Ultrathin and Atomically Flat Transition-Metal Oxide: Promising Building Blocks for Metal-Insulator Electronics.

PubMed

Cui, Qingsong; Sakhdari, Maryam; Chamlagain, Bhim; Chuang, Hsun-Jen; Liu, Yi; Cheng, Mark Ming-Cheng; Zhou, Zhixian; Chen, Pai-Yen

2016-12-21

We present a new and viable template-assisted thermal synthesis method for preparing amorphous ultrathin transition-metal oxides (TMOs) such as TiO 2 and Ta 2 O 5 , which are converted from crystalline two-dimensional (2D) transition-metal dichalcogenides (TMDs) down to a few atomic layers. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning transmission electron microscopy (STEM) were used to characterize the chemical composition and bonding, surface morphology, and atomic structure of these ultrathin amorphous materials to validate the effectiveness of our synthesis approach. Furthermore, we have fabricated metal-insulator-metal (MIM) diodes using the TiO 2 and Ta 2 O 5 as ultrathin insulating layers with low potential barrier heights. Our MIM diodes show a clear transition from direct tunneling to Fowler-Nordheim tunneling, which was not observed in previously reported MIM diodes with TiO 2 or Ta 2 O 5 as the insulating layer. We attribute the improved performance of our MIM diodes to the excellent flatness and low pinhole/defect densities in our TMO insulting layers converted from 2D TMDs, which enable the low-threshold and controllable electron tunneling transport. We envision that it is possible to use the ultrathin TMOs converted from 2D TMDs as the insulating layer of a wide variety of metal-insulator and field-effect electronic devices for various applications ranging from microwave mixing, parametric conversion, infrared photodetection, emissive energy harvesting, to ultrafast electronic switching.

Solvothermal synthesis of TiO2 nanocrystals with {001} facets using titanic acid nanobelts for superior photocatalytic activity

NASA Astrophysics Data System (ADS)

Cao, Yuhui; Zong, Lanlan; Li, Qiuye; Li, Chen; Li, Junli; Yang, Jianjun

2017-01-01

Anatase TiO2 nanocrystals exposed with {001} facets were fabricated by solvothermal strategy in HF-C4H9OH mixed solution, using titanic acid nanobelts (TAN) as a precursor. The shape of TAN is a long flat plane with a high aspect ratio, and F- is easily adsorbed on the surface of the nanobelts, inducing a higher exposure of {001} facet of TiO2 nanoparticles during the structure reorganization. The exposed percentage of {001} facets could vary from 40 to 77% by adjusting the amount of HF. The as-prepared samples were characterized by transmission electron microscopy, N2 adsorption-desorption isotherms, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscope. The photocatalytic measurement showed that TiO2 nanocrystals with 77% {001} facets exhibited much superior photocatalytic activity for photodegradation of methyl orange, methylene blue, and rhodamine B. And what's more, the mineralization rate of methyl orange was as high as 96% within 60 min. The photocatalytic enhancement is due to a large amount of the high energetic {001} facets exposing, the special truncated octahedral morphology and a stronger ability for dyes adsorption.

Fabrication of ion bombardment induced rippled TiO₂ surfaces to influence subsequent organic thin film growth.

PubMed

Kratzer, Markus; Szajna, Konrad; Wrana, Domink; Belza, Wojciech; Krok, Franciszek; Teichert, Christian

2018-05-23

Control over organic thin film growth is a central issue in the development of organic electronics. The anisotropy and extended size of the molecular building blocks introduce a high degree of complexity within the formation of thin films. This complexity can be even increased for substrates with induced, sophisticated morphology and anisotropy. Thus, targeted structuring like ion beam mediated modification of substrates in order to create ripples, pyramids, or pit structures provides a further degree of freedom in manipulating the growth morphology of organic thin films. We provide a comprehensive review of recent work on para-hexaphenyl (C36H26, 6P) as a typical representative of the class of small, rod-like conjugated molecules and rutile TiO2(110) as an example for a transparent oxide electrode to demonstrate the effect of ion beam induced nanostructuring on organic thin film growth. Starting from molecular growth on smooth, atomically flat TiO2(110) (11) surfaces, we investigate the influence of the ripple size on the resulting 6P thin films. The achieved 6P morphologies are either crystalline nano-needles composed of flat lying molecules or islands consisting of upright standing 6P, which are elongated in ripple direction. The islands' length to width ratio can be controlled by tuning of the ripples' shape. © 2018 IOP Publishing Ltd.

Film Levitation of Droplet Impact on Heated Nanotube Surfaces

NASA Astrophysics Data System (ADS)

Duan, Fei; Tong, Wei; Qiu, Lu

2017-11-01

Contact boiling of an impacting droplet impacting on a heated surface can be observed when the surface temperature is able to activate the nucleation and growth of vapor bubbles, the phenomena are related to nature and industrial application. The dynamic boiling patterns us is investigated when a single falling water droplet impacts on a heated titanium (Ti) surface covered with titanium oxide (TiO2) nanotubes. In the experiments, the droplets were generated from a flat-tipped needle connected to a syringe mounted on a syringe pump. The droplet diameter and velocity before impacting on the heated surface are measured by a high-speed camera with the Weber number is varied from 45 to 220. The dynamic wetting length, spreading diameter, levitation distance, and the associated parameter are measured. Interesting film levitation on titanium (Ti) surface has been revealed. The comparison of the phase diagrams on the nanotube surface and bare Ti surface suggests that the dynamic Leidenfrost point of the surface with the TiO2 nanotubes has been significantly delayed as compared to that on a bare Ti surface. The delay is inferred to result from the increase in the surface wettability and the capillary effect by the nanoscale tube structure. The further relation is discussed.

DFT study on the interaction of TiO2 (001) surface with HCHO molecules

NASA Astrophysics Data System (ADS)

Wu, Guofei; Zhao, Cuihua; Guo, Changqing; Chen, Jianhua; Zhang, Yibing; Li, Yuqiong

2018-01-01

The interactions of formaldehyde (HCHO) molecule with TiO2 (001) surface were studied using density functional theory calculations. HCHO molecules are dissociated by the cleavage of Csbnd H bonds after adsorption on TiO2 surface. The strong interactions between HCHO melecules and TiO2 surface are largely attributed to the bonding of hydrogen of HCHO and oxygen of TiO2 surface, which is mainly from the hybridization of the H 1s, O 2p and O 2s. The newly formed Hsbnd O bonds cause the structure changes of TiO2 surface, and lead to the cleavage of Osbnd Ti bond of TiO2 surface. The Csbnd O bond that the dissociated remains of HCHO and newly formed Hsbnd O bond can be oxidized to form carbon dioxide and water in subsequent action by oxygen from the atomosphere. The charges transfer from HCHO to TiO2 surface, and the sum amount of the charges transferred from four HCHO molecules to TiO2 surface is bigger than that from one HCHO molecule to TiO2 surface due to the combined interaction of four HCHO molecules with TiO2 surface.

Structural changes of anodic layer on titanium in sulfate solution as a function of anodization duration in constant current mode

NASA Astrophysics Data System (ADS)

Komiya, Shinji; Sakamoto, Kouta; Ohtsu, Naofumi

2014-03-01

The present study investigated the effect of anodization time, in constant current mode, on the anodic oxide layer formed on titanium (Ti). Anodization of the Ti substrate was　carried out in a 0.1 M (NH4)2SO4 aqueous solution with reaction times of various durations, after which the characteristics and photocatalytic activity were investigated in detail. The TiO2 layer fabricated in a short duration exhibited comparatively flat surface morphology and an anatase-type crystal structure. This layer acted as a photocatalyst only under ultraviolet light (UV) illumination. Upon prolonging the anodization, the layer structure changed drastically. The surface morphology became rough, and the crystal structure changed to rutile-type TiO2. Furthermore, the layer showed photocatalytic activity both under UV and visible light illumination. Further anodization increased the amount of methylene blue (MB) adsorbed on the surface, but did not cause additional change to the structure of the anodic layer. The surface morphology and crystal structure of the anodic layer were predominantly controlled by the anodization time; thus, the anodization time is an important parameter for controlling the characteristics of the anodic layer.

TiO2 fotokatalyse in de gasfase van morfologisch ontwerp tot plasmoneffecten

NASA Astrophysics Data System (ADS)

Verbruggen, Sammy

In this PhD TiO2 gas phase photocatalysis is investigated in all its facets. Work has been done on the level of the reactor as well as the catalyst and structural as well as electronic improvements have been proposed. Apart from actual experiments, also theoretical models and a techno-economic assessment have been carried out. The first main achievement is the development of a cost and material-efficient immobilization method and testing procedure. The design, based on glass bead supports packed around a lamp in a cylindrical glass reactor tube, offers the advantages of good immobilization, efficient light utilization, intimate contact with gaseous pollutants and a catalyst weight gain by a factor of 25 compared to self-supporting pellets. The reactor is used for performing a cost effectiveness analysis on six different commercial photocatalytic materials. The second achievement is the fundamental insight that is gathered in the driving factors for gas phase photocatalytic reactions. Structural properties such as large surface area and accessible pores seem to dominate over electronic properties. This knowledge is exploited in the development of well-immobilized, spacious T1O2 thin films. These films are prepared by depositing a thin, conformal TiO2 layer onto sacrificial carbonaceous templates by means of atomic layer deposition. After calcination, the sacrificial template is removed, TiO2 is crystallized into the anatase phase and the as-deposited continuous TiO2 layer has transformed into an interconnected network of nanoparticles. This way open thin films are prepared with surface area enhancement factors of up to 260 with regard to a dense, flat TiO 2 film. Thus obtained films exhibit superior photocatalytic activity compared to a commercial reference film. The final achievement is the extension of TiO2 photoactivity toward the visible light region of the spectrum. This is done by exploiting surface plasmon resonance effects of gold-silver alloy nanoparticles. Surface plasmon resonance can be regarded as a collective oscillation of free electrons in a metal. This way incident (visible) light energy can be 'captured' in the resonance and subsequently transferred to T1O2. First, a theoretical model is established that enables to predict the plasmon resonance wavelength of such alloy nanoparticles, based on the combined effect of particle size and alloy composition. It is shown that the feature of alloying presents high wavelength tunability of the visible light response. Next, alloy nanoparticles are deposited on TiO2. Thus obtained plasmonic photocatalysts are tested towards their self-cleaning performance in the degradation of stearic acid located at the catalyst-air interface. The highest quantum efficiency is obtained when the resonance wavelength of the plasmonic catalyst exactly matches that of the incident light. This is demonstrated for the case of Au 0.3Ag0.7, nanoparticles on TiO2 under 490 nm illumination, provided by LEDs.

Surface-area-controlled synthesis of porous TiO2 thin films for gas-sensing applications

NASA Astrophysics Data System (ADS)

Park, Jae Young; Kim, Ho-hyoung; Rana, Dolly; Jamwal, Deepika; Katoch, Akash

2017-03-01

Surface-area-controlled porous TiO2 thin films were prepared via a simple sol-gel chemical route, and their gas-sensing properties were thoroughly investigated in the presence of typical oxidizing NO2 gas. The surface area of TiO2 thin films was controlled by developing porous TiO2 networked by means of controlling the TiO2-to-TTIP (titanium isopropoxide, C12H28O4Ti) molar ratio, where TiO2 nanoparticles of size ˜20 nm were used. The sensor’s response was found to depend on the surface area of the TiO2 thin films. The porous TiO2 thin-film sensor with greater surface area was more sensitive than those of TiO2 thin films with lesser surface area. The improved sensing ability was ascribed to the porous network formed within the thin films by TiO2 sol. Our results show that surface area is a key parameter for obtaining superior gas-sensing performance; this provides important guidelines for preparing and using porous thin films for gas-sensing applications.

Structural characterization of oxidized titanium surfaces

NASA Astrophysics Data System (ADS)

Jobin, M.; Taborelli, M.; Descouts, P.

1995-05-01

Oxidized titanium surfaces resulting from various processes have been structurally characterized by means of scanning force microscopy, x-ray photoemission spectroscopy (XPS), x-ray diffraction, and electron energy-loss spectroscopy (EELS) with losses in the 0-100 eV range. It has been found that the surface morphology has a granular structure for electropolished titanium and for titanium evaporated on mica at low substrate temperature (570 K), but changes to flat terraces for the films evaporated at higher temperature (770 K). Angular-dependent XPS has revealed the presence of a Ti2O3 suboxide at the Ti/TiO2 interface for electropolished titanium. Dry oxidation has been performed at 770 and 970 K on both weakly and highly crystallized evaporated titanium films oriented along (0001). In the case of underlying crystallized metallic titanium, the resulting TiO2 films are crystallized with the anatase (004) orientation for oxidation at 770 K and with rutile (200) orientation for oxidation at 970 K. EELS spectra interpreted in terms of the molecular orbitals of a (TiO6)8- cluster show that the local octahedral environment of titanium atoms is preserved on native oxides, even if these oxides are not crystallized.

Infiltration of methylammonium metal halide in highly porous membranes using sol-gel-derived coating method

NASA Astrophysics Data System (ADS)

Kwon, Seung Lee; Jin, Young Un; Kim, Byeong Jo; Han, Man Hyung; Han, Gill Sang; Shin, Seunghak; Lee, Sangwook; Jung, Hyun Suk

2017-09-01

Organic-inorganic halide perovskites (OIHPs) has emerged as promising optoelectronic materials for solar cells and light-emitting diodes. OIHPs are usually coated on a flat surface or mesoporous scaffold for the applications. Herein, we report a facile sol-gel-derived solution route for coating methylammonium lead iodide (MAPbI3) perovskite layers onto various nanoporous structures. We found that lead-acetate solution has superior infiltration property onto surface of oxide membranes, and it can easily be converted to MAPbI3 by sequential transform to PbO, PbI2, and finally MAPbI3. Excellent pore-filling and full coverage of the nanostructures with the final MAPbI3 perovskite material are demonstrated via this sol-gel-derived solution route, using mesoporous TiO2, TiO2 nanorods, and high-aspect ratio nanopores in anodic aluminum oxide membranes. Given that this sol-gel-based method fills nanopores better than other conventional coating methods for OIHPs, this method may find wide applications in nanostructured OIHPs-based optoelectronic systems.

First-principles atomistic Wulff constructions for an equilibrium rutile TiO2 shape modeling

NASA Astrophysics Data System (ADS)

Jiang, Fengzhou; Yang, Lei; Zhou, Dali; He, Gang; Zhou, Jiabei; Wang, Fanhou; Chen, Zhi-Gang

2018-04-01

Identifying the exposed surfaces of rutile TiO2 crystal is crucial for its industry application and surface engineering. In this study, the shape of the rutile TiO2 was constructed by applying equilibrium thermodynamics of TiO2 crystals via first-principles density functional theory (DFT) and Wulff principles. From the DFT calculations, the surface energies of six low-index stoichiometric facets of TiO2 are determined after the calibrations of crystal structure. And then, combined surface energy calculations and Wulff principles, a geometric model of equilibrium rutile TiO2 is built up, which is coherent with the typical morphology of fully-developed equilibrium TiO2 crystal. This study provides fundamental theoretical guidance for the surface analysis and surface modification of the rutile TiO2-based materials from experimental research to industry manufacturing.

NC-AFM observation of atomic scale structure of rutile-type TiO2(110) surface prepared by wet chemical process.

PubMed

Namai, Yoshimichi; Matsuoka, Osamu

2006-04-06

We succeeded in observing the atomic scale structure of a rutile-type TiO2(110) single-crystal surface prepared by the wet chemical method of chemical etching in an acid solution and surface annealing in air. Ultrahigh vacuum noncontact atomic force microscopy (UHV-NC-AFM) was used for observing the atomic scale structures of the surface. The UHV-NC-AFM measurements at 450 K, which is above a desorption temperature of molecularly adsorbed water on the TiO2(110) surface, enabled us to observe the atomic scale structure of the TiO2(110) surface prepared by the wet chemical method. In the UHV-NC-AFM measurements at room temperature (RT), however, the atomic scale structure of the TiO2(110) surface was not observed. The TiO2(110) surface may be covered with molecularly adsorbed water after the surface was prepared by the wet chemical method. The structure of the TiO2(110) surface that was prepared by the wet chemical method was consistent with the (1 x 1) bulk-terminated model of the TiO2(110) surface.

Thin films of Ag–Au nanoparticles dispersed in TiO2: influence of composition and microstructure on the LSPR and SERS responses

NASA Astrophysics Data System (ADS)

Borges, Joel; Ferreira, Catarina G.; Fernandes, João P. C.; Rodrigues, Marco S.; Proença, Manuela; Apreutesei, Mihai; Alves, Eduardo; Barradas, Nuno P.; Moura, Cacilda; Vaz, Filipe

2018-05-01

Thin films containing monometallic (Ag,Au) and bimetallic (Ag–Au) noble nanoparticles were dispersed in TiO2, using reactive magnetron sputtering and post-deposition thermal annealing. The influence of metal concentration and thermal annealing in the (micro)structural evolution of the films was studied, and its correlation with the localized surface plasmon resonance (LSPR) and surface enhanced Raman spectroscopy (SERS) behaviours was evaluated. The Ag/TiO2 films presented columnar to granular microstructures, developing Ag clusters at the surface for higher annealing temperatures. In some cases, the films presented dendrite-type fractal geometry, which led to an almost flat broadband optical response. The Au/TiO2 system revealed denser microstructures, with Au nanoparticles dispersed in the matrix, whose size increased with annealing temperature. This microstructure led to the appearance of LSPR bands, although some Au segregation to the surface hindered this effect for higher concentrations. The structural results of the Ag–Au/TiO2 system suggested the formation of bimetallic Ag–Au nanoparticles, which presence was supported by the appearance of a single narrow LSPR band. In addition, the Raman spectra of Rhodamine-6G demonstrated the viability of these systems for SERS applications, with some indication that the Ag/TiO2 system might be preferential, contrasting to the notorious behaviour of the bimetallic system in terms of LSPR response.

Interfacial Cation-Defect Charge Dipoles in Stacked TiO2/Al2O3 Gate Dielectrics.

PubMed

Zhang, Liangliang; Janotti, Anderson; Meng, Andrew C; Tang, Kechao; Van de Walle, Chris G; McIntyre, Paul C

2018-02-14

Layered atomic-layer-deposited and forming-gas-annealed TiO 2 /Al 2 O 3 dielectric stacks, with the Al 2 O 3 layer interposed between the TiO 2 and a p-type germanium substrate, are found to exhibit a significant interface charge dipole that causes a ∼-0.2 V shift of the flat-band voltage and suppresses the leakage current density for gate injection of electrons. These effects can be eliminated by the formation of a trilayer dielectric stack, consistent with the cancellation of one TiO 2 /Al 2 O 3 interface dipole by the addition of another dipole of opposite sign. Density functional theory calculations indicate that the observed interface-dependent properties of TiO 2 /Al 2 O 3 dielectric stacks are consistent in sign and magnitude with the predicted behavior of Al Ti and Ti Al point-defect dipoles produced by local intermixing of the Al 2 O 3 /TiO 2 layers across the interface. Evidence for such intermixing is found in both electrical and physical characterization of the gate stacks.

Fine tuning and orientation control of surface Cu complexes on TiO2(110) premodified with mercapto compounds: the effect of different mercapto group positions.

PubMed

Takakusagi, Satoru; Nojima, Hirotaka; Ariga, Hiroko; Uehara, Hiromitsu; Miyazaki, Kotaro; Chun, Wang-Jae; Iwasawa, Yasuhiro; Asakura, Kiyotaka

2013-09-07

Three-dimensional structures of vacuum-deposited Cu species formed on TiO2(110) surfaces premodified with three mercaptobenzoic acid (MBA) isomers were studied using polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS). We explored the possibility of fine tuning and orientation control of the surface Cu structures, including their coordination and configuration against the surface, according to the different mercapto group positions of the three MBA isomers (o-, m-, and p-MBA). Almost linear S-Cu-O (lattice O of TiO2) surface compounds were formed on the three MBA-modified TiO2(110) surfaces; however, the orientation of the Cu species on the o- and m-MBA-modified TiO2(110) surfaces (40-45° inclined from the surface normal) was different from that on the p-MBA-modified TiO2(110) surface (60° from the surface normal). This work suggests that the selection of a different MBA isomer for premodification of a single crystal TiO2(110) surface enables fine tuning and orientation control of surface Cu complexes.

High-surface-area mesoporous TiO2 microspheres via one-step nanoparticle self-assembly for enhanced lithium-ion storage

NASA Astrophysics Data System (ADS)

Wang, Hsin-Yi; Chen, Jiazang; Hy, Sunny; Yu, Linghui; Xu, Zhichuan; Liu, Bin

2014-11-01

Mesoporous TiO2 microspheres assembled from TiO2 nanoparticles with specific surface areas as high as 150 m2 g-1 were synthesized via a facile one-step solvothermal reaction of titanium isopropoxide and anhydrous acetone. Aldol condensation of acetone gradually releases structural H2O, which hydrolyzes and condenses titanium isopropoxide, forming TiO2 nanocrystals. Simultaneous growth and aggregation of TiO2 nanocrystals leads to the formation of high-surface-area TiO2 microspheres under solvothermal conditions. After a low-temperature post-synthesis calcination, carbonate could be incorporated into TiO2 as a dopant with the carbon source coming from the organic byproducts during the synthesis. Carbonate doping modifies the electronic structure of TiO2 (e.g., Fermi level, Ef), and thus influences its electrochemical properties. Solid electrolyte interface (SEI) formation, which is not common for titania, could be initiated in carbonate-doped TiO2 due to elevated Ef. After removing carbonate dopants by high-temperature calcination, the mesoporous TiO2 microspheres showed much improved performance in lithium insertion and stability at various current rates, attributed to a synergistic effect of high surface area, large pore size and good anatase crystallinity.Mesoporous TiO2 microspheres assembled from TiO2 nanoparticles with specific surface areas as high as 150 m2 g-1 were synthesized via a facile one-step solvothermal reaction of titanium isopropoxide and anhydrous acetone. Aldol condensation of acetone gradually releases structural H2O, which hydrolyzes and condenses titanium isopropoxide, forming TiO2 nanocrystals. Simultaneous growth and aggregation of TiO2 nanocrystals leads to the formation of high-surface-area TiO2 microspheres under solvothermal conditions. After a low-temperature post-synthesis calcination, carbonate could be incorporated into TiO2 as a dopant with the carbon source coming from the organic byproducts during the synthesis. Carbonate doping modifies the electronic structure of TiO2 (e.g., Fermi level, Ef), and thus influences its electrochemical properties. Solid electrolyte interface (SEI) formation, which is not common for titania, could be initiated in carbonate-doped TiO2 due to elevated Ef. After removing carbonate dopants by high-temperature calcination, the mesoporous TiO2 microspheres showed much improved performance in lithium insertion and stability at various current rates, attributed to a synergistic effect of high surface area, large pore size and good anatase crystallinity. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04729j

Comparison of self-cleaning properties of three titania coatings on float glass

NASA Astrophysics Data System (ADS)

Piispanen, Minna; Hupa, Leena

2011-11-01

This work compares the self-cleaning properties of experimental TiO2 and TiO2-Ag coatings on float glass with a commercial self-cleaning glass. In the experimental surfaces, TiO2 coating was applied to float glass via the sol-gel route, while TiO2-Ag coating was applied by the liquid flame spray method, which deposits TiO2-Ag composite nanoparticles on the surface. The effect of the coatings on the surface wettability and the activation time for achieving hydrophilicity was studied through water contact angle as a function of exposure time to UV light. The surface morphology was investigated by using scanning electron microscopy (SEM) and confocal optical microscopy. The photocatalytic activity of the coatings was examined with methylene blue and stearic acid degradation tests. Finally, the soil attachment to the surfaces was tested with a sebum-based model soil. The sol-gel TiO2 coating became superhydrophilic within a few hours, while the activation time needed for the commercial titania coated glass was several days. The surface with the TiO2-Ag nanoparticles did not show any marked changes in the water contact angle. The commercial titania coated and the sol-gel TiO2 surfaces showed self-cleaning properties and clearly lower attachment of soil than the uncoated and TiO2-Ag coated surfaces. The difference in the interaction of the surfaces with the organic contaminants was assumed to depend mainly on differences in the thickness of the coatings.

S180 cell growth on low ion energy plasma treated TiO 2 thin films

NASA Astrophysics Data System (ADS)

Dhayal, Marshal; Cho, Su-In; Moon, Jun Young; Cho, Su-Jin; Zykova, Anna

2008-03-01

X-ray photoelectron spectroscopy (XPS) was used to characterise the effects of low energy (<2 eV) argon ion plasma surface modification of TiO 2 thin films deposited by radio frequency (RF) magnetron sputter system. The low energy argon ion plasma surface modification of TiO 2 in a two-stage hybrid system had increased the proportion of surface states of TiO 2 as Ti 3+. The proportion of carbon atoms as alcohol/ether (C sbnd OX) was decreased with increase the RF power and carbon atoms as carbonyl (C dbnd O) functionality had increased for low RF power treatment. The proportion of C( dbnd O)OX functionality at the surface was decreased at low power and further increase in power has showed an increase in its relive proportion at the surface. The growth of S180 cells was observed and it seems that cells are uniformly spreads on tissue culture polystyrene surface and untreated TiO 2 surfaces whereas small-localised cell free area can be seen on plasma treated TiO 2 surfaces which may be due to decrease in C( dbnd O)OX, increase in C dbnd O and active sites at the surface. A relatively large variation in the surface functionalities with no change in the surface roughness was achieved by different RF plasma treatments of TiO 2 surface whereas no significant change in S180 cell growth with different plasma treatments. This may be because cell growth on TiO 2 was mainly influenced by nano-surface characteristics of oxide films rather than surface chemistry.

Understanding the effect of surface/bulk defects on the photocatalytic activity of TiO2: anatase versus rutile.

PubMed

Yan, Junqing; Wu, Guangjun; Guan, Naijia; Li, Landong; Li, Zhuoxin; Cao, Xingzhong

2013-07-14

The sole effect of surface/bulk defects of TiO2 samples on their photocatalytic activity was investigated. Nano-sized anatase and rutile TiO2 were prepared by hydrothermal method and their surface/bulk defects were adjusted simply by calcination at different temperatures, i.e. 400-700 °C. High temperature calcinations induced the growth of crystalline sizes and a decrease in the surface areas, while the crystalline phase and the exposed facets were kept unchanged during calcination, as indicated by the characterization results from XRD, Raman, nitrogen adsorption-desorption, TEM and UV-Vis spectra. The existence of surface/bulk defects in calcined TiO2 samples was confirmed by photoluminescence and XPS spectra, and the surface/bulk defect ratio was quantitatively analyzed according to positron annihilation results. The photocatalytic activity of calcined TiO2 samples was evaluated in the photocatalytic reforming of methanol and the photocatalytic oxidation of α-phenethyl alcohol. Based on the characterization and catalytic results, a direct correlation between the surface specific photocatalytic activity and the surface/bulk defect density ratio could be drawn for both anatase TiO2 and rutile TiO2. The surface defects of TiO2, i.e. oxygen vacancy clusters, could promote the separation of electron-hole pairs under irradiation, and therefore, enhance the activity during photocatalytic reaction.

High surface area TiO2/SBA-15 nanocomposites: Synthesis, microstructure and adsorption-enhanced photocatalysis

NASA Astrophysics Data System (ADS)

Wei, J. Q.; Chen, X. J.; Wang, P. F.; Han, Y. B.; Xu, J. C.; Hong, B.; Jin, H. X.; Jin, D. F.; Peng, X. L.; Li, J.; Yang, Y. T.; Ge, H. L.; Wang, X. Q.

2018-06-01

Mesoporous SBA-15 was used to anchor TiO2 nanoparticles into the mesopores to form high surface area TiO2/SBA-15 nanocomposites, and then the influence of mesoporous-structure on the photocatalytic performance was investigated. TiO2/SBA-15 nanocomposites possessed the high specific surface area and appropriate pore size, indicating the excellent adsorption performance. TiO2/SBA-15 nanocomposites exhibited the higher photocatalytic activity to degrade dyes (methylene blue: MB) than TiO2 (removing SBA-15), which should attributed to the excellent adsorption performance of the nanocomposites. MB was absorbed to form the higher concentration near TiO2/SBA-15 photocatalysts, and the photocatalytic degradation for MB was improved.

Band edge movement and structural modifications in transition metal doped TiO2 nanocrystals for the application of DSSC

NASA Astrophysics Data System (ADS)

Patle, L. B.; Huse, V. R.; Chaudhari, A. L.

2017-10-01

Nanocrystalline undoped and transition metal ion doped (TM:Cu2+, Mn2+ and Fe3+) TiO2 nanoparticles, with 1 mol% were synthesized by a simple and cost effective modified co-precipitation method at room temperature and were successfully used as photoanode for dye sensitized solar cell (DSSC). The effect of transition metal ions into TiO2 nano crystalline powder has been systematically investigated using x-ray diffraction (XRD), UV-Vis spectroscope, scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive x-ray spectroscopy (EDX). The results of XRD confirm nanocrystalline anatase tetragonal structure of prepared undoped and TM doped TiO2 semiconductor. The influence of doping on band edge movement has been estimated using UV-visible spectroscopy. The SEM results indicate that microscopic effect of doping on morphology of the TiO2. The peaks of EDX signify incorporation of transition metal cations into TiO2 lattice. The effect of doping on flat band potential was estimated using interpolation on Mott-Schottky plot. The performances of DSSCs of undoped and doped TiO2 photoelectrodes were investigated under light illumination. In comparison with undoped and (Cu2+, Fe3+) doped TiO2 photoanodes we found that incorporation of Mn2+ into TiO2 exhibits improvement in photoconversion efficiency (η). There is increase in photoconversion efficiency of DSSCs with Mn2+ doped TiO2 by 6% as compared to that of undoped TiO2 photoanode.

High-Level ab Initio Predictions for the Ionization Energies, Bond Dissociation Energies, and Heats of Formation of Titanium Oxides and Their Cations (TiOn/TiOn+, n = 1 and 2).

PubMed

Pan, Yi; Luo, Zhihong; Chang, Yih-Chung; Lau, Kai-Chung; Ng, C Y

2017-01-26

The ionization energies (IEs) of TiO and TiO 2 and the 0 K bond dissociation energies (D 0 ) and the heats of formation at 0 K (ΔH° f0 ) and 298 K (ΔH° f298 ) for TiO/TiO + and TiO 2 /TiO 2 + are predicted by the wave-function-based CCSDTQ/CBS approach. The CCSDTQ/CBS calculations involve the approximation to the complete basis set (CBS) limit at the coupled cluster level up to full quadruple excitations along with the zero-point vibrational energy (ZPVE), high-order correlation (HOC), core-valence (CV) electronic, spin-orbit (SO) coupling, and scalar relativistic (SR) effect corrections. The present calculations yield IE(TiO) = 6.815 eV and are in good agreement with the experimental IE value of 6.819 80 ± 0.000 10 eV determined in a two-color laser-pulsed field ionization-photoelectron (PFI-PE) study. The CCSDT and MRCI+Q methods give the best predictions to the harmonic frequencies: ω e (ω e + ) = 1013 (1069) and 1027 (1059) cm -1 and the bond lengths r e (r e + ) = 1.625 (1.587) and 1.621 (1.588) Å, for TiO (TiO + ) compared with the experimental values. Two nearly degenerate, stable structures are found for TiO 2 cation: TiO 2 + (C 2v ) structure has two equivalent TiO bonds, while the TiO 2 + (C s ) structure features a long and a short TiO bond. The IEs for the TiO 2 + (C 2v )←TiO 2 and TiO 2 + (C s )←TiO 2 ionization transitions are calculated to be 9.515 and 9.525 eV, respectively, giving the theoretical adiabatic IE value in good agreement with the experiment IE(TiO 2 ) = 9.573 55 ± 0.000 15 eV obtained in the previous vacuum ultraviolet (VUV)-PFI-PE study of TiO 2 . The potential energy surface of TiO 2 + along the normal vibrational coordinates of asymmetric stretching mode (ω 3 + ) is nearly flat and exhibits a double-well potential with the well of TiO 2 + (C s ) situated around the central well of TiO 2 + (C 2v ). This makes the theoretical calculation of ω 3 + infeasible. For the symmetric stretching (ω 1 + ), the current theoretical predictions overestimate the experimental value of 829.1 ± 2.0 cm -1 by more than 100 cm -1 . This work together with the previous experimental and theoretical investigations supports the conclusion that the CCSDTQ/CBS approach is capable of providing reliable IE and D 0 predictions for TiO/TiO + and TiO 2 /TiO 2 + with error limits less than or equal to 60 meV. The CCSDTQ/CBS calculations give the predictions of D 0 (Ti + -O) - D 0 (Ti-O) = 0.004 eV and D 0 (O-TiO) - D 0 (O-TiO + ) = 2.699 eV, which are also consistent with the respective experimental determination of 0.008 32 ± 0.000 10 and 2.753 75 ± 0.000 18 eV.

Processing and Characterization of Nanoparticle Coatings for Quartz Crystal Microbalance Measurements

PubMed Central

Torrey, Jessica D.; Kirschling, Teresa L.; Greenlee, Lauren F.

2015-01-01

The quartz-crystal microbalance is a sensitive and versatile tool for measuring adsorption of a variety of compounds (e.g. small molecules, polymers, biomolecules, nanoparticles and cells) to surfaces. While the technique has traditionally been used for measuring adsorption to flat surfaces and thin ridged films, it can also be extended to study adsorption to nanoparticle surfaces when the nanoparticles are fixed to the crystal surface. The sensitivity and accuracy of the measurement depend on the users’ ability to reproducibly prepare a thin uniform nanoparticle coating. This study evaluated four coating techniques, including spin coating, spray coating, drop casting, and electrophoretic deposition, for two unique particle chemistries [nanoscale zero valent iron (nZVI) and titanium dioxide (TiO2)] to produce uniform and reproducible nanoparticle coatings for real-time quartz-crystal microbalance measurements. Uniform TiO2 coatings were produced from a 50 mg/mL methanol suspension via spin coating. Nanoscale zero-valent iron was best applied by spray coating a low concentration 1.0 mg/mL suspended in methanol. The application of multiple coatings, rather than an increase in the suspension concentration, was the best method to increase the mass of nanoparticles on the crystal surface while maintaining coating uniformity. An upper mass threshold was determined to be approximately 96 µg/cm2; above this mass, coatings no longer maintained their uniform rigid characteristic, and a low signal to noise ratio resulted in loss of measurable signal from crystal resonances above the fundamental. PMID:26958434

Surface force analysis of glycine adsorption on different crystal surfaces of titanium dioxide (TiO2).

PubMed

Ganbaatar, Narangerel; Imai, Kanae; Yano, Taka-Aki; Hara, Masahiko

2017-01-01

Surface force analysis with atomic force microscope (AFM) in which a single amino acid residue was mounted on the tip apex of AFM probe was carried out for the first time at the molecular level on titanium dioxide (TiO 2 ) as a representative mineral surface for prebiotic chemical evolution reactions. The force analyses on surfaces with three different crystal orientations revealed that the TiO 2 (110) surface has unique characteristics for adsorbing glycine molecules showing different features compared to those on TiO 2 (001) and (100). To examine this difference, we investigated thermal desorption spectroscopy (TDS) and the interaction between the PEG cross-linker and the three TiO 2 surfaces. Our data suggest that the different single crystal surfaces would provide different chemical evolution field for amino acid molecules.

Influence of the surface chemistry on TiO2 - TiO2 nanocontact forces as measured by an UHV-AFM

NASA Astrophysics Data System (ADS)

Kunze, Christian; Giner, Ignacio; Torun, Boray; Grundmeier, Guido

2014-03-01

Particle-wall contact forces between a TiO2 film coated AFM tip and TiO2(1 1 0) single crystal surfaces were analyzed by means of UHV-AFM. As a reference system an octadecylphosphonic acid monolayer covered TiO2(1 1 0) surface was studied. The defect chemistry of the TiO2 substrate was modified by Ar ion bombardment, water dosing at 3 × 10-6 Pa and an annealing step at 473 K which resulted in a varying density of Ti(III) states. The observed contact forces are correlated to the surface defect density and are discussed in terms of the change in the electronic structure and its influence on the Hamaker constant.

Engineering the Surface/Interface Structures of Titanium Dioxide Micro and Nano Architectures towards Environmental and Electrochemical Applications

PubMed Central

Wang, Xiaoliang; Zhao, Yanyan; Mølhave, Kristian

2017-01-01

Titanium dioxide (TiO2) materials have been intensively studied in the past years because of many varied applications. This mini review article focuses on TiO2 micro and nano architectures with the prevalent crystal structures (anatase, rutile, brookite, and TiO2(B)), and summarizes the major advances in the surface and interface engineering and applications in environmental and electrochemical applications. We analyze the advantages of surface/interface engineered TiO2 micro and nano structures, and present the principles and growth mechanisms of TiO2 nanostructures via different strategies, with an emphasis on rational control of the surface and interface structures. We further discuss the applications of TiO2 micro and nano architectures in photocatalysis, lithium/sodium ion batteries, and Li–S batteries. Throughout the discussion, the relationship between the device performance and the surface/interface structures of TiO2 micro and nano structures will be highlighted. Then, we discuss the phase transitions of TiO2 nanostructures and possible strategies of improving the phase stability. The review concludes with a perspective on the current challenges and future research directions. PMID:29120393

Photoassist-phosphorylated TiO2 as a catalyst for direct formation of 5-(hydroxymethyl)furfural from glucose.

PubMed

Hattori, Masashi; Kamata, Keigo; Hara, Michikazu

2017-02-01

Photo-assisted phosphorylation of an anatase TiO 2 catalyst was examined to improve its catalytic performance for the direct production of 5-(hydroxymethyl)furfural (HMF), a versatile chemical platform, from glucose. In phosphorylation based on simple esterification between phosphoric acid and surface OH groups on anatase TiO 2 with water-tolerant Lewis acid sites, the density of phosphates immobilized on TiO 2 is limited to 2 phosphates nm -2 , which limits selective HMF production. Phosphorylation of the TiO 2 surface under fluorescent light irradiation increases the surface phosphate density to 50%, which is higher than the conventional limit, thus preventing the adsorption of hydrophilic glucose molecules on TiO 2 and resulting in a more selective HMF production over photoassist-phosphorylated TiO 2 .

Modification of TiO(2) nanotube surfaces by electro-spray deposition of amoxicillin combined with PLGA for bactericidal effects at surgical implantation sites.

PubMed

Lee, Jung-Hwan; Moon, Seung-Kyun; Kim, Kwang-Mahn; Kim, Kyoung-Nam

2013-01-01

To fabricate the antibiotic-releasing coatings on TiO(2) nanotube surfaces for wide applications of implant and bone plate in medical and dental surgery, the optimal deposition time of amoxicillin/PLGA solution simultaneously performing non-toxicity and a high bactericidal effect for preventing early implant failures was found. FE-SEM, ESD and FT-IR were used for confirming deposition of amoxicillin/PLGA on the TiO(2) surface. Also, the elution of amoxicillin/PLGA in a TiO(2) nanotube surface was measured by a UV-VIS spectrophotometer. The bactericidal effect of amoxicillin on the TiO(2) nanotube surface was evaluated by using Staphylococcus aureus (S. aureus). The cytotoxicity and cell proliferation were observed by WST assay using MC3T3-E1 osteoblast cells. The results indicated that the TiO(2) nanotube surface controlled by electro-spray deposition time with amoxicillin/PLGA solution could provide a high bactericidal effect against S. aureus by the bactericidal effect of amoxicillin, as well as good osteoblast cell proliferation at the TiO(2) nanotube surface without toxicity. This study used electro-spray deposition (ESD) methodology to obtain amoxicillin deposition in nanotube structures of TiO(2) and found the optimal deposition time of amoxicillin/PLGA solution simultaneously performing non-toxicity and a high bactericidal effect for preventing early implant failures.

Defect assisted coupling of a MoS2/TiO2 interface and tuning of its electronic structure.

PubMed

Chen, Guifeng; Song, Xiaolin; Guan, Lixiu; Chai, Jianwei; Zhang, Hui; Wang, Shijie; Pan, Jisheng; Tao, Junguang

2016-09-02

Although MoS2 based heterostructures have drawn increased attention, the van der Waals forces within MoS2 layers make it difficult for the layers to form strong chemical coupled interfaces with other materials. In this paper, we demonstrate the successful strong chemical attachment of MoS2 on TiO2 nanobelts after appropriate surface modifications. The etch-created dangling bonds on TiO2 surfaces facilitate the formation of a steady chemically bonded MoS2/TiO2 interface. With the aid of high resolution transmission electron microscope measurements, the in-plane structure registry of MoS2/TiO2 is unveiled at the atomic scale, which shows that MoS2[1-10] grows along the direction of TiO2[001] and MoS2[110] parallel to TiO2[100] with every six units of MoS2 superimposed on five units of TiO2. Electronically, type II band alignments are realized for all surface treatments. Moreover, the band offsets are delicately correlated to the surface states, which plays a significant role in their photocatalytic performance.

Selective Catalytic Reduction of NO by NH 3 with WO 3-TiO 2 Catalysts: Influence of Catalyst Synthesis Method

DOE PAGES

He, Yuanyuan; Ford, Michael E.; Zhu, Minghui; ...

2016-02-02

A series of supported WO 3/TiO 2 catalysts was prepared by a new synthesis procedure involving co-precipitation of an aqueous TiO(OH) 2 and (NH 4) 10W 12O 41*5H 2O slurry under controlled pH conditions. The morphological properties, molecular structures, surface acidity and surface chemistry of the supported WO 3/TiO 2 catalysts were determined with BET, in situ Raman, in situ IR and temperature-programmed surface reaction (TPSR) spectroscopy, respectively. Isotopic 18O- 16O exchange demonstrated that tungsten oxide was exclusively present as surface WO x species on the TiO 2 support with mono-oxo W=O coordination. In contrast to previous studies employing impregnationmore » synthesis that found only surface one mono-oxo O=WO 4 site on TiO 2, the co-precipitation procedure resulted in the formation of two distinct surface WO x species: mono-oxo O=WO 4 (~1010-1017 cm -1) on low defect density patches of TiO 2 and a second mono-oxo O=WO 4 (~983-986 cm -1) on high defect density patches of TiO 2. The concentration of the second WO x surface species increases as a function of solution pH. Both surface WOx sites, however, exhibited the same NO/NH 3 SCR reactivity. The co-precipitated WO 3-TiO 2 catalysts synthesized in alkaline solutions exhibited enhanced performance for the NO/NH 3 SCR reaction that is ascribed to the greater number of surface defects on the resulting TiO2 support. For the co-precipitated catalyst prepared at pH10, surface NH 4 + species on Br nsted acid sites were found to be more reactive than surface NH 3* species on Lewis acid sites for SCR of NO with NH 3.« less

Enhanced photocatalytic activity of TiO2 by surface fluorination in degradation of organic cationic compound.

PubMed

Yang, Shi-ying; Chen, You-yuan; Zheng, Jian-guo; Cui, Ying-jie

2007-01-01

Experiments were carried out to investigate the influence of TiO2 surface fluorination on the photodegradation of a representative organic cationic compound, Methylene Blue (MB). The electropositive MB shows poor adsorption on TiO2 surface; its degradation performs a HO-radical-mediated mechanism. In the F-modified system, the kinetic reaction rate enlarged more than 2.5 fold that was attributed mainly to the accumulating adsorption of MB and the increased photogenerated hole available on the F-modified TiO2 surface.

Effect of dissolved ozone or ferric ions on photodegradation of thiacloprid in presence of different TiO2 catalysts.

PubMed

Cernigoj, Urh; Stangar, Urska Lavrencic; Jirkovský, Jaromír

2010-05-15

Combining TiO(2) photocatalysis with inorganic oxidants (such as O(3) and H(2)O(2)) or transition metal ions (Fe(3+), Cu(2+) and Ag(+)) often leads to a synergic effect. Electron transfer between TiO(2) and the oxidant is usually involved. Accordingly, the degree of synergy could be influenced by TiO(2) surface area. With this in mind, the disappearance of thiacloprid, a neonicotinoid insecticide, was studied applying various photochemical AOPs and different TiO(2) photocatalysts. In photocatalytic ozonation experiments, synergic effect of three different TiO(2) photocatalysts was quantified. Higher surface area resulted in a more pronounced synergic effect but an increasing amount of TiO(2) did not influence the degree of the synergy. This supports the theory that the synergy is a consequence of adsorption of ozone on the TiO(2) surface. No synergy was observed in photocatalytic degradation of thiacloprid in the presence of dissolved iron(III) species performed under varied experimental conditions (concentration, age of iron(III) solution, different TiO(2) films, usage of TiO(2) slurries). This goes against the literature for different organic compounds (i.e., monuron). It indicates different roles of iron(III) in the photodegradation of different organic molecules. Moreover, TiO(2) surface area did not affect photodegradation efficiency in iron(III)-based experiments which could confirm absence of electron transfer between TiO(2) photocatalyst and iron(III). Copyright (c) 2009 Elsevier B.V. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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

2015-02-01

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

Influence of N2 annealing on TiO2 tubes structure and its photocatalytic activity

NASA Astrophysics Data System (ADS)

Chen, Xiaoxiang; Pan, Zhanchang; Yu, Ke; Xiao, Jun; Wu, Shoukun; Li, Jinghong; Chen, Chun; Lin, Yingsheng; Hu, Guanghui; Xu, Yanbin

2018-02-01

In this work, the TiO2 tubes (TBs) were prepared by solvothermal method. The morphology and phase structure of TiO2 TBs is significantly affected by N2 annealing temperature. XRD was used to characterize the phase structure of the as-prepared samples. The morphology and surface areas were characterized by SEM and N2 adsorption-desorption, which show that the tubes were assembled with about 100-nm nanosheets and small ball particles under 400 and 600 °C N2 annealing; when temperature reached 800 °C, the surface of tubes appeared a lot of collapse and many large holes. In addition, the surface areas of 400 °C TiO2, 600 °C TiO2, and 800 °C TiO2 TBs were significantly affected by N2 annealing. Most importantly, the UV-vis and electrochemical tests demonstrate 600 °C TiO2 TBs exhibit higher absorption intensity and photocurrent; thus, it possess on better photocatalytic activity. Therefore, the photocatalytic performance for TiO2 TBs is significantly co-affected by surface area and mix-phase. [Figure not available: see fulltext.

Photosensitizing effects of nanometer TiO2 on chlorothalonil photodegradation in aqueous solution and on the surface of pepper.

PubMed

Tan, Yong Qiang; Xiong, Hai Xia; Shi, Tao Zhong; Hua, Ri Mao; Wu, Xiang Wei; Cao, Hai Qun; Li, Xue De; Tang, Jun

2013-05-29

The present study examined the effects of anatase nanometer TiO2 on photochemical degradation of chlorothalonil in aqueous solution and on the plant surface. Results showed that nanometer TiO2 exhibited a strong photosensitizing effect on the degradation of chlorothalonil both in aqueous solution and on the surface of green pepper. The photosensitization rate was the highest in the sunlight compared to illumination under high-pressure mercury and UV lamps. Use of distinct hydroxyl radical scavengers indicated that nanometer TiO2 acted by producing hydroxyl radicals with strong oxidizing capacity. Notably, nanometer TiO2 facilitated complete photodegradation of chlorothalonil with no detectable accumulation of the intermediate chlorothalonil-4-hydroxy. Nanometer TiO2 was also active on the surface of green pepper under natural sunlight both inside and outside of plastic greenhouse. These results together suggest that nanometer TiO2 can be used as a photosensitizer to accelerate degradation of the pesticides under greenhouse conditions.

Fabrication of TiO2-modified polytetrafluoroethylene ultrafiltration membranes via plasma-enhanced surface graft pretreatment

NASA Astrophysics Data System (ADS)

Qian, Yingjia; Chi, Lina; Zhou, Weili; Yu, Zhenjiang; Zhang, Zhongzhi; Zhang, Zhenjia; Jiang, Zheng

2016-01-01

Surface hydrophilic modification of polymer ultrafiltration membrane using metal oxide represents an effective yet highly challenging solution to improve water flux and antifouling performance. Via plasma-enhanced graft of poly acryl acid (PAA) prior to coating TiO2, we successfully fixed TiO2 functional thin layer on super hydrophobic polytetrafluoroethylene (PTFE) ultrafiltration (UF) membranes. The characterization results evidenced TiO2 attached on the PTFE-based UF membranes through the chelating bidentate coordination between surface-grafted carboxyl group and Ti4+. The TiO2 surface modification may greatly reduce the water contact angle from 115.8° of the PTFE membrane to 35.0° without degradation in 30-day continuous filtration operations. The novel TiO2/PAA/PTFE membranes also exhibited excellent antifouling and self-cleaning performance due to the intrinsic hydrophilicity and photocatalysis properties of TiO2, which was further confirmed by the photo-degradation of MB under Xe lamp irradiation.

Decomposition of banten ilmenite by caustic fusion process for TiO2 photocatalytic applications

NASA Astrophysics Data System (ADS)

Aristanti, Y.; Supriyatna, Y. I.; Masduki, N. P.; Soepriyanto, S.

2018-01-01

Decomposition of Banten ilmenite by caustic fusion process for TiO2 photocatalytic applications has been done. Caustic fusion process using NaOH to obtain sodium titanate compound which is soluble in sulfuric acid (H2SO4) to produces TiOSO4 as a precursor. Synthesis of TiO2 from TiOSO4 precursors by variations of pH hydrolysis are 1.0 (TiO2 A), 1.5 (TiO2 B) and 2.0 (TiO2 C). XRD pattern identified TiO2 structures crystals are anatase phase and traces α-Fe2O3 as an impurity. Presence of Fe2O3 as an impurities give positive effect on TiO2 photocatalytic activity that is to narrower the band gap energy thus facilitates of electrons excitation from valence band to conduction band and enlarge the specific surface area thus reaction between Rhodamin B solution and TiO2 surface can be faster. TiO2 A, TiO2 B and TiO2 C was compared to TiO2 M (commercial TiO2) in Rhodamin B solution for the photocatalytic activity where the maximum TiO2 degradation efficiency was obtained at TiO2 C 80.0 % while TiO2 M 59.8 %.

Preparation of Pd-loaded La-doped TiO2 nanotubes and investigation of their photocatalytic activity under visible light

NASA Astrophysics Data System (ADS)

Zong, Lanlan; Li, Qiuye; Zhang, Jiwei; Wang, Xiaodong; Yang, Jianjun

2013-11-01

Orthorhombic titanic acid nanotubes (TAN) have large BET surface area and small-diameter one-dimensional nanotubular morphology, so they can work as a good supporter and a precursor of TiO2. However, in our former research, we found that calcination of TAN to anatase TiO2 would destroy the nanotubular structure and decrease the BET surface area sharply. In this work, we utilized the pillar effect of the foreign nanoparticles (La2O3) to keep the nanotubular morphology of TiO2, and obtained the anatase TiO2 nanotubes with large BET surface area. For improving the photocatalytic activity, Pd nanoparticles were loaded as the electron traps on the surface of La-doped TiO2 by photo-deposition method. The photocatalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, diffuse reflectance spectra, and N2 adsorption-desorption isotherms measurement. Their photocatalytic activities were evaluated by the removal of propylene under visible light irradiation ( λ ≥ 420 nm). The results showed that the photocatalytic activity of Pd-loaded La-doped TiO2 nanotubes improved effectively compared with that of La-doped TiO2 and pure TiO2.

Crystalline TiO 2 grafted with poly(2-methacryloyloxyethyl phosphorylcholine) via surface-initiated atom-transfer radical polymerization

NASA Astrophysics Data System (ADS)

Zhao, Yuancong; Tu, Qiufen; Wang, Jin; Huang, Qiongjian; Huang, Nan

2010-12-01

Crystalline TiO 2 films were prepared by unbalanced magnetron sputtering and the structure was confirmed by XRD. An organic layer of 11-hydroxyundecylphosphonic acid (HUPA) was prepared on the TiO 2 films by self-assembling, and the HUPA on TiO 2 films was confirmed by FTIR analysis. Simultaneously, hydroxyl groups were introduced in the phosphonic acid molecules to provide a functionality for further chemical modification. 2-Methacryloyloxyethyl phosphorylcholine (MPC), a biomimetic monomer, was chemically grafted on the HUPA surfaces at room temperature by surface-initiated atom-transfer radical polymerization. The surface characters of TiO 2 films modified by poly-MPC were confirmed by FTIR, XPS and SEM analysis. Platelet adhesion experiment revealed that poly-MPC modified surface was effective to inhibit platelet adhesion in vitro.

Superhydrophilic TiO2 thin film by nanometer scale surface roughness and dangling bonds

NASA Astrophysics Data System (ADS)

Bharti, Bandna; Kumar, Santosh; Kumar, Rajesh

2016-02-01

A remarkable enhancement in the hydrophilic nature of titanium dioxide (TiO2) films is obtained by surface modification in DC-glow discharge plasma. Thin transparent TiO2 films were coated on glass substrate by sol-gel dip coating method, and exposed in DC-glow discharge plasma. The plasma exposed TiO2 film exhibited a significant change in its wetting property contact angle, which is a representative of wetting property, has reduced to considerable limits 3.02° and 1.85° from its initial value 54.40° and 48.82° for deionized water and ethylene glycol, respectively. It is elucidated that the hydrophilic property of plasma exposed TiO2 films dependent mainly upon nanometer scale surface roughness. Variation, from 4.6 nm to 19.8 nm, in the film surface roughness with exposure time was observed by atomic force microscopy (AFM). Analysis of variation in the values of contact angle and surface roughness with increasing plasma exposure time reveal that the surface roughness is the main factor which makes the modified TiO2 film superhydrophilic. However, a contribution of change in the surface states, to the hydrophilic property, is also observed for small values of the plasma exposure time. Based upon nanometer scale surface roughness and dangling bonds, a variation in the surface energy of TiO2 film from 49.38 to 88.92 mJ/m2 is also observed. X-ray photoelectron spectroscopy (XPS) results show change in the surface states of titanium and oxygen. The observed antifogging properties are the direct results of the development of the superhydrophilic wetting characteristics to TiO2 films.

Structural, electronic and optical properties of CO adsorbed on the defective anatase TiO2 (101) surface; a DFT study

NASA Astrophysics Data System (ADS)

Rafique, Muhammad; Shuai, Yong; Hassan, Muhammad

2017-08-01

This paper illustrates the study of stable structural, electronic and optical properties of carbon mono oxide (CO) molecule adsorbed on pure anatase TiO2 (101) surface and CO molecule adsorbed on defective anatase TiO2 (101) surface containing oxygen (O) atom subsurface vacancy using first-principles study calculations based on density functional theory (DFT) method. A foreign molecule CO was added in the interstitial space of anatase TiO2 (101) surface. It was observed that, adsorption of CO molecule is not favorable on pure anatase TiO2 (101) surface, however adsorption process is improved when subsurface contains O atom vacancy defect. In case of anatase TiO2 (101) surface containing subsurface vacancy, adsorption process is exothermic, resulting in stable structures. The adsorption energies calculated for CO molecules adsorbed at O2c site, at defect site and at Ti5c site of anatase surface containing subsurface O vacancy are 0.16 eV (at O2c), 0.32 eV (at defect site) and 0.43 eV (at Ti5c) site. DOS and PDOS plots are calculated for all the structures. Results indicated that CO molecule adsorption introduces surface states at the Fermi energy level (EF) as shown in partial density of states (PDOS) plots. The dielectric matrix and absorption coefficient (α) for defective anatase TiO2 (101) surface, CO adsorbed at O2c site, at defect site and at Ti5C site of anatase TiO2 (101) surface containing O atom subsurface vacancy has been calculated within the random phase approximation (RPA) using VASP (Vienna ab-initio simulation package) code. It was observed that upon CO adsorption at defective anatase surface, real and imaginary dielectric function peaks were shifted towards lower energy level and a small absorption peak was observed at 1.1 eV energy level which is not present in case of defective anatase (101) surface. CO adsorption produces a red shift in the absorption spectrum of anatase TiO2 (101) surface containing subsurface O atom vacancy.

Formation of hydroxyl radicals and kinetic study of 2-chlorophenol photocatalytic oxidation using C-doped TiO2, N-doped TiO2, and C,N Co-doped TiO2 under visible light.

PubMed

Ananpattarachai, Jirapat; Seraphin, Supapan; Kajitvichyanukul, Puangrat

2016-02-01

This work reports on synthesis, characterization, adsorption ability, formation rate of hydroxyl radicals (OH(•)), photocatalytic oxidation kinetics, and mineralization ability of C-doped titanium dioxide (TiO2), N-doped TiO2, and C,N co-doped TiO2 prepared by the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy were used to analyze the titania. The rate of formation of OH(•) for each type of titania was determined, and the OH-index was calculated. The kinetics of as-synthesized TiO2 catalysts in photocatalytic oxidation of 2-chlorophenol (2-CP) under visible light irradiation were evaluated. Results revealed that nitrogen was incorporated into the lattice of titania with the structure of O-Ti-N linkages in N-doped TiO2 and C,N co-doped TiO2. Carbon was joined to the Ti-O-C bond in the C-doped TiO2 and C,N co-doped TiO2. The 2-CP adsorption ability of C,N co-doped TiO2 and C-doped TiO2 originated from a layer composed of a complex carbonaceous mixture at the surface of TiO2. C,N co-doped TiO2 had highest formation rate of OH(•) and photocatalytic activity due to a synergistic effect of carbon and nitrogen co-doping. The order of photocatalytic activity per unit surface area was the same as that of the formation rate of OH(•) unit surface area in the following order: C,N co-doped TiO2 > C-doped TiO2 > N-doped TiO2 > undoped TiO2.

Effect of Surface-Modified TiO2 Nanoparticles on the Anti-Ultraviolet Aging Performance of Foamed Wheat Straw Fiber/Polypropylene Composites

PubMed Central

Xuan, Lihui; Han, Guangping; Wang, Dong; Cheng, Wanli; Gao, Xun; Chen, Feng; Li, Qingde

2017-01-01

Surface modification and characterization of titanium dioxide (TiO2) nanoparticles and their roles in thermal, mechanical, and accelerated aging behavior of foamed wheat straw fiber/polypropylene (PP) composites are investigated. To improve the dispersion of nanoparticles and increase the possible interactions between wheat straw fiber and the PP matrix, the surface of the TiO2 nanoparticles was modified with ethenyltrimethoxy silane (A171), a silane coupling agent. The grafting of A171 on the TiO2 nanoparticles’ surface was characterized by Fourier transform infrared spectroscopy (FTIR). The wheat straw fibers treated with A171 and modified TiO2 nanoparticles were characterized by FTIR and thermogravimetric analysis (TGA). FTIR spectra confirmed that the organic functional groups of A171 were successfully grafted onto the TiO2 nanoparticles and wheat straw fibers, and the modified TiO2 nanoparticles were adsorbed onto the wheat straw fibers. Thermogravimetric analysis showed that a higher thermal stability of the wheat straw fiber was obtained with the modified TiO2 nanoparticles. The flexural, tensile, and impact properties were improved. A higher ultraviolet (UV) stability of the samples treated with modified TiO2 nanoparticles was exhibited by the study of the color change and loss in mechanical properties. PMID:28772816

Preparation and photocatalytic properties of nanometer-sized magnetic TiO2/SiO2/CoFe2O4 composites.

PubMed

Li, Hansheng; Zhang, Yaping; Wu, Qin; Wang, Xitao; Liu, Changhao

2011-11-01

Magnetic TiO2/SiO2/CoFe2O4 nanoparticles (TiO2/SCFs) were prepared by a sol-gel process in a reverse microemulsion combined with solvent-thermal technique. TiO2/SCFs were characterized by Fourier transform infrared spectrometry, thermogravimetric analysis-differential scanning calorimetry, X-ray diffraction, Raman spectrometry, TEM, BET specific surface area measurement, and magnetic analysis. Structure analyses indicated that TiO2/SCFs presented a core-shell structure with TiO2 uniformly coating on SiO2/CoFe2O4 nanomagnets (SCFs) and typical ferromagnetic hysteresis. TiO2/SCFs showed larger specific surface area and better photocatalytic activities than TiO2 and TiO2/CoFe2O4 photocatalysts prepared by the same method. The doping interaction between TiO2 and CoFe2O4 reduced thanks to the inert SiO2 mesosphere.

Efficient adsorption concentration and photolysis of acetaldehyde on titania-mesoporous silica composite

NASA Astrophysics Data System (ADS)

Yamaguchi, Satoshi; Matsumoto, Akihiko

2017-07-01

Titania-mesoporous silica composite (TiO2/MCM) was prepared by hydrolysis of titaniumtetraisopropoxide (TTIP) with the presence of mesoporous silica MCM-41. The TiO2/MCM samples consisted of highly dispersed TiO2 on the surface of MCM-41. Dynamic adsorption and photocatalytic decomposition features for acetaldehyde (CH3CHO) were measured by flow method. The amount of CH3CHO decomposition on TiO2/MCM-41 increased with the TiO2 amount, suggesting that a large amount of CH3CHO was adsorbed on mesopores of MCM-41 of the TiO2/MCM and was efficiently decomposed on finely dispersed TiO2 surface by ultraviolet irradiation.

Influence of Operating Parameters on Surface Properties of RF Glow Discharge Oxygen Plasma Treated TiO2/PET Film for Biomedical Application

EPA Science Inventory

Thin transparent titania (TiO2) films were coated on the surface of flexible poly (ethylene terephthalate) (PET) surface using standard sol gel techniques. The TiO2/PET thin film surfaces were further modified by exposing the films to a RF glow discharge oxygen plasma. The exposu...

Effects of titanium nanotubes on the osseointegration, cell differentiation, mineralisation and antibacterial properties of orthopaedic implant surfaces.

PubMed

Su, E P; Justin, D F; Pratt, C R; Sarin, V K; Nguyen, V S; Oh, S; Jin, S

2018-01-01

The development and pre-clinical evaluation of nano-texturised, biomimetic, surfaces of titanium (Ti) implants treated with titanium dioxide (TiO 2 ) nanotube arrays is reviewed. In vitro and in vivo evaluations show that TiO 2 nanotubes on Ti surfaces positively affect the osseointegration, cell differentiation, mineralisation, and anti-microbial properties. This surface treatment can be superimposed onto existing macro and micro porous Ti implants creating a surface texture that also interacts with cells at the nano level. Histology and mechanical pull-out testing of specimens in rabbits indicate that TiO 2 nanotubes improves bone bonding nine-fold (p = 0.008). The rate of mineralisation associated with TiO 2 nanotube surfaces is about three times that of non-treated Ti surfaces. In addition to improved osseointegration properties, TiO 2 nanotubes reduce the initial adhesion and colonisation of Staphylococcus epidermidis Collectively, the properties of Ti implant surfaces enhanced with TiO 2 nanotubes show great promise. Cite this article: Bone Joint J 2018;100-B(1 Supple A):9-16. ©2018 The British Editorial Society of Bone & Joint Surgery.

Markedly Enhanced Surface Hydroxyl Groups of TiO2 Nanoparticles with Superior Water-Dispersibility for Photocatalysis

PubMed Central

Wu, Chung-Yi; Tu, Kuan-Ju; Deng, Jin-Pei; Lo, Yu-Shiu; Wu, Chien-Hou

2017-01-01

The benefits of increasing the number of surface hydroxyls on TiO2 nanoparticles (NPs) are known for environmental and energy applications; however, the roles of the hydroxyl groups have not been characterized and distinguished. Herein, TiO2 NPs with abundant surface hydroxyl groups were prepared using commercial titanium dioxide (ST-01) powder pretreated with alkaline hydrogen peroxide. Through this simple treatment, the pure anatase phase was retained with an average crystallite size of 5 nm and the surface hydroxyl group density was enhanced to 12.0 OH/nm2, estimated by thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Especially, this treatment increased the amounts of terminal hydroxyls five- to six-fold, which could raise the isoelectric point and the positive charges on the TiO2 surface in water. The photocatalytic efficiency of the obtained TiO2 NPs was investigated by the photodegradation of sulforhodamine B under visible light irradiation as a function of TiO2 content, pH of solution, and initial dye concentration. The high surface hydroxyl group density of TiO2 NPs can not only enhance water-dispersibility but also promote dye sensitization by generating more hydroxyl radicals. PMID:28772926

Density functional theory study on the metal-support interaction between a Au9 cluster and an anatase TiO2(001) surface.

PubMed

Jiang, Zong-You; Zhao, Zong-Yan

2017-08-23

Noble metals supported on TiO 2 surfaces have shown extraordinary photocatalytic properties in many important processes such as hydrogenation, water splitting, degradation of hazards, and so on. Using density functional theory calculations, this work has systematically investigated the microstructure and electronic structure of three different Au 9 isomers loaded on anatase TiO 2 (001) surface. The calculated results show that the interaction between the Au 9 cluster and the TiO 2 support is closely related to the adsorption site and the stability of the Au 9 cluster in the gas phase. The adsorption energy of the 2D configuration is larger than that of the 3D configuration of the Au 9 cluster, owing to the stronger interactions between more adsorption sites. The stable adsorption site for Au 9 clusters deposited on the anatase TiO 2 (001) surface tends to be the O 2c -O 2c hollow site. The presentation of the MIGS of the Au 9 cluster, the disappearance of surface states of the TiO 2 (001) surface, and the shifting of the Fermi level from the top of the valence band to the bottom of the conduction band suggest strong interactions between the Au 9 clusters and the TiO 2 (001) surface. Importantly, the electron transfer from the Au 9 clusters to the TiO 2 support occurs mainly through Au-O 2c interactions, which are mainly localized at the contact layer of the Au 9 clusters. These conclusions are useful to understand various physical and chemical properties of noble metal clusters loaded onto an oxide surface, and helpful to design novel metal/semiconductor functional composite materials and devices.

Preparation and Characterisation of Hydroxyapatite Coatings on Nanotubular TiO2 Surface Obtained by Sol-Gel Process.

PubMed

Shin, Jin-Ho; Kim, Jung-Hwa; Koh, Jeong-Tae; Lim, Hyun-Pil; Oh, Gye-Jeong; Lee, Seok-Woo; Lee, Kwang-Min; Yun, Kwi-Dug; Park, Sang-Won

2015-08-01

Hydroxyapatite (HA) coating on titanium dioxide (TiO2) nanotubular surface has been developed to complement the defects of both TiO2 and HA. A sol-gel processing technique was used to coat HA on TiO2 nanotubular surface. All the titanium discs were blasted with resorbable blast media (RBM). RBM-blasted Ti surface, anodized Ti surface, and sol-gel HA coating on the anodized Ti surface were prepared. The characteristics of samples were observed using scanning electron microscopy and X-ray photoemission spectroscopy. Biologic responses were evaluated with human osteosarcoma MG63 cells in vitro. The top of the TiO2 nanotubes was not completely covered by HA particles when the coating time was less than 60 sec. It was demonstrated the sol-gel derived HA film was well-crystallized and this enhanced biologic responses in early stage cell response.

Enhancing antimicrobial activity of TiO2/Ti by torularhodin bioinspired surface modification.

PubMed

Ungureanu, Camelia; Dumitriu, Cristina; Popescu, Simona; Enculescu, Monica; Tofan, Vlad; Popescu, Marian; Pirvu, Cristian

2016-02-01

Implant-associated infections are a major cause of morbidity and mortality. This study was performed using titanium samples coated by anodization with a titanium dioxide (TiO2) shielded nanotube layer. TiO2/Ti surface was modified by simple immersion in torularhodin solution and by using a mussel-inspired method based on polydopamine as bio adhesive for torularhodin immobilization. SEM analysis revealed tubular microstructures of torularhodin and the PDA ability to function as a catchy anchor between torularhodin and TiO2 surface. Corrosion resistance was associated with TiO2 barrier oxide layer and nano-organized oxide layer and the torularhodin surface modification does not bring significant changes in resistance of the oxide layer. Our results demonstrated that the torularhodin modified TiO2/Ti surface could effectively prevent adhesion and proliferation of Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, and Pseudomonas aeruginosa. The new modified titanium surface showed good biocompatibility and well-behaved haemocompatibility. This biomaterial with enhanced antimicrobial activity holds great potential for future biomedical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Synergistic effects between TiO2 and carbon nanotubes (CNTs) in a TiO2/CNTs system under visible light irradiation.

PubMed

Wu, Chung-Hsin; Kuo, Chao-Yin; Chen, Shih-Ting

2013-01-01

This study synthesized a TiO2/carbon nanotubes (CNTs) composite via the sol-gel method. The surface characteristics of the TiO2/CNTs composite were determined by X-ray diffraction, transmission electron microscopy, specific surface area analyser, ultraviolent (UV)-vis spectroscopy, X-ray photoelectron spectroscopy and Raman spectrometer. The photocatalytic activity ofthe TiO2/CNTs composite was evaluated by decolourizing C.I. Reactive Red 2 (RR2) under visible light irradiation. Furthermore, the effects of calcination temperature, pH, RR2 concentration, and the TiO2/CNTs composite dosage on RR2 decolourization were determined simultaneously. The optimal calcination temperature to generate TiO2 and the TiO2/CNTs composite was 673 K, as the percentage of anatase crystallization at this temperature was highest. The specific surface area of the TiO2/CNTs composite and TiO2 were 45 and 42 m2/g, respectively. The band gap of TiO2 and the TiO2/CNTs composite was 2.97 and 2.71 eV by UV-vis measurements, respectively. Experimental data indicate that the Ti-O-C bond formed in the TiO2/CNTs composite. The RR2 decolourization rates can be approximated by pseudo-first-order kinetics; moreover, only the TiO2/CNTs composite had photocatalytic activity under visible light irradiation. At pH 7, the RR2 decolourization rate constant of 0.5, 1 and 2 g/L TiO2/CNTs addition was 0.005, 0.0015, and 0.0047 min(-1), respectively. Decolourization rate increased as pH and the RR2 concentration decreased. The CNTs functioned as electron acceptors, promoting separation of photoinduced electron-hole pairs to retard their recombination; thus, photocatalytic activity of the TiO2/CNTs composite exceeded that of TiO2.

Combined Embedding of N/F-Doping and CaCO3 Surface Modification in the TiO2 Photoanode for Dye-Sensitized Solar Cells.

PubMed

Park, Su Kyung; Yun, Tae Kwan; Bae, Jae Young

2016-03-01

N/F-doping and CaCO3 surface modification was carried out in TiO2 photoelectrodes for dye-sensitized solar cells (DSSCs). The combined effect of the N/F doped TiO2 and the CaCO3 coating showed a great increase of the short-circuit current (J(sc)), and photoelectric conversion efficiency (η) of the prepared cells; the efficiency (η) was improved from 7.00% of a commercial TiO2 photoelectrode to 7.90% of an uncoated N/F-doped electrode, and to 9.09% of a N/F-doped and CaCO3 surface modified electrode. An enhanced photoresponse in N/F-doped TiO2 nanoparticles generate more photo-excited electrons, as supported by measured UV-Vis diffuse reflectance spectra. A successive CaCO3 surface modification then forms a barrier on the surface of the N/F-doped TiO2 particles; the higher basicity of the CaCO3 modified TiO2 facilitates the dye adsorption, as supported by the direct measurement of the amount of adsorbed dye.

Proline adsorption on TiO 2(1 1 0) single crystal surface: A study by high resolution photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Fleming, G. J.; Adib, K.; Rodriguez, J. A.; Barteau, M. A.; Idriss, H.

