Oxide Research Articles (Page 1)

Prediction of Tl(I) adsorption onto metal oxides and identification of critical factors using a machine learning-based model.

Industrial emissions, particularly from flue gases, pose significant risks to environmental sustainability and public health. Conventional air quality monitoring systems often suffer from high costs, delayed reporting, and limited detection capabilities. This study presents a cost-effective, real-time air quality monitoring solution using an electronic nose (eNose) system integrated with Metal Oxide Semiconductor (MOS) gas sensors. These sensors target key pollutants, such as carbon monoxide (CO) and carbon dioxide (CO2), which also serve as indicators of transformer faults in industrial settings. The eNose system leverages machine learning for both regression and classification tasks, enabling accurate quantification of pollutant levels and categorization of air quality into defined categories. Principal Component Analysis (PCA) is employed to optimize feature extraction, enhancing model precision and efficiency. Notably, the system integrates digitally controlled buck converters for automatic temperature regulation, reducing sampling time from 390 to 130 seconds. Additionally, a redesigned airtight sensor chamber and optimized airflow design, along with the use of Tedlar bags, improve sample integrity and minimize interference. Hardware development involved prototyping on breadboards using LM2575, LM2576, and LM2574 ICs, followed by the creation of a compact 10 cm × 10 cm PCB for efficient power management. Multimeter testing verified reliable electrical connections. Experimental validation showed the system achieved over 91% accuracy in distinguishing between "good" and "bad" air quality levels. Strong correlations between sensor output and pollutant concentrations confirm system reliability. This research demonstrates a scalable, efficient tool for real-time air quality monitoring and fault detection in industrial environments.

Oxygen vacancies driven Pd - MoO3 / f - MWCNTs nanocomposite for electrochemical sensing of Pb (II).

Transition metal high-entropy alloys (HEAs) demonstrate exceptional catalytic performance due to their structural complexity, featuring rich local atomic configurations, tunable electronic structures, and abundant active sites. However, this structural versatility poses both thermodynamic and kinetic challenges to conventional wet-chemical synthesis routes. Herein, we develop a novel solution plasma strategy that enables the direct synthesis of HEA catalysts in aqueous media. Through the FeCoNiCrMn electrode discharge in pure water, uniform HEAs nanoparticles (≈200 nm) are successfully anchored onto a variety of oxide substrates. The HEAs/TiO2 catalyst achieves a CO generation rate of 298.1 mmol/gHEAs/h, representing ca. an order-of-magnitude higher activity than single-metal catalysts under both thermocatalytic and photothermal conditions. Advanced structural characterization reveals a dual-phase core-shell architecture consisting of a metallic alloy core and surface oxides preferentially enriched at CrMn sites. This spatially resolved structure enables cooperative catalysis, where CrMn-rich oxide domains promote H2 dissociation, CoNi metallic regions facilitate CO2 reduction, and Fe sites present in mixed valence states serve as electron and oxygen transfer bridges. We further identify a self-limiting oxidation mechanism intrinsic to plasma synthesis, which ensures charge redistribution at the metal-oxide interfaces and synergistically enhances photothermal catalysis. This work establishes an energy-efficient synthetic route for HEAs and elucidates structure-function relationships critical for advancing multimetallic catalytic systems.

Laser-induced graphene (LIG) has driven significant advances in wearable electronics, advanced healthcare, and energy devices. However, achieving diverse functionalities and high-performance for practical use requires integrating functional materials, which remains challenging due to poor synthesis results or complex chemical treatments. Herein, direct, seedless growth of transition-metal-oxide (MO) crystalline nanorods on LIG is demonstrated, even under lattice-mismatch conditions, via a non-epitaxial process. Ultrafast laser pyrolysis during LIG formation introduces nitrogen- and oxygen-containing surface groups that facilitate the nucleation of MO during subsequent synthesis, enabling the selective growth of MO nanorods exclusively on LIG patterns without additional lattice-matching or patterning steps. Through this non-epitaxial growth, crystalline orthorhombic WO3·0.33 H2O and β-FeOOH nanorods are successfully synthesized on LIG micro-patterns. As a proof-of-concept, LIG electrodes integrated with these crystalline MO nanorods are employed in all-solid-state micro-supercapacitors, exhibiting significantly enhanced capacitive performance owing to the electrochemical reactivity of the MO nanorods, together with excellent mechanical and cyclic stability. Beyond this demonstration, the non-epitaxial strategy offers a versatile route for harnessing the diverse functionalities of MO nanostructures, unlocking new possibilities in graphene-based electronics.

