Rhombohedral α-Fe2O3 Research Articles

Microstructural, morphological, and optical properties of Fe2O3 nanoparticles obtained from Fe-MIM MOF

Abstract This study explores the microstructural, morphological, and optical properties of Fe2O3 nanoparticles synthesized from the pyrolysis of ZIF-8 like Fe-MIM metal-organic frameworks (MOFs). Using X-ray diffraction (XRD) profile analysis methods, including the modified Scherrer, Williamson-Hall (W-H), size strain plot, and Halder-Wagner methods, the impact of annealing temperature on the microstructural parameters and crystal defects of the obtained Fe2O3 nanoparticles was investigated. The nanoparticles exhibited high crystallinity and a rhombohedral α-Fe2O3 phase. Morphological analysis through transmission electron microscopy (TEM) revealed distinct structural features, while UV-vis spectroscopy was employed to examine their optical properties. The results indicated that higher annealing temperatures enhance crystallinity, reduce defect density, and improve atomic mobility. This comprehensive analysis provides valuable insights into the synthesis-structure-property relationships of Fe2O3 nanoparticles, highlighting their potential applications in many applications.

Synthesis and enhanced electrical properties of Ag-doped α-Fe2O3 nanoparticles in PVA films for nanoelectronic applications

Rhombohedral α-Fe2O3 nanoparticles doped with silver (Ag-α-Fe2O3) were successfully synthesized using a hydrothermal method. The structural characteristics and morphology of the synthesized nanoparticles were examined using X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM), wherein the Raman peak was observed at 218/cm. The electrical properties of the Ag-doped α-Fe2O3 nanoparticles layered in polyvinyl alcohol (PVA) film were analyzed through I-V curves, impedance graphs, and measurements of dielectric constant (Ɛ) and dielectric loss (Ɛ′). Through the I-V curve, a current value of 3.68 × 10−2 μA was obtained, which was 52 % greater than that of the PVA film at an applied voltage of ± 100 V. The results demonstrated that the Ag-doped α-Fe2O3 in the PVA film exhibited enhanced electrical properties, with significant increases in both dielectric constant (0.5 × 103) and dielectric loss (11 × 103). Ag-doped α-Fe2O3 in PVA film, therefore, appears to be a promising applicants in Nano electronics.

Synthesis and Characterization of Lauha Bhasma

The preparation of ayurvedic bhasma is particularly challenging, as mass production in modern facilities often lacks the standardized equipment needed to ensure consistent quality, leading to concerns about toxic elements like mercury and arsenic in the final products. Addressing these concerns necessitates the standardization of the synthesis process through the implementation of stringent quality control measures at every stage of preparation. This study is dedicated to the synthesis and comprehensive characterization of lauha (iron) bhasma, employing both traditional methodologies and advanced analytical techniques. The synthesis process began with samanya shodhana (general purification), followed by vishesh shodhana (special purification) and marana (incineration) The resultant product then underwent amrutikaran, involving heating with aloe vera extract at an elevated temperature of 750°C.The synthesized lauha bhasma was meticulously characterized using a combination of classical Ayurvedic techniques and modern analytical methods, including Fourier Transform Infrared Spectroscopy (FTIR), Atomic Absorption Spectroscopy (AAS), X-ray Diffraction (XRD), Brunauer-Emmett-Teller (BET) surface analysis, Scanning Electron Microscopy (SEM), Particle Size Distribution (PSD), and Energy Dispersive X-ray (EDX) analysis. The final product, post-Amrutikaran, successfully passed all traditional Ayurvedic evaluations, affirming the proper formation of bhasma. XRD analysis revealed the formation of rhombohedral α-Fe₂O₃ with only trace amounts of free iron, indicating high purity. SEM and PSD analyses demonstrated the creation of nanosized particles ranging from 50 to 200 nm, complemented by a specific surface area of 12.55 m²/g as determined by BET studies. Crucially, EDX analysis confirmed that the amrutikaran process effectively eliminated mercury from the bhasma, ensuring its safety and compliance with stringent quality standards.