2007-12-01

The surface chemistry and binding of DL-proline were investigated on the oxidised (stoichiometric) and reduced (sub-stoichiometric) TiO 2(1 1 0) single crystal surfaces. TiO 2 was chosen as the substrate as it best represents the surface of a biomedical implant, which bio-molecules interact with during the healing of bone/teeth fractures (molecular recognition). High resolution X-ray photoelectron spectroscopy (HR-XPS) studies of the C1s and N1s regions revealed that DL-proline is present in two forms (dissociated and zwitterionic) on the oxidised TiO 2 surface. On TiO 2(1 1 0) surfaces reduced by Ar + sputtering, a significant increase in the amount of zwitterionic proline at the surface was detected when compared with the oxidised surface. Study of the temperature effect showed that in both cases the zwitterionic structure was the less stable structure. The reason for its relative instability appears to be thermodynamic.

Fast diffusion of silver in TiO2 nanotube arrays

PubMed Central

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

2016-01-01

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

Preparation of Transparent Bulk TiO2/PMMA Hybrids with Improved Refractive Indices via an in Situ Polymerization Process Using TiO2 Nanoparticles Bearing PMMA Chains Grown by Surface-Initiated Atom Transfer Radical Polymerization.

PubMed

Maeda, Satoshi; Fujita, Masato; Idota, Naokazu; Matsukawa, Kimihiro; Sugahara, Yoshiyuki

2016-12-21

Transparent TiO 2 /PMMA hybrids with a thickness of 5 mm and improved refractive indices were prepared by in situ polymerization of methyl methacrylate (MMA) in the presence of TiO 2 nanoparticles bearing poly(methyl methacrylate) (PMMA) chains grown using surface-initiated atom transfer radical polymerization (SI-ATRP), and the effect of the chain length of modified PMMA on the dispersibility of modified TiO 2 nanoparticles in the bulk hybrids was investigated. The surfaces of TiO 2 nanoparticles were modified with both m-(chloromethyl)phenylmethanoyloxymethylphosphonic acid bearing a terminal ATRP initiator and isodecyl phosphate with a high affinity for common organic solvents, leading to sufficient dispersibility of the surface-modified particles in toluene. Subsequently, SI-ATRP of MMA was achieved from the modified surfaces of the TiO 2 nanoparticles without aggregation of the nanoparticles in toluene. The molecular weights of the PMMA chains cleaved from the modified TiO 2 nanoparticles increased with increases in the prolonging of the polymerization period, and these exhibited a narrow distribution, indicating chain growth controlled by SI-ATRP. The nanoparticles bearing PMMA chains were well-dispersed in MMA regardless of the polymerization period. Bulk PMMA hybrids containing modified TiO 2 nanoparticles with a thickness of 5 mm were prepared by in situ polymerization of the MMA dispersion. The transparency of the hybrids depended significantly on the chain length of the modified PMMA on the nanoparticles, because the modified PMMA of low molecular weight induced aggregation of the TiO 2 nanoparticles during the in situ polymerization process. The refractive indices of the bulk hybrids could be controlled by adjusting the TiO 2 content and could be increased up to 1.566 for 6.3 vol % TiO 2 content (1.492 for pristine PMMA).

A study on the preparation of floating photocatalyst supported by hollow TiO2 and its performance

NASA Astrophysics Data System (ADS)

Wang, Jingang; He, Bin; Kong, Xiang Z.

2015-02-01

This research used hollow glass microspheres (HGMS) as carrier and polystyrene (PSt) as template. PSt was loaded on HGMS surface through the modification by silane coupler. Next, amorphous titanium dioxide (TiO2) produced through tetrabutyl titanate (TBT) hydrolysis precipitated on PSt surface, forming HGMS/PSt/TiO2 particles. Lastly, using the calcinations method, this research obtained anatase TiO2, eliminated PSt, and ultimately acquired composite particles with hollow TiO2 loaded on HGMS surface (HGMSHT). SEM results presented that hollow TiO2 was compact on HGMS surface and a multilayer network structure was formed. The specific surface area of HGMSHT particles was 26 m2/g, which was much larger than that of HGMS/TiO2 (HGMST) composite particles (5.6 m2/g) through direct TBT hydrolysis. Results of catalytic degradation experiment with Rhodamine B and phenol under UV light and sunlight demonstrated that due to larger TiO2 load capacity and specific surface area, the catalytic activity of HGMSHT composite particles was significantly more desirable than that of HGMST, and the catalyst presented satisfactory stability.

Photocatalytic Oxidation of Acetone Over High Thermally Stable TiO2 Nanosheets With Exposed (001) Facets.

PubMed

Shi, Ting; Duan, Youyu; Lv, Kangle; Hu, Zhao; Li, Qin; Li, Mei; Li, Xiaofang

2018-01-01

Anatase TiO 2 (A-TiO 2 ) usually exhibits superior photocatalytic activity than rutile TiO 2 (R-TiO 2 ). However, the phase transformation from A-TiO 2 to R-TiO 2 will inevitably happens when the calcination temperature is up to 600°C, which hampers the practical applications of TiO 2 photocatalysis in hyperthermal situations. In this paper, high energy faceted TiO 2 nanosheets (TiO 2 -NSs) with super thermal stability was prepared by calcination of TiOF 2 cubes. With increase in the calcination temperature from 300 to 600°C, TiOF 2 transforms into TiO 2 hollow nanoboxes (TiO 2 -HNBs) assembly from TiO 2 -NSs via Ostwald Rippening process. Almost all of the TiO 2 -HNBs are disassembled into discrete TiO 2 -NSs when calcination temperature is higher than 700°C. Phase transformation from A-TiO 2 to R-TiO 2 begins at 1000°C. Only when the calcination temperature is higher than 1200°C can all the TiO 2 -NSs transforms into R-TiO 2 . The 500°C-calcined sample (T500) exhibits the highest photoreactivity toward acetone oxidation possibly because of the production of high energy TiO 2 -NSs with exposed high energy (001) facets and the surface adsorbed fluorine. Surface oxygen vacancy, due to the heat-induced removal of surface adsorbed fluoride ions, is responsible for the high thermal stability of TiO 2 -NSs which are prepared by calcination of TiOF 2 cubes.

Nanoparticle-induced oxidation of corona proteins initiates an oxidative stress response in cells†

PubMed Central

Jayaram, Dhanya T.; Runa, Sabiha; Kemp, Melissa L.

2017-01-01

Titanium dioxide nanoparticles (TiO2 NPs), used as pigments and photocatalysts, are ubiquitous in our daily lives. Previous work has observed cellular oxidative stress in response to the UV-excitation of photocatalytic TiO2 NPs. In comparison, most human exposure to TiO2 NPs takes place in the dark, in the lung following inhalation or in the gut following consumption of TiO2 NP food pigment. Our spectroscopic characterization shows that both photocatalytic and food grade TiO2 NPs, in the dark, generate low levels of reactive oxygen species (ROS), specifically hydroxyl radicals and superoxides. These ROS oxidize serum proteins that form a corona of proteins on the NP surface. This protein layer is the interface between the NP and the cell. An oxidized protein corona triggers an oxidative stress response, detected with PCR and western blotting. Surface modification of TiO2 NPs to increase or decrease surface defects correlates with ROS generation and oxidative stress, suggesting that NP surface defects, likely oxygen vacancies, are the underlying cause of TiO2 NP-induced oxidative stress. PMID:28537609

Seed-mediated photodeposition route to Ag-decorated SiO2@TiO2 microspheres with ideal core-shell structure and enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Ma, Jianqi; Guo, Xiaohua; Ge, Hongguang; Tian, Guanghui; Zhang, Qiang

2018-03-01

Ag-decorated SiO2@TiO2 microspheres (SiO2@TiO2-Ag) with ideal core-shell structure and enhanced photocatalytic activity were successfully fabricated by combining both coating anatase TiO2 on the surface of SiO2 spheres and subsequent depositing face-centered cubic Ag nanoparticles (NPs) on the coated TiO2 surface via novel sol-gel method and Ag-seed-mediated photodeposition (PD) route, respectively. The morphology, structure, composition and optical properties of the resulting composites were characterized in detail. The results reveal that the monodisperse SiO2 spheres of ∼260 nm were covered uniformly and perfectly by the TiO2 nanoparticle coating layer with the thickness of ca. 55 nm by the novel sol-gel method. Further, homogeneously and highly dispersed Ag NPs with an average size of 8 ± 1.5 nm were strongly anchored onto the TiO2 surface in SiO2@TiO2 core-shell spheres by the modified PD process (Ag-seed-mediated PD route), whereas polydispersed Ag aggregates and detached Ag NPs were irregularly deposited over the TiO2 surface in previous works, which is the inherent problem and has not been effectively solved for depositing noble metal NPs such as Au, Ag, Pt, Pd on TiO2 surface by conventional PD method. The formation mechanism of small and uniformly dispersed Ag NPs with narrow size distribution via the modified PD method is tentatively explained by both nucleation kinetics and growth kinetics. The key reason is that the pre-deposited seeds firmly tethered on SiO2@TiO2 spheres served as nucleation sites and anchoring points for the further nucleation and subsequent growth of Ag via photoreduction of Ag+.

The double peaks and symmetric path phenomena in the catalytic activity of Pd/Al2O3-TiO2 catalysts with different TiO2 contents

NASA Astrophysics Data System (ADS)

Zhang, Shen; Guo, Yuyu; Li, Xingying; Wu, Xu; Li, Zhe

2018-06-01

Physicochemical properties of Pd/Al2O3-TiO2 catalysts with different amounts of TiO2 contents were investigated by XRD, nitrogen adsorption-desorption, FTIR, NH3-TPD, H2-TPR and XPS techniques. Catalysts of different compositions were tested in the ethanol oxidation reaction to study the effects of TiO2 contents. Double peaks and symmetric path phenomena were observed at certain temperatures with the increase in TiO2 contents. The symmetric peak phenomena and the diverse activity fluctuations have been ascribed to the controlling factors such as temperature and compositions. With the increase in TiO2 content, the surface area, adsorbed oxygen contents and surface acid quantity decreased gradually. The large surface area and adsorbed oxygen contents were conducive to the performance, while increased acid amounts were not beneficial for ethanol oxidation. At 150 and 175 °C, Pd/AT(X1

X-ray photoelectron spectroscopy characterization of composite TiO 2-poly(vinylidenefluoride) films synthesised for applications in pesticide photocatalytic degradation

NASA Astrophysics Data System (ADS)

Losito, I.; Amorisco, A.; Palmisano, F.; Zambonin, P. G.

2005-02-01

X-ray photoelectron spectroscopy (XPS) was adopted for the analytical characterization of composite titanium dioxide-poly(vinylidenefluoride) (TiO 2-PVDF) films developed for applications in the photocatalytic degradation of pollutants. The composites were deposited on glass substrates by casting or spin coating from TiO 2-PVDF suspensions in dimethylformamide (DMF). XPS data on the TiO 2-PVDF surface composition were used to optimize preparation conditions (composition of the TiO 2/PVDF suspension, deposition technique) in terms of titanium dioxide surface amount and film stability. The use of spin-coating deposition and the increase of TiO 2 amount in the DMF suspensions were found to improve the titanium surface content, although high TiO 2/PVDF ratios led to film instability. PVDF-TiO 2 films were also used in preliminary photocatalytic degradation tests on isoproturon, a phenylurea herbicide, under solar UV irradiation; the results were compared to direct photolysis to evaluate the catalytic efficiency of immobilized TiO 2 and the role played by the PVDF film during the degradation process.

Concentrated solar energy used for sintering magnesium titanates for electronic applications

NASA Astrophysics Data System (ADS)

Apostol, Irina; Rodríguez, Jose; Cañadas, Inmaculada; Galindo, Jose; Mendez, Senen Lanceros; de Abreu Martins, Pedro Libȃnio; Cunha, Luis; Saravanan, Kandasamy Venkata

2018-04-01

Solar energy is an important renewable source of energy with many advantages: it is unlimited, clean and free. The main objective of this work was to sinter magnesium titanate ceramics in a solar furnace using concentrated solar energy, which is a novel and original process. The direct conversion of solar power into high temperature makes this process simple, feasible and ecologically viable/environmentally sustainable. We performed the solar sintering experiments at Plataforma Solar de Almeria-CIEMAT, Spain. This process takes place in a vertical axis solar furnace (SF5-5 kW) hosting a mobile flat mirror heliostat, a fixed parabolic mirror concentrator, an attenuator and a test table the concentrator focus. We sintered (MgO)0.63(TiO2)0.37, (MgO)0.49(TiO2)0.51, (MgO)0.50(TiO2)0.50 ceramics samples in air at about 1100 °C for a duration of 16 min, 1 h, 2 h and 3 h in the solar furnace. The MgO/TiO2 ratio and the dwell time was varied in order to obtain phase pure MgTiO3 ceramic. We obtained a pure MgTiO3 geikielite phase by solar sintering of (MgO)0.63(TiO2)0.37 samples at 1100 °C (16 min-3 h). Samples of (MgO)0.63(TiO2)0.37, solar sintered at 1100 °C for 3 h, resulted in well-sintered, non-porous samples with good density (3.46 g/cm3). The sintered samples were analyzed by XRD for phase determination. The grain and surface morphology was observed using SEM. Electrical measurements were carried out on solar sintered samples. The effect of processing parameters on microstructure and dielectric properties were investigated and is presented.

Spinous TiO₂ and Au@TiO₂ octahedral nanocages: amorphisity-to-crystallinity transition-driven surface structural construction and photocatalytic study.

PubMed

Li, Jie; Zu, Lianhai; Li, Ying; Jin, Chao; Qin, Yao; Shi, Donglu; Yang, Jinhu

2014-07-15

Novel spinous TiO2 and Au@TiO2 octahedral nanocages have been prepared through a well-designed three-step strategy including templated TiO2 wet coating, subsequent structural ripening and final template removal or transformation. The strategy is built on an amorphisity-to-crystallinity transition-driven surface structural construction, which emphasizes the critical steps of crystallization-controlled TiO2 coating and consequent structural ripening. The influence of some key parameters, such as coating temperature, ripening temperature and ripening time, on the structure and morphology of the spinous TiO2 and Au@TiO2 nanocages have been investigated. In addition, in photocatalytic measurements, the prepared spinous TiO2-based nanocages exhibit enhanced photocatalytic efficiency relative to spinousless TiO2-based nanocages as well as P-25, owing to their structure advantages resulting from spinous surfaces. The photocatalytic activity of these TiO2 based photocatalysts has been systematically studied through the corresponding ·OH radical measurements. The synthetic strategy may work as a general method, through similarly designing, to realize surface structure engineering for various materials such as metals, hydroxide and other oxides besides TiO2. Copyright © 2014 Elsevier Inc. All rights reserved.

Hydrophilicity, photocatalytic activity and stability of tetraethyl orthosilicate modified TiO2 film on glazed ceramic surface

NASA Astrophysics Data System (ADS)

Zhang, Peng; Tian, Jie; Xu, Ruifen; Ma, Guojun

2013-02-01

A new, simple, and low-cost method has been developed to enhance the surface properties of TiO2 film. Degussa P25-TiO2 nanoparticles were modified by tetraethyl orthosilicate (TEOS) on glazed ceramic tiles. Effects of tetraethyl orthosilicate modification on microstructure, crystal structure, hydrophilicity, photocatalytic activity and stability of the film were investigated. The obtained results showed that P25-TiO2/TEOS particles exhibited better dispersion, higher surface area, bigger surface roughness and smaller particle size comparing to pure P25-TiO2 particles, which resulted in better hydrophilicity after 10 days in a dark place and higher photocatalytic activity under visible light irradiation. 68% of Rhodamine B was degraded by P25-TiO2/TEOS film in 25 h with the light intensity of 5000 ± 500 lx, and degradation rate reached to 82% with the light intensity of 10,000 ± 1000 lx. Furthermore, two fundamentally different systems, in which the films recycle for repetitive degradation after soaked in dye solution and for discoloration after depositing dye on the surfaces, respectively, were measured to confirm that P25-TiO2/TEOS film showed excellently stable performances. Therefore the P25-TiO2/TEOS film we obtained has good washing resistance and would be a promising candidate for practical applications.

Investigation of the surface potential of TiO2 (110) by frequency-modulation Kelvin probe force microscopy

NASA Astrophysics Data System (ADS)

Kou, Lili; Li, Yan Jun; Kamijyo, Takeshi; Naitoh, Yoshitaka; Sugawara, Yasuhiro

2016-12-01

We investigate the surface potential distribution on a TiO2 (110)-1 × 1 surface by Kelvin probe force microscopy (KPFM) and atom-dependent bias-distance spectroscopic mapping. The experimental results demonstrate that the local contact potential difference increases on twofold-coordinated oxygen sites, and decreases on OH defects and fivefold-coordinated Ti sites. We propose a qualitative model to explain the origin of the surface potential of TiO2 (110). We qualitatively calculate the surface potential induced by chemical potential and permanent surface dipole. The calculated results agree with our experimental ones. Therefore, we suggest that the surface potential of TiO2 (110) is dominated not only by the permanent surface dipole between the tip apex atom and surface, but also by the dipoles induced by the chemical interaction between the tip and sample. The KPFM technique demonstrate the possibility of investigation of the charge transfer phenomenon on TiO2 surface under gas conditions. It is useful for the elucidation of the mechanism of the catalytic reactions.

Investigation of the surface potential of TiO2 (110) by frequency-modulation Kelvin probe force microscopy.

PubMed

Kou, Lili; Li, Yan Jun; Kamijyo, Takeshi; Naitoh, Yoshitaka; Sugawara, Yasuhiro

2016-12-16

We investigate the surface potential distribution on a TiO 2 (110)-1 × 1 surface by Kelvin probe force microscopy (KPFM) and atom-dependent bias-distance spectroscopic mapping. The experimental results demonstrate that the local contact potential difference increases on twofold-coordinated oxygen sites, and decreases on OH defects and fivefold-coordinated Ti sites. We propose a qualitative model to explain the origin of the surface potential of TiO 2 (110). We qualitatively calculate the surface potential induced by chemical potential and permanent surface dipole. The calculated results agree with our experimental ones. Therefore, we suggest that the surface potential of TiO 2 (110) is dominated not only by the permanent surface dipole between the tip apex atom and surface, but also by the dipoles induced by the chemical interaction between the tip and sample. The KPFM technique demonstrate the possibility of investigation of the charge transfer phenomenon on TiO 2 surface under gas conditions. It is useful for the elucidation of the mechanism of the catalytic reactions.

Tunable growth of TiO2 nanostructures on Ti substrates

NASA Astrophysics Data System (ADS)

Peng, Xinsheng; Wang, Jingpeng; Thomas, Dan F.; Chen, Aicheng

2005-10-01

A simple and facile method is described to directly synthesize TiO2 nanostructures on titanium substrates by oxidizing Ti foil using small organic molecules as the oxygen source. The effect of reaction temperature and oxygen source on the formation of the TiO2 nanostructures has been studied using scanning electron microscopy, x-ray diffraction, transmission electron microscopy, Raman spectroscopy and water contact angle measurement. Polycrystalline grains are formed when pure oxygen and formic acid are used as the oxygen source; elongated micro-crystals are produced when water vapour is used as the oxygen source; oriented and aligned TiO2 nanorod arrays are synthesized when ethanol, acetaldehyde or acetone are used as the oxygen source. The growth mechanism of the TiO2 nanostructures is discussed. The diffusion of Ti atoms to the oxide/gas interface via the network of the grain boundaries of the thin oxide layer is the determining factor for the formation of well-aligned TiO2 nanorod arrays. The wetting properties of the TiO2 nanostructured surfaces formed are dictated by their structure, varying from a hydrophilic surface to a strongly hydrophobic surface as the surface structure changes from polycrystalline grains to well-aligned nanorod arrays. This tunable growth of TiO2 nanostructures is desirable for promising applications of TiO2 nanostructures in the development of optical devices, sensors, photo-catalysts and self-cleaning coatings.

Construction of hydrophobic wood surfaces by room temperature deposition of rutile (TiO2) nanostructures

Treesearch

Rongbo Zheng; Mandla A. Tshabalala; Qingyu Li; Hongyan Wang

2015-01-01

A convenient room temperature approach was developed for growing rutile TiO2 hierarchical structures on the wood surface by direct hydrolysis and crystallization of TiCl3 in saturated NaCl aqueous solution.The morphology and the crystal structure of TiO2 coated on the wood surface were characterized...

Antibacterial activity of DLC films containing TiO2 nanoparticles.

PubMed

Marciano, F R; Lima-Oliveira, D A; Da-Silva, N S; Diniz, A V; Corat, E J; Trava-Airoldi, V J

2009-12-01

Diamond-like carbon (DLC) films have been the focus of extensive research in recent years due to their potential applications as surface coatings on biomedical devices. Titanium dioxide (TiO2) in the anatase crystalline form is a strong bactericidal agent when exposed to near-UV light. In this work we investigate the bactericidal activity of DLC films containing TiO2 nanoparticles. The films were grown on 316L stainless-steel substrates from a dispersion of TiO2 in hexane using plasma-enhanced chemical vapor deposition. The composition, bonding structure, surface energy, stress, and surface roughness of these films were also evaluated. The antibacterial tests were performed against Escherichia coli (E. coli) and the results were compared to the bacterial adhesion force to the studied surfaces. The presence of TiO2 in DLC bulk was confirmed by Raman spectroscopy. As TiO2 content increased, I(D)/I(G) ratio, hydrogen content, and roughness also increased; the films became more hydrophilic, with higher surface free energy and the interfacial energy of bacteria adhesion decreased. Experimental results show that TiO2 increased DLC bactericidal activity. Pure DLC films were thermodynamically unfavorable to bacterial adhesion. However, the chemical interaction between the E. coli and the studied films increased for the films with higher TiO2 concentration. As TiO2 bactericidal activity starts its action by oxidative damage to the bacteria wall, a decrease in the interfacial energy of bacteria adhesion causes an increase in the chemical interaction between E. coli and the films, which is an additional factor for the increasing bactericidal activity. From these results, DLC with TiO2 nanoparticles can be useful for producing coatings with antibacterial properties.

Temperature-programmed desorption study of NO reactions on rutile TiO2(110)-1×1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Boseong; Dohnálek, Zdenek; Szanyi, János

2016-10-01

Systematic temperature-programmed desorption (TPD) studies of NO adsorption and reactions on rutile TiO2(110)-1×1 surface reveal several distinct reaction channels in a temperature range of 50 – 500 K. NO readily reacts on TiO2(110) to form N2O which desorbs between 50 and 200 K (LT N2O channels), which leaves the TiO2 surface populated with adsorbed oxygen atoms (Oa) as a byproduct of N2O formation. In addition, we observe simultaneous desorption peaks of NO and N2O at 270 K (HT1 N2O) and 400 K (HT2 N2O), respectively, both of which are attributed to reaction-limited processes. No N-derived reaction product desorbs from TiO2(110)more » surface above 500 K or higher, while the surface may be populated with Oa’s and oxidized products such as NO2 and NO3. The adsorbate-free TiO2 surface with oxygen vacancies can be regenerated by prolonged annealing at 850 K or higher. Detailed analysis of the three N2O desorption yields reveals that the surface species for the HT channels are likely to be various forms of NO dimers.« less

Temperature-programmed desorption study of NO reactions on rutile TiO 2(110)-1×1

DOE PAGES

Kim, Boseong; Dohnalek, Zdenek; Szanyi, Janos; ...

2016-02-24

In this study, systematic temperature-programmed desorption (TPD) studies of NO adsorption and reactions on rutile TiO 2(110)-1 × 1 surface reveal several distinct reaction channels in a temperature range of 50–500 K. NO readily reacts on TiO 2(110) to form N 2O, which desorbs between 50 and 200 K (LT N 2O channels), which leaves the TiO 2 surface populated with adsorbed oxygen atoms (O a) as a by-product of N 2O formation. In addition, we observe simultaneous desorption peaks of NO and N 2O at 270 K (HT1 N 2O) and 400 K (HT2 N 2O), respectively, both ofmore » which are attributed to reaction-limited processes. No N-derived reaction product desorbs from TiO 2(110) surface above 500 K or higher, while the surface may be populated with Oa's and oxidized products such as NO 2 and NO 3. The adsorbate-free TiO 2 surface with oxygen vacancies can be regenerated by prolonged annealing at 850 K or higher. Detailed analysis of the three N 2O desorption yields reveals that the surface species for the HT channels are likely to be various forms of NO dimers.« less

The Effects of Anchor Groups on (1) TiO2-Catalyzed Photooxidation and (2) Linker-Assisted Assembly on TiO2

NASA Astrophysics Data System (ADS)

Anderson, Ian Mark

Quantum dot-sensitized solar cells (QDSSCs) are a popular target for research due to their potential for highly efficient, easily tuned absorption. Typically, light is absorbed by quantum dots attached to a semiconductor substrate, such as TiO2, via bifunctional linker molecules. This research aims to create a patterned monolayer of linker molecules on a TiO2 film, which would in turn allow the attachment of a patterned layer of quantum dots. One method for the creation of a patterned monolayer is the functionalization of a TiO2 film with a linker molecule, followed by illumination with a laser at 355 nm. This initiates a TiO 2-catalyzed oxidation reaction, causing loss of surface coverage. A second linker molecule can then be adsorbed onto the TiO2 surface in the illuminated area. Towards that end, the behaviors of carboxylic and phosphonic acids adsorbed on TiO2 have been studied. TiO2 films were functionalized by immersion in solutions a single adsorbate and surface coverage was determined by IR spectroscopy. It is shown that phosphonic acids attain higher surface coverage than carboxylic acids, and will displace them from TiO2 when in a polar solvent. Alkyl chain lengths, which can influence stabilities of monolayers, are shown not to have an effect on this relationship. Equilibrium binding data for the adsorption of n-hexadecanoic acid to TiO2 from a THF solution are presented. It is shown that solvent polarity can affect monolayer stability; carboxylates and phosphonates undergo more desorption into polar solvents than nonpolar. Through illumination, it was possible to remove nearly all adsorbed linkers from TiO2. However, the illuminated areas were found not to be receptive to attachment by a second adsorbate. A possible reason for this behavior is presented. I also report on the synthesis and characterization of a straight-chain, thiol-terminated phosphonic acid. Initial experiments involving monolayer formation and quantum dot attachment are presented. Finally, it was found that quantum dots attach in high amounts to linker-functionalized TiO2 when suspended in pyridine. This increased surface attachment was present even when the linker molecule used lacked a functional group which would bind to the CdSe surface.

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

PubMed

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. Copyright © 2014 Elsevier Inc. All rights reserved.

A Surface Science Perspective on TiO2 Photocatalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henderson, Michael A.

2011-06-15

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

The influence of local electric fields on photoinduced absorption in dye-sensitized solar cells.

PubMed

Cappel, Ute B; Feldt, Sandra M; Schöneboom, Jan; Hagfeldt, Anders; Boschloo, Gerrit

2010-07-07

The dye-sensitized solar cell (DSC) challenges conventional photovoltaics with its potential for low-cost production and its flexibility in terms of color and design. Transient absorption spectroscopy is widely used to unravel the working mechanism of DSCs. A surprising, unexplained feature observed in these studies is an apparent bleach of the ground-state absorption of the dye, under conditions where the dye is in the ground state. Here, we demonstrate that this feature can be attributed to a change of the local electric field affecting the absorption spectrum of the dye, an effect related to the Stark effect first reported in 1913. We present a method for measuring the effect of an externally applied electric field on the absorption of dye monolayers adsorbed on flat TiO(2) substrates. The measured signal has the shape of the first derivative of the absorption spectra of the dyes and reverses sign along with the reversion of the direction of the change in dipole moment upon excitation relative to the TiO(2) surface. A very similar signal is observed in photoinduced absorption spectra of dye-sensitized TiO(2) electrodes under solar cell conditions, demonstrating that the electric field across the dye molecules changes upon illumination. This result has important implications for the analysis of transient absorption spectra of DSCs and other molecular optoelectronic devices and challenges the interpretation of many previously published results.

Study of the Effect of Nanoparticles and Surface Morphology on Reverse Osmosis and Nanofiltration Membrane Productivity

PubMed Central

Fang, Yuming; Duranceau, Steven J.

2013-01-01

To evaluate the significance of reverse osmosis (RO) and nanofiltration (NF) surface morphology on membrane performance, productivity experiments were conducted using flat-sheet membranes and three different nanoparticles, which included SiO2, TiO2 and CeO2. In this study, the productivity rate was markedly influenced by membrane surface morphology. Atomic force microscopy (AFM) analysis of membrane surfaces revealed that the higher productivity decline rates associated with polyamide RO membranes as compared to that of a cellulose acetate NF membrane was due to the inherent ridge-and-valley morphology of the active layer. The unique polyamide active layer morphology was directly related to the surface roughness, and was found to contribute to particle accumulation in the valleys causing a higher flux decline than in smoother membranes. Extended RO productivity experiments using laboratory grade water and diluted pretreated seawater were conducted to compare the effect that different nanoparticles had on membrane active layers. Membrane flux decline was not affected by particle type when the feed water was laboratory grade water. On the other hand, membrane productivity was affected by particle type when pretreated diluted seawater served as feed water. It was found that CeO2 addition resulted in the least observable flux decline, followed by SiO2 and TiO2. A productivity simulation was conducted by fitting the monitored flux data into a cake growth rate model, where the model was modified using a finite difference method to incorporate surface thickness variation into the analysis. The ratio of cake growth term (k1) and particle back diffusion term (k2) was compared in between different RO and NF membranes. Results indicated that k2 was less significant for surfaces that exhibited a higher roughness. It was concluded that the valley areas of thin-film membrane surfaces have the ability to capture particles, limiting particle back diffusion. PMID:24956946

Development of high dispersed TiO2 paste for transparent screen-printable self-cleaning coatings on glass

NASA Astrophysics Data System (ADS)

Wang, Yuanhao; Lu, Lin; Yang, Hongxing; Che, Quande

2013-01-01

This paper reports a cheap and facile method to fabricate transparent self-cleaning coatings on glass by screen-printing high dispersed TiO2 paste. Three kinds of ZrO2 beads with diameter of 2, 1, and 0.1-0.2 mm were utilized to investigate their influence on the grinding and dispersion of the commercial TiO2 powder in the ball mill. From the SEM images, surface profiler and transmittance spectrum it could be demonstrated that the smallest ZrO2 bead with the diameter of 0.1-0.2 mm was the best candidate to disperse the TiO2 powder into nanoscale size to make the high dispersed TiO2 paste which was the key factor to achieve a smooth, high transparent TiO2 coating. The surface wettability measurement showed that all the screen-printed coatings had super hydrophilic surfaces, which was independent to the surface morphology. However, the coating with the highest transparency showed the lowest photocatalytic activity which is mainly due to the light loss.

Surface Modified TiO2 Obscurants for Increased Safety and Performance

DTIC Science & Technology

2012-11-01

based obscurant devices in performance. 15. SUBJECT TERMS Obscurant, visible, IR , smoke, TiO2, aerosol, particle, surface modification...hexamethyldimethoxysilane IR Infrared wavelength LabRAM Lab scale Resonant Acoustic Mixer from Resodyn Corporation LPM Liters Per Minute M106 Currently fielded (Army...trinitrophloroglucinol UV-Vis Ultraviolet-visible wavelengths KEYWORDS Obscurant, visible, IR , smoke, TiO2, aerosol, particle, surface modification

Elementary photocatalytic chemistry on TiO2 surfaces.

PubMed

Guo, Qing; Zhou, Chuanyao; Ma, Zhibo; Ren, Zefeng; Fan, Hongjun; Yang, Xueming

2016-07-07

Photocatalytic hydrogen production and pollutant degradation provided both great opportunities and challenges in the field of sustainable energy and environmental science. Over the past few decades, we have witnessed fast growing interest and efforts in developing new photocatalysts, improving catalytic efficiency and exploring the reaction mechanism at the atomic and molecular levels. Owing to its relatively high efficiency, nontoxicity, low cost and high stability, TiO2 becomes one of the most extensively investigated metal oxides in semiconductor photocatalysis. Fundamental studies on well characterized single crystals using ultrahigh vacuum based surface science techniques could provide key microscopic insight into the underlying mechanism of photocatalysis. In this review, we have summarized recent progress in the photocatalytic chemistry of hydrogen, water, oxygen, carbon monoxide, alcohols, aldehydes, ketones and carboxylic acids on TiO2 surfaces. We focused this review mainly on the rutile TiO2(110) surface, but some results on the rutile TiO2(011), anatase TiO2(101) and (001) surfaces are also discussed. These studies provided fundamental insights into surface photocatalysis as well as stimulated new investigations in this exciting field. At the end of this review, we have discussed how these studies can help us to develop new photocatalysis models.

Tailoring of TiO2 films by H2SO4 treatment and UV irradiation to improve anticoagulant ability and endothelial cell compatibility.

PubMed

Liao, Yuzhen; Li, Linhua; Chen, Jiang; Yang, Ping; Zhao, Ansha; Sun, Hong; Huang, Nan

2017-07-01

Surfaces with dual functions that simultaneously exhibit good anticoagulant ability and endothelial cell (EC) compatibility are desirable for blood contact materials. However, these dual functions have rarely been achieved by inorganic materials. In this study, titanium dioxide (TiO 2 ) films were treated by sulphuric acid (H 2 SO 4 ) and ultraviolet (UV) irradiation successively (TiO 2 H 2 SO 4 -UV), resulting in good anticoagulant ability and EC compatibility simultaneously. We found that UV irradiation improved the anticoagulant ability of TiO 2 films significantly while enhancing EC compatibility, though not significantly. The enhanced anticoagulant ability could be related to the oxidation of surface-adsorbed hydrocarbons and increased hydrophilicity. The H 2 SO 4 treatment improved the anticoagulant ability of TiO 2 films slightly, while UV irradiation improved the anticoagulant ability strongly. The enhanced EC compatibility could be related to the increased surface roughness and positive charges on the surface of the TiO 2 films. Furthermore, the time-dependent degradation of the enhanced EC compatibility and anticoagulant ability of TiO 2 H 2 SO 4 -UV was observed. In summary, TiO 2 H 2 SO 4 -UV expressed both excellent anticoagulant ability and good EC compatibility at the same time, which could be desirable for blood contact materials. However, the compatibility of TiO 2 H 2 SO 4 -UV with smooth muscle cells (SMCs) and macrophages was also improved. More effort is still needed to selectively improve EC compatibility on TiO 2 films for better re-endothelialization. Copyright © 2017 Elsevier B.V. All rights reserved.

Hydrogenated TiO2 Branches Coated Mn3O4 Nanorods as an Advanced Anode Material for Lithium Ion Batteries.

PubMed

Wang, Nana; Yue, Jie; Chen, Liang; Qian, Yitai; Yang, Jian

2015-05-20

Rational design and delicate control on the component, structure, and surface of electrodes in lithium ion batteries are highly important to their performances in practical applications. Compared with various components and structures for electrodes, the choices for their surface are quite limited. The most widespread surface for numerous electrodes, a carbon shell, has its own issues, which stimulates the desire to find another alternative surface. Here, hydrogenated TiO2 is exemplified as an appealing surface for advanced anodes by the growth of ultrathin hydrogenated TiO2 branches on Mn3O4 nanorods. High theoretical capacity of Mn3O4 is well matched with low volume variation (∼4%), enhanced electrical conductivity, good cycling stability, and rate capability of hydrogenated TiO2, as demonstrated in their electrochemical performances. The proof-of-concept reveals the promising potential of hydrogenated TiO2 as a next-generation material for the surface in high-performance hybrid electrodes.

Influence of square wave anodization on the electronic properties and structures of the passive films on Ti in sulfuric acid solution

NASA Astrophysics Data System (ADS)

Long, Y.; Li, D. G.; Chen, D. R.

2017-12-01

Two types of square wave anodization (type 1 and type 2) were employed in this work to form a passive film on Ti in a 0.5 M H2SO4 solution. The influences of the anodization potential and duration on the electronic properties and structures of the passive films were studied by Mott-Schottky plots, auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The results showed that the donor density, ND, of the passive film decreased and the flat band potential, EFB, shifted to the positive direction with the increase of the anodization duration and high anodization potential irrespective of whether type 1 or type 2 was used. Moreover, the passive film that formed on Ti using type 1 had a lower donor density and a more positive flat band potential than that on Ti using type 2 at one fixed anodization duration (only exchanging the anodization order of 1 V and the high potential). XPS analysis revealed that the outmost passive film was only composed of TiO2, the inner passive film was mainly composed of TiO2 with some amount of TiO and Ti2O3, and the TiO2 concentration in the outermost passive film increased with the increase of the anodization duration and the high potential in the case of using type 1 or type 2, implying an increased degree of crystallinity. The AES results showed that the O/Ti atomic ratio of the passive film obviously increased with the increasing anodization duration and high potential, demonstrating the increased homogeneous characteristic of the passive film; this was in agreement with the Mott-Schottky and XPS results.

Modifications of nano-titania surface for in vitro evaluations of hemolysis, cytotoxicity, and nonspecific protein binding

NASA Astrophysics Data System (ADS)

Datta, Aparna; Dasgupta, Sayantan; Mukherjee, Siddhartha

2017-04-01

In the past decade, a variety of drug carriers based on mesoporous silica nanoparticles has been extensively reported. However, their biocompatibility still remains debatable, which motivated us to explore the porous nanostructures of other metal oxides, for example titanium dioxide (TiO2), as potential drug delivery vehicles. Herein, we report the in vitro hemolysis, cytotoxicity, and protein binding of TiO2 nanoparticles, synthesized by a sol-gel method. The surface of the TiO2 nanoparticles was modified with hydroxyl, amine, or thiol containing moieties to examine the influence of surface functional groups on the toxicity and protein binding aspects of the nanoparticles. Our study revealed the superior hemocompatibility of pristine, as well as functionalized TiO2 nanoparticles, compared to that of mesoporous silica, the present gold standard. Among the functional groups studied, aminosilane moieties on the TiO2 surface substantially reduced the degree of hemolysis (down to 5%). Further, cytotoxicity studies by MTT assay suggested that surface functional moieties play a crucial role in determining the biocompatibility of the nanoparticles. The presence of NH2- functional groups on the TiO2 nanoparticle surface enhanced the cell viability by almost 28% as compared to its native counterpart (at 100 μg/ml), which was in agreement with the hemolysis assay. Finally, nonspecific protein adsorption on functionalized TiO2 surfaces was examined using human serum albumin and it was found that negatively charged surface moieties, like -OH and -SH, could mitigate protein adsorption to a significant extent.

Preparation of RuO2-TiO2/Nano-graphite composite anode for electrochemical degradation of ceftriaxone sodium.

PubMed

Li, Dong; Guo, Xiaolei; Song, Haoran; Sun, Tianyi; Wan, Jiafeng

2018-06-05

Graphite-like material is widely used for preparing various electrodes for wastewater treatment. To enhance the electrochemical degradation efficiency of Nano-graphite (Nano-G) anode, RuO 2 -TiO 2 /Nano-G composite anode was prepared through the sol-gel method and hot-press technology. RuO 2 -TiO 2 /Nano-G composite was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and N 2 adsorption-desorption. Results showed that RuO 2 , TiO 2 and Nano-G were composited successfully, and RuO 2 and TiO 2 nanoparticles were distributed uniformly on the surface of Nano-G sheet. Specific surface area of RuO 2 -TiO 2 /Nano-G composite was higher than that of TiO 2 /Nano-G composite and Nano-G. Electrochemical performances of RuO 2 -TiO 2 /Nano-G anode were investigated by cyclic voltammetry, electrochemical impedance spectroscopy. RuO 2 -TiO 2 /Nano-G anode was applied to electrochemical degradation of ceftriaxone. The generation of hydroxyl radical (OH) was measured. Results demonstrated that RuO 2 -TiO 2 /Nano-G anode displayed enhanced electrochemical degradation efficiency towards ceftriaxone and yield of OH, which is derived from the synergetic effect between RuO 2 , TiO 2 and Nano-G, which enhance the specific surface area, improve the electrochemical oxidation activity and lower the charge transfer resistance. Besides, the possible degradation intermediates and pathways of ceftriaxone sodium were identified. This study may provide a viable and promising prospect for RuO 2 -TiO 2 /Nano-G anode towards effective electrochemical degradation of antibiotics from wastewater. Copyright © 2018 Elsevier B.V. All rights reserved.

Noble metal nanoparticle-decorated TiO2 nanobelts for enhanced photocatalysis

NASA Astrophysics Data System (ADS)

He, Haiyan; Yang, Ping; Jia, Changchao; Miao, Yanping; Zhao, Jie; Du, Yingying

2014-07-01

TiO2 nanobelts have been fabricated through a hydrothermal method and subsequently sulfuric-acid-corrosion-treated for a rough surface. Noble metal nanoparticles such as Ag and Au were deposited on the coarse surface of TiO2 nanobelts via a coprecipitation procedure. Ag-TiO2 nanobelts were prepared in ethanolic solution contained silver nitrate (AgNO3) and sodium hydroxide (NaOH). Au-TiO2 nanobelts were obtained in chloroauric acid (HAuCl4) using sodium borohydride (NaBH4) as the reductant. It is confirmed by the results of XRD patterns together with the SEM images that the composite of noble metal and TiO2 nanobelts were obtained successfully and the Ag or Au nanoparticles were well-dispersed on the TiO2 nanobelts. Moreover, the as-prepared Ag and Au nanoparticle-decorated TiO2 nanobelts represent an enhanced photocatalytic activity compared with pure TiO2 nanobelts, which is due to the fact that the Ag and Au nanoparticles on the surface of TiO2 nanobelts act as sinks for the photogenerated electrons and promote the separation of the electrons and holes.

Surface modification of mixed-phase hydrogenated TiO2 and corresponding photocatalytic response

NASA Astrophysics Data System (ADS)

Samsudin, Emy Marlina; Hamid, Sharifah Bee Abd; Juan, Joon Ching; Basirun, Wan Jefrey; Kandjani, Ahmad Esmaielzadeh

2015-12-01

Preparation of highly photo-activated TiO2 is achievable by hydrogenation at constant temperature and pressure, with controlled hydrogenation duration. The formation of surface disorders and Ti3+ is responsible for the color change from white unhydrogenated TiO2 to bluish-gray hydrogenated TiO2. This color change, together with increased oxygen vacancies and Ti3+ enhanced the solar light absorption from UV to infra-red region. Interestingly, no band gap narrowing is observed. The photocatalytic activity in the UV and visible region is controlled by Ti3+ and oxygen vacancies respectively. Both Ti3+ and oxygen vacancies increases the electron density on the catalyst surface thus facilitates rad OH radicals formation. The lifespan of surface photo-excited electrons and holes are also sustained thus prevents charge carrier recombination. However, excessive amount of oxygen vacancies deteriorates the photocatalytic activity as it serves as charge traps. Hydrogenation of TiO2 also promotes the growth of active {0 0 1} facets and facilitates the photocatalytic activity by higher concentration of surface OH radicals. However, the growth of {0 0 1} facets is small and insignificant toward the overall photo-kinetics. This work also shows that larger role is played by Ti3+ and oxygen vacancies rather than the surface disorders created during the hydrogenation process. It also demonstrates the ability of hydrogenated TiO2 to absorb wider range of photons even though at a similar band gap as unhydrogenated TiO2. In addition, the photocatalytic activity is shown to be decreased for extended hydrogenation duration due to excessive catalyst growth and loss in the total surface area. Thus, a balance in the physico-chemical properties of hydrogenated TiO2 is crucial to enhance the photocatalytic activity by simply controlling the hydrogenation duration.

Locating structures and evolution pathways of reconstructed rutile TiO2(011) using genetic algorithm aided density functional theory calculations.

PubMed

Ding, Pan; Gong, Xue-Qing

2016-05-01

Titanium dioxide (TiO2) is an important metal oxide that has been used in many different applications. TiO2 has also been widely employed as a model system to study basic processes and reactions in surface chemistry and heterogeneous catalysis. In this work, we investigated the (011) surface of rutile TiO2 by focusing on its reconstruction. Density functional theory calculations aided by a genetic algorithm based optimization scheme were performed to extensively sample the potential energy surfaces of reconstructed rutile TiO2 structures that obey (2 × 1) periodicity. A lot of stable surface configurations were located, including the global-minimum configuration that was proposed previously. The wide variety of surface structures determined through the calculations performed in this work provide insight into the relationship between the atomic configuration of a surface and its stability. More importantly, several analytical schemes were proposed and tested to gauge the differences and similarities among various surface structures, aiding the construction of the complete pathway for the reconstruction process.

Selective adsorption of bovine hemoglobin on functional TiO2 nano-adsorbents: surface physic-chemical properties determined adsorption activity

NASA Astrophysics Data System (ADS)

Guo, Shiguang; Zhang, Jianghua; Shao, Mingxue; Zhang, Xia; Liu, Yufeng; Xu, Junli; Meng, Hao; Han, Yide

2015-04-01

Surface functionalized nanoparticles are efficient adsorbents which have shown good potential for protein separation. In this work, we chose two different types of organic molecules, oleic acid (OA) and 3-glycidoxypropyltrimethoxy silane (GPTMS), to functionalize the surface of TiO2 nanoparticles, and we studied the effects of this modification on their surface physicochemical properties in correlation with their selective adsorption of proteins. The results showed that the surface zeta potential and the surface water wettability of the modified TiO2 were significantly changed in comparison with the original TiO2 nanoparticles. The adsorption activities of bovine hemoglobin (BHb) and bovine serum albumin (BSA) on these functionalized TiO2 samples were investigated under different conditions, including pH values, contact time, ion strength, and initial protein concentration. In comparison with the non-specific adsorption of original TiO2, however, both the OA-TiO2 and GPTMS-TiO2 exhibited increased BHb adsorption and decreased BSA adsorption at the same time. Using a binary protein mixture as the adsorption object, a higher separation factor (SF) was obtained for OA-TiO2 under optimum conditions. The different adsorption activities of BHb and BSA on the modified TiO2 were correlated with different interactions at the protein/solid interface, and the chemical force as well as the electrostatic force played an important role in the selective adsorption process.

Promoted Fixation of Molecular Nitrogen with Surface Oxygen Vacancies on Plasmon-Enhanced TiO2 Photoelectrodes.

PubMed

Li, Chengcheng; Wang, Tuo; Zhao, Zhi-Jian; Yang, Weimin; Li, Jian-Feng; Li, Ang; Yang, Zhilin; Ozin, Geoffrey A; Gong, Jinlong

2018-05-04

A hundred years on, the energy-intensive Haber-Bosch process continues to turn the N 2 in air into fertilizer, nourishing billions of people while causing pollution and greenhouse gas emissions. The urgency of mitigating climate change motivates society to progress toward a more sustainable method for fixing N 2 that is based on clean energy. Surface oxygen vacancies (surface O vac ) hold great potential for N 2 adsorption and activation, but introducing O vac on the very surface without affecting bulk properties remains a great challenge. Fine tuning of the surface O vac by atomic layer deposition is described, forming a thin amorphous TiO 2 layer on plasmon-enhanced rutile TiO 2 /Au nanorods. Surface O vac in the outer amorphous TiO 2 thin layer promote the adsorption and activation of N 2 , which facilitates N 2 reduction to ammonia by excited electrons from ultraviolet-light-driven TiO 2 and visible-light-driven Au surface plasmons. The findings offer a new approach to N 2 photofixation under ambient conditions (that is, room temperature and atmospheric pressure). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pt-Enhanced Mesoporous Ti3+/TiO2 with Rapid Bulk to Surface Electron Transfer for Photocatalytic Hydrogen Evolution.

PubMed

Lian, Zichao; Wang, Wenchao; Li, Guisheng; Tian, Fenghui; Schanze, Kirk S; Li, Hexing

2017-05-24

Pt-doped mesoporous Ti 3+ self-doped TiO 2 (Pt-Ti 3+ /TiO 2 ) is in situ synthesized via an ionothermal route, by treating metallic Ti in an ionic liquid containing LiOAc, HOAc, and a H 2 PtCl 6 aqueous solution under mild ionothermal conditions. Such Ti 3+ -enriched environment, as well as oxygen vacancies, is proven to be effective for allowing the in situ reduction of Pt 4+ ions uniformly located in the framework of the TiO 2 bulk. The photocatalytic H 2 evolution of Pt-Ti 3+ /TiO 2 is significantly higher than that of the photoreduced Pt loaded on the original TiO 2 and commercial P25. Such greatly enhanced activity is due to the various valence states of Pt (Pt n+ , n = 0, 2, or 3), forming Pt-O bonds embedded in the framework of TiO 2 and ultrafine Pt metal nanoparticles on the surface of TiO 2 . Such Pt n+ -O bonds could act as the bridges for facilitating the photogenerated electron transfer from the bulk to the surface of TiO 2 with a higher electron carrier density (3.11 × 10 20 cm -3 ), about 2.5 times that (1.25 × 10 20 cm -3 ) of the photoreduced Pt-Ti 3+ /TiO 2 sample. Thus, more photogenerated electrons could reach the Pt metal for reducing protons to H 2 .

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

NASA Astrophysics Data System (ADS)

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

2015-10-01

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

Preparation of weak-light-driven TiO2-based catalysts via adsorbed-layer nanoreactor synthesis and enhancement of their photo-degradation performance in seawater

NASA Astrophysics Data System (ADS)

Wang, Ting; Xu, Zhi-yong; Zhu, Yi-chen; Wu, Li-guang; Yuan, Hao-xuan; Li, Chang-chun; Liu, Ya-yu; Cai, Jing

2017-11-01

Graphene oxide (GO) was first employed as a support in preparing TiO2 nanoparticles by adsorbed-layer nanoreactor synthesis (ALNS). Both TiO2 crystallization and GO reduction simultaneously occurred during solvothermal treatment with alcohol as a solvent. By transmission electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and photoluminescence spectroscopy, the results showed that TiO2 nanoparticles with less than 10 nm of size distributed very homogeneously on the GO surface. Tight interaction between TiO2 particles and GO surface could effectively inhibit the aggregation of TiO2 particles, during solvothermal treatment for anatase TiO2 formation. Alcohol could also reduce oxygenated functional groups on GO surface after solvothermal treatment. TiO2 particles with small size and the decrease in oxygenated functional groups on the GO surface both caused high separation efficiency of photo-generated charge carriers, thus resulting in high photo-degradation performance of catalysts. Strong phenol adsorption on photocatalyst was key to enhancing photo-degradation efficiency for phenol in seawater. Moreover, the change in catalyst structure was minimal at different temperatures of solvothermal treatment. But, the degradation rate and efficiency for phenol in seawater were obviously enhanced because of the sensitive structure-activity relationship of catalysts under weak-light irradiation.

Charge-transfer complex formation between TiO2 nanoparticles and thiosalicylic acid: A comprehensive experimental and DFT study

NASA Astrophysics Data System (ADS)

Milićević, Bojana; Đorđević, Vesna; Lončarević, Davor; Dostanić, Jasmina M.; Ahrenkiel, S. Phillip; Dramićanin, Miroslav D.; Sredojević, Dušan; Švrakić, Nenad M.; Nedeljković, Jovan M.

2017-11-01

Under normal conditions, titanium dioxide does not absorb visible light photons due to large band gap. Nevertheless, when titanium dioxide nanoparticles (TiO2 NPs) are surface-modified with thiosalicylic acid (TSA), their optical properties are altered owing to the formation of charge transfer complex that initiates absorption in the visible spectral range. Colloidal and sol-gel techniques were used to synthesize uniform TiO2 NPs of different sizes (average diameters in the range 4-15 nm), and effects of their subsequent modification by TSA molecules were compared with effect of modification of commercial Degussa TiO2 powder. Thorough microstructural characterization of TiO2 nanoparticulates was performed including transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis, as well as nitrogen adsorption-desorption isotherms. Optical measurements revealed that all surface-modified TiO2 samples with TSA have similar spectral features independent of their morphological differences, and, more importantly, absorption onset of modified TiO2 samples was found to be red-shifted by 1.0 eV compared to the unmodified ones. The mode of binding between TSA and surface Ti atoms was analyzed by infrared spectroscopy. Finally, the quantum chemical calculations, based on density functional theory, were performed to support optical characterization of surface-modified TiO2 with TSA.

Tunable top-down fabrication and functional surface coating of single-crystal titanium dioxide nanostructures and nanoparticles

NASA Astrophysics Data System (ADS)

Ha, Seungkyu; Janissen, Richard; Ussembayev, Yera Ye.; van Oene, Maarten M.; Solano, Belen; Dekker, Nynke H.

2016-05-01

Titanium dioxide (TiO2) is a key component of diverse optical and electronic applications that exploit its exceptional material properties. In particular, the use of TiO2 in its single-crystalline phase can offer substantial advantages over its amorphous and polycrystalline phases for existing and yet-to-be-developed applications. However, the implementation of single-crystal TiO2 has been hampered by challenges in its fabrication and subsequent surface functionalization. Here, we introduce a novel top-down approach that allows for batch fabrication of uniform high-aspect-ratio single-crystal TiO2 nanostructures with targeted sidewall profiles. We complement our fabrication approach with a functionalization strategy that achieves dense, uniform, and area-selective coating with a variety of biomolecules. This allows us to fabricate single-crystal rutile TiO2 nanocylinders tethered with individual DNA molecules for use as force- and torque-transducers in an optical torque wrench. These developments provide the means for increased exploitation of the superior material properties of single-crystal TiO2 at the nanoscale.Titanium dioxide (TiO2) is a key component of diverse optical and electronic applications that exploit its exceptional material properties. In particular, the use of TiO2 in its single-crystalline phase can offer substantial advantages over its amorphous and polycrystalline phases for existing and yet-to-be-developed applications. However, the implementation of single-crystal TiO2 has been hampered by challenges in its fabrication and subsequent surface functionalization. Here, we introduce a novel top-down approach that allows for batch fabrication of uniform high-aspect-ratio single-crystal TiO2 nanostructures with targeted sidewall profiles. We complement our fabrication approach with a functionalization strategy that achieves dense, uniform, and area-selective coating with a variety of biomolecules. This allows us to fabricate single-crystal rutile TiO2 nanocylinders tethered with individual DNA molecules for use as force- and torque-transducers in an optical torque wrench. These developments provide the means for increased exploitation of the superior material properties of single-crystal TiO2 at the nanoscale. Electronic supplementary information (ESI) available: Experimental details (ESI Methods) of the optic axis orientation of TiO2 nanocylinders, Cr etch mask fabrication, surface functionalization and its evaluation using fluorescence microscopy, preparation of DNA constructs, assembly of flow cells, bioconjugation of TiO2 nanocylinders, OTW instrumentation and measurements; TiO2 dry etching optimization and the etching parameters employed (Tables S1 and S2); dimensional analysis of TiO2 nanocylinders (Table S3); diverse applications of TiO2 at the nanoscale (Fig. S1); selection of etch mask material (Fig. S2); control of sidewall profiles in TiO2 etching (Fig. S3); size distributions of TiO2 nanocylinders (Fig. S4); quantitative comparisons of different surface linker molecules (Fig. S5); DLS measurements on TiO2 nanocylinders (Fig. S6); optical trap calibration (Fig. S7); and supplementary references. See DOI: 10.1039/c6nr00898d

Electronic coupling in iron oxide-modified TiO2 leads to a reduced band gap and charge separation for visible light active photocatalysis.

PubMed

Nolan, Michael

2011-10-28

In recent experiments Tada et al. have shown that TiO(2) surfaces modified with iron oxide display visible light photocatalytic activity. This paper presents first principles simulations of iron oxide clusters adsorbed at the rutile TiO(2) (110) surface to elucidate the origin of the visible light photocatalytic activity of iron oxide modified TiO(2). Small iron oxide clusters adsorb at rutile (110) surface and their presence shifts the valence band so that the band gap of the composite is narrowed towards the visible, thus confirming the origin of the visible light activity of this composite material. The presence of iron oxide at the TiO(2) surface leads to charge separation, which is the origin of enhanced photocatalytic efficiency, consistent with experimental photoluminesence and photocurrent data. Surface modification of a metal oxide is thus an interesting route in the development of visible light photocatalytic materials. This journal is © the Owner Societies 2011

Computational study of TiO2 Brookite (100), (010) and (210) surface doped with Ruthenium for application in Dye Sensitised Solar Cells

NASA Astrophysics Data System (ADS)

Dima, R. S.; Maluta, N. E.; Maphanga, R. R.; Sankaran, V.

2017-10-01

Titanium dioxide (TiO2) polymorphs are widely used in many energy-related applications due to their peculiar electronic and physicochemical properties. The electronic structures of brookite TiO2 surfaces doped with transition metal ruthenium have been investigated by ab initio band calculations based on the density functional theory with the planewave ultrasoft pseudopotential method. The generalized gradient approximation (GGA) was used in the scheme of Perdew-Burke-Ernzerhof (PBE) to describe the exchange-correlation functional. All calculations were carried out with CASTEP (Cambridge Sequential Total EnergyPackage) code in Materials Studio of Accelrys Inc. The surface structures of Ru doped TiO2 were constructed by cleaving the 1 × 1 × 1 optimized bulk structure of brookite TiO2. The results indicate that Ru doping can narrow the band gap of TiO2, leading to the improvement in the photoreactivity of TiO2, and simultaneously maintain strong redox potential. The theoretical calculations could provide meaningful guide to develop more active photocatalysts with visible light response.

Top-down synthesized TiO2 nanowires as a solid matrix for surface-assisted laser desorption/ionization time-of-flight (SALDI-TOF) mass spectrometry.

PubMed

Kim, Jo-Il; Park, Jong-Min; Hwang, Seung-Ju; Kang, Min-Jung; Pyun, Jae-Chul

2014-07-11

Top-down synthesized TiO2 nanowires are presented as an ideal solid matrix to analyze small biomolecules at a m/z of less than 500. The TiO2 nanowires were synthesized as arrays using a modified hydrothermal process directly on the surface of a Ti plate. Finally, the feasibility of the TiO2 nanowires in the anatase phase as a solid matrix. The crystal and electronic structures of the top-down TiO2 nanowires were analyzed at each step of the hydrothermal process, and the optimal TiO2 nanowires were identified by checking their performance toward the ionization of analytes in surface-assisted laser desorption/ionization time-of-flight (SALDI-TOF) mass spectrometry. Finally, the feasibility of the TiO2 nanowires in the anatase phase as a solid matrix for SALDI-TOF mass spectrometry was demonstrated using eight types of amino acids and peptides as model analytes. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhancing the surface properties of the immobilized Degussa P-25 TiO2 for the efficient photocatalytic removal of methylene blue from aqueous solution

NASA Astrophysics Data System (ADS)

Nawi, M. A.; Zain, Salmiah Md.

2012-06-01

A method has been developed for enhancing the surface properties of immobilized Degussa P-25 TiO2 nanoparticles on glass plate supports with excellent photocatalytic activity. The immobilization technique utilized a dip-coating method involving a coating solution containing Degussa P-25 TiO2 particles, epoxidized natural rubber (ENR-50) and poly vinyl chloride (PVC) in a mixture of toluene and dichloromethane. The optimum ratio of ENR/PVC blend was found to be 1:2. Immobilization process of the composite appeared to reduce the specific surface area by at least half of the pristine P-25 TiO2 particles. However, a systematic removal of ENR-50 additive via a 5 h photocatalytic process enabled the immobilized photocatalyst (P-25TiO2/ENR/PVC/5 h) to regenerate the surface area to within 86% of the pristine P-25 TiO2 particles, produce bigger pore volume and smaller particle size. The enhanced surface properties of the immobilized P-25/ENR/PVC/5 h photocatalyst system generated a photocatalytic performance as good as the slurry method of the P-25 TiO2 nanoparticles for the photocatalytic degradation of MB dye in aqueous solution. The immobilized P-25TiO2/ENR/PVC/5 h catalyst plate was also found to be highly reusable up to at least 10 runs without losing its photocatalytic efficiency. Above all, the system could avoid tedious filtration step of the treated water as normally observed with the aqueous slurry system.

Location Of Hole And Electron Traps On Nanocrystalline Anatase TiO2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mercado, Candy C.; Knorr, Fritz J.; McHale, Jeanne L.

2012-05-17

The defect photoluminescence from TiO2 nanoparticles in the anatase phase is reported for nanosheets which expose predominantly (001) surfaces, and compared to that from conventional anatase nanoparticles which expose mostly (101) surfaces. Also reported is the weak defect photoluminescence of TiO2 nanotubes, which we find using electron back-scattered diffraction to consist of walls which expose (110) and (100) facets. The nanotubes exhibit photoluminescence that is blue-shifted and much weaker than that from conventional TiO2 nanoparticles. Despite the preponderance of (001) surfaces in the nanosheet samples, they exhibit photoluminescence similar to that of conventional nanoparticles. We assign the broad visible photoluminescencemore » of anatase nanoparticles to two overlapping distributions: hole trap emission associated with oxygen vacancies on (101) exposed surfaces, which peaks in the green, and a broader emission extending into the red which results from electron traps on under-coordinated titanium atoms, which are prevalent on (001) facets. The results of this study suggest how morphology of TiO2 nanoparticles could be optimized to control the distribution and activity of surface traps. Our results also shed light on the mechanism by which the TiCl4 surface treatment heals traps on anatase and mixed-phase TiO2 films, and reveals distinct differences in the trap-state distributions of TiO2 nanoparticles and nanotubes. The molecular basis for electron and hole traps and their spatial separation on different facets is discussed.« less

Surface modification of layered perovskite Sr2TiO4 for improved CO2 photoreduction with H2O to CH4.

PubMed

Kwak, Byeong Sub; Do, Jeong Yeon; Park, No-Kuk; Kang, Misook

2017-11-27

Layered perovskite Sr 2 TiO 4 photocatalyst was synthesized by using sol-gel method with citric acid. In order to increase the surface area of layered perovskite Sr 2 TiO 4 , and thus to improve its photocatalytic activity for CO 2 reduction, its surface was modified via hydrogen treatment or exfoliation. The physical and chemical properties of the prepared catalysts were characterized by X-ray diffraction, high-resolution transmission electron microscopy, elemental mapping analysis, energy-dispersive X-ray spectroscopy, N 2 adsorption-desorption, UV-Vis spectroscopy, X-ray photoelectron spectroscopy, photoluminescence, and electrophoretic light scattering. CO 2 photoreduction was performed in a closed reactor under 6 W/cm 2 UV irradiation. The gaseous products were analyzed using a gas chromatograph equipped with flame ionization and thermal conductivity detectors. The exfoliated Sr 2 TiO 4 catalyst (E-Sr 2 TiO 4 ) exhibited a narrow band gap, a large surface area, and high dispersion. Owing to these advantageous properties, E-Sr 2 TiO 4 photocatalyst showed an excellent catalytic performance for CO 2 photoreduction reaction. The rate of CH 4 production from the photoreduction of CO 2 with H 2 O using E-Sr 2 TiO 4 was about 3431.77 μmol/g cat after 8 h.

Additional Effects of Silver Nanoparticles on Bactericidal Efficiency Depend on Calcination Temperature and Dip-Coating Speed▿

PubMed Central

Le, Nhung Thi Tuyet; Nagata, Hirofumi; Aihara, Mutsumi; Takahashi, Akira; Okamoto, Toshihiro; Shimohata, Takaaki; Mawatari, Kazuaki; Kinouchi, Yhosuke; Akutagawa, Masatake; Haraguchi, Masanobu

2011-01-01

There is an increasing interest in the application of photocatalytic properties for disinfection of surfaces, air, and water. Titanium dioxide is widely used as a photocatalyst, and the addition of silver reportedly enhances its bactericidal action. However, the synergy of silver nanoparticles and TiO2 is not well understood. The photocatalytic elimination of Bacillus atrophaeus was examined under different calcination temperatures, dip-coating speeds, and ratios of TiO2, SiO2, and Ag to identify optimal production conditions for the production of TiO2- and/or TiO2/Ag-coated glass for surface disinfection. Photocatalytic disinfection of pure TiO2 or TiO2 plus Ag nanoparticles was dependent primarily on the calcination temperature. The antibacterial activity of TiO2 films was optimal with a high dip-coating speed and high calcination temperature (600°C). Maximal bacterial inactivation using TiO2/Ag-coated glass was also observed following high-speed dip coating but with a low calcination temperature (250°C). Scanning electron microscopy (SEM) showed that the Ag nanoparticles combined together at a high calcination temperature, leading to decreased antibacterial activity of TiO2/Ag films due to a smaller surface area of Ag nanoparticles. The presence of Ag enhanced the photocatalytic inactivation rate of TiO2, producing a more pronounced effect with increasing levels of catalyst loading. PMID:21724887

SnO2/TiO2 bilayer thin films exhibiting superhydrophilic properties

NASA Astrophysics Data System (ADS)

Talinungsang, Nibedita Paul; Purkayastha, Debarun Dhar

2017-05-01

Nanostructured thin films of TiO2, SnO2, and SnO2/TiO2 have been deposited by sol-gel method. The films are characterized by X-ray diffraction, wettability and optical properties. In the present work, we have achieved a way of converting hydrophilic to super-hydrophilic state by incorporating TiO2 buffer layer in between substrate and SnO2 film, which has its utility in anti-fogging surfaces. The decrease in contact angle of water over SnO2/TiO2 bilayer is attributed to the increase in roughness of the film as well as surface energy of the substrate.

The effect of anatase TiO2 surface structure on the behavior of ethanol adsorption and its initial dissociation step: A DFT study

NASA Astrophysics Data System (ADS)

Zhang, Riguang; Liu, Zhixue; Ling, Lixia; Wang, Baojun

2015-10-01

The perfect and defective surfaces of anatase TiO2 including (1 0 1) and (0 0 1) surfaces have been chosen to probe into the effect of anatase TiO2 surface structure on the behavior of ethanol adsorption and initial dissociation step. Here, the results are obtained by density functional theory (DFT) calculation together with the periodic slab model. Our results show that the surface structure of anatase TiO2 can obviously affect the behavior of ethanol adsorption and the catalytic activity of its initial dissociation step; firstly, on the perfect and defective surfaces of anatase (1 0 1), ethanol dominantly exists in the form of molecule adsorption; however, ethanol is the dissociative adsorption on the hydroxylated anatase (0 0 1), and the coexistences of molecular and dissociation adsorption modes on the perfect anatase (0 0 1). On the other hand, the initial dissociation step of ethanol with molecule adsorption prefers to begin with its O-H bond cleavage leading to CH3CH2O and H species rather than the cleavage of its α-C-H, β-C-H, C-C and C-O bonds, namely, the preferable O-H bond cleavage for the initial dissociation step of ethanol is independent of the surface structure of anatase TiO2; however, the corresponding catalytic activity of ethanol initial dissociation step with the O-H bond cleavage on different anatase TiO2 surfaces is in the following order: hydroxylated (0 0 1) > perfect (0 0 1) > defective (1 0 1) > perfect (1 0 1), suggesting that the catalytic activity for the initial dissociation step of ethanol is sensitive to the surface structure of anatase TiO2, and the hydroxylated (0 0 1) is the most favorable surface. Among these surfaces, the most favorable product for the initial dissociation step of ethanol is CH3CH2O species.

Synthesis of Cr3+-doped TiO2 nanoparticles: characterization and evaluation of their visible photocatalytic performance and stability.

PubMed

Mendiola-Alvarez, Sandra Yadira; Guzmán-Mar, Jorge Luis; Turnes-Palomino, Gemma; Maya-Alejandro, Fernando; Caballero-Quintero, Adolfo; Hernández-Ramírez, Aracely; Hinojosa-Reyes, Laura

2017-09-28

Cr 3+ -doped TiO 2 nanoparticles (Ti-Cr) were synthesized by microwave-assisted sol-gel method. The Ti-Cr catalyst was characterized by X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, N 2 adsorption-desorption analysis, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy (XPS) and zetametry. The anatase mesoporous Ti-Cr material exhibited a specific surface area of 54.5 m 2 /g. XPS analysis confirmed the proper substitution of Ti 4+ cations by Cr 3+ cations in the TiO 2 matrix. The particle size was of average size of 17 nm for the undoped TiO 2 but only 9.5 nm for Ti-Cr. The Cr atoms promoted the formation of hydroxyl radicals and modified the surface adsorptive properties of TiO 2 due to the increase in surface acidity of the material. The photocatalytic evaluation demonstrated that the Ti-Cr catalyst completely degraded (4-chloro-2-methylphenoxy) acetic acid under visible light irradiation, while undoped TiO 2 and P25 allowed 45.7% and 31.1%, respectively. The rate of degradation remained 52% after three cycles of catalyst reuse. The higher visible light photocatalytic activity of Ti-Cr was attributed to the beneficial effect of Cr 3+ ions on the TiO 2 surface creating defects within the TiO 2 crystal lattice, which can act as charge-trapping sites, reducing the electron-hole recombination process.

Oxidative dehydrogenation of isobutane over vanadia catalysts supported by titania nanoshapes

DOE PAGES

Kraemer, Shannon K.; Rondinone, Adam Justin; Tsai, Yu-Tung; ...

2015-11-02

Support plays a complex role in catalysis by supported metal oxides and the exact support effect still remains elusive. One of the approaches to gain fundamental insights into the support effect is to utilize model support systems. In this study, we employed for the first time titania nanoshapes as the model supports and investigated how the variation of surface structure of the support (titania, TiO 2) impacts the catalysis of supported oxide (vanadia, VO x). TiO 2 truncated rhombi, spheres and rods were synthesized via hydrothermal method and characterized with XRD and TEM. These TiO 2 nanoshapes represent different mixturesmore » of surface facets including [1 0 1], [0 1 0] and [0 0 1] and were used to support vanadia. The structure of supported VO x species was characterized in detail with in situ Raman spectroscopy as a function of loading on the three TiO 2 nanoshapes. Oxidative dehydrogenation (ODH) of isobutane to isobutene was used as a model reaction to test how the support shape influences the activity, selectivity and activation energy of the surface VO x species. It was shown that the shape of TiO 2 support does not pose evident effect on either the structure of surface VO x species or the catalytic performance of surface VO x species in isobutane ODH reaction. Finally, this insignificant support shape effect was ascribed to the small difference in the surface oxygen vacancy formation energy among the different TiO 2 surfaces and the multi-faceting nature of the TiO 2 nanoshapes.« less

Oxidative dehydrogenation of isobutane over vanadia catalysts supported by titania nanoshapes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kraemer, Shannon; Rondinone, Adam J.; Tsai, Yu-Tong

2016-04-01

Support plays a complex role in catalysis by supported metal oxides and the exact support effect still remains elusive. One of the approaches to gain fundamental insights into the support effect is to utilize model support systems. In this paper, we employed for the first time titania nanoshapes as the model supports and investigated how the variation of surface structure of the support (titania, TiO2) impacts the catalysis of supported oxide (vanadia, VOx). TiO2 truncated rhombi, spheres and rods were synthesized via hydrothermal method and characterized with XRD and TEM. These TiO2 nanoshapes represent different mixtures of surface facets includingmore » [1 0 1], [0 1 0] and [0 0 1] and were used to support vanadia. The structure of supported VOx species was characterized in detail with in situ Raman spectroscopy as a function of loading on the three TiO2 nanoshapes. Oxidative dehydrogenation (ODH) of isobutane to isobutene was used as a model reaction to test how the support shape influences the activity, selectivity and activation energy of the surface VOx species. It was shown that the shape of TiO2 support does not pose evident effect on either the structure of surface VOx species or the catalytic performance of surface VOx species in isobutane ODH reaction. This insignificant support shape effect was ascribed to the small difference in the surface oxygen vacancy formation energy among the different TiO2 surfaces and the multi-faceting nature of the TiO2 nanoshapes.« less

Synergistic effect of surface self-doping and Fe species-grafting for enhanced photocatalytic activity of TiO2 under visible-light

NASA Astrophysics Data System (ADS)

Kong, Lina; Wang, Changhua; Wan, Fangxu; Zheng, Han; Zhang, Xintong

2017-02-01

Surface grafting of transition-metal complexes or oxides is an appealing way to enhance the photocatalytic activity of TiO2 under visible-light excitation. However, the performance of these co-catalysts assistant TiO2 photocatalysts is still not sufficient enough due to their relatively weak visible-light absorption. Herein, we report a simple impregnation treatment with ferric ethoxide/ethanol solvent, followed with mild heating which can significantly enhance the visible-light absorption and photocatalytic activity of TiO2. XPS and EPR analyses manifest that the oxygen vacancies (VOs) and Fe-species are simultaneously introduced to the surface of TiO2. The chemical state and photocatalytic activity of the Fe-species-grafted TiO2 - x is dependent on the heating temperature after impregnation. The sample heat-treated at 250 °C exhibits the optimal photocatalytic performance for β-naphthol degradation with rate constant 6.0, 2.7, and 3.9 times higher than that of TiO2, TiO2 - x, and Fe-TiO2, respectively. The activity enhancement is discussed on the basis of the synergistic effect and energy-level matching of surface VOs and Fe-species co-catalyst, i.e. the VOs defects states increase the visible-light absorption and the Fe-species in the form of FeOOH promote the consumption of photo-generated electrons through multi-electron reduction of adsorbed molecule oxygen.

