Spectroscopic studies on liquid crystalline n-hexyloxy-cyanobiphenyl with dispersed citrate-capped gold nanoparticles in visible region

ABSTRACT

In the present manuscript, the characterisation was done on liquid crystalline n-hexyloxycyanobiphenyl (6ocb) compound with dispersed citrate-capped gold nanoparticles (Au NPs) at different concentrations. It is observed that the birefringence enhances with increase in concentration of Au NPs. Also, strong Vander Waal’s interaction takes place due to well capping between the Au NPs and 6ocb molecules. The refractive indices are determined by using modified spectrometer at different wavelengths. The orientational order parameter has been determined from various theoretical molecular internal field models namely, Kuczynski, Effective geometry, Haller’s extrapolation and Vuks. The dispersive power ω is estimated for two consecutive wavelengths for the case of <n>, n_e and n_o at different wavelengths found to be constant with temperature. The values of cross-over temperature, T_CO determined from the temperature gradients of n_e and n_o. Further, the refractive indices measured are fitted with two and three coefficient Cauchy model. Three coefficient Cauchy model is favourable than two coefficient Cauchy model for high birefringence liquid crystals. The results obtained are compared and discussed. Further, the phase transitions can be easily identified by GMSD Image processing method with Matlab tool to reduce the costly equipment’s usage in finding the heat flow with respect to temperature.

Graphical abstract

KEYWORDS:

• 6ocb
• birefringence
• orientational order parameter
• dispersive power
• cross-over temperature
• Cauchy’s constants

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work was supported by K L Deemed to be University under internal funding [Project File No: KLEF/IF/SEP/2019/002].