The bisbenzothiazole-p-tert-butylcalix[4]arene-thiourea Langmuir–Blodgett thin films: preparation, optical properties, swelling dynamics and gas sensing properties via host–guest principles

Abstract

Calix[4]arene-based materials have been investigated to develop selective, sensitive, and low cost chemical sensors due to their simple, low cost synthesis, and wide range of chemical and physical properties. In this study, bisbenzothiazole-p-tert-butylcalix[4]arene-thiourea (BBTC[4]T) molecules were employed to produce thin films via Langmuir–Blodgett (LB) thin film fabrication technique. The optical properties and gas sensing abilities of these BBTC[4]T LB films were examined by Surface Plasmon Resonance (SPR) method. In order to illuminate the optical properties of calix[4]arene-based LB films the Winspall software was utilized by fitting the experimental data obtained from SPR device. The values of 1.23 ± 0.07 nm and 1.53 ± 0.05 were determined for the thickness per monolayer and the refractive index of BBTC[4]T-based LB films, respectively. The fabricated optical sensor was employed for its sensing abilities against to organic vapours (acetone, ethyl alcohol, methyl alcohol and isopropyl alcohol) via the mechanism of host–guest interaction. The current study also describes the diffusion coefficients of these organic vapours to illuminate the swelling dynamics’ BBTC[4]T-based LB thin films by performing the early-time Fick’s diffusion equation. The responses of calix[4]arene-based optical sensor in terms of the shift in reflective intensity and the values of diffusion coefficients showed that BBTC[4]T molecules can be developed as potential chemical sensor element for acetone vapour compared to alcohol vapours.