Microstructure and antibacterial property of in situ TiO(2) nanotube layers/titanium biocomposites.

PubMed

Cui, C X; Gao, X; Qi, Y M; Liu, S J; Sun, J B

2012-04-01

The TiO(2) nanotube layer was in situ synthesized on the surface of pure titanium by the electrochemical anodic oxidation. The diameter of nano- TiO(2) nanotubes was about 70~100 nm. The surface morphology and phase compositions of TiO(2) nanotube layers were observed and analyzed using the scanning electron microscope (SEM). The important processing parameters, including anodizing voltage, reaction time, concentration of electrolyte, were optimized in more detail. The photocatalytic activity of the nano- TiO(2) nanotube layers prepared with optimal conditions was evaluated via the photodegradation of methylthionine in aqueous solution. The antibacterial property of TiO(2) nanotube layers prepared with optimal conditions was evaluated by inoculating Streptococcus mutans on the TiO(2) nanotube layers in vitro. The results showed that TiO(2) nanotube layers/Ti biocomposites had very good antibacterial activity to resist Streptococcus mutans. As a dental implant biomaterial, in situ TiO(2) nanotube layer/Ti biocomposite has better and wider application prospects. Copyright © 2012 Elsevier Ltd. All rights reserved.

In vitro assessment of photocatalytic titanium oxide surface modified stainless steel orthodontic brackets for antiadherent and antibacterial properties against Lactobacillus acidophilus.

PubMed

Shah, Alok Girish; Shetty, Pradeep Chandra; Ramachandra, C S; Bhat, N Sham; Laxmikanth, S M

2011-11-01

To assess the antiadherent and antibacterial properties of surface modified stainless steel orthodontic brackets with photocatalytic titanium oxide (TiO(2)) against Lactobacillus acidophilus. This study was done on 120 specimens of stainless steel preadjusted edgewise appliance (PEA) orthodontic brackets. The specimens were divided into four test groups. Each group consisted of 30 specimens. Groups containing uncoated brackets acted as a control group for their respective experimental group containing coated brackets. Surface modification of brackets was carried out by the radiofrequency (RF) magnetron sputtering method with photocatalytic TiO(2). Brackets then were subjected to microbiological tests for assessment of the antiadherent and antibacterial properties of photocatalytic TiO(2) coating against L acidophilus. Orthodontic brackets coated with photocatalytic TiO(2) showed an antiadherent effect against L acidophilus compared with uncoated brackets. The bacterial mass that was bound to the TiO(2)-coated brackets was less when compared with the uncoated brackets. Furthermore, TiO(2)-coated brackets had a bactericidal effect on L acidophilus, which causes dental caries. Surface modification of orthodontic brackets with photocatalytic TiO(2) can be used to prevent the accumulation of dental plaque and the development of dental caries during orthodontic treatment.

Interface architecture between TiO2/perovskite, perovskite/hole transport layer, and perovskite grain boundary(Conference Presentation)

NASA Astrophysics Data System (ADS)

Hayase, Shuzi; Hirotani, Daisuke; Moriya, Masahiro; Ogomi, Yuhei; Shen, Qing; Yoshino, Kenji; Toyoda, Taro

2016-09-01

In order to examine the interface structure of TiO2/perovskite layer, quartz crystal microbalance sensor (QCM) was used. On the QCM sensor, TiO2 layer was fabricated and the PbI2 solution in Dimethylformamide (DMF) was passed on the QCM sensor to estimate the adsorption density of the PbI2 on the titania2. The amount of PbI2 adsorption on TiO2 surface increased as the adsorption time and leveled off at a certain time. PbI2 still remained even after the solvent only (DMF) was passed on the TiO2 layer on QCM (namely rinsing with DMF), suggesting that the PbI2 was tightly bonded on the TiO2 surface. The bonding structure was found to be Ti-O-Pb linkage by XPS analysis. We concluded that the Ti-OH on the surface of TiO2 reacts with I-Pb-I to form Ti-O-Pb-I and HI (Fig.1 B). The surface trap density was measured by thermally stimulated current (TSC) method. Before the PbI2 passivation, the trap density of TiO2 was 1019 cm3. The trap density decreased to 1016/cm3 after the PbI2 passivation, suggesting that the TiO2 surface trap was passivated with I-Pb-I. The passivation density was tuned by the concentration of PbI2 in DMF, by which TiO2 layer was passivated. Perovskite solar cells were fabricated on the passivated TiO2 layer with various PbI2 passivation densities by one step process (mixture of PbI2 + MAI in DMF). It was found that Jsc increased with an increase in the Ti-O-Pb density. We concluded that the interface between TiO2 and perovskite layer has passivation structure consisting of Ti-O-Pb-I which decreases the trap density of the interfaces and supresses charge recombination. The effect of Cl anion on high efficiency is still controversial when perovskite layer is prepared by one step method from the mixture of MAI and PbCl2. It was found that adsorption density of PbCl2 on TiO2 surface was much higher than that of PbI2 from the experiment using QCM sensor. After the surface was washed with DMF, Cl and Pb were detected. These results suggest that the TiO2 surface was much more passivated by PbCl2 than by PbI2. This may explain partially the high efficiency when the perovskite layer was fabricated by one step process consisting of MAI and PbCl2 solution. We also observed that the crystal size increased with an increase in the amount of Cl anion which of course one of the explanation of the high efficiency. The interface of hole transport layer/perovskite layer, and between perovskite layer /perovskite layer (grain boundary) was passivated with organic amines. The passivation was also effective for increasing Voc and Jsc. This was explained by the results of transient absorption spectroscopy that the charge recombination time between hole transport payer/perovskite layer increased from 0.3 μsec to 60 μsec.

Comparative study on the process behavior and reaction kinetics in sonocatalytic degradation of organic dyes by powder and nanotubes TiO2.

PubMed

Pang, Yean Ling; Abdullah, Ahmad Zuhairi

2012-05-01

Sonocatalytic degradation of various organic dyes (Congo Red, Reactive Blue 4, Methyl Orange, Rhodamine B and Methylene Blue) catalyzed by powder and nanotubes TiO(2) was studied. Both catalysts were characterized using transmission electron microscope (TEM), surface analyzer, Raman spectroscope and thermal gravimetric analyzer (TGA). Sonocatalytic activity of powder and nanotubes TiO(2) was elucidated based on the degradation of various organic dyes. The former catalyst was favorable for treatment of anionic dyes, while the latter was more beneficial for cationic dyes. Sonocatalytic activity of TiO(2) nanotubes could be up to four times as compared to TiO(2) powder under an ultrasonic power of 100 W and a frequency of 42 kHz. This was associated with the higher surface area and the electrostatic attraction between dye molecules and TiO(2) nanotubes. Fourier transform-infrared spectrometer (FT-IR) was used to identify changes that occurred on the functional group in Rhodamine B molecules and TiO(2) nanotubes after the reaction. Sonocatalytic degradation of Rhodamine B by TiO(2) nanotubes apparently followed the Langmuir-Hinshelwood adsorption kinetic model with surface reaction rate of 1.75 mg/L min. TiO(2) nanotubes were proven for their high potential to be applied in sonocatalytic degradation of organic dyes. Copyright © 2011 Elsevier B.V. All rights reserved.

Optimization of amino group density on surfaces of titanium dioxide nanoparticles covalently bonded to a silicone substrate for antibacterial and cell adhesion activities.

PubMed

Okada, Masahiro; Yasuda, Shoji; Kimura, Tsuyoshi; Iwasaki, Mitsunobu; Ito, Seishiro; Kishida, Akio; Furuzono, Tsutomu

2006-01-01

A composite consisting of titanium dioxide (TiO2) particle, the surface of which was modified with amino groups, and a silicone substrate through covalent bonding at their interface was developed, and antibacterial and cell adhesion activities of the composite were evaluated. The density of the amino groups on the TiO2 particle surface was controlled by the reaction time of the modification reaction. The degradation rate of CH3CHO in the presence of the TiO2 particles under UV irradiation decreased with an increase in the amino group density on the TiO2 surface. On the other hand, the number of L929 cells adhering on the TiO2/silicone composite increased with an increase in the amino group density. From the above two results, the optimum density of amino groups for both photoreactivity and cell adhesiveness was estimated to be 2.0-4.0 molecules/nm2. The optimum amino group-modified TiO2/silicone composite sheet (amino group density, 3.0 molecules/nm2) showed an effective antibacterial activity for Escherichia coli bacteria under UV irradiation. (c) 2005 Wiley Periodicals, Inc

Mechanism of H adatoms improving the O2 reduction reaction on the Zn-modified anatase TiO2 (101) surface studied by first principles calculation.

PubMed

Liu, Liangliang; Li, Chongyang; Jiang, Man; Li, Xiaodong; Huang, Xiaowei; Wang, Zhu; Jia, Yu

2018-06-05

First principles calculations were performed to cast insight into the mechanism of the improvement of O2 reduction reaction (ORR) activity by Zn and H interstitials on the anatase TiO2 (101) surface. For the Zn-modified anatase TiO2 (101) surface, both surface and subsurface Zn interstitials could contribute to O2 adsorption and dissociation, but the dissociation barriers of O2 molecules are still too high, which limits the ORR activity. After a H adatom is introduced onto the Zn-modified anatase TiO2 (101) surface, the highest energy barriers are greatly reduced compared with those of the Zn-modified surface. Meanwhile, it is observed that the dissociation barriers decrease almost linearly with the increase of the charge difference of adsorption O2 between initial and transition state configurations. Specifically, subsurface Zn and surface H interstitials facilitate O2 dissociation and subsequent oxidation reactions, and further frequency analysis shows that these dissociation processes are frequent even at the room temperature of 300 K. In a word, this work provides a theoretical support to design a high ORR activity catalyst of the TiO2 nanocrystal comparable to precious Pt catalysts.

Interrelationship between TiO2 nanoparticle size and kind/size of dyes in the mechanism and conversion efficiency of dye sensitized solar cells.

PubMed

Tahay, Pooya; Babapour Gol Afshani, Meisam; Alavi, Ali; Parsa, Zahra; Safari, Nasser

2017-05-10

In order to provide a comprehensive investigation of TiO 2 nanoparticle size in relation with different dye types in DSSCs, three sizes of TiO 2 nanoparticles and two different dye types including a porphyrin dye (T2) and a ruthenium dye (N3) were synthesized. Steady state current-voltage (J-V) characteristics were investigated for the fabricated DSSCs and the results demonstrated that the optimum TiO 2 nanoparticle size changed with the dye type. The obtained J-V data were interpreted by cyclic voltammetry, UV-visible absorption spectroscopy, BET measurement, DFT calculation, IPCE measurement and impedance spectroscopy. The results for the N3 dye show that the surface area of the TiO 2 nanoparticles is a key factor for the N3 cells, which is restricted by TiO 2 pore diameter and surface state traps. In contrast, the density of localized states of the TiO 2 film under the LUMO state of the porphyrin dyes is the dominating factor for the performance of the solar cells, which is restricted by the surface area of the TiO 2 nanoparticles. These obtained results represent a significant advance in the development of porphyrin, ruthenium and even solid electrolyte DSSCs.

TiO2 nanoparticles aggregation and disaggregation in presence of alginate and Suwannee River humic acids. pH and concentration effects on nanoparticle stability.

PubMed

Loosli, Frédéric; Le Coustumer, Philippe; Stoll, Serge

2013-10-15

The behavior of manufactured TiO2 nanoparticles is studied in a systematic way in presence of alginate and Suwannee River humic acids at variable concentrations. TiO2 nanoparticles aggregation, disaggregation and stabilization are investigated using dynamic light scattering and electrophoretic experiments allowing the measurement of z-average hydrodynamic diameters and zeta potential values. Stability of the TiO2 nanoparticles is discussed by considering three pH-dependent electrostatic scenarios. In the first scenario, when pH is below the TiO2 nanoparticle point of zero charge, nanoparticles exhibit a positively charged surface whereas alginate and Suwannee River humic acids are negatively charged. Fast adsorption at the TiO2 nanoparticles occurs, promotes surface charge neutralization and aggregation. By increasing further alginate and Suwannee River humic acids concentrations charge inversion and stabilization of TiO2 nanoparticles are obtained. In the second electrostatic scenario, at the surface charge neutralization pH, TiO2 nanoparticles are rapidly forming aggregates. Adsorption of alginate and Suwannee River humic acids on aggregates leads to their partial fragmentation. In the third electrostatic scenario, when nanoparticles, alginate and Suwannee River humic acids are negatively charged, only a small amount of Suwannee River humic acids is adsorbed on TiO2 nanoparticles surface. It is found that the fate and behavior of individual and aggregated TiO2 nanoparticles in presence of environmental compounds are mainly driven by the complex interplay between electrostatic attractive and repulsive interactions, steric and van der Waals interactions, as well as concentration ratio. Results also suggest that environmental aquatic concentration ranges of humic acids and biopolymers largely modify the stability of aggregated or dispersed TiO2 nanoparticles. Copyright © 2013 Elsevier Ltd. All rights reserved.

Synthesis of TiO2-poly(3-hexylthiophene) hybrid particles through surface-initiated Kumada catalyst-transfer polycondensation.

PubMed

Boon, Florian; Moerman, David; Laurencin, Danielle; Richeter, Sébastien; Guari, Yannick; Mehdi, Ahmad; Dubois, Philippe; Lazzaroni, Roberto; Clément, Sébastien

2014-09-30

TiO2/conjugated polymers are promising materials in solar energy conversion where efficient photoinduced charge transfers are required. Here, a "grafting-from" approach for the synthesis of TiO2 nanoparticles supported with conjugated polymer brushes is presented. Poly(3-hexylthiophene) (P3HT), a benchmark material for organic electronics, was selectively grown from TiO2 nanoparticles by surface-initiated Kumada catalyst-transfer polycondensation. The grafting of the polymer onto the surface of the TiO2 nanoparticles by this method was demonstrated by (1)H and (13)C solid-state NMR, X-ray photoelectron spectrometry, thermogravimetric analysis, transmission electron microscopy, and UV-visible spectroscopy. Sedimentation tests in tetrahydrofuran revealed improved dispersion stability for the TiO2@P3HT hybrid material. Films were produced by solvent casting, and the quality of the dispersion of the modified TiO2 nanoparticles was evaluated by atomic force microscopy. The dispersion of the P3HT-coated TiO2 NPs in the P3HT matrix was found to be homogeneous, and the fibrillar structure of the P3HT matrix was maintained which is favorable for charge transport. Fluorescence quenching measurements on these hybrid materials in CHCl3 indicated improved photoinduced electron-transfer efficiency. All in all, better physicochemical properties for P3HT/TiO2 hybrid material were reached via the surface-initiated "grafted-from" approach compared to the "grafting-onto" approach.

Effects of adsorbed pyridine derivatives and ultrathin atomic-layer-deposited alumina coatings on the conduction band-edge energy of TiO2 and on redox-shuttle-derived dark currents.

PubMed

Katz, Michael J; Vermeer, Michael J D; Farha, Omar K; Pellin, Michael J; Hupp, Joseph T

2013-01-15

Both the adsorption of t-butylpyridine and the atomic-layer deposition of ultrathin conformal coatings of insulators (such as alumina) are known to boost open-circuit photovoltages substantially for dye-sensitized solar cells. One attractive interpretation is that these modifiers significantly shift the conduction-edge energy of the electrode, thereby shifting the onset potential for dark current arising from the interception of injected electrons by solution-phase redox shuttle components such as Co(phenanthroline)(3)(3+) and triiodide. For standard, high-area, nanoporous photoelectrodes, band-edge energies are difficult to measure directly. In contrast, for flat electrodes they are readily accessible from Mott-Schottky analyses of impedance data. Using such electrodes (specifically TiO(2)), we find that neither organic nor inorganic electrode-surface modifiers shift the conduction-band-edge energy sufficiently to account fully for the beneficial effects on electrode behavior (i.e., the suppression of dark current). Additional experiments reveal that the efficacy of ultrathin coatings of Al(2)O(3) arises chiefly from the passivation of redox-catalytic surface states. In contrast, adsorbed t-butylpyridine appears to suppress dark currents mainly by physically blocking access of shuttle molecules to the electrode surface. Studies with other derivatives of pyridine, including sterically and/or electronically diverse derivatives, show that heterocycle adsorption and the concomitant suppression of dark current does not require the coordination of surface Ti(IV) or Al(III) atoms. Notably, the favorable (i.e., negative) shifts in onset potential for the flow of dark current engendered by organic and inorganic surface modifiers are additive. Furthermore, they appear to be largely insensitive to the identity of shuttle molecules.

Inverse Design, Development and Characterization of Catalytic Adsorbates at Semiconductor/Liquid Interfaces

DTIC Science & Technology

2016-07-08

theoretical determination of orientation of Re(I) bipyridyl complexes for CO2 reduction on Au and on TiO2 . We have recently determined the binding...crystalline TiO2 (110) surfaces relative to (001) surfaces using vibrational sum frequency generation (SFG) spectroscopy. The SFG signal shows an...isotropic distribution with the rotation of the TiO2 (001) surface relative to the incident plane, but an anisotropic distribution with the rotation

Interface engineered construction of porous g-C3N4/TiO2 heterostructure for enhanced photocatalysis of organic pollutants

NASA Astrophysics Data System (ADS)

Li, Ya-Nan; Chen, Zhao-Yang; Wang, Min-Qiang; Zhang, Long-zhen; Bao, Shu-Juan

2018-05-01

A porous g-C3N4/TiO2 with hierarchical heterostructure has been successfully fabricated through a in situ assembling of small needle-like TiO2 on the surface of ultrathin g-C3N4 sheets. The ultrathin g-C3N4 sheets with carbon vacancies and rich hydroxyl groups were found to facilitate the nucleation and in situ growth of TiO2 and also to modulate the surface chemical activity of the g-C3N4/TiO2 hierarchical heterostructure. The as-designed photocatalytic heterojunction degraded Acid Orange with 82% efficiency after 10 min under simulated solar light, and possessed excellent cycle stability. Relative physical characterizations and photochemical experiments reveal that engineering the interface/surface of g-C3N4 plays a vital role in effectively constructing heterostructures of g-C3N4/TiO2, thus realizing efficient photoinduced electron-hole separation during photocatalytic process.

Surface Properties and Catalytic Performance of Activated Carbon Fibers Supported TiO2 Photocatalyst

NASA Astrophysics Data System (ADS)

Yang, Huifen; Fu, Pingfeng

Activated carbon fibers supported TiO2 photocatalyst (TiO2/ACF) in felt-form was successfully prepared with a dip-coating process using organic silicon modified acrylate copolymer as a binder followed by calcination at 500°C in a stream of Ar gas. The photocatalyst was characterized by SEM, XRD, XPS, FTIR, and BET surface area. Most of carbon fibers were coated with uniformly distributed TiO2 clusters of nearly 100 nm. The loaded TiO2 layer was particulate for the organic binder in the compact film was carbonized. According to XPS and FTIR analysis, amorphous silica in carbon grains was synthesized after carbonizing organic silicon groups, and the Ti-O-Si bond was formed between the interface of loaded TiO2 and silica. Additionally, the space between adjacent carbon fibers still remained unfilled after TiO2 coating, into which both UV light and polluted solutions could penetrate to form a three-dimensional environment for photocatalytic reactions. While loaded TiO2 amount increased to 456 mg TiO2/1 g ACF, the TiO2/ACF catalyst showed its highest photocatalytic activity, and this activity only dropped about 10% after 12 successive runs, exhibiting its high fixing stability of coated TiO2.

Hydrophobic surface modification of TiO2 nanoparticles for production of acrylonitrile-styrene-acrylate terpolymer/TiO2 composited cool materials

NASA Astrophysics Data System (ADS)

Qi, Yanli; Xiang, Bo; Tan, Wubin; Zhang, Jun

2017-10-01

Hydrophobic surface modification of TiO2 was conducted for production of acrylonitrile-styrene-acrylate (ASA) terpolymer/titanium dioxide (TiO2) composited cool materials. Different amount of 3-methacryloxypropyl-trimethoxysilane (MPS) was employed to change hydrophilic surface of TiO2 into hydrophobic surface. The hydrophobic organosilane chains were successfully grafted onto TiO2 through Sisbnd Osbnd Ti bonds, which were verified by Fourier transformed infrared spectra and X-ray photoelectron spectroscopy. The water contact angle of the sample added with TiO2 modified by 5 wt% MPS increased from 86° to 113°. Besides, all the ASA/TiO2 composites showed significant improvement in both solar reflectance and cooling property. The reflectance of the composites throughout the near infrared (NIR) region and the whole solar wavelength is increased by 113.92% and 43.35% compared with pristine ASA resin. Simultaneously, significant drop in temperature demonstrates excellent cooling property. A maximum decrease approach to 27 °C was observed in indoor temperature test, while a decrease around 9 °C tested outdoors is achieved.

Reflectance modulation using SiO2/TiO2 multilayer structures prepared by sol-gel spin coating process for optical applications

NASA Astrophysics Data System (ADS)

Dubey, R. S.; Ganesan, V.

2017-11-01

Passive devices made of SiO2/TiO2 bilayers have been demanded for the molding of electromagnetic waves in optical waveguides, microcavities, solar cells, sensors and so on. Here, we present the fabrication and characterization of SiO2/TiO2 multilayer structures as reflectors. The refractive indices were found to be 1.43 & 2.0 with thicknesses 230 & 70 nm corresponding to the SiO2 and TiO2 films respectively. AFM surface topography study showed little bit large surface roughness of the TiO2 as compared to SiO2 film due to its large grain size. The corresponding reflectance enhancement was noticed with the increased number of bilayers of SiO2/TiO2 films. Furthermore, six alternate layers of SiO2/TiO2 demonstrated the as much as 78% reflectance in the near-infrared wavelength range.

Influence of catalyst synthesis method on selective catalytic reduction (SCR) of NO by NH 3 with V 2O 5-WO 3/TiO 2 catalysts

DOE PAGES

He, Yuanyuan; Ford, Michael E.; Zhu, Minghui; ...

2016-04-14

We compared the molecular structures, surface acidity and catalytic activity for NO/NH 3/O 2 SCR of V 2O 5-WO 3/TiO 2 catalysts for two different synthesis methods: co-precipitation of aqueous vanadium and tungsten oxide precursors with TiO(OH) 2 and by incipient wetness impregnation of the aqueous precursors on a reference crystalline TiO 2 support (P25; primarily anatase phase). Bulk analysis by XRD showed that co-precipitation results in small and/or poorly ordered TiO 2(anatase) particles and that VO x and WO x do not form solid solutions with the bulk titania lattice. Surface analysis of the co-precipitated catalyst by High Sensitivity-Lowmore » Energy Ion Scattering (HS-LEIS) confirms that the VO x and WO x are surface segregated for the co-precipitated catalysts. In situ Raman and IR spectroscopy revealed that the vanadium and tungsten oxide components are present as surface mono-oxo O = VO 3 and O = WO 4 sites on the TiO 2 supports. Co-precipitation was shown for the first time to also form new mono-oxo surface VO 4 and WO 4 sites that appear to be anchored at surface defects of the TiO 2 support. IR analysis of chemisorbed ammonia showed the presence of both surface NH 3 * on Lewis acid sites and surface NH 4 +* on Brønsted acid sites. TPSR spectroscopy demonstrated that the specific SCR kinetics was controlled by the redox surface VO 4 species and that the surface kinetics was independent of TiO 2 synthesis method or presence of surface WO 5 sites. SCR reaction studies revealed that the surface WO5 sites possess minimal activity below ~325 °C and their primary function is to increase the adsorption capacity of ammonia. A relationship between the SCR activity and surface acidity was not found. The SCR reaction is controlled by the surface VO 4 sites that initiate the reaction at ~200 °C. The co-precipitated catalysts were always more active than the corresponding impregnated catalysts. Finally, we ascribe the higher activity of the co-precipitated catalysts to the presence of the new surface WO x sites associated surface defects on the TiO 2 support that increase the ammonia adsorption capacity.« less

Surface modification of TiO2 nanotubes with osteogenic growth peptide to enhance osteoblast differentiation.

PubMed

Lai, Min; Jin, Ziyang; Su, Zhiguo

2017-04-01

To investigate the influence of surface-biofunctionalized substrates on osteoblast behavior, a layer of aligned TiO 2 nanotubes with a diameter of around 70nm was fabricated on titanium surface by anodization, and then osteogenic growth peptide (OGP) was conjugated onto TiO 2 nanotubes through the intermediate layer of polydopamine. The morphology, composition and wettability of different surfaces were characterized by field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements, respectively. The effects of OGP-modified TiO 2 nanotube substrates on the morphology, proliferation and differentiation of osteoblasts were examined in vitro. Immunofluorescence staining revealed that the OGP-functionalized TiO 2 nanotubes were favorable for cell spreading. However, there was no significant difference in cell proliferation observed among the different groups. Cells grown onto OGP-functionalized TiO 2 nanotubes showed significantly higher (p<0.05 or p<0.01) levels of alkaline phosphatase (ALP) and mineralization after 4, 7 and 14days of culture, respectively. Cells grown on OGP-functionalized TiO 2 nanotubes had significantly higher (p<0.05 or p<0.01) expression of osteogenic-related genes including runt related transcription factor 2 (Runx2), ALP, collagen type I (Col I), osteopontin (OPN) and osteocalcin (OC) after 14days of culture. These data suggest that surface functionalization of TiO 2 nanotubes with OGP was beneficial for cell spreading and differentiation. This study provides a novel platform for the development and fabrication of titanium-based implants that enhance the propensity for osseointegration between the native tissue and implant interface. Copyright © 2016 Elsevier B.V. All rights reserved.

Synthesis and characterization of Cu-Zn/TiO2 for the photocatalytic conversion of CO2 to methane.

PubMed

Rana, Adeem Ghaffar; Ahmad, Waqar; Al-Matar, Ali; Shawabkeh, Reyad; Aslam, Zaheer

2017-05-01

Different Cu-Zn/TiO 2 catalysts were synthesized by using the wet impregnation method. The prepared catalysts were used for the conversion of CO 2 into methane by photocatalysis. Various characterization techniques were used to observe the surface morphology, crystalline phase, Brunauer-Emmett-Teller (BET) surface area, presence of impregnated Cu and Zn, and functional group. Scanning electron microscope analysis showed spherical morphology, and slight agglomeration of catalyst particles was observed. BET analysis revealed that the surface area of the catalyst was decreased from 10 to 8.5 m 2 /g after impregnation of Cu and Zn over TiO 2 support. Synergetic effect of Cu and Zn over TiO 2 support (Cu 2.6 /TiO 2 , Zn 0.5 /TiO 2 and Cu 2.6 -Zn 0.5 /TiO 2 ) and the effects of Cu loading (0, 1.8, 2.1, 2.6 and 2.9 wt%) were also investigated at different feed molar ratios of H 2 /CO 2 (2:1 and 4:1). The Cu 2.6 -Zn 0.5 /TiO 2 catalyst showed a maximum conversion of 14.3% at a feed molar ratio of 4. The addition of Zn over the catalyst surface increased the conversion of CO 2 from 10% to 14.3% which might be due to synergy of Cu and Zn over TiO 2 support.

Controlled preparation of M(Ag, Au)/TiO2 through sulfydryl-assisted method for enhanced photocatalysis

NASA Astrophysics Data System (ADS)

Xia, Hongbo; Wu, Suli; Bi, Jiajie; Zhang, Shufen

2017-11-01

Here a simple and effective method was explored to fabricate M/TiO2 (M = Ag, Au) composites, which required neither pre-treatment of TiO2 nor any additives as reducing agent. Using amorphous TiO2 spheres functionalized with SH groups as starting materials, the noble metallic ions (Ag, Au) can be adsorbed by TiO2 due to their special affinity with SH groups, which is beneficial to the uniform dispersion of metallic ions on the surface of TiO2. Then the adsorbed ions were reduced to form noble metal nanoparticles by heating process (95 °C) directly without additive as reduction agent. Meanwhile, the amorphous TiO2 was transformed into anatase phase during the heating process. Thus, the transformation of TiO2 along with the reduction of noble metallic ions (Ag, Au) was simultaneously carried out by heating. The XRD patterns proved the formation of anatase TiO2 after heating. The characterizations of XPS and TEM proved the formation of Ag and Au nanoparticles on the surface of TiO2. The element mapping indicated that Ag nanoparticles are dispersed uniformly on the surface of TiO2. The photocatalytic activity of the composites has been investigated by the degradation of methyl orange under visible light irradiation. The results showed that when Ag/TiO2 (2.8 wt%) was used as photocatalyst, about 98% of the MO molecules were degraded in 70 min.

Preparation and application of nanoglued binary titania-silica aerogel.

PubMed

Luo, Liang; Cooper, Adrienne T; Fan, Maohong

2009-01-15

Nanoglued binary titania (TiO2)-silica (SiO2) aerogel, as a novel type of photocatalyst, has been synthesized on glass substrates. Using an about-to-gel SiO2 sol as nanoglue, anatase TiO2 aerogel was immobilized into a three-dimensional mesoporous network of the SiO2. Factorial designs were employed to optimize both TiO2 aerogel and binary TiO2-SiO2 aerogel synthesis. Characterization of the as-prepared TiO2 and binary samples by surface area, porosity, and surface chemical composition showed that the photocatalysts were high-surface-area nanoporous materials, with a Ti4+ valency. The binary aerogel exhibited high photocatalytic activity for the degradation of methylene blue (MB) under simulated solar light; the reaction followed the pseudo first-order Langmuir-Hinshelwood (L-H) kinetic model. Fluorescence spectroscopy revealed that the hydroxyl (*OH) radical was formed during the illumination of the binary TiO2-SiO2 aerogel in a solution of probe molecules, which corroborates the probable mechanism of hydroxyl radical oxidation of contaminants in photocatalytic reactions.

The Effects of Biopolymers Composite Based Waste Cooking Oil and Titanium Dioxide Fillers as Superhydrophobic Coatings.

NASA Astrophysics Data System (ADS)

Marsi, N.; Rus, A. Z. M.

2017-08-01

This project presents the effect of biopolymer composite surface coating on TiO2 fillers by analysing the static water contact angle, SEM micrographs, porosity, density and refractive index of biopolymer doped with different loading of TiO2. The different ratio loading of 0.5, 1.0, 1.5, 2.0 and 2.5 (wt/wt%) TiO2 can be used to improve the material properties in practical use for outdoor application especially to enhance the stability of surface coating. It is found that the smooth surfaces with a low ratio loading of TiO2 fillers on biopolymer composite surface coating increases the static water contact angle up to 162.29°. It is interpreted with respect to nano- features existing on the surface of the water repellent creates a thin superhydrphobic layer. The relationship between porosity and density is indirectly proportional where the higher the loading of TiO2 filler produce the lower porosity up to 0.86% of the surface coating. The movement from shorter to longer of wavelength was observed before and after exposure indicates that there are optimization of absorption of UV-B radiation as the amount of delocalisation.

Modelling free and oxide-supported nanoalloy catalysts: comparison of bulk-immiscible Pd-Ir and Au-Rh systems and influence of a TiO2 support.

PubMed

Demiroglu, Ilker; Fan, Tian-E; Li, Z Y; Yuan, Jun; Liu, Tun-Dong; Piccolo, Laurent; Johnston, Roy L

2018-05-24

The relative stabilities of different chemical arrangements of Pd-Ir and Au-Rh nanoalloys (and their pure metal equivalents) are studied, for a range of compositions, for fcc truncated octahedral 38- and 79-atom nanoparticles (NPs). For the 38-atom NPs, comparisons are made of pure and alloy NPs supported on a TiO2(110) slab. The relative energies of different chemical arrangements are found to be similar for Pd-Ir and Au-Rh nanoalloys, and depend on the cohesive and surface energies of the component metals. For supported nanoalloys on TiO2, the interaction with the surface is greater for Ir (Rh) than Pd (Au): most of the pure NPs and nanoalloys preferentially bind to the TiO2 surface in an edge-on configuration. When Au-Rh nanoalloys are bound to the surface through Au, the surface binding strength is lower than for the pure Au NP, while the Pd-surface interaction is found to be greater for Pd-Ir nanoalloys than for the pure Pd NP. However, alloying leads to very little difference in Ir-surface and Rh-surface binding strength. Comparing the relative stabilities of the TiO2-supported NPs, the results for Pd-Ir and Au-Rh nanoalloys are the same: supported Janus NPs, whose Ir (Rh) atoms bind to the TiO2 surface, bind most strongly to the surface, becoming closer in energy to the core-shell configurations (Ir@Pd and Rh@Au) which are favoured for the free particles.

Surface modification of the TiO2 nanoparticle surface enables fluorescence monitoring of aggregation and enhanced photoreactivity.

PubMed

Kamps, Kara; Leek, Rachael; Luebke, Lanette; Price, Race; Nelson, Megan; Simonet, Stephanie; Eggert, David Joeseph; Ateşin, Tülay Aygan; Brown, Eric Michael Bratsolias

2013-01-01

Chemically and biologically modified nanoparticles are increasingly considered as viable and multifunctional tools to be used in cancer theranostics. Herein, we demonstrate that coordination of alizarin blue black B (ABBB) to the TiO(2) nanoparticle surface enhances the resulting nanoparticles by (1) creating distinct fluorescence emission spectra that differentiate smaller TiO(2) nanoparticles from larger TiO(2) nanoparticle aggregates (both in vitro and intracellular) and (2) enhancing visible light activation of TiO(2) nanoparticles above previously described methods to induce in vitro and intracellular damage to DNA and other targets. ABBB-TiO(2) nanoparticles are characterized through sedimentation, spectral absorbance, and gel electrophoresis. The possible coordination modes of ABBB to the TiO(2) nanoparticle surface are modeled by computational methods. Fluorescence emission spectroscopy studies indicate that ABBB coordination on TiO(2) nanoparticles enables discernment between nanoparticles and nanoparticle aggregates both in vitro and intracellular through fluorescence confocal microscopy. Visible light activated ABBB-TiO(2) nanoparticles are capable of inflicting increased DNA cleavage through localized production of reactive oxygen species as visualized by plasmid DNA damage detected through gel electrophoresis and atomic force microscopy. Finally, visible light excited ABBB-TiO(2) nanoparticles are capable of inflicting damage upon HeLa (cervical cancer) cells by inducing alterations in DNA structure and membrane associated proteins. The multifunctional abilities of these ABBB-TiO(2) nanoparticles to visualize and monitor aggregation in real time, as well as inflict visible light triggered damage upon cancer targets will enhance the use of TiO(2) nanoparticles in cancer theranostics.

The Effect of Interfacial Chemical Bonding in TiO2-SiO2 Composites on Their Photocatalytic NOx Abatement Performance

PubMed Central

Hakki, Amer; Yang, Lu; Wang, Fazhou; Macphee, Donald E.

2017-01-01

The chemical bonding of particulate photocatalysts to supporting material surfaces is of great importance in engineering more efficient and practical photocatalytic structures. However, the influence of such chemical bonding on the optical and surface properties of the photocatalyst and thus its photocatalytic activity/reaction selectivity behavior has not been systematically studied. In this investigation, TiO2 has been supported on the surface of SiO2 by means of two different methods: (i) by the in situ formation of TiO2 in the presence of sand quartz via a sol-gel method employing tetrabutyl orthotitanium (TBOT); and (ii) by binding the commercial TiO2 powder to quartz on a surface silica gel layer formed from the reaction of quartz with tetraethylorthosilicate (TEOS). For comparison, TiO2 nanoparticles were also deposited on the surfaces of a more reactive SiO2 prepared by a hydrolysis-controlled sol-gel technique as well as through a sol-gel route from TiO2 and SiO2 precursors. The combination of TiO2 and SiO2, through interfacial Ti-O-Si bonds, was confirmed by FTIR spectroscopy and the photocatalytic activities of the obtained composites were tested for photocatalytic degradation of NO according to the ISO standard method (ISO 22197−1). The electron microscope images of the obtained materials showed that variable photocatalyst coverage of the support surface can successfully be achieved but the photocatalytic activity towards NO removal was found to be affected by the preparation method and the nitrate selectivity is adversely affected by Ti-O-Si bonding. PMID:28715384

Osteogenic potential of in situ TiO2 nanowire surfaces formed by thermal oxidation of titanium alloy substrate

NASA Astrophysics Data System (ADS)

Tan, A. W.; Ismail, R.; Chua, K. H.; Ahmad, R.; Akbar, S. A.; Pingguan-Murphy, B.

2014-11-01

Titanium dioxide (TiO2) nanowire surface structures were fabricated in situ by a thermal oxidation process, and their ability to enhance the osteogenic potential of primary osteoblasts was investigated. Human osteoblasts were isolated from nasal bone and cultured on a TiO2 nanowires coated substrate to assess its in vitro cellular interaction. Bare featureless Ti-6Al-4V substrate was used as a control surface. Initial cell adhesion, cell proliferation, cell differentiation, cell mineralization, and osteogenic related gene expression were examined on the TiO2 nanowire surfaces as compared to the control surfaces after 2 weeks of culturing. Cell adhesion and cell proliferation were assayed by field emission scanning electron microscope (FESEM) and Alamar Blue reduction assay, respectively. The nanowire surfaces promoted better cell adhesion and spreading than the control surface, as well as leading to higher cell proliferation. Our results showed that osteoblasts grown onto the TiO2 nanowire surfaces displayed significantly higher production levels of alkaline phosphatase (ALP), extracellular (ECM) mineralization and genes expression of runt-related transcription factor (Runx2), bone sialoprotein (BSP), ostoepontin (OPN) and osteocalcin (OCN) compared to the control surfaces. This suggests the potential use of such surface modification on Ti-6Al-4V substrates as a promising means to improve the osteointegration of titanium based implants.

Removal of phenanthrene in aqueous solution containing photon competitors by TiO2-C-Ag film supported on fiberglass.

PubMed

González-Ramírez, Denisse Fabiola; Ávila-Pérez, Pedro; Torres-Bustillos, Luis G; Aguilar-López, Ricardo; Montes-Horcasitas, María C; Esparza-García, Fernando J; Rodríguez-Vázquez, Refugio

2017-07-03

Surface interactions with pollutants and photons are key factors that affect the applications of TiO 2 in environmental remediation. In this study, the solubilizing agents dimethylsulfoxide and polyoxyethylene sorbitan monooleate, which act as photon competitors, had no effect on the photocatalytic activity of TiO 2 -C-Ag film in phenanthrene (PHE) removal. Fiberglass with TiO 2 -C-Ag coating removed 91.1 ± 5.2 and 99.7 ± 0.4% of PHE in treatments using UVA (365-465 nm) and UVC (254 nm) irradiation, respectively. The use of fiberglass as a support increased the superficial area, thus allowing PHE sorption. C and Ag, which are electrically active impurities in TiO 2 , enhanced its photocatalytic activity and thus the attraction of the pollutant to its surface. The use of high-frequency UV light (UVC) decreased the amount of carbon species deposited on the TiO 2 CAg film surface. X-ray photoelectron spectroscopy of the TiO 2 -C-Ag film revealed extensive oxidation of the carbon deposited on the film under UVC light and loss of electrons from Ag clusters by conversion of Ag 0 to Ag 3+ .

Study on nanomagnets supported TiO2 photocatalysts prepared by a sol-gel process in reverse microemulsion combining with solvent-thermal technique.

PubMed

Li, Hansheng; Zhang, Yaping; Wang, Shiying; Wu, Qin; Liu, Changhao

2009-09-30

A sol-gel process in reverse microemulsion combined with solvent-thermal technique was developed for synthesizing a series of nanomagnets supported TiO(2) (TiO(2)/NMs) photocatalysts in this study. The structure of TiO(2)/NMs photocatalysts was characterized by Fourier transform infrared (FTIR), TG-DSC, X-ray diffraction (XRD), Raman spectrometry, TEM, BET, and VSM. The influence of CoFe(2)O(4) dosage on the photocatalytic activity and magnetism of TiO(2)/NMs photocatalysts was investigated. The results showed that nanosized anatase TiO(2) were uniformly coated on spinel CoFe(2)O(4) in the prepared TiO(2)/NMs photocatalysts. They possessed typical ferromagnetic hysteresis and performed better photocatalytic activity in degradation of methylene blue than TiO(2) prepared by the same method. The existence of CoFe(2)O(4) nanomagnets played an important role on the crystalline grain size of TiO(2) and the specific surface area of the prepared TiO(2)/NMs photocatalysts, thus had an important influence on its photocatalytic performance and magnetism. The photocatalytic performance of TiO(2)/NMs photocatalysts is related to their specific surface area, crystalline grain sizes of TiO(2) and particle size, as well as the doping effect of Fe(3+). The highest photocatalytic activity in degradation of methylene blue for TiO(2)/NMs photocatalysts at the CoFe(2)O(4) content of 20wt.% was achieved, with k(p) 28.32% higher than that of pure TiO(2) photocatalyst. Moreover, the experiments on recycled use of TiO(2)/NMs photocatalyst demonstrated a good repeatability of the photocatalytic activity.

Fabrication of SnO2-TiO2 core-shell nanopillar-array films for enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Cheng, Hsyi-En; Lin, Chun-Yuan; Hsu, Ching-Ming

2017-02-01

Immobilized or deposited thin film TiO2 photocatalysts are suffering from a low photocatalytic activity due to either a low photon absorption efficiency or a high carrier recombination rate. Here we demonstrate that the photocatalytic activity of TiO2 can be effectively improved by the SnO2-TiO2 core-shell nanopillar-array structure which combines the benefits of SnO2/TiO2 heterojunction and high reaction surface area. The SnO2-TiO2 core-shell nanopillar-array films were fabricated using atomic layer deposition and dry etching techniques via barrier-free porous anodic alumina templates. The photocatalytic activity of the prepared films was evaluated by methylene blue (MB) bleaching under 352 nm UV light irradiation. The results show that the photocatalytic activity of TiO2 film was 45% improved by introducing a SnO2 film between TiO2 and ITO glass substrate and was 300% improved by using the SnO2-TiO2 core-shell nanopillar-array structure. The 45% improvement by the SnO2 interlayer is attributed to the SnO2/TiO2 heterojunction which separates the photogenerated electron-hole pairs in TiO2 for MB degradation, and the high photocatalytic activity of the SnO2-TiO2 core-shell nanopillar-array films is attributed to the three dimensional SnO2/TiO2 heterojunction which owns both the carrier separation ability and the high photocatalytic reaction surface area.

A mini-review on rare earth metal-doped TiO2 for photocatalytic remediation of wastewater.

PubMed

Saqib, Najm Us; Adnan, Rohana; Shah, Irfan

2016-08-01

Titanium dioxide (TiO2) has been considered a useful material for the treatment of wastewater due to its non-toxic character, chemical stability and excellent electrical and optical properties which contribute in its wide range of applications, particularly in environmental remediation technology. However, the wide band gap of TiO2 photocatalyst (anatase phase, 3.20 eV) limits its photocatalytic activity to the ultraviolet region of light. Besides that, the electron-hole pair recombination has been found to reduce the efficiency of the photocatalyst. To overcome these problems, tailoring of TiO2 surface with rare earth metals to improve its surface, optical and photocatalytic properties has been investigated by many researchers. The surface modifications with rare earth metals proved to enhance the efficiency of TiO2 photocatalyts by way of reducing the band gap by shifting the working wavelength to the visible region and inhibiting the anatase-to-rutile phase transformations. This review paper summarises the attempts on modification of TiO2 using rare earth metals describing their effect on the photocatalytic activities of the modified TiO2 photocatalyst.

Effect of annealing ambience on the formation of surface/bulk oxygen vacancies in TiO2 for photocatalytic hydrogen evolution

NASA Astrophysics Data System (ADS)

Hou, Lili; Zhang, Min; Guan, Zhongjie; Li, Qiuye; Yang, Jianjun

2018-01-01

The surface and bulk oxygen vacancy have a prominent effect on the photocatalytic performance of TiO2. In this study, TiO2 possessing different types and concentration of oxygen vacancies were prepared by annealing nanotube titanic acid (NTA) at various temperatures in air or vacuum atmosphere. TiO2 with the unitary bulk single-electron-trapped oxygen vacancies (SETOVs) formed when NTA were calcined in air. Whereas, TiO2 with both bulk and surface oxygen vacancies were obtained when NTA were annealed in vacuum. The series of TiO2 with different oxygen vacancies were systematically characterized by TEM, XRD, PL, XPS, ESR, and TGA. The PL and ESR analysis verified that surface oxygen vacancies and more bulk oxygen vacancies could form in vacuum atmosphere. Surface oxygen vacancies can trap electron and hinder the recombination of photo-generated charges, while bulk SETOVs act as the recombination center. The surface or bulk oxygen vacancies attributed different roles on the photo-absorbance and activity, leading that the sample of NTA-A400 displayed higher hydrogen evolution rate under UV light, whereas NTA-V400 displayed higher hydrogen evolution rate under visible light because bulk SETOVs can improve visible light absorption because sub-band formed by bulk SETOVs prompted the secondary transition of electron excited.

Molecular and dissociative adsorption of DMMP, Sarin and Soman on dry and wet TiO2(110) using density functional theory

NASA Astrophysics Data System (ADS)

Quintero, Yenny Cardona; Nagarajan, Ramanathan

2018-09-01

Titania, among the metal oxides, has shown promising characteristics for the adsorption and decontamination of chemical warfare nerve agents, due to its high stability and rapid decomposition rates. In this study, the adsorption energy and geometry of the nerve agents Sarin and Soman, and their simulant dimethyl methyl phosphonate (DMMP) on TiO2 rutile (110) surface were calculated using density functional theory. The molecular and dissociative adsorption of the agents and simulant on dry as well as wet metal oxide surfaces were considered. For the wet system, computations were done for the cases of both molecularly adsorbed water (hydrated conformation) and dissociatively adsorbed water (hydroxylated conformation). DFT calculations show that dissociative adsorption of the agents and simulant is preferred over molecular adsorption for both dry and wet TiO2. The dissociative adsorption on hydrated TiO2 shows higher stability among the different configurations considered. The dissociative structure of DMMP on hydrated TiO2 (the most stable one) was identified as the dissociation of a methyl group and its adsorption on the TiO2 surface. For the nerve agents Sarin and Soman on hydrated TiO2 the dissociative structure was by the dissociation of the F atom from the molecule and its interaction with a Ti atom from the surface, which could indicate a reduction in the toxicity of the products. This study shows the relevance of water adsorption on the metal oxide surface for the stability and dissociation of the simulant DMMP and the nerve agents Sarin and Soman on TiO2.

Three-dimensional assembly structure of anatase TiO2 hollow microspheres with enhanced photocatalytic performance

NASA Astrophysics Data System (ADS)

Tang, Yihao; Zhan, Shuai; Wang, Li; Zhang, Bin; Ding, Minghui

The pure anatase TiO2 hollow microspheres are synthesized by a one-step template-free hydrothermal route. By defining temperature and time limits, we produce TiO2 hollow microspheres with a fluoride-mediated self-transformation. The surface morphology of TiO2 hollow microspheres was studied by SEM. The hollow microspheres have diameters of about 800 nm and are remarkably uniform. The UV-light photocatalytic activity and the stability/multifunction of TiO2 hollow microspheres structure were evaluated by photocatalytic degradation of methylene blue and photocatalytic hydrogen evolution. The excellent photocatalytic activity is attributed to large specific surface area, more active sites, unique hollow structures, and improved light scattering.

Surface micro-dissolve method of imparting self-cleaning property to cotton fabrics in NaOH/urea aqueous solution

NASA Astrophysics Data System (ADS)

Fan, Tao; Hu, Ruimin; Zhao, Zhenyun; Liu, Yiping; Lu, Ming

2017-04-01

A simple and economical micro-dissolved process of embedding titanium dioxide (TiO2) nanoparticles into surface zone of cotton fabrics was developed. TiO2 was coated on cotton fabrics in 7% wt NaOH/12% wt urea aqueous solution at low temperature. Photocatalytic efficiency of cotton fabrics treated with TiO2 nanoparticles was studied upon measuring the photocatalytic decoloration of Rhodamine B (RhB) under ultraviolet irradiation. Self-cleaning property of cotton fabric coated with TiO2 was evaluated with color depth of samples (K/S value). The treated fabrics were characterized using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Fourier transform infrared spectroscopy (FITR), tensile strength, stiffness and whiteness. The results indicated, TiO2 nanoparticles could be embedded on the surface layer of cotton fabrics throuth surface micro-dissolve method. Treated cotton fabrics possessed distinct photocatalytic efficiency and self-cleaning properties. Tensile strength and whiteness of modified cotton fabrics appeared moderately increasement.

Modified surface of titanium dioxide nanoparticles-based biosensor for DNA detection

NASA Astrophysics Data System (ADS)

Nadzirah, Sh.; Hashim, U.; Rusop, M.

2018-05-01

A new technique was used to develop a simple and selective picoammeter DNA biosensor for identification of E. coli O157:H7. This biosensor was fabricated from titanium dioxide nanoparticles that was synthesized by sol-gel method and spin-coated on silicon dioxide substrate via spinner. 3-Aminopropyl triethoxy silane (APTES) was used to modify the surface of TiO2. Simple surface modification approach has been applied; which is single dropping of APTES onto the TiO2 nanoparticles surface. Carboxyl modified probe DNA has been bind onto the surface of APTES/TiO2 without any amplifier element. Electrical signal has been used as the indicator to differentiate each step (surface modification of TiO2 and probe DNA immobilization). The I-V measurements indicate extremely low current (pico-ampere) flow through the device which is 2.8138E-10 A for pure TiO2 nanoparticles, 2.8124E-10 A after APTES modification and 3.5949E-10 A after probe DNA immobilization.

Effect of HCl and H2SO4 treatment of TiO2 powder on the photosensitized degradation of aqueous rhodamine B under visible light.

PubMed

Park, Se-Keun; Shin, Hyunho

2014-10-01

The acid treatments of TiO2 nanopowder with HCI or H2SO4 solution increase the concentration of the hydroxyl group on TiO2 surfaces compared to bare TiO2, which acts as a Brønsted acid site. For the case of the HCl-treated TiO2, the dissociation of Brønsted acid (proton donor) sites on TiO2 leads to a drop in the pH levels of rhodamine B (RhB) dye solutions (leading to the protonation of the RhB molecule), which allows the physisorption of the uncharged carboxyl acid group on the positively charged TiO2 surface. The carboxyl acid group is believed to afford a more efficient charge injection from the Visible-light-excited RhB to the conduction band of TiO2 compared to the N-ethyl group, yielding a significantly enhanced photodegradation of RhB mainly via the N-de-ethylation pathway. For the case of the H2SO4-treated TiO2, although the dissociation of Brønsted acid sites on TiO2 is also achieved, its photoactivity is much lower than that of the HCl-treated TiO2. It seems that the presence of SO4(2-) on the H2SO4-treated TiO2 behaves as an *OH scavenger to prevent the photodegradation of the dye.

Study the target effect on the structural, surface and optical properties of TiO2 thin film fabricated by RF sputtering method

NASA Astrophysics Data System (ADS)

Vyas, Sumit; Tiwary, Rohit; Shubham, Kumar; Chakrabarti, P.

2015-04-01

The effect of target (Ti metal target and TiO2 target) on Titanium Dioxide (TiO2) thin films grown on ITO coated glass substrate by RF magnetron sputtering has been investigated. A comparative study of both the films was done in respect of crystalline structure, surface morphology and optical properties by using X-ray diffractometer (XRD), Atomic Force Microscopy (AFM) studies and ellipsometric measurements. The XRD results confirmed the crystalline structure and indicated that the deposited films have the intensities of anatase phase. The surface morphology and roughness values indicated that the film using Ti metal target has a smoother surface and densely packed with grains as compared to films obtained using TiO2 target. A high transmission in the visible region, and direct band gap of 3.67 eV and 3.75 eV for films derived by using Ti metal and TiO2 target respectively and indirect bandgap of 3.39 eV for the films derived from both the targets (Ti metal and TiO2 target) were observed by the ellipsometric measurements.

Photocatalytic reduction of heavy metal ions on derivatized titanium dioxide nano-particle surface studied by XAFS

NASA Astrophysics Data System (ADS)

Chen, Lin X.; Rajh, Tijana; Mićić, Olga Wang, Zhiyu; Tiede, David M.; Thurnauer, Marion

1997-12-01

Photoreduction of heavy metal ions, Cu 2- and Hg 2+, on TiO 2 nano-particle surfaces, has been investigated by XAFS measurements. The effects of TiO 2 surface modification reagents on the reaction efficiency have been studied. We observed a significant reaction efficiency enhancement when amino acid alanine was added to a mixture of 0.01 M Cu 2+ and TiO 2 nano-particles. Fifty percent of the adsorbed Cu 2+ has been reduced to Cu 0 after 1-h illumination with a UV-enhanced xenon lamp. Photoreduction of Hg 2+ on TiO 2 colloid surfaces was also investigated without and with thiolactic acid (TLA). In this case, the photoreduction efficiency for Hg 2+ was lowered. Structures of metal ion surroundings in various complexes as well as their role in photoreduction of metal ions are discussed.

Clarification of the interaction between Au atoms and the anatase TiO2 (112) surface using density functional theory

NASA Astrophysics Data System (ADS)

Tada, Kohei; Koga, Hiroaki; Okumura, Mitsutaka; Tanaka, Shingo

2018-04-01

A model (112) surface slab of anatase TiO2 (112) was optimized, and the adsorption of Au atoms onto the (112) surface was investigated by first-principles calculations based on DFT (density functional theory) with the generalized gradient approximation (GGA). Furthermore, the results were compared with those of Au/anatase TiO2 (101) system. The (112) surface has a ridge and a groove (zig-zag structure). The Au atoms were strongly adsorbed in the grooves but became unstable as they climbed toward the ridges, and the promotion of electrons in the 5d orbitals to the 6s and 6p orbitals in the absorbed Au atom occurred. At the Au/anatase TiO2 interface, the Au-Ti4+ coordinate bond in the (112) system is stronger than that in the (101) system because the promotion of electrons is greater in the former interaction than the latter. The results suggest that Au/anatase TiO2 catalysts with a higher dispersion of Au nanoparticles could be prepared when the (112) surface is preferentially exposed.

Nanostructured Gd3+-TiO2 surfaces for self-cleaning application

NASA Astrophysics Data System (ADS)

Saif, M.; El-Molla, S. A.; Aboul-Fotouh, S. M. K.; Ibrahim, M. M.; Ismail, L. F. M.; Dahn, Douglas C.

2014-06-01

Preparation of self-cleaning surfaces based on lanthanide modified titanium dioxide nanoparticles has rarely been reported. In the present work, gadolinium doped titanium dioxide thin films (x mol Gd3+-TiO2 where x = 0.000, 0.005, 0.008, 0.010, 0.020 and 0.030 mol) were synthesized by sol-gel method and deposited using doctor-blade method. These films were characterized by studying their structural, optical and electrical properties. Doping with gadolinium decreases the band gap energy and increase conductivity of thin films. The photo self-cleaning activity in term of quantitative determination of the active oxidative species (rad OH) produced on the thin film surfaces was evaluated using fluorescent probe method. The results show that, the highly active thin film is the 0.020 Gd3+-TiO2. The structural, morphology, optical, electrical and photoactivity properties of Gd3+-TiO2 thin films make it promising surfaces for self-cleaning application. Mineralization of commercial textile dye (Remazol Red RB-133, RR) and durability using 0.020Gd3+-TiO2 film surface was studied.

Experimental study of the visible-light photocatalytic activity of oxygen-deficient TiO2 prepared with Ar/H2 plasma surface treatment

NASA Astrophysics Data System (ADS)

Nakano, Takuma; Yazawa, Shota; Araki, Shota; Kogoshi, Sumio; Katayama, Noboru; Kudo, Yusuke; Nakanishi, Tetsuya

2015-01-01

Oxygen-deficient TiO2 (TiO2-x) has been proposed as a visible-light-responsive photocatalyst. TiO2-x thin films were prepared by Ar/H2 plasma surface treatment, applying varying levels of microwave input power and processing times. The highest visible light photocatalytic activity was observed when using an input power of 200 W, a plasma processing time of 10 min, and a 1:1 \\text{Ar}:\\text{H}2 ratio, conditions that generate an electron temperature of 5.7(±1.0) eV and an electron density of 8.5 × 1010 cm-3. The maximum formaldehyde (HCHO) removal rate of the TiO2-x film was 2.6 times higher than that obtained from a TiO2-xNx film under the same test conditions.

DFT study of benzyl alcohol/TiO2 interfacial surface complex: reaction pathway and mechanism of visible light absorption.

PubMed

Zhao, Lei; Gu, Feng Long; Kim, Minjae; Miao, Maosheng; Zhang, Rui-Qin

2017-09-24

We propose a new pathway for the adsorption of benzyl alcohol on the surface of TiO 2 and the formation of interfacial surface complex (ISC). The reaction free energies and reaction kinetics were thoroughly investigated by density functional calculations. The TiO 2 surfaces were modeled by clusters consisting of 4 Ti atoms and 18 O atoms passivated by H, OH group and H 2 O molecules. Compared with solid-state calculations utilizing the periodicity of the materials, such cluster modeling allows inclusion of the high-order correlation effects that seem to be essential for the adsorption of organic molecules onto solid surfaces. The effects of both acidity and solvation are included in our calculations, which demonstrate that the new pathway is competitive with a previous pathway. The electronic structure calculations based on the relaxed ISC structures reveal that the chemisorption of benzyl alcohol on the TiO 2 surface greatly alters the nature of the frontier molecular orbitals. The resulted reduced energy gap in ISC matches the energy of visible light, showing how the adsorption of benzyl alcohol sensitizes the TiO 2 surface. Graphical Abstract The chemisorption of benzyl alcohol on TiO 2 surface greatly alters the nature of the frontier molecular orbitals and the formed interfacial surface complex can be sensitized by visible light.

Opposite effect of photocorrosion on photocatalytic performance among various AgxMyOz/TiO2 (M = C, P) photocatalysts: A novel effective method for preparing Ag/TiO2 composite

NASA Astrophysics Data System (ADS)

Feng, Caixia; Pang, Yuhua; Wang, Yan; Sun, Mingming; Zhang, Chenyan; Zhang, Ling; Zhou, Yanmei; Li, Deliang

2016-07-01

Three kinds of hybrids, Ag2CO3/TiO2, Ag2C2O4/TiO2 and Ag3PO4/TiO2 comprising of P25-TiO2 and silver-containing photocatalyst, (together coded as AgxMyOz/TiO2 (M = C, P)) were prepared via a facile precipitation method. The photocatalytic activity and stability of the as-prepared AgxMyOz/TiO2 was compared by monitoring the oxidation of propylene under visible light irradiation. Results showed that both Ag2CO3/TiO2 and Ag2C2O4/TiO2 exhibit perfect performance with a high propylene degradation removal rate of 88% and 78%, respectively, during four successive experimental runs. On the contrary, for Ag3PO4/TiO2, the photocatalytic activity gradually declines to 8% from 32% under the same conditions. In order to explore the reason for the above remarkable difference in activity and stability over AgxMyOz/TiO2, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and UV-vis diffuse reflectance spectroscopy (DRS) were used to investigate the change of AgxMyOz/TiO2 before and after irradiation. It was found that three silver-containings, Ag2CO3, Ag2C2O4 and Ag3PO4 on the surface of TiO2, all experienced photo-corrosion to various extents during irradiation process. Surprisingly, the effect of photo-corrosion on visible light activity and stability among various AgxMyOz/TiO2 is very different. For both Ag2CO3 and Ag2C2O4, they are easily decomposed into metallic Ag and CO2, and gaseous CO2 escaped from catalyst leaving silver nanoparticles on the surface of TiO2 resulted in the formation of plasmonic photocatalyst Ag/TiO2. The synergetic effect between surface plasma resonance of silver and interfacial electron transfer over the obtained Ag/TiO2 heterojunctions is in favor of the superior photocatalytic performance under visible light. While for Ag3PO4/TiO2, Ag3PO4 on the surface of TiO2 is partially photo-decomposed into Ag and phosphorus oxide and the phosphorus oxide covering on the surface of undecomposed Ag3PO4/TiO2 deactivates its photocatalytic performance. By comparison with the traditional Ag/TiO2 synthesized by photochemical reduction method, it was found that the photo-corrosion of Ag2CO3/TiO2 or Ag2C2O4/TiO2 can be used as a more effective method for preparing Ag/TiO2 composite.

Deposition of gold nanoparticles from colloid on TiO2 surface

NASA Astrophysics Data System (ADS)

Rehacek, Vlastimil; Hotovy, Ivan

2017-11-01

In this paper, experimental results are presented on the deposition of colloidal gold nanoparticles on the surfaces of TiO2 prepared on silicon/silicon dioxide. Important procedures, such as titanium dioxide surface hydrophilization as well as functionalization by an organosilane coupling agent (3-aminopropyl) trimethoxysilane and (3-mercaptopropyl) trimethoxysilane were investigated in order to obtain a metal oxide surface with the most convenient properties for immobilization of gold nanoparticles having a dense and uniform distribution. TiO2 nanotips prepared by reactive ion etching of oxide surface covered with self-mask gold nanoparticles are demonstrated.

Highly sensitive biofunctionalized mesoporous electrospun TiO(2) nanofiber based interface for biosensing.

PubMed

Mondal, Kunal; Ali, Md Azahar; Agrawal, Ved V; Malhotra, Bansi D; Sharma, Ashutosh

2014-02-26

The surface modified and aligned mesoporous anatase titania nanofiber mats (TiO2-NF) have been fabricated by electrospinning for esterified cholesterol detection by electrochemical technique. The electrospinning and porosity of mesoporous TiO2-NF were controlled by use of polyvinylpyrrolidone (PVP) as a sacrificial carrier polymer in the titanium isopropoxide precursor. The mesoporous TiO2-NF of diameters ranging from 30 to 60 nm were obtained by calcination at 470 °C and partially aligned on a rotating drum collector. The functional groups such as -COOH, -CHO etc. were introduced on TiO2-NF surface via oxygen plasma treatment making the surface hydrophilic. Cholesterol esterase (ChEt) and cholesterol oxidase (ChOx) were covalently immobilized on the plasma treated surface of NF (cTiO2-NF) via N-ethyl-N0-(3-dimethylaminopropyl carbodiimide) and N-hydroxysuccinimide (EDC-NHS) chemistry. The high mesoporosity (∼61%) of the fibrous film allowed enhanced loading of the enzyme molecules in the TiO2-NF mat. The ChEt-ChOx/cTiO2-NF-based bioelectrode was used to detect esterified cholesterol using electrochemical technique. The high aspect ratio, surface area of aligned TiO2-NF showed excellent voltammetric and catalytic response resulting in improved detection limit (0.49 mM). The results of response studies of this biosensor show excellent sensitivity (181.6 μA/mg dL(-1)/cm(2)) and rapid detection (20 s). This proposed strategy of biomolecule detection is thus a promising platform for the development of miniaturized device for biosensing applications.

Effect of nuclear vibrations, temperature, and orientation on injection and recombination conditions in amino-phenyl acid dyes on TiO2

NASA Astrophysics Data System (ADS)

Manzhos, Sergei; Segawa, Hiroshi; Yamashita, Koichi

2012-06-01

Adsorption geometry, nuclear vibrations, and molecular orientation of the dye with respect to the oxide surface affect significantly the performance of dye-sensitized solar cells. We compute the influence of these factors on injection and recombination conditions in organic amino-phenyl acid dyes differing by the donor group on the anatase (101) surface of titania. Nuclear motions affect significantly and differently between the dyes the driving force to injection Δ G. A temperature increase from 300 to 350 K does not have a noticeable effect on the distribution of injection rates in all studied system. Molecular dynamics simulations predict configurations in which dyes tend to lay flat on the oxide surface. The resulting proximity of the oxidation equivalent hole to the oxide is expected to promote recombination. Temporal evolution of the driving force to injection is found to be independent of dye orientation and uncorrelated to the oscillations of the Odye Ti bonds through which the dye is attached to the surface. We conclude that the dynamics of Δ G(t) is explained by uncorrelated evolution of the energies of the dye excited state and of the conduction band minimum of the oxide due to their respective vibrations. This suggests that it must be possible to control independently conditions of recombination (e.g. by preventing the dye oxidation hole from approaching TiO2 by using co-adsorbates) and of injection (e.g. by designing dyes where non-equilibrium geometries strongly destabilize dye's LUMO to increase Δ G).

Growing TiO2 nanowires on the surface of graphene sheets in supercritical CO2: characterization and photoefficiency.

PubMed

Farhangi, Nasrin; Medina-Gonzalez, Yaocihuatl; Chowdhury, Rajib Roy; Charpentier, Paul A

2012-07-27

Tremendous interest exists towards synthesizing nanoassemblies for dye-sensitized solar cells (DSSCs) using earth-abundant and -friendly materials with green synthetic approaches. In this work, high surface area TiO(2) nanowire arrays were grown on the surface of functionalized graphene sheets (FGSs) containing -COOH functionalities acting as a template by using a sol-gel method in the green solvent, supercritical carbon dioxide (scCO(2)). The effect of scCO(2) pressure (1500, 3000 and 5000 psi), temperature (40, 60 and 80 °C), acetic acid/titanium isopropoxide monomer ratios (HAc/TIP = 2, 4 and 6), functionalized graphene sheets (FGSs)/TIP weight ratios (1:20, 1:40 and 1:60 w/w) and solvents (EtOH, hexane) were investigated. Increasing the HAc/TIPweight ratio from 4 to 6 in scCO(2) resulted in increasing the TiO(2) nanowire diameter from 10 to 40 nm. Raman and high resolution XPS showed the interaction of TiO(2) with the -COOH groups on the surface of the graphene sheets, indicating that graphene acted as a template for polycondensation growth. UV-vis diffuse reflectance and photoluminescence spectroscopy showed a reduction in titania's bandgap and also a significant reduction in electron-hole recombination compared to bare TiO(2) nanowires. Photocurrent measurements showed that the TiO(2)nanowire/graphene composites prepared in scCO(2) gave a 5× enhancement in photoefficiency compared to bare TiO(2) nanowires.

Growing TiO2 nanowires on the surface of graphene sheets in supercritical CO2: characterization and photoefficiency

NASA Astrophysics Data System (ADS)

Farhangi, Nasrin; Medina-Gonzalez, Yaocihuatl; Chowdhury, Rajib Roy; Charpentier, Paul A.

2012-07-01

Tremendous interest exists towards synthesizing nanoassemblies for dye-sensitized solar cells (DSSCs) using earth-abundant and -friendly materials with green synthetic approaches. In this work, high surface area TiO2 nanowire arrays were grown on the surface of functionalized graphene sheets (FGSs) containing -COOH functionalities acting as a template by using a sol-gel method in the green solvent, supercritical carbon dioxide (scCO2). The effect of scCO2 pressure (1500, 3000 and 5000 psi), temperature (40, 60 and 80 °C), acetic acid/titanium isopropoxide monomer ratios (HAc/TIP = 2, 4 and 6), functionalized graphene sheets (FGSs)/TIP weight ratios (1:20, 1:40 and 1:60 w/w) and solvents (EtOH, hexane) were investigated. Increasing the HAc/TIPweight ratio from 4 to 6 in scCO2 resulted in increasing the TiO2 nanowire diameter from 10 to 40 nm. Raman and high resolution XPS showed the interaction of TiO2 with the -COOH groups on the surface of the graphene sheets, indicating that graphene acted as a template for polycondensation growth. UV-vis diffuse reflectance and photoluminescence spectroscopy showed a reduction in titania’s bandgap and also a significant reduction in electron-hole recombination compared to bare TiO2 nanowires. Photocurrent measurements showed that the TiO2nanowire/graphene composites prepared in scCO2 gave a 5× enhancement in photoefficiency compared to bare TiO2 nanowires.

Surface-modified TiO2 powders with phenol derivatives: A comparative DFT and experimental study

NASA Astrophysics Data System (ADS)

Sredojević, Dušan N.; Kovač, Tijana; Džunuzović, Enis; Ðorđević, Vesna; Grgur, Branimir N.; Nedeljković, Jovan M.

2017-10-01

The charge transfer complex formation between TiO2 powder and variety of phenol derivatives (phenol, 4-nitrophenol, 4-bromophenol, 4-tert-butylphenol, hydroquinone) was achieved. The red-shift of optical absorption was observed upon surface modification of TiO2 powders with phenol derivatives. The influence of substituent functional groups in para position on the optical band gap and conduction band edge of inorganic/organic hybrids was studied using reflection spectroscopy and cyclic voltammetry. The experimental findings were supported by density functional theory calculations. The measured reflection spectra of surface-modified TiO2 powders with phenol derivatives were compared with calculated electronic excitation spectra of corresponding model systems.

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

NASA Astrophysics Data System (ADS)

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

2016-05-01

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.

Incorporation of TiO2 nanotubes in a polycrystalline zirconia: Synthesis of nanotubes, surface characterization, and bond strength.

PubMed

Dos Santos, Angélica Feltrin; Sandes de Lucena, Fernanda; Sanches Borges, Ana Flávia; Lisboa-Filho, Paulo Noronha; Furuse, Adilson Yoshio

2018-04-05

Despite numerous advantages such as high strength, the bond of yttria-stabilized zirconia polycrystal (Y-TZP) to tooth structure requires improvement. The purpose of this in vitro study was to evaluate the incorporation of TiO 2 nanotubes into zirconia surfaces and the bond strength of resin cement to the modified ceramic. TiO 2 nanotubes were produced by alkaline synthesis, mixed with isopropyl alcohol (50 wt%) and applied on presintered zirconia disks. The ceramics were sintered, and the surfaces were characterized by confocal laser microscopy, scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDS) analysis. For bond strength, the following 6 groups (n=16) were evaluated: without TiO 2 and Single Bond Universal; with TiO 2 nanotubes and Single Bond Universal; without TiO 2 nanotubes and Z-prime; with TiO 2 nanotubes and Z-prime; without TiO 2 and Signum Zirconia Bond; with TiO 2 and Signum Zirconia Bond. After sintering, resin cement cylinders, diameter of 1.40 mm and 1 mm in height, were prepared and polymerized for 20 seconds. Specimens were stored in water at 37°C for 30 days and submitted to a shear test. Data were analyzed by 2-way ANOVA and Tukey honest significant difference (α=.05) tests. EDS analysis confirmed that nanoagglomerates were composed of TiO 2 . The shear bond strength showed statistically significant differences among bonding agents (P<.001). No significant differences were found with the application of nanotubes, regardless of the group analyzed (P=.682). The interaction among the bonding agent factors and addition of nanotubes was significant (P=.025). Nanotubes can be incorporated into zirconia surfaces. However, this incorporation did not improve bond strength. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

TiO2 Nanoparticle-Induced Oxidation of the Plasma Membrane: Importance of the Protein Corona.

