超临界合成Pt修饰的TiO2用于光催化CO2还原制备太阳能燃料

考察了超临界条件下合成TiO2基光催化剂的性质,尤其是在超临界CO2下得到的分散在TiO2上Pt的特性,并与商品化TiO2性能进行了比较.另外,所得催化剂的光催化活性用CO2光还原制太阳能燃料进行了评价.结果表明,该催化剂可得到具有比商用TiO2更好或类似的性能(高比表面积、结晶度、表面羟基浓度,大的孔容、增强的可见光吸收、高的甲烷生成速率)而用于CO2还原制备燃料的反应中.这可归因于该催化剂超临界介质合成过程.     

Photocatalytic activity of silver-modified titanium dioxide at solid–liquid and solid–gas interfaces

Silver-modified titania samples (Ag–TiO₂) with varying silver content (0.1–1.0 wt%) were prepared. Silver-modification of titanium dioxide was examined by TEM, XRD, XPS and DR-UV–vis spectroscopy. Ag or AgO_x particles on TiO₂ surface could not be observed by XRD and TEM investigation, however the color of the Ag–TiO₂ samples varied between light rose and purple-brown. XPS measurements revealed that silver exists mainly in oxide form. The photocatalytic activity of pure and Ag–TiO₂ samples were compared both in solid–liquid and in solid–gas interfaces. In the liquid phase the 2,2′-thiodiethanol was used as test molecule. Ethanol photodegradation was examined in gas phase at dry initial condition. It was shown that the rate of photooxidation of organic compounds significantly enhanced by silver-modification of titania.     

A study of the effect of the synthesis conditions of titanium dioxide on its morphology and cell toxicity properties

In this study, titanium dioxide nanoparticles (NPs) were synthesized using the home microwave method, and the effect of the microwave irradiation time on the structure of NPs was investigated. In addition, the morphological effect of these NPs on the toxicity of HDMSCs cells was investigated. The crystalline structure and morphology of the NPs were analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FE-SEM); the cytotoxicity was determined by the methyl thiazolyl tetrazolium (MTT) assay. X-ray diffraction analysis revealed that all thin films had a polycrystalline nature with an anatase phase of TiO₂. It was also found that the crystallite size increased with increasing microwave radiation time. The FTIR spectrum showed Ti-O-Ti properties by the peak in the range between 527 and 580 cm^?1. Further, the FE-SEM images showed that the grain size increased with increasing irradiation time. The MTT assay results showed that the accumulation of NPs leads to toxicity.     

Fabrication and superhydrophobicity of fluorinated titanium dioxide nanocoatings

This study demonstrates the fabrication of a stable superhydrophobic surface with low contact angle hysteresis (CAH) using an arrangement of nanoscale TiO₂ spheres. The control of precursor quantity is selected as the key factor in determining surface roughness that significantly intensifies water contact angle (CA) of TiO₂ films. After surface fluorination treatment, the anatase-type crystalline surfaces exhibit good water repellency (CA 166.1°), low CAH (6°), and superhydrophobic stability (>60 min). Enhanced water repellency is attributed to the fact that the higher density of TiO₂ spheres results in more tortuous three-phase contact line, leading to the self-cleaning effect. Such a unique textured surface imparts many promising potentials for engineering and the development of optics devices with robust superhydrophobic materials.     

Thick titanium dioxide films for semiconductor photocatalysis

Thick paste TiO₂ films are prepared and tested for photocatalytic and photoinduced superhydrophilic (PSH) activity. The films are effective photocatalysts for the destruction of stearic acid using near or far UV and all the sol–gel films tested exhibited a quantum yield for this process of typically 0.15%. These quantum yields are significantly greater (4–8-fold) than those for titania films produced by an APCVD technique, including the commercial self-cleaning glass product Activ™. The films are mechanically robust and optically clear and, as photocatalysts for stearic acid removal, are photochemically stable and reproducible. The kinetics of stearic acid photomineralisation are zero order with an activation energy of ca. 2.5 kJ mol⁻¹. All titania films tested, including those produced by APCVD, exhibit PSH. The light-induced fall, and dark recovery, in the water droplet contact angle made with titania paste films are similar in profile shape to those described by others for thin titania films produced by a traditional sol–gel route.     

