Dual-function amperometric sensors based on poly(diallydimethylammoniun chloride)-functionalized reduced graphene oxide/manganese dioxide/gold nanoparticles nanocomposite

In this paper, reduced graphene oxide (RGO)/manganese dioxide (MnO₂)/gold nanoparticles (AuNPs) nanocomposite was prepared by a facile, eco-friendly and controllable route, and the morphology of RGO/MnO₂/AuNPs nanocomposite was characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) analyzer, X-ray diffraction (XRD) spectrum, and Fourier transform infrared spectrum (FT-IR), respectively. And then, taking full advantage of the synergistic effect among RGO, MnO₂ and AuNPs, poly(diallyldimethylammonium chloride) (PDDA)-functionalized RGO/MnO₂/AuNPs nanocomposite was immobilized on the surface of glassy carbon (GC) electrode to fabricate a novel nonenzymatic hydrogen peroxide sensor, and the results demonstrated that the sensor showed excellent electrocatalytic activity toward H₂O₂ with ultrahigh sensitivity of 1132.8 μA mM^-1 cm^-2 and low detection limit of 0.6 μM (S/N = 3). In addition, a glucose biosensor was further fabricated by immobilizing glucose oxidase (GOD) on the surface of the PDDA-RGO/MnO₂/AuNPs-modified GC electrode. In glucose determination, the glucose biosensor exhibited excellent performance with a high sensitivity of 83.7 μA mM^-1 cm^-2, a low detection limit of 1.8 μM (S/N = 3), and a small K_m value of 1.54 mM. Moreover, the prepared hydrogen peroxide sensor and glucose biosensor were applied to in real samples with satisfactory results, indicating the prepared sensors are promising in practical application.