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Sample records for photocatalytic nano-crystalline titania

  1. Synthesis and photocatalytic activity of titania microspheres with hierarchical structures

    SciTech Connect

    Cheng, Qian-Qian; Cao, Ying; Yang, Lin; Zhang, Pei-Pei; Wang, Kui; Wang, Hua-Jie

    2011-03-15

    Research highlights: {yields} Lauryl alcohol directs the formation of titania with hierarchical structures. {yields} Hierarchical structures endow the higher specific area to titania. {yields} Titania had a higher photocatalytic activity than commercial Degussa P25. {yields} The synthesis process of the target product is low-cost. -- Abstract: A combined sol-gel and solvothermal process was introduced to fabricate the titania microspheres with hierarchical structures by using lauryl alcohol as the structure-directing agent. Scanning electron microscope, high-resolution transmission electron microscope, Fourier transform infrared spectrograph and powder X-ray powder diffraction indicated that the molar ratio of lauryl alcohol, water and tetra-n-butyl titanate was the key factor for the formation of the mono-dispersed titania with anatase phase and the optimal ratio was 1.2:4:1. The diameter of the end-product was 523 {+-} 74 nm and it was composed of smaller nanoparticles with about 6.8 nm size in diameter. Photocatalytic activity of the end-product was investigated by employing Rhodamine B and Methylene blue as the model compounds. The target microspheres exhibited the higher photocatalytic efficiency compared with commercial Degussa P25 titania and this result might be due to the hierarchical structures of microspheres according to the analysis of Brunauer-Emmett-Teller specific surface areas.

  2. Photocatalytic activity of titania coatings synthesised by a combined laser/sol–gel technique

    SciTech Connect

    Adraider, Y.; Pang, Y.X.; Nabhani, F.; Hodgson, S.N.; Sharp, M.C.; Al-Waidh, A.

    2014-06-01

    Highlights: • Sol–gel method was used to prepare titania coatings. • Titania thin films were coated on substrate surface by dip coating. • Fibre laser was employed to irradiate the titania coated surfaces. • Photocatalytic efficiency of titania coatings was significantly improved after laser processing. - Abstract: Titania coatings were prepared using sol–gel method and then applied on the substrate surface by dip coating. Fibre laser (λ = 1064 nm) in continuous wave mode was used to irradiate the titania coated surfaces at different specific energies. The ATR-FTIR, XRD, SEM, EDS and contact angle measurement were employed to analyse surface morphology, phase composition and crystalline structure of laser-irradiated titania coatings, whilst the photocatalytic activity was evaluated by measuring the decomposition of methylene blue (MB) after exposure to the visible light for various illumination times. Results showed that the laser-irradiated titania coatings demonstrate significant different composition and microstructure in comparison with the as-coated from the same sol–gel titania. Photocatalytic efficiency of titania coatings was significantly improved after laser processing. The photocatalytic activity of laser-irradiated titania coatings was higher than that of the as-coated titania. The titania coating processed at laser specific energy of 6.5 J/mm{sup 2} exhibited the highest photocatalytic activity among all titania samples.

  3. Engineering titania nanostructure to tune and improve its photocatalytic activity.

    PubMed

    Cargnello, Matteo; Montini, Tiziano; Smolin, Sergey Y; Priebe, Jacqueline B; Delgado Jaén, Juan J; Doan-Nguyen, Vicky V T; McKay, Ian S; Schwalbe, Jay A; Pohl, Marga-Martina; Gordon, Thomas R; Lu, Yupeng; Baxter, Jason B; Brückner, Angelika; Fornasiero, Paolo; Murray, Christopher B

    2016-04-12

    Photocatalytic pathways could prove crucial to the sustainable production of fuels and chemicals required for a carbon-neutral society. Electron-hole recombination is a critical problem that has, so far, limited the efficiency of the most promising photocatalytic materials. Here, we show the efficacy of anisotropy in improving charge separation and thereby boosting the activity of a titania (TiO2) photocatalytic system. Specifically, we show that H2 production in uniform, one-dimensional brookite titania nanorods is highly enhanced by engineering their length. By using complimentary characterization techniques to separately probe excited electrons and holes, we link the high observed reaction rates to the anisotropic structure, which favors efficient carrier utilization. Quantum yield values for hydrogen production from ethanol, glycerol, and glucose as high as 65%, 35%, and 6%, respectively, demonstrate the promise and generality of this approach for improving the photoactivity of semiconducting nanostructures for a wide range of reacting systems. PMID:27035977

  4. Photocatalytic activity of a hierarchically macro/mesoporous titania.

    PubMed

    Wang, Xinchen; Yu, Jimmy C; Ho, Chunman; Hou, Yidong; Fu, Xianzhi

    2005-03-15

    Light-harvesting macroporous channels have been successfully incorporated into a mesoporous TiO(2) framework to increase its photocatalytic activity. This bimodal porous material was characterized by X-ray diffractometry in both low-angle and wide-angle ranges, N(2) adsorption-desorption analysis, scanning and transmission electron microscopy, FT-IR, and diffuse reflectance spectroscopy. Ethylene photodegradation in gas-phase medium was employed as a probe reaction to evaluate the photocatalytic reactivity of the catalysts. The results reveal that sintering temperature significantly affects the structural stability and photocatalytic activity of titania. The catalyst which calcined at 350 degrees C possessed an intact macro/mesoporous structure and showed photocatalytic reactivity about 60% higher than that of commercial P25 titania. When the sample was calcined at 500 degrees C, the macroporous structure was retained but the mesoporous structure was partly destroyed. Further heating at temperatures above 600 degrees C destroyed both macro- and mesoporous structures, accompanied by a loss in photocatalytic activity. The high photocatalytic performance of the intact macro/mesoporous TiO(2) may be explained by the existence of macrochannels that increase photoabsorption efficiency and allow efficient diffusion of gaseous molecules. PMID:15752052

  5. Photocatalytic Degradation of Azo Dyes using Doped Titania Fibers

    NASA Astrophysics Data System (ADS)

    Shanmugasundaram, Prasad

    Photo-catalytic degradation using semiconductor particle as dispersion in aqueous medium has been gaining increased attention over the past several years. Their versatility in application makes them unique along with their easy processing techniques and low cost. Titania semiconductor is one of the most important members of this family. It has been widely used for various applications ranging from environmental to bio-medical. Titanium dioxide has gained importance as an effective photo-catalyst because of its advantages over other semiconductor oxides which include high photo-stability, inexpensive, reusable property, chemical and biological inertness, high reactivity, non-toxicity, corrosion resistance, operation at ambient temperatures and its ability to treat trace level pollutants. Its use as a photocatalyst is primarily because of its band gap of 3.0-3.3 eV which can be effectively activated under ultraviolet radiation (wavelength lambda < 400 nm), which leads to electron jump from valence to conduction band. This project aims at developing electrospun titania fibers doped with copper in order to study and demonstrate photocatalytic activity in the visible light spectrum, resulting in quick formation of holes which are ready to react with water to form -OH radicals. A comparative study of pure titania and copper doped titania for degradation of azo dyes were carried out. SEM, EDAX, XRD were carried out to thoroughly understand the structure of the fibers. The photocatalytic activity measurements for different dyes were noted using Uv-Vis method. The fibers when fully developed will be disposable photocatalytic materials for degrading dyes, Organic pollutants and for bio-medical applications when exposed to visible light.

  6. In vitro apatite formation on nano-crystalline titania layer aligned parallel to Ti6Al4V alloy substrates with sub-millimeter gap.

    PubMed

    Hayakawa, Satoshi; Matsumoto, Yuko; Uetsuki, Keita; Shirosaki, Yuki; Osaka, Akiyoshi

    2015-06-01

    Pure titanium substrates were chemically oxidized with H2O2 and subsequent thermally oxidized at 400 °C in air to form anatase-type titania layer on their surface. The chemically and thermally oxidized titanium substrate (CHT) was aligned parallel to the counter specimen such as commercially pure titanium (cpTi), titanium alloy (Ti6Al4V) popularly used as implant materials or Al substrate with 0.3-mm gap. Then, they were soaked in Kokubo's simulated body fluid (SBF, pH 7.4, 36.5 °C) for 7 days. XRD and SEM analysis showed that the in vitro apatite-forming ability of the contact surface of the CHT specimen decreased in the order: cpTi > Ti6Al4V > Al. EDX and XPS surface analysis showed that aluminum species were present on the contact surface of the CHT specimen aligned parallel to the counter specimen such as Ti6Al4V and Al. This result indicated that Ti6Al4V or Al specimens released the aluminum species into the SBF under the spatial gap. The released aluminum species might be positively or negatively charged in the SBF and thus can interact with calcium or phosphate species as well as titania layer, causing the suppression of the primary heterogeneous nucleation and growth of apatite on the contact surface of the CHT specimen under the spatial gap. The diffusion and adsorption of aluminum species derived from the half-sized counter specimen under the spatial gap resulted in two dimensionally area-selective deposition of apatite particles on the contact surfaces of the CHT specimen. PMID:25989935

  7. Photoactive transparent nano-crystalline glass-ceramic for remazole red dye degradation

    SciTech Connect

    Gad-Allah, Tarek A.; Margha, Fatma H.

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► Preparation and characterization of novel transparent nanocrystalline glass-ceramic. ► Precipitation of photoactive phases by using controlled heat-treatment. ► Conservation of transparency along with photoactivity. ► Using the prepared nanocrystalline glass-ceramic in water purification. -- Abstract: Transparent glass ceramic material was prepared from alkali-borosilicate glass containing titania by proper heat treatment scheme. The prepared samples were characterized using differential thermal analysis, X-ray diffraction, transmission electron microscope, selected area electron diffraction and UV–visible spectroscopy. The applied heat treatment program allowed the crystallization of nano-crystalline anatase, rutile, barium titanate, titanium borate and silicate phases while maintaining the transparency. The precipitated nano-crystalline anatase and rutile phases were responsible for the observed high photocatalytic activity of the prepared samples. Samples of 24.29 and 32.39 TiO{sub 2} wt% showed better efficiency for the decolorization of remazole red dye compared with commercial-TiO{sub 2} used in preparation of glass-ceramic. The reuse of prepared glass-ceramic photocatalyst with nearly same efficiency for different times was also proved.

  8. Titania produced from Ti-salt flocculated sludge: photocatalytic activity under solar light.

    PubMed

    Shon, Ho Kyong; Okour, Yousef; Park, Se Min; Kim, Jong Beom; Kim, Jong-Ho

    2014-08-01

    In this study, titania photocatalyst was produced from the wastewater sludge of Ti-salt flocculation. The high photocatalytic activity of titania reported was evaluated based on a single organic substrate. However, the photocatalytic activity is a substrate-specific; one photocatalyst showed different photocatalytic degradation rates for different substrates. Thus, to investigate the substrate-specific photocatalytic activity of titania, various substrates of humic acid (HA), dichloroacetic acid (DCA), rhodamine B (RhB), metsulfuron methyl (M&M) and phenol were used under simulated solar light irradiation. Results showed titania had a high activity rate for RhB, moderate activity for HA and DCA and low activity for M&M and phenol indicating substrate-specific activities. When compared with Degussa-P25, titania showed higher activity for M&M, while the opposite was observed for HA and phenol. The specific-substrate behaviour of titania could depend on specific physicochemical and electronic interactions between titania, substrates, and their intermediates compounds formed. PMID:25936122

  9. Hollow mesoporous titania microspheres: New technology and enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Feng, Zhenliang; Wei, Wenrui; Wang, Litong; Hong, Ruoyu

    2015-12-01

    Hollow titania microspheres (HTS) were fabricated via a sol-gel process by coating the hydrolysis product of titanium tetrabutoxide (TBOT) onto the amino (-NH2) modified porous polystyrene cross-linked divinyl benzene (PS-DVB) microspheres under changing atmospheric pressure, followed by calcination in nitrogen and air atmosphere. Particularly, the atmospheric pressure was continuously and regularly changed during the formation process of PS-DVB@TiO2 microspheres. Then the TiO2 particles were absorbed into the pores and onto the surface of PS-DVB as well. The resultant HTS (around 2 μm in diameter) featured a high specific surface area (84.37 m2/g), anatase crystal and stable hollow microsphere structure, which led to high photocatalysis activity. The photocatalytic degradation of malachite green (MG) organic dye solution was conducted under ultraviolet (UV) light irradiation, which showed a high photocatalytic ability (81% of MG was degraded after UV irradiation for 88 min). Therefore, it could be potentially applied for the treatment of wastewater contaminated by organic pollutants.

  10. Preparation of hollow titania spheres and their photocatalytic activity under visible light.

    PubMed

    Liu, Chun; Yin, Hengbo; Shi, Liping; Wang, Aili; Feng, Yonghai; Shen, Linqin; Wu, Zhanao; Wu, Gang; Jiang, Tao

    2014-09-01

    Hollow titania spheres with different shell thicknesses were facilely prepared starting from TiCl4 and using ploystyrene methyl acrylic acid latexes as the sacrificial templates. The average diameters of the hollow titania spheres ranging from 294 to 340 nm were tuned by changing the weight ratios of TiO2 to ploystyrene methyl acrylic acid latex from 0.8:1 to 1.4:1. The hollow titania spheres were constructed by the small-sized anatase TiO2 nanoparticles with the average diameter of ca. 18 nm (SEM). In addition to UV light absorption caused by the primary anatase TiO2 nanoparticles, the hollow titania spheres also had visible light absorption performance. Photocatalytic results showed that all the hollow titania spheres had higher photocatalytic activity for the degradation of phenol under visible light irradiation than the commercial TiO2 nanoparticles (P25). The photocatalytic activity of the hollow titania spheres increased with the increase in sell thickness, being consistent with their visible light absorbance. The visible light photocatalytic activity was probably due to the presence of additional energy levels between valence and conduction bands, which were caused by the formation of oxygen bridging bonds between the primary TiO2 nanoparticles. PMID:25924373

  11. Photocatalytic properties of CoOx-loaded nano-crystalline perovskite oxynitrides ABO2N (A = Ca, Sr, Ba, La; B = Nb, Ta)

    NASA Astrophysics Data System (ADS)

    Oehler, Florian; Ebbinghaus, Stefan G.

    2016-04-01

    Highly crystalline niobium- and tantalum-based oxynitride perovskite nanoparticles were obtained from hydrothermally synthesized oxide precursors by thermal ammonolysis at different temperatures. The samples were studied with respect to their morphological, optical and thermal properties as well as their photocatalytic activity in the decomposition of methyl orange. Phase pure oxynitrides were obtained at rather low ammonolysis temperatures between 740 °C (CaNbO2N) and 1000 °C (BaTaO2N). Particle sizes were found to be in the range 27 nm-146 nm and large specific surface areas up to 37 m2 g-1 were observed. High photocatalytic activities were found for CaNbO2N and SrNbO2N prepared at low ammonolysis temperatures. CoOx as co-catalyst was loaded on the oxynitride particles resulting in a strong increase of the photocatalytic activities up to 30% methyl orange degradation within 3 h for SrNbO2N:CoOx.

  12. Macrostructure-dependent photocatalytic property of high-surface-area porous titania films

    SciTech Connect

    Kimura, T.

    2014-11-01

    Porous titania films with different macrostructures were prepared with precise control of condensation degree and density of the oxide frameworks in the presence of spherical aggregates of polystyrene-block-poly(oxyethylene) (PS-b-PEO) diblock copolymer. Following detailed explanation of the formation mechanisms of three (reticular, spherical, and large spherical) macrostructures by the colloidal PS-b-PEO templating, structural variation of the titania frameworks during calcination were investigated by X-ray diffraction and X-ray photoelectron spectroscopy. Then, photocatalytic performance of the macroporous titania films was evaluated through simple degradation experiments of methylene blue under an UV irradiation. Consequently, absolute surface area of the film and crystallinity of the titania frameworks were important for understanding the photocatalytic performance, but the catalytic performance can be improved further by the macrostructural design that controls diffusivity of the targeted molecules inside the film and their accessibility to active sites.

  13. Preparation and visible light photocatalytic activity of N-doped titania.

    PubMed

    Hu, Yulong; Liu, Hongfang; Chen, Weiran; Chen, Debin; Yin, Jiwei; Guo, Xingpeng

    2010-03-01

    N-doped titania powders were prepared with titanium tetraisopropoxide (TTIP) as the titanium source and urea as the nitrogen source by the sol-gel method. The samples were characterized using X-ray diffraction (XRD), diffuse reflectance spectrum (DRS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The XRD and TEM results indicated that urea played an important role in controlling the size and aggregation process of titania nanoparticles. As an appropriate amount of urea was added into the titania sol, the size of the particles decreased. However, the excess urea reduced the dispersion of the particles and resulted in the aggregation. At the same time, the size of particle increased, and the size distribution broadened. The XPS and DRS results showed that the nitrogen was incorporated into titania lattice successfully, which brought about the redshift of the absorption edge and induced the photocatalytic activity in the visible light region. The photocatalytic experiments showed that the N-doped titania nanoparticles could effectively photodegrade methyl orange (MO) aqueous solution under visible light irradiation. The photocatalytic activity increased with the increase of the nitrogen doping level in the titania lattice, but decreased with the increase of the particle size and the organic surface residues caused by excess urea. PMID:20355662

  14. Effect of calcination temperature on the photocatalytic reduction and oxidation processes of hydrothermally synthesized titania nanotubes.

    SciTech Connect

    Viayan, B.; Dimitrijevic, N. M.; Rajh, T.; Gray, K.; Northwestern Univ.

    2010-08-05

    Titania nanotubes having diameters 8 to 12 nm and lengths of 50-300 nm were prepared using a hydrothermal method. Further, the titania nanotubes were calcined over the temperature range 200-800 C in order to enhance their photocatalytic properties by altering their morphology. The calcined titania nanotubes were characterized by using X-ray diffraction and surface area analysis and their morphological features were studied by scanning and transmission electron microscopy. Nanotubes calcined at 400 C showed the maximum extent of photocatalyitc reduction of carbon dioxide to methane, whereas samples calcined at 600 C produced maximum photocatalytic oxidation of acetaldehyde. Electron paramagnetic resonance (EPR) spectroscopy was used to interrogate the effects of nanotube structure on the charge separation and trapping as a function of calcination temperature. EPR results indicated that undercoordinated titania sites are associated with maximum CO{sub 2} reduction occurring in nanotubes calcined at 400 C. Despite the collapse of the nantube structure to form nanorods and the concomitant loss of surface area, the enhanced charge separation associated with increased crystallinity promoted high rates of oxidation of acetaldehyde in titania materials calcined at 600 C. These results illustrate that calcination temperature allows us to tune the morphological and surface features of the titania nanostructures for particular photocatalytic reactions.

  15. The immobilization of titania nanoparticles on hyaluronan films and their photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Pasqui, Daniela; Atrei, Andrea; Barbucci, Rolando

    2009-01-01

    We have developed a method to bind titania nanoparticles onto hyaluronic films (HA) photoimmobilized on silanized glass. Titania nanoparticles were deposited on the HA films from commercially available dispersions by casting and dip-coating methods at various pH values. XPS was used to monitor the deposition of titania and to estimate the surface coverage of the nanoparticles. The topography of the titania-modified HA films was investigated by means of AFM. XPS results indicate that the titania surface coverage depends on the preparation method and the pH of the dispersion. We found that the maximum titania nanoparticle surface coverage was obtained by the casting method with the formation of aggregates and multilayers of particles. The titania surface coverage for the surfaces prepared by the dip-coating method is pH-dependent. The surfaces prepared at pH 2 show a surface coverage of 65% and a rather uniform distribution of particles. We found that titania nanoparticles are anchored in a stable way to the HA substrate in a phosphate buffer solution (PBS) and that the interaction between the HA and the titania is through the carbonyl group of carboxylates and amidic groups of the polymer. AFM images clearly show that titania nanoparticles are uniformly distributed over the HA films. By measuring the average diameter and the average height of the nanoparticles deposited on HA films it appears that the particles are partially embedded in the polysaccharide films. The results of the study on the photobleaching of methylene blue indicate that the characteristic photocatalytic activity of titania is maintained when the nanoparticles are anchored to the HA substrate.

  16. Single-step preparation, characterization and photocatalytic mechanism of mesoporous Fe-doped sulfated titania

    NASA Astrophysics Data System (ADS)

    Yang, Ying; Zhong, Hui; Tian, Congxue; Jiang, Zhiqiang

    2011-07-01

    Mesoporous Fe-doped sulfated titania photocatalysts were prepared by one-step thermal hydrolysis of industrial titanyl sulfate and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and N2 adsorption-desorption techniques. The effects of the m(Fe)/m(TiO2) on the structures of the titania photocatalysts were investigated. The photocatalytic activity of the mesoporous Fe-doped sulfated titania catalysts was evaluated using the photooxidation of methylene blue in aqueous solutions under UV light irradiation. The results indicated that Fe3+ substitutes Ti4+ in titania lattice, which induced the formation of oxygen vacancies. The oxygen vacancies are favorable to the dissociation adsorption H2O and formation of surface hydroxyl group. Fe3+ captures the photoinduced electrons or holes that are conductive to the efficient separation of the photogenerated carriers, but too many doping Fe3+ will promote recombination of the photogenerated carrier. Sulfur species in the form of sulfate are incorporated into the network of Tisbnd Osbnd Ti and coordinated to titania in bidentate model, resulting in the strong inductive effect, large specific surface area, and mesoporous structure. All these are beneficial to improve the photocatalytic activities of the mesoporous Fe-doped sulfated titania photocatalysts.

  17. Effects of calcining temperature on photocatalytic activity of Fe-doped sulfated titania.

    PubMed

    Yang, Ying; Tian, Congxue

    2012-01-01

    Using industrial titanyl sulfate as a raw material, Fe-doped sulfated titania (FST) photocatalysts were prepared by using the one-step thermal hydrolysis method and characterized using XRD, SEM, TGA-DSC, FTIR, UV-Vis DRS and N(2) adsorption-desorption techniques. The effects of calcining temperature on the structure of the titania were investigated. The photocatalytic activity of the FST was evaluated using the photodegradation of methylene blue and photooxidation of phenol in aqueous solutions under UV and visible light irradiation, respectively. The results evinced that Ti(4+) is substituted by Fe(3+) in titania lattice and forms impurity level within the band gap of titania, which consequently induces the visible light absorption and visible-light-driven photocatalytic activity. The synergistic effects of Fe-doping and sulfation are beneficial to the efficient separation of the photogenerated carriers and also improve the quantum efficiency of photocatalysis. In addition, Brönsted acidity arisen from the strong inductive effect of sulfate is also conducive to enhancing the photocatalytic performance of FST. However, when the calcining temperature is higher than 800°C, sulfur species and surface hydroxyl groups decompose and desorb from FST and the specific surface area decreases sharply. Moreover, severe sintering and rutile phase formation occur simultaneously. All these are detrimental to photocatalytic activity of FST. PMID:22486465

  18. Preparation of gold/silver/titania trilayered nanorods and their photocatalytic activities.

    PubMed

    Horiguchi, Yoshimasa; Kanda, Takashi; Torigoe, Kanjiro; Sakai, Hideki; Abe, Masahiko

    2014-01-28

    Gold/silver/titania trilayered nanorods have been prepared by the successive deposition of silver and titania layers on gold nanorod cores, and their photocatalytic activities were investigated under visible-light illumination (λ > 420 nm). The photocatalytic activity of the trilayered nanorods in the oxidation of 2-propanol depends on both the Au/Ag composition and the thickness of the TiO2 shell. It increases with increasing Ag content up to [Au]/[Ag] = 1:5 (molar ratio) and then decreases with further increasing Ag content. The photocatalytic activity also increases with increasing TiO2 shell thickness up to 10 nm and then decreases with further increases in the shell thickness. These effects were explained by electron-transfer and energy-transfer mechanisms. PMID:24401090

  19. Augmented photocatalytic activity and luminescence response of Tb³⁺ doped nanoscale titania systems

    SciTech Connect

    Paul, Nibedita; Deka, Amrita; Mohanta, Dambarudhar

    2014-10-14

    The present work reports on the effect of Tb³⁺ doping on the luminescence and photocatalytic performance of nano-structured titania derived through a sol-gel route. X-ray diffraction patterns have revealed the existence of anatase phase with and without Tb³⁺ doping and with an improved orientation factor along (004) and (200) planes. Transmission electron microscopy and selective area electron diffraction studies, while exhibiting ample poly-crystallinity feature, have predicted an average particle size of ~9 nm and ~6 nm for the un-doped and 5% Tb³⁺ doped nano-titania samples; respectively. Apart from emissions accompanied by different types of defects, Tb³⁺ related transitions, such as, ⁵D₃ → ⁷F₅, ⁵D₃ → ⁷F₄, and ⁵D₄ → ⁷F₆ were identified in the photoluminescence spectra. Brunauer-Emmett-Teller surface area analysis, as carried out on a Tb³⁺ doped nano-titania system, has demonstrated a more-open hysteretic loop owing to significant difference of N₂ adsorption/desorption rates. The photocatalytic activity of nano-titania, as evaluated from the nature of degradation of methyl orange under UV illumination, exhibited the highest efficiency for a Tb³⁺ doping level of 2.5%. The augmented photocatalytic degradation has also been discussed in the light of a model based on pseudo first-order kinetics.

  20. Synthesis of nano titania particles embedded in mesoporous SBA-15: characterization and photocatalytic activity.

    PubMed

    Yang, Jun; Zhang, Jun; Zhu, Liwei; Chen, Shaoyuan; Zhang, Yuanming; Tang, Yu; Zhu, Yulei; Li, Yongwang

    2006-09-21

    Supported nanocrystalline titanium dioxide (TiO2) has been prepared by a post-synthesis step via Ti-alkoxide hydrolysis through the use of mesoporous SBA-15 silica. TiO2/SBA-15 composites with various TiO2 loading have been prepared and characterized by X-ray diffraction, nitrogen adsorption, Fourier transform infrared spectroscopy and diffusive reflective UV-vis spectroscopy. The addition of mesoporous SBA-15 prevents the anatase to rutile phase transformation and the growth of crystal grain. TiO2 did not block the SBA-15 pores, and their surface was fully accessible for nitrogen adsorption. Calcination in air of the composites up to 800 degrees C did not change the nanocrystal phase and slightly increased the domain size from 5.0 to 7.5 nm, indicating that the anatase TiO2 grains in the mesostructures have a relatively high thermal stability and proper pore diameter allows controlling the size of obtained titania particles. The TiO2/SBA-15 composites prepared by this study showed much higher photodegradation ability for methylene blue (MB) than commercial pure TiO2 nanoparticles P-25. Experimental results indicate that the photocatalytic activity of titania/silica mixed materials depends on the adsorption ability of composite and the photocatalytic activity of the titania, and there is an optimal ratio of Ti:Si, too high or low Ti:Si ratio will lower the photodegradation ability of the composites. PMID:16621269

  1. Synthesis and Characterisation of Silica-Modified Titania for Photocatalytic Decolouration of Crystal Violet.

    PubMed

    Shahid, Mohammad; El Saliby, Ibrahim; Tijing, Leonard D; McDonagh, Andrew; Park, Se Min; Lee, Kwang Young; Shon, Ho Kyong; Kim, Jong-Ho

    2015-07-01

    In the past few years, silica-modified titania has drawn increasing attention due to their special properties making them ideal candidates for a wide range of applications. In this study, we report a novel method for the synthesis of silica-modified titania by a sol-gel method using sodium silicate solution (1 M). The hydrolysis and condensation reactions of titanium dioxide (TiO2, Degussa Aeroxide® P25) in sodium silicate solution proceeded with citric acid (3 M) as a catalyst. The orbital shaking method was followed for the removal of sodium salt formed during the sol-gel process. Solvent exchange was carried out using methanol and hexane. Finally, chemical modification of the gel was conducted using trimethylchlorosilane followed by ambient pressure drying. The obtained silica-modified titania was characterised for nanostructural analysis using scanning electron microscopy and transmission electron microscopy. The nitrogen adsorption-desorption measurements were employed to investigate the BET surface area, pore structure and pore volume of specimens. Thermal gravimetric analysis showed exothermic peaks at temperature range of 90-190 °C representing the oxidation of organic groups from--Si-R network. The silica-modified titania showed high photocatalytic activity and an easy recovery using crystal violet as model water pollutant. PMID:26373134

  2. Titania by spray pyrolysis for photocatalytic destruction of organics in aqueous solutions

    SciTech Connect

    Fotou, G.P.; Himebaugh, L.; Kodas, T.T.; Wu, M.

    1996-12-31

    In this study, the potential of spray pyrolysis and spray calcination for the synthesis of effective titanium dioxide photocatalysts is explored. The product titanium dioxide powders were used in the photoassisted oxidation of salicylic acid in aqueous solutions. Titania particles were produced by spray pyrolysis of dihydroxybis titanium solutions in water at concentrations between 20 to 70% by volume at temperatures from 500 to 1100{degrees}C. Powders were made by spray calcination of titanium hydrolysate solutions at temperatures from 700 to 900 {degrees}C. Spray pyrolysis produced titania particles which were partially hollow. Spray calcination resulted in agglomerates which consisted of 15 nm primary particles that showed high photoactivity in the photooxidation of aqueous salicylic acid solutions. Doping with palladium oxide or ruthenium oxides did not improve the photocatalytic activity of these powders. 6 refs., 3 figs.

  3. Impact of ultrasonic dispersion on the photocatalytic activity of titania aggregates

    PubMed Central

    Babick, Frank; Kühn, Klaus; Nguyen, Minh Tan; Stintz, Michael; Cuniberti, Gianaurelio

    2015-01-01

    Summary The effectiveness of photocatalytic materials increases with the specific surface area, thus nanoscale photocatalyst particles are preferred. However, such nanomaterials are frequently found in an aggregated state, which may reduce the photocatalytic activity due to internal obscuration and the extended diffusion path of the molecules to be treated. This paper investigates the effect of aggregate size on the photocatalytic activity of pyrogenic titania (Aeroxide® P25, Evonik), which is widely used in fundamental photocatalysis research. Well-defined and reproducible aggregate sizes were achieved by ultrasonic dispersion. The photocatalytic activity was examined by the color removal of methylene blue (MB) with a laboratory-scale setup based on a plug flow reactor (PFR) and planar UV illumination. The process parameters such as flow regime, optical path length and UV intensity are well-defined and can be varied. Our results firstly show that a complete dispersion of the P25 aggregates is not practical. Secondly, the photocatalytic activity is not further increased beyond a certain degree of dispersion, which probably corresponds to a critical size for which UV irradiation can penetrate the aggregate without significant obscuration. PMID:26734533

  4. Impact of ultrasonic dispersion on the photocatalytic activity of titania aggregates.

    PubMed

    Le, Hoai Nga; Babick, Frank; Kühn, Klaus; Nguyen, Minh Tan; Stintz, Michael; Cuniberti, Gianaurelio

    2015-01-01

    The effectiveness of photocatalytic materials increases with the specific surface area, thus nanoscale photocatalyst particles are preferred. However, such nanomaterials are frequently found in an aggregated state, which may reduce the photocatalytic activity due to internal obscuration and the extended diffusion path of the molecules to be treated. This paper investigates the effect of aggregate size on the photocatalytic activity of pyrogenic titania (Aeroxide(®) P25, Evonik), which is widely used in fundamental photocatalysis research. Well-defined and reproducible aggregate sizes were achieved by ultrasonic dispersion. The photocatalytic activity was examined by the color removal of methylene blue (MB) with a laboratory-scale setup based on a plug flow reactor (PFR) and planar UV illumination. The process parameters such as flow regime, optical path length and UV intensity are well-defined and can be varied. Our results firstly show that a complete dispersion of the P25 aggregates is not practical. Secondly, the photocatalytic activity is not further increased beyond a certain degree of dispersion, which probably corresponds to a critical size for which UV irradiation can penetrate the aggregate without significant obscuration. PMID:26734533

  5. Iron phthalocyanine modified mesoporous titania nanoparticles for photocatalytic activity and CO2 capture applications.

    PubMed

    Ramacharyulu, P V R K; Muhammad, Raeesh; Praveen Kumar, J; Prasad, G K; Mohanty, Paritosh

    2015-10-21

    An iron(II)phthalocyanine (Fepc) modified mesoporous titania (Fepc-TiO2) nanocatalyst with a specific surface area of 215 m(2) g(-1) has been synthesized by a hydrothermal method. Fepc-TiO2 degrades one of the highly toxic chemical warfare agents, sulfur mustard (SM), photocatalytically under sunlight with an exposure time of as low as 70 min. Furthermore, the mesoporous Fepc-TiO2 also captured 2.1 mmol g(-1) of CO2 at 273 K and 1 atm. PMID:26393761

  6. Water-plasma-assisted synthesis of black titania spheres with efficient visible-light photocatalytic activity.

    PubMed

    Panomsuwan, Gasidit; Watthanaphanit, Anyarat; Ishizaki, Takahiro; Saito, Nagahiro

    2015-06-01

    Black titania spheres (H-TiO2-x) were synthesized via a simple green method assisted by water plasma at a low temperature and atmospheric pressure. The in situ production of highly energetic hydroxyl and hydrogen species from water plasma are the prominent factors in the oxidation and hydrogenation reactions during the formation of H-TiO2-x, respectively. The visible-light photocatalytic activity toward the dye degradation of H-TiO2-x can be attributed to the synergistic effect of large-surface area, visible-light absorption and the existence of oxygen vacancies and Ti(3+) sites. PMID:25946395

  7. Study on the effect of different acids on the structure and photocatalytic activity of mesoporous titania

    NASA Astrophysics Data System (ADS)

    Ao, Yanhui; Xu, Jingjing; Fu, Degang

    2009-10-01

    Nanocrystalline mesoporous titania was synthesized via a combined sol-gel process with surfactant-assisted templating method using cetyltrimethyl ammonium bromide (CTAB) as the structure-directing agent. The process was catalyzed by different acid (hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid). The prepared samples were characterized by XRD, TEM, BET and FT-IR. The photocatalytic activity of the samples was determined by degradation of phenol in aqueous solution. Results showed that different acid had different effect on the structure and crystal phase of the samples. The sample adjusted by phosphoric acid showed highest surface area and photocatalytic activity. The formation mechanism of the samples catalyzed by different acid was also discussed.

  8. Photocatalytic properties of porous titania grown by oblique angle deposition

    NASA Astrophysics Data System (ADS)

    Riley, M. J.; Williams, B.; Condon, G. Y.; Borja, J.; Lu, T. M.; Gill, W. N.; Plawsky, J. L.

    2012-04-01

    High surface area nanorods of titanium dioxide were grown by oblique angle deposition on a transparent substrate to investigate their effectiveness as photocatalytic agents for the destruction of organic contaminants in air and water. Optical transmission measurements were made that allowed for an estimation of the porosity of the film (75%-78%). Comparing transmission measurements with those from a dense anatase film showed that the penetration depth for the light into the nanorod film was 2.5 times that in a dense, anatase film. The photocatalytic degradation of indigo carmine dye on the porous films was shown to depend on film thickness and annealing conditions. The effectiveness of the film was assessed by observing the change in absorbance of the dye at 610 nm over time and quantifying the film performance using a pseudo-first-order reaction rate model. Reaction rates increased as the film thickness increased from 600 nm to 1000 nm, but leveled out or decreased at thicknesses beyond 1500 nm. A transport/reaction model was used to show that there exists an optimal geometry that maximizes the overall reaction rate and that such a geometry can be simply produced using glancing angle deposition. The nanorod films were benchmarked against nanoparticle films and were shown to perform as well as 0.73 g/L of 25-nm-diameter anatase nanoparticles with surface area of 50 m2/g.

  9. Fabrication of nanocomposites composed of silver cyanamide and titania for improved photocatalytic hydrogen generation.

    PubMed

    Meng, Hao; Li, Xiaoxue; Zhang, Xia; Liu, Yufeng; Xu, Yan; Han, Yide; Xu, Junli

    2015-12-14

    Highly efficient composite photocatalysts composed of silver cyanamide (Ag2NCN) and anatase titania (TiO2) were fabricated through a chemical precipitation process of silver nitrate and cyanamide in TiO2 suspensions. The TiO2 nanoparticles around 15 nm were immobilized on the surface of rectangular Ag2NCN particles to form a hetero-structure, and the contents of TiO2 were varied to tune the structure and the photocatalytic performances. In comparison with single TiO2 or Ag2NCN, the TiO2/Ag2NCN nanocomposites exhibited a prominent improved photocatalytic activity in the hydrogen generation, and the hydrogen evolution rate (1494.0 μmol (g h)(-1)) was higher than most of the reported TiO2-composite photocatalysts. Based on the structure investigation, the photocatalytic mechanism of these TiO2/Ag2NCN nanocomposites was proposed. The enhanced photocatalytic activity was attributed to three points: the matched energy level between TiO2 and Ag2NCN promoted the electron-hole transfer and thus inhibited the recombination of photogenerated electrons and holes; the great electron storage capacity of metallic silver produced in the photocatalytic process also facilitated the charge separation; in addition, the expanded absorption spectrum because of the composite structure enhanced the UV and visible light response ability. These TiO2/Ag2NCN nanocomposites also presented good photocatalytic stability in the typical cycle tests. This work provided new insights into fabricating highly efficient composite photocatalysts containing silver and TiO2 for hydrogen generation. PMID:26515664

  10. Enhancement of photocatalytic performance of plasmon-assisted metallic ion doped titania

    NASA Astrophysics Data System (ADS)

    Fan, Jimin; Zhao, Zhihuan; Gong, Chao; Cheng, Bin; Xue, Yongqiang; Yin, Shu

    2015-11-01

    Plasmonic assisted metallic ion doped titania was synthesized successfully by combining the hydrothermal and photoreduction methods. The chromium ion doping resulted to smaller particle size and preferable crystallinity than pure TiO2. Ag@AgI-TiO2-Cr showed the smallest band gap of 1.9 eV, corresponding to the wavelength range until 652 nm. The Ag-AgI plasmonic effect promoted electron transfer and accelerated photocatalytic reaction. Excellent visible light induced MO degradation was effectively realized. The sample Ag@AgI-TiO2-Cr exhibited the best photodegradation activity, which might be related to its smallest band gap, larger specific surface area of 178.3 m2 g-1 and the maximum equilibrium adsorption quantity of 18.0 mg/g.

  11. Plasmonic silver nanoparticles loaded titania nanotube arrays exhibiting enhanced photoelectrochemical and photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Nishanthi, S. T.; Iyyapushpam, S.; Sundarakannan, B.; Subramanian, E.; Pathinettam Padiyan, D.

    2015-01-01

    A combination of electrochemical anodization and photochemical reduction is employed to fabricate highly ordered silver loaded titania nanotubes (Ag/TNT) arrays. The Ag/TNT samples show an extended optical absorbance from UV to visible region owing to the surface plasmon resonance effect of Ag. The photoluminescence intensity of Ag/TNT is significantly lower than that of pure titania revealing a decrease in charge carrier recombination. The photoelectrochemical properties of the prepared samples are studied using linear sweep and transient photocurrent measurements. Compared with pure TNT, the Ag loaded samples show a higher photoelectrochemical activity. The results demonstrate an efficient separation of photogenerated electron-hole pairs and the consequent increase in lifetime of charge carriers by Ag/TNT. The photocatalytic results of methyl orange dye degradation show that the Ag/TNT-3-05 sample exhibits the maximum degradation efficiency of 98.85% with kinetic rate constant of 0.0236(5) min-1 for 180 min light illumination.

  12. Suspension Plasma Spray Fabrication of Nanocrystalline Titania Hollow Microspheres for Photocatalytic Applications

    NASA Astrophysics Data System (ADS)

    Ren, Kun; Liu, Yi; He, Xiaoyan; Li, Hua

    2015-10-01

    Hollow inorganic microspheres with controlled internal pores in close-cell configuration are usually constructed by submicron-sized particles. Fast and efficient large-scale production of the microspheres with tunable sizes yet remains challenging. Here, we report a suspension plasma spray route for making hollow microspheres from nano titania particles. The processing permits most nano particles to retain their physiochemical properties in the as-sprayed microspheres. The microspheres have controllable interior cavities and mesoporous shell of 1-3 μm in thickness. Spray parameters and organic content in the starting suspension play the key role in regulating the efficiency of accomplishing the hollow sphere structure. For the ease of collecting the spheres for recycling use, ferriferous oxide particles were used as additives to make Fe3O4-TiO2 hollow magnetic microspheres. The spheres can be easily recycled through external magnetic field collection after each time use. Photocatalytic anti-bacterial activities of the hollow spheres were assessed by examining their capability of degrading methylene blue and sterilizing Escherichia coli bacteria. Excellent photocatalytic performances were revealed for the hollow spheres, giving insight into their potential versatile applications.