Wurtzite CdS ratio tunability on α-Fe2O3/CdS synergistic heterostructure for enhanced UV-induced photocatalytic decomposition of rhodamine 6G dye pollutant

Hematite α-Fe2O3 exhibits a slow catalytic reaction rate and low performance in aqueous pollutant decomposition. In this work, α-Fe2O3/CdS binary heterostructure composites were created by introducing different ratios of wurtzite CdS into α-Fe2O3 within 0–100 wt% via precipitation and impregnation methods. The photocatalytic performance of α-Fe2O3/CdS was enhanced for the decomposition of aqueous rhodamine 6G (R6G) dye under ultraviolet (UV) irradiation. SEM images reveal that higher CdS loading results in increased interfacial contact between rod-like CdS and spherical-shaped α-Fe2O3. XRD and FTIR results confirm the coexistence of rhombohedral α-Fe2O3 and hexagonal CdS phases, with peak strength proportional to the ratio of component loading, as the respective elements were verified through EDX analysis. The UV-Vis spectroscopic analysis exhibits an enhancement in optical absorption and band gap broadening as the CdS loading rises. α-Fe2O3/CdS with increased CdS loading exhibits faster and more efficient R6G degradation under UV exposure, as evidenced by greater rate constants and degradation efficiency, with optimal CdS loading of 90 wt% achieving a maximum efficiency of 79.14%. The present heterostructure could be employed in future wastewater remediation for effective removal of organic dye pollutants, further promoting clean water preservation for global environmental sustainability.

α-Fe2O3/CeO2 S-scheme heterojunction photocatalyst for enhanced photocatalytic H2 evolution

High photo-stability and effective charge separation are pivotal for hydrogen production over the photocatalysts through solar energy. Here mesoporous CeO2 nanorods were hydrothermally synthesized using cetyltrimethyl ammonium bromide and tetrapropylammonium hydroxide as the template to construct the novel S-scheme heterojunction α-Fe2O3/CeO2 photocatalyst. The obtained heterojunction Fe2O3/CeO2 photocatalyst exhibited outstanding enhanced H2 evolution under visible illumination. The XRD results indicated that the Fe2O3/CeO2 nanocomposites revealed rhombohedral α-Fe2O3 and cubic CeO2 structures without impurities. TEM images revealed the formation of CeO2 nanorods with 400 nm length and 20 nm width decorated with Fe2O3 NPs (10 nm). The optimized S-scheme Fe2O3/CeO2 nanocomposites displayed a superior photocatalytic H2 evolution rate of 2973.2 µmolg−1h−1, which was promoted 5.43 folds greater than that of CeO2 nanorods (547.05 µmolg−1h−1). The electron transport channels in S-scheme Fe2O3/CeO2 nanocomposites interfacial junctions facilitated the directional migration spatial and separation of photocarriers. The H2 evolution rate over the obtained Fe2O3/CeO2 photocatalyst was significantly promoted due to its synergistic effect, porous architecture, oxygen vacancies, small particle size and high visible light absorption ability. There was no decrease in the H2 evolution rate after five cycles of photocatalytic H2 evolution, which could verify the durability and stability of the Fe2O3/CeO2 nanocomposite. The photoluminescence (PL) and electrophotochemical responses were conducted to determine the charge carriers separation rate and understand the photocatalytic mechanism.

Synthesis of carbon supported iron oxide nanochips and their composite with glutathione: A novel electrochemical sensitive material

