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Sample records for hierarchical anatase tio2

  1. Preparation and tribological properties of stearic acid-modified hierarchical anatase TiO 2 microcrystals

    Science.gov (United States)

    Qian, Jianhua; Yin, Xiangyu; Wang, Ning; Liu, Lin; Xing, Jinjuan

    2012-01-01

    Hierarchical TiO2 microcrystals were synthesized through a facile solvothermal method. X-ray diffraction (XRD) and scanning electron microscope (SEM) measurements were used to characterize the structure of the as-prepared samples. The results indicated that the synthesized hierarchical titania (TiO2) microspheres were composed of numerous anatase phase TiO2 particles. The as-prepared samples were chemically modified with stearic acid to improve their dispersion in oil. Fourier transmission infrared spectroscopy (FT-IR) and thermogravimetry analysis (TGA) were carried out to evaluate the characteristics of the modified TiO2 microcrystals. The tribological properties of the modified TiO2 microcrystals as additives of liquid paraffin were studied by a four-ball tester, and the results showed that they could significantly improve anti-wear performance, friction-reduction property and load-carrying capacity of liquid paraffin. These advantages make the modified TiO2 microcrystals promising for green lubricating oil additives.

  2. Morphology and interfacial energetics controls for hierarchical anatase/rutile TiO2 nanostructured array for efficient photoelectrochemical water splitting.

    Science.gov (United States)

    Yang, Jih-Sheng; Liao, Wen-Pin; Wu, Jih-Jen

    2013-08-14

    In this work, a three-dimensional (3D) hierarchical TiO2 nanostructured array is constructed on the basis of the considerations of morphology and interfacial energetics for photoelectrochemical water splitting. The photoelectrode is composed of a core-shell structure where the core portion is a rutile TiO2 nanodendrite (ND) array and the shell portion is rutile and anatase TiO2 nanoparticles (NPs) sequentially located on the surface. The TiO2 ND array provides a fast electron transport pathway due to its quasi-single-crystalline structure. The 3D configuration with NPs in the shell portion provides a larger surface area for more efficient photocharge separation without significantly sacrificing the electron collection efficiency. Moreover, anatase TiO2 NPs constructed on the surface of the ND/rutile TiO2 NP nanostructured array enhance charge separation and suppress charge recombination at the interfacial region due to the higher conduction band edge of anatase TiO2 compared to that of rutile TiO2. A photocurrent density and photoconversion efficiency of 2.08 mA cm(-2) at 1.23 V vs reversible hydrogen electrode (RHE) and 1.13% at 0.51 V vs RHE are, respectively, attained using the hierarchical TiO2 nanostructured array photoelectrochemical cell under illumination of AM 1.5G (100 mW cm(-2)).

  3. Synthesis of hierarchical anatase TiO 2 nanostructures with tunable morphology and enhanced photocatalytic activity

    KAUST Repository

    Rahal, Raed

    2012-01-01

    A facile one-pot method to prepare three-dimensional hierarchical nanostructures of titania with good control over their morphologies without the use of hydrofluoric acid is developed. The reaction is performed under microwave irradiation conditions in pure water, and enables enhanced photocatalytic activity. This study indicates that photocatalytic activity depends not only on the surface area but also on the morphology of the titania. © 2012 The Royal Society of Chemistry.

  4. Rational design of anatase TiO2 architecture with hierarchical nanotubes and hollow microspheres for high-performance dye-sensitized solar cells

    Science.gov (United States)

    Gu, Jiuwang; Khan, Javid; Chai, Zhisheng; Yuan, Yufei; Yu, Xiang; Liu, Pengyi; Wu, Mingmei; Mai, Wenjie

    2016-01-01

    Large surface area, sufficient light-harvesting and superior electron transport property are the major factors for an ideal photoanode of dye-sensitized solar cells (DSSCs), which requires rational design of the nanoarchitectures and smart integration of state-of-the-art technologies. In this work, a 3D anatase TiO2 architecture consisting of vertically aligned 1D hierarchical TiO2 nanotubes (NTs) with ultra-dense branches (HTNTs, bottom layer) and 0D hollow TiO2 microspheres with rough surface (HTS, top layer) is first successfully constructed on transparent conductive fluorine-doped tin oxide glass through a series of facile processes. When used as photoanodes, the DSSCs achieve a very large short-current density of 19.46 mA cm-2 and a high overall power conversion efficiency of 8.38%. The remarkable photovoltaic performance is predominantly ascribed to the enhanced charge transport capacity of the NTs (function as the electron highway), the large surface area of the branches (act as the electron branch lines), the pronounced light harvesting efficiency of the HTS (serve as the light scattering centers), and the engineered intimate interfaces between all of them (minimize the recombination effect). Our work demonstrates a possibility of fabricating superior photoanodes for high-performance DSSCs by rational design of nanoarchitectures and smart integration of multi-functional components.

  5. Anatase TiO2 nanorod-decoration for highly efficient photoenergy conversion.

    Science.gov (United States)

    Kim, Dong Hoe; Seong, Won Mo; Park, Ik Jae; Yoo, Eun-Sang; Shin, Seong Sik; Kim, Ju Seong; Jung, Hyun Suk; Lee, Sangwook; Hong, Kug Sun

    2013-12-07

    In recent studies of inorganic materials for energy applications, surface modification processes have been shown to be among the most effective methods to enhance the performance of devices. Here, we demonstrate a facile nano-decoration method which is generally applicable to anatase TiO2 nanostructures, as well as a nano-decorated hierarchical TiO2 nanostructure which improves the energy conversion efficiency of a dye-sensitized solar cell (DSSC). Using a facile sol-gel method, 0-D, 1-D, and 2-D type anatase TiO2 nanostructures were decorated with 200 nm long anatase TiO2 nanorods to create various hierarchical nanostructures. A structural analysis reveals that the branched nanorod has a highly crystalline anatase phase with anisotropic growth in the [001] longitudinal direction. When one of the hierarchical structures, a chestnut bur-like nanostructure, was employed in a dye-sensitized solar cell as a scattering layer, offering increased dye-loading properties, preserving a sufficient level of light-scattering ability and preserving superior charge transport and recombination properties as well, the energy conversion efficiency of the cell improved by 19% (from 7.16% to 9.09%) compared to a cell with a 0-D TiO2 sphere as a scattering layer. This generally applicable anatase nanorod-decorating method offers potential applications in various energy-conversion applications, especially in DSSCs, quantum-dot solar cells, photoelectrochemical water-splitting devices, photocatalysis, and lithium ion batteries.

  6. Improved lithium storage properties of electrospun TiO2 with tunable morphology: from porous anatase to necklace rutile.

    Science.gov (United States)

    Yang, Yang; Wang, Haiying; Zhou, Qiwen; Kong, Mengqi; Ye, Haitao; Yang, Gang

    2013-11-07

    Three-dimensional TiO2 with tunable morphology and crystalline phase was successfully prepared by the electrospinning technique and subsequent annealing. Porous-shaped anatase TiO2, cluster-shaped anatase TiO2, hierarchical-shaped rutile (minor) TiO2 and nano-necklace rutile (major) TiO2 were achieved at 500, 600, 700 and 800 °C, respectively. The mechanism of the formation of these tailored morphologies and crystallinity was investigated. Lithium insertion properties were evaluated by galvanostatic and potentiostatic modes in half-cell configurations. By combining the large surface area, open mesoporosity and stable crystalline phase, the porous-shaped anatase TiO2 exhibited the highest capacity, best rate and cycling performance among the four samples. The present results demonstrated the usefulness of three-dimensional TiO2 as an anode for lithium storage with improved electrode performance.

  7. Anatase TiO2 nanorod-decoration for highly efficient photoenergy conversion

    Science.gov (United States)

    Kim, Dong Hoe; Seong, Won Mo; Park, Ik Jae; Yoo, Eun-Sang; Shin, Seong Sik; Kim, Ju Seong; Jung, Hyun Suk; Lee, Sangwook; Hong, Kug Sun

    2013-11-01

    In recent studies of inorganic materials for energy applications, surface modification processes have been shown to be among the most effective methods to enhance the performance of devices. Here, we demonstrate a facile nano-decoration method which is generally applicable to anatase TiO2 nanostructures, as well as a nano-decorated hierarchical TiO2 nanostructure which improves the energy conversion efficiency of a dye-sensitized solar cell (DSSC). Using a facile sol-gel method, 0-D, 1-D, and 2-D type anatase TiO2 nanostructures were decorated with 200 nm long anatase TiO2 nanorods to create various hierarchical nanostructures. A structural analysis reveals that the branched nanorod has a highly crystalline anatase phase with anisotropic growth in the [001] longitudinal direction. When one of the hierarchical structures, a chestnut bur-like nanostructure, was employed in a dye-sensitized solar cell as a scattering layer, offering increased dye-loading properties, preserving a sufficient level of light-scattering ability and preserving superior charge transport and recombination properties as well, the energy conversion efficiency of the cell improved by 19% (from 7.16% to 9.09%) compared to a cell with a 0-D TiO2 sphere as a scattering layer. This generally applicable anatase nanorod-decorating method offers potential applications in various energy-conversion applications, especially in DSSCs, quantum-dot solar cells, photoelectrochemical water-splitting devices, photocatalysis, and lithium ion batteries.In recent studies of inorganic materials for energy applications, surface modification processes have been shown to be among the most effective methods to enhance the performance of devices. Here, we demonstrate a facile nano-decoration method which is generally applicable to anatase TiO2 nanostructures, as well as a nano-decorated hierarchical TiO2 nanostructure which improves the energy conversion efficiency of a dye-sensitized solar cell (DSSC). Using a facile

  8. Synergistic manipulation of micro-nanostructures and composition: anatase/rutile mixed-phase TiO2 hollow micro-nanospheres with hierarchical mesopores for photovoltaic and photocatalytic applications.

    Science.gov (United States)

    Zhu, Qing; Qian, Jieshu; Pan, Hao; Tu, Luo; Zhou, Xingfu

    2011-09-30

    The construction of nanocrystals with controllable composition and desirable micro-nanostructures is a well-known challenge. A combination of favorable composition and optimized micro-nanostructures can enhance the performance of a material significantly. Using TiO(2) as an example, we demonstrate here a facile approach to prepare anatase/rutile mixed-phase TiO(2) hollow micro-nanospheres with hierarchical mesopores. Our strategy relies on polymer-assisted assembly of ∼ 5 nm nano-building blocks into three-dimensional hierarchical hollow micro-nanospheres in a mixed alcohol-water solution. This superior micro-nanostructure endows the sample with hierarchical mesopores and a high surface area of 106 m(2) g(-1). We also show that, due to the synergetic effects of the mixed-phase composition and the micro-nanostructures, the sample exhibited significantly improved photovoltaic performance and similar photocatalytic performance compared with the commercial Degussa P25. These results suggested that our sample has great potential for future photovoltaic and photocatalytic applications.

  9. High-pressure polymorphs of anatase TiO2

    DEFF Research Database (Denmark)

    Arlt, T.; Bermejo, M.; Blanco, M. A.

    2000-01-01

    The equation of state of anatase TiO2 has been determined experimentally-using polycrystalline as well as single-crystal material-and compared with theoretical calculations using the ab initio perturbed ion model. The results are highly consistent, the zero-pressure bulk modulus being 179(2) GPa...

  10. Band alignment of rutile and anatase TiO2

    Science.gov (United States)

    Scanlon, David O.; Dunnill, Charles W.; Buckeridge, John; Shevlin, Stephen A.; Logsdail, Andrew J.; Woodley, Scott M.; Catlow, C. Richard A.; Powell, Michael. J.; Palgrave, Robert G.; Parkin, Ivan P.; Watson, Graeme W.; Keal, Thomas W.; Sherwood, Paul; Walsh, Aron; Sokol, Alexey A.

    2013-09-01

    The most widely used oxide for photocatalytic applications owing to its low cost and high activity is TiO2. The discovery of the photolysis of water on the surface of TiO2 in 1972 launched four decades of intensive research into the underlying chemical and physical processes involved. Despite much collected evidence, a thoroughly convincing explanation of why mixed-phase samples of anatase and rutile outperform the individual polymorphs has remained elusive. One long-standing controversy is the energetic alignment of the band edges of the rutile and anatase polymorphs of TiO2 (ref. ). We demonstrate, through a combination of state-of-the-art materials simulation techniques and X-ray photoemission experiments, that a type-II, staggered, band alignment of ~ 0.4 eV exists between anatase and rutile with anatase possessing the higher electron affinity, or work function. Our results help to explain the robust separation of photoexcited charge carriers between the two phases and highlight a route to improved photocatalysts.

  11. Mussel-Directed Synthesis of Nitrogen-Doped Anatase TiO2.

    Science.gov (United States)

    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.

  12. Improvement of solar energy conversion with Nb-incorporated TiO2 hierarchical microspheres.

    Science.gov (United States)

    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.

  13. Efficient photodegradation of organic dye using anatase TiO2 plants as catalyst

    Science.gov (United States)

    Bahadur, Jitendra; Pal, Kaushik

    2017-08-01

    Anatase TiO2 hierarchical nanostructures with higher photocatalytic activity are of special importance in various applications. We have reported the synthesis of TiO2 as water chestnut plants like morphology via facile hydrothermal method, by using Titanium (IV) butoxide (TBOT) as a precursor solution. It is found that TiO2 nanoparticles work as seed and completely convert into water chestnut plants like structure or morphology, which are composed of crystallized anatase nanocrystals. X-ray diffraction spectra confirmed the presence of anatase phase of crystallized TiO2 plants (TPs). The average life time delay for generated charge carriers in TPs was calculated to be around 2.45 ns, which reflects slow recombination of charge carriers. The prepared TPs show excellent photocatalytic performance when applied in photo degradation of Rhodamine B organic dye. The unique features exhibited by TPs make them a promising candidate for vast potential applications in field such as solar cells, photocatalysis, supercapacitor, lithium ion batteries and some related fields. [Figure not available: see fulltext.

  14. Surface hydroxyl groups direct cellular response on amorphous and anatase TiO2 nanodots.

    Science.gov (United States)

    Hong, Yi; Yu, Mengfei; Lin, Jun; Cheng, Kui; Weng, Wenjian; Wang, Huiming

    2014-11-01

    In this study, we investigated the differences between amorphous and anatase TiO2 at the biomolecular level which could explain differences in the osteoblast response on these surfaces. The number of surface hydroxyl groups in the TiOHT form on amorphous and anatase TiO2 was found to be the most important factor, resulting in adsorption of bovine serum albumin as a monolayer on amorphous TiO2 nanodots but as a multilayer on anatase TiO2 nanodots. The reason for this is that the presence of more TiOHT groups on amorphous TiO2 nanodots attracts more -NH3+ groups on BSA molecules, causing the conformation of surface-bound BSA molecules to differ from those adsorbed on anatase TiO2 nanodots. Fibronectin which is subsequently adsorbed on anatase TiO2 nanodots then retains a more active conformation for osteoblast adhesion and mineralization.

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

    Science.gov (United States)

    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.

  16. Anatase TiO2 sheet-assisted synthesis of Ti(3+) self-doped mixed phase TiO2 sheet with superior visible-light photocatalytic performance: Roles of anatase TiO2 sheet.

    Science.gov (United States)

    Zhang, Xiaojie; Zuo, Guoqing; Lu, Xin; Tang, Changqing; Cao, Shuo; Yu, Miao

    2017-03-15

    On the basis of measurements, such as field emission scanning electron microscope, UV-Vis diffuse reflectance spectra, X-ray diffraction, electron paramagnetic resonance, photoluminescence spectra, and photocurrent measurements, the roles of anatase TiO2 sheet on synthesizing Ti(3+) self-doped mixed phase TiO2 nanosheets (doped TiO2 (A/R, TiO2 (A))) and on improving the performance for photocatalytic CO2 reduction were explored systematically. High surface area anatase TiO2 nanosheets (TiO2 (A)) as a substrate, structure directing agent, and inhibitor, mediated the synthesis of Ti(3+) self-doped mixed phase TiO2 nanosheets. Addition of TiO2 (A) significantly improved not only visible light absorption of doped TiO2 (A/R, TiO2 (A)), but also the efficiency of photo-excited charges separations due to the existence of interfacial regions of anatase-rutile TiO2 junctions. Finally, a possible mechanism for interfacial charge transfer at the anatase-rutile TiO2 interface and for photocatalytic CO2 reduction over Pt loaded doped TiO2 (A/R, TiO2 (A)) were proposed.

  17. Hydrogen donor in anatase TiO2

    Science.gov (United States)

    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.

  18. Highly thermal stable and highly crystalline anatase TiO2 for photocatalysis.

    Science.gov (United States)

    Li, Wei; Bai, Yang; Liu, Chang; Yang, Zhuhong; Feng, Xin; Lu, Xiaohua; van der Laak, Nicole K; Chan, Kwong-Yu

    2009-07-15

    In the absence of any doping and modification, the anatase-to-rutile phase transformation was inhibited at high temperatures giving rise to highly thermal stable and highly crystalline anatase TiO2 fibers. The initial formation of the TiO2(B) phase is found to be key in inhibiting this transformation. The intermediate structure of the TiO2 fiber comprises an inner anatase core with an outer TiO2(B) shell, which has a specific crystallographic orientation with respect to the anatase structure. During the calcination process from 300 to 800 degrees C, both the TiO2(B) shell and the bulk anatase crystal structure was preserved. At temperatures of 800-900 degrees C the TiO2(B)-to-anatase transformation was finished and a near-pure and thermally stable anatase fiber was obtained. This final product shows the same activity as a standard commercial photocatalyst Degussa P-25 when measured against unit mass, and 5 times the activity when measured with respect to the unit surface area. The anatase TiO2 fibers presented here have considerable interest as practical photocatalysts for water purification, as they can be easily recycled without a decrease in their photocatalytic activity and can be prepared at large scale and at low cost.

  19. Interaction between nanoparticulate anatase TiO2 and lactate dehydrogenase.

    Science.gov (United States)

    Duan, Yanmei; Li, Na; Liu, Chao; Liu, Huiting; Cui, Yaling; Wang, Han; Hong, Fashui

    2010-09-01

    In order to study the mechanisms underlying the effects of TiO(2) nanoparticles on lactate dehydrogenase (LDH, EC1.1.1.27), Institute of Cancer Research region mice were injected with nanoparticulate anatase TiO(2) (5 nm) of various doses into the abdominal cavity daily for 14 days. We then examined LDH activity in vivo and in vitro and direct evident for interaction between nanoparticulate anatase TiO(2) and LDH using spectral methods. The results showed that nanoparticulate anatase TiO(2) could significantly activate LDH in vivo and in vitro; the kinetics constant (Km) and Vmax were 0.006 microM and 1,149 unit mg(-1) protein min(-1), respectively, at a low concentration of nanoparticulate anatase TiO(2), and 3.45 and 0.031 microM and 221 unit mg(-1) protein min(-1), respectively, at a high concentration of nanoparticulate anatase TiO(2). By fluorescence spectral assays, the nanoparticulate anatase TiO(2) was determined to be directly bound to LDH, and the binding constants of the binding site were 1.77 x 10(8) L mol(-1) and 2.15 x 10(7) L mol(-1), respectively, and the binding distance between nanoparticulate anatase TiO(2) and the Trp residue of LDH was 4.18 nm, and nanoparticulate anatase TiO(2) induced the protein unfolding. It was concluded that the binding of nanoparticulate anatase TiO(2) altered LDH structure and function.

  20. Synthesis of anatase and rutile TiO2 nanostructures from natural ilmenite

    Science.gov (United States)

    Wahyuingsih, Sayekti; Ramelan, Ari Handono; Pramono, Edi; Sulistya, Ariantama Djati; Argawan, Panji Rofa; Dharmawan, Frenandha Dwi; Rinawati, Ludfiaastu; Hanif, Qonita Awliya; Sulistiyono, Eko; Firdiyono, Florentinus

    2016-02-01

    Nanostructure anatase and rutile type TiO2 were synthesized from dissolution roasted ilmenite from natural ilmenite sand as the starting materials. Anatase TiO2 and rutile TiO2 (high crystallinity) with the diameters of 20-100 nm were obtained by calcined soluble ilmenite sand produced by leaching process. Calcinations of the xerogel TiO2 from liquor products were conducted for 4 hours at temperature of 450 °C. The samples were characterized by XRD (X-ray diffraction), STA (simultant thermal analysis), TEM (Transmission Electron Microscopy), and BET surface area. Titania Anatase-Rutile form as a mixture were produced by titania slag with the hydrolysis product. While, in another route, complete titania anatase phase was produced through hydrolysis and condensation steps of leach liquors. This synthesis methods provide a simple route to fabricate nanostructure TiO2 from low cost material.

  1. Porous Anatase TiO2 Thin Films for NH3 Vapour Sensing

    Science.gov (United States)

    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.

  2. TiO2-Based Nanomaterials for Gas Sensing-Influence of Anatase and Rutile Contributions.

    Science.gov (United States)

    Zakrzewska, K; Radecka, M

    2017-12-01

    The paper deals with application of three nanomaterial systems: undoped TiO2, chromium-doped TiO2:Cr and TiO2-SnO2 synthesized by flame spray synthesis (FSS) technique for hydrogen sensing. The emphasis is put on the role of anatase and rutile polymorphic forms of TiO2 in enhancing sensitivity towards reducing gases. Anatase-to-rutile transformation is achieved by annealing of undoped TiO2 in air at 700 °C, specific Cr doping and modification with SnO2. Undoped TiO2 and TiO2-SnO2 exhibit n-type behaviour and while TiO2: 5 at.% Cr is a p-type semiconductor. X-ray diffraction (XRD) has been applied to determine anatase-to-rutile weight ratio as well as anatase and rutile crystal size. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been used to characterize the structure and morphological parameters. Optical reflectometry enabled to find and compare the band gaps E g of anatase and rutile predominated compositions. Electrical properties, i.e. the electrical conductivity and values of constant phase element (CPE), have been established on the basis of impedance spectroscopy. Dynamic responses of the electrical resistance as a function of hydrogen concentration revealed that predominance of rutile in anatase/rutile mixture is beneficial for gas sensing. Partial transformation to rutile in all three material systems under study resulted in an increased sensitivity towards hydrogen. It is proposed that this effect can be explained in a similar way as in photocatalysis, i.e. by specific band alignment and electron transfer from rutile to anatase to facilitate oxygen preadsorption on the surface of anatase grains.

  3. Mobility enhanced photoactivity in sol-gel grown epitaxial anatase TiO2 films.

    Science.gov (United States)

    Jung, Hyun Suk; Lee, Jung-Kun; Lee, Jaegab; Kang, Bo Soo; Jia, Quanxi; Nastasi, Michael; Noh, Jun Hong; Cho, Chin-Moo; Yoon, Sung Hoon

    2008-03-18

    Epitaxial anatase thin films were grown on single-crystal LaAlO3 substrates by a sol-gel process. The epitaxial relationship between TiO2 and LaAlO3 was found to be [100]TiO2||[100]LaAlO3 and (001)TiO2||(001)LaAlO3 based on X-ray diffraction and a high-resolution transmission electron microscopy. The epitaxial anatase films show significantly improved photocatalytic properties, compared with polycrystalline anatase film on fused silica substrate. The increase in the photocatalytic activity of epitaxial anatase films is explained by enhanced charge carrier mobility, which is traced to the decreased grain boundary density in the epitaxial anatase film.

  4. Enhanced Photoelectrochemical Performance from Rationally Designed Anatase/Rutile TiO2 Heterostructures.

    Science.gov (United States)

    Cao, Fengren; Xiong, Jie; Wu, Fangli; Liu, Qiong; Shi, Zhiwei; Yu, Yanhao; Wang, Xudong; Li, Liang

    2016-05-18

    In a photoelectrochemical (PEC) cell for water splitting, the critical issue is charge separation and transport, which is usually completed by designing semiconductor heterojunctions. TiO2 anatase-rutile mixed junctions could largely improve photocatalytic properties, but impairs PEC water splitting performance. We designed and prepared two types of TiO2 heterostructures with the anatase thin film and rutile nanowire phases organized in different sequences. The two types of heterostructures were used as PEC photoanodes for water splitting and demonstrated completely opposite results. Rutile nanowires on anatase film demonstrated enhanced photocurrent density and onset potential, whereas strong negative performance was obtained from anatase film on rutile nanowire structures. The mechanism was investigated by photoresponse, light absorption and reflectance, and electrochemical impedance spectra. This work revealed the significant role of phase sequence in performance gain of anatase-rutile TiO2 heterostructured PEC photoanodes.

  5. Low-Temperature Preparation and Properties of High Activity Anatase TiO2 Aqueous Sols

    Science.gov (United States)

    Liu, Qingju; Na, Wei; Zhu, Zhongqi; Zhang, Jin

    2011-06-01

    Anatase TiO2 aqueous sols were prepared below 70 °C by sol method. The influences of preparing conditions on the crystal structures and stability of the sols were investigated with X-ray diffraction (XRD) and Zeta potential. The photocatalytic activities of the anatase TiO2 aqueous sols were characterized by degradation of methyl orange and methylene blue under ultraviolet light, fluorescent light and sunlight. The sols demonstrate higher photocatalytic activity than that of Degussa P25-TiO2.

  6. Excess electrons at anatase TiO2 surfaces and interfaces: insights from first principles simulations

    Science.gov (United States)

    Selçuk, Sencer; Selloni, Annabella

    2017-07-01

    TiO2 is an important technological material with widespread applications in photocatalysis, photovoltaics and self-cleaning surfaces. Excess electrons from intrinsic defects, dopants and photoexcitation play a key role in the properties of TiO2 that are relevant to its energy-related applications. The picture of excess and photoexcited electrons in TiO2 is based on the polaron model, where the electron forms a localized state that is stabilized by an accompanying lattice distortion. Here, we focus on excess and photoexcited electrons in anatase, the TiO2 polymorph most relevant to photocatalysis and solar energy conversion. For anatase, evidence of both small and large electron polarons has been reported in the literature. In addition, several studies have revealed a remarkable dependence of the photocatalytic activity of anatase on the crystal surface. After an overview of experimental studies, we briefly discuss recent progress in the theoretical description of polaronic states in TiO2, and finally present a more detailed account of our computational studies on the trapping and dynamics of excess electrons near the most common anatase surfaces and aqueous interfaces. The results of these studies provide a bridge between surface science experiments under vacuum conditions and observations of crystal-face-dependent photocatalysis on anatase, and support the idea that optimization of the ratio between different anatase facets can help enhance the photocatalytic activity of this material.

  7. Dye-Sensitized Solar Cells with Anatase TiO2 Nanorods Prepared by Hydrothermal Method

    Directory of Open Access Journals (Sweden)

    Ming-Jer Jeng

    2013-01-01

    Full Text Available The hydrothermal method provides an effective reaction environment for the synthesis of nanocrystalline materials with high purity and well-controlled crystallinity. In this work, we started with various sizes of commercial TiO2 powders and used the hydrothermal method to prepare TiO2 thin films. We found that the synthesized TiO2 nanorods were thin and long when smaller TiO2 particles were used, while larger TiO2 particles produced thicker and shorter nanorods. We also found that TiO2 films prepared by TiO2 nanorods exhibited larger surface roughness than those prepared by the commercial TiO2 particles. It was found that a pure anatase phase of TiO2 nanorods can be obtained from the hydrothermal method. The dye-sensitized solar cells fabricated with TiO2 nanorods exhibited a higher solar efficiency than those fabricated with commercial TiO2 nanoparticles directly. Further, triple-layer structures of TiO2 thin films with different particle sizes were investigated to improve the solar efficiency.

  8. Preparation of nanorod-like anatase TiO2 nanocrystals and their photovoltaic properties.

    Science.gov (United States)

    Zhang, Qinghong; Li, Shuang; Li, Yaogang; Wang, Hongzhi

    2011-12-01

    Anatase TiO2 nanocrystals with the high specific surface area were prepared by the hydrothermal treatment of anatase TiO2 sols at the temperature of 150 degrees C and above. When TiO2 sols with a lower content of TiO2 and at a relatively high pH value were hydrothermal treated, the dispersible and nanorod-like TiO2 nanocrystals were formed via the oriented attachment. The nanorod-like TiO2 nanocrystals with an aspect ratio of larger than 5 and a mean diameter of less than 7 nm were obtained in the absence of organic compounds. The as-prepared TiO2 nanocrystals were characterized with X-ray diffraction, transmission electron microscopy and BET surface area techniques. The TiO2 nanostructures were deposited on the FTO conductive glass as the anodic electrode for the dye-sensitized solar cells (DSSCs) and assembled into solar cells. The derived solar cells showed a conversion efficiency of 6.12% under 1 sun illumination of simulated sunlight and external quantum efficiency (EQE) of more than 60% at the wavelength of 550 nm. The DSSCs from the anatase nanorods has a higher open circuit voltage compared to the spherical nanocrystals.

  9. First principle study of the electronic structure of hafnium-doped anatase TiO2

    Institute of Scientific and Technical Information of China (English)

    Li Lezhong; Yang Weiqing; DingYingchun; Zhu Xinghua

    2012-01-01

    Crystal structures and electronic structures of hafnium doping anatase TiO2 were calculated by first principles with the plane-wave ultrasoft pseudopotential method based on the density functional theory within the generalized gradient approximation.The calculated results show that the lattice parameters a and c of Hf-doped anatase TiO2 are larger than those of intrinsic TiO2 under the same calculated condition.The calculated band structure and density of states show that the conduction band width of Hf-doped TiO2 is broadened which results in the band gap of Hf-doped being smaller than the band gap of TiO2.

  10. Preparation of {0 1 0}-faceted anatase TiO2 nanocuboids from peroxotitanium complex solution

    Science.gov (United States)

    Miao, Yigao; Gao, Jiacheng

    2012-12-01

    {0 1 0}-faceted anatase TiO2 nanocuboids have been fabricated by hydrothermal route using peroxotitanium complex solution as precursor. The effects of reaction time, the amount of urea and temperature on the formation of {0 1 0}-faceted anatase TiO2 were characterized by XRD, FESEM and TEM. The growth mechanism of nanocuboids was proposed that the nanocuboids were formed by the transition from H2Ti2O5·H2O phase to anatase TiO2 in the basic condition. The photocatalytic performance of the prepared samples was tested in the degradation of Rhodamine B and the anatase nanocuboids exhibited enhanced photocatalytic activity compared with the standard P25 powders.

  11. Brookite versus anatase TiO2 photocatalysts: phase transformations and photocatalytic activities.

    Science.gov (United States)

    Kandiel, Tarek A; Robben, Lars; Alkaim, Ayad; Bahnemann, Detlef

    2013-04-01

    Titanium dioxide nanoparticles consisting of pure anatase, anatase-rich, brookite-rich, and pure brookite modifications were synthesized and characterized by X-ray diffraction, field emission-scanning electron microscopy and nitrogen adsorption. The phase transformations among the three modifications of TiO2 (anatase, brookite, and rutile) and the photocatalytic activities of these nanoparticles were investigated by heat treatment over the temperature range from 400 to 800 °C and by the photooxidation of methanol, respectively. Direct transformation of anatase and brookite to rutile was observed, while in the case of the anatase-brookite mixture, anatase transforms firstly to brookite and then to rutile. The photocatalytic activity measurements indicate that brookite nanoparticles exhibit higher photocatalytic activities than anatase, and a comparable activity to that of the anatase-rich nanoparticles. The phase transformations and photocatalytic results are discussed regarding their dependence on crystallite size, surface area, and phase composition.

  12. Enhanced Photocatalytic Activity of Pure Anatase Tio2 and Pt-Tio2 Nanoparticles Synthesized by Green Microwave Assisted Route

    OpenAIRE

    Filippo, Emanuela; Carlucci, Claudia; Capodilupo,Agostina Lina; Perulli,Patrizia; Conciauro,Francesca; Corrente, Giuseppina Anna; Gigli, Giuseppe; Ciccarella, Giuseppe

    2015-01-01

    High-yield, rapid and facile synthesis of elongated pure anatase titania nanoparticles has been achieved through a nonaqueous microwave-based approach. The residual organics onto nanoparticles surfaces were completely removed through a new treatment under ozone flow, at room temperature in air. Such an ozone cleaning method revealed an effective inexpensive dry process of removing organic contaminants from nanoparticles surfaces. The TiO2 elongated nanoparticles having a length of 13.8 ±...

  13. Novel assembly and electrochemical properties of anatase TiO2-graphene aerogel 3D hybrids as lithium-ion battery anodes

    Science.gov (United States)

    Zhang, Jingjie; Zhou, Yizhuo; Zheng, Guangping; Huang, Qiuying; Zheng, Xiucheng; Liu, Pu; Zhang, Jianmin; Guan, Xinxin

    2016-10-01

    TiO2-graphene aerogel (TiO2-GA) 3D hybrids were directly assembled via a one-pot hydrothermal process followed by freeze-drying without using any structure-directing agent. The hybrids with a hierarchical structure exhibited large surface area (SBET = 283.6 m2 g-1) and high pore volume (Vp = 0.278 cm3 g-1), in which the ultradispersed TiO2 nanoparticles were in a single crystal phase of anatase. When used as the anodes for lithium ion battery, the TiO2-GA hybrids exhibited higher reversible capacity, more stable cycling performance and better rate-capability than TiO2 ascribed to the unique 3D nanoporous structure and the synergistic interaction of GA and TiO2.

  14. Preparation and Photocatalytic Behaviors of Nanoporous Polyoxotungstate-Anatase TiO2 Composites

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Nanoporous anatase TiO2 crystalline particles coupled with Keggin or Wells-Dawson unit, H3PW12O40/TiO2 or H6P2W18O62/TiO2, were prepared at a low temperature (200 ℃) using sol-gel method combined with hydrothermal treatment at programmed temperature. The as-prepared composites have uniform anatase phase, and they exhibit both micro-and mesoporosities with pore sizes of 0.6 and 4.0 nm, respectively, and their average size is lower than 10 nm. Photocatalytic tests show the composites exhibit relatively higher photocatalytic activities to decompose the organocholorine pesticide hexachlorobenzene(HCB) than anatase TiO2, the starting polyoxotungstates, and Eu2O3/TiO2 prepared by using sol-gel method, and this was attributed to (1) the synergistic effect of photoactive anatase TiO2 with the polyoxotungstate, and (2) the fascinating physical and chemical properties of the porous materials.

  15. A floating macro/mesoporous crystalline anatase TiO2 ceramic with enhanced photocatalytic performance for recalcitrant wastewater degradation.

    Science.gov (United States)

    Xing, Zipeng; Zhou, Wei; Du, Fan; Qu, Yang; Tian, Guohui; Pan, Kai; Tian, Chungui; Fu, Honggang

    2014-01-14

    A macro/mesoporous anatase TiO2 ceramic floating photocatalyst has been successfully synthesized using highly thermally stable mesoporous TiO2 powder as a precursor, followed by a camphene-based freeze-casting process and high-temperature calcinations. The ceramics are characterized in detail by X-ray diffraction, Raman spectra, scanning electron microscopy, transmission electron microscopy and N2 adsorption-desorption isotherms. The results indicate that the TiO2 ceramics present hierarchical macro/mesoporous structures, which maintain high porosity and high compressive strength at the optimal sintering temperature of 800 °C. The ordered mesoporous TiO2 network still possesses high thermal stability and inhibits the anatase-to-rutile phase transformation during calcinations. The obtained ceramics exhibit good adsorptive and photocatalytic activity for the degradation of octane and rhodamine B, and the total organic carbon removal ratio is up to 98.8% and 98.6% after photodegradation for 3 h, respectively. The roles of active species in the photocatalytic process are compared using different types of active species scavengers, and the degradation mechanism is also proposed. Furthermore, the ceramics are recyclable, and no clear changes are observed after ten cycles. In addition, the ceramics are also active in the photodegradation of phenol, thiobencarb, and atrazine. Therefore, these novel floating photocatalysts will have wide applications, including the removal of floating organic pollutants from the wastewater surfaces or the removal of soluble organic pollutants from wastewater.

  16. Determination of conduction and valence band electronic structure of anatase and rutile TiO2

    Indian Academy of Sciences (India)

    Jakub Szlachetko; Katarzyna Michalow-Mauke; Maarten Nachtegaal; Jacinto Sá

    2014-03-01

    Electronic structures of rutile and anatase polymorph of TiO2 were determined by resonant inelastic X-ray scattering measurements and FEFF9.0 calculations. Difference between crystalline structures led to shifts in the rutile Ti -band to lower energy with respect to anatase, i.e., decrease in band gap. Anatase possesses localized states located in the band gap where electrons can be trapped, which are almost absent in the rutile structure. This could well explain the reported longer lifetimes in anatase. It was revealed that HR-XAS is insufficient to study in-depth unoccupied states of investigated materials because it overlooks the shallow traps.

  17. Hierarchical architectures TiO2: pollen-inducted synthesis, remarkable crystalline-phase stability, tunable size, and reused photo-catalysis.

    Science.gov (United States)

    Dou, Lingling; Gao, Lishuang; Yang, Xiaohui; Song, Xiuqin

    2012-02-15

    TiO(2) with hierarchical architectures, tunable crystalline phase and thermal stability is successfully fabricated on a large scale through a facile hydrolysis process of TiCl(4) combining with inducing of pollen. The structure of the as-prepared TiO(2) is characterized by X-ray diffraction, Raman spectroscopy, infrared spectra, and scanning electron microscopy. The experimental results indicate that different phases (anatase, rutile or mixed crystallite) of TiO(2) can be synthesized by controlling the experimental conditions. The pure phase of rutile or anatase can be obtained at 100°C, while the pure phase of anatase can be retained after being annealed at 900°C. The hierarchical structures TiO(2) are constitute through self-assembly of nanoparticles or nanorods TiO(2), which exhibit high and reused photo-catalytic properties for degradation of methylene blue.

  18. Hierarchical TiO2 nanospheres with dominant {001} facets: facile synthesis, growth mechanism, and photocatalytic activity.

    Science.gov (United States)

    Li, Hongmei; Zeng, Yangsu; Huang, Tongcheng; Piao, Lingyu; Yan, Zijie; Liu, Min

    2012-06-11

    Hierarchical TiO(2) nanospheres with controlled surface morphologies and dominant {001} facets were directly synthesized from Ti powder by a facile, one-pot, hydrothermal method. The obtained hierarchical TiO(2) nanospheres have a uniform size of 400-500 nm and remarkable 78 % fraction of {001} facets. The influence of the reaction temperature, amount of HF, and reaction time on the morphology and the exposed facets was systematically studied. A possible growth mechanism speculates that Ti powder first dissolves in HF solution, and then flowerlike TiO(2) nanostructures are formed by assembly of TiO(2) nanocrystals. Because of the high concentration of HF in the early stage, these TiO(2) nanostructures were etched, and hollow structures formed on the surface. After the F(-) ions were effectively absorbed on the crystal surfaces, {001} facets appear and grow steadily. At the same time, the {101} facets also grow and meet the {101} facets from adjacent truncated tetragonal pyramids, causing coalescence of these facets and formation of nanospheres with dominant {001} facets. With further extension of the reaction time, single-crystal {001} facets of hierarchical TiO(2) nanospheres are dissolved and TiO(2) nanospheres with dominant {101} facets are obtained. The photocatalytic activities of the hierarchical TiO(2) nanospheres were evaluated and found to be closely related to the exposed {001} facets. Owing to the special hierarchical architecture and high percentage of exposed {001} facets, the TiO(2) nanospheres exhibit much enhanced photocatalytic efficiency (almost fourfold) compared to P25 TiO(2) as a benchmark material. This study provides new insight into crystal-facet engineering of anatase TiO(2) nanostructures with high percentage of {001} facets as well as opportunities for controllable synthesis of 3D hierarchical nanostructures.

  19. Synthesis and photocatalytic redox properties of anatase TiO2 single crystals

    Science.gov (United States)

    Dong, Yeshuo; Fei, Xuening; Liu, Zhifeng; Zhou, Yongzhu; Cao, Lingyun

    2017-02-01

    The anatase TiO2 single crystals were synthesized through a solvothermal route and their morphology and structure were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Energy Dispersive X-ray Spectrometer (EDX). Characterization and photocatalytic activity experiments proposed that the simultaneous exposure of (001) and (101) facets could facilitate charge separation. While, due to the effect of surface substitution, the (001) facets were easier to be corroded with the increasing synthesis time. Moreover, the as-synthesized anatase TiO2 single crystals with (001) facets showed superior photocatalytic oxidation properties. Besides, the research on the plausible competitive mechanism of oxidation and reduction in the same reaction system suggested that the oxidation reaction was the predominant one with the increasing proportion of water on anatase TiO2 single crystals possessing the high reactivity of the (001) facets.

  20. Directed synthesis of hierarchical nanostructured TiO2 catalysts and their morphology-dependent photocatalysis for phenol degradation.

    Science.gov (United States)

    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.

  1. Controlled synthesis of hierarchical TiO2 nanoparticles on glass fibres and their photocatalytic performance.

    Science.gov (United States)

    Chen, Lin; Yang, Sudong; Mäder, Edith; Ma, Peng-Cheng

    2014-09-07

    This paper reports the synthesis of novel photocatalysts consisting of TiO2 nanoparticles and glass fibres (GF) using a two-step process. The method involves the hydrolysis of titanium tetrachloride in the presence of GF and a following hydrothermal process under alkaline conditions. Various techniques are employed to characterize the morphology, structure and crystallinity of TiO2 on the fibre surface. The results show that depending on the experiment setups, TiO2 nanoparticles exhibit spherical or flake-like morphology, forming characteristic hierarchical structures along with flexible GF. Flake-like TiO2/GF exhibits much enhanced photocatalytic activity thanks to the large surface area and the hetero-junction of anatase and TiO2-B phases observed in its structure. An interesting observation is that the alkali treatment of GF leads to the formation of porous structures on the fibre surface, facilitating the adsorption-concentration-promoted photocatalytic process. The removal ratio of the organic dye by employing TiO2/GF remains more than 80% after six cyclic runs, showing the reusability of photocatalysts in real application. The novelty of this work lies in the synergy arising from materials with unique morphologies, structures and availabilities as well as capabilities in separating photogenerated electron-hole pairs, which have not been specifically considered previously in photocatalytic semiconductors.

  2. TiO2 anatase with a bandgap in the visible region.

    Science.gov (United States)

    Dette, Christian; Pérez-Osorio, Miguel A; Kley, Christopher S; Punke, Paul; Patrick, Christopher E; Jacobson, Peter; Giustino, Feliciano; Jung, Soon Jung; Kern, Klaus

    2014-11-12

    TiO2 anatase plays a central role in energy and environmental research. A major bottleneck toward developing artificial photosynthesis with TiO2 is that it only absorbs ultraviolet light, owing to its large bandgap of 3.2 eV. If one could reduce the bandgap of anatase to the visible region, TiO2-based photocatalysis could become a competitive clean energy source. Here, using scanning tunneling microscopy and spectroscopy in conjunction with density functional theory calculations, we report the discovery of a highly reactive titanium-terminated anatase surface with a reduced bandgap of less than 2 eV, stretching into the red portion of the solar spectrum. By tuning the surface preparation conditions, we can reversibly switch between the standard anatase surface and the newly discovered low bandgap surface phase. The identification of a TiO2 anatase surface phase with a bandgap in the visible and high chemical reactivity has important implications for solar energy conversion, photocatalysis, and artificial photosynthesis.

  3. Synthesis and Photocatalytic Activity of Anatase TiO2 Nanoparticles-coated Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Xie Yi

    2009-01-01

    Full Text Available Abstract 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.

  4. Hydrogenated Anatase TiO2 as Lithium-Ion Battery Anode: Size-Reactivity Correlation.

    Science.gov (United States)

    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.

  5. New understanding of the difference of photocatalytic activity among anatase, rutile and brookite TiO2.

    Science.gov (United States)

    Zhang, Jinfeng; Zhou, Peng; Liu, Jianjun; Yu, Jiaguo

    2014-10-14

    In general, anatase TiO2 exhibits higher photocatalytic activities than rutile TiO2. However, the reasons for the differences in photocatalytic activity between anatase and rutile are still being debated. In this work, the band structure, density of states, and effective mass of photogenerated charge carriers for anatase, rutile and brookite TiO2 are investigated by the first-principle density functional theory calculation. The results indicate that anatase appears to be an indirect band gap semiconductor, while rutile and brookite belong to the direct band gap semiconductor category. Indirect band gap anatase exhibits a longer lifetime of photoexcited electrons and holes than direct band gap rutile and brookite because the direct transitions of photogenerated electrons from the conduction band (CB) to valence band (VB) of anatase TiO2 is impossible. Furthermore, anatase has the lightest average effective mass of photogenerated electrons and holes as compared to rutile and brookite. The lightest effective mass suggests the fastest migration of photogenerated electrons and holes from the interior to surface of anatase TiO2 particle, thus resulting in the lowest recombination rate of photogenerated charge carriers within anatase TiO2. Therefore, it is not surprising that anatase usually shows a higher photocatalytic activity than rutile and brookite. This investigation will provide some new insight into understanding the difference of photocatalytic activity among anatase, rutile and brookite.

  6. Plasmonic photocatalysis properties of Au nanoparticles precipitated anatase/rutile mixed TiO2 nanotubes.

    Science.gov (United States)

    Wen, Yan; Liu, Bitao; Zeng, Wei; Wang, Yuhua

    2013-10-21

    Anatase/rutile mixed titania nanotubes (TiO2 NTs) precipitated with gold nanoparticles (Au NPs), i.e. Au/TiO2, have been synthesized and investigated on visible photocatalysis properties. A deposition-precipitation (DP) method was adopted to reduce the gold precursor to Au NPs within the preformed TiO2 NTs by the emulsion electrospinning technique. The optimal visible photocatalytic activity was found in the sample Au3(DP350)/TiO2 with a loading of 3 wt% Au NPs and calcining at 350 °C. Through transmission electron microscopy, Au NPs of 4.16 nm diameter were observed at the interface between the anatase and rutile phases in the optimal Au3(DP350)/TiO2 sample, and these joint active sites at the interface were beneficial for charge separation. The obtained optimal photocatalytic efficiency of Au3(DP350)/TiO2 was ascribed to the synergistic effect of the enhanced visible absorption and the anatase/rutile mixed-phase composition, and the possible mechanism for this was discussed in detail.

  7. The Acute Liver Injury in Mice Caused by Nano-Anatase TiO2

    Science.gov (United States)

    Ma, Linglan; Zhao, Jinfang; Wang, Jue; Liu, Jie; Duan, Yanmei; Liu, Huiting; Li, Na; Yan, Jingying; Ruan, Jie; Wang, Han; Hong, Fashui

    2009-11-01

    Although it is known that nano-TiO2 or other nanoparticles can induce liver toxicities, the mechanisms and the molecular pathogenesis are still unclear. In this study, nano-anatase TiO2 (5 nm) was injected into the abdominal cavity of ICR mice for consecutive 14 days, and the inflammatory responses of liver of mice was investigated. The results showed the obvious titanium accumulation in liver DNA, histopathological changes and hepatocytes apoptosis of mice liver, and the liver function damaged by higher doses nano-anatase TiO2. The real-time quantitative RT-PCR and ELISA analyses showed that nano-anatase TiO2 can significantly alter the mRNA and protein expressions of several inflammatory cytokines, including nucleic factor-κB, macrophage migration inhibitory factor, tumor necrosis factor-α, interleukin-6, interleukin-1β, cross-reaction protein, interleukin-4, and interleukin-10. Our results also implied that the inflammatory responses and liver injury may be involved in nano-anatase TiO2-induced liver toxicity.

  8. Completely oriented anatase TiO2 nanoarrays: topotactic growth and orientation-related efficient photocatalysis

    Science.gov (United States)

    Yang, Jingling; Wu, Qili; He, Shiman; Yan, Jing; Shi, Jianying; Chen, Jian; Wu, Mingmei; Yang, Xianfeng

    2015-08-01

    A TiO2 film has been facilely grown on a Ti foil via a general and simple acid vapor oxidation (AVO) strategy. Based on detailed characterization by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), we found that the TiO2 film was composed of anatase nanoarrays highly oriented along their direction, resulting in a large exposed {001} top surface on the film. The growth mechanism based on a topotactic transformation was proposed according to a careful study of time-dependent experimental results. Resulting from the evaluation of photocatalytic performance compared with a commercial TiO2 photocatalyst (Degussa P25), the as-prepared oriented anatase TiO2 film showed higher efficiency for degradation of atrazine and acid orange II (AOII). The performance of photocatalysis is highly relevant to the preferential orientation. The efficient photocatalysis could be attributed to the highly reactive {001} facets on the anatase nanoarrays with super-hydrophilicity.A TiO2 film has been facilely grown on a Ti foil via a general and simple acid vapor oxidation (AVO) strategy. Based on detailed characterization by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), we found that the TiO2 film was composed of anatase nanoarrays highly oriented along their direction, resulting in a large exposed {001} top surface on the film. The growth mechanism based on a topotactic transformation was proposed according to a careful study of time-dependent experimental results. Resulting from the evaluation of photocatalytic performance compared with a commercial TiO2 photocatalyst (Degussa P25), the as-prepared oriented anatase TiO2 film showed higher efficiency for degradation of atrazine and acid orange II (AOII). The performance of photocatalysis is highly relevant to the preferential orientation. The efficient photocatalysis could be attributed to the highly reactive {001

  9. First-principles study on anatase TiO2 codoped with nitrogen and praseodymium

    Science.gov (United States)

    Gao, Pan; Wu, Jing; Liu, Qing-Ju; Zhou, Wen-Fang

    2010-08-01

    The crystal structures, electronic structures and optical properties of nitrogen or/and praseodymium doped anatase TiO2 were calculated by first principles with the plane-wave ultrasoft pseudopotential method based on density functional theory. Highly efficient visible-light-induced nitrogen or/and praseodymium doped anatase TiO2 nanocrystal photocatalyst were synthesized by a microwave chemical method. The calculated results show that the photocatalytic activity of TiO2 can be enhanced by N doping or Pr doping, and can be further enhanced by N+Pr codoping. The band gap change of the codoping TiO2 is more obvious than that of the single ion doping, which results in the red shift of the optical absorption edges. The results are of great significance for the understanding and further development of visible-light response high activity modified TiO2 photocatalyst. The photocatalytic activity of the samples for methyl blue degradation was investigated under the irradiation of fluorescent light. The experimental results show that the codoping TiO2 photocatalytic activity is obviously higher than that of the single ion doping. The experimental results accord with the calculated results.

  10. Methanol Conversion into Dimethyl Ether on the Anatase TiO2(001) Surface.

    Science.gov (United States)

    Xiong, Feng; Yu, Yan-Yan; Wu, Zongfang; Sun, Guanghui; Ding, Liangbing; Jin, Yuekang; Gong, Xue-Qing; Huang, Weixin

    2016-01-11

    Exploring reactions of methanol on TiO2 surfaces is of great importance in both C1 chemistry and photocatalysis. Reported herein is a combined experimental and theoretical calculation study of methanol adsorption and reaction on a mineral anatase TiO2(001)-(1×4) surface. The methanol-to-dimethyl ether (DME) reaction was unambiguously identified to occur by the dehydration coupling of methoxy species at the fourfold-coordinated Ti(4+) sites (Ti(4c)), and for the first time confirms the predicted higher reactivity of this facet compared to other reported TiO2 facets. Surface chemistry of methanol on the anatase TiO2(001)-(1×4) surface is seldom affected by co-chemisorbed water. These results not only greatly deepen the fundamental understanding of elementary surface reactions of methanol on TiO2 surfaces but also show that TiO2 with a high density of Ti(4c) sites is a potentially active and selective catalyst for the important methanol-to-DME reaction.

  11. Specific Facets-Dominated Anatase TiO2: Fluorine-Mediated Synthesis and Photoactivity

    Directory of Open Access Journals (Sweden)

    Maria Vittoria Dozzi

    2013-05-01

    Full Text Available Semiconductors crystal facet engineering has become an important strategy for properly tuning and optimizing both the physicochemical properties and the reactivity of photocatalysts. In this review, a concise survey of recent results obtained in the field of specific surface-oriented anatase TiO2 crystals preparation is presented. The attention is mainly focused on the fluorine-mediated hydrothermal and/or solvothermal processes employed for the synthesis and the assembly of anatase micro/nanostructures with dominant {001} facets. Their peculiar photocatalytic properties and potential applications are also presented, with a particular focus on photocatalysis-based environmental clean up and solar energy conversion applications. Finally, the most promising results obtained in the engineering of TiO2 anatase crystal facets obtained by employing alternative, possibly more environmentally friendly methods are critically compared.

  12. High photocatalytic activity of mixed anatase-rutile phases on commercial TiO2 nanoparticles

    Science.gov (United States)

    Ruu Siah, Wai; Lintang, Hendrik O.; Shamsuddin, Mustaffa; Yuliati, Leny

    2016-02-01

    Titanium dioxide (TiO2) is well-known as an active photocatalyst for degradation of various organic pollutants. Over the years, a wide range of TiO2 nanoparticles with different phase compositions, crystallinities, and surface areas have been developed. Due to the different methods and conditions used to synthesize these commercial TiO2 nanoparticles, the properties and photocatalytic performance would also be different from each other. In this study, the photocatalytic removal of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5- trichlorophenoxyacetic acid (2,4,5-T) was investigated on commercial Evonik P25, Evonik P90, Hombikat UV100 and Hombikat N100 TiO2 nanoparticles. Upon photocatalytic tests, it was found that overall, the photocatalytic activities of the P25 and the P90 were higher than the N100 and the UV100 for the removal of both 2,4-D and 2,4,5-T. The high activities of the P25 and the P90 could be attributed to their phase compositions, which are made up of a mixture of anatase and rutile phases of TiO2. Whereas, the UV100 and the N100 are made up of 100% anatase phase of TiO2. The synergistic effect of the anatase/rutile mixture was reported to slow down the recombination rate of photogenerated electron-hole pairs. Consequently, the photocatalytic activity was increased on these TiO2 nanoparticles.

  13. Facile synthesis of hierarchical porous TiO(2) ceramics with enhanced photocatalytic performance for micropolluted pesticide degradation.

    Science.gov (United States)

    Xing, Zipeng; Zhou, Wei; Du, Fan; Zhang, Linlin; Li, Zhenzi; Zhang, Hang; Li, Wei

    2014-10-08

    In this research, hierarchical porous TiO2 ceramics were successfully synthesized through a camphene-based freeze-drying route. The well-dispersed TiO2 slurries were first frozen and dried at room temperature, followed by high-temperature sintering. The ceramics were analyzed by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. Results indicated that the obtained TiO2 ceramics could inhibit undesirable anatase-to-rutile phase transformation and grain growth even at temperatures as high as 800 °C. In this experiment, optimal compressive strength and porosity of the TiO2 ceramics were produced with the initial TiO2 slurry content of ∼15 wt %. The resultant TiO2 ceramics performed excellently in the photodegradation of atrazine and thiobencarb, and the total organic carbon removal efficiency was up to 95.7% and 96.7%, respectively. More importantly, the TiO2 ceramics were easily recyclable. No obvious changes of the photocatalytic performance were observed after six cycles. Furthermore, the ceramics also effectively degraded other pesticides such as dimethoate, lindane, dipterex, malathion, and bentazone. These hierarchical porous TiO2 ceramics have potential applications in environmental cleanup.

  14. Facile embedding of single vanadium atoms at the anatase TiO2(101) surface.

    Science.gov (United States)

    Koust, Stig; Arnarson, Logi; Moses, Poul G; Li, Zheshen; Beinik, Igor; Lauritsen, Jeppe V; Wendt, Stefan

    2017-04-05

    To understand the structure-reactivity relationships for mixed-metal oxide catalysts, well-defined systems are required. Mixtures of vanadia and titania (TiO2) are of particular interest for application in heterogeneous catalysis, with TiO2 often acting as the support. By utilizing high-resolution scanning tunneling microscopy, we studied the interaction of vanadium (V) with the anatase TiO2(101) surface in the sub-monolayer regime. At 80 K, metallic V nucleates into homogeneously distributed clusters onto the terraces with no preference for nucleation at the step edges. However, embedding of single V atoms into TiO2 occurs following annealing at room temperature. In conjunction with X-ray photoelectron spectroscopy data and density functional theory calculations, we propose that monomeric V atoms occupy positions of regular surface Ti sites, i.e., Ti atoms are substituted by V atoms.

  15. Anatase TiO2/cellulose hybrid paper: Synthesis, characterizations, and photocatalytic activity for degradation of indigo carmine dye

    Science.gov (United States)

    Jiao, Yue; Wan, Caichao; Li, Jian

    We report a facile easy method to deposit anatase titania (TiO2) on cellulose paper. The anatase TiO2/cellulose paper (ATCP) was characterized by scanning electron microscopy, transmission electron microscope, energy dispersive X-ray spectrometer, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. This hybrid paper with the anatase TiO2 content of around 13.86wt.% can serve as an eco-friendly flexible photocatalyst, which can rapidly degrade blue indigo carmine dye into a colorless solution within 30min under UV radiation. Moreover, compared to commercially available TiO2 P25 and anatase TiO2 powder, a faster decomposition rate of indigo carmine dye was acquired when using ATCP. These results suggest that this hybrid paper might be useful in the treatment of organic dye wastewater.

  16. The enhancement of ferromagnetism in Ta-doped anatase TiO2 system by iron co-doping

    Science.gov (United States)

    Muhammady, S.; Kurniawan, R.; Nurfani, E.; Sutjahja, I. M.; Winata, T.; Darma, Y.

    2016-11-01

    The ferromagnetic properties of Ta-doped and (Ta,Fe)-doped anatase TiO2 as diluted ferromagnetic materials has been studied within spin-polarized generalized gradient approximation (GGA) and GGA + U method. We observed a ferromagnetic properties in Ta- doped anatase TiO2, with a total magnetic moment of 1.00 μ B /supercell, which mainly arised due to Ti 3d and O 2p states upon Ef. Furthermore, the enhancement of ferromagnetism, mainly arising due to Fe 3d states, in (Ta,Fe)-doped anatase TiO2 was observed up to 5.00 μB /supercell, 5 times larger than that in Ta-doped TiO2. Our results confirmed the important role of Fe doping for the ferromagnetism enhancement in Ta-doped anatase TiO2.

  17. Sonocatalytic degradation of methyl orange in the presence of (nanometer and ordinary) anatase TiO2 powders

    Institute of Scientific and Technical Information of China (English)

    WANG Jun; GUO Bao-dong; ZHANG Zhao-hong; ZHANG Xiang-dong; WU Jing; LI Hong

    2005-01-01

    The nanometer and ordinary anatase titanium dioxide(TiO2 ) powders were adopted as the sonocatalysts for the degradation of methyl orange used as a model compound for the first time. It was found that the sonocatalytic degradation effect of methyl orange in the presence of TiO2 powder were much better than that without TiO2, but the sonocatalytic activity of the nanometer anatase TiO2 particle was obviously higher than that of ordinary anatase TiO2 particle. Although there are many factors influencing sonocatalytic degradation of methyl orange, the experimental results showed that the best degradation ratio of methyl orange could be obtained when the experimental conditions were: initial concentration 15 mg/L, nanometer anatase TiO2 adding amount 750 mg/L, ultrasonic frequency 40 kHz, output power 50 W, pH = 3.0 and temperature 40℃ within 150 min. In addition, the catalytic activity of reused nanometer anatase TiO2 catalyst was also studied and found to decline gradually comparing with initial nanometer anatase TiO2 catalyst. All experiments indicated that the method of the sonocatalytic degradation of organic pollutants in the presence of TiO2 powder was an advisable choice for non- or lowtransparent organic wastewaters.

  18. Extraordinary Performance of Carbon‐Coated Anatase TiO2 as Sodium‐Ion Anode

    Science.gov (United States)

    Tahir, Muhammad Nawaz; Oschmann, Bernd; Buchholz, Daniel; Dou, Xinwei; Lieberwirth, Ingo; Panthöfer, Martin; Tremel, Wolfgang

    2015-01-01

    The synthesis of in situ polymer‐functionalized anatase TiO2 particles using an anchoring block copolymer with hydroxamate as coordinating species is reported, which yields nanoparticles (≈11 nm) in multigram scale. Thermal annealing converts the polymer brushes into a uniform and homogeneous carbon coating as proven by high resolution transmission electron microscopy and Raman spectroscopy. The strong impact of particle size as well as carbon coating on the electrochemical performance of anatase TiO2 is demonstrated. Downsizing the particles leads to higher reversible uptake/release of sodium cations per formula unit TiO2 (e.g., 0.72 eq. Na+ (11 nm) vs only 0.56 eq. Na+ (40 nm)) while the carbon coating improves rate performance. The combination of small particle size and homogeneous carbon coating allows for the excellent electrochemical performance of anatase TiO2 at high (134 mAh g−1 at 10 C (3.35 A g−1)) and low (≈227 mAh g−1 at 0.1 C) current rates, high cycling stability (full capacity retention between 2nd and 300th cycle at 1 C) and improved coulombic efficiency (≈99.8%). PMID:27134618

  19. Low-temperature electrodeposition approach leading to robust mesoscopic anatase TiO2 films.

    Science.gov (United States)

    Patra, Snehangshu; Andriamiadamanana, Christian; Tulodziecki, Michal; Davoisne, Carine; Taberna, Pierre-Louis; Sauvage, Frédéric

    2016-02-25

    Anatase TiO2, a wide bandgap semiconductor, likely the most worldwide studied inorganic material for many practical applications, offers unequal characteristics for applications in photocatalysis and sun energy conversion. However, the lack of controllable, cost-effective methods for scalable fabrication of homogeneous thin films of anatase TiO2 at low temperatures (ie. < 100 °C) renders up-to-date deposition processes unsuited to flexible plastic supports or to smart textile fibres, thus limiting these wearable and easy-to-integrate emerging technologies. Here, we present a very versatile template-free method for producing robust mesoporous films of nanocrystalline anatase TiO2 at temperatures of/or below 80 °C. The individual assembly of the mesoscopic particles forming ever-demonstrated high optical quality beads of TiO2 affords, with this simple methodology, efficient light capture and confinement into the photo-anode, which in flexible dye-sensitized solar cell technology translates into a remarkable power conversion efficiency of 7.2% under A.M.1.5G conditions.

  20. Completely oriented anatase TiO2 nanoarrays: topotactic growth and orientation-related efficient photocatalysis.

    Science.gov (United States)

    Yang, Jingling; Wu, Qili; He, Shiman; Yan, Jing; Shi, Jianying; Chen, Jian; Wu, Mingmei; Yang, Xianfeng

    2015-09-07

    A TiO2 film has been facilely grown on a Ti foil via a general and simple acid vapor oxidation (AVO) strategy. Based on detailed characterization by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), we found that the TiO2 film was composed of anatase nanoarrays highly oriented along their direction, resulting in a large exposed {001} top surface on the film. The growth mechanism based on a topotactic transformation was proposed according to a careful study of time-dependent experimental results. Resulting from the evaluation of photocatalytic performance compared with a commercial TiO2 photocatalyst (Degussa P25), the as-prepared oriented anatase TiO2 film showed higher efficiency for degradation of atrazine and acid orange II (AOII). The performance of photocatalysis is highly relevant to the preferential orientation. The efficient photocatalysis could be attributed to the highly reactive {001} facets on the anatase nanoarrays with super-hydrophilicity.

  1. Optimization of macropore evolution towards high photocatalytic activity enhancement in meso/macro porous Anatase TiO2

    Science.gov (United States)

    Nair, Radhika V.; Gayathri, P. K.; Siva Gummaluri, Venkata; Vijayan, C.

    2017-01-01

    We report on an optimization strategy for macro pore evolution leading to the design of highly photocatalytic 3D hierarchical meso/macroporous TiO2 via much simpler, faster and cost effective synthesis scheme. Meso/macro porous TiO2 is an excellent candidate material for photocatalytic applications owing to the availability of internal surfaces as active sites for redox reactions. The current research scenario focuses on the design of highly efficient photocatalytic systems as well as rapid, facile and cost effective methods of synthesis and optimization of parameters. The present report is on the gradual evolution of macropores in anatase TiO2 by the effective control of pH of the solvent, reaction time, temperature, solvent ratio and reactant concentration via a facile hydrothermal method in this regard. 3D hierarchical macroporous structures are obtained at pH 7 within a comparatively short reaction time of 5 h and demonstrated to be highly photocatalytic (with rate constant four times that of P25 nanoparticles) through photodegradation of Rhodamine B dye.

  2. Study of defect-induced ferromagnetism in hydrogenated anatase TiO2:Co

    Science.gov (United States)

    Singhal, R. K.; Samariya, Arvind; Kumar, Sudhish; Xing, Y. T.; Jain, D. C.; Dolia, S. N.; Deshpande, U. P.; Shripathi, T.; Saitovitch, Elisa B.

    2010-06-01

    Electronic and magnetic properties of Co-doped TiO2 polycrystalline pellets (Ti0.95Co0.05O2) have been investigated using x-ray diffraction, x-ray photoemission, magnetization, and resistance measurements. The as-synthesized and hydrogenated specimens crystallize in the anatase type tetragonal structure containing very small (˜4.4%) rutile phase. The dopant ions of Co are found to be divalent and well incorporated into TiO2 lattice, substituting the Ti site within the anatase phase, with no evidence of metallic Co or any other oxides of Co. The Co doping induces a weak ferromagnetic ordering in the diamagnetic TiO2 host matrix. Interestingly, when the Co-doped TiO2 is annealed in hydrogen atmosphere, it shows a giant enhancement in magnetization. However, an extended reheating in air causes this H-induced magnetization to vanish and the sample regains the as-prepared status. Our findings indicate that ferromagnetism originates from the doped matrix rather than any magnetic clusters and strongly correlated with oxygen vacancies in the doped TiO2. The induced ferromagnetic ordering is found to be a reversible process with regard to oxygen vacancy defects that could be induced or removed, respectively, upon introduction or removal of these defects.

  3. Self-templated synthesis of TiO2 hierarchical structure photocatalyst with high efficiency and good sedimentation property

    Science.gov (United States)

    Wang, Xiaoning; Sang, Yuanhua; Yu, Xin; Liu, Baishan; Liu, Hong

    2016-10-01

    The balance between highly efficient photocatalysis and a good emulsion/water extraction property is crucial for the practical application of TiO2 photocatalysts. The TiO2 hierarchical structure was synthesized via a hydrothermal treatment of H2Ti3O7 nanobelts with TiF4. The hydrolysis of TiF4 supplies the TiO2 nucleus, and HF, which is derived from the hydrolysis process, acts as a corrosive to etch the H2Ti3O7 nanobelt, resulting in a dynamic dissolution and precipitation process. The etching process resulted in self-generated TiF4 and initiated hydrolysis to generate new TiO2 primary particles. Induced by F etching process, Ti3+ defects were formed in the hierarchical structures, which was beneficial to the photocatalytic property. This hydrolysis-etching-hydrolysis process allows for template dissolution and self-assembly of anatase TiO2 nanobelts to form the TiO2 hierarchical structures. This process balances the nanominiaturization and sedimentation property requirements by the photocatalytic and emulsion/water extraction properties. This simple hydrolysis-etching-hydrolysis process can be applied to the synthesis of many other hierarchical structures.

  4. Controlled formation of anatase and rutile TiO2 thin films by reactive magnetron sputtering

    Directory of Open Access Journals (Sweden)

    Damon Rafieian

    2015-09-01

    Full Text Available We discuss the formation of TiO2 thin films via DC reactive magnetron sputtering. The oxygen concentration during sputtering proved to be a crucial parameter with respect to the final film structure and properties. The initial deposition provided amorphous films that crystallise upon annealing to anatase or rutile, depending on the initial sputtering conditions. Substoichiometric films (TiOx<2, obtained by sputtering at relatively low oxygen concentration, formed rutile upon annealing in air, whereas stoichiometric films formed anatase. This route therefore presents a formation route for rutile films via lower (<500 °C temperature pathways. The dynamics of the annealing process were followed by in situ ellipsometry, showing the optical properties transformation. The final crystal structures were identified by XRD. The anatase film obtained by this deposition method displayed high carriers mobility as measured by time-resolved microwave conductance. This also confirms the high photocatalytic activity of the anatase films.

  5. Photocatalytic Activity Enhancement of Anatase TiO2 by Using TiO

    Directory of Open Access Journals (Sweden)

    Zhenrui Chen

    2014-01-01

    Full Text Available We employed high-energy ball-milling technique to fabricate TiO/TiO2 heterogeneous nanostructures. XRD proved the existence of TiO/TiO2 heterogeneous structures. SEM and HRTEM investigation evidenced that the mean particle size and mean grain size of the as-prepared samples are 23 nm and 13 nm, respectively. UV-Vis spectra exhibited that TiO has enhanced the visible light absorption of TiO2 and has changed the Eg of TiO2. UPS examination indicated that the electron work function (EWF of TiO is higher than that of TiO2. Photocatalytic degradation experiments revealed that an appropriate TiO content can enhance the photocatalytic activity of pure anatase TiO2. The best photocatalytic activity of TiO/TiO2 heterogeneous nanostructures is even better than that of Au-deposited TiO2 by keeping high degradation efficiency of 93%. The internal electrical field producing in TiO/TiO2 heterogeneous nanostructures was considered to be dominantly responsible for the enhanced photocatalytic activity. Therefore, the substitution of TiO with noble metal in TiO2 will be widely used in the future due to its low cost. This study also provides a clear direction of enhancing photocatalytic activity of TiO2: incorporating a guest compound into TiO2 with an appropriate content if the compound has much higher electron work function than that of TiO2.

  6. Growth and structure of MBE grown TiO2 anatase films with rutile nano-crystallites

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Rui; Wang, Chong M.; McCready, David E.; Droubay, Timothy C.; Chambers, Scott A.

    2007-03-15

    We have grown TiO2 anatase films with rutile nanocrystalline inclusions using molecular beam epitaxy under different growth conditions. This model system is important for investigating the role of rutile/anatase interfaces in heterogeneous photocatalysis. To control the film structure, we grew a pure anatase (001) layer at a slow rate and then increased the growth rate to drive the nucleation of rutile particles. Structure analysis indicates that the rutile phase has four preferred orientations in the anatase film.

  7. A fast-reliable methodology to estimate the concentration of rutile or anatase phases of TiO2

    Science.gov (United States)

    Zanatta, A. R.

    2017-07-01

    Titanium-dioxide (TiO2) is a low-cost, chemically inert material that became the basis of many modern applications ranging from, for example, cosmetics to photovoltaics. TiO2 exists in three different crystal phases - Rutile, Anatase and, less commonly, Brookite - and, in most of the cases, the presence or relative amount of these phases are essential to decide the TiO2 final application and its related efficiency. Traditionally, X-ray diffraction has been chosen to study TiO2 and provides both the phases identification and the Rutile-to-Anatase ratio. Similar information can be achieved from Raman scattering spectroscopy that, additionally, is versatile and involves rather simple instrumentation. Motivated by these aspects this work took into account various TiO2 Rutile+Anatase powder mixtures and their corresponding Raman spectra. Essentially, the method described here was based upon the fact that the Rutile and Anatase crystal phases have distinctive phonon features, and therefore, the composition of the TiO2 mixtures can be readily assessed from their Raman spectra. The experimental results clearly demonstrate the suitability of Raman spectroscopy in estimating the concentration of Rutile or Anatase in TiO2 and is expected to influence the study of TiO2-related thin films, interfaces, systems with reduced dimensions, and devices like photocatalytic and solar cells.

  8. Structural study of TiO2 nanotube based to the (101) anatase surface

    Science.gov (United States)

    Dargouthi, Sarra; Minot, Christian; Tangour, Bahoueddine

    2017-02-01

    This work concerns six TiO2 (n,0) nanotubes specifically: (9,0) (10,0) (11,0) (12,0) (13,0) and (14,0). They are obtained by winding a film from the (101) anatase surface, this plane surface serving as a reference. We show that the rolling up is a destabilizing factor. Indeed, the winding provokes a rapprochement between two successive bridged oxygen atoms thus inducing repulsion between them. Structure of nanotubes leads to modulate the O-O distance from 2.845 Å to 4.541 Å whereas the unique value of the anatase is 3.809 Å. This modulation of the internuclear distance O-O may play a role in the reactivity of TiO2 process involving two neighboring oxygen and can allow the proper choice of the nanotube to be used in catalysis.

  9. Ab initio calculations of electronic structure of anatase TiO2

    Institute of Scientific and Technical Information of China (English)

    Chen Qiang; Cao Hong-Hong

    2004-01-01

    This paper presents the results of the self-consistent calculations on the electronic structure of anatase phase of TiO2. The calculations were performed using the full potential-linearized augmented plane wave method (FP-LAPW)in the framework of the density functional theory (DFT) with the generalized gradient approximation (GGA). The fully optimized structure, obtained by minimizing the total energy and atomic forces, is in good agreement with experiment.We also calculated the band structure and the density of states. In particular, the calculated band structure prefers an indirect transition between wlence and conduction bands of anatase TiO2, which may be helpful for clarifying the ambiguity in other theoretical works.

  10. Glycine assisted synthesis of flower-like TiO 2 hierarchical spheres and its application in photocatalysis

    KAUST Repository

    Tao, Yugui

    2012-11-01

    Flower-like anatase TiO 2 hierarchical spheres assembled by nanosheets were synthesized by glycine assistant via a simple hydrothermal approach and after-annealing process. These flower-like spheres are about 2 μm in diameter with sheet thickness about 20 nm. Results showed reaction time, temperature, solution pH and glycine dosage all played an important role in control of shape and size of the as-synthesized TiO 2 nanocrystals. The photocatalytic activity of this nano-TiO 2 was evaluated by the photocatalytic oxidation decomposition of methyl orange under sunlight illumination in the presence of hydrogen peroxide (H 2O 2). The photocatalytic activity of the obtained TiO 2 was higher than that of commercial TiO 2. © 2012 Elsevier B.V.

