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Query: KEGG:D01931 (TiO2)
 11,320 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this study, the photoelectrocatalytic behavior of bromide and generation of bromine using TiO2 was investigated in the separate anode and cathode reaction chambers. Our results show that the generation of bromine begins around a flatband potential of -0.34 V vs. standard calomel electrode (SCE) at pH 3.0 under UV illumination and increases with an increase in positive potential, finally reaching a steady-state concentration at 1.0 V vs. SCE. Maximum bromine formation occurs over the range of pH 4-6, decreasing sharply at conditions where the pH>7.
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PMID:Behavior of bromide in the photoelectrocatalytic process and bromine generation using nanoporous titanium dioxide thin-film electrodes. 1463 54

A new approach involving the introduction of the common cationic surfactant cetyltrimethylammonium bromide (CTAB) for modifying a rutile TiO2 film during its formation from hydrolyzed TiCl4 solution has been adopted, intending to improve the photoelectrochemical properties of the pertinent dye-sensitized solar cell. CTAB-routed films were found to consist of smaller clusters of near-spherical TiO2 particles, compared with larger clusters of long rod-shaped particles in the absence of CTAB. As a consequence, the photocurrent and photovoltage of the cell fabricated by using CTAB have increased significantly, leading to a conversion efficiency increase, compared with those of the cell prepared without CTAB. On the basis of FE-SEM, BET, and XRD analyses, the increases are attributed to decreased particle size, improved interparticle connectivity, and enhanced crystallinity of the CTAB-promoted TiO2 particles and decreased void volume in the film. Faster growth of the TiO2 film was another beneficial effect of CTAB. A mechanism is proposed for the beneficial role of CTAB during the film formation.
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PMID:Beneficial role of cetyltrimethylammonium bromide in the enhancement of photovoltaic properties of dye-sensitized rutile TiO2 solar cells. 1527 95

Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) was used to identify the structures formed during the adsorption of sodium polyacrylate (NaPA) on charged TiO2 particles and to determine the subsequent interaction of the adsorbed polymer structure with cationic and anionic surfactants. The nature of the polymer structure was deduced from the adsorbed amount in tandem with the information obtained from monitoring the change in the relative intensity of the COO- and COOH infrared bands. In particular, it is found that the relative number of COO- and COOH groups on the polymer backbone for the adsorbed state differs from that of the same polymer in solution. This difference is due to a shift in the population of COO-/COOH groups on the polymer backbone that arises when the COO- groups bind to positively charged sites on the surface. A change in the number COO-/COOH groups on the polymer is thus related to a change in the bound fraction of polymer. It is shown that the initial NaPA approaching the bare surface adopts a flat conformation with high bound fraction. Once the bare sites on the surface are covered, the accommodation of additional polymer on the surface requires the existing adsorbed layer to adopt a conformation with a lower bound fraction. When the adsorbed NaPA is probed with a solution containing the anionic surfactant sodium dodecyl sulfate (SDS), the SDS competes for surface sites and displaces some of the bound NaPA segments from the surface, giving rise to an polymer layer adsorbed with an even lower bound fraction. In contrast, addition of a solution containing the cationic surfactant cetyltrimethylammonium bromide (CTAB) results in the binding of the surfactant directly to the free COO- sites on the adsorbed polymer backbone. Confirmation of a direct interaction of the CTAB headgroup with the free COO- groups of the polymer is provided by intensity changes in the headgroup IR bands of the CTAB.
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PMID:Interaction of sodium polyacrylate adsorbed on TiO2 with cationic and anionic surfactants. 1554 81