In this study, bare iron oxide nanochips (NCs), carbon-supported iron oxide nanochips (C@α-Fe2O3), and glutathione-supported C@α-Fe2O3 nanocomposite (Glu/C@α-Fe2O3) were synthesized. As-synthesized materials were inspected using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), and a UV-visible absorption approach. Physical investigations confirmed the synthesis of rhombohedral phased α-Fe2O3, whereas FESEM certified nano-sized material formation. Voltammetry and impedance studies were used to evaluate and compare the electrochemical sensing activities. The electrochemical behavior of the Glu/C@α-Fe2O3 nanohybrid was investigated using differential pulse voltammetry (DPV) to identify their sensitivity towards 2-nitrophenol (2-NP) and 4-nitrophenol (4-NP). The stability of the square wave voltammetry SWV signals was detected in the range of 50–0.05 μM for both 2-NP and 4-NP. All electrochemical factors that influence the effectiveness of the developed sensors, including pH of the medium, accumulation time, and the influence of supporting electrolytes were thoroughly investigated. The sensor-based on our prepared electroactive material demonstrated remarkable electrocatalytic activity and good conductivity with a broad linear range, a low detection limit and high sensitivity for nitrophenol isomer reduction. We also tested the sensor for practical applications in water samples. These results showed that the suggested method could be used in the future to detect potentially dangerous environmental pollutants in water samples.

From Himba indigenous knowledge to engineered Fe2O3 UV-blocking green nanocosmetics

This contribution reports on the physical properties of the natural Namibian red Ochre used by the Himba Community in a form of a formulation, so called Otjize as a skin protective and beauty cream. The morphological and crystallographic studies of this red ochre validated its nano-scaled dominating phase of rhombohedral α-Fe2O3 nanocrystals with an additional hydrolized oxide component in a form of γ-FeOOH. The optical investigations showed that such a red ochre exhibits an exceptional UV filtration and a significant IR reflectivity substantiating its effectiveness as an effective UV-blocking & solar heat IR reflector in support of the low skin cancer rate within the Namibian Himba community. In addition, such nanocrystals exhibited a non-negligible antibacterial response against E. Coli & S. Aurus. This study seems confirming the effectiveness of the indigenous Otjize as an effective skin UV protection cream with a sound antimicrobial efficacy against e-Coli & S-Aurus.

Preparation of Fe2O3-ZnO Nanocomposites: Structure and Optical Properties

Background: The synthesis of Fe2O3/ZnO nanocomposites has gained wide acceptance in recent years due to its magnetic, photoluminescence and catalytic properties, and as an active element in gas sensors. This type of composite particle has potential biological and biomedical applications such as the detection of cancer cells, bacteria and viruses, and for magnetic separation. Objective: In the present study, first we synthesized the Fe2O3/ZnO nanoparticles, and then the structural, optical and surface morphological properties were investigated by XRD, HRTEM, FESEM, XRF and FTIR analyses. Methods: Fe2O3-ZnO nanoparticles were fabricated by a solgel synthesis method by combining iron chloride hexahydrate and zinc sulfate heptahydrate. In the beginning, 2g of Polyvinylpyrrolidone (PVP) stabilizer was dissolved in 100 mL deionized water and then 5 g FeCl3 was added to the solution with stirring at room temperature. Then 5g of ZnSO4 was added to the solution and synthesis temperature was increased to 100 °C. The product was evaporated for 3 hours, cooled to room temperature and finally calcined at 600 °C for 3 hours. Result: The XRD results showed single-phase Fe2O3-ZnO nanocomposites with a hexagonal wurtzite structure of ZnO and spinel phase of rhombohedral α-Fe2O3. The crystallite size of as-prepared sample was determined at about 45 nm and annealed one was calculated around 40 nm. The SEM images showed that the Fe-Zn nanoparticles changed from spherical shape to rod shape by increasing the temperature after annealing. The TEM studies showed the core-shell nanoparticles with a mean diameter of 47 nm. The sharp peaks in the FTIR spectrum determined the stretching vibrations of Fe and Zn groups in the frequencies of 620, 565 cm-1 and 410 cm-1. Conclusion: The XRD data indicates a single-phase Fe2O3-ZnO structure. The SEM images show that the nanoparticles changed from sphere-like shape to rod-like shape by increasing the annealing temperature. TEM image exhibits the core-shell Fe-Zn nanoparticles with an average diameter of about 37 nm. From the FTIR data, it is shown that the presence of Fe-Zn stretching mode and the intensity of the peaks increased by increasing the annealing temperature. XRF analysis showed peaks of iron and ferrite elements, and an increase in the Zn weight percent was observed from 26.35 %Wt. to 49.26 %Wt. with increasing temperature.

