Copper Nanoparticles Atomized into Zerovalent Copper Single Atoms at Water/Mineral Interfaces Mediated by <i>ortho</i> -Phenolic Hydroxyl of Dissolved Organic Matter

The interaction of copper nanoparticles (CuNPs) from anthropogenic and natural sources in the environment with dissolved organic matter (DOM) governs their occurrence, fate, and transportation. Here, we report that DOM can mediate CuNP transformation into atomically dispersed zerovalent copper single atoms (Cu⁰-SAs) at water/mineral interfaces. The mechanism proposes that the <i>ortho</i>-phenolic hydroxyl of DOM likely forms the five-membered ring structure with copper atoms on the CuNP surface, inducing inner-sphere electron transfer to weaken Cu-Cu bonds and enabling the liberation of Cu⁰-SAs and stabilization via Cu-O bonds on natural mineral surfaces, which diverges fundamentally from the conventional dissolution process. Cu⁰-SAs represent a paradoxical species that exhibit both relatively high environmental toxicity and stability, combining enhanced bactericidal activity, decreased copper ion leaching compared with parent CuNPs, and resistance to aggregation under reducing conditions. This study unveils an unreported CuNP transformation process in the environment, demonstrating Cu⁰-SAs as an emerging yet significant copper species. Our findings should be helpful for better understanding the fate, migration, and toxicity of copper in the ecosystem by identifying atomic-level copper intermediates.