Oxygen Vacancies Research Articles

The Impact of the Final Sintering Temperature on the Microstructure and Dielectric Properties of Ba0.75Ca0.25TiO3 Perovskite Ceramics

Ba0.75Ca0.25TiO3 ceramics were successfully synthesized by a simple solid-state reaction method. This study examined the influence of sintering temperature on the structure, microstructure, dielectric properties and electrical behavior of the material. The XRD analysis reveals that the tetragonal phase (P4mm) is dominant in all the synthesized materials, with those sintered at T = 1400 °C and T = 1450 °C being single-phase, while others exhibit a minor orthorhombic phase (Pbnm). Higher sintering temperatures promoted better grain boundary formation and larger grain sizes. The electric permittivity increased with temperature up to T = 1400 °C, followed by a sharp decline at T = 1450 °C. Additionally, the Curie temperature decreased with increasing sintering temperature, indicating changes in phase transition characteristics. Thermal analysis showed that higher sintering temperatures led to sharper heat capacity peaks, while pyroelectric and thermally stimulated depolarization currents were maximized at T = 1400 °C due to oxygen vacancies. These findings highlight the significant impact of sintering temperature on the material’s structural and functional properties.

Comprehensive study on lithium-ion battery cathode LiNixCoyMn1-x-yO2 as an air electrode for protonic ceramic fuel cells

The protonic ceramic fuel cells (PCFCs) exhibits a remarkable high-energy conversion efficiency and significant application potential at low temperatures. In this context, the layered ternary lithium-ion batteries (LIB) material, LiNixCoyMn1-x-yO2 (LNCM), is explored as a potential cathode for PCFCs. Utilizing density functional theory (DFT) calculations, we have conducted a comprehensive analysis of oxygen vacancies, hydration energy, density of states, and other pertinent properties to evaluate these ternary materials. Both theoretical and experimental findings suggest that LiNi0.5Co0.2Mn0.3O2 (LNCM523) may offer the optimal performance as a PCFCs cathode. Notably, after calcination in air at 700 °C for 100 h, LNCM523 displayed no phase transition or the emergence of new phases. The impedance of LNCM523, measured on a BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BZCYYb) electrolyte, is 0.225 Ω cm2 at 650 °C. At this temperature, the peak power density of the single cell reaches 355 mW cm−2. Moreover, during a 100-h stability test conducted at 550 °C, the output performance of the single cell remained unaltered. In electrolysis mode, at 650 °C and 1.3 V, the current density for electrolysis water attained 1.75 A cm−2. Based on these promising results, LNCM emerges as a viable cathode candidate for PCFCs.

Development of Technology for the Synthesis of Nanocrystalline Cerium Oxide Under Production Conditions with the Best Regenerative Activity and Biocompatibility for Further Creation of Wound-Healing Agents