Investigation on photocatalytic activity of bio-treated α-Fe2O3 nanoparticles using Phyllanthus niruri and Moringa stenopetala leaf extract against methylene blue and phenol molecules: Kinetics, mechanism and stability

In this article, Bio-treatment of α-Fe2O3 nanostructure using Phyllanthus niruri and Moringa stenopetala leaf extract as an effective reducing agent is carried out. The preparation of the rhombohedral α-Fe2O3 nanostructure is confirmed using X-ray diffraction analysis. The adsorption of biomolecules on the surface of the α-Fe2O3 nanostructure is confirmed using FT-IR. The chemical state analysis of green treated α-Fe2O3 nanoparticles was carried out using XPS techniques and it confirms the existence of Fe-2p and O-1s elements. The surface area of Moringa stenopetala leaf extract treated α-Fe2O3 nanoparticles were identified using BET analysis and it is found to be 58 m2/g. The formation of spherical shaped α-Fe2O3 nanoparticles was identified using HR-TEM analysis and EDX reveals the absence of any other impurities. The reactive species trapping experiment confirms the rapid production of O2•- and •OH radicals during photocatalytic process. The degradation efficiency of PNFO and MSFO against MB after 180 min was estimated to be 92% and 96%, respectively. The degradation efficiency of PNFO and MSFO against phenol after 240 min was estimated to be 90% and 92%, respectively.

Structural and optical properties of α-Fe2O3 nanoparticles realized by simple thermal decomposition route

Herein, we present the synthesis and thermal treatment effect of Hematite (α-Fe2O3). Hematite nanoparticles were prepared by repeated calcination of a precursor obtained from Fe(NO3)3.9H2O and Hexamethylenetetramine (HMTA). Thermal treatment of the precursor at 400 °C for 4 h, resulted in the formation of Fe3O4 nanoparticles, which on repeated calcination at 400 °C, 500 °C and 600 °C, resulted in α-Fe2O3 nanoparticles. Synthesized samples were characterized by using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy and UV–vis spectroscopy techniques. XRD result reveals the formation of cubic Fe3O4 phase at 400 °C, which is transformed into rhombohedral α-Fe2O3 polymorphs on repeated calcination. Crystallinity of the α-Fe2O3 is enhanced on repeated calcination up to 500 °C after that it gets slightly amorphized at 600 °C. Raman and FTIR results further corroborate the XRD result. Optical band gap of most crystalline α-Fe2O3, as estimated from UV–vis results, is 1.87 eV. Urbach energy of the samples has been calculated from absorption data, which shows the minimum value for most crystalline material. These findings demonstrate the close relation between structure and optical properties of α-Fe2O3.

Study of α-Fe2O3@ ZnO nanoleaves: Morphological and optical study

In this paper, α-Fe2O4@ZnO nanoparticles (NPs) were synthesized by coprecipitation method in the presence of PVP and EG surfactants. The samples were charactrized by x-ray fluorescence (XRF), x-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and fourier transform infrared spectroscopy (FTIR). The XRD results exhibited rhombohedral α-Fe2O3 and wurtzite structure of ZnO. The SEM images showed that the NPs changed from rod-shape to nanoleaves particles after heat treatment. The TEM studies displayed the formation of Fe2O3@ZnO core-shell of as-synthesized NPs. The stretching vibrations peaks in FTIR in the wavenumber of 532 cm-1 and 473 cm-1 ascribed to the Fe and Zn groups. The XRF data indicated decreasing of the Fe weight percent from 22 %Wt. to 25 %Wt., after heat treatment.

