Gotowa bibliografia na temat „Hematite nanomaterial”

ABSTRACTDespite a wealth of studies examining the toxicity of engineered nanomaterials, current knowledge on their cytotoxic mechanisms (particularly from a physical perspective) remains limited. In this work, we imaged and quantitatively characterized the biomechanical (hardness and elasticity), adhesive, and surface electrical properties ofEscherichia colicells with and without exposure to hematite nanoparticles (NPs) in an effort to advance our understanding of the cytotoxic impacts of nanomaterials. Both scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed thatE. colicells had noticeable deformation with hematite treatment for 45 min with a statistical significance. The hematite-treated cells became significantly harder or stiffer than untreated ones, as evidenced by indentation and spring constant measurements. The average indentation of the hematite-treatedE. colicells was 120 nm, which is significantly lower (P< 0.01) than that of the untreated cells (approximately 400 nm). The spring constant of hematite-treatedE. colicells (0.28 ± 0.11 nN/nm) was about 20 times higher than that of untreated ones (0.01 ± 0.01 nN/nm). The zeta potential ofE. colicells, measured by dynamic light scattering (DLS), was shown to shift from −4 ± 2 mV to −27 ± 8 mV with progressive surface adsorption of hematite NPs, a finding which is consistent with the local surface potential measured by Kelvin probe force microscopy (KPFM). Overall, the reported findings quantitatively revealed the adverse impacts of nanomaterial exposure on physical properties of bacterial cells and should provide insight into the toxicity mechanisms of nanomaterials.

Three forms of Saccharum munja had been utilized for a comparison among uptake of chromium metal from aqueous media. Scanning electron microscope characterization of sorbents revealed microporous and tubular structure in modified nanomaterial. Fourier transform infrared analysis explored different surface attaching ionic groups like hydroxyl, carbonyl also nitro groups, responsible for metal uptake from solution. Experiments on concentration factor suggested maximum percent sorption capacity of 89.65 by hematite loaded Saccharum munja biochar. Adsorption equilibrium data implication on isotherms and error functions favored experimental findings. Calculation of two forms of different isotherms for example Dubinin-Radushkevich, Langmuir, Temkin and Freundlich isotherm supported adsorption experiments with high R2>0.9 values for all sorbents. Error analysis indicated favorable results by five errors but chi-square test error values were minimum in both linear data and non-linear data. Kinetic modeling results indicated high rate of adsorption as shown by their large R2 value and closely related k, Qe and h values. Thermodynamic results showed that biosorption reactions were endothermic and spontaneous. These results also suggest that hematite loaded nanomaterials are good biosorbents for chromium metal uptake in minimum concentration and high output. Desorption study was essential for recovery of nanomaterial to be used again and again in experiments.

Abstract The magnetic iron oxides are classified into three phases known as Magnetite (Fe3O4), Magnetite (-Fe2O3), Hematite (-Fe2O3).The ferric oxide synthesis with the excess of the ferrous oxide nanoparticles was carried out by the co-precipitation method. The precursors Ferric sulphate hydrate and Ferrous sulphate heptahydrate taken in the molar ratio of 1:2 in 100 ml of water and 30 ml of Hydrochloric acid added to initiate precipitation at 90 OC with vigorous stirring the ammonia solution was added. The prepared materials are characterized by XRD, and UV-Vis spectroscopy. The XRD showed formation of phase and crystallization of the nanomaterial is prepared. The UV-Vis spectroscopy used to determine the reflectance and absorptance as well as the optical bandgap of the nanomaterial, in the range of 800 nm to 200 nm. The analysis indicated formation of ferrous oxide impregnated ferric oxide nanoparticles with desired optical band gap.