  11. In-situ synthesized mesoporous TiO2-B/anatase microparticles:Improved anodes for lithium ion batteries☆

    Institute of Scientific and Technical Information of China (English)

    Wei Zhuang; Linghong Lu; Wei Li; Rong An; Xin Feng; Xinbing Wu; Yudan Zhu; Xiaohua Lu

    2015-01-01

    Mesoporous TiO2-B/anatase microparticles have been in-situ synthesized from K2Ti2O5 without template. The TiO2-B phase around the particle surface accelerates the diffusion of charges through the interface, while the anatase phase in the core maintains the capacity stability. The heterojunction interface between the main polymorph of anatase and the trace of TiO2-B exhibits promising lithium ion battery performance. This trace of 5%(by mass) TiO2-B determined by Raman spectra brings the first discharge capacity of this material to 247 mA·h·g−1, giving 20%improvement com-pared to the anatase counterpart. Stability testing at 1 C reveals that the capacity maintains at 171 mA·h·g−1, which is better than 162 mA·h·g−1 for single phase anatase or 159 mA·h·g−1 for TiO2-B. The mesoporous TiO2-B/anatase microparticles also show superior rate performance with 100 mA·h·g−1 at 40 C, increased by nearly 25%as compared to pure anatase. This opens a possibility of a general design route, which can be applied to other metal oxide electrode materials for rechargeable batteries and supercapacitors.

  12. Low temperature synthesis of hierarchical TiO2 nanostructures for high performance perovskite solar cells by pulsed laser deposition.

    Science.gov (United States)

    Yang, Bin; Mahjouri-Samani, Masoud; Rouleau, Christopher M; Geohegan, David B; Xiao, Kai

    2016-10-21

    A promising way to advance perovskite solar cells is to improve the quality of the electron transport material -e.g., titanium dioxide (TiO2) - in a direction that increases electron transport and extraction. Although dense TiO2 films are easily grown in solution, efficient electron extraction suffers due to a lack of interfacial contact area with the perovskites. Conversely, mesoporous films do offer high surface-area-to-volume ratios, thereby promoting efficient electron extraction, but their morphology is relatively difficult to control via conventional solution synthesis methods. Here, a pulsed laser deposition method was used to assemble TiO2 nanoparticles into TiO2 hierarchical architectures exhibiting an anatase crystal structure, and prototype solar cells employing these structures yielded power conversion efficiencies of ∼14%. Our approach demonstrates a way to grow high aspect-ratio TiO2 nanostructures for improved interfacial contact between TiO2 and perovskite materials, leading to high electron-hole pair separation and electron extraction efficiencies for superior photovoltaic performance. Compared to previous pulsed laser deposition-synthesized TiO2 mesoporous crystalline networks that needed post-thermal annealing at 500 °C to form mesoporous crystalline networks, our relatively low temperature (300 °C) TiO2 processing method may promote reduced energy-consumption during device fabrication, as well as enable compatibility with flexible polymer substrates such as polyimide.

  13. Alternating voltage induced ordered anatase TiO2 nanopores: An electrochemical investigation of sodium storage

    Science.gov (United States)

    Li, Simin; Xie, Lingling; Hou, Hongshuai; Liao, Hanxiao; Huang, Zhaodong; Qiu, Xiaoqing; Ji, Xiaobo

    2016-12-01

    Anatase TiO2 nanopores are successfully prepared through alternating voltage induced electrochemical synthesis (AVIES) approach at room temperature. When utilizing TiO2 nanoporous materials as an anode for Na-ion battery, it delivers a reversible charge-discharge capacity of around 180 mA h g-1 at 0.2 C (67 mA g-1) after 200 cycles. Meanwhile, it also shows a good cycling performance and a high rate capability due to unique nanoporous structures, which promote electrolyte wetting and facilitate diffusion of Na+. Additionally, cyclic voltammetry demonstrate that the sodium-ion storage of as-prepared TiO2 is a cooperative control behavior of diffusion and capacitance, but mainly controlled by capacitive behavior, which further facilitates a rapid (de-)intercalation of Na+.

  14. Infrared study of laser synthesized anatase TiO2 nanopowders

    Science.gov (United States)

    Grujic-Brojcin, M.; Scepanovic, M. J.; Dohcevic-Mitrovic, Z. D.; Hinic, I.; Matovic, B.; Stanisic, G.; Popovic, Z. V.

    2005-05-01

    Nanosized titanium dioxide (TiO2) is synthesized by laser-induced pyrolysis using titanium isopropoxide as a liquid precursor. The specific surface area of as-produced nanopowders measured by the Brunauer-Emmett-Teller method (BET) varies from 84 to 110 m2 g-1. X-ray diffraction (XRD) and Raman scattering showed that the TiO2 nanocrystals had an anatase structure. The grain size of the nanoparticles was estimated from scanning electron microscopy, XRD and BET measurements. The reflection spectra of nanocrystalline TiO2 pressed pellets has been measured in the region between 80 and 1500 cm-1 by Fourier transform infrared spectroscopy. To interpret the experimental results, a model based on a generalized Bruggeman effective medium approximation of a dielectric function has been proposed. It is based on the polycrystalline character of TiO2 nanoparticles including island-structure and porosity of the nanopowders, along with the anatase single crystal dielectric functions. Thus, by comparing the results of calculated and experimental infrared (IR) spectra, the values of microscopic parameters of nanocrystalline powders can be deduced.

  15. First-principle Calculations of V/Fe Doped Anatase TiO2

    Institute of Scientific and Technical Information of China (English)

    CAO Hong-hong; CHEN Qiang; WANG Tian-min

    2006-01-01

    The electronic structures of the titanium dioxide(TiO2) doped with V and Fe were analyzed by using first-principle calculations based on the density functional theory(DFT) with the full potential linearized augmented plane wave method (FP-LAPW). The fully optimized structure and the relaxation introduced by impurity were obtained by minimizing the total energy and atomic forces. The unit cell of the V-doped anatase TiO2 is smaller than that of the non-doped one, but for the Fe-doped one, the case is just the opposite. It is found that the apical Ti-O and impurity-O bond lengths of the V/Fe-doped anatase TiO2 are greater than those of the non-doped structure, but smaller for the equatorial bond length. Through the band structures and the density of states, the V-doped TiO2 is shown to be a kind of half-metal, while the Fe-doped TiO2 a kind of metal. The magnetic moments of the V/Fe-doped system are mainly generated by the dopants. The results may be helpful for us to understand the experimental outcome of this system.

  16. Rutile TiO2 nanowires on anatase TiO2 nanofibers: a branched heterostructured photocatalysts via interface-assisted fabrication approach.

    Science.gov (United States)

    Wang, Changhua; Zhang, Xintong; Shao, Changlu; Zhang, Yanli; Yang, Jikai; Sun, Panpan; Liu, Xueping; Liu, Hong; Liu, Yichun; Xie, Tengfeng; Wang, Dejun

    2011-11-01

    A water-dichloromethane interface-assisted hydrothermal method was employed to grow rutile TiO(2) nanowires (NWs) on electrospun anatase TiO(2) nanofibers (NFs), using highly reactive TiCl(4) as precursor. The water-dichloromethane interface inhibited the formation of rutile NWs in water phase, but promoted the selective radial growth of densely packed rutile NWs on anatase NFs to form a branched heterojunction. The density and length of rutile NWs could be readily controlled by varying reaction parameters. A formation mechanism for the branched heterojunction was proposed which involved (1) the entrapment of rutile precursor nanoparticles at water-dichloromethane interface, (2) the growth of rutile NWs on anatase NFs via Ostwald ripening through the scavengering of interface-entrapped rutile nanoparticles. The heterojunction formed at anatase NF and rutile NW enhanced the charge separation of both under ultraviolet excitation, as evidenced by photoluminescence and surface photovoltage spectra. The branched TiO(2) heterostructures showed higher photocatalytic activity in degradation of rodamine B dye solution than anatase NFs, and the mixture of anatase NFs, and P25 powders, which was discussed in terms of the synergistic effect of enhanced charge separation by anatase-rutile heterojunction, high activity of rutile NWs, and increased specific area of branched heterostructures.

  17. Ultrasonic Degradation of Methyl Orange in Presence of Y2O3 Doping Anatase TiO2 Catalyst

    Institute of Scientific and Technical Information of China (English)

    Wang Jun; Guo Baodong; Pan Zhijun; Liu Zhenrong; Wen Fuyu; Zhang Zhaohong

    2004-01-01

    Various affecting factors and degradation mechanism were studied on ultrasonic degradation of methyl orange adopting Y2O3 doping anatase TiO2 catalyst prepared in laboratory.In the experiment, the UV-VIS spectrophotometer was used to follow and inspect the degradation process of methyl orange.The results indicate that the ultrasonic degradation ratios of methyl orange in the presence of anatase TiO2 catalyst are much better than those without catalyst.Moreover, the catalytic performance of Y2O3 doping anatase TiO2 catalyst is obviously higher than that of anatase TiO2 catalyst without doping.The optimal conditions were adopted in this work and the degradation and COD elimination ratio of methyl orange got to98% and 99.0% in 90 min, respectively.

  18. An effective method for the preparation of high temperature stable anatase TiO2 photocatalysts

    Science.gov (United States)

    Fagan, Rachel; Synnott, Damian W.; McCormack, Declan E.; Pillai, Suresh C.

    2016-05-01

    An efficient, rapid and straightforward method for the preparation of nitrogen and fluorine (N, F) codoped high temperature stable anatase using a microwave pre-treatment is reported. Using a single source, ammonium fluoride (NH4F) for both nitrogen and fluorine, effective doping of the precursor titanium isopropoxide (TTIP) was possible. These samples were characterised for their structural and optical properties using X-ray diffraction (XRD), Fourier Transform IR (FTIR), Raman spectroscopy and UV-vis spectroscopy. In terms of the anatase to rutile transition enhancement using a novel microwave assisted technique, the sample prepared in a composition of 1:8 TiO2: NH4F at 1200 °C was seen to be most effective, having stable anatase present at 57.1% compared to undoped TiO2 being 100% rutile from 900 °C. This method involves the production of ammonium oxofluorotitanates (NH4TiOF3) at low temperatures. The inclusion of these intermediates greatly reduces the particle size growth and delays the anatase to rutile transition. The photocatalytic activity of these materials was studied by analysing the degradation of an organic dye, rhodamine 6G as a model system and the rate constant was calculated by pseudo-first-order kinetics. These results showed that the doped sample (0.0225 min-1) was three times more active than the undoped sample (0.0076 min-1) and over seven times faster than the commercial TiO2 photocatalyst standard Degussa P-25 calcined at 1200 °C (0.0030 min-1). The formation of intermediate compounds, oxofluorotitanates, was identified as the major reason for a delay in the anatase to rutile transition.

  19. Hydrofluoric Acid Controlled TiO2 Phase Transformation from Rutile to Anatase at Room Temperature and Their Photocatalytic Performance.

    Science.gov (United States)

    Ge, Suxiang; Li, Dapeng; Jia, Gaoyang; Wang, Beibei; Yang, Zhen; Yang, Zongyang; Qiao, Hui; Zhang, Yange; Zheng, Zhi

    2015-09-01

    In this study, we first present rutile TiO2 superstructures could be successfully transformed into anatase TiO2 nanoparticles at room temperature by adjusting the amount of hydrofluoric acid (HF) used in aqueous solution. Photocatalytic experiments demonstrated that the as prepared anatase TiO2 exhibited better photocatalytic performance than that of rutile TiO2. We further studied the photocatalytic degradation of RhB on different TiO2 via active species trapping experiments and confirmed that the presence of surface F- on TiO2 was beneficial for the formation of *OH, which was thought to be mainly responsible for the enhancement of photocatalytic performance.

  20. Preparation of Hierarchical Anatase TiO2 Nanowire Arrays on Ti-foil Substrate for CdSe Quantum-dot Sensitized Solar Cells%分等级锐钛矿TiO2纳米线阵列的制备及其在CdSe量子点敏化太阳电池中的应用

    Institute of Scientific and Technical Information of China (English)

    徐杨帆

    2014-01-01

    量子点敏化太阳电池是一种新型的第三代高效太阳电池,具有极大的应用前景。本文利用水热法,首先在柔性的钛片基底上生长了光滑的TiO2纳米线阵列,并通过第二步水热反应制备出具有分支结构的分等级TiO2纳米线阵列,研究了其在CdSe量子点敏化太阳电池中的应用。实验结果表明,具有分支结构的分等级材料具有更高的表面积以负载敏化剂,同时保持了一维纳米阵列高效的电子传输特性,因此相比于光滑纳米线阵列,其光电转换效率提升近一倍,在标准光强下测试达到0.72%。%As one type of the third generation solar cells, quantum dot sensitized solar cells (QDSSCs) has a bright future in application. In this paper, the hierarchical anatase TiO2 NWs arrays were synthesized through a two-step hydrother-mal growth process on a flexible titanium foil substrate. The HNW photoelectrode offered a high surface area to load sen-sitizer while maintaining its well elctron tranfer ability. Therefore, the power conversion efficiency of CdSe Quantum-dot sensitized solar cells based on such photoelectrode showed a significant enhancement compared to TiO2 nanowire with similar thickness,which achieved 0.72%.

  1. C-doped mesoporous anatase TiO2 comprising 10nm crystallites.

    Science.gov (United States)

    Xie, Chong; Yang, Shenghui; Li, Beibei; Wang, Hongkong; Shi, Jian-Wen; Li, Guodong; Niu, Chunming

    2016-08-15

    We report a C-doped mesoporous anatase TiO2 with high surface area synthesized using multi-walled carbon nanotube (MWCNT) mat as a "rigid" template and carbon doping source. The characterization by SEM, HRTEM, X-ray diffraction and nitrogen adsorption revealed that TiO2 samples have a porous structure which are figuratively a inverse copy of MWCNT network and pore walls are formed by interconnected TiO2 nanoparticles with average diameter of ∼10nm. We found that annealing temperatures from 400 to 1000°C before MWCNT template removal had very limited effect on particle size (∼10nm), surface area (112-129m(2)/g) and total pore volume (0.74-0.85m(2)/g) of the samples through a significantly delayed phase transition from anatase to rutile started at 800°C, resulting in only ∼9.1% conversion at 1000°C. The pore size distribution is in mesopore range from 6 to 60nm peaked at ∼24nm. XPS analysis showed a relatively strong C1s peak at 288.4eV, indicating C doping at Ti sites, which is responsible for red shift of adsorption edge of UV-vis spectra and photocatalytic activity in visible-light region.

  2. Dispersion and Structure Studies of Molybdenum Oxide on Anatase TiO2

    Institute of Scientific and Technical Information of China (English)

    ZI Feng-lan; GUO Hong-you; WU Nian-zu; XIE Ya-ning; HU Tian-dou

    2004-01-01

    X-ray photoelectron spectroscopy(XPS) and extended X-ray absorption fine structure(EXAFS) were used to characterize the structure of the mixture of molybdenum oxide and anatase calcined at 723 K. The results indicate that molybdenum oxide can disperse onto the surface of anatase(TiO2) and the dispersion threshold is 11.2 mg in per gram of MoO3 or 4.8 Mo atoms/nm2 TiO2. When the content of MoO3 is below the dispersion threshold, MoO3 species is in highly dispersed state interacting strongly with TiO2 support and in discrete tetrahedral coordination, [MoO4], on the surface of TiO2. When the MoO3 loading is above this value, MoO3 exists in both dispersed phase and crystalline phase. MoO3 in dispersed phase is still a discrete [MoO4] tetrahedron; MoO3 in crystal phase is in octahedral coordination.

  3. Sonocatalytic damage of bovine serum albumin (BSA) in the presence of nanometer anatase titanium dioxide (TiO2).

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    Wang, Jun; Wu, Jing; Zhang, Zhaohong; Zhang, Xiangdong; Pan, Zhijun; Wang, Lei; Xu, Liang

    2006-01-01

    The nanometer anatase titanium dioxide (TiO2) (a kind of crystal type of TiO2) powder was adopted as the sonocatalyst for the damage of bovine serum albumin (BSA) used as a model protein by low-power ultrasound (US) (80 kHz, 80 W). The effects of several factors on the damage of BSA molecule were reviewed by means of ultraviolet destruction and circular dichroism spectra. It was found that the BSA molecule underwent destruction of the secondary structure and loss of the alpha-helical configuration to a certain extent under ultrasonic irradiation in the presence of nanometer anatase TiO2 powder and that the damage caused by US integrated with TiO2 was more serious than those by only US or only TiO2. Furthermore, the damage degree was aggravated with the increase of TiO2, added to saturation, and then it was slowly weakened with the excessive TiO2. When a suitable amount of acid or base was added into the BSA solution, the sonocatalytic damage was also aggravated. Because the functions of proteins are decided by their space configurations, the changes of the configurations might cause the forfeiture of their function, even the apoptosis or necrosis of cells. Perhaps, an effective method of killing cancer cells by sonocatalytic damage of protein molecules in the presence of nanometer anatase TiO2 could be obtained from these experimental results.

  4. First-principles study of atomic structure and electronic properties of Si and F doped anatase TiO2

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    Li Hongping

    2015-09-01

    Full Text Available Chemical doping represents one of the most effective ways in engineering electronic structures of anatase TiO2 for practical applications. Here, we investigate formation energies, geometrical structures, and electronic properties of Si-, F-doped and Si/F co-doped anatase TiO2 by using spin-polarized density functional theory calculation. We find that the co-doped TiO2 is thermodynamically more favorable than the Si- and F-doped TiO2- Structural analysis shows that atomic impurity varies crystal constants slightly. Moreover, all the three doped systems show a pronounced narrowing of band gap by 0.33 eV for the F-doped TiO2, 0.17 eV for the Si-doped TiO2, and 0.28 eV for the Si/F-co-doped TiO2, which could account for the experimentally observed redshift of optical absorption edge. Our calculations suggest that the Si/F-co-doping represents an effective way in tailoring electronic structure and optical properties of anatase TiO2.

  5. Anatase TiO2 Nanospindle/Activated Carbon (AC Composite Photocatalysts with Enhanced Activity in Removal of Organic Contaminant

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    Wuyi Zhou

    2012-01-01

    Full Text Available This paper embarks upon the three levels of analysis ranging from nanoscale materials synthesis to combination and functionality. Firstly, we have prepared anatase TiO2 nanospindles with an even length of about 200 nm and a central width of about 25 nm by hydrothermal synthesis method at 100°C for 6 h. Secondly, we have dispersed TiO2 nanospindles on the surface of activated carbon (AC and fabricated TiO2/AC composite via a dip-coating method. Thirdly, the TiO2/AC composite has been studied as the photocatalyst to remove the organic contaminants in the waste water and exhibits excellent degradation rate in comparison with pure anatase TiO2 nanospindles.

  6. Effect on Electron Structure and Magneto-Optic Property of Heavy W-Doped Anatase TiO2.

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    Hou, Qingyu; Zhao, Chunwang; Guo, Shaoqiang; Mao, Fei; Zhang, Yue

    2015-01-01

    The spin or nonspin state of electrons in W-doped anatase TiO2 is very difficult to judge experimentally because of characterization method limitations. Hence, the effect on the microscopic mechanism underlying the visible-light effect of W-doped anatase TiO2 through the consideration of electronic spin or no-spin states is still unknown. To solve this problem, we establish supercell models of W-doped anatase TiO2 at different concentrations, followed by geometry optimization and energy calculation based on the first-principle planewave norm conserving pseudo-potential method of the density functional theory. Calculation results showed that under the condition of nonspin the doping concentration of W becomes heavier, the formation energy becomes greater, and doping becomes more difficult. Meanwhile, the total energy increases, the covalent weakens and ionic bonds strengthens, the stability of the W-doped anatase TiO2 decreases, the band gap increases, and the blue-shift becomes more significant with the increase of W doping concentration. However, under the condition of spin, after the band gap correction by the GGA+U method, it is found that the semimetal diluted magnetic semiconductors can be formed by heavy W-doped anatase TiO2. Especially, a conduction electron polarizability of as high as near 100% has been found for the first time in high concentration W-doped anatase TiO2. It will be able to be a promising new type of dilute magnetic semiconductor. And the heavy W-doped anatase TiO2 make the band gap becomes narrower and absorption spectrum red-shift.

  7. Effect on Electron Structure and Magneto-Optic Property of Heavy W-Doped Anatase TiO2.

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    Qingyu Hou

    Full Text Available The spin or nonspin state of electrons in W-doped anatase TiO2 is very difficult to judge experimentally because of characterization method limitations. Hence, the effect on the microscopic mechanism underlying the visible-light effect of W-doped anatase TiO2 through the consideration of electronic spin or no-spin states is still unknown. To solve this problem, we establish supercell models of W-doped anatase TiO2 at different concentrations, followed by geometry optimization and energy calculation based on the first-principle planewave norm conserving pseudo-potential method of the density functional theory. Calculation results showed that under the condition of nonspin the doping concentration of W becomes heavier, the formation energy becomes greater, and doping becomes more difficult. Meanwhile, the total energy increases, the covalent weakens and ionic bonds strengthens, the stability of the W-doped anatase TiO2 decreases, the band gap increases, and the blue-shift becomes more significant with the increase of W doping concentration. However, under the condition of spin, after the band gap correction by the GGA+U method, it is found that the semimetal diluted magnetic semiconductors can be formed by heavy W-doped anatase TiO2. Especially, a conduction electron polarizability of as high as near 100% has been found for the first time in high concentration W-doped anatase TiO2. It will be able to be a promising new type of dilute magnetic semiconductor. And the heavy W-doped anatase TiO2 make the band gap becomes narrower and absorption spectrum red-shift.

  8. Molybdenum-Loaded Anatase TiO2 Nanoparticles With Enhanced Optoelectronics Properties

    Science.gov (United States)

    Bargougui, R.; Bouazizi, N.; Ammar, S.; Azzouz, A.

    2017-01-01

    The structural, optical and electrical properties of molybdenum nanoparticles (Mo-NPs)-loaded anatase TiO2 were investigated using x-ray diffraction, UV-Vis diffuse reflectance, and Fourier transform infrared and complex impedance spectroscopy. x-ray diffraction showed that Mo-NPs incorporation induced a decrease in particle size from 30 nm to 21 nm of TiO2 and TiO2-Mo, respectively, producing a slight structure expansion. Mo-NPs dispersion resulted in a slight decrease in the optical band gap energy from 3.85 eV to 3.51 eV. Slight shifts towards higher wavelengths were attributed to the change in the acceptor capacity level induced by Mo-NPs. In addition, the ac impedance studies show the effect of Mo-NPs incorporation that appeared to be responsible for conductance of enhancement. The conduction mechanism is based on space charge-limited current via deep levels with different energy positions in the band gap. The temperature dependence of electrical properties showed that both capacitance and conductance of TiO2-Mo samples increased with increasing temperature. At low frequency, the relaxation phenomenon is related to the surface effect. The results will be beneficial to further developing titanium dioxide photo-catalysts.

  9. Simple way to make Anatase TiO2 films on FTO glass for promising solar cells

    OpenAIRE

    Raghavender, A. T.; Samantilleke, A. P.; Sá,Pedro; Almeida, B. G.; Vasilevskiy, Mikhail; Nguyen Hoa Hong

    2011-01-01

    TiO2 is a wide bandgap semiconductor material used as the photo anode in dye sensitized solar cells (DSSC). The fabrication of TiO2 on conductive glass substrates plays an important role in the solar cell efficiency, since the thickness of the TiO2 coating affects the transmission, photoconductive properties and the efficiency of solar cells. The uncorrected transmission in our fabricated films is as high as 80%, and the bandgap obtained is similar to that of bulk anatase TiO2, co...

  10. Anatase TiO2 Nanospindle/Activated Carbon (AC) Composite Photocatalysts with Enhanced Activity in Removal of Organic Contaminant

    OpenAIRE

    Wuyi Zhou; Peng Zhang; Weian Liu

    2012-01-01

    This paper embarks upon the three levels of analysis ranging from nanoscale materials synthesis to combination and functionality. Firstly, we have prepared anatase TiO2 nanospindles with an even length of about 200 nm and a central width of about 25 nm by hydrothermal synthesis method at 100°C for 6 h. Secondly, we have dispersed TiO2 nanospindles on the surface of activated carbon (AC) and fabricated TiO2/AC composite via a dip-coating method. Thirdly, the TiO2/AC composite has been studied ...

  11. Adsorption and reactions of O2 on anatase TiO2.

    Science.gov (United States)

    Li, Ye-Fei; Aschauer, Ulrich; Chen, Jia; Selloni, Annabella

    2014-11-18

    CONSPECTUS: The interaction of molecular oxygen with titanium dioxide (TiO2) surfaces plays a key role in many technologically important processes such as catalytic oxidation reactions, chemical sensing, and photocatalysis. While O2 interacts weakly with fully oxidized TiO2, excess electrons are often present in TiO2 samples. These excess electrons originate from intrinsic reducing defects (oxygen vacancies and titanium interstitials), doping, or photoexcitation and form polaronic Ti(3+) states in the band gap near the bottom of the conduction band. Oxygen adsorption involves the transfer of one or more of these excess electrons to an O2 molecule at the TiO2 surface. This results in an adsorbed superoxo (O2(-)) or peroxo (O2(2-)) species or in molecular dissociation and formation of two oxygen adatoms (2 × O(2-)). Oxygen adsorption is also the first step toward oxygen incorporation, a fundamental reaction that strongly affects the chemical properties and charge-carrier densities; for instance, it can transform the material from an n-type semiconductor to a poor electronic conductor. In this Account, we present an overview of recent theoretical work on O2 adsorption and reactions on the reduced anatase (101) surface. Anatase is the TiO2 polymorph that is generally considered most active in photocatalysis. Experiments on anatase powders have shown that the properties of photoexcited electrons are similar to those of excess electrons from reducing defects, and therefore, oxygen on reduced anatase is also a model system for studying the role of O2 in photocatalysis. Experimentally, the characteristic Ti(3+) defect states disappear after adsorption of molecular oxygen, which indicates that the excess electrons are indeed trapped by O2. Moreover, superoxide surface species associated with two different cation surface sites, possibly a regular cation site and a cation close to an anion vacancy, were identified by electron paramagnetic resonance spectroscopy. On the

  12. Characterization of anatase TiO2 nanopowder by variable-temperature Raman spectroscopy

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    Šćepanović Maja J.

    2009-01-01

    Full Text Available Raman spectroscopy has been used for characterization of commercial nanosized TiO2 powder with declared grain size of 5 nm. The Raman spectra measured in Stokes and anti-Stokes regime confirm the anatase phase of TiO2 powder in temperature range 25-1173K. It is shown that phonon-confinement (due to small grain size and nonstoichiometry (caused by laser irradiation in vacuum have a great influence on blueshift and broadening of the main Eg Raman mode at low temperatures, while the influence of the strong anharmonic effect becomes dominant at higher temperatures. The phonon confinement effect decreases due to the crystallite growth at temperatures above 673K.

  13. Anatase-brookite mixed phase nano TiO2 catalyzed homolytic decomposition of ammonium nitrate.

    Science.gov (United States)

    Vargeese, Anuj A; Muralidharan, Krishnamurthi

    2011-09-15

    Compared to the conventional ammonium perchlorate based solid rocket propellants, burning of ammonium nitrate (AN) based propellants produce environmentally innocuous combustion gases. Application of AN as propellant oxidizer is restricted due to low reactivity and low energetics besides its near room temperature polymorphic phase transition. In the present study, anatase-brookite mixed phase TiO(2) nanoparticles (~ 10 nm) are synthesized and used as catalyst to enhance the reactivity of the environmental friendly propellant oxidizer ammonium nitrate. The activation energy required for the decomposition reactions, computed by differential and non-linear integral isoconversional methods are used to establish the catalytic activity. Presumably, the removal of NH(3) and H(2)O, known inhibitors of ammonium nitrate decomposition reaction, due to the surface reactions on active surface of TiO(2) changes the decomposition pathway and thereby the reactivity.

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

    Science.gov (United States)

    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. Thermal catalytic oxidation of octachloronaphthalene over anatase TiO2 nanomaterial and its hypothesized mechanism

    Science.gov (United States)

    Su, Guijin; Li, Qianqian; Lu, Huijie; Zhang, Lixia; Huang, Linyan; Yan, Li; Zheng, Minghui

    2015-12-01

    As an environmentally-green technology, thermal catalytic oxidation of octachloronaphthalene (CN-75) over anatase TiO2 nanomaterials was investigated at 300 °C. A wide range of oxidation intermediates, which were investigated using various techniques, could be of three types: naphthalene-ring, single-benzene-ring, and completely ring-opened products. Reactive oxygen species on anatase TiO2 surface, such as O2-• and O2-, contributed to oxidative degradation. Based on these findings, a novel oxidation degradation mechanism was proposed. The reaction at (101) surface of anatase TiO2 was used as a model. The naphthalene-ring oxidative products with chloronaphthols and hydroxyl-pentachloronaphthalene-dione, could be formed via attacking the carbon of naphthalene ring at one or more positions by nucleophilic O2-. Lateral cleavage of the naphthalene ring at different C1-C10 and C4-C9, C1-C2 and C4-C9, C1-C2 or and C3-C4 bond positions by electrophilic O2-• could occur. This will lead to the formation of tetrachlorophenol, tetrachloro-benzoic acid, tetrachloro-phthalaldehyde, and tetrachloro-acrolein-benzoic acid, partially with further transformation into tetrachlorobenzene-dihydrodiol and tetrachloro-salicylic acid. Unexpectedly, the symmetric half section of CN-75 could be completely remained with generating the intricate oxidative intermediates characteristically containing tetrachlorobenzene structure. Complete cleavage of naphthalene ring could produce the ring-opened products, such as formic and acetic acids.

  16. Soft-Templated Self-Assembly of Mesoporous Anatase TiO2/Carbon Composite Nanospheres for High-Performance Lithium Ion Batteries.

    Science.gov (United States)

    Wu, Ruofei; Shen, Shuiyun; Xia, Guofeng; Zhu, Fengjuan; Lastoskie, Christian; Zhang, Junliang

    2016-08-10

    Mesoporous anatase TiO2/carbon composite nanospheres (designated as meso-ATCCNs) were successfully synthesized via a facile soft-templated self-assembly followed by thermal treatment. Structural and morphological analyses reveal that the as-synthesized meso-ATCCNs are composed of primary TiO2 nanoparticles (∼5 nm), combined with in situ deposited carbon either on the surface or between the primary TiO2 nanoparticles. When cycled in an extended voltage window from 0.01 to 3.0 V, meso-ATCCNs exhibit excellent rate capabilities (413.7, 289.7, and 206.8 mAh g(-1) at 200, 1000, and 3000 mA g(-1), respectively) as well as stable cyclability (90% capacity retention over 500 cycles at 1000 mA g(-1)). Compared with both mesoporous TiO2 nanospheres and bulk TiO2, the superior electrochemical performance of the meso-ATCCNs electrode could be ascribed to a synergetic effect induced by hierarchical structure that includes uniform TiO2 nanoparticles, the presence of hydrothermal carbon derived from phenolic resols, a high surface area, and open mesoporosity.

  17. Photocatalytic Studies of Anatase and Rutile phase TiO2 Nanocrystals Prepared via Solvothermal method

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    S.Perumal

    2015-08-01

    Full Text Available Nanocrystals of TiO2 photocatalyst have been synthesized by solvothermal method. The photocatalysts were characterized by XRD, UV–Vis spectroscopy and photocatalytic study. The analysis from X-ray diffraction revealed that the annealed product at 1000˚C shows crystal phase of rutile and all others are in anatase phase. FTIR spectra show the vibration of Ti-O bands around 650 cm-1 . UV-Vis spectra indicated the band gap value of annealed samples.

  18. Template-free synthesis of hierarchical TiO2 structures and their application in dye-sensitized solar cells.

    Science.gov (United States)

    Shao, Fang; Sun, Jing; Gao, Lian; Yang, Songwang; Luo, Jianqiang

    2011-06-01

    We demonstrate here the synthesis of a hierarchical TiO(2) architecture without any surfactants or templates. Two kinds of structure existed simultaneously, the ordered nanoarrays at bottom provided direct conduction pathway for photo generated electrons, while the upper micro-flowers consisted of nanobelt as building units increased the light harvesting ability as the scattering part. The formation mechanism of the hierarchical architecture has been proposed by studying the morphology evolution processes upon reaction time. The performance of dye-sensitized solar cells based on the obtained hierarchical anatase TiO(2) has been also studied, giving a J(SC) = 12.44 mA cm(-2), V(OC) = 0.64 V, FF = 69.05%, and η = 5.53%, which is superior than commercial TiO(2) (P25). The UV-vis results prove that the obtained morphology is beneficial to light-scattering and thus increases the light harvesting ability. This hierarchical TiO(2) structure offers great potential for the development of high-efficiency DSSCs. © 2011 American Chemical Society

  19. Adsorption and solar light decomposition of acetone on anatase TiO2 and niobium doped TiO2 thin films.

    Science.gov (United States)

    Mattsson, Andreas; Leideborg, Michael; Larsson, Karin; Westin, Gunnar; Osterlund, Lars

    2006-01-26

    Adsorption and solar light decomposition of acetone was studied on nanostructured anatase TiO2 and Nb-doped TiO2 films made by sol-gel methods (10 and 20 mol % NbO2.5). A detailed characterization of the film materials show that films contain only nanoparticles with the anatase modification with pentavalent Nb oxide dissolved into the anatase structure, which is interpreted as formation of substituted Nb=O clusters in the anatase lattice. The Nb-doped films displayed a slight yellow color and an enhanced the visible light absorption with a red-shift of the optical absorption edge from 394 nm for the pure TiO2 film to 411 nm for 20 mol % NbO2.5. In-situ Fourier transform infrared (FTIR) transmission spectroscopy shows that acetone adsorbs associatively with eta1-coordination to the surface cations on all films. On Nb-doped TiO2 films, the carbonyl bonding to the surface is stabilized, which is evidenced by a lowering of the nu(C=O) frequency by about 20 cm(-1) to 1672 cm(-1). Upon solar light illumination acetone is readily decomposed on TiO2, and stable surface coordinated intermediates are formed. The decomposition rate is an order of magnitude smaller on the Nb-doped films despite an enhanced visible light absorption in these materials. The quantum yield is determined to be 0.053, 0.004 and 0.002 for the pure, 10% Nb:TiO2, and 20%Nb:TiO2, respectively. Using an interplay between FTIR and DFT calculations we show that the key surface intermediates are bidentate bridged formate and carbonate, and H-bonded bicarbonate, respectively, whose concentration on the surface can be correlated with their heats of formation and bond strength to coordinatively unsaturated surface Ti and Nb atoms at the surface. The oxidation rate of these intermediates is substantially slower than the initial acetone decomposition rate, and limits the total oxidation rate at t>7 min on TiO2, while no decrease of the rate is observed on the Nb-doped films. The rate of degradation of key surface

  20. Band structure engineering of anatase TiO2 by metal-assisted P-O coupling.

    Science.gov (United States)

    Wang, Jiajun; Meng, Qiangqiang; Huang, Jing; Li, Qunxiang; Yang, Jinlong

    2014-05-07

    In this work, we demonstrate that the metal-assisted P-O coupling is an effective approach to improve the photoelectrochemical properties of TiO2. The (Sc + P) and (In + P) codoping effects on electronic structures and photocatalytic activities of anatase TiO2 are examined by performing hybrid density functional theory calculations. It is found that the coupling of P dopant with the second-nearest neighboring O atom assisted by acceptor metals (Sc/In) leads to the fully occupied and delocalized intermediate bands within the band gap of anatase TiO2, which is driven by the P-O antibonding states (π*). This metal-assisted P-O coupling can prevent the recombination of photogenerated electron-hole pairs and effectively reduce the band gap of TiO2. Moreover, the band edge alignments in (Sc + P) and (In + P) codoped anatase TiO2 are desirable for water-splitting. The calculated optical absorption curves indicate that (Sc + P) and (In + P) codoping in anatase TiO2 can also effectively enhance the visible light absorption.

  1. Association of anatase (TiO2) and microbes: unusual fossilization effect or a potential biosignature?

    Science.gov (United States)

    Glamoclija, Mihaela; Andrew Steele,; Marc Fries,; Juergen Schieber,; Voytek, Mary A.; Charles S. Cockell,

    2015-01-01

    We combined microbial paleontology and molecular biology methods to study the Eyreville B drill core from the 35.3-Ma-old Chesapeake Bay impact structure,Virginia, USA. The investigated sample is a pyrite vein collected from the 1353.81-1353.89 m depth interval, located within a section of biotite granite. The granite is a pre-impact rock that was disrupted by the impact event. A search for inorganic (mineral) biosignatures revealed the presence of micron-size rod morphologies of anatase (TiO2) embedded in chlorite coatings on pyrite grains. Neither the Acridine Orange microbial probe nor deoxyribonucleic acid (DNA) extraction followed by polymerase chain reaction (PCR) amplifi cation showed the presence of DNA or ribonucleic acid (RNA) at the location of anatase rods, implying the absence of viable cells in the investigated area. A Nile Red microbial probe revealed the presence of lipids in the rods. Because most of the lipids are resistant over geologic time spans, they are good biomarkers, and they are an indicator of biogenicity for these possibly 35-Ma-old microbial fossils. The mineral assemblage suggests that rod morphologies are associated with low-temperature (<100 °C) hydrothermal alteration that involved aqueous fl uids. The temporal constraints on the anatase fossils are still uncertain because pre-impact alteration of the granite and postimpact heating may have provided identical conditions for anatase precipitation and microbial preservation.

  2. Photocatalytic degradation of dyes and organic contaminants in water using nanocrystalline anatase and rutile TiO2

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    Rajesh J. Tayade et al

    2007-01-01

    Full Text Available Nanocrystalline TiO2 was synthesized by controlled hydrolysis of titanium tetraisopropoxide. The anatase phase was converted to rutile phase by thermal treatment at 1023 K for 11 h. The catalysts were characterized by X-ray diffraction (XRD, diffuse reflectance spectroscopy (DRS, Fourier-transform infrared absorption spectrophotometry (FT-IR and N2 adsorption (BET at 77 K. This study compare the photocatalytic activity of the anatase and rutile phases of nanocrystalline TiO2 for the degradation of acetophenone, nitrobenzene, methylene blue and malachite green present in aqueous solutions. The initial rate of degradation was calculated to compare the photocatalytic activity of anatase and rutile nanocrystalline TiO2 for the degradation of different substances under ultraviolet light irradiation. The higher photocatalytic activity was obtained in anatase phase TiO2 for the degradation of all substances as compared with rutile phase. It is concluded that the higher photocatalytic activity in anatase TiO2 is due to parameters like band-gap, number of hydroxyl groups, surface area and porosity of the catalyst.

  3. Sol-gel synthesis of mesoporous anatase-brookite and anatase-brookite-rutile TiO2 nanoparticles and their photocatalytic properties.

    Science.gov (United States)

    Mutuma, Bridget K; Shao, Godlisten N; Kim, Won Duck; Kim, Hee Taik

    2015-03-15

    TiO2 photocatalysts with a mixture of different TiO2 crystal polymorphs have customarily been synthesized hydrothermally at high temperatures using complicated and expensive equipment. In this study TiO2 nanoparticles with a mixture of TiO2 crystals were synthesized using a modified sol-gel method at low temperature. In order to form nanoparticles with different polymorphs a series of samples were obtained at pH 2, 4, 7 and 9. Raw samples were calcined at different temperatures ranging from 200 to 800°C to evaluate the effect of the calcination temperature on the physico-chemical properties of the samples. XRD results revealed that a mixture of anatase and brookite can be obtained in the as-synthesized samples and in those calcined up to 800°C depending on the pH used to obtain the final product. Indeed, a mixture of anatase brookite and rutile; or a sample with only rutile phase can be yielded through further calcination of the as-prepared samples at temperatures ⩾600°C due to phase transformation. The photocatalytic performance of the samples with a mixture of anatase-brookite; anatase-brookite-rutile; and anatase-rutile (Degussa P25 TiO2) was exquisitely investigated in the degradation of methylene blue solutions. The samples obtained at pH 2 and calcined at 200°C possessed the highest activity of all due to its superior properties. This study elucidates a facile method suitable for the synthesis of TiO2 with different mixtures of TiO2 polymorphs with desirable properties for various applications.

  4. Niobium doping induced morphological changes and enhanced photocatalytic performance of anatase TiO2

    Science.gov (United States)

    Wu, Ming-Chung; Lin, Ting-Han; Chih, Jyun-Sian; Hsiao, Kai-Chi; Wu, Po-Yeh

    2017-04-01

    In order to develop high-performance photocatalysts that are easy to produce even in industrial quantities, we developed a facile method of preparing niobium-doped titanium dioxide (Nb:TiO2) by hydrothermal synthesis and followed by thermal annealing treatment. Niobium-ion doping has been considered as an effective way to improve Nb:TiO2 performance for applications in photocatalysis. Niobium-ion doping of anatase TiO2 induced the morphological changes of Nb:TiO2. Morphological analysis shows sub-microscale fibers at doping concentration lower than 1.00 mol % and nanoscale rods at the doping concentration higher than 1.00 mol %. For the catalyzed photodegradation of methyl orange under visible light irradiation, 0.50 mol % Nb:TiO2 shows the highest activity among the synthesized Nb:TiO2 specimens. Also, for photocatalytic hydrogen generation, its photocatalytic activity is even higher than that of commercial TiO2-P25. In this study, we demonstrated the fabrication of a series of superior Nb:TiO2 specimens. It is a reasonable alternative to commercial TiO2 materials for various applications in the decomposition of organic dyes under visible light irradiation.

  5. Removal of nitric oxide by the highly reactive anatase TiO2 (001) surface: a density functional theory study.

    Science.gov (United States)

    Zhao, Wenwen; Tian, Feng Hui; Wang, Xiaobin; Zhao, Linghuan; Wang, Yun; Fu, Aiping; Yuan, Shuping; Chu, Tianshu; Xia, Linhua; Yu, Jimmy C; Duan, Yunbo

    2014-09-15

    In this paper, density functional theory (DFT) calculation was employed to study the adsorption of nitric oxide (NO) on the highly reactive anatase TiO2 (001) surface. For comparison, the adsorption of NO on the (101) surface was also considered. Different from the physical adsorption on the (101) surface, NO molecules are found to chemisorb on the TiO2 (001) surface. The twofold coordinate oxygen atoms (O2c) on the anatase (001) surface are the active sites. Where NO is oxidized into a nitrite species (NO2(-)) trapping efficiently on the surface, with one of the surface Ti5c-O2c bonds adjacent to the adsorption site broken. Our results, therefore, supply a theoretical guidance to remove NO pollutants using highly reactive anatase TiO2 (001) facets.

  6. Cellulose Tailored Anatase TiO2 Nanospindles in Three-Dimensional Graphene Composites for High-Performance Supercapacitors.

    Science.gov (United States)

    Ding, Yangbin; Bai, Wei; Sun, Jinhua; Wu, Yu; Memon, Mushtaque A; Wang, Chao; Liu, Chengbin; Huang, Yong; Geng, Jianxin

    2016-05-18

    The morphologies of transition metal oxides have decisive impact on the performance of their applications. Here, we report a new and facile strategy for in situ preparation of anatase TiO2 nanospindles in three-dimensional reduced graphene oxide (RGO) structure (3D TiO2@RGO) using cellulose as both an intermediate agent eliminating the negative effect of graphene oxide (GO) on the growth of TiO2 crystals and as a structure-directing agent for the shape-controlled synthesis of TiO2 crystals. High-resolution transmission electron microscopy and X-ray diffractometer analysis indicated that the spindle shape of TiO2 crystals was formed through the restriction of the growth of high energy {010} facets due to preferential adsorption of cellulose on these facets. Because of the 3D structure of the composite, the large aspect ratio of the TiO2 nanospindles, and the exposed high-energy {010} facets of the TiO2 crystals, the 3D TiO2@RGO(Ce 1.7) exhibited excellent capacitive performance as an electrode material for supercapacitors, with a high specific capacitance (ca. 397 F g(-1)), a high energy density (55.7 Wh kg(-1)), and a high power density (1327 W kg(-1)) on the basis of the masses of RGO and TiO2. These levels of capacitive performance far exceed those of previously reported TiO2-based composites.

  7. Phosphorus-doped TiO2 catalysts with stable anatase-brookite biphase structure: synthesis and photocatalytic performance.

    Science.gov (United States)

    Feng, Huajun; Zhang, Min-Hong; Yu, Liya E

    2013-07-01

    Phosphorus-doped (P-doped) TiO2 catalysts with a stable anatase-brookite biphase structure were successfully synthesized by integrating ultrasonication with phosphorus doping and Pluronic P123 surfactant. The synthesized catalysts were characterized using X-ray diffraction, transmission electron microscopy, nitrogen adsorption-desorption, Fourier transform infrared, and UV-visible diffuse reflectance spectra. Ultrasonication facilitates the appearance of brookite phase. Phosphorus doping was demonstrated an effective strategy to stabilize the anatase-brookite biphase structure and inhibits undesirable grain growth. Triblock copolymer Pluronic P123 used in the reaction facilitates the formation of catalyst particles with mesoporous structure and large surface area and prevents particles from agglomeration. The low band-gap of brookite phase enables the synthesized P-doped TiO2 catalysts outperform commercial P25 TiO2 and N-doped TiO2 in the degradation of methylene blue under both solar light and visible light irradiation.

  8. The effect of blood protein adsorption on cellular uptake of anatase TiO2 nanoparticles.

    Science.gov (United States)

    Allouni, Zouhir E; Gjerdet, Nils R; Cimpan, Mihaela R; Høl, Paul J

    2015-01-01

    Protein adsorption onto nanoparticles (NPs) in biological fluids has emerged as an important factor when testing biological responses to NPs, as this may influence both uptake and subsequent toxicity. The aim of the present study was to quantify the adsorption of proteins onto TiO2 NPs and to test the influence on cellular uptake. The surface composition of the particles was characterized by thermal analysis and by X-ray photoelectron spectroscopy. The adsorption of three blood proteins, ie, human serum albumin (HSA), γ-globulins (Glbs), and fibrinogen (Fib), onto three types of anatase NPs of different sizes was quantified for each protein. The concentration of the adsorbed protein was measured by ultraviolet-visible spectrophotometry using the Bradford method. The degree of cellular uptake was quantified by inductivity coupled plasma mass spectroscopy, and visualized by an ultra-high resolution imaging system. The proteins were adsorbed onto all of the anatase NPs. The quantity adsorbed increased with time and was higher for the smaller particles. Fib and Glbs showed the highest affinity to TiO2 NPs, while the lowest was seen for HSA. The adsorption of proteins affected the surface charge and the hydrodynamic diameter of the NPs in cell culture medium. The degree of particle uptake was highest in protein-free medium and in the presence HSA, followed by culture medium supplemented with Glbs, and lowest in the presence of Fib. The results indicate that the uptake of anatase NPs by fibroblasts is influenced by the identity of the adsorbed protein.

  9. Electrospun anatase-phase TiO2 nanofibers with different morphological structures and specific surface areas.

    Science.gov (United States)

    He, Guangfei; Cai, Yibing; Zhao, Yong; Wang, Xiaoxu; Lai, Chuilin; Xi, Min; Zhu, Zhengtao; Fong, Hao

    2013-05-15

    Electrospun anatase-phase TiO2 nanofibers with desired morphological structure and relatively high specific surface area are expected to outperform other nanostructures (e.g., powder and film) of TiO2 for various applications (particularly dye-sensitized solar cell and photo-catalysis). In this study, systematic investigations were carried out to prepare and characterize electrospun anatase-phase TiO2 nanofibers with different morphological structures (e.g., solid, hollow/tubular, and porous) and specific surface areas. The TiO2 nanofibers were generally prepared via electrospinning of precursor nanofibers followed by pyrolysis at 500°C. For making hollow/tubular TiO2 nanofibers, the technique of co-axial electrospinning was utilized; while for making porous TiO2 nanofibers, the etching treatment in NaOH aqueous solution was adopted. The results indicated that the hollow/tubular TiO2 nanofibers (with diameters of ~300-500 nm and wall-thickness in the range from tens of nanometers to ~200 nm) had the BET specific surface area of ~27.3 m(2)/g, which was approximately twice as that of the solid TiO2 nanofibers (~15.2 m(2)/g) with diameters of ~200-300 nm and lengths of at least tens of microns. Porous TiO2 nanofibers made from the precursor of Al2O3/TiO2 composite nanofibers had the BET specific surface area of ~106.5 m(2)/g, whereas porous TiO2 nanofibers made from the precursor of ZnO/TiO2 composite nanofibers had the highest BET specific surface area of ~148.6 m(2)/g.

  10. Niobium-Doped (001)-Dominated Anatase TiO2 Nanosheets as Photoelectrode for Efficient Dye-Sensitized Solar Cells.

    Science.gov (United States)

    Jiang, Lei; Sun, Lei; Yang, Dong; Zhang, Jian; Li, Ya-Juan; Zou, Kun; Deng, Wei-Qiao

    2017-03-13

    TiO2 nanocrystals with different reactive facets have attracted extensive interest since they were first synthesized. The anatase TiO2 nanocrystals with (001) or (100) dominate facets were considered to be excellent electrode materials to enhance the cell performance of dye-sensitized solar cells. However, which reactive facet presents the best surface for benefiting photovoltaic effect is still unknown. We report a systematic study of various anatase TiO2 surfaces interacting with N719 dye by means of density functional theory calculations in combination with microscopic techniques. The (001) surface interacting with N719 would have the lowest work function, leading to the best photovoltaic performances. To further increase the efficiency, Nb dopant was incorporated into the anatase TiO2 nanocrystals. Based on the theoretical prediction, we proposed and demonstrated novel Nb-doped (001)-dominated anatase TiO2 nanosheets as photoelectrode in a dye-sensitized solar cell to further enhance the open-circuit voltage. And a power conversion efficiency of 10% was achieved, which was 22% higher than that of the undoped device (P25 as an electrode).

  11. First-Principles Band Calculations on Electronic Structures of Ag-Doped Rutile and Anatase TiO2

    Institute of Scientific and Technical Information of China (English)

    HOU Xing-Gang; LIU An-Dong; HUANG Mei-Dong; LIAO Bin; WU Xiao-Ling

    2009-01-01

    The electronic structures of Ag-doped rutile and anatase TiO2 are studied by first-principles band calculations based on density funetionai theory with the full-potentiai linearized-augraented-plane-wave method.New occupied bands ore found between the band gaps of both Ag-doped rutile and anatase TiO2.The formation of these new bands Capri be explained mainly by their orbitals of Ag 4d states mixed with Ti 3d states and are supposed to contribute to their visible light absorption.

  12. Structural and optical characterization of electrodeposited CdSe in mesoporous anatase TiO2 for regenerative quantum-dot-sensitized solar cells.

    Science.gov (United States)

    Sauvage, Frédéric; Davoisne, Carine; Philippe, Laetitia; Elias, Jamil

    2012-10-05

    We investigated CdSe-sensitized TiO(2) solar cells by means of electrodeposition under galvanostatic control. The electrodeposition of CdSe within the mesoporous film of TiO(2) gives rise to a uniform, thickness controlled, conformal layer of nanostructured CdSe particles intimately wrapping the anatase TiO(2) nanoparticles. This technique has the advantage of providing not only a fast method for sensitization ( panels. XRD together with SAED analysis highlight that the deposit of CdSe is exclusively constituted of the hexagonal polymorph. In addition, hierarchical growth has also been shown, starting from the formation of a TiO(2)-CdSe core-shell structure followed by the growth of an assembly of CdSe nanoparticles resembling cauliflowers. This assembly exhibits at its core a mosaic texture with crystallites of about 3 nm in size, in contrast to a shell composed of well-crystallized single crystals between 5 and 10 nm in size. Preliminary results on the photovoltaic performance of such a nanostructured composite of TiO(2) and CdSe show 0.8% power conversion efficiency under A.M.1.5 G conditions-100 mW cm(-2) in association with a new regenerative redox couple based on cobalt(+III/+II) polypyridil complex (V(oc ) = 485 mV, J(sc ) = 4.26 mA cm (-2), ff=0.37).

  13. Quantum Monte Carlo study of the energetics of the rutile, anatase, brookite, and columbite TiO$_2$ polymorphs

    OpenAIRE

    Trail, John; Monserrat, Bartomeu; Ríos, Pablo López; Maezono, Ryo; Needs, Richard J.

    2016-01-01

    The relative energies of the low-pressure rutile, anatase, and brookite polymorphs and the high-pressure columbite polymorph of TiO$_2$ have been calculated as a function of temperature using the diffusion quantum Monte Carlo (DMC) method and density functional theory (DFT). The vibrational energies are found to be important on the scale of interest and significant quartic anharmonicity is found in the rutile phase. Static-lattice DFT calculations predict that anatase is lower in energy than ...

  14. Alignment of TiO2 (Anatase Crystal of Dye-Sensitized Solar Cells by External Magnetic Field

    Directory of Open Access Journals (Sweden)

    Na-Yeong Hong

    2013-01-01

    Full Text Available In this study, magnetic field (B was applied on TiO2 (anatase of dye-sensitized solar cell (DSC for alignment of crystal. Magnetic field was applied on TiO2 when deposited TiO2 on the fluorine tin oxide (FTO was dried at 373 K for crystalline orientation. And applying time of B was varied 0~25 min. Characteristics of the magnetic field applied TiO2 films were analyzed by X-ray diffraction (XRD, high resolution transmission electron microscopy (HRTEM, scanning electron microscopy (SEM, and electrochemical impedance spectroscopy (EIS. Current-voltage characteristics were also analyzed using solar simulator, and it was confirmed that the energy conversion efficiency of 41% was increased. Finally, it was identified that the magnetic field affected orientation of TiO2, resulting in the enhancement of the performance of the DSC.

  15. Anatase (101)-like Structural Model Revealed for Metastable Rutile TiO2(011) Surface.

    Science.gov (United States)

    Xu, Meiling; Shao, Sen; Gao, Bo; Lv, Jian; Li, Quan; Wang, Yanchao; Wang, Hui; Zhang, Lijun; Ma, Yanming

    2017-03-08

    Titanium dioxide has been widely used as an efficient transition metal oxide photocatalyst. However, its photocatalytic activity is limited to the ultraviolet spectrum range due to the large bandgap beyond 3 eV. Efforts to reduce the bandgap to achieve a broader spectrum range of light absorption have been successfully attempted via the experimental synthesis of dopant-free metastable surface structures of rutile-type TiO2 (011) 2 × 1. This new surface phase possesses a reduced bandgap of ∼2.1 eV, showing great potential for an excellent photocatalyst covering a wide range of visible light. There is a need to establish the atomistic structure of this metastable surface to understand the physical cause for the bandgap reduction and to improve the future design of photocatalysts. Here, we report computational investigations in an effort to unravel this surface structure via swarm structure-searching simulations. The established structure adopts the anatase (101)-like structure model, where the topmost 2-fold O atoms form a quasi-hexagonal surface pattern and bond with the unsaturated 5-fold and 4-fold Ti atoms in the next layer. The predicted anatase (101)-like surface model can naturally explain the experimental observation of the STM images, the electronic bandgap, and the oxidation state of Ti(4+). Dangling bonds on the anatase (101)-like surface are abundant making it a superior photocatalyst. First-principles molecular dynamics simulations have supported the high photocatalytic activity by showing that water and formic acid molecules dissociate spontaneously on the anatase (101)-like surface.

  16. Investigation on the sonocatalytic degradation of acid red B in the presence of nanometer TiO2 catalysts and comparison of catalytic activities of anatase and rutile TiO2 powders.

    Science.gov (United States)

    Wang, Jun; Jiang, Yuefeng; Zhang, Zhaohong; Zhang, Xiangdong; Ma, Teng; Zhang, Guan; Zhao, Gang; Zhang, Peng; Li, Ying

    2007-07-01

    Here, the nanometer anatase and rutile titanium dioxide (TiO(2)) powders were introduced to act as the sonocatalysts during the ultrasonic degradation of azo dye-acid red B which was chosen as model compound. The ultrasound of low power was used as an irradiation source to induce TiO(2) particles performing catalytic activity. It was found that the processes of sonocatalytic degradation were different between nanometer anatase TiO(2) and nanometer rutile TiO(2). For nanometer anatase TiO(2) catalyst, the acid red B was mainly oxidated by the holes on the surface of nanometer anatase TiO(2) particles, so that the decolorization and degradation happened at the same time. For the nanometer rutile TiO(2) catalyst, the acid red B was mainly oxidated by the *OH radicals from the ultrasonic cavitation, so that the decolorization of azo bond takes place primarily, and then the degradation of naphthyl ring does. The intermediates of acid red B in the presence of nanometer anatase and rutile TiO(2) powders have been monitored by UV-vis spectra and high performance liquid chromatography (HPLC), respectively. All experiments indicated that the degradation effect of acid red B in the presence of nanometer anatase TiO(2) powder was obviously better than that in the presence of nanometer rutile TiO(2) powder. Hence, the method of sonocatalytic degradation for organic pollutants in the presence of nanometer anatase TiO(2) powder is expected to be promising as an advisable choice for the treatment of organic wastewaters in future.

  17. Microstructure evolution characteristics induced by oxygen vacancy generation in anatase TiO2 based resistive switching devices

    Science.gov (United States)

    Liu, Chen; Gao, Bin; Huang, Peng; Kang, Jinfeng

    2017-03-01

    In this work, first principle calculations are employed to study the microstructure characteristics of the anatase TiO2 resistive switching material associated with the generation of oxygen vacancy (V o) based nanofilaments during the switching process. The calculations indicate that both the magnéli phase Ti4O7 and V o-defect phase of anatase TiO2 may be formed with the generation of oxygen vacancies during the forming and SET processes. Based on the calculations, a new physical insight is proposed to clarify the microstructure evolution characteristics of the anatase TiO2 resistive switching material and the correlation with resistive switching behaviors. During the forming or SET process, the anatase TiO2 is first excited to a transition state with the generation of oxygen vacancies, then fully relaxes to a stable V o-defect state. This V o-defect state may either recover to the original state with the recombination of the oxygen vacancies, which causes the reversible resistive switching behavior, or further transform to a much more stable state—the magnéli phase Ti4O7, through a phase transition process with the generation of many more oxygen vacancies. The phase transition from V o- defective anatase phase to magnéli phase Ti4O7 causes the failure of the resistive switching due to the significantly reduced possibility of the reversible phase transition from the magnéli phase to the anatase phase, compared with the possibility of the recombination from the V o-defective anatase.

  18. Electronic hole localization in rutile and anatase TiO2 - Self-interaction correction in Delta-SCF DFT

    DEFF Research Database (Denmark)

    Zawadzki, Pawel; Jacobsen, Karsten Wedel; Rossmeisl, Jan

    2011-01-01

    processes within DFT. The correction removes the non-linearity of energy for fractional excitations. We show that the self-trapped and the delocalized hole states have comparable stability in rutile TiO2 whereas in anatase the former is favoured. The theoretical prediction of the adiabatic Potential Energy...

  19. Effect of Nano-anatase TiO2 on Spectral Characterization of Photosystem Ⅱ Particles from Spinach

    Institute of Scientific and Technical Information of China (English)

    HONG Fa-shui; YANG Ping; GAO Feng-qing; LIU Chao; ZHENG Lei; YANG Fan; ZHOU Juan

    2005-01-01

    The photosystem I (PS Ⅱ) particles were purified by means of nano-anatase TiO2 treatment of spinach and studied by spectroscopy. The results show that the electron transport and the oxygen-evolving rate of PS I are accelerated after it has been treated with nano-anatase TiO2; the UV-Vis absorption spectrum of PS I particles is increased; the red shift of fluorescence emission peak of PS I is 2 nm; the peak intensity is decreased; the PS Ⅱ signal I s of low temperature electron paramagnetic resonanace(EPR) spectrum is intensified under light, and the PS I circular dichroism(CD) spectrum is similar to that of control. It is suggested that nano-anatase TiO2 might bind to the PS I reaction center complex and intensify the function of the PS I electron donor, however, nano-anatase TiO2 treatment does not change the configuration of the PS Ⅱ reaction center complex.

  20. Effects of Li+ co-doping on properties of Eu3+ activated TiO2 anatase nanoparticles

    Science.gov (United States)

    Milićević, Bojana; Đorđević, Vesna; Vuković, Katarina; Dražić, Goran; Dramićanin, Miroslav D.

    2017-10-01

    Sol-gel technique for the synthesis of anatase TiO2 at 420 °C produces nanocrystals of 10-20 nm in size with Ti4+ in crystal volume and Ti3+ at terminal planes of the crystal. The study of Li+ co-doping effects on the structure, morphology, absorption, and luminescence of Eu3+ activated TiO2 anatase nanocrystals is presented. Pure anatase structure is achieved up to 9 at.% Li, with significant improvement in crystallinity of europium doped anatase TiO2. The Li+ co-doping reduces the unit cell volume of the crystal, induces the blue shift of the absorption edge, lengthens the lifetime of Eu3+5D0 excited state, and improves the Eu3+ emission intensity up to 37.5%. Judd-Ofelt analysis of Eu3+ emission showed enhancement of quantum efficiency from 66.4% to 98.7% when TiO2:Eu3+ was co-doped with 9 at.% of Li.

  1. Combined ATR-FTIR and DFT Study of Cyclohexanone Adsorption on Hydrated TiO2 Anatase Surfaces

    NARCIS (Netherlands)

    Almeida, Ana Rita; Calatayud, Monica; Tielens, Frederik; Moulijn, Jacob A.; Mul, Guido

    2011-01-01

    The adsorption of cyclohexanone on different planes ((100), (101), and (001)) of anatase TiO2, with variable level of hydration, was evaluated by density functional theory (DFT) calculations. Surface hydration was found to affect the cyclohexanone adsorption enthalpy and the calculated infrared abso

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

    Science.gov (United States)

    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...

  3. Electronic hole localization in rutile and anatase TiO2 - Self-interaction correction in Delta-SCF DFT

    DEFF Research Database (Denmark)

    Zawadzki, Pawel; Jacobsen, Karsten Wedel; Rossmeisl, Jan

    2011-01-01

    processes within DFT. The correction removes the non-linearity of energy for fractional excitations. We show that the self-trapped and the delocalized hole states have comparable stability in rutile TiO2 whereas in anatase the former is favoured. The theoretical prediction of the adiabatic Potential Energy...

  4. Nanostructured anatase TiO2 densified at high pressure as advanced visible light photocatalysts.

    Science.gov (United States)

    Carini, Giovanni; Parrino, Francesco; Palmisano, Giovanni; Scandura, Gabriele; Citro, Ilaria; Calogero, Giuseppe; Bartolotta, Antonino; Di Marco, Gaetano

    2015-09-26

    This study reports on characterization and photoactivity of nanostructured TiO2 samples, which have been permanently densified under high pressures, up to 2.1 GPa. Commercial Mirkat 211 anatase has been used as a benchmark sample, in order to investigate the effect of unidirectional high pressure on structural, optical and photocatalytic properties of TiO2. Vibrational Raman spectroscopy shows that the treatment does not cause transitions among the different crystalline phases of titanium dioxide. UV-vis diffuse reflectance spectra reveal that increasing pressure gives rise to a shift of the absorption onset towards higher wavelength enhancing the photoactivity under visible radiation. Samples are also photo-electrochemically characterized and tested in the gas phase with partial oxidation of ethanol to acetaldehyde under visible irradiation. Compaction up to 0.8 GPa depresses both the alcohol conversion and the aldehyde yield, while samples treated under higher pressures show enhanced characteristics of conversion compared to the pristine material. Moreover, promising results in the reduction of CO2 are also obtained under UV-visible radiation.

  5. DFT-based Theoretical Calculation of Nb- and W-doped Anatase TiO2

    Science.gov (United States)

    Suenaga, Takahiro; Kamisaka, Hideyuki; Nakamura, Hisao; Yamashita, Koichi

    2010-03-01

    The structure and electronic states in the Nb-doped TiO2 (TNO) and W-doped TiO2 (TWO) in anatase phase were investigated from the first-principle using DFT-based band structure method. In addition to the cases where the dopant substituting a Ti atom, cells containing a dopant (MTi; M = Nb, W) and an oxygen vacancy (VO) were calculated in order to clarify the role of the oxygen vacancy in the system. Furthermore, cells containing two dopants and an oxygen vacancy (2MTi--VO), and cells with a dopant and two oxygen vacancies (MTi--2VO) were calculated. Energetically stable structures were found among the sampled 2WTi--VO and WTi--2VO cells, while the corresponding structures in TNO did not show any significant energy stabilization. Impurity states were found in the stable 2WTi--VO and WTi--2VO structures, and an approach of the two WTi atoms was observed in the former. The present results rationalize the lower electronic conductivity of TWO than that of TNO, and suggest possible formation of complex structures consisting of the WTi dopants and the oxygen vacancies.

  6. Structural and optical properties of anatase TiO2 heteroepitaxial films prepared by MOCVD

    Science.gov (United States)

    Zhao, Wei; Feng, Xianjin; Xiao, Hongdi; Luan, Caina; Ma, Jin

    2016-11-01

    High-quality single-crystal anatase TiO2(a-TiO2) thin films have been obtained on SrTiO3 (STO) substrates using the metalorganic chemical vapor deposition (MOCVD) method. The optimal preparation process was explored. The lattice structure and epitaxial relationship were investigated by X-ray diffraction (XRD, both θ-2θ and Φ scans) and transmission electron microscopy (TEM). The results indicated that the film prepared at 550 °C with the Ti precursor molar flow rate of 4×10-7 mol/min had the best single crystalline quality, for which a clear epitaxial relationship of a-TiO2 (001)||STO (100) with a-TiO2 [100]||STO [001bar] could be inferred. The elemental composition and proportion were studied by the X-ray photoelectron spectroscopy (XPS) method, which proved the deposited film approximated stoichiometric TiO2. The samples showed high transparency of 70-80% in the visible range.

  7. Surface Complexation at the TiO(2) (anatase)/Aqueous Solution Interface: Chemisorption of Catechol.

    Science.gov (United States)

    Rodríguez; Blesa; Regazzoni

    1996-01-15

    Catechol adsorbs at the TiO(2) (anatase)/aqueous solution interface forming inner-sphere surface complexes. The UV-visible differential reflectance spectrum of surface titanium-catecholate complexes presents a band centered at 420 nm which corresponds to the ligand to metal charge transfer transition within the surface complexes. At pH values below pK(a1), the surface excess of catechol is almost insensitive toward pH and presents a Langmuirian dependence with the concentration of uncomplexed catechol. The ratio Gamma(max):N(S) (N(S) being the measured density of available OH surface groups) indicates a prevailing 1 to 2 ligand exchange adsorption stoichiometry. In the range pH >/= pK(a1), the catechol surface excess decreases markedly with increasing pH. Formation of 1 to 1 surface complexes produces an excess of negative surface charge that is revealed by the shift of the iep to lower pH values. The reported data, which are supplemented with information on the charging behavior of TiO(2) suspended in indifferent electrolyte solutions, are interpreted in terms of the multi-site surface complexation model. In this model, two types of surface OH groups are considered: identical withTiOH(1/3-) and identical withOH(1/3+). Although both surface groups undergo protonation-deprotonation reactions, only identical withTiOH(1/3-) are prone to chemisorption.

  8. Density functional theory studies on the structural and physical properties of Cu-doped anatase TiO2(101) surface

    Science.gov (United States)

    Zhang, Wei; Yin, Jiu-Ren; Tang, Xian-Qiong; Zhang, Ping; Ding, Yan-Huai

    2017-01-01

    Structure and physical properties of anatase TiO2 (101) surface doped with copper have been studied by using density functional theory. Results show that Cu@Ti and Cu@O systems behave as p and n type semiconductors, respectively. Anatase TiO2 (101) surface exhibits a blue shift in optical absorption spectra compared with pure TiO2 bulk materials. Enhanced photocatalytic activity at wavelength around 400 nm could be contributed by the change in electronic structure.

  9. Photocatalytic Oxidation of Propylene on Pd-Loaded Anatase TiO2 Nanotubes Under Visible Light Irradiation.

    Science.gov (United States)

    Li, Chen; Zong, Lanlan; Li, Qiuye; Zhang, Jiwei; Yang, Jianjun; Jin, Zhensheng

    2016-12-01

    TiO2 nanotubes attract much attention because of their high photoelectron-chemical and photocatalytic efficiency. But their large band gap leads to a low absorption of the solar light and limits the practical application. How to obtain TiO2 nanotubes without any dopant and possessing visible light response is a big challenge nowadays. Orthorhombic titanic acid nanotubes (TAN) are a special precursor of TiO2, which possess large Brunauer-Emmett-Teller (BET) surface areas and strong ion exchange and adsorption capacity. TAN can transform to a novel TiO2 with a large amount of single-electron-trapped oxygen vacancies (SETOV) during calcination, while their nanotubular structure would be destroyed, and a BET surface area would decrease remarkably. And interestingly, SETOV can lead to a visible light response for this kind of TiO2. Herein, glucose was penetrated into TAN by the vacuum inhalation method, and TAN would dehydrate to anatase TiO2, and glucose would undergo thermolysis completely in the calcination process. As a result, the pure TiO2 nanotubes with visible light response and large BET surface areas were obtained. For further improving the photocatalytic activity, Pd nanoparticles were loaded as the foreign electron traps on TiO2 nanotubes and the photocatalytic oxidation efficiency of propylene was as high as 71 % under visible light irradiation, and the photostability of the catalyst kept over 90 % after 4 cyclic tests.

  10. Anatase TiO(2) nanosheets with exposed (001) facets: improved photoelectric conversion efficiency in dye-sensitized solar cells.

    Science.gov (United States)

    Yu, Jiaguo; Fan, Jiajie; Lv, Kangle

    2010-10-01

    Dye-sensitized solar cells (DSSCs) are fabricated based on anatase TiO(2) nanosheets (TiO(2)-NSs) with exposed {001} facets, which were obtained by a simple one-pot hydrothermal route using HF as a morphology controlling agent and Ti(OC(4)H(9))(4) as precursor. The prepared samples were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis absorption spectroscopy and N(2) adsorption-desorption isotherms. The photoelectric conversion performances of TiO(2)-NSs solar cells are also compared with TiO(2) nanoparticles (TiO(2)-NPs) and commercial-grade Degussa P25 TiO(2) nanoparticle (P25) solar cells at the same film thickness, and their photoelectric conversion efficiencies (η) are 4.56, 4.24 and 3.64%, respectively. The enhanced performance of the TiO(2)-NS solar cell is due to their good crystallization, high pore volume, large particle size and enhanced light scattering. The prepared TiO(2) nanosheet film electrode should also find wide-ranging potential applications in various fields including photocatalysis, catalysis, electrochemistry, separation, purification and so on.

  11. Anatase TiO2 nanosheets with exposed (001) facets: improved photoelectric conversion efficiency in dye-sensitized solar cells

    Science.gov (United States)

    Yu, Jiaguo; Fan, Jiajie; Lv, Kangle

    2010-10-01

    Dye-sensitized solar cells (DSSCs) are fabricated based on anatase TiO2 nanosheets (TiO2-NSs) with exposed {001} facets, which were obtained by a simple one-pot hydrothermal route using HF as a morphology controlling agent and Ti(OC4H9)4 as precursor. The prepared samples were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis absorption spectroscopy and N2 adsorption-desorption isotherms. The photoelectric conversion performances of TiO2-NSs solar cells are also compared with TiO2 nanoparticles (TiO2-NPs) and commercial-grade Degussa P25 TiO2 nanoparticle (P25) solar cells at the same film thickness, and their photoelectric conversion efficiencies (η) are 4.56, 4.24 and 3.64%, respectively. The enhanced performance of the TiO2-NS solar cell is due to their good crystallization, high pore volume, large particle size and enhanced light scattering. The prepared TiO2 nanosheet film electrode should also find wide-ranging potential applications in various fields including photocatalysis, catalysis, electrochemistry, separation, purification and so on.

  12. Dissimilar anisotropy of electron versus hole bulk transport in anatase TiO2: Implications for photocatalysis

    Science.gov (United States)

    Kim, Donghun; Yeo, Byung Chul; Shin, Dongbin; Choi, Heechae; Kim, Seungchul; Park, Noejung; Han, Sang Soo

    2017-01-01

    Recent studies on crystal facet manipulation of anatase TiO2 in photocatalysis have revealed that reduction and oxidation reactions preferably occur on (100)/(101) and (001) facets, respectively; however, a fundamental understanding of their origin is lacking. Here, as a result of first-principles calculations, we suggest that a dissimilar trend in the anisotropy of electron vs hole bulk transport in anatase TiO2 can be a dominant underlying mechanism for the difference in photochemical activity. Photoexcited electrons and holes are driven to different facets, i.e., electrons on (100)/(101) and holes on (001), leading to the observed preference for either reduction or oxidation. This trend of electrons vs holes found in pure TiO2 applies even for cases where a variety of dopants or defects is introduced.

  13. Anatase TiO2 nanotube powder film with high crystallinity for enhanced photocatalytic performance

    Science.gov (United States)

    Lin, Jia; Liu, Xiaolin; Zhu, Shu; Liu, Yongsheng; Chen, Xianfeng

    2015-03-01

    We report on the synthesis of TiO2 nanotube (NT) powders using anodic oxidation and ultrasonication. Compared to free-standing NT array films, the powder-type NTs can be easily fabricated in a cost-effective way. Particularly, without the substrate effect arising from underlying Ti metals, highly crystallized NT powders with intact tube structures and pure anatase phase can be obtained using high-temperature heat treatment. The application of NTs with different crystallinity for the photocatalytic decomposition of methylene blue (MB) was then demonstrated. The results showed that with increasing annealing temperature, the photocatalytic decomposition rate was gradually enhanced, and the NT powder electrode annealed at 650°C showed the highest photoactivity. Compared to typical NTs annealed at 450°C, the rate constant increased by 2.7-fold, although the surface area was 21% lower. These findings indicate that the better photocatalytic activity was due to the significantly improved crystallinity of anatase anodic NTs in powder form, resulting in a low density of crystalline defects. This simple and efficient approach is applicable for scaled-up water purification and other light utilization applications.

  14. Distinctive toxicity of TiO2 rutile/anatase mixed phase nanoparticles on Caco-2 cells.

    Science.gov (United States)

    Gerloff, Kirsten; Fenoglio, Ivana; Carella, Emanuele; Kolling, Julia; Albrecht, Catrin; Boots, Agnes W; Förster, Irmgard; Schins, Roel P F

    2012-03-19

    Titanium dioxide has a long-standing use as a food additive. Micrometric powders are, e.g., applied as whiteners in confectionary or dairy products. Possible hazards of ingested nanometric TiO(2) particles for humans and the potential influence of varying specific surface area (SSA) are currently under discussion. Five TiO(2)-samples were analyzed for purity, crystallinity, primary particle size, SSA, ζ potential, and aggregation/agglomeration. Their potential to induce cytotoxicity, oxidative stress, and DNA damage was evaluated in human intestinal Caco-2 cells. Only anatase-rutile containing samples, in contrast to the pure anatase samples, induced significant LDH leakage or mild DNA damage (Fpg-comet assay). Evaluation of the metabolic competence of the cells (WST-1 assay) revealed a highly significant correlation between the SSA of the anatase samples and cytotoxicity. The anatase/rutile samples showed higher toxicity per unit surface area than the pure anatase powders. However, none of the samples affected cellular markers of oxidative stress. Our findings suggest that both SSA and crystallinity are critical determinants of TiO(2)-toxicity toward intestinal cells.

