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Sol-Gel Preparation of Thick TiO<sub>2</sub> Films for Structural Coloration
摘要： We studied sol-gel processing of thick and crack-free TiO2 films to synthesize structural color materials. The viscosity of the alkoxide-based precursor sols was stabilized by the addition of acetyl acetone, which improved control of the spin coating thickness. We used a TiO2/SiO2/TiO2 triple-layer structure and second-order reflection conditions to produce structural coloration. This design yielded a sharp spectral peak and bright coloration; however, a TiO2 layer with a thickness greater than 200 nm was required, which is much thicker than that required for the first-order of reflection. Crack formation in the thick films was suppressed by the addition of ethyl cellulose to the precursor sols. As a consequence, color-tuned TiO2/SiO2/TiO2 films were successfully prepared and exhibited various bright colors in the visible light wavelength range, including two primary colors of light, namely blue and green. Green coloration from flake-shaped particles was also demonstrated.
关键词： TiO2,structural color,crack formation,flake-like powders,sol-gel method
更新于2025-09-23 15:22:29
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Nitrogen dopedTiO2photoactive in visible light
摘要： In this research TiO2 modified with nitrogen has been prepared. The synthesis method used was sol gel from the hydrolysis of titanium tetrabutoxide with urea solution, combined with a low temperature treatment at atmospheric pressure. The theoretical mole ratio N/Ti was equal to 0.5 and the theoretical mole ratio HNO3/TiO2 was equal to 0.5. The solid obtained was calcined at different temperatures in static air with high heating rate and residence time of 1 hour. The samples were characterized by X-ray diffraction, FTIR Raman and diffuse reflectance spectroscopy, thermodifferential and thermogravimetric analysis and specific surface area. All calcined solids exhibit absorption in the visible range. The Raman spectroscopy and X-ray diffraction revealed for all the heat treatments, the presence of crystalline phases corresponding to anatase and brookite polymorphism. The photocatalytic activity of the catalysts was tested in degradation of an artificial dye under visible light, yielding the best results for the sample treated at 250°C. Our results allow to say that this behaviour is due to the absorption of visible light, good efficiency for the adsorption of the dye and presence of two crystalline phases that decreases the recombination of photogenerated electrons and holes. The synthesis technique used allows obtaining solids with textural and attractive photocatalytic properties.
关键词： photocatalysis,TiO2-N,Characterization,synthesis
更新于2025-09-23 15:22:29
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Retraction： Wetting Behavior of Single Crystal TiO<sub>2</sub> by Liquid Iron
摘要： The wetting behavior of TiO2 by liquid iron was investigated by using the sessile drop method. A partial melting behavior was found to appear at the temperature below the melting point of the pure iron. Also a solid solution TiOx–FeO phase was observed between the pure iron and TiO2 substrate. The formation of this reaction layer is due to the reaction among the pure iron, TiO2 substrate and the oxygen gas. The main source of the oxygen gas for reaction is from the TiO2 substrate decomposition and a low partial pressure of oxygen near the sample.
关键词： TiO2,wettability,partial pressure oxygen,decomposition
更新于2025-09-23 15:22:29
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Photocatalytic Degradation of Estriol Using Iron-Doped TiO2 under High and Low UV Irradiation
摘要： Iron-doped TiO2 nanoparticles (Fe-TiO2) were synthesized and photocatalitically investigated under high and low ?uence values of UV radiation. The Fe-TiO2 physical characterization was performed using X-ray Powder Diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Diffuse Re?ectance Spectroscopy (DRS), and X-ray Photoelectron Spectroscopy (XPS). The XPS evidenced that the ferric ion (Fe3+) was in the TiO2 lattice and unintentionally added co-dopants were also present because of the precursors of the synthetic method. The Fe3+ concentration played a key role in the photocatalytic generation of hydroxyl radicals (?OH) and estriol (E3) degradation. Fe-TiO2 accomplished E3 degradation, and it was found that the catalyst with 0.3 at.% content of Fe (0.3 Fe-TiO2) enhanced the photocatalytic activity under low UV irradiation compared with TiO2 without intentionally added Fe (zero-iron TiO2) and Aeroxide? TiO2 P25. Furthermore, the enhanced photocatalytic activity of 0.3 Fe-TiO2 under low UV irradiation may have applications when radiation intensity must be controlled, as in medical applications, or when strong UV absorbing species are present in water.