PubMed

Runa, Sabiha; Lakadamyali, Melike; Kemp, Melissa L; Payne, Christine K

2017-09-21

Titanium dioxide (TiO 2 ) nanoparticles, used as pigments and photocatalysts, are widely present in modern society. Inhalation or ingestion of these nanoparticles can lead to cellular-level interactions. We examined the very first step in this cellular interaction, the effect of TiO 2 nanoparticles on the lipids of the plasma membrane. Within 12 h of TiO 2 nanoparticle exposure, the lipids of the plasma membrane were oxidized, determined with a malondialdehyde assay. Lipid peroxidation was inhibited by surface passivation of the TiO 2 nanoparticles, incubation with an antioxidant (Trolox), and the presence of serum proteins in solution. Subsequent experiments determined that serum proteins adsorbed on the surface of the TiO 2 nanoparticles, forming a protein corona, inhibit lipid peroxidation. Super-resolution fluorescence microscopy showed that these serum proteins were clustered on the nanoparticle surface. These protein clusters slow lipid peroxidation, but by 24 h, the level of lipid peroxidation is similar, independent of the protein corona or free serum proteins. Additionally, over 24 h, this corona of proteins was displaced from the nanoparticle surface by free proteins in solution. Overall, these experiments provide the first mechanistic investigation of plasma membrane oxidation by TiO 2 nanoparticles, in the absence of UV light and as a function of the protein corona, approximating a physiological environment.

The effect of TiO2 phase on the surface plasmon resonance of silver thin film

NASA Astrophysics Data System (ADS)

Hong, Ruijin; Jing, Ming; Tao, Chunxian; Zhang, Dawei

2016-10-01

A series of silver films with various thicknesses were deposited on TiO2 covered silica substrates by magnetron sputtering at room temperature. The effects of TiO2 phase on the structure, optical properties and surface plasmon resonance of silver thin films were investigated by x-ray diffraction, optical absorption and Raman scattering measurements, respectively. By adjusting the silver layer thickness, the resonance wavelength shows a redshift, which is due to a change in the electromagnetic field coupling strength from the localized surface plasmons excited between the silver thin film and TiO2 layer. Raman scattering measurement results showed that optical absorption plays an important role in surface plasmon enhancement, which is also related to different crystal phase.

Synthesis and characterization of TiO₂ and TiO₂/Ag for use in photodegradation of methylviologen, with kinetic study by laser flash photolysis.

PubMed

Ramos, Dayana Doffinger; Bezerra, Paula C S; Quina, Frank H; Dantas, Renato F; Casagrande, Gleison A; Oliveira, Silvio C; Oliveira, Márcio R S; Oliveira, Lincoln C S; Ferreira, Valdir S; Oliveira, Samuel L; Machulek, Amilcar

2015-01-01

This paper reports the synthesis, characterization, and application of TiO2 and TiO2/Ag nanoparticles for use in photocatalysis, employing the herbicide methylviologen (MV) as a substrate for photocatalytic activity testing. At suitable metal to oxide ratios, increases in silver surface coating on TiO2 enhanced the efficiency of heterogeneous photocatalysis by increasing the electron transfer constant. The sol-gel method was used for TiO2 synthesis. P25 TiO2 was the control material. Both oxides were subjected to the same silver incorporation process. The materials were characterized by conventional spectroscopy, SEM micrography, X-ray diffraction, calculation of surface area per mass of catalyst, and thermogravimetry. Also, electron transfers between TiO2 or TiO2/Ag and MV in the absence and presence of sodium formate were investigated using laser flash photolysis. Oxides synthesized with 2.0 % silver exhibited superior photocatalytic activity for MV degradation.

TiO2-BASED Composite Films for the Photodegradation of Oxytetracycline

NASA Astrophysics Data System (ADS)

Li, Hui; Guan, Ling-Xiao; Feng, Ji-Jun; Li, Fang; Yao, Ming-Ming

2015-02-01

The spread of the antibiotic oxytetracycline (OTC) has been thought as a threat to the safety of drinking water. In this paper, the photocatalytic activity of the nanocrystalline Fe/Ca co-doped TiO2-SiO2 composite film for the degradation of OTC was studied. The films were characterized by field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy (EDS), N2 adsorption/desorption isotherms, photoluminescence (PL) spectra, and UV-Vis diffraction reflectance absorption spectra (DRS). The FE-SEM results indicated that the Fe/Ca co-doped TiO2-SiO2 film was composed of smaller nanoparticles compared to pure TiO2 or TiO2-SiO2 film. The BET surface area results showed that the specific surface area of the pure TiO2, TiO2-SiO2 and Ca2+/Fe3+ co-doped TiO2-SiO2 is 118.3 m2g-1, 294.3 m2g-1 and 393.7 m2g-1, respectively. The DRS and PL spectra revealed that the Fe/Ca co-doped TiO2-SiO2 film had strong visible light adsorption and diminished electrons/holes recombination. Experimental results showed that the Fe/Ca co-doped TiO2-SiO2 film is effective in the degradation of OTC under both UV and visible light irradiation.

Natural fiber templated TiO2 microtubes via a double soaking sol-gel route and their photocatalytic performance

NASA Astrophysics Data System (ADS)

Yang, Li; Li, Xu; Wang, Ziru; Shen, Yun; Liu, Ming

2017-10-01

TiO2 microtubes with a yam-like surface were prepared for the first time through a simple and efficient double soaking sol-gel route by utilizing Platanus acerifolia seed fibers as bio-templates. The physicochemical properties of the samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Brunauer Emmett Teller (BET) surface analysis and Ultraviolet-visible absorption spectroscopy (UV-vis). The results showed that the obtained TiO2 microtubes had an anatase phase and were composed of a smooth internal wall and a rough yam-like external wall with an average diameter of 24 μm and the wall thickness of 2 μm. The surface area and pore volume of the as-prepared TiO2 microtubes reached 128.271 m2/g and 0.149 cm3/g, respectively. The UV-vis analysis displayed a favorable extension of light absorption capacity of TiO2 microtubes. The synthetic mechanism was preliminarily discussed as well. The moisture in the natural fiber templates facilitated the mild hydrolysis of titanium sol, leaving a prime layer on the surface of the fibers, and subsequently assisted in the successful preparation of TiO2 microtubes with a yam-like surface without requiring specific control of hydrolysis. Photocatalytic experiments indicated that the as-obtained TiO2 microtubes exhibited a higher efficiency than commercial P25 in the degradation of tetracycline hydrochloride.

Effect of nanostructured titanium on anodization growth of self-organized TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Zhang, Lan; Han, Yong

2010-02-01

To understand the effect of substrate microstructure on the formation of TiO2 nanotubes, anodic oxidizations of commercially pure titanium subjected to surface mechanical attrition treatment (SMATed-Ti) and unSMATed-Ti in a glycol solution containing NH4F and small amounts of water were investigated. The SMATed-Ti exhibit a nanocrystallized surface layer containing a high density of grain boundaries compared with unSMATed-Ti. The anodization results show that the formed TiO2 nanotube layer on the SMATed-Ti is much thicker than that on the unSMATed-Ti. It is indicated that nanocrystallized Ti is propitious to the growth of TiO2 nanotubes; grain boundaries and dislocations play the leading role in accelerating the reaction rate and ion diffusion coefficient during anodization. In addition, nanocrystallization of Ti does not change surface morphologies and phase components of the TiO2 nanotubes.

Air Purification Pavement Surface Coating by Atmospheric Pressure Cold Plasma

NASA Astrophysics Data System (ADS)

Westergreen, Joe; Pedrow, Patrick; Shen, Shihui; Jobson, Bertram

2011-10-01

This study develops an atmospheric pressure cold plasma (APCP) reactor to produce activated radicals from precursor molecules, and to immobilize nano titanium dioxide (TiO2) powder to substrate pavement materials. TiO2 has photocatalytic properties and under UV light can be used to oxidize and remove volatile organic compounds (VOCs) and nitrogen oxides (NOx) from the atmosphere. Although TiO2 treated paving materials have great potential to improve air quality, current techniques to adhere TiO2 to substrate materials are either not durable or reduce direct contact of TiO2 with UV light, reducing the photocatalytic effect. To solve this technical difficulty, this study introduces APCP techniques to transportation engineering to coat TiO2 to pavement. Preliminary results are promising and show that TiO2 can be incorporated successfully into an APCP environment and can be immobilized at the surface of the asphalt substrate. The TiO2 coated material with APCP shows the ability to reduce nitrogen oxides when exposed to UV light in an environmental chamber. The plasma reactor utilizes high voltage streamers as the plasma source.

Biological consequences from interaction of nanosized titanium(iv) oxides with defined human blood components

NASA Astrophysics Data System (ADS)

Stella, Aaron

The utility of engineered nanomaterials is growing, particularly the titanium(iv) oxide (titanium dioxide, TiO2) nanoparticles. TiO 2 is very useful for brightening paints, and coloring foods. Nano-sized TiO2 is also useful for sunscreens, cosmetics, and can be utilized as a photocatalyst. However, the nanometer size of the TiO2 nanoparticle is a characteristic that may contribute oxidative stress to red blood cells (RBCs) in humans. This study utilized screening methods to evaluate different forms of TiO2 nanoparticles which differ by primary particle size, specific surface area, crystalline phase, and surface polarity. RBCs are rich in the intracellular antioxidant glutathione (GSH). HPLC analysis revealed that some TiO2 nanoparticles caused oxidation of GSH to glutathione disulfide (GSSG). Vitamin E is a major membrane-bound antioxidant. Vitamin E levels were then determined by HPLC in the RBC membrane after exposure to TiO2 nanoparticles. The HPLC results showed that each nanoparticle oxidized RBC glutathione and membrane vitamin E at different rates. When hemoglobin was mixed with each TiO2 nanoparticle, hemoglobin was adsorbed at varying rates to the surface of the nanoparticles. Similarly, the aminothiol homocysteine was also adsorbed at different rates by the TiO2 nanoparticles. Using light microscopy, some TiO2 nanoparticles caused the formation of RBC aggregates which significantly changed the RBC morphology. The aggregation data was quantified using a hemacytometer. The TiO2 nanoparticles also caused hemolysis of RBCs. Hemolysis is considered to be a toxic endpoint for RBCs. Changes in the nucleated lymphocyte gene expression of certain oxidative stress genes were also observed using real-time polymerase chain reaction (qPCR). The data indicates that RBCs can ultimately be hemolyzed by biological oxidative damage resulting from a combination of oxidative mechanisms. Additionally, the TiO2 nanoparticles demonstrated the ability to adsorb biomolecules to their surface which could be useful for nanomedicine purposes or biosensing applications. The changes in lymphocyte gene expression at different doses indicate that these TiO2 nanoparticles are capable of disrupting nuclear activity. The use of multiple screening methods provided an effective approach to evaluate nano-bio interactions. The use of a biologically-relevant matrix combined with specific detection methods yielded results which accurately predict biological adversity.

TiO2 micro-flowers composed of nanotubes and their application to dye-sensitized solar cells.

PubMed

Kim, Woong-Rae; Park, Hun; Choi, Won-Youl

2014-02-24

TiO2 micro-flowers were made to bloom on Ti foil by the anodic oxidation of Ti-protruding dots with a cylindrical shape. Arrays of the Ti-protruding dots were prepared by photolithography, which consisted of coating the photoresists, attaching a patterned mask, illuminating with UV light, etching the Ti surface by reactive ion etching (RIE), and stripping the photoresist on the Ti foil. The procedure for the blooming of the TiO2 micro-flowers was analyzed by field emission scanning electron microscopy (FESEM) as the anodizing time was increased. Photoelectrodes of dye-sensitized solar cells (DSCs) were fabricated using TiO2 micro-flowers. Bare TiO2 nanotube arrays were used for reference samples. The short-circuit current (Jsc) and the power conversion efficiency of the DSCs based on the TiO2 micro-flowers were 4.340 mA/cm2 and 1.517%, respectively. These values of DSCs based on TiO2 micro-flowers were higher than those of bare samples. The TiO2 micro-flowers had a larger surface area for dye adsorption compared to bare TiO2 nanotube arrays, resulting in improved Jsc characteristics. The structure of the TiO2 micro-flowers allowed it to adsorb dyes very effectively, also demonstrating the potential to achieve higher power conversion efficiency levels for DSCs compared to a bare TiO2 nanotube array structure and the conventional TiO2 nanoparticle structure.

TiO2 micro-flowers composed of nanotubes and their application to dye-sensitized solar cells

PubMed Central

2014-01-01

TiO2 micro-flowers were made to bloom on Ti foil by the anodic oxidation of Ti-protruding dots with a cylindrical shape. Arrays of the Ti-protruding dots were prepared by photolithography, which consisted of coating the photoresists, attaching a patterned mask, illuminating with UV light, etching the Ti surface by reactive ion etching (RIE), and stripping the photoresist on the Ti foil. The procedure for the blooming of the TiO2 micro-flowers was analyzed by field emission scanning electron microscopy (FESEM) as the anodizing time was increased. Photoelectrodes of dye-sensitized solar cells (DSCs) were fabricated using TiO2 micro-flowers. Bare TiO2 nanotube arrays were used for reference samples. The short-circuit current (Jsc) and the power conversion efficiency of the DSCs based on the TiO2 micro-flowers were 4.340 mA/cm2 and 1.517%, respectively. These values of DSCs based on TiO2 micro-flowers were higher than those of bare samples. The TiO2 micro-flowers had a larger surface area for dye adsorption compared to bare TiO2 nanotube arrays, resulting in improved Jsc characteristics. The structure of the TiO2 micro-flowers allowed it to adsorb dyes very effectively, also demonstrating the potential to achieve higher power conversion efficiency levels for DSCs compared to a bare TiO2 nanotube array structure and the conventional TiO2 nanoparticle structure. PMID:24565201

TiO2 micro-flowers composed of nanotubes and their application to dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Kim, Woong-Rae; Park, Hun; Choi, Won-Youl

2014-02-01

TiO2 micro-flowers were made to bloom on Ti foil by the anodic oxidation of Ti-protruding dots with a cylindrical shape. Arrays of the Ti-protruding dots were prepared by photolithography, which consisted of coating the photoresists, attaching a patterned mask, illuminating with UV light, etching the Ti surface by reactive ion etching (RIE), and stripping the photoresist on the Ti foil. The procedure for the blooming of the TiO2 micro-flowers was analyzed by field emission scanning electron microscopy (FESEM) as the anodizing time was increased. Photoelectrodes of dye-sensitized solar cells (DSCs) were fabricated using TiO2 micro-flowers. Bare TiO2 nanotube arrays were used for reference samples. The short-circuit current ( J sc) and the power conversion efficiency of the DSCs based on the TiO2 micro-flowers were 4.340 mA/cm2 and 1.517%, respectively. These values of DSCs based on TiO2 micro-flowers were higher than those of bare samples. The TiO2 micro-flowers had a larger surface area for dye adsorption compared to bare TiO2 nanotube arrays, resulting in improved J sc characteristics. The structure of the TiO2 micro-flowers allowed it to adsorb dyes very effectively, also demonstrating the potential to achieve higher power conversion efficiency levels for DSCs compared to a bare TiO2 nanotube array structure and the conventional TiO2 nanoparticle structure.

Antibacterial effect of hydrogen peroxide-titanium dioxide suspensions in the decontamination of rough titanium surfaces.

PubMed

Wiedmer, David; Petersen, Fernanda Cristina; Lönn-Stensrud, Jessica; Tiainen, Hanna

2017-07-01

The chemical decontamination of infected dental implants is essential for the successful treatment of peri-implantitis. The aim of this study was to assess the antibacterial effect of a hydrogen peroxide-titanium dioxide (H 2 O 2 -TiO 2 ) suspension against Staphylococcus epidermidis biofilms. Titanium (Ti) coins were inoculated with a bioluminescent S. epidermidis strain for 8 h and subsequently exposed to H 2 O 2 with and without TiO 2 nanoparticles or chlorhexidine (CHX). Bacterial regrowth, bacterial load and viability after decontamination were analyzed by continuous luminescence monitoring, live/dead staining and scanning electron microscopy. Bacterial regrowth was delayed on surfaces treated with H 2 O 2 -TiO 2 compared to H 2 O 2 . H 2 O 2 -based treatments resulted in a lower bacterial load compared to CHX. Few viable bacteria were found on surfaces treated with H 2 O 2 and H 2 O 2 -TiO 2 , which contrasted with a uniform layer of dead bacteria for surfaces treated with CHX. H 2 O 2 -TiO 2 suspensions could therefore be considered an alternative approach in the decontamination of dental implants.

Synthesis of TiO2-CNT hybrid nanocatalyst and its application in direct oxidation of H2S to S

NASA Astrophysics Data System (ADS)

Daraee, Maryam; Baniadam, Majid; Rashidi, Alimorad; Maghrebi, Morteza

2018-07-01

In this study, a TiO2-CNT hybrid catalyst has been synthesized and its catalytic activity in the oxidation of H2S to S has been investigated and compared with those of TiO2 nanoparticles and pyrolyzed TiO2-CNT hybrid (P-TiO2-CNT). The optimum catalyst amount was determined using central composite design (CCD) method. Catalysts were characterized by various analytical techniques. The H2S conversion, sulfur selectivity and yield at the optimal temperature of 200 °C and O2/H2S ratio of 0.5 were 98.3, 99.5 and 97%, respectively. TiO2-CNT16% catalyst has a higher surface area than TiO2 nanoparticles and P-TiO2-CNT. In addition, the former catalyst gives a high conversion of H2S and sulfur selectivity at 200 °C and O2/H2S ratio of 0.5 compared with the latter two catalysts. The superior conversion (over 10%) of TiO2-CNT16% hybrid compared to TiO2 nanoparticles can be attributed to the synergistic effects of TiO2 and CNT, the reduced band gap of TiO2-CNT16% hybrid and high specific surface area of the catalyst.

Water adsorption on TiO2 surfaces probed by soft X-ray spectroscopies: bulk materials vs. isolated nanoparticles

PubMed Central

Benkoula, Safia; Sublemontier, Olivier; Patanen, Minna; Nicolas, Christophe; Sirotti, Fausto; Naitabdi, Ahmed; Gaie-Levrel, François; Antonsson, Egill; Aureau, Damien; Ouf, François-Xavier; Wada, Shin-Ichi; Etcheberry, Arnaud; Ueda, Kiyoshi; Miron, Catalin

2015-01-01

We describe an experimental method to probe the adsorption of water at the surface of isolated, substrate-free TiO2 nanoparticles (NPs) based on soft X-ray spectroscopy in the gas phase using synchrotron radiation. To understand the interfacial properties between water and TiO2 surface, a water shell was adsorbed at the surface of TiO2 NPs. We used two different ways to control the hydration level of the NPs: in the first scheme, initially solvated NPs were dried and in the second one, dry NPs generated thanks to a commercial aerosol generator were exposed to water vapor. XPS was used to identify the signature of the water layer shell on the surface of the free TiO2 NPs and made it possible to follow the evolution of their hydration state. The results obtained allow the establishment of a qualitative determination of isolated NPs’ surface states, as well as to unravel water adsorption mechanisms. This method appears to be a unique approach to investigate the interface between an isolated nano-object and a solvent over-layer, paving the way towards new investigation methods in heterogeneous catalysis on nanomaterials. PMID:26462615

Properties of ordered titanium templates covered with Au thin films for SERS applications

NASA Astrophysics Data System (ADS)

Grochowska, Katarzyna; Siuzdak, Katarzyna; Sokołowski, Michał; Karczewski, Jakub; Szkoda, Mariusz; Śliwiński, Gerard

2016-12-01

Currently, roughened metal nanostructures are widely studied as highly sensitive Raman scattering substrates that show application potential in biochemistry, food safety or medical diagnostic. In this work the structural properties and the enhancement effect due to surface enhanced Raman scattering (SERS) of highly ordered nano-patterned titanium templates covered with thin (5-20 nm) gold films are reported. The templates are formed by preparation of a dense structure of TiO2 nanotubes on a flat Ti surface (2 × 2 cm2) and their subsequent etching down to the substrate. SEM images reveal the formation of honeycomb nanostructures with the cavity diameter of 80 nm. Due to the strongly inhomogeneous distribution of the electromagnetic field in the vicinity of the Au film discontinuities the measured average enhancement factor (107-108) is markedly higher than observed for bare Ti templates. The enhancement factor and Raman signal intensity can be optimized by adjusting the process conditions and thickness of the deposited Au layer. Results confirm that the obtained structures can be used in surface enhanced sensing.

Tuning the relative concentration ratio of bulk defects to surface defects in TiO2 nanocrystals leads to high photocatalytic efficiency.

PubMed

Kong, Ming; Li, Yuanzhi; Chen, Xiong; Tian, Tingting; Fang, Pengfei; Zheng, Feng; Zhao, Xiujian

2011-10-19

TiO(2) nanocrystals with tunable bulk/surface defects were synthesized and characterized with TEM, XRD, BET, positron annihilation, and photocurrent measurements. The effect of defects on photocatalytic activity was studied. It was found for the first time that decreasing the relative concentration ratio of bulk defects to surface defects in TiO(2) nanocrystals could significantly improve the separation efficiency of photogenerated electrons and holes, thus significantly enhancing the photocatalytic efficiency.

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

PubMed

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

2015-05-01

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

Composite WO3/TiO2 nanostructures for high electrochromic activity.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reyes, Karla Rosa; Stephens, Zachary Dan.; Robinson, David B.

2013-05-01

A composite material consisting of TiO2 nanotubes (NTs) with WO3 electrodeposited homogeneously on its surface has been fabricated, detached from its substrate, and attached to a fluorine-doped tin oxide film on glass for application to electrochromic (EC) reactions. A paste of TiO2 made from commercially available TiO2 nanoparticles creates an interface for the TiO2 NT film to attach to the FTO glass, which is conductive and does not cause solution-phase ions in an electrolyte to bind irreversibly with the material. The effect of NT length on the current density and the EC contrast of the material were studied. The ECmore » redox reaction seen in this material is diffusion- limited, having relatively fast reaction rates at the electrode surface. The composite WO3/TiO2 nanostructures showed higher ion storage capacity, better stability, enhanced EC contrast and longer memory time compared with the pure WO3 and TiO2.« less

Au nanostructure-decorated TiO2 nanowires exhibiting photoactivity across entire UV-visible region for photoelectrochemical water splitting.

PubMed

Pu, Ying-Chih; Wang, Gongming; Chang, Kao-Der; Ling, Yichuan; Lin, Yin-Kai; Fitzmorris, Bob C; Liu, Chia-Ming; Lu, Xihong; Tong, Yexiang; Zhang, Jin Z; Hsu, Yung-Jung; Li, Yat

2013-08-14

Here we demonstrate that the photoactivity of Au-decorated TiO2 electrodes for photoelectrochemical water oxidation can be effectively enhanced in the entire UV-visible region from 300 to 800 nm by manipulating the shape of the decorated Au nanostructures. The samples were prepared by carefully depositing Au nanoparticles (NPs), Au nanorods (NRs), and a mixture of Au NPs and NRs on the surface of TiO2 nanowire arrays. As compared with bare TiO2, Au NP-decorated TiO2 nanowire electrodes exhibited significantly enhanced photoactivity in both the UV and visible regions. For Au NR-decorated TiO2 electrodes, the photoactivity enhancement was, however, observed in the visible region only, with the largest photocurrent generation achieved at 710 nm. Significantly, TiO2 nanowires deposited with a mixture of Au NPs and NRs showed enhanced photoactivity in the entire UV-visible region. Monochromatic incident photon-to-electron conversion efficiency measurements indicated that excitation of surface plasmon resonance of Au is responsible for the enhanced photoactivity of Au nanostructure-decorated TiO2 nanowires. Photovoltage experiment showed that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was attributable to the effective surface passivation of Au NPs. Furthermore, 3D finite-difference time domain simulation was performed to investigate the electrical field amplification at the interface between Au nanostructures and TiO2 upon SPR excitation. The results suggested that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was partially due to the increased optical absorption of TiO2 associated with SPR electrical field amplification. The current study could provide a new paradigm for designing plasmonic metal/semiconductor composite systems to effectively harvest the entire UV-visible light for solar fuel production.

Single-walled carbon nanotube-facilitated dispersion of particulate TiO2 on ZrO2 ceramic membrane filters.

PubMed

Yao, Yuan; Li, Gonghu; Gray, Kimberly A; Lueptow, Richard M

2008-07-15

We report that SWCNTs substantially improve the uniformity and coverage of TiO2 coatings on porous ZrO2 ceramic membrane filters. The ZrO2 filters were dip coated with 100 nm anatase TiO2, TiO2/SWCNT composites, a TiO2+SWCNT mixture, and a TiO2/MWCNT composite at pH 3, 5, and 8. Whereas the TiO2+SWCNT mixture and the TiO2/MWCNT composite promote better coverage and less clumping than TiO2 alone, the TiO2/SWCNT composite forms a complete uniform coating without cracking at pH 5 ( approximately 100% coverage). A combination of chemical and electrostatic effects between TiO2 and SWCNTs forming the composite as well as between the composite and the ZrO2 surface explains these observations.

Fe doped TiO2 nanofibers on the surface of graphene sheets for photovoltaics applications

NASA Astrophysics Data System (ADS)

Farhangi, Nasrin; Medina-Gonzalez, Yaocihuatl; Charpentier, Paul A.

2011-08-01

Highly ordered, visible light driven TiO2 nanowire arrays doped with Fe photocatalysts were grown on the surface of functionalized graphene sheets (FGSs) using a sol-gel method with titanium isopropoxide (TIP) monomer, acetic acid (HAc) as the polycondensation agent and iron chloride in the green solvent, supercritical carbon dioxide (scCO2). The morphology of the synthesized materials was studied by SEM and TEM, which showed uniform formation of Fe doped TiO2 nanofibers on the surface of graphene sheets, which acted as a template for nanowire growth through surface -COOH functionalities. Increasing Fe content in the nanowires did not change the morphology significantly. Optical properties of the synthesized composites were examined by UV spectroscopy which showed a significant reduction in band gap with increasing Fe content, i.e. 2.25 eV at 0.6% Fe. The enhancement of the optical properties of synthesized materials was confirmed by photocurrent measurement. The optimum sample containing 0.6% Fe doped TiO2 on the graphene sheets increased the power conversation efficiency by 6-fold in comparison to TiO2 alone.

Recent Advances in TiO2 -Based Nanostructured Surfaces with Controllable Wettability and Adhesion.

PubMed

Lai, Yuekun; Huang, Jianying; Cui, Zequn; Ge, Mingzheng; Zhang, Ke-Qin; Chen, Zhong; Chi, Lifeng

2016-04-27

Bioinspired surfaces with special wettability and adhesion have attracted great interest in both fundamental research and industry applications. Various kinds of special wetting surfaces have been constructed by adjusting the topographical structure and chemical composition. Here, recent progress of the artificial superhydrophobic surfaces with high contrast in solid/liquid adhesion has been reviewed, with a focus on the bioinspired construction and applications of one-dimensional (1D) TiO2-based surfaces. In addition, the significant applications related to artificial super-wetting/antiwetting TiO2-based structure surfaces with controllable adhesion are summarized, e.g., self-cleaning, friction reduction, anti-fogging/icing, microfluidic manipulation, fog/water collection, oil/water separation, anti-bioadhesion, and micro-templates for patterning. Finally, the current challenges and future prospects of this renascent and rapidly developing field, especially with regard to 1D TiO2-based surfaces with special wettability and adhesion, are proposed and discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modulation of Crystal Surface and Lattice by Doping: Achieving Ultrafast Metal-Ion Insertion in Anatase TiO2.

PubMed

Wang, Hsin-Yi; Chen, Han-Yi; Hsu, Ying-Ya; Stimming, Ulrich; Chen, Hao Ming; Liu, Bin

2016-10-26

We report that an ultrafast kinetics of reversible metal-ion insertion can be realized in anatase titanium dioxide (TiO 2 ). Niobium ions (Nb 5+ ) were carefully chosen to dope and drive anatase TiO 2 into very thin nanosheets standing perpendicularly onto transparent conductive electrode (TCE) and simultaneously construct TiO 2 with an ion-conducting surface together with expanded ion diffusion channels, which enabled ultrafast metal ions to diffuse across the electrolyte/solid interface and into the bulk of TiO 2 . To demonstrate the superior metal-ion insertion rate, the electrochromic features induced by ion intercalation were examined, which exhibited the best color switching speed of 4.82 s for coloration and 0.91 s for bleaching among all reported nanosized TiO 2 devices. When performed as the anode for the secondary battery, the modified TiO 2 was capable to deliver a highly reversible capacity of 61.2 mAh/g at an ultrahigh specific current rate of 60 C (10.2 A/g). This fast metal-ion insertion behavior was systematically investigated by the well-controlled electrochemical approaches, which quantitatively revealed both the enhanced surface kinetics and bulk ion diffusion rate. Our study could provide a facile methodology to modulate the ion diffusion kinetics for metal oxides.

Computational insights into crystal plane dependence of thermal activity of anion (C and N)-substituted titania.

PubMed

V, Sai Phani Kumar; Arya, Rahul; Deshpande, Parag A

2017-11-29

Geometry optimizations of anion (C and N) doped anatase TiO 2 were carried out by using DFT+U calculations. Various anion vacancy sites were examined to study the synergistic effects of anion doping accompanied with anion vacancy formation on lattice oxygen activation. Two non-identical crystal planes (0 0 1) and (1 0 0) were chosen for C and N substitutions. Energetically favoured N-vacancy pairs were identified on TiO 2 surfaces. Substitution of N along with anion vacancies at various sites was energetically more favoured than that of C-doping in bulk TiO 2 while the energies were comparable for surface substitutions. Bond length distributions due to the formation of differential bonds were determined. Net oxygen activation and accompanying reversible oxygen exchange capacities were compared for TiO 2-2x C x and TiO 2-3x N 2x . Substitution of C in the surface exposed (1 0 0) plane of TiO 2 resulted in 47.6% and 23.8% of bond elongation and compression, respectively, resulting in 23.8% of net oxygen activation which was higher when compared to N substitution in the (1 0 0) plane of TiO 2 resulting in a net oxygen activation of 17%.

Reaction of silanes in supercritical CO2 with TiO2 and Al2O3.

PubMed

Gu, Wei; Tripp, Carl P

2006-06-20

Infrared spectroscopy was used to investigate the reaction of silanes with TiO2 and Al2O3 using supercritical CO2 (Sc-CO2) as a solvent. It was found that contact of Sc-CO2 with TiO2 leads to partial removal of the water layer and to the formation of carbonate, bicarbonate, and carboxylate species on the surface. Although these carbonate species are weakly bound to the TiO2 surface and can be removed by a N2 purge, they poison the surface, resulting in a lower level of reaction of silanes with TiO2. Specifically, the amount of hexamethyldisilazane adsorbed on TiO2 is about 10% of the value obtained when the reaction is performed from the gas phase. This is not unique to TiO2, as the formation of carbonate species also occurs upon contact of Al2O3 with Sc-CO2 and this leads to a lower level of reaction with hexamethyldisilazane. This is in contrast to reactions of silanes on SiO2 where Sc-CO2 has several advantages over conventional gaseous or nonaqueous methods. As a result, caution needs to be applied when using Sc-CO2 as a solvent for silanization reactions on oxides other than SiO2.

Photochemical tuning of ultrathin TiO2/ p-Si p-n junction properties via UV-induced H doping

NASA Astrophysics Data System (ADS)

Lee, Sang Yeon; Kim, Jinseo; Ahn, Byungmin; Cho, In Sun; Yu, Hak Ki; Seo, Hyungtak

2017-03-01

We report a modified TiO2/ p-Si electronic structure that uses ultraviolet exposure for the incorporation of H. This structure was characterized using various photoelectron spectroscopic techniques. The ultraviolet (UV) exposure of the TiO2 surface allowed the Fermi energy level to be tuned by the insertion of H radicals, which induced changes in the heterojunction TiO2/ p-Si diode properties. The UV exposure of the TiO2 surface was performed in air. On UVexposure, a photochemical reaction involving the incorporation of UV-induced H radicals led to the creation of a surface Ti-O-OH group and caused interstitial H doping (Ti-H-O) in the bulk, which modified the electronic structures in different ways, depending on the location of the H. On the basis of the band alignment determined using a combined spectroscopic analysis, it is suggested that the UV-induced H incorporation into the TiO2 could be utilized for the systematic tuning of the heterojunction property for solar cells, photocatalytic applications, and capacitors.

Preparation of nanocrystalline TiN coated cubic boron nitride powders by a sol-gel process.

PubMed

Park, Hee S; Umer, M Adeel; Ryu, Ho J; Hong, Soon H

2011-01-01

Cubic boron nitride (cBN) particles coated with 20 wt% nanocrystalline TiN were prepared by coating the surface of cBN particles with TiO2, followed by nitridation with NH3 gas at 900 degrees C. Coating of TiO2 on cBN powders was accomplished by a sol-gel process from a solution of titanium (IV) isopropoxide and anhydrous ethanol. An amorphous TiO(x) layer of 50 nm thickness was homogenously formed on the surface of the cBN particles by the sol-gel process. The amorphous layer was then crystallized to an anatase TiO2 phase through calcination in air at 400 degrees C. The crystallized TiO2 layer was 50 nm in thickness, and the size of TiO2 particles comprising the layer was nearly 10 nm. The TiO2 on cBN surfaces was completely converted into nanocrystalline TiN of uniform particles 20 nm in size on cBN particles by nitridation under flowing NH3 gas.

Nanoporous Aluminum Oxide Membranes Coated with Atomic Layer Deposition-Grown Titanium Dioxide for Biomedical Applications: An In Vitro Evaluation.

PubMed

Petrochenko, Peter E; Kumar, Girish; Fu, Wujun; Zhang, Qin; Zheng, Jiwen; Liang, Chengdu; Goering, Peter L; Narayan, Roger J

2015-12-01

The surface topographies of nanoporous anodic aluminum oxide (AAO) and titanium dioxide (TiO2) membranes have been shown to modulate cell response in orthopedic and skin wound repair applications. In this study, we: (1) demonstrate an improved atomic layer deposition (ALD) method for coating the porous structures of 20, 100, and 200 nm pore diameter AAO with nanometer-thick layers of TiO2 and (2) evaluate the effects of uncoated AAO and TiO2-coated AAO on cellular responses. The TiO2 coatings were deposited on the AAO membranes without compromising the openings of the nanoscale pores. The 20 nm TiO2-coated membranes showed the highest amount of initial protein adsorption via the micro bicinchoninic acid (micro-BCA) assay; all of the TiO2-coated membranes showed slightly higher protein adsorption than the uncoated control materials. Cell viability, proliferation, and inflammatory responses on the TiO2-coated AAO membranes showed no adverse outcomes. For all of the tested surfaces, normal increases in proliferation (DNA content) of L929 fibroblasts were observed over from 4 hours to 72 hours. No increases in TNF-alpha production were seen in RAW 264.7 macrophages grown on TiO2-coated AAO membranes compared to uncoated AAO membranes and tissue culture polystyrene (TCPS) surfaces. Both uncoated AAO membranes and TiO2-coated AAO membranes showed no significant effects on cell growth and inflammatory responses. The results suggest that TiO2-coated AAO may serve as a reasonable prototype material for the development of nanostructured wound repair devices and orthopedic implants.

Photocatalytic degradation of NOx in a pilot street canyon configuration using TiO2-mortar panels.

PubMed

Maggos, Th; Plassais, A; Bartzis, J G; Vasilakos, Ch; Moussiopoulos, N; Bonafous, L

2008-01-01

Titanium dioxide is the most important photocatalysts used for purifying applications. If a TiO2- containing material is left outdoors as a form of flat panels, it is activated by sunlight to remove harmful NOx gases during the day. The photocatalytic efficiency of a TiO2-treated mortar for removal of NOx was investigated in the frame of this work. For this purpose a fully equipped monitoring system was designed at a pilot site. This system allows the in situ evaluation of the de-polluting properties of a photocatalytic material by taking into account the climatologic phenomena in street canyons, accurate measurements of pollution level and full registration of meteorological data The pilot site involved three artificial canyon streets, a pollution source, continuous NOx measurements inside the canyons and the source as well as background and meteorological measurements. Significant differences on the NOx concentration level were observed between the TiO2 treated and the reference canyon. NOx values in TiO2 canyon were 36.7 to 82.0% lower than the ones observed in the reference one. Data arising from this study could be used to assess the impact of the photocatalytic material on the purification of the urban environment.

Preparation of rutile TiO(2) coating by thermal chemical vapor deposition for anticoking applications.

PubMed

Tang, Shiyun; Wang, Jianli; Zhu, Quan; Chen, Yaoqiang; Li, Xiangyuan

2014-10-08

To inhibit the metal catalytic coking and improve the oxidation resistance of TiN coating, rutile TiO2 coating has been directly designed as an efficient anticoking coating for n-hexane pyrolysis. TiO2 coatings were prepared on the inner surface of SS304 tubes by a thermal CVD method under varied temperatures from 650 to 900 °C. The rutile TiO2 coating was obtained by annealing the as-deposited TiO2 coating, which is an alternative route for the deposition of rutile TiO2 coating. The morphology, elemental and phase composition of TiO2 coatings were characterized by SEM, EDX and XRD, respectively. The results show that deposition temperature of TiO2 coatings has a strong effect on the morphology and thickness of as-deposited TiO2 coatings. Fe, Cr and Ni at.% of the substrate gradually changes to 0 when the temperature is increased to 800 °C. The thickness of TiO2 coating is more than 6 μm and uniform by metalloscopy, and the films have a nonstoichiometric composition of Ti3O8 when the deposition temperature is above 800 °C. The anticoking tests show that the TiO2 coating at a deposition temperature of 800 °C is sufficiently thick to cover the cracks and gaps on the surface of blank substrate and cut off the catalytic coke growth effect of the metal substrate. The anticoking ratio of TiO2 coating corresponding to each 5 cm segments is above 65% and the average anticoking ratio of TiO2 coating is up to 76%. Thus, the TiO2 coating can provide a very good protective layer to prevent the substrate from severe coking efficiently.

Biocorrosion of TiO2 nanoparticle coating of Ti-6Al-4V in DMEM under specific in vitro conditions

NASA Astrophysics Data System (ADS)

Höhn, Sarah; Virtanen, Sannakaisa

2015-02-01

A TiO2 nanoparticle coating was prepared on a biomedical Ti-6Al-4V alloy using "spin-coating" technique with a colloidal suspension of TiO2 nanopowders with the aim to optimize the surface morphology (e.g., roughness) for improved biocompatibility. The influence of a TiO2 nanoparticle (NP) coating on the corrosion behavior, metal ion release, and biomimetic apatite formation was studied in DMEM, at 37.5 °C with a continuous supply of 5% CO2. Electrochemical impedance spectroscopy measurements indicate a formation of a new layer on the surface of the NP-coated sample upon 28 days immersion in DMEM. Scanning electron microscopy (SEM) and X-ray spectroscopy confirm that the surface of the NP-coated Ti-6Al-4V shows a complete coverage by a Ca-phosphate layer in contrast to the non-coated Ti-6Al-4V alloy. Hence, the TiO2-NP coating strongly enhances biomimetic apatite formation on the alloy surface. In addition, the TiO2-NP coating can efficiently reduce Al-release from the alloy, for which the bare Ti-6Al-4V alloy is significant for at least 28 days of immersion in DMEM.

Highly efficient low-temperature plasma-assisted modification of TiO2 nanosheets with exposed {001} facets for enhanced visible-light photocatalytic activity.

PubMed

Li, Beibei; Zhao, Zongbin; Zhou, Quan; Meng, Bo; Meng, Xiangtong; Qiu, Jieshan

2014-11-03

Anatase TiO2 nanosheets with exposed {001} facets have been controllably modified under non-thermal dielectric barrier discharge (DBD) plasma with various working gas, including Ar, H2 , and NH3 . The obtained TiO2 nanosheets possess a unique crystalline core/amorphous shell structure (TiO2 @TiO2-x ), which exhibit the improved visible and near-infrared light absorption. The types of dopants (oxygen vacancy/surface Ti(3+) /substituted N) in oxygen-deficient TiO2 can be tuned by controlling the working gases during plasma discharge. Both surface Ti(3+) and substituted N were doped into the lattice of TiO2 through NH3 plasma discharge, whereas the oxygen vacancy or Ti(3+) (along with the oxygen vacancy) was obtained after Ar or H2 plasma treatment. The TiO2 @TiO2-x from NH3 plasma with a green color shows the highest photocatalytic activity under visible-light irradiation compared with the products from Ar plasma or H2 plasma due to the synergistic effect of reduction and simultaneous nitridation in the NH3 plasma. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Excess electrons in reduced rutile and anatase TiO2

NASA Astrophysics Data System (ADS)

Yin, Wen-Jin; Wen, Bo; Zhou, Chuanyao; Selloni, Annabella; Liu, Li-Min

2018-05-01

As a prototypical photocatalyst, TiO2 is a material of scientific and technological interest. In photocatalysis and other applications, TiO2 is often reduced, behaving as an n-type semiconductor with unique physico-chemical properties. In this review, we summarize recent advances in the understanding of the fundamental properties and applications of excess electrons in reduced, undoped TiO2. We discuss the characteristics of excess electrons in the bulk and at the surface of rutile and anatase TiO2 focusing on their localization, spatial distribution, energy levels, and dynamical properties. We examine specific features of the electronic states for photoexcited TiO2, for intrinsic oxygen vacancy and Ti interstitial defects, and for surface hydroxyls. We discuss similarities and differences in the behaviors of excess electrons in the rutile and anatase phases. Finally, we consider the effect of excess electrons on the reactivity, focusing on the interaction between excess electrons and adsorbates.

Pyrrole-regulated precipitation of titania nanorods on polymer fabrics for photocatalytic degradation of trace toluene in air

NASA Astrophysics Data System (ADS)

Gu, Yi-Jie; Wen, Wei; Xu, Yang; Wu, Jin-Ming

2018-03-01

When compared with nanoparticulate counterparts, TiO2 thin films with vertically aligned one-dimensional (1D) nanostructures exhibit enhanced photocatalytic activity because of the highly accessible surface area. The perpendicular of the 1D nanostructure reduces the charge migration path and hence the carrier recombination rate, which also contributes to the photocatalytic activity. Furthermore, TiO2 thin films on flexible substrates are more suitable to degrade pollutants in either water or air because of its easy recovery and free-bending shape. In this study, flexible polyethylene fabrics were firstly coated with a sol-gel nanoparticulate TiO2 seed layer. Quasi-aligned TiO2 nanorods were then precipitated homogeneously under an atmospheric pressure and a low temperature not exceeding 80 °C, using a peroxy-titanium complex precursor with the additive of pyrrole. It is found that the density of TiO2 nanorods increased with the increasing amount of pyrrole monomers. The resultant TiO2 film on polyethylene fabrics exhibited a much reduced band gap of ca. 2.86 eV, which can be attributed to the surface oxygen deficiencies. When utilized to assist photocatalytic degradation of trace toluene in air under the UV light illumination, the TiO2 film exhibited a gradually increased photocatalytic activity upon the increasing cycles for up to six, because of the gradual removal of trace organics on the TiO2 surface. The highest photocatalytic efficiency is recorded to be 5 times that of TiO2 nanotube arrays, which are regarded as an excellent photocatalyst for air cleaning.

Enhanced osteogenic activity and anti-inflammatory properties of Lenti-BMP-2-loaded TiO2 nanotube layers fabricated by lyophilization following trehalose addition

PubMed Central

Zhang, Xiaochen; Zhang, Zhiyuan; Shen, Gang; Zhao, Jun

2016-01-01

To enhance biocompatibility and osseointegration between titanium implants and surrounding bone tissue, numerous efforts have been made to modify the surface topography and composition of Ti implants. In this paper, Lenti-BMP-2-loaded TiO2 nanotube coatings were fabricated by lyophilization in the presence of trehalose to functionalize the surface. We characterized TiO2 nanotube layers in terms of the following: surface morphology; Lenti-BMP-2 and trehalose release; their ability to induce osteogenesis, proliferation, and anti-inflammation in vitro; and osseointegration in vivo. The anodized TiO2 nanotube surfaces exhibited an amorphous glassy matrix perpendicular to the Ti surface. Both Lenti-BMP-2 and trehalose showed sustained release over the course of 8 days. Results from real-time quantitative polymerase chain reaction studies demonstrated that lyophilized Lenti-BMP-2/TiO2 nanotubes constructed with trehalose (Lyo-Tre-Lenti-BMP-2) significantly promoted osteogenic differentiation of bone marrow stromal cells but not their proliferation. In addition, Lyo-Tre-Lenti-BMP-2 nanotubes effectively inhibited lipopolysaccharide-induced interleukin-1β and tumor necrosis factor-α production. In vivo, the formulation also promoted osseointegration. This study presents a promising new method for surface-modifying biomedical Ti-based implants to simultaneously enhance their osteogenic potential and anti-inflammatory properties, which can better satisfy clinical needs. PMID:26869786

Coating stainless steel plates with Ag/TiO2 for chlorpyrifos decontamination

NASA Astrophysics Data System (ADS)

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

2016-05-01

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

Surface interactions and degradation of a fluoroquinolone antibiotic in the dark in aqueous TiO 2 suspensions

DOE PAGES

Peterson, Jonathan W.; Gu, Baohua; Seymour, Michael D.

2015-06-15

Fluoroquinolone antibiotics (FQs) are important drugs used in human and veterinary medicine. Their detection in natural waters and waste water treatment plants, along with increased resistance to FQs among some bacteria, have generated an increased interest in the fate of these drugs in the environment. Partitioning of FQs between an aqueous solution and attendant substrates depends, in part, on the surface reactivity of the adsorbent, commonly a function of particle size, surface charge, and functional groups. In this paper, this study investigated the surface interactions between the FQ drug ofloxacin (OFL) and titanium oxide (TiO 2), a common catalyst andmore » widely-observed constituent in many consumer products. Raman and fluorescence spectroscopic techniques, as well as LC/MS, were used to determine the OFL moieties present on TiO 2 surfaces and in attendant solutions. Raman spectra indicate that the C==O (ketone) group of the quinolone core, the NH + of the piperazinyl ring, and CH 3 of benzoxazine core are the most active in sorption onto the TiO 2 surface. Raman spectra also show that the sorbed benzoxazine–quinolone core and piperazinyl moieties are readily desorbed from the surface by re-suspending samples in water. Importantly, we found that OFL could be degraded by reacting with TiO 2 even in the dark. Complementary LC/MS analysis of the attendant supernatants indicates the presence of de-piperazinylated and de-carboxylated OFL breakdown products in supernatant solutions. Together, both Raman and LC/MS analyses indicate that TiO 2 breaks the compound into piperazinyl and carboxylate groups which attach to the surface, whereas de-carboxylated and hydroxylated quinolone moieties remain in solution. Finally, the present study thus identifies the sorption mechanisms and breakdown products of OFL during dark reactions with TiO 2, which is critically important for understanding the fate and transport of OFL as it enters the soil and aquatic environment.« less

Surface interactions and degradation of a fluoroquinolone antibiotic in the dark in aqueous TiO2 suspensions.

PubMed

Peterson, Jonathan W; Gu, Baohua; Seymour, Michael D

2015-11-01

Fluoroquinolone antibiotics (FQs) are important drugs used in human and veterinary medicine. Their detection in natural waters and waste water treatment plants, along with increased resistance to FQs among some bacteria, have generated an increased interest in the fate of these drugs in the environment. Partitioning of FQs between an aqueous solution and attendant substrates depends, in part, on the surface reactivity of the adsorbent, commonly a function of particle size, surface charge, and functional groups. This study investigated the surface interactions between the FQ drug ofloxacin (OFL) and titanium oxide (TiO2), a common catalyst and widely-observed constituent in many consumer products. Raman and fluorescence spectroscopic techniques, as well as LC/MS, were used to determine the OFL moieties present on TiO2 surfaces and in attendant solutions. Raman spectra indicate that the CO (ketone) group of the quinolone core, the NH(+) of the piperazinyl ring, and CH3 of benzoxazine core are the most active in sorption onto the TiO2 surface. Raman spectra also show that the sorbed benzoxazine-quinolone core and piperazinyl moieties are readily desorbed from the surface by re-suspending samples in water. Importantly, we found that OFL could be degraded by reacting with TiO2 even in the dark. Complementary LC/MS analysis of the attendant supernatants indicates the presence of de-piperazinylated and de-carboxylated OFL breakdown products in supernatant solutions. Together, both Raman and LC/MS analyses indicate that TiO2 breaks the compound into piperazinyl and carboxylate groups which attach to the surface, whereas de-carboxylated and hydroxylated quinolone moieties remain in solution. The present study thus identifies the sorption mechanisms and breakdown products of OFL during dark reactions with TiO2, which is critically important for understanding the fate and transport of OFL as it enters the soil and aquatic environment. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis of TiO2/functionalized graphene sheets (FGSs) nanocomposites in super critical CO2

NASA Astrophysics Data System (ADS)

Farhangi, Nasrin; Medina-Gonzalez, Yaocihuatl; Chen, Bo; Charpentier, Paul A.

2010-06-01

Highly ordered TiO2 nanowire arrays were prepared on the surface of Functionalized Graphene sheets (FGSs) by solgel method using titanium isopropoxide monomer with acetic acid as the polycondensation agent in the green solvent, supercritical carbon dioxide (sc-CO2). Morphology of synthesized materials was studied by SEM and TEM. Optical properties of the nanocomposites studied by UV spectroscopy which showed high absorption in visible area as well as reduction in their band gap compared to TiO2. By high resolution XPS, chelating bidentate structure of TiO2 with carboxylic group on the surface of graphene sheets can be confirmed. Improvement in the optical properties of the synthesized composites compared to TiO2 alone was confirmed by photocurrent measurements.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bossa, Nathan; Chaurand, Perrine; Levard, Clément

Nanomaterials are increasingly being used to improve the properties and functions of common building materials. A new type of self-cleaning cement incorporating TiO 2 nanomaterials (TiO 2-NMs) with photocatalytic properties is now marketed. This promising cement might provide air pollution-reducing properties but its environmental impact must be validated. During cement use and aging, an altered surface layer is formed that exhibits increased porosity. The surface layer thickness alteration and porosity increase with the cement degradation rate. The hardened cement paste leaching behavior has been fully documented, but the fate of incorporated TiO 2-NMs and their state during/after potential release ismore » currently unknown. In this study, photocatalytic cement pastes with increasing initial porosity were leached at a lab-scale to produce a range of degradation rates concerning the altered layer porosity and thickness. No dissolved Ti was released during leaching, only particulate TiO 2-NM release was detected. The extent of release from this batch test simulating accelerated worst-case scenario was limited and ranged from 18.7 ± 2.1 to 33.5 ± 5.1 mg of Ti/m 2 of cement after 168 h of leaching. TiO 2-NMs released into neutral aquatic media (simulate pH of surface water) were not associated or coated by cement minerals. The TiO 2-NM release mechanism is suspected to start from freeing of TiO 2-NMs in the altered layer pore network due to partial cement paste dissolution followed by diffusion into the bulk pore solution to the surface. The extent of TiO 2-NM release was not solely related to the cement degradation rate.« less

Biocompatibility and Surface Properties of TiO2 Thin Films Deposited by DC Magnetron Sputtering

PubMed Central

López-Huerta, Francisco; Cervantes, Blanca; González, Octavio; Hernández-Torres, Julián; García-González, Leandro; Vega, Rosario; Herrera-May, Agustín L.; Soto, Enrique

2014-01-01

We present the study of the biocompatibility and surface properties of titanium dioxide (TiO2) thin films deposited by direct current magnetron sputtering. These films are deposited on a quartz substrate at room temperature and annealed with different temperatures (100, 300, 500, 800 and 1100 °C). The biocompatibility of the TiO2 thin films is analyzed using primary cultures of dorsal root ganglion (DRG) of Wistar rats, whose neurons are incubated on the TiO2 thin films and on a control substrate during 18 to 24 h. These neurons are activated by electrical stimuli and its ionic currents and action potential activity recorded. Through X-ray diffraction (XRD), the surface of TiO2 thin films showed a good quality, homogeneity and roughness. The XRD results showed the anatase to rutile phase transition in TiO2 thin films at temperatures between 500 and 1100 °C. This phase had a grain size from 15 to 38 nm, which allowed a suitable structural and crystal phase stability of the TiO2 thin films for low and high temperature. The biocompatibility experiments of these films indicated that they were appropriated for culture of living neurons which displayed normal electrical behavior. PMID:28788667

Hydrogenated TiO2 nanotube photonic crystals for enhanced photoelectrochemical water splitting

NASA Astrophysics Data System (ADS)

Meng, Ming; Zhou, Sihua; Yang, Lun; Gan, Zhixing; Liu, Kuili; Tian, Fengshou; Zhu, Yu; Li, ChunYang; Liu, Weifeng; Yuan, Honglei; Zhang, Yan

2018-04-01

We report the design, fabrication and characterization of novel TiO2 nanotube photonic crystals with a crystalline core/disordered shell structure as well as substantial oxygen vacancies for photoelectrochemical (PEC) water splitting. The novel TiO2 nanotube photonic crystals are fabricated by annealing of anodized TiO2 nanotube photonic crystals in hydrogen atmosphere at various temperatures. The optimized novel TiO2 nanotube photonic crystals produce a maximal photocurrent density of 2.2 mA cm-2 at 0.22 V versus Ag/AgCl, which is two times higher that of the TiO2 nanotube photonic crystals annealed in air. Such significant PEC performance improvement can be ascribed to synergistic effects of the disordered surface layer and oxygen vacancies. The reduced band gap owing to the disordered surface layer and localized states induced by oxygen vacancies can enhance the efficient utilization of visible light. In addition, the disordered surface layer and substantial oxygen vacancies can promote the efficiency for separation and transport of the photogenerated carriers. This work may open up new opportunities for the design and construction of the high efficient and low-cost PEC water splitting system.

Hydrogenated TiO2 nanotube photonic crystals for enhanced photoelectrochemical water splitting.

PubMed

Meng, Ming; Zhou, Sihua; Yang, Lun; Gan, Zhixing; Liu, Kuili; Tian, Fengshou; Zhu, Yu; Li, ChunYang; Liu, Weifeng; Yuan, Honglei; Zhang, Yan

2018-04-02

We report the design, fabrication and characterization of novel TiO 2 nanotube photonic crystals with a crystalline core/disordered shell structure as well as substantial oxygen vacancies for photoelectrochemical (PEC) water splitting. The novel TiO 2 nanotube photonic crystals are fabricated by annealing of anodized TiO 2 nanotube photonic crystals in hydrogen atmosphere at various temperatures. The optimized novel TiO 2 nanotube photonic crystals produce a maximal photocurrent density of 2.2 mA cm -2 at 0.22 V versus Ag/AgCl, which is two times higher that of the TiO 2 nanotube photonic crystals annealed in air. Such significant PEC performance improvement can be ascribed to synergistic effects of the disordered surface layer and oxygen vacancies. The reduced band gap owing to the disordered surface layer and localized states induced by oxygen vacancies can enhance the efficient utilization of visible light. In addition, the disordered surface layer and substantial oxygen vacancies can promote the efficiency for separation and transport of the photogenerated carriers. This work may open up new opportunities for the design and construction of the high efficient and low-cost PEC water splitting system.

Methanethiol chemistry on TiO 2-supported Ni clusters

NASA Astrophysics Data System (ADS)

Ozturk, O.; Park, J. B.; Black, T. J.; Rodriguez, J. A.; Hrbek, J.; Chen, D. A.

2008-10-01

The thermal decomposition of methanethiol on Ni clusters grown on TiO 2(1 1 0) was studied by temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS) and low energy ion scattering (LEIS). On all of the Ni surfaces investigated, methane and hydrogen were observed as gaseous products in the TPD experiments, and the only sulfur-containing species that desorbed from the surface was methanethiol itself at low temperatures. The two pathways for methanethiol reaction were hydrodesulfurization to produce methane and nonselective decomposition, which leaves atomic carbon and sulfur on the surface. From high resolution XPS studies, methyl thiolate was identified as the surface intermediate for reaction on TiO 2 and on all of the Ni surfaces investigated, similar to what is observed on single-crystal Ni surfaces. However, the binding sites for methyl thiolate on the 1 ML (monolayer) Ni clusters were different from those on the Ni clusters at coverages of 2.5 ML and higher, based on the S(2p) binding energies for methyl thiolate. No distinct changes in activity or selectivity were observed for the smaller Ni clusters grown at low coverage compared to the more film-like Ni surfaces other than what could be accounted for by changes in total surface area. Interactions between the Ni clusters and the TiO 2 support had two main effects on chemical activity. First, carbon was oxidized by oxygen from the TiO 2 lattice to produce CO at temperatures above 800 K. Second, annealing induced encapsulation of the Ni clusters by reduced TiO x and chemisorbed oxygen. At 800 K, the Ni clusters were totally encapsulated, resulting in a complete loss of methanethiol activity; partial encapsulation at 700 K caused a smaller decrease in activity accompanied by increased oxidation of carbon by lattice oxygen.

Synthesis of TiO2 NRs - ZnO Composite for Dye Sensitized Solar Cell Photoanodes

NASA Astrophysics Data System (ADS)

Wahyuningsih, S.; Ramelan, A. H.; Hidayat, R.; Fadillah, G.; Munawaroh, H.; Saputri, L. N. M. Z.

2017-07-01

Composite of TiO2 NRs - ZnO were synthesized for DSSCs photoanode materials. TiO2 NRs was synthesized from TiO2 anatase by mechanochemical technique using ball milling process with agitation speed of 1000 rpm. While, the further hydrothermal refluxing process was conducted at 120°C under various concentration of NaOH in aqueous solution. The starting material of ZnO was prepared from ZnSO4.7H2O as a precursor. The hydrothermal treated TiO2 was added to the ZnO powder in a certain composition of 1:1, 1:2 and 2:1 (w/w), and the mixtures were then annealed at 400°C. The resulting material was characterized by X-ray diffraction (XRD), Surface area analyzer (SAA), Transmission electron microscopy (TEM), and Thermogravimetry/Differential thermal analysis (TG/DTA). The TiO2 revolution occurs from anatase phase into brookite phase. Rutile TiO2 phase was increasing when the NaOH was added at about 12 M. Nanograf of TEM showed the optimum condition for the formation of TiO2 NRs was obtained when 12 M NaOH was used. Structural transformation to 1D nanorods of TiO2 capable increase surface area up to 79 m2/g. TiO2 NRs-ZnO composite was prepared from TiO2 NRs and ZnO using comparation of TiO2 NRs: ZnO = 1:1, 1:2, dan 2:1. Anatase phase TiO2 as a single phase TiO2 was obtained in the TiO2-ZnO composite (1:1 w/w) upon heating the sample until 400°C. Difference TiO2 NRs-ZnO composite materials were investigated as good photovoltaic materials. Evaluation of the performance of DSSCs was conducted by I-V Keithley 2602A measurement indicate that photoanode built of TiO2 NRs - ZnO thin film has a higher solar cell efficiency than that of TiO2 thin film photoanode.

Architecture engineering toward highly active palladium integrated titanium dioxide yolk-double-shell nanoreactor for catalytic applications

NASA Astrophysics Data System (ADS)

Liu, Baocang; Wang, Qin; Yu, Shengli; Jing, Peng; Liu, Lixia; Xu, Guangran; Zhang, Jun

2014-09-01

Rational design of the hierarchical architecture of a material with well controlled functionality is crucially important for improving its properties. In this paper, we present the general strategies for rationally designing and constructing three types of hierarchical Pd integrated TiO2 double-shell architectures, i.e. yolk-double-shell TiO2 architecture (Pd@TiO2/Pd@TiO2) with yolk-type Pd nanoparticles residing inside the central cavity of the hollow TiO2 structure; ultrafine Pd nanoparticles homogenously dispersed on both the external and internal surfaces of the inner TiO2 shell; and double-shell TiO2 architecture (@TiO2/Pd@TiO2) with Pd nanoparticles solely loaded on the external surface of the inner TiO2 shell, and double-shell TiO2 architecture (@TiO2@Pd@TiO2) with Pd nanoparticles dispersed in the interlayer space of double TiO2 shells, via newly developed Pd2+ ion-diffusion and Pd sol impregnation methodologies. These architectures are well controlled in structure, size, morphology, and configuration with Pd nanoparticles existing in various locations. Owing to the variable synergistic effects arising from the location discrepancies of Pd nanoparticle in the architectures, they exhibit remarkable variations in catalytic activity. In particular, different from previously reported yolk-shell structures, the obtained yolk-double-shell Pd@TiO2/Pd@TiO2 architecture, which is revealed for the first time, possesses a uniform hierarchical structure, narrow size distribution, and good monodispersibility, and it creates two Pd-TiO2 interfaces on the external and internal surfaces of the inner TiO2 shell, leading to the strongest synergistic effect of Pd nanoparticles with TiO2 shell. Furthermore, the interlayer chamber between the double TiO2 shells connecting with the central cavity of the hollow TiO2 structure through the mesoporous TiO2 wall forms a nanoreactor for enriching the reactants and preventing the deletion of Pd nanoparticles during the reaction, thus greatly accelerating the reaction speed. Owing to its structural features, yolk-double-shell Pd@TiO2/Pd@TiO2 architecture exhibits extremely high catalytic performance on the Suzuki-Miyaura coupling reaction. The synthetic methodologies are robust for fabricating double-shell architectures with various configurations for applications such as in catalysis, drug delivery, and medicine release. The obtained double-shell architectures may be used as novel catalyst systems with highly efficient catalytic performance for other catalytic reactions.Rational design of the hierarchical architecture of a material with well controlled functionality is crucially important for improving its properties. In this paper, we present the general strategies for rationally designing and constructing three types of hierarchical Pd integrated TiO2 double-shell architectures, i.e. yolk-double-shell TiO2 architecture (Pd@TiO2/Pd@TiO2) with yolk-type Pd nanoparticles residing inside the central cavity of the hollow TiO2 structure; ultrafine Pd nanoparticles homogenously dispersed on both the external and internal surfaces of the inner TiO2 shell; and double-shell TiO2 architecture (@TiO2/Pd@TiO2) with Pd nanoparticles solely loaded on the external surface of the inner TiO2 shell, and double-shell TiO2 architecture (@TiO2@Pd@TiO2) with Pd nanoparticles dispersed in the interlayer space of double TiO2 shells, via newly developed Pd2+ ion-diffusion and Pd sol impregnation methodologies. These architectures are well controlled in structure, size, morphology, and configuration with Pd nanoparticles existing in various locations. Owing to the variable synergistic effects arising from the location discrepancies of Pd nanoparticle in the architectures, they exhibit remarkable variations in catalytic activity. In particular, different from previously reported yolk-shell structures, the obtained yolk-double-shell Pd@TiO2/Pd@TiO2 architecture, which is revealed for the first time, possesses a uniform hierarchical structure, narrow size distribution, and good monodispersibility, and it creates two Pd-TiO2 interfaces on the external and internal surfaces of the inner TiO2 shell, leading to the strongest synergistic effect of Pd nanoparticles with TiO2 shell. Furthermore, the interlayer chamber between the double TiO2 shells connecting with the central cavity of the hollow TiO2 structure through the mesoporous TiO2 wall forms a nanoreactor for enriching the reactants and preventing the deletion of Pd nanoparticles during the reaction, thus greatly accelerating the reaction speed. Owing to its structural features, yolk-double-shell Pd@TiO2/Pd@TiO2 architecture exhibits extremely high catalytic performance on the Suzuki-Miyaura coupling reaction. The synthetic methodologies are robust for fabricating double-shell architectures with various configurations for applications such as in catalysis, drug delivery, and medicine release. The obtained double-shell architectures may be used as novel catalyst systems with highly efficient catalytic performance for other catalytic reactions. Electronic supplementary information (ESI) available: Synthetic schemes, TEM, SEM, XRD, FTIR, UV-DRS spectra, TPR, and catalytic data. See DOI: 10.1039/c4nr02692f

Effect of TiO2 addition on surface microstructure and bioactivity of fluorapatite coatings deposited using Nd:YAG laser.

PubMed

Chien, Chi-Sheng; Ko, Yu-Sheng; Kuo, Tsung-Yuan; Liao, Tze-Yuan; Lee, Tzer-Min; Hong, Ting-Fu

2014-04-01

To study the effect of titania (TiO2) addition on the surface microstructure and bioactivity of fluorapatite coatings, fluorapatite was mixed with TiO2 in 1:0.5 (FA + 0.5TiO2), 1:0.8 (FA + 0.8TiO2), and 1:1 (FA + TiO2) ratios (wt%) and clad on Ti-6Al-4V substrates using an Nd:YAG laser system. The experimental results show that the penetration depth of the weld decreases with increasing TiO2 content. Moreover, the subgrain structure of the coating layer changes from a fine cellular-like structure to a cellular-dendrite-like structure as the amount of TiO2 increases. Consequently, as the proportion of TiO2 decreases (increase in fluorapatite content), the Ca/P ratio of the coating layer also decreases. The immersion of specimens into simulated body fluid resulted in the formation of individual apatite. With a lower Ca/P ratio before immersion, the growth of the apatite was faster and then the coating layer provided a better bioactivity. X-ray diffraction analysis results show that prior to simulated body fluid immersion, the coating layer in all three specimens was composed mainly of fluorapatite, CaTiO3, and Al2O3 phases. Following simulated body fluid immersion, a peak corresponding to hydroxycarbonated apatite appeared after 2 days in the FA + 0.5TiO2 and FA + 0.8TiO2 specimens and after 7 days in the FA + TiO2 specimen. Overall, the results show that although the bioactivity of the coating layer tended to decrease with increasing TiO2 content, in accordance with the above-mentioned ratios, the bioactivity of all three specimens remained generally good.

Spectroscopic and first principles investigation on 4-[(4-pyridinylmethylene)amino]-benzoic acid bearing pyridyl and carboxyl anchoring groups

NASA Astrophysics Data System (ADS)

Zhang, Lei; Wang, Qiaoyi

2018-03-01

We report a combined experimental and computational investigation on the structure and photophysics of 4-[(4-pyridinylmethylene)amino]-benzoic acid, a functional molecule bearing two anchoring groups for attachment onto a TiO2 surface and perovskite surface, for potential solar cell application. This molecule possesses interesting adsorption properties in perovskite solar cell because the pyridyl group serves as the Lewis base and targets Lewis acidic sites in the perovskite surface, while the carboxyl group targets TiO2 surface, improving the coupling between the perovskite surface and the TiO2 surface. The electronic structures of the molecule and its photochemistry are revealed by the UV-vis absorption spectra and the fluorescence spectra under visible light irradiation, which are combined with density functional theory (DFT) and time-dependent density functional theory (TDDFT) analysis. Considering the bi-anchoring groups and the conjugated π system embedded in the molecule, we anticipate it can molecular engineer the TiO2/perovskite interface in perovskite solar cell.

Comparing the Effects of Particulate Matter on the Ocular Surfaces of Normal Eyes and a Dry Eye Rat Model.

PubMed

Han, Ji Yun; Kang, Boram; Eom, Youngsub; Kim, Hyo Myung; Song, Jong Suk

2017-05-01

To compare the effect of exposure to particulate matter on the ocular surface of normal and experimental dry eye (EDE) rat models. Titanium dioxide (TiO2) nanoparticles were used as the particulate matter. Rats were divided into 4 groups: normal control group, TiO2 challenge group of the normal model, EDE control group, and TiO2 challenge group of the EDE model. After 24 hours, corneal clarity was compared and tear samples were collected for quantification of lactate dehydrogenase, MUC5AC, and tumor necrosis factor-α concentrations. The periorbital tissues were used to evaluate the inflammatory cell infiltration and detect apoptotic cells. The corneal clarity score was greater in the EDE model than in the normal model. The score increased after TiO2 challenge in each group compared with each control group (normal control vs. TiO2 challenge group, 0.0 ± 0.0 vs. 0.8 ± 0.6, P = 0.024; EDE control vs. TiO2 challenge group, 2.2 ± 0.6 vs. 3.8 ± 0.4, P = 0.026). The tear lactate dehydrogenase level and inflammatory cell infiltration on the ocular surface were higher in the EDE model than in the normal model. These measurements increased significantly in both normal and EDE models after TiO2 challenge. The tumor necrosis factor-α levels and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells were also higher in the EDE model than in the normal model. TiO2 nanoparticle exposure on the ocular surface had a more prominent effect in the EDE model than it did in the normal model. The ocular surface of dry eyes seems to be more vulnerable to fine dust of air pollution than that of normal eyes.

Photocatalytic bacterial inactivation by TiO2-coated surfaces

PubMed Central

2013-01-01

The aim of this study was the evaluation of the photoactivated antibacterial activity of titanium dioxide (TiO2)-coated surfaces. Bacterial inactivation was evaluated using TiO2-coated Petri dishes. The experimental conditions optimized with Petri dishes were used to test the antibacterial effect of TiO2-coated ceramic tiles. The best antibacterial effect with Petri dishes was observed at 180, 60, 30 and 20 min of exposure for Escherichia coli, Staphylococcus aureus, Pseudomonas putida and Listeria innocua, respectively. The ceramic tiles demonstrated a photoactivated bactericidal effect at the same exposure time. In general, no differences were observed between the antibacterial effect obtained with Petri dishes and tiles. However, the photochemical activity of Petri dishes was greater than the activity of the tiles. Results obtained indicates that the TiO2-coated surfaces showed a photoactivated bactericidal effect with all bacteria tested highlighting that the titania could be used in the ceramic and building industry for the production of coated surfaces to be placed in microbiologically sensitive environments, such as the hospital and food industry. PMID:24090112

Adsorption of Eu(III) onto TiO2: effect of pH, concentration, ionic strength and soil fulvic acid.

PubMed

Tan, Xiaoli; Fang, Ming; Li, Jiaxing; Lu, Yi; Wang, Xiangke

2009-08-30

The effects of pH, initial Eu(III) concentration, ionic strength and fulvic acid (FA) on the adsorption of Eu(III) on TiO(2) are investigated by using batch techniques. The results indicate that the presence of FA strongly enhances the adsorption of Eu(III) on TiO(2) at low pH values. Besides, the adsorption of Eu(III) on TiO(2) is significantly dependent on pH values and independent of ionic strength. The adsorption of Eu(III) on TiO(2) is attributed to inner-sphere surface complexation. The diffuse layer model (DLM) is applied to simulate the adsorption data, and fits the experimental data well with the aid of FITEQL 3.2. X-ray photoelectron spectroscopy (XPS) is performed to study the species of Eu(III) adsorbed on the surfaces of TiO(2)/FA-TiO(2) hybrids at a molecular level, which suggest that FA act as "bridge" between Eu(III) and TiO(2) particles to enhance the ability to adsorb Eu(III) in solution.

On the advancement of quantum dot solar cell performance through enhanced charge carrier dynamics

NASA Astrophysics Data System (ADS)

Baker, David R.

The quantum dot solar cell is one of the few solar technologies which promises to compete with fossil fuels, but work is still needed to increase its performance. Electron transfer kinetics at interfaces and limitations of the redox couple within the cell, are responsible for lowering power conversion efficiency. Several techniques which are able to increase electron transfer within the working electrode and at the counter electrode/electrolyte interface are discussed in this dissertation. Trap sites on the surface of CdSe quantum dots are created when mercaptopropionic acid (MPA) is added to the suspension. The trap sites are emissive creating a loss pathway for photogenerated charges which will manifest as reduced photocurrent. MPA displaces amines on the surface of CdSe creating Se vacancies. Emission properties are controlled by the concentration of MPA. Because trap sites are generated, a more successful method to sensitize TiO2 films is the SILAR technique which directly grows quantum dots on the desired surface. Anodically etched TiO2 nanotubes yield photocurrents 20% greater than TiO2 nanoparticles because of longer electron diffusion lengths. Peak incident photon to charge carrier efficiencies of TiO2 nanotube samples show a doubling of photocurrent in the visible region compared to nanoparticles. The TiO2 substrates are sensitized with CdS by the SILAR process which is found to utilize both the inside and outside surfaces of the TiO2 nanotubes. Etched TiO2 nanotubes are removed from the underlying titanium foil in order to use spectroscopic techniques. Ultrafast transient absorption shows the extremely fast nature of charge injection from SILAR CdS into TiO 2 nanotubes. Surface area analysis of TiO2 nanotube powder gives an area of 77m2/g, a value 1.5 times larger than traditional TiO2 nanoparticles. By isolating the counter electrode with a salt bridge the effect of the polysulfide electrolyte is found to act as an electron scavenger on the working electrode. Though activity at the platinum counter electrode increases with the presence of polysulfides, the activity is too low to counteract scavenging at the working electrode. Cu2S, CoS and PbS electrochemically show promise as alternatives to platinum. Cu2S and CoS produce higher photocurrents and fill factors, greatly improving cell performance.

