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Gospodinka Gicheva Anna-Maria Panniello Michela Corricelli Angela Agostiano Ceco Dushkin Georgi Yordanov 《Journal of Materials Science》2012,47(1):374-381
Fluorescent polystyrene microspheres are prepared by the incorporation of fluorescent CdSe/CdS core/shell semiconductor nanocrystals
(quantum dots, QDs) using the emulsification/solvent evaporation method. The radiative exciton recombination dynamics is investigated
by nanosecond time-resolved fluorescence spectroscopy at ambient conditions. The time constants of fast and slow fluorescence
decay in QDs, dispersed in toluene, were 3.5 and 17.8 ns, respectively. For the QD-tagged microspheres, the time constants
of fast and slow processes were ~2–3 and ~11–12 ns, respectively, and did not depend significantly on the QD-content of the
microspheres. The fast decay component could be attributed to the recombination of delocalized exciton in the internal core
states, and the slow component was attributed to the localized exciton in the surface states. It was found that the ratio
of amplitudes of the fast and slow processes also changed after incorporation of QDs in microspheres. The observed differences
in fluorescence decay between non-entrapped QDs and QD-tagged microspheres were probably due to energy transfer between the
nanocrystals, which were in close proximity inside the microspheres. The obtained fluorescent QD-tagged microspheres are characterized
by the other methods as well, which makes them of value for various applications as optical materials. 相似文献
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Georgi G. Yordanov Gospodinka D. Gicheva Ceco D. Dushkin 《Materials Chemistry and Physics》2009,113(2-3):507-510
This work presents the observation of a photo-activated fluorescence from core/shell quantum dots of CdSe/CdS incorporated in a poly(butylmethacrylate) matrix. Upon illumination with UV-light, the intensity of fluorescence from the quantum dots increases as seen by naked eyes at ambient conditions. This allows its utilization in optical memory media based on thin films of CdSe/CdS polymer nanocomposites suitable for practical application. The quantum dots are synthesized by the hot-injection method and embedded in poly(butylmethacrylate) matrix by radical polymerization with 1,1′-azobis-(cyclohexanecarbonitrile). The fluorescence of quantum dots quenched during the polymerization process, but appeared again after illumination of the nanocomposite material with UV-light. The fluorescence properties of quantum dots are governed by the presence of trioctylphosphine oxide in the matrix, which allows control of the optical memory effect. 相似文献
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A method for solving a heat-conduction problem for multiply connected domains is proposed based on consecutive solution of problems for doubly connected domains. To provide an example the heat-conduction problem is solved for a circle with two circular holes.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 31, No. 6, pp. 1120–1125, December, 1976. 相似文献
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