  13. Preparation and photocatalytic activity of eccentric Au-titania core-shell nanoparticles by block copolymer templates.

    PubMed

    Li, Xue; Fu, Xiaoning; Yang, Hui

    2011-02-21

    A novel route for a preparation of eccentric Au-titania core-shell nanoparticles using gold nanoparticles (AuNPs) with block copolymer shells as a template is reported. AuNPs with poly(2-vinyl pyridine)-block-poly(ethylene oxide) (PVP-b-PEO) block copolymer shells are first prepared by UV irradiation of the solution of PVP-b-PEO/HAuCl(4) complexes. Then the sol-gel reaction of titanium tetra-isopropoxide (TTIP) selectively on the surfaces of AuNPs leads to Au-titania core-shell composite nanoparticles. The eccentric Au-titania core-shell nanoparticles are obtained from the Au-titania core-shell composite nanoparticles by removal of organic interlayer by UV treatment. Photocatalytic activities of the resulting eccentric core-shell nanoparticles are investigated in terms of the degradation of methylene blue (MB). The results show that the eccentric core-shell structures endow the catalyst with greatly enhanced photocatalytic activity. PMID:21157597

  14. Titania modification with a ruthenium(II) complex and gold nanoparticles for photocatalytic degradation of organic compounds.

    PubMed

    Zheng, Shuaizhi; Wei, Zhishun; Yoshiiri, Kenta; Braumüller, Markus; Ohtani, Bunsho; Rau, Sven; Kowalska, Ewa

    2016-01-01

    Titania of fine anatase nanoparticles (ST01) was modified successively with two components, i.e., a ruthenium(II) complex with phosphonic anchoring groups [Ru(bpy)2(4,4'-(CH2PO3H2)2bpy)](2+) bpy = 2,2'-bipyridine (Ru(II)CP) and gold nanoparticles (Au). Various compositions of two titania modifiers were investigated, i.e., Au, Au + Ru(II)CP, Au + 0.5Ru(II)CP, Ru(II)CP, 0.5Ru(II)CP and 0.25Ru(II)CP, where Au and Ru(II)CP correspond to 0.81 mol% and 0.34 mol% (with respect to titania), respectively. In the case of hybrid photocatalysts, the sequence of modification (ruthenium(II) complex adsorption or gold deposition) was investigated to check its influence on the resultant properties and thus photocatalytic performance. Diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM) were applied to characterize the structural properties of the prepared photocatalysts, which confirmed the successful introduction of modifiers of the ruthenium(II) complex and/or gold NPs. Different distributions of gold particle sizes and chemical compositions were obtained for the hybrid photocatalysts prepared with an opposite sequence. It was found that photocatalytic activities depended on the range of used irradiation (UV/vis or vis) and the kind of modifier in different ways. Gold NPs improved the photocatalytic activities, while Ru(II)CP inhibited the reactions under UV/vis irradiation, i.e., methanol dehydrogenation and acetic acid degradation. Oppositely, Ru(II)CP greatly enhanced the photocatalytic activities for 2-propanol oxidation under visible light irradiation. PMID:26661372

  15. Silica-Titania Composite (STC)'s Performance in the Photocatalytic Oxidation of Polar VOCs

    NASA Technical Reports Server (NTRS)

    Levine, Lanfang H.; Coutts, Janelle; Richards, Jeffrey; Mazyck, David; Mazyck, David

    2011-01-01

    The objective of this paper is to determine the performance of a Silica-Titania Composite (STC) in the photocatalytic oxidation (PCO) of polar VOCs for potential applications in trace contaminant control within space habitats such as the ISS and CEV Orion. Tests were carried out in a bench scale STC-packed annular reactor under continuous illumination by either a UV-C germicidal lamp(lambda (sub max) = 254 nm) or UV-A fluorescent BLB (lambda(sub max) = 365 nm) for the removal of ethanol (a predominant polar VOC in the ISS cabin). The STC's performance was evaluated in terms of the ethanol mineralization rate, mineralization efficiency, and the extent of its oxidation intermediate (acetaldehyde) formation in response to the type of light source (photon energy and photon flux) and relative humidity (RH) implemented. Results demonstrated that acetaldehyde was the only quantifiable intermediate in the effluent under UV illumination, but was not found in the dark adsorption experiments. The mineralization rate increased with an increase in photon energy (UV-C greater than UV-A), even though both lamps were adjusted to emit the same incident photon flux, and also increased with increasing photon flux. However, photonic efficiency decreased as the photon flux increased. More importantly, a higher photon flux gave rise to a lower effluent acetaldehyde concentration. The effect of RH on PCO was complex and intriguing because it affected both physical adsorption and photocatalytic oxidation. In general, increasing RH caused a decrease in adsorption capacity for ethanol and reduced the mineralization efficiency with a concomitant higher acetaldehyde evolution rate. The effect of RH was less profound than that of photon flux.

  16. Highly thermostable anatase titania-pillared clay for the photocatalytic degradation of airborne styrene.

    PubMed

    Lim, Melvin; Zhou, Yan; Wood, Barry; Wang, Lian Zhou; Rudolph, Victor; Lu, Gao Qing

    2009-01-15

    Airborne styrene is a suspected human carcinogen, and traditional ways of mitigation include the use of adsorption technologies (activated carbon or zeolites) or thermal destruction. These methods presenttheir own shortcomings, i.e., adsorbents need to be regenerated or replaced regularly, and relatively large energy inputs are required in thermal treatment. Photocatalysis offers a potentially sustainable and clean means of controlling such fugitive emissions of styrene in air. The present study demonstrates a new type of well-characterized, highly thermostable titania-pillared clay photocatalysts for airborne styrene decomposition in a custom-designed fluidized-bed photoreactor. This photocatalytic system is found to be capable of destroying up to 87% of 300 ppmV airborne styrene in the presence of ultraviolet (UV) irradiation. The effects of relative humidity (RH: 0 or 20%) are also studied, together with the arising physical structures (in terms of porosity and surface characteristics) of the catalysts when subjected to relatively high calcination temperatures of 1000-1200 degrees C. Such a temperature range may be encountered, e.g., in flue gas emissions (1). It is found that relative humidity levels of 20% retard the degradation efficiencies of airborne styrene when using highly porous catalysts. PMID:19238991

  17. Preparation and Characterization of Polyhedral Oligomeric Silsesquioxane-Containing, Titania-Thiol-Ene Composite Photocatalytic Coatings, Emphasizing the Hydrophobic-Hydrophilic Transition.

    PubMed

    Jefferson, LaCrissia U; Netchaev, Anton D; Jefcoat, Jennifer A; Windham, Amber D; McFarland, Frederick M; Guo, Song; Buchanan, Randy K; Buchanan, J Paige

    2015-06-17

    Coatings prepared from titania-thiol-ene compositions were found to be both self-cleaning, as measured by changes in water contact angle, and photocatalytic toward the degradation of an organic dye. Stable titania-thiol-ene dispersions at approximately 2 wt % solids were prepared using a combination of high-shear mixing and sonication in acetone solvent from photocatalytic titania, trisilanol isobutyl polyhedral oligomeric silsesquioxane (POSS) dispersant, and select thiol-ene monomers, i.e., trimethylolpropane tris(3-mercaptopropionate) (TMPMP), pentaerythritol allyl ether (APE), and 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TTT). The dispersed particle compositions were characterized by DLS and TEM. The synthetic methods employed yield a strongly bound particle/POSS complex, supported by IR, 29Si NMR, and TGA. The factors of spray techniques, carrier solvent volatility, and particle size and size distributions, in combination, likely all contribute to the highly textured but uniform surfaces observed via SEM and AFM. Polymer composites possessed thermal transitions (e.g., Tg) consistent with composition. In general, the presence of polymer matrix provided mechanical integrity, without significantly compromising or prohibiting other critical performance characteristics, such as film processing, photocatalytic degradation of adsorbed contaminants, and the hydrophobic-hydrophilic transition. In all cases, coatings containing photocatalytic titania were converted from superhydrophobic to superhydrophilic, as defined by changes in the water contact angle. The superhydrophilic state of samples was considered persistent, since long time durations in complete darkness were required to observe any significant hydrophobic return. In a preliminary demonstration, the photocatalytic activity of prepared coatings was confirmed through the degradation of crystal violet dye. This work demonstrates that a scalable process can be found to prepare titania

  18. One-pot solvothermal synthesis of dual-phase titanate/titania Nanoparticles and their adsorption and photocatalytic Performances

    SciTech Connect

    Cheng, Yu Hua; Gong, Dangguo; Tang, Yuxin; Ho, Jeffery Weng Chye; Tay, Yee Yan; Lau, Wei Siew; Wijaya, Olivia; Lim, Jiexiang; Chen, Zhong

    2014-06-01

    Dual phase titanate/titania nanoparticles undergo phase transformation gradually with the increase of solvothermal synthesis temperature from 100 °C to 200 °C, and eventually are fully transformed into anatase TiO{sub 2}. The crystal structure change results in the changes of optical absorption, sensitizer/dopant formation and surface area of the materials which finally affect the overall dye removal ability. Reactions under dark and light have been conducted to distinguish the contributions of surface adsorption from photocatalytic degradation. The sample synthesized at 160 °C (S160) shows the best performances for both adsorption under dark and photocatalytic degradation of methylene blue (MB) under visible light irradiation. The adsorption mechanism for S160 is determined as monolayer adsorption based on the adsorption isotherm test under dark condition, and an impressive adsorption capacity of 162.19 mg/g is achieved. For the photocatalytic application, this sample at 0.1 g/L loading is also able to degrade 20 ppm MB within 6 hours under the visible light (>420 nm) condition. - Graphical abstract: The effect of solvothermal synthesis temperature on the formation and dye removal performance of dual phase titanate/titania nanoparticles was unveiled and optimized. - Highlights: • Low temperature one-pot solvothermal synthesis of dual-phase photocatalysts. • Correlation of the synthesis temperature is made with the phase composition. • Adsorption isotherm, kinetics, photocatalytic degradation were studied. • Synthesis at 160 °C yields the best material for adsorption of MB in dark. • The same sample also shows the best visible light degradation of MB.

  19. Effect of calcination temperature on physical parameters and photocatalytic activity of mesoporous titania spheres using chitosan/poly(vinyl alcohol) hydrogel beads as a template

    NASA Astrophysics Data System (ADS)

    Jiang, R.; Zhu, H.-Y.; Chen, H.-H.; Yao, J.; Fu, Y.-Q.; Zhang, Z.-Y.; Xu, Y.-M.

    2014-11-01

    Mesoporous titania spheres were prepared by modified sol-gel method using chitosan/poly(vinyl alcohol) hydrogel beads as a template. Effects of calcination temperature on physical parameters were investigated by X-ray diffraction (XRD), N2 adsorption-desorption, Fourier transform infrared (FT-IR) spectra, thermogravimetry and differential thermal analyses (TG-DTA), high-resolution transmission electron microscope (HRTEM) and scanning electron microscopy (SEM). The photocatalytic activity of mesoporous titania spheres prepared was also evaluated by photocatalytic degradation of phenol as a model molecule under UV irradiation. With increasing calcination temperature, average crystallite size and pore size increased. In contrast, Brunauer-Emmett-Teller (BET) specific surface areas, porosity and pore volumes steadily decreased. Results of characterization proved that prepared titania spheres with highly organized pores were mesoporous structure. The photocatalytic activity of mesoporous titania spheres calcined at 500 °C was more effective than those calcined at other temperatures, which were attributed to the porous structure, large BET surface area, crystalline, and smaller crystallite size. This work may provide new insights into the preparation of novel mesoporous titania spheres and further practical applications in the treatment of wastewater.

  20. Boron and nitrogen co-doped titania with enhanced visible-light photocatalytic activity for hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Li, Yuexiang; Ma, Gangfeng; Peng, Shaoqin; Lu, Gongxuan; Li, Shuben

    2008-08-01

    A visible-light boron and nitrogen co-doped titania (B-N-TiO 2) photocatalyst was prepared by sol-gel method with titanium tetra- n-butyl oxide, urea and boric acid as precursors. The photocatalyst was characterized by Fourier Transform Infrared (FT-IR), UV-vis diffusive reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), BET and electrochemistry method. Photocatalytic activity for hydrogen production over platinized B-N-TiO 2 under visible-light ( λ ≥ 420 nm) irradiation was investigated. In nitrogen doped titania (N-TiO 2) N sbnd Ti sbnd O bond is formed, which extends the absorption edge to the visible-light region. A part of doping boron enters into titania lattice and most of the boron exists at the surface of the catalyst. The crystallite size of B-N-TiO 2 decreases compared to N-TiO 2, while its photocurrent and the surface hydroxyl group increase. Furthermore, doping boron could act as shallow traps for photoinduced electrons to prolong the life of the electrons and holes. Therefore, the visible-light activity of B-N-iO 2 increases greatly compared with that of N-TiO 2.

  1. Hexagonal pillar structure of heteroepitaxial titania-vanadia nanocrystal films for high performance in thermochromic and photocatalytic properties.

    PubMed

    Zhou, Pei-Yin; Cheng, Chih-Chia; Huang, Chi-Hsien; Chen, Jem-Kun

    2016-04-01

    In this study, we employed the mixture of titanium and vanadium sols with various ratios in WO3 and poly(vinylpyrrolidone) solution to generate the precursors of W-doped titania-vanadia composites. The heteroepitaxial W-doped titania-vanadia crystals (HWTVCs) with various structures were obtained after a calcination process at 700 °C for 3 h. The structure transformation of HWTVCs was highly relative to the ratio of titanium to vanadium sols. A hexagonal pillar structure was found at a ratio of 0.25 for titanium to vanadium sols. The scales of the hexagonal pillars could be apparently divided into two groups. The scale of one group ranged from 80 to 130 nm while the scale of the other ranged from 300 to 950 nm. The heteroepitaxial crystals with hexagonal pillar structure enhanced the visible transmittance, near-infrared switching efficiency and the ability to photocatalytically degrade the organic component under visible light irradiation. Such bifunctional (photocatalytic and thermochromic) nanomaterials might have applications in energy-saving smart windows. PMID:26972307

  2. Highly hydrophilic poly(vinylidene fluoride)/meso-titania hybrid mesoporous membrane for photocatalytic membrane reactor in water

    PubMed Central

    Wang, Meng; Yang, Guang; Jin, Peng; Tang, Hao; Wang, Huanhuan; Chen, Yong

    2016-01-01

    The high hydrophobicity of poly(vinylidene fluoride) (PVDF) membrane remains an obstacle to be applied in some purification processes of water or wastewater. Herein, a highly hydrophilic hybrid mesoporous titania membrane composed of mesoporous anatase titania (meso-TiO2) materials inside the three-dimensional (3D) macropores of PVDF membrane was successfully prepared by using the dual-templated synthesis method combined with solvent extraction and applied as the photocatalytic membrane reactor for the photodegredation of organic dye in water. The structure and the properties of as-prepared hybrid membranes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption–desorption and contact angle measurements. It was found that the hydrophilicity of PVDF membrane can be significantly improved by filling mesoporous TiO2 inside the 3D macropores of PVDF membrane. Moreover, such a PVDF/meso-TiO2 hybrid membrane exhibits promising photocatalytic degradation of dye in water due to the existence of mesoporous anatase TiO2 materials inside PVDF membrane. This study provides a new strategy to simultaneously introduce hydrophilicity and some desirable properties into PVDF and other hydrophobic membranes. PMID:26754440

  3. Highly hydrophilic poly(vinylidene fluoride)/meso-titania hybrid mesoporous membrane for photocatalytic membrane reactor in water.

    PubMed

    Wang, Meng; Yang, Guang; Jin, Peng; Tang, Hao; Wang, Huanhuan; Chen, Yong

    2016-01-01

    The high hydrophobicity of poly(vinylidene fluoride) (PVDF) membrane remains an obstacle to be applied in some purification processes of water or wastewater. Herein, a highly hydrophilic hybrid mesoporous titania membrane composed of mesoporous anatase titania (meso-TiO2) materials inside the three-dimensional (3D) macropores of PVDF membrane was successfully prepared by using the dual-templated synthesis method combined with solvent extraction and applied as the photocatalytic membrane reactor for the photodegredation of organic dye in water. The structure and the properties of as-prepared hybrid membranes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption-desorption and contact angle measurements. It was found that the hydrophilicity of PVDF membrane can be significantly improved by filling mesoporous TiO2 inside the 3D macropores of PVDF membrane. Moreover, such a PVDF/meso-TiO2 hybrid membrane exhibits promising photocatalytic degradation of dye in water due to the existence of mesoporous anatase TiO2 materials inside PVDF membrane. This study provides a new strategy to simultaneously introduce hydrophilicity and some desirable properties into PVDF and other hydrophobic membranes. PMID:26754440

  4. Highly hydrophilic poly(vinylidene fluoride)/meso-titania hybrid mesoporous membrane for photocatalytic membrane reactor in water

    NASA Astrophysics Data System (ADS)

    Wang, Meng; Yang, Guang; Jin, Peng; Tang, Hao; Wang, Huanhuan; Chen, Yong

    2016-01-01

    The high hydrophobicity of poly(vinylidene fluoride) (PVDF) membrane remains an obstacle to be applied in some purification processes of water or wastewater. Herein, a highly hydrophilic hybrid mesoporous titania membrane composed of mesoporous anatase titania (meso-TiO2) materials inside the three-dimensional (3D) macropores of PVDF membrane was successfully prepared by using the dual-templated synthesis method combined with solvent extraction and applied as the photocatalytic membrane reactor for the photodegredation of organic dye in water. The structure and the properties of as-prepared hybrid membranes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption-desorption and contact angle measurements. It was found that the hydrophilicity of PVDF membrane can be significantly improved by filling mesoporous TiO2 inside the 3D macropores of PVDF membrane. Moreover, such a PVDF/meso-TiO2 hybrid membrane exhibits promising photocatalytic degradation of dye in water due to the existence of mesoporous anatase TiO2 materials inside PVDF membrane. This study provides a new strategy to simultaneously introduce hydrophilicity and some desirable properties into PVDF and other hydrophobic membranes.

  5. Rare earth oxide-doped titania nanocomposites with enhanced photocatalytic activity towards the degradation of partially hydrolysis polyacrylamide

    NASA Astrophysics Data System (ADS)

    Li, Jinhuan; Yang, Xia; Yu, Xiaodan; Xu, Leilei; Kang, Wanli; Yan, Wenhua; Gao, Hongfeng; Liu, Zhonghe; Guo, Yihang

    2009-01-01

    Rare-earth oxide-doped titania nanocomposites (RE 3+/TiO 2, where RE = Eu 3+, Pr 3+, Gd 3+, Nd 3+, and Y 3+) were prepared by a one-step sol-gel-solvothermal method. The products exhibited anatase phase structure, mesoporosity, and interesting surface compositions with three oxygen species and two titanium species. The products were used as the photocatalysts to degrade a partially hydrolysis polyacrylamide (HPAM) under UV-light irradiation, a very useful polymer in oil recovery. For comparison, Degussa P25 and as-prepared pure TiO 2 were also tested under the same conditions. The enhanced photocatalytic activity was obtained on as-prepared Eu 3+ (Gd 3+, Pr 3+)/TiO 2 composites, and the reasons were explained. Finally, the degradation pathway of HPAM over the RE 3+/TiO 2 composite was put forward based on the intermediates produced during the photocatalysis procedure.

  6. Nitrogen-modified nano-titania: True phase composition, microstructure and visible-light induced photocatalytic NOx abatement

    NASA Astrophysics Data System (ADS)

    Tobaldi, D. M.; Pullar, R. C.; Gualtieri, A. F.; Otero-Irurueta, G.; Singh, M. K.; Seabra, M. P.; Labrincha, J. A.

    2015-11-01

    Titanium dioxide (TiO2) is a popular photocatalyst used for many environmental and anti-pollution applications, but it normally operates under UV light, exploiting ∼5% of the solar spectrum. Nitrification of titania to form N-doped TiO2 has been explored as a way to increase its photocatalytic activity under visible light, and anionic doping is a promising method to enable TiO2 to harvest visible-light by changing its photo-absorption properties. In this paper, we explore the insertion of nitrogen into the TiO2 lattice using our green sol-gel nanosynthesis method, used to create 10 nm TiO2 NPs. Two parallel routes were studied to produce nitrogen-modified TiO2 nanoparticles (NPs), using HNO3+NH3 (acid-precipitated base-peptised) and NH4OH (totally base catalysed) as nitrogen sources. These NPs were thermally treated between 450 and 800 °C. Their true phase composition (crystalline and amorphous phases), as well as their micro-/nanostructure (crystalline domain shape, size and size distribution, edge and screw dislocation density) was fully characterised through advanced X-ray methods (Rietveld-reference intensity ratio, RIR, and whole powder pattern modelling, WPPM). As pollutants, nitrogen oxides (NOx) are of particular concern for human health, so the photocatalytic activity of the NPs was assessed by monitoring NOx abatement, using both solar and white-light (indoor artificial lighting), simulating outdoor and indoor environments, respectively. Results showed that the onset of the anatase-to-rutile phase transformation (ART) occurred at temperatures above 450 °C, and NPs heated to 450 °C possessed excellent photocatalytic activity (PCA) under visible white-light (indoor artificial lighting), with a PCA double than that of the standard P25 TiO2 NPs. However, higher thermal treatment temperatures were found to be detrimental for visible-light photocatalytic activity, due to the effects of four simultaneous occurrences: (i) loss of OH groups and water adsorbed

  7. Synthesis of Nano-Crystalline Gamma-TiAl Materials

    NASA Technical Reports Server (NTRS)

    Hales, Stephen J.; Vasquez, Peter

    2003-01-01

    One of the principal problems with nano-crystalline materials is producing them in quantities and sizes large enough for valid mechanical property evaluation. The purpose of this study was to explore an innovative method for producing nano-crystalline gamma-TiAl bulk materials using high energy ball milling and brief secondary processes. Nano-crystalline powder feedstock was produced using a Fritsch P4(TM) vario-planetary ball mill recently installed at NASA-LaRC. The high energy ball milling process employed tungsten carbide tooling (vials and balls) and no process control agents to minimize contamination. In a collaborative effort, two approaches were investigated, namely mechanical alloying of elemental powders and attrition milling of pre-alloyed powders. The objective was to subsequently use RF plasma spray deposition and short cycle vacuum hot pressing in order to effect consolidation while retaining nano-crystalline structure in bulk material. Results and discussion of the work performed to date are presented.

  8. Photocatalytic degradation of agricultural N-heterocyclic organic pollutants using immobilized nanoparticles of titania.

    PubMed

    Mahmoodi, Niyaz Mohammad; Arami, Mokhtar; Limaee, Nargess Yousefi; Gharanjig, Kamaladin

    2007-06-25

    Degradation and mineralization of two agricultural organic pollutants (Diazinon and Imidacloprid as N-heterocyclic aromatics) in aqueous solution by nanophotocatalysis using immobilized titania nanoparticles were investigated. Insecticides, Diazinon and Imidacloprid, are persistent pollutants in agricultural soil and watercourses. A simple and effective method was developed to immobilization of titania nanoparticles. UV-vis, ion chromatography (IC) and chemical oxygen demand (COD) analyses were employed. The effects of operational parameters such as H(2)O(2) and inorganic anions (NO(3)(-), Cl(-) and SO(4)(2-)) were investigated. The mineralization of Diazinon and Imidacloprid was evaluated by monitoring of the formed inorganic anions. The selected pollutants are effectively degraded following first order kinetics model. Results show that the nanophotocatalysis using immobilized titania nanoparticle is an effective method for treatment Diazinon and Imidacloprid from contaminated water. PMID:17145132

  9. Mixed phase lamellar titania-titanate anchored with Ag2O and polypyrrole for enhanced adsorption and photocatalytic activity.

    PubMed

    Kumar, Rajeev

    2016-09-01

    Ag2O/TiO2/polypyrrole composite was synthesized by stepwise modification of the rutile TiO2 though hydrothermal alkaline treatment to obtain mixed phase sodium titanate/titania (Na-TiO2) followed ion-exchange replacement of Na(+) by Ag(+) to get Ag2O/TiO2 (through precipitation) and H2O2 oxidative polymerization of pyrrole onto Ag2O/TiO2 to get final composite Ag2O/TiO2/polypyrrole (Ag2O/TiO2/PPY). Composite materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), Diffuse reflectance ultraviolet-visible spectroscopy (UV-vis DRS) and Raman analysis. The synthesized materials showed increase in the optical property, adsorption and photocatalytic scavenging of the methylene blue (MB). The adsorption capacity of MB onto the prepared materials was observed in the following order: TiO2photocatalytic decontamination of MB was as follows: TiO2photocatalytic decontamination was observed at pH 9. The kinetics studies revealed that the adsorption of MB followed the pseudo-first-order kinetic model. While kinetics for MB degradation were well defined by the Langmuir-Hinshelwood model at low and high concentrations. The obtained results demonstrate that the synergistic effect of adsorption and visible light photocatalysis is enough capable for 100% removal of MB from aquatic solution. PMID:27244593

  10. Probing the Effects of Templating on the UV and Visible Light Photocatalytic Activity of Porous Nitrogen-Modified Titania Monoliths for Dye Removal.

    PubMed

    Nursam, Natalita M; Wang, Xingdong; Tan, Jeannie Z Y; Caruso, Rachel A

    2016-07-13

    Porous nitrogen-modified titania (N-titania) monoliths with tailored morphologies were prepared using phase separation and agarose gel templating techniques. The doping and templating process were simultaneously carried out in a one-pot step using alcohol amine-assisted sol-gel chemistry. The amount of polymer used in the monoliths that were prepared using phase separation was shown to affect both the physical and optical properties: higher poly(ethylene glycol) content increased the specific surface area, porosity, and visible light absorption of the final materials. For the agarose-templated monoliths, the infiltration conditions affected the monolith morphology. A porous monolith with high surface area and the least shrinkage was obtained when the N containing alkoxide precursor was infiltrated into the agarose scaffolds at 60 °C. The effect of the diverse porous morphologies on the photocatalytic activity of N-titania was studied for the decomposition of methylene blue (MB) under visible and UV light irradiation. The highest visible light activity was achieved by the agarose-templated N-titania monolith, in part due to higher N incorporation. This sample also showed better UV activity, partly because of the higher specific surface area (up to 112 m(2) g(-1)) compared to the phase separation-induced monoliths (up to 103 m(2) g(-1)). Overall, agarose-templated, porous N-titania monoliths provided better features for effectively removing the MB contaminant. PMID:27347742

  11. Supercritical-assistant liquid crystal template approach to synthesize mesoporous titania/multiwalled carbon nanotube composites with high visible-light driven photocatalytic performance

    SciTech Connect

    Liu, Chen; Li, Youji Xu, Peng; Li, Ming; Huo, Pingxiang

    2014-12-15

    Graphical abstract: We investigate the influence of mesoporous titania content upon the visible-light driven photocatalytic performance of MPT/MWCNTs in phenol degradation. - Highlights: • MPT/MWCNTs were fabricated by liquid-crystal template in supercritical CO{sub 2}. • MPT/MWCNTs show high visible-light driven photoactivity for phenol degradation. • MPT/MWCNTs also show high reusable photoactivity under visible irradiation. • MPT content can control visible-light driven photoactivity of MPT/MWCNTs. • MPT is not easily broken away from from MPT/MWCNT composites. - Abstract: Mesoporous titania (MPT) was deposited onto multiwalled carbon nanotubes (MWCNTs) by deposition of titanium sol containing liquid-crystal template with assistant of supercritical CO{sub 2}. The products were characterized with various analytical techniques to determine their structural, morphological, optical absorption and photocatalytic properties. The results indicate that in photocatalytic degradation of phenol under visible light, the mixtures or composites of MPT and MWCNT show the high efficiency because of synergies between absorbing visible light, releasing electrons and facilitating transfer of charge carriers of MWCNTs and providing activated centers of MPT. Because of the mutual constraint between MPT and MWCNTs on the photocatalytic efficiency, the optimal loading of MPT in MPT/MWCNT-3 for phenol degradation is 48%. Because the intimate contact between MWCNTs and MPT is more beneficial to electron transformation, photoactivity of mixture is lower than that of composites with high reusable performance. The optimum conditions of phenol degradation were obtained.

  12. Effect of Sn on the physical and photocatalytic properties of sprayed titania thin films

    NASA Astrophysics Data System (ADS)

    Martinez, Arturo I.; Acosta, Dwight; Lopez, Alcides; Cedillo, Gerardo

    2004-05-01

    TiO2 alloys in thin film configuration with different amounts of SnO2 have been studied. In this work we present the effects of tin on the structural, optical, morphological and photocatalytical properties of TiO2 thin films prepared by spray pyrolysis. The prepared alloys shown a greater porosity and a smaller band-gap energies than those pure TiO2 thin films, therefore, they exhibit a greater photocatalytic activity in the degradation of methylene blue. The degradation products have been identified by ^1H nuclear magnetic resonance (NMR) as dimethylamine hydrochloride, methanethiol and methylamine. Additionally, it has been found that these small organic compounds can be degraded to mineral compounds by means photocatalytic reactions with TiO2 and TiO_2/SnO2 thin films.

  13. Synthesis of Cr,N-codoped titania nanotubes and their visible-light-driven photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Fan, Jinmin; Zhao, Zhihuan; Wang, Jianye; Zhu, Lixiao

    2015-01-01

    Cr and N-codoped TiO2 nanotubes with larger specific surface area and smaller band gap energy compared with pure TiO2 nanotubes were prepared via a two-step process of hydrothermal and post-impregnation method. The obtained catalysts were characterized by TEM, XRD, XPS, BET, FT-IR and UV-Vis DRS measurements for investigating nanostructure, crystal phase, specific surface area, bonding state and light-harvesting properties of these samples, respectively. Additionally, the effects of doping amount of Cr ions on the morphology, crystal structure, optical adsorption and photocatalytic activity of codoped TiO2 nanotubes were investigated. The photocatalytic activity was evaluated by degradation of methyl orange (MO) under visible light for 100 min. It was found that the highest photocatalytic activity could be realized when the concentration of Cr was 1.06%, and the degradation rate was up to 97.16%, far higher than that of undoped TiO2 nanotubes (10.56%). In addition, photocatalytic degradation of MO on codoped TiO2 nanotubes surface was proven to be in accordance with the first-order kinetics.

  14. Biotemplated synthesis of high specific surface area copper-doped hollow spherical titania and its photocatalytic research for degradating chlorotetracycline

    NASA Astrophysics Data System (ADS)

    Bu, Dan; Zhuang, Huisheng

    2013-01-01

    Copper-doped titania (Cu/TiO2) hollow microspheres were fabricated using the rape pollen as biotemplates via an improved sol-gel method and a followed calcinations process. In the fabricated process, a titanium(IV)-isopropoxide-based sol directly coated onto the surface of rape pollen. Subsequently, after calcinations, rape pollen was removed by high temperature and the hollow microsphere structure was retained. The average diameter of as-obtained hollow microspheres is 15-20 μm and the thickness of shell is approximately 0.6 μm. Knowing from XRD results, the main crystal phase of microspheres is anatase, coupled with rutile. The specific surface area varied between 141.80 m2/g and 172.51 m2/g. This hollow sphere photocatalysts with high specific surface area exhibited stronger absorption ability and higher photoactivity, stimulated by visible light. The degradation process of chlortetracycline (CTC) solution had been studied. The degradated results indicate that CTC could be effective degradated by fabricated hollow spherical materials. And the intermediate products formed in the photocatalytic process had been identified.

  15. Photocatalytic and photoelectrocatalytic degradation of the drug omeprazole on nanocrystalline titania films in alkaline media: Effect of applied electrical bias on degradation and transformation products.

    PubMed

    Tantis, Iosif; Bousiakou, Leda; Frontistis, Zacharias; Mantzavinos, Dionissios; Konstantinou, Ioannis; Antonopoulou, Maria; Karikas, George-Albert; Lianos, Panagiotis

    2015-08-30

    Photocatalytic and photoelectrocatalytic degradation of the drug omeprazole has been studied in the presence of nanocrystalline titania films supported on glass slides or transparent FTO electrodes in alkaline environment. Its photocatalytic degradation rate was assessed by its UV absorbance and by HPLC, while its transformation products were analyzed by HR-LC-MS. Based on UV absorbance, omeprazole can be photocatalytically degraded at an average rate of 6.7×10(-4)min(-1) under low intensity UVA irradiation of 1.5mWcm(-2) in the presence of a nanoparticulate titania film. This corresponds to degradation of 1.4mg of omeprazole per gram of the photocatalyst per liter of solution per hour. The photodegradation rate can be accelerated in a photoelectrochemical cell by applying a forward bias. In this case, the maximum rate reached under the present conditions was 11.6×10(-4)min(-1) by applying a forward bias of +0.6V vs. Ag/AgCl. Four major transformation products were successfully identified and their profiles were followed by HR-LC-MS. The major degradation path includes the scission of the sulfoxide bridge into the corresponding pyridine and benzimidazole ring derivates and this is accompanied by the release of sulfate anions in the reaction mixture. PMID:25855613

  16. Synthesis of Carbon Nanotube-Nanotubular Titania Composites by Catalyst-Free CVD Process: Insights into the Formation Mechanism and Photocatalytic Properties.

    PubMed

    Alsawat, Mohammed; Altalhi, Tariq; Gulati, Karan; Santos, Abel; Losic, Dusan

    2015-12-30

    This work presents the synthesis of carbon nanotubes (CNTs) inside titania nanotube (TNTs) templates by a catalyst-free chemical vapor deposition (CVD) approach as composite platforms for photocatalytic applications. The nanotubular structure of TNTs prepared by electrochemical anodization provides a unique platform to grow CNTs with precisely controlled geometric features. The formation mechanism of carbon nanotubes inside nanotubular titania without using metal catalysts is explored and explained. The structural features, crystalline structures, and chemical composition of the resulting CNTs-TNTs composites were systematically characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The deposition time during CVD process was used to determine the formation mechanism of CNTs inside TNTs template. The photocatalytic properties of CNTs-TNTs composites were evaluated via the degradation of rhodamine B, an organic model molecule, in aqueous solution under mercury-xenon Hg (Xe) lamp irradiation monitored by UV-visible spectroscopy. The obtained results reveal that CNTs induces a synergestic effect on the photocatalytic activity of TNTs for rhodamine B degradation, opening new opportunities to develop advanced photocatalysts for environmental and energy applications. PMID:26587676

  17. Photocatalytic Properties of Silver Core/Titania Shell Nano-Wires Grown on a Glass Substrate Using a Glycothermal Process Assisted by a Photochemical Reaction.

    PubMed

    Song, Duck-Hyun; Hirato, Tetsuji

    2015-07-01

    A silver core/titania shell nano-wire film was successfully prepared on a glass substrate via a glycothermal process that was assisted by a photochemical reaction using tetra-n-butyl titanate as the titanium source and silver nitrate as the silver source in an autoclave with ethylene glycol as a solvent. The morphology, diameter, length, and density of the core/shell nano-wires that were synthesized could be varied by changing the silver/titanium molar ratio of the starting materials. The samples produced were characterized by X-ray diffraction and scanning electron microscopy. The photocatalytic activity of the silver core/titania shell nano-wire film was investigated by measuring the photodegradation rate of rhodamine B in aqueous solution. PMID:26373082

  18. Enhanced photocatalytic H2-production activity of graphene-modified titania nanosheets

    NASA Astrophysics Data System (ADS)

    Xiang, Quanjun; Yu, Jiaguo; Jaroniec, Mietek

    2011-09-01

    Graphene-modified TiO2 nanosheets with exposed (001) facets (graphene/TiO2) were prepared by microwave-hydrothermal treatment of graphene oxide (GO) and hydrothermally synthesized TiO2 nanosheets with exposed (001) facets in an ethanol-water solvent. These nanocomposite samples showed high photocatalytic H2-production activity in aqueous solutions containing methanol, as sacrificial reagent, even without Pt co-catalyst. The optimal graphene content was found to be ~1.0 wt%, giving a H2-production rate of 736 μmol h-1 g-1 with a quantum efficiency (QE) of 3.1%, which exceeded the rate observed on pure TiO2 nanosheets by more than 41 times. This high photocatalytic H2-production activity is due to the deposition of TiO2 nanosheets on graphene sheets, which act as an electron acceptor to efficiently separate the photogenerated charge carriers. The observed enhancement in the photocatalytic activity is due to the lower absolute potential of graphene/graphene z.rad- (-0.08 V vs. SHE, pH = 0) in comparison to the conduction band (-0.24 V) of anatase TiO2, meanwhile the aforementioned absolute value is higher than the reduction potential of H+ (0 V), which favors the electron transfer from the conduction band (CB) of TiO2 to graphene sheets and the reduction of H+, thus enhancing photocatalytic H2-production activity. The proposed mechanism for the observed photocatalytic performance of TiO2 nanosheets, modified with a small amount of graphene, was further confirmed by photoluminescence spectroscopy and transient photocurrent response. This work not only shows a possibility for the utilization of low cost graphene sheets as a substitute for noble metals (such as Pt) in the photocatalytic H2-production but also for the first time shows a significant enhancement in the H2-production activity by using metal-free carbon material as an effective co-catalyst.

  19. Enhanced photocatalytic H₂-production activity of graphene-modified titania nanosheets.

    PubMed

    Xiang, Quanjun; Yu, Jiaguo; Jaroniec, Mietek

    2011-09-01

    Graphene-modified TiO(2) nanosheets with exposed (001) facets (graphene/TiO(2)) were prepared by microwave-hydrothermal treatment of graphene oxide (GO) and hydrothermally synthesized TiO(2) nanosheets with exposed (001) facets in an ethanol-water solvent. These nanocomposite samples showed high photocatalytic H(2)-production activity in aqueous solutions containing methanol, as sacrificial reagent, even without Pt co-catalyst. The optimal graphene content was found to be ∼1.0 wt%, giving a H(2)-production rate of 736 μmol h(-1) g(-1) with a quantum efficiency (QE) of 3.1%, which exceeded the rate observed on pure TiO(2) nanosheets by more than 41 times. This high photocatalytic H(2)-production activity is due to the deposition of TiO(2) nanosheets on graphene sheets, which act as an electron acceptor to efficiently separate the photogenerated charge carriers. The observed enhancement in the photocatalytic activity is due to the lower absolute potential of graphene/graphene˙(-) (-0.08 V vs. SHE, pH = 0) in comparison to the conduction band (-0.24 V) of anatase TiO(2), meanwhile the aforementioned absolute value is higher than the reduction potential of H(+) (0 V), which favors the electron transfer from the conduction band (CB) of TiO(2) to graphene sheets and the reduction of H(+), thus enhancing photocatalytic H(2)-production activity. The proposed mechanism for the observed photocatalytic performance of TiO(2) nanosheets, modified with a small amount of graphene, was further confirmed by photoluminescence spectroscopy and transient photocurrent response. This work not only shows a possibility for the utilization of low cost graphene sheets as a substitute for noble metals (such as Pt) in the photocatalytic H(2)-production but also for the first time shows a significant enhancement in the H(2)-production activity by using metal-free carbon material as an effective co-catalyst. PMID:21826308

  20. Synthesis and photocatalytic activity of ytterbium-doped titania/diatomite composite photocatalysts

    NASA Astrophysics Data System (ADS)

    Tang, Wenjian; Qiu, Kehui; Zhang, Peicong; Yuan, Xiqiang

    2016-01-01

    Ytterbium-doped titanium dioxide (Yb-TiO2)/diatomite composite materials with different Yb concentrations were prepared by sol-gel method. The phase structure, morphology, and chemical composition of the as-prepared composites were well characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), and ultraviolet-visible (UV-vis) diffuse reflection spectroscopy. The XRD and Raman spectroscopy analysis indicated that the TiO2 existed in the form of pure anatase in the composites. The SEM images exhibited the well deposition and dispersion of TiO2 nanoparticles with little agglomeration on the surfaces of diatoms. The UV-vis diffuse reflection spectra showed that the band gap of TiO2 could be narrowed by the introduction of Yb species, which was further affected by doping concentration of Yb. The photocatalytic activity of synthesized samples was investigated by the degradation of methylene blue (MB) under UV light irradiation. It was observed that the photocatalytic degradation followed a pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. Compared to TiO2 and TiO2/diatomite, the Yb-TiO2/diatomite composites exhibited higher photocatalytic activity toward degradation of MB using UV light irradiation.

