Electrocatalytic Nitrite Determination Using Iron Phthalocyanine Modified Gold Nanoparticles

Electrochemical detection of nitrite was achieved via electrodeposition of gold nanoparticles (AuNPs) onto glassy carbon electrodes, followed by 3-mercaptopropionic acid (MPA) self-assembly, enabling attachment of an iron(III) monoamino-phthalocyanine (FeMAPc) catalyst via amide bond formation. The use of scanning electron microscopy, energy dispersive X-ray spectroscopy and ultraviolet-visible spectroscopy realised surface characterisation while cyclic voltammetry and electrochemical impedance spectroscopy techniques were applied for electrochemical interrogation. The electrochemical behaviour of nitrite at the bare (GCE), AuNPs/GCE, FeMAPc/GCE and FeMAPc-MPA/AuNPs/GCE was further scrutinised using differential pulse voltammetry in phosphate buffer solution (0.1M PBS, pH 5.8). Overall the FeMAPc-MPA/AuNPs/GCE resulted in sensitivity 14.5 nA/mu M, which was double that of AuNPs/GCE, 2.4 times FeMAPc/GCE and 3.5 times the response at a bare GCE, with linear range 1.9 mu M-2.04 mM (PBS, pH 5.8) and LOD 0.21 mu M. An interference study revealed that the proposed sensor (FeMAPc-MPA/AuNPs/GCE) exhibited a selective response in the presence of interfering anions and the analytical capability of the sensor was demonstrated via nitrite ion determination in real water samples.