Amperometric sensing of nitrite at nanomolar concentrations by using carboxylated multiwalled carbon nanotubes modified with titanium nitride nanoparticles.

A glassy carbon electrode (GCE) was modified with a nanocomposite prepared from carboxylated multiwalled carbon nanotubes (c-MWCNT) and titanium nitride (TiN) nanoparticles to obtain a sensor for nitrite. The nanocomposite was characterized by transmission electron microscopy, elemental mapping, X-ray diffraction, and Raman spectroscopy. Electrochemical studies results show the modified GCE to possess a low electrochemical resistance (Rct = 7 Ω) and a large electroactive surface (A = 0.112 cm). The heterogeneous electron transfer rate (k) is found to be 1.26 × 10 cm s. Due to the excellent synergistic effect of c-MWCNT and TiN, the GCE displays and excellent performance in terms of nitrite sensing. At a typical working voltage of +0.8 V (vs. Ag/AgCl), the limit of detection (LOD) is as low as 4 nM, and the useful analytical range extends from 6 nM to 950 μM. This is much better than the LODs of previously reported nitrite sensors. The sensor is fast (response time 4 s), selective, and long-term stable. It was applied to the determination of nitrite in spiked water and meat samples and gave good recoveries. Graphical abstract Schematic presentation of electrochemical determination of nitrite using carboxylated multiwalled carbon nanotubes modified with titanium nitride nanoparticles modified electrode.