  1. Preparation and characterization of photocatalytic carbon dots-sensitized electrospun titania nanostructured fibers

    SciTech Connect

    Li, Haopeng; Zhu, Yihua; Cao, Huimin; Yang, Xiaoling; Li, Chunzhong

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► The TiO{sub 2}-CDs nanostructured fibers are fabricated by using APS combining the electrospinning TiO{sub 2} nanostructured fibers and CDs. ► The CD can work as a photosensitizer in the degradation of rhodamine B under visible light irradiation. ► The TiO{sub 2}-CDs nanostructured fibers exhibit enhanced photocatalytic efficiency and can be easily handled and recycled. -- Abstract: The carbon dots (CDs) are new functional carbon-aceous materials. Compared to conventional dye molecules and semiconductor quantum dots, CDs are superior in chemical inertness and low toxicity. The TiO{sub 2}-CDs nanostructured fibers were fabricated by combining the electrospinning technique and reflux method. Compared with the pure TiO{sub 2} nanostructured fibers and P25, the TiO{sub 2}-CDs nanostructured fibers exhibited enhanced photocatalytic efficiency of photodegradation of rhodamine B (RhB) under visible light irradiation. The enhanced photocatalytic activity of TiO{sub 2}-CDs nanostructured fibers could be attributed to the presence of CDs embedded in TiO{sub 2} nanostructured fibers. The CD can work as a photosensitizer in the degradation. Furthermore, the TiO{sub 2}-CDs nanostructured fibers could be easily handled and recycled due to their one-dimensional nanostructural property.

  2. The structure and the photocatalytic activity of titania based nanotube and nanofiber coatings

    NASA Astrophysics Data System (ADS)

    Radtke, A.; Piszczek, P.; Topolski, A.; Lewandowska, Ż.; Talik, E.; Andersen, I. Hald; Nielsen, L. Pleth; Heikkilä, M.; Leskelä, M.

    2016-04-01

    The photocatalytic activity of TiO2 based nanotube (TNT) and nanofiber (TNF) coatings has been investigated, in correlation to their structure, morphology, specific surface area, acidity and the amount of surface H2O molecules and sbnd OH groups. Characterization of these materials was carried out using grazing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). The photocatalytic activity has been quantified by two different methods, based on the photodegradation of methylene blue (the pattern of water-soluble organic pollutant) and acetone (the pattern of volatile organic pollutant), respectively. Results of our investigations revealed that TNF coatings were significantly more active in case of both photodegradation processes in air and water, as compared to TNT, even if the specific surface area of TNF films was smaller than the adequate surface area of TNT. The microstructure of produced materials, the amount of adsorbed sbnd OH groups and H2O molecules located on the surface of materials, and the acidity of the surface, were the main factors which affect their photoactivity. Photocatalytic properties of tubular and porous TiO2-based materials are the resultant of the compilation of individual factors impact and any of them cannot be neglected.

  3. Lifetime and regeneration of immobilized titania for photocatalytic removal of aqueous hexavalent chromium.

    PubMed

    Tuprakay, Seree; Liengcharernsit, Winai

    2005-09-30

    Immobilized titania (TiO2) batch reactors reduced hexavalent chromium (Cr(VI)) in the form of potassium dichromate (K2Cr2O7) to trivalent chromium (Cr(III)) in aqueous solution at pH 3 under 171 W/m2 light intensity. The light source was a 125-W ultraviolet (UV) lamp. The Cr(VI) reduction showed zero-order kinetics (k0), while the Cr(VI) adsorption fitted with first-order kinetics (k(1st)). Adsorption capacity increased with increasing initial Cr(VI) concentration, and the area of immobilized TiO2 limited the reduction efficiency. The lifetime of fresh immobilized TiO2 was approximately 14 h. In addition, the regeneration of TiO2 with 3M sodium hydroxide (NaOH) was necessary to improve adsorption reaction. PMID:16046253

  4. Cathodoluminescence evaluation of oxygen vacancy population in nanostructured titania thin films for photocatalytic applications.

    PubMed

    Battiston, Simone; Leto, Andrea; Minella, Marco; Gerbasi, Rosalba; Miorin, Enrico; Fabrizio, Monica; Daolio, Sergio; Tondello, Eugenio; Pezzotti, Giuseppe

    2010-04-29

    Room-temperature results of cathodoluminescence (CL) spectroscopy investigations are presented for nanostructured titanium dioxide (anatase) thin films (500 nm thick) deposited via RF magnetron sputtering on high-purity silica substrates. The collected CL bands of the anatase thin films, as deposited and after different annealing cycles, showed a broad morphology consisting of three Voigtian bands located at 500, 550, and 610 nm that were partially overlapping. The overall CL emission increased with increasing temperature and time of the annealing cycle as a consequence of the increased crystallinity of the thin film. A clear trend was found for the oxygen-vacancy-related band (located at 610 nm), whose relative intensity decreased, as compared with the as-grown sample, after annealing in air; the higher the annealing temperature, the lower the relative intensity. We evaluated the photoactivity of the nanostructured thin film samples by measuring their photocatalytic activity in aqueous solution toward the degradation of phenol. A relationship between the decrease in oxygen vacancy concentration as a consequence of the annealing and the increase in the photoactivity was highlighted. PMID:20373795

  5. Nonaqueous seeded growth of flower-like mixed-phase titania nanostructures for photocatalytic applications

    SciTech Connect

    Hsu, Y.-C.; Lin, H.-C.; Chen, C.-H.; Liao, Y.-T.; Yang, C.-M.

    2010-09-15

    A nonaqueous seeded-grown synthesis of three-dimensional TiO{sub 2} nanostructures in the benzyl alcohol reaction system was reported. The synthesis was simple, high-yield, and requires no structural directing or capping agents. It could be largely accelerated by applying microwave heating. The TiO{sub 2} nanostructures had a unique flower-like morphology and high surface area. Furthermore, the structural analyses suggested that the nanostructures had a non-uniform distribution of crystalline phases, with the inner part rich in anatase and the outer part rich in rutile. After heat treatments, the mixed-phase TiO{sub 2} nanostructures exhibited high photocatalytic activities for the photodegradation of methylene blue as compared to Degussa P25. The high photoactivities may be associated with the high surface area and the synergistic effect resulting from the anisotropic mixed-phase nanostructures. The results demonstrate the uniqueness of the nonaqueous seeded growth and the potential of the TiO{sub 2} nanostructures for practical applications. - Graphical abstract: Flower-like TiO{sub 2} nanostructures synthesized by a nonaqueous seeded growth without using any structural directing or capping agents.

  6. Ab initio simulations on N and S co-doped titania nanotubes for photocatalytic applications

    NASA Astrophysics Data System (ADS)

    Chesnokov, Andrei; Lisovski, Oleg; Bocharov, Dmitry; Piskunov, Sergei; Zhukovskii, Yuri F.; Wessel, Michael; Spohr, Eckhard

    2015-09-01

    In this paper we present the results of quantum chemical modeling for energetically stable anatase (001) TiO2 nanotubes, undoped, doped, and codoped with N{}{{O}} and S{}{{O}} atoms. We calculate the electronic structure of one-dimensional (1D) nanotubes and zero-dimensional (0D) atomic fragments cut out from these nanotubes, employing hybrid density functional theory with a partial incorporation of an exact, nonlocal Hartree-Fock exchange within the formalism of the linear combination of atomic orbitals, as implemented in both CRYSTAL and NWChem total energy codes. Structural optimization of 1D nanotubes has been performed using CRYSTAL09 code, while the cut-out 0D fragments have been modelled using the NWChem code. The electronic properties of the studied systems prove that the band structure of the pristine TiO2 nanotube can be substantially modified by introducing substitutional impurity defects. The N-doped nanotube creates a midgap state that largely has a nitrogen 2p character. The S-doped nanotube has a defect state that almost coincides with the top of the valence bond for the pristine material. For nanotubes codoped with both S and N, we observe a downward shift of the gap state of nitrogen relative to the purely N-doped state by about 0.3 eV. This results in a system with a filled gap state about 0.3 eV below the O2/H2O oxidation level, making it a very promising candidate for photocatalytic hydrogen generation under visible light, because due to the presence of sulfur, the bottom of the conduction band is only about 2.2 eV above the occupied midgap state, and also, clearly above the standard hydrogen electrode level.

  7. Fabrication and characterization of nano-crystalline diamond films

    SciTech Connect

    Gruen, D.M.; Pan, X.; Krauss, A.R.; Liu, S.; Luo, J.; Foster, C.M.

    1993-11-01

    Highly uniform, smooth nano-crystalline diamond films have been fabricated with a magneto-active microwave CVD system. Top and bottom magnet currents were 145A and 60A, while microwave power and substrate temperature were controlled at 1500W and 850{degrees}C during deposition. Total processing pressure was regulated at 40 Pa (300 mTorr), with gas flow rates of 30 sccm of hydrogen, 2.4 sccm of methane and 1 sccm of oxygen. Diamond films obtained under the above conditions have grain sizes between 0.1--0.3 {mu}m, a growth rate of 0.1{mu}m/hr and a mean roughness of 14.95 nm. Characterization techniques have involved XRD, Raman spectroscopy, SEM, AFM and TEM. Both X-ray and electron diffraction patterns show no evidence of non-diamond phases. Although a high density of twins and stacking faults were revealed by HREM, compact diamond grains and clean intergranular boundaries (no graphitic or amorphous phases) were observed.

  8. Transparent Nano-Crystalline TiO2 films

    NASA Astrophysics Data System (ADS)

    Sakthivel, K.; Venkatachalam, T.; Renugadevi, R.

    2011-10-01

    Thin films of TiO2 have been deposited on well cleaned glass substrates by Sol-Gel dip-drive coating technique. The films have been prepared at three different pH values (3, 5, and 9) of Sol and annealed in muffle furnace at three distinct temperatures (350 °C, 450 °C, and 550 °C) for one hour and are allowed to cool to room temperature. The films were characterized by XRD, EDAX, SEM and UV-Vis Spectrophotometer. The as deposited films were found to be amorphous in nature. The annealed films exhibit anatase in crystalline structure. The EDAX results have shown that all the films are maintained with TiO2 in composition. The XRD results reveal that they are nano-crystalline in nature and the crystalline nature increases with annealing temperature and pH of the Sol. The transmittance and absorbance spectra have shown that the films are transparent and band gap of the films are of the order of 3 eV. The ab initio studies of TiO2 (using GGA) was performed with Vienna ab initio Simulation package and the band structure and effective masses of the electrons and holes were determined.

  9. Influence of physicochemical-electronic properties of transition metal ion doped polycrystalline titania on the photocatalytic degradation of Indigo Carmine and 4-nitrophenol under UV/solar light

    NASA Astrophysics Data System (ADS)

    Devi, L. Gomathi; Kumar, S. Girish

    2011-01-01

    To understand the role of dopant inside TiO2 matrix, anatase TiO2 was doped with transition metal ions like Mn2+, Fe3+, Ru3+ and Os3+ having unique half filled electronic configuration and their photocatalytic activity was probed in the degradation of Indigo Carmine (IC) and 4-nitrophenol (NP) under UV/solar light. For comparison, TiO2 was also doped with V5+, Ni2+ and Zn2+ metal ions having d0, d8 and d10 electronic configuration respectively. Irrespective of excitation source UV/solar light and nature of the organic pollutant, photocatalytic activities of doped photocatalysts followed the order: Mn2+-TiO2 > Fe3+-TiO2 > Ru3+-TiO2 ≥ Os3+-TiO2 > Zn2+-TiO2 > V5+-TiO2 > Ni2+-TiO2 at an optimum concentration of dopant. Based on the experimental results obtained, it is proposed that the existence of dopant with half filled electronic configuration in TiO2 matrix which is known to enhance the photocatalytic activity is not universal! Rather it is a complex function of several physicochemical-electronic properties of doped titania. Enhanced photocatalytic activity of Mn2+ (0.06 at.%)-TiO2 was attributed to the combined factors of high positive reduction potential of Mn2+/Mn3+ pairs, synergistic effects in the mixed polymorphs of anatase and rutile, smaller crystallite size with high intimate contact between two phases and favorable surface structure of the photocatalyst. Despite the intense research devoted to transition metal ion doped TiO2, it is rather difficult to make unifying conclusion which is highlighted in this study.

  10. A simple route to synthesize mesoporous titania from TiOSO4: Influence of the synthesis conditions on the structural, pigments and photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Yang, Guang; Ding, Hao; Chen, Daimei; Ao, Weihua; Wang, Jian; Hou, Xifeng

    2016-07-01

    The work obtained mesoporous TiO2 white pigments using titanyl sulfate as titanium source with a simple, low-temperature method simplifying the synthesis process and reducing the energy consumption. We investigated the effects of the aging temperature and aging time on the structure and pigments properties of the samples. The structure and morphology of mesoporous samples were characterized by X-ray diffraction and transmission electron microscopy. The obtained mesoporous TiO2 showed excellent pigments properties of whiteness (93.91%), hiding power (12.37 g m-2), and lightness value (97.89), respectively. Moreover, such materials showed outstanding photodegradation performance of organic dyes under UV light irradiation. The current research provided an alternative route to prepare mesoporous TiO2 micspheres white pigments with well photocatalytic performance for indoor purification on industrial scale. It has great significance in titania white pigments field.

  11. Synthesis and evaluation of iron-doped titania/silane based hydrogel for the adsorptional photocatalytic degradation of Victoria blue under visible light.

    PubMed

    Anirudhan, Thayyath S; Divya, Peethambaran L; Nima, Jayachandran; Sandeep, Sadanandan

    2014-11-15

    Novel photocatalyst, poly(itaconic acid-co-2-acrylamido-2-methylpropane-1-sulfonic acid) iron doped titania/silane was successfully prepared by the polymerization of iron doped titania/silane and two functional monomers, itaconic acid and 2-acrylamido-2-methylpropane-1-sulfonic acid in aqueous solution using ethylene glycol dimethacrylate as cross-linker and benzoylperoxide as initiator. The sample was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Diffuse reflectance spectroscopy (DRS) techniques. Effects of various factors like pH, adsorbent dose, contact time, and ionic strength on the adsorption capacity of photocatalyst for Victoria blue (VB) were studied by batch adsorption experiments. The kinetic data were found to follow pseudo-second-order kinetic model with low chi square, χ(2) values and R(2) values closer to unity. The equilibrium data were in well agreement with Langmuir isotherm model and maximum adsorption capacity was found to be 153.89 mg/g. The swelling capacity of the adsorbent with changes in pH, time and temperature was also investigated. The kinetics of photocatalytic degradation of VB by the photocatalyst found to follow first-order kinetics. The regeneration and repeated use of photocatalyst were also examined upto four cycles. The prepared photocatalyst was found to be efficient photocatalyst-cum-adsorbent for the degradation of VB from aqueous solutions under solar light. PMID:25168582

  12. Formation of Nano-crystalline Todorokite from Biogenic Mn Oxides

    SciTech Connect

    Feng, X.; Zhu, M; Ginder-Vogel, M; Ni, C; Parikh, S; Sparks, D

    2010-01-01

    Todorokite, as one of three main Mn oxide phases present in oceanic Mn nodules and an active MnO{sub 6} octahedral molecular sieve (OMS), has garnered much interest; however, its formation pathway in natural systems is not fully understood. Todorokite is widely considered to form from layer structured Mn oxides with hexagonal symmetry, such as vernadite ({delta}-MnO{sub 2}), which are generally of biogenic origin. However, this geochemical process has not been documented in the environment or demonstrated in the laboratory, except for precursor phases with triclinic symmetry. Here we report on the formation of a nanoscale, todorokite-like phase from biogenic Mn oxides produced by the freshwater bacterium Pseudomonas putida strain GB-1. At long- and short-range structural scales biogenic Mn oxides were transformed to a todorokite-like phase at atmospheric pressure through refluxing. Topotactic transformation was observed during the transformation. Furthermore, the todorokite-like phases formed via refluxing had thin layers along the c* axis and a lack of c* periodicity, making the basal plane undetectable with X-ray diffraction reflection. The proposed pathway of the todorokite-like phase formation is proposed as: hexagonal biogenic Mn oxide {yields} 10-{angstrom} triclinic phyllomanganate {yields} todorokite. These observations provide evidence supporting the possible bio-related origin of natural todorokites and provide important clues for understanding the transformation of biogenic Mn oxides to other Mn oxides in the environment. Additionally this method may be a viable biosynthesis route for porous, nano-crystalline OMS materials for use in practical applications.

  13. Formation of nano-crystalline todorokite from biogenic Mn oxides

    NASA Astrophysics Data System (ADS)

    Feng, Xiong Han; Zhu, Mengqiang; Ginder-Vogel, Matthew; Ni, Chaoying; Parikh, Sanjai J.; Sparks, Donald L.

    2010-06-01

    Todorokite, as one of three main Mn oxide phases present in oceanic Mn nodules and an active MnO 6 octahedral molecular sieve (OMS), has garnered much interest; however, its formation pathway in natural systems is not fully understood. Todorokite is widely considered to form from layer structured Mn oxides with hexagonal symmetry, such as vernadite (δ-MnO 2), which are generally of biogenic origin. However, this geochemical process has not been documented in the environment or demonstrated in the laboratory, except for precursor phases with triclinic symmetry. Here we report on the formation of a nanoscale, todorokite-like phase from biogenic Mn oxides produced by the freshwater bacterium Pseudomonas putida strain GB-1. At long- and short-range structural scales biogenic Mn oxides were transformed to a todorokite-like phase at atmospheric pressure through refluxing. Topotactic transformation was observed during the transformation. Furthermore, the todorokite-like phases formed via refluxing had thin layers along the c∗ axis and a lack of c∗ periodicity, making the basal plane undetectable with X-ray diffraction reflection. The proposed pathway of the todorokite-like phase formation is proposed as: hexagonal biogenic Mn oxide → 10-Å triclinic phyllomanganate → todorokite. These observations provide evidence supporting the possible bio-related origin of natural todorokites and provide important clues for understanding the transformation of biogenic Mn oxides to other Mn oxides in the environment. Additionally this method may be a viable biosynthesis route for porous, nano-crystalline OMS materials for use in practical applications.

  14. The enhanced photocatalytic performance of Z-scheme two-dimensional/two-dimensional heterojunctions from graphitic carbon nitride nanosheets and titania nanosheets.

    PubMed

    Chen, Binhe; Li, Peiran; Zhang, Shisheng; Zhang, Wei; Dong, Xiaoping; Xi, Fengna; Liu, Jiyang

    2016-09-15

    A direct solid state Z-scheme photocatalytic system was fabricated by assembling two-dimensional (2D) g-C3N4 nanosheets (CNNS) and titania nanosheets (TNS), which were obtained from the delamination of their corresponding layered precursors. By introducing TNS, the interlayer restacking of CNNS was effectively prohibited, forming uniform CNNS/TNS composites. The tightly contacted CNNS/TNS interface promoted the charge transfer and therefore improved the separation ratio of photogenerated electron-hole pairs. The photocatalytic performance of CNNS/TNS in various mass ratios was investigated for dye degradation, and the degradation rate of optimal sample 0.7CNNS/0.3TNS was 2.34 and 48.5 times higher than those of proton flocculated pure CNNS and TNS, respectively. Superoxide radicals and hydroxyl radicals were determined as the main active species by the quenching experiment. Moreover, the enhanced generation of superoxide radicals and hydroxyl radicals was confirmed by the absorption spectra of nitroblue tetrazolium and the photoluminescence spectra of 2-hydroxy terephthalic acid, respectively. Finally, we proposed a possible Z-scheme mechanism based on the theoretical calculation and the experimental results. PMID:27309946

  15. Influence of post-treatment operations on structural properties and photocatalytic activity of octahedral anatase titania particles prepared by an ultrasonication-hydrothermal reaction.

    PubMed

    Wei, Zhishun; Kowalska, Ewa; Ohtani, Bunsho

    2014-01-01

    The influence of changes in structural and physical properties on the photocatalytic activity of octahedral anatase particles (OAPs), exposing eight equivalent {101} facets, caused by calcination (2 h) in air or grinding (1 h) in an agate mortar was studied with samples prepared by ultrasonication (US; 1 h)-hydrothermal reaction (HT; 24 h, 433 K). Calcination in air at temperatures up to 1173 K induced particle shape changes, evaluated by aspect ratio (AR; d001/d101 = depth vertical to anatase {001} and {101} facets estimated by the Scherrer equation with data obtained from X-ray diffraction (XRD) patterns) and content of OAP and semi-OAP particles, without transformation into rutile. AR and OAP content, as well as specific surface area (SSA), were almost unchanged by calcination at temperatures up to 673 K and were then decreased by elevating the calcination temperature, suggesting that calcination at a higher temperature caused dull-edging and particle sintering, the latter also being supported by the analysis of particle size using XRD patterns and scanning electron microscopic (SEM) images. Time-resolved microwave conductivity (TRMC) showed that the maximum signal intensity (Imax), corresponding to a product of charge-carrier density and mobility, and signal-decay rate, presumably corresponding to reactivity of charge carriers, were increased with increase in AR, suggesting higher photocatalytic activity of OAPs than that of dull-edged particles. Grinding also decreased the AR, indicating the formation of dull-edged particles. The original non-treated samples showed activities in the oxidative decomposition of acetic acid (CO2 system) and dehydrogenation of methanol (H2 system) comparable to and lower than those of a commercial anatase titania (Showa Denko Ceramics FP-6), respectively. The activities of calcined and ground samples for the CO2 system and H2 system showed almost linear relations with AR and Imax, respectively, suggesting that those activities may

  16. Visible-Light-Responsive Photocatalytic Flow Reactor Composed of Titania Film Photosensitized by Metal Complex-Clay Hybrid.

    PubMed

    Goto, Takehito; Ogawa, Makoto

    2015-06-17

    Synthetic saponite containing a photosensitizing metal complex, tris(2,2'-bipyridine)ruthenium(II)), in the interlayer space was complexed with anatase nanoparticles to obtain transparent hybrid film photocatalyst. The catalyst film was mounted in a flow reactor device to catalyze such photocatalytic reactions as the decomposition of aqueous acetic acid and N-alkylation of benzylamine with ethanol. PMID:26029789

  17. Photocatalytic discoloration of Acid Red 14 aqueous solution using titania nanoparticles immobilized on graphene oxide fabricated plate.

    PubMed

    Akerdi, Abdollah Gholami; Bahrami, S Hajir; Arami, Mokhtar; Pajootan, Elmira

    2016-09-01

    Textile industry consumes remarkable amounts of water during various operations. A significant portion of the water discharge to environment is in the form of colored contaminant. The present research reports the photocatalytic degradation of anionic dye effluent using immobilized TiO2 nanoparticle on graphene oxide (GO) fabricated carbon electrodes. Acid Red 14 (AR 14) was used as model compound. Graphene oxide nanosheets were synthesized from graphite powder using modified Hummer's method. The nanosheets were characterized with field emission scanning electron microscope (FESEM) images, X-ray diffraction (XRD) and FTIR spectrum. The GO nanoparticles were deposited on carbon electrode (GO-CE) by electrochemical deposition (ECD) method and used as catalyst bed. TiO2 nanoparticles were fixed on the bed (GO-CE- TiO2) with thermal process. Photocatalytic processes were carried out using a 500 ml solution containing dye in batch mode. Each photocatalytic treatment were carried out for 120 min. Effect of dye concentration (mg/L), pH of solution, time (min) and TiO2 content (g/L) on the photocatalytic decolorization was investigated. PMID:27309674

  18. Preparation, characterization of Au (or Pt)-loaded titania nanotubes and their photocatalytic activities for degradation of methyl orange

    NASA Astrophysics Data System (ADS)

    Zhao, Qian; Li, Mei; Chu, Jinyu; Jiang, Tingshun; Yin, Hengbo

    2009-01-01

    TiO 2 nanotubes were prepared by hydrothermal method and Au (or Pt) was loaded on TiO 2 nanotubes by photodeposition method. The photocatalysts were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and N 2 adsorption technique, respectively. The photocatalytic properties of the samples were also investigated. The results show that TiO 2 nanotubes with uniform diameter were prepared, and they have specific surface areas over 400 m 2/g. The specific surface areas of TiO 2 nanotubes decrease with the increasing of calcining temperature, and crystalline phase of TiO 2 in the wall of nanotubes was transformed from anatase into rutile phase in calcination process. The photocatalytic activities of TiO 2 nanotubes are higher than that of nanosized TiO 2, and the photocatalytic activities of TiO 2 nanotubes were enhanced after loading Au (or Pt). After irradiation for 40 min under a 300 W of middle-pressure mercury lamp (MPML), the degradation rate of methyl orange solution using the Au/TiNT-500 (or Pt/TiNT-500) as a catalyst can reach 96.1% (or 95.1%). On the other hand, Au-loaded sample has evident adsorption peak in visible range, indicating that Au-loaded TiO 2 nanotubes are hopeful to become visible light photocatalyst.

  19. Exfoliated and reorganized graphite oxide on titania nanoparticles as an auxiliary co-catalyst for photocatalytic solar conversion.

    PubMed

    Park, Yiseul; Kang, Seung-Hee; Choi, Wonyong

    2011-05-28

    The hybrid of graphite oxide (GO)/TiO(2) was prepared through the spontaneous exfoliation of bulky graphite oxide and reorganization with TiO(2) nanoparticles as a solar conversion and hydrogen-generating photocatalyst. GO/TiO(2) showed enhanced activities for both photocurrent generation (in an electrode form) and hydrogen production (in a slurry form) than those of bare TiO(2) under UV light irradiation. The enhanced photocatalytic activity of GO/TiO(2) is ascribed to the ability of graphitic layers in accepting and transporting electrons from excited TiO(2), promoting the charge separation. When GO was hybridized with platinized TiO(2) (Pt/TiO(2)), it showed a marked synergistic effect for the photocatalytic hydrogen production compared with GO/TiO(2) and Pt/TiO(2). This indicates that the cheap and abundant carbon material can be a good candidate for an electron attracting reservoir and an auxiliary co-catalyst for the photocatalytic hydrogen production. PMID:21483932

  20. H2 production by the photocatalytic reforming of cellulose and raw biomass using Ni, Pd, Pt and Au on titania

    PubMed Central

    Jones, W.; Hardacre, C.; Bowker, M.

    2016-01-01

    Here, we report a method for sustainable hydrogen production using sunlight and biomass. It is shown that cellulose can be photoreformed to produce hydrogen, even in solid form, by use of metal-loaded titania photocatalysts. The experiments performed verified that the process is enabled by initial hydrolysis via glucose, which itself is shown to be efficiently converted to produce hydrogen by photocatalysis. Importantly, it is shown that not only precious metals such as Pt, Pd and Au can be used as the metal component, but also much more economic and less environmentally damaging Ni is effective. Even more importantly, we show for the first time, to the best our knowledge, that fescue grass as raw biomass can be effective for hydrogen production without significant pre-treatment. This provides additional benefits for the efficiency of biomass hydrogen production, because fewer processing steps for the raw material are required than in the production of purer forms of cellulose, for example. PMID:27493561

  1. Atomic thin titania nanosheet-coupled reduced graphene oxide 2D heterostructures for enhanced photocatalytic activity and fast lithium storage

    NASA Astrophysics Data System (ADS)

    Li, Dong Jun; Huang, Zhegang; Hwang, Tae Hoon; Narayan, Rekha; Choi, Jang Wook; Kim, Sang Ouk

    2016-03-01

    Realizing practical high performance materials and devices using the properties of 2D materials is of key research interest in the materials science field. In particular, building well-defined heterostructures using more than two different 2D components in a rational way is highly desirable. In this paper, a 2D heterostructure consisting of atomic thin titania nanosheets densely grown on reduced graphene oxide surface is successfully prepared through incorporating polymer functionalized graphene oxide into the novel TiO2 nanosheets synthesis scheme. As a result of the synergistic combination of a highly accessible surface area and abundant interface, which can modulate the physicochemical properties, the resultant heterostructure can be used in high efficiency visible light photocatalysis as well as fast energy storage with a long lifecycle. [Figure not available: see fulltext.

  2. Silica-titania composite aerogel photocatalysts by chemical liquid deposition of titania onto nanoporous silica scaffolds.

    PubMed

    Zu, Guoqing; Shen, Jun; Wang, Wenqin; Zou, Liping; Lian, Ya; Zhang, Zhihua

    2015-03-11

    Silica-titania composite aerogels were synthesized by chemical liquid deposition of titania onto nanoporous silica scaffolds. This novel deposition process was based on chemisorption of partially hydrolyzed titanium alkoxides from solution onto silica nanoparticle surfaces and subsequent hydrolysis and condensation to afford titania nanoparticles on the silica surface. The titania is homogeneously distributed in the silica-titania composite aerogels, and the titania content can be effectively controlled by regulating the deposition cycles. The resultant composite aerogel with 15 deposition cycles possessed a high specific surface area (SSA) of 425 m(2)/g, a small particle size of 5-14 nm, and a large pore volume and pore size of 2.41 cm(3)/g and 18.1 nm, respectively, after heat treatment at 600 °C and showed high photocatalytic activity in the photodegradation of methylene blue under UV-light irradiation. Its photocatalytic activity highly depends on the deposition cycles and heat treatment. The combination of small particle size, high SSA, and enhanced crystallinity after heat treatment at 600 °C contributes to the excellent photocatalytic property of the silica-titania composite aerogel. The higher SSAs compared to those of the reported titania aerogels (<200 m(2)/g at 600 °C) at high temperatures combined with the simple method makes the silica-titania aerogels promising candidates as photocatalysts. PMID:25664480

  3. Microemulsion-mediated solvothermal synthesis and photocatalytic properties of crystalline titania with controllable phases of anatase and rutile.

    PubMed

    Shen, Xiaojun; Zhang, Jinlong; Tian, Baozhu

    2011-08-30

    Titanium oxide with different ratios of anatase to rutile has been prepared by the microemulsion-mediated solvothermal method. The resulting samples were investigated by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, UV-vis diffuse reflectance spectra, transmission electron microscopy and Brunauer-Emmett-Teller analysis. The contents of anatase and rutile in the TiO(2) particles have been successfully controlled by simply adjusting the amount of urea in the aqueous phase of the microemulsion. Both the degradation of Rhodamine B in aqueous solutions and mineralization of TOC revealed that the catalyst containing 47.6% anatase have presented the highest photocatalytic activity. A proposed mechanism is discussed to interpret the evolution of the phases based on the effect of different amount of urea. PMID:21684078

  4. Voltammetric and impedance behaviours of surface-treated nano-crystalline diamond film electrodes

    SciTech Connect

    Liu, F. B.; Jing, B.; Cui, Y.; Di, J. J.; Qu, M.

    2015-04-15

    The electrochemical performances of hydrogen- and oxygen-terminated nano-crystalline diamond film electrodes were investigated by cyclic voltammetry and AC impedance spectroscopy. In addition, the surface morphologies, phase structures, and chemical states of the two diamond films were analysed by scanning probe microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results indicated that the potential window is narrower for the hydrogen-terminated nano-crystalline diamond film than for the oxygen-terminated one. The diamond film resistance and capacitance of oxygen-terminated diamond film are much larger than those of the hydrogen-terminated diamond film, and the polarization resistances and double-layer capacitance corresponding to oxygen-terminated diamond film are both one order of magnitude larger than those corresponding to the hydrogen-terminated diamond film. The electrochemical behaviours of the two diamond film electrodes are discussed.

  5. The Effect of Photon Source on Heterogeneous Photocatalytic Oxidation of Ethanol by a Silica-Titania Composite

    NASA Technical Reports Server (NTRS)

    Coutts, Janelle L.; Levine, Lanfang H.; Richards, Jeffrey T.; Mazyck, David W.

    2011-01-01

    The objective of this study was to distinguish the effect of photon flux (i.e., photons per unit time reaching a surface) from that of photon energy (i.e., wavelength) of a photon source on the silica-titania composite (STC)-catalyzed degradation of ethanol in the gas phase. Experiments were conducted in a bench-scale annular reactor packed with STC pellets and irradiated with either a UV-A fluorescent black light blue lamp ((gamma)max=365 nm) at its maximum light intensity or a UV-C germicidal lamp ((gamma)max=254 nm) at three levels of light intensity. The STC-catalyzed oxidation of ethanol was found to follow zero-order kinetics with respect to CO2 production, regardless of the photon source. Increased photon flux led to increased EtOH removal, mineralization, and oxidation rate accompanied by lower intermediate concentration in the effluent. The oxidation rate was higher in the reactor irradiated by UV-C than by UV-A (38.4 vs. 31.9 nM/s) at the same photon flux, with similar trends for mineralization (53.9 vs. 43.4%) and reaction quantum efficiency (i.e., photonic efficiency, 63.3 vs. 50.1 nmol CO2 (mu)mol/photons). UV-C irradiation also led to decreased intermediate concentration in the effluent . compared to UV-A irradiation. These results demonstrated that STC-catalyzed oxidation is enhanced by both increased photon flux and photon energy.

  6. Achieving significantly enhanced visible-light photocatalytic efficiency using a polyelectrolyte: the composites of exfoliated titania nanosheets, graphene, and poly(diallyl-dimethyl-ammonium chloride)

    NASA Astrophysics Data System (ADS)

    Zhang, Qian; An, Qi; Luan, Xinglong; Huang, Hongwei; Li, Xiaowei; Meng, Zilin; Tong, Wangshu; Chen, Xiaodong; Chu, Paul K.; Zhang, Yihe

    2015-08-01

    A high-performance visible-light-active photocatalyst is prepared using the polyelectrolyte/exfoliated titania nanosheet/graphene oxide (GO) precursor by flocculation followed by calcination. The polyelectrolyte poly(diallyl-dimethyl-ammonium chloride) serves not only as an effective binder to precipitate GO and titania nanosheets, but also boosts the overall performance of the catalyst significantly. Unlike most titania nanosheet-based catalysts reported in the literature, the composite absorbs light in the UV-Vis-NIR range. Its decomposition rate of methylene blue is 98% under visible light. This novel strategy of using a polymer to enhance the catalytic performance of titania nanosheet-based catalysts affords immense potential in designing and fabricating next-generation photocatalysts with high efficiency.A high-performance visible-light-active photocatalyst is prepared using the polyelectrolyte/exfoliated titania nanosheet/graphene oxide (GO) precursor by flocculation followed by calcination. The polyelectrolyte poly(diallyl-dimethyl-ammonium chloride) serves not only as an effective binder to precipitate GO and titania nanosheets, but also boosts the overall performance of the catalyst significantly. Unlike most titania nanosheet-based catalysts reported in the literature, the composite absorbs light in the UV-Vis-NIR range. Its decomposition rate of methylene blue is 98% under visible light. This novel strategy of using a polymer to enhance the catalytic performance of titania nanosheet-based catalysts affords immense potential in designing and fabricating next-generation photocatalysts with high efficiency. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03256c

  7. Assessment of formulation robustness for nano-crystalline suspensions using failure mode analysis or derisking approach.

    PubMed

    Nakach, Mostafa; Authelin, Jean-René; Voignier, Cecile; Tadros, Tharwat; Galet, Laurence; Chamayou, Alain

    2016-06-15

    The small particle size of nano-crystalline suspensions can be responsible for their physical instability during drug product preparation (downstream processing), storage and administration. For that purpose, the commercial formulation needs to be sufficiently robust to various triggering conditions, such as ionic strength, shear rate, wetting/dispersing agent desorption by dilution, temperature and pH variation. In our previous work we described a systematic approach to select the suitable wetting/dispersant agent for the stabilization of nano-crystalline suspension. In this paper, we described the assessment of the formulation robustness (stabilized using a mixture of sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP) and) by measuring the rate of perikinetic (diffusion-controlled) and orthokinetic (shear-induced) aggregation as a function of ionic strength, temperature, pH and dilution. The results showed that, using the SDS/PVP system, the critical coagulation concentration is about five times higher than that observed in the literature for suspension colloidaly stable at high concentration. The nano-suspension was also found to be very stable at ambient temperature and at different pH conditions. Desorption test confirmed the high affinity between API and wetting/dispersing agent. However, the suspension undergoes aggregation at high temperature due to the desorption of the wetting/dispersing agent and disaggregation of SDS micelles. Furthermore, aggregation occurs at very high shear rate (orhokinetic aggregation) by overcoming the energy barrier responsible for colloidal stability of the system. PMID:27102992

  8. Effect Of Chromium Underlayer On The Properties Of Nano-Crystalline Diamond Films

    SciTech Connect

    Garratt, Elias; AlFaify, Salem; Yoshitake, T.; Katamune, Yuki; Bowden, Mark; Nandasiri, Manjula I.; Ghantasala, S.; Mancini, D. C.; Thevuthasan, Suntharampillai; Kayani, A.

    2013-01-11

    This paper investigated the effect of chromium underlayer on the structure, microstructure and composition of the nano-crystalline diamond films. Nano-crystalline diamond thin films were deposited at high temperature in microwave-induced plasma diluted with nitrogen, on silicon substrate with a thin film of chromium as an underlayer. The composition, structure and microstructure of the deposited layers were analyzed using non-Rutherford Backscattering Spectrometry, Raman Spectroscopy, Near-Edge X-Ray Absorption Fine Structure, X-ray Diffraction and Atomic Force Microscopy. Nanoindentation studies showed that the films deposited on chromium underlayer have higher hardness values compared to those deposited on silicon without an underlayer. Diamond and graphitic phases of the films evaluated by x-ray and optical spectroscopic analysis determined consistency between sp2 and sp3 phases of carbon in chromium sample to that of diamond grown on silicon. Diffusion of chromium was observed using ion beam analysis which was correlated with the formation of chromium complexes by x-ray diffraction.

  9. Seasonal variation in the properties of titania photocatalysts produced from Ti-salt flocculated bioresource sludge.

    PubMed

    Okour, Y; Shon, H K; Liu, H; Kim, J B; Kim, J H

    2011-05-01

    Ti-salt flocculation of biologically treated sewage effluent (BTSE) was carried out on monthly basis during one year to trace the seasonal variation in the properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts. Titania photocatalysts were produced from incineration of Ti-salt flocculated sludge at 600°C. The physio-chemical properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts were investigated. The photocatalytic activity of titania was examined using different substrates of rhodamine B and humic acid under UV light irradiation. Results indicated that the flocculation performance of Ti-salt was not affected by the seasonal variation of BTSE. BTSE characteristics resulted in marginal effect in titania characterisation and photocatalytic activity. Titania photocatalysts produced from Ti-salt flocculated sludge in different seasons showed constant anatase phase, high BET surface area and high photocatalytic activity. PMID:21144742

  10. Synthesis of nano-crystalline hydroxyapatite and ammonium sulfate from phosphogypsum waste

    SciTech Connect

    Mousa, Sahar; Hanna, Adly

    2013-02-15

    Graphical abstract: TEM micrograph of dried HAP at 800 °C. -- Abstract: Phosphogypsum (PG) waste which is derived from phosphoric acid manufacture by using wet method was converted into hydroxyapatite (HAP) and ammonium sulfate. Very simple method was applied by reacting PG with phosphoric acid in alkaline medium with adjusting pH using ammonia solution. The obtained nano-HAP was dried at 80 °C and calcined at 600 °C and 900 °C for 2 h. Both of HAP and ammonium sulfate were characterized by X-ray diffraction (XRD) and infrared spectroscopy (IR) to study the structural evolution. The thermal behavior of nano-HAP was studied; the particle size and morphology were estimated by using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). All the results showed that HAP nano-crystalline and ammonium sulfate can successfully be produced from phosphogypsum waste.

