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Titanium dioxide (TiO2) is an excellent photocatalyst and transparent conducting oxide. It has two major crystal structures: rutile and anatase. Anatase TiO2 is valuable from an industrial point of view because it typically displays better photocatalytic and electronic transport properties than rutile TiO2. To further extract the functional properties of TiO2, understanding the correlation between the electronic structure and the crystal structure is essential. Because the electronic structure strongly depends on the crystal structure, introducing lattice distortion to rutile TiO2 should effectively modulate its electronic structure. Here, we show that Nb-doped rutile TiO2 epitaxial films on (1 1 ¯ 00) α-Al2O3 substrates exhibit anatase-like optoelectronic properties due to orthorhombic lattice distortions and experimentally observe the change in the electronic structure. Reducing the film thickness increases the orthorhombic distortion ratio (b/a) up to 3.4%. As b/a increases, the carrier effective mass decreases from 35 to 3 m0 (m0: electron mass) and the optical bandgap significantly increases. The present observations provide insight into regulating the TiO2 physical properties and should be beneficial for designing TiO2-based photocatalysts and transparent conducting electrodes. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) is an excellent photocatalyst and transparent conducting oxide. It has two major crystal structures: rutile and anatase. Anatase TiO2 is valuable from an industrial point of view because it typically displays better photocatalytic and electronic transport properties than rutile TiO2. To further extract the functional properties of TiO2, understanding the correlation between the electronic structure and the crystal structure is essential. Because the electronic structure strongly depends on the crystal structure, introducing lattice distortion to rutile TiO2 should effectively modulate its electronic structure. Here, we show that Nb-doped rutile TiO2 epitaxial films on (1 1 ¯ 00) α-Al2O3 substrates exhibit anatase-like optoelectronic properties due to orthorhombic lattice distortions and experimentally observe the change in the electronic structure. Reducing the film thickness increases the orthorhombic distortion ratio (b/a) up to 3.4%. As b/a increases, the carrier effective mass decreases from 35 to 3 m0 (m0: electron mass) and the optical bandgap significantly increases. The present observations provide insight into regulating the TiO2 physical properties and should be beneficial for designing TiO2-based photocatalysts and transparent conducting electrodes. [ABSTRACT FROM AUTHOR]

This work involves the introduction of niobium oxide into lanthanum aluminate (LaAlO3) via a conventional solid-state reaction technique to yield LaAlO3:Nb (LaNbxAl1−xO3+δ) samples with Nb5+ doping levels ranging from 0.00 to 0.25 mol%. This study presents a comprehensive investigation of the effects of niobium doping on the phase evolution, defect control, and reflectance of LaNbxAl1−xO3+δ powder. Powder X-ray diffraction (XRD) analysis confirms the perovskite structure in all powders, and XRD and transmission electron microscopy (TEM) reveal successful doping of Nb5+ into LaNbxAl1−xO3+δ. The surface morphology was analyzed by scanning electron microscopy (SEM), and the results show that increasing the doping concentration of niobium leads to fewer microstructural defects. Oxygen vacancy defects in different compositions are analyzed at 300 K, and as the doping level increases, a clear trend of defect reduction is observed. Notably, LaNbxAl1−xO3+δ with 0.15 mol% Nb5+ exhibits excellent reflectance properties, with a maximum infrared reflectance of 99.7%. This study shows that LaNbxAl1−xO3+δ powder materials have wide application potential in the field of high reflectivity coating materials due to their extremely low microstructural defects and oxygen vacancy defects. [ABSTRACT FROM AUTHOR]

In this work, evidence of isothermal magnetic entropy change ( ∆ S M ) over a broad temperature region is presented in a series of La1.4Sr1.6Mn2−xNbxO7 Ruddlesden–Popper compounds with niobium modification (Nb) (0.0 ≤ x ≤ 0.15) at the manganese (Mn) site. The ceramic samples were obtained through a solid-state sintering method in optimized conditions. All compounds predominantly possessed Ruddlesden–Popper phase while a few additional reflections were resolved in Nb-doped compounds which indicates the separation of structural phases. These peaks are assigned to a separate layered perovskite and single perovskite with tetragonal symmetry and hexagonal symmetry, respectively. The microstructure of the pure sample reveals uniform grain morphology but in Nb-doped specimens chiefly three types of grains were found. It was assumed that the inter-connected large particles were of R-P phase which is dominant in both parent and x = 0.05 compounds, while the hexagonal and polygonal morphology of grains in higher concentrations of dopants directly corroborates with the symmetry of single perovskite and additional layered perovskite phases, respectively. The parent compound exhibits a single ∆ S M curve, whereas all Nb-substituted samples display bifurcated ∆ S M curves. This indicated two transition regions with multiple magnetic components, attributed to distinct structural phases. The highest ∆ S M values obtained for components corresponding to the R-P phase are 2.32 Jkg−1k−1, 0.75 Jkg−1k−1, 0.58 Jkg−1k−1 and 0.43 Jkg−1k−1 and for the second component located around room temperature are 0.0 Jkg−1k−1, 0.2 Jkg−1k−1, 0.28 Jkg−1k−1 and 0.35 Jkg−1k−1 for x = 0.0, 0.05, 0.10 and 0.15 compositions, respectively, at 2.5 T. Due to the collective participation of both components the ∆ S M was expanded through a broad temperature range upon Nb doping. [ABSTRACT FROM AUTHOR]

Reaction of (arylimido)niobium(V) tris(diethylamide) complexes, Nb(NAr)(NEt2)3, prepared by treating Nb(NAr)Cl3(dme) (dme=1,2‐dimethoxyethane) with 3.0 equiv. of LiNEt2, with 1.0 equiv. of phenol afforded the corresponding phenoxide complexes, Nb(NAr)(NEt2)2(O‐2,6‐R2C6H3) [1 a–c, 2 a–c; Ar=2,6‐Me2C6H3 (1) 2,6‐iPr2C6H3 (2); R=tBu (a), iPr (b), Me (c)], which were identified by NMR spectroscopy, elemental analysis and the structures for 2 b, c were determined by X‐ray crystallographic analysis. [ABSTRACT FROM AUTHOR]