  15. Comparison between P25 and anatase-based TiO2 quasi-solid state dye sensitized solar cells

    Institute of Scientific and Technical Information of China (English)

    LUO Fen; WANG LiDuo; QIU Yong

    2008-01-01

    Pure anatase TiO2 films have been made via hydration of titanium isopropoxide using a sol-gel tech-nique, while mixed TiO2 films which contained both anatase and rutile TiO2 were made from commercial P25 powder. Quasi-solid state dye-sensitized solar cells were fabricated with these two kinds of mesoporous films and a comparison study was carried out. The result showed that the open-circuit photovoltages (Voc) for both kinds of cells were essentially the same, whereas the short-circuit photo-currents (Isc) of the anatase-based cells were about 33% higher than that of the P25-based cells. The highest photocurrent intensity of the anatase-based cell was 6.12 mA/cm2 and that of the P25-based cell was 4.60 mA/cm2. Under an illumination with the light intensity of 30 mW/cm2, the corresponding en-ergy conversion efficiencywas measured to be 7.07% and 6.89% for anatase-based cells and P25-based cells, respectively.

  16. Uniform Gold Nanoparticles Decorated {001}-Faceted Anatase TiO2 Nanosheets for Enhanced Solar Light Photocatalytic Reactions.

    Science.gov (United States)

    Shi, Huimin; Zhang, Shi; Zhu, Xupeng; Liu, Yu; Wang, Tao; Jiang, Tian; Zhang, Guanhua; Duan, Huigao

    2017-10-09

    The {001}-faceted anatase TiO2 micro/nanocrystals have been widely investigated for enhancing the photocatalysis and photoelectrochemical performance of TiO2 nanostructures but their practical applications still require improved energy conversion efficiency under solar light and enhanced cycling stability. In this work, we demonstrate the controlled growth of ultrathin {001}-faceted anatase TiO2 nanosheets on flexible carbon cloth for enhancing the cycling stability, and the solar light photocatalytic performance of the synthesized TiO2 nanosheets can be significantly improved by decorating with vapor-phase deposited uniformly-distributed plasmonic gold nanoparticles. The fabricated Au-TiO2 hybrid system shows an eight-fold solar light photocatalysis enhancement factor in photo-degrading Rhodamine B, a high photocurrent density of 300 μA cm-2 under the illumination of AM 1.5G, and 100% recyclability under consecutive long-term cycling measurement. Combined with electromagnetic simulations and systematic control experiments, it is believed that the tandem type separation and transition of plasmon-induced hot electrons from Au nanoparticles to {001} facet of anatase TiO2, and then to neighboring {101} facet is responsible to the enhanced solar light photochemical performance of the hybrid system. The Au-TiO2 nanosheet system well addresses the problems of limited solar-light response of anatase TiO2 and fast recombination of photo-generated electron-hole pairs, representing a promising high-performance recyclable solar light responded system for practical photocatalytic reactions.

  17. Two phase morphology limits lithium diffusion in TiO(2)(anatase): a (7)Li MAS NMR study.

    Science.gov (United States)

    Wagemaker, M; van de Krol, R; Kentgens, A P; van Well, A A; Mulder, F M

    2001-11-21

    7Li magic angle spinning solid-state nuclear magnetic resonance is applied to investigate the lithium local environment and lithium ion mobility in tetragonal anatase TiO(2) and orthorhombic lithium titanate Li(0.6)TiO(2). Upon lithium insertion, an increasing fraction of the material changes its crystallographic structure from anatase TiO(2) to lithium titanate Li(0.6)TiO(2). Phase separation occurs, and as a result, the Li-rich lithium titanate phase is coexisting with the Li-poor TiO(2) phase containing only small Li amounts approximately equal to 0.01. In both the anatase and the lithium titanate lattice, Li is found to be hopping over the available sites with activation energies of 0.2 and 0.09 eV, respectively. This leads to rapid microscopic diffusion rates at room temperature (D(micr) = 4.7 x 10(-12) cm(2)s(-1) in anatase and D(micr) = 1.3 x 10(-11) cm(2)s(-1) in lithium titanate). However, macroscopic intercalation data show activation energies of approximately 0.5 eV and smaller diffusion coefficients. We suggest that the diffusion through the phase boundary is determining the activation energy of the overall diffusion and the overall diffusion rate itself. The chemical shift of lithium in anatase is independent of temperature up to approximately 250 K but decreases at higher temperatures, reflecting a change in the 3d conduction electron densities. The Li mobility becomes prominent from this same temperature showing that such electronic effects possibly facilitate the mobility.

  18. Hierarchical TiO2 microspheres: synergetic effect of {001} and {101} facets for enhanced photocatalytic activity.

    Science.gov (United States)

    Zheng, Zhaoke; Huang, Baibiao; Lu, Jibao; Qin, Xiaoyan; Zhang, Xiaoyang; Dai, Ying

    2011-12-23

    Well-faceted nanocrystals of anatase TiO(2) with specific reactive facets have attracted extraordinary research interest due to their many intrinsic shape-dependent properties. In this work, hierarchical TiO(2) microspheres consisting of anatase nanosheets or decahedrons were synthesized by means of a facile hydrothermal technique; meanwhile, the percentage of {001} facets can be tuned from 82 to 45%. Importantly, by investigating the photo-oxidation reactions for ˙OH radical generation and photoreduction reactions for hydrogen evolution, the TiO(2) microspheres consisting of nano-decahedrons with 45% {001} facets show superior photoreactivity (more than 4.8-times) compared to the nanosheets with 82% {001} facets. By analyzing the results of scanning electron microscopy (SEM), photoluminescence (PL) and first-principles density functional theory (DFT) calculations, a model of charge separation between the well-formed {001} and {101} facets is proposed, and the enhanced photocatalytic efficiency is largely attributed to the efficient separation of photogenerated charges among the crystal facets co-exposed.

  19. Optimization of photoelectrochemical water splitting performance on hierarchical TiO 2 nanotube arrays

    KAUST Repository

    Zhang, Z.

    2012-02-10

    In this paper, we show that by varying the voltages during two-step anodization the morphology of the hierarchical top-layer/bottom-tube TiO 2 (TiO 2 NTs) can be finely tuned between nanoring/nanotube, nanopore/nanotube, and nanohole-nanocave/nanotube morphologies. This allows us to optimize the photoelectrochemical (PEC) water splitting performance on the hierarchical TiO 2 NTs. The optimized photocurrent density and photoconversion efficiency in this study, occurring on the nanopore/nanotube TiO 2 NTs, were 1.59 mA cm -2 at 1.23 V vs. RHE and 0.84% respectively, which are the highest values ever reported on pristine TiO 2 materials under illumination of AM 1.5G. Our findings contribute to further improvement of the energy conversion efficiency of TiO 2-based devices.

  20. Effect of anatase TiO2 nanoparticles on the growth of RSC-364 rat synovial cell.

    Science.gov (United States)

    Wang, Jiangxue; Ma, Jiawei; Dong, Linmeng; Hou, Ying; Jia, Xiaoling; Niu, Xufeng; Fan, Yubo

    2013-06-01

    Nanoscale materials (such as TiO2, hydroxyapatite nanoparticles) have gained much concern in the coating of implants for cell adhesion and growth to improve the osteoconductivity. However, due to attrition and corrosion, the wear particles would be generated from the joint in living organism, and influence the physiological function of synovial membranes in joint cavity. In this study, the potential cytotoxicity of anatase TiO2 nanoparticles (TiO2 NPs) on rat synovial cell line 364 (RSC-364) was investigated. After treatment with different concentrations of TiO2 NPs (0, 3, 30, 300 microg/ml), the viability of RSC-364 cells were decreased in a dose-dependent manner. TiO2 NPs exposure could disrupt the integrity of cell plasma membrane, leading to the increased leakage of lactate dehydrogenase (LDH) into the culture medium. TiO2 NPs were uptaken by RSC-364 cells. The ultrastructure of RSC-364 cells was changed such as nuclear shrinkage and mitochondrial swelling. The reactive oxygen species (ROS) was over-produced especially in the cells exposed to 30 and 300 microg/ml TiO2 NPs. The activities of endogeneous antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), were significantly decreased. The increased lipid peroxidation product (malondialdehyde, MDA) suggests the oxidative damage in cells. The flow cytometry detected that the cell cycle was blocked in G0/G1 phase, inhibiting the cell proliferation. These preliminary results indicate the oxidative stress injury and cytotoxicity of anatase TiO2 NPs on rat synovial cells. The reasonable and safe application of nanomaterials in artificial implants needs further study.

  1. Cytotoxicity Evaluation of Anatase and Rutile TiO2 Thin Films on CHO-K1 Cells in Vitro

    Directory of Open Access Journals (Sweden)

    Blanca Cervantes

    2016-07-01

    Full Text Available Cytotoxicity of titanium dioxide (TiO2 thin films on Chinese hamster ovary (CHO-K1 cells was evaluated after 24, 48 and 72 h of culture. The TiO2 thin films were deposited using direct current magnetron sputtering. These films were post-deposition annealed at different temperatures (300, 500 and 800 °C toward the anatase to rutile phase transformation. The root-mean-square (RMS surface roughness of TiO2 films went from 2.8 to 8.08 nm when the annealing temperature was increased from 300 to 800 °C. Field emission scanning electron microscopy (FESEM results showed that the TiO2 films’ thickness values fell within the nanometer range (290–310 nm. Based on the results of the tetrazolium dye and trypan blue assays, we found that TiO2 thin films showed no cytotoxicity after the aforementioned culture times at which cell viability was greater than 98%. Independently of the annealing temperature of the TiO2 thin films, the number of CHO-K1 cells on the control substrate and on all TiO2 thin films was greater after 48 or 72 h than it was after 24 h; the highest cell survival rate was observed in TiO2 films annealed at 800 °C. These results indicate that TiO2 thin films do not affect mitochondrial function and proliferation of CHO-K1 cells, and back up the use of TiO2 thin films in biomedical science.

  2. Synergistic effect between anatase and rutile TiO2 nanoparticles in dye-sensitized solar cells.

    Science.gov (United States)

    Li, Gonghu; Richter, Christiaan P; Milot, Rebecca L; Cai, Lawrence; Schmuttenmaer, Charles A; Crabtree, Robert H; Brudvig, Gary W; Batista, Victor S

    2009-12-01

    A synergistic effect between anatase and rutile TiO2 is known, in which the addition of rutile can remarkably enhance the photocatalytic activity of anatase in the degradation of organic contaminants. In this study, mixed-phase TiO2 nanocomposites consisting of anatase and rutile nanoparticles (NPs) were prepared for use as photoanodes in dye-sensitized solar cells (DSSCs) and were characterized by using UV-vis spectroscopy, powder X-ray diffraction and scanning electron microscopy. The addition of 10-15% rutile significantly improved light harvesting and the overall solar conversion efficiency of anatase NPs in DSSCs. The underlying mechanism for the synergistic effect in DSSCs is now explored by using time-resolved terahertz spectroscopy. It is clearly demonstrated that photo-excited electrons injected into the rutile NPs can migrate to the conduction band of anatase NPs, enhancing the photocurrent and efficiency. Interfacial electron transfer from rutile to anatase, similar to that in heterogeneous photocatalysis, is proposed to account for the synergistic effect in DSSCs. Our results further suggest that the synergistic effect can be used to explain the beneficial effect of TiCl4 treatment on DSSC efficiency.

  3. Preparation of anatase TiO2 thin film by low temperature annealing as an electron transport layer in inverted polymer solar cells

    Science.gov (United States)

    Noh, Hongche; Oh, Seong-Geun; Im, Seung Soon

    2015-04-01

    To prepare the anatase TiO2 thin films on ITO glass, amorphous TiO2 colloidal solution was synthesized through the simple sol-gel method by using titanium (IV) isopropoxide as a precursor. This amorphous TiO2 colloidal solution was spread on ITO glass by spin-coating, then treated at 450 °C to obtain anatase TiO2 film (for device A). For other TiO2 films, amorphous TiO2 colloidal solution was treated through solvothermal process at 180 °C to obtain anatase TiO2 colloidal solution. This anatase TiO2 colloidal solution was spread on ITO glass by spin coating, and then annealed at 200 °C (for device B) and 130 °C (for device C), respectively. The average particle size of amorphous TiO2 colloidal solution was about 1.0 nm and that of anatase TiO2 colloidal solution was 10 nm. The thickness of TiO2 films was about 15 nm for all cases. When inverted polymer solar cells were fabricated by using these TiO2 films as an electron transport layer, the device C showed the highest PCE (2.6%) due to the lack of defect, uniformness and high light absorbance of TiO2 films. The result of this study can be applied for the preparation of inverted polymer solar cell using TiO2 films as a buffer layer at low temperature on plastic substrate by roll-to roll process.

  4. Electronic properties of atomic layer deposition films, anatase and rutile TiO2 studied by resonant photoemission spectroscopy

    Science.gov (United States)

    Das, C.; Richter, M.; Tallarida, M.; Schmeisser, D.

    2016-07-01

    The TiO2 films are prepared by atomic layer deposition (ALD) method using titanium isopropoxide precursors at 250 °C and analyzed using resonant photoemission spectroscopy (resPES). We report on the Ti2p and O1s core levels, on the valence band (VB) spectra and x-ray absorption spectroscopy (XAS) data, and on the resonant photoelectron spectroscopy (resPES) profiles at the O1s and the Ti3p absorption edges. We determine the elemental abundance, the position of the VB maxima, the partial density of states (PDOS) in the VB and in the conduction band (CB) and collect these data in a band scheme. In addition, we analyze the band-gap states as well as the intrinsic states due to polarons and charge-transfer excitations. These states are found to cause multiple Auger decay processes upon resonant excitation. We identify several of these processes and determine their relative contribution to the Auger signal quantitatively. As our resPES data allow a quantitative analysis of these defect states, we determine the relative abundance of the PDOS in the VB and in CB and also the charge neutrality level. The anatase and rutile polymorphs of TiO2 are analyzed in the same way as the TiO2 ALD layer. The electronic properties of the TiO2 ALD layer are compared with the anatase and rutile polymorphs of TiO2. In our comparative study, we find that ALD has its own characteristic electronic structure that is distinct from that of anatase and rutile. However, many details of the electronic structure are comparable and we benefit from our spectroscopic data and our careful analysis to find these differences. These can be attributed to a stronger hybridization of the O2p and Ti3d4s states for the ALD films when compared to the anatase and rutile polymorphs.

  5. Gold nanoparticles located at the interface of anatase/rutile TiO2 particles as active plasmonic photocatalysts for aerobic oxidation.

    Science.gov (United States)

    Tsukamoto, Daijiro; Shiraishi, Yasuhiro; Sugano, Yoshitsune; Ichikawa, Satoshi; Tanaka, Shunsuke; Hirai, Takayuki

    2012-04-11

    Visible-light irradiation (λ > 450 nm) of gold nanoparticles loaded on a mixture of anatase/rutile TiO(2) particles (Degussa, P25) promotes efficient aerobic oxidation at room temperature. The photocatalytic activity critically depends on the catalyst architecture: Au particles with anatase/rutile TiO(2) particles behave as the active sites for reaction. This photocatalysis is promoted via plasmon activation of the Au particles by visible light followed by consecutive electron transfer in the Au/rutile/anatase contact site. The activated Au particles transfer their conduction electrons to rutile and then to adjacent anatase TiO(2). This catalyzes the oxidation of substrates by the positively charged Au particles along with reduction of O(2) by the conduction band electrons on the surface of anatase TiO(2). This plasmonic photocatalysis is successfully promoted by sunlight exposure and enables efficient and selective aerobic oxidation of alcohols at ambient temperature.

  6. Synthesis, Characterization, and Photocatalysis of Well-Dispersible Phase-Pure Anatase TiO2 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Xiuzhen Wei

    2013-01-01

    Full Text Available High-purity anatase TiO2 nanoparticles were prepared using an improved sol-hydrothermal method. The as-prepared sample was characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, Brunauer-Emmett-Teller (BET, and UV-vis diffuse reflectance spectra. TEM results showed that the average particle size of all TiO2 particles was calculated to be (10 ± 1 nm. The XRD analysis indicated that the present sample was fully crystallized and appeared to be highly phase-pure anatase. The BET analysis showed that the as-prepared sample had a very large specific surface area of 186.25 m2/g. The photocatalytic performance of TiO2 nanoparticles was evaluated by photocatalytic degradation of X-3B and X-BR solutions. The degradation results revealed that the as-prepared TiO2 showed slightly higher photocatalytic activities than P25. Whereas, the as-synthesized TiO2 can settle down and be separated easily after the photocatalytic reaction finishes.

  7. Low-Temperature Synthesis of Anatase TiO2 Nanoparticles with Tunable Surface Charges for Enhancing Photocatalytic Activity

    Science.gov (United States)

    Li, Ye; Qin, Zhenping; Guo, Hongxia; Yang, Hanxiao; Zhang, Guojun; Ji, Shulan; Zeng, Tingying

    2014-01-01

    In this work, the positively or negatively charged anatase TiO2 nanoparticles were synthesized via a low temperature precipitation-peptization process (LTPPP) in the presence of poly(ethyleneimine) (PEI) and poly(sodium4- styrenesulfonate) (PSS). X-ray diffraction (XRD) pattern and high-resolution transmission electron microscope (HRTEM) confirmed the anatase crystalline phase. The charges of the prepared TiO2, PEI-TiO2 and PSS-TiO2 nanoparticles were investigated by zeta potentials. The results showed that the zeta potentials of PEI-TiO2 nanoparticles can be tuned from +39.47 mV to +95.46 mV, and that of PSS-TiO2 nanoparticles can be adjusted from −56.63 mV to −119.32 mV. In comparison with TiO2, PSS-TiO2 exhibited dramatic adsorption and degradation of dye molecules, while the PEI modified TiO2 nanoparticles showed lower photocatalytic activity. The photocatalytic performances of these charged nanoparticles were elucidated by the results of UV-vis diffuse reflectance spectra (DRS) and the photoluminescence (PL) spectra, which indicated that the PSS-TiO2 nanoparticles showed a lower recombination rate of electron-hole pairs than TiO2 and PEI-TiO2. PMID:25506839

  8. Anatase TiO2@C composites with porous structure as an advanced anode material for Na ion batteries

    Science.gov (United States)

    Shi, Xiaodong; Zhang, Zhian; Du, Ke; Lai, Yanqing; Fang, Jing; Li, Jie

    2016-10-01

    In this paper, we propose a facile strategy to synthesize the porous structure TiO2@C composites through a two-step method, in which the precursor of MIL-125(Ti) was firstly prepared by solvent thermal method and then calcined under inert atmosphere. When employed as anodes for Na ion batteries, TiO2@C composites can exhibit a superior cyclability with a reversible sodium storage capacity of 148 mAh g-1 at the current density 0.5 A g-1 after 500 cycles and an excellent rate performance with a capacity of 88.9 mAh g-1 even the current reached to 2.5 A g-1 due to the dispersion of anatase TiO2 throughout amorphous carbon matrix and the synergistic effect between the anatase TiO2 nanocrystals and carbon matrix, which can availably enhance the electric conductivity and alleviate the volumetric variation of TiO2 during the insertion/extraction process of Na+.

  9. Facet-dependent trapping and dynamics of excess electrons at anatase TiO2 surfaces and aqueous interfaces

    Science.gov (United States)

    Selcuk, Sencer; Selloni, Annabella

    2016-10-01

    Excess electrons from intrinsic defects, dopants and photoexcitation play a key role in many of the properties of TiO2. Understanding their behaviour is important for improving the performance of TiO2 in energy-related applications. We focus on anatase, the TiO2 polymorph most relevant in photocatalysis and solar energy conversion. Using first-principles simulations, we investigate the states and dynamics of excess electrons from different donors near the most common anatase (101) and (001) surfaces and aqueous interfaces. We find that the behaviour of excess electrons depends strongly on the exposed anatase surface, the environment and the character of the electron donor. Whereas no electron trapping is observed on the (101) surface in vacuo, an excess electron at the aqueous (101) interface can trigger water dissociation and become trapped into a stable surface Ti3+-bridging OH complex. By contrast, electrons avoid the (001) surface, indicating that oxidation reactions are favoured on this surface. Our results provide a bridge between surface science experiments and observations of crystal-face-dependent photocatalysis on anatase, and support the idea that optimization of the ratio between {101} and {001} facets could provide a way to enhance the photocatalytic activity of this material.

  10. Efficient, Green Non-aqueous Microwave-assisted Synthesis of Anatase TiO2 and Pt Loaded TiO2 Nanorods with High Photocatalytic Performance

    OpenAIRE

    Emanuela Filippo; Agostina Lina Capodilupo; Claudia Carlucci; Patrizia Perulli; Francesca Conciauro; Giuseppina Anna Corrente; Barbara Federica Scremin; Giuseppe Gigli; Giuseppe Ciccarella

    2015-01-01

    A high-yield synthesis of pure anatase titania nanorods has been achieved through a nonaqueous microwave-based approach. The residual organics on nanoparticles surfaces were completely removed under ozone flow at room temperature in air. The TiO2 nanorods, with average lengths of 27.6 ± 5.8 nm and average diameters of 3.2 ± 0.4 nm, were characterized by powder X-Ray diffraction, transmission electron microscopy, selected area diffraction, BET surface area analysis and FT-IR spectroscopy. The ...

  11. Photo-induced degradation of Ru(Ⅱ) complex absorbed on anatase TiO2 thin film electrode

    Institute of Scientific and Technical Information of China (English)

    WANG DeLiang; WANG GuangLong; ZHAO JianHua; CHEN Bo

    2007-01-01

    Photo-induced degradation of a monolayer of Ru(II) complex absorbed on anatase TiO2 thin film was studied by using resonant micro-Raman spectroscopy. Under intense light radiation of a laser and in the absence of a reducing agent, the dye decomposed quickly. When the dye-sensitized TiO2 thin film electrode was covered by a reducing agent, namely the Ⅰ-/Ⅰ-3 redox couple, the photo-induced decomposing rate was slowed by a factor of ~106. In both cases, the dye decomposed with time under an exponential law.

  12. Synthesis of hierarchical TiO2 nanowires with densely-packed and omnidirectional branches.

    Science.gov (United States)

    Lee, Daeho; Rho, Yoonsoo; Allen, Frances I; Minor, Andrew M; Ko, Seung Hwan; Grigoropoulos, Costas P

    2013-11-21

    In this study, a hierarchical TiO2 nanostructure with densely-packed and omnidirectional branches grown by a hydrothermal method is introduced. This morphology is achieved via high-concentration TiCl4 treatment of upright backbone nanowires (NWs) followed by hydrothermal growth. Secondary nanobranches grow in all directions from densely distributed, needle-like seeds on the jagged round surface of the backbone NWs. In addition, hierarchical, flower-like branches grow on the top surface of each NW, greatly increasing the surface area. For dye-sensitized solar cell (DSSC) applications, the TiO2 nanostructure demonstrated a photoconversion efficiency of up to 6.2%. A parametric study of the DSSC efficiency showed that branched TiO2 DSSCs can achieve nearly four times the efficiency of non-branched TiO2 nanowire DSSCs, and up to 170% the efficiency of previously-reported sparsely-branched TiO2 NW DSSCs.

  13. The effect of Ta dopant on the electronic and optical properties of anatase TiO2: a first-principles study

    Science.gov (United States)

    Muhammady, Shibghatullah; Nurfani, Eka; Kurniawan, Robi; Magdalena Sutjahja, Inge; Winata, Toto; Darma, Yudi

    2017-02-01

    We study the electronic and optical properties of pure and Ta-doped anatase TiO2 structures using a plane-wave-based first-principles calculation. The pure anatase TiO2 has an indirect band gap of 2.76 eV, while the Ta-doped anatase TiO2 is a metal. Zero-energy dielectric constants of 4.02 and 3.48 were found for E || a and E || c, respectively, in the pure anatase TiO2. Based on the calculated imaginary parts of the dielectric function (ε 2), the pure anatase TiO2 has anisotropic interband transition edges of 2.75 eV and 3.55 eV for E || a and E || c respectively, which show an optical dichroism. The Ta-doped anatase TiO2 is found to have metallic behaviour, which is clearly observable through the significantly high electronic absorption in ε 2 at the zero energy level. However, the Ta-doped TiO2 also shows anisotropic interband transition edges of 2.55 eV and 3.45 eV for E || a and E || c, respectively, based on ε 2. Based on these results, Ta dopant plays an important role for the semiconductor-to-metallic transformation in anatase TiO2. At the same time, Ta dopant also promotes the red-shift of the interband transition edges and enhances the dichroism. This study presents the significant modification in the optical properties of anatase TiO2 due to the presence of Ta dopant based on the dielectric functions.

  14. Boron-Doped Anatase TiO2 as a High-Performance Anode Material for Sodium-Ion Batteries.

    Science.gov (United States)

    Wang, Baofeng; Zhao, Fei; Du, Guodong; Porter, Spencer; Liu, Yong; Zhang, Peng; Cheng, Zhenxiang; Liu, Hua Kun; Huang, Zhenguo

    2016-06-29

    Pristine and boron-doped anatase TiO2 were prepared via a facile sol-gel method and the hydrothermal method for application as anode materials in sodium-ion batteries (SIBs). The sol-gel method leads to agglomerated TiO2, whereas the hydrothermal method is conducive to the formation of highly crystalline and discrete nanoparticles. The structure, morphology, and electrochemical properties were studied. The crystal size of TiO2 with boron doping is smaller than that of the nondoped crystals, which indicates that the addition of boron can inhibit the crystal growth. The electrochemical measurements demonstrated that the reversible capacity of the B-doped TiO2 is higher than that for the pristine sample. B-doping also effectively enhances the rate performance. The capacity of the B-doped TiO2 could reach 150 mAh/g at the high current rate of 2C and the capacity decay is only about 8 mAh/g over 400 cycles. The remarkable performance could be attributed to the lattice expansion resulting from B doping and the shortened Li(+) diffusion distance due to the nanosize. These results indicate that B-doped TiO2 can be a good candidate for SIBs.

  15. CdSe nanocrystal sensitized anatase TiO2 (001) tetragonal nanosheet-array films for photovoltaic application.

    Science.gov (United States)

    Feng, Shuanglong; Yang, Junyou; Liu, Ming; Liu, Yong

    2013-02-01

    CdSe nanocrystal sensitized TiO2 nanosheet array heterostructure films were fabricated by a two-step method. Firstly, a single crystalline anatase TiO2 tetragonal nanosheet-array film on a transparent conductive fluorine-doped tin oxide (FTO) substrate was successfully prepared by hydrothermal method. Then, CdSe nanocrystalline sensitizers were deposited on the TiO2 nanosheet array by CBD method. The products were characterized with XRD, SEM, TEM and UV-vis absorption spectroscopy. The effect of the CdSe nanocrystal deposition time and the length of the TiO2 sheet on the photovoltaic performance of the resulting CdSe/TiO2 nanosheet array electrodes were also investigated. In comparison with the non-sensitized TiO2 nanosheet array, the photocurrent of CdSe sensitized TiO2 nanosheet has a great enhancement, which gives some insight to the fundamental mechanism of the performance improvement.

  16. The Photocatalytic Reduction of Hexavalent Chromium by Controllable Mesoporous Anatase TiO2 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Vorrada Loryuenyong

    2014-01-01

    Full Text Available Titania (TiO2 nanoparticles with periodical mesopore size (up to 150 Å have successfully been synthesized by sol-gel template method, using titanium(IV tetraisopropoxide as a starting precursor and isopropanol as a solvent. Different quantities of activated carbon (0%, 5%, and 10% by weight were used as templates to control the porosity and particle size of titania nanoparticles. The templates were completely removed during the calcination in air at 500°C for 3 hr. The results showed that the specific surface area of titania is increased with increasing activated carbon content. The optical bandgap of synthesized titania exhibits a blue shift by 0.3–0.6 eV when compared to the reported value for the bulk anatase and rutile phases. The photocatalytic activity of porous titania is determined with its reduction efficiency of hexavalent chromium (Cr6+. The reduction efficiency is optimized under ultraviolet illumination.

  17. Nano-Anatase TiO2 for High Performance Optical Humidity Sensing on Chip

    Directory of Open Access Journals (Sweden)

    Mahdiar Ghadiry

    2015-12-01

    Full Text Available An on-chip optical humidity sensor using Nano-anatase TiO2 coating is presented here. The coating material was prepared so that the result is in solution form, making the fabrication process quick and simple. Then, the solution was effortlessly spin-coated on an SU8 straight channel waveguide. Investigating the sensitivity and performance (response time of the device revealed a great linearity in the wide range (35% to 98% of relative humidity (RH. In addition, a variation of more than 14 dB in transmitted optical power was observed, with a response time of only ~0.7 s. The effect of coating concentration and UV treatment was examined on the performance and repeatability of the sensor. Interesting observations were found, and the attributed mechanisms were described. In addition, the proposed sensor was extensively compared with other state-of-the-art proposed counterparts from the literature and remarkable advantages were found. Since a high sensitivity of ~0.21 dB/%RH and high dynamic performances were demonstrated, this sensor is proposed for use in biomedical applications.

  18. Investigation of curcumin as sensitizer for anatase TiO2 nanoparticles in photodegradation of of phenazopyridine with visible light

    Directory of Open Access Journals (Sweden)

    ZYOUD Ahed H.

    2014-11-01

    Full Text Available This work describes a photodegradation catalyst, for water organic contaminants in visible light, based on curcumin (a natural dye sensitized TiO2 (anatase nanoparticles. Phenazopyridine (a pharmaceutically active gradient was used as a contaminant. A 400 nm, and shorter, cut of filter was used to confirm only visible light was used in photodegradation process with no UV radiation. The catalyst system was characterized by electronic absorption spectroscopy and XRD. The particle size forthe catalyst nanaprticles was calculated using Scherrer equation and found to be ~45 nm in average. Different reaction parameters were studied, such as effect of contaminant concentration, amount of loaded catalyst, and pH value on the photodegradation rate. Turn number (T.N. and quantum yield (Q.Y. values were calculated for comparative assessment of the catalyst effeciency. The results show the ability of curcumin dyes to sensitize TiO2 anatase nanoparticles in photodegradation phenazopyridine under visible radiation.

  19. Dye-Sensitized Solar Cells with Anatase TiO2 Nanorods Prepared by Hydrothermal Method

    OpenAIRE

    Ming-Jer Jeng; Yi-Lun Wung; Liann-Be Chang; Lee Chow

    2013-01-01

    The hydrothermal method provides an effective reaction environment for the synthesis of nanocrystalline materials with high purity and well-controlled crystallinity. In this work, we started with various sizes of commercial TiO2 powders and used the hydrothermal method to prepare TiO2 thin films. We found that the synthesized TiO2 nanorods were thin and long when smaller TiO2 particles were used, while larger TiO2 particles produced thicker and shorter nanorods. We also found that TiO2 films ...

  20. Investigation of curcumin as sensitizer for anatase TiO2 nanoparticles in photodegradation of of phenazopyridine with visible light

    OpenAIRE

    ZYOUD Ahed H.; Hilal, Hikmat S.

    2014-01-01

    This work describes a photodegradation catalyst, for water organic contaminants in visible light, based on curcumin (a natural dye) sensitized TiO2 (anatase) nanoparticles. Phenazopyridine (a pharmaceutically active gradient) was used as a contaminant. A 400 nm, and shorter, cut of filter was used to confirm only visible light was used in photodegradation process with no UV radiation. The catalyst system was characterized by electronic absorption spectroscopy and XRD. The particle...

  1. Enhanced electrorheological performance and antisedimentation property of mesoporous anatase TiO2 shell prepared by hydrothermal process

    Science.gov (United States)

    Wang, Jiahui; Chen, Guowei; Yin, Jianbo; Luo, Chunrong; Zhao, Xiaopeng

    2017-03-01

    Mesoporous anatase TiO2 hollow microspheres (MTHMs) with a high surface area (231.1 m2 g‑1) were synthesized by sol-gel template-assisted approach and hydrothermal process. The materials possessed a uniform diameter of about 620 nm and a mesoporous shell with thickness of about 180 nm. The microspheres were used as dispersing materials for electrorheological (ER) fluids, which exhibited better ER performance and antisedimentation property than common anatase TiO2 hollow microspheres and ordinary anatase TiO2 particles. The yield stress of the MTHM-based ER fluid (30.0 vol%) was approximately 7.8 kPa under an electric field of 3 kV mm‑1, and the sedimentation ratio was maintained above 78% after 250 h. The good ER activity of the MTHM-based ER fluid was mainly attributed to the high surface effect provided by mesoporous and hollow structure of the MTHMs, leading to a high interfacial polarization under the action of an external electric field. The mesoporous and hollow structure also improved the antisedimentation property of the suspensions by lowering the density of microspheres.

  2. Experimental and theoretical study of the electronic properties of Cu-doped anatase TiO2.

    Science.gov (United States)

    Navas, Javier; Sánchez-Coronilla, Antonio; Aguilar, Teresa; Hernández, Norge C; de los Santos, Desireé M; Sánchez-Márquez, Jesús; Zorrilla, David; Fernández-Lorenzo, Concha; Alcántara, Rodrigo; Martín-Calleja, Joaquín

    2014-02-28

    A good correlation was obtained between the electronic properties of Cu-doped anatase TiO2 by virtue of both physical chemistry characterization and theoretical calculations. Pure and Cu-doped TiO2 were synthesized. The composition, structural and electronic properties, and the band gap energy were obtained using several techniques. The method of synthesis used produces Cu-doped anatase TiO2, and XRD, XPS and Raman spectroscopy indicate that Cu atoms are incorporated in the structure by substitution of Ti atoms, generating a distortion of the structure and oxygen vacancies. In turn, the band gap energy of the synthesized samples decrease drastically with the Cu doping. Moreover, periodic density functional theory (DFT-periodic) calculations were carried out both to model the experimentally observed doped structures and to understand theoretically the experimental structures obtained, the formation of oxygen vacancies and the values of the band gap energy. From the analysis of density of states (DOS), projected density of states (PDOS) and the electron localization function (ELF) a decrease in the band gap is predicted upon increasing the Cu doping. Thus, the inclusion of Cu in the anatase structure implies a covalent character in the Cu-O interaction, which involves the appearance of new states in the valence band maximum with a narrowing in the band gap.

  3. Influence of anatase and rutile phase in TiO2 upon the photocatalytic degradation of methylene blue under solar irradiation in presence of activated carbon.

    Science.gov (United States)

    Matos, J; Montaña, R; Rivero, E; Escudero, A; Uzcategui, D

    2014-01-01

    The influence of activated carbon (AC) on the photocatalytic activity of different crystalline TiO2 phases was verified in the photocatalytic degradation of methylene blue under UV and solar irradiation. The results showed a volcano trend with a maximum photoactivity for the crystalline phase ratio of anatase:rutile equal to 80:20 both under UV or solar irradiation. By contrast, in presence of AC the photocatalytic activity of the binary materials of TiO2/AC followed an exponential trend, increasing as a function of the increase in anatase proportion in the TiO2 framework. The increase in the photoactivity of the binary material TiO2/AC relative to neat TiO2 was up to 22 and about 17 times higher under UV and visible irradiation, respectively. The present results suggest that AC interacts more efficiently with anatase phase than with rutile phase.

  4. Anatase TiO2 nanocrystals anchored at inside of SBA-15 mesopores and their optical behavior

    Science.gov (United States)

    Araújo, M. M.; Silva, L. K. R.; Sczancoski, J. C.; Orlandi, M. O.; Longo, E.; Santos, A. G. D.; Sá, J. L. S.; Santos, R. S.; Luz, G. E.; Cavalcante, L. S.

    2016-12-01

    In this paper, a new synthesis method was proposed to obtain anatase titanium oxide (TiO2) nanocrystals anchored into SBA-15 molecular sieve, as a matrix assigned by the in-situ anchoring (ISA) method. Pure SBA-15 and modified with TiO2 nanocrystals at different Si/Ti molar ratios (R = 75, 50, and 25) were structurally characterized by X-ray diffraction (XRD), Micro-Raman and Fourier Transform infrared (FTIR) spectroscopies. Specific surface area, pore volume and average pore diameter were estimated using both Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods, respectively. Morphological aspects of these samples were observed by means of field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). Optical properties were investigated by ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy. XRD patterns, Micro-Raman and FT-IR spectra indicate the TiO2 nanocrystals crystallized in a tetragonal structure anchored into the SBA-15 mesopores. BET and BJH methods prove a large amount of TiO2 nanocrystals were anchored inside of SBA-15 mesopores due to increase in surface area and average pore size of SBA-15 matrix. FE-SEM and TEM images showed the pure SBA-15 has an elongated hexagon-shaped microstructure, and an average size of 7.34 nm for 2D hexagonal mesopores. Moreover, ISA method was able to avoid blocking of mesopores, in addition promotes a significant increasing the impregnation rate of anatase TiO2 nanocrystals in SBA-15 matrix. A growth mechanism was proposed in order to explain the stages involved in the formation of TiO2-SBA mesoporous. UV-vis spectra revealed a dependence of the optical band gap energy (Egap) with the decreasing of Si/Ti molar ratios.

  5. The Effect of Ce-N Codoping on the Electronic Structure and Optical Property of Anatase TiO2: a First-Principles Study

    Science.gov (United States)

    Mao, Fei; Hou, Qingyu; Zhao, Chunwang; Guo, Shaoqiang; Zhang, Yue

    2014-01-01

    Based on the first-principles plane wave ultra-soft pseudo potential (USP) method of density function theory pure N and Ce doped and Ce-N codoping anatase TiO2 supercell models were established, respectively, and calculated their energy in this paper. The calculated results show that the three doping systems compared to the pure anatase TiO2 band gap narrowed which results in red-shift of the optical absorption edges and Ce-N codoped anatase TiO2 have the most obvious visible effect. Meanwhile, synergy is very effective for the separation of electron-hole pairs and the electrons have a better lifespan. Research found that the trend of the donor's movements at the shallow level of Ce-N codoped anatase TiO2 is not obvious. This is due to its very thick shell, resulting in shielding effect of the outer layer of the Ce-4f.

  6. Preparation of TiO2 anatase nanocrystals by TiCl4 hydrolysis with additive H2SO4.

    Directory of Open Access Journals (Sweden)

    Wenbing Li

    Full Text Available A new methodology was developed to synthesize uniform titania anatase nanocrystals by the hydrolysis of titanium chloride in sulfuric acid aqueous solutions at 0-90°C. The samples were characterized by Raman spectroscopy, UV-visible spectroscopy, transmission electron microscopy (TEM, electron diffraction (ED, and an Energy dispersive X-ray spectroscopy (EDS. The effects of the reaction temperature, mole ratio of SO(4(2- to Ti(4+, and the calcinations temperature on the particle size and crystal phase were investigated. Depending on the acidity, the hydrolysis temperature, and the calcination temperature, rhombic anatase nanocrystals sizes in the range of 10 nm to 50 nm were obtained. In the additive of sulfuric acid, Raman spectra and electron diffraction confirmed that the nanoparticles are composed of anatase TiO(2. No other titania phases, such as rutile or brookite, were detected.

  7. Dye-sensitized solar cells based on anatase TiO 2 hollow spheres/carbon nanotube composite films

    Science.gov (United States)

    Yu, Jiaguo; Fan, Jiajie; Cheng, Bei

    Dye-sensitized solar cells (DSSCs) based on anatase TiO 2 hollow spheres (TiO2HS)/multi-walled carbon nanotubes (CNT) nanocomposite films are prepared by a directly mechanical mixing and doctor blade method. The prepared samples are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV-vis absorption spectroscopy and N 2 adsorption-desorption isotherms. The photoelectric conversion performances of the DSSCs based on TiO2HS/CNT composite film electrodes are also compared with commercial-grade Degussa P25 TiO 2 nanoparticles (P25)/CNT composite solar cells at the same film thickness. The results indicate that the photoelectric conversion efficiencies (η) of the TiO2HS/CNT composite DSSCs are dependent on CNT loading in the electrodes. A small amount of CNT clearly enhances DSSC efficiency, while excessive CNT loading significantly lowers their performance. The former is because CNT enhance the transport of electrons from the films to FTO substrates. The latter is due to high CNT loading shielding the visible light from being adsorbed by dyes.

  8. First-principles study on codoping effect to enhance photocatalytic activity of anatase TiO2

    Science.gov (United States)

    Bai, Yujie; Zhang, Qinfang; Zheng, Fubao; Yang, Yun; Meng, Qiangqiang; Zhu, Lei; Wang, Baolin

    2017-03-01

    Codopant is an effective approach to modify the bandgap and band edge positions of transition metal oxide. Here, the electronic structures as well as the optical properties of pristine, mono-doped (N/P/Sb) and codoped (Sb, N/P) anatase TiO2 have been systematically investigated based on density functional theory calculations. It is found that mono-doped TiO2 exhibits either unoccupied or partially occupied intermediate state within the energy gap, which promotes the recombination of electron-hole pairs. However, the presence of (Sb, N/P) codopant not only effectively reduces the width of bandgap by introducing delocalized occupied intermediate states, but also adjusts the band edge alignment to enhance the hydrogen evolution activity of TiO2. Moreover, the optical absorption spectrum for (Sb, N/P) codoped TiO2, which is favored under oxygen-rich condition, demonstrates the improvement of its visible light absorption. These findings will promote the potential application of (Sb, N/P) codoped TiO2 photocatalysis for water splitting under visible light irradiation.

  9. Direct formation of anatase TiO2 nanoparticles on carbon nanotubes by atomic layer deposition and their photocatalytic properties

    Science.gov (United States)

    Huang, Sheng-Hsin; Liao, Shih-Yun; Wang, Chih-Chieh; Kei, Chi-Chung; Gan, Jon-Yiew; Perng, Tsong-Pyng

    2016-10-01

    TiO2 with different morphology was deposited on acid-treated multi-walled carbon nanotubes (CNTs) by atomic layer deposition at 100 °C-300 °C to form a TiO2@CNT structure. The TiO2 fabricated at 100 °C was an amorphous film, but became crystalline anatase nanoparticles when fabricated at 200 °C and 300 °C. The saturation growth rates of TiO2 nanoparticles at 300 °C were about 1.5 and 0.4 Å/cycle for substrate-enhanced growth and linear growth processes, respectively. It was found that the rate constants for methylene blue degradation by the TiO2@CNT structure formed at 300 °C were more suitable to fit with second-order reaction. The size of 9 nm exhibited the best degradation efficiency, because of the high specific area and appropriate diffusion length for the electrons and holes.

  10. Hierarchical structured TiO2 photoanodes for dye-sensitized solar cells.

    Science.gov (United States)

    Shih, Yen-Chen; Chu, Ann-Kuo; Huang, Wen-Yao

    2012-04-01

    A novel approach has been developed to fabricate hills-like hierarchical structured TiO2 photoanodes for dye-sensitized solar cells (DSSCs). The appropriately aggregated TiO2 clusters in the photoanode layer could cause stronger light scattering and higher dye loading that increases the efficiency of photovoltaic device. For detailed light-harvesting study, different molecular weights of polyvinyl alcohol (PVA) were used as binders for TiO2 nanoparticles (P-25 Degussa) aggregation. A series of TiO2 films with dissimilar morphology, the reflection of TiO2 films, absorbance of attached dye, amount of dye loading, and performance of fabricated DSSC devices, were measured and investigated. An optimized device had energy conversion efficiency of 4.47% having a higher dye loading and good light harvesting, achieving a 23% increase of short-circuit current J(sc) in DSSCs.

  11. Adsorption of organic molecules on rutile TiO2 and anatase TiO2 single crystal surfaces.

    Science.gov (United States)

    Thomas, Andrew G; Syres, Karen L

    2012-06-07

    The interaction of organic molecules with titanium dioxide surfaces has been the subject of many studies over the last few decades. Numerous surface science techniques have been utilised to understand the often complex nature of these systems. The reasons for studying these systems are hugely diverse given that titanium dioxide has many technological and medical applications. Although surface science experiments investigating the adsorption of organic molecules on titanium dioxide surfaces is not a new area of research, the field continues to change and evolve as new potential applications are discovered and new techniques to study the systems are developed. This tutorial review aims to update previous reviews on the subject. It describes experimental and theoretical work on the adsorption of carboxylic acids, dye molecules, amino acids, alcohols, catechols and nitrogen containing compounds on single crystal TiO(2) surfaces.

  12. Morphological effects of Au13 clusters on the adsorption of CO2 over anatase TiO2(101)

    Science.gov (United States)

    Liu, Li; Liu, Zhongbo; Sun, Honggang; Zhao, Xian

    2017-03-01

    Density functional theory was employed to investigate the interaction between CO2 and anatase TiO2(101) surface in the presence of Au13 clusters. Two Au13 clusters (icosahedral and cuboctahedral) were used to identify correlations among activity, structural stability, and morphology of supported Au13 clusters on the TiO2(101) surface. The effects of oxygen vacancy were also studied. A strong morphological effect of Au13 clusters on the adsorption and activation of CO2 over anatase TiO2 (101) has been identified. The structural dynamic fluxionality of Au13 clusters, i.e., its adaptability toward the adsorbed CO2, plays an important role in the bonding and activation of CO2. The flexibility of the icosahedral Au13 cluster allows it to readjust so as to enable the maximum orbital overlap between the Au13 clusters and CO2, making the stabilization of CO2 feasible. In contrast, the cuboctahedral Au13 cluster tends to maintain its own structure even after CO2 adsorption, resulting in weaker CO2 binding strength. The presence of oxygen vacancy was found to introduce additional adsorption sites, and CO2 adsorption on defective TiO2(101) surface can be substantially modified by the presence of the cuboctahedral Au13 cluster. In addition, we find that the interfacial site is the preferred adsorption site for CO2 adsorption and activation on the Au13/TiO2(101) surface. These findings shed light on the importance of cluster dynamics during catalytic reaction and provide key guidelines for engineering more efficient metal-oxide interfaces in catalysis.

  13. Effect of sodium on photovoltaic properties of dye-sensitized solar cells assembled with anatase TiO2 nanosheets with exposed {001} facets.

    Science.gov (United States)

    Wu, Xia; Lu, Gaoqing Max; Wang, Lianzhou

    2013-02-01

    Anatase TiO(2) nanosheets with exposed reactive {001} facets were prepared in the presence of HF. The photovoltaic properties of NaOH-washed anatase TiO(2) nanosheets with exposed {001} facets were investigated by assembling the TiO(2) as photoanodes in dye-sensitized solar cells (DSSCs). A decreased overall efficiency and increased recombination rate was observed in comparison with the H(2)O-washed counterpart by both dark current scan and open-circuit voltage decay scan, and XPS confirmed that the deleterious effect of sodium ions is responsible for this reduced efficiency in DSSCs.

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

    Science.gov (United States)

    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.

  15. Effects of V heavy doping on the magnetic and optical properties in anatase TiO2

    Science.gov (United States)

    Hou, Qingyu; Zhao, Chunwang; Qu, Lingfeng

    2017-01-01

    A half-metal diluted magnetic semiconductor (DMS) can be formed in heavy V-doped TiO2. Contradictory experimental results in the literature have reported about the absorption spectra blueshift and redshift results in heavy V-doped TiO2. This study aims to reveal the mechanism of half-metal DMS in heavy V-doped TiO2 and solve the problem of absorption spectra blueshift and redshift in the doping system. In this study, models of the unit cells of pure anatase TiO2 and two V heavy-doped supercells of Ti0.96875V0.03125O2 and Ti0.9375V0.0625O2 were constructed based on density functional theory, which uses the first-principles plane-wave ultrasoft pseudopotential method. All models were obtained through geometry optimization. Local density approximation (LDA) + U was used to calculate the band structure, density of states (DOS), orbital charge and absorption spectrum of the doping system. The calculated results under the condition of electron spin showed that in the heavy doping concentration range, the volume of supercells increases, the total energy and formation energy decrease and the stability of the supercells increases as V doping concentration increases. Furthermore, the interaction of p-p states is weaker than that of p-d states, which results in the valence band maximum shifting toward the low-energy region, and also the optical bandgap becomes narrower as well as the redshift and intensity of the absorption spectrum become more notable. Noticeably, the hybrid coupling effect of Ti-3d and V-3d states becomes stronger, and the magnetic moment increases. The Fermi levels of spin-up band structure within the conduction band, which form the n-type degenerate semiconductors, and the Fermi levels of spin-down band structure within the bandgap indicate that the doping system has semiconductor features. Therefore, V-doped anatase TiO2 is an extremely promising DMS because of its high electron polarizability of nearly 100%. The calculation results are consistent with

  16. Emerging giant resonant exciton induced by Ta substitution in anatase TiO2: A tunable correlation effect

    Science.gov (United States)

    Yong, Z.; Trevisanutto, P. E.; Chiodo, L.; Santoso, I.; Barman, A. R.; Asmara, T. C.; Dhar, S.; Kotlov, A.; Terentjevs, A.; Della Sala, F.; Olevano, V.; Rübhausen, M.; Venkatesan, T.; Rusydi, A.

    2016-05-01

    Titanium dioxide (TiO2) has rich physical properties with potential implications for both fundamental physics and new applications. To date, the main focus of applied research is to tune its optical properties, which is usually done via doping and/or nanoengineering. However, understanding the role of d electrons in materials and possible functionalization of d -electron properties are still major challenges. Herewith, within a combination of an innovative experimental technique, high-energy optical conductivity, and state-of-the-art ab initio electronic structure calculations, we report an emerging, novel resonant exciton in the deep ultraviolet region of the optical response. The resonant exciton evolves upon low-concentration Ta substitution in anatase TiO2 films. It is surprisingly robust and related to strong electron-electron and electron-hole interactions. The d - and f -orbital localization, due to Ta substitution, plays an unexpected role, activating strong electronic correlations and dominating the optical response under photoexcitation. Our results shed light on a new optical phenomenon in anatase TiO2 films and on the possibility of tuning electronic properties by Ta substitution.

  17. Computational Study of the Adsorption of Dimethyl Methylphosphonate (DMMP) on the (0 1 0) Surface of Anatase TiO2 With and Without Faceting

    Science.gov (United States)

    2010-02-02

    Computational study of the adsorption of dimethyl methylphosphonate (DMMP) on the (0 1 0) surface of anatase TiO2 with and without faceting V.M...DMMP) on the (0 1 0) surface of anatase TiO2, which is isostructural with the (1 0 0), has been studied using density functional theory and two...also close to those found elsewhere for the rutile (1 1 0) and anatase (1 0 1) surfaces. A possible first step in the dissociative adsorption of DMMP

  18. Photocatalytic activity of magnetically anatase TiO2 with high crystallinity and stability for dyes degradation: Insights into the dual roles of SiO2 interlayer between TiO2 and CoFe2O4

    Science.gov (United States)

    Yang, Zewei; Shi, Yingying; Wang, Bing

    2017-03-01

    A novel magnetically separable photocatalyst comprising hollow TiO2-SiO2-CoFe2O4 (TSC) was prepared. In the TSC photocatalyst, an SiO2 interlayer between CoFe2O4 core and TiO2 shell is used to both weaken adverse influence of the magnetic core on photocatalysis and increase the temperature of the transition from anatase to rutile phase TiO2, thus increasing the anatase TiO2 crystallinity. Such an interlayer promotes photocatalytic activity by changing the competition between the injecting process and reacting process of the photogenerated carriers. The photocatalytic activity of TSC was determined for degradation of dye molecules in water under either UV or visible light. The photocatalytic reaction of cationic dyes was governed by rad OH radicals, while O2rad - was the main active species in the initial photoreaction of anionic dyes.

  19. Effect of Yb2O3 Additive on Transformation Behavior of Anatase for TiO2/( O' + β' )-Sialon Multi phase Ceramics

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    TiO2/(O' + β')-Sialon multiphase ceramics were prepared with nano Ti O2 (anatase) powder and (O' + β')-Sialon powder as raw materials. Effect of Yb2O3 additive on transformation behavior of anatase for TiO2/(O' + β')-Sialon multi phase ceramic was investigated and its influence mechanism was discussed. XRD was employed for the analysis of phase composition and lattice parameters. The results show that even though Yb2O3 has no obvious influence on starting temperature of phase transformation, it significantly accelerates the transformation process, which displays a weakened effect with more Yb2O3 addition. There exist two forms of the added Yb2O3: some enters TiO2 lattice and the other deposits on the surface of TiO2. The function of Yb2O3 on phase transformation of anatase can be attributed to the coaction of active and negative influence mechanisms as follows: some Ybn+ enter TiO2 lattice and replace Ti4+ , as well as the redox reaction between Yb3 + and TiO2, which promote the transformation, whereas other Yb2O3 deposits on the surface of TiO2, and TiO-Yb bond is formed by the coaction of Yb3 + and TiO2, which inhibit the process.

  20. Particle concentration effect in adsorption/desorption of Zn(II) on anatase type nano TiO2

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Adsorption/desorption in a new Zn(II)-TiO2 adsorption system was investigated at different particle concentrations (Cp). TEM, SEM and XRD analyses revealed that the TiO2 particles were an aggregation of nano-sized (approximately 10 nm) pure anatase-type TiO2. Adsorption experiments were carried out with particle concentrations of 100, 400 and 1000 mg/L, and their adsorption isotherms were found to decline successively, showing an obvious Cp effect. Desorption experiments indicated that adsorption in this system was irreversible, and the irreversibility increased with increasing Cp. These phenomena could be explained by the MEA (metastable equilibrium adsorption) theory and the Cp effect could be modeled well with an MEA-Freundlich-type Cp effect isotherm equation. This study may help understand environmental behavior of contaminants on ultrafine natural particles.

  1. Structural and electronic properties of Mg and Mg-Nb co-doped TiO2 (101) anatase surface

    Science.gov (United States)

    Sasani, Alireza; Baktash, Ardeshir; Mirabbaszadeh, Kavoos; Khoshnevisan, Bahram

    2016-10-01

    In this paper, by using density functional theory, Mg and Nb-Mg co-doping of TiO2 anatase (101) surfaces are studied. By studying the formation energy of the defects and the bond length distribution of the surface, it is shown that Mg defects tend to stay as far as possible to induce least possible lattice distortion while Nb and Mg defects stay close to each other to cause less stress to the surface. By investigating band structure of the surface and changes stemmed from the defects, potential effects of Mg and Mg-Nb co-doping of TiO2 surface on dye-sensitized solar cells are investigated. In this study, it is shown that the Nb-Mg co-doping could increase JSC of the surface while slightly decreasing VOC compared to Mg doped surface, which might result in an increase in efficiency of the DSSCs compared to Nb or Mg doped surfaces.

  2. Room-temperature synthesis of single-phase anatase TiO2 by aging and its self-cleaning properties.

    Science.gov (United States)

    Qi, Kaihong; Xin, John H

    2010-12-01

    A facile process to synthesize single-phase anatase titanium dioxide nanocrystallites at room temperature was presented. The process included a sol-gel reaction in an aqueous media followed by aging at room temperature. The anatase TiO2 was characterized using XRD, TEM and SEM. The cotton fabrics-coated by the anatase nanocrystallites possessed significant photocatalytic self-cleaning properties as demonstrated by their ability to decompose a colorant and degrade red wine and coffee stains, which was equivalent to that of prepared by heating or hydrothermal methods described previously. The anatase TiO2-coated cotton substrate also showed a high UPF rating of 50+, which means excellent UV protection to human wearers. The study of the adhesion between the anatase TiO2 and the cotton substrate showed that even after 20 times of repeated launderings, the-coated substrate was still capable of decomposing stains, which indicated its photocatalytic power, though this was reduced compared to that before laundering. The tensile strength results of the anatase TiO2-coated cotton fabrics indicate that the anatase TiO2 will not damage the cotton substrate even after 20 h of continuous UV irradiation. The method of preparing single-phase anatase TiO2 revealed in this study not only eliminates the need for high temperature processing, which means energy saving, but also broadens its applications to poor acid-resistant and low thermal stability materials such as many of the biomaterials and cellulosic materials.

  3. A General Method for Preparing Anatase TiO2 Treelike-Nanoarrays on Various Metal Wires for Fiber Dye-Sensitized Solar Cells

    Science.gov (United States)

    Chu, Liang; Li, Luying; Su, Jun; Tu, Fanfan; Liu, Nishuang; Gao, Yihua

    2014-03-01

    Anatase TiO2 tree-like nanoarrays were prepared on various metal wires (Ti, W, Ni, etc.) through one-step facile hydrothermal reaction. The anatase TiO2 tree-like nanoarrays consist of long TiO2 nanowire trunks with direct charge transport channels, and a large number of short TiO2 nanorod branches with large surface areas. Fiber dye-sensitized solar cells (FDSSCs) based on the anatase TiO2 tree-like nanoarrays deposited on Ti wires can achieve outstanding power conversion efficiency (PCE) of 6.32%, while FDSSCs on W wires have lower PCE of 3.24% due to the formation of WO3 layer, which might enhance recombination of charges. When the substrate is changed to a Nicole oxide wire, a novel p-n heterojunction can be obtained. This universal method is simple, facile, and low cost for preparing anatase TiO2 treelike-nanoarrays on various metal wires, which may find potential applications in fabrication of optoelectronic devices.

  4. Defects in rutile and anatase polymorphs of TiO2: kinetics and thermodynamics near grain boundaries.

    Science.gov (United States)

    Uberuaga, Blas P; Bai, Xian-Ming

    2011-11-02

    The direct consequence of irradiation on a material is the creation of point defects-typically interstitials and vacancies, and their aggregates-but it is the ultimate fate of these defects that determines the material's radiation tolerance. Thus, understanding how defects migrate and interact with sinks, such as grain boundaries, is crucial for predicting the evolution of the material. We examine defect properties in two polymorphs of TiO(2)-rutile and anatase-to determine how these materials might respond differently to irradiation. Using molecular statics and temperature accelerated dynamics, we focus on two issues: how point defects interact with a representative grain boundary and how they migrate in the bulk phase. We find that grain boundaries in both polymorphs are strong sinks for all point defects, though somewhat stronger in rutile than anatase. Further, the defect kinetics are very different in the two polymorphs, with interstitial species diffusing quickly in rutile while oxygen defects-both interstitials and vacancies-are fast diffusers in anatase. These results allow us to speculate on how grain boundaries will modify the radiation tolerance of these materials. In particular, grain boundaries in rutile will lead to a space charge layer at the boundary and a vacancy-rich damage structure, while in anatase the damage structure would likely be more stoichiometric, but with larger defects consisting primarily of Ti ions.

  5. Electronic structures of anatase (TiO2)1-x(TaON)x solid solutions: a first-principles study.

    Science.gov (United States)

    Dang, Wenqiang; Chen, Hungru; Umezawa, Naoto; Zhang, Junying

    2015-07-21

    Sensitizing wide band gap photo-functional materials under visible-light irradiation is an important task for efficient solar energy conversion. Although nitrogen doping into anatase TiO2 has been extensively studied for this purpose, it is hard to increase the nitrogen content in anatase TiO2 because of the aliovalent nitrogen substituted for oxygen, leading to the formation of secondary phases or defects that hamper the migration of photoexcited charge carriers. In this paper, electronic structures of (TiO2)1-x(TaON)x (0 ≤ x ≤ 1) solid solutions, in which the stoichiometry is satisfied with the co-substitution of Ti for Ta along with O for N, are investigated within the anatase crystal structure using first-principles calculations. Our computational results show that the solid solutions have substantially narrower band gaps than TiO2, without introducing any localized energy states in the forbidden gap. In addition, in comparison with the pristine TiO2, the solid solution has a direct band gap when the content of TaON exceeds 0.25, which is advantageous to light absorption. The valence band maximum (VBM) of the solid solutions, which is mainly composed of N 2p states hybridized with O 2p, Ti 3d or Ta 5d orbitals, is higher in energy than that of pristine anatase TiO2 consisting of non-bonding O 2p states. On the other hand, incorporating TaON into TiO2 causes the formation of d-d bonding states through π interactions and substantially lowers the conduction band minimum (CBM) because of the shortened distance between some metal atoms. As a result, the anatase (TiO2)1-x(TaON)x is expected to become a promising visible-light absorber. In addition, some atomic configurations are found to possess exceptionally narrow band gaps.

  6. Morphology-controlled cactus-like branched anatase TiO2 arrays with high light-harvesting efficiency for dye-sensitized solar cells

    Science.gov (United States)

    Wu, Wu-Qiang; Rao, Hua-Shang; Feng, Hao-Lin; Guo, Xin-Dong; Su, Cheng-Yong; Kuang, Dai-Bin

    2014-08-01

    The present work establishes a facile process for one-step hydrothermal growth of vertically aligned anatase cactus-like branched TiO2 (CBT) arrays on a transparent conducting oxide (TCO) substrate. Various CBT morphologies are obtained by adjusting the potassium titanium oxide oxalate (PTO) reactant concentration (from 0.05 M to 0.15 M) and this yields a morphologically-controllable branched TiO2 arrays geometry. The CBT arrays consist of a vertically oriented nanowire (NW) or nanosheet (NS) stem and a host of short nanorod (NR) branches. The hierarchical CBT arrays demonstrate their excellent candidatures as photoanodes, which are capable of exhibiting high light-harvesting efficiency in dye-sensitized solar cells (DSSCs). Consequently, DSSCs based on 7 μm long optimized CBT arrays (0.05 M PTO), which are assembled with high density and high aspect-ratio NR branches, exhibit an impressive power conversion efficiency of 6.43% under AM 1.5G one sun illumination. The high performance can be attributed to the prominent light-harvesting efficiency, resulting from larger surface area and superior light-scattering capability.

  7. (THE ANTIBACTERIAL ACTIVITY OF VANADIUM- AND CHROMIUM DOPED TiO2-ANATASE

    Directory of Open Access Journals (Sweden)

    Hari Sutrisno

    2016-09-01

    Full Text Available Samples of vanadium- and -chromium doped TiO2-anatas have been conducted antibacterial activity against the bacteria Escherichia coli (E. Coli. The minimum kill concentration (MBC against the bacteria of E. Coli is determined by liquid dilution method. The antibacterial activity test of 0; 2.3; 3.3; 4.9% wt. vanadium doped TiO2-anatas and 0; 1.1; 3.9; 4.4% wt. chromium doped TiO2-anatas have been performed against bacteria of E. Coli in the absence of light (dark. The test results indicate that the presence of 3.3 and 4.9 in %wt. vanadium-TiO2-anatas are able to inhibit the growth of bacteria E. Coli, contrary all chromium doped TiO2-anatas are not able to inhibit the growth of bacteria of E. Coli.

  8. Porous (001)-faceted anatase TiO2 nanorice thin film for efficient dye-sensitized solar cell

    Science.gov (United States)

    Shah, Athar Ali; Umar, Akrajas Ali; Mat Salleh, Muhamad

    2016-01-01

    Anatase TiO2 structures with nanorice-like morphology and high exposure of (001) facet has been successfully synthesized on an ITO surface using ammonium Hexafluoro Titanate and Hexamethylenetetramine as precursor and capping agent, respectively, under a microwave-assisted liquid-phase deposition method. These anatase TiO2 nanoparticles were prepared within five minutes of reaction time by utilizing an inverter microwave system at a normal atmospheric pressure. The morphology and the size (approximately from 6 to 70 nm) of these nanostructures can be controlled. Homogenous, porous, 5.64 ± 0.002 μm thick layer of spongy-nanorice with facets (101) and (001) was grown on ITO substrate and used as a photo-anode in a dye-sensitized solar cell (DSSC). This solar cell device has emerged out with 4.05 ± 0.10% power conversion efficiency (PCE) and 72% of incident photon-to-current efficiency (IPCE) under AM1.5 G illumination.

  9. Porous (001-faceted anatase TiO2 nanorice thin film for efficient dye-sensitized solar cell

    Directory of Open Access Journals (Sweden)

    Shah Athar Ali

    2016-01-01

    Full Text Available Anatase TiO2 structures with nanorice-like morphology and high exposure of (001 facet has been successfully synthesized on an ITO surface using ammonium Hexafluoro Titanate and Hexamethylenetetramine as precursor and capping agent, respectively, under a microwave-assisted liquid-phase deposition method. These anatase TiO2 nanoparticles were prepared within five minutes of reaction time by utilizing an inverter microwave system at a normal atmospheric pressure. The morphology and the size (approximately from 6 to 70 nm of these nanostructures can be controlled. Homogenous, porous, 5.64 ± 0.002 μm thick layer of spongy-nanorice with facets (101 and (001 was grown on ITO substrate and used as a photo-anode in a dye-sensitized solar cell (DSSC. This solar cell device has emerged out with 4.05 ± 0.10% power conversion efficiency (PCE and 72% of incident photon-to-current efficiency (IPCE under AM1.5 G illumination.

  10. Graphene-Wrapped Anatase TiO2 Nanofibers as High-Rate and Long-Cycle-Life Anode Material for Sodium Ion Batteries

    Science.gov (United States)

    Yeo, Yeolmae; Jung, Ji-Won; Park, Kyusung; Kim, Il-Doo

    2015-09-01

    Anatase TiO2 has been suggested as a potential sodium anode material, but the low electrical conductivity of TiO2 often limits the rate capability, resulting in poor electrochemical properties. To address this limitation, we propose graphene-wrapped anatase TiO2 nanofibers (rGO@TiO2 NFs) through an effective wrapping of reduced graphene oxide (rGO) sheets on electrospun TiO2 NFs. To provide strong electrostatic interaction between the graphene oxide (GO) sheets and the TiO2 NFs, poly(allylamine hydrochloride) (PAH) was used to induce a positively charged TiO2 surface by the immobilization of the -NH3+ group and to promote bonding with the negatively charged carboxylic acid (-COO-) and hydroxyl (-O-) groups on the GO. A sodium anode electrode using rGO@TiO2 NFs exhibited a significantly improved initial capacity of 217 mAh g-1, high capacity retention (85% after 200 cycles at 0.2C), and a high average Coulombic efficiency (99.7% from the second cycle to the 200th cycle), even at a 5C rate, compared to those of pristine TiO2 NFs. The improved electrochemical performances stem from highly conductive properties of the reduced GO which is effectively anchored to the TiO2 NFs.

  11. Improving photoelectrochemical activity of dye sensitized solar cell by a bilayered electrode with an overlayer of mesoporous anatase TiO2

    Institute of Scientific and Technical Information of China (English)

    Jun Jiang; Jian Zhang; Feng Gu; Wei Shao; Chunzhong Li; Mengkai Lu

    2011-01-01

    For better performance of dye sensitized solar cells (DSSCs), a bilayer structured electrode was constructed by employing a mesoporous anatase TiO2 overlayer above a commercial P25 TiO2 nanoparticles underlayer. The mesoporous anatase TiO2, prepared through a facile surfactant-assisted sol-gel process,possessed large pore size and well inter-connected network structure, both beneficial for dye adsorption and electron transfer. The dye adsorption capability of the mesoporous TiO2 was nearly twice that of the P25 counterpart. In the electrode, the mesoporous TiO2 film enhanced both dye adsorption and lightharvest, to increase photocurrent (Jsc) from 12.32 to 14.78 mA/cm2. Compared to the single P25 TiO2 film,the synergy of the mesoporous TiO2 and the P25 TiO2 nanoparticle films in the electrode resulted in a 24% improvement in light-to-electricity conversion efficiency (η). This bilayered electrode provides an alternative approach for further developing a photovoltaic device with better cell performance.

  12. Direct Observation of Charge Separation on Anatase TiO2 Crystals with Selectively Etched {001} Facets.

    Science.gov (United States)

    Liu, Xiaogang; Dong, Guojun; Li, Shaopeng; Lu, Gongxuan; Bi, Yingpu

    2016-03-09

    Synchronous illumination X-ray photoelectron spectroscopy (SIXPS) was employed for the first time to directly identify the photogenerated charge separation and transfer on anatase TiO2 single-crystals with selectively etched {001} facets. More specifically, for the TiO2 crystals with intact {001} and {101} facets, most of photogenerated charge carriers rapidly recombined, and no evident electron-hole separation was detected. With selectively etching on {001} facets, high efficient charge separation via hole transfer to titanium and electron to oxygen was clearly observed. However, when the {001} facets were completely etched into a hollow structure, the recombination for photogenerated electron-hole pairs would dominate again. These demonstrations clearly reveal that the appropriate corrosion on {001} facets could facilitate more efficient electron-hole separation and transfer. As expected, the optimized TiO2 microcrystals with etched {001} facets could achieve a hydrogen generation rate of 74.3 μmol/h/g, which is nearly 7 times higher than the intact-TiO2 crystals.

  13. The annealing temperature dependence of anatase TiO2 thin films prepared by the electron-beam evaporation method

    Science.gov (United States)

    Taherniya, Atefeh; Raoufi, Davood

    2016-12-01

    In this paper, we report on titanium dioxide (TiO2) thin films deposited by an electron beam evaporation method on quartz glass substrates (15 × 15 × 2 mm3 in size), followed by post-annealing at 300 °C to 600 °C for an annealing time of up to 2 h. The substrate temperature during the film deposition was kept at 150 °C. The effect of post-growth thermal annealing on the structural and optical properties of TiO2 thin films were systematically studied as a function of annealing temperature. We found that the as-deposited TiO2 films are amorphous in structure, while the films started to crystallize into the anatase phase when annealed at temperatures ≥450 °C. An increase in annealing temperature results in a decrease of transmittance percentage and also in optical band gap energy. The refractive indices of the films were evaluated from the measured transmittance spectra using the envelope method. An increase in the refractive index with an increase of annealing temperature was observed.

  14. Preparation of anatase TiO2 with assistance of surfactant OP-10 and its electrochemical properties as an anode material for lithium ion batteries

    Institute of Scientific and Technical Information of China (English)

    YI Jin; TAN Chunlin; LI Weishan; LEI Jianfei; HAO Liansheng

    2010-01-01

    With the assistance of nonionic surfactant(OP-10)and surface-selective surfactant(CH3COOH),anatase TiO2 was prepared as an anode material for lithium ion batteries.The morphology,the crystal structure,and the electrochemical properties of the prepared anatase TiO2 were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),electrochemical impedance spectroscopy(EIS),and galvanostatic charge and discharge test.The result shows that the prepared anatase TiO2 has high discharge capacity and good cyclic stability.The maximum discharge capacity is 313 mAh·g-1,and there is no significant capacity decay from the second cycle.

  15. Photocatalytic degradation of acridine dyes using anatase and rutile TiO2.

    Science.gov (United States)

    Zubieta, C E; Messina, P V; Schulz, P C

    2012-06-30

    The adsorption and photodegradation of acridine orange (AO) and acriflavine (AF) dyes on two mesoporous titania crystalline phases, anatase and rutile, were experimentally studied. Anatase and rutile were characterized by nitrogen adsorption, electron scanning and transmission microscopy, and X-ray diffraction. The adsorption capacity of rutile was higher than that of anatase, while the reverse is observed for photodegradation of both dyes. The adsorption of AF on both adsorbents was higher than that of AO, which was related with the smaller size of AF molecules compared with those of AO, therefore the access of AF to the adsorption sites is favored.

  16. Diffusivity and Mobility of Adsorbed Water Layers at TiO2 Rutile and Anatase Interfaces

    Directory of Open Access Journals (Sweden)

    Niall J. English

    2015-12-01

    Full Text Available Molecular-dynamics simulations have been carried out to study diffusion of water molecules adsorbed to anatase-(101 and rutile-(110 interfaces at room temperature (300 K. The mean squared displacement (MSD of the adsorbed water layers were determined to estimate self-diffusivity therein, and the mobility of these various layers was gauged in terms of the “swopping” of water molecules between them. Diffusivity was substantially higher within the adsorbed monolayer at the anatase-(101 surface, whilst the anatase-(101 surface’s more open access facilitates easier contact of adsorbed water molecules with those beyond the first layer, increasing the level of dynamical inter-layer exchange and mobility of the various layers. It is hypothesised that enhanced ease of access of water to the anatase-(101 surface helps to rationalise experimental observations of its comparatively greater photo-activity.

  17. Photocatalytic Activity Enhancement of Anatase TiO2 by Using TiO

    OpenAIRE

    Zhenrui Chen; Wei Zhong; Zhutian Liang; Weiqian Li; Guannan He; Yinzhen Wang; Wei Li; Yuandong Xie; Qinyu He

    2014-01-01

    We employed high-energy ball-milling technique to fabricate TiO/TiO2 heterogeneous nanostructures. XRD proved the existence of TiO/TiO2 heterogeneous structures. SEM and HRTEM investigation evidenced that the mean particle size and mean grain size of the as-prepared samples are 23 nm and 13 nm, respectively. UV-Vis spectra exhibited that TiO has enhanced the visible light absorption of TiO2 and has changed the Eg of TiO2. UPS examination indicated that the electron work function (EWF) of TiO ...

  18. Electronic and optical properties study on Fesbnd B co-doped anatase TiO2

    Science.gov (United States)

    Li, Xuechao; Shi, Jianhao; Chen, Hao; Wan, Rundong; Leng, Chongyan; Lei, Ying

    2016-09-01

    We investigate the density of states and optical properties for Fe, 2B and (Fe, 2B) doped TiO2 with DFT calculations. The calculated results reveal mono-doping introduces midgap states which are half-occupied and easy to become the recombination centers of charge carriers, thus inhibiting the enhancement of photocatalystic activity. The coupling of 2p-3d states in the (Fe, 2B) compensated co-doped TiO2 makes gap states couple with the valence bands edge, thus greatly causing the band gap narrowing and higher visible light absorption. Moreover, the gap states cannot become recombination centers of the photoexcited carriers, thus promoting the separation of electron-hole pairs, prolonging the lifetime of carriers. The analysis of electron density indicates more electrons from Fe transfer to adjacent B, realizing the charge compensation and forming a stronger Fesbnd B bond. Therefore, the (Fe, 2B) compensated co-doped TiO2 exhibits the higher visible-light photocatalystic activity than those of pure and solely doped TiO2.

  19. Controlled formation of anatase and rutile TiO2 thin films by reactive magnetron sputtering

    NARCIS (Netherlands)

    Rafieian, Damon; Ogieglo, Wojciech; Savenije, Tom; Lammertink, Rob G.H.

