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Sample records for ag co-modified tio2

  1. Au-loaded TiO2 and Ag-loaded TiO2 synthesized by modified sol-gel/impregnation method as photocatalysts

    NASA Astrophysics Data System (ADS)

    Ninsonti, Hathaithip; Sriwichai, Saengrawee; Wetchakun, Natda; Kangwansupamonkon, Wiyong; Phanichphant, Sukon

    2016-02-01

    In this work, Au-loaded TiO2 and Ag-loaded TiO2 nanoparticles were synthesized by modified sol-gel method together with impregnation method. The samples were characterized by their physicochemical properties using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy in order to obtain the correlation between structure and photocatalytic properties. XRD results indicated unloaded TiO2, Au-loaded TiO2 and Ag-loaded TiO2 nanoparticles were all in the anatase phase with average crystallite size in the range of 10-13 nm. In addition, XPS analysis confirmed the presence of Au and Ag elements in Au-loaded TiO2 and Ag-loaded TiO2 nanoparticles, respectively. The photocatalytic activities of TiO2, Au-loaded TiO2 and Ag-loaded TiO2 nanoparticles were evaluated through the mineralization of formic acid under UV-light illumination. The results showed that Au-loading and Ag-loading could effectively improve the photocatalytic activities of TiO2. Furthermore, Au-loaded TiO2 exhibited a higher photocatalytic activity than Ag-loaded TiO2.

  2. Ag Nanorods Coated with Ultrathin TiO2 Shells as Stable and Recyclable SERS Substrates

    NASA Astrophysics Data System (ADS)

    Ma, Lingwei; Huang, Yu; Hou, Mengjing; Xie, Zheng; Zhang, Zhengjun

    2015-10-01

    TiO2-coated Ag nanorods (Ag@TiO2 NRs) have been fabricated as multifunctional surface-enhanced Raman scattering (SERS) substrates. Uniform TiO2 shells could sufficiently protect the internal Ag NRs against oxidation and sulfuration, thus the temporal stability of SERS substrates was markedly improved. Meanwhile, due to the synergetic effect between crystalline TiO2 and Ag, the nanocomposites could clean themselves via photocatalytic degradation of the adsorbed molecules under ultraviolet irradiation and water dilution, making the SERS substrates renewable. Such Ag@TiO2 NRs were shown to serve as outstanding SERS sensors featuring high sensitivity, superior stability and recyclability.

  3. Ag Nanorods Coated with Ultrathin TiO2 Shells as Stable and Recyclable SERS Substrates

    PubMed Central

    Ma, Lingwei; Huang, Yu; Hou, Mengjing; Xie, Zheng; Zhang, Zhengjun

    2015-01-01

    TiO2-coated Ag nanorods (Ag@TiO2 NRs) have been fabricated as multifunctional surface-enhanced Raman scattering (SERS) substrates. Uniform TiO2 shells could sufficiently protect the internal Ag NRs against oxidation and sulfuration, thus the temporal stability of SERS substrates was markedly improved. Meanwhile, due to the synergetic effect between crystalline TiO2 and Ag, the nanocomposites could clean themselves via photocatalytic degradation of the adsorbed molecules under ultraviolet irradiation and water dilution, making the SERS substrates renewable. Such Ag@TiO2 NRs were shown to serve as outstanding SERS sensors featuring high sensitivity, superior stability and recyclability. PMID:26486994

  4. Structural, morphological, optical and photocatalytic investigation of Ag-doped TiO2

    NASA Astrophysics Data System (ADS)

    Kundu, Virender Singh; Singh, Davender; Maan, A. S.; Tanwar, Amit

    2016-05-01

    The pure and Ag-doped TiO2 nanoparticles were prepared by using Titanium isoproxide (TTIP), silver nitrate sodium hydroxide and sodium hydroxide. The calcined nanoparticles at 400°C were characterized by means of X-ray diffraction (XRD). XRD analyses reveal that the nanoparticles of various doping concentration were having anatase phase. The particle size was calculated by Scherrer formula and was found 11.08 nm for pure TiO2 and 8.86 nm for 6 mol % Ag doped TiO2. The morphology and nature of nanoparticles was analyzed by using scanning electron microscope (SEM), the optical absorption spectra of pure TiO2 and Ag-doped TiO2 nanoparticles showed that absorption edge increases towards longer wavelength from 390 nm (pure) to 450 nm (doped), also band gap energy calculated from Tauc's plot decrease from 3.20eV to 2.92eV with increase in doing. The measurement of photocatalytic properties of pure TiO2 and Ag-doped TiO2 nanoparticles showed that Ag-doped TiO2 degrades MB dye more efficiently than pure TiO2.

  5. Fabrication and photocatalytic activity of TiO2 derived nanotubes with Ag ions doping.

    PubMed

    Liu, Fang; Lai, Shuting; Huang, Peilin; Liu, Yingju; Xu, Yuehua; Fang, Yueping; Zhou, Wuyi

    2012-11-01

    Ag/TiO2 nanotubes with uniform distribution were successfully prepared by a hydrothermal-dipping method. The synthesized samples were characterized by XRD, TEM and FTIR, respectively. The results exhibited that the morphological structure of the TiO2 nanotubes was improved by the doping of Ag ions. The photocatalytic degradation experiment indicated that the photocatalytic activity of the Ag/TiO2 nanotubes indicated better photocatalytic activity than pure TiO2 nanotubes since silver was able to help the electron-hole separation by attracting photoelectrons. The optimal mol ration of TiO2 and AgNO3 was 25:1.

  6. Photocatalytic antibacterial performance of TiO2 and Ag-doped TiO2 against S. aureus. P. aeruginosa and E. coli.

    PubMed

    Gupta, Kiran; Singh, R P; Pandey, Ashutosh; Pandey, Anjana

    2013-01-01

    This paper reports the structural and optical properties and comparative photocatalytic activity of TiO2 and Ag-doped TiO2 nanoparticles against different bacterial strains under visible-light irradiation. The TiO2 and Ag-doped TiO2 photocatalysts were synthesized by acid catalyzed sol-gel technique and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis spectroscopy and photoluminescence (PL). The XRD pattern revealed that the annealed sample of TiO2 has both anatase and rutile phases while only an anatase phase was found in Ag-doped TiO2 nanoparticles. The decreased band-gap energy of Ag-doped TiO2 nanoparticles in comparison to TiO2 nanoparticles was investigated by UV-vis spectroscopy. The rate of recombination and transfer behaviour of the photoexcited electron-hole pairs in the semiconductors was recorded by photoluminescence. The antimicrobial activity of TiO2 and Ag-doped TiO2 nanoparticles (3% and 7%) was investigated against both gram positive (Staphylococcus aureus) and gram negative (Pseudomonas aeruginosa, Escherichia coli) bacteria. As a result, the viability of all three microorganisms was reduced to zero at 60 mg/30 mL culture in the case of both (3% and 7% doping) concentrations of Ag-doped TiO2 nanoparticles. Annealed TiO2 showed zero viability at 80 mg/30 mL whereas doped Ag-TiO2 7% showed zero viability at 40 mg/30 mL culture in the case of P. aeruginosa only.

  7. Effects of TiO2 coating dosage and operational parameters on a TiO2/Ag photocatalysis system for decolorizing Procion red MX-5B.

    PubMed

    Lin, Yu-Chih; Lee, Ho-Shan

    2010-07-15

    In this study, titanium dioxide (TiO(2)) powder was coated onto the surface of a dendritic silver (Ag) carrier to synthesize TiO(2)/Ag for decolorizing Procion red MX-5B (MX-5B), and related operation factors were also studied. The results showed that even without ultraviolet-A (UVA) irradiation, the Ag carrier from the TiO(2)/Ag catalyst had oxidizing ability, which could effectively degrade MX-5B color, but TiO(2) was ineffective. In addition, TiO(2) from TiO(2)/Ag demonstrated photocatalysis performance when irradiated, and the Ag carrier further showed an electron-scavenging ability to mitigate electron-hole pair recombination, which can improve the photocatalytic efficacy. With the oxidization and electron-scavenging ability of Ag and the photocatalysis ability of TiO(2), TiO(2)/Ag can decolor MX-5B more efficiently than TiO(2). The heavier Ag carrier also improves the solid-liquid separation of nano-TiO(2), making TiO(2)/Ag more suitable for application in slurry systems of photocatalytic water treatment. When the TiO(2)/Ag coating ratio was 50% by weight, there was a sufficient amount of TiO(2) on Ag's surface with a good distribution, and it exhibited a good photocatalysis decolorizing effect. In a study of how operational factors impact the decolorizing of MX-5B in the TiO(2)/Ag photocatalysis system with UVA irradiation (UVA-TiO(2)/Ag), the decolorization efficiency was optimal when the solution was maintained at pH 6.35. The addition of 0.01 M hydrogen peroxide (H(2)O(2)) aided the photocatalysis decolorization efficiency, although excessive H(2)O(2) reacted with hydroxyl free radicals and decreased the active groups in the system, thereby reducing the photocatalysis activity. An operating temperature of 40 degrees C was conducive to MX-5B decolorization, which was better than operating at room temperature.

  8. TiO2 nanowire and TiO2 nanowire doped Ag-PVP nanocomposite for antimicrobial and self-cleaning cotton textile.

    PubMed

    Hebeish, A A; Abdelhady, M M; Youssef, A M

    2013-01-16

    The TiO(2) nanowire (TiO(2) Nw) was successfully prepared via hydrothermal method through TiO(2) nanoparticle (TiO(2) Np). TiO(2) Np doped silver and TiO(2) Nw doped silver were prepared via photo-reducing Ag(+) ions to Ag metal on the TiO(2) Np or TiO(2) Nw surfaces. The prepared nanomaterials were evaluated using X-ray (XRD) diffraction pattern, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Bleached untreated cotton fabric and PVP treated cotton fabrics were coated with the synthesized nanomaterials using pad-dry-cure method. Photocatalytic activity of untreated and coated cotton fabrics with TiO(2) nanomaterials was investigated through the fabric self cleaning of MB dye stains. Also, the PVP finished cotton fabric modified by nanomaterials demonstrated antimicrobial activity against Gram positive bacteria, Gram negative bacteria and fungi. The mechanical properties of coated cotton fabric (tear strength, surface roughness, tensile strength and elongation at break) were examined.

  9. Both Enhanced Biocompatibility and Antibacterial Activity in Ag-Decorated TiO2 Nanotubes

    PubMed Central

    Lan, Ming-Ying; Liu, Chia-Pei; Huang, Her-Hsiung; Lee, Sheng-Wei

    2013-01-01

    In this study, Ag is electron-beam evaporated to modify the topography of anodic TiO2 nanotubes of different diameters to obtain an implant with enhanced antibacterial activity and biocompatibility. We found that highly hydrophilic as-grown TiO2 nanotubes became poorly hydrophilic with Ag incorporation; however they could effectively recover their wettability to some extent under ultraviolet light irradiation. The results obtained from antibacterial tests suggested that the Ag-decorated TiO2 nanotubes could greatly inhibit the growth of Staphylococcus aureus. In vitro biocompatibility evaluation indicated that fibroblast cells exhibited an obvious diameter-dependent behavior on both as-grown and Ag-decorated TiO2 nanotubes. Most importantly, of all samples, the smallest diameter (25-nm-diameter) Ag-decorated nanotubes exhibited the most obvious biological activity in promoting adhesion and proliferation of human fibroblasts, and this activity could be attributed to the highly irregular topography on a nanometric scale of the Ag-decorated nanotube surface. These experimental results demonstrate that by properly controlling the structural parameters of Ag-decorated TiO2 nanotubes, an implant surface can be produced that enhances biocompatibility and simultaneously boosts antibacterial activity. PMID:24124484

  10. Both enhanced biocompatibility and antibacterial activity in Ag-decorated TiO2 nanotubes.

    PubMed

    Lan, Ming-Ying; Liu, Chia-Pei; Huang, Her-Hsiung; Lee, Sheng-Wei

    2013-01-01

    In this study, Ag is electron-beam evaporated to modify the topography of anodic TiO2 nanotubes of different diameters to obtain an implant with enhanced antibacterial activity and biocompatibility. We found that highly hydrophilic as-grown TiO2 nanotubes became poorly hydrophilic with Ag incorporation; however they could effectively recover their wettability to some extent under ultraviolet light irradiation. The results obtained from antibacterial tests suggested that the Ag-decorated TiO2 nanotubes could greatly inhibit the growth of Staphylococcus aureus. In vitro biocompatibility evaluation indicated that fibroblast cells exhibited an obvious diameter-dependent behavior on both as-grown and Ag-decorated TiO2 nanotubes. Most importantly, of all samples, the smallest diameter (25-nm-diameter) Ag-decorated nanotubes exhibited the most obvious biological activity in promoting adhesion and proliferation of human fibroblasts, and this activity could be attributed to the highly irregular topography on a nanometric scale of the Ag-decorated nanotube surface. These experimental results demonstrate that by properly controlling the structural parameters of Ag-decorated TiO2 nanotubes, an implant surface can be produced that enhances biocompatibility and simultaneously boosts antibacterial activity.

  11. Tailoring of antibacterial Ag nanostructures on TiO2 nanotube layers by magnetron sputtering.

    PubMed

    Uhm, Soo-Hyuk; Song, Doo-Hoon; Kwon, Jae-Sung; Lee, Sang-Bae; Han, Jeon-Geon; Kim, Kyoung-Nam

    2014-04-01

    To reduce the incidence of postsurgical bacterial infection that may cause implantation failure at the implant-bone interface, surface treatment of titanium implants with antibiotic materials such as silver (Ag) has been proposed. The purpose of this work was to create TiO2 nanotubes using plasma electrolytic oxidation (PEO), followed by formation of an antibacterial Ag nanostructure coating on the TiO2 nanotube layer using a magnetron sputtering system. PEO was performed on commercially pure Ti sheets. The Ag nanostructure was added onto the resulting TiO2 nanotube using magnetron sputtering at varying deposition rates. Field emission scanning electron microscopy and transmission electron microscopy were used to characterize the surface, and Ag content on the TiO2 nanotube layer was analyzed by X-ray diffraction and X-ray photoelectron spectroscopy. Scanning probe microscopy for surface roughness and contact angle measurement were used to indirectly confirm enhanced TiO2 nanotube hydrophilicity. Antibacterial activity of Ag ions in solution was determined by inductively coupled plasma mass spectrometry and antibacterial testing against Staphylococcus aureus (S. aureus). In vitro, TiO2 nanotubes coated with sputtered Ag resulted in significantly reduced S. aureus. Cell viability assays showed no toxicity for the lowest sputtering time group in the osteoblastic cell line MC3T3-E1. These results suggest that a multinanostructured layer with a biocompatible TiO2 nanotube and antimicrobial Ag coating is a promising biomaterial that can be tailored with magnetron sputtering for optimal performance.

  12. The Synthesis of Ag-Doped Mesoporous TiO2

    SciTech Connect

    Li, Xiaohong S.; Fryxell, Glen E.; Wang, Chong M.; Engelhard, Mark H.

    2008-04-15

    Ag-doped mesoporous titanium oxide was prepared using non-ionic surfactants and easily handled titanium precursors, under mild reaction conditions. In contrast to the stabilizing effect of Cd-doping on mesoporous TiO2, Ag-doping was found to significantly destabilize the mesoporous structure.

  13. Fabrication of plasmonic AgBr/Ag nanoparticles-sensitized TiO2 nanotube arrays and their enhanced photo-conversion and photoelectrocatalytic properties

    NASA Astrophysics Data System (ADS)

    Wang, Qingyao; Qiao, Jianlei; Jin, Rencheng; Xu, Xiaohui; Gao, Shanmin

    2015-03-01

    Plasmonic photosensitizer AgBr/Ag nanospheres supported on TiO2 nanotube arrays (TiO2 NTs) are prepared by successive ionic layer adsorption and reaction (SILAR) technique followed by photoreduction methods. The structural and surface morphological properties of AgBr/Ag nanoparticles sensitized TiO2 NTs and their photoelectrochemical performance are investigated and discussed. A detailed formation mechanism of the TiO2 NTs/AgBr/Ag is proposed. The TiO2 NTs/AgBr/Ag exhibit excellent photocurrent and photoelectrocatalytic activities under visible light irradiation. Efficient utilization of solar energy to create electron-hole pairs is attributed to the significant visible light response and surface plasmon resonance of Ag nanoparticles. This finding indicates that the high photosensitivity of the TiO2 NTs-based surface plasmon resonance materials could be applied toward the development of new plasmonic visible-light-sensitive photovoltaic fuel cells and photocatalysts.

  14. Enhanced photocatalysis by coupling of anatase TiO2 film to triangular Ag nanoparticle island.

    PubMed

    Xu, Jinxia; Xiao, Xiangheng; Ren, Feng; Wu, Wei; Dai, Zhigao; Cai, Guangxu; Zhang, Shaofeng; Zhou, Juan; Mei, Fei; Jiang, Changzhong

    2012-01-01

    In order to overcome the low utilization ratio of solar light and high electron-hole pair recombination rate of TiO2, the triangular Ag nanoparticle island is covered on the surface of the TiO2 thin film. Enhancement of the photocatalytic activity of the Ag/TiO2 nanocomposite system is observed. The increase of electron-hole pair generation is caused by the enhanced near-field amplitudes of localized surface plasmon of the Ag nanoparticles. The efficiently suppressed recombination of electron-hole pair caused by the metal-semiconductor contact can also enhance the photocatalytic activity of the TiO2 film. PMID:22548875

  15. Enhanced photocatalysis by coupling of anatase TiO2 film to triangular Ag nanoparticle island

    PubMed Central

    2012-01-01

    In order to overcome the low utilization ratio of solar light and high electron-hole pair recombination rate of TiO2, the triangular Ag nanoparticle island is covered on the surface of the TiO2 thin film. Enhancement of the photocatalytic activity of the Ag/TiO2 nanocomposite system is observed. The increase of electron-hole pair generation is caused by the enhanced near-field amplitudes of localized surface plasmon of the Ag nanoparticles. The efficiently suppressed recombination of electron-hole pair caused by the metal-semiconductor contact can also enhance the photocatalytic activity of the TiO2 film. PMID:22548875

  16. Synthesis and characterization of Ag deposited TiO2 particles by laser ablation in water

    NASA Astrophysics Data System (ADS)

    Liu, C. H.; Hong, M. H.; Zhou, Y.; Chen, G. X.; Saw, M. M.; Hor, A. T. S.

    2007-12-01

    Ag deposited TiO2 (Ag/TiO2) particles were synthesized by laser ablation of silver and titanium targets in de-ionized (DI) water. Post-annealing makes the structure stable and the materials change to crystalline state. It is a new approach to form Ag/TiO2 particles with a simple system and non-toxic materials. TiO2 particles with size from 20 to 30 nm coated with silver nano-clusters were observed. The silver nano-clusters can enhance the absorption capability of TiO2 photocatalysts. UV-vis spectrum analysis shows that there is a strong absorption peak at around 400 nm. It is attributed to Ag nanoparticles surface plasmon resonance (SPR) effect. This effect helps to improve the spectral characteristics of TiO2 nanoparticles with its absorption spectra shifted to a longer wavelength region. From the above properties, Ag/TiO2 nanoparticles would have new potential applications in photocatalyst and photo-anode.

  17. Contact potential barriers and characterization of Ag-doped composite TiO2 nanotubes

    NASA Astrophysics Data System (ADS)

    Li, Jingling; Chen, Wenzhe; Yu, Hualiang; Wu, Bo; Huang, Wenbo; Wang, Mingxiu; Huang, Shizhen; Lin, Wei; Zhang, Likun; Li, Shiping

    2014-04-01

    Ag-doping TiO2 composite nanotubes (Ag-TNTs) were synthesized by alkaline fusion followed by hydrothermal treatment. The microstructure and morphology of the materials were characterized by XRD, TEM, XPS, SPS (surface photovoltage spectroscopy), FISPS (electric field-induced surface photovoltage spectroscopy) and Raman spectroscopy. First-principles calculations based on density-functional theory (DFT) showed the formation of several impurity levels near the top of the valence band in the band gap (Eg) of rutile TiO2 due to Ag doping. A "double junction" is proposed, involving a Schottky junction and p-n junction (denoted as "Ag-p-n junction") occurring between the Ag particles and the nanotube surface, as well as forming inside TiO2 nanotubes, respectively. The strongly built-in electric field of the junctions promotes the separation of photo-holes and photoelectrons, enhancing the photocatalytic efficiency. XRD results indicated that the composite Ag-TNTs exist as a mixture of anatase and rutile phases. XPS results showed that Ti4+ is the primary state of Ti. Raman spectral analysis of Ag-TNTs revealed the presence of a new peak at 271 cm-1. The red-shift of the absorption light wavelength of Ag-TNTs was 0.16 eV (20 nm) due to a considerable narrowing of Eg by the existing impurity levels.

  18. Controlled synthesis and photocatalysis of sea urchin-like Fe3O4@TiO2@Ag nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhao, Yilin; Tao, Chengran; Xiao, Gang; Wei, Guipeng; Li, Linghui; Liu, Changxia; Su, Haijia

    2016-02-01

    Based on the synergistic photocatalytic activities of nano-sized TiO2 and Ag, as well as the magnetic properties of Fe3O4, a sea urchin-like Fe3O4@TiO2@Ag nanocomposite (Fe3O4@TiO2@Ag NCs) is controllably synthesized with tunable cavity size, adjustable shell layer of TiO2 nanofiber, higher structural stability and larger specific surface area. Here, Fe3O4@TiO2@Ag NCs are obtained with Fe3O4 as the core and nanofiber TiO2/Fe3O4/Ag nanoheterojunctions as the shell; and Ag nanoparticles with diameter of approximately 4 nm are loaded both on TiO2 nanofibers and inside the cavities of sea urchin-like Fe3O4@TiO2 nanocomposites uniformly. Ag nanoparticles lead to the production of more photogenerated charges in the TiO2/Fe3O4/Ag heterojunction via LSPR absorption, and enhance the band-gap absorption of TiO2, while the Fe3O4 cocatalyst provides the active sites for oxygen reduction by the effective transfer of photogenerated electrons to oxygen. So the photocatalytic performance is improved due to the synergistic effect of TiO2/Fe3O4/Ag nanoheterojunctions. As photocatalysts under UV and visible irradiation, the as-synthesized nanocomposites display enhanced photocatalytic and recycling properties for the degradation of ampicillin. Moreover, they present better broad-spectrum antibiosis under visible irradiation. The enhanced photocatalytic activity and excellent chemical stability, in combination with the magnetic recyclability, makes this multifunctional nanostructure a promising candidate for antibiosis and remediation in aquatic environmental contamination in the future.Based on the synergistic photocatalytic activities of nano-sized TiO2 and Ag, as well as the magnetic properties of Fe3O4, a sea urchin-like Fe3O4@TiO2@Ag nanocomposite (Fe3O4@TiO2@Ag NCs) is controllably synthesized with tunable cavity size, adjustable shell layer of TiO2 nanofiber, higher structural stability and larger specific surface area. Here, Fe3O4@TiO2@Ag NCs are obtained with Fe3O4 as the

  19. Assessment of antimicrobial activity of nanosized Ag doped TiO(2) colloids.

    PubMed

    Yaşa, Ihsan; Lkhagvajav, Natsag; Koizhaiganova, Meruyert; Celik, Erdal; Sarı, Ozcan

    2012-07-01

    In the present research, the antimicrobial effects of nanosized silver (Ag) doped TiO(2) colloidal solutions prepared using a sol-gel technique were investigated. In order to determine the solution characteristics, the turbidity, viscosity and pH of the colloidal solutions were measured. Differential thermal analysis-thermogravimetry equipment was used to determine the chemical structures and reaction types of the films formed from these solutions. The morphology of Ag doped TiO(2) nanoparticles was evaluated by atomic force microscopy. The disc diffusion method was employed to explore antimicrobial activity, and the Broth Microdilution method was used to obtain MIC values of nanosized Ag doped TiO(2) colloidal solutions against the test microorganisms Escherichia coli, Staphylococcus aureus, Candida albicans, Bacillus subtilis, and Salmonella typhimurium. It was found that the silver doped TiO(2) nanoparticles inhibited the growth and multiplication of the test microorganisms, including the fungus C. albicans. Antimicrobial activity was observed against all tested microorganisms at a very low concentration of 1.125-2.81 μg/ml of nano silver in 1-25 % Ag-TiO(2) solutions.

  20. Antibacterial ability and osteogenic activity of porous Sr/Ag-containing TiO2 coatings.

    PubMed

    He, Xiaojing; Zhang, Xiangyu; Bai, Long; Hang, Ruiqiang; Huang, Xiaobo; Qin, Lin; Yao, Xiaohong; Tang, Bin

    2016-01-01

    Implant-associated infection and poor osseointegration remains a major clinical challenge in Ti-based implant materials. A versatile strategy to endow Ti-based implants with long-term antibacterial ability as well as better osteogenic activity is highly desirable for high quality implantation. Strontium (Sr) has been shown to be a significant element to favor bone growth by promoting new bone formation and inhibiting bone resorption. In this study, a novel duplex-treatment technique encompassing magnetron sputtering with micro-arc oxidation is utilized to fabricate porous Sr/Ag-containing TiO2 coatings loaded with different concentrations of Ag and Sr. All coatings are porous with pore size less than 5 µm. Ag is primarily distributed homogeneously inside the pores, and the concentrations of Ag in Sr/Ag-containing TiO2 coatings with low and high Ag contents are 0.40 at.% and 0.83 at.% respectively. We have demonstrated that this kind of coating displays long-lasting antibacterial ability even up to 28 d due to the incorporation of Ag. Further, Sr/Ag-containing TiO2 coatings with optimum Ag and Sr contents revealed good cytocompatibility, enhanced osteoblast spreading and osseointegration, which stemmed primarily from the synergistic effect exerted by the porous surface topography and the bioactive element Sr. However, this study has also identified, for the first time, that proper addition of Ag would further facilitate osteogenic effects. Besides, Sr may be able to alleviate the potential cytotoxic effect of excessive Ag. Thus, integration of optimum functional elements Ag and Sr into Ti-based implant materials would be expected to expedite osseointegration while simultaneously sustaining long-term antibacterial activity, which would provide new insights for relevant fundamental investigations and biomedical applications. PMID:27508428

  1. Preparation of magnetic Fe3O4/TiO2/Ag composite microspheres with enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Wu, Zheng; Chen, Liangwei; Zhang, Lianjie; Li, Xuelian; Xu, Haifeng; Wang, Hongyan; Zhu, Guang

    2016-02-01

    The novel three-component Fe3O4/TiO2/Ag composite mircospheres were prepared via a facile chemical deposition route. The Fe3O4/TiO2 mircospheres were first prepared by the solvothermal method, and then Ag nanoparticles were anchored onto the out-layer of TiO2 by the tyrosine-reduced method. The as-prepared magnetic Fe3O4/TiO2/Ag composite mircospheres were applied as photocatalysis for the photocatalytic degradation of methylene blue. The results indicate that the photocatalytic activity of Fe3O4/TiO2/Ag composite microspheres is superior to that of Fe3O4/TiO2 due to the dual effects of the enhanced light absorption and reduction of photoelectron-hole pair recombination in TiO2 with the introduction of Ag NPs. Moreover, these magnetic Fe3O4/TiO2/Ag composite microspheres can be completely removed from the dispersion with the help of magnetic separation and reused with little or no loss of catalytic activity.

  2. Ag-loaded TiO2/reduced graphene oxide nanocomposites for enhanced visible-light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Vasilaki, E.; Georgaki, I.; Vernardou, D.; Vamvakaki, M.; Katsarakis, N.

    2015-10-01

    In this work, Ag nanoparticles were loaded by chemical reduction onto TiO2 P25 under different loadings ranging from 1 up to 4 wt% and hydrothermally deposited on reduced graphene oxide sheets. Chemical reduction was determined to be an effective preparation approach for Ag attachment to titania, leading to the formation of small silver nanoparticles with an average diameter of 4.2 nm. The photocatalytic performance of the hybrid nanocomposite materials was evaluated via methylene blue (MB) dye removal under visible-light irradiation. The rate of dye decolorization was found to depend on the metal loading, showing an increase till a threshold value of 3 wt%, above which the rate drops. Next, the as prepared sample of TiO2/Ag of better photocatalytic response, i.e., at a 3 wt% loading value, was hydrothermally deposited on a platform of reduced graphene oxide (rGO) of tunable content (mass ratio). TiO2/Ag/rGO coupled nanocomposite presented significantly enhanced photocatalytic activity compared to the TiO2/Ag, TiO2/rGO composites and bare P25 titania semiconductor photocatalysts. In particular, after 45 min of irradiation almost complete decolorization of the dye was observed for the TiO2/Ag/rGO nanocatalyst, while the respective removal efficiency was 92% for TiO2/Ag, 93% for TiO2/rGO and only 80% for the bare TiO2 nanoparticles. This simple step by step preparation strategy allows for optimum exploitation of the advanced properties of metal plasmonic effect and reduced graphene oxide as the critical host for boosting the overall photocatalytic activity towards visible-light.

  3. Ag@helical chiral TiO2 nanofibers for visible light photocatalytic degradation of 17α-ethinylestradiol.

    PubMed

    Zhang, Chi; Li, Yi; Wang, Dawei; Zhang, Wenlong; Wang, Qing; Wang, Yuming; Wang, Peifang

    2015-07-01

    Ag-modified helical chiral TiO2 NFs (Ag@chiral TiO2 NFs) were fabricated and characterized by ultraviolet-visible absorption spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. This novel material exhibited efficient photocatalytic activity for the degradation of 17α-ethinylestradiol (EE2) in water under visible light irradiation with an optimum size of deposited silver nanoparticles (Ag NPs) in the range of 12 ∼ 14 nm. The pseudo-first-order rate constant (k obs) for EE2 photodegradation by Ag@chiral TiO2 NFs increased by up to a factor of 20.1 when compared with that of pure chiral TiO2 NFs. The high photocatalytic activity can be attributed to the interactions between helical chiral TiO2 NFs and surface plasmon resonance effect of Ag NPs. The new catalyst retains its photocatalytic activity at least up to five consecutive cycles. The results clearly demonstrate the feasibility of using Ag@chiral TiO2 NFs for the photocatalytic removal of EE2 and other endocrine-disrupting chemicals from water. PMID:25721529

  4. Synthesis and visible light photoactivity of anatase Ag, and garlic loaded TiO2 nanocrystalline catalyst

    EPA Science Inventory

    An excellent visible light activated Ag and S doped TiO2 nanocatalyst was prepared by using AgNO3 and garlic (Allium sativum) as Ag+ and sulfur sources, respectively. The catalyst resisted the change from anatase to rutile phase even at calcination at 700 oC. The photocatalytic e...

  5. Controlled synthesis of Ag-coated TiO2 nanofibers and their enhanced effect in photocatalytic applications

    NASA Astrophysics Data System (ADS)

    Guan, Hongyu; Wang, Xiaohong; Guo, Yihang; Shao, Changlu; Zhang, Xintong; Liu, Yichun; Louh, Rong-Fuh

    2013-09-01

    Novel nanostructured Ag/TiO2 hybrid nanofibers (NFs) have been successfully prepared via a simple electrospinning process combined with silver mirror reaction. The Ag/TiO2 NFs demonstrated a unique morphology with evenly distributed Ag nanoparticles uniformly deposited onto the surface of each individual TiO2 NFs. The loading capacity and size of Ag NPs can be easily controlled by varying the silver mirror reaction time. Compared with pristine TiO2 NFs, such heterogeneous Ag/TiO2 nanocomposites exhibited preferable photocatalytic activity during photocatalytic degradation of rhodamine-B under the simulated sunlight irradiation and this enhanced photocatalytic performance was driven by combination and interaction between TiO2 and Ag NPs.

  6. Antibacterial Activity of As-Annealed TiO2 Nanotubes Doped with Ag Nanoparticles against Periodontal Pathogens.

    PubMed

    Yeniyol, Sinem; He, Zhiming; Yüksel, Behiye; Boylan, Robert Joseph; Urgen, Mustafa; Ozdemir, Tayfun; Ricci, John Lawrence

    2014-01-01

    It is important to develop functional transmucosal implant surfaces that reduce the number of initially adhering bacteria and they need to be modified to improve the anti-bacterial performance. Commercially pure Ti sheets were anodized in an electrolyte containing ethylene glycol, distilled water and ammonium fluoride at room temperature to produce TiO2 nanotubes. These structures were then annealed at 450°C to transform them to anatase. As-annealed TiO2 nanotubes were then treated in an electrolyte containing 80.7 g/L NiSO4 ·7H2O, 41 g/L MgSO4 ·7H2O, 45 g/L H3BO3, and 1.44 g/L Ag2SO4 at 20°C by the application of 9 V AC voltage for doping them with silver. As-annealed TiO2 nanotubes and as-annealed Ag doped TiO2 nanotubes were evaluated by SEM, FESEM, and XRD. Antibacterial activity was assessed by determining the adherence of A. actinomycetemcomitans, T. forsythia, and C. rectus to the surface of the nanotubes. Bacterial morphology was examined using an SEM. As-annealed Ag doped TiO2 nanotubes revealed intense peak of Ag. Bacterial death against the as-annealed Ag doped TiO2 nanotubes were detected against A. actinomycetemcomitans, T. forsythia, and C. rectus indicating antibacterial efficacy.

  7. Reduced graphene oxide and Ag wrapped TiO2 photocatalyst for enhanced visible light photocatalysis

    NASA Astrophysics Data System (ADS)

    Leong, Kah Hon; Sim, Lan Ching; Bahnemann, Detlef; Jang, Min; Ibrahim, Shaliza; Saravanan, Pichiah

    2015-10-01

    A well-organised reduced graphene oxide (RGO) and silver (Ag) wrapped TiO2 nano-hybrid was successfully achieved through a facile and easy route. The inherent characteristics of the synthesized RGO-Ag/TiO2 were revealed through crystalline phase, morphology, chemical composition, Raman scattering, UV-visible absorption, and photoluminescence analyses. The adopted synthesis route significantly controlled the uniform formation of silver nanoparticles and contributed for the absorption of light in the visible spectrum through localized surface plasmon resonance effects. The wrapped RGO nanosheets triggered the electron mobility and promoted visible light shift towards red spectrum. The accomplishment of synergised effect of RGO and Ag well degraded Bisphenol A under visible light irradiation with a removal efficiency of 61.9%.

  8. Photocatalytic comparison of Cu- and Ag-doped TiO2/GF for bioaerosol disinfection under visible light

    NASA Astrophysics Data System (ADS)

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2015-12-01

    Photocatalysts, TiO2/glass fiber (TiO2/GF), Cu-doped TiO2/glass fiber (Cu-TiO2/GF) and Ag-doped TiO2/glass fiber (Ag-TiO2/GF), were synthesized by a sol-gel method. They were then used to disinfect Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in bioaerosols under visible light irradiation. TiO2/GF did not show any significant disinfection effect. Both Cu and Ag acted as intermediate agents to enhance separation efficiency of electron-hole pairs of TiO2, leading to improved photocatalytic activity of Cu-TiO2/GF and Ag-TiO2/GF under visible light. Cu in Cu-TiO2/GF acted as a defective agent, increasing the internal quantum efficiency of TiO2, while Ag in Ag-TiO2/GF acted as a sensitive agent, enhancing the transfer efficiency of the electrons generated. The highest disinfection efficiencies of E. coli and S. aureus by Cu-TiO2/GF were 84.85% and 65.21%, respectively. The highest disinfection efficiencies of E. coli and S. aureus by Ag-TiO2/GF were 94.46% and 73.12%, respectively. Among three humidity conditions - 40±5% (dry), 60±5% (moderate), and 80±5% (humid) - the moderate humidity condition showed the highest disinfection efficiency for both E. coli and S. aureus. This study also showed that a Gram-negative bacterium (E. coli) were more readily disinfected by the photocatalysts than a Gram-positive bacterium (S. aureus).

  9. Enhanced visible-light photocatalytic performances of Ag3PO4 surface-modified with small amounts of TiO2 and Ag

    NASA Astrophysics Data System (ADS)

    Wang, Desong; Li, Lei; Luo, Qingzhi; An, Jing; Li, Xueyan; Yin, Rong; Zhao, Mangmang

    2014-12-01

    A novel approach has been developed to prepare an efficient visible-light photocatalyst using Ag3PO4 and TiO2 sol as precursors. First, Ag3PO4 particles were dipped into TiO2 sol for 5 min and were filtered quickly. Second, Ag3PO4 particles adsorbing a small amount of TiO2 sol were aged for 24 h to form TiO2 gel on their surface. Finally, Ag3PO4 particles covered by TiO2 gel were calcined at 450 °C for 2 h to obtain the surface-modified Ag3PO4 sample. The surface-modified Ag3PO4 was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, UV-vis diffuse reflection spectroscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. The visible-light photocatalytic performances of the surface-modified Ag3PO4 were evaluated by the photodegradation of methyl orange or phenol solution. The results showed that the surface-modified Ag3PO4 exhibited much higher visible-light photocatalytic activity and stability than pure Ag3PO4. As the amount of TiO2 gel on the Ag3PO4 surface increased, the visible-light photocatalytic activity increased first and then decreased. The surface-modification of Ag3PO4 obviously decreased its solubility in water environment due to the protection of TiO2 and Ag nanocrystals on the surface. The visible-light photocatalytic mechanism of the surface-modified Ag3PO4 has been discussed.

  10. Chemical assembly of TiO2 and TiO2@Ag nanoparticles on silk fiber to produce multifunctional fabrics.

    PubMed

    Li, Guohong; Liu, Hong; Zhao, Hongshi; Gao, Yuqiang; Wang, Jiyang; Jiang, Huaidong; Boughton, R I

    2011-06-01

    A carefully designed surface modification technique for the manufacture of multifunctional silk textile nanocomposite materials is successfully developed by the functionalization of silk with TiO(2) and TiO(2)@Ag nanoparticles (NPs). The NPs are assembled onto a silk substrate through covalent linkages, including enediol ligand-metal oxide bonding, resin dehydration and the acylation of silk. Owing to the strong chemical bonding, silk fibroin fabric (SFF) and the NPs form a stable composite system. The functionalized SFF, especially TiO(2)@Ag NP-functionalized SFF are endowed with remarkable UV protection properties, and an efficient anti-bacterial capability toward Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Furthermore, the nearly total photodegradation of methylene orange (MO) under UV illumination illustrates that functionalized SFF possesses high photocatalytic and self-cleaning capability. This multifunctional silk material satisfies the market demand for natural "smart" products, and is a promising practical material for use in the textile industry, hospital sterilization and environmental cleanup. PMID:21419419

  11. Understanding the dispersion of Ag on high surface area TiO2 supports using XPS intensity ratios

    NASA Astrophysics Data System (ADS)

    Davis, Zenda D.; Tatarchuk, Bruce J.

    2015-10-01

    Silver-titania (Ag/TiO2) adsorbents, in the range of 4 wt% Ag, display high selectivity toward sulfur heterocyclic compounds from complex fuel streams containing other aromatics. An experimental investigation of Ag on TiO2 has been undertaken to understand the state of dispersion and growth of Ag. XPS is one of the more promising characterization tools for the state of dispersion. Silver loading from 1 wt% to 20 wt% on 150 m2/g titania was investigated. Ag/Ti intensity ratios increased linearly with Ag content up to 4 wt% and increased less significantly thereafter from 8 wt% to 20 wt% indicating nucleation and growth of Ag crystallites. Inelastic mean free path (IMFP) calculations were used to estimate Ag crystallite size based on the attenuation of the Ag signal, realizing in this regime there is insufficient Ag to attenuate background titania. At 4, 8, 12, and 20 wt% the estimated average crystallite sizes were 0.35, 0.71, 0.84, and 1.11 nm respectively. Ag loadings up to 4 wt% were present in the form of Ag+1 adatoms presumably occupying TiO2 surface defects. Saturation of surface TiO2 defects is in good agreement with quantitative sulfur heterocycle adsorption.

  12. Preparation of Ag deposited TiO2 (Ag/TiO2) composites and investigation on visible-light photocatalytic degradation activity in magnetic field

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Ma, C. H.; Wang, J.; Li, S. G.; Li, Y.

    2014-12-01

    In this study, Ag deposited TiO2 (Ag/TiO2) composites were prepared by three different methods (Ultraviolet Irradiation Deposition (UID), Vitamin C Reduction (VCR) and Sodium Borohydride Reduction (SBR)) for the visible-light photocatalytic degradation of organic dyes in magnetic field. And then the prepared Ag deposited TiO2 (Ag/TiO2) composites were characterized physically by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The visible-light photocatalytic activities of these three kinds of Ag deposited TiO2 (Ag/TiO2) composites were examined and compared through the degradation of several organic dyes under visible-light irradiation in magnetic field. In addition, some influence factors such as visible-light irradiation time, organic dye concentration, revolution speed, magnetic field intensity and organic dye kind on the visible-light photocatalytic activity of Ag deposited TiO2 (Ag/TiO2) composite were reviewed. The research results showed that the presence of magnetic field significantly enhanced the visible-light photocatalytic activity of Ag deposited TiO2 (Ag/TiO2) composites and then contributed to the degradation of organic dyes.

  13. Effects of TiO2 and Ag nanoparticles on polyhydroxybutyrate biosynthesis by activated sludge bacteria.

    PubMed

    Priester, John H; Van De Werfhorst, Laurie C; Ge, Yuan; Adeleye, Adeyemi S; Tomar, Shivira; Tom, Lauren M; Piceno, Yvette M; Andersen, Gary L; Holden, Patricia A

    2014-12-16

    Manufactured nanomaterials (MNMs) are increasingly incorporated into consumer products that are disposed into sewage. In wastewater treatment, MNMs adsorb to activated sludge biomass where they may impact biological wastewater treatment performance, including nutrient removal. Here, we studied MNM effects on bacterial polyhydroxyalkanoate (PHA), specifically polyhydroxybutyrate (PHB), biosynthesis because of its importance to enhanced biological phosphorus (P) removal (EBPR). Activated sludge was sampled from an anoxic selector of a municipal wastewater treatment plant (WWTP), and PHB-containing bacteria were concentrated by density gradient centrifugation. After starvation to decrease intracellular PHB stores, bacteria were nutritionally augmented to promote PHB biosynthesis while being exposed to either MNMs (TiO2 or Ag) or to Ag salts (each at a concentration of 5 mg L(-1)). Cellular PHB concentration and PhyloChip community composition were analyzed. The final bacterial community composition differed from activated sludge, demonstrating that laboratory enrichment was selective. Still, PHB was synthesized to near-activated sludge levels. Ag salts altered final bacterial communities, although MNMs did not. PHB biosynthesis was diminished with Ag (salt or MNMs), indicating the potential for Ag-MNMs to physiologically impact EBPR through the effects of dissolved Ag ions on PHB producers. PMID:25409530

  14. Removal of 4-Nitrophenol from Water Using Ag-N-P-Tridoped TiO2 by Photocatalytic Oxidation Technique.

    PubMed

    Achamo, Temesgen; Yadav, O P

    2016-01-01

    Photocatalytic oxidation using semiconductor nanoparticles is an efficient, eco-friendly, and cost-effective process for the removal of organic pollutants, such as dyes, pesticides, phenols, and their derivatives in water. In the present study, nanosize Ag-N-P-tridoped titanium(IV) oxide (TiO2) was prepared by using sol-gel-synthesized Ag-doped TiO2 and soybean (Glycine max) or chickpea (Cicer arietinum) seeds as nonmetallic bioprecursors. As-synthesized photocatalysts were characterized using X-ray diffraction, Fourier transform infrared, and ultra violet (UV)-visible spectroscopic techniques. Average crystallite size of the studied photocatalysts was within 39-46 nm. Whereas doped Ag in TiO2 minimized the photogenerated electron-hole recombination, doped N and P extended its photoabsorption edge to visible region. Tridoping of Ag, N, and P in TiO2 exhibited synergetic effect toward enhancing its photocatalytic degradation of 4-nitrophenol (4-NP), separately, under UV and visible irradiations. At three hours, degradations of 4-NP over Ag-N-P-tridoped TiO2 under UV and visible radiations were 73.8 and 98.1%, respectively.

  15. Removal of 4-Nitrophenol from Water Using Ag-N-P-Tridoped TiO2 by Photocatalytic Oxidation Technique.

    PubMed

    Achamo, Temesgen; Yadav, O P

    2016-01-01

    Photocatalytic oxidation using semiconductor nanoparticles is an efficient, eco-friendly, and cost-effective process for the removal of organic pollutants, such as dyes, pesticides, phenols, and their derivatives in water. In the present study, nanosize Ag-N-P-tridoped titanium(IV) oxide (TiO2) was prepared by using sol-gel-synthesized Ag-doped TiO2 and soybean (Glycine max) or chickpea (Cicer arietinum) seeds as nonmetallic bioprecursors. As-synthesized photocatalysts were characterized using X-ray diffraction, Fourier transform infrared, and ultra violet (UV)-visible spectroscopic techniques. Average crystallite size of the studied photocatalysts was within 39-46 nm. Whereas doped Ag in TiO2 minimized the photogenerated electron-hole recombination, doped N and P extended its photoabsorption edge to visible region. Tridoping of Ag, N, and P in TiO2 exhibited synergetic effect toward enhancing its photocatalytic degradation of 4-nitrophenol (4-NP), separately, under UV and visible irradiations. At three hours, degradations of 4-NP over Ag-N-P-tridoped TiO2 under UV and visible radiations were 73.8 and 98.1%, respectively. PMID:27081309

  16. Photocatalytic antibacterial effect of TiO(2) film formed on Ti and TiAg exposed to Lactobacillus acidophilus.

    PubMed

    Choi, Jung-Yoon; Kim, Kyung-Ho; Choy, Kwang-Chul; Oh, Keun-Taek; Kim, Kyoung-Nam

    2007-02-01

    When irradiated under near-ultraviolet (UV) light, TiO(2) exhibits strong bactericidal activity. The TiO(2) photocatalyst would be effective on orthodontic appliances after its antibacterial effect on the carcinogenic microorganism Lactobacillus acidophilus is evaluated. To compare the antibacterial effect of two crystalline forms of TiO(2), rutile and anatase, thermal oxidation and anodic oxidation were employed to form each structure, respectively. The antibacterial effect of TiO(2) film on TiAg was also compared with that on Ti. Bacterial solutions were pipetted onto the TiO(2)-coated specimen and illuminated with UVA (2 x 15 W, black light, 356 nm) up to 100 min and the reaction solutions were incubated to count the colony-forming units. The antibacterial activity of the coated specimens was similar to that of the uncoated group. The antibacterial activity of the coated specimens of TiAg was not different from that of Ti. TiO(2) coatings formed on both Ti and TiAg specimens did not exhibit cytotoxicity on the L-929 cells of mice. PMID:16850466

  17. Sequential laser and ultrasonic wave generation of TiO2@Ag core-shell nanoparticles and their anti-bacterial properties.

    PubMed

    Hamad, Abubaker Hassan; Li, Lin; Liu, Zhu; Zhong, Xiang Li; Wang, Tao

    2016-02-01

    Core-shell nanoparticles have unusual physical, chemical and biological properties. Until now, for the Ag and TiO2 combination, only Ag core and TiO2 shell nanoparticles have been practically demonstrated. In this investigation, novel TiO2@Ag core-shell (TiO2 core and Ag shell) nanoparticles were produced via ultrasonic vibration of Ag-TiO2 compound nanoparticles. A bulk Ti/Ag alloy plate was used to generate colloidal Ag-TiO2 compound nanoparticles via picosecond laser ablation in deionised water. The colloidal nanoparticles were then sonicated in an ultrasonic bath to generate TiO2@Ag core-shell nanoparticles. They were characterised using a UV-VIS spectrometer, transmission electron microscopy (TEM), high-angle annular dark-field-Scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The Ag-TiO2 compound and the TiO2@Ag core-shell nanoparticles were examined for their antibacterial activity against Escherichia coli (E. coli) JM109 strain bacteria and compared with those of Ag and TiO2 nanoparticles. The antibacterial activity of the core-shell nanoparticles was slightly better than that of the compound nanoparticles at the same concentration under standard laboratory light conditions and both were better than the TiO2 nanoparticles but not as good as the Ag nanoparticles.

  18. Towards TiO2sbnd Ag porous nanocomposites based SERS sensors for chemical pollutant detection

    NASA Astrophysics Data System (ADS)

    Iancu, Vlad; Baia, Lucian; Tarcea, Nicolae; Popp, Jürgen; Baia, Monica

    2014-09-01

    Since the TiO2 environmental friendly character and the affinity of a large variety of molecules to bind to the silver surfaces are well-known, novel porous nanoarchitectures based on TiO2 aerogel and Ag colloidal particles deposited on a poly(methyl methacrylate) (PMMA) substrate were obtained. The ability of the deposited porous structures to detect by surface-enhanced Raman spectroscopy (SERS) contaminant species adsorbed from aqueous media was tested. The morphological particularities of the bulk samples during the deposition on the PMMA substrates were preserved. The SERS detection efficiency was assessed by using congo red as a test molecule. No matter the average size of the Ag nanoparticles, the lowest detectable concentrations were found be of around 5 × 10-6 M for all samples. The morphological parameters such as median pore diameter and cumulative pore volume were also taken into consideration when discussing the detection performances. Moreover, calibration curves have been obtained in order to estimate an unknown concentration of the analyte. The obtained results show the real potential of the prepared porous composites for further use in the development of new SERS-based sensors for monitoring of water quality, especially when the contaminants are dye molecules.

  19. Contributions of Ag Nanowires to the Photoelectric Conversion Efficiency Enhancement of TiO2 Dye-Sensitized Solar Cells.

    PubMed

    Liu, Yunyu; She, Guangwei; Qi, Xiaopeng; Mu, Lixuan; Wang, Xuesong; Shi, Wensheng

    2015-09-01

    Ag nanowires (AgNWs) were employed in mesoporous TiO2 dye-sensitized solar cells (DSSCs) to enhance the photoelectric conversion efficiency (PCE). The possible reasons for PCE improvement, i.e., improvement in electron transport and light harvesting due to light scattering and plasmonic resonance effect of AgNWs are investigated. Electrochemical impedance spectra (EIS) study proved that addition of AgNWs can enhance the conductivity of TiO2 thin film photoanode, which is an important reason for the increase of photocurrent. Furthermore, through the comparison experiments as well as the UV-Vis absorption and IPCE characterization, contributions of the light scattering and plasmonic resonance effect to the enhancement of light harvest, and thus PCE of the DSSCs were demonstrated. It was found that fast electron transport of AgNWs played more important role for the PCE improvement than the light harvest enhancement due to light scattering and plasmonic effect. Based on these investigations, the AgNWs modified TiO2 thin film DSSCs were optimized. After integrating AgNWs into the photoanode, the photocurrent increased significantly and PCE increased -50% comparing with the pure TiO2-based DSSCs.

  20. Contributions of Ag Nanowires to the Photoelectric Conversion Efficiency Enhancement of TiO2 Dye-Sensitized Solar Cells.

    PubMed

    Liu, Yunyu; She, Guangwei; Qi, Xiaopeng; Mu, Lixuan; Wang, Xuesong; Shi, Wensheng

    2015-09-01

    Ag nanowires (AgNWs) were employed in mesoporous TiO2 dye-sensitized solar cells (DSSCs) to enhance the photoelectric conversion efficiency (PCE). The possible reasons for PCE improvement, i.e., improvement in electron transport and light harvesting due to light scattering and plasmonic resonance effect of AgNWs are investigated. Electrochemical impedance spectra (EIS) study proved that addition of AgNWs can enhance the conductivity of TiO2 thin film photoanode, which is an important reason for the increase of photocurrent. Furthermore, through the comparison experiments as well as the UV-Vis absorption and IPCE characterization, contributions of the light scattering and plasmonic resonance effect to the enhancement of light harvest, and thus PCE of the DSSCs were demonstrated. It was found that fast electron transport of AgNWs played more important role for the PCE improvement than the light harvest enhancement due to light scattering and plasmonic effect. Based on these investigations, the AgNWs modified TiO2 thin film DSSCs were optimized. After integrating AgNWs into the photoanode, the photocurrent increased significantly and PCE increased -50% comparing with the pure TiO2-based DSSCs. PMID:26716285

  1. Synthesis of Ag-decorated porous TiO2 nanowires through a sunlight induced reduction method and its enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Yao, Yun-Chang; Dai, Xin-Rong; Hu, Xiao-Ye; Huang, Su-Zhen; Jin, Zhen

    2016-11-01

    In this work, Ag-decorated porous TiO2 nanowires were successfully synthesized via a facile and low-cost sunlight induced reduction method. The cooperation of sunlight irradiation and ethanol reduction results the formation and decoration of the Ag nanoparticles on the porous TiO2 nanowires. The structure of the Ag-decorated porous TiO2 nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Energy dispersive spectroscopy (EDS) measurements. It can be seen that the Ag nanoparticles are well dispersed within the porous TiO2 nanowires. The as-prepared Ag-decorated porous TiO2 nanowires exhibits excellent photocatalytic properties. The photocatalytic tests show that 10 ppm methylene blue can be photodegraded within 60 min. And the photodegradation ratio of the Ag-decorated porous TiO2 nanowires much higher than that of P25 and porous TiO2 nanowires. Moreover, the Ag-decorated porous TiO2 nanowires also reveal good photocatalytic activity towards to other organic pollutions, such as phenol and R6G. Therefore, it is believed that the Ag-decorated porous TiO2 nanowires can be used as a potential high performance photocatalyst in wastewater treatment.

  2. Effective passivation of Ag nanowire-based flexible transparent conducting electrode by TiO2 nanoshell

    NASA Astrophysics Data System (ADS)

    Lee, Dong Geon; Lee, Dongjun; Yoo, Jin Sun; Lee, Sangwook; Jung, Hyun Suk

    2016-08-01

    Silver nanowire-based flexible transparent electrodes have critical problem, in spite of their excellent electrical and optical properties, that the electrical conductance and transparency degrade within several days in air because of oxidation of silver. To prevent the degradation of the silver nanowire, we encapsulated Ag-NWs with thin TiO2 barrier. Bar-coated silver nanowires on flexible polymer substrate were laminated at 120 °C, followed by atomic layer deposition of TiO2 nanoshell. With 20 nm of TiO2 nanoshells on silver nanowires, the transparent electrode keeps its electrical and optical properties over 2 months. Moreover, the TiO2-encapsulated silver nanowire-based transparent electrodes exhibit excellent bending durability.

  3. Preparation and use of photocatalytically active segmented Ag|ZnO and coaxial TiO2-Ag nanowires made by templated electrodeposition.

    PubMed

    Maijenburg, A Wouter; Rodijk, Eddy J B; Maas, Michiel G; Ten Elshof, Johan E

    2014-05-02

    Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and reduction half reactions, and fast electron (hole) diffusion and charge separation. Nanowires present suitable architectures to meet these requirements. Axially segmented Ag|ZnO and radially segmented (coaxial) TiO2-Ag nanowires with a diameter of 200 nm and a length of 6-20 µm were made by templated electrodeposition within the pores of polycarbonate track-etched (PCTE) or anodized aluminum oxide (AAO) membranes, respectively. In the photocatalytic experiments, the ZnO and TiO2 phases acted as photoanodes, and Ag as cathode. No external circuit is needed to connect both electrodes, which is a key advantage over conventional photo-electrochemical cells. For making segmented Ag|ZnO nanowires, the Ag salt electrolyte was replaced after formation of the Ag segment to form a ZnO segment attached to the Ag segment. For making coaxial TiO2-Ag nanowires, a TiO2 gel was first formed by the electrochemically induced sol-gel method. Drying and thermal annealing of the as-formed TiO2 gel resulted in the formation of crystalline TiO2 nanotubes. A subsequent Ag electrodeposition step inside the TiO2 nanotubes resulted in formation of coaxial TiO2-Ag nanowires. Due to the combination of an n-type semiconductor (ZnO or TiO2) and a metal (Ag) within the same nanowire, a Schottky barrier was created at the interface between the phases. To demonstrate the photocatalytic activity of these nanowires, the Ag|ZnO nanowires were used in a photocatalytic experiment in which H2 gas was detected upon UV illumination of the nanowires dispersed in a methanol/water mixture. After 17 min of illumination, approximately 0.2 vol% H2 gas was detected from a suspension of ~0.1 g of Ag|ZnO nanowires in a 50 ml 80 vol% aqueous methanol solution.

  4. Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

    PubMed Central

    Maijenburg, A. Wouter; Rodijk, Eddy J.B.; Maas, Michiel G.; ten Elshof, Johan E.

    2014-01-01

    Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and reduction half reactions, and fast electron (hole) diffusion and charge separation. Nanowires present suitable architectures to meet these requirements. Axially segmented Ag|ZnO and radially segmented (coaxial) TiO2-Ag nanowires with a diameter of 200 nm and a length of 6-20 µm were made by templated electrodeposition within the pores of polycarbonate track-etched (PCTE) or anodized aluminum oxide (AAO) membranes, respectively. In the photocatalytic experiments, the ZnO and TiO2 phases acted as photoanodes, and Ag as cathode. No external circuit is needed to connect both electrodes, which is a key advantage over conventional photo-electrochemical cells. For making segmented Ag|ZnO nanowires, the Ag salt electrolyte was replaced after formation of the Ag segment to form a ZnO segment attached to the Ag segment. For making coaxial TiO2-Ag nanowires, a TiO2 gel was first formed by the electrochemically induced sol-gel method. Drying and thermal annealing of the as-formed TiO2 gel resulted in the formation of crystalline TiO2 nanotubes. A subsequent Ag electrodeposition step inside the TiO2 nanotubes resulted in formation of coaxial TiO2-Ag nanowires. Due to the combination of an n-type semiconductor (ZnO or TiO2) and a metal (Ag) within the same nanowire, a Schottky barrier was created at the interface between the phases. To demonstrate the photocatalytic activity of these nanowires, the Ag|ZnO nanowires were used in a photocatalytic experiment in which H2 gas was detected upon UV illumination of the nanowires dispersed in a methanol/water mixture. After 17 min of illumination, approximately 0.2 vol% H2 gas was detected from a suspension of ~0.1 g of Ag|ZnO nanowires in a 50 ml 80 vol% aqueous methanol solution. PMID:24837535

  5. Highly active Ag clusters stabilized on TiO2 nanocrystals for catalytic reduction of p-nitrophenol

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Zhao, Zhe; Ou, Dingrong; Tu, Baofeng; Cui, Daan; Wei, Xuming; Cheng, Mojie

    2016-11-01

    Ag/TiO2 nanocomposites comprising of Ag clusters on TiO2 nanocrystal surfaces are of great significance in catalysts and advanced functional materials. Herein a novel method to synthesize Ag/TiO2 nanocomposites with Ag clusters under 2 nm on TiO2 nanocrystal surfaces have been developed. The success of this method relies on a silver mirror reaction in toluene, which refers to the reduction of silver-dodecylamine complexes by acetaldehyde in the presence of mono-dispersed TiO2 nanocrystals. The prepared Ag/TiO2 nanocomposites have been characterized by FT-IR spectra, UV-vis absorption spectra, X-ray diffraction (XRD) analysis, ultra high resolution scanning electron microscope (Ultra-HRSEM), high resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectra (XPS). Catalytic activity of Ag/TiO2 nanocomposites is evaluated for the reduction of p-nitrophenol (4-NP) into p-aminophenol (4-AP) by NaBH4. Results demonstrate that Ag/TiO2 nanocomposites have shown an outstanding catalytic activity as well as a good stability in successive reduction of 4-NP. Noticeably, TOF of Ag/TiO2-0.75 nanocomposites obtained in this work is the highest among Ag based catalysts previously reported.

  6. Synthesis and characterization of high photocatalytic activity and stable Ag3PO4/TiO2 fibers for photocatalytic degradation of black liquor

    NASA Astrophysics Data System (ADS)

    Cai, Li; Long, Qiyi; Yin, Chao

    2014-11-01

    The TiO2 fiber was prepared by using cotton fiber as a template, and then Ag3PO4/TiO2 fibers were synthesized via in situ Ag3PO4 particles onto the surface of TiO2 fiber. Their structure and physical properties were characterized by means of scanning electron microscopy (SEM), specific surface analyzer, X-ray diffraction (XRD), UV-vis absorption spectra and photoluminescence spectra (PL). SEM analysis indicated that the well-defined surface morphology of natural cotton fiber was mostly preserved in TiO2 and Ag3PO4/TiO2 fibers. Compared with TiO2 fiber, the absorbance wavelengths of Ag3PO4/TiO2 fibers were apparently red shifted and the PL intensities revealed a significant decrease. By using the photocatalytic degradation of black liquor as a model reaction, the visible light and ultraviolet light catalytic efficiencies of TiO2, Ag3PO4 and Ag3PO4/TiO2 fibers were evaluated. The reaction results showed that Ag3PO4/TiO2 fibers had stronger photocatalytic activity and excellent chemical stability in repeated and long-term applications. Therefore, the prepared Ag3PO4/TiO2 fibers could act as an efficient catalyst for the photocatalytic degradation of black liquor, which suggested their promising applications. It was proposed that the •OH radicals played the leading role in the photocatalytic degradation of the black liquor by Ag3PO4/TiO2 fibers system.

  7. Antibacterial Activity of As-Annealed TiO2 Nanotubes Doped with Ag Nanoparticles against Periodontal Pathogens

    PubMed Central

    Yeniyol, Sinem; He, Zhiming; Yüksel, Behiye; Boylan, Robert Joseph; Ürgen, Mustafa; Özdemir, Tayfun; Ricci, John Lawrence

    2014-01-01

    It is important to develop functional transmucosal implant surfaces that reduce the number of initially adhering bacteria and they need to be modified to improve the anti-bacterial performance. Commercially pure Ti sheets were anodized in an electrolyte containing ethylene glycol, distilled water and ammonium fluoride at room temperature to produce TiO2 nanotubes. These structures were then annealed at 450°C to transform them to anatase. As-annealed TiO2 nanotubes were then treated in an electrolyte containing 80.7 g/L NiSO4·7H2O, 41 g/L MgSO4·7H2O, 45 g/L H3BO3, and 1.44 g/L Ag2SO4 at 20°C by the application of 9 V AC voltage for doping them with silver. As-annealed TiO2 nanotubes and as-annealed Ag doped TiO2 nanotubes were evaluated by SEM, FESEM, and XRD. Antibacterial activity was assessed by determining the adherence of A. actinomycetemcomitans, T. forsythia, and C. rectus to the surface of the nanotubes. Bacterial morphology was examined using an SEM. As-annealed Ag doped TiO2 nanotubes revealed intense peak of Ag. Bacterial death against the as-annealed Ag doped TiO2 nanotubes were detected against A. actinomycetemcomitans, T. forsythia, and C. rectus indicating antibacterial efficacy. PMID:25202230

  8. Fabrication of bioactive, antibacterial TiO2 nanotube surfaces, coated with magnetron sputtered Ag nanostructures for dental applications.

    PubMed

    Uhm, Soo-Hyuk; Lee, Sang-Bae; Song, Doo-Hoon; Kwon, Jae-Sung; Han, Jeon-Geon; Kim, Kyoung-Nam

    2014-10-01

    We investigated whether a silver coating on an anodic oxidized titania (TiO2) nanotube surface would be useful for preventing infections in dental implants. We used a magnetron sputtering process to deposit Ag nanoparticles onto a TiO2 surface. We studied different sputtering input power densities and maintained other parameters constant. We used scanning electron microscopy, X-ray diffraction, and contact angle measurements to characterize the coated surfaces. Staphylococcus aureus was used to evaluate antibacterial activity. The X-ray diffraction analysis showed peaks that corresponded to metallic Ag, Ti, O, and biocompatible anatase phase TiO2 on the examined surfaces. The contact angles of the Ag nanoparticle-loaded surfaces were significantly lower at 2.5 W/cm2 input power under pulsed direct current mode compared to commercial, untreated Ti surfaces. In vitro antibacterial analysis indicated that a significantly reduced number of S. aureus were detected on an Ag nanoparticle-loaded TiO2 nanotube surface compared to control untreated surfaces. No cytotoxicity was noted, except in the group treated with 5 W/cm2 input power density, which was the highest input of power density we tested for the magnetron sputtering process. Overall, we concluded that it was feasible to create antibacterial Ag nanoparticle-loaded titanium nanotube surfaces with magnetron sputtering. PMID:25942879

  9. Antimicrobial activity and cytocompatibility of Ag plasma-modified hierarchical TiO2 film on titanium surface.

    PubMed

    Li, Jinhua; Liu, Xuanyong; Qiao, Yuqin; Zhu, Hongqin; Ding, Chuanxian

    2014-01-01

    To improve the antimicrobial ability and cytocompatibility of biomedical titanium implants, many efforts have been made to modify their surface topography and chemical composition. In this work, Ag plasma-modified hierarchical TiO2 film was fabricated on titanium surface via acid etching to produce micropit, hydrothermal treatment to generate TiO2 nanorod and subsequent plasma immersion ion implantation process to impregnate Ag into TiO2 surface. In view of the potential clinical applications, their antimicrobial activity, bioactivity and cytocompatibility were systematically evaluated. The hierarchical TiO2 film showed enhanced bioactivity and bacteriostatic effect on both microbes due to more negative zeta potential, constructing the first defense line against microbial adhesion by electrostatic repulsion. Addition of embedded Ag remarkably enhanced the antimicrobial efficiency toward both microbes based on Schottky contact without Ag(+) release, establishing the second defense line targeting microbial membrane. Furthermore, the addition of Ag degraded the bioactivity very little and exerted nearly no adverse or even promoted effect on MG63 cell functions, including adhesion, spreading and proliferation. This work illustrates a two-defense-line antimicrobial activity in darkness with both prior electrostatic repulsion to inhibit most microbes adhesion and posterior biocidal action to kill residual ones that luckily infiltrated through the first defense line, and provide proof of concept using both clinically relevant human pathogens. In conclusion, the Ag-embedded hierarchical TiO2 film with excellent antimicrobial activity, bioactivity and cytocompatibility provides a promising candidate for orthopedic and dental implants. PMID:24077111

  10. Ag nanoparticle-deposited TiO2 nanotube arrays for electrodes of Dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Kawamura, Go; Ohmi, Hayato; Tan, Wai Kian; Lockman, Zainovia; Muto, Hiroyuki; Matsuda, Atsunori

    2015-05-01

    Dye-sensitized solar cells composed of a photoanode of Ag nanoparticle (NP)-deposited TiO2 nanotube (TNT) arrays were fabricated. The TNT arrays were prepared by anodizing Ti films on fluorine-doped tin oxide (FTO)-coated glass substrates. Efficient charge transportation through the ordered nanostructure of TNT arrays should be carried out compared to conventional particulate TiO2 electrodes. However, it has been a big challenge to grow TNT arrays on FTO glass substrates with the lengths needed for sufficient light-harvesting (tens of micrometers). In this work, we deposited Ag nanoparticles (NPs) on the wall of TNT arrays to enhance light-harvesting property. Dye-sensitized solar cells with these Ag NP-deposited TNT arrays yielded a higher power conversion efficiency (2.03 %) than those without Ag NPs (1.39 %).

  11. Enhancement of the photoelectric performance of dye-sensitized solar cells using Ag-doped TiO2 nanofibers in a TiO2 film as electrode.

    PubMed

    Jin, En Mei; Zhao, Xing Guan; Park, Ju-Young; Gu, Hal-Bon

    2012-01-01

    For high solar conversion efficiency of dye-sensitized solar cells [DSSCs], TiO2 nanofiber [TN] and Ag-doped TiO2 nanofiber [ATN] have been extended to be included in TiO2 films to increase the amount of dye loading for a higher short-circuit current. The ATN was used on affected DSSCs to increase the open circuit voltage. This process had enhanced the exit in dye molecules which were rapidly split into electrons, and the DSSCs with ATN stop the recombination of the electronic process. The conversion efficiency of TiO2 photoelectrode-based DSSCs was 4.74%; it was increased to 6.13% after adding 5 wt.% ATN into TiO2 films. The electron lifetime of DSSCs with ATN increased from 0.29 to 0.34 s and that electron recombination was reduced.

  12. A new dielectric ta-C film coating of Ag-nanoparticle hybrids to enhance TiO2 photocatalysis

    NASA Astrophysics Data System (ADS)

    Liu, Fanxin; Tang, Chaojun; Wang, Zhenlin; Sui, Chenghua; Ma, Hongtao

    2014-03-01

    We have demonstrated a novel method to enhance TiO2 photocatalysis by adopting a new ultrathin tetrahedral-amorphous-carbon (ta-C) film coating on Ag nanoparticles to create strong plasmonic near-field enhancement. The result shows that the decomposition rate of methylene blue on the Ag/10 Å ta-C/TiO2 composite photocatalyst is ten times faster than that on a TiO2 photocatalyst and three times faster than that on a Ag/TiO2 photocatalyst. This can be ascribed to the simultaneous realization of two competitive processes: one that excites the surface plasmons (SPs) of the ta-C-film/Ag-nanoparticle hybrid and provides a higher electric field near the ta-C/TiO2 interface compared to Ag nanoparticles alone, while the other takes advantage of the dense diamond-like ta-C layer to help reduce the transfer of photogenerated electrons from the conduction band of TiO2 to the metallic surface, since any electron transfer will suppress the excitation of SP modes in the metal nanoparticles.

  13. Mass preparation and novel visible light photocatalytic activity of C and Ag Co-modified ZnO nanocrystals.

    PubMed

    Zhang, Xiao-Yan; Deng, Ya-Juan; Liu, Jin-Ku; Lu, Yi; Yang, Xiao-Hong

    2015-12-01

    A combustion method was developed to synthesize the C and Ag co-modified ZnO NCs to enhance its photocatalytic efficiency and practicability. The results showed that the doped Ag was significant to promote the photocatalytic activity, and the optimum content was 2% molar ratio of Ag to Zn atom. The degradation rate under visible light increased by 150% compared with C-ZnO NCs, while by more 1233.3% than pure ZnO photocatalyst. There were some new little particles with grain size about 10 nm on the C-ZnO NCs surface, which may state for the existence of Ag atoms. The synergy effect of Ag and carbon elements was proposed to explain the mechanism of enhanced photocatalytic performance under visible light irradiation. PMID:26254866

  14. Photodeposition of Ag2S on TiO2 nanorod arrays for quantum dot-sensitized solar cells

    PubMed Central

    2013-01-01

    Ag2S quantum dots were deposited on the surface of TiO2 nanorod arrays by a two-step photodeposition. The prepared TiO2 nanorod arrays as well as the Ag2S deposited electrodes were characterized by X-ray diffraction, scanning electron microscope, and transmission electron microscope, suggesting a large coverage of Ag2S quantum dots on the ordered TiO2 nanorod arrays. UV–vis absorption spectra of Ag2S deposited electrodes show a broad absorption range of the visible light. The quantum dot-sensitized solar cells (QDSSCs) based on these electrodes were fabricated, and the photoelectrochemical properties were examined. A high photocurrent density of 10.25 mA/cm2 with a conversion efficiency of 0.98% at AM 1.5 solar light of 100 mW/cm2 was obtained with an optimal photodeposition time. The performance of the QDSSC at different incident light intensities was also investigated. The results display a better performance at a lower incident light level with a conversion efficiency of 1.25% at 47 mW/cm2. PMID:23286551

  15. Improved performance of Ag-doped TiO2 synthesized by modified sol-gel method as photoanode of dye-sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Gupta, Arun Kumar; Srivastava, Pankaj; Bahadur, Lal

    2016-08-01

    Ag-doped TiO2 with Ag content ranging from 1 to 7 mol% was synthesized by a modified sol-gel route, and its performance as the photoanode of dye-sensitized solar cells (DSSCs) was compared with undoped TiO2 photoanode. Titanium(IV)isopropoxide was used as precursor and hexamethylenetetramine as the capping agent. XRD results show the formation of TiO2 nanoparticles with an average crystallite size of 5 nm (1 % Ag-doped TiO2) and 9 nm (undoped TiO2), respectively. The TiO2 nanopowder was used to prepare its thin film photoelectrode using doctor's blade method. Significant improvement in light-to-energy conversion efficiency was achieved when thin films of 1 % Ag-doped TiO2 were applied as photoanode in DSSC taking N719 as the sensitizer dye. As evidenced by EIS measurements, the electron lifetime of DSSC with Ag-doped TiO2 increased from 1.33 (for undoped TiO2) to 2.05 ms. The short-circuit current density ( J sc), open-circuit voltage ( V oc), fill factor (FF) and the overall energy conversion efficiency ( η) were 1.07 mA cm-2, 0.72 V, 0.73 and 0.40 %, respectively, with the use of 1 % Ag-doped TiO2 photoanode, whereas with undoped TiO2 under similar conditions, J sc = 0.63 mA cm-2, V oc = 0.70 V, fill factor 0.45 and conversion efficiency 0.14 % could be obtained. Therefore, compared with the reference DSSC containing an undoped TiO2 photoanode, the power conversion efficiency of the cell based on Ag-doped TiO2 has been remarkably enhanced by ~70 %. The substantial improvement in the device performance is attributed to the reduced band-gap energy, retarded charge recombination and greater surface coverage of the sensitizing dye over Ag-doped TiO2, which ultimately resulted in improved IPCE, J SC and η values.

  16. Efficiency enhancements in Ag nanoparticles-SiO2-TiO2 sandwiched structure via plasmonic effect-enhanced light capturing

    PubMed Central

    2013-01-01

    TiO2-SiO2-Ag composites are fabricated by depositing TiO2 films on silica substrates embedded with Ag nanoparticles. Enhancement of light absorption of the nanostructural composites is observed. The light absorption enhancement of the synthesized structure in comparison to TiO2 originated from the near-field enhancement caused by the plasmonic effect of Ag nanoparticles, which can be demonstrated by the optical absorption spectra, Raman scattering investigation, and the increase of the photocatalytic activity. The embedded Ag nanoparticles are formed by ion implantation, which effectively prevents Ag to be oxidized through direct contact with TiO2. The suggested incorporation of plasmonic nanostructures shows a great potential application in a highly efficient photocatalyst and ultra-thin solar cell. PMID:23402586

  17. Synthesis and visible-light-induced catalytic activity of Ag2S-coupled TiO2 nanoparticles and nanowires

    NASA Astrophysics Data System (ADS)

    Xie, Yi; Heo, Sung Hwan; Kim, Yong Nam; Yoo, Seung Hwa; Cho, Sung Oh

    2010-01-01

    We present the synthesis and visible-light-induced catalytic activity of Ag2S-coupled TiO2 nanoparticles (NPs) and TiO2 nanowires (NWs). Through a simple wet chemical process from a mixture of peroxo titanic acid (PTA) solution, thiourea and AgAc, a composite of Ag2S NPs and TiO2 NPs with sizes of less than 7 nm was formed. When the NP composite was further treated with NaOH solution followed by annealing at ambient conditions, a new nanocomposite material comprising Ag2S NPs on TiO2 NWs was created. Due to the coupling with such a low bandgap material as Ag2S, the TiO2 nanocomposites could have a visible-light absorption capability much higher than that of pure TiO2. As a result, the synthesized Ag2S/TiO2 nanocomposites exhibited much higher catalytic efficiency for the decomposition of methyl orange than commercial TiO2 (Degussa P25, Germany) under visible light.

  18. Photocatalytic characteristics for the nanocrystalline TiO2 on the Ag-doped CaAl2O4:(Eu,Nd) phosphor

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Sik; Sung, Hyun-Je; Kim, Bum-Joon

    2015-04-01

    This study investigated the photocatalytic behavior of nanocrystalline TiO2 deposited on Ag-doped long-lasting phosphor (CaAl2O4:Eu2+,Nd3+). The CaAl2O4:Eu2+,Nd3+ phosphor powders were prepared via conventional sintering using CaCO3, Al2O3, Eu2O3, and Nd2O3 as raw materials according to the appropriate molar ratios. Silver nanoparticles were loaded on the phosphor by mixing with an aqueous Ag-dispersion solution. Nanocrystalline TiO2 was deposited on Ag-doped CaAl2O4:Eu2+,Nd3+ powders via low-pressure chemical vapor deposition (LPCVD). The TiO2 coated on the phosphor was actively photo-reactive under irradiation with visible light and showed much faster benzene degradation than pure TiO2, which is almost non-reactive. The coupling of TiO2 with phosphor may result in an energy band bending in the junction region, which then induces the TiO2 crystal at the interface to be photo-reactive under irradiation with visible light. In addition, the intermetallic compound of CaTiO3 that formed at the interface between TiO2 and the CaAl2O4:(Eu2+,Nd3+) phosphor results in the formation of oxygen vacancies and additional electrons that promote the photodecomposition of benzene gas. The addition of Ag nanoparticles enhanced the photocatalytic reactivity of the TiO2/CaAl2O4:Eu2+,Nd3+ phosphor. TiO2 on the Ag-doped phosphor presented a higher benzene gas decomposition rate than the TiO2 did on the phosphor without Ag-doping under both irradiation with ultraviolet and visible light.

  19. Synthesis of Ag-doped TiO2 nanoparticles by combining laser decomposition of titanium isopropoxide and ablation of Ag for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Al-Kamal, Ahmed Kamal

    Nanostructured powders of TiO2 and Ag-doped TiO2 are synthesized by a novel pulsed-laser process that combines laser ablation of a silver (Ag) disc with laser decomposition of a titanium tetra-isopropoxide (TTIP) solution. Nanoparticles are formed by rapid condensation of vaporized species in the plasma plume generated by the high power laser, resulting in the formation of rapidly quenched Ag-doped TiO2 nanoparticles that have far-from-equilibrium or metastable structures. The uniqueness of the new ablation process is that it is a one-step process, in contrast to the two-step process developed by previous researchers in the field. Moreover, its ability to synthesize an extended-solid solution phase of Ag in TiO 2 may also be unique. The present work implies that other oxide phases, such as Al2O3, MgO and MgAl2O4, can be doped with normally insoluble metals, such as Pt and Ir, thus opening new opportunities for catalytic applications. Again, there is the prospect of being able to synthesize nanopowders of diamond, c-BN, and mixtures thereof, which are of interest for applications in machine tools, rock-drill bits, and lightweight armor. A wet-chemistry method is also investigated, which has much in common with that adopted by previous workers in the field. However, photo-voltaic properties do not measure up to expectations based on published data. A possible explanation is that the selected Ag concentrations are too high, so that recombination of holes and electrons occurs via a quantum-tunneling mechanism reduces photo-activity. Future work, therefore, will investigate lower concentrations of Ag dopant in TiO2, while also examining the effects of metastable states, including extended solid solution, amorphous, and semi-crystalline structures.

  20. Decorated TiO2 Nanoparticles with La and Ag Elements to Improve Photocatalytic Activity Under Visible Light for the Degradation of MO.

    PubMed

    Wang, Qinghua; Gao, Xuechuan; Zhang, Renfei; Shen, Beibei; Tan, Zhibing; Li, Zhao; Yu, Shiyong

    2016-04-01

    Visible-light photocatalyst of TiO2/La/Ag nanocomposites were successfully synthesized via the conventional sol-gel method and reducing agent of Ag+. The photocatalytic activities were evaluated by methyl orange (MO) degradation. They have remarkable photocatalytic activities compared to TiO2-Anatase, which is thanks to the separation of electron-hole pairs by Ag nanoparticles and lanthanum. The products were characterized by a series of techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and Uv-vis. The results show that spherical nanocomposites have been prepared with the size 300 nm and Ag nanoparticles (~10 nm) are dispersed uniformly onto the surface of TiO2/La, which forms TiO2/La/Ag nanocomposites. TiO2/La/Ag nanocomposites have good absorption in the visible region (700 nm > λ > 400 nm). The reasons are as follows: (1) the efficient separation of photogenerated electrons and holes of the photocatalysts on the surface of TiO2/La/Ag nanocomposites and (2) a wide visible-light photoabsorption range (700 nm > λ > 400 nm). Therefore, this study may provide some new idea for the rational design and the facile synthesis of composite catalysts with a green, efficient pathway. PMID:27451670

  1. Enhanced sunlight photocatalytic activity of Ag3PO4 decorated novel combustion synthesis derived TiO2 nanobelts for dye and bacterial degradation.

