Fe-doped In2O3 Research Articles

Efficient photo-Fenton reaction for tetracycline and antibiotic resistant bacteria removal using hollow Fe-doped In2O3 nanotubes: From theoretical research to practical application

The low exposure of active sites and the slow electron transfer rate still restrict the wide application of the photo-Fenton system of Fe-based photocatalyst in practical water treatment. Herein, we prepared a hollow Fe-doped In2O3 nanotube (h-Fe-In2O3) catalyst for activating hydrogen peroxide (H2O2) to remove tetracycline (TC) and antibiotic resistant bacteria (ARB). Incorporation of Fe could shorten the band gap and increase the absorption capacity of visible light. Meanwhile, the increase of electron density at the Fermi level promotes the interfacial electron transport. The large specific surface area of the tubular structure exposes more Fe active site and the Fe-O-In site reduces the energy barrier of H2O2 activation, resulting in more and faster formation of hydroxyl radicals (•OH). After continuous operation for 600 min, the h-Fe-In2O3 reactor still can remove 85% TC and about 3.5 log ARB in secondary effluent, showing good stability and durability for practical wastewater treatment.

Effects of substitutional Fe and oxygen vacancies on room temperature ferromagnetism of Fe-doped In2O3 dilute magnetic nanowires

The magnetic behavior and origin of dilute magnetic nanowires are critical for further development and application of nanoscale spintronic devices. In this work, the Fe doping into single-crystalline In 2 O 3 nanowires are fabricated using chemical vapor deposition (CVD) method to research these problems based on theoretical and experimental analysis. The XRD, XPS, TEM and XAS results show that the deposited Fe-doped In 2 O 3 nanowires possess the cubic bixbyite structure and the doped Fe ions substitute for the In sites of In 2 O 3 lattice with +2 and + 3 mixed valences. The PL results prove the existence of single ionized oxygen vacancies as well as the defect complexes of donor (oxygen vacancy)-acceptor (Fe impurity) pairs. The intrinsic room temperature ferromagnetism can be observed for the Fe-doped In 2 O 3 nanowires and the saturation magnetization largely enhance with Fe doping. The first principles calculations show that the introducing of oxygen vacancy defects can cause strong hybridization between Fe 3d and O 2p orbitals at the Fermi level, resulting in the transition from antiferromagnetic to ferromagnetic coupling between the Fe ions. These results open up the possibilities for exploring spin-electronic devices. • Effects of Fe doping on local structure, optical and magnetic properties of Fe-doped In 2 O 3 nanowires are studied. • The doped Fe ions substitute for the In sites of In 2 O 3 lattice with +2 and + 3 mixed valences. • Single ionized oxygen vacancies and the defect complexes of donor -acceptor pairs can be observed. • Introducing of oxygen vacancies results in the transition from antiferromagnetic to ferromagnetic coupling between Fe ions.

Magnetic behavior and site occupancy in Fe-doped In2O3 nanoparticles

(In1-xFex)2O3 monophasic nanoparticles were prepared by a freeze-drying process followed by heat treatment after which they were characterized by magnetization measurements and Mössbauer spectroscopy at temperatures ranging from 300 to 4.2 K. The iron cations were trivalent and substituted for the indium cations in both cationic sites, 24d and 8b, of the oxide matrix, showing an occupancy preference that depends on x. Two different magnetic regimes were observed after varying the temperature of the doped samples, and both correlated with the iron magnetic moments. At room temperature, the moments at the site 24d were partially ordered with ferromagnetic alignment, whereas those at the site 8b showed paramagnetic behavior. After decreasing the temperature, both sublattices become progressively ordered and more robustly below 50 K.

Optical transmittance and electrical transport investigations of Fe-doped In2O3 thin films

Optical transmittance and electrical transport investigations of Fe-doped In2O3 thin films

Mesoporous Fe-doped In2O3 nanorods derived from metal organic frameworks for enhanced nitrogen dioxide detection at low temperature

