PERMITTIVITY DISPERSION FEATURES OF A NEMATIC LIQUID CRYSTAL WITH QUANTUM DOTS

Abstract

Subject of Research. The paper deals with research of dielectric properties of suspensions for a nematic liquid crystal (LC) with positive dielectric anisotropy Δε = 10.5, doped with semiconductor quantum dots (QDs) CdSe / ZnS, and dependence on their concentration in the range of 0.05-0.3 wt. %. Methods. The studies were carried out by the method of dielectric spectroscopy. A special flat titanium cell with the distance between the electrodes equal to 250 μm was used for the measurement. The voltage was applied to the electrodes. The dispersion of parallel and normal parts of the real and imaginary components of the dielectric permittivity was measured in the range from 50 Hz to 6.5 MHz at the orienting magnetic field equal to 4 • 105 A / m applied to a cell. Main Results. Deviation of the permittivity spectra of suspensions with QDs concentration growth was observed from a spectrum of the pure LC. It was caused by losses of free ions on the conductivity at frequencies below 103 Hz. The shift of a peak in the suspension spectrum at frequencies above 106 Hz is associated with relaxation of the LC molecules orientation. It has been shown that  lowering in the range of 103 -104 Hz with concentration increasing up to 0.3 wt. % did not exceed 4%. Practical Relevance Obtained results give the possibility to explain the change in macroscopic properties of the liquid crystal as a result of doping.

Keywords

• liquid crystals
• quantum dots
• dielectric spectroscopy