Green Synthesis of MnO₂ Nanoparticles with Aqueous Extract of Star Apple Leaves (Chrysophyllum cainito L.)

Chemistry Department, Faculty of Mathematics and Natural Sciences, Universitas Negeri Malang, Semarang Street 5, 65145, Indonesia

^* Corresponding author: nazriati.fmipa@um.ac.id

Abstract

Nanomaterials are materials with a size of ≤100 nm and are important for technology in today’s digital era. MnO₂ is one of the most studied metal oxides nowadays because of its abundance, low toxicity, and environmentally friendly. This material can be synthesized via redox reactions. The reagents commonly used in this reaction are typically toxic and environmentally unfriendly, such as H₂SO₄, HCl and HNO₃. Therefore, through this research, the synthesis of MnO₂ was carried out using an aqueous extract of star apple leaves. Because the aqueous extract of star apple leaves is known to contain secondary metabolites which have -OH, -C=O, and -C-N groups. These groups act as reducing and capping agents for the synthesis of MnO₂ NPs. In addition, this study investigated the effect of the various synthesis methods on the formation of MnO₂ NPs. Based on the results of LC-MS characterization, the aqueous extract of star apple leaves contains myricetin. Myricetin has -C=O and -OH groups which are reactive to MnO_4^- ions in aqueous solution, so that MnO_4^- is reduced to MnO₄. This fact is supported by the results of the P-XRD characterization, which proves the presence of R-MnO₂ and γ- MnO₂ were obtained.