Mesoporous Fe-doped In2O3 nanorods derived from metal-organic frameworks (In/Fe-MIL-68s) were synthesized for NO2 detection. The morphologies, structures and NO2 gas-sensing performances of the Fe–In2O3 nanorods were systematically investigated. Texture characterizations demonstrate that the as-prepared Fe–In2O3 nanorods show rich porous structures, high specific surface areas and reduced grain sizes. Gas-sensing measurements display that the Fe–In2O3 nanorods derived from In/Fe-MIL-68s with the Fe(Ⅲ) content of 5 mol.% (Fe(5)-In2O3) exhibit high response (82) and short response/recovery time (70/65 s) towards 2 ppm NO2 at 80 °C compared with their counterparts. Besides, superior selectivity and good stability are observed. The sensing mechanism studies reveal that the improved gas-sensing performances are attributed to the decrease in the gran size, the formation of rich oxygen vacancies and band gaps narrowing caused by Fe(Ⅲ) doping. Therefore, this work indicates that the Fe–In2O3 nanorods derived from metal-organic frameworks precursors can be a promising candidate for NO2 detection.

Enhancement of saturation magnetisation through the addition of a nonmagnetic element in substitutional Fe-doped In2O3 powder

Iron-doped indium oxide is a promising material for spin electronics (spintronics) applications. Herein, an experimental investigation of the effect of adding a nonmagnetic element (magnesium) on the enhancement of the room-temperature ferromagnetism in substitutional iron-doped In2O3 powder was conducted. A new doping process, which avoids the formation of Fe nanoclusters in (In0.85Fe0.15−xMgx)2O3 (x = 0.00, 0.01, 0.03, 0.05) powders, was developed. The resulting powders were characterised by X-ray diffraction (XRD), superconducting quantum interference device, Mössbauer spectroscopy, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy. The XRD analysis revealed that Fe and Mg ions were incorporated into the In3+ sites in the In2O3 lattice without altering the cubic bixbyite structure. Magnetic measurements indicated the coexistence of ferromagnetic and paramagnetic phases. Room-temperature ferromagnetic behaviour with remarkable enhancement of the saturation magnetisation was observed for decreasing Fe ions and increasing nonmagnetic Mg concentrations. Mössbauer spectra confirmed the coexistence of ferromagnetic (sextet) and paramagnetic (doublet) phases, with a clear effect of Mg concentration. The enhancement in the magnetic moment with increasing Mg doping is attributed to the large defects and oxygen vacancies induced in In2O3 by Fe and Mg co-doping. These results will be useful for the development of Fe-doped In2O3 semiconductor materials for advanced applications.

(In1-xFex)2O3 nanostructures for photocatalytic degradation of various dyes

In this work, Fe-doped In2O3 nanostructures have been prepared using a simple chemical route. Various physio-chemical properties have been investigated. XRD results show that Fe dopant induces no impurity phase in cubic In2O3. For optical properties, Fe dopant induced blue-shift appears in absorption spectrum of In2O3. A comparison of photocatalytic activity of neat In2O3 and Fe-doped In2O3 nanoparticles has been obtained. An enhancement of UV light triggered photocatalytic activity to photodegrade methylene blue, RhB and methyl orange upto 83%, 95.36% and 93.77% respectively has been achieved. The existence of oxygen vacancies in Fe doped In2O3 and optimized bandgap makes Fe doped In2O3 a potential photocatalyst.

Fe-doped In2O3 nanostructures synthesized via a freeze-drying process: Structural and optical properties

(In1−xFex)2O3 nanoparticles were prepared by freeze-drying an aqueous solution of indium acetate and iron acetate followed by heat treatment. The samples were characterized by high-resolution X-ray diffraction, transmission electron microscopy, Fourier transform infrared and UV–Vis diffuse reflectance spectroscopy. The x ≤ 0.12 nanoparticles were shown to be monophasic and crystallized with the bixbyite structure. Iron doping the In2O3 semiconductor reduced the lattice parameter, crystallite size, and optical bandgap.

Preparation of Fe-doped In2O3 gas sensing semiconductor by one-step impregnation with enhanced ethanol sensing

Abstract Here we demonstrate high-performance ethanol sensors based on Fe-doped In2O3 mesoporous nanospheres. By using FDU-12 as template via a facile one-step impregnation method Fe-doped In2O3 were synthesized, which display high surface area, uniform shape, ordered mesoporous structure and small particle size. The Fe-doped In2O3 exhibited a larger response to ethanol gases than pure In2O3 under all measured concentrations. Furthermore, the effect of Fe/In molecular ratio on sensing property was investigated by comparing their response. The enhanced sensing properties could result from the unique mesoporous structure and the synergic electronic interaction between the guest Fe dopant and the host In2O3 material.

