Influence of CdSe quantum dot on molecular/ionic relaxation phenomenon and change in physical parameters of ferroelectric liquid crystal

Abstract

Spherical cadmium selenide (CdSe) quantum dots (QDs), capped with octadecylamine, dispersed in ferroelectric liquid crystal (FLC), can remarkably alter the electro-optical (E-O) parameters (material parameters) of the host compound. Here we present an E-O, dielectric, surface anchoring and fluorescence study demonstrating that the physical properties of host FLC strongly depend on the dopant (QD) concentration. The addition of QDs in FLC changes the surface anchoring of FLC molecules, which results the change in E-O parameters of pristine FLC as a function of QDs concentration. The ion–polarisation coupling induces a new temperature-dependent weak ionic relaxation mode (TDWIRM) in FLC–QDs mixture at a certain concentration of QDs. Dipolar coupling between CdSe QDs and FLC molecules readjust the dielectric properties and molecular/ionic relaxation phenomenon in the FLC–QDs mixtures. The fluorescence of FLC–QDs mixtures is probably due to the coupling between the exciton and photon in LC medium, which leads the radiative process. The behaviour of fluorescence property of FLC–QDs mixtures reveals that the concentration of uniform-sized QDs only changes the fluorescence intensity of the FLC–QDs mixtures.

Keywords:

• quantum dot
• electro-optical property
• relaxation mode
• anchoring energy

Additional information

Funding

The authors are thankful to Department of Science and Technology, Government of India for the financial assistance for present work in the form of project. The author DPS is thankful to CSIR, India, for the grant of SRF fellowship [no. 09/107(0363)/2012-EMR-I]. DPS is also thankful to CEFIPRA for Raman-Charpak fellowship in France. Authors SP and TV are thankful to UGC, New Delhi for providing financial assistance in the form of UGC-BSR Fellowship. RM is thankful to UGC research award.