Trimetallic doped hematite (α-Fe₂O₃) nanoparticles using biomolecules of Azadirachta indica leaf extract for photocatalytic dye removal: insights into catalyst stability and reusability

The utilization of biomolecules extracted from plants for synthesizing nanoparticles (NPs) has gained considerable attention due to its eco-friendly, cost-effective, and sustainable attributes. In this research, a straightforward and environmentally friendly method was used for manufacturing Cu-Zn-Co trimetallic-doped (TD) α-Fe₂O₃ NPs. This process involves the use of an aqueous extract derived from Azadirachta indica leaves, serving both as capping and stabilizing agents during the NPs synthesis. The incorporation of distinct metal precursors in the preparation of TD α-Fe₂O₃ NPs leads to remarkable changes in their physicochemical properties. These NPs exhibit superior characteristics compared to their monometallic counterparts in various aspects and carried out comprehensive characterization using techniques such as powder XRD, UV-Vis spectroscopy, FT-IR spectroscopy, Raman spectroscopy, SEM, EDX, TEM, SAED, and VSM techniques. XRD analysis revealed that the TD α-Fe₂O₃ NPs within encapsulation exhibit a rhombohedral crystal lattice structure, with a crystalline diameter size of 16.2 nm. These TD α-Fe₂O₃ NPs display an average particle size of 15.4 nm, demonstrating spheroidal morphology. The band gap of the TD α-Fe₂O₃ NPs is measured to be within the range of 2.44 eV. The biologically synthesized TD α-Fe₂O₃ NPs exhibited significant photocatalytic activity in the degradation of dyes like Rhodamine Blue (RhB), Malachite Green (MG), Bismarck Brown (BB), and Fluorescein Sodium (FS). This activity was evaluated in terms of percentage degradation, degradation efficiency, reusability, and the influence of pH, of the dyes RhB, MG, BB, and FS through photocatalysis can be characterized as adhering to pseudo-first-order kinetics. Additionally, we delved into the mechanism of photodegradation involving the green synthesized TD α-Fe₂O₃ NPs. This research illuminates the potential of these NPs as efficient photocatalysts for the degradation of various dyes and contributes to our understanding of their application.