In Situ Growth of Cu/CuO/Cu₂O Nanocrystals within Hybrid Nanofibers for Adsorptive Arsenic Removal

Nanomaterials such as copper nanoparticles have attracted significant attention because of their interesting size- and shape-dependent properties. However, their increased instability remains a challenge. This study therefore focuses on the growth of copper/copper oxide nanocrystals within nanofiber scaffolds, achieved by thermal reduction of poly(vinyl alcohol) nanofibers cross-linked with copper(II) acetate. A reduction temperature of up to 800 °C in 15% H₂balanced in N₂was found to lead to the formation of copper-based nanofibers (CuNFs) of sub-250-nm diameter that presented a core-sheath morphology, resulting from copper efflorescence. Enrobing a hydrolysis-resistant polymer core, the sheath layer was found to be composed of a discrete distribution of polymer-embedded crystalline nanospheres with diameters below 20 nm and of round crystallites of up to 65 nm protruding at the surface of CuNFs. With a significant proportion in copper intermediary states, this heterogeneous material is promising for various applications benefiting from the surface reactivity and versatile efficiency from the simultaneous presence of a transition metal and transition-metal oxide. For instance, with a material dose of 0.20 g·L^-1and an initial arsenic(V) concentration of 120 mg·L^-1, CuNFs yielded up to 96.5% arsenic(V) removal. This route for the manufacture of copper hybrid nanofibers can be adapted to other transition metals and blends.