This study uses plane wave density functional theory (DFT) to investigate the effect of certain metal carbides (Niobium carbide, Vanadium carbide, Titanium carbide, and Manganese sulfide) on hydrogen embrittlement in pipeline steels. Our results predict that the interaction of hydrogen molecules with these metal carbides occurs in the long range with binding energy varying in the energy window [0.043 eV to 0.70 eV].In addition, our study shows the desorption of H2 molecules from these metal carbides in the chemisorptions. Since atomic state hydrogen interacts with NbC, VC, TiC, and MnS to cause embrittlement, we classified the strength of the hydrogen trapping as TiC + H > VC + H > NbC + H> MnS + H. In addition, our study reveals that the carbon site is a more favorable hydrogen-trapping site than the metal one. [ABSTRACT FROM AUTHOR]

The present study aimed a significant investigation of interesterification reaction to produce fatty acid methyl esters (FAME) from degummed soybean oil (DSO) in pressurized methyl acetate (MeA) catalyzed by niobium phosphate (NbOPO4). It investigated a glycerol-free route for biodiesel production from a low-cost feedstock concerning the problem of high cost and surplus glycerol production. NbOPO4 was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and nitrogen adsorption/desorption. Important factors in FAME production including temperature, catalyst content, and DSO:MeA molar ratio (MR) were investigated through an experimental design in two reaction times (60 min and 180 min). Response surface methodology was used to optimize important reaction variables. It was possible to obtain an FAME yield of 87.48% at 345 °C, 8 wt% of catalyst, and an MR of 1:35 in 60 min of reaction. The decomposition phenomenon was evident, achieving 64.14% at 345 °C and 8 wt% of catalyst, mainly due to prolonged exposure to large amounts of catalyst and high temperatures. The catalyst was shown to be active in the experimental conditions investigated. The reuse test pointed out a decrease in activity of up to 34.59%, which may be related to the adsorption of contaminants and mass loss. [ABSTRACT FROM AUTHOR]

The effect of niobium ions with high‐valence doping on high‐voltage LiNi0.5Mn1.5O4 (LNMO) materials was investigated. LiNi0.5Mn1.5−xNbxO4 was prepared by doping high‐valent niobium ions into LiNi0.5Mn1.5O4 material using the organic assisted combustion method. The experimental samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), electrochemical impedance (EI), and cyclic voltammetry (CV) analysis. The experimental results show that ‐doping with high‐valence niobium ions changes the orientation of the crystal plane growth of spinel particles, and the morphology of these particles changes from the octahedral shape before doping to the spherical shape after doping. With the increase in doping amount, the crystal structure changes gradually, resulting in the Li0.96Nb1.01O3 impurity phase. The doping of high valence‐niobium ions increases the content of Mn3+ in the material, resulting in the appearance of a 4 V discharge platform and the formation of a 4.7 and 4 V discharge platforms. The doping of Nb can improve the cycling stability of LiNi0.5Mn1.5O4 material, but the specific capacity of the material is reduced. [ABSTRACT FROM AUTHOR]

The main dielectric properties of several ceramic materials having niobium in their composition, proposed to take part in 5G telecommunication devices, are reviewed. A preliminary basic presentation of 5G systems, the requirements for implementing their use, a concise review of the ceramic compositions containing niobium that have been studied thus far, and an evaluation of their performance are detailed. A survey is presented, including more than 80 different compositions containing niobium, focusing on key parameters, such as dielectric constant, quality factor, temperature coefficient, and sintering temperature. These parameters play a role for assessing the potential application of these ceramics in 5G devices. [ABSTRACT FROM AUTHOR]

Cemented carbide (WC–Co), which has a low coefficient of thermal expansion, is employed as a substrate rather than the more typical Si, Ti, and Nb ones. BDD films are deposited on this substrate using hot filament chemical vapor deposition with various [B]/[C]gas ratios. Physical and electrochemical characteristics of the WC–Co/BDD electrodes are investigated by field emission scanning electron microscopy, Micro-Raman spectroscopy, and cyclic voltammetric. The addition of boron atoms is found to reduce the grain size and sp3(diamond)/sp2 (graphite) ratio in the films. Also, heavy boron doping is likely to cause substantial residual stress in the films. The electrodes with the various doping levels exhibit a wide potential window greater than 3.5 V and featureless background current in 0.5 mol L−1 of H2SO4 solution. Only the highly doped electrodes showed quasi-reversible behavior in the K3[Fe (CN)6] redox system. These electrochemical performances of BDD films on the WC–Co substrate are similar to or even slightly better than that on the commonly used substrates. Subsequently, the electrode with the preferred [B]/[C]gas ratio (5000 ppm) is characterized by repeated oxidizing phenol studies and accelerated life tests (ALT). Remarkably, with an excellent current efficiency of 94%, the average COD value drops from 1142 to 78 mg L−1. Moreover, the BDD films with thickness of 10 μm have a long service life of around 1600 h in the ALT of 3 mol L−1 of H2SO4 electrolyte at the constant current density of 1 A cm−2. Overall, the WC–Co/BDD electrode shows great potential for efficient oxidation processes and long-term durability. [ABSTRACT FROM AUTHOR]

Niobium pentoxide (Nb2O5) is a polymorphic ceramic with semiconductor characteristics applied in various fields of study. In this work, the Nb2O5 synthesis by the spray pyrolysis route was compared to the hydrothermal technique. The obtained materials were characterized by N2 physisorption (BET‐N2), average particle size distribution by dynamic light scattering (DLS), X‐ray diffractometry (XRD), transmission electron microscopy (TEM), and X‐ray fluorescence (XRF) spectroscopy. The material synthesized by the spray pyrolysis technique presented high specific area and pore volume, high crystallinity, homogeneity, and nanometric particles, thus representing a potential technique for the Nb2O5 synthesis. [ABSTRACT FROM AUTHOR]

