Photo-Induced Hot Water Treatment for the Synthesis of Metal Oxide Nanostructures.

Metal oxide nanostructures (MONSTRs) have attracted considerable attention due to their unique physical and chemical properties. However, scalable and cost-effective synthesis remains a significant challenge. This study introduces photo-induced hot water treatment (PIHWT) as a new technique for fabricating MONSTRs, with the potential to "activate" materials that might not easily respond to hot water treatment (HWT) and to shorten synthesis time for responsive materials. Copper was selected as a model material to demonstrate PIHWT's effectiveness. Characterization via scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, energy-dispersive X-ray spectroscopy (EDS), and UV-vis Tauc plot indicates that PIHWT may accelerate the phase transition from Cu2O to CuO relative to HWT. XRD revealed dominant CuO peaks in PIHWT-treated samples. XPS detected Cu2+ species at 8 and 24 h. Raman spectroscopy showed a dominant CuO phase with only a weak residual Cu2O peak, compared to predominantly Cu2O in HWT samples at 8 h. After 24 h, PIHWT yielded thicker, longer, and more uniform leaf-like CuO nanostructures (NSs). These results demonstrate that PIHWT shows potential as a scalable, cost-effective route to high-quality CuO NSs.