Plant-mediated synthesis of Mn₃O₄ nanoparticles: challenges and applications

Abstract

This review focuses on the green synthesis methods, challenges, and applications of manganese oxide (Mn3O4) nanoparticles investigated in the past five years. Mn3O4 nanoparticles offer some unique properties that are attributed in part to the presence of mixed oxidation states of manganese (i.e., +2 and +3) in the particle, which can be utilized in a wide range of redox-sensitive applications, such as in developing supercapacitive energy storage materials. In addition, the green synthesis of Mn3O4 nanoparticles through plant extracts has potential uses in sustainable nanotechnology. Various plant extract-mediated synthesis techniques for Mn3O4 nanoparticles have been investigated and presented. By comparing the size and structure of the synthesized Mn3O4 nanoparticles, we have observed a consistent pattern of obtaining spherical particles with a size ranging from 16 to 50 nm. The morphology of the generated Mn3O4 nanoparticles can be influenced by the annealing temperature and the composition of the plant extract used during the nanoparticle synthesis. Additionally, numerous applications for the greenly produced Mn3O4 nanoparticles have been demonstrated. Mn3O4 nanoparticles derived from plant extracts have been found to possess antimicrobial properties, supercapacitive and electrochemical capabilities, and excellent pollutant degradation efficiency. However, the magnetic properties of these nanoparticles synthesized by plant extracts are yet to be explored for potential biomedical applications. Finally, challenges to existing synthetic methods and future perspectives on the potential applications of these green synthesized Mn3O4 nanoparticles are highlighted.