A promising voltammetric biosensor based on glutamate dehydrogenase/FeO/graphene/chitosan nanobiocomposite for sensitive ammonium determination in PM.

A novel NH voltammetric electrochemical biosensor was constructed by immobilizing glutamate dehydrogenase (GLDH)/FeO/graphene (GR)/chitosan (CS) nanobiocomposite onto a glassy carbon electrode (GCE). On the GLDH/FeO/GR/CS/GCE, GLDH catalyzed the reversible reaction, i.e., the reductive amination of α-ketoglutaric acid and the oxidative deamination of L-glutamate. The electrons produced in the enzymatic reactions were transferred to the surface of the electrode via the [Fe(CN)] couple, which helped for the amplification of the electrochemical signal. The electrochemical detection of NH was based on the fact that the enhanced response current was proportional to the NH concentration. Owing to the combination of the advantages of the synergistic effects of FeO nanospheres, GR and CS, a promising platform for NH sensing was provided. Under optimum conditions, the introduced biosensor had a linear range of 0.4-2.0 μM for NH with the detection and quantification limits of 0.08 and 0.27 μM, respectively. Moreover, the biosensor exhibited good sensitivity and excellent reproducibility. It could retain 91.8% of its original response after two weeks of storage at 4 °C, suggesting satisfactory stability. Additionally, the proposed biosensor was successfully applied to detect NH levels in PM samples, indicating its feasibility for application in NHmonitoring in the environmental fields.