Enhancing the adsorption capacity of green/chemical synthesized hematite nanoparticles by copper doping: removal of toxic Congo red dye and antioxidant activity

Cu-doped hematite (α-Fe 2 O 3 ) nanoparticles (NPs) were recently created through a chemically (PVP) or green route using Azadirachta indica (Neem) leaves extract synthesized to examine the effects of doping on photocatalytic and antioxidant activities. Structural, optical, functional groups, morphological, and magnetic aspects of the produced NPs were analyzed using XRD, FT-IR, UV–vis, Raman, SEM, EDX, TEM, and VSM techniques. These techniques of characterization verified that the Cu 2+ ions were successfully doped in α-Fe 2 O 3 NPs. The Scherrer formula was used to determine the crystallite size of synthesized materials. For doped samples, rhombohedral phase crystallite size decreased gradually from 24 to 16 nm in the corundum structure. SEM and TEM images demonstrated the doping of Cu with spherically shaped, and particle size 9–16 nm α-Fe 2 O 3 NPs. The band gap energy of doped α-Fe 2 O 3 NPs, calculated from UV–visible spectroscopic investigation of synthesized samples, was 2.28 and 2.54 eV, respectively. The strong photocatalytic activity of doped hematite was supported by its narrowing band gap energy. By comparing saturation magnetization (Ms) values between chemical and green doped α-Fe 2 O 3 NPs using VSM spectra, it is evident that doping has a substantial impact on the magnetic properties of NPs. The degradation efficiency of Congo red followed a pseudo-first-order reaction kinetic model, and a potential photocatalytic reaction mechanism was also explored. Doped hematite nanoparticles also possess significant flavonoid and phenolic characteristics, as well as high 1,1-diphenyl-2-picrylhydrazyl (DPPH) based on a total reducing power potential, total antioxidant potential, and free radical-scavenging activity. Copper-doped α-Fe 2 O 3 NPs samples made through chemical or green synthesis displayed significantly improved photocatalytic and antioxidant capabilities.