Highly selective and sensitive colorimetric detection of nitrite in drinking water by acetic acid-capped hierarchical flower-like NiO nanosheets structure

In the current work, the sensing of nitrite (NO₂^–) in drinking water was analyzed by a simple and fast colorimetric method, with outstanding sensitivity and selectivity. For this purpose, we have fabricated the three-dimensional (3D) hierarchical flower-like acetic acid-capped NiO nanosheets (NSs) with enhanced surface area and exposed active sites. Different characterization techniques were carried out to elaborate the formation and structural analysis of prepared NiO NSs-based colorimetric sensor, which includes SEM imaging, AFM analysis, XRD, FTIR and BET analysis. The prepared colorimetric sensor was effectively used for the highly sensitive and selective detection of NO₂^– in drinking water, which exhibit excellent performance including a wide linear nitrite range of 1 × 10^–8–3.6 × 10^–6 M, where limit of detection (LOD) value is 2.0 × 10^–7 M (0.2 μM) and limit of quantification (LOQ) is 6.8 × 10^–7 M (0.68 μM) having R² of 0.999. Moreover, the sensor also suggests strong selectivity toward nitrite as compared to other interfering species present in water sample. Further, different parameters were applied for experimental optimization to obtain the optimal performance of colorimetric sensor, which includes (a) amount of acetic acid-capped NiO NSs, (b) different pH values, (c) different exposure times, (d) different TMB concentrations and (e) different H₂O₂ concentrations. As a result, we analyzed that the prepared colorimetric nitrite sensing method can be reliably used in real-time analysis for future research work.