Preparation of manganese porphyrin/niobium tungstate nanocomposites for enhanced electrochemical detection of nitrite

The sandwich-structured MnTMPyP/NbWO₆ nanocomposites were synthesized by the electrostatic self-assembly of the manganese porphyrin (MnTMPyP) cations with the exfoliated niobium tungstate [NbWO₆]⁻ nanosheets. Various analytical techniques such as X-ray diffraction patterns, scanning electron micrograph, transmission electron microscope, energy-dispersive spectroscopy, UV–Vis absorption spectra and Fourier transform infrared spectra were used to determine the structure, composition and morphology of the as-prepared samples. It can be concluded that MnTMPyP cations were inserted into interlayer spacing of the [NbWO₆]⁻ nanosheets and arranged in an inclined single layer at 58°. The MnTMPyP/NbWO₆ nanocomposites modified electrode exhibited excellent electro-catalytic oxidation activity toward nitrite in 0.2 mol L⁻¹ and pH 7.0 phosphate buffer solution. Additionally, the oxidation peak current is proportional to the square root of scan rates, indicating that the redox reaction of nitrite is a typical diffusion-controlled process. Also, the sensitivity and detection limit for nitrite at the modified electrode was evaluated as 3.80 × 10⁻⁵ mol L⁻¹ over a concentration range from 1.20 × 10⁻⁴ to 3.57 × 10⁻³ mol L⁻¹ by using differential pulse voltammetry.