    2015-01-01

    We discuss the formation of TiO2 thin films via DC reactive magnetron sputtering. The oxygen concentration during sputtering proved to be a crucial parameter with respect to the final film structure and properties. The initial deposition provided amorphous films that crystallise upon annealing to an

  20. Facile synthesis of carbon-mediated porous nanocrystallite anatase TiO2 for improved sodium insertion capabilities as an anode for sodium-ion batteries

    Science.gov (United States)

    Wu, Feng; Luo, Rui; Xie, Man; Li, Li; Zhang, Xiaoxiao; Zhao, Luzi; Zhou, Jiahui; Wang, KangKang; Chen, Renjie

    2017-09-01

    Porous carbon-mediated nanocrystallite anatase TiO2 composites are synthesized successfully via a simple dilatory hydrolysis-calcination method. The structural and morphological characterizations reveal that carbon-mediated TiO2 with a carbon content of 9.9 wt % (C2-TiO2) shows a combination of mesoporous and macroporous structures with a pore volume of 0.20 cm3 g-1 and surface area of 40.3 m2 g-1. Notably, C2-TiO2 delivered enhanced electrochemical performances of a high charge capacity of 259 mA h g-1 at 0.1 C and a high rate performance of 110 mA h g-1 after 150 cycles, even at 1 C. A significant decrease is also observed in the electrochemical impedance of the carbon-mediated samples, which explains superior electrochemical performance. Compared with the bare anatase TiO2 (B-TiO2), improved sodium storage capabilities of carbon-mediated samples are attributed to the participation of carbon to form a symbiotic structure with TiO2, which not only increases pore volume of the samples but serves as highly conductive network to provide a Na+ diffusion path during the insertion/de-insertion of sodium ions. All of these encouraging results suggest that carbon-mediated TiO2 has a great potential for improving sodium insertion capabilities with a facile and low-cost synthesis process.

  1. Low-temperature Preparation of Photocatalytic TiO2 Thin Films on Polymer Substrates by Direct Deposition from Anatase Sol

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Anatase TiO2 sol was synthesized under mild conditions (75C and ambient pressure) by hydrolysis of titaniumn-butoxide in abundant acidic aqueous solution and subsequent reflux to enhance crystallization. At room temperature and in ambient atmosphere, crystalline TiO2 thin films were deposited on polymethylmethacrylate (PMMA), SiO2-coated PMMA and SiO2-coated silicone rubber substrates from the as-prepared TiO2 sol by a dip-coating process. SiO2 layers prior to TiO2 thin films on polymer substrates could not only protect the substrates from the photocatalytic decomposition of the TiO2 thin films but also enhance the adhesion of the TiO2 thin films to the substrates. Field-emission type scanning electron microscope (FE-SEM) investigations revealed that the average particle sizes of the nanoparticles composing the TiO2 thin films were about 35~47 nm. The TiO2 thin films exhibited high photocatalytic activities in the degradation of reactive brilliant red dye X-3B in aqueous solution under aerated conditions. The preparation process of photocatalytic TiO2 thin films on the polymer substrates was quite simple and a low temperature route.

  2. Gold nanoparticles-immobilized, hierarchically ordered, porous TiO2 nanotubes for biosensing of glutathione.

    Science.gov (United States)

    Mers, Sv Sheen; Kumar, Elumalai Thambuswamy Deva; Ganesh, V

    2015-01-01

    Glutathione (GSH) is vital for several functions of our human body such as neutralization of free radicals and reactive oxygen compounds, maintaining the active forms of vitamin C and E, regulation of nitric oxide cycle, iron metabolism, etc. It is also an endogenous antioxidant in most of the biological reactions. Given the importance of GSH, a simple strategy is proposed in this work to develop a biosensor for quantitative detection of GSH. This particular biosensor comprises of gold nanoparticles (Au NPs)-immobilized, hierarchically ordered titanium dioxide (TiO2) porous nanotubes. Hexagonally arranged, honeycomb-like nanoporous tubular TiO2 electrodes are prepared by using a simple electrochemical anodization process by applying a constant potential of 30 V for 24 hours using ethylene glycol consisting of ammonium fluoride as an electrolytic medium. Structural morphology and crystalline nature of such TiO2 nanotubes are analyzed using field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). Interestingly, nanocomposites of TiO2 with Au NPs is prepared in an effort to alter the intrinsic properties of TiO2, especially tuning of its band gap. Au NPs are prepared by a well-known Brust and Schiffrin method and are immobilized onto TiO2 electrodes which act as a perfect electrochemical sensing platform for GSH detection. Structural characterization and analysis of these modified electrodes are performed using FESEM, XRD, and UV-visible spectroscopic studies. GSH binding events on Au NPs-immobilized porous TiO2 electrodes are monitored by electrochemical techniques, namely, cyclic voltammetry (CV) and chronoamperometry (CA). Several parameters such as sensitivity, selectivity, stability, limit of detection, etc are investigated. In addition, Au NPs dispersed in aqueous medium are also explored for naked-eye detection of GSH using UV-visible spectroscopy in order to compare the performance of the proposed sensor. Our studies clearly indicate

  3. Where Do Photogenerated Holes Go in Anatase:Rutile TiO2? A Transient Absorption Spectroscopy Study of Charge Transfer and Lifetime.

    Science.gov (United States)

    Kafizas, Andreas; Wang, Xiuli; Pendlebury, Stephanie R; Barnes, Piers; Ling, Min; Sotelo-Vazquez, Carlos; Quesada-Cabrera, Raul; Li, Can; Parkin, Ivan P; Durrant, James R

    2016-02-11

    Anatase:rutile TiO2 junctions are often shown to be more photocatalytically active than anatase or rutile alone, but the underlying cause of this improvement is not fully understood. Herein, we employ transient absorption spectroscopy to study hole transfer across the anatase:rutile heterojunction in films as a function of phase composition. By exploiting the different signatures in the photoinduced absorption of trapped charges in anatase and rutile, we were able to separately track the yield and lifetime of holes in anatase and rutile sites within phase composites. Photogenerated holes transfer from rutile to anatase on submicrosecond time scales. This hole transfer can significantly increase the anatase hole yield, with a 20:80 anatase:rutile composite showing a 5-fold increase in anatase holes observed from the microsecond. Hole transfer does not result in an increase in charge-carrier lifetime, where an intermediate recombination dynamic between that of pure anatase (t1/2 ≈ 0.5 ms) and rutile (t1/2 ≈ 20 ms) is found in the anatase:rutile junction (t1/2 ≈ 4 ms). Irrespective of what the formal band energy alignment may be, we demonstrate the importance of trap-state energetics for determining the direction of photogenerated charge separation across heterojunctions and how transient absorption spectroscopy, a method that can specifically track the migration of trapped charges, is a useful tool for understanding this behavior.

  4. Improved electron-hole separation and migration in anatase TiO2 nanorod/reduced graphene oxide composites and their influence on photocatalytic performance.

    Science.gov (United States)

    Žerjav, Gregor; Arshad, Muhammad Shahid; Djinović, Petar; Junkar, Ita; Kovač, Janez; Zavašnik, Janez; Pintar, Albin

    2017-03-30

    The as-synthesized TiO2 nanorods a-TNR (amorphous TiO2 layer covering the crystalline anatase TiO2 core) and TNR (fully crystalline anatase TiO2) were decorated with reduced graphene oxide (rGO) to synthesize two series of TiO2 + rGO composites with different nominal loadings of GO (from 4 to 20 wt%). The structural, surface and electronic properties of the obtained TiO2 + rGO composites were analyzed and correlated to their performance in the photocatalytic oxidation of aqueous bisphenol A solution. X-ray photoelectron spectroscopy (XPS) analyses revealed that charge separation in TiO2 + rGO composites is improved due to the perfect matching of TiO2 and rGO valence band maxima (VBM). Cyclic voltammetry (CV) experiments revealed that the peak-to-peak separations (ΔEp) are the lowest and the oxidation current densities are the highest for composites with a nominal 10 wt% GO content, meaning that it is much easier for the charge carriers to percolate through the solid, resulting in improved charge migration. Due to the high charge carrier mobility in rGO and perfect VBM matching between TiO2 and rGO, the electron-hole recombination in composites was suppressed, resulting in more electrons and holes being able to participate in the photocatalytic reaction. rGO amounts above 10 wt% decreased the photocatalytic activity; thus, it is critical to optimize its amount in the TiO2 + rGO composites for achieving the highest photocatalytic activity. BPA degradation rates correlated completely with the results of the CV measurements, which directly evidenced improved charge separation and migration as the crucial parameters governing photocatalysis.

  5. Growth of anatase and rutile phase TiO2 nanoparticles using pulsed laser ablation in liquid: Influence of surfactant addition and ablation time variation

    Science.gov (United States)

    Chaturvedi, Amita; Joshi, M. P.; Mondal, P.; Sinha, A. K.; Srivastava, A. K.

    2017-02-01

    Titanium dioxide (TiO2) nanoparticles were grown using nanosecond pulsed laser ablation of Ti target in DI water and in 0.001 M sodium dodecyl sulfate (SDS) surfactant aqueous solution. Growth was carried out with varying ablation times i. e. 30 min, 60 min and 90 min. The objective of our study was to investigate the influence of variations in liquid ambience conditions on the growth of the nanoparticles in a pulsed laser ablation in liquid (PLAL) process. Size, composition and optical properties of the grown TiO2 nanoparticles were investigated using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), optical absorption, photoluminescence (PL) spectroscopy and X-ray diffraction (XRD) studies. The obtained nanoparticles of TiO2 were found almost spherical in shape and polycrystalline in nature in both the liquid mediums i.e. DI water and aqueous solution of surfactant. Nanoparticles number density was also found to increase with increasing ablation time in both the liquid mediums. However crystalline phase of the grown TiO2 nanoparticles differs with the change in liquid ambience conditions. Selected area electron diffraction (SAED), PL and XRD studies suggest that DI water ambience is favorable for the growth of anatase phase TiO2 nanoparticles for all ablation times. While Surfactant added water ambience is favorable for the growth of rutile phase TiO2 nanoparticles but for shorter ablation times of 30 min and 60 min only, for longer ablation time of 90 min anatase phase was also observed along with the rutile phase TiO2 nanoparticles. The formation of anatase phase in DI water and rutile and anatase phase in aqueous solution of surfactant is explained on the basis of varying thermodynamic conditions with the two different liquid ambiences and different ablation times.

  6. DFT study with inclusion of the Grimme potential on anatase TiO2: structure, electronic, and vibrational analyses.

    Science.gov (United States)

    Albuquerque, Anderson R; Garzim, Marcos L; Santos, Iêda M G dos; Longo, Valeria; Longo, Elson; Sambrano, Julio R

    2012-11-29

    Periodic DFT/B3LYP calculations for TiO(2) anatase bulk were carried out including semiempirical dispersive interactions (DFT-D2) to pure Khon-Sham DFT energy. From this standard methodology, van der Waals (vdW) radii were optimized to 1.4214 Å for titanium and 1.3420 Å for oxygen centers in order to achieve a better structural description. The results from this approach (here named DFT/B3LYP-D*) showed a better description for lattice constants, vibrational IR and Raman, energy band gaps, and bulk modulus than default DFT/B3LYP and DFT/B3LYP-D. The dispersion correction showed more reliable results and was necessary to achieve a good agreement with reported single crystal results, without new formalism or additional computational cost.

  7. Strong out-of-plane magnetic anisotropy in ion irradiated anatase TiO2 thin films

    Directory of Open Access Journals (Sweden)

    M. Stiller

    2016-12-01

    Full Text Available The temperature and field dependence of the magnetization of epitaxial, undoped anatase TiO2 thin films on SrTiO3 substrates was investigated. Low-energy ion irradiation was used to modify the surface of the films within a few nanometers, yet with high enough energy to produce oxygen and titanium vacancies. The as-prepared thin film shows ferromagnetism which increases after irradiation with low-energy ions. An optimal and clear magnetic anisotropy was observed after the first irradiation, opposite to the expected form anisotropy. Taking into account the experimental parameters, titanium vacancies as di-Frenkel pairs appear to be responsible for the enhanced ferromagnetism and the strong anisotropy observed in our films. The magnetic impurities concentrations was measured by particle-induced X-ray emission with ppm resolution. They are ruled out as a source of the observed ferromagnetism before and after irradiation.

  8. Acetylene hydrogenation on anatase TiO2(101) supported Pd4 cluster: oxygen deficiency effect.

    Science.gov (United States)

    Yang, Jie; Cao, Li-Xin; Wang, Gui-Chang

    2012-07-01

    Acetylene hydrogenation on both the perfect and oxygen defective anatase TiO(2)(101) surfaces supported Pd(4) cluster has been studied using density functional theory calculations with a Hubbard U correction (DFT + U). The adsorbed Pd(4) cluster on the perfect surface prefers to form a tetrahedral structure, while it likely moves to the oxygen defective site to form a distorted tetrahedral structure by removing a bridging oxygen atom. For the defective surface, it exhibits a stronger ability to capture Pd(4) cluster as charge transfer is significantly performed due to the oxygen deficiency. Moreover, it is found that the oxygen defective surface shows higher activity for acetylene hydrogenation, and the possible reason may lie in the weaker adsorption strength between the Pd cluster and the adsorbed molecules on the defective surface as compared to the case on the perfect surface.

  9. Oxidative trends of TiO2—hole trapping at anatase and rutile surfaces

    DEFF Research Database (Denmark)

    Zawadzki, Pawel; Laursen, Anders B.; Jacobsen, Karsten Wedel;

    2012-01-01

    position is dependent on the type of surface termination. Such variations in hole state energies can lead to differences in photocatalytic activity among rutile and anatase surface facets. We find that the calculated hole state energies correlate with photo-deposition and photo-etching rates. We...

  10. Effect of anatase nanoparticles (TiO2) on parsley seed germination (Petroselinum crispum) in vitro.

    Science.gov (United States)

    Dehkourdi, Elahe Hashemi; Mosavi, Mousa

    2013-11-01

    Nano priming is a new method for the increase of seedling vigor and improvement of germination percentage and seedling growth. The experiments to evaluate the effect of different concentrations of nano-anatase on germination parameters of parsley as a completely randomized design with five replications were performed in a tissue culture laboratory of the Department of Horticulture, Shahid Chamran University of Ahvaz. In addition, nano-anatase at four concentrations (10, 20, 30, and 40 mg/ml) was added to the Murashige and Skoog medium. At the end of the experiment, the percentage of germination, germination rate index, root and shoot length, fresh weight of seedlings, vigor index, and chlorophyll content were evaluated. The results showed that an increase in the concentration of nano-anatase caused a significant increase in the percentage of germination, germination rate index, root and shoot length, fresh weight, vigor index, and chlorophyll content of seedlings. The best concentration of nano-anatase was 30 mg/ml.

  11. Optimisation of anatase TiO2 thin film growth on LaAlO3(0 0 1) using pulsed laser deposition

    Science.gov (United States)

    Krupski, K.; Sanchez, A. M.; Krupski, A.; McConville, C. F.

    2016-12-01

    Optimisation of epitaxial anatase TiO2 thin films grown on LaAlO3(0 0 1) substrates was performed using ultra-high vacuum based pulsed laser deposition (PLD) and studied by in-situ reflection high-energy electron diffraction (RHEED). In addition, ex-situ X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning transmission electron microscopy (STEM) were performed to characterise the bulk properties of these thin films. The deposited TiO2 thin film is demonstrated to have anatase phase and bonded directly to the LaAlO3(0 0 1) substrate. In a separate ultra-high vacuum system low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) measurements were performed and a well-ordered two-domain (1 × 4) and (4 × 1) reconstruction of anatase surface was observed. Analysis of the STM measurements indicates the coexistence of atomic steps of both 2.5 Å and 5.0 Å, confirming the existence of two TiO2 domains. The atomic resolution STEM images reveal that the TiO2/LaAlO3 interface to be terminated with LaO layer and that the anatase-TiO2 reconstruction was found to be stable during the film growth.

  12. Chemisorption of CH2O on N-doped TiO2 anatase nanoparticle as modified nanostructure media: A DFT study

    Science.gov (United States)

    Abbasi, Amirali; Sardroodi, Jaber Jahanbin; Ebrahimzadeh, Alireza Rastkar

    2016-12-01

    The structural and electronic properties of N-doped TiO2 anatase nanoparticles and their effects on the adsorption of formaldehyde molecule have been investigated using the density functional theory computations. Given the need to better understand the behavior of the adsorbed CH2O molecule on the anatase nanoparticle, we report results of density functional theory studies of the N-doped nanoparticles, as well as complex systems consisting of the CH2O molecule bound to a TiO2 nanoparticle. N-doped nanoparticle was obtained by substitution of nitrogen atom of TiO2 instead of oxygen atom. Adsorptions of the CH2O molecule on the dangling oxygen atom, twofold coordinated oxygen atom and doped nitrogen atom sites of the pristine and N-doped anatase nanoparticles were investigated. The results presented include structural parameters such as adsorption energies, bond lengths and bond angles and electronic properties such as density of states, spin distribution densities and molecular orbitals. It was found that the adsorption of the CH2O molecule on the dangling oxygen of considered N-doped TiO2 anatase nanoparticles is energetically more favorable than the adsorption on the undoped ones. It means a more stable configuration compared to the undoped nanoparticle adsorption, but not as stable as the CH2O adsorption on the doped nitrogen site of N-doped nanoparticles.

  13. Electronic hole transfer in rutile and anatase TiO2: Effect of a delocalization error in the density functional theory on the charge transfer barrier height

    DEFF Research Database (Denmark)

    Zawadzki, Pawel; Rossmeisl, Jan; Jacobsen, Karsten Wedel

    2011-01-01

    where charge localization is strongly coupled to lattice distortion. As an example we calculate the adiabatic PES for the hole transfer process in rutile and anatase TiO2. (Semi) local DFT leads to qualitatively wrong, barrierless curves. Removal of the nonlinearity improves the PES shape and allows us...

  14. Correlation of the depletion layer with the Helmholtz layer in the anatase TiO2-H2O interface via molecular dynamics simulations.

    Science.gov (United States)

    Sang, Lixia; Zhang, Yudong; Wang, Jun; Zhao, Yangbo; Chen, Yi-Tung

    2016-06-01

    Molecular dynamics simulations have been conducted to study the interaction between anatase TiO2(001), (100), and (101) surfaces and water at room temperature. The dynamic interfacial structure and properties of water on anatase TiO2 surfaces are obtained by analyzing the water density, the diffusion coefficient of water, the surface charge distribution, electric fields and the electrostatic potential distribution. The simulation results have revealed that a highly-ordered water layer structure can be formed near to the anatase TiO2 surface and have also given the Helmholtz layer width and potential drop at the water-TiO2 interface. By correlating the Helmholtz layer with the depletion layer, the depletion layer widths of three surfaces (001), (100), and (101) have been calculated as 474 Å, 237 Å and 99 Å, respectively. The resulting order of the photoelectrochemical activity of the anatase TiO2 surfaces is (001) > (100) > (101), which is consistent with the experimental results. This study may provide a useful correlation of the depletion layer with the Helmholtz layer based on simulations results for the prediction of the behavior and the control of photon-energy conversion devices.

  15. Electronic Structures of S/C-Doped TiO2 Anatase (101 Surface: First-Principles Calculations

    Directory of Open Access Journals (Sweden)

    Qili Chen

    2014-01-01

    Full Text Available The electronic structures of sulfur (S or carbon (C-doped TiO2 anatase (101 surfaces have been investigated by density functional theory (DFT plane-wave pseudopotential method. The general gradient approximation (GGA + U (Hubbard coefficient method has been adopted to describe the exchange-correlation effects. All the possible doping situations, including S/C dopants at lattice oxygen (O sites (anion doping, S/C dopants at titanium (Ti sites (cation doping, and the coexisting of anion and cation doping, were studied. By comparing the formation energies, it was found that the complex of anion and cation doping configuration forms easily in the most range of O chemical potential for both S and C doping. The calculated density of states for various S/C doping systems shows that the synergistic effects of S impurities at lattice O and Ti sites lead a sharp band gap narrowing of 1.35 eV for S-doped system comparing with the pure TiO2 system.

  16. Photocatalytic Anatase TiO2 Thin Films on Polymer Optical Fiber Using Atmospheric-Pressure Plasma.

    Science.gov (United States)

    Baba, Kamal; Bulou, Simon; Choquet, Patrick; Boscher, Nicolas D

    2017-04-06

    Due to the undeniable industrial advantages of low-temperature atmospheric-pressure plasma processes, such as low cost, low temperature, easy implementation, and in-line process capabilities, they have become the most promising next-generation candidate system for replacing thermal chemical vapor deposition or wet chemical processes for the deposition of functional coatings. In the work detailed in this article, photocatalytic anatase TiO2 thin films were deposited at a low temperature on polymer optical fibers using an atmospheric-pressure plasma process. This method overcomes the challenge of forming crystalline transition metal oxide coatings on polymer substrates by using a dry and up-scalable method. The careful selection of the plasma source and the titanium precursor, i.e., titanium ethoxide with a short alkoxy group, allowed the deposition of well-adherent, dense, and crystalline TiO2 coatings at low substrate temperature. Raman and XRD investigations showed that the addition of oxygen to the precursor's carrier gas resulted in a further increase of the film's crystallinity. Furthermore, the films deposited in the presence of oxygen exhibited a better photocatalytic activity toward methylene blue degradation assumedly due to their higher amount of photoactive {101} facets.

  17. Hierarchically multifunctional K-OMS-2/TiO2/Fe3O4 heterojunctions for the photocatalytic oxidation of humic acid under solar light irradiation.

    Science.gov (United States)

    Zhang, Tong; Yan, Xiaoli; Sun, Darren Delai

    2012-12-01

    A multifunctional heterojunctioned K-OMS-2/TiO(2)/Fe(3)O(4) (KTF) nanocomposite was successfully synthesized using a combination of hydrothermal and co-precipitation techniques. The resultant sample was characterized by XRD, FESEM, TEM, N(2) adsorption, XPS and VSM. Its photocatalytic activity was demonstrated in the photocatalytic degradation of humic acid (HA). Morphology characterization showed the hierarchical structure of the synthesized material, and XRD results revealed that both the rutile and anatase TiO(2) structures are present in the sample. The average pore diameters and BET surface area of the synthesized KTF heterojunctions were 40 nm and 134.42 m(2)/g, respectively. XPS spectra confirmed the presence of Fe(3)O(4) and TiO(2) in the synthesized material, and the valences of Mn were kept at +3 and +4 after the grafting of Fe(3)O(4) and TiO(2). The synthesized material showed good magnetic response and photocatalytic activity under simulated solar light irradiation, and 85.7% of HA was decomposed after 120 min in the presence of KTF nanocomposites. The reusability study suggested that the magnetic recovered material was stable enough for multiple recycling usages, verifying its potential application in water purification.

  18. Influence of cerium ions on the anatase-rutile phase transition of TiO2 prepared by sol-gel auto-igniting synthesis

    Institute of Scientific and Technical Information of China (English)

    YAN Qingzhi; SU Xintai; ZHOU Yanping; GE Changchun

    2005-01-01

    The anatase-rutile phase transformation of TiO2 doped cerium up to 5 mol% was studied by X-ray diffraction and X-ray photoelectron spectroscopy. The samples were prepared by sol-gel auto-igniting synthesis process from a TiO(NO3)2-Ce(NO3)2-NH4NO3-citric acid complex compound system. The combusted amorphous powders were calcined at different temperatures. Significant structural changes were observed during the various stages of the phase transformation.It was concluded that at low dopant contents, cerium ions were incorporated into the TiO2 structure, and the anatase phase was stabilized; but at larger amounts, part of the dopant was segregated on the surface of TiO2 and the rutile formation was accelerated at elevated calcination temperature.

  19. Radially oriented mesoporous TiO2 microspheres with single-crystal-like anatase walls for high-efficiency optoelectronic devices.

    Science.gov (United States)

    Liu, Yong; Che, Renchao; Chen, Gang; Fan, Jianwei; Sun, Zhenkun; Wu, Zhangxiong; Wang, Minghong; Li, Bin; Wei, Jing; Wei, Yong; Wang, Geng; Guan, Guozhen; Elzatahry, Ahmed A; Bagabas, Abdulaziz A; Al-Enizi, Abdullah M; Deng, Yonghui; Peng, Huisheng; Zhao, Dongyuan

    2015-05-01

    Highly crystalline mesoporous materials with oriented configurations are in demand for high-performance energy conversion devices. We report a simple evaporation-driven oriented assembly method to synthesize three-dimensional open mesoporous TiO2 microspheres with a diameter of ~800 nm, well-controlled radially oriented hexagonal mesochannels, and crystalline anatase walls. The mesoporous TiO2 spheres have a large accessible surface area (112 m(2)/g), a large pore volume (0.164 cm(3)/g), and highly single-crystal-like anatase walls with dominant (101) exposed facets, making them ideal for conducting mesoscopic photoanode films. Dye-sensitized solar cells (DSSCs) based on the mesoporous TiO2 microspheres and commercial dye N719 have a photoelectric conversion efficiency of up to 12.1%. This evaporation-driven approach can create opportunities for tailoring the orientation of inorganic building blocks in the assembly of various mesoporous materials.

  20. Comparison of catalytic activities for photocatalytic and sonocatalytic degradation of methylene blue in present of anatase TiO2-CNT catalysts.

    Science.gov (United States)

    Zhang, Kan; Zhang, Feng Jun; Chen, Ming Liang; Oh, Won Chun

    2011-05-01

    Anatase TiO(2)-CNT catalysts with high specific surface areas were prepared by depositing TiO(2) particles on the surface of carbon nanotubes (CNTs) using a modified sol-gel technique. These catalysts prepared with different amounts of CNTs were characterized by nitrogen adsorption, Fourier Transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD), Raman spectroscopy, energy dispersive X-ray (EDX) and ultraviolet-visible (UV-Vis) spectroscopy. The catalytic activity of the anatase TiO(2)-CNT catalysts was assessed by examining the degradation of methylene blue (MB) from model aqueous solutions as a probe reaction under visible light and ultrasonic irradiation. The synergistic effect of the greater surface area and catalytic activities of the composite catalysts was examined in terms of the strong adsorption ability and interphase interaction by comparing the different amounts and roles of CNTs in the catalysts.

  1. Atomic Layer Deposition of p-Type Epitaxial Thin Films of Undoped and N-Doped Anatase TiO2.

    Science.gov (United States)

    Vasu, K; Sreedhara, M B; Ghatak, J; Rao, C N R

    2016-03-01

    Employing atomic layer deposition, we have grown p-type epitaxial undoped and N-doped anatase TiO2(001) thin films on c-axis Al2O3 substrate. From X-ray diffraction and transmission electron microscopy studies, crystallographic relationships between the film and the substrate are found to be (001)TiO2//(0001)Al2O3 and [1̅10]TiO2//[011̅0]Al2O3. N-doping in TiO2 thin films enhances the hole concentration and mobility. The optical band gap of anatase TiO2 (3.23 eV) decreases to 3.07 eV upon N-doping. The epitaxial films exhibit room-temperature ferromagnetism and photoresponse. A TiO2-based homojunction diode was fabricated with rectification from the p-n junction formed between N-doped p-TiO2 and n-TiO2.

  2. Photoanode based on chain-shaped anatase TiO2 nanorods for high-efficiency dye-sensitized solar cells.

    Science.gov (United States)

    Rui, Yichuan; Li, Yaogang; Wang, Hongzhi; Zhang, Qinghong

    2012-10-01

    Anatase TiO(2) nanorods with large specific surface areas and high crystallinity have been synthesized by surfactant-free hydrothermal treatment of water-soluble peroxotitanium acid (PTA). X-ray diffraction and TEM analysis showed that all TiO(2) nanorods derived from PTA in different hydrothermal processes were in the anatase phase, and high aspect ratio TiO(2) nanorods with chain-shaped structures were formed at 150 °C for 24 h by oriented growth. The nanorods were fabricated as photoanodes for high-efficiency dye-sensitized solar cells (DSSCs). DSSCs fabricated from the chain-shaped TiO(2) nanorods gave a highest short-circuit current density of 14.8 mA cm(-2) and a maximum energy conversion efficiency of 7.28 %, as a result of the presence of far fewer surface defects and grain boundaries than are present in commercial P25 TiO(2) nanoparticles. Electrochemical impedance spectroscopy also confirmed that DSSCs based on the TiO(2) nanorods have enhanced electron transport properties and a long electron lifetime. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Photocatalytic antibacterial effects on TiO2-anatase upon UV-A and UV-A/VIS threshold irradiation.

    Science.gov (United States)

    Wu, Yanyun; Geis-Gerstorfer, Jürgen; Scheideler, Lutz; Rupp, Frank

    2016-01-01

    Photocatalysis mediated by the anatase modification of titanium dioxide (TiO2) has shown antibacterial effects in medical applications. The aim of this study was to investigate the possibility of expanding the excitation wavelengths for photocatalytic antibacterial effects from ultraviolet (UV) into the visible light range. After deposition of salivary pellicle and adhesion of Streptococcus gordonii on anatase, different irradiation protocols were applied to induce photocatalysis: ultraviolet A (UV-A) > 320 nm; ultraviolet/visible (UV-A/VIS) light > 380 nm and > 390 nm; and VIS light 400-410 nm. A quartz crystal microbalance with dissipation (QCM-D) tests and microscopic examination were used to observe the photoinduced antibacterial effects. Salivary pellicle could be photocatalytically decomposed under all irradiation protocols. In contrast, effective photocatalytic attack of bacteria could be observed by UV-A as well as by UV-A/VIS at 380 nm < λ < 390 nm only. Wavelengths above 380 nm show promise for in situ therapeutic antifouling applications.

  4. Supercritical Propanol-Water Synthesis and Comprehensive Size Characterisation of Highly Crystalline anatase TiO 2 Nanoparticles

    Science.gov (United States)

    Hald, Peter; Becker, Jacob; Bremholm, Martin; Pedersen, Jan S.; Chevallier, Jacques; Iversen, Steen B.; Iversen, Bo B.

    2006-08-01

    Highly crystalline anatase TiO 2 nanoparticles have been synthesised in less than 1 min in a supercritical propanol-water mixture using a continuous flow reactor. The synthesis parameter space ( T, P, concentration) has been explored and the average particle size can be accurately controlled within 10-18 nm with narrow size distributions (2-3 nm). At subcritical conditions amorphous products are obtained, whereas a broad range of T and P in the supercritical regime gives 11-14 nm particles. At high temperature and pressure, the particles size increase to 18 nm. The nanoparticles have been extensively characterised with powder X-ray diffraction (PXRD), transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) with excellent agreement on size and size distribution parameters. The SAXS analysis suggests disk-shaped particles with diameters that are approximately double the height. For comparison, a series of conventional autoclave sol-gel syntheses have been carried out. These also produce phase-pure anatase nanoparticles, but with much broader size distributions and at much longer synthesis times (hours). The study demonstrates that synthesis in supercritical fluids is a very promising method for manipulating the size and size distribution of nanoparticles, thus removing one of the key limitations in many applications of nanomaterials.

  5. 3D hierarchical rutile TiO2 and metal-free organic sensitizer producing dye-sensitized solar cells 8.6% conversion efficiency.

    Science.gov (United States)

    Lin, Jianjian; Heo, Yoon-Uk; Nattestad, Andrew; Sun, Ziqi; Wang, Lianzhou; Kim, Jung Ho; Dou, Shi Xue

    2014-08-29

    Three-dimensional (3D) hierarchical nanoscale architectures comprised of building blocks, with specifically engineered morphologies, are expected to play important roles in the fabrication of 'next generation' microelectronic and optoelectronic devices due to their high surface-to-volume ratio as well as opto-electronic properties. Herein, a series of well-defined 3D hierarchical rutile TiO2 architectures (HRT) were successfully prepared using a facile hydrothermal method without any surfactant or template, simply by changing the concentration of hydrochloric acid used in the synthesis. The production of these materials provides, to the best of our knowledge, the first identified example of a ledgewise growth mechanism in a rutile TiO2 structure. Also for the first time, a Dye-sensitized Solar Cell (DSC) combining a HRT is reported in conjunction with a high-extinction-coefficient metal-free organic sensitizer (D149), achieving a conversion efficiency of 5.5%, which is superior to ones employing P25 (4.5%), comparable to state-of-the-art commercial transparent titania anatase paste (5.8%). Further to this, an overall conversion efficiency 8.6% was achieved when HRT was used as the light scattering layer, a considerable improvement over the commercial transparent/reflector titania anatase paste (7.6%), a significantly smaller gap in performance than has been seen previously.

  6. Thermodynamically driven one-dimensional evolution of anatase TiO2 nanorods: one-step hydrothermal synthesis for emerging intrinsic superiority of dimensionality.

    Science.gov (United States)

    Chen, Jiazang; Yang, Hong Bin; Miao, Jianwei; Wang, Hsin-Yi; Liu, Bin

    2014-10-29

    In photoelectrochemical cells, there exists a competition between transport of electrons through the porous semiconductor electrode toward the conducting substrate and back-reaction of electrons to recombine with oxidized species on the semiconductor-electrolyte interface, which determines the charge collection efficiency and is strongly influenced by the density and distribution of electronic states in band gap and architectures of the semiconductor electrodes. One-dimensional (1D) anatase TiO2 nanostructures are promising to improve charge transport in photoelectrochemical devices. However, the conventional preparation of 1D anatase nanostructures usually steps via a titanic acid intermediate (e.g., H2Ti3O7), which unavoidably introduces electronic defects into the host lattice, resulting in undesired shielding of the intrinsic role of dimensionality. Here, we manage to promote the 1D growth of anatase TiO2 nanostructures by adjusting the growth kinetics, which allows us to grow single-crystalline anatase TiO2 nanorods through a one-step hydrothermal reaction. The synthesized anatase nanorods possess a lower density of trap states and thus can simultaneously facilitate the diffusion-driven charge transport and suppress the electron recombination. Moreover, the electronically boundary free nanostructures significantly enhance the trap-free charge diffusion coefficient of the anatase nanorods, which enables the emergence of the intrinsic superiority of dimensionality. By virtue of these merits, the anatase nanorods synthesized in this work take obvious advantages over the conventional anatase counterparts in photoelectrochemical systems (e.g., dye-sensitized solar cells) by showing more efficient charge transport and collection and higher energy conversion efficiency.

  7. Synergistic effect of nanocavities in anatase TiO2 nanobelts for photocatalytic degradation of methyl orange dye in aqueous solution.

    Science.gov (United States)

    Praveen Kumar, D; Lakshmana Reddy, N; Karthikeyan, M; Chinnaiah, N; Bramhaiah, V; Durga Kumari, V; Shankar, M V

    2016-09-01

    Nanocavities are empty voids exposed on the surface of one dimensional TiO2 nanostructured material. Often, they exhibited beneficial optical and electrical properties that leads to efficient photocatalytic reactions. This study reports formation of nanocavities on anatase TiO2 nanobelts (TNB) through dehydroxylation of surface hydroxyl groups during calcination process (350-600°C). The morphological and crystal structure analysis of TNB-500, -550 and -600 displayed the nanobelts shape with high density of nano-size cavities and increase in average diameter with calcination temperature. The SAED patterns confirm the anatase TiO2 phase. The enhanced light absorption properties of biphasic anatase/TiO2-B and anatase TiO2 than H2Ti3O7 are attributed to transformation of crystal structure upon calcination process. The catalytic activity was evaluated for degradation of methyl orange dye in aqueous solution under solar light irradiation. The reaction variables such as calcination temperature, amount of catalyst and pH of the methyl orange dye solution were studied and discussed in detail. Under optimal experimental conditions TNB-550 photocatalyst displayed highest degradation performance about 8 folds higher than H2Ti3O7. The high performance is explained as due to synergistic properties of one dimensional anatase TiO2 with high density of nanocavities leading to one dimensional transfer of electrons and high absorption co-efficient in UV-A spectrum are suitable for efficient red-ox reactions. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. Synthesis and Characterization of Hierarchical Structured TiO2 Nanotubes and Their Photocatalytic Performance on Methyl Orange

    Directory of Open Access Journals (Sweden)

    Kai Liu

    2015-01-01

    Full Text Available Hierarchical structured TiO2 nanotubes were prepared by mechanical ball milling of highly ordered TiO2 nanotube arrays grown by electrochemical anodization of titanium foil. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, specific surface area analysis, UV-visible absorption spectroscopy, photocurrent measurement, photoluminescence spectra, electrochemical impedance spectra, and photocatalytic degradation test were applied to characterize the nanocomposites. Surface area increased as the milling time extended. After 5 h ball milling, TiO2 hierarchical nanotubes exhibited a corn-like shape and exhibited enhanced photoelectrochemical activity in comparison to commercial P25. The superior photocatalytic activity is suggested to be due to the combined advantages of high surface area of nanoparticles and rapid electron transfer as well as collection of the nanotubes in the hierarchical structure. The hierarchical structured TiO2 nanotubes could be applied into flexible applications on solar cells, sensors, and other photoelectrochemical devices.

  9. Gold nanoparticles-immobilized, hierarchically ordered, porous TiO2 nanotubes for biosensing of glutathione

    Directory of Open Access Journals (Sweden)

    Sheen Mers SV

    2015-10-01

    Full Text Available SV Sheen Mers,1,2 Elumalai Thambuswamy Deva Kumar,1 V Ganesh1,2 1Electrodics and Electrocatalysis (EEC Division, Council of Scientific and Industrial Research–Central Electrochemical Research Institute (CSIR–CECRI, Karaikudi, Tamil Nadu, India; 2Academy of Scientific and Innovative Research (AcSIR, New Delhi, India Abstract: Glutathione (GSH is vital for several functions of our human body such as neutralization of free radicals and reactive oxygen compounds, maintaining the active forms of vitamin C and E, regulation of nitric oxide cycle, iron metabolism, etc. It is also an endogenous antioxidant in most of the biological reactions. Given the importance of GSH, a simple strategy is proposed in this work to develop a biosensor for quantitative detection of GSH. This particular biosensor comprises of gold nanoparticles (Au NPs-immobilized, hierarchically ordered titanium dioxide (TiO2 porous nanotubes. Hexagonally arranged, honeycomb-like nanoporous tubular TiO2 electrodes are prepared by using a simple electrochemical anodization process by applying a constant potential of 30 V for 24 hours using ethylene glycol consisting of ammonium fluoride as an electrolytic medium. Structural morphology and crystalline nature of such TiO2 nanotubes are analyzed using field emission scanning electron microscope (FESEM and X-ray diffraction (XRD. Interestingly, nanocomposites of TiO2 with Au NPs is prepared in an effort to alter the intrinsic properties of TiO2, especially tuning of its band gap. Au NPs are prepared by a well-known Brust and Schiffrin method and are immobilized onto TiO2 electrodes which act as a perfect electrochemical sensing platform for GSH detection. Structural characterization and analysis of these modified electrodes are performed using FESEM, XRD, and UV-visible spectroscopic studies. GSH binding events on Au NPs-immobilized porous TiO2 electrodes are monitored by electrochemical techniques, namely, cyclic voltammetry (CV and

  10. Screened coulomb hybrid DFT study on electronic structure and optical properties of anionic and cationic Te-doped anatase TiO2

    KAUST Repository

    Harb, Moussab

    2013-06-27

    The origin of the enhanced visible-light optical absorption in Te-doped bulk anatase TiO2 is investigated in the framework of DFT and DFPT within HSE06 in order to ensure accurate electronic structure and optical transition predictions. Various oxidation states of Te species are considered based on their structural location in bulk TiO2. In fact, TiO (2-x)Tex (with isolated Te2- species at Te-Te distance of 8.28 Å), TiO2Tex (with isolated TeO 2- species at Te-Te distance of 8.28 Å), TiO2Te 2x (with two concomitant TeO2- species at Te-Te distance of 4.11 Å), and Ti(1-2x)O2Te2x (with two neighboring Te4+ species at nearest-neighbor Te-Te distance of 3.05 Å) show improved optical absorption responses in the visible range similarly as it is experimentally observed in Te-doped TiO2 powders. The optical absorption edges of TiO(2-x)Tex, TiO 2Tex, and TiO2Te2x are found to be red-shifted by 400 nm compared with undoped TiO2 whereas that of Ti(1-2x)O2Te2x is red-shifted by 150 nm. On the basis of calculated valence and conduction band edge positions of Te-doped TiO2, only TiO(2-x)Tex and Ti (1-2x)O2Te2x show suitable potentials for overall water splitting under visible-light irradiation. The electronic structure analysis revealed narrower band gaps of 1.12 and 1.17 eV with respect to undoped TiO2, respectively, resulting from the appearance of new occupied electronic states in the gap of TiO2. A delocalized nature of the gap states is found to be much more pronounced in TiO (2-x)Tex than that with Ti(1-2x)O 2Te2x due to the important contribution of numerous O 2p orbitals together with Te 5p orbitals. © 2013 American Chemical Society.

  11. Synthesis and photocatalytic properties of Palladium-loaded three dimensional flower-like anatase TiO2 with dominant {001} facets.

    Science.gov (United States)

    Bai, Xue; Lv, Lingling; Zhang, Xiaoyuan; Hua, Zulin

    2016-04-01

    Palladium-loaded (Pd-loaded) anatase TiO2 with dominant {001} facets used as photocatalysts was prepared by a two-step process. Three dimensional flower-like structures of anatase TiO2 with exposed {001} facets were synthesized by solvothermal method, and then Pd nanoparticles were photodeposited onto the {101} surface of TiO2 by UV reduction. The resulting Pd/TiO2 was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-vis diffuse reflectance spectra. Characterization results indicated that the flower-like structures of anatase TiO2 were assembled by two dimensional nanosheets with a thickness of approximately 10nm and a length of approximately 1.0μm. The Pd/TiO2 nanocomposites with improved visible-light-harvesting capability, high charge-hole mobility, and low electron-hole recombination exhibited improved photocatalytic performance in degrading bisphenol A. This study provided new insights into the fabrication and practical application of high-performance photocatalysts in degrading organic pollutants.

  12. 銳鈦型TiO2性能研究 II.銳鈦型TiO2的光化學活性封閉及表徵%Studies on the Properties of Anatase TiO2 II.The Encapsulation and Characterization of Photochemical Activity of Anatase TiO2

    Institute of Scientific and Technical Information of China (English)

    高丕英; 溫占秀; 方圖南; 於遵巨集; 古巨集晨

    1999-01-01

      In this paper,the hydrothermal surface modification with silica was applied to encapsulate the surface photochemiacl activity of anatase TiO2. The reducing reaction of Cr2O72- was used to evaluate the integraty of the encapsulation layer. Some factors,e.g., TiO2 slurry solid concentration,temperature and pH,as well as reaction time which dominate the encapsulation, were studied too.

  13. Gold nanoparticles-immobilized, hierarchically ordered, porous TiO2 nanotubes for biosensing of glutathione

    Science.gov (United States)

    Mers, SV Sheen; Kumar, Elumalai Thambuswamy Deva; Ganesh, V

    2015-01-01

    Glutathione (GSH) is vital for several functions of our human body such as neutralization of free radicals and reactive oxygen compounds, maintaining the active forms of vitamin C and E, regulation of nitric oxide cycle, iron metabolism, etc. It is also an endogenous antioxidant in most of the biological reactions. Given the importance of GSH, a simple strategy is proposed in this work to develop a biosensor for quantitative detection of GSH. This particular biosensor comprises of gold nanoparticles (Au NPs)-immobilized, hierarchically ordered titanium dioxide (TiO2) porous nanotubes. Hexagonally arranged, honeycomb-like nanoporous tubular TiO2 electrodes are prepared by using a simple electrochemical anodization process by applying a constant potential of 30 V for 24 hours using ethylene glycol consisting of ammonium fluoride as an electrolytic medium. Structural morphology and crystalline nature of such TiO2 nanotubes are analyzed using field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). Interestingly, nanocomposites of TiO2 with Au NPs is prepared in an effort to alter the intrinsic properties of TiO2, especially tuning of its band gap. Au NPs are prepared by a well-known Brust and Schiffrin method and are immobilized onto TiO2 electrodes which act as a perfect electrochemical sensing platform for GSH detection. Structural characterization and analysis of these modified electrodes are performed using FESEM, XRD, and UV-visible spectroscopic studies. GSH binding events on Au NPs-immobilized porous TiO2 electrodes are monitored by electrochemical techniques, namely, cyclic voltammetry (CV) and chronoamperometry (CA). Several parameters such as sensitivity, selectivity, stability, limit of detection, etc are investigated. In addition, Au NPs dispersed in aqueous medium are also explored for naked-eye detection of GSH using UV-visible spectroscopy in order to compare the performance of the proposed sensor. Our studies clearly indicate

  14. Further understanding of the adsorption mechanism of N719 sensitizer on anatase TiO2 films for DSSC applications using vibrational spectroscopy and confocal Raman imaging.

    Science.gov (United States)

    Lee, Kee Eun; Gomez, Mario A; Elouatik, Samir; Demopoulos, George P

    2010-06-15

    Vibrational spectroscopic studies of N719 dye-adsorbed TiO(2) films have been carried out by using SERRS, ATR-FTIR, and confocal Raman imaging. The high wavenumber region (3000-4000 cm(-1)) of dye adsorbed TiO(2) is analyzed via Raman and IR spectroscopy to investigate the role of surface hydroxyl groups in the anchoring mode. As a complementary technique, confocal Raman imaging is employed to study the distribution features of key dye groups (COO-, bipyridine, and C=O) on the anatase surface. Sensitized TiO(2) films made from two different nanocrystalline anatase powders are investigated: a commercial one (Dyesol) and our synthetic variety produced through aqueous synthesis. It is proposed the binding of the N719 dye to TiO(2) to occur through two neighboring carboxylic acid/carboxylate groups via a combination of bidentate-bridging and H-bonding involving a donating group from the N719 (and/or Ti-OH) units and acceptor from the Ti-OH (and/or N719) groups. The Raman imaging distribution of COO(-)(sym) on TiO(2) was used to show the covalent bonding, while the distribution of C=O mode was applied to observe the electrostatically bonded groups.

  15. Fabrication of phase and morphology controlled pure rutile and rutile/anatase TiO2 nanostructures in functional ionic liquid/water

    Science.gov (United States)

    Shahi, Satwant Kaur; Kaur, Navneet; Singh, Vasundhara

    2016-01-01

    In this paper, pure rutile and anatase-rutile TiO2 nanoparticles have been successfully synthesised via a green route by hydrolysis of titanium tetrachloride with room temperature acidic ionic liquid 3-methyl-1-(3-sulfonylpropyl) imidazolium trifluoromethanesulfonate [HO3S(CH2)3MIM][CF3SO3] in aqueous medium. The influence of pH of the solution by varying molar ratio of substrate and ionic liquid has been investigated in both sol⿿gel and hydrothermal synthesis of TiO2 with significant variation in phase, phase composition (ratio of rutile to anatase) and morphology as indicated by various structural analysis such as XRD, TEM, BET, Raman and UV⿿vis absorption spectroscopy. The results indicate formation of a bunch of aligned thin flaky nano-rods of TiO2 which look like nano-flowers with a crystal size of 3⿿5 nm by sol⿿gel method, while in case of hydrothermal method well-defined rutile solid nanorods of TiO2 were formed with variable length in the range of 120⿿170 nm and 20⿿24 nm in width. The photocatalytic activity of the prepared TiO2 samples has been determined by the photodegradation of methyl orange dye (20 ppm) under UV light. Best photocatalytic activity was exhibited by sample S-2 prepared via sol⿿gel method.

  16. Effects of nano anatase-rutile TiO2 volume fraction with natural dye containing anthocyanin on the dye sensitized solar cell performance

    Science.gov (United States)

    Agustini, S.; Wahyuono, R. A.; Sawitri, D.; Risanti, D. D.

    2013-09-01

    Since its first development, efforts to improve efficiency of Dye Sensitized Solar Cell (DSSC) are continuously carried out, either through selection of dye materials, the type of semiconductor, counter electrode design or the sandwiched structure. It is widely known that anatase and rutile are phases of TiO2 that often being used for fabrication of DSSC. Rutile is thermodynamically more stable phase having band-gap suitable for absorption of sunlight spectrum. On the other hand, anatase has higher electrical conductivity, capability to adsorp dye as well as higher electron diffusion coefficient than those of rutile. Present research uses mangosteen pericarp and Rhoeo spathacea extracted in ethanol as natural dye containing anthocyanin. These dyes were characterized by using UV-Vis and FTIR, showing that the absorption maxima peaks obtained at 389 nm and 413 nm, for mangosteen and Rhoeo spathacea, respectively. The nano TiO2 was prepared by means of co-precipitation method. The particle size were 9-11 nm and 54.5 nm for anatase and rutile, respectively, according to Scherrer's equation. DSSCs were fabricated in various volume fractions of anatase and rutile TiO2. The fabricated DSSCs were tested under 17 mW/cm2 of solar irradiation. The current-voltage (I-V) characteristic of DSSCs employing 75%: 25% volume fraction of anatase and rutile TiO2 have outstanding result than others. The highest conversion efficiencies of 0.037% and 0.013% are obtained for DSSC employing natural dye extract from mangosteen pericarp and Rhoeo spathacea, respectively.

  17. Hierarchically structured suspended TiO2 nanofibers for use in UV and pH sensor devices.

    Science.gov (United States)

    Lee, Won Seok; Park, Yang-Seok; Cho, Yoon-Kyoung

    2014-08-13

    Photoelectrochemical sensors based on hierarchically structured titanium dioxide (TiO2) nanofibers (NFs) were fabricated by combination of electrospinning, carbon microelectromechanical systems (MEMS), and hydrothermal reaction. During the electrospinning step, a rotating drum collector was used to align and position NFs of titanium tetraisopropoxide (TTIP) in polyvinylpyrrolidone (PVP) on top of a carbon-MEMS structure. Following calcination under vacuum, a stable ohmic contact was obtained between suspended TiO2-carbon NFs (TiO2/C NF) and the carbon electrodes. Subsequent to this, a hierarchical nanostructure of TiO2 nanowires (TiO2 NWs) was hydrothermally synthesized onto the TiO2/C NFs and successfully utilized as UV and pH sensors. This is the first demonstration of a semiconductor-based nanofiber sensor suspended on carbon electrodes that has been achieved by a relatively simple and cost-effective electrospinning method. Furthermore, these sensors demonstrate a high sensitivity, as well as a stable ohmic contact, due to the large surface area of the TiO2 NWs and the carbon-carbon contact between the suspended TiO2/C NFs and carbon electrodes.

  18. Probing the charge recombination in rGO decorated mixed phase (anatase-rutile) TiO2 multi-leg nanotubes

    Science.gov (United States)

    Rambabu, Y.; Jaiswal, Manu; Roy, Somnath C.

    2016-11-01

    Recombination of photo-generated charges is one of the most significant challenges in designing efficient photo-anode for photo electrochemical water oxidation. In the case of TiO2, mixed phase (anatase-rutile) junctions often shown to be more effective in suppressing electron-hole recombination compared to a single (anatase or rutile) phase. Here, we report the study of bulk and surface recombination process in TiO2 multi-leg nanotube (MLNTs) anatase-rutile (A-R) junctions decorated with reduced graphene oxide (rGO) layers, through an analysis of the photo-current and impedance characteristics. To quantify the charge transport/transfer process involved in these junctions, holes arriving at the interface of semiconductor/electrolyte were collected by adding H2O2 to the electrolyte. This enabled us to interpret the bulk and surface recombination process involved in anatase/rutile/rGO junctions for photo-electrochemical water oxidation. We correlated this quantification to the electrochemical impedance spectroscopy (EIS) measurements, and showed that in anatase/rutile junction the increase in PEC performance was due to suppression in electron-hole recombination rate at the surface states that effectively enhances the hole transfer rate to the electrolyte. On the other hand, in rGO wrapped A-R MLNTs junction it was due to both phenomenon i.e decrease in bulk recombination rate as well as increase in hole transfer rate to the electrolyte at the semiconductor/electrolyte interface.

  19. Synthesis of [111]- and {010}-faceted anatase TiO2 nanocrystals from tri-titanate nanosheets and their photocatalytic and DSSC performances.

    Science.gov (United States)

    Chen, Changdong; Ikeuchi, Yasushi; Xu, Linfeng; Sewvandi, Galhenage A; Kusunose, Takafumi; Tanaka, Yasuhiro; Nakanishi, Shunsuke; Wen, Puhong; Feng, Qi

    2015-05-07

    [111]- and {010}-faceted anatase nanocrystals with controllable crystal size and morphology were synthesized from tri-titanate H2Ti3O7 nanosheets by hydrothermal reaction. The nanostructures and the formation reaction mechanism of the obtained TiO2 nanocrystals were investigated using XRD, FE-SEM, and TEM. Furthermore, the photocatalytic and dye-sensitized solar cell (DSSC) performances of the synthesized anatase nanocrystals were also characterized. Two types of reactions occur in the formation process of the anatase nanocrystals. One is an in situ topochemical conversion reaction of the layered titanate structure to an anatase structure, and another is the dissolution-deposition reaction on the particle surface, which splits the formed nanosheet-like particles into small TiO2 nanocrystals. The surface photocatalytic activity and the DSSC performance of the anatase nanocrystals are dependent on the crystal facet exposed on the particle surface, which increases in the order of non-facet DSSC performance, which is enhanced in the order of non-facet < [111]-facet < {010}-facet.

  20. Hierarchical synthesis of corrugated photocatalytic TiO2 microsphere architectures on natural pollen surfaces

    Science.gov (United States)

    Erdogan, Deniz Altunoz; Ozensoy, Emrah

    2017-05-01

    Biomaterials are challenging, yet vastly promising templates for engineering unusual inorganic materials with unprecedented surface and structural properties. In the current work, a novel biotemplate-based photocatalytic material was synthesized in the form of corrugated TiO2 microspheres by utilizing a sol-gel methodology where Ambrosia trifida (Ab, Giant ragweed) pollen was exploited as the initial biological support surface. Hierarchically synthesized TiO2 microspheres were structurally characterized in detail via SEM-EDX, Raman spectroscopy, XRD and BET techniques in order to shed light on the surface chemistry, crystal structure, chemical composition and morphology of these novel material architectures. Photocatalytic functionality of the synthesized materials was demonstrated both in gas phase as well as in liquid phase. Along these lines, air and water purification capabilities of the synthesized TiO2 microspheres were established by performing photocatalytic oxidative NOx(g) storage and Rhodamine B(aq) degradation experiments; respectively. The synthetic approach presented herein offers new opportunities to design and create sophisticated functional materials that can be used in micro reactor systems, adsorbents, drug delivery systems, catalytic processes, and sensor technologies.

  1. Effect Of Non-metal Elements (C, N, S) As Anionic Dopants On Electronic Structure Of Tio2-Anatase By Density-Functional Theory Approach

    OpenAIRE

    Hari Sutrisno

    2016-01-01

    This article is a theoritical approach to calculate the electronic structure of undoped- and non-metal anions doped-TiO2-anatase. The objective of the research is to calculate abinitio the band structure and the density of states (DOS) of undoped-, C-, N-, and S-doped TiO2-anatase. Kohn-Sham equations are performed with the density functional theory (DFT) using the local density approximation (LDA) for exchange-correlation functional. The first-principle calculations were done using supercell...

  2. Formation of TiO2 photoanodes by simultaneous electrophoretic deposition of anatase and rutile particles for photoassisted electrolytic copper ions removal

    Directory of Open Access Journals (Sweden)

    Yeimmy Y. Peralta-Ruiz

    2012-01-01

    Full Text Available The influence of Anatasa/Rutile ratio on TiO2 films, grown by electrophoretic deposition was studied in the photoassisted electrolytic copper ions removal from cyanide solutions. The proper dispersant dosage allowing the simultaneous electrophoretic deposition of Anatase and Rutile was chosen based on electrokinetic measurements; evidenced by the XRD spectra of the formed films. The evaluation of films photoassisted electrolytic copper ion removal showeds that it is possible to enhance the activity of Anatase films by adding some Rutile exploiting the synergetic interaction between these two materials, achieve by its proper deposition.

  3. Mechanisms of Visible Light Photocatalysis in N-Doped Anatase TiO2 with Oxygen Vacancies from GGA+U Calculations

    Directory of Open Access Journals (Sweden)

    Hsuan-Chung Wu

    2013-01-01

    Full Text Available We have systematically studied the photocatalytic mechanisms of nitrogen doping in anatase TiO2 using first-principles calculations based on density functional theory, employing Hubbard U (8.47 eV on-site correction. The impurity formation energy, charge density, and electronic structure properties of TiO2 supercells containing substitutional nitrogen, interstitial nitrogen, or oxygen vacancies were evaluated to clarify the mechanisms under visible light. According to the formation energy, a substitutional N atom is better formed than an interstitial N atom, and the formation of an oxygen vacancy in N-doped TiO2 is easier than that in pure TiO2. The calculated results have shown that a significant band gap narrowing may only occur in heavy nitrogen doping. With light nitrogen doping, the photocatalysis under visible light relies on N-isolated impurity states. Oxygen vacancies existence in N-doped TiO2 can improve the photocatalysis in visible light because of a band gap narrowing and n-type donor states. These findings provide a reasonable explanation of the mechanisms of visible light photocatalysis in N-doped TiO2.

  4. The influence of anatase-rutile mixed phase and ZnO blocking layer on dye-sensitized solar cells based on TiO2nanofiberphotoanodes

    Science.gov (United States)

    Ding, Jianning; Li, Yan; Hu, Hongwei; Bai, Li; Zhang, Shuai; Yuan, Ningyi

    2013-01-01

    High performance is expected in dye-sensitized solar cells (DSSCs) that utilize one-dimensional (1-D) TiO2 nanostructures owing to the effective electron transport. However, due to the low dye adsorption, mainly because of their smooth surfaces, 1-D TiO2 DSSCs show relatively lower efficiencies than nanoparticle-based ones. Herein, we demonstrate a very simple approach using thick TiO2 electrospun nanofiber films as photoanodes to obtain high conversion efficiency. To improve the performance of the DSCCs, anatase-rutile mixed-phase TiO2 nanofibers are achieved by increasing sintering temperature above 500°C, and very thin ZnO films are deposited by atomic layer deposition (ALD) method as blocking layers. With approximately 40-μm-thick mixed-phase (approximately 15.6 wt.% rutile) TiO2 nanofiber as photoanode and 15-nm-thick compact ZnO film as a blocking layer in DSSC, the photoelectric conversion efficiency and short-circuit current are measured as 8.01% and 17.3 mA cm-2, respectively. Intensity-modulated photocurrent spectroscopy and intensity-modulated photovoltage spectroscopy measurements reveal that extremely large electron diffusion length is the key point to support the usage of thick TiO2 nanofibers as photoanodes with very thin ZnO blocking layers to obtain high photocurrents and high conversion efficiencies.

  5. Shape-dependence of the thermal and photochemical reactions of methanol on nanocrystalline anatase TiO2

    Science.gov (United States)

    Bennett, David A.; Cargnello, Matteo; Diroll, Benjamin T.; Murray, Christopher B.; Vohs, John M.

    2016-12-01

    Structure-activity relationships and the influence of particle size and shape on the partial- and photo-oxidation of methanol on nanocrystalline anatase TiO2 were investigated using temperature-programmed desorption. The study employed two distinct nanoparticle morphologies: truncated bipyramids exposing primarily {101} facets, and flatter platelets exposing primarily {001} surfaces, whose nominal sizes ranged from 10 to 25 nm. The platelets were found to be more active for thermally-driven reactions, such as coupling of methoxide groups to produce dimethyl ether, and deoxygenation to produce methane. A dependence of the reactivity of {001} facets for the coupling of methoxide groups to produce dimethyl ether on facet size was also observed. In contrast to the thermally-driven reactions, the bipyramidal nanoparticles were observed to be more active for a range of photochemical reactions, including oxidation and coupling to produce methyl formate, and photo-decomposition of surface methoxide species. This study also shows how well-defined nanocrystals can be used to help bridge the materials gap between studies of single crystal model catalysts and their high surface area industrial analogs.

  6. Solvent effects on microstructures and properties of three-dimensional hierarchical TiO2 microsphere structures synthesized via solvothermal approach

    Science.gov (United States)

    Xu, Shiping; Sun, Xiang; Gao, Yuan; Yue, Min; Yue, Qinyan; Gao, Baoyu

    2017-09-01

    One-step solvothermal method has been proved to be a simple and efficient route to synthesize three-dimensional (3D) hierarchical TiO2 microsphere structures, but discrepant properties of the solvent media had been claimed as the major factors determining microstructures and properties of the final products. In this study, several typical solvents, including alkane, aromatic hydrocarbons, halohydrocarbon, ketone, organic acid, mono- and dihydric alcohols, were selected to comprehensively investigate the effect of solvents on the morphology, crystal structure, specific surface area, porous property and light harvesting capability of the final products. According to the experimental results, a good interface separating titanium precursor with aqueous phase in the reaction solution, created by non-polar solvents, or polar solvents which are immiscible with titanium precursor, was the decisive factor for the formation of quasi-3D urchin-like TiO2 microspheres self-assembled from one-dimensional (1D) nanostructures, and concentrated H+ induced by organic acid medium was also helpful. Meanwhile, without the liquid-liquid interface or extremely low solution pH, anatase TiO2 sphere structures with big specific surface area comprising of nanoparticles or nanosheets would be formed, and performed well in photodegradation of pollutants in water.

  7. A DFT study on the interaction of Co with an anatase TiO2 (001)-(1×4) surface

    Institute of Scientific and Technical Information of China (English)

    Zhijun Zuo; Wei Huang; Peide Han; Zhihong Li; Jian Huang

    2009-01-01

    The substitution/adsorption structures of Co on an anatase TiO2 (001)-(1×4) surface are investigated using the DFT/local density approximation (LDA) method.Theoretical calculation shows that the Co ion prefers to be adsorbed on the surface of anatase TiO2.The density of states (DOS) analysis finds that the Co 3d is located mainly in the energy gap region.The Co 3d partial density of states (PDOS) indicates that there is a substantial degree of hybridization between O 2s and Co 3d in valence band (VB) regions in the substitution models.The conclusion is that the mode of substitution is more active when the catalyst is a higher-energy surface.

  8. Anomalous Hall effect suppression in anatase Co:TiO2 by the insertion of an interfacial TiO2 buffer layer

    NARCIS (Netherlands)

    Lee, Y.J.; Jong, de M.P.; Wiel, van der W.G.; Kim, Y.; Brock, J.D.

    2010-01-01

    We present the effect of introducing a TiO2 buffer layer at the SrTiO3/Co:TiO2 interface on the magnetic and structural properties of anatase Co:TiO2 (1.4 at. % Co). Inserting the buffer layer leads to suppression of the room-temperature anomalous Hall effect, accompanied by a reduced density of Co

  9. High-temperature superconductivity in single-unit-cell FeSe films on anatase TiO2(001)

    OpenAIRE

    Ding, Hao; Lv, Yan-Feng; Zhao, Kun; Wang, Wen-Lin; Wang, Lili; Song, Can-Li; Chen, Xi; Ma, Xu-Cun; Xue, Qi-Kun

    2016-01-01

    We report on the observation of high-temperature ($T_\\textrm{c}$) superconductivity and magnetic vortices in single-unit-cell FeSe films on anatase TiO$_2$(001) substrate by using scanning tunneling microscopy. A systematic study and engineering of interfacial properties has clarified the essential roles of substrate in realizing the high-$T_\\textrm{c}$ superconductivity, probably via interface-induced electron-phonon coupling enhancement and charge transfer. By visualizing and tuning the oxy...

  10. Anomalous Hall effect suppression in anatase Co:TiO2 by the insertion of an interfacial TiO2 buffer layer

    NARCIS (Netherlands)

    Lee, Y.J.; de Jong, Machiel Pieter; van der Wiel, Wilfred Gerard; Kim, Y.; Brock, J.D.

    2010-01-01

    We present the effect of introducing a TiO2 buffer layer at the SrTiO3 /Co:TiO2 interface on the magnetic and structural properties of anatase Co:TiO2 1.4 at. % Co. Inserting the buffer layer leads to suppression of the room-temperature anomalous Hall effect, accompanied by a reduced density of Co

  11. Adsorption of croconate dyes on TiO2 anatase (101) surface: A periodic DFT study to understand the binding of diketo groups

    Indian Academy of Sciences (India)

    Avinash L Puyad; Ch Ramesh Kumar; K Bhanuprakash

    2012-01-01

    The adsorption of model croconate dyes on the stoichiometric TiO2 anatase (101) surface has been studied by means of periodic density functional calculations to understand the adsorption of the diketo (-COCO-) groups. Past experimental and theoretical results have shown the strong binding ability of the acid group (-COOH) to the TiO2 surface but here the theoretical studies predicts the binding strength of the diketo group to be also significant and comparable with that of the -COOH group. This may cause a competitive binding between the keto groups and the acid groups on the TiO2 surface in the case of croconate dyes and cause a reduction in the efficiency of the DSSC.

  12. Research on the Electrochemical Performance of Rutile and Anatase Composite TiO2 Nanotube Arrays in Lithium-Ion Batteries.

    Science.gov (United States)

    Wei, Jiang; Liu, Jian-Xiong; Wu, Zheng-Yu; Zhan, Zhao-Lin; Shi, Jin; Xu, Kun

    2015-07-01

    Titanium dioxide is considered as an ideal anode material for lithium-ion batteries. It has many different polymorphs such as anatase and rutile, etc. Both nano-scale rutile and anatase exhibit large potential in accommodating Li ions. Although the electrochemical performance of the rutile or anatase has been studied very well, their combined effect in lithium battery is still unclear at present. In our work, a kind of rutile and anatase composite TiO2 nanotube arrays was synthesized by two steps: anodization and heat treatment. The characteristics of the composite arrays were examined by XRD, SEM, and TEM. The first discharge capacity and charge capacity at 0.1 C (1C = 335 mA h g(-1)) of the composite is about 230 mA h g(-1), and 210 mA h g(-1), which are higher than pure anatase of 180 mA h g(-1) and 173 mA h g(-1). The composite remain about 80% of its initial capacities (185 mA h g(-1)) after 100 cycles. Two anodic peaks around 1.8 V and 2.2 V can be found in the composite in the cyclic voltammetry curves, while there is only one anodic peak in anatase. The separation of anodic and cathodic peak potentials of composite is less than that of anantase, indicating a better charge/discharge reversibility. The electrochemical impedance spectrum test shows the resistance of the composite is larger than that of pure anatase due to that the composite have more grain boundaries. The higher specific capacities of composite arrays may ascribe to the rutile's larger amount of lithium ions insertion and the defects facilitate lithium ions migration. Our work demonstrates that a better electrochemical performance of TiO2 can be achieved by synthesizing the composite material.

  13. α-Fe2O3/TiO2 3D hierarchical nanostructures for enhanced photoelectrochemical water splitting.

    Science.gov (United States)

    Han, Hyungkyu; Riboni, Francesca; Karlicky, Frantisek; Kment, Stepan; Goswami, Anandarup; Sudhagar, Pitchaimuthu; Yoo, Jeongeun; Wang, Lei; Tomanec, Ondrej; Petr, Martin; Haderka, Ondrej; Terashima, Chiaki; Fujishima, Akira; Schmuki, Patrik; Zboril, Radek

    2017-01-07

    We report the fabrication of 3D hierarchical hetero-nanostructures composed of thin α-Fe2O3 nanoflakes branched on TiO2 nanotubes. The novel α-Fe2O3/TiO2 hierarchical nanostructures, synthesized on FTO through a multi-step hydrothermal process, exhibit enhanced performances in photo-electrochemical water splitting and in the photocatalytic degradation of an organic dye, with respect to pure TiO2 nanotubes. An enhanced separation of photogenerated charge carriers is here proposed as the main factor for the observed photo-activities: electrons photogenerated in TiO2 are efficiently collected at FTO, while holes are transferred to the α-Fe2O3 nanobranches that serve as charge mediators to the electrolyte. The morphology of α-Fe2O3 that varies from ultrathin nanoflakes to nanorod/nanofiber structures depending on the Fe precursor concentration was shown to have a significant impact on the photo-induced activity of the α-Fe2O3/TiO2 composites. In particular, it is shown that for an optimized photo-electrochemical structure, a combination of critical factors should be achieved such as (i) TiO2 light absorption and photo-activation vs.α-Fe2O3-induced shadowing effect and (ii) the availability of free TiO2 surface vs.α-Fe2O3-coated surface. Finally, theoretical analysis, based on DFT calculations, confirmed the optical properties experimentally determined for the α-Fe2O3/TiO2 hierarchical nanostructures. We anticipate that this new multi-step hydrothermal process can be a blueprint for the design and development of other hierarchical heterogeneous metal oxide electrodes suitable for photo-electrochemical applications.

  14. Fabrikasi Dye Sensitized Solar Cell (DSSC Berdasarkan Fraksi Volume TiO2 Anatase-Rutile dengan Garcinia mangostana dan Rhoeo Spathacea sebagai Dye Fotosensitizer

    Directory of Open Access Journals (Sweden)

    Sustia Agustini

    2013-09-01

    Full Text Available Sejak pertama kali dikembangkan, usaha untuk meningkatkan efisiensi Dye Sensitized Solar Cell (DSSC terus dilakukan. Mulai dari pemilihan bahan pewarna, jenis semikonduktor yang digunakan, desain counter elektroda, struktur sandwich atau yang lainnya. Anatase dan rutile adalah fase dari TiO2 yang sering digunakan untuk fabrikasi DSSC. Penelitian ini menggunakan kulit manggis dan Rhoeo spathacea yang diekstrak menggunakan ethanol sebagai pewarna alami yang mengandung antosianin. Pewarna tersebut dikarakterisasi menggunakan UV-Vis dan FTIR, dan menunjukkan absorpsi pada panjang gelombang 392 nm untuk kulit manggis dan 413 nm untuk Rhoeo spathacea. TiO2 disintesis menggunakan metode co-precipitation. Ukuran partikel yang dihasilkan adalah 11 nm untuk anatase and 54,5 nm untuk rutile dengan menggunakan persamaan Scherrer. DSSC difabrikasi dengan variasi fraksi volume TiO2 anatase dan rutile. DSSC diuji dibawah cahaya matahari dengan daya sebesar 17 mW/cm2. Kurva arus-tegangan (I-V DSSC yang dihasilkan fraksi volume 75%:25% memperlihatkan hasil terbaik dibanding yang lain. Efisiensi tertinggi adalah 0.037% dan 0.013% dihasilkan oleh DSSC dengan pewarna alami dari kulit manggis dan Rhoeo spathacea.

  15. Effect of Tb2O3 additive on structure of anatase and photocatalytic activity of TiO2/(O'+β')-Sialon multi-phase ceramics

    Institute of Scientific and Technical Information of China (English)

    YANG Jian; PAN Limei; XUE Xiangxin; WANG Mei; QIU Tai

    2009-01-01

    Effect of rare earth oxide Tb2O3 additive on transformation behavior and grain growth of anatase and photocatalytic activity for TiO2/(O'+β')-Sialon multi-phase ceramic was investigated and the mechanism was discussed. X-ray diffractometer (XRD) was employed for the analysis of phase composition, grain size and lattice parameters of anatase. Photocatalyfic activity of the composites was investigated through its photocatalytic degradation to methylene blue (MB) solution. The results showed that Tb2O3 significantly inhibited the transfor-marion process, which displayed an appreciably intensified effect with increasing Tb203 content. It could be attributed to the coaction of the active and passive influence mechanisms. For Tb3+ entering TiO2 lattice, replacing Ti4+ accelerated the transformation, whereas the lattice distortion caused by it was unfavorable for the process. On the other hand, the redox reaction between Tb3+ and TiO2 as well as the Tb2O3 deposited on the surface of TiO2 inhibited the transformation. The addition of Tb2O3 effectively restrained the grain growth of TiO2 and the effect became significant with the increase of its content. With the increase of Tb2O3 addition, the photocatalytic activity of the catalysts in-creased and then dropped after reaching the maximum at about 2%. The action mechanism of Tb2O3 could be attributed to its optical proper-ties and its effect on phase transformation, grain growth and crystal structure of TiO2.

  16. Electrospun hierarchical TiO2 nanorods with high porosity for efficient dye-sensitized solar cells.

    Science.gov (United States)

    Chen, Hong-Yan; Zhang, Teng-Long; Fan, Jie; Kuang, Dai-Bin; Su, Cheng-Yong

    2013-09-25

    Ultraporous anatase TiO2 nanorods with a composite structure of mesopores and macropores fabricated via a simple microemulsion electrospinning approach were first used as photoanode materials for high-efficiency dye-sensitized solar cells (DSSCs). The special multiscale porous structure was formed by using low-cost paraffin oil microemulsion droplets as the soft template, which can not only provide enhanced adsorption sites for dye molecules but also facilitate the electrolyte diffusion. The morphology, porosity, and photovoltaic and electron dynamic characteristics of the porous TiO2 nanorod based DSSCs were investigated in detail by scanning electron microscopy (SEM), N2 sorption measurements, current density-voltage (J-V) curves, UV-vis diffuse reflectance spectra, electrochemical impedance spectroscopy (EIS), intensity modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS), and open-circuit voltage decay (OCVD) measurements. The results revealed that, although fewer amounts of dyes were anchored on the porous TiO2 nanorod films, they exhibited stronger light scattering ability, fast electrolyte diffusion, and extended electron lifetime compared to the commercial P25 nanoparticles. A power conversion efficiency of 6.07% was obtained for the porous TiO2 nanorod based DSSCs. Moreover, this value can be further improved to 8.53% when bilayer structured photoanode with porous TiO2 nanorods acting as the light scattering layer was constructed. This study demonstrated that the porous TiO2 nanorods can work as promising photoanode materials for DSSCs.

  17. Interaction of Photoactive[Fe(CN)6]4-with TiO2 Anatase(101) Surface:A Periodic Density Functional Theory Study

    Institute of Scientific and Technical Information of China (English)

    XU Ying; CHEN Wen-Kai; CAO Mei-Juan; LIU Shu-Hong; LI Jun-Qian

    2007-01-01

    The plane-wave pseudopotential function method, based on density-functional theory, has been used to calculate the adsorption, electronic band structures, orbitals and optical absorption spectrum of [Fe(CN)6]4- on TiO2 anatase(101) surface. Our calculations reveal that the surface-modified anatase system has large adsorption energy and a much narrower band gap.[Fe(CN)6]4- adsorption on the (101) surface could lead to a large red shift of the anatase optical absorption threshold, which extends into a visible region significantly. The calculated results are in agreement with the experiment and other theoretical studies reasonably. It is very important for the understanding and further development ofphotovoltaic materials that are active under visible light.