Background/Objectives: The issue of effective wound healing remains highly relevant. The objective of the study is to develop an optimal method for the synthesis of nanosized cerium oxide powder obtained via the thermal decomposition of cerium carbonate precipitated from aqueous nitrate solution for the technical creation of new drugs in production conditions; the select modification of synthesis under different conditions based on the evaluation of the physicochemical characteristics of the obtained material and its biological activity, and an evaluation of the broad-spectrum effect on cells involved in the regeneration of skin structure as well as antimicrobial properties. Methods: Several modes of the industrial synthesis of cerium dioxide nanoparticles (NPs) were carried out. The synthesis stages and the chemical and physical parameters of the obtained NPs were described using transmission electron microscopy (TEM), X-ray diffraction, Raman spectroscopy, and mass spectrometry. The cell cultures of human fibroblasts and keratinocytes were cultured with different concentrations of different nanoceria variations, and the cytotoxicity and the metabolic and proliferative activity were investigated. An MTT test and cell counting were performed. The antimicrobial activity of CeO2 variations at a concentration of 0.1–0.0001 M against Pseudomonas aeruginosa was studied. Results: The purity of the synthesized nanoceria powders in all the batches was >99.99%. According to TEM data, the size of the NPs varied from 1 nm to 70 nm under different conditions and methodologies. The most optimal technology for the synthesis of the nanoceria with the maximum biological effect was selected. A method for obtaining the most bioactive NPs of optimal size (up to 10 nm) was proposed. The repeatability of the results of the proposed method of nanoceria synthesis in terms of particle size was confirmed. It was proven that the more structural defects on the surface of the CeO2 crystal lattice, the higher the efficiency of the NPs due to oxygen vacancies. The strain provided the best redox activity and antioxidant properties of the nanoceria, which was demonstrated by better regenerative potential on various cell lines. The beneficial effect of synthesized nanoceria on the proliferative and metabolic activity of the cell lines involved in skin regeneration (human fibroblasts, human keratinocytes) was demonstrated. The antimicrobial effect of synthesized nanoceria on the culture of the most-resistant-to-modern-antibiotics microorganism Pseudomonas aeruginosa was confirmed. The optimal concentrations of the nanoceria to achieve the maximum biological effect were determined (10−3 M). Conclusions: It was possible to develop a method for the industrial synthesis of nanoceria, which can be used to produce drugs and medical devices containing CeO2 NPs.

Structural stability and enhanced electrochemical performance of Co-free Li-rich layered Mn-based Li1.2Mn0.6Ni0.2O2 cathodes via F doping at the O site of lithium-ion batteries

Li-rich Mn-based Co-free layered oxides (LLOs) are promising cathode materials for lithium-ion batteries (LIBs). However, they exhibit capacity loss and low initial Coulombic efficiency. Herein, an F-doped Li1.2Mn0.6Ni0.2O1.9F0.10 material has been prepared by the high-temperature solid-state method, with numerous oxygen vacancies on the surface to accelerate Li + transport. The electrochemical performance of Li1.2Mn0.6Ni0.2O1.9F0.10 considerably improved after the treatment. A high-capacity retention of 86.9 % after 100 charge/discharge cycles at 1C was achieved for Li1.2Mn0.6Ni0.2O1.9F0.10. Results revealed that F doping replaces part of O2−, forming more force between the TM-F bonds (compared to the TM-O bond), which inhibits the cation mixing phenomenon. The layered structure stability of the material is improved after F doping, and the migration energy barrier of Li+ is reduced, which promotes the migration of Li+, thereby improving the electrochemical performance of Li1.2Mn0.6Ni0.2O2.

Regulating oxygen vacancies to optimize the electronic structure and catalytic activity of tungsten oxides for hydrogen evolution reaction

The undesirable intrinsic activity of tungsten oxides derived from poor conductivity and adverse hydrogen absorption energy is insufficient for their practical application. Herein, the tungsten oxides with adjustable oxygen vacancies were synthesized by a facile pyrolysis of ammonium paratungstate hydrate in controllable atmospheres. The structural characterizations confirmed that oxygen vacancies and crystalline phases in tungsten oxides depend on the pyrolysis atmosphere. The electrochemical test indicated a strong dependence between catalytic activity and oxygen vacancies in tungsten oxides. Combining experimental results and density functional theory calculations verified that introducing oxygen vacancies into tungsten oxides effectively modulates the surface electronic structure. The enhanced electronic conductivity by reducing band gap accelerates the electron transfer from catalysts into the reactive species. The optimized hydrogen adsorption energy by electron migration from O into W promotes the activation of reactive species at W sites and the desorption from O sites, thereby accelerating the reaction kinetics.

