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ZnO Nanosheets Abundant in Oxygen Vacancies Derived from Metal-Organic Frameworks for ppb-Level Gas Sensing
摘要： Surmounting the inhomogeniety issue of gas sensors and realizing their reproducible ppb-level gas sensing are highly desirable for widespread deployments of sensors to build networks in applications of industrial safety and indoor/outdoor air quality monitoring. Herein, a strategy is proposed to substantially improve the surface homogeneity of sensing materials and gas sensing performance via chip-level pyrolysis of as-grown ZIF-L (ZIF stands for zeolitic imidazolate framework) films to porous and hierarchical zinc oxide (ZnO) nanosheets. A novel approach to generate adjustable oxygen vacancies is demonstrated, through which the electronic structure of sensing materials can be fine-tuned. Their presence is thoroughly verified by various techniques. The sensing results demonstrate that the resultant oxygen vacancy-abundant ZnO nanosheets exhibit significantly enhanced sensitivity and shortened response time toward ppb-level carbon monoxide (CO) and volatile organic compounds encompassing 1,3-butadiene, toluene, and tetrachloroethylene, which can be ascribed to several reasons including unpaired electrons, consequent bandgap narrowing, increased specific surface area, and hierarchical micro–mesoporous structures. This facile approach sheds light on the rational design of sensing materials via defect engineering, and can facilitate the mass production, commercialization, and large-scale deployments of sensors with controllable morphology and superior sensing performance targeted for ultratrace gas detection.
关键词： metal-organic frameworks,oxygen vacancies,ppb-level gas sensing,defect engineering,ZnO nanosheets
更新于2025-09-19 17:15:36
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Glucose-assisted hydrothermal synthesis of plasmonic Bi deposited nested Bi2O2?xCO3 photocatalysts with enhanced photocatalytic activity
摘要： Crystal defects play an important role on the physical and chemical properties of semiconductors. In this work, a series of Bi/Bi2O2?xCO3 photocatalysts have been fabricated by an one-pot hydrothermal method, where glucose is used as reducing and morphological control agent. The phase structure, morphology, optical and photoelectrochemical properties of the photocatalysts are characterized by various techniques. These oxygen vacancies (OVs) have been confirmed and characterized by ESR spectroscopy and XPS spectra. The Bi/Bi2O2?xCO3 photocatalysts exhibits highest removal efficiency of Lanasol Red 5B and ciprofloxacin. The corresponding degradation rate constant for Lanasol Red 5B is about 2.28 times higher than that of Bi2O2CO3 under simulated solar irradiation, and 10.9 times under visible light irradiation, respectively. Radical scavenger experiments futher indicated that holes (h+) and hydroxyl radical (OH) are the main active species for Lanasol Red 5B degradation. This enhanced photocatalytic performance can be rationalized by the synergistic effects of Bi plasmon and OVs, resulting in, enhanced light-harvesting and electron- hole separation ability of Bi/Bi2O2?xCO3 photocatalysts.
关键词： Oxygen vacancies,Bi2O2CO3,Bi plasmon,Nested,Synergistic effects
更新于2025-09-19 17:13:59
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Facile synthesis of ZnO microrod photodetectors by solid-state reaction
摘要： In this study, ZnO microrods were directly synthesized via a single-step solid-state reaction using ZnO powders mixed with graphite without a catalyst under an air atmosphere, instead of using vacuum systems and flowing gases. The structure, growth mechanism, and electrical and optical properties of the microrods were investigated under varying growth conditions. The high-resolution transmission electron microscopy images confirmed the formation of single-crystal ZnO microrods. The photoluminescence spectra of the microrods showed green emission, suggesting the formation of non-stoichiometric ZnO microrods due to the formation of oxygen vacancies during sintering. The length and width of the ZnO microrods could be modulated by controlling the graphite content, sintering temperature, and residual time. A simple photodetector consisting of a single-crystal ZnO microrod on a SiO2-coated Si substrate was fabricated. The photodetector exhibited a linear current–voltage curve in visible light. The slope of the curve increased under ultraviolet (UV) irradiation, maintaining a linear shape of the curve. The curve reversibly returned to the initial shape in the absence of UV illumination. The UV on-off current ratio increased because of the decrease in the off-current by compensating for the oxygen vacancies through annealing in an oxygen atmosphere. Thus, in this study, we proposed a simple and efficient approach to fabricate single-crystal ZnO microrods for application in low-cost photodetectors.