  18. A one-step thermal decomposition method to prepare anatase TiO2 nanosheets with improved adsorption capacities and enhanced photocatalytic activities

    Science.gov (United States)

    Li, Wenting; Shang, Chunli; Li, Xue

    2015-12-01

    Anatase TiO2 nanosheets (NSs) with high surface area have been prepared via a one-step thermal decomposition of titanium tetraisopropoxide (TTIP) in oleylamine (OM), and their adsorption capacities and photocatalytic activities are investigated by using methylene blue (MB) and methyl orange (MO) as model pollutants. During the synthesis procedure, only one type of surfactant, oleylamine (OM), is used as capping agents and no other solvents are added. Structure and properties of the TiO2 NSs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption analysis, UV-vis spectrum, X-ray photoelectron spectroscopy (XPS) and Photoluminescence (PL) methods. The results indicate that the TiO2 NSs possess high surface area up to 378 m2 g-1. The concentration of capping agents is found to be a key factor controlling the morphology and crystalline structure of the product. Adsorption and photodegradation experiments reveal that the prepared TiO2 NSs possess high adsorption capacities of model pollutants MB and high photocatalytic activity, showing that TiO2 NSs can be used as efficient pollutant adsorbents and photocatalytic degradation catalysts of MB in wastewater treatment.

  19. Origin of the Enhanced Visible-Light Absorption in N-Doped Bulk Anatase TiO 2 from First-Principles Calculations

    KAUST Repository

    Harb, M.

    2011-10-06

    Extension of the absorption properties of TiO2 photocatalytic materials to the visible part of the solar spectrum is of major importance for energy and cleaning up applications. We carry out a systematic study of the N-doped anatase TiO2 material using spin-polarized density functional theory (DFT) and the range-separated hybrid HSE06 functional. The thermodynamic stability of competitive N-doped TiO2 structural configurations is studied as a function of the oxygen chemical potential and of various chemical doping agents: N2, (N2 + H2), NH3, N2H4. We show that the diamagnetic TiO (2-3x)N2x system corresponding to a separated substitutional N species (with 2-4% N impurities) and formation of one-half concentration of O vacancies (1-2 atom %) is an optimal configuration thermodynamically favored by NH3, N2H4, and (N2 + H2) chemical doping agents presenting a dual nitrating-reducing character. The simulated UV-vis absorption spectra using the perturbation theory (DFPT) approach demonstrates unambiguously that the diamagnetic TiO(2-3x)N2x system exhibits the enhanced optical absorption in N-doped TiO2 under visible-light irradiation. Electronic analysis further reveals a band gap narrowing of 0.6 eV induced by delocalized impurity states located at the top of the valence band of TiO 2. A fruitful comparison with experimental data is furnished. © 2011 American Chemical Society.

  20. Ultrafast-Charging and Long-Life Li-Ion Battery Anodes of TiO2-B and Anatase Dual-Phase Nanowires.

    Science.gov (United States)

    Li, Kaikai; Li, Baohua; Wu, Junxiong; Kang, Feiyu; Kim, Jang-Kyo; Zhang, Tong-Yi

    2017-10-06

    Ideal lithium-ion batteries (LIBs) should possess a high power density, be charged extremely fast (e.g., 100C), and have a long service life. To achieve them all, all battery components, including anodes, cathodes, and electrolytes should have excellent structural and functional characteristics. The present work reports ultrafast-charging and long-life LIB anodes made from TiO2-B/anatase dual-phase nanowires. The dual-phase nanowires are fabricated with anatase TiO2 nanoparticles through a facile and cost-effective hydrothermal process, which can be easily scaled up for mass production. The anodes exhibit remarkable electrochemical performance with reversible capacities of ∼225, 172, and 140 mAh g(-1) at current rates of 1C, 10C, and 60C, respectively. They deliver exceptional capacity retention of not less than 126 and 93 mAh g(-1) after 1000 cycles at 60C and 100C, respectively, potentially worthwhile for high-power applications. These values are among the best when the high-rate capabilities are compared with the literature data for similar TiO2-based anodes. The Ragone plot confirms both the exceptionally high energy and power densities of the devices prepared using the dual-phase nanowires. The electrochemical tests and operando Raman spectra present fast electrochemical kinetics for both Li(+) and electron transports in the TiO2 dual-phase nanowires than in anatase nanoparticles due to the excellent Li(+) diffusion coefficient and electronic conductivity of nanowires.

  1. New insight into the enhanced visible-light photocatalytic activities of B-, C- and B/C-doped anatase TiO2 by first-principles.

    Science.gov (United States)

    Yu, Jiaguo; Zhou, Peng; Li, Qin

    2013-08-07

    The geometry structures, formation energies and electronic properties of the B-, C- and B/C-doped anatase TiO2 were investigated by the density functional theory (DFT) calculations of first-principles. The results indicated that the visible-light absorption and photocatalytic activities of the B-, C- and B/C-doped anatase TiO2 were not only influenced by the energy gaps (Eg) and the distributions of impurity states, but also affected by the locations of Fermi levels (EF) and the energies of the edges of band gaps (Ev for the top of valence bands and Ec for the bottom of conduction bands). However, the above four factors changed with the doped models of TiO2. The impurity states in the band gaps reduced the maximum energy gaps in the band gaps, which is responsible for the absorption of visible light. The Fermi levels at the bottom of conduction bands indicated the existence of Ti(3+) ions, which enhanced the separation rates of photogenerated electrons and holes. Further, the energies of the edges of band gaps, determining the dominant types of oxidants (O2(-), hole, ˙OH) in the photocatalytic degradation, were discussed. Moreover, the stability of the doped TiO2 depended on its growth conditions (O-rich or Ti-rich environment). The O-rich growth condition is beneficial to the substitutional B and C atoms to Ti atoms, while the Ti-rich growth condition is favorable to the other doped TiO2 including the most stable co-doped TiO2 with the interstitial B atom and the substitutional C atom to O atom. In addition, our results also showed that the B/C-doped TiO2 inherited the partial electronic properties of single-doped TiO2, but also exhibited many new electronic properties, implying that the electronic properties of co-doped systems are not a mechanical mixture of those of both single-doped systems.

  2. Characterisation, phase stability and surface chemical properties of photocatalytic active Zr and Y co-doped anatase TiO2 nanoparticles

    Science.gov (United States)

    Mattsson, Andreas; Lejon, Christian; Bakardjieva, Snejana; Štengl, Vaclav; Österlund, Lars

    2013-03-01

    We report on the characterization, phase stability, surface chemical and photocatalytic properties of Zr and Y co-doped anatase TiO2 nanoparticles prepared by homogenous hydrolysis methods using urea as precipitating agent. The materials were analyzed by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, BET isotherm and BJH pore size distribution measurements. It is shown that Y and Zr ions replace Ti ions in the anatase TiO2 structures up to a critical total dopant concentration of approximately 13 wt%. The co-doped particles show increased phase stability compared to pure anatase TiO2 nanoparticles. The anatase to rutile phase transformation is shown to be preceded by cation segregation and dissolution with concomitant precipitation of Y2Ti2-xZrxO7 and ZrTiO4. Co-doping modifies the optical absorption edge with a resulting attenuation of the Urbach tail. The band gap is slightly blue-shifted at high doping concentrations, and red shifted at lower doping concentrations. Formic acid adsorption was used as a probe molecule to investigate surface chemical properties and adsorbate structures. It was found that the relative abundance of monodentate formate compared to bidentate coordinated formate decreases with increasing doping concentration. This is attributed to an increased surface acidity with increasing dopant concentration. Photodegradation of formic acid occurred on all samples. With mode-resolved in situ FTIR spectroscopy it is shown that the rate of photodegradation of monodentate formate species are higher than for bidentate formate species. Thus our results show that the trend of decreasing photo-degradation rate with increasing dopant concentration can be explained by the adsorbate structure, which is controlled by the acidity of the surface.

  3. (0 0 1) Facet-exposed anatase-phase TiO2 nanotube hybrid reduced graphene oxide composite: Synthesis, characterization and application in photocatalytic degradation

    Science.gov (United States)

    Zhou, Xun; Shi, Tiejun; Wu, Jing; Zhou, Haiou

    2013-12-01

    Reduced graphene oxide (RGO) and TiO2 nanotube (TNT) with (0 0 1) facet-exposed anatase phase are covalently bonded together to synthesize TNT hybrid RGO (RGO-TNT) through consecutive process such as hydrothermal reaction, HCl washing, lyophilization and heat treatment with graphene oxide (GO), TiO2 powder and high concentration NaOH solution as the starting materials. The TNT with the diameter between 10 and 20 nm characterized by high resolution transmission electron microscopy (HRTEM) is in anatase phase proven by X-ray diffraction (XRD) and HRTEM. Additionally, the more active (0 0 1) facet is exposed identified by HRTEM. More significantly, TNT is bridged to RGO by Csbnd Ti bond by the measurement of X-ray photoelectron spectroscopy (XPS). The photoluminescence (PL) spectra has testified that RGO in RGO-TNT can transfer and accept photoelectrons from TNT. The photocatalytic activity of RGO-TNT for degrading methylene blue (MB) is enhanced by contrast with pure TNT, and changeable by adjusting the mass ratios of GO to TiO2 powder. Simultaneously, lyophilization is benefit for maintaining the high active surface area of RGO-TNT, which is deeply in relationship with a higher photocatalytic activity. After four running cycles of photocatalytic degradation, RGO-TNT has shown a high stability and perfect reproducibility.

  4. Hydrothermal fabrication of quasi-one-dimensional single-crystalline anatase TiO2 nanostructures on FTO glass and their applications in dye-sensitized solar cells.

    Science.gov (United States)

    Liao, Jin-Yun; Lei, Bing-Xin; Wang, Yu-Fen; Liu, Jun-Min; Su, Cheng-Yong; Kuang, Dai-Bin

    2011-01-24

    One-dimensional and quasi-one-dimensional semiconductor nanostructures are desirable for dye-sensitized solar cells (DSSCs), since they can provide direct pathways for the rapid collection of photogenerated electrons, which could improve the photovoltaic performance of the device. Quasi-1D single-crystalline anatase TiO(2) nanostructures have been successfully prepared on transparent, conductive fluorine-doped tin oxide (FTO) glass with a growth direction of [101] through a facile hydrothermal approach. The influences of the initial titanium n-butoxide (TBT) concentration, hydrothermal reaction temperature, and time on the length of quasi-1D anatase TiO(2) nanostructures and on the photovoltaic performance of DSSCs have been investigated in detail. A power conversion efficiency of 5.81% has been obtained based on the prepared TiO(2) nanostructure photoelectrode 6.7 μm thick and commercial N719 dye, with a short-circuit current density of 13.3 mA cm(-2) , an open-circuit voltage of 810 mV, and a fill factor of 0.54. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Synthesis of mesoporous anatase TiO2 nanotubes by a hydrothermal treatment and their use in solid-state dye-sensitized solar cells.

    Science.gov (United States)

    Seo, Min-Kang; Park, Soo-Jin

    2011-05-01

    Mesoporous anatase TiO2 nanotubes (NTs) with the diameter of about 7 12 nm and the length of several hundred nanometers were synthesized by a hydrothermal method on commercial TiO2 particles in NaOH followed by HCI washing. The samples were characterized by X-ray diffraction (XRD), transmitting electron microscopy (TEM), and Brunauer-Emmet-Teller (BET) measurements. The hydrothermal treatment temperature at 130 degrees C was shown to affect not only the extent of particle-to-sheet conversion, and thus the resulting structures of the NTs, but also the anatase-to-rutile transformation. The surface area of the NTs was 200 m2g(-1). This value was much higher in comparison to TiO2 nanoparticles of 50 m2g(-1). It was also found that the NT photoelectrodes had a pronounced impact on the performance of solar cells as compared to nanoparticle ones. This was probably due to lead to a significantly higher specific dye loading and, for certain hydrothermal treatments, resulting in a doubling of the solar cell efficiency (in our case from 2.84% to 4.03% of AM 1.5 conditions).

  6. Ellipsoidal TiO2 hierarchitectures with enhanced photovoltaic performance.

    Science.gov (United States)

    Peng, Wenqin; Yanagida, Masatoshi; Chen, Han; Han, Liyuan

    2012-04-23

    Hierarchical TiO(2) ellipsoids 250-500 nm in size have been synthesized on a large scale by a template-free hydrothermal route. The submicrometer-sized hierarchitectures are assembled from highly crystallized anatase nanorods about 17 nm in diameter with macroporous cavities on the outer shells. Based on the time-dependent morphological evolution under hydrothermal conditions, an oriented attachment process is proposed to explain formation of the hierarchical structures. Such hierarchical TiO(2) not only adsorbs large amounts of dye molecules due to high surface area, but also shows good light scattering caused by the submicrometer size. The TiO(2) hierarchitectures were deposited on top of a transparent TiO(2) nanocrystalline main layer to construct a double-layered photoanode for dye-sensitized solar cell (DSC) application, exhibiting enhanced light harvesting and power-conversion efficiency compared to a commercial TiO(2)-based electrode.

  7. Probing the charge recombination in rGO decorated mixed phase (anatase-rutile TiO2 multi-leg nanotubes

    Directory of Open Access Journals (Sweden)

    Y. Rambabu

    2016-11-01

    Full Text Available Recombination of photo-generated charges is one of the most significant challenges in designing efficient photo-anode for photo electrochemical water oxidation. In the case of TiO2, mixed phase (anatase-rutile junctions often shown to be more effective in suppressing electron-hole recombination compared to a single (anatase or rutile phase. Here, we report the study of bulk and surface recombination process in TiO2 multi-leg nanotube (MLNTs anatase-rutile (A-R junctions decorated with reduced graphene oxide (rGO layers, through an analysis of the photo-current and impedance characteristics. To quantify the charge transport/transfer process involved in these junctions, holes arriving at the interface of semiconductor/electrolyte were collected by adding H2O2 to the electrolyte. This enabled us to interpret the bulk and surface recombination process involved in anatase/rutile/rGO junctions for photo-electrochemical water oxidation. We correlated this quantification to the electrochemical impedance spectroscopy (EIS measurements, and showed that in anatase/rutile junction the increase in PEC performance was due to suppression in electron-hole recombination rate at the surface states that effectively enhances the hole transfer rate to the electrolyte. On the other hand, in rGO wrapped A-R MLNTs junction it was due to both phenomenon i.e decrease in bulk recombination rate as well as increase in hole transfer rate to the electrolyte at the semiconductor/electrolyte interface.

  8. New insights into the origin of visible-light photocatalytic activity in Se-modified anatase TiO2 from screened coulomb hybrid DFT calculations

    KAUST Repository

    Harb, Moussab

    2013-12-05

    We report a systematic study on the optoelectronic properties of Se-modified anatase TiO2 investigated by DFT (including the perturbation theory approach DFPT) within the screened coulomb hybrid HSE06 formalism to guarantee accurate band gap and electronic excitation predictions. Various selenium species at substitutional sites for O or Ti, at interstitial sites, as well as at mixed substitutional/interstitial sites are studied. Among the explored structures, Ti(1-2x)O2Se2x (containing Se4+ species), TiO(2-x)Sex (containing Se2- species), and TiO(2-x)Se2x (containing Se2 2- species) reveal significant enhanced visible-light optical absorption spectra with new absorption features appearing at 500, 600, and 690 nm, respectively. Our calculated spectra are found to be in good agreement with those obtained in available experimental works. The band gap narrowing in these materials originates from incorporation of newly occupied electronic levels within 0.5-1.5 eV above the original valence band of TiO 2, leading to new narrowed band gaps of 2.5, 2.0, and 1.8 eV respectively. Our calculations also reveal suitable band positions of Ti (1-2x)O2Se2x and TiO(2-x)Se x for overall water splitting, whereas TiO(2-x)Se 2x shows an unsuitable valence band position for the oxygen evolution reaction. In contrast, the localized electronic character of the new occupied states on the Se 4p orbitals and only on the O 2p orbitals linked to the Se species makes the holes mobility limited in this material and the recombination rate of charge carriers greatly increased in the bulk. © 2013 American Chemical Society.

  9. Neodymium-Doped TiO2 with Anatase and Brookite Two Phases: Mechanism for Photocatalytic Activity Enhancement under Visible Light and the Role of Electron

    Directory of Open Access Journals (Sweden)

    Douga Nassoko

    2012-01-01

    Full Text Available Titanium dioxide (TiO2 doped with neodymium (Nd, one rare earth element, has been synthesized by a sol-gel method for the photocatalytic degradation of rhodamine-B under visible light. The prepared samples are characterized by X-ray diffractometer, Raman spectroscopy, UV-Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller measurement. The results indicate that the prepared samples have anatase and brookite phases. Additionally, Nd as Nd3+ may enter into the lattice of TiO2 and the presence of Nd3+ substantially enhances the photocatalytic activity of TiO2 under visible light. In order to further explore the mechanism of photocatalytic degradation of organic pollutant, photoluminescence spectrometer and scavenger addition method have been employed. It is found that hydroxide radicals produced by Nd-doped TiO2 under visible light are one of reactive species for Rh-B degradation and photogenerated electrons are mainly responsible for the formation of the reactive species.

  10. Photocatalytic degradation of phenanthrene on soft surfaces in the presence of nanometer anatase TiO2 under UV-light

    Institute of Scientific and Technical Information of China (English)

    Jiali Gu; Dianbo Dong; Lingxue Kong; Yong Zheng; Xiaojun Li

    2012-01-01

    The effect of nanometer anatasc TiO2 was investigated on the photocatalytic degradation of phcnanthrene on soil surfaces under a variety of conditions.After being spiked with phenanthrene,soil samples loaded with different amounts of TiO2 (0 wt.%,1 wt.%,2wt.%,3 wt.%,and 4 wt.%) were exposed to UV-light irradiation for 25 hr.The results indicated that the photocatalytic degradation of phenanthrene followed the pseudo first-order kinetics.TiO2 significantly accelerated the degradation of phenanthrene with the half-life reduced from 45.90 to 31.36 hr for TiO2 loading of 0 wt.% and 4 wt.%,respectively.In addition,the effects of H2O2,light intensity and humie acid on the degradation of phenanthrene were investigated.The degradation of phenanthrene increased with the concentration of H2O2,light intensity and the concentration of humic acids.It has been demonstrated that the photocatalytic method in the presence of nanometer anatase TiO2 was a very promising technology for the treatments of soil polluted with organic substances in the future.

  11. High performance, environmentally friendly and low cost anodes for lithium-ion battery based on TiO 2 anatase and water soluble binder carboxymethyl cellulose

    Science.gov (United States)

    Mancini, M.; Nobili, F.; Tossici, R.; Wohlfahrt-Mehrens, M.; Marassi, R.

    The challenge of producing lithium-ion batteries meeting performance requirements and low environmental impact is strictly related to the choice of materials as well as to the manufacturing processes. Most electrodes are currently prepared using poly(vinilydene fluoride) (PVDF) as binder. This fluorinated polymer is expensive and requires the use of a volatile and toxic organic solvent such as N-methyl-pyrrolidone (NMP) in the processing. Water soluble sodium carboxymethyl cellulose (CMC) can be a suitable substitute for PVDF as binder for both anodes and cathodes eliminating the necessity of NMP and thus decreasing the cost and the environmental impact of battery production. In this work, CMC has been successfully used to prepare efficient and stable anatase TiO 2 anodes by optimizing the electrode manufacturing process in terms of composition and compression. The stability and the high rate performances of the TiO 2/CMC are described and compared with those of TiO 2/PVDF electrodes. The compatibility of the TiO 2/CMC with a LiFePO 4 cathode in a full-cell is also reported.

  12. Visible-light photocatalytic properties of Mo-C codoped anatase TiO2 films prepared by magnetron sputtering

    Science.gov (United States)

    Zhe-Peng, Zhang; Biao, Yu; Hai-Bo, Fan; Xin-Liang, Zheng; He-Bao, Yao

    2015-12-01

    A range of different contents of Mo-C codoped TiO2 films were sputtered by using home-made Mo-C codoped TiO2 targets, which were sintered by mixing the Mo2C and TiO2 powder with different mole ratio. We found that the Mo and C ions were successfully incorporated into the lattice of TiO2 films. As a result, the band gap of TiO2 was reduced and the visible-light photocatalytic property was enhanced. The photocatalytic performance of Mo-C codoped TiO2 films was strictly relevant with the band gap and there was a best codoping concentration of 0.01% for the TiO2 film, which processed the smallest band gap and the best photocatalytic property. If the codoping concentration increased, the photocatalytic performance decreased dramatically. Our results suggest that sputtering technique is a convenient method to prepare Mo-C codoped TiO2 films with tunable doping content and high photocatalytic performance.

  13. A new preparation of doped photocatalytic TiO2 anatase nanoparticles: a preliminary study for the removal of pollutants in confined museum areas

    Science.gov (United States)

    Greco, Enrico; Ciliberto, Enrico; Cirino, Antonio M. E.; Capitani, Donatella; Di Tullio, Valeria

    2016-05-01

    The use of nanotechnology in conservation is a relatively new concept. Usually, classical cleanup methods take into account the use of other chemicals: On the one hand they help the environment destroying pollutants, but on the other hand they often become new pollutants. Among the new oxidation methods called advanced oxidation processes, heterogeneous photocatalysis has appeared an emerging technology with several economic and environmental advantages. A new sol-gel method of synthesis of TiO2 anatase is reported in this work using lithium and cobalt (II) salts. The activation energy of the doped photocatalyst was analyzed by solid-state UV-Vis spectrophotometer. The mobility of Li ions on TiO2 NPs surface was studied by 7Li MAS NMR spectroscopy. Use of doped nanotitania is suggested from authors for the removal of pollutants in confined areas containing goods that must be preserved from decomposition and aging phenomena.

  14. Coupling of Nanocrystalline Anatase TiO2 to Porous Nanosized LaFeO3 for Efficient Visible-Light Photocatalytic Degradation of Pollutants

    Directory of Open Access Journals (Sweden)

    Muhammad Humayun

    2016-01-01

    Full Text Available In this work we have successfully fabricated nanocrystalline anatase TiO2/perovskite-type porous nanosized LaFeO3 (T/P-LFO nanocomposites using a simple wet chemical method. It is clearly demonstrated by means of atmosphere-controlled steady-state surface photovoltage spectroscopy (SPS responses, photoluminescence spectra, and fluorescence spectra related to the formed OH− radical amount that the photogenerated charge carriers in the resultant T/P-LFO nanocomposites with a proper mole ratio percentage of TiO2 display much higher separation in comparison to the P-LFO alone. This is highly responsible for the improved visible-light activities of T/P-LFO nanocomposites for photocatalytic degradation of gas-phase acetaldehyde and liquid-phase phenol. This work will provide a feasible route to synthesize visible-light responsive nano-photocatalysts for efficient solar energy utilization.

  15. Effect of Electronegativity and Charge Balance on the Visible-Light-Responsive Photocatalytic Activity of Nonmetal Doped Anatase TiO2

    Directory of Open Access Journals (Sweden)

    Jibao Lu

    2012-01-01

    Full Text Available The origin of visible light absorption and photocatalytic activity of nonmetal doped anatase TiO2 were investigated in details in this work based on density functional theory calculations. Our results indicate that the electronegativity is of great significance in the band structures, which determines the relative positions of impurity states induced by the doping species, and further influences the optical absorption and photocatalytic activities of doped TiO2. The effect of charge balance on the electronic structure was also discussed, and it was found that the charge-balance structures may be more efficient for visible light photocatalytic activities. In addition, the edge positions of conduction band and valence band, which determine the ability of a semiconductor to transfer photoexcited electrons to species adsorbed on its surface, were predicted as well. The results may provide a reference to further experimental studies.

  16. Superior electrode performance of mesoporous hollow TiO2 microspheres through efficient hierarchical nanostructures

    Science.gov (United States)

    Zhang, Feng; Zhang, Yu; Song, Shuyan; Zhang, Hongjie

    2011-10-01

    Mesoporous hollow TiO2 microspheres with controlled size and hierarchical nanostructures are designed from a process employing in suit template-assisted and hydrothermal methods. The results show that the hollow microspheres composed of mesoporous nanospheres possess very stable reversible capacity of 184 mAh g-1 at 0.25C and exhibit extremely high power of 122 mAh g-1 at the high rate of 10C. The superior high-rate and high-capacity performance of the sample is attributed to the efficient hierarchical nanostructures. The hollow structure could shorten the diffusion length for lithium ion in the microspheres. The large mesoporous channels between the mesoporous nanospheres provide an easily-accessed system which facilitates electrolyte transportation and lithium ion diffusion within the electrode materials. The electrolyte, flooding the mesoporous channels, can also lead to a high electrolyte/electrode contact area, facilitating transport of lithium ions across the electrolyte/electrode interface. The small mesopores in the meosporous nanospheres can make the electrolyte and lithium ion further diffuse into the interior of electrode materials and increase electrolyte/electrode contact area. The small nanoparticles can also ensure high reversible capacity.

  17. Doping anatase TIO_{2} with group V-b and VI-b transition metal atoms : a hybrid functional first-principles study

    OpenAIRE

    Matsubara, Masahiko; Saniz, Rolando; Partoens, Bart; Lamoen, Dirk

    2017-01-01

    Abstract: We investigate the role of transition metal atoms of group V-b (V, Nb, and Ta) and VI-b (Cr, Mo, and W) as n- or p-type dopants in anatase TiO2 using thermodynamic principles and density functional theory with the HeydScuseriaErnzerhof HSE06 hybrid functional. The HSE06 functional provides a realistic value for the band gap, which ensures a correct classification of dopants as shallow or deep donors or acceptors. Defect formation energies and thermodynamic transition levels are calc...

  18. Green synthesis of anatase TiO(2) nanocrystals with diverse shapes and their exposed facets-dependent photoredox activity.

    Science.gov (United States)

    Roy, Nitish; Park, Yohan; Sohn, Youngku; Leung, Kam Tong; Pradhan, Debabrata

    2014-10-08

    The exposed facets of a crystal are known to be one of the key factors to its physical, chemical and electronic properties. Herein, we demonstrate the role of amines on the controlled synthesis of TiO2 nanocrystals (NCs) with diverse shapes and different exposed facets. The chemical, physical and electronic properties of the as-synthesized TiO2 NCs were evaluated and their photoredox activity was tested. It was found that the intrinsic photoredox activity of TiO2 NCs can be enhanced by controlling the chemical environment of the surface, i.e.; through morphology evolution. In particular, the rod shape TiO2 NCs with ∼25% of {101} and ∼75% of {100}/{010} exposed facets show 3.7 and 3.1 times higher photocatalytic activity than that of commercial Degussa P25 TiO2 toward the degradation of methyl orange and methylene blue, respectively. The higher activity of the rod shape TiO2 NCs is ascribed to the facetsphilic nature of the photogenerated carriers within the NCs. The photocatalytic activity of TiO2 NCs are found to be in the order of {101}+{100}/{010} (nanorods) > {101}+{001}+{100}/{010} (nanocuboids and nanocapsules) > {101} (nanoellipsoids) > {001} (nanosheets) providing the direct evidence of exposed facets-depended photocatalytic activity.

  19. Enhanced dye-sensitized solar cells performance using anatase TiO2 mesocrystals with the Wulff construction of nearly 100% exposed {101} facets as effective light scattering layer.

    Science.gov (United States)

    Zhou, Yu; Wang, Xinyu; Wang, Hai; Song, Yeping; Fang, Liang; Ye, Naiqing; Wang, Linjiang

    2014-03-28

    Anatase TiO2 mesocrystals with a Wulff construction of nearly 100% exposed {101} facets were successfully synthesized by a facile, green solvothermal method. Their morphology, and crystal structure are characterized by powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). Accordingly, a possible growth mechanism of anatase TiO2 mesocrystals is elucidated in this work. The as-prepared single anatase TiO2 mesocrystal's mean center diameter is about 500 nm, and the length is about 1 μm. They exhibit high light adsorbance, high reflectance and low transmittance in the visible region due to the unique nearly 100% exposed {101} facets. When utilized as the scattering layer in dye-sensitized solar cells (DSSCs), such mesocrystals effectively enhanced light harvesting and led to an increase of the photocurrent of the DSSCs. As a result, by using an anatase TiO2 mesocrystal film as a scattering overlayer of a compact commercial P25 TiO2 nanoparticle film, the double layered DSSCs show a power conversion efficiency of 7.23%, indicating a great improvement compared to the DSSCs based on a P25 film (5.39%) and anatase TiO2 mesocrystal films, respectively. The synergetic effect of P25 and the mesocrystals as well as the latters unique feature of a Wulff construction of nearly 100% exposed (101) facets are probably responsible for the enhanced photoelectrical performance. In particular, we explore the possibility of the low surface area and exposed {101} facets as an efficient light scattering layer of DSSCs. Our work suggests that anatase TiO2 mesocrystals with the Wulff construction is a promising candidate as a superior scattering material for high-performance DSSCs.

  20. Excellent photocatalytic degradation activities of ordered mesoporous anatase TiO2-SiO2 nanocomposites to various organic contaminants.

    Science.gov (United States)

    Dong, Weiyang; Sun, Yaojun; Ma, Qingwei; Zhu, Li; Hua, Weiming; Lu, Xinchun; Zhuang, Guoshun; Zhang, Shicheng; Guo, Zhigang; Zhao, Dongyuan

    2012-08-30

    Ordered 2-D hexagonal mesoporous TiO(2)-SiO(2) nanocomposites consisted of anatase TiO(2) nanocrystals and amorphous SiO(2) nanoparticles, with large mesochannels and high specific surface areas, have been extensively and detailedly evaluated using various cationic dyes (methylene blue, safranin O, crystal violet, brilliant green, basic fuchsin and rhodamine-6G), anionic dyes (acid fuchsin, orange II, reactive brilliant red X3B and acid red 1) and microcystin-LR. We use mesoporous 80TiO(2)-20SiO(2)-900 for the degradation of cationic dyes and MC-LR, due to the dominant adsorption of SiOH groups and synergistic role of coupled adsorption and photocatalytic oxidation. For anionic dyes, due to the adsorption results predominantly from TiOH groups, our strategy realizes the enhanced photocatalytic oxidation by strong surface acids and larger available specific surface area. Based on this, we prepared 90TiO(2)-10SiO(2)-700 to degrade them. The results show that our samples exhibit excellent degradation activities to all the contaminants, which are much higher than that of P25 photocatalyst. The dyes are not only decolorized promptly but degraded readily as well. It is strongly indicated that our mesoporous nanocomposites are considerably stable and reusable. These results demonstrate that our mesoporous TiO(2)-SiO(2) nanocomposites present extensive and promising application in the fast and highly efficient degradation of various organic pollutants. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. The Electronic Structures and Optical Properties of Alkaline-Earth Metals Doped Anatase TiO2: A Comparative Study of Screened Hybrid Functional and Generalized Gradient Approximation

    Directory of Open Access Journals (Sweden)

    Jin-Gang Ma

    2015-08-01

    Full Text Available Alkaline-earth metallic dopant can improve the performance of anatase TiO2 in photocatalysis and solar cells. Aiming to understand doping mechanisms, the dopant formation energies, electronic structures, and optical properties for Be, Mg, Ca, Sr, and Ba doped anatase TiO2 are investigated by using density functional theory calculations with the HSE06 and PBE functionals. By combining our results with those of previous studies, the HSE06 functional provides a better description of electronic structures. The calculated formation energies indicate that the substitution of a lattice Ti with an AEM atom is energetically favorable under O-rich growth conditions. The electronic structures suggest that, AEM dopants shift the valence bands (VBs to higher energy, and the dopant-state energies for the cases of Ca, Sr, and Ba are quite higher than Fermi levels, while the Be and Mg dopants result into the spin polarized gap states near the top of VBs. The components of VBs and dopant-states support that the AEM dopants are active in inter-band transitions with lower energy excitations. As to optical properties, Ca/Sr/Ba are more effective than Be/Mg to enhance absorbance in visible region, but the Be/Mg are superior to Ca/Sr/Ba for the absorbance improvement in near-IR region.

  2. TiO2 anatase's bulk and (001) surface, structural and electronic properties: A DFT study on the importance of Hubbard and van der Waals contributions

    Science.gov (United States)

    Araujo-Lopez, Eduard; Varilla, Luis Alcala; Seriani, Nicola; Montoya, Javier A.

    2016-11-01

    Theoretical ab initio studies done so far on the structural properties of the titanium dioxide anatase (001) surface, have not reported simultaneously the complete set of cell and interatomic parameters for this system or its bulk. Here we present a complete report of these quantities within a spin polarized Density Functional Theory calculation, including also the Hubbard term and the van der Waals dispersion contribution. We show that within this approach it is possible to find a description of TiO2 anatase using DFT, that correlates better with experimental results than most theoretical studies reported previously. This good level of agreement has an advantage with respect to other very accurate studies which have performed computationally expensive calculations involving hybrid functionals, in that our method tends to be faster while also including the van der Waals dispersion contributions in addition to the treatment of correlations. The observed high-quality description of a system like TiO2 within this approach is important and encouraging; specially because it treats properly a d-shell element that is possibly going to have, for many applications of interest, long-range interaction with molecules, e.g. in studies of photocatalysis, where one needs all the relevant physics of the system to be included. We support this claim with an example of the effects that long-range interactions have on a CO2 molecule at the (001) surface.

  3. Layer-by-layer assembly of TiO(2) colloids onto diatomite to build hierarchical porous materials.

    Science.gov (United States)

    Jia, Yuxin; Han, Wei; Xiong, Guoxing; Yang, Weishen

    2008-07-15

    TiO(2) colloids with the most probably particle size of 10 nm were deposited on the surface of macroporous diatomite by a layer-by-layer (LBL) assembly method with using phytic acid as molecular binder. For preparation of colloidal TiO(2), titanium(IV) isopropoxide (Ti(C(3)H(7)O)(4)) was used as titanium precursor, nitric acid (HNO(3)) as peptizing agent and deionized water and isopropanol (C(3)H(7)OH) as solvent. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N(2) adsorption-desorption, and UV-vis spectra are used to assess the morphology and physical chemistry properties of the resulting TiO(2) coated diatomite. It was shown that the mesoporosity has been introduced into macroporous diatomite by LBL deposition. The mesoporosity was originated from close-packing of the uniform TiO(2) nanoparticles. More TiO(2) could be coated on the surface of diatomite by increasing the deposition cycles. This hierarchical porous material has potential for applications in catalytic reactions involved diffusion limit, especially in photocatalytic reactions.

  4. Cellulose nanofiber-templated three-dimension TiO2 hierarchical nanowire network for photoelectrochemical photoanode

    Science.gov (United States)

    Li, Zhaodong; Yao, Chunhua; Wang, Fei; Cai, Zhiyong; Wang, Xudong

    2014-12-01

    Three dimensional (3D) nanostructures with extremely large porosity possess a great promise for the development of high-performance energy harvesting and storage devices. In this paper, we developed a high-density 3D TiO2 fiber-nanorod (NR) heterostructure for efficient photoelectrochemical (PEC) water splitting. The hierarchical structure was synthesized on a ZnO-coated cellulose nanofiber (CNF) template using atomic layer deposition (ALD)-based thin film and NR growth procedures. The tubular structure evolution was in good agreement with the recently discovered vapor-phase Kirkendall effect in high-temperature ALD processes. The NR morphology was formed via the surface-reaction-limited pulsed chemical vapor deposition (SPCVD) mechanism. Under Xenon lamp illumination without and with an AM 1.5G filter or a UV cut off filter, the PEC efficiencies of a 3D TiO2 fiber-NR heterostructure were found to be 22-249% higher than those of the TiO2-ZnO bilayer tubular nanofibers and TiO2 nanotube networks that were synthesized as reference samples. Such a 3D TiO2 fiber-NR heterostructure offers a new route for a cellulose-based nanomanufacturing technique, which can be used for large-area, low-cost, and green fabrication of nanomaterials as well as their utilizations for efficient solar energy harvesting and conversion.

  5. A mixture of anatase and rutile TiO2 nanoparticles induces histamine secretion in mast cells

    Directory of Open Access Journals (Sweden)

    Chen Eric Y

    2012-01-01

    Full Text Available Abstract Background Histamine released from mast cells, through complex interactions involving the binding of IgE to FcεRI receptors and the subsequent intracellular Ca2+ signaling, can mediate many allergic/inflammatory responses. The possibility of titanium dioxide nanoparticles (TiO2 NPs, a nanomaterial pervasively used in nanotechnology and pharmaceutical industries, to directly induce histamine secretion without prior allergen sensitization has remained uncertain. Results TiO2 NP exposure increased both histamine secretion and cytosolic Ca2+ concentration ([Ca2+]C in a dose dependent manner in rat RBL-2H3 mast cells. The increase in intracellular Ca2+ levels resulted primarily from an extracellular Ca2+ influx via membrane L-type Ca2+ channels. Unspecific Ca2+ entry via TiO2 NP-instigated membrane disruption was demonstrated with the intracellular leakage of a fluorescent calcein dye. Oxidative stress induced by TiO2 NPs also contributed to cytosolic Ca2+ signaling. The PLC-IP3-IP3 receptor pathways and endoplasmic reticulum (ER were responsible for the sustained elevation of [Ca2+]C and histamine secretion. Conclusion Our data suggests that systemic circulation of NPs may prompt histamine release at different locales causing abnormal inflammatory diseases. This study provides a novel mechanistic link between environmental TiO2 NP exposure and allergen-independent histamine release that can exacerbate manifestations of multiple allergic responses.

  6. A Long-Lived Mononuclear Cyclopentadienyl Ruthenium Complex Grafted onto Anatase TiO2 for Efficient CO2 Photoreduction.

    Science.gov (United States)

    Huang, Haowei; Lin, Jinjin; Zhu, Gangbei; Weng, Yuxiang; Wang, Xuxu; Fu, Xianzhi; Long, Jinlin

    2016-07-11

    This work shows a novel artificial donor-catalyst-acceptor triad photosystem based on a mononuclear C5 H5 -RuH complex oxo-bridged TiO2 hybrid for efficient CO2 photoreduction. An impressive quantum efficiency of 0.56 % for CH4 under visible-light irradiation was achieved over the triad photocatalyst, in which TiO2 and C5 H5 -RuH serve as the electron collector and CO2 -reduction site and the photon-harvester and water-oxidation site, respectively. The fast electron injection from the excited Ru(2+) cation to TiO2 in ca. 0.5 ps and the slow backward charge recombination in half-life of ca. 9.8 μs result in a long-lived D(+) -C-A(-) charge-separated state responsible for the solar-fuel production.

  7. Ab initio study on the band structure of P-doped anatase TiO2%磷掺杂锐钛矿二氧化钛能带结构的从头计算研究

    Institute of Scientific and Technical Information of China (English)

    王丽丽; 李阳; 刘颖; 刘跃

    2012-01-01

    The microstructures of pure and P-doped anatase TiO2 were optimized by ab initio method. Evidences for the possibility of studying band structures and density states using the density functional theory (DFT) with super cell model of P-doped anatase TiO2 were investigated. The results obtained by the calculations on the P-doped anatase TiO2 are significant for analyzing the mechanism of photo-catalysis of TiO2 and for improving catalytic activity of anatase TiO2.%用密度泛函方法优化了锐钛矿二氧化钛及其磷掺杂锐钛矿二氧化钛的晶体结构.研究揭示了用超胞模型研究未掺杂和P掺杂锐钛矿TiO2能带结构和态密度的可行性.计算结果对于提高TiO2光催化活性有意义.

  8. A method for adjusting nitrogen doping amount in anatase TiO2 single crystals with well-faceted shape and micron size

    Science.gov (United States)

    Shen, Shaishai; Niu, Jinan; Shen, Shitai; Zhou, Lu; Chen, Hui; Zhang, Shenghui; Ling, Yihan; Liu, Zhangsheng; Feng, Peizhong; Ou, Xuemei; Qiang, Yinghuai

    2017-08-01

    A new approach was developed to adjust N doping amount in anatase single crystals with well-faceted shape and micron size, using a novel liquid dopant from the chemical recycling of the wasted supernatant solution in our previous experiments. The dependence of microstructure and property evolution on N doping amount was investigated systematically. The results show that all prepared N-doped samples are pure anatase with the morphology of truncated octahedral bipyramid including both {001} and {110} reactive facets. With the increase of N doping, the single crystals become angular and the thickness decreases, the aggregation of crystals increases, the photo-absorption capacity in visible region is enhanced and the absorption band edge is gradually red-shifted. The photocatalytic efficiency of the samples for the degradation of methylene blue (MB) or phenol under visible light irradiation gradually increases, but when the volume of dopant increases to 2 ml, the photoactivity of TiO2 decreases. The optimal volume of N dopant is 1 ml and A(6:1) shows the highest photodegradation rate. The effective N doping of wasted supernatant is mainly due to the previously formation of Ti-N linkage, and hence a N doping mechanism is proposed. This work provides a new opportunity for in-situ modification of anatase single crystals with well-faceted shape and micron size, and hence, a basis for development of some advanced materials, for example porous single crystals.

  9. Recombination reduction on lead halide perovskite solar cells based on low temperature synthesized hierarchical TiO2 nanorods

    Science.gov (United States)

    Jaramillo-Quintero, Oscar A.; Solís de La Fuente, Mauricio; Sanchez, Rafael S.; Recalde, Ileana B.; Juarez-Perez, Emilio J.; Rincón, Marina E.; Mora-Seró, Iván

    2016-03-01

    Intensive research on the electron transport material (ETM) has been pursued to improve the efficiency of perovskite solar cells (PSCs) and decrease their cost. More importantly, the role of the ETM layer is not yet fully understood, and research on new device architectures is still needed. Here, we report the use of three-dimensional (3D) TiO2 with a hierarchical architecture based on rutile nanorods (NR) as photoanode material for PSCs. The proposed hierarchical nanorod (HNR) films were synthesized by a two-step low temperature (180 °C) hydrothermal method, and consist of TiO2 nanorod trunks with optimal lengths of 540 nm and TiO2 nanobranches with lengths of 45 nm. Different device configurations were fabricated with TiO2 structures (compact layer, NR and HNR) and CH3NH3PbI3, using different synthetic routes, as the active material. PSCs based on HNR-CH3NH3PbI3 achieved the highest power conversion efficiency compared to PSCs with other TiO2 structures. This result can be ascribed mainly to lower charge recombination as determined by impedance spectroscopy. Furthermore, we have observed that the CH3NH3PbI3 perovskite deposited by the two-step route shows higher efficiency, surface coverage and infiltration within the structure of 3D HNR than the one-step CH3NH3PbI3-xClx perovskite.Intensive research on the electron transport material (ETM) has been pursued to improve the efficiency of perovskite solar cells (PSCs) and decrease their cost. More importantly, the role of the ETM layer is not yet fully understood, and research on new device architectures is still needed. Here, we report the use of three-dimensional (3D) TiO2 with a hierarchical architecture based on rutile nanorods (NR) as photoanode material for PSCs. The proposed hierarchical nanorod (HNR) films were synthesized by a two-step low temperature (180 °C) hydrothermal method, and consist of TiO2 nanorod trunks with optimal lengths of 540 nm and TiO2 nanobranches with lengths of 45 nm. Different

  10. Release of Phosphorous Impurity from TiO2 Anatase and Rutile Nanoparticles in Aquatic Environments and Its Implications

    Science.gov (United States)

    Phosphorus-bearing materials as an additive have been popularly used in nanomaterial synthesis and the residual phosphorus within the nanoparticles (NPs) can be of an environmental concern. For instance, phosphorus within pristine commercial TiO2 NPs greatly influences the surfac...

  11. Bilayer hollow/spindle-like anatase TiO2 photoanode for high efficiency dye-sensitized solar cells

    Science.gov (United States)

    Wang, Guanxi; Zhu, Xunjin; Yu, Jiaguo

    2015-03-01

    Derived from a hollow TiO2 nanoparticle (HNP) as underlayer and a TiO2 spindle (SP) as light scattering overlayer, a new bilayer single-crystalline photoanode (HNP/SP) is fabricated for dye-sensitized solar cell (DSSC) application. The prepared bilayer TiO2 photoanode and two comparative HNP/HNP and SP/SP ones are fully characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV-vis absorption spectroscopy and N2 adsorption-desorption isotherms. An overall photoelectric conversion efficiency of 8.65% has been achieved for HNP/SP DSSC, which is 25% higher than that of HNP/HNP DSSC, and also far superior to that of SP/SP or conventional P25 DSSC. The improved photovoltaic performance of HNP/SP DSSC is attributed to the synergic effects, i.e. the single-crystalline bilayer structure favoring for rapid interfacial electron transport, the relatively large specific surface area of HNP for effective dye adsorption, and the 1D geometry of single-crystalline TiO2 spindles for direct electron transport pathway and strong light scattering effect.

  12. Silicon Impurity Release and Surface Transformation of TiO2 Anatase and Rutile Nanoparticles in Water Environments

    Science.gov (United States)

    Surface transformation can affect the stability, reactivity, and toxicity of titanium dioxide (TiO2) nanoparticles (NPs) when released to water environments. Herein, we investigated the release kinetics of Si impurity frequently introduced during NP synthesis and the resulting ef...

  13. Photoinduced superhydrophilicity of TiO2 thin film with hierarchical Cu doping

    Directory of Open Access Journals (Sweden)

    Zhifeng Liu, Yun Wang, Xinli Peng, Yabin Li, Zhichao Liu, Chengcheng Liu, Jing Ya and Yizhong Huang

    2012-01-01

    Full Text Available Hydrophilic Cu–TiO2 thin films with a gradient in the Cu concentration were prepared on glass by layer-by-layer dip-coating from TiO2 precursors. The effects of the Cu doping on the structure and properties of TiO2 self-cleaning thin films are discussed. The Cu gradient markedly affects the hydrophilicity of the films, with the water contact angle significantly reduced compared with those of the pure or uniformly doped TiO2 thin films. This enhanced hydrophilicity is explained by the more efficient absorption of the solar light and by the reduced recombination of photoexcited electrons and holes in the TiO2 films containing a gradient of Cu dopants.

  14. Assembly of CdS Quantum Dots onto Hierarchical TiO2 Structure for Quantum Dots Sensitized Solar Cell Applications

    OpenAIRE

    Syed Mansoor Ali; Mohamed Aslam; W. A. Farooq; Amanullah Fatehmulla; Atif, M

    2015-01-01

    Quantum dot (QD) sensitized solar cells based on Hierarchical TiO2 structure (HTS) consisting of spherical nano-urchins on transparent conductive fluorine doped tin oxide glass substrate is fabricated. The hierarchical TiO2 structure consisting of spherical nano-urchins on transparent conductive fluorine doped tin oxide glass substrate synthesized by hydrothermal route. The CdS quantum dots were grown by the successive ionic layer adsorption and reaction deposition method. The quantum dot sen...

  15. Morphologically tuned 3D/1D rutile TiO2 hierarchical hybrid microarchitectures engineered by one-step surfactant free hydrothermal method

    Science.gov (United States)

    Maria John, Maria Angelin Sinthiya; Ramamurthi, K.; Sethuraman, K.; Ramesh Babu, R.

    2017-05-01

    Present investigation reports on the surfactant free hydrothermal synthesize of the morphologically tuned hierarchical hybrid rutile titanium oxide (TiO2) microarchitectures showing three dimensional microflower structures and cook pine tree like structures on the one dimensional nanorods formed over TiO2 seed layer coated glass substrates by tuning growth temperature. TiO2 seed layer of ∼100 nm thick was coated on the glass substrates employing sol-gel spin coating method and then rutile TiO2 microarchitectures were synthesized on the TiO2 seed layer by one-step surfactant free hydrothermal method. Deposited samples were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, UV-vis spectroscopy and photoluminescence spectroscopy techniques. Influence of the growth temperature on the crystallinity, morphology and optical properties along with the growth mechanism to achieve hierarchical microarchitectures was investigated. Present work revealed that the structural, morphological and optical properties of the TiO2 hierarchical microarchitectures strongly depend on the growth temperature. Further we proposed a model for the cause to effect possible morphological changes of rutile TiO2 microarchitectures as a function of growth temperatures on the TiO2 seeded glass substrates.

  16. Effect of the specific surface area on thermodynamic and kinetic properties of nanoparticle anatase TiO2 in lithium-ion batteries

    Science.gov (United States)

    Madej, Edyta; Klink, Stefan; Schuhmann, Wolfgang; Ventosa, Edgar; La Mantia, Fabio

    2015-11-01

    Anatase TiO2 nanoparticles with a specific surface area of 100 m2 g-1 and 300 m2 g-1 have been investigated as negative insertion electrode material for lithium-ion batteries. Galvanostatic intermittent titration (GITT) and electrochemical impedance spectroscopy (EIS) were used to investigate the effect of the specific surface area on the performance of the material. GITT was performed at C/10 rate, followed by an EIS measurement after each relaxation step. Separation of kinetic and thermodynamic contributions to the overpotential of the phase transformation on Li+ (de-)insertion allowed revealing a dependency of both terms on the specific surface area. The material with higher surface area undergoes intrinsic transformation during the initial cycles affecting the thermodynamics of (de-)insertion while the sample with lower surface area shows large and asymmetric kinetic hindrances. For the material with 15 nm particles, Li+ de-insertion appears to have a higher resistance than lithium insertion.

  17. Tailoring the electronic structure of anatase TiO2(001) surface through W and N codoping: a DFT calculation

    Science.gov (United States)

    Li, Zongbao; Wang, Xia; Xing, Xiaobo; Wang, Ying

    2017-02-01

    Using density functional theory, we calculated the geometries, band structures and densities of states of W-doped, N-doped, and W/N-codoped anatase TiO4 (001) and (101) surfaces, as well as while the formation energies, based on the overall reaction energy diagram. The calculated results reveal that, on the two surfaces, the absorption of W atoms are more stable than that of N atoms while a larger energy barrier blocks the transfer of W atoms from the surfaces to the body. For TiO2(001), the W-doping and the N/W-codoping lead to a visible lattice distortion while the recombination of photo-generated electron-holes pairs is reduced. A comprehensive analysis of the electronic structures show that the band-gap narrows and a new W-N bond appears, which obviously enhance the photocatalytic activity.

  18. High-Temperature Superconductivity in Single-Unit-Cell FeSe Films on Anatase TiO_{2}(001).

    Science.gov (United States)

    Ding, Hao; Lv, Yan-Feng; Zhao, Kun; Wang, Wen-Lin; Wang, Lili; Song, Can-Li; Chen, Xi; Ma, Xu-Cun; Xue, Qi-Kun

    2016-08-05

    We report on the observation of high-temperature (T_{c}) superconductivity and magnetic vortices in single-unit-cell FeSe films on anatase TiO_{2}(001) substrate by using scanning tunneling microscopy. A systematic study and engineering of interfacial properties has clarified the essential roles of substrate in realizing the high-T_{c} superconductivity, probably via interface-induced electron-phonon coupling enhancement and charge transfer. By visualizing and tuning the oxygen vacancies at the interface, we find their very limited effect on the superconductivity, which excludes interfacial oxygen vacancies as the primary source for charge transfer between the substrate and FeSe films. Our findings have placed severe constraints on any microscopic model for the high-T_{c} superconductivity in FeSe-related heterostructures.

  19. Central role of TiO2 anatase grain boundaries on resistivity of CaCu3Ti4O12-based materials probed by Raman spectroscopy

    Science.gov (United States)

    De Almeida-Didry, Sonia; Autret, Cécile; Honstettre, Christophe; Lucas, Anthony; Zaghrioui, Mustapha; Pacreau, François; Gervais, François

    2016-11-01

    This study focuses on characterization and control of grain boundaries to enhance the properties of CaCu3Ti4O12 (CCTO) ceramics capacitors for industrial applications. A novel factor deals with TiO2 anatase revealed by Raman scattering in grain boundaries, found as a dominant parameter of largest sample resistivity, consistent with higher grain boundary resistivity and higher breakdown voltage. Four selected samples of CCTO-based compositions showing very different properties in terms of permittivity ranging from 1000 to 684 000 measured at 1 kHz, capacitance of grain boundaries ranging from 8 10-10 to 4.5 10-7 F cm-1, grain boundary resistivity ranging from 193 to 30,000,000 Ω cm and sample resistivity extending from 450 to 1011 Ω cm. The relationship between permittivity weighted by grain size and capacitance of grain boundaries confirms the internal barrier layer capacitance model over 5 orders of magnitude.

  20. A periodic density functional theory investigation of tetrazole derivatives adsorbed on anatase TiO2 surface applied in dye-sensitized solar cell

    Science.gov (United States)

    Karami, Marzieh; Beni, Ali Reza Salimi; Hosseinzadeh, Behzad

    2017-10-01

    In the current investigation, four different additives namely 2H-tetrazole (2HTz), 2H-tetrazole-5-amine (5ATz), 2H-tetrazole-5-thiol (5TTz) and 4-tert-butylpyridine (TBP) are utilized to examine the interaction of these additives with anatase TiO2 (101), (100) and (001) surfaces under vacuum condition. In addition, analyses of adsorption mode and electronic structure using a periodic density functional theory method is performed to find the interaction of acetonitrile solvent. The obtained results revealed that these four additives are adsorbed into the sorbent surface as the following order of (100) open-circuit photovoltage of dye-sensitized solar cells. Besides, the obtained results demonstrated that although addition of the acetonitrile solvent leads to a reduction in adsorption energy, it improves the shift trend of Fermi energy except for 2HTz and 5TTz-TiO2 (001) systems.

  1. Fabrication of α-Fe2O3/TiO2 bi-functional composites with hierarchical and hollow structures and their application in water treatment

    Science.gov (United States)

    Li, Yinhui; Zhang, Na; Chen, Jianxin; Li, Ruijuan; Li, Liang; Li, Kunyu

    2016-02-01

    The α-Fe2O3/TiO2 bi-functional composites with hierarchical and hollow structures are fabricated through a hydrothermal route. The adsorption performance and photocatalytic activity of the composites towards Pb2+ are investigated in this work. Different adsorption kinetics models and equilibrium models are used to explore the adsorption behavior of hierarchical α-Fe2O3/TiO2 hollow spheres. Experimental data show that adsorption kinetics of the hierarchical α-Fe2O3/TiO2 hollow spheres can be fitted well by the pseudo-second-order model, while the isothermal data can be perfectly described by the Langmuir adsorption model. The maximum adsorption capacity of the hierarchical α-Fe2O3/TiO2 hollow spheres is 32.36 mg g-1. Moreover, the hierarchical α-Fe2O3/TiO2 hollow spheres possess photocatalytic oxidation character under simulated solar light irradiation. The results demonstrate that the hierarchical α-Fe2O3/TiO2 hollow spheres, as effective and cheap materials, can be applied to the removal of heavy metal ions from wastewater.

  2. Photo-electrochemical properties of graphene wrapped hierarchically branched nanostructures obtained through hydrothermally transformed TiO2 nanotubes

    Science.gov (United States)

    Rambabu, Y.; Jaiswal, Manu; Roy, Somnath C.

    2017-10-01

    Hierarchically structured nanomaterials play an important role in both light absorption and separation of photo-generated charges. In the present study, hierarchically branched TiO2 nanostructures (HB-MLNTs) are obtained through hydrothermal transformation of electrochemically anodized TiO2 multi-leg nanotubes (MLNT) arrays. Photo-anodes based on HB-MLNTs demonstrated 5 fold increase in applied bias to photo-conversion efficiency (%ABPE) over that of TiO2 MLNTs without branches. Further, such nanostructures are wrapped with reduced graphene oxide (rGO) films to enhance the charge separation, which resulted in ∼6.5 times enhancement in %ABPE over that of bare MLNTs. We estimated charge transport (η tr) and charge transfer (η ct) efficiencies by analyzing the photo-current data. The ultra-fine nano branches grown on the MLNTs are effective in increasing light absorption through multiple scattering and improving charge transport/transfer efficiencies by enlarging semiconductor/electrolyte interface area. The charge transfer resistance, interfacial capacitance and electron decay time have been estimated through electrochemical impedance measurements which correlate with the results obtained from photocurrent measurements.

  3. The effects of copper doping on photocatalytic activity at (101) planes of anatase TiO2: A theoretical study

    Science.gov (United States)

    Assadi, M. Hussein N.; Hanaor, Dorian A. H.

    2016-11-01

    Copper dopants are varyingly reported to enhance photocatalytic activity at titanium dioxide surfaces through uncertain mechanisms. In order to interpret how copper doping might alter the performance of titanium dioxide photocatalysts in aqueous media we applied density functional theory methods to simulate surface units of doped anatase (101) planes. By including van der Waals interactions, we consider the energetics of adsorbed water at anatase surfaces in pristine and copper doped systems. Simulation results indicate that copper dopant at anatase (101) surfaces is most stable in a 2+ oxidation state and a disperse configuration, suggesting the formation of secondary CuO phases is energetically unfavourable. In agreement with previous reports, water at the studied surface is predicted to exhibit molecular adsorption with this tendency slightly enhanced by copper. Results imply that the enhancement of photoactivity at anatase surfaces through Cu doping is more likely to arise from electronic interactions mediated by charge transfer and inter-bandgap states increasing photoexcitation and extending surface-hole lifetimes rather than through the increased density of adsorbed hydroxyl groups.

  4. Meso-structured coatings of TiO2-anatase obtained by EISA method with photovoltaic activity; Recubrimientos meso-estructurados de TiO2-anatasa obtenido por el metodo EISA con actividad fotovoltaica

    Energy Technology Data Exchange (ETDEWEB)

    Arconada, N.; Castro, Y.; Duran, A.

    2010-07-01

    This paper reports the preparation of mesoporous and meso-structured TiO2-anatase thin films using the sol-gel route combining with the evaporation induced self-assembly method (EISA). Titania sols were prepared from TiCl4 using different no-ionic pore generating agents: Pluronic F127, Brij58 and Triton X100. The films were deposited by dipping and then characterised was performed by Fourier Transform Infrared Spectroscopy, Low angle and Graxing X-Ray Diffraction and Transmission Electronic Microscopy to analyse the crystallization of the inorganic network and the direction order of the meso-structured porosity. Spectral Ellipsometry studies were performed to obtain the absorption-desorption isotherms and to determine pore size distribution, pore volume and specific surface area and exposed surface area of the films. The photocatalytic activity was studied through the degradation of methyl orange in aqueous solution (c= 3mg/L) under ultraviolet-visible light exposure. Thickness, refraction index and contact angles change with the type of substrate used to deposit the films. Higher thickness and low refraction index and contact angle were obtained onto glass-slides substrate. The best photocatalytic activity was obtained for the 0.005 F127 at RH 20-70% and 0.3 Triton at RH 50%, which correspond with lowest pore size and highest Sexp. The TiO2 films obtained with 0.005 F127 at RH 20 and 20-70% and Brij58 at RH 50% show a perfect meso-structured order. (Author).

  5. Size-Tunable Olive-Like Anatase TiO2 Coated with Carbon as Superior Anode for Sodium-Ion Batteries.

    Science.gov (United States)

    Chen, Jun; Zhang, Yan; Zou, Guoqiang; Huang, Zhaodong; Li, Simin; Liao, Hanxiao; Wang, Jufeng; Hou, Hongshuai; Ji, Xiaobo

    2016-10-01

    Olive-shaped anatase TiO2 with tunable sizes in nanoscale are designed employing polyvinyl alcohol (PVA) as structure directing agents to exert dramatic impacts on structure shaping and size manipulation. Notably, the introduced PVA simultaneously serves as carbon sources, bringing about a homogenous carbon layer with intimate coupling interfaces for boosted electronic conductivity. Constructed from tiny crystalline grains, the uniformly dispersed carbon-coated TiO2 nano-olives (TOC) possess subtle loose structure internally for prompt Na(+) transportations. When utilized for sodium-ion storage, the size effects are increasingly significant at high charge-discharge rates, leading to the much superior rate performances of TOC with the smallest size. Bestowed by the improved Na(+) adsorption and diffusion kinetics together with the promoted electron transfer, it delivers a high specific capacity of 267 mAh g(-1) at 0.1 C (33.6 mA g(-1) ) and sustains 110 mAh g(-1) at a rather high rate of 20 C. Even after cycled at 10 C over 1000 cycles, a considerable capacity of 125 mAh g(-1) with a retention of 94.6% is still obtained, highlighting its marvelous long-term cyclability and high-rate capabilities. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Anionic or Cationic S-Doping in Bulk Anatase TiO 2 : Insights on Optical Absorption from First Principles Calculations

    KAUST Repository

    Harb, Moussab

    2013-05-02

    Using first principles calculations, we investigate the structural, electronic, optical, and energetic properties of S-doped anatase TiO2 bulk systems. To ensure accurate band gap predictions, we use the HSE06 exchange correlation functional, and the absorption spectra are obtained with density functional perturbation (DFPT) theory by employing HSE06. Various oxidation states (anionic and cationic) of sulfur are considered depending on the location in bulk TiO2: in interstitial position or in substitution for either oxygen or titanium atoms. Among the explored structures, two anionic and one cationic configurations induce an improved optical absorption response in the visible region as observed experimentally. Moreover, we undertake a thermodynamic analysis as a function of the chemical potential of oxygen and considering three relevant sulfur chemical doping agents (S 2, H2S, and thiourea). It highlights that cationic configurations (S4+ and S6+) are strongly stabilized in a wide range of oxygen chemical potential (including standard conditions), whereas anionic species are stabilized only at very low chemical potential of oxygen. The metastable cationic Ti(1-2x)O2S2x system involving the presence of S4+ species in substitution for Ti 4+, with the formation of SO2 units, should offer the best compromise between the thermodynamic conditions and the expected optical properties. © 2013 American Chemical Society.

  7. Comparative density functional theory and density functional tight binding study of arginine and arginine-rich cell penetrating peptide TAT adsorption on anatase TiO2.

    Science.gov (United States)

    Li, Wenxuan; Kotsis, Konstantinos; Manzhos, Sergei

    2016-07-20

    We present a comparative density functional theory (DFT) and density functional tight binding (DFTB) study of geometries and electronic structures of arginine (Arg), arginine adsorbed on the anatase (101) surface of titania in several adsorption configurations, and of an arginine-rich cell penetrating peptide TAT and its adsorption on the surface of TiO2. Two DFTB parameterizations are considered, tiorg-0-1/mio-1-1 and matsci-0-3. While there is good agreement in the structures and relative energies of Arg and peptide conformers between DFT and DFTB, both adsorption geometries and energies are noticeably different for Arg adsorbed on TiO2. The tiorg-0-1/mio-1-1 parameterization performs better than matsci-0-3. We relate this difference to the difference in electronic structures resulting from the two methods (DFT and DFTB) and specifically to the band alignment between the molecule and the oxide. We show that the band alignment of TAT and TiO2 modeled with DFTB is qualitatively correct but that with DFT using the PBE functional is not. This is specific to the modeling of large molecules where the HOMO is close to the conduction band of the oxide. We therefore report a case where the approximate DFT-based method - DFTB (with which the correct band structure can be effectively obtained) - performs better than the DFT itself with a functional approximation feasible for the modeling of large bio-inorganic interfaces, i.e. GGA (as opposed to hybrid functionals which are impractical at such a scale). Our results highlight the utility of the DFTB method for the modeling of bioinorganic interfaces not only from the CPU cost perspective but also from the accuracy point of view.

  8. Direct Low-Temperature Growth of Single-Crystalline Anatase TiO2 Nanorod Arrays on Transparent Conducting Oxide Substrates for Use in PbS Quantum-Dot Solar Cells.

    Science.gov (United States)

    Chung, Hyun Suk; Han, Gill Sang; Park, So Yeon; Shin, Hee-Won; Ahn, Tae Kyu; Jeong, Sohee; Cho, In Sun; Jung, Hyun Suk

    2015-05-20

    We report on the direct growth of anatase TiO2 nanorod arrays (A-NRs) on transparent conducting oxide (TCO) substrates that can be directly applied to various photovoltaic devices via a seed layer mediated epitaxial growth using a facile low-temperature hydrothermal method. We found that the crystallinity of the seed layer and the addition of an amine functional group play crucial roles in the A-NR growth process. The A-NRs exhibit a pure anatase phase with a high crystallinity and preferred growth orientation in the [001] direction. Importantly, for depleted heterojunction solar cells (TiO2/PbS), the A-NRs improve both electron transport and injection properties, thereby largely increasing the short-circuit current density and doubling their efficiency compared to TiO2 nanoparticle-based solar cells.

  9. Fluorine- and iron-modified hierarchical anatase microsphere photocatalyst for water cleaning: facile wet chemical synthesis and wavelength-sensitive photocatalytic reactivity.

    Science.gov (United States)

    Liu, Shaohong; Sun, Xudong; Li, Ji-Guang; Li, Xiaodong; Xiu, Zhimeng; Yang, He; Xue, Xiangxin

    2010-03-16

    High photocatalytic efficiency, easy recovery, and no biological toxicity are three key properties related to the practical application of anatase photocatalyst in water cleaning, but seem to be incompatible. Nanoparticles-constructed hierarchical anatase microspheres with high crystallinity and good dispersion prepared in this study via one-step solution processing at 90 degrees C under atmospheric pressure by using ammonium fluotitanate as the titanium source and urea as the precipitant can reconcile these three requirements. The hierarchical microspheres were found to grow via an aggregative mechanism, and contact recrystallization occurred at high additions of the FeCl(3) electrolyte into the reaction system. Simultaneous incorporation of fluorine and iron into the TiO(2) matrix was confirmed by combined analysis of X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV-vis absorption spectroscopy. Surface structure and morphology changes of the microspheres induced by high-temperature annealing were clearly observed by field-emission scanning electron microscopy, especially for the phase-transformed particles. The original nanoparticles-constructed rough surfaces partially became smooth, resulting in a sharp drop in photocatalytic efficiency. Interestingly, iron loading has detrimental effects on the visible-light photocatalytic activity of both the as-prepared and the postannealed anatase microspheres but greatly enhances the photocatalytic activity of the as-prepared anatase microspheres under UV irradiation. No matter under UV or visible-light irradiation, the fluorine-loaded anatase microspheres and especially the postannealed ones show excellent photocatalytic performance. The underlying mechanism of fluorine and iron loading on the photocatalytic efficacy of the anatase microspheres was discussed in detail. Beyond photocatalytic applications, this kind of material is of great importance to the assembling of

  10. Density functional theory analysis of the structural and electronic properties of TiO2 rutile and anatase polytypes: performances of different exchange-correlation functionals.

    Science.gov (United States)

    Labat, Frédéric; Baranek, Philippe; Domain, Christophe; Minot, Christian; Adamo, Carlo

    2007-04-21

    The two polymorphs of TiO2, rutile and anatase, have been investigated at the ab initio level using different Hamiltonians with all-electron Gaussian and projector augmented plane wave basis sets. Their equilibrium lattice parameters, relative stabilities, binding energies, and band structures have been evaluated. The calculations have been performed at the Hartree-Fock, density functional theory (DFT), and hybrid (B3LYP and PBE0) levels. As regards DFT, the local density and generalized gradient (PBE) approximations have been used. Our results show an excellent agreement with the experimental band structures and binding energies for the B3LYP and PBE0 functionals, while the best structural descriptions are obtained at the PBE0 level. However, no matter which Hamiltonian and method are used, anatase is found more stable than rutile, in contrast with recent experimental reports, although the relative stabilities of the two phases are very close to each other. Nevertheless, based on the overall results, the hybrid PBE0 functional appears as a good compromise to obtain an accurate description of both structural and electronic properties of solids.

  11. Interaction between Human Serum Albumin and Different Anatase TiO2 Nanoparticles: A Nano-bio Interface Study

    Directory of Open Access Journals (Sweden)

    Viviana Vergaro

    2015-10-01

    was different for the diverse range of nanocrystals tested. Surface roughness measurements showed that on some of the nanocrystals, HSA were arranged in a more globular manner. A lower protein affinity was found for nanocrys‐ tals that had a smaller primary particle size, which may correspond to their higher biocompatibility. This nano-bio interface research aimed to study the HSA protein-TiO2 anatase nanocrystals under conditions similar to those for in vitro and in vivo toxicity analyses.

  12. Structural and electronic properties of Mg and Mg-Nb co-doped TiO2 (101) anatase surface

    Energy Technology Data Exchange (ETDEWEB)

    Sasani, Alireza [Department of Science, Karaj Islamic Azad University, Karaj, Alborz, P.O. Box 31485-313 (Iran, Islamic Republic of); Baktash, Ardeshir [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167 (Iran, Islamic Republic of); Mirabbaszadeh, Kavoos, E-mail: mirabbas@aut.ac.ir [Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran, P. O. Box 15875-4413 (Iran, Islamic Republic of); Khoshnevisan, Bahram [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167 (Iran, Islamic Republic of)

    2016-10-30

    Highlights: • Formation energy of Mg and Mg-Nb co-doped TiO{sub 2} anatase surface (101) is studied. • Effect of Mg defect to the TiO{sub 2} anatase (101) surface and bond length distribution of the surface is studied and it is shown that Mg defects tend to stay far from each other. • Effect of Mg and Nb to the bond length distribution of the surface studied and it is shown that these defects tend to stay close to each other. • Effects of Mg and Mg-Nb defects on DSSCs using TiO{sub 2} anatase hosting these defects are studied. - Abstract: In this paper, by using density functional theory, Mg and Nb-Mg co-doping of TiO{sub 2} anatase (101) surfaces are studied. By studying the formation energy of the defects and the bond length distribution of the surface, it is shown that Mg defects tend to stay as far as possible to induce least possible lattice distortion while Nb and Mg defects stay close to each other to cause less stress to the surface. By investigating band structure of the surface and changes stemmed from the defects, potential effects of Mg and Mg-Nb co-doping of TiO{sub 2} surface on dye-sensitized solar cells are investigated. In this study, it is shown that the Nb-Mg co-doping could increase J{sub SC} of the surface while slightly decreasing V{sub OC} compared to Mg doped surface, which might result in an increase in efficiency of the DSSCs compared to Nb or Mg doped surfaces.

  13. Anatase TiO{sub 2} hierarchical nanospheres with enhanced photocatalytic activity for degrading methyl orange

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Liqin; Xu, Wence [School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 (China); Zhu, Shengli, E-mail: slzhu@tju.edu.cn [School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin, 300072 (China); Cui, Zhenduo [School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 (China); Yang, Xianjin [School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin, 300072 (China); Inoue, Akihisa [School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 (China); International Institute of Green Materials, Josai International University, Togane, 283-8555 (Japan)

    2016-02-15

    Anatase TiO{sub 2} hierarchical nanospheres were synthesized through a simple way combining dealloying and hydrothermal methods. The photocatalytic activity of the obtained products and Degussa P25 were evaluated by the degradation of methyl orange (MO) aqueous solution at different initial pH values and concentrations. The anatase TiO{sub 2} hierarchical nanospheres exhibited excellent photocatalytic activity for the degradation of methyl orange under ultraviolet–visible light irradiation. The photocatalytic efficiency of the anatase TiO{sub 2} increased with the decrease of pH at first then decreased and it also decreased with the increase of MO concentration. The superior photocatalytic performance of anatase TiO{sub 2} hierarchical nanospheres is attributed to its crystal phase, microstructure, and particularly surface acidity. The enhancement of surface acidity reduces the electron–hole pair recombination, and further increases the photocatalytic efficiency. - Highlights: • Anatase TiO{sub 2} nanospheres was prepared by chemical dealloying method. • The anatase TiO{sub 2} nanospheres exhibited good photocatalytic activity. • Sulfate ions adsorbed on TiO{sub 2} was beneficial for the photocatalytic performance.

  14. Hierarchical interfaces induce high dielectric permittivity in nanocomposites containing TiO2@BaTiO3 nanofibers

    Science.gov (United States)

    Zhang, Xin; Chen, Weiwei; Wang, Jianjun; Shen, Yang; Gu, Lin; Lin, Yuanhua; Nan, Ce-Wen

    2014-05-01

    Interface issues are common and crucial in nanocomposites or nanohybrid systems since the interface area is enormous on the nanoscale. In the 0-3 dimensional polymer nanocomposites, in which nano-inclusions (0-dimension) are embedded in a 3-dimensionally connected polymer matrix, enhanced dielectric permittivity could be induced by the interfacial polarization at the interfaces between the nano-inclusions and the polymer matrix. In this contribution, we propose and demonstrate that the topological structure of the interface plays an equally important role as the area of the interface in determining the dielectric polarization of polymer nanocomposites. TiO2 nanofibers embedded with BaTiO3 nanoparticles are prepared via electrospinning and then fused with polyvinyl difluoride (PVDF) into polymer nanocomposite films. Modulation of hierarchical interfaces is thus achieved for these nanocomposites. The confinement of these additional interfaces inside the TiO2 nanofibers leads to percolated networks formed by the interfacial regions. The dielectric permittivity of the polymer nanocomposites is thus enhanced by ~300% over the PVDF matrix at a low filler loading of 11 vol%. A phase-field simulation study indicates that the enhanced dielectric permittivity could be attributed to the increased polarization in the percolated interfacial regions inside the TiO2 nanofibers. The instantaneous electrical breakdown of the TiO2@BaTiO3 nanofibers studied by the in situ transmission electron microscopy method further reveals the striking feature that the breakdown behavior of the nanofibers changes from semiconductive to metallic with the incorporation of insulating BaTiO3 nanoparticles.Interface issues are common and crucial in nanocomposites or nanohybrid systems since the interface area is enormous on the nanoscale. In the 0-3 dimensional polymer nanocomposites, in which nano-inclusions (0-dimension) are embedded in a 3-dimensionally connected polymer matrix, enhanced dielectric

  15. Photovoltaic and Impedance Properties of Hierarchical TiO2 Nanowire Based Quantum Dot Sensitized Solar Cell

    Directory of Open Access Journals (Sweden)

    Amanullah Fatehmulla

    2015-01-01

    Full Text Available Growth and characterization of TiO2 nanowire (NW assemblies on FTO glass using a typical hydrothermal synthesis have been reported. CdS quantum dots (QDs have been deposited on TiO2 nanowires by successive ion layer adsorption and reaction (SILAR method. FESEM image exhibits the flower-like hierarchical TiO2 bunch of nanowires. HRTEM image confirms the size of CdS QDs between 5 and 6 nm. XRD and absorption studies revealed proper growth of CdS quantum dots on TiO2 nanowires. At AM 1.5 illumination intensity, the solar cell, with the configuration FTO/TiO2-NW/CdS-QDs/Pt-FTO, displays a short circuit current (Jsc of 1.295 mA and an open circuit voltage (Voc of 0.38 V. The Voc and Jsc showed linear behavior at higher illumination intensities. The peak in power-voltage characteristics at various illuminations showed a shift towards higher Voc values. Capacitance-voltage (C-V, conductance-voltage (G-V, and series resistance-voltage (Rs-V measurements of the cell in the frequency ranging from 5 kHz to 5 MHz showed decreasing trend of capacitance with increase of frequency whereas increase in conductance and decrease in resistance have been noticed with increase of frequency. All the results including the individual behavior of the plots of capacitance, conductance, and series resistance as a function of bias voltage have been discussed.