    PubMed

    Eswar, Neerugatti KrishnaRao; Ramamurthy, Praveen Chandrashekarapura; Madras, Giridhar

    2015-07-01

    This study demonstrates the synthesis of TiO2 nanobelts using solution combustion derived TiO2 with enhanced photocatalytic activity for dye degradation and bacterial inactivation. Hydrothermal treatment of combustion synthesized TiO2 resulted in unique partially etched TiO2 nanobelts and Ag3PO4 was decorated using the co-precipitation method. The catalyst particles were characterized using X-ray diffraction analysis, BET surface area analysis, diffuse reflectance and electron microscopy. The photocatalytic properties of the composites of Ag3PO4 with pristine combustion synthesized TiO2 and commercial TiO2 under sunlight were compared. Therefore the studies conducted proved that the novel Ag3PO4/unique combustion synthesis derived TiO2 nanobelt composites exhibited extended light absorption, better charge transfer mechanism and higher generation of hydroxyl and hole radicals. These properties resulted in enhanced photodegradation of dyes and bacteria when compared to the commercial TiO2 nanocomposite. These findings have important implications in designing new photocatalysts for water purification.

  2. Mechanism of strong visible light photocatalysis by Ag2O-nanoparticle-decorated monoclinic TiO2(B) porous nanorods

    NASA Astrophysics Data System (ADS)

    Paul, Kamal Kumar; Ghosh, Ramesh; Giri, P. K.

    2016-08-01

    We report on the ultra-high rate of photodegradation of organic dyes under visible light illumination on Ag2O-nanoparticle-decorated (NP) porous pure B-phase TiO2 (TiO2(B)) nanorods (NRs) grown by a solvothermal route. The as-grown TiO2(B) NRs are found to be nanoporous in nature and the Ag2O NPs are uniformly decorated over its surface, since most of the pores work as nucleation sites for the growth of Ag2O NPs. The effective band gap of the TiO2(B)/Ag2O heterostructure (HS), with a weight ratio of 1:1, has been significantly reduced to 1.68 eV from the pure TiO2(B) band gap of 2.8 eV. Steady state and time-resolved photoluminescence (PL) studies show the reduced intensity of visible PL and slower recombination dynamics in the HS samples. The photocatalytic degradation efficiency of the TiO2(B)/Ag2O HS has been investigated using aqueous methyl orange and methylene blue as reference dyes under visible light (390–800 nm) irradiation. It is found that photodegradation by the TiO2(B)/Ag2O HS is about one order of magnitude higher than that of bare TiO2(B) NRs and Ag2O NPs. The optimized TiO2(B)/Ag2O HS exhibited the highest photocatalytic efficiency, with 88.2% degradation for 30 min irradiation. The corresponding first order degradation rate constant is 0.071 min‑1, which is four times higher than the reported values. Furthermore, cyclic stability studies show the high stability of the HS photocatalyst for up to four cycles of use. The major improvement in photocatalytic efficiency has been explained on the basis of enhanced visible light absorption and band-bending-induced efficient charge separation in the HS. Our results demonstrate the long-term stability and superiority of the TiO2(B)/Ag2O HS over the bare TiO2(B) NRs and other TiO2-based photocatalysts for its cutting edge application in hydrogen production and environmental cleaning driven by solar light photocatalysis.

  3. Mechanism of strong visible light photocatalysis by Ag2O-nanoparticle-decorated monoclinic TiO2(B) porous nanorods

    NASA Astrophysics Data System (ADS)

    Paul, Kamal Kumar; Ghosh, Ramesh; Giri, P. K.

    2016-08-01

    We report on the ultra-high rate of photodegradation of organic dyes under visible light illumination on Ag2O-nanoparticle-decorated (NP) porous pure B-phase TiO2 (TiO2(B)) nanorods (NRs) grown by a solvothermal route. The as-grown TiO2(B) NRs are found to be nanoporous in nature and the Ag2O NPs are uniformly decorated over its surface, since most of the pores work as nucleation sites for the growth of Ag2O NPs. The effective band gap of the TiO2(B)/Ag2O heterostructure (HS), with a weight ratio of 1:1, has been significantly reduced to 1.68 eV from the pure TiO2(B) band gap of 2.8 eV. Steady state and time-resolved photoluminescence (PL) studies show the reduced intensity of visible PL and slower recombination dynamics in the HS samples. The photocatalytic degradation efficiency of the TiO2(B)/Ag2O HS has been investigated using aqueous methyl orange and methylene blue as reference dyes under visible light (390-800 nm) irradiation. It is found that photodegradation by the TiO2(B)/Ag2O HS is about one order of magnitude higher than that of bare TiO2(B) NRs and Ag2O NPs. The optimized TiO2(B)/Ag2O HS exhibited the highest photocatalytic efficiency, with 88.2% degradation for 30 min irradiation. The corresponding first order degradation rate constant is 0.071 min-1, which is four times higher than the reported values. Furthermore, cyclic stability studies show the high stability of the HS photocatalyst for up to four cycles of use. The major improvement in photocatalytic efficiency has been explained on the basis of enhanced visible light absorption and band-bending-induced efficient charge separation in the HS. Our results demonstrate the long-term stability and superiority of the TiO2(B)/Ag2O HS over the bare TiO2(B) NRs and other TiO2-based photocatalysts for its cutting edge application in hydrogen production and environmental cleaning driven by solar light photocatalysis.

  4. Mechanism of strong visible light photocatalysis by Ag2O-nanoparticle-decorated monoclinic TiO2(B) porous nanorods.

    PubMed

    Paul, Kamal Kumar; Ghosh, Ramesh; Giri, P K

    2016-08-01

    We report on the ultra-high rate of photodegradation of organic dyes under visible light illumination on Ag2O-nanoparticle-decorated (NP) porous pure B-phase TiO2 (TiO2(B)) nanorods (NRs) grown by a solvothermal route. The as-grown TiO2(B) NRs are found to be nanoporous in nature and the Ag2O NPs are uniformly decorated over its surface, since most of the pores work as nucleation sites for the growth of Ag2O NPs. The effective band gap of the TiO2(B)/Ag2O heterostructure (HS), with a weight ratio of 1:1, has been significantly reduced to 1.68 eV from the pure TiO2(B) band gap of 2.8 eV. Steady state and time-resolved photoluminescence (PL) studies show the reduced intensity of visible PL and slower recombination dynamics in the HS samples. The photocatalytic degradation efficiency of the TiO2(B)/Ag2O HS has been investigated using aqueous methyl orange and methylene blue as reference dyes under visible light (390-800 nm) irradiation. It is found that photodegradation by the TiO2(B)/Ag2O HS is about one order of magnitude higher than that of bare TiO2(B) NRs and Ag2O NPs. The optimized TiO2(B)/Ag2O HS exhibited the highest photocatalytic efficiency, with 88.2% degradation for 30 min irradiation. The corresponding first order degradation rate constant is 0.071 min(-1), which is four times higher than the reported values. Furthermore, cyclic stability studies show the high stability of the HS photocatalyst for up to four cycles of use. The major improvement in photocatalytic efficiency has been explained on the basis of enhanced visible light absorption and band-bending-induced efficient charge separation in the HS. Our results demonstrate the long-term stability and superiority of the TiO2(B)/Ag2O HS over the bare TiO2(B) NRs and other TiO2-based photocatalysts for its cutting edge application in hydrogen production and environmental cleaning driven by solar light photocatalysis. PMID:27333816

  5. Mesoporous TiO2 nanoparticles containing Ag ion with excellent antimicrobial activity at remarkable low silver concentrations.

    PubMed

    Naik, Kshipra; Chatterjee, Amrita; Prakash, Halan; Kowshik, Meenal

    2013-04-01

    Mesoporous Ag-TiO2 nanoparticles with TiO2 homogenous anatase crystalline phase was synthesized using a one-pot sol-gel method. The sample was calcined at 100 degrees C and characterized by XRD, HR TEM, EDAX, IR spectroscopy, DRS, N2 adsorption-desorption isotherm and Brunauer-Emmett-Teller (BET) analysis. The BET surface area of the sample was 266 m2/g and the crystallite size as calculated using Scherrer formula was 3.76 nm. The Ag-TiO2 nanoparticles exhibited excellent antimicrobial activity against representative Gram-positive and Gram-negative bacterial cultures and Candida albicans. Complete inhibition of microorganisms was achieved at a very low Ag-TiO2 concentration, in the range of 1.0 to 20 microg/mL (effective Ag concentrations were 11.7 to 234 ppb) in less than 2 h under ambient conditions, without the requirement of photoactivation. Silver ion release studies showed that about 18% of silver ions were present in solution. Thus, it may be inferred that the antimicrobial activity is due to Ag ions released from the TiO2 matrix. The mesoporous nature and antimicrobial activity at low concentrations without photoactivation are important aspects which make this material an excellent candidate for potential application as disinfectant and/or antimicrobial agent.

  6. UV-visible light-activated Ag-decorated, monodisperse TiO2 aggregates for treatment of the pharmaceutical oxytetracycline.

    PubMed

    Han, Changseok; Likodimos, Vlassis; Khan, Javed Ali; Nadagouda, Mallikarjuna N; Andersen, Joel; Falaras, Polycarpos; Rosales-Lombardi, Pablo; Dionysiou, Dionysios D

    2014-10-01

    Noble metal Ag-decorated, monodisperse TiO2 aggregates were successfully synthesized by an ionic strength-assisted, simple sol-gel method and were used for the photocatalytic degradation of the antibiotic oxytetracycline (OTC) under both UV and visible light (UV-visible light) irradiation. The synthesized samples were characterized by X-ray diffraction analysis (XRD); UV-vis diffuse reflectance spectroscopy; environmental scanning electron microscopy (ESEM); transmission electron microscopy (TEM); high-resolution TEM (HR-TEM); micro-Raman, energy-dispersive X-ray spectroscopy (EDS); and inductively coupled plasma optical emission spectrometry (ICP-OES). The results showed that the uniformity of TiO2 aggregates was finely tuned by the sol-gel method, and Ag was well decorated on the monodisperse TiO2 aggregates. The absorption of the samples in the visible light region increased with increasing Ag loading that was proportional to the amount of Ag precursor added in the solution over the tested concentration range. The Brunauer, Emmett, and Teller (The BET) surface area slightly decreased with increasing Ag loading on the TiO2 aggregates. Ag-decorated TiO2 samples demonstrated enhanced photocatalytic activity for the degradation of OTC under UV-visible light illumination compared to that of pure TiO2. The sample containing 1.9 wt% Ag showed the highest photocatalytic activity for the degradation of OTC under both UV-visible light and visible light illumination. During the experiments, the detected Ag leaching for the best TiO2-Ag photocatalyst was much lower than the National Secondary Drinking Water Regulation for Ag limit (0.1 mg L(-1)) issued by the US Environmental Protection Agency.

  7. Density functional theory calculations for the investigation of (Ag, N) codoping effect on the electronic and optical properties of anatase TiO2

    NASA Astrophysics Data System (ADS)

    Khan, Matiullah; Cao, Wenbin; Li, Jing; Zaman, Muhammad Iqbal; Manan, Abdul

    2014-04-01

    Efficient absorption of light in visible range and enhance separation of photoexcited electron-hole pairs (EHPs) are crucial for improving the photoactivity of metal nonmetal codoped TiO2. By using density functional theory (DFT) calculations, an effective metal (Ag) and nonmetal (N) codoping approach is described to modify the photoelectrochemical properties of titanium dioxide ( TiO2). Nitrogen (N) doping introduces isolated N-2p states above the valence band maximum (VBM) which acts as an electron trap to promote EHP recombination. For Ag-doped TiO2, Ag-4d states are introduced above the VBM which leads to the band gap narrowing. Silver (Ag) and nitrogen codoped TiO2 possess stable configuration, narrowed band gap and best visible light absorption. Defect pair binding energy calculation shows that individual dopants, located at a distance of 8.951 Å bind each other, which indicates that the defect pair is stable compared to the isolated impurities in the host lattice. Ag and N codoped TiO2 shows better visible light absorption as compared to other doped models due to the reduced band gap. N doping reduces the band gap of TiO2 while Ag doping enhances the EHPs separation, so their combined presence in a sample would improve the photocatalytic activity due to their synergistic codoping effect. Our calculations provide reasonable explanation for the experimental findings.

  8. Preparation of TiO(2)/Ag colloids with ultraviolet resistance and antibacterial property using short chain polyethylene glycol.

    PubMed

    Su, W; Wei, S S; Hu, S Q; Tang, J X

    2009-12-30

    TiO(2)/Ag nano-antibacterial material was prepared at low temperature using polyethylene glycol (PEG-600) as reducing and stabilizing agent. The size and shape as well as the optical properties of the nano-materials were characterized with transmission electron microscopy (TEM) and UV-vis spectroscopy (UV-vis). The results showed that the average particle size of TiO(2) among these nano-materials was around 50-150 nm, and the average particle size of nano-silver was around 20 nm. Formation of Ag nano-particles on the surface of TiO(2) was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and the antibacterial activity was also investigated. By the antibacterial activity study and ultraviolet resistance test, it is noted that growth inhibition rates against E. coli was 99.99% as the concentration of nano-particles dispersion solution was 10 ppm, the minimum UV protective effect could be achieved as the concentration was 290 ppm.

  9. Photocatalytic Properties of TiO2 Thin Films Modified with Ag and Pt Nanoparticles Deposited by Gas Flow Sputtering.

    PubMed

    Maicu, M; Glöss, D; Frach, Peter; Hecker, D; Gerlach, G; Córdoba, José M

    2015-09-01

    In this work, a gas flow sputtering (GFS) process which allows the production and deposition of metal nanoparticles (NPs) in a vacuum environment is described. Aim of the study is to prove the potential of this technology for the fabrication of new TiO2 films with enhanced photocatalytic properties. For this purpose, Ag and Pt NPs have been produced and deposited on photocatalytic float glass coated with TiO2 thin films by magnetron sputtering. The influence of the process parameters and of the metal amount on the final properties of the particles (quantity, size, size distribution, oxidation state etc.,) was widely investigated. Moreover, the effect of the NPs on the photocatalytic activity of the resulting materials was evaluated for the case of the decomposition of stearic acid (SA) during UV-A irradiation. The reduction of the water contact angle (WCA) during the irradiation period was measured in order to test the photo-induced super-hydrophilicity (PSH).

  10. Improved conversion efficiency of Ag2S quantum dot-sensitized solar cells based on TiO2 nanotubes with a ZnO recombination barrier layer

    PubMed Central

    2011-01-01

    We improve the conversion efficiency of Ag2S quantum dot (QD)-sensitized TiO2 nanotube-array electrodes by chemically depositing ZnO recombination barrier layer on plain TiO2 nanotube-array electrodes. The optical properties, structural properties, compositional analysis, and photoelectrochemistry properties of prepared electrodes have been investigated. It is found that for the prepared electrodes, with increasing the cycles of Ag2S deposition, the photocurrent density and the conversion efficiency increase. In addition, as compared to the Ag2S QD-sensitized TiO2 nanotube-array electrode without the ZnO layers, the conversion efficiency of the electrode with the ZnO layers increases significantly due to the formation of efficient recombination layer between the TiO2 nanotube array and electrolyte. PMID:21777458

  11. A stable and high resolution optical waveguide biosensor based on dense TiO2/Ag multilayer film

    NASA Astrophysics Data System (ADS)

    Jin, Zhao; Guan, Weiming; Liu, Chang; Xue, Tianyu; Wang, Qiyu; Zheng, Weitao; Cui, Xiaoqiang

    2016-07-01

    Optical waveguide (OWG) biosensor has attracted much attention according to the high sensitivity and resolution compared with conventional surface plasmon resonance (SPR) biosensor. Nanoporous materials are usually used as the waveguide layer for absorbing analytes into the porous structure and enhancing the sensor signal. However, this kind of waveguide layer provides poor protection to the metal film and leads to the damage of the biosensor. Ag film can provide great sensitivity in SPR sensing comparing to other metal but was rarely used because of its poor chemical stability. Fabricating high stability Ag based SPR biosensor is still a challenge. In this work we produce an OWG biosensor using a dense TiO2 film as the waveguide layer which provides high resolution and remarkable protection to the metal film. This waveguide structure makes long time detection possible using Ag as the metal layer and is able to lead an enhancement of sensitivity comparing to the Au-based biosensor.

  12. Synthesis and characterization of cube-like Ag@AgCl-doped TiO2/fly ash cenospheres with enhanced visible-light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Liu, Shaomin; Zhu, Jinglin; Yang, Qing; Xu, Pengpeng; Ge, Jianhua; Guo, Xuetao

    2016-03-01

    A cube-like Ag@AgCl-doped TiO2/fly ash cenosphere composite (denoted Ag@AgCl-TiO2/fly ash cenospheres) was successfully synthesized via a two-step approach. The as-prepared catalysts were characterized by scanning electron microscopy, X-ray diffraction, diffuse reflectance ultraviolet-visible spectroscopy, Brunauer-Emmett-Teller, and X-ray photoelectron spectroscopy. The photocatalytic experiment showed that the rhodamine B degradation rate with Ag@AgCl-TiO2/fly ash cenospheres was 1.56 and 1.33 times higher than that with AgCl-TiO2/fly ash cenospheres and Ag@AgCl, respectively. The degradation ratio of rhodamine B with Ag@AgCl-TiO2/fly ash cenospheres was nearly 100% within 120 min under visible light. Analysis of active species indicated that radO2- and h+ dominated the reaction, and radOH participated in the photocatalytic reactions as an active species. A mechanism for the photocatalytic degradation by the Ag@AgCl-TiO2/fly-ash cenospheres was also proposed based on the experimental results.

  13. Enhanced hydrogen evolution from water splitting using Fe-Ni codoped and Ag deposited anatase TiO2 synthesized by solvothermal method

    NASA Astrophysics Data System (ADS)

    Sun, Tao; Liu, Enzhou; Liang, Xuhua; Hu, Xiaoyun; Fan, Jun

    2015-08-01

    In this paper, the Fe-Ni co-doped and Ag deposited anatase TiO2 (Fe-Ni/Ag/TiO2) nanocomposites were successfully prepared by a simple one-pot solvothermal approach. The investigations indicated that all as-prepared TiO2 samples were single anatase phase, and the impurity level was generated due to the Fe3+ or Ni2+ being located in the intrinsic band gap of TiO2, while the Ag+ ions could be transformed into metallic silver due to the reduction reaction and then loaded onto the surface of TiO2. Compared with pure TiO2, Fe-Ni/Ag/TiO2 composites with the sizes of Ag nanoparticles from 1.0 to 3.0 nm displayed the well optical property including higher visible light absorption activity and lower electron-hole pair recombination rate, and its absorption wavelength edge moved remarkably with a red shift to 700 nm. The photocatalytic water splitting was performed to produce H2 over the samples, and the experimental results indicate that Fe-Ni/Ag/TiO2 composites presented the highest H2 evolution rate, it can reach up to 793.86 μmol h-1 gcat-1 (λ > 400 nm for 6 h, energy efficiency is 0.25%), which was much higher than that of pure TiO2 for 9.57 μmol h-1 gcat-1. In addition, a tentative photocatalytic mechanism is proposed to understand the enhancement mechanism over Fe-Ni codoped and Ag deposited anatase TiO2.

  14. In situ plasmonic Ag nanoparticle anchored TiO2 nanotube arrays as visible-light-driven photocatalysts for enhanced water splitting

    NASA Astrophysics Data System (ADS)

    Ge, Ming-Zheng; Cao, Chun-Yan; Li, Shu-Hui; Tang, Yu-Xin; Wang, Lu-Ning; Qi, Ning; Huang, Jian-Ying; Zhang, Ke-Qin; Al-Deyab, S. S.; Lai, Yue-Kun

    2016-02-01

    An ultrasonication-assisted in situ deposition strategy was utilised to uniformly decorate plasmonic Ag nanoparticles on vertically aligned TiO2 nanotube arrays (NTAs) to construct a Ag@TiO2 NTA composite. The Ag nanoparticles act as efficient surface plasmon resonance (SPR) photosensitizers to drive photocatalytic water splitting under visible light irradiation. The Ag nanoparticles were uniformly deposited on the surface and inside the highly oriented TiO2 nanotubes. The visible-light-driven hydrogen production activities of silver nanoparticle anchored TiO2 nanotube array photocatalysts were evaluated using methanol as a sacrificial reagent in water under a 500 W Xe lamp with a UV light cutoff filter (λ >= 420 nm). It was found that the hydrogen production rate of the Ag@TiO2 NTAs prepared with ultrasonication-assisted deposition for 5 min was approximately 15 times higher than that of its pristine TiO2 NTAs counterpart. The highly efficient photocatalytic hydrogen evolution is attributed to the SPR effect of Ag for enhanced visible light absorption and boosting the photogenerated electron-hole separation/transfer. This strategy is promising for the design and construction of high efficiency TiO2 based photocatalysts for solar energy conversion.An ultrasonication-assisted in situ deposition strategy was utilised to uniformly decorate plasmonic Ag nanoparticles on vertically aligned TiO2 nanotube arrays (NTAs) to construct a Ag@TiO2 NTA composite. The Ag nanoparticles act as efficient surface plasmon resonance (SPR) photosensitizers to drive photocatalytic water splitting under visible light irradiation. The Ag nanoparticles were uniformly deposited on the surface and inside the highly oriented TiO2 nanotubes. The visible-light-driven hydrogen production activities of silver nanoparticle anchored TiO2 nanotube array photocatalysts were evaluated using methanol as a sacrificial reagent in water under a 500 W Xe lamp with a UV light cutoff filter (λ >= 420 nm

  15. Effect of TiO2-Ag2O additives on the formation of calcium phosphate based functionally graded bioceramics.

    PubMed

    Manjubala, I; Sampath Kumar, T S

    2000-10-01

    The combined effect of titanium dioxide and silver oxide on the in situ formation of biphasic calcium phosphate ceramics was investigated. Titania (5-20 mol%) was mixed with pure hydroxyapatite (HA) or HA containing Ag2O (10-20 mol%) and was heated to 900 degrees C for 12 h. The sintered samples were found to contain tricalcium phosphate (beta-TCP) and other phases along with HA depending upon the amount as well as the type of the additives used as evidenced by X-ray powder diffraction (XRD) and fourier transform infrared (FT-IR) spectroscopic studies. Enhanced TCP formation with reduced impurity phases was observed with TiO2-Ag2O addition. In vitro solubility study in phosphate buffer at physiological conditions shows the resorbable nature of these materials. A functionally graded material (FGM) structure was formed by spreading TiO2-Ag2O mixture on the surface of the HA green compact and heating at 900 degrees C. The FGM shows gradient structure of TCP and HA from the surface to the interior of the pellet in addition to titania and silver phases.

  16. In situ plasmonic Ag nanoparticle anchored TiO2 nanotube arrays as visible-light-driven photocatalysts for enhanced water splitting.

    PubMed

    Ge, Ming-Zheng; Cao, Chun-Yan; Li, Shu-Hui; Tang, Yu-Xin; Wang, Lu-Ning; Qi, Ning; Huang, Jian-Ying; Zhang, Ke-Qin; Al-Deyab, S S; Lai, Yue-Kun

    2016-03-01

    An ultrasonication-assisted in situ deposition strategy was utilised to uniformly decorate plasmonic Ag nanoparticles on vertically aligned TiO2 nanotube arrays (NTAs) to construct a Ag@TiO2 NTA composite. The Ag nanoparticles act as efficient surface plasmon resonance (SPR) photosensitizers to drive photocatalytic water splitting under visible light irradiation. The Ag nanoparticles were uniformly deposited on the surface and inside the highly oriented TiO2 nanotubes. The visible-light-driven hydrogen production activities of silver nanoparticle anchored TiO2 nanotube array photocatalysts were evaluated using methanol as a sacrificial reagent in water under a 500 W Xe lamp with a UV light cutoff filter (λ ≥ 420 nm). It was found that the hydrogen production rate of the Ag@TiO2 NTAs prepared with ultrasonication-assisted deposition for 5 min was approximately 15 times higher than that of its pristine TiO2 NTAs counterpart. The highly efficient photocatalytic hydrogen evolution is attributed to the SPR effect of Ag for enhanced visible light absorption and boosting the photogenerated electron-hole separation/transfer. This strategy is promising for the design and construction of high efficiency TiO2 based photocatalysts for solar energy conversion. PMID:26878901

  17. Theoretical and photo-electrochemical studies of surface plasmon induced visible light absorption of Ag loaded TiO2 nanotubes for water splitting

    NASA Astrophysics Data System (ADS)

    Gross, P. A.; Javahiraly, N.; Geraldini Sabat, N.; Cottineau, T.; Savinova, E. R.; Keller, V.

    2016-10-01

    Vertically aligned TiO2 nanotubes (TiO2-NTs), obtained by anodization in organic electrolyte, are decorated with 15 nm Ag nanoparticles prepared by a micro-wave assisted polyol synthesis. The Ag/TiO2 system is characterized by electronic microscopies in order to build a Finite Differential Time Domain (FDTD) model to simulate the interaction of light with the system. By combining UV-visible spectroscopy and FDTD simulations, the observed red shift in the surface plasmon resonance wavelength of the Ag nanoparticles, deposited on TiO2, is explained. The Ag/TiO2-NT system is used as photoanode in a photoelectrochemical water splitting setup and shows an increasing Incident Photon to Current Conversion Efficiency (IPCE) in the visible light domain with an increasing amount of deposited Ag. The spectral position of this activity enhancement coincides with the one expected from the FDTD calculations for the surface plasmon resonance of the Ag nanoparticles deposited on TiO2.

  18. Migration of Ag- and TiO2-(Nano)particles from textiles into artificial sweat under physical stress: experiments and exposure modeling.

    PubMed

    von Goetz, N; Lorenz, C; Windler, L; Nowack, B; Heuberger, M; Hungerbühler, K

    2013-09-01

    Engineered nanoparticles (ENP) are increasingly used to functionalize textiles taking advantage, e.g., of the antimicrobial activity of silver (Ag)-ENP or the UV-absorption of titania (TiO2)-ENP. Mobilization and migration of ENPs from the textile into human sweat can result in dermal exposure to these nanoobjects and their aggregates and agglomerates (NOAA). In this study we assessed exposure to NOAA migrating from commercially available textiles to artificial sweat by an experimental setup that simulates wear-and-tear during physical activity. By combining physical stress with incubation in alkaline and acidic artificial sweat solutions we experimentally realized a worst case scenario for wearing functionalized textiles during sports activities. This experimental approach is not limited to NOAA, but can be used for any other textile additive. Out of four investigated textiles, one T-shirt and one pair of trousers with claimed antimicrobial properties were found to release Ag <450 nm in detectable amounts (23-74 μg/g/L). Textiles containing TiO2 for UV protection did not release significant amounts of TiO2 <450 nm, but the antimicrobial T-shirt released both TiO2 and Ag <450 nm. The silver was present in dissolved and particulate form, whereas TiO2 was mainly found as particulate. On the basis of our experimental results we calculated external dermal exposure to Ag and TiO2 for male and female adults per use. For silver, maximal amounts of 17.1 and 8.2 μg/kg body weight were calculated for total and particulate Ag <450 nm, respectively. For TiO2, the exposure levels amount to maximal 11.6 μg/kg body weight for total (mainly particulate) TiO2. In comparison with other human exposure pathways, dermal exposure to NOAA from textiles can be considered comparably minor for TiO2-NOAA, but not for Ag-NOAA.

  19. Disinfection of Escherichia coli Gram negative bacteria using surface modified TiO2: optimization of Ag metallization and depiction of charge transfer mechanism.

    PubMed

    Gomathi Devi, LakshmipathiNaik; Nagaraj, Basavalingaiah

    2014-01-01

    The antibacterial activity of silver deposited TiO2 (Ag-TiO2 ) against Gram negative Escherichia coli bacteria was investigated by varying the Ag metal content from 0.10 to 0.50% on the surface of TiO2 . Ag depositions by the photoreduction method were found to be stable. Surface silver metallization was confirmed by EDAX and XPS studies. Photoluminescence studies show that the charge carrier recombination is less for 0.1% Ag-TiO2 and this catalyst shows superior bactericidal activity under solar light irradiation compared to Sol gel TiO2 (SG-TiO2 ) due to the surface plasmon effect. The energy levels of deposited Ag are dependent on the Ag content and it varies from -4.64 eV to -1.30 eV with respect to the vacuum energy level based on atomic silver to bulk silver deposits. The ability of electron transfer from Ag deposit to O2 depends on the position of the energy levels. The 0.25% and 0.50% Ag depositions showed detrimental effect on bactericidal activity due to the mismatch of energy levels. The effect of the EROS (External generation of the Reactive Oxygen Species by 0.1% Ag-TiO2 ) and IROS (Interior generation of Reactive Oxygen Species within the bacteria) on the bactericidal inactivation is discussed in detail. PMID:24995499

  20. Photocatalytic Properties of TiO2 Thin Films Modified with Ag and Pt Nanoparticles Deposited by Gas Flow Sputtering.

    PubMed

    Maicu, M; Glöss, D; Frach, Peter; Hecker, D; Gerlach, G; Córdoba, José M

    2015-09-01

    In this work, a gas flow sputtering (GFS) process which allows the production and deposition of metal nanoparticles (NPs) in a vacuum environment is described. Aim of the study is to prove the potential of this technology for the fabrication of new TiO2 films with enhanced photocatalytic properties. For this purpose, Ag and Pt NPs have been produced and deposited on photocatalytic float glass coated with TiO2 thin films by magnetron sputtering. The influence of the process parameters and of the metal amount on the final properties of the particles (quantity, size, size distribution, oxidation state etc.,) was widely investigated. Moreover, the effect of the NPs on the photocatalytic activity of the resulting materials was evaluated for the case of the decomposition of stearic acid (SA) during UV-A irradiation. The reduction of the water contact angle (WCA) during the irradiation period was measured in order to test the photo-induced super-hydrophilicity (PSH). PMID:26716202

  1. Synthesis and characterization of TiO 2/Ag/polymer ternary nanoparticles via surface-initiated atom transfer radical polymerization

    NASA Astrophysics Data System (ADS)

    Park, Jung Tae; Koh, Joo Hwan; Seo, Jin Ah; Cho, Yong Soo; Kim, Jong Hak

    2011-08-01

    We report on the novel ternary hybrid materials consisting of semiconductor (TiO 2), metal (Ag) and polymer (poly(oxyethylene methacrylate) (POEM)). First, a hydrophilic polymer, i.e. POEM, was grafted from TiO 2 nanoparticles via the surface-initiated atom transfer radical polymerization (ATRP) technique. These TiO 2-POEM brush nanoparticles were used to template the formation of Ag nanoparticles by introduction of a AgCF 3SO 3 precursor and a NaBH 4 aqueous solution for reduction process. Successful grafting of polymeric chains from the surface of TiO 2 nanoparticles and the in situ formation of Ag nanoparticles within the polymeric chains were confirmed using transmission electron microscopy (TEM), UV-vis spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). FT-IR spectroscopy also revealed the specific interaction of Ag nanoparticles with the C dbnd O groups of POEM brushes. This study presents a simple route for the in situ synthesis of both metal and polymer confined within the semiconductor, producing ternary hybrid inorganic-organic nanomaterials.

  2. Design of Ag@C@SnO2@TiO2 yolk-shell nanospheres with enhanced photoelectric properties for dye sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Zhao, Peilu; Li, Dan; Yao, Shiting; Zhang, Yiqun; Liu, Fengmin; Sun, Peng; Chuai, Xiaohong; Gao, Yuan; Lu, Geyu

    2016-06-01

    The hierarchical Ag@C@SnO2@TiO2 nanospheres (ACSTS) have been successfully synthesized by deposition of SnO2 and TiO2 on the Ag@C templates layer by layer. The size of ACSTS is ca. 360 nm while the Ag@C cores have an average diameter of about 300 nm. The rough and porous shell structure consisting of SnO2 and TiO2 ensures a large specific surface area (115.5 m2 g-1). To demonstrate how such a unique structure might lead to more excellent photovoltaic property, several kinds of dye-sensitized solar cells (DSSCs) are also fabricated using different nanospheres based photoanodes. It is found that the ACSTS based DSSC exhibits an obvious improvement in cell performance. According to various technical characterization, the ACSTS can provide dual-functions of light absorption and charge transfer, hence resulting in an enhanced short-circuit photocurrent density of 18.68 mA cm-2 and a higher FF of 63% compared with other DSSCs. The ACSTS cell finally obtains a PCE of up to 8.62%, increasing by 70.4% and 10.2% than hollow TiO2 nanospheres and Ag@C@TiO2 nanospheres based cells, respectively. The improved photovoltaic properties of ACSTS cell can be mainly ascribed to the unique microstructure and the synergistic effect of the encapsulated Ag@C cores.

  3. A First-Principle Study of Synergized O2 Activation and CO Oxidation by Ag Nanoparticles on TiO2(101) Support.

    PubMed

    Jia, Chuanyi; Zhang, Guozhen; Zhong, Wenhui; Jiang, Jun

    2016-04-27

    We performed density functional theory (DFT) calculations to investigate the synergized O2 activation and CO oxidation by Ag8 cluster on TiO2(101) support. The excellent catalytic activity of the interfacial Ag atoms in O2 dissociation is ascribed to the positive polarized charges, upshift of Ag d-band center, and assistance of surface Ti5c atoms. CO oxidation then takes place via a two-step mechanism coupled with O2 dissociation: (i) CO + O2 → CO2 + O and (ii) CO + O → CO2. The synergistic effect of CO and O2 activations reduces the oxidation energy barrier (Ea) of reaction (i), especially for the up-layered Ag atoms not in contact with support. It is found that the coadsorbed CO and O2 on the up-layered Ag atoms form a metal-stable four-center O-O-CO structure motif substantially promoting CO oxidation. On the oxygen defective Ag8/TiO2(101) surface, because of the decreased positive charges and the down-shift of d-band centers in Ag, the metal cluster exhibits low O2 adsorption and activation abilities. Although the dissociation of O2 is facilitated by the TiO2(101) defect sites, the dissociated O atoms would cover the defects so strongly that further CO oxidation would be prohibited unless much extra energy is introduced to recreate oxygen defects. PMID:27049335

  4. Electrodeposited AgInSe2 onto TiO2 films for semiconductor-sensitized solar cell application: The influence of electrodeposited time

    NASA Astrophysics Data System (ADS)

    Chen, Lung-Chuan; Ho, Yi-Ching; Yang, Ru-Yuan; Chen, Jean-Hong; Huang, Chao-Ming

    2012-06-01

    The influence of electrodeposited time (EDT) on Ag-In-Se species growth onto TiO2 films for possible semiconductor-sensitized solar cells (SSSCs) application was investigated. XRD analysis illustrated that the Ag-In-Se film was predominantly comprised by AgInSe2 species with tetragonal body structure and crystal size of 6.05-7.50 nm when EDT was in the region of 15-60 min at a bias of -1.25 V (verse Hg/Hg2SO4 (MSE)). Scanning electron microscope (SEM) indicated a high porosity of AgInSe2/ITO morphology, permitting electrolytes freely percolated through these films. The prepared AgInSe2 films exhibited n-type semiconductor behavior with two band gap energies at 1.27 and 1.80 eV. Photoelectrochemical measurement reflected that open circuit potential varied little with EDT, however, significant change was associated with short circuit current and fill factor (FF), causing the AgInSe2/TiO2 films with EDT of 45 min exhibited the best solar to electricity conversion efficiency of 0.26%. The AgInSe2/TiO2 films with EDT of 45 min demonstrated the longest electron lifetime according to the open circuit voltage decay analysis.

  5. Facile synthesis of hierarchical Ag3PO4/TiO2 nanofiber heterostructures with highly enhanced visible light photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Xie, Jinlei; Yang, Yefeng; He, Haiping; Cheng, Ding; Mao, Minmin; Jiang, Qinxu; Song, Lixin; Xiong, Jie

    2015-11-01

    Heterostructured semiconductor nanostructures have provoked great interest in the areas of energy, environment and catalysis. Herein, we report a novel hierarchical Ag3PO4/TiO2 heterostructure consisting of nearly spherical Ag3PO4 particles firmly coupled on the surface of TiO2 nanofibers (NFs). The construction of Ag3PO4/TiO2 heterostructure with tailored morphologies, compositions and optical properties was simply achieved via a facile and green synthetic strategy involving the electrospinning and solution-based processes. Owing to the synergetic effects of the components, the resulting hybrid heterostructures exhibited much improved visible light photocatalytic performance, which could degrade the RhB dye completely in 7.5 min. In addition, the coupling of Ag3PO4 particles with UV-light-sensitive TiO2 NFs enabled full utilization of solar energy and less consumption of noble metals, significantly appealing for their practical use in new energy sources and environmental issues. The developed synthetic strategy was considered to be applicable for the rational design and construction of other heterostructured catalysts.

  6. Efficient removal of herbicide 2,4-dichlorophenoxyacetic acid from water using Ag/reduced graphene oxide co-decorated TiO2 nanotube arrays.

    PubMed

    Tang, Yanhong; Luo, Shenglian; Teng, Yarong; Liu, Chengbin; Xu, Xiangli; Zhang, Xilin; Chen, Liang

    2012-11-30

    A new photocatalyst, Ag nanoparticles (NPs) and reduced graphene oxide (RGO) co-decorated TiO(2) nanotube arrays (NTs) (Ag/RGO-TiO(2) NTs), was designed and facilely produced by combining electrodeposition and photoreduction processes. The structures and properties of the photocatalysts were characterized. The ternary catalyst exhibited almost 100% photocatalytic removal efficiency of typical herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from water under simulated solar light irradiation. The photodegradation rate toward 2,4-D over Ag/RGO-TiO(2) NTs is 11.3 times that over bare TiO(2) NTs. After 10 successive cycles with 1600 min of irradiation, Ag/RGO-TiO(2) NTs maintained as high 2,4-D removal efficiency as 97.3% with excellent stability and easy recovery, which justifies the photocatalytic system a promising application for herbicide removal from water. PMID:23062512

  7. Efficient removal of herbicide 2,4-dichlorophenoxyacetic acid from water using Ag/reduced graphene oxide co-decorated TiO2 nanotube arrays.

    PubMed

    Tang, Yanhong; Luo, Shenglian; Teng, Yarong; Liu, Chengbin; Xu, Xiangli; Zhang, Xilin; Chen, Liang

    2012-11-30

    A new photocatalyst, Ag nanoparticles (NPs) and reduced graphene oxide (RGO) co-decorated TiO(2) nanotube arrays (NTs) (Ag/RGO-TiO(2) NTs), was designed and facilely produced by combining electrodeposition and photoreduction processes. The structures and properties of the photocatalysts were characterized. The ternary catalyst exhibited almost 100% photocatalytic removal efficiency of typical herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from water under simulated solar light irradiation. The photodegradation rate toward 2,4-D over Ag/RGO-TiO(2) NTs is 11.3 times that over bare TiO(2) NTs. After 10 successive cycles with 1600 min of irradiation, Ag/RGO-TiO(2) NTs maintained as high 2,4-D removal efficiency as 97.3% with excellent stability and easy recovery, which justifies the photocatalytic system a promising application for herbicide removal from water.

  8. Sonophotocatalytic degradation of dye C.I. Acid Orange 7 by TiO2 and Ag nanoparticles immobilized on corona pretreated polypropylene non-woven fabric.

    PubMed

    Marković, Darka; Šaponjić, Zoran; Radoičić, Marija; Radetić, Tamara; Vodnik, Vesna; Potkonjak, Branislav; Radetić, Maja

    2015-05-01

    This study discusses the possibility of using corona pre-treated polypropylene (PP) non-woven fabric as a support for immobilization of colloidal TiO2 and Ag nanoparticles in order to remove dye C.I. Acid Orange 7 from aqueous solution. Dye removal efficiency by sonocatalysis, photocatalysis and sonophotocatalysis was evaluated on corona pre-treated fabric loaded with TiO2 nanoparticles, corona pre-treated fabric double loaded with TiO2 nanoparticles and corona pre-treated fabrics loaded with TiO2 nanoparticles before and after deposition of Ag nanoparticles. In addition, the stability of PP non-woven fabric during these processes was investigated. The substrates were characterized by SEM, EDX and AAS analyses. The change of the dye concentration was evaluated by UV-VIS spectrophotometry. Unlike sonocatalysis and photocatalysis, complete dye removal from both solution and non-woven fabric was obtained already after 240-270 min of sonophotocatalysis. Corona pre-treated PP non-woven fabric loaded with Ag nanoparticles prior to deposition of TiO2 nanoparticles provided excellent degradation efficiency and superior reusability. Sonophotocatalytic degradation of dye in the presence of all investigated samples was the most prominent in acidic conditions. Although this nanocomposite system ensured fast discoloration of dye solution, TOC values of water measured after sonophotocatalysis were not satisfactory because of PP degradation. Therefore, it is suggested to include TOC evaluation in each case study where different supports for TiO2 nanoparticles are used since these nanoparticles may guarantee the dye removal from solution but the stability of support could be problematic causing even more serious environmental impact.

  9. Ag doped hollow TiO2 nanoparticles as an effective green fungicide against Fusarium solani and Venturia inaequalis phytopathogens

    NASA Astrophysics Data System (ADS)

    Sankar Boxi, Siddhartha; Mukherjee, Khushi; Paria, Santanu

    2016-02-01

    Chemical-based pesticides are widely used in agriculture to protect crops from insect infestation and diseases. However, the excessive use of highly toxic pesticides causes several human health (neurological, tumor, cancer) and environmental problems. Therefore nanoparticle-based green pesticides have become of special importance in recent years. The antifungal activities of pure and Ag doped (solid and hollow) TiO2 nanoparticles are studied against two potent phytopathogens, Fusarium solani (which causes Fusarium wilt disease in potato, tomato, etc) and Venturia inaequalis (which causes apple scab disease) and it is found that hollow nanoparticles are more effective than the other two. The antifungal activities of the nanoparticles were further enhanced against these two phytopathogens under visible light exposure. The fungicidal effect of the nanoparticles depends on different parameters, such as particle concentration and the intensity of visible light. The minimum inhibitory dose of the nanoparticles for V. inaequalis and F. solani are 0.75 and 0.43 mg/plate. The presence of Ag as a dopant helps in the formation of stable Ag-S and disulfide bonds (R-S-S-R) in cellular protein, which leads to cell damage. During photocatalysis generated •OH radicals loosen the cell wall structure and this finally leads to cell death. The mechanisms of the fungicidal effect of nanoparticles against these two phytopathogens are supported by biuret and triphenyl tetrazolium chloride analyses and field emission electron microscopy. Apart from the fungicidal effect, at a very low dose (0.015 mg/plate) the nanoparticles are successful in arresting production of toxic napthoquinone pigment for F. solani which is related to the fungal pathogenecity. The nanoparticles are found to be effective in protecting potatoes affected by F. solani or other fungi from spoiling.

  10. Ag doped hollow TiO2 nanoparticles as an effective green fungicide against Fusarium solani and Venturia inaequalis phytopathogens.

    PubMed

    Boxi, Siddhartha Sankar; Mukherjee, Khushi; Paria, Santanu

    2016-02-26

    Chemical-based pesticides are widely used in agriculture to protect crops from insect infestation and diseases. However, the excessive use of highly toxic pesticides causes several human health (neurological, tumor, cancer) and environmental problems. Therefore nanoparticle-based green pesticides have become of special importance in recent years. The antifungal activities of pure and Ag doped (solid and hollow) TiO2 nanoparticles are studied against two potent phytopathogens, Fusarium solani (which causes Fusarium wilt disease in potato, tomato, etc) and Venturia inaequalis (which causes apple scab disease) and it is found that hollow nanoparticles are more effective than the other two. The antifungal activities of the nanoparticles were further enhanced against these two phytopathogens under visible light exposure. The fungicidal effect of the nanoparticles depends on different parameters, such as particle concentration and the intensity of visible light. The minimum inhibitory dose of the nanoparticles for V. inaequalis and F. solani are 0.75 and 0.43 mg/plate. The presence of Ag as a dopant helps in the formation of stable Ag-S and disulfide bonds (R-S-S-R) in cellular protein, which leads to cell damage. During photocatalysis generated (•)OH radicals loosen the cell wall structure and this finally leads to cell death. The mechanisms of the fungicidal effect of nanoparticles against these two phytopathogens are supported by biuret and triphenyl tetrazolium chloride analyses and field emission electron microscopy. Apart from the fungicidal effect, at a very low dose (0.015 mg/plate) the nanoparticles are successful in arresting production of toxic napthoquinone pigment for F. solani which is related to the fungal pathogenecity. The nanoparticles are found to be effective in protecting potatoes affected by F. solani or other fungi from spoiling. PMID:26808118

  11. Ag doped hollow TiO2 nanoparticles as an effective green fungicide against Fusarium solani and Venturia inaequalis phytopathogens.

    PubMed

    Boxi, Siddhartha Sankar; Mukherjee, Khushi; Paria, Santanu

    2016-02-26

    Chemical-based pesticides are widely used in agriculture to protect crops from insect infestation and diseases. However, the excessive use of highly toxic pesticides causes several human health (neurological, tumor, cancer) and environmental problems. Therefore nanoparticle-based green pesticides have become of special importance in recent years. The antifungal activities of pure and Ag doped (solid and hollow) TiO2 nanoparticles are studied against two potent phytopathogens, Fusarium solani (which causes Fusarium wilt disease in potato, tomato, etc) and Venturia inaequalis (which causes apple scab disease) and it is found that hollow nanoparticles are more effective than the other two. The antifungal activities of the nanoparticles were further enhanced against these two phytopathogens under visible light exposure. The fungicidal effect of the nanoparticles depends on different parameters, such as particle concentration and the intensity of visible light. The minimum inhibitory dose of the nanoparticles for V. inaequalis and F. solani are 0.75 and 0.43 mg/plate. The presence of Ag as a dopant helps in the formation of stable Ag-S and disulfide bonds (R-S-S-R) in cellular protein, which leads to cell damage. During photocatalysis generated (•)OH radicals loosen the cell wall structure and this finally leads to cell death. The mechanisms of the fungicidal effect of nanoparticles against these two phytopathogens are supported by biuret and triphenyl tetrazolium chloride analyses and field emission electron microscopy. Apart from the fungicidal effect, at a very low dose (0.015 mg/plate) the nanoparticles are successful in arresting production of toxic napthoquinone pigment for F. solani which is related to the fungal pathogenecity. The nanoparticles are found to be effective in protecting potatoes affected by F. solani or other fungi from spoiling.

  12. A novel ethanol gas sensor based on TiO2/Ag0.35V2O5 branched nanoheterostructures

    NASA Astrophysics Data System (ADS)

    Wang, Yuan; Liu, Lixin; Meng, Chuanmin; Zhou, Yun; Gao, Zhao; Li, Xuhai; Cao, Xiuxia; Xu, Liang; Zhu, Wenjun

    2016-09-01

    Much greater surface-to-volume ratio of hierarchical nanostructures renders them attract considerable interest as prototypical gas sensors. In this work, a novel resistive gas sensor based on TiO2/Ag0.35V2O5 branched nanoheterostructures is fabricated by a facile one-step synthetic process and the ethanol sensing performance of this device is characterized systematically, which shows faster response/recovery behavior, better selectivity, and higher sensitivity of about 9 times as compared to the pure TiO2 nanofibers. The enhanced sensitivity of the TiO2/Ag0.35V2O5 branched nanoheterostructures should be attributed to the extraordinary branched hierarchical structures and TiO2/Ag0.35V2O5 heterojunctions, which can eventually result in an obvious change of resistance upon ethanol exposure. This study not only indicates the gas sensing mechanism for performance enhancement of branched nanoheterostructures, but also proposes a rational approach to design nanostructure based chemical sensors with desirable performance.

  13. A novel ethanol gas sensor based on TiO2/Ag0.35V2O5 branched nanoheterostructures.

    PubMed

    Wang, Yuan; Liu, Lixin; Meng, Chuanmin; Zhou, Yun; Gao, Zhao; Li, Xuhai; Cao, Xiuxia; Xu, Liang; Zhu, Wenjun

    2016-01-01

    Much greater surface-to-volume ratio of hierarchical nanostructures renders them attract considerable interest as prototypical gas sensors. In this work, a novel resistive gas sensor based on TiO2/Ag0.35V2O5 branched nanoheterostructures is fabricated by a facile one-step synthetic process and the ethanol sensing performance of this device is characterized systematically, which shows faster response/recovery behavior, better selectivity, and higher sensitivity of about 9 times as compared to the pure TiO2 nanofibers. The enhanced sensitivity of the TiO2/Ag0.35V2O5 branched nanoheterostructures should be attributed to the extraordinary branched hierarchical structures and TiO2/Ag0.35V2O5 heterojunctions, which can eventually result in an obvious change of resistance upon ethanol exposure. This study not only indicates the gas sensing mechanism for performance enhancement of branched nanoheterostructures, but also proposes a rational approach to design nanostructure based chemical sensors with desirable performance. PMID:27615429

  14. A novel ethanol gas sensor based on TiO2/Ag0.35V2O5 branched nanoheterostructures

    PubMed Central

    Wang, Yuan; Liu, Lixin; Meng, Chuanmin; Zhou, Yun; Gao, Zhao; Li, Xuhai; Cao, Xiuxia; Xu, Liang; Zhu, Wenjun

    2016-01-01

    Much greater surface-to-volume ratio of hierarchical nanostructures renders them attract considerable interest as prototypical gas sensors. In this work, a novel resistive gas sensor based on TiO2/Ag0.35V2O5 branched nanoheterostructures is fabricated by a facile one-step synthetic process and the ethanol sensing performance of this device is characterized systematically, which shows faster response/recovery behavior, better selectivity, and higher sensitivity of about 9 times as compared to the pure TiO2 nanofibers. The enhanced sensitivity of the TiO2/Ag0.35V2O5 branched nanoheterostructures should be attributed to the extraordinary branched hierarchical structures and TiO2/Ag0.35V2O5 heterojunctions, which can eventually result in an obvious change of resistance upon ethanol exposure. This study not only indicates the gas sensing mechanism for performance enhancement of branched nanoheterostructures, but also proposes a rational approach to design nanostructure based chemical sensors with desirable performance. PMID:27615429

  15. Role of Ag2S coupling on enhancing the visible-light-induced catalytic property of TiO2 nanorod arrays

    PubMed Central

    Li, Zhengcao; Xiong, Shan; Wang, Guojing; Xie, Zheng; Zhang, Zhengjun

    2016-01-01

    In order to obtain a better photocatalytic performance under visible light, Ag2S-coupled TiO2 nanorod arrays (NRAs) were prepared through the electron beam deposition with glancing angle deposition (GLAD) technique, annealing in air, followed by the successive ionic layer absorption and reaction (SILAR) method. The properties of the photoelectrochemical and photocatalytic degradation of methyl orange (MO) were thus conducted. The presence of Ag2S on TiO2 NRAs was observed to have a significant improvement on the response to visible light. It’s resulted from that Ag2S coupling can improve the short circuit photocurrent density and enhance the photocatalytic activity remarkably. PMID:26790759

  16. SiO(2) /TiO(2) hollow nanoparticles decorated with Ag nanoparticles: enhanced visible light absorption and improved light scattering in dye-sensitized solar cells.

    PubMed

    Hwang, Sun Hye; Shin, Dong Hoon; Yun, Juyoung; Kim, Chanhoi; Choi, Moonjung; Jang, Jyongsik

    2014-04-01

    Hollow SiO2 /TiO2 nanoparticles decorated with Ag nanoparticles (NPs) of controlled size (Ag@HNPs) were fabricated in order to enhance visible-light absorption and improve light scattering in dye-sensitized solar cells (DSSCs). They exhibited localized surface plasmon resonance (LSPR) and the LSPR effects were significantly influenced by the size of the Ag NPs. The absorption peak of the LSPR band dramatically increased with increasing Ag NP size. The LSPR of the large Ag NPs mainly increased the light absorption at short wavelengths, whereas the scattering from the SiO2 /TiO2 HNPs improved the light absorption at long wavelengths. This enabled the working electrode to use the full solar spectrum. Furthermore, the SiO2 layer thickness was adjusted to maximize the LSPR from the Ag NPs and avoid corrosion of the Ag NPs by the electrolyte. Importantly, the power conversion efficiency (PCE) increased from 7.1 % with purely TiO2 -based DSSCs to 8.1 % with HNP-based DSSCs, which is an approximately 12 % enhancement and can be attributed to greater light scattering. Furthermore, the PCEs of Ag@HNP-based DSSCs were 11 % higher (8.1 vs. 9.0 %) than the bare-HNP-based DSSCs, which can be attributed to LSPR. Together, the PCE of Ag@HNP-based DSSCs improved by a total of 27 %, from 7.1 to 9.0 %, due to these two effects. This comparative research will offer guidance in the design of multifunctional nanomaterials and the optimization of solar-cell performance.

  17. Correlations of Optical Absorption, Charge Trapping, and Surface Roughness of TiO2 Photoanode Layer Loaded with Neat Ag-NPs for Efficient Perovskite Solar Cells.

    PubMed

    Yang, Dongwook; Jang, Jae Gyu; Lim, Joohyun; Lee, Jin-Kyu; Kim, Sung Hyun; Hong, Jong-In

    2016-08-24

    We systematically investigated the effect of silver nanoparticles (Ag-NPs) on the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Neat, spherical Ag-NPs at loading levels of 0.0, 0.5, 1.0, and 2.0 wt % were embedded into the titanium dioxide (TiO2) photoanode layer. The plasmonic effect of the Ag-NPs strongly enhanced the incident light absorption over a wide range of the visible wavelength region in addition to the inherent absorbance of the perovskite sensitizer. The low conduction energy level of the Ag-NPs compared to that of TiO2 provides trap sites for free charge carriers. Thus, the correlation between the enhancement of the optical absorption and the number of charge traps provided by the Ag-NPs is critical to determine the device performance, especially current density (Jsc) and PCE. This is confirmed by the quantitative comparison of the incident light absorption and the time-resolved photoluminescence decay according to the loading levels of the Ag-NPs in the TiO2 layer. The absorption enhancement from 380 to 750 nm in the UV-visible spectrum is proportional to the increase in the loading levels of the Ag-NPs. However, the Jsc increases with the device with 0.5 wt % Ag-NPs and gradually decreases with increases in the loading level above 0.5 wt % because of the different contributions to the absorbance and the charge trapping by different Ag-NP loading levels. In addition, the suppression of the surface roughness with dense packing by the Ag-NPs helps to improve the Jsc and the following PCE. Consequently, the PCE of the PSC with 0.5 wt % Ag-NPs is increased to 11.96%. These results are attributed to the balance between increased absorbance by the localized surface plasmon resonance and the decreased charge trapping as well as the decreased surface roughness of the TiO2 layer with the Ag-NPs. PMID:27471777

  18. A robust super-paramagnetic TiO2:Fe3O4:Ag nanocomposite with enhanced photo and bio activities on polyester fabric via one step sonosynthesis.

    PubMed

    Harifi, Tina; Montazer, Majid

    2015-11-01

    High intensity ultrasound was used for the synthesis and simultaneous deposition of TiO2:Fe3O4:Ag nanocomposites on polyester surface providing a feasible route for imparting magnetic and enhanced antibacterial and self-cleaning activities with controllable hydrophilicity/hydrophobicity at low temperature. Synergistic impact of sonochemistry and physical effects of ultrasound originating from implosive collapse of bubbles were responsible for the formation and adsorption of nanomaterials on the fabric surface during ultrasound irradiation. The increase in photocatalytic activity of TiO2 was obtained attributing to the co-operation of iron oxide and silver nanoparticles nucleated on TiO2 surface boosting the electron-hole pair separation and prolonging their recombination rate. The process was further optimized in terms of reagents concentrations including Fe(2+)/TiO2 and Ag/TiO2 molar ratios using central composite design in order to achieve the best self-cleaning property of the treated fabric. The magnetic measurements indicated the super-paramagnetic behavior of the treated fabric with saturation magnetization of 4.5 (emu/g). Findings suggest the potential of the proposed facial method in producing an intelligent fabric with durable multi-functional activities that can be suitable for various applications including medical, military, bio-separation, bio-sensors, magneto graphic printing, magnetic screens and magnetic filters.

  19. A robust super-paramagnetic TiO2:Fe3O4:Ag nanocomposite with enhanced photo and bio activities on polyester fabric via one step sonosynthesis.

    PubMed

    Harifi, Tina; Montazer, Majid

    2015-11-01

    High intensity ultrasound was used for the synthesis and simultaneous deposition of TiO2:Fe3O4:Ag nanocomposites on polyester surface providing a feasible route for imparting magnetic and enhanced antibacterial and self-cleaning activities with controllable hydrophilicity/hydrophobicity at low temperature. Synergistic impact of sonochemistry and physical effects of ultrasound originating from implosive collapse of bubbles were responsible for the formation and adsorption of nanomaterials on the fabric surface during ultrasound irradiation. The increase in photocatalytic activity of TiO2 was obtained attributing to the co-operation of iron oxide and silver nanoparticles nucleated on TiO2 surface boosting the electron-hole pair separation and prolonging their recombination rate. The process was further optimized in terms of reagents concentrations including Fe(2+)/TiO2 and Ag/TiO2 molar ratios using central composite design in order to achieve the best self-cleaning property of the treated fabric. The magnetic measurements indicated the super-paramagnetic behavior of the treated fabric with saturation magnetization of 4.5 (emu/g). Findings suggest the potential of the proposed facial method in producing an intelligent fabric with durable multi-functional activities that can be suitable for various applications including medical, military, bio-separation, bio-sensors, magneto graphic printing, magnetic screens and magnetic filters. PMID:25899439

  20. Bonding and Anti-bonding Modes of Plasmon Coupling Effects in TiO2-Ag Core-shell Dimers

    PubMed Central

    Li, Quanshui; Zhang, Zhili

    2016-01-01

    Bonding and anti-bonding modes of plasmon coupling effects are numerically investigated in TiO2-Ag core-shell nano dimers. First, splitting phenomena of the coupled anti-bonding modes are observed under the longitudinal polarization when the distance between the monomers decreases to a certain level. Second, one of the split resonance modes is identified to be formed by the dipole anti-bonding mode of the monomers from charge density distribution patterns. Those split modes have similar redshift behaviors as the coupled dipole bonding modes in the same situations. Furthermore, the intensities of those anti-bonding modes weaken with decreasing distance between the monomers, because of the interaction of the induced dipole moment in the monomers and the charge distribution variation on the facing surfaces of the gap by the coulomb attraction. Other split bands are the higher-order mode (octupole-like or triakontadipole-like), which do not have obvious peak-shift behavior, and the intensities have very little attenuation with decreasing distance. Finally, the coupling of the bonding and anti-bonding modes under the longitudinal polarization is symmetric (bonding). PMID:26763719

  1. Bonding and Anti-bonding Modes of Plasmon Coupling Effects in TiO2-Ag Core-shell Dimers.

    PubMed

    Li, Quanshui; Zhang, Zhili

    2016-01-01

    Bonding and anti-bonding modes of plasmon coupling effects are numerically investigated in TiO2-Ag core-shell nano dimers. First, splitting phenomena of the coupled anti-bonding modes are observed under the longitudinal polarization when the distance between the monomers decreases to a certain level. Second, one of the split resonance modes is identified to be formed by the dipole anti-bonding mode of the monomers from charge density distribution patterns. Those split modes have similar redshift behaviors as the coupled dipole bonding modes in the same situations. Furthermore, the intensities of those anti-bonding modes weaken with decreasing distance between the monomers, because of the interaction of the induced dipole moment in the monomers and the charge distribution variation on the facing surfaces of the gap by the coulomb attraction. Other split bands are the higher-order mode (octupole-like or triakontadipole-like), which do not have obvious peak-shift behavior, and the intensities have very little attenuation with decreasing distance. Finally, the coupling of the bonding and anti-bonding modes under the longitudinal polarization is symmetric (bonding). PMID:26763719

  2. Enhanced photo-catalytic activity of Sr and Ag co-doped TiO2 nanoparticles for the degradation of Direct Green-6 and Reactive Blue-160 under UV & visible light.

    PubMed

    Naraginti, Saraschandra; Thejaswini, T V L; Prabhakaran, D; Sivakumar, A; Satyanarayana, V S V; Arun Prasad, A S

    2015-10-01

    This work is focused on sol-gel synthesis of silver and strontium co-doped TiO2 nanoparticles and their utilization as photo-catalysts in degradation of two textile dyes. Effect of pH, intensity of light, amount of photo-catalyst, concentration of dye, sensitizers, etc., were studied to optimize conditions for obtaining enhanced photo-catalytic activity of synthesized nanoparticles. XRD, BET, HR-TEM, EDAX and UV-Vis (diffused reflectance mode) techniques were used to characterize the nanoparticles. Interestingly, band gap of Sr and Ag co-doped TiO2 nanoparticles showed considerable narrowing (2.6 eV) when compared to Ag doped TiO2 (2.7 eV) and undoped TiO2 (3.17 eV) nanoparticles. Incorporation of Ag and Sr in the lattice of TiO2 could bring isolated energy levels near conduction and valence bands thus narrowing band gap. The XRD analysis shows that both Ag and Sr nanoparticles are finely dispersed on the surface of titania framework, without disturbing its crystalline structure. TEM images indicate that representative grain sizes of Ag-doped TiO2 & Sr and Ag co-doped TiO2 nanoparticles are in the range of 8-20 nm and 11-25 nm, respectively. Effective degradation of Direct Green-6 (DG-6) and Reactive Blue-160 (RB-160) under UV and visible light has been achieved using the photo-catalysts. Sr and Ag co-doped TiO2 photo-catalysts showed higher catalytic activity during degradation process in visible region when compared to Ag-doped and undoped TiO2 nanoparticles which could be attributed to the interactive effect caused by band gap narrowing and enhancement in charge separation. For confirming degradation of the dyes, total organic carbon (TOC) content was monitored periodically.

  3. Photochemically deposited nano-Ag/sol-gel TiO2-In2O3 mixed oxide mesoporous-assembled nanocrystals for photocatalytic dye degradation.

    PubMed

    Sreethawong, Thammanoon; Ngamsinlapasathian, Supachai; Yoshikawa, Susumu

    2014-05-01

    This work focused on the improvement of the photocatalytic activity for Congo Red (CR) azo dye degradation of mesoporous-assembled 0.95 TiO2-0.05 In2O3 mixed oxide photocatalyst (with a TiO2-to-In2O3 molar ratio of 0.95:0.05) by loading with Ag nanoparticles. The mesoporous-assembled 0.95TiO2-0.05In2O3 mixed oxide photocatalyst was synthesized by a hydrolytic sol-gel method with the aid of a structure-directing surfactant, prior to loading with various Ag contents (0.5-2 wt.%) by a photochemical deposition method. The optimum Ag loading content was found to be 1.5 wt.%, exhibiting a great increase in photocatalytic CR dye degradation activity. The 1.5 wt.% Ag-loaded 0.95TiO2-0.05In2O3 mixed oxide photocatalyst was further applied for the CR dye degradation in the presence of water hardness. Different types (Ca2+ and Ca2+ -Mg2+ mixture) and concentrations (200 and 500 mg/l) of water hardness were investigated. The results showed that the water hardness reduced the photocatalytic CR dye degradation activity, particularly for the extremely hard water with 500 mg/l of Ca2+ -Mg2+ mixture. The adjustment of initial solution pH of the CR dye-containing hard water to an appropriate value was found to improve the photocatalytic CR dye degradation activity under the identical reaction conditions.

  4. Performance improvement of TiO2/Ag/TiO2 multilayer transparent conducting electrode films for application on photodetectors

    NASA Astrophysics Data System (ADS)

    Zhu, Meng-Qi; Jin, Han-Dong; Bi, Peng-Qing; Zong, Fu-Jian; Ma, Jin; Hao, Xiao-Tao

    2016-03-01

    TiO2/Ag/TiO2 (TAT) multilayer transparent conducting electrodes were deposited onto glass substrates by room temperature sputtering. The impact of Ag sputtering current on the film morphology, and the optical and electrical properties were discussed. The increase in the sputtering current led to a more continuous Ag middle layer. As the Ag middle layer became continuous, the TAT electrodes had lower sheet resistance and higher transmittance. In addition, an optimized TAT electrode with a figure of merit of 15.97× {{10}-2}{{Ω }-1} was obtained at an Ag thickness of 16 nm and a sputtering current of 0.48 A. Finally, organic photodetectors were also fabricated based on TAT electrodes and the performance is comparable to reference devices with commercially purchased Sn-doped In2O3 (ITO) electrodes.

  5. Visible-Light-Responsive Photocatalysis: Ag-Doped TiO2 Catalyst Development and Reactor Design Testing

    NASA Technical Reports Server (NTRS)

    Coutts, Janelle L.; Hintze, Paul E.; Meier, Anne; Shah, Malay G.; Devor, Robert W.; Surma, Jan M.; Maloney, Phillip R.; Bauer, Brint M.; Mazyck, David W.

    2016-01-01

    In recent years, the alteration of titanium dioxide to become visible-light-responsive (VLR) has been a major focus in the field of photocatalysis. Currently, bare titanium dioxide requires ultraviolet light for activation due to its band gap energy of 3.2 eV. Hg-vapor fluorescent light sources are used in photocatalytic oxidation (PCO) reactors to provide adequate levels of ultraviolet light for catalyst activation; these mercury-containing lamps, however, hinder the use of this PCO technology in a spaceflight environment due to concerns over crew Hg exposure. VLR-TiO2 would allow for use of ambient visible solar radiation or highly efficient visible wavelength LEDs, both of which would make PCO approaches more efficient, flexible, economical, and safe. Over the past three years, Kennedy Space Center has developed a VLR Ag-doped TiO2 catalyst with a band gap of 2.72 eV and promising photocatalytic activity. Catalyst immobilization techniques, including incorporation of the catalyst into a sorbent material, were examined. Extensive modeling of a reactor test bed mimicking air duct work with throughput similar to that seen on the International Space Station was completed to determine optimal reactor design. A bench-scale reactor with the novel catalyst and high-efficiency blue LEDs was challenged with several common volatile organic compounds (VOCs) found in ISS cabin air to evaluate the system's ability to perform high-throughput trace contaminant removal. The ultimate goal for this testing was to determine if the unit would be useful in pre-heat exchanger operations to lessen condensed VOCs in recovered water thus lowering the burden of VOC removal for water purification systems.

  6. Plasmon-exciton coupling at Ag nanocluster decorated TiO2(110) surface studied by time-resolved two-photon photoemission spectroscopy

    NASA Astrophysics Data System (ADS)

    Tan, Shijing; Argondizzo, Adam; Petek, Hrvoje

    We study the spectroscopy and electron dynamics at Ag nanocluster decorated TiO2(110) surface upon photoexcitation of plasmonic modes by two-photon photoemission spectroscopy (2PP). Depositing Ag onto a reduced rutile TiO2(110) surface at room temperature forms pancake-like Ag particles with an average diameter of 4 nm and height of 1.5 nm. Measurements of the 2PP yield from Ag/TiO2 surface with tunable femtosecond laser excitation show enhancement at plasmonic resonances. Exciting with s-polarization (S -->) the plasmonic resonance enhancement has a single peak at 3.1 eV, whereas with p-polarization (P -->) there is an additional more intense resonance at 3.8 eV. We attribute the 3.1 and 3.8 eV peaks to the in-plane and the surface-normal plasmon modes respectively. Crystal azimuth orientation dependent excitation with (S -->) shows an anisotropy in the 2PP spectra for the 3.1 eV in-plane plasmon mode when the laser electric field is aligned in the [001] vs. [ 1 1 0 ] directions. The existence of two plasmon modes and the in-plane plasmon anisotropy imply that the plasmon modes are perturbed by coherent coupling with excitons in the rutile TiO2 substrate. We speculate that plasmon-exciton resonant energy transfer could play an important role in the plasmonically enhanced photocatalysis at the Ag/TiO2 surface.

  7. Multi-functional TiO2/Si/Ag(Cr)/TiNx coatings for low-emissivity and hydrophilic applications

    NASA Astrophysics Data System (ADS)

    Loka, Chadrasekhar; Park, Kyoung Ryeol; Lee, Kee-Sun

    2016-02-01

    Multi-functional (coatings with some additional functional properties such as high transparency, antireflection, hydrophilicity and antifogging) coatings are indispensable for the modern energy saving systems. In this regard, we deposited TiO2/Si/Ag(Cr)/TiNx multilayer thin films on soda-lime glass by using RF and DC magnetron sputtering to achieve a multi-functional thin film stack with the combination low-emissivity (low-e) and hydrophilicity properties in addition to the high transparency. Primary deposition of Ag(Cr)/TiNx was tried for the low-e effect and successfully obtained a very low emissivity value of 0.067, and then Si and TiO2 films with different bandgap were subsequently deposited to provide the hydrophilic properties. X-ray diffraction results revealed the anatase phase formation of TiO2 after annealing the films at 673 K by using the rapid thermal annealing system. Rutherford Backscattering Spectrometry (RBS) was carried out to determine the chemical composition and elemental depth distribution. The multilayer stack exhibited superhydrophilicity with a water contact angle of about 5° after irradiation by UV light. A Heterojunction film with wide and narrow bandgap semiconductor materials was effective to improve the hydrophilicity. The films exhibited a high visible transmittance (∼85.5%, at 550 nm) and low infrared transmittance (7%, at 2000 nm) including low-e and superhydrophilicity.

  8. Synthesize and characterize of Ag3VO4/TiO2 nanorods photocatalysts and its photocatalytic activity under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Zou, Xuejun; Dong, Yuying; Zhang, Xiaodong; Cui, Yubo

    2016-03-01

    In this paper, in order to expand the light response range of TiO2, Ag3VO4/TiO2 nanorods photocatalysts were fabricated by a simple sol-gel method with microwave and hydrothermal method. The as-prepared samples were characterized by XRD, SEM, DRS, XPS and N2 adsorption-desorption. Meanwhile, their photocatalytic properties were investigated by the degradation of toluene under visible light irradiation. The degradation conversation of toluene had gotten to about 70% in 1% Ag3VO4/TiO2 nanorods after reaction 4 h. The predominant photocatalytic activity can be attributed to its strong absorption in visible light region and excellent charge separation characteristics. By using in situ FTIR, benzyl alcohol and benzaldehyde species could be observed during the reaction and the formed intermediates would be partially oxidized into CO2 and H2O. Electron spin resonance confirmed that OHrad and O2rad - were involved in the photocatalytic degradation of toluene.

  9. CO 2 Adsorption on Anatase TiO 2 (101) Surfaces in the Presence of Subnanometer Ag/Pt Clusters: Implications for CO 2 Photoreduction

    DOE PAGES

    Yang, Chi-Ta; Wood, Brandon C.; Bhethanabotla, Venkat R.; Joseph, Babu

    2014-10-20

    We show how CO2 adsorption on perfect and reduced anatase TiO2 (101) surfaces can be substantially modified by the presence of surface Ag and Pt octamer clusters, using density functional theory calculations. Furthermore, we found that adsorption was affected even at sites where the adsorbate was not in direct contact with the octamer, which we attributed to charge donation to CO2 from the Ag/Pt-modified surface, as well as an electrostatic competition between attractive (Ti–O) and repulsive (Ti–C) interactions. Additionally, TiO2-supported Pt octamers offer key advantages that could be leveraged for CO2 photoreduction, including providing additional stable adsorption sites for bentmore » CO2 species and facilitating charge transfer to aid in CO2– anion formation. Electronic structure analysis suggests these factors arise primarily from the hybridization of the bonding molecular orbitals of CO2 with d orbitals of the Pt atoms. Our results show that, for adsorption on TiO2-supported Pt octamers, the O–C–O bending and C–O asymmetric stretching frequencies can be used as reliable indicators of the presence of the CO2– anion intermediate as well as to distinguish unique adsorption geometries or sites. Finally, we suggest a possible pathway for subsequent CO2 dissociation to CO at the surface of a reduced anatase TiO2 (101)-supported Pt octamer, which has a computed energy barrier of 1.01 eV.« less

  10. TiO2 nanotube composite layers as delivery system for ZnO and Ag nanoparticles - an unexpected overdose effect decreasing their antibacterial efficacy.

    PubMed

    Roguska, A; Belcarz, A; Pisarek, M; Ginalska, G; Lewandowska, M

    2015-06-01

    Enhancement of biocompatibility and antibacterial properties of implant materials is potentially beneficial for their practical value. Therefore, the use of metallic and metallic oxide nanoparticles as antimicrobial coatings components which induce minimized antibacterial resistance receives currently particular attention. In this work, TiO2 nanotubes layers loaded with ZnO and Ag nanoparticles were designed for biomedical coatings and delivery systems and evaluated for antimicrobial activity. TiO2 nanotubes themselves exhibited considerable and diameter-dependent antibacterial activity against planktonic Staphylococcus epidermidis cells but favored bacterial adhesion. Loading of nanotubes with moderate amount of ZnO nanoparticles significantly diminished S. epidermidis cell adhesion and viability just after 1.5h contact with modified surfaces. However, an increase of loaded ZnO amount unexpectedly altered the structure of nanoparticle-nanolayer, caused partial closure of nanotube interior and significantly reduced ZnO solubility and antibacterial efficacy. Co-deposition of Ag nanoparticles enhanced the antibacterial properties of synthesized coatings. However, the increase of ZnO quantity on Ag nanoparticles co-deposited surfaces favored the adhesion of bacterial cells. Thus, ZnO/Ag/TiO2 nanotube composite layers may be promising delivery systems for combating post-operative infections in hard tissue replacement procedures. However, the amount of loaded antibacterial agents must be carefully balanced to avoid the overdose and reduced efficacy.

  11. Bioinspired anchoring AgNPs onto micro-nanoporous TiO2 orthopedic coatings: Trap-killing of bacteria, surface-regulated osteoblast functions and host responses.

    PubMed

    Jia, Zhaojun; Xiu, Peng; Li, Ming; Xu, Xuchen; Shi, Yuying; Cheng, Yan; Wei, Shicheng; Zheng, Yufeng; Xi, Tingfei; Cai, Hong; Liu, Zhongjun

    2016-01-01

    The therapeutic applications of silver nanoparticles (AgNPs) against biomedical device-associated infections (BAI), by local delivery, are encountered with risks of detachment, instability and nanotoxicity in physiological milieus. To firmly anchor AgNPs onto modified biomaterial surfaces through tight physicochemical interactions would potentially relieve these concerns. Herein, we present a strategy for hierarchical TiO2/Ag coating, in an attempt to endow medical titanium (Ti) with anticorrosion and antibacterial properties whilst maintaining normal biological functions. In brief, by harnessing the adhesion and reactivity of bioinspired polydopamine, silver nanoparticles were easily immobilized onto peripheral surface and incorporated into interior cavity of a micro/nanoporous TiO2 ceramic coating in situ grown from template Ti. The resulting coating protected the substrate well from corrosion and gave a sustained release of Ag(+) up to 28 d. An interesting germicidal effect, termed "trap-killing", was observed against Staphylococcus aureus strain. The multiple osteoblast responses, i.e. adherence, spreading, proliferation, and differentiation, were retained normal or promoted, via a putative surface-initiated self-regulation mechanism. After subcutaneous implantation for a month, the coated specimens elicited minimal, comparable inflammatory responses relative to the control. Moreover, this simple and safe functionalization strategy manifested a good degree of flexibility towards three-dimensional sophisticated objects. Expectedly, it can become a prospective bench to bedside solution to current challenges facing orthopedics.

  12. Antifungal activity of Ag:hydroxyapatite thin films synthesized by pulsed laser deposition on Ti and Ti modified by TiO2 nanotubes substrates

    NASA Astrophysics Data System (ADS)

    Eraković, S.; Janković, A.; Ristoscu, C.; Duta, L.; Serban, N.; Visan, A.; Mihailescu, I. N.; Stan, G. E.; Socol, M.; Iordache, O.; Dumitrescu, I.; Luculescu, C. R.; Janaćković, Dj.; Miškovic-Stanković, V.

    2014-02-01

    Hydroxyapatite (HA) is a widely used biomaterial for implant thin films, largely recognized for its excellent capability to chemically bond to hard tissue inducing the osteogenesis without immune response from human tissues. Nowadays, intense research efforts are focused on development of antimicrobial HA doped thin films. In particular, HA doped with Ag (Ag:HA) is expected to inhibit the attachment of microbes and contamination of metallic implant surface. We herewith report on nano-sized HA and Ag:HA thin films synthesized by pulsed laser deposition on pure Ti and Ti modified with 100 nm diameter TiO2 nanotubes (fabricated by anodization of Ti plates) substrates. The HA-based thin films were characterized by SEM, AFM, EDS, FTIR, and XRD. The cytotoxic activity was tested with HEp2 cells against controls. The antifungal efficiency of the deposited layers was tested against the Candida albicans and Aspergillus niger strains. The Ti substrates modified with TiO2 nanotubes covered with Ag:HA thin films showed the highest antifungal activity.

  13. Conductive and transparent multilayer films for low-temperature TiO2/Ag/SiO2 electrodes by E-beam evaporation with IAD

    PubMed Central

    2014-01-01

    Conductive and transparent multilayer thin films consisting of three alternating layers (TiO2/Ag/SiO2, TAS) have been fabricated for applications as transparent conducting oxides. Metal oxide and metal layers were prepared by electron-beam evaporation with ion-assisted deposition, and the optical and electrical properties of the resulting films as well as their energy bounding characteristics and microstructures were carefully investigated. The optical properties of the obtained TAS material were compared with those of well-known transparent metal oxide glasses such as ZnO/Ag/ZnO, TiO2/Ag/TiO2, ZnO/Cu/ZnO, and ZnO/Al/ZnO. The weathering resistance of the TAS film was improved by using a protective SiO2 film as the uppermost layer. The transmittance spectra and sheet resistance of the material were carefully measured and analyzed as a function of the layer thickness. By properly adjusting the thickness of the metal and dielectric films, a low sheet resistance of 6.5 ohm/sq and a high average transmittance of over 89% in the 400 to 700 nm wavelength regions were achieved. We found that the Ag layer played a significant role in determining the optical and electrical properties of this film. PMID:24433437

  14. TiO2 nanotube composite layers as delivery system for ZnO and Ag nanoparticles - an unexpected overdose effect decreasing their antibacterial efficacy.

    PubMed

    Roguska, A; Belcarz, A; Pisarek, M; Ginalska, G; Lewandowska, M

    2015-06-01

    Enhancement of biocompatibility and antibacterial properties of implant materials is potentially beneficial for their practical value. Therefore, the use of metallic and metallic oxide nanoparticles as antimicrobial coatings components which induce minimized antibacterial resistance receives currently particular attention. In this work, TiO2 nanotubes layers loaded with ZnO and Ag nanoparticles were designed for biomedical coatings and delivery systems and evaluated for antimicrobial activity. TiO2 nanotubes themselves exhibited considerable and diameter-dependent antibacterial activity against planktonic Staphylococcus epidermidis cells but favored bacterial adhesion. Loading of nanotubes with moderate amount of ZnO nanoparticles significantly diminished S. epidermidis cell adhesion and viability just after 1.5h contact with modified surfaces. However, an increase of loaded ZnO amount unexpectedly altered the structure of nanoparticle-nanolayer, caused partial closure of nanotube interior and significantly reduced ZnO solubility and antibacterial efficacy. Co-deposition of Ag nanoparticles enhanced the antibacterial properties of synthesized coatings. However, the increase of ZnO quantity on Ag nanoparticles co-deposited surfaces favored the adhesion of bacterial cells. Thus, ZnO/Ag/TiO2 nanotube composite layers may be promising delivery systems for combating post-operative infections in hard tissue replacement procedures. However, the amount of loaded antibacterial agents must be carefully balanced to avoid the overdose and reduced efficacy. PMID:25842121

  15. In situ fabrication of Ag3PO4/TiO2 nanotube heterojunctions with enhanced visible-light photocatalytic activity.

    PubMed

    Tong, Zhen Wei; Yang, Dong; Sun, Yuan Yuan; Tian, Yao; Jiang, Zhong Yi

    2015-05-14

    Ag3PO4/TiO2 nanotube (TNT) heterojunctions were fabricated via a facile in situ growth method. Hemispherical Ag3PO4 nanocrystals were uniformly grown on the TNT surface, and their size was confined to 5-10 nm. A joint area was distinctly observed between the Ag3PO4 nanocrystals and TNT, indicating the formation of a Ag3PO4/TNT heterojunction. Compared with pure Ag3PO4, the Ag3PO4/TNT heterojunction possesses more active sites, less bulk defects, more efficient electron-hole separation, as well as better dye adsorption properties, and thus exhibits a significantly elevated photocatalytic activity for Rhodamine B (RhB) degradation. The study of the reactive species demonstrates that the photocatalytic degradation of RhB over the Ag3PO4/TNT heterojunction is primarily driven by both photogenerated h(+) and ˙OH radicals. This easily-fabricated Ag3PO4/TNT heterojunction with promising photocatalytic activity may find potential applications in energy and environmental related areas. PMID:25884048

  16. In situ fabrication of Ag3PO4/TiO2 nanotube heterojunctions with enhanced visible-light photocatalytic activity.

    PubMed

    Tong, Zhen Wei; Yang, Dong; Sun, Yuan Yuan; Tian, Yao; Jiang, Zhong Yi

    2015-05-14

    Ag3PO4/TiO2 nanotube (TNT) heterojunctions were fabricated via a facile in situ growth method. Hemispherical Ag3PO4 nanocrystals were uniformly grown on the TNT surface, and their size was confined to 5-10 nm. A joint area was distinctly observed between the Ag3PO4 nanocrystals and TNT, indicating the formation of a Ag3PO4/TNT heterojunction. Compared with pure Ag3PO4, the Ag3PO4/TNT heterojunction possesses more active sites, less bulk defects, more efficient electron-hole separation, as well as better dye adsorption properties, and thus exhibits a significantly elevated photocatalytic activity for Rhodamine B (RhB) degradation. The study of the reactive species demonstrates that the photocatalytic degradation of RhB over the Ag3PO4/TNT heterojunction is primarily driven by both photogenerated h(+) and ˙OH radicals. This easily-fabricated Ag3PO4/TNT heterojunction with promising photocatalytic activity may find potential applications in energy and environmental related areas.

