Ionic impurities in nematic liquid crystal doped with quantum dots CdSe/ZnS

We investigated the dielectric losses and the ionic currents in the nematic liquid crystal (NLC) doped with semiconductor quantum dots (QDs) of CdSe/ZnS core - shell type and covered with trioctylphosphine oxide (TOPO) molecules. The dielectric loss tangent of the NLC composites increased with increasing the QDs concentration from 0.1 to 0.3wt%. The density of mobile ions in the composites increased linearly and the average values of ions mobility in the composites decreased with increasing the QDs concentration. The fast ions with the mobility of about 10(-10)m(2)/V<bold>s and the slow ions with the mobility of about </bold>10(-11)m(2)/V<bold>s were detected in the NLC composites</bold>. The growth of the content of slow ions took place with increasing the QDs concentrations. Increasing the dielectric loss tangent was observed with increasing the duration of sonication time of the NLC composites to prepare homogeneous suspensions. The fragmentation of the CdS/ZnS shell as a result of the sonication may lead to the appearance of the slow ions in the NLC composites. [GRAPHICS] .