  16. Dual phase Li4Ti5O12-TiO2 hierarchical hollow microspheres as anode materials for high rate lithium-ion batteries

    Science.gov (United States)

    Zhu, Kunxu; Hu, Guoxin

    2017-01-01

    Dual phase Li4Ti5O12-TiO2 hierarchical hollow microspheres composed of nanosheets are successfully fabricated by the calcination of hydrothermal product obtained from lithium peroxotitanate complex solution. Low-cost industrial H2TiO3 particles are chosen as titanium sources, which is significant for the inexpensive and large-scale production of Li4Ti5O12-TiO2 composite material. The Li4Ti5O12-TiO2 electrode yields excellent rate capability (151, 139 and 134 mA h g-1 at 10, 20 and 25 C, respectively) and good cycling stability (96% capacity retention after 500 cycles at 10 C). The mesoporous hierarchical morphology and high grain boundary density are likely the contributing factors to the excellent electrochemical performance of Li4Ti5O12-TiO2 composite.

  17. TiO2 hierarchical porous film constructed by ultrastable foams as photoanode for quantum dot-sensitized solar cells

    Science.gov (United States)

    Du, Xing; He, Xuan; Zhao, Lei; Chen, Hui; Li, Weixin; Fang, Wei; Zhang, Wanqiu; Wang, Junjie; Chen, Huan

    2016-11-01

    It reported a novel and simple method for the first time to prepare TiO2 hierarchical porous film (THPF) using ultrastable foams as a soft template to construct porous structures. Moreover, dodecanol as one foam component was creatively used as solvent during the synthesis of CdSe quantum dots (QDs) to decrease reaction temperature and simplify precipitation process. The result showed that hierarchical pores in scale of microns introduced by foams were regarded to benefit for high coverage and unimodal distribution of QDs on the surface of THPF to increase the efficiencies of light-harvesting, charge-collection and charge-transfer. The increased efficiencies caused an enhancement in quantum efficiency of the cell and thus remarkably increased the short circuit current density (Jsc). In addition, the decrease of charge recombination resulted in the increase of the open circuit voltage (Voc) as well. The QDSSC based on THPF exhibited about 2-fold higher power conversion efficiency (η = 2.20%, Jsc = 13.82 mA cm-2, Voc = 0.572 V) than that of TiO2 nanoparticles film (TNF) (η = 1.06%, Jsc = 6.70 mA cm-2, Voc = 0.505 V). It provided a basis to use foams both as soft template and carrier to realize simultaneously construction and in-situ sensitization of photoanode in further work.

  18. Electronic and optical properties of anatase and rutile TiO_2:Nb%锐钛矿相和金红石相TiO_2:Nb的光电性能研究

    Institute of Scientific and Technical Information of China (English)

    章瑞铄; 刘涌; 滕繁; 宋晨路; 韩高荣

    2012-01-01

    采用基于密度泛函理论的第一性原理计算了锐钛矿相和金红石相TiO_2:Nb的晶体结构、电子结构和光学性质.结果表明,在相等的摩尔掺杂浓度下(6.25%),锐钛矿相TiO_2:Nb的导带底电子有效质量小于金红石相TiO_2:Nb,且前者室温载流子浓度是后者的两倍左右,即具有更大的施主杂质电离率,从而解释了锐钛矿相TiO_2:Nb比金红石相TiO_2:Nb具有更优异电学性能的实验现象.光学计算也表明锐钛矿相在可见光区有更大的透过率,从而在理论上解释了锐铁矿相TiO_2:Nb比金红石相'riO_2:Nb更适于做透明导电材料的原因.计算结果与实验数据能较好符合.%First-principles calculations based on the density functional theory are used to study the crystal structure,electronic and optical properties of Nb doped anatase and rutile TiO_2.The calculated results reveal that anatase TiO_2:Nb has a smaller effective mass and carriers nearly twice lager than those of rutile TiO_2:Nb under the same doping concentration.And anatase TiO_2:Nb also exhibits a greater room-temperature ionization of donors.Besides,the calculated optical properties indicate that anatase TiO_2:Nb has a more excellent transparency than rutile TiO_2:Nb.All the results suggest that anatase TiO_2:Nb is more applicable to transparent conductive oxides.The calculated results consist well with the available experimental results.

  19. High photocatalytic activity of hierarchical SiO2@C-doped TiO2 hollow spheres in UV and visible light towards degradation of rhodamine B.

    Science.gov (United States)

    Zhang, Ying; Chen, Juanrong; Hua, Li; Li, Songjun; Zhang, Xuanxuan; Sheng, Weichen; Cao, Shunsheng

    2017-10-15

    Ongoing research activities are targeted to explore high photocatalytic activity of TiO2-based photocatalysts for the degradation of environmental contaminants under UV and visible light irradiation. In this work, we devise a facile, cost-effective technique to in situ synthesize hierarchical SiO2@C-doped TiO2 (SCT) hollow spheres for the first time. This strategy mainly contains the preparation of monodisperse cationic polystyrene spheres (CPS), sequential deposition of inner SiO2, the preparation of the sandwich-like CPS@SiO2@CPS particles, and formation of outer TiO2. After the one-step removal of CPS templates by calcination at 450°C, hierarchical SiO2@C-doped TiO2 hollow spheres are in situ prepared. The morphology, hierarchical structure, and properties of SCT photocatalyst were characterized by TEM. SEM, STEM Mapping, BET, XRD, UV-vis spectroscopy, and XPS. Results strongly confirm the carbon doping in the outer TiO2 lattice of SCT hollow spheres. When the as-synthesized SCT hollow spheres were employed as a photocatalyst for the degradation of Rhodamine B under visible-light and ultraviolet irradiation, the SCT photocatalyst exhibits a higher photocatalytic activity than commercial P25, effectively overcoming the limitations of poorer UV activity for many previous reported TiO2-based photocatalysts due to doping. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Tuning the Photocatalytic Activity of Anatase TiO2 Thin Films by Modifying the Preferred <001> Grain Orientation with Reactive DC Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    B. Stefanov

    2014-08-01

    Full Text Available Anatase TiO2 thin films were deposited by DC reactive magnetron sputtering on glass substrates at 20 mTorr pressure in a flow of an Ar and O2 gas mixture. The O2 partial pressure (PO2 was varied from 0.65 mTorr to 1.3 mTorr to obtain two sets of films with different stoichiometry. The structure and morphology of the films were characterized by secondary electron microscopy, atomic force microscopy, and grazing-angle X-ray diffraction complemented by Rietveld refinement. The as-deposited films were amorphous. Post-annealing in air for 1 h at 500 °C resulted in polycrystalline anatase film structures with mean grain size of 24.2 nm (PO2 = 0.65 mTorr and 22.1 nm (PO2 = 1.3 mTorr, respectively. The films sputtered at higher O2 pressure showed a preferential orientation in the <001> direction, which was associated with particle surfaces exposing highly reactive {001} facets. Films sputtered at lower O2 pressure exhibited no, or very little, preferential grain orientation, and were associated with random distribution of particles exposing mainly the thermodynamically favorable {101} surfaces. Photocatalytic degradation measurements using methylene blue dye showed that <001> oriented films exhibited approximately 30% higher reactivity. The measured intensity dependence of the degradation rate revealed that the UV-independent rate constant was 64% higher for the <001> oriented film compared to randomly oriented films. The reaction order was also found to be higher for <001> films compared to randomly oriented films, suggesting that the <001> oriented film exposes more reactive surface sites.

  1. Fabrication of hierarchically porous TiO2 nanofibers by microemulsion electrospinning and their application as anode material for lithium-ion batteries.

    Science.gov (United States)

    Zhang, Jin; Cai, Yibing; Hou, Xuebin; Song, Xiaofei; Lv, Pengfei; Zhou, Huimin; Wei, Qufu

    2017-01-01

    Titanium dioxide (TiO2) nanofibers have been widely applied in various fields including photocatalysis, energy storage and solar cells due to the advantages of low cost, high abundance and nontoxicity. However, the low conductivity of ions and bulk electrons hinder its rapid development in lithium-ion batteries (LIB). In order to improve the electrochemical performances of TiO2 nanomaterials as anode for LIB, hierarchically porous TiO2 nanofibers with different tetrabutyl titanate (TBT)/paraffin oil ratios were prepared as anode for LIB via a versatile single-nozzle microemulsion electrospinning (ME-ES) method followed by calcining. The experimental results indicated that TiO2 nanofibers with the higher TBT/paraffin oil ratio demonstrated more axially aligned channels and a larger specific surface area. Furthermore, they presented superior lithium-ion storage properties in terms of specific capacity, rate capability and cycling performance compared with solid TiO2 nanofibers for LIB. The initial discharge and charge capacity of porous TiO2 nanofibers with a TBT/paraffin oil ratio of 2.25 reached up to 634.72 and 390.42 mAh·g(-1), thus resulting in a coulombic efficiency of 61.51%; and the discharge capacity maintained 264.56 mAh·g(-1) after 100 cycles, which was much higher than that of solid TiO2 nanofibers. TiO2 nanofibers with TBT/paraffin oil ratio of 2.25 still obtained a high reversible capacity of 204.53 mAh·g(-1) when current density returned back to 40 mA·g(-1) after 60 cycles at increasing stepwise current density from 40 mA·g(-1) to 800 mA·g(-1). Herein, hierarchically porous TiO2 nanofibers have the potential to be applied as anode for lithium-ion batteries in practical applications.

  2. Assembly of CdS Quantum Dots onto Hierarchical TiO2 Structure for Quantum Dots Sensitized Solar Cell Applications

    Directory of Open Access Journals (Sweden)

    Syed Mansoor Ali

    2015-05-01

    Full Text Available Quantum dot (QD sensitized solar cells based on Hierarchical TiO2 structure (HTS consisting of spherical nano-urchins on transparent conductive fluorine doped tin oxide glass substrate is fabricated. The hierarchical TiO2 structure consisting of spherical nano-urchins on transparent conductive fluorine doped tin oxide glass substrate synthesized by hydrothermal route. The CdS quantum dots were grown by the successive ionic layer adsorption and reaction deposition method. The quantum dot sensitized solar cell based on the hierarchical TiO2 structure shows a current density JSC = 1.44 mA, VOC = 0.46 V, FF = 0.42 and η = 0.27%. The QD provide a high surface area and nano-urchins offer a highway for fast charge collection and multiple scattering centers within the photoelectrode.

  3. Preparation of Hierarchical Mesoporous TiO2 Nanosheet Using China Rose Petal as Template%以花瓣为模板制备TiO2分层介孔纳米片

    Institute of Scientific and Technical Information of China (English)

    赵晓兵; 王芳; 钱君超

    2012-01-01

    Hierarchical mesoporous TiO2 nanosheets were prepared using China rose petal as biotemplate through facile infiltration and thermal decomposition. For characterization of texture, X-ray diffraction spec-troscopy( XRD) , field emission scanning electron microscopy ( FESEM), transmission electron microscopy (TEM) , UV-Vis diffuse reflectance spectra(UV-Vis/DRS) and nitrogen adsorption-desorption measurements were adopted. The results demonstrate that the biomorphic structure of anatase TiO2 nanosheets with the thickness of ca. 4 nm is obtained. There exist mesopores with pore size of about 4 nm on the surface of the TiO2 nanosheets. Hierarchical mesoporous TiO2 nanosheets exhibit a clear red shift(20 nm) comparing with Degus-sa P25, which could be excited by visible irradiation and enhance the visible activity. Hierarchical mesoporous TiO2 nanosheets display the superior photocatalytic activity for the degradation of methylene blue under sunlight irradiation, with a which degradation rate as high as 98%.%以月季花花瓣为模板,经钛盐溶液浸渍后煅烧,合成了新型TiO2分层介孔纳米片.采用X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、环境扫描电子显微镜(ESEM)、透射电子显微镜(TEM)、紫外-可见漫反射光谱(UV-Vis/DRS)和氮气吸附-脱附曲线分析等手段对样品进行了表征.结果表明,所得样品由厚度约4 nm的具有生物形态结构的锐钛矿型TiO2纳米片组成.TiO2薄层表面存在大量介孔,其孔径集中分布于4 nm左右.由紫外-可见漫反射吸收光谱可知,材料的吸收边较纳米TiO2(P25)红移了约20 nm,因而具有更高的可见光光催化活性.TiO2分层介孔纳米片在阳光下表现出较强的光催化活性,在90 min内对亚甲基蓝的降解率可达98%,远高于TiO2纳米粉.

  4. Unexpected observation of spatially separated Kondo scattering and ferromagnetism in Ta alloyed anatase TiO2 thin films.

    Science.gov (United States)

    Sarkar, T P; Gopinadhan, K; Motapothula, M; Saha, S; Huang, Z; Dhar, S; Patra, A; Lu, W M; Telesio, F; Pallecchi, I; Ariando; Marré, D; Venkatesan, T

    2015-08-12

    We report the observation of spatially separated Kondo scattering and ferromagnetism in anatase Ta0.06Ti0.94O2 thin films as a function of thickness (10-200 nm). The Kondo behavior observed in thicker films is suppressed on decreasing thickness and vanishes below ~25 nm. In 200 nm film, transport data could be fitted to a renormalization group theory for Kondo scattering though the carrier density in this system is lower by two orders of magnitude, the magnetic entity concentration is larger by a similar magnitude and there is strong electronic correlation compared to a conventional system such as Cu with magnetic impurities. However, ferromagnetism is observed at all thicknesses with magnetic moment per unit thickness decreasing beyond 10 nm film thickness. The simultaneous presence of Kondo and ferromagnetism is explained by the spatial variation of defects from the interface to surface which results in a dominantly ferromagnetic region closer to substrate-film interface while the Kondo scattering is dominant near the surface and decreasing towards the interface. This material system enables us to study the effect of neighboring presence of two competing magnetic phenomena and the possibility for tuning them.

  5. Effects of adsorbed F, OH, and Cl ions on formaldehyde adsorption performance and mechanism of anatase TiO2 nanosheets with exposed {001} facets.

    Science.gov (United States)

    Zhou, Peng; Zhu, Xiaofeng; Yu, Jiaguo; Xiao, Wei

    2013-08-28

    Formaldehyde (HCHO), as the main indoor air pollutant, is highly needed to be removed by adsorption or catalytic oxidation from the indoor air. Herein, the F(-), OH(-), and Cl(-)-modified anatase TiO2 nanosheets (TNS) with exposed {001} facets were prepared by a simple hydrothermal and post-treatment method, and their HCHO adsorption performance and mechanism were investigated by the experimental analysis and theoretical simulations. Our results indicated that the adsorbed F(-), OH(-), and Cl(-) ions all could weaken the interaction between the HCHO and TNS surface, leading to the serious reduction of HCHO adsorption performance of TNS. However, different from F(-) and Cl(-) ions, OH(-) ion could induce the dissociative adsorption of HCHO by capturing one H atom from HCHO, resulting in the formation of one formyl group and one H2O-like group. This greatly reduced the total energy of the HCHO adsorption system. Thus, the adsorbed OH(-) ions could provide the additional active centers for HCHO adsorption. As a result, the NaOH-treated TNS showed the best HCHO adsorption performance mainly because its surface F(-) was replaced by OH(-). This study will provide new insight into the design and fabrication of high performance adsorbents for removing indoor HCHO and, also, will enhance the understanding of the HCHO adsorption mechanism.

  6. Role of molar concentration in structural, optical and gas sensing performance of anatase phase TiO2 nanofilms: automated nebulizer spray pyrolysis (ANSP) technique

    Science.gov (United States)

    Gopala Krishnan, V.; Elango, P.; Ganesan, V.

    2017-07-01

    TiO2 nanofilms were deposited on a glass substrate at 500 °C using automated nebulizer spray pyrolysis. The anatase polycrystalline structure with increased grain size and variations of surfactant planes ( T c) were influenced by molar concentration on XRD study. AFM study shows the average roughness values were increased with increase in molar concentration. A granular domain like microstructure with crack and void-free particle was examined by FESEM. The maximum transmittance 95.5% (529.6 nm) for x = 0.05 M/L, further increment of molar concentration showed the decremented transmittance with red shift absorption edge and the calculated band gap values ( E g = 3.53-3.20 eV) also noted. The gas sensing performances of films were studied with respect to various gas sensing parameters and the ammonia (NH3) gas showed better sensing response ( S max = 89%) at 150 °C for 300 ppm gas concentration against other gases (C2H6O, CH4O, C3H8O and C3H6O).

  7. Anatase TiO2 pillar-nanoparticle composite fabricated by layer-by-layer assembly for high-efficiency dye-sensitized solar cells.

    Science.gov (United States)

    Zhang, Guoliang; Pan, Kai; Zhou, Wei; Qu, Yang; Pan, Qingjing; Jiang, Baojiang; Tian, Guohui; Wang, Guofeng; Xie, Ying; Dong, Youzhen; Miao, Xiaohuan; Tian, Chungui

    2012-11-07

    The anatase TiO(2) pillar (PL)-TiO(2) nanoparticle (NP) composite is fabricated via layer-by-layer assembly. The composition of the nanostructures (i.e. the pillar-to-nanoparticle ratio) can be conveniently tuned by controlling the experimental conditions of the layer-by-layer assembly. It has been used to fabricate photoelectrodes for high-efficiency dye-sensitized solar cells (DSSCs), which combine the advantages of the rapid electron transport in PLs with the high surface area of NPs. It was found that, with optimum preparation conditions, DSSCs with the composite photoelectrode show a better photoelectrical conversion efficiency (8.06%) than those with either the naked PL photoelectrode or the mechanically mixed PL-NP photoelectrode. This is explained by the photoelectron injection drive force and the interfacial electron transport of the DSSCs, which are quantitatively characterized using the surface photovoltage spectra and electrochemical impedance spectroscopy measurements. It is evident that the DSSC with the optimal PL/NP ratio displays the largest photoelectron injection drive force and the fastest interfacial electron transfer.

  8. In-situ preparation of hierarchical flower-like TiO2/carbon nanostructures as fillers for polymer composites with enhanced dielectric properties

    Science.gov (United States)

    Xu, Nuoxin; Zhang, Qilong; Yang, Hui; Xia, Yuting; Jiang, Yongchang

    2017-01-01

    Novel three-dimensional hierarchical flower-like TiO2/carbon (TiO2/C) nanostructures were in-situ synthesized via a solvothermal method involving calcination of organic precursor under inert atmosphere. The composite films comprised of P (VDF-HFP) and as-prepared hierarchical flower-like TiO2/C were fabricated by a solution casting and hot-pressing approach. The results reveal that loading the fillers with a small amount of carbon is an effective way to improve the dielectric constant and suppress the dielectric loss. In addition, TiO2/C particles with higher carbon contents exhibit superiority in promoting the dielectric constants of composites when compared with their noncarbon counterparts. For instance, the highest dielectric constant (330.6) of the TiO2/C composites is 10 times over that of noncarbon-TiO2-filled ones at the same filler volume fraction, and 32 times over that of pristine P (VDF-HFP). The enhancement in the dielectric constant can be attributed to the formation of a large network, which is composed of local micro-capacitors with carbon particles as electrodes and TiO2 as the dielectric in between. PMID:28262766

  9. In-situ preparation of hierarchical flower-like TiO2/carbon nanostructures as fillers for polymer composites with enhanced dielectric properties

    Science.gov (United States)

    Xu, Nuoxin; Zhang, Qilong; Yang, Hui; Xia, Yuting; Jiang, Yongchang

    2017-03-01

    Novel three-dimensional hierarchical flower-like TiO2/carbon (TiO2/C) nanostructures were in-situ synthesized via a solvothermal method involving calcination of organic precursor under inert atmosphere. The composite films comprised of P (VDF-HFP) and as-prepared hierarchical flower-like TiO2/C were fabricated by a solution casting and hot-pressing approach. The results reveal that loading the fillers with a small amount of carbon is an effective way to improve the dielectric constant and suppress the dielectric loss. In addition, TiO2/C particles with higher carbon contents exhibit superiority in promoting the dielectric constants of composites when compared with their noncarbon counterparts. For instance, the highest dielectric constant (330.6) of the TiO2/C composites is 10 times over that of noncarbon-TiO2-filled ones at the same filler volume fraction, and 32 times over that of pristine P (VDF-HFP). The enhancement in the dielectric constant can be attributed to the formation of a large network, which is composed of local micro-capacitors with carbon particles as electrodes and TiO2 as the dielectric in between.

  10. Enhanced photovoltaic performance of fully flexible dye-sensitized solar cells based on the Nb2O5 coated hierarchical TiO2 nanowire-nanosheet arrays

    Science.gov (United States)

    Liu, Wenwu; Hong, Chengxun; Wang, Hui-gang; Zhang, Mei; Guo, Min

    2016-02-01

    Nb2O5 coated hierarchical TiO2 nanowire-sheet arrays photoanode was synthesized on flexible Ti-mesh substrate by using a hydrothermal approach. The effect of TiO2 morphology and Nb2O5 coating layer on the photovoltaic performance of the flexible dye sensitized solar cells (DSSCs) based on Ti-mesh supported nanostructures were systematically investigated. Compared to the TiO2 nanowire arrays (NWAs), hierarchical TiO2 nanowire arrays (HNWAs) with enlarged internal surface area and strong light scattering properties exhibited higher overall conversion efficiency. The introduction of thin Nb2O5 coating layers on the surface of the TiO2 HNWAs played a key role in improving the photovoltaic performance of the flexible DSSC. By separating the TiO2 and electrolyte (I-/I3-), the Nb2O5 energy barrier decreased the electron recombination rate and increased electron collection efficiency and injection efficiency, resulting in improved Jsc and Voc. Furthermore, the influence of Nb2O5 coating amounts on the power conversion efficiency were discussed in detail. The fully flexible DSSC based on Nb2O5 coated TiO2 HNWAs films with a thickness of 14 μm displayed a well photovoltaic property of 4.55% (Jsc = 10.50 mA cm-2, Voc = 0.75 V, FF = 0.58). The performance enhancement of the flexible DSSC is largely attributed to the reduced electron recombination, enlarged internal surface area and superior light scattering ability of the formed hierarchical nanostructures.

  11. CdS/CdSe Co-sensitized Solar Cells Based on Hierarchically Structured SnO2/TiO2 Hybrid Films

    Science.gov (United States)

    Chen, Zeng; Wei, Chaochao; Li, Shengjun; Diao, Chunli; Li, Wei; Kong, Wenping; Zhang, Zhenlong; Zhang, Weifeng

    2016-06-01

    SnO2 nanosheet-structured films were prepared on a fluorine-doped tin oxide (FTO) substrate using ZnO nanosheet as template. The as-prepared SnO2 nanosheets contained plenty of nano-voids and were generally vertical to the substrate. TiO2 nanoparticles were homogeneously deposited into the intervals between the SnO2 nanosheets to prepare a hierarchically structured SnO2/TiO2 hybrid film. The hybrid films were co-sensitized with CdS and CdSe quantum dots. The sensitized solar cells assembled with the SnO2/TiO2 hybrid film showed much higher photoelectricity conversion efficiency than the cells assembled with pure TiO2 films. The lifetime of photoinduced electron was also investigated through electrochemical impedance spectroscopy, which showed that the SnO2/TiO2 hybrid film electrode is as long as the TiO2 film electrode.

  12. CdS/CdSe Co-sensitized Solar Cells Based on Hierarchically Structured SnO2/TiO2 Hybrid Films.

    Science.gov (United States)

    Chen, Zeng; Wei, Chaochao; Li, Shengjun; Diao, Chunli; Li, Wei; Kong, Wenping; Zhang, Zhenlong; Zhang, Weifeng

    2016-12-01

    SnO2 nanosheet-structured films were prepared on a fluorine-doped tin oxide (FTO) substrate using ZnO nanosheet as template. The as-prepared SnO2 nanosheets contained plenty of nano-voids and were generally vertical to the substrate. TiO2 nanoparticles were homogeneously deposited into the intervals between the SnO2 nanosheets to prepare a hierarchically structured SnO2/TiO2 hybrid film. The hybrid films were co-sensitized with CdS and CdSe quantum dots. The sensitized solar cells assembled with the SnO2/TiO2 hybrid film showed much higher photoelectricity conversion efficiency than the cells assembled with pure TiO2 films. The lifetime of photoinduced electron was also investigated through electrochemical impedance spectroscopy, which showed that the SnO2/TiO2 hybrid film electrode is as long as the TiO2 film electrode.

  13. Hierarchical top-porous/bottom-tubular TiO 2 nanostructures decorated with Pd nanoparticles for efficient photoelectrocatalytic decomposition of synergistic pollutants

    KAUST Repository

    Zhang, Zhonghai

    2012-02-22

    In this paper, top-porous and bottom-tubular TiO 2 nanotubes (TiO 2 NTs) loaded with palladium nanoparticles (Pd/TiO 2 NTs) were fabricated as an electrode for an enhanced photoelectrocatalytic (PEC) activity toward organic dye decomposition. TiO 2 NTs with a unique hierarchical top-porous and bottom-tubular structure were prepared by a facile two-step anodization method and Pd nanoparticles were decorated onto the TiO 2 NTs via a photoreduction process. The PEC activity of Pd/TiO 2 NTs was investigated by decomposition of methylene blue (MB) and Rhodamine B (RhB). Because of formation Schottky junctions between TiO 2 and Pd, which significantly promoted the electron transfer and reduced the recombination of photogenerated electrons and holes, the Pd/TiO 2 NT electrode showed significantly higher PEC activities than TiO 2 NTs. Interestingly, an obvious synergy between two dyes was observed and corresponding mechanism based on facilitated transfer of electrons and holes as a result of a suitable energy level alignment was suggested. The findings of this work provide a fundamental insight not only into the fabrication but also utility of Schottky junctions for enhanced environmental remediation processes. © 2012 American Chemical Society.

  14. Hierarchical-structured anatase-titania/cellulose composite sheet with high photocatalytic performance and antibacterial activity.

    Science.gov (United States)

    Luo, Yan; Huang, Jianguo

    2015-02-02

    Bulk hierarchical anatase-titania/cellulose composite sheets were fabricated by subjecting an ultrathin titania gel film pre-deposited filter paper to a solvo-co-hydrothermal treatment by using titanium butoxide as the precursor to grow anatase-titania nanocrystallites on the cellulose nanofiber surfaces. The titanium butoxide specie is firstly absorbed onto the nanofibers of the cellulose substance through a solvothermal process, which was thereafter hydrolyzed and crystallized upon the subsequent hydrothermal treatment, leading to the formation of fine anatase-titania nanoparticles with sizes of 2-5 nm uniformly anchored on the cellulose nanofibers. The resulting anatase-titania/cellulose composite sheet shows a significant photocatalytic performance towards degradation of a methylene blue dye, and introduction of silver nanoparticles into the composite sheet yields an Ag-NP/anatase-titania/cellulose composite material possessing excellent antibacterial activity against both Gram-positive and Gram-negative bacteria. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. TiO2纳米片/巢状分级结构纳米阵列薄膜的制备及其在染料敏化太阳能电池中的应用%Fabrication of Nanosheet/Nestlike Nanoarray Hierarchical TiO2 Film for Dye-Sensitized Solar Cell

    Institute of Scientific and Technical Information of China (English)

    常萌蕾; 李新军

    2012-01-01

    A hierarchical configuration of TiO2 nanoarray film,comprising a nestlike TiO2 nanoarray layer integrated with a nanosheet network overlayer,was constructed.The hierarchical TiO2 film was obtained by the post-hydrothermal treatment with NaOH solution on hydrothermally synthesized TiO2-derived nanostructured arrays grown on fluorine-doped tin oxide substrate (FTO).The TiO2 films were characterized by field-emission scanning electron microscope (FE-SEM),X-ray diffraction (XRD),ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy,and absorbance spectroscopy.FE-SEM shows that the hierarchical TiO2 film with a thickness of 1.5 μm is composed of a nanosheet overlayer (~0.2 μm height) and the nestlike nanoarray layer (~1.3 μm height).XRD patterns display that the TiO2 films have pure anatase phase structure.UV-Vis spectra reveal enhanced light scattering and dye adsorption ability of the hierarchical TiO2 film.For the dye-sensitized solar cell (DSSC) based on the nanosheet/nestlike nanoarray hierarchical TiO2 film,a short-circuit current (Jac) of 7.79 mA· cm-2,open-circuit voltage (Voc) of 0.80 V,fill factor (FF) of 0.40,and photoelectric conversion efficiency (η) of 2.48% are achieved.Within the dye-sensitized solar cell,the photoelectric conversion efficiency of the hierarchical TiO2 film was nearky ten times higher than that of nanostructured array film.%采用水热合成法在氟掺杂二氧化锡(FTO)导电玻璃基底上得到TiO2纳米阵列薄膜,并进一步通过NaOH溶液水热处理制备了由巢状纳米阵列及纳米片覆盖层构成的TiO2纳米阵列分级结构一体化薄膜.采用场发射扫描电镜(FE-SEM),X射线衍射(XRD),紫外-可见(UV-Vis)漫反射光谱和吸收光谱技术对TiO2薄膜的结构和性质进行表征.FE-SEM结果表明:分级结构TiO2薄膜膜厚为1.5 μm,薄膜由一层纳米片覆盖层(约0.2 μm高)和一层巢状纳米阵列层(约1.3 μm高)组成.XRD谱图表明TiO2薄膜为锐钛矿相.UV-Vis

  16. Fe­S共掺杂锐钛矿相TiO2的第一性原理研究%First­principles study on Fe­S co­doped anatase TiO2

    Institute of Scientific and Technical Information of China (English)

    吴国浩; 郑树凯; 刘磊

    2013-01-01

      利用基于密度泛函理论的第一性原理平面波超软赝势方法对未掺杂、Fe和S单掺杂及Fe­S共掺杂锐钛矿相TiO2的电子结构进行计算,分析Fe、S单掺杂及Fe­S共掺杂对锐钛矿相TiO2的晶体结构、能带、态密度和光吸收性质的影响。结果表明,掺杂后 TiO2的晶格发生畸变,原子间键长的变化使晶格发生膨胀;掺杂后 TiO2的禁带宽度减小,并在禁带中引入杂质能级,导致TiO2的吸收带边红移;与Fe和S单掺杂相比,Fe­S共掺杂锐钛矿相TiO2的吸收带边红移程度更大。%The electronic structures of Fe­doped, S­doped and Fe­S co­doped anatase TiO2 were calculated by the first­principles plane wave ultra­soft pseudo­potential method based on the density functional theory (DFT). The effects of doping on crystal structures, energy bands, density of states (DOS) and optical properties were analyzed. The results show that, after doping the lattices of TiO2 are distorted by the doping and the bond length change of atoms leads to the lattice expansion. The impurity levels in the band gap and the decrease of the forbidden band width lead to the red­shift of absorption band edge in anatase TiO2. Fe­S co­doped anatase TiO2 shows a stronger red­shift in the absorption band edge than the single Fe­doped and single S doped samples in the optical spectra.

  17. Hierarchical nanostructures of copper(II) phthalocyanine on electrospun TiO(2) nanofibers: controllable solvothermal-fabrication and enhanced visible photocatalytic properties.

    Science.gov (United States)

    Zhang, Mingyi; Shao, Changlu; Guo, Zengcai; Zhang, Zhenyi; Mu, Jingbo; Cao, Tieping; Liu, Yichun

    2011-02-01

    In the present work, 2,9,16,23-tetranitrophthalocyanine copper(II) (TNCuPc)/TiO(2) hierarchical nanostructures were successfully fabricated by a simple combination method of electrospinning technique and solvothermal processing. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), UV-vis diffuse reflectance (DR), Fourier transform infrared spectrum (FT-IR), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric and differential thermal analysis (TG-DTA) were used to characterize the as-synthesized TNCuPc/TiO(2) hierarchical nanostructures. The results showed that the secondary TNCuPc nanostructures were not only successfully grown on the primary TiO(2) nanofibers substrates but also uniformly distributed without aggregation. By adjusting the solvothermal fabrication parameters, the TNCuPc nanowires or nanoflowers were facilely fabricated, and also the loading amounts of TNCuPc could be controlled on the TNCuPc/TiO(2) hierarchical nanostructural nanofibers. And, there might exist the interaction between TNCuPc and TiO(2). A possible mechanism for the formation of TNCuPc/TiO(2) hierarchical nanostructures was suggested. The photocatalytic studies revealed that the TNCuPc/TiO(2) hierarchical nanostructures exhibited enhanced photocatalytic efficiency of photodegradation of Rhodamine B (RB) compared with the pure TNCuPc or TiO(2) nanofibers under visible-light irradiation.

  18. Hierarchical rutile TiO2 flower cluster-based high efficiency dye-sensitized solar cells via direct hydrothermal growth on conducting substrates.

    Science.gov (United States)

    Ye, Meidan; Liu, Hsiang-Yu; Lin, Changjian; Lin, Zhiqun

    2013-01-28

    Dye-sensitized solar cells (DSSCs) based on hierarchical rutile TiO(2) flower clusters prepared by a facile, one-pot hydrothermal process exhibit a high efficiency. Complex yet appealing rutile TiO(2) flower films are, for the first time, directly hydrothermally grown on a transparent conducting fluorine-doped tin oxide (FTO) substrate. The thickness and density of as-grown flower clusters can be readily tuned by tailoring growth parameters, such as growth time, the addition of cations of different valence and size, initial concentrations of precursor and cation, growth temperature, and acidity. Notably, the small lattice mismatch between the FTO substrate and rutile TiO(2) renders the epitaxial growth of a compact rutile TiO(2) layer on the FTO glass. Intriguingly, these TiO(2) flower clusters can then be exploited as photoanodes to produce DSSCs, yielding a power conversion efficiency of 2.94% despite their rutile nature, which is further increased to 4.07% upon the TiCl(4) treatment.

  19. Hierarchical growth of TiO2 nanosheets on anodic ZnO nanowires for high efficiency dye-sensitized solar cells

    Science.gov (United States)

    Miles, David O.; Lee, Chang Soo; Cameron, Petra J.; Mattia, Davide; Kim, Jong Hak

    2016-09-01

    We present a novel route to hierarchical core-shell structures consisting of an anodic ZnO nanowire core surrounded by a shell of TiO2 nanosheets (ZNW@TNS). This material combines the beneficial properties of enhanced electron transport, provided by the nanowire core, with the high surface area and chemical stability of the TiO2 shell. Quasi-solid-state dye-sensitized solar cells (qssDSSCs) are prepared using different quantities of either the bare ZnO nanowires or the hierarchical nanowire structures and the effect on cell performance is examined. It is found that whilst the addition of the bare ZnO nanowires results in a decrease in cell performance, significant improvements can be achieved with the addition of small quantities of the hierarchical structures. Power conversion efficiencies of up to 7.5% are achieved under 1 Sun, AM 1.5 simulated sunlight, with a ∼30% increase compared to non-hierarchical mesoporous TiO2 films. A solid-state DSSC (ssDSSC) with a single component solid polymer also exhibits excellent efficiency of 7.2%. The improvement in cell performance is related to the improved light scattering, surface area and electron transport properties via the use of reflectance spectroscopy, BET surface area measurements and electrochemical impedance spectroscopy.

  20. Cocatalyzing Pt/PtO Phase-Junction Nanodots on Hierarchically Porous TiO2 for Highly Enhanced Photocatalytic Hydrogen Production.

    Science.gov (United States)

    Ren, Xiao-Ning; Hu, Zhi-Yi; Jin, Jun; Wu, Liang; Wang, Chao; Liu, Jing; Liu, Fu; Wu, Min; Li, Yu; Tendeloo, Gustaaf Van; Su, Bao-Lian

    2017-09-06

    Phase-junctions between a cocatalyst and its semiconductor host are quite effective to enhance the photocatalytic activity and are widely studied, while reports on the phase-juncted cocatalyst are still rare. In this work, we report the deposition of the Pt/PtO phase-juncted nanodots as cocatalyst via NaOH modification of an interconnected meso-macroporous TiO2 network with high surface area and inner-particle mesopores to enhance the performance of photocatalytic H2 production. Our results show that NaOH modification can largely influence Pt/PtO phase-juncted nanodot formation and dispersity. Compared to the TiO2 nanoparticles, the hierarchically meso-macroporous TiO2 network containing 0.18 wt % Pt/PtO phase-juncted cocatalyst demonstrates a highest photocatalytic H2 rate of 13 mmol g(-1) h(-1) under simulated solar light, and possesses a stable cycling activity without obvious decrease after five cycles. Such high H2 production performance can be attributed to both the phase-juncted Pt/PtO providing more active sites while PtO suppresses the undesirable hydrogen back reaction, and the special hierarchically porous TiO2 network with inner-particle mesopores presenting short diffusion path lengths for photogenerated electrons and enhanced light harvesting efficiency. This work suggests that Pt/PtO phase-juncted cocatalyst on hierarchically porous TiO2 nanostructures is a promising strategy for advanced photocatalytic H2 production.

  1. Template-free synthesis of hierarchical TiO2 hollow microspheres as scattering layer for dye-sensitized solar cells

    Science.gov (United States)

    Rui, Yichuan; Wang, Linlin; Zhao, Jiachang; Wang, Hongzhi; Li, Yaogang; Zhang, Qinghong; Xu, Jingli

    2016-04-01

    Hierarchical TiO2 hollow microspheres were synthesized by a 2-step process consisting of thermal hydrolysis and subsequent solvothermal reaction. Quasi-monodispersed solid TiO2 microspheres aggregated by amorphous particles were firstly obtained by the controlled thermal hydrolysis of titanium sulfate, and then the solid structures transformed to hollow ones and crystallized during the subsequent solvothermal treatment. SEM and TEM images of the samples revealed that the morphological evolution was in perfect accordance with the inside-out Ostwald ripening mechanism. The rich porosity and unique hierarchical hollow structure endow the TiO2 microspheres with a large specific surface area of 108.0 m2 g-1. As an effective anode material for dye-sensitized solar cells, TiO2 hollow microspheres showed good capability of dye adsorption and strong light scattering, leading to a comparable energy conversion efficiency to the commercial 18NR-T transparent titania. Finally, a high efficiency of 7.84% was achieved for the bi-layer DSSC by coating the hollow microspheres on top of the 18NR-T titania as the light scattering layer.

  2. Energy Storage: Nitrogen-Doped Ordered Mesoporous Anatase TiO2 Nanofibers as Anode Materials for High Performance Sodium-Ion Batteries (Small 26/2016).

    Science.gov (United States)

    Wu, Ying; Liu, Xiaowu; Yang, Zhenzhong; Gu, Lin; Yu, Yan

    2016-07-01

    On page 3522, Y. Yu and co-workers fabricate nitrogen-doped ordered mesoporous TiO2 nanofibers (denoted as N-MTO) by electrospinning and subsequent nitridation treatment. Nitrogen atoms are successfully doped into the TiO2 lattice, accompanied by the formation of Ti(3+) and oxygen vacancies, contributing to the improvement of electronic conductivity of TiO2 . When used as an anode for a sodium-ion battery, the N-MTO demonstrates excellent rate capability and superior long cycling performance.

  3. Construction of hierarchical nanostructured TiO2/Bi2MoO6 heterojunction for improved visible light photocatalysis.

    Science.gov (United States)

    Zhang, Wei-De; Zhu, Li

    2012-08-01

    In this study, Bi2MoO6 hollow microspheres were modified by depositing TiO2 nanoparticles through a simple hydrothermal method. The prepared TiO2/Bi2MoO6 photocatalysts were characterized by scanning and transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The photocatalytic performance of the heterostructured catalysts was evaluated by degradation of methylene blue (MB) under visible-light irradiation (lambda>420 nm). The photocatalysts based on nanostructured Bi2MoO6 and TiO2 exhibit much higher photocatalytic activity than the single-phase Bi2MoO6 or TiO2 and the mechanical mixture of Bi2MoO6 and TiO2 for degradation of MB under the same conditions. The results reported in this study provide insight into constructing other heterostructured photocatalysts.

  4. Controllable Synthesis and Tunable Photocatalytic Properties of Ti(3+)-doped TiO2.

    Science.gov (United States)

    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.

  5. LATTICE DEFORMATION AND PHASE TRANSFORMATION FROM NANO-SCALE ANATASE TO NANO-SCALE RUTILE TiO2 PREPARED BY A SOL-GEL TECHNIQUE

    Institute of Scientific and Technical Information of China (English)

    Yanqun Shao; Dian Tang; Jinghua Sun; Yekun Lee; Weihao Xiong

    2004-01-01

    Nano-scale rutile phase was transformed from nano-scale anatase upon heating, which was prepared by a sol-gel technique. The XRD data corresponding to the anatase and rutile phases were analyzed and the grain sizes of as-derived phases were calculated by Sherrer equation. The lattice parameters of the as-derived anatase and rutile unit cells were calculated and compared with those of standard lattice parameters on PDF cards. It was shown that the smaller the grain sizes, the larger the lattice deformation. The lattice parameter a has the negative deviation from the standard and the lattice parameter c has the positive deviation for both phases. The particles sizes had preferential influence on the longer parameter between the lattice parameters of a and c. With increasing temperatures, the lattice parameters of a and c in both phases approached to the equilibrium state. The larger lattice deformation facilitated the nucleation process, which lowered the transformation temperature. During the transformation from nano-scale anatase to rutile, besides the mechanism involving retention of the {112} pseudo-close-packed planes of oxygen in anatase as the{100} pseudo-close-packed planes in rutile, the new phase occurred by relaxation of lattice deformation and adjustment of the atomic sites in parent phase. The orientation relationships were suggested to be anatase {101}//rutile {101} and anatase //rutile, and the habit plane was anatase (101),

  6. Unusual Changes in Electronic Band-Edge Energies of the Nanostructured Transparent n-Type Semiconductor Zr-Doped Anatase TiO2 (Ti1-xZrxO2; x < 0.3).

    Science.gov (United States)

    Mieritz, Daniel G; Renaud, Adèle; Seo, Dong-Kyun

    2016-07-05

    By the establishment of highly controllable synthetic routes, electronic band-edge energies of the n-type transparent semiconductor Zr-doped anatase TiO2 have been studied holistically for the first time up to 30 atom % Zr, employing powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen gas sorption measurements, UV/vis spectroscopies, and Mott-Schottky measurements. The materials were produced through a sol-gel synthetic procedure that ensures good compositional homogeneity of the materials, while introducing nanoporosity in the structure, by achieving a mild calcination condition. Vegard's law was discovered among the homogeneous samples, and correlations were established between the chemical compositions and optical and electronic properties of the materials. Up to 20% Zr doping, the optical energy gap increases to 3.29 eV (vs 3.19 eV for TiO2), and the absolute conduction band-edge energy increases to -3.90 eV (vs -4.14 eV). The energy changes of the conduction band edge are more drastic than what is expected from the average electronegativities of the compounds, which may be due to the unnatural coordination environment around Zr in the anatase phase.

  7. Enhanced Visible-Light Photocatalytic Performance of Nanosized Anatase TiO2 Doped with CdS Quantum Dots for Cancer-Cell Treatment

    Directory of Open Access Journals (Sweden)

    Kangqiang Huang

    2012-01-01

    Full Text Available CdS quantum-dots-(QDs-doped TiO2 nanocomposites were successfully synthesized using the sol-gel technique and characterized by SEM, TEM, XRD, EDS, UV-Vis, and FS. They were then used as a new “photosensitizer” based on photodynamic therapy (PDT for cancer-cell treatment. The photocatalytic activities of CdS-TiO2 on leukemia tumors were investigated by using Cell Counting Kit-8 (CCK-8 assay. The ultrastructural morphology of treated cells was also studied by AFM. The experimental results indicated that an obvious inhibition of tumor growth would be observed in groups treated with CdS-TiO2 nanocomposites, and the PDT efficiency in the presence of CdS-doped TiO2 was significantly higher than that of TiO2, revealing that the photocatalytic activities of TiO2 could be effectively enhanced by the modification of CdS QDs. Additionally, CdS- TiO2 can exhibit a very high photodynamic efficiency of 80.5% at a final concentration of 200 μg/mL under visible-light irradiation. CdS-TiO2 nanocomposites in this case were regarded as a promising application for cancer-cell treatment.

  8. Improving the Photocatalytic Activity of Modified Anatase TiO2 with Different Concentrations of Aluminum under Visible Light: Mechanistic Survey.

    Science.gov (United States)

    Afshar, Shahrara; Pordel, Shabnam; Tahmouresilerd, Babak; Azad, Alireza

    2016-11-01

    Visible light-driven Al-doped TiO2 with different aluminum contents (2, 5 and 10 mol%) were synthesized via a facile sol-gel method. Fourier transform infrared (FTIR), UV-visible diffuse reflectance, energy dispersive X-ray (EDX) spectroscopy as well as X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electron microscopy (SEM) methods were used for the characterization of the obtained nanoparticles. The photocatalytic performance of the samples was evaluated by the degradation of rhodamine B (RhB) under visible light irradiation. The yield of the degradation RhB was estimated to be 71%, 89%, 65% and 56%, for the bare TiO2 , 2%, 5% and 10% Al-doped TiO2 , respectively. It was found that 2 mol% of Al-doped TiO2 shows the best photocatalytic performance. In low concentration of dopant, separation of photogenerated electron-hole pairs promoted, and subsequently, the degradation efficiency increased. It was proposed that the degradation of RhB by 2 mol% Al-doped TiO2 photocatalyst follows both N-deethylation and chromophore cleavage mechanisms, while the N-deethylation still predominated over cleavage of dye chromophore structure. The key role of hydroxyl radicals in RhB degradation was verified by the effects of scavengers. In addition, the photocatalyst can be reused for three runs without any significant loss of its catalytic activity.

  9. Synthesis of Pt-Loaded Self-Interspersed Anatase TiO2 with a Large Fraction of (001) Facets for Efficient Photocatalytic Nitrobenzene Degradation.

    Science.gov (United States)

    Wang, Wei-Kang; Chen, Jie-Jie; Li, Wen-Wei; Pei, Dan-Ni; Zhang, Xing; Yu, Han-Qing

    2015-09-16

    TiO2 is capable of directly utilizing solar energy for sustainable energy harvest and water purification. Facet-dependent performance of TiO2 has attracted enormous interests due to its tunable photocatalytic activity toward photoredox transformations, but information about the noble-metal-loaded TiO2 for its facet-dependent photocatalytic performance, especially in pollutant degradation systems, is limited. In this work, inspired by our previous theoretical calculations about the roles of the crystal surface in Pt-loaded TiO2 in its enhanced photocatalytic capacity, TiO2 nanocrystals with interspersed polyhedron nanostructures and coexposed (001) and (101) surfaces as a support of Pt nanoparticles are prepared in a simple and relatively green route. Also, their performance for photocatalytic degradation of nitrobenzene (NB), a model organic pollutant, is explored. The experimental results demonstrate that the NB photodegradation and photoconversion efficiencies are significantly enhanced by uniformly loading Pt nanoparticles on the crystal surfaces, but the Pt nanoparticles deposited on only the (101) surface have no contribution to the improved NB photodegradation. Furthermore, the liquid chromatography mass spectrometry results also show that NB photodegradation tends to proceed on the (001) surface of Pt/TiO2 for the generation of nitrophenol intermediates through the photooxidation pathway. This work provides a new route to design and construct advanced photocatalysts toward pollutant photoredox conversions and deepens our fundamental understanding about crystal surface engineering.

  10. Hole-Conductor-Free Mesoscopic TiO2/CH3NH3PbI3 Heterojunction Solar Cells Based on Anatase Nanosheets and Carbon Counter Electrodes.

    Science.gov (United States)

    Rong, Yaoguang; Ku, Zhiliang; Mei, Anyi; Liu, Tongfa; Xu, Mi; Ko, Songguk; Li, Xiong; Han, Hongwei

    2014-06-19

    A hole-conductor-free fully printable mesoscopic TiO2/CH3NH3PbI3 heterojunction solar cell was developed with TiO2 nanosheets containing high levels of exposed (001) facets. The solar cell embodiment employed a double layer of mesoporous TiO2 and ZrO2 as a scaffold infiltrated by perovskite as a light harvester. No hole conductor or Au reflector was employed. Instead, the back contact was simply a printable carbon layer. The perovskite was infiltrated from solution through the porous carbon layer. The high reactivity of (001) facets in TiO2 nanosheets improved the interfacial properties between the perovskite and the electron collector. As a result, photoelectric conversion efficiency of up to 10.64% was obtained with the hole-conductor-free fully printable mesoscopic TiO2/CH3NH3PbI3 heterojunction solar cell. The advantages of fully printable technology and the use of low-cost carbon-materials-based counter electrode and hole-conductor-free structure provide this design a promising prospect to approach low-cost photovoltaic devices.

  11. First-Principles Study of Adsorption of Dimethyl Methylphosphonate on the TiO2 Anatase (001) Surface: Formation of a Stable Titanyl (Ti=O) Site

    Science.gov (United States)

    2011-03-10

    Anatase (001) Surface: Formation of a Stable Titanyl (TidO) Site V. M. Bermudez Electronics Science and Technology Division, Naval Research Laboratory...bond at a 5-fold-coordinated Ti5c site. Figure 1 shows a model 25 for the corresponding structure on anatase (101) and also identifies the T5c, Ti6c...the UHV experimental data, computational results for DMMP on OH-free rutile (110) and anatase (101) and (100) surfaces24,25 find that dissociation is

  12. First-principles study of N/Cu co-dop ed anatase TiO2%N/Cu共掺杂锐钛矿型TiO2第一性原理研究∗

    Institute of Scientific and Technical Information of China (English)

    杨军; 苗仁德; 章曦

    2015-01-01

    基于密度泛函理论的第一性原理平面波超软赝势法,采用局域自旋密度近似加Hubbard U值方法研究了纯锐钛矿型TiO2, N, Cu单掺杂TiO2及N/Cu共掺杂TiO2的晶体结构、电子结构和光学性质。研究结果表明,掺杂后晶格发生相应畸变,晶格常数变大。 N和Cu的掺杂在TiO2禁带中引入杂质能级,禁带宽度发生相应改变。对于N掺杂TiO2禁带宽度减小较弱,而Cu掺杂和N/Cu共掺TiO2禁带宽度显著降低,导致吸收光谱明显红移,光学催化性增强,有利于实际应用。%Using the first-principles plane-wave ultra-soft pseudo-potential method based on the density functional theory, the structures, electronic-structures and optical properties of pure anatase TiO2, N (Cu) doped TiO2, and N/Cu co-doped TiO2 crystal are studied by the local-spin density approximation plus Hubbard U method. It is shown that the lattice constants become larger because of the lattice distortion caused by doping. Impurity levels in the band gap of TiO2 are introduced by N and Cu doping, and the forbidden band width is correspondingly changed. For N doped TiO2, the reduction of the band gap is weak, while the N/Cu co-doped TiO2 band gap decreases remarkably. It leads to a red shift of visible absorption spectrum and enhances optical catalysis. The effect is useful for the practical application of photo-catalytic.

  13. Dynamics of charge at water-to-semiconductor interface: Case study of wet [0 0 1] anatase TiO2 nanowire

    Science.gov (United States)

    Huang, Shuping; Balasanthiran, Choumini; Tretiak, Sergei; Hoefelmeyer, James D.; Kilina, Svetlana V.; Kilin, Dmitri S.

    2016-12-01

    The behavior of water molecules on the surfaces of the TiO2 nanowire grown in [0 0 1] direction has been investigated by combining theoretical calculations and experiments. Calculated UV-visible absorption spectra reproduce the main features of the experimental spectra. Computations predict that a photoexcitation followed by a sequence of relaxation events results in photoluminescence across the gap. TiO2 nanowires in vacuum and aqueous environment exhibit different dynamics of photo-excited charge carriers. In water, computed relaxation of electrons (holes) is approximately 2 (4) times faster compared with vacuum environment. Faster relaxation of holes vs. electrons and specific spatial localization of holes result to formation of long lived charge transfer excitation with positive charge at the surface of the nanowire. Comparison of relaxation process in TiO2/water interfaces focusing on different surfaces and nanostructures has potential in identifying structural characteristics of TiO2 materials important for efficient photo-electrochemical water splitting.

  14. 蒸汽处理钛酸制备锐钛矿相TiO2纳米晶体的光催化性能%Photocatalytic Properties of Anatase TiO2 Nanocrystal Prepared by Steam Treatment

    Institute of Scientific and Technical Information of China (English)

    董国义; 高琳洁; 王颖; 刘清波; 李志强; 韦志仁

    2011-01-01

    Sodium titanate fibers with lengths over 10 fun and widths of 10-100 nm were synthesized via hydrothermal method using anatase TiO2 as titanium source and NaOH as mineralizer, the products were characterized by transmission electron microscopy ( TEM ) and X-ray diffraction ( XRD ). Using steam hydrothermal method to further treat sodium titanate nanofibers which was washed by HC1, anatase TiO2 nanofibers with character of self-organizing were synthesized. Their degradation performance of methylene blue under 1 kW ultraviolet lamp and long-term stability was investigated. Photocatalytic experiments indicated that the obtained anatase TiO2 nanofibers are highly active for methylene blue, and these nanocrystal catalysts could be easily recycled without decreasing of the photocatalytic activity.%采用水热法,以锐钛矿相TiO2为原料,10 mol/L NaOH溶液作为矿化剂,合成了钛酸钠纤维.用XRD和TEM对产物进行了表征,观察到纤维长度超过10 μm,宽度为10~100 nm.酸洗后对其进行二次蒸汽处理,得到了具有自组织趋势的锐钛矿相纳米TiO2晶体纤维.以1 kW紫外灯为光源,分析了合成的锐钛矿相TiO2纳米晶体的光催化降解亚甲基蓝性能及其长期稳定性.结果表明:合成的锐钛矿相TiO2纳米晶体对亚甲基蓝的光降解活性很高,纳米晶体易回收,且循环使用光催化活性没有发生衰减.

  15. W-N共掺杂锐钛矿相TiO2的第一性原理计算%First Principle Calculation of W-N Co-doped Anatase TiO2

    Institute of Scientific and Technical Information of China (English)

    郑树凯; 吴国浩; 刘磊; 王芳

    2013-01-01

    The band structure,electronic density of states and absorption spectrum of W-N co-doped anatase TiO2 were calculated using first principle based on the density functional theory.The results indicate that W-N co-doping does not change the band gap of anatase TiO2,while N 2p doping energy level is incorporated into the band gap above the valence band maximum,and its Fermi energy level is located at the conduction band.W 5d orbital provides contributions to the bottom edge of valence band and conduction band,whereas N 2p contributes its orbital to the upper edge of valence band maximum and the isolated doping energy level located in the band gap.W-N co-doping enhances the absorption ability of anatase TiO2 in the wave length range from 340 to 800 nm.%利用基于密度泛函理论的第一性原理方法对W-N共掺杂锐钛矿相TiO2的能带结构、电子态密度及吸收光谱进行计算.结果表明,W-N共掺杂未改变锐钛矿相TiO2的禁带宽度,仅在TiO2价带顶附近引入N的2p杂质能级,并且掺杂系统的费米能级处于导带之内;W的5d轨道主要对TiO2的价带底下边沿和导带有贡献,N的2p轨道主要对TiO2的价带顶上边沿和禁带内的孤立能级有贡献;W-N共掺杂增强了锐钛矿相TiO2在340~800 nm波长范围内的光吸收能力.

  16. Preparation and Analysis of Nano-Crystallite Anatase Phase TiO2 Thin Films%纳米锐钛矿型TiO2薄膜的制备及分析

    Institute of Scientific and Technical Information of China (English)

    辛荣生; 林钰; 蔡彬; 胡斌

    2011-01-01

    采用反应磁控溅射法在玻璃衬底上制备锐钛矿相TiO2薄膜,研究了工艺条件中的氧氩流量比对薄膜润湿角的影响以及溅射气压对薄膜微观结构的影响.对不同氧氩流量比(分别为1/40,1/20,1/10和1/5)时制备的TiO2薄膜进行润湿角测量,润湿角照片显明:氧氩比1/5时薄膜润湿角可减小到8°左右,即提高氧氩比能增强TiO2薄膜的自洁净性能.X射线衍射(XRD)分析表明:当溅射气压降到1.0 Pa时,可以得到锐钛矿型TiO2薄膜晶体,0.5Pa时的XRD图衍射峰更为明显.用分光光度计测量了TiO2薄膜的紫外吸收光谱.由光谱曲线上光吸收阈值与半导体带隙之间的关系计算出了TiO2薄膜的禁带宽度为3.42 eV,表明TiO2薄膜的吸收边出现了一定的蓝移.根据 XRD图谱计算TiO2薄膜的晶粒尺寸,得到的薄膜晶粒尺寸在十几纳米左右,由此说明了TiO2薄膜吸收边发生蓝移的原因;按照锐钛矿相TiO2薄膜XRD图25.3°衍射峰对应的(101)晶面,由Bragg方程计算出其晶面间距为0.3521 nm.表明TiO2薄膜晶体发生了一定的晶格畸变.%The anatase phase TiO2 thin films were prepared on the glass substrates by DC reactive magnetron sputtenng method.The influence of technological condition, such as the O2/Ar flow ratio, on contact angle of the filma and the sputtering pressure on the microstructure of the films, was studied respectively.The contact angle of TiO2 films prepared in different O2/Ar flow ratio ( 1/40 , 1/20,1/10 and 1/5 ) were measured respectively.The contact angle photograph showed that the film contact angle could be reduced to 8° or so when the O2/Ar ratio was 1/5 , this meant that the self-clean property of TiO2 films could be enhanced by increasing O2/Ar ratio.Analysis of X-ray diffraction ( XRD) ahowed that the crystal of anatase phase TiO2 films could be obtained when the sputtering pressure was decreased to 1.0 Pa, the diffraction peak of XRD apectrum was more prominent when the

  17. Microwave-assisted solvothermal synthesis of hierarchical TiO2 microspheres for efficient electro-field-assisted-photocatalytic removal of tributyltin in tannery wastewater.

    Science.gov (United States)

    Zhao, Yang; Huang, Zhiding; Chang, Wenkai; Wei, Chao; Feng, Xugen; Ma, Lin; Qi, Xiaoxia; Li, Zenghe

    2017-07-01

    Organotin compounds have been widely used in recent decades, however, the residential tributyltin (TBT) in environment has potential harmful effects on human health due to the disruption of endocrine system even at trace level. Herein, this work reports on an effective electro-field-assisted-photocatalytic technique for removal of TBT by applying an electric field to photocatalysis of as-prepared hierarchical TiO2 microspheres. The synthesis of catalytic materials is based on a self-assembly process induced by microwave-assisted solvothermal reaction. Hierarchical TiO2 microspheres consisting of nanowires can be obtained in short time with this facile method and possess high surface area and superior optical properties. As the catalyst, it was found that the reaction rate constant of electro-field-assisted-photocatalytic removal (0.0488 min(-1)) of TBT exhibited almost a 9 fold improvement as compared to that of photocatalysis (0.0052 min(-1)). The proposed mechanism of electro-field-assisted-photocatalytic removal of TBT was verified by using (117)Sn-enriched TBT spike solution as an isotopic tracer. In addition, varying impacts from some key reaction conditions, such as voltage of potential, pH value and the presence of Cr and formaldehyde were also discussed. The overall satisfactory TBT removal performance of the proposed electro-field-assisted-photocatalysis procedure with hierarchical TiO2 microspheres, which was validated using actual tannery wastewater samples from three different kinds of tanning procedures. These attributes suggest that this electro-field-assisted-photocatalysis may have broad applications for the treatment of tannery wastewater. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. 锐钛矿相TiO2纳米纤维制备与摩擦学性能%Preparation of Anatase TiO2 Nanofiber and Its Tribological Properties as Additive in Liquid Paraffin

    Institute of Scientific and Technical Information of China (English)

    刘琳; 阴翔宇; 张月; 钱建华

    2013-01-01

    Anatase TiO2 nanofiber was prepared via an available alkaline hydrothermal method and surface modified. The obtained products were characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM) measurements and Fourier transform infrared spectroscopy (FT-IR). The as-prepared TiO2 nanofiber could be well dispersed in liquid paraffin, and its tribological properties as additive were evaluated with a four-ball tester. The results showed that the as-prepared TiO2 nanofiber exhibited good performance in anti-wear and friction-reduction, load-carrying capacity, and extreme pressure properties. When addition amount of the as-prepared TiO2 nanofiber was 1.5% of mass fraction in liquid paraffin, the best anti-friction wear reducing and bearing capacity enhancing were obtained, which made the TiO2 nanofiber promising for green lubricating oil additives.%采用简便且可重复性较好的碱熔法制备锐钛矿相TiO2,采用简便的表面修饰技术对其进行表面改性,得到TiO2纳米纤维,并采用XRD、SEM和FT-IR方法对其进行表征.利用四球摩擦试验机考察其作为油品润滑添加剂的摩擦学性能.结果表明,所合成的TiO2纳米纤维为锐钛矿相结构,结晶度和纯度较高,而且在油品中具有良好的分散性;TiO2纳米纤维具有良好的抗磨减摩性能,并能够很好地提高油品承载能力,当其加入量为1.5%(质量分数)时,抗磨减摩以及提高承载能力的效果最好.这些特性使得锐钛矿相TiO2纳米纤维有望在未来成为绿色润滑油添加剂.

  19. Palladium nanoparticles anchored to anatase TiO2 for enhanced surface plasmon resonance-stimulated, visible-light-driven photocatalytic activity

    Directory of Open Access Journals (Sweden)

    Kah Hon Leong

    2015-02-01

    Full Text Available Freely assembled palladium nanoparticles (Pd NPs on titania (TiO2 nano photocatalysts were successfully synthesized through a photodeposition method using natural sunlight. This synthesized heterogeneous photocatalyst (Pd/TiO2 was characterized through field emission scanning electron microscopy (FESEM, high resolution transmission electron microscopy (HRTEM, X-ray diffraction (XRD, BET surface area, UV–vis diffuse reflectance spectra (UV-DRS, Raman and photoluminescence (PL analyses. The simple and smart synthesis anchored well the deposition with controlled Pd NPs size ranging between 17 and 29 nm onto the surface of TiO2. Thus, it gives the characteristic for Pd NPs to absorb light in the visible region obtained through localized surface plasmon resonance (LSPRs. Apparently, the photocatalytic activity of the prepared photocatalysts was evaluated by degrading the endocrine disrupting compound (EDC amoxicillin (AMX excited under an artificial visible light source. In the preliminary run, almost complete degradation (97.5% was achieved in 5 h with 0.5 wt % Pd loading and the degradation followed pseudo-first-order kinetics. The reusability trend proved the photostability of the prepared photocatalysts. Hence, the study provides a new insight about the modification of TiO2 with noble metals in order to enhance the absorption in the visible-light region for superior photocatalytic performance.

  20. Synthesis and chemical modifications of in-situ grown anatase TiO2 microspheres with isotropically exposed {0 0 1} facets for superhydrophobic and self-cleaning properties

    Science.gov (United States)

    Hu, Wanbiao; Yu, Yuanlie; Chen, Hua; Lau, Kenny; Craig, Vincent; Brink, Frank; Withers, Ray L.; Liu, Yun

    2015-12-01

    Excellent and robust hydrophobic materials generally benefit from specifically exposed surfaces i.e. always the low-energy surfaces, and well-defined micro/nano-structures that are achieved through advanced facilities and complicated process with a high cost. We hereof demonstrate that the superhydrophobicity and further self-cleaning properties are also attainable based on high-energy crystalline facets by an appropriate chemical modification. Specifically, anatase TiO2 microspheres were large-scale synthesized to exhibit isotropically exposed high-energy {0 0 1} facets through optimizing the HF/H2O2/H2O ratio during hydrothermal processes. The formation of the microspheres was uncovered to be an in-situ ;growth-cum-assembly; grown mechanism. Such high-energy {0 0 1} facets facilitate the strong coupling between the resultant TiO2 microspheres and the modifier (2,2,3,3,4,4,5,5-octafluoro-1-pentanol) because the {0 0 1} facets offer abundant active sites for chemical bonding, showing great merits for superhydrophobicity (with water contact angle of 154 ± 2°, 6 μl droplets), and further stably surface self-cleaning i.e. easily removing surface contamination (e.g. Al2O3 powders). This integrated strategy represents a milestone in design and fabrication of delicate composites with high-energy surfaces for specific functions and properties.

  1. High open voltage and superior light-harvesting dye-sensitized solar cells fabricated by flower-like hierarchical TiO2 composed with highly crystalline nanosheets

    Science.gov (United States)

    Que, Ya-Ping; Weng, Jian; Hu, Lin-Hua; Wu, Ji-Huai; Dai, Song-Yuan

    2016-03-01

    The morphology, microstructure and crystallography of titanium dioxide (TiO2) have great effect on the photoelectric performance of dye-sensitized solar cells (DSSCs). Herein, flower-like 3D TiO2 microstructures based on well-defined high-crystalline nanosheets are synthesized through a facile hydrothermal method. Especially, morphological evolution process and mechanism of this hierarchical structure are investigated. Due to the highly crystalline nature and smaller surface area of these nanosheets, the corresponding device shows an extremely high open-current voltage up to 0.84 V, which results from the less electron recombination. When applied as a scattering layer on top of the nanoparticle layer, the power conversion efficiency (PCE) can be significantly improved and give birth to a PCE value of 9.6%, which is 24.6% higher than that of an analogous device using nanoparticles (NP) (7.7%). As reflected by diffusion reflection spectra, intensity of the modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) and electrochemical impedance spectra (EIS), this hierarchical structure can not only enhance light harvesting, but also reduce electron recombination, facilitate electron transport and improve electron collection efficiency.

  2. Synthesis of hierarchical TiO2 flower-rod and application in CdSe/CdS co-sensitized solar cell

    Science.gov (United States)

    Yu, Libo; Li, Zhen; Liu, Yingbo; Cheng, Fa; Sun, Shuqing

    2014-12-01

    A hierarchical double-layered TiO2 flower-rod structure composed of three-dimensional (3D) TiO2 flowers and one-dimensional (1D) nanorods on transparent fluorine-doped tin oxide (FTO) conducting glass has been synthesized by a facile hydrothermal method. The possible formation mechanism of the hierarchical architecture is also proposed. When used in CdSe/CdS quantum dots co-sensitized solar cells (QDSSCs), the 1D ordered rutile nanorods at bottom can accelerate the electron transfer rate by providing direct electrical pathway for photogenerated electrons, while the 3D flowers formed on the top of nanorods can increase the adsorption of QDs due to the enlarged areas, and can also be used as a scattering layer. The performance of the CdSe/CdS/TiO2 flower-rod solar cell can achieve a short-circuit current density (Jsc) of 13.46 mA cm-2, and a open-circuit voltage (Voc) of 0.42 V, with a maximum power conversion efficiency of 2.31% under one sun illumination (AM 1.5 G, 100 mW cm-2), which is greatly higher than that of CdSe/CdS/TiO2 nanorod solar cell (1.63%).

  3. Computational Study of the Adsorption of Dimethyl Methylphosphonate (DMMP) on the (010) Surface of Anatase TiO2 With and Without Faceting

    Science.gov (United States)

    2009-12-05

    unfa- ceted surface via a Ti5c---O bond to a methoxy O atom. At the RHF level used in geometry opti- mization the resulting structure was less stable...of the unfa- ceted anatase (010) surfacea atomb this workc ref. 37d ref. 22e Ti5c 0.02; -0.15 0.04; -0.14 0.02; -0.16 O|| 0.02; +0.18 0.04; +0.18

  4. First-principles study of the electronic and optical properties of the (Y, N)-codoped anatase TiO2 photocatalyst

    Institute of Scientific and Technical Information of China (English)

    Lin Yan-Ming; Jiang Zhen-Yi; Hu Xiao-Yun; Zhang Xiao-Dong; Fan Jun; Miao Hui; Shang Yi-Bo

    2012-01-01

    First-principles plane-wave pseudopotential calculations are performed to study the geometrical structures,formation energies,and electronic and optical properties of Y-doped,N-doped,and (Y,N)-codoped TiO2.The calculated results show that Y and N codoping leads to lattice distortion,easier separation of photogenerated electron-hole pairs and band gap narrowing. The optical absorption spectra indicate that an obvious red-shift occurs upon Y and N codoping,which enhances visible-light photocatalytic activity.

  5. Facile hydrothermal synthesis of TiO2-Bi2WO6 hollow superstructures with excellent photocatalysis and recycle properties.

    Science.gov (United States)

    Hou, Ya-Fei; Liu, Shu-Juan; Zhang, Jing-huai; Cheng, Xiao; Wang, You

    2014-01-21

    One-dimensional mesoporous TiO2-Bi2WO6 hollow superstructures are prepared using a hydrothermal method and their photocatalysis and recycle properties are investigated. Experimental results indicate that anatase TiO2 nanoparticles are coupled with hierarchical Bi2WO6 hollow tubes on their surfaces. The TiO2-Bi2WO6 structure has a mesoporous wall and the pores in the wall are on average 21 nm. The hierarchical TiO2-Bi2WO6 heterostructures exhibit the highest photocatalytic activity in comparison with P25, pure Bi2WO6 hollow tube and mechanical mixture of Bi2WO6 tube and TiO2 nanoparticle in the degradation of rhodamine B (RhB) under simulated sunlight irradiation. The as-prepared TiO2-Bi2WO6 heterostructures can be easily recycled through sedimentation and they retains their high photocatalytic activity during the cycling use in the simulated sunlight-driving photodegradation process of RhB. The prepared mesoporous TiO2-Bi2WO6 with hollow superstructure is therefore a promising candidate material for water decontamination use.

  6. Solvothermal Synthesis of Hierarchical TiO2 Microstructures with High Crystallinity and Superior Light Scattering for High-Performance Dye-Sensitized Solar Cells.

    Science.gov (United States)

    Li, Zhao-Qian; Mo, Li-E; Chen, Wang-Chao; Shi, Xiao-Qiang; Wang, Ning; Hu, Lin-Hua; Hayat, Tasawar; Alsaedi, Ahmed; Dai, Song-Yuan

    2017-09-20

    In this article, hierarchical TiO2 microstructures (HM-TiO2) were synthesized by a simple solvothermal method adopting tetra-n-butyl titanate as the titanium source in a mixed solvent composed of N,N-dimethylformamide and acetic acid. Due to the high crystallinity and superior light-scattering ability, the resultant HM-TiO2 are advantageous as photoanodes for dye-sensitized solar cells. When assembled to the entire photovoltaic device with C101 dye as a sensitizer, the pure HM-TiO2-based solar cells showed an ultrahigh photovoltage up to 0.853 V. Finally, by employing the as-obtained HM-TiO2 as the scattering layer and optimizing the architecture of dye-sensitized solar cells, both higher photovoltage and incident photon-to-electron conversion efficiency value were harvested with respect to TiO2 nanoparticles-based dye-sensitized solar cells, resulting in a high power conversion efficiency of 9.79%. This work provides a promising strategy to develop photoanode materials with outstanding photoelectric conversion performance.

  7. Microsphere assembly of TiO2 mesoporous nanosheets with highly exposed (101) facets and application in a light-trapping quasi-solid-state dye-sensitized solar cell

    Science.gov (United States)

    Tao, Xiyun; Ruan, Peng; Zhang, Xiang; Sun, Hongxia; Zhou, Xingfu

    2015-02-01

    The morphology of nano-titania has a significant effect on the photoelectric properties of dye-sensitized solar cells. In this study, microsphere assembly of a TiO2 mesoporous nanosheet constructed by nanocuboids was conducted via a simple hydrothermal process. The XRD pattern indicated that the hierarchical mesoporous microspheres are anatase phase with decreased (004) peaks. Raman spectrum shows enhanced Eg peaks at 143 and 638 cm-1 caused by the symmetric stretching vibration of O-Ti-O of the (101) crystalline facet in anatase TiO2. FESEM and TEM images show that well monodispersed TiO2 microspheres with a diameter of 2 μm are assembled by TiO2 mesoporous nanosheets with exposed (101) facets. The oriented attachment of TiO2 nanocuboids along the (101) direction leads to the formation of mesoporous titania nanosheets. The UV-Vis spectrum shows that the mesoporous TiO2 nanosheets have high scattering ability and light absorption by dye. Quasi-solid-state dye-sensitized solar cells that incorporate these microspheres into the top scattering layers exhibit a prominent improvement in the power conversion efficiency of 7.51%, which shows a 45.8% increase in the overall conversion efficiency when compared with the spine hierarchical TiO2 microspheres (5.15%). There is the potential application for microsphere assembly of mesoporous TiO2 nanosheets in quasi-solid-state dye-sensitized solar cells with excellent stability.

  8. One-step synthesis of vertically aligned anatase thornbush-like TiO2 nanowire arrays on transparent conducting oxides for solid-state dye-sensitized solar cells.

