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An Optical Emission Spectroscopy Study of Plasma–Precursor Interactions in Solution Precursor Plasma Spray
摘要： In this work, optical emission spectroscopy is used to study plasma–liquid precursor interactions in a plasma spray process. A mapping of the plasma jet is performed with a bundle of seven optical fibers while injecting various liquid precursors. The decomposition of two suspensions containing a titania (TiO2) powder in different solvents and that of one solution containing titanium butoxide is analyzed inside a radio frequency thermal plasma. For each precursor, the evolution of both temperature and titanium density along the plasma jet is observed. Two different plasma compositions were used to study their effects on the precursor decomposition. For each experiment, x-ray diffraction was performed on the collected powder to correlate OES observations with the structure and composition of the powder. Comparing these results brings a new understanding of the precursor decomposition inside the plasma, while the noted contrasts between water and ethanol as solvent, and between the use of a powder and that of an alkoxide as a source of titanium, help to assess the effect of these parameters on the plasma spray process.
关键词： titanium dioxide,optical emission spectroscopy,suspension plasma spray,plasma–precursor interactions,solution precursor plasma spray
更新于2025-09-09 09:28:46
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Dark-blue titanium dioxide: Effect of phenothiazine on structural and optical properties of nanocrystalline anatase TiO2
摘要： We studied the effect of the phenothiazine (PTZ) surface doping on the structural and optical properties of nanocrystalline titanium dioxide powder with a single anatase phase (A-TiO2). We found that the mixing and interaction of PTZ and A-TiO2 leads to the intense dark-blue color of PTZ-doped A-TiO2 (A/PTZ). The appearance of new bands in the Fourier transform IR spectrum indicated the formation of PTZ?+ radical cations and reduced Ti3+species as well as extra oxygen vacancies (VO) in the TiO2 matrix. The UV-vis absorption spectrum of A/PTZ exhibited a strong increase in absorption in the visible region (>400 nm). The doping of A-TiO2 with PTZ causes a noticeable redshift of the absorption edge and a significant narrowing of the band gap by 0.24 and 0.49 eV for direct and indirect electronic transitions, respectively. The photoluminescence spectra show that the photoluminescence originating from Ti3+ and [VO-Ti3+] states for A/PTZ is much stronger than for A-TiO2, but the excitonic photoluminescence of A/PTZ is quenched. An increased number of surface defects in A/PTZ can essentially increase the nonradiative charge recombination and photoluminescence quenching, and therefore may considerably enhance the photoactivity of the dark-blue TiO2 in the visible range of the spectrum.
关键词： Optical properties,Spectroscopy,Phenothiazine,Titanium dioxide,Nanostructures
更新于2025-09-09 09:28:46
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Characterisation and photocatalytic assessment of TiO2 nano-polymorphs: Influence of crystallite size and influence of thermal treatment on paint coatings and dye fading kinetics
摘要： A study on the thermal effects on TiO2 rutile and anatase nano-powders was undertaken and displayed some unusual photoactivity and crystal structure properties. Rutile nano-particles with different crystallite sizes were characterised and the possible effect on activity were investigated. One of the rutile samples appeared to have trace amounts of anatase and was annealed at high temperatures at 1172 K and 1272 K to highlight the thermodynamic stability phenomenon of titania. Parallel to this study, anatase nano-particles were investigated before and after being annealed up to 1022 K. For all the samples used in this work, characterisation was undertaken using micro-Raman microscopy/XRD and Scanning Electron Microscopy (SEM) while photoactivity assessment was made by measuring and monitoring the photodegradation of a mixture of dye methyl-orange (MeO) and nano-powders under UV-light for 3h30 minutes in suspension. The study revealed that rutile nano-powder samples were thermodynamically stable even at very high temperatures and poorly active but with an unusual photoactive feature. Concerning the anatase samples; SEM investigation revealed a questioning size growth as the samples showed a different particle size depending on the temperature of thermal treatment. It revealed that annealing at 672 K seemed to be a key temperature as the particles change from a polyhedral structure to a two-dimensional structure showing a platelet like shape. The photocatalytic studies of the anatase nano-particles showed a very high activity especially before annealing. This highlighted the fact that the anatase phase can subsist at high temperatures such as 1022 K and exhibit a persistence in photoactivity even though it has decreased significantly after 672 K. SEM analysis was in accordance with the photoactivity investigation. Nevertheless, the most interesting feature of the results emanates from the reaction order study and rate constant analysis taken from the kinetic shape of the graph of the degradation of MeO as a function of the irradiation time for the different particle sized rutile nanoparticles. Here a zero-order reaction was determined and as a consequence raised questions about the theory of the mechanism of the activities of titania in terms of surface chemistry, surface area dependence and photoactivity. For example, for the nano-rutiles the sample with a 25 nm crystallite size was the most active and the sample with the smallest crystallite size (15nm) was the least active and yet was found to contain trace levels of nano-anatase. This effect was also substantiated by UV absorption and weathering studies on doped isocyanate-acrylic paint films. UV analysis clearly shows that the absorptivity of the nanoparticles plays a role and correlates with the photoactivity. The 15nm particles have decreased absorptivity in the near UV and hence decreased activity.