  11. High pressure nano-crystalline microstructure of shock compressed single crystal iron

    SciTech Connect

    Hawreliak, J; Kalantar, D; Stolken, J; Remington, B; Lorenzana, H; Wark, J

    2007-12-11

    We discuss the first grain size measurements made during shock compression using in situ x-ray diffraction. Our experiments have shown unambiguously that single crystal iron shock loaded above 13 GPa along the [100] direction will transform from the ambient {alpha}-phase (BCC) to a highly ordered polycrystalline {epsilon}-phase (HCP). Here, we present a detailed shape analysis of the diffraction peaks using a modified Warren-Averbach method to quantify the microstructure of shock compressed high pressure iron. The {epsilon}-phase was determined through this method to have grain sizes between of 2 and 15 nm, in reasonable agreement with results from large scale MD simulations. We conclude that single crystal iron becomes nano-crystalline in shock transforming from the {alpha} to {epsilon} phase.

  12. Low energy radiation stability of nano-crystalline cubic Zirconia films

    NASA Astrophysics Data System (ADS)

    Kalita, Parswajit; Ghosh, Santanu; Avasthi, Devesh K.

    2016-07-01

    The radiation stability of nano-crystalline cubic Zirconia films was investigated under 41 keV He ion irradiation. These ions were chosen to simulate alpha particles (produced during fission events) because of the similar electronic energy loss in Zirconia. The ZrO2 films, with an average grain size of 8 nm, were grown on Si (1 0 0) substrates by electron beam assisted thermal evaporation. Although the cubic structure was retained upon irradiation, a slight reduction in crystallinity in the irradiated films was detected as compared to the as-deposited film. No bulk amorphization was however observed for any of the fluences and hence these films are radiation tolerant to alpha particles.

  13. Nano-crystalline porous tin oxide film for carbon monoxide sensing

    NASA Technical Reports Server (NTRS)

    Liu, Chung-Chiun (Inventor); Savinell, Robert F. (Inventor); Jin, Zhihong (Inventor)

    2000-01-01

    A tin oxide sol is deposited on platinum electrodes (12) of a sensor (10). The sol is calcined at a temperature of 500 to 800.degree. C. to produce a thin film of tin oxide with a thickness of about 150 nm to 2 .mu. and having a nano-crystalline structure with good stability. The sensor rapidly detects reducing gases, such as carbon monoxide, or hydrocarbons and organic vapors. Sensors using films calcined at around 700.degree. C. have high carbon monoxide selectivity with a response time of around 4 minutes and a recovery time of 1 minute, and therefore provide good detection systems for detection of trace amounts of pollutants such as toxic and flammable gases in homes, industrial settings, and hospitals.

  14. The composite of nitrogen-doped anatase titania plates with exposed {001} facets/graphene nanosheets for enhanced visible-light photocatalytic activity.

    PubMed

    Shi, Jian-Wen; Ai, Hui-Ying; Chen, Jian-Wei; Cui, Hao-Jie; Fu, Ming-Lai

    2014-09-15

    Composite photocatalysts composed of nitrogen-doped anatase TiO2 plates with exposed {001} facets (NTS) and graphene nanosheets (G) were firstly synthesized by a facile one-pot hydrothermal process. The morphologies, structural properties, and photocatalytic activities of the resultant NTS/G composites were investigated in detail. Graphene nanosheets were demonstrated play three important roles in the NTS/G composites, as transporter of photo-excited electrons, extender of light absorption range and enhancer of adsorptive capacity, respectively. Due to the effective charge anti-recombination, the efficient utilization of the visible light and the high adsorptive capacity to target pollutants, the composites exhibited significant improvement in photocatalytic degradation of methylene blue under visible light irradiation. Based on the results, the mechanism of enhanced visible-light photocatalytic activity on NTS/G composites was proposed. PMID:24998060

  15. Self-organized vanadium and nitrogen co-doped titania nanotube arrays with enhanced photocatalytic reduction of CO2 into CH4

    PubMed Central

    2014-01-01

    Self-organized V-N co-doped TiO2 nanotube arrays (TNAs) with various doping amount were synthesized by anodizing in association with hydrothermal treatment. Impacts of V-N co-doping on the morphologies, phase structures, and photoelectrochemical properties of the TNAs films were thoroughly investigated. The co-doped TiO2 photocatalysts show remarkably enhanced photocatalytic activity for the CO2 photoreduction to methane under ultraviolet illumination. The mechanism of the enhanced photocatalytic activity is discussed in detail. PMID:24948893

  16. Synthesis and characterization of nano crystalline BaFe{sub 12}O{sub 19} powders by low temperature combustion

    SciTech Connect

    Huang Jianguo; Zhuang Hanrui; Li Wenlan

    2003-01-01

    Nano crystalline BaFe{sub 12}O{sub 19} powders have been prepared at a relatively low calcination temperature by a gel combustion technique using citric acid as a fuel/reductant and nitrates as oxidants. The effects of processing parameters, such as Ba/Fe ratio, citric acid/nitrates ratio, reaction temperature on the powder characteristics and magnetic properties of the resultant barium ferrites were investigated. By controlling the molar ratio of citric acid to metal nitrates, nano crystalline BaFe{sub 12}O{sub 19} powders with different particle sizes have been obtained. Phase attributes, microstructures and magnetic properties of the powders were characterized using X-ray diffraction analysis, X-ray line-broadening technique, Fourier transform infrared spectroscopy measurements, transmission electron microscopy and vibrating sample magnetometer. The maximum saturation magnetization value and intrinsic coercivity value for the obtained barium hexaferrites are 59.36 emu/g and 5540 Oe.

  17. Nano-crystalline powders and suspensions generated using a flow-through hydrothermal process, Part 1: Characterization

    SciTech Connect

    Darab, J.G.; Buehler, M.F.; Linehan, J.C.; Matson, D.W.

    1994-04-01

    A wide range of ultra-fine, nano-crystalline powders and suspensions have been produced using Rapid Thermal Decomposition of precursors in Solution (RTDS). These materials include single and multi-component iron-, 11 zirconium-, titanium-, nickel-, and chromium-oxide/oxyhydroxide powders. RTDS is a flow-through hydrothermal process capable of producing nano-crystalline particulate material at rates of up to 100 grams of solid per hour. We present the results of characterization efforts on RTDS iron oxyhydroxide and zirconium oxide systems. As-collected RTDS suspensions were characterized using optical light scattering. Separated RTDS powders were evaluated using X-ray diffraction, electron microscopy, gas adsorption analysis, thermal gravimetric analysis, and chemical analysis.

  18. Preparation of titania nanotube-Cd0.65Zn0.35S nanocomposite by a hydrothermal sulfuration method for efficient visible-light-driven photocatalytic hydrogen production

    NASA Astrophysics Data System (ADS)

    Li, Juan; Wu, Liangpeng; Long, Lizhen; Xi, Min; Li, Xinjun

    2014-12-01

    Titania nanotube-Cd0.65Zn0.35S nanocomposite (Cd0.65Zn0.35S-TiO2) was synthesized from titanate nanotubes for ion change of Cd2+ and Zn2+ followed by hydrothermal sulfuration treatment using thiourea as sulfur source. The Cd0.65Zn0.35S-TiO2 with enhanced crystallinity of TiO2 nanotube can be obtained by increasing hydrothermal temperature from 90 °C to 120 °C. And further increasing hydrothermal temperature to 150 °C, TiO2 nanotubes collapse and transform into irregular shaped particles. The photocatalytic activity for hydrogen production of the prepared Cd0.65Zn0.35S-TiO2 with different hydrothermal temperature was investigated under visible-light irradiation. The result shows that the Cd0.65Zn0.35S-TiO2 with hydrothermal temperature of 120 °C presents the highest hydrogen evolution rate and photostability, which can be attributed to a rapid charge transfer at the interface between Cd0.65Zn0.35S and TiO2 nanotube due to the increased crystallinity and unique 1-D nanotubular structure of TiO2.

  19. Oxidation-Based Continuous Laser Writing in Vertical Nano-Crystalline Graphite Thin Films

    NASA Astrophysics Data System (ADS)

    Loisel, Loïc; Florea, Ileana; Cojocaru, Costel-Sorin; Tay, Beng Kang; Lebental, Bérengère

    2016-05-01

    Nano and femtosecond laser writing are becoming very popular techniques for patterning carbon-based materials, as they are single-step processes enabling the drawing of complex shapes without photoresist. However, pulsed laser writing requires costly laser sources and is known to cause damages to the surrounding material. By comparison, continuous-wave lasers are cheap, stable and provide energy at a more moderate rate. Here, we show that a continuous-wave laser may be used to pattern vertical nano-crystalline graphite thin films with very few macroscale defects. Moreover, a spatially resolved study of the impact of the annealing to the crystalline structure and to the oxygen ingress in the film is provided: amorphization, matter removal and high oxygen content at the center of the beam; sp2 clustering and low oxygen content at its periphery. These data strongly suggest that amorphization and matter removal are controlled by carbon oxidation. The simultaneous occurrence of oxidation and amorphization results in a unique evolution of the Raman spectra as a function of annealing time, with a decrease of the I(D)/I(G) values but an upshift of the G peak frequency.

  20. Synthesis and characterization of nano crystalline nickel zinc ferrite for chlorine gas sensor at room temperature

    SciTech Connect

    Pawar, C. S.; Gujar, M. P.; Mathe, V. L.

    2015-06-24

    Nano crystalline Nickel Zinc ferrite (Ni{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4}) thin films were synthesized by Sol Gel method for gas response. The phase and microstructure of the obtained Ni{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). The nanostructured Ni{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} thin film shows single spinel phase. Magnetic study was obtained with the help of VSM. The effects of working temperature on the gas response were studied. The results reveal that the Ni{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} thin film gas sensor shows good selectivity to chlorine gas at room temperature. The sensor shows highest sensitivity (∼50%) at room temperature, indicating its application in detecting chlorine gas at room temperature in the future.

  1. Oxidation-Based Continuous Laser Writing in Vertical Nano-Crystalline Graphite Thin Films.

    PubMed

    Loisel, Loïc; Florea, Ileana; Cojocaru, Costel-Sorin; Tay, Beng Kang; Lebental, Bérengère

    2016-01-01

    Nano and femtosecond laser writing are becoming very popular techniques for patterning carbon-based materials, as they are single-step processes enabling the drawing of complex shapes without photoresist. However, pulsed laser writing requires costly laser sources and is known to cause damages to the surrounding material. By comparison, continuous-wave lasers are cheap, stable and provide energy at a more moderate rate. Here, we show that a continuous-wave laser may be used to pattern vertical nano-crystalline graphite thin films with very few macroscale defects. Moreover, a spatially resolved study of the impact of the annealing to the crystalline structure and to the oxygen ingress in the film is provided: amorphization, matter removal and high oxygen content at the center of the beam; sp(2) clustering and low oxygen content at its periphery. These data strongly suggest that amorphization and matter removal are controlled by carbon oxidation. The simultaneous occurrence of oxidation and amorphization results in a unique evolution of the Raman spectra as a function of annealing time, with a decrease of the I(D)/I(G) values but an upshift of the G peak frequency. PMID:27194181

  2. Oxidation-Based Continuous Laser Writing in Vertical Nano-Crystalline Graphite Thin Films

    PubMed Central

    Loisel, Loïc; Florea, Ileana; Cojocaru, Costel-Sorin; Tay, Beng Kang; Lebental, Bérengère

    2016-01-01

    Nano and femtosecond laser writing are becoming very popular techniques for patterning carbon-based materials, as they are single-step processes enabling the drawing of complex shapes without photoresist. However, pulsed laser writing requires costly laser sources and is known to cause damages to the surrounding material. By comparison, continuous-wave lasers are cheap, stable and provide energy at a more moderate rate. Here, we show that a continuous-wave laser may be used to pattern vertical nano-crystalline graphite thin films with very few macroscale defects. Moreover, a spatially resolved study of the impact of the annealing to the crystalline structure and to the oxygen ingress in the film is provided: amorphization, matter removal and high oxygen content at the center of the beam; sp2 clustering and low oxygen content at its periphery. These data strongly suggest that amorphization and matter removal are controlled by carbon oxidation. The simultaneous occurrence of oxidation and amorphization results in a unique evolution of the Raman spectra as a function of annealing time, with a decrease of the I(D)/I(G) values but an upshift of the G peak frequency. PMID:27194181

  3. Controllable formation of nano-crystalline in Sb4Te films by Zn doping

    NASA Astrophysics Data System (ADS)

    Wang, Guoxiang; Chen, Yimin; Shen, Xiang; Lu, Yegang; Dai, Shixun; Nie, Qiuhua; Xu, Tiefeng

    2015-01-01

    We investigated the optical, electrical, and thermal properties of Zn-doped Sb4Te films for application in phase change memory. Together with well-documented results of Zn-doped Sb2Te3, Sb2Te, Sb7Te3, and Sb3Te systems, we plotted the ternary amorphous-phase forming-region of Zn-Sb-Te. Zn-doping increased the crystallization temperature and data retention ability of Sb4Te films. We identified the optimal composition as Zn28.6(Sb4Te)71.4, which presents reversible optical performance between the amorphous and crystalline states. The minimum time for onset crystallization was 15 ns and the required pulse width for complete crystallization was 165 ns at 70 mW. Furthermore, in all of the Zn-doped Sb-Te films, it was confirmed that Zn-doping can effectively control the growth of nano-crystalline grains and allows only a single phase to form during crystallization.

  4. Neural learning circuits utilizing nano-crystalline silicon transistors and memristors.

    PubMed

    Cantley, Kurtis D; Subramaniam, Anand; Stiegler, Harvey J; Chapman, Richard A; Vogel, Eric M

    2012-04-01

    Properties of neural circuits are demonstrated via SPICE simulations and their applications are discussed. The neuron and synapse subcircuits include ambipolar nano-crystalline silicon transistor and memristor device models based on measured data. Neuron circuit characteristics and the Hebbian synaptic learning rule are shown to be similar to biology. Changes in the average firing rate learning rule depending on various circuit parameters are also presented. The subcircuits are then connected into larger neural networks that demonstrate fundamental properties including associative learning and pulse coincidence detection. Learned extraction of a fundamental frequency component from noisy inputs is demonstrated. It is then shown that if the fundamental sinusoid of one neuron input is out of phase with the rest, its synaptic connection changes differently than the others. Such behavior indicates that the system can learn to detect which signals are important in the general population, and that there is a spike-timing-dependent component of the learning mechanism. Finally, future circuit design and considerations are discussed, including requirements for the memristive device. PMID:24805040

  5. Nano-crystalline silicon solar cell architecture with absorption at the classical 4n2 limit

    SciTech Connect

    Biswas, Rana; Xu, Chun

    2011-07-04

    We develop a periodically patterned conformal photonic-plasmonic crystal based solar architecture for a nano-crystalline silicon solar cell, through rigorous scattering matrix simulations. The solar cell architecture has a periodic array of tapered silver nano-pillars as the back-reflector coupled with a conformal periodic structure at the top of the cell. The absorption and maximal current, averaged over the entire range of wavelengths, for this solar cell architecture is at the semi-classical 4n{sup 2} limit over a range of common thicknesses (500-1500 nm) and slightly above the 4n{sup 2} limit for a 500 nm nc-Si cell. The absorption exceeds the 4n{sup 2} limit, corrected for reflection loss at the top surface. The photonic crystal cell current is enhanced over the flat Ag back-reflector by 60%, for a thick 1000 nm nc-Si layer, where predicted currents exceed 31 mA/cm{sup 2}. The conformal structure at the top surface focuses light within the absorber layer. There is plasmonic concentration of light, with intensity enhancements exceeding 7, near the back reflector that substantially enhances absorption.

  6. Pulse I–V characterization of a nano-crystalline oxide device with sub-gap density of states

    NASA Astrophysics Data System (ADS)

    Kim, Taeho; Hur, Ji-Hyun; Jeon, Sanghun

    2016-05-01

    Understanding the charge trapping nature of nano-crystalline oxide semiconductor thin film transistors (TFTs) is one of the most important requirements for their successful application. In our investigation, we employed a fast-pulsed I–V technique for understanding the charge trapping phenomenon and for characterizing the intrinsic device performance of an amorphous/nano-crystalline indium-hafnium-zinc-oxide semiconductor TFT with varying density of states in the bulk. Because of the negligible transient charging effect with a very short pulse, the source-to-drain current obtained with the fast-pulsed I–V measurement was higher than that measured by the direct-current characterization method. This is because the fast-pulsed I–V technique provides a charge-trap free environment, suggesting that it is a representative device characterization methodology of TFTs. In addition, a pulsed source-to-drain current versus time plot was used to quantify the dynamic trapping behavior. We found that the charge trapping phenomenon in amorphous/nano-crystalline indium-hafnium-zinc-oxide TFTs is attributable to the charging/discharging of sub-gap density of states in the bulk and is dictated by multiple trap-to-trap processes.

  7. Pulse I-V characterization of a nano-crystalline oxide device with sub-gap density of states.

    PubMed

    Kim, Taeho; Hur, Ji-Hyun; Jeon, Sanghun

    2016-05-27

    Understanding the charge trapping nature of nano-crystalline oxide semiconductor thin film transistors (TFTs) is one of the most important requirements for their successful application. In our investigation, we employed a fast-pulsed I-V technique for understanding the charge trapping phenomenon and for characterizing the intrinsic device performance of an amorphous/nano-crystalline indium-hafnium-zinc-oxide semiconductor TFT with varying density of states in the bulk. Because of the negligible transient charging effect with a very short pulse, the source-to-drain current obtained with the fast-pulsed I-V measurement was higher than that measured by the direct-current characterization method. This is because the fast-pulsed I-V technique provides a charge-trap free environment, suggesting that it is a representative device characterization methodology of TFTs. In addition, a pulsed source-to-drain current versus time plot was used to quantify the dynamic trapping behavior. We found that the charge trapping phenomenon in amorphous/nano-crystalline indium-hafnium-zinc-oxide TFTs is attributable to the charging/discharging of sub-gap density of states in the bulk and is dictated by multiple trap-to-trap processes. PMID:27094772

  8. Sono-assisted photocatalytic degradation of styrene-acrylic acid copolymer in aqueous media with nano titania particles and kinetic studies.

    PubMed

    Saien, J; Delavari, H; Solymani, A R

    2010-05-15

    The ultrasonic irradiation (28 kHz, 50 W) in pre-cavitations regime was employed to enhance the degradation rate of styrene-acrylic acid copolymer in aqueous media with nano titania photocatalyst particles. A stainless steel cylindrical sono-photo reactor with capacity of about 1.25 L, equipped with a UV lamp (250 W) was used. The influence of operational parameters, i.e. catalyst concentration, pH and temperature was studied and the role of active species was also distinguished. For an initial substrate concentration of 30 mg L(-1), under mild applied conditions of 30 mg L(-1) of photocatalyst, 25 degrees C and natural pH, a degradation and mineralization conversion of 96% and 91%, respectively, was achieved using sono-assisted photocatalysis process in about only 60 min. These efficiencies are much higher than those obtained with only photocatalysis process. Meanwhile, the threshold of cavitations was found corresponded to catalyst concentration of about 70 mg L(-1). Kinetic studies based on Langmuir-Hinshelwood and power law models in addition to the results from radical scavenger usage revealed that for sono-assisted process, the substrate undergoes degradation mainly via electron-hole redox on the surface of titania particles. It is while for the only photocatalysis process, the reaction proceeds via hydroxyl radicals in the solution bulk. PMID:20092940

  9. Tubular structured hierarchical mesoporous titania material derived from natural cellulosic substances and application as photocatalyst for degradation of methylene blue

    SciTech Connect

    Huang, Haiqing; Liu, Xiaoyan; Huang, Jianguo

    2011-11-15

    Graphical abstract: Bio-inspired, tubular structured hierarchical mesoporous titania material with high photocatalytic activity under UV light was fabricated employing natural cellulosic substance (cotton) as hard template and cetyltrimethylammonium bromide (CTAB) surfactant as soft template using a one-pot sol-gel method. Highlights: {yields} Tubular structured mesoporous titania material was fabricated by sol-gel method. {yields} The titania material faithfully recorded the hierarchical structure of the template substrate (cotton). {yields} The titania material exhibited high photocatalytic activity in decomposition of methylene blue. -- Abstract: Bio-inspired, tubular structured hierarchical mesoporous titania material was designed and fabricated employing natural cellulosic substance (cotton) as hard template and cetyltrimethylammonium bromide (CTAB) surfactant as soft template by one-pot sol-gel method. The tubular structured hierarchical mesoporous titania material processes large specific surface area (40.23 m{sup 2}/g) and shows high photocatalytic activity in the photodegradation of methylene blue under UV light irradiation.

  10. Synthesis and characterization of zirconium-doped mesoporous nano-crystalline TiO2

    NASA Astrophysics Data System (ADS)

    Bineesh, Kanattukara Vijayan; Kim, Dong-Kyu; Park, Dae-Won

    2010-07-01

    A series of zirconium-doped nano-titania (Zr/TiO2) with various amounts of Zr were prepared by sol-gel method using titanium(iv) isopropoxide and zirconium nitrate as precursors. Zr/TiO2 samples were characterized using X-ray diffraction (XRD), surface area-pore volume measurements, infrared (FTIR) spectroscopy, UV-vis-diffuse reflectance spectroscopy (UV-vis-DRS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, thermogravimetric (TG) analysis, and transmission electron microscopy (TEM) techniques. XRD data and Raman spectra indicated that even after 5 mol% doping of zirconium in the crystal lattice of TiO2, the samples were phase pure with the anatase structure. The crystalline size of the anatase decreased with increasing Zr content. An increase in the BET surface area was also observed after doping of zirconium on nano-titania.

  11. Synthesis and characterization of zirconium-doped mesoporous nano-crystalline TiO2.

    PubMed

    Bineesh, Kanattukara Vijayan; Kim, Dong-Kyu; Park, Dae-Won

    2010-07-01

    A series of zirconium-doped nano-titania (Zr/TiO(2)) with various amounts of Zr were prepared by sol-gel method using titanium(iv) isopropoxide and zirconium nitrate as precursors. Zr/TiO(2) samples were characterized using X-ray diffraction (XRD), surface area-pore volume measurements, infrared (FTIR) spectroscopy, UV-vis-diffuse reflectance spectroscopy (UV-vis-DRS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, thermogravimetric (TG) analysis, and transmission electron microscopy (TEM) techniques. XRD data and Raman spectra indicated that even after 5 mol% doping of zirconium in the crystal lattice of TiO(2), the samples were phase pure with the anatase structure. The crystalline size of the anatase decreased with increasing Zr content. An increase in the BET surface area was also observed after doping of zirconium on nano-titania. PMID:20648353

  12. Development of Micro and Nano Crystalline CVD Diamond TL/OSL Radiation Detectors for Clinical Applications

    NASA Astrophysics Data System (ADS)

    Barboza-Flores, Marcelino

    2015-03-01

    Modern radiotherapy methods requires the use of high photon radiation doses delivered in a fraction to small volumes of cancer tumors. An accurate dose assessment for highly energetic small x-ray beams in small areas, as in stereotactic radiotherapy, is necessary to avoid damage to healthy tissue surrounding the tumor. Recent advances on the controlled synthesis of CVD diamond have demonstrated the possibility of using high quality micro and nano crystalline CVD as an efficient detector and dosimeter suitable for high energy photons and energetic particle beams. CVD diamond is a very attractive material for applications in ionizing radiation dosimetry, particularly in the biomedical field since the radiation absorption by a CVD diamond is very close to that of soft tissue. Furthermore, diamond is stable, non-toxic and radiation hard. In the present work we discuss the CVD diamond properties and dosimeter performance and discuss its relevance and advantages of various dosimetry methods, including thermally stimulated luminescence (TL) as well as optically stimulated luminescence (OSL). The recent CVD improved method of growth allows introducing precisely controlled impurities into diamond to provide it with high dosimetry sensitivity. For clinical dosimetry applications, high accuracy of dose measurements, low fading, high sensitivity, good reproducibility and linear dose response characteristics are very important parameters which all are found in CVD diamonds specimens. In some cases, dose linearity and reproducibility in CVD diamond have been found to be higher than standard commercial TLD materials like LiF. In the present work, we discuss the state-of-the art developments in dosimetry applications using CVD diamond. The financial support from Conacyt (Mexico) is greatly acknowledged

  13. Hydrogen peroxide route to Sn-doped titania photocatalysts

    PubMed Central

    2012-01-01

    Background The work aims at improving photocatalytic activity of titania under Vis light irradiation using modification by Sn ions and an original, simple synthesis method. Tin-doped titania catalysts were prepared by thermal hydrolysis of aqueous solutions of titanium peroxo-complexes in the presence of SnCl4 or SnCl2 using an original, proprietary "one pot" synthesis not employing organic solvents, metallo-organic precursors, autoclave aging nor post-synthesis calcination. The products were characterized in details by powder diffraction, XPS, UV–vis, IR, and Raman spectroscopies, electron microscopy and surface area and porosity measurements Results The presence of tin in synthesis mixtures favors the formation of rutile and brookite at the expense of anatase, decreases the particle size of all formed titania polymorphs, and extends light absorption of titania to visible light region >400 nm by both red shift of the absorption edge and introduction of new chromophores. The photocatalytic activity of titania under UV irradiation and >400 nm light was tested by decomposition kinetics of Orange II dye in aqueous solution Conclusions Doping by Sn improves titania photoactivity under UV light and affords considerable photoactivity under >400 nm light due to increased specific surface area and a phase heterogeneity of the Sn-doped titania powders. PMID:23035821

  14. Copper NPs decorated titania: A novel synthesis by high energy US with a study of the photocatalytic activity under visible light.

    PubMed

    Stucchi, Marta; Bianchi, Claudia L; Pirola, Carlo; Cerrato, Giuseppina; Morandi, Sara; Argirusis, Christos; Sourkouni, Georgia; Naldoni, Alberto; Capucci, Valentino

    2016-07-01

    The most important drawback of the use of TiO2 as photocatalyst is its lack of activity under visible light. To overcome this problem, the surface modification of commercial micro-sized TiO2 by means of high-energy ultrasound (US), employing CuCl2 as precursor molecule to obtain both metallic copper as well as copper oxides species at the TiO2 surface, is here. We have prepared samples with different copper content, in order to evaluate its impact on the photocatalytic performances of the semiconductor, and studied in particular the photodegradation in the gas phase of some volatile organic molecules (VOCs), namely acetone and acetaldehyde. We used a LED lamp in order to have only the contribution of the visible wavelengths to the TiO2 activation (typical LED lights have no emission in the UV region). We employed several techniques (i.e., HR-TEM, XRD, FT-IR and UV-Vis) in order to characterize the prepared samples, thus evidencing different sample morphologies as a function of the various copper content, with a coherent correlation between them and the photocatalytic results. Firstly, we demonstrated the possibility to use US to modify the TiO2, even when it is commercial and micro-sized as well; secondly, by avoiding completely the UV irradiation, we confirmed that pure TiO2 is not activated by visible light. On the other hand, we showed that copper metal and metal oxides nanoparticles strongly and positively affect its photocatalytic activity. PMID:26964952

  15. Heterogeneous photocatalytic reduction of Cr(VI) in UV-irradiated titania suspensions: Effect of protons, ammonium ions, and other interfacial aspects

    SciTech Connect

    Chenthamarakshan, C.R.; Rajeshwar, K.; Wolfrum, E.J.

    2000-03-21

    Heterogeneous photocatalytic reactions in UV-irradiated TiO{sub 2} suspensions are comprised of two conjugate reaction pathways involving the photogenerated electrons and holes, respectively. The role of the hole reaction pathway in the dynamics of the photocatalytic reduction of Cr(VI) is a major focus of this study. It is shown that proton supply plays a crucial role in this reduction reaction. Thus, the Cr(VI) photoreduction kinetics switch from first order to zero order as the proton concentration is systematically increased in the aqueous suspensions. Ammonium ions are also shown to exert a dramatic accelerating influence on Cr(VI) reduction in media of initial pH6. This new observation is rationalized by considering that these species act as hole scavengers. The consequent improvement in quantum yield combines with the facile proton generation upon NH{sub 4}{sup +} photooxidation, to result in the observed rate enhancement. Other interfacial aspects (i.e. adsorption) are also discussed.

  16. Superlattice assembly of graphene oxide (GO) and titania nanosheets: fabrication, in situ photocatalytic reduction of GO and highly improved carrier transport.

    PubMed

    Cai, Xingke; Ma, Renzhi; Ozawa, Tadashi C; Sakai, Nobuyuki; Funatsu, Asami; Sasaki, Takayoshi

    2014-11-01

    Two different kinds of two-dimensional (2D) materials, graphene oxide (GO) and titanium oxide nanosheets (Ti₀.₈₇O2(0.52-)), were self-assembled layer-by-layer using a polycation as a linker into a superlattice film. Successful construction of an alternate molecular assembly was confirmed by atomic force microscopy and UV-visible absorption spectroscopy as well as X-ray diffraction analysis. Exposure of the resulting film to UV light effectively promoted photocatalytic reduction of GO as well as decomposition of the polycation, which are due to their intimate molecular-level contact. The reduction completed within 3 hours, bringing about a decrease of the sheet resistance by ∼10(6). This process provides a clean and mild route to reduced graphene oxide (rGO), showing advantages over other chemical and thermal reduction processes. A field-effect-transistor device was fabricated using the resulting superlattice assembly of rGO/Ti₀.₈₇O₂(0.52-) as a channel material. The rGO in the film was found to work as a unipolar n-type conductor, which is in contrast to ambipolar or unipolar p-type behavior mostly reported for rGO films. This unique property may be associated with the electron doping effect from Ti₀.₈₇O₂(0.52-) nanosheets. A significant improvement in the conductance and electron carrier mobility by more than one order of magnitude was revealed, which may be accounted for by the heteroassembly with Ti₀.₈₇(0.52-) nanosheets with a high dielectric constant as well as the better 2D structure of rGO produced via the soft photocatalytic reduction. PMID:25340970

  17. Photocatalytic degradation of methyl blue by silver ion-doped titania: Identification of degradation products by GC-MS and IC analysis.

    PubMed

    Sahoo, Chittaranjan; Gupta, Ashok K

    2015-01-01

    An anionic triphenyl methane dye, methyl blue ((disodium;4-[4-[[4-(4-sulfonatoanilino)phenyl]-[4-(4-sulfonatophenyl)azaniumylidenecyclohexa-2,5-dien-1-ylidene]methyl]anilino]benzene sulfonate) was degraded photocatalytically with undoped micro-TiO2- and Ag(+)-doped micro TiO2 in a slurry-type batch reactor under UV irradiation and the efficiency was compared with that obtained using nano-TiO2- and Ag(+)-doped nano-TiO2. The influence of different parameters, i.e., photocatalyst loading, dye concentration, initial pH, temperature, depth of solution, interfering ions and electron acceptors on the dye degradation was investigated. The decolorization and mineralization efficiency was better for Ag(+)-doped micro-TiO2 than undoped micro-TiO2. Nano-TiO2 was more efficient than micro-TiO2, while Ag(+)-doped nano-TiO2 was the most efficient of all. Cost analysis showed degradation using micro-TiO2- and Ag(+)-doped micro-TiO2 are much cheaper than that using nano-TiO2 and Ag(+)-doped nano-TiO2. Therefore Ag(+)-doped micro-TiO2 was used for the detailed study. The degradation products formed were identified using GC-MS analysis after photocatalytic degradation for 180 min with Ag(+) -doped micro TiO2. Ion chromatography analysis was carried out for anions to identify the end products of degradation. PMID:26230736

  18. Biotemplated diatom silica-titania materials for air purification.

    PubMed

    Van Eynde, Erik; Tytgat, Tom; Smits, Marianne; Verbruggen, Sammy W; Hauchecorne, Birger; Lenaerts, Silvia

    2013-04-01

    We present a novel manufacture route for silica-titania photocatalysts using the diatom microalga Pinnularia sp. Diatoms self-assemble into porous silica cell walls, called frustules, with periodic micro-, meso- and macroscale features. This unique hierarchical porous structure of the diatom frustule is used as a biotemplate to incorporate titania by a sol-gel methodology. Important material characteristics of the modified diatom frustules under study are morphology, crystallinity, surface area, pore size and optical properties. The produced biosilica-titania material is evaluated towards photocatalytic activity for NOx abatement under UV radiation. This research is the first step to obtain sustainable, well-immobilised silica-titania photocatalysts using diatoms. PMID:23128085

  19. Photocatalysis of phenol and salicyclic acid by nanostructured titania powders

    SciTech Connect

    Fotou, G.P.; Pratsinis, S.E.

    1995-12-31

    The photocatalytic destruction of phenol and salicylic acid was studied in aqueous suspensions of titania powders made in flame reactors. These powders were made in six hydrocarbon diffusion flames by hydrolysis and oxidation of TiCl{sub 4} that resulted in powders of high specific surface area and high anatase content. The photoactivity of the flame-made titania powders was compared with that of commercially available powders. Doping the titania with SiO{sub 2} was detrimental to the photoactivity of the powders in aerated solutions in contrast to non-aerated solutions. Titania powders in the range of 20-40 nm containing small amounts of rutile were more active than pure anatase powders. The phenol degradation reaction followed a first-order law while the Langmuir-Hinshelwood model was found to most accurately represent the photodegradation of salicylic acid.

  20. Nucleation and crystallization behaviors of nano-crystalline lithium–mica glass–ceramic prepared via sol–gel method

    SciTech Connect

    Tohidifar, M.R.; Alizadeh, P.; Riello, P.

    2012-06-15

    Graphical abstract: The effects of nucleation and crystallization treatments on nano-crystalline lithium–mica glass–ceramic, synthesized by sol–gel technique, were investigated. It was found that MgF{sub 2} crystals act as nuclei centers for the mica crystallization so that a large quantity of mica crystallites was obtained following nucleation process. The crystallization activation energy for both the un-nucleated and nucleated samples was measured as 400.2 and 229.6 kJ mol{sup −1}, respectively. The calculated Avrami exponents demonstrated that the growth mechanism of mica crystallites changes from the needle-like to three-dimensional growth with applying the appropriate nucleation treatment ▪. Highlights: ► Crystallization temperature shifts to 625 from 680 °C following nucleation process. ► Activation energy of crystallization for the nucleated specimen is 229.6 kJ mol{sup −1}. ► Crystallization activation energy for the un-nucleated specimen is 400.2 kJ mol{sup −1}. ► Needle-like growth is predominant growth mechanism for un-nucleated sample. ► Three-dimensional growth is predominant growth mechanism for nucleated sample. -- Abstract: The paper investigates the effects of nucleation and crystallization treatments on nano-crystalline lithium–mica glass–ceramics, taking the composition LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2} (x = 0.5) and 8 mass% MgF{sub 2} synthesized by sol–gel technique. Here, X-ray diffraction, thermal analysis and transmission electron microscopy were used to assess the structural evolutions of as-synthesized nano-crystalline lithium–mica glass–ceramics. It was found that MgF{sub 2} crystals perform as nuclei centers for the mica crystallization hence; a large quantity of mica crystallites obtained following the nucleation process at 400 °C for 12 h. For both the un-nucleated and nucleated samples, the crystallization activation energy was measured as 400.2 and 229.6 kJ mol{sup −1

  1. Characterisation of nano-crystalline titanium dioxide films grown by atmospheric pressure plasma electrolytic deposition

    NASA Astrophysics Data System (ADS)

    Paulmier, Thierry; Bell, John M.; Fredericks, Peter M.

    2006-01-01

    A new atmospheric pressure plasma electrolytic process has been developed for the deposition of TiO II crystalline thin films on metal substrate. Contrary to the other deposition techniques, the process occurs in a liquid precursor, composed of titanium tetraisopropoxide and absolute ethanol. A plasma discharge is created and confined around the cathode in a superheated vapour sheath surrounded by the liquid phase, inducing the production of a thin TiO II coating at the surface of the cathode. Because of the flexibility of the operating parameters, this technology allows the rapid deposition of thin films with a wide range of structural and physical properties. This process enables therefore the production of nanocrystalline titania films with adjustable morphology and structure (anatase, rutile) by adjusting the operating voltage, current intensity, the treatment time and calcination temperature. The analysis of the structure and composition of these TiO II coatings have been carried out by Scanning Electron Microscopy, Transmission Electron Microscopy, Raman spectroscopy, X-ray Photoelectron Spectroscopy and X-Ray Diffraction. A thorough study has been performed to understand the influence of the operating parameters on the properties and structure of the coatings.

  2. Titania coated hollow glass microspheres for environmental applications

    NASA Astrophysics Data System (ADS)

    Koopman, Mark C.

    The potential applicability of titania coated hollow glass microspheres (HGMs) to the photocatalytic degradation of microbiological and organic chemical water pollutants could have dramatic positive effects on improving the quality of industrial wastewaters that empty into rivers and streams, as well as potential use in economically improving the quality of drinking water. Heterogeneous photocatalysis using titania has been extensively studied since the 1990's because of its non-toxic nature, its high quantum yield of electrons and photo-holes, and its ability to use ambient solar radiation as a power source. Although titania embodies extraordinarily attractive properties for a range of environmental applications, a viable substrate or method of using the material effectively has not been recognized. HGMs are particularly attractive as a support for titania because of their low density and high surface area to volume ratio, but details of how they react to imposed loading, wear, and impact have not been addressed, nor have materials engineering analyses that could maximize their utility been made. In this study we have examined the microstructure, morphology and micro-compression properties of two types of titania coated hollow microspheres, a commercially produced HGM and cenospheres, a derivative of fly ash. Comparisons of uncoated and titania coated hollow microspheres showed improved failure loads and facture energies for the titania coated materials over the uncoated hollow microspheres. Also, the relationship between failure load and hollow microsphere diameter was characterized and the function employed to explain part of the gain in average failure load for the HGMs. Microscopic examination of titania coated HGMs that were subjected to various turbulent conditions, as well as intentional fracture, indicated good interfacial integrity, which supports the viability of both types of HGMs for potential applications. The photocatalytic reactivity of the titania

  3. Nano-Crystalline Diamond Films with Pineapple-Like Morphology Grown by the DC Arcjet vapor Deposition Method

    NASA Astrophysics Data System (ADS)

    Li, Bin; Zhang, Qin-Jian; Shi, Yan-Chao; Li, Jia-Jun; Li, Hong; Lu, Fan-Xiu; Chen, Guang-Chao

    2014-08-01

    A nano-crystlline diamond film is grown by the dc arcjet chemical vapor deposition method. The film is characterized by scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD) and Raman spectra, respectively. The nanocrystalline grains are averagely with 80 nm in the size measured by XRD, and further proven by Raman and HRTEM. The observed novel morphology of the growth surface, pineapple-like morphology, is constructed by cubo-octahedral growth zones with a smooth faceted top surface and coarse side surfaces. The as-grown film possesses (100) dominant surface containing a little amorphous sp2 component, which is far different from the nano-crystalline film with the usual cauliflower-like morphology.

  4. A 4F2-cross-point phase change memory using nano-crystalline doped GeSbTe material

    NASA Astrophysics Data System (ADS)

    Takaura, Norikatsu; Kinoshita, Masaharu; Tai, Mitsuharu; Ohyanagi, Takasumi; Akita, Kenichi; Morikawa, Takahiro

    2015-04-01

    This paper reports on the use of nano-crystalline doped GeSbTe, or nano-GST, to fabricate a cross-point phase change memory with 4F2 cell size and test results obtained for it. We show the characteristics of a poly-Si diode select device with a high on-off ratio and data writing in a 4F2 memory cell array. The advantages of nano-GST over conventional GeSbTe are presented in terms of neighboring disturbance and 4F2 cross-point array formation. The memory cells’ high drivability, low power, and selective write and read performances are demonstrated. The scalability of the diode current density is also presented.

