Electrochemical incorporation of hemin in a ZnO-PPy nanocomposite on a Pt electrode as NOx sensor

An electrochemical NOx sensor was fabricated based on the incorporation of hemin on a ZnO-PPy nanocomposite modified Pt electrode. Scanning electron microscopy, energy dispersive X-ray analysis and cyclic voltammetry were used to confirm the successful stepwise assembly procedure for the sensor. The electrocatalytical behavior of the sensor was investigated by cyclic voltammetry. The hemin-ZnO-PPy-Pt electrode exhibited characteristic hemin reversible redox peaks at 0.035 V and -0.11 V vs. Ag/AgCl respectively. The hemin-ZnO-PPy-Pt electrode exhibited 3-fold enhanced electrocatalytic activity towards NOx compared to the hemin-PPy-Pt electrode. The electrocatalytic response of the sensor was proportional to the NOx concentration in the range of 0.8 to 2000 mu M (r(2) = 0.9974) with a sensitivity of 0.04 mu A mu M-1 cm(-2) and detection limit of 0.8 mu M for the hemin-ZnO-PPy-Pt electrode. The low detection limit, wide linear range and enhanced sensitivity of the present sensor make it valuable for potential applications. In addition, this sensor exhibited good reproducibility and stability.