Discriminative detection of indoor volatile organic compounds using a sensor array based on pure and Fe-doped In2O3 nanofibers

Representative indoor volatile organic compounds (VOCs) such as benzene, xylene, toluene, formaldehyde, and ethanol need to be detected in a highly sensitive and discriminative manner because of their different impact on human health. In this study, pure and 0.05, 0.1, 0.3, and 0.5 at% Fe-doped In2O3 nanofibers were prepared by electrospinning and their gas sensing characteristics toward the aforementioned VOCs were investigated. The doping of In2O3 nanofiber sensor with 0.05 and 0.1 at% Fe shifted the temperature to show the maximum responses to benzene, xylene, and toluene, and reduced responses to ethanol and formaldehyde, thus demonstrating changed gas selectivity. The gas sensing characteristics of 0.5 at% Fe-doped In2O3 nanofiber sensor were substantially different from those of the other sensors. Significantly different gas sensing patterns of pure and Fe-doped In2O3 sensors could be used to discriminate between the five different VOCs at 375 °C and to distinguish between the aromatic and non-aromatic gases at all sensing temperatures. The mechanism underlying the Fe-induced change in gas sensing characteristics has been discussed in relation to the variation of catalytic activity, morphology, oxygen adsorption, and charge carrier concentration.

Ferromagnetic order in substitutional Fe-doped In2O3 powder

We report an experimental investigation of the room-temperature ferromagnetism of an Fe-doped In2O3 system. (In1−xFex)2O3(x = 0.00, 0.02, 0.06,0.10,0.14 or 0.18) powders were prepared by a standard solid-state reaction method followed by sintering in air at 1200 °C for 48 h. The influence of Fe-doping concentration on the structural and magnetic properties of the In2O3 samples was studied. X-ray diffraction analysis reveals that Fe ions are incorporated into the In3+ sites of the In2O3 lattice without altering the cubic bixbyite structure. Magnetic characterization shows ferromagnetic behavior at room temperature for all the Fe-doped In2O3 samples. The observed ferromagnetism is attributed to the oxygen vacancies induced by substitution of Fe into In3+ sites and vacuum annealing. A model of ferromagnetic exchange interactions was proposed to explain the ferromagnetism in this system.

Formation of Fe-doped In2O3 nanowires and influence evolution of Fe ions on its photoluminescence property

In2O3 and Fe-doped In2O3 nanowires (NWs) were prepared on a Si substrate by using the CVD method. Structure analysis showed that the preparation of Fe-doped In2O3 NWs formed the body-centered cubic structure, which is nearly consistent with that of the In2O3. Importantly, the characteristic peak at (222) and (400) of Fe-doped In2O3 shifted to high angle, owing to the ionic radii of Fe3+ ions (0.79 Å) is much smaller than that of In3+ ions (0.94 Å). Morphology showed that the nanowires, with diameters of 100–150 nm and lengths of tens to hundreds of micrometers, grew along the [100] direction with spacing distance at 0.506 nm. Fluorescence test results showed that the spectral peak of Fe-doped In2O3 nanowires shifted to 419 and 438 nm, 3 nm blue-shifted compared with that of In2O3 NWs in 416 and 435 nm. Thanks to the assessment of the first-principle calculations by using density functional theory, the crystal structures of In2O3 and Fe-doped In2O3 NWs have been designed. It can be found that the doped Fe3+ ions introduced the distortion of the crystal lattice and produced more oxygen vacancies in the crystal lattice, the total volume and valence charge is obviously decreasing from 128.46 to 105.51 and 88 to 78, respectively. Further research found that the doped Fe atoms lead to a smaller band gap, from 1.7 eV to around 0.7 eV, resulting in the blue shift of the PL spectrum. The distortion of the crystal lattice should be responsible for the decrease of the band gap of the In2O3 semiconductor. Thus, the formation of Fe-doped In2O3 NWs is facile and the assessment using first-principle calculations can offer a much deeper understanding of the influence of Fe ions on its photoluminescence property.

Intrinsic or Interface Clustering-Induced Ferromagnetism in Fe-Doped In2O3-Diluted Magnetic Semiconductors.

