Ce-doped indium oxide nanozymes with peroxidase-like activity induced by cerium–indium synergy for colourimetric detection of H2O2

In this work, InCex nanoparticles with different In–Ce ratios were synthesized by a simple co-precipitation method and InCex nanoparticles could be used as a mimic of peroxidase to catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 and produce the typical blue ox TMB. In addition, the prepared InCex nanoparticles showed excellent peroxidase-like catalytic properties compared with pure CeO2 and pure In2O3. InCe0.1 exhibited the best peroxidase-like activity, which was mainly attributed to the indium–cerium synergy, which accelerated the TMB and H2O2 electron transfer rate between them. Based on the above findings, a facile and sensitive H2O2 detection system with a sensitive response range of 10–100 μM and a detection limit of 5 μM for H2O2 was successfully proposed. This work synthesizes nanomaterials with peroxidase-like activity by modifying In2O3 through a simple co-precipitation method and offers new insights into the search for novel peroxidase mimics.