  17. Magnetically separable Fe3O4@SiO2@TiO2-Ag microspheres with well-designed nanostructure and enhanced photocatalytic activity.

    PubMed

    Chi, Yue; Yuan, Qing; Li, Yanjuan; Zhao, Liang; Li, Nan; Li, Xiaotian; Yan, Wenfu

    2013-11-15

    Major efforts in modern material chemistry are devoted to the design and fabrication of nanostructured systems with tunable physical-chemical properties for advanced catalytic applications. Here, a novel Fe3O4@SiO2@TiO2-Ag nanocomposite has been synthesized and characterized by a series of techniques including SEM, TEM, XRD, XPS as well as magnetization measurement and subsequently tested for the photocatalytic activities. The well-designed nanocomposite exhibits significantly superior activity to that of the commercial Degussa P25 thanks to the suppression of electron-hole pairs from recombination by Ag nanoparticles, and can be easily recycled by applying an external magnetic field while maintaining the catalytic activity without significant decrease even after running 10 times. The unique nanostructure makes Fe3O4@SiO2@TiO2-Ag a highly efficient, recoverable, stable, and cost-effective photocatalytic system offering broad opportunities in the field of catalyst synthesis and application. PMID:24076477

  18. UV-vis light activated Ag decorated monodisperse TiO2 for treatment of pharmaceuticals in water

    EPA Science Inventory

    Recently, many researchers have made a lot of effort to utilize the visible light portion of the solar spectrum to activate TiO2 photocatalyst for environmental applications, such as water, air, and soil remediation. The deposition of noble metals on photocatalysts is of great in...

  19. Highly efficient and recyclable triple-shelled Ag@Fe3O4@SiO2@TiO2 photocatalysts for degradation of organic pollutants and reduction of hexavalent chromium ions

    NASA Astrophysics Data System (ADS)

    Su, Jianwei; Zhang, Yunxia; Xu, Sichao; Wang, Shuan; Ding, Hualin; Pan, Shusheng; Wang, Guozhong; Li, Guanghai; Zhao, Huijun

    2014-04-01

    Herein, we demonstrate the design and fabrication of the well-defined triple-shelled Ag@Fe3O4@SiO2@TiO2 nanospheres with burr-shaped hierarchical structures, in which the multiple distinct functional components are integrated wonderfully into a single nanostructure. In comparison with commercial TiO2 (P25), pure TiO2 microspheres, Fe3O4@SiO2@TiO2 and annealed Ag@Fe3O4@SiO2@TiO2 nanocomposites, the as-obtained amorphous triple-shelled Ag@Fe3O4@SiO2@TiO2 hierarchical nanospheres exhibit a markedly enhanced visible light or sunlight photocatalytic activity towards the photodegradation of methylene blue and photoreduction of hexavalent chromium ions in wastewater. The outstanding photocatalytic activities of the plasmonic photocatalyst are mainly due to the enhanced light harvesting, reduced transport paths for both mass and charge transport, reduced recombination probability of photogenerated electrons/holes, near field electromagnetic enhancement and efficient scattering from the plasmonic nanostructure, increased surface-to-volume ratio and active sites in three dimensional (3D) hierarchical porous nanostructures, and improved photo/chemical stability. More importantly, the hierarchical nanostructured Ag@Fe3O4@SiO2@TiO2 photocatalysts could be easily collected and separated by applying an external magnetic field and reused at least five times without any appreciable reduction in photocatalytic efficiency. The enhanced photocatalytic activity and excellent chemical stability, in combination with the magnetic recyclability, make these multifunctional nanostructures promising candidates to remediate aquatic contaminants and meet the demands of future environmental issues.Herein, we demonstrate the design and fabrication of the well-defined triple-shelled Ag@Fe3O4@SiO2@TiO2 nanospheres with burr-shaped hierarchical structures, in which the multiple distinct functional components are integrated wonderfully into a single nanostructure. In comparison with commercial TiO2

  20. Time-resolved imaging of positive pulsed corona-induced surface streamers on TiO2 and γ-Al2O3-supported Ag catalysts

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Ha; Teramoto, Yoshiyuki; Ogata, Atsushi

    2016-10-01

    We report the first instance of time-resolved imaging of surface streamers in air propagating on the surface of titanium dioxide (TiO2) and alumina (γ-Al2O3) beads at ambient temperature and atmospheric pressure. The propagation velocity of primary streamers was found to be dependent primarily on the applied voltage and the type of catalyst. The presence of Ag nanoparticles enhanced the propagation velocity of primary streamers in both TiO2 and γ-Al2O3. Some of the primary streamers passed through a partial discharge, which resulted in enhanced discharge intensity. Through successive steps, the partial discharge served as a staging point for primary streamers, and promoted their propagation toward the next catalyst bead. For a given configuration and catalyst, the velocity of the primary streamer was largely influenced by applied voltage and catalyst type. For a mesh-to-mesh reactor with Ag/ TiO2 catalyst, the primary streamer reached about 660 km s‑1. Secondary streamers occurred with much slower velocities after the primary streamer had disappeared. In contrast to primary streamers, secondary streamer velocities were almost completely independent of the applied voltage on both TiO2 (150  ±  50 km s‑1) and γ-Al2O3 (70  ±  10 km s‑1). Detailed time-resolved imaging data on surface streamers can provide important insight into understanding and modeling plasma-catalysis, which can accelerate the progress of research and development in this area.

  1. Adhesion and inactivation of Gram-negative and Gram-positive bacteria on photoreactive TiO2/polymer and Ag-TiO2/polymer nanohybrid films

    NASA Astrophysics Data System (ADS)

    Tallósy, Szabolcs Péter; Janovák, László; Nagy, Elisabeth; Deák, Ágota; Juhász, Ádám; Csapó, Edit; Buzás, Norbert; Dékány, Imre

    2016-05-01

    The aim of this study was to develop photoreactive surface coatings, possessing antibacterial properties and can be activated under visible light illumination (λmax = 405 nm) using LED-light source. The photocatalytically active titanium dioxide (TiO2) was functionalized with silver nanoparticles (Ag NPs) and immobilized in polyacrylate based nanohybrid thin film in order to facilitate visible light activity (λAg/TiO2,max = 500 nm). First, the photocatalytic activity was modelled by following ethanol vapor degradation. The plasmonic functionalization resulted in 15% enhancement of the activity compared to pure TiO2. The photoreactive antimicrobial (5 log reduction of cfu in 2 h) surface coatings are able to inactivate clinically relevant pathogen strains (methicillin resistant Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa) within short time (60-120 min) due to the formed and quantified reactive oxygen species (ROS). The existence of electrostatic interactions between the negatively charged bacteria (from -0.89 to -3.19 μeq/109 cfu) and positively charged photocatalyst particles (in the range of +0.38 and +12.3 meq/100 g) was also proven by charge titration measurements. The surface inactivation of the bacteria and the photocatalytic degradation of the cell wall component were also confirmed by fluorescence and transmission electron microscopic observations, respectively. According to the results an effective sterilizing system and prevention strategy can be developed and carried out against dangerous microorganisms in health care.

  2. Enhancing carrier generation in TiO2 by a synergistic effect between plasmon resonance in Ag nanoparticles and optical interference.

    PubMed

    Cacciato, Giuseppe; Bayle, Maxime; Pugliara, Alessandro; Bonafos, Caroline; Zimbone, Massimo; Privitera, Vittorio; Grimaldi, Maria Grazia; Carles, Robert

    2015-08-28

    Silver nanoparticles have been embedded at a few nanometer distance from the free surface of titania/silica multilayers using low energy ion beam synthesis. Transmission electron microscopy shows the presence of 3 nm-sized crystalline particles. Reflectance spectroscopy on these composite substrates shows an increase of the light capture efficiency in the visible range. This behaviour is interpreted as a synergistic effect between plasmon polariton resonance and Fabry-Perot interferences. Plasmon-resonant Raman spectroscopy is deeply used to analyze, on one hand confinement of vibrations and electronic excitations in Ag NPs, and on the other hand coupling of polar TiO2 phonons with injected photo-generated carriers. It is shown how these new Ag/TiO2 nanocomposite films appear as very promising to enhance the efficiency and enlarge the spectral sensitivity of plasmo-electronics devices. PMID:26198669

  3. Ramification of variable thickness on MHD TiO2 and Ag nanofluid flow over a slendering stretching sheet using NDM

    NASA Astrophysics Data System (ADS)

    Acharya, Nilankush; Das, Kalidas; Kumar Kundu, Prabir

    2016-09-01

    The present investigation reveals the effect of variable thickness on the steady two-dimensional boundary layer flows of a TiO2-water and Ag-water nanofluid through a slendering stretching sheet. The whole analysis has been performed in the presence of variable magnetic field and variable surface temperature. Similarity transformation has been introduced to renovate the non-linear partial differential equations into ordinary ones and then they were solved using the innovative technique of Natural decomposition method (NDM). The influence of pertinent parameters on velocity and temperature distribution has been illustrated by means of graphs and tables approach. Our analysis conveys that the temperature of the nanofluid reduces due to enhancing of the variable thickness parameter. The rate of heat transfer is significantly reduced for the Ag-water nanofluid with the positive impact of nanoparticle volume fraction.

  4. Enhancing carrier generation in TiO2 by a synergistic effect between plasmon resonance in Ag nanoparticles and optical interference

    NASA Astrophysics Data System (ADS)

    Cacciato, Giuseppe; Bayle, Maxime; Pugliara, Alessandro; Bonafos, Caroline; Zimbone, Massimo; Privitera, Vittorio; Grimaldi, Maria Grazia; Carles, Robert

    2015-08-01

    Silver nanoparticles have been embedded at a few nanometer distance from the free surface of titania/silica multilayers using low energy ion beam synthesis. Transmission electron microscopy shows the presence of 3 nm-sized crystalline particles. Reflectance spectroscopy on these composite substrates shows an increase of the light capture efficiency in the visible range. This behaviour is interpreted as a synergistic effect between plasmon polariton resonance and Fabry-Perot interferences. Plasmon-resonant Raman spectroscopy is deeply used to analyze, on one hand confinement of vibrations and electronic excitations in Ag NPs, and on the other hand coupling of polar TiO2 phonons with injected photo-generated carriers. It is shown how these new Ag/TiO2 nanocomposite films appear as very promising to enhance the efficiency and enlarge the spectral sensitivity of plasmo-electronics devices.Silver nanoparticles have been embedded at a few nanometer distance from the free surface of titania/silica multilayers using low energy ion beam synthesis. Transmission electron microscopy shows the presence of 3 nm-sized crystalline particles. Reflectance spectroscopy on these composite substrates shows an increase of the light capture efficiency in the visible range. This behaviour is interpreted as a synergistic effect between plasmon polariton resonance and Fabry-Perot interferences. Plasmon-resonant Raman spectroscopy is deeply used to analyze, on one hand confinement of vibrations and electronic excitations in Ag NPs, and on the other hand coupling of polar TiO2 phonons with injected photo-generated carriers. It is shown how these new Ag/TiO2 nanocomposite films appear as very promising to enhance the efficiency and enlarge the spectral sensitivity of plasmo-electronics devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02406d

  5. A study on photocatalytic activity of micro-arc oxidation TiO2 films and Ag+/MAO-TiO2 composite films

    NASA Astrophysics Data System (ADS)

    Xiang, N.; Song, R. G.; Xiang, B.; Li, H.; Wang, Z. X.; Wang, C.

    2015-08-01

    First, micro-arc oxidation (MAO) TiO2 films have been prepared on pure titanium in a phosphate-based electrolyte, and then the Ag+/MAO-TiO2 composite films have been fabricated by Ag+ impregnation in this paper. The microstructure and composition of MAO-TiO2 films and Ag+/MAO-TiO2 composite films have been studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). The photocatalytic activity of both films was evaluated by photocatalytic decolorization of methylene blue (MB) in aqueous solution as a model pollutant under sunlight irradiation simulation with homemade ultraviolet-visible spectroscopy (UV-vis). The results showed that the photocatalytic activity of MAO-TiO2 films increased with increasing the applied voltage and concentration in a certain scope. The morphology of Ag+/MAO-TiO2 composite films were of significantly difference and superior photocatalytic activity compared to the MAO-TiO2 film. Also, Ag+ impregnation was able to enhance the photocatalytic efficiency of MAO-TiO2 film.

  6. Highly efficient and recyclable triple-shelled Ag@Fe3O4@SiO2@TiO2 photocatalysts for degradation of organic pollutants and reduction of hexavalent chromium ions.

    PubMed

    Su, Jianwei; Zhang, Yunxia; Xu, Sichao; Wang, Shuan; Ding, Hualin; Pan, Shusheng; Wang, Guozhong; Li, Guanghai; Zhao, Huijun

    2014-05-21

    Herein, we demonstrate the design and fabrication of the well-defined triple-shelled Ag@Fe3O4@SiO2@TiO2 nanospheres with burr-shaped hierarchical structures, in which the multiple distinct functional components are integrated wonderfully into a single nanostructure. In comparison with commercial TiO2 (P25), pure TiO2 microspheres, Fe3O4@SiO2@TiO2 and annealed Ag@Fe3O4@SiO2@TiO2 nanocomposites, the as-obtained amorphous triple-shelled Ag@Fe3O4@SiO2@TiO2 hierarchical nanospheres exhibit a markedly enhanced visible light or sunlight photocatalytic activity towards the photodegradation of methylene blue and photoreduction of hexavalent chromium ions in wastewater. The outstanding photocatalytic activities of the plasmonic photocatalyst are mainly due to the enhanced light harvesting, reduced transport paths for both mass and charge transport, reduced recombination probability of photogenerated electrons/holes, near field electromagnetic enhancement and efficient scattering from the plasmonic nanostructure, increased surface-to-volume ratio and active sites in three dimensional (3D) hierarchical porous nanostructures, and improved photo/chemical stability. More importantly, the hierarchical nanostructured Ag@Fe3O4@SiO2@TiO2 photocatalysts could be easily collected and separated by applying an external magnetic field and reused at least five times without any appreciable reduction in photocatalytic efficiency. The enhanced photocatalytic activity and excellent chemical stability, in combination with the magnetic recyclability, make these multifunctional nanostructures promising candidates to remediate aquatic contaminants and meet the demands of future environmental issues. PMID:24710730

  7. The structural studies of Ag containing TiO2-SiO2 gels and thin films deposited on steel

    NASA Astrophysics Data System (ADS)

    Adamczyk, Anna; Rokita, Magdalena

    2016-06-01

    FTIR spectroscopic structural studies of titania-silica monolith samples as well as thin films deposited on steel were described in this work. Thin films were synthesized by the sol-gel method applying the dip coating as separate one-component TiO2 and/or SiO2 layers or as two-component TiO2-SiO2 thin films. Silver nanoparticles were incorporated into the structure from pure SiO2 sol, deposited then as an additional layer in those hybrid multilayers systems. Except the spectroscopic studies, XRD diffraction, SEM microscopy with EDX analysis and AFM microscopy were applied. The structural studies allow to describe and compare the structure and the morphology of thin films, as well those Ag free as Ag containing ones, also by the comparison with the structure of bulk samples. In FTIR spectra, the band observed at about 613 cm-1 can be connected with the presence of the non-tetrahedral cation in the structure and is observed only in the spectra of Ag containing bulk samples and thin films. The bands at 435-467 cm-1 are due to the stretching vibrations of Ti-O bonds or as well to the bending vibrations of O-Si-O one. In the ranges of 779-799 cm-1 and 1027-1098 cm-1, the bands ascribed to the symmetric stretching vibrations and asymmetric vibrations of Si-O-Si connections, respectively, are observed. SEM and AFM images gave the information on the microstructure and the topography of samples surface. XRD measurements confirmed the presence of only amorphous phase in samples up to 500 °C and allowed to observe the tendency of their crystallization.

  8. Enhanced photocatalytic, electrochemical and photoelectrochemical properties of TiO2 nanotubes arrays modified with Cu, AgCu and Bi nanoparticles obtained via radiolytic reduction

    NASA Astrophysics Data System (ADS)

    Nischk, Michał; Mazierski, Paweł; Wei, Zhishun; Siuzdak, Katarzyna; Kouame, Natalie Amoin; Kowalska, Ewa; Remita, Hynd; Zaleska-Medynska, Adriana

    2016-11-01

    TiO2 nanotubes arrays (NTs), obtained via electrochemical anodization of Ti foil, were modified with monometallic (Cu, Bi) and bimetallic (AgCu) nanoparticles. Different amounts of metals' precursors were deposited on the surface of NTs by the spin-coating technique, and the reduction of metals was performed via gamma radiolysis. Surface modification of titania was studied by EDS and XPS analysis. The results show that AgCu nanoparticles exist in a Agcore-Cushell form. Photocatalytic activity was examined under UV irradiation and phenol was used as a model pollutant of water. Over 95% of phenol degradation was achieved after 60 min of irradiation for almost all examined samples, but only slight difference in degradation efficiency (about 3%) between modified and bare NTs was observed. However, the initial phenol degradation rate and TOC removal efficiency was significantly enhanced for the samples modified with 0.31 and 0.63 mol% of Bi as well as for all the samples modified with Cu and AgCu nanoparticles in comparison with bare titania nanotubes. The saturated photocurrent, under the influence of simulated solar light irradiation, for the most active Bi- and AgCu-modified samples, was over two times higher than for pristine NTs. All the examined materials were resistant towards photocorrosion processes that enables their application for long term processes induced by light.

  9. Necrosis of Staphylococcus aureus by the Electrospun Fe- and Ag-Doped TiO2 Nanofibers

    PubMed Central

    Aboelzahab, Asem; Azad, Abdul-Majeed; Goel, Vijay

    2012-01-01

    Postsurgery infections cause prolonged hospitalization, incurring increased patient and hospital costs, making it increasingly vital to develop an effective solution for the mitigation and elimination of infection buildup at these sites. Incorporation of a bactericidal device at the infection-prone sites provides the capability of attacking bacterial growth even after the patient has left the hospital. Polycrystalline titanium dioxide (TiO2) is photoactive and possesses antibacterial properties that can mitigate the onset of these infections and aid in wound healing. In this work, TiO2 nanofibers were synthesized by electrospinning. Doping with iron as well as with silver (5 wt% and 1 wt%, resp.) was also carried out to increase their effectiveness towards bactericidal properties. The electrospun fibers were processed and tested in the presence of light in the suspensions of methicillin-susceptible Staphylococcus aureus (MSSA) bacteria, which are the leading infection-inducing bacteria among hospital patients. It was found that upon brief activation (cf. 30 s) by an infrared laser source, greater than 90% of the S. aureus was rendered inactive within cf. 10 min. of exposure, thereby showing the potential of titania nanofibers for effective mitigation of infection. PMID:24977085

  10. Electroluminescence from perovskite LEDs with the structure of Ag/Spiro-OMeTAD/CH3NH3PbI3/TiO2/FTO

    NASA Astrophysics Data System (ADS)

    Wang, Minhuan; Shi, Yantao; Bian, Jiming; Dong, Qingshun; Sun, Hongjun; Liu, Hongzhu; Luo, Yingmin; Zhang, Yuzhi

    2016-10-01

    The perovskite light-emitting diodes (Pe-LEDs) with the structure of Ag/Spiro-OMeTAD/CH3NH3PbI3/TiO2/FTO were synthesized, where the CH3NH3PbI3 perovskite layer was deposited by a two-step spin-coating process. A dominant near-infrared electroluminescence (EL) at 773 nm was detected from the Pe-LEDs under forward bias at room temperature. The origin and mechanism of the EL were discussed in comparison with the photoluminescence (PL) spectra, and it was attributed to the radiative recombination of electrons and holes confined in the CH3NH3PbI3 emissive layer. Moreover, the corresponding energy band diagrams was proposed to illustrate the carrier transport mechanism in the Pe-LED device.

  11. Evolution of structural and magnetic properties of Co-doped TiO2 thin films irradiated with 100 MeV Ag7+ ions

    NASA Astrophysics Data System (ADS)

    Mohanty, P.; Singh, V. P.; Mishra, N. C.; Ojha, S.; Kanjilal, D.; Rath, Chandana

    2014-08-01

    In continuation to our earlier studies where we have shown room temperature ferromagnetism observed in TiO2 and Co-doped TiO2 (CTO) thin films independent of their phase (Mohanty et al 2012 J. Phys. D: Appl. Phys. 45 325301), here the modifications in structure and magnetic properties in CTO thin films using 100 MeV Ag7+ ion irradiation are reported. Owing to the important role of defects in tailoring the magnetic properties of the material, we vary the ion fluence from 5 × 1011 to 1 × 1012 ions cm-2 to create post-deposition defects. While the film deposited under 0.1 mTorr oxygen partial pressure retains its crystallinity showing radiation-resistant behaviour even at a fluence of 1 × 1012 ions cm-2, films deposited under 1 to 300 mTorr oxygen partial pressure becomes almost amorphous at the same fluence. Using Poisson's law, the diameter of the amorphized region surrounding the ion path is calculated to be ˜4.2 nm from the x-ray diffraction peak intensity ((1 1 0) for rutile phase) as a function of ion fluence. The saturation magnetization (Ms) decreases exponentially similar to the decrease in x-ray peak intensity with fluence, indicating magnetic disordered region surrounding the ion path. The diameter of the magnetic disordered region is found to be ˜6.6 nm which is larger than the diameter of the amorphized latent track. Therefore, it is confirmed that swift heavy ion irradiation induces a more significant magnetic disorder than the structural disorder.

  12. Large-scale homogeneously distributed Ag-NPs with sub-10 nm gaps assembled on a two-layered honeycomb-like TiO2 film as sensitive and reproducible SERS substrates

    NASA Astrophysics Data System (ADS)

    Hu, Xiaoye; Meng, Guowen; Huang, Qing; Xu, Wei; Han, Fangming; Sun, Kexi; Xu, Qiaoling; Wang, Zhaoming

    2012-09-01

    We present a surface-enhanced Raman scattering (SERS) substrate featured by large-scale homogeneously distributed Ag nanoparticles (Ag-NPs) with sub-10 nm gaps assembled on a two-layered honeycomb-like TiO2 film. The two-layered honeycomb-like TiO2 film was achieved by a two-step anodization of pure Ti foil, with its upper layer consisting of hexagonally arranged shallow nano-bowls of 160 nm in diameter, and the lower layer consisting of arrays of about fifty vertically aligned sub-20 nm diameter nanopores. The shallow nano-bowls in the upper layer divide the whole TiO2 film into regularly arranged arrays of uniform hexagonal nano-cells, leading to a similar distribution pattern for the ion-sputtered Ag-NPs in each nano-cell. The lower layer with sub-20 nm diameter nanopores prevents the aggregation of the sputtered Ag-NPs, so that the Ag-NPs can get much closer with gaps in the sub-10 nm range. Therefore, large-scale high-density and quasi-ordered sub-10 nm gaps between the adjacent Ag-NPs were achieved, which ensures homogeneously distributed ‘hot spots’ over a large area for the SERS effect. Moreover, the honeycomb-like structure can also facilitate the capture of target analyte molecules. As expected, the SERS substrate exhibits an excellent SERS effect with high sensitivity and reproducibility. As an example, the SERS substrate was utilized to detect polychlorinated biphenyls (PCBs, a kind of persistent organic pollutants as global environmental hazard) such as 3,3‧,4,4‧-pentachlorobiphenyl (PCB-77) with concentrations down to 10-9 M. Therefore the large-scale Ag-NPs with sub-10 nm gaps assembled on the two-layered honeycomb-like TiO 2 film have potentials in SERS-based rapid trace detection of PCBs.

  13. Photoinduced reversible changes in morphology of plasmonic Ag nanorods on TiO2 and application to versatile photochromism.

    PubMed

    Kazuma, Emiko; Tatsuma, Tetsu

    2012-02-01

    We achieved reversible changes in length and spectrum of Ag nanorods based on plasmon-induced photoelectrochemical reactions. The changes are applied to multi-wavelength and dual-polarization photochromism in visible-infrared regions. It allows display of invisible images viewable only by infrared cameras. Also possible is display of superimposed visible and invisible images.

  14. A nanotechnology based new approach for chemotherapy of Cutaneous Leishmaniasis: TIO2@AG nanoparticles - Nigella sativa oil combinations.

    PubMed

    Abamor, Emrah Sefik; Allahverdiyev, Adil M

    2016-07-01

    Since toxicity and resistance are the major drawbacks of current antileishmanial drugs, studies have been recently focused on combination therapy in fight against leishmaniasis. Combination therapy generally provides opportunity to decrease toxicity of applied agents and enhance their antimicrobial performance. Moreover, this method can be effective in preventing drug resistance. Highly antileishmanial effects of silver doped titanium dioxide nanoparticles (TiAgNps) and Nigella sativa oil were demonstrated in previous studies. However, toxicity is still an important factor preventing use of these molecules in clinic. By considering high antileishmanial potential of each agent and basic principles of combination therapy, we propose that use of combinations including non-toxic concentrations of TiAgNps and N. sativa oil may compose more effective and safer formulations against Leishmania parasites. Therefore, the main goal of the present study was to investigate antileishmanial effects of non-toxic concentrations of TiAgNps and Nigella sativa oil combinations on promastigote and amastigote-macrophage culture systems and also to develop nanotechnology based new antileishmanial strategies against Cutaneous Leishmaniasis. Numerous parameters such as proliferation, metabolic activity, apoptosis, amastigote-promastigote conversion, infection index analysis and nitric oxide production were used to detect antileishmanial efficacies of combinations. Investigated all parameters demonstrated that TiAgNps-N. sativa oil combinations had significant antileishmanial effect on each life forms of parasites. Tested combinations were found to decrease proliferation rates of Leishmania tropica promastigotes in a range between 1,5-25 folds and metabolic activity values between 2 and 4 folds indicating that combination applications lead to virtually inhibition of promastigotes and elimination of parasites were directly related to apoptosis manner. TiAgNps-N. sativa combinations also

  15. A nanotechnology based new approach for chemotherapy of Cutaneous Leishmaniasis: TIO2@AG nanoparticles - Nigella sativa oil combinations.

    PubMed

    Abamor, Emrah Sefik; Allahverdiyev, Adil M

    2016-07-01

    Since toxicity and resistance are the major drawbacks of current antileishmanial drugs, studies have been recently focused on combination therapy in fight against leishmaniasis. Combination therapy generally provides opportunity to decrease toxicity of applied agents and enhance their antimicrobial performance. Moreover, this method can be effective in preventing drug resistance. Highly antileishmanial effects of silver doped titanium dioxide nanoparticles (TiAgNps) and Nigella sativa oil were demonstrated in previous studies. However, toxicity is still an important factor preventing use of these molecules in clinic. By considering high antileishmanial potential of each agent and basic principles of combination therapy, we propose that use of combinations including non-toxic concentrations of TiAgNps and N. sativa oil may compose more effective and safer formulations against Leishmania parasites. Therefore, the main goal of the present study was to investigate antileishmanial effects of non-toxic concentrations of TiAgNps and Nigella sativa oil combinations on promastigote and amastigote-macrophage culture systems and also to develop nanotechnology based new antileishmanial strategies against Cutaneous Leishmaniasis. Numerous parameters such as proliferation, metabolic activity, apoptosis, amastigote-promastigote conversion, infection index analysis and nitric oxide production were used to detect antileishmanial efficacies of combinations. Investigated all parameters demonstrated that TiAgNps-N. sativa oil combinations had significant antileishmanial effect on each life forms of parasites. Tested combinations were found to decrease proliferation rates of Leishmania tropica promastigotes in a range between 1,5-25 folds and metabolic activity values between 2 and 4 folds indicating that combination applications lead to virtually inhibition of promastigotes and elimination of parasites were directly related to apoptosis manner. TiAgNps-N. sativa combinations also

  16. Saltwater ecotoxicology of Ag, Au, CuO, TiO2, ZnO and C60 engineered nanoparticles: An overview.

    PubMed

    Minetto, D; Volpi Ghirardini, A; Libralato, G

    2016-01-01

    This review paper examined 529 papers reporting experimental nanoecotoxicological original data. Only 126 papers referred to saltwater environments (water column and sediment) including a huge variety of species (n=51), their relative endpoints and engineered nanoparticles (ENPs) (n=38). We tried to provide a synthetic overview of the ecotoxicological effects of ENPs from existing data, refining papers on the basis of cross-cutting selection criteria and supporting a "mind the gap" approach stressing on missing data for hazard and risk assessment. After a codified selection procedure, attention was paid to Ag, Au, CuO, TiO2, ZnO and C60 ENPs, evidencing and comparing the observed nanoecotoxicity range of effect. Several criticisms were evidenced: i) some model organisms are overexploited like microalgae and molluscs compared to annelids, echinoderms and fish; ii) underexploited model organisms: mainly bacteria and fish; iii) exposure scenario variability: high species-specific and ENP scenarios including organism life stage and way of administration/spiking of toxicants; iv) scarce comparability between results due to exposure scenario variability; v) micro- and mesocosms substantially unexplored; vi) mixture effects: few examples are available only for ENPs and traditional pollutants; mixtures of ENPs have not been investigated yet; vii) effects of ions and ENPs: nAg, nCuO and nZnO toxicity aetiology is still a matter of discussion; viii) size and morphology effects of ENPs: scarcely investigated, justified and understood. Toxicity results evidenced that: nAu>nZnO>nAg>nCuO>nTiO2>C60. PMID:27107224

  17. Photodeposition of Ag or Pt onto TiO2 nanoparticles decorated on step edges of HOPG.

    PubMed

    Taing, James; Cheng, Ming H; Hemminger, John C

    2011-08-23

    Ordered linear arrays of titanium dioxide nanoparticles were fabricated on highly oriented pyrolytic graphite utilizing a step edge decoration method. Ag- or Pt-based nanoparticles were then photodeposited onto the titanium dioxide nanoparticles (∼18 nm) to simultaneously verify photocatalytic activity and to demonstrate a viable route to load the titanium dioxide nanoparticles with metals. Scanning electron microscopy and atomic force microscopy determined the morphology, size, and distribution of the particles. X-ray photoelectron spectroscopy confirmed the identity of the titanium dioxide nanoparticles, and transmission electron microscopy showed that some of the particles were rutile single crystals. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy determined the chemical composition of the metal-based nanoparticles selectively loaded on the linear arrays of titanium dioxide nanoparticles.

  18. A two-oxide nanodiode system made of double-layered p-type Ag2O@n-type TiO2 for rapid reduction of 4-nitrophenol.

    PubMed

    Ahmed Zelekew, Osman; Kuo, Dong-Hau

    2016-02-14

    The n-type TiO2 semiconductor nanoparticles were coated on the p-type Ag2O nanoparticles deposited on SiO2 spherical particles through a simple sol-gel method for catalytic reduction of 4-nitrophenol. The as-prepared spherical composite abbreviated as SiO2/Ag2O@TiO2 was characterized by different techniques and tested as a catalyst towards 4-nitrophenol (4-NP) reduction into 4-aminophenol (4-AP) with NaBH4 as a reducing agent at room temperature. This work combines an interesting design with the n-type TiO2 rich in electrons outward and the p-type Ag2O rich in electronic holes inward to form the p/n junction for the purpose of efficiently separating the charge carrier to have a longer lifetime of outward electrons for catalytic reduction reactions. The SiO2/Ag2O@TiO2 composite catalyst showed the best performance in the reduction of 4-NP to 4-AP within 30 seconds. Our results reveal that the p-n junction combined composite sphere was superior and efficient in reduction of 4-nitrophenol without using the light source. The conversion mechanism is proposed here. Overall, the SiO2/Ag2O@TiO2 composite can be used as a cost-effective reduction catalyst for converting the toxic 4-NP into useful 4-AP, an industrial organic intermediate compound.

  19. Tuning the charge state of Ag and Au atoms and clusters deposited on oxide surfaces by doping: a DFT study of the adsorption properties of nitrogen- and niobium-doped TiO2 and ZrO2.

    PubMed

    Schlexer, Philomena; Ruiz Puigdollers, Antonio; Pacchioni, Gianfranco

    2015-09-14

    The charge state of Ag and Au atoms and clusters (Ag4 and Au4, Ag5 and Au5) adsorbed on defective TiO2 anatase(101) and tetragonal ZrO2(101) has been systematically investigated as a function of oxide doping and defectivity using a DFT+U approach. As intrinsic defects, we have considered the presence of oxygen vacancies. As extrinsic defects, substitutional nitrogen- and niobium-doping have been investigated, respectively. Both surface and sub-surface defects and dopants have been considered. Whereas on surfaces with oxygen vacancies or Nb-doping, atoms and clusters may become negatively charged, N-doping always leads to the formation of positively charged adsorbates, independently of the supporting material (TiO2 or ZrO2). This suggests the possibility to tune the electronic properties of supported metal clusters by selective doping of the oxide support, an effect that may result in complete changes in chemical reactivity.

  20. Green synthesis of highly crystalline and visible-light sensitive C-, N- and S- codoped with Ag TiO2 nanocatalyst

    EPA Science Inventory

    Titanium dioxide (TiO2) has been a focus of attention as chemically stable, relatively nontoxic, inexpensive and highly efficient photocatalyst applicable for a wide array of uses. However, main disadvantage that severely limits its wider use is the large band gap, 3.0 eV and 3.2...

  1. A two-oxide nanodiode system made of double-layered p-type Ag2O@n-type TiO2 for rapid reduction of 4-nitrophenol.

    PubMed

    Ahmed Zelekew, Osman; Kuo, Dong-Hau

    2016-02-14

    The n-type TiO2 semiconductor nanoparticles were coated on the p-type Ag2O nanoparticles deposited on SiO2 spherical particles through a simple sol-gel method for catalytic reduction of 4-nitrophenol. The as-prepared spherical composite abbreviated as SiO2/Ag2O@TiO2 was characterized by different techniques and tested as a catalyst towards 4-nitrophenol (4-NP) reduction into 4-aminophenol (4-AP) with NaBH4 as a reducing agent at room temperature. This work combines an interesting design with the n-type TiO2 rich in electrons outward and the p-type Ag2O rich in electronic holes inward to form the p/n junction for the purpose of efficiently separating the charge carrier to have a longer lifetime of outward electrons for catalytic reduction reactions. The SiO2/Ag2O@TiO2 composite catalyst showed the best performance in the reduction of 4-NP to 4-AP within 30 seconds. Our results reveal that the p-n junction combined composite sphere was superior and efficient in reduction of 4-nitrophenol without using the light source. The conversion mechanism is proposed here. Overall, the SiO2/Ag2O@TiO2 composite can be used as a cost-effective reduction catalyst for converting the toxic 4-NP into useful 4-AP, an industrial organic intermediate compound. PMID:26790613

  2. Fast diffusion of silver in TiO2 nanotube arrays.

    PubMed

    Zhang, Wanggang; Liu, Yiming; Zhou, Diaoyu; Wang, Hui; Liang, Wei; Yang, Fuqian

    2016-01-01

    Using magnetron sputtering and heat treatment, Ag@TiO2 nanotubes are prepared. The effects of heat-treatment temperature and heating time on the evolution of Ag nanofilms on the surface of TiO2 nanotubes and microstructure of Ag nanofilms are investigated by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Ag atoms migrate mainly on the outmost surface of the TiO2 nanotubes, and fast diffusion of Ag atoms is observed. The diffusivity for the diffusion of Ag atoms on the outmost surface of the TiO2 nanotubes at 400 °C is 6.87 × 10(-18) m(2)/s, which is three orders of magnitude larger than the diffusivities for the diffusion of Ag through amorphous TiO2 films. The activation energy for the diffusion of Ag atoms on the outmost surface of the TiO2 nanotubes in the temperature range of 300 to 500 °C is 157 kJ/mol, which is less than that for the lattice diffusion of Ag and larger than that for the grain boundary diffusion. The diffusion of Ag atoms leads to the formation of Ag nanocrystals on the outmost surface of TiO2 nanotubes. Probably there are hardly any Ag nanocrystals formed inside the TiO2 nanotubes through the migration of Ag. PMID:27547630

  3. Fast diffusion of silver in TiO2 nanotube arrays

    PubMed Central

    Zhang, Wanggang; Liu, Yiming; Zhou, Diaoyu; Wang, Hui

    2016-01-01

    Summary Using magnetron sputtering and heat treatment, Ag@TiO2 nanotubes are prepared. The effects of heat-treatment temperature and heating time on the evolution of Ag nanofilms on the surface of TiO2 nanotubes and microstructure of Ag nanofilms are investigated by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Ag atoms migrate mainly on the outmost surface of the TiO2 nanotubes, and fast diffusion of Ag atoms is observed. The diffusivity for the diffusion of Ag atoms on the outmost surface of the TiO2 nanotubes at 400 °C is 6.87 × 10−18 m2/s, which is three orders of magnitude larger than the diffusivities for the diffusion of Ag through amorphous TiO2 films. The activation energy for the diffusion of Ag atoms on the outmost surface of the TiO2 nanotubes in the temperature range of 300 to 500 °C is 157 kJ/mol, which is less than that for the lattice diffusion of Ag and larger than that for the grain boundary diffusion. The diffusion of Ag atoms leads to the formation of Ag nanocrystals on the outmost surface of TiO2 nanotubes. Probably there are hardly any Ag nanocrystals formed inside the TiO2 nanotubes through the migration of Ag. PMID:27547630

  4. Photocatalytic performance of the SiO2 sphere/ n-type TiO2/ p-type CuBiS2 composite catalysts coated with different contents of Ag nanoparticles under ultraviolet and visible light irradiations

    NASA Astrophysics Data System (ADS)

    Abdullah, Hairus; Kuo, Dong-Hau

    2016-08-01

    Photocatalytic performance of the SiO2 sphere/ n-type TiO2/ p-type CuBiS2 composite catalysts with different contents of silver nanoparticles (abbreviated as SiO2/ n-TiO2/ p-CuBiS2/Ag) toward the photodegradation of Acid Black 1 ( AB 1) dye under ultraviolet (UV) and visible light was investigated. The composite catalyst spheres were analyzed their crystal structure, microstructure, optical absorbance capabilities, and photodegradation capabilities of AB 1 dye. The best photodegradation performances of the 20 mg composite powder with only ~5 mg photoactive catalysts showed the degradation of AB 1 dye in 5 min under UV and 60 min under visible light irradiations. The concept of composite catalyst with numerous nano p- n diodes and its photodegradation mechanism were proposed.

  5. Influence of silver doping on surface defect characteristics of TiO2

    NASA Astrophysics Data System (ADS)

    Tripathi, S. K.; Rani, Mamta

    2015-08-01

    In the present work, we proposed a novel silver doped TiO2 polyethylene conjugated films to improve the performance of DSSCs. Oxides nanoparticles dispersed in a semiconducting polymer form the active layer of a solar cell. Localized surface plasmon resonance effects associated with spatially dispersed silver (Ag) nanoparticles can be exploited to enhance the light-harvesting efficiency, the photocurrent density and the overall light-to electrical-energy-conversion efficiency of high-area DSSCs based TiO2 photoanodes. Silver doped titanium dioxide (TiO2:Ag) is prepared by sol-gel technique and deposited on fluorine doped indium oxide (FTO) coated glass substrates by using doctor blade technique at 550°C from aqueous solutions of titanium butoxide and silver nitrate precursors. The effect of Ag doping on electrical properties of films is studied. The Ag-TiO2 films are about 548 times more photosensitive as compare to the pure TiO2 sample. The presence of metallic Ag nanoparticles and oxygen vacancy on the surface of TiO2 nanoparticles promotes the separation of photogenerated electron-hole pairs and thus enhances the photosensitivity. Photoconduction mechanism of all prepared samples is investigated by performing transient photoconductivity measurements on TiO2 and Ag-TiO2 films keeping intensity of light constant.

  6. Quantum-dot-sensitized TiO2 inverse opals for photoelectrochemical hydrogen generation.

    PubMed

    Cheng, Chuanwei; Karuturi, Siva Krishna; Liu, Lijun; Liu, Jinping; Li, Hongxing; Su, Liap Tat; Tok, Alfred Iing Yoong; Fan, Hong Jin

    2012-01-01

    A new nanoarchitecture photoelectrode design comprising CdS quantum-dot-sensitized, optically and electrically active TiO(2) inverse opals is developed for photoelectrochemical water splitting. The photoelectrochemical performance shows high photocurrent density (4.84 mA cm(-2) at 0 V vs. Ag/AgCl) under simulated solar-light illumination. PMID:22009604

  7. Quantum-dot-sensitized TiO2 inverse opals for photoelectrochemical hydrogen generation.

    PubMed

    Cheng, Chuanwei; Karuturi, Siva Krishna; Liu, Lijun; Liu, Jinping; Li, Hongxing; Su, Liap Tat; Tok, Alfred Iing Yoong; Fan, Hong Jin

    2012-01-01

    A new nanoarchitecture photoelectrode design comprising CdS quantum-dot-sensitized, optically and electrically active TiO(2) inverse opals is developed for photoelectrochemical water splitting. The photoelectrochemical performance shows high photocurrent density (4.84 mA cm(-2) at 0 V vs. Ag/AgCl) under simulated solar-light illumination.

  8. Hydrogen plasma reduced black TiO2sbnd B nanowires for enhanced photoelectrochemical water-splitting

    NASA Astrophysics Data System (ADS)

    Tian, Zhangliu; Cui, Huolei; Zhu, Guilian; Zhao, Wenli; Xu, JiJian; Shao, Feng; He, Jianqiao; Huang, Fuqiang

    2016-09-01

    Black TiO2 with various nanostructures and phase constitutions have been reported to exhibit excellent photocatalytic and photoelectrochemical (PEC) performance. Here, we report the fabrication of black nanostructured TiO2sbnd B through hydrogen plasma assisted reduction and its enhanced PEC properties for the first time. Both the obtained TiO2sbnd B and black TiO2sbnd B are single crystalline nanowires, while the black TiO2sbnd B samples exhibit much stronger visible and infrared light absorption. The optimal black TiO2sbnd B sample obtained by hydrogen plasma treatment at 425 °C yields a photocurrent density of 0.85 mA cm-2, a rather low onset potential of -0.937 VAg/AgCl and a high applied bias photon-to-current efficiency (ABPE) of 0.363%, which is far superior to the TiO2sbnd B (0.15 mA cm-2 photocurrent, -0.917 VAg/AgCl onset potential and 0.138% ABPE). The significantly enhanced PEC performance of the black TiO2sbnd B is ascribed to the introduction of moderate surface oxygen vacancies. These results indicate that the black TiO2sbnd B is a promising material for PEC application and solar energy utilization.

  9. Promotion effect of Pd on TiO2 for visible light photocatalytic degradation of gaseous formaldehyde.

    PubMed

    Wu, Ren-Jang; Liu, Yung-Shiuan; Lai, Hsiao-Fang; Wang, Jhe-Hao; Chavali, Murthy

    2014-09-01

    TiO2 and Pd doped TiO2 (Pd/TiO2) nanoparticles were prepared by sol gel method. Pd/TiO2 material was characterized by XRD, TEM, TPR, XPS and BET. From XRD data, the crystalline type of TiO2 is known to as Anatase type. TiO2 and Pd/TiO2 were in the order of 9-10 nm and 10-13 nm respectively. The photocatalytic activities of the TiO2 and Pd/TiO2 nanomaterials were evaluated and compared for the photodegradation of formaldehyde (HCHO). HCHO degradation on Pd/TiO2 catalyst, at 60 min, the degradation rate of gaseous HCHO is 95%. Using Pd/TiO2, the rate was faster than TiO2 or doped with other metals (Au/TiO2; Ag/TiO2; Pt/TiO2).

  10. Novel phosphorus doped carbon nitride modified TiO2 nanotube arrays with improved photoelectrochemical performance

    NASA Astrophysics Data System (ADS)

    Su, Jingyang; Geng, Ping; Li, Xinyong; Zhao, Qidong; Quan, Xie; Chen, Guohua

    2015-10-01

    Novel phosphorus-doped graphitic-carbon nitride (P-C3N4) modified vertically aligned TiO2 nanotube arrays (NTs) were designed and synthesized. They can significantly enhance the conduction and utilization of photogenerated charge carriers of TiO2 NTs. The heterostructure was successfully fabricated through a three-step process: electrochemical anodization and wet-dipping followed by thermal polymerization. The prepared P-C3N4/TiO2 NTs exhibit enhanced light-absorption characteristics and improved charge separation and transfer ability, thus resulting in a 3-fold photocurrent (1.98 mA cm-2 at 0 V vs. Ag/AgCl) compared with that of pure TiO2 NTs (0.66 mA cm-2 at 0 V vs. Ag/AgCl) in 1 M NaOH solution. The prepared P-C3N4/TiO2 NT photoelectrodes also present excellent photocatalytic and photoelectrocatalytic capabilities in the degradation of methylene blue (MB). The kinetic rate of P-C3N4/TiO2 NTs in the photoelectrocatalytic process for MB is 2.7 times that of pristine TiO2 NTs. Furthermore, the prepared sample was used as a photoanode for solar-driven water splitting, giving a H2 evolution rate of 36.6 μmol h-1 cm-2 at 1.0 V vs. RHE under simulated solar light illumination. This novel structure with a rational design for a visible light response shows potential for metal free materials in photoelectrochemical applications.Novel phosphorus-doped graphitic-carbon nitride (P-C3N4) modified vertically aligned TiO2 nanotube arrays (NTs) were designed and synthesized. They can significantly enhance the conduction and utilization of photogenerated charge carriers of TiO2 NTs. The heterostructure was successfully fabricated through a three-step process: electrochemical anodization and wet-dipping followed by thermal polymerization. The prepared P-C3N4/TiO2 NTs exhibit enhanced light-absorption characteristics and improved charge separation and transfer ability, thus resulting in a 3-fold photocurrent (1.98 mA cm-2 at 0 V vs. Ag/AgCl) compared with that of pure TiO2 NTs (0

  11. Photocatalytic and antibacterial properties of a TiO2/nylon-6 electrospun nanocomposite mat containing silver nanoparticles.

    PubMed

    Pant, Hem Raj; Pandeya, Dipendra Raj; Nam, Ki Taek; Baek, Woo-Il; Hong, Seong Tshool; Kim, Hak Yong

    2011-05-15

    Silver-impregnated TiO(2)/nylon-6 nanocomposite mats exhibit excellent characteristics as a filter media with good photocatalytic and antibacterial properties and durability for repeated use. Silver nanoparticles (NPs) were successfully embedded in electrospun TiO(2)/nylon-6 composite nanofibers through the photocatalytic reduction of silver nitrate solution under UV-light irradiation. TiO(2) NPs present in nylon-6 solution were able to cause the formation of a high aspect ratio spider-wave-like structure during electrospinning and facilitated the UV photoreduction of AgNO(3) to Ag. TEM images, UV-visible and XRD spectra confirmed that monodisperse Ag NPs (approximately 4 nm in size) were deposited selectively upon the TiO(2) NPs of the prepared nanocomposite mat. The antibacterial property of a TiO(2)/nylon-6 composite mat loaded with Ag NPs was tested against Escherichia coli, and the photoactive property was tested against methylene blue. All of the results showed that TiO(2)/nylon-6 nanocomposite mats loaded with Ag NPs are more effective than composite mats without Ag NPs. The prepared material has potential as an economically friendly photocatalyst and water filter media because it allows the NPs to be reused.

  12. The effect of polyaniline on TiO2 nanoparticles as anode materials for lithium ion batteries.

    PubMed

    Zheng, Haitao; Ncube, Ntombizodwa M; Raju, Kumar; Mphahlele, Nonhlanhla; Mathe, Mkhulu

    2016-01-01

    Polyaniline (PANI) additives have been shown to have a significant effect on titanium dioxide (TiO2) nanoparticles as lithium ion battery anode materials. TiO2/PANI composites were prepared using a solid coating method with different ratios of PANI and then characterized using XRD and SEM. These composites have shown increased reversible capacity compared with pure TiO2. At the current rate of 20 and 200 mAg(-1), maximum capacities were also found on 15 % PANI incorporated TiO2 composite with 281 mAh g(-1) and 168.2 mAh g(-1), respectively, and 230 and 99.6 mAh g(-1) were obtained in the case of pure TiO2. Among all the composite materials, 10 % PANI incorporated TiO2 composite exhibited the highest reversible capacity with cycle stability after 100 cycles at the current rate of 200 mAg(-1), suggestive that the optimal ratio is 10 % PANI of TiO2/polyaniline. The cycle stability showed swift fade when the ratio of PANI in the composites exceeded 10 % though the highest initial capacity was achieved on 15 % PANI in the composites. These results suggest that PANI has effectively enhanced the reversible capacity of commercial TiO2, and may be a promising polymer matrix materials for lithium ion batteries. PMID:27330896

  13. The effect of polyaniline on TiO2 nanoparticles as anode materials for lithium ion batteries.

    PubMed

    Zheng, Haitao; Ncube, Ntombizodwa M; Raju, Kumar; Mphahlele, Nonhlanhla; Mathe, Mkhulu

    2016-01-01

    Polyaniline (PANI) additives have been shown to have a significant effect on titanium dioxide (TiO2) nanoparticles as lithium ion battery anode materials. TiO2/PANI composites were prepared using a solid coating method with different ratios of PANI and then characterized using XRD and SEM. These composites have shown increased reversible capacity compared with pure TiO2. At the current rate of 20 and 200 mAg(-1), maximum capacities were also found on 15 % PANI incorporated TiO2 composite with 281 mAh g(-1) and 168.2 mAh g(-1), respectively, and 230 and 99.6 mAh g(-1) were obtained in the case of pure TiO2. Among all the composite materials, 10 % PANI incorporated TiO2 composite exhibited the highest reversible capacity with cycle stability after 100 cycles at the current rate of 200 mAg(-1), suggestive that the optimal ratio is 10 % PANI of TiO2/polyaniline. The cycle stability showed swift fade when the ratio of PANI in the composites exceeded 10 % though the highest initial capacity was achieved on 15 % PANI in the composites. These results suggest that PANI has effectively enhanced the reversible capacity of commercial TiO2, and may be a promising polymer matrix materials for lithium ion batteries.

  14. Antibacterial activity of single crystalline silver-doped anatase TiO2 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangyu; Li, Meng; He, Xiaojing; Hang, Ruiqiang; Huang, Xiaobo; Wang, Yueyue; Yao, Xiaohong; Tang, Bin

    2016-05-01

    Well-ordered, one-dimensional silver-doped anatase TiO2 nanowire (AgNW) arrays have been prepared through a hydrothermal growth process on the sputtering-deposited AgTi layers. Electron microscope analyses reveal that the as-synthesized AgNW arrays exhibit a single crystalline phase with highly uniform morphologies, diameters ranging from 85 to 95 nm, and lengths of about 11 μm. Silver is found to be doped into TiO2 nanowire evenly and mainly exists in the zerovalent state. The AgNW arrays show excellent efficient antibacterial activity against Escherichia coli (E. coli), and all of the bacteria can be killed within 1 h. Additionally, the AgNW arrays can still kill E. coli after immersion for 60 days, suggesting the long-term antibacterial property. The technique reported here is environmental friendly for formation of silver-containing nanostructure without using any toxic organic solvents.

  15. One pot preparation of silver nanoparticles decorated TiO2 mesoporous microspheres with enhanced antibacterial activity.

    PubMed

    Chen, Yuemei; Deng, Yuanming; Pu, Yitao; Tang, Bijun; Su, Yikun; Tang, Jiaoning

    2016-08-01

    We report a simple "one-pot" solvothermal preparation of silver nanoparticles (Ag NPs) decorated mesoporous titania (TiO2) microspheres as an effective antibacterial agent. TBOT as Ti source was hydrolyzed and crystallized in media composed of acetic acid and ethanol, in which esterification catalyzed by TBOT occurred for in-situ "controlled water release". AgNO3 as Ag source was reduced by ethanol to form Ag NPs embedded in the TiO2 microspheres. The effect of AgNO3 and HAc on the morphology of Ag/TiO2 was investigated. The Ag/TiO2 with various Ag content showed excellent antibacterial activities with extremely low minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Escherichia coli and Staphylococcus aureus when compared with colloidal Ag NPs. PMID:27157724

  16. Optical and structural characterization of TiO2 films doped with silver nanoparticles obtained by sol-gel method

    NASA Astrophysics Data System (ADS)

    Ivanova, T.; Harizanova, A.; Koutzarova, T.; Vertruyen, B.

    2013-12-01

    Nanostructured titanium oxide films with incorporated Ag nanoparticles were deposited by sol-gel spin coating method. The films were annealed at 300 °C, 400 °C, 500 °C and 600 °C in oxygen and nitrogen ambient. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and UV-VIS spectroscopy had been applied for studying the influence of the thermal treatments and the gas ambient on the structural and optical properties of TiO2 and TiO2:Ag films. The XRD analysis revealed the presence of metallic Ag phase without traces of silver oxides and these results were confirmed by FTIR spectra. It has been revealed that the annealing temperatures and the ambient, where the annealing is carried out is crucial for TiO2 crystallization, when there is Ag incorporation and especially for appearance of anatase and rutile phase. The nitrogen and oxygen ambient influences quite different the crystallization of TiO2:Ag films. Transmission and absorption spectra have been analyzed. Optical band gap values were evaluated for pure titania and Ag incorporated TiO2 films.

  17. Preparation and characterization of Cu-doped TiO2 materials for electrochemical, photoelectrochemical, and photocatalytic applications

    NASA Astrophysics Data System (ADS)

    Ganesh, Ibram; Kumar, Polkampally P.; Annapoorna, Ibram; Sumliner, Jordan M.; Ramakrishna, Mantripragada; Hebalkar, Neha Y.; Padmanabham, Gade; Sundararajan, Govindan

    2014-02-01

    The Cu-doped TiO2 (Cu = 0-50 wt.%) powders and thin films were prepared by following a homogeneous co-precipitation method and sol-gel dip-coating technique, respectively, and were treated through 400-800 °C, and then thoroughly investigated by following various characterization techniques. The characterization results suggest that the pure TiO2 powder formed at 550 °C is in rutile phase, whereas the 0.1-10 wt.% Cu-doped TiO2 powders formed at 550 °C are mainly in anatase phase. These latter powders possess low band-gap energies (3.247-3.265 eV) and flat-band potentials amenable to water oxidation reaction. The 0.5-wt.% Cu-doped TiO2 thin film formed at 550 °C exhibited n-type semiconducting behavior and considerable photocurrent among various investigated powders. The CO2 reduction with a Faradaic efficiency of 82% and ˜ 96% CO selectivity in a two-compartment electrochemical cell was noted at -2500 mV (vs. Ag/Ag+) on pre-reduced (at -2000 mV vs. Ag/AgCl) 50 wt.% Cu-doped TiO2 thin film electrode in conjunction with an ionic liquid. The UV-light-induced TiO2 was found to be responsible for photocatalytic methylene blue (MB) degradation, and TiO2 is not sensitized by MB. The in situ formed compounds of TiO2 and CuO/Cu2O were found to absorb visible light, but showed little visible-light-induced photocatalytic activity.

  18. Semitransparent inverted polymer solar cells employing a sol-gel-derived TiO2 electron-selective layer on FTO and MoO3/Ag/MoO3 transparent electrode

    PubMed Central

    2014-01-01

    We report a new semitransparent inverted polymer solar cell (PSC) with a structure of glass/FTO/nc-TiO2/P3HT:PCBM/MoO3/Ag/MoO3. Because high-temperature annealing which decreased the conductivity of indium tin oxide (ITO) must be handled in the process of preparation of nanocrystalline titanium oxide (nc-TiO2), we replace glass/ITO with a glass/fluorine-doped tin oxide (FTO) substrate to improve the device performance. The experimental results show that the replacing FTO substrate enhances light transmittance between 400 and 600 nm and does not change sheet resistance after annealing treatment. The dependence of device performances on resistivity, light transmittance, and thickness of the MoO3/Ag/MoO3 film was investigated. High power conversion efficiency (PCE) was achieved for FTO substrate inverted PSCs, which showed about 75% increase compared to our previously reported ITO substrate device at different thicknesses of the MoO3/Ag/MoO3 transparent electrode films illuminated from the FTO side (bottom side) and about 150% increase illuminated from the MoO3/Ag/MoO3 side (top side). PMID:25332693

  19. TiO2 nanofibrous interface development for Raman detection of environmental pollutants

    NASA Astrophysics Data System (ADS)

    Maznichenko, D.; Selvaganapathy, P. R.; Venkatakrishnan, K.; Tan, B.

    2012-12-01

    Sensor development has been reliant on planar Au and Ag nanoparticle research. The current findings explored a unique 3-D network of crystalline TiO2 nanoparticles linked as nanofibers. In addition to the favorability of using TiO2 for chemical and bio-molecular sensing, the nanofiber network provides molecular diffusion control and an increased confocal volume signal. Controlled femtosecond laser synthesis is also demonstrated that directly impacts surface-enhanced Raman spectroscopy detection of two common environmentally harmful chemicals: bisphenol A and diclofenac sodium salt. These findings assert that 3-D nanofibrous network porosity optimization is crucial for Raman monitoring of drinking water.

  20. Localized control of light-matter interactions by using nanoscale asymmetric TiO2.

    PubMed

    Zhou, Shifeng; Matsuoka, Tomoyo; Shimotsuma, Yasuhiko; Sakakura, Masaaki; Nishi, Masayuki; Hong, Zhanglian; Qiu, Jianrong; Hirao, Kazuyuki; Miura, Kiyotaka

    2012-11-23

    This paper reports an asymmetry structure-mediated route for highly localized control of light-matter interactions by using tapered TiO(2). We demonstrate for the first time that the growth habit of Ag nanostructures on tapered TiO(2) can be tuned by controllable photolysis. Site-selective anchoring of Ag nanoparticles or nanowires on tapered TiO(2) can be achieved by simply changing the external light. We further show that the obtained tapered TiO(2)-Ag hetero-nanostructures present excellent light-trapping ability over a wide range of wavelengths which is considered to originate from the unique synergistic effects of graded waveguiding and plasmonic light trapping. This improved photon-management capability renders the prepared substrate a very promising candidate for optical sensing application. For this purpose, an enhanced sensitivity for trace detection is confirmed. These findings open up promising avenues for tailoring of light-matter interactions which are of special interest for studying controllable photolysis activation processes and diverse applications such as nanostructure growth, trace detection, photocatalysis and solar cells.

  1. Porous TiO2 Assembled from Monodispersed Nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Xu; Duan, Weijie; Chen, Yan; Jiao, Shihui; Zhao, Yue; Kang, Yutang; Li, Lu; Fang, Zhenxing; Xu, Wei; Pang, Guangsheng

    2016-03-01

    Porous TiO2 were assembled by evaporating or refluxing TiO2 colloid, which was obtained by dispersing the TiO2 nanoparticles with a crystallite size (d XRD) of 3.2 nm into water or ethanol without any additives. Porous transparent bulk TiO2 was obtained by evaporating the TiO2-C2H5OH colloid at room temperature for 2 weeks, while porous TiO2 nanospheres were assembled by refluxing the TiO2-H2O colloid at 80 °C for 36 h. Both of the porous TiO2 architectures were pore-size-adjustable depending on the further treating temperature. Porous TiO2 nanospheres exhibited enhanced photocatalysis activity compared to the nanoparticles.

  2. Instability of Hydrogenated TiO2

    SciTech Connect

    Nandasiri, Manjula I.; Shutthanandan, V.; Manandhar, Sandeep; Schwarz, Ashleigh M.; Oxenford, Lucas S.; Kennedy, John V.; Thevuthasan, Suntharampillai; Henderson, Michael A.

    2015-11-06

    Hydrogenated TiO2 (H-TiO2) is toted as a viable visible light photocatalyst. We report a systematic study on the thermal stability of H-implanted TiO2 using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA). Protons (40 keV) implanted at a ~2 atom % level within a ~120 nm wide profile of rutile TiO2(110) were situated ~300 nm below the surface. NRA revealed that this H-profile broadened preferentially toward the surface after annealing at 373 K, dissipated out of the crystal into vacuum at 473 K, and was absent within the beam sampling depth (~800 nm) at 523 K. Photoemission showed that the surface was reduced in concert with these changes. Similar anneals had no effect on pristine TiO2(110). The facile bulk diffusivity of H in rutile, as well as its activity toward interfacial reduction, significantly limits the utilization of H-TiO2 as a photocatalyst. This work was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. The research was performed using the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.

  3. Sol-gel TiO2 films as NO2 gas sensors

    NASA Astrophysics Data System (ADS)

    Georgieva, V.; Gadjanova, V.; Grechnikov, A.; Donkov, N.; Sendova-Vassileva, M.; Stefanov, P.; Kirilov, R.

    2014-05-01

    TiO2 films were prepared by a sol-gel technique with commercial TiO2 powder as a source material (P25 Degussa AG). After a special treatment, printing paste was prepared. The TiO2 layers were formed by means of drop-coating on Si-control wafers and on the Au-electrodes of quartz resonators. The surface morphology of the films was examined by scanning electron microscopy (SEM). Their structure was studied by Raman spectroscopy and the surface composition was determined by X-ray photoelectron spectroscopy (XPS). The layers had a grain-like surface morphology and consisted mainly of anatase TiO2 phase. The sensitivity of the TiO2 films to NO2 was assessed by the quartz crystal microbalance (QCM) technique. To this end, the films were deposited on both sides of a 16-MHz QCM. The sensing characteristic of the TiO2-QCM structure was investigated by measuring the resonant frequency shift (ΔF) of the QCM due to the mass loading caused by NO2 adsorption. The Sauerbrey equation was applied to establish the correlation between the QCM frequency changes measured after exposure to different NO2 concentrations and the mass-loading of the QCM. The experiments were carried out in a dynamic mode on a special laboratory setup with complete control of the process parameters. The TiO2 films were tested in the NO2 concentration interval from 10 ppm to 5000 ppm. It was found that a TiO2 loading of the QCM by 5.76 kHz corresponded to a system sensitive to NO2 concentrations above 250 ppm. On the basis of the frequency-time characteristics (FTCs) measured, AF at different NO2 concentrations was defined, the adsorption/desorption cycles were studied and the response and recovery times were estimated. The results obtained show that the process is reversible in the NO2 interval investigated. The results further suggested that TiO2 films prepared by a sol-gel method on a QCM can be used as a sensor element for NO2 detection.

  4. Removal of 4-Nitrophenol from Water Using Ag–N–P-Tridoped TiO2 by Photocatalytic Oxidation Technique

    PubMed Central

    Achamo, Temesgen; Yadav, O. P.

    2016-01-01

    Photocatalytic oxidation using semiconductor nanoparticles is an efficient, eco-friendly, and cost-effective process for the removal of organic pollutants, such as dyes, pesticides, phenols, and their derivatives in water. In the present study, nanosize Ag–N–P-tridoped titanium(IV) oxide (TiO2) was prepared by using sol–gel-synthesized Ag-doped TiO2 and soybean (Glycine max) or chickpea (Cicer arietinum) seeds as nonmetallic bioprecursors. As-synthesized photocatalysts were characterized using X-ray diffraction, Fourier transform infrared, and ultra violet (UV)–visible spectroscopic techniques. Average crystallite size of the studied photocatalysts was within 39–46 nm. Whereas doped Ag in TiO2 minimized the photogenerated electron–hole recombination, doped N and P extended its photoabsorption edge to visible region. Tridoping of Ag, N, and P in TiO2 exhibited synergetic effect toward enhancing its photocatalytic degradation of 4-nitrophenol (4-NP), separately, under UV and visible irradiations. At three hours, degradations of 4-NP over Ag–N–P-tridoped TiO2 under UV and visible radiations were 73.8 and 98.1%, respectively. PMID:27081309

  5. Existence, release, and antibacterial actions of silver nanoparticles on Ag–PIII TiO2 films with different nanotopographies

    PubMed Central

    Li, Jinhua; Qiao, Yuqin; Zhu, Hongqin; Meng, Fanhao; Liu, Xuanyong

    2014-01-01

    Nanotopographical TiO2 films (including nanorod, nanotip, and nanowire topographies) were successfully fabricated on the metallic Ti surface via hydrothermal treatment and then underwent Ag plasma immersion ion implantation to incorporate Ag with TiO2. The surface morphology, phase component, and chemical composition before and after Ag–PIII were characterized. In view of the potential clinical applications, both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus were used to estimate their antimicrobial effect. The nanostructured TiO2 films on a Ti surface exhibit a better bacteriostatic effect on both microbes compared to the pristine Ti. The nanotopographies of the TiO2 films affect the nucleation, growth, and distribution of Ag nanoparticles in the films during Ag–PIII process. The Ag nanoparticles are completely embedded into the nanorod film while partially exposed out of the nanotip and nanowire films, which account for the significant differences in the release behaviors of Ag ions in vitro. However, no significant difference exists in their antimicrobial activity against both microbes. The antimicrobial actions of the Ag@TiO2 system described here consist of two methods – the contact-killing action and the release-killing action. Nevertheless, based on the observed results, the contact-killing action should be regarded as the main method to destroy microbes for all the Ag plasma-modified TiO2 nanofilms. This study provides insight to optimize the surface design of Ti-based implants to acquire more effective antimicrobial surfaces to meet clinical applications. PMID:25075186

  6. Photocatalytic degradation of aqueous propoxur solution using TiO2 and Hbeta zeolite-supported TiO2.

    PubMed

    Mahalakshmi, M; Vishnu Priya, S; Arabindoo, Banumathi; Palanichamy, M; Murugesan, V

    2009-01-15

    Photocatalytic activity of TiO2 and zeolites supported TiO2 were investigated using propoxur as a model pollutant. Hbeta, HY and H-ZSM-5 zeolites were examined as supports for TiO2. Hbeta was chosen as the TiO2 support based on the adsorption capacity of propoxur on these zeolites (Hbeta>HY=H-ZSM-5). TiO2/Hbeta photocatalysts with different wt.% were prepared and characterized by XRD, FT-IR and BET surface area. The progress of photocatalytic degradation of aqueous propoxur solution using TiO2 (Degussa P-25) and TiO2 supported on Hbeta zeolite was monitored using TOC analyzer, HPLC and UV-vis spectrophotometer. The degradation of propoxur was systematically studied by varying the experimental parameters in order to achieve maximum degradation efficiency. The initial rate of degradation with TiO2/Hbeta was higher than with bare TiO2. TOC results revealed that TiO2 requires 600min for complete mineralization of propoxur whereas TiO2/Hbeta requires only 480min. TiO2/Hbeta showed enhanced photodegradation due to its high adsorption capacity on which the pollutant molecules are pooled closely and hence degraded effectively.

  7. Feasibility of Silver Doped TiO2/Glass Fiber Photocatalyst under Visible Irradiation as an Indoor Air Germicide

    PubMed Central

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2014-01-01

    This study investigated the feasibility of using Ag-TiO2 photocatalyst supported on glass fiber (Ag-TiO2/GF) prepared by a sol-gel method as an indoor air germicide. An experimental model was designed to investigate the bacterial disinfection efficiency of Staphylococcus (Staph), the most popular bacterium in hospitals in Korea, by the Ag-TiO2/GF photocatalyst. The silver content in Ag/TiO2 was altered from 1 to 10% to investigate the optimal ratio of Ag doped on TiO2/glass fiber (TiO2/GF) for photocatalytic disinfection of Staph. This study confirmed that Ag in Ag-TiO2/GF could work as an electron sink or donor to increase photocatalytic activity and promote the charge separation of electron-hole pairs generated from TiO2 after photon absorption. Ag also acts as an intermediate agent for the transfer of photo-generated electrons from the valence band of TiO2 to an acceptor (O2 gas) to promote photo-oxidation processes. The photocatalytic disinfection activity of Ag-TiO2/GF under visible light increased with the increase in silver content up to 7.5% and then slightly decreased with further increasing silver content. The highest disinfection efficiency and disinfection capacity of Staph using 7.5% Ag-TiO2/GF were 75.23% and 20 (CFU∙s−1∙cm−2) respectively. The medium level of humidity of 60% ± 5% showed better photocatalytic disinfection than the lower (40% ± 5%) or higher (80% ± 5%) levels. PMID:24658408

  8. TiO2-TiO2 composite resistive humidity sensor: ethanol crosssensitivity

    NASA Astrophysics Data System (ADS)

    Ghalamboran, Milad; Saedi, Yasin

    2016-03-01

    The fabrication method and characterization results of a TiO2-TiO2 composite bead used for humidity sensing along with its negative cross-sensitivity to ethanol vapor are reported. The bead shaped resistive sample sensors are fabricated by the drop-casting of a TiO2 slurry on two Pt wire segments. The dried bead is pre-fired at 750°C and subsequently impregnated with a Ti-based sol. The sample is ready for characterization after a thermal annealing at 600°C in air. Structurally, the bead is a composite of the micron-sized TiO2 crystallites embedded in a matrix of nanometric TiO2 particle aggregates. The performance of the beads as resistive humidity sensors is recorded at room temperature in standard humidity level chambers. Results evince the wide dynamic range of the sensors fabricated in the low relative humidity range. While the sensor conductance is not sensitive to ethanol vapor in dry air, in humid air, sensor's responses are negatively affected by the contaminant.

  9. Photocatalysis: effect of light-activated nanoscale formulations of TiO(2) on Xanthomonas perforans and control of bacterial spot of tomato.

    PubMed

    Paret, Mathews L; Vallad, Gary E; Averett, Devron R; Jones, Jeffrey B; Olson, Stephen M

    2013-03-01

    Protection of crops from bacterial diseases presents a continuing challenge, mandating the development of novel agents and approaches. Photocatalysis is a process where chemically reactive oxygen species are catalytically generated by certain minerals in the presence of light. These reactive oxygen species have the capacity to destroy organic molecular structures critical to pathogen viability. In this study, the antibacterial potential of photocatalytic nanoscale titanium dioxide (TiO(2)), nanoscale TiO(2) doped (incorporation of other materials into the structure of TiO(2)) with silver (TiO(2)/Ag), and nanoscale TiO(2) doped with zinc (TiO(2)/Zn; AgriTitan) was evaluated against Xanthomonas perforans, the causal agent for bacterial spot disease of tomato. In vitro experiments on photocatalytic activity and dose dependency were conducted on glass cover slips coated with the nanoscale formulations by adding a known population of X. perforans strain Xp-F7 and illuminating the cover slips under a visible light source. TiO(2)/Ag and TiO(2)/Zn had high photocatalytic activity against X. perforans within 10 min of exposure to 3 × 10(4) lux. Greenhouse studies on naturally and artificially infected transplants treated with TiO(2)/Zn at ≈500 to 800 ppm significantly reduced bacterial spot severity compared with untreated and copper control. Protection was similar to the grower standard, copper + mancozeb. The use of TiO(2)/Zn at ≈500 to 800 ppm significantly reduced disease incidence in three of the four trials compared with untreated and copper control, and was comparable to or better than the grower standard. The treatments did not cause any adverse effects on tomato yield in any of the field trials. PMID:23190116

  10. The Effect of TiO2 on the Wetting Behavior of Silver-copper Oxide Braze Filler Metals

    SciTech Connect

    Weil, K. Scott; Kim, Jin Yong Y.; Hardy, John S.; Darsell, Jens T.

    2006-03-01

    A series of silver-copper oxide ceramic brazing alloys was compositionally modified by doping with small amounts of titania. Subsequent contact angle measurements indicate that concentrations as low as 0.5 mol% TiO2 can significantly enhance wettability over a wide range of binary Ag-CuOx compositions.

  11. A facile strategy to fabricate high-quality single crystalline brookite TiO2 nanoarrays and their photoelectrochemical properties

    NASA Astrophysics Data System (ADS)

    Choi, Mingi; Yong, Kijung

    2014-10-01

    Vertically aligned high-quality single crystalline brookite TiO2 nanoarrays were synthesized for the first time using an environmentally benign one-step hydrothermal reaction. They have a unique bullet-shaped structure which has a length of 700-1000 nm and a width of 150-250 nm with a sharpened tip structure. By adjusting the concentration of NaOH in hydrothermal reaction, we could also synthesize other types of TiO2 nanostructures including anatase TiO2 nanotubes/nanowires. The morphologies and crystal structures of the products were confirmed by scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. Their vertically aligned structures facilitate their application as photoanodes in photoelectrochemical cells, and the photoelectrochemical properties such as photocurrent density and open circuit voltage were measured in a three-electrode electrochemical cell with TiO2 nanoarrays, Ag/AgCl and a Pt flag as the working, reference and counter electrodes, respectively, incorporating a 0.1 M NaOH electrolyte solution. The fabricated brookite TiO2 nanoarrays exhibited a highly enhanced photocurrent density and a longer electron lifetime compared with anatase TiO2 nanoarrays with similar lengths.Vertically aligned high-quality single crystalline brookite TiO2 nanoarrays were synthesized for the first time using an environmentally benign one-step hydrothermal reaction. They have a unique bullet-shaped structure which has a length of 700-1000 nm and a width of 150-250 nm with a sharpened tip structure. By adjusting the concentration of NaOH in hydrothermal reaction, we could also synthesize other types of TiO2 nanostructures including anatase TiO2 nanotubes/nanowires. The morphologies and crystal structures of the products were confirmed by scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. Their vertically aligned structures facilitate their application as photoanodes in photoelectrochemical

  12. Photodegradation of Orange II by mesoporous TiO2.

    PubMed

    Kuang, Liyuan; Zhao, Yaping; Liu, Lu

    2011-09-01

    Mesoporous TiO(2) microspheres were prepared by a hydrothermal reaction and are characterized in this paper. Decoloration and mineralization during photodegradation of Orange II by mesoporous TiO(2) at different pH values, formation of sulfate, relative luminosity to luminous bacteria and recycling experiments of the catalyst were studied. The FTIR results further suggested that the novel mesoporous TiO(2) can not only decolor and mineralize dyes completely but also can be effectively reused several times. On the basis of the research, mesoporous TiO(2) would be a promising photocatalyst for practical use. PMID:21833403

  13. Structural investigations of hybrid TiO2/CNTs nanomaterials.

    PubMed

    Lin, Kuan-Nan; Liou, Wei-Jen; Lin, Hong-Ming; Yang, Tsung-Yeh; Lin, Chung-Kwei

    2010-05-01

    In the present study, pure TiO2 and hybrid TiO2/CNTs nanomaterials are prepared by sol gel technique. Post heat treatment is performed at 600, 800, and 1000 degrees C, respectively. The structural characterizations are performed by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction and synchrotron X-ray absorption spectroscopy techniques. Experimental results show that anatase to rutile transformation can be observed for pure TiO2 nanomaterials after heat treatment at 800 degrees C. The anatase to rutile transformation is inhibited by carbon nanotubes, and therefore only anatase phases for TiO2 nanomaterials can be observed in the hybrid nanomaterials. The 600 degrees C hybrid nanomaterials show a microstructure with CNTs covered by continuous TiO2 films of numerous small nanoparticles. After applying heat treatment on the hybrid nanomaterials at 1000 degrees C, only TiO2 nanoparticles adhere individually to the uncovered CNTs. Though all hybrid nanomaterials exhibit anatase TiO2, synchrotron X-ray absorption spectra investigations reveal that hybrid TiO2/CNTs exhibit different electronic properties as compared to those of pure TiO2 nanomaterials.

  14. Correlation between dispersion properties of TiO2 colloidal sols and photoelectric characteristics of TiO2 films.

    PubMed

    Jung, Hyun Suk; Lee, Sang-Wook; Kim, Jin Young; Hong, Kug Sun; Lee, Young Cheol; Ko, Kyung Hyun

    2004-11-15

    TiO2 film for use as dye-sensitized solar cell was prepared using the TiO2 colloidal sols (unpeptized sol and peptized sol). The optical properties and photocurrent-voltage characteristics of the resultant films were investigated. The optical transmittance of TiO2 thin film prepared from the peptized colloidal sol was over 90%, while that of TiO2 film from the unpeptized sol was under 80%. The TiO2 photoelectrode prepared from the peptized colloidal sol showed low photoelectric conversion efficiency (eta), 1.30%, whereas the efficiency of photoelectrode from the unpeptized sol was 2.21%. The high optical transmittance and low conversion efficiency of TiO2 film from the peptized sol are discussed in terms of dense microstructure due to the drying nature of well-dispersed colloidal sol.

  15. Electrospun TiO(2) fiber composite photoelectrodes for water splitting.

    PubMed

    Regonini, D; Teloeken, A C; Alves, A K; Berutti, F A; Gajda-Schrantz, K; Bergmann, C P; Graule, T; Clemens, F

    2013-11-27

    This work has focused on the development of electrospun TiO2 fiber composite photoelectrodes for hydrogen production by water splitting. For comparison, similar photoelectrodes were also developed using commercial TiO2 (Aeroxide P25) nanoparticles (NPs). Dispersions of either fibers or P25 NPs were used to make homogenous TiO2 films on fluorine-doped SnO2 (FTO) glass substrates by a doctor blade (DB) technique. Scanning electron microscopy (SEM) analysis revealed a much lower packing density of the DB fibers, with respect to DB-P25 TiO2 NPs; this was also directly reflected by the higher photocurrent measured for the NPs when irradiating the photoelectrodes at a light intensity of 1.5AM (1 sun, 1000 W/m(2)). For a better comparison of fibers vs. NPs, composite photoelectrodes by dip-coating (onto FTO) TiO2 sol-gel (SG) matrixes containing an equal amount (5 or 20 wt %) of either fibers or P25 NPs were also investigated. It emerged that the photoactivity of the fibers was significantly higher. For composites containing 5 wt % TiO2 fibers, a photocurrent of 0.5 mA/cm(2) (at 0.23 V vs Ag/AgCl) was measured, whereas 5 wt % P25 NPs only provided 0.2 mA/cm(2). When increasing to 20 wt % fibers or NPs, the photocurrent decreased, because of the formation of microcracks in the photoelectrodes, because of the shrinkage of the sol-gel. The high photoactivity of the fiber-based electrodes could be confirmed by incident photon to current efficiency (IPCE) measurements. Remarkably, the IPCE of composites containing 5 wt % fibers was between 35% and 40% in the region of 380-320 nm, and when accounting for transmission/reflection losses, the absorbed photon to current efficiency (APCE) was consistently over 60% between 380 nm and 320 nm. The superior photoactivity is attributed to the enhanced electron transport in the electrospun fibers, with respect to P25 NPs. According to this study, it is clear that the electronic connectivity ensured by the sol-gel also

  16. Assessing Photocatalytic Oxidation Using Modified TiO 2 Nanomaterials for Virus Inactivation in Drinking Water: Mechanisms and Application

    NASA Astrophysics Data System (ADS)

    Liga, Michael Vincent

    Photocatalytic oxidation is an alternative water treatment method under consideration for disinfecting water. Chlorine disinfection can form harmful byproducts, and some viruses (e.g. adenoviruses) are resistant to other alternative disinfection methods. Photocatalytic oxidation using nano-sized photocatalytic particles (e.g. TiO2, fullerene) holds promise; however, it is limited by its low efficiency and long required treatment times. This research focuses on improving virus inactivation by photocatalytic oxidation by modifying catalysts for improved activity, by analyzing virus inactivation kinetics, and by elucidating the inactivation mechanisms of adenovirus serotype 2 (AdV2) and bacteriophage MS2. Modifying TiO2 with silver (nAg/TiO2) or silica (SiO2-TiO2) improves the inactivation kinetics of bacteriophage MS2 by a factor of 3-10. nAg/ TiO2 increases hydroxyl radical (HO·) production while SiO2 increases the adsorption of MS2 to TiO 2. These results suggest that modifying the photocatalyst surface to increase contaminant adsorption is an important improvement strategy along with increasing HO· production. The inactivation kinetics of AdV2 by P25 TiO2 is much slower than the MS2 inactivation kinetics and displays a strong shoulder, which is not present in the MS2 kinetics. nAg/TiO2 initially improves the inactivation rate of AdV2. SiO2-TiO2 reduces the AdV2 inactivation kinetics since adsorption is not significantly enhanced, as it is with MS2. Amino-C60 is highly effective for AdV2 inactivation under visible light irradiation, making it a good material for use in solar disinfection systems. The efficacy of amino-fullerene also demonstrates that singlet oxygen is effective for AdV2 inactivation. When exposed to irradiated TiO2, AdV2 hexon proteins are heavily damaged resulting in the release of DNA. DNA damage is also present but may occur after capsids break. With MS2, the host interaction protein is rapidly damaged, but not the coat protein. The kinetics

  17. Acetaldehyde photochemistry on TiO2(110)

    SciTech Connect

    Zehr, Robert T.; Henderson, Michael A.