Interactions of aqueous NOM with nanoscale TiO2: implications for ceramic membrane filtration-ozonation hybrid process.

PubMed

Kim, Jeonghwan; Shan, Wenqian; Davies, Simon H R; Baumann, Melissa J; Masten, Susan J; Tarabara, Volodymyr V

2009-07-15

The combined effect of pH and calcium on the interactions of nonozonated and ozonated natural organic matter (NOM) with nanoscale TiO2 was investigated. The approach included characterization of TiO2 nanoparticles and NOM, extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) modeling of NOM-TiO2 and NOM-NOM interactions, batch study on the NOM adsorption onto TiO2 surface, and bench-scale study on the treatment of NOM-containing feed waters using a hybrid process that combines ozonation and ultrafiltration with a 5 kDa ceramic (TiO2 surface) membrane. It was demonstrated that depending on pH and TiO2 loading, the adsorption of NOM species is controlled by either the availability of divalent cations or by preozonation of NOM. XDLVO surface energy analysis predicts NOM adsorption onto TiO2 in the ozone-controlled regime but not in the calcium-controlled regime. In both regimes, short-range NOM-NOM and NOM-TiO2 interactions were governed by acid-base and van der Waals forces, whereas the role of electrostatic forces was relatively insignificant. Ozonation increased the surface energy of NOM, contributing to the hydrophilic repulsion component of the NOM-NOM and NOM-TiO2 interactions. In the calcium-controlled regime, neither NOM-TiO2 nor NOM-NOM interaction controlled adsorption. Non-XDLVO interactions such as intermolecular bridging by calcium were hypothesized to be responsible for the observed adsorption behavior. Adsorption data proved to be highly predictive of the permeate flux performance.

[Preparation and catalytic activity of surface-modification CNTs/TiO2 composite photocatalysts].

PubMed

Wang, Huan-Ying; Li, Wen-Jun; Chang, Zhi-Dong; Zhou, Hua-Lei; Guo, Hui-Chao

2011-09-01

A novel kind of carbon nanotubes/titanium dioxide (CNTs/TiO2) composite photocatalyst was prepared by a modified sol-gel method in which the nanoscaled TiO2 particles were uniformly deposited on the CNTs modified with poly(vinyl pyrrolidone) (PVP). The composites were characterized by a range of analytical techniques including high resolution transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results show the successful covering of the CNTs with PVP, forming core-shell structure. The nanoscaled TiO2 particles were uniformly deposited on the surface of CNTs reducing the bare CNTs which avoid losing the absorption and scattering of photons. The combination of CNTs and TiO2 particles imply the enhanced interactions between the CNTs and TiO2 interface which possibly becomes heterojunction. The composites become mesoporous crystalline TiO2 (anatase) clusters after annealing at 500 degrees C, and the surface area increases obviously. The photocatalytic activities of surface modification CNTs/TiO2 (smCNTs/TiO2) composites are extremely enhanced from the results of the photodegradation of methylene blue (MB).

Determining the Catalytic Activity of Transition Metal-Doped TiO2 Nanoparticles Using Surface Spectroscopic Analysis

NASA Astrophysics Data System (ADS)

Yang, Sena; Lee, Hangil

2017-11-01

The modified TiO2 nanoparticles (NPs) to enhance their catalytic activities by doping them with the five transition metals (Cr, Mn, Fe, Co, and Ni) have been investigated using various surface analysis techniques such as scanning electron microscopy (SEM), Raman spectroscopy, scanning transmission X-ray microscopy (STXM), and high-resolution photoemission spectroscopy (HRPES). To compare catalytic activities of these transition metal-doped TiO2 nanoparticles (TM-TiO2) with those of TiO2 NPs, we monitored their performances in the catalytic oxidation of 2-aminothiophenol (2-ATP) by using HRPES and on the oxidation of 2-ATP in aqueous solution by taking electrochemistry (EC) measurements. As a result, we clearly investigate that the increased defect structures induced by the doped transition metal are closely correlated with the enhancement of catalytic activities of TiO2 NPs and confirm that Fe- and Co-doped TiO2 NPs can act as efficient catalysts.

A novel drug delivery of 5-fluorouracil device based on TiO2/ZnS nanotubes.

PubMed

Faria, Henrique Antonio Mendonça; de Queiroz, Alvaro Antonio Alencar

2015-11-01

The structural and electronic properties of titanium oxide nanotubes (TiO2) have attracted considerable attention for the development of therapeutic devices and imaging probes for nanomedicine. However, the fluorescence response of TiO2 has typically been within ultraviolet spectrum. In this study, the surface modification of TiO2 nanotubes with ZnS quantum dots was found to produce a red shift in the ultra violet emission band. The TiO2 nanotubes used in this work were obtained by sol-gel template synthesis. The ZnS quantum dots were deposited onto TiO2 nanotube surface by a micelle-template inducing reaction. The structure and morphology of the resulting hybrid TiO2/ZnS nanotubes were investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction techniques. According to the results of fluorescence spectroscopy, pure TiO2 nanotubes exhibited a high emission at 380nm (3.26eV), whereas TiO2/ZnS exhibited an emission at 410nm (3.02eV). The TiO2/ZnS nanotubes demonstrated good bio-imaging ability on sycamore cultured plant cells. The biocompatibility against mammalian cells (Chinese Hamster Ovarian Cells-CHO) suggesting that TiO2/ZnS may also have suitable optical properties for use as biological markers in diagnostic medicine. The drug release characteristic of TiO2/ZnS nanotubes was explored using 5-fluorouracil (5-FU), an anticancer drug used in photodynamic therapy. The results show that the TiO2/ZnS nanotubes are a promising candidate for anticancer drug delivery systems. Copyright © 2015 Elsevier B.V. All rights reserved.

Construction of titanium dioxide nanorod/graphite microfiber hybrid electrodes for a high performance electrochemical glucose biosensor

NASA Astrophysics Data System (ADS)

Zhang, Jian; Yu, Xin; Guo, Weibo; Qiu, Jichuan; Mou, Xiaoning; Li, Aixue; Liu, Hong

2016-04-01

The demand for a highly sensitive and selective glucose biosensor which can be used for implantable or on-time monitoring is constantly increasing. In this work, TiO2 nanorods were synthesized in situ on the surface of graphite microfibers to yield TiO2 nanorod/graphite microfiber hybrid electrodes. The TiO2 nanorods not only retain the high activity of the immobilized glucose molecule, but also promote the direct electron transfer process on the electrode surface. As a working electrode in an electrochemical glucose biosensor in a flowing system, the microfiber hybrid electrodes exhibit high sensitivity, selectivity and stability. Due to its simplicity, low cost, high stability, and unique morphology, the TiO2 nanorod/graphite microfiber hybrid electrode is expected to be an excellent candidate for an implantable biosensor or for in situ flow monitoring.The demand for a highly sensitive and selective glucose biosensor which can be used for implantable or on-time monitoring is constantly increasing. In this work, TiO2 nanorods were synthesized in situ on the surface of graphite microfibers to yield TiO2 nanorod/graphite microfiber hybrid electrodes. The TiO2 nanorods not only retain the high activity of the immobilized glucose molecule, but also promote the direct electron transfer process on the electrode surface. As a working electrode in an electrochemical glucose biosensor in a flowing system, the microfiber hybrid electrodes exhibit high sensitivity, selectivity and stability. Due to its simplicity, low cost, high stability, and unique morphology, the TiO2 nanorod/graphite microfiber hybrid electrode is expected to be an excellent candidate for an implantable biosensor or for in situ flow monitoring. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01360k

TiO2 nanoparticles versus TiO2-SiO2 nanocomposites: A comparative study of photo catalysis on acid red 88

NASA Astrophysics Data System (ADS)

Balachandran, K.; Venckatesh, Rajendran; Sivaraj, Rajeshwari; Rajiv, P.

2014-07-01

A novel, simple, less time-consuming and cost-effective wet chemical technique was used to synthesis TiO2 nanoparticles and TiO2-SiO2 nanocomposites using Titanium tetra isopropoxide (TTIP) as a precursor relatively at low temperature in acidic pH. Titania sol was prepared by hydrolysis of TTIP and was mixed with silicic acid and tetrahydrofuran mixture. The reaction was carried out under vigorous stirring for 6 h and dried at room temperature. The resulting powders were characterized by UV-Visible spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction, scanning electron microscope (SEM) and transmission electron microscope (TEM). The grain size of the particles was calculated by X-ray diffraction, surface morphology and chemical composition was determined from scanning electron microscopy-energy dispersive spectroscopy, metal oxide stretching was confirmed from FT-IR spectroscopy, band gap was calculated using UV-Visible spectroscopy. Surface area of the composite as calculated by BET analyzer and it was found to be 65 and 75 m2/g for TiO2 and TiO2-SiO2 respectively. The photocatalytic experiments were performed with aqueous solution of acid red 88 with TiO2 and TiO2-SiO2 batch studies for 4 h irradiation, direct photolysis of TiO2 and TiO2-SiO2 contributed 94.2% and 96.5% decomposition in solar radiation for the optimized concentration of acid red 88.

Hyperbranched polyglycerol-grafted titanium oxide nanoparticles: synthesis, derivatization, characterization, size separation, and toxicology

NASA Astrophysics Data System (ADS)

Qin, Hongmei; Maruyama, Kyouhei; Amano, Tsukuru; Murakami, Takashi; Komatsu, Naoki

2016-10-01

We have been developing surface functionalization of various nanoparticles including nanodiamond and iron oxide nanoparticles in view of biomedical applications. In this context, TiO2 nanoparticles (TiO2 NP) are functionalized with polyglycerol (PG) to provide water-dispersible TiO2-PG, which is further derivatized through multi-step organic transformations. The resulting TiO2-PG and its derivatives are fully characterized by various analyses including solution-phase 1H and 13C NMR. TiO2-PG was size-tuned with centrifugation by changing the acceleration and duration. At last, no cytotoxicity of TiO2 NP, TiO2-PG, and TiO2-PG functionalized with RGD peptide was observed under dark conditions.

The effect of bulk/surface defects ratio change on the photocatalysis of TiO2 nanosheet film

NASA Astrophysics Data System (ADS)

Wang, Fangfang; Ge, Wenna; Shen, Tong; Ye, Bangjiao; Fu, Zhengping; Lu, Yalin

2017-07-01

The photocatalysis behavior of TiO2 nanosheet array films was studied, in which the ratio of bulk/surface defects were adjusted by annealing at different temperature. Combining positron annihilation spectroscopy, EPR and XPS, we concluded that the bulk defects belonged to Ti3+ related vacancy defects. The results show that the separation efficiency of photogenerated electrons and holes could be significantly improved by optimizing the bulk/surface defects ratio of TiO2 nanosheet films, and in turn enhancing the photocatalysis behaviors.

Determination of surface morphology of TiO2 nanostructure using synchrotron radiation

NASA Astrophysics Data System (ADS)

Das, Gangadhar; Kumar, Manoj; Biswas, A. K.; Khooha, Ajay; Mondal, Puspen; Tiwari, M. K.

2017-05-01

Nanostructures of Titanium oxide (TiO2) are being studied for many promising applications, e.g., solar photovoltaics, solar water splitting for H2 fuel generation etc., due to their excellent photo-catalytic properties. We have synthesized low-dimensional TiO2 nanoparticles by gas phase CW CO2 laser pyrolysis. The laser synthesis process has been optimized for the deposition of highly pure, nearly mono-dispersed TiO2 nanoparticles on silicon substrates. Hard x-ray standing wave-field (XSW) measurements in total reflection geometry were carried out on the BL-16 beamline of Indus-2 synchrotron radiation facility in combination with x-ray reflectivity and grazing incidence x-ray fluorescence measurements for the determination of surface morphology of the deposited TiO2 nanostructures. The average particle size of TiO2 nanostructure estimated using transmission electron microscopy (TEM) was found to closely agree with the XSW and grazing incidence x-ray diffraction (GIXRD) results.

Photocatalytic mechanism of high-activity anatase TiO2 with exposed (001) facets from molecular-atomic scale: HRTEM and Raman studies

NASA Astrophysics Data System (ADS)

Wu, Jun; Shi, Chentian; Zhang, Yupeng; Fu, Qiang; Pan, Chunxu

2017-12-01

Anatase TiO2 with a variant percentage of exposed (001) facets was prepared under hydrothermal processes by adjusting the volume of HF, and the photocatalytic mechanism was studied from atomic-molecular scale by HRTEM and Raman spectroscopy. It was revealed that: 1) From HRTEM observations, the surface of original TiO2 with exposed (001) facets was clean without impurity, and the crystal lattice was clear and completed; however, when mixed with methylene blue (MB) solution, there were many 1 nm molecular absorbed at the surface of TiO2; after the photocatalytic experiment, MB molecules disappeared and the TiO2 lattice image became fuzzy. 2) The broken path of the MB chemical bond was obtained by Raman spectroscopy, i.e., after the irradiation of the light, the vibrational mode of C-N-C disappeared due to the chemical bond breakage, and the groups containing C-N bond and carbon rings were gradually decomposed. Accordingly, we propose that the driving force for breaking the chemical bond and the disappearance of groups is from the surface lattice distortion of TiO2 during photocatalyzation.

Angle dependent antireflection property of TiO2 inspired by cicada wings

NASA Astrophysics Data System (ADS)

Zada, Imran; Zhang, Wang; Li, Yao; Sun, Peng; Cai, Nianjin; Gu, Jiajun; Liu, Qinglei; Su, Huilan; Zhang, Di

2016-10-01

Inspired by cicada wings, biomorphic TiO2 with antireflective structures (ARSs) was precisely fabricated using a simple, inexpensive, and highly effective sol-gel process combined with subsequent calcination. It was confirmed that the fabricated biomorphic TiO2 not only effectively inherited the ARS but also exhibited high-performance angle dependent antireflective properties ranging from normal to 45°. Reflectance spectra demonstrated that the reflectivity of the biomorphic TiO2 with ARSs gradually changed from 1.4% to 7.8% with the increasing incidence angle over a large visible wavelength range. This angle dependent antireflective property is attributed to an optimized gradient refractive index between air and TiO2 via ARSs on the surface. Such surfaces with ARSs may have potential application in solar cells.

A new recipe for preparing oxidized TiO2(1 1 0) surfaces: An STM study

NASA Astrophysics Data System (ADS)

Hansen, Jonas Ø.; Matthiesen, Jesper; Lira, Estephania; Lammich, Lutz; Wendt, Stefan

2017-12-01

Using high-resolution scanning tunneling microscopy (STM), we have studied the oxidation of rutile TiO2(1 1 0)-(1 × 1) surfaces with Had species at room temperature. We followed the evolution of various stable species as function of the O2 exposure, and the nature of the ultimately dominating species in the Ti troughs is described. When O2 saturation was accomplished using a glass-capillary array doser, we found that on-top O (Oot) adatoms are the predominant surface species. In contrast, when O2 was supplied via backfilling of the chamber the predominant surface species are tentatively assigned to terminal OH groups. We argue that unintended reactions with the chamber walls have a strong influence on the formed surface species, explaining scattered results in the literature. On the basis of our STM data we propose an alternative, easy way of preparing oxidized TiO2(1 1 0) surfaces with Oot adatoms (o-TiO2). It is certain that o-TiO2(1 1 0) surfaces prepared according to this recipe do not have any residual surface O vacancies. This contradicts the situation when oxidizing reduced TiO2(1 1 0) surfaces with O vacancies, where some O vacancies persist.

Adsorption and photocatalysis for methyl orange and Cd removal from wastewater using TiO2/sewage sludge-based activated carbon nanocomposites

PubMed Central

Eltaher, M. A.; Abdou, A. N. A.

2017-01-01

Nanocomposite TiO2/ASS (TiO2 nanoparticle coated sewage sludge-based activated carbon) was synthesized by the sol-gel method. The changes in surface properties of the TiO2/ASS nanocomposite were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray fluorescence. The prepared TiO2/ASS nanocomposite was applied for simultaneous removal of methyl orange dye (MO) and Cd2+ from bi-pollutant solution. The factors influencing photocatalysis (TiO2 : ASS ratios, initial pollutant concentrations, solution pH, nanocomposite dosage and UV irradiation time) were investigated. The results revealed that high removal efficiency of methyl orange dye (MO) and Cd2+ from bi-pollutant solution was achieved with TiO2/ASS at a ratio (1 : 2). The obtained results revealed that degradation of MO dye on the TiO2/ASS nanocomposite was facilitated by surface adsorption and photocatalytic processes. The coupled photocatalysis and adsorption shown by TiO2/ASS nanocomposite resulted in faster and higher degradation of MO as compared to MO removal by ASS adsorbent. The removal efficiency of MO by ASS adsorbent and TiO2/ASS (1 : 2) nanocomposite at optimum pH value 7 were 74.14 and 94.28%, respectively, while for Cd2+ it was more than 90%. The experimental results fitted well with the second-order kinetic reaction. PMID:29308227

Adsorption and photocatalysis for methyl orange and Cd removal from wastewater using TiO2/sewage sludge-based activated carbon nanocomposites.

PubMed

Rashed, M Nageeb; Eltaher, M A; Abdou, A N A

2017-12-01

Nanocomposite TiO 2 /ASS (TiO 2 nanoparticle coated sewage sludge-based activated carbon) was synthesized by the sol-gel method. The changes in surface properties of the TiO 2 /ASS nanocomposite were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray fluorescence. The prepared TiO 2 /ASS nanocomposite was applied for simultaneous removal of methyl orange dye (MO) and Cd 2+ from bi-pollutant solution. The factors influencing photocatalysis (TiO 2  : ASS ratios, initial pollutant concentrations, solution pH, nanocomposite dosage and UV irradiation time) were investigated. The results revealed that high removal efficiency of methyl orange dye (MO) and Cd 2+ from bi-pollutant solution was achieved with TiO 2 /ASS at a ratio (1 : 2). The obtained results revealed that degradation of MO dye on the TiO 2 /ASS nanocomposite was facilitated by surface adsorption and photocatalytic processes. The coupled photocatalysis and adsorption shown by TiO 2 /ASS nanocomposite resulted in faster and higher degradation of MO as compared to MO removal by ASS adsorbent. The removal efficiency of MO by ASS adsorbent and TiO 2 /ASS (1 : 2) nanocomposite at optimum pH value 7 were 74.14 and 94.28%, respectively, while for Cd 2+ it was more than 90%. The experimental results fitted well with the second-order kinetic reaction.

Adsorption and photocatalysis for methyl orange and Cd removal from wastewater using TiO2/sewage sludge-based activated carbon nanocomposites

NASA Astrophysics Data System (ADS)

Rashed, M. Nageeb; Eltaher, M. A.; Abdou, A. N. A.

2017-12-01

Nanocomposite TiO2/ASS (TiO2 nanoparticle coated sewage sludge-based activated carbon) was synthesized by the sol-gel method. The changes in surface properties of the TiO2/ASS nanocomposite were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray fluorescence. The prepared TiO2/ASS nanocomposite was applied for simultaneous removal of methyl orange dye (MO) and Cd2+ from bi-pollutant solution. The factors influencing photocatalysis (TiO2 : ASS ratios, initial pollutant concentrations, solution pH, nanocomposite dosage and UV irradiation time) were investigated. The results revealed that high removal efficiency of methyl orange dye (MO) and Cd2+ from bi-pollutant solution was achieved with TiO2/ASS at a ratio (1 : 2). The obtained results revealed that degradation of MO dye on the TiO2/ASS nanocomposite was facilitated by surface adsorption and photocatalytic processes. The coupled photocatalysis and adsorption shown by TiO2/ASS nanocomposite resulted in faster and higher degradation of MO as compared to MO removal by ASS adsorbent. The removal efficiency of MO by ASS adsorbent and TiO2/ASS (1 : 2) nanocomposite at optimum pH value 7 were 74.14 and 94.28%, respectively, while for Cd2+ it was more than 90%. The experimental results fitted well with the second-order kinetic reaction.

Architecture engineering toward highly active palladium integrated titanium dioxide yolk-double-shell nanoreactor for catalytic applications.

PubMed

Liu, Baocang; Wang, Qin; Yu, Shengli; Jing, Peng; Liu, Lixia; Xu, Guangran; Zhang, Jun

2014-10-21

Rational design of the hierarchical architecture of a material with well controlled functionality is crucially important for improving its properties. In this paper, we present the general strategies for rationally designing and constructing three types of hierarchical Pd integrated TiO2 double-shell architectures, i.e. yolk-double-shell TiO2 architecture (Pd@TiO2/Pd@TiO2) with yolk-type Pd nanoparticles residing inside the central cavity of the hollow TiO2 structure; ultrafine Pd nanoparticles homogenously dispersed on both the external and internal surfaces of the inner TiO2 shell; and double-shell TiO2 architecture (@TiO2/Pd@TiO2) with Pd nanoparticles solely loaded on the external surface of the inner TiO2 shell, and double-shell TiO2 architecture (@TiO2@Pd@TiO2) with Pd nanoparticles dispersed in the interlayer space of double TiO2 shells, via newly developed Pd(2+) ion-diffusion and Pd sol impregnation methodologies. These architectures are well controlled in structure, size, morphology, and configuration with Pd nanoparticles existing in various locations. Owing to the variable synergistic effects arising from the location discrepancies of Pd nanoparticle in the architectures, they exhibit remarkable variations in catalytic activity. In particular, different from previously reported yolk-shell structures, the obtained yolk-double-shell Pd@TiO2/Pd@TiO2 architecture, which is revealed for the first time, possesses a uniform hierarchical structure, narrow size distribution, and good monodispersibility, and it creates two Pd-TiO2 interfaces on the external and internal surfaces of the inner TiO2 shell, leading to the strongest synergistic effect of Pd nanoparticles with TiO2 shell. Furthermore, the interlayer chamber between the double TiO2 shells connecting with the central cavity of the hollow TiO2 structure through the mesoporous TiO2 wall forms a nanoreactor for enriching the reactants and preventing the deletion of Pd nanoparticles during the reaction, thus greatly accelerating the reaction speed. Owing to its structural features, yolk-double-shell Pd@TiO2/Pd@TiO2 architecture exhibits extremely high catalytic performance on the Suzuki-Miyaura coupling reaction. The synthetic methodologies are robust for fabricating double-shell architectures with various configurations for applications such as in catalysis, drug delivery, and medicine release. The obtained double-shell architectures may be used as novel catalyst systems with highly efficient catalytic performance for other catalytic reactions.

Optimizing the photochemical conversion of UV-vis light of silver-nanoparticles decorated TiO2 nanotubes based photoanodes

NASA Astrophysics Data System (ADS)

Gaidi, M.; Trabelsi, K.; Hajjaji, A.; Chourou, M. L.; Alhazaa, A. N.; Bessais, B.; El Khakani, M. A.

2018-01-01

Homogeneous decoration of TiO2 nanotubes (NTs) by Ag metallic nanoparticles (NPs) was carried out by a relatively simple photoreduction process. This Ag-NPs decoration was found to improve the photoconversion efficiency of the TiO2-NTs based photoanodes. The x-ray photoelectron spectroscopy and x-ray diffraction analyses confirmed that all the Ag-NPs are metallic and the underlying TiO2-NTs crystallize in the anatase phase after their annealing at 400 °C, respectively. Transmission electron microscopy observations have confirmed the effective decoration of the TiO2-NTs’ surface by Ag-NPs, and allowed to measure the average Ag-NPs size, which was found to increase linearly from (4 ± 2) nm to (16 ± 4) nm when the photoreduction time is increased from 5 to 20 min. The diffuse reflectivity of the Ag-NPs decorated TiO2-NTs was found to decrease significantly as compared to the undecorated TiO2-NTs. Interestingly, the Ag-NPs decorated TiO2-NTs exhibited a significantly enhanced photochemical response, under visible radiation, with regards to the undecorated NTs. This enhancement was found to reach its maximum for the TiO2-NTs decorated with Ag-NPs having the optimal average diameter of ˜8.5 nm. The maximum photoconversion efficiency of Ag-NPs decorated TiO2-NTs was about two times greater than for the undecorated ones. This improved photo-electro-chemical response is believed to be associated with the additional absorption of visible light of Ag-NPs through the localized surface plasmon resonance phenomenon. This interpretation is supported by the fact that the photoluminescence intensity of the Ag-NPs decorated TiO2-NTs was found to decrease significantly as compared to undecorated NTs, due to charge carriers trapping in the Ag NPs. This demonstrates that Ag-NPs decoration promotes photogenerated charges separation in the TiO2-NTs, increasing thereby their capacity for current photogeneration. The surface decoration of TiO2 NTs by noble metals NPs is expected to impact positively the use of TiO2-NTs based photoanodes in some energetic applications such as hydrogen generation and photo-electrochemical solar cells.

Optimizing the photochemical conversion of UV-vis light of silver-nanoparticles decorated TiO2 nanotubes based photoanodes.

PubMed

Gaidi, M; Trabelsi, K; Hajjaji, A; Chourou, M L; Alhazaa, A N; Bessais, B; El Khakani, M A

2018-01-05

Homogeneous decoration of TiO 2 nanotubes (NTs) by Ag metallic nanoparticles (NPs) was carried out by a relatively simple photoreduction process. This Ag-NPs decoration was found to improve the photoconversion efficiency of the TiO 2 -NTs based photoanodes. The x-ray photoelectron spectroscopy and x-ray diffraction analyses confirmed that all the Ag-NPs are metallic and the underlying TiO 2 -NTs crystallize in the anatase phase after their annealing at 400 °C, respectively. Transmission electron microscopy observations have confirmed the effective decoration of the TiO 2 -NTs' surface by Ag-NPs, and allowed to measure the average Ag-NPs size, which was found to increase linearly from (4 ± 2) nm to (16 ± 4) nm when the photoreduction time is increased from 5 to 20 min. The diffuse reflectivity of the Ag-NPs decorated TiO 2 -NTs was found to decrease significantly as compared to the undecorated TiO 2 -NTs. Interestingly, the Ag-NPs decorated TiO 2 -NTs exhibited a significantly enhanced photochemical response, under visible radiation, with regards to the undecorated NTs. This enhancement was found to reach its maximum for the TiO 2 -NTs decorated with Ag-NPs having the optimal average diameter of ∼8.5 nm. The maximum photoconversion efficiency of Ag-NPs decorated TiO 2 -NTs was about two times greater than for the undecorated ones. This improved photo-electro-chemical response is believed to be associated with the additional absorption of visible light of Ag-NPs through the localized surface plasmon resonance phenomenon. This interpretation is supported by the fact that the photoluminescence intensity of the Ag-NPs decorated TiO 2 -NTs was found to decrease significantly as compared to undecorated NTs, due to charge carriers trapping in the Ag NPs. This demonstrates that Ag-NPs decoration promotes photogenerated charges separation in the TiO 2 -NTs, increasing thereby their capacity for current photogeneration. The surface decoration of TiO 2 NTs by noble metals NPs is expected to impact positively the use of TiO 2 -NTs based photoanodes in some energetic applications such as hydrogen generation and photo-electrochemical solar cells.

Electrochemical and in vitro behavior of the nanosized composites of Ti-6Al-4V and TiO2 fabricated by friction stir process

NASA Astrophysics Data System (ADS)

Zhang, Chengjian; Ding, Zihao; Xie, Lechun; Zhang, Lai-Chang; Wu, Laizhi; Fu, Yuanfei; Wang, Liqiang; Lu, Weijie

2017-11-01

Although Ti-6Al-4V has been widely used in biomaterial field. Compared with other classes of materials, it still encounters some problems such as low surface hardness and relative low biocompatibility. To solve these problems friction stir processing (FSP) was applied to fabricate a nanosized composite layer of TiO2 and Ti-6Al-4V. Uniform distribution of TiO2 particles with some clusters on the surface of alloy can be observed. Due to severe plastic deformation and stirring heat, nanocrystallines and amorphous TiO2 can be observed in stir zone. FSPed samples show significant improvement in surface microhardness and biocompatibility due to its modified structure compared with original sample. In addition, through corrosion behaviors of the samples in simulated body fluid, it is found that FSP can enhance whilst TiO2 reduces the possibility and corrosion rate of material in environment of human body.

Development of DNA biosensor based on TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Nadzirah, Sh.; Hashim, U.; Rusop, M.

2018-05-01

A novel technique of DNA hybridization on the TiO2 nanoparticles film was developed by dropping a single droplet of target DNA onto the surface of TiO2 for the study of various concentrations of target DNA. The surface of TiO2 nanoparticle film was functionalized with APTES and covalently immobilized with 1 µM probe DNA on the silanized TiO2 nanoparticles surface. The effect of silanization, immobilization and hybridization were quantitatively measured by the output current signal obtained using a picoammeter. The 1 µM target DNA was found to be the most effective target towards the 1 µM probe DNA as the output current signal was within range; while the output current signal of the 10 µM target DNA was observed to beyond the range of the probe DNA control due to the excessive concentration as compared to the probe DNA. This approach has several advantages such as rapid, simple, low cost, and sensitive current signal during detection of different target DNA concentrations.

Chalcogenide Sensitized Carbon Based TiO2 Nanomaterial For Solar Driven Applications

NASA Astrophysics Data System (ADS)

Pathak, Pawan

The demand for renewable energy is growing because fossils fuels are depleting at a rapid pace. Solar energy an abundant green energy resource. Utilizing this resource in a smart manner can resolve energy-crisis related issues. Sun light can be efficiently harvested using semiconductor based materials by utilizing photo-generated charges for numerous beneficial applications. The main goal of this thesis is to synthesize different nanostructures of TiO2, develop a novel method of coupling and synthesizing chalcogenide nanocrystals with TiO2 and to study the charge transportation effects of the various carbon allotropes in the chalcogenide nanocrystal sensitized TiO2 nanostructure. We have fabricated different nanostructures of TiO2 as solar energy harvesting materials. Effects of the different phases of TiO2 have also been studied. The anatase phase of TiO2 is more photoactive than the rutile phase of TiO2, and the higher dimension of the TiO2 can increase the surface area of the material which can produce higher photocurrent. Since TiO2 only absorbs in the UV range; to increase the absorbance TiO2 should be coupled to visible light absorbing materials. This dissertation presents a simple approach to synthesize and couple chalcogenide nanocrystals with TiO2 nanostructure to form a heterostructured composite. An atmospheric pressure based, single precursor, one-pot approach has been developed and tested to assemble chalcogenide nanocrystal on the TiO2 surface. Surface characterization using microscopy, X-ray diffraction, and elemental analysis indicates the formation of nanocrystals along the nanotube walls and inter-tubular spacing. Optical measurements indicate that the chalcogenide nanocrystals absorb in the visible region and demonstrate an increase in photocurrent in comparison to bare TiO2 nanostructure. The CdS synthesized TiO2 nanostructure produced the highest photocurrent as measured in the three electrode system. We have also assembled the PbS nanocrystal sensitized photoanode using the one pot method. Finally, the charge transportation effect of carbon allotropes has been studied. For this we assembled TiO2 conductive carbon chalcogenide nanocomposite system. Surface and elemental characterization using electron microscopy, EDX (energy dispersive x-ray) and x-ray diffraction pattern, provide the insights into the assembly of the nanostructure. Optical absorbance, Photo chronometry, Linear sweep voltammetry, and electrochemical impedance analysis have been used to provide opto-electronic performance of the material. We have studied the loading effect of various carbon allotropes, [fullerene (C 60), reduced graphene oxide (RGO), carbon nanotubes (CNTs), and graphene quantum dots (GQDs)], loading effect of chalcogenide, and effect of nitrogen doping on the carbon allotropes to optimize the performance of the heterostructure. This dissertation is expected to impact the materials synthesis strategies and assemble the nanostructures used in composite electrode driven applications in the area of photo electrochemistry, PV, solar-fuels, and other associated topics of energy storage and sensing.

Photocatalytic growth of Ag nanocrystals on hydrothermally synthesized multiphasic TiO2/reduced graphene oxide (rGO) nanocomposites and their SERS performance

NASA Astrophysics Data System (ADS)

Guo, Tian-Long; Li, Ji-Guang; Sun, Xudong; Sakka, Yoshio

2017-11-01

TiO2/reduced graphene oxide (rGO) nanocomposites were prepared via a facile one-step hydrothermal method using TiCl3 as the TiO2 precursor. Cetyltrimethyl ammonium bromide (CTAB) was introduced as a stabilizer for GO in solution. The effects of GO content, Ti3+ concentration and urea additive on phase constituent and morphology of the TiO2 crystallites in the nanocomposites were systematically investigated. UV-vis absorption ability of the as-made composites was further tested and discussed. Ag nanocrystals (NCs) were photocatalytically grown on the surfaces of biphasic (anatase + brookite) and triphasic (anatase + brookite + rutile) TiO2/rGO nanocomposites to evaluate their surface-enhanced Raman scattering (SERS) performances. Morphology evolution of the Ag NCs in response to different photocatalytic ability of the TiO2/rGO nanocomposite was also investigated in detail. The nanocomposite with triphasic TiO2 of proper phase constituents was confirmed to favor the growth of Ag particles of two distinctly different sizes and to produce SERS substrates of substantially better performance.

DFT Studies of Adsorption of Cu7-atom Nanoclusters on TiO2 Surfaces and Application to Methanol Steam Reforming Reactions

NASA Astrophysics Data System (ADS)

Taft, Michael J., Sr.

Alcohol conversion to hydrogen, via steam reforming, is an alternative energy process that is promising for the future of clean energy economies. With advancements in fuel cell technologies, on-board hydrogen reforming could leverage already existing automotive designs and fuel infrastructure. The design of catalytic materials with tunable properties requires a level of insight that has yet to be achieved experimentally. The central objective of this project is to develop a working model of metal-oxide surface mediated copper clusters, since such catalytic beds have a wide-range of applications. More specifically, we investigate the catalytic framework of this process with theoretical models of the active metal (Cu) and metal­oxide support (TiO2). We employ a Density Functional Theory (DFT)-Generalized Gradient Approximation (GGA) approach for the quantum level electronic structure calculations of Cu, TiO2 and CH3OH. Additionally, we have generated anatase (A(001), A(101)) and rutile (R(100), R(110)) surface morphologies and 7­atom copper cluster complexes with those planes. To examine the possible influence of TiO2 on the adsorption properties of our active metal, Cu7, we have carried out adsorption studies with CH3OH. Our final data and observations predict that the Cu7 cluster adopts a symmetric pentagonal bipyramidal geometry with D5h symmetry. We find that the anatase morphology has a greater overall stability than rutile. The adsorption strength of the Cu7 cluster has been predicted in this study to be according to the following order: A(001) > A(101)> R(110). Indeed, the R(100) surface appears to be an unfavorable surface for metal cluster binding. Our data indicates that copper cluster stabilization on the metal-oxide surface depends on the nature of the crystal face. Again, we studied the adsorption properties of methanol on nascent Cu7 cluster, Cu7-TiO 2 complex and on pure TiO2-surface in A(001) polymorphic form. The calculations revealed that methanol adsorbs more efficiently on TiO2-bound copper clusters than either the copper cluster alone or the surface of TiO2. Additionally, we find that the metal-oxide support plays a significant role in stabilizing the catalytic reactions of CH3OH adsorption. Here, we have shown that TiO2 clearly enhances the catalytic properties of copper clusters.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henderson, Michael A.; Lyubinetsky, Igor

The field of heterogeneous photocatalysis has grown considerably in the decades since Fujishima and Honda's ground-breaking publications of photoelectrochemistry on TiO2. Numerous review articles continue to point to both progress made in the use of heterogeneous materials (such as TiO2) to perform photoconversion processes, and the many opportunities and challenges in heterogeneous photocatalysis research such as solar energy conversion and environmental remediation. The past decade has also seen an increase in the use of molecular-level approaches applied to model single crystal surfaces in an effort to obtain new insights into photocatalytic phenomena. In particular, scanning probe techniques (SPM) have enabledmore » researchers to take a ‘nanoscale’ approach to photocatalysis that includes interrogation of the reactivities of specific sites and adsorbates on a model photocatalyst surface. The rutile TiO2(110) surface has become the prototypical oxide single crystal surface for fundamental studies of many interfacial phenomena. In particular, TiO2(110) has become an excellent model surface for probing photochemical and photocatalytic reactions at the molecular level. A variety of experimental approaches have emerged as being ideally suited for studying photochemical reactions on TiO2(110), including desorption-oriented approaches and electronic spectroscopies, but perhaps the most promising techniques for evaluating site-specific properties are those of SPM. In this review, we highlight the growing use of SPM techniques in providing molecular-level insights into surface photochemistry on the model photocatalyst surface of rutile TiO2(110). Our objective is to both illustrate the unique knowledge that scanning probe techniques have already provided the field of photocatalysis, and also to motivate a new generation of effort into the use of such approaches to obtain new insights into the molecular level details of photochemical events occurring at interfaces. Discussion will start with an examination of how scanning probe techniques are being used to characterize the TiO2(110) surface in ways that are relevant to photocatalysis. We will then discuss specific classes of photochemical reaction on TiO2(110) for which SPM has proven indispensible in providing unique molecular-level insights, and conclude with discussion of future areas in which SPM studies may prove valuable to photocatalysis on TiO2. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. I.L. was partially supported by a Pacific Northwest National Laboratory (PNNL) Chemical Imaging Initiative project. PNNL is a multiprogram national laboratory operated for DOE by Battelle.« less

Surface-enhanced Raman scattering of amorphous TiO2 thin films by gold nanostructures: Revealing first layer effect with thickness variation

NASA Astrophysics Data System (ADS)

Degioanni, S.; Jurdyc, A.-M.; Bessueille, F.; Coulm, J.; Champagnon, B.; Vouagner, D.

2013-12-01

In this paper, amorphous titanium dioxide (TiO2) thin films have been deposited on a commercially available Klarite substrate using the sol-gel process to produce surface-enhanced Raman scattering (SERS). The substrate consists of square arrays of micrometer-sized pyramidal pits in silicon with a gold coating. Several thin TiO2 layers have been deposited on the surface to study the influence of film thickness. Ultimately, we obtained information on SERS of an amorphous TiO2 layer by gold nanostructures, whose range is less than a few nanometers. Mechanisms responsible for the enhancement are the product of concomitant chemical and electromagnetic effects with an important contribution from plasmon-induced charge transfer.

Growth of rutile TiO2 on the convex surface of nanocylinders: from nanoneedles to nanorods and their electrochemical properties

NASA Astrophysics Data System (ADS)

Kong, Junhua; Wei, Yuefan; Zhao, Chenyang; Toh, Meng Yew; Yee, Wu Aik; Zhou, Dan; Phua, Si Lei; Dong, Yuliang; Lu, Xuehong

2014-03-01

In this work, bundles of rutile TiO2 nanoneedles/nanorods are hydrothermally grown on carbon nanofibers (CNFs), forming free-standing mats consisting of three dimensional hierarchical nanostructures (TiO2-on-CNFs). Morphologies and structures of the TiO2-on-CNFs are studied using a field-emission scanning electron microscope (FESEM), transmission electron microscope (TEM), X-ray diffractometer (XRD) and thermogravimetric analyzer (TGA). Their electrochemical properties as electrodes in lithium ion batteries (LIBs) are investigated and correlated with the morphologies and structures. It is shown that the lateral size of the TiO2 nanoneedles/nanorods ranges from a few nanometers to tens of nanometers, and increases with the hydrothermal temperature. Small interspaces are observed between individual nanoneedles/nanorods, which are due to the diverging arrangement of nanoneedles/nanorods induced by growing on the convex surface of nanocylinders. It is found that the growth process can be divided into two stages: initial growth on the CNF surface and further growth upon re-nucleation on the TiO2 bundles formed in the initial growth stage. In order to achieve good electrochemical performance in LIBs, the size of the TiO2 nanostructures needs to be small enough to ensure complete alloying and fast charge transport, while the further growth stage has to be avoided to realize direct attachment of TiO2 nanostructures on the CNFs, facilitating electron transport. The sample obtained after hydrothermal treatment at 130 °C for 2 h (TiO2-130-2) shows the above features and hence exhibits the best cyclability and rate capacity among all samples; the cyclability and rate capacity of TiO2-130-2 are also superior to those of other rutile TiO2-based LIB electrodes.In this work, bundles of rutile TiO2 nanoneedles/nanorods are hydrothermally grown on carbon nanofibers (CNFs), forming free-standing mats consisting of three dimensional hierarchical nanostructures (TiO2-on-CNFs). Morphologies and structures of the TiO2-on-CNFs are studied using a field-emission scanning electron microscope (FESEM), transmission electron microscope (TEM), X-ray diffractometer (XRD) and thermogravimetric analyzer (TGA). Their electrochemical properties as electrodes in lithium ion batteries (LIBs) are investigated and correlated with the morphologies and structures. It is shown that the lateral size of the TiO2 nanoneedles/nanorods ranges from a few nanometers to tens of nanometers, and increases with the hydrothermal temperature. Small interspaces are observed between individual nanoneedles/nanorods, which are due to the diverging arrangement of nanoneedles/nanorods induced by growing on the convex surface of nanocylinders. It is found that the growth process can be divided into two stages: initial growth on the CNF surface and further growth upon re-nucleation on the TiO2 bundles formed in the initial growth stage. In order to achieve good electrochemical performance in LIBs, the size of the TiO2 nanostructures needs to be small enough to ensure complete alloying and fast charge transport, while the further growth stage has to be avoided to realize direct attachment of TiO2 nanostructures on the CNFs, facilitating electron transport. The sample obtained after hydrothermal treatment at 130 °C for 2 h (TiO2-130-2) shows the above features and hence exhibits the best cyclability and rate capacity among all samples; the cyclability and rate capacity of TiO2-130-2 are also superior to those of other rutile TiO2-based LIB electrodes. Electronic supplementary information (ESI) available: FESEM image of carbonized electrospinning-derived carbon nanofibers. FESEM images of TiO2 nanostructures grown on carbon nanofibers using titanium(iv) isopropoxide and titanium(iv) butoxide as precursors. TGA curves of the samples from 24 h hydrothermal growth at 90 °C, 130 °C and 180 °C. The cycling capacity of pure carbon nanofibers at a current rate of 50 mA g-1 and a voltage range of 1.0-2.8 V. The cycling capacity of the samples from 24 h hydrothermal growth at 90 °C, 130 °C and 180 °C. See DOI: 10.1039/c3nr04308h

Three-level cobblestone-like TiO2 micro/nanocones for dual-responsive water/oil reversible wetting without fluorination

NASA Astrophysics Data System (ADS)

Zhou, Chen; Li, Guoqiang; Li, Chuanzong; Zhang, Zhen; Zhang, Yachao; Wu, Sizhu; Hu, Yanlei; Zhu, Wulin; Li, Jiawen; Chu, Jiaru; Hu, Zhijia; Wu, Dong; Yu, Liandong

2017-10-01

In this work, a kind of three-level cobblestone-like anatase TiO2 microcone array was fabricated on titanium sheets by femtosecond laser-induced self-assembly. This three level structure consisted of cobblestone-like features (15-25 μm in height and 20-35 μm in diameter), ˜460 nm ripple-like features, and smaller particles (10-500 nm). The formation of microcone arrays can be ascribed to the interaction of alternant laser beam ablation. TiO2 surfaces display dual-responsive water/oil reversible wetting via heat treatment and selective UV irradiation without fluorination. It is indicated that three-level scale surface roughness can amplify the wetting character of the Ti surface, and the mechanism for reversible switching between extreme wettabilities is caused by the conversion between Ti-OH and Ti-O. Moreover, the double-faced superhydrophobic and double-faced superhydrophilic Ti samples were constructed, which exhibited stable superhydrophobicity and underwater superoleophobicity in water-oil solution, respectively, even when strongly shaken. Finally, we present the hybrid-patterned TiO2 surface and realized reversible switching pattern wettability.

Integrated titanium dioxide (TiO2) nanoparticles on interdigitated device electrodes (IDEs) for pH analysis

NASA Astrophysics Data System (ADS)

Azizah, N.; Hashim, U.; Arshad, M. K. Md.; Gopinath, Subash C. B.; Nadzirah, Sh.; Farehanim, M. A.; Fatin, M. F.; Ruslinda, A. R.; Ayub, R. M.

2016-07-01

Titanium dioxide (TiO2) nanoparticles based Interdigitated Device Electrodes (IDEs) Nanobiosensor device was developed for intracellular biochemical detection. Fabrication and characterization of pH sensors using IDE nanocoated with TiO2 was studied in this paper. In this paper, a preliminary assessment of this intracellular sensor with electrical measurement under different pH levels. 3-aminopropyltriethoxysilane (APTES) was used to enhance the sensitivity of titanium dioxide layer as well as able to provide surface modification by undergoing protonation and deprotonation process. Different types of pH solution provide different resistivity and conductivity towards the surface. Base solution has the higher current compared to an acid solution. Amine and oxide functionalized TiO2 based IDE exhibit pH-dependent could be understood in terms of the change in surface charge during protonation and deprotonation. The simple fabrication process, high sensitivity, and fast response of the TiO2 based IDEs facilitate their applications in a wide range of areas. The small size of semiconductor TiO2 based IDE for sensitive, label-free, real time detection of a wide range of biological species could be explored in vivo diagnostics and array-based screening.

Immobilization of TiO 2 nanofibers on titanium plates for implant applications

NASA Astrophysics Data System (ADS)

Lim, Jin Ik; Yu, Bin; Woo, Kyung Mi; Lee, Yong-Keun

2008-12-01

Nanofibers have shown good biological performances such as improved cell adhesion and differentiation; therefore, nanofibrous modification of dental and bone implants might enhance osseo-integration. The purpose of this study was to investigate the nanofibrous modification of titanium implants. TiO 2 nanofibers were fabricated by the electrospinning method using a mixture of Ti(IV)isopropoxide and poly(vinyl pyrrolidone) (PVP) in acidic alcohol solution. Then the nanofibers were immobilized on the NaOH/HCl-treated titanium plates by inducing the alcohol condensation reaction of Ti(IV)isopropoxide with Ti-OH group on the titanium surface and subsequent calcination (500-1000 °C). The immobilized TiO 2 nanofibers were characterized by SEM, XRD and a simulated removal test. The diameter of the TiO 2 nanofibers could be controlled within the range of 20-350 nm by changing the amounts of Ti(IV)isopropoxide and PVP. Phase transformation from anatase to rutile was observed after calcination. After the simulated removal test, TiO 2 nanofibers remained on titanium surface. These TiO 2 nanofibers on titanium plates could be used for the surface modification of titanium implants to improve the osseo-integration.

Theoretical studies of arsenite adsorption and its oxidation mechanism on a perfect TiO 2 anatase (1 0 1) surface

NASA Astrophysics Data System (ADS)

Wei, Zhigang; Zhang, Shaowen; Pan, Zhanchang; Liu, Yue

2011-11-01

There are many areas in the world where the ground water has been contaminated by arsenic. TiO2 is one of the most promising materials that can remove arsenic from groundwater supplies by the adsorption-based processes. The TiO2 surface is capable of photo-catalytic oxidation (PCO) changing the arsenite [As(III)] to arsenate [As(V)] which is more easily absorbed by the surface, increasing the efficiency of the process. In this paper, a density functional theory calculation has been performed to investigate the adsorption of As(III) on a perfect TiO2 anatase (1 0 1) surface. All the As(III) solution species such as H3AsO3, H2AsO3-, HAsO32- and AsO33- are put onto the surface with many different possible attitudes to obtain the adsorption energy. Based on the adsorption energy and the concentration of H3AsO3, H2AsO3-, HAsO32- and AsO33- in an aqueous solution, the bidentate binuclear (BB) adsorption configurations of H2AsO3- on the surface are more favorable at low As(III) concentrations, whereas BB form and monodentate mononuclear (MM) form may coexist at higher concentrations. By calculating H2AsO3- co-adsorption with water and oxygen, we can confirm the deep acceptor character of an adsorbed O2 molecule which implies that surface superoxide (or hydroperoxyl radical) plays an important role during the PCO process of As(III) on TiO2 surface.

Heterogeneous production and loss of HOx by airborne TiO2 particles and implications for climate change mitigation strategies

NASA Astrophysics Data System (ADS)

Moon, D. R.; Heard, D. E.; Ingham, T.; Chipperfield, M.; Seakins, P. W.; Baeza Romero, M. T. T.; Taverna, G. S.

2016-12-01

It is suggested that injection of TiO2 particles into the stratosphere to back-scatter solar radiation maybe an effective measure to mitigate the effects of global warming. TiO2 particles are well suited to this application because of their high refractive index.1 However, the effect of such a measure on stratospheric chemistry is not fully understood. HO2 is a key atmospheric species in both the troposphere and the stratosphere and is responsible for 40% of ozone destruction in the lower stratosphere.2 In addition to this, application of TiO2 coatings to surfaces within the urban environment are used to abate ambient levels of NO2 and for their self-cleaning properties. This study investigates the heterogeneous reaction between airborne sub-micron TiO2 particles and HO2 radicals using an aerosol flow tube and the FAGE (fluorescence assay by gas expansion) technique to monitor HO2 uptake. The dependence of the uptake coefficient (γHO2) to relative humidity (RH) has been determined. Experiments performed in dark conditions at the most stratospherically relevant RH (11.1%) determined γHO2 = (2.08 ± 0.11) × 10-2. A positive dependence of γHO2 with RH was observed which showed a correlation between γHO2 and the number of monolayers of water adsorbed on the particle surface. Experiments illuminated with near-UV light (365 nm) were performed and showed significant production of HO2 from the aerosols into the gas phase. The concentrations were dependent on light flux, RH and total particle surface area. While the production of HOx in the gas phase has been observed close to TiO2 surfaces in the presence of H2O23,4 it is believed that this phenomena has not been observed from airborne TiO2 particles and parameterized in this way before. Emissions of HO2 from the surface of TiO2 particles in the stratosphere could rule out the application of TiO2 particles for use within solar-radiation management schemes. The TOMCAT 3-D chemical transport model was used to predict the effect of the injection of TiO2 particles into the stratosphere. Uptake and production of HO2 along with other studied heterogeneous reactions with TiO2 particles are considered. The predicted changes to [HO2], [O3] and other species will be presented. Pope, F. D. et al. (2010) Wennberg, P. O. et. al. (1994) Murakami, Y. et al. (2006) Bahrini, C. et al. (2010)

Antibacterial photocatalytic activity of different crystalline TiO2 phases in oral multispecies biofilm.

PubMed

Pantaroto, Heloisa N; Ricomini-Filho, Antonio P; Bertolini, Martinna M; Dias da Silva, José Humberto; Azevedo Neto, Nilton F; Sukotjo, Cortino; Rangel, Elidiane C; Barão, Valentim A R

2018-07-01

Titanium dioxide (TiO 2 ) incorporation in biomaterials is a promising technology due to its photocatalytic and antibacterial activities. However, the antibacterial potential of different TiO 2 crystalline structures on a multispecies oral biofilm remains unknown. We hypothesized that the different crystalline TiO 2 phases present different photocatalytic and antibacterial activities. Three crystalline TiO 2 films were deposited by magnetron sputtering on commercially pure titanium (cpTi), in order to obtain four groups: (1) machined cpTi (control); (2) A-TiO 2 (anatase); (3) M-TiO 2 (mixture of anatase and rutile); (4) R-TiO 2 (rutile). The morphology, crystalline phase, chemical composition, hardness, elastic modulus and surface free energy of the surfaces were evaluated. The photocatalytic potential was assessed by methylene blue degradation assay. The antibacterial activity was evaluated on relevant oral bacteria, by using a multispecies biofilm (Streptococcus sanguinis, Actinomyces naeslundii and Fusobacterium nucleatum) formed on the treated titanium surfaces (16.5h) followed by UV-A light exposure (1h) to generate reactive oxygen species production. All TiO 2 films presented around 300nm thickness and improved the hardness and elastic modulus of cpTi surfaces (p<0.05). A-TiO 2 and M-TiO 2 films presented superior photocatalytic activity than R-TiO 2 (p<0.05). M-TiO 2 revealed the greatest antibacterial activity followed by A-TiO 2 (≈99.9% and 99% of bacterial reduction, respectively) (p<0.001 vs. control). R-TiO 2 had no antibacterial activity (p>0.05 vs. control). This study brings new insights on the development of extra oral protocols for the photocatalytic activity of TiO 2 in oral biofilm-associated disease. Anatase and mixture-TiO 2 showed antibacterial activity on this oral bacterial biofilm, being promising surface coatings for dental implant components. Copyright © 2018 The Academy of Dental Materials. All rights reserved.

Bacteria Adherence Properties of Nitrogen-Doped TiO2 Coatings by Plasma Surface Alloying Technique

NASA Astrophysics Data System (ADS)

Wang, Hefeng; Tang, Bin; Li, Xiuyan; Fan, Ailan

Titanium nitride coatings on 316L stainless steel (S. S) were obtained by plasma surface alloying technique. Nitrogen-doped titanium dioxide (TiO2-xNx) was synthesized by oxidative annealing the resulted TiNx coatings in air. The reference TiO2 samples were also prepared by oxidation of sputtered Ti coatings. The as-prepared coatings were characterized by X-ray diffraction, glow discharge optical emission spectrometer (GDOES), scanning electron microscopy, X-ray hotoelectron spectroscopy and UV-Vis spectrophotometry, respectively. The bacteria adherence property of the TiO2-xNx coatings on stainless steel on the oral bacteria Streptococcus Mutans was investigated and compared with that of stainless steel by fluorescence microscopy. The mechanism of the bacteria adherence was discussed. The results show that the TiO2-xNx coatings are composed of anatase crystalline structure. SEM measurement indicates a rough surface morphology with three-dimensional homogenous protuberances after annealing treatment. Optical properties reveal an extended tailing of the absorption edge toward the visible region due to nitrogen presence. The band gap of the N-doped sample is reduced from 2.29 eV to 1.90 eV compared with the pure TiO2 one. Because of the different roughness and microstructure, the TiO2-xNx coatings inhibit the bacteria adherence.

An In Silico study of TiO2 nanoparticles interaction with twenty standard amino acids in aqueous solution

NASA Astrophysics Data System (ADS)

Liu, Shengtang; Meng, Xuan-Yu; Perez-Aguilar, Jose Manuel; Zhou, Ruhong

2016-11-01

Titanium dioxide (TiO2) is probably one of the most widely used nanomaterials, and its extensive exposure may result in potentially adverse biological effects. Yet, the underlying mechanisms of interaction involving TiO2 NPs and macromolecules, e.g., proteins, are still not well understood. Here, we perform all-atom molecular dynamics simulations to investigate the interactions between TiO2 NPs and the twenty standard amino acids in aqueous solution exploiting a newly developed TiO2 force field. We found that charged amino acids play a dominant role during the process of binding to the TiO2 surface, with both basic and acidic residues overwhelmingly preferred over the non-charged counterparts. By calculating the Potential Mean Force, we showed that Arg is prone to direct binding onto the NP surface, while Lys needs to overcome a ~2 kT free energy barrier. On the other hand, acidic residues tend to form “water bridges” between their sidechains and TiO2 surface, thus displaying an indirect binding. Moreover, the overall preferred positions and configurations of different residues are highly dependent on properties of the first and second solvation water. These molecular insights learned from this work might help with a better understanding of the interactions between biomolecules and nanomaterials.

Size-Selective Synthesis and Stabilization of Small Silver Nanoparticles on TiO 2 Partially Masked by SiO 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bo, Zhenyu; Eaton, Todd R.; Gallagher, James R.

Controlling metal nanoparticle size is one of the principle challenges in developing new supported catalysts. Typical methods where a metal salt is deposited and reduced can result in a polydisperse mixture of metal nanoparticles, especially at higher loading. Polydispersity can exacerbate the already significant challenge of controlling sintering at high temperatures, which decreases catalytic surface area. Here, we demonstrate the size-selective photoreduction of Ag nanoparticles on TiO2 whose surface has been partially masked with a thin SiO2 layer. To synthesize this layered oxide material, TiO2 particles are grafted with tert-butylcalix[4]arene molecular templates (~2 nm in diameter) at surface densities ofmore » 0.05–0.17 templates.nm–2, overcoated with ~2 nm of SiO2 through repeated condensation cycles of limiting amounts of tetraethoxysilane (TEOS), and the templates are removed oxidatively. Ag photodeposition results in uniform nanoparticle diameters ≤ 3.5 nm (by transmission electron microscopy (TEM)) on the partially masked TiO2, whereas Ag nanoparticles deposited on the unmodified TiO2 are larger and more polydisperse (4.7 ± 2.7 nm by TEM). Furthermore, Ag nanoparticles on the partially masked TiO2 do not sinter after heating at 450 °C for 3 h, while nanoparticles on the control surfaces sinter and grow by at least 30%, as is typical. Overall, this new synthesis approach controls metal nanoparticle dispersion and enhances thermal stability, and this facile synthesis procedure is generalizable to other TiO2-supported nanoparticles and sizes and may find use in the synthesis of new catalytic materials.« less

Enhanced the hydrophobic surface and the photo-activity of TiO2-SiO2 composites

NASA Astrophysics Data System (ADS)

Wahyuni, S.; Prasetya, A. T.

2017-02-01

The aim of this research is to develop nanomaterials for coating applications. This research studied the effect of various TiO2-SiO2 composites in acrylic paint to enhance the hydrophobic properties of the substrate. Titanium dioxide containing silica in the range 20-35 mol% has been synthesized using sol-gel route. The XRD’s spectra show that increasing SiO2 content in the composite, decreasing its crystalline properties but increasing the surface area. TiO2-SiO2 composite was dispersed in acrylic paint in 2% composition by weight. The largest contact angle was 70, which produced by the substrate coated with TS-35-modified acrylic paint. This study also investigated the enhanced photo-activity of TiO2-SiO2 modified with poly-aniline. The XRD spectra show that the treatment does not change the crystal structure of TiO2. The photo-activity of the composite was evaluated by degradation of Rhodamine-B with visible light. The best performance of the degradation process was handled by the composite treated with 0.1mL anilines per gram of TiO2-SiO2 composite (TSP-A). On the other side, the contact angle 70 has not shown an excellent hydrophobic activity. However, the AFM spectra showed that nanoroughness has started to form on the surface of acrylic paint modified with TiO2-SiO2 than acrylic alone.

Reactive wetting properties of TiO2 nanoparticles predicted by ab initio molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Brandt, Erik G.; Agosta, Lorenzo; Lyubartsev, Alexander P.

2016-07-01

Small-sized wet TiO2 nanoparticles have been investigated by ab initio molecular dynamics simulations. Chemical and physical adsorption of water on the TiO2-water interface was studied as a function of water content, ranging from dry nanoparticles to wet nanoparticles with monolayer coverage of water. The surface reactivity was shown to be a concave function of water content and driven by surface defects. The local coordination number at the defect was identified as the key factor to decide whether water adsorption proceeds through dissociation or physisorption on the surface. A consistent picture of TiO2 nanoparticle wetting at the microscopic level emerges, which corroborates existing experimental data and gives further insight into the molecular mechanisms behind nanoparticle wetting. These calculations will facilitate the engineering of metal oxide nanoparticles with a controlled catalytic water activity.Small-sized wet TiO2 nanoparticles have been investigated by ab initio molecular dynamics simulations. Chemical and physical adsorption of water on the TiO2-water interface was studied as a function of water content, ranging from dry nanoparticles to wet nanoparticles with monolayer coverage of water. The surface reactivity was shown to be a concave function of water content and driven by surface defects. The local coordination number at the defect was identified as the key factor to decide whether water adsorption proceeds through dissociation or physisorption on the surface. A consistent picture of TiO2 nanoparticle wetting at the microscopic level emerges, which corroborates existing experimental data and gives further insight into the molecular mechanisms behind nanoparticle wetting. These calculations will facilitate the engineering of metal oxide nanoparticles with a controlled catalytic water activity. Electronic supplementary information (ESI) available: Simulation data on equilibration of energies and structures (root-mean-square-deviations and coordination numbers); radial distribution functions for all O-Ti pairs over the entire data domain; comparison of coordination number distributions for dry and wet nanoparticles; dynamics of water reactivity; high-resolution electron density for the rutile NP. A movie of the simulation trajectory for the rutile (TiO2)24.30H2O system. See DOI: 10.1039/C6NR02791A

Influence of TiO2(110) surface roughness on growth and stability of thin organic films.

PubMed

Szajna, K; Kratzer, M; Wrana, D; Mennucci, C; Jany, B R; Buatier de Mongeot, F; Teichert, C; Krok, F

2016-10-14

We have investigated the growth and stability of molecular ultra-thin films, consisting of rod-like semiconducting para-hexaphenyl (6P) molecules vapor deposited on ion beam modified TiO 2 (110) surfaces. The ion bombarded TiO 2 (110) surfaces served as growth templates exhibiting nm-scale anisotropic ripple patterns with controllable parameters, like ripple depth and length. In turn, by varying the ripple depth one can tailor the average local slope angle and the local step density/terrace width of the stepped surface. Here, we distinguish three types of substrates: shallow, medium, and deep rippled surfaces. On these substrates, 6P sub-monolayer deposition was carried out in ultra-high vacuum by organic molecular beam evaporation (OMBE) at room temperature leading to the formation of islands consisting of upright standing 6P molecules, which could be imaged by scanning electron microscopy and atomic force microscopy (AFM). It has been found that the local slope and terrace width of the TiO 2 template strongly influences the stability of OMBE deposited 6P islands formed on the differently rippled substrates. This effect is demonstrated by means of tapping mode AFM, where an oscillating tip was used as a probe for testing the stability of the organic structures. We conclude that by increasing the local slope of the TiO 2 (110) surface the bonding strength between the nearest neighbor standing molecules is weakened due to the presence of vertical displacement in the molecular layer in correspondence to the TiO 2 atomic step height.

Study on preparation of SnO2-TiO2/Nano-graphite composite anode and electro-catalytic degradation of ceftriaxone sodium.

PubMed

Guo, Xiaolei; Wan, Jiafeng; Yu, Xiujuan; Lin, Yuhui

2016-12-01

In order to improve the electro-catalytic activity and catalytic reaction rate of graphite-like material, Tin dioxide-Titanium dioxide/Nano-graphite (SnO 2 -TiO 2 /Nano-G) composite was synthesized by a sol-gel method and SnO 2 -TiO 2 /Nano-G electrode was prepared in hot-press approach. The composite was characterized by X-ray photoelectron spectroscopy, fourier transform infrared, Raman, N 2 adsorption-desorption, scanning electrons microscopy, transmission electron microscopy and X-ray diffraction. The electrochemical performance of the SnO 2 -TiO 2 /Nano-G anode electrode was investigated via cyclic voltammetry and electrochemical impedance spectroscopy. The electro-catalytic performance was evaluated by the degradation of ceftriaxone sodium and the yield of ·OH radicals in the reaction system. The results demonstrated that TiO 2 , SnO 2 and Nano-G were composited successfully, and TiO 2 and SnO 2 particles dispersed on the surface and interlamination of the Nano-G uniformly. The specific surface area of SnO 2 modified anode was higher than that of TiO 2 /Nano-G anode and the degradation rate of ceftriaxone sodium within 120 min on SnO 2 -TiO 2 /Nano-G electrode was 98.7% at applied bias of 2.0 V. The highly efficient electro-chemical property of SnO 2 -TiO 2 /Nano-G electrode was attributed to the admirable conductive property of the Nano-G and SnO 2 -TiO 2 /Nano-G electrode. Moreover, the contribution of reactive species ·OH was detected, indicating the considerable electro-catalytic activity of SnO 2 -TiO 2 /Nano-G electrode. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of Dispersoid on Sulfonium Ionic Liquid Based Gel Polymer Electrolyte for Lithium Secondary Battery.

PubMed

Muthupradeepa, R; Sivakumar, M; Subadevi, R; Suryanarayanan, V; Liu, Wei-Ren

2018-01-01

The present study emphases on the effect of toting of TiO2 filler on the electrochemical enactment of polymer electrolyte containing PVdF-co-HFP(30) + SEt3TFSI(10) + EC/PC(60) + TiO2(x) wt% (Poly (vinylidene fluoride-co-hexafluoropropylene + Triethylsulfoniumbis(trifluoromethylsulfonyl)imide + Ethylene carbonate/Propylene carbonate (1:1 ratio) + Titanium dioxide) for lithium battery applications. Composite electrolytes with different weight percentages of TiO2 were prepared and characterized by different surface analytical, thermal and electrochemical techniques. With gradual increase of the amount of TiO2 upto 6 wt%, broadening of the prominent peak has been noted, suggesting a decrease in the degree of crystallinity upon the addition of TiO2, as revealed by X-ray diffraction (XRD). Raman and FT-IR studies confirm the presence of various functional groups, present in the matrix. The electrolyte with TiO2 (6 wt%) has maximum stability of 460 °C, as confirmed by thermal analysis. Conductivity of the composite polymer electrolytes increases upto 6 wt% of TiO2 (3.42 × 10-3 S/cm at 303 K) and further addition, causes a dip down in conductivity, indicating an improvement in the ionic conductivity and thermal stability with the incorporation of TiO2 filler. Surface morphologic images show the presence of surface and cavity in the polymer matrix, filled with the filler uniformly. Voltammetric studies confirm the electrochemical stability of films upto 4.62 V. Coin cell containing Li anode and LiFePO4 cathode along with polymer electrolyte/6 wt% TiO2 filler, delivers a first discharge capacity of 145 mAh/g with the working voltage of 3.4 V.

Biomimetic Water-Collecting Fabric with Light-Induced Superhydrophilic Bumps.

PubMed

Wang, Yuanfeng; Wang, Xiaowen; Lai, Chuilin; Hu, Huawen; Kong, Yeeyee; Fei, Bin; Xin, John H

2016-02-10

To develop an efficient water-collecting surface that integrates both fast water-capturing and easy drainage properties is of high current interest for addressing global water issues. In this work, a superhydrophobic surface was fabricated on cotton fabric via manipulation of both the surface roughness and surface energy. This was followed by a subsequent spray coating of TiO2 nanosol that created light-induced superhydrophilic bumps with a unique raised structure as a result of the interfacial tension of the TiO2 nanosol sprayed on the superhydrophobic fiber surface. These raised TiO2 bumps induce both a wettability gradient and a shape gradient, synergistically accelerating water coalescence and water collection. The in-depth study revealed that the quantity and the distribution of the TiO2 had a significant impact on the final water collection efficiency. This inexpensive and facilely fabricated fabric biomimicks the desert beetle's back and spider silk, which are capable of fog harvesting without additional energy consumption.

Electronic structure and photoabsorption of Ti 3+ ions in reduced anatase and rutile TiO 2

DOE PAGES

Wen, Bo; Hao, Qunqing; Yin, Wen-Jin; ...

2018-01-01

We have used two-photon photoemission (2PPE) spectroscopy and first-principles density functional theory calculations to investigate the electronic structure and photoabsorption of the reduced anatase TiO 2 (101) and rutile TiO 2 (110) surfaces.

Photo degradation of methyl orange by attapulgite-SnO2-TiO2 nanocomposites.

PubMed

Zhang, Lili; Lv, Fujian; Zhang, Weiguang; Li, Rongqing; Zhong, Hui; Zhao, Yijiang; Zhang, Yu; Wang, Xin

2009-11-15

Photocatalytic removal of methyl orange under ultraviolet radiation has been studied using attapulgite (ATT) composites, which were synthesized by depositing SnO(2)-TiO(2) hybrid oxides on the surface of ATT to form a composite photocatalyst (denoted ATT-SnO(2)-TiO(2)) using an in situ sol-gel technique. Results showed that SnO(2)-TiO(2) nanocomposite particles with average size of about 10nm were loaded successfully on to the surface of ATT fibers and were widely dispersed. Correspondingly, the photocatalytic activity of ATT was improved significantly by loading SnO(2)-TiO(2). The photoactivity of the composite photocatalyst decreased in the sequence ATT-SnO(2)-TiO(2)>ATT-SnO(2)>ATT-TiO(2)>ATT. In order to achieve the best photocatalyst, the molar ratio of SnO(2) and TiO(2) in the ATT-SnO(2)-TiO(2) composites was adjusted to give a series with proportions r=n(Ti)/(n(Ti)+n(Sn))=0.0, 0.25, 0.33, 0.50, 0.67, 0.75, 0.80, 0.82, 0.86, 1.0. Results indicated that the proportion of SnO(2) and TiO(2) had a critical effect on the photocatalytic activity, which increased as the content of TiO(2) increased to r0.82. The highest degradation rate of methyl orange was 99% within 30 min obtained by using ATT-SnO(2)-TiO(2) with r=0.82. The repeated use of the composite photocatalyst was also confirmed.

Osteoconductivity and Hydrophilicity of TiO2 Coatings on Ti Substrates Prepared by Different Oxidizing Processes

PubMed Central

Yamamoto, Dai; Kawai, Ikki; Kuroda, Kensuke; Ichino, Ryoichi; Okido, Masazumi; Seki, Azusa

2012-01-01

Various techniques for forming TiO2 coatings on Ti have been investigated for the improvement of the osteoconductivity of Ti implants. However, it is not clear how the oxidizing process affects this osteoconductivity. In this study, TiO2 coatings were prepared using the following three processes: anodizing in 0.1 M H3PO4 or 0.1 M NaOH aqueous solution; thermal oxidation at 673 K for 2 h in air; and a two-step process of anodizing followed by thermal oxidation. The oxide coatings were evaluated using SEM, XRD, and XPS. The water contact angle on the TiO2 coatings was measured as a surface property. The osteoconductivity of these samples was evaluated by measuring the contact ratio of formed hard tissue on the implanted samples (defined as the R B-I value) after 14 d implantation in rats' tibias. Anatase was formed by anodizing and rutile by thermal oxidation, but the difference in the TiO2 crystal structure did not influence the osteoconductivity. Anodized TiO2 coatings were hydrophilic, but thermally oxidized TiO2 coatings were less hydrophilic than anodized TiO2 coatings because they lacked in surface OH groups. The TiO2 coating process using anodizing without thermal oxidation gave effective improvement of the osteoconductivity of Ti samples. PMID:23316128

Nanostructured TiO2 and ZnO prepared by using pressurized hot water and their eco-toxicological evaluation

NASA Astrophysics Data System (ADS)

Troppová, Ivana; Matějová, Lenka; Sezimová, Hana; Matěj, Zdeněk; Peikertová, Pavlína; Lang, Jaroslav

2017-06-01

The eco-toxicological effects of unconventionally prepared nanostructured TiO2 and ZnO were evaluated in this study, since both oxides are keenly investigated semiconductor photocatalysts in the last three decades. Unconventional processing by pressurized hot water was applied in order to crystallize oxide materials as an alternative to standard calcination. Acute biological toxicity of the synthesized oxides was evaluated using germination of Sinapis alba seed (ISO 11269-1) and growth of Lemna minor fronds (ISO 20079) and was compared to commercially available TiO2 Degussa P25. Toxicity results revealed that synthesized ZnO as well as TiO2 is toxic contrary to commercial TiO2 Degussa P25 which showled stimulation effect to L. minor and no toxicity to S. alba. ZnO was significantly more toxic than TiO2. The effect of crystallite size was considered, and it was revealed that small crystallite size and large surface area are not the toxicity-determining factors. Factors such as the rate of nanosized crystallites aggregation and concentration, shape and surface properties of TiO2 nanoparticles affect TiO2 toxicity to both plant species. Seriously, the dissolution of Ti4+ ions from TiO2 was also observed which may contribute to its toxicity. In case of ZnO, the dissolution of Zn2+ ions stays the main cause of its toxicity.

