Visual colorimetric detection of tin(II) and nitrite using a molybdenum oxide nanomaterial-based three-input logic...

We report a molybdenum oxide (MoO₃) nanomaterial-based three-input logic gate that uses Sn²⁺, NO₂^-, and H⁺ ions as inputs. Under acidic conditions, Sn²⁺ is able to reduce MoO₃ nanosheets, generating oxygen-vacancy-rich MoO_3-x nanomaterials along with strong localized surface plasmon resonance (LSPR) and an intense blue solution as the output signal. When NO₂^- is introduced, the redox reaction between the MoO₃ nanosheets and Sn²⁺ is strongly inhibited because the NO₂^- consumes both H⁺ and Sn²⁺. The three-input logic gate was employed for the visual colorimetric detection of Sn²⁺ and NO₂^- under different input states. The colorimetric assay's limit of detection for Sn²⁺ and the lowest concentration of NO₂^- detectable by the assay were found to be 27.5 nM and 0.1 μM, respectively. The assay permits the visual detection of Sn²⁺ and NO₂^- down to concentrations as low as 2 μM and 25 μM, respectively. The applicability of the logic-gate-based colorimetric assay was demonstrated by using it to detect Sn²⁺ and NO₂^- in several water sources.