Biological synthesis, physico-chemical characterization of undoped and Co doped α-Fe2O3 nanoparticles using Tribulus terrestris leaf extract and its antidiabetic, antimicrobial applications

Hematite (α-Fe2O3) nanoparticles (NPs) were chemically and thermodynamically more stable among iron oxide nanoparticles. Doping of Co2+ metal ion in α-Fe2O3 can modify the structural, optical and magnetic properties of NPs and also enhances the potential of the biomedical applications. In the current study, undoped and Co doped hematite nanoparticles were synthesised by co-precipitation method using Tribulus terrestris L. leaf extract as bio-reductant. The magnetic, optical and structural investigations were studied with the help of Ultraviolet-visible (UV-Vis), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy equipped with Energy Dispersive X-ray (SEM-EDX) Spectroscopy, Vibrating Sample Magnetometer (VSM) and X-ray Diffraction (XRD) Spectroscopy. XRD analysis shows that synthesized nanoparticles were in hematite phase, rhombohedral in structure. XRD spectral pattern clearly evidenced that prepared α-Fe2O3 and Co-Fe2O3 NPs were highly crystalline with no impurity peaks. Using VSM spectra, the M-H curve indicates that saturation magnetisation (Ms) value increases for Co-Fe2O3 NPs than undoped α-Fe2O3 NPs, it can be clearly seen that doping largely affects the magnetic nature of nanoparticles. In the UV-Vis spectra, absorption maxima increases and band gap value decreases for cobalt doped hematite nanoparticles indicating the substitution of Fe2+ ions by Co2+ ions in α-Fe2O3 lattice sites. Antidiabetic and antimicrobial activity of the synthesized undoped and Co doped hematite NPs were tested by alpha-amylase inhibitory and disc diffusion method. The Co-Fe2O3 NPs have greatly inhibited the digestive enzyme and microbial strains as compared to undoped α-Fe2O3 NPs.

Small Hematite Nanoparticles from the Kiruna-Type Ore; Evaluation of Declined Balance Limit of the Attrition Process and Their Catalytic Properties

Hematite nanoparticles possess unique properties which have motivated substantial attention for numerous applications, including environmental remediation and wastewater treatment as a promising novel technology. The magnetite-silicate raw material of Kiruna-type ore has been introduced as an innovative precursor, decreasing the attrition balance limit for large-scale production of the ball-mill-derived hematite nanoparticles below the critical size. In this study, the hypothesis and the postulated role of quartz in the effective size reduction process were further investigated. The prepared samples were characterized in detail via X-ray fluorescence (XRF) and powder X-ray diffractometry (pXRD) to be compared with the previous results. Furthermore, the catalytic and photocatalytic activities of the obtained nanoparticles were evaluated in the oxidation reaction of a common persistent sulfo-organic contaminant. The results exposed outstanding reactivity, particularly in their photocatalytic performance, suggesting them as a strong oxidizing agent and active photocatalyst, which greatly promises many possible applications including water and environmental remediation.

Mossbauer Investigations in Hematite Nanoparticles

Hematite nanoparticles of average size 20 nm were synthesized using the sol-gel method, and the structural characterizations were conducted using XRD and TEM. The XRD profile revealed a small fraction of the maghemite phase and the main hematite phase. Mössbauer spectroscopy was used to study the magnetic structure of the particles and revealed a third but very slight non-magnetic phase. Mössbauer spectrum shows 35% of the nanoparticles exhibiting superparamagnetism. The weighted average Morin transition temperature for the particles determined by Mössbauer is 262 K, which is remarkably similar to the bulk value and higher than the Morin transition determined by VSM (about 250 K). The reported findings on the hematite nanoparticles will help understand the enhanced ferromagnetic behavior of the hematite nanoparticles at room temperature, which is crucial for potential applications.

Simple One-Step Leaf Extract-Assisted Preparation of α-Fe2O3 Nanoparticles, Physicochemical Properties, and Its Sunlight-Driven Photocatalytic Activity on Methylene Blue Dye Degradation

Hematite nanoparticles have been prepared from Moringa oleifera leaf extracts. Phytochemicals are derived from plant extracts which act as a stabilizing and capping agent as well as a surfactant. This green route protocol is attractive owing to its speed, reliability, and ecofriendly and cost-effective qualities. The synthesized iron oxide nanoparticles were subjected to three different calcination temperatures (500, 600, and 700°C). The crystallinity nature and phase purity have been confirmed by powder X-ray diffraction (PXRD). Optical properties have been studied by UV-visible (UV-vis) and diffuse reflectance spectroscopy (DRS). A very narrow bandgap was observed, and absorbance was observed at the visible region. Photoluminescence spectra have exhibited a multicolor emission band from the near UV to visible region due to defect centers (F centers). EDX (energy dispersive X-ray spectrum) has given information on the stoichiometric ratio of Fe and O. The functional groups which are responsible for nanoparticle formation have been identified by Fourier transformed infrared spectroscopy (FTIR), surface morphology transformation has been illustrated by scanning electron microscopy (SEM) studies, and VSM measurements have exhibited a hysteresis curve that shows the weak and strong ferromagnetic behavior in nature at RT. TEM micrographs have confirmed that particles are in the nanorange, matching the results from the XRD report. The SAED pattern gives information on the polycrystalline nature of hematite nanoparticles. TG-DSC characterization revealed phase transition, decomposition, and weight loss information. Frequency-dependent electrical properties were studied. Here, we report what the present studies have revealed: that hematite nanopowder prepared from the green route is environmentally friendly, takes a short time to prepare, is an economical and promising candidate material for electromagnetic devices and ferromagnet manufacturing, and is a photocatalyst in water treatment applications without adding additives (H2O2).