Sol-flame synthesis of cobalt-doped TiO2 nanowires with enhanced electrocatalytic activity for oxygen evolution reaction.

PubMed

Cai, Lili; Cho, In Sun; Logar, Manca; Mehta, Apurva; He, Jiajun; Lee, Chi Hwan; Rao, Pratap M; Feng, Yunzhe; Wilcox, Jennifer; Prinz, Fritz B; Zheng, Xiaolin

2014-06-28

Doping nanowires (NWs) is of crucial importance for a range of applications due to the unique properties arising from both impurities' incorporation and nanoscale dimensions. However, existing doping methods face the challenge of simultaneous control over the morphology, crystallinity, dopant distribution and concentration at the nanometer scale. Here, we present a controllable and reliable method, which combines versatile solution phase chemistry and rapid flame annealing process (sol-flame), to dope TiO2 NWs with cobalt (Co). The sol-flame doping method not only preserves the morphology and crystallinity of the TiO2 NWs, but also allows fine control over the Co dopant profile by varying the concentration of Co precursor solution. Characterizations of the TiO2:Co NWs show that Co dopants exhibit 2+ oxidation state and substitutionally occupy Ti sites in the TiO2 lattice. The Co dopant concentration significantly affects the oxygen evolution reaction (OER) activity of TiO2:Co NWs, and the TiO2:Co NWs with 12 at% of Co on the surface show the highest OER activity with a 0.76 V reduction of the overpotential with respect to undoped TiO2 NWs. This enhancement of OER activity for TiO2:Co NWs is attributed to both improved surface charge transfer kinetics and increased bulk conductivity.

Design of hybrid nanoheterostructure systems for enhanced quantum and solar conversion efficiencies in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Kılıç, Bayram; Telli, Hakan; Tüzemen, Sebahattin; Başaran, Ali; Pirge, Gursev

2015-04-01

Dye sensitized solar cells (DSSCs) with an innovative design involving controlled-morphology vertically aligned (VA) ZnO nanowires within mesoporous TiO2 structures with ultrahigh surface area for implementation as photoanodes are herein reported. Although TiO2 nanostructures exhibit excellent power conversion efficiency, the electron transport rate is low owing to low electron mobility. To overcome this, ZnO nanowires with high electron mobility have been investigated as potential candidates for photoanodes. However, the power conversion efficiency of ZnO nanowires is still lower than that of TiO2 owing to their low internal surface area. Consequently, in this work, vertical growth of ZnO nanowires within mesoporous TiO2 structures is carried out to increase their solar power conversion efficiency. The photovoltaic performance of solar cells using ZnO nanowires, mesoporous TiO2, and TiO2/ZnO hybrid structures are compared. The VA TiO2/ZnO hybrid structures are found to provide direct electron transfer compared with the tortuous pathway of zero-dimensional nanostructures, resulting in an increased conversion efficiency. It is demonstrated that the light scattering of the photoanode film is increased and electron recombination is decreased when an appropriate amount of mesoporous TiO2 is used as a substrate for ZnO nanowires. The DSSC fabricated with the TiO2/ZnO hybrid photoanode prepared with 15.8 wt. % TiO2 showed the highest conversion efficiency of 7.30%, approximately 5%, 18%, and 40% higher than that of DSSCs fabricated with 3.99 wt. % TiO2, pure TiO2, and pure ZnO photoanodes, respectively.

The design, fabrication, and photocatalytic utility of nanostructured semiconductors: focus on TiO2-based nanostructures

PubMed Central

Banerjee, Arghya Narayan

2011-01-01

Recent advances in basic fabrication techniques of TiO2-based nanomaterials such as nanoparticles, nanowires, nanoplatelets, and both physical- and solution-based techniques have been adopted by various research groups around the world. Our research focus has been mainly on various deposition parameters used for fabricating nanostructured materials, including TiO2-organic/inorganic nanocomposite materials. Technically, TiO2 shows relatively high reactivity under ultraviolet light, the energy of which exceeds the band gap of TiO2. The development of photocatalysts exhibiting high reactivity under visible light allows the main part of the solar spectrum to be used. Visible light-activated TiO2 could be prepared by doping or sensitizing. As far as doping of TiO2 is concerned, in obtaining tailored material with improved properties, metal and nonmetal doping has been performed in the context of improved photoactivity. Nonmetal doping seems to be more promising than metal doping. TiO2 represents an effective photocatalyst for water and air purification and for self-cleaning surfaces. Additionally, it can be used as an antibacterial agent because of its strong oxidation activity and superhydrophilicity. Therefore, applications of TiO2 in terms of photocatalytic activities are discussed here. The basic mechanisms of the photoactivities of TiO2 and nanostructures are considered alongside band structure engineering and surface modification in nanostructured TiO2 in the context of doping. The article reviews the basic structural, optical, and electrical properties of TiO2, followed by detailed fabrication techniques of 0-, 1-, and quasi-2-dimensional TiO2 nanomaterials. Applications and future directions of nanostructured TiO2 are considered in the context of various photoinduced phenomena such as hydrogen production, electricity generation via dye-sensitized solar cells, photokilling and self-cleaning effect, photo-oxidation of organic pollutant, wastewater management, and organic synthesis. PMID:24198485

SiO2/TiO2/Ag multilayered microspheres: Preparation, characterization, and enhanced infrared radiation property

NASA Astrophysics Data System (ADS)

Ye, Xiaoyun; Cai, Shuguang; Zheng, Chan; Xiao, Xueqing; Hua, Nengbin; Huang, Yanyi

2015-08-01

SiO2/TiO2/Ag core-shell multilayered microspheres were successfully synthesized by the combination of anatase of TiO2 modification on the surfaces of SiO2 spheres and subsequent Ag nanoparticles deposition and Ag shell growth with face-centered cubic (fcc) Ag. The composites were characterized by TEM, FT-IR, UV-vis, Raman spectroscopy and XRD, respectively. The infrared emissivity values during 8-14 μm wavelengths of the composites were measured. The results revealed that TiO2 thin layers with the thickness of ∼10 nm were coated onto the SiO2 spheres of ∼220 nm in diameter. The thickness of the TiO2 layers was controlled by varying the amount of TBOT precursor. Homogeneous Ag nanoparticles of ∼20 nm in size were successfully deposited by ultrasound on the surfaces of SiO2/TiO2 composites, followed by complete covering of Ag shell. The infrared emissivity value of the SiO2/TiO2 composites was decreased than that of pure SiO2. Moreover, the introduction of the Ag brought the remarkably lower infrared emissivity value of the SiO2/TiO2/Ag multilayered microspheres with the lowest value down to 0.424. Strong chemical effects in the interface of SiO2/TiO2 core-shell composites and high reflection performance of the metal Ag are two decisive factors for the improved infrared radiation performance of the SiO2/TiO2/Ag multilayered microspheres.

Adsorption and Recovery of Polyphenolic Flavonoids Using TiO 2-Functionalized Mesoporous Silica Nanoparticles

DOE PAGES

Khan, M. Arif; Wallace, William T.; Islam, Syed Z.; ...

2017-08-21

Exploiting specific interactions with titania (TiO 2) has been proposed for the separation and recovery of a broad range of biomolecules and natural products, including therapeutic polyphenolic flavonoids which are susceptible to degradation, such as quercetin. Functionalizing mesoporous silica with TiO 2 has many potential advantages over bulk and mesoporous TiO 2 as an adsorbent for natural products, including robust synthetic approaches leading to high surface area, stable separation platforms. Here, TiO 2 surface functionalized mesoporous silica nanoparticles (MSNPs) are synthesized and characterized as a function of TiO 2 content (up to 636 mg TiO2/g). The adsorption isotherms of twomore » polyphenolic flavonoids, quercetin and rutin, were determined (0.05-10 mg/ml in ethanol), and a 100-fold increase in the adsorption capacity was observed relative to functionalized nonporous particles with similar TiO 2 surface coverage. An optimum extent of functionalization (approximately 440 mg TiO 2/g particles) is interpreted from characterization techniques including grazing incidence x-ray scattering (GIXS), high resolution transmission electron microscopy (HRTEM) and nitrogen adsorption, which examined the interplay between the extent of TiO 2 functionalization and the accessibility of the porous structures. The recovery of flavonoids is demonstrated using ligand displacement in ethanolic citric acid solution (20% w/v), in which greater than 90% recovery can be achieved in a multistep extraction process. The radical scavenging activity (RSA) of the recovered and particle-bound quercetin as measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay demonstrates greater than 80% retention of antioxidant activity by both particle-bound and recovered quercetin. In conclusion, these mesoporous titanosilicate materials can serve as a synthetic platform to isolate, recover, and potentially deliver degradation-sensitive natural products to biological systems.« less

Adsorption and Recovery of Polyphenolic Flavonoids Using TiO 2-Functionalized Mesoporous Silica Nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, M. Arif; Wallace, William T.; Islam, Syed Z.

Exploiting specific interactions with titania (TiO 2) has been proposed for the separation and recovery of a broad range of biomolecules and natural products, including therapeutic polyphenolic flavonoids which are susceptible to degradation, such as quercetin. Functionalizing mesoporous silica with TiO 2 has many potential advantages over bulk and mesoporous TiO 2 as an adsorbent for natural products, including robust synthetic approaches leading to high surface area, stable separation platforms. Here, TiO 2 surface functionalized mesoporous silica nanoparticles (MSNPs) are synthesized and characterized as a function of TiO 2 content (up to 636 mg TiO2/g). The adsorption isotherms of twomore » polyphenolic flavonoids, quercetin and rutin, were determined (0.05-10 mg/ml in ethanol), and a 100-fold increase in the adsorption capacity was observed relative to functionalized nonporous particles with similar TiO 2 surface coverage. An optimum extent of functionalization (approximately 440 mg TiO 2/g particles) is interpreted from characterization techniques including grazing incidence x-ray scattering (GIXS), high resolution transmission electron microscopy (HRTEM) and nitrogen adsorption, which examined the interplay between the extent of TiO 2 functionalization and the accessibility of the porous structures. The recovery of flavonoids is demonstrated using ligand displacement in ethanolic citric acid solution (20% w/v), in which greater than 90% recovery can be achieved in a multistep extraction process. The radical scavenging activity (RSA) of the recovered and particle-bound quercetin as measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay demonstrates greater than 80% retention of antioxidant activity by both particle-bound and recovered quercetin. In conclusion, these mesoporous titanosilicate materials can serve as a synthetic platform to isolate, recover, and potentially deliver degradation-sensitive natural products to biological systems.« less

Elucidation of Active Sites for the Reaction of Ethanol on TiO 2 /Au(111)

DOE PAGES

Boyle, David T.; Wilke, Jeremy A.; Palomino, Robert M.; ...

2017-03-17

Obtaining a molecular-level understanding of the reaction of alcohols with heterogeneous model catalysts is critical for improving industrial catalytic processes, such as the production of H 2 from alcohols. Gold has been shown to be an excellent oxidation catalyst once oxygen is added to it. The use of reducible oxides provides a source of oxygen on Au(111) for the reaction of ethanol, which is easily regenerated in the presence of an oxygen background. In this work, ethanol operates as a probe molecule to investigate the role of Au(111), TiO 2 nanoparticles, and TiO 2/Au interfacial surface sites on the catalyticmore » properties of TiO 2/Au(111). Ultrahigh vacuum temperature-programmed desorption (TPD) studies with ethanol/Au(111) elucidate previously unreported adsorption sites for ethanol. Ethanol molecularly adsorbs to Au terrace sites, step edges, and undercoordinated kink sites with adsorption energies of -51.7, -55.8, and -65.1 kJ/mol, respectively. In a TPD coverage study of ethanol on TiO 2/Au(111) indicates ethanol undergoes dissociative adsorption to form H*(a) and CH 3CH 2O*(a) on the inverse model catalyst surface. The desorption temperature of low coverages of ethanol from TiO2/Au(111) (Tdes ≈ 235 K) is at an intermediate temperature between the desorption temperatures from bulk Au(111) and TiO 2(110), indicating both Au and TiO 2 play a role in the adsorption of ethanol. Both low-temperature adsorption and high-temperature reactions are studied and indicate that ethanol-derived products such as acetaldehyde and ethylene desorb from TiO 2/Au(111) at ~500 K. Here, we report the identification of catalytically active sites on TiO 2/Au(111) as interfacial sites between the oxide and Au(111) surface through the use of temperature-programmed desorption and infrared reflection absorption spectroscopy.« less

Elucidation of Active Sites for the Reaction of Ethanol on TiO 2 /Au(111)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyle, David T.; Wilke, Jeremy A.; Palomino, Robert M.

Obtaining a molecular-level understanding of the reaction of alcohols with heterogeneous model catalysts is critical for improving industrial catalytic processes, such as the production of H 2 from alcohols. Gold has been shown to be an excellent oxidation catalyst once oxygen is added to it. The use of reducible oxides provides a source of oxygen on Au(111) for the reaction of ethanol, which is easily regenerated in the presence of an oxygen background. In this work, ethanol operates as a probe molecule to investigate the role of Au(111), TiO 2 nanoparticles, and TiO 2/Au interfacial surface sites on the catalyticmore » properties of TiO 2/Au(111). Ultrahigh vacuum temperature-programmed desorption (TPD) studies with ethanol/Au(111) elucidate previously unreported adsorption sites for ethanol. Ethanol molecularly adsorbs to Au terrace sites, step edges, and undercoordinated kink sites with adsorption energies of -51.7, -55.8, and -65.1 kJ/mol, respectively. In a TPD coverage study of ethanol on TiO 2/Au(111) indicates ethanol undergoes dissociative adsorption to form H*(a) and CH 3CH 2O*(a) on the inverse model catalyst surface. The desorption temperature of low coverages of ethanol from TiO2/Au(111) (Tdes ≈ 235 K) is at an intermediate temperature between the desorption temperatures from bulk Au(111) and TiO 2(110), indicating both Au and TiO 2 play a role in the adsorption of ethanol. Both low-temperature adsorption and high-temperature reactions are studied and indicate that ethanol-derived products such as acetaldehyde and ethylene desorb from TiO 2/Au(111) at ~500 K. Here, we report the identification of catalytically active sites on TiO 2/Au(111) as interfacial sites between the oxide and Au(111) surface through the use of temperature-programmed desorption and infrared reflection absorption spectroscopy.« less

Cytocompatibility and antibacterial activity of titania nanotubes incorporated with gold nanoparticles.

PubMed

Yang, Tingting; Qian, Shi; Qiao, Yuqing; Liu, Xuanyong

2016-09-01

TiO2 nanotubes prepared by electrochemical anodization have received considerable attention in the biomedical field. In this work, different amounts of gold nanoparticles were immobilized onto TiO2 nanotubes using 3-aminopropyltrimethoxysilane as coupling agent. Field emission scanning electron microscopy and X-ray photoelectron spectroscopy were used to investigate the surface morphology and composition. Photoluminescence spectra and surface zeta potential were also measured. The obtained results indicate that the surface modified gold nanoparticles can significantly enhance the electron storage capability and reduce the surface zeta potential compared to pristine TiO2 nanotubes. Moreover, the surface modified gold nanoparticles can stimulate initial adhesion and spreading of rat bone mesenchymal stem cells as well as proliferation, while the osteogenous performance of TiO2 nanotubes will not be reduced. The gold-modified surface presents moderate antibacterial effect on both Staphylococcus aureus and Escherichia coli. It should be noted that the surface modified fewer gold nanoparticles has better antibacterial effect compared to the surface of substantial modification of gold nanoparticles. Our study illustrates a composite surface with favorable cytocompatibility and antibacterial effect and provides a promising candidate for orthopedic and dental implant. Copyright © 2016 Elsevier B.V. All rights reserved.

Adsorption and oxidation of oxalic acid on anatase TiO2 (001) surface: A density functional theory study.

PubMed

Sun, Tao; Wang, Yun; Zhang, Haimin; Liu, Porun; Zhao, Huijun

2015-09-15

Anatase TiO2 (001) surfaces have attracted great interest for photo-degradation of organic species recently due to their high reactivity. In this work, adsorption properties and oxidation mechanisms of oxalic acid on the anatase TiO2 (001) surface have been theoretically investigated using the first-principles density functional theory. Various possible adsorption configurations are considered by diversifying the connectivity of carboxylic groups with the surface. It is found that the adsorption of oxalic acid on the anatase (001) surface prefer the dissociative states. A novel double-bidentate configuration has been found due to the structural match between oxalic acid and the (001) surface. More charge is transferred from the adsorbed oxalic acid to the surface with the double-bidentate configuration when comparing with other adsorption structures. Thus, there is a positive correlation relationship between the transferred charge amount and the interfacial bond numbers when oxalic acid adsorbs on the anatase TiO2 (001) surface. The adsorption energies with dispersion corrections have demonstrated that the van der Waals interactions play an important role in the adsorption, especially when adsorbates are close to the surface. Copyright © 2015 Elsevier Inc. All rights reserved.

Preparation of TiO2-SiO2 via sol-gel method: Effect of Silica precursor on Catalytic and Photocatalytic properties

NASA Astrophysics Data System (ADS)

Fatimah, I.

2017-02-01

TiO2-SiO2have been synthesized by the sol-gel method from titanium isopropoxide and varied silica precursors: tetraethyl orthosilicate and tetra methyl ortho silicate. To study the effect of the precursor, prepared materials were characterized by X-ray diffraction, scanning electron microscopy, Diffuse Reflectance UV-vis optical absorption, and also gas sorption analysis. XRD patterns showed the formation of TiO2 anatase in the TiO2-SiO2 composite with different crystallite size from different silica precursor as well as the different surface morphology. The DRUV-vis absorption spectra exhibit similar band gap energy correspond to 3.21eV value while the surface area, pore volume and pore radius of the materials seems to be affected by the precursor. The higher specific surface area contributes to give the enhanced activity in phenol hydroxylation and methylene blue photodegradation.

Bulk oxygen vacancies enriched TiO2 and its enhanced visible photocatalytic performance

NASA Astrophysics Data System (ADS)

Xu, Liming; Ma, Xujun; Sun, Na; Chen, Feng

2018-05-01

Via a vacuum thermal treatment, oxygen vacancy (Ov) was introduced into TiO2 bulk lattice during the phase transformation from amorphous TiO2 to anatase. High-resolution transmission electron microscopy (HRTEM), Raman spectra and X-ray diffraction (XRD) confirm the involvement of Ov causes more violent changes in both bulk and surface structure. Electron paramagnetic resonance (EPR) demonstrated as-obtained V350 gets about a 40-times enhanced Ov signal compared with pure TiO2 (A350) and a 10-times larger signal than that of common Ov modified TiO2 (A450-V350), which clearly illustrates the high concentration of Ov in its bulk lattice. The much enriched Ovs in both bulk and surface lattices of TiO2 help V350 get an enhanced capacity in either visible light harvest or photocarriers generation. And a much higher visible photocatalytic activity for Aicd Orange 7 degradation was finally achieved by V350.

Characteristics of the mechanical milling on the room temperature ferromagnetism and sensing properties of TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Bolokang, A. S.; Cummings, F. R.; Dhonge, B. P.; Abdallah, H. M. I.; Moyo, T.; Swart, H. C.; Arendse, C. J.; Muller, T. F. G.; Motaung, D. E.

2015-03-01

We report on the correlation between defect-related emissions, the magnetization and sensing of TiO2 nanoparticles (NPs) prepared by milling method. Surface morphology analyses showed that the size of the TiO2 NPs decreases with milling time. Raman and XRD studies demonstrated that the structural properties of the TiO2 transform to orthorhombic structure upon milling. Magnetization improved with an increase of a defect-related band originating from oxygen vacancies (VO), which can be ascribed to a decrease in the size of the NPs due to the milling time. Moreover, the longer-milled TiO2 exhibited enhanced gas-sensing properties to humidity in terms of sensor response, with about 12 s response time at room temperature. A combination of photoluminescence, X-ray photoelectron spectroscopy, vibrating sample magnetometer and sensing analyses demonstrated that a direct relation exists between the magnetization, sensing and the relative occupancy of the VO present on the surface of TiO2 NPs.

Synthesis of nanocrystalline TiO 2 in toluene by a solvothermal route

NASA Astrophysics Data System (ADS)

Kim, Chung-Sik; Moon, Byung Kee; Park, Jong-Ho; Tae Chung, Su; Son, Se-Mo

2003-07-01

A solvothermal synthetic method to TiO 2 nanoparticles has been investigated in toluene solutions with titanium isopropoxide (TIP) as precursor. Weight ratios of precursor to solvent prepared in the mixture are 5/100, 10/100, 20/100, 30/100 and 40/100. At the weight ratio of 10/100, 20/100 and 30/100, TiO 2 nanocrystalline particles were obtained after synthesis at 250°C for 3 h in an autoclave. X-ray diffraction and tranmission electron microscopy shows that the product has uniform anatase structure with average particle size below 20 nm. As the composition of TIP in the solution increases, the particle size of TiO 2 powder tends to increase. At 5/100 and 40/100, however, pale yellow colloidal solution is obtained after synthesis and crystalline phase of TiO 2 is not produced. The specific surface area of the TiO 2 nanocrystalline powder was also investigated using BET surface area analyzer.

Potential impact of inorganic nanoparticles on macronutrient digestion: titanium dioxide nanoparticles slightly reduce lipid digestion under simulated gastrointestinal conditions.

PubMed

Li, Qian; Li, Ti; Liu, Chengmei; DeLoid, Glen; Pyrgiotakis, Georgios; Demokritou, Philip; Zhang, Ruojie; Xiao, Hang; McClements, David Julian

Titanium dioxide (TiO 2 ) particles are used in some food products to alter their optical properties, such as whiteness or brightness. These additives typically contain a population of TiO 2 nanoparticles (d < 100 nm), which has led to concern about their potential toxicity. The objective of this study was to examine the impact of TiO 2 particles on the gastrointestinal fate of oil-in-water emulsions using a simulated gastrointestinal tract (GIT) that includes mouth, stomach, and small intestine phases. Theoretical predictions suggested that TiO 2 nanoparticles might inhibit lipid digestion through two physicochemical mechanisms: (i) a fraction of the lipase adsorbs to TiO 2 particle surfaces, thereby reducing the amount available to hydrolyze lipid droplets; (ii) some TiO 2 particles adsorb to the surfaces of lipid droplets, thereby reducing the lipid surface area exposed to lipase. The importance of these mechanisms was tested by passing protein-coated lipid droplets (2%, w/w) through the simulated GIT in the absence and presence of TiO 2 (0.5%, w/w) nanoparticles (18 nm) and fine particles (167 nm). Changes in particle characteristics (size, organization, and charge) and lipid digestion were then measured. Both TiO 2 nanoparticles and fine particles had little impact on the aggregation state and charge of the lipid droplets in the different GIT regions, as well as on the rate and extent of lipid digestion. This suggests that the theoretically predicted impact of particle size on lipid digestion was not seen in practice.

TiO2 and its composites as effective photocatalyst for glucose degradation processes

NASA Astrophysics Data System (ADS)

Kukh, A. A.; Ivanenko, I. M.; Astrelin, I. M.

2018-03-01

Titanium-dioxide photocatalyst was impregnated onto the activated carbon using originally developed low-temperature sol-gel method to form a TiO2:AC composite material. 15% (mass.) solution Ti2(SO4)3 in sulphuric acid was used as a precursor for photocatalyst synthesis. The highly effective composite material was obtained through a combination of properties of titanium dioxide and activated carbon. Synthesized composites TiO2 with activated carbon demonstrate highly developed surface characteristics and exhibit significantly higher activity in comparison with samples of pure TiO2 synthesized the same way, existing analogues of pure TiO2 synthesized from TiCl3 and even industrial photocatalyst. This was testified by the degradation of 1% aqueous glucose solution using TiO2:AC, samples of pure TiO2 and commercial TiO2 AEROXIDE® TiO2 P25 produced by EVONIK Industries.

Characterization of the Interactions between Titanium Dioxide Nanoparticles and Polymethoxyflavones Using Surface-Enhanced Raman Spectroscopy.

PubMed

Cao, Xiaoqiong; Ma, Changchu; Gao, Zili; Zheng, Jinkai; He, Lili; McClements, David Julian; Xiao, Hang

2016-12-14

Nanosized titanium dioxide (TiO 2 ) particles are commonly present in TiO 2 food additives (E171) and have been associated with potential adverse effects on health. However, little knowledge is available regarding the interactions between TiO 2 nanoparticles (NPs) and other food components, such as flavonoids. In this study, we aim to study the molecular interactions between TiO 2 anatase NPs and three structurally closely related polymethoxyflavones (PMFs, flavonoids found in citrus fruits), namely, 3',4'-didemethylnobiletin (DDN), 5-demethylnobiletin (5DN), and 5,3',4'-tridemethylnobiletin (TDN), using ultraviolet-visible (UV-vis) spectrometry and surface-enhanced Raman spectroscopy (SERS). In the UV-vis absorption spectra, bathochromic effects were observed after DDN and TDN conjugated with TiO 2 NPs. The results from SERS analysis clearly demonstrated that DDN and TDN could bind TiO 2 NPs with the functional groups 3'-OH and 4'-OH on ring B and formed charge-transfer complexes. However, 5DN with functional groups C═O on ring C and 5-OH on ring A could not bind TiO 2 NPs. Knowledge on the molecular interactions between TiO 2 NPs and food components, such as flavonoids, will facilitate the understanding of the fate of TiO 2 NPs during food processing and in the gastrointestinal tract after oral consumption.

Efficient dechlorination of chlorinated solvent pollutants under UV irradiation by using the synthesized TiO2 nano-sheets in aqueous phase.

PubMed

Ndong, Landry Biyoghe Bi; Ibondou, Murielle Primaelle; Miao, Zhouwei; Gu, Xiaogang; Lu, Shuguang; Qiu, Zhaofu; Sui, Qian; Mbadinga, Serge Maurice

2014-05-01

Titanium dioxide (TiO2), which is the widely used photo-catalyst, has been synthesized by simple hydrothermal solution containing tetrabutyl titanate and hydrofluoric acid. The synthesized product has been applied to photo-degradation in aqueous phase of chlorinated solvents, namely tetrachloroethene (PCE), trichloroethene (TCE) and 1,1,1-trichloroethane (TCA). The photo-degradation results revealed that the degradation of these harmful chemicals was better in UV/synthesized TiO2 system compared to UV/commercial P25 system and UV only system. The photo-catalytic efficiency of the synthesized TiO2 was 1.4, 1.8 and 3.0 folds higher compared to the commercial P25 for TCA, TCE and PCE degradation, respectively. Moreover, using nitrobenzene (NB) as a probe of hydroxyl radical (·OH), the degradation rate was better over UV/synthesized TiO2, suggesting the high concentration of ·OH generated in UV/synthesized TiO2 system. In addition, ·OH concentration was confirmed by the strong peak displayed in EPR analysis over UV/synthesized TiO2 system. The characterization result using XRD and TEM showed that the synthesized TiO2 was in anatase form and consisted of well-defined sheet-shaped structures having a rectangular outline with a thickness of 4 nm, side length of 50 nm and width of 33 nm and a surface 90.3 m(2)/g. XPS analysis revealed that ≡Ti-F bond was formed on the surface of the synthesized TiO2. The above results on both photocatalytic activity and the surface analysis demonstrated the good applicability of the synthesized TiO2 nano-sheets for the remediation of chlorinated solvent contaminated groundwater. Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

A sinter-resistant catalytic system fabricated by maneuvering the selectivity of SiO2 deposition onto the TiO2 surface versus the Pt nanoparticle surface.

PubMed

Lu, Ping; Campbell, Charles T; Xia, Younan

2013-10-09

A triphasic catalytic system (Pt/TiO2-SiO2) with an "islands in the sea" configuration was fabricated by controlling the selectivity of SiO2 deposition onto the surface of TiO2 versus the surface of Pt nanoparticles. The Pt surface was exposed, while the nanoparticles were supported on TiO2 and isolated from each other by SiO2 to achieve both significantly improved sinter resistance up to 700 °C and outstanding activity after high-temperature calcination. This work not only demonstrates the feasibility of using a new triphasic system with uncovered catalyst to maximize the thermal stability and catalytic activity but also offers a general approach to the synthesis of high-performance catalytic systems with tunable compositions.

Study of TiO2 anatase nano and microstructures with dominant {001} facets for NO oxidation.

PubMed

Sofianou, Maria-Veronica; Trapalis, Christos; Psycharis, Vassils; Boukos, Nikos; Vaimakis, Tiverios; Yu, Jiaguo; Wang, Wenguang

2012-11-01

TiO(2) anatase nanoplates and hollow microspheres were fabricated by a solvothermal-hydrothermal method using titanium isopropoxide as a titanium precursor and hydrofluoric acid as a capping agent in order to enhance the formation of the {001} crystal facets of the anatase nanocrystals. These different morphological structures of TiO(2) anatase can be achieved by only changing the solvent, keeping the amount of the precursor and of the capping agent identical during the solvothermal-hydrothermal process. After calcination of the samples, the adsorbed fluoride atoms on the {001} crystal facets of the TiO(2) anatase nanocrystals were completely removed from their surface according to XPS analysis. The calcined TiO(2) anatase structures were higher crystallized and the specific surface area of the catalysts increased, enhancing their photocatalytic activity in comparison to the non-calcined TiO(2) anatase structures. All TiO(2) anatase samples with adsorbed as well as non-adsorbed fluoride atoms on their {001} crystal facets, exhibited a higher photonic efficiency than Degussa P25, which was used as a reference. The fluoride free TiO(2) anatase nanoplates exhibited the best photocatalytic activity in oxidizing the NO gas to NO(2) and NO(3) (-).

Oriented epitaxial TiO2 nanowires for water splitting

NASA Astrophysics Data System (ADS)

Hou, Wenting; Cortez, Pablo; Wuhrer, Richard; Macartney, Sam; Bozhilov, Krassimir N.; Liu, Rong; Sheppard, Leigh R.; Kisailus, David

2017-06-01

Highly oriented epitaxial rutile titanium dioxide (TiO2) nanowire arrays have been hydrothermally grown on polycrystalline TiO2 templates with their orientation dependent on the underlying TiO2 grain. Both the diameter and areal density of the nanowires were tuned by controlling the precursor concentration, and the template surface energy and roughness. Nanowire tip sharpness was influenced by precursor solubility and diffusivity. A new secondary ion mass spectrometer technique has been developed to install additional nucleation sites in single crystal TiO2 templates and the effect on nanowire growth was probed. Using the acquired TiO2 nanowire synthesis knowhow, an assortment of nanowire arrays were installed upon the surface of undoped TiO2 photo-electrodes and assessed for their photo-electrochemical water splitting performance. The key result obtained was that the presence of short and dispersed nanowire arrays significantly improved the photocurrent when the illumination intensity was increased from 100 to 200 mW cm-2. This is attributed to the alignment of the homoepitaxially grown nanowires to the [001] direction, which provides the fastest charge transport in TiO2 and an improved pathway for photo-holes to find water molecules and undertake oxidation. This result lays a foundation for achieving efficient water splitting under conditions of concentrated solar illumination.

TiO2 nanoparticles versus TiO2-SiO2 nanocomposites: a comparative study of photo catalysis on acid red 88.

PubMed

Balachandran, K; Venckatesh, Rajendran; Sivaraj, Rajeshwari; Rajiv, P

2014-07-15

A novel, simple, less time-consuming and cost-effective wet chemical technique was used to synthesis TiO2 nanoparticles and TiO2-SiO2 nanocomposites using Titanium tetra isopropoxide (TTIP) as a precursor relatively at low temperature in acidic pH. Titania sol was prepared by hydrolysis of TTIP and was mixed with silicic acid and tetrahydrofuran mixture. The reaction was carried out under vigorous stirring for 6h and dried at room temperature. The resulting powders were characterized by UV-Visible spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction, scanning electron microscope (SEM) and transmission electron microscope (TEM). The grain size of the particles was calculated by X-ray diffraction, surface morphology and chemical composition was determined from scanning electron microscopy-energy dispersive spectroscopy, metal oxide stretching was confirmed from FT-IR spectroscopy, band gap was calculated using UV-Visible spectroscopy. Surface area of the composite as calculated by BET analyzer and it was found to be 65 and 75 m(2)/g for TiO2 and TiO2-SiO2 respectively. The photocatalytic experiments were performed with aqueous solution of acid red 88 with TiO2 and TiO2-SiO2 batch studies for 4h irradiation, direct photolysis of TiO2 and TiO2-SiO2 contributed 94.2% and 96.5% decomposition in solar radiation for the optimized concentration of acid red 88. Copyright © 2014 Elsevier B.V. All rights reserved.

Tungsten-doped TiO2/reduced Graphene Oxide nano-composite photocatalyst for degradation of phenol: A system to reduce surface and bulk electron-hole recombination.

PubMed

Yadav, Manisha; Yadav, Asha; Fernandes, Rohan; Popat, Yaksh; Orlandi, Michele; Dashora, Alpa; Kothari, D C; Miotello, Antonio; Ahuja, B L; Patel, Nainesh

2017-12-01

Recombination of photogenerated charges is the main factor affecting the photocatalytic activity of TiO 2 . Here, we report a combined strategy of suppressing both the bulk as well as the surface recombination processes by doping TiO 2 with tungsten and forming a nanocomposite with reduced graphene oxide (rGO), respectively. Sol-gel method was used to dope and optimize the concentration of W in TiO 2 powder. UV-Vis, XPS, PL and time resolved PL spectra along with DFT calculations indicate that W 6+ in TiO 2 lattice creates an impurity level just below the conduction band of TiO 2 to act as a trapping site of electrons, which causes to improve the lifetime of the photo-generated charges. Maximum reduction in the PL intensity and the improvement in charge carrier lifetime was observed for TiO 2 doped with 1 at.% W (1W-TiO 2 ), which also displayed the highest photo-activity for the degradation of p-nitro phenol pollutant in water. Tuning of rGO/TiO 2 ratio (weight) disclosed that the highest activity can be achieved with the composite formed by taking equal amounts of TiO 2 and rGO (1:1), in which the strong interaction between TiO 2 and rGO causes an effective charge transfer via bonds formed near the interface as indicated by XPS. Both these optimized concentrations were utilized to form the composite rGO/1W-TiO 2 , which showed the highest activity in photo-degradation of p-nitro phenol (87%) as compared to rGO/TiO 2 (42%), 1W-TiO 2 (62%) and pure TiO 2 (29%) in 180 min. XPS and PL results revealed that in the present nanocomposite, tungsten species traps the excited electron to reduce the interband recombination in the bulk, while the interaction between TiO 2 and rGO creates a channel for fast transfer of excited electrons towards the latter before being recombined on the surface defect sites. Copyright © 2017 Elsevier Ltd. All rights reserved.

SaOS-2 cell response to macro-porous boron-incorporated TiO2 coating prepared by micro-arc oxidation on titanium.

PubMed

Huang, Qianli; Elkhooly, Tarek A; Liu, Xujie; Zhang, Ranran; Yang, Xing; Shen, Zhijian; Feng, Qingling

2016-10-01

The aims of the present study were to develop boron-incorporated TiO2 coating (B-TiO2 coating) through micro-arc oxidation (MAO) and subsequently evaluate the effect of boron incorporation on the in vitro biological performance of the coatings. The physicochemical properties of B-TiO2 coating and its response to osteoblast like cells (SaOS-2) were investigated compared to the control group without boron (TiO2 coating). The morphological and X-ray diffraction results showed that both coatings exhibited similar surface topography and phase composition, respectively. However, the incorporation of B led to an enhancement in the surface hydrophilicity of B-TiO2 coating. The spreading of SaOS-2 cells on B-TiO2 coating was faster than that on TiO2 coating. The proliferation rate of SaOS-2 cells cultured on B-TiO2 decreased after 5days of culture compared to that on TiO2 coating. SaOS-2 cells cultured on B-TiO2 coating exhibited an enhanced alkaline phosphatase (ALP) activity, Collagen I synthesis and in vitro mineralization compared to those on TiO2 coating. The present findings suggest that B-TiO2 coating is a promising candidate surface for orthopedic implants. Copyright © 2016 Elsevier B.V. All rights reserved.

One-step formation of TiO2 hollow spheres via a facile microwave-assisted process for photocatalytic activity

NASA Astrophysics Data System (ADS)

Mohamad Alosfur, Firas K.; Ridha, Noor J.; Hafizuddin Haji Jumali, Mohammad; Radiman, S.

2018-04-01

Mesoporous TiO2 hollow spherical nanostructures with high surface areas were successfully prepared using a microwave method. The prepared hollow spheres had a size range between 200 and 500 nm. The spheres consisted of numerous smaller TiO2 nanoparticles with an average diameter of 8 nm. The particles had an essentially mesoporous structure, with a pore size in the range of 2-50 nm. The results confirmed that the synthesised of anatase TiO2 nanoparticles with specific surface area approximately 172.3 m2 g-1. The effect of ultraviolet and visible light irradiation and catalyst dosage on the TiO2 photocatalytic activity was studied by measuring the degradation rate of methylene blue. The maximum dye degradation performances with low catalyst loading (30 mg) were 99% and 63.4% using the same duration of ultraviolet and visible light irradiation, respectively (120 min).

Chitosan/titanium dioxide nanocomposite coatings: Rheological behavior and surface application to cellulosic paper.

PubMed

Tang, Yanjun; Hu, Xiulan; Zhang, Xinqi; Guo, Daliang; Zhang, Junhua; Kong, Fangong

2016-10-20

Incorporation of nanofillers into a polymeric matrix has received much attention as a route to reinforced polymer nanocomposites. In the present work, an environmentally friendly chitosan (CTS)/titanium dioxide (TiO2) nanocomposite coating was designed/prepared and subsequently employed for imparting antibacterium and improved mechanical properties to cellulosic paper via surface coating. Effect of TiO2 nanoparticle loadings on the rheological behavior of nanocomposite coatings was investigated. Surface application of CTS/TiO2 nanocomposite coatings to cellulosic paper was performed, and the antibacterial activity and mechanical properties of surface-coated cellulosic paper were examined. Results showed that the increased TiO2 nanoparticle loadings decreased the viscosity and dynamic viscoelasticity of the as-prepared coatings, and improved the antibacterial activity and mechanical properties of surface-coated cellulosic paper. The optimum loading of TiO2 nanoparticles was identified at 10%. This work suggested that CTS/TiO2 nanocomposite coatings may have the potential to be used as a promising antibacterial protective coating for paper packaging. Copyright © 2016 Elsevier Ltd. All rights reserved.

Density functional theory studies of TiO2 for photocatalysis and Li storage applications

NASA Astrophysics Data System (ADS)

Kim, Yong-Hoon; Lee, Ji Il; Lee, Dong Ki; Lee, Gyu Heon; Kang, Jeung Ku

We present two theory-experiment collaboration studies of anatase TiO2 for energy applications. First, we discuss a hydrogen-nitrogen co-doped TiO2 (HN-TiO2) as a photocatalyst, and show that the interstitially introduced HN contributes to the increase of solar-to-fuel conversion efficiency. We find that the variation of valence band maximum (VBM) of NH-TiO2 extends the photoactive spectrum to the visible light, and argue that created mid-gap states produce efficient electron and hole conduction channels. Next, we consider experimentally fabricated hierarchical TiO2 nanocrystals integrated with binder-free porous graphene (PG) network foam for a Li storage application. It was found that the TiO2-PG facilitated rapid ionic transfer during the Li-ion insertion/extraction process. We clarify the mechanisms by showing that Li ion migration into the TiO2-PG interface stabilize the binder-free oxide-graphene interface. Atomistic mechanism of Li ion insertion and migration is discussed by comparing cases between an isolated Li ion, when the crowding effect is included, and when the surface Li ions are present. We found that the supply of additional surface Li ions significantly reduce the Li insertion barrier, driving a spontaneous domino-like concerted Li insertion at the oxide surface region.

[Preparation and Photocatalytic Properties of Supported TiO2 Photocatalytic Material].

PubMed

Guo, Yu; Jin, Yu-jia; Wu, Hong-mei; Li, Dong-xin

2015-06-01

Titanium dioxide (TiO2) supported on spherical alumina substrate was prepared by using sol-gel method combined with dip-coating process. The surface morphology and structure of the synthesized samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) pattern. The results show that the morphology of the supported TiO2 composite material was obviously different from that of the original support. It reveals a layer formed by anatase TiO2 nanoparticles of 10-20 nm was deposited on the alumina substrate. Energy dispersive X-ray spectroscopy (EDX) analyses on the spherical alumina substrate and the resulting TiO2 composite catalyst were performed to determine the TiO2 loading content in the samples. It indicates that the TiO2 loading content on alumina substrate could be effectively increased by increasing the times of dip-coating alumina support in TiO2 sol. When dip-coating times increased to 5, the TiO2 loading content increased from 3.8 Wt. % to 15.7 Wt. %. In addition, the photocatalytic performances of the supported TiO2 materials prepared by different dip-coating times have been investigated by degrading methylene blue. It was found that the surface morphology of the supported TiO2 material was not only improved, but also the photocatalytic activity could be promoted significantly by increasing the dip-coating times. When the alumina substrate was dip-coated in TiO2 sol from 1 to 4 times, the degradation rate of methylene blue increased from 40% to 83.1%. However, after dip-coating the alumina support in TiO2 sol for 5 times, the degradation of methylene blue was only up to 85.6%. This indicates that the photocatalytic activity increased slowly when the TiO2 content in the supported catalyst was up to some extent. It is attributed to the continuous dip-coating resulted in less opportunities and weak intensity of illumination for the TiO2 nano-particles that under lower layer. The photocatalytic activity was relatively stable after repeated use of the supported TiO2 material for 5 times.

Ultra-fine structural characterization and bioactivity evaluation of TiO2 nanotube layers.

PubMed

Jang, JaeMyung; Kwon, TaeYub; Kim, KyoHan

2008-10-01

For an application as biomedical materials of high performance with a good biocompatibility, the TiO2 nanotube-type oxide film on Ti substrate has been fabricated by electrochemical method, and the effects of surface characteristics of TiO2 naotube layer have been investigated. The surface morphology of TiO2 nanotube layer depends on factors such as anodizing time, current density, and electrolyte temperature. Moreover, the cell and pore size gradually were increased with the passage of anodizing time. X-ray diffraction (XRD) results indicated that the TiO2 nanotube layer formed in acidic electrolytes was mainly composed of anatase structure containing rutile. From the analysis of chemical states of TiO2 nanotube layer using X-ray photoelectron spectroscopy (XPS), Ti2p, P2p and O1s were observed in the nanotubes layer, which were penetrated from the electrolyte into the oxide layer during anodic process. The incorporated phosphate species were found mostly in the forms of HPO4-, PO4-, and PO3-. From the result of biological evaluation in simulated body fluid (SBF) the TiO2 nanotube layer was effective for bioactive property.

Facile synthesis of one-dimensional hollow Sb2O3@TiO2 composites as anode materials for lithium ion batteries

NASA Astrophysics Data System (ADS)

Wang, Zhaomin; Cheng, Yong; Li, Qian; Chang, Limin; Wang, Limin

2018-06-01

Metallic Sb is deemed as a promising anode material for lithium ion batteries (LIBs) due to its flat voltage platform and high security. Nevertheless, the limited capacity restricts its large-scale application. Therefore, a simple and effective method to explore novel antimony trioxide with high capacity used as anode material for LIBs is imperative. In this work, we report a facile and efficient strategy to fabricate 1D hollow Sb2O3@TiO2 composites by using the Kirkendall effect. When used as an anode material for LIBs, the optimal Sb2O3@TiO2 composite displays a high reversible discharge capacity of 593 mAh g-1 at a current density of 100 mA g-1 after 100 cycles and a relatively superior discharge capacity of 439 mAh g-1 at a current density of 500 mA g-1 even after 600 cycles. In addition, a reversible discharge capacity of 334 mAh g-1 can also be obtained even at a current density of 2000 mA g-1. The excellent cycling stability and rate performance of the Sb2O3@TiO2 composite can be attributed to the synergistic effect of TiO2 shell and hollow structure of Sb2O3, both of which can effectively buffer the volume expansion and maintain the integrity of the electrode during the repeated charge-discharge cycles.

Transition regime from step-flow to step-bunching in the growth of epitaxial SrRuO3 on (001) SrTiO3

NASA Astrophysics Data System (ADS)

Gura, Anna; Bertino, Giulia; Bein, Benjamin; Dawber, Matthew

2018-04-01

We present a study of the surface morphology of SrRuO3 thin films grown on TiO2 terminated (001) SrTiO3 substrates using an off-axis RF magnetron sputtering deposition technique. We investigated the step bunching formation and the evolution of the films by varying deposition parameters. The thin films were characterized using atomic force microscopy methods, allowing us to study the various growth regimes of SrRuO3 as a function of the growth parameters. We observe a strong influence of both the miscut angle and growth temperature on the evolution of the SrRuO3 surface morphology. In addition, a thickness dependence is present. Remarkably, the formation of a smooth, regular, and uniform "fish-skin" structure at the step-bunch transition is observed. The fish-skin morphology results from the merging of 2D flat islands predicted by previous models. The direct observation of surface evolution allows us to better understand the different growth regimes of SrRuO3 thin films.

Hydrophilic TiO2 porous spheres anchored on hydrophobic polypropylene membrane for wettability induced high photodegrading activities.

PubMed

Niu, Fang; Zhang, Le-Sheng; Chen, Chao-Qiu; Li, Wei; Li, Lin; Song, Wei-Guo; Jiang, Lei

2010-08-01

TiO(2) porous nanospheres on polypropylene (PP) films (TiO(2)/PP composite) are produced at ambient temperature. Particle/pore size match up is the key anchoring point to overcome the low affinity between hydrophilic materials and hydrophobic materials. With the hydrophilic TiO(2) catalyst evenly dispersed on a hydrophobic surface, the aqueous solution will selectively skip the substrate and wet the catalysts. Such a wettability-induced smart system maximizes the degrading activity of the TiO(2) catalyst. In photodegrading reactions, the resulting TiO(2)/PP composite film exhibits a 10 times higher activity in flow-type setup than the same TiO(2) catalyst in a traditional batch-type setup.

Improving surface-enhanced Raman scattering properties of TiO(2) nanoparticles by metal Co doping.

PubMed

Yang, Libin; Qin, Xiaoyu; Gong, Mengdi; Jiang, Xin; Yang, Ming; Li, Xiuling; Li, Guangzhi

2014-04-05

In this paper, pure and different amount Co ions doped TiO2 nanoparticles were synthesized by a sol-hydrothermal method and were served as SERS-active substrate. The effect of metal Co doping on SERS properties of TiO2 nanoparticles was mostly investigated. The results indicate that abundant metal doping energy levels can be formed in the energy gap of TiO2 by an appropriate amount Co ions doping, which can promote the charge transfer from TiO2 to molecule, and subsequently enhance SERS signal of adsorbed molecule on TiO2 substrate, and improve remarkably SERS properties of TiO2 nanoparticles. Copyright © 2013 Elsevier B.V. All rights reserved.

Adsorption and photocatalytic degradation of pharmaceuticals and pesticides by carbon doped-TiO2 coated on zeolites under solar light irradiation.

PubMed

An, Ye; de Ridder, David Johannes; Zhao, Chun; Schoutteten, Klaas; Bussche, Julie Vanden; Zheng, Huaili; Chen, Gang; Vanhaecke, Lynn

2016-01-01

To evaluate the performance of zeolite-supported carbon-doped TiO(2) composite catalysts toward target pollutants under solar light irradiation, the adsorption and photocatalytic degradation of 18 pharmaceuticals and pesticides with distinguishing features (molecular size and volume, and photolysis) were investigated using mordenite zeolites with SiO(2)/Al(2)O(3) ratios of 18 and 240. Different quantities of carbon-doped TiO(2) were coated on the zeolites, and then the finished composite catalysts were tested in demineralized, surface, and hospital wastewater samples, respectively. The composite photocatalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, and surface area and porosity analyses. Results showed that a dispersed layer of carbon-doped TiO(2) is formed on the zeolite surface; this layer blocks the micropores of zeolites and reduces their surface area. However, these reductions did not significantly affect adsorption onto the zeolites. Our results demonstrated that zeolite-supported carbon-doped TiO(2) systems can effectively degrade 18 pharmaceuticals and pesticides in demineralized water under natural and simulated solar light irradiation. In surface and hospital wastewaters, zeolite-supported carbon-doped TiO(2) systems present excellent anti-interference capability against radical scavengers and competitive organics for pollutants removal, and higher pollutants adsorption on zeolites evidently enhances the removal rate of target pollutants in surface and hospital wastewater samples with a complicated matrix.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lei, Yu; Liu, Bin; Lu, Junling

The effect of residue chlorine on the synthesis of well-dispersed Pd nanoparticles on TiO2 supports using Pd atomic layer deposition (ALD) was investigated. The dispersion of Pd nanoparticles was compared over chlorine-containing and chlorine-free TiO2 supports prepared by selecting proper precursors. The detailed X-ray photoelectron spectroscopy and scanning transmission electron microscopy characterizations showed that higher dispersion of Pd nanoparticles was achieved on the chlorine-containing TiO2 surface than the chlorine-free TiO2. The preparation of TiO2 thin films and Pd nanoparticles was characterized by in situ FT-IR. The temperature required for complete deligation of palladium hexafluoroacetylacetonate decreased from 175 to 100 degreesmore » C with the presence of chlorine on the TiO2 surface. Density functional theory calculations confirm that Pdligand bond strength could be weakened as Pd binds to the Cl sites. The water-gas-shift reaction was chosen as the model reaction, and the catalytic performance of the ALD Pd catalysts was discussed. Compared to reported catalysts, the Pd nanocatalysts supported by TiO2/SiO2 mixed oxides showed promising performance in the low-temperature water-gas-shift reaction.« less

Improving device performance of perovskite solar cells by micro-nanoscale composite mesoporous TiO2

NASA Astrophysics Data System (ADS)

Ting, Hungkit; Zhang, Danfei; He, Yihao; Wei, Shiyuan; Li, Tieyi; Sun, Weihai; Wu, Cuncun; Chen, Zhijian; Wang, Qi; Zhang, Guoyi; Xiao, Lixin

2018-02-01

In perovskite solar cells, the morphology of the porous TiO2 electron transport layer (ETL) largely determines the quality of the perovskites. Here, we chose micro-scale TiO2 (0.2 µm) and compared it with the conventional nanoscale TiO2 (20 nm) in relation to the crystallinity of perovskites. The results show that the micro-scale TiO2 is favorable for increasing the grain size of the perovskites and enhancing the light scattering. However, the oversized TiO2 results in an uneven surface. The evenness of the perovskites can be improved by nanoscale TiO2, while the crystallinity and compactness are not as good as those of the films based on micro-scale TiO2. To combine the advantages of both micro-scale and nanoscale TiO2, by mixing 0.2 µm/20 nm TiO2 with a ratio of 1:2 as the composite ETL, the device average power conversion efficiency was increased to 11.2% from 9.9% in the case of only 20 nm TiO2.

Aggregation behaviour and electron injection/recombination dynamics of symmetrical and unsymmetrical Zn-phthalocyanines on TiO2 film.

PubMed

Ashokkumar, R; Kathiravan, A; Ramamurthy, P

2014-01-21

We have synthesized symmetrical and unsymmetrical Zn-phthalocyanine derivatives (PZnPc, MPZnPc and TPZnPc) for dye sensitized solar cells (DSSCs). Steady state and time-resolved absorption and fluorescence studies were performed in DMF solvent and on a TiO2 surface. The mode and extent of aggregation (H- and J-aggregates) of ZnPc adsorbed on a TiO2 surface were demonstrated. MPZnPc shows both H- and J-aggregation, while TPZnPc shows only H-aggregation. Moreover, the fluorescence of ZnP/TiO2 was completely quenched and this was assigned to electron injection from excited ZnPc to TiO2. Energy level calculations show both ZnPc deriviatives have enough driving force to inject electrons into the conduction band of TiO2. Furthermore, the radical cation of ZnPc was observed in nanosecond transient absorption measurements.

Chemical modification of TiO2 surfaces with methylsilanes and characterization by infrared absorption spectroscopy

NASA Technical Reports Server (NTRS)

Finklea, H. O.; Vithanage, R.

1982-01-01

Infrared absorption spectra of methylsilanes bonded to a TiO2 powder were obtained. The reacting silanes include Me sub (4-n)SiX sub n (n=1-4; X=Cl, OMe) and hexamethyldisilazane (HMDS). Reactions were performed on hydroxylated-but-anhydrous TiO2 surfaces in the gas phase. IR spectra confirm the presence of a bonded silane layer. Terminal surface OH groups are found to react more readily than bridging OH groups. By-products of the modification adsorp tenaciously to the surface. The various silanes show only small differences in their ability to sequester surface OH groups. Following hydrolysis in moist air, Si-OH groups are observed only for the tetrafunctional silanes.

Integration of Enzymes in Polyaniline-Sensitized 3D Inverse Opal TiO2 Architectures for Light-Driven Biocatalysis and Light-to-Current Conversion.

PubMed

Riedel, Marc; Lisdat, Fred

2018-01-10

Inspired by natural photosynthesis, coupling of artificial light-sensitive entities with biocatalysts in a biohybrid format can result in advanced photobioelectronic systems. Herein, we report on the integration of sulfonated polyanilines (PMSA1) and PQQ-dependent glucose dehydrogenase (PQQ-GDH) into inverse opal TiO 2 (IO-TiO 2 ) electrodes. While PMSA1 introduces sensitivity for visible light into the biohybrid architecture and ensures the efficient wiring between the IO-TiO 2 electrode and the biocatalytic entity, PQQ-GDH provides the catalytic activity for the glucose oxidation and therefore feeds the light-driven reaction with electrons for an enhanced light-to-current conversion. Here, the IO-TiO 2 electrodes with pores of around 650 nm provide a suitable interface and morphology needed for the stable and functional assembly of polymer and enzyme. The IO-TiO 2 electrodes have been prepared by a template approach applying spin coating, allowing an easy scalability of the electrode height and surface area. The successful integration of the polymer and the enzyme is confirmed by the generation of an anodic photocurrent, showing an enhanced magnitude with increasing glucose concentrations. Compared to flat and nanostructured TiO 2 electrodes, the three-layered IO-TiO 2 electrodes give access to a 24-fold and 29-fold higher glucose-dependent photocurrent due to the higher polymer and enzyme loading in IO films. The three-dimensional IO-TiO 2 |PMSA1|PQQ-GDH architecture reaches maximum photocurrent densities of 44.7 ± 6.5 μA cm -2 at low potentials in the presence of glucose (for a three TiO 2 layer arrangement). The onset potential for the light-driven substrate oxidation is found to be at -0.315 V vs Ag/AgCl (1 M KCl) under illumination with 100 mW cm -2 , which is more negative than the redox potential of the enzyme. The results demonstrate the advantageous properties of IO-TiO 2 |PMSA1|PQQ-GDH biohybrid architectures for the light-driven glucose conversion with improved performance.

Hybrid TiO2/ZnO and TiO2/Al plasmon impregnated ZnO nanocomposite photoanodes for DSSCs: synthesis and characterisation

NASA Astrophysics Data System (ADS)

Pugazhendhi, K.; D’Almeida, Steven; Naveen Kumar, P.; Sahaya Selva Mary, J.; Tenkyong, Tenzin; Sharmila, D. J.; J, Madhavan; Merline Shyla, J.

2018-04-01

The proposed work reports the synthesis and characterisation of novel and hybrid nanocomposites TiO2/ZnO and TiO2/Al plasmon impregnated ZnO, prepared using sol-gel method. X-Ray Diffraction analysis confirmed the crystalline nature of the nanocomposites with high degree of purity and the crystallite size was found to be 22 nm (TiO2/ZnO) and 21 nm (TiO2/Al-ZnO) using Scherrer’s formula. The surface chemistry, elemental compositions and purity were investigated and established using Energy Dispersive X-ray Analysis. The specific surface area of TiO2/ZnO was observed to be 23 m2 g‑1 whereas on comparison, a slight decrease was observed in the case of TiO2/Al-ZnO to 19 m2 g‑1 from Brunauer–Emmett–Teller analysis and in addition, both the samples were identified to be mesoporous in nature. The vibrational assignments were observed using Fourier Transform Infra-Red spectroscopy and results confirmed the existence of TiO2, ZnO and Al groups. The electrical response of the nanocomposites to the incident radiation with applied electric field was examined using Field Dependent Dark and Photo conductivity studies. The observed measurements revealed that the photocurrent values are greater than the dark currents which confirmed the photoconductive nature of the nanocomposites. While both the prepared nanocomposites qualify as good candidates for usage as efficient photoanodes for DSSCs, TiO2/Al-ZnO indicates a slight edge over the other.

Effect of substrate surface treatment on electrochemically assisted photocatalytic activity of N-S co-doped TiO2 films

NASA Astrophysics Data System (ADS)

Parada-Gamboa, N. J.; Pedraza-Avella, J. A.; Meléndez, A. M.

2017-01-01

To investigate whether different metal surface treatments, performed on meshes of stainless steel 304 and titanium, affect the photocatalytic activity (PCA) of supported modified anodic TiO2 films, metallic substrates were coated with titanium isopropoxide sol-gel precursor modified with thiourea. Substrates were pretreated by some of the following techniques: a) sandblasting, b) pickling, c) hydroxylation and d) passivation. The as-prepared electrode materials were characterized by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and voltammetry in the dark and under light UVA irradiation. PCA of modified N-S-TiO2 electrodes was evaluated by electrochemically assisted photocatalytic degradation of methyl orange. The results of XPS revealed that N and S were incorporated into the lattice of TiO2. FESEM showed that surface roughness and thickness of films varies depending on surface treatment. Voltammetric and XPS characterization of N-S co-doped TiO2 films supported on stainless steel revealed that their surface contains alpha-Fe2O3/FeOOH. Accordingly, iron contamination of the films coming from stainless steel was detrimental to the degradation of methyl orange. Prior to sol-gel coating process, sandblasting followed by nitric acid passivation for stainless steel or hydrofluoric acid pickling process in the case of titanium improved the PCA of N-S co-doped TiO2 films.

Band edge engineering of TiO2@DNA nanohybrids and implications for capacitive energy storage devices

NASA Astrophysics Data System (ADS)

Imani, Roghayeh; Pazoki, Meysam; Tiwari, Ashutosh; Boschloo, G.; Turner, Anthony P. F.; Kralj-Iglič, V.; Iglič, Aleš

2015-06-01

Novel mesoporous TiO2@DNA nanohybrid electrodes, combining covalently encoded DNA with mesoporous TiO2 microbeads using dopamine as a linker, were prepared and characterised for application in supercapacitors. Detailed information about donor density, charge transfer resistance and chemical capacitance, which have an important role in the performance of an electrochemical device, were studied by electrochemical methods. The results indicated the improvement of electrochemical performance of the TiO2 nanohybrid electrode by DNA surface functionalisation. A supercapacitor was constructed from TiO2@DNA nanohybrids with PBS as the electrolyte. From the supercapacitor experiment, it was found that the addition of DNA played an important role in improving the specific capacitance (Cs) of the TiO2 supercapacitor. The highest Cs value of 8 F g-1 was observed for TiO2@DNA nanohybrids. The nanohybrid electrodes were shown to be stable over long-term cycling, retaining 95% of their initial specific capacitance after 1500 cycles.Novel mesoporous TiO2@DNA nanohybrid electrodes, combining covalently encoded DNA with mesoporous TiO2 microbeads using dopamine as a linker, were prepared and characterised for application in supercapacitors. Detailed information about donor density, charge transfer resistance and chemical capacitance, which have an important role in the performance of an electrochemical device, were studied by electrochemical methods. The results indicated the improvement of electrochemical performance of the TiO2 nanohybrid electrode by DNA surface functionalisation. A supercapacitor was constructed from TiO2@DNA nanohybrids with PBS as the electrolyte. From the supercapacitor experiment, it was found that the addition of DNA played an important role in improving the specific capacitance (Cs) of the TiO2 supercapacitor. The highest Cs value of 8 F g-1 was observed for TiO2@DNA nanohybrids. The nanohybrid electrodes were shown to be stable over long-term cycling, retaining 95% of their initial specific capacitance after 1500 cycles. Electronic supplementary information (ESI) available: The HRTEM analysis of TiO2 microbeads, XPS spectra of modified electrodes (Ti 2p and O 1s peaks), total number of surface states vs applied potential (calculated DOS) of modified electrodes, circuit used for EIS data fitting, specific capacitance of FTO/TiO2/DA/DNA calculated from Galvanostatic charge-discharge test versus cycle number. See DOI: 10.1039/c5nr02533h

Improved photoelectrical performance of graphene supported highly crystallized anatase TiO2

NASA Astrophysics Data System (ADS)

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

2015-08-01

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

Synthesis and structural characteristics of high surface area TiO2 aerogels by ultrasonic-assisted sol-gel method

NASA Astrophysics Data System (ADS)

Qingge, Feng; Huidong, Cai; Haiying, Lin; Siying, Qin; Zheng, Liu; Dachao, Ma; Yuyang, Ye

2018-02-01

TiO2 aerogel is a unique three-dimensional porous nano-particle material with the characteristics of high specific surface area and good light transmittance. In this paper, a novel method involving ultrasonic-assisted sol-gel, solvent exchange, and vacuum drying was successfully developed to synthesis the TiO2 aerogel. The morphology and properties of the prepared TiO2 aerogels were characterized by the Brunauer-Emmett-Teller theory (BET), x-ray diffraction, field-emission scanning electron microscopy, energy dispersive spectroscopy, thermogravimetric analysis-differential thermal analysis, Fourier transform infrared spectroscopy, and Raman spectroscopy. The adsorption and photocatalytic activity of TiO2 aerogels was evaluated by monitoring the degradation of Rhodamine B solution. Our results indicated that: (1) with an optimum ratio of Ti:H2O = 8:1 the BET surface area, average pore diameter, and total pore volume of TiO2 aerogel are enhanced to 563.6 m2 g-1, 3.01 nm, and 0.42 cm3 g-1, respectively; (2) the TiO2 aerogels possessed controllable crystal form depending on the thermal treatments conditions. The crystal face (101) of anatase, complete anatase, mixed state of anatase and rutile, and rutile were obtained by increasing the temperature from 200 °C-300 °C, from 400 °C-500 °C, 600 °C, and from 700 °C-1000 °C, respectively; and (3) the excellent catalytic activity of the as-prepared TiO2 aerogels for the ultraviolet photolytic degradation of Rhodamine B had attributed to the synergistic effect of adsorption and photoactivity.

Visible light focusing flat lenses based on hybrid dielectric-metal metasurface reflector-arrays

PubMed Central

Fan, Qingbin; Huo, Pengcheng; Wang, Daopeng; Liang, Yuzhang; Yan, Feng; Xu, Ting

2017-01-01

Conventional metasurface reflector-arrays based on metallic resonant nanoantenna to control the wavefront of light for focusing always suffer from strong ohmic loss at optical frequencies. Here, we overcome this challenge by constructing a non-resonant, hybrid dielectric-metal configuration consisting of TiO2 nanofins associated with an Ag reflector substrate that provides a broadband response and high polarization conversion efficiency in the visible range. A reflective flat lens based on this configuration shows an excellent focusing performance with the spot size close to the diffraction limit. Furthermore, by employing the superimposed phase distribution design to manipulate the wavefront of the reflected light, various functionalities, such as multifocal and achromatic focusing, are demonstrated for the flat lenses. Such a reflective flat lens will find various applications in visible light imaging and sensing systems. PMID:28332611

TiO2 nanofibers resembling 'yellow bristle grass' in morphology by a soft chemical transformation.

PubMed

Nandan, Sandeep; Deepak, T G; Nair, Shantikumar V; Nair, A Sreekumaran

2015-05-28

We synthesized a uniquely shaped one-dimensional (1-D) TiO2 nanostructure having the morphology of yellow bristle grass with high surface area by the titanate route under mild reaction conditions. The electrospun TiO2-SiO2 composite nanofibers upon treatment with concentrated NaOH at 80 °C under ambient pressure for 24 h resulted in sodium titanate (Na2Ti3O7) nanostructures. The Na2Ti3O7 nanostructures have an overall 1-D fibrous morphology but the highly porous fiber surfaces were decorated with layered thorn-like features (a morphology resembling that of yellow bristle grass) resulting in high surface area (113 m(2) g(-1)) and porosity. The Na2Ti3O7 nanostructures were converted into TiO2 nanostructures of the same morphology by acidification (0.1 N HCl) followed by low temperature sintering (110 °C) processes. Dye-sensitized solar cells (DSCs) constructed out of the material (cells of area 0.20 cm(2) and thickness 12 μm) showed a power conversion efficiency (η) of 8.02% in comparison with commercial P-25 TiO2 (η = 6.1%).

Interactions of ciprofloxacin (CIP), titanium dioxide (TiO2) nanoparticles and natural organic matter (NOM) in aqueous suspensions.

PubMed

Fries, Elke; Crouzet, Catherine; Michel, Caroline; Togola, Anne

2016-09-01

The aim of the present study was to investigate interactions of the antibiotic ciprofloxacin (CIP), titanium dioxide nanoparticles (TiO2 NP) and natural organic matter (NOM) in aqueous suspensions. The mean hydrodynamic diameter of particles of TiO2 NP and NOM in the suspensions ranged from 113 to 255nm. During batch experiments the radioactivity resulting from (14)CIP was determined in the filtrate (filter pore size 100nm) by scintillation measurements. Up to 72h, no significant sorption of NOM to TiO2 NP was observed at a TiO2 NP concentration of 5mg/L. When the concentration of TiO2 NP was increased to 500mg/L, a small amount of NOM of 9.5%±0.6% was sorbed at 72h. The low sorption affinity of NOM on TiO2 NP surfaces could be explained by the negative charge of both components in alkaline media or by the low hydrophobicity of the NOM contents. At a TiO2 NP concentration of 5mgL(-1), the sorption of CIP on TiO2 NP was insignificant (TiO2 NP/CIP ratio: 10). When the TiO2 NP/CIP ratio was increased to 1000, a significant amount of 53.6%±7.2% of CIP was sorbed on TiO2 NP under equilibrium conditions at 64h. In alkaline media, CIP is present mainly as zwitterions which have an affinity to sorb on negatively charged TiO2 NP surfaces. The sorption of CIP on TiO2 NP in the range of TiO2 NP concentrations currently estimated for municipal wastewater treatment plants is estimated to be rather low. The Freundlich sorption coefficients (KF) in the presence of NOM of 2167L(n)mgmg(-n)kg(-1) was about 10 times lower than in the absence of NOM. This is an indication that the particle fraction of NOM<100nm could play a role as a carrier for ionic organic micro-pollutants as CIP. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of Cu2O morphology on photocatalytic hydrogen generation and chemical stability of TiO2/Cu2O composite.

PubMed

Zhu, Lihong; Zhang, Junying; Chen, Ziyu; Liu, Kejia; Gao, Hong

2013-07-01

Improving photocatalytic activity and stability of TiO2/Cu2O composite is a challenge in generating hydrogen from water. In this paper, the TiO2 film/Cu2O microgrid composite was prepared via a microsphere lithography technique, which possesses a remarkable performance of producing H2 under UV-vis light irradiation, in comparison with pure TiO2 film, Cu2O film and TiO2 film/Cu2O film. More interesting is that in TiO2 film/Cu2O microgrid, photo-corrosion of Cu2O can be retarded. After deposition of Pt on its surface, the photocatalytic activity of TiO2/Cu2O microgrid in producing H2 is improved greatly.

Self-organized TiO2 nanotube arrays in the photocatalytic degradation of methylene blue under UV light irradiation

NASA Astrophysics Data System (ADS)

Chung, Eun Hyuk; Baek, Seong Rim; Yu, Seong Mi; Kim, Jong Pil; Hong, Tae Eun; Kim, Hyun Gyu; Bae, Jong-Seong; Jeong, Euh Duck; Khan, F. Nawaz; Jung, Ok-sang

2015-04-01

Nanostructured titanium dioxide (NTiO2) is known to possess efficient photocatalytic activity and to have diverse applications in many fields due to its chemical stability, high surface area/volume ratio, high transmittance, and high refractive index in the visible and the near-ultraviolet regions. These facts prompted us to develop TiO2 nanotube (TiO2 NT) arrays through electrochemical anodic oxidation involving different electrolytes comprised of phosphoric acid — hydrofluoric acid aqueous systems by varying the voltage and the time. The annealing temperature of the nanotubes, TiO2 NTs, were varied to modify the surface morphology and were characterized by using X-ray diffraction and scanning electron microscopy. Scanning electron microscopy and X-ray diffraction results showed that the samples had uniform morphologies and good crystalline structures of the anatase phase at lower annealing temperatures and of the rutile phase at higher annealing temperatures. A secondary-ion mass-spectrometry analysis was used to investigate the surface atoms and to conduct a depth profile analysis of the TiO2 NTs. The efficiency of the photocatalytic activity of the TiO2 NT arrays in degrading methylene blue (MB) was investigated under UV-Vis light irradiation. The maximum photocatalytic activity was achieved for the samples with lower annealing temperatures due to their being in the anatase phase and having a higher surface area and a smaller crystal size, which play important roles in the degradation of organic pollutants.

Characterization and Comparison of Photocatalytic Activity Silver Ion doped on TiO2(TiO2/Ag+) and Silver Ion doped on Black TiO2(Black TiO2/Ag+)

NASA Astrophysics Data System (ADS)

Kim, Jin Yi; Sim, Ho Hyung; Song, Sinae; Noh, Yeoung Ah; Lee, Hong Woon; Taik Kim, Hee

2018-03-01

Titanium dioxide (TiO2) is one of the representative ceramic materials containing photocatalyst, optic and antibacterial activity. The hydroxyl radical in TiO2 applies to the intensive oxidizing agent, hence TiO2 is suitable to use photocatalytic materials. Black TiO2was prepared through reduction of amorphous TiO2 conducting under H2 which leads to color changes. Its black color is proven that absorbs 100% light across the whole-visible light, drawing enhancement of photocatalytic property. In this study, we aimed to compare the photocatalytic activity of silver ion doped on TiO2(TiO2/Ag+) and silver ion doped on black TiO2(black TiO2/Ag+) under visible light range. TiO2/Ag+ was fabricated following steps. 1) TiO2 was synthesized by a sol-gel method from Titanium tetraisopropoxide (TTIP). 2) Then AgNO3 was added during an aging process step for silver ion doping on the surface of TiO2. Moreover, Black TiO2/Ag+ was obtained same as TiO2/Ag+ except for calcination under H2. The samples were characterized X-ray diffraction (XRD), UV-visible reflectance (UV-vis DRS), and Methylene Blue degradation test. XRD analysis confirmed morphology of TiO2. The band gap of black TiO2/Ag+ was confirmed (2.6 eV) through UV-vis DRS, which was lower than TiO2/Ag+ (2.9 eV). The photocatalytic effect was conducted by methylene blue degradation test. It demonstrated that black TiO2/Ag+ had a photocatalytic effect under UV light also visible light.

