Search Results (89)

In this study, we aimed to develop a high-performance, anti-fouling ultrafiltration membrane by integrating photocatalytic and Fenton-like functions into a polymer matrix, in order to address the critical challenge of membrane fouling and achieve simultaneous separation and degradation of organic pollutants. To this end, a novel Fe-V_O-TiO₂-embedded polyethersulfone (PES) composite membrane was designed and fabricated using a facile phase inversion method. The key innovation lies in the incorporation of Fe-V_O-TiO₂ nanoparticles containing abundant bulk-phase single-electron-trapped oxygen vacancies, which not only modulate membrane morphology and hydrophilicity but also enable sustained generation of reactive oxygen species for the pollutant degradation under light irradiation and H₂O₂. The optimized Fe-V_O-TiO₂-PES-0.04 membrane exhibited a significantly enhanced pure water flux of 222.6 L·m⁻²·h⁻¹ (2.2 times higher than the pure PES membrane) while maintaining a high bovine serum albumin (BSA) retention of 93% and an improved hydrophilic surface. More importantly, the membrane demonstrated efficient and stable synergistic Photocatalytic-Fenton activity, achieving 82% degradation of norfloxacin (NOR) and retaining 75% efficiency after eight consecutive cycles. A key finding is the membrane’s Photocatalytic-Fenton-assisted self-cleaning capability, with an 80% flux recovery after methylene blue (MB) fouling, which was attributed to in situ reactive oxygen species (·OH) generation (verified by ESR). This work provides a feasible strategy for designing multifunctional membranes with enhanced antifouling performance and extended service life through built-in catalytic self-cleaning. Full article

In this work, we report optical and photoelectrochemical properties of BiVO₄ synthesized by microwave, sonochemical, sol–gel, and direct deposition on conductive substrate methods. Structural and morphological characterization using XRD, SEM, and AFM confirmed the presence of both monoclinic and tetragonal phases, with variations in particle size and surface roughness. UV-Vis spectroscopy revealed band gaps in the range of 2.38–2.51 eV. Photoelectrochemical performance was evaluated through measurements of photocurrents under varying illumination wavelengths and applied potentials. BiVO₄ as a thin film exhibited the highest photocurrent intensity due to its superior semiconductor–substrate contact. In contrast, BiVO₄ samples obtained as a powder showed significantly lower photocurrents but demonstrated the photocurrent switching effects, attributed to the presence of surface trap states and oxygen vacancies. The obtained results highlight the importance of synthesis strategy in tailoring BiVO₄ properties for use as a photoelectrochemical cell and suggest potential applications in molecular electronics, such as logic gates and memory devices. Full article

Amorphous indium gallium zinc oxide (a-IGZO) is widely used as an oxide semiconductor in the electronics industry due to its low leakage current and high field-effect mobility. However, a-IGZO suffers from notable limitations, including crystallization at temperatures above 600 °C and the high cost of indium. To address these issues, nitrogen-doped zinc oxynitride (ZnON), which can be processed at room temperature, has been proposed. Nitrogen in ZnON effectively reduces oxygen vacancies (V_O), resulting in enhanced field-effect mobility and improved stability under positive bias stress (PBS) compared to IGZO. In this study, selective deep ultraviolet femtosecond (DUV fs) laser annealing was applied to the channel region of ZnON thin-film transistors (TFTs), enabling rapid threshold voltage (Vth) modulation within microseconds, without the need for vacuum processing. Based on the electrical characteristics of both Vth-modulated and pristine ZnON TFTs, an NMOS inverter was fabricated, demonstrating reliable performance. These results suggest that laser annealing is a promising technique, applicable to various logic circuits and electronic devices. Full article

Tungsten-doped vanadium dioxide (W-VO₂) shows semiconductor-to-metal phase transition properties at room temperature, which is an ideal thermo-chromic smart window material. However, low visual transmittance and solar modulation limit its application in building energy saving. In this paper, a W-VO_2−x@AA core-shell nanoparticle is proposed to improve the thermo-chromic performance of W-VO₂. Oxygen vacancies were used to promote the connection of W-VO_2−x nanoparticles with L-ascorbic acid (AA) molecules. Oxygen vacancies were tuned in W-VO₂ nanoparticles by thermal annealing temperatures in vacuum, and W-VO_2−x@AA nanoparticles were synthesized by the hydrothermal method. A smart window was formed by dispersing W-VO_2−x@AA core-shell nanoparticles into PVP evenly and spin-coating them on the surface of glass. The visual transmittance of this smart window reaches up to 67%, and the solar modulation reaches up to 12.1%. This enhanced thermo-chromic performance is related to the electron density enhanced by the AA surface molecular coordination effect through W dopant and oxygen vacancies. This work provides a new strategy to enhance the thermo-chromic performance of W-VO₂ and its application in the building energy-saving field. Full article