关键词： oxygen vacancies,solid-state reaction,single-crystal,ZnO microrods,photodetector
更新于2025-09-19 17:13:59
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Fabrication of pyramid-BiVO4/CdSe composite with controlled surface oxygen vacancies boosting efficient carriersa?? separation for photocathodic protection
摘要： In order to solve the bottleneck problem of weak efficiency of carriers’ separation and transfer in BiVO4 photocatalyst, a novel pyramid-BiVO4 with sufficient oxygen vacancies was successfully synthesized via a low-temperature solvothermal method. By adjusting solution pH and adding SDBS surfactant, the prepared samples could have a variety of controllable morphologies and exposed {001} facets, which were determined by SEM, XRD, and BET methods. XPS O1s peak and ESR signals indicated that pyramid-BiVO4 exhibited higher oxygen vacancies concentration than others. Besides, CdSe quantum dots (QDs) were introduced to construct BiVO4/CdSe heterojunctions composite based photoanode to further promote solar harvesting and carrier separation. The photoelectrochemical experimental results showed that 304 stainless steel (304SS) coupled with 8V-BC photoanode showed an enhanced photocurrent density (608 μA?cm-2) and maximum potential drop (708 mV), which were equivalent to 5.06 times and 2.10 times that of the original BiVO4, respectively. Mechanism study illustrated that the ultra-high performance of the 8V-BC photoanode was attributed to the synergistic effect of enriched oxygen vacancies, exposed {001} facets, enlarged visible light absorption and larger specific surface area.
关键词： oxygen vacancies,photocathodic protection,CdSe,BiVO4,morphology controlled
更新于2025-09-19 17:13:59
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Photocatalytic producing dihydroxybenzenes from phenol enabled by gathering oxygen vacancies in ultrathin porous ZnO nanosheets
摘要： As an energy-efficient and environmental friendliness method, solar sunlight-driven photo-oxidation catalysis process for organic chemicals synthesis has gained enormous attention, but still faces huge challenge in developing highly-efficient photocatalysts material. Two-dimensional materials engineering and surface defect engineering of photocatalysts both provide an effective strategy to improve the catalytic activity. Inspired by these pathway, we design and synthesize ultrathin porous ZnO nanosheets featuring abundant oxygen vacancies specific to producing dihydroxybenzenes based on a photocatalytic oxidation process. Several valid characterizations had been employed to discern the structural character of the obtained model catalyst, revealing that the resultant ZnO sheets afford an average thickness of 3 nm, and abundant surface porosity, thereby contributing to the rich oxygen vacancies. Such a structure could generate a synergistic effect to enhance the optical absorption and improve the transportation rate of photogenerated charge carriers from the materials design. As expected, the specific ultrathin ZnO nanosheets exhibited a greatly-improved photocatalytic activity for oxidation of phenol to dihydroxybenzenes (31.5% conversion & almost 76.7% selectivity of DHB), near 3 and 4 times higher, respectively than its counterparts that one with few oxygen vacancies and Bulk-ZnO. Impressively, the obtained catalyst showed durable catalytic activity without any activity loss during the five recycling. Finally, the feasible oxidation mechanism was proposed and testified by the controlled scavenger experiments. This study provides a novel reference on how to design high-performance photocatalytic material.