Bismuth ferrite, or BiFeO3, is a highly promising material within the realm of multiferroics due to its stable structures, small band gap and cost-effectiveness. The present study employed a facile and eco-friendly approach to synthesize high-purity niobium-doped and -undoped bismuth ferrite (BiFeO3) nanostructure with hydrothermal method. The findings of the study indicate that the produced Nb-doped BFO exhibited nanoflake morphology as verified by SEM analysis. The observed trend in the photocatalytic efficiency of the material was found to be closely associated with the change in the band gap energy, which decreased from 2.36 eV to 2.03 eV with niobium dopant. The present study assessed the photocatalytic performance of both doped and pristine BiFeO3 for the decomposition of rhodamine B (RhB) under visible source of light radiation. The photocatalytic behavior of niobium-doped BiFeO3 for the mineralization of RhB was observed with increase upon contact time to visible light. The observed phenomenon can be ascribed to the effective dissociation of photogenerated electron (e−) and hole (h+) pairs, as well as the significant absorption of visible light, as opposed to the pristine BiFeO3. The scavenger analysis revealed that hydroxyl species, radical and holes species play a significant role in the photocatalytic mineralization of RhB. Later research revealed that the kinetics of the photocatalytic RhB decomposition followed the Langmuir–Hinshelwood model. [ABSTRACT FROM AUTHOR]

Crystals of (Cs0.8Rb0.2)4(NbO)2[Si8O21] were prepared by mild hydrothermal synthesis; sp. gr. P , a = 6.9990(3) Å, b= 7.8273(4) Å, c = 11.0613(5) Å, α = 77.048(4)°, β = 89.809(3)°, γ = 71.996(4)°. This synthesis of niobium compounds is more feasible than the synthesis performed previously under high-temperature and high-pressure conditions. As opposed to the known Cs- and Rb-containing silicates, the isomorphous incorporation of Cs and Rb cations in two sites was observed in the new variety, which was confirmed by the structural data and crystal-chemical characteristics. This is evidence of the ion-exchange properties of the crystals of this structural type. [ABSTRACT FROM AUTHOR]

NbSe2 nanoparticles, the representative member of the VB TMDCs group, have garnered significant attention due to their unique structural and optical properties, which make them promising candidates for various applications in nanoelectronics and optoelectronics. In this paper, the authors report on the synthesis of NbSe2 nanoparticles via the sonochemical method at ambient temperature with controlled size, well-defined crystal structure, and desirable optical properties. The investigation of the compositional and structural analysis revealed that the synthesized nanoparticles are well-defined, near stoichiometry, with a hexagonal crystal structure belonging to the space group P63mmc. The other morphological and optical characteristics of the synthesized nanoparticles studied through scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), UV-VIS NIR spectroscopy, etc., were discussed here. [ABSTRACT FROM AUTHOR]

4-Nitroaniline (4-NTA) is considered to be an environmental pollutant that is extremely hazardous to the ecosystem which is found in an inclusive range of industrial chemicals that includes dyes, pigments, fungicides, and pesticides. When 4-NTA occurs in water it seems to be highly carcinogenic to human beings. In consequence, there's a critical need for monitoring and identifying ecologically highly hazardous 4-NTA, specifically in water samples. Herein, the design of a novel niobium carbide/reduced graphene oxide aerogel (NC/rGO-A) was prepared to perform effective electrochemical recognition of 4-NTA in environmental water samples. The specific features of rGO-A with high porosity, and higher electrical conductivity, when coordinated with metal carbide, will sufficiently provide higher active sites resulting in excellent performances. Various methods of investigation have been employed to identify the physical and chemical characteristics. The fabricated NC/rGO-A sample over the screen-printed carbon electrode (SPCE) has been subjected to sensing investigation with a wide linear range of 0.039−1602 µM with good sensitivity 27.96 μA μM−1 cm2, the limit of detection at 4.6 nM for 4-NTA detection. Furthermore, the designed 4-NTA sensing exhibited excellent anti-interference, reproducibility, repeatability, and stability. The as-developed sensor's electrochemical analysis outcomes indicate the superior performance inherent in the developed composites. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract The main dielectric properties of several ceramic materials having niobium in their composition, proposed to take part in 5G telecommunication devices, are reviewed. A preliminary basic presentation of 5G systems, the requirements for implementing their use, a concise review of the ceramic compositions containing niobium that have been studied thus far, and an evaluation of their performance are detailed. A survey is presented, including more than 80 different compositions containing niobium, focusing on key parameters, such as dielectric constant, quality factor, temperature coefficient, and sintering temperature. These parameters play a role for assessing the potential application of these ceramics in 5G devices.

Calcium vapor reduction of niobium oxide compounds has been studied at temperatures from 1023 to 1123 K. The adiabatic temperature of calcium reduction of niobium pentoxide (3020 K) and the Mg4Nb2O9 niobate (2525 K) has been determined by thermodynamic modeling with the TERRA software suite. We have assessed the effects of process temperature, reduction time, and precursor powder particle size on the degree of reduction, specific surface area, and pore structure of the niobium powders. [ABSTRACT FROM AUTHOR]

A special generative manufacturing (AM) process was developed for the partial integration of active ingredients into open-porous matrix structures. A mixture of a silver-containing solution as an antibacterial material with an alginate hydrogel as a carrier system was produced as the active ingredient. The AM process developed was used to introduce the active ingredient solution into an open-porous niobium containing a β-titanium matrix structure, thus creating a reproducible active ingredient delivery system. The matrix structure had already been produced in a separate AM process by means of selective laser melting (SLM). The main advantage of this process is the ability to control porosity with high precision. To determine optimal surface conditions for the integration of active ingredients into the matrix structure, different surface conditions of the titanium substrate were tested for their impact on wetting behaviour of a silver-containing hydrogel solution. The solution-substrate contact angle was measured and evaluated to determine the most favourable surface condition. To develop the generative manufacturing process, an FDM printer underwent modifications that permitted partial application of the drug solution to the structure in accordance with the bioprinting principle. The modified process enabled flexible control and programming of both the position and volume of the applied drug. Furthermore, the process was able to fill up to 95% of the titanium matrix body pore volume used. The customised application of drug carriers onto implants as a drug delivery system can be achieved via the developed process, providing an alternative to established methods like dip coating that lack this capability. [ABSTRACT FROM AUTHOR]