In this study, zinc–tin oxide (ZTO) thin films were prepared via radio-frequency magnetron sputtering to examine the influence of annealing temperature on the performance of thin-film transistors (TFTs) and their resistive-load inverters. The findings reveal that annealing modulates the concentration and spatial distribution of oxygen vacancies (V_O), which directly affect carrier density and interface trap density, ultimately determining the electrical behavior of inverters. At the optimal annealing temperature of 600 °C, the V_O concentration was effectively moderated, resulting in a TFT with a mobility of 12.39 cm² V⁻¹ s⁻¹, a threshold voltage of 6.13 V, an on/off current ratio of 1.09 × 10⁸, and a voltage gain of 11.77 in the corresponding inverter. However, when the V_O concentration deviated from this optimal range, whether in excess or deficiency, the gain was reduced and power consumption increased. This V_O engineering strategy enables the simultaneous optimization of both TFT and inverter performance without relying on rare elements, offering a promising pathway toward the development of low-cost, large-area, flexible, and transparent electronic devices. Full article

Vanadium-based cathodes are promising for aqueous zinc-ion batteries (ZIBs) due to the large interlayer distance. However, the poor stability of electrode materials due to the dissolution effects has severely hindered the commercial development. To address this challenge, we propose an in situ NH₄⁺ pre-intercalation strategy to enhance the electrochemical performance of Na_0.76V₆O₁₅ (NaVO), thereby optimizing its structural stability and ionic conductivity. Moreover, NH₄⁺ pre-intercalation introduced a large number of oxygen vacancies and defects into the material, causing the reduction of V⁵⁺ to V⁴⁺. This transformation suppresses the dissolution and enhances its conductivity, thereby significantly improving the electrochemical performance. This modified NaNVO cathodes deliver a higher capacity of 456 mAh g⁻¹ at 0.1 A g⁻¹, with a capacity retention of 88% after 140 cycles and a long lifespan, maintaining 99% of its initial capacity after 2300 cycles. This work provided a new way to optimize the cathode for aqueous zinc-ion batteries. Full article

This study presents a comprehensive analysis of the modifications in electronic structure and magnetism resulting from electronic excitation in pulsed laser-deposited Ba_0.7Sr_0.3Fe_xTi_(1−x)O₃ thin films, specifically for compositions with x = 0, 0.1, and 0.2. To investigate the effects of electronic energy loss (S_e) within the lattice, we performed 120 MeV Ag ion irradiation at varying fluences (1 × 10¹² ions/cm² and 5 × 10¹² ions/cm²) and compared the results with those of the pristine sample. The S_e induces lattice damage by generating ion tracks along its trajectory, which subsequently leads to a reduction in peak intensity observed in X-ray diffraction patterns. Atomic force microscopy micrographs indicate that irradiation resulted in a decrease in average grain height, accompanied by a more homogeneous grain distribution. X-ray photoelectron spectroscopy reveals a significant increase in oxygen vacancy (V_O) concentration as ion fluence increases. Ferromagnetism exhibits progressive deterioration with rising irradiation fluence. Due to the high S_e and multiple ion impact processes, cation interstitial defects are highly likely, which may overshadow the influence of V_O in inducing ferromagnetism, thereby contributing to an overall decline in magnetic properties. Furthermore, the elevated S_e potentially disrupts bound magnetic polarons, leading to a degradation of long-range ferromagnetism. Collectively, this investigation elucidates the electronic excitation-induced modulation of ferromagnetism, employing Fe impurity incorporation and irradiation techniques for precise defect engineering. Full article

The urgent need for sustainable CO₂ conversion technologies has driven the development of advanced photocatalysts that harness solar energy. This study employs a CTAB-assisted solvothermal method to fabricate a Z-scheme heterojunction Fe-MOFs/V_O-Bi₂WO₆ (FM/V_O-BWO) for photocatalytic CO₂ reduction. Positron annihilation lifetime spectroscopy (PALS) was employed to confirm the existence of oxygen vacancies, while spherical aberration-corrected transmission electron microscope (STEM) characterization verified the successful construction of heterointerfaces. X-ray absorption fine structure (XAFS) spectra confirmed that the defect configuration and heterostructure changed the surface chemical valence state. The optimized 1.0FM/V_O-BWO composite demonstrated exceptional photocatalytic performance, achieving CO and CH₄ yields of 60.48 and 4.3 μmol/g, respectively, under visible-light 11.8- and 1.5-fold enhancements over pristine Bi₂WO₆. The enhanced performance is attributed to oxygen vacancy-induced active sites facilitating CO₂ adsorption/activation. In situ molecular spectroscopy confirmed the formation of critical CO₂-derived intermediates (COOH* and CHO*) through surface interactions involving four-coordinated and two-coordinated hydrogen-bonded water molecules. Furthermore, the accelerated interfacial charge transfer efficiency mediated by the Z-scheme heterojunction has been conclusively demonstrated. This work establishes a paradigm for defect-mediated heterojunction design, offering a sustainable route for solar fuel production. Full article