    2008-07-01

    The ultraviolet (UV) photon induced decomposition of acetaldehyde absorbed on the oxidized retile TIO2(110) surface was studied with photon stimulated desorption (PSD) and theral programmed desorption (TPD). Acetaldehyde desorbs molecularly from TiO2(110) with minor decomposition channels yielding butene on the reduced TiO2 surface and acetate on the oxidized TiO2 surface. Acetaldehyde absorbed on oxidized TiO2(110) undergoes a facile thermal reaction to form a photoactive acetaldehyde-oxygen complex. UV irradiation of the acetaldehyde-oxygen complex resulting in the ejection of methyl radical into gas phase and conversion of the surface bound fragment to formate.

  18. Acetaldehyde Photochemistry on TiO2(110)

    SciTech Connect

    Zehr, Robert T.; Henderson, Michael A.

    2008-07-01

    The ultraviolet (UV) photon induced decomposition of acetaldehyde adsorbed on the oxidized rutile TiO2(110) surface was studied with photon stimulated desorption (PSD) and thermal programmed desorption (TPD). Acetaldehyde desorbs molecularly from TiO2(110) with minor decomposition channels yielding butene on the reduced TiO2 surface and acetate on the oxidized TiO2 surface. Acetaldehyde adsorbed on oxidized TiO2(110) undergoes a facile thermal reaction to form a photoactive acetaldehyde-oxygen complex. UV irradiation of the acetaldehyde-oxygen complex initiated photofragmentation of the complex resulting in the ejection of methyl radical into gas phase and conversion of the surface bound fragment to formate.

  19. Nanocrystalline TiO2 films containing sulfur and gold: Synthesis, characterization and application to immobilize and direct electrochemistry of cytochrome c

    NASA Astrophysics Data System (ADS)

    Rafiee-Pour, Hossain-Ali; Hamadanian, Masood; Koushali, Samaneh Katebi

    2016-02-01

    In this paper, nanoporous titanium dioxide (TiO2) film was used for cytochrome c (cyt c) immobilization as an electrode substrate for electrochemical redox activity of the adsorbed cyt c. The result of cyclic voltammetry exhibited a pair of well-defined and quasi-reversible peaks for direct electron transfer of cyt c (formal potential [E0‧ = (Epa + Epc)/2] of 53 mV versus Ag/AgCl). In addition the effect of metal and nonmetal ions (Au, S) co-doping on the efficiency of TiO2 nanoparticles (prepared by combining sol-gel and photo-deposition methods) on the cyt c immobilization process was investigated. The results exhibited that the Au, S-co-doped TiO2 (Au/S-TiO2) with a spheroidal shape demonstrates a smaller grain size than the pure TiO2. Meanwhile, the UV-vis DRS of Au/S-TiO2 showed a considerable red shift to the visible region. As a result, it was found that 4% Au/0.1% S-TiO2 had the highest efficiency for cytochrome c immobilization. The results showed that the peak currents were higher after the annealing of the TiO2 film. This observation suggests that the use of TiO2 films may be advantageous for the development of nanoporous biosensors employing reductive electrochemistry.

  20. Facile electrochemical synthesis of antimicrobial TiO2 nanotube arrays

    PubMed Central

    Zhao, Yu; Xing, Qi; Janjanam, Jagadeesh; He, Kun; Long, Fei; Low, Ke-Bin; Tiwari, Ashutosh; Zhao, Feng; Shahbazian-Yassar, Reza; Friedrich, Craig; Shokuhfar, Tolou

    2014-01-01

    Infection-related complications have been a critical issue for the application of titanium orthopedic implants. The use of Ag nanoparticles offers a potential approach to incorporate antimicrobial properties into the titanium implants. In this work, a novel and simple method was developed for synthesis of Ag (II) oxide deposited TiO2 nanotubes (TiNTs) using electrochemical anodization followed by Ag electroplating processes in the same electrolyte. The quantities of AgO nanoparticles deposited in TiNT were controlled by selecting different electroplating times and voltages. It was shown that AgO nanoparticles were crystalline and distributed throughout the length of the nanotubes. Inductively coupled plasma mass spectrometry tests showed that the quantities of released Ag were less than 7 mg/L after 30 days at 37°C. Antimicrobial assay results show that the AgO-deposited TiNTs can effectively kill the Escherichia coli bacteria. Although the AgO-deposited TiNTs showed some cytotoxicity, it should be controllable by optimization of the electroplating parameters and incorporation of cell growth factor. The results of this study indicated that antimicrobial properties could be added to nanotextured medical implants through a simple and cost effective method. PMID:25429214

  1. Effect of TiO2 blocking layer on TiO2 nanorod arrays based dye sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Sivakumar, R.; Paulraj, M.

    2016-05-01

    Highly ordered rutile titanium dioxide nanorod (TNR) arrays (1.2 to 6.2 μm thickness) were grown on TiO2 blocking layer chemically deposited on fluorine doped tin oxide (FTO) substrate and were used as photo-electrodes to fabricate dye sensitized solar cells (DSSC's). Homogeneous layer of TiO2 on FTO was achieved by using aqueous peroxo- titanium complex (PTC) solutions via chemical bath deposition. Structural and morphological properties of the prepared samples were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) measurements. TNR arrays (6.2 μm) with TiO2 blocking layer showed higher energy conversion efficiency (1.46%) than that without TiO2 blocking layer. The reason can be ascertained to the suppression of electron-hole recombination at the semiconductor/electrolyte interface by the effect of TiO2 blocking layer.

  2. Preparation and photocatalytic activity of bicrystal phase TiO2 nanotubes containing TiO2-B and anatase

    NASA Astrophysics Data System (ADS)

    Huang, Chuanxi; Zhu, Kerong; Qi, Mengyao; Zhuang, Yonglong; Cheng, Chao

    2012-06-01

    Bicrystal phase TiO2 nanotubes (NTS) containing monoclinic TiO2-B and anatase were prepared by the hydrothermal reaction of anatase nanoparticles with NaOH aqueous solution and a heat treatment. Their structure was characterized by XRD, TEM and Raman spectra. The results showed that the bicrystal phase TiO2 NTS were formed after calcining H2Ti4O9·H2O NTS at 573 K. The bicrystal phase TiO2 NTS exhibit significantly higher photocatalytic activity than the single phase anatase NTS and Dessuga P-25 nanoparticles in the degradation of Methyl Orange aqueous solution under ultraviolet light irradiation, which is attributed to the large surface and interface areas of the bicrystal phase TiO2 NTS.

  3. Visible and UV functionality of TiO2 ternary nanocomposites on cotton

    NASA Astrophysics Data System (ADS)

    Pakdel, Esfandiar; Daoud, Walid A.; Sun, Lu; Wang, Xungai

    2014-12-01

    This research intends to increase the photocatalytic efficiency of cotton fabrics coated with TiO2-based nanocomposites under illumination particularly visible light. The fabrics were functionalized using a low-temperature sol-gel method of TiO2/Metal/SiO2 nanocomposite systems. Integrating silica and noble metals into TiO2 sol was put forth for boosting its functionality. Three noble metals (gold (Au), platinum (Pt) and silver (Ag)) with four different concentrations were employed. The photocatalytic activity of the functionalized fabrics was assessed through coffee stain-removal test and photodecomposition of methylene blue (MB) under UV and visible light. The impact of coating layers on fabrics' hydrophilicity was analyzed through measuring the water contact angle as well as the water absorption time. The fabrics were characterized using XRD, SEM and EDS. It was corroborated that the presence of silica enhanced the self-stain-removal capability of fabrics under UV. Moreover, the self-cleaning property of fabrics improved under both UV and visible light after integrating the metals into the colloids. In the same line, the self-cleaning activity threshold of fabrics was shifted to visible region.

  4. Photocatalytic TiO2 nanoparticles enhanced polymer antimicrobial coating

    NASA Astrophysics Data System (ADS)

    Wei, Xiaojin; Yang, Zhendi; Tay, See Leng; Gao, Wei

    2014-01-01

    Copper (Cu) containing coatings can provide sustainable protection against microbial contamination. However, metallic Cu coatings have not been widely used due to the relatively high cost, poor corrosion resistance, and low compatibility with non-metal substrates. Titanium dioxide (TiO2) possesses antibacterial functions by its photocatalytic properties which can destroy bacteria or suppress their reproduction. TiO2 also has the function of improving the mechanical properties through particle dispersion strengthening. We have recently developed an innovative polymer based coating system containing fine particles of Cu and TiO2 nanoparticles. These polymer based coatings simultaneously display excellent antimicrobial and good mechanical properties. The results showed that the addition of TiO2 has improved the antimicrobial property under sunlight, which provides extended applications in outdoor environment. The elimination of 106 bacterial by contacting the coatings without TiO2 needs 5 h, while contacting with the Cu/TiO2- 1 wt.% TiO2 took only 2 h to kill the same amount of bacteria. The coatings also presented enhanced hardness and wear resistance after adding TiO2. The width of wear track decreased from 270 μm of the Cu-polymer coating to 206 μm of Cu/TiO2-polymer coatings with 10 wt.% TiO2. Synchrotron Infrared Microscopy was used to in-situ and in-vivo study the bacteria killing process at the molecular level. The real-time chemical images of bacterial activities showed that the bacterial cell membranes were damaged by the Cu and TiO2 containing coatings

  5. The effect of silver nanoparticles/graphene-coupled TiO2 beads photocatalyst on the photoconversion efficiency of photoelectrochemical hydrogen production.

    PubMed

    Ke, Chun-Ren; Guo, Jyun-Sheng; Su, Yen-Hsun; Ting, Jyh-Ming

    2016-10-28

    In this work, a novel configuration of the photoelectrochemical hydrogen production device is demonstrated. It is based on TiO2 beads as the primary photoanode material with the addition of a heterostructure of silver nanoparticles/graphene. The heterostructure not only caters to a great improvement in light harvesting efficiency (LHE) but also enhances the charge collection efficiency. For LHE, the optimized cell based on TiO2 beads/Ag/graphene shows a 47% gain as compared to the cell having a photoanode of commercial P25 TiO2 powders. For the charge collection efficiency, there is a pronounced improvement of an impressive value of 856%. The reason for the improvement in light absorption is attributed to either the light scattering of TiO2 beads or the surface plasmonic resonance on the Ag nanoparticles/graphene. The photoconversion efficiency (PCE) of the resulting cells is also presented and discussed. The PCE of the TiO2 beads/Ag/graphene cell is approximately 2.5 times than that of pure P25 cell. PMID:27658375

  6. The effect of silver nanoparticles/graphene-coupled TiO2 beads photocatalyst on the photoconversion efficiency of photoelectrochemical hydrogen production.

    PubMed

    Ke, Chun-Ren; Guo, Jyun-Sheng; Su, Yen-Hsun; Ting, Jyh-Ming

    2016-10-28

    In this work, a novel configuration of the photoelectrochemical hydrogen production device is demonstrated. It is based on TiO2 beads as the primary photoanode material with the addition of a heterostructure of silver nanoparticles/graphene. The heterostructure not only caters to a great improvement in light harvesting efficiency (LHE) but also enhances the charge collection efficiency. For LHE, the optimized cell based on TiO2 beads/Ag/graphene shows a 47% gain as compared to the cell having a photoanode of commercial P25 TiO2 powders. For the charge collection efficiency, there is a pronounced improvement of an impressive value of 856%. The reason for the improvement in light absorption is attributed to either the light scattering of TiO2 beads or the surface plasmonic resonance on the Ag nanoparticles/graphene. The photoconversion efficiency (PCE) of the resulting cells is also presented and discussed. The PCE of the TiO2 beads/Ag/graphene cell is approximately 2.5 times than that of pure P25 cell.

  7. The effect of silver nanoparticles/graphene-coupled TiO2 beads photocatalyst on the photoconversion efficiency of photoelectrochemical hydrogen production

    NASA Astrophysics Data System (ADS)

    Ke, Chun-Ren; Guo, Jyun-Sheng; Su, Yen-Hsun; Ting, Jyh-Ming

    2016-10-01

    In this work, a novel configuration of the photoelectrochemical hydrogen production device is demonstrated. It is based on TiO2 beads as the primary photoanode material with the addition of a heterostructure of silver nanoparticles/graphene. The heterostructure not only caters to a great improvement in light harvesting efficiency (LHE) but also enhances the charge collection efficiency. For LHE, the optimized cell based on TiO2 beads/Ag/graphene shows a 47% gain as compared to the cell having a photoanode of commercial P25 TiO2 powders. For the charge collection efficiency, there is a pronounced improvement of an impressive value of 856%. The reason for the improvement in light absorption is attributed to either the light scattering of TiO2 beads or the surface plasmonic resonance on the Ag nanoparticles/graphene. The photoconversion efficiency (PCE) of the resulting cells is also presented and discussed. The PCE of the TiO2 beads/Ag/graphene cell is approximately 2.5 times than that of pure P25 cell.

  8. Growth of TiO2 nanoparticles under heat treatment

    NASA Astrophysics Data System (ADS)

    Bahadur, J.; Sen, D.; Mazumder, S.; Sastry, P. U.; Paul, B.

    2013-02-01

    The effect of heat treatment, on growth of NiO doped TiO2, have been investigated. The nanoparticle size has been estimated by small-angle x-ray scattering. The average particle size increases with increasing temperature. The growth of crystallite size has been probed by X-ray diffraction. A polymorphic phase transition of TiO2 is observed beyond 600°C due to growth of TiO2 nanoparticles beyond 14 nm of size.

  9. Low temperature crystallisation of mesoporous TiO2.

    PubMed

    Kohn, Peter; Pathak, Sandeep; Stefik, Morgan; Ducati, Caterina; Wiesner, Ulrich; Steiner, Ullrich; Guldin, Stefan

    2013-11-01

    Conducting mesoporous TiO2 is rapidly gaining importance for green energy applications. To optimise performance, its porosity and crystallinity must be carefully fine-tuned. To this end, we have performed a detailed study on the temperature dependence of TiO2 crystallisation in mesoporous films. Crystal nucleation and growth of initially amorphous TiO2 derived by hydrolytic sol-gel chemistry is compared to the evolution of crystallinity from nanocrystalline building blocks obtained from non-hydrolytic sol-gel chemistry, and mixtures thereof. Our study addresses the question whether the critical temperature for crystal growth can be lowered by the addition of crystalline nucleation seeds.

  10. TiO2-graphene nanocomposites for gas-phase photocatalytic degradation of volatile aromatic pollutant: is TiO2-graphene truly different from other TiO2-carbon composite materials?

    PubMed

    Zhang, Yanhui; Tang, Zi-Rong; Fu, Xianzhi; Xu, Yi-Jun

    2010-12-28

    The nanocomposites of TiO(2)-graphene (TiO(2)-GR) have been prepared via a facile hydrothermal reaction of graphene oxide and TiO(2) in an ethanol-water solvent. We show that such a TiO(2)-GR nanocomposite exhibits much higher photocatalytic activity and stability than bare TiO(2) toward the gas-phase degradation of benzene, a volatile aromatic pollutant in air. By investigating the effect of different addition ratios of graphene on the photocatalytic activity of TiO(2)-GR systematically, we find that the higher weight ratio in TiO(2)-GR will decrease the photocatalytic activity. Analogous phenomenon is also observed for the liquid-phase degradation of dyes over TiO(2)-GR. In addition, the key features for TiO(2)-GR including enhancement of adsorptivity of pollutants, light absorption intensity, electron-hole pairs lifetime, and extended light absorption range have also been found in the composite of TiO(2) and carbon nanotubes (TiO(2)-CNT). These strongly manifest that TiO(2)-GR is in essence the same as other TiO(2)-carbon (carbon nanotubes, fullerenes, and activated carbon) composite materials on enhancement of photocatalytic activity of TiO(2), although graphene by itself has unique structural and electronic properties. Notably, this key fundamental question remains completely unaddressed in a recent report ( ACS Nano 2010 , 4 , 380 ) regarding liquid-phase degradation of dyes over the TiO(2)-GR photocatalyst. Thus, we propose that TiO(2)-GR cannot provide truly new insights into the fabrication of TiO(2)-carbon composite as high-performance photocatalysts. It is hoped that our work could avert the misleading message to the readership, hence offering a valuable source of reference on fabricating TiO(2)-carbon composites for their application as a photocatalyst in the environment cleanup. PMID:21117654

  11. SYNTHESIZING ORGANIC COMPOUNDS USING LIGHT-ACTIVATED TIO2

    EPA Science Inventory

    High-value organic compounds have been synthesized successfully from linear and cyclic hydrocarbons, by photocatalytic oxidation using a semiconductor material, titanium dioxide (TiO2). Various hydrocarbons were partially oxgenated in both liquid and gaseous phase reactors usi...

  12. Photocatalytic metamaterials: TiO2 inverse opals.

    PubMed

    Sordello, Fabrizio; Duca, Clara; Maurino, Valter; Minero, Claudio

    2011-06-01

    The study of the photocatalytic activity of TiO(2) inverse opals showed that these structures behave as metamaterials: their properties arise principally from the 3D periodic structure of the material and marginally from porosity, reflectivity and scattering.

  13. Investigation of physical properties of TiO2 nanolayers

    NASA Astrophysics Data System (ADS)

    Struk, Przemyslaw; Pustelny, Tadeusz

    2015-12-01

    We present applications of titanium dioxide wide bandgap oxide semiconductor and its application in integrated optics devices. The paper is focus on research of physical properties TiO2 such as: spectral transmittance, refractive index, extinction coefficient in the UV-VIS-IR range of light as well as surface topography. In addition we show the numerical calculation and optical characterization of fabricated optical planar waveguide based on TiO2.

  14. Density functional theory study of interactions between glycine and TiO2/graphene nanocomposites

    NASA Astrophysics Data System (ADS)

    Wang, Meng-hao; Guo, Ya-nan; Wang, Qun; Zhang, Xia-shi-yao; Huang, Jing-jing; Lu, Xiong; Wang, Ke-feng; Zhang, Hong-ping; Leng, Yang

    2014-04-01

    The interactions of glycine (Gly) with TiO2, graphene (G), graphene oxide (GO), TiO2/G and TiO2/GO nanocomposites were investigated by density functional theory (DFT). The results indicate that the interactions between Gly and TiO2 in TiO2/G nanocomposites are stronger than that between Gly and bare TiO2 surfaces, which suggests G helps to strengthen the interaction of amino acids with TiO2 surfaces. In TiO2/GO nanocomposites, the interactions of Gly and TiO2 are slightly weaker than that between Gly and bare TiO2 surfaces, which reveals that GO is not conducive to the interaction of amino acids with TiO2 surfaces.

  15. TiO2 optical sensor for amino acid detection

    NASA Astrophysics Data System (ADS)

    Tereshchenko, Alla; Viter, Roman; Konup, Igor; Ivanitsa, Volodymyr; Geveliuk, Sergey; Ishkov, Yuriy; Smyntyna, Valentyn

    2013-11-01

    A novel optical sensor based on TiO2 nanoparticles for Valine detection has been developed. In the presented work, commercial TiO2 nanoparticles (Sigma Aldrich, particle size 32 nm) were used as sensor templates. The sensitive layer was formed by a porphyrin coating on a TiO2 nanostructured surface. As a result, an amorphous layer between the TiO2 nanostructure and porphyrin was formed. Photoluminescence (PL) spectra were measured in the range of 370-900 nm before and after porphyrin application. Porphyrin adsorption led to a decrease of the main TiO2 peak at 510 nm and the emergence of an additional peak of high intensity at 700 nm. Absorption spectra (optical density vs. wavelenght, measured from 300 to 1100 nm) showed IR shift Sorret band of prophiryn after deposition on metal oxide. Adsorption of amino acid quenched PL emission, related to porphyrin and increased the intensity of the TiO2 emission. The interaction between the sensor surface and the amino acid leads to the formation of new complexes on the surface and results in a reduction of the optical activity of porphyrin. Sensitivity of the sensor to different concentrations of Valine was calculated. The developed sensor can determine the concentration of Valine in the range of 0.04 to 0.16 mg/ml.

  16. The effect of TiO2/aluminosilicate nanocomposite additives on the mechanical and thermal properties of polyacrylic coatings

    NASA Astrophysics Data System (ADS)

    Nosrati, Rahimeh; Olad, Ali

    2015-12-01

    The commercial grade polyacrylic latex was modified in order to prepare a mechanical and thermal improved coating. TiO2/Ag-exchanged-aluminosilicate nanocomposites with montmorillonite, zeolite-A and clinoptilolite aluminosilicates were prepared and used as additive in the matrix of polyacrylic latex to achieve a coating with proper mechanical and thermal properties. X-ray diffraction patterns and FESEM were used to characterize the composition, structure, and morphology of the nanocomposite additives. Polyacrylic coatings modified by TiO2/Ag-exchanged-aluminosilicate nanocomposite additives showed higher adhesion strength and hardness compared to unmodified commercial grade polyacrylic coatings. Differential Scanning Calorimetry (DSC) analysis showed lower glass transition temperature for modified polyacrylic coatings than that of unmodified polyacrylic coatings. The tensile tests were also carried out for unmodified and modified polyacrylic coatings. According to the results, the modified polyacrylic based coating with TiO2/Ag-exchanged-clinoptilolite nanocomposite additive was the best coating considering most of useful properties.

  17. Structural, Optical and Thermal Investigations of TiO2 and S-Doped TiO2 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Bhatnagar, Divyanshu; Kumar, Ashavani

    2011-12-01

    Titanium dioxide (TiO2) and sulfur doped titanium dioxide (S-doped TiO2) nanoparticles are synthesized by Coprecipitation technique using titanium trichloride (TiCl3) as precursor, ammonium hydroxide (NH4OH) as solvent and sodium sulfite as source of sulfur. The X-ray diffraction (xrd) pattern reveals that TiO2 Nanoparticles are in anatase phase and anatase content decreases with increasing S-doping. The Differential Scanning Calorimetry (DSC) analysis elucidates the metastable anatase phase changes to stable rutile phase at 746 °C temperature. The UV/Vis study predicts larger band gap of TiO2 Nanoparticles as compare to bulk and blue shift with increasing S-doping.

  18. TiO2 (B) nanosheets mediate phase selective synthesis of TiO2 nanostructured photocatalyst

    NASA Astrophysics Data System (ADS)

    Wang, Yuxi; Wang, Changhua; Zhang, Xintong; Sun, Panpan; Kong, Lina; Wei, Yongan; Zheng, Han; Liu, Yichun

    2014-02-01

    Phase selective synthesis is particularly valuable in revealing performance of photocatalyst existing as several polymorphic phases. In this work, we develop a general soft chemical route that used a TiO2 (B) nanosheet as a precursor to synthesize TiO2 nanostructures of desired phase. Benefiting from the structural similarity and ultrathin thickness feature, TiO2 (B) nanosheet precursor can readily transform to pure phase of anatase, rutile and brookite as well as mixed phase of brookite/anatase. A possible dissolution-recrystallization mechanism is proposed for the phase transition of TiO2 (B) nanosheets to other phases. Photocatalytic activity tests demonstrated that the brookite/anatase mixture had the highest activity in degrading acetaldehyde under UV light irradiation, due to the synergistic effect of high crystallinity, large surface area and mixed phase structure.

  19. TiO2 fotokatalyse in de gasfase van morfologisch ontwerp tot plasmoneffecten

    NASA Astrophysics Data System (ADS)

    Verbruggen, Sammy

    . Surface plasmon resonance can be regarded as a collective oscillation of free electrons in a metal. This way incident (visible) light energy can be 'captured' in the resonance and subsequently transferred to T1O2. First, a theoretical model is established that enables to predict the plasmon resonance wavelength of such alloy nanoparticles, based on the combined effect of particle size and alloy composition. It is shown that the feature of alloying presents high wavelength tunability of the visible light response. Next, alloy nanoparticles are deposited on TiO2. Thus obtained plasmonic photocatalysts are tested towards their self-cleaning performance in the degradation of stearic acid located at the catalyst-air interface. The highest quantum efficiency is obtained when the resonance wavelength of the plasmonic catalyst exactly matches that of the incident light. This is demonstrated for the case of Au 0.3Ag0.7, nanoparticles on TiO2 under 490 nm illumination, provided by LEDs.

  20. Selective aerobic oxidation mediated by TiO(2) photocatalysis.

    PubMed

    Lang, Xianjun; Ma, Wanhong; Chen, Chuncheng; Ji, Hongwei; Zhao, Jincai

    2014-02-18

    TiO2 is one of the most studied metal oxide photocatalysts and has unparal-leled efficiency and stability. This cheap, abundant, and non-toxic material has the potential to address future environmental and energy concerns. Understanding about the photoinduced interfacial redox events on TiO2 could have profound effect on the degradation of organic pollutants, splitting of H2O into H2 and O2, and selective redox organic transformations. Scientists traditionally accept that for a semiconductor photocatalyst such as TiO2 under the illumination of light with energy larger than its band gap, two photocarriers will be created to carry out their independent reduction and oxidation processes. However, our recent discoveries indicate that it is the concerted rather than independent effect of both photocarriers of valence band hole (hvb(+)) and conduction band electron (ecb(-)) that dictate the product formation during interfacial oxidation event mediated by TiO2 photocatalysis. In this Account, we describe our recent findings on the selective oxidation of organic substrates with O2 mediated by TiO2 photocatalysis. The transfer of O-atoms from O2 to the corresponding products dominates the selective oxidation of alcohols, amines, and alkanes mediated by TiO2 photocatalysis. We ascribe this to the concerted effect of both hvb(+) and ecb(-) of TiO2 in contribution to the oxidation products. These findings imply that O2 plays a unique role in its transfer into the products rather than independent role of ecb(-) scavenger. More importantly, ecb(-) plays a crucial role to ensure the high selectivity for the oxygenation of organic substrates. We can also use the half reactions such as those of the conduction band electron of TiO2 for efficient oxidation reactions with O2. To this end, efficient selective oxidation of organic substrates such as alcohols, amines, and aromatic alkanes with O2 mediated by TiO2 photocatalysis under visible light irradiation has been achieved. In summary, the concerted effect of hvb(+) and ecb(-) to implement one oxidation event could pave the way for selective oxofunctionalization of organic substrates with O2 by metal oxide photocatalysis. Furthermore, it could also deepen our understanding on the role of O2 and the elusive nature of oxygen species at the interface of TiO2, which, in turn, could shed new light on avant-garde photocatalytic selective redox processes in addressing the energy and environmental challenges of the future.

  1. Selective aerobic oxidation mediated by TiO(2) photocatalysis.

    PubMed

    Lang, Xianjun; Ma, Wanhong; Chen, Chuncheng; Ji, Hongwei; Zhao, Jincai

    2014-02-18

    TiO2 is one of the most studied metal oxide photocatalysts and has unparal-leled efficiency and stability. This cheap, abundant, and non-toxic material has the potential to address future environmental and energy concerns. Understanding about the photoinduced interfacial redox events on TiO2 could have profound effect on the degradation of organic pollutants, splitting of H2O into H2 and O2, and selective redox organic transformations. Scientists traditionally accept that for a semiconductor photocatalyst such as TiO2 under the illumination of light with energy larger than its band gap, two photocarriers will be created to carry out their independent reduction and oxidation processes. However, our recent discoveries indicate that it is the concerted rather than independent effect of both photocarriers of valence band hole (hvb(+)) and conduction band electron (ecb(-)) that dictate the product formation during interfacial oxidation event mediated by TiO2 photocatalysis. In this Account, we describe our recent findings on the selective oxidation of organic substrates with O2 mediated by TiO2 photocatalysis. The transfer of O-atoms from O2 to the corresponding products dominates the selective oxidation of alcohols, amines, and alkanes mediated by TiO2 photocatalysis. We ascribe this to the concerted effect of both hvb(+) and ecb(-) of TiO2 in contribution to the oxidation products. These findings imply that O2 plays a unique role in its transfer into the products rather than independent role of ecb(-) scavenger. More importantly, ecb(-) plays a crucial role to ensure the high selectivity for the oxygenation of organic substrates. We can also use the half reactions such as those of the conduction band electron of TiO2 for efficient oxidation reactions with O2. To this end, efficient selective oxidation of organic substrates such as alcohols, amines, and aromatic alkanes with O2 mediated by TiO2 photocatalysis under visible light irradiation has been achieved. In summary, the concerted effect of hvb(+) and ecb(-) to implement one oxidation event could pave the way for selective oxofunctionalization of organic substrates with O2 by metal oxide photocatalysis. Furthermore, it could also deepen our understanding on the role of O2 and the elusive nature of oxygen species at the interface of TiO2, which, in turn, could shed new light on avant-garde photocatalytic selective redox processes in addressing the energy and environmental challenges of the future. PMID:24164388

  2. Enhanced photovoltaic performance of inverted hybrid bulk-heterojunction solar cells using TiO2/reduced graphene oxide films as electron transport layers

    NASA Astrophysics Data System (ADS)

    Morais, Andreia; Alves, João Paulo C.; Lima, Francisco Anderson S.; Lira-Cantu, Monica; Nogueira, Ana Flavia

    2015-01-01

    In this study, we investigated inverted hybrid bulk-heterojunction solar cells with the following configuration: fluorine-doped tin oxide (FTO) |TiO2/RGO|P3HT:PC61BM|V2O5 or PEDOT:PSS|Ag. The TiO2/GO dispersions were prepared by sol-gel method, employing titanium isopropoxide and graphene oxide (GO) as starting materials. The GO concentration was varied from 0.1 to 4.0 wt%. The corresponding dispersions were spin-coated onto FTO substrates and a thermal treatment was performed to remove organic materials and to reduce GO to reduced graphene oxide (RGO). The TiO2/RGO films were characterized by x-ray diffraction, Raman spectroscopy, and microscopy techniques. Atomic force microscopy (AFM) images showed that the addition of RGO significantly changes the morphology of the TiO2 films, with loss of uniformity and increase in surface roughness. Independent of the use of V2O5 or PEDOT: PSS films as the hole transport layer, the incorporation of 2.0 wt% of RGO into TiO2 films was the optimal concentration for the best organic photovoltaic performance. The solar cells based on TiO2/RGO (2.0 wt%) electrode exhibited a ˜22.3% and ˜28.9% short circuit current density (Jsc) and a power conversion efficiency enhancement, respectively, if compared with the devices based on pure TiO2 films. Kelvin probe force microscopy images suggest that the incorporation of RGO into TiO2 films can promote the appearance of regions with different charge dissipation capacities.

  3. Characterization and photocatalytic performance evaluation of various metal ion-doped microstructured TiO2 under UV and visible light.

    PubMed

    Sahoo, Chittaranjan; Gupta, Ashok K

    2015-01-01

    Commercially available microcrystalline TiO2 was doped with silver, ferrous and ferric ion (1.0 mol %) using silver nitrate, ferrous sulfate and ferric nitrate solutions following the liquid impregnation technology. The catalysts prepared were characterised by FESEM, XRD, FTIR, DRS, particle size and micropore analysis. The photocatalytic activity of the prepared catalysts was tested on the degradation of two model dyes, methylene blue (3,7-bis (Dimethylamino)-phenothiazin-5-ium chloride, a cationic thiazine dye) and methyl blue (disodium;4-[4-[[4-(4-sulfonatoanilino)phenyl]-[4-(4-sulfonatophenyl)azaniumylidenecyclohexa-2,5-dien-1-ylidene]methyl]anilino]benzene sulfonate, an anionic triphenyl methane dye) under irradiation by UV and visible light in a batch reactor. The efficiency of the photocatalysts under UV and visible light was compared to ascertain the light range for effective utilization. The catalysts were found to have the anatase crystalline structure and their particle size is in a range of 140-250 nm. In the case of Fe(2+) doped TiO2 and Fe(3+) doped TiO2, there was a greater shift in the optical absorption towards the visible range. Under UV light, Ag(+) doped TiO2 was the most efficient catalyst and the corresponding decolorization was more than 99% for both the dyes. Under visible light, Fe(3+) doped TiO2 was the most efficient photocatalyst with more than 96% and 90% decolorization for methylene blue and methyl blue, respectively. The kinetics of the reaction under both UV and visible light was investigated using the Langmuir-Hinshelwood pseudo-first-order kinetic model. Kinetic measurements confirmed that, Ag(+) doped TiO2 was most efficient in the UV range, while Fe(3+) doped TiO2 was most efficient in the visible range.

  4. Evidence for the intrinsic nature of band-gap states electrochemically observed on atomically flat TiO2(110) surfaces.

    PubMed

    Takata, Shintaro; Miura, Yoshihiro; Matsumoto, Yuji

    2014-12-01

    Using an ultra-high vacuum (UHV) electrochemistry approach with pulsed laser deposition (PLD), we investigated the band-gap state for TiO2(110). In the PLD chamber, a TiO2(110) surface was cleaned by annealing in O2 enough for it to exhibit a sharp (1 × 1) reflection high energy electron diffraction (RHEED) pattern. The cleaned TiO2(110)-(1 × 1) sample then underwent electrochemical measurements without exposure to air, showing the band-gap state at -0.14 V vs. Ag by Mott-Schottky plot analysis. The band-gap state gradually disappeared under UV illumination at +0.6 V vs. Ag due to photoetching, and reappeared on reduction in a vacuum and/or deposition of a fresh TiO2 film. These results indicated that the electrochemically observed band-gap state for TiO2(110) was a defect state due to oxygen deficiency, most probably identical to that observed under UHV, which does not necessarily exist on the surface. A quantitative analysis of the defect density suggests that the origin of this defect state is not the surface bridging hydroxyls or oxygen vacancies, but rather the interstitial Ti(3+) ions in the subsurface region.

  5. Lithium insertion in nanostructured TiO(2)(B) architectures.

    PubMed

    Dylla, Anthony G; Henkelman, Graeme; Stevenson, Keith J

    2013-05-21

    Electric vehicles and grid storage devices have potentialto become feasible alternatives to current technology, but only if scientists can develop energy storage materials that offer high capacity and high rate capabilities. Chemists have studied anatase, rutile, brookite and TiO2(B) (bronze) in both bulk and nanostructured forms as potential Li-ion battery anodes. In most cases, the specific capacity and rate of lithiation and delithiation increases as the materials are nanostructured. Scientists have explained these enhancements in terms of higher surface areas, shorter Li(+) diffusion paths and different surface energies for nanostructured materials allowing for more facile lithiation and delithiation. Of the most studied polymorphs, nanostructured TiO2(B) has the highest capacity with promising high rate capabilities. TiO2(B) is able to accommodate 1 Li(+) per Ti, giving a capacity of 335 mAh/g for nanotubular and nanoparticulate TiO2(B). The TiO2(B) polymorph, discovered in 1980 by Marchand and co-workers, has been the focus of many recent studies regarding high power and high capacity anode materials with potential applications for electric vehicles and grid storage. This is due to the material's stability over multiple cycles, safer lithiation potential relative to graphite, reasonable capacity, high rate capability, nontoxicity, and low cost (Bruce, P. G.; Scrosati, B.; Tarascon, J.-M. Nanomaterials for Rechargeable Lithium Batteries. Angew. Chem., Int. Ed.2008, 47, 2930-2946). One of the most interesting properties of TiO2(B) is that both bulk and nanostructured forms lithiate and delithiate through a surface redox or pseudocapacitive charging mechanism, giving rise to stable high rate charge/discharge capabilities in the case of nanostructured TiO2(B). When other polymorphs of TiO2 are nanostructured, they still mainly intercalate lithium through a bulk diffusion-controlled mechanism. TiO2(B) has a unique open crystal structure and low energy Li(+) pathways from surface to subsurface sites, which many chemists believe to contribute to the pseudocapacitive charging. Several disadvantages exist as well. TiO2(B), and titania in general, suffers from poor electronic and ionic conductivity. Nanostructured TiO2(B) also exhibits significant irreversible capacity loss (ICL) upon first discharge (lithiation). Nanostructuring TiO2(B) can help alleviate problems with poor ionic conductivity by shortening lithium diffusion pathways. Unfortunately, this also increases the likelihood of severe first discharge ICL due to reactive Ti-OH and Ti-O surface sites that can cause unwanted electrolyte degradation and irreversible trapping of Li(+). Nanostructuring also results in lowered volumetric energy density, which could be a considerable problem for mobile applications. We will also discuss these problems and proposed solutions. Scientists have synthesized TiO2(B) in a variety of nanostructures including nanowires, nanotubes, nanoparticles, mesoporous-ordered nanostructures, and nanosheets. Many of these structures exhibit enhanced Li(+) diffusion kinetics and increased specific capacities compared to bulk material, and thus warrant investigation on how nanostructuring influences lithiation behavior. This Account will focus on these influences from both experimental and theoretical perspectives. We will discuss the surface charging mechanism that gives rise to the increased lithiation and delithiation kinetics for TiO2(B), along with the influence of dimensional confinement of the nanoarchitectures, and how nanostructuring can change the lithiation mechanism considerably. PMID:23425042

  6. Photocatalytic performance of TiO2-zeolite templated carbon composites in organic contaminant degradation.

    PubMed

    Donphai, Waleeporn; Kamegawa, Takashi; Chareonpanich, Metta; Nueangnoraj, Khanin; Nishihara, Hirotomo; Kyotani, Takashi; Yamashita, Hiromi

    2014-12-01

    TiO2 composites with zeolite templated carbon (TiO2-ZTC) and activated carbon (TiO2-AC) were prepared and used as the photocatalysts for comparative studies with pure TiO2. TiO2-ZTC exhibited the highest rate of methylene blue degradation with a rate approximately 4 and 400 times higher than those of TiO2-AC and pure TiO2, respectively. Moreover, the highest catalytic performance of TiO2-ZTC in gas-phase degradation of acetone was approximately 1.1 and 12.9 times higher than TiO2-AC and pure TiO2, respectively. These outstanding performances could be attributed to high surface area, pore volume, and hydrophobic surface properties, leading to improvement in the adsorption properties of organic molecules.

  7. Photocatalytic Properties of TiO2 Porous Network Film.

    PubMed

    Yu, Lianqing; Zhi, Qianqian; Huang, Chengxing; Zhang, Yaping; Dong, Kaituo; Neppolian, B

    2015-09-01

    Three-dimensional porous network TiO2 film (PW-film) and nanoparticles film were synthesized on surface of the Ti foil by a facile method to investigate both the photoelectrochemical and photocatalytic properties. The prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray diffraction spectroscopy (XRD) techniques. Methylene blue was used as a target molecule to estimate the photocatalytic activity of the films. Results revealed that the hydrothermal temperature and time have great influence on the crystal type and film morphology of TiO2 catalysts. A higher hydrothermal temperature is benefit for the formation of anatase phase of TiO2 nanotubes with PW-film, which had a large number of nodes. After investigation of the photoelectrochemical properties, a maximum photoconversion efficiency of 4.79% is observed for nanoparticles film with rutile phase of TiO2 under UV light illumination, which was incredible 2 times higher than that of the PW-film with anatase phase. It was shown that the morphology of TiO2 film contributes more significant effect on photocatalytic and photoelectric performance than its crystal type. PMID:26716214

  8. Photocatalytic Properties of TiO2 Porous Network Film.

    PubMed

    Yu, Lianqing; Zhi, Qianqian; Huang, Chengxing; Zhang, Yaping; Dong, Kaituo; Neppolian, B

    2015-09-01

    Three-dimensional porous network TiO2 film (PW-film) and nanoparticles film were synthesized on surface of the Ti foil by a facile method to investigate both the photoelectrochemical and photocatalytic properties. The prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray diffraction spectroscopy (XRD) techniques. Methylene blue was used as a target molecule to estimate the photocatalytic activity of the films. Results revealed that the hydrothermal temperature and time have great influence on the crystal type and film morphology of TiO2 catalysts. A higher hydrothermal temperature is benefit for the formation of anatase phase of TiO2 nanotubes with PW-film, which had a large number of nodes. After investigation of the photoelectrochemical properties, a maximum photoconversion efficiency of 4.79% is observed for nanoparticles film with rutile phase of TiO2 under UV light illumination, which was incredible 2 times higher than that of the PW-film with anatase phase. It was shown that the morphology of TiO2 film contributes more significant effect on photocatalytic and photoelectric performance than its crystal type.

  9. Hydrogen Impurity Defects in Rutile TiO2

    PubMed Central

    Mo, Li-Bin; Wang, Yu; Bai, Yang; Xiang, Qing-Yun; Li, Qun; Yao, Wen-Qing; Wang, Jia-Ou; Ibrahim, Kurash; Wang, Huan-Hua; Wan, Cai-Hua; Cao, Jiang-Li

    2015-01-01

    Hydrogen-related defects play crucial roles in determining physical properties of their host oxides. In this work, we report our systematic experimental and theoretical (based on density functional theory) studies of the defect states formed in hydrogenated-rutile TiO2 in gaseous H2 and atomic H. In gas-hydrogenated TiO2, the incorporated hydrogen tends to occupy the oxygen vacancy site and negatively charged. The incorporated hydrogen takes the interstitial position in atom-hydrogenated TiO2, forming a weak O-H bond with the closest oxygen ion, and becomes positive. Both states of hydrogen affect the electronic structure of TiO2 mainly through changes of Ti 3d and O 2p states instead of the direct contributions of hydrogen. The resulted electronic structures of the hydrogenated TiO2 are manifested in modifications of the electrical and optical properties that will be useful for the design of new materials capable for green energy economy. PMID:26627134

  10. Hydrogen Impurity Defects in Rutile TiO2

    NASA Astrophysics Data System (ADS)

    Mo, Li-Bin; Wang, Yu; Bai, Yang; Xiang, Qing-Yun; Li, Qun; Yao, Wen-Qing; Wang, Jia-Ou; Ibrahim, Kurash; Wang, Huan-Hua; Wan, Cai-Hua; Cao, Jiang-Li

    2015-12-01

    Hydrogen-related defects play crucial roles in determining physical properties of their host oxides. In this work, we report our systematic experimental and theoretical (based on density functional theory) studies of the defect states formed in hydrogenated-rutile TiO2 in gaseous H2 and atomic H. In gas-hydrogenated TiO2, the incorporated hydrogen tends to occupy the oxygen vacancy site and negatively charged. The incorporated hydrogen takes the interstitial position in atom-hydrogenated TiO2, forming a weak O-H bond with the closest oxygen ion, and becomes positive. Both states of hydrogen affect the electronic structure of TiO2 mainly through changes of Ti 3d and O 2p states instead of the direct contributions of hydrogen. The resulted electronic structures of the hydrogenated TiO2 are manifested in modifications of the electrical and optical properties that will be useful for the design of new materials capable for green energy economy.

  11. Bifunctional 4MBA mediated recyclable SERS-based immunoassay induced by photocatalytic activity of TiO2 nanotube arrays.

    PubMed

    Wang, Xiaolong; Zhou, Lu; Lai, Wei; Jiang, Tao; Zhou, Jun

    2016-09-14

    We first report here a novel recyclable surface-enhanced Raman scattering (SERS)-based immunoassay via the photocatalytic ability of anatase titania nanotube (TiO2-NT) arrays. In this immunoassay, an immune probe was realized by immobilizing anti-CA19-9 onto Ag@SiO2@Ag three core-shell nanoparticles (TCSNPs), which showed a much higher SERS activity than bare Ag NPs with an enhancement ratio of 1.75. Then, the vertically oriented TiO2-NT immune substrate was synthesized by ultra-fast anodic oxidation of flexible titanium foils and functionalised with 4-mercaptobenzoic acid (4MBA) molecules to link them with anti-CA19-9. The immunoassay using the above immune probe and the substrate exhibited a wide linear range from 1000 to 0.5 U mL(-1) and a low detection limit of 0.5 U mL(-1) for CA19-9 due to the excellent SERS performance of Ag@SiO2@Ag TCSNPs. More importantly, the linkage between TiO2-NTs and 4MBA was destroyed by catalyzing 4MBA into 4-sulfobenzoate upon UV irradiation in O2-saturated water. The target antigen and the immune probe were simultaneously removed leading to a recyclable immunoassay and a detection limit of 5 U mL(-1) was achieved after six cycles. The simplicity and versatility of this strategy may bridge the technology gap between academia and practical detection, which makes it promising for clinical SERS-based immunoassay. PMID:27523026

  12. Electrorheological Response of POLYANILINE-TIO2 Composite Suspensions

    NASA Astrophysics Data System (ADS)

    Sung, J. H.; Lee, I.; Choi, H. J.; Choi, S. B.

    As an organic/inorganic hybrid possessing advantages from the combination of their own unique properties, conducting polyaniline (PANI)-titanium dioxide (TiO2) hybrid particles were synthesized by an oxidation polymerization of aniline, and their ER characteristics were examined. Our aim was to study the ER behavior of highly potential ER-active particles using conducting polymer and TiO2 nanoparticle with relatively high dielectric constant. In addition, we also investigated its ER behavior as a function of particle fraction of TiO2 under an applied electric field. The result was interpreted in terms of the dielectric relaxation mismatch. The fast relaxation time of PANI/TiO2 hybrid was considered to enhance electrostatic force over shear force under a hydrodynamic flow, showing its improved ER performance.

  13. Different methods in TiO2 photodegradation mechanism studies: gaseous and TiO2-adsorbed phases.

    PubMed

    Deveau, Pierre-Alexandre; Arsac, Fabrice; Thivel, Pierre-Xavier; Ferronato, Corinne; Delpech, Françoise; Chovelon, Jean-Marc; Kaluzny, Pascal; Monnet, Christine

    2007-06-18

    The development of photocatalysis processes offers a significant number of perspectives especially in gaseous phase depollution. It is proved that the photo-oxidizing properties of photocatalyst (TiO(2)) activated by UV plays an important role in the degradation of volatile organic compounds (VOC). Heterogeneous photocatalysis is based on the absorption of UV radiations by TiO(2). This phenomenon leads to the degradation and the oxidation of the compounds, according to a mechanism that associates the pollutant's adsorption on the photocatalyst and radical degradation reactions. The main objective of the study is the understanding of the TiO(2)-photocatalysis phenomenon including gaseous and adsorbed phase mechanisms. Results obtained with three different apparatus are compared; gaseous phases are analysed and mechanisms at the gaseous phase/photocatalyst interface are identified. This study leads to improve understanding of various mechanisms during pollutant photodegradation: adsorption of pollutants on TiO(2) first takes place, then desorption and/or photodegradation, and finally, desorption of degradation products on TiO(2). The association of analytical methods and different processes makes the determination of all parameters that affect the photocatalytic process possible. Mastering these parameters is fundamental for the design and construction of industrial size reactors that aim to purify the atmosphere.

  14. A Surface Science Perspective on TiO2 Photocatalysis

    SciTech Connect

    Henderson, Michael A.

    2011-06-15

    The field of surface science provides a unique approach to understanding bulk, surface and interfacial phenomena occurring during TiO2 photochemistry and photocatalysis. This review highlights, from a surface science perspective, recent literature providing molecular-level insights into phonon-initiated events on TiO2 surfaces obtained in seven key scientific issues: (1) photon absorption, (2) charge transport and trapping, (3) electron transfer dynamics, (4) the adsorbed state, (5) mechanisms, (6) poisons and promoters, and (7) phase and form.

  15. The role of surface modification for TiO2 nanoparticles in cancer cells.

    PubMed

    Xie, Jin; Pan, Xiaobo; Wang, Mengyan; Ma, Jiong; Fei, Yiyan; Wang, Pei-Nan; Mi, Lan

    2016-07-01

    Titanium dioxide nanoparticles (TiO2 NPs) have a potential in the field of biological application. However, its poor dispersibility in water hampered its applications. In this study, 3-phosphonopropionic acid and 3-aminopropyl-triethoxysilane were respectively used for surface modification on TiO2 NPs with negative and positive surface charges (denoted as TiO2-COOH and TiO2-NH2). Zeta potentials of the prepared samples with high absolute value demonstrate the great improvement in their dispersibility. In terms of viability experiment, both TiO2-COOH and TiO2-NH2 showed low cytotoxicity. The cellular uptake efficiency and the uptake pathways of TiO2-COOH and TiO2-NH2 for cancer cells were studied. The exocytosis of TiO2-NH2 was also observed in the experiment. PMID:27003465

  16. Photocatalytic Degradation of Methylene Blue under UV Light Irradiation on Prepared Carbonaceous TiO2

    PubMed Central

    Che Ramli, Zatil Amali; Asim, Nilofar; Isahak, Wan N. R. W.; Emdadi, Zeynab; Ahmad-Ludin, Norasikin; Yarmo, M. Ambar; Sopian, K.

    2014-01-01

    This study involves the investigation of altering the photocatalytic activity of TiO2 using composite materials. Three different forms of modified TiO2, namely, TiO2/activated carbon (AC), TiO2/carbon (C), and TiO2/PANi, were compared. The TiO2/carbon composite was obtained by pyrolysis of TiO2/PANi prepared by in situ polymerization method, while the TiO2/activated carbon (TiO2/AC) was obtained after treating TiO2/carbon with 1.0 M KOH solution, followed by calcination at a temperature of 450°C. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TG-DTA), Brunauer-Emmet-Teller (BET), and UV-Vis spectroscopy were used to characterize and evaluate the prepared samples. The specific surface area was determined to be in the following order: TiO2/AC > TiO2/C > TiO2/PANi > TiO2 (179 > 134 > 54 > 9 m2 g−1). The evaluation of photocatalytic performance for the degradation of methylene blue under UV light irradiation was also of the same order, with 98 > 84.7 > 69% conversion rate, which is likely to be attributed to the porosity and synergistic effect in the prepared samples. PMID:25013855

  17. Electrochemical characterization of TiO2/WOx nanotubes for photocatalytic application

    PubMed Central

    2014-01-01

    TiO2/WOx nanotubes have unique photo-energy retention properties that have gathered scientific interest. Herein, we report the synthesis, morphological characterization, and the electrochemical characterization of TiO2/WOx nanotubes compared with pure TiO2 nanotubes, prepared by anodization technique. Significant structural differences were not observed in TiO2/WOx nanotubes as observed by using scanning electron microscopy and transmission electron microscopy. The charge transfer resistance of TiO2/WOx before and after photo irradiation determined by using electrochemical impedance spectroscopy proves the inherent energy retention property which was not observed in pure TiO2 nanotubes. PMID:25346647

  18. Nano TiO2 Composite PVDF Polymer Electrolyte

    NASA Astrophysics Data System (ADS)

    Chiang, Chin-Yeh; Chu, Peter P.

    2002-12-01

    Physical and transport properties of lithium ion conducting polymer electrolyte formed by dispersing nanoscale particles and tubes of TiO2 into poly (vinyl dine fluoride) (PVDF) - lithium salt complexes are discussed. The composite in polymer is enhancing the interfacial interaction, ionic conductivity and mechanical strength due to the high surface area of the particle and the tube. DSC studies elucidate that both the crystallinity and melting temperatures of PVDF are decreased with increasing salt content. Blending with TiO2 particles also decreases melting temperature and crystallinity of PVDF, however nano-tube TiO2 shows even more dramatic effects compared to the particles in reducing PVDF crystallinity and the melting temperature. Even with the improved miscibility and higher salt dissociation, the ionic conductivities is reduced for the TiO2 nano particle composite, but increased about 20 fold in the nano-tube composite. The discrepancies are related to the difference of morphology as evidence from SEM micrograph.

  19. Doping of TiO2 for sensitized solar cells.

    PubMed

    Roose, Bart; Pathak, Sandeep; Steiner, Ullrich

    2015-11-21

    This review gives a detailed summary and evaluation of the use of TiO2 doping to improve the performance of dye sensitized solar cells. Doping has a major effect on the band structure and trap states of TiO2, which in turn affect important properties such as the conduction band energy, charge transport, recombination and collection. The defect states of TiO2 are highly dependent on the synthesis method and thus the effect of doping may vary for different synthesis techniques, making it difficult to compare the suitability of different dopants. High-throughput methods may be employed to achieve a rough prediction on the suitability of dopants for a specific synthesis method. It was however found that nearly every employed dopant can be used to increase device performance, indicating that the improvement is not so much caused by the dopant itself, as by the defects it eliminates from TiO2. Furthermore, with the field shifting from dye sensitized solar cells to perovskite solar cells, the role doping can play to further advance this emerging field is also discussed.

  20. ALMA observations of TiO2 around VY CMa

    NASA Astrophysics Data System (ADS)

    De Beck, Elvire; Vlemmings, Wouter; Muller, Sébastien; Black, John H.; O'Gorman, Eamon; Richards, Anita M. S.; Baudry, Alain; Maercker, Matthias; Decin, Leen; Humphreys, Elizabeth M.

    2016-07-01

    Titanium dioxide, TiO2, is a refractory species that could play a crucial role in the dust-condensation sequence around oxygen-rich evolved stars. We present and discuss the detections of 15 emission lines of TiO2 with ALMA in the complex environment of the red supergiant VY CMa. The observations reveal a highly clumpy, anisotropic outflow in which the TiO2 emission likely traces gas exposed to the stellar radiation field. We find evidence for a roughly east-west oriented, accelerating bipolar-like structure, of which the blue component runs into and breaks up around a solid continuum component. We see a distinct tail to the south-west for some transitions, consistent with features seen in the optical and near-infrared. We find that a significant fraction of TiO2 remains in the gas phase outside the dust-formation zone and suggest that this species might play only a minor role in the dust-condensation process around extreme oxygen-rich evolved stars like VY CMa.

  1. Protein Corona Prevents TiO2 Phototoxicity

    PubMed Central

    Garvas, Maja; Testen, Anze; Umek, Polona; Gloter, Alexandre; Koklic, Tilen; Strancar, Janez

    2015-01-01

    Background & Aim TiO2 nanoparticles have generally low toxicity in the in vitro systems although some toxicity is expected to originate in the TiO2-associated photo-generated radical production, which can however be modulated by the radical trapping ability of the serum proteins. To explore the role of serum proteins in the phototoxicity of the TiO2 nanoparticles we measure viability of the exposed cells depending on the nanoparticle and serum protein concentrations. Methods & Results Fluorescence and spin trapping EPR spectroscopy reveal that the ratio between the nanoparticle and protein concentrations determines the amount of the nanoparticles’ surface which is not covered by the serum proteins and is proportional to the amount of photo-induced radicals. Phototoxicity thus becomes substantial only at the protein concentration being too low to completely coat the nanotubes’ surface. Conclusion These results imply that TiO2 nanoparticles should be applied with ligands such as proteins when phototoxic effects are not desired - for example in cosmetics industry. On the other hand, the nanoparticles should be used in serum free medium or any other ligand free medium, when phototoxic effects are desired – as for efficient photodynamic cancer therapy. PMID:26083725

  2. Photocatalytic bacterial inactivation by TiO2-coated surfaces.

    PubMed

    Bonetta, Silvia; Bonetta, Sara; Motta, Francesca; Strini, Alberto; Carraro, Elisabetta

    2013-01-01

    The aim of this study was the evaluation of the photoactivated antibacterial activity of titanium dioxide (TiO2)-coated surfaces. Bacterial inactivation was evaluated using TiO2-coated Petri dishes. The experimental conditions optimized with Petri dishes were used to test the antibacterial effect of TiO2-coated ceramic tiles. The best antibacterial effect with Petri dishes was observed at 180, 60, 30 and 20 min of exposure for Escherichia coli, Staphylococcus aureus, Pseudomonas putida and Listeria innocua, respectively. The ceramic tiles demonstrated a photoactivated bactericidal effect at the same exposure time. In general, no differences were observed between the antibacterial effect obtained with Petri dishes and tiles. However, the photochemical activity of Petri dishes was greater than the activity of the tiles.Results obtained indicates that the TiO2-coated surfaces showed a photoactivated bactericidal effect with all bacteria tested highlighting that the titania could be used in the ceramic and building industry for the production of coated surfaces to be placed in microbiologically sensitive environments, such as the hospital and food industry.

  3. Effect of metal-ion doping on the characteristics and photocatalytic activity of TiO2 nanotubes for the removal of toluene from water.

    PubMed

    Yuan, Rongfang; Zhou, Beihai; Hua, Duo; Shi, Chunhong; Ma, Li

    2014-01-01

    Toluene is an extensively used reagent that could cause water pollution and endanger human health. In this work, an O3/UV/ion-doped TiO2 nanotubes process was investigated to obtain the optimum TiO2 nanotubes for effective toluene decomposition. Photocatalytic activity is found to be influenced by the doped-ion type by affecting the ionic radius, valence state, and configuration of the dopant. The calcination temperature and doping concentration, which change the weight fractions of the anatase phase (fA), the Brunauer-Emmett-Teller surface area (SBET), and the energy band gap (Eg) of the catalyst, also affect the photocatalytic activity. When TiO2 is doped with ions, SBET decreases and Eg becomes narrower. The photocatalytic activities of TiO2 for toluene removal increase after doping with Ag(+), Al(3+), Cu(2+), Fe(3+), Mn(2+), Ni(2+), V(5+), and Zn(2+). Moreover, the 1.0% Fe(3+)-doped TiO2 nanotubes calcined at 550 °C have the highest catalytic activity, with a toluene removal efficiency of 70.7%.

  4. Fate of pristine TiO2 nanoparticles and aged paint-containing TiO2 nanoparticles in lettuce crop after foliar exposure.

    PubMed

    Larue, Camille; Castillo-Michel, Hiram; Sobanska, Sophie; Trcera, Nicolas; Sorieul, Stéphanie; Cécillon, Lauric; Ouerdane, Laurent; Legros, Samuel; Sarret, Géraldine

    2014-05-30

    Engineered TiO2 nanoparticles (TiO2-NPs) are present in a large variety of consumer products, and are produced in largest amount. The building industry is a major sector using TiO2-NPs, especially in paints. The fate of NPs after their release in the environment is still largely unknown, and their possible transfer in plants and subsequent impacts have not been studied in detail. The foliar transfer pathway is even less understood than the root pathway. In this study, lettuces were exposed to pristine TiO2-NPs and aged paint leachate containing TiO2-NPs and microparticles (TiO2-MPs). Internalization and in situ speciation of Ti were investigated by a combination of microscopic and spectroscopic techniques. Not only TiO2-NPs pristine and from aged paints, but also TiO2-MPs were internalized in lettuce leaves, and observed in all types of tissues. No change in speciation was noticed, but an organic coating of TiO2-NPs is likely. Phytotoxicity markers were tested for plants exposed to pristine TiO2-NPs. No acute phytotoxicity was observed; variations were only observed in glutathione and phytochelatin levels but remained low as compared to typical values. These results obtained on the foliar uptake mechanisms of nano- and microparticles are important in the perspective of risk assessment of atmospheric contaminations. PMID:24709478

  5. Fate of pristine TiO2 nanoparticles and aged paint-containing TiO2 nanoparticles in lettuce crop after foliar exposure.

    PubMed

    Larue, Camille; Castillo-Michel, Hiram; Sobanska, Sophie; Trcera, Nicolas; Sorieul, Stéphanie; Cécillon, Lauric; Ouerdane, Laurent; Legros, Samuel; Sarret, Géraldine

    2014-05-30

    Engineered TiO2 nanoparticles (TiO2-NPs) are present in a large variety of consumer products, and are produced in largest amount. The building industry is a major sector using TiO2-NPs, especially in paints. The fate of NPs after their release in the environment is still largely unknown, and their possible transfer in plants and subsequent impacts have not been studied in detail. The foliar transfer pathway is even less understood than the root pathway. In this study, lettuces were exposed to pristine TiO2-NPs and aged paint leachate containing TiO2-NPs and microparticles (TiO2-MPs). Internalization and in situ speciation of Ti were investigated by a combination of microscopic and spectroscopic techniques. Not only TiO2-NPs pristine and from aged paints, but also TiO2-MPs were internalized in lettuce leaves, and observed in all types of tissues. No change in speciation was noticed, but an organic coating of TiO2-NPs is likely. Phytotoxicity markers were tested for plants exposed to pristine TiO2-NPs. No acute phytotoxicity was observed; variations were only observed in glutathione and phytochelatin levels but remained low as compared to typical values. These results obtained on the foliar uptake mechanisms of nano- and microparticles are important in the perspective of risk assessment of atmospheric contaminations.

  6. Optimization for visible light photocatalytic water splitting: gold-coated and surface-textured TiO2 inverse opal nano-networks.

    PubMed

    Kim, Kwanghyun; Thiyagarajan, Pradheep; Ahn, Hyo-Jin; Kim, Sun-I; Jang, Ji-Hyun

    2013-07-21

    A gold nanoparticle-coated and surface-textured TiO2 inverse opal (Au/st-TIO) structure that provides a dramatic improvement of photoelectrochemical hydrogen generation has been fabricated by nano-patterning of TiO2 precursors on TiO2 inverse opal (TIO) and subsequent deposition of gold NPs. The surface-textured TiO2 inverse opal (st-TIO) maximizes the photon trapping effects triggered by the large dimensions of the structure while maintaining the adequate surface area achieved by the small dimensions of the structure. Au NPs are incorporated to further improve photoconversion efficiency in the visible region via surface plasmon resonance. st-TIO and Au/st-TIO exhibit a maximum photocurrent density of ∼0.58 mA cm(-2) and ∼0.8 mA cm(-2), which is 2.07 and 2.86 times higher than that of bare TIO, respectively, at an applied bias of +0.5 V versus an Ag/AgCl electrode under AM 1.5 G simulated sunlight illumination via a photocatalytic hydrogen generation reaction. The excellent performance of the surface plasmon-enhanced mesoporous st-TIO structure suggests that tailoring the nanostructure to proper dimensions, and thereby obtaining excellent light absorption, can maximize the efficiency of a variety of photoconversion devices. PMID:23733045

  7. Optimization for visible light photocatalytic water splitting: gold-coated and surface-textured TiO2 inverse opal nano-networks.

    PubMed

    Kim, Kwanghyun; Thiyagarajan, Pradheep; Ahn, Hyo-Jin; Kim, Sun-I; Jang, Ji-Hyun

    2013-07-21

    A gold nanoparticle-coated and surface-textured TiO2 inverse opal (Au/st-TIO) structure that provides a dramatic improvement of photoelectrochemical hydrogen generation has been fabricated by nano-patterning of TiO2 precursors on TiO2 inverse opal (TIO) and subsequent deposition of gold NPs. The surface-textured TiO2 inverse opal (st-TIO) maximizes the photon trapping effects triggered by the large dimensions of the structure while maintaining the adequate surface area achieved by the small dimensions of the structure. Au NPs are incorporated to further improve photoconversion efficiency in the visible region via surface plasmon resonance. st-TIO and Au/st-TIO exhibit a maximum photocurrent density of ∼0.58 mA cm(-2) and ∼0.8 mA cm(-2), which is 2.07 and 2.86 times higher than that of bare TIO, respectively, at an applied bias of +0.5 V versus an Ag/AgCl electrode under AM 1.5 G simulated sunlight illumination via a photocatalytic hydrogen generation reaction. The excellent performance of the surface plasmon-enhanced mesoporous st-TIO structure suggests that tailoring the nanostructure to proper dimensions, and thereby obtaining excellent light absorption, can maximize the efficiency of a variety of photoconversion devices.

  8. The Spectrophotometric Features of Lunar Mare Regions with Higher Content of TIO2

    NASA Astrophysics Data System (ADS)

    Busarev, V. V.

    1988-03-01

    The author investigates spectrophotometrically 8 lunar mare regions with higher content of TiO2. The spectral features attributed to TiO2 and ilmenite in the reflectance spectra of these regions are described.

  9. TiO2 anode materials for lithium-ion batteries with different morphology and additives

    NASA Astrophysics Data System (ADS)

    Liu, Xiang; Ng, Yip Hang; Leung, Yu Hang; Liu, Fangzhou; Djurišic, Aleksandra B.; Xie, Mao Hai; Chan, Wai Kin

    2014-03-01

    Electrochemical performances of different TiO2 nanostructures, TiO2/CNT composite and TiO2 with titanium isopropoxide (TTIP) treatment anode were investigated. For different TiO2 nanostructures, we investigated vertically aligned TiO2 nanotubes on Ti foil and TiO2 nanotube-powders fabricated by rapid breakdown anodization technique. The morphology of the prepared samples was characterized by scanning probe microscopy (SEM). The electrochemical lithium storage abilities were studied by galvanostatic method. In addition, carbon nanotubes (CNT) additives and solution treatment process of TiO2 anode were investigated, and the results show that the additives and treatment could enhance the cycling performance of the TiO2 anode on lithium ion batteries.

  10. Enhancement of visible-light photocatalytic activity of silver and mesoporous carbon co-modified Bi2WO6

    NASA Astrophysics Data System (ADS)

    Zhao, Qian; Gong, Ming; Liu, Wangping; Mao, Yulin; Le, Shukun; Ju, Shang; Long, Fei; Liu, Xiufang; Liu, Kai; Jiang, Tingshun

    2015-03-01

    Ordered mesoporous carbon CMK-3 was prepared by hard template method using SBA-15 as template, sucrose as carbon source. Flower/sphere-like Bi2WO6 and CMK-3/Bi2WO6 photocatalysts were synthesized by hydrothermal method, and then Ag/Bi2WO6 and Ag/Bi2WO6/CMK-3 composite photocatalysts were prepared via a photoreduction process. The samples were characterized by XRD, UV-vis, TEM (HR-TEM), SEM, N2 physical adsorption and PL and their photocatalytic activities were evaluated by the photocatalytic degradation of methylene blue (MB) under visible light irradiation. The results show that both incorporating of CMK-3 and Ag loading greatly improved the photocatalytic activity of Bi2WO6, and the content of CMK-3 and silver have an impact on the photocatalytic activity of Bi2WO6. The photocatalytic activity of Ag/Bi2WO6/CMK-3 photocatalyst is superior to the activities of CMK-3/Bi2WO6 and Ag/Bi2WO6 under comparable conditions, and Ag/Bi2WO6/CMK-3 photocatalyst has high stability and is easy to be recycled. Also, the mechanism for the enhancement of the photocatalytic activity of CMK-3 and Ag co-modified Bi2WO6 was also investigated.

  11. Scanning tunneling microscopy studies of metal clusters supported on TiO 2 (110): Morphology and electronic structure

    NASA Astrophysics Data System (ADS)

    Lai, X.; Clair, T. P. St.; Valden, M.; Goodman, D. W.

    1998-12-01

    A brief review of our laboratory's recent scanning tunneling microscopy (STM) studies on nanoclusters supported on TiO 2(110) is presented. Particular emphasis is placed on the system {Au}/{TiO2(110) }. The nucleation and growth of the clusters, which were vapor-deposited on TiO 2(110) under ultra high vacuum (UHV) conditions, were investigated using STM. It was found that Au, Pd, and Ag clusters all grow in a three-dimensional (3D) (Volmer-Weber) fashion on TiO 2(110), but that at low coverages, quasi-two dimensional (quasi-2D) Au and Pd clusters were observed. These quasi-2D clusters are characterized by heights of 1-2 atomic layers. Annealing studies show that Au and Pd clusters form large microcrystals with well-defined hexagonal shapes. Al clusters, which have a strong interaction with the substrate, are oxidized upon deposition, “wetting” the surface and forming small clusters. In addition to the topographic studies, the local electronic properties of these clusters have been studied using scanning tunneling spectroscopy (STS) to measure the cluster band gaps. The electronic structure was found to be cluster size-dependent, as seen by the appearance of a band gap as the cluster size decreased. More specifically, the onset of cluster metallic properties correlates with the transition from quasi-2D to 3D cluster growth.

  12. Robust superamphiphobic film from electrospun TiO2 nanostructures.

    PubMed

    Ganesh, V Anand; Dinachali, Saman Safari; Nair, A Sreekumaran; Ramakrishna, Seeram

    2013-03-13

    Rice-shaped TiO2 nanostructures are fabricated by electrospinning for creating a robust superamphiphobic coating on glass substrates. The as-fabricated TiO2 nanostructures (sintered at 500 °C) are superhydrophilic in nature which upon silanization turn into superamphiphobic surface with surface contact angle (SCA) values achieved using water (surface tension, γ = 72.1 mN/m) and hexadecane (surface tension, γ = 27.5 mN/m) being 166° and 138.5°, respectively. The contact angle hysteresis for the droplet of water and hexadecane are measured to be 2 and 12°, respectively. Thus, we have successfully fabricated superior self-cleaning coatings that possess exceptional superamphiphobic property by employing a simple, cost-effective, and scalable technique called electrospinning. Furthermore, the coating showed good mechanical and thermal stability with strong adherence to glass surface, thus revealing the potential for real applications.

  13. Electrokinetic behaviour of porous TiO2-coated implants.

    PubMed

    Lorenzetti, Martina; Luxbacher, Thomas; Kobe, Spomenka; Novak, Saša

    2015-06-01

    It is known that the "race for the surface" determining the in vivo response is strictly connected to the physico-chemical properties of the material, especially at its surface. Accordingly, the study of surface roughness, charge and wettability is fundamental to predict the bio-response to the implant. In this work, streaming potential was chosen as a reliable method to quantify the solid surface charge of hydrothermally treated (HT) TiO2-anatase nano-crystalline coatings, grown on titanium substrates. The influence of metal and ionic conductance on the zeta potential values was taken into account, allowing for the correlation of the surface charge with the coating porosity, the semiconductor character of the TiO2 nano-crystals and the metallic nature of the bulk titanium.

  14. Spectroscopic investigation of PVA-TIO2 membranes gamma irradiated

    NASA Astrophysics Data System (ADS)

    Todica, Mihai; Udrescu, Luciana; Damian, Grigore; Astilean, Simion

    2013-07-01

    The modifications of the PVA-TiO2 membranes exposed to gamma radiations were investigated by ESR and XRD methods. The ESR spectra show the appearance of a strong signal associated with the breaking of the polymeric chain and the appearance of the unpaired electrons. The mechanism is influenced by the concentration of TiO2. The modification of local order of the polymeric chains after irradiation is confirmed by XRD method.

  15. Tunable polaronic conduction in anatase TiO2.

    PubMed

    Moser, S; Moreschini, L; Jaćimović, J; Barišić, O S; Berger, H; Magrez, A; Chang, Y J; Kim, K S; Bostwick, A; Rotenberg, E; Forró, L; Grioni, M

    2013-05-10

    Oxygen vacancies created in anatase TiO(2) by UV photons (80-130 eV) provide an effective electron-doping mechanism and induce a hitherto unobserved dispersive metallic state. Angle resolved photoemission reveals that the quasiparticles are large polarons. These results indicate that anatase can be tuned from an insulator to a polaron gas to a weakly correlated metal as a function of doping and clarify the nature of conductivity in this material. PMID:23705725

  16. Tunable Polaronic Conduction in Anatase TiO2

    NASA Astrophysics Data System (ADS)

    Moser, S.; Moreschini, L.; Jaćimović, J.; Barišić, O. S.; Berger, H.; Magrez, A.; Chang, Y. J.; Kim, K. S.; Bostwick, A.; Rotenberg, E.; Forró, L.; Grioni, M.

    2013-05-01

    Oxygen vacancies created in anatase TiO2 by UV photons (80-130 eV) provide an effective electron-doping mechanism and induce a hitherto unobserved dispersive metallic state. Angle resolved photoemission reveals that the quasiparticles are large polarons. These results indicate that anatase can be tuned from an insulator to a polaron gas to a weakly correlated metal as a function of doping and clarify the nature of conductivity in this material.

  17. Synthesis of TiO2 and TiO2-Pt and their application in photocatalytic degradation of humic acid.

    PubMed

    Chen, Wenzhao; Ran, Xianqiang; Jiang, Xu; Min, Hongyang; Li, Dandan; Zou, Liyin; Fan, Jianwei; Li, Guangming

    2014-01-01

    The deposit of noble metal on titanium dioxide (TiO2) has been considered as an effective strategy to improve the activity of TiO2. In this study, TiO2 nanoparticles were prepared using a sol-gel route followed by heat treatment at elevated temperatures (573 K, 773 K, and 973 K). TiO2-Pt catalyst (1 wt%) was prepared by depositing Pt on the surface of the prepared TiO2 nanoparticles. TiO2 and TiO2-Pt were used as heterogeneous catalysts to remove humic acid with UV-light (120 W) illumination. TiO2 prepared at low temperature with smaller particle size and larger specific surface area had stronger activity on humic acid degradation. Deposit of Pt would favor separation of photogenerated charges and enhance the photocatalyst activity, but its coating of the active site also inhibited degradation of humic acid. The addition of H202 enhanced degradation of humic acid for more active oxygen produced. Low pH (pH = 4) was helpful to adsorb humic acid on the surface of TiO2 and, correspondingly, enhance degradation of humic acid (44.4%).

  18. TiO2-polymer composites for biomedical applications.

    PubMed

    Peña, J; Vallet-Regí, M; San Román, J

    1997-04-01

    Composite hydrogels of poly(acrylic acid) (PAA) and poly-(methyl metacrylate) (PMMA) reinforced with a bioceramic, TiO2, have been prepared by reactive moulding from a mixture of the bioceramic with PMMA beads and acrylic acid. Cylindrical specimens with various TiO2-polymer compositions, but a constant 3:1 PAA/PMMA ratio were obtained, and their corresponding swelling behavior was followed at pH = 7.0 and pH = 8.0 in buffered solution at 37 degrees C. The composition and structure of the composites prepared was studied by thermogravimetry, 1H-NMR spectroscopy and scanning electron microscopy. The composites prepared present a considerable consistency, even in hydrated media, since their swelling behavior is rather sensitive to the pH of the media. Specific polar interactions of the carboxylic groups of the hydrophilic polymer component PAA with the surface of TiO2 particles, modulate the behavior of the composites against the hydration processes at different pH.

  19. Photocatalytic cleavage of single TiO2/DNA nanoconjugates.

    PubMed

    Tachikawa, Takashi; Asanoi, Yoshiaki; Kawai, Kiyohiko; Tojo, Sachiko; Sugimoto, Akira; Fujitsuka, Mamoru; Majima, Tetsuro

    2008-01-01

    TiO(2)/DNA nanoconjugates were successfully fabricated by using the catechol moiety as a binding functional group, which was confirmed by steady-state absorption and fluorescence spectroscopies. Upon UV irradiation, the photocatalytic cleavage of the TiO(2)/DNA nanoconjugates was observed at the single-molecule level by using wide-field fluorescence microscopy. The decrease in the number of conjugates, which was estimated from the luminescent spots due to semiconductor quantum dots modified at the DNA strand, was significantly inhibited by a single A/C mismatch in the DNA sequences. This result strongly suggests that the migration of holes, which are injected from the photoexcited TiO(2) into the DNA, through the DNA bases plays an important role in the photocatalytic cleavage of the conjugates. The influences of the photogenerated reactive oxygen species (ROS) on the cleavage efficiency were also examined. According to the experimental results, it was concluded that oxidation of the catechol moiety and/or the DNA damage are key reactions in this process.

  20. Raman spectroscopy of ball-milled TiO 2

    NASA Astrophysics Data System (ADS)

    Gajović, A.; Stubičar, M.; Ivanda, M.; Furić, K.

    2001-05-01

    Raman spectroscopy was applied to study structural and dimensional changes during high-energy ball milling of TiO 2 anatase. Milling was performed for up to 10 h using two different sets of grinding tools (wolfram carbide (WC) and agate). The diminution of the TiO 2 particle to nanometric size was monitoring by low-frequency Raman spectroscopy. The nanometric sizes were confirmed by transmission electron microscopy (TEM). After short milling time by WC the bands of high-pressure TiO 2 II phase (α-PbO 2 structure) were detected in Raman spectrum. Prolonged milling time was needed for transformation to rutil. When milling was performed by agate, the time necessary for both phase transitions was longer, presumably because of lower ball-to-powder weight ratio. The low-frequency Raman band of the prolonged milled samples was broad, which suggests the wide dispersion in nano-particle dimensions. The position of the low-frequency band in longer-milled samples indicated dimensions smaller than 20 nm, since the diameter of the particle is inversely proportional to the low-frequency mode of the spherical particles. These results were in agreement with the TEM results.

  1. 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.

  2. Optofluidic microreactors with TiO2-coated fiberglass.

    PubMed

    Li, Lin; Chen, Rong; Zhu, Xun; Wang, Hong; Wang, Yongzhong; Liao, Qiang; Wang, Dongye

    2013-12-11

    Optofluidic microreactors are promising prospects for photocatalytic reactions. However, because the flow type in conventional designs is typically laminar, the mass transport mainly relies on diffusion, and thus the rate of mass transport is limited. Accordingly, poor mass transport reduces the photocatalytic reaction rate. To alleviate the limitation of mass transport, in this work, we proposed a novel optofluidic microreactor with TiO2-coated fiberglasses immersed in the microreaction chamber. Such a design enables enhanced mass transport by shortening the transport length and inducing the perturbation to liquid flow so as to improve the performance. We demonstrated the feasibility of the optofluidic microreactor with the TiO2-coated fiberglass by the photocatalytic water treatment of methylene blue under UV irradiation. Results showed that the proposed optofluidic microreactor yielded much higher degradation efficiency than did the conventional optofluidic microreactor as a result of enhanced mass transport. The microreactor with the TiO2-coated fiberglass showed a 2-3-fold improvement in the reaction rate constant as opposed to conventional ones. The maximal increment of the degradation efficiency can reach more than 40%. PMID:24262010

  3. BIOLOGICAL RESPONSE TO NANO-SCALE TIO2: ROLE OF PARTICLE DOSE, SHAPE AND RETENTION

    PubMed Central

    Silva, Rona M.; TeeSy, Christel; Franzi, Lisa; Weir, Alex; Westerhoff, Paul; Evans, James E.; Pinkerton, Kent E.

    2015-01-01

    TiO2 is one of the most widely used nanomaterials, valued for its highly refractive, photocatalytic and pigmenting properties. TiO2 is also classified by the International Agency for Research on Cancer (IARC) as a possible human carcinogen. The objectives of this study were to establish a lowest observed effect level (LOEL) for nano-scale TiO2, determine TiO2 uptake in the lungs, and estimate toxicity based on physico-chemical properties and retention in the lungs. In vivo lung toxicity of nano-scale TiO2 using varying forms of well-characterized, highly-dispersed TiO2 was assessed. Anatase/rutile P25 spheres (TiO2-P25), pure anatase spheres (TiO2-A), and anatase nanobelts (TiO2-NB) were tested. To determine the effects of dose and particle characteristics, male Sprague-Dawley rats were given TiO2 (0, 20, 70, or 200 µg) via intratracheal instillation. Broncho-alveolar lavage fluid (BALF) and lung tissue were obtained for analysis 1 and 7 days post exposure. Despite abundant TiO2 inclusions in all exposed animals, only TiO2-NB elicited any significant degree of inflammation seen in BALF at the 1-day time-point. This inflammation resolved by 7 days; although, TiO2 particles had not cleared from alveolar macrophages recovered from the lung. Histological examination showed TiO2-NB caused cellular changes at day 1 which were still evident at day 7. We conclude TiO2-NB is the most inflammatory with a lowest observable effect level of 200 µg at 1 day post instillation. PMID:24156719

  4. Zirconium and silver co-doped TiO2 nanoparticles as visible light catalyst for reduction of 4-nitrophenol, degradation of methyl orange and methylene blue

    NASA Astrophysics Data System (ADS)

    Naraginti, Saraschandra; Stephen, Finian Bernard; Radhakrishnan, Adhithya; Sivakumar, A.

