<p>Triple transition (Ni, Cu, and Zn) doped hematite nanoparticles (α-Fe₂O₃ NPs) have made significant advances in biological, environmental, as well as other interdisciplinary fields of study, due to their stability and relative lack of toxicity. The α-Fe₂O₃ NPs has been made simple, effective, and ecologically benign by utilizing the reducing and capping capability of <i>Azadirachta indica</i> aqueous leaf extract. Synthesized material has been studied by XRD, UV–visible, Raman, FTIR, VSM, SEM, and TEM techniques. Doped α-Fe₂O₃ NPs possessed a rhombohedral phase and corundum structure that was exceptionally pure and well crystalline. The synthesized α-Fe₂O₃ NPs had a size of 22.83&#xa0;nm and were irregular-spheroidal in shape, according to SEM and TEM examination. Synthesized NPs show ferromagnetic characteristics, according to VSM research. The photocatalytic activity of doped α-Fe₂O₃ NPs was evaluated through the efficient degradation of methyl orange (MO, 95%), methylene blue (MB, 97%), Congo red (CR, 92%), and eosin yellowish (EY, 90%) under visible light irradiation for 90–100&#xa0;min. The reaction kinetics followed a pseudo-first-order model, as indicated by the linear relationship between ln (C₀/C_t) and irradiation time. The degradation kinetics followed a pseudo-first-order model, with high regression coefficients (R² ranging from 0.91 to 0.95), indicating good linearity and consistency. As a result, the NPs are suited for applications where reusability is a crucial essential feature due to the modest drop in the photocatalytic activity after four cycles. This current study examines the effects of α-Fe₂O₃ NPs on the seed germination of <i>Vigna radiata</i> (mung bean) and phytotoxicity study biomass accumulation <i>Allium cepa</i> (onion) through a series of germination assays. For this reason, it is crucial to manage the materials size, morphology, and magnetic properties to produce well-tailored photocatalysts.</p> Graphical Abstract <p></p>