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

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 MoO3-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.