Fabrication of high photosensitivity nanostructured n-Fe2O3/p-Si heterojunction photodetector by rapid thermal oxidation of chemically sprayed FeS2 film

In this study, we have reported a novel route for the preparation of α-Fe2O3 by rapid thermal oxidation RTO of chemical sprayed FeS2 film at 550 °C/20 s condition under oxygen ambient. The direct optical band gap of Fe2O3 was 2.6 eV, while its indirect energy gap was 1.7 eV. The x-ray diffraction XRD studies show that the FeS2 film has pyrite cubic structure and changed to rhombohedral α-Fe2O3 film after oxidation. Scanning electron microscope SEM and transmission electron microscope TEM investigations confirm the formation of Fe2O3 nanorods with a diameter of 65 nm. Energy dispersive x-ray analysis EDX confirms complete conversion of the FeS2 to Fe2O3 film after RTO process. Raman shift data of Fe2O3 shows the presence of five Raman active vibration modes indexed to A1g and E1g modes. The dark and illuminated current-voltage properties of n-Fe2O3/p-Si heterojunctions have been investigated in the absence of the buffer layer and the ideality factor of n-Fe2O3/p-Si was 2.7. The responsivity of Fe2O3/Si photodetector was 0.51 A W−1 at 500 nm and 0.37 A W−1 at 850 nm. The specific detectivity of the photodetectors was measured as a function of wavelength. The rise time of the photodetector was measured and it was around 60 ns. The energy band line-up of n-Fe2O3/p-Si heterojunction was demonstrated under illumination condition.

Fabrication and magnetic transformation from paramagnetic to ferrimagnetic of ZnFe2O4 hollow spheres

Abstract ZnFe2O4 hollow spheres (ZFHs) with sizes of 200–302 nm were synthesized by simple impregnating method using the as-prepared phenolic formaldehyde (PF) spheres as templates and subsequent annealing at 500–700 °C. The prepared ZFHs are assembled by a large number of small nanoparticles with sizes of 15–20 nm, and many mesopores exist among these nanoparticles. The samples annealed at 500–550 °C exhibit a single cubic spinel structure, while higher annealing temperature leads to the formation of hexagonal ZnO and rhombohedral α-Fe2O3 secondary phases. The size of the assembled nanoparticles increases with the increase in annealing temperature. Novel magnetic transformation from paramagnetic to ferrimagnetic is induced by the reduction of annealing temperature and the saturation magnetization significantly increases from 2.3 to 13.5 A·m2/kg. The effect of the formation of hollow sphere structure on the redistribution of Fe3+ and Zn2+ in the spinel structure was studied.

Iron Oxide Nanoparticles as Potential Scaffold for Photocatalytic and Sensing Applications.

Herein, we report photocatalytic and fluorescence sensing applications of iron oxide (α-Fe₂O₃) nanoparticles synthesized by facile low-temperature simple solution process. The synthesized nanoparticles were characterized by several techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) attached with energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), UV-visible spectroscopy and fluorescence spectroscopy. The detailed analysis revealed that the synthesized nanoparticles were well-crystalline, grown in very high density and possessing rhombohedral α-Fe₂O₃ crystal structure. The prepared nanoparticles were used as efficient scaffold for photocatalytic and sensing applications. The detailed photocatalysis results revealed that in presence of an appropriate amount of α-Fe₂O₃ nanoparticles as photocatalyst, a significant dye degradation of methyl orange (MO) was observed in 140 min. In addition, the fabricated florescence sensor based on α-Fe₂O₃ nanoparticles exhibited a low detection limit of ∼3.33 μM/L towards picric acid. The observed results clearly confirmed that the synthesized α-Fe₂O₃ nanoparticles are potential scaffold for photocatalysis and sensing applications.