The present study focuses on the refractory upgrade and reuse of the mining wastes/by-products of the magnesite mine “Grecian Magnesite SA” (Chalkidiki, N. Greece), by the addition of hematite (α-Fe2O3) nanomaterial. These by-products were also examined after the application of thermal pre-treatment, i.e., treated at 850 °C for 30 min, prior to sintering. Different thermal treatments and times were applied, aiming to induce the formation of forsterite and attempting to examine the respective effects on the refractory properties of up-cycled products. The results indicate that hematite addition of 5 wt.% can improve the major refractory parameters of products, whereas the applied thermal pre-treatment was not found to be particularly beneficial. Nevertheless, the optimum results were realized after thermal treatment at 1300 °C for 120 min heating time, also revealing that the initial mineralogical content of the examined mineral wastes is a key factor for the subsequent upgrade ranking of the final product.

Hybrid nanostructured sorbents were fabricatedviathe deposition and growth of hematite nanoparticles on carbon nanotubes, and fundamental aspects of their performance toward common heavy metal pollutants were evaluated.

The α-Fe2O3 Nanoparticles were successfully synthesized by Sol-Gel method and the powder was calcinated at 4000. SEM, XRD, FTIR, EDX studies were carried out for characterization. The XRD confirmed that nanoparticles were Hematite (α-Fe2O3 ) having crystalline size of 11.55nm which confirms the Hematite(α-Fe2O3) on comparison with obtained spectra against Joint Committee on Powder Diffraction Standards Database(JCPDS) and SEM morphology indicated that IronOxide Nanoparticles were of flower shape at higher magnifications . The FTIR showed the bonds between functional groups and Fe-O group, O-H bending and vibration bonds. The presence of FeO, Fe, C, in nanomaterial was confirmed by EDX . Synthesized iron oxide α-Fe2O3 (Hematite) crystalline size of 11.55nm was used in the study of photo catalytic reduction of Cadmium (II) .Different parameters like Metal concentration, Dosage of Nanoparticles, Contact time and pH were studied. pH maintained for the solutions of different concentrations were 4,5,6,7 and 10. Concentration of cadmium solution taken for the study were 2,4,6,8 and 10ppm. Keeping concentration and dosage constant, pH was varied. Then concentration was varied by keeping dosage and pH constant. Then dosage was varied by keeping concentration and pH constant. Dosage of iron oxide taken was 50 mg, 75mg, 100mg, 125 mg and 150mg. It was observed that photo catalytic reduction by Iron oxide nanoparticles (IONP) was more effective at metal concentration 4ppm, IONP dosage 100mg, pH 5, and contact time of 150 min with 97.02% reduction of Cadmium (II).

ABSTRACTRecently, photoelectrochemical (PEC) water splitting using semiconductor photoanode has received great attention due production of hydrogen through clean energy. The alpha hematite (α Fe2O3) is one of the candidate amongst photoanodic materials, which is chemically stable, abundant in nature with a band gap of 2.0-2. 2eV allowing to be harvesting in the visible light. However, it has also drawn back due to high recombination rate of electron–hole pair revealing the low concentration of charges and lower device performance. In common with α-Fe2O3, the titanium dioxide (TiO2) has been known as one of the most explored photoanode electrode material due to its physical and chemical stability in aqueous and non-toxicity. However, TiO2 has large bandgap (3.0-3.2 eV) that results in absorbing UV light and very small part of visible region. Incorporation of TiO2 in α-Fe2O3 could achieve better efficiencies as photoanode materials by enhancing the electric conductivity, limited hole diffusion length, and both materials can absorb light in both UV and visible spectrum range. However, the photoanodic properties of α-Fe2O3 with different concentrations of TiO2 are mostly unknown. Under this work, α-Fe2O3-TiO2 nanomaterial was synthesized using a hydrothermal method. The α-Fe2O3-TiO2 nanomaterials containing different weight percentage (2.5, 5, 16, 25, and 50) of TiO2 to α-Fe2O3 were characterized using SEM, XRD, UV-Vis, FTIR and Raman techniques, respectively. The electrochemical properties of α-Fe2O3-TiO2 nanomaterials were investigated by cyclic voltammetry and chronoamperometry techniques, respectively.

