Understanding the property-activity relationships of polyhedral cuprous oxide nanocrystals in terms of reactive crystallographic facets

The property-activity relationship is usually established to understand the toxicity mechanism of nanomaterials. In the present study, different morphological Cu2O nanocrystals, octahedrons, truncated octahedrons, cuboctahedrons, and cubes, were synthesized to precisely tuning the (100) and (111) facet percentages in purpose of systematically investigating the toxicity role of crystallographic facets in BEAS-2B and RAW 264.7 cells. It was found that the toxicity of polyhedral Cu₂O nanocrystals was highly dependent on the exposed (100) surface after short-term exposure because (100) facets could produce more reactive oxygen species (ROS) than (111) facets; however, after long-termexposure, their toxicity showed again the correlation with total surface property because toxic copper ions were largely released from the whole nanocrystal surface irrespective of (100) or (111) facet and this copper dissolution caused the collapse of surface crystals and the vanishing of ROS. This study reveals the potential hazard of crystallographic facets based on ROS and metal dissolution mechanism at the different exposure time.