Electrochemical Detection of Nitrite Based on Difference of Surface Charge of Self-Assembled Monolayers

In this work, we reported a simple and sensitive electrochemical method for nitrite detection via Griess reaction. Specifically, naphthylethylenediamine (NEA) was immobilized onto the gold electrode to form positively charged self-assembled monolayers (SAMs). The positive charges on electrode facilitated the access of the negatively charged [Fe(CN)6]3-/4- probes to the electrode surface. The nitrite-mediated Griess reaction between NEA and sulphanilic acid (SA) on the electrode surface leaded to the formation of negatively charged SAMs, which produced a barrier for the electron transfer between the redox probe and the electrode. The results were demonstrated by cyclic voltammetry and electrochemical impedance spectroscopy. The increase in the impedance of NEA-modified electrodes is proportional to the increase of nitrite concentration. A detection limit of 20 nM for nitrite detection was achieved.