Hematite α-Fe2O3 induced magnetic and electrical behavior of NiFe2O4 and CoFe2O4 ferrite nanoparticles

Abstract In this paper, we have investigated the structural, magnetic and electrical properties of ferrites (NiFe2O4 and CoFe2O4), hematite α-Fe2O3, NiFe2O4/α-Fe2O3 and CoFe2O4/α-Fe2O3 nanoparticles. These nanoparticles were synthesized by a chemical combustion method. The cubic phase of spinel NiFe2O4 and CoFe2O4 and rhombohedral α-Fe2O3 is studied by X-ray diffraction technique. The Williamson-Hall plot is used to find the lattice strain and nanoparticles size of each NiFe2O4, CoFe2O4, α-Fe2O3 and their composites. The cation distribution on A and B-sites of NiFe2O4 and CoFe2O4 ferrites with the influence of α-Fe2O3 results to mixed spinel structure, is calculated by Bertaut method of X-ray diffraction intensity. The average particles size of present nanoparticles is measured with Scherrer’s relation, Williamson-Hall plot and the transmission electron microscopy, which confirmed particles size that lies in 47–147 nm. The magnetic results are pointy depends on nano-size, cation distribution, content of ferrite in α-Fe2O3 and exchange interaction among Fe3+/Fe2+ ions. The major advantage of NiFe2O4/α-Fe2O3 and CoFe2O4/α-Fe2O3 nanocomposites is to observe stability in magnetization up to higher temperature. This may due to antiferromagnetic behavior of α-Fe2O3 over ferrimagnetic NiFe2O4 and CoFe2O4. The rich Fe content in α-Fe2O3 composite and the interfacial polarization based on Wagner–Sillar effect might be enhanced dielectric properties. In order to explore the effects of observed variations in the microstructure and cation distribution on the dielectric properties, the impedance data is used to extract grains and grain boundaries effects.

Controllable synthesis of rhombohedral α-Fe2O3 efficient for photocatalytic degradation of bisphenol A

One-step controllable synthesis of rhombohedral α-Fe2O3 photocatalyst has been successfully developed by P123 soft template assisted method. A combination analysis of XRD, BET, SEM and HRTEM has documented that P123 surfactant plays a crucial role in the controllable synthesis of rhombohedral α-Fe2O3 with the exposure of (110) and (012). The as-obtained α-Fe2O3 material is efficient for the photocatalytic degradation of Bisphenol A (BPA). About 91% of BPA (30 mg/L) was degraded by using 1 g/L α-Fe2O3 within 6 h under the simulated sunlight irradiation, which was almost twice higher than that of commercial Fe2O3. More importantly, reaction intermediates (e.g., 4, 4′-methylenediphenol, phenol and lactic acid) were confirmed by LC–MS/MS analysis, and the rational pathway of BPA degradation was finally proposed.

Direct Synthesis of Iron Oxide (α-Fe2O3) Nanoparticles by the Combustion Approach

A facile and rapid combustion method was developed to synthesis to produce iron oxide (α-Fe2O3) nanopowder using dissolution of iron nitrate (as the oxidant) and glycine (as fuel) as the starting materials. Generally, combustion synthesis of different oxides involves a self-sustained reaction between a metal nitrates (oxidizer) and a urea, glycine, citric acid, hydrazine (fuel). Stoichiometric amounts of iron nitrate and glycine were dissolved in deionized water and poured into a quartz container can be mixed well by magnetic stirring for 1/2 h, which makes them almost as homogeneous mixtures, which was placed in a furnace at 300 °C. Initially, the solution boils and undergoes dehydration followed by decomposition with the evolution of large amount of gases with white fumes coming out from the exhaust opening provided on the top of the furnace in 15 minutes. After the solution reaches the point of spontaneous combustion, it begins burning and releases lots of heat, vaporizes all the solution instantly and becomes a foamy white solid powder. X-ray diffraction studies confirmed that the resultant powder with well-crystalline structure of pure α-Fe2O3 are produced using a single approach while simultaneously avoiding additional calcination procedures. Morphological analysis of the spherical structure of nanoparticle was achieved by SEM analyses is in the range of 35 nm and the study of the chemical the Fe2O3 bonds created was made possible by FTIR analysis. The XRD, FTIR and Raman spectra confirmed the formation of rhombohedral structural α-Fe2O3. Overall glycine-nitrate combustion synthesis has an outstanding potential for producing pure powder form of α-Fe2O3 nano particles, which leads to use in applications require high strength crystalline material.

