Development of an assay for colorimetric and fluorometric detection of H₂S

Hydrogen sulfide is a highly toxic gas that can produce extremely rapid CNS and respiratory depression and sometimes becomes fatal at high concentrations. There is no proven antidote for hydrogen sulfide poisoning. Hence, it is important to reduce the production of H₂S in several industries, such as oil and gas refining and mining industries. As a consequence, researchers are always inquisitive about inventing different sensing devices or useful tools to detect H₂S selectively in a cost-effective manner. Colorimetric and fluorometric detection methods are the most attractive owing to their simplicity, profitability, ease of understanding, and "on-spot" detection convenience. In this research, we developed some colorimetric and fluorometric chemosensors and established an assay for the easy detection of H₂S following a specific mechanism. The sensing mechanisms were well established through exhaustive spectroscopic studies and theoretical calculations. We first synthesized a series of chemosensors using 2-hydroxy naphthaldehyde as a primary fluorophore. The chemosensors were developed by incorporating various electron-releasing and donating groups while keeping the binding site unchanged. Subsequently, we compared their efficiency and binding ability towards H₂S with a possible mechanism. The chemosensor was employed through a paper strip for demonstration as an "in-field" device by changing the naked-eye and fluorescence color both in liquid and gas phases.