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Selective Photooxidation of Amines and Sulfides Triggered by a Superoxide Radical Using a Novel Visible-Light-Responsive Metal–Organic Framework
摘要： Photocatalysis is an efficient and sustainable approach to convert solar energy into chemical energy, simultaneously supplying valuable chemicals. In this study, a novel metal–organic framework (MOF) compound is constructed from anthracene-based organic linkers, which shows visible-light absorption and efficient photoinduced charge generation property. It was applied for triggering photooxidation of benzylamines and sulfides in the presence of environmental benign oxidants of molecular oxygen or hydrogen peroxide. Results show that it is a highly selective photocatalyst for oxidation reactions to produce valuable imines or sulfoxides. We further investigate the underlying mechanism for these photocatalytic reactions by recognizing reactive oxygen species in the reactions. It has been demonstrated that the superoxide radical (O2??), generated by electron transfer from a photoexcited MOF to oxidants, serves as the main active species for the oxidations. The work demonstrates the great potential of photoactive MOFs for the transformation of organic chemicals into valuable complexes.
关键词： sulfide,photocatalysis,metal–organic framework,benzylamine,oxidation
更新于2025-09-23 15:23:52
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Microstructure and Properties of Graphene Oxide-doped TiO2 Coating on Titanium by Micro Arc Oxidation
摘要： Micro arc oxidation (MAO) coatings doped with graphene oxide (GO) were prepared on pure titanium by adding GO and sodium dodecyl benzene sulfonate (SDBS) into a sodium silicate solution. The as-deposited coatings were comparatively analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The binding forces of the MAO, MAO+GO and MAO+GO+SDBS three coatings were measured by a scratch tester. The mechanical property of the three coatings was analyzed using the nano-indentation technique. The corrosion resistance of the coatings was tested by the electrochemical system in 3.5% NaCl solution. The photocatalytic activity of the prepared samples was evaluated by determining the degradation of methylene blue (MB) solution. The results showed that compared to the MAO coating, the morphologies and phase compositions of MAO+GO and MAO+GO+SDBS composite coatings were significantly different. These two composite coatings all had superior photocatalytic activity. Especially, the MAO+GO composite coating still had enhanced binding force and excellent corrosion resistance. Furthermore, the relationship between the microstructure and the properties of these three MAO coatings was analyzed.
关键词： pure titanium,graphene oxide,micro arc oxidation,properties,microstructure
更新于2025-09-23 15:23:52
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Degradation of benzothiophene in diesel oil by LaZnAl layered double hydroxide: photocatalytic performance and mechanism
摘要： A new type of photocatalytic La3+–Zn2+–Al3+–MoO4 2- layered double hydroxide (LDH) material (molar ratio, La/Zn/Al = 1:7:2) was prepared by a complexing agent-assisted homogeneous precipitation technique. The structure of the prepared LDH material was systematically studied. Under UV irradiation, the desulfurization efficiency of the LDH material was 87% in 2 h. For La3+–Zn2+–Al3+–MoO4 2- LDH material, the introduction of MoO4 2- increased the interlayer space for promoting the adsorption of benzothiophene (BT), and MoO4 2- might provide active sites for the oxidation of BT, resulting in the high desulfurization efficiency.
关键词： Photocatalytic activities,Catalytic oxidation mechanism,LDH,Homogeneous precipitation
更新于2025-09-23 15:23:52
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A Production-Accessible Method: Spectrophotometric Iron Speciation in Wine Using Ferrozine and Ethylenediaminetetraacetic Acid
摘要： Wine oxidation is reported to be linked to the iron species present in the wine, but spectrophotometric speciation is plagued by unstable measurements due to alterations to the reduction potential of iron by complexing agents. Ferrozine raises the reduction potential of iron by complexing preferentially to iron(II), inducing the reduction of iron(III) during analysis; here, EDTA is added to chelate iron(III) and to stabilize the forms of iron. Bisulfite addition allows the use of ferrozine for red wine analysis by mitigating color interference. Measurements agree with values from a previous method for iron(II) and from FAAS for total iron. Spike recoveries were in the range of 103.5?110.1%. The method is linear for iron concentrations in the range of 0.10?6.00 mg L?1 and offers good precision (CV 0.4?10.1%) and low limits of detection (0.02 mg L?1) and quantification (0.06 mg L?1). The method demonstrated changes to iron speciation during the oxygenation of red wines.
