Green synthesis of manganese based nanoparticles mediated by Eucalyptus robusta and Corymbia citriodora for agricultural applications

Nanotechnology has impacted several areas, including agriculture, as it has the potential to provide more sustainable fertilizers and pesticides, resulting in increased crop productivity and reduced environmental impacts without losing efficiency. In this study, we synthesized green manganese nanocomposites (MnNPs) from two plant extracts of different species: Eucalyptus robusta (ER) and Corymbia citriodora (CC), evaluating its efficiency as a nanofertilizer in the treatment of corn seeds (Zea mays). Wet chemical precipitation was used as the synthesis method. The effect of the synthesis time and the extract concentration on crystallite size, composition, average diameter, and yield, applying a factorial design. The highest ER extract concentration favored a reduction in crystallite size, while the opposite occurred for CC extract. The nanoparticles were characterized with field emission gun scanning electron microscope (FEG-SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), and X-ray diffraction (XRD). TEM images show different sizes and morphologies: spherical (16.61–23.68 nm) from the ER extract, and needle (21.77–28.63 nm) from the CC extract. The Rietveld refinement shows the composition of the MnNPs, with the ER extract Mn2O3 and K1.33Mn8O16 were obtained, and with the CC extract MnO2, potassium and MnCO3 were obtained. Their performance as nanofertilizers was evaluated and compared with two commercial benchmarks (MnCl and KMnO4) and a control group (water) considering 1) a germination test and 2) the length and fresh and dry weight of the radicular and aerial systems. The germination analysis did not show statistical differences. However, when evaluating the quality of the root and the leaf system, the nanoparticles were statistically superior to the control group, highlighting MnNP synthesized with 40 g∙L−1 of ER extract robusta at a concentration of 0.25 mg∙mL−1, revealing that the nanoparticles synthesized by a green route are promising as nanofertilizers. [Display omitted] •One step green synthesis of MnNPs is reported.•Leaf extract of Corymbia citriodora and Eucalyptus robusta were used.•Reaction time and extract concentration impact the size and composition of MnNPs.•The eucalyptus species influences the morphology of MnNPs.•The synthesized MnNPs are not phytotoxic and can be used as nanofertilizers.