Fabrication of carbon paste electrode containing a new inorganic–organic hybrid based on [SiW12O40]4− polyoxoanion and Nile blue and its electrocatalytic activity toward nitrite reduction

• Synthesized a new inorganic–organic hybrid compound consisting of SiW12 and Nile blue.
• Hybrid compound possess new synergy properties and poor solubility in water.
• Electroreduction of nitrite by NB2SiW12 modified carbon paste electrode.
• The electrode has a good mechanical and chemical stability and reproducibility.
• The proposed sensor is suitable for use in real water sample.

In this study, a new inorganic–organic hybrid compound consisting of a Keggin type polyoxometalate, H4SiW12O40 (SiW12), and Nile blue (NB) was synthesized and characterized. The (NB)2H2SiW12O40 (NB2SiW12) hybrid compound was characterized by Fourier transform infrared (FT-IR), elemental (CHNS) analysis, UV–Vis and thermogravimetry techniques, and used as a bulk modifier to fabricate a chemically modified carbon paste electrode (CPE) by direct mixing. The electrochemical behavior of the newly NB2SiW12 composite CPE was analyzed by cyclic voltammetry, and the electrode was applied for nitrite reduction, exhibiting high electrocatalytic activity. Determination of nitrite by fixed potential amperometry was done under various experimental conditions and, at the optimum conditions, the linear response ranged from 5 to 1200 μM with a high sensitivity of and a low detection limit. The electrode has the remarkable advantage of surface renewal owing to bulk modification, as well as simple preparation, good mechanical and chemical stability and reproducibility. No noticeable interferences from other ionic species usually found in natural water were observed. The new developed electrode has been successfully applied for detection of nitrite in real water samples.