Electrochromic materials exhibit a reversible change of color on application of external voltage and have important applications in smart windows, low energy display technology, and active camouflage. Transition metal oxides have better long-term stability than organics but are limited by their narrow range of colors. For good optical contrast, the active electrochromic layer has a typical thickness of 0.1-1 μm, which determines the energy requirement for switching and the response time. Thicker layers have better optical contrast between states but can be brittle, or prone to delamination, limiting their long-term stability and use on flexible surfaces. In this work, we investigate the electrochromic properties of ultrathin (<100 nm) inorganic electrochromic films. We show that with the addition of a metal backing, we can use an optical resonance known as the zeroth-order Fabry-Perot mode to achieve a high optical contrast of 41.2%. Coloration efficiency values of 205 cm2/C are demonstrated for films as thin as 25 nm and a time response of 2.1 s and 2.5 s for coloring and bleaching, respectively. Cycling stability and optical memory (bistability) are key parameters for practical electrochromic applications. We demonstrate that a sub1 nm Ti adhesion layer is sufficient to stabilize the films for >250 cycles without degrading the optical contrast. The adhesion layer is shown to also significantly improve the optical memory (bistability) of the films. With an extremely low energy consumption of 1.76 mJ/cm2 per switch and an optical contrast loss rate of 3% per hour, the films have a power requirement of 170 nW/cm2 when refreshed every 3 h. Compared to the state of the art, we demonstrate a reduction of 10 times the energy required to switch using 20 times less material.

Electronic flat bands associated with quenched kinetic energy and heavy electron mass have attracted great interest for promoting strong electronic correlations and emergent phenomena such as high-temperature charge fractionalization and superconductivity. Intense experimental and theoretical research has been devoted to establishing the rich nontrivial metallic and heavy fermion phases intertwined with such localized electronic states. Here, we investigate the transition metal oxide spinel LiV2O4, an enigmatic heavy fermion compound lacking localized f orbital states. We use angle-resolved photoemission spectroscopy and dynamical mean-field theory to reveal a kind of correlation-induced flat band with suppressed interatomic electron hopping arising from intra-atomic Hund's coupling. The appearance of heavy quasiparticles is ascribed to a proximate orbital-selective Mott state characterized by fluctuating local moments as evidenced by complementary magnetotransport measurements. The spectroscopic fingerprints of long-lived quasiparticles and their disappearance with increasing temperature further support the emergence of a high-temperature "bad" metal state observed in transport data. This work resolves a long-standing puzzle on the origin of heavy fermion behavior and unconventional transport in LiV2O4. Simultaneously, it opens a path to achieving flat bands through electronic interactions in d-orbital systems with geometrical frustration, potentially enabling the realization of exotic phases of matter such as the fractionalized Fermi liquids.

Cost-effective, high-capacity rechargeable stationary batteries are essential for supporting an integrated power grid that depends on sustainable energy sources. Sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs) are both rechargeable energy storage technologies based on the reversible movement of ions between the anode and cathode during charge and discharge cycles. LIBs have dominated the market for decades because of their high energy density, long cycle life, and proven commercial viability; however, their complex recycling, high cost, and limited lithium availability raise concerns about their future use. On the other hand, SIBs are emerging as a promising alternative, especially for large-scale energy storage, due to the abundance of sodium in Earth's crust compared to lithium, making SIBs more sustainable and potentially more affordable. In this review, the benefits of SIBs are examined, and highlighted the important role of layered transition metal oxides (LTMOs) in achieving high-performance SIBs. Current challenges in utilizing LTMOs are discussed, and explored various strategies to enhance their electrochemical properties. Additionally, a comparative analysis of the recycling processes for LIBs and SIBs is presented to evaluate the sustainability of SIBs for long-term applications.

High-entropy oxides (HEOs) consist of multiple principal metal cations and oxygen anions, which enhances compositional versatility and promotes the emergence of atypical properties within oxide materials. Nonetheless, precisely shaping HEOs in hollow nanostructures remains a significant challenge due to the disparate nucleation and growth kinetics of the various metal oxide compositions in HEOs. Herein, we present a strategy for the synthesis of multicomponent hollow nanocubes HEOs libraries from ternary to octonary. We utilized a template-assisted route inspired by coordinating etching and integrating thermal treatment to synthesize HEOs hollow nanocubes through the selection of coordinating etchant and optimization of the reaction conditions. This approach demonstrates the potential for precisely designing high-quality HEOs hollow nanocubes with diverse compositions at low temperature, with promising prospects for various applications.

