A critical review on the biosynthesis, properties, applications and future outlook of green MnO nanoparticles.

MnO nanoparticles have played a vital role in biomedical, catalysis, electrochemical and energy storage fields, but requiring toxic chemicals in the fabrication intercepts their applications. There is an increasing demand for biosynthesis of MnO nanoparticles using green sources such as plant species in accordance with the purposes of environmental mitigation and production cost reduction. Here, we review recent advancements on the use of natural compounds such as polyphenols, reducing sugars, quercetins, etc. Extracted directly from low-cost and available plants for biogenic synthesis of MnO nanoparticles. Role of these phytochemicals and formation mechanism of bio-medicated MnO nanoparticles are shed light on. MnO nanoparticles own small particle size, high crystallinity, diverse morphology, high surface area and stability. Thanks to higher biocompatibility, bio-mediated synthesized MnO nanoparticles exhibited better antibacterial, antifungal, and anticancer activity than chemically synthesized ones. In terms of wastewater treatment and energy storage, they also served as efficient adsorbents and catalyst. Moreover, several aspects of limitation and future outlook of bio-mediated MnO nanoparticles in the fields are analyzed. It is expected that the present work not only expands systematic understandings of synthesis methods, properties and applications MnO nanoparticles but also pave the way for the nanotechnology revolution in combination with green chemistry and sustainable development.