关键词： hydroxyl radical,estriol,iron-doped TiO2,photocatalytic activity,low UV irradiation
更新于2025-09-23 15:22:29
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Highly Selective Photocatalytic Reduction of o-Dinitrobenzene to o-Phenylenediamine over Non-Metal-Doped TiO2 under Simulated Solar Light Irradiation
摘要： Photocatalytic reduction and hydrogenation reaction of o-dinitrobenzene in the presence of oxalic acid over anatase-brookite biphasic TiO2 and non-metal-doped anatase-brookite biphasic TiO2 photocatalysts under solar simulated light was investigated. Compared with commercial P25 TiO2, the prepared un-doped and doped anatase-brookite biphasic TiO2 exhibited a high selectivity towards the formation of o-nitroaniline (85.5%) and o-phenylenediamine ~97%, respectively. The doped anatase-brookite biphasic TiO2 has promoted photocatalytic reduction of the two-nitro groups of o-dinitrobenzene to the corresponding o-phenylenediamine with very high yield ~97%. Electron paramagnetic resonance analysis, Transient Absorption Spectroscopy (TAS) and Photoluminescence analysis (PL) were performed to determine the distribution of defects and the fluorescence lifetime of the charge carriers for un-doped and doped photocatalysts. The superiority of the doped TiO2 photocatalysts is accredited to the creation of new dopants (C, N, and S) as hole traps, the formation of long-lived Ti3+ defects which leads to an increase in the fluorescence lifetime of the formed charge carriers. The schematic diagram of the photocatalytic reduction of o-dinitrobenzene using the doped TiO2 under solar light was also illustrated in detail.
关键词： selectivity,photocatalysis,non-metal-doped TiO2,nitroaromatic compounds,reduction
更新于2025-09-23 15:22:29
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Recent Development of Photocatalysts Containing Carbon Species: A Review
摘要： Undoubtedly, carbon-based (nano)composites can be promising photocatalysts with improved photocatalytic activity due to the coupling effect from the incorporation of carbon species. In this mini-review, we focus on the recent development of photocatalysts based on carbon-based (nano)composites. TiO2 is well-known as a typical photocatalyst. Special attention is paid to the various types of carbon–TiO2 composites such as C-doped TiO2, N–C-doped TiO2, metal–C-doped TiO2, and other co-doped C/TiO2 composites. Various synthetic strategies including the solvothermal/hydrothermal method, sol–gel method, and template-directed method are reviewed for the preparation of carbon-based TiO2 composites. C/graphitic carbon nitride (g-C3N4) composites and ternary C-doped composites are also summarized and ascribed to the unique electronic structure of g-C3N4 and the synergistic effect of the ternary interfaces, respectively. In the end, we put forward the future perspective of the photocatalysts containing carbon species based on our knowledge.
关键词： (nano)composites,synergistic effect,g-C3N4,C-doped,photocatalysts,TiO2
更新于2025-09-23 15:22:29
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Photocatalytic Hydrogen Production Under Near-UV Using Pd-Doped Mesoporous TiO2 and Ethanol as Organic Scavenger
摘要： Photocatalysis can be used advantageously for hydrogen production using a light source (near-UV light), a noble metal-doped semiconductor and an organic scavenger (2.0 v/v% ethanol). With this end, palladium was doped on TiO2 photocatalysts at different metal loadings (0.25 to 5.00 wt%). Photocatalysts were synthetized using a sol-gel method enhancing morphological properties with a soft template precursor. Experiments were carried out in the Photo-CREC Water II reactor system developed at CREC-UWO (Chemical Reactor Engineering Centre- The University of Western Ontario) Canada. This novel unit offers hydrogen storage and symmetrical irradiation allowing precise irradiation measurements for macroscopic energy balances. Hydrogen production rates followed in all cases a zero-order reaction, with quantum yields as high as 30.8%.