A new sensor for ammonia based on cyanidin-sensitized titanium dioxide film operating at room temperature

Design and fabrication of an ammonia sensor operating at room temperature based on pigment-sensitized TiO₂ films was described. TiO₂ was prepared by sol–gel method and deposited on glass slides containing gold electrodes. Then, the film immersed in a 2.5 × 10⁻⁴ M ethanol solution of cyanidin to absorb the pigment. The hybrid organic–inorganic formed film here can detect ammonia reversibly at room temperature. The relative change resistance of the films at a potential difference of 1.5 V is determined when the films are exposed to atmospheres containing ammonia vapors with concentrations over the range 10–50 ppm. The relative change resistance, S, of the films increased almost linearly with increasing concentrations of ammonia (r = 0.92). The response time to increasing concentrations of the ammonia is about 180–220 s, and the corresponding values for decreasing concentrations 240–270 s. At low humidity, ammonia could be ionized by the cyanidin on the TiO₂ film and thereby decrease in the proton concentration at the surface. Consequently, more positively charged holes at the surface of the TiO₂ have to be extracted to neutralize the adsorbed cyanidin and water film. The resistance response to ammonia of the sensors was nearly independent on temperature from 10 to 50 °C. These results are not actually as good as those reported in the literature, but this preliminary work proposes simpler and cheaper processes to realize NH₃ sensor for room temperature applications.     

Photocatalytic and magnetic titanium dioxide/polystyrene/magnetite composite hybrid polymer particles

Novel multifunctional titanium dioxide (TiO₂)/polystyrene/magnetite composite hybrid polymer particle dispersions with TiO₂ nanoparticles in the surface and magnetite nanoparticles encapsulated inside the polymer matrix were produced by Pickering miniemulsion polymerization in one single step. Whereas TiO₂ nanoparticles were used to impart photocatalytic functionality and colloidal stability, magnetite nanoparticles were incorporated to allow an easy extraction for recovery and reuse of the composite multifunctional particles. The morphology of the composite particles was assessed by scanning transition electron microscopy (STEM) and energy‐dispersive X‐ray spectroscopy (EDX). The paramagnetism of the particles was analyzed using a SQUID magnetometer and their photocatalytic activity was assessed by degrading methylene blue (MB) solutions under UV light and by recovering and reusing of the particles in five consecutive cycles. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3350–3356     

The photostability of wool doped with photocatalytic titanium dioxide nanoparticles

Photoyellowing of wool is a serious problem for the wool industry. This study assessed the role of photocatalytic nanocrystalline titanium dioxide (P-25) as a potential antagonist or catalyst in the photoyellowing of wool. Untreated, bleached and bleached and fluorescent-whitened wool slivers were processed into fine wool powders for the purpose of even and intimate mixing with the TiO₂ nanoparticles in the solid state. Pure wool and wool/TiO₂ mixtures were then compressed into solid discs for a photoyellowing study under simulated sunlight and under UVB and UVC radiations. Yellowness and photo-induced chemiluminescence (PICL) measurements showed that nanocrystalline TiO₂ could effectively reduce the rate of photoyellowing by inhibiting free radical generation in doped wool, and that a higher concentration of TiO₂ contributed to a lower rate of photooxidation and reduced photoyellowing. Hence nanocrystalline TiO₂ acts primarily as a UV absorber on wool in dry conditions and not as a photocatalyst.     