  5. Characterization of Nano-Crystalline Diamond like Carbon (DLC) Films with Substrate Temperature Using Dense Plasma Focusing Method

    SciTech Connect

    Yadav, Vikram S; Dhubkarya, D. C.; Singh, Yashpal; Sahu, Devendra K; Singh, Manveer; Kumar, Kuldeep

    2010-06-17

    Nano-crystalline Diamond like Carbon (DLC) film has been grown by Dense Plasma Focusing Method (DPF) using pure graphite Plasma, on different substrate (glass/silica) at different substrate temperature. The films were grown at substrate temperature 100 deg. C, 150 deg. C and 300 deg. C by the high dense plasma of energy 1.3 k Joule on glass and silica. Raman spectra confirmed that sp{sup 3} content is grown in the films under various conditions. The Raman spectra of these films show a broad asymmetric peak which narrow with sp{sup 2} decreasing contents. We believe that our data presented here may be used as reference of DLC characterization.

  6. A study of structural and mechanical properties of nano-crystalline tungsten nitride film synthesis by plasma focus

    NASA Astrophysics Data System (ADS)

    Hussnain, Ali; Singh Rawat, Rajdeep; Ahmad, Riaz; Hussain, Tousif; Umar, Z. A.; Ikhlaq, Uzma; Chen, Zhong; Shen, Lu

    2015-02-01

    Nano-crystalline tungsten nitride thin films are synthesized on AISI-304 steel at room temperature using Mather-type plasma focus system. The surface properties of the exposed substrate against different deposition shots are examined for crystal structure, surface morphology and mechanical properties using X-ray diffraction (XRD), atomic force microscope, field emission scanning electron microscope and nano-indenter. The XRD results show the growth of WN and WN2 phases and the development of strain/stress in the deposited films by varying the number of deposition shots. Morphology of deposited films shows the significant change in the surface structure with different ion energy doses (number of deposition shots). Due to the effect of different ion energy doses, the strain/stress developed in the deposited film leads to an improvement of hardness of deposited films.

  7. Effects of calcination on microscopic and mesoscopic structures in Ca- and Sr-doped nano-crystalline lanthanum chromites

    SciTech Connect

    Bhatt, Himal; Bahadur, J.; Deo, M.N.; Ramanathan, S.; Pandey, K.K.; Sen, D.; Mazumder, S.; Sharma, Surinder M.

    2011-01-15

    Calcination behavior of nano-crystalline lanthanum chromites doped with calcium and strontium has been probed by Fourier transform infrared spectroscopy, X-ray diffraction and small-angle neutron scattering as a function of temperature. Infrared spectroscopic results imply that over a range of temperatures, some intermediate phase of dopant chromates evolve and then dissolve back, which has also been confirmed by the XRD. Neutron scattering data reveal a fractal type correlation of building blocks in virgin powders. Increase in fractal dimension and reduction in upper cutoff vis-a-vis the densification of agglomerates were found with increasing calcination temperature. Calcination, beyond 900 {sup o}C, results in breaking down of the fractal morphology almost completely. Such shrinkage event also results in a modification of the microscopic structure. These changes have been attributed to the compaction of agglomerates of both Ca- and Sr-doped lanthanum chromites, assisted via liquid state sintering by the melting of the intermediate phases at intermediate calcination stages. -- Graphical Abstract: Dopant chromates evolve as intermediate phases during calcination of Ca- and Sr-doped nano-crystalline lanthanum chromites at intermediate temperatures, around 900 {sup o}C, evident from infrared spectroscopy. Such an event results in a modification of the microscopic and mesoscopic structures. Display Omitted Research highlights: {yields} Meso/microscopic structures of La{sub 0.7}Ca{sub 0.3}CrO{sub 3} and La{sub 0.8}Sr{sub 0.2}CrO{sub 3} modify during calcination. {yields} Transient phases CaCrO{sub 4} and SrCrO{sub 4} appear at intermediate temperatures. {yields} Bond length, unit cell volume, etc. modify as intermediate phases evolve and extinct. {yields} Compaction of the agglomerates takes place due to liquid state assisted sintering.

  8. Atomic structure of titania nanosheet with vacancies

    PubMed Central

    Ohwada, Megumi; Kimoto, Koji; Mizoguchi, Teruyasu; Ebina, Yasuo; Sasaki, Takayoshi

    2013-01-01

    Titania nanosheets are two-dimensional single crystallites of titanium oxide with a thickness of one titanium or two oxygen atoms, and they show attractive material properties, such as photocatalytic reactions. Since a titania (Ti0.87O2) nanosheet is synthesized by the delamination of a parent layered K0.8Ti1.73Li0.27O4 crystal using a soft chemical procedure, substantial Ti vacancies are expected to be included and affect the material properties. The atomic arrangement of a titania nanosheet with vacancies has not been revealed owing to the difficulties of direct observation. Here, we have directly visualized the atomic arrangement and Ti vacancies of a titania nanosheet using advanced lower-voltage transmission electron microscopy (TEM). Analyses of the results of first-principles calculations and TEM image simulations for various Ti vacancy structure models indicate that two particular oxygen atoms around each Ti vacancy are desorbed, suggesting the sites where atomic reduction first occurs. PMID:24077611

  9. Degradation and toxicity reduction of textile wastewater using immobilized titania nanophotocatalysis.

    PubMed

    Mahmoodi, Niyaz Mohammad; Arami, Mokhtar

    2009-01-01

    The feasibility and performance of photocatalytic degradation and toxicity reduction of textile dye (Acid Blue 25) have been studied at pilot scale in an immobilized titania nanoparticle photocatalytic reactor. UV-Vis, Ion Chromatography (IC) and chemical oxygen demand (COD) analyses were employed to obtain the details of the photocatalytic dye degradation. The effects of operational parameters such as H2O2, pH and dye concentration on the photocatalytic degradation of Acid Blue 25 were investigated. The aliphatic carboxylic acid intermediates and inorganic anions generated during the dye degradation process were analyzed. Daphnia magna bioassay has been used to test the progress of toxicity during the treatment process. Total disappearance of dye was attained. During the photocatalytic treatment process, the residual acute toxicity was reduced. The results showed that immobilized titania nanophotocatalysis capable to degradation and toxicity reduction of acid dye textile wastewater. PMID:18948013

  10. Carbon nanosheet-titania nanocrystal composites from reassembling of exfoliated graphene oxide layers with colloidal titania nanoparticles

    SciTech Connect

    Liu Yongjun; Aizawa, Mami; Peng Wenqing; Wang Zhengming; Hirotsu, Takahiro

    2013-01-15

    Nanoporous composites of carbon nanosheets (CNS) and titania nanoparticles (NPs) were synthesized by reassembling of delaminated graphite oxide (GO) layers with titania clear sol (TCS), and their structural and porous properties were examined by various physico-chemical methods such as XRD, TG/DTA, FT-IR, Raman, FE-SEM/TEM, and low temperature N{sub 2} adsorption. It was found that the facile approach, which utilizes the electrostatic attraction between the negatively charged GO layers and the positively charged TCS particles, leads to a well composed CNS and ultrafine TiO{sub 2} NPs material whose titania amount reaches up to 71 wt%. The titania phase in these composite materials is mainly anatase, which is resistible against high temperature calcination, but also contains a little amount of rutile and brookite depending on synthesis condition. The porosity of the composite is improved and partially affected by the size distributions of TiO{sub 2} NPs. The unique structure, better porosity, and compatible surface affinity of these composites bring about an adsorption concentration-promoted photocatalytic effects toward organic dyes by successfully combining both properties of CNS and titania NPs. - Graphical Abstract: Carbon nanosheet-titania nanocrystal composites can be synthesized by a facile delamination-reassembling method from graphene oxide and colloidal titania. Highlights: Black-Right-Pointing-Pointer A facile delamination-reassembling method for graphene oxide-titania nanocomposite. Black-Right-Pointing-Pointer A nanoporous composite containing mixed phase titania nanocrystals. Black-Right-Pointing-Pointer Partition effect of carbon nanosheets preventing TiO{sub 2} nanoparticles from aggregating. Black-Right-Pointing-Pointer Adsorption concentration-promoted photocatalysis.

  11. Titania-supported silver-based bimetallic nanoparticles as photocatalysts.

    PubMed

    Barakat, M A; Al-Hutailah, R I; Hashim, M H; Qayyum, E; Kuhn, J N

    2013-06-01

    Photocatalytic process has shown recently a great potential as an environmental friendly and clean remediation technology for organic pollutants in wastewater. This work described the synthesis of silver-based bimetallic nanoparticles using colloid chemistry and the subsequent immobilization onto titania to form composite photocatalytic materials (titania-supported Ag-Pt nanoparticles). The photocatalysts were characterized by X-ray diffraction, electron microscopy, and nitrogen physisorption. The catalytic activity of the photocatalysts was evaluated by photocatalytic degradation of phenol and 2-chlorophenol (2-CP) in synthetic wastewater solutions. The photocatalytic processes were conducted in a batch photoreactor containing appropriate solutions of phenol and 2-CP with UV irradiation of 450 W. UV-visible spectrophotometer was used for analyzing the concentration of phenol and 2-CP in solutions. Parameters affecting the photocatalytic process such as the solution pH, phenol and 2-CP concentrations, and catalyst concentration were investigated. The results obtained revealed that TiO(2)-supported Ag/Pt nanoparticles showed a higher activity for UV-photocatalytic degradation of both phenol and 2-CP pollutants in the solution (as compared to the plain rutile TiO(2)). The photodegradation processes were optimized by the 0.5-g/L catalyst with a pollutant concentration of 50 mg/L for all the samples. Complete degradation for both phenol and 2-CP was achieved after 120 min. PMID:23161501

  12. The anti-microbial activity of titania-nickel ferrite composite nanoparticles

    NASA Astrophysics Data System (ADS)

    Rana, S.; Misra, R. D. K.

    2005-12-01

    A novel approach to synthesize a new generation of composite nanoparticles consisting of a photocatalytic shell of anatase-titania and a magnetic core of nickel ferrite has been adopted combining reverse micelle and chemical hydrolysis techniques. Titania is an effective anti-microbial agent that can be directly sprayed on infected areas of the human body or environment. Unfortunately, titania is an electrical insulator and is difficult to extract from the sprayed surface after treatment. The titania photocatalytic shell provides good antimicrobial capability that renders the bacteria inactive and removes the organic pollutants, while the nickel ferrite magnetic core enables controlled delivery of composite nanoparticles through the application of a small magnetic field, encouraging their application as removable anti-microbial photocatalyst nanoparticles.

  13. Hydrogenated blue titania with high solar absorption and greatly improved photocatalysis.

    PubMed

    Zhu, Guilian; Shan, Yufeng; Lin, Tianquan; Zhao, Wenli; Xu, Jijian; Tian, Zhangliu; Zhang, Hui; Zheng, Chong; Huang, Fuqiang

    2016-02-18

    Hydrogenated black titania, with a crystalline core/amorphous shell structure, has attracted global interest due to its excellent photocatalytic properties. However, the understanding of its structure-property relationships remains a great challenge and a more effective method to produce hydrogenated titania is desirable. Herein, we report a TiH2 assisted reduction method to synthesize bluish hydrogenated titania (TiO2-x:H) that is highly crystallized. The characteristic amorphous shells, which are essential for the enhancement of solar absorption and photocatalysis in many reported hydrogenated titania, are completely removed by hydrogen peroxide. The blue TiO2-x:H sample without amorphous shells delivers not only significantly improved visible- and infrared-light absorption but also greatly enhanced photocatalytic activity compared to pristine TiO2. Its water decontamination is 2.5 times faster and the hydrogen production was 1.9-fold higher over pristine TiO2. Photoelectrochemical measurement reveals greatly improved carrier density and photocurrent (a 4.3-fold increase) in the reduced TiO2-x:H samples. This work develops a facile and versatile method to prepare hydrogenated titania and proposes a new understanding of the hydrogenated titania that doped hydrogen atoms, instead of the amorphous shells, are essential for its high photocatalytic performance. PMID:26858035

  14. Building a nano-crystalline α-alumina layer at a liquid metal/sapphire interface by ultrasound.

    PubMed

    Cui, Wei; Yan, Jiuchun; Dai, Yan; Li, Dandan

    2015-01-01

    Transitional layers at the metal/ceramic interface play an very important role in ceramic joining. In this study, sapphire blocks were ultrasonically dipped in liquid Sn-Zn-Al alloy. It is found that the ultrasound promoted rapid oxidation reaction of aluminum at the Sn-Zn-Al/sapphire interface at 230°C in the ambient atmosphere, resulting in the formation of a nano-crystalline α-Al2O3 layer (NCAL). In a ∼2nm boundary layer of the NCAL, the lattice matches the sapphire substrate well. Thus, a smooth transition of the lattice from sapphire to metal was formed through the NCAL. Ultrasonically soldered sapphire joints were made with Sn-Zn-Al as the filler alloy. Compressive shear strength of the joints reached 43-48MPa, which is relatively high comparing to other Al2O3 joints made of Sn alloys doped with Ti or Rear Earth elements. Thus, a new mechanism of ultrasonic soldering, i.e. building an oxide transitional layer on the surface of the solid, was revealed. We expect this sonochemical process to be applicable to other metal/oxide systems. PMID:24882591

  15. Sintering effects on structure, morphology, and electrical properties of sol-gel synthesized, nano-crystalline erbium oxide

    NASA Astrophysics Data System (ADS)

    Bakhsh, Allah; Maqsood, Asghari

    2012-12-01

    The nano-crystalline erbium oxide powder was synthesized through the sol-gel technique. The effect of sintering temperature from 250°C to 1400°C on structure, morphology, and electrical properties was studied. The results were compared with the microcrystalline erbium oxide purchased from the market. The synthesized erbium oxide showed fiber like nanostructures. Dielectric properties at different sintering temperatures were measured in the frequency range 100 Hz to 5MHz. The synthesized erbium oxide had the highest dielectric constant at 650°C. The behavior of the dissipation factor tan δ for sol-gel synthesized material was distinct from that of the purchased material; it was higher at low frequencies and then decreased with the increase in frequency. The synthesized material sintered at different temperatures exhibited a similar sort of frequency-dependent response for permittivity (ɛ) and resistivity ( ρ). This was in accordance with Koop's theory of dielectrics. For the microcrystalline material, frequency dependence of permittivity and resistivity was not uniform. The results showed that sol-gel synthesized erbium oxide could be a good candidate for high-k applications.

  16. Activation energy of the growth of ion-beam-synthesized nano-crystalline 3C SiC

    NASA Astrophysics Data System (ADS)

    Intarasiri, S.; Dangtip, S.; Hallén, A.; Jensen, J.; Yu, L. D.; Possnert, G.; Singkarat, S.

    2007-04-01

    In this experiment, carbon ions at 40 keV were implanted into (1 0 0) high-purity p-type silicon wafers at 400 °C to a fluence of 6.5 × 1017 ions/cm2. Subsequent thermal annealing of the implanted samples was performed in a vacuum furnace at 800-1000 °C. Glancing incidence X-ray diffraction (GIXRD) was used to characterize the crystalline quality and estimate the grain size of nano-crystalline 3C-SiC. Activation energy for the growth of 3C-SiC was evaluated following the annealing behaviour of the GIXRD-characteristic 3C-SiC (1 1 1) peaks. It was found that the 3C-SiC was directly formed during ion implantation at this substrate temperature and the activation energy of the process was about 0.05 eV. Such a low energy was explained in terms of ion beam induced precipitate formation.

  17. Nano-crystalline Ag-PbTe thermoelectric thin films by a multi-target PLD system

    NASA Astrophysics Data System (ADS)

    Cappelli, E.; Bellucci, A.; Medici, L.; Mezzi, A.; Kaciulis, S.; Fumagalli, F.; Di Fonzo, F.; Trucchi, D. M.

    2015-05-01

    It has been evaluated the ability of ArF pulsed laser ablation to grow nano-crystalline thin films of high temperature PbTe thermoelectric material, and to obtain a uniform and controlled Ag blending, through the entire thickness of the film, using a multi-target system in vacuum. The substrate used was a mirror polished technical alumina slab. The increasing atomic percentage of Ag effect on physical-chemical and electronic properties was evaluated in the range 300-575 K. The stoichiometry and the distribution of the Ag component, over the whole thickness of the samples deposited, have been studied by XPS (X-ray photoelectron spectroscopy) and corresponding depth profiles. The crystallographic structure of the film was analyzed by grazing incidence X-ray diffraction (GI-XRD) system. Scherrer analysis for crystallite size shows the presence of nano-structures, of the order of 30-35 nm. Electrical resistivity of the samples, studied by the four point probe method, as a function of increasing Ag content, shows a typical semi-conductor behavior. From conductivity values, carrier concentration and Seebeck parameter determination, the power factor of deposited films was calculated. Both XPS, Hall mobility and Seebeck analysis seem to indicate a limit value to the Ag solubility of the order of 5%, for thin films of ∼200 nm thickness, deposited at 350 °C. These data resulted to be comparable to theoretical evaluation for thin films but order of magnitude lower than the corresponding bulk materials.

  18. Nano crystalline Bi2(VO5) phases in lithium bismuth borate glasses containing mixed vanadium-nickel oxides

    NASA Astrophysics Data System (ADS)

    Yadav, Arti; Khasa, S.; Dahiya, M. S.; Agarwal, A.

    2016-05-01

    Glass composition 7V2O5.23Li2O.20Bi2O3.50B2O3 and x(2NiO.V2O5).(30-x)Li2O.20Bi2O3.50B2O3, x=0, 2, 5, 7 and 10, were produced by conventional melt quenching technique. The quenched amorphous glass samples were annealed at temperatures 400°C and 500°C for 6 hours. The Bi2(VO5) crystallite were grown in all prepared glass matrix. Tn vanadium lithium bismuth borate glass (annealed), the some phrase of V2O5-crystal were observed along with the nano crystalline Bi2(VO5) phase. The sharp peaks in FTTR spectra of all annealed compositions were also compatible with the XRD diffraction peaks of the system under investigation. Average crystalline size (D) of the Bi2(VO5) nano-crystallite was ~30nm for samples annealed at 400°C and ~42nm for samples annealed at 500°C. Lattice parameter and the lattice strain for all the samples was also calculated corresponding to the (113) plane of Bi2(VO5) crystallite.

  19. Microwave Plasma Source for Fabrication of Micro- and Nano-Crystalline Diamond Thin Films for Electronic Devices

    NASA Astrophysics Data System (ADS)

    Paosawatyanyong, Boonchoat; Rujisamphan, Nopporn; Bhanthumnavin, Worawan

    2013-01-01

    The design and utilization of an affordable compact-size high-density plasma reactor for micro- and nano-crystalline diamond (MCD/NCD) thin film deposition is presented. The system is based on a 2.45 GHz domestic microwave oven magnetron. A switching power supply module, which yields a low-voltage high-current AC filament feeding and a high-voltage low-current DC cathode bias, is constructed to serve as the magnetron power source. With a high stability of the power module combined with the usage of water cooling gaskets, over 100 h of plasma processing time was achieved without overheating or causing any damage to the magnetron. Depositions of well-faceted MCD/NCD thin films, with distinct diamond Raman characteristics, were obtained using H2-CH4 discharge with 1-5% CH4. Metal-semiconductor diode structures were fabricated using gold and aluminum as ohmic and rectifying contacts, respectively, and their responses to DC signals revealed a high rectification ratio of up to 106 in the intrinsic MCD/NCD devices.

  20. Effect of lead ion concentration on the structural and optical properties of nano-crystalline PbS thin films

    NASA Astrophysics Data System (ADS)

    Zaman, S.; Mehmood, S. K.; Mansoor, M.; Asim, M. M.

    2014-06-01

    PbS thin films have received considerable attention because of their potential applications in opto-electronics applications. Spontaneous reaction of lead acetate and thiourea in aqueous hydrazine hydrate has been used for depositing PbS thin films on glass substrates. Structural and optical properties of PbS thin films are greatly influenced by the morality of the reactants and crystal defects in the lattice. Our work focuses on the variation in lead ion concentration and its effect on the structural and optical properties of PbS thin films. The deposited films were analyzed using XRD, SEM, spectrophotometer and dark resistance measurement. XRD patterns indicated the formation of major phase of nano crystalline PbS with minor presence of lead oxide phase. We also noticed that peak intensity ratio of I111/I200 varied by changing the Pb ion concentration. The film thickness and dark resistance increased whereas optical band gap decreased with the decreasing Pb ion concentration. SEM scans showed that the grain size is less than 100 nm and is not affected by varying Pb ion concentration.

  1. [Research on the mineral phase and component of non-crystalline and nano-crystalline corrosion products on bronzes unearthed from Shang Tomb in Xingan].

    PubMed

    Cheng, Xiao-lin; Pan, Lu

    2012-05-01

    The patinas on bronzes in Shang Tomb of Xingan were powdery, pale green, which were more like "bronze disease", but the mineral composition of patinas was not paratacamite or atacamite. Micro X-ray diffraction (XRD) and high performance transmission electroscope (HTEM) showed that the patinas were mainly composed of non-crystalline and nano-crystalline SnO2, and the size of nano-crystalline particle was in the range of 4-5.7 nm; Moreover, the energy-dispersive X-ray spectrometry showed that element tin is the primary ingredient of the sample, as well as little copper, silicon, lead and iron were detected. By studying the crystal lattice stripe image of the nanometer SnO2, it was deduced that the chemical formula of nano-crystalline SnO2 did not include other elements; The Raman spectrum of the sample showed that there were not any characteristic peaks of SnO2, the spectrum was more like non-crystalline SnO2, and the weak and broad peak of 973 cm(-1) indicated that the sample may contain silicate grains, It was inferred that little of copper, silicon, lead and iron should exist in the form of non-crystalline silicate particles. PMID:22827070

  2. Titania-Silica Materials for Enhanced Photocatalysis.

    PubMed

    Rico-Santacruz, Marisa; Serrano, Elena; Marcì, Giuseppe; García-López, Elisa I; García-Martínez, Javier

    2015-12-01

    Mesoporous titania-organosilica nanoparticles comprised of anatase nanocrystals crosslinked with organosilica moieties have been prepared by direct co-condensation of a titania precursor, tetrabuthylortotitanate (TBOT), with two organosilica precursors, 1,4-bis(triethoxysilyl) benzene (BTEB) and 1,2-bis(triethoxysilyl) ethane (BTEE), in mild conditions and in the absence of surfactant. These hybrid materials show both high surface areas (200-360 m(2)  g(-1) ) and pore volumes (0.3 cm(3)  g(-1) ) even after calcination, and excellent photoactivity in the degradation of rhodamine 6G and in the partial oxidation of propene under UV irradiation, especially after the calcination of the samples. During calcination, there is a change in the Ti(IV) coordination and an increase in the content of SiOTi moieties in comparison with the uncalcined materials, which seems to be responsible for the enhanced photocatalytic activity of hybrid titania-silica materials as compared to both uncalcined samples and the control TiO2 . PMID:26503306

  3. New High Aspect-Ratio Titania Nanotubes

    NASA Astrophysics Data System (ADS)

    Panaitescu, Eugen; Richter, Christiaan; Menon, Latika

    2007-03-01

    Titanium oxide nanotubes show great promise in photocatalytic, gas sensing, biological, and other applications. Techniques for the fabrication of titania nanotubes include electrodeposition in polymer molds starting from alumina templates, anodization of titanium in fluoride containing solutions, and hydrothermal treatment of nano- and micropowders. We have developed a new synthesis route for the production of new ultra-high aspect-ratio (over 1000:1) titania nanotubes by anodization in chloride containing acid solutions. The fabrication process occurs rapidly, in a fraction of the time when compared with other methods such as anodization in the highly toxic fluoride-containing electrolytes. We have demonstrated nanotubes with diameters as small as 25 nm, and lengths of up to 50 μm, and we have produced them with varying carbon content through the addition of organic acids in the electrolyte. This opens up new possibilities for many advanced applications of such nanotubes. Various synthesis conditions (pH, chloride content, electrolyte nature), and their influence on morphology, composition, and crystalline structure will be presented. Preliminary results on photocatalytic and transmission properties will also be discussed.

  4. Effect of Argon/Oxygen Flow Rate Ratios on DC Magnetron Sputtered Nano Crystalline Zirconium Titanate Thin Films

    NASA Astrophysics Data System (ADS)

    Rani, D. Jhansi; Kumar, A. GuruSampath; Sarmash, T. Sofi; Chandra Babu Naidu, K.; Maddaiah, M.; Rao, T. Subba

    2016-06-01

    High transmitting, non absorbent, nano crystalline zirconium titanate (ZT) thin films suitable for anti reflection coatings (ARC) were deposited on to glass substrates by direct current (DC) magnetron reactive sputtering technique, under distinct Argon to Oxygen (Ar/O2) gas flow rate ratios of 31/1, 30/2, 29/3 and 28/4, with a net gas flow (Ar + O2) of 32sccm, at an optimum substrate temperature of 250°C. The influence of the gas mixture ratio on the film properties has been investigated by employing x-ray diffraction (XRD), ultra violet visible (UV-vis) spectroscopy, atomic force microscopy (AFM), energy dispersive x-ray analysis (EDX) and four point probe methods. The films showed a predominant peak at 30.85° with (111) orientation. The crystallite size reduced from 22.94 nm to 13.5 nm and the surface roughness increased from 11.53 nm to 50.58 nm with increase in oxygen content respectively. The films deposited at 31/1 and 30/2 showed almost similar chemical composition. Increased oxygen content results an increase in electrical resistivity from 3.59 × 103 to 2.1 × 106 Ωm. The film deposited at Ar/O2 of 28/4 exhibited higher average optical transmittance of 91%, but its refractive index is higher than that of what is required for ARC. The films deposited at 31/1 and 30/2 of Ar/O2 possess higher transmittance (low absorbance) apart from suitable refractive index. Thus, these films are preferable candidates for ARC.

  5. Effect of Argon/Oxygen Flow Rate Ratios on DC Magnetron Sputtered Nano Crystalline Zirconium Titanate Thin Films

    NASA Astrophysics Data System (ADS)

    Rani, D. Jhansi; Kumar, A. GuruSampath; Sarmash, T. Sofi; Chandra Babu Naidu, K.; Maddaiah, M.; Rao, T. Subba

    2016-04-01

    High transmitting, non absorbent, nano crystalline zirconium titanate (ZT) thin films suitable for anti reflection coatings (ARC) were deposited on to glass substrates by direct current (DC) magnetron reactive sputtering technique, under distinct Argon to Oxygen (Ar/O2) gas flow rate ratios of 31/1, 30/2, 29/3 and 28/4, with a net gas flow (Ar + O2) of 32sccm, at an optimum substrate temperature of 250°C. The influence of the gas mixture ratio on the film properties has been investigated by employing x-ray diffraction (XRD), ultra violet visible (UV-vis) spectroscopy, atomic force microscopy (AFM), energy dispersive x-ray analysis (EDX) and four point probe methods. The films showed a predominant peak at 30.85° with (111) orientation. The crystallite size reduced from 22.94 nm to 13.5 nm and the surface roughness increased from 11.53 nm to 50.58 nm with increase in oxygen content respectively. The films deposited at 31/1 and 30/2 showed almost similar chemical composition. Increased oxygen content results an increase in electrical resistivity from 3.59 × 103 to 2.1 × 106 Ωm. The film deposited at Ar/O2 of 28/4 exhibited higher average optical transmittance of 91%, but its refractive index is higher than that of what is required for ARC. The films deposited at 31/1 and 30/2 of Ar/O2 possess higher transmittance (low absorbance) apart from suitable refractive index. Thus, these films are preferable candidates for ARC.

  6. Efficiency of sensitizing nano-titania with organic dyes and peroxo complexes

    NASA Astrophysics Data System (ADS)

    Savinkina, Elena; Obolenskaya, Lubov; Kuzmicheva, Galina

    2015-01-01

    A new method of sensitizing titania by treatment of the reaction mixture with Methylene Blue, Methyl Red or hydrogen peroxide is developed; the sensitizer was introduced into the reaction mixture while synthesizing nanosize TiO2 from titanyl sulfate. The samples prepared by this method are compared to the samples prepared by cold impregnation of Methylene Blue, Methyl Red or hydrogen peroxide on titania, pre-synthesized by sulfate method, or commercial Degussa P25 and Hombikat UV100. The samples were characterized by X-ray diffraction; their photocatalytic activity was studied in the model reaction of Methyl Orange decomposition in aqueous solution under UV and visible light. The highest photocatalytic activity under visible light was found for titania, sensitized with titanium peroxo complexes by the new method. It is also active for photodegradation of salicylic acid under visible light.

  7. Heterogeneous photocatalytic oxidation of toxic organic waste waters with supported semiconductor

    SciTech Connect

    Renzi, C.; Mazzarino, I.; Baldi, G.

    1996-12-31

    The photocatalytic oxidation of coumaric acid by dissolved oxygen in aqueous solution was carried using supported Titania catalysts. Thin catalytic layers on inert supports were obtained by Physical Vapor Deposition. The oxidation process was performed in two experimental reactors: a small-scale batch apparatus and a pilot-size continuous photocatalytic reactor (CPR). 6 refs., 6 figs., 1 tab.

  8. Depth-dependent crystallinity of nano-crystalline silicon induced by step-wise variation of hydrogen dilution during hot-wire CVD

    NASA Astrophysics Data System (ADS)

    Arendse, C. J.; van Heerden, B. A.; Muller, T. F. G.; Cummings, F. R.; Oliphant, C. J.; Malgas, G. F.; Motaung, D. E.

    2015-06-01

    To induce an amorphous surface in a nano-crystalline silicon (nc-Si:H) thin film, the hydrogen dilution was reduced step-wise at fixed time intervals from 90 - 50% during the hotwire chemical vapour deposition process. This contribution reports on the structural properties of the resultant nc-Si:H thin film as a function of the deposition time. Raman spectroscopy, confirmed by high resolution transmission spectroscopy, indicates crystalline uniformity in the growth direction, accompanied by the progression of an amorphous surface layer as the deposition time is increased. The silicon- and oxygen bonding configurations were probed using infrared spectroscopy and electron energy loss spectroscopy. The growth mechanism is ascribed to the improved etching rate by atomic hydrogen in nano-crystalline silicon towards the film/substrate interface region. The optical properties were calculated by applying the effective medium approximation theory, where the existence of bulk and interfacial layers, as inferred from cross-sectional microscopy, were taken into account.

  9. Structural morphology, upconversion luminescence and optical thermometric sensing behavior of Y2O3:Er3+/Yb3+ nano-crystalline phosphor

    NASA Astrophysics Data System (ADS)

    Joshi, C.; Dwivedi, A.; Rai, S. B.

    2014-08-01

    Infrared-to-visible upconverting rare earths Er3+/Yb3+ co-doped Y2O3 nano-crystalline phosphor samples have been prepared by solution combustion method followed by post-heat treatment at higher temperatures. A slight increase in average crystallite size has been found on calcinations verified by X-ray analysis. Transmission electron microscopy (TEM) confirms the nano-crystalline nature of the as-prepared and calcinated samples. Fourier transform infrared (FTIR) analysis shows the structural changes in as-prepared and calcinated samples. Upconversion and downconversion emission recorded using 976 and 532 nm laser sources clearly demonstrates a better luminescence properties in the calcinated samples as compared to as-prepared sample. Upconversion emission has been quantified in terms of standard chromaticity diagram (CIE) showing a shift in overall upconversion emission of as-prepared and calcinated samples. Temperature sensing behaviour of this material has also been investigated by measurement of fluorescence intensity ratio (FIR) of various signals in green emission in the temperature range of 315 to 555 K under 976 nm laser excitation.

  10. Hydrogenated blue titania with high solar absorption and greatly improved photocatalysis

    NASA Astrophysics Data System (ADS)

    Zhu, Guilian; Shan, Yufeng; Lin, Tianquan; Zhao, Wenli; Xu, Jijian; Tian, Zhangliu; Zhang, Hui; Zheng, Chong; Huang, Fuqiang

    2016-02-01

    Hydrogenated black titania, with a crystalline core/amorphous shell structure, has attracted global interest due to its excellent photocatalytic properties. However, the understanding of its structure-property relationships remains a great challenge and a more effective method to produce hydrogenated titania is desirable. Herein, we report a TiH2 assisted reduction method to synthesize bluish hydrogenated titania (TiO2-x:H) that is highly crystallized. The characteristic amorphous shells, which are essential for the enhancement of solar absorption and photocatalysis in many reported hydrogenated titania, are completely removed by hydrogen peroxide. The blue TiO2-x:H sample without amorphous shells delivers not only significantly improved visible- and infrared-light absorption but also greatly enhanced photocatalytic activity compared to pristine TiO2. Its water decontamination is 2.5 times faster and the hydrogen production was 1.9-fold higher over pristine TiO2. Photoelectrochemical measurement reveals greatly improved carrier density and photocurrent (a 4.3-fold increase) in the reduced TiO2-x:H samples. This work develops a facile and versatile method to prepare hydrogenated titania and proposes a new understanding of the hydrogenated titania that doped hydrogen atoms, instead of the amorphous shells, are essential for its high photocatalytic performance.Hydrogenated black titania, with a crystalline core/amorphous shell structure, has attracted global interest due to its excellent photocatalytic properties. However, the understanding of its structure-property relationships remains a great challenge and a more effective method to produce hydrogenated titania is desirable. Herein, we report a TiH2 assisted reduction method to synthesize bluish hydrogenated titania (TiO2-x:H) that is highly crystallized. The characteristic amorphous shells, which are essential for the enhancement of solar absorption and photocatalysis in many reported hydrogenated titania, are

  11. Synthesis and polymorphic control for visible light active titania nanoparticles

    NASA Astrophysics Data System (ADS)

    Kaewgun, Sujaree

    Titania (TiO2) is useful for many applications in photocatalysis, antimicrobials, pigment, deodorization, and decomposition of harmful organics and undesirable compounds in the air and waste water under UV irradiation. Among the three phases of TiO2, Rutile, Anatase, and Brookite, studies have been more focused on the anatase and rutile phases. Pure brookite is the most difficult phase to prepare, even under hydrothermal conditions. Predominantly brookite phase TiO2 nanoparticles were prepared by the Water-based Ambient Condition Sol (WACS) process in our laboratory. The objectives of this research were to enhance visible light active (VLA) photocatalytic properties of polymorphic brookite TiO2 by minimizing the lattice defects and narrowing band gap of titania by nitrogen and/or carbon chromophone, and to investigate the deactivation, reusability, and regeneration of the VLA titania in order to design better titania catalysts for organic compound degradation applications. In order to study the influence of hydroxyl content on photocatalytic activities (PCAs) of polymorphic titania nanoparticles, the WACS samples were post-treated by a Solvent-based Ambient Condition Sol (SACS) process in sec-butanol (sec-BuOH). All samples were characterized for phase composition, surface area, hydroxyl contamination, and particle morphology by x-ray diffraction, N2 physisorption, FT-IR, solid state 1H NMR and scanning electron microscopy, and then compared to a commercial titania, Degussa P25. Evaluation of methyl orange (MO) degradation under UV irradiation results showed that the lower lattice hydroxyl content in SACS titania enhanced the PCA. As-prepared titania and SACS samples, which have similar surface areas and crystallinity, were compared in order to prove that the superior PCA came from the reduction in the lattice hydroxyl content. To enhance PCA and VLA properties of WACS, an alternative high boiling point polar solvent, N-methylpyrrolidone (NMP), was utilized in the

  12. Optical, Electrical and Catalytic Properties Of Titania Nanotubes

    NASA Astrophysics Data System (ADS)

    AbdElmoula, Mohamed

    In past decades revolutionary developments took place in many aspects of science. One of the leading developments is in the field of material science where there is great interest in developing new materials for various applications. Massive number of applications will change the entire life of mankind on earth and in space. Nanomaterials science is considered the pioneer in this new era. Titania nanotube is considered a very important material due to its promising applications in many fields ranging from energy harvesting to sensors and photocatalytic applications. Electrochemical anodization method is used to fabricate titania nanotube arrays, this method is preferred than other methods for many reasons, for example it has good degree of controlling tube length, tube diameter and tube wall thickness. In addition to controlling tube parameter this method provides a scalable, easy and cheap technique for future industrial applications. My work in this thesis is focused on this kind of nanotubes arrays. In this dissertation we will provide an introduction to fabrication of titania nanotube arrays. We will provide an overview about the reported methods of fabrication and the advantage of each method. Also we will describe some anticipated application and the challenges to make these nanotubes functional and efficient. Secondly, we will carry out a comprehensive study of the electrical transport of a single titania nanotube, where we have been able to study for the first time the electrical transport properties of a single titania nanotube using E-beam Lithography technique. Also we will explore parameters that affect these transport properties such as annealing conditions and the morphology of the nanotube. We will describe a study of the optical properties of free standing titania nanotube arrays, where we will investigate the transmission, reflection and absorption of electromagnetic spectrum from 300nm to 1000nm (which cover the infrared, visible light and ultra

  13. Synthesis, Characterization and Exploration of Multiferroic Properties in Nano-Crystalline Tb1-xYxMnO3 (0 ≤ x ≤ 0.4).

    PubMed

    Shukla, R; Chakraborty, Keka R; Mandal, B P; Kaushik, S D; Mukadam, M D; Lawes, G; Naik, R; Kumarasiri, A; Siruguri, V; Yusuf, S M; Tyagil, A K

    2016-04-01

    We report the synthesis and electric properties of nano-crystalline Tb1-xYxMnO3 (x = 0, 0.1, 0.2, 0.3 and 0.4) compounds prepared by gel-combustion method. These samples were characterized by a number of techniques including X-ray diffraction (XRD), Raman spectroscopy, specific-heat measurement, neutron diffraction, and magnetic field dependent pyrocurrent measurement. All the samples crystallize in the orthorhombic structure with space group Pnma at room temperature. Anomalies were observed in low temperature specific-heat measurement corresponding to magnetic and electric phase transitions. The magnetic phase transitions occurred at ~35, ~22-28 and ~7 K for all the samples. Signatures of coupling between magnetic and electric order parameters were revealed by pyrocurrent measurements carried out in presence of magnetic fields. PMID:27451770

  14. REUSABLE ADSORBENTS FOR DILUTE SOLUTIONS SEPARATION. 5: PHOTODEGRADATION OF ORGANIC COMPOUNDS ON SURFACTANT-MODIFIED TITANIA. (R828598C753)

    EPA Science Inventory

    A semiconductor titania (TiO2) surface was modified by surfactant adsorption to make it more hydrophobic and to increase the adsorption of hydrophobic organic compounds (HOCs) and their photodegradation rates under UV irradiation. Photocatalytic experiments using Ti...

  15. Fabrication of AgAu alloy-TiO2 core-shell nanoparticles and their photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao-yu; Yuan, Shu-long; Yuan, Yu-zhen; Li, Xue

    2015-01-01

    In this paper, for improving the photocatalytic efficiency of titania (TiO2) nanoparticles (NPs), AgAu alloy-TiO2 core-shell NPs are fabricated via a sol-gel (SG) process in the presence of AgAu alloy NPs with block copolymer shells as templates. The photocatalytic activities of the AgAu-TiO2 NPs on the photodecomposition of methylene blue (MB) are investigated. The AgAu-TiO2 composite NPs coated with 5.0% titania related to block copolymers show higher photocatalytic activity than the other samples in which the titania contents are larger than 5.0%. The results indicate that the increase of the thickness of the TiO2 shell leads to the decrease of the photocatalytic activity.

  16. Titania bound sodium titanate ion exchanger

    DOEpatents

    DeFilippi, Irene C. G.; Yates, Stephen Frederic; Shen, Jian-Kun; Gaita, Romulus; Sedath, Robert Henry; Seminara, Gary Joseph; Straszewski, Michael Peter; Anderson, David Joseph

    1999-03-23

    This invention is method for preparing a titania bound ion exchange composition comprising admixing crystalline sodium titanate and a hydrolyzable titanium compound and, thereafter drying the titania bound crystalline sodium titanate and subjecting the dried titania bound ion exchange composition to optional compaction and calcination steps to improve the physical strength of the titania bound composition.

  17. Functionalization of a cotton fabric surface with titania nanosols: applications for self-cleaning and UV-protection properties.