Abstract This paper provides an in-depth examination of carbon–carbon bond formation processes facilitated by heterogeneous catalysts. It highlights the crucial roles of active sites, structure-activity relationships (SARs), stability determinants, and classifications of catalysts. Active sites, characterized by distinct atomic arrangements, reduce the activation energy and enhance reaction selectivity and efficiency. The SAR framework elucidates the effect of structural characteristics, including pore size, surface area, crystal structure, and metal distribution, on catalytic performance. Stability challenges, such as heat deterioration, sintering, leaching, and poisoning, were analyzed. This indicates that resin-based catalysts exhibit greater durability and recyclability compared to metal oxides and silica-based systems. Comparative evaluations highlight the trade-offs between activity, stability, and industrial applicability, with resin-based catalysts exhibiting superiority in sustainable processes. The metal oxides offer durability in high-temperature applications. Case studies on methods such as benzene hydrogenation and carbon monoxide oxidation highlight the practical importance of catalyst design in these reactions. Emerging advances in nanocatalysis, green chemistry, and computer modeling are examined, highlighting their potential to enhance catalyst engineering. This study emphasizes the significance of understanding active site dynamics and structural influences in developing efficient, durable, and sustainable catalytic systems. The study facilitates substantial progress in chemical synthesis and the development of industrial catalysts.

Metal-organic frameworks (MOFs), due to their highly ordered structure, ultra-high specific surface area, and adjustable porosity, have become highly promising new energy storage materials. This article reviews the applications of MOFs and their derivatives in energy storage devices such as supercapacitors and lithium/sodium-ion batteries, and discusses the design principles for enhancing their conductivity, optimizing their porous structures, and strengthening their structural stability. Although MOFs can be directly used as electrode materials due to their advantages such as adjustable structure and large specific surface area, their inherent poor conductivity and the decrease in ion transmission efficiency with increasing thickness limit their practical applications. Through carbonization treatment, the conductivity can be significantly enhanced and a stable porous carbon framework can be formed, such as the C-ZIF-67 material; while when combined with carbon materials, conductive polymers or metal oxides (such as PANI/MIL-101), multiple advantages can be integrated, significantly improving the electrochemical performance, mechanical strength and cycle life, thus becoming an effective strategy to break through the practical application bottleneck of MOFs. This article summarizes the current challenges in the industrialization process of MOF materials, such as costs, structural control, and processing difficulties. It proposes solutions including green synthesis, machine learning-assisted design, and the construction of conductive composite structures.

Abstract Water pollution from industries, particularly from textile industries, is a major environmental and health concern due to untreated effluent containing toxic, non-biodegradable, carcinogenic dyes. Among various wastewater purification techniques, semiconductor-based photocatalysis offers a sustainable remediation strategy due to its low cost, operational simplicity, and environmental compatibility. The present study explored the photocatalytic degradation of methyl orange (MO) and methylene blue (MB) dyes using ZnO, CuO, and ZnO–CuO metal oxide nanocomposites synthesized via the co-precipitation method. Structural characterization using XRD (x-ray diffraction) confirmed the formation of highly crystalline, phase-pure nanostructures with crystallite sizes between 12–26 nm. Infrared spectroscopy revealed distinctive Zn-O and Cu-O bond stretches between 400–600 cm −1 , and Scanning Electron Microscopy (SEM) images confirmed nanostructured morphologies suitable for catalysis. The band gaps estimated by UV–Vis spectroscopy were found to be 3.14 eV for ZnO, 2.20 eV for CuO, and 2.42 eV for the ZnO-CuO nanocomposite. Photocatalytic degradation study carried out under UV light revealed that CuO exhibited the highest degradation efficiency for MB (94% in 40 min), while ZnO showed superior performance for MO (84.7% in 40 min). The 1:1 ZnO-CuO nanocomposite under the present conditions achieves the MB degradation efficiency of CuO, while exhibiting less photocatalytic activity for MO compared to ZnO. Kinetic studies and PZC (point of zero charge) values, determined by the pH drift method, confirm the correlation between surface properties and the observed dye degradation efficiencies. The varied degradation behaviour may be due to the interplay between band gap energies, surface adsorption affinities, and dye structures. The optimized synthesis of ZnO-CuO nanocomposites through band gap engineering and heterojunction formation presents a promising path for future research in enhancing photocatalytic efficiency. The study highlights the potential of low-cost binary metal oxide nanostructures as a sustainable and eco-friendly alternative for wastewater management techniques.