Five percent Fe-doped In2O3 films were deposited using a pulsed laser deposition system. X-ray diffraction and transmission electron microscopy analysis show that the films deposited under oxygen partial pressures of 10-3 and 10-5 Torr are uniform without clusters or secondary phases. However, the film deposited under 10-7 Torr has a Fe-rich phase at the interface. Magnetic measurements demonstrate that the magnetization of the films increases with decreasing oxygen partial pressure. Muon spin relaxation (μSR) analysis indicates that the volume fractions of the ferromagnetic phases in PO2 = 10-3, 10-5, and 10-7 Torr-deposited samples are 23, 49, and 68%, respectively, suggesting that clusters or secondary phases may not be the origin of the ferromagnetism and that the ferromagnetism is not carrier-mediated. We propose that the formation of magnetic bound polarons is the origin of the ferromagnetism. In addition, both μSR and polarized neutron scattering demonstrate that the Fe-rich phase at the interface has a lower magnetization compared to the uniformly distributed phases.

The dramatic enhancement of ferromagnetism and band gap in Fe-doped In2O3 nanodot arrays

Ordered Fe-doped In2O3 nanodot arrays with diameters between 35 nm and 80 nm are fabricated using pulsed laser deposition with the aid of ultrathin porous anodized aluminumoxide templates. The 5 at.% Fe doped In2O3 nanodot arrays are shown to consist of the cubic bixbyite structure of In2O3. The nanodot arrays are demonstrated to be doped by Fe ions with mixed valences of +2 and +3, ruling out the presence of cluster and secondary phase related to Fe. The nanodot arrays exhibit the ferromagnetism at room temperature, where the magnetic moment increases as the dot size is reduced, rising to a maximum of about 230 emu/cm3 (equivalent to an average moment on the Fe ions of 15.30 µB/Fe). This indicates an effect due to the surface of the nanodot arrays. The optical band width is also increased to 4.55 eV for the smallest dot array, thus indicating that the surface states are responsible for the magnetism and also enhance the band gap due to Burstein-Moss effect. Our results will be benefit for understanding the physical properties of oxide semiconductor nanostructures in the application of nano-spintronics devices.

Probing the Role of Dopant Oxidation State in the Magnetism of Diluted Magnetic Oxides Using Fe-Doped In2O3 and SnO2 Nanocrystals

Investigation of the origin of high-Curie temperature ferromagnetism in diluted magnetic oxides has become one of the focal points of research on solid-state magnetism. While several possible mechanisms have been proposed theoretically, broader experimental evidence is still lacking. Here we report a comparative study of the electronic structure and magnetic properties of colloidal Fe-doped In2O3 and SnO2 nanocrystals, as building blocks for grain-boundary-rich diluted magnetic oxide films. The dopant ions in both nanocrystal host lattices are principally in 3+ oxidation state, with possibly a minor presence of Fe2+ in In2O3, and no conclusive evidence of the presence of Fe2+ in SnO2 nanocrystals. Subsequently, we found that Fe-doped In2O3 nanocrystalline films exhibit only minor ferromagnetic ordering (with a magnetic moment of less than ca. 0.1 μB/Fe) and decreasing saturation magnetization with increasing doping concentration at room temperature. The saturation magnetic moment of Fe-doped SnO2 nanocrys...

Effects of Fe-Doping on the Structural and Magnetic Properties of Indium Oxide Nanoparticles Synthesized by Bottom up Techniqu

We study Fe doped In2O3 nanoparticles (NPs) from structural and magnetic point of view. X-ray diffraction (XRD) and transmission electron microscopy (TEM) reveal cubic bixbyite structure for both pure and Fe doped samples thereby confirming successful incorporation of Fe in host In2O3 lattice. Average crystallite size of pure and Fe doped (5% and 10%) In2O3 as calculated by Scherer’s formula shows slight increase from 21 nm for pure to 27 nm for the sample with 10% Fe content. The Williamson Hall (WH) method was also utilized to further determine crystallite size and Fe induced strain in In2O3 lattice. The crystallite sizes by WH plot are found to be 18 nm (for undoped), 22 nm (for 5% Fe) and 24 nm (for 10% Fe). These values are in good agreement with TEM results. Energy dispersive x-ray spectroscopy (EDX) indicates the existence of some oxygen vacancies in Fe doped In2O3 samples. Magnetic measurements show that all Fe doped In2O3 NPs exhibit typical ferromagnetic hysteresis loop with saturation magnetization Ms increasing with increasing Fe concentration. Temperature dependence of field cooled (FC) and zero field cooled (ZFC) magnetizations show no divergence and transition from ferromagnetism to paramagnetism in the temperature range of 5 to 300 K. This evidences a robust room-temperature-ferromagnetism (RTFM) in these NPs. The RTFM of our samples is attributed to the presence of oxygen vacancies in our samples.

