The paper presents on the synthesis and optical properties of mesomorphic composites, based on a glassy liquid-crystalline caprylate matrix, with CdSе/ZnS hetero-nanoparticles. The synthesis of complex core-shell semiconductor nanoparticles was carried out by fusing together a cadmium caprylate composite with CdSе nanoparticles and zinc caprylate composite with ZnS nanoparticles. The cadmium and zinc chalcogenide nanoparticles have been synthesized in molten cadmium caprylate and zinc caprylate respectively.
It has been found by optical spectroscopy that the have hetero-nanoparticles a core-shell structure. The effect of the composition (molar ratio of the components) of CdSе/ZnS hetero-nanoparticles on their spectral characteristics has been studied. It has been shown that the nanocomposites with hetero-nanoparticles are characterized by a more intense exciton fluorescence band than composites with individual CdSе or ZnS nanoparticles. It has been found that by varying the hetero-nanoparticle composition, one can change the core-shell thickness ratio and adjust thereby the absorption and emission band edge. As the number of ZnS nanoparticles in CdSе/ZnS hetero-nanoparticles increases some narrowing of the long- wavelength emission region first takes plase, which may be attributed to a reduction in the recombination of the smaller number of surface trapped exciton, and then, at a large ZnS content, a broadening of the long- wavelength emission region takes plase due to the extended CdSе/ZnS surface.
It has been found that the main contribution to the exciton fluorescence of nanocomposites with CdSе/ZnS hetero-nanoparticles is made by cadmium selenide nanoparticles, and that zinc sulfide nanoparticles enhance exciton fluorescence, also due to decrease in surface emission. It has been shown that the nanocomposites with hetero-nanoparticles are characterized by a more intense exciton fluorescence band that the nanocomposites with individual CdSе. The highest emission is observed in the case of the 35-55 % ZnS content of the shell, and at a smaller or larger amount of ZnS, emission intensity decreases.
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