    2015-01-01

    Catalytic activity of Zr and Ag co-doped TiO2 nanoparticles on the reduction of 4-nitrophenol, degradation of methylene blue and methyl orange was studied using sodium borohydride as reducing agent. The nanoparticles were characterized using X-ray diffraction, energy dispersive X-ray, high resolution transmission electron microscopy, selected area electron diffraction and UV-Vis spectroscopy. The rate of the reduction/degradation was found to increase with increasing amount of the photocatalyst which could be attributed to higher dispersity and small size of the nanoparticles. The catalytic activity of Zr and Ag co-doped TiO2 nanoparticles showed no significant difference even after recycling the catalyst four times indicating a promising potential for industrial application of the prepared photocatalyst.

  5. Photocatalytic degradation of rhodamine B by anchored TiO2 nanowires.

    PubMed

    Wang, Chih-Chieh; Yu, Chung-Yi; Kei, Chi-Chung; Perng, Tsong-Pyng

    2011-01-01

    Rutile TiO2 nanowires anchored on silica were fabricated by annealing TiO2 nanoparticles dispersed on silicon or quartz substrate by means of a polystyrene nanosphere monolayer template at 1000 degrees C for 1 h without any catalyst. The diameter and length of the nanowires were 30-80 nm and 1-3 microm, respectively. The growth direction of the nanowires is [112]. The photocatalytic activities of TiO2 nanoparticles and anchored nanowires were evaluated. TiO2 nanowires had higher photocatalytic activity for rhodamine B than TiO2 nanoparticles.

  6. Silver-loaded nitrogen-doped yolk-shell mesoporous TiO2 hollow microspheres with enhanced visible light photocatalytic activity.

    PubMed

    Jiang, Zhifeng; Wei, Wei; Mao, Danjun; Chen, Cheng; Shi, Yunfei; Lv, Xiaomeng; Xie, Jimin

    2015-01-14

    Silver-loaded nitrogen-doped yolk-shell mesoporous TiO2 hollow microspheres (Ag-N-TiO2-YSM) were prepared by employing acetic acid as the hollowing controller and triethanolamine as the N source for the first time. Ag nanoparticles (NPs) were uniformly deposited by a simple in situ photo-reduction method, which can prevent the aggregation of Ag NPs. The efficiency of the as-prepared samples was investigated by monitoring the degradation of rhodamine B and ciprofloxacin under visible light irradiation. The experimental results indicate that N-doped yolk-shell mesoporous TiO2 hollow microspheres show higher photocatalytic activity than P25 TiO2 under visible light irradiation because of N doping and the unique yolk-shell structure. In addition, Ag-N-TiO2-YSM shows enhanced activity compared with N-TiO2-YSM due to the SPR absorption of silver NPs and the fast generation, separation and transportation of the photogenerated carriers. Moreover, the Ag contents can affect the photocatalytic activity of the Ag-N-TiO2-YSM composite. A suitable amount of Ag deposition gives the highest photocatalytic activity. A higher loading does not improve the photocatalytic activity of N-TiO2-YSM further. The active species generated in the photocatalytic system were also investigated. Based on our experimental results, a possible photocatalytic mechanism was proposed. The strategy presented here gives a promising route towards the development of delicate metal@hollow semiconductor composites for many applications in photocatalysis.

  7. Photocatalytic Water-Splitting Characteristic of Electric Reduced Black TiO2 Nanorods

    NASA Astrophysics Data System (ADS)

    Yun, Jong-Won; Ryu, Ki Yeon; Kim, Sunho; Jang, Se-Jung; Kim, Yong Soo

    In various reduction methods of TiO2, the electric reduction could apply to anodized TiO2 nanotube. However, it is not suitable to reduce TiO2 nanorods(NRs) grown on fluorine doped tin oxide (FTO) substrate using hydrothermal method, because those are easily peeled off due to lattice mismatching between FTO and TiO2 NRs. In this talk, we will demonstrate electric reduced-black TiO2 NRs with strong adhesion on FTO substrate for an effective visible photocatalyst. To fabricate the reduced-black TiO2 NRs, we firstly deposited TiO2 seed layer on FTO glass using RF-sputtering for mitigating the exfoliation, then grow TiO2 NRs with hydrothermal method. Finally, TiO2 NRs were reduced with electric bias. The final reduced-black TiO2 NRs exhibit a higher photocurrent density, 0.9 mA/cm2 in comparison with pure-TiO2 NRs. This result indicates that our reduced-black TiO2 NRs has lower bandgap with modified valance band position and enhance the surface reactivity with oxygen defect generation. This research was supported by Priority Research Centers Program (2009-0093818), the Basic Science Research Program (2015-019609) and Basic Research Lab Program (2014-071686) through National Research Foundation of Korea (NRF) funded by the Korean government.

  8. Reaction pathways of dimethyl phthalate degradation in TiO2-UV-O2 and TiO2-UV-Fe(VI) systems.

    PubMed

    Yuan, Bao-ling; Li, Xiang-zhong; Graham, Nigel

    2008-05-01

    The photocatalytic degradation of dimethyl phthalate (DMP) in aqueous TiO2 suspension under UV illumination has been investigated using oxygen (O2) and ferrate (Fe(VI)) as electron acceptors. The experiments demonstrated that Fe(VI) was a more effective electron acceptor than O2 for scavenging the conduction band electrons from the surface of the catalyst. Some major intermediate products from DMP degradation were identified by HPLC and GC/MS analyses. The analytical results identified dimethyl 3-hydroxyphthalate and dimethyl 2-hydroxyphthalate as the two main intermediate products from the DMP degradation in the TiO2-UV-O2 system, while in contrast phthalic acid was found to be the main intermediate product in the TiO2-UV-Fe(VI) system. These findings indicate that DMP degradation in the TiO2-UV-O2 and TiO2-UV-Fe(VI) systems followed different reaction pathways. An electron spin resonance analysis confirmed that hydroxyl radicals existed in the TiO2-UV-O2 reaction system and an unknown radical species (most likely an iron-oxo species) is suspected to exist in the TiO2-UV-Fe(VI) reaction system. Two pathway schemes of DMP degradation in the TiO2-UV-O2 and TiO2-UV-Fe(VI) reaction systems are proposed. It is believed that the radicals formed in the TiO2-UV-O2 reaction system preferably attack the aromatic ring of the DMP, while in contrast the radicals formed in the TiO2-UV-Fe(VI) reaction systems attack the alkyl chain of DMP.

  9. Enhanced photoelectrochemical and photocatalytic activity of WO3-surface modified TiO2 thin film.

    PubMed

    Qamar, Mohammad; Drmosh, Qasem; Ahmed, Muhammad I; Qamaruddin, Muhammad; Yamani, Zain H

    2015-01-01

    Development of nanostructured photocatalysts for harnessing solar energy in energy-efficient and environmentally benign way remains an important area of research. Pure and WO3-surface modified thin films of TiO2 were prepared by magnetron sputtering on indium tin oxide glass, and photoelectrochemical and photocatalytic activities of these films were studied. TiO2 particles were <50 nm, while deposited WO3 particles were <20 nm in size. An enhancement in the photocurrent was observed when the TiO2 surface was modified WO3 nanoparticles. Effect of potential, WO3 amount, and radiations of different wavelengths on the photoelectrochemical activity of TiO2 electrodes was investigated. Photocatalytic activity of TiO2 and WO3-modified TiO2 for the decolorization of methyl orange was tested. Graphical abstractWO3-surface modified TiO2 film showing better photocatalytic and photoelectrocatalytic activity. PMID:25852351

  10. Study of TiO2 nanotubes as an implant application

    NASA Astrophysics Data System (ADS)

    Hazan, Roshasnorlyza; Sreekantan, Srimala; Mydin, Rabiatul Basria S. M. N.; Abdullah, Yusof; Mat, Ishak

    2016-01-01

    Vertically aligned TiO2 nanotubes have become the primary candidates for implant materials that can provide direct control of cell behaviors. In this work, 65 nm inner diameters of TiO2 nanotubes were successfully prepared by anodization method. The interaction of bone marrow stromal cells (BMSC) in term of cell adhesion and cell morphology on bare titanium and TiO2 nanotubes is reported. Field emission scanning electron microscopy (FESEM) analysis proved interaction of BMSC on TiO2 nanotubes structure was better than flat titanium (Ti) surface. Also, significant cell adhesion on TiO2 nanotubes surface during in vitro study revealed that BMSC prone to attach on TiO2 nanotubes. From the result, it can be conclude that TiO2 nanotubes are biocompatible to biological environment and become a new generation for advanced implant materials.

  11. Biodistribution and Clearance of TiO2 Nanoparticles in Rats after Intravenous Injection

    PubMed Central

    Elgrabli, Dan; Beaudouin, Remy; Jbilou, Nawel; Floriani, Magali; Pery, Alexandre; Rogerieux, Françoise; Lacroix, Ghislaine

    2015-01-01

    Titanium dioxide (TiO2) nanoparticles are used in many applications. Due to their small size, easy body penetration and toxicological adverse effects have been suspected. Numerous studies have tried to characterize TiO2 translocation after oral, dermal or respiratory exposure. In this study, we focused on TiO2 nanoparticle biodistribution, clearance and toxicological effects after intravenous injection, considering TiO2 translocation in the blood occurs. Using ICP-OES, transmission electron microscopy, and histological methods, we found TiO2 accumulation in liver, lungs and spleen. We estimated TiO2 nanoparticles’ half life in the body to about 10 days. Clinical biomarkers were also quantified for 56 days to identify potential toxicological impact on lungs, blood, liver, spleen and kidneys. Results showed absence of toxicological effects after TiO2 intravenous injection at concentrations of 7.7 to 9.4 mg/kg. PMID:25909957

  12. Plasmonic silver quantum dots coupled with hierarchical TiO2 nanotube arrays photoelectrodes for efficient visible-light photoelectrocatalytic hydrogen evolution

    PubMed Central

    Lian, Zichao; Wang, Wenchao; Xiao, Shuning; Li, Xin; Cui, Yingying; Zhang, Dieqing; Li, Guisheng; Li, Hexing

    2015-01-01

    A plasmonic Ag/TiO2 photocatalytic composite was designed by selecting Ag quantum dots (Ag QDs) to act as a surface plasmon resonance (SPR) photosensitizer for driving the visible-light driven photoelectrocatalytic hydrogen evolution. Vertically oriented hierarchical TiO2 nanotube arrays (H-TiO2-NTAs) with macroporous structure were prepared through a two-step method based on electrochemical anodization. Subsequently, Ag QDs, with tunable size (1.3-21.0 nm), could be uniformly deposited on the H-TiO2 NTAs by current pulsing approach. The unique structure of the as-obtained photoelectrodes greatly improved the photoelectric conversion efficiency. The as-obtained Ag/H-TiO2-NTAs exhibited strong visible-light absorption capability, high photocurrent density, and enhanced photoelectrocatalytic (PEC) activity toward photoelectrocatalytic hydrogen evolution under visible-light irradiation (λ > 420 nm). The enhancement in the photoelectric conversion efficiency and activity was ascribed to the synergistic effects of silver and the unique hierarchical structures of TiO2 nanotube arrays, strong SPR effect, and anti-shielding effect of ultrafine Ag QDs. PMID:26067850

  13. Plasmonic silver quantum dots coupled with hierarchical TiO2 nanotube arrays photoelectrodes for efficient visible-light photoelectrocatalytic hydrogen evolution.

    PubMed

    Lian, Zichao; Wang, Wenchao; Xiao, Shuning; Li, Xin; Cui, Yingying; Zhang, Dieqing; Li, Guisheng; Li, Hexing

    2015-01-01

    A plasmonic Ag/TiO2 photocatalytic composite was designed by selecting Ag quantum dots (Ag QDs) to act as a surface plasmon resonance (SPR) photosensitizer for driving the visible-light driven photoelectrocatalytic hydrogen evolution. Vertically oriented hierarchical TiO2 nanotube arrays (H-TiO2-NTAs) with macroporous structure were prepared through a two-step method based on electrochemical anodization. Subsequently, Ag QDs, with tunable size (1.3-21.0 nm), could be uniformly deposited on the H-TiO2 NTAs by current pulsing approach. The unique structure of the as-obtained photoelectrodes greatly improved the photoelectric conversion efficiency. The as-obtained Ag/H-TiO2-NTAs exhibited strong visible-light absorption capability, high photocurrent density, and enhanced photoelectrocatalytic (PEC) activity toward photoelectrocatalytic hydrogen evolution under visible-light irradiation (λ>420 nm). The enhancement in the photoelectric conversion efficiency and activity was ascribed to the synergistic effects of silver and the unique hierarchical structures of TiO2 nanotube arrays, strong SPR effect, and anti-shielding effect of ultrafine Ag QDs. PMID:26067850

  14. Bimodal TiO2 Contents of Mare Basalts at Apollo and Luna Sites and Implications for TiO2 Derived from Clementine Spectral Reflectance

    NASA Technical Reports Server (NTRS)

    Gillis, J. J.; Jolliff, B. L.

    2001-01-01

    A revised algorithm to estimate Ti contents of mare regions centered on Apollo and Luna sites shows a bimodal distribution, consistent with mare-basalt sample data. A global TiO2 map shows abundant intermediate TiO2 basalts in western Procellarum. Additional information is contained in the original extended abstract.

  15. Facile Scalable Synthesis of TiO2/Carbon Nanohybrids with Ultrasmall TiO2 Nanoparticles Homogeneously Embedded in Carbon Matrix.

    PubMed

    Wang, Xiaoyan; Meng, Jian-Qiang; Wang, Meimei; Xiao, Ying; Liu, Rui; Xia, Yonggao; Yao, Yuan; Metwalli, Ezzeldin; Zhang, Qian; Qiu, Bao; Liu, Zhaoping; Pan, Jing; Sun, Ling-Dong; Yan, Chun-Hua; Müller-Buschbaum, Peter; Cheng, Ya-Jun

    2015-11-01

    A facile scalable synthesis of TiO2/C nanohybrids inspired by polymeric dental restorative materials has been developed, which creates ultrasmall TiO2 nanoparticles homogeneously embedded in the carbon matrix. The average size of the nanoparticles is tuned between about 1 and 5 nm with the carbon content systematically increased from 0% to 65%. Imaging analysis and a scattering technique have been applied to investigate the morphology of the TiO2 nanoparticles. The composition, nature of carbon matrix, crystallinity, and tap density of the TiO2/C nanohybrids have been studied. The application of the TiO2/C nanohybrids as lithium-ion battery anode is demonstrated. Unusual discharge/charge profiles have been exhibited, where characteristic discharge/charge plateaus of crystalline TiO2 are significantly diminished. The tap density, cyclic capacities, and rate performance at high current densities (10 C, 20 C) of the TiO2/C nanohybrid anodes have been effectively improved compared to the bare carbon anode and the TiO2/C nanohybrids with larger particle size. PMID:26465800

  16. Visible light catalysis of rhodamine B using nanostructured Fe(2)O(3), TiO(2) and TiO(2)/Fe(2)O(3) thin films.

    PubMed

    Mahadik, M A; Shinde, S S; Mohite, V S; Kumbhar, S S; Moholkar, A V; Rajpure, K Y; Ganesan, V; Nayak, J; Barman, S R; Bhosale, C H

    2014-04-01

    The Fe(2)O(3), TiO(2) and TiO(2)/Fe(2)O(3) composite films are deposited using spray pyrolysis method onto glass and FTO coated substrates. The structural, morphological, optical and photocatalytic properties of Fe(2)O(3), TiO(2) and TiO(2)/Fe(2)O(3) thin films are studied. XRD analysis confirms that films are polycrystalline with rhombohedral and tetragonal crystal structures for Fe2O3 and TiO(2) respectively. The photocatalytic activity was tested for the degradation of Rhrodamine B (Rh B) in aqueous medium. The rate constant (-k) was evaluated as a function of the initial concentration of species. Substantial reduction in concentrations of organic species was observed from COD and TOC analysis. Photocatalytic degradation effect is relatively higher in case of the TiO(2)/Fe(2)O(3) than TiO(2) and Fe(2)O(3) thin film photoelectrodes in the degradation of Rh B and 98% removal efficiency of Rh B is obtained after 20min. The photocatalytic experimental results indicate that TiO(2)/α-Fe(2)O(3) photoelectrode is promising material for removing of water pollutants.

  17. Positive role of incorporating P-25 TiO2 to mesoporous-assembled TiO2 thin films for improving photocatalytic dye degradation efficiency.

    PubMed

    Sreethawong, Thammanoon; Ngamsinlapasathian, Supachai; Yoshikawa, Susumu

    2014-09-15

    In this work, a simple and effective strategy to improve the photocatalytic dye degradation efficiency of the mesoporous-assembled TiO2 nanoparticle thin films by incorporating small contents of commercial P-25 TiO2 during the thin film preparation was developed. The mesoporous-assembled TiO2 nanoparticles were synthesized by a sol-gel method with the aid of a mesopore-directing surfactant, followed by homogeneously mixing with P-25 TiO2 prior to the thin film coating on glass substrate. The mesoporous-assembled TiO2 film with 5 wt.% P-25 TiO2 incorporation and calcined at 400°C provided an improved photocatalytic Acid Black (AB) dye degradation efficiency. The increase in number of coated layers to the optimum four layers of the aforementioned film was found to further improve the degradation efficiency. The recyclability test of this 5 wt.% P-25 TiO2-incorporated mesoporous-assembled TiO2 film with four coated layers revealed that it can be reused for multiple cycles without a requirement of post-treatment while the degradation efficiency was retained.

  18. Enhanced Dispersion of TiO2 Nanoparticles in a TiO2/PEDOT:PSS Hybrid Nanocomposite via Plasma-Liquid Interactions

    PubMed Central

    Liu, Yazi; Sun, Dan; Askari, Sadegh; Patel, Jenish; Macias-Montero, Manuel; Mitra, Somak; Zhang, Richao; Lin, Wen-Feng; Mariotti, Davide; Maguire, Paul

    2015-01-01

    A facile method to synthesize a TiO2/PEDOT:PSS hybrid nanocomposite material in aqueous solution through direct current (DC) plasma processing at atmospheric pressure and room temperature has been demonstrated. The dispersion of the TiO2 nanoparticles is enhanced and TiO2/polymer hybrid nanoparticles with a distinct core shell structure have been obtained. Increased electrical conductivity was observed for the plasma treated TiO2/PEDOT:PSS nanocomposite. The improvement in nanocomposite properties is due to the enhanced dispersion and stability in liquid polymer of microplasma treated TiO2 nanoparticles. Both plasma induced surface charge and nanoparticle surface termination with specific plasma chemical species are proposed to provide an enhanced barrier to nanoparticle agglomeration and promote nanoparticle-polymer binding. PMID:26497265

  19. Enhanced Dispersion of TiO2 Nanoparticles in a TiO2/PEDOT:PSS Hybrid Nanocomposite via Plasma-Liquid Interactions

    NASA Astrophysics Data System (ADS)

    Liu, Yazi; Sun, Dan; Askari, Sadegh; Patel, Jenish; Macias-Montero, Manuel; Mitra, Somak; Zhang, Richao; Lin, Wen-Feng; Mariotti, Davide; Maguire, Paul

    2015-10-01

    A facile method to synthesize a TiO2/PEDOT:PSS hybrid nanocomposite material in aqueous solution through direct current (DC) plasma processing at atmospheric pressure and room temperature has been demonstrated. The dispersion of the TiO2 nanoparticles is enhanced and TiO2/polymer hybrid nanoparticles with a distinct core shell structure have been obtained. Increased electrical conductivity was observed for the plasma treated TiO2/PEDOT:PSS nanocomposite. The improvement in nanocomposite properties is due to the enhanced dispersion and stability in liquid polymer of microplasma treated TiO2 nanoparticles. Both plasma induced surface charge and nanoparticle surface termination with specific plasma chemical species are proposed to provide an enhanced barrier to nanoparticle agglomeration and promote nanoparticle-polymer binding.

  20. A computational study of the TiO2 molecule

    NASA Technical Reports Server (NTRS)

    Ramana, M. V.; Phillips, D. H.

    1988-01-01

    A computational investigation of the ground 1A1 and lowest energy B2 states of the titanium dioxide molecule has been carried out. The treatment utilized SCF calculations in an extended basis followed by a CI treatment for each geometry. The ground state geometry agrees well with experiment, while the agreement between the computed vibrational frequency nu1 and the experimental value for a matrix isolated TiO2 is less satisfactory. Population analysis for the ground state indicates less than one excess electron on each oxygen atom. The first excited state has a linear geometry and the singlet and triplet are essentially degenerate.

  1. TIO2 Based Electrorheological Fluid with High Yield Stress

    NASA Astrophysics Data System (ADS)

    Shen, Rong; Wang, Xuezhao; Wen, Weijia; Lu, Kunquan

    We have fabricated several TiO2 based ER fluids with doping and without designed doping, which exhibit the high yield stress up to more than 100kPa. The titanium oxide nanoparticles were synthesized by using wet chemical method. The ER effect of those materials is dominated by the special additives, such as amide or its ramification, as well as the remained molecules or ions in the sample preparation. It is found that the yield stress is also strongly dependent on the viscosity of the oil. The prepared ER fluids possess other attractive characters, for instance the current density is low and against sedimentation.

  2. Origin of unexpected magnetism in Cu-doped TIO2

    NASA Astrophysics Data System (ADS)

    Li, Q. K.; Wang, B.; Woo, C. H.; Wang, H.; Zhu, Z. Y.; Wang, R.

    2008-01-01

    Cu-doped TiO2 has recently been found to exhibit unexpected room temperature ferromagnetism. In the present work, possible defect structures and the associated magnetism are calculated within the generalized gradient approximation using the projector augmented wave method (PAW). In particular, structures of the vacancy-Cu impurity complex are studied. Our results show that the magnetism is caused by: 1) the hybridization of p-d orbitals between the Cu and O ions, and 2) the spin polarization of the 3d orbital of Cu and of the 2p orbital of O ions.

  3. Improved photoelectrical performance of graphene supported highly crystallized anatase TiO2

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Sun, Qiong; Zhao, Mei; Li, Yang; Liu, Qiuhong; Dong, Lifeng

    2015-08-01

    In this study, titanium oxysulfate (TiOSO4) and graphene were used as titanium source and supporter, respectively, to synthesize anatase TiO2-graphene (TiO2-G) composite. Crystal structure, morphology, and composition of TiO2-G were investigated by X-ray diffraction, scanning electron microscope, transmission electron microscope, and thermogravimetric analysis. Both TiO2-G and blank TiO2 powders exhibit spindle-shaped structure with the long axis along [001]. Compared to unsupported TiO2, TiO2 nanoparticles uniformly formed on graphene surface. When fabricated into dye-sensitized solar cells, photoelectrical conversion efficiency of TiO2-G (2.3 %) was much higher than that of blank TiO2 (0.89 %) prepared at the same conditions. Moreover, high sintering temperature enhanced photoelectrical performance of the composite. When the temperature was increased from 450 to 600 °C, the efficiency was improved from 1.5 to 2.6 %. The findings above demonstrate that TiO2-G has great potential for applications in dye-sensitized solar cells.

  4. Physiological effect of anatase TiO2 nanoparticles on Lemna minor.

    PubMed

    Song, Guanling; Gao, Yuan; Wu, Hao; Hou, Wenhua; Zhang, Chunyang; Ma, Huiquan

    2012-09-01

    Manufactured metal oxide nanoparticles (NPs) are being used on a large scale, and these particles will inevitably reach a body of water through wastewater and urban runoff. The ecotoxicological study of these NPs on hydrophyte is limited at present. Lemna minor was exposed to media with different concentrations of titanium dioxide (TiO(2)) NPs or bulk TiO(2) for 7 d. The changes in plant growth, chlorophyll, antioxidant defense enzymes (peroxidase [POD], catalase [CAT], and superoxide dismutase [SOD] activities), and malondialdehyde (MDA) content were measured in the present study. The particle size of TiO(2) NPs and the zeta potential of TiO(2) NPs and of bulk TiO(2) in the culture media were also analyzed to complementally study the toxicity of these materials on duckweed. The results showed that the effect of TiO(2) NPs on plant growth was more obvious than bulk TiO(2.) Titanium dioxide NPs stimulated plant growth in low concentrations, but inhibited plant growth at high concentrations. The POD, SOD, and CAT activity of Lemna minor increased when TiO(2) NP concentration was lower than 200 mg/L to eliminate accumulated reactive oxygen species in plant cells. The SOD activity decreased when the TiO(2) NP concentration was higher than 200 mg/L, and the plant cell membrane encountered serious damage from 500 mg/L TiO(2) NP concentration in the culture media.

  5. TiO2 coated microfluidic devices for recoverable hydrophilic and hydrophobic patterns

    NASA Astrophysics Data System (ADS)

    Lee, Jin-Hyung; Kim, Sang Kyung; Park, Hyung-Ho; Kim, Tae Song

    2015-03-01

    We report a simple method for modifying the surfaces of plastic microfluidic devices through dynamic coating process with a nano-colloidal TiO2 sol. The surface of the thermoplastic, cyclic olefin copolymer (COC) was coated with the TiO2 film, that displayed an effective photocatalytic property. The hydrophilic surface is obtained in the TiO2-coated zone of a microfluidic channel, and TiO2 coated surface degradation can be reversed easily by UV irradiation. The present work shows a photocatalytic activity concerning the effect of TiO2 coating density, which is controlled by the number of coating cycles. The hydrophilized surface was characterized by the contact angle of water and the TiO2 coated COC surface reduced the water contact angle from 85° to less than 10° upon UV irradiation. The photocatalytic effect of the layer that was coated five times with TiO2 was excellent, and the super-hydrophilicity of the TiO2 surface could be promptly recovered after 10 months of storage at atmospheric conditions. The COC microfluidic devices, in which TiO2 has been freshly deposited and aged for 10 months, were capable of generating water-in oil-in water (W/O/W) double emulsions easily and uniformly by simple control of the flow rates for demonstration of excellent hydrophilic patterning and recovery of the TiO2 coated in the microchannels.

  6. The interplay of peptide sequence and local structure in TiO2 biomineralization.

    PubMed

    Choi, Noori; Tan, Lihan; Jang, Ji-ryang; Um, Yu Mi; Yoo, Pil J; Choe, Woo-Seok

    2012-10-01

    Using cyclic constrained TiO(2) binding peptides STB1 (CHKKPSKSC), RSTB1 (CHRRPSRSC) and linear peptide LSTB1 (AHKKPSKSA), it was shown that while affinity of the peptide to TiO(2) is essential to enable TiO(2) biomineralization, other factors such as biomineralization kinetics and peptide local structure need to be considered to predict biomineralization efficacy. Cyclic and linear TiO(2) binding peptides show significantly different biomineralization activities. Cyclic STB1 and RSTB1 could induce TiO(2) precipitation in the presence of titanium(IV)-bis-ammonium-lactato-dihydroxide (TiBALDH) precursor in water or tris buffer at pH 8. In contrast, linear LSTB1 was unable to mineralize TiO(2) under the same experimental conditions despite its high affinity to TiO(2) comparable with STB1 and/or RSTB1. LSTB1 being a flexible molecule could not render the stable condensation of TiBALDH precursor to form TiO(2) particles. However, in the presence of phosphate buffer ions, the structure of LSTB1 is stabilized, leading to efficient condensation of TiBALDH and TiO(2) particle formation. This study demonstrates that peptide-mediated TiO(2) mineralization is governed by a complicated interplay of peptide sequence, local structure, kinetics and the presence of mineralizing aider such as phosphate ions.

  7. Activity of Laccase Immobilized on TiO2-Montmorillonite Complexes

    PubMed Central

    Wang, Qingqing; Peng, Lin; Li, Guohui; Zhang, Ping; Li, Dawei; Huang, Fenglin; Wei, Qufu

    2013-01-01

    The TiO2-montmorillonite (TiO2-MMT) complex was prepared by blending TiO2 sol and MMT with certain ratio, and its properties as an enzyme immobilization support were investigated. The pristine MMT and TiO2-MMT calcined at 800 °C (TiO2-MMT800) were used for comparison to better understand the immobilization mechanism. The structures of the pristine MMT, TiO2-MMT, and TiO2-MMT800 were examined by HR-TEM, XRD and BET. SEM was employed to study different morphologies before and after laccase immobilization. Activity and kinetic parameters of the immobilized laccase were also determined. It was found that the TiO2 nanoparticles were successfully introduced into the MMT layer structure, and this intercalation enlarged the “d value” of two adjacent MMT layers and increased the surface area, while the calcination process led to a complete collapse of the MMT layers. SEM results showed that the clays were well coated with adsorbed enzymes. The study of laccase activity revealed that the optimum pH and temperature were pH = 3 and 60 °C, respectively. In addition, the storage stability for the immobilized laccase was satisfactory. The kinetic properties indicated that laccase immobilized on TiO2-MMT complexes had a good affinity to the substrate. It has been proved that TiO2-MMT complex is a good candidate for enzyme immobilization. PMID:23771020

  8. A facile method for the structure control of TiO2 particles at low temperature

    NASA Astrophysics Data System (ADS)

    Li, Zhaoqing; Zhu, Yun; Wang, Lianwen; Wang, Jiatai; Guo, Qian; Li, Jiangong

    2015-11-01

    Crystalline and amorphous TiO2 particles have important potential applications in photocatalysis, structural ceramics, solar batteries and nanoglasses. Hence controlling the structure of TiO2 particles is of practical importance. Crystalline TiO2 particles are usually prepared by calcination of their amorphous precursor. Here a facile method was developed to control the structure of TiO2 particles at a low temperature. TiO2 particles were prepared by sol-gel method; and it was found that during the washing process, the TiO2 particles washed with water are crystalline whereas the TiO2 particles washed with ethanol are amorphous. Further analyses indicate that ethanol washing may introduce an organic cover layer on the TiO2 particles which hinders the crystallization of amorphous TiO2 particles. Therefore, the structure of TiO2 particles, amorphous or crystalline (anatase), can be controlled just by changing the washing medium, water or ethanol. This method seems a common method for controlling the (amorphous or crystalline) structure of metal oxides and hydroxides and was verified in the preparation of ZrO2, FeO(OH), and Al(OH)3 particles.

  9. Immobilization of TiO2 nanofibers on reduced graphene sheets: Novel strategy in electrospinning.

    PubMed

    Pant, Hem Raj; Adhikari, Surya Prasad; Pant, Bishweshwar; Joshi, Mahesh K; Kim, Han Joo; Park, Chan Hee; Kim, Cheol Sang

    2015-11-01

    A simple and efficient approach is developed to immobilize TiO2 nanofibers onto reduced graphene oxide (RGO) sheets. Here, TiO2 nanofiber-intercalated RGO sheets are readily produced by two-step procedure involving the use of electrospinning process to fabricate TiO2 precursor containing polymeric fibers on the surface of GO sheets, followed by simultaneous TiO2 nanofibers formation and GO reduction by calcinations. GO sheets deposited on the collector during electrospinning/electrospray can act as substrate on to which TiO2 precursor containing polymer nanofibers can be deposited which give TiO2 NFs doped RGO sheets on calcinations. Formation of corrugated structure cavities of graphene sheets decorated with TiO2 nanofibers on their surface demonstrates that our method constitutes an alternative top-down strategy toward fabricating verities of nanofiber-decorated graphene sheets. It was found that the synthesized TiO2/RGO composite revealed a remarkable increased in photocatalytic activity compared to pristine TiO2 nanofibers. Therefore, engineering of TiO2 nanofiber-intercalated RGO sheets using proposed facile technique can be considered a promising method for catalytic and other applications.

  10. Freeze-dried PVP-Ag+ precursors to novel AgBr/AgCl-Ag hybrid nanocrystals for visible-light-driven photodegradation of organic pollutants

    NASA Astrophysics Data System (ADS)

    Chen, Deliang; Chen, Qianqian; Zhang, Wenjie; Ge, Lianfang; Shao, Gang; Fan, Bingbing; Lu, Hongxia; Zhang, Rui; Yang, Daoyuan; Shao, Guosheng

    2015-04-01

    AgBr/AgCl-Ag nanocrystals with various molar Br-to-Ag ratios (RBr/Ag = 0, 1/3, 1/2, 2/3, 1) and different photoreduction times (0-20 min) were synthesized via stepwise liquid-solid reactions using the freeze-dried PVP-Ag+ hybrid as the Ag source, followed by a photoreduction reaction. The AgBr/AgCl-Ag7.5(1:2) nanocrystals obtained take on a spherical morphology with a particle-size range of 58 ± 15 nm. The photocatalytic performance of AgBr/AgCl-Ag nanocrystals was evaluated by photodegrading organic dyes, 4-chlorophenol and isopropanol under artificial visible light (λ ⩾ 420 nm, 100 mW cm-2). For the decomposition of rhodamine B, the AgBr/AgCl-Ag7.5(1:2) nanocrystals has a photodegradation rate of ∼0.87 min-1, ∼159 times higher than that (∼0.0054 min-1) of TiO2 (P25), whereas the AgCl-Ag and AgBr-Ag nanocrystals have photodegradation rates of 0.35 min-1 and 0.45 min-1, respectively. The efficient separation of photogenerated electron-hole pairs in the ternary system consisting of AgBr, AgCl and Ag species plays a key role in the enhancement of photocatalytic performance.

  11. Coating stainless steel plates with Ag/TiO2 for chlorpyrifos decontamination

    NASA Astrophysics Data System (ADS)

    Abdel Fattah, Wafa I.; Gobara, Mohammed M.; El-Hotaby, Walid; Mostafa, Sherif F. M.; Ali, Ghareib W.

    2016-05-01

    Spray coatings of either nanosilver (Ag), titanium (TiO2) or nanosilver titanium (Ag/TiO2) on stainless steel substrates prepared by sol-gel process were successfully achieved. The efficiency of the Ag/TiO2 coat onto 316 stainless steel surface towards cloropyrifos degradation as a chemical warfare agent (CWA) was proved. The crystalline structure and morphological characterization, as well as surface roughness measurements, were assessed. X-ray diffraction results proved the crystalline TiO2 anatase phase. The uniform distribution of Ag along with TiO2 nanoparticles was evidenced through transmission electron microscopy and scanning electron microscopy mapping. The hydrophilic nature of individual Ag, TiO2 and Ag/TiO2 coats was proved by contact angle measurements. The loading of Ag nanoparticles influenced positively the Ag/TiO2 coats surface roughness. The photocatalytic cloropyrifos degradation achieved about 50% within one-hour post UV treatment proving, therefore, the promising Ag/TiO2 continued decontamination efficiency. In conclusion, tuning the physical and morphological properties of TiO2 coated on stainless steel surface could be significantly enhanced by Ag nanoparticles incorporation. The developed Ag/TiO2 coat could be conveniently applied as CWA decontaminant.

  12. Coating stainless steel plates with Ag/TiO2 for chlorpyrifos decontamination

    NASA Astrophysics Data System (ADS)

    Abdel Fattah, Wafa I.; Gobara, Mohammed M.; El-Hotaby, Walid; Mostafa, Sherif F. M.; Ali, Ghareib W.

    2016-05-01

    Spray coatings of either nanosilver (Ag), titanium (TiO2) or nanosilver titanium (Ag/TiO2) on stainless steel substrates prepared by sol–gel process were successfully achieved. The efficiency of the Ag/TiO2 coat onto 316 stainless steel surface towards cloropyrifos degradation as a chemical warfare agent (CWA) was proved. The crystalline structure and morphological characterization, as well as surface roughness measurements, were assessed. X-ray diffraction results proved the crystalline TiO2 anatase phase. The uniform distribution of Ag along with TiO2 nanoparticles was evidenced through transmission electron microscopy and scanning electron microscopy mapping. The hydrophilic nature of individual Ag, TiO2 and Ag/TiO2 coats was proved by contact angle measurements. The loading of Ag nanoparticles influenced positively the Ag/TiO2 coats surface roughness. The photocatalytic cloropyrifos degradation achieved about 50% within one-hour post UV treatment proving, therefore, the promising Ag/TiO2 continued decontamination efficiency. In conclusion, tuning the physical and morphological properties of TiO2 coated on stainless steel surface could be significantly enhanced by Ag nanoparticles incorporation. The developed Ag/TiO2 coat could be conveniently applied as CWA decontaminant.

  13. TXM-NEXAFS of TiO2-Based Nanostructures

    NASA Astrophysics Data System (ADS)

    Guttmann, P.; Bittencourt, C.; Ke, X.; Van Tendeloo, G.; Umek, P.; Arcon, D.; Ewels, C. P.; Rehbein, S.; Heim, S.; Schneider, G.

    2011-09-01

    In this work, electronic properties of individual TiOx-pristine nanoribbons (NR) prepared by hydrothermal treatment of anatase TiO2 micro-particles were studied using the HZB transmission x-ray microscope (TXM) at the BESSY II undulator beamline U41-FSGM. NEXAFS is ideally suited to study TiO2-based materials because both the O K-edge and Ti L-edge features are very sensitive to the local bonding environment, providing diagnostic information about the crystal structures and oxidation states of various forms of titanium oxides and sub-oxides. TXM-NEXAFS combines full-field x-ray microscopy with spectroscopy, allowing the study of the electronic structure of individual nanostructures with spatial resolution better than 25 nm and a spectral resolution of up to E/ΔE = 10000. The typical image field in TXM-NEXAFS measurements is about 10 μm×10 μm, which is large compared to the individual nanoparticle. Therefore, one image stack already contains statistically significant data. In addition, the directional electric field vector (Ē) of the x-rays can be used as a "search tool" for the direction of chemical bonds of the atom selected by its absorption edge.

  14. Ultrasensitive photoelectrochemical immunoassay for CA19-9 detection based on CdSe@ZnS quantum dots sensitized TiO2NWs/Au hybrid structure amplified by quenching effect of Ab2@V(2+) conjugates.

    PubMed

    Zhu, Hua; Fan, Gao-Chao; Abdel-Halim, E S; Zhang, Jian-Rong; Zhu, Jun-Jie

    2016-03-15

    A novel, enhanced photoelectrochemical immunoassay was established for sensitive and specific detection of carbohydrate antigen 19-9 (CA19-9, Ag). In this protocol, TiO2 nanowires (TiO2NWs) were first decorated with Au nanoparticles to form TiO2NWs/Au hybrid structure, and then coated with CdSe@ZnS quantum dots (QDs) via the layer-by-layer method, producing TiO2NWs/Au/CdSe@ZnS sensitized structure, which was employed as the photoelectrochemical matrix to immobilize capture CA19-9 antibodies (Ab1); whereas, bipyridinium (V(2+)) molecules were labeled on signal CA19-9 antibodies (Ab2) to form Ab2@V(2+) conjugates, which were used as signal amplification elements. The TiO2NWs/Au/CdSe@ZnS sensitized structure could adequately absorb light energy and dramatically depress electron-hole recombination, resulting in evidently enhanced photocurrent intensity of the immunosensing electrode. While target Ag were detected, the Ab2@V(2+) conjugates could significantly decrease the photocurrent detection signal because of strong electron-withdrawing property of V(2+) coupled with evident steric hindrance of Ab2. Thanks to synergy effect of TiO2NWs/Au/CdSe@ZnS sensitized structure and quenching effect of Ab2@V(2+) conjugates, the well-established photoelectrochemical immunoassay exhibited a low detection limit of 0.0039 U/mL with a wide linear range from 0.01 U/mL to 200 U/mL for target Ag detection. This proposed photoelectrochemical protocol also showed good reproducibility, specificity and stability, and might be applied to detect other important biomarkers. PMID:26433066

  15. Ultrasensitive photoelectrochemical immunoassay for CA19-9 detection based on CdSe@ZnS quantum dots sensitized TiO2NWs/Au hybrid structure amplified by quenching effect of Ab2@V(2+) conjugates.

    PubMed

    Zhu, Hua; Fan, Gao-Chao; Abdel-Halim, E S; Zhang, Jian-Rong; Zhu, Jun-Jie

    2016-03-15

    A novel, enhanced photoelectrochemical immunoassay was established for sensitive and specific detection of carbohydrate antigen 19-9 (CA19-9, Ag). In this protocol, TiO2 nanowires (TiO2NWs) were first decorated with Au nanoparticles to form TiO2NWs/Au hybrid structure, and then coated with CdSe@ZnS quantum dots (QDs) via the layer-by-layer method, producing TiO2NWs/Au/CdSe@ZnS sensitized structure, which was employed as the photoelectrochemical matrix to immobilize capture CA19-9 antibodies (Ab1); whereas, bipyridinium (V(2+)) molecules were labeled on signal CA19-9 antibodies (Ab2) to form Ab2@V(2+) conjugates, which were used as signal amplification elements. The TiO2NWs/Au/CdSe@ZnS sensitized structure could adequately absorb light energy and dramatically depress electron-hole recombination, resulting in evidently enhanced photocurrent intensity of the immunosensing electrode. While target Ag were detected, the Ab2@V(2+) conjugates could significantly decrease the photocurrent detection signal because of strong electron-withdrawing property of V(2+) coupled with evident steric hindrance of Ab2. Thanks to synergy effect of TiO2NWs/Au/CdSe@ZnS sensitized structure and quenching effect of Ab2@V(2+) conjugates, the well-established photoelectrochemical immunoassay exhibited a low detection limit of 0.0039 U/mL with a wide linear range from 0.01 U/mL to 200 U/mL for target Ag detection. This proposed photoelectrochemical protocol also showed good reproducibility, specificity and stability, and might be applied to detect other important biomarkers.

  16. Synthesis of visible light-activated TiO 2 photocatalyst via surface organic modification

    NASA Astrophysics Data System (ADS)

    Jiang, Dong; Xu, Yao; Hou, Bo; Wu, Dong; Sun, Yuhan

    2007-05-01

    A visible light-activated TiO 2 photocatalyst was successfully synthesized by the surface organic modification to sol-gel-hydrothermal synthesized TiO 2. The surface hydroxyls of TiO 2 nanoparticles reacted with the active -NCO groups of tolylene diisocyanate (TDI) to form a surface complex that was confirmed by the FT-IR and XPS spectra. Due to the existence of surface complex, the absorption edge of as-prepared TDI-modified TiO 2 nanomaterial extended well into visible region. Compared with unmodified TiO 2 and Degussa P25, the TDI-modified TiO 2 photocatalysts showed higher activity for the photocatalytic degradation of methylene blue under visible light irradiation.

  17. Microwave irradiation induced band gap tuning of MoS2-TiO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Shakya, Jyoti; Mohanty, T.

    2016-05-01

    The MoS2-TiO2 nanocomposites have been synthesized by sol-gel method and characterized by different microscopic and spectroscopic techniques. The crystallinity of these nanocomposites has been confirmed by X-ray diffraction (XRD) analysis. The Raman spectrum of MoS2-TiO2 nanocomposites consists of three distinct peaks (E1 g, E1 2g and A1g) which are associated with TiO2 and MoS2. The morphological study is carried out by scanning electron microscope. The effect of microwave irradiation on the band gap of MoS2-TiO2 nanocomposites has been investigated; it is observed that the microwave irradiation causes decrease in the band gap of MoS2-TiO2 nanocomposites. The microwave treated MoS2-TiO2 thin films offers a novel process route in treating thin films for commercial applications.

  18. The state of nano-sized titanium dioxide (TiO2) may affect sunscreen performance.

    PubMed

    Tyner, K M; Wokovich, A M; Godar, D E; Doub, W H; Sadrieh, N

    2011-06-01

    In the past several years, there has been a trend in the sunscreen/cosmetics industry to replace micron-sized titanium dioxide (TiO(2)) particles with nanoscale materials. The increased use of nanoscale TiO(2) has resulted in questions about these and other nanoproducts. This study examines the effects of using nanoscale TiO(2) on ultraviolet (UV) attenuation in simple to complex sunscreen formulations. UV light attenuation, product stability, and potential damage to the skin barrier were examined with both nanoscale and microscale TiO(2) particles. Results indicate that none of the formulations decreased the barrier function of the skin and the best UV attenuation occurs when the TiO(2) particles are stabilized with a coating and evenly distributed such as with non-agglomerated coated nanoscale materials. This indicates that nanoscale TiO(2) may have better efficacy while lacking toxicity. PMID:21265867

  19. Engineering of highly ordered TiO2 nanopore arrays by anodization

    NASA Astrophysics Data System (ADS)

    Wang, Huijie; Huang, Zhennan; Zhang, Li; Ding, Jie; Ma, Zhaoxia; Liu, Yong; Kou, Shengzhong; Yang, Hangsheng

    2016-07-01

    Finite element analysis was used to simulate the current density distributions in the TiO2 barrier layer formed at the initial stage of Ti anodization. The morphology modification of the barrier layer was found to induce current density distribution change. By starting the anodization with proper TiO2 barrier layer morphology, the current density distribution can be adjusted to favor the formation of either nanotube arrays or nanopore arrays of anodic TiO2. We also found that the addition of sodium acetate into the electrolyte suppressed both the field-assisted chemical dissolution of TiO2 and the TiF62- hydrolysis induced TiO2 deposition during anodization, and thus further favored the nanopore formation. Accordingly, highly ordered anodic TiO2 nanopore arrays, similar to anodic aluminum oxide nanopore arrays, were successfully prepared.

  20. Review of the progress in preparing nano TiO2: an important environmental engineering material.

    PubMed

    Wang, Yan; He, Yiming; Lai, Qinghua; Fan, Maohong

    2014-11-01

    TiO2 nanomaterial is promising with its high potential and outstanding performance in photocatalytic environmental applications, such as CO2 conversion, water treatment, and air quality control. For many of these applications, the particle size, crystal structure and phase, porosity, and surface area influence the activity of TiO2 dramatically. TiO2 nanomaterials with special structures and morphologies, such as nanospheres, nanowires, nanotubes, nanorods, and nanoflowers are thus synthesized due to their desired characteristics. With an emphasis on the different morphologies of TiO2 and the influence factors in the synthesis, this review summarizes fourteen TiO2 preparation methods, such as the sol-gel method, solvothermal method, and reverse micelle method. The TiO2 formation mechanisms, the advantages and disadvantages of the preparation methods, and the photocatalytic environmental application examples are proposed as well. PMID:25458670

  1. Enhanced performance of natural dye sensitised solar cells fabricated using rutile TIO2 nanorods

    NASA Astrophysics Data System (ADS)

    Akila, Y.; Muthukumarasamy, N.; Agilan, S.; Mallick, Tapas K.; Senthilarasu, S.; Velauthapillai, Dhayalan

    2016-08-01

    Due to the lower cost, natural dye molecules are good alternatives for the ruthenium based sensitizers in the dye-sensitized solar cells. In this article, we have reported the natural sensitizer based dye-sensitized solar cells fabricated using TiO2 nanorods. Rutile phase TiO2 nanorods have been synthesized by template free hydrothermal method which results in TiO2 nanorods in the form of acropora corals. These TiO2 nanorods have been sensitized by flowers of Sesbania grandiflora, leaves of Camellia sinensis and roots of Rubia tinctorum. The maximum conversion efficiency of 1.53% has been obtained for TiO2 nanorods based solar cells sensitized with the leaves of Camellia sinensis. The flowers of Sesbania grandiflora and roots of Rubia tinctorum sensitized TiO2 nanorods based solar cells exhibited an efficiency of 0.65% and 1.28% respectively.

  2. Antibacterial effect of silver modified TiO2/PECVD films

    NASA Astrophysics Data System (ADS)

    Hájková, P.; Patenka, P. Å.; Krumeich, J.; Exnar, P.; Kolouch, A.; Matoušek, J.; Kočí, P.

    2009-08-01

    This paper deals with photocatalytic activity of silver treated TiO2 films. The TiO2 films were deposited on glass substrates by plasma enhanced chemical vapor deposition (PECVD) in a vacuum reactor with radio frequency (RF) low temperature plasma discharge in the mixture of oxygen and titanium isopropoxide vapors (TTIP). The depositions were performed under different deposition conditions. Subsequently, the surface of TiO2 films was modified by deposition of silver nanoparticles. Photocatalytic activity of both silver modified and unmodified TiO2 films was determined by decomposition of the model organic matter (acid orange 7). Selected TiO2 samples were used for tests of antibacterial activity. These tests were performed on Gram-negative bacteria Escherichia coli. The results clearly proved that presence of silver clusters resulted in enhancement of the photocatalytic activity, which was up to four times higher than that for pure TiO2 films.

  3. Effect of calcination temperature on the photocatalytic properties of electrospun TiO2 nanofibers.

    PubMed

    Lee, Young-In; Lee, Jong-Sik; Park, Eun-Sil; Jang, Dae-Hwan; Lee, Jae-Eun; Kim, Kahee; Myung, Nosang V; Choa, Yong-Ho

    2014-10-01

    In this study, TiO2 nanofibers with a high aspect ratio and a large specific surface area were synthesized using the electrospinning technique, and the effect of calcination temperature on their crystal structure, diameter, specific surface area and photocatalytic activity was systematically investigated. The electrospun, as-prepared PVP/TTIP nanofibers were several tens of micrometers in length with a diameter of 74 nm. TiO2 nanofibers with an average diameter of 50 nm were prepared after calcination at various temperatures. The calcination temperature significantly influenced the photocatalytic and material properties of TiO2 including grain size and specific surface area. When compared to other nanostructured TiO2 materials, such as commercial TiO2 nanoparticles (P25, Degussa), the TiO2 nanofibers exhibited greater photocatalytic activity for the degradation of acetaldehyde and ammonia. PMID:25942911

  4. Conducting Interface in Oxide Homojunction: Understanding of Superior Properties in Black TiO2.

    PubMed

    Lü, Xujie; Chen, Aiping; Luo, Yongkang; Lu, Ping; Dai, Yaomin; Enriquez, Erik; Dowden, Paul; Xu, Hongwu; Kotula, Paul G; Azad, Abul K; Yarotski, Dmitry A; Prasankumar, Rohit P; Taylor, Antoinette J; Thompson, Joe D; Jia, Quanxi

    2016-09-14

    Black TiO2 nanoparticles with a crystalline core and amorphous-shell structure exhibit superior optoelectronic properties in comparison with pristine TiO2. The fundamental mechanisms underlying these enhancements, however, remain unclear, largely due to the inherent complexities and limitations of powder materials. Here, we fabricate TiO2 homojunction films consisting of an oxygen-deficient amorphous layer on top of a highly crystalline layer, to simulate the structural/functional configuration of black TiO2 nanoparticles. Metallic conduction is achieved at the crystalline-amorphous homointerface via electronic interface reconstruction, which we show to be the main reason for the enhanced electron transport of black TiO2. This work not only achieves an unprecedented understanding of black TiO2 but also provides a new perspective for investigating carrier generation and transport behavior at oxide interfaces, which are of tremendous fundamental and technological interest. PMID:27482629

  5. Structural and Optical Characterization of Synthesized TiO2 Nanopowder Using Sol-Gel Technique

    NASA Astrophysics Data System (ADS)

    Lourduraj, S.; Williams, R. Victor

    2016-02-01

    The nanocrystalline TiO2 powder was synthesized by sol-gel method. The XRD analysis reveals that TiO2 powder was highly crystalline (anatase phase) and nanostructured with tetragonal system. The average crystallite size after calcined at 673K is found to be 7.7nm. The surface morphological studies using scanning electron microscopy (SEM) exhibit that the formation of nanosized TiO2 particles with less densification nature. Atomic force microscopy (AFM) topography exhibits the uniform distribution of spherical-shaped particles. The energy dispersive X-ray spectroscopy (EDX) confirms the presence of Titanium and Oxygen in synthesized TiO2 nanopowder. The value of optical bandgap of TiO2 nanopowder calculated from UV-Visible spectrum is 3.45eV. The presence of TiO2 particles is confirmed from the dominant fourier transform infrared (FTIR) peaks at 621cm-1 and 412cm-1.

  6. Photocatalytic activity of TiO2 nanomaterials for methylene blue dye degradation

    NASA Astrophysics Data System (ADS)

    Lee, Deuk Yong; Son, Siwon; Jeon, Min-Seok; Lee, Myung-Hyun; Kim, Bae-Yeon

    2016-04-01

    TiO2 nanomaterials were prepared by a sol-gel derived electrospinning, calcination from 500°C to 650°C, and subsequent mechanical grinding to investigate the effect of calcination temperature on crystal structure, crystallinity, and photocatalytic activity of methylene blue (MB). XRD results indicated that TiO2 nanorods calcined at 500°C is composed of anatase TiO2 only. However, mixed crystals of anatase and rutile were observed for TiO2 calcined above 550°C. Higher MB degradation was found for the TiO2 nanorods calcined at 550°C probably due to the mixed crystals and larger surface area. However, the improved photocatalytic activity was achieved for TiO2 nanotube due to the synergic combinations of mixed crystals, larger specific surface area, and light trapping effect.

  7. Ammonia sensing behaviors of TiO2-PANI/PA6 composite nanofibers.

    PubMed

    Wang, Qingqing; Dong, Xianjun; Pang, Zengyuan; Du, Yuanzhi; Xia, Xin; Wei, Qufu; Huang, Fenglin

    2012-01-01

    Titanium dioxide-polyaniline/polyamide 6 (TiO(2)-PANI/PA6) composite nanofibers were prepared by in situ polymerization of aniline in the presence of PA6 nanofibers and a sputtering-deposition process with a high purity titanium sputtering target. TiO(2)-PANI/PA6 composite nanofibers and PANI/PA6 composite nanofibers were fabricated for ammonia gas sensing. The ammonia sensing behaviors of the sensors were examined at room temperature. All the results indicated that the ammonia sensing property of TiO(2)-PANI/PA6 composite nanofibers was superior to that of PANI/PA6 composite nanofibers. TiO(2)-PANI/PA6 composite nanofibers had good selectivity to ammonia. It was also found that the content of TiO(2) had a great influence on both the morphology and the sensing property of TiO(2)-PANI/PA6 composite nanofibers. PMID:23235446

  8. Surface Treatment for Effective Dye Adsorption on Nanocrystalline TiO2

    NASA Astrophysics Data System (ADS)

    Yanagida, Masatoshi; Han, Chen; Han, Liyuan

    2012-10-01

    To improve the efficiency of dye-sensitized solar cells (DSCs) by controlling dye adsorption on TiO2 surface, the effect of surface treatments on the properties of [NBu4]2[Ru(Htcterpy)(NCS)3] (black dye; [NBu4]: tetrabutylammonium cation; H3tcterpy: 4,4',4''-tricarboxy-2,2':6',2''-terpyridine) on nanocrystalline TiO2 films was investigated by analysis of the photovoltaic performance and the electron transport properties. Although the surface treatments do not affect on the condition band edge of TiO2, the amount of dye on TiO2 increases. The enhancement of dye adsorption by treatment of TiO2 in HCl solution is more effective than that by dipping the dye solution containing deoxycholic acid (DCA) as additive. But the charge recombination between an electron in TiO2 and I3- in the electrolyte can be reduced by the DCA treatment.

  9. Electrical Conductivity Characteristic of TiO2 Nanowires From Hydrothermal Method

    NASA Astrophysics Data System (ADS)

    Azlishah Othman, Mohd; Faridah Amat, Noor; Hisham Ahmad, Badrul; Rajan, Jose

    2014-04-01

    One dimensional nanostructures of titanium dioxide (TiO2) were synthesized via hydrothermal method by mixing TiO2 as precursor in aqueous solution of NaOH as solvent. Then, heat and washing treatment was applied. Thus obtained wires had diameter ~15nm. TiO2 nanowires will be used as a network in solar cell such dye-sensitized solar cell in order to improve the performance of electron movement in the device. To improve the performance of electron movement, the characteristics of TiO2 nanowires have been analyses using field emission scanning electron microscopy (FESEM) analysis, x-ray diffractometer (XRD) analysis and brunauer emmett teller (BET) analysis. Finally, electrical conductivity of TiO2 nanowires was determined by measuring the resistance of the TiO2 nanowires paste on microscope glass.

  10. In situ growth of TiO2 in interlayers of expanded graphite for the fabrication of TiO2-graphene with enhanced photocatalytic activity.

    PubMed

    Jiang, Baojiang; Tian, Chungui; Zhou, Wei; Wang, Jianqiang; Xie, Ying; Pan, Qingjiang; Ren, Zhiyu; Dong, Youzhen; Fu, Dan; Han, Jiale; Fu, Honggang

    2011-07-18

    We present a facile route for the preparation of TiO(2)-graphene composites by in situ growth of TiO(2) in the interlayer of inexpensive expanded graphite (EG) under solvothermal conditions. A vacuum-assisted technique combined with the use of a surfactant (cetyltrimethylammonium bromide) plays a key role in the fabrication of such composites. Firstly, the vacuum environment promotes full infusion of the initial solution containing Ti(OBu)(4) and the surfactant into the interlayers of EG. Subsequently, numerous TiO(2) nanoparticles uniformly grow in situ in the interlayers with the help of the surfactant, which facilitates the exfoliation of EG under the solvothermal conditions in ethanol, eventually forming TiO(2)-graphene composites. The as-prepared samples have been characterized by Raman and FTIR spectroscopies, SEM, TEM, AFM, and thermogravimetic analysis. It is shown that a large number of TiO(2) nanoparticles homogeneously cover the surface of high-quality graphene sheets. The graphene exhibits a multi-layered structure (5-7 layers). Notably, the TiO(2)-graphene composite (only 30 wt % of which is TiO(2)) synthesized by subsequent thermal treatment at high temperature under nitrogen shows high photocatalytic activity in the degradation of phenol under visible and UV lights in comparison with bare Degussa P25. The enhanced photocatalytic performance is attributed to increased charge separation, improved light absorbance and light absorption width, and high adsorptivity for pollutants.

  11. One-pot synthesis of peacock-shaped TiO2 light scattering layer with TiO2 nanorods film for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Kim, Hyun Sik; Kim, Young-Jea; Lee, Wonjoo; Kang, Soon Hyung

    2013-05-01

    A titanium dioxide (TiO2) film, showing distinctive functions and morphology, was prepared using the hydrothermal method by controlling the ratio of HCl:CH3COOH in acidic medium. A one-dimensional (1-D) TiO2 nanorod (NR) film was synthesized with a length of 2 μm using a 1:2 ratio of HCl:CH3COOH, whereas a 1-D TiO2 NR film with peacock shaped TiO2 nanobundles as a light scattering layer (LSL) was acquired by employing a 2:1 ratio of HCl:CH3COOH. This LSL exhibited remarkable dual functions with respect to high light harvesting, which was attributable to the large surface area of the micrometer-sized TiO2 nanobundles, consisting of small-sized TiO2 NRs of 30-40 nm in diameter and a light scattering effect in the long wavelength region of 550-700 nm. Accordingly, the dual functions of the LSL resulted in a sharp increase in conversion efficiency (3.93%) that was about twice that (1.49%) of TiO2 NR film synthesized using a 1:2 ratio of HCl:CH3COOH. In particular, a considerably enhanced short-circuit photocurrent (Jsc) was mainly responsible for the resulting increase in overall efficiency with a moderate increase in fill factor and slightly reduced open-circuit voltage.

  12. Eco-friendly synthesis of TiO2, Au and Pt doped TiO2 nanoparticles for dye sensitized solar cell applications and evaluation of toxicity

    NASA Astrophysics Data System (ADS)

    Gopinath, K.; Kumaraguru, S.; Bhakyaraj, K.; Thirumal, S.; Arumugam, A.

    2016-04-01

    Driven by the demand of pure TiO2, Au and Pt doped TiO2 NPs were successfully synthesized using Terminalia arjuna bark extract. The eco-friendly synthesized NPs were characterized by UV-Vis-DRS, ATR-FT-IR, PL, XRD, Raman, SEM with EDX and TEM analysis. The synthesized NPs were investigation for dye sensitized solar cell applications. UV-Vis-Diffused Reflectance Spectra clearly showed that the expected TiO2 inter band absorption below 306 nm, incorporation of gold shows surface plasma resonant (SPR) near 555 nm and platinum incorporated TiO2 NPs shows absorbance at 460 nm. The energy conversion efficiency for Au doped TiO2 NPs when compared to pure and Pt doped TiO2 NPs. In addition to that, Au noble metal present TiO2 matrix and an improve open-circuit voltage (Voc) of DSSC. Synthesized NPs was evaluated into antibacterial and antifungal activities by disk diffusion method. It is observed that NPs have not shown any activities in all tested bacterial and fungal strains. In this eco-friendly synthesis method to provide non toxic and environmental friendly nanomaterials can be used for solar energy device application.

  13. Investigation of photocatalytic degradation of phenol by Fe(III)-doped TiO2 and TiO2 nanoparticles

    PubMed Central

    2014-01-01

    In this study Fe (III)-doped TiO2 nanoparticles were synthesized by sol–gel method at two atomic ratio of Fe/Ti, 0.006 and 0.034 percent. Then the photoactivity of them was investigated on degradation of phenol under UV (<380 nm) irradiation and visible light (>380 nm). Results showed that at appropriate atomic ratio of Fe to Ti (% 0.034) photoactivity of Fe(III)–doped TiO2 nanoparticles increased. In addition, the effects of various operational parameters on photocatalytic degradation, such as pH, initial concentration of phenol and amount of photocatalyst were examined and optimized. At all different initial concentration, highest degradation efficiency occurred at pH = 3 and 0.5 g/L Fe(III)–doped TiO2 dosage. With increase in initial concentration of phenol, photocatalytic degradation efficiency decreased. Photoactivity of Fe (III)-doped TiO2 under UV irradiation and visible light at optimal condition (pH = 3 and catalyst dosage = and 0.5 g/L) was compared with P25 TiO2 nanoparticles. Results showed that photoactivity of Fe(III)-doped TiO2 under visible light was more than P25 TiO2 photoactivity, but it was less than P25 TiO2 photoactivity under UV irradiation. Also efficiency of UV irradiation alone and amount of phenol adsorption on Fe(III)-doped TiO2 at dark condition was investigated. PMID:25105016

  14. Investigation of photocatalytic degradation of phenol by Fe(III)-doped TiO2 and TiO2 nanoparticles.

    PubMed

    Hemmati Borji, Saeedeh; Nasseri, Simin; Mahvi, Amir Hossein; Nabizadeh, Ramin; Javadi, Amir Hossein

    2014-01-01

    In this study Fe (III)-doped TiO2 nanoparticles were synthesized by sol-gel method at two atomic ratio of Fe/Ti, 0.006 and 0.034 percent. Then the photoactivity of them was investigated on degradation of phenol under UV (<380 nm) irradiation and visible light (>380 nm). Results showed that at appropriate atomic ratio of Fe to Ti (% 0.034) photoactivity of Fe(III)-doped TiO2 nanoparticles increased. In addition, the effects of various operational parameters on photocatalytic degradation, such as pH, initial concentration of phenol and amount of photocatalyst were examined and optimized. At all different initial concentration, highest degradation efficiency occurred at pH = 3 and 0.5 g/L Fe(III)-doped TiO2 dosage. With increase in initial concentration of phenol, photocatalytic degradation efficiency decreased. Photoactivity of Fe (III)-doped TiO2 under UV irradiation and visible light at optimal condition (pH = 3 and catalyst dosage = and 0.5 g/L) was compared with P25 TiO2 nanoparticles. Results showed that photoactivity of Fe(III)-doped TiO2 under visible light was more than P25 TiO2 photoactivity, but it was less than P25 TiO2 photoactivity under UV irradiation. Also efficiency of UV irradiation alone and amount of phenol adsorption on Fe(III)-doped TiO2 at dark condition was investigated.

  15. Hunting for the elusive shallow traps in TiO2 anatase.

    PubMed

    Antila, Liisa J; Santomauro, Fabio G; Hammarström, Leif; Fernandes, Daniel L A; Sá, Jacinto

    2015-07-11

    Understanding electron mobility on TiO2 is crucial because of its applications in photocatalysis and solar cells. This work shows that shallow traps believed to be involved in electron migration in TiO2 conduction band are formed upon band gap excitation, i.e., are not pre-existing states. The shallow traps in TiO2 results from large polarons and are not restricted to surface.

  16. [TiO2-Induced Photodegradation of Levofloxacin by Visible Light and Its Mechanism].

    PubMed

    Guo, Hong-sheng; Liu, Ya-nan; Qiao, Qi; Wei, Hong; Dong, Cheng-xing; Xue, Jie; Li, Ke-bin

    2015-05-01

    Levofloxacin is an emerging pollutant. Single levofloxacin and TiO2 have no visible-light activity. However, photodegradation of levofloxacin dramatically enhanced in the presence of TiO2 under visible light irradiation. Considering this finding, he photodegradation of levofloxacin over TiO2 was investigated under visible light irradiation. Effects of TiO2 dosage, levofloxacin concentration, and solution pH on levofloxacin photodegradation were examined by monitoring its concentration decay with time. The results showed that levofloxacin photodegradation fitted the Langmuir-Hinshelwood kinetic model. Solution pH, TiO2 dose, and levofloxacin concentration had significant effects on the photodegradation rates. In addition, batch adsorption experiments revealed that adsorption of levofloxacin on TiO2 conformed to the pseudo-second-order kinetics and the Langmuir isotherm. DRS spectrum of levofloxacin-adsorbed TiO2 suggested that a surface complex was formed between levofloxacin and TiO2. Addition of radical scavengers and N2-degassing affecting levofloxacin photodegradation indicated that the superoxide ion radical was mainly active species. UV-Vis spectra of a deaerated TiO2 and levofloxacin suspensions further confirmed that the electron injection into TiO2 conduction band took place under visible light irradiation. Based on these results, a charge-transfer mechanism initiated by photoexcitation of TiO2/ levofloxacin surface complex was proposed for levofloxacin photocatalytic degradation over TiO2 under visible light. This study indicates that the charge-transfer-complex-mediated photocatalytic technique has promising applications in the removal of colorless organic pollutants.

  17. Interstitial Boron-Doped TiO2 Thin Films: The Significant Effect of Boron on TiO2 Coatings Grown by Atmospheric Pressure Chemical Vapor Deposition.

    PubMed

    Quesada-González, Miguel; Boscher, Nicolas D; Carmalt, Claire J; Parkin, Ivan P

    2016-09-28

    The work presented here describes the preparation of transparent interstitial boron-doped TiO2 thin-films by atmospheric pressure chemical vapor deposition (APCVD). The interstitial boron-doping, on TiO2, proved by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), is shown to enhance the crystallinity and significantly improve the photocatalytic activity of the TiO2 films. The synthesis, highly suitable for a reel-to-reel process, has been carried out in one step. PMID:27622709

  18. A comparative study of doped and un-doped sol-gel TiO2 and P25 TiO2 (photo)electrodes.

    PubMed

    Pooarporn, Y; Worayingyong, A; Wörner, M; Songsiriritthigul, P; Braun, A M

    2007-01-01

    Doped and undoped titanium dioxide films have been deposited on indium tin oxide glass using the sol-gel technique. The percentage of rutile in the prepared TiO2, calcined at 823 K and determined by X-ray diffraction, was 23% compared to 24% of rutile in P25-TiO2. Cerium doped TiO2 showed mainly the anatase phase, as characterised by both X-ray diffraction and Raman spectroscopy. The electrochemical and photoelectrochemical properties of the films were studied by cyclic voltammetry and electrochemical impedance spectroscopy. The (photo)electrochemical characteristics of the different films are reported and discussed.

  19. Interstitial Boron-Doped TiO2 Thin Films: The Significant Effect of Boron on TiO2 Coatings Grown by Atmospheric Pressure Chemical Vapor Deposition.

    PubMed

    Quesada-González, Miguel; Boscher, Nicolas D; Carmalt, Claire J; Parkin, Ivan P

    2016-09-28

    The work presented here describes the preparation of transparent interstitial boron-doped TiO2 thin-films by atmospheric pressure chemical vapor deposition (APCVD). The interstitial boron-doping, on TiO2, proved by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), is shown to enhance the crystallinity and significantly improve the photocatalytic activity of the TiO2 films. The synthesis, highly suitable for a reel-to-reel process, has been carried out in one step.

  20. Self-cleaning properties of TiO2/palygorskite and TiO2/halloysite nanocomposite coatings

    NASA Astrophysics Data System (ADS)

    Panagiotaras, Dionisios; Kaplani, Eleni; Stathatos, Elias; Papoulis, Dimitrios

    2014-10-01

    Tubular halloysite and microfibrous palygorskite clay mineral combined with nanocrystalline TiO2 are involved in the preparation of nanocomposite films on glass substrates via sol-gel route at 450°C. The synthesis employing nonionic surfactant molecule as pore directing agent along with the acetic acid-based sol-gel route without addition of water molecules. Drying and thermal treatment of composite films ensure elimination of organic material lead to the formation of TiO2 nanoparticles homogeneously distributed on the palygorskite and halloysite surfaces. Nanocomposite films without cracks of active anatase crystal phase on palygorskite and halloysite surfaces are characterized by microscopy techniques, UV-Vis spectroscopy, and porosimetry methods in order to examine their structural properties. The composite palygorskite-TiO2 and halloysite/TiO2 films with variable quantities of palygorskite and halloysite were tested as photocatalysts in the photo-oxidation of Basic Blue 41 azo dye in water. These nanocomposite films proved to be most promising photocatalysts and highly effective to dye's decoloration in spite of small amount of palygorskite/TiO2 or halloysite/TiO2 catalyst immobilized onto glass substrates.

  1. Positron annihilation lifetime characterization of oxygen ion irradiated rutile TiO2

    NASA Astrophysics Data System (ADS)

    Luitel, Homnath; Sarkar, A.; Chakrabarti, Mahuya; Chattopadhyay, S.; Asokan, K.; Sanyal, D.

    2016-07-01

    Ferromagnetic ordering at room temperature has been induced in rutile phase of TiO2 polycrystalline sample by O ion irradiation. 96 MeV O ion induced defects in rutile TiO2 sample has been characterized by positron annihilation spectroscopic techniques. Positron annihilation results indicate the formation of cation vacancy (VTi, Ti vacancy) in these irradiated TiO2 samples. Ab initio density functional theoretical calculations indicate that in TiO2 magnetic moment can be induced either by creating Ti or O vacancies.

  2. Defective TiO2 with oxygen vacancies: synthesis, properties and photocatalytic applications

    NASA Astrophysics Data System (ADS)

    Pan, Xiaoyang; Yang, Min-Quan; Fu, Xianzhi; Zhang, Nan; Xu, Yi-Jun

    2013-04-01

    Titanium dioxide (TiO2), as an important semiconductor metal oxide, has been widely investigated in the field of photocatalysis. The properties of TiO2, including its light absorption, charge transport and surface adsorption, are closely related to its defect disorder, which in turn plays a significant role in the photocatalytic performance of TiO2. Among all the defects identified in TiO2, oxygen vacancy is one of the most important and is supposed to be the prevalent defect in many metal oxides, which has been widely investigated both by theoretical calculations and experimental characterizations. Here, we give a short review on the existing strategies for the synthesis of defective TiO2 with oxygen vacancies, and the defect related properties of TiO2 including structural, electronic, optical, dissociative adsorption and reductive properties, which are intimately related to the photocatalytic performance of TiO2. In particular, photocatalytic applications with regard to defective TiO2 are outlined. In addition, we offer some perspectives on the challenge and new direction for future research in this field. We hope that this tutorial minireview would provide some useful contribution to the future design and fabrication of defective semiconductor-based nanomaterials for diverse photocatalytic applications.Titanium dioxide (TiO2), as an important semiconductor metal oxide, has been widely investigated in the field of photocatalysis. The properties of TiO2, including its light absorption, charge transport and surface adsorption, are closely related to its defect disorder, which in turn plays a significant role in the photocatalytic performance of TiO2. Among all the defects identified in TiO2, oxygen vacancy is one of the most important and is supposed to be the prevalent defect in many metal oxides, which has been widely investigated both by theoretical calculations and experimental characterizations. Here, we give a short review on the existing strategies for the synthesis of defective TiO2 with oxygen vacancies, and the defect related properties of TiO2 including structural, electronic, optical, dissociative adsorption and reductive properties, which are intimately related to the photocatalytic performance of TiO2. In particular, photocatalytic applications with regard to defective TiO2 are outlined. In addition, we offer some perspectives on the challenge and new direction for future research in this field. We hope that this tutorial minireview would provide some useful contribution to the future design and fabrication of defective semiconductor-based nanomaterials for diverse photocatalytic applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00476g

  3. Annealing of TiO2 Films Deposited on Si by Irradiating Nitrogen Ion Beams

    SciTech Connect

    Yokota, Katsuhiro; Yano, Yoshinori; Miyashita, Fumiyoshi

    2006-11-13

    Thin TiO2 films were deposited on Si at a temperature of 600 deg. C by an ion beam assisted deposition (IBAD) method. The TiO2 films were annealed for 30 min in Ar at temperatures below 700 deg. C. The as-deposited TiO2 films had high permittivities such 200 {epsilon}o and consisted of crystallites that were not preferentially oriented to the c-axis but had an expanded c-axis. On the annealed TiO2 films, permittivities became lower with increasing annealing temperature, and crystallites were oriented preferentially to the (110) plane.

  4. A comparative study of TiO2 nanoparticles synthesized in premixed and diffusion flames

    NASA Astrophysics Data System (ADS)

    Ma, Hsiao-Kang; Yang, Hsiung-An

    2010-12-01

    Previous studies have been shown that synthesis of titania (TiO2) crystalline phase purity could be effectively controlled by the oxygen concentration through titanium tetra-isopropoxide (TTIP) via premixed flame from a Bunsen burner. In this study, a modified Hencken burner was used to synthesize smaller TiO2 nanoparticles via short diffusion flames. The frequency of collisions among particles would decrease and reduce TiO2 nanoparticle size in a short diffusion flame height. The crystalline structure of the synthesized nanoparticles was characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), Barrett-Joyner-Halenda (BJH) and Brunauer-Emmett-Teller (BET) measurements. The characteristic properties of TiO2 nanoparticles synthesized from a modified Hencken burner were compared with the results from a Bunsen burner and commercial TiO2 (Degussa P25). The results showed that the average particle size of 6.63 nm from BET method was produced by a modified Hencken burner which was smaller than the TiO2 in a Bunsen burner and commercial TiO2. Moreover, the rutile content of TiO2 nanoparticles increased as the particle collecting height increased. Also, the size of TiO2 nanoparticles was highly dependent on the TTIP loading and the collecting height in the flame.

  5. Solar-driven photocatalytic treatment of diclofenac using immobilized TiO2-based zeolite composites.

    PubMed

    Kovacic, Marin; Salaeh, Subhan; Kusic, Hrvoje; Suligoj, Andraz; Kete, Marko; Fanetti, Mattia; Stangar, Urska Lavrencic; Dionysiou, Dionysios D; Bozic, Ana Loncaric

    2016-09-01

    The study is aimed at evaluating the potential of immobilized TiO2-based zeolite composite for solar-driven photocatalytic water treatment. In that purpose, TiO2-iron-exchanged zeolite (FeZ) composite was prepared using commercial Aeroxide TiO2 P25 and iron-exchanged zeolite of ZSM5 type, FeZ. The activity of TiO2-FeZ, immobilized on glass support, was evaluated under solar irradiation for removal of diclofenac (DCF) in water. TiO2-FeZ immobilized in a form of thin film was characterized for its morphology, structure, and composition using scanning electron microscopy/energy-dispersive x-ray spectroscopy (SEM/EDX). Diffuse reflectance spectroscopy (DRS) was used to determine potential changes in band gaps of prepared TiO2-FeZ in comparison to pure TiO2. The influence of pH, concentration of hydrogen peroxide, FeZ wt% within the composite, and photocatalyst dosage on DCF removal and conversion efficiency by solar/TiO2-FeZ/H2O2 process was investigated. TiO2-FeZ demonstrated higher photocatalytic activity than pure TiO2 under solar irradiation in acidic conditions and presence of H2O2.

  6. Mesoporous submicrometer TiO(2) hollow spheres as scatterers in dye-sensitized solar cells.

    PubMed

    Dadgostar, Shabnam; Tajabadi, Fariba; Taghavinia, Nima

    2012-06-27

    Hierarchical submicrometer TiO2 hollow spheres with outer diameter of 300-700 nm and shell thickness of 200 nm are synthesized by liquid phase deposition of TiO2 over carbon microspheres as sacrificial templates. The final TiO2 hollow spheres are applied as a scattering layer on top of a transparent nanocrystalline TiO2 film, serving as the photoanode of a dye-sensitized solar cell (DSC). In addition to efficient light scattering, the mesoporous structure of TiO2 hollow spheres provides a high surface area, 74 m(2)/g, which allows for higher dye loading. This dual functioning suggests that TiO2 hollow spheres may be good replacements for conventional TiO2 spheres as scatterers in DSCs. A high efficiency of 8.3% is achieved with TiO2 hollow spheres, compared with 6.0% for the electrode with 400 nm spherical TiO2 scatterers, at identical conditions. PMID:22606936

  7. Improvement of solar energy conversion with Nb-incorporated TiO2 hierarchical microspheres.

    PubMed

    Hoang, Son; Ngo, Thong Q; Berglund, Sean P; Fullon, Raymond R; Ekerdt, John G; Mullins, C Buddie

    2013-07-22

    Niobium-modified TiO2 hierarchical spherical micrometer-size particles, which consist of many nanowires, are synthesized by solvothermal synthesis and studied as photoelectrodes for water photo-oxidation and dye-sensitized solar cell (DSSC) applications. Incorporation of Nb leads to a rutile-to-anatase TiO2 phase transition in the TiO2 hierarchical spheres (HSs), with the anatase percentage increasing from 0% for the pristine TiO2 HSs to 47.6% for the 1.82 at.% Nb-incorporated TiO2 sample. Incorporation of Nb leads to significant improvements in water photo-oxidation with the photocurrents reaching 70.5 μA cm(-2) at 1.23 V versus the reversible hydrogen electrode, compared with 28.3 μA cm(-2) for the pristine TiO2 sample. The photoconversion efficiency of Nb:TiO2 HS-based DSSCs reaches 6.09±0.15% at 0.25 at.% Nb, significantly higher than that for the pristine TiO2 HS cells (3.99±0.02%). In addition, the incident-photon-to-current efficiency spectra for DSSCs show that employing TiO2 and Nb:TiO2 HSs provides better light harvesting, especially of long-wavelength photons, than anatase TiO2 nanoparticle-based DSSCs. PMID:23512241

  8. [Preparation of mixed crystal TiO2 nanoparticles and photocatalytic degradation of toxic organic pollutants].

    PubMed

    Deng, An-Ping; Yang, Jing; Wang, Shu-Lian; Huang, Ying-Ping; Yang, Yong

    2010-12-01

    Mixed crystal TiO2 nanoparticles were prepared from a precursor of TiO2 by hydrothermal-steam method. The effects of the reaction temperature and the reaction time on the photocatalytic activity of the brookite TiO2 were studied. The TiO2 samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Photocatalytic degradation of organic dye sulforhodamine B (SRB) under UV light (lambda < or = 387 nm) was used as probe reaction to evaluate the properties of the TiO2. The result showed that TiO2 prepared under 150 degrees C for 24 h had high photocatalytic activity. The size of the mixed crystal TiO2 was 14.20 nm. Brookite and anatase phase of the mixed crystal TiO2 were 63.6% and 36.4%, respectively. The dye discoloration and degradation rates were tracked, and the intermediate products hydrogen peroxide (H2O2) and hydrogen radicals (*OH) were determined during the photocatalytic experiments. The results indicated that photocatalytic degradation of brookite TiO2 mainly referred to the *OH radical mechanism. After 5 h, the mineralization and oxidation rates of SRB and 2,4-DCP mineralization were 89% and 78%, respectively. The catalyst showed good stability with no significant changes in catalytic properties after 5 cycles of SRB photocatalytic degradation experiments.