Facile synthesis and characterization of N-doped TiO2/C nanocomposites with enhanced visible-light photocatalytic performance

NASA Astrophysics Data System (ADS)

Jia, Tiekun; Fu, Fang; Yu, Dongsheng; Cao, Jianliang; Sun, Guang

2018-02-01

Ultrafine anatase N-doped TiO2 nanocrystals modified with carbon (denoted as N-doped TiO2/C) were successfully prepared via a facile and low-cost approach, using titanium tetrachloride, aqueous ammonia and urea as starting materials. The phase composition, surface chemical composition, morphological structure, electronic and optical properties of the as-prepared photocatalysts were well characterized and analyzed. On the basis of Raman spectral characterization combining with the results of X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM), it could be concluded that N dopant ions were successfully introduced into TiO2 crystal lattice and carbon species were modified on the surface or between the nanoparticles to form N-doped TiO2/C nanocomposites. Compared with that of bare TiO2, the adsorption band edge of N-doped TiO2/C nanocomposites were found to have an evident red-shift toward visible light region, implying that the bandgap of N-doped TiO2/C nanocomposites is narrowed and the visible light absorption capacity is significantly enhanced due to N doping and carbon modification. The photoactivity of the as-prepared photocatalytsts was tested by the degradation of Rhodamine B (RhB) under visible light (λ > 420 nm), and the results showed that the N-doped TiO2/C nanocomposites exhibited much higher photodegradation rate than pure TiO2 and N-doped TiO2, which was mainly attributed to the synergistic effect of the enhanced light harvesting, augmented catalytic active sites and efficient separation of photogenerated electron-hole pairs.

Surface acidity scales: Experimental measurements of Brønsted acidities on anatase TiO2 and comparison with coinage metal surfaces

NASA Astrophysics Data System (ADS)

Silbaugh, Trent L.; Boaventura, Jaime S.; Barteau, Mark A.

2016-08-01

The first quantitative surface acidity scale for Brønsted acids on a solid surface is presented through the use of titration-displacement and equilibrium experiments on anatase TiO2. Surface acidities of species on TiO2 correlated with gas phase acidities, as was previously observed in qualitative studies of Brønsted acid displacement on Ag(110), Cu(110) and Au(111). A 90% compression of the surface acidity scale relative to the gas phase was observed due to compensation from the covalent component of the conjugate base - surface bond. Adsorbed conjugate bases need not be completely anionic for correlations with gas phase acidities to hold. Positive and negative substituent effects, such as substituted fluorine and hydrocarbon sidechain dispersion interactions with the surface, may modify the surface acidity scale, in agreement with previous experimental and theoretical work on Au(111).

Multi-applicative tetragonal TiO2/SnO2 nanocomposites for photocatalysis and gas sensing

NASA Astrophysics Data System (ADS)

Patil, S. M.; Dhodamani, A. G.; Vanalakar, S. A.; Deshmukh, S. P.; Delekar, S. D.

2018-04-01

TiO2-based mixed metal oxide heteronanostructures have multiple applications in photocatalysis and gas sensing because of their charge transport properties. In this study, we prepared tetragonal TiO2/SnO2 nanocomposites (NCs) with different weight percentages using a simple wet impregnation method. The physicochemical properties of the NCs were investigated using X-ray diffraction, Fourier transform-infrared spectroscopy, ultraviolet-visible spectroscopy, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and Brunauer-Emmett-Teller surface area analysis. The results showed that the surface area of the NCs increased significantly and the anatase TiO2 was sensitized after the addition of a small amount of cassiterite SnO2 NPs. We systematically studied the as-prepared NCs during the photocatalytic degradation of Congo Red dye under visible light irradiation (λ > 420 nm) and NH3 gas sensing, which demonstrated the efficient photocatalytic performance and the superior sensing response of the catalyst with a weight composition of 25% SnO2 in TiO2 (4:1) compared with the other NCs or the bare individual nanoparticles. The improved photocatalytic and gas sensing performance of the TiO2/SnO2 (4:1) NCs may be attributed to the increased active surface area, the increased adsorption of the dye and target gas molecules, as well as efficient electron-hole charge separation and transfer.

Bacterial adhesion and inactivation on Ag decorated TiO2-nanotubes under visible light: Effect of the nanotubes geometry on the photocatalytic activity.

PubMed

Hajjaji, A; Elabidi, M; Trabelsi, K; Assadi, A A; Bessais, B; Rtimi, S

2018-06-05

This study investigates the effect of the diameter of TiO 2 nanotubes and silver decorated nanotubes on optical properties and photocatalytic inactivation of Escherichia coli under visible light. The TiO 2 nanotubes (TiO 2 -NTs) were prepared using the electrochemical method varying the anodization potential starting from 20 V until 70 V. The Ag nanoparticles were carried out using the photoreduction process under the same experimental conditions. The diameter size was determined using the scanning electronic microscopy (SEM). TiO 2 -NTs diameter reached ∼100 nm at 70 V. Transmission electronic microscopy (TEM) imaging confirmed the TiO 2 -NTs surface decoration by silver nanoparticles. The Ag-NPs average size was found to be equal to 8 nm. The X-Ray diffraction (XRD) analysis confirm that all TiO 2 -NTs crystallize in the anatase phases regardless the used anodization potential. The decrease of the photoluminescence (PL) intensity of Ag NPs decorated TiO 2 -NTs indicates the decrease of the specific area when the nanotubes diameter increases. The UV-vis absorbance show that the absorption edges was bleu shifted with the increasing of nanotubes diameter, which can be explained by the increase of the crystallites average size. The bacterial adhesion and inactivation tests were carried in the dark and under light. Bacteria were seen to adhere on TiO 2 -NTs in the dark; however, under light the bacteria were killed before they establish a strong contact with the TiO 2 -NTs and Ag/TiO 2 -NTs surfaces. Bacterial inactivation kinetics were faster when the anodizing potential of the NTs-preparation increases. A total bacterial inactivation was obtained on ∼100 nm nanotubes diameter within 90 min. This result was attributed to the enhancement of the TNTs crystallinity leading to reduced surface defects. Redox catalysis was seen to occur under light on the TiO 2 -NTs and Ag/TiO 2 -NTs. the photo-induced antibacterial activity on the AgO/Ag 2 O decorated TiO 2 -NTs was attributed to the interfacial charge transfer mechanism (IFCT). Copyright © 2018 Elsevier B.V. All rights reserved.

TiO2-PANI/Cork composite: A new floating photocatalyst for the treatment of organic pollutants under sunlight irradiation.

PubMed

Sboui, Mouheb; Nsib, Mohamed Faouzi; Rayes, Ali; Swaminathan, Meenakshisundaram; Houas, Ammar

2017-10-01

A novel photocatalyst based on TiO 2 -PANI composite supported on small pieces of cork has been reported. It was prepared by simple impregnation method of the polyaniline (PANI)-modified TiO 2 on cork. The TiO 2 -PANI/Cork catalyst shows the unique feature of floating on the water surface. The as-synthesized catalyst was characterized by X-ray diffraction (XRD), scanning electron micrograph (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectra (UV-vis DRS) and the Brunauer-Emmett-Teller (BET) surface area analysis. Characterization suggested the formation of anatase highly dispersed on the cork surface. The prepared floating photocatalyst showed high efficiency for the degradation of methyl orange dye and other organic pollutants under solar irradiation and constrained conditions, i.e., no-stirring and no-oxygenation. The TiO 2 -PANI/Cork floating photocatalyst can be reused for at least four consecutive times without significant decrease of the degradation efficiency. Copyright © 2017. Published by Elsevier B.V.

Sol-gel TiO2 films as NO2 gas sensors

NASA Astrophysics Data System (ADS)

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

2014-05-01

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

Study on plasma pre-functionalized PVC film grafted with TiO2/PVP to improve blood compatible and antibacterial properties

NASA Astrophysics Data System (ADS)

Suganya, Arjunan; Shanmugavelayutham, Gurusamy; Serra Rodríguez, Carmen

2017-04-01

Research into the design of new biopolymers/polymer functionalized with nanoparticles is of tremendous interest to the medical sector, particularly with regard to blood-contacting devices. In this present study, a steady blood compatible and active antibacterial coating was fabricated by the grafting of titanium dioxide (TiO2)/polyvinylpyyrolidone (PVP) onto a polyvinyl chloride (PVC) film surface via the direct-current glow discharge plasma method. To enhance the chemical interaction between TiO2/PVP and PVC, the surfaces of the PVC films were functionalized by different plasmas (air, argon, and oxygen) before coating. In this study, the plasma parameters were varied, such as treatment time of about 5-20 min for a constant power of 100 W, potential 300 V, and a constant gas pressure of 2 Pa for air, argon, and oxygen gas environment. Then, the different plasma treatments on the PVC films, TiO2/PVP were grafted using a simple dip-coating method. In addition, the TiO2/PVP-grafted PVC films were characterized by contact angle, attenuated total reflectance Fourier transform infrared spectroscopy, field-emission scanning electron microscope, and x-ray photo electron spectroscopy. Importantly, TiO2/PVP is grafted onto the PVC surface due to the plasma-based retained functionality and demonstrates adhesive efficiency, which was observed by XPS. The bio-stability of the TiO2/PVP-modified PVC film was evaluated by in vitro platelet activation analysis and protein adsorption analysis. Then, the antibacterial properties were evaluated by the agar diffusion method against Escherichia coli. The result reveals that the grafting of TiO2/PVP was slightly higher for the 15 min oxygen plasma-functionalized PVC, which significantly decreases the platelet adhesion and protein adsorption. Moreover, the antibacterial properties of the 15 min oxygen plasma-functionalized PVC with TiO2/PVP-grafted film is also greatly improved compared with an air- and argon-functionalized surface. Our present study demonstrates that the plasma treatment is a beneficial and eco-friendly method to achieve higher hydrophilicity. Furthermore, our results indicated that the plasma-modified PVC exhibits appropriate anti-fouling performance.

Molecular Hydrogen Formation from Proximal Glycol Pairs on TiO2(110)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Long; Li, Zhenjun; Smith, R. Scott

2014-04-16

Understanding hydrogen formation on TiO2 surfaces is of great importance as it could provide fundamental insight into water splitting for hydrogen production using solar energy. In this work, hydrogen formation from glycols having different numbers of methyl end-groups have been studied using temperature pro-grammed desorption on reduced, hydroxylated, and oxidized TiO2(110) surfaces. The results from OD-labeled glycols demon-strate that gas-phase molecular hydrogen originates exclusively from glycol hydroxyl groups. The yield is controlled by a combi-nation of glycol coverage, steric hindrance, TiO2(110) order and the amount of subsurface charge. Combined, these results show that proximal pairs of hydroxyl aligned glycol moleculesmore » and subsurface charge are required to maximize the yield of this redox reaction. These findings highlight the importance of geometric and electronic effects in hydrogen formation from adsorbates on TiO2(110).« less

Enhanced light-harvesting by plasmonic hollow gold nanospheres for photovoltaic performance

PubMed Central

Lv, Jindian; Wu, Huaping; Chai, Guozhong; Liu, Aiping

2018-01-01

A ‘sandwich'-structured TiO2NR/HGN/CdS photoanode was successfully fabricated by the electrophoretic deposition of hollow gold nanospheres (HGNs) on the surface of TiO2 nanorods (NRs). The HGNs presented a wide surface plasmon resonance character in the visible region from 540 to 630 nm, and further acted as the scatter elements and light energy ‘antennas' to trap the local-field light near the TiO2NR/CdS layer, resulting in the increase of the light harvesting. An outstanding enhancement in the photochemical behaviour of TiO2NR/HGN/CdS photoanodes was attained by the contribution of HGNs in increasing the light absorption and the number of electron-hole pairs of photosensitive semiconductors. The optimized photochemical performance of TiO2NR/HGN/CdS photoanodes by using plasmonic HGNs demonstrated their potential application in energy conversion devices. PMID:29410838

Enhanced light-harvesting by plasmonic hollow gold nanospheres for photovoltaic performance.

PubMed

Ding, Hao; Lv, Jindian; Wu, Huaping; Chai, Guozhong; Liu, Aiping

2018-01-01

A 'sandwich'-structured TiO 2 NR/HGN/CdS photoanode was successfully fabricated by the electrophoretic deposition of hollow gold nanospheres (HGNs) on the surface of TiO 2 nanorods (NRs). The HGNs presented a wide surface plasmon resonance character in the visible region from 540 to 630 nm, and further acted as the scatter elements and light energy 'antennas' to trap the local-field light near the TiO 2 NR/CdS layer, resulting in the increase of the light harvesting. An outstanding enhancement in the photochemical behaviour of TiO 2 NR/HGN/CdS photoanodes was attained by the contribution of HGNs in increasing the light absorption and the number of electron-hole pairs of photosensitive semiconductors. The optimized photochemical performance of TiO 2 NR/HGN/CdS photoanodes by using plasmonic HGNs demonstrated their potential application in energy conversion devices.

Novel bamboo structured TiO2 nanotubes for energy storage/production applications

NASA Astrophysics Data System (ADS)

Samuel, J. J.; Beh, K. P.; Cheong, Y. L.; Yusuf, W. A. A.; Yam, F. K.

2018-04-01

Nanostructured TiO2 received much attention owing to its high surface-to-volume ratio, which can be advantageous in energy storage and production applications. However, the increase in energy consumption at present and possibly the foreseeable future has demanded energy storage and production devices of even higher performance. A direct approach would be manipulating the physical aspects of TiO2 nanostructures, particularly, nanotubes. In this work, dual voltage anodization system has been implemented to fabricate bamboo shaped TiO2 nanotubes, which offers even greater surface area. This unique nanostructure would be used in Dye Sensitized Solar Cell (DSSC) fabrication and its performance will be evaluated and compared along other forms of TiO2 nanotubes. The results showed that bamboo shaped nanotubes indeed are superior morphologically, with an increase of efficiency of 107% at 1.130% efficiency when compared to smooth walled nanotubes at 0.546% efficiency.

Photocatalytic self-cleaning TiO2 coatings on carbonatic stones

NASA Astrophysics Data System (ADS)

Bergamonti, Laura; Bondioli, Federica; Alfieri, Ilaria; Lorenzi, Andrea; Mattarozzi, Monica; Predieri, Giovanni; Lottici, Pier Paolo

2016-02-01

A self-cleaning coating based on TiO2 nanoparticles obtained by sol-gel method in an alkaline environment has been tested on different types of carbonatic stones: Botticino, Carrara and Pietra Dorata, frequently used in historic buildings. XRD and Raman measurements confirmed the nanocrystalline nature of titania in anatase form, with 5-10 nm crystal size, and evidenced a small amount of brookite. A fast photocatalytic oxidation by TiO2 coatings of the stained stones with methyl orange and methylene blue under UV lamp irradiation has been assessed. The enhancement of surface wettability due to UV-induced TiO2 hydrophilicity has been evidenced by contact angle measurements. ESEM/EDS showed a surface distribution of the coating fairly homogeneous. The coating does not introduce significant colorimetric changes of the stones and does not alter the water capillarity absorption. Thus, the alkaline nanocrystalline TiO2 is promising for self-cleaning coatings on carbonatic stones.

Surface Properties of Titanium dioxide and its Structural Modifications by Reactions with Transition Metals

NASA Astrophysics Data System (ADS)

Halpegamage, Sandamali

Surfaces of metal oxides play a vital role in many technologically important applications. The surfaces of titanium dioxide, in particular, show quite promising properties that can be utilized in solid-state gas sensing and photocatalysis applications. In the first part of this dissertation we investigate these properties of TiO2 surfaces through a vigorous surface scientific approach. In the second part, we investigate the possibilities of modifying the TiO2 surfaces by depositing multi-component transition metal oxide monolayers so that the properties of bare TiO2 surface can be influenced in a beneficial way. For instance, via formation of new surface sites or cations that have different valance states, the chemisorption and catalytic properties can be modified. We use sophisticated experimental surface science techniques that are compatible with ultra-high vacuum technology for surface characterization. All the experimental results, except for the photocatalysis experiments, were compared to and verified by supporting DFT-based theoretical results produced by our theory collaborators. TiO2 based solid-state gas sensors have been used before for detecting trace amounts of explosives such as 2,4-dinitrololuene (DNT), a toxic decomposition product of the explosive 2,4,6-trinitrotoluene (TNT) that have very low vapor pressure. However, the adsorption, desorption and reaction mechanism were not well- understood. Here, we investigate 2,4-DNT adsorption on rutile-TiO2(110) surface in order to gain insight about these mechanisms in an atomistic level and we propose an efficient way of desorbing DNT from the surface through UV-light induced photoreactions. TiO2 exists in different polymorphs and the photocatalytic activity differs from one polymorph to another. Rutile and anatase are the most famous forms of TiO2 in photocatalysis and anatase is known to show higher activity than rutile. The photoactivity also varies depending on the surface orientation for the same polymorph. So far, a reasonable explanation as to why these differences exist was not reported. In our studies, we used high quality epitaxial rutile and anatase thin films which enabled isolating the surface effects from the bulk effects and show that it is the difference between the charge carrier diffusion lengths that causes this difference in activities. In addition to that, using different surface orientations of rutile-TiO 2, we show that the anisotropic bulk charge carrier mobility may contribute to the orientation dependent photoactivity. Moreover, we show that different surface preparation methods also affect the activity of the sample and vacuum reduction results in an enhanced activity. In an effort to modify the TiO2 surfaces with monolayer/mixed monolayer oxides, we carried out experiments on (011) orientation of single crystal rutile TiO2 with few of the selected transition metal oxides namely Fe, V, Cr and Ni. We found that for specific oxidation conditions a monolayer mixed oxide is formed for all M (M= Fe, V, Cr, Ni), with one common structure with the composition MTi2O5. For small amounts of M the surface segregates into pure TiO2(011)-2x1 and into domains of MTi2O5 indicating that this mixed monolayer oxide is a low energy line phase in a compositional surface phase diagram. The oxygen pressure required for the formation of this unique monolayer structure increases in the order of V

ZrO2-modified mesoporous nanocrystalline TiO2-xNx as efficient visible light photocatalysts.

PubMed

Wang, Xinchen; Yu, Jimmy C; Chen, Yilin; Wu, Ling; Fu, Xianzhi

2006-04-01

Mesoporous nanocrystalline TiO2-xNx and TiO2-xNx/ZrO2 visible-light photocatalysts have been prepared by a sol-gel method. The photocatalysts were characterized by XRD, N2 adsorption-desorption, TEM, XPS, UV/Vis, and IR spectroscopy. The photocatalytic activity of the samples was evaluated by the decomposition of ethylene in air under visible light (lambda > 450 nm) illumination. Results revealed that nitrogen was doped into the lattice of TiO2 by the thermal treatment of NH3-adsorbed TiO2 hydrous gels, converting the TiO2 into a visible-light responsive catalyst. The introduction of ZrO2 into TiO2-xNx considerably inhibits the undesirable crystal growth during calcination. Consequently, the ZrO2-modified TiO2-xNx displays higher porosity, higher specific surface area, and an improved thermal stability over the corresponding unmodified TiO2-xNx samples.

Development of Titanium Dioxide (TiO2 ) Nanocoatings on Food Contact Surfaces and Method to Evaluate Their Durability and Photocatalytic Bactericidal Property.

PubMed

Yemmireddy, Veerachandra K; Farrell, Glenn D; Hung, Yen-Con

2015-08-01

Titanium dioxide (TiO2 ) is a well-known photocatalyst for its excellent bactericidal property under UVA light. The purpose of this study was to develop physically stable TiO2 coatings on food contact surfaces using different binding agents and develop methods to evaluate their durability and microbicidal property. Several types of organic and inorganic binders such as polyvinyl alcohol, polyethylene glycol, polyurethane, polycrylic, sodium and potassium silicates, shellac resin, and other commercial binders were used at 1:1 to 1:16 nanoparticle to binder weight ratios to develop a formulation for TiO2 coating on stainless steel surfaces. Among the tested binders, polyurethane, polycrylic, and shellac resin were found to be physically more stable when used in TiO2 coating at 1:4 to 1:16 weight ratio. The physical stability of TiO2 coatings was determined using adhesion strength and scratch hardness tests by following standard ASTM procedures. Further, wear resistance of the coatings was evaluated based on a simulated cleaning procedure used in food processing environments. TiO2 coating with polyurethane at a 1:8 nanoparticle to binder weight ratio showed the highest scratch hardness (1.08 GPa) followed by coating with polycrylic (0.68 GPa) and shellac (0.14 GPa) binders. Three different techniques, namely direct spreading, glass cover-slip, and indented coupon were compared to determine the photocatalytic bactericidal property of TiO2 coatings against Escherichia coli 0157:H7 at 2 mW/cm(2) UVA light intensity. Under the tested conditions, the indented coupon technique was found to be the most appropriate method to determine the bactericidal property of TiO2 coatings and showed a reduction of 3.5 log CFU/cm(2) in 2 h. © 2015 Institute of Food Technologists®

The Effect of Ambient Titanium Dioxide Microparticle Exposure to the Ocular Surface on the Expression of Inflammatory Cytokines in the Eye and Cervical Lymph Nodes.

PubMed

Eom, Youngsub; Song, Jong Suk; Lee, Hyun Kyu; Kang, Boram; Kim, Hyeon Chang; Lee, Hyung Keun; Kim, Hyo Myung

2016-12-01

To investigate the ocular immune response following exposure to airborne titanium dioxide (TiO2) microparticles. Rats in the TiO2-exposed group (n = 10) were exposed to TiO2 particles for 2 hours twice daily for 5 days, while the controls (n = 10) were not. Corneal staining score and tear lactic dehydrogenase (LDH) activity were measured to evaluate ocular surface damage, serum immunoglobulin (Ig) G and E were assayed by using enzyme-linked immunosorbent assay, and the size of cervical lymph nodes was measured. In addition, the expression of interleukin (IL)-4, IL-17, and interferon (IFN)-γ in the anterior segment of the eyeball and cervical lymph nodes was measured by immunohistochemistry, real-time reverse transcription-polymerase chain reaction (RT-PCR), and Western blot analysis. Median corneal staining score (3.0), tear LDH activity (0.24 optical density [OD]), and cervical lymph node size (36.9 mm2) were significantly higher in the TiO2-exposed group than in the control group (1.0, 0.13 OD, and 26.7 mm2, respectively). Serum IgG and IgE levels were found to be significantly elevated in the TiO2-exposed group (P = 0.021 and P = 0.021, respectively). Interleukin 4 expression was increased in the anterior segment of the eyeball and lymph nodes following TiO2 exposure, as measured by immunostaining, real-time RT-PCR, and Western blot. In addition, IL-17 and IFN-γ levels were also increased following TiO2 exposure compared to controls as measured by immunostaining. Exposure to airborne TiO2 induced ocular surface damage. The Type 2 helper T-cell pathway seems to play a dominant role in the ocular immune response following airborne TiO2 exposure.

Adsorption of toxic metal ion Cr(VI) from aqueous state by TiO2-MCM-41: equilibrium and kinetic studies.

PubMed

Parida, Kulamani; Mishra, Krushna Gopal; Dash, Suresh Kumar

2012-11-30

This paper deals with the immobilization of various weight percentage of TiO(2) on mesoporous MCM-41, characterization of the materials by X-ray diffraction (XRD), nitrogen adsorption-desorption, Fourier Transform Infrared (FTIR) analysis, UV-vis diffuse reflectance spectroscopy (DRS) and evaluation of the adsorption capacity toward Cr(VI) removal. It is found that the MCM-41 structure retained after loading of TiO(2) but the surface area and pore diameter decreased due to pore blockage. Adsorption of Cr(VI) from aqueous state was investigated on TiO(2)-MCM-41 by changing various parameters such as pH, metal ion concentration, and the temperature. When TiO(2) loading was more than 20 wt.%, the adsorption activity (25)TiO(2)-MCM-41 reduced significantly due to considerable decrease in the surface area. It is also observed that TiO(2) and neat MCM-41 exhibits very less Cr(VI) adsorption compared to TiO(2)-MCM-41. The adsorption of Cr(VI) onto (20)TiO(2)-MCM-41 at pH~5.5 and temperature 323 K was 91% at 100mg/L Cr(VI) metal ion concentration in 80 min. The experimental data fitted well to Langmuir and Freundlich isotherms. The adsorption of Cr(VI) on TiO(2)-MCM-41 followed a second order kinetics with higher values of intra-particle diffusion rate. Thermodynamic parameters suggested that the adsorption process is endothermic in nature and desorption studies indicated a chemisorption mode. Copyright © 2012 Elsevier B.V. All rights reserved.

Titania/CnTAB Nanoskeleton as adsorbent and photocatalyst for removal of alkylphenols dissolved in water.

PubMed

Sakai, Toshio; Da Loves, Albar; Okada, Tomohiko; Mishima, Shozi

2013-03-15

We report here on the removal of alkylphenols (phenol, 4-n-propylphenol, 4-n-heptylphenol and 4-nonylphenol) dissolved in water using the composite particles of nanocrystalline titania and alkyltrimethylammonium bromide (CnH2n+1N(CH3)3Br, CnTAB; n=12, 14, 16 and 18) (named as TiO2/CnTAB Nanoskeleton) as adsorbents and photocatalysts. In particular, the adsorption of alkylphenols onto TiO2/CnTAB Nanoskeleton in water was investigated in terms of hydrophobic interaction between alkylphenols and CnTAB, surface area, pore structure and crystal size of TiO2/CnTAB Nanoskeleton. We revealed that CnTAB incorporated in the TiO2/CnTAB Nanoskeleton promotes the adsorption of alkylphenols onto TiO2/CnTAB Nanoskeleton due to the hydrophobic interaction between alkylphenols and CnTAB. On the other hand, the surface area, pore structure and crystal size of TiO2/CnTAB Nanoskeleton did not affect the adsorption of alkylphenols onto TiO2/CnTAB Nanoskeleton. We also found that the alkylphenols dissolved in water were completely removed by the combination of adsorption and photocatalytic degradation by the TiO2/CnTAB Nanoskeleton under UV irradiation. These results prove that the TiO2/CnTAB Nanoskeleton acts as in tandem an adsorbent and a photocatalyst for removal of alkylphenols dissolved in water. Copyright © 2013 Elsevier B.V. All rights reserved.

Quasiparticle Interfacial Level Alignment of Highly Hybridized Frontier Levels: H2O on TiO2(110)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Migani, Annapaola; Mowbray, Duncan J.; Zhao, Jin

Knowledge of the frontier levels’ alignment prior to photoirradiation is necessary to achieve a complete quantitative description of H2O photocatalysis on TiO2(110). Although H2O on rutile TiO2(110) has been thoroughly studied both experimentally and theoretically, a quantitative value for the energy of the highest H2O occupied levels is still lacking. For experiment, this is due to the H2O levels being obscured by hybridization with TiO2(110) levels in the difference spectra obtained via ultraviolet photoemission spectroscopy (UPS). For theory, this is due to inherent difficulties in properly describing many-body effects at the H2O–TiO2(110) interface. Using the projected density of states (DOS)more » from state-of-the-art quasiparticle (QP) G0W0, we disentangle the adsorbate and surface contributions to the complex UPS spectra of H2O on TiO2(110). We perform this separation as a function of H2O coverage and dissociation on stoichiometric and reduced surfaces. Due to hybridization with the TiO2(110) surface, the H2O 3a1 and 1b1 levels are broadened into several peaks between 5 and 1 eV below the TiO2(110) valence band maximum (VBM). These peaks have both intermolecular and interfacial bonding and antibonding character. We find the highest occupied levels of H2O adsorbed intact and dissociated on stoichiometric TiO2(110) are 1.1 and 0.9 eV below the VBM. We also find a similar energy of 1.1 eV for the highest occupied levels of H2O when adsorbed dissociatively on a bridging O vacancy of the reduced surface. In both cases, these energies are significantly higher (by 0.6 to 2.6 eV) than those estimated from UPS difference spectra, which are inconclusive in this energy region. Finally, we apply self-consistent QPGW (scQPGW1) to obtain the ionization potential of the H2O–TiO2(110) interface.« less

Quasiparticle interfacial level alignment of highly hybridized frontier levels: H2O on TiO2(110).

PubMed

Migani, Annapaola; Mowbray, Duncan J; Zhao, Jin; Petek, Hrvoje

2015-01-13

Knowledge of the frontier levels' alignment prior to photoirradiation is necessary to achieve a complete quantitative description of H2O photocatalysis on TiO2(110). Although H2O on rutile TiO2(110) has been thoroughly studied both experimentally and theoretically, a quantitative value for the energy of the highest H2O occupied levels is still lacking. For experiment, this is due to the H2O levels being obscured by hybridization with TiO2(110) levels in the difference spectra obtained via ultraviolet photoemission spectroscopy (UPS). For theory, this is due to inherent difficulties in properly describing many-body effects at the H2O-TiO2(110) interface. Using the projected density of states (DOS) from state-of-the-art quasiparticle (QP) G0W0, we disentangle the adsorbate and surface contributions to the complex UPS spectra of H2O on TiO2(110). We perform this separation as a function of H2O coverage and dissociation on stoichiometric and reduced surfaces. Due to hybridization with the TiO2(110) surface, the H2O 3a1 and 1b1 levels are broadened into several peaks between 5 and 1 eV below the TiO2(110) valence band maximum (VBM). These peaks have both intermolecular and interfacial bonding and antibonding character. We find the highest occupied levels of H2O adsorbed intact and dissociated on stoichiometric TiO2(110) are 1.1 and 0.9 eV below the VBM. We also find a similar energy of 1.1 eV for the highest occupied levels of H2O when adsorbed dissociatively on a bridging O vacancy of the reduced surface. In both cases, these energies are significantly higher (by 0.6 to 2.6 eV) than those estimated from UPS difference spectra, which are inconclusive in this energy region. Finally, we apply self-consistent QPGW (scQPGW1) to obtain the ionization potential of the H2O-TiO2(110) interface.

Fabrication and photoactivity of ionic liquid-TiO2 structures for efficient visible-light-induced photocatalytic decomposition of organic pollutants in aqueous phase.

PubMed

Gołąbiewska, Anna; Paszkiewicz-Gawron, Marta; Sadzińska, Aleksandra; Lisowski, Wojciech; Grabowska, Ewelina; Zaleska-Medynska, Adriana; Łuczak, Justyna

2018-01-01

To investigate the effect of the ionic liquid (IL) chain length on the surface properties and photoactivity of TiO 2 , a series of TiO 2 microspheres have been synthesized via a solvothermal method assisted by 1-methyl-3-octadecylimidazolium chloride ([ODMIM][Cl]) and 1-methyl-3-tetradecylimidazolium chloride ([TDMIM][Cl]). All as-prepared samples were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), scanning transmission microscopy (STEM) and the Brunauer-Emmett-Teller (BET) surface area method, whereas the photocatalytic activity was evaluated by the degradation of phenol in aqueous solution under visible light irradiation (λ > 420 nm). The highest photoefficiency (four times higher than pristine TiO 2 ) was observed for the TiO 2 sample obtained in the presence of [TDMIM][Cl] for a IL to TiO 2 precursor molar ratio of 1:3. It was revealed that interactions between the ions of the ionic liquid and the surface of the growing titanium dioxide spheres results in a red-shift of absorption edge for the IL-TiO 2 semiconductors. In this regard, the direct increase of the photoactivity of IL-TiO 2 in comparison to pristine TiO 2 was observed. The active species trapping experiments indicated that O 2 •- is the main active species, created at the surface of the IL-TiO 2 material under visible-light illumination, and is responsible for the effective phenol degradation.

Structure of a model TiO2 photocatalytic interface

NASA Astrophysics Data System (ADS)

Hussain, H.; Tocci, G.; Woolcot, T.; Torrelles, X.; Pang, C. L.; Humphrey, D. S.; Yim, C. M.; Grinter, D. C.; Cabailh, G.; Bikondoa, O.; Lindsay, R.; Zegenhagen, J.; Michaelides, A.; Thornton, G.

2017-04-01

The interaction of water with TiO2 is crucial to many of its practical applications, including photocatalytic water splitting. Following the first demonstration of this phenomenon 40 years ago there have been numerous studies of the rutile single-crystal TiO2(110) interface with water. This has provided an atomic-level understanding of the water-TiO2 interaction. However, nearly all of the previous studies of water/TiO2 interfaces involve water in the vapour phase. Here, we explore the interfacial structure between liquid water and a rutile TiO2(110) surface pre-characterized at the atomic level. Scanning tunnelling microscopy and surface X-ray diffraction are used to determine the structure, which is comprised of an ordered array of hydroxyl molecules with molecular water in the second layer. Static and dynamic density functional theory calculations suggest that a possible mechanism for formation of the hydroxyl overlayer involves the mixed adsorption of O2 and H2O on a partially defected surface. The quantitative structural properties derived here provide a basis with which to explore the atomistic properties and hence mechanisms involved in TiO2 photocatalysis.

Structure of a model TiO2 photocatalytic interface.

PubMed

Hussain, H; Tocci, G; Woolcot, T; Torrelles, X; Pang, C L; Humphrey, D S; Yim, C M; Grinter, D C; Cabailh, G; Bikondoa, O; Lindsay, R; Zegenhagen, J; Michaelides, A; Thornton, G

2017-04-01

The interaction of water with TiO 2 is crucial to many of its practical applications, including photocatalytic water splitting. Following the first demonstration of this phenomenon 40 years ago there have been numerous studies of the rutile single-crystal TiO 2 (110) interface with water. This has provided an atomic-level understanding of the water-TiO 2 interaction. However, nearly all of the previous studies of water/TiO 2 interfaces involve water in the vapour phase. Here, we explore the interfacial structure between liquid water and a rutile TiO 2 (110) surface pre-characterized at the atomic level. Scanning tunnelling microscopy and surface X-ray diffraction are used to determine the structure, which is comprised of an ordered array of hydroxyl molecules with molecular water in the second layer. Static and dynamic density functional theory calculations suggest that a possible mechanism for formation of the hydroxyl overlayer involves the mixed adsorption of O 2 and H 2 O on a partially defected surface. The quantitative structural properties derived here provide a basis with which to explore the atomistic properties and hence mechanisms involved in TiO 2 photocatalysis.

Light-controlled plasmon switching using hybrid metal-semiconductor nanostructures.

PubMed

Paudel, Hari P; Leuenberger, Michael N

2012-06-13

We present a proof of concept for the dynamic control over the plasmon resonance frequencies in a hybrid metal-semiconductor nanoshell structure with Ag core and TiO(2) coating. Our method relies on the temporary change of the dielectric function ε of TiO(2) achieved through temporarily generated electron-hole pairs by means of a pump laser pulse. This change in ε leads to a blue shift of the Ag surface plasmon frequency. We choose TiO(2) as the environment of the Ag core because the band gap energy of TiO(2) is larger than the Ag surface plasmon energy of our nanoparticles, which allows the surface plasmon being excited without generating electron-hole pairs in the environment at the same time. We calculate the magnitude of the plasmon resonance shift as a function of electron-hole pair density and obtain shifts up to 126 nm at wavelengths around 460 nm. Using our results, we develop the model of a light-controlled surface plasmon polariton switch.

Amino acid adsorption on anatase (101) surface at vacuum and aqueous solution: a density functional study.

PubMed

Liu, Liuxie; Li, Kai; Chen, Xiao; Liang, Xiaoqin; Zheng, Yan; Li, Laicai

2018-03-29

The adsorption of 20 amino acids (AAs) on the (101) surface of anatase titanium dioxide (TiO 2 ) has been investigated under the scheme of density functional theory. Through the analysis of adsorption geometries, amino group and side chains of AAs have been identified as the major side to adsorb on TiO 2 , while the carboxyl group prefers to stay outside to avoid the repulsion between negatively charged oxygen from TiO 2 and AAs. On the surface, two-coordinated oxygen is the major site to stabilize AAs through O-H interactions. The above conclusion does not change when it is in the aqueous solution based on the calculations with AAs surrounded by explicit water molecules. The above knowledge is helpful in predicting how AAs and even peptides adsorb on inorganic materials. Graphical abstract The adsorption of 20 amino acids (AAs) on the (101) surface of anatase titanium dioxide (TiO 2 ) has been investigated under the scheme of density functional theory.

Photoinduced Charge Transfer from Titania to Surface Doping Site

PubMed Central

Inerbaev, Talgat; Hoefelmeyer, James D.; Kilin, Dmitri S.

2013-01-01

We evaluate a theoretical model in which Ru is substituting for Ti at the (100) surface of anatase TiO2. Charge transfer from the photo-excited TiO2 substrate to the catalytic site triggers the photo-catalytic event (such as water oxidation or reduction half-reaction). We perform ab-initio computational modeling of the charge transfer dynamics on the interface of TiO2 nanorod and catalytic site. A slab of TiO2 represents a fragment of TiO2 nanorod in the anatase phase. Titanium to ruthenium replacement is performed in a way to match the symmetry of TiO2 substrate. One molecular layer of adsorbed water is taken into consideration to mimic the experimental conditions. It is found that these adsorbed water molecules saturate dangling surface bonds and drastically affect the electronic properties of systems investigated. The modeling is performed by reduced density matrix method in the basis of Kohn-Sham orbitals. A nano-catalyst modeled through replacement defect contributes energy levels near the bottom of the conduction band of TiO2 nano-structure. An exciton in the nano-rod is dissipating due to interaction with lattice vibrations, treated through non-adiabatic coupling. The electron relaxes to conduction band edge and then to the Ru cite with faster rate than hole relaxes to the Ru cite. These results are of the importance for an optimal design of nano-materials for photo-catalytic water splitting and solar energy harvesting. PMID:23795229

Photoinduced Charge Transfer from Titania to Surface Doping Site.

PubMed

Inerbaev, Talgat; Hoefelmeyer, James D; Kilin, Dmitri S

2013-05-16

We evaluate a theoretical model in which Ru is substituting for Ti at the (100) surface of anatase TiO 2 . Charge transfer from the photo-excited TiO 2 substrate to the catalytic site triggers the photo-catalytic event (such as water oxidation or reduction half-reaction). We perform ab-initio computational modeling of the charge transfer dynamics on the interface of TiO 2 nanorod and catalytic site. A slab of TiO 2 represents a fragment of TiO 2 nanorod in the anatase phase. Titanium to ruthenium replacement is performed in a way to match the symmetry of TiO 2 substrate. One molecular layer of adsorbed water is taken into consideration to mimic the experimental conditions. It is found that these adsorbed water molecules saturate dangling surface bonds and drastically affect the electronic properties of systems investigated. The modeling is performed by reduced density matrix method in the basis of Kohn-Sham orbitals. A nano-catalyst modeled through replacement defect contributes energy levels near the bottom of the conduction band of TiO 2 nano-structure. An exciton in the nano-rod is dissipating due to interaction with lattice vibrations, treated through non-adiabatic coupling. The electron relaxes to conduction band edge and then to the Ru cite with faster rate than hole relaxes to the Ru cite. These results are of the importance for an optimal design of nano-materials for photo-catalytic water splitting and solar energy harvesting.

Transition metal ions effect on the properties and photocatalytic activity of nanocrystalline TiO2 prepared in an ionic liquid.

PubMed

Ghasemi, S; Rahimnejad, S; Setayesh, S Rahman; Rohani, S; Gholami, M R

2009-12-30

TiO(2) and transition metal (Cr, Mn, Fe, Co, Ni, Cu, and Zn) doped TiO(2) nanoparticles were synthesized by the sol-gel method using 2-hydroxylethylammonium formate as an ionic liquid. All the prepared samples were calcined at 500 degrees C and characterized by X-ray diffraction (XRD), BET surface area determination, energy dispersive X-ray (EDX) analysis, diffuse reflectance spectroscopy (DRS), and Fourier transformed infrared (FT-IR) techniques. The studies revealed that transition metal (TM) doped nanoparticles have smaller crystalline size and higher surface area than pure TiO(2). Dopant ions in the TiO(2) structure caused significant absorption shift into the visible region. The results of photodegradation of Acid Blue92 (AB92) in aqueous medium under UV light showed that photocatalytic activity of TiO(2) nanoparticles was significantly enhanced by the presence of some transition metal ions. Chemical Oxygen Demand (COD) of dye solutions were done at regular intervals gave a good idea about mineralization of dye.

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

PubMed

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.

Effects of suspended titanium dioxide nanoparticles on cake layer formation in submerged membrane bioreactor.

PubMed

Zhou, Lijie; Zhang, Zhiqiang; Xia, Siqing; Jiang, Wei; Ye, Biao; Xu, Xiaoyin; Gu, Zaoli; Guo, Wenshan; Ngo, Huu-Hao; Meng, Xiangzhou; Fan, Jinhong; Zhao, Jianfu

2014-01-01

Effects of the suspended titanium dioxide nanoparticles (TiO2 NPs, 50 mg/L) on the cake layer formation in a submerged MBR were systematically investigated. With nanometer sizes, TiO2 NPs were found to aggravate membrane pore blocking but postpone cake layer fouling. TiO2 NPs showed obvious effects on the structure and the distribution of the organic and the inorganic compounds in cake layer. Concentrations of fatty acids and cholesterol in the cake layer increased due to the acute response of bacteria to the toxicity of TiO2 NPs. Line-analysis and dot map of energy-dispersive X-ray were also carried out. Since TiO2 NPs inhibited the interactions between the inorganic and the organic compounds, the inorganic compounds (especially SiO2) were prevented from depositing onto the membrane surface. Thus, the postponed cake layer fouling was due to the changing features of the complexes on the membrane surface caused by TiO2 NPs. Copyright © 2013 Elsevier Ltd. All rights reserved.

Mechanical Grinding Preparation and Characterization of TiO2-Coated Wollastonite Composite Pigments

PubMed Central

Chen, Wanting; Liang, Yu; Hou, Xifeng; Zhang, Jing; Ding, Hao; Sun, Sijia; Cao, Hu

2018-01-01

TiO2-coated wollastonite composite pigments were prepared by the mechano-chemical grinding of wollastonite and TiO2 powder together in a wet ultrafine stirred mill. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and infrared spectra were used to investigate the microstructures and morphologies of the composite and the reaction mechanism. The results indicate that the TiO2-coated wollastonite composite pigments have similar properties to titanium dioxide pigment, showing much better properties than dry and wet mixing of wollastonite and TiO2. The hiding power of TiO2-coated wollastonite composite pigments (45% TiO2) is 17.97 g/m2, reaching 81.08% of titanium dioxide. A firm combination between wollastonite and TiO2 is obtained through a surface dehydroxylation reaction during the mechano-chemical method. PMID:29649116

A Close Look at the Structure of the TiO2-APTES Interface in Hybrid Nanomaterials and Its Degradation Pathway: An Experimental and Theoretical Study

PubMed Central

2016-01-01

The surface functionalization of TiO2-based materials with alkylsilanes is attractive in several cutting-edge applications, such as photovoltaics, sensors, and nanocarriers for the controlled release of bioactive molecules. (3-Aminopropyl)triethoxysilane (APTES) is able to self-assemble to form monolayers on TiO2 surfaces, but its adsorption geometry and solar-induced photodegradation pathways are not well understood. We here employ advanced experimental (XPS, NEXAFS, AFM, HR-TEM, and FT-IR) and theoretical (plane-wave DFT) tools to investigate the preferential interaction mode of APTES on anatase TiO2. We demonstrate that monomeric APTES chemisorption should proceed through covalent Si–O–Ti bonds. Although dimerization of the silane through Si–O–Si bonds is possible, further polymerization on the surface is scarcely probable. Terminal amino groups are expected to be partially involved in strong charge-assisted hydrogen bonds with surface hydroxyl groups of TiO2, resulting in a reduced propensity to react with other species. Solar-induced mineralization proceeds through preferential cleavage of the alkyl groups, leading to the rapid loss of the terminal NH2 moieties, whereas the Si-bearing head of APTES undergoes slower oxidation and remains bound to the surface. The suitability of employing the silane as a linker with other chemical species is discussed in the context of controlled degradation of APTES monolayers for drug release and surface patterning. PMID:28191270

Data on the effect of improved TiO2/FTO interface and Ni(OH)2 cocatalyst on the photoelectrochemical performances and stability of CdS cased ZnIn2S4/TiO2 heterojunction.

PubMed

Mahadik, Mahadeo A; Shinde, Pravin S; Lee, Hyun Hwi; Cho, Min; Jang, Jum Suk

2018-04-01

This data article presents the experimental evidences of the effect of TiO 2 -fluorine doped tin oxide interface annealing and Ni(OH) 2 cocatalysts on the photoelectrochemical, structural, morphological and optical properties of Ni(OH) 2 /CdS/ZnIn 2 S 4 /TiO 2 heterojunction. The Raman spectroscopy exhibits the sharp features of the rutile phase of TiO 2 and in agreement with the X-ray diffraction data. The band gap energy of the 500 °C sample was found to be 3.12 eV, further it was increased to 3.20, 3.22 eV for samples annealed at 600 and 700 °C respectively. The decrease in the band gap energy at 500 °C related to the oxygen vacancies and was analysed by photoluminescence spectroscopy analysis. The synthesis, characterization methods and other experimental details of TiO 2 based heterostructure are also provided. The presence of CdS and ZnIn 2 S 4 coating on surface of TiO 2 electrodes providing a high surface area, extended visible absorption and helps to improve the change separation. This data article contains data related to the research article entitled "Highly efficient and stable 3D Ni(OH) 2 /CdS/ZnIn 2 S 4 /TiO 2 heterojunction under solar light: Effect of an improved TiO 2 /FTO interface and cocatalyst" (Mahadik et al., 2017) [1].

Heterogeneous UV/Fenton degradation of bisphenol A catalyzed by synergistic effects of FeCo2O4/TiO2/GO.

PubMed

Bai, Xue; Lyu, Lingling; Ma, Wenqiang; Ye, Zhengfang

2016-11-01

A new method for bisphenol A (BPA) degradation in aqueous solution was developed. The characteristics of BPA degradation in a heterogeneous ultraviolet (UV)/Fenton reaction catalyzed by FeCo 2 O 4 /TiO 2 /graphite oxide (GO) were studied. The properties of the synthesized catalysts were characterized using scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometry. FeCo 2 O 4 and TiO 2 were grown as spherical shape, rough surface, and relatively uniform on the surface of GO (FeCo 2 O 4 /TiO 2 /GO). Batch tests were conducted to evaluate the effects of the initial pH, FeCo 2 O 4 /TiO 2 /GO dosage, and H 2 O 2 concentration on BPA degradation. In a system with 0.5 g L -1 of FeCo 2 O 4 /TiO 2 /GO and 10 mmol L -1 of H 2 O 2 , approximately 90 % of BPA (20 mg L -1 ) was degraded within 240 min of UV irradiation at pH 6.0. The reused FeCo 2 O 4 /TiO 2 /GO catalyst retained its activity after three cycles, which indicates that it is stable and reusable. The heterogeneous UV/Fenton reaction catalyzed by FeCo 2 O 4 /TiO 2 /GO is a promising advanced oxidation technology for treating wastewater that contains BPA.

Solvothermal synthesis of hierarchical TiO2 nanostructures with tunable morphology and enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Fan, Zhenghua; Meng, Fanming; Zhang, Miao; Wu, Zhenyu; Sun, Zhaoqi; Li, Aixia

2016-01-01

This paper presents controllable growth and photocatalytic activity of TiO2 hierarchical nanostructures by solvothermal method at different temperatures. It is revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) that the morphology of TiO2 can be effectively controlled as rose-like, chrysanthemum-like and sea-urchin-like only changing solvothermal temperature. BET surface area analysis confirms the presence of a mesoporous network in all the nanostructures, and shows high surface area at relatively high temperature. The photocatalytic activities of the photocatalysts are evaluated by the photodegradation of RhB under UV light irradiation. The TiO2 samples exhibit high activity on the photodegradation of RhB, which is higher than that of the commercial P25. The enhancement in photocatalytic performance can be attributed to the synergetic effect of the surface area, crystallinity, band gap and crystalline size.

Preferred Molecular Orientation of Coumarin 343 on TiO 2 Surfaces: Application to Dye-Sensitized Solar Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCree-Grey, Jonathan; Cole, Jacqueline M.; Evans, Peter J.

2015-07-21

The dye…TiO2 interfacial structure in working electrodes of dye-sensitized solar cells (DSCs) is known to influence its photovoltaic device performance. Despite this, direct and quantitative reports of such structure remain sparse. This case study presents the application of X-ray reflectometry to determine the preferred structural orientation and molecular packing of the organic dye, coumarin 343, adsorbed onto amorphous TiO2. Results show that the dye molecules are, on average, tilted by 61.1° relative to the TiO2 surface, and are separated from each other by 8.2 Å. These findings emulate the molecular packing arrangement of a monolayer of coumarin 343 within itsmore » crystal structure. This suggests that the dye adsorbs onto TiO2 in one of its lowest energy configurations, i.e. dye…TiO2 self assembly is driven more by thermodynamic rather than kinetic means. Complementary DSC device tests illustrate that this interfacial structure compromises photovoltaic performance, unless a suitably sized co-adsorbant is interdispersed between the coumarin 343 chromophores on the TiO2 surface.« less

Photocatalytic degradation of clofibric acid, carbamazepine and iomeprol using conglomerated TiO2 and activated carbon in aqueous suspension.

PubMed

Ziegmann, Markus; Frimmel, Fritz H

2010-01-01

The combination of powdered activated carbon (PAC) and TiO(2) has been tested for synergistic/antagonistic effects in the photocatalytic degradation of carbamazepine, clofibric acid and iomeprol. Synergistic effects are thought to be caused by rapid adsorption on the PAC surface followed by diffusion to the TiO(2) surface and photocatalytic degradation. The Freundlich constant K(F) was used for comparing the sorption properties of the three substances and it was found that K(F) for clofibric acid was 3 times lower than for carbamazepine and iomeprol, regardless of the kind of PAC used. A PAC with a distinct tendency to form conglomerates was selected so that a high percentage of the PAC surface was in direct proximity to the TiO(2) surface. The photocatalytic degradation of the pharmaceutically active compounds studied followed pseudo-first order kinetics. Synergistic effects only occurred for clofibric acid (factor 1.5) and an inverse relationship between adsorption affinity and synergistic effects was found. High affinity of the target substances to the PAC surface seemed to be counterproductive for the photocatalytic degradation.

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

PubMed Central

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

2014-01-01

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

Compressibility of porous TiO2 nanoparticle coating on paperboard

PubMed Central

2013-01-01

Compressibility of liquid flame spray-deposited porous TiO2 nanoparticle coating was studied on paperboard samples using a traditional calendering technique in which the paperboard is compressed between a metal and polymer roll. Surface superhydrophobicity is lost due to a smoothening effect when the number of successive calendering cycles is increased. Field emission scanning electron microscope surface and cross‒sectional images support the atomic force microscope roughness analysis that shows a significant compressibility of the deposited TiO2 nanoparticle coating with decrease in the surface roughness and nanoscale porosity under external pressure. PACS 61.46.-w; 68.08.Bc; 81.07.-b PMID:24160373

Nanocomposite coatings on biomedical grade stainless steel for improved corrosion resistance and biocompatibility.

PubMed

Nagarajan, Srinivasan; Mohana, Marimuthu; Sudhagar, Pitchaimuthu; Raman, Vedarajan; Nishimura, Toshiyasu; Kim, Sanghyo; Kang, Yong Soo; Rajendran, Nallaiyan

2012-10-24

The 316 L stainless steel is one of the most commonly available commercial implant materials with a few limitations in its ease of biocompatibility and long-standing performance. Hence, porous TiO(2)/ZrO(2) nanocomposite coated over 316 L stainless steels was studied for their enhanced performance in terms of its biocompatibility and corrosion resistance, following a sol-gel process via dip-coating technique. The surface composition and porosity texture was studied to be uniform on the substrate. Biocompatibility studies on the TiO(2)/ZrO(2) nanocomposite coatings were investigated by placing the coated substrate in a simulated body fluid (SBF). The immersion procedure resulted in the complete coverage of the TiO(2)/ZrO(2) nanocomposite (coated on the surface of 316 L stainless steel) with the growth of a one-dimensional (1D) rod-like carbonate-containing apatite. The TiO(2)/ZrO(2) nanocomposite coated specimens showed a higher corrosion resistance in the SBF solution with an enhanced biocompatibility, surpassing the performance of the pure oxide coatings. The cell viability of TiO(2)/ZrO(2) nanocomposite coated implant surface was examined under human dermal fibroblasts culture, and it was observed that the composite coating enhances the proliferation through effective cellular attachment compared to pristine 316 L SS surface.

Enhancement of solar hydrogen evolution from water by surface modification with CdS and TiO2 on porous CuInS2 photocathodes prepared by an electrodeposition-sulfurization method.

PubMed

Zhao, Jiao; Minegishi, Tsutomu; Zhang, Li; Zhong, Miao; Gunawan; Nakabayashi, Mamiko; Ma, Guijun; Hisatomi, Takashi; Katayama, Masao; Ikeda, Shigeru; Shibata, Naoya; Yamada, Taro; Domen, Kazunari

2014-10-27

Porous films of p-type CuInS2, prepared by sulfurization of electrodeposited metals, are surface-modified with thin layers of CdS and TiO2. This specific porous electrode evolved H2 from photoelectrochemical water reduction under simulated sunlight. Modification with thin n-type CdS and TiO2 layers significantly increased the cathodic photocurrent and onset potential through the formation of a p-n junction on the surface. The modified photocathodes showed a relatively high efficiency and stable H2 production under the present reaction conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of a power and photon energy of incident light on near-field etching properties

NASA Astrophysics Data System (ADS)

Yatsui, T.; Saito, H.; Nishioka, K.; Leuschel, B.; Soppera, O.; Nobusada, K.

2017-12-01

We developed a near-field etching technique for realizing an ultra-flat surfaces of various materials and structures. To elucidate the near-field etching properties, we have investigated the effects of power and the photon energy of the incident light. First, we established theoretically that an optical near-field with photon energy lower than the absorption edge of the molecules can induce molecular vibrations. We used nanodiamonds to study the power dependence of the near-field etching properties. From the topological changes of the nanodiamonds, we confirmed the linear-dependence of the etching volume with the incident power. Furthermore, we studied the photon energy dependence using TiO2 nanostriped structures, which revealed that a lower photon energy results in a lower etching rate.

Characterization and improved solar light activity of vanadium doped TiO2/diatomite hybrid catalysts.

PubMed

Wang, Bin; Zhang, Guangxin; Leng, Xue; Sun, Zhiming; Zheng, Shuilin

2015-03-21

V-doped TiO2/diatomite composite photocatalysts with different vanadium concentrations were synthesized by a modified sol-gel method. The diatomite was responsible for the well dispersion of TiO2 nanoparticles on the matrix and consequently inhibited the agglomeration. V-TiO2/diatomite hybrids showed red shift in TiO2 absorption edge with enhanced absorption intensity. Most importantly, the dopant energy levels were formed in the TiO2 bandgap due to V(4+) ions substituted to Ti(4+) sites. The 0.5% V-TiO2/diatomite photocatalyst displayed narrower bandgap (2.95 eV) compared to undoped sample (3.13 eV) and other doped samples (3.05 eV) with higher doping concentration. The photocatalytic activities of V doped TiO2/diatomite samples for the degradation of Rhodamine B under stimulated solar light illumination were significantly improved compared with the undoped sample. In our case, V(4+) ions incorporated in TiO2 lattice were responsible for increased visible-light absorption and electron transfer to oxygen molecules adsorbed on the surface of TiO2 to produce superoxide radicals ˙O2(-), while V(5+) species presented on the surface of TiO2 particles in the form of V2O5 contributed to e(-)-h(+) separation. In addition, due to the combination of diatomite as support, this hybrid photocatalyst could be separated from solution quickly by natural settlement and exhibited good reusability. Copyright © 2014 Elsevier B.V. All rights reserved.

The preparation and characterization of La doped TiO 2 nanoparticles and their photocatalytic activity

NASA Astrophysics Data System (ADS)

Liqiang, Jing; Xiaojun, Sun; Baifu, Xin; Baiqi, Wang; Weimin, Cai; Honggang, Fu

2004-10-01

In this paper, pure and La doped TiO2 nanoparticles with different La content were prepared by a sol-gel process using Ti (OC4H9)4 as raw material, and also were characterized by XRD, TG-DTA, TEM, XPS, DRS and Photoluminescence (PL) spectra. We mainly investigated the effects of calcining temperature and La content on the properties and the photocatalytic activity for degrading phenol of as-prepared TiO2 samples, and also discussed the relationships between PL spectra and photocatalytic activity as well as the mechanisms of La doping on TiO2 phase transformation. The results showed that La3+ did not enter into the crystal lattices of TiO2 and was uniformly dispersed onto TiO2 as the form of La2O3 particles with small size, which possibly made La dopant have a great inhibition on TiO2 phase transformation; La dopant did not give rise to a new PL signal, but it could improve the intensity of PL spectra with a appropriate La content, which was possibly attributed to the increase in the content of surface oxygen vacancies and defects after doping La; La doped TiO2 nanoparticles calcined at 600°C exhibited higher photocatalytic activity, indicating that 600°C was an appropriate calcination temperature. The order of photocatalytic activity of La doped TiO2 samples with different La content was as following: 1>1.5>3>0.5>5>0 mol%, which was the same as the order of their PL intensity, namely, the stronger the PL intensity, the higher the photocatalytic activity, demonstrating that there were certain relationships between PL spectra and photocatalytic activity. This could be explained by the points that PL spectra mainly resulted from surface oxygen vacancies and defects during the process of PL, while surface oxygen vacancies and defects could be favorable in capturing the photoinduced electrons during the process of photocatalytic reactions.

New evidence for hybrid acrylic/TiO2 films inducing bacterial inactivation under low intensity simulated sunlight.

PubMed

Bonnefond, Audrey; González, Edurne; Asua, Jose María; Leiza, Jose Ramon; Kiwi, John; Pulgarin, Cesar; Rtimi, Sami

2015-11-01

This study addresses the preparation and characterization of hybrid films prepared from Titanium dioxide (TiO2) Pickering stabilized acrylic polymeric dispersion as well as their bacterial inactivation efficiency under sunlight irradiation. Complete bacterial inactivation under low intensity simulated solar light irradiation (55 mW/cm(2)) was observed within 240 min for the films containing 10 weight based on monomers (wbm) % of TiO2, whereas 360 min were needed for the films containing 20 wbm% of TiO2. The hybrid films showed repetitive Escherichia coli (E. coli) inactivation under light irradiation. TiO2 released from the films surfaces was measured by inductively coupled plasma mass spectrometry (IPC-MS), obtaining values of ∼ 0.5 and 1 ppb/cm(2) for the films containing 10 wbm% and 20 wbm% of TiO2, respectively, far below the allowed cytotoxicity level for TiO2 (200 ppb). Transmission electron microscopy (TEM) of the hybrid films showed that TiO2 nanoparticles (NPs) were located at the polymer particle's surface forming a continuous inorganic network inside the film matrix. Atomic force microscopy (AFM) images showed differences in the TiO2 dispersion between the air-film and film-substrate interfaces. Films containing 10 wbm% of TiO2 had higher roughness (Rg) at both interfaces than the one containing 20 wbm% of TiO2 inducing an increase in the bacterial adhesion as well as the bacterial inactivation kinetics. The highly oxidative OH-radicals participating in the bacterial inactivation were determined by fluorescence. Copyright © 2015 Elsevier B.V. All rights reserved.

Enhancement of Power Conversion Efficiency of TiO₂-Based Dye-Sensitized Solar Cells on Various Acid Treatment.

PubMed

Sireesha, Pedaballi; Sun, Wei-Gang; Su, Chaochin; Kathirvel, Sasipriya; Lekphet, Woranan; Akula, Suri Babu; Li, Wen-Ri

2017-01-01

The surface modification of the TiO2 photoelectrode film is one of the promising ways to improve the photovoltaic performance of dye-sensitized solar cell (DSSC). In this work for the acid treatment of TiO2 powder, fluorine containing compounds such as trifluoroacetic acid was carried out to enhance the properties of photoanode. In order to investigate the effect of trifluoroacetyl group, the TiO2 nanopowders were also treated with different acids such as acetic acid, nitric acid, hydrochloric acid, and sulfuric acid and their properties were compared. The TiO2 powders treated with both acetic acid and TFA have possessed smooth surface morphologies as well as enhanced particle dispersions with reduced particle sizes. Photoelectrodes prepared for these two kinds of TiO2 powders accommodated high amounts of dye loading and exhibited excellent light transmittance (wavelength region of 400–600 nm). Electrochemical impedance spectroscopy analysis showed the smallest radius of the semicircle which indicates the enhanced rate of electron transport for the cell based photoelectrode with trifluoroacetic acid treated TiO2 powder. The solar cell from the untreated TiO2 film showed the power conversion efficiency of 8.86% and the highest efficiency of 9.51% was achieved by the cell fabricated from trifluoroacetic acid treated TiO2 film.

Effect of sulfate ions on the crystallization and photocatalytic activity of TiO2/diatomite composite photocatalyst

NASA Astrophysics Data System (ADS)

Zhang, Jinjun; Wang, Xiaoyan; Wang, Jimei; Wang, Jing; Ji, Zhijiang

2016-01-01

TiO2 nanoparticles were immobilized on diatomite by hydrolysis-deposition method using titanium tetrachloride as precursor. The effect of sulfate ions on the crystallization and photocatalytic activity of TiO2/diatomite composite photocatalyst was characterized by TG-DSC, XRD, BET surface area, SEM, FT-IR spectroscopy, XPS and UV-vis diffuse reflectance spectra. The results indicate that addition of a small amount of sulfate ions promotes the formation of anatase phase and inhibits the transformation from anatase to rutile. On the other hand, sulfate ions immobilized on the surface of TiO2/diatomite have strong affinity for electrons, capturing the photo-generated electrons, which hinders the recombination of electrons and holes.

The role of poly(methacrylic acid) conformation on dispersion behavior of nano TiO2 powder

NASA Astrophysics Data System (ADS)

Singh, Bimal P.; Nayak, Sasmita; Samal, Samata; Bhattacharjee, Sarama; Besra, Laxmidhar

2012-02-01

To exploit the advantages of nanoparticles for various applications, controlling the dispersion and agglomeration is of paramount importance. Agglomeration and dispersion behavior of titanium dioxide (TiO2) nanoparticles was investigated using electrokinetic and surface chemical properties. Nanoparticles are generally stabilized by the adsorption of a dispersant (polyelectrolyte) layer around the particle surface and in this connection ammonium salt of polymethacrylic acid (Darvan C) was used as dispersant to stabilize the suspension. The dosages of polyelectrolyte were optimized to get best dispersion stability by techniques namely particle charge detector (13.75 mg/g) and adsorption (14.57 mg/g). The surface charge of TiO2 particles changed significantly in presence of dispersant Darvan C and isoelectric point (iep) shifted significantly towards lower pH from 5.99 to 3.37. The shift in iep has been quantified in terms of free energy of interaction between the surface sites of TiO2 and the adsorbing dispersant Darvan C. Free energies of adsorption were calculated by electrokinetic data (-9.8 RT unit) and adsorption isotherms (-10.56 RT unit), which corroborated well. The adsorption isotherms are of typical Langmuir type and employed for calculation of free energy. The results indicated that adsorption occurs mainly through electrostatic interactions between the dispersant molecule and the TiO2 surface apart from hydrophobic interactions.

Amine functionalized TiO2-carbon nanotube composite: synthesis, characterization and application to glucose biosensing

NASA Astrophysics Data System (ADS)

Tasviri, Mahboubeh; Rafiee-Pour, Hossain-Ali; Ghourchian, Hedayatollah; Gholami, Mohammad Reza

2011-12-01

The synthesis of amine functionalized TiO2-coated multiwalled carbon nanotubes (NH2-TiO2-CNTs) using sol-gel method was investigated. The synthesized nanocomposite was characterized with XRD, FTIR spectroscopy, BET test and SEM imaging. The results demonstrated a unique nanostructure with no destruction of the CNTs' shape. In addition, the presence of amine groups on the composite surface was confirmed by FTIR. This nanocomposite was used for one-step immobilization of glucose oxidase (GOx) to sense glucose. The result of cyclic voltammetry showed a pair of well-defined and quasi-reversible peaks for direct electron transfer of GOx in the absence of glucose. Also, the result of electrochemical impedance spectroscopy indicated that GOx was successfully immobilized on the surface of NH2-TiO2-CNTs. Furthermore, good amperometric response showed that immobilized GOx on the NH2-TiO2-CNTs exhibits exceptional bioelectrocatalytic activity toward glucose oxidation.

Revealing the relationship between the photocatalytic property and structure characteristic of reduced TiO2 by hydrogen and carbon monoxide treatment.

PubMed

Liu, Yunpeng; Li, Yuhang; Yang, Siyuan; Lin, Yuan; Zuo, Jianliang; Liang, Hong; Peng, Feng

2018-06-04

The hydrogenation (reduction) has been considered as an effective method to improve the photocatalytic activity of TiO2, however, the underlying relationship between structure and photocatalytic performance has still not been adequately unveiled so far. Herein, to obtain insight into the effect of structure on photocatalytic activity, two types of reduced TiO2 were prepared by CO (CO-TiO2) and H2 (H-TiO2), respectively. For H-TiO2, Ti-H bonds and oxygen vacancies are formed on the surface of H-TiO2, resulting in a more disorder surface lattice. However, for CO-TiO2, the more Ti-OH bonds are formed on the surface and the more bulk oxygen vacancies are introduced, the disorder layer of CO-TiO2 is relatively thin owing to the most of surface vacancies repaired by Ti-OH bonds. Under the simulated solar irradiation, the photocatalytic H2 evolution rate of CO-TiO2 reaches 7.17 mmol g-1 h-1, which is 4.14 and 1.50 times those of TiO2 and H-TiO2, respectively. The photocatalytic degradation rate constant of methyl orange on CO-TiO2 is 2.45 and 6.39 times those on H-TiO2 and TiO2. The superior photocatalytic activity of CO-TiO2 is attributed to the effective separation and transfer of the photo-generated electron-hole pairs, due to the synergistic effects of oxygen vacancies and surface Ti-OH bonds. This study reveals the relation between the photocatalytic property and structure, and provides a new method to prepare highly active TiO2 for H2 production and environmental treatment. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In situ growth of hierarchical Al2O3 nanostructures onto TiO2 nanofibers surface: super-hydrophilicity, efficient oil/water separation and dye-removal.

PubMed

Fu, Wanlin; Dai, Yunqian; Tian, Jilan; Huang, Chaobo; Liu, Zhongche; Liu, Ken; Yin, Linzhi; Huang, Fangfang; Lu, Yingwei; Sun, Yueming

2018-08-24

Developing a facile strategy to synthesize template-free TiO 2 membrane with stable super-hydrophilic surface is still a daunting challenge. In this work, super-hydrophilicity (close to 0°) and underwater super-oleophobicity (165°) have been successfully demonstrated on a hierarchical Al 2 O 3 /TiO 2 membrane, which is prepared via a facile electrospinning method followed by simple calcination in air. The precisely-tuned Al 2 O 3 heterojunctions grew in situ and dispersed uniformly on the TiO 2 surface, resulting in an 'island in the sea' configuration. Such a unique feature allows not only achieving super-hydrophilicity by maximizing the surface roughness and enhancing the hydrogen bonding, but also improving the adsorption capacity toward different toxic dyes utilizing the abundant adsorption sites protected by the hierarchical nanostructure during sintering. The new Al 2 O 3 /TiO 2 nanofibrous membrane can serve as a novel filter for gravity driven oil/water separation along with dye removal, achieving 97.7% of oil/water separation efficiency and 98% of dye capture, thanks to their superb wettability and the sophisticated adsorptive performance. Our presented fabrication strategy can be extended to a wide range of ceramic materials and inspires their advanced applications in water purification under harsh liquid-phase environments.

Quantum chemical investigation on the role of Li adsorbed on anatase (101) surface nano-materials on the storage of molecular hydrogen.

PubMed

Srinivasadesikan, V; Raghunath, P; Lin, M C

2015-06-01

Lithiation of TiO2 has been shown to enhance the storage of hydrogen up to 5.6 wt% (Hu et al. J Am Chem Soc 128:11740-11741, 2006). The mechanism for the process is still unknown. In this work we have carried out a study on the adsorption and diffusion of Li atoms on the surface and migration into subsurface layers of anatase (101) by periodic density functional theory calculations implementing on-site Coulomb interactions (DFT+U). The model consists of 24 [TiO2] units with 11.097 × 7.655 Å(2) surface area. Adsorption energies have been calculated for different Li atoms (1-14) on the surface. A maximum of 13 Li atoms can be accommodated on the surface at two bridged O, Ti-O, and Ti atom adsorption sites, with 83 kcal mol(-1) adsorption energy for a single Li atom adsorbed between two bridged O atoms from where it can migrate into the subsurface layer with 27 kcal mol(-1) energy barrier. The predicted adsorption energies for H2 on the lithiated TiO2 (101) surface with 1-10 Li atoms revealed that the highest adsorption energies occurred on 1-Li, 5-Li, and 9-Li surfaces with 3.5, 4.4, and 7.6 kcal mol(-1), respectively. The values decrease rapidly with additional H2 co-adsorbed on the lithiated surfaces; the maximum H2 adsorption on the 9Li-TiO2(a) surface was estimated to be only 0.32 wt% under 100 atm H2 pressure at 77 K. The result of Bader charge analysis indicated that the reduction of Ti occurred depending on the Li atoms covered on the TiO2 surface.

Comparative study on the effect of H2 pre-adsorption on CO oxidation in O2-poor atmosphere over Au/TiO2 and TiO2: Temperature programmed surface reaction by a multiplexed mass spectrometer testing

NASA Astrophysics Data System (ADS)

Si, Ruiru; Liu, Junfeng; Zhang, Yujuan; Chen, Xun; Dai, Wenxin; Fu, Xianzhi

2016-11-01

The behaviors of H2 pre-adsorption on CO oxidation in an O2-poor stream containing a trace H2O over Au/TiO2 and TiO2 have been investigated by a temperature programmed surface reaction testing, respectively. It was found that the H2 pre-adsorption could keep CO oxidation without H2O consumption over Au/TiO2, but suppress CO oxidation over TiO2. The chemisorption testing showed that the H2 adsorption at Au/TiO2 could benefit to the formation of Ti-bonded hydroxyl species (Ti4+-OH), while the H2 adsorption at TiO2 would consume the Ti-bonded hydroxyl species and form the bridge hydroxyl species (Ti4+-OH-Ti4+). These results show that only the Ti-bonded hydroxyl species (not all kinds of hydroxyl species) could act as the active species of oxidizing CO. Furthermore, it is suggested that the dissociative hydrogen adsorbed at Au sites could activate the lattice oxygen of TiO2 to form the active Ti-bonded hydroxyl species (hydrogen spillover from Au to TiO2), which exhibit a strong reducibility than the H directly adsorbed at TiO2.

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

DOE PAGES

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

2014-10-20

We show how CO 2 adsorption on perfect and reduced anatase TiO 2 (101) surfaces can be substantially modified by the presence of surface Ag and Pt octamer clusters, using density functional theory calculations. Furthermore, we found that adsorption was affected even at sites where the adsorbate was not in direct contact with the octamer, which we attributed to charge donation to CO 2 from the Ag/Pt-modified surface, as well as an electrostatic competition between attractive (Ti–O) and repulsive (Ti–C) interactions. Additionally, TiO 2-supported Pt octamers offer key advantages that could be leveraged for CO 2 photoreduction, including providing additionalmore » stable adsorption sites for bent CO 2 species and facilitating charge transfer to aid in CO 2– anion formation. Electronic structure analysis suggests these factors arise primarily from the hybridization of the bonding molecular orbitals of CO 2 with d orbitals of the Pt atoms. Our results show that, for adsorption on TiO 2-supported Pt octamers, the O–C–O bending and C–O asymmetric stretching frequencies can be used as reliable indicators of the presence of the CO 2– anion intermediate as well as to distinguish unique adsorption geometries or sites. Finally, we suggest a possible pathway for subsequent CO 2 dissociation to CO at the surface of a reduced anatase TiO 2 (101)-supported Pt octamer, which has a computed energy barrier of 1.01 eV.« less

Food grade titanium dioxide disrupts intestinal brush border microvilli in vitro independent of sedimentation.

