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    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
    (Springer, 2022) Bozkurt, S.; Durmaz, M.; Erdogan, M.; Erdogan, C. Ozkaya; Capan, R.; Acikbas, Y.
    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.
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    Optical and organic vapor properties of Calix[4]arene based macrocyclic Langmuir-Blodgett thin films
    (Natl Inst Optoelectronics, 2021) Acikbas, Y.; Zeybeka, N.; Ozkaya, C.; Sirit, A.; Erdogan, M.; Capan, R.; Bozkurt, S.
    Surface Plasmon Resonance (SPR) optical chemical sensors based on 25,27-Bis(N-[[(2R)-2-hydroxy-3-[[(1R)-1-(hydroxymethyl)propyl]amino]propyl]asetamide))-26,28-dihydroxy-5,11,17,23-tetra(tert-butyl)calix[4]arene (NHDACx) films were fabricated to sense dichloromethane, acetone, and benzene at room temperature. Calix[4]arene based macrocyclic thin films, as gas sensing film, were fabricated by Langmuir-Blodgett (LB) thin film technique with different thicknesses, and characterized by SPR and UV-Visible spectrophotometer. The experimental SPR data were fitted using the Winspall software to evaluate optical properties of the NHDACx film such as the parameter of thickness and refractive index. Values of the thickness and refractive index of NHDACx LB films were determined as 1.29 +/- 0.06 nm for the thickness per monolayer, and 1.54 +/- 0.07 for the refractive index. Exposed to above mentioned organic vapors, the responses of the optical sensors, Delta I, were measured. Optical sensor with 7.9 nm NHDACx film shows higher response to the saturated concentration of all vapors than the others, due to the amount of the adsorbed vapor molecules onto the surface of NHDACx film. Sensing mechanisms are based on changing photodetector response and optical properties of the gas sensing element. As a result, NHDACx optical LB thin film sensors exhibits high response, a good sensitivity and selectivity for saturated dichloromethane vapor than other vapors. These optical thin film sensors were potential candidates for organic vapor sensing applications with simple and low cost preparation at room temperature.