  9. Controllable Synthesis and Tunable Photocatalytic Properties of Ti3+-doped TiO2

    PubMed Central

    Ren, Ren; Wen, Zhenhai; Cui, Shumao; Hou, Yang; Guo, Xiaoru; Chen, Junhong

    2015-01-01

    Photocatalysts show great potential in environmental remediation and water splitting using either artificial or natural light. Titanium dioxide (TiO2)-based photocatalysts are studied most frequently because they are stable, non-toxic, readily available, and highly efficient. However, the relatively wide band gap of TiO2 significantly limits its use under visible light or solar light. We herein report a facile route for controllable synthesis of Ti3+-doped TiO2 with tunable photocatalytic properties using a hydrothermal method with varying amounts of reductant, i.e., sodium borohydride (NaBH4). The resulting TiO2 showed color changes from light yellow, light grey, to dark grey with the increasing amount of NaBH4. The present method can controllably and effectively reduce Ti4+ on the surface of TiO2 and induce partial transformation of anatase TiO2 to rutile TiO2, with the evolution of nanoparticles into hierarchical structures attributable to a high pressure and strong alkali environment in the synthesis atmosphere; in this way, the photocatalytic activity of Ti3+-doped TiO2 under visible-light can be tuned. The as-developed strategy may open up a new avenue for designing and functionalizing TiO2 materials for enhancing visible light absorption, narrowing band gap, and improving photocatalytic activity. PMID:26044406

  10. Tuning hydrophobicity of TiO2 layers with silanization and self-assembled nanopatterning.

    PubMed

    Van, Trong Nghia; Lee, Young Keun; Lee, Jaesang; Park, Jeong Young

    2013-03-01

    The wettability of TiO2 layers is controlled by forming highly ordered arrays of nanocones using nanopatterning, based on self-assembly and dry etching. Nanopatterning of TiO2 layers is achieved via formation of self-assembled monolayers of SiO2 spheres fabricated using the Langmuir-Blodgett technique, followed by dry etching. Three types of TiO2 layers were fabricated using the sol-gel technique, sputtering, and thermal process in order to address the relationship between the wettability and the structure of TiO2 nanostructures. Compared to a thin film TiO2 layer, the nanopatterned TiO2 samples show a smaller static water contact angle (i.e., where the water contact angle decreases as the etching time increases), which is attributed to the Wenzel equation. When TiO2 layers are coated by 1H,1H,2H,2H-perfluorooctyltrichlorosilane, we observed the opposite behavior, exhibiting superhydrophobicity (up to contact angle of 155°) on the nanopatterned TiO2 layers. Self-assembled nanopatterning of the TiO2 layer may provide an advanced method for producing multifunctional transparent layers with self-cleaning properties.

  11. Sonochemical synthesis of TiO(2 nanoparticles on graphene for use as photocatalyst.

    PubMed

    Guo, Jingjing; Zhu, Shenmin; Chen, Zhixin; Li, Yao; Yu, Ziyong; Liu, Qinglei; Li, Jingbo; Feng, Chuanliang; Zhang, Di

    2011-09-01

    Using ultrasonication we succeed in a controlled incorporation of TiO(2) nanoparticles on the graphene layers homogeneously in a few hours. The average size of the TiO(2) nanoparticles was controlled at around 4-5 nm on the sheets without using any surfactant, which is attributed to the pyrolysis and condensation of the dissolved TiCl(4) into TiO(2) by ultrasonic waves. The photocatalytic activity of the resultant graphene-TiO(2) composites containing 25 wt.% TiO(2) is better than that of commercial pure TiO(2). This is partly due to the extremely small size of the TiO(2) nanoparticles and partly due to the graphene-TiO(2) composite structure consisting of homogeneous dispersion of crystalline TiO(2) nanoparticles on the graphene sheets. As the graphene in the composites has a very good contact with the TiO(2) nanoparticles it enhances the photo-electron conversion of TiO(2) by reducing the recombination of photo-generated electron-hole pairs. PMID:21482166

  12. On the Crystal Structural Control of Sputtered TiO2 Thin Films

    NASA Astrophysics Data System (ADS)

    Jia, Junjun; Yamamoto, Haruka; Okajima, Toshihiro; Shigesato, Yuzo

    2016-07-01

    In this study, we focused on the origin on the selective deposition of rutile and anatase TiO2 thin films during the sputtering process. The observation on microstructural evolution of the TiO2 films by transmission electron microscopy revealed the coexistence of rutile and anatase TiO2 phases in the initial stage under the preferential growth conditions for the anatase TiO2; the observations further revealed that the anatase phase gradually dominated the crystal structure with increasing film thickness. These results suggest that the bombardment during the sputtering deposition did not obviously affect the TiO2 crystal structure, and this was also confirmed by off-axis magnetron sputtering experiments. We also investigated the mechanism of the effect of Sn impurity doping on the crystal structure using first-principles calculations. It is found that the formation energy of Sn-doped rutile TiO2 is lower than that of Sn-doped anatase TiO2; this suggests that the Sn-doped TiO2 favours the rutile phase. These results offer a guideline for the utilization of selective deposition of rutile and anatase TiO2 thin films in various industrial applications.

  13. Controllable Synthesis and Tunable Photocatalytic Properties of Ti(3+)-doped TiO2.

    PubMed

    Ren, Ren; Wen, Zhenhai; Cui, Shumao; Hou, Yang; Guo, Xiaoru; Chen, Junhong

    2015-06-05

    Photocatalysts show great potential in environmental remediation and water splitting using either artificial or natural light. Titanium dioxide (TiO2)-based photocatalysts are studied most frequently because they are stable, non-toxic, readily available, and highly efficient. However, the relatively wide band gap of TiO2 significantly limits its use under visible light or solar light. We herein report a facile route for controllable synthesis of Ti(3+)-doped TiO2 with tunable photocatalytic properties using a hydrothermal method with varying amounts of reductant, i.e., sodium borohydride (NaBH4). The resulting TiO2 showed color changes from light yellow, light grey, to dark grey with the increasing amount of NaBH4. The present method can controllably and effectively reduce Ti(4+) on the surface of TiO2 and induce partial transformation of anatase TiO2 to rutile TiO2, with the evolution of nanoparticles into hierarchical structures attributable to a high pressure and strong alkali environment in the synthesis atmosphere; in this way, the photocatalytic activity of Ti(3+)-doped TiO2 under visible-light can be tuned. The as-developed strategy may open up a new avenue for designing and functionalizing TiO2 materials for enhancing visible light absorption, narrowing band gap, and improving photocatalytic activity.

  14. Environment-friendly biomimetic synthesis of TiO2 nanomaterials for photocatalytic application

    NASA Astrophysics Data System (ADS)

    Bao, Shu-Juan; Lei, Chao; Xu, Mao-Wen; Cai, Chang-Jun; Jia, Dian-Zeng

    2012-05-01

    We have demonstrated an environment-friendly biomimetic synthesis method for the preparation of TiO2 nanomaterials with different crystal phases and morphologies. This is the first time that it has been found that the crystal phase of TiO2 can be controlled just by using different biotemplates, and cannot be changed by calcination up to 750 °C. In our experiment, anatase TiO2 was obtained by using yeast and albumen templates, while rutile TiO2 was formed by using dandelion pollen as the template.

  15. Solar-driven photocatalytic treatment of diclofenac using immobilized TiO2-based zeolite composites.

    PubMed

    Kovacic, Marin; Salaeh, Subhan; Kusic, Hrvoje; Suligoj, Andraz; Kete, Marko; Fanetti, Mattia; Stangar, Urska Lavrencic; Dionysiou, Dionysios D; Bozic, Ana Loncaric

    2016-09-01

    The study is aimed at evaluating the potential of immobilized TiO2-based zeolite composite for solar-driven photocatalytic water treatment. In that purpose, TiO2-iron-exchanged zeolite (FeZ) composite was prepared using commercial Aeroxide TiO2 P25 and iron-exchanged zeolite of ZSM5 type, FeZ. The activity of TiO2-FeZ, immobilized on glass support, was evaluated under solar irradiation for removal of diclofenac (DCF) in water. TiO2-FeZ immobilized in a form of thin film was characterized for its morphology, structure, and composition using scanning electron microscopy/energy-dispersive x-ray spectroscopy (SEM/EDX). Diffuse reflectance spectroscopy (DRS) was used to determine potential changes in band gaps of prepared TiO2-FeZ in comparison to pure TiO2. The influence of pH, concentration of hydrogen peroxide, FeZ wt% within the composite, and photocatalyst dosage on DCF removal and conversion efficiency by solar/TiO2-FeZ/H2O2 process was investigated. TiO2-FeZ demonstrated higher photocatalytic activity than pure TiO2 under solar irradiation in acidic conditions and presence of H2O2. PMID:27255319

  16. The role of interfacial effects on enhanced catalytic performance of TiO2 -graphene nanocomposites

    NASA Astrophysics Data System (ADS)

    Chakarov, Dinko; Sellappan, Raja

    2014-03-01

    Graphene-containining TiO2 nanocomposites have significantly higher photocatalytic activity compared to bare TiO2 films. The enhancement is result of improved transport and higher efficiency of the charge carries separation at carbon-TiO2 interface. These effects were assessed by comparison of six anatase-graphene structures, fabricated by different synthesizing techniques and referenced to the performance of TiO2-graphitic-carbon and TiO2-Au thin films. The work was financially supported by The Nordic Energy Research Council through project N-I-S-F-D.

  17. Nitrogen doped TiO2 nano-particles: Phase control by solution combustion method

    NASA Astrophysics Data System (ADS)

    Bapna, Komal; Choudhary, R. J.; Phase, D. M.; Shastri, Sheetal; Prasad, R.; Ahuja, B. L.

    2016-05-01

    N-doped TiO2 nano powders were prepared by sol-gel solution combustion method. The influence of different fuels (urea and citric acid) used in obtaining N-TiO2 nano particles in similar conditions (heat treatment, amount of precursors) has been investigated. The growth of different phases of TiO2 (anatase and rutile) is strongly affected by the ligands and the dehydration reaction. Reduction in the band gap of TiO2 and features observed in the XPS spectra confirm the incorporation of N into TiO2 matrix.

  18. Tuning hydrophobicity of TiO2 layers with silanization and self-assembled nanopatterning.

    PubMed

    Van, Trong Nghia; Lee, Young Keun; Lee, Jaesang; Park, Jeong Young

    2013-03-01

    The wettability of TiO2 layers is controlled by forming highly ordered arrays of nanocones using nanopatterning, based on self-assembly and dry etching. Nanopatterning of TiO2 layers is achieved via formation of self-assembled monolayers of SiO2 spheres fabricated using the Langmuir-Blodgett technique, followed by dry etching. Three types of TiO2 layers were fabricated using the sol-gel technique, sputtering, and thermal process in order to address the relationship between the wettability and the structure of TiO2 nanostructures. Compared to a thin film TiO2 layer, the nanopatterned TiO2 samples show a smaller static water contact angle (i.e., where the water contact angle decreases as the etching time increases), which is attributed to the Wenzel equation. When TiO2 layers are coated by 1H,1H,2H,2H-perfluorooctyltrichlorosilane, we observed the opposite behavior, exhibiting superhydrophobicity (up to contact angle of 155°) on the nanopatterned TiO2 layers. Self-assembled nanopatterning of the TiO2 layer may provide an advanced method for producing multifunctional transparent layers with self-cleaning properties. PMID:23413954

  19. Characterization of manufactured TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Motzkus, C.; Macé, T.; Vaslin-Reimann, S.; Ausset, P.; Maillé, M.

    2013-04-01

    Technological advances in nanomaterials have allowed the development of new applications in industry, increasing the probability of finding airborne manufactured and engineered nano-objects in the workplace, as well as in ambient air. Scientific studies on health and environmental risks have indicated that airborne nano-objects in ambient air have potential adverse effects on the health of exposed workers and the general population. For regulatory purposes, ambient measurements of particulate matter are based on the determination of mass concentrations for PM10 and PM2.5, as regulated in the European Directive 2008/50/EC. However, this legislation is not suitable for airborne manufactured and engineered nano-objects. Parameters characterising ultrafine particles, such as particle number concentration and size distribution, are under consideration for future health-based legislation, to monitor workplaces and to control industrial processes. Currently, there are no existing regulations covering manufactured airborne nano-objects. There is therefore a clear, unaddressed need to focus on the toxicology and exposure assessment of nano-objects such as titanium dioxide (TiO2), which are manufactured and engineered in large quantities in industry. To perform reliable toxicology studies it is necessary to determine the relevant characteristics of nano-objects, such as morphology, surface area, agglomeration, chemical composition, particle size and concentration, by applying traceable methods. Manufacturing of nanomaterials, and their use in industrial applications, also require traceable characterisation of the nanomaterials, particularly for quality control of the process. The present study arises from the OECD WPMN sponsorship programme, supported by the French Agency for Environmental and Occupational Health Safety (ANSES), in order to develop analytical methods for the characterization of TiO2 nanoparticles in size and count size distribution, based on different techniques to characterize five different manufactured TiO2 nanoparticles. In this study, different measurement techniques have been implemented: Transmission Electron Microscopy (TEM), Scanning Mobility Particle Sizer (SMPS) and Aerodynamic Particle Sizer (APS). The TEM results lead to a relatively good agreement between data from the manufacturer and our characterizations of primary particle size. With regard to the dustiness, the results show a strong presence of agglomerates / aggregates of primary particles and a significant presence of emitted airborne nanoparticles with a diameter below 100 nm (composed of isolated primary particles and small aggregates / agglomerates formed from a few primary particles): the number proportion of these particles varies from 0 to 44 % in the measurement range 14-360 nm depending on the types of powders and corrections of measurements.

  20. Surface acidity scales: Experimental measurements of Brønsted acidities on anatase TiO2 and comparison with coinage metal surfaces

    NASA Astrophysics Data System (ADS)

    Silbaugh, Trent L.; Boaventura, Jaime S.; Barteau, Mark A.

    2016-08-01

    The first quantitative surface acidity scale for Brønsted acids on a solid surface is presented through the use of titration-displacement and equilibrium experiments on anatase TiO2. Surface acidities of species on TiO2 correlated with gas phase acidities, as was previously observed in qualitative studies of Brønsted acid displacement on Ag(110), Cu(110) and Au(111). A 90% compression of the surface acidity scale relative to the gas phase was observed due to compensation from the covalent component of the conjugate base - surface bond. Adsorbed conjugate bases need not be completely anionic for correlations with gas phase acidities to hold. Positive and negative substituent effects, such as substituted fluorine and hydrocarbon sidechain dispersion interactions with the surface, may modify the surface acidity scale, in agreement with previous experimental and theoretical work on Au(111).

  1. Hydrogen donor in anatase TiO2

    NASA Astrophysics Data System (ADS)

    Lavrov, E. V.

    2016-01-01

    An IR absorption study of hydrogen-related defects in natural single-crystalline anatase TiO2 has been carried out. A complex with IR absorption lines at 3412 and 3417 cm-1 is shown to act as a donor with ionization energy of tens of meV. The two lines are identified as stretching local vibrational modes of the O-H bonds of the donor in the neutral and positive charge states, respectively. The defect is unstable against annealing at approximately 300 ∘C and a storage at room temperature on the time scale of a few weeks. These findings suggest that interstitial hydrogen is a plausible model of this defect.

  2. TiO2 doped with nitrogen: synthesis and characterization.

    PubMed

    Abazović, Nadica D; Montone, Amelia; Mirenghi, Luciana; Janković, Ivana A; Comor, Mirjana I

    2008-02-01

    In this study, nitrogen-doped titanium dioxide (TiO2) powders were synthesized in two ways: by heating of titanium hydroxide with urea and by direct hydrolysis of titanium tetraisopropoxide (TTIP) with ammonium hydroxide. The samples were characterized by structural (XRD), analytical (XPS), optical (UV/Vis absorption/reflection and Raman spectroscopy) and morphological (SEM, TEM) techniques. The characterization suggested that the doped materials have anatase crystalline form without any detectable peaks that correspond to dopants. The absorption threshold of titanium dioxide was moved in the visible range of optical spectrum from 3.2 eV to 2.20 eV. Particle sizes of synthesized powders were obtained from XRD measurements and from TEM data ranging from 6-20 nm. XPS and Raman spectroscopy were used for detection of nitrogen in doped samples. PMID:18464379

  3. Fabrication N, F, and N/F-Doped TiO2 Photoelectrodes for Dye-Sensitized Solar Cells.

    PubMed

    Park, Su Kyung; Yun, Tae Kwan; Bae, Jae Young

    2015-08-01

    In this study, pure TiO2, N-doped TiO2, F-doped TiO2, and N/F-doped TiO2 particles were successfully synthesized through the hydrolysis of TiCl4 in the presence of ammonia water and NH4F, respectively. The introduction of doping materials did not affect the crystalline structure. No absorption peak for pure TiO2 was observed above the wavelength of 400 nm. However, the N-doped TiO2 and N/F-doped TiO2 powders exhibited a new absorption peak in the visible light region between 400 and 530 nm. The Jsc value of DSSCs based on the N/F-doped TiO2 electrode was increased by 10% compared to DSSCs using a pure TiO2 electrode, and the energy conversion efficiency was increased by 12%.

  4. N-doped TiO 2: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Di Valentin, Cristiana; Finazzi, Emanuele; Pacchioni, Gianfranco; Selloni, Annabella; Livraghi, Stefano; Paganini, Maria Cristina; Giamello, Elio

    2007-10-01

    Nitrogen doped titanium dioxide is attracting a continuously increasing attention because of its potential as material for environmental photocatalysis. In this paper we review experimental and theoretical work done on this system in our groups in recent years. The analysis is largely based on electron paramagnetic resonance (EPR) spectra and on their interpretation based on high-level ab initio calculations. N-doped anatase TiO 2 contains thermally stable single N-atom impurities either as charged diamagnetic Nb- centers or as neutral paramagnetic Nbrad centers (b stays for bulk). The N-atoms can occupy both interstitial or substitutional positions in the solid, with some evidence for a preference for interstitial sites. All types of N b centers give rise to localized states in the band-gap of the oxide, thus accounting for the related reduction of absorption band edge. The relative abundance of these species depends on the oxidation state of the solid. In fact, upon reduction, oxygen vacancies form and transfer electrons from Ti 3+ ions to the Nbrad with formation of Ti 4+ and Nb-. EPR spectra measured under irradiation show that the N b centers are responsible for visible light absorption with promotion of electrons from the localized N-impurity states to the conduction band or to electron scavengers like O 2 adsorbed on the surface. These results provide an unambiguous characterization of the electronic states associated with N-impurities in TiO 2 and a realistic picture of the processes occurring in the solid under irradiation with visible light.

  5. (In,Sn)2O3/TiO2/Pt Schottky-type diode switch for the TiO2 resistive switching memory array

    NASA Astrophysics Data System (ADS)

    Shin, Yong Cheol; Song, Jaewon; Kim, Kyung Min; Choi, Byung Joon; Choi, Seol; Lee, Hyun Ju; Kim, Gun Hwan; Eom, Taeyong; Hwang, Cheol Seong

    2008-04-01

    A Schottky-type diode switch consisting of a Pt /(In,Sn)2O3/TiO2/Pt stack was fabricated for applications to cross-bar type resistive-switching memory arrays. The high (0.55eV) and low potential barrier at the TiO2/Pt and TiO2/(In,Sn)2O3 junctions, respectively, constitute the rectifying properties of the stacked structure. The forward/reverse current ratio was as high as ˜1.6×104 at an applied voltage of ˜1V. When Pt /TiO2/Pt memory was connected to this diode in series, there was an insignificant interference on the memory function from the diode under the forward bias and virtually no resistive switching under a reverse bias.

  6. Highly recoverable TiO2-GO nanocomposites for stormwater disinfection.

    PubMed

    Wang, Gen; Feng, Wenjun; Zeng, Xiangkang; Wang, Zhouyou; Feng, Chuanping; McCarthy, David T; Deletic, Ana; Zhang, Xiwang

    2016-05-01

    A highly recoverable titanium dioxide-graphene oxide (TiO2-GO) composite was developed by a facile method of ultrasonic treatment of GO nanosheets and TiO2 nanoparticles, which should overcome the separation problem of nanosized TiO2 from treated water. Separability of the prepared samples was systematically investigated by gravity settling experiments. The samples' photocatalytic activity for stormwater disinfection was also studied under the irradiation of a solar simulator. The results demonstrated that TiO2-GO showed high efficient separability due to its accelerated settling behaviour. Zeta-potential analysis showed that the accelerated sedimentation of the catalyst was attributed to the aggregation of TiO2-GO resulting from the electrostatic attraction between TiO2 and GO. The TiO2-GO composite with a mass ratio of 100:2 (TiO2-2%GO) achieved both higher separability and good photocatalytic activity for stormwater disinfection. Its suspension became clear (turbidity < 50 NTU) after 8 h of sedimentation, while 99.5% of E.coli were deactivated in 90 min. The TiO2-GO composite exhibited excellent durability; no apparent change in the separability of TiO2-2%GO was observed after 10 treatment cycles (15 h in total), while only slight decrease in the photocatalytic activity was noted. In conclusion, the developed TiO2-GO composite showed promising results for stormwater disinfection. PMID:26991482

  7. High pressure structural phase transitions of TiO2 nanomaterials

    NASA Astrophysics Data System (ADS)

    Quan-Jun, Li; Bing-Bing, Liu

    2016-07-01

    Recently, the high pressure study on the TiO2 nanomaterials has attracted considerable attention due to the typical crystal structure and the fascinating properties of TiO2 with nanoscale sizes. In this paper, we briefly review the recent progress in the high pressure phase transitions of TiO2 nanomaterials. We discuss the size effects and morphology effects on the high pressure phase transitions of TiO2 nanomaterials with different particle sizes, morphologies, and microstructures. Several typical pressure-induced structural phase transitions in TiO2 nanomaterials are presented, including size-dependent phase transition selectivity in nanoparticles, morphology-tuned phase transition in nanowires, nanosheets, and nanoporous materials, and pressure-induced amorphization (PIA) and polyamorphism in ultrafine nanoparticles and TiO2-B nanoribbons. Various TiO2 nanostructural materials with high pressure structures are prepared successfully by high pressure treatment of the corresponding crystal nanomaterials, such as amorphous TiO2 nanoribbons, α-PbO2-type TiO2 nanowires, nanosheets, and nanoporous materials. These studies suggest that the high pressure phase transitions of TiO2 nanomaterials depend on the nanosize, morphology, interface energy, and microstructure. The diversity of high pressure behaviors of TiO2 nanomaterials provides a new insight into the properties of nanomaterials, and paves a way for preparing new nanomaterials with novel high pressure structures and properties for various applications. Project supported by the National Basic Research Program of China (Grant No. 2011CB808200), the National Natural Science Foundation of China (Grant Nos. 11374120, 11004075, 10979001, 51025206, 51032001, and 21073071), and the Cheung Kong Scholars Programme of China.

  8. Plasma surface modified TiO2 nanoparticles: improved photocatalytic oxidation of gaseous m-xylene.

    PubMed

    Sumitsawan, Sulak; Cho, Jai; Sattler, Melanie L; Timmons, Richard B

    2011-08-15

    Titanium dioxide (TiO(2)) is a preferred catalyst for photocatalytic oxidation of many air pollutants. In an effort to enhance its photocatalytic activity, TiO(2) was modified by pulsed plasma treatment. In this work, TiO(2) nanoparticles, coated on a glass plate, were treated with a plasma discharge of hexafluoropropylene oxide (HFPO) gas. By appropriate adjustment of discharge conditions, it was discovered that the TiO(2) particles can be either directly fluorinated (Ti-F) or coated with thin perfluorocarbon films (C-F). Specifically, under relatively high power input, the plasma deposition process favored direct surface fluorination. The extent of Ti-F formation increased with increasing power input. In contrast, at lower average power inputs, perfluorocarbon films are deposited on the surface of the TiO(2) particles. The plasma surface modified TiO(2) nanoparticles were subsequently employed as catalysts in the photocatalytic oxidation of m-xylene in air, as carried out inside a batch reactor with closed loop constant gas circulation. Both types of modified TiO(2) were significantly more catalytically active than that of the unmodified particles. For example, the rate constant of m-xylene degradation was increased from 0.012 min(-1) with untreated TiO(2) to 0.074 min(-1) with fluorinated TiO(2). Although it is not possible to provide unequivocal reasons for this increased photocatalytic activity, it is noted that the plasma surface treatment converted the TiO(2) from hydrophilic to highly hydrophobic, which would provide more facile catalyst adsorption of the xylene from the flowing air. Also, based on literature reports, the use of fluorinated TiO(2) reduces electron-hole recombination rates, thus increasing the photocatalytic activity. PMID:21761865

  9. TiO2 nanoparticles versus TiO2-SiO2 nanocomposites: A comparative study of photo catalysis on acid red 88

    NASA Astrophysics Data System (ADS)

    Balachandran, K.; Venckatesh, Rajendran; Sivaraj, Rajeshwari; Rajiv, P.

    2014-07-01

    A novel, simple, less time-consuming and cost-effective wet chemical technique was used to synthesis TiO2 nanoparticles and TiO2-SiO2 nanocomposites using Titanium tetra isopropoxide (TTIP) as a precursor relatively at low temperature in acidic pH. Titania sol was prepared by hydrolysis of TTIP and was mixed with silicic acid and tetrahydrofuran mixture. The reaction was carried out under vigorous stirring for 6 h and dried at room temperature. The resulting powders were characterized by UV-Visible spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction, scanning electron microscope (SEM) and transmission electron microscope (TEM). The grain size of the particles was calculated by X-ray diffraction, surface morphology and chemical composition was determined from scanning electron microscopy-energy dispersive spectroscopy, metal oxide stretching was confirmed from FT-IR spectroscopy, band gap was calculated using UV-Visible spectroscopy. Surface area of the composite as calculated by BET analyzer and it was found to be 65 and 75 m2/g for TiO2 and TiO2-SiO2 respectively. The photocatalytic experiments were performed with aqueous solution of acid red 88 with TiO2 and TiO2-SiO2 batch studies for 4 h irradiation, direct photolysis of TiO2 and TiO2-SiO2 contributed 94.2% and 96.5% decomposition in solar radiation for the optimized concentration of acid red 88.

  10. TiO2 nanoparticles versus TiO2-SiO2 nanocomposites: a comparative study of photo catalysis on acid red 88.

    PubMed

    Balachandran, K; Venckatesh, Rajendran; Sivaraj, Rajeshwari; Rajiv, P

    2014-07-15

    A novel, simple, less time-consuming and cost-effective wet chemical technique was used to synthesis TiO2 nanoparticles and TiO2-SiO2 nanocomposites using Titanium tetra isopropoxide (TTIP) as a precursor relatively at low temperature in acidic pH. Titania sol was prepared by hydrolysis of TTIP and was mixed with silicic acid and tetrahydrofuran mixture. The reaction was carried out under vigorous stirring for 6h and dried at room temperature. The resulting powders were characterized by UV-Visible spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction, scanning electron microscope (SEM) and transmission electron microscope (TEM). The grain size of the particles was calculated by X-ray diffraction, surface morphology and chemical composition was determined from scanning electron microscopy-energy dispersive spectroscopy, metal oxide stretching was confirmed from FT-IR spectroscopy, band gap was calculated using UV-Visible spectroscopy. Surface area of the composite as calculated by BET analyzer and it was found to be 65 and 75 m(2)/g for TiO2 and TiO2-SiO2 respectively. The photocatalytic experiments were performed with aqueous solution of acid red 88 with TiO2 and TiO2-SiO2 batch studies for 4h irradiation, direct photolysis of TiO2 and TiO2-SiO2 contributed 94.2% and 96.5% decomposition in solar radiation for the optimized concentration of acid red 88. PMID:24682063

  11. TiO2 nanoparticles versus TiO2-SiO2 nanocomposites: a comparative study of photo catalysis on acid red 88.

    PubMed

    Balachandran, K; Venckatesh, Rajendran; Sivaraj, Rajeshwari; Rajiv, P

    2014-07-15

    A novel, simple, less time-consuming and cost-effective wet chemical technique was used to synthesis TiO2 nanoparticles and TiO2-SiO2 nanocomposites using Titanium tetra isopropoxide (TTIP) as a precursor relatively at low temperature in acidic pH. Titania sol was prepared by hydrolysis of TTIP and was mixed with silicic acid and tetrahydrofuran mixture. The reaction was carried out under vigorous stirring for 6h and dried at room temperature. The resulting powders were characterized by UV-Visible spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction, scanning electron microscope (SEM) and transmission electron microscope (TEM). The grain size of the particles was calculated by X-ray diffraction, surface morphology and chemical composition was determined from scanning electron microscopy-energy dispersive spectroscopy, metal oxide stretching was confirmed from FT-IR spectroscopy, band gap was calculated using UV-Visible spectroscopy. Surface area of the composite as calculated by BET analyzer and it was found to be 65 and 75 m(2)/g for TiO2 and TiO2-SiO2 respectively. The photocatalytic experiments were performed with aqueous solution of acid red 88 with TiO2 and TiO2-SiO2 batch studies for 4h irradiation, direct photolysis of TiO2 and TiO2-SiO2 contributed 94.2% and 96.5% decomposition in solar radiation for the optimized concentration of acid red 88.

  12. For the inactivation of mold spores by UVC irradiation, with ozone acting as a promoter, TiO2 nanoparticles may act better as a "sun block" than as a photocatalytic disinfectant.

    PubMed

    Gong, Jia-You; Chen, Yen-Chi; Huang, Yi-Ting; Tsai, Ming-Chien; Yu, Kuo-Pin

    2014-09-01

    Fungal spores are known as critical indoor allergens, and indoor air purification techniques including photocatalytic disinfection using titanium dioxide (TiO2), ultraviolet germicidal irradiation (UVGI) and ozonation, have been considerably investigated. However, most of the research is in regard to photocatalytic disinfection, focused on the anti-bacterial efficacy of TiO2 nanoparticles (NPs). Furthermore, some research even showed that the photocatalytic antifungal efficacy of TiO2 NPs may not be that significant. Thus, investigating the reasons behind the non-significant antifungal efficacy of TiO2 photocatalytic disinfection and enhancing the antifungal efficacy is indispensable. In this study, ozone was employed to improve the photocatalytic antifungal efficacy of the TiO2 NPs and nano-metal supported on TiO2 NPs. The commercial TiO2 NPs (Degussa (Evonik) P25) served as a good support, and incipient wetness impregnation was successfully exploited to prepare oxidized nano-metals (Ag, Cu and Ni) in this study. There were two surfaces (quartz and putty) used in the inactivation experiments of Aspergillus niger spores which were manipulated under two conditions: exposed to ultraviolet (UVC) light , and exposed to UVC and ozone simultaneously. The SEM images demonstrated that the spores were sheltered from UVC light in the microcracks between TiO2 agglomerates. When irradiating with UVC, the A. niger spores on the two testing surfaces, without TiO2 NPs, were inactivated faster than those with TiO2 NPs, implying a "sun block" effect of this material and a lower photocatalytic antifungal efficacy than UVGI. On both surfaces, the inactivation rate constants (k) of A. niger spores exposed to UVC and ozone simultaneously (on quartz: k = 2.09-6.94 h(-1), on putty: k = 3.17-6.66 h(-1)) were better than those exposed to only UVC (on quartz: k = 1.80-5.89 h(-1); on putty: k = 2.97-3.98 h(-1)), indicating ozone can enhance the UVGI antifungal efficacy. PMID:25007943

  13. The effect of metal cluster deposition route on structure and photocatalytic activity of mono- and bimetallic nanoparticles supported on TiO2 by radiolytic method

    NASA Astrophysics Data System (ADS)

    Klein, Marek; Nadolna, Joanna; Gołąbiewska, Anna; Mazierski, Paweł; Klimczuk, Tomasz; Remita, Hynd; Zaleska-Medynska, Adriana

    2016-08-01

    TiO2 (P25) was modified with small and relatively monodisperse mono- and bimetallic clusters (Ag, Pd, Pt, Ag/Pd, Ag/Pt and Pd/Pt) induced by radiolysis to improve its photocatalytic activity. The as-prepared samples were characterized by X-ray fluorescence spectrometry (XRF), photoluminescence spectrometry (PL), diffuse reflectance spectroscopy (DRS), X-ray powder diffractometry (XRD), scanning transition electron microscopy (STEM) and BET surface area analysis. The effect of metal type (mono- and bimetallic modification) as well as deposition method (simultaneous or subsequent deposition of two metals) on the photocatalytic activity in toluene removal in gas phase under UV-vis irradiation (light-emitting diodes- LEDs) and phenol degradation in liquid phase under visible light irradiation (λ > 420 nm) were investigated. The highest photoactivity under Vis light was observed for TiO2 co-loaded with platinum (0.1%) and palladium (0.1%) clusters. Simultaneous addition of metal precursors results in formation of larger metal nanoparticles (15-30 nm) on TiO2 surface and enhances the Vis-induced activity of Ag/Pd-TiO2 up to four times, while the subsequent metal ions addition results in formation of metal particle size ranging from 4 to 20 nm. Subsequent addition of metal precursors results in formation of BNPs (bimetallic nanoparticle) composites showing higher stability in four cycles of toluene degradation under UV-vis. Obtained results indicated that direct electron transfer from the BNPs to the conduction band of the semiconductor is responsible for visible light photoactivity, whereas superoxide radicals (such as O2rad- and rad OOH) are responsible for pollutants degradation over metal-TiO2 composites.

  14. Preparation of hollow TiO2 nanoparticles through TiO2 deposition on polystyrene latex particles and characterizations of their structure and photocatalytic activity

    PubMed Central

    2012-01-01

    In a mixed solvent of water and ethanol, polystyrene/titanium dioxide (PSt/TiO2) composite particles of core-shell structure were prepared by hydrolysis of tetrabutyl titanate in the presence of cationic PSt particles or anionic PSt particles surface-treated using γ-aminopropyl triethoxysilane. Hollow TiO2 particles were obtained through calcination of the PSt/TiO2 core-shell particles to burn off the PSt core or through dissolution of the core by tetrahydrofuran (THF). An alternative process constituted of preheating the PSt/TiO2 particles at 200°C to allow partial crystallization followed by calcination or PSt dissolution by THF. The outcome TiO2 particles thus prepared were examined by TEM, and hollow TiO2 particles were observed. The crystalline phase structure and phase transformation were characterized, which revealed that preheating before the removal of the PSt core was useful to achieve the desired hollow TiO2 particles, and the calcination process was beneficial to the formation of anatase and rutile structures. The tests of TiO2 particles as catalyst in the photodegradation of Rhodamine B demonstrated that a much higher catalytic activity was observed with the TiO2 hollow particles prepared through calcination combined with preheating. PMID:23176612

  15. Hydrothermal Etching Treatment to Rutile TiO2 Nanorod Arrays for Improving the Efficiency of CdS-Sensitized TiO2 Solar Cells.

    PubMed

    Wan, Jingshu; Liu, Rong; Tong, Yuzhu; Chen, Shuhuang; Hu, Yunxia; Wang, Baoyuan; Xu, Yang; Wang, Hao

    2016-12-01

    Highly ordered TiO2 nanorod arrays (NRAs) were directly grown on an F:SnO2 (FTO) substrate without any seed layer by hydrothermal route. For a larger surface area, the second-step hydrothermal treatment in hydrochloric acid was carried out to the as-prepared TiO2 NRAs. The results showed that the center portion of the TiO2 nanorods were dissolved in the etching solution to form a nanocave at the initial etching process. As the etching time extended, the tip parts of the nanocave wall split into lots of nanowires with a reduced diameter, giving rise to a remarkable increase of specific surface area for the TiO2 NRAs. The TiO2 films after etching treatment were sensitized by CdS quantum dots (QDs) to fabricate quantum dot-sensitized solar cells (QDSSCs), which exhibited a significant improvement in the photocurrent density in comparison with that of the un-treated device, this mainly attributed to the enhancement of QD loading and diffused reflectance ability. Through modifying the etching TiO2 films with TiCl4, a relatively high power conversion efficiency (PCE) of 3.14 % was obtained after optimizing the etching time.

  16. Hydrothermal Etching Treatment to Rutile TiO2 Nanorod Arrays for Improving the Efficiency of CdS-Sensitized TiO2 Solar Cells

    NASA Astrophysics Data System (ADS)

    Wan, Jingshu; Liu, Rong; Tong, Yuzhu; Chen, Shuhuang; Hu, Yunxia; Wang, Baoyuan; Xu, Yang; Wang, Hao

    2016-01-01

    Highly ordered TiO2 nanorod arrays (NRAs) were directly grown on an F:SnO2 (FTO) substrate without any seed layer by hydrothermal route. For a larger surface area, the second-step hydrothermal treatment in hydrochloric acid was carried out to the as-prepared TiO2 NRAs. The results showed that the center portion of the TiO2 nanorods were dissolved in the etching solution to form a nanocave at the initial etching process. As the etching time extended, the tip parts of the nanocave wall split into lots of nanowires with a reduced diameter, giving rise to a remarkable increase of specific surface area for the TiO2 NRAs. The TiO2 films after etching treatment were sensitized by CdS quantum dots (QDs) to fabricate quantum dot-sensitized solar cells (QDSSCs), which exhibited a significant improvement in the photocurrent density in comparison with that of the un-treated device, this mainly attributed to the enhancement of QD loading and diffused reflectance ability. Through modifying the etching TiO2 films with TiCl4, a relatively high power conversion efficiency (PCE) of 3.14 % was obtained after optimizing the etching time.

  17. An efficient photoanode consisting of TiO2 nanoparticle-filled TiO2 nanotube arrays for dye sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Li, Quantong; Li, Siqian; Wang, Yi; Ye, Cong; Ruterana, Pierre; Wang, Hao

    2014-12-01

    An efficient photoanode consisting of TiO2 nanoparticle-filled TiO2 nanotube (TNT) arrays is prepared by a sol-gel process through hydrolysis and condensation of titaniumtetrachloride in an aqueous medium containing alcohol and ammonia. By introducing the TiO2 nanoparticles of proper particle size ∼20 nm into TNT arrays, the surface area, dye adsorption, short-circuit photocurrent density (Jsc), open circuit voltage (Voc) and the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs) are significantly improved (up to 107% enhancement on PCE). Particularly, the addition of alcohol and ammonia in TiO2 sol results in more hydroxyl groups chemisorbed onto the surface of the photoanodes, which is favorable for achieving large amount of dye adsorption. The influence of sol-treating time on the microstructure, morphology of photoanodes and the corresponding photovoltaic performance of DSSCs are investigated. It is found that immersing the TNT arrays into TiO2 sol for 0.5-2 h gives PCE of DSSC higher than 9.6%, and the highest PCE of 9.86% is achieved in DSSC when treating the TNT arrays with TiO2 sol for 2 h.

  18. Improved performance of dye-sensitized solar cells using TiO2 nanotubes infiltrated by TiO2 nanoparticles using a dipping-rinsing-hydrolysis process

    NASA Astrophysics Data System (ADS)

    Lin, Lu-Yin; Chen, Chia-Yuan; Yeh, Min-Hsin; Tsai, Keng-Wei; Lee, Chuan-Pei; Vittal, R.; Wu, Chun-Guey; Ho, Kuo-Chuan

    2013-12-01

    An efficient back-illuminated dye-sensitized solar cell (DSSC) is made with a flexible Ti-foil based photoanode composed of a composite TiO2 film with TiO2 nanotubes (TNT) and TiO2 nanoparticles (TNP). The composite TiO2 film is fabricated through a novel dipping-rinsing-hydrolysis (DRH) process by inserting TiO2 into TNT and sintering the product to form TNP inside TNT. By directly placing TiO2 nanoparticles into TNT, the former grow internally from the base of TNT to occupy it completely. This solves previous problems of incomplete filling of TNP into TNT, which used partial penetration of TiCl4 reactant from the top of the TNT. In the present case, the TNP are grown from the base of TNT. A DSSC containing TNT and TNP prepared in this way shows a photoelectric efficiency of 6.45%, which is much higher than that (4.21%) of a DSSC with untreated TNT. The films are characterized by using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The improvement in the photoelectric efficiency is explained by using electrochemical impedance spectroscopy (EIS), incident photon-to-current conversion efficiency (IPCE) analysis, and UV-absorption spectra analysis.

  19. Effect of silver-doping on the crystal structure, morphology and photocatalytic activity of TiO2 nanofibers

    NASA Astrophysics Data System (ADS)

    Barakat, N. A. M.; Kim, H. Y.

    2012-09-01

    In this study, effect of sliver-doping on the crystal structure, the nanofibrous morphology and the photocatalytic activity of titanium oxide nanofibers have been investigated. Silver-doped TiO2 nanofibers having different silver contents were prepared by calcination of electrospun nanofiber mats consisting of silver nitrate, titanium isopropoxide and poly(vinyl acetate) at 600 °C. The results affirmed formation of silver-doped TiO2 nanofibers composed of anatase and rutile when the silver nitrate content in the original electrospun solution was more than 3 wt%. The rutile phase content was directly proportional with the AgNO3 concentration in the electrospun solution. Negative impact of the silver-doping on the nanofibrous morphology was observed as increase the silver content caused to decrease the aspect ratio, i.e. producing nanorods rather nanofibers. However, silver-doping leads to modify the surface roughness. Study of the photocatalytic degradation of methylene blue dye clarified that increase the silver content strongly enhances the dye oxidation process.

  20. Synthesis of spindle-shaped AgI/TiO2 nanoparticles with enhanced photocatalytic performance

    NASA Astrophysics Data System (ADS)

    Yang, Liu; Gao, Minggang; Dai, Bin; Guo, Xuhong; Liu, Zhiyong; Peng, Banghua

    2016-11-01

    A novel synthetic route has been developed to prepare silver iodide (AgI) loaded spindle-shaped TiO2 nanoparticles (NPs). The morphology and crystallinity characterization revealed that small AgI NPs, with an average diameter of 15 nm were dispersed on the surface and interior of nanoporous anatase TiO2 support. High-resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET) surface area, Raman and X-ray photoelectron spectroscopy (XPS) were used to identify the nanoporous structure of TiO2 and the existence of AgI NPs. Diffuse reflectance spectra (DRS) showed that AgI/TiO2 composite exhibited a remarkable enhancement of visible light absorption, which is ascribed to the addition of AgI. For illustrating the superior property of this hybrid as photocatalyst, the degradation experiments were carried out for processing rhodamine B (RhB) solution under visible light irradiation and it was found that the photocatalytic activity was dramatically improved for AgI/TiO2 compared with nanoporous TiO2 and commercial P25 TiO2. The enhanced photocatalytic properties could be attributed to the large surface area of porous TiO2, good stability of AgI particles, and the effective charge separation due to the synergetic effect between AgI and TiO2 that can facilitate the separation of electron-hole pairs. Our novel composite based on nanoporous spindle-shaped TiO2 represents a promising new pathway for the design of high-performance photocatalysts for environmental applications.

  1. A TiO2 abundance map for the northern maria

    NASA Technical Reports Server (NTRS)

    Johnson, T. V.; Saunders, R. S.; Matson, D. L.; Mosher, J. A.

    1977-01-01

    A map of TiO2 abundance for most of the northern maria is presented. The telescopic data base used is the 0.38/0.56-micron ratio mosaic from Johnson et at. (1977). The titanium content has been estimated using the correlation established by Charette et al. (1974). The combination of observational, processing, and calibration errors indicates that the TiO2 map is accurate to + or - 2% (wt% TiO2) for high TiO2 content (more than 5%) and + or - 1% for low values of TiO2. Analysis of the lunar sample and telescopic data suggests strongly that the spectral parameter mapped is sensitive primarily to TiO2 abundance in the range 3-9% and does not correlate directly with iron content. It is suggested, however, that for the low TiO2 mare regions (less than 2-3% TiO2) there may be a relation between the spectral ratio and iron content and that some of the reddest mare areas in the Imbrium region may have low iron contents as well as low titanium abundances.

  2. Neurotoxicity and biochemical responses in the earthworm Pheretima hawayana exposed to TiO2NPs.

    PubMed

    Khalil, Abdelmonem M

    2015-12-01

    Serious concerns have been expressed about potential risks of manufactured TiO2NPs. In this research, toxicity of nanoparticulate and bulk TiO2 were examined to the earthworm Pheretima hawayana. The 24-h median lethal concentration (LC50) and sublethal endpoints were assessed. Both NPs and their bulk counterparts were toxic. The 24-h LC50 for TiO2NPs (145.36 mg kg(-1)) was highly toxic than that of bulk TiO2 (357.77 mg kg(-1)). The aim of the present work is to evaluate the suitability of P. hawayana and its biochemical responses to be used as a bioindicator organism and biomarkers of TiO2 toxicity. Earthworms were exposed to three sublethal concentrations of TiO2NPs (1, 10 and 100 µg kg(-1)) for 28 days to test acetylcholinesterase (AChE), antioxidant enzymes (superoxide dismutase: SOD and catalase: CAT) activities and MDA content. The response of the antioxidant enzymes combined with AChE inhibition and MDA accumulation indicated that TiO2NPs could induce significant impairments to the earthworms at the actual environment tested concentrations. The results pointed out the high sensitivity of the antioxidant and oxidative stress related responses to TiO2NPs exposure, demonstrating their usefulness in environmental monitoring and risk assessment. The study highlights also the usefulness of earthworm P. hawayana as potential bioindicator species for assessing the risk of nanoparticles environmental contamination.

  3. Charge Separation in TiO2/BDD Heterojunction Thin Film for Enhanced Photoelectrochemical Performance.

    PubMed

    Terashima, Chiaki; Hishinuma, Ryota; Roy, Nitish; Sugiyama, Yuki; Latthe, Sanjay S; Nakata, Kazuya; Kondo, Takeshi; Yuasa, Makoto; Fujishima, Akira

    2016-01-27

    Semiconductor photocatalysis driven by electron/hole has begun a new era in the field of solar energy conversion and storage. Here we report the fabrication and optimization of TiO2/BDD p-n heterojunction photoelectrode using p-type boron doped diamond (BDD) and n-type TiO2 which shows enhanced photoelectrochemical activity. A p-type BDD was first deposited on Si substrate by microwave plasma chemical vapor deposition (MPCVD) method and then n-type TiO2 was sputter coated on top of BDD grains for different durations. The microstructural studies reveal a uniform disposition of anatase TiO2 and its thickness can be tuned by varying the sputtering time. The formation of p-n heterojunction was confirmed through I-V measurement. A remarkable rectification property of 63773 at 5 V with very small leakage current indicates achieving a superior, uniform and precise p-n junction at TiO2 sputtering time of 90 min. This suitably formed p-n heterojunction electrode is found to show 1.6 fold higher photoelectrochemical activity than bare n-type TiO2 electrode at an applied potential of +1.5 V vs SHE. The enhanced photoelectrochemical performance of this TiO2/BDD electrode is ascribed to the injection of hole from p-type BDD to n-type TiO2, which increases carrier separation and thereby enhances the photoelectrochemical performance. PMID:26756353

  4. Effect of TiO2 nanotubes arrays on osseointegration of orthodontic miniscrew.

    PubMed

    Jang, Insan; Shim, Seong-Cheol; Choi, Dong-Soon; Cha, Bong-Kuen; Lee, Jae-Kwan; Choe, Byung-Hak; Choi, Won-Youl

    2015-08-01

    To increase the stability of orthodontic miniscrews, TiO2 nanotube arrays were fabricated on the surface of Ti miniscrews and the effect of those arrays on the osseointegration of miniscrews was evaluated. Highly ordered TiO2 nanotube arrays were grown on the surface of orthodontic miniscrews. Ethylene glycol based electrolyte was used in the anodic oxidation process. Two-step anodic oxidation was conducted to obtain clean and open windows in TiO2 nanotube arrays. The diameter and length of the TiO2 nanotube arrays were ~ 70 nm and ~ 5 μm, respectively. The miniscrews with TiO2 nanotube arrays were implanted in the legs of New Zealand white rabbits for 8 weeks. Histological osseointegration was assessed by bone-to-implant contact ratio, and three-dimensional bone volume ratio was measured by micro-computed tomography analysis. The miniscrews with TiO2 nanotube arrays had a greater mean bone-to-implant contact ratio of 52.8 % than the control, 29.3 %. Mean bone volume ratio (BV/TV) was also higher in the miniscrews with TiO2 nanotube arrays, at 81.2 % than those in the control via micro-CT analysis. Our findings support that TiO2 nanotube arrays on the surface of miniscrews enhance osseointegration and improve the stability of the miniscrew.

  5. Neurotoxicity and biochemical responses in the earthworm Pheretima hawayana exposed to TiO2NPs.

    PubMed

    Khalil, Abdelmonem M

    2015-12-01

    Serious concerns have been expressed about potential risks of manufactured TiO2NPs. In this research, toxicity of nanoparticulate and bulk TiO2 were examined to the earthworm Pheretima hawayana. The 24-h median lethal concentration (LC50) and sublethal endpoints were assessed. Both NPs and their bulk counterparts were toxic. The 24-h LC50 for TiO2NPs (145.36 mg kg(-1)) was highly toxic than that of bulk TiO2 (357.77 mg kg(-1)). The aim of the present work is to evaluate the suitability of P. hawayana and its biochemical responses to be used as a bioindicator organism and biomarkers of TiO2 toxicity. Earthworms were exposed to three sublethal concentrations of TiO2NPs (1, 10 and 100 µg kg(-1)) for 28 days to test acetylcholinesterase (AChE), antioxidant enzymes (superoxide dismutase: SOD and catalase: CAT) activities and MDA content. The response of the antioxidant enzymes combined with AChE inhibition and MDA accumulation indicated that TiO2NPs could induce significant impairments to the earthworms at the actual environment tested concentrations. The results pointed out the high sensitivity of the antioxidant and oxidative stress related responses to TiO2NPs exposure, demonstrating their usefulness in environmental monitoring and risk assessment. The study highlights also the usefulness of earthworm P. hawayana as potential bioindicator species for assessing the risk of nanoparticles environmental contamination. PMID:26398239

  6. Synergetic effects in novel hydrogenated F-doped TiO2 photocatalysts

    NASA Astrophysics Data System (ADS)

    Samsudin, Emy Marlina; Abd Hamid, Sharifah Bee; Juan, Joon Ching; Basirun, Wan Jefrey; Centi, Gabriele

    2016-05-01

    The synergistic effect between fluorine and hydrogen in hydrogenated F-doped TiO2 photocatalysts is evaluated for the photocatalytic degradation of atrazine. The interaction between fluorine and hydrogen species in hydrogenated F-doped TiO2 overcomes the limitations of individual F-doped TiO2 and hydrogenated TiO2 photocatalyst properties. Hydrogenated F-doped TiO2 is photo-active under UV, visible and infrared light illumination with efficient electrons and holes separations. The optimized concentration of surface vacancies and Ti3+ centers coupled with enhanced surface hydrophilicity facilitates the production of surface-bound and free hydroxyl radicals. The surface of the catalyst contains dbnd Tisbnd F, dbnd Tisbnd OH, dbnd Tisbnd Ovacancy and dbnd Tisbnd H bonds as evidenced by XPS, Raman, FTIR and HR-TEM analysis. This combination also triggers the formation of new Ti3+ occupied states under the conduction band of hydrogenated F-doped TiO2. Moreover, the change in the pore structure from cylindrical to slits and larger surface area facilitates surface charge interactions. The thermal stability is also enhanced and a single anatase phase is obtained. The size of the particles of hydrogenated F-doped TiO2 is also uniform with defined and homogeneous crystal structure. This synergetic effect between fluorine and hydrogen opens up new alternatives in improving the properties of TiO2 and its photocatalytic activity.

  7. Preparation and characterization of whey protein film incorporated with TiO2 nanoparticles.

    PubMed

    Zhou, J J; Wang, S Y; Gunasekaran, S

    2009-09-01

    Biodegradable titanium dioxide (TiO(2))/whey protein isolate (WPI) blend films were made by casting denatured WPI film solutions incorporated with TiO(2) nanoparticles. X-ray diffraction, UV-vis spectra, and fluorescence spectra of the films showed the successful incorporation of TiO(2) nanoparticles into the WPI matrix and indicated the interactions between TiO(2) and WPI. Mechanical tests revealed the antiplasticizing effect of TiO(2) nanoparticles on the WPI/TiO(2) film. Small amounts (<1 wt%) of added TiO(2) nanoparticles significantly increase the tensile properties of WPI film, but also decrease the moisture barrier properties. The addition of higher amounts (>1 wt%) of TiO(2) improves moisture barrier properties but lowers the tensile properties of the film. Microstructural evaluation confirmed the aggregation and distribution of TiO(2) nanoparticles within the WPI matrix and validated the results of functional properties of the WPI/TiO(2) film.

  8. Comparison of photocatalytic properties of TiO2 thin films and fibers

    NASA Astrophysics Data System (ADS)

    Ozdemir, Mehtap; Kurt, Metin; Ozyuzer, Lutfi; Aygun, Gulnur

    2016-10-01

    Efficiency of solar panels degrades as a result of organic contamination such as airborne particles, bird droppings and leaves. Any foreign object on photovoltaic panels reduces the sunlight entering the absorbing surface of the solar panels. Since this leads to a major problem decreasing in energy production, solar panels should be cleaned. The self-cleaning method can be preferred. There are some methods to clean the surface of solar panels. Among the self-cleaning materials, TiO2 is the most preferable ones because of its powerful photocatalytic properties. In this study, photocatalytic TiO2 were produced in two different nanostructures: nanofibers and thin films. TiO2 nanofibers were successfully produced by electrospinning. TiO2 thin films were fabricated by reactive magnetron sputtering technique. Both TiO2 nanofiber and thin film structures were heat-treated to form TiO2 in anatase phase at 600 °C for 2 h in air. Then, they were evaluated by SEM analyses for morphology, X-ray diffraction (XRD) analyses for phase structures, X-ray photoelectron spectroscopy (XPS) for the chemical state and atomic concentration, and UV-spectrometer for photocatalytic performance. The results indicate that photocatalytic and transmittance properties of TiO2 thin films are better than those of nanofibers. Consequently, TiO2 based thin films exhibit better performance for solar cell applications due to the surface cleanliness.

  9. Effect of TiO2 nanotubes arrays on osseointegration of orthodontic miniscrew.

    PubMed

    Jang, Insan; Shim, Seong-Cheol; Choi, Dong-Soon; Cha, Bong-Kuen; Lee, Jae-Kwan; Choe, Byung-Hak; Choi, Won-Youl

    2015-08-01

    To increase the stability of orthodontic miniscrews, TiO2 nanotube arrays were fabricated on the surface of Ti miniscrews and the effect of those arrays on the osseointegration of miniscrews was evaluated. Highly ordered TiO2 nanotube arrays were grown on the surface of orthodontic miniscrews. Ethylene glycol based electrolyte was used in the anodic oxidation process. Two-step anodic oxidation was conducted to obtain clean and open windows in TiO2 nanotube arrays. The diameter and length of the TiO2 nanotube arrays were ~ 70 nm and ~ 5 μm, respectively. The miniscrews with TiO2 nanotube arrays were implanted in the legs of New Zealand white rabbits for 8 weeks. Histological osseointegration was assessed by bone-to-implant contact ratio, and three-dimensional bone volume ratio was measured by micro-computed tomography analysis. The miniscrews with TiO2 nanotube arrays had a greater mean bone-to-implant contact ratio of 52.8 % than the control, 29.3 %. Mean bone volume ratio (BV/TV) was also higher in the miniscrews with TiO2 nanotube arrays, at 81.2 % than those in the control via micro-CT analysis. Our findings support that TiO2 nanotube arrays on the surface of miniscrews enhance osseointegration and improve the stability of the miniscrew. PMID:26149697

  10. Sonocatalytic removal of an organic dye using TiO2/Montmorillonite nanocomposite.

    PubMed

    Khataee, Alireza; Sheydaei, Mohsen; Hassani, Aydin; Taseidifar, Mojtaba; Karaca, Semra

    2015-01-01

    The sonocatalytic performance of the synthesized TiO2/Montmorillonite K10 (TiO2/MMT) nanocomposite was studied in removal of Basic Blue 3 (BB3) from water. The TiO2/MMT nanocomposite was prepared by hydrothermal method. Scanning electron microscope, X-ray diffraction and Fourier transform infrared were used to characterize the synthesized nanocomposite. The average size of TiO2 nanoparticles decreased from 60-80nm to 40-60nm through the immobilization of this semiconductor on the surface of MMT. The obtained results indicated that the sonocatalytic activity of TiO2/MMT nanocomposite was higher than that of pure TiO2 nanoparticles and MMT particles. Furthermore, the main influence factors on the sonocatalytic activity such as the BB3 concentration, pH of solution, TiO2/MMT dose, power of ultrasonic generator, and inorganic salts were studied. The intermediates of BB3 degradation during the sonocatalytic process in the presence of the TiO2/MMT nanocomposite have been monitored by gas chromatography-mass spectrometry. PMID:25060118

  11. Novel photocatalytic antibacterial activity of TiO2 microspheres exposing 100% reactive {111} facets.

    PubMed

    Sun, Liang; Qin, Ying; Cao, Qingqing; Hu, Bingqing; Huang, Zhiwei; Ye, Ling; Tang, Xingfu

    2011-12-21

    TiO(2) microspheres constructed by well-crystallized faceted nanorods with high aspect ratios expose 100% photocatalytic reactive {111} facets on the spherical surface. The microspheres demonstrated excellent photocatalytic antibacterial activity towards Staphylococcus aureus due to effective suppression of photoinduced electron-hole pair recombination and active TiO(2)@˙OH core-shell structure. PMID:22051605

  12. Sunlight highly photoactive Bi2WO6-TiO2 heterostructures for rhodamine B degradation.

    PubMed

    Colón, G; Murcia López, S; Hidalgo, M C; Navío, J A

    2010-07-14

    Highly efficient Bi(2)WO(6)-TiO(2) heterostructures are synthesized by means of a hydrothermal method; they have high photoactivity for the degradation of rhodamine B under sunlike irradiation. An interesting synergetic effect between TiO(2) and Bi(2)WO(6) leads to an improved charge carrier separation mechanism, causing the excellent photocatalytic performance.

  13. Enhancement in photo-induced hydrophilicity of TiO2/CNT nanostructures by applying voltage

    NASA Astrophysics Data System (ADS)

    Abdi, Yaser; Khalilian, Maryam; Arzi, Ezatollah

    2011-06-01

    Carbon nanotube (CNT) arrays were synthesized by plasma-enhanced chemical vapour deposition on a silicon substrate. Cabbage-like TiO2 nanostructures on the CNTs were produced by atmospheric-pressure chemical vapour deposition. Scanning electron microcopy was used to study the morphology of the TiO2/CNT structures while x-ray diffraction and Fourier transform infrared (FTIR) spectroscopy were used to verify the characteristics of the prepared nanostructures. Their hydrophilicity under UV and visible light was investigated and compared with the activity of thin films of TiO2. The TiO2/CNTs showed a highly improved photocatalytic activity in comparison with the TiO2 film. The excellent visible-light-induced hydrophilicity of the TiO2/CNTs was attributed to the generation of electron-hole pairs by visible light excitation with a low recombination rate. The results of this study showed that the fabricated cabbage-like TiO2/CNT nanostructures have a super-hydrophilic surface without further UV irradiation. Electrical measurements showed that a p-n junction was formed at the interface of the TiO2/CNTs. Consequently, a super-hydrophilic surface was achieved by applying an electric bias voltage. Visible-light- and electro-induced hydrophilicity of the obtained nanostructure was reported in this work.

  14. TiO2@C core-shell nanoparticles formed by polymeric nano-encapsulation

    PubMed Central

    Vasei, Mitra; Das, Paramita; Cherfouth, Hayet; Marsan, Benoît; Claverie, Jerome P.

    2014-01-01

    TiO2 semiconducting nanoparticles are known to be photocatalysts of moderate activity due to their high band-gap and high rate of electron-hole recombination. The formation of a shell of carbon around the core of TiO2, i.e., the formation of TiO2@C nanoparticles, is believed to partly alleviate these problems. It is usually achieved by a hydrothermal treatment in a presence of a sugar derivative. We present here a novel method for the formation of highly uniform C shell around TiO2 nanoparticles. For this purpose, TiO2 nanoparticles were dispersed in water using an oligomeric dispersant prepared by Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization. Then the nanoparticles were engaged into an emulsion polymerization of acrylonitrile, resulting in the formation of a shell of polyacrylonitrile (PAN) around each TiO2 nanoparticles. Upon pyrolysis, the PAN was transformed into carbon, resulting in the formation of TiO2@C nanoparticles. The structure of the resulting particles was elucidated by X-Ray diffraction, FTIR, UV-VIS and Raman spectroscopy as well as TEM microscopy. Preliminary results about the use of the TiO2@C particles as photocatalysts for the splitting of water are presented. They indicate that the presence of the C shell is responsible for a significant enhancement of the photocurrent. PMID:25072054

  15. TiO2@C Core-Shell Nanoparticles Formed by Polymeric Nano-Encapsulation

    NASA Astrophysics Data System (ADS)

    Vasei, Mitra; Das, Paramita; Cherfouh, Hayet; Marsan, Benoit; Claverie, Jerome

    2014-07-01

    TiO2 semiconducting nanoparticles are known to be photocatalysts of moderate activity due to their high band-gap and high rate of electron-hole recombination. The formation of a shell of carbon around the core of TiO2, i.e. the formation of TiO2@C nanoparticles, is believed to partly alleviate these problems. It is usually achieved by a hydrothermal treatment in a presence of a sugar derivative. We present here a novel method for the formation of highly uniform C shell around TiO2 nanoparticles. For this purpose, TiO2 nanoparticles were dispersed in water using an oligomeric dispersant prepared by Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization. Then the nanoparticles were engaged into an emulsion polymerization of acrylonitrile, resulting in the formation of a shell of polyacrylonitrile (PAN) around each TiO2 nanoparticles. Upon pyrolisis, the PAN was transformed into carbon, resulting in the formation of TiO2@C nanoparticles. The structure of the resulting particles was elucidated by X-Ray diffraction, FTIR, UV-VIS and Raman spectroscopy as well as TEM microscopy. Preliminary results about the use of the TiO2@C particles as photocatalysts for the splitting of water are presented. They indicate that the presence of the C shell is responsible for a significant enhancement of the photocurrent.

  16. TiO2@C core-shell nanoparticles formed by polymeric nano-encapsulation.

    PubMed

    Vasei, Mitra; Das, Paramita; Cherfouth, Hayet; Marsan, Benoît; Claverie, Jerome P

    2014-01-01

    TiO2 semiconducting nanoparticles are known to be photocatalysts of moderate activity due to their high band-gap and high rate of electron-hole recombination. The formation of a shell of carbon around the core of TiO2, i.e., the formation of TiO2@C nanoparticles, is believed to partly alleviate these problems. It is usually achieved by a hydrothermal treatment in a presence of a sugar derivative. We present here a novel method for the formation of highly uniform C shell around TiO2 nanoparticles. For this purpose, TiO2 nanoparticles were dispersed in water using an oligomeric dispersant prepared by Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization. Then the nanoparticles were engaged into an emulsion polymerization of acrylonitrile, resulting in the formation of a shell of polyacrylonitrile (PAN) around each TiO2 nanoparticles. Upon pyrolysis, the PAN was transformed into carbon, resulting in the formation of TiO2@C nanoparticles. The structure of the resulting particles was elucidated by X-Ray diffraction, FTIR, UV-VIS and Raman spectroscopy as well as TEM microscopy. Preliminary results about the use of the TiO2@C particles as photocatalysts for the splitting of water are presented. They indicate that the presence of the C shell is responsible for a significant enhancement of the photocurrent. PMID:25072054

  17. TiO2 hollow spheres composed of highly crystalline nanocrystals exhibit superior lithium storage properties.

    PubMed

    Zhang, Genqiang; Wu, Hao Bin; Song, Taeseup; Paik, Ungyu; Lou, Xiong Wen David

    2014-11-10

    While the synthesis of TiO2 hollow structures is well-established, in most cases it is particularly difficult to control the crystallization of TiO2 in solution or by calcination. As a result, TiO2 hollow structures do not really exhibit enhanced lithium storage properties. Herein, we report a simple and cost-effective template-assisted method to synthesize anatase TiO2 hollow spheres composed of highly crystalline nanocrystals, in which carbonaceous (C) spheres are chosen as the removable template. The release of gaseous species from the combustion of C spheres may inhibit the growth of TiO2 crystallites so that instead small TiO2 nanocrystals are generated. The small size and high crystallinity of primary TiO2 nanoparticles and the high structural integrity of the hollow spheres gives rise to significant improvements in the cycling stability and rate performance of the TiO2 hollow spheres. PMID:25124735

  18. Improvement of Ultrasonic Disinfection Power Using TiO2 Photocatalyst

    NASA Astrophysics Data System (ADS)

    Dadjour, Mahmoud Farshbaf; Ogino, Chiaki; Matsumura, Susumu; Nakamura, Shinichi; Shimizu, Nobuaki

    2005-03-01

    The disinfection power of an ultrasonic system was enhanced using TiO2-photocatalyst in the irradiating solutions. Cultures of Legionella were used in the irradiation system with and without TiO2. A significant decrease in the concentration of viable cells was observed during irradiation in the presence of TiO2. The rate of cell killing was higher in the presence of TiO2 than it was with Al2O3, and was proportional to the amount of TiO2 used in the irradiating samples. There was no significant effect of cell concentration on the rate of cell killing in the range of 103 to 107 CFU/ml. Addition of OH radical scavengers such as glutathione, ascorbic acid and histidine to the irradiating solutions reduced the rate of disinfection, thus indicating the primary role of OH radicals in this process.

  19. Surface morphology of titanium dioxide (TiO2) nanoparticles on aluminum interdigitated device electrodes (IDEs)

    NASA Astrophysics Data System (ADS)

    Azizah, N.; Hashim, U.; Arshad, M. K. Md.; Gopinath, Subash C. B.; Nadzirah, Sh.; Farehanim, M. A.; Fatin, M. F.; Ruslinda, A. R.; Ayub, R. M.

    2016-07-01

    Titanium dioxide (TiO2) nanoparticles based Interdigitated Device Electrodes (IDEs) Nanobiosensor device was developed for intracellular biochemical detection. Fabrication and characterization of Scanning Electron Microscopy (SEM) using IDE nanocoated with TiO2 was studied in this paper. SEM analysis was carried out at 10 kV acceleration volatege and a 9.8 mA emission current to compare IDE with and without TiO2 on the surface area. The simple fabrication process, high sensitivity, and fast response of the TiO2 based IDEs facilitate their applications in a wide range of areas. The small size of semiconductor TiO2 based IDE for sensitive, label-free, real time detection of a wide range of biological species could be explored in vivo diagnostics and array-based screening.

  20. Surface properties and biocompatibility of nanostructured TiO2 film deposited by RF magnetron sputtering.

    PubMed

    Majeed, Asif; He, Jie; Jiao, Lingrui; Zhong, Xiaoxia; Sheng, Zhengming

    2015-01-01

    Nanostructured TiO2 films are deposited on a silicon substrate using 150-W power from the RF magnetron sputtering at working pressures of 3 to 5 Pa, with no substrate bias, and at 3 Pa with a substrate bias of -50 V. X-ray diffraction (XRD) analysis reveals that TiO2 films deposited on unbiased as well as biased substrates are all amorphous. Surface properties such as surface roughness and wettability of TiO2 films, grown in a plasma environment, under biased and unbiased substrate conditions are reported according to the said parameters of RF power and the working pressures. Primary rat osteoblasts (MC3T3-E1) cells have been cultured on nanostructured TiO2 films fabricated at different conditions of substrate bias and working pressures. The effects of roughness and hydrophilicity of nanostructured TiO2 films on cell density and cell spreading have been discussed.

  1. Dramatic activity of mixed-phase TiO2 photocatalyst synthesized by hydrothermal method

    NASA Astrophysics Data System (ADS)

    Li, Huiquan; Xu, Bolian; Fan, Yining

    2013-02-01

    The mixed-phase TiO2 photocatalysts with different anatase/rutile/brookite ratios and high specific surface area (157-218 m2/g) were prepared by hydrothermal method at 100 °C and the effect of rutile content in TiO2 on the BET surface area, light absorption and separation efficiency of photogenerated charge carriers was studied and correlated to the photocatalytic activity of TiO2. Rutile content increased from 0% to 100% by increasing the amount of TiCl4 in aqueous phase and the initial pH value of reaction solution played an important role in the phase composition of TiO2. The photocatalytic mechanism of mixed-phase TiO2 was discussed.

  2. Highly flexible coaxial nanohybrids made from porous TiO2 nanotubes.

    PubMed

    Wang, Daoai; Liu, Ying; Wang, Chengwei; Zhou, Feng; Liu, Weimin

    2009-05-26

    Anatase TiO(2), an n-type semiconductor, has gained considerable research interest over several decades due to its photocatalytic activity. Most recently, its properties for photoelectrical conversion in solar cells has been explored. Anodized TiO(2) nanotube (NT) arrays have been developed and possess improved photocatalytic, sensing, photoelectrolystic, and photovoltaic properties. The present work describes using TiO(2) as the building block to form ordered heterojunctions via simple electrodeposition with materials of potential interest, including conducting polymers (polypyrrole, poly(3-hexylthiophene)), inorganic semiconducting materials (CdS), and metals (Ni and Au, etc.). A key finding is that the synthesized TiO(2) NT-nanowires(nanotubes) nanohybrids are highly flexible after being peeled off from mother substrates, which is in contrast to more fragile pure TiO(2) NTs. These highly flexible coaxial nanohybrids are expected to have potent applications.

  3. Electrochromic properties of spray deposited TiO 2-doped WO 3 thin films

    NASA Astrophysics Data System (ADS)

    Patil, P. S.; Mujawar, S. H.; Inamdar, A. I.; Sadale, S. B.

    2005-08-01

    TiO 2-doped WO 3 thin films were deposited onto fluorine-doped tin oxide coated conducting glass substrates using spray pyrolysis technique at 525 °C. The volume percentage of TiO 2 dopant was varied from 13% to 38%. The thin film samples were transparent, uniform and strongly adherent to the substrates. Electrochromical properties of TiO 2-doped WO 3 thin films were studied with the help of cyclic voltammetry (CV), chronoamperometry (CA) and chronocoulometry (CC) techniques. It has been found that TiO 2 doping in WO 3 enhances its electrochromic performance. Colouration efficiency becomes almost double and samples exhibit increasingly high reversibility with TiO 2 doping concentrations, in the studied range.

  4. A simple hydrothermal preparation of TiO 2 nanomaterials using concentrated hydrochloric acid

    NASA Astrophysics Data System (ADS)

    Nguyen Phan, Thuy-Duong; Pham, Hai-Dinh; Viet Cuong, Tran; Jung Kim, Eui; Kim, Sunwook; Woo Shin, Eun

    2009-12-01

    A TiO 2 nanostructure was synthesized via a simple method using only concentrated hydrochloric acid as the morphological/crystallographic controlling agent. Microscopy images showed that the texture of the TiO 2 powder could be easily engineered and tuned by tailoring the HCl volume, creating cuboid, flower, cauliflower, and ball-shaped particles. Three-dimensional TiO 2 microparticles resulted from the self-assembly of nanostructured sub-units including nanocubes, nanoprisms, and nanorods. The crystalline anatase and rutile phases were also identified depending on the acidic medium. HCl played a key role in orchestrating the structures and morphologies of the TiO 2 nanoscale materials. The phase transformation and morphological changes were strongly related to the crystal growth mechanism of the TiO 2 nanostructure.

  5. Fabrication of TiO2 Colloidal Crystal Films and Characterization of Their Photocatalytic Properties

    SciTech Connect

    Huang, Wei; Wang, Feng; Wang, Wei

    2011-01-01

    We have studied hydrolysis of organic alkyltitanate compounds and optimized reaction condition for synthesis of monodisperse titania (TiO2 colloidal particles with controlled size from nanometer to submicron. The synthesized TiO2 colloidal particles were further surface-modified with hydrophobic silane coupling agent. With the monodisperse hydrophobic particles, we fabricated TiO2 colloidal crystal thin films through transferring self-assembled colloidal crystal monolayer from water surface onto solid substrates. The TiO2 colloidal crystal films exhibit enhanced interaction with visible light. Consequently, in comparison with plain TiO2 particle thin film, the thin film with colloidal crystal structure shows enhanced photocatalytic activity, as evaluated through photodegradation of organic dye methyl orange in solution under simulated solar light.

  6. The Effect of WO 3 on the Photocatalytic Activity of TiO 2

    NASA Astrophysics Data System (ADS)

    Do, Y. R.; Lee, W.; Dwight, K.; Wold, A.

    1994-01-01

    Samples of WO 3/TiO 2 mixed oxide powders were prepared by two methods: (1) the incipient wetness impregnation of an aqueous ammonia solution of H 2WO 4 onto TiO 2 (P25), followed by heat treatment and (2) the ultrasonic nebulization and flame hydrolysis of a mixed isopropanol solution of tungsten(V) pentaethoxide and titanium(IV) tetraisopropoxide. The photocatalytic activities of TiO 2-based catalysts were evaluated by the degradation of 1,4-dichlorobenzene (DCB). The addition of WO 3 to TiO 2 greatly increased its photocatalytic behavior. This may be related to an increase in the transfer of electrons from the TiO 2 to the outer system, via the formation of an intermediate W(V) species.

  7. Enhanced adsorption of atrazine from aqueous solution by molecularly imprinted TiO2 film

    NASA Astrophysics Data System (ADS)

    Zhang, Chunjing; Yan, Jinlong; Zhang, Chunxiao; Yang, Zhengpeng

    2012-07-01

    TiO2 film imprinted by atrazine molecule at the surface of quartz crystal was prepared using molecular imprinting and surface sol-gel process. The molecularly imprinted TiO2 film was characterized by scanning electron microscopy and cyclic voltammetry, and the atrazine adsorption was investigated by quartz crystal microbalance (QCM) technique. In comparison with non-imprinted TiO2 film, the molecularly imprinted TiO2 film exhibits high selectivity for atrazine, better reversibility and a much higher adsorption capacity for the target molecule, the adsorption equilibrium constant estimated from the in situ frequency measurement is about 6.7 × 104 M-1, which is thirteen times higher than that obtained on non-imprinted TiO2 film.

  8. Synthesis and Photocatalytic Activity of Anatase TiO2 Nanoparticles-coated Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Xie, Yi; Heo, Sung Hwan; Yoo, Seung Hwa; Ali, Ghafar; Cho, Sung Oh

    2010-03-01

    A simple and straightforward approach to prepare TiO2-coated carbon nanotubes (CNTs) is presented. Anatase TiO2 nanoparticles (NPs) with the average size ~8 nm were coated on CNTs from peroxo titanic acid (PTA) precursor even at low temperature of 100 °C. We demonstrate the effects of CNTs/TiO2 molar ratio on the adsorption capability and photocatalytic efficiency under UV-visible irradiation. The samples showed not only good optical absorption in visible range, but also great adsorption capacity for methyl orange (MO) dye molecules. These properties facilitated the great enhancement of photocatalytic activity of TiO2 NPs-coated CNTs photocatalysts. The TiO2 NPs-coated CNTs exhibited 2.45 times higher photocatalytic activity for MO degradation than that of pure TiO2.

  9. A Multiscale TiO2 Nanorod Array for Ultrasensitive Capture of Circulating Tumor Cells.

    PubMed

    Sun, Na; Li, Xinpan; Wang, Zhili; Zhang, Ruihua; Wang, Jine; Wang, Kewei; Pei, Renjun

    2016-05-25

    In this work, a uniform multiscale TiO2 nanorod array is fabricated to provide a "multi-scale interacting platform" for cell capture, which exhibits excellent capture specificity and sensitivity of the target cells after modification with bovine serum albumin (BSA) and DNA aptamer. After studying the capture performance of the BSA-aptamer TiO2 nanorod substrates and other nanostructured substrates, we can conclude that the multisacle TiO2 nanorod substrates could indeed effectively enhance the capture yields of target cancer cells. The capture yield of artificial blood samples on the BSA-aptamer TiO2 nanorod substrates is up to 85%-95%, revealing the potential application of the TiO2 nanorods on efficient and sensitive capture of rare circulating tumor cells. PMID:27176724

  10. Surface properties and biocompatibility of nanostructured TiO2 film deposited by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Majeed, Asif; He, Jie; Jiao, Lingrui; Zhong, Xiaoxia; Sheng, Zhengming

    2015-02-01

    Nanostructured TiO2 films are deposited on a silicon substrate using 150-W power from the RF magnetron sputtering at working pressures of 3 to 5 Pa, with no substrate bias, and at 3 Pa with a substrate bias of -50 V. X-ray diffraction (XRD) analysis reveals that TiO2 films deposited on unbiased as well as biased substrates are all amorphous. Surface properties such as surface roughness and wettability of TiO2 films, grown in a plasma environment, under biased and unbiased substrate conditions are reported according to the said parameters of RF power and the working pressures. Primary rat osteoblasts (MC3T3-E1) cells have been cultured on nanostructured TiO2 films fabricated at different conditions of substrate bias and working pressures. The effects of roughness and hydrophilicity of nanostructured TiO2 films on cell density and cell spreading have been discussed.

  11. [Mechanism and kinetics of phenol degradation by TiO2 photocatalytic combined technologies].

    PubMed

    Zhang, Yi; Huang, Ruo-Nan; Wang, Xiao-Min; Wang, Qi; Cong, Yan-Qing

    2013-02-01

    The combination H2O2, or electrical catalytic (EC) system with TiO2 photbcatalytic system for phenol degradation was investigated. The catalytic systems of TiO2/UV, H2O2/UV, TiO2/UV/H2O2 and TiO2/UV/EC were compared to investigate the phenol degradation mechanism and kinetic model. The degradation of phenol in TiO2/UV/H2O2 and TiO2/UV/EC system is more effective than that in TiO2/UV system. With the solution pH of 6, TiO, concentration of 0.2 g.L-1, UV illumination of 2 h, the photocatalysis removal efficiency of phenol reaches to 86%, if the current density of 12 mA.cm-2 is added, the removal efficiency of phenol could reach to 100%. The energy utilization in different catalytic systems was also compared. When phenol is degraded in 15 min, in TiO2/UV/EC system the energy utilization is the highest of 0.0306 g.(kW. h)-1 with the energy consumption of 0.0640 kW.h-1. It indicates that much more energy is used in TiO2/UV/EC system for phenol degradation. During the analysis of intermediate products in different catalysis systems, the first-order kinetic model of phenol degradation and intermediate products such as hydroquinone, catechol and benzoquinone formation were established. The kinetic model is validated the phenol degradation pathway in different catalysis systems, and also indicates the TiO2/UV/EC system could enhance phenol and intermediate products degradation.

  12. Comparing multistep immobilized metal affinity chromatography and multistep TiO2 methods for phosphopeptide enrichment.

    PubMed

    Yue, Xiaoshan; Schunter, Alissa; Hummon, Amanda B

    2015-09-01

    Phosphopeptide enrichment from complicated peptide mixtures is an essential step for mass spectrometry-based phosphoproteomic studies to reduce sample complexity and ionization suppression effects. Typical methods for enriching phosphopeptides include immobilized metal affinity chromatography (IMAC) or titanium dioxide (TiO2) beads, which have selective affinity and can interact with phosphopeptides. In this study, the IMAC enrichment method was compared with the TiO2 enrichment method, using a multistep enrichment strategy from whole cell lysate, to evaluate their abilities to enrich for different types of phosphopeptides. The peptide-to-beads ratios were optimized for both IMAC and TiO2 beads. Both IMAC and TiO2 enrichments were performed for three rounds to enable the maximum extraction of phosphopeptides from the whole cell lysates. The phosphopeptides that are unique to IMAC enrichment, unique to TiO2 enrichment, and identified with both IMAC and TiO2 enrichment were analyzed for their characteristics. Both IMAC and TiO2 enriched similar amounts of phosphopeptides with comparable enrichment efficiency. However, phosphopeptides that are unique to IMAC enrichment showed a higher percentage of multiphosphopeptides as well as a higher percentage of longer, basic, and hydrophilic phosphopeptides. Also, the IMAC and TiO2 procedures clearly enriched phosphopeptides with different motifs. Finally, further enriching with two rounds of TiO2 from the supernatant after IMAC enrichment or further enriching with two rounds of IMAC from the supernatant TiO2 enrichment does not fully recover the phosphopeptides that are not identified with the corresponding multistep enrichment. PMID:26237447

  13. Characteristics of ionic polymer-metal composite with chemically doped TiO2 particles

    NASA Astrophysics Data System (ADS)

    Jung, Youngsoo; Kim, Seong Jun; Kim, Kwang J.; Lee, Deuk Yong

    2011-12-01

    Many studies have investigated techniques to improve the bending performance of ionic polymer-metal composite (IPMC) actuators, including 'doping' of metal particles in the polymer membrane usually by means of physical processes. This study is mainly focused on the characterization of the physical, electrochemical and electromechanical properties of TiO2-doped ionic polymer membranes and IPMCs prepared by the sol-gel method, which results in a uniform distribution of the particles inside the polymer membrane. X-ray and UV-visible spectra indicate the presence of anatase-TiO2 in the modified membranes. TiO2-doped membranes (0.16 wt%) exhibit the highest level of water uptake. The glass transition temperature of these membranes, measured using differential scanning calorimetry (DSC), increases with the increase of the amount of TiO2 in the membrane. Dynamic mechanical analysis (DMA) demonstrated that the storage modulus of dried TiO2-doped ionic polymer membranes increases as the amount of TiO2 in the membrane increases, whereas the storage modulus of hydrated samples is closely related to the level of water uptake. Electrochemical impedance spectroscopy (EIS) shows that the conductivity of TiO2-doped membranes decreases with increasing TiO2 content in spite of an internal resistance drop in the samples. Above all, bending deflection of TiO2-doped IPMC decreased with higher TiO2 content in the membrane while the blocking force of each sample increased with the higher TiO2 content. Additionally, it was determined that the lifetime of IPMC is strongly dependent on the level of water uptake.

