van Schooten, Kipp J. and Huang, Jing and Baker, William J. and Talapin, Dmitri V. and Boehme, Christoph and Lupton, John M. (2013) Spin-Dependent Exciton Quenching and Spin Coherence in CdSe/CdS Nanocrystals. NANO LETTERS, 13 (1). pp. 65-71. ISSN 1530-6984, 1530-6992
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Large surface-to-volume ratios of semiconductor nanocrystals cause susceptibility to charge trapping, which can modify luminescence yields and induce single-particle blinking. Optical spectroscopies cannot differentiate between bulk and surface traps in contrast to spin-resonance techniques, which in principle avail chemical information on such trap sites. Magnetic resonance detection via spin-controlled photoluminescence enables the direct observation of interactions between emissive excitons and trapped charges. This approach allows the discrimination of three radical species located in two functionally different trap states in CdSe/CdS nanocrystals, underlying the fluorescence quenching and thus blinking mechanisms: a spin-dependent Auger process in charged particles; and a charge-separated state pair process, which leaves the particle neutral. The paramagnetic trap centers offer control of the energy transfer yield from the wide-gap CdS to the narrow-gap CdSe, that is, light harvesting within the heterostructure. Coherent spin motion within the trap states of the CdS arms of nanocrystal tetrapods is reflected by spatially remote luminescence from CdSe cores with surprisingly long coherence times of >300 ns at 3.5 K, illustrating coherent control of light harvesting.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | CORE-SHELL NANOCRYSTALS; QUANTUM DOTS; MAGNETIC-RESONANCE; SURFACE TRAPS; RELAXATION; DYNAMICS; BLINKING; LIGHT; DARK; CDS; CdSe/CdS nanocrystals; spin coherence; electron-spin resonance; light harvesting; trap states; blinking |
| Subjects: | 500 Science > 530 Physics |
| Divisions: | Physics > Institute of Experimental and Applied Physics > Chair Professor Lupton > Group John Lupton |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 30 Apr 2020 12:00 |
| Last Modified: | 30 Apr 2020 12:00 |
| URI: | https://pred.uni-regensburg.de/id/eprint/17514 |
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