关键词： nano-particles,titanium dioxide,crystal size,temperature treatment,anatase,isocyanate-acrylic paint,methyl orange,rutile,photocatalysis
更新于2025-09-09 09:28:46
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Modeling and Optimization of the Photocatalytic Reduction of Molecular Oxygen to Hydrogen Peroxide over Titanium Dioxide
摘要： This study focuses on understanding the mechanisms for optimization of the photocatalytic hydrogen peroxide production over TiO2 (Aeroxide P25). Via precise control of the reaction parameters (pH, temperature, catalyst amount, oxygen content, sacrificial electron donor and light intensity) it is possible to tune either the apparent quantum yield or the production rate. As a result of the optimization, apparent quantum yields of up to 19.8 % and production rates of up to 83 μM min-1 were obtained. We also observed a light dependent change of the reaction order and an interdependency of the light intensity and catalyst amount and developed a well-fitting kinetic model for it, which might also be applied to other reactions. Furthermore, a previously unreported inactivation of the photocatalyst in case of water oxidation is described.
关键词： titanium dioxide (TiO2),hydrogen peroxide (H2O2),oxygen reduction,catalyst inactivation,light intensity,photocatalysis
更新于2025-09-09 09:28:46
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CO2 Adsorption Property of Amine-Modified Amorphous TiO2 Nanoparticles with a High Surface Area
摘要： Carbon dioxide capture and storage (CCS) technologies have attracted a great deal of attention as effective measures to prevent global warming. Adsorption methods using porous materials seem to have several advantages over the liquid absorption methods. In this study, we have developed a synthesis method of new amorphous titanium dioxide (TiO2) nanoparticles with a diameter of 3 nm, a high surface area of 617 m2/g and a large amount of OH groups. Next, the surface of the amorphous TiO2 nanoparticles was modified using ethylenediamine to examine whether CO2 adsorption increases. Amorphous TiO2 nanoparticles were successfully modified with ethylenediamine, which was used in excess due to the presence of a large amount of hydroxyl groups. The amorphous TiO2 nanoparticles modified with ethylenediamine show a higher CO2 adsorption capacity (65 cm3/g at 0 ?C, 100 kPa) than conventional TiO2 and mesoporous SiO2. We discuss the origin of the higher CO2 adsorption capacity in terms of the high specific surface area of the amorphous TiO2 nanoparticles and the modification with ethylenediamine on the surface of the amorphous TiO2 nanoparticles. The optimization of the amount of ethylenediamine bound on the particles increased the CO2 adsorption capacity without pore blocking.
关键词： titanium dioxide,nanoparticles,amorphous,ethylenediamine modification,CO2 adsorption
更新于2025-09-09 09:28:46
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High Photoconversion Efficiency Obtained from Novel TiO2 Photoanodes
摘要： High photoconversion efficiency for photoelectrochemical water splitting was obtained using nanocaves TiO2 and highly uniformed TiO2 nanotubes. The photoanodes were synthesized via electrochemical anodization of a titanium foil in a glycerol-based solution containing NH4F at 10 V. Pulse electrodeposition was used to incorporate Cu ions into the uniform TiO2 nanotubes. The photoconversion efficiency performance was examined under simulated visible light illumination (? ≥ 380 nm) in a 1 M solution of NaOH. The photocurrent density, the Mott-Schottky, the EIS, and the photoconversion efficiency measurements were determined. The highest photocurrent density i.e. 5.77 mA cm-2 at 1.23 V vs. RHE was obtained from nanocaves TiO2 photoanode. The incorporation of Cu resulted in a reduction in photocatalytic activity of the oxygen evaluation reaction (OER) and an increase of the hydrogen evolution reaction (HER).
