Citrate-functionalized osmium nanoparticles with peroxidase-like specific activity for highly efficient degradation of phenolic pollutants

Platinum group metals-based nanomaterials have shown promise as enzyme mimics, and attracted much attention in the fields of chemical catalysis, biosensor, therapy and pollutants degradation. Surprisingly, only a few works exist on the exploration of osmium-based nanozymes, and the catalytic activities and applicable potentials thereof have not been comprehensively understood. Herein, we prepared a kind of citrate-functionalized osmium nanoparticles (Os-citrate NPs) by one-pot synthesis strategy. The obtained Os-citrate NPs can boost hydrogen peroxide (H2O2) to produce hydroxyl radical (•OH), enabling it to serve as a peroxidase mimic. Steady-state kinetics revealed that Os-citrate NPs is rather potent and peroxidase-like specific nanozyme. Doping a certain amount of osmium oxides (OsO2) in the surface of Os-citrate NPs can greatly improve the production of •OH from H2O2, enhancing the peroxidase-like specific activity. We applied this Os-citrate catalyst in advanced oxidative degradation of phenolic pollutants. In a wide pH range of 2.0–10, 4-nitrophenol could be fast degraded by the combination of H2O2 with Os-citrate NPs. As a proof-of-concept, the Os-citrate nanozyme was successfully employed in highly efficient degradation of phenolic pollutants. To the best of our knowledge, this is the first report on the application of Os-based peroxidase-like nanozymes in highly efficient degradation of organic pollutants.