关键词： Quantum Yield,Photo-CREC Water II reactor,Palladium,Hydrogen production,TiO2
更新于2025-09-23 15:22:29
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Photocatalytic Mechanisms for Peroxymonosulfate Activation through the Removal of Methylene Blue: A Case Study
摘要： Industrial activity is one of the most important sources of water pollution. Yearly, tons of non-biodegradable organic pollutants are discharged, at the least, to wastewater treatment plants. However, biological conventional treatments are unable to degrade them. This research assesses the efficiency of photocatalytic activation of peroxymonosulfate (PMS) by two different iron species (FeSO4 and Fe3+-citrate) and TiO2. These substances accelerate methylene blue removal by the generation of hydroxyl and sulfate radicals. The required pH and molar ratios PMS:Fe are crucial variables in treatment optimization. The kinetic removal is reduced by the appearance of scavenger reactions in acidic and basic conditions, as well as by the excess of PMS or iron. The best performance is achieved using an Fe3+-citrate as an iron catalyst, reaching the total removal of methylene blue after 15 min of reaction, with a molar ratio of 3.25:1 (1.62 mM of PMS and 0.5 mM Fe3+-citrate). Fe3+-citrate reached higher methylene blue removal than Fe2+ as a consequence of the photolysis of Fe3+-citrate. This photolysis generates H2O2 and a superoxide radical, which together with hydroxyl and sulfate radicals from PMS activation attack methylene blue, degrading it twice as fast as Fe2+ (0.092 min?1 with Fe2+ and 0.188 min?1 with Fe3+-citrate). On the other hand, a synergistic effect between PMS and titanium dioxide (TiO2) was observed (SPMS/TiO2/UV-A = 1.79). This synergistic effect is a consequence of PMS activation by reaction with the free electron on the surface of TiO2. No differences were observed by changing the molar ratio (1.04:1; 0.26:1 and 0.064:1 PMS:TiO2), reaching total removal of methylene blue after 80 min of reaction.
关键词： iron activation,peroxymonosulfate,sulfate radicals,synergistic effect,TiO2 activation,dye
更新于2025-09-23 15:22:29
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Charge Transfer Tuned by the Surrounding Dielectrics in TiO2-Ag Composite Arrays
摘要： TiO2/Ag bilayer ?lms sputtered onto a 2D polystyrene (PS) bead array in a magnetron sputtering system were found to form a nanocap-shaped nanostructure composed of a TiO2-Ag composite on each PS bead, in which the Ag nanoparticles were trapped partially or fully in the TiO2 matrix, depending on the TiO2 thickness. X-ray Photoelectron Spectroscopy (XPS) results showed the opposite shifts of binding energy for Ti 2p and Ag 3d, indicating the transfer of electrons from metallic Ag to TiO2 owing to the Ag-O-TiO2 composite formation. UV-Vis absorption spectra showed the blue shifts of the surface plasma resonance peaks, and the maximum absorption peak intensity was obtained for TiO2 at 30 nm. The surface-enhanced Raman scattering (SERS) peak intensity ?rst increased and then decreased when the TiO2 thickness changed. The observations of SERS, XPS, and UV-Vis absorption spectra were explained by the dependency of the charge-transfer process on TiO2 thickness, which was ascribed to the changing dielectric properties in the metal/semiconductor system.
关键词： electronic transfer,TiO2-Ag composites,surrounding dielectrics
更新于2025-09-23 15:22:29
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TiO2 Nanotubes with Nanograss Structure: The Effect of the Anodizing Voltage on the Formation Mechanism and Structure Properties
摘要： Titanium dioxide nanotubes (TiO2 NTs) with a nanograss structure were synthesized in a fluoride organic electrolyte based on ethylene glycol under a potentiostatic anodization regime. By varying the anodization voltage, significant morphological differences were obtained, and the upper NTs’ surface has a nanograss appearance caused by the thinning of top tube walls, the result of the vertical splitting mechanism of nanograss growth. The samples were characterized using techniques such as scanning electron microscopy, x-ray diffraction, UV–visible spectroscopy and Mott–Schottky (MS) analysis. The obtained results show that samples annealed at 500°C for 3 h crystallized into anatase form and displayed the apparition of rutile phase at higher anodization voltage, where the morphology was significantly improved with thicker tube walls. The MS measurement of all samples displays a n-type semiconductor nature and the flat band potential (Ufb) takes less negative values by the increasing anodization voltage. As a result, TiO2 NTs with a nanograss structure expedite electron–hole separation, therefore, providing a lower recombination rate.
关键词： nanograss,TiO2 nanotubes,anodization process,nanomaterials,properties
更新于2025-09-23 15:22:29