Experimental study on enrichment of heavy metals by modified mullite during co-combustion of lignite with eucalyptus wood

ABSTRACT Modifying the content of oxygen vacancies (OVs) has emerged as a crucial approach to tailoring silicate's adsorption properties, microstructure, conductivity, and catalytic performance. Some studies have reported the formation of OVs during ammonia treatment. However, there are limited studies on the production of OV-enriched mullite by treating it with N-containing compounds at low temperatures. In this work, formamide, urea, and ammonium acetate were used as ammonia-assisted reduction modifiers to induce oxygen vacancies in mullite at 30 ℃, 60 ℃, and 90 °C. The aim was to enhance the enrichment effect of heavy metals (Cr, Cu, Mn, Ni, Pb, Zn) during the co-combustion of coal and biomass. The modified mullite was analyzed by using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The results indicated that the particle size of mullite decreased, and the concentration of internal Al3+ ions and oxygen vacancies was enhanced. Coal-biomass-mullite combustion experiments were conducted in a tubular furnace at 900 °C, revealing a significant enhancement in the enrichment of heavy metals during the combustion process, particularly when the modification temperature was 60 °C using ammonium acetate as the modifier. This work holds significant importance for developing novel heavy metal adsorbents and the reduction of pollutant emissions from coal-biomass co-combustion in industrial applications.

Dual quenching ECL strategy based on AgInZnS quantum dots and a new co-reaction promoter oxygen vacancy-modified P5AIn/TiO2 for sensitive CEA detection

A novel electrochemiluminescence (ECL) biosensor for the sensitive detection of carcinoembryonic antigen (CEA) was constructed, utilizing environmentally friendly AgInZnS quantum dots (AgInZnS QDs) and a new co-reaction promoter enriched with oxygen vacancies, namely titanium dioxide/poly(5-aminoindole) (Ov-TiO2/P5AIn). The composite of P5AIn and TiO2 significantly enhanced the reaction rate of AgInZnS QDs with tripropylamine (TPrA). In addition, the presence of oxygen vacancies significantly enhances the electron migration rate of the electrode material, leading to more efficient catalysis of TPrA+ generation and a significant enhancement of ECL signals. Furthermore, a dual-quenching sensing strategy was employed using cuprous oxide-triaminophenol (Cu2O@APF) as the quencher, enabling the biosensor to switch. Through dual quenching of the ECL emission from AgInZnS QDs by Cu2O and APF, the biosensor achieves an extremely low “off” state of the ECL signal. Furthermore, a signal amplification strategy driven by the synergistic action of exonuclease III (ExoIII) and restriction endonuclease (Nt.BbvCI) was designed for a dual-site DNA walker, achieving cyclic amplification of the target signal and ECL signal, thereby turning the signal “on” again. The above mechanism significantly improved the specificity and sensitivity of the biosensor for CEA detection. The prepared biosensor exhibits good stability, selectivity, and sensitivity. The linear range for CEA detection is 5 × 10−14 to 10−8 M, with a detection limit of 16 fM. Additionally, the biosensor demonstrates satisfactory analytical capability for CEA in real blood samples. This strategy provides a reliable new approach for the sensitive detection of CEA and other tumor markers.

Visible Light-Sensitive Sustainable Quantum Dot Crystals of Co/Mg Doped Natural Hydroxyapatite Possessing Antimicrobial Activity and Biocompatibility.

Cutting-edge research in advanced materials is increasingly turning toward the development of novel multifunctional nanomaterials for use in high-tech applications. This research uses the solid-state method as a solvent-free technique to create multifunctional quantum dot (QD) hydroxyapatite (HA) crystals from bovine bone waste. By incorporating cobalt (Co) and magnesium (Mg) into the HA structure, the crystallinity of the hexagonal HA nanoparticles (99.7%), showing QD crystals is enhanced. Oxygen vacancies on the surfaces of the HA nanoparticles contributed to their bandgap falling within the visible light range. In addition, the dopants substituted calcium in the HA crystal structure and generated a divalent oxidation state, shifting the bandgap of natural HA toward red wavelengths (3.26 to 1.94eV). Moreover, the incorporation of Co led to magnetization within the HA structure through spin polarization. Additionally, the doped QD crystals of HA nanoparticles showed significant antimicrobial activity against Escherichia coli, Staphylococcus aureus, and bacteriophages MS2, particularly under visible light exposure. In short, the Co/Mg co-doped HA nanoparticles exhibited ferromagnetic properties, sensitivity to visible light, biocompatibility, and considerable antimicrobial effects, establishing their potential as sustainable multifunctional materials for biomedical applications, especially in anti-infection treatments.