    PubMed

    Abidi, Noureddine; Cabrales, Luis; Hequet, Eric

    2009-10-01

    In this study, cotton fabric was successfully modified by titania nanosols prepared by means of the sol-gel process with tetrabutyl orthotitanate [Ti(OC(4)H(9))(4)] as the active ingredient. The cotton fabric was padded with the nanosol solution, dried at 60 degrees C, and cured at 150 degrees C. Scanning electron microscopy showed the presence of a titania film on the fiber surface. The photocatalytic properties of titania-nanosol-treated cotton fabric were investigated. The results showed that stains of coffee and red wine were successfully decomposed by exposure of the stained fabric to UV radiation. Furthermore, titania-nanosol treatment imparted to the cotton fabric a very good protection against UV radiation. The durability of the treatment was investigated by performing repeated home laundering, and the results showed no effect of laundering on the UV-protection efficiency. PMID:20355847

  18. Nanostructuring titania by embossing with polymer molds made from anodic alumina templates.

    PubMed

    Goh, Chiatzun; Coakley, Kevin M; McGehee, Michael D

    2005-08-01

    We demonstrate a method for embossing titania sol--gel precursor with poly(methyl methacrylate) (PMMA) molds to make thin films of titania that have dense arrays of 35--65 nm diameter pores, whose features are 1 order of magnitude smaller than those previously demonstrated for sol--gel molding. We show that the high modulus of PMMA is necessary to preserve small features with high aspect ratios on the mold for nanopatterning. The molds are prepared by thermally infiltrating PMMA into anodic alumina templates, whose pore dimensions and depths are adjustable by varying anodization conditions. The difficulties associated with mold release from a master are avoided by wet etching the template. These titania films, and others made with other semiconductors, could be useful for photovoltaic, photocatalytic, and sensing applications where nanostructuring of surfaces with controlled dimensions are essential. PMID:16089486

  19. Synthesis of nano-crystalline LiSr xMn 2 - xO 4 powder by a novel sol-gel thermolysis process for Li-ion polymer battery

    NASA Astrophysics Data System (ADS)

    Subramania, A.; Angayarkanni, N.; Vasudevan, T.

    Cubic spinel nano-crystalline LiSr xMn 2 - xO 4 (x = 0.10, 0.15, 0.20, 0.25) powders are prepared at low temperature by means of a facile gel-polymer thermolysis process by calcining the prepared precursor samples at 340 °C to obtain the products. X-ray diffraction and scanning electron microscopic analyses confirm that the products consists of nano-crystalline particles with uniform distribution. The effect of calcinations on the crystallinity of the cubic spinel LiSr xMn 2 - xO 4 powder is examined by differential scanning colorimetric analysis. In order to asses the electrochemical reversibility of the cathode material, cyclic voltametry studies are performed by fabricating button cells with the configuration of carbon/MPPE/LiSr xMn 2 - xO 4.

  20. Improving the long-term stability of Ti6Al4V abutment screw by coating micro/nano-crystalline diamond films.

    PubMed

    Xie, Youneng; Zhou, Jing; Wei, Qiuping; Yu, Z M; Luo, Hao; Zhou, Bo; Tang, Z G

    2016-10-01

    Abutment screw loosening is the most common complication of implanting teeth. Aimed at improving the long-term stability of them, well-adherent and homogeneous micro-crystalline diamond (MCD) and nano-crystalline diamond (NCD) were deposited on DIO(®) (Dong Seo, Korea) abutment screws using a hot filament chemical vapor deposition (HFCVD) system. Compared with bare DIO(®) screws, diamond coated ones showed higher post reverse toque values than the bare ones (p<0.05) after cyclic loading one million times under 100N, and no obvious flaking happened after loading test. Diamond coated disks showed lower friction coefficients of 0.15 and 0.18 in artificial saliva when countered with ZrO2 than that of bare Ti6Al4V disks of 0.40. Though higher cell apoptosis rate was observed on film coated disks, but no significant difference between MCD group and NCD group. And the cytotoxicity of diamond films was acceptable for the fact that the cell viability of them was still higher than 70% after cultured for 72h. It can be inferred that coating diamond films might be a promising modification method for Ti6Al4V abutment screws. PMID:27393893

  1. Evidence of quantum correction to conductivity and variable range hopping conduction in nano-crystalline Cu{sub 3}N thin film

    SciTech Connect

    Sahoo, Guruprasad Jain, Mahaveer K.

    2015-10-15

    We have investigated the temperature dependent carrier transport properties of nano-crystalline copper nitride thin films synthesized by modified activated reactive evaporation. The films, prepared in a Cu-rich growth condition are found to be highly disordered and the carrier transport in these films is mainly attributed to the impurity band conduction. We have observed that no single conduction mechanism is appropriate to elucidate the carrier transport in the entire temperature range of 20 – 300 K. Therefore, we have employed different conduction mechanisms in different temperature regimes. The carrier transport of the films in the low temperature regime (20 – 150 K) has been interpreted by implementing quantum correction to the conductivity. In the high temperature regime (200 – 300 K), the conduction mechanism has been successfully analyzed on the basis of Mott’s variable range hopping mechanism. Furthermore, it can be predicted that copper ions present at the surface of the crystallites are responsible for the hopping conduction mechanism.

  2. A micro-scale hot wire anemometer based on low stress (Ni/W) multi-layers deposited on nano-crystalline diamond for air flow sensing

    NASA Astrophysics Data System (ADS)

    Talbi, A.; Gimeno, L.; Gerbedoen, J.-C.; Viard, R.; Soltani, A.; Mortet, V.; Preobrazhensky, V.; Merlen, A.; Pernod, P.

    2015-12-01

    A linear array of microscale thermal anemometers has been designed, fabricated and characterized. The sensitive element consists of a self-compensated-stress multilayer (Ni/W) patterned to form a wire with length, width, and thickness close to 200 μm, 5 μm and 2 μm respectively. The wire is deposited and supported by prongs made of nano-crystalline diamond (NCD) of about 2 μm in thickness. Due to its high Young’s modulus, NCD allows a very high mechanical toughness without the need for thicker support for the hot wire. Also, depending on grain size, the NCD is able to present thermal conductivity smaller than 10 W mK-1, providing good thermal insulation from the substrate and less conductive end losses to the prongs. The sensor was characterized experimentally. Its electrical and thermal properties were obtained first in the absence of fluid flow. The results confirm the effectiveness of thermal insulation and the mechanical robustness of the structure. The fluidic characterizations were performed and analysed in the case of an airflow with velocities of up to 30 m s-1.

  3. Spray pyrolysis growth of a high figure of merit, nano-crystalline, p-type transparent conducting material at low temperature

    NASA Astrophysics Data System (ADS)

    Farrell, L.; Norton, E.; O'Dowd, B. J.; Caffrey, D.; Shvets, I. V.; Fleischer, K.

    2015-07-01

    In this letter, we demonstrate a low temperature (≈345 °C) growth method for Cu deficient CuCrO2 performed by spray pyrolysis using metal-organic precursors and a simple air blast nozzle. Smooth films were grown on glass substrates with a highest conductivity of 12 S/cm. The most conductive samples retain transparencies above 55% resulting in a figure of merit as high as 350 μS, which is the best performing p-type transparent conducting material grown by solution methods to date. Remarkably, despite the nano-crystallinity of the films, properties comparable with crystalline CuCrO2 are observed. No postannealing of the films is required in contrast to previous reports on crystalline material. The low processing temperature of this method means that the material can be deposited on flexible substrates. As this is a solution based technique, it is more attractive to industry as physical vapour deposition methods are slow and costly in comparison.

  4. Effect of Gas Sources on the Deposition of Nano-Crystalline Diamond Films Prepared by Microwave Plasma Enhanced Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Weng, Jun; Xiong, Liwei; Wang, Jianhua; Man, Weidong; Chen, Guanhu

    2010-12-01

    Nano-crystalline diamond (NCD) films were deposited on silicon substrates by a microwave plasma enhanced chemical vapor deposition (MPCVD) reactor in C2H5OH/H2 and CH4/H2/O2 systems, respectively, with a constant ratio of carbon/hydrogen/oxygen. By means of atomic force microscopy (AFM) and X-ray diffraction (XRD), it was shown that the NCD films deposited in the C2H5OH/H2 system possesses more uniform surface than that deposited in the CH4/H2/O2 system. Results from micro-Raman spectroscopy revealed that the quality of the NCD films was different even though the plasmas in the two systems contain exactly the same proportion of elements. In order to explain this phenomenon, the bond energy of forming OH groups, energy distraction in plasma and the deposition process of NCD films were studied. The experimental results and discussion indicate that for a same ratio of carbon/hydrogen/oxygen, the C2H5OH/H2 plasma was beneficial to deposit high quality NCD films with smaller average grain size and lower surface roughness.

  5. Synthesis of micro- or nano-crystalline diamond films on WC-Co substrates with various pretreatments by hot filament chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Wei, Qiu-ping; Yu, Z. M.; Ashfold, Michael N. R.; Ye, J.; Ma, L.

    2010-04-01

    Diamond films deposited on tungsten carbide can lead to major improvements in the life and performance of cutting tools. However, deposition of diamond onto cemented tungsten carbide (WC-Co) is problematic due to the cobalt binder in the WC. This binder provides additional toughness to the tool but results in poor adhesion and low nucleation density of any diamond film. A two-step chemical etching pretreatment (Murakami reagent and Caro acid, (MC)-pretreatment) and a boronization pretreatment have both been used extensively to improve adhesion of CVD diamond film on WC-Co substrates. Here we discuss the applicability of MC-pretreatment for a range of Co-containing WC-Co substrates, and demonstrate a controlled synthesis process based on liquid boronizing pretreatment for obtaining smooth and dense micro- or nano-crystalline diamond films on high Co-containing WC-Co substrates. Substrate treatments and deposition parameters were found to have major influences on the smoothness, structure and quality of the diamond films. The best quality diamond films were achieved under conditions of relatively high substrate temperature ( Ts) and the best adhesion was achieved at Ts = 800 °C.

  6. Anomalous behavior of B1g mode in highly transparent anatase nano-crystalline Nb-doped Titanium Dioxide (NTO) thin films

    NASA Astrophysics Data System (ADS)

    Gautam, Subodh K.; Gautam, Naina; Singh, R. G.; Ojha, S.; Shukla, D. K.; Singh, Fouran

    2015-12-01

    The effect of Niobium doping and size of crystallites on highly transparent nano-crystalline Niobium doped Titanium Dioxide (NTO) thin films with stable anatase phase are reported. The Nb doping concentration is varied within the solubility limit in TiO2 lattice. Films were annealed in controlled environment for improving the crystallinity and size of crystallites. Elemental and thickness analysis were carried out using Rutherford backscattering spectrometry and cross sectional field emission scanning electron microscopy. Structural characteristics reveal a substitutional incorporation of Nb+5 in the TiO2 lattice which inhibits the anatase crystallites growth with increasing the doping percentage. The micro-Raman (MR) spectra of films with small size crystallites shows stiffening of about 4 cm-1 for the Eg(1) mode and is ascribed to phonon confinement and non-stoichiometry. In contrast, B1g mode exhibits a large anomalous softening of 20 cm-1 with asymmetrical broadening; which was not reported for the case of pure TiO2 crystallites. This anomalous behaviour is explained by contraction of the apical Ti-O bonds at the surface upon substitutional Nb5+ doping induced reduction of Ti4+ ions also known as hetero-coordination effect. The proposed hypotheses is manifested through studying the electronic structure and phonon dynamics by performing the near edge x-ray absorption fine structure (NEXAFS) and temperature dependent MR down to liquid nitrogen temperature on pure and 2.5 at.% doped NTO films, respectively.

  7. High-rate nano-crystalline Li 4Ti 5O 12 attached on carbon nano-fibers for hybrid supercapacitors

    NASA Astrophysics Data System (ADS)

    Naoi, Katsuhiko; Ishimoto, Shuichi; Isobe, Yusaku; Aoyagi, Shintaro

    A lithium titanate (Li 4Ti 5O 12)-based electrode which can operate at unusually high current density (300 C) was developed as negative electrode for hybrid capacitors. The high-rate Li 4Ti 5O 12 electrode has a unique nano-structure consisting of unusually small nano-crystalline Li 4Ti 5O 12 (ca. 5-20 nm) grafted onto carbon nano-fiber anchors (nc-Li 4Ti 5O 12/CNF). This nano-structured nc-Li 4Ti 5O 12/CNF composite are prepared by simple sol-gel method under ultra-centrifugal force (65,000 N) followed by instantaneous annealing at 900 °C for 3 min. A model hybrid capacitor cell consisting of a negative nc-Li 4Ti 5O 12/CNF composite electrode and a positive activated carbon electrode showed high energy density of 40 Wh L -1 and high power density of 7.5 kW L -1 comparable to conventional EDLCs.

  8. Fabrication of Self-Cleaning, Reusable Titania Templates for Nanometer and Micrometer Scale Protein Patterning.

    PubMed

    Moxey, Mark; Johnson, Alexander; El-Zubir, Osama; Cartron, Michael; Dinachali, Saman Safari; Hunter, C Neil; Saifullah, Mohammad S M; Chong, Karen S L; Leggett, Graham J

    2015-06-23

    The photocatalytic self-cleaning characteristics of titania facilitate the fabrication of reuseable templates for protein nanopatterning. Titania nanostructures were fabricated over square centimeter areas by interferometric lithography (IL) and nanoimprint lithography (NIL). With the use of a Lloyd's mirror two-beam interferometer, self-assembled monolayers of alkylphosphonates adsorbed on the native oxide of a Ti film were patterned by photocatalytic nanolithography. In regions exposed to a maximum in the interferogram, the monolayer was removed by photocatalytic oxidation. In regions exposed to an intensity minimum, the monolayer remained intact. After exposure, the sample was etched in piranha solution to yield Ti nanostructures with widths as small as 30 nm. NIL was performed by using a silicon stamp to imprint a spin-cast film of titanium dioxide resin; after calcination and reactive ion etching, TiO2 nanopillars were formed. For both fabrication techniques, subsequent adsorption of an oligo(ethylene glycol) functionalized trichlorosilane yielded an entirely passive, protein-resistant surface. Near-UV exposure caused removal of this protein-resistant film from the titania regions by photocatalytic degradation, leaving the passivating silane film intact on the silicon dioxide regions. Proteins labeled with fluorescent dyes were adsorbed to the titanium dioxide regions, yielding nanopatterns with bright fluorescence. Subsequent near-UV irradiation of the samples removed the protein from the titanium dioxide nanostructures by photocatalytic degradation facilitating the adsorption of a different protein. The process was repeated multiple times. These simple methods appear to yield durable, reuseable samples that may be of value to laboratories that require nanostructured biological interfaces but do not have access to the infrastructure required for nanofabrication. PMID:26042335

  9. Hemocompatibility of titania nanotube arrays.

    PubMed

    Smith, Barbara S; Yoriya, Sorachon; Grissom, Laura; Grimes, Craig A; Popat, Ketul C

    2010-11-01

    Hemocompatibility is a key consideration for the long-term success of blood contacting biomaterials; hence, there is a critical need to understand the physiological response elicited from blood/nano-biomaterial interactions. In this study, we have investigated the adsorption of key blood serum proteins, in vitro adhesion and activation of platelets, and clotting kinetics of whole blood on titania nanotube arrays. Previous studies have demonstrated improved mesenchymal stem cell functionality, osteoblast phenotypic behavior, localized drug delivery, and the production of endothelial cell ECM on titania nanotube arrays. Furthermore, these titania nanotube arrays have elicited minimal levels of monocyte activation and cytokine secretion, thus exhibiting a very low degree of immunogenicity. Titania nanotube arrays were fabricated using anodization technique and the surface morphology was examined through scanning electron microscopy (SEM). The crystalline phases were identified using glancing angled X-ray diffraction (GAXRD). Nanoindentation and scratch tests were used to characterize the mechanical properties of titania nanotube arrays. The adsorption of key blood proteins (albumin, fibrinogen, and immunoglobulin-g) was evaluated using a micro-BCA assay and X-ray photoelectron spectroscopy (XPS). The adhesion and activation of platelets was investigated using live-cell staining, MTT assay, and SEM. Whole blood clotting kinetics was evaluated by measuring the free hemoglobin concentration, and SEM was used to visualize the clot formation. Our results indicate increased blood serum protein adsorption, platelet adhesion and activation, and whole blood clotting kinetics on titania nanotube arrays. PMID:20629021

  10. Titanium dioxide-assisted photocatalytic induction of prophages to lytic cycle.

    PubMed

    Skorb, Ekaterina V; Andreeva, Daria V; Raiski, Andrey P; Belyasova, Natalya A; Möhwald, Helmuth; Sviridov, Dmitry V

    2011-12-01

    The investigations on the kinetics of photocatalytic inactivation of bacteriophages, lactic bacteria and lysogenic lactic bacteria have shown that the rate of bacterial inactivation is ca. 10 times less than the inactivation of bacteriophages. Titania-assisted photorelease of bacteriophages from lysogenic bacteria proves that photogenerated reactive oxygen species affect the deoxyribonucleic acid (DNA) of bacteria before their deactivation. On this basis a novel photocatalytic method of a prophage induction to the lytic cycle and detection of lysogenic bacteria is proposed. PMID:22057553

  11. Development and characterization of silica and titania based nano structured materials for the removal of indoor and outdoor air pollutants

    NASA Astrophysics Data System (ADS)

    Peiris, Thelge Manindu Nirasha

    Solar energy driven catalytic systems have gained popularity in environmental remediation recently. Various photocatalytic systems have been reported in this regard and most of the photocatalysts are based on well-known semiconducting material, Titanium Dioxide, while some are based on other materials such as Silicon Dioxide and various Zeolites. However, in titania based photocatalysts, titania is actively involved in the catalytic mechanism by absorbing light and generating exitons. Because of this vast popularity of titania in the field of photocatalysis it is believed that photocatalysis mainly occurs via non-localized mechanisms and semiconductors are extremely important. Even though it is still rare, photocatalysis could be localized and possible without use of a semiconductor as well. Thus, to support localized photocatalytic systems, and to compare the activity to titania based systems, degradation of organic air pollutants by nanostructured silica, titania and mixed silica titania systems were studied. New materials were prepared using two different approaches, precipitation technique (xerogel) and aerogel preparation technique. The prepared xerogel samples were doped with both metal (silver) and non-metals (carbon and sulfur) and aerogel samples were loaded with Chromium, Cobalt and Vanadium separately, in order to achieve visible light photocatalytic activity. Characterization studies of the materials were carried out using Nova BET analysis, DR UV-vis spectrometry, powder X-ray diffraction, X-ray photoelectron Spectroscopy, FT-IR spectroscopy, Transmission Electron Microscopy, etc. Kinetics of the catalytic activities was studied using a Shimadzu GCMS-QP 5000 instrument using a closed glass reactor. All the experiments were carried out in gaseous phase using acetaldehyde as the model pollutant. Kinetic results suggest that chromium doped silica systems are good UV and visible light active photocatalysts. This is a good example for a localized

  12. Chemically Assisted Photocatalytic Oxidation System

    NASA Technical Reports Server (NTRS)

    Andino, Jean; Wu, Chang-Yu; Mazyck, David; Teixeira, Arthur A.

    2009-01-01

    The chemically assisted photocatalytic oxidation system (CAPOS) has been proposed for destroying microorganisms and organic chemicals that may be suspended in the air or present on surfaces of an air-handling system that ventilates an indoor environment. The CAPOS would comprise an upstream and a downstream stage that would implement a tandem combination of two partly redundant treatments. In the upstream stage, the air stream and, optionally, surfaces of the air-handling system would be treated with ozone, which would be generated from oxygen in the air by means of an electrical discharge or ultraviolet light. In the second stage, the air laden with ozone and oxidation products from the first stage would be made to flow in contact with a silica-titania photocatalyst exposed to ultraviolet light in the presence of water vapor. Hydroxyl radicals generated by the photocatalytic action would react with both carbon containing chemicals and microorganisms to eventually produce water and carbon dioxide, and ozone from the first stage would be photocatalytically degraded to O2. The net products of the two-stage treatment would be H2O, CO2, and O2.

  13. Polymer embedded nanocrystalline titania sorbent for 99Mo-99mTc generator.

    PubMed

    Chakravarty, Rubel; Shukla, Rakesh; Gandhi, Shyamla; Ram, Ramu; Dash, Ashutosh; Venkatesh, Meera; Tyagi, A K

    2008-09-01

    A new sorbent material, polymer embedded nano crystalline titania (Titanium Polymer-TiP) has been developed, from titanium (IV) chloride and isopropyl alcohol, for the adsorption of 99Mo, which is a precursor to 99mTc, a workhorse in radio-pharmaceuticals. The infrared absorption spectra of the TiP showed peaks corresponding to Ti-O groups. X-ray diffraction pattern of the adsorbent corresponded to rutile TiO2. The surface area of this polymer was 30 m2/g with an average pore size of 40 nm. The average crystallite size of TiO2, embedded in polymer, was found to be 5 nm. TEM micrograph of the adsorbent revealed the network of polymer with dispersed titania phase. Potential of this adsorbent for the preparation of 99Mo-99mTc generator has been explored. 99Mo could be adsorbed on to the adsorbent column containing TiP at pH 1 from which 99mTC could be eluted with normal (0.9%) saline solution with an elution yield of approximately 80%. The quality of the 99mTcO4 obtained was in accordance with the international specifications applicable for radiopharmaceutical use. A process demonstration run was carried out with 1.1 GBq (30 mCi) 99Mo activity level making use of the above adsorbent and consistent results were obtained over a period of one week, which is generally the shelf life of 99MO-99mTC generator. PMID:19049039

  14. Titania Deposition on PMR-15

    NASA Technical Reports Server (NTRS)

    Meador, Mary B.; Sutter, James K.; Pizem, Hillel; Gershevitz, Olga; Goffer, Yossi; Frimer, Aryeh A.; Sukenik, Chaim N.; Sampathkumaran, Uma; Milhet, Xavier; McIlwain, Alan

    2005-01-01

    The formation, degree of crystallinity and adherence of dense titania (TiO2) thin film coatings on a high-temperature polyimide resin (PMR-15) can be influenced by the chemical composition of the polymer surface. Furthermore, solution deposition conditions can be adjusted to provide additional control over the morphology and crystallinity of the titania films. Recipes for solution-based titania deposition that used a slowly-hydrolyzing titanium fluoride salt in the presence of boric acid as a fluoride scavenger allowed growth of films up to 750 nm thick in 22 h. By adjusting solution pH and temperature, either amorphous titania or oriented crystalline anatase films could be formed. Surface sulfonate groups enhance the adhesion of solution-deposited oxide thin film coatings. While most sulfonation procedures severely damaged the PMR-15 surface, the use of chlorosulfonic acid followed by hydrolysis of the installed chlorosulfonyl groups provided effective surface sulfonation without significant surface damage. In some cases, the oxide deposition solution caused partial hydrolysis of the polymer surface, which itself was sufficient to allow adhesion of the titania film through chelation of titanium ions by exposed benzoic acid groups on the polymer surface.

  15. Nano-crystalline p-ZnGa{sub 2}Te{sub 4}/n-Si as a new heterojunction diode

    SciTech Connect

    Sakr, G.B.; Fouad, S.S.; Yahia, I.S.; Abdel Basset, D.M.; Yakuphanoglu, F.

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► ZnGa{sub 2}Te{sub 4}/Si thin film was prepared by thermal evaporation technique. ► XRD and AFM graphs support the nano-crystalline of the studied device. ► Dark current–voltage characteristics of the heterojunction diode were investigated. ► Electrical parameters and conduction mechanism were determined. ► Conduction mechanisms were controlled by TE, SCLC and TCLC. -- Abstract: In this communication, ZnGa{sub 2}Te{sub 4} thin film was prepared by thermal evaporation technique on n-Si substrate. P-ZnGa{sub 2}Te{sub 4}/n-Si heterojunction diode was fabricated. The structure of ZnGa{sub 2}Te{sub 4} thin film was checked by XRD pattern and confirmed by AFM micrographs. The dark current–voltage characteristics of the heterojunction diode were investigated to determine the electrical parameters and conduction mechanism as a function of forward and reverse biasing conditions in the range (−10 V to 10 V) at temperature interval (303–423 K). The conduction mechanism was controlled by thermionic emission, space charge limited (SCLC) and trap-charge limited current (TCLC) mechanisms. The basic parameters such as the series resistance R{sub s}, the shunt resistance R{sub sh}, the ideality factor n and the barrier height φ{sub b} of the diode, the total density of trap states N{sub 0} and the exponential trapping distribution P{sub o} were determined. The obtained results showed that ZnGa{sub 2}Te{sub 4} is a good candidate for the applications of electronic devices.

  16. Anomalous behavior of B{sub 1g} mode in highly transparent anatase nano-crystalline Nb-doped Titanium Dioxide (NTO) thin films

    SciTech Connect

    Gautam, Subodh K. E-mail: fouran@gmail.com; Ojha, S.; Singh, Fouran E-mail: fouran@gmail.com; Gautam, Naina; Singh, R. G.; Shukla, D. K.

    2015-12-15

    The effect of Niobium doping and size of crystallites on highly transparent nano-crystalline Niobium doped Titanium Dioxide (NTO) thin films with stable anatase phase are reported. The Nb doping concentration is varied within the solubility limit in TiO{sub 2} lattice. Films were annealed in controlled environment for improving the crystallinity and size of crystallites. Elemental and thickness analysis were carried out using Rutherford backscattering spectrometry and cross sectional field emission scanning electron microscopy. Structural characteristics reveal a substitutional incorporation of Nb{sup +5} in the TiO{sub 2} lattice which inhibits the anatase crystallites growth with increasing the doping percentage. The micro-Raman (MR) spectra of films with small size crystallites shows stiffening of about 4 cm{sup −1} for the E{sub g(1)} mode and is ascribed to phonon confinement and non-stoichiometry. In contrast, B{sub 1g} mode exhibits a large anomalous softening of 20 cm{sup −1} with asymmetrical broadening; which was not reported for the case of pure TiO{sub 2} crystallites. This anomalous behaviour is explained by contraction of the apical Ti-O bonds at the surface upon substitutional Nb{sup 5+} doping induced reduction of Ti{sup 4+} ions also known as hetero-coordination effect. The proposed hypotheses is manifested through studying the electronic structure and phonon dynamics by performing the near edge x-ray absorption fine structure (NEXAFS) and temperature dependent MR down to liquid nitrogen temperature on pure and 2.5 at.% doped NTO films, respectively.

  17. Commercial and home-made nitrogen modified titanias. A short reflection about the advantageous/disadvantageous properties of nitrogen doping in the frame of their applicability

    NASA Astrophysics Data System (ADS)

    Pap, Zs.; Mogyorósi, K.; Veréb, G.; Dombi, A.; Hernádi, K.; Danciu, V.; Baia, L.

    2014-09-01

    As visible light driven photocatalysis became more and more intensively studied, the first commercial products showed up on the market. Simultaneously controversial results appeared in the literature generating an intensive debate regarding the advantages and draw-backs of nitrogen doping of titania. Hence, the present work focuses on two commercially available and four sol-gel made nitrogen modified titania powders regarding their structure and activity. It is demonstrated that the interstitial nitrogen entities “leak out” from the catalysts if the material is irradiated with UV light, while substitutional nitrogen remains stable. However, the latter one was proven to be less important in the photocatalytic point of view. These observations were also valid in the case of sol-gel made nitrogen modified titanias. Furthermore, the results obtained after applying different spectroscopic methods (IR, XPS and DRS) shown that the yellow color of the titanias, does not necessary mean that a successful doping is achieved.

  18. Photocatalytic and photoelectrocatalytic degradation of the antibacterial agent ciprofloxacin.

    PubMed

    Tantis, Iosif; Bousiakou, Leda; Karikas, George-Albert; Lianos, Panagiotis

    2015-03-01

    Photocatalytic and photoelectrocatalytic degradation of the antibacterial fluoroquinolone drug, ciprofloxacin, has been studied in the presence of nanocrystalline titania films supported on glass slides or transparent electrodes. The degradation has been examined either in pure water or in the presence of NaOH or NaCl. Titania films can photocatalytically or photoelectrocatalytically degrade ciprofloxacin. In the presence of NaOH, the degradation rate was lower than in pure water and this is explained by the fact that at high pH values attraction of ciprofloxacin to the titania surface is discouraged. In the presence of NaCl, the degradation rate was the highest, thanks to Cl-based radicals which can be photocatalytically created by interacting with photogenerated holes. Application of a forward (anodic) bias increased the photodegradation rate in the presence of both electrolytes while a reverse (cathodic) bias decreased the photodegradation rate. Electrocatalytic effects, i.e. degradation of ciprofloxacin in the dark or in the absence of a photocatalyst under an applied bias of up to ±1.0 V vs. Ag/AgCl, were not detected in the case of NaOH and were of limited importance in the case of NaCl. PMID:25436477

  19. Synthesis of mesoporous TiO2-curcumin nanoparticles for photocatalytic degradation of methylene blue dye.

    PubMed

    Abou-Gamra, Z M; Ahmed, M A

    2016-07-01

    Herein, we demonstrate a facile route for synthesis a new photocatalyst based on TiO2-curcumin nanoparticles for photodegradation of methylene blue dye under UV and visible light irradiation. The photocatalyst was prepared by sol-gel method using chitosan as biodegradable polymer. The crystalline and the nanostructure were characteristic X-ray diffraction [XRD], adsorption-desorption isotherm and high resolution transmission electron microscopy [HRTEM]. However, the optical features of the samples were investigated by a UV-visible spectrophotometer. It is obvious to notice the removal of the majority of methylene blue dye on a pure titania surface via adsorption mechanism owing to the high surface area and to the organized mesoporous nature of the solid sample. Incorporation of curcumin on titania surface changes the removal direction from adsorption to the photocatalytic pathway. Various photocatalytic experiments were performed to investigate the influence of initial dye concentration, weight of catalyst, stirring and light intensity on the photocatalytic degradation of methylene blue as primary pollutant model. Chemical oxygen demand [COD] test confirms the complete degradation of methylene blue dye. The exceptional photocatalytic reactivity of titania-curcumin nanoparticles is referred to reduction in band gap energy and to the facility of electron transfer from II* curcumin energy level to titania conduction band which increases the concentration of reactive oxygen superoxide radicals which in turn prevents the electron-hole recombination. The effect of various scavengers on the methylene blue dye degradation was investigated using ethanol, ascorbic acid and methyl viologen. The results have pointed out that O2(-) and HO(.) are considered the main active species in the degradation process. A plausible pathway and mechanism for the photocatalytic degradation of methylene blue by titania-curcumin nanoparticles were illustrated. PMID:27107333

  20. Titania Nanostructures for Optoelectronics Applications

    NASA Astrophysics Data System (ADS)

    Wang, Lili

    Titanium dioxide (titania) nanotubular structure discovered in 2001 have been attracting extensive interest due to their widely applications in photocatalysis, catalysis and solar cells. The final products of titania nanotube (TiNT) arrays can be synthesized in three forms. One is in form of ordered arrays attached to original Ti substrate, another one is in form of free-standing arrays and the last form is white powders. In this dissertation, we review the development history of these three types of TiNT arrays and introduce the fabrication process of TiNTs products in detail including morphology characterization, fabrication parameter study and optimization of synthesis condition. Since titania is a semiconductor with large band gap (3.2 eV), the large bandgap leads to only UV light absorption, which constitutes less than 5% of the whole solar spectrum. In order to efficiently harvest solar energy for the solar cells made of titania, several methods depositing TiNT arrays with metal oxides to improve the light harvesting are presented in this dissertation. A comprehensive study of forced hydrolysis method is carried out and investigated. Preliminary devices are built up in DSSCs concept based on the hybrid structure of TiO2/Fe2O3. Some important parameters, such as open circuit voltage (VOC), short circuit current (ISC), and fill factor (FF) are evaluated. Optical properties of the samples with the hybrid architecture are studied to achieve an optimal performance in DSSCs-type solar cells.

  1. Ceramic ultrafiltration membranes with photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Bell, Deborah Wildman

    The photocatalytic properties of ceramic ultrafilters have been utilized in the development of a novel in-situ membrane cleaning process for ultrafiltration membranes fabricated from titania. The use of the photoactive membrane layer mitigates the effects of foulants in the system, thereby yielding an increase in the observed overall flux without sacrificing rejection of the solute by the membrane. Photocatalytic membranes of titania supported on porous tubes of alpha-alumina were fabricated using sol-gel techniques. These membranes were developed on the basis of the results of two-level factorial experimental designs. Electron microscopy and x-ray spectrometry were employed to evaluate coverage of the support by the membrane, the thickness of the membrane, and the presence of defects in the membrane. The photocatalytic membrane system was characterized to determine both morphological and performance parameters. Morphological parameters included the pore diameters, Darcy coefficients, and the individual resistances associated with each of the porous layers comprising the composite photocatalytic membrane. Performance parameters included the nominal molecular weight cutoff values of the ceramic membranes, the rate of permeation of pure solvent in the presence and the absence of UV illumination through the porous layers of interest, and the ability of the photocatalytic membrane to resist fouling and maintain permselectivity in the presence of UV illumination. The photocatalytic membranes were used to ultrafilter aqueous solutions of polymeric organic foulants present at an initial concentration of 1 x 10-3 M. Formation of a gel layer of foulant on the surface of the membrane was observed in the presence and in the absence of UV radiation; however, the results of permeability experiments indicated that formation of this foulant layer was significantly retarded (by a factor of two) in the presence of UV radiation. Improvement in the flow rate of permeate through the

  2. Cold-Setting Inkjet Printed Titania Patterns Reinforced by Organosilicate Binder.

    PubMed

    Králová, Marcela; Dzik, Petr; Kašpárek, Vít; Veselý, Michal; Cihlář, Jaroslav

    2015-01-01

    A hybrid organo-silica sol was used as a binder for reinforcing of commercial titanium dioxide nanoparticles (Evonic P25) deposited on glass substrates. The organo-silica binder was prepared by the sol-gel process and mixtures of titania nanoparticles with the binder in various ratios were deposited by materials printing technique. Patterns with both positive and negative features down to 100 µm size and variable thickness were reliably printed by Fujifilm Dimatix inkjet printer. All prepared films well adhered onto substrates, however further post-printing treatment proved to be necessary in order to improve their reactivity. The influence of UV radiation as well as of thermal sintering on the final electrochemical and photocatalytic properties was investigated. A mixture containing 63 wt % of titania delivered a balanced compromise of mechanical stability, generated photocurrent density and photocatalytic activity. Although the heat treated samples yielded generally higher photocurrent, higher photocatalytic activity towards model aqueous pollutant was observed in the case of UV cured samples because of their superhydrophilic properties. While heat sintering remains the superior processing method for inorganic substrates, UV-curing provides a sound treatment option for heat sensitive ones. PMID:26378515

  3. Adsorption and degradation of model volatile organic compounds by a combined titania-montmorillonite-silica photocatalyst.

    PubMed

    Chen, Jiangyao; Li, Guiying; He, Zhigui; An, Taicheng

    2011-06-15

    A series of adsorptive photocatalysts, combined titania-montmorillonite-silica were synthesized. The resultant photocatalysts consisted of more and more spherically agglomerated TiO(2) particles with increasing of TiO(2) content, and anatase was the only crystalline phase with nano-scale TiO(2) particles. With increasing of the cation exchange capacity to TiO(2) molar ratio, specific surface area and pore volume increased very slightly. In a fluidized bed photocatalytic reactor by choosing toluene, ethyl acetate and ethanethiol as model pollutants, all catalysts had relatively high adsorption capacities and preferred to adsorb higher polarity pollutants. Langmuir isotherm model better described equilibrium data compared to Freundlich model. Competitive adsorptions were observed for the mixed pollutants on the catalysts, leading to decrease adsorption capacity for each pollutant. The combined titania-montmorillonite-silica photocatalyst exhibited excellent photocatalytic removal ability to model pollutants of various components. Almost 100% of degradation efficiency was achieved within 120 min for each pollutant with about 500 ppb initial concentration, though the efficiencies of multi-component compounds slightly decreased. All photocatalytic reactions followed the Langmuir-Hinshelwood model. Degradation rate constants of multi-component systems were lower than those for single systems, following the order of toluene

  4. Platinum nanoparticles on electrospun titania nanofibers as hydrogen sensing materials working at room temperature.

    PubMed

    Fratoddi, Ilaria; Macagnano, Antonella; Battocchio, Chiara; Zampetti, Emiliano; Venditti, Iole; Russo, Maria V; Bearzotti, Andrea

    2014-08-01

    Platinum nanoparticles (PtNPs), with diameters of 3-10 nm, were synthesized by water phase reduction, using 3-mercapto-1-propanesulfonate (3MPS) as a hydrophilic capping agent. PtNPs were deposited by a dipcoating technique on titania nanofibers (TiO2NFs), obtained by electrospinning. The investigated properties of the Pt-TiO2 hybrid at room temperature show that this material combines the properties of photoconduction of titania and the photocatalytic activity of the hybrid. To assess the best performance of Pt-TiO2, different measurements were performed at room temperature, comparing hydrogen response under UV of the uncoated TiO2NFs, compared with the Pt-TiO2 system prepared with two different amounts of PtNPs. During the sensing tests toward hydrogen an enhancement of photoconductivity (150%), an increase in response (400%) and an overall improvement of their dynamic behaviour were observed. PMID:24981799

  5. Stability and prospect of UV/H2O2 activated titania films for biomedical use

    NASA Astrophysics Data System (ADS)

    Unosson, Erik; Welch, Ken; Persson, Cecilia; Engqvist, Håkan

    2013-11-01

    Biomedical implants and devices that penetrate soft tissue are highly susceptible to infection, but also accessible for UV induced decontamination through photocatalysis if coated with suitable surfaces. As an on-demand antibacterial strategy, photocatalytic surfaces should be able to maintain their antibacterial properties over repeated activation. This study evaluates the surface properties and photocatalytic performance of titania films obtained by H2O2-oxidation and heat treatment of Ti and Ti-6Al-4V substrates, as well as the prospect of assisting photocatalytic reactions with H2O2 for improved efficiency. H2O2-oxidation generated a nanoporous coating, and subsequent heat treatment above 500 °C resulted in anatase formation. Tests using photo-assisted degradation of rhodamine B showed that prior to heat treatment, an initially high photocatalytic activity (PCA) of H2O2-oxidized substrates decayed significantly with repeated testing. Heat treating the samples at 600 °C resulted in stable yet lower PCA. Addition of 3% H2O2 during the photo-assisted reaction led to a substantial increase in PCA due to synergetic effects at the surface and H2O2 photolysis, the effect being most notable for non-heat treated samples. Both heat treated and non-heat treated samples showed stable PCA through repeated tests with H2O2-assisted photocatalysis, indicating that the combination of H2O2-oxidized titania films, UV light and added H2O2 can improve efficiency of these photocatalytic surfaces.

  6. Platinum nanoparticles on electrospun titania nanofibers as hydrogen sensing materials working at room temperature

    NASA Astrophysics Data System (ADS)

    Fratoddi, Ilaria; Macagnano, Antonella; Battocchio, Chiara; Zampetti, Emiliano; Venditti, Iole; Russo, Maria V.; Bearzotti, Andrea

    2014-07-01

    Platinum nanoparticles (PtNPs), with diameters of 3-10 nm, were synthesized by water phase reduction, using 3-mercapto-1-propanesulfonate (3MPS) as a hydrophilic capping agent. PtNPs were deposited by a dipcoating technique on titania nanofibers (TiO2NFs), obtained by electrospinning. The investigated properties of the Pt-TiO2 hybrid at room temperature show that this material combines the properties of photoconduction of titania and the photocatalytic activity of the hybrid. To assess the best performance of Pt-TiO2, different measurements were performed at room temperature, comparing hydrogen response under UV of the uncoated TiO2NFs, compared with the Pt-TiO2 system prepared with two different amounts of PtNPs. During the sensing tests toward hydrogen an enhancement of photoconductivity (150%), an increase in response (400%) and an overall improvement of their dynamic behaviour were observed.Platinum nanoparticles (PtNPs), with diameters of 3-10 nm, were synthesized by water phase reduction, using 3-mercapto-1-propanesulfonate (3MPS) as a hydrophilic capping agent. PtNPs were deposited by a dipcoating technique on titania nanofibers (TiO2NFs), obtained by electrospinning. The investigated properties of the Pt-TiO2 hybrid at room temperature show that this material combines the properties of photoconduction of titania and the photocatalytic activity of the hybrid. To assess the best performance of Pt-TiO2, different measurements were performed at room temperature, comparing hydrogen response under UV of the uncoated TiO2NFs, compared with the Pt-TiO2 system prepared with two different amounts of PtNPs. During the sensing tests toward hydrogen an enhancement of photoconductivity (150%), an increase in response (400%) and an overall improvement of their dynamic behaviour were observed. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01400f

  7. Structural characteristics of mixed oxides MOx/SiO2 affecting photocatalytic decomposition of methylene blue

    NASA Astrophysics Data System (ADS)

    Gun'ko, V. M.; Blitz, J. P.; Bandaranayake, B.; Pakhlov, E. M.; Zarko, V. I.; Sulym, I. Ya.; Kulyk, K. S.; Galaburda, M. V.; Bogatyrev, V. M.; Oranska, O. I.; Borysenko, M. V.; Leboda, R.; Skubiszewska-Zięba, J.; Janush, W.