In order to conserve the energy used for remediation of harmful metals from aqueous media, an adsorption process was performed. It is efficient and low-cost method with zero carbon emissions as compared to other methods. A hematite-based novel nanomaterial loaded onto biochar was utilized for the remediation of toxic cadmium metal ions from aqueous media. Saccharum munja has been employed as low-cost feedstock to prepare the biochar. Three adsorbents i.e., raw Saccharum munja (SM), Saccharum munja biochar (SMBC) and hematite-loaded Saccharum munja bichar (HLSMBC) were used in batch adsorption tests to study uptake of metal ions by optimizing the experimental parameters. Experimental data and calculated results revealed maximum sorption efficiency of Cd(II) removal was given by HLSMBC (72 ppm) and SMBC (67.73 ppm) as compared with SM (48.7 ppm). Among adsorption isotherms applied on work best fit for Cd(II) adsorption on SM was found for a Freundlich isotherm with high values of correlation coefficient R2 ≥ 0.9 for all sorbents and constant 1/n values between 0–1. Equilibrium results were evaluated using five different types of errors functions. Thermodynamic studies suggested feasible, spontaneous and endothermic nature of adsorption process, while, the ∆H parameter < 80 kJ/mol indicated physiosorption and positive ∆S values promoted randomness of ions with increase in adsorption process. Data fitted into type I of pseudo second order kinetics having R2 ≥ 0.98 and rate constants K2 (0–1). Desorption process was also performed for storage, conservation and reuse of sorbent and sorbate materials.

Barium hexaferrite (BaFe12O19) has attracted research attention due to its diverse applications. This study reports the synthesis of barium M-hexaferrite (BaFe12-2xCoxZnxO19) powder using co-precipitation of BaCO3 and FeCl3.6H2O powder, Co and Zn powder as a dopant material on the variation of x = 0, 0.2, 0.4, 0.6, 0.8, and 1. Results show that co-precipitation is an effective method for the synthesis of nanomaterial barium M-hexaferrites (BaFe12-2xCoxZnxO19) containing >89% of Fe elements and an average particle size of 50 nm. The DTA/TGA analyses show phase transformation at T ≤ 285°C and T = 750-840°C. The results of refinement using the Rietveld method show that the barium M-hexaferrite phase begins to form at low temperatures, with the best yield at x = 0.4. At high temperatures T > 740°C, it tends to form single-phase α-Fe2O3 (hematite). Substitution ion dopant Co/Zn only slightly changes the lattice parameters of the hexagonal basic crystal structure

Orientador: Prof. Dr. Flavio Leandro de Souza
Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2016.
Com a crescente demanda energética mundial e a necessidade de desenvolvimento nos métodos renováveis para obtenção de energia surge o interesse nas Células Fotoeletroquímicas, dispositivos que possibilitam a conversão da energia da radiação solar em energia química na forma de hidrogênio molecular. Grande parte da pesquisa na área das células fotoeletroquímicas é voltada para a eficiência de conversão energética e barateamento de custos de produção. Com base nisso o presente trabalho tem foco no desenvolvimento de eletrodos usados nesse dispositivo, sintetizados usando hematita em condição hidrotermal, buscando a melhoria dos métodos de síntese para redução de custos, impacto ambiental e eficiência energética. A síntese utilizada teve o intuito de reduzir ao máximo a quantidade de reagentes à base de cloro, que podem interferir negativamente no crescimento das estruturas e analisar a influência de alguns parâmetros alterados durante o processo: tempo de síntese, atmosfera de tratamento térmico e concentração de reagentes. Foi concluído, com base nas caracterizações morfológicas e eletroquímicas aplicadas nas amostras, que a síntese hidrotermal utilizada gerou eletrodos fotossensíveis sendo mais efetiva nos tempos de 1 hora, com tratamento térmico em atmosfera de nitrogênio e com uso de 0,076 mol.L-1 de sulfato de sódio e 0,15 mol.L-1 de cloreto de ferro, contribuindo com a redução da quantidade de cloro utilizado. A melhor fotocorrente obtida para os eletrodos foi por meio da amostra F1Ny chegando a 0,936 mA.cm-2.
The increase of global energy demand and the need for renewable sources results on the interest in devices know as photoelectrochemical cells. This device enables the conversion of solar radiation energy into chemical energy in the form of molecular hydrogen. Most of the research in the area of the photoelectrochemical cells is focused on the energy conversion efficiency and reduction of production costs. This work aimed the development of electrodes used in photoelectrochemical cells, synthesized using hematite in hydrothermal condition, seeking the improvement of synthesis methods to reduce costs, environmental impact and energy efficiency. The synthesis used was intended to reduce the amount of chlorine based reagents that can negatively impact the growth of structures and analyze the influence of some parameters changes during the process: synthesis time, atmosphere used in the heat treatment and reagents concentration. It was concluded through morphological and electrochemical characterization that the hydrothermal synthesis has generated photosensitive electrodes. The most promising electrode produced was synthesized for 1 hour, them treated in nitrogen atmosphere and using 0.076 mol.L-1 of sulfate sodium and 0.15 mol.L-1 of iron chloride, contributing to reduce the amount of chlorine used in relation to other methods generally discussed in the literature. The best photocurrent obtained was 0.936 mA.cm-2.