Anode Glow Discharge Electrolysis Synthesis of Flower-Like α-MnO2 Nanospheres: Structure, Formation Mechanism, and Supercapacitor Performance.

A novel green synthesis strategy-anode glow discharge electrolysis (AGDE) was employed for one-step preparation of α-MnO2 in 2 g L-1 KMnO4 solution, in which Pt needle and carbon rod were regarded as anode and cathode, respectively. The optimal preparation condition is 400 V for 60 min and the power consumption is below 45 W. The XRD, Raman spectra, XPS and EPR proved that α-MnO2 with structural defects (oxygen vacancies) is obtained. SEM and TEM revealed that α-MnO2 shows a flower-like nanospheres with a diameter of 165 nm, which is assembled by many nanosheets. A possible formation mechanism is that the MnO2 is generated via the reduction of MnO4 - by H⋅ and eaq - in plasma-liquid interface. Electrochemical test found that MnO2 nanospheres exhibit a specific capacitance of 365 F g-1 at 1 A g-1, and capacity retention of 79.8 % after 10,000 cycles at 5 A g-1. The assembled asymmetric supercapacitor shows the maximum energy density of 23.1 Wh kg-1 at power density of 1.89 kW kg-1. In brief, AGDE is a simple, facile and green technique for the synthesis of α-MnO2 without adding extra chemicals, and prepared α-MnO2 can be considered as an excellent candidate of electrode materials for supercapacitor.

Mechanism study on the influence of surface properties on the synthesis of dimethyl carbonate from CO2 and methanol over ceria catalysts

The direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol has attracted much attention as an environmentally benign and alternative route for conventional routes. Herein, a series of cerium oxide catalysts with various textural features and surface properties were prepared by the one-pot synthesis method for the direct DMC synthesis from CO2 and methanol, and the structure-performance relationship was investigated in detail. Characterization results revealed that both of surface acid-base properties and the oxygen vacancies contents decreased with the rising crystallinity at increasingly higher calcination temperature accompanied by an unexpectedly volcano-shaped trend of DMC yield observed on the catalysts. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies indicated that the adsorption rate of methanol is slower than that of CO2 and the methanol activation state largely influences the formation of key intermediate. Although the enhanced surface acidity-basicity and oxygen vacancies brought by low-temperature calcination could facilitate the activation of CO2, the presence of excess strongly basic sites on low-crystallinity sample was detrimental to DMC synthesis due to the preferred formation of unreactive mono/polydentate carbonates as well as the further impediment of methanol activation. Moreover, with the use of 2-cyanopyridine as a dehydration reagent, the DMC synthesis was found to be both influenced by the promotion from the rapid in situ removal of water and the inhibition from the competitive adsorption of hydration products on the same active sites.

Dual zinco-phobic/-philic ferroelectric nanorods coated mesh for stable Zn anode

Aqueous Zn-ion batteries are emerging as a promising option for energy storage systems due to their safety and environmental benefits. However, their stability and reversibility are often hindered by dendrite growth and interfacial side reactions. In this study, we introduce an innovative strategy to address these issues by engineering an artificial interfacial layer (AIL) on Zn anode surface. This AIL is composed of a dual zinco-phobic/-philic ferroelectric nanorods (FE NRs) mesh, which contrasts with the traditional BaTiO3 nanoparticles. The BTO NRs, particularly those with exposed P4/mmm (100) and (211) facets enriched with oxygen vacancy, facilitate a partial phase transition from the FE tetragonal P4mm phase to the paraelectric tetragonal P4/mmm phase, thereby creating dual zinco-phobic/-philic sites. Additionally, the integration of microchannels within the FE BTO NRs mesh can efficiently modulate the electric field distribution and Zn2+ concentration, leading to a more uniform Zn deposition, as conformed by electrochemical simulations. The Zn anode coated with the FE BTO NRs mesh exhibits impressive performance, achieving an ultralong cycle life of 3050 h at 1 mA cm−2 and 1mAh cm−2. It sustains a Coulombic efficiency exceeding 99.8 % over 2000 cycles, highlighting its exceptional reversibility. These findings underscore the potential of the dual zinco-phobic/-philic FE NRs mesh in overcoming the challenges faced in aqueous metal-ion batteries, showcasing its versatility and the significant performance enhancements it can offer.

