Investigation of electro-optical and dielectric properties of pure and dispersed nematic liquid-crystal

ABSTRACT

In this study, 4-(Trans-4ʹ-n-Pentylcyclohexyl) Benzonitrile (PCH5) has been employed as a host liquid crystal (LC) to disperse carbon quantum dots (CQDs). The investigation delves into the dielectric behaviour and electro-optical properties of dispersed nematic systems featuring both pure and CQD-incorporated compositions. We examined the impact of CQD dispersion on various parameters such as relative permittivity, dielectric loss, AC conductivity, birefringence, and threshold voltage in the nematic liquid crystal (NLC) PCH5 at concentrations of 0.1, 0.3, and 0.5 wt%. These properties demonstrate notable changes upon the addition of CQDs to the nematic PCH5 system, influenced by both the dopant concentration and the applied electric field. Birefringence, determined using the transmittance method, reveals higher values in dispersed systems, influenced by factors such as dopant concentration, temperature range, and chemical composition. Furthermore, the composite systems with dispersed CQDs exhibit significantly reduced threshold voltages. The observed findings are attributed to the interactions between CQDs and nematic molecules. Also, we explored potential applications for the dispersed systems investigated in this study.

GRAPHICAL ABSTRACT

KEYWORDS:

• NLC PCH5
• carbon quantum dots
• dielectric properties
• threshold voltage
• birefringence

Acknowledgments

The research grant from DST and SERB, as well as the experimental facilities provided by APJ Kalam Centre for Innovation, are all gratefully acknowledged by the authors. R. Manohar acknowledges the “MID CAREER AWARD” from the UGC. The author Govind Pathak is thankful to CSIR, New Delhi, India (File No. 09/0107(12335)/2021-EMR-I) for financial assistance in the form of Research Associate fellowship.

Disclosure statement

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

Additional information

Funding

The work is supported by the Science and Engineering Research Board (SERB) for providing the research grant as a research project (File No.: CRG/2021/006430).