关键词： reduction potential,oxidation,wine,spectrophotometry,ferrozine,iron speciation
更新于2025-09-23 15:23:52
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Spectroscopy of Oxygen-Sensitive Material for Measuring Contact Lens Oxygen Transmissibility
摘要： Purpose: Oxygen permeability or transmissibility is a crucial parameter for contact lenses to ensure that extended wear will not induce corneal hypoxia. This work tests a new method of using the oxidation of cysteamine, an oxygen-sensitive chemical, to quantify the oxygen transmissibility of current commercial contact lenses and contact lenses loaded with vitamin E. Methods: 3D printing was used to modify eye drop bottles and quartz cuvettes to create systems that allowed insertion of a contact lens in between the cysteamine solution and air. Both systems were exposed to atmospheric conditions where the only path of entry for oxygen was through the contact lens. The entering oxygen reacted with cysteamine, and the rate of cysteamine oxidation was measured using UV-vis spectrophotometry. The rate was then stoichiometrically related to oxygen transmissibility. Results: The eye drop method predicted transmissibility values within 9% of established, commercial values. The cuvette method predicted values within 10% of established values for silicone hydrogel lenses without any correction factor and within 11% for poly-hydroxyethyl-methacrylate lenses after correcting for oxygen entering the system. Incorporation of 20% (w/w) vitamin E into Acuvue? Oasys? lenses did not have a significant impact on the oxygen transmissibility. Conclusions: Both methods presented in this work can reliably measure oxygen transmissibility of contacts lenses or other materials. Further improvements in manufacturing could lead to improved accuracy and reliability, allowing wider use of this method for quantifying the oxygen transport in contact lenses.
关键词： oxidation,oxygen permeability,spectrophotometry,3D printing,contact lens
更新于2025-09-23 15:23:52
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Using first principles calculations to interpret XANES experiments: Extracting the Size-dependence of the (<i>p, T</i>) phase diagram of sub-nanometer Cu clusters in an O<sub>2</sub> environment
摘要： We have used ab initio density functional theory together with ab initio atomistic thermodynamics, and in situ X-ray absorption near edge spectroscopy (XANES) experiments, to study the oxidation of sub-nanometer clusters of CunOx supported on a hydroxylated amorphous alumina substrate in an O2-rich environment. We obtain (p, T) phase diagrams; these differ notably for the nanoclusters compared to the bulk. Both theory and experiment suggest that in the presence of oxygen, the cluster will oxidize from its elemental state to the oxidized state as temperature decreases. We obtain a clear trend for the transition Cun→ CunOn/2: we see that smaller the cluster, greater is the tendency toward oxidation. However, we do not see a monotonic size-dependent trend for the transition CunOn/2→ CunOn. We suggest that theoretically computed Bader charges constitute a simple yet quantitative way to align experimental measures of XANES edges with theoretical calculations, so as to yield oxidation states for nanoclusters. Our results have important implications for the use of small clusters in fields such as nanocatalysis and nanomedicine.
关键词： cluster,DFT,XANES,copper,oxidation
更新于2025-09-23 15:23:52
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A novel growth strategy of TiO<sub>2</sub> anodic films using surface residual stress as driving force
摘要： The relationship between residual stress and growth behavior of anodic titanium oxide films (TiO2) was investigated in terms of defect chemistry and the nanocrystalline materials thermodynamic. The results showed that the surface residual stress can be controlled by acting on the duration of the surface mechanical attrition treatment (SMAT). When samples are processed by grinding for 30 min, the residual stress value reaches a maximum of 73.13 MPa, approximately 7.2 times higher than the one obtained with untreated sample. Under these conditions, the thickness of the anodic film was about 1200 nm, three times that of the TA2 anodic film. Furthermore, the results of electrochemical tests showed that following the surface mechanical attrition treatment, the anodic film show lower density vacancies, higher resistance to the diffusion of Cl-, higher density, and an improved corrosion resistance when compared to TA2. Generally speaking, the growth behavior of the anodic film can be improved by identifying the suitable residual stress.
关键词： Surface mechanical attrition treatment,Anodic oxidation,Corrosion resistance,Growth mechanism
更新于2025-09-23 15:23:52
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Photoluminescence properties of Er3+/Yb3+ doped ZrO2 coatings formed by plasma electrolytic oxidation
摘要： In the present work, down- and up-conversion photoluminescence properties of Er3+/Yb3+ doped ZrO2 coatings formed by plasma electrolytic oxidation of zirconium in electrolyte containing Er2O3 and Yb2O3 particles were investigated. Down-conversion PL analysis shows that emission spectra of ZrO2:Er3+/Yb3+ coatings excited with 280 nm radiation are composed of broad PL band related to ZrO2 host and bands assigned to f-f transitions of Er3+. The main PL emission bands of Er3+ at around 548 nm and 560 nm are related to 4S3/2→4I15/2 transition. PL excitation spectra monitored at 548 nm feature broad band in the region from 250 nm to 350 nm which is associated with the electron transfer transition from 2p orbital of O2? to 4f orbital of Er3+ and transitions of ZrO2. On the other hand, bands in PL excitation spectra ranging from 350 nm to 535 nm are related to 4f transitions of the Er3+ from the ground state 4I15/2 to higher energy levels. Down-conversion PL intensity decreases with increasing concentration of Yb3+ in coating due to energy transfer from Er3+ to Yb3+. ZrO2:Er3+/Yb3+ coatings show intense green (4S3/2→4I15/2) and red (4F9/2→4I15/2) up-conversion PL emission under the excitation with a 980 nm diode laser. With increasing Yb3+ concentration red up-conversion PL intensity increases more rapidly with respect to green emission, because red up-conversion PL intensity strongly depends on Yb3+ concentration, i.e. 4F9/2 state of Er3+ is directly excited by energy transfer from excited Yb3+.
关键词： up-conversion,Photoluminescence,Er3+/Yb3+,Down-conversion,Plasma electrolytic oxidation
更新于2025-09-23 15:23:52
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Photocatalytic oxidation of thiophene over cerium doped TiO2 thin film
摘要： Samples of TiO2 and TiO2 doped with 2% and 8% cerium ions were prepared by a sol-gel method and used as photocatalysts for the oxidation of vaporized thiophene. X-ray diffraction patterns showed a mixed phase of anatase and rutile for TiO2, while 2%Ce/TiO2 and 8%Ce/TiO2 were dominated by the anatase phase. As seen in the transmission electron microscopy image, the particle size of Ce/TiO2 was about 10 nm which was smaller than the undoped TiO2. The extended x-rays absorption fine structures revealed the substitutional effect of cerium in the TiO2 structure. Cerium-doped TiO2 exhibited a smaller photocurrent compared to that of TiO2, which suggested the electrons were trapped by cerium ions. In situ diffuse reflectance infrared spectroscopy under UV irradiation and x-ray photoemission spectroscopy were used to investigate the photocatalytic oxidation of thiophene on the prepared catalysts. Doping of cerium ions in TiO2 resulted in an enhanced adsorption of thiophene on the catalyst surface. The oxidation products of carboxylic acid with small amounts of sulfate ions were observed. As seen from the infrared absorption spectrum, 2%Ce/TiO2 and 8%Ce/TiO2 exhibited higher photocatalytic activity than those of the undoped TiO2.
关键词： Thiophene oxidation,Thin film,Cerium,Photocatalysis,Titanium dioxide
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE International Conference on Electronics, Computing and Communication Technologies (CONECCT) - Bangalore (2018.3.16-2018.3.17)] 2018 IEEE International Conference on Electronics, Computing and Communication Technologies (CONECCT) - AlInN/GaN MIS-HEMTs with High Pressure Oxidized Aluminium as Gate Dielectric
摘要： AlInN/GaN metal insulator semiconductor high electron mobility transistor (MIS-HEMT) with high pressure oxidized aluminium as gate dielectric is investigated in this paper. The fabricated MIS-HEMT shows more than six orders of reduction in the gate leakage current in reverse bias and more than three orders of reduction in forward bias compared to the reference HEMT devices also fabricated on same substrates. A maximum drain current of 750 mA/mm was achieved due to improvement in the gate swing for MIS-HEMT. The MIS-HEMT devices also showed good improvement in the subthreshold slope and ID,ON/ID,OFF ratio compared to HEMT devices.
关键词： gate leakage current,MIS-HEMT,high pressure oxidation,AlInN/GaN,HEMT,Al2O3
更新于2025-09-23 15:23:52