FePt nanoparticles-decorated graphene oxide nanosheets as enhanced peroxidase mimics for sensitive response to H₂O₂

Bimetallic-based nanoparticles usually display improved catalytic performance compared to monometallic counterparts. Herein, the well-dispersed FePt nanoparticles decorated on the surface of graphene oxide (GO) nanosheets have been successfully synthesized by a simple polyol protocol method. The FePt/GO nanocomposites were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), magnetic property measurement system (MPMS), and Fourier transform infrared spectra (FT-IR), respectively. Interestingly, FePt/GO nanocomposites demonstrated the highly intrinsic peroxidase-like activity and can rapidly catalyze to oxidize the substrate 3,3',5,5'-tetramethylbenzidine (TMB) into a blue product oxidized TMB (oxTMB), in the presence of H₂O₂ only in 30 s observed by the naked eye. Electron spin resonance (ESR) revealed that the underlying catalytic mechanism of FePt/GO nanocomposites was attributed to the generation of hydroxyl radicals (OH) from decomposing of H₂O₂, due to the synergistic effect between FePt nanoparticles and GO nanosheets. Moreover, H₂O₂ can be detected over a wide linear detection range of 0.03-0.5 mM with a detection limit of 2.2 × 10^-5 M. Based on the mimic enzyme FePt/GO, a colorimetric ultrasensitive H₂O₂ sensor was constructed with the help of TMB in buffer solution.