Highly luminescent nanocomposites of nematic liquid crystal and hybrid quantum dots CdSe/CdS with ZnS shell

Abstract

This work is focused on synthesis of highly luminescent hybrid CdSe/CdS ”core/shell” quantum dots (QDs) with different core sizes and an additional ZnS shell. These quantum dots were doped into a nematic liquid crystal (NLC) phase to obtain new composites. According to the dielectric and femtosecond laser spectroscopy data, sizes of the QD cores and built-up additional ZnS shells are correlated with luminescence and dielectric characteristics of the ZhK-1282 and QD composites. With larger QD cores in the ZhK-1282, a decrease in dielectric relaxation frequency of the LC molecules rotating around their short axis is observed, same for the activation energy of this process. A shift to a shorter wavelength of the LC main luminescence peak and the strong luminescence quenching effect can be observed for the composites with the 2 nm QD cores. This effect is the result of nonradiative excitation energy transfer from LCs to QDs in the composite. The adhesion work values have been calculated for all the samples, alignment substances and substrates. Optimized homeotropic aligning layers with the best composite anchoring parameters have been selected both for normal glass and glass with a sputtered indium tin oxide (ITO) layer.