Optical properties and zeta potential of carbon quantum dots (CQDs) dispersed nematic liquid crystal 4′- heptyl-4-biphenylcarbonitrile (7CB)

In this work, carbon quantum dots (CQDS) of three concentrations 0.1, 0.2 and 0.5 wt% have been dispersed in nematic liquid crystal 4'-Heptyl-4-biphenylcarbonitrile (7 CB). The results on the optical properties and zeta potential of pure and CQDs dispersed nematic 7CB have been reported. It has been observed that the dispersion of CQDs in host nematic matrix induces quenching of photoluminescence and reduces the Ultra-Violet-Visible (UV-Vis) absorbance of pure nematic at a lower wavelength. From the result of fluorescence decay profile, the fluorescence life time of pristine and dispersed nematic systems have been obtained. No remarkable changes in nematic lifetime in the presence of CQDs have been observed, which confirm that no energy is transferred from nematic to CQDs. Further, it has been found that due to dispersion of CQDs the numerical values of zeta potential are increased for the dispersed systems with 0.1 and 0.2 wt% concentrations of CQDs as compared to pure 7 CB. This result demonstrates that the study of zeta potential provides useful information on the stability and aggregation of the CQDs dispersed nematic systems.