Regensburg 2022 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 12: Poster 1
CPP 12.58: Poster
Montag, 5. September 2022, 18:00–20:00, P1
Dye-induced Fluorescence Quenching of Quantum Dots having Different Excited State Lifetimes and Confinement Potentials — •Saleem Al-Maskari1, Abey Issac1, Eklas Al-Ghattami1, SR Varanasi1, R.G. Sumesh Sofin1, and Osama K. Abou-Zied2 — 1Department of Physics, College of Science, Sultan Qaboos University, Muscat, 123, Oman — 2Department of Chemistry, College of Science, Sultan Qaboos University, Muscat, 123, Oman
We study the role of quantum confinement and the excited-state lifetime on the fluorescence quenching of heavy metal free quantum dots (QDs). Two different types of QDs are selected, namely CuInS2/ZnS (CIS) and InP/ZnS (InP). Quantum confinement in CIS QDs is weak (exciton Bohr radius aB = 4.3 nm versus particle size = 3.5 nm) whereas that in InP QDs is strong (aB = 15 nm versus particle size = 3.9 nm). Moreover, the excited-state lifetime of CIS QDs is ca. 298 ns whereas that of InP QDs is ca. 37 ns. Rhodamine 575 (Rh575) dye molecules adsorbed on the surface of QDs are used as the quencher. Stern-Volmer analysis of steady-state and time-resolved optical spectroscopy data reveal that in CIS-Rh575 and InP-Rh575 assemblies, although static and dynamic quenching are present, dynamic quenching is dominating. Further, quenching is more efficient in CIS-Rh575 assembly. We propose a model based on the quantum mechanical tunneling of the excited QD electron onto the dye induced surface states and subsequent non-radiative relaxation as the quenching mechanism. In addition, the long-lived excited state of CIS QDs support the tunneling mediated quenching in CIS-Rh575 assembly.