关键词： Titanium dioxide nanotubes,water splitting,Photocurrent density,Photoelectrochemical,Anodization
更新于2025-09-09 09:28:46
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Impact of Hydrogen Peroxide on Photocatalytic Destruction of Anionic SAS in a Reactor with Immobilized TiO2
摘要： Using sodium dodecylbenzenesulfonate the article showed high efficiency of photocatalytic system H2O2/TiO2/UV for deep destruction (~ 90% in terms of TOC) of anionic SAS in a aqueous medium (C0 = 50 mg/dm3, pH0 5.9) in a reactor containing wide-porous ceramic block with immobilized TiO2 on its surface. The TiO2 film for a long time preserved a stable photocatalytic activity
关键词： titanium dioxide,sodium dodecylbenzolsulfonate,hydrogen peroxide,photocatalysis,oxidation,anionic SAS
更新于2025-09-09 09:28:46
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Effect of TiO2 on highly elastic, stretchable UV protective nanocomposite films formed by using a combination of k-Carrageenan, xanthan gum and gellan gum
摘要： The hydrogel based composite film was prepared from k-carrageenan (k-C), xanthan gum (X) and gellan gum (G) by solvent casting method. The transparent films made from these gellable materials with synergistic hydrogel composition have soft texture, good elasticity and excellent break strength. The k-C/X/G based nanocomposite films prepared from different weight ratio of TiO2 nanoparticles were characterized for new packaging materials. The morphology, structure and microstructure properties of the k-C/X/G and TiO2 nanocomposite films were characterized by FT-IR, XRD and SEM analysis. By the incorporation of TiO2 in the k-C/X/G nanocomposite films, the tensile strength, tensile modulus, Tg and thermal stability of the films were greatly enhanced. Due to the hydrophobic nature of the TiO2 nanoparticles there is an increase in contact angle whereas moisture content of the films decreased. The water vapor permeability (WVP) and ultra violet lights transmittance decrease upon increasing the TiO2 content. The k-C/X/G and TiO2 nanocomposites effectively shield the UV light, exhibited partial microbial activity against Staphylococcus aureus and have a high potential for the application in food and non-food industries as UV shielding packaging materials.
关键词： nanocomposites,titanium dioxide,thermal properties,gellan gum,xanthan gum,water barrier properties,mechanical properties,k-Carrageenan
更新于2025-09-09 09:28:46
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TiO2-SiO2-PMMA Terpolymer Floating Device for the Photocatalytic Remediation of Water and Gas Phase Pollutants
摘要： Floating photocatalytic devices are highly sought-after as they represent good candidates for practical application in pollutant remediation of large water basins. Here, we present a multilayer floating device for the photocatalytic remediation of contaminants present in water as well as of volatile species close to the water surface. The device was prepared on a novel tailored ter-polymer substrate based on methylmethacrylate, α-methylstyrene and perfluoroctyl methacrylate. The ad hoc synthesized support presents optimal characteristics in terms of buoyancy, transparency, gas permeability, mechanical, UV and thermal stability. The adhesion of the TiO2 top layer was favoured by the adopted casting procedure, followed by a corona pre-treatment and by the deposition of an intermediate SiO2 layer, the latter aimed also at protecting the polymer support from photocatalytic oxidation. The device was characterized by contact angle measurement, UV-vis transmittance and scanning electron microscopy. The final device was tested for the photocatalytic degradation of an emerging water pollutant as well as of vapors of a model volatile organic compound. Relevant activity was observed also under simulated solar irradiation and the device showed good stability and recyclability, prospecting its use for the photocatalytic degradation of pollutants in large water basins.
关键词： titanium dioxide,tetracycline,ethanol,composite,photocatalytic oxidation,polymethylmethacrylate
更新于2025-09-09 09:28:46
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<i>In vitro</i> evaluation of visible light-activated titanium dioxide photocatalysis for in-office dental bleaching
摘要： The evaluation of the photocatalysis of visible light activated titanium dioxide employed in hydrogen peroxide (H2O2) was carried using seven H2O2 solutions (3.5 and 35%) and/or methylene blue (MB), with or without light irradiation (LI); the absorbance of MB was the bleaching indicator. Color analysis was performed on bovine teeth (n=12) using two different concentrations of H2O2, 6 and 35% associated with titanium dioxide (TiO2). Data were analyzed with one and two-way ANOVA, and significance level of p<0.05. Solutions containing MB, H2O2 at 3.5 or 35%, and TiO2, followed by LI, showed significant difference when compared with other groups. Greater MB reduction was found in 35% concentration. H2O2 35%+TiO2 gel showed no difference in comparison to control group. All groups for the color analysis assay showed ΔE higher than 3.3. In conclusion, TiO2 and H2O2 association is a promisor alternative for reducing the clinical time of in-office dental bleaching.
关键词： Hydrogen peroxide,Tooth bleaching,Titanium dioxide
更新于2025-09-09 09:28:46