Anisotropic Cu2O nanostructures: A promising remediation for per- and polyfluoroalkyl substances

Abstract

Copper oxide (Cu2O) exhibits exceptional optical properties and phase stability at the nanoscale level making it highly desirable in nanotechnology applications. Its unique and distinctive properties make it highly feasible for diverse applications, which include environmental remediation, energy conversion, and catalysis. In this study, we tailor the surface and facet orientation of Cu2O nanoparticles to enhance their efficacy in addressing environmental contaminants such as per- and polyfluorinated substances (PFAS). By adjusting the ratios of the precursor and capping agent, we have synthesized Cu2O nanocubes (NCs) and octahedra (Oh) with average sizes of 450 nm and 650 nm, respectively. The time-dependent UV–Vis interaction studies revealed significant redshifts in absorption spectra upon the addition of Cu2O NCs and Oh to the PFAS solutions, indicative of the changes in the surroundings upon the interaction. FT-IR spectra further confirmed the sorption of PFAS on Cu2O nanostructures with stronger adsorption observed for longer-chain PFAS due to enhanced hydrophobic interactions. XPS analysis further provided insights into the surface composition changes after post-interaction, indicating the presence of PFAS on Cu2O nanostructures. The zeta potential analysis supported the role of electrostatic interactions in PFAS removal. Our results demonstrate that Cu2O Oh exhibits superior PFAS adsorption compared to Cu2O NCs, which is attributed to the exposed facets of a copper atom having a positive surface charge and facilitating electrostatic interactions. Specifically, Cu-terminated (110) or (111) surfaces exhibit enhanced sorption capacity, while the reduced reactivity of Cu-terminated Cu2O (100) surfaces is linked to high energy barrier holes at the surface region. Overall, this study elucidates the interaction mechanisms between Cu2O nanostructures and PFAS which underscores the significance of surface engineering for optimizing their performance in environmental remediation strategies.