    Science.gov (United States)

    Roh, Dong Kyu; Chi, Won Seok; Ahn, Sung Hoon; Jeon, Harim; Kim, Jong Hak

    2013-08-01

    Herein, we report a facile synthesis of high-density anatase-phase vertically aligned thornbush-like TiO2 nanowires (TBWs) on transparent conducting oxide glasses. Morphologically controllable TBW arrays of 9 μm in length are generated through a one-step hydrothermal reaction at 200 °C over 11 h using potassium titanium oxide oxalate dehydrate, diethylene glycol (DEG), and water. The TBWs consist of a large number of nanoplates or nanorods, as confirmed by SEM and TEM imaging. The morphologies of TBWs are controllable by adjusting DEG/water ratios. TBW diameters gradually decrease from 600 (TBW600) to 400 (TBW400) to 200 nm (TBW200) and morphologies change from nanoplates to nanorods with an increase in DEG content. TBWs are utilized as photoanodes for quasi-solid-state dye-sensitized solar cells (qssDSSCs) and solid-state DSSCs (ssDSSCs). The energy-conversion efficiency of qssDSSCs is in the order: TBW200 (5.2%)>TBW400 (4.5%)>TBW600 (3.4%). These results can be attributed to the different surface areas, light-scattering effects, and charge transport rates, as confirmed by dye-loading measurements, reflectance spectroscopy, and incident photon-to-electron conversion efficiency and intensity-modulated photovoltage spectroscopy/intensity-modulated photocurrent spectroscopy analyses. TBW200 is further treated with a graft-copolymer-directed organized mesoporous TiO2 to increase the surface area and interconnectivity of TBWs. As a result, the energy-conversion efficiency of the ssDSSC increases to 6.7% at 100 mW cm(-2) , which is among the highest values for N719-dye-based ssDSSCs. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. A DFT study of the acid-base properties of anatase TiO2 and tetragonal ZrO2 by adsorption of CO and CO2 probe molecules

    Science.gov (United States)

    Chen, Hsin-Yi Tiffany; Tosoni, Sergio; Pacchioni, Gianfranco

    2016-10-01

    We have performed a comparative study of the acid-base characteristics of the surfaces of anatase TiO2 and tetragonal ZrO2. To this end we performed DFT + U calculations on CO and CO2 probe molecules adsorbed both on terraces and steps of the two oxides. For titania, CO adsorption results in a moderate adsorption energy (about - 0.3 eV) and in a positive shift of the Csbnd O stretching frequency (about + 40 cm- 1), typical of Lewis acid sites, with no clear difference in the acidity between terraces or steps. For zirconia we found a similar CO binding energy as for titania, and a CO vibrational shift that depends on the location of the Zr cation: negligible on terraces, similar to TiO2 on steps. We conclude that the acidic properties are similar in the two oxide surfaces. Things are different for CO2 adsorption. On titania the interaction is weak and surface carbonates compete with physisorbed CO2, indicating a weak basic character. On the contrary, on zirconia three types of stable carbonates have been identified. Their vibrational frequencies are consistent with IR measurements reported in the literature. The most stable species forms on steps of the t-ZrO2 surface and consists of a CO32 - unit which lies flat on the surface with the O atoms pointing towards three Zr ions. The species forms spontaneously by extraction of a lattice oxygen by an incoming CO2 molecule. The different reactivity points towards a much more pronounced basic character of zirconia compared to titania, at least if measured by CO2 adsorption.

  10. Mesoporous anatase TiO2 nanorods as thermally robust anode materials for Li-ion batteries: detailed insight into the formation mechanism.

    Science.gov (United States)

    Seisenbaeva, Gulaim A; Nedelec, Jean-Marie; Daniel, Geoffrey; Tiseanu, Carmen; Parvulescu, Vasile; Pol, Vilas G; Abrego, Luis; Kessler, Vadim G

    2013-12-16

    Uniformly mesoporous and thermally robust anatase nanorods were produced with quantitative yield by a simple and efficient one-step approach. The mechanism of this process was revealed by insertion of Eu(3+) cations from the reaction medium as luminescent probes. The obtained structure displays an unusually high porosity, an active surface area of about 300 m(2) g(-1) and a specific capacity of 167 mA h g(-1) at a C/3 rate, making it attractive as an anode electrode for Li-ion batteries. An additional attractive feature is its remarkable thermal stability; heating to 400 °C results in a decrease in the active surface area to a still relatively high value of 110 m(2) g(-1) with conservation of open mesoporosity. Thermal treatment at 800 °C or higher, however, causes transformation into a non-porous rutile monolith, as commonly observed with nanoscale titania.

  11. Pulsed supercritical synthesis of anatase TiO2 nanoparticles in a water-isopropanol mixture studied by in situ powder X-ray diffraction

    Science.gov (United States)

    Eltzholtz, Jakob Rostgaard; Tyrsted, Christoffer; Jensen, Kirsten Marie Ørnsbjerg; Bremholm, Martin; Christensen, Mogens; Becker-Christensen, Jacob; Iversen, Bo Brummerstedt

    2013-02-01

    A new step in supercritical nanoparticle synthesis, the pulsed supercritical synthesis reactor, is investigated in situ using synchrotron powder X-ray diffraction (PXRD) to understand the formation of nanoparticles in real time. This eliminates the common problem of transferring information gained during in situ studies to subsequent laboratory reactor conditions. As a proof of principle, anatase titania nanoparticles were synthesized in a 50/50 mixture of water and isopropanol near and above the critical point of water (P = 250 bar, T = 300, 350, 400, 450, 500 and 550 °C). The evolution of the reaction product was followed by sequentially recording PXRD patterns with a time resolution of less than two seconds. The crystallite size of titania is found to depend on both temperature and residence time, and increasing either parameter leads to larger crystallites. A simple adjustment of either temperature or residence time provides a direct method for gram scale production of anatase nanoparticles of average crystallite sizes between 7 and 35 nm, thus giving the option of synthesizing tailor-made nanoparticles. Modeling of the in situ growth curves using an Avrami growth model gave an activation energy of 66(19) kJ mol-1 for the initial crystallization. The in situ PXRD data also provide direct information about the size dependent macrostrain in the nanoparticles and with decreasing crystallite size the unit cell contracts, especially along the c-direction. This agrees well with previous ex situ results obtained for hydrothermal synthesis of titania nanoparticles.A new step in supercritical nanoparticle synthesis, the pulsed supercritical synthesis reactor, is investigated in situ using synchrotron powder X-ray diffraction (PXRD) to understand the formation of nanoparticles in real time. This eliminates the common problem of transferring information gained during in situ studies to subsequent laboratory reactor conditions. As a proof of principle, anatase titania

  12. Exceptional performance of a high voltage spinel LiNi0.5Mn1.5O4 cathode in all one dimensional architectures with an anatase TiO2 anode by electrospinning

    Science.gov (United States)

    Arun, Nagasubramanian; Aravindan, Vanchiappan; Jayaraman, Sundaramurthy; Shubha, Nageswaran; Ling, Wong Chui; Ramakrishna, Seeram; Madhavi, Srinivasan

    2014-07-01

    We report for the first time the synthesis and extraordinary performance of a high voltage spinel LiNi0.5Mn1.5O4 fiber cathode in all one dimensional (1D) architecture. Structural and morphological features are analyzed by various characterization techniques. Li-insertion/extraction properties are evaluated in a half-cell assembly (Li/LiNi0.5Mn1.5O4) and subsequently in full-cell configuration with an anatase TiO2 fiber anode. In both half- and full-cell assemblies, gelled polyvinylidene fluoride-co-hexafluoropropylene (PVdF-HFP) is used as the separator-cum-electrolyte. All the one dimensional components used for fabricating Li-ion cells are prepared by a simple and scalable electrospinning technique. The full-cell, LiNi0.5Mn1.5O4/gelled PVdF-HFP/TiO2 delivered the reversible capacity of ~102 mA h g-1 at 0.1 C rate with an operating potential of ~2.8 V. Excellent rate capability and stable cycling profiles are noted for such a full-cell assembly with a capacity retention of ~86% after 400 cycles.

  13. Ionic liquid assisted chemical strategy to TiO2 hollow nanocube assemblies with surface-fluorination and nitridation and high energy crystal facet exposure for enhanced photocatalysis.

    Science.gov (United States)

    Yu, Shengli; Liu, Baocang; Wang, Qin; Gao, Yuxi; Shi, Ying; Feng, Xue; An, Xiaoting; Liu, Lixia; Zhang, Jun

    2014-07-09

    Realization of anionic nonmetal doping and high energy crystal facet exposure in TiO2 photocatalysts has been proven to be an effective approach for significantly improving their photocatalytic performance. A facile strategy of ionic liquid assisted etching chemistry by simply hydrothermally etching hollow TiO2 spheres composed of TiO2 nanoparticles with an ionic liquid of 1-butyl-3-methylimidazolium tetrafluoroborate without any other additives is developed to create highly active anatase TiO2 nanocubes and TiO2 nanocube assemblies. With this one-pot ionic liquid assisted etching process, the surface-fluorination and nitridation and high energy {001} crystal facets exposure can be readily realized simultaneously. Compared with the benchmark materials of P25 and TiO2 nanostructures with other hierarchical architectures of hollow spheres, flaky spheres, and spindles synthesized by hydrothermally etching hollow TiO2 spheres with nonionic liquid of NH4F, the TiO2 nanocubes and TiO2 nanocube assemblies used as efficient photocatalysts show super high photocatalytic activity for degradation of methylene blue, methyl orange, and rhodamine B, due to their surface-fluorination and nitridation and high energy crystal facet exposure. The ionic liquid assisted etching chemistry is facile and robust and may be a general strategy for synthesizing other metal oxides with high energy crystal facets and surface doping for improving photocatalytic activity.

  14. Green Strategy to Single Crystalline Anatase TiO 2 Nanosheets with Dominant (001) Facets and Its Lithiation Study toward Sustainable Cobalt-Free Lithium Ion Full Battery

    KAUST Repository

    Ming, Hai

    2015-11-03

    A green hydrothermal strategy starting from the Ti powders was developed to synthesis a new kind of well dispersed anatase TiO nanosheets (TNSTs) with dominant (001) facets, successfully avoiding using the HF by choosing the safe substitutes of LiF powder. In contrast to traditional approaches targeting TiO with dominant crystal facets, the strategy presented herein is more convenient, environment friendly and available for industrial production. As a unique structured anode applied in lithium ion battery, the TNSTs could exhibit an extremely high capacity around 215 mAh g at the current density of 100 mA g and preserved capacity over 140 mAh g enduring 200 cycles at 400 mA g. As a further step toward commercialization, a model of lithiating TiO was built for the first time and analyzed by the electrochemical characterizations, and full batteries employing lithiated TNSTs as carbon-free anode versus spinel LiNiMnO (x = 0, 0.5) cathode were configured. The full batteries of TNSTs/LiMnO and TNSTs/LiNiMnO have the sustainable advantage of cost-effective and cobalt-free characteristics, and particularly they demonstrated high energy densities of 497 and 580 Wh kg (i.e., 276 and 341 Wh kg ) with stable capacity retentions of 95% and 99% respectively over 100 cycles. Besides the intriguing performance in batteries, the versatile synthetic strategy and unique characteristics of TNSTs may promise other attracting applications in the fields of photoreaction, electro-catalyst, electrochemistry, interfacial adsorption photovoltaic devices etc.

  15. 电泳法制备具有{001}面TiO2纳米片分级球散射层的染敏太阳电池光电极%Dye-Sensitized Solar Cells with An Electrophoresis-Deposited Layer of {001} Exposed Nanosheet-Based Hierarchical TiO2 Spheres

    Institute of Scientific and Technical Information of China (English)

    唐泽坤; 黄欢; 管杰; 于涛; 邹志刚

    2012-01-01

    Anatase TiO2 nanosheet-based hierarchical spheres (HSs) with nearly 100% exposed {001} facets were synthesized via a facile solvothermal process.Using these hierarchical spheres as a scattering layer on nanocrystaline TiO2 film,bi-layered dye-sensitized solar cells (DSSCs) have been fabricated by electrophoresis deposition method,which well preserved the fragile hierarchical structure.Owing to the superior dye adsorption and light scattering effect of HSs,an overall energy conversion efficiency of 7.38% is achieved,which is 26% higher than that of nanoparticle-based photoanode.%利用简便的溶剂热法,制得了由锐钛矿相的纳米片组成的、{001}面接近100%暴露的TiO2分级球形结构.利用电泳沉积法,将所得的TiO2分级球形结构作为散射层引入到染料敏化太阳电池(DSSC)中,并很好地保护了这种脆弱的分级结构.由于这种分级球形结构比TiO2纳米颗粒具有更好的染料吸附性能和光散射性能,使用这种TiO2分级球形结构作为散射层的DSSC达到了7.38%的光电转换效率,较之基于TiO2纳米颗粒的DSSC有了26%的提高.

  16. Study on the Phase Transformation Behavior of Nanosized Amorphous TiO2

    Institute of Scientific and Technical Information of China (English)

    Huaqing XIE; Tonggeng XI; Qinghong ZHANG; Qingren WU

    2003-01-01

    Nanosized amorphous TiO2 powders with a specific surface area of 501 m2.g-1 were prepared by hydrolysis. Aftercalcined at 400℃ for 2 h, the prepared amorphous TiO2 powders were fully transformed into anatase crystallitesthe samples of nanosized amorphous TiO2 mixed with microsized anatase, nanosized anatase, or nanosized α-Al2O3respectively. Effects of sample packing, anatase addition, or α-Al2O3 addition on the crystallization behavior ofnanosized amorphous TiO2 were analyzed.

  17. 锐钛矿型TiO2薄膜的低温制备及其光催化性能研究%Low-temperature preparation and photocatalytic performance of anatase TiO2 thin films

    Institute of Scientific and Technical Information of China (English)

    李勇; 艾凡荣; 闫洪

    2012-01-01

    Nano-TiO2 thin films were prepared at low temperature by an improved sol-gel method and dip-coating technique. The phase and crystal structure, surface morphology and optical absorption properties of the prepared TiO2 films were characterized by X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FTIR), scanning electron microscope (SEM) and ultraviolet-visible spectrometer (UV-Vis), respectively. The photocatalytic activity of the TiO2 films was evaluated through degrading the methylene blue solution under UV radiation. The results show that the Nano-TiO2 thin films prepared at low temperature possess an anatase structure and a uniform dense surface, and show a strong UV absorption. With the Nano-TiO2 films as the photocatalyst, 67.4% of the methylene blue solution is degraded after exposure to UV radiation for 48 h.%采用改进的sol-gel法及浸渍-提拉工艺在低温条件下制备了纳米TiO2薄膜.利用X射线衍射仪(XRD)、傅里叶变换红外光谱仪( FTIR)、扫描电镜(SEM)及紫外-可见光光谱仪(UV-Vis)对所制TiO2薄膜的物相结构、表面形貌以及光吸收特性进行了表征,并利用紫外光照降解亚甲基蓝溶液的方法考察了TiO2薄膜的光催化活性.结果表明:低温制备的纳米TiO2薄膜为锐钛矿结构,表面均匀致密,且对紫外光表现出较强的吸收特性.在紫外光照射48 h后,该TiO2薄膜对亚甲基蓝溶液的降解率为67.4%.

  18. PHOTOCATALYTIC DEGRADATION OF RHODAMINE B ON ANATASE TiO2 WITH {001 } FACETS%{001}面TiO2光催化降解罗丹明B的研究

    Institute of Scientific and Technical Information of China (English)

    冯氏云; 全凤; 胡芸; 韦朝海

    2013-01-01

    A series of anatase TiO2 nanosheets with exposed {001 } facets were synthesized by a hydrothermal method using tetrabutyl titanate as a titanium source and HF solution as the solvent.The photocatalytic activities of the samples were evaluated by rhodamine B degradation.The influences of different reaction temperature、pH and catalyst dosage on the photocatalytic activity were investigated.TiO2 with exposed {001 } facets had good anatase crystal structure and showed strong adsorption for UV light.When the reaction temperature was 180 ℃,the pH of solution was 2,and the catalyst dosage was 1 g/T,the sample showed the highest photocatalytic activity for the degradation of rhodamine B,which could reach 100% under UV irradiation for 20 min.%以钛酸四丁酯为钛源、HF为形貌控制剂,采用水热法在不同反应温度条件下制备纳米片状{001}面TiO2,并以罗丹明B的光催化降解为模型反应,考察了不同反应温度对{001}面TiO2形貌结构的影响,研究了反应温度、pH及催化剂投加量对光催化活性的影响.结果表明,所有{001}面TiO2均具有良好的锐钛矿相衍射峰,并且在紫外光区域具有明显的光吸收;当反应温度为180℃、溶液pH为2、投加量为1g/L时,样品对罗丹明B光催化降解活性最高,紫外光照射20 min后罗丹明B降解率可达100%.

  19. One-Pot Route towards Active TiO2 Doped Hierarchically Porous Cellulose: Highly Efficient Photocatalysts for Methylene Blue Degradation

    Directory of Open Access Journals (Sweden)

    Xiaoxia Sun

    2017-03-01

    Full Text Available In this study, novel photocatalyst monolith materials were successfully fabricated by a non-solvent induced phase separation (NIPS technique. By adding a certain amount of ethyl acetate (as non-solvent into a cellulose/LiCl/N,N-dimethylacetamide (DMAc solution, and successively adding titanium dioxide (TiO2 nanoparticles (NPs, cellulose/TiO2 composite monoliths with hierarchically porous structures were easily formed. The obtained composite monoliths possessed mesopores, and two kinds of macropores. Scanning Electron Microscope (SEM, Energy Dispersive Spectroscopy (EDS, Fourier Transform Infrared Spectroscopy (FT-IR, X-ray Diffraction (XRD, Brunauer-Emmett-Teller (BET, and Ultraviolet-visible Spectroscopy (UV-Vis measurements were adopted to characterize the cellulose/TiO2 composite monolith. The cellulose/TiO2 composite monoliths showed high efficiency of photocatalytic activity in the decomposition of methylene blue dye, which was decomposed up to 99% within 60 min under UV light. Moreover, the composite monoliths could retain 90% of the photodegradation efficiency after 10 cycles. The novel NIPS technique has great potential for fabricating recyclable photocatalysts with highly efficiency.

  20. Interface actions between TiO2 and porous diatomite on the structure and photocatalytic activity of TiO2-diatomite

    Science.gov (United States)

    Xia, Yue; Li, Fangfei; Jiang, Yinshan; Xia, Maosheng; Xue, Bing; Li, Yanjuan

    2014-06-01

    TiO2-diatomite photocatalysts were prepared by sol-gel process with various pre-modified diatomite. In order to obtain diatomite with different surface characteristics, two modification approaches including calcination and phosphoric acid treatment on the micro-structure of diatomite are introduced. The photocatalysts were characterized by XRD, XPS, nitrogen adsorption-desorption isotherms and micromorphology analysis. The results indicate that, compared with pure TiO2, the anatase-to-rutile phase transition temperature of TiO2 loaded on diatomite carrier is significantly increased to nearly 900 °C, depending on the different pretreatment method of diatomite. The photocatalytic activities of different samples were evaluated by their degradation rate of methyl orange (MO) dye under UV and visible-light irradiation. The samples prepared by phosphoric acid pretreatment method exhibit the highest photocatalytic activity. After 90 min of UV irradiation, about 90% of MO is decomposed by the best effective photocatalyst. And after 8 h visible-light irradiation, nearly 60% of MO is decomposed by the same sample. Further mechanism investigation reveals that the H3PO4 pretreatment process can obviously change the surface features of diatomite carrier, cause the formation of Si-O-Ti bond, increase the binding strength between TiO2 and diatomite, restrain crystal growth of loaded TiO2, and thus form thermal-stable mesoporous structure at the granular spaces. It helps to build micro-, meso- and macro-porous hierarchical porous structure in TiO2-diatomite, and improves the charge and mass transfer efficiency during catalyzing process, resulting in the significantly increased photocatalytic activity of TiO2-diatomite pretreated by phosphoric acid.

  1. Photochemistry on TiO2: Mechanisms Behind the Surface Chemistry

    Science.gov (United States)

    2009-01-21

    ation in air causes water droplets to wet the TiO2 film surface, resulting in a lowering of the contact angle over time. The anatase TiO2 film was...have shown that under these conditions, the contact angle decreases slowly during interrupted irradiation periods, as shown in Fig. 9. Both anatase

  2. Alternative structure of TiO2 with higher energy valence band edge

    Science.gov (United States)

    Coh, Sinisa; Yu, Peter Y.; Aoki, Yuta; Saito, Susumu; Louie, Steven G.; Cohen, Marvin L.

    2017-02-01

    We propose an alternative structure of TiO2 anatase that has a higher energy oxygen p -like valence band maximum than pristine TiO2 anatase and thus has a much better alignment with the water splitting levels. This alternative structure is unique when considering a large subspace of possible structural distortions of TiO2 anatase. We propose two routes towards this state and argue that one of them might have been realized in the recently discovered so-called black TiO2.

  3. Photocatalytic Property of TiO2 Films Deposited by Pulsed DC Magnetron Sputtering

    Institute of Scientific and Technical Information of China (English)

    Wenjie ZHANG; Shenglong ZHU; Ying LI; Fuhui WANG

    2004-01-01

    TiO2 thin films were prepared by DC magnetron sputtering with the oxygen flow rate higher than the threshold. The film deposited for 5 h was of anatase phase with a preferred orientation along the direction, but the films deposited for 2 and 3 h were amorphous. The transmittance and photocatalytic activity of the TiO2 films increased constantly with increasing film thickness. When the annealing temperature was lower than 700℃, only anatase grew in the TiO2 film. TiO2 phase changed from anatase to rutile when the annealing temperature was above 800℃. The photocatalytic activity decreased with increasing annealing temperature.

  4. High Efficiency Dye-Sensitized Solar Cells Based on the Anatase TiO2 Sols%基于锐钛矿相二氧化钛溶胶的高效染料敏化太阳能电池

    Institute of Scientific and Technical Information of China (English)

    郝艳明; 石国英; 钱迪峰; 张青红

    2011-01-01

    用稀硝酸或双氧水对TiO2沉淀进行处理,分别得到锐钛矿相TiO2溶胶及过氧钛酸溶液,两者经水热处理后通过“定向附着”得到比表面积均大于100m2/g的TiO2纳米棒溶胶,制成染料敏化太阳能电池后,电池的开路电压得到提高.溶胶在导电玻璃上形成致密阻挡层,也能渗入到Degussa P25为原料经刮涂法制备的光阳极内,消除其中的大孔与缺陷.溶胶修饰的电极经过烧结、组装电池后,AM1.5模拟太阳光照下电池的光电转化效率由4.15%提高到5.63%.%TiO2 precipitates were treated with dilute HNO3 solution or H2O2 solution, anatase TiO2 sols and peroxotitanium acid (PTA) solution were obtained, respectively. Both anatase TiO2 sols and PTA solution were subjected to further hydrothermal treatment, and TiO2 nanorod sols with a specific surface area of more than 100m2/g were formed via the oriented attachment mechanism. The anatase nanorods were used to fabricate dye-sensitized solar cells (DSSCs), and cells with a higher open-circuit voltage were observed. The anatase nanorod sols were also used to make compact layers over FTO conductive glass, and infiltrated into porous TiO2 layers using Degussa P25 titania as raw material by doctor-blade technique to elimination large pores and defects in DSSCs anodes. The sols treated anodes were sintered and assembled into DSSCs, and the photoelectric conversion efficiency of resulted DSSCs increased from 4.15% to 5.63% under AM1.5 simulated solar irradiation.

  5. Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

    Institute of Scientific and Technical Information of China (English)

    GAO Yu-zhou; ZHANG Hui-chen; WANG Liang; YAN Li

    2004-01-01

    TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.

  6. Influence of coating material on laser damage threshold of TiO2 films

    Institute of Scientific and Technical Information of China (English)

    Jianke Yao; Zhengxiu Fan; Hongbo He; Jianda Shao

    2007-01-01

    @@ The optical property, structure, surface properties (roughness and defect density) and laser-induced damage threshold (LIDT) of TiO2 films deposited by electronic beam (EB) evaporation of TiO2 (rutile), TiO2 (anatase) and TiO2 + Ta2O5 composite materials are comparatively studied. All films show the polycrystalline anatase TiO2 structure. The loose sintering state and phase transformation during evaporating TiO2 anatase slice lead to the high surface defect density, roughness and extinction coefficient, and low LIDT of films. The TiO2 + Ta2O5 composite films have the lowest extinction coefficient and the highest LIDT among all samples investigated. Guidance of selecting materials for high LIDT laser mirrors is given.OCIS codes: 310.3840, 140.3330.

  7. Theory studies on electronic structure and optical properties of N-Al co-doped anatase TiO2%N-Al共掺杂TiO2电子结构及光学性质的理论研究

    Institute of Scientific and Technical Information of China (English)

    荆涛; 张苹; 阚伟; 田景芝; 邓启刚

    2015-01-01

    应用基于密度泛函理论的第一性原理平面波超软赝势方法研究N和Al单掺杂和共掺杂锐钛矿相TiO2的电子结构、能带结构、态密度及光学性质。结果表明,掺杂后TiO2的晶格常数、原子间的键长、晶胞体积都发生了不同程度的变化;单掺杂和共掺杂均使得禁带宽度减小,而且位于价带和导带之间的杂质能级能够捕获由价带跃迁至导带的电子,减少光生载流子的复合率,提高TiO2的光催化性能;与单掺杂相比,共掺杂能级分裂较明显,吸收光谱红移幅度更大。%The electronic structures of N-doped, Al-doped and N-Al co-doped anatase TiO2 were investigated by the first-principles plane wave ultra-soft pseudo-potential method based on the density functional theory (DFT). The crystal structures, energy bands, density of states (DOS) and optical properties were analyzed. The results indicate that the lattices, cell volumes of TiO2 and bond length of atoms of TiO2 after doping have different degrees of change. The band gap of single doped samples is narrowed as the same as the N-Al co-doped TiO2. Also the impurity energy levels appear near the Fermi level,which can reduce the recombination rates of photoexcited carriers, so, the photo catalysis efficiency of TiO2 is improved. The N-Al co-doped anatase TiO2 shows a stronger red-shift in the absorption edge than the single doped samples, and its energy level splitting is more obvious.

  8. Reduced electron recombination of dye-sensitized solar cells based on TiO2 spheres consisting of ultrathin nanosheets with [001] facet exposed

    Directory of Open Access Journals (Sweden)

    Hongxia Wang

    2012-05-01

    Full Text Available An anatase TiO2 material with hierarchically structured spheres consisting of ultrathin nanosheets with 100% of the [001] facet exposed was employed to fabricate dye-sensitized solar cells (DSCs. Investigation of the electron transport and back reaction of the DSCs by electrochemical impedance spectroscopy showed that the spheres had a threefold lower electron recombination rate compared to the conventional TiO2 nanoparticles. In contrast, the effective electron diffusion coefficient, Dn, was not sensitive to the variation of the TiO2 morphology. The TiO2 spheres showed the same Dn as that of the nanoparticles. The influence of TiCl4 post-treatment on the conduction band of the TiO2 spheres and on the kinetics of electron transport and back reactions was also investigated. It was found that the TiCl4 post-treatment caused a downward shift of the TiO2 conduction band edge by 30 meV. Meanwhile, a fourfold increase of the effective electron lifetime of the DSC was also observed after TiCl4 treatment. The synergistic effect of the variation of the TiO2 conduction band and the electron recombination determined the open-circuit voltage of the DSC.

  9. On the Crystal Structural Control of Sputtered TiO2 Thin Films.

    Science.gov (United States)

    Jia, Junjun; Yamamoto, Haruka; Okajima, Toshihiro; Shigesato, Yuzo

    2016-12-01

    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.

  10. On the Crystal Structural Control of Sputtered TiO2 Thin Films

    Science.gov (United States)

    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.

  11. Preparation and tribological properties of stearic acid-modified hierarchical anatase TiO{sub 2} microcrystals

    Energy Technology Data Exchange (ETDEWEB)

    Qian Jianhua, E-mail: liulin@bhu.edu.cn [Key Laboratory of Function Compounds of Liaoning Province, College of Chemistry, Chemical Engineering and Food Safety, Bohai University, Jinzhou 121000 (China); Yin Xiangyu; Wang Ning; Liu Lin; Xing Jinjuan [Key Laboratory of Function Compounds of Liaoning Province, College of Chemistry, Chemical Engineering and Food Safety, Bohai University, Jinzhou 121000 (China)

    2012-01-15

    Hierarchical TiO{sub 2} microcrystals were synthesized through a facile solvothermal method. X-ray diffraction (XRD) and scanning electron microscope (SEM) measurements were used to characterize the structure of the as-prepared samples. The results indicated that the synthesized hierarchical titania (TiO{sub 2}) microspheres were composed of numerous anatase phase TiO{sub 2} particles. The as-prepared samples were chemically modified with stearic acid to improve their dispersion in oil. Fourier transmission infrared spectroscopy (FT-IR) and thermogravimetry analysis (TGA) were carried out to evaluate the characteristics of the modified TiO{sub 2} microcrystals. The tribological properties of the modified TiO{sub 2} microcrystals as additives of liquid paraffin were studied by a four-ball tester, and the results showed that they could significantly improve anti-wear performance, friction-reduction property and load-carrying capacity of liquid paraffin. These advantages make the modified TiO{sub 2} microcrystals promising for green lubricating oil additives.

  12. Green microwave switching from oxygen rich yellow anatase to oxygen vacancy rich black anatase TiO₂ solar photocatalyst using Mn(II) as 'anatase phase purifier'.

    Science.gov (United States)

    Ullattil, Sanjay Gopal; Periyat, Pradeepan

    2015-12-07

    Green and rapid microwave syntheses of 'yellow oxygen rich' (YAT-150) and 'black oxygen vacancy rich' (BAT-150) anatase TiO2 nanoparticles are reported for the first time. YAT-150 was synthesized using only titanium(iv) butoxide and water as precursors. The in situ precursor modification by Mn(ii) acetate switched anatase TiO2 from YAT-150 to BAT-150. The entry of Mn(2+) into the crystal lattice of anatase TiO2 paved the way for peak texturing in the existing peak orientations along with the origin of three new anatase TiO2 peaks in the (103), (213) and (105) directions. The as synthesized ultra-small (∼5 nm) yellow and black anatase TiO2 nanoparticles were found to be two fold and four fold more photoactive than the commercially available photocatalyst Degussa-P25 under sunlight illumination.

  13. N,Fe,La三掺杂锐钛矿型TiO2能带调节的理论与实验研究∗%Theoretical and exp erimental studies on N, Fe, La co-doped anatase TiO2 band adjustment

    Institute of Scientific and Technical Information of China (English)

    王庆宝; 张仲; 徐锡金; 吕英波; 张芹

    2015-01-01

    采用基于密度泛函理论(DFT)的平面波超软赝势方法(PWPP),利用Material studio计算N, Fe, La三种元素掺杂引起的锐钛矿TiO2晶体结构、能带结构和态密度变化.并通过溶胶-凝胶法制得锐钛矿型本征TiO2, N, Fe共掺杂TiO2和N, Fe, La共掺杂TiO2;用X射线衍射和扫描电镜表征结构;紫外-可见分光光度计检测TiO2对甲基橙的降解效率变化.计算结果表明,由于N, Fe, La三掺杂TiO2的晶格体积、键长等发生变化,导致晶体对称性下降,光生电子-空穴对有效分离,同时在导带底和价带顶形成杂质能级, TiO2禁带宽度由1.78 eV变为1.35 eV,减小25%,光吸收带边红移,态密度数增加,电子跃迁概率提升,光催化能力增加.实验结果表明:离子掺杂使颗粒变小,粒径大小:本征TiO2>N/Fe_TiO2>N/Fe/La_TiO2,并测得N/Fe/La_TiO2发光峰425 nm,能隙减小,光催化能力比N/Fe_TiO2强,增强原因是杂质能级和电子态数量增加引起.%Based on the plane wave method (PWPP) of densiy functional theory (DFT) we model the N, Fe, La three elements co-doped anatase TiO2 crystal structure and calculate its band structure and density of states with Material Studio. By the sol-gel method, the intrinsic anatase TiO2 and the anatase TiO2 with N, Fe, La three elements co-doping are prepared and investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). Results indicate that the changes of the N, Fe, La co-doped TiO2 lattice volume and its bond length will result in a decline of the crystal symmetry and the effective separation of the electron-hole pair. Impurity level appearing at the bottom of the conduction band and at the top of valence band leads to the decrease of the TiO2 forbidden band width(1.78 eV to 1.35 eV, reduced by 25%), the red shift of light absorption edge, the increase of density of states as well as, the improve ment of electron transition probability and the photocatalytic efficiency of TiO2. Ion

  14. Thermo-selective TmxTi1-xO2-x/2 nanoparticles: from Tm-doped anatase TiO2 to a rutile/pyrochlore Tm2Ti2O7 mixture. An experimental and theoretical study with a photocatalytic application

    Science.gov (United States)

    Navas, Javier; Sánchez-Coronilla, Antonio; Aguilar, Teresa; de Los Santos, Desireé M.; Hernández, Norge C.; Alcántara, Rodrigo; Fernández-Lorenzo, Concha; Martín-Calleja, Joaquín

    2014-10-01

    This is an experimental and theoretical study of thulium doped TiO2 nanoparticles. From an experimental perspective, a method was used to synthesize thulium-doped TiO2 nanoparticles in which Tm3+ replaces Ti4+ in the lattice, which to our knowledge has neither been reported nor studied theoretically so far. Different proportions of anatase and rutile phases were obtained at different annealing temperatures, and XRD and Raman spectroscopy also revealed the presence of a pyrochlore phase (Tm2Ti2O7) at 1173 K. Thus, the structure of the Tm-doped nanoparticles was thermally-controlled. Furthermore, XPS showed the presence of Tm3+ in the samples synthesized, which produces oxygen vacancies to maintain the local neutrality in the lattice. The presence of Tm3+ in the samples led to changes in the UV-Vis absorption spectra, so they showed photoluminescence properties and new states in the band gap, which produce a new lower energy electronic transition than the main TiO2 one. Periodic DFT calculations were performed to understand the experimentally produced structures. The production of oxygen vacancies was analysed and the changes generated in the structure were fully detailed. The DOS and PDOS analyses confirmed the experimental results obtained using UV-Vis spectroscopy, and showed that the new electronic states in the band gap are due to interactions of the f state of Tm and the p state of O. Likewise, the charge study and the ELF analysis indicate that when Tm is introduced into the TiO2 structure, the Ti-O bond around the oxygen vacancy is strengthened. Finally, an example of a photocatalytic application was developed to show the high efficiency of the samples due to the heterojunction in the interfaces of the phases in the samples, which improved the charge separation and the good charge carrier mobility due to the presence of the pyrochlore phase, as was also shown theoretically.This is an experimental and theoretical study of thulium doped TiO2 nanoparticles. From

  15. Enhanced efficiency of dye-sensitized solar cells with novel synthesized TiO2.

    Science.gov (United States)

    Ju, Ki-Young; Cho, Jung-Min; Cho, Sung-June; Yun, Je-Jung; Mun, Soo-San; Han, Eun-Mi

    2010-05-01

    An anatase TiO2 and three kinds of novel TiO2 nanoparticles were prepared by a hydrothermal method for dye-sensitized solar cells (DSSCs), which were obtained by mixing NaOH (10 M), KOH (14 M) and LiOH (10 M) solution with an anatase TiO2 powder, respectively. The TiO2 working electrodes of DSSCs were prepared and the photoelectric properties of the cells were characterized. The influence of different poly(ethylene glycol) contents in TiO2 films with and without HNO3 treatment on the electron transfer in DSSCs were investigated. It is found that the DSSC with HNO3 (0.002 mol/l)-treated film containing 16.7 wt% PEG shows the higher power conversion efficiency of 6.0%, which was mainly depended on the degrees of TiO2 pore size and uniformity of TiO2 films.

  16. Photocatalytic antibacterial performance of Sn(4+)-doped TiO(2) thin films on glass substrate.

    Science.gov (United States)

    Sayilkan, Funda; Asiltürk, Meltem; Kiraz, Nadir; Burunkaya, Esin; Arpaç, Ertuğrul; Sayilkan, Hikmet

    2009-03-15

    Pure anatase, nanosized and Sn(4+) ion doped titanium dioxide (TiO(2)) particulates (TiO(2)-Sn(4+)) were synthesized by hydrothermal process. TiO(2)-Sn(4+) was used to coat glass surfaces to investigate the photocatalytic antibacterial effect of Sn(4+) doping to TiO(2) against gram negative Escherichia coli (E. coli) and gram positive Staphylococcus aureus (S. aureus). Relationship between solid ratio of TiO(2)-Sn(4+) in coatings and antibacterial activity was reported. The particulates and the films were characterized using particle size analyzer, zeta potential analyzer, Brunauer-Emmett-Teller (BET), X-ray diffractometer (XRD), SEM, AAS and UV/VIS/NIR techniques. The results showed that TiO(2)-Sn(4+) is fully anatase crystalline form and easily dispersed in water. Increasing the solid ratio of TiO(2)-Sn(4+) from 10 to 50% in the coating solution increased antibacterial effect.

  17. Enhanced simultaneous PEC eradication of bacteria and antibiotics by facilely fabricated high-activity {001} facets TiO2 mounted onto TiO2 nanotubular photoanode.

    Science.gov (United States)

    Li, Guiying; Nie, Xin; Chen, Jiangyao; Wong, Po Keung; An, Taicheng; Yamashita, Hiromi; Zhao, Huijun

    2016-09-15

    Biohazards and coexisted antibiotics are two groups of emerging contaminants presented in various aquatic environments. They can pose serious threat to the ecosystem and human health. As a result, inactivation of biohazards, degradation of antibiotics, and simultaneous removal of them are highly desired. In this work, a novel photoanode with a hierarchical structured {001} facets exposed nano-size single crystals (NSC) TiO2 top layer and a perpendicularly aligned TiO2 nanotube array (NTA) bottom layer (NSC/NTA) was successfully fabricated. The morphology and facets of anatase TiO2 nanoparticles covered on the top of NTA layer could be controlled by adjusting precalcination temperature and heating rate as the pure NTA was clamped with glasses. Appropriate recalcination can timely remove surface F from {001} facets, and the photocatalytic activity of the resultant photoanode was subsequently activated. NSC/NTA photoanode fabricated under 500 °C precalcination with 20 °C min(-1) followed by 550 °C recalcination possessed highest photoelectrocatalytic efficiency to simultaneously remove bacteria and antibiotics. Results suggest that two-step calcination is necessary for fabrication of high photocatalytic activity NSC/NTA photoanode. The capability of simultaneous eradication of bacteria and antibiotics shows great potential for development of a versatile approach to effectively purify various wastewaters contaminated with complex pollutants.

  18. Decolorization of Methylene Blue with TiO2 Sol via UV Irradiation Photocatalytic Degradation

    OpenAIRE

    2010-01-01

    TiO2 sol was prepared for the degradation of methylene blue (MB) solution under ultraviolet (UV) irradiation. The absorption spectra of MB indicated that the maximum wavelength, 663 nm, almost kept the same. The performance of 92.3% for color removal was reached after 160 min. The particle size of TiO2 sol was about 22.5 nm. X-ray diffraction showed that TiO2 consisted of a single anatase phase. The small size and anatase phase probably resulted in high photocatalytic activity of TiO2 sol. Th...

  19. Energetics of nanocrystalline TiO2

    Science.gov (United States)

    Ranade, M. R.; Navrotsky, A.; Zhang, H. Z.; Banfield, J. F.; Elder, S. H.; Zaban, A.; Borse, P. H.; Kulkarni, S. K.; Doran, G. S.; Whitfield, H. J.

    2002-01-01

    The energetics of the TiO2 polymorphs (rutile, anatase, and brookite) were studied by high temperature oxide melt drop solution calorimetry. Relative to bulk rutile, bulk brookite is 0.71 ± 0.38 kJ/mol (6) and bulk anatase is 2.61 ± 0.41 kJ/mol higher in enthalpy. The surface enthalpies of rutile, brookite, and anatase are 2.2 ± 0.2 J/m2, 1.0 ± 0.2 J/m2, and 0.4 ± 0.1 J/m2, respectively. The closely balanced energetics directly confirm the crossover in stability of nanophase polymorphs inferred by Zhang and Banfield (7). An amorphous sample with surface area of 34,600 m2/mol is 24.25 ± 0.88 kJ/mol higher in enthalpy than bulk rutile. PMID:11880610

  20. Surface CuO, Bi2O3, and CeO2 Species Supported in TiO2-Anatase: Study of Interface Effects in Toluene Photodegradation Quantum Efficiency.

    Science.gov (United States)

    Muñoz-Batista, Mario J; Kubacka, Anna; Fontelles-Carceller, Olga; Tudela, David; Fernández-García, Marcos

    2016-06-08

    The enhancement of active triggered by surface deposition of Cu, Bi, and Ce containing oxidic species onto a high surface area anatase is analyzed through the calculation of the quantum efficiency for toluene photodegradation under UV and Sunlight-type illumination. To this end, series of Cu, Bi, and Ce containing oxides supported on anatase were synthesized having a growing content of the Cu, Bi, and Ce surface species and characterized with X-ray diffraction and photoelectron, UV-visible, and photoluminescence spectroscopies as well as transmission electron microscopy. Utilizing the surface concentration of Cu, Bi, and Ce species as a tool, we analyzed the influence of the system physicochemical properties affecting quantum efficiency in anatase-based materials. First, employing small surface concentrations of the Cu, Bi, and Ce species deposited onto (the unperturbed) anatase, we provided evidence that all steps of the photocatalytic event, including light absorption, charge recombination, as well as surface interaction with the pollutant and chemical output as to activity and selectivity have significance in the quantitative assessment of the enhancement of the efficiency parameter. Second, we analyzed samples rendering maximum quantum efficiency within all these series of materials. The study indicates that maximum enhancement over anatase displays a magnitude strongly dependent on the efficiency level of calculation and would thus require the use of the most accurate one, and that it occurs through a balance between optoelectronic and chemical properties of the composite materials. The (Cu, Bi, Ce) oxide-anatase interface plays a major role modulating the optoelectronic properties of the solids and thus the efficiency observable.

  1. TiO2分级结构/Ag3 PO4复合材料的可见光催化性能%Photocatalytic Performance of Hierarchical TiO2/Ag3 PO4 Composite Under Visible-light Illumination

    Institute of Scientific and Technical Information of China (English)

    李卫兵; 冯昌; 岳继光; 华方霞; 补钰煜

    2015-01-01

    Urchin-like TiO2 nanomaterial with hierarchical structure(PTHSs) was prepared, then Ag3PO4 nanomaterial with visible-light response was deposited on the hierarchical TiO2 by simple deposition precipitation method, thus a series of PTHSs/Ag3 PO4 composites with efficient visible-light photocatalytic per-formance and stability was synthesized. The photocatalytic performance of the PTHSs/Ag3 PO4 composites for degrading Rhodamine B( RhB) was analyzed. The results show that the photocatalytic performance of PTHSs/Ag3PO4 composite is significantly superior to that of pure Ag3PO4 and that of TiO2(P25)/Ag3PO4 composite. The composite with a PTHSs/Ag3 PO4 molar ratio of 1∶1 showed the best photocatalytic performance and it could decolorize the RhB completely in 6 min under visible light illumination. This is because that the urchin-like TiO2 nanomaterial can provide more load sites than TiO2 nanoparticle for loading Ag3 PO4 . And the hierarchical TiO2 can also improve the contact between the surfaces of TiO2 and Ag3 PO4 so that the separated efficiency of photo-generated electrons-holes by Ag3 PO4 is improved. Meanwhile during the photodegradation process, a little Ag+ on the surface of Ag3 PO4 are gradually reduced to Ag0 , by the plasma resonace effect of which, the absorption and conversion capability of the composite for photon are enhanced and the photocataly-tic performance of the composite material for degrading dyes is further enhanced.%制备了具有分级结构的海胆状TiO2纳米材料,并通过原位沉积法将可见光响应的Ag3 PO4纳米颗粒沉积到TiO2的纳米分级结构上,合成了具有高效稳定可见光催化性能的系列TiO2分级结构/Ag3 PO4复合材料,对比测试了系列材料对罗丹明B( RhB)的光催化降解性能。结果表明, TiO2分级结构/Ag3 PO4复合材料光催化性能明显高于纯相的Ag3 PO4光催化剂,同时也明显优于TiO2( P25)/Ag3 PO4复合光催化剂,其中分级结构TiO2与Ag3 PO4摩尔比为1

  2. Remarkable Charge Separation and Photocatalytic Efficiency Enhancement through Interconnection of TiO2 Nanoparticles by Hydrothermal Treatment.

    Science.gov (United States)

    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.

  3. Electrorheological Effects of Cerium-Doped TiO2

    Institute of Scientific and Technical Information of China (English)

    尹剑波; 赵晓鹏

    2001-01-01

    It is found that the doping of cerium ion into anatase TiO2 can improve the electrorheological (ER) effects of TiO2 and broaden the operational temperature range. Especially, the substitution of 7-11 mol% of the cerium dopant for Ti can obtain a relatively high shear stress, t-7.4kPa (at 4kV/mm), which is ten times larger than that of pure TiO2 ER fluid. Also, the typical Ce-doped TiO2 ER fluid shows the highest shear stress at 80℃, but 40℃ for pure TiO2 ER fluid. The dielectric loss and dielectric constant at a low frequency of TiO2 is improved by the doping of cerium, and the temperature dependence of the dielectric properties shows an obvious differnce between pure and doped TiO2 ER fluids. These can well explain the ER behaviour of doped TiO2. Furthermore, the change of rheological and dielectric properties is discussed on the basis of the lattice distortion and defects in TiO2 arising from the doping of cerium.

  4. Influence of annealing on optical and photovoltaic properties of nanostructured TiO2 films

    Science.gov (United States)

    Serikov, T. M.; Ibrayev, N. Kh; Smagulov, Zh Kh; Kuterbekov, К. А.

    2017-01-01

    Spectral and kinetic characteristics of the photoluminescence of TiO2 films obtained from TiO2 nanoparticles and nanotubes were studied. Luminescence spectra typical for the TiO2 with anatase structure were observed under UV excitation of the films. Heat treatment of the films at T=1273 K leads to a long-wavelength shift of the photoluminescence band with maximum at 850 nm, which corresponds to the rutile structure. The luminescence duration of rutile films is longer than the luminescence duration of the anatase films as for nanoparticles and for nanotubes. The photovoltaic properties of TiO2 films with different structures were investigated. It was established that anatase structured films have a higher photocurrent than the rutile structured film. By impedance spectroscopy method it was found that the electron transport resistance in the nanotube films is higher but the recombination rate is lower than in the TiO2 nanoparticle films.

  5. Surface ζ potential and photocatalytic activity of rare earths doped TiO2

    Institute of Scientific and Technical Information of China (English)

    SONG Mianxin; BIAN Liang; ZHOU Tianliang; ZHAO Xiaoyong

    2008-01-01

    The iso-electric point of different rare earths (La, Ce, Y) doped anatase TiO2 was set out, and three organisms with different sur-face electrical properties (methylene blue trihydrate-positive electricity, methyl orange-negative electricity, methyl red-neutral electricity) were selected as photodegradable models. The result showed that the photocatalytic activity of 0.5wt.%Y ions doped anatase TiO2 was better than those of the others. The relationship between Zeta (ζ) potential and the photocatalytic activity of different RE doped anatase TiO2 were also investigated. The Y-doped anatase TiO2 was found with the special two iso-electric points and three ζ potential values.

  6. The Study of Metal Sulfide as Efficient Counter Electrodes on the Performances of CdS/CdSe/ZnS-co-sensitized Hierarchical TiO2 Sphere Quantum Dot Solar Cells

    Science.gov (United States)

    Buatong, Nattha; Tang, I.-Ming; Pon-On, Weeraphat

    2017-03-01

    The effects of using different counter electrode metal sulfides on the performances of solar cells made with CdS/CdSe/ZnS quantum dots co-sensitized onto hierarchical TiO2 spheres (HTSs) used as photo-electrode are reported. The HTS in the QDSSCs is composed of an assembly of numerous TiO2 spheres made by the solvolthermal method. The photoelectrical performance of HTS/CdS/CdSe/ZnS coupled to CuS or to Cu2ZnSn(S1 - x Se x )4 with x = 0, 0.5, or 1.0 counter electrodes (CEs) were compared to those coupled to Pt CE. The HTS/CdS/CdSe/ZnS coupled to the CuS CE showed the highest power conversion efficiency η (of 3.46%). The efficiencies η of 1.88, 2.64, and 2.06% were obtained for CZTS ( x = 0), CZTS0.5Se0.5 ( x = 0.5), and CZTSe ( x = 1), respectively. These are significantly higher than those using a standard Pt CE ( η = 0.37%). These higher efficiencies are the results of the higher electrocatalytic activities when the metal sulfide CEs are used.

  7. The Study of Metal Sulfide as Efficient Counter Electrodes on the Performances of CdS/CdSe/ZnS-co-sensitized Hierarchical TiO2 Sphere Quantum Dot Solar Cells.

    Science.gov (United States)

    Buatong, Nattha; Tang, I-Ming; Pon-On, Weeraphat

    2017-12-01

    The effects of using different counter electrode metal sulfides on the performances of solar cells made with CdS/CdSe/ZnS quantum dots co-sensitized onto hierarchical TiO2 spheres (HTSs) used as photo-electrode are reported. The HTS in the QDSSCs is composed of an assembly of numerous TiO2 spheres made by the solvolthermal method. The photoelectrical performance of HTS/CdS/CdSe/ZnS coupled to CuS or to Cu2ZnSn(S1 - x Se x )4 with x = 0, 0.5, or 1.0 counter electrodes (CEs) were compared to those coupled to Pt CE. The HTS/CdS/CdSe/ZnS coupled to the CuS CE showed the highest power conversion efficiency η (of 3.46%). The efficiencies η of 1.88, 2.64, and 2.06% were obtained for CZTS (x = 0), CZTS0.5Se0.5 (x = 0.5), and CZTSe (x = 1), respectively. These are significantly higher than those using a standard Pt CE (η = 0.37%). These higher efficiencies are the results of the higher electrocatalytic activities when the metal sulfide CEs are used.

  8. Characteristics of dye-sensitized solar cell with TiO2 anode under UV irradiation

    Science.gov (United States)

    Lee, Ming-Kwei; Hsiao, Chih-Chen; Weng, Hao-Wei

    2016-03-01

    The anatase phase crystalline quality of commercial TiO2 (P25) nanoparticle sintered in air and N2 is improved. Compared DSSC with air-sintered TiO2 anode, DSSC with N2-sintered TiO2 anode has better performance mainly from high optical absorption efficiency. Under UV irradiation, organic contaminants adsorbed on TiO2 are dissociated by the photocatalysis, and the dye adsorption is enhanced. The DSSC performance with UV-treated/N2-sintered TiO2 anode is further improved.

  9. Preparation of Hierarchical Porous S and N Co-doped TiO2 and Its Continuous-flow Visible Light Photocatalysis%多孔硫、氮共掺杂TiO2的制备及连续流动可见光光催化活性

    Institute of Scientific and Technical Information of China (English)

    曹广秀; 曹广连; 仇晓阳

    2012-01-01

    以聚合物凝胶为模板,硫酸氧钛为钛源,合成了多孔硫、氮共掺杂TiO2可见光光催化剂.利用XRD、FE-SEM、TEM、UV-vis和XPS等方法对样品的结构、形貌、可见光吸收及掺杂元素的化学形态进行了表征.结果表明掺杂TiO2为锐钛矿相结构,其网状骨架是由介孔和大孔组成,组成大孔的壁厚在100~300 nm之间,大孔的孔径约为300 nm,有少量的Ti-S、Ti-O-S、O-Ti-N键存在于样品中.连续降解废水中亚甲基蓝溶液结果表明:该方法合成的多孔、自支持的硫、氮共掺杂TiO2可见光光催化剂,具有高效耐久的特性.%Hierarchical porous S and N co-doped TiO2 was synthesized using simple polymer gel template and titanyl sulfate as titanium source and characterized by XRD, FE-SEM, TEM, UV-vis and XPS methods. The result of XRD showed that TiO2 was in the anatase phase. FE-SEM showed a network-like structure containing meso/macropores. The macropores had diameter of ca. 300 nm and a wall thickness of 100-300 nm. XPS results revealed that Ti-S,Ti-O-S and O-Ti-N bonds have formed. The sample had excellent visible light photocatalytic activity and high durability of photocatalytic activity for the degradation of methylene blue (MB) solution in tube reactor.

  10. Effects of Co-addition of DBS and PEG on Wetting Performance of TiO2 Film

    Institute of Scientific and Technical Information of China (English)

    QU Yi-chun; JING Li-qiang; WANG Wen-xin; FU Hong-gang; LIU Yang

    2011-01-01

    Nanocrystalline anatase TiO2 films with indium tin oxide(ITO) coated glass as the film substrate were fabricated through spin-coating technique. The TiO2 pastes were prepared with sodium dodecylbenzenesulfonate(DBS)modified TiO2 nanocrystals, synthesized by sol-hydrothermal processes in advance, together with different amounts of polyethylene glycol(PEG) macromolecules. The as-prepared films were mainly characterized by ultraviolet-visible (UV-Vis) spectroscopy, field emission scanning electron microscopy(FE-SEM) and water contact angle(WCA) measurement. Effects of the addition of DBS and PEG on the wetting performance of the resulting films and relevant mechanisms were principally investigated. The results show that the as-prepared film displays super-hydrophilic property after co-addition of DBS and PEG although it is not exposed to ultraviolet light prior to the WCA measurement. This appealing result is mainly attributed to the produced micro- and nanometer-scale hierarchical surface structure with uniformly dispersed micro papillae. Each papilla was made up of a great number of TiO2 nanoparticles.The possible formation mechanisms related to the DBS amphiphilic property of the characteristic surface were also suggested. Moreover, the resulting film also exhibits considerable durability in the superhydrophilicity, which is very useful for practical application in self-cleaning, anti-fogging, and bacteria-resistant fields.

  11. Hydrothermal synthesis of TiO2 Nanotubes: Microwave heating versus conventional heating

    CSIR Research Space (South Africa)

    Sikhwivhilu, LM

    2010-01-01

    Full Text Available The influence of the method of synthesis in the properties of the tubular structures derived from TiO2 was investigated using XRD, SEM and BET analysis. The use of microwave irradiation resulted in the formation of TiO2 tubes comprising anatase...

  12. A novel TiO2 composite for photocatalytic wastewater treatment

    NARCIS (Netherlands)

    Hamdy, Mohamed S.; Saputera, Wibawa H.; Groenen, Edgar J.; Mul, Guido

    2014-01-01

    A novel TiO2 composite consisting of Anatase interacting with a Ti3+-containing Rutile phase was synthesized by heating a mixture of TiO2 (Hombikat) and Ti2O3 in air at different temperatures ranging from 300 °C up to 900 °C. The preparation of the samples was analyzed by Thermal Gravimetric

  13. Effect of HCl on the Formation of TiO2 Nanocrystallites

    Directory of Open Access Journals (Sweden)

    Nguyen Trong Tung

    2016-01-01

    Full Text Available TiO2 nanocrystals are prepared by pyrolysis of titanium tetrachloride (TiCl4 as precursor in HCl aqueous solution at 80°C. The experimental results show that the HCl concentrations in the synthesizing medium and the following aging are the essential factors affecting the phase formation and phase composition of the resulting TiO2 nanocrystals. The TiO2 suspended in the HCl media is predominant anatase in uniform cluster and the TiO2 deposited in the sedimentation is predominant rutile in the rod-like structure. In the anatase phase, TiO2 crystallites have particle structure of 4–11 nm in mean size depending on the HCl concentration and aging time. In the rutile phase, the mean size of rutile TiO2 is 12-13 nm and there is not much change with HCl environment and aging time. The mean size of TiO2 of around 11-12 nm is considered to be the critical point of phase transition from anatase to rutile in HCl media. Consequence, TiO2 nanocrystallites in pure anatase and rutile phase can be extracted and segregated from the colloidal suspension and the deposited parts in the synthesizing media.

  14. A novel TiO2 composite for photocatalytic wastewater treatment

    NARCIS (Netherlands)

    Hamdy, Mohamed S.; Saputera, Wibawa H.; Groenen, Edgar J.; Mul, Guido

    2014-01-01

    A novel TiO2 composite consisting of Anatase interacting with a Ti3+-containing Rutile phase was synthesized by heating a mixture of TiO2 (Hombikat) and Ti2O3 in air at different temperatures ranging from 300 °C up to 900 °C. The preparation of the samples was analyzed by Thermal Gravimetric Analysi

  15. Atomic-scale investigation of a new phase transformation process in TiO2 nanofibers.

    Science.gov (United States)

    Lei, Yimin; Li, Jian; Wang, Zhan; Sun, Jun; Chen, Fuyi; Liu, Hongwei; Ma, Xiaohua; Liu, Zongwen

    2017-03-30

    Crystallography of phase transformation combining transmission electron microscopy (TEM) with in situ heating techniques and X-ray diffraction (XRD) can provide critical information regarding solid-state phase transitions and the transition-induced interfaces in TiO2 nanomaterials theoretically and experimentally. Two types of reduced titanium oxides (Ti3O5, Ti6O11) are found during ex situ and in situ heating of TiO2 (B) nanofibers with a specific morphology of the {100} single form (SF) in air and vacuum. The results indicate that the phase transformation process from TiO2 (B) follows the TiO2 (B) → Ti3O5 → Ti6O11 → anatase sequence for the nanofibers with the {100} SF. The occurrence of such a phase transition is selective to the morphology of TiO2 (B) nanofibers. The corresponding orientation relationships (COR) between the four phases are revealed according to the TEM characterization. Four types of coherent interfaces, following the CORs are also found. They are TiO2 (B)/Ti3O5, TiO2 (B)/Ti6O11, Ti6O11/anatase and TiO2 (B)/anatase respectively. The habit plane for the TiO2 (B) to Ti3O5 transition is calculated as the {100}TB by using the invariant line model. The detailed atomic transformation mechanism is elucidated based on the crystallographic features of the four phases.

  16. Double-Shelled TiO2 Hollow Spheres Assembled with TiO2 Nanosheets.

    Science.gov (United States)

    Zhang, Chao; Zhou, Yuming; Zhang, Yiwei; Zhao, Shuo; Fang, Jiasheng; Sheng, Xiaoli; Zhang, Tao; Zhang, Hongxing

    2017-02-08

    High-quality double-shelled TiO2 hollow spheres (DHS-Ti) assembled with TiO2 nanosheets have been synthesized for the first time through a simple hydrothermal treatment of sSiO2 @TiO2 (TiO2 -coated solid SiO2 spheres). The double-shelled structure shows a high BET surface area up to 417.6 m(2)  g(-1) . Anatase DHS-Ti of high crystallinity can be obtained without structural collapse by calcination treatment. The effects of cetyl trimethylammonium bromide (CTAB) concentration, pH, and hydrothermal reaction temperature have also been investigated with a series of contrast experiments. A formation mechanism involving the in situ growth of amorphous TiO2 nanosheets followed by the redeposition of dissolved silica species is proposed. Lastly, the DHS-Ti forming strategy can be extended as a general strategy to fabricate various morphological hollow nanostructures and double-shelled Pt nanocatalysts by rationally selecting functional sSiO2 nanoparticles as core materials. This work could open up a new strategy for controllable synthesis of complex hollow structures and other functional materials.

  17. Effects of TiO2 structures in dye-sensitized solar cell.

    Science.gov (United States)

    Kim, Bok-Min; Rho, Seon-Gyun; Kang, Choon-Hyoung

    2011-02-01

    In this work, the effects of crystalline structure of the TiO2, which is incorporated in fabrication of the n-type electrode, on the DSSC performance were investigated in terms of the energy conversion efficiency. In this effort, TiO2 nanoparticle pastes with varying contents of rutile and anatase structures were prepared by using the ethanol mixing method. The most efficient photo-electro-chemical performance was achieved for the DSSC fabricated with the TiO2 paste in which the anatase form of the nanocrystal extends to 90%.

  18. Optimized method for preparation of TiO2 nanoparticles dispersion for biological study.

    Science.gov (United States)

    Zhang, Xiaoqiang; Yin, Lihong; Tang, Meng; Pu, Yuepu

    2010-08-01

    The objective of the present study was to develop a practical method to prepare a stable dispersion of TiO2 nanoparticles for biological studies. To address this matter a variety of different approaches for suspension of nanoparticles were conducted. TiO2 (rutile/anatase) dispersions were prepared in distilled water following by treated with different ultrasound energies and various dispersion stabilizers (1.0% carboxymethyl cellulose, 0.5% hydroxypropyl methyl cellulose K4M, 100% fetal bovine serum, and 2.5% bovine serum albumin). The average size of dispersed TiO2 (rutile/anatase) nanoparticles was measured by dynamic light scattering device. Agglomerate sizes of TiO2 in distilled water and 100% FBS were estimated using TEM analysis. Sedimentation rate of TiO2 (rutile/anatase) nanoparticles in dispersion was monitored by optical absorbance detection. In vitro cytotoxicity of various stabilizers in 16-HBE cells was measured using MTT assay. The optimized process for preparation of TiO2 (rutile/anatase) nanoparticles dispersion was first to vibrate the nanoparticles by vortex and disperse particles by ultrasonic vibration in distilled water, then to add dispersion stabilizers to the dispersion, and finally to sonicate the nanoparticles in dispersion. TiO2 (rutile/anatase) nanoparticles were disaggregated sufficiently with an ultrasound energy of 33 W for 10 min. The formation of TiO2 (rutile/anatase) agglomerates in distilled water was decreased obviously by addition of 1.0% CMC, 0.5% HPMC K4M, 100% FBS and 2.5% BSA. For the benefit of cell growth, FBS is the most suitable stabilizer for preparation of TiO2 (rutile/anatase) particle dispersions and subsequent investigation of the in vivo and in vitro behavior of TiO2 (rutile/anatase) nanoparticles. This method is practicable to prepare a stable dispersion of TiO2 (rutile/anatase) nanoparticles for at least 120 h.

  19. Study of concentration-dependent cobalt ion doping of TiO2 and TiO(2-x)Nx at the nanoscale.

    Science.gov (United States)

    Gole, James L; Prokes, Sharka M; Glembocki, O J; Wang, Junwei; Qiu, Xiaofeng; Burda, Clemens

    2010-07-01

    Experiments with a porous sol-gel generated TiO(2) nanocolloid and its corresponding oxynitride TiO(2-x)N(x) are carried out to evaluate those transformations which accompany additional doping with transition metals. In this study, doping with cobalt (Co(ii)) ions is evaluated using a combination of core level and VB-photoelectron and optical spectroscopy, complementing data obtained from Raman spectroscopy. Raman spectroscopy suggests that cobalt doping of porous sol-gel generated anatase TiO(2) and nitridated TiO(2-x)N(x) introduces a spinel-like structure into the TiO(2) and TiO(2-x)N(x) lattices. TEM and XPS data complemented by valence band-photoelectron spectra demonstrate that metallic cobalt clusters are not formed even at high doping levels. As evidenced by Raman spectroscopy, the creation of a spinel-like structure is commensurate with the room temperature conversion of the oxide and its oxynitride from the anatase to the rutile form. The onset of this kinetically driven process correlates with the formation of spinel sites within the TiO(2) and TiO(2-x)N(x) particles. Despite their visible light absorption, the photocatalytic activity of these cobalt seeded systems is diminished relative to the oxynitride TiO(2-x)N(x).

  20. Blocking layer effect on dye-sensitized solar cells assembled with TiO2 nanorods prepared by dc reactive magnetron sputtering

    OpenAIRE

    Meng Lijian; Li Can

    2011-01-01

    Three different thickness dense TiO2 (150 nm, 300 nm and 450 nm respectively) films were deposited on ITO substrates by dc reactive magnetron sputtering technique. These dense TiO2 films were used as the blocking layers. After that, TiO2 nanorod films were deposited on these dense TiO2 films by same technique. Both the dense and nanorod TiO2 films have an anatase phase. The dense TiO2 films have an orientation along the [101] direction and the TiO2 nanorod films show a very strong orientation...

  1. First- principles Study of Effect of Electronic Structures and Red- shift on Heavy S doping Anatase TiO2%S高掺杂对锐钛矿TiO2电子结构和红移影响的第一性原理研究

    Institute of Scientific and Technical Information of China (English)

    侯清玉

    2011-01-01

    基于密度泛函理论框架下的第一性原理平面波超软赝势方法,建立了未掺杂单胞和两种不同掺杂S原子浓度的锐钛矿TiO2模型,分别对模型进行了几何结构优化、态密度分布、能带分布、差分电荷密度分布、集居数和吸收光谱的计算.结果发现:掺杂后O原子2p态、S原子3p态和Ti原子3d态在导带内发生了强烈的杂化耦合作用,Ti原子3d态的电子向S原子3p态转移,引起导带下移;O原子2p态和S原子3p态在价带中杂化耦合作用,引起价带上移,引起了带隙变窄发生红移现象,同时,高掺杂S原子浓度越高红移越显著,计算结果与实验结果相一致.%In order to investigate the effect of heavy S - doping on the electronic structure of anatase TiO2, and to discover the mechanism of its band gap narrowed after S - doping, we carry out first - principles studies based on density - functional theory ( DFT) for anatase TiO2 system. We study the band structures, densities of states, difference to the electron density, population analysis and spectrum of absorption. The result shows that after S - doping, a strong hybrid coupling would happen at the conduction band ( CB) area of S atoms 3p orbit, 0 atoms 2p orbit and Ti atoms 3d orbit, which would lead to electrons of Ti atoms on the 3d orbit moving to 3p orbit of S atoms, conduction band becoming lower, and valence band arising becoming raise. Band gap would become narrow and the red shift electrophoresis would happen. Moreover, the effect of red shift increases with the concentration of S atoms increasing. The result of experiment is agreement with the theoretical result.

  2. The Heterogeneous Photocatalytic Oxidation of Hydrocarbons on Platinized TiO2 Powders.

    Science.gov (United States)

    1980-08-28

    presence of catalyst. Platinized anatase has a higher efficiency than plain anatase powder (see experiments 2 and 7). The results shown in experiments 3...Measurements. The photocatalytic activities of suspended platinized anatase powders were correlated with the behavior of TiO 2 single crystal electrodes in...photoelectrochemical (PEC) measurements as shown in Figure 1. The current-potential behavior of a rutile single crystal electrode was examined in an

  3. Mo + C codoped TiO(2) using thermal oxidation for enhancing photocatalytic activity.

    Science.gov (United States)

    Zhang, Jun; Pan, Chunxu; Fang, Pengfei; Wei, Jianhong; Xiong, Rui

    2010-04-01

    The photocatalytic activity of TiO(2) is enhanced mainly through heightening absorption of UV-vis light and improving the separation efficiency of photoinduced electrons and holes. The recent new theoretical research revealed that the TiO(2) codoped with Mo + C is considered to be an optimal doping system. On the basis of this theory, the Mo + C codoped TiO(2) powders were first experimentally synthesized by thermal oxidizing a mixture of TiC and MoO(3) powders in the air. The XRD patterns and the XPS survey spectrum showed that carbon (C) acted as a Ti-O-C band structure and molybdenum (Mo) existed as Mo(6+) in anatase TiO(2). The Mo+C codoped TiO(2) had a 32 nm red shift of the spectrum onset compared with pure anatase TiO(2), and its band gap was reduced from 3.20 to 2.97 eV. The photocurrent of the Mo + C codoped TiO(2) was about 4 times as high as that of pure anatase TiO(2), and its photocatalytic activity on decomposition of methylene blue was enhanced.

  4. Effect of Microstructure of TiO2 Thin Films on Optical Band Gap Energy

    Institute of Scientific and Technical Information of China (English)

    TIAN Guang-Lei; HE Hong-Bo; SHAO Jian-Da

    2005-01-01

    @@ TiO2 coatings are prepared on fused silica with conventional electron beam evaporation deposition. After annealed at different temperatures for four hours, the spectra and XRD patterns of TiO2 thin film are obtained. XRD patterns reveal that only anatase phase can be observed in TiO2 coatings regardless of the different annealing temperatures, and with the increasing annealing temperature, the grain size gradually increases. The relationship between the energy gap and microstructure of anatase is determined and discussed. The quantum confinement effect is observed that with the increasing grain size of TiO2 thin film, the band gap energy shifts from 3.4eV to 3.21 eV. Moreover, other possible influence of the TiO2 thin-film microstructure, such as surface roughness and thin film absorption, on band gap energy is also expected.

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    Kiran Gupta

    2013-06-01

    Full Text Available 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. Atomic Layer Deposition TiO2 Films and TiO2/SiNx Stacks Applied for Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    Zu-Po Yang

    2016-08-01

    Full Text Available Titanium oxide (TiO2 films and TiO2/SiNx stacks have potential in surface passivation, anti-reflection coatings and carrier-selective contact layers for crystalline Si solar cells. A Si wafer, deposited with 8-nm-thick TiO2 film by atomic layer deposition, has a surface recombination velocity as low as 14.93 cm/s at the injection level of 1.0 × 1015 cm−3. However, the performance of silicon surface passivation of the deposited TiO2 film declines as its thickness increases, probably because of the stress effects, phase transformation, atomic hydrogen and thermal stability of amorphous TiO2 films. For the characterization of 66-nm-thick TiO2 film, the results of transmission electron microscopy show that the anatase TiO2 crystallinity forms close to the surface of the Si. Secondary ion mass spectrometry shows the atomic hydrogen at the interface of TiO2 and Si which serves for chemical passivation. The crystal size of anatase TiO2 and the homogeneity of TiO2 film can be deduced by the measurements of Raman spectroscopy and spectroscopic ellipsometry, respectively. For the passivating contacts of solar cells, in addition, a stack composed of 8-nm-thick TiO2 film and a plasma-enhanced chemical-vapor-deposited 72-nm-thick SiNx layer has been investigated. From the results of the measurement of the reflectivity and effective carrier lifetime, TiO2/SiNx stacks on Si wafers perform with low reflectivity and some degree of surface passivation for the Si wafer.

  8. Photocatalytic Properties of TiO2 Porous Network Film.

    Science.gov (United States)

    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. Photodegradation of sugarcane vinasse: evaluation of the effect of vinasse pre-treatment and the crystalline phase of TiO2

    Directory of Open Access Journals (Sweden)

    Renata Padilha de Souza

    2016-04-01

    Full Text Available In this work, photocatalysis was employed in the treatment of vinasse using TiO2 and UV light. The parameters investigated were: TiO2 phases (anatase and rutile and vinasse pre-treatments (coagulation/flocculation and dilution. The TiO2 catalysts employed were: Kronos without thermal treatment (100% anatase, calcined at 1000°C (33.5% anatase and immobilized on glass slides (100% anatase; and P25 Degussa without thermal treatment (86.6% anatase. The results showed that natural coagulant removed about 50, 85 and 97% of COD, color and turbidity, respectively. However, pre-treatment followed by photocatalysis with TiO2 87% anatase removed 67% of COD within 48h of irradiation. Bioassays with Artemia salina confirmed the efficacy of the methodology. The treatments reduced the toxicity of vinasse by up to 10 times.

  10. Optical absorption and electrical transport in hybrid TiO2 and polymer nanocomposite films

    Science.gov (United States)

    Zhou, Xi-Song; Li, Zheng; Wang, Ning; Lin, Yuan-Hua; Nan, Ce-Wen

    2006-06-01

    Hybrid nanofilms of poly(2-methoxy-5-ethylhexyloxy-1,4-phenylene)vinylene (MEH-PPV) and anatase-TiO2 nanoparticles were prepared. The results showed that the optical absorption spectra and electrical transport properties of the TiO2/MEH-PPV nanocomposite films were strongly dependent on the particle size and concentration of TiO2 nanoparticles in the hybrid films. In comparison with pure TiO2 nanofilms, the hybrid TiO2/MEH-PPV films presented a shift of the absorption edge to the lower-energy region, and an obvious nonlinear current-voltage characteristic.

  11. 锐钛矿相和金红石相Nb:TiO2电学性质的GGA(+U)法研究*%Investigation on the electrical prop erties of anatase and rutile Nb-dop ed TiO2 by GGA(+U)

    Institute of Scientific and Technical Information of China (English)

    杨振辉; 王菊; 刘涌; 王慷慨; 苏婷; 郭春林; 宋晨路; 韩高荣

    2014-01-01

    采用基于密度泛函理论第一性原理GGA和GGA+U相结合的方法研究了不同掺杂浓度下锐钛矿相和金红石相Nb:TiO2的晶体结构、电子结构以及稳定性。结果表明:锐钛矿相Nb:TiO2能带结构与简并半导体类似,呈类金属导电机理。金红石相Nb:TiO2呈半导体导电机理。 Nb原子比Ti原子电离产生出更多的电子。锐钛矿相Nb:TiO2中Nb原子的电离率比金红石相Nb:TiO2的大。以上结果说明锐钛矿相Nb:TiO2比金红石相Nb:TiO2更适宜用作TCO材料;掺杂浓度对其杂质能级,费米能级和有效质量都有影响。 Nb原子掺杂浓度越高,材料电离率呈降低趋势;形成能计算结果显示:在富钛条件下不利于Nb原子的掺杂,而在富氧条件下有利于Nb原子的掺杂。对于金红石相和锐钛矿相Nb:TiO2,不论是在贫氧或富氧条件下,随着Nb原子掺杂浓度的提高,形成能均增大。%Crystal structure, electronic properties, and stability of anatase and rutile Nb-doped TiO2 (Nb:TiO2) compounds with different doping concentrations are studied by the combination of GGA and GGA+U methods within the density functional theory based first-principle calculation. And the main research work and contents are listed as follows: The anatase Nb:TiO2 appears as a degenerated semiconductor which behaves as an intrinsic metal. Its metallic property arises from Nb substitution into the Ti site, providing electrons to the conduction band. In contrast, the rutile Nb:TiO2 shows insulating behaviors. Ionization efficiency of Nb in anatase Nb:TiO2 is higher than that in rutile. We expect that anatase Nb:TiO2 is a potential material for transparent conducting oxide (TCO) while rutile Nb:TiO2 is not. The doped systems show different electronic characteristics, such as band structure, Fermi energy, and effective mass of carriers at different doping levels. In higher dopant concentration nNb , the ionization efficiency decreases

  12. Photocatalytic Degradation of Mecoprop and Clopyralid in Aqueous Suspensions of Nanostructured N-doped TiO2

    Directory of Open Access Journals (Sweden)

    Tatiana Giannakopoulou

    2010-04-01

    Full Text Available The work describes a study of the oxidation power of N-doped and undoped anatase TiO2, as well as TiO2 Degussa P25 suspensions for photocatalytic degradation of the herbicides RS-2-(4-chloro-o-tolyloxypropionic acid (mecoprop and 3,6-dichloro-pyridine-2-carboxylic acid (clopyralid using visible and UV light. Undoped nanostructured TiO2 powder in the form of anatase was prepared by a sol-gel route. The synthesized TiO2, as well as TiO2 Degussa P25 powder, were modified with urea to introduce nitrogen into the structure. N-doped TiO2 appeared to be somewhat more efficient than the starting TiO2 (anatase powder when visible light was used for mecoprop degradation. N-doped TiO2 Degussa P25 was also slightly more efficient than TiO2 Degussa P25. However, under the same experimental conditions, no degradation of clopyralid was observed in the presence of any of the mentioned catalysts. When the kinetics of mecoprop degradation was studied using UV light, more efficient were the undoped powders, while in the case of clopyralid, N-doped TiO2 Degussa P25 powder was most efficient, which is probably a consequence of the difference in the molecular structure of the two herbicides.

