Nanotechnology has created a significant domain by giving materials unique properties. Zinc oxide nanoparticles (ZnO-NPs) possess diverse applications across various fields, including medicine, cosmetics, personal hygiene products, environmental pollution, and energy engineering. This adaptability is due to their exceptional physical characteristics, including photocatalytic activities, as well as their biological properties, which encompass antimicrobial, anticarcinogenic, bioimaging, and anti-diabetic effects. Traditional methods for synthesizing ZnO nanoparticles are associated with considerable adverse effects, with general toxicity being the most prominent concern. A more cost-effective and environmentally friendly method for producing nanoparticles may exist. Green chemistry emerges as the most effective approach to address this challenge. This paper reviews the recent advances in the green synthesis of ZnO-NPs, photocatalyst activity, and their biomedical applications. Additionally, the suboptimal performance of solar devices incorporating zinc oxide nanoparticles has been investigated. This limited efficiency is primarily attributed to insufficient surface passivation, significant charge recombination at contact interfaces, and the absence of a stable thermodynamic equilibrium within the system. Furthermore, ZnO-NPs are regarded as the premier choice for medical imaging, particularly within the framework of cancer treatment techniques. Prospective uses of ZnO-NPs encompass the development of anti- bacterial textiles, the creation of cost-effective and environmentally sustainable electrochemical biosensors, and a potent agent capable of addressing antibiotic-resistant bacterial pathogens. Looking ahead, optimizing scalable green synthesis protocols and addressing biocompatibility concerns will be critical for translating laboratory-scale findings into real-world applications in healthcare and sustainable technology.