  14. Characterization and comparison of photocatalytic activities of prepared TiO2/graphene nanocomposites using titanium butoxide and TiO2 via microwave irradiation method

    NASA Astrophysics Data System (ADS)

    Darvishi, Motahareh; Seyed-Yazdi, Jamileh

    2016-08-01

    Photocatalysis based on TiO2 nanostructures with nanoscale hybridization of graphene, is a promising method to create highly conductive composite materials and surfaces with enhanced light absorption. In this study, graphite-oxide (GO) was produced by improved Hummers’ method followed by synthesis of TiO2/graphene nanocomposites. We used two precursors, titanium butoxide (TBO) and commercial TiO2, to produce nanocomposites in a mixture of water/ethanol and graphene-oxide, for hydrolysis of titania precursors on graphene-oxide sheets resulting in the formation of nanocomposites. Microwave irradiation is used to reduce graphene-oxide into graphene. TiO2/graphene nanocomposites in both cases demonstrate enhancement of overall photocatalytic activity compared with titania precursors which was examined by degradation of methylene blue (MB). In this study, nanocomposites were synthesized with different mass ratios of GO compare to titania precursors (i.e. GO: 1, 5 and 8 wt%). Photocatalytic performance increased with the increasing content of graphene in both cases. The reduction rate of MB for TiO2 was 62% and for TiO2/graphene (TiO2/G) (GO: 8 wt%) was 85% after 90 min, and for TBO and TBO/G (GO: 8 wt%) was 3% and 99.95%, respectively. SEM, XRD, Fourier transform infrared and UV–vis spectroscopy were used to characterize the synthesized nanocomposites. FTIR analysis demonstrates the formation of Ti–O–C bonds and confirms the formation of nanocomposites made of graphene and titania nanoparticles.

  15. Characterization and comparison of photocatalytic activities of prepared TiO2/graphene nanocomposites using titanium butoxide and TiO2 via microwave irradiation method

    NASA Astrophysics Data System (ADS)

    Darvishi, Motahareh; Seyed-Yazdi, Jamileh

    2016-08-01

    Photocatalysis based on TiO2 nanostructures with nanoscale hybridization of graphene, is a promising method to create highly conductive composite materials and surfaces with enhanced light absorption. In this study, graphite-oxide (GO) was produced by improved Hummers’ method followed by synthesis of TiO2/graphene nanocomposites. We used two precursors, titanium butoxide (TBO) and commercial TiO2, to produce nanocomposites in a mixture of water/ethanol and graphene-oxide, for hydrolysis of titania precursors on graphene-oxide sheets resulting in the formation of nanocomposites. Microwave irradiation is used to reduce graphene-oxide into graphene. TiO2/graphene nanocomposites in both cases demonstrate enhancement of overall photocatalytic activity compared with titania precursors which was examined by degradation of methylene blue (MB). In this study, nanocomposites were synthesized with different mass ratios of GO compare to titania precursors (i.e. GO: 1, 5 and 8 wt%). Photocatalytic performance increased with the increasing content of graphene in both cases. The reduction rate of MB for TiO2 was 62% and for TiO2/graphene (TiO2/G) (GO: 8 wt%) was 85% after 90 min, and for TBO and TBO/G (GO: 8 wt%) was 3% and 99.95%, respectively. SEM, XRD, Fourier transform infrared and UV-vis spectroscopy were used to characterize the synthesized nanocomposites. FTIR analysis demonstrates the formation of Ti-O-C bonds and confirms the formation of nanocomposites made of graphene and titania nanoparticles.

  16. Synthesis, characterization and photocatalytic activity of fluorine doped TiO2 nanoflakes synthesized using solid state reaction method.

    PubMed

    Umadevi, M; Parimaladevi, R; Sangari, M

    2014-01-01

    Fluorine doped TiO2 were synthesized by solid state reaction method. Optical and structural properties of fluorine doped TiO2 were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, UV-vis diffusion reflectance spectroscopy and scanning electron microscopic techniques. The prepared fluorine doped TiO2 was smaller in size with respect to pure TiO2 and it is tetragonal in crystalline structure. Nanoflakes like structure of pure and fluorine doped TiO2 was confirmed from SEM image. Fluorine doped TiO2 shows smaller band gap, high strain and dislocation density when compared to pure TiO2. It also has higher photocatalytic activity with respect to pure TiO2.

  17. First-principles calculations of high-pressure phase transition of TiO2 during decompression: From baddeleyite-type TiO2 to α-PbO2-type TiO2

    NASA Astrophysics Data System (ADS)

    Murata, Hidenobu; Taniguchi, Takashi; Tanaka, Isao

    2016-10-01

    First-principles calculations were used to investigate the phase transition from baddeleyite-type to α-PbO2-type TiO2 during decompression. An intermediate structure was found, and its space group is Pbc21, which is polarized along [001]. The phase transition was mainly caused by oxygen diffusion, which has low activation energy for the phase transition. The activation energy increased as the pressure decreased. These results suggest that rapid decompression and preventing oxygen diffusion would be an effective way of recovering baddeleyite-type TiO2.

  18. XAS study of TiO2-based nanomaterials

    NASA Astrophysics Data System (ADS)

    Schneider, K.; Zajac, D.; Sikora, M.; Kapusta, Cz.; Michalow-Mauke, K.; Graule, Th.; Rekas, M.

    2015-07-01

    X-Ray Absorption Spectroscopy studies of the W (0-1 at% W) and Mo-doped TiO2 (0-1 at% Mo) nanoparticle specimens at the K edges of titanium and molybdenum as well as at the L2 L3 edges of tungsten are presented. The materials were prepared with Flame Spray Synthesis process by oxidation of metal-organic precursors. The Ti:K edge spectra in the XANES range show pre-edge and post-edge features characteristic for anatase. A decrease of the amplitude of the EXAFS function with doping is observed and attributed to a softening of the crystal lattice. The Mo EXAFS functions show a considerable decrease of the second-neighbour-shell peak with increasing Mo content, which is attributed to an increased number of cation vacancies. For tungsten a less pronounced effect is observed. The Mo and W XANES spectra do not show noticeable changes with doping level, which indicates their unchanged oxidation states.

  19. [Background irradiated photocatalysis of TiO2 thin films].

    PubMed

    Cen, Ji-wen; Li, Xin-jun; Liang, Yuan-yuan; He, Ming-xing; Zheng, Shao-jian; Feng, Man-zhi

    2005-05-01

    In terms of the UV irradiating directions, photocatalysis with TiO2 thin films can be divided into two types, the background irradiated photocatalysis and the foreground irradiated one. Comparatively, background irradiated photocatalysis has an advantage of avoiding the UV light attenuation which foreground irradiated one suffers when the light is going through the solution. In this article, the influence of the thickness of the films, the wavelength of light source and non-uninformly doping with V on the photocatalytic efficiency of the catalyst in case of background irradiated photocatalysis is investigated, and simultaneously it is compared with foreground irradiated one. The results show that in case of background irradiated photocatalysis there is an optimal thickness of the film according to the wavelength of the light source that is limited in the range of 300 nm to 388 nm, which is quite different from foreground irradiated one. But in both cases, the catalyst's photocatalytic activities are improved by non-uniformly doped with V.

  20. Coupled cluster calculations on TiO2 nanoclusters

    SciTech Connect

    Berardo, Enrico; Hu, Hanshi; Kowalski, Karol; Zwijnenburg, Martijn A.

    2013-08-14

    The excitation energies of the four lowest-lying singlet excited states of the TiO2 Ti2O4 and Ti3O6 clusters are calculated by a variety of different Equation-of-Motion Coupled Cluster (EOM-CC) approaches in order to obtain benchmark values for the optical excitations of titanium dioxide clusters. More specifically we investigate what is the effect of the inclusion of triple excitations "triples" in the (EOM-)CC scheme on the calculated excited states of those clusters. While for the monomer and dimer the inclusion of triples causes only a rigid shift in the excitation energies, in the case of the trimer the crossing of the interested states is observed. Coupled cluster approaches where triples are treated perturbatively were found to offer no advantage over EOM-CCSD, whereas the active-space methods (EOM-CCSDt(II/I)) proved to yield results very close to the full EOM-CCSDT, but at a much lower computational cost.

  1. An in-situ synthesis of Ag/AgCl/TiO2/hierarchical porous magnesian material and its photocatalytic performance

    NASA Astrophysics Data System (ADS)

    Yang, Lu; Wang, Fazhou; Shu, Chang; Liu, Peng; Zhang, Wenqin; Hu, Shuguang

    2016-02-01

    The absorption ability and photocatalytic activity of photocatalytic materials play important roles in improving the pollutants removal effects. Herein, we reported a new kind of photocatalytic material, which was synthesized by simultaneously designing hierarchical porous magnesian (PM) substrate and TiO2 catalyst modification. Particularly, PM substrate could be facilely prepared by controlling its crystal phase (Phase 5, Mg3Cl(OH)5·4H2O), while Ag/AgCl particles modification of TiO2 could be achieved by in situ ion exchange between Ag+ and above crystal Phase. Physiochemical analysis shows that Ag/AgCl/TiO2/PM material has higher visible and ultraviolet light absorption response, and excellent gas absorption performance compared to other controls. These suggested that Ag/AgCl/TiO2/PM material could produce more efficient photocatalytic effects. Its photocatalytic reaction rate was 5.21 and 30.57 times higher than that of TiO2/PM and TiO2/imporous magnesian substrate, respectively. Thus, this material and its intergration synthesis method could provide a novel strategy for high-efficiency application and modification of TiO2 photocatalyst in engineering filed.

  2. An in-situ synthesis of Ag/AgCl/TiO2/hierarchical porous magnesian material and its photocatalytic performance

    PubMed Central

    Yang, Lu; Wang, Fazhou; Shu, Chang; Liu, Peng; Zhang, Wenqin; Hu, Shuguang

    2016-01-01

    The absorption ability and photocatalytic activity of photocatalytic materials play important roles in improving the pollutants removal effects. Herein, we reported a new kind of photocatalytic material, which was synthesized by simultaneously designing hierarchical porous magnesian (PM) substrate and TiO2 catalyst modification. Particularly, PM substrate could be facilely prepared by controlling its crystal phase (Phase 5, Mg3Cl(OH)5·4H2O), while Ag/AgCl particles modification of TiO2 could be achieved by in situ ion exchange between Ag+ and above crystal Phase. Physiochemical analysis shows that Ag/AgCl/TiO2/PM material has higher visible and ultraviolet light absorption response, and excellent gas absorption performance compared to other controls. These suggested that Ag/AgCl/TiO2/PM material could produce more efficient photocatalytic effects. Its photocatalytic reaction rate was 5.21 and 30.57 times higher than that of TiO2/PM and TiO2/imporous magnesian substrate, respectively. Thus, this material and its intergration synthesis method could provide a novel strategy for high-efficiency application and modification of TiO2 photocatalyst in engineering filed. PMID:26883972

  3. An in-situ synthesis of Ag/AgCl/TiO2/hierarchical porous magnesian material and its photocatalytic performance.

    PubMed

    Yang, Lu; Wang, Fazhou; Shu, Chang; Liu, Peng; Zhang, Wenqin; Hu, Shuguang

    2016-02-17

    The absorption ability and photocatalytic activity of photocatalytic materials play important roles in improving the pollutants removal effects. Herein, we reported a new kind of photocatalytic material, which was synthesized by simultaneously designing hierarchical porous magnesian (PM) substrate and TiO2 catalyst modification. Particularly, PM substrate could be facilely prepared by controlling its crystal phase (Phase 5, Mg3Cl(OH)5 · 4H2O), while Ag/AgCl particles modification of TiO2 could be achieved by in situ ion exchange between Ag(+) and above crystal Phase. Physiochemical analysis shows that Ag/AgCl/TiO2/PM material has higher visible and ultraviolet light absorption response, and excellent gas absorption performance compared to other controls. These suggested that Ag/AgCl/TiO2/PM material could produce more efficient photocatalytic effects. Its photocatalytic reaction rate was 5.21 and 30.57 times higher than that of TiO2/PM and TiO2/imporous magnesian substrate, respectively. Thus, this material and its intergration synthesis method could provide a novel strategy for high-efficiency application and modification of TiO2 photocatalyst in engineering filed.

  4. A general templated method to homogeneous and composition-tunable hybrid TiO2 nanocomposite fibers.

    PubMed

    Xu, Ximing; Li, Xiaona; Lin, Pingyong; Chen, Ting; Yuan, Rusheng; Ding, Zhengxin; Wu, Ling; Wang, Xuxu; Li, Zhaohui

    2011-03-01

    Sequential impregnations of metal ions and titanium tetraisopropoxide (TTIP) into activated carbon fibers (ACF) followed by a solvothermal treatment has been found to be a general method in the preparations of homogeneous and composition-tunable hybrid TiO(2) hierarchical nanocomposite fibers like WO(3)/TiO(2), Fe(2)O(3)/TiO(2) and SnO(2)/TiO(2). PMID:21225065

  5. An easy-to-fabricate low-temperature TiO2 electron collection layer for high efficiency planar heterojunction perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Conings, B.; Baeten, L.; Jacobs, T.; Dera, R.; D'Haen, J.; Manca, J.; Boyen, H.-G.

    2014-08-01

    Organometal trihalide perovskite solar cells arguably represent the most auspicious new photovoltaic technology so far, as they possess an astonishing combination of properties. The impressive and brisk advances achieved so far bring forth highly efficient and solution processable solar cells, holding great promise to grow into a mature technology that is ready to be embedded on a large scale. However, the vast majority of state-of-the-art perovskite solar cells contains a dense TiO2 electron collection layer that requires a high temperature treatment (>450 °C), which obstructs the road towards roll-to-roll processing on flexible foils that can withstand no more than ˜150 °C. Furthermore, this high temperature treatment leads to an overall increased energy payback time and cumulative energy demand for this emerging photovoltaic technology. Here we present the implementation of an alternative TiO2 layer formed from an easily prepared nanoparticle dispersion, with annealing needs well within reach of roll-to-roll processing, making this technology also appealing from the energy payback aspect. Chemical and morphological analysis allows to understand and optimize the processing conditions of the TiO2 layer, finally resulting in a maximum obtained efficiency of 13.6% for a planar heterojunction solar cell within an ITO/TiO2/CH3NH3PbI3-xClxpoly(3-hexylthiophene)/Ag architecture.

  6. Combinatorial solar cell libraries for the investigation of different metal back contacts for TiO2-Cu2O hetero-junction solar cells.

    PubMed

    Rühle, S; Barad, H N; Bouhadana, Y; Keller, D A; Ginsburg, A; Shimanovich, K; Majhi, K; Lovrincic, R; Anderson, A Y; Zaban, A

    2014-04-21

    Here we present a comprehensive investigation of TiO2-Cu2O hetero-junction solar cells with different back contacts (Au, ITO, Cu or Ag). Combinatorial hetero-junction libraries consisting of a linear TiO2 thickness gradient produced by spray pyrolysis and a bell shaped Cu2O profile synthesized by pulsed laser deposition were chosen to investigate the impact of the two metal oxide layer thicknesses. The back contacts were deposited as round patches onto a grid of 13 × 13 points, 169 contacts for each contact material, forming a library containing 4 × 13 × 13 = 676 back contacts. Each back contact represented a solar cell with an individual TiO2 and Cu2O thickness. I-V measurements show that all four materials provide an ohmic contact and that the open circuit voltage of ∼300 mV is rather independent of both layer thicknesses and contact material. The size of the Cu2O crystals drastically decreases with distance from the center of deposition, which leads to a drastic increase of series resistance when the crystal size is <50 nm. PMID:24615619

  7. Combinatorial solar cell libraries for the investigation of different metal back contacts for TiO2-Cu2O hetero-junction solar cells.

    PubMed

    Rühle, S; Barad, H N; Bouhadana, Y; Keller, D A; Ginsburg, A; Shimanovich, K; Majhi, K; Lovrincic, R; Anderson, A Y; Zaban, A

    2014-04-21

    Here we present a comprehensive investigation of TiO2-Cu2O hetero-junction solar cells with different back contacts (Au, ITO, Cu or Ag). Combinatorial hetero-junction libraries consisting of a linear TiO2 thickness gradient produced by spray pyrolysis and a bell shaped Cu2O profile synthesized by pulsed laser deposition were chosen to investigate the impact of the two metal oxide layer thicknesses. The back contacts were deposited as round patches onto a grid of 13 × 13 points, 169 contacts for each contact material, forming a library containing 4 × 13 × 13 = 676 back contacts. Each back contact represented a solar cell with an individual TiO2 and Cu2O thickness. I-V measurements show that all four materials provide an ohmic contact and that the open circuit voltage of ∼300 mV is rather independent of both layer thicknesses and contact material. The size of the Cu2O crystals drastically decreases with distance from the center of deposition, which leads to a drastic increase of series resistance when the crystal size is <50 nm.

  8. The preparation, surface structure, zeta potential, surface charge density and photocatalytic activity of TiO2 nanostructures of different shapes

    NASA Astrophysics Data System (ADS)

    Grover, Inderpreet Singh; Singh, Satnam; Pal, Bonamali

    2013-09-01

    Titania based nanocatalysts such as sodium titanates of different morphology having superior surface properties are getting wide importance in photocatalysis research. Despite having sodium (Na) contents and its high temperature synthesis (that generally deteriorate the photoreactivity), these Na-titanates often exhibit better photoactivity than P25-TiO2 catalyst. Hence, this work demonstrated the influence of crystal structure, BET surface area, surface charge, zeta potential (ζ) and metal loading on the photocatalytic activity of as-prepared sodium titanate nanotube (TNT) and titania nanorod (TNR). Straw like hollow orthorhombic-TNT (Na2Ti2O5·H2O) particles (W = 9-12 nm and L = 82-115 nm) and rice like pure anatase-TNR particles (W = 8-13 nm and L = 81-134 nm) are obtained by the hydrothermal treatment of P25-TiO2 with NaOH, which in fact, altered the net surface charge of TNT and TNR particles. The observed ζ = -2.82 (P25-TiO2), -13.5 (TNT) and -22.5 mV (TNR) are significantly altered by the Ag and Cu deposition. It has been found here that TNT displayed best photocatalytic activity for the imidacloprid insecticide (C9H10ClN5O2) degradation to CO2 formation under UV irradiation because of its largest surface area 176 m2 g-1 among the catalysts studied.

  9. Graphene Oxide Modified TiO2 Micro Whiskers and Their Photo Electrochemical Performance.

    PubMed

    Rambabu, Y; Jaiswal, Manu; Roy, Somnath C

    2016-05-01

    Harnessing the solar energy and producing clean fuel hydrogen through efficient photo-electrochemical water splitting has remained one of the most challenging endeavors in materials science. The core problem is to develop a suitable photo-catalyst material that absorbs a significant part of the solar spectrum and produces electron-hole pairs that can be easily separated without recombination. In the recent times, the composite of Titanium dioxide with graphene have been investigated to explore the advantages of both class of materials. Here we report on the photo-electrochemical properties of reduced graphene oxide functionalised TiO2 whiskers. The TiO2 whiskers are obtained from potassium titanium oxide (KTi8O16) synthesized through hydrothermal technique followed by ion exchange method and heat treatment. Graphene oxide was deposited on the as prepared TiO2 whiskers using hydrothermal method. As formed samples were characterized by Raman spectroscopy to confirm the presence of reduced graphene oxide (RGO) attached to TiO2 whiskers. Comparative photo electrochemical studies were carried out for TiO2 and reduced graphene oxide modified TiO2 whiskers. Among these, RGO modified TiO2 whiskers show significantly higher photo current density possibly due to enhancement in charge separation ability and longer electron life times. PMID:27483830

  10. Visible-light responsive dye-modified TiO 2 photocatalyst

    NASA Astrophysics Data System (ADS)

    Jiang, Dong; Xu, Yao; Wu, Dong; Sun, Yuhan

    2008-03-01

    A series of dye-modified TiO 2 photocatalysts were synthesized using dye Chrysoidine G (CG), tolylene-2,4-diisocyanate (TDI), and commercial TiO 2 (Degussa P25) as starting materials. TDI was used as a bridging molecule whose two -NCO groups reacted with Ti-OH of TiO 2 and -NH 2 groups of CG, respectively. As a result, special organic complexes were formed on the TiO 2 surface via stable π-conjugated chemical bonds between TiO 2 and dye molecules, confirmed by FT-IR, XPS, and UV-vis spectra. Due to the existence of π-conjugated surface organic complexes, the as-synthesized photocatalysts showed a great improvement in visible absorption (400-550 nm). Methylene blue, as a photodegradation target, was used to evaluate the photocatalytic performance, and the dye-modified TiO 2 exhibited much better activity under the visible light irradiation than bare TiO 2.

  11. Electrospinning Synthesis and Photocatalytic Activity of Mesoporous TiO2 Nanofibers

    PubMed Central

    Li, Jing; Qiao, Hui; Du, Yuanzhi; Chen, Chen; Li, Xiaolin; Cui, Jing; Kumar, Dnt; Wei, Qufu

    2012-01-01

    Titanium dioxide (TiO2) nanofibers in the anatase structure were successfully prepared via electrospinning technique followed by calcination process. The morphologies, crystal structure, surface area, and the photocatalytic activity of resulting TiO2 nanofibers were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen sorption, and UV-vis spectroscopy. The results revealed that calcination temperature had greatly influenced the morphologies of TiO2 nanofibers, but no obvious effect was noticed on the crystal structure of TiO2 nanofibers. The photocatalytic properties of TiO2 nanofibers were evaluated by photocatalytic degradation of rhodamine B (RhB) in water under visible light irradiation. It was observed that TiO2 nanofibers obtained by calcination at 500°C for 3 hours exhibited the most excellent photocatalytic activity. We present a novel and simple method to fabricate TiO2 nanofibers with high-photocatalytic activity. PMID:22619598

  12. Water-dispersible TiO2 nanoparticles via a biphasic solvothermal reaction method

    NASA Astrophysics Data System (ADS)

    Mohan, Rajneesh; Drbohlavova, Jana; Hubalek, Jaromir

    2013-12-01

    A biphasic solvothermal reaction method has been used for the synthesis of TiO2 nanoparticles (NPs). In this method, hydrolysis and nucleation occur at the interface of organic phase (titanium (IV) n-propoxide and stearic acid dissolved in toluene) and water phase ( tert-butylamine dissolved in water) resulting in the nucleation of the stearic acid-capped TiO2 NPs. These NPs are hydrophilic due to hydrophobic stearic acid ligands and could be dispersed in toluene, but not in water. These stearic acid-capped TiO2 NPs were surface-modified with 2,3-dimercaptosuccinic acid (DMSA) in order to make them water soluble. The resultant TiO2 NPs were easily redispersed in water without any noticeable aggregation. The Rietveld profile fitting of X-ray diffraction (XRD) pattern of the TiO2 NPs revealed highly crystalline anatase structure. The average crystallite size of TiO2 NPs was calculated to be 6.89 nm, which agrees with TEM results. These results have important implications for the use of TiO2 in biomedical, environmental, and industrial applications.

  13. Self-cleaning and superhydrophilic wool by TiO2/SiO2 nanocomposite

    NASA Astrophysics Data System (ADS)

    Pakdel, Esfandiar; Daoud, Walid A.; Wang, Xungai

    2013-06-01

    Wool fabrics were functionalised using TiO2 and TiO2/SiO2 nanocomposites through a low-temperature sol-gel method. Titanium terta isopropoxide (TTIP) and tetra ethylorthosilicate (TEOS) were employed as precursors of TiO2 and SiO2, respectively. Nanocomposite sols were devised based on three molar ratio percentages of TiO2/SiO2 70:30, 50:50, and 30:70 to investigate the role of each component. The self-cleaning and hydrophilicity of wool fabrics were analysed based on the removal of coffee stain under UV and water droplet contact angle measurements, respectively. It was observed that applying TiO2/SiO2 50:50 and 30:70 sols to wool rendered the fabric superhydrophilic. Fabrics functionalised with TiO2/SiO2 30:70 showed the highest efficiency in stain removal, followed by samples functionalised with TiO2/SiO2 50:50.

  14. Enhanced photocatalytic activity of supported TiO2 by selective surface modification of zeolite Y

    NASA Astrophysics Data System (ADS)

    Guesh, Kiros; Márquez-Álvarez, Carlos; Chebude, Yonas; Díaz, Isabel

    2016-08-01

    Zeolite Y was treated using ammonium acetate and ammonium fluoride sequentially. As a consequence the aluminum from the surface was selectively removed. Then, loading with TiO2 (20 wt%) led to a final photocatalyst. The samples were characterized by X-ray diffraction (XRD), elemental analysis (ICP-OES), N2 adsorption, diffuse reflectance UV-vis spectroscopy (DRS), photoluminescence spectroscopy (PL), and X-ray photoelectron spectroscopy (XPS). It was found that 50% of the Al atoms were removed from the surface of the zeolite without affecting the framework structure. The TiO2/treated zeolite sample yielded 92% photocatalytic degradation of 10 ppm methyl orange (MO), a model pollutant, while the TiO2/parent zeolite converted only 7.6%. The mass normalized turnover rate (TORm) of the treated zeolite loaded with TiO2 was about 12 times higher than that of the parent zeolite loaded with the same amount of TiO2 precursor. This higher photocatalytic activity of the TiO2 supported on treated zeolite can be attributed to a more efficient interaction of the TiO2 with the zeolite leading to higher adsorption capacity. Reusability of the photocatalysts was assessed by performing three consecutive reaction cycles that showed no significant loss of photocatalytic activity.

  15. Inverted polymer solar cells with employing of electrochemical-anodizing synthesized TiO2 nanotubes

    NASA Astrophysics Data System (ADS)

    Mehdi, Ahmadi; Sajjad Rashidi, Dafeh; Hamed, Fatehy

    2016-04-01

    An inverted structure of polymer solar cells based on Poly(3-hexylthiophene)(P3HT):[6-6] Phenyl-(6) butyric acid methyl ester (PCBM) with using thin films of TiO2 nanotubes and nanoparticles as an efficient cathode buffer layer is developed. A total of three cells employing TiO2 thin films with different thickness values are fabricated. Two cells use layers of TiO2 nanotubes prepared via self-organized electrochemical-anodizing leading to thickness values of 203 and 423.7 nm, while the other cell uses only a simple sol-gel synthesized TiO2 thin film of nanoparticles with a thickness of 100 nm as electron transport layer. Experimental results demonstrate that TiO2 nanotubes with these thickness values are inefficient as the power conversion efficiency of the cell using 100-nm TiO2 thin film is 1.55%, which is more than the best power conversion efficiency of other cells. This can be a result of the weakness of the electrochemical anodizing method to grow nanotubes with lower thickness values. In fact as the TiO2 nanotubes grow in length the series resistance (R s) between the active polymer layer and electron transport layer increases, meanwhile the fill factor of cells falls dramatically which finally downgrades the power conversion efficiency of the cells as the fill factor falls.

  16. Fullerene C70 decorated TiO2 nanowires for visible-light-responsive photocatalyst

    NASA Astrophysics Data System (ADS)

    Cho, Er-Chieh; Ciou, Jing-Hao; Zheng, Jia-Huei; Pan, Job; Hsiao, Yu-Sheng; Lee, Kuen-Chan; Huang, Jen-Hsien

    2015-11-01

    In this study, we have synthesized C60 and C70-modified TiO2 nanowire (NW) through interfacial chemical bonding. The results indicate that the fullerenes (C60 and C70 derivatives) can act as sinks for photogenerated electrons in TiO2, while the fullerene/TiO2 is illuminated under ultraviolet (UV) light. Therefore, in comparison to the pure TiO2 NWs, the modified TiO2 NWs display a higher photocatalytic activity under UV irradiation. Moreover, the fullerenes also can function as a sensitizer to TiO2 which expand the utilization of solar light from UV to visible light. The results reveal that the C70/TiO2 NWs show a significant photocatalytic activity for degradation of methylene blue (MB) in visible light region. To better understand the mechanism responsible for the effect of fullerenes on the photocatalytic properties of TiO2, the electron only devices and photoelectrochemical cells based on fullerenes/TiO2 are also fabricated and evaluated.

  17. Simplified TiO2 force fields for studies of its interaction with biomolecules

    NASA Astrophysics Data System (ADS)

    Luan, Binquan; Huynh, Tien; Zhou, Ruhong

    2015-06-01

    Engineered TiO2 nanoparticles have been routinely applied in nanotechnology, as well as in cosmetics and food industries. Despite active experimental studies intended to clarify TiO2's biological effects, including potential toxicity, the relation between experimentally inferred nanotoxicity and industry standards for safely applying nanoparticles remains somewhat ambiguous with justified concerns. Supplemental to experiments, molecular dynamics simulations have proven to be efficacious in investigating the molecular mechanism of a biological process occurring at nanoscale. In this article, to facilitate the nanotoxicity and nanomedicine research related to this important metal oxide, we provide a simplified force field, based on the original Matsui-Akaogi force field but compatible to the Lennard-Jones potentials normally used in modeling biomolecules, for simulating TiO2 nanoparticles interacting with biomolecules. The force field parameters were tested in simulating the bulk structure of TiO2, TiO2 nanoparticle-water interaction, as well as the adsorption of proteins on the TiO2 nanoparticle. We demonstrate that these simulation results are consistent with experimental data/observations. We expect that simulations will help to better understand the interaction between TiO2 and molecules.

  18. Controllable atomic layer deposition of one-dimensional nanotubular TiO2

    NASA Astrophysics Data System (ADS)

    Meng, Xiangbo; Banis, Mohammad Norouzi; Geng, Dongsheng; Li, Xifei; Zhang, Yong; Li, Ruying; Abou-Rachid, Hakima; Sun, Xueliang

    2013-02-01

    This study aimed at synthesizing one-dimensional (1D) nanostructures of TiO2 using atomic layer deposition (ALD) on anodic aluminum oxide (AAO) templates and carbon nanotubes (CNTs). The precursors used are titanium tetraisopropoxide (TTIP, Ti(OCH(CH3)2)4) and deionized water. It was found that the morphologies and structural phases of as-deposited TiO2 are controllable through adjusting cycling numbers of ALD and growth temperatures. Commonly, a low temperature (150 °C) produced amorphous TiO2 while a high temperature (250 °C) led to crystalline anatase TiO2 on both AAO and CNTs. In addition, it was revealed that the deposition of TiO2 is also subject to the influences of the applied substrates. The work well demonstrated that ALD is a precise route to synthesize 1D nanostructures of TiO2. The resultant nanostructured TiO2 can be important candidates in many applications, such as water splitting, solar cells, lithium-ion batteries, and gas sensors.

  19. Heterostructured TiO2 Nanorod@Nanobowl Arrays for Efficient Photoelectrochemical Water Splitting.

    PubMed

    Wang, Wenhui; Dong, Jingya; Ye, Xiaozhou; Li, Yang; Ma, Yurong; Qi, Limin

    2016-03-01

    Heterostructured TiO2 nanorod@nanobowl (NR@NB) arrays consisting of rutile TiO2 nanorods grown on the inner surface of arrayed anatase TiO2 nanobowls are designed and fabricated as a new type of photoanodes for photoelectrochemical (PEC) water splitting. The unique heterostructures with a hierarchical architecture are readily fabricated by interfacial nanosphere lithography followed by hydrothermal growth. Owing to the two-dimensionally arrayed structure of anatase nanobowls and the nearly radial alignment of rutile nanorods, the TiO2 NR@NB arrays provide multiple scattering centers and hence exhibit an enhanced light harvesting ability. Meanwhile, the large surface area of the NR@NB arrays enhances the contact with the electrolyte while the nanorods offer direct pathways for fast electron transfer. Moreover, the rutile/anatase phase junction in the NR@NB heterostructure improves charge separation because of the facilitated electron transfer. Accordingly, the PEC measurements of the TiO2 NR@NB arrays on the fluoride-doped tin oxide (FTO) substrate show significantly enhanced photocatalytic properties for water splitting. Under AM1.5G solar light irradiation, the unmodified TiO2 NR@NB array photoelectrode yields a photocurrent density of 1.24 mA cm(-2) at 1.23 V with respect to the reversible hydrogen electrode, which is almost two times higher than that of the TiO2 nanorods grown directly on the FTO substrate. PMID:26779803

  20. Graphene Oxide Modified TiO2 Micro Whiskers and Their Photo Electrochemical Performance.

    PubMed

    Rambabu, Y; Jaiswal, Manu; Roy, Somnath C

    2016-05-01

    Harnessing the solar energy and producing clean fuel hydrogen through efficient photo-electrochemical water splitting has remained one of the most challenging endeavors in materials science. The core problem is to develop a suitable photo-catalyst material that absorbs a significant part of the solar spectrum and produces electron-hole pairs that can be easily separated without recombination. In the recent times, the composite of Titanium dioxide with graphene have been investigated to explore the advantages of both class of materials. Here we report on the photo-electrochemical properties of reduced graphene oxide functionalised TiO2 whiskers. The TiO2 whiskers are obtained from potassium titanium oxide (KTi8O16) synthesized through hydrothermal technique followed by ion exchange method and heat treatment. Graphene oxide was deposited on the as prepared TiO2 whiskers using hydrothermal method. As formed samples were characterized by Raman spectroscopy to confirm the presence of reduced graphene oxide (RGO) attached to TiO2 whiskers. Comparative photo electrochemical studies were carried out for TiO2 and reduced graphene oxide modified TiO2 whiskers. Among these, RGO modified TiO2 whiskers show significantly higher photo current density possibly due to enhancement in charge separation ability and longer electron life times.

  1. Thiourea-Modified TiO2 Nanorods with Enhanced Photocatalytic Activity.

    PubMed

    Wu, Xiaofeng; Fang, Shun; Zheng, Yang; Sun, Jie; Lv, Kangle

    2016-02-01

    Semiconductor TiO2 photocatalysis has attracted much attention due to its potential application in solving the problems of environmental pollution. In this paper, thiourea (CH4N2S) modified anatase TiO2 nanorods were fabricated by calcination of the mixture of TiO2 nanorods and thiourea at 600 °C for 2 h. It was found that only N element was doped into the lattice of TiO2 nanorods. With increasing the weight ratio of thiourea to TiO2 (R) from 0 to 8, the light-harvesting ability of the photocatalyst steady increases. Both the crystallization and photocatalytic activity of TiO2 nanorods increase first and then decrease with increase in R value, and R2 sample showed the highest crystallization and photocatalytic activity in degradation of Brilliant Red X3B (X3B) and Rhodamine B (RhB) dyes under visible light irradiation (λ > 420 nm). The increased visible-light photocatalytic activity of the prepared N-doped TiO2 nanorods is due to the synergistic effects of the enhanced crystallization, improved light-harvesting ability and reduced recombination rate of photo-generated electron-hole pairs. Note that the enhanced visible photocatalytic activity of N-doped nanorods is not based on the scarification of their UV photocatalytic activity.

  2. N-doped TiO2 Prepared by RF DBD Plasma

    NASA Astrophysics Data System (ADS)

    Sun, Zhi-Guang; Liu, Jing-Lin; Li, Xiao-Song; Zhai, Zhao-Jun; Zhu, Ai-Min; Laboratory of Plasma Physical Chemistry Team

    2014-10-01

    TiO2 is the most promising photocatalyst because of its chemical stable, nontoxic, low cost, high photocatalytic activity and other attractive properties. Anatase has the highest photocatalytic activity among the three crystal form of TiO2. However, the 3.2 eV bandgap of anatase TiO2 makes it can only utilize the ultraviolet part of solar spectrum. Nitrogen doping is an effective method to extend the absorption range of anatase to visible light. N-doped TiO2 preparation methods, such as heat treatment under NH3 flow, the hydrolytic precipitation and the sol-gel process, have been reported. In this work, preparation of N-doped TiO2 was explored by radio-frequency (RF) dielectric barrier discharge (DBD) plasma using Ar as discharge gas. TiCl4, O2 and N2 were used as Ti, O and N precursors, respectively. In addition, H2 was added to the plasma. X-ray photoelectron spectra (XPS) showed nitrogen was successfully doped into the as-prepared TiO2. Further investigations on structure, composition and optical property of the as-prepared TiO2 samples were conducted by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and UV-Vis absorption spectra techniques.

  3. Hydrogenated Anatase TiO2 as Lithium-Ion Battery Anode: Size-Reactivity Correlation.

    PubMed

    Zheng, Jing; Liu, Lei; Ji, Guangbin; Yang, Qifan; Zheng, Lirong; Zhang, Jing

    2016-08-10

    An improved hydrogenation strategy for controllable synthesis of oxygen-deficient anatase TiO2 (H-TiO2) is performed via adjusting the particle size of starting rectangular anatase TiO2 nanosheets from 90 to 30 nm. The morphology and structure characterizations obviously demonstrate that the starting materials of TiO2 nanosheets are transformed into nanoparticles with distinct size reduction; meanwhile, the concentration of oxygen vacancy is gradually increased with the decreasing particle size of starting TiO2. As a result, the Li-storage performance of H-TiO2 is not only much better than that of the pure TiO2 but also elevated stage by stage with the decreasing particle size of starting TiO2; especially the H-TiO2 with highest concentration of oxygen vacancy from smallest TiO2 nanosheets shows the best Li-storage performance with a stable discharge capacity 266 mAh g(-1) after 100 cycles at 1 C. Such excellent performance should be attributed to the joint action from oxygen vacancy and size effect, which promises significant enhancement of high electronic conductivity without weakening Li(+) diffusion via hydrogenation strategy. PMID:27434151

  4. Nanostructured TiO2 Films Attached CdSe QDs Toward Enhanced Photoelectrochemical Performance.

    PubMed

    Du, Yingying; Yang, Ping; Liu, Yunshi; Zhao, Jie; He, Haiyan; Miao, Yanping

    2016-06-01

    TiO2 films consisted of small nanoparticles were fabricated via a spinning coating method on fluorine doped in tin oxide (FTO) slide glass. After calcination, the films were subsequently sensitized by CdSe quantum dots (QDs) using mercaptopropionic acid (MPA) as a bifunctional surface modifier. Upon UV light irradiation, CdSe QDs inject electrons into TiO2 nanoparticles, thus resulting in the generation of photocurrent in QD-sensitized solar cell. The results indicate that TiO2 films sensitized by CdSe QDs have achieved 1.5-fold enhancement in photocurrent compared with pure TiO2 films, indicating that CdSe QDs can improve the photocurrent by promoting the separation of photoinduced charge carriers. In addition, the photocurrent enhances as the thickness of TiO2 films increased. Such improved photoelectrochemical performance is ascribed to the basis of improved interfacial charge transport of the TiO2-CdSe composite films. Combining QDs on TiO2 thin films is a promising and effective way to enhance the photoelectrochemical performance, which is important in QD-sensitized solar cell application. PMID:27427714

  5. Size of TiO(2) nanoparticles influences their phototoxicity: an in vitro investigation.

    PubMed

    Xiong, Sijing; George, Saji; Ji, Zhaoxia; Lin, Sijie; Yu, Haiyang; Damoiseaux, Robert; France, Bryan; Ng, Kee Woei; Loo, Say Chye Joachim

    2013-01-01

    To uncover the size influence of TiO(2) nanoparticles on their potential toxicity, the cytotoxicity of different-sized TiO(2) nanoparticles with and without photoactivation was tested. It was demonstrated that without photoactivation, TiO(2) nanoparticles were inert up to 100 μg/ml. On the contrary, with photoactivation, the toxicity of TiO(2) nanoparticles significantly increased, which correlated well with the specific surface area of the particles. Our results also suggest that the generation of hydroxyl radicals and reactive oxygen species (ROS)-mediated damage to the surface-adsorbed biomolecules could be the two major reasons for the cytotoxicity of TiO(2) nanoparticles after photoactivation. Higher ROS generation from smaller particles was detected under both biotic and abiotic conditions. Smaller particles could adsorb more proteins, which was confirmed by thermogravimetric analysis. To further investigate the influence of the generation of hydroxyl radicals and adsorption of protein, poly (ethylene-alt-maleic anhydride) (PEMA) and chitosan were used to coat TiO(2) nanoparticles. The results confirmed that surface coating of TiO(2) nanoparticles could reduce such toxicity after photoactivation, by hindering adsorption of biomolecules and generation of hydroxyl radical (·OH) during photoactivation.

  6. Rubber sheet strewn with TiO2 particles: photocatalytic activity and recyclability.

    PubMed

    Sriwong, Chaval; Wongnawa, Sumpun; Patarapaiboolchai, Orasa

    2012-01-01

    A new method for the preparation of rubber sheet strewn with titanium dioxide particles (TiO2-strewn sheet) is presented. This simple and low cost method is based on the use of TiO2 powder (Degussa P25) being strewn onto the sheet made from rubber latex (60% HA) through a steel sieve. The characteristic of the TiO2-strewn sheet was studied by using scanning electron microscopy/energy dispersive X-ray spectrometer (SEM/EDS) and X-ray diffractometer (XRD) techniques. The photocatalytic activity of TiO2-strewn rubber sheet was evaluated using Indigo Carmine (IC) dye as a model for organic dye pollutant in water. The results showed that the TiO2-strewn sheet could degrade IC dye solution under UV light irradiation. The effects of pH, initial concentration, and the intensity of UV light on the photodegradation were also investigated. Kinetics of the photocatalytic degradation was of the first-order reaction. The used TiO2-strewn sheet can be recovered and reused. The recycling uses did not require any cleaning between successive uses and no decline in the photodegradation efficiency was observed compared with freshly prepared TiO2-strewn sheet. PMID:22655360

  7. Enhanced photocatalytic activity in anodized WO3-loaded TiO2 nanotubes

    NASA Astrophysics Data System (ADS)

    Nazari, M.; Golestani-Fard, F.; Bayati, R.; Eftekhari-Yekta, B.

    2015-04-01

    In this work, TiO2 and WO3-grafted TiO2 nanotubes were grown via anodizing of titanium substrates in tungstate containing electrolytes. The samples were characterized in detail by XRD, XPS, SEM, EDX, and UV-Vis spectrophotometry techniques. Besides, photocatalytic characteristics were evaluated through measuring the degradation rate of 4-chlorophenol to establish a correlation between structure and photochemical properties. We were able to control morphology and growth mode of nanotubes from a tubular to a worm-like structure by changing the electrolyte composition. The samples possessed an anatase-rutile matrix where the anatase/rutile ratio was found to increase with the concentration of tungstate in the electrolyte. We attributed this observation to change in electrical conductivity of the electrolyte and the heat generated on the substrates. It was unambiguously revealed that a composite of WO3 and TiO2 forms and, in parallel, tungsten is doped into the crystalline lattice of TiO2. The maximum photocatalytic reaction rate constant for TiO2 and WO3-TiO2 samples was determined to be 0.0131 and 0.0174 min-1 respectively. The grafting TiO2 nanotubes with WO3 enhances the photocatalytic activity mainly due to the hindrance of charge carrier recombination and the formation of a more acidic surface. We established a correlation between structure, stoichiometry, and photocatalytic characteristics of nanotubes.

  8. Heterostructured TiO2 Nanorod@Nanobowl Arrays for Efficient Photoelectrochemical Water Splitting.

    PubMed

    Wang, Wenhui; Dong, Jingya; Ye, Xiaozhou; Li, Yang; Ma, Yurong; Qi, Limin

    2016-03-01

    Heterostructured TiO2 nanorod@nanobowl (NR@NB) arrays consisting of rutile TiO2 nanorods grown on the inner surface of arrayed anatase TiO2 nanobowls are designed and fabricated as a new type of photoanodes for photoelectrochemical (PEC) water splitting. The unique heterostructures with a hierarchical architecture are readily fabricated by interfacial nanosphere lithography followed by hydrothermal growth. Owing to the two-dimensionally arrayed structure of anatase nanobowls and the nearly radial alignment of rutile nanorods, the TiO2 NR@NB arrays provide multiple scattering centers and hence exhibit an enhanced light harvesting ability. Meanwhile, the large surface area of the NR@NB arrays enhances the contact with the electrolyte while the nanorods offer direct pathways for fast electron transfer. Moreover, the rutile/anatase phase junction in the NR@NB heterostructure improves charge separation because of the facilitated electron transfer. Accordingly, the PEC measurements of the TiO2 NR@NB arrays on the fluoride-doped tin oxide (FTO) substrate show significantly enhanced photocatalytic properties for water splitting. Under AM1.5G solar light irradiation, the unmodified TiO2 NR@NB array photoelectrode yields a photocurrent density of 1.24 mA cm(-2) at 1.23 V with respect to the reversible hydrogen electrode, which is almost two times higher than that of the TiO2 nanorods grown directly on the FTO substrate.

  9. Hydrogenated Anatase TiO2 as Lithium-Ion Battery Anode: Size-Reactivity Correlation.

    PubMed

    Zheng, Jing; Liu, Lei; Ji, Guangbin; Yang, Qifan; Zheng, Lirong; Zhang, Jing

    2016-08-10

    An improved hydrogenation strategy for controllable synthesis of oxygen-deficient anatase TiO2 (H-TiO2) is performed via adjusting the particle size of starting rectangular anatase TiO2 nanosheets from 90 to 30 nm. The morphology and structure characterizations obviously demonstrate that the starting materials of TiO2 nanosheets are transformed into nanoparticles with distinct size reduction; meanwhile, the concentration of oxygen vacancy is gradually increased with the decreasing particle size of starting TiO2. As a result, the Li-storage performance of H-TiO2 is not only much better than that of the pure TiO2 but also elevated stage by stage with the decreasing particle size of starting TiO2; especially the H-TiO2 with highest concentration of oxygen vacancy from smallest TiO2 nanosheets shows the best Li-storage performance with a stable discharge capacity 266 mAh g(-1) after 100 cycles at 1 C. Such excellent performance should be attributed to the joint action from oxygen vacancy and size effect, which promises significant enhancement of high electronic conductivity without weakening Li(+) diffusion via hydrogenation strategy.

  10. Graphene oxide modified TiO2 nanotube arrays: enhanced visible light photoelectrochemical properties

    NASA Astrophysics Data System (ADS)

    Song, Peng; Zhang, Xiaoyan; Sun, Mingxuan; Cui, Xiaoli; Lin, Yuehe

    2012-02-01

    Novel nanocomposite films, based on graphene oxide (GO) and TiO2 nanotube arrays, were synthesized by assembling GO on the surface of self-organized TiO2 nanotube arrays through a simple impregnation method. The composite films were characterized with field emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy and UV-vis diffuse reflectance spectroscopy. The photoelectrochemical properties of the composite nanotube arrays were investigated under visible light illumination. Remarkably enhanced visible light photoelectrochemical response was observed for the GO decorated TiO2 nanotube composite electrode compared with pristine TiO2 nanotube arrays. The sensitizing effect of GO on the photoelectrochemical response of the TiO2 nanotube arrays was demonstrated and about 15 times enhanced maximum photoconversion efficiency was obtained with the presence of GO. An enhanced photocatalytic activity of the TiO2 nanotube arrays towards the degradation of methyl blue was also demonstrated after modification with GO. The results presented here demonstrate GO to be efficient for the improved utilization of visible light for TiO2 nanotube arrays.

  11. Graphene oxide modified TiO2 nanotube arrays: enhanced visible light photoelectrochemical properties.

    PubMed

    Song, Peng; Zhang, Xiaoyan; Sun, Mingxuan; Cui, Xiaoli; Lin, Yuehe

    2012-03-01

    Novel nanocomposite films, based on graphene oxide (GO) and TiO(2) nanotube arrays, were synthesized by assembling GO on the surface of self-organized TiO(2) nanotube arrays through a simple impregnation method. The composite films were characterized with field emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy and UV-vis diffuse reflectance spectroscopy. The photoelectrochemical properties of the composite nanotube arrays were investigated under visible light illumination. Remarkably enhanced visible light photoelectrochemical response was observed for the GO decorated TiO(2) nanotube composite electrode compared with pristine TiO(2) nanotube arrays. The sensitizing effect of GO on the photoelectrochemical response of the TiO(2) nanotube arrays was demonstrated and about 15 times enhanced maximum photoconversion efficiency was obtained with the presence of GO. An enhanced photocatalytic activity of the TiO(2) nanotube arrays towards the degradation of methyl blue was also demonstrated after modification with GO. The results presented here demonstrate GO to be efficient for the improved utilization of visible light for TiO(2) nanotube arrays. PMID:22297577

  12. Properties of TiO2 thin films and a study of the TiO2-GaAs interface

    NASA Technical Reports Server (NTRS)

    Chen, C. Y.; Littlejohn, M. A.

    1977-01-01

    Titanium dioxide (TiO2) films prepared by chemical vapor deposition were investigated in this study for the purpose of the application in the GaAs metal-insulator-semiconductor field-effect transistor. The degree of crystallization increases with the deposition temperature. The current-voltage study, utilizing an Al-TiO2-Al MIM structure, reveals that the d-c conduction through the TiO2 film is dominated by the bulk-limited Poole-Frenkel emission mechanism. The dependence of the resistivity of the TiO2 films on the deposition environment is also shown. The results of the capacitance-voltage study indicate that an inversion layer in an n-type substrate can be achieved in the MIS capacitor if the TiO2 films are deposited at a temperature higher than 275 C. A process of low temperature deposition followed by the pattern definition and a higher temperature annealing is suggested for device fabrications. A model, based on the assumption that the surface state densities are continuously distributed in energy within the forbidden band gap, is proposed to interpret the lack of an inversion layer in the Al-TiO2-GaAs MIS structure with the TiO2 films deposited at 200 C.

  13. Effects of TiO2 content on the microstructure, mechanical properties and photocatalytic activity of three dimensional TiO2-Graphene composite prepared by hydrothermal reaction

    NASA Astrophysics Data System (ADS)

    Shi, Xiangru; Chen, Jian; Wang, Wenxiu; Wang, Zengmei; Zhang, Yao; Guo, Xinli

    2016-07-01

    A series of three dimensional (3D) porous TiO2-graphene (TGR) hydrogel samples with different mass ratio of graphene to TiO2 were obtained using a one-step hydrothermal method. Their microstructure, mechanical properties, and photocatalytic activity were investigated. The TGR samples exhibited well defined interconnected 3D porous network microstructure and good mechanical strength. Moreover, the pore size and the compressive strength could be easily adjusted by changing the content of TiO2, showing a decreasing tendency with the increase of the relative content of TiO2. The results of the photodegradation of methylene blue indicated that the photocatalytic activity of the TGR samples can be significantly enhanced, compared to the pure TiO2 nanoparticles. The TGR sample also showed good durability and reusability. The mechanisms resulting in the improvement of photocatalytic activity were investigated with DRS, PL spectra, and adsorption experiment under dark conditions. It was found that adsorption is the dominant factor for the enhanced photocatalytic activity.

  14. Resistive switching characteristics in memristors with Al2O3/TiO2 and TiO2/Al2O3 bilayers

    NASA Astrophysics Data System (ADS)

    Alekseeva, Liudmila; Nabatame, Toshihide; Chikyow, Toyohiro; Petrov, Anatolii

    2016-08-01

    Differences between the resistive switching characteristics of Al2O3/TiO2 and TiO2/Al2O3 bilayer structures, fabricated by atomic layer deposition at 200 °C and post-deposition annealing, were studied in Pt bottom electrode (Pt-BE)/insulator/Pt top electrode (Pt-TE) capacitors. The Pt-BE/Al2O3/TiO2/Pt-TE capacitor exhibits stable bipolar resistive switching with an on-resistance/off-resistance ratio of ∼102 controlled by a small voltage of ±0.8 V. The forming process occurs in two steps of breaking of the Al2O3 layer and transfer of oxygen vacancies (VO) into the TiO2 layer. The capacitor showed poor endurance, particularly in the high-resistance state under vacuum conditions. This indicates that the insulating TiO2 layer without VO is not formed near the Al2O3 layer because oxygen cannot be introduced from the exterior. On the other hand, in the Pt-BE/TiO2/Al2O3/Pt-TE capacitor, multilevel resistive switching with several applied voltage-dependent nonvolatile states is observed. The switching mechanism corresponds to the Al2O3 layer’s trapped VO concentration, which is controlled by varying the applied voltage.

  15. Photoinduced Stepwise Oxidative Activation of a Chromophore–Catalyst Assembly on TiO2

    SciTech Connect

    Song, Wenjing; Glasson, Christopher R. K.; Luo, Hanlin; Hanson, Kenneth G.; Brennaman, Kyle M.; Concepcion, Javier J.; Meyer, Thomas J.

    2011-07-08

    To probe light-induced redox equivalent separation and accumulation, we prepared ruthenium polypyridyl molecular assembly [(dcb)2Ru(bpy-Mebim2py)Ru(bpy)(OH2)]4+ (RuaII–RubII–OH2) with Rua as light-harvesting chromophore and Rub as water oxidation catalyst (dcb = 4,4'-dicarboxylic acid-2,2'-bipyridine; bpy-Mebim2py = 2,2'-(4-methyl-[2,2':4',4''-terpyridine]-2'',6''-diyl)bis(1-methyl-1H-benzo[d]imidazole); bpy = 2,2'-bipyridine). When bound to TiO2 in nanoparticle films, it undergoes MLCT excitation, electron injection, and oxidation of the remote -RubII–OH2 site to give TiO2(e–)–RuaII–RubIII–OH23+ as a redox-separated transient. The oxidized assembly, TiO2–RuaII–RubIII–OH23+, similarly undergoes excitation and electron injection to give TiO2(e–)–RuaII–RubIV=O2+, with RubIV=O2+ a known water oxidation catalyst precursor. Injection efficiencies for both forms of the assembly are lower than those for [Ru(bpy)2(4,4'-(PO3H2)2bpy)]2+ bound to TiO2 (TiO2–Ru2+), whereas the rates of back electron transfer, TiO2(e–) → RubIII–OH23+ and TiO2(e–) → RubIV=O2+, are significantly decreased compared with TiO2(e–) → Ru3+ back electron transfer.

  16. [Spectrum characterization and fine structure of copper phthalocyanine-doped TiO2 microcavities].

    PubMed

    Liu, Cheng-lin; Zhang, Xin-yi; Zhong, Ju-hua; Zhu, Yi-hua; He, Bo; Wei, Shi-qiang

    2007-10-01

    Copper phthalocyanine-doped TiO2 microcavities were fabricated by chemistry method. Their spectrum characterization was studied by Fourier transform infrared (FTIR) and Raman spectroscopy, and their fine structure was analyzed by X-ray absorption fine structure (XAFS). The results show that there is interaction of copper phthalocyanine (CuPc) and TiO2 microcavities after TiO2 microcavities was doped with CuPc. For example, there is absorption at 900.76 cm(-1) in FTIR spectra, and the "red shift" of both OH vibration at 3392.75 cm(-1) and CH vibration at 2848.83 cm(-1). There exist definite peak shifts and intensity changes in infrared absorption in the C-C or C-N vibration in the planar phthalocyanine ring, the winding vibration of C-H inside and C-N outside plane of benzene ring. In Raman spectrum, there are 403.4, 592.1 and 679.1 cm(-1) characterized peaks of TiO2 in CuPc-doped TiO2 microcavities, but their wave-numbers show shifts to anatase TiO2. The vibration peaks at 1586.8 and 1525.6 cm(-1) show that there exists the composite material of CuPc and TiO2. These changes are related to the plane tropism of the molecule structure of copper phthalocyanine. XAFS showed tetrahedron TiO4 structure of Ti in TiO2 microcavities doped with copper phthalocyanine, and the changes of inner "medial distances" and the surface structure of TiO2 microcavities.

  17. Effect of TiO2 Nanoparticles on Tensile Strength of Dental Acrylic Resins.

    PubMed

    Shirkavand, Saeed; Moslehifard, Elnaz

    2014-01-01

    Background and aims. Adding further fillers to dental resins may enhance their physical characteristics. The aim of this study was to evaluate the tensile strength of heat-curing acrylic resin reinforced by TiO2nanoparticles added into the resin matrix. Materials and methods. Commercially available TiO2 nanoparticles were obtained and characterized using X-ray diffrac-tion (XRD) and scanning electron microscopy (SEM) to determine their crystalline structure, particle size and morphology. TiO2-acrylic resin nanocomposite was prepared by mixing 0.5, 1 and 2 (wt%) of surface modified TiO2 nanoparticles in an amalgamator providing three groups of samples. Before curing, the obtained paste was packed into steel molds. After cur-ing, the specimens were removed from the molds. The tensile strength test samples were prepared according to ISO 1567. Results. Two crystalline phases were found in TiO2 nanoparticles including: (i) anatase as the major one, and (ii) rutile. The average particle size calculated according to the Scherrer equation was 20.4 nm, showing a normal size distribution. According to SEM images, the nanocomposite with 1wt% TiO2 nanoparticles had a better distribution compared to other groups. In addition, the group by 1wt% TiO2 exhibited higher tensile strength with a significant difference compared to other groups. ANOVA showed significant differences between the contents of TiO2 particles in acrylic resin (F = 22.19; P < 0.001). Conclusion. A considerable increase in tensile strength was observed with titania NPs reinforcement agents in 1wt% by weight. Further increase of TiO2 nanoparticles decreased the tensile strength.

  18. Antibacterial activity of DLC films containing TiO2 nanoparticles.

    PubMed

    Marciano, F R; Lima-Oliveira, D A; Da-Silva, N S; Diniz, A V; Corat, E J; Trava-Airoldi, V J

    2009-12-01

    Diamond-like carbon (DLC) films have been the focus of extensive research in recent years due to their potential applications as surface coatings on biomedical devices. Titanium dioxide (TiO2) in the anatase crystalline form is a strong bactericidal agent when exposed to near-UV light. In this work we investigate the bactericidal activity of DLC films containing TiO2 nanoparticles. The films were grown on 316L stainless-steel substrates from a dispersion of TiO2 in hexane using plasma-enhanced chemical vapor deposition. The composition, bonding structure, surface energy, stress, and surface roughness of these films were also evaluated. The antibacterial tests were performed against Escherichia coli (E. coli) and the results were compared to the bacterial adhesion force to the studied surfaces. The presence of TiO2 in DLC bulk was confirmed by Raman spectroscopy. As TiO2 content increased, I(D)/I(G) ratio, hydrogen content, and roughness also increased; the films became more hydrophilic, with higher surface free energy and the interfacial energy of bacteria adhesion decreased. Experimental results show that TiO2 increased DLC bactericidal activity. Pure DLC films were thermodynamically unfavorable to bacterial adhesion. However, the chemical interaction between the E. coli and the studied films increased for the films with higher TiO2 concentration. As TiO2 bactericidal activity starts its action by oxidative damage to the bacteria wall, a decrease in the interfacial energy of bacteria adhesion causes an increase in the chemical interaction between E. coli and the films, which is an additional factor for the increasing bactericidal activity. From these results, DLC with TiO2 nanoparticles can be useful for producing coatings with antibacterial properties. PMID:19758597

  19. TiO2-BASED Composite Films for the Photodegradation of Oxytetracycline

    NASA Astrophysics Data System (ADS)

    Li, Hui; Guan, Ling-Xiao; Feng, Ji-Jun; Li, Fang; Yao, Ming-Ming

    2015-02-01

    The spread of the antibiotic oxytetracycline (OTC) has been thought as a threat to the safety of drinking water. In this paper, the photocatalytic activity of the nanocrystalline Fe/Ca co-doped TiO2-SiO2 composite film for the degradation of OTC was studied. The films were characterized by field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy (EDS), N2 adsorption/desorption isotherms, photoluminescence (PL) spectra, and UV-Vis diffraction reflectance absorption spectra (DRS). The FE-SEM results indicated that the Fe/Ca co-doped TiO2-SiO2 film was composed of smaller nanoparticles compared to pure TiO2 or TiO2-SiO2 film. The BET surface area results showed that the specific surface area of the pure TiO2, TiO2-SiO2 and Ca2+/Fe3+ co-doped TiO2-SiO2 is 118.3 m2g-1, 294.3 m2g-1 and 393.7 m2g-1, respectively. The DRS and PL spectra revealed that the Fe/Ca co-doped TiO2-SiO2 film had strong visible light adsorption and diminished electrons/holes recombination. Experimental results showed that the Fe/Ca co-doped TiO2-SiO2 film is effective in the degradation of OTC under both UV and visible light irradiation.

  20. Photodegradation of phenanthrene by N-doped TiO2 photocatalyst.

    PubMed

    Sirisaksoontorn, Weekit; Thachepan, Surachai; Songsasen, Apisit

    2009-07-15

    The photodegradation of phenanthrene has been catalyzed by nanostructures of TiO2 doped with nitrogen, N-doped TiO2. The N-doped TiO2 was prepared from the sol-gel reaction of Titanium(IV) bis(ethyl acetoacetato)diisopropoxide with 25% ammonia solution. The N-doped TiO2 was calcined at various temperatures from 300 to 700 degrees C. X-ray diffraction (XRD) results showed that N-doped TiO2 remained amorphous at 300 degrees C but anatase-to-rutile transformation started at 400 degrees C and was complete at 700 degrees C. The average particle size calculated from Scherrer's equation was in the range of 9-51 nm with surface area (S(BET)) of 253.7-4.8 m2/g. X-ray photoelectron spectroscopy (XPS) results confirmed the incorporation of nitrogen atoms (Ti-N bond) in the N-doped catalyst. Moreover, the percentage of nitrogen determined by Elemental analysis was 0.236% of N-doped calcined at 400 degrees C. UV-Vis reflection spectra indicated that N-doped TiO2 calcined at 400 degrees C shifted to the higher absorption edge in the range of visible light. N-doped TiO2 calcined at 400 degrees C successfully catalyzed the photodegradation of phenanthrene (80% conversion) whereas N-doped TiO2 calcined at 500 degrees C and P25 TiO2 failed as catalysts.

  1. Effect of TiO2 Nanoparticles on Tensile Strength of Dental Acrylic Resins

    PubMed Central

    Shirkavand, Saeed; Moslehifard, Elnaz

    2014-01-01

    Background and aims. Adding further fillers to dental resins may enhance their physical characteristics. The aim of this study was to evaluate the tensile strength of heat-curing acrylic resin reinforced by TiO2nanoparticles added into the resin matrix. Materials and methods. Commercially available TiO2 nanoparticles were obtained and characterized using X-ray diffrac-tion (XRD) and scanning electron microscopy (SEM) to determine their crystalline structure, particle size and morphology. TiO2-acrylic resin nanocomposite was prepared by mixing 0.5, 1 and 2 (wt%) of surface modified TiO2 nanoparticles in an amalgamator providing three groups of samples. Before curing, the obtained paste was packed into steel molds. After cur-ing, the specimens were removed from the molds. The tensile strength test samples were prepared according to ISO 1567. Results. Two crystalline phases were found in TiO2 nanoparticles including: (i) anatase as the major one, and (ii) rutile. The average particle size calculated according to the Scherrer equation was 20.4 nm, showing a normal size distribution. According to SEM images, the nanocomposite with 1wt% TiO2 nanoparticles had a better distribution compared to other groups. In addition, the group by 1wt% TiO2 exhibited higher tensile strength with a significant difference compared to other groups. ANOVA showed significant differences between the contents of TiO2 particles in acrylic resin (F = 22.19; P < 0.001). Conclusion. A considerable increase in tensile strength was observed with titania NPs reinforcement agents in 1wt% by weight. Further increase of TiO2 nanoparticles decreased the tensile strength. PMID:25587380

  2. Antibacterial activity of DLC films containing TiO2 nanoparticles.

    PubMed

    Marciano, F R; Lima-Oliveira, D A; Da-Silva, N S; Diniz, A V; Corat, E J; Trava-Airoldi, V J

    2009-12-01

    Diamond-like carbon (DLC) films have been the focus of extensive research in recent years due to their potential applications as surface coatings on biomedical devices. Titanium dioxide (TiO2) in the anatase crystalline form is a strong bactericidal agent when exposed to near-UV light. In this work we investigate the bactericidal activity of DLC films containing TiO2 nanoparticles. The films were grown on 316L stainless-steel substrates from a dispersion of TiO2 in hexane using plasma-enhanced chemical vapor deposition. The composition, bonding structure, surface energy, stress, and surface roughness of these films were also evaluated. The antibacterial tests were performed against Escherichia coli (E. coli) and the results were compared to the bacterial adhesion force to the studied surfaces. The presence of TiO2 in DLC bulk was confirmed by Raman spectroscopy. As TiO2 content increased, I(D)/I(G) ratio, hydrogen content, and roughness also increased; the films became more hydrophilic, with higher surface free energy and the interfacial energy of bacteria adhesion decreased. Experimental results show that TiO2 increased DLC bactericidal activity. Pure DLC films were thermodynamically unfavorable to bacterial adhesion. However, the chemical interaction between the E. coli and the studied films increased for the films with higher TiO2 concentration. As TiO2 bactericidal activity starts its action by oxidative damage to the bacteria wall, a decrease in the interfacial energy of bacteria adhesion causes an increase in the chemical interaction between E. coli and the films, which is an additional factor for the increasing bactericidal activity. From these results, DLC with TiO2 nanoparticles can be useful for producing coatings with antibacterial properties.

  3. Doping of TiO 2 Polymorphs for Altered Optical and Photocatalytic Properties

    DOE PAGES

    Nie, Xiliang; Zhuo, Shuping; Maeng, Gloria; Sohlberg, Karl

    2009-01-01

    Tmore » his paper reviews recent investigations of the influence of dopants on the optical properties of TiO 2 polymorphs.he common undoped polymorphs of TiO 2 are discussed and compared.he results of recent doping efforts are tabulated, and discussed in the context of doping by elements of the same chemical group. Dopant effects on the band gap and photocatalytic activity are interpreted with reference to a simple qualitative picture of the TiO 2 electronic structure, which is supported with first-principles calculations.« less

  4. Synthesis and characterization of TiO2 nanostructure thin films grown by thermal CVD

    NASA Astrophysics Data System (ADS)

    Rizal, Umesh; Das, Soham; Kumar, Dhruva; Swain, Bhabani S.; Swain, Bibhu P.

    2016-04-01

    Thermal Chemical Vapor Deposition (CVD) deposited Titanium dioxide nanostructures (TiO2-NSs) were grown by using Ti powder and O2 precursors on Si/SiO2 (100) substrate. The microstructure and vibration properties of TiO2-NSs were characterized by Fourier transform infrared (FTIR), SEM, and photoluminescence (PL) spectroscopy. The role of O2 flow rate on TiO2-NSs revealed decreased deposition rate, however, surface roughness has been increased resulted into formation of nanostructure thin films.

  5. Photoelectrochemical deoxyribonucleic acid sensing on a nanostructured TiO2 electrode

    NASA Astrophysics Data System (ADS)

    Tokudome, Hiromasa; Yamada, Yoko; Sonezaki, Shuji; Ishikawa, Hiroshi; Bekki, Makoto; Kanehira, Koki; Miyauchi, Masahiro

    2005-11-01

    A nanostructured TiO2 electrode chemisorbed with probe deoxyribonucleic acid (DNA) can photoelectrochemically detect a dye-labeled target DNA molecule. After the hybridization between the probe and target DNA molecules, light irradiation generates electrons in the dye molecules, and these electrons are injected into the TiO2 electrode. The resulting photocurrent can be measured and corresponds to the concentration of target DNA. This sensor can quantitatively detect target DNA at lower than nanomolar concentrations. In addition, by utilizing two different dyes, different DNA sequences can be detected on the TiO2 electrode.

  6. Schottky junction/ohmic contact behavior of a nanoporous TiO(2) thin film photoanode in contact with redox electrolyte solutions.

    PubMed

    Kaneko, Masao; Ueno, Hirohito; Nemoto, Junichi

    2011-01-01

    The nature and photoelectrochemical reactivity of nanoporous semiconductor electrodes have attracted a great deal of attention. Nanostructured materials have promising capabilities applicable for the construction of various photonic and electronic devices. In this paper, a mesoporous TiO(2) thin film photoanode was soaked in an aqueous methanol solution using an O(2)-reducing Pt-based cathode in contact with atmospheric air on the back side. It was shown from distinct photocurrents in the cyclic voltammogram (CV) that the nanosurface of the mesoporous n-TiO(2) film forms a Schottky junction with water containing a strong electron donor such as methanol. Formation of a Schottky junction (liquid junction) was also proved by Mott-Schottky plots at the mesoporous TiO(2) thin film photoanode, and the thickness of the space charge layer was estimated to be very thin, i.e., only 3.1 nm at -0.1 V vs Ag/AgCl. On the other hand, the presence of [Fe(CN)(6)](4-) and the absence of methanol brought about ohmic contact behavior on the TiO(2) film and exhibited reversible redox waves in the dark due to the [Fe(CN)(6)](4-/3-) couple. Further studies showed that multiple Schottky junctions/ohmic contact behavior inducing simultaneously both photocurrent and overlapped reversible redox waves was found in the CV of a nanoporous TiO(2) photoanode soaked in an aqueous redox electrolyte solution containing methanol and [Fe(CN)(6)](4-). That is, the TiO(2) nanosurface responds to [Fe(CN)(6)](4-) to give ohmic redox waves overlapped simultaneously with photocurrents due to the Schottky junction. Additionally, a second step photocurrent generation was observed in the presence of both MeOH and [Fe(CN)(6)](4-) around the redox potential of the iron complex. It was suggested that the iron complex forms a second Schottky junction for which the flat band potential (E(fb)) lies near the redox potential of the iron complex.

  7. Enhanced Photodetection from TiO2-SiO x -TiO2 One-Dimensional Device

    NASA Astrophysics Data System (ADS)

    Choudhuri, Bijit; Mondal, Aniruddha; Saha, Ardhendu

    2016-08-01

    In this work, TiO2 nanowires (NWs)/SiO x zigzag (ZZ) film/TiO2 NWs structure-based devices were fabricated using glancing angle deposition and oblique angle deposition techniques. An investigation of the optoelectronic properties of the devices will be presented. The NWs-ZZ-NWs structure showed an average of 1.6 times enhancement in absorbance value as compared to the absorbance of the structure that contains only NWs. When irradiated with white light, NWs-ZZ-NWs- and only NWs-based devices exhibited a maximum 6.3 and 2.7 times greater light-to-dark current ratio, respectively, at -3 V. The maximum photoresponsivity and internal gain at the wavelength of 370 nm were calculated to be 57 A/W and 191, respectively, for the NWs-ZZ-NWs devices. The rise and fall time for the NWs-ZZ-NWs and NW devices were 16.56 s and 8.2 s, and 8.39 s and 7.31 s, respectively.

  8. Splitting of magnetic dipole modes in anisotropic TiO 2 micro-spheres: Splitting of magnetic dipole modes in anisotropic TiO 2 micro-spheres

    DOE PAGES

    Khromova, Irina; Kužel, Petr; Brener, Igal; Reno, John L.; Chung Seu, U-Chan; Elissalde, Catherine; Maglione, Mario; Mounaix, Patrick; Mitrofanov, Oleg

    2016-06-27

    Monocrystalline titanium dioxide (TiO2) micro-spheres support two orthogonal magnetic dipole modes at terahertz (THz) frequencies due to strong dielectric anisotropy. For the first time, we experimentally detected the splitting of the first Mie mode in spheres of radii inline imagem through near-field time-domain THz spectroscopy. By fitting the Fano lineshape model to the experimentally obtained spectra of the electric field detected by the sub-wavelength aperture probe, we found that the magnetic dipole resonances in TiO2 spheres have narrow linewidths of only tens of gigahertz. Lastly, anisotropic TiO2 micro-resonators can be used to enhance the interplay of magnetic and electric dipolemore » resonances in the emerging THz all-dielectric metamaterial technology.« less

  9. Hybrid Ag@TiO2 core-shell nanostructures with highly enhanced photocatalytic performance

    NASA Astrophysics Data System (ADS)

    Yang, X. H.; Fu, H. T.; Wong, K.; Jiang, X. C.; Yu, A. B.

    2013-10-01

    A new synthetic approach has been developed to prepare silver@titanium dioxide (Ag@TiO2) core-shell nanostructures with controllable size, shape, crystal phase and function at ambient conditions (e.g. in water, ≤100 ° C). This approach shows a few unique features, including short reaction time (a few minutes) for forming core-shell nanostructures, no requirement of high temperature calcinations for generating TiO2 (e.g. at ˜100 ° C in our case), tunable TiO2 shell thickness, high yield and good reproducibility. The experimental results show that the Ag@TiO2 core-shell nanostructures exhibit excellent photocatalytic activity compared to the commercial TiO2 (P25) and Ag-doped TiO2 nanocomposite in the degradation of organic dye molecules (e.g. methyl orange) with ultraviolet (UV) irradiation. This could be attributed to the large surface area of TiO2 nanoparticles for maximum harvesting of UV light, mixed anatase and rutile crystalline phases in the TiO2 shell and the effective charge separation between Ag and TiO2 that can reduce the possible recombination of electron-hole (e--h+) pairs within TiO2 generated under UV radiation. To further understand the charge separation situation within Ag-TiO2 composites, theoretical simulation (e.g. density functional theory, DFT) was employed in this study. The DFT simulation results indicate that for the Ag@TiO2 core-shell nanostructures, photo-generated electrons transfer readily from the external TiO2 layer to the internal Ag layer with heavy accumulation compared to those doping Ag on TiO2 surfaces, which may reduce the recombination of e--h+ pairs and thus enhance the photocatalytic efficiency. The findings may open a new strategy to synthesize TiO2-based photocatalysts with highly enhanced efficiency for environmental remediation applications.

  10. Antifungal activity of TiO2 photocatalysis against Penicillium expansum in vitro and in fruit tests.

    PubMed

    Maneerat, Chamorn; Hayata, Yasuyoshi

    2006-03-15

    The antifungal activity of TiO2 photocatalytic reaction in the form of TiO2 powder and TiO2 coated on a plastic film against Penicillium expansum was investigated in vitro and in fruit tests. The mixture of P. expansum conidial suspension and TiO2 powder was added to potato dextrose agar (PDA) plates for vitro test. The TiO2 photocatalytic reaction reduced conidial germination of the fungal pathogen. It was found that the ability of the TiO2 photocatalytic reaction to suppress P. expansum growth correlated to the amount of TiO2 added. Lower numbers of viable colonies of P. expansum were observed with increasing amount of TiO2. Regardless of the kind of selected fruit inoculated with P. expansum, both TiO2 powder and TiO2-coated film exhibited antifungal activity to control fruit rot. Development of Penicillium rot in apple was significantly (P = 0.05) retarded by the TiO2 photocatalytic reaction. Similarly the TiO2 photocatalytic reaction was the only treatment where no tomato fruit rot was noticeable after 1 week of storage. TiO2-coated film also decreased brown lesions and Penicillium rot infection in lemons. The mean severity fruit rot scores (browning and softening flesh) were 3.2 and 1.9 for uncoated and TiO2-coated film, respectively. Our findings suggest that "TiO2 photocatalytic reaction" shows antifungal activity against P. expansum which may have potential for postharvest disease control.

  11. Electron channeling in TiO2 coated Cu layers

    NASA Astrophysics Data System (ADS)

    Zheng, Pengyuan; Zhou, Tianji; Gall, Daniel

    2016-05-01

    Electron transport in metal conductors with ∼5–30 nm width is dominated by surface scattering. In situ transport measurements as a function of surface chemistry demonstrate that the primary parameter determining the surface scattering specularity is the localized surface density of states at the Fermi level N(E f ). In particular, the measured sheet resistance of epitaxial Cu(001) layers with thickness d Cu = 9–25 nm increases when coated with d Ti = 0.1–4.0 monolayers (MLs) of Ti, but decreases again during exposure to 37 Pa of O2. These resistivity changes are a function of d Cu and d Ti and are due to a transition from partially specular electron scattering at the Cu surface to completely diffuse scattering at the Cu–Ti interface, and the recovery of surface specularity as the Ti is oxidized. X-ray reflectivity and photoelectron spectroscopy indicate the formation of a 0.47 ± 0.03 nm thick Cu2O surface layer on top of the TiO2–Cu2O during air exposure, while density functional calculations of TiO x cap layers as a function of x = 0–2 and d Ti = 0.25–1.0 ML show a reduction of N(E f ) by up to a factor of four. This reduction is proposed to be the key cause for the recovery of surface specularity and results in electron confinement and channeling in the Cu layer upon Ti oxidation. Transport measurements at 293 and 77 K confirm the channeling and demonstrate the potential for high-conductivity metal nanowires by quantifying the surface specularity parameter p = 0.67 ± 0.05, 0.00 ± 0.05, and 0.35 ± 0.05 at the Cu–vacuum, Cu–Ti, and Cu–TiO2 interfaces.

  12. Electrokinetic Properties of TiO2 Nanotubular Surfaces

    NASA Astrophysics Data System (ADS)

    Lorenzetti, Martina; Gongadze, Ekaterina; Kulkarni, Mukta; Junkar, Ita; Iglič, Aleš

    2016-08-01

    Surface charge is one of the most significant properties for the characterisation of a biomaterial, being a key parameter in the interaction of the body implant with the surrounding living tissues. The present study concerns the systematic assessment of the surface charge of electrochemically anodized TiO2 nanotubular surfaces, proposed as coating material for Ti body implants. Biologically relevant electrolytes (NaCl, PBS, cell medium) were chosen to simulate the physiological conditions. The measurements were accomplished as titration curves at low electrolytic concentration (10-3 M) and as single points at fixed pH but at various electrolytic concentrations (up to 0.1 M). The results showed that all the surfaces were negatively charged at physiological pH. However, the zeta potential values were dependent on the electrolytic conditions (electrolyte ion concentration, multivalence of the electrolyte ions, etc.) and on the surface characteristics (nanotubes top diameter, average porosity, exposed surface area, wettability, affinity to specific ions, etc.). Accordingly, various explanations were proposed to support the different experimental data among the surfaces. Theoretical model of electric double layer which takes into account the asymmetric finite size of ions in electrolyte and orientational ordering of water dipoles was modified according to our specific system in order to interpret the experimental data. Experimental results were in agreement with the theoretical predictions. Overall, our results contribute to enrich the state-of-art on the characterisation of nanostructured implant surfaces at the bio-interface, especially in case of topographically porous and rough surfaces.

  13. Electrokinetic Properties of TiO2 Nanotubular Surfaces.

    PubMed

    Lorenzetti, Martina; Gongadze, Ekaterina; Kulkarni, Mukta; Junkar, Ita; Iglič, Aleš

    2016-12-01

    Surface charge is one of the most significant properties for the characterisation of a biomaterial, being a key parameter in the interaction of the body implant with the surrounding living tissues. The present study concerns the systematic assessment of the surface charge of electrochemically anodized TiO2 nanotubular surfaces, proposed as coating material for Ti body implants. Biologically relevant electrolytes (NaCl, PBS, cell medium) were chosen to simulate the physiological conditions. The measurements were accomplished as titration curves at low electrolytic concentration (10(-3) M) and as single points at fixed pH but at various electrolytic concentrations (up to 0.1 M). The results showed that all the surfaces were negatively charged at physiological pH. However, the zeta potential values were dependent on the electrolytic conditions (electrolyte ion concentration, multivalence of the electrolyte ions, etc.) and on the surface characteristics (nanotubes top diameter, average porosity, exposed surface area, wettability, affinity to specific ions, etc.). Accordingly, various explanations were proposed to support the different experimental data among the surfaces. Theoretical model of electric double layer which takes into account the asymmetric finite size of ions in electrolyte and orientational ordering of water dipoles was modified according to our specific system in order to interpret the experimental data. Experimental results were in agreement with the theoretical predictions. Overall, our results contribute to enrich the state-of-art on the characterisation of nanostructured implant surfaces at the bio-interface, especially in case of topographically porous and rough surfaces. PMID:27562014

  14. Conversion of Nanocellulose Aerogel into TiO2 and TiO2@C Nano-thorns by Direct Anhydrous Mineralization with TiCl4. Evaluation of Electrochemical Properties in Li Batteries.

