Research progress and prospect of copper oxide nanoparticles with controllable nanostructure, morphology, and function via green synthesis

The study on copper oxide (CuO) nanoparticles has been extensively conducted over the decades due to their wide applications and increase in market demand. However, conventional production methods of CuO nanoparticles have some limitations, such as the use of hazardous materials, high energy consumption, and high production costs. Green synthesis of CuO nanoparticles and other functional materials using natural sources like plants and microorganism has emerged as an alternative, promoting an environmental friendliness with low cost and energy consumption. This study aims to provide a comprehensive and up-to-date overview of green synthesis method for nanostructured materials, especially CuO nanoparticles, explore their future direction. This paper reviews the history, milestones, and progress of studies on CuO nanoparticles, including their applications in various fields, green synthesis using plants and microorganisms, and the green synthesis mechanism. It also examines factors such as extract and concentration, precursor, pH, and temperature, which were reported in previous studies. The gaps, limitations, and challenges in this area of research are highlighted in the Future Outlook section. Looking ahead, the future development of green synthesis could be directed towards the use of isolated pure compounds, as this approach has the potential to reduce impurities and contaminants, create synergistic effects, and improve control and reproducibility. Thus, green synthesis serves a dual purpose: contributing to sustainability by minimizing the use of harmful chemicals and enabling the customization of nanostructured materials. This allows for precise manipulation of size, morphology, properties, and performance to suit specific applications. By analyzing the future direction and limitation of green synthesis, we expect that this review will inspire novel strategies and mechanism for the green synthesis of nanostructured functional materials using natural sources.