The X-ray standing wave technique was used to probe the sensitivity of Zn2+ and Sr2+ ion adsorption to changes in both the adsorbed ion coverage and the background electrolyte species and concentrations at the rutile (alpha-TiO2) (110)-aqueous interface. Measurements were made with various background electrolytes (NaCl, NaTr, RbCl, NaBr) at concentrations as high as 1 m. The results demonstrate that Zn2+ and Sr2+ reside primarily in the condensed layer and that the ion heights above the Ti-O surface plane are insensitive to ionic strength and the choice of background electrolyte (with <0.1 A changes over the full compositional range). The lack of any specific anion coadsorption upon probing with Br-, coupled with the insensitivity of Zn2+ and Sr2+ cation heights to changes in the background electrolyte, implies that anions do not play a significant role in the adsorption of these divalent metal ions to the rutile (110) surface. Absolute ion coverage measurements for Zn2+ and Sr2+ show a maximum Stern-layer coverage of approximately 0.5 monolayer, with no significant variation in height as a function of Stern-layer coverage. These observations are discussed in the context of Gouy-Chapman-Stern models of the electrical double layer developed from macroscopic sorption and pH-titration studies of rutile powder suspensions. Direct comparison between these experimental observations and the MUltiSIte Complexation (MUSIC) model predictions of cation surface coverage as a function of ionic strength revealed good agreement between measured and predicted surface coverages with no adjustable parameters.
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PMID:Zn2+ and Sr2+ adsorption at the TiO2 (110)-electrolyte interface: influence of ionic strength, coverage, and anions. 1615 Apr 54

Highly crystalline TiO2 nanorods with lengths of 100-300 nm and diameters of 20-30 nm have been synthesized by a hydrothermal process in a cetyltrimethylammonium bromide surfactant solution. The microstructure measured by X-ray diffraction and high-resolution transmission electron microscopy was a pure highly crystalline anatase phase with a long nanorod shape. The addition of a triblock copolymer poly(ethylene oxide)100-poly(propylene oxide) 65-poly(ethylene oxide)100 (F127) decreased the length of the nanorods and kept the rod shape of the particles even after sintering at high temperatures. The rod shape kept under high calcination temperatures contributed to the achievement of the high conversion efficiency of light-to-electricity as discussed in the paper. A high conversion efficiency of light-to-electricity of 7.29% was obtained with the TiO2 single-crystalline anatase nanorod cell.
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PMID:Dye-sensitized solar cells based on a single-crystalline TiO2 nanorod film. 1647 88

We found that Br-/Br3- is more suitable than an I-/I3- couple in dye-sensitized solar cells in terms of higher open-circuit photovoltage (Voc) production and higher overall energy conversion efficiency (eta) if the dye sensitizer has a more positive potential than that of Br-/Br3-. Under simulated AM1.5 one sun, an eosin Y dye-sensitized solar cell containing 0.4 M LiBr + 0.04 M Br2 electrolyte in acetonitrile yielded a short-circuit photocurrent (Jsc) of 4.63 mA cm(-2), Voc of 0.813 V, and fill factor (FF) of 0.693, corresponding to 2.61% of eta. Under the same conditions except for the electrolyte 0.4 M LiI + 0.04 M I2 in acetonitrile instead, the device produced 1.67% of eta (Jsc = 5.15 mA cm(-2), Voc = 0.451 V, FF = 0.721). Replacement of I-/I3- with Br-/Br3- in eosin Y dye-sensitized solar cells yielded a significant increase in Voc offset by slight decreases in Jsc and FF, leading to an increase in eta by 56%. The significant gain in Voc was attributed to the enlarged energy level difference between the redox potential of the electrolyte and the Fermi level of TiO2 and the suppressed charge recombination as well. The rate for charge recombination between bromine and the injected electrons was determined to be first order in bromine.
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PMID:Efficient eosin y dye-sensitized solar cell containing Br-/Br3- electrolyte. 1685 24

Mesoporous titanium dioxide nanosized powder with high specific surface area and anatase wall was synthesized via hydrothermal process by using cetyltrimethylammonium bromide (CTAB) as surfactant-directing agent and pore-forming agent. The resulting materials were characterized by XRD, nitrogen adsorption, FESEM, TEM, and FT-IR spectroscopy. The as-synthesized mesoporous TiO2 nanoparticles have mean diameter of 17.6 nm with mean pore size of 2.1 nm. The specific surface area of the as-synthesized mesoporous nanosized TiO2 exceeded 430 m2/g and that of the samples after calcination at 600 degrees C still have 221.9 m2/g. The mesoporous TiO2 nanoparticles show significant activities on the oxidation of Rhodamine B (RB). The large surface area, small crystalline size, and well-crystallized anatase mesostructure can explain the high photocatalytic activity of mesoporous TiO2 nanoparticles calcined at 400 degrees C.
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PMID:Synthesis of titanium dioxide nanoparticles with mesoporous anatase wall and high photocatalytic activity. 1686 52