Defect engineering has emerged as a powerful approach to enhance the photocatalytic activity of metal oxides, yet the role of oxygen vacancies, commonly regarded as the Shockley-Read-Hall charge recombination centers, remains controversial. Taking bismuth oxybromide (BiOBr) as a prototypical photocatalyst, we demonstrate a dual-defect strategy incorporating both surface Br (VBr) and bulk O (VO) vacancies to suppress recombination and enhance CO2 reduction. While the VO alone results in significant charge losses, the VBr improves CO2 adsorption and lowers its LUMO to effectively capture photoexcited electrons from the VO-induced defect state for the subsequent reaction. Formation of a donor-acceptor pair between the CO2 LUMO and the valence band maximum facilitates long-lived charge separation due to weak nonadiabatic coupling. The strategy extends to vacancy-transition metal doping, further lowering reaction barriers and advancing defect engineering principles. The study provides a comprehensive understanding of defect-dependent photocatalytic reactions, forming a basis for defect engineering in photocatalysis.

Abstract Sodium‐ion batteries (SIBs) have emerged as a cost‐effective alternative to lithium‐ion batteries due to the natural abundance and wide geographic distribution of sodium resources, which mitigate concerns over the scarcity and price volatility of lithium. However, the larger ionic radius of Na + (1.02 Å) compared to Li + (0.76 Å) produces inferior diffusion kinetics and structural stability. Therefore, layered transitional metal oxide cathode materials have extensively utilized high entropy doping to suppress undesirable phase transitions, improve kinetic performance, and enhance cationic and oxygen redox reversibility. Although the compositional tunability of high entropy doping offers considerable potential, it also introduces significant structural and chemical complexity. This necessitates the precise selection and optimization of dopant elements to target specific limitations observed in conventional low entropy systems. Accordingly, this review comprehensively evaluates the impact of dopant strategies and configurational entropy on the performance of compositionally proximate high entropy materials. It offers a systematic guide for rationally tailoring high entropy techniques to overcome interconnected performance‐limiting obstacles across diverse undoped systems. The review clarifies the definitional controversy surrounding the term “high entropy” and elucidates the theoretical limitations that hinder the accurate prediction of high entropy materials before concluding with an outline of prospective research directions.

Understanding the Role of Transition Metal Oxides as Hole-Selective Contacts for Enhanced Efficiency in Selenium Solar Cells

Abstract HfO 2 –based ferroelectric is extensively studied for semiconductor applications due to its compatibility with complementary metal–oxide–semiconductor technology and stable ferroelectric behavior in the thin films. However, achieving robust ferroelectricity in micrometer–thick HfO 2 –based films remains challenging, as the metastable polar orthorhombic phase is difficult to stabilize in thicker films. In this study, by controlling micro– and nanostructures in crystal grains, 3–µm–thick Ce–doped HfO 2 (Ce:HfO 2 ) films fabricated via chemical solution deposition (CSD) exhibit robust ferroelectricity, characterized by high remnant polarization, low leakage current, and minimal wake–up effect. The films display a distinctive {111}–preferred oriented single crystal–like columnar structures with embedded nanopores, which likely results from competitive grain growth mediated by the surface of the underlayer during the thermal treatment from gel to crystal in the CSD process. This work demonstrates a promising strategy to enable robust ferroelectricity in micrometer–thick HfO 2 –based films and facilitates the expansion of thick–film applications such as piezoelectric devices, pyroelectric devices, electrocaloric devices, and power electronics.

