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Salicylic acid complexed with TiO2 for visible light-driven selective oxidation of amines into imines with air
摘要： The interplay of salicylic acid (SA) and reactive oxygen species (ROS) can modulate biotic and abiotic stress of plants, essential biological aerobic oxidation processes. Meanwhile, ROS plays a critical role in TiO2 photocatalytic system for the degradation of organic species. Herein, we developed a system consisted of SA and TiO2 aiming at the selective oxidation of organic molecules by ROS. Interestingly, SA complexed with TiO2 leads to ligand-to-metal charge transfer (LMCT) under visible light irradiation. The charge transfer from ligand (chemically adsorbed SA) to metal (conduction band of TiO2) activates O2 to ROS, superoxide (O2?). The positive charge located at ligand SA is connected with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) catalysis for direct two-electron oxidation of amines and later regenerated by O2. SA and its derivatives were screened as ligands of TiO2 for the selective aerobic oxidation of amines into imines under blue light-emitting diode (LED) irradiation in which 5-CH3O-SA (5-methoxysalicylic acid, 0.8 mol%) complexed with anatase TiO2 and coupled with TEMPO (5 mol%) confers significantly better results than the others. By this visible light LMCT route, both primary amines and secondary amines can be selectively oxidized into corresponding imines with atmosphere O2 as the terminal oxidant. Importantly, the desired product of N-benzylidenebenzylamine can be isolated in 92% yield.
关键词： Salicylic acid,Titanium dioxide,Amines,Photocatalysis,Surface complex
更新于2025-09-04 15:30:14
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Synthesis, characterization and photocatalytic activity of boron-doped titanium dioxide nanotubes
摘要： Two-step hydrothermal method was used to prepare undoped and boron-doped one-dimensional titanium dioxide (TiO2) nanotubes. Structural properties, thermal stability and microstructural features of the fabricated undoped titanium dioxide nanotubes (TNTs) and boron-doped titanium dioxide nanotubes (BTNTs) were characterized by Xeray diffraction, Raman, Fourieretransform infrared spectroscopy, nitrogen adsorption-desorption isotherms, scanning and transmission electron microscopy techniques. The photocatalytic activity of the fabricated nanotubes was evaluated by using methylene blue degradation. Boron addition to the titanium dioxide nanotubes up to 5% increased the photocatalytic methylene blue degradation ef?ciency. The achieved highest degradation ef?ciency was 81% and it was determined that higher (>5%) boron doped into the titanium dioxide nanotubes resulted in a decreased degradation ef?ciency.
关键词： Titanium dioxide nanotubes,Photocatalyst,Boron,Hydrothermal synthesis,Spectroscopy
更新于2025-09-04 15:30:14
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Photocatalytic Degradation of Wood Coated with a Combination of Rutile TiO2 Nanostructures and Low-Surface Free-Energy Materials
摘要： To test the hypothesis that wood coated with rutile TiO2 nanostructures can undergo degradation because of the photocatalytic activity of TiO2, three sets of wood specimens were aged at an accelerated rate. These three sets consisted of blank wood (BW), HDTMOS/MTMOS-coated wood (WHM), and TiO2/HDTMOS/MTMOS-coated wood (WTHM). After exposure to 155-h UV irradiation, the wettability of WTHM changed from hydrophobic to hydrophilic. This indicated that the initial low-surface free-energy materials underwent degradation because of the photocatalytic activity of TiO2. After exposure to 960 h of UV light irradiation and water spray, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) of WTHM showed that rutile TiO2 nanostructures had partially peeled off the wood surface. This suggested that the adjacent wood surface also suffered degradation because of the photocatalytic activity of TiO2. Although the rutile TiO2 coating noticeably enhanced the color stability during UV light aging, it made a relatively small contribution to the color stability of the wood during UV light and water spray weathering process. This study suggests that to derive the greatest benefit from modification of wood surfaces with rutile TiO2 nanostructures for weathering resistance, it is necessary to take measures to inhibit the photocatalytic activity of TiO2 or to fix the TiO2 coating on the wood surface.