Adsorption of tricarboxylic acid biosurfactant derived from spiculisporic acid on titanium dioxide surface

In the present study, adsorption isotherms of a polycarboxylic-acid-type biosurfantant, the sodium salt of (2-(2-carboxyethyl)-3-decyl maleic anhydride) (DCMA-3Na), on TiO₂, zeta potential, and changes in particle aggregate size as a function of biosurfactant concentration, solid-liquid ratio and pH were systematically investigated. The adsorption of DCMA-3Na on the surface of TiO₂ shows a relatively weak dependence on pH, unlike the adsorption behavior of chemically-synthesized surfactants. Adsorption of DCMA-3Na still occurs at pH above the isoelectric points of TiO₂ due to the buffering capacity, which is due to three carboxylate functional groups in the hydrophilic moiety of DCMA-3Na. Since DCMA-3Na has three anionic head groups, the zeta potential of TiO₂ at pH 3 decreases very steeply from positive to negative values as the surface charges are neutralized by the adsorption of biosurfactants. Trends in zeta potentials as a function of equilibrium DCMA-3Na concentration are quite closely related to the changes in flocculation of individual TiO₂ particles.     

Influence of transition metal-doped titanium(IV) dioxide on the photodegradation of polyethylene

The effects of adding dispersed powders of various forms of titanium(IV) dioxide on the photodegradation of polyethylene have been examined from the following points of view: effect of crystal form, concentration of pigment, transition metal ion, dopant concentration, calcination temperature of pigment, and pigment coating.The rate of photodegradation of polyethylene is reduced by adding certain grades of TiO₂ such as coated TiO₂ particles or TiO₂ doped with small percentages of Cr or Mn ions. The rate is increased on adding TiO₂ doped with V and especially Mo or W ions. The anatase form of TiO₂ is more photoactive than the rutile form, and the effect of increasing the calcination temperature of the pigment is to reduce photoactivity by boosting the rutile fraction. The concentration dependences of the degradation rates are complex, but can be directly related to the percentage of anatase achieved after calcination. Even the most aggressive of the metal-doped pigments are less photoactive than the Degussa P25 material, containing both rutile and anatase.     

Photodimerization and photooxygenation of 9-vinylcarbazole catalyzed by titanium dioxide and magnesium perchlorate

<正>Photoreaction of 9-vinylcarbazole in acetonitrile in the presence of titanium dioxide and a catalytic amount of magnesium perchlorate gave 3,6-di(9-carbazolyl)-1,2-dioxane as a photooxygenated product via photodimerization of 9-vinylcarbazole.The photoreaction proceeds via an electron transfer mechanism,where magnesium perchlorate accelerated formation of the photo-oxygenated product.     

Exploration of silver decoration concentration to enhance photocatalytic efficiency of titanium dioxide photocatalysts

Ag decoration on TiO₂ is favorable to absorption of visible light and wider absorption range. Ag nanoparticles playing the role of electron receivers on TiO₂ surface enhance photodegradation. However, excess Ag nanoparticles caused reduced specific surface area of photocatalysts and increased probability of charge recombination, resulting in lower photocatalytic efficiency. In this study, the influence of various Ag decoration concentrations on photocatalytic activity was investigated. Surface treatment by nitric acid after Ag decoration was performed to avoid excessive Ag deposition. The extent of Ag elimination and its impacts on photocatalytic activity were also explored. An optimum Ag content in the photocatalyst was achieved and photocatalytic efficiency was obviously improved. It was found that the number of calcination times affected the crystallinity and stability of photocatalysts. Better photocatalytic efficiency could be obtained after twice calcinations.     