Effects of the addition of a supramolecular assembly of cetyltrimethylammonium bromide in SiO2-TiO2 gel films on the formation of anatase type TiO2 nanocrystals with hot-water treatment were investigated. Anatase nanocrystals were formed in the whole SiO2-TiO2 gel films with the addition of cetyltrimethylammonium bromide by the treatment, whereas the nanocrystals were formed only on the film surface in the case of gel films without cetyltrimethylammonium bromide. Cetyltrimethylammonium bromide molecules in the SiO2-TiO2 gel films were completely removed by the hot-water treatment and the following UV irradiation. In the usual procedure for preparation of porous materials, the removal of template molecular assemblies required high temperature treatment over 400 degrees C. In this system, all the processes were performed at temperatures less than 100 degrees C. Additionally, the porous structure produced by the removal of micellar assembly allowed anatase nanocrystals to be formed inside the films. Therefore, the method presented in this work provides us with the novel photocatalyst coatings of porous membrane with highly-dispersed TiO2 nanocrystals via low temperature process.
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PMID:Effects of addition of supramolecular assembly on the anatase nanocrystalline precipitation of sol-gel derived SiO2-TiO2 coating films by hot-water treatment. 1702 87

Photo-catalytic oxidation with TiO2 as the photo-catalyst is one of the most efficient methods of advanced oxidation for the degradation of organic pollutants. It can completely oxidise many of the persistent organic pollutants into small molecules such as H2O and CO2. However, a number of factors currently limit the large-scale adaptation of the technology in industries. The catalytic activity of TiO2 is normally only effective in the UV irradiation range and it has been difficult to utilise irradiations in higher wavelengths. The immobilisation of the catalyst for large-scale operations has also been difficult and reduces the efficiency of the photo-oxidation reactions. Nanometer particles of TiO2 are highly photo-effective but difficult to recover and reuse. In this paper, mesoporous TiO2 catalyst with an average pore size of 5 nm was prepared by using a tartaric sol-gel method with cetyl trimethyl ammonium bromide as template agent. UV irradiation was also applied during the preparation process to modify the surface characteristics of the photo-catalyst. The catalyst was then analysed and characterised by using a number of techniques. Results indicated that UV irradiation during the preparation process of the mesoporous TiO2 catalyst changed its surface characteristics. It was observed that the UV irradiated TiO2 catalyst has higher absorbance in the visible wavelength region (400-650 nm), indicating a potential shift of the effective photo-catalytic wavelengths.
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PMID:Preparation and characterisation of mesoporous TiO2 photo-catalyst. 1714 62

The effective TiO2 photocatalytic degradation of pyridaben in an acetronitrile/water dispersion has been investigated in previous work, but could not be achieved in the case of real waters. In this paper, photocatalytic degradation of pyridaben on TiO2 particles under UV light (lambda> 360 nm) illumination in surfactant CTAB (cetyltrimethyl ammonium bromide) aqueous dispersions was studied. 1H NMR was used to determine quantitative information about the adsorption mode of pyridaben in CTAB micelles. The results showed that the upfield 1H shifts were largest for long chain protons of CTAB, indicating that the hydrophobic aromatic rings were primarily located in this region. Adsorption models on TiO2 surface were thus proposed. The reaction rates decreased with the increase of pH value, which can be attributed to the surface charge variations of pyridaben adsorbed onto TiO2 particles. The adsorption isotherms at different pH values confirmed that preadsorption on the surface of TiO2 particles was prerequisite for efficient degradation. Furthermore, an oxidation reagent such as H2O2 was added to the photocatalytic system, which may act as an alternative electron acceptor and result in a notably enhanced rate of pollutant destruction. On the basis of intermediates identified by GC/MS, a degradation pathway was proposed.
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PMID:Photocatalytic degradation of pesticide pyridaben. 3. In surfactant/TiO2 aqueous dispersions. 1726 57


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