关键词： Coating,Hydrophobic,Rutile,Wood,Titanium dioxide,Weathering,Nanostructure,Photocatalytic
更新于2025-09-04 15:30:14
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Photoelectrochemically Active N‐Adsorbing Ultrathin TiO <sub/>2</sub> Layers for Water‐Splitting Applications Prepared by Pyrolysis of Oleic Acid on Iron Oxide Nanoparticle Surfaces under Nitrogen Environment
摘要： Highly performing photocatalytic surfaces are nowadays highly desirable in energy fields, mainly due to their applicability as photo water-splitting electrodes. One of the current challenges in this field is the production of highly controllable and efficient photoactive surfaces on many substrates. Atomic layer deposition has allowed the deposition of photoactive TiO2 layers over wide range of materials and surfaces. However, nitrogen doping of the growing layers, a highly effective way of controlling the absorption edges of photoactive surfaced, is still a challenging task. Here, the preparation of hierarchical nanostructured surfaces based on Langmuir–Schaefer and atomic layer deposition is proposed. Ultrathin TiO2 layers that are photoelectrochemically active in water splitting are prepared by a relatively low-temperature catalytic decomposition of oleic acid capping layers of iron oxide nanoparticles and the posterior nitrogen adsorption. The results evidence that simple N-adsorption is sufficient to narrow the bandgap of TiO2 layers that is equal to bandgap narrowing (0.12 eV) observed for substitutionally N-doped materials. The photocatalytic activity tests of the prepared surfaces in water-splitting applications demonstrate ≈90% increase in the activity of the N-adsorbing TiO2 layers.
关键词： Langmuir–Schaefer,magnetite (Fe3O4),photocatalysis,titanium dioxide (TiO2),atomic layer deposition (ALD)
更新于2025-09-04 15:30:14
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Photofunctionalizing effects of hydroxyapatite combined with TiO <sub/>2</sub> on bone regeneration in rabbit calvarial defects
摘要： The hydrophilicity of bone graft material generally used as a carrier can play an important role in regulating bone morphogenetic protein (BMP) expression at the bone graft site. The hydrophilicity, altering physicochemical properties, and enhancing biological capabilities, can be increased via surface modi?cation through ultraviolet (UV) photofunctionalization and the effect on de novo osteogenesis could be further improved. Therefore, this study aimed to assess the effects of UV-irradiated TiO2-coated hydroxyapatite (HA) in combination with rhBMP-2 on bone regeneration in rabbit calvarial defects. The hydrophilicity of HA and TiO2-coated HA pellets was evaluated by measuring the contact angle of water droplets with UV irradiation. To compare de novo osteogenesis in rabbit calvarial defects, the rabbits were segregated into four different groups: negative control, HA, TiO2-coated HA, and TiO2-coated HA with UV; histomorphometric analysis and micro-computed tomography (μCT) imaging were performed after 4 and 8 weeks. In vivo analysis revealed that de novo osteogenesis occurred on the critical size defects in all groups and was signi?cantly increased in the TiO2-coated HA with UV group than in other groups (p < 0.05). The present results indicate that UV photofunctionalization promotes de novo osteogenesis.