Fabrication and formaldehyde sensing performance of Fe-doped In2O3hollow microspheres via a one-pot method

Pure and Fe-doped In2O3 hollow microspheres (HMSs) constructed from numerous nanoparticles have been successfully synthesized via a simple and efficient one-pot method combined with a subsequent thermal treatment. Various techniques were employed to acquire the crystalline and morphological information of the as-obtained samples. Structural characterization indicated that the as-prepared Fe-doped In2O3 HMSs displayed a porous structure with a coarse surface and a diameter of approximately 1 μm. The lattice constants for In2O3 in the Fe-doped product were slightly smaller than those in the pure one, which could be apparently revealed by XRD results. Furthermore, gas sensing performance of the pure In2O3, Fe-doped In2O3 and pure Fe2O3-based gas sensors to the ppm level of formaldehyde (HCHO) vapor was also systematically investigated at a low operating temperature of 260 °C. It has been demonstrated that the Fe-doped In2O3 sensor showed enhanced sensing properties compared with the pure ones with a response of about 12.9 to 100 ppm of HCHO vapor, as well as good selectivity for indoor carcinogenic gases and long-term stability. The enhanced sensing properties could result from the unique hollow structure with a porous shell and the synergic electronic interaction between the guest α-Fe2O3 dopant and the host In2O3 material.

Conducting mechanisms and magnetic behaviours of Fe-doped In2O3 nanocrystalline films

The relation between conducting mechanism and magnetic behaviour of Fe-doped In2O3 thin films was investigated. The films were prepared by sol gel method followed by spin coating techniques and characterized by X-rays diffractions, field emission electron microscopy, transmission electron microscopy, Hall Effect at room and low temperature, X-ray photoelectron spectroscopy and vibrating sample magnetometer. Films’ lattice parameter decreased with increasing of Fe content. Average grain size of films ranged between 8.4 and 13nm. Oxygen vacancies of films tended to reduce with increasing of Fe doping. Films with x=0.025 and 0.05 showed typical semiconducting behaviour while transition from metallic- to semiconducting-like behaviour was observed at 190K and 230K for films with x=0.075 and x=0.15, respectively. No trend had been found between films saturation magnetization, Ms, and free charge carriers. The magnetic behaviour of films has a correlation with localized electrons of Nearest-Neighbour Hopping conduction.

The gas-sensing and structure properties of Fe-doped In2O3 nanotubes by electrospinning technique

Fe-doped In2O3 nanotubes were successfully synthesized by electrospinning technique followed by subsequent heat treatment. The as-prepared samples appeared as an apparently open-end one-dimensional (1D) and tubular-like morphology with the diameter of approximately 150 nm and the wall thickness about 20 nm. The diffraction peak of the obtained nanotubes shifts toward bigger angle direction with the increase of the Fe content. Comparing to the In2O3 nanotubes, the Fe-doped In2O3 nanotubes exhibit better sensing characteristics toward ethanol gases, including higher sensing response, lower operating temperature and higher selectivity. Enhanced sensing properties are attributed to 1D hollow nanostructures and the role of doping Fe element.

Fabrication and Characterization of Fe-Doped In2O3 Dilute Magnetic Semiconducting Nanowires**Supported by the National Basic Research Program of China under Grant Nos 2014CB921101, 2014CB921103 and 2013CB922103, the National Natural Science Foundation of China under Grant Nos 11274003, 61176088 and 61274102, the Program for the New Century Excellent Talents in University under Grant No NCET-11-0240, the PAPD Project, and the Fundamental Research

Fe-doped In2O3 dilute magnetic semiconducting nanowires are fabricated on Au-deposited Si substrates by the chemical vapor deposition technique. It is confirmed by energy dispersive x-ray spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS) and Raman spectroscopy that Fe has been successfully doped into lattices of In2O3 nanowires. The EDS measurements reveal a large amount of oxygen vacancies existing in the Fe-doped In2O3 nanowires. The Fe dopant exists as a mixture of Fe2+ and Fe3+, as revealed by the XPS. The origin of room-temperature ferromagnetism in Fe-doped In2O3 nanowires is explained by the bound magnetic polaron model.