ZnCo₂O₄ Nanoflowers Grown on Co₃O₄ Nanowire-Decorated Cu Foams for in Situ Profiling of H₂O₂ in Live Cells and Biological Media

A robust real-time quantification method is essential to understand the physiological roles of endogenous H2O2 in biological systems. For this purpose, we described a binary transition-metal oxide (TMO)-based nanointerface, i.e., spinal zinc cobaltite/cobalt oxide ternary nanoarrays (ZnCo2O4/Co3O4) on a Cu foam (CF). The ZnCo2O4/Co3O4/CF facilitates H2O2 reduction at a minimized overpotential (−0.10 V vs Ag/AgCl). which is several millivolts away from the voltammetric regions of common biological and oxygen interferences, making the electrode highly selective in the presence of 5-fold excess concentrations of biological species. In the presence of ZnCo2O4, the electrocatalytic capability of Co3O4 has increased significantly by enlarging the electrochemical active area of the electrode (0.538 cm2). A substantial improvement in the stability (97.24%) and reproducibility (relative standard deviation = 3.14%) are attained because the direct growth of nanomaterials is generated on CF in close proximity with the electrode surface and strengthens the affinity. The modified electrode endows ultrasensitivity (detection limit = 1 nM) and quantifies the amount of H2O2 released from mammalian cells (8.7 × 10–14 mol). Binary TMOs hold promise in tailoring a reliable H2O2-detecting interface for real-time, in vivo applications.