Niobium oxide supported on ZrO2 and mixed oxide of NbOx-ZrO2 was prepared and characterized. Mechanical treatment was followed by the microwave heating procedure of catalysts with more advanced textural parameters. The amount of Lewis (LAS) and Brønsted (BAS) acid sites rose with the increasing Nb content in the catalysts. The catalytic properties of samples of niobia-zirconia (NbZr samples, NbZr catalysts) were studied in a cellulose hydrolysis–dehydration reaction at 453 K under an inert Ar atmosphere in a batch reactor. Glucose and 5-hydroxumethylfurfural (5-HMF) were the major products. The initial reaction rate could be tuned by the density of acid sites on the surface of solid. At a low density of acid sites (0.1–0.3 µmol·m−2), the initial reaction rate had a pronounced inverse correlation. Increasing the LAS/BAS from 0.3 to 2.5 slightly stimulated the formation of the target products. The catalytic properties of NbZr catalysts prepared by microwave treatment were studied in cellulose transformation in a flow set-up. Glucose was found to be the major product. The maximum yield of glucose was observed in the presence of the sample of 17%Nb/ZrO2. Increasing Nb content resulted in the formation of Nb-associated acid centers and, in turn, increasing catalyst acidity and activity. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides are studied due to the possibility of creating nanoscale semiconductor devices, as well as fundamental issues of magnetic ordering. We researched the crystal structure and magnetic properties of niobium dichalcogenide Mn0.30NbS2. The results of the X-ray study showed the possible existence of an intermediate 2 3 a0·2 3 a0 structure between the "basic" superstructures. Also, two local maximums were found in the temperature dependence of the dynamic magnetic susceptibility. These features can indirectly confirm the presence of a transition superstructure and reflect the two-step nature of the magnetic ordering. [ABSTRACT FROM AUTHOR]

Supercapacitors have proven themselves as a subject of interest over the years for energy storage. As a result, it is not surprising that significant effort has been put into supercapacitor research. However, a device with all desirable properties still needs to be developed, requiring special attention. A simple synthesis of porous magnesium niobium silver phosphate (Mg3Nb1−xAgx(PO4)3) nanocomposites is presented using a novel mixed solvent solution and a hydrothermal method. The MgNbAgPO4 anode with an interconnected porous structure not only offers a large number of active sites for divalent ion trapping but also improves charge transfer kinetics. As a result, the Mg3Nb1−xAgx(PO4)3 anode has a high specific capacity of 958 C g−1 using a binder‐free electrode and better rate capability. The full‐cell design is also built with Mg3Nb1−xAgx(PO4)3 and activated carbon (AC). The hierarchical pore structure and appropriate functional groups Mg3Nb1−xAgx(PO4)3 anode deliver a maximum energy density of 57 Wh kg−1, a high power density of 1200 kW kg−1, and anti‐self‐discharge solid behavior. The analysis of the charge storage mechanism suggests that Mg3Nb1−xAgx(PO4)3//AC supercapattery involves adsorption/desorption and Faradic reactions to store charge. This study opens the path for high‐performance Mg3Nb1−xAgx(PO4)3 electrode and gives a better knowledge of charge storage. [ABSTRACT FROM AUTHOR]

Nb-doped ZnO (NbxZn1−xO, NZO) thin films with various Nb additions (x = 0, 0.2, 0.5, and 0.8 at. %) were deposited on Pt/TiO2/SiO2/Si substrates by radio frequency magnetron sputtering. The Nb doping concentration was found to affect the microstructure, the number of oxygen vacancies, and work function of the Pt/NZO/Pt structures. Among the various devices, the film with 0.5 at. % Nb addition showed a better switching-voltage stability [i.e., the optimal coefficient of variation (Cv) for reset (7.02%) and set (2.73%) operations, respectively], a high endurance (∼1000 cycles), and lower reset (0.57 V) and set (1.83 V) voltages due to a larger number of oxygen vacancies and a lower work function. In general, the results show that the present NZO thin films are promising candidates for stable and low power-consumption resistive random access memory applications. [ABSTRACT FROM AUTHOR]

Memory resistive devices using a ZnO dielectric layer are promising due to the transparent nature, lower operating voltage, synthesis compatible with semiconductor processing, and ability to control using magnetic fields. In the present work, niobium incorporated MoS2 films in combination with ZnO are used to form diode-resistor devices with memory. The two device structures p-Si-SiO2/Pt/MoS2(Nb)/ZnO/Ag and p-Si-SiO2/Pt/ZnO/Ag are grown using laser physical vapor deposition. The resistive characteristics are investigated as a function of temperature for comparison. The unipolar I-V characteristics of Pt/ZnO/Ag device films were found to be nonreproducible, and the temperature dependence was irregular for negative polarity. The unipolar I-V characteristics of Pt/MoS2(Nb)/ZnO/Ag device films were found to be reproducible. The temperature dependence of the I-V characteristics was regular for both polarities. The presence of a MoS2 film is found to improve and distinguish the effect of the polarity of the applied field on the unipolar device characteristics by the formation of a p-n device configuration. The conductance in the transition from a low resistance state to a high resistance state was found to follow the Schottky emission with the apparent barrier height being influenced by the p-n junction. [ABSTRACT FROM AUTHOR]

[Display omitted] • NbO/NbC/rGO nanocomposite as an electrocatalyst is reported for the first time. • The nanocomposite shows high catalytic performance to MTX detection. • The developed sensor has low detection limit, and high sensitivity for MTX detection. Engineering the nanostructure of an electrocatalyst is crucial in developing a high-performance electrochemical sensor. This work exhibits the hydrothermal followed by annealing synthesis of niobium oxide/niobium carbide/reduced graphene oxide (NbO/NbC/rGO) ternary nanocomposite. The oval-shaped NbO/NbC nanoparticles cover the surface of rGO evenly, and the rGO nanosheets are interlinked to produce a micro-flower-like architecture. The NbO/NbC/rGO nanocomposite-modified electrode is presented here for the first time for the rapid and sensitive electrochemical detection of the anticancer drug methotrexate (MTX). Down-sized NbO/NbC nanoparticles and rGO's high surface area provide many active sites with a rapid electron transfer rate, making them ideal for MTX detection. In comparison to previously reported MTX sensors, the developed drug sensor exhibits a lower oxidation potential and a higher peak current responsiveness. The constructed sensors worked analytically well under optimal conditions, as shown by a low detection limit of 1.6 nM, a broad linear range of 0.1–850 µM, and significant recovery findings (∼98 %, (n = 3)) in real samples analysis. Thus, NbO/NbC/rGO nanocomposite material for high-performance electrochemical applications seems promising. [ABSTRACT FROM AUTHOR]