Structural and thermoelectric properties of hydrothermal-processed Ag-doped Fe2O3

Fe2-xAgxO3 (0 ≤ x ≤ 0.04) nanopowders with various Ag contents were synthesized at different hydrothermal reaction temperatures (150 °C and 180 °C). Their structural properties were fully investigated through an X-ray diffraction, a Fourier transform infrared spectroscopy, and an X-ray photoelectron spectroscopy. The hydrothermal reaction temperature, time, and Ag content remarkably affected the morphological characteristics and crystal structure of the synthesized powders. The Fe2-xAgxO3 (0 ≤ x ≤ 0.04) powders synthesized at 150 °C for 6 h and the Fe2-xAgxO3 (0.02 ≤ x ≤ 0.04) powders synthesized at 180 °C for 12 h formed the orthorhombic α-FeOOH phase with a rod-like morphology, whereas the Fe2-xAgxO3 (0 ≤ x ≤ 0.01) powders synthesized at 180 °C for 12 h formed the rhombohedral α-Fe2O3 phase with a spherical-like morphology. The Fe1.98Ag0.02O3 fabricated by utilizing Fe1.98Ag0.02O3 powders synthesized at 180 °C showed the largest power factor (0.64 ×10−5 Wm−1 K−2) and dimensionless figure-of-merit (0.0036) at 800 °C.

Deformations of the α-Fe2O3 rhombohedral lattice across the Néel temperature

High-resolution synchrotron radiation powder diffraction patterns of α-Fe2O3 measured between room temperature and 1100 K, i.e. above the Néel temperature T N = 950 K, have been analyzed. The integral breadths of the Bragg peaks show a hkl-dependent anisotropy, both below and above T N. This anisotropy can be quantitatively described by using a statistical peak-broadening model [Stephens (1999). J. Appl. Cryst. 32, 281]. Model calculations show that the rhombohedral α-Fe2O3 lattice is deformed and the deformation leads to a monoclinic lattice with the unique monoclinic axis along the hexagonal [110] direction both below and above T N. The monoclinic symmetry of bulk α-Fe2O3 is compatible with α-Fe2O3 nanowire growth along the [110] direction reported in Fu et al. [Chem. Phys. Lett. (2001), 350, 491].

Single step combustion synthesis, characterization and photocatalytic application of α-Fe2O3-Bi2S3 heterojunctions for efficient and selective reduction of structurally diverse nitroarenes

A series of α-Fe2O3-Bi2S3 heterojunction materials were prepared by a one-step autocombustion method employing thiourea as fuel. The heterojunction materials were characterized using XRD, UV–Vis-DRS, FTIR, PL, XPS, FESEM, TEM and HRTEM analytical techniques. XRD study indicated presence of rhombohedral α-Fe2O3 and orthorhombic Bi2S3 in the heterojunction materials. The heterojunctions displayed better optical absorption in the visible region and enhanced charge carrier separation characteristics. The oxidation state of the constituent elements on the surface was established from XPS study. IR study showed the characteristic vibrational features of both α-Fe2O3 and Bi2S3 phases. Microscopic studies indicated presence of well dispersed α-Fe2O3 nanorods in a continuous Bi2S3 matrix. The α-Fe2O3 nanorods were typically 30–50nm in diameter and 120–150nm in length growing isotopically in different direction from a single nucleation point. The calculated band positions of both components indicated a facile electrons transfer from the conduction band of α-Fe2O3 to Bi2S3 whereas migration of holes occurs in the reverse direction yielding a type-II heterojunction. The α-Fe2O3-Bi2S3 heterojunctions materials were evaluated as selective and efficient photocatalyst for the hydrogen transfer reduction of nitroarenes under visible light illumination. Structurally diverse nitroarenes could be selectively reduced to the corresponding amines in high yield and purity using α-Fe2O3-Bi2S3 as photocatalyst.