关键词： oxygen vacancies,ZnO,ultrathin nanosheets,oxidation of phenol,photocatalytic
更新于2025-09-12 10:27:22
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Carbon Quantum Dots (CQDs) Decorated Bi2O3-x Hybrid Photocatalysts with Promising NIR-Light-Driven Photodegradation Activity for AO7
摘要： In this work, Bi2O3-x with surface oxygen vacancies was prepared through the NaBH4 reduction of Bi2O3. After that, carbon quantum dots (CQDs) were deposited onto the surface of the Bi2O3-x to obtain a series of the CQDs/Bi2O3-x composites. The HRTEM and XPS characterizations of the CQDs/Bi2O3-x composites suggest that the thickness of surface oxygen vacancies could be adjusted by changing the concentration of NaBH4 solution, and the intimate contact between CQDs and the Bi2O3-x is achieved. Acid orange 7 (AO7) was adopted as the target reactant for investigating the photocatalytic degradation activities of the CQDs/Bi2O3-x composites under simulated sunlight and NIR light irradiation. It is found that the photocatalytic activities of the samples are closely related to the concentration of NaBH4 and content of CQDs. The Bi2O3-x samples exhibit enhanced simulated-sunlight-driven photocatalytic activity compared with Bi2O3. Specifically, the optimal degradation efficiency of AO7 is achieved over the 3R-Bi2O3-x (concentration of NaBH4: 3 mmol/L), which is 1.38 times higher than the degradation AO7 efficiency over Bi2O3. After the decoration of the 3R-Bi2O3-x surface with CQDs, the simulated-sunlight-driven photocatalytic activity of the CQDs/Bi2O3-x composite could be further enhanced. Among the samples, the 15C/3R-Bi2O3-x sample reveals the highest photocatalytic activity, leading to an AO7 degradation percentage of ~97% after 60 min irradiation. Different from Bi2O3 and the 3R-Bi2O3-x, the 15C/3R-Bi2O3-x sample also exhibits near-infrared (NIR)-light-driven photocatalytic degradation activity. In addition, the intrinsic photocatalytic activity of CQDs/Bi2O3-x composite was further confirmed by the degradation of phenol under simulated sunlight and NIR light irradiation. The photocurrent response and electrochemical impedance spectroscopy (EIS) measurements confirm the efficient migration and separation of photogenerated charges in the CQDs/Bi2O3-x samples. The ?OH and h+ are proved to be the main reactive species in the simulated sunlight and NIR light photocatalytic processes over the CQDs/Bi2O3-x composites. According to the above experiments, the photocatalytic degradation mechanisms of the CQDs/Bi2O3-x composites under simulated sunlight and NIR light illumination were proposed.
关键词： photocatalytic,composites,oxygen vacancies,CQDs,Bi2O3
更新于2025-09-12 10:27:22
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Oxygen‐vacancy‐controlled magnetic properties with magnetic pole inversion in BiFeO <sub/>3</sub> ‐based multiferroics
摘要： Oxygen vacancies which are generally present in ferrite oxide may significantly affect their magnetic properties. A comprehensive understanding of the relationship between oxygen vacancies and magnetism is of great importance. In this work, we report an oxygen vacancy concentration dependence of magnetism in a single‐phase multiferroic BiFeO3 (BFO)‐based system. The BiFeO3‐DyFeO3 (BDFO) solid solution is synthesized with controlled oxygen vacancies and is characterized by X‐ray powder diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and AC impedance spectroscopy. The magnetic properties, especially magnetic pole inversion, are found to be highly dependent on oxygen vacancy concentration. The oxygen vacancies generate a Weiss molecular field on the Dy3+ ions in the magnetic field range of 570‐1000 Oe depending on the oxygen vacancy concentration, and result in a residual net magnetization by breaking the balance between the two nearly antiparallel spin lattices of Fe3+ ions. This work demonstrates an effective way to control oxygen vacancies and thereby the magnetic properties and sheds light on the relationship between oxygen vacancies and magnetism in BFO‐based multiferroics.