The recent momentum in energy research has simplified converting solar to electrical energy through photoelectrochemical (PEC) cells. There are numerous benefits to these PEC cells, such as the inexpensive fabrication of thin film, reduction in absorption loss (due to transparent electrolyte), and a substantial increase in the energy conversion efficiency. Alpha-hematite ([U+F061]-Fe2O3) has received considerable attention as a photoanode for water-splitting applications in photoelectrochemical (PEC) devices. The alpha-hematite ([U+F061]-Fe2O3) nanomaterial is attractive due to its bandgap of 2.1eV allowing it to absorb visible light. Other benefits of [U+F061]-Fe2O3 include low cost, chemical stability and availability in nature, and excellent photoelectrochemical (PEC) properties to split water into hydrogen and oxygen. However, [U+F061]-Fe2O3 suffers from low conductivity, slow surface kinetics, and low carrier diffusion that causes degradation of PEC device performance. The low carrier diffusion of [U+F061]-hematite is related to higher resistivity, slow surface kinetics, low electron mobility, and higher electro-hole combinations. All the drawbacks of [U+F061]-Fe2O3, such as low carrier mobility and electronic diffusion properties, can be enhanced by doping, which forms the nanocomposite and nanostructure films. In this study, all nanomaterials were synthesized utilizing the sol-gel technique and investigated using Scanning Electron Microscopy (SEM), X-ray Diffractometer (XRD), UV-Visible Spectrophotometer (UV-Vis), Fourier Transform Infrared Spectroscopy (FTIR), Raman techniques, Particle Analyzer, Cyclic Voltammetry (CV), and Chronoamperometry, respectively. The surface morphology is studied by SEM. X-Ray diffractometer (XRD) is used to identify the crystalline phase and to estimate the crystalline size. FTIR is used to identify the chemical bonds as well as functional groups in the compound. A UV-Vis absorption spectral study may assist in understanding electronic structure of the optical band gap of the material. Cyclic voltammetry and chronoamperometry were used to estimate the diffusion coefficient and study electrochemical activities at the electrode/electrolyte interface. In this investigation, the [U+F061]-Fe2O3 was doped with various materials such as metal oxide (aluminum, Al), dichalcogenide (molybdenum disulfide, MoS2), and co-catalyst (titanium dioxide, TiO2). By doping or composite formation with different percentage ratios (0.5, 10, 20, 30) of aluminum (Al) containing [U+F061]-Fe2O3, the mobility and carrier diffusion properties of [U+F061]-hematite ([U+F061]-Fe2O3) can be enhanced. The new composite, Al-[U+F061]-Fe2O3, improved charge transport properties through strain introduction in the lattice structure, thus increasing light absorption. The increase of Al contents in [U+F061]-Fe2O3 shows clustering due to the denser formation of the Al-[U+F061]-Fe2O3 particle. The presence of aluminum causes the change in structural and optical and morphological properties of Al-[U+F061]-Fe2O3 more than the properties of the [U+F061]-Fe2O3 photocatalyst. There is a marked variation in the bandgap from 2.1 to 2.4 eV. The structure of the composite formation Al-[U+F061]-Fe2O3, due to a high percentage of Al, shows a rhombohedra structure. The photocurrent (35 A/cm2) clearly distinguishes the enhanced hydrogen production of the Al-[U+F061]-Fe2O3 based photocatalyst. This work has been conducted with several percentages (0.1, 0.2, 0.5, 1, 2, 5) of molybdenum disulfide (MoS2) that has shown enhanced