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

ABSTRACT

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 0.3 wt%. 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 m²/V·s and the slow ions with the mobility of about 10^–11 m²/V·s were detected in the NLC composites. 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.

Graphical Abstract

KEYWORDS:

• Nematic liquid crystal
• quantum dots
• dielectric loss tangent
• ionic currents
• ions density
• ions mobility

Acknowledgements

This work was supported by the Ministry of Education and Science of the Russian Federation under [No. 3.92.2014/K] and Russian Foundation for Basic Research under [Grant No. 16-02-00041 A].

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Ministry of Education and Science of the Russian Federation: Grant Number [3.92.2014/K]; Russian Foundation for Basic Research Grant Number [16-02-00041 A].