Biosynthesis and characterization of MnO2 and Zn/Mn2O4 NPs using Ziziphus spina-Christi aqueous leaves extract: Effect of decoration on photodegradation activity against various organic dyes

An aqueous leaf extract of Ziziphus spina-Christi is used to synthesize manganese oxide nanoparticles (MnO 2 NPs) and zinc-coated manganese oxide nanoparticles (Zn/Mn 2 O 4 NC). The study aims to investigate the photocatalytic degradation efficiency of MnO 2 NPs and Zn/Mn2O4 NC in relation to the azo dyes methylene blue (MB), m-Toluidine (mT), and P-Toluidine (pT). X-ray diffraction analysis (XRD) confirmed the crystalline nature of the biosynthesized MnO2 NPs and Zn/Mn 2 O 4 , revealing their respective crystallite sizes to be approximately 14.65 nm and 22.97 nm. The scanning electron microscope (SEM) images demonstrated that the MnO 2 NPs exhibit a tetragonal and spherical shape, while the Zn/Mn 2 O 4 particles possess a spherical shape. UV–vis spectroscopy measurements indicated that the MnO 2 NPs and Zn/Mn 2 O 4 exhibit indirect bandgaps with energy values of 1.46 eV and 1.14 eV, respectively. Fourier transform infrared (FTIR) analysis revealed the presence of organic compounds containing C O and OH groups, such as carbohydrates, phenolic acids, tannins, and flavonoids derived from Ziziphus spina-Christi , suggesting a high likelihood of stability for the biosynthetic MnO 2 and Zn/Mn 2 O 4 materials. Interestingly, the photocatalytic degradation of the biosynthetic MnO 2 and Zn/Mn 2 O 4 provided good efficacy against the Methylene Blue (MB), m-Toluidine (mT), and P-Toluidine (pT) where the Zn/Mn 2 O 4 exhibit an excellent degradation were 99.2, 99.8 and 98.4 % after 75 min. The biosynthetic MnO 2 NPs and Zn/Mn 2 O 4 NCs resulting from using aqueous ZSCLE were cost-effective and eco-friendly, and the decoration of MnO 2 NPs by Zn improved their effectiveness.