Influence of transition metal-doped titanium(IV) dioxide on the photodegradation of polystyrene

The effects of adding dispersed powders of various forms of titanium(IV) dioxide on the photodegradation of polystyrene have been examined using FT-IR spectroscopy from the following points of view: effect of crystal form, concentration of pigment, transition metal ion, dopant concentration, calcination temperature of pigment, and pigment coating.The rate of photodegradation of polystyrene is reduced by adding certain grades of TiO₂ such as coated TiO₂ particles or TiO₂ doped with small percentages of Cr or Mn ions. The rate is increased on adding TiO₂ doped with V and especially Mo or W ions. The anatase form of TiO₂ is more photoactive than the rutile form, as is the effect of increasing the calcination temperature of the pigment. The concentration dependences of the degradation rates are complex, but can be directly related to the percentage of anatase achieved after calcination. Even the most aggressive of the metal-doped pigments are less photoactive than a Degussa P25 material, containing rutile and anatase.     

Photocatalysed degradation of uracil in aqueous titanium dioxide suspensions: mechanisms, pH and cadmium chloride effects

Upon UV irradiation, in O₂ saturated aqueous titanium dioxide suspensions, uracil is almost completely mineralised. Most of the organic compounds occurring during the photodegradation process have been identified by means of liquid chromatography and mass spectrometry coupled techniques (LC–MS). The first step of the mineralisation leads to the formation of uracilglycol. Then, the main products generated during the photodegradation exhibit new functions such as polyol, carboxylic and aldehyde. The presence of urea has been clearly evidenced. At the end of the process, the ultimate step is the formation of nitrate and ammonium ions. The formation kinetics of intermediate products are modified by pH variation and CdCl₂ addition.     

Photocatalytic decomposition of tetrachloroethylene in the gas phase with titanium dioxide as catalyst

The gas phase photocatalytic destruction of tetrachloroethylene (PCE) was investigated by using an in situ photocatalytic reactor with FT-IR analysis in batch mode. The main products of PCE degradation are CO₂ and COCl₂, with trichloroacetylchloride as an intermediate. It was found that the rate of PCE degradation and the appearance of products in the gas phase are highly dependent on their adsorption properties on the surface of the catalyst, besides other reaction conditions, such as the intensity of irradiation and the composition of the reaction mixture.     

Photoactivity of mechanochemically prepared nanoparticulate titanium dioxide investigated by EPR spectroscopy

Titanium dioxide nanopowders were prepared by mechanochemical synthesis in a high-energy ball mill using TiOSO₄·xH₂O and Na₂CO₃ followed by annealing in the temperature range 200–800 °C. The UVA photonic efficiency of radical processes on synthesized TiO₂ powders was determined by in situ EPR spectroscopy, using, as indicators, the N-oxide spin trapping agents (5,5-dimethyl-1-pyrroline N-oxide and 5-(diisopropoxy-phosphoryl)-5-methyl-1-pyrroline N-oxide) or the radical cation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate, ABTS⁺). The results obtained by monitoring the photoinduced generation of hydroxyl radical spin adducts correlated with those found by the investigation of the photoreduction of ABTS⁺. The presence of iron and chromium ions, which were evidenced in samples milled in steel, decreased the photonic efficiency of radical processes. The presence of a sulfate salt matrix during the annealing process distinctly inhibits the transformation of anatase to rutile. The highest photocatalytic activity was shown by anatase samples which were prepared by milling in corundum and annealed at 700 °C. They were composed of crystallites with a mean size of 25–30 nm and well developed crystal faces.     

Hydrogen production from water by visible light using zinc porphyrin-sensitized platinized titanium dioxide

The rate of H₂ evolution from aqueous suspensions of Pt/TiO₂ with deposited zinc porphyrin in the presence of an electron donor (EDTA, triethanolamine, ascorbic and oxalic acids) during irradiation by visible light (λ > 520 nm) was optimized with respect to the concentrations of platinum, zinc porphyrin and electron donor. The relationship between the rate of hydrogen evolution and pH has a maximum at pH 4–5 for EDTA, ascorbic and oxalic acids, as does the adsorption of these donors on TiO₂. In the case of triethanolamine, H₂ production increases sharply in alkaline solutions when the triethanolamine molecules are deprotonated. The photostability of the photosensitizer increases on the semiconductor. Turn-over numbers for the zinc porphyrins varied from 50 for water-soluble zinc porphyrin up to 150–185 for water-insoluble sensitizers.     

