Diatomic active sites nanozymes: Enhanced peroxidase-like activity for dopamine and intracellular H₂O₂ detection

Considering intracellular hydrogen peroxide (H₂O₂) plays pivotal roles in the regulation of serial biological processes, the in-situ detection of intracellular H₂O₂ has attracted an extensive attention. In the present work, an atomically dispersed diatomic active sites Nanozymes (FeN₃/PtN₄-single-atom nanozymes (SAzyme)) was prepared exhibiting enhanced peroxidase-like activity. The obvious synergistic effect between Fe–Pt heteronuclear diatomic active sites was confirmed by series of characterization and density functional theory (DFT). The peroxidase-like activity of Fe-sites could be substantially enhanced by the bonded Pt-sites via the modulation effect. As a consequence, the gap between the d-band centre (ε_d) of Fe 3d orbitals and the Fermi energy level was narrowed and the electronic interaction could be strengthened, leading to a lower free energy barrier and a lower activation energy as well as fortified metal–O bonding in the kinetic pathway. Therefore, the constructed FeN₃/PtN₄-SAzyme exhibited higher peroxidase-like activity than that of FeN₄-SAzyme. The FeN₃/PtN₄-SAzyme-assisted oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) facilitated the colorimetric detection of dopamine (DA), an important biomolecule. The linear detection range and limit of detection (LOD) of DA and H₂O₂ were 1–10 μM, 0.01–1.0 mM and 0.109 μM, 7.97 μM, respectively. In addition, the constructed SAzymes were also applied for the in-situ detection of intracellular H₂O₂, expanding the application scope of the newborn SAzymes.