关键词： hydroxyapatite,rabbit calvarial defects,ultraviolet,bone regeneration,titanium dioxide
更新于2025-09-04 15:30:14
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Effect of TiO<sub>2</sub>-rGO heterojunction on electron collection efficiency and mechanical properties of fiber-shaped dye-sensitized solar cells
摘要： It is demonstrated that the incorporation of graphene materials into oxide-based photoanodes can greatly increase the photoelectrochemical devices’ performances. In this work, reduced graphene oxide (rGO) has been incorporated into P25-TiO2 nanoparticle (NP) based photoanodes for fiber-shaped dye-sensitized solar cells (FDSSCs). Results showed that the rGO nanosheets have been uniformly dispersed within P25 nanoparticle layers. And as expected, the incorporation of rGO increased the FDSSCs’ short current density from 8.344 to 12.935 mA cm-2, open circuit voltage from 0.775 to 0.798 V, resulting into their power conversion efficiency (PCE) from 3.940% to 5.364%. This large increasement in PCE could be due to two aspects, i.e., the improved electron transport properties via rGO and the enhanced separation of photogenerated hole-electron pairs via rGO-TiO2 heterojunction. Furthermore, the incorporation of rGO can also make the FDSSCs have good mechanical properties, which is very crucial for their future applications in smart wearable electronics. In addition, based on our analysis, a possible rGO/multi-NP coupling enhancement mechanism was proposed.
关键词： fiber-shape,heterojunction,dye-sensitized solar cells,titanium dioxide,reduce graphene oxide (rGO)
更新于2025-09-04 15:30:14
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TiO2-catalyzed photodegradation of aromatic compounds: relevance of susceptibility to oxidation and electrophilic attack by hydroxyl radical
摘要： The application of nanostructured titanium dioxide (TiO2) as catalyst for the photodegradation of drugs and dyes is well established. We aimed to evaluate the importance of the reactivity of aromatic compounds submitted to photodegradation. Specifically, we were interested in the correlation between susceptibility to oxidation and/or to electrophilic attack and the efficiency of degradation. We demonstrated that hydroxyl radical (HO˙) is the most relevant species generated in the photodegradation process. Considering that HO˙ has both oxidizing and electrophilic features, the efficiency of degradation of selected aromatic compounds was performed. The choice was based on their susceptibility to oxidation and/or to electrophilic attack. Benzoic acid (C1), salicylic acid (C2), and protocatechuic acid (C3) were compared regarding their oxidability using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and were ranked as follows: C3 ? C2~C1. These compounds were efficiently photodegraded and no significant difference was observed among them. To assess the importance of susceptibility to electrophilic attack, anisole (C4), acetophenone (C5), and nitrobenzene (C6) were selected. Compared to C5 and C6, the higher susceptibility of C4 to electrophilic attack was demonstrated using hypochlorous acid, an electrophilic reagent. The photodegradation showed that C4 was also more susceptible to degradation compared to C5 and C6. In summary, we found that by acting as a powerful oxidant/electrophile agent, HO˙ was able to promote the degradation of aromatic moieties. Considering that the majority of drugs and dyes bear aromatic moieties, our findings explain the great success of photodegradation using metal oxides as catalysts.
关键词： Pharmaceutical drugs,Aromatic compounds,Titanium dioxide,Nanostructured catalysts,Electrophilic susceptibility,Photodegradation
更新于2025-09-04 15:30:14
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The effect of TiO <sub/>2</sub> nanopigment on the optical properties of polyester fabric in UV–VIS–NIR regions
摘要： The particle size parameter is a key factor that affects radiative properties of nano-pigments, and consequently, pigments of the same type but different sizes represent different spectral performance. Therefore, current study dealt with a systematic experimental investigation on the effect of TiO2 pigmented coatings on spectral reflectance and color performance of white and colored polyester fabrics in UV, VIS, and NIR region of electromagnetic spectrum, with a special emphasis on VIS region. In order to accomplish this target, polyester fabrics were coated with TiO2 nanopigment with various concentrations and different diameters, and their reflectance spectra were measured using spectrophotometric method. Two-way analysis of variance (ANOVA) was utilized to investigate the significance of the effect of TiO2 nanopigment on the color performance of coated fabrics. According to experimental observations, an organized color shift appears in color coordinate of fabrics coated with TiO2 nanopigment of various sizes. Moreover, although TiO2 nanopigment with 35 nm diameter has the most significant impact on short wavelength region (UV region), the effect of pigment with 250 nm diameter is more noticeable on NIR region as long wavelength region.