Understanding the potential of coal gangue as photocatalyst for antibiotic degradation: The role of abundant oxygen vacancies and electron-hole pairs

Coal gangue (CG) offers promising potential as a cost-effective photocatalyst for antibiotic degradation. However, current approaches do not emphasize the origin of its photocatalytic activity. This study investigates the photocatalytic activity of CG through a comparative analysis with one-pot aerobic/anaerobic calcinated CG. The potential application of CG as a photocatalyst for tetracycline (TC) decontamination in water was evaluated under dark and light. Characterization results identified anatase and kaolinite as the critical photosensitive minerals in CG. Batch removal experiments indicated that CG achieved up to 98 % TC removal at 1 g/L dosage, with most biotoxic intermediates reduced to below 0.9 mg L−1 Lethal Concentration 50 (LC50) of Fathead minnow (Pimephales promelas). Degradation pathways identified by density functional theory (DFT) and quantitative structure-activity relationship (QSAR) indicated that superoxide anion (⁎O2−) and electron-hole (e−-h+) pairs were predominant contributors to TC photodegradation. Theoretical calculations suggest that the oxygen vacancies on the CG surface can accelerate the production of ⁎O2−, while fast electron transport channels within surface hydroxyl groups facilitate e− and h+ separation. The findings of this research elucidate the origin of CG's photocatalytic activity and highlight the potential to serve as a photocatalyst for low-cost antibiotic removal, offering a promising solution for coal waste management and utilization.

Long-Term Selective Photoelectrochemical Glycerol Oxidation via Oxygen Vacancy Modulated Tungsten Oxide with Self-Healing.

The photoelectrochemical selective oxidation of biowaste glycerol into the high value-added material, along with hydrogen production, holds significant promise for advancing renewable and sustainable energy technologies. Here, the surface oxygen state of tungsten oxide is modified to selectively oxidize glycerol into glyceraldehyde, a high-value-added material, and the selectivity is maintained over a prolonged period using the photo-stimulated self-recovery capability. The surface-coordinated photoelectrode exhibits high charge transfer efficiency to glycerol and favorable glycerol adsorption capacity, enabling the selective conversion of glycerol. At 1.2 VRHE in a 2m glycerol electrolyte adjusted to pH 2, the tungsten oxide photoelectrode achieves a photocurrent density of 2.58mA cm-2 and a production rate of 378.8mmol m-2h-1 with selectivity of 86.1%. The high selectivity is preserved for 18 h by utilizing the self-healing capability of tungsten oxide to restore initial states modified by photoelectrochemical oxidation. This work sheds light on the design of highly efficient metal oxide photoelectrodes for selective biomass oxidation over extended periods.

Engineering the Co/CoO heterostructure to trigger the in-situ generation of abundant high-valent cobalt species for enhanced electroreduction of nitrate to ammonia

The CoO-based materials are promising candidates for electrochemical nitrate reduction reaction to ammonia (eNO3RR). Herein, Zn/Co bimetallic MOFs are adopted to construct Co/CoO Schottky heterostructures, where the Co-CoO interfaces are engineered by controlling the Zn/Co ratio. The interface-optimized Co/CoO displays an NH3 yield of 713 µmol/h cm−2 and a maximum Faradaic efficiency of 99.16 % due to the synergistic effect between CoO and Co and abundant oxygen vacancies. The more the Co-CoO interfaces, the more the in-situ generated high-valent cobalt species (CoOOH), and the higher the catalytic performance. Therefore, the high-valent cobalt species are considered the true active sites. When used as a cathode in a rechargeable Zn-NO3− battery, the Co/CoO heterostructure achieves a power density of 4.7 mW cm−2 and an NH3 yield of 131.7 µmol/h cm−2 with robust working stability.