Exploration of alternatives for supplementing indium tin oxide electrode is currently trending due to scarcity of indium, leading to a steep increase in the cost of related optoelectronic components. Codoping of niobium (Nb) and fluorine (F) into SnO2 lattice as cationic and anionic dopants, respectively, is explored by spray deposition technique. A fixed 10 wt% F and varying Nb concentration from 0 to 5 wt% is incorporated into the SnO2 lattice. X‐ray diffraction reveals substitution of Nb and F into the SnO2 lattice without altering the structure. Optical transmittance is found to increase with Nb content up to 4% of Nb (77.59%), and it decreases thereafter. Scanning electron microscope and optical profiler imply a relatively smooth surface with sharp‐tipped particles which vary with Nb concentration. Sheet resistance decreases up to 3 wt% of Nb doping and increases thereafter. Contact angle measurement indicates that upon doping with Nb, the films turn hydrophilic. Among the deposited films, 4 wt% of Nb‐doped film shows the highest figure of merit of 5.01 × 10−3 Ω−1. The surface work function of the 4 wt% Nb‐doped SnO2 film is 4,687.85 meV. The optimal films are tested as electrodes in dye‐sensitized solar cells and are discussed in detail. [ABSTRACT FROM AUTHOR]

Herein, we describe the synthesis and evaluation of hierarchical mesoporous orthorhombic niobium oxide (T-Nb2O5) as an anode material for rechargeable lithium-ion batteries (LIB). The as-synthesized material addresses key challenges such as beneficial porous structure, poor rate capability, and cycling performance of the anode for Li-ion devices. The physicochemical characterization results reveal hierarchical porous nanostructure morphology with agglomerated particles and a 20 to 25 nm dimension range. Moreover, the sample has a high specific surface area (~65 m2 g−1) and pore volume (0.135 cm3 g−1). As for the application in Li-ion devices, the T-Nb2O5 delivered an initial discharging capacity as high as 225 mAh g−1 at 0.1 A g−1 and higher rate capability as well as remarkable cycling features (~70% capacity retention after 300 cycles at 250 mA g−1) with 98% average Coulombic efficiency (CE). Furthermore, the scan rate-dependent charge storage mechanism of the T-Nb2O5 electrode material was described, and the findings demonstrate that the electrode shows an evident and highly effective pseudocapacitive Li intercalation behaviour, which is crucial for understanding the electrode process kinetics. The origin of the improved performance of T-Nb2O5 results from the high surface area and mesoporous structure of the nanoparticles. [ABSTRACT FROM AUTHOR]

Hypertension, as a leading risk factor for cardiovascular diseases, is associated with oxidative stress and impairment of endogenous antioxidant mechanisms, but there is still a tremendous knowledge gap between hypertension treatment and nanomedicines. Herein, we report a specific nanozyme based on ultrathin two‐dimensional (2D) niobium carbide (Nb2C) MXene, termed Nb2C MXenzyme, to fight against hypertension by achieving highly efficient reactive oxygen species elimination and inflammatory factors inhibition. The biocompatible Nb2C MXenzyme displays multiple enzyme‐mimicking activities, involving superoxide dismutase, catalase, glutathione peroxidase, and peroxidase, inducing cytoprotective effects by resisting oxidative stress, thereby alleviating inflammatory response and reducing blood pressure, which is systematically demonstrated in a stress‐induced hypertension rat model. This strategy not only opens new opportunities for nanozymes to treat hypertension but also expands the potential biomedical applications of 2D MXene nanosystems. [ABSTRACT FROM AUTHOR]

Agglomerates of ε -NbN hexagonal prismatic faceted grains with a size between 5 and 50 μm were formed by heating Nb 2 O 5 or NbFeO 4 powder and Na lump in a BN crucible at 900–1100 °C under an Ar atmosphere. Wavelength-dispersive X-ray analysis demonstrated that the ε -NbN faceted grains have a nearly stoichiometric composition. In addition to the ε -NbN grains, powders of niobium nitrides containing δ -NbN and Nb 2 N, and water-soluble Na 3 BO 3 were included in the sample prepared from Nb 2 O 5 at 1100 °C, while powders of Fe and Na 3 BO 3 , and a trace of δ -NbN were included in the sample from NbFeO 4. These reactions were attributed to metathesis reactions in which the oxygen in the oxides and the nitrogen in the solid nitrogen source, BN, were replaced by the formation of Na 3 BO 3. An extra amount of nitrogen supplied from the starting material enhances the formation of ε -NbN and suppressed the formation of δ -NbN and Nb 2 N. [ABSTRACT FROM AUTHOR]

In the present study, by adding graphene to a photoconductive photodetector with a niobium pentoxide (Nb2O5) absorber layer and exploiting the photogating effect, the responsivity of the photodetector is significantly improved. In this photodetector, the Nb2O5 layer detects the light, and the graphene improves the responsivity based on the photogating effect. The photocurrent and the percentage ratio of the photocurrent to dark current of the Nb2O5 photogating photodetector are compared with those of the corresponding photoconductive photodetector. Also, the Nb2O5 photoconductive and photogating photodetectors are compared with titanium dioxide (TiO2) photoconductive and photogating photodetectors in terms of responsivity at different applied (drain-source) voltages and gate voltages. The results show that the Nb2O5 photodetectors have better figures of merit (FOMs) in comparison with the TiO2 ones. [ABSTRACT FROM AUTHOR]

Chemical reactions of ball-mill activated [Nb6I11] with alcohol solutions of Mg alcoholates result in the formation of the three new hexanuclear Nb cluster compounds [Nb6I8(HOCH3)6][Nb6(OCH3)18]·2CH3OH (1), (PPh4)2[Nb6(OC2H5)12I6]·C2H5OH (2) and (PPN)2[Nb6(OC2H5)12I6] (3). They contain cluster anions, which have the edges of the Nb6 octahedra, i.e. the inner coordination sites, μ2-bridged by the O atoms of methanolato or ethanolato ligands. Thereby, they represent further characterized members of the so far very small group of hexanuclear cluster alcoholates. The terminal metal sites are bonded to further methanolato (1) or iodido ligands (2 and 3). Sterically demanding organic cations (PPh4+, PPN+, 2 and 3) or a cationic Nb6 cluster complex with terminal methanol ligands [Nb6I8(HOCH3)6]2+ in 1 compensate the negative charges of the cluster anions. Compound 1 is the first example of a M6 cluster ion pair of both the text-book known edge-bridged [M6X12] and face-bridged [M6X8] cluster units. The structures of the three title compounds were determined by means of single-crystal X-ray structure analysis. [ABSTRACT FROM AUTHOR]

The synthesis and the crystal structure of the double cluster compound [Nb6Cl14(MeCN)4][Nb6Cl14(pyz)4]·6CH3CN are described. The synthesis is based on a partial ligand exchange reaction, which proceeds upon dissolving [Nb6Cl14(pyz)4]·2CH2Cl2 in acetonitrile. The compound is built up of two discrete neutral cluster units, which consist of octahedra of Nb6 atoms coordinated by 12 edge-bridging chlorido and two terminal chlorido ligands, and four acetonitrile ligands on one and four pyrazine ligands on the other cluster unit. Co-crystallized acetonitrile molecules are also present. The single-crystal structure determination has revealed a cluster arrangement in which the [Nb6Cl14(pyz)4] units are connected by (halogen) lone-pair–(pyrazine) π interactions. These lead to chains of [Nb6Cl14(pyz)4] clusters. These chains are further connected to cluster layers by (nitrile-halogen) dipole–dipole interactions, in which the [Nb6Cl14(MeCN)4] and co-crystallized MeCN molecules are also involved. These cluster layers are arranged parallel to the crystallographic {011} plane. [ABSTRACT FROM AUTHOR]

Hafnium oxide is widely used in optical coating materials because of its high refractive index, broad band gap, high laser damage threshold and its high transparency in the wavelength range from ultraviolet to middle infrared (0.20–12 μm). However, hafnium oxide has some defects such as strong crystallinity and poor surface quality, which results in enhanced absorption and reflection of light wave and limits its application in optical field. As a pentoxide with high transparency and excellent optical properties in the wavelength range from ultraviolet to mid-infrared(0.35–9 μm), the doping of niobium pentoxide can effectively improve the surface quality and optical properties of the films. Mixed films with different chemical compositions were prepared by ion beam assisted deposition, and the microstructure, crystallinity, surface quality, optical properties and mechanical properties of the mixed films with different chemical compositions were investigated. The doping of niobium pentoxide inhibits the crystallization of hafnium oxide, optimizes the surface quality of the films, and improves the refractive index and mechanical properties of mixed films, effectively broadens the application of hafnium oxide in the field of optical films. [ABSTRACT FROM AUTHOR]

The industrial processes for recovery of niobium and tantalum oxides depend on hydrofluoric acid, which is a highly toxic and corrosive reagent with significant environmental consequences. This study presents a fluoride-free, rapid, and energy-efficient process for niobium and tantalum extraction from columbite using microwave-assisted alkali treatment and solvent extraction. Microwave treatment was optimized using an experimental design to obtain a statistical model for maximum dissolution. It was found that it is possible to obtain a temperature of more than 600 °C within 4 min of microwave treatment with potassium hydroxide. Water leaching of the microwave-treated sample resulted in dissolution of 93.57 pct niobium, 88.12 pct tantalum, 11.17 pct tin, and 21.09 pct iron. Solvent extraction with methyltrioctylammonium chloride was used to separate niobium and tantalum from aqueous solution. Approx. 96.2 pct niobium along with 93.4 pct tantalum was co-extracted at the organic-to-aqueous phase ratio of 2/1 in a two-stage counter-current extraction with 0.29 M extractant. Selective stripping of niobium from the loaded organic solution was performed with a mixture of 0.5 M nitric and oxalic acid, while tantalum stripping was achieved with high nitric acid concentration (1 M). Finally, > 98 pct pure niobium oxide and Ta-rich mixed oxide were prepared by the precipitation of the purified solution. [ABSTRACT FROM AUTHOR]

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Trichloro niobium(V) complexes 3 and 4 with the sulfur- or selenium-bridged [OEO]-type bis(phenolate) ligands (E = S, Se) were synthesized and fully characterized on the basis of their NMR spectroscopic data and X-ray crystallographic analysis. In the crystalline state of 4, the [OSeO]-core of the ligand was coordinated to the niobium center in a fac-fashion. The corresponding tribenzyl niobium(V) complexes 5 and 6 were also prepared by the reactions of 3 and 4 with 3 equivalents of PhCH2MgCl in toluene. The X-ray diffraction analysis of 6 revealed that the distorted six-coordinated niobium center incorporated in the [OSeO]-type ligand took a mer-fashion, and one benzyl ligand was coordinated to the niobium center by η2-fashion. Complexes 5 and 6 were tested for the phenylacetylene polymerization that produced poly(phenylacetylene)s (PPAs), oligomers, and triphenylbenzenes (TPBs) depending on the chalcogen atom in the [OEO]-type ligand. [ABSTRACT FROM AUTHOR]

Tricarballylate esters are considered as an appealing class of biobased plasticizers. This work focusses on the production of tricarballylate esters from citrate esters through a one‐pot sequential dehydration‐hydrogenation process, in order to circumvent the undesired decarboxylation side reaction in the synthesis of tricarballylic acid directly from citric acid. High yields up to 93 % of different tricarballylate esters were obtained with a self‐synthesised bifunctional 0.2 wt % Pd/Nb2O5.nH2O catalyst employed in methylcyclohexane as inert solvent. [ABSTRACT FROM AUTHOR]

