Naked eye detection of arsenite, arsenate, and H2S by a Schiff base naphthaldehyde conjugate using a single paper strip, based on a deprotonation mechanism†

Considering the significant toxicity of arsenite (AsO₂⁻), arsenate (AsO₄³⁻), and hydrogen sulphide (H₂S), the early detection of these ions and gas using simple methods like naked-eye chemosensing could have substantial implications for environmental and industrial applications. With these factors in mind, we have developed a novel and straightforward colorimetric chemosensor called NADNP (2-hydroxy naphthaldehyde conjugated 2,4-dinitrophenyl hydrazine) for swift paper-based colorimetric detection of arsenite, arsenate, and H₂S, based on a deprotonation mechanism. NADNP exhibits strong binding affinity towards sulfide, arsenite, and arsenate, with very lower detection limits (LOD) of 0.17 μM, 0.15 μM and 0.15 μM respectively, and the binding stoichiometry between these detected ions and NADNP is determined to be 1 : 1 through Job's plot analysis. Structural elucidation and electronic properties calculation have been conducted via DFT (Density Functional Theory) studies for correlation with the spectroscopic analyses. The ‘three-in-one’ paper strip-based chemosensor could be considered a promising colorimetric tool for rapid, cost-effective, selective, and sensitive “on-spot” sensing and monitoring of arsenite, arsenate, and sulfide in environmental samples.