PubMed

Faust, James J; Doudrick, Kyle; Yang, Yu; Westerhoff, Paul; Capco, David G

2014-06-01

Bulk- and nano-scale titanium dioxide (TiO2) has found use in human food products for controlling color, texture, and moisture. Once ingested, and because of their small size, nano-scale TiO2 can interact with a number of epithelia that line the human gastrointestinal tract. One such epithelium responsible for nutrient absorption is the small intestine, whose constituent cells contain microvilli to increase the total surface area of the gut. Using a combination of scanning and transmission electron microscopy it was found that food grade TiO2 (E171 food additive coded) included ∼25% of the TiO2 as nanoparticles (NPs; <100 nm), and disrupted the normal organization of the microvilli as a consequence of TiO2 sedimentation. It was found that TiO2 isolated from the candy coating of chewing gum and a commercially available TiO2 food grade additive samples were of the anatase crystal structure. Exposure to food grade TiO2 additives, containing nanoparticles, at the lowest concentration tested within this experimental paradigm to date at 350 ng/mL (i.e., 100 ng/cm(2) cell surface area) resulted in disruption of the brush border. Through the use of two independent techniques to remove the effects of gravity, and subsequent TiO2 sedimentation, it was found that disruption of the microvilli was independent of sedimentation. These data indicate that food grade TiO2 exposure resulted in the loss of microvilli from the Caco-2BBe1 cell system due to a biological response, and not simply a physical artifact of in vitro exposure.

Approach to Multifunctional Device Platform with Epitaxial Graphene on Transition Metal Oxide (Postprint)

DTIC Science & Technology

2015-09-23

with a metal oxide ( TiO2 ). Our novel direct synthesis of graphene/ TiO2 heterostructure is achieved by C60 deposition on transition Ti metal surface...of TiO2 and C 2p orbitals in the conduction band of graphene enabled by Coulomb interactions at the interface. In addition, this heterostructure...provides a platform for realization of bottom gated graphene field effect devices with graphene and TiO2 playing the roles of channel and gate dielectric

Liquid-phase deposition of TiO2 nanoparticles on core-shell Fe3O4@SiO2 spheres: preparation, characterization, and photocatalytic activity

NASA Astrophysics Data System (ADS)

Ma, Jian-Qi; Guo, Shao-Bo; Guo, Xiao-Hua; Ge, Hong-Guang

2015-07-01

To prevent and avoid magnetic loss caused by magnetite core phase transition involving in high-temperature crystallization of amorphous sol-gel TiO2, core-shell Fe3O4@SiO2@TiO2 composite spheres were synthesized via non-thermal process of TiO2. First, core-shell Fe3O4@SiO2 particles were synthesized through a solvothermal method followed by a sol-gel process. Second, anatase TiO2 nanoparticles (NPs) were directly coated on Fe3O4@SiO2 surface by liquid-phase deposition method, which uses (NH4)2TiF6 as Ti source for TiO2 and H3BO3 as scavenger for F- ions at 50 °C. The morphology, structure, composition, and magnetism of the resulting composites were characterized and their photocatalytic activities were also evaluated. The results demonstrate that TiO2 NPs with an average size of 6-8 nm were uniformly deposited on the Fe3O4@SiO2 surface. Magnetic hysteresis curves indicate that the composite spheres exhibit superparamagnetic characteristics with a magnetic saturation of 32.5 emu/g at room temperature. The magnetic TiO2 composites show high photocatalytic performance and can be recycled five times by magnetic separation without major loss of activity, which meant that they can be used as efficient and conveniently renewable photocatalyst.

2D layered insulator hexagonal boron nitride enabled surface passivation in dye sensitized solar cells.

PubMed

Shanmugam, Mariyappan; Jacobs-Gedrim, Robin; Durcan, Chris; Yu, Bin

2013-11-21

A two-dimensional layered insulator, hexagonal boron nitride (h-BN), is demonstrated as a new class of surface passivation materials in dye-sensitized solar cells (DSSCs) to reduce interfacial carrier recombination. We observe ~57% enhancement in the photo-conversion efficiency of the DSSC utilizing h-BN coated semiconductor TiO2 as compared with the device without surface passivation. The h-BN coated TiO2 is characterized by Raman spectroscopy to confirm the presence of highly crystalline, mixed monolayer/few-layer h-BN nanoflakes on the surface of TiO2. The passivation helps to minimize electron-hole recombination at the TiO2/dye/electrolyte interfaces. The DSSC with h-BN passivation exhibits significantly lower dark saturation current in the low forward bias region and higher saturation in the high forward bias region, respectively, suggesting that the interface quality is largely improved without impeding carrier transport at the material interface. The experimental results reveal that the emerging 2D layered insulator could be used for effective surface passivation in solar cell applications attributed to desirable material features such as high crystallinity and self-terminated/dangling-bond-free atomic planes as compared with high-k thin-film dielectrics.

Synthesis and characterization of Ag-doped TiO2 nanotubes on Ti-6Al-4V and Ti-6Al-7Nb alloy

NASA Astrophysics Data System (ADS)

Ulfah, Ika Maria; Bachtiar, Boy M.; Murnandityas, Arnita Rut; Slamet

2018-05-01

The present paper is focused on comparative behavior of nanotubes growth on Ti-6Al-4V and Ti-6Al-7Nb alloy using electrochemical anodization method. These alloys were anodized in electrolytes solution containing glycerol, water and 0.5wt.% of NH4F. Silver-doped TiO2 nanotubes were synthesized using photo-assisted deposition (PAD) at various Ag loading concentration in 0.05 M, 0.10 M, and 0.15 M. The phase composition and morphological characteristics were investigated by XRD and FESEM/EDX, respectively. The surface wettability was measured by contact angle meter. The results showed that TiO2 nanotubes can be grown on these surface alloys. XRD profiles revealed crystal formation of anatase, rutile and Ag on these surface alloys. According to FESEM images, the average nanotube diameter of Ti-6Al-4V alloy and Ti-6Al-7Nb alloy are 134 nm and 120 nm, respectively. EDX-Mapping analysis showed that Ag desposited over surface of TiO2 nanotubes. The surface wettability indicated hydrophilicity properties on Ti-4Al-4V alloy and Ti-6Al-7Nb alloy surface. This study may contribute to the development of silver-doped TiO2 nanotubes on Ti-6Al-4V alloy and Ti-6Al-7Nb alloy can be considered in various photocatalytic applications such as biomedical devicesdue to photocatalytic mechanism and antibacterial ability.

Growth of beta-MnO2 Films on TiO2(110) by Oxygen-Plasma-Assisted Molecular Beam Epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chambers, Scott A.; Liang, Yong

Discusses the essential need to understand the heterogeneous chemistry of mineral surfaces at a molecular level for accurate modeling of surface complexion processes in natural environments. Describes the first MBE growth and characterization of ultrathin films of B-MnO2 on TiO2 (110).

Visible-light induced anti-bacterial and self-cleaning waterborne polyacrylic coating modified with TiO2/polypyrrole nanocomposite; preparation and characterization

NASA Astrophysics Data System (ADS)

Nosrati, Rahimeh; Olad, Ali; Maryami, Fatemeh

2018-07-01

Nowadays, self-cleaning technology is used in various industries to decreasing the time, energy consumption and costs of surface servicing as well as the increasing of surface durability. Self-cleaning and anti-bacterial coatings can be made by the addition of suitable additives to a polymer matrix with good properties. In the present research, TiO2/polypyrrole nanocomposites were prepared in different TiO2 to polypyrrole weight ratios and used in various percent as an additive in waterborne commercial grade polyacrylic latex. Characterization and evaluation of structural and morphological features of nanocomposites and coatings were performed by FTIR, XRD, UV-Vis and FESEM techniques. By the addition of prepared nanocomposites as an additive to the polyacrylic matrix, the hydrophilic, water resistant, anti-bacterial, and photocatalytic coatings were prepared. The TiO2 to polypyrrole weight ratio of TiO2/polypyrrole nanocomposites and the percent of nanocomposite additive in the polymeric matrix were optimized. According to the results, the coating containing 2% and 3% of TiO2/polypyrrole nanocomposite with TiO2 to polypyrrole weight ratio of 100:10 are proposed as the best coating formulations in the formulations examined in this work, due to their good properties in the most of experiments.

Phase quantification by X-ray photoemission valence band analysis applied to mixed phase TiO2 powders

NASA Astrophysics Data System (ADS)

Breeson, Andrew C.; Sankar, Gopinathan; Goh, Gregory K. L.; Palgrave, Robert G.

2017-11-01

A method of quantitative phase analysis using valence band X-ray photoelectron spectra is presented and applied to the analysis of TiO2 anatase-rutile mixtures. The valence band spectra of pure TiO2 polymorphs were measured, and these spectral shapes used to fit valence band spectra from mixed phase samples. Given the surface sensitive nature of the technique, this yields a surface phase fraction. Mixed phase samples were prepared from high and low surface area anatase and rutile powders. In the samples studied here, the surface phase fraction of anatase was found to be linearly correlated with photocatalytic activity of the mixed phase samples, even for samples with very different anatase and rutile surface areas. We apply this method to determine the surface phase fraction of P25 powder. This method may be applied to other systems where a surface phase fraction is an important characteristic.

Growth of TiO2 nanofibers on FTO substrates and their application in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Suryana, R.; Rahmawati, L. R.; Triyana, K.

2016-11-01

Growth of TiO2 nanofibers on fluorine-doped tin oxide (FTO) substrates have been performed using electrospinning method. Homogenous TiO2 solution as nanofibers material was prepared with titanium tetraisopropoxide (TTIP), ethanol, acetic acid and polyvinyl pyrrolidone (PVP) which was stirred for 24 h. TiO2 solution was loaded into the syringe pump. Electrospun voltage was operated under 15 kV with optimum distance between syringe tip and collector was 15 cm. FTO substrates were attached on the collector surface. Electrospinning coating time was varied at 15 min, 30 min, 45 min, and 60 min. Then TiO2 nanofibers layer was annealed at temperature of 450° C for 3 h. X-ray diffraction spectrum of TiO2 nanofibers showed major anatase peaks at 25.3°, 48.0° and 37.8° correlating crystal orientation of (101), (200), and (004), respectively while only one rutile peak at 27.5°(110). TiO2 nanofibers diameter was measured using atomic force microscopy (AFM). TiO2 nanofibers have diameter in range of 100-1000 nm. The obtained-TiO2 nanofibers were applied in dye-sensitized solar cell (DSSC) with beta-carotene as dye, carbon as catalyst, and I-/I3- redox couple as electrolyte. DSSC performance was analyzed from I-V characterization. Growth of TiO2 nanofibers at electrospinning time for 45 min has highest efficiency that is 0.016%. It is considered that TiO2 nanofibers at electrospinning time for 45 min can produce optimum thickness so that it is speculated many dyes adsorb on the nanofiber surfaces and many electrons diffuse toward the electrodes.

Apatite-forming PEEK with TiO2 surface layer coating.

PubMed

Kizuki, Takashi; Matsushita, Tomiharu; Kokubo, Tadashi

2015-01-01

Polyetheretherketone (PEEK) is widely used in orthopedic implants, such as spinal fusion devices, because of its moderate elastic modulus, as well as relatively high mechanical strength. However, it does not bond to living bone, and hence it needs autograft to be fixed to the bone. In this study, we attempted to add bone-bonding properties to PEEK by coating with TiO2 synthesized by the sol-gel process. When a TiO2 sol solution consisting of titanium isopropoxide, water, ethanol, and nitric acid was deposited on a PEEK substrate without any pretreatment, the formed TiO2 gel layer was easily peeled off after subsequent treatments. However, when the same solution was deposited on PEEK that was preliminarily subjected to UV or O2 plasma treatment, the deposited TiO2 gel layer strongly adhered to the substrate even after subsequent treatments. The strong adhesion was attributed to the interaction among the C-O, C=O, and O-C=O groups on the PEEK owing to the UV or O2 plasma treatment and the Ti-O bond of the TiO2 gel. Apatite did not form on the as-formed TiO2 gel layer in a simulated body fluid (SBF) even within 3 days; however, apatite formed after soaking in 0.1 M HCl solution at 80 °C for 24 h. This apatite formation was attributed to positive surface charge of the TiO2 gel layer induced by the acid treatment. The PEEK with the TiO2 gel layer coating formed by the proposed process is expected to bond to living bone, because a positively charged titanium oxide which facilitates the formation of apatite in SBF within a short period is known to bond to living bone.

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

EPA Science Inventory

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...

Calcination Conditions on the Properties of Porous TiO2 Film

NASA Astrophysics Data System (ADS)

Zhang, Wenjie; Pei, Xiaobei; Bai, Jiawei; He, Hongbo

2014-03-01

Porous TiO2 films were deposited on SiO2 precoated glass-slides by sol-gel method using PEG1000 as template. The strongest XRD diffraction peak at 2θ = 25.3° is attributed to [101] plane of anatase TiO2 in the film. The increases of calcination temperature and time lead to stronger diffraction peak intensity. High transmittance and blue shift of light absorption edge are the properties of the film prepared at high calcination temperature. The average pore size of the films increases with the increasing calcination temperature as the result of TiO2 crystalline particles growing up and aggregation, accompanied with higher specific surface area. Photocatalytic activity of porous TiO2 films increases with the increasing calcination temperature. The light absorption edge of the films slightly moves to longer wavelength region along with the increasing calcination time. The mesoporous film calcinated at 500 °C for 2 h has the highest transmittance, the maximum surface area, and the maximum total pore volume. Consequently, the optimum degradation activity is achieved on the porous TiO2 film calcinated at 500 °C for 2 h.

An external template-free route to uniform semiconducting hollow mesospheres and their use in photocatalysis

NASA Astrophysics Data System (ADS)

Yang, Di; Wang, Mengye; Zou, Bin; Zhang, Gu Ling; Lin, Zhiqun

2015-07-01

Solid amorphous TiO2 mesospheres were synthesized by controlled hydrolysis of Ti-containing precursors. Subsequently, solid TiO2 mesospheres were exploited as scaffolds and subjected to a one-step external template-free hydrothermal treatment, yielding intriguing hollow anatase TiO2 mesospheres. The synthetic protocol was optimized by investigating the effect of buffer reagents and fluoride ions on the formation of hollow TiO2 spheres. The diameter of hollow mesospheres, ranging from 308 to 760 nm, can be readily tailored by varying the precursor concentration. The average thickness of a shell composed of TiO2 nanocrystals was approximately 40 nm with a mean crystal size of 12.4-20.0 nm. Such hollow TiO2 mesospheres possessed a large surface area and were employed in photocatalytic degradation of methylene blue under UV irradiation. Interestingly, the synthetic conditions were found to exert a significant influence on the photocatalytic ability of hollow TiO2 mesospheres. The correlation between the degradation ability of hollow TiO2 mesospheres and the precursor concentration as well as the hydrothermal time was scrutinized. The optimal photocatalytic performance of hollow TiO2 mesospheres was identified.Solid amorphous TiO2 mesospheres were synthesized by controlled hydrolysis of Ti-containing precursors. Subsequently, solid TiO2 mesospheres were exploited as scaffolds and subjected to a one-step external template-free hydrothermal treatment, yielding intriguing hollow anatase TiO2 mesospheres. The synthetic protocol was optimized by investigating the effect of buffer reagents and fluoride ions on the formation of hollow TiO2 spheres. The diameter of hollow mesospheres, ranging from 308 to 760 nm, can be readily tailored by varying the precursor concentration. The average thickness of a shell composed of TiO2 nanocrystals was approximately 40 nm with a mean crystal size of 12.4-20.0 nm. Such hollow TiO2 mesospheres possessed a large surface area and were employed in photocatalytic degradation of methylene blue under UV irradiation. Interestingly, the synthetic conditions were found to exert a significant influence on the photocatalytic ability of hollow TiO2 mesospheres. The correlation between the degradation ability of hollow TiO2 mesospheres and the precursor concentration as well as the hydrothermal time was scrutinized. The optimal photocatalytic performance of hollow TiO2 mesospheres was identified. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02685g

Potassium and water coadsorption on TiO 2(110): OH-induced anchoring of potassium and the generation of single-site catalysts

DOE PAGES

Grinter, David C.; R. Remesal, Elena; Luo, Si; ...

2016-09-15

Potassium deposition on TiO 2(110) results in reduction of the substrate and formation of loosely bound potassium species that can move easily on the oxide surface to promote catalytic activity. The results of density functional calculations predict a large adsorption energy (~3.2 eV) with a small barrier (~0.25 eV) for diffusion on the oxide surface. In scanning tunneling microscopy images, the adsorbed alkali atoms lose their mobility when in contact with surface OH groups. Furthermore, K adatoms facilitate the dissociation of water on the titania surface. Lastly, the K–(OH) species generated are good sites for the binding of gold clustersmore » on the TiO 2(110) surface, producing Au/K/TiO 2(110) systems with high activity for the water–gas shift.« less

A highly sensitive biological detection substrate based on TiO2 nanowires supporting gold nanoparticles

NASA Astrophysics Data System (ADS)

Zeng, Yuan; Tan, Hai-jun; Cheng, Xiu-Lan; Chen, Rui; Wang, Ying

2011-12-01

Surface enhanced Raman scattering (SERS) has attracted widespread concern in the field of bioassay because it can enhance normally weak Raman signal by several orders of magnitude and facilitate the highly sensitive detection of molecules. Conventional SERS substrates are prepared by placing metal nanoparticles on a planar surface. Here we show a unique SERS substrate stacked by disordered TiO2 nanowires (TiO2-NWs) supportig gold nanocrystals. The structure can be easily fabricated by chemical synthesis at low cost. The COMSOL model simulation shows the designed SERS substrate is capable of output high Local Field Enhancement (LFE) in the Near Infrared region (NIR) that is the optimal wavelength in bio-detection because of both the unique coupling enhancement effect amony nearby Au nanocrystals on TiO2-NWs and the Suface Plasmon Resonance (SPR) effect of TiO2 -NWs. The as-prepared transparent and freestanding SERS substrate is capable of detecting extremely low concentration R6G molecular, showing much higher Raman signal because of the extremely large surface area and the uniqueTiO2-NWs self-assemblied by Au nanocrystals. These results provide a new approach to ultrasensitive bioassay device.

Photocatalytic properties and selective antimicrobial activity of TiO2(Eu)/CuO nanocomposite

NASA Astrophysics Data System (ADS)

Michal, Robert; Dworniczek, Ewa; Caplovicova, Maria; Monfort, Olivier; Lianos, Panagiotis; Caplovic, Lubomir; Plesch, Gustav

2016-05-01

TiO2(Eu)/CuO nanocomposites were prepared by precipitation method. The anatase nanocrystallites with a size of 26 nm exhibited well crystallized and characteristical dipyramidal morphology and {1 0 1} and {0 0 1} faceting. Transmission electron microscopy photographs with atomic resolution showed that the Eu(III) dopants were bounded on surface of titania. In the composites, the CuO nanocrystals exhibiting a monoclinic tenorite structure with a size in the range from 2 to 5 nm were grafted to the surface of titania. The influence of copper(II) oxide led to distinct selectivity in the photocatalytic and antimicrobial properties of the investigated TiO2(Eu)/CuO nanocomposites. While the presence of CuO nanocrystals strongly increased the photocatalytic production of hydrogen by ethanol reforming, it decreased the activity in photoinduced total mineralization of phenol comparing with non-modified TiO2(Eu). In investigated TiO2(Eu)/CuO powders, the photoinduced antimicrobial activity against membranes of Enterococcus species was influenced by the selective binding of CuO to the surface of the microorganism leading to distinct selectivity in their action. The activity against Enterococcus faecalis was higher than against Enterococcus faecium.

Hydroxyapatite-TiO2-SiO2-Coated 316L Stainless Steel for Biomedical Application

NASA Astrophysics Data System (ADS)

Sidane, Djahida; Khireddine, Hafit; Bir, Fatima; Yala, Sabeha; Montagne, Alex; Chicot, Didier

2017-07-01

This study investigated the effectiveness of titania (TiO2) as a reinforcing phase in the hydroxyapatite (HAP) coating and silica (SiO2) single layer as a bond coat between the TiO2-reinforced hydroxyapatite (TiO2/HAP) top layer and 316L stainless steel (316L SS) substrate on the corrosion resistance and mechanical properties of the underlying 316L SS metallic implant. Single layer of SiO2 film was first deposited on 316L SS substrate and studied separately. Water contact angle measurements, X-ray photoelectron spectroscopy, and Fourier transform infrared spectrophotometer analysis were used to evaluate the hydroxyl group reactivity at the SiO2 outer surface. The microstructural and morphological results showed that the reinforcement of HAP coating with TiO2 and SiO2 reduced the crystallite size and the roughness surface. Indeed, the deposition of 50 vol pct TiO2-reinforced hydroxyapatite layer enhanced the hardness and the elastic modulus of the HAP coating, and the introduction of SiO2 inner layer on the surface of the 316L SS allowed the improvement of the bonding strength and the corrosion resistance as confirmed by scratch studies, nanoindentation, and cyclic voltammetry tests.

Potential Impacts from Using Photoactive Roads as AN Air Quality Mitigation Strategy

NASA Astrophysics Data System (ADS)

Toro, C.; Jobson, B. T.; Shen, S.; Chung, S. H.; Haselbach, L.

2013-12-01

Mobile sources are major contributors to photochemical air pollution in urban areas. It has been proposed that the use of TiO2 coated roadways ('photoactive roads') could be an effective approach to reduce mobile source emissions by oxidizing NOx and VOC emissions at the roadway surface. However, studies have shown that formation of HONO and aldehydes can occur from some TiO2 treated surfaces during the photocatalytic oxidation of NOx and VOC, respectively. By changing the NOx-to-VOC ratio and generating photolabile HOx radical precursors, photoactive roads may enhance ozone formation rates in urban areas. In this work we present results that quantify NOx and VOC loss rates onto TiO2 treated asphalt and concrete samples, as well as HONO and aldehydes yields that result from the photocatalytic process. The treatment used a commercially available product. These objectives are relevant considering that the quantification of pollutant loss rates and yields of byproducts have not been determined for asphalt and that in the US more than 90% of the roadway surface is made of this material. Surface reaction probabilities (γ) and byproduct yields were determined using a CSTR photochemical chamber under varying conditions of water vapor and UV-A light intensity. Our results indicate that asphalt surfaces have a significantly higher molar yield of HONO compared to concrete surfaces with similar TiO2 loading. Concrete surfaces have reaction probabilities with NO one order of magnitude higher than asphalt samples. Fresh asphalt samples showed negligible photocatalytic activity, presumably due to absorption of TiO2 into the bitumen substrate. Laboratory-prepared asphalt samples with a higher degree of exposed aggregates showed increased HONO molar yields when compared to real-road asphalt samples, whose HONO molar yield was ~1%. Preliminary results for aldehydes formation showed similar molar yields between aged asphalt and concrete, even though aged asphalt samples had twice the TiO2 loading than concrete samples.

Efficiency Enhancement of Nanotextured Black Silicon Solar Cells Using Al2O3/TiO2 Dual-Layer Passivation Stack Prepared by Atomic Layer Deposition.

PubMed

Wang, Wei-Cheng; Tsai, Meng-Chen; Yang, Jason; Hsu, Chuck; Chen, Miin-Jang

2015-05-20

In this study, efficient nanotextured black silicon (NBSi) solar cells composed of silicon nanowire arrays and an Al2O3/TiO2 dual-layer passivation stack on the n(+) emitter were fabricated. The highly conformal Al2O3 and TiO2 surface passivation layers were deposited on the high-aspect-ratio surface of the NBSi wafers using atomic layer deposition. Instead of the single Al2O3 passivation layer with a negative oxide charge density, the Al2O3/TiO2 dual-layer passivation stack treated with forming gas annealing provides a high positive oxide charge density and a low interfacial state density, which are essential for the effective field-effect and chemical passivation of the n(+) emitter. In addition, the Al2O3/TiO2 dual-layer passivation stack suppresses the total reflectance over a broad range of wavelengths (400-1000 nm). Therefore, with the Al2O3/TiO2 dual-layer passivation stack, the short-circuit current density and efficiency of the NBSi solar cell were increased by 11% and 20%, respectively. In conclusion, a high efficiency of 18.5% was achieved with the NBSi solar cells by using the n(+)-emitter/p-base structure passivated with the Al2O3/TiO2 stack.

SnO 2 nanowires decorated with forsythia-like TiO 2 for photoenergy conversion

DOE PAGES

Park, Ik Jae; Park, Sangbaek; Kim, Dong Hoe; ...

2017-05-17

Here, we report forsythia-like TiO 2-decorated SnO 2 nanowires on fluorine-doped SnO 2 electrode as a photoelectrode of dye-sensitized solar cells. When SnO 2 nanowires grown via vapor-liquid-solid reaction were soaked in TiCl 4 solution, leaf-shaped rutile TiO 2 was grown onto the surface of the nanowires. The TiO 2 decoration increases the short circuit current (J sc), open circuit voltage (V oc) and fill factor (FF) of dye-sensitized solar cells. Further, electron lifetime increased by employing an atomic-layer-deposited TiO 2 nanoshell between the TiO 2 leaves and the SnO 2 nanowire, due to preventing charge recombination at the nanowire/electrolytemore » interface.« less

SnO 2 nanowires decorated with forsythia-like TiO 2 for photoenergy conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Ik Jae; Park, Sangbaek; Kim, Dong Hoe

Here, we report forsythia-like TiO 2-decorated SnO 2 nanowires on fluorine-doped SnO 2 electrode as a photoelectrode of dye-sensitized solar cells. When SnO 2 nanowires grown via vapor-liquid-solid reaction were soaked in TiCl 4 solution, leaf-shaped rutile TiO 2 was grown onto the surface of the nanowires. The TiO 2 decoration increases the short circuit current (J sc), open circuit voltage (V oc) and fill factor (FF) of dye-sensitized solar cells. Further, electron lifetime increased by employing an atomic-layer-deposited TiO 2 nanoshell between the TiO 2 leaves and the SnO 2 nanowire, due to preventing charge recombination at the nanowire/electrolytemore » interface.« less

Ultraviolet and Visible Photochemistry of Methanol at 3D Mesoporous Networks: TiO2 and Au-TiO2

DTIC Science & Technology

2013-05-23

methanol photochemistry at three-dimensionally (3D) networked aerogels of TiO2 or Au–TiO2 reveals that incorporated Au nanoparticles strongly sensitize...the oxide nanoarchitecture to visible light. Methanol dissociatively adsorbs at the surfaces of TiO2 and Au–TiO2 aerogels under dark, high-vacuum...photochemistry at three-dimensionally (3D) networked aerogels of TiO2 or Au–TiO2 reveals that incorporated Au nanoparticles strongly sensitize the oxide

Bi-functional anodic TiO2 oxide: Nanotubes for wettability control and barrier oxide for uniform coloring

NASA Astrophysics Data System (ADS)

Kim, Sunkyu; Jung, Minkyeong; Kim, Moonsu; Choi, Jinsub

2017-06-01

A uniformly colored TiO2, on which the surface is functionalized with nanotubes to control wettability, was prepared by a two-step anodization; the first anodization was carried out to prepare nanotubes for a super-hydrophilic or -hydrophobic surface and the second anodization was performed to fabricate a thin film barrier oxide to ensure uniform coloring. The effect of the nanotubes on barrier oxide coloring was examined by spectrophotometry and UV-vis-IR spectroscopy. We found four different regimes governing the color changes in terms of anodization voltage, indicating that the color of the duplex TiO2 was primarily determined by the thickness of the barrier oxide layer formed during the second anodization step. The surface wettability, as confirmed by the water contact angle, revealed that the single barrier TiO2 yielded 74.6° ± 2.1, whereas the nanotubes on the barrier oxide imparted super-hydrophilic properties as a result of increasing surface roughness as well as imparting a higher hydrophobicity after organic acid treatment.

Phenol degradation by TiO2 photocatalysts combined with different pulsed discharge systems.

PubMed

Zhang, Yi; Lu, Jiani; Wang, Xiaoping; Xin, Qing; Cong, Yanqing; Wang, Qi; Li, Chunjuan

2013-11-01

Films of TiO2 nanotubes distributed over the inner surface of a discharge reactor cylinder (CTD) or adhered to a stainless steel electrode surface (PTD) in a discharge reactor were compared with a single-discharge (SD) system to investigate their efficiencies in phenol degradation. Morphology studies indicated that the TiO2 film was destroyed in the PTD system, but that there was no change in the CTD system after discharge. X-ray diffraction results revealed that the anatase phase of the original sample was preserved in the CTD system, but that an anatase-to-rutile phase transformation occurred in the PTD system after discharge. The highest efficiencies of phenol degradation and total organic carbon (TOC) mineralization were observed in the CTD system, and there was no decrease in phenol degradation efficiency upon reuse of a TiO2 film, indicating high catalysis activity and stability of the TiO2 photocatalysts in the combined treatment. TiO2 photocatalysts favored the formation of hydrogen peroxide and disfavored the formation of ozone. A greater degree of oxidation of intermediates and higher energy efficiency in phenol oxidation were observed with the TiO2-plasma systems, especially in the CTD system, compared to those with the SD system. Copyright © 2013 Elsevier Inc. All rights reserved.

Enhanced osteogenic activity and anti-inflammatory properties of Lenti-BMP-2-loaded TiO₂ nanotube layers fabricated by lyophilization following trehalose addition.

PubMed

Zhang, Xiaochen; Zhang, Zhiyuan; Shen, Gang; Zhao, Jun

2016-01-01

To enhance biocompatibility and osseointegration between titanium implants and surrounding bone tissue, numerous efforts have been made to modify the surface topography and composition of Ti implants. In this paper, Lenti-BMP-2-loaded TiO2 nanotube coatings were fabricated by lyophilization in the presence of trehalose to functionalize the surface. We characterized TiO2 nanotube layers in terms of the following: surface morphology; Lenti-BMP-2 and trehalose release; their ability to induce osteogenesis, proliferation, and anti-inflammation in vitro; and osseointegration in vivo. The anodized TiO2 nanotube surfaces exhibited an amorphous glassy matrix perpendicular to the Ti surface. Both Lenti-BMP-2 and trehalose showed sustained release over the course of 8 days. Results from real-time quantitative polymerase chain reaction studies demonstrated that lyophilized Lenti-BMP-2/TiO2 nanotubes constructed with trehalose (Lyo-Tre-Lenti-BMP-2) significantly promoted osteogenic differentiation of bone marrow stromal cells but not their proliferation. In addition, Lyo-Tre-Lenti-BMP-2 nanotubes effectively inhibited lipopolysaccharide-induced interleukin-1β and tumor necrosis factor-α production. In vivo, the formulation also promoted osseointegration. This study presents a promising new method for surface-modifying biomedical Ti-based implants to simultaneously enhance their osteogenic potential and anti-inflammatory properties, which can better satisfy clinical needs.

Nanocrystals in compression: unexpected structural phase transition and amorphization due to surface impurities.

PubMed

Liu, Gang; Kong, Lingping; Yan, Jinyuan; Liu, Zhenxian; Zhang, Hengzhong; Lei, Pei; Xu, Tao; Mao, Ho-Kwang; Chen, Bin

2016-06-09

We report an unprecedented surface doping-driven anomaly in the compression behaviors of nanocrystals demonstrating that the change of surface chemistry can lead to an interior bulk structure change in nanoparticles. In the synchrotron-based X-ray diffraction experiments, titania nanocrystals with low concentration yttrium dopants at the surface are found to be less compressible than undoped titania nanocrystals. More surprisingly, an unexpected TiO2(ii) phase (α-PbO2 type) is induced and obvious anisotropy is observed in the compression of yttrium-doped TiO2, in sharp contrast to the compression behavior of undoped TiO2. In addition, the undoped brookite nanocrystals remain with the same structure up to 30 GPa, whereas the yttrium-doped brookite amorphizes above 20 GPa. The abnormal structural evolution observed in yttrium-doped TiO2 does not agree with the reported phase stability of nano titania polymorphs, thus suggesting that the physical properties of the interior of nanocrystals can be controlled by the surface, providing an unconventional and new degree of freedom in search for nanocrystals with novel tunable properties that can trigger applications in multiple areas of industry and provoke more related basic science research.

One-pot engineering TiO2/graphene interface for enhanced adsorption and photocatalytic degradation of multiple organics.

PubMed

Song, Jianhua; Ling, Yun; Xie, Yu; Liu, Lianjun; Zhu, Huihua

2018-06-13

It is challenging to design a multifunctional structure or composite for simultaneously adsorb and photocatalytic degrade organic pollutants in water. Towards this goal, this work innovatively engineered interfacial sites between TiO2 particles and reduced graphene oxide (RGO) sheets by employing in situ one-pot one-step solvothermal method. The interface was associated with the content of RGO, solvothermal time and solvent ratio of n-pentanol to n-hexane. It was found that when at a moderate amount of RGO (25%), TiO2 nanoparticles were well dispersed on the surface of RGO or wrapped by RGO, thus leading to a fully contact and strong interaction to form Ti - O - C interfacial structure. But when at a low content of RGO (6%), TiO2 aggregates were mixture of nanosheets, nanoparticles and nanorods. 25%RGO/TiO2 also had 175% higher surface area (146m2/g), 95% larger volume (0.339 cm3/g) and smaller band gap than 6%RGO/TiO2. More importantly, 25%RGO/TiO2 demonstrated higher adsorption efficiency (25%) and 4 times faster degradation rate than TiO2 (0%). It also exhibited good capability to eliminate multiple organics and stable long-term cycle performance (up to 93% retention after 30 cycles). Its superiority was attributed to the large surface area and unique interface between TiO2 and RGO, which not only provided more active sites to capture pollutants but also enhanced charge transfer (3 µA/cm2, 5 times higher than TiO2). This work offered a promising way to purify water through engineering new materials structure and integrating adsorption and photodegradation technologies. © 2018 IOP Publishing Ltd.

Theoretical study of new potential semiconductor surfaces performance for dye sensitized solar cell usage: TiO2-B (001), (100) and H2Ti3O7 (100)

NASA Astrophysics Data System (ADS)

German, Estefania; Faccio, Ricardo; Mombrú, Álvaro W.

2017-12-01

Hydrogen titanate (H2Ti3O7) and TiO2-B polymorph are potential surfaces identified experimentally in the last years, which need to be analyzed. To study their performance as surfaces for dye sensitized solar cells (DSSC), a set of dye adsorption configurations were evaluated on them, as model dye the small and organic catechol molecule was used. We have calculated adsorption geometry, energy, electronic transfer from dye to semiconductor adsorbent and frontier orbitals by means of density functional theory (DFT). Results show that vacancy-like defected H2Ti3O7 (100) and TiO2-B (100) surfaces present favorable adsorption energies. Finally, an adequate energy level alignment make both surfaces prone to be adequate for direct electron transfer upon excitation, from catechol to the conduction band of the semiconductors, with bands located in the Visible region of the electromagnetic spectrum. Additionally, the band structure alignment indicates an increase in the open circuit voltage, in reference to I2/I3- redox pair potential. All these characteristics make hydrogen titanate (H2Ti3O7) and TiO2-B polymorph promising for DSSC applications.

TiO2-NT electrodes modified with Ag and diamond like carbon (DLC) for hydrogen production by alkaline water electrolysis

NASA Astrophysics Data System (ADS)

Baran, Evrim; Baz, Zeynep; Esen, Ramazan; Yazici Devrim, Birgül

2017-10-01

In present work, the two-step anodization technique was applied for synthesis of TiO2 nanotube (NT). Silver and diamond like carbon (DLC) were coated on the surface of as prepared TiO2-NT using chemical reduction method and MW ECR plasma system. The morphology, composition and structure of the electrodes were examined by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The results showed that Ag nanoparticles, having size in the range of 48-115 nm, are evenly distributed on the top, inside and outside surface of TiO2-NT and when DLC was coated on the surface of TiO2-NT and TiO2-NT-Ag, the top of nanotubes were partially open and the pore diameter of hexagonal structure decreased from 165 nm to of 38-80 nm. On the other hand, the microhardness test and contact angle measurements revealed that additions of Ag and diamond like carbon have a positive effect on the mechanical properties of TiO2-NT film. The electrocatalytic properties of the electrodes towards the hydrogen evolution reaction (HER) were investigated by the electrochemical measurements recorded in 1 M KOH solution. In addition, long-term durability of electrodes towards HER and the energy consumption of alkaline electrolysis were investigated. The energy requirement showed that while the deposition of silver provides approximately 14.95% savings of the energy consumption, the DLC coating causes increase in energy consumption.

Phosphorous-doped TiO2 nanoparticles: synthesis, characterization, and visible photocatalytic evaluation on sulfamethazine degradation.

PubMed

Mendiola-Alvarez, Sandra Yadira; Hernández-Ramírez, Ma Aracely; Guzmán-Mar, Jorge Luis; Garza-Tovar, Lorena Leticia; Hinojosa-Reyes, Laura

2018-05-24

Mesoporous phosphorous-doped TiO 2 (TP) with different wt% of P (0.5, 1.0, and 1.5) was synthetized by microwave-assisted sol-gel method. The obtained materials were characterized by XRD with cell parameters refinement approach, Raman, BET-specific surface area analysis, SEM, ICP-OES, UV-Vis with diffuse reflectance, photoluminescence, FTIR, and XPS. The photocatalytic activity under visible light was evaluated on the degradation of sulfamethazine (SMTZ) at pH 8. The characterization of the phosphorous materials (TP) showed that incorporation of P in the lattice of TiO 2 stabilizes the anatase crystalline phase, even increasing the annealing temperature. The mesoporous P-doped materials showed higher surface area and lower average crystallite size, band gap, and particle size; besides, more intense bands attributed to O-H bond were observed by FTIR analysis compared with bare TiO 2 . The P was substitutionally incorporated in the TiO 2 lattice network as P 5+ replacing Ti 4+ to form Ti-O-P bonds and additionally present as PO 4 3-  on the TiO 2 surface. All these characteristics explain the observed superior photocatalytic activity on degradation (100%) and mineralization (32%) of SMTZ under visible radiation by TP catalysts, especially for P-doped TiO 2 1.0 wt% calcined at 450 °C (TP1.0-450). Ammonium, nitrate, and sulfate ions released during the photocatalytic degradation were quantified by ion chromatography; the nitrogen and sulfur mass balance evidenced the partial mineralization of this recalcitrant molecule.

Preparation of TiO2/boron-doped diamond/Ta multilayer films and use as electrode materials for supercapacitors

NASA Astrophysics Data System (ADS)

Shi, Chao; Li, Hongji; Li, Cuiping; Li, Mingji; Qu, Changqing; Yang, Baohe

2015-12-01

We report nanostructured TiO2/boron-doped diamond (BDD)/Ta multilayer films and their electrochemical performances as supercapacitor electrodes. The BDD films were grown on Ta substrates using electron-assisted hot filament chemical vapor deposition. Ti metal layers were deposited on the BDD surfaces by radio frequency magnetron sputtering, and nanostructured TiO2/BDD/Ta thin films were prepared by electrochemical etching and thermal annealing. The successful formation of TiO2 and Ta layered nanostructures was demonstrated using scanning electron and transmission electron microscopies. The electrochemical responses of these electrodes were evaluated by examining their use as electrical double-layer capacitors, using cyclic voltammetry, and galvanostatic charge/discharge and impedance measurements. When the TiO2/BDD/Ta film was used as the working electrode with 0.1 M Na2SO4 as the electrolyte, the capacitor had a specific capacitance of 5.23 mF cm-2 at a scan rate of 5 mV s-1 for a B/C ratio of 0.1% w/w. Furthermore, the TiO2/BDD/Ta film had improved electrochemical stability, with a retention of 89.3% after 500 cycles. This electrochemical behavior is attributed to the quality of the BDD, the surface roughness and electrocatalytic activities of the TiO2 layer and Ta nanoporous structures, and the synergies between them. These results show that TiO2/BDD/Ta films are promising as capacitor electrodes for special applications.

TiO2 Nanostructure Synthesized by Sol-Gel for Dye Sensitized Solar Cells as Renewable Energy Source

NASA Astrophysics Data System (ADS)

Ramelan, A. H.; Wahyuningsih, S.; Saputro, S.; Supriyanto, E.; Hanif, Q. A.

2017-02-01

The use of renewable materials as a constituent of a smart alternative energy such as the use of natural dyes for light harvesting needs to be developed. Synthesis of anatase titanium dioxide (TiO2) and fabrication Dye-Sensitized Solar Cell (DSSC) using dye-based of anthocyanin from purple sweet potato (Ipomoea batatas L.) as a photosensitizer had been done. Synthesis TiO2 through sol-gel process with the addition of triblock copolymer Pluronic F127 template was controlled at pH 3 whereas calcination was carried out at a temperature of 500 °C, 550 °C and 600 °C. The obtained TiO2 were analyzed by XRD, SAA, and SEM. The conclusion is anatase TiO2 obtained until annealing up to 600 °C. Self-assembly Pluronic F127 triblock copolymer capable of restraining the growth of TiO2 crystals. Retention growth of TiO2 mesoporous produces material character that can be used as builders photoanode DSSC with natural sensitizer anthocyanin from purple sweet potatoes. Based on the analysis of X-ray diffraction patterns and surface area analyser, the higher the calcination temperature the greater the size of the anatase crystals is obtained, however, the smaller its surface area. Purple sweet potato anthocyanin’s dyed on to TiO2 was obtained a good enough performance for DSSC’s and gain the optimum performance from DSSC’s system built with mesoporous TiO2 annealed 550 °C using flavylium form anthocyanin.

Synthesis of nanoporous TiO2 materials using a doubly surfactant system and applying them as useful adsorbents

NASA Astrophysics Data System (ADS)

Anbia, Mansoor; Khosravi, Faezeh

Hydrothermal and non-hydrothermal nanoporous TiO2 materials were synthesized via a doubly surfactant route by using cationic cetyltrimethylammonium bromide and anionic sodium dodecyl sulfate surfactants as the molecular template/structure directing agent. Hydrothermal treatment was performed for comparison. The bulk chemical and phase compositions, crystalline structures, particle morphologies, thermal stabilities and surface texturing were determined by means of X-ray powder analysis, SEM and N2 sorptiometry. The nanoporous TiO2 materials were found to have a spherical morphology with a diameter range of 50-200 nm and a high surface area (390 m2 g-1). Hydrothermal and non-hydrothermal nanoporous TiO2 materials were applied for adsorption of heavy metal cations and the toxic organic compound, copper phthalocyanine, from water for evaluation of their adsorption properties. Both nanoporous TiO2 materials were found to have similar adsorption capacities toward heavy metal cations and CuPc. Both hydrothermal and non-hydrothermal TiO2 nanoporous materials were found to have very good potential for application as a new adsorbent especially for adsorbing heavy metal cations from wastewaters.

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

NASA Astrophysics Data System (ADS)

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.

Nanostructured Silica-Titania Hybrid using Dendritic Fibrous Nanosilica as a Photocatalyst.

PubMed

Bayal, Nisha; Singh, Rustam; Polshettiwar, Vivek

2017-05-22

A new method has been developed to fabricate active TiO 2 photocatalysts by tuning the morphology of the catalyst support. A sustainable solution-phase TiO 2 deposition on dendritic fibrous nanosilica (DFNS) protocol is developed, which is better than the complex and expensive atomic layer deposition technique. In general, catalytic activity decreases with an increased TiO 2 loading on conventional mesoporous silica because of the loss of the surface area caused by the blocking of pores. Notably, in the case of the dendritic fibrous nanosilica KCC-1 as a support, because of its open fibrous morphology, even at the highest TiO 2 loading, a relatively large amount of surface area remained intact. This improved the accessibility of active sites, which increased the catalytic performance of the KCC-1/TiO 2 photocatalyst. KCC-1-supported TiO 2 is a superior photocatalyst in terms of H 2 generation (26.4 mmol gTiO2 -1  h -1 ) under UV light. This study may provide a new direction for photocatalyst development through the morphology control of the support. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure and Formation Mechanism of Black TiO 2 Nanoparticles

DOE PAGES

Tian, Mengkun; Mahjouri-Samani, Masoud; Eres, Gyula; ...

2015-10-27

The remarkable properties of black TiO 2 are due to its disordered surface shell surrounding a crystalline core. However, the chemical composition and the atomic and electronic structure of the disordered shell and its relationship to the core remain poorly understood. Using advanced transmission electron microscopy methods, we show that the outermost layer of black TiO 2 nanoparticles consists of a disordered Ti 2O 3 shell. The measurements show a transition region that connects the disordered Ti 2O 3 shell to the perfect rutile core consisting first of four to five monolayers of defective rutile, containing clearly visible Ti interstitialmore » atoms, followed by an ordered reconstruction layer of Ti interstitial atoms. Our data suggest that this reconstructed layer presents a template on which the disordered Ti 2O 3 layers form by interstitial diffusion of Ti ions. In contrast to recent reports that attribute TiO 2 band-gap narrowing to the synergistic action of oxygen vacancies and surface disorder of nonspecific origin, our results point to Ti 2O 3, which is a narrow-band-gap semiconductor. In conclusion, as a stoichiometric compound of the lower oxidation state Ti 3+ it is expected to be a more robust atomic structure than oxygen-deficient TiO 2 for preserving and stabilizing Ti 3+ surface species that are the key to the enhanced photocatalytic activity of black TiO 2.« less

Synthesis of calcium-phosphorous doped TiO2 nanotubes by anodization and reverse polarization: A promising strategy for an efficient biofunctional implant surface

NASA Astrophysics Data System (ADS)

Alves, Sofia A.; Patel, Sweetu B.; Sukotjo, Cortino; Mathew, Mathew T.; Filho, Paulo N.; Celis, Jean-Pierre; Rocha, Luís A.; Shokuhfar, Tolou

2017-03-01

The modification of surface features such as nano-morphology/topography and chemistry have been employed in the attempt to design titanium oxide surfaces able to overcome the current dental implants failures. The main goal of this study is the synthesis of bone-like structured titanium dioxide (TiO2) nanotubes enriched with Calcium (Ca) and Phosphorous (P) able to enhance osteoblastic cell functions and, simultaneously, display an improved corrosion behavior. To achieve the main goal, TiO2 nanotubes were synthetized and doped with Ca and P by means of a novel methodology which relied, firstly, on the synthesis of TiO2 nanotubes by anodization of titanium in an organic electrolyte followed by reverse polarization and/or anodization, in an aqueous electrolyte. Results show that hydrophilic bone-like structured TiO2 nanotubes were successfully synthesized presenting a highly ordered nano-morphology characterized by non-uniform diameters. The chemical analysis of such nanotubes confirmed the presence of CaCO3, Ca3(PO4)2, CaHPO4 and CaO compounds. The nanotube surfaces submitted to reverse polarization, presented an improved cell adhesion and proliferation compared to smooth titanium. Furthermore, these surfaces displayed a significantly lower passive current in artificial saliva, and so, potential to minimize their bio-degradation through corrosion processes. This study addresses a very simple and promising multidisciplinary approach bringing new insights for the development of novel methodologies to improve the outcome of osseointegrated implants.

Atomic layer deposition of TiO2 on surface modified nanoporous low-k films.

PubMed

Levrau, Elisabeth; Devloo-Casier, Kilian; Dendooven, Jolien; Ludwig, Karl F; Verdonck, Patrick; Meersschaut, Johan; Baklanov, Mikhail R; Detavernier, Christophe

2013-10-01

This paper explores the effects of different plasma treatments on low dielectric constant (low-k) materials and the consequences for the growth behavior of atomic layer deposition (ALD) on these modified substrates. An O2 and a He/H2 plasma treatment were performed on SiCOH low-k films to modify their chemical surface groups. Transmission FTIR and water contact angle (WCA) analysis showed that the O2 plasma changed the hydrophobic surface completely into a hydrophilic surface, while the He/H2 plasma changed it only partially. In a next step, in situ X-ray fluorescence (XRF), ellipsometric porosimetry (EP), and Rutherford backscattering spectroscopy (RBS) were used to characterize ALD growth of TiO2 on these substrates. The initial growth of TiO2 was found to be inhibited in the original low-k film containing only Si-CH3 surface groups, while immediate growth was observed in the hydrophilic O2 plasma treated film. The latter film was uniformly filled with TiO2 after 8 ALD cycles, while pore filling was delayed to 17 ALD cycles in the hydrophobic film. For the He/H2 plasma treated film, containing both Si-OH and Si-CH3 groups, the in situ XRF data showed that TiO2 could no longer be deposited in the He/H2 plasma treated film after 8 ALD cycles, while EP measurements revealed a remaining porosity. This can be explained by the faster deposition of TiO2 in the hydrophilic top part of the film than in the hydrophobic bulk which leaves the bulk porous, as confirmed by RBS depth profiling. The outcome of this research is not only of interest for the development of advanced interconnects in ULSI technology, but also demonstrates that ALD combined with RBS analysis is a handy approach to analyze the modifications induced by a plasma treatment on a nanoporous thin film.

Photocatalysis effect of nanometer TiO2 and TiO2-coated ceramic plate on Hepatitis B virus.

PubMed

Zan, Ling; Fa, Wenjun; Peng, Tianyou; Gong, Zhen-Kui

2007-02-01

The photocatalysis effect of nanometer TiO2 particles and TiO2-coated ceramic plate on Hepatitis B virus surface antigen (HBsAg) was investigated. The ELISA (enzyme-linked immunosorbent assay) standard method was used to assess the efficiency of TiO2 material to destroy the HBsAg. The research has shown that the suspension of TiO2 (0.5g/L) can destroy most of the HBsAg under the irradiation of mercury lamp, with the light intensity of 0.6mW/cm(2) at 365nm wavelength, or under the sunlight irradiation for a few hours. TiO2-coated ceramic plates can also destroy the HBsAg under the irradiation of mercury lamp, with the light intensity of 0.05mW/cm(2) at 365nm wavelength or under the room daylight for a few hours.

Effect of Ti Substrate Ion Implantation on the Physical Properties of Anodic TiO2 Nanotubes

NASA Astrophysics Data System (ADS)

Jedi-Soltanabadi, Zahra; Ghoranneviss, Mahmood; Ghorannevis, Zohreh; Akbari, Hossein

2018-03-01

The influence of nitrogen-ion implantation on the titanium (Ti) surface is studied. The nontreated Ti and the Ti treated with ion implantation were anodized in an ethylene-glycol-based electrolyte solution containing 0.3 wt% ammonium fluoride (NH4F) and 3 vol% deionized (DI) water at a potential of 60 V for 1 h at room temperature. The current density during the growth of the TiO2 nanotubes was monitored in-situ. The surface roughnesses of the Ti substrates before and after the ion implantation were investigated with atomic force microscopy (AFM). The surface roughness was lower for the treated Ti substrate. The morphology of the anodic TiO2 nanotubes was studied by using field-emission scanning electron microscopy (FESEM). Clearly, the titanium nanotubes grown on the treated substrate were longer. In addition, some ribs were observed on their walls. The optical band gap of the anodic TiO2 nanotubes was characterized by using a diffuse reflection spectral (DRS) analysis. The anodic TiO2 nanotubes grown on the treated Ti substrate revealed a band gap energy of approximately 3.02 eV.

Creation of hydrophobic surfaces using a paint containing functionalized oxide particles

NASA Astrophysics Data System (ADS)

Sino, Paul Albert L.; Herrera, Marvin U.; Balela, Mary Donnabelle L.

2017-05-01

Hydrophobic surfaces were created by coating various substrates (aluminum sheet, soda-lime glass, silicon carbide polishing paper, glass with double-sided adhesive) with paint containing functionalized oxide particles. The paint was created by functionalizing oxide particles (ground ZnO, TiO2 nanoparticles, or TiO2 microparticles) with fluorosilane molecules in absolute ethanol. Water contact angle of samples shows that the coated substrate becomes hydrophobic (water contact angle ≥ 90°). Among the oxides that were used, ground ZnO yielded contact angle exemplifying superhydrophobicity (water contact angle ≥ 150°). Scanning electron micrograph of paint-containing TiO2 nanoparticles shows rough functionalized oxides structures which probably increase the hydrophobicity of the surface.

TiO2 coatings via atomic layer deposition on polyurethane and polydimethylsiloxane substrates: Properties and effects on C. albicans growth and inactivation process

NASA Astrophysics Data System (ADS)

Pessoa, R. S.; dos Santos, V. P.; Cardoso, S. B.; Doria, A. C. O. C.; Figueira, F. R.; Rodrigues, B. V. M.; Testoni, G. E.; Fraga, M. A.; Marciano, F. R.; Lobo, A. O.; Maciel, H. S.

2017-11-01

Atomic layer deposition (ALD) surges as an attractive technology to deposit thin films on different substrates for many advanced biomedical applications. Herein titanium dioxide (TiO2) thin films were successful obtained on polyurethane (PU) and polydimethylsiloxane (PDMS) substrates using ALD. The effect of TiO2 films on Candida albicans growth and inactivation process were also systematic discussed. TiCl4 and H2O were used as precursors at 80 °C, while the reaction cycle number ranged from 500 to 2000. Several chemical, physical and physicochemical techniques were used to evaluate the growth kinetics, elemental composition, material structure, chemical bonds, contact angle, work of adhesion and surface morphology of the ALD TiO2 thin films grown on both substrates. For microbiological analyses, yeasts of standard strains of C. albicans were grown on non- and TiO2-coated substrates. Next, the antifungal and photocatalytic activities of the TiO2 were also investigated by counting the colony-forming units (CFU) before and after UV-light treatment. Chlorine-doped amorphous TiO2 films with varied thicknesses and Cl concentration ranging from 2 to 12% were obtained. In sum, the ALD TiO2 films suppressed the yeast-hyphal transition of C. albicans onto PU, however, a high adhesion of yeasts was observed. Conversely, for PDMS substrate, the yeast adhesion did not change, as observed in control. Comparatively to control, the TiO2-covered PDMS had a reduction in CFU up to 59.5% after UV treatment, while no modification was observed to TiO2-covered PU. These results pointed out that ALD chlorine-doped amorphous TiO2 films grown on biomedical polymeric surfaces may act as fungistatic materials. Furthermore, in case of contamination, these materials may also behave as antifungal materials under UV light exposure.

Toxicogenomics analysis of mouse lung responses following exposure to titanium dioxide nanomaterials reveal their disease potential at high doses

PubMed Central

Rahman, Luna; Wu, Dongmei; Johnston, Michael; William, Andrew; Halappanavar, Sabina

2017-01-01

Titanium dioxide nanoparticles (TiO2NPs) induce lung inflammation in experimental animals. In this study, we conducted a comprehensive toxicogenomic analysis of lung responses in mice exposed to six individual TiO2NPs exhibiting different sizes (8, 20 and 300nm), crystalline structure (anatase, rutile or anatase/rutile) and surface modifications (hydrophobic or hydrophilic) to investigate whether the mechanisms leading to TiO2NP-induced lung inflammation are property specific. A detailed histopathological analysis was conducted to investigate the long-term disease implications of acute exposure to TiO2NPs. C57BL/6 mice were exposed to 18, 54, 162 or 486 µg of TiO2NPs/mouse via single intratracheal instillation. Controls were exposed to dispersion medium only. Bronchoalveolar lavage fluid (BALF) and lung tissue were sampled on 1, 28 and 90 days post-exposure. Although all TiO2NPs induced lung inflammation as measured by the neutrophil influx in BALF, rutile-type TiO2NPs induced higher inflammation with the hydrophilic rutile TiO2NP showing the maximum increase. Accordingly, the rutile TiO2NPs induced higher number of differentially expressed genes. Histopathological analysis of lung sections on Day 90 post-exposure showed increased collagen staining and fibrosis-like changes following exposure to the rutile TiO2NPs at the highest dose tested. Among the anatase, the smallest TiO2NP of 8nm showed the maximum response. The anatase TiO2NP of 300nm was the least responsive of all. The results suggest that the severity of lung inflammation is property specific; however, the underlying mechanisms (genes and pathways perturbed) leading to inflammation were the same for all particle types. While the particle size clearly influenced the overall acute lung responses, a combination of small size, crystalline structure and hydrophilic surface contributed to the long-term pathological effects observed at the highest dose (486 µg/mouse). Although the dose at which the pathological changes were observed is considered physiologically high, the study highlights the disease potential of certain TiO2NPs of specific properties. PMID:27760801

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

NASA Astrophysics Data System (ADS)

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

2013-04-01

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

Tailoring the interface using thiophene small molecules in TiO2/P3HT hybrid solar cells.

PubMed

Freitas, Flavio S; Clifford, John N; Palomares, Emilio; Nogueira, Ana F

2012-09-14

In this paper we focus on the effect of carboxylated thiophene small molecules as interface modifiers in TiO(2)/P3HT hybrid solar cells. Our results show that small differences in the chemical structure of these molecules, for example, the presence of the -CH(2)- group in the 2-thiopheneacetic acid (TAA), can greatly increase the TiO(2) surface wettability, improving the TiO(2)/polymer contact. This effect is important to enhance exciton splitting and charge separation.

Synthesis and characterization of a stable, label-free optical biosensor from TiO2-coated porous silicon.

PubMed

Li, Jianlin; Sailor, Michael J

2014-05-15

A nanoscale layer of TiO2 is coated on the inner pore walls of a porous silicon (PSi) film by room-temperature infiltration of a TiO2 sol-gel precursor and firing at 500 °C. The PSi:TiO2 composite films are characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), energy dispersive X-ray spectral analysis (EDS), scanning electron microscopy (SEM) and reflective interferometric Fourier transform spectroscopy (RIFTS). The analysis indicates that TiO2 conformally coats the inner pore surfaces of the PSi film. The film displays greater aqueous stability in the pH range 2-12 relative to a PSi:SiO2 surface. A label-free optical interference immunosensor based on the TiO2-coated PSi film is demonstrated by real-time monitoring of the physical adsorption of protein A, followed by the specific binding of rabbit anti-sheep immunoglobulin (IgG) and then specific capture of sheep IgG. The time to achieve equilibrium for the physical adsorption of protein A on the surface of TiO2-coated PSi film is significantly greater than that of PSi film. The specificity of the protein A and rabbit anti-sheep IgG construct on the sensor is confirmed by tests with non-binding chicken IgG. The sensitivity of the immunosensor is shown to be 8210 ± 170 nm/refractive index unit (RIU). Copyright © 2013 Elsevier B.V. All rights reserved.

Visible Light-Driven H 2 Production over Highly Dispersed Ruthenia on Rutile TiO 2 Nanorods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen-Phan, Thuy-Duong; Luo, Si; Vovchok, Dimitriy

2016-01-04

The immobilization of miniscule quantities of RuO 2 (~0.1%) onto one-dimensional (1D) TiO 2 nanorods (NRs) allows H 2 evolution from water under visible light irradiation. Rod-like rutile TiO 2 structures, exposing preferentially (110) surfaces, are shown to be critical for the deposition of RuO 2 to enable photocatalytic activity in the visible region. The superior performance is rationalized on the basis of fundamental experimental studies and theoretical calculations, demonstrating that RuO 2(110) grown as 1D nanowires on rutile TiO 2(110), which occurs only at extremely low loads of RuO 2, leads to the formation of a heterointerface that efficientlymore » adsorbs visible light. The surface defects, band gap narrowing, visible photoresponse, and favorable upward band bending at the heterointerface drastically facilitate the transfer and separation of photogenerated charge carriers« less

Visible Light-Driven H 2 Production over Highly Dispersed Ruthenia on Rutile TiO 2 Nanorods

DOE PAGES

Nguyen-Phan, Thuy-Duong; Luo, Si; Vovchok, Dimitriy; ...

2015-12-02

The immobilization of miniscule quantities of RuO 2 (~0.1%) onto one-dimensional (1D) TiO 2 nanorods (NRs) allows H 2 evolution from water under visible light irradiation. In addition, rod-like rutile TiO 2 structures, exposing preferentially (110) surfaces, are shown to be critical for the deposition of RuO 2 to enable photocatalytic activity in the visible region. The superior performance is rationalized on the basis of fundamental experimental studies and theoretical calculations, demonstrating that RuO 2(110) grown as 1D nanowires on rutile TiO 2(110), which occurs only at extremely low loads of RuO 2, leads to the formation of a heterointerfacemore » that efficiently adsorbs visible light. The surface defects, band gap narrowing, visible photoresponse, and favorable upward band bending at the heterointerface drastically facilitate the transfer and separation of photogenerated charge carriers.« less

The preparation, surface structure, zeta potential, surface charge density and photocatalytic activity of TiO2 nanostructures of different shapes

NASA Astrophysics Data System (ADS)

Grover, Inderpreet Singh; Singh, Satnam; Pal, Bonamali

2013-09-01

Titania based nanocatalysts such as sodium titanates of different morphology having superior surface properties are getting wide importance in photocatalysis research. Despite having sodium (Na) contents and its high temperature synthesis (that generally deteriorate the photoreactivity), these Na-titanates often exhibit better photoactivity than P25-TiO2 catalyst. Hence, this work demonstrated the influence of crystal structure, BET surface area, surface charge, zeta potential (ζ) and metal loading on the photocatalytic activity of as-prepared sodium titanate nanotube (TNT) and titania nanorod (TNR). Straw like hollow orthorhombic-TNT (Na2Ti2O5·H2O) particles (W = 9-12 nm and L = 82-115 nm) and rice like pure anatase-TNR particles (W = 8-13 nm and L = 81-134 nm) are obtained by the hydrothermal treatment of P25-TiO2 with NaOH, which in fact, altered the net surface charge of TNT and TNR particles. The observed ζ = -2.82 (P25-TiO2), -13.5 (TNT) and -22.5 mV (TNR) are significantly altered by the Ag and Cu deposition. It has been found here that TNT displayed best photocatalytic activity for the imidacloprid insecticide (C9H10ClN5O2) degradation to CO2 formation under UV irradiation because of its largest surface area 176 m2 g-1 among the catalysts studied.

Performance of Bi2O3/TiO2 prepared by sol-gel on p-Cresol degradation under solar and visible light.

PubMed

Vigil-Castillo, Héctor H; Hernández-Ramírez, Aracely; Guzmán-Mar, Jorge L; Ramos-Delgado, Norma A; Villanueva-Rodríguez, Minerva

2018-05-21

Photocatalytic degradation of p-Cresol was evaluated using the mixed oxide Bi 2 O 3 /TiO 2 (containing 2 and 20% wt. Bi 2 O 3 referred as TB2 and TB20) and was compared with bare TiO 2 under simulated solar radiation. Materials were prepared by the classic sol-gel method. All solids exhibited the anatase phase by X-ray diffraction (XRD) and Raman spectroscopy. The synthesized materials presented lower crystallite size and Eg value, and also higher surface area as Bi 2 O 3 amount was increased. Bi content was quantified showing near to 70% of theoretical values in TB2 and TB20. Bi 2 O 3 incorporation also was demonstrated by X-ray photoelectron spectroscopy (XPS). Characterization of mixed oxides suggests a homogeneous distribution of Bi 2 O 3 on TiO 2 surface. Photocatalytic tests were carried out using a catalyst loading of 1 g L -1 under simulated solar light and visible light. The incorporation of Bi 2 O 3 in TiO 2 improved the photocatalytic properties of the synthesized materials obtaining better results with TB20 than the unmodified TiO 2 under both radiation sources.

Control of crystallographic texture and surface morphology of Pt/Tio2 templates for enhanced PZT thin film texture.

PubMed

Fox, Austin J; Drawl, Bill; Fox, Glen R; Gibbons, Brady J; Trolier-McKinstry, Susan

2015-01-01

Optimized processing conditions for Pt/TiO2/SiO2/Si templating electrodes were investigated. These electrodes are used to obtain [111] textured thin film lead zirconate titanate (Pb[ZrxTi1-x ]O3 0 ≤ x ≤ 1) (PZT). Titanium deposited by dc magnetron sputtering yields [0001] texture on a thermally oxidized Si wafer. It was found that by optimizing deposition time, pressure, power, and the chamber pre-conditioning, the Ti texture could be maximized while maintaining low surface roughness. When oxidized, titanium yields [100]-oriented rutile. This seed layer has as low as a 4.6% lattice mismatch with [111] Pt; thus, it is possible to achieve strongly oriented [111] Pt. The quality of the orientation and surface roughness of the TiO2 and the Ti directly affect the achievable Pt texture and surface morphology. A transition between optimal crystallographic texture and the smoothest templating surface occurs at approximately 30 nm of original Ti thickness (45 nm TiO2). This corresponds to 0.5 nm (2 nm for TiO2) rms roughness as determined by atomic force microscopy and a full-width at half-maximum (FWHM) of the rocking curve 0002 (200) peak of 5.5/spl degrees/ (3.1/spl degrees/ for TiO2). A Pb[Zr0.52Ti 0.48]O3 layer was deposited and shown to template from the textured Pt electrode, with a maximum [111] Lotgering factor of 87% and a minimum 111 FWHM of 2.4/spl degrees/ at approximately 30 nm of original Ti.

Immobilization of Ag nanoparticles/FGF-2 on a modified titanium implant surface and improved human gingival fibroblasts behavior.

PubMed

Ma, Qianli; Mei, Shenglin; Ji, Kun; Zhang, Yumei; Chu, Paul K

2011-08-01

The objective of this study was to form a rapid and firm soft tissue sealing around dental implants that resists bacterial invasion. We present a novel approach to modify Ti surface by immobilizing Ag nanoparticles/FGF-2 compound bioactive factors onto a titania nanotubular surface. The titanium samples were anodized to form vertically organized TiO(2) nanotube arrays and Ag nanoparticles were electrodeposited onto the nanotubular surface, on which FGF-2 was immobilized with repeated lyophilization. A uniform distribution of Ag nanoparticles/FGF-2 was observed on the TiO(2) nanotubular surface. The L929 cell line was used for cytotoxicity assessment. Human gingival fibroblasts (HGFs) were cultured on the modified surface for cytocompatibility determination. The Ag/FGF-2 immobilized samples displayed excellent cytocompatibility, negligible cytotoxicity, and enhanced HGF functions such as cell attachment, proliferation, and ECM-related gene expression. The Ag nanoparticles also exhibit some bioactivity. In conclusion, this modified TiO(2) nanotubular surface has a large potential for use in dental implant abutment. Copyright © 2011 Wiley Periodicals, Inc.

Application of concrete surfaces as novel substrate for immobilization of TiO2 nano powder in photocatalytic treatment of phenolic water.

PubMed

Delnavaz, Mohammad; Ayati, Bita; Ganjidoust, Hossein; Sanjabi, Sohrab

2015-01-01

In this study, concrete application as a substrate for TiO2 nano powder immobilization in heterogeneous photocatalytic process was evaluated. TiO2 immobilization on the pervious concrete surface was done by different procedures containing slurry method (SM), cement mixed method (CMM) and different concrete sealer formulations. Irradiation of TiO2 was prepared by UV-A and UV-C lamps. Phenolic wastewater was selected as a pollutant and efficiency of the process was determined in various operation conditions including influent phenol concentration, pH, TiO2 concentration, immobilization method and UV lamp intensity. The removal efficiency of photocatalytic process in 4 h irradiation time and phenol concentration ranges of 25-500 mg/L was more than 80 %. Intermediates were identified by GC/Mass and spectrophotometric analysis. According to the results, photocatalytic reactions followed the pseudo-first-order kinetics and can effectively treate phenol under optimal conditions.

Effect of TiO2 nanoparticles doping on structural and electrical properties of PVA: NaBr polymer electrolyte

NASA Astrophysics Data System (ADS)

Sagar, Rohan N.; Ravindrachary, V.; Guruswamy, B.; Hegde, Shreedatta; Mahanthesh, B. K.; Kumari, R. Padma

2018-05-01

The effect of TiO2 nanoparticles on morphology and electrical properties of PVA: NaBr composite films were carried out using various techniques. The pure and TiO2 nanoparticle doped PVA: NaBr composite films were prepared using solvent casting method. The FTIR spectral studies shows that the Ti+ ions of TiO2 interacts with hydroxyl group (OH) of PVA via hydrogen bonding and forms the charge transfer complexes (CTC). These interactions are of inter/intra molecular type and affects the surface morphology as well as the electrical properties of composite films. XRD study shows that the crystallinity of the composite increases with doping level. SEM studies shows that the increase in roughness of the surface of the composite films and uniform dispersion of nanofillers in polymer matrix. Electrical properties are analyzed using impedance analyzer and higher conductivity (10-4Scm-1) is achieved for 5 wt % TiO2 doping concentration.

Effect of TiO2 modification with amino-based self-assembled monolayer on inverted organic solar cell

NASA Astrophysics Data System (ADS)

Tozlu, Cem; Mutlu, Adem; Can, Mustafa; Havare, Ali Kemal; Demic, Serafettin; Icli, Sıddık

2017-11-01

The effects of surface modification of titanium dioxide (TiO2) on the performance of inverted type organic solar cells (i-OSCs) was investigated in this study. A series of benzoic acid derivatized self-assembled monolayer (SAM) molecules of 4‧-[(hexyloxy)phenyl]amino-3,5-biphenyl dicarboxylic acid (CT17) and 4‧-[1-naphthyl (phenyl)amino]biphenyl-4-carboxylic acid (CT19) were utilized to modify the interface between TiO2 buffer layer and poly-3 hexylthiophene (P3HT):[6,6]-phenyl C61 butyric acid methyl ester (PC61BM) active layer having the device structure of ITO/TiO2/SAM/P3HT:PC61BM/MoO3/Ag. The work function and surface wetting properties of TiO2 buffer layer served as electron transporting layer between ITO and PC61BM active layer were tuned by SAM method. The solar cell of the SAM modified devices exhibited better performance. The power conversion efficiency (PCE) of i-OSCs devices with bare TiO2 electrodes enhanced from 2.00% to 2.21% and 2.43% with CT17 and CT19 treated TiO2 electrodes, respectively. The open circuit voltage (Voc) of the SAM treated TiO2 devices reached to 0.60 V and 0.61 V, respectively, while the Voc of untreated TiO2 was 0.57 V. The water contact angle of i-OSCs with CT17 and CT19 SAMs was also higher than the value of the unmodified TiO2 electrode. These results show that inserting a monolayer at the interface between organic and inorganic layers is an useful alternative method to improve the performance of i-OSCs.

Visible light activated TiO2/microcrystalline cellulose nanocatalyst to destroy organic contaminants in water.

EPA Science Inventory

Hybrid TiO2/microcrystalline cellulose (MC) nanophotocatalyst was prepared in situ by a facile and simple synthesis utilizing benign precursors such as MC and TiCl4. The as-prepared nanocomposite was characterized by XRD, XPS, BET surface area analyzer, UV–vis DRS and TGA. Surfac...

Chemical synthesis of CdS onto TiO2 nanorods for quantum dot sensitized solar cells

NASA Astrophysics Data System (ADS)

Pawar, Sachin A.; Patil, Dipali S.; Lokhande, Abhishek C.; Gang, Myeng Gil; Shin, Jae Cheol; Patil, Pramod S.; Kim, Jin Hyeok

2016-08-01

A quantum dot sensitized solar cell (QDSSC) is fabricated using hydrothermally grown TiO2 nanorods and successive ionic layer adsorption and reaction (SILAR) deposited CdS. Surface morphology of the TiO2 films coated with different SILAR cycles of CdS is examined by Scanning Electron Microscopy which revealed aggregated CdS QDs coverage grow on increasing onto the TiO2 nanorods with respect to cycle number. Under AM 1.5G illumination, we found the TiO2/CdS QDSSC photoelectrode shows a power conversion efficiency of 1.75%, in an aqueous polysulfide electrolyte with short-circuit photocurrent density of 4.04 mA/cm2 which is higher than that of a bare TiO2 nanorods array.

A first principle simulation of competitive adsorption of SF6 decomposition components on nitrogen-doped anatase TiO2 (101) surface

NASA Astrophysics Data System (ADS)

Dong, Xingchen; Zhang, Xiaoxing; Cui, Hao; Zhang, Jun

2017-11-01

Gas insulated switchgear has been widely used in modern electric systems due to its significantly excