Post-transition Metal Oxides Research Articles

One-pot bioinspired synthesis of PbO/CuO/FeO trimetallic oxide nanocomposite using Vitis vinifera fruit juice for highly sensitive electrochemical detection of 4-Nitrotoluene

The determination of explosive nitroaromatic chemicals has prompted concerns about human safety around the world. In this work, we demonstrate an electrochemical sensor based on trimetallic oxide nanocomposites modified screen-printed carbon electrode (SPCE) for the detection of nitroaromatic compounds. Trimetallic oxide nanocomposites are multiphase materials containing ternary metal oxides. Because of their high specific surface area, superior electron transport capabilities, and favourable catalytic behaviour, they are frequently employed as antibacterial materials, catalysts, and sensors. In order to combat the problems associated with high manufacturing costs, low selectivity, and low sensitivity of conventional sensors, this paper reports on the construction of an electrochemical sensor for 4-nitrotoluene (4-NT) using a trimetallic oxide nano-sensor. The nano-sensor is composed of transition metal oxides copper and iron combined with post-transition lead metal oxide. In this study, we prepared a PbO/CuO/FeO TMO NCs sample with different individual metal oxides synthesized by a green reduction method using Vitis vinifera fruit juice. SEM was used to observe and validate structural and morphological variations brought on by various metal compositions. The four bio-synthesized materials comprise dispersed multiphase matrices containing varying shapes of nanoparticles with different morphologies. The elemental and phase arrangements of the synthesized samples were investigated employing UV, FT-IR, XRD, and EDAX approaches. The findings of the electrochemical measurements indicate that the SPCE modified with PbO/CuO/FeO TMO NCs has enhanced sensing capabilities over CuO, FeO, and PbO NPs for 4-NT; the limit of detection is 4.512 nM and sensitivity is −0.531 μA nM−1 for the developed sensor. Notably, recovery values (99.2–101.7 %) in water samples showed that evaluating interfering species from different contaminants had no effect on the sensing of 4-NT. All of these findings show that the newly developed sensor performs well in terms of reproducibility, selectivity, and sensitivity for the detection of 4-NT

Universal strain engineering for enhancing the hole mobility and dopability in p-type semiconductors

Modern electronic and optoelectronic devices rely on the development of the complementary pair of n-type and p-type semiconductors. However, it is often seen that n-type semiconductors are easier to realize and offer superior performances than their p-type counterparts, with p-type semiconductors showing much lower hole mobility and inefficient carrier doping. Here, by using first-principles studies, we demonstrate that lattice strain engineering can be a universal approach to enhance the hole mobility and dopability in p-type semiconductors. A broad class of p-type semiconductors, including anion p orbital derived valence band compounds (nitrides, oxides, halides, and chalcogenides), s orbital based post-transition metal oxides (e.g., SnO), and d-orbital based transition metal oxides (e.g., NiO), have been applied on strain to demonstrate their valence band modulation ability for the purpose of increasing the hole mobility and p-type dopability. We show that compressive lattice strain generally results in an upshifted valence band edge and reduced effective hole mass, leading to enhanced p-type dopability and increased hole mobility. Our work highlights strain engineering as a universal and effective approach for achieving better performed p-type compound semiconductors.

Enabling high capacity and reversible Li storage in indium(III) oxide anode surrounded by carbon nanotube matrix

In2O3 is one of the post-transition metal oxides that can be a potential anode material for the Li-ion batteries (LIBs) because of its high theoretical capacity (869 mAh g−1) and low operating voltage (0.8 V vs Li/Li+) compared to other metal oxides. However, they have rarely been used in practical applications because of typical challenges such as irreversible capacity, unstable cycling stability, and poor coulombic efficiency. In this study, carbon nanotubes (CNTs) were successfully combined with In2O3 nanoparticles (NPs) via a solvothermal process. The In2O3 NPs and CNTs were homogeneously mixed by controlling the CNT dispersion (functionalization and appropriate solvent) and mixing sequence (dissolving the In2O3 precursor in the CNT-dispersed solution followed by thermal annealing). In addition, an increase in the oxygen vacancies in the In2O3 NPs by controlling the thermal annealing conditions (In2O3/CNT_Ar) could enhance robust binding with CNTs, increase the number of Li-ion binding sites, and improve the electrical conductivity. Therefore, at an appropriate ratio of In2O3 and CNT (92:8, w/w), the In2O3/CNT_Ar demonstrated remarkable cycling performance (830 mAh g−1 at a current density of 200 mA g−1 after 100 cycles) and rate capability (65% retention at 5 A g−1 relative to 100 mA g−1), which outperformed most In2O3-based anodes previously studied. Therefore, In2O3/CNT_Ar is a promising anode material for use in next-generation LIBs.

