| Autor: |
Dutta P; Department of Chemistry, Michigan State University, East Lansing, Michigan 48824-1322, USA., Tang Y; Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824-1322, USA., Mi C; Department of Chemistry, Michigan State University, East Lansing, Michigan 48824-1322, USA., Saniepay M; Department of Chemistry, Michigan State University, East Lansing, Michigan 48824-1322, USA., McGuire JA; Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824-1322, USA., Beaulac R; Department of Chemistry, Michigan State University, East Lansing, Michigan 48824-1322, USA. |
| Abstrakt: |
Organic free radicals related to the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical are known as photoluminescence-quenchers when coupled to group II-chalcogenide colloidal quantum dots (QDs), but the mechanism responsible for this phenomenon has so far remained unresolved. Using a combination of time-resolved photoluminescence and transient absorption spectroscopies, we demonstrate that photoexcited colloidal CdSe QDs coupled to 4-amino-TEMPO undergo highly efficient reductive quenching, that is, hole transfer from the valence band of the quantum dot to the organic paramagnetic species. Interestingly, the process is shown to occur on a subpicosecond time scale for bound 4AT; such a large rate constant for the extraction of holes from photoexcited CdSe QD by a molecular species is rare and underlines the potential that TEMPO derivatives can play in mediating efficient redox processes involving colloidal CdSe QDs. |