Superior selective adsorption of organic dye is still a big challenge in the process of dye wastewater treatment. Meanwhile, low-price and environmentally friendly biomass-based adsorbents show huge potential in the fields of separation and purification. In this study, we adopted the “hydrolysis–calcination method” to develop a novel in situ anchoring strategy for ultrasmall TiO_2−x on carbonized bacterial cellulose (CBC), which was derived from natural bacterial cellulose. Notably, 3D networks of porous CBC played a dual role for both providing hydrolytic sites and controlling the oxygen vacancies (V_o) of TiO_2−x. As for the single-dye adsorption, the TiO_2−x/CBC had a strong adsorption ability (101.4 mg/g) for removing methylene blue (MB), which was much higher than that of methyl orange (MO), malachite green (MG), rhodamine B (RhB), and tetracyclines (TC). Moreover, under the optimized carbonization temperature (T_c) of 300 °C, the TiO_2−x/CBC-300 exhibited an outstanding separation efficiency of 97.07% for the MB/MO solution. Detailed analysis confirmed that T_c was a key regulator for adjusting the V_o concentration, which directly influenced the surface charge density and, further, the separation efficiency of TiO_2−x/CBC. Additionally, the used adsorbent could be easily regenerated from washing by ethanol. After 4 regenerations, the adsorption efficiency declined only by 6.9% after 20 min and 13.6% after 120 min adsorption, respectively. Ultimately, this oxygen vacancy-rich TiO_2−x/BC system illuminated good prospects for mixed dye wastewater adsorption and separation. Full article

In this study, Zn-doped Ga₂O₃ polycrystalline samples were prepared by solid-phase sintering, and the effects of Zn doping on the optical properties of Ga₂O₃ were investigated. It is found that the introduced Zn ions disrupted the Ga-O bonds and formed Zn_Ga, altering the Ga-O vibration modes and causing a blue shift in the related Raman mode. From near-infrared to visible light-range was a transparent region for Zn-doped Ga₂O₃. The fundamental optical bandgap underwent a decrease with increasing Zn doping content, primarily due to the p-d orbital hybridization of the O 2p and Zn 3d orbitals causing an upward shift valence band maximum and band renormalization effect-induced band-tails. The recombination of electrons at donor levels (V_O) and holes at acceptor levels (V_Ga or V_O-V_Ga) gave rise to blue-green luminescence. Zn doping increased the concentration oxygen vacancies (V_O), resulting in significant blue-green luminescence enhancement in Zn-doped Ga₂O₃. Additionally, Zn doping resulted in a noticeable reduction in the red luminescence of Ga₂O₃, which may be attributed to Zn doping suppressing nitrogen incorporation from the air during high-temperature preparation processes. Full article

In this work, the simulation of deoxidation–oxidation of oxygen vacancies (V_Os) in an oxide matrix with embedded conductive nanocrystals (c-NCs) is carried out for the development of bipolar resistive switching memories (BRSMs). We have employed the three-dimensional kinetic Monte Carlo (3D-kMC) method to simulate the RS behavior of BRSMs. The c-NC is modeled as fixed oxygen vacancy (f-V_O) clusters, defined as sites with zero recombination probability. The three-dimensional oxygen vacancy configuration (3D-V_OC) obtained for each voltage step of the simulation is used to calculate the resistive state and the electrical current. It was found that the c-NC reduces the voltage required to switch the memory state from a high to a low resistive state due to the increase in a nonhomogeneous electrical field between electrodes. Full article