  13. The effects of hierarchical micro/nanosurfaces decorated with TiO2 nanotubes on the bioactivity of titanium implants in vitro and in vivo

    Science.gov (United States)

    Ding, Xianglong; Zhou, Lei; Wang, Jingxu; Zhao, Qingxia; Lin, Xi; Gao, Yan; Li, Shaobing; Wu, Jingyi; Rong, Mingdeng; Guo, Zehong; Lai, Chunhua; Lu, Haibin; Jia, Fang

    2015-01-01

    In the present work, a hierarchical hybrid micro/nanostructured titanium surface was obtained by sandblasting with large grit and acid etching (SLA), and nanotubes of different diameters (30 nm, 50 nm, and 80 nm) were superimposed by anodization. The effect of each SLA-treated surface decorated with nanotubes (SLA + 30 nm, SLA + 50 nm, and SLA + 80 nm) on osteogenesis was studied in vitro and in vivo. The human MG63 osteosarcoma cell line was used for cytocompatibility evaluation, which showed that cell adhesion and proliferation were dramatically enhanced on SLA + 30 nm. In comparison with cells grown on the other tested surfaces, those grown on SLA + 80 nm showed an enhanced expression of osteogenesis-related genes. Cell spread was also enhanced on SLA + 80 nm. A canine model was used for in vivo evaluation of bone bonding. Histological examination demonstrated that new bone was formed more rapidly on SLA-treated surfaces with nanotubes (especially SLA + 80 nm) than on those without nanotubes. All of these results indicate that SLA + 80 nm is favorable for promoting the activity of osteoblasts and early bone bonding. PMID:26635472

  14. Enhanced degradation of persistent pharmaceuticals found in wastewater treatment effluents using TiO2 nanobelt photocatalysts

    Science.gov (United States)

    Liang, Robert; Hu, Anming; Li, Wenjuan; Zhou, Y. Norman

    2013-10-01

    Pharmaceuticals in wastewater effluents are a current and emerging global problem and the development of cost-effective methods to facilitate their removal is needed to mitigate this issue. Advanced oxidation processes (AOPs), in particular UV/TiO2, have potential for wastewater treatment. In this study, TiO2 anatase phase nanobelts (30-100 nm in width and 10 μm in length) have been synthesized using a high temperature hydrothermal method as a means to photocatalyze the oxidation of pharmaceutical contaminants. We have investigated a model dye (malachite green), three pharmaceuticals and personal care products—naproxen, carbamazepine, and theophylline—that are difficult to oxidize without AOP processes. TiO2 nanobelts were exposed to 365 nm UV illumination and the measured photocatalytic degradation rates and adsorption parameters of pharmaceuticals were explored using kinetic models. Furthermore we have determined the degree of pharmaceutical degradation as a function of solution pH, illumination time, temperature, and concentration of contaminant. In addition, the roles of active oxygen species—hydroxyl radial (OH·), positive holes (h+), and hydrogen peroxide (H2O2)—involved were also investigated in the degradation process. These studies offer additional applications of hierarchical TiO2 nanobelt membranes, including those harnessing sunlight for water treatment.

  15. Inverted organic solar cells based on Cd-doped TiO2 as an electron extraction layer

    Science.gov (United States)

    Ranjitha, A.; Muthukumarasamy, N.; Thambidurai, M.; Velauthapillai, Dhayalan; Madhan Kumar, A.; Gasem, Zuhair M.

    2014-10-01

    Nanocrystalline Cd-doped TiO2 thin films have been prepared by sol-gel method. X-ray diffraction analysis reveals that TiO2 and Cd-doped TiO2 nanocrystalline thin films are of anatase phase. The average grain size of TiO2 and Cd-doped TiO2 nanocrystalline thin films was found to lie in the range of 15-18 nm. Solar cells have been fabricated with a device structure of ITO/Cd-doped TiO2/P3HT:PC71BM/MoO3/Al configuration. The power conversion efficiency of the inverted organic solar cell with Cd-doped TiO2 is 3.06% and is higher than that of TiO2 based organic solar cell (2.64%).

  16. Preparation and characterization of SO42-/TiO2 and S2O82-/TiO2 catalysts

    Institute of Scientific and Technical Information of China (English)

    MA Xuedan; GUO Daishi; JIANG Qizhong; MA Zifeng; MA Zhengfei; YE Weidong; LI Chunbo

    2007-01-01

    Nanosizedsolid superacidsSO42-/TiO2and S2O82-/TiO2,as well as MCM-41-supported SO42-/ZrO2,were prepared.Their structures,acidities,and catalytic activities were investigated and compared using XRD,N2 adsorptiondesorption,and in situ FTIR-pyridine adsorption,as well as an evaluation reaction with pseudoionone cyclization.The results showed that SO42-/TIO2 and S2Os2-/TiO2 possess not only nanosized particles with diameters < 7.0 nm,a BET surface greater than 140 cm2/g and relatively regular mesostructures with pores around 4.0 nm,but also a pure anatase phase and strong acidity.Different from the Lewis acid nature of SO42-/ZrO2/MCM-41,SO42-/TIO2 and S2O8Z-/TiO2 exhibit mainly Bronsted acidities.The strongest Bronsted acid sites were produced on SO42-/TIO2 promoted with H2804,while Lewis acid sites on S2082-/TIO2 even stronger than those on SO42-/ZrO2/MCM-41 were generated when persulfate solution was used as sulfating agent.Because of their distinct acid natures,SO42-/TIO2 and $2082-/TIO2 exhibited catalytic activities for the cyclization ofpseudoionone that were much higher than that of SO42-/ZrO2/MCM-41.It can be concluded that the existence of more Bronsted acid sites was favorable for proton participation in the cyclization reaction.

  17. Fabrication and Characteristics of Macroporous TiO2 Photocatalyst

    Directory of Open Access Journals (Sweden)

    Guiyun Yi

    2014-01-01

    Full Text Available Macroporous TiO2 photocatalyst was synthesized by a facile nanocasting method using polystyrene (PS spherical particles as the hard template. The synthesized photocatalyst was characterized by transmission electron microscope (TEM, scanning electron microscopy (SEM, thermogravimetry-differential thermogravimetry (TG-DTG, X-ray diffraction (XRD, and N2-sorption. TEM, SEM, and XRD characterizations confirmed that the macroporous TiO2 photocatalyst is composed of anatase phase. The high specific surface area of 87.85 m2/g can be achieved according to the N2-sorption analysis. Rhodamine B (RhB was chosen as probe molecule to evaluate the photocatalytic activity of the TiO2 catalysts. Compared with the TiO2 materials synthesized in the absence of PS spherical template, the macroporous TiO2 photocatalyst sintered at 500°C exhibits much higher activity on the degradation of RhB under the UV irradiation, which can be assigned to the well-structured macroporosity. The macroporous TiO2 material presents great potential in the fields of environmental remediation and energy conversion and storage.

  18. Photocatalytic Oxidation of Diethyl Sulfide Vapor over TiO2-Based Composite Photocatalysts

    Directory of Open Access Journals (Sweden)

    Dmitry Selishchev

    2014-12-01

    Full Text Available Composite TiO2/activated carbon (TiO2/AC and TiO2/SiO2 photocatalysts with TiO2 contents in the 10 to 80 wt. % range were synthesized by the TiOSO4 thermal hydrolysis method and characterized by AES, BET, X-ray diffraction and FT-IR ATR methods. All TiO2 samples were in the anatase form, with a primary crystallite size of about 11 nm. The photocatalytic activities of the TiO2/AC and TiO2/SiO2 samples were tested in the gas-phase photocatalytic oxidation (PCO reaction of diethyl sulfide (DES vapor in a static reactor by the FT-IR in situ method. Acetaldehyde, formic acid, ethylene and SO2 were registered as the intermediate products which finally were completely oxidized to the final oxidation products – H2O, CO2, CO and SO42− ions. The influence of the support on the kinetics of DES PCO and on the TiO2/AC and TiO2/SiO2 samples’ stability during three long-term DES PCO cycles was investigated. The highest PCO rate was observed for TiO2/SiO2 photocatalysts. To evaluate the activity of photocatalysts the turnover frequency values (TOF were calculated for three photocatalysts (TiO2, TiO2/AC and TiO2/SiO2 for the same amount of mineralized DES. It was demonstrated that the TOF value for composite TiO2/SiO2 photocatalysts was 3.5 times higher than for pure TiO2.

  19. Photocatalytic oxidation of diethyl sulfide vapor over TiO2-based composite photocatalysts.

    Science.gov (United States)

    Selishchev, Dmitry; Kozlov, Denis

    2014-12-19

    Composite TiO2/activated carbon (TiO2/AC) and TiO2/SiO2 photocatalysts with TiO2 contents in the 10 to 80 wt. % range were synthesized by the TiOSO4 thermal hydrolysis method and characterized by AES, BET, X-ray diffraction and FT-IR ATR methods. All TiO2 samples were in the anatase form, with a primary crystallite size of about 11 nm. The photocatalytic activities of the TiO2/AC and TiO2/SiO2 samples were tested in the gas-phase photocatalytic oxidation (PCO) reaction of diethyl sulfide (DES) vapor in a static reactor by the FT-IR in situ method. Acetaldehyde, formic acid, ethylene and SO2 were registered as the intermediate products which finally were completely oxidized to the final oxidation products - H2O, CO2, CO and SO42- ions. The influence of the support on the kinetics of DES PCO and on the TiO2/AC and TiO2/SiO2 samples' stability during three long-term DES PCO cycles was investigated. The highest PCO rate was observed for TiO2/SiO2 photocatalysts. To evaluate the activity of photocatalysts the turnover frequency values (TOF) were calculated for three photocatalysts (TiO2, TiO2/AC and TiO2/SiO2) for the same amount of mineralized DES. It was demonstrated that the TOF value for composite TiO2/SiO2 photocatalysts was 3.5 times higher than for pure TiO2.

  20. Electrochemical Behavior of TiO2 Nanoparticle Doped WO3 Thin Films

    Directory of Open Access Journals (Sweden)

    Suvarna R. Bathe

    2014-01-01

    Full Text Available Nanoparticle TiO2 doped WO3 thin films by pulsed spray pyrolysis technique have been studied on fluorine tin doped (FTO and glass substrate. XRD shows amorphous nature for undoped and anatase phase of TiO2 having (101 plane for nanoparticle TiO2 doped WO3 thin film. SEM shows microfibrous reticulated porous network for WO3 with 600 nm fiber diameter and nanocrystalline having size 40 nm for TiO2 nanoparticle doped WO3 thin film. TiO2 nanoparticle doped WO3 thin film shows ~95% reversibility due to may be attributed to nanocrystalline nature of the film, which helpful for charge insertion and deinsertion process. The diffusion coefficient for TiO2 nanoparticle doped WO3 film is less than undoped WO3.

  1. Photocatalytic degradation of monoethanolamine in wastewater using nanosized TiO2 loaded on clinoptilolite

    Science.gov (United States)

    Khodadoust, Saeid; Sheini, Azarmidokht; Armand, Nezam

    2012-06-01

    The use of titanium dioxide (TiO2) as photocatalyst to degrade the organic compounds is an effective method of oxidation process and has been widely studied in environmental engineering. In this investigation photocatalytic degradation of monoethanolamine (MEA) using TiO2 (in form of anatase) loaded on surface of clinoptilolite (CP) (TiO2-CP) in wastewater was studied. The surface interaction between TiO2 and CP was investigated by means of transmission electron microscope (TEM), atom force microscope (AFM), IR and X-ray diffraction (XRD). Then the effects of some parameters such as pH, amount of photocatalyst, and initial concentration of MEA on degradation percentage of MEA were examined. The obtained results show that the TiO2-CP is an active photocatalyst as compared with TiO2 nanopowders. All these results indicated that this proposed method can be useful for the development of wastewater treatment applications.

  2. Properties of TiO2 Thin Films Prepared by Magnetron Sputtering

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    With rapid progressive application of TiO2 thin films, magnetron sputtering becomes a very interesting method to prepare such multi-functional thin films. This paper focuses on influences of various deposition processes and deposition rate on the structures and properties of TiO2 thin films. Anatase, rutile or amorphous TiO2 films with various crystalline structures and different photocatalytic, optical and electrical properties can be produced by varying sputtering gases, substrate temperature, annealing process, deposition rate and the characteristics of magnetron sputtering. This may in turn affect the functions of TiO2 films in many applications. Furthermore, TiO2-based composites films can overcome many limitations and improve the properties of TiO2 films.

  3. Formation Mechanistism Study of TiO2 Film Comprising Nanotubes and Nanoparticles

    Science.gov (United States)

    Yang, Di; Wang, Yi-quan; Ren, Guo-bin; Feng, Shuai; Chen, Yuan-yuan; Wang, Wen-zhong

    2012-02-01

    A novel titanium dioxide (TiO2) film comprising both nanotubes and nanopaticles was fabricated by an anodization process of the modified titanium. The local electric field at the anodized surface was simulated and its influence on the morphology of the TiO2 film was discussed. The results show that the electric field strength is enhanced by the covering. The growth rate of TiO2 increases with the assist of the local electric field. However, TiO2 dissolution is hindered since the local electric field prevents [TiF6]6- from diffusing. It means that the balance condition for the formation of nanotubes is broken, and TiO2 nanoparticles are formed. Moreover, the crystal structure of the TiO2 film was confirmed using X-ray diffraction and Raman analysis. The anatase is a main phase for the proposed film.

  4. Study on UV Shielding TiO2 Thin Film Prepared by Sol-Gel Method

    Institute of Scientific and Technical Information of China (English)

    Shihai Zhao; Xiaohui Wang; Shaobo Xin; Qiang Jiang; Xiaoping Liang

    2006-01-01

    Titanium dioxide (TiO2) thin films were prepared on microscopes slides by sol-gel and dip-coating processes from specially formulated sols. The results show that there exists anatase and rutile structure of TiO2 when heat treatment temperature is 450℃, and at 800℃, TiO2 particle size is of below 100 nm and rutile structure is presented. In the range of 360 nm~400 nm the transmittance of TiO2 sol increases with the increasing of the concentration of Ti(OC4H9)4 in ethanol solution.The transmittance of TiO2 films with various number of the layer is measured to be 0% below 320 nm, and the three-layer TiO2 film is of the best UV resistance in the range of 320 nm~400 nm.

  5. Synthesis and characterization of TiO2 and Ag/TiO2 nanostructure

    Science.gov (United States)

    Gahlot, Swati; Thakur, Amit Kumar; Kulshrestha, Vaibhav; Shahi, V. K.

    2013-02-01

    Single phase anatase TiO2 nanoparticles were prepared using Titanium tertachloride (TiCl4) as precursor through an inexpensive method. Well dispersed nanocomposites of silver at TiO2 were synthesized successfully by photochemical route. Both TiO2 and Ag/TiO2 were characterized using X-Ray Diffraction (XRD) and transmission electron microscopy (TEM). The particle size of TiO2 is found to be ˜ 11 nm and ˜ 22 nm for Ag/TiO2, by XRD and confirmed by TEM. TEM micrographs also show the single phase crystal of TiO2 and confirm the deposition of silver among TiO2.

  6. Hydroxyapatite growth on anodic TiO2 nanotubes.

    Science.gov (United States)

    Tsuchiya, Hiroaki; Macak, Jan M; Müller, Lenka; Kunze, Julia; Müller, Frank; Greil, Peter; Virtanen, Sannakaisa; Schmuki, Patrik

    2006-06-01

    In the present work, we study the growth of hydroxyapatite formation on different TiO(2) nanotube layers. The nanotube layers were fabricated by electrochemical anodization of titanium in fluoride-containing electrolytes. To study various nanotube lengths, layers with an individual tube diameter of 100 nm were grown to a thickness of approximately 2 mum or 500 nm. The ability to form apatite on the nanotube layers was examined by immersion tests combined with SEM, XRD and FT-IR investigations. For reference, experiments were also carried out on compact anodic TiO(2) layers. The results clearly show that the presence of the nanotubes on a titanium surface enhances the apatite formation and that the 2-mum thick nanotube layer triggers deposition faster than the thinner layers. Tubes annealed to anatase, or a mixture of anatase and rutile are clearly more efficient in promoting apatite formation than the tubes in their "as-formed" amorphous state.

  7. Photocatalytic Hydrogen or Oxygen Evolution from Water over S- or N-Doped TiO2 under Visible Light

    Directory of Open Access Journals (Sweden)

    Kazumoto Nishijima

    2008-01-01

    Full Text Available S- or N-doping of TiO2 powder having an anatase or rutile phase extended the photocatalytic activity for water oxidation and reduction under UV light and visible light irradiation. For the reduction of water, anatase-doped TiO2 showed higher level of activity than that of doped TiO2 having a rutile phase using ethanol as an electron donor. Furthermore, the activity level of S-doped TiO2 for hydrogen evolution was higher than that of N-doped TiO2 photocatalysts under visible light. Photocatalytic oxidation of water on doped TiO2 having a rutile phase proceeded with fairly high efficiency when Fe3+ ions were used as electron acceptors compared to that on doped TiO2 having an anatase phase. In addition, water splitting under visible light irradiation was achieved by construction of a Z-scheme photocatalysis system employing the doped TiO2 having anatase and rutile phases for H2 and O2 evolution and the I−/IO3− redox couple as an electron relay.

  8. Photocatalytic Degradation of Dicofol and Pyrethrum with Boric and Cerous Co-doped TiO2 under Light Irradiation

    Institute of Scientific and Technical Information of China (English)

    GONG Lifen; ZOU Jing; ZENG Jinbin; CHEN Wenfeng; CHEN Xi; WANG Xiaoru

    2009-01-01

    Boric and cerous co-doped nano titanium dioxide (B/Ce co-doped TiO2) was synthesized using a sol-gel tech-nique, which involved the hydrolyzation of tetrabutyl titanate with the addition of boric acid and cerous nitrate. The B/Ce co-doped TiO2 was employed for the photocatalytic degradation of dicofol, cyfluthrin and fenvalerate under light irradiation. XRD, TEM, Fr-IR and UV-Vis DRS methods were used to characterize the crystalline structure. Experimental results showed that only the anatase signal phase was found for B/Ce co-doped TiO2, but multiplicate phases, including anatase, rutile and less brookite phases, were identified both in the pure TiO2 nanoparticles and Ce-doped TiO2 nanoparticles. The band gap value of B/Ce co-doped nano TiO2 was narrower than that of undoped nano TiO2. Compared to undoped TiO2, a stronger absorption in the range of 420 to 850 nm was found for B/Ce co-doped nano TiO2, which presented a higher photocatalytic activity in the degradation of dicofol, cyfluthrin and fenvalerate than both Ce doped nano TiO2 and pure nano TiO2 under the same light irradiation.

  9. First-Principles Calculations on Electronic Structures of N/F-Doped and N-F-Codoped TiO2 Anatase(101)Surfaces%N/F掺杂和N-F双掺杂锐钛矿相TiO2(101)表面电子结构的第一性原理计算

    Institute of Scientific and Technical Information of China (English)

    陈琦丽; 唐超群

    2009-01-01

    采用密度泛函理论(DFT)平面波赝势方法计算了N/F掺杂和N-F双掺杂锐钛矿相TiO2(101)表面的电子结构.由于DFT方法存在对过渡金属氧化物带隙能的计算结果总是与实际值严重偏离的缺陷,本文也采用DFT+U(Hubbard系数)方法对模型的电子结构进行了计算.DFT的计算结果表明N掺杂后,N2p轨道与O 2p和Ti 3d价带轨道的混合会导致TiO2带隙能的降低,而F掺杂以及氧空位的引入对材料的电子结构没有明显的影响.DFT+U的计算却给出截然不间的结果,N掺杂并没有导致带隙能的降低,而只是在带隙中引入一个孤立的杂质能级,反而F掺杂以及氧空位的引入带来明显的带隙能降低.DFT+U的计算结果与一些实验测量结果能够较好地符合.%Electronic structures of nitrogen(N)/fluorine(F)-doped and N-F-codoped TiO2 anatase(101)surfaces were investigated by density functional theory(DFT)plane-wave pseudopotential method.Since DFT calculations performed on transition metal oxides always lead to a severe underestimation of the band gap,DFT+U(Hubbard coefficient)method was also adopted to calculate the electronic structures.DFT results demonstrated that mixing of N 2p states with O 2p and Ti 3d valence band(VB)states contributes to the band gap reduction of TiO2 whereas F doping and the introduction of oxygen vacancies have no obvious effect on the electronic structure.However,from DFT+U,no obvious band gap narrowing was observed by N-doping except for the isolated N 2p states lying in the gap.In DFT+U calculation,F-doping as well as the introduction of oxygen vacancies leads to an obvious band gap narrowing.Results from DFT+U calculations accord well with some experimental results.

  10. Structure and photoluminescence of the TiO2 films grown by atomic layer deposition using tetrakis-dimethylamino titanium and ozone.

    Science.gov (United States)

    Jin, Chunyan; Liu, Ben; Lei, Zhongxiang; Sun, Jiaming

    2015-01-01

    TiO2 films were grown on silicon substrates by atomic layer deposition (ALD) using tetrakis-dimethylamino titanium and ozone. Amorphous TiO2 film was deposited at a low substrate temperature of 165°C, and anatase TiO2 film was grown at 250°C. The amorphous TiO2 film crystallizes to anatase TiO2 phase with annealing temperature ranged from 300°C to 1,100°C in N2 atmosphere, while the anatase TiO2 film transforms into rutile phase at a temperature of 1,000°C. Photoluminescence from anatase TiO2 films contains a red band at 600 nm and a green band at around 515 nm. The red band exhibits a strong correlation with defects of the under-coordinated Ti(3+) ions, and the green band shows a close relationship with the oxygen vacancies on (101) oriented anatase crystal surface. A blue shift of the photoluminescence spectra reveals that the defects of under-coordinated Ti(3+) ions transform to surface oxygen vacancies in the anatase TiO2 film annealing at temperature from 800°C to 900°C in N2 atmosphere.

  11. Local Bonding Analysis of the Valence and Conduction Band Features of TiO2

    Science.gov (United States)

    2007-01-01

    anatase than with rutile .33 The shape of the L3 spectrum in Fig. 2 is also more qualitatively similar to XAS spectra of anatase surfaces shown in the...annealed TiO2 surfaces of anatase and rutile at photon ener- gies of 40–80 eV would appear to reveal a stronger similarity to the resonance behavior...of the anatase surfaces than to rutile , for which the Ti 3p→4sp resonance at 54 eV is dominant.7 However, it is clear from the same study that the CIS

  12. Synthesis and characterization of monoclinic TiO2 nanosheets

    Institute of Scientific and Technical Information of China (English)

    WU Yu; XU Boqing

    2005-01-01

    A novel two-step method for the synthesis of monoclinic titanium oxide (i.e. TiO2(B)) nanosheets is presented in this report. The method is featured by two steps: 1) synthesis of hydrogen titanate nanosheets, followed by 2) calcination of the titanate nanosheets at elevated temperatures. The hydrogen titanate nanosheets were prepared first by autoclaving anatase TiO2 powders, obtained by air calcining an ethanol-gel of Ti(OH)4 at 500℃, in aqueous NaOH (10 mol/L) at 150―200℃, and then by washing with hydrochloric acid under supersonic irradiation. While sizes of the nanosheets were found to increase with increasing the temperature of the hydrothermal treatment, the calcination at 400―500℃ of the hydrogen titanate nanosheets that were synthesized at higher autoclaving temperatures (180―200℃) produced monoclinic TiO2 nanosheets with a uniform morphology. By contrast, the same calcination of the titanate nanosheets synthesized at the autoclaving temperature 180℃ led to anatase TiO2 nanoparticles.

  13. Fabrication of TiO2 nanorod assembly grafted rGO (rGO@TiO2-NR) hybridized flake-like photocatalyst

    Science.gov (United States)

    Lv, Kangle; Fang, Shun; Si, Lingling; Xia, Yang; Ho, Wingkei; Li, Mei

    2017-01-01

    To efficiently separate the photo-generated electron-hole pairs of TiO2 hybrid, anatase TiO2 nanorod assembly grafted reduced graphene oxides (rGO@TiO2-NR) hybrid was successfully fabricated using potassium titanium oxalate (PTO) and graphene oxides (GO) as starting materials and diethylene glycol (DEG) as reductant. The effect of GO content on the structure and photocatalytic activity of rGO@TiO2-NR composite was systematically studied. Results show that, in the absence of GO, only TiO2 microsphere assembly is obtained from TiO2 nanorods. The presence of GO results in the formation of a flake-like TiO2-nanorod-assembled grafted rGO hybrid. The photocatalytic activity of rGO@TiO2-NR composite increases first and then decreases with increase in the amount of GO from 0 wt.% to 10 wt.%. The hybridized S4 sample prepared with 4 wt.% GO possesses the highest photocatalytic activity with a constant rate of 0.039 min-1 in the photocataytic degradation of Brilliant X-3B dye (X3B); this sample was enhanced more than three times when compared with pure TiO2 sample (0.012 min-1). The enhanced photocatalytic activity of the rGO@TiO2-NR hybrid was attributed to the strong interaction between TiO2 nanorods and rGO. The unique hierarchical structure of 1D nanorod assembly TiO2-rGO flakes facilitates the injection and transfer of photo-generated electrons from TiO2 to graphene, thus retarding the recombination of electron-hole pairs and enhancing the photocatalytic activity. The enlarged BET surface areas, not only increasing the number of active sites, but also facilitating the adsorption of the dye, and improved light-harvesting ability also contribute to the enhanced photoreactivity of rGO@TiO2-NR hybrid.

  14. Photocatalytic activity enhancing for TiO2 photocatalyst by doping with La

    Institute of Scientific and Technical Information of China (English)

    WEN Chen; DENG Hua; TIAN Jun-ying; ZHANG Ji-mei

    2006-01-01

    La doped nanocrystalline TiO2 photocatalyst was developed by sol-gel method. The prepared La-TiO2 photocatalysts with anatase phases were characterized by X-ray diffractometry (XRD),UV-Vis absorption spectroscopy,and photoluminescence spectra (PL). The photocatalytic activity was evaluated by the photocatalytic degradation of phenol in solution under sunlight irradiation. The results show that the crystallinity of anatase is improved by La doping. Moreover,La not only suppresses phase transition from anatase to rutile but also exhibits an absorption in the λ≥ 400 nm range. The photocatalytic activity of La-doped TiO2 photocatalysts exceeds that of pure TiO2 photocatalyst prepared by the same method when the molar ratio of La to Ti is kept at 0.3%.

  15. Visible and near-infrared electroluminescence from TiO2/p+-Si heterostructured device

    Directory of Open Access Journals (Sweden)

    Yang Yang

    2014-04-01

    Full Text Available We report on visible and near-infrared (NIR electroluminescence (EL from the device based on the TiO2/p+-Si heterostructure, in which the TiO2 film is composed of anatase and rutile phases. As the device is applied with sufficiently high forward bias with the positive voltage connecting to p+-Si, the visible EL peaking at ∼600 nm along with the NIR EL centered at ∼810 nm occur simultaneously. It is proposed that the oxygen vacancies in the anatase TiO2 and Ti3+ defect states in the rutile TiO2 are the responsible centers for the visible and NIR EL, respectively.

  16. Preparation, Characterization and Visible Light Photocatalytic Activity of Nitrogen-doped TiO2

    Institute of Scientific and Technical Information of China (English)

    WANG Zhengpeng; GONG Wenqi; HONG Xiaoting; CAI Weimin; JIANG Juhui; ZHOU Baoxue

    2006-01-01

    The N- doped TiO2 polycrystalline powder was synthesized through calcining the hydrolysis product of tetra-butyl titanate with ammonia. The photocatalytic activity of N-doped TiO2 powder with anatase phase calcined at 400 ℃ was 2.7 times higher than that of Degussa P25 for phenol decomposition under visible light. All samples had mesoporous structures. X- ray photoelectron spectroscopy corfirmed that a trace amount of N atoms remained in the anatase polycrystalline TiO2 powder when calcined at 400 ℃ as substitutional atoms at the oxygen sites. UV-Vis and EPR analyses indicated that oxygen vacancy states were created during the course of N-doped TiO2 powder formation. It is considered that substitutional N atoms, oxygen vacancy states, large BET surface areas and mesoporous structure are important factors for the N-doped photocatalyst to present a high vis-activity.

  17. Extraordinary effects of an argon atmosphere on TiO2 photocatalysis.

    Science.gov (United States)

    Ide, Y; Hattori, H; Sano, T

    2014-05-07

    When used as a photocatalyst under solar light, TiO2 tends to show a low photocatalytic activity. We report here that even TiO2 exhibits a high photocatalytic activity toward the decomposition (mineralization) of aqueous organic contaminants under simulated solar light when used under an Ar atmosphere (Ar flow). The photocatalytic decomposition rate of a cationic dye, crystal violet, and the CO2 evolution rate over TiO2 (P25, mainly composed of anatase and rutile) under Ar flow were substantially higher than those obtained in air and under air, O2, N2 and CO2 flows. Similar positive effects of Ar flow on photocatalytic reactions were observed when another cationic dye, basic violet 4, and TiO2 (anatase) were used, suggesting the versatility of Ar flow for improving photocatalytic activities.

  18. PHOTOCATALYTIC PROPERTIES OF Cr DOPED TiO2–SiO2 NANOSTRUCTURE THIN FILM

    OpenAIRE

    Akbar Eshaghi; Ameneh Eshaghi

    2012-01-01

    Cr doped TiO2–SiO2 nanostructure thin film on glass substrates was prepared by a sol-gel dip coating method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-vis spectrophotometer were used to characterize the structural, chemical and optical properties of the thin film. The XRD showed that thin films contain only anatase phase. FE-SEM images illustrated that anatase average crystallite size in the pure TiO2 and Cr doped TiO2–SiO2 thin films are 15 nm and 10 nm, respecti...

  19. Phase-dependant photochemistry of TiO2 nanoparticles in the degradation of organic dye methylene blue under solar light irradiation

    Science.gov (United States)

    Prasannalakshmi, P.; Shanmugam, N.

    2017-09-01

    This paper describes the photochemistry of nanoparticles of TiO2 in anatase, anatase/rutile, and rutile phases for the degradation of methylene blue (MB) under solar light irradiation. For this process, TiO2 nanoparticles were synthesized by a sol-gel method, and different phases were achieved by annealing the prepared particles at various temperatures. Further, the annealed products were subjected to structural, optical, and morphological characterizations. The photocatalytic measurements show that TiO2 in the anatase phase possesses superior activity towards the degradation of MB due to its smaller crystallite size, enhanced BET surface area, higher pore size, and low charge transfer resistance.

  20. Comparison study on photocatalytic oxidation of pharmaceuticals by TiO2-Fe and TiO2-reduced graphene oxide nanocomposites immobilized on optical fibers.

    Science.gov (United States)

    Lin, Lu; Wang, Huiyao; Jiang, Wenbin; Mkaouar, Ahmed Radhi; Xu, Pei

    2017-03-08

    Incorporating reduced graphene oxide (rGO) or Fe(3+) ions in TiO2 photocatalyst could enhance photocatalytic degradation of organic contaminants in aqueous solutions. This study characterized the photocatalytic activities of TiO2-Fe and TiO2-rGO nanocomposites immobilized on optical fibers synthesized by polymer assisted hydrothermal deposition method. The photocatalysts presented a mixture phase of anatase and rutile in the TiO2-rGO and TiO2-Fe nanocomposites. Doping Fe into TiO2 particles (2.40eV) could reduce more band gap energy than incorporating rGO (2.85eV), thereby enhancing utilization efficiency of visible light. Incorporating Fe and rGO in TiO2 decreased significantly the intensity of TiO2 photoluminescence signals and enhanced the separation rate of photo-induced charge carriers. Photocatalytic performance of the synthesized nanocomposites was measured by the degradation of three pharmaceuticals under UV and visible light irradiation, including carbamazepine, ibuprofen, and sulfamethoxazole. TiO2-rGO exhibited higher photocatalytic activity for the degradation of pharmaceuticals under UV irradiation, while TiO2-Fe demonstrated more suitable for visible light oxidation. The results suggested that the enhanced photocatalytic performance of TiO2-rGO could be attributed to reduced recombination rate of photoexcited electrons-hole pairs, but for TiO2-Fe nanocomposite, narrower band gap would contribute to increased photocatalytic activity.

  1. Electrospinning Synthesis and Photocatalytic Activity of Mesoporous TiO2 Nanofibers

    OpenAIRE

    Jing Li; Hui Qiao; Yuanzhi Du; Chen Chen; Xiaolin Li; Jing Cui; Dnt Kumar; Qufu Wei

    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 ...

  2. Single-Step Synthesis of SnS₂ Nanosheet-Decorated TiO₂ Anatase Nanofibers as Efficient Photocatalysts for the Degradation of Gas-Phase Diethylsulfide.

    Science.gov (United States)

    Christoforidis, Konstantinos C; Sengele, Armelle; Keller, Valérie; Keller, Nicolas

    2015-09-02

    We report on a facile one-step soft hydrothermal process for synthesizing 1D anatase TiO2 nanofibers decorated with ultrathin SnS2 nanosheets. H-titanate nanofibers were used as preshaped Ti precursor. Under controlled conditions, the H-titanate structure was transformed into anatase maintaining the fibril morphology, while at the same time SnS2 nanosheets were grown in situ on the surface of the nanofibers. The successful formation of SnS2 nanosheets on the TiO2 nanofibers was confirmed by high-resolution TEM, and together with XPS spectroscopy, the tight interface formed between the SnS2 and the anatase TiO2 nanofibers was verified. The 1D SnS2/TiO2 hierarchical nanostructures with semiconductor heterojunction were proven to be very efficient under artificial solar irradiation in the photocatalytic degradation of gaseous diethylsulfide as simulant for live yperite chemical warfare agent as well as model substrate for malodorous organosulfide volatile organic compounds. SnS2 did not operate as a visible light sensitizer for TiO2 but rather as an oxidizing agent and charge-carrier separator. The semiconductor ratio in the heterostructure controlled the photoactivity. Samples with no or high content of SnS2 were less active than those with moderate SnS2 content. Enhanced reactivity was ascribed to an efficient separation of the photogenerated charge carriers driven by the differences in band edge positions and favored by the tight interface within the coupled heterostructure.

  3. High-Temperature Stable Anatase Titanium Oxide Nanofibers for Lithium-Ion Battery Anodes.

    Science.gov (United States)

    Lee, Sangkyu; Eom, Wonsik; Park, Hun; Han, Tae Hee

    2017-08-02

    Control of the crystal structure of electrochemically active materials is an important approach to fabricating high-performance electrodes for lithium-ion batteries (LIBs). Here, we report a methodology for controlling the crystal structure of TiO2 nanofibers by adding aluminum isopropoxide to a common sol-gel precursor solution utilized to create TiO2 nanofibers. The introduction of aluminum cations impedes the phase transformation of electrospun TiO2 nanofibers from the anatase to the rutile phase, which inevitably occurs in the typical annealing process utilized for the formation of TiO2 crystals. As a result, high-temperature stable anatase TiO2 nanofibers were created in which the crystal structure was well-maintained even at high annealing temperatures of up to 700 °C. Finally, the resulting anatase TiO2 nanofibers were utilized to prepare LIB anodes, and their electrochemical performance was compared to pristine TiO2 nanofibers that contain both anatase and rutile phases. Compared to the electrode prepared with pristine TiO2 nanofibers, the electrode prepared with anatase TiO2 nanofibers exhibited excellent electrochemical performances such as an initial Coulombic efficiency of 83.9%, a capacity retention of 89.5% after 100 cycles, and a rate capability of 48.5% at a current density of 10 C (1 C = 200 mA g(-1)).

  4. Characterization and photocatalytic activity for methylene blue degradation of iron-deposited TiO2 photocatalyst

    Institute of Scientific and Technical Information of China (English)

    徐悦华; 王良焱; 黄琮; 李新军; 李芳柏; 郑少健; 张琦

    2003-01-01

    Iron-deposited TiO2 was prepared by photo-reducing ferric ions. The photocatalytic activity of methylene blue degradation was enhanced after TiO2 was deposited with iron, and the optimum n(Fe)/n(Ti) is 0.25%. TiO2 and iron-deposited TiO2 are anatase and rutile, and anatase is the dominant crystalline phase. In all samples, the XRD patterns indicate that there are no characteristic peaks of iron to be detected. XPS confirms that Fe3+and Fe2+ are present on the surface of 0.5% iron-deposited TiO2, however they are not susceptible to XRD detection. The thermodynamics analysis shows that the alternative possibility of reduction from the Fe3+/Fe2+ couple seems plausible, but Fe2+ can not be reduced to Fe. The fluorescence intensity weakens after iron is deposited on TiO2, because iron deposited traps photo-generated electrons and holes. The fluorescence intensity order of TiO2 and iron-deposited TiO2, from strong to weak, is in good agreement with that of photocatalytic reactiveness TiO2 and iron-deposited TiO2, from low to high.

  5. Cr-doping effects on unoccupied d-band electronic structure of TiO2

    Science.gov (United States)

    Wojtaszek, K.; Tyrala, K.; Czapla-Masztafiak, J.; Sa, J.; Szlachetko, J.

    2016-11-01

    Resonant X-ray emission spectroscopy (RXES) was applied to probe the electronic states above Fermi level for Cr-doped anatase TiO2. The results reveal doping-induced electronic band on low energy side of unoccupied electronic states. The experimental RXES data in combination with theoretical simulations allowed distinguishing electronic state changes on both, d-localized and d-delocalized orbitals of Cr-doped anatase TiO2. The detailed information on unoccupied electronic states is crucial in order to correlate enhanced light absorption properties with catalytic activity of the material.

  6. Characteristics of Boron Decorated TiO2 Nanoparticles for Dye-Sensitized Solar Cell Photoanode

    Directory of Open Access Journals (Sweden)

    Ching-Yuan Ho

    2015-01-01

    Full Text Available Different boron weight percents on mixed-phase (anatase and rutile TiO2 nanoparticles were synthesized to investigate structure morphology, defect states, luminescence properties, and energy conversion. The measured results indicate that boron doping of TiO2 both increases the crystallite size and rutile-phase percent in an anatase matrix. Decreasing the band gap by boron doping can extend the absorption to the visible region, while undoped TiO2 exhibits high UV absorption. Oxygen vacancy defects generated by boron ions reduce Ti+4 and affect electron transport in dye-sensitized solar cells. Excess electrons originating from the oxygen vacancies of doped TiO2 downward shift in the conduction band edge and prompt the transfer of photoelectrons from the conduction band of the rutile phase to the lower energy anatase trapping sites; they then separate charges to enhance the photocurrent and Jsc. Although the resistance of the electron recombination (Rk between doped TiO2 photoanode and the electrolyte for the doped TiO2 sample is lower, a longer electron lifetime (τ of 19.7 ms with a higher electron density (ns of 2.1 × 1018 cm−3 contributes to high solar conversion efficiency.

  7. Photoreactive TiO2/carbon nanotube composites: synthesis and reactivity.

    Science.gov (United States)

    Yao, Yuan; Li, Gonghu; Ciston, Shannon; Lueptow, Richard M; Gray, Kimberly A

    2008-07-01

    Electron-hole recombination limits the efficiency of TiO2 photocatalysis. We have investigated the efficacy with which anatase/carbon nanotube (CNT) composite materials reduce charge recombination and enhance reactivity. We synthesized nanostructured assemblies composed of different proportions of anatase (5 or 100 nm) and either single-or multi-walled CNTs. The composites were prepared using a simple low temperature process in which CNTs and anatase nanoparticles were dispersed in water, dehydrated at 80 degrees C, and dried at 104 degrees C. The structures of the various TiO2/CNT composites were characterized by scanning electron microscopy (SEM) and their function was tested by phenol oxidation. Charge recombination was compared by measuring the photoluminescence spectra of select composites. We found that a nanostructured composite assembled from the 100 nm anatase and single-walled CNTs (SWCNTs) exhibited enhanced and selective photocatalytic oxidation of phenol in comparison to both pure anatase and Degussa P25. A mechanism for the enhanced reactivity is proposed in which electrons are shuttled from TiO2 particles to the SWCNTs as a result of an optimal TiO2/ CNT arrangement that stabilizes charge separation and reduces charge recombination. In addition, the SWCNT assembly provides better catalyst-support (dispersal and connection) than multi-walled CNTs.

  8. Silver-Doping Induced Lattice Distortion in TiO2 Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    WU Xue-Wei; WU Da-Jian; LIU Xiao-Jun

    2009-01-01

    The Ag-doping effects on TiO2 nanoparticles are investigated by means of x-ray diffraction (XRD) and Raman scattering spectroscopy. XRD and Raman results indicate that Ag-doping stabilizes the rutile phase in TiO2.We find an Ag-doping induced lattice expansion in both anatase and rutile phases. The Ag-doping has different influences on the lattice distortion for anatase and rutile phases, that is, the c/a-value for the anatase phasedecreases w/th 0.5% Ag-doping and then increases with 1% Ag-doping while that for the rutile phase shows agradual increase with increasing Ag-doping. We have ascribed the different variations of lattice distortion due to Ag-doping to the change of interfacial interaction between the anatase and rutile phases induced by different Ag concentratious.

  9. Toxicity of TiO2 nanoparticles to Escherichia coli: effects of particle size, crystal phase and water chemistry.

    Directory of Open Access Journals (Sweden)

    Xiuchun Lin

    Full Text Available Controversial and inconsistent results on the eco-toxicity of TiO2 nanoparticles (NPs are commonly found in recorded studies and more experimental works are therefore warranted to elucidate the nanotoxicity and its underlying precise mechanisms. Toxicities of five types of TiO2 NPs with different particle sizes (10∼50 nm and crystal phases were investigated using Escherichia coli as a test organism. The effect of water chemistry on the nanotoxicity was also examined. The antibacterial effects of TiO2 NPs as revealed by dose-effect experiments decreased with increasing particle size and rutile content of the TiO2 NPs. More bacteria could survive at higher solution pH (5.0-10.0 and ionic strength (50-200 mg L(-1 NaCl as affected by the anatase TiO2 NPs. The TiO2 NPs with anatase crystal structure and smaller particle size produced higher content of intracellular reactive oxygen species and malondialdehyde, in line with their greater antibacterial effect. Transmission electron microscopic observations showed the concentration buildup of the anatase TiO2 NPs especially those with smaller particle sizes on the cell surfaces, leading to membrane damage and internalization. These research results will shed new light on the understanding of ecological effects of TiO2 NPs.

  10. Toxicity of TiO2 nanoparticles to Escherichia coli: effects of particle size, crystal phase and water chemistry.

    Science.gov (United States)

    Lin, Xiuchun; Li, Jingyi; Ma, Si; Liu, Gesheng; Yang, Kun; Tong, Meiping; Lin, Daohui

    2014-01-01

    Controversial and inconsistent results on the eco-toxicity of TiO2 nanoparticles (NPs) are commonly found in recorded studies and more experimental works are therefore warranted to elucidate the nanotoxicity and its underlying precise mechanisms. Toxicities of five types of TiO2 NPs with different particle sizes (10∼50 nm) and crystal phases were investigated using Escherichia coli as a test organism. The effect of water chemistry on the nanotoxicity was also examined. The antibacterial effects of TiO2 NPs as revealed by dose-effect experiments decreased with increasing particle size and rutile content of the TiO2 NPs. More bacteria could survive at higher solution pH (5.0-10.0) and ionic strength (50-200 mg L(-1) NaCl) as affected by the anatase TiO2 NPs. The TiO2 NPs with anatase crystal structure and smaller particle size produced higher content of intracellular reactive oxygen species and malondialdehyde, in line with their greater antibacterial effect. Transmission electron microscopic observations showed the concentration buildup of the anatase TiO2 NPs especially those with smaller particle sizes on the cell surfaces, leading to membrane damage and internalization. These research results will shed new light on the understanding of ecological effects of TiO2 NPs.

  11. Visible light induced photodegradation of organic pollutants on nitrogen and fluorine co-doped TiO2 photocatalyst

    Institute of Scientific and Technical Information of China (English)

    WANG Zheng-peng; XU Jun; CAI Wei-min; ZHOU Bao-xue; HE Zheng-guang; CAI Chun-guang; HONG Xiao-ting

    2005-01-01

    The nitrogen and fluorine co-doped TiO2 polycrystalline powder was synthesized by calcinations of the hydrolysis product of tetrabutyl titanate with ammonium fluoride. Nitrogen and fluorine co-doping causes the absorption edge of TiO2 to shift to a lower energy region.The photocatalytic activity of co-doped TiO2 with anatase phases was found to be 2.4 times higher than that of the commercial TiO2photocatalyst Degussa P25 for phenol decomposition under visible light irradiation. The co-doped TiO2 powders only contain anatase phases even at 1000℃. Apparently, ammonium fluoride added retarded phase transformation of the TiO2 powders from anatase to rutile.The substitutional fluorine and interstitial nitrogen atoms in co-doped TiO2 polycrystalline powder were responsible for the vis light response and caused the absorption edge of TiO2 to shift to a lower energy region.

  12. Extruded expanded polystyrene sheets coated by TiO2 as new photocatalytic materials for foodstuffs packaging

    Science.gov (United States)

    Loddo, V.; Marcì, G.; Palmisano, G.; Yurdakal, S.; Brazzoli, M.; Garavaglia, L.; Palmisano, L.

    2012-11-01

    Nanostructured, photoactive anatase TiO2 sol prepared under very mild conditions using titanium tetraisopropoxide as the precursor is used to functionalise extruded expanded polystyrene (XPS) sheets by spray-coating resulting in stable and active materials functionalised by TiO2 nanoparticles. Photocatalytic tests of these sheets performed in a batch reactor in gas-solid system under UV irradiation show their successful activity in degrading probe molecules (2-propanol, trimethylamine and ethene). Raman spectra ensure the deposition of TiO2 as crystalline anatase phase on the polymer surface. The presence of TiO2 with respect to polymer surface can be observed in SEM images coupled to EDAX mapping allowing to monitor the surface morphology and the distribution of TiO2 particles. Finally thermoforming of these sheets in industrial standard equipment leads to useful containers for foodstuffs.

  13. Heterogeneous photocatalytic decomposition of benzene on lanthanum-doped TiO2 film at ambient temperature.

    Science.gov (United States)

    Zhang, Shicheng; Zheng, Zhijian; Wang, Jinhe; Chen, Jianmin

    2006-12-01

    Lanthanum-doped anatase TiO2 thin films on glass prepared via a sol-gel process have been shown to have much higher photocatalytic activity for the degradation of gaseous benzene than pure anatase TiO2 thin film. The photodecomposition of benzene on both types of TiO2 films follows the first-order kinetics while the CO(2) and CO formation followed the zero-order kinetics. GC/MS identification of the intermediates produced during the photodegradation of benzene revealed that doping lanthanum into TiO2 thin film favors a cleavage of benzene ring. An optimal lanthanum amount with respect to photocatalytic activity was about 2.5 wt% (La2O3/TiO2).

  14. Hydrothermal growth of highly monodispersed TiO2 nanoparticles: Functional properties and dye-sensitized solar cell performance

    Science.gov (United States)

    Navaneethan, M.; Nithiananth, S.; Abinaya, R.; Harish, S.; Archana, J.; Sudha, L.; Ponnusamy, S.; Muthamizhchelvan, C.; Ikeda, H.; Hayakawa, Y.

    2017-10-01

    Monodispersed anatase TiO2 nanoparticles were synthesized by hydrothermal method using citric acid as a capping agent. The effect of citric acid and the growth time on the formation of TiO2, functional properties and dye-sensitized solar cell performances were investigated. X-ray diffraction pattern (XRD) and Raman spectroscopy results revealed that the TiO2 nanoparticles possess the anatase phase. Transmission electron microscopy (TEM) measurement revealed the formation of spherical nanoparticles with monodispersity in size and morphology. An average size of 14 nm was obtained for the growth period of 15 h. The maximum efficiency (η) of dye-sensitized solar cell was achieved for TiO2 nanoparticles grown for 15 h as 7.66% which was higher than that of commercial P25 TiO2 (5.23%) and uncapped nanoparticles (3.68%).

  15. Photoinduced properties of nanocrystalline TiO2 sol–gel derived thin films

    Indian Academy of Sciences (India)

    Akbar Eshaghi; Mahmoud Pakshir; Reza Mozaffarinia

    2010-08-01

    In this paper, nanostructure TiO2 thin films were deposited on glass substrates by sol–gel dip coating technique. X-ray diffraction and Fourier transform infrared spectroscopy were used to determine film behaviour. The super-hydrophilicity was assessed by contact angle measurement. Photocatalytic properties of these films were evaluated by degradation of methylene blue under UV irradiation. The XRD pattern of TiO2 powder samples confirmed the presence of polycrystalline anatase phase with a crystal size of 17 nm. The results indicated that UV light irradiation had significant effect on super-hydrophilic and photocatalytic properties of TiO2 thin films.

  16. Growth of TiO2 Nanorods by Sol-gel Template Process

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this work, TiO2 nanorods with uniform diameter of about 100 nm and a length of several micrometers were successfully prepared by the sol-gel template method. Also the influence of molar ratios of precursor on the morphology and structure of TiO2 nanorods has been investigated. The prepared samples were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results indicated that the TiO2 nanorods were crystallized in the anatase and rutile phases, after annealing to 400-700℃ up to 2 h.

  17. Photocatalytic activity of porous TiO2 films prepared by anodic oxidation

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; TAO Jie; WANG Tao; WANG Ling

    2007-01-01

    Anatase titanium dioxide is an active photocatalyst, however, it is difficult to be immobilized on the substrate.The crystalline TiO2 porous film was prepared directly on the surface of pure titanium by anodic oxidation. The film was then used for photocatalysis via the methyl orange degradation method. The effects of anodization voltage, pH value, TiO2 film area and degradation time on the photocatalyst were investigated respectively by UV-visible spectrum. It was indicated that the TiO2 film prepared by anodic oxidation at 140 V had the best photocatalysis capability and the degradation of methyl orange was accelerated with acid addition.

  18. TiO2 Nanocrystals Grown on Graphene as Advanced Photocatalytic Hybrid Materials

    OpenAIRE

    Liang, Yongye; Wang, Hailiang; Casalongue, Hernan Sanchez; Chen, Zhuo; Dai, Hongjie

    2010-01-01

    Graphene/TiO2 nanocrystals hybrid is successfully prepared by directly growing TiO2 nanocrystals on graphene oxide (GO) sheets. The direct growth of nanocrystals on GO sheets was achieved by a two-step method, in which TiO2 was coated on GO sheets by hydrolysis first and crystallized into anatase nanocrystals by hydrothermal treatment in second step. Slow hydrolysis reaction through the use of EtOH/H2O mixed solvents and addition of H2SO4 allows the selectively growing TiO2 on GO and suppress...

  19. Preparation of Nanometer-structured TiO2 Thin Films by Sol-Gel Method

    Institute of Scientific and Technical Information of China (English)

    HE Feng; LI Qian-tao; HU Wang-kai; DENG Tao

    2002-01-01

    The transparent anatase TiO2 nanometer thin films were prepared by the sol-gel method on soda-lime glass. X-ray diffraction, thermal analysis and UV-visible spectrophotometer were used to analyze the formation of the phases. Only increasing the heat-treatment time, the average grain size has no obvious change. The mechanism of grain growth in TiO2 thin film is probably as follows: the grain of coating will become grain core later; TiO2 sol constantly deposited on the surface of TiO2 grain and formed membrane with increasing of coating cycle times; TiO2 grain in the film grow steadily.

  20. Formation Mechanistism Study of TiO2 Film Comprising Nanotubes and Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    Di Yang; Yi-quan Wang; Guo-bin Ren; Shuai Feng; Yuan-yuan Chen; Wen-zhong Wang

    2012-01-01

    A novel titanium dioxide (TiO2) film comprising both nanotubes and nanopaticles was fabricated by an anodization process of the modified titanium.The local electric field at the anodized surface was simulated and its influence on the morphology of the TiO2 film was discussed.The results show that the electric field strength is enhanced by the covering.The growth rate of TiO2 increases with the assist of the local electric field.However,TiO2 dissolution is hindered since the local electric field prevents [TiF6]6- from diffusing.It means that the balance condition for the formation of nanotubes is broken,and TiO2 nanoparticles are formed.Moreover,the crystal structure of the TiO2 film was confirmed using X-ray diffraction and Raman analysis.The anatase is a main phase for the proposed film.

  1. Formaldehyde degradation by photocatalytic Ag-doped TiO2 film of glass fiber roving.

    Science.gov (United States)

    Ubolchonlakate, Kornkanok; Sikong, Lek; Tontai, Tienchai

    2010-11-01

    The photocatalytic Ag doped TiO2 porous films were prepared by sol-gel method and dip coated on glass fiber roving. The sol composed of titanium (IV) isopropoxide, triethanolamine, ethanol and nitric acid followed by calcination of the film at 500 degrees C for 1 hour with a heating rate of 3 degrees C/min. The surface morphology and properties of synthesized TiO2 films were characterized by X-ray diffraction, atomic forced microscope and scanning electron microscope. A laboratory photocatalytic reactor was set up to carry out photoactivity of the prepared catalysts. The results show that TiO2-Ag and TiO2-Ag-TEA porous films give highest rate of formaldehyde gas degradation. It can be noted that triethanolamine exhibits two effects on TiO2 composite films; one is its effect on porous film structure and second is a reverse effect of hindrance of anatase growth.

  2. Photocatalytic Activity of Toluene under UV-LED Light with TiO2 Thin Films

    OpenAIRE

    Thammasak Rojviroon; Apirat Laobuthee; Sanya Sirivithayapakorn

    2012-01-01

    Titanium dioxide (TiO2) and ferric-doped TiO2 (Fe-TiO2) thin films were synthesized on the surface of 304 stainless steel sheets using a simplified sol-gel preparation method. The Fe-TiO2 thin films were prepared with weight-to-volume ratios of /TiO2 of 0.3%, 0.5%, and 0.7%, respectively. The crystalline phase structures of the prepared TiO2 and Fe-TiO2 thin films were entirely anatase. The measured optical band gaps of the TiO2, 0.3% Fe-TiO2, 0.5% Fe-TiO2, and 0.7% Fe-TiO2 thin films were 3....

  3. Microwave Assisted Synthesis, Modification With Platinum And Photocatalytical Properties of TiO2 Nanofibers

    Directory of Open Access Journals (Sweden)

    Reinis DRUNKA

    2016-05-01

    Full Text Available In the present work formation of active TiO2 nanoparticles in microwave synthesis and their modification with platinum were studied. Anatase nanopowder and 10 M KOH solution were used as raw materials. Microwave assisted synthesis method permited to obtain TiO2 nanofibres and nanowires with a diameter of 10 nm and a specific surface area in the range of 70 – 150 m2/g. In order to modify TiO2 nanofibers with platinum it was stirred in H2PtCl6 solution under UV irradiation. Photocatalytic activity was determined by degradation of the methylene blue (MB solution under UV and visible light irradiation. The obtained samples showed higher photocatalytic activity with respect to pure TiO2 nanofibers. The doped TiO2 nanofibers were appropriate for degradation of harmful organic compounds as well as for hydrogen production by water splitting.

  4. A single TiO2-coated side-glowing optical fiber for photocatalytic wastewater treatment

    Institute of Scientific and Technical Information of China (English)

    HU Yan; XU Jingjing; YUAN Chunwei; LIN Jian; YIN Zhidong

    2005-01-01

    By means of TiO2-layer-on-SiO2-layer, anatase TiO2 was deposited on novel side- glowing optical fibers, which can provide side UV radiation along the whole fiber length. FE-SEM images show that the double layers adhered well to the side-glowing optical fiber, and the TiO2 coating was homogeneous and smooth. The decomposition reaction of reactive brilliant red dye X-3B on a single TiO2-coated side-glowing optical fiber indicated that the side-scattering UV light intensity was strong enough for photocatalytic oxidation reaction. Therefore, TiO2-coated side-glowing optical fibers open up a new way to use the optical fiber reactor in photocatalytic wastewater treatment.

  5. Mechanochemical Synthesis of TiO2 Nanocomposites as Photocatalysts for Benzyl Alcohol Photo-Oxidation

    Directory of Open Access Journals (Sweden)

    Weiyi Ouyang

    2016-05-01

    Full Text Available TiO2 (anatase phase has excellent photocatalytic performance and different methods have been reported to overcome its main limitation of high band gap energy. In this work, TiO2-magnetically-separable nanocomposites (MAGSNC photocatalysts with different TiO2 loading were synthesized using a simple one-pot mechanochemical method. Photocatalysts were characterized by a number of techniques and their photocatalytic activity was tested in the selective oxidation of benzyl alcohol to benzaldehyde. Extension of light absorption into the visible region was achieved upon titania incorporation. Results indicated that the photocatalytic activity increased with TiO2 loading on the catalysts, with moderate conversion (20% at high benzaldehyde selectivity (84% achieved for 5% TiO2-MAGSNC. These findings pointed out a potential strategy for the valorization of lignocellulosic-based biomass under visible light irradiation using designer photocatalytic nanomaterials.

  6. Mechanochemical Synthesis of TiO2 Nanocomposites as Photocatalysts for Benzyl Alcohol Photo-Oxidation

    Science.gov (United States)

    Ouyang, Weiyi; Kuna, Ewelina; Yepez, Alfonso; Balu, Alina M.; Romero, Antonio A.; Colmenares, Juan Carlos; Luque, Rafael

    2016-01-01

    TiO2 (anatase phase) has excellent photocatalytic performance and different methods have been reported to overcome its main limitation of high band gap energy. In this work, TiO2-magnetically-separable nanocomposites (MAGSNC) photocatalysts with different TiO2 loading were synthesized using a simple one-pot mechanochemical method. Photocatalysts were characterized by a number of techniques and their photocatalytic activity was tested in the selective oxidation of benzyl alcohol to benzaldehyde. Extension of light absorption into the visible region was achieved upon titania incorporation. Results indicated that the photocatalytic activity increased with TiO2 loading on the catalysts, with moderate conversion (20%) at high benzaldehyde selectivity (84%) achieved for 5% TiO2-MAGSNC. These findings pointed out a potential strategy for the valorization of lignocellulosic-based biomass under visible light irradiation using designer photocatalytic nanomaterials. PMID:28335221

  7. Formation of crystalline TiO2 by anodic oxidation of titanium

    Institute of Scientific and Technical Information of China (English)

    Zixue Su; Linjie Zhang; Feilong Jiang; Maochun Hongn

    2013-01-01

    Formation of crystalline TiO2 (anatase) films by anodic oxidation of titanium foils in ethylene glycol (EG) based electrolytes at room temperature has been investigated. By varying the anodizing parameters such as the amounts of water and NH4F added, applied voltage and anodization time, anodic TiO2 films with different crystalline structures were obtained. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray powder diffraction (XRD) characterizations were employed to determine the morphologies and crystalline structures of as-prepared anodic TiO2 films. The results indicate that crystallization of anodic TiO2 films was generally facilitated by high fluoride concentration, high applied voltage and longer anodization time, and the formation of anodic TiO2 films with best crystallinity could only be achieved when optimized amounts of water were added.

  8. Hydrogen Sensing with Ni-Doped TiO2 Nanotubes

    Directory of Open Access Journals (Sweden)

    Congqin Ning

    2013-07-01

    Full Text Available Doping with other elements is one of the efficient ways to modify the physical and chemical properties of TiO2 nanomaterials. In the present work, Ni-doped TiO2 nanotubes were fabricated through anodic oxidation of NiTi alloy and further annealing treatment. The hydrogen sensing properties of the nanotube sensor were investigated. It was found that the Ni-doped TiO2 nanotubes were sensitive to an atmosphere of 1,000 ppm hydrogen, showing a good response at both room temperature and elevated temperatures. A First-Principle simulation revealed that, in comparison with pure anatase TiO2 oxide, Ni doping in the TiO2 oxide could result in a decreased bandgap. When the oxide sensor adsorbed a certain amount of hydrogen the bandgap increased and the acceptor impurity levels was generated, which resulted in a change of the sensor resistance.

  9. Effect of TiO2 surface properties on the scr activity of Nox emission abatement catalysis

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    NOx emission abatement catalysts V2O5 supported on variousTiO2 including anatase, rutile and mixture of both have beeninvestigated with various physico-chemical measurements such asBET, NH3-TPD, NARP, XRD and so on, and the effect of TiO2 surfaceproperties on the SCR activity of V2O5/TiO2 catalysts was studied.It has been found that the TiO2 surface properties had strongaffect on the SCR activity of V2O5/TiO2 catalysts. The strongeracidic property resulted the higher exposure of active sites aswell as the higher SCR activity.

  10. Comparison of electrode structures and photovoltaic properties of porphyrin-sensitized solar cells with TiO2 and Nb, Ge, Zr-added TiO2 composite electrodes.

    Science.gov (United States)

    Imahori, Hiroshi; Hayashi, Shinya; Umeyama, Tomokazu; Eu, Seunghun; Oguro, Akane; Kang, Soonchul; Matano, Yoshihiro; Shishido, Tetsuya; Ngamsinlapasathian, Supachai; Yoshikawa, Susumu

    2006-12-19

    Electrode structures and photovoltaic properties of porphyrin-sensitized solar cells with TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were examined to disclose the effects of partial substitution of Ti atom by the other metals in the composite electrodes. The TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were prepared by sol-gel process using laurylamine hydrochloride as a template for the formation of micellar precursors yielding well-defined mesoporous nanocrystalline structures, as in the cases of the formation of silica and titania tubules and nanoparticles by the templating mechanism. The TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were characterized by transmission electron microscopy, BET surface area analysis, X-ray diffraction analysis, Raman spectroscopy, and impedance measurements. The TiO2 anatase nanocrystalline structure is retained after doping a small amount (5 mol %) of Nb, Ge, or Zr into the TiO2 structure, suggesting the homogeneous distribution of the doped metals with replacing Ti atom by the doped metal. The power conversion efficiency of the porphyrin-sensitized solar cells increases in the order Zr-added TiO2 (0.8%) TiO2 (1.2%) TiO2 (2.0%) TiO2 cells (2.4%) under the same conditions. The improvement of cell performance of the Ge-added TiO2 cell results from the negative shift of the conduction band of the Ge-added TiO2 electrode. The Ge-added TiO2 cell exhibited a maximum power conversion efficiency of 3.5% when the porphyrin was adsorbed onto the surface of the Ge-added TiO2 electrode with a thickness of 4 microm in MeOH for 1 h.

  11. Enhanced photocatalytic activity in anodized WO3-loaded TiO2 nanotubes

    Science.gov (United States)

    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.

  12. Electrospun TiO2 electrodes for dye-sensitized solar cells

    Science.gov (United States)

    Song, Mi Yeon; Kim, Do Kyun; Ihn, Kyo Jin; Jo, Seong Mu; Kim, Dong Young

    2004-12-01

    We report the new application of electrospun TiO2 fibres as an electrode for dye-sensitized solar cells (DSSCs). TiO2 fibre electrode was electrospun directly onto a conducting glass substrate from a mixture of titanium(IV) propoxide and poly(vinyl acetate) (PVAc) in dimethyl formamide. The TiO2 fibres are composed of one-dimensionally aligned nanofibrils about 20 nm thick with an islands-in-a-sea morphology, which was obtained from the phase separation of TiO2 gel and PVAc during the solidification process. The porous structure of the electrospun TiO2 electrode was found to be efficiently penetrated by a viscous polymer gel electrolyte. In order to improve the photocurrent generation, we treated the electrospun TiO2 electrode with TiCl4 aqueous solution. The rutile crystal was grown on the surface of anatase TiO2 fibres. An additional TiO2 layer increased the volume fraction of active materials, resulting in an increase of sensitizer adsorption. The energy conversion efficiency obtained from electrospun TiO2 electrodes with a PVDF-HFP gel electrolyte was over 90% of that from a liquid electrolyte system.

  13. Synthesis and characterization of Ag doped TiO2 heterojunction films and their photocatalytic performances

    Science.gov (United States)

    Demirci, Selim; Dikici, Tuncay; Yurddaskal, Metin; Gultekin, Serdar; Toparli, Mustafa; Celik, Erdal

    2016-12-01

    In this study, undoped and silver (Ag) doped titanium dioxide (TiO2) films were successfully synthesized by sol-gel spin coating technique on the Si substrates. Photocatalytic activities of the TiO2 films with different Ag content were investigated for the degradation of methylene blue (MB) under UV light irradiation. The crystal phase structure, surface morphology, chemical and optical properties of Ag-doped TiO2 films were characterized using an X-ray diffractometer (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV-vis spectrophotometer, and FTIR spectrophotometer. The results showed that the Ag-doped TiO2 films calcined at 500 °C had the crystalline anatase phases and the surface morphologies with some cracks. Ag substitution into TiO2 matrix enhanced the photocatalytic activity of TiO2 films under UV light irradiation as compared to the undoped TiO2 film. Furthermore, the results indicated that the 0.7% Ag doped TiO2 film exhibited a superior photocatalytic activity than that of undoped and other Ag-doped TiO2 films. This study demonstrated the potential of an application of Ag doped films to efficiently treat dissolved organic contaminants in water.

  14. Photodecomposition of volatile organic compounds using TiO2 nanoparticles.

    Science.gov (United States)

    Jwo, Ching-Song; Chang, Ho; Kao, Mu-Jnug; Lin, Chi-Hsiang

    2007-06-01

    This study examined the photodecomposition of volatile organic compounds (VOCs) using TiO2 catalyst fabricated by the Submerged Arc Nanoparticle Synthesis System (SANSS). TiO2 catalyst was employed to decompose volatile organic compounds and compare with Degussa-P25 TiO2 in terms of decomposition efficiency. In the electric discharge manufacturing process, a Ti bar, applied as the electrode, was melted and vaporized under high temperature. The vaporized Ti powders were then rapidly quenched under low-temperature and low-pressure conditions in deionized water, thus nucleating and forming nanocrystalline powders uniformly dispersed in the base solvent. The average diameter of the TiO2 nanoparticles was 20 nm. X-ray diffraction analysis confirmed that the nanoparticles in the deionized water were Anatase type TiO2. It was found that gaseous toluene exposed to UV irradiation produced intermediates that were even harder to decompose. After 60-min photocomposition, Degussa-P25 TiO2 reduced the concentration of gaseous toluene to 8.18% while the concentration after decomposition by SANSS TiO2 catalyst dropped to 0.35%. Under UV irradiation at 253.7 +/- 184.9 nm, TiO2 prepared by SANSS can produce strong chemical debonding energy, thus showing great efficiency, superior to that of Degussa-P25 TiO2, in decomposing gaseous toluene and its intermediates.

  15. Novel TiO2/C nanocomposites: synthesis, characterization, and application as a photocatalyst for the degradation of organic pollutants.

    Science.gov (United States)

    da Costa, Elias; Zamora, Patricio P; Zarbin, Aldo J G

    2012-02-15

    Novel TiO(2)/carbon nanocomposites were prepared through the pyrolysis of TiO(2)/poly(furfuryl alcohol) hybrid materials, which were obtained by the sol-gel method, starting from titanium tetraisopropoxide (TTIP) and furfuryl alcohol (FA) precursors. Six different TiO(2)/C samples were prepared based on different TiO(2) nanoparticle sizes and TiO(2)/FA ratios. All of the samples were characterized using X-ray diffraction, infrared, and Raman spectroscopy. The results indicated effective FA polymerization onto the TiO(2) (anatase) nanoparticles, polymer conversion to disordered carbon following the pyrolysis, and a simultaneous TiO(2) anatase-rutile phase transition. The resulting TiO(2)/carbon composites were used as photocatalysts in the advanced oxidative process (AOP) for the degradation of reactive organic dyes in aqueous solution. The results indicate excellent photocatalytic performance (degradation of 99% of the dye after 60 min) with several advantages over traditional TiO(2)-based photocatalysts. Copyright © 2011 Elsevier Inc. All rights reserved.

  16. Fe-doped TiO 2 thin films

    Science.gov (United States)

    Mardare, Diana; Nica, Valentin; Teodorescu, Cristian-Mihail; Macovei, Dan

    2007-09-01

    The reactive sputtering technique was used to obtain undoped and Fe-doped TiO 2 thin films deposited on glass substrates. At 250 °C substrate temperature, undoped TiO 2 films crystallize in a mixed rutile/anatase phase, while Fe-doped films exhibit the rutile phase only. Presence of Fe 3+ ions into the TiO 2 lattice is suggested by the intensity variation of forbidden 1s → 3d transitions between the Ti and Fe K-edges. Ti K-edge EXAFS data are assessed to a mixture of the two kinds of surroundings, a rutile-like crystalline phase, identified also by X-ray diffraction, and a nanosized or amorphous anatase-like surrounding. The local atomic order about Fe atoms is quite different and could be related also to an amorphous phase. The Swanepoel method is used to obtain the dispersion of the refractive index below the interband absorption edge. The dispersion energy, the single-oscillator energy and the coordination number of the Ti atoms are evaluated using the single-oscillator model (Wemple-DiDomenico).

  17. Facile synthesis of bird's nest-like TiO2 microstructure with exposed (001) facets for photocatalytic degradation of methylene blue

    Science.gov (United States)

    Zhang, Guozhong; Zhang, Shuqu; Wang, Longlu; Liu, Ran; Zeng, Yunxiong; Xia, Xinnian; Liu, Yutang; Luo, Shenglian

    2017-01-01

    The scrupulous design of hierarchical structure and highly active crystal facets exposure is essential for the creation of photocatalytic system. However, it is still a big challenge for scrupulous design of TiO2 architectures. In this paper, bird's nest-like anatase TiO2 microstructure with exposed highly active (001) surface has been successfully synthesized by a facile one-step solvothermal method. Methylene blue (MB) is chosen as a model pollutant to evaluate photocatalytic activity of as-obtained TiO2 samples. The results show that the photocatalytic activity of the bird's nest-like sample is more excellent than P25 in the degradation of MB due to high specific surface area and highly active (001) crystal facets exposure when tested under simulated solar light. Besides, it can be readily separated from the photocatalytic system by sedimentation after photocatalytic reaction, which is a significant advantage against conventional powder photocatalyst. The bird's nest-like microspheres with novel structure may have potential application in photocatalysis and other fields.

  18. The Photocatalytic Activity and Compact Layer Characteristics of TiO2 Films Prepared Using Radio Frequency Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    H. C. Chang

    2014-01-01

    Full Text Available TiO2 compact layers are used in dye-sensitized solar cells (DSSCs to prevent charge recombination between the electrolyte and the transparent conductive substrate (indium tin oxide, ITO; fluorine-doped tin oxide, FTO. Thin TiO2 compact layers are deposited onto ITO/glass by means of radio frequency (rf magnetron sputtering, using deposition parameters that ensure greater photocatalytic activity and increased DSSC conversion efficiency. The photoinduced decomposition of methylene blue (MB and the photoinduced hydrophilicity of the TiO2 thin films are also investigated. The photocatalytic performance characteristics for the deposition of TiO2 films are improved by using the Grey-Taguchi method. The average transmittance in the visible region exceeds 85% for all samples. The XRD patterns of the TiO2 films, for sol-gel with spin coating of porous TiO2/TiO2 compact/ITO/glass, show a good crystalline structure. In contrast, without the TiO2 compact layer (only porous TiO2, the peak intensity of the anatase (101 plane in the XRD patterns for the TiO2 film has a lower value, which demonstrates inferior crystalline quality. With a TiO2 compact layer to prevent charge recombination, a higher short-circuit current density is obtained. The DSSC with the FTO/glass and Pt counter electrode demonstrates the energy conversion efficiency increased.

  19. Effect of pyrolytic temperature on the properties of TiO2/ITO films for hydrogen sensing.

    Science.gov (United States)

    Vijayalakshmi, K; Jereil, S David; Karthick, K

    2015-03-05

    Titanium dioxide (TiO2) thin films were prepared on ITO (222) coated glass substrates by spray pyrolysis technique. The influence of substrate temperature on the orientation, phase, vibrational bands and band gap energy of TiO2 films were discussed. The X-ray diffraction patterns of the films revealed preferentially oriented (101) TiO2 anatase phase at the substrate temperature of 300°C and 350°C. Fourier transform infrared spectra of the films showed the significant sharpening of absorption band at ∼645cm(-1) with increase in substrate temperature, which clearly indicates the formation of anatase phase dependent on substrate temperature. Fourier Raman Spectra of the films showed the significant presence of long range order anatase TiO2 phase. The optical measurements of the film prepared at different substrate temperatures revealed the direct band gap of 3.15-3.63eV and indirect band gap of 3.48-3.73eV, characteristic of TiO2 anatase phase. To understand the enhancement of sensing performances of TiO2 films with substrate temperature, the gas sensing mechanism of the films towards 400sccm of hydrogen at room temperature was studied and discussed.

  20. Structural analysis of TiO2 and TiO2-Ag thin films and their antibacterial behaviors

    Science.gov (United States)

    Hsieh, J. H.; Yu, R. B.; Chang, Y. K.; Li, C.

    2012-01-01

    TiO2 (rutile and anatase) thin films was first prepared using reactive sputtering, in an Ar+O2 plasma. In the 2nd stage of the experiment, various amounts (3, 7, and 10 at. %) of Ag was doped into the rutile film in order to form TiO2-Ag thin films. These films were annealed for one hour in Ar atmosphere, at 300, 400, and 500 °C. The films' structures were then examined using X-ray diffractometry. FESEM (field-emission scaning electron microscopy) was used to investigate the surface emergence of Ag particles. As for the examination of optical band gaps and absorption of these films, UV-Vis-NIR photometer was used. The results show that, in as-deposited condition, the addition of Ag might disrupt the growth of crystalline structure and cause the formation of amorphous films. After annealing, it is found that the structure tends to become anatase phase which is a metastable phase between amorphous titanium oxide and rutile. More importantly, the absorption of the Ag-doped films would be enhanced in the visible-light range. Some of the enhancement is clearly due to plasmon resonance effect. The Ag-doped samples have shown some antibacterial effect in dark. When irradiated with light, the samples show a synergistic behavior combining the bactericidal effect of Ag ions and photocatalytic effect of TiO2.