关键词： nanopigment,polyester fabric,reflectance spectra,optical property,titanium dioxide
更新于2025-09-04 15:30:14
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Desinfec??o de água cinza por fotocatálise heterogênea
摘要： Proper disinfection of greywater is needed to ensure the safety of its reuse, especially in applications with potential for human exposure. Various advanced oxidation processes have been used in recent years for the degradation of organic contaminants, as well as for disinfection of water and wastewater. The purpose of this study was to test TiO2 supported in microtubes to disinfect greywater by photocatalysis in order to reuse it in sanitary bowl. The greywater used in the experiments was collected after passing through a treatment system consisting of an evapotranspiration tank followed by constructed wetland with horizontal flow. Batch tests were conducted using a cylindrical photochemical reactor of 1.0 L (total volume of the reactor), filled with small glass Pyrex cylinders with supported TiO2. For disinfection tests, the processes UV, H2O2, UV/TiO2, UV/H2O2 and UV/TiO2/H2O2 were used. It was possible to obtain a homogeneous layer of TiO2 deposited in small Pyrex glass tubes with an average thickness of 35.3 μm; this layer was able to promote an increase in the greywater disinfection. However, even with a greater disinfection power of TiO2 compared with photolysis (UV), the processes with hydrogen peroxide was much more efficient in disinfection (total inactivation of total coliforms, enterococci and Pseudomonas aeruginosa) and in the removal of organic matter in terms of chemical oxygen demand (around 60%). Samples stored at a room temperature and wrapped in plastic dark showed no bacterial regrowth after 24 hours of storage after the experiments, thus showing the viability of treated greywater for domestic reuse.
关键词： advanced oxidation processes,greywater,titanium dioxide
更新于2025-09-04 15:30:14
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Interfacing CRYSTAL/AMBER to Optimize QM/MM Lennard–Jones Parameters for Water and to Study Solvation of TiO2 Nanoparticles
摘要： Metal oxide nanoparticles (NPs) are regarded as good candidates for many technological applications, where their functional environment is often an aqueous solution. The correct description of metal oxide electronic structure is still a challenge for local and semilocal density functionals, whereas hybrid functional methods provide an improved description, and local atomic function-based codes such as CRYSTAL17 outperform plane wave codes when it comes to hybrid functional calculations. However, the computational cost of hybrids are still prohibitive for systems of real sizes, in a real environment. Therefore, we here present and critically assess the accuracy of our electrostatic embedding quantum mechanical/molecular mechanical (QM/MM) coupling between CRYSTAL17 and AMBER16, and demonstrate some of its capabilities via the case study of TiO2 NPs in water. First, we produced new Lennard–Jones (LJ) parameters that improve the accuracy of water–water interactions in the B3LYP/TIP3P coupling. We found that optimizing LJ parameters based on water tri- to deca-mer clusters provides a less overstructured QM/MM liquid water description than when fitting LJ parameters only based on the water dimer. Then, we applied our QM/MM coupling methodology to describe the interaction of a 1 nm wide multilayer of water surrounding a spherical TiO2 nanoparticle (NP). Optimizing the QM/MM water–water parameters was found to have little to no effect on the local NP properties, which provide insights into the range of influence that can be attributed to the LJ term in the QM/MM coupling. The effect of adding additional water in an MM fashion on the geometry optimized nanoparticle structure is small, but more evident effects are seen in its electronic properties. We also show that there is good transferability of existing QM/MM LJ parameters for organic molecules–water interactions to our QM/MM implementation, even though these parameters were obtained with a different QM code and QM/MM implementation, but with the same functional.
关键词： water,geometry optimization,nanoparticles,QM/MM,molecular dynamics,force field parameters,titanium dioxide,multiscale
更新于2025-09-04 15:30:14