Green Synthesis and Characterization of CuO Nanostructures Using Curcuma longa Extract: Optimization of Precursor Concentration

CuO nanoparticles were synthesized via a green route using Curcuma longa extract as both reducing and capping agents. The influence of precursor concentration (0.025–0.1 M) on the morphology, size distribution, and structural quality of the nanostructures was systematically investigated. Characterization by SEM, XRD, FTIR, UV–Vis spectroscopy, and EDX identified an optimal sheet‑like morphology at 0.05 M (sample S2), with an average thickness of 18 nm, minimal aggregation, and high homogeneity. FTIR spectra confirmed characteristic Cu–O stretching vibrations, and XRD patterns revealed a phase‑pure monoclinic CuO crystal structure. UV–Vis analysis showed a distinct absorption peak at 376 nm corresponding to the optical band gap, while EDX confirmed elemental purity. These results demonstrate that Curcuma longa–mediated synthesis offers an eco‑friendly, scalable approach for producing CuO nanostructures suitable for catalysis, sensing, and environmental remediation applications.