Tuning the Electronic And Transport Properties of CaMoO4 Nanofibers with High-Spin Ni for Efficient and Stable Supercapacitors.

Calcium molybdate (CaMoO4) has recently garnered considerable attention for supercapacitors due to its stable crystal structure and cost-effective preparation. However, CaMoO4 prepared by traditional processes still suffered from insufficient electrochemical active sites and poor electrical conductivity so far, thus leading to the performance of CaMoO4-based supercapacitors being inferior to the state-of-the-art ones. CaMoO4 nanofibers with a high specific surface area exhibit great potential for supercapacitors due to their ability to offer increased charge storage. Herein, mesoporous CaMoO4 nanofibers anchored with Ni nanoparticles were fabricated via electrospinning combined with subsequent thermal treatment. Density functional theory calculation and UV-vis spectrophotometer results show that high-spin state Ni nanoparticles can tune the electronic structure of CaMoO4 nanofibers, decreasing the band gap by about 0.67 eV. Electron paramagnetic resonance (EPR) studies imply that Ni doping influences the electronic structure by reducing the oxygen vacancy concentration and introducing hyperfine structures associated with Ni spins. These can result in higher power and energy density in supercapacitors. As a result, a specific capacitance of 1253.7 F·g-1 at a current density of 0.5 A·g-1 and an 86% retention rate after 2000 cycles at a higher current density of 5 A·g-1 have been achieved for Ni0.25Ca0.75MoO4-based supercapacitor. Furthermore, an asymmetric supercapacitor (ASC) device with the optimized CaMoO4/Ni//AC structure has been demonstrated with the energy density of 49.43 Wh·kg-1 and power density of 2700 W·kg-1, thus enabling lightening a red light-emitting diode. The current strategy might pave the way for CaMoO4 for practical applications for high-power supercapacitors.

The Role of Oxygen Vacancy on the Carbon Dioxide Photoreduction Using Monoclinic and Tetragonal-phase Zirconium Oxide

The Role of Oxygen Vacancy on the Carbon Dioxide Photoreduction Using Monoclinic and Tetragonal-phase Zirconium Oxide

Significantly reduced lattice defects and improved dielectric properties of MgTiO3 based microwave ceramics via supercritical-fluid assisted oxidation technology

Lattice defects play a crucial role in determining the microwave dielectric properties of ceramics. We herein report a simple way to significantly improve the dielectric properties of MgTiO3 based microwave ceramics by restoring the oxygen vacancy via supercritical assisted oxidation (SAO) technology. The high penetrability of SCCO2 fluid makes the OH− groups easy to approach oxygen vacancy, which react with the dangling bonds to form A-O-A (A=Ti/Mg) covalent coordinate bonds. The oxygen vacancy concentration in MgTiO3-CaTiO3 ceramics significantly decreases from 26.7 % to 18.5 % and the Ti-O bond strength is strengthened after SAO treatment. Furthermore, the activation energy Ea increases to 0.60 eV from 0.52 eV, indicating a lower defects density as well. Consequently, MgTiO3-CaTiO3 ceramics treated by SAO exhibit better high-temperature stability in dielectric properties and the Q×f values of MgTiO3-CaTiO3 ceramics increase by 11.3∼19.0 % due to the decreased defects concentration, thereby demonstrating the potential of supercritical fluid technology in achieving performance optimization of microwave dielectric ceramics.

Homojunction-Incorporated Oxygen Vacancy Functionalized Spherical TiO2 Nanocrystals for the Electrochemical Detection of Chemical Oxygen Demand.

