Regensburg 2013 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 27: Nanoparticles and Composite Materials II

CPP 27.4: Talk

Wednesday, March 13, 2013, 15:45–16:00, H39

Electrochemical Manipulation of Single CdSe/ZnS Quantum Dots — •Nicole Amecke, David Plotzki, and Frank Cichos — Molecular Nanophotonics Group, University of Leipzig

Despite immense research on semiconductor quantum dots (QDs), the mechanisms of their intensity fluctuations remain a highly speculative subject. Most fluctuations are attributed to non-radiative decay channels arising from charges and fluctuating trap states at the QD interface, surface or close environment. A more specific assignment is difficult, especially due to the extraordinary statistics, which resemble power law distributions of bright and dark periods over several decades in time. With electrochemistry we can access those trap states as well as charges, while simultaneously monitoring QD intensity, lifetime and spectra. In this way we can observe the influence of reduction and oxidation processes on the fluorescence of each single QD. We find, that there is a preferred electrochemical potential for QD-fluorescence. Lower potentials introduce electrons in the conduction band, while higher potentials introduce trap states for the electron. The desired potentials depend on substrate, QD size and vary from dot to dot. The time dependence of the reaction to a potential step indicates a rearrangement of traps and charges in the QD environment.