A model compound of hybrid ethynyl-thiourea featuring nitro substitution at the para-position of the molecular framework was designed, synthesised and structurally elucidated. In this work, the characteristic response of the nitro-substituted ethynyl-thiourea derivative (NETh) towards carbon monoxide (CO) gas was evaluated via UV-Vis spectrophotometer under optimised absorbance response. NETh exposed to CO gas within the concentration range of 10-30 ppm exhibited the highest sensing response of 11.78% towards the lowest CO concentration (10 ppm). The calculated interaction distance and interaction energy between NETh and CO molecules were modelled using density functional theory (DFT) via Gaussian09 software, and the results revealed that the preferred active site of interaction between NETh and CO was at the alkene position (H atom at cis position to carbonyl, C=O).