Chemical oxygen demand (COD) is a critical criterion for the analytical assessment of the degree of organic contaminants in an aqueous system. Typically, toxic and expensive reagents are employed in standardized COD analysis methods, leading to secondary pollution. In this work, we developed a rapid electrochemical method for COD detection based on the oxidation of hydroxyl radicals for organics in water by using oxygen vacancy doped anatase/rutile-TiO2 nanoparticles as electrooxidation catalysts. Homojunction interface generated increasing oxygen vacancies for enhancing electron-transfer rate and accelerating H2O oxidation to substantially improve ·OH yield. Oxygen vacancy further increased the oxygen evolution potential of the material. Initially, glucose was chosen as a standard analyte to evaluate electrochemical responses, and water from urban wastewater treatment plants was assessed as real samples subsequently. Excellent analytical characteristics were achieved with the A/R-TiO2 sensor under the optimal conditions, exhibiting a linear range from 1 to 300 mg L-1 and detection limit of 0.1 mg L-1 COD. The estimated COD values obtained from the samples were highly consistent with those determined using the conventional standard dichromate method. We have presented a fast, cost-effective, and ecologically sustainable method that outperforms the standard COD analysis method and holds great potential for the accurate determination of COD and boasts high detection sensitivity and a broad linear range.

Effect of Deposition Temperature on Zn Interstitials and Oxygen Vacancies in RF-Sputtered ZnO Thin Films and Thin Film-Transistors

ZnO thin films were deposited using RF sputtering by varying the argon:oxygen gas flow rates and substrate temperatures. Structural, optical and electrical characterization of ZnO thin films were systematically carried out using X-Ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectroscopy, X-Ray photoelectron spectroscopy (XPS) and Hall measurements. Film deposited at room temperature and annealed at 300 °C exhibited low O2 incorporation with localized defects and a high percentage of Zn interstitials. A large crystalline size and fewer grain boundaries resulted in a high Hall mobility of 46.09 cm2/V-s Deposition at higher substrate temperatures resulted in improvement in O2 incorporation through the annihilation of localized defects and decrease in oxygen vacancies and Zn interstitials. Urbach tails within the bandgap were identified using the absorption spectrum and compared with the % defects from XPS. Bottom-gate thin-film transistors were subsequently fabricated on a SiO2/p-Si substrate using the combination of RF sputtering, wet etching and photolithography. Variation in the substrate temperature showed performance enhancement in terms of the leakage current, threshold voltage, sub-threshold swing and ION/IOFF ratio. Thin-film transistor (TFT) devices deposited at 300 °C resulted in an O2-rich surface through chemisorption, which led to a reduction in the leakage current of up to 10−12 A and a 10-fold reduction in the sub-threshold swing (SS) from 30 V to 2.8 V. Further TFT optimization was carried out by reducing the ZnO thickness to 50 nm, which resulted in a field-effect mobility of 1.1 cm2/V-s and ION/IOFF ratio of 105.

Copper-based photocatalysts with natural organic ligands for efficient removal of tetracycline under visible light

The excessive use of broad-spectrum antibiotics, such as tetracycline, presents a significant challenge to human survival and development. Oxygen vacancies (OVs) metal-organic framework (MOF) materials were synthesized using natural organic acids (L-malic acid, L-aspartic acid, and L-asparagine) with similar structures but different charge densities, along with copper as the metal linking agent. The presence of oxygen vacancies in the catalyst provides abundant active sites for photocatalytic reactions. The employment of flexible straight-chain organic ligands devoid of rigid polycyclic rings, combined with the incorporation of different substituents to induce variations in charge density, the resulting catalysts exhibit distinct photocatalytic activities under visible light. Density functional theory calculations confirm that L-asparagine exhibits the largest electron density difference, and the Cu-based MOF (Cu-ASU) synthesized as an organic ligand exhibits the highest photocatalytic activity under visible light excitation. The catalyst displayed remarkable photocatalytic activity against tetracycline antibiotics under identical conditions (with removal rates of 93.5 % for tetracycline, 81.4 % for terramycin, and 95.6 % for chloramphenicol hydrochloride). This provides a novel approach for the design and synthesis of photocatalysts for the removal of antibiotics from water.