Abstract
Characterization of samples of cadmium selenide quantum dots (CdSe) QDs dissolved in toluene colloidal solutions at a concentration of 1.4 mg/ml was carried out through UV–Vis absorption and photoluminescence (PL) spectroscopy. The size-dependent absorption and red-shifted PL emission peak wavelengths could be tuned between 510–576 and 545–606 nm respectively. Optical absorption spectral measurements yielded CdSe QDs having diameters about ~ 2.44–3.69 nm with energy gaps 2.32–2.08 eV which are higher than the bulk CdSe (1.74 eV) reminiscent of quantum confinement. This is found to be in good agreement with the semi-empirical pseudopotential model. In addition, the first excitonic absorption transition 1S(e)1S3/2(h) oscillator strength and the corresponding fluorescence radiative decay time of CdSe QDs are assessed using relevant Einstein relations for absorption and emission in a two-level system. The elaborated calculations would anticipate that the transition oscillator scale with the CdSe QD radius as ~ R2.54. Correspondingly, the calculated radiative decay times decrease from 56.4 to 23.2 ns which scale with CdSe QDs radius as ~ R−2.155 in fairly good agreement with experimental values reported in the literature.
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Authors are deeply grateful to members of the Nanotechnology Lab. at the National Institute of Laser Enhanced Sciences (NILES) and the esteemed staff of the solid-state Lab. at physics department, faculty of science, Cairo University.
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Aboulfotouh, A., Fikry, M., Mohamed, M. et al. Spectroscopic study of oscillator strength and radiative decay time of colloidal CdSe quantum dots. Opt Quant Electron 50, 115 (2018). https://doi.org/10.1007/s11082-018-1375-6
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DOI: https://doi.org/10.1007/s11082-018-1375-6