curves of QDs obtained in the presence and absence of Rhodamine 640 dye have been recorded and the values of spectral overlap, Förster distance, and transfer efficiency are determined. The fluorescence resonance energy transfer of these systems was investigated as a function of spectral overlap between the QD donor emission and acceptor absorption as well as composition of the QDs. It is found that the efficiency significantly increases with varying compositions of the QD. In addition, the fluorescence quenching studies have been carried out using both absorption and emission data. The present study opens up the possibility of such QD-dye pairs performing as sensitive chemical and biosensors.