关键词： oxygen vacancies,bismuth ferrite BiFeO3,magnetic pole inversion
更新于2025-09-11 14:15:04
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Multifunctional p‐Type Carbon Quantum Dots: a Novel Hole Injection Layer for High‐Performance Perovskite Light‐Emitting Diodes with Significantly Enhanced Stability
摘要： Excess electrons from intrinsic oxygen vacancies play a key role in the surface chemistry and catalytic properties of metal oxides. This effect in actinide dioxides is particularly critical (AnO2), the most common nuclear fuels, where radiation can induce the formation of vacancies. However, the behavior of excess electrons on AnO2 surfaces has not been fully explored. In this article, we present a first-principle study of the electronic structure of excess electrons from oxygen vacancies on AnO2 (111) surfaces (An = Th, U, Pu). The low-energy solutions for the excess electrons are searched via U-ramping and occupation matrix control. The excess electrons are found to localize at the vacancy site on ThO2 and move to the metal 5f orbitals on the PuO2 surface, with UO2 as the intermediate case. This change significantly affects the catalytic properties of the AnO2 surfaces. In the presence of water, the excess electrons lead to the exothermic splitting of H2O and formation of molecular H2 on ThO2 and UO2 surfaces, while on the PuO2 surface the formation of H2 is thermodynamically unfavorable. This work has vital implications in the surface chemistry and corrosion of AnO2 and hence the handling and long-term storage of spent nuclear fuels.
关键词： oxygen vacancies,catalytic properties,nuclear fuels,excess electrons,actinide dioxides,water splitting
更新于2025-09-11 14:15:04
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Oxygen vacancies in the bulk and at neutral domain walls in hexagonal
摘要： We use density functional calculations to investigate the accommodation and migration of oxygen vacancies in bulk hexagonal YMnO3, and to study interactions between neutral ferroelectric domain walls and oxygen vacancies. Our calculations show that oxygen vacancies in bulk YMnO3 are more stable in the Mn-O layers than in the Y-O layers. Migration barriers of the planar oxygen vacancies are high compared to oxygen vacancies in perovskites, and to previously reported values for oxygen interstitials in h-YMnO3. The calculated polarization decreases linearly with vacancy concentration, while the out-of-plane lattice parameter expands in agreement with previous experiments. In contrast to ferroelectric perovskites, oxygen vacancies are found to be more stable in bulk than at domain walls. The tendency of oxygen vacancies to segregate away from neutral domain walls is explained by unfavorable Y-O bond lengths caused by the local strain field at the domain walls.
关键词： oxygen vacancies,ferroelectric domain walls,hexagonal YMnO3,density functional calculations,migration barriers
更新于2025-09-11 14:15:04
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Systematic enumeration and proficient chemical sensing applications of Eu3+@CeO2 nanocrystals
摘要： Current study displayed the application of hydrothermal method for the preparation of highly crystalline nanocrystals of Eu3+ doped cerium oxide (Eu@CeO2) particles. The influence of doping percentage and annealing effects were studied on the crystalline nature and morphology of particles. The size, optical properties and lattice parameters were calculated as a function of dopant concentrations and their discrepancies were explained in detail. Integration of Eu3+ ions on CeO2 could unlock a new trail to optimize the photoluminescence properties of formed nanocrystals. The generated oxygen vacancies (Vo··) have the ability to affect the characteristic features of cerium oxide in solid state. The variations in the nature of surface defect in presence of Eu3+ ions with CeO2 nanoparticles were explained with the results of XPS studies. The obtained results validated that defect-induced band gap modification by Eu3+ ion doping on CeO2 could be employed as effective chemical sensor for harmful metal ions in real water samples.
关键词： photoluminescence,lattice parameter,crystalline,doped Cerium oxide,oxygen vacancies,hydrothermal
更新于2025-09-11 14:15:04