A. Daud, K. A. Wahid, W. Khairul
Jul 1, 2019
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Influential Citations
9
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Journal
Organic Electronics
Abstract
Abstract Ethynylated-thiourea derivatives of 4-ethylbenzoyl-3-(4-ethynylbenzonitrile-phenyl)-thiourea (2a), and 4-methylbenzoyl-3-(4-ethynylbenzonitrile-phenyl)-thiourea (2b) were successfully designed, synthesised, characterised and were used as sensing layers for the detection of carbon dioxide (CO2) gas. Resistive-type CO2 gas sensor featuring 2a and 2b (6 μL with concentration of 1 × 10−3 M) were drop-coated onto interdigitated electrodes (IDEs) surface. The surface morphology of coated IDEs with 2a and 2b were analyzed via Scanning Electron Microscopy (SEM). Upon exposure to 10–1000 ppm CO2 at 65–70% relative humidity (RH), their synergistic effects on CO2 sensing were subsequently examined through the variance in resistance values before and after exposure to CO2. The response (%) of these sensors increased significantly to a value of 25% operated at room temperature upon the increment of CO2 concentration. Both sensors showed no obvious deterioration in the sensing response during recurrent usage which gave the good indicator of the regeneration and reproducibility technique with low relative standard deviation (RSD) values in the range 0.174%–1.698%. Furthermore, they also showed fast response (τres) and recovery (τrec) time significantly for CO2 absorption and desorption. Their molecular response towards CO2 and mechanism of detection were evaluated via density functional theory (DFT) at B3LYP/6-31G (d,p) level of theory. The unique properties of ethynylated-thiourea derivatives are attributed by the presence of -NH-C=O for H-bonding interaction between ethynylated-thiourea derivatives and CO2 analyte.