Formulation of Manganese Zinc Spinel Ferrite (Mn0.5Zn0.5Fe2O4) Nanoparticles for the Growth Promotion of Plants

This research investigates the uptake and potential contribution of engineered manganese-zinc (MnZn) spinel ferrite nanoparticles (Mn0.5Zn0.5Fe2O4 NPs) to the growth performance of pumpkin (Cucurbita maxima L.). For this purpose, MnZn spinel ferrites were synthesized, and their structural, microstructural, and magnetic properties were determined. NPs (50, 100, 200, and 400 mg L−1) were applied to pumpkin seedlings in a hydroponic system for a week, and the root, stem, and leaf tissues were screened for NPs-uptake by using X-ray powder diffraction (XRD), vibrating sample magnetometry (VSM), and X-ray fluorescence (XRF). Besides, the effect of NPs treatments on some phenological parameters such as pigmentation, photosynthetic efficiency, and biomass was determined. The results showed that MnZn spinel ferrite treatment significantly increased Mn, Zn, and Fe content in the root, stem, and leaf. The Fe, Zn, and Mn content in the leaves increased by approximately 48, 67, and 20 times, respectively, when 400 mg L−1 was applied. Similarly, the magnitude of magnetization of root, stem, and leaf specimens confirmed the incorporation and translocation of magnetic NPs into plant tissues. Besides, the photosynthetic efficiency, pigmentation, and fresh weight were significantly enhanced, suggesting growth improvement by engineered NPs. NP concentrations for the most efficient plant growth were determined as 100 and 200 mg L−1. However, higher NP concentrations suppressed the growth due to the migration/translocation of excess NPs. These findings revealed the potential of engineered MnZn spinel ferrite NPs as nano-fertilizers to provide essential micronutrients, Mn, Zn, and Fe in this study. However, environmental concerns must be considered when using NPs at large scales.