The textile industry emits daily massive amounts of sewage rich in non-biodegradable organic compounds, especially in textile dyes. Such contaminants are highly soluble in water, which makes their removal difficult. Other studies suggest their carcinogenicity, toxicity, and mutagenicity. A promising chemical treatment of textile wastewater is the photodegradation of dye molecules in the process of photocatalysis in the presence of a photocatalyst. One-dimensional nanostructures exhibit a high surface-to-volume ratio and a quantum confinement effect, making them ideal candidates for nanophotocatalyst material. Nb2O5 is gaining popularity in optical applications among other metal oxides with a wide band gap, and electrospun niobium oxide nanostructures, despite their ease and low cost, can increase the chemical removal of textile dyes from wastewater. Facile synthesis of electrospun one-dimensional niobium oxide nanofibers is presented. The nanophotocatalysts morphology, structure, chemical bonds and optical properties were examined. Based on photodegradation of aqueous solutions (ph = 6) of methylene blue and rhodamine B, the photocatalytic activity was established. The photocatalytic efficiency after 180 minutes of ultraviolet irradiation in the presence of Nb2O5 nanofibers was as follows: 84.9% and 31.8% for methylene blue and rhodamine B decolorization, respectively. [ABSTRACT FROM AUTHOR]

The Health and environmental hazards of benzene and nitrobenzene (NB) derivatives have remained a topic of interest of researchers. In silico methods for prediction of toxicity of chemicals have proved their worth in accurate forecast of environmental as well as health toxicity and are strongly recommended by regulatory authorities. Two quantitative structure–toxicity relationship (QSTR) models explaining Scenedesmus obliquus toxicity trends among 39 benzene derivatives and Tetrahymena pyriformis toxicity of 103 NB and 392 benzene derivatives are developed using semiempirical quantum chemical parameters. The best constructed QSTR models have good fitting ability (R2 = 0.8053, 0.7591, and 0.8283) and robustness (Q2LOO = 0.7507, 0.7227, and 0.8194; Q2LMO = 0.7338, 0.7153, and 0.8172). The external predictivity of all the models are quite good (R2EXT = 0.8256, 0.9349, and 0.8698). Electronegativity, Cosmo volume, total energy, and molecular weight are responsible for the increase and decrease of toxicity of benzene derivatives against S. obliquus while electronegativity, electrophilicity index, the heat of formation, total energy, hydrophobicity, and cosmo volume are responsible for modulation of toxicity of NB and benzene derivatives toward T. pyriformis. These models fulfill the requirements of all the five OECD principles. [ABSTRACT FROM AUTHOR]

We study the effect of chemo-mechanical polishing on the surface and superconducting properties of niobium coupons obtained from three separate sources and having different hardness. The chemo-mechanical polishing follows a route of abrasive polishing with SiC, followed by lapping with diamond paste and final treatment by alumina slurry and colloidal silica suspension. The polished surfaces were characterized using atomic force microscopy, confocal microscopy, x-ray diffraction and residual stress measurements. The effect of this polishing schedule on the magnetic field for first penetration, the thermodynamic critical fields and the superheating fields are compared for all three samples. The pinning force density in all the three samples shows an unusual scaling mechanism which is quite anomalous. Stress measurements show that our polishing procedure does not significantly alter the residual stress state of the material compared to the as-cut (or unpolished) condition. The results of our experiments on small samples of niobium could provide useful information for understanding the behavior of superconducting radio frequency (SCRF) cavities which are processed using a chemo-mechanical polishing method in place of the usual chemical polishing routines. [ABSTRACT FROM AUTHOR]

In this study, the effect of aging on current transport properties and the interface band structure of the Au/Nb-doped SrTiO3 (NSTO) junction was investigated. The as-fabricated Au/NSTO junctions showed extremely small rectification and exhibited rectifying current conduction and colossal electroresistance (CER) effect after exposure to air. In contrast, the Au/NSTO junctions kept in vacuum did not exhibit such aging behavior. Interestingly, the Au/NSTO junction capped with a Pt overlayer showed small rectification even after air exposure for one week. The changes in the potential profile with increasing air exposure time were assessed by X-ray photoemission techniques. The aforementioned time-dependent behaviors originated because of oxygen diffusion through the Au electrode, and it was found that oxygen stoichiometry at the electrode interface played an important role in the CER phenomena at the metal/NSTO junctions. [ABSTRACT FROM AUTHOR]

Nb2O5 is a promising metal oxide electrode material for supercapacitors because of outstanding structural stability and wide electrochemical window, but low inherent conductivity hinders its many applications. This article reports one way for the synthesis of Nb2O5–graphene heterojunction composites using ethylene diamine tetraacetic acid and boron-functionalized graphene quantum dots (p-GQDs). p-GQDs were immobilized on graphene sheets by π–π stacking, followed by coordination with Nb(V), reduction into a hydrogel with ascorbic acid and annealing in nitrogen. The resulting Nb2O5-p-GQD-G offers a three-dimensional structure, ultrasmall size of Nb2O5 nanorods, PN junctions and Schottky heterojunctions. These dramatically improve the inherent conductivity, number of electrochemically active sites and a voltage window range. The n-Nb2O5-p-GQD-G electrode indicates a capacitance of 267.4 F g−1 at the current density of 1.0 A g−1, which is more than 1.5-fold that of the n-Nb2O5-n-GQD-G electrode, verifying that the formation of PN junctions can enhance the capacitance. The symmetrical supercapacitor with n-Nb2O5-p-GQD-G electrodes provides high specific capacitance (794 F g−1 at the current density of 0.2 A g−1 and 167.2 F g−1 at the current density of 2.0 A g−1), cycling stability (a capacity retention of 98.8% after 10 000 cycles at the current density of 1.5 A g−1) and energy density (110.3 W h Kg−1 at the power density of 200 W kg−1). [ABSTRACT FROM AUTHOR]

The world scenario regarding consumption and demand for products based on fossil fuels has demonstrated the imperative need to develop new technologies capable of using renewable resources. In this context, the use of biomass to obtain chemical intermediates and fuels has emerged as an important area of research in recent years, since it is a renewable source of carbon in great abundance. It has the benefit of not contributing to the additional emission of greenhouse gases since the CO2 released during the energy conversion process is consumed by it through photosynthesis. In the presented review, the authors provide an update of the literature in the field of biomass transformation with the use of niobium-containing catalysts, emphasizing the versatility of niobium compounds for the conversion of different types of biomass. [ABSTRACT FROM AUTHOR]

