Authenticating the green synthesised CuONPs through XRD profiles

The efficient conversion of copper nanoparticles (CuNPs) to copper oxide (CuO) is of significant importance for applications in catalysis and antibacterial activity. While green synthesis methods for CuO nanoparticles (CuONPs) have gained widespread attention, inconsistencies in X-ray diffraction (XRD) profiles across studies suggest variations in the final product's structural properties. This study conducts a comprehensive literature review of 125 published articles to compare the XRD profiles of CuO NPs produced via green synthesis and chemical synthesis. Specifically, we investigate the impact of thermal annealing on the structural and optical properties of CuONPs. Our findings reveal that annealing at optimal temperatures facilitates the formation of a homogeneous crystalline structure, characterized by a distinct XRD profile featuring two prominent peaks with a 'rugby goal-like' shape. This characteristic XRD pattern is consistently observed in both chemically and green-synthesized CuO NPs. However, in the absence of annealing, green-synthesized CuONPs exhibit an atypical XRD profile, significantly differing from the annealed samples. These results underscore the critical role of thermal treatment in optimizing the structural properties of CuONPs and highlight the need for further research into the nature of green-synthesized products without annealing.