Universal non-polar switching in carbon-doped transition metal oxides (TMOs) and post TMOs

Transition metal oxides (TMOs) and post-TMOs (PTMOs), when doped with carbon, show non-volatile current–voltage characteristics, which are both universal and repeatable. We have shown spectroscopic evidence of the introduction of carbon-based impurity states inside the existing larger bandgap effectively creating a smaller bandgap, which we suggest could be a Mott–Hubbard-like correlation effects. Our findings indicate new insights for yet to be understood unipolar and nonpolar resistive switching in the TMOs and PTMOs. We have shown that device switching is not thermal-energy dependent and have developed an electronic-dominated switching model that allows for the extreme temperature operation (from 1.5 to 423 K) and state retention up to 673 K for a 1 h bake. Importantly, we have optimized the technology in an industrial process and demonstrated integrated 1-transistor/1-resistor arrays up to 1 kbit with 47 nm devices on 300 mm wafers for advanced node CMOS-compatible correlated electron random access memory. These devices are shown to operate with 2 ns write pulses and retain the memory states up to 200 °C for 24 h. The collection of attributes shown, including scalability to state-of-the-art dimensions, non-volatile operation to extreme low and high temperatures, fast write, and reduced stochasticity as compared to filamentary memories, such as resistive random-access memories, shows the potential for a highly capable two-terminal back-end-of-line non-volatile memory.

Reversible Tuning of Mie Resonances in the Visible Spectrum.

Dielectric optical nanoantennas are promising as fundamental building blocks in next generation color displays, metasurface holograms, and wavefront shaping optical devices. Due to the high refractive index of the nanoantenna material, they support geometry-dependent Mie resonances in the visible spectrum. Although phase change materials, such as the germanium-antimony-tellurium alloys, and post-transition metal oxides, such as ITO, have been used to tune antennas in the near-infrared spectrum, reversibly tuning the response of dielectric antennas in the visible spectrum remains challenging. In this paper, we designed and experimentally demonstrated dielectric nanodisc arrays exhibiting reversible tunability of Mie resonances in the visible spectrum. We achieved tunability by exploiting phase transitions in Sb2S3 nanodiscs. Mie resonances within the nanodisc give rise to structural colors in the reflection mode. Crystallization and laser-induced amorphization of these Sb2S3 resonators allow the colors to be switched back and forth. These tunable Sb2S3 nanoantenna arrays could enable the next generation of high-resolution color displays, holographic displays, and miniature LiDAR systems.

Assessment of transition metal oxides, post transition metal oxides in suspended or settled dust particles by wavelength dispersive X-rays fluorescence (WD-XRF)

Settled dust or suspended particles of dust in air contains transition and post-transition metal oxides like Chromium oxide {Cr2O3}, Manganese oxide {MnO}, Nickel oxide {NiO}, Copper oxide {CuO}, Zinc oxide {ZnO}, Titanium oxide {TiO2}, Iron oxide {Fe2O3}, Zirconium oxide {ZrO2}, Lead oxide {PbO} and Aluminum oxide {Al2O3} and the study was carried out to find out the composition of these metallic oxides and the comparison between them with X-Ray Fluorescence Spectrometer (Chemical Analysis Instrument) by making solid beads of settled dust. Their average percent composition is found as 0.043, 0.0109, 0.013, 0.049, 0.425, 0.485, 5.39, 0.365, 0.031, and 5.55 respectively. Total of four areas were chosen to study within Karachi, a busiest and highly populated city of Pakistan. This study provides helpful data for future research and assignments as the studied metal oxides are the dynamics for environment pollution. Key words: Settled dust, X-ray fluorescence spectrometer, environment, earth sciences.

Photoelectrochemical water splitting using post-transition metal oxides for hydrogen production: a review

Photoelectrochemical water splitting using post-transition metal oxides for hydrogen production: a review

What We Currently Know about Carbon‐Supported Metal and Metal Oxide Nanomaterials in Electrochemical CO2 Reduction

AbstractElectrochemical reduction of CO2 is considered important in enhancing the circular‐economy design; it can suppress harmful greenhouse‐gas emissions while, combined with intermittent renewable energy sources, it can employ the surplus energy for production of important chemicals and fuels. In the process, electrocatalysts play an important role as the mediators of the highly active and selective conversion of CO2. Transition and post transition metals and their oxides are an important electrocatalyst group. For practical reasons, these metals need to be applied as nanoparticles supported on highly conducting materials enabling fabrication of 3D electrodes. In this minireview, we focus on gathering our current knowledge on the effects which transition and post transition metal and metal oxide nanoparticles supported on different carbons may have on electrochemical reduction of CO2. We focus on literature of studies conducted in aqueous conditions, under as similar conditions as possible, to ensure comparability. This approach enables us to highlight possible support effects and issues that complicate making conclusions on support effects.

A Review on X-ray Excited Emission Decay Dynamics in Inorganic Scintillator Materials

Scintillator materials convert high-energy radiation into photons in the ultraviolet to visible light region for radiation detection. In this review, advances in X-ray emission dynamics of inorganic scintillators are presented, including inorganic halides (alkali-metal halides, alkaline-earth halides, rare-earth halides, oxy-halides, rare-earth oxyorthosilicates, halide perovskites), oxides (binary oxides, complex oxides, post-transition metal oxides), sulfides, rare-earth doped scintillators, and organic-inorganic hybrid scintillators. The origin of scintillation is strongly correlated to the host material and dopants. Current models are presented describing the scintillation decay lifetime of inorganic materials, with the emphasis on the short-lived scintillation decay component. The whole charge generation and the de-excitation process are analyzed in general, and an essential role of the decay kinetics is the de-excitation process. We highlighted three decay mechanisms in cross luminescence emission, exitonic emission, and dopant-activated emission, respectively. Factors regulating the origin of different luminescence centers controlling the decay process are discussed.

BiSbWO6: Band Energies Tuning of a Mixed Sb(5s)/Bi(6s) Lone-Pair-Electrons System

Post-transition metal oxides with electronic configuration ns2-md0 have been highlighted as efficient photocatalysts due to their favorable optoelectronic properties. Of the ns2-md0 class of materials, none have received greater attention than BiVO4. Due to the localized V 3d conduction orbitals, BiVO4 charge transport properties are affected by the formation of small polaronic states. Alternatively, one may consider materials with more delocalized conduction bands, such as W 5d0 compounds. One such example is the russellite mineral, or Bi2WO6. Density functional theory is used to calculate the electronic properties of Sb-alloyed Bi2WO6, and to study the effects of introducing Sb 5s orbitals to the band structure. In studying the configurational space of BiSbWO6, we provided new insights into the behavior of mixed Sb(5s)/Bi(6s) lone-pair electrons in post-transition metal oxides. We find that local distortions caused by Sb 5s lone-pair electrons indirectly lead to upshifts in both valence and conduction band edges. To isolate the role of the lone pairs, we compare the observed effects to those in a WO3 control model that is subject to structural deformations. These insights may be further extended and applied more generally to mixed post-transition metal oxides in pursuit of new efficient solar absorbing materials.

Turning indium oxide into high-performing electrode materials via cation substitution strategy: Preserving single crystalline cubic structure of 2D nanoflakes towards energy storage devices

Enhancement in electrochemical performance of electrode materials has been the recent focus for material development of electrochemical energy storage devices. For the first time, we turn a post transition metal oxide, indium oxide (In2O3), into a high capacity, excellent stability and rate capability electrode by introducing suitable cations. Various electrode materials M-In2O3 (where M is Co, Fe, Mg, Mn, Ni, and Zn) have been prepared by simple and inexpensive cation substitution route. Among all, the optimal promoter Co–In2O3 electrode deliver higher specific capacity (4.8 times) and rate capability (1.3 times) than bare In2O3. The capacitive contribution and diffusion contribution reactions have been studied for all the electrodes. The capacitive distribution has been increased by Mg and Zn substitution and the diffusion contribution has been enhanced with Co, Fe, Mn, and Ni substitution. Furthermore, structural and electronic properties of In2O3 substituted with the cations have been studied through first principles density functional theory calculations. Moreover, seven asymmetric supercapacitor devices have been assembled by using In2O3 and M-In2O3 as the positive and the reduced graphene oxide as the negative electrode materials. The wrist watch, stop watch, and LEDs have been successfully operated, illustrate the prospective of electrode materials towards practical applications.

Origin of high carrier concentration in amorphous wide-bandgap oxides: Role of disorder in defect formation and electron localization in In2O3−x

Structural disorder has been known to suppress carrier concentration and carrier mobility in common covalent semiconductors, such as silicon, by orders of magnitude. This is expected from a reduced overlap of the electron clouds on neighboring orbitals and the formation of localized tail states near the band edges caused by local distortions and lack of periodicity in the amorphous phase. In striking contrast to the covalent semiconductors, wide-bandgap oxides of post-transition metals with ionic bonding not only allow for crystalline-like electron mobility upon amorphization, but also exhibit two orders of magnitude higher carrier concentration in the disordered phase as compared to the crystalline oxide. Here, the results of computationally intensive ab initio molecular dynamics simulations, comprehensive structural analysis, and accurate density-functional calculations reveal complex interplay between local distortions, coordination, and long-range bond morphology and help establish the microscopic origin of carrier generation and transport across the crystalline–amorphous transition in In2O3−x. Departing from traditional oxygen vacancy in crystalline oxides, the derived structural descriptors help categorize “defects” in disordered ionic oxides, quantify the degree of the associated electron localization and binding energy, and determine their role in the resulting electronic and optical properties. The results will be instrumental in the development of next-generation transparent amorphous semiconductors with a combination of properties not achievable in Si-based architectures.

On the spectroscopy of Bi3+ in d10 post-transition metal oxides

The optical spectroscopy of Bi3+ in d10-based post transition metal oxides (i. e. gallates, germanates, antimonates indates, stannates) is reviewed and analyzed in the frame of empirical models. 20 different compounds are examined. From this, a methodology is introduced to identify the preferred doping sites for Bi3+ and predict the intra- or extra-ionic origin of the Bi3+ emission in these systems. Further, the emission process in calcite-structured InBO3:Bi and GaBO3:Bi is reconsidered.

Understanding the origin of bandgap problem in transition and post-transition metal oxides.

Improving electronic structure calculations for practical and technologically important materials has been a never-ending pursue. This is especially true for transition and post-transition metal oxides for which the current first-principles approaches still suffer various drawbacks. Here, we present a hierarchical-hybrid functional approach built on the use of pseudopotentials. The key is to introduce different amounts of exact exchange to core and valence electrons. It allows for treating the delocalization errors of sp and d electrons differently, which have been known to be an important source of error for the band structure. Using wurtzite ZnO as a prototype, we show that the approach is successful in simultaneously reproducing the bandgap and d-band position. Importantly, the same approach, without having to change the hybrid mixing parameters from those of Zn, works reasonably well for other binary 3d transition and post-transition metal oxides across board. Our findings thus point out a new direction of systematically improving the exchange functional in first-principles calculations.

Octahedral Sb2O3 as high-performance anode for lithium and sodium storage

Abstract Among a succession of promising electrode materials of post-transition metal oxides, Sb2O3 has drawn growing attention on energy storage field owing to its high theoretical capacity and abundant resources. Nevertheless, the inherent flaw of serious volume variation during the process of ion insertion/desertion greatly hinders the application of Sb2O3 in energy storage system. Therefore, an octahedral Sb2O3 is prepared via facile and low cost approach as anode materials for lithium-ion batteries and sodium-ion batteries. Such obtained octahedral Sb2O3 composite exhibits high specific charge capacity of 640.8 mA h g−1 at a current density of 0.2 A g−1 after 50 cycles in lithium-ion batteries. Due to the excellent electrochemical properties for lithium ions storage, the obtained octahedral Sb2O3 is further studied on sodium ions storage. And the electrode delivers a specific charge capacity of 435.6 mA h g−1 at a current density of 0.1 A g−1 after 50 cycles. Briefly, this work could open up a new method to use Sb2O3 as rechargeable anode materials in scalable application and offer a reference for the development of antimony compounds in energy storage domain.

Imprinted Oxide and MIP/Oxide Hybrid Nanomaterials for Chemical Sensors †.

The oxides of transition, post-transition and rare-earth metals have a long history of robust and fast responsive recognition elements for electronic, optical, and gravimetric devices. A wide range of applications successfully utilized pristine or doped metal oxides and polymer-oxide hybrids as nanostructured recognition elements for the detection of biologically relevant molecules, harmful organic substances, and drugs as well as for the investigative process control applications. An overview of the selected recognition applications of molecularly imprinted sol-gel phases, metal oxides and hybrid nanomaterials composed of molecularly imprinted polymers (MIP) and metal oxides is presented herein. The formation and fabrication processes for imprinted sol-gel layers, metal oxides, MIP-coated oxide nanoparticles and other MIP/oxide nanohybrids are discussed along with their applications in monitoring bioorganic analytes and processes. The sensor characteristics such as dynamic detection range and limit of detection are compared as the performance criterion and the miniaturization and commercialization possibilities are critically discussed.

Synthesis and Characterisation of Nanocomposites of TiO₂ and MgAl₂O₄ for Gas Sensing Applications.

In this study, a conventional mixed oxide method was used to prepare nanocomposites of titanium dioxide and magnesium aluminate samples. The synthesis process of a low concentration of posttransition metal oxide like TiO2 with pre-transition metal oxides like MgO and Al₂O3 and its gas sensing behaviour were investigated. The present work focuses on applying different nanocomposite samples of (TiO2) x and MgAl₂O₄ (at x = 0 magnesium aluminate namely MA; x = 0°25 and 0.75 N namely MAT0.25 and MAT0.75 at 4 and 10 wt% of TiO2 in MgAl₂O₄ respectively and TiO₂ namely T) for gas sensing applications (O₂, CO and H₂ gases). The composite samples were characterized by their X-ray diffraction pattern, Fourier transform infrared spectroscopy, a particle size analyzer, X-ray fluorescent spectroscopy, scanning electron microscopy, ultraviolet visible spectroscopy, and Brunauer–Emmett–Teller methods. The response to changes in gas pressure (from 0.5 to 2 bar) was quantitatively studied in all samples (MA, MAT0.25, MAT0.75 and T) at different operating temperatures from 300 to 600 K. All samples showed a fast and improved gas response at different operating temperatures. Moreover, it was observed that the gas response of the composite sample, MAT0.75 increased by 11% more than the pure titanium sample at an operating temperature of 360 K, on the passage of O₂ gas.

Chemical and structural properties of ternary post-transition metal oxide thin films: InZnO, InGaO and GaZnO

The chemical states of ternary post-transition metal oxide thin films of InGaO, GaZnO and InZnO were investigated using X-ray photoelectron spectroscopy. Detailed binding energy (BE) analyses revealed certain evolution in chemistry in the ternary oxides compared to the reference binary oxides of In2O3, ZnO, or Ga2O3. In particular, O 1s BEs were changed with the compositions, which suggests that the charge transfer (CT) between In3+/Ga3+/Zn2+ and O2− ions is significant. Results of extended X-ray absorption fine structure analyses further showed that the first shell coordination (cation–O bond) is roughly maintained even though the ternary oxide films were structurally disordered. This implies that the CT process via O2− ions can influence the charge reconstructions in the ternary oxide systems.

(Invited) Advances in Oxide Thin-Film Transistors in Recent Decade and Their Future

Electronic devices using oxide semiconductor based thin-film transistors (TFTs) were commercialized for the first time in 2012 as backplane active-matrix circuits for flat-panel displays after almost half a century from their first demonstration in 1964. Such a miraculous revival was induced by discovery of high-mobility semiconductor materials made from amorphous oxides of post-transition metals and invention of TFTs using them for their channel materials in 2004. The present paper provides a historical review of oxide semiconductor based TFTs, their recent advances in the recent decade along the strategy and scenario, and a prediction of their future.

Synthesis, features and solar-light-driven photocatalytic activity of TiO2 nanotube arrays loaded with SnO2.

In the present study TiO2 nanotube arrays (TNTs) were loaded with a post-transition metal oxide particles namely SnO2 via incipient wet impregnation method by varying its concentration (1.59 wt%, 2.25 wt% and 2.84 wt%). The photocatalytic activity of the prepared photocatalyst was evaluated for the degradation of methylene blue (MB) in presence of natural solar light irradiation. The morphological analyses revealed that the prepared TNTs had average inner diameter of 109 nm, wall thickness of 15 nm and tube length of 7-10 μm, respectively, while the crystalline phase and Raman spectra confirmed the 100% anatase mineral form of TiO2. Further, the presence of SnO2 in TNTs was confirmed by high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The visible light absorption properties of TNTs improved drastically with increasing SnO2 loadings. The coupling effect of SnO2 and TiO2 significantly enhanced degradation efficiency of MB. An 84% degradation of MB was achieved in 6 h of irradiation under clear sky condition.