This paper describes experimental studies and a mathematical model of mechanical activation and high-temperature synthesis during the Nb–2Si combustion. The model is constructed in the macroscopic approximation. Synthesis regimes are determined depending on the duration of joint mechanical activation of the reagents. The kinetic parameters of grinding of the initial powder mixture and the mechanochemical synthesis of the reaction product are obtained on the basis of experimental data by the inverse problem method. [ABSTRACT FROM AUTHOR]

A simple solid-state reaction was applied to synthesize Fe-doped perovskite-type PBFNO catalysts, and methylene blue decomposition studies were performed in the form of visible light according to the changes in the Fe doping content (0.4 to 1.9 mol ratio compared with Bi mol) and the amount of catalyst used (0.05 to 0.2 g used). As the Fe doping content increases, the absorbance and bang gap energy of the PBFNOs sample rapidly increase and decrease, respectively, because the Fe dopant in the PBNO lattice acts as an intermediate band between the valence and conduction bands of the PBNO and reduces the band gap energy. As a result, it showed a performance degradation of approximately 42% compared to the maximum performance. In addition, the presence of Fe dopants in the PBNO lattice greatly reduces the intensity of the photoluminescent lines. This is because the Fe dopant can play an important role in light-induced electron transfer and as a hole trap, reducing the recombination rate. Additionally, when too much photocatalyst was used (>0.1 g used), the Fe dopant played an important role as a light-induced electron transfer and hole trap, reducing the recombination rate and lowering the overall photocatalytic activity by 51%. In particular, 0.1 g of PBNO-0.2-F showed continuous catalytic activity, even when the photocatalytic reaction proceeded for 180 min. Therefore, this study demonstrates that the Fe-doped aurivillius-phase PBFNO photocatalyst is very promising for the dye manufacturing industry. [ABSTRACT FROM AUTHOR]

In the present study, we demonstrated a new strategy to decorate TiO2 nanoparticles on the surface of Nb2O5 nanorods to obtain a unique TiO2/Nb2O5 nanocomposite (NC). In order to achieve a high catalytic activity, TiO2/Nb2O5 NC was dispersed and anchored over reduced graphene oxide (rGO). The ratio between rGO and TiO2/Nb2O5 NC was varied to obtain two types of rGO/TiO2/Nb2O5 composites i.e. Cat-A and Cat-B. Cat-A (rGO:TiO2/Nb2O5 ~ 1: 0.3 wt/wt) showed higher photocatalytic degradation efficiency under visible light irradiation in comparison to Cat-B (rGO:TiO2/Nb2O5 ~ 1:0.6 wt/wt). In contrast, Cat-B showed enhanced catalytic activity for the reaction involving reduction of p-nitrophenol to p-amino phenol in the presence of NaBH4 as a reductant. The higher photocatalytic activity of Cat-A and catalytic reduction of Cat-B can be attributed to (i) high charge carrier mobility of rGO; (ii) strong acidity of crystal planes of Nb2O5 nanorods; and (iii) the synergistic effect of rGO and TiO2/Nb2O5 nanocomposites. [ABSTRACT FROM AUTHOR]

In this work, the photovoltaic outputs of the lead‐free FASnI3‐based perovskite solar cells are discussed by using Solar Cell Capacitance Simulator in One Dimension. The device outputs estimated theoretically in this study are almost equal to the experimental results, thereby verifying accuracy of this simulation. To find the decent electron transport layer (ETL), herein, various ETLs are presented instead of C60/BCP in the experimental FASnI3‐based perovskite solar cell (PSC). The designed FASnI3 PSC utilizing niobium pentoxide (Nb2O5) as an ETL with an appropriate band alignment and a low lattice mismatch at FASnI3/ETL interface provides better efficiency by decreasing recombination at front side. The performances of the proposed PSC are also measured by altering the thickness and doping of ETL and absorber, interface defects, and series and shunt resistances. Furthermore, this paper reports the calculation of recombination coefficients at absorber/ETL interface, depletion region, and quasi‐neutral region. An improved efficiency of 22.24% is evaluated at optimized thicknesses of 100 nm for HTL, 500 nm for absorber, 50 nm for ETL, and 50 nm for ITO for the proposed inverted PSC of ITO/PEDOT:PSS/FASnI3/Nb2O5/Ag. These results suggest that chemically stable and less‐toxic Nb2O5 can be applied as a useful ETL in inverted PSCs for further improving the performances. [ABSTRACT FROM AUTHOR]

Silicon carbide based composites with 30, 40 and 50 wt % of Ti and NbC as sintering additives were prepared by hot-press method. Molar ratio of Ti:NbC was kept at 1:1.8. The two step sintering was performed in order to avoid the squeezing out the melted titanium above 1668 °C. Composite powders were sintered at 1650 °C for 3 h and subsequently at 1850 °C for 1 h under mechanical pressure of 30 MPa in Ar atmosphere. XRD pattern confirmed the formation of (Ti, Nb)C ss in the SiC matrix. Composite with 50% of Ti–NbC phase showed the extraordinary electrical conductivity of 2.4 × 105 S/m which was achieved by homogeneous distribution of Ti and NbC in SiC matrix and forming a continuous conductive network. Prepared composites show complex magnetic properties, diamagnetism originated from SiC matrix, paramagnetism caused by Ti and NbC admixing, as well as weak ferromagnetism probably coming from impurities contained in the initial powders. Samples with 30 and 40 wt % of Ti and NbC exhibit superconducting state below 2 K. [ABSTRACT FROM AUTHOR]

In recent times, much attention has been given to the study of the interaction between biomimetic assemblies with graphene oxide (GO), as the outcome of these interactions has a substantial impact on the biological and physicochemical properties of both the biomimetic assemblies and GO. Several applications of GO have been established over the years, and GO has the potential to be used as a biomedical material. In this article, we report the interaction of a red-emitting molecule, Nile blue A (NB), in the presence of four different bile salt aggregates as well as in the presence and absence of GO using various spectroscopic techniques. In the presence of different bile salts in water and varying concentrations of GO, NB undergoes a transition from the monomeric form to a J-dimer involving NB–bile salt interactions. The equilibrium between the H-dimer and J-dimer form of NB is also perturbed in the presence of GO and varying the concentration of bile salts. Raman spectroscopy establishes the fact that NB does indeed interact with the various functional groups present on the GO surface. [ABSTRACT FROM AUTHOR]