44,859 research outputs found

    Metallic and Insulating Adsorbates on Graphene

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    We directly compare the effect of metallic titanium (Ti) and insulating titanium dioxide (TiO2) on the transport properties of single layer graphene. The deposition of Ti results in substantial n-type doping and a reduction of graphene mobility by charged impurity scattering. Subsequent exposure to oxygen largely reduces the doping and scattering by converting Ti into TiO2. In addition, we observe evidence for short-range scattering by TiO2 impurities. These results illustrate the contrasting scattering mechanisms for identical spatial distributions of metallic and insulating adsorbates

    Fouling and inactivation of titanium dioxide-based photocatalytic systems

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    Copyright © 2015 Taylor & Francis Group, LLC. Titanium dioxide is an effective photocatalyst for the breakdown of many environmental contaminants. The complex mixtures that can occur in water matrices can significantly affect the breakdown of the contaminants in water by titanium dioxide (TiO2). The authors discuss a wide variety of foulants and inhibitors of photocatalytic TiO2 systems and review different methods that can be effective for their fouling prevention. Approaches to regenerate a fouled or contaminated TiO2 catalysts are explored and the effect of substrates on immobilized titanium dioxide is also reviewed

    An investigation into the effect of thickness of titanium dioxide and gold-silver nanoparticle titanium dioxide composite thin-films on photocatalytic activity and photo-induced oxygen production in a sacrificial system

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    Thin films of titanium dioxide and titanium dioxide with incorporated gold and silver nanoparticles were deposited onto glass microscope slides, steel and titanium foil coupons by two sol–gel dip-coating methods. The film's photocatalytic activity and ability to evolve oxygen in a sacrificial solution were assessed. It was found that photocatalytic activity increased with film thickness (from 50 to 500 nm thick samples) for the photocatalytic degradation of methylene blue in solution and resazurin redox dye in an intelligent ink dye deposited on the surface. Contrastingly, an optimum film thickness of [similar]200 nm for both composite and pure films of titanium dioxide was found for water oxidation, using persulfate (S2O82−) as a sacrificial electron acceptor. The nanoparticle composite films showed significantly higher activity in oxygen evolution studies compared with plain TiO2 films

    Influence of Doping of Titanium Dioxide by Zirconium and Niobium on its Morphology

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    Structure porosity and specific surface area of undoped and doped nanodispersed titanium dioxide with Zr, Nb was investigated. The porous structure of TiO2 is caused by its intervals between nanoparticles and their agglomerates. Surface morphology of obtained materials was determined by isotherms of nitrogen adsorption-desorption. Specific surface area of nanodispersed titanium dioxide, according to the results, consists 182 m2/g. It was found, that during doping of titanium dioxide with zirconium comparing to origin TiO2 specific surface increases in 30 %, and for niobium-doped decreases in 20 %. Pore-size distribution for TiO2 correspond to the value of 10-15 nm. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3553

    Fabrication of dye Rhoeospathacea with concentration variation in dye-sensitized solar cells (DSSC)

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    Dye-sensitized solar cell (DSSC) is a device that directly converts visible light into electrical energy. In this work we used dye was extracted from Rhoeo spathacea. A natural dye was directly mixed with TiO2 anatase to obtain dyed titanium dioxide which can be used as photoanode for DSSC by varying the volume of dye. The first variation is 2 ml dye mixed with 1 ml of TiO2, and the second variation is 3 ml dye mixed with 1 ml of TiO2. The absorbance spectra of the dye and dye titanium dioxide have been investigated by spectroscopy UV-Visible Lambda 25 and the conversion efficiency of dye titanium dioxide used Keithley 2602A meter. The DSSC based on dye titanium dioxide with varying volume of dye showed that the efficiency of the the second variation is 0,033% which is higher than the first variation (0,023%) as obtained from I-V characterization.

    Effect of Annealing Temperature On Iron Doped Titanium Dioxide Thin Films Prepared By Spin Coating Technique

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    Iron (Fe) doped titanium dioxide (TiO2) thin films have been successfully deposited by using spin coating technique. X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) were employed to characterize the microstructure and crystallite morphology of the films. It was indicated that the rutile crystal orientation appears due to increasing annealing temperature of the thin films. Furthermore, increasing annealing temperature of the thin films yielded an increasing of porosity value which is related to the application on gas sensor films. Keywords: Iron doped titanium dioxide, Spin coating, Porosity valu

    Tunable Functionality and toxicity studies of Titanium Dioxide Nanotube Layers

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    In this work, we have developed economic process to elaborate scalable titanium dioxide nanotube layers which show a tunable functionality. The titanium dioxide nanotube layers was prepared by electrochemical anodization of Ti foil in 0.4 wt% hydrofluoric acid solution. The nanotube layers structure and morphology were characterized using x-ray diffraction and scanning electron microscopy. The surface topography and wettability was studied according to the anodization time. The sample synthesized while the current density reached a local minimum displayed higher contact angle. Beyond this point, the contact angles decrease with the anodization time. Photo-degradation of acid orange 7 in aqueous solution was used as a probe to assess the photo-catalytic activity of titanium dioxide nanotube layers under UV irradiation. We obtained better photocatalitic activity for the sample elaborate at higher current density. Finally we use the Ciliated Protozoan T. pyriformis, an alternative cell model used for in vitro toxicity studies, to predict the toxicity of titanium dioxide nanotube layers in biological system. We did not observe any characteristic effect in the presence of the titanium dioxide nanotube layers on two physiological parameters related to this organism, non-specific esterases activity and population growth rate

    Comparative study of arsenic removal efficiency from water by adsorption and photocatalytic oxidation with titanium dioxide

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    Titanium dioxide, a well-known adsorbent material, has been extensively tested in environmental applications, especially in separation technologies. In the present study, TiO2 nanoparticles were synthesized by using sol-gel method for removing arsenic ions from water. Several water/titanium molar ratios were prepared in order to obtain optimum crystalline structure, morphology, and particle size of titanium dioxide nanoparticles. Two types of TiO2 minerals which were rutile and anatese were mainly synthesized at different calcination temperatures. After characterization of synthesized powders by X-ray diffraction and scanning electron microscopy (SEM), batch adsorption experiments were carried out to analyze removal capacity of the titanium nanoparticles. The maximum % of removal of arsenic was found ~77% at pH 3, respectively when 0.1 g rutile type TiO2 nanoparticles were used at the As0 5 ppm. Anatase type of TiO2 nanoparticles had also closer adsorption capacity which was ~63% at pH 6 with the same initial arsenic concentration. In the light of experimental results, titanium dioxide nanoparticles (TiO2) are found as a promising adsorbent material for arsenic removal from water. However, the effectiveness of TiO2 nanoparticles in removing arsenic species from water have been enhanced by the photocatalytic oxidation by conversion of arsenide ions (As3+) to arsenate ions (As5+), which adsorbs more strongly onto the solid phase of adsorbent than arsenite ions (As3+). Therefore, in the present study the photocatalytic oxidation of As3+ to As5+ is investigated in UV-illuminated and solar irradiated TiO2. Residual arsenic concentrations of the solutions treated with titanium dioxide nanoparticles were measured with a Varian, Vista-Pro CCD simultaneous inductively coupled plasma ICP-OES spectrophotometer. The adsorption isotherms, thermodynamic and kinetic parameters with and without presence of photocatalytic oxidation reaction are obtained to analyze arsenic removal capacity of the TiO2 nanoparticles
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