photocatalytic activity due to its bonding, chemical composition, and nanoparticle growth on the graphene films. The MoS2 material has a bandgap of 1.8 eV that works in visible light, responding as a photocatalyst. The photocurrent and electrode/electrolyte interface of MoS2-[U+F061]-Fe2O3 nanocomposite films were investigated using electrochemical techniques. The MoS2 material could help to play a central role in charge transfer with its slow recombination of electron-hole pairs created due to photo-energy with the charge transfer rate between surface and electrons. The bandgap of the MoS2 doped [U+F061]-Fe2O3 nanocomposite has been estimated to be vary from 1.94 to 2.17 eV. The nanocomposite MoS2-[U+F061]-Fe2O3 films confirmed to be rhombohedral structure with a lower band gap than Al-[U+F061]-Fe2O3 nanomaterial. The nanocomposite MoS2-[U+F061]-Fe2O3 films revealed a more enhanced photocurrent (180 μA/cm2) than pristine [U+F061]-Fe2O3 and other transition metal doped Al-[U+F061]-Fe2O3 nanostructured films. The p-n configuration has been used because MoS2 can remove the holes from the n-type semiconductor by making a p-n configuration. The photoelectrochemical properties of the p-n configuration of MoS2-α-Fe2O3 as the n-type and ND-RRPHTh as the p-type deposited on both n-type silicon and FTO-coated glass plates. The p-n photoelectrochemical cell is stable and allows for eliminating the photo-corrosion process. Nanomaterial-based electrodes [U+F061]-Fe2O3-MoS2 and ND-RRPHTh have shown an improved hydrogen release compared to [U+F061]-Fe2O3, Al-[U+F061]-Fe2O3 and MoS2-[U+F061]-Fe2O3 nanostructured films in PEC cells. By using p-n configuration, the chronoamperometry results showed that 1% MoS2 in MoS2-[U+F061]-Fe2O3 nanocomposite can be a suitable structure to obtain a higher photocurrent density. The photoelectrochemical properties of the p-n configuration of MoS2-α-Fe2O3 as n-type and ND-RRPHTh as p-type showed 3-4 times higher (450 A/cm2) in current density and energy conversion efficiencies than parent electrode materials in an electrolyte of 1M of NaOH in PEC cells. Titanium dioxide (TiO2) is known as one of the most explored electrode materials due to its physical and chemical stability in aqueous materials and its non-toxicity. TiO2 has been investigated because of the low cost for the fabrication of photoelectrochemical stability and inexpensive material. Incorporation of various percentages (2.5, 5, 16, 25, 50) of TiO2 in Fe2O3 could achieve better efficiencies as the photoanode by enhancing the electron concentration and low combination rate, and both materials can have a wide range of wavelength which could absorb light in both UV and visible spectrum ranges. TiO2 doped with [U+F061]-Fe2O3 film was shown as increasing contacting area with the electrolyte, reducing e-h recombination and shift light absorption along with visible region. The [U+F061]-Fe2O3-TiO2 nanomaterial has shown a more enhanced photocurrent (800 μA/cm2) than metal doped [U+F061]-Fe2O3 photoelectrochemical devices.

Due to their unique structural and magnetic properties, magnetic nanotubes could be used in the field of neuroscience. In this study, hematite and maghemite nanotubes were synthesized and characterized. These magnetic nanotubes with coupled proteins such as albumin or laminin were used to investigate the interaction of nanotubes and their influence on somatosensory neurons from the dorsal root ganglion of rat. Our results indicated differential effects of magnetic nanotubes on neuronal growth based on the nanomaterial.