Photoelectrochemical sensor based on N-ZnO/Fe@Fe2O3/g-C3N4 nanomaterials for detection of hydrogen peroxide

ABSTRACT In this work, a photoelectrochemical (PEC) sensor for hydrogen peroxide (H 2 O 2 ) detection was fabricated based on an ITO/N-ZnO/AuNPs/Fe@Fe₂O₃/g-C₃N₄ (CNFZ) electrode assembled with graphitic carbon nitride (g-C₃N₄). Herein, CNFZ is the abbreviation of ITO/N-ZnO/AuNPs/Fe@Fe₂O₃/g-C₃N₄.The g-C 3 N 4 material was prepared using melamine as the precursor via calcination in a muffle furnace. N-ZnO, AuNPs, and Fe@Fe 2 O 3 were synthesized via by a stirring-assisted method. N-ZnO was first drop-cast onto the surface of indium tin oxide (ITO) conductive glass. Subsequently, g-C 3 N 4 , Fe@Fe 2 O 3 , and AuNPs were mixed at room temperature and then coated onto the prefabricated ITO/N-ZnO electrode substrate to obtain the CNFZ electrode. Horseradish peroxidase (HRP) was immobilized onto the CNFZ electrode through chemical cross-linking. Under illumination, all the photocatalytic materials (g-C 3 N 4 , Fe@Fe 2 O 3 , N-ZnO, and AuNPs) all exhibited excellent performance in enhancing the photoelectrochemical activity of HRP. The key factors affecting the performance of the HRP/CNFZ electrode were also investigated, including the concentration of HRP. The HRP concentration ranged from 10~16 μM, the electrode showed a linear regression equation: I (μA) = −0.68× C HRP (ng/mL) + 3.56 ( R ² = 0.969). Furthermore, the HRP/CNFZ electrode was applied for the detection of H 2 O 2 and exhibited outstanding photocatalytic activity toward H₂O₂. When the H 2 O 2 concentration ranged from 1.0×10 -8 to 1.6×10 -5 M, the linear regression equation was I (μA) = 5.02+533.83 C (mM), R 2 =0.987. The limit of detection (LOD) was calculated to be 4.5 nM. These results confirm that the CNFZ electrode possesses favorable photocatalytic activity, which enhances the conversion of light energy to electrical energy. The as-prepared HRP/CNFZ electrode exhibits promising potential for the eletrocatalytisis of H 2 O 2 . This work provides new strategies for constructing multifunctional optoelectronic materials and developing advanced PEC sensors for H 2 O 2 detection.