    2012-06-01

    A series of photocatalysts based on silica (nanoparticulate) supported titania, ceria, and ceria/zirconia were synthesized and characterized by a variety of techniques including surface area measurements, X-ray diffraction, Fourier transform infrared spectroscopy, zeta potential, surface charge density, and photocatalytic behavior toward methylene blue decomposition. Thermal treatment at 600 °C increases the anatase content of the titania based catalysts detected by XRD. Changes in the infrared spectra before and after thermal treatment indicate that at low temperature there are more tbnd Sisbnd Osbnd Titbnd bonds than at high temperature. As these bonds break upon heating the SiO2 and TiO2 separate, allowing the TiO2 anatase phase to form. This results in an increased catalytic activity for the thermally treated samples. Nearly all titania based samples exhibit a negative surface charge density at pH 7 (initial pH of photocatalytic studies) which aids adsorption of methylene blue. The crystallinity of ceria and ceria/zirconia based catalysts are in some cases limited, and in others non-existent. Even though the energy band gap (Eg) can be lower for these catalysts than for the titania based catalysts, their photocatalytic properties are inferior.

  8. Preparation of nanodispersed titania using stabilized ammonium nitrate melts

    SciTech Connect

    Raciulete, Monica; Kachina, Anna; Puzenat, Eric; Afanasiev, Pavel

    2010-10-15

    An expedite one-step approach using simple precursors has been proposed to obtain metallic oxide compounds and exemplified by preparation of highly dispersed TiO{sub 2}. The technique consists in heating to 400-500 {sup o}C of molten ammonium nitrate stabilized with an organic nitrogen-containing compound (urea, melamine, ammonium oxalate) and containing dissolved metal salt precursor (TiOCl{sub 2}). The crystallites of the resulting TiO{sub 2} demonstrated variable size and shape as a function of stabilizer used. Their activity in photocatalytic oxidation of formic acid also depends on the nature of the stabilizer. The catalysts as-prepared showed high photocatalytic performance, superior to that of the Degussa P25 reference. Nitrogen containing stabilizers play a double role of increasing the process safety and modifying the properties of the solid products. - Graphical abstract: Ammonium nitrate melts stabilized by nitrogen-containing organic molecules can be applied for expedite one-step preparation of highly dispersed oxides, as exemplified by synthesis of titania photocatalysts.

  9. Structure of Amorphous Titania Nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Chen, B.; Banfield, J. F.; Waychunas, G. A.

    2008-12-01

    Ultrafine (2 - 3 nm) titania (TiO2) nanoparticles show only diffuse scattering by both conventional powder x-ray diffraction and electron diffraction. We used synchrotron wide-angle x-ray scattering (WAXS) to probe the atomic correlations in this amorphous material. The atomic pair-distribution function (PDF) derived from Fourier transform of the WAXS data was used for reverse Monte Carlo (RMC) simulations of the atomic structure of the small nanoparticles. Molecular dynamics simulations were used to generate input structures for the RMC. X-ray absorption spectroscopy (XAS) simulations were used to screen candidate structures obtained from the RMC. The structure model that best describes both the WAXS and XAS data consists of particles with a highly distorted shell and a small strained anatase-like crystalline core. The average coordination number of Ti is 5.3 and the Ti-O bond length peaks at 1.940 Å. Relative to bulk titania, the reduction of the coordination number is primarily due to the truncation of the Ti-O octahedra at the titania nanoparticle surface, and the shortening of the Ti-O bond length is due to bond contraction in the distorted shell. Core-shell structures in ultrafine nanoparticles may be common in many materials (e.g. ZnS).

  10. Nanocasting of Periodic Mesoporous Materials as an Effective Strategy to Prepare Mixed Phases of Titania.

    PubMed

    Mahoney, Luther; Rasalingam, Shivatharsiny; Wu, Chia-Ming; Koodali, Ranjit T

    2015-01-01

    Mesoporous titanium dioxide materials were prepared using a nanocasting technique involving silica SBA-15 as the hard-template. At an optimal loading of titanium precursor, the hexagonal periodic array of pores in SBA-15 was retained. The phases of titanium dioxide could be easily varied by the number of impregnation cycles and the nature of titanium alkoxide employed. Low number of impregnation cycles produced mixed phases of anatase and TiO₂(B). The mesoporous TiO₂ materials were tested for solar hydrogen production, and the material consisting of 98% anatase and 2% TiO₂(B) exhibited the highest yield of hydrogen from the photocatalytic splitting of water. The periodicity of the pores was an important factor that influenced the photocatalytic activity. This study indicates that mixed phases of titania containing ordered array of pores can be prepared by using the nanocasting strategy. PMID:26670222

  11. A novel route for synthesis of UV-resistant hydrophobic titania-containing silica aerogels by using potassium titanate as precursor.

    PubMed

    Wei, Wei; Lü, Xiaomeng; Jiang, Deli; Yan, Zaoxue; Chen, Min; Xie, Jimin

    2014-07-01

    Developing a novel and facile way to synthesize composite aerogels plays an important role in the applications of aerogels. UV-resistant hydrophobic titania-containing silica aerogels are prepared for the first time using potassium titanate as precursor by a modified ambient pressure drying method. The well established silica-titania networks, which can be tuned from 10 to 30 nm by adjusting the precursor content in the preparation process, provide effective confinement of spherical solid clusters. The UV-resistant hydrophobic composite aerogels show excellent photocatalytic dye degradation activity under visible light irradiation. This can be ascribed to the insert of suitable titania into the silica organizational structure. The present work gives a promising method of one pot synthesis and surface modification of aerogel composite structures, which have a broader application as photocatalyst. PMID:24825183

  12. Preparation of gold/titania core-shell nanocomposites with a tunable shell thickness.

    PubMed

    Kanda, Takashi; Komata, Kazuyoshi; Torigoe, Kanjiro; Endo, Takeshi; Sakai, Kenichi; Abe, Masahiko; Sakai, Hideki

    2014-01-01

    Gold/titania nanocomposites with a core-shell structure were prepared by sol-gel reaction of titanium tetrabutoxide (TTBO) with gold nanoparticles, core-stabilized with cetyltrimethylammonium bromide (CTAB), using a ternary mixture of alcohol/acetonitrile/water as solvent. TEM characterization of the resulting constructs revealed spherical nanocomposites, each containing a single gold core. The mean diameter of the gold cores was 13 nm, while the thicknesses of titania shells were readily tuned in the range 4-30 nm by varying the alkyl chain length of the alcohol. In addition, the gold nanoparticles exhibited a deep red color, with an intense extinction peak at 527 nm, owing to their surface plasmon resonance (SPR) properties. When the Au nanoparticles were coated with a titania shell, their color changed to purple and the SPR peak shifted to a higher wavelength of 537 nm. Furthermore, the core-shell nanocomposites were found to display photocatalytic activity for the oxidation of 2-propanol under illumination by visible light (λ=500-560 nm). PMID:24717542

  13. Electrochemical coating of dental implants with anodic porous titania for enhanced osteointegration

    PubMed Central

    Shayganpour, Amirreza; Rebaudi, Alberto; Cortella, Pierpaolo; Diaspro, Alberto

    2015-01-01

    Summary Clinical long-term osteointegration of titanium-based biomedical devices is the main goal for both dental and orthopedical implants. Both the surface morphology and the possible functionalization of the implant surface are important points. In the last decade, following the success of nanostructured anodic porous alumina, anodic porous titania has also attracted the interest of academic researchers. This material, investigated mainly for its photocatalytic properties and for applications in solar cells, is usually obtained from the anodization of ultrapure titanium. We anodized dental implants made of commercial grade titanium under different experimental conditions and characterized the resulting surface morphology with scanning electron microscopy equipped with an energy dispersive spectrometer. The appearance of nanopores on these implants confirm that anodic porous titania can be obtained not only on ultrapure and flat titanium but also as a conformal coating on curved surfaces of real objects made of industrial titanium alloys. Raman spectroscopy showed that the titania phase obtained is anatase. Furthermore, it was demonstrated that by carrying out the anodization in the presence of electrolyte additives such as magnesium, these can be incorporated into the porous coating. The proposed method for the surface nanostructuring of biomedical implants should allow for integration of conventional microscale treatments such as sandblasting with additive nanoscale patterning. Additional advantages are provided by this material when considering the possible loading of bioactive drugs in the porous cavities. PMID:26665091

  14. Effects of mineral tourmaline particles on the photocatalytic activity of TiO2 thin films.

    PubMed

    Meng, Junping; Liang, Jinsheng; Ou, Xiuqin; Ding, Yan; Liang, Guangchuan

    2008-03-01

    Titania composite thin films (T/TiO2) containing tourmaline particles were prepared by a sol-gel method, using alkoxide solutions as precursor. The tourmaline particles and thin films were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and so on. The effects of tourmaline on the photocatalytic activity of TiO2 were measured with methyl orange as an objective photodegradation substance. The results showed that the photocatalytic degradation of methyl orange conformed to the first-order kinetic equation and the composite thin films had better photocatalytic activity due to the cooperation of polarity and the far infrared emission of tourmaline. The T/TiO2 thin films including 0.5 wt% tourmaline exhibited better photocatalytic activity when heat-treated at 250 degrees C for 3 h, than pure TiO2 thin films under the ultraviolet irradiation. PMID:18468139

  15. Effect of annealing temperature on titania nanoparticles

    NASA Astrophysics Data System (ADS)

    Manikandan, K.; Arumugam, S.; Chandrasekaran, G.

    2014-04-01

    Titania polycrystalline samples are prepared by using sol-gel route hydrolyzing a alkoxide titanium precursor under acidic conditions. The as prepared samples are treated with different calcination temperatures. The anatase phase of titania forms when treated below 600°C, above that temperature the anatase phase tends to transform into the rutile phase of titania. The experimental determination of average grain size, phase formation, lattice parameters and the crystal structures of titania samples at different calcinations is done using X-ray diffraction (XRD). Fourier Transform Infra-red Spectroscopy (FTIR), UV-vis-NIR spectroscopy and Scanning Electron Microscopy (SEM) and Energy Dispersive Analysis X-ray are used to characterize the samples to bring impact on the respective properties.

  16. Effect of annealing temperature on titania nanoparticles

    SciTech Connect

    Manikandan, K. Arumugam, S.; Chandrasekaran, G.

    2014-04-24

    Titania polycrystalline samples are prepared by using sol-gel route hydrolyzing a alkoxide titanium precursor under acidic conditions. The as prepared samples are treated with different calcination temperatures. The anatase phase of titania forms when treated below 600°C, above that temperature the anatase phase tends to transform into the rutile phase of titania. The experimental determination of average grain size, phase formation, lattice parameters and the crystal structures of titania samples at different calcinations is done using X-ray diffraction (XRD). Fourier Transform Infra-red Spectroscopy (FTIR), UV-vis-NIR spectroscopy and Scanning Electron Microscopy (SEM) and Energy Dispersive Analysis X-ray are used to characterize the samples to bring impact on the respective properties.

  17. Scanning photo-electrochemical microscopy as a versatile tool to investigate dye-sensitized nano-crystalline surfaces for solar cells

    NASA Astrophysics Data System (ADS)

    Figgemeier, Egbert; Kylberg, William H.; Bozic, Biljana

    2006-04-01

    Self-assembled monolayers (SAMs) of metal complexes are a central component of functional chemical systems for energy conversion like in e.g. the dye-sensitized photoelectrochemical solar cells or photocatalytic processes at semiconductor surfaces. In this context, scanning electrochemical microscopy (SECM) under illumination is a most valuable tool for the understanding of elementary processes of such systems. SECM comprises an ultra-microelectrode (UME), which is incorporated into a 3- or 4-electrode, respectively, electrochemical setup and which can be positioned with sub-micrometer resolution in 3 dimensions relative to a substrate. In our system, we used Pt-UMEs and dye-sensitized nano-structured electrodes as substrates. The substrate can be illuminated from the backside, which resembles working conditions of solar cell arrangements. The electrolyte consists of 2-methoxypropionitrile in conjunction with redox couples as they are used in dye-sensitized nano-structured solar cell. With this setup the photoelectrochemistry in close contact to the substrate surface initiated by the injection of electrons from the dye into the conduction band of the TiO II due to illumination at working conditions has been investigated. In this contribution we present the general principle of the method as well as an initial validation by relating photocurrents measured with the SECM and solar cell performances.

  18. Free-standing carbon nanotube-titania photoactive sheets.

    PubMed

    Koo, Youngmi; Malik, Rachit; Alvarez, Noe; Shanov, Vesselin N; Schulz, Mark; Sankar, Jag; Yun, Yeoheung

    2015-06-15

    We report on the development of a new photoactive material via titania (TiO2) nanoparticle deposition on free-standing aligned carbon nanotube (CNT) sheets. Controlling homogeneous dispersion of negatively charged TiO2 nanoparticles, achieved by adjusting pH higher than the point of zero charge (PZC), influenced electrochemical deposition of TiO2 on CNT sheets substrate. Varying deposition time with constant voltage, 5 V allowed different thickness of TiO2 to be deposited layer on the CNT sheets. The thickness and morphology of CNT-TiO2 sheets was verified by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Electrochemical experiments show that diffusion coefficient of Fe(CN)6(3-) was 5.56×10(-6) cm(2) s(-1) at pristine CNT sheets and 2.19×10(-6) cm(2) s(-1) at the CNT-TiO2 sheets. Photocatalytic activity for CNT-TiO2 sheets exhibits high photocurrent density (when deposition time=30 min, 4.3 μA cm(-2) in N2, 13.4 μA cm(-2) in CO2). This paper proved a possibility to use CNT-TiO2 sheets based on highly-aligned CNT sheets substrate as new photoactive material. PMID:25725399

  19. Preparation and characterization of sulfur-modified mesoporous titania photocatalyst

    NASA Astrophysics Data System (ADS)

    Shi, Zhongliang; Liu, Guiqing; Sun, Na; Yao, Shuhua; Wang, Shaofeng

    2013-08-01

    Sulfur-modified mesoporous titania (S-MTiO2) was investigated as a potential photocatalyst under visible light. The photocatalyst was prepared by template method using thiourea and tetrabutyl titanate (Ti(OC4H9)4) as precursors and Pluronic P123 as template. The photoabsorbance of as-prepared photocatalyst was measured by UV-vis absorption spectroscopy, which confirmed the extension of absorption into the visible region. The microstructure of S-MTiO2 was characterized using X-ray diffraction (XRD) and N2 adsorption-desorption measurements. The micro crystal of the S-doped photocatalyst consisted of anatase phase and no significant influence on the nature of crystal formation. X-ray photoelectron spectroscopy (XPS) measurements indicated the presence of C in the prepared photocatalyst in addition to S. The photo-catalytic performance was studied by photodegradation methyl orange (MO) in water under visible light irradiation. The calcination temperature and the doping content influenced the photoactivity.

  20. Photocatalytic coatings for environmental applications.

    PubMed

    Allen, Norman S; Edge, Michele; Sandoval, Gonzalo; Verran, Jo; Stratton, John; Maltby, Julie

    2005-01-01

    are shown to exhibit effective light stabilization in various water- and oil-based paint media in comparison with conventional organic stabilizers. Hindered piperidine stabilizers are shown to provide no additional benefits in this regard, often exhibiting strong antagonism. The use of photocatalytic titania nanoparticles in the development of self-cleaning paints and microbiological surfaces is also demonstrated in this study. In the former case, surface erosion is shown to be controlled by varying the ratio of admixture of durable pigmentary-grade rutile (heavily coated) and a catalytic-grade anatase nanoparticle. For environmental applications in the development of coatings for destroying atmospheric pollutants such as nitrogen oxide gases (NO(X)), stable substrates are developed with photocatalytic nanoparticle-grade anatase. In this study, porosity of the coatings through calcium carbonate doping is shown to be crucial in the control of the effective destruction of atmospheric NO(X) gases. For the development of microbiological substrates for the destruction of harmful bacteria, effective nanoparticle anatase titania is shown to be important, with hydrated high surface area particles giving the greatest activity. PMID:15279507

  1. Microwave-assisted synthesis of porous carbon-titania and highly crystalline titania nanostructures.

    PubMed

    Parker, Alison; Marszewski, Michal; Jaroniec, Mietek

    2013-03-01

    Porous carbon-titania and highly crystalline titania nanostructured materials were obtained through a microwave-assisted one-pot synthesis. Resorcinol and formaldehyde were used as carbon precursors, triblock copolymer Pluronic F127 as a stabilizing agent, and titanium isopropoxide as a titania precursor. This microwave-assisted one-pot synthesis involved formation of carbon spheres according to the recently modified Stöber method followed by hydrolysis and condensation of titania precursor. This method afforded carbon-titania composite materials containing anatase phase with specific surface areas as high as 390 m(2) g(-1). The pure nanostructured titania, obtained after removal of carbon through calcination of the composite material in air, was shown to be the anatase phase with considerably higher degree of crystallinity and the specific surface area as high as 130 m(2) g(-1). The resulting titania, because of its high surface area, well-developed porosity, and high crystallinity, is of great interest for catalysis, water treatment, lithium batteries, and other energy-related applications. PMID:23432344

  2. Synthesis and Characterisation of Porous Titania-Silica Composite Aerogel for NO(x) and Acetaldehyde Removal.

    PubMed

    Lee, Kwang Young; Park, Se Min; Kim, Jong Beom; El Saliby, Ibrahim; Shahid, Mohammad; Kim, Geon-Joong; Shon, Ho Kyong; Kim, Jong-Ho

    2016-05-01

    In this study, the synthesis of porous titania-silica (TiO2-SiO2) composite aerogel at ambient pressure by using non-hazardous chemicals as a source of silica was investigated. TiO2-SiO2 composite aerogels were characterised and their photocatalytic performances were investigated for the removal efficiency of acetaldehyde and NO(x) under UV light. Results showed that porous composite aerogel with aggregated morphology, high surface area and an increased mesoporosity were formed. TiO2-SiO2(1.8) composite, with high Ti/Si ratio, showed the best results in terms of photocatalytic removal of acetaldehyde and nitrogen oxide. PMID:27483782

  3. Photocatalytic activity of titanium dioxide modified by Fe2O3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Wodka, Dawid; Socha, Robert P.; Bielańska, Elżbieta; Elżbieciak-Wodka, Magdalena; Nowak, Paweł; Warszyński, Piotr

    2014-11-01

    Photocatalytic activity of Fe2O3/TiO2 composites obtained by precipitation was investigated. The composite material containing 1.0 wt% of iron(III) oxide nanoparticles was obtained by depositing Fe2O3 on the Evonic-Degussa P25 titania surface. SEM, XPS, DRS, CV and EIS techniques were applied to examine synthetized pale orange photocatalyst. The XPS measurements revealed that iron is present mainly in the +3 oxidation state but iron in the +2 oxidation state can be also detected. Electrochemical analysis indicated that surface modification of Degussa P25 by Fe2O3 causes the appearance of surface states in such a material. Nevertheless, based on the DRS measurement it was shown that iron(III) oxide nanoparticles modified the P25 spectral properties but they did not change the band gap width. The photocatalytic activity of Fe2O3/TiO2 composite was compared to photocatalytic activity of pristine P25 in photooxidation reaction of model compounds: oxalic acid (OxA) and formic acid (FA). Photodecomposition reaction was investigated in a batch reactor containing aqueous suspension of a photocatalyst illuminated by either UV or artificial sunlight (halogen lamp). The tests proved that nanoparticles deposited on titania surface triggers the increase in photocatalytic activity, this increase depends however on the decomposed substance.

  4. Parameters Influencing the Photocatalytic Activity of Suspension-Sprayed TiO2 Coatings

    NASA Astrophysics Data System (ADS)

    Toma, Filofteia-Laura; Berger, Lutz-Michael; Shakhverdova, Irina; Leupolt, Beate; Potthoff, Annegret; Oelschlägel, Kathrin; Meissner, Tobias; Gomez, José Antonio Ibáñez; de Miguel, Yolanda

    2014-10-01

    Photocatalytic properties of titania have been studied very intensively for a variety of applications, including air and water purification. In order to clarify the influence of the phase composition and other parameters, thermal spraying with suspensions was applied to produce photocatalytically active titania coatings starting from two commercially available anatase and rutile submicron powders. Aqueous suspensions containing 40% solids by weight were sprayed with an HVOF process using ethylene as the fuel gas. The spray parameters were chosen in order to produce mechanically stable coatings and to preserve a high content of the initial crystalline phases of the powders. The coating microstructures, phase compositions, and surface properties were characterized. The photocatalytic performance was evaluated by degradation of the pink dye Rhodamine B (RB) using two techniques: degradation of an aqueous solution of RB and discoloration of impregnated RB. All the coatings exhibited photocatalytic activity to varying degrees, depending on the phase composition as well as other factors, namely, the coating microstructure, surface morphology, surface hydroxylation, light absorption, and interaction with the pollutant.

  5. SEM/TEM characterization of periodical novel amorphous/nano-crystalline micro-composites obtained by laser interference structuring: The system HAlO-Al?Al2O3

    SciTech Connect

    Petersen, Christian; Lasagni, Andres Fabian; Holzapfel, Christian; Daniel, Claus; M�cklich, Frank; Veith, Michael

    2007-01-01

    Abstract Layers of the metastable, amorphous HAlO are synthesized by chemical vapor deposition from the molecular compound tert-butoxyalane ([tBu-O-AlH2]2). At temperatures above 500 C, these layers transform to biphasic Al Al2O3 due to the elimination of di-hydrogen. The interaction of HAlO films with short laser pulses causes partial transformation of amorphous HAlO into nano-crystalline Al Al2O3. Using an interference pattern of two coherent high-power Nd:YAG laser beams produces local and periodic heating, inducing crystallization at equally distant lines in the HAlO layer. Depending on the laser fluence, different morphologies and different amounts of crystalline phases are obtained. In this study, the surface morphology and the distribution of crystalline phases of the structured samples are analyzed using SEM, FIB and TEM. The two-dimensional structures consist of periodic variations of morphology, chemical composition, and phase identity with a well-defined long-range order. When bio-functionalized, the structured samples may be used as carriers for structurally controlled cell-cultivation.

  6. Anomalous electrical relaxation and polaron conduction in nano-crystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}

    SciTech Connect

    Kumar, N. S. Krishna; Shahid, T. S.; Govindaraj, G.

    2015-06-24

    Nano-crystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} was synthesized by chemical co-precipitation method and characterized with X-ray diffraction. Ac electrical impedance data are taken for the frequency range of 1Hz to 1MHz for various temperatures from 303K to 483K. The ac electrical conduction deviates from the Debye type relaxation which indicates polaron type conduction. In the present study unique anomalous relaxation function in time and frequency domain is used to investigate deviation from the Debye relaxation. The physical basis of anomalous or non-Debye process is explained in terms of change in Debye dipole μ{sub D}=ρr{sub D} of charge ρ into gρ due to the molecular charge interaction and defect disorder. This interaction shifts the Debye relaxation rate τ to a slow relaxation rate τ{sup g}. The fraction 0

  7. Synthesis of nano-crystalline (Ba 0.5Sr 0.5)Co 0.8Fe 0.2O 3- δ cathode material by a novel sol-gel thermolysis process for IT-SOFCs

    NASA Astrophysics Data System (ADS)

    Subramania, A.; Saradha, T.; Muzhumathi, S.

    Nano-crystalline (Ba 0.5Sr 0.5)Co 0.8Fe 0.2O 3- δ powder has been successfully synthesized by a novel sol-gel thermolysis method using a unique combination of PVA and urea. The decomposition and crystallization behaviour of the gel precursor was studied by TG/DTA analysis. The gel precursor was calcined at different temperatures and the phase evoluation was studied by X-ray diffraction (XRD) analysis. From the result of X-ray diffraction patterns, it is found that a cubic perovskite (Ba 0.5Sr 0.5)Co 0.8Fe 0.2O 3- δ was formed by calcining the precursor at 450 °C for 5 h, but the well-crystalline cubic perovskite (Ba 0.5Sr 0.5)Co 0.8Fe 0.2O 3- δ was obtained by calcining the precursor at 650 °C for 5 h. Morphological analysis of the powder calcined at various temperatures was done by scanning electron microscope (SEM). Thermogravimetric (TG) results showed the lattice oxygen loss of the product was about ∼2% in its original weight in the temperature range 40-900 °C. Finally, thermal expansion and electrical conductivity of the synthesized material were measured by dilatometer and four-probe dc method, respectively.

  8. The enhancement of photovoltaic parameters in dye-sensitized solar cells of nano-crystalline SnO2 by incorporating with large SrTiO3 particles.

    PubMed

    Aponsu, G M L P; Wijayarathna, T R C K; Perera, I K; Perera, V P S; Siriwardhana, A C P K

    2013-05-15

    In this paper, the performance of nano-porous electrodes made of a composite material of SrTiO3 and SnO2 are compared with those made of bare SnO2. When these particular devices are analyzed in a comparative mode the results confirmed the enhancement of photovoltaic parameters in the former device. The performance of respective cells were examined by several methods including I-V characteristic measurements, photocurrent action spectra, dark I-V measurements, Mott-Schottky measurements and X-ray diffraction measurements. Even though such improvements in this particular cell could be explicated by the formation of a potential energy barrier of SrTiO3 particles of comparably large width at the SrTiO3/SnO2 interface, the passivation of voids in the SnO2 film by SrTiO3 particles to a certain extent could not be totally ruled out. Besides, high energetic electrons injected by dye molecules move more credibly through mini-bands formed in the chain of nano-crystalline SnO2 particles to the back contact. The blocking of the recombination path and the shifting up of the uppermost electron occupied level of SnO2 accompanying the conduction band edge in the SrTiO3/SnO2 composite film, may have lead to the observed enhancement of the fill factor and photovoltage, respectively. PMID:23501715

  9. Solar thermal harvesting for enhanced photocatalytic reactions.

    PubMed

    Hashemi, Seyyed Mohammad Hosseini; Choi, Jae-Woo; Psaltis, Demetri

    2014-03-21

    The Shockley-Queisser limit predicts a maximum efficiency of 30% for single junction photovoltaic (PV) cells. The rest of the solar energy is lost as heat and due to phenomena such as reflection and transmission through the PV and charge carrier recombination. In the case of photocatalysis, this maximum value is smaller since the charge carriers should be transferred to acceptor molecules rather than conductive electrodes. With this perspective, we realize that at least 70% of the solar energy is available to be converted into heat. This is specifically useful for photocatalysis, since heat can provide more kinetic energy to the reactants and increase the number of energetic collisions leading to the breakage of chemical bonds. Even in natural photosynthesis, at the most 6% of the solar spectrum is used to produce sugar and the rest of the absorbed photons are converted into heat in a process called transpiration. The role of this heating component is often overlooked; in this paper, we demonstrate a coupled system of solar thermal and photocatalytic decontamination of water by titania, the most widely used photocatalyst for various photo reactions. The enhancement of this photothermal process over solely photocatalytic water decontamination is demonstrated to be 82% at 1× sun. Our findings suggest that the combination of solar thermal energy capture with photocatalysis is a suitable strategy to utilize more of the solar spectrum and improve the overall performance. PMID:24480846

  10. Photocatalytic transformation of CO2 to CH4 and CO on acidic surface of TiO2 anatase

    NASA Astrophysics Data System (ADS)

    Civiš, Svatopluk; Ferus, Martin; Knížek, A.; Kubelík, P.; Kavan, L.; Zukalová, M.

    2016-06-01

    Recently, many studies have demonstrated that carbon dioxide can be converted to methane on TiO2 surface by a photocatalytic process. We show that such a photo-reduction can be significantly affected by the presence of an acidic proton in powder samples of titania. Using in situ absorption gas-phase rovibrational spectroscopic detection of CH4, CO and CO2, we demonstrate that proton enhancement positively affects transformation of intermediate derivatives to methane during the photo-irradiation process via several reactions in which the electron transfer inside titania is coupled to oxygen transfer to the Ti3+ centers of TiO2 structure. The yield of CH4 or CO depends on the surface conditioning of titania: the formation of CH4 is boosted by a presence of adsorbed HCl, while the formation of CO is boosted by adsorbed H2SO4.

  11. V photometry of Titania, Oberon, and Triton

    SciTech Connect

    Goguen, J.D.; Hammel, H.B.; Brown, R.H.

    1989-02-01

    The phase angle and orbital brightness variations of Titania, Oberon, and Triton are presently obtained through analysis of V filter photometry obtained at Mauna Kea in 1982-1983. While Titania and Oberon exhibit magnitude variations with phase angle comparable to those of low-to-moderate albedo asteroids observed within several deg of opposition, Triton's phase variation is distinctly different from these and has a phase coefficient consistent with either a high-albedo regolith or an optically thick nonparticulate scattering layer (perhaps an atmosphere, or an ocean). A low-albedo regolith cannot on the strength of these data be ruled out, however. 39 references.

  12. Mesoporous silica-titania composed materials.

    PubMed

    Messina, Paula V; Morini, Marcela A; Sierra, María B; Schulz, Pablo C

    2006-08-01

    Titania mesosized particles were obtained by TiCl4 hydrolysis in Aerosol OT/water/n-hexane microemulsion. These particles were incorporated in surfactant templated silica mesoporous materials of MCM-41 and MCM-50 structures. Results depended on the surfactant: hexadecyltrimethylammonium bromide templated materials retained the honeycomb structure with small modifications in their characteristics. The dodecyltrimethylammonium bromide templated material changed from honeycomb to lamellar structure when the titania particles were included, with dramatic changes in the structure characteristics. The didodecyldimethylammonium bromide templated lamellar structure was retained after TIO2 inclusion, with a slight increase in the specific area, pore diameter and pore walls thickness. PMID:16600274

  13. Photocatalytic and thermal catalytic oxidation of acetaldehyde on Pt/TiO{sub 2}

    SciTech Connect

    Falconer, J.L.; Magrini-Bair, K.A.

    1998-10-01

    Low concentrations of acetaldehyde in air (60 ppm) were oxidized over TiO{sub 2} (Degussa P25) and 0.5% Pt/TiO{sub 2} catalysts from 24 to 200 C by photocatalytic and thermal catalytic reactions. On Pt/TiO{sub 2}, the contribution by photocatalytic oxidation (PCO) is a maximum at 140 C, where conversion is 2.8 times that at 24 C. Titania without Pt deactivates rapidly during PCO at elevated temperature due to a thermal catalytic reaction that takes place in parallel with PCO, but the addition of Pt dramatically slows deactivation. Apparently, Pt supplies spillover oxygen onto the TiO{sub 2}, and the oxygen oxidizes the acetaldehyde decomposition products in a dark reaction. Deactivated TiO{sub 2} without Pt was regenerated by PCO at room temperature. Seven distinct reactions (photocatalytic and thermal catalytic) are identified on Pt/TiO{sub 2}.

  14. Structural and adsorption characteristics and catalytic activity of titania and titania-containing nanomaterials.

    PubMed

    Gun'ko, V M; Blitz, J P; Zarko, V I; Turov, V V; Pakhlov, E M; Oranska, O I; Goncharuk, E V; Gornikov, Y I; Sergeev, V S; Kulik, T V; Palyanytsya, B B; Samala, R K

    2009-02-01

    Morphological, structural, adsorption, and catalytic properties of highly disperse titania prepared using sulfate and pyrogenic methods, and fumed titania-containing mixed oxides, were studied using XRD, TG/DTA, nitrogen adsorption, (1)H NMR, FTIR, microcalorimetry on immersion of oxides in water and decane, thermally stimulated depolarization current (TSDC) and catalytic photodecomposition of methylene blue (MB). Phase composition and aggregation characteristics of nanoparticles (pore size distribution) of sulfate and pyrogenically prepared titania are very different; temperature dependent structural properties are thus very different. Catalytic activity for the photodecomposition of MB is greatest (per gram of TiO(2) for the pure oxide materials) for non-treated ultrafine titania PC-500, which has the largest S(BET) value and smallest particle size of the materials studied. However, this activity calculated per m(2) is higher for PC-105, possessing a much smaller S(BET) value than PC-500. The activity per unit surface area of titania is greatest for the fumed silica-titania mixed oxide ST20. Calcination of PC-500 at 650 degrees C leads to enhancement of anatase content and catalytic activity, but heating at 800 and 900 degrees C lowers the anatase content (since rutile appears) and diminishes catalytic activity, as well as the specific surface area because of nanoparticle sintering. PMID:18996539

  15. Chitosan as a potential stabilizing agent for titania nanoparticle dispersions for preparation of multifunctional cotton fabric.

    PubMed

    Goyal, Nidhi; Rastogi, Deepali; Jassal, Manjeet; Agrawal, Ashwini K

    2016-12-10

    Titania (TiO2) nanoparticle dispersions in water were prepared using chitosan (CS) as the stabilizing agent. The dispersion stability was evaluated with respect to storage time, hydrodynamic particle size, and zeta potential. The effect of the molecular weight of CS and presence of non-ionic polymers (poly(vinyl alcohol) and poly(ethylene glycol)) as co-dispersants was investigated. Despite the increase in size of dispersed particles, the long-term storage stability of the dispersions improved with increasing concentration and molecular weight of CS. The TiO2/CS dispersions were applied on cotton fabric and characterized. The presence of CS did not seriously affect the photocatalytic self-cleaning activity (SCA) of TiO2; with CS, a SCA of 89% was achieved compared with a value of 96% without CS. In addition, the TiO2/CS-treated cotton fabrics provided UV protection and significant antimicrobial activity. PMID:27577907

  16. Effect of titania nanotubes on the flux and separation performance of polyethersulfone membranes

    NASA Astrophysics Data System (ADS)

    Subramaniam, M. N.; Goh, P. S.; Ismail, A. F.; Lau, W. J.

    2016-06-01

    The improvement of membrane performances in terms of separation and permeation is a constant research problem. In this study, polyethersulfone (PES) hollow fiber nanocomposite membranes were fabricated with titania nanotubes (TNT) synthesized via hydrothermal method used as inorganic filler to improve separation and membrane permeation. The membranes were prepared using dry/wet phase inversion process. The concentration of PES was fixed at 18% and TNT was added at concentration of 0.1% wt. The membranes were characterized in terms of pure water permeation rate (PWP), proteins (BSA) rejection, porosity and water contact angle. The results showed that addition of TNT improves the water flux and rejection rate as well as increasing hydrophilicity of the membrane. The flux of membrane is improved more than 20% while the rejection has been improved from 79% to 96%. The addition of TNT into the membrane matrix has shown that photocatalytic property can be introduced to a normal membrane.

  17. Nano-Titania Photocatalyst Loaded on W-MCM-41 Support and Its Highly Efficient Degradation of Methylene Blue

    NASA Astrophysics Data System (ADS)

    Shankar, H.; Saravanan, R.; Narayanan, V.; Stephen, A.

    2011-07-01

    Most of the azo dyes produced in textile, printing, paper manufacturing, pulp processing and pharmaceutical industries contain different organic contaminants. These dyes can enter the body through ingestion and the high content in living systems can prove to be carcinogenic. Therefore photocatalytic degradation of such toxic organic compounds in water, in the presence of semiconductor powders has received much attention over the last two decades. Nanocrystalline titanium dioxide, TiO2, is a well studied and commonly used material for photocatalytic applications. However, the control of particle size, monodispersity, large catalytic surface for sufficient adsorption of organic pollutants, recovery and recycle of TiO2 nanoparticles are challenging tasks. Hence in the present study, titania was introduced into the nanopores (2-10 nm size) of MCM-41 to produce stable nanoparticles of uniform size and shape. Further, in order to lengthen the life time of the excited electrons/holes during photoreaction, tungsten atoms were incorporated in to the MCM-41 silica matrix in addition to titania loading.

  18. Composite TiO2/clays materials for photocatalytic NOx oxidation

    NASA Astrophysics Data System (ADS)

    Todorova, N.; Giannakopoulou, T.; Karapati, S.; Petridis, D.; Vaimakis, T.; Trapalis, C.

    2014-11-01

    TiO2 photocatalyst received much attention for air purification applications especially for removal of air pollutants like NOx, VOCs etc. It has been established that the activity of the photocatalyst can be significantly enhanced by its immobilization onto suitable substrates like inorganic minerals, porous silica, hydroxyapatite, adsorbent materials like activated carbon, various co-catalysts such as semiconductors, graphene, reduced graphite oxide, etc. In the present work, photocatalytic composite materials consisted of mineral substrate and TiO2 in weight ratio 1:1 were manufactured and examined for oxidation and removal of nitric oxides NOx (NO and NO2). Commercial titania P25 (Evonik-Degussa) and urea-modified P25 were used as photocatalytically active components. Inorganic minerals, namely kunipia, talk and hydrotalcite were selected as supporting materials due to their layered structure and expected high NOx adsorption capability. Al3+ and Ca2+ intercalation was applied in order to improve the dispersion of TiO2 and its loading into the supporting matrix. The X-ray diffraction analysis and Scanning Electron Microscopy revealed the binary structure of the composites and homogeneous dispersion of the photocatalyst into the substrates. The photocatalytic behavior of the materials in NOx oxidation and removal was investigated under UV and visible light irradiation. The composite materials exhibited superior photocatalytic activity than the bare titania under both types of irradiation. Significant visible light activity was recorded for the composites containing urea-modified titania that was accredited to the N-doping of the semiconductor. Among the different substrates, the hydrotalcite caused highest increase in the NOx removal, while among the intercalation ions the Ca2+ was more efficient. The results were related to the improved dispersion of the TiO2 and the synergetic activity of the substrates as NOx adsorbers.

