Dispersion of thiol capped AuNPs in rufigallol derivative discotic liquid crystal-Enhanced one dimensional electrical conductivity

ABSTRACT

Rufigallol is one of the earliest systems reported to form discotic columnar mesophase at room temperature. In the present study, we have studied the impact of surface-functionalised gold nanoparticles (AuNPs) on the impedance response of a rufigallol derivative discotic liquid crystal in the frequency range of 1 Hz–40 MHz. The experimental results show that nanoparticle doping marginally alters the permittivity of the discotic host and significantly increases its conductivity. A Debye-type relaxation process in the low MHz regime originates due to the hopping of mobile charge carriers and the alignment of dispersed AuNPs in the host matrix. The dispersed systems are also characterised using techniques, viz. Differential Scanning Calorimetry (DSC), Polarised Light Microscopy (PLM), Ultraviolet-visible (UV–Vis) spectroscopy and Small Angle X-ray Scattering (SAXS). Both dielectric and texture studies confirm the formation of a well-ordered columnar structure of the discotic phase at room temperature. These results are supported by SAXS studies as well, which suggest an increase in π- π orbital overlapping in dispersed samples. The study also illustrates the variation of different hexagonal lattice reflection planes with respect to the decrease in temperature.

KEYWORDS:

• Rufigallol
• discotic liquid crystal
• gold nanoparticles
• thiol-capped
• impedance measurements
• small angle X-ray

Acknowledgments

We wish to thank the Department of Science and Technology, Government of India, New Delhi, for financial support under FIST Grant No, SR/FST/PSI-216/2016. One of us (R.U.) thanks the University Grants Commission, New Delhi, for support through a University Research Fellowship. Rahul also thanks Mr. Abhinav Lal for his advice in some points.

Disclosure statement

No potential conflict of interest was reported by the author(s).