Monitoring of potential cytotoxic and inhibitory effects of titanium dioxide using on-line and non-invasive cell-based impedance spectroscopy

Titanium dioxide (TiO₂) nanoparticles (NPs) with different sizes and structures were probed for plausible cytotoxicity using electric cell-substrate impedance sensing (ECIS), a non-invasive and on-line procedure for continuous monitoring of cytotoxicity. For insect cells (Spodoptera frugiperda Sf9), the ECIS₅₀ values, i.e., the concentration required to achieve 50% inhibition of the response, differed depending on the size and shape of the TiO₂ nanostructure. The lowest ECIS₅₀ value (158 ppm) was observed for the needle shaped rutile TiO₂ (10 nm × 40 nm, 15.5 nm nominal particle size), followed by 211 ppm for P-25 (34.1 nm, 80% anatase and 20% rutile), 302 ppm for MTI5 (5.9 nm, 99% anatase) and 417 ppm for Hombitan LW-S bulk TiO₂ (169.5 nm, 99% anatase). Exposure of TiO₂ NPs to UV light at 254 nm or 365 nm exhibited no significant effect on the ECIS₅₀ value due to the aggregation of TiO₂ NPs with diminishing photocatalytic activities. Chinese hamster lung fibroblast V79 cells, exhibited no significant cytotoxicity/inhibition up to 400 ppm with P25, MTI₅ and bulk TiO₂. However, a noticeable inhibitory effect was observed (ECIS₅₀ value of 251 ppm) with rutile TiO₂ as cell spreading on the electrode surface was prevented     

Adsorbate-substrate interaction between chlorodifluoromethane and titanium dioxide: Infrared spectroscopy and density functional theory studies

Infrared spectra of chlorodifluoromethane (CHClF₂) adsorbed on titanium dioxide (TiO₂) at room temperature have been investigated for the first time. From the comparison between the adsorption characteristics and the gas-phase spectra it can be deduced that the molecule interacts with the surface Lewis acid site (Ti⁴⁺) mainly through the Cl atom even if also the adsorption with one F atom is also observed. Moreover, the spectra show the presence of H-bonds between the CH group and the surface Lewis basic site (OH⁻ or O²⁻). In order to obtain more information on the molecule orientation and the variation of the structural parameters, a DFT-B3LYP study has been carried out considering the anatase (1 0 1) surface and evaluating the adsorption energetics in terms of interaction, distortion and binding energies. The obtained geometries confirm that both the acid-base interactions through Cl or F atoms are possible and suggest the formation of one H-bond between the CH group of the molecule and the Lewis basic site of the surface. The calculated vibrational frequencies of the adsorbed molecule have been found to be in reasonable agreement with the experimental data.     

Rheology and UV-protecting properties of complex suspensions of titanium dioxides and zinc oxides

Ultra-fine particles of titanium dioxide (TiO(2)) and zinc oxides (ZnO) are very attractive as UV-protecting ingredients in cosmetic products. The UV-scattering behavior of complex suspensions in a silicone oil is studied in relation to rheological properties. To control the dispersion stability of suspensions, three polyoxyethylene (POE)-modified silicones of branch-type, (AB)(n)-type, and ABA-type are used as dispersants. Irrespective of molecular structure, the dispersants can stabilize the TiO(2) and ZnO particles and the flow of both single suspensions is Newtonian with low viscosity. However, the Newtonian flow profiles and high dispersion states are maintained only for complex suspensions prepared with ABA-type dispersant. Since the POE groups which are incorporated between terminal silicones groups attach to the particle surfaces, the steric stabilization is responsible for low viscosity and high dispersions. Because the UV scattering of suspensions is determined by the sizes of flocculated structures, the high transmittance in the visible ranges and low transmittance in the UVA and UVB ranges can be achieved in the presence of ABA-type dispersant.