Abstract Apoptosis, traditionally regarded as a straightforward cell‐suicide process triggered by cellular stress, plays a vital role in development, immune function, and disease progression. This research presents a synthetic model of the intrinsic (mitochondrial) apoptosis pathway, focusing on programmed cell death initiated by severe DNA damage. Through an in vitro approach, the study quantitatively analyzes apoptotic behavior using mathematical formulations of key regulatory proteins, modeled with ordinary differential equations using Law of Mass Action. A comprehensive system model is developed to capture the full signaling cascade of apoptosis. Furthermore, a novel cytomorphic model is introduced, employing Metal Oxide Semiconductor (MOS) technology to simulate molecular dynamics by drawing parallels with electron flow in transistors. The analytical output of the model reveals time‐dependent protein activity profiles, accurately representing the distinct phases of apoptosis. Notably, simulations show a rapid rise in Caspase‐3 activity following an apoptotic trigger, consistent with its role as an executioner caspase. The electronic circuit model is validated against experimental data from cell culture studies, reinforcing its accuracy and biological relevance. Additionally, the hardware implementation of the apoptosis‐based cytomorphic system is realized using the NI myRIO 1900 tool, demonstrating practical feasibility and integration potential. These findings demonstrate that MOS‐based electronic analogs of apoptosis pathways can effectively mimic protein behavior, offering a faster, more cost‐effective, and safer platform for pharmaceutical research and drug development.

To sustainably support the ongoing energetic transition, we need metal oxides capable of converting energy and produce sensing devices. However, these materials suffer from a high economic cost of manufacturing, and their production in a sustainable way is, to date, a milestone. Additionally, the technical challenges, such as scalability and integration on silicon for industrial processing using microelectronic technologies, impose strict conditions for the entire materials process. In this work, we engineer α-quartz virtual substrates up to 4 inches, facilitating the large-scale and sustainable integration of epitaxial ZnO microwire films on silicon. These materials are manufactured on silicon by using solution chemistry, providing single-chip solutions that can meet strict economic constraints for developing sustainable devices at a lower cost. Through this integrative technology, we demonstrate the microfabrication of epitaxial (110)ZnO/(100)α-quartz/(100)silicon piezoelectric membrane resonators at the wafer scale with potential applications in energy conversion and sensing. We combined four-dimensional (4D) STEM diffraction and piezoelectric force microscopy (PFM) to establish a correlation between out-of-plane crystalline strain and piezoelectric response in epitaxial (110)ZnO at the microscale. Finally, we proved the fabrication of 800 nm thick (110)ZnO suspended membranes that can be transferred to flexible substrates, making them suitable for flexible devices.

Abstract BaSi 2 composed of abundant elements is anticipated as a new material for thin-film solar cells. BaSi 2 films formed by sputtering exhibit very high spectral sensitivity, but p/n control via impurity doping is difficult. Therefore, we plan a solar cell structure where the sputter-deposited undoped BaSi₂ film is sandwiched between an electron transport layer (ETL) and a hole transport layer (HTL). Previously, metal oxides such as MoO x and NiO used in crystalline Si solar cells have been considered for the HTL in BaSi 2 solar cells. However, this paper selected 3,3'-Bi[1,4]benzoxazino[2,3,4-kl]phenoxazine (HN-D2) as an organic material with an ionization potential ( IP ) close to that of BaSi 2 (~4.5 eV) The IP and optical absorption edge of HN-D2 films formed by vacuum evaporation were evaluated. Furthermore, we formed junctions with BaSi 2 and found that HN-D2 functions as HTL for BaSi 2 , as evidenced by its photoresponse spectra and external quantum efficiency spectra.

As a transition-metal oxide semiconductor with variable tungsten valence states and abundant oxygen vacancies, WO3-xhas attracted broad interest because its localized surface plasmon resonance performance can be tuned via controlling the concentration of oxygen vacancies. In this work, Cs-doped WO3-xnanosheets (Cs-WO3-x) were synthesized by solvothermal method. Subsequently, Cs-WO3-xwere further annealed in hydrogen and air atmosphere, respectively, forming a compact, highly crystalline surface layer (with thickness of ∼14 nm) on the surface while retaining abundant oxygen vacancy defects in the center region (denoted as a-Cs-WO3-x). As a proof-of-concept, the as-prepared nanosheets were employed as light harvesting materials in photocatalytic degradation of methyl orange (MO), a-Cs-WO3-xnanosheets demonstrate significantly improved degradation efficiency with respect to WO3-xand Cs-WO3-xcounterparts. The enhanced performance can be attributed to the hot-carrier transfer routes, which relies on not only direct electron transfer but also the more efficient plasmon-induced resonant energy transfer pathway. This work develops new pathway and provides important insights into the regulation of oxygen vacancies.