English abstract
Förster resonance energy transfer (FRET) is a non-radiative excitation energy transfer from the donor to the acceptor. Since the energy transfer rate has
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dependence of donor-acceptor distance, FRET process is highly sensitive to the variations of donor-acceptor distance. However, in such donor-acceptor assembles, the photoluminescence quenching of the donor cannot be solely assigned to the FRET process, rather non-FRET process, for example, trapping of photoexcited donor charge carriers into trap states formed due to the attachment of acceptor, is also highly probable.
In this project firstly we investigated FRET from InP/ZnS QDs to Sulforhodamine640 (zwitterionic), Rhodamine640 (cationic) and Nileblue690 (cationic) dye molecules using photoluminescence quenching as a tool. Our steady state and time-resolved Stern-Volmer analysis reveal the difference in the interactions of dye molecules with the QD surface. Further, 10 to 20% difference between the dynamic (Kd) and static (Ks) quenching constants indicate that in addition to the FRET process, trapping of CB electron into the dye-induced surface states is operative.
Secondly, we investigated the FRET cascade from InP QDs to Rhodamine640 and then from Rhodamine640 to different acceptors (Nileblue690, Oxazine725 and Oxazine750) in QD-dye-dye assemblies. Our results show that multiple energy transfer pathways present in such nanoassemblies leads to the excitation energy transfer from one location to another. We believe that our findings shed some light on the field of artificial light harvesting and imaging applications.