    PubMed

    Henry, Aurélien; Plumejeau, Sandrine; Heux, Laurent; Louvain, Nicolas; Monconduit, Laure; Stievano, Lorenzo; Boury, Bruno

    2015-07-15

    Nanostructured TiO2 and TiO2@C nanocomposites were prepared by an original process combining biotemplating and mineralization of aerogels of nanofibrillated cellulose (NFC). A direct one step treatment of NFC with TiCl4 in strictly anhydrous conditions allows TiO2 formation at the outermost part of the nanofibrils while preserving their shape and size. Such TiO2@cellulose composites can be transformed into TiO2 nanotubes (TiO2-NT) by calcination in air at 600 and 900 °C, or into TiO2@C nanocomposites by pyrolysis in argon at 600 and 900 °C. Detailed characterization of these materials is reported here, along with an assessment of their performance as negative electrode materials for Li-ion batteries. PMID:25881329

  15. Dip coated TiO2 nanostructured thin film: synthesis and application

    NASA Astrophysics Data System (ADS)

    Vanaraja, Manoj; Muthukrishnan, Karthika; Boomadevi, Shanmugam; Karn, Rakesh Kumar; Singh, Vijay; Singh, Pramod K.; Pandiyan, Krishnamoorthy

    2016-02-01

    TiO2 thin film was fabricated by dip coating method using titanium IV chloride as precursor and sodium carboxymethyl cellulose as thickening as well as capping agent. Structural and morphological features of TiO2 thin film were characterized by X-ray diffractometer and field emission scanning electron microscope, respectively. Crystallinity of the film was confirmed with high-intensity peak at (101) plane, and its average crystallite size was found to be 28 nm. The ethanol-sensing properties of TiO2 thin film was studied by the chemiresistive method. Furthermore, various gases were tested in order to verify the selectivity of the sensor. Among the several gases, the fabricated TiO2 sensor showed very high selectivity towards ethanol at room temperature.

  16. Photocatalytic Property of TiO2-Vermiculite Composite Nanofibers via Electrospinning.

    PubMed

    Tang, Chao; Hu, Meiling; Fang, Minghao; Liu, Yangai; Wu, Xiaowen; Liu, Wenjuan; Wang, Meng; Huang, Zhaohui

    2015-12-01

    Titanium dioxide (TiO2) is one of the most common photocatalysts. In this study, TiO2-vermiculite composite nanofibers with a mesh structure and a diameter of approximately 300 nm were prepared via sol-gel approach combined with electrospinning technique. The samples were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible spectroscopy, etc. The photocatalytic property was also evaluated. The TiO2-vermiculite composite nanofibers annealed at 550 °C for 3 h exhibited the best absorption and photo-degradation ability for the treatment of methylene blue. The results implied that the combination of mineral vermiculite powders with TiO2 enhanced the absorption-degradation performance of the as-prepared photocatalytic materials, consequently promoting the materials' ability to degrade methylene blue. PMID:26130024

  17. Effects of Mn doping on surface enhanced Raman scattering properties of TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Xue, Xiangxin; Ji, Wei; Mao, Zhu; Li, Zhishi; Ruan, Weidong; Zhao, Bing; Lombardi, John R.

    2012-09-01

    TiO2 and Mn-doped TiO2 (1%, 3% and 5%) nanoparticles (NPs) were synthesized by a sol-hydrothermal method for surface-enhanced Raman spectroscopy study. When using the 4-mercaptobenzoic acid (4-MBA) as the probing molecule, optimum SERS signals were observed on the Mn-TiO2 (3%) samples. On the 3% Mn doped TiO2 substrate, 4-MBA molecules exhibit a higher SERS intensity by a factor of six as compared with the native enhancement of 4-MBA adsorbed on pure TiO2 NPs. The possible mechanism for the phenomena is also discussed. This study opens up a new dimension for the family of SERS substrates.

  18. Comparison of Au and TiO2 based catalysts for the synthesis of chalcogenide nanowires

    NASA Astrophysics Data System (ADS)

    Schönherr, P.; Prabhakaran, D.; Jones, W.; Dimitratos, N.; Bowker, M.; Hesjedal, T.

    2014-06-01

    We present a comparative study of TiO2-based and Au catalysts for the physical vapor deposition of (Bi1-xSbx)2Se3 topological insulator nanowires. The standard Au nanoparticle catalyst was compared to five TiO2 nanoparticle based catalysts (anatase, rutile, P-25, high surface area anatase, and TiO2 supported Au particles). The use of Au nanoparticles seriously harms the properties of nanowires, thereby limiting their application. In contrast, TiO2 based catalysts lead to the residue-free growth of nanowires with a higher degree of crystallinity. Homogeneous nanowire ensembles are achieved with the mixed phase P-25 catalyst, and a possible growth mechanism is proposed.

  19. Molecular Hydrogen Formation from Proximal Glycol Pairs on TiO2(110)

    SciTech Connect

    Chen, Long; Li, Zhenjun; Smith, R. Scott; Kay, Bruce D.; Dohnalek, Zdenek

    2014-04-16

    Understanding hydrogen formation on TiO2 surfaces is of great importance as it could provide fundamental insight into water splitting for hydrogen production using solar energy. In this work, hydrogen formation from glycols having different numbers of methyl end-groups have been studied using temperature pro-grammed desorption on reduced, hydroxylated, and oxidized TiO2(110) surfaces. The results from OD-labeled glycols demon-strate that gas-phase molecular hydrogen originates exclusively from glycol hydroxyl groups. The yield is controlled by a combi-nation of glycol coverage, steric hindrance, TiO2(110) order and the amount of subsurface charge. Combined, these results show that proximal pairs of hydroxyl aligned glycol molecules and subsurface charge are required to maximize the yield of this redox reaction. These findings highlight the importance of geometric and electronic effects in hydrogen formation from adsorbates on TiO2(110).

  20. Atomic Structure of the Anatase TiO2(001) Surface

    SciTech Connect

    Xia, Yaobiao; Zhu, Ke; Kaspar, Tiffany C.; Du, Yingge; Birmingham, Blake; Park, Kenneth T.; Zhang, Zhenrong

    2013-08-16

    Understanding the structure of well-defined anatase TiO2 surfaces is critical for deciphering site-specific thermal and photo- reaction mechanisms on anatase TiO2. Using UHV scanning tunneling microscopy (STM), we have studied the atomic structure of anatase TiO2(001) epitaxial thin films grown by oxygen plasma assisted molecular beam epitaxy. Bright rows of the (1×4) reconstructed surface are resolved as three types of features with different sizes. High-resolution STM images taken from the same area at different bias voltages show that these individual features are originated from combinations of two basic atomic building blocks. We propose a modified added molecule model for the anatase TiO2 (001) surface structure.

  1. Phase stability frustration on ultra-nanosized anatase TiO2

    PubMed Central

    Patra, Snehangshu; Davoisne, Carine; Bouyanfif, Houssny; Foix, Dominique; Sauvage, Frédéric

    2015-01-01

    This work sheds light on the exceptional robustness of anatase TiO2 when it is downsized to an extreme value of 4 nm. Since at this size the surface contribution to the volume becomes predominant, it turns out that the material becomes significantly resistant against particles coarsening with temperature, entailing a significant delay in the anatase to rutile phase transition, prolonging up to 1000 °C in air. A noticeable alteration of the phase stability diagram with lithium insertion is also experienced. Lithium insertion in such nanocrystalline anatase TiO2 converts into a complete solid solution until almost Li1TiO2, a composition at which the tetragonal to orthorhombic transition takes place without the formation of the emblematic and unwished rock salt Li1TiO2 phase. Consequently, excellent reversibility in the electrochemical process is experienced in the whole portion of lithium content. PMID:26042388

  2. Porous Anatase TiO2 Thin Films for NH3 Vapour Sensing

    NASA Astrophysics Data System (ADS)

    Ponnusamy, Dhivya; Madanagurusamy, Sridharan

    2015-12-01

    Anatase titanium dioxide (TiO2) thin films were deposited onto cleaned glass substrates by a direct current (DC) reactive magnetron sputtering technique for different deposition times from 10 min to 40 min, which resulted in films of different thicknesses. Characterization techniques, such as x-ray diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM) were used to characterize the structural and morphological properties of the TiO2 thin films. XRD patterns showed the formation of (101) crystal anatase facets. The grain size values of the film increased with increased deposition time, and the films deposited at 40 min exhibited a porous structure. Anatase TiO2 thin films exhibited excellent sensing response, fast response and recovery time, as well as good stability and selectivity towards ammonia (NH3). The enhanced NH3 sensing behavior of anatase TiO2 films is attributed to the porous morphology and oxygen vacancies.

  3. TiO2 Nanoparticles as a Soft X-ray Molecular Probe

    SciTech Connect

    Larabell, Carolyn; Ashcroft, Jared M.; Gu, Weiwei; Zhang, Tierui; Hughes, Steven M.; Hartman, Keith B.; Hofmann, Cristina; Kanaras, Antonios G.; Kilcoyne, David A.; Le Gros, Mark; Yin, Yadong; Alivisatos, A. Paul; Larabell, Carolyn A.

    2007-06-30

    With the emergence of soft x-ray techniques for imaging cells, there is a pressing need to develop protein localization probes that can be unambiguously identified within the region of x-ray spectrum used for imaging. TiO2 nanocrystal colloids, which have a strong absorption cross-section within the "water-window" region of x-rays, areideally suited as soft x-ray microscopy probes. To demonstrate their efficacy, TiO2-streptavidin nanoconjugates were prepared and subsequently labeled microtubules polymerized from biotinylated tubulin. The microtubules were imaged using scanning transmission x-ray microscopy (STXM), and the TiO2 nanoparticle tags were specifically identified using x-ray absorption near edge spectroscopy (XANES). These experiments demonstrate that TiO2 nanoparticles are potential probes for protein localization analyses using soft x-ray microscopy.

  4. Molecular design of TiO2 for gigantic red shift via sublattice substitution.

    PubMed

    Shao, Guosheng; Deng, Quanrong; Wan, Lin; Guo, Meilan; Xia, Xiaohong; Gao, Yun

    2010-11-01

    The effects of 3d transition metal doping in TiO2 phases have been simulated in detail. The results of modelling indicate that Mn has the biggest potential among 3d transition metals, for the reduction of energy gap and the introduction of effective intermediate bands to allow multi-band optical absorption. On the basis of theoretical formulation, we have incorporated considerable amount of Mn in nano-crystalline TiO2 materials. Mn doped samples demonstrate significant red shift in the optical absorption edge, with a secondary absorption edge corresponding to theoretically predicted intermediate bands/states. The gigantic red shift achievable in Mn-doped TiO2 is expected to extend the useful TiO2 functionalities well beyond the UV threshold via the optical absorption of both visible and infrared photon irradiance.

  5. Probing interactions between TiO 2 photocatalyst and adsorbing species using quartz crystal microbalance

    NASA Astrophysics Data System (ADS)

    Morand, R.; Noworyta, K.; Augustynski, J.

    2002-10-01

    Photoactivity of nanocrystalline TiO 2 films is shown to be strongly affected by the presence in aqueous solution of salicylic acid, known to form Ti(IV)salicylate surface complexes. In particular, the photooxidation of methanol - an effective hole scavenger - at TiO 2 appears to be in part, or even completely inhibited by the additions of increasing amounts of salicylic acid. The chemisorption of salicylic and also phthalic acid on TiO 2 was followed using quartz crystal microbalance, QCM. The observed resonant frequency changes of the quartz crystal bearing TiO 2 films, accompanying increasing additions of the benzoic acids to the contacting solutions, indicate large displacement of water as a consequence of the adsorbent-imparted hydrophobicity of the interface.

  6. Amine functionalized TiO2-carbon nanotube composite: synthesis, characterization and application to glucose biosensing

    NASA Astrophysics Data System (ADS)

    Tasviri, Mahboubeh; Rafiee-Pour, Hossain-Ali; Ghourchian, Hedayatollah; Gholami, Mohammad Reza

    2011-12-01

    The synthesis of amine functionalized TiO2-coated multiwalled carbon nanotubes (NH2-TiO2-CNTs) using sol-gel method was investigated. The synthesized nanocomposite was characterized with XRD, FTIR spectroscopy, BET test and SEM imaging. The results demonstrated a unique nanostructure with no destruction of the CNTs' shape. In addition, the presence of amine groups on the composite surface was confirmed by FTIR. This nanocomposite was used for one-step immobilization of glucose oxidase (GOx) to sense glucose. The result of cyclic voltammetry showed a pair of well-defined and quasi-reversible peaks for direct electron transfer of GOx in the absence of glucose. Also, the result of electrochemical impedance spectroscopy indicated that GOx was successfully immobilized on the surface of NH2-TiO2-CNTs. Furthermore, good amperometric response showed that immobilized GOx on the NH2-TiO2-CNTs exhibits exceptional bioelectrocatalytic activity toward glucose oxidation.

  7. Deposition of Co-doped TiO2 Thin Films by sol-gel method

    NASA Astrophysics Data System (ADS)

    Boutlala, A.; Bourfaa, F.; Mahtili, M.; Bouaballou, A.

    2016-03-01

    Cobalt doped TiO2 thin films have been prepared by sol-gel method onto glass substrate at room temperature. in this present work, we are interesting to study the effect of Cobalt doped TiO2 thin films.the concentration of Co was varied from 0 to 6%at .The obtained films have been annealed at 500°C for 2 hours. X-ray diffraction patterns showed that Co: TiO2 films are polycrystalline with a tetragonal anatase and orthorhombic brookite types structures. The surface morphologies of the TiO2 doped with cobalt thin films were evaluated by Atomic Force Microscopy (AFM). The optical properties were studied by mean of UV-visible and near infrared spectroscopy.The calculated optical band gap decreases from 3.30 to 2.96 eV with increasing Co doping.

  8. OXYGENATION OF HYDROCARBONS USING NANOSTRUCTURED TIO2 AS A PHOTOCATALYST: A GREEN ALTERNATIVE

    EPA Science Inventory

    High-value organic compounds have been synthesized successfully from linear and cyclic saturated hydrocarbons by a photocatalytic oxidation process using a semiconductor material, titanium dioxide (TiO2). Various hydrocarbons were partially oxygenated in both aqueous and gaseous...

  9. Composite TiO2-Carbon nano films with enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Chakarov, Dinko; Sellappan, Raja

    2011-03-01

    Composite TiO2-carbon thin films prepared by physical vapor deposition techniques on fused silica substrates show enhanced photocatalytic activity, as compared to pure TiO2 films of similar thickness, towards decomposition of methanol to CO2 and water. Raman and XRD measurements confirm that annealed TiO2 films exhibit anatase structure while the carbon layer becomes graphitic. Characteristic for the composite films is an enhanced optical absorption in the visible range. The presence of the carbon film causes a shift of the TiO2 absorption edge and modifies its grain size to be smaller. The observed enhancement is attributed to synergy effects at the carbon-TiO2 interface, resulting in smaller crystallite size and anisotropic charge carrier transport, which in turn reduces their recombination probability. Supported by N-INNER through the Solar Hydrogen project (P30938-1 Solväte).

  10. Room temperature alcohol sensing by oxygen vacancy controlled TiO2 nanotube array

    NASA Astrophysics Data System (ADS)

    Hazra, A.; Dutta, K.; Bhowmik, B.; Chattopadhyay, P. P.; Bhattacharyya, P.

    2014-08-01

    Oxygen vacancy (OV) controlled TiO2 nanotubes, having diameters of 50-70 nm and lengths of 200-250 nm, were synthesized by electrochemical anodization in the mixed electrolyte comprising NH4F and ethylene glycol with selective H2O content. The structural evolution of TiO2 nanoforms has been studied by field emission scanning electron microscopy. Variation in the formation of OVs with the variation of the structure of TiO2 nanoforms has been evaluated by photoluminescence and X-ray photoelectron spectroscopy. The sensor characteristics were correlated to the variation of the amount of induced OVs in the nanotubes. The efficient room temperature sensing achieved by the control of OVs of TiO2 nanotube array has paved the way for developing fast responding alcohol sensor with corresponding response magnitude of 60.2%, 45.3%, and 36.5% towards methanol, ethanol, and 2-propanol, respectively.

  11. Microwave-assisted synthesis of nanocrystalline TiO2 for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Kuo, Ta-Chuan; Guo, Tzung-Fang; Chen, Peter

    2012-09-01

    The main purposes of this study are replacing conventional hydro-thermal method by microwave heating using water as reaction medium to rapidly synthesize TiO2.Titanium tetraisopropoxide (TTIP) was hydrolyzed in water. The solution is subsequently processed with microwave heating for crystal growth. The reaction time could be shortened into few minutes. Then we chose different acids as dispersion agents to prepare TiO2 paste for investigating the effects of dispersion on the power conversion efficiency of dye-sensitized solar cells (DSCs). The photovoltaic performance of the microwave-assisted synthesized TiO2 achieved power conversion efficiency of 6.31% under AM 1.5 G condition (100 mW/cm2). This PCE value is compatible with that of the devices made from commercial TiO2.

  12. Preparation TiO2 core-shell nanospheres and application as efficiency drug detection sensor

    PubMed Central

    2014-01-01

    In this paper, we report the facile preparation of monodisperse titanium dioxide-diltiazem/tetrachlorobismuth core-shell nanospheres (TiO2@DTMBi), in which, diltiazem (DTM)/tetrachlorobismuth (BiCl4) complexes were employed as electroactive materials. The morphology, size, formation, and structure of the obtained TiO2@DTMBi spheres were investigated by transmission electron microscopy, scanning electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, and X-ray diffraction. The optimal condition of obtained monodisperse 40-nm TiO2@DTMBi spheres was researched. The results of using TiO2@DTMBi nanospheres as proposed drug sensor indicate a wide linear range (10-7 to 10-1 M) and a very low detection limit of 0.20 μg/mL. PMID:25246870

  13. Photocatalytic Property of TiO2-Vermiculite Composite Nanofibers via Electrospinning.

    PubMed

    Tang, Chao; Hu, Meiling; Fang, Minghao; Liu, Yangai; Wu, Xiaowen; Liu, Wenjuan; Wang, Meng; Huang, Zhaohui

    2015-12-01

    Titanium dioxide (TiO2) is one of the most common photocatalysts. In this study, TiO2-vermiculite composite nanofibers with a mesh structure and a diameter of approximately 300 nm were prepared via sol-gel approach combined with electrospinning technique. The samples were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible spectroscopy, etc. The photocatalytic property was also evaluated. The TiO2-vermiculite composite nanofibers annealed at 550 °C for 3 h exhibited the best absorption and photo-degradation ability for the treatment of methylene blue. The results implied that the combination of mineral vermiculite powders with TiO2 enhanced the absorption-degradation performance of the as-prepared photocatalytic materials, consequently promoting the materials' ability to degrade methylene blue.

  14. Photocatalytic Property of TiO2-Vermiculite Composite Nanofibers via Electrospinning

    NASA Astrophysics Data System (ADS)

    Tang, Chao; Hu, Meiling; Fang, Minghao; Liu, Yangai; Wu, Xiaowen; Liu, Wenjuan; Wang, Meng; Huang, Zhaohui

    2015-07-01

    Titanium dioxide (TiO2) is one of the most common photocatalysts. In this study, TiO2-vermiculite composite nanofibers with a mesh structure and a diameter of approximately 300 nm were prepared via sol-gel approach combined with electrospinning technique. The samples were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible spectroscopy, etc. The photocatalytic property was also evaluated. The TiO2-vermiculite composite nanofibers annealed at 550 °C for 3 h exhibited the best absorption and photo-degradation ability for the treatment of methylene blue. The results implied that the combination of mineral vermiculite powders with TiO2 enhanced the absorption-degradation performance of the as-prepared photocatalytic materials, consequently promoting the materials' ability to degrade methylene blue.

  15. Morphology dependent catalytic activity of TiO2 nanostructures towards photodegradation of Rose Bengal

    NASA Astrophysics Data System (ADS)

    Malik, Ritu; Kumar, Ashok; Nehra, S. P.; Rana, Pawan S.

    2015-08-01

    This work deals with the synthesis of TiO2 nanostructures using sol-gel and hydrothermal method for evaluating their photodegradation performance towards decolorization of Rose Bengal (RB). A combination of characterization techniques including X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) and UV-Vis spectroscopy were utilized to evaluate the structural, morphological and optical properties of the obtained nanostructures. It was observed that the TiO2 nanoparticles prepared using hydrothermal method were highly crystalline and possess higher band gap value, even when same conditions of temperature, pressure, precursor ratios and solvent amount was kept constant while synthesizing TiO2 nanostructures via sol-gel method. The obvious effect of porous morphology exhibited by TiO2 nanoparticles prepared using hydrothermal route is reflected in its decolorization performance whereby 92.5% of the RB dye solution was degraded in 70 min of irradiation time.

  16. TiO2 impregnated graphene nanostructures: An effectual photocatalysts for water remediation application

    NASA Astrophysics Data System (ADS)

    Rakkesh, R. Ajay; Durgalakshmi, D.; Balakumar, S.

    2015-06-01

    In this work, we describe the fabrication of nanohybrid TiO2 impregnated Graphene nanostructures by modified Hummer's method. The chemically impregnated TiO2-Graphene hybrid nanostructures drastically enhanced their photodegradation activity of methylene blue (MB) dye in an aqueous medium compare to pure TiO2 nanoparticles. The enhancement in the photocatalytic activity was ascribed by a heterojunction between TiO2-Graphene interfaces. It remarkably decreased the recombination rate and likewise increased the number of holes participating in the photodegradation process, confirmed by XPS analysis. This study can provide a new insight for constructing the hybrid photocatalysts, which can be used in environmental pollution and water treatment applications.

  17. Mussel-Directed Synthesis of Nitrogen-Doped Anatase TiO2.

    PubMed

    Xie, Jingjing; Xie, Hao; Su, Bao-Lian; Cheng, Yi-Bing; Du, Xiaodong; Zeng, Hui; Wang, Menghu; Wang, Weimin; Wang, Hao; Fu, Zhengyi

    2016-02-24

    Structure-forming processes leading to biominerals are well worth learning in pursuit of new synthetic techniques. Strategies that attempt to mimic nature in vitro cannot replace an entire complex natural organism, requiring ingenuity beyond chemists' hands. A "bioprocess-inspired synthesis" is demonstrated for fabrication of N-doped TiO2 materials at ambient temperature by direct implantation of precursor into living mussels. The amorphous precursor transforms into N-doped anatase TiO2 with a hierarchical nanostructure. Synthetic TiO2 exhibits high phase stability and enhanced visible-light photocatalytic activity as a result of modifications to its band gap during in vivo mineralization. Intracellular proteins were found to be involved in TiO2 mineralization. Our findings may inspire material production by new synthetic techniques, especially under environmentally benign conditions.

  18. Microbicidal activity of TiO2 nanoparticles synthesised by sol-gel method.

    PubMed

    Priyanka, Karathan Parakkandi; Sukirtha, Thiruvangium Henry; Balakrishna, Kagalagodu Manjunthiah; Varghese, Thomas

    2016-04-01

    In this study, the authors investigated antimicrobial activity of TiO2 nanoparticles (NPs) synthesised by sol-gel method. As synthesised TiO2 NPs were characterised by X-ray diffraction, scanning electron microscopy and ultraviolet-visible absorption spectroscopy. The antimicrobial activity of calcined TiO2 nanoparticle samples was examined in day light on Gram positive bacteria (Staphylococcus aureus, Streptococcus pneumonia and Bacillus subtilis), Gram negative bacteria (Proteus vulgaris, Pseudomonas aeruginosa and Escherichia coli) and fungal test pathogen Candida albicans. The synthesised TiO2 NPs were found to be effective in visible light against Streptococcus pneumonia, Staphylococcus aureus, Proteus vulgaris, Pseudomonas aeruginosa and Candida albicans. PMID:27074858

  19. Room-Temperature Ferromagnetism in TiO2 Nanocrystals Synthesized by the Controlled Hydrolysis Procedure.

    PubMed

    Gu, Deen; Sun, Zhanhong; Zhou, Lv; Hu, Yongda; Jiang, Yadong

    2016-03-01

    TiO2 nanocrystals were prepared by a controlled hydrolysis procedure at room temperature. The effect of V-doping, N-doping and V/N codoping on the lattice parameters and magnetic properties of TiO2 nanocrystals was investigated by means of X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy and vibration sample magnetometry. Doping performed at room temperature causes the expansion of lattice parameters. Undoped and doped TiO2 nanocrystals show room-temperature ferromagnetism. A monotonic correlation between saturation magnetization and the ratio of the lattice parameter c to a (c/a) was observed. Saturation magnetization of TiO2 nanocrystals increases with the value of c/a.

  20. Pulsed electric field assisted sol-gel preparation of TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Mani, Rajaboopathi; Han, Bing; Louhi-Kultanen, Marjatta

    2016-10-01

    This work studies the effect of a pulsed electric field (PEF) on the precipitation and properties of TiO2 nanoparticles. TiO2 nanoparticles were prepared using pulsed DC electric field assisted sol-gel method. The duration of the PEF treatment was varied to investigate its effect on the particle size of TiO2 nanoparticles. The nanoparticles were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, UV diffuse reflectance spectroscopy (UV-DRS) and transmission electron microscopy (TEM). It was found that TiO2 particles prepared with pulsed electric field assisted sol-gel method had enhanced average crystallite size due to the effect of the pulsed electric field on primary nucleation. The effect of electric field on nanoparticle preparation is interesting which can be used to control the grain and crystallite size of nanoparticle.

  1. Novel hollow mesoporous 1D TiO2 nanofibers as photovoltaic and photocatalytic materials.

    PubMed

    Zhang, Xiang; Thavasi, Velmurugan; Mhaisalkar, S G; Ramakrishna, Seeram

    2012-03-01

    Hollow mesoporous one dimensional (1D) TiO(2) nanofibers are successfully prepared by co-axial electrospinning of a titanium tetraisopropoxide (TTIP) solution with two immiscible polymers; polyethylene oxide (PEO) and polyvinylpyrrolidone (PVP) using a core-shell spinneret, followed by annealing at 450 °C. The annealed mesoporous TiO(2) nanofibers are found to having a hollow structure with an average diameter of 130 nm. Measurements using the Brunauer-Emmett-Teller (BET) method reveal that hollow mesoporous TiO(2) nanofibers possess a high surface area of 118 m(2) g(-1) with two types of mesopores; 3.2 nm and 5.4 nm that resulted from gaseous removal of PEO and PVP respectively during annealing. With hollow mesoporous TiO(2) nanofibers as the photoelectrode in dye sensitized solar cells (DSSC), the solar-to-current conversion efficiency (η) and short circuit current (J(sc)) are measured as 5.6% and 10.38 mA cm(-2) respectively, which are higher than those of DSSC made using regular TiO(2) nanofibers under identical conditions (η = 4.2%, J(sc) = 8.99 mA cm(-2)). The improvement in the conversion efficiency is mainly attributed to the higher surface area and mesoporous TiO(2) nanostructure. It facilitates the adsorption of more dye molecules and also promotes the incident photon to electron conversion. Hollow mesoporous TiO(2) nanofibers with close packing of grains and crystals intergrown with each other demonstrate faster electron diffusion, and longer electron recombination time than regular TiO(2) nanofibers as well as P25 nanoparticles. The surface effect of hollow mesoporous TiO(2) nanofibers as a photocatalyst for the degradation of rhodamine dye was also investigated. The kinetic study shows that the hollow mesoporous surface of the TiO(2) nanofibers influenced its interactions with the dye, and resulted in an increased catalytic activity over P25 TiO(2) nanocatalysts. PMID:22315140

  2. Directed synthesis of hierarchical nanostructured TiO2 catalysts and their morphology-dependent photocatalysis for phenol degradation.

    PubMed

    Liu, Lu; Liu, Huajie; Zhao, Ya-Ping; Wang, Yuqiu; Duan, Yueqin; Gao, Guandao; Ge, Ming; Chen, Wei

    2008-04-01

    Nanostructured TiO2 with different hierarchical morphologies were synthesized via a warmly hydrothermal route. The properties of the products were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, N2 adsorption, UV-vis spectroscopy, etc. Two of the products, TiO2 1D nanorods (one-dimensional rutile TiO2 nanorods) and TiO2 3D0D microspheres (three-dimensional anatase TiO2 nanoparticle-assembled microspheres) exhibited superior photocatalytic effects on phenol degradation under UV illumination, compared with TiO2 3D1D microspheres (three-dimensional rutile TiO2 nanorods-assembled microspheres). Moreover, TiO2 3D0D was superior to TiO2 1D, as indicated by a 30% higher mineralization of dissolved phenol. Dihydroxybenze, 4,4'-dihydroxybiphenyl, benzoquinone, maleic anhydride, etc. were identified as the degradation intermediates. The excellent catalytic effect was attributed to the structural features of TiO2 1D nanorods and TiO2 3D0D microspheres, that is, a larger amount of surface active sites and a higher band gap energy resulted in more efficient decomposition of organic contaminants. PMID:18504963

  3. Directed synthesis of hierarchical nanostructured TiO2 catalysts and their morphology-dependent photocatalysis for phenol degradation.

    PubMed

    Liu, Lu; Liu, Huajie; Zhao, Ya-Ping; Wang, Yuqiu; Duan, Yueqin; Gao, Guandao; Ge, Ming; Chen, Wei

    2008-04-01

    Nanostructured TiO2 with different hierarchical morphologies were synthesized via a warmly hydrothermal route. The properties of the products were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, N2 adsorption, UV-vis spectroscopy, etc. Two of the products, TiO2 1D nanorods (one-dimensional rutile TiO2 nanorods) and TiO2 3D0D microspheres (three-dimensional anatase TiO2 nanoparticle-assembled microspheres) exhibited superior photocatalytic effects on phenol degradation under UV illumination, compared with TiO2 3D1D microspheres (three-dimensional rutile TiO2 nanorods-assembled microspheres). Moreover, TiO2 3D0D was superior to TiO2 1D, as indicated by a 30% higher mineralization of dissolved phenol. Dihydroxybenze, 4,4'-dihydroxybiphenyl, benzoquinone, maleic anhydride, etc. were identified as the degradation intermediates. The excellent catalytic effect was attributed to the structural features of TiO2 1D nanorods and TiO2 3D0D microspheres, that is, a larger amount of surface active sites and a higher band gap energy resulted in more efficient decomposition of organic contaminants.

  4. Efficient solar photocatalytic activity of TiO2 coated nano-porous silicon by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Sampath, Sridhar; Maydannik, Philipp; Ivanova, Tatiana; Shestakova, Marina; Homola, Tomáš; Bryukvin, Anton; Sillanpää, Mika; Nagumothu, Rameshbabu; Alagan, Viswanathan

    2016-09-01

    In the present study, TiO2 coated nano-porous silicon (TiO2/PS) was prepared by atomic layer deposition (ALD) whereas porous silicon was prepared by stain etching method for efficient solar photocatalytic activity. TiO2/PS was characterized by FESEM, AFM, XRD, XPS and DRS UV-vis spectrophotometer. Absorbance spectrum revealed that TiO2/PS absorbs complete solar light with wave length range of 300 nm-800 nm and most importantly, it absorbs stronger visible light than UV light. The reason for efficient solar light absorption of TiO2/PS is that nanostructured TiO2 layer absorbs UV light and nano-porous silicon layer absorbs visible light which is transparent to TiO2 layer. The amount of visible light absorption of TiO2/PS directly increases with increase of silicon etching time. The effect of silicon etching time of TiO2/PS on solar photocatalytic activity was investigated towards methylene blue dye degradation. Layer by layer solar absorption mechanism was used to explain the enhanced photocatalytic activity of TiO2/PS solar absorber. According to this, the photo-generated electrons of porous silicon will be effectively injected into TiO2 via hetero junction interface which leads to efficient charge separation even though porous silicon is not participating in any redox reactions in direct.

  5. Study of TiO2 nanomembranes obtained by an induction heated MOCVD reactor

    NASA Astrophysics Data System (ADS)

    Crisbasan, A.; Chaumont, D.; Sacilotti, M.; Crisan, A.; Lazar, A. M.; Ciobanu, I.; Lacroute, Y.; Chassagnon, R.

    2015-12-01

    Nanostructures of TiO2 were grown using the metal oxide chemical vapor deposition (MOCVD) technique. The procedure used induction heating on a graphite susceptor. This specific feature and the use of cobalt and ferrocene catalysts resulted in nanomembranes never obtained by common MOCVD reactors. The present study discusses the preparation of TiO2 nanomembranes and the dependence of nanomembrane structure and morphology on growth parameters.

  6. Kinetics and mechanism of photolysis and TiO2 photocatalysis of triclosan.

    PubMed

    Son, Hyun-Seok; Ko, Gwangpyo; Zoh, Kyung-Duk

    2009-07-30

    The degradations of triclosan (5-chloro-2-(2,4-dichlorophenoxy)-phenol), a potent broad-spectrum antimicrobial agent, were compared in TiO2-only in the dark condition, photolysis, and TiO2 photocatalysis with a UV-A lamp. TiO2 photocatalysis more effectively degraded and mineralized triclosan compared to TiO2-only and photolysis conditions. While triclosan removed only 30% by TiO2-only condition within 20 min, the triclosan degradation in photolysis and photocatalysis at the same time was 75 and 82%, respectively, and TOC removal was significantly higher in photocatalysis than in photolysis. The data of kinetics showed that triclosan adsorption onto TiO2 was fitted to Langmuir isotherm, and TiO2 photocatalysis was fitted to Langmuir-Hinshelwood model (b=27.99 mM(-1), K(triclosan)=9.49 mM(-1)). The neutral range of pH was favorable to photocatalysis due to the charge effect between TiO2 and triclosan. The addition of 2-propanol, a radical scavenger, significantly reduced the degradation of triclosan both in photolysis and photocatalysis. Dioxin-type intermediates such as dibenzo-dichloro-p-dioxin (DCDD), dibenzo-p-dioxin were produced in photolysis with and without 2-propanol, and also in photocatalysis with 2-propanol, but these intermediates were not detected in photocatalysis without 2-propanol. This result indicates that the photocatalytic degradation of triclosan is mainly achieved by radicals, and these radicals can further degrade dioxin-type intermediates once they are produced in photocatalysis.

  7. Characterization and improved solar light activity of vanadium doped TiO2/diatomite hybrid catalysts.

    PubMed

    Wang, Bin; Zhang, Guangxin; Leng, Xue; Sun, Zhiming; Zheng, Shuilin

    2015-03-21

    V-doped TiO2/diatomite composite photocatalysts with different vanadium concentrations were synthesized by a modified sol-gel method. The diatomite was responsible for the well dispersion of TiO2 nanoparticles on the matrix and consequently inhibited the agglomeration. V-TiO2/diatomite hybrids showed red shift in TiO2 absorption edge with enhanced absorption intensity. Most importantly, the dopant energy levels were formed in the TiO2 bandgap due to V(4+) ions substituted to Ti(4+) sites. The 0.5% V-TiO2/diatomite photocatalyst displayed narrower bandgap (2.95 eV) compared to undoped sample (3.13 eV) and other doped samples (3.05 eV) with higher doping concentration. The photocatalytic activities of V doped TiO2/diatomite samples for the degradation of Rhodamine B under stimulated solar light illumination were significantly improved compared with the undoped sample. In our case, V(4+) ions incorporated in TiO2 lattice were responsible for increased visible-light absorption and electron transfer to oxygen molecules adsorbed on the surface of TiO2 to produce superoxide radicals ˙O2(-), while V(5+) species presented on the surface of TiO2 particles in the form of V2O5 contributed to e(-)-h(+) separation. In addition, due to the combination of diatomite as support, this hybrid photocatalyst could be separated from solution quickly by natural settlement and exhibited good reusability.

  8. Photocatalytic degradation of acetaminophen in modified TiO2 under visible irradiation.

    PubMed

    Dalida, Maria Lourdes P; Amer, Kristine Marfe S; Su, Chia-Chi; Lu, Ming-Chun

    2014-01-01

    This study investigated the photocatalytic degradation of acetaminophen (ACT) in synthetic titanium dioxide (TiO2) solution under a visible light (λ >440 nm). The TiO2 photocatalyst used in this study was synthesized via sol-gel method and doped with potassium aluminum sulfate (KAl(SO4)2) and sodium aluminate (NaAlO2). The influence of some parameters on the degradation of acetaminophen was examined, such as initial pH, photocatalyst dosage, and initial ACT concentration. The optimal operational conditions were also determined. Results showed that synthetic TiO2 catalysts presented mainly as anatase phase and no rutile phase was observed. The results of photocatalytic degradation showed that LED alone degraded negligible amount of ACT but with the presence of TiO2/KAl(SO4)2, 95% removal of 0.10-mM acetaminophen in 540-min irradiation time was achieved. The synthetic TiO2/KAl(SO4)2 presented better photocatalytic degradation of acetaminophen than commercially available Degussa P-25. The weak crystallinity of synthesized TiO2/NaAlO2 photocatalyst showed low photocatalytic degradation than TiO2/KAl(SO4)2. The optimal operational conditions were obtained in pH 6.9 with a dose of 1.0 g/L TiO2/KAl(SO4)2 at 30 °C. Kinetic study illustrated that photocatalytic degradation of acetaminophen fits well in the pseudo-first order model. Competitive reactions from intermediates affected the degradation rate of ACT, and were more obvious as the initial ACT concentration increased.

  9. Synthesis, characterization, and photocatalytic activity of TiO(2-x)N(x) nanocatalyst.

    PubMed

    Wang, Y Q; Yu, X J; Sun, D Z

    2007-06-01

    Nitrogen-doped titanium dioxide powders were prepared by wet method, that is, the hydrolysis of acidic tetra-butyl titanate using aqueous ammonia solution, followed by calcination at temperatures about 350 degrees C. The catalysts exhibited photocatalytic activity in the visible light region owing to N-doping. The light absorption onset of TiO(2-x)N(x) was shifted to the visible region at 459 nm compared to 330 nm of pure TiO(2). An obvious decrease in the band gap was observed by the optical absorption spectroscopy, which resulted from N2p localized states above the valence band of TiO(2-x)N(x) (compared to TiO(2)). The TiO(2-x)N(x) catalyst was characterized to be anatase with oxygen-deficient stoichiometry by X-ray diffraction (XRD), surface photovoltage spectroscopy (SPS) and X-ray photoelectron spectroscopy (XPS). The binding energy of N1s measured by XPS characterization was 396.6 eV (TiN bonds, beta-N) and 400.9 eV (NN bonds, gamma-N(2)), respectively. The photocatalytic activity of TiO(2-x)N(x) under visible light was induced by the formation of beta-N in the structure. Photocatalytic decomposition of benzoic acid solutions was carried out in the ultraviolet and visible (UV-vis) light region, and the TiO(2-x)N(x) catalyst showed higher activity than pure TiO(2). PMID:17116365

  10. Characterization and improved solar light activity of vanadium doped TiO2/diatomite hybrid catalysts.

    PubMed

    Wang, Bin; Zhang, Guangxin; Leng, Xue; Sun, Zhiming; Zheng, Shuilin

    2015-03-21

    V-doped TiO2/diatomite composite photocatalysts with different vanadium concentrations were synthesized by a modified sol-gel method. The diatomite was responsible for the well dispersion of TiO2 nanoparticles on the matrix and consequently inhibited the agglomeration. V-TiO2/diatomite hybrids showed red shift in TiO2 absorption edge with enhanced absorption intensity. Most importantly, the dopant energy levels were formed in the TiO2 bandgap due to V(4+) ions substituted to Ti(4+) sites. The 0.5% V-TiO2/diatomite photocatalyst displayed narrower bandgap (2.95 eV) compared to undoped sample (3.13 eV) and other doped samples (3.05 eV) with higher doping concentration. The photocatalytic activities of V doped TiO2/diatomite samples for the degradation of Rhodamine B under stimulated solar light illumination were significantly improved compared with the undoped sample. In our case, V(4+) ions incorporated in TiO2 lattice were responsible for increased visible-light absorption and electron transfer to oxygen molecules adsorbed on the surface of TiO2 to produce superoxide radicals ˙O2(-), while V(5+) species presented on the surface of TiO2 particles in the form of V2O5 contributed to e(-)-h(+) separation. In addition, due to the combination of diatomite as support, this hybrid photocatalyst could be separated from solution quickly by natural settlement and exhibited good reusability. PMID:25497036

  11. Bacterial responses to Cu-doped TiO(2) nanoparticles.

    PubMed

    Wu, Bing; Huang, Rick; Sahu, Manoranjan; Feng, Xueyang; Biswas, Pratim; Tang, Yinjie J

    2010-03-01

    The toxicity of Cu-doped TiO(2) nanoparticles (NPs, 20nm), synthesized by a flame aerosol reactor, to Mycobacterium smegmatis and Shewanella oneidensis MR-1, is the primary focus of this study. Both doped and non-doped TiO(2) NPs (20nm) tended to agglomerate in the medium solution, and therefore did not penetrate into the cell and damage cellular structures. TiO(2) particles (<100mg/L) did not apparently interfere with the growth of the two species in aqueous cultures. Cu-doped TiO(2) NPs (20mg/L) significantly reduced the M. smegmatis growth rate by three fold, but did not affect S. oneidensis MR-1 growth. The toxicity of Cu-doped TiO(2) NPs was driven by the release of Cu(2+) from the parent NPs. Compared to equivalent amounts of Cu(2+), Cu-doped TiO(2) NPs exhibited higher levels of toxicity to M. smegmatis (P-value<0.1). Addition of EDTA in the culture appeared to significantly decrease the anti-mycobacterium activity of Cu-doped TiO(2) NPs. S. oneidensis MR-1 produced a large amount of extracellular polymeric substances (EPS) under NP stress, especially extracellular protein. Therefore, S. oneidensis MR-1 was able to tolerate a much higher concentration of Cu(2+) or Cu-doped TiO(2) NPs. S. oneidensis MR-1 also adsorbed NPs on cell surface and enzymatically reduced ionic copper in culture medium with a remediating rate of 61microg/(liter x OD(600) x hour) during its early exponential growth phase. Since the metal reducing Shewanella species can efficiently "clean" metal-oxide NPs, the activities of such environmentally relevant bacteria may be an important consideration for evaluating the ecological risk of metal-oxide NPs. PMID:19931887

  12. Remarkable Charge Separation and Photocatalytic Efficiency Enhancement through Interconnection of TiO2 Nanoparticles by Hydrothermal Treatment.

    PubMed

    Ide, Yusuke; Inami, Nozomu; Hattori, Hideya; Saito, Kanji; Sohmiya, Minoru; Tsunoji, Nao; Komaguchi, Kenji; Sano, Tsuneji; Bando, Yoshio; Golberg, Dmitri; Sugahara, Yoshiyuki

    2016-03-01

    Although tremendous effort has been directed to synthesizing advanced TiO2 , it remains difficult to obtain TiO2 exhibiting a photocatalytic efficiency higher than that of P25, a benchmark photocatalyst. P25 is composed of anatase, rutile, and amorphous TiO2 particles, and photoexcited electron transfer and subsequent charge separation at the anatase-rutile particle interfaces explain its high photocatalytic efficiency. Herein, we report on a facile and rational hydrothermal treatment of P25 to selectively convert the amorphous component into crystalline TiO2 , which is deposited between the original anatase and rutile particles to increase the particle interfaces and thus enhance charge separation. This process produces a new TiO2 exhibiting a considerably enhanced photocatalytic efficiency. This method of synthesizing this TiO2 , inspired by a recently burgeoning zeolite design, promises to make TiO2 applications more feasible and effective.

  13. Efficient removal of toluene and benzene in gas phase by the TiO2/Y-zeolite hybrid photocatalyst.

    PubMed

    Takeuchi, Masato; Hidaka, Manabu; Anpo, Masakazu

    2012-10-30

    Efficient removal of toluene or benzene molecules thinly diffused in gas phase was achieved by using TiO(2)/Y-zeolite hybrid photocatalysts. TiO(2) of 10 wt% hybridized with a hydrophobic USY zeolite showed higher photocatalytic reactivity as compared to TiO(2) hybridized with hydrophilic H-Y or Na-Y zeolites. This phenomenon can be explained by the fact that the hydrophobic USY zeolite efficiently adsorbs the organic compounds and smoothly supplies them onto the TiO(2) photocatalyst surface. However, the toluene or benzene molecules, which are strongly trapped on the hydrophilic H(+) or Na(+) sites of zeolite, cannot diffuse onto the TiO(2) surfaces, resulting in lower photocatalytic reactivity. Although the adsorption capacity of the pure TiO(2) sample rapidly deteriorated, the TiO(2)/Y-zeolite hybrid system maintained a high adsorption efficiency to remove such aromatic compounds for a long period. PMID:22947182

  14. Structural and optical properties of terbium in TiO 2 matrix

    NASA Astrophysics Data System (ADS)

    Domaradzki, Jaroslaw; Prociow, Eugeniusz L.; Kaczmarek, Danuta; Borkowska, Agnieszka; Berlicki, Tadeusz; Prociow, Krystyna

    2009-07-01

    TiO 2 thin films doped with different concentration of Tb have been prepared and study of terbium photoluminescence in TiO 2 host has been presented. Thin films were deposited on silicon and SiO 2 substrates by magnetron sputtering of Ti-Tb mosaic target in oxygen atmosphere. XRD examinations show nanocrystalline nature of prepared thin films with TiO 2-anatase and -rutile phases depending on concentration of Tb. Optical transmission study has shown the red shift of the fundamental absorption edge of TiO 2 with the increase of terbium content in the thin film. Also, the transparency decreased with increasing in amount of Tb. Photoluminescence (PL) spectra, measured upon UV excitation at 302 nm at room temperature, show a dominating green luminescence corresponding to 5D 4- 7F 5 transition at 545 nm for TiO 2-rutile thin film with 2.6 at.% of Tb. The superposition of PL peaks from Tb and TiO 2 host matrix was also observed at 491 nm.

  15. Surface Plasmon Enhanced Photocatalysis of Au/Pt-decorated TiO2 Nanopillar Arrays

    PubMed Central

    Shuang, Shuang; Lv, Ruitao; Xie, Zheng; Zhang, Zhengjun

    2016-01-01

    The low quantum yields and lack of visible light utilization hinder the practical application of TiO2 in high-performance photocatalysis. Herein, we present a design of TiO2 nanopillar arrays (NPAs) decorated with both Au and Pt nanoparticles (NPs) directly synthesized through successive ion layer adsorption and reaction (SILAR) at room temperature. Au/Pt NPs with sizes of ~4 nm are well-dispersed on the TiO2 NPAs as evidenced by electron microscopic analyses. The present design of Au/Pt co-decoration on the TiO2 NPAs shows much higher visible and ultraviolet (UV) light absorption response, which leads to remarkably enhanced photocatalytic activities on both the dye degradation and photoelectrochemical (PEC) performance. Its photocatalytic reaction efficiency is 21 and 13 times higher than that of pure TiO2 sample under UV-vis and visible light, respectively. This great enhancement can be attributed to the synergy of electron-sink function of Pt and surface plasmon resonance (SPR) of Au NPs, which significantly improves charge separation of photoexcited TiO2. Our studies demonstrate that through rational design of composite nanostructures one can harvest visible light through the SPR effect to enhance the photocatalytic activities initiated by UV-light, and thus realize more effectively utilization of the whole solar spectrum for energy conversion. PMID:27215703

  16. Facile synthesis of porous TiO2 nanospheres and their photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Huang, Jiarui; Ren, Haibo; Liu, Xiaosi; Li, Xuexue; Shim, Jae-Jin

    2015-05-01

    Uniform and monodisperse porous TiO2 nanospheres were synthesized by a hydrothermal method. Techniques of X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller (BET) nitrogen adsorption-desorption, UV-vis absorption spectroscopy, and transmission electron microscopy were used to characterize the structure and morphology of the products. The BET surface area of the porous TiO2 nanospheres was calculated to be 26.1 cm2 g-1. In addition, the obtained porous TiO2 nanospheres were used as catalyst to photodegrade methylene blue, Rhodamine B, methyl orange, p-nitrophenol, and eosin B. Compared to commercial TiO2 powder, the as-prepared porous TiO2 nanospheres exhibited higher catalytic activities due to their large surface areas and porous nanostructures. The photocatalytic reaction rate constant of the porous TiO2 nanospheres in photocatalytic decomposition of methylene blue and Rhodamine B under simulated solar light were calculated as 0.0545 min-1 and 0.0579 min-1, respectively. Moreover, the catalyst was demonstrated to have good stability and reusability.

  17. Superhydrophilic graphene-loaded TiO2 thin film for self-cleaning applications.

    PubMed

    Anandan, Srinivasan; Rao, Tata Narasinga; Sathish, Marappan; Rangappa, Dinesh; Honma, Itaru; Miyauchi, Masahiro

    2013-01-01

    We develop a simple approach to fabricate graphene-loaded TiO(2) thin films on glass substrates by the spin-coating technique. Our graphene-loaded TiO(2) films were highly conductive and transparent and showed enhanced photocatalytic activities. More significantly, graphene/TiO(2) films displayed superhydrophilicity within a short time even under a white fluorescent light bulb, as compared to a pure TiO(2) film. The enhanced photocatalytic activity of graphene/TiO(2) films is attributed to its efficient charge separation, owing to electrons injection from the conduction band of TiO(2) to graphene. The electroconductivity of the graphene-loaded TiO(2) thin film also contributes to the self-cleaning function by its antifouling effect against particulate contaminants. The present study reveals the ability of graphene as a low cost cocatalyst instead of expensive noble metals (Pt, Pd), and further shows its capability for the application of self-cleaning coatings with transparency. The promising characteristics of (inexpensive, transparent, conductive, superhydrophilic, and highly photocatalytically active) graphene-loaded TiO(2) films may have the potential use in various indoor applications.

  18. Location Of Hole And Electron Traps On Nanocrystalline Anatase TiO2

    SciTech Connect

    Mercado, Candy C.; Knorr, Fritz J.; McHale, Jeanne L.; Usmani, Shirin M.; Ichimura, Andrew S.; Saraf, Laxmikant V.

    2012-05-17

    The defect photoluminescence from TiO2 nanoparticles in the anatase phase is reported for nanosheets which expose predominantly (001) surfaces, and compared to that from conventional anatase nanoparticles which expose mostly (101) surfaces. Also reported is the weak defect photoluminescence of TiO2 nanotubes, which we find using electron back-scattered diffraction to consist of walls which expose (110) and (100) facets. The nanotubes exhibit photoluminescence that is blue-shifted and much weaker than that from conventional TiO2 nanoparticles. Despite the preponderance of (001) surfaces in the nanosheet samples, they exhibit photoluminescence similar to that of conventional nanoparticles. We assign the broad visible photoluminescence of anatase nanoparticles to two overlapping distributions: hole trap emission associated with oxygen vacancies on (101) exposed surfaces, which peaks in the green, and a broader emission extending into the red which results from electron traps on under-coordinated titanium atoms, which are prevalent on (001) facets. The results of this study suggest how morphology of TiO2 nanoparticles could be optimized to control the distribution and activity of surface traps. Our results also shed light on the mechanism by which the TiCl4 surface treatment heals traps on anatase and mixed-phase TiO2 films, and reveals distinct differences in the trap-state distributions of TiO2 nanoparticles and nanotubes. The molecular basis for electron and hole traps and their spatial separation on different facets is discussed.

  19. Micropatterning of TiO2 Thin Films by MOCVD and Study of Their Growth Tendency

    PubMed Central

    Hwang, Ki-Hwan; Kang, Byung-Chang; Jung, Duk Young; Kim, Youn Jea; Boo, Jin-Hyo

    2015-01-01

    In this work, we studied the growth tendency of TiO2 thin films deposited on a narrow-stripe area (<10 μm). TiO2 thin films were selectively deposited on OTS patterned Si(100) substrates by MOCVD. The experimental data showed that the film growth tendency was divided into two behaviors above and below a line patterning width of 4 μm. The relationship between the film thickness and the deposited area was obtained as a function of f(x) = a[1 − e(−bx)]c. To find the tendency of the deposition rate of the TiO2 thin films onto the various linewidth areas, the relationship between the thickness of the TiO2 thin film and deposited linewidth was also studied. The thickness of the deposited TiO2 films was measured from the alpha-step profile analyses and cross-sectional SEM images. At the same time, a computer simulation was carried out to reveal the relationship between the TiO2 film thickness and deposited line width. The theoretical results suggest that the mass (velocity) flux in flow direction is directly affected to the film thickness. PMID:25799219

  20. Controllable hydrothermal synthesis, optical and photocatalytic properties of TiO2 nanostructures

    NASA Astrophysics Data System (ADS)

    Xu, Yanyan; Zhang, Maocui; Zhang, Miao; Lv, Jianguo; Jiang, Xishun; He, Gang; Song, XuePing; Sun, Zhaoqi

    2014-10-01

    Different surface morphologies of TiO2 thin films were prepared by hydrothermal synthesis method on Ti substrates through changing reaction time. The microstructure, composition, optical properties and photocatalytic properties of TiO2 thin films were systematically investigated by x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectrometer and ultraviolet-visible spectroscopy. As the reaction time increases, anatase structure and brookite structure of TiO2 films respectively increases and decreases, corresponding to surface morphology changes from irregular structure to regular geometrical shape structure. These structural changes are accompanied by significant variations of optical properties and photocatalytic properties including a widening of the band gap from 2.86 to 3.19 eV, photocatalytic degradation efficiency from 92.5 to 98.1% and photocatalytic degradation rate from 0.032 to 0.048 min-1. Among all samples, TiO2-1 shows the best photocatalytic properties. Compositional analysis indicates that TiO2 surface layer contains Ti and O elements, the ratio of Ti:O is 1:2.28 which is close to the atom ratio of TiO2.

  1. Photoluminescence studies of nitrogen-doped TiO2 powders prepared by annealing with urea

    NASA Astrophysics Data System (ADS)

    Kawai, T.; Kishimoto, Y.; Kifune, K.

    2012-11-01

    Photoluminescence and excitation spectra have been investigated for undoped and nitrogen-doped TiO2 powders at low temperatures. A broad luminescence band peaking at 2.25 eV is observed in the undoped TiO2 powders. The 2.25 eV luminescence band exhibits a sharp rise from 3.34 eV in the excitation spectrum reflecting the fundamental absorption edge of anatase TiO2. On the other hand, the N-doped TiO2 powders obtained by annealing with urea at 350 and 500°C exhibit broad luminescence bands around 2.89 and 2.63 eV, respectively. The excitation spectra for these luminescence bands rise from the lower energy side of the fundamental absorption edge of anatase TiO2. The origin of the luminescence bands and N-related energy levels formed in the band-gap of TiO2 are discussed.

  2. Photoactive TiO2 coatings obtained by Plasma Electrolytic Oxidation in refrigerated electrolytes

    NASA Astrophysics Data System (ADS)

    Franz, Silvia; Perego, Daniele; Marchese, Ottavia; Lucotti, Andrea; Bestetti, Massimiliano

    2016-11-01

    The effect of synthesis conditions on the properties of nanoporous TiO2 coatings obtained by PEO in refrigerated electrolytes have been investigated. Linear sweep voltammetry was carried out on the TiO2 coatings, in dark and under UV-C irradiation, in order to assess the photoelectrochemical behavior of samples. The largest photocurrents (0.18 mA/cm2) were measured on TiO2 coatings obtained by PEO in refrigerated aqueous solutions. UV-vis spectra revealed that lowering the processing temperature from 20 to -3.5 °C induced a blue-shift of the absorption band of the TiO2 coatings from 3.05 to 3.42 eV. The main advantage of PEO in refrigerated aqueous solutions over current approaches, based on anodic oxidation and thermal treatments, is that the synthesis of photoactive TiO2 coatings can be carried out in a relatively easy, quick and reproducible way, without annealing pre- and post-treatments. Furthermore, by controlling the solution temperature in PEO process, the photocurrent of the resulting TiO2 coating reaches quite high values.

  3. Charge transfer in photorechargeable composite films of TiO2 and polyaniline

    NASA Astrophysics Data System (ADS)

    Nomiyama, Teruaki; Sasabe, Kenichi; Sakamoto, Kenta; Horie, Yuji

    2015-07-01

    A photorechargeable battery (PRB) is a photovoltaic device having an energy storage function in a single cell. The photoactive electrode of PRB is a bilayer film consisting of bare porous TiO2 and a TiO2-polyaniline (PANi) mixture that work as a photovoltaic current generator and an electrochemical energy storage by ion dedoping, respectively. To study the charge transfer between TiO2 and PANi, the photorechargeable quantum efficiency QE ([electron count on discharge]/[incident photon count on photocharge]) was measured by varying the thickness LS of the TiO2-PANi mixture. The quantum efficiency QEuv for UV photons had a maximum of ˜7% at LS ˜ 7 µm. The time constant τTP for the charge transfer was about 10-1 s, which was longer ten times or more than the lifetime of excited electrons within TiO2. These facts reveal that the main rate-limiting factor in the photocharging process is the charge transfer between TiO2 and PANi.

  4. Photocatalytic Oxidation of Volatile Organic Compounds Over Electrospun Activated TIO2/CARBON Nanofiber Composite

    NASA Astrophysics Data System (ADS)

    Gholamvand, Zahra; Aboutalebi, Seyed Hamed; Keyanpour-Rad, Mansoor

    In this study, TiO2/PAN-based fibers were prepared by electrospinning a composite solution containing both the desirable contents of TiO2 and a 10 wt. % PAN polymer solution dissolved in N, N-dimethylformamide. The TiO2 loaded electrospun PAN nanofibers were then carbonized at 1000 °C in N2 atmosphere furnace after stabilization at 230 °C in air. Then CNF/TiO2 nanofibers were oxidized at 450 °C in air. The morphology and structure of the TiO2-embeded carbon nanofibers were investigated by SEM and Raman spectroscopy. Specific surface area was determined using BET equation from N2 adsorption analysis. Photocatalytic tests were conducted in a UV illuminated set-up specialized for the filters using ethanol vapor. The results have shown that ethanol vapor was efficiently degraded on TiO2/CNF composite nanofiber mat under UV illumination. The aim of this study was to further investigate the feasibility of TiO2/ACF for practical indoor air purification.

  5. Nanocomposites of TiO2/cyanoethylated cellulose with ultra high dielectric constants

    NASA Astrophysics Data System (ADS)

    Madusanka, Nadeesh; Shivareddy, Sai G.; Hiralal, Pritesh; Eddleston, Mark D.; Choi, Youngjin; Oliver, Rachel A.; Amaratunga, Gehan A. J.

    2016-05-01

    A novel dielectric nanocomposite containing a high permittivity polymer, cyanoethylated cellulose (CRS) and TiO2 nanoparticles was successfully prepared with different weight percentages (10%, 20% and 30%) of TiO2. The intermolecular interactions and morphology within the polymer nanocomposites were analysed. TiO2/CRS nanofilms on SiO2/Si wafers were used to form metal-insulator-metal type capacitors. Capacitances and loss factors in the frequency range of 1 kHz-1 MHz were measured. At 1 kHz CRS-TiO2 nanocomposites exhibited ultra high dielectric constants of 118, 176 and 207 for nanocomposites with 10%, 20% and 30% weight of TiO2 respectively, significantly higher than reported values of pure CRS (21), TiO2 (41) and other dielectric polymer-TiO2 nanocomposite films. Furthermore, all three CRS-TiO2 nanocomposites show a loss factor <0.3 at 1 kHz and low leakage current densities (10-6-10-7 A cm-2). Leakage was studied using conductive atomic force microscopy and it was observed that the leakage is associated with TiO2 nanoparticles embedded in the CRS polymer matrix. A new class of ultra high dielectric constant hybrids using nanoscale inorganic dielectrics dispersed in a high permittivity polymer suitable for energy management applications is reported.

  6. Surface Plasmon Enhanced Photocatalysis of Au/Pt-decorated TiO2 Nanopillar Arrays.

    PubMed

    Shuang, Shuang; Lv, Ruitao; Xie, Zheng; Zhang, Zhengjun

    2016-01-01

    The low quantum yields and lack of visible light utilization hinder the practical application of TiO2 in high-performance photocatalysis. Herein, we present a design of TiO2 nanopillar arrays (NPAs) decorated with both Au and Pt nanoparticles (NPs) directly synthesized through successive ion layer adsorption and reaction (SILAR) at room temperature. Au/Pt NPs with sizes of ~4 nm are well-dispersed on the TiO2 NPAs as evidenced by electron microscopic analyses. The present design of Au/Pt co-decoration on the TiO2 NPAs shows much higher visible and ultraviolet (UV) light absorption response, which leads to remarkably enhanced photocatalytic activities on both the dye degradation and photoelectrochemical (PEC) performance. Its photocatalytic reaction efficiency is 21 and 13 times higher than that of pure TiO2 sample under UV-vis and visible light, respectively. This great enhancement can be attributed to the synergy of electron-sink function of Pt and surface plasmon resonance (SPR) of Au NPs, which significantly improves charge separation of photoexcited TiO2. Our studies demonstrate that through rational design of composite nanostructures one can harvest visible light through the SPR effect to enhance the photocatalytic activities initiated by UV-light, and thus realize more effectively utilization of the whole solar spectrum for energy conversion. PMID:27215703

  7. Degradability of Treated Ethion Insecticide by TiO2 Photocatalysis.

    PubMed

    Hassarangsee, Siriporn; Uthaibutra, Jamnong; Nomura, Nakao; Whangchai, Kanda

    2015-01-01

    Ethion, an insecticide, is widely used with fruit and vegetable crops. This research studied the reduction and oxidative degradation of standard ethion by TiO2 photocatalysis. A standard ethion solution (1 mg L(-1)) was treated with different concentrations of TiO2 powder (5, 10, 20, 40 and 60 mg mL(-1)) for 0, 15, 30, 45 and 60 min. The amount of ethion residue was detected by gas chromatography with flame photometric detection (GC-FPD) and the concentration of anions produced as major degradation products was determined by Ion Chromatography (IC). The TiO2 photocatalysis efficiently reduced ethion concentrations, with the highest degradation rate occurring within the first 15 min of reaction. The reaction produced sulphate and phosphate anions. The TiO2photocatalysis reduced 1 mg L(-1) ethion to 0.18 mg L(-1) when treated with 60 mg mL(-1) TiO2 powder for 60 min. The lethal concentration (LC50) of standard ethion was also estimated and compared to the treated ethion. All treatments, especially 60 mg mL(-1) TiO2 powder, markedly detoxified ethion, as tested with brine shrimp (Artemia salina L.), with an LC50 value of 765.8 mg mL(-1), compared to the control of 1.01 mg mL(-1). PMID:26353413

  8. Bifunctional ultraviolet/ultrasound responsive composite TiO2/polyelectrolyte microcapsules.

    PubMed

    Gao, Hui; Wen, Dongsheng; Tarakina, Nadezda V; Liang, Jierong; Bushby, Andy J; Sukhorukov, Gleb B

    2016-03-01

    Designing and fabricating multifunctional microcapsules are of considerable interest in both academic and industrial research aspects. This work reports an innovative approach to fabricate composite capsules with high UV and ultrasound responsive functionalities that can be used as external triggers for controlled release, yet with enhanced mechanical strength that can make them survive in a harsh environment. Needle-like TiO2 nanoparticles (NPs) were produced in situ into layer-by-layer (LbL) polyelectrolyte (PE) shells through the hydrolysis of titanium butoxide (TIBO). These rigid TiO2 NPs yielded the formed capsules with excellent mechanical strength, showing a free standing structure. A possible mechanism is proposed for the special morphology formation of the TiO2 NPs and their reinforcing effects. Synergistically, their response to UV and ultrasound was visualized via SEM, with the results showing an irreversible shell rapture upon exposure to either UV or ultrasound irradiation. As expected, the release studies revealed that the dextran release from the TiO2/PE capsules was both UV-dependent and ultrasound-dependent. Besides, the biocompatibility of the capsules with the incorporation of amorphous TiO2 NPs was confirmed by an MTT assay experiment. All these pieces of evidence suggested a considerable potential medicinal application of TiO2/PE capsules for controlled drug delivery. PMID:26878702

  9. Exposure to TiO2 nanoparticles increases Staphylococcusaureusinfection of HeLa cells

    NASA Astrophysics Data System (ADS)

    Xu, Yan; Wei, Ming-Tzo; Walker, Stephen. G.; Wang, Hong Zhan; Gondon, Chris; Brink, Peter; Guterman, Shoshana; Zawacki, Emma; Applebaum, Eliana; Rafailovich, Miriam; Ou-Yang, H. Daniel; Mironava, Tatsiana

    TiO2 is one of the most common nanoparticles in industry from food additives to energy generation. Even though TiO2 is also used as an anti-bacterial agent in combination with UV, we found that, in the absence of UV, exposure of HeLa cells to TiO2 nanoparticles largely increased their risk of bacterial invasion. HeLa cells cultured with low dosage rutile and anatase TiO2 nanoparticles (0.1 mg/ml) for 24 hrs prior to exposure to bacteria had 350% and 250% respectively more bacteria infected per cell. The increase was attributed to increased LDH leakage, and changes in the mechanical response of the cell membrane. On the other hand, macrophages exposed to TiO2 particles ingested 40% fewer bacteria, further increasing the risk of infection. In combination, these two factors raise serious concerns regarding the impact of exposure to TiO2 nanoparticles on the ability of organisms to resist bacterial infection.

  10. Spherical TiO2 aggregates with different building units for dye-sensitized solar cells.

    PubMed

    Liu, Zhaohui; Su, Xunjia; Hou, Genliang; Bi, Song; Xiao, Zhou; Jia, Haipeng

    2013-09-01

    Tailoring the architectures of spherical TiO2 aggregates is crucial to obtain superior photovoltaic properties and promote their application in dye-sensitized solar cells (DSSCs). Herein, we synthesized spherical TiO2 aggregates using different building units, including nanocrystallites, nanorods, nanosheets, and nanotubes, via a hydrothermal method, and studied the effect of the building units on the performances of DSSCs. The aggregates assembled by uniform nanosheet and nanotube building units were synthesized with the use of spherical TiO2 nanorod aggregates as titanium sources in an alkaline hydrothermal reaction. Compared with TiO2 nanoparticles, the spherical TiO2 aggregates possess higher surface area, more efficient light scattering ability, and better electron transport properties. Among the four types of spherical TiO2 aggregates; the nanorod, nanotube, and nanosheet aggregates demonstrate better electron transport properties than the nanocrystallite aggregates; the nanotube and nanosheet aggregates exhibit more efficient light scattering than the nanocrystallite and nanorod aggregates; and the nanotube aggregates show the highest surface area. Thus the DSSC based on nanotube aggregates exhibited the highest energy conversion efficiency of 7.48%, which is 16.0%, 9.7%, and 19.5% higher than those of the DSSCs based on the nanosheet, nanorod, and nanocrystallite aggregates, respectively.

  11. Self-cleaning and mechanical properties of modified white cement with nanostructured TiO2.

    PubMed

    Khataee, R; Heydari, V; Moradkhannejhad, L; Safarpour, M; Joo, S W

    2013-07-01

    In the present study, self-cleaning and mechanical properties of white Portland cement by addition of commercial available TiO2 nanoparticles with the average particle size of 80 nm were investigated. X-ray diffraction (XRD), transmission electron microscopy (TEM) and BET were used to characterize TiO2 nanoparticles. For determination of self-cleaning properties of TiO2-modified white cement, colorimetric tests in decolorization of C.I. Basic Red 46 (BR46) in comparison to unmodified cement samples was applied. The results indicated that with increasing the amount of TiO2 nanoparticles in modified cement, self-cleaning property of the samples increased. The mechanical properties of TiO2-modified and unmodified cement samples, such as time of setting of hydraulic cement, compressive strength of hydraulic cement mortar and flexural strength of hydraulic cement mortar were examined. The results indicated that addition of TiO2 nanoparticles up to maximum replacement level of 1.0% improved compressive and flexural strength and decreased its setting time.

  12. Structure and high photocatalytic activity of (N, Ta)-doped TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Le, N. T. H.; Thanh, T. D.; Pham, V.-T.; Phan, T. L.; Lam, V. D.; Manh, D. H.; Anh, T. X.; Le, T. K. C.; Thammajak, N.; Hong, L. V.; Yu, S. C.

    2016-10-01

    A hydrothermal method was used to prepare three nano-crystalline samples of TiO2 (S1), N-doped TiO2 (S2), and (N, Ta)-codoped TiO2 (S3) with average crystallite sizes (D) of 13-25 nm. X-ray diffraction studies confirmed a single phase of the samples with a tetragonal/anatase structure. A slight increase in the lattice parameters was observed when N and/or Ta dopants were doped into the TiO2 host lattice. Detailed analyses of extended X-ray absorption spectra indicated that N- and/or Ta-doping into TiO2 nanoparticles influenced the co-ordination number and radial distance (R) of Ti ions in the anatase structure. Concerning their absorption spectra, (N, Ta)-doping narrowed the band gap (Eg) of TiO2 from 3.03 eV for S1 through 2.94 eV for S2 to 2.85 eV for S3. Such results revealed the applicability of these nanoparticles in the photocatalytic field working in the ultraviolet (UV)-visible region. Among these, photocatalytic activity of S3 was the strongest. By using S3 as a catalyst powder, the degradation efficiency of methylene blue solution was about 99% and 93% after irradiation of UV-visible light for 75 min and visible-light for 180 min, respectively.

  13. Equilibration Kinetics and Chemical Diffusion of Indium-Doped TiO2.

    PubMed

    Nowotny, Janusz; Alim, Mohammad A

    2015-04-30

    The present work reports the gas/solid equilibration kinetics for In-doped TiO2 (0.4 atom % In) at elevated temperatures (1023-1273 K) in the gas phase of controlled oxygen activity [10(-13) Pa < p(O2) < 10(5) Pa]. Thus, the determined chemical diffusion coefficient is considered in terms of a microdiffusion coefficient that is reflective of the transport kinetics within very narrow ranges of oxygen activities. In analogy to pure TiO2, the chemical diffusion coefficient for In-doped TiO2 exhibits a maximum at the n-p transition point. The activation energy of the chemical diffusion exhibits a decrease with temperature from 200 kJ/mol at 1023 K to an insignificant value at 1273 K. This effect is reflective of a segregation-induced electrical potential barrier blocking the transport of defects. The absolute value of the chemical diffusion coefficient for In-doped TiO2 is larger from that of pure TiO2 by a factor of approximately 10. The effect of indium on the diffusion rate is considered in terms of the associated concentration of oxygen vacancies, which are formed in order to satisfy the charge neutrality for In-doped TiO2.

  14. First-principles study on transition metal-doped anatase TiO2.

    PubMed

    Wang, Yaqin; Zhang, Ruirui; Li, Jianbao; Li, Liangliang; Lin, Shiwei

    2014-01-28

    The electronic structures, formation energies, and band edge positions of anatase TiO2 doped with transition metals have been analyzed by ab initio band calculations based on the density functional theory with the planewave ultrasoft pseudopotential method. The model structures of transition metal-doped TiO2 were constructed by using the 24-atom 2 × 1 × 1 supercell of anatase TiO2 with one Ti atom replaced by a transition metal atom. The results indicate that most transition metal doping can narrow the band gap of TiO2, lead to the improvement in the photoreactivity of TiO2, and simultaneously maintain strong redox potential. Under O-rich growth condition, the preparation of Co-, Cr-, and Ni-doped TiO2 becomes relatively easy in the experiment due to their negative impurity formation energies, which suggests that these doping systems are easy to obtain and with good stability. The theoretical calculations could provide meaningful guides to develop more active photocatalysts with visible light response.

  15. Phenol degradation by TiO2 photocatalysts combined with different pulsed discharge systems.

    PubMed

    Zhang, Yi; Lu, Jiani; Wang, Xiaoping; Xin, Qing; Cong, Yanqing; Wang, Qi; Li, Chunjuan

    2013-11-01

    Films of TiO2 nanotubes distributed over the inner surface of a discharge reactor cylinder (CTD) or adhered to a stainless steel electrode surface (PTD) in a discharge reactor were compared with a single-discharge (SD) system to investigate their efficiencies in phenol degradation. Morphology studies indicated that the TiO2 film was destroyed in the PTD system, but that there was no change in the CTD system after discharge. X-ray diffraction results revealed that the anatase phase of the original sample was preserved in the CTD system, but that an anatase-to-rutile phase transformation occurred in the PTD system after discharge. The highest efficiencies of phenol degradation and total organic carbon (TOC) mineralization were observed in the CTD system, and there was no decrease in phenol degradation efficiency upon reuse of a TiO2 film, indicating high catalysis activity and stability of the TiO2 photocatalysts in the combined treatment. TiO2 photocatalysts favored the formation of hydrogen peroxide and disfavored the formation of ozone. A greater degree of oxidation of intermediates and higher energy efficiency in phenol oxidation were observed with the TiO2-plasma systems, especially in the CTD system, compared to those with the SD system.

  16. Nanocomposites of TiO2/cyanoethylated cellulose with ultra high dielectric constants

    NASA Astrophysics Data System (ADS)

    Madusanka, Nadeesh; Shivareddy, Sai G.; Hiralal, Pritesh; Eddleston, Mark D.; Choi, Youngjin; Oliver, Rachel A.; Amaratunga, Gehan A. J.

    2016-05-01

    A novel dielectric nanocomposite containing a high permittivity polymer, cyanoethylated cellulose (CRS) and TiO2 nanoparticles was successfully prepared with different weight percentages (10%, 20% and 30%) of TiO2. The intermolecular interactions and morphology within the polymer nanocomposites were analysed. TiO2/CRS nanofilms on SiO2/Si wafers were used to form metal–insulator–metal type capacitors. Capacitances and loss factors in the frequency range of 1 kHz–1 MHz were measured. At 1 kHz CRS-TiO2 nanocomposites exhibited ultra high dielectric constants of 118, 176 and 207 for nanocomposites with 10%, 20% and 30% weight of TiO2 respectively, significantly higher than reported values of pure CRS (21), TiO2 (41) and other dielectric polymer-TiO2 nanocomposite films. Furthermore, all three CRS-TiO2 nanocomposites show a loss factor <0.3 at 1 kHz and low leakage current densities (10‑6–10‑7 A cm‑2). Leakage was studied using conductive atomic force microscopy and it was observed that the leakage is associated with TiO2 nanoparticles embedded in the CRS polymer matrix. A new class of ultra high dielectric constant hybrids using nanoscale inorganic dielectrics dispersed in a high permittivity polymer suitable for energy management applications is reported.

  17. The adsorption and photo-degradation of oxalic acid at the TiO2 surface.

    NASA Astrophysics Data System (ADS)

    Mendive, Cecilia; Blesa, Miguel; Bahnemann, Detlef

    2006-03-01

    Oxalic acid is the simplest model compound to study the heterogeneous photocatalytic oxidation of pollutants on TiO2 containing more than one carboxylate group. We have carried out a study of a system of an oxalic acid solution in contact with a thin film of TiO2 particles employing ATR - FTIR in combination with quantum chemical calculations. Thus, possible adsorption structures have been identified and molecular dynamic simulations have been used to compare their predictions with the experimental data. It was found that the adsorption of oxalic acid on TiO2 in the dark can be explained in terms of two surface complexation modes for the anatase phase and only one surface complexation mode for the rutile phase. We have found that under illumination one of the complexes on the anatase phase preferably undergoes photo-degradation. At the same time water molecules are desorbed from the TiO2 surface by a thermal mechanism induced by the absorption of photons. Both processes favor the adsorption of more molecules of oxalic acid at the TiO2 surface which is thus enriched in the second complexation mode. A similar mechanism was found to occur on the rutile phase. The only complexation mode appears not to be photo-sensitive but the TiO2 surface is enriched in oxalic acid under illumination due to the replacement of photo-desorbed water molecules.

  18. Preparation, performance and adsorption activity of TiO2 nanoparticles entrapped PVDF hybrid membranes

    NASA Astrophysics Data System (ADS)

    Zhang, Xia; Wang, Yang; You, Yuting; Meng, Hao; Zhang, Jianghua; Xu, Xinxin

    2012-12-01

    The TiO2 nanoparticles entrapped poly(vinylidenefluoride) (PVDF) hybrid membranes were prepared through impregnating the pre-treated PVDF film in the TiO2 suspension. SEM, XRD, TG and ATR-IR analyses were used to character the hybrid membranes. The results showed that the TiO2 nanoparticles with average size about 44 nm were deposited on the surface and inner pores of PVDF films. The pre-treatment of PVDF with cetyltrimethyl ammonium bromide (CTAB) is benefit for TiO2loading. The ATR-IR spectra revealed that physical interaction played important role in the construction of hybrid membranes. The adsorption behavior of Cu2+ on the hybrid membranes was studied, and a promoted adsorption and elution efficiency of PVDF/TiO2 hybrid membranes were observed compared with that of the pristine PVDF film. Meanwhile, the surface contact angle, pure water flux and static adsorption of bovine serum albumin (BSA) on the hybrid membranes were also measured to study the effects of TiO2 nanoparticles. It was found that the TiO2 nanoparticles improved the surface hydrophilicity and permeability of PVDF membranes, and the decreasing adsorption capacity of BSA indicated the promoted antifouling ability of PVDF membranes. Such the PVDF/TiO2 hybrid membranes exhibit potential applications in the separation and pre-concentration of metal ions.

  19. Photoelectrochemical Properties of CuS-GeO2-TiO2 Composite Coating Electrode.

    PubMed

    Wen, Xinyu; Zhang, Huawei

    2016-01-01

    The ITO (indium tin oxide) conductive glass-matrix CuS-GeO2-TiO2 composite coating was generated via EPD (electrophoretic deposition) and followed by a sintering treatment at 450°C for 40 minutes. Characterizations of the CuS-GeO2-TiO2 composite coating were taken by SEM (scanning electron microscope), XRD (X-ray diffraction), EDX (energy dispersive X-ray), UV-Vis DRS (ultraviolet-visible diffuse reflection spectrum), and FT-IR (Fourier transform infrared spectroscopy). Results showed that CuS and GeO2 had dispersed in this CuS-GeO2-TiO2 composite coating (mass percentages for CuS and GeO2 were 1.23% and 2.79%, respectively). The electrochemical studies (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel polarization) of this CuS-GeO2-TiO2 composite coating electrode were performed in pH = 9.51 Na2CO3-NaHCO3 buffer solution containing 0.50 mol/L CH3OH under the conditions of visible light, ultraviolet light (λ = 365 nm), and dark (without light irradiation as control), respectively. Electrochemical studies indicated that this CuS-GeO2-TiO2 composite coating electrode had better photoelectrocatalytic activity than the pure TiO2 electrode in the electrocatalysis of methanol under visible light. PMID:27055277

  20. Photoelectrochemical Properties of CuS-GeO2-TiO2 Composite Coating Electrode.

    PubMed

    Wen, Xinyu; Zhang, Huawei

    2016-01-01

    The ITO (indium tin oxide) conductive glass-matrix CuS-GeO2-TiO2 composite coating was generated via EPD (electrophoretic deposition) and followed by a sintering treatment at 450°C for 40 minutes. Characterizations of the CuS-GeO2-TiO2 composite coating were taken by SEM (scanning electron microscope), XRD (X-ray diffraction), EDX (energy dispersive X-ray), UV-Vis DRS (ultraviolet-visible diffuse reflection spectrum), and FT-IR (Fourier transform infrared spectroscopy). Results showed that CuS and GeO2 had dispersed in this CuS-GeO2-TiO2 composite coating (mass percentages for CuS and GeO2 were 1.23% and 2.79%, respectively). The electrochemical studies (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel polarization) of this CuS-GeO2-TiO2 composite coating electrode were performed in pH = 9.51 Na2CO3-NaHCO3 buffer solution containing 0.50 mol/L CH3OH under the conditions of visible light, ultraviolet light (λ = 365 nm), and dark (without light irradiation as control), respectively. Electrochemical studies indicated that this CuS-GeO2-TiO2 composite coating electrode had better photoelectrocatalytic activity than the pure TiO2 electrode in the electrocatalysis of methanol under visible light.