  19. The effect of process parameters on the Liquid Flame Spray generated titania nanoparticles.

    PubMed

    Aromaa, Mikko; Keskinen, Helmi; Mäkelä, Jyrki M

    2007-11-01

    Nanoparticles have become important in many applications. It is essential to be able to control the particle size because the properties of nanoparticles change dramatically with particle size. An efficient way to generate nanoparticles is via aerosol processes. In this study we used Liquid Flame Spray consisting of liquid precursor droplets sprayed into a high-speed hydrogen/oxygen flame where they evaporate, vapours react and nucleate to form titania nanoparticles. Using flame methods, also dopants and sensitizers can easily be introduced in order to, e.g. improve the photocatalytic activity of the nanomaterial. To obtain a practical guideline in order to tailor the final nanoparticle size in the process, we have systematically studied the effects of different process parameters on the particle size of titania. Titania is used, e.g. as a photocatalyst, and then both particle size and crystal structure are important when looking at the efficiency. In this work, the generated nanoparticle size has been measured by aerosol instrumentation and the particle morphology has been verified with transmission electron microscopy. In Liquid Flame Spray method, there are several adjustable parameters such as precursor feed rate into the flame; concentration of the precursor; precursor material itself as well as solvent used in the precursor; mass flow of combustion gases and also the mechanical design of the torch used. We used metal organic based titanium precursors in alcohol solvents, predominantly ethanol and 2-propanol. Large differences in particle production between the precursors were found. Differences could also be seen for various solvents. As for precursor feed in the flame, the more mass is introduced the larger the nanoparticles are, i.e. precursor concentration and precursor feed rate have an impact on particle size. A similar phenomenon can be discovered for the combustion gas flow rates. Torch design also plays an important role in controlling the particle

  20. Critical aspects in the production of periodically ordered mesoporous titania thin films.

    PubMed

    Soler-Illia, Galo J A A; Angelomé, Paula C; Fuertes, M Cecilia; Grosso, David; Boissiere, Cedric

    2012-04-21

    Periodically ordered mesoporous titania thin films (MTTF) present a high surface area, controlled porosity in the 2-20 nm pore diameter range and an amorphous or crystalline inorganic framework. These materials are nowadays routinely prepared by combining soft chemistry and supramolecular templating. Photocatalytic transparent coatings and titania-based solar cells are the immediate promising applications. However, a wealth of new prospective uses have emerged on the horizon, such as advanced catalysts, perm-selective membranes, optical materials based on plasmonics and photonics, metamaterials, biomaterials or new magnetic nanocomposites. Current and novel applications rely on the ultimate control of the materials features such as pore size and geometry, surface functionality and wall structure. Even if a certain control of these characteristics has been provided by the methods reported so far, the needs for the next generation of MTTF require a deeper insight in the physical and chemical processes taking place in their preparation and processing. This article presents a critical discussion of these aspects. This discussion is essential to evolve from know-how to sound knowledge, aiming at a rational materials design of these fascinating systems. PMID:22419250

  1. Photocatalytic Destruction of Tetracycline Hydrochloride on the Surface of Titanium Dioxide Films Modified by Gold Nanoparticles

    NASA Astrophysics Data System (ADS)

    Linnik, O. P.; Zhukovskiy, M. A.; Starukh, G. N.; Smirnova, N. P.; Gaponenko, N. V.; Asharif, A. M.; Khoroshko, L. S.; Borisenko, V. E.

    2015-01-01

    Films of titania (TiO2) and titania modified with gold nanoparticles (TiO2:Au) were synthesized by a sol-gel method on substrates of glass, aluminum, and aluminum with a layer of nanotextured aluminum or porous anodic alumina. The photocatalytic activity of the samples was investigated in an aqueous solution of the antibiotic tetracycline hydrochloride (TC). TC decomposition was observed in the presence of all samples as a reduction of the solution optical density in the range below 500 nm. Titania was in the crystalline anatase phase with incorporated spherical gold nanoparticles primarily of sizes 1-10 nm after heat treatment at 400°C. Modification of TiO2 films with gold nanoparticles on glass or aluminum substrates did not increase the photocatalytic activity of the samples. It was found that complexes of TC with Al3+ in solution formed only in the presence of gold nanoparticles in the film either in the dark or with UV irradiation.

  2. Assessment of compatibility and durability of photocatalytic TiO2 for stone coating

    NASA Astrophysics Data System (ADS)

    Calia, Angela; Lettieri, Maria Teresa; Licciulli, Antonio; Masieri, Maurizio

    2014-05-01

    The use of Titanium dioxide nano-particles has received increasing attention in many fields as these particles can trap and decompose organic and inorganic soiling matter and air pollutants by a photocatalytic process, providing new functional properties in terms of self-cleaning and depolluting performances to the treated materials. Since recent years, the use of photocatalytic TiO2 as external coating for natural stones has been allowed thanks to the fine-tuning of nano-titania preparation, overcoming the initial limits of application related to a necessary thermal treatment. Notwithstanding nano-titania benefits, the potential of its application as stone coating needs to be assessed with respect to basic requirements involved for any surface stone treatment, especially in the field of the preservation of historical-architectural heritage. They concern the harmlessness with respect to the original characteristics of the stones, the effectiveness and durability of the treatments themselves. In this work we present the study for the assessment of compatibility of Titania coatings applied to calcareous stones paying attention to their effects on chromatic properties, water absorption by capillarity, permeability to water vapour, water wettability. The durability of the coatings under mechanical action in laboratory simulated conditions was also investigated.

  3. Titania-lanthanum phosphate photoactive and hydrophobic new generation catalyst

    NASA Astrophysics Data System (ADS)

    Jyothi, Chembolli K.; Jaimy, Kanakkanmavudi B.; Ghosh, Swapankumar; Sankar, Sasidharan; Smitha, V. S.; Warrier, K. G. K.

    2011-07-01

    Titania-lanthanum phosphate nanocomposites with multifunctional properties have been synthesized by aqueous sol-gel method. The precursor sols with varying TiO 2:LaPO 4 ratios were applied as thin coating on glass substrates in order to be transparent, hydrophobic, photocatalytically active coatings. The phase compositions of the composite powders were identified by powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). The anatase phase of TiO 2 in TiO 2-LaPO 4 composite precursors was found to be stable even on annealing at 800 °C. The glass substrates, coated with TL1 (TiO 2-LaPO 4 composition with 1 mol% LaPO 4) and TL50 (composite precursor containing TiO 2 and LaPO 4 with molar ratio 1:1) sols and annealed at 400 °C, produced contact angles of 74° and 92°, respectively, though it is only 62° for pure TiO 2 coating. The glass substrates, coated with TL50 sol, produced surfaces with relatively high roughness and uneven morphology. The TL1 material, annealed at 800 °C, has shown the highest UV photoactivity with an apparent rate constant, kapp=24×10 -3 min -1, which is over five times higher than that observed with standard Hombikat UV 100 ( kapp=4×10 -3 min -1). The photoactivity combined with a moderate contact angle (85.3°) shows that this material has a promise as an efficient self-cleaning precursor.

  4. Nitrogen-sensitized dual phase titanate/titania for visible-light driven phenol degradation

    SciTech Connect

    Cheng, Yu Hua; Subramaniam, Vishnu P.; Gong, Dangguo; Tang, Yuxin; Highfield, James; Pehkonen, Simo O.; Pichat, Pierre; Chen, Zhong

    2012-12-15

    A dual-phase material (DP-160) comprising hydrated titanate (H{sub 2}Ti{sub 3}O{sub 7}{center_dot}xH{sub 2}O) and anatase (TiO{sub 2}) was synthesized in a low-temperature one-pot process in the presence of triethylamine (TEA) as the N-source. The unique structure exhibits strong visible light absorption. The chromophore is linked to Ti-N bonds derived from both surface sensitization and sub-surface (bulk) doping. From transmission electron microscope (TEM) and textural studies by N{sub 2} physisorption, the composite exists as mesoporous particles with a grain size of {approx}20 nm and mean pore diameter of 3.5 nm, responsible for the high surface area ({approx}180 m{sup 2}/g). DP-160 demonstrated photocatalytic activity in the degradation of phenol under visible light ({lambda}>420 nm). The activity of the composite was further enhanced by a small addition (0.001 M) of H{sub 2}O{sub 2}, which also gave rise to some visible light activity in the control samples. This effect is believed to be associated with the surface peroxo-titanate complex. GC-MS analyses showed that the intermediate products of phenol degradation induced by visible light irradiation of DP-160 did not differ from those obtained by UV (band-gap) irradiation of TiO{sub 2}. The overall performance of the composite is attributed to efficient excitation via inter-band states (due to N-doping), surface sensitization, improved adsorptive properties of aromatic compounds due to the N-carbonaceous overlayer, and the presence of heterojunctions that are known to promote directional charge transfer in other mixed-phase titanias like Degussa P25. - graphical abstract: Nitrogen-sensitized dual phase titanate/titania photocatalyst showing extended visible light absorption and efficient photocatalytic degradation of phenol. Highlights: Black-Right-Pointing-Pointer Low temperature one-pot synthesis of visible light active dual phase photocatalyst. Black-Right-Pointing-Pointer The dual phase consists of

  5. Influence of dye content on the conduction band edge of titania in the steam-treated dye-dispersing titania electrodes.

    PubMed

    Setiawan, Rudi Agus; Nishikiori, Hiromasa; Tanaka, Nobuaki; Fujii, Tsuneo

    2014-01-01

    The titania and dye-dispersing titania electrodes were prepared by a nitric acid-catalyzed sol-gel process. The dye-dispersing titania contains the dye molecules dispersed on the surface of the individual nanosized titania particles. The photo-cyclic voltammetry (Photo-CV) and photoelectric measurements of the dye-dispersing titania electrodes were conducted to clarify the factors changing the conduction band edge of the titania and the open-circuit voltage (Voc ) of the electrodes. The remaining nitrate ions caused a negative shift of conduction band edge of the titania of the dye-dispersing titania. The conduction band edge of the titania was shifted in a negative direction in the electrode containing a greater amount of the dye. These results are due to the adsorption of nitrate ions and the dye-titania complex formation on the titania particle surface. The effect of the dye-titania complex formation on the shift in the titania conduction band edge was greater than that of the adsorption of nitrate ions due to strong interaction between the dye and titania through the carboxylate and quinone-like groups of the dye. The shift in the titania conduction band edge corresponded to the change in the Voc value. PMID:24893823

  6. Three-dimensional developing flow model for photocatalytic monolith reactors

    SciTech Connect

    Hossain, Md.M.; Raupp, G.B.; Hay, S.O.; Obee, T.N.

    1999-06-01

    A first-principles mathematical model describes performance of a titania-coated honeycomb monolith photocatalytic oxidation (PCO) reactor for air purification. The single-channel, 3-D convection-diffusion-reaction model assumes steady-state operation, negligible axial dispersion, and negligible homogeneous reaction. The reactor model accounts rigorously for entrance effects arising from the developing fluid-flow field and uses a previously developed first-principles radiation-field submodel for the UV flux profile down the monolith length. The model requires specification of an intrinsic photocatalytic reaction rate dependent on local UV light intensity and local reactant concentration, and uses reaction-rate expressions and kinetic parameters determined independently using a flat-plate reactor. Model predictions matched experimental pilot-scale formaldehyde conversion measurements for a range of inlet formaldehyde concentrations, air humidity levels, monolith lengths, and for various monolith/lamp-bank configurations. This agreement was realized without benefit of any adjustable photocatalytic reactor model parameters, radiation-field submodel parameters, or kinetic submodel parameters. The model tends to systematically overpredict toluene conversion data by about 33%, which falls within the accepted limits of experimental kinetic parameter accuracy. With further validation, the model could be used in PCO reactor design and to develop quantitative energy utilization metrics.

  7. Black Nb2O5 nanorods with improved solar absorption and enhanced photocatalytic activity.

    PubMed

    Zhao, Wenli; Zhao, Wei; Zhu, Guilian; Lin, Tianquan; Xu, Fangfang; Huang, Fuqiang

    2016-03-01

    Black titania, with greatly improved solar absorption, has demonstrated its effectiveness in photocatalysis and photoelectrochemical cells (PEC), inspiring us to explore the blackening of other wide band-gap oxide materials for enhanced performance. Herein, we report the fabrication of black, reduced Nb2O5 nanorods (r-Nb2O5), with active exposed (001) surfaces, and their enhanced photocatalytic and PEC properties. Black r-Nb2O5 nanorods were obtained via reduction of pristine Nb2O5 by molten aluminum in a two-zone furnace. Unlike the black titania, r-Nb2O5 nanorods are well-crystallized, without a core-shell structure, which makes them outstanding in photocatalytic stability. Substantial Nb(4+) cation and oxygen vacancies (VO) were introduced into r-Nb2O5, resulting in the enhanced absorption in both the visible and near-infrared regions and improved charge separation and transport capability. The advantage of the r-Nb2O5 was also proved by its more efficient photoelectrochemical performance (138 times at 1.23 VRHE) and higher photocatalytic hydrogen-generation activity (13 times) than pristine Nb2O5. These results indicate that black r-Nb2O5 is a promising material for PEC application and photocatalysis. PMID:26906245

  8. Room-temperature embedment of anatase titania nanoparticles into porous cellulose aerogels

    NASA Astrophysics Data System (ADS)

    Jiao, Yue; Wan, Caichao; Li, Jian

    2015-07-01

    In this paper, a facile easy method for room-temperature embedment of anatase titania (TiO2) nanoparticles into porous cellulose aerogels was reported. The obtained anatase TiO2/cellulose (ATC) aerogels were characterized by scanning electron microscopy, energy-dispersive X-ray spectrometer, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, nitrogen adsorption measurements, and thermogravimetric analysis. The results showed that high-purity anatase TiO2 nanoparticles with sizes of 3.69 ± 0.77 nm were evenly dispersed in the cellulose aerogels, which leaded to the significant improvement in specific surface area and pore volume of ATC aerogels. Meanwhile, the hybrid ATC aerogels also had a high loading content of TiO2 (ca. 17.7 %). Furthermore, through a simple photocatalytic degradation test of indigo carmine dye under UV light, ATC aerogels exhibited superior photocatalytic activity and shape stability, which might be useful in some fields like governance of water pollution, and chemical leaks.

  9. Zr doped anatase supported reticulated ceramic foams for photocatalytic water purification

    SciTech Connect

    Plesch, G.; Vargová, M.; Vogt, U.F.; Gorbár, M.; Jesenák, K.

    2012-07-15

    Highlights: ► Thick photocatalytic anatase films on macroporous reticulated ceramic foams. ► Alumina and alumina–mullite macroporous reticulated foams as photocatalyst support. ► Zr doping significantly improves the TiO{sub 2} film activity in phenol photomineralization. ► Comparison of photocatalytic activity of thick films and powder suspensions. -- Abstract: Titanium dioxide films were deposited on macroporous reticulated Al{sub 2}O{sub 3} and alumina–mullite foams with pore sizes of 15 ppi (pores per inch). Coatings were prepared from suspensions of precursor powders of Aeroxide{sup ®} P25 nanopowder and precipitated TiO{sub 2} by using a dip coating process. The TiO{sub 2} forms films with a thickness of ∼2–20 μm. The photocatalytic activity was characterized as the mineralization rate of an aqueous phenol solution under UVA irradiation by the TOC technique. Precipitated TiO{sub 2} films have nearly the same photocatalytic activity as a titania suspension, in which powder aggregates have a size comparable with the thickness of the films. Samples made of Aeroxide{sup ®} P25 nanopowder, in which the size of aggregates is ∼0.1 μm show higher efficiency of photodecomposition in suspensions with films. The doping of precipitated anatase with Zr(IV) in the atomic ratio Zr/Ti = 0.008 significantly improves the photocatalytic activity of the foam supported titania. Zr doped anatase films show better performance as the films prepared only from Aeroxide{sup ®} P25 nanopowder.

  10. High visible light photocatalytic property of Co2+-doped TiO2 nanoparticles with mixed phases

    NASA Astrophysics Data System (ADS)

    Zhao, Cong; Shu, Xin; Zhu, Da-chuan; Wei, Shang-hai; Wang, Yu-xin; Tu, Ming-jing; Gao, Wei

    2015-12-01

    Mixed phases Co2+-doped TiO2 nanoparticles have been prepared by a novel method combined with sol-gel and hydrothermal methods. The section of sol-gel method, sol, provides an unstable colloidal reaction system for the next reaction process. The hydrothermal method is to treat the above reaction system to prepare undoped and doped samples. The as-prepared samples have been characterized by XRD, SEM, TEM, HRTEM and UV-vis spectroscopy. The results show that the as-prepared samples contain three titania polymorphs: brookite, rutile and anatase phases. These titania polymorphs probably form polymorph-junctions that can extend the lifetime of photogenerated electron-hole pairs. The photocatalytic activity has been evaluated by the photocatalytic degradation of Rhodamine B in air under visible-light irradiation. The degradation results indicate that the photocatalytic activity of as-prepared samples is higher than that of Degussa P25, especially the doped sample. This is ascribed to the fact that the phases with smaller band gap can enhance visible-light photocatalytic activity, the polymorph-junctions effectively extend the photoelectron lifetime and the nano size effect and Co-doping induce the shift of the absorption edge into the visible-light region. Furthermore, the XRD, SEM, and TEM data indicate that Co2+-doping results in the decrease of particle size.

  11. Investigation of titania membranes for nanofiltration

    SciTech Connect

    Wildman, D.L.; Peterson, R.A.; Hill, C.G. Jr.

    1994-12-31

    The development of ceramic membranes for industrial scale separations is receiving increased attention because of the numerous potential benefits that these inorganic membranes offer over their organic counterparts. These benefits include increased thermal stability, ability to operate over a broader range of pH values, and increased resistance to organic solvents. One method for the synthesis of ceramic membranes involves sol-gel techniques. Titania sols have been fabricated which are characterized by mean particle diameters of ca. 8 nm. Membranes fabricated from these sols are characterized by pore diameters of approximately 15 {angstrom}. Permselectivity measurements of these titania membranes indicate that their molecular weight cut-off value is less than 200. Rejection coefficients for several molecular species increased with increasing applied pressure in a manner which was not predicted from theoretical considerations. Rejection coefficients for several nitrate salts and permeability data for selected non-aqueous solvents were measured. Rejection coefficients for cupric and zinc nitrate salts were approximately 25%.

  12. Electrochemical performance of granulated titania nanoparticles

    NASA Astrophysics Data System (ADS)

    Wilhelm, O.; Pratsinis, S. E.; de Chambrier, E.; Crouzet, M.; Exnar, I.

    The electrochemical performance of Li-ion insertion into electrodes made of various sizes of anatase titania nanoparticles embedded in larger granulated entities (1-10 μm) is investigated. The granules are formed by spray drying of a suspension containing titania nanoparticles made by hydrolyzing titanium tetraisopropoxide (TTIP). Depending on the three process steps, i.e. hydrolysis-condensation, hydrothermal processing and spray drying, different properties for the electrode made from these granules can be achieved in terms of phase composition, specific surface area (SSA) and specific charge capacity. Hydrothermally processed (HP) particles are more resistant to calcination than sol-gel precipitated (SGP) ones and have a higher SSA which leads to a better performance with respect to specific charge capacity. Electrodes made from granulated nanoparticles have superior specific charge capacity than from non-granulated ones as the former have more inter-particle contacts.

  13. Hydrogen sulfide conversion with nanophase titania

    DOEpatents

    Beck, D.D.; Siegel, R.W.

    1996-08-20

    A process is described for disassociating H{sub 2}S in a gaseous feed using an improved catalytic material in which the feed is contacted at a temperature of at least about 275 C with a catalyst of rutile nanocrystalline titania having grain sizes in the range of from about 1 to about 100 nanometers. Other transition metal catalysts are disclosed, each of nanocrystalline material with grain sizes in the 1-100 nm range. 5 figs.

  14. Synthesis of Micro/Nano Crystalline Ceramics

    NASA Astrophysics Data System (ADS)

    Mathew, Philip; Isac, Sheelakumari; Abraham, Rosalin; Isac, Jayakumari

    2008-04-01

    As a matter of fact almost every industrial production line, office and home is dependant on ceramic materials. Newly designed devices incorporate ceramic materials because of their useful chemical, electrical, mechanical, thermal and structural properties. The effectiveness of a large system depends critically on its ceramic components. That is ceramics are important, first because they comprise a large basic industry and second because their properties are essential for many applications. Ceramics are more stable than metals both in chemical and thermal environments. In this work the authors describes a method for the preparation of PBT ceramics material from lead oxide (PbO), barium carbonate and titanium oxide based on pre-calcinations of oxides. The results were analyzed by X-ray Diffraction (XRD), Infrared Spectroscopy (IR) and TGA. XRD and SEM studies revealed that its particle size is in nanometer range. Dielectric studies were conducted at a frequency range of 100 KHz to 13 MHz. Mechanical properties were calculated.

  15. ONE-DIMENSIONAL PLASMONIC NANO-PHOTOCATALYSTS: SYNTHESIS, CHARACTERIZATION AND PHOTOCATALYTIC ACTIVITY

    SciTech Connect

    Murph, S.

    2011-08-14

    This study describes a simple two-step approach to coat gold nanorods with a silica/titania shell. Gold nanorods with an aspect ratio of 2.5 (L = 48 {+-} 2 and d = 19 {+-} 1) are synthesized by a silver-seed mediated growth approach according to our previously reported procedure (Hunyadi Murph ACS Symposium Series, Volume 1064, Chapter 8, 2011, 127-163 and reference herein). Gold nanorods are grown on pre-formed gold nano-seeds in the presence of surfactant, cetyltrimethylammonium bromide (CTAB), and a small amount of silver ions. A bifunctional linker molecule which has a thiol group at one end and a silane group at the other is used to derivatize gold nanorods. The silane group is subsequently reacted with both sodium silicate and titanium isopropoxide to a silica/titania shell around the gold nanorods. By fine tuning the reaction conditions, the silica/titania shell thickness can be controlled from {approx}5 to {approx}40nm. The resulting nanomaterials are stable, amenable to scale up and can be isolated without core aggregation or decomposition. These new materials have been characterized by scanning electron microscopy, energy dispersive X-ray analysis, UV-Vis spectroscopy and dynamic light scattering analysis. Photocatalytic activity of Au-silica/titania nanomaterials under visible and UV illumination is measured via degradation of a model dye, methyl orange (MO) under visible and UV illumination. The results indicate a 3 fold improvement in the photocatalytic decomposition rate of MO under visible illumination vs. UV illumination.

  16. UV-induced photocatalytic degradation of aqueous acetaminophen: the role of adsorption and reaction kinetics.

    PubMed

    Basha, Shaik; Keane, David; Nolan, Kieran; Oelgemöller, Michael; Lawler, Jenny; Tobin, John M; Morrissey, Anne

    2015-02-01

    Nanostructured titania supported on activated carbon (AC), termed as integrated photocatalytic adsorbents (IPCAs), were prepared by ultrasonication and investigated for the photocatalytic degradation of acetaminophen (AMP), a common analgesic and antipyretic drug. The IPCAs showed high affinity towards AMP (in dark adsorption studies), with the amount adsorbed proportional to the TiO2 content; the highest adsorption was at 10 wt% TiO2. Equilibrium isotherm studies showed that the adsorption followed the Langmuir model, indicating the dependence of the reaction on an initial adsorption step, with maximum adsorption capacity of 28.4 mg/g for 10 % TiO2 IPCA. The effects of initial pH, catalyst amount and initial AMP concentration on the photocatalytic degradation rates were studied. Generally, the AMP photodegradation activity of the IPCAs was better than that of bare TiO2. Kinetic studies on the photocatalytic degradation of AMP under UV suggest that the degradation followed Langmuir-Hinshelwood (L-H) kinetics, with an adsorption rate constant (K) that was considerably higher than the photocatalytic rate constant (k r), indicating that the photocatalysis of AMP is the rate-determining step during the adsorption/photocatalysis process. PMID:25173973

  17. Towards TiO2 nanotubes modified by WO3 species: influence of ex situ crystallization of precursor on the photocatalytic activities of WO3/TiO2 composites

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Dong, Bohua; Su, Ge; Gao, Rongjie; Liu, Wei; Song, Liang; Cao, Lixin

    2015-09-01

    TiO2 nanotubes (TNT) crystallized at different temperatures were loaded with WO3 hydrate through the reaction between (NH4)6W7O24·6H2O and an aqueous solution of HCl. The photocatalytic activities of nanocomposites firstly increase and then decrease as a function of the crystallized temperature of the TNT precursor. The structural, morphologic and optical properties of WO3/TiO2 nanocomposites were also investigated in this study. The samples, initially anatase titania (573 K-773 K), presented phase transition to rutile titania at 873 K. With the crystallized temperature increasing, an evolution of samples morphology changing from nanotube-like structure to nanorod-like structure was observed. Meanwhile, the absorption edge of samples exhibited a red shift, and correspondingly their band gap decreased. Consistent with x-ray diffraction diffractograms, the existence of rutile titania as an impurity in the precursor TNT, crystallized at higher than 873 K, depressed photocatalytic activity evidently. As a result, the degradation rate of methyl orange (MO) increased with the samples crystallinity firstly, and then reduced due to the appearance of rutile titania. In our experimental conditions, the optimal photocatalytic activity was achieved for the sample crystalized at 773 K. Its degradation rate could reach 98.76% after 90 min UV light irradiation.

  18. Enhanced Optical Absorption Induced by Dense Nanocavities Inside Titania Nanorods

    SciTech Connect

    Han,W.; Wu, L.; Klie, R.; Zhu, Y.

    2007-01-01

    Titania, a wide band gap semiconductor, can generate powerful oxidants and reductants by absorbing photon energies. Titania has been extensively used in photoelectrochemical systems, such as dye-sensitized titania, a wide band gap semiconductor, can generate powerful oxidants and reductants by absorbing photon energies. To improve the photoreactivity of titania, several approaches, including doping and metal loading have been proposed. Nanocavities are isolated entities inside a solid and hence are very different from nanoporous, whose pores (often amorphous and irregular) connect together and open to the surface. Dense polyhedral nanocavities inside single-crystalline anatase titania nanorods were successfully synthesized by simply heating titanate nanorods. The size of the nanocavities is typically about 10 nm. The surfaces of the nanocavity polyhedron are determined to be the crystallographic low-index planes of the titania crystal. We found that these dense nanocavities significantly enhance the optical absorption coefficient of titania in the near-ultraviolet region, thereby providing a new approach to increasing the photoreactivity of the titania nanorods in the applications related to absorbing photons.

  19. Electrochemical biosensing based on polypyrrole/titania nanotube hybrid.

    PubMed

    Xie, Yibing; Zhao, Ye

    2013-12-01

    The glucose oxidase (GOD) modified polypyrrole/titania nanotube enzyme electrode is fabricated for electrochemical biosensing application. The titania nanotube array is grown directly on a titanium substrate through an anodic oxidation process. A thin film of polypyrrole is coated onto titania nanotube array to form polypyrrole/titania nanotube hybrid through a normal pulse voltammetry process. GOD-polypyrrole/titania nanotube enzyme electrode is prepared by the covalent immobilization of GOD onto polypyrrole/titania nanotube hybrid via the cross-linker of glutaraldehyde. The morphology and microstructure of nanotube electrodes are characterized by field emission scanning electron microscopy and Fourier transform infrared analysis. The biosensing properties of this nanotube enzyme electrode have been investigated by means of cyclic voltammetry and chronoamperometry. The hydrophilic polypyrrole/titania nanotube hybrid provides highly accessible nanochannels for GOD encapsulation, presenting good enzymatic affinity. As-formed GOD-polypyrrole/titania nanotube enzyme electrode well conducts bioelectrocatalytic oxidation of glucose, exhibiting a good biosensing performance with a high sensitivity, low detection limit and wide linear detection range. PMID:24094220

  20. Enhanced Photovoltaic Properties of Potassium-Adsorbed Titania Nanotubes

    SciTech Connect

    Richter, C.; Jaye, C; Fischer, D; Lewis, L; Willey, R; Menon, L

    2009-01-01

    It is demonstrated that vertically-aligned titania nanotube planar arrays fabricated by electrochemical anodization using standard potassium-containing electrolytes invariably contain a significant amount of surface-adsorbed potassium ions, hitherto undetected, that affect the titania photoelectrochemical or PEC performance. Synchrotron-based near edge X-ray absorption fine structure (NEXAFS) spectroscopy reveals the strong ionic nature of surface potassium-titania bonds that alters the PEC performance over that of pure titania nanotubes through reduction of the external electrical bias needed to produce hydrogen at maximum efficiency. This result implies that the external electrical energy input required per liter of solar hydrogen produced with potassium-adsorbed titania nanotubes may be reduced. Tailoring the potassium content may thus be an alternative means to fine-tune the photoelectrochemical response of TiO2 nanotube-based PEC electrodes.

  1. A review on plasmonic metal-TiO2 composite for generation, trapping, storing and dynamic vectorial transfer of photogenerated electrons across the Schottky junction in a photocatalytic system

    NASA Astrophysics Data System (ADS)

    Gomathi Devi, L.; Kavitha, R.

    2016-01-01

    The titania based nanomaterials are an attractive candidates for energy and environmental applications. TiO2 is one of the most important photocatalyst for its special multiple characteristics like high reactivity, low toxicity, low cost, high flexibility, long term stability especially in aqueous medium, shows relatively high energy conversion efficiency, easy to prepare several modifications with various morphologies, with good recycle ability, favorable band edge positions and superior physicochemical and optoelectronic properties. However, large band gap of titania and massive charge carrier recombination impairs its wide photocatalytic applications. As an alternative to various strategies reported extensively in literature, noble metal deposition on the titania surface seems to be effective and reliable method for increasing the life time of excitonic pairs and to extend the band gap absorption to visible range of the solar spectrum. In this focused review, we discuss the fundamental and critical issues in the photocatalytic activity of metal deposited titania taking into consideration the influence of various parameters like preparation methods, metal dispersion on titania, formation of heterojunctions and optimum metal loadings on the interfacial charge carrier dynamics. The metal deposition onto the varied hierarchical morphology, crystal structure, defective surface of titania along with extended modification like simultaneous doping and heterostructure coupling with other semiconductors is also highlighted. It was revealed that deposited metal is involved in multiple crucial roles like; (i) it serves as passive electron sink with high capacity to store electrons to suppress photogenerated charge carrier recombination; (ii) it facilitates rapid dioxygen reduction to generate reactive free radicals; (iii) visible light response for titania can be achieved through surface plasmon resonance effect; (iv) direct excitation of metal nanoparticles especially

  2. Structural morphological and optoelectronic study of titania and gold doped titania nanoparticles grown by sol-gel technique

    NASA Astrophysics Data System (ADS)

    Jadhav, Yogesh A.; Gattu, Ketan P.; Ghule, Anil; Sharma, Ramphal

    2013-02-01

    Here in this work, the titania (TiO2), gold ion doped titania (Au+3TiO2) and gold nanoparticles doped titania (Au NPs TiO2) have been prepared by sol-gel technique. In a typical synthesis titanium tetrachloride (TiCl4) is treated with citric acid in presence of methanol as solvents, forms titanium citrate complex sol at 40°C. This sol forms a viscous gel after 2 h of stirring and heating at 60 °C. The pre-synthesized Au+3 ions and Au NPs were then added drop wise to the titanium citrate complex sol to form gold ion doped titania (Au+3TiO2) and gold nanoparticles doped titania. The products obtained were calcined at 700 °C. The obtained particles were studied for their structural, morphological, optical and electrical properties.

  3. Preparation, characterization, and photocatalytic studies on anatase nano-TiO{sub 2} at internal air lift circulating photocatalytic reactor

    SciTech Connect

    Xu, Hang Li, Mei; Jun, Zhang

    2013-09-01

    Graphical abstract: The micro morphological structure of the nano-TiO{sub 2} particles was also observed with TEM, as shown in figure. The TEM images clearly exhibited the homogeneous microstructure of particles with a size of around 10–15 nm. - Highlights: • Nano-TiO{sub 2} was prepared by complex techniques of sol–gel, micro-emulsion and solvent thermal. • The size of TiO{sub 2} was nano level and uniformity. • Nano-TiO{sub 2} exhibited high photo-catalytic activity at internal air lift circulating reactor. • The best nano-TiO{sub 2} dosage was obtained. - Abstract: Anatase nano-titania (TiO{sub 2}) powder was prepared by using a sol–gel process mediated in reverse microemulsion combined with a solvent thermal technique. The structures of the obtained TiO{sub 2} were characterized by TG-DSC, XRD, TEM. The photocatalytic decomposition of methylene blue (MB) on nano-TiO{sub 2} was studied by using an internal air lift circulating photocatalytic reactor. The results show that the anatase structure appears in the calcination temperature range of 400–510 °C, while the transformation of anatase into rutile takes place above 510 °C. The homogeneous microstructure of nano-TiO{sub 2} particles was obtained with a size of around 10–15 nm. In the photocatalytic performance, degradation process follows pseudo first order kinetics with different dosages of photocatalyst and initial MB concentrations and optimal TiO{sub 2} dosage is 0.1 g/L with neutral medium.

  4. Photocatalytic/Magnetic Composite Particles

    NASA Technical Reports Server (NTRS)

    Wu, Chang-Yu; Goswami, Yogi; Garretson, Charles; Andino, Jean; Mazyck, David

    2007-01-01

    Photocatalytic/magnetic composite particles have been invented as improved means of exploiting established methods of photocatalysis for removal of chemical and biological pollutants from air and water. The photocatalytic components of the composite particles are formulated for high levels of photocatalytic activity, while the magnetic components make it possible to control the movements of the particles through the application of magnetic fields. The combination of photocatalytic and magnetic properties can be exploited in designing improved air- and water treatment reactors.

  5. Photocatalytic efficiencies of self-cleaning glasses. Influence of physical factors.

    PubMed

    Peruchon, L; Puzenat, E; Herrmann, J M; Guillard, C

    2009-07-01

    Two commercial types of self-cleaning glass (SCG) have been tested to confirm the real photocatalytic nature of their properties. This was done by using four photocatalytic tests: (i) in the gas phase with the total oxidation of acetylene; (ii) in water with the total degradation of malic acid, (iii) in water with the total degradation of methylene blue, and (iv) in the solid phase with the total oxidative degradation of a layer of stearic acid deposited on the self-cleaning glass surface, in contact with the superficial titania coating. The influence of various factors (temperature, humidity, wavelength, radiant flux, presence of inorganic particles stuck at the glass surface) was explained in line with the fundamentals of photocatalysis. The results helped to understand the behaviour of self-cleaning glass. PMID:19582281

  6. Formation and Characteristics of Anatase-Type Titania Solid Solution Nanoparticles Doped with Nb5+ M (M = Ga3+, Al3+, Sc3+)

    NASA Astrophysics Data System (ADS)

    Hirano, Masanori; Ito, Takaharu

    2011-10-01

    Anatase-type titania solid solutions co-doped with Nb5+ and cation M (M = Ga3+, Al3+, Sc3+) with composition Ti1-2XNbXMXO2 were directly formed as nanoparticles from precursor solutions of TiOSO4, NbCl5, and metal salts (Ga(SO4)3, Al(NO3)3, and Sc(NO3)3) under mild hydrothermal conditions at 180 °C for 5 h using the hydrolysis of urea. The effect of co-doped cation M on the formation and properties of anatase-type titania solid solutions was investigated. The region of anatse-type solid solution depended on the co-doped cation M. The composition range of anatase-type titania solid solution in the case of M = Sc3+ was much wider than that in the case of M = Ga3+ and Al3+. The increase in the amount of co-doped cation M = Ga3+, Al3+ enhanced the crystallite growth of anatase solid solutions under the hydrothermal conditions. The solid solutions co-doped with M = Al3+ showed the most improved photocatalytic activity in the three cations. The anatase-to-rutile phase transformation of solid solutions was promoted at lower temperature via the presence of co-doped cation M = Ga3+.

  7. Light Scattering Study of Titania Aerosols

    NASA Astrophysics Data System (ADS)

    Oh, Choonghoon; Sorensen, Chris

    1997-03-01

    We studied the fractal morphology of titania aerosols by light scattering. Titania aerosols were generated by the thermal decomposition of titanium tetraisopropoxide (TTIP) in a silica tube furnace. TTIP was evaporated at temperatures up to 80^circC and its vapor was carried by dry nitrogen to a furnace with temperature in the range of 400 - 600^circC. A TEM analysis of the generated particles showed a typical DLCA structure with a monomer diameter about 50 nm. The particles were then made to flow through a narrow outlet as a laminar stream. The light scattering from these particles was measured using a He-Ne laser as a light source. The measured structure factor clearly showed the Rayleigh, Guinier, and fractal regimes. The fractal morphological parameters, such as the cluster radius of gyration, the fractal dimension, and the fractal prefactor were studied from the structure factor as a function of particle generation conditions. The cluster radius of gyration was about 1 μm and showed a modest dependency on the generation conditions. The fractal dimension was about 1.7 in all cases. These results are in good agreement with the TEM analysis.

  8. Novel multifunctional titania-silica-lanthanum phosphate nanocomposite coatings through an all aqueous sol-gel process.

    PubMed

    Smitha, Venu Sreekala; Jyothi, Chembolli Kunhatta; Peer, Mohamed A; Pillai, Saju; Warrier, Krishna Gopakumar

    2013-04-01

    A novel nanocomposite coating containing titania, silica and lanthanum phosphate prepared through an all aqueous sol-gel route exhibits excellent self-cleaning ability arising from the synergistic effect of the constituents in the nanocomposite. A highly stable titania-silica-lanthanum phosphate nanocomposite sol having particle size in the range of 30-50 nm has been synthesized starting from a titanyl sulphate precursor, which was further used for the development of photocatalytically active composite coatings on glass. The coatings prepared by the dip coating technique as well as the nanocomposite powders are heat treated and characterized further for their morphology and multifunctionality. The nanocomposite containing 1.5 wt% LaPO4 has shown a surface area as high as 138 m(2) g(-1) and a methylene blue degradation efficiency of 94% in two hours of UV exposure. The composite coating has shown very good homogeneity evidenced by transparency as high as 99.5% and low wetting behaviour. The present novel approach for energy conserving, aqueous derived, self-cleaning coatings may be suitable for large scale industrial applications. PMID:23358559

  9. Photocatalytic conversion of gaseous ethylbenzene on lanthanum-doped titanium dioxide nanotubes.

    PubMed

    Cheng, Zhuo-Wei; Feng, Li; Chen, Jian-Meng; Yu, Jian-Ming; Jiang, Yi-Feng

    2013-06-15

    The photocatalytic properties of titanium dioxide (TiO₂) make it an attractive material for environmental remediation. In the present study, lanthanum (La(3+))-doped TiO2 nanotubes with excellent photocatalytic activity were fabricated by a combination of sol-gel method and hydrothermal technique. The optimal preparation parameters were determined by the structural characterization using a range of methods and the photocatalytic degradation of gaseous ethylbenzene (EB). Compared with pure TiO₂ nanoparticles, 1.2%-La(3+)-doped - titania nanotubes (1.2%-La(3+)-TNTs) exhibited higher activity under 254 nm UV for conversion of EB. The initial EB concentrations and relative humidity (RH) obviously influenced the photocatalytic activity of 1.2%-La(3+)-TNTs. Kinetic analysis showed that surface adsorption and surface reaction controlled the rate-determining step for RH of 40-50% and >80%, respectively. Gas chromatography and mass spectrometry were used to analyze the intermediates generated in the conversion of EB, allowing a tentative decomposition pathway to be proposed. The prepared photocatalyst exhibited enhanced EB conversion compared with undoped TiO₂, and showed a promise for the decomposition of recalcitrant compounds before subsequent biopurification. PMID:23643959

  10. Synthesis and photocatalytic activity of mesoporous cerium doped TiO{sub 2} as visible light sensitive photocatalyst

    SciTech Connect

    Aman, Noor; Satapathy, P.K.; Mishra, T.; Mahato, M.; Das, N.N.

    2012-02-15

    Graphical abstract: Cerium doped titania having optimum 5 wt% of cerium can decompose methylene blue and reduce selenium (IV) efficiently under visible light. Highlights: Black-Right-Pointing-Pointer Effect of cerium doping on the surface properties and visible light mediated photocatalytic reaction is studied. Black-Right-Pointing-Pointer Cerium doping increases the anatase phase stability, surface area (up to 137 m{sup 2}/g) and visible light absorption. Black-Right-Pointing-Pointer Importance of Ce{sup 3+}/Ce{sup 4+}, oxygen vacancy, surface area and crystallinity is correlated with improved catalytic activity. Black-Right-Pointing-Pointer Material with 5 wt% Ce is found to be most active photocatalyst for methylene blue decomposition and Se (IV) reduction. -- Abstract: Cerium doped titania materials were synthesized varying the cerium concentration from 0 to 10 wt%. Materials are characterised by XRD, TEM, XPS and N{sub 2} adsorption desorption method. Surface area and visible light absorption substantially increases and crystallite size decreases with the increasing cerium content. Cerium doping stabilizes the anatase phase and surface area even at 600 Degree-Sign C calcination. Photocatalytic activity towards methylene blue decomposition and selenium (IV) reduction is found to increase with the cerium content up to 5 wt% and then decreases. Materials calcined at 600 Degree-Sign C shows better activity than that calcined at 400 Degree-Sign C, even though surface area decreases. Anatase crystallinity mostly decides the photocatalytic activity rather than only surface area. It can be concluded that the optimum visible light absorption and oxygen vacancy with 5% cerium doping enhances the photocatalytic activity. In addition photocatalytic performance is found to depend on the presence of Ce{sup 4+}/Ce{sup 3+} rather than only visible light absorption.