Defects and heteroatom doping are two refined microstructural factors that significantly affect the performance of photocatalytic materials. Coupling defect and doping engineering is a powerful approach for designing efficient photocatalysts. In this research, we successfully construct dual defect-engineered BiVO₄ nanosheets (BVO-N-OV) by introducing N doping and oxygen vacancies through ammonium oxalate-assisted thermal treatment of BiVO₄ nanosheets. Due to the combined enhancement of band structure and surface properties from N doping and oxygen vacancies, the obtained BVO-N-OV nanosheets demonstrate improved visible light absorption, effective charge transfer efficiency, and increased active sites. As a result, the constructed BVO-N-OV/PMS system demonstrates significantly enhanced ciprofloxacin (CIP) removal performance under visible light illumination. The highest rate constant for CIP degradation over BVO-N-OV/PMS system is 7.9, 1.9, and 6.6 times greater than pristine BiVO₄ (BVO), oxygen vacancy-enriched BiVO₄ (BVO-OV), and N-doped BiVO₄ (BVO-N), respectively. Even in a broad pH range (3.0–11.0) with various anions, the BVO-N-OV/PMS/Vis system still demonstrates stable and excellent CIP removal performance. This study seeks to provide valuable insights into the interaction between defect and doping engineering in photocatalytic activation of PMS, thereby proposing new strategies for designing effective photocatalyst/PMS systems for wastewater treatment. Full article

Energy levels associated with several crystalline defects, such as zinc (V_Zn) and oxygen (V_O) vacancies, Zn and O interstitials (Zn_i and O_i respectively), Zn and O antisite defects, and charged oxygen vacancies Vo-, among others, are generated by the introduction of cobalt (Co) into the structure. The effective introduction of Co into the Zn occupancy site was evaluated by XRD and electron paramagnetic resonance. The EPR spectra remain consistent across all doping concentrations of Co²⁺ ions and revealed intriguing features linked to four distinct Co²⁺ paramagnetic centers; among them, a pair of Co²⁺ ions exhibited ferromagnetic coupling. ZnO nanocrystals doped with cobalt were produced by sol gel and their use as photocatalysts were evaluated in the degradation of the Congo red pollutant. The degradation efficiency improved by more than 50% when compared to the efficiency of pure ZnO nanocrystals at the same activity time. Full article

Epoxidation of long-chain α-olefins (LAOs) is a process of paramount importance, particularly in the preparation of epoxides. Traditional epoxidation methods, such as the chlorohydrin method and peracid method, suffer from issues such as poor selectivity, by-product formation, and environmental pollution. Mukaiyama epoxidation, with its mild reaction conditions and exceptional selectivity, has attracted widespread attention and considerable research. Transition metal oxide catalysts show potential in the reaction; however, the catalytic efficiency still require substantial improvement due to dilemma of substance activation. In this study, a synergistic enhancement method was employed, achieved through the creation of oxygen vacancies and the electron-rich nature of Cu. The substitution of Cu with Sn in CuO facilitates the creation of oxygen vacancy (Vo), thereby enhancing absorption and activation of O₂. The conversion for O₂ activation paves the way for the formation of benzoyl peroxy radicals. Moreover, the interaction between Sn and Cu promotes charge transfer from Sn to Cu, resulting in an electron-rich Cu surface that significantly accelerates the dehydrogenation of benzaldehyde. The synergistic enhancement protocol exhibits near-quantitative performance, delivering an oxide yield of 92.9%. This study introduces an innovative dual-promotion catalytic strategy for Mukaiyama epoxidation utilizing readily available O₂, providing profound insights into the optimization design of transition metal oxide catalysts and beyond. Full article

CeO₂ has a potential application in the purification of organic dye wastewater because of the abundant oxygen vacancy (V_O) defects in its crystals. In this study, a cubic CeO₂ microsphere with layered interleaved symmetrical 3D flower-like morphology was synthesized, and its adsorption capacity for acid orange 7 (AO7) was further enhanced by Y doping. The impact of varying amounts of Y ions on the phase composition, lattice parameters, and morphology of the product was investigated, revealing that 4 mol.% was determined as the doping level limit of Y ions in CeO₂ crystals. XPS, Raman, and H₂−TPR techniques were employed to compare surface species changes before and after 4 mol.% Y doping in the CeO₂ crystals, including O−Ce(III), O−Ce(IV), O−Y(III), and V_O correlation, yielding a rough quantitative assessment of these species. The 4 mol.% Y-doped CeO₂ (2.0 g/L) demonstrated the highest removal rate for 20 mg/L of AO7 dye within just 20 min to reach adsorption–desorption equilibrium, half the time required by undoped CeO₂, achieving an impressive adsorption rate of 94.6%, compared to only 69.5% for undoped CeO₂ at 20 min. The adsorption capacity of undoped CeO₂ was enhanced by 19.05% through the doping of 4 mol.% Y, achieving a value of 16.56 mg/L. The feasibility of enhancing the adsorption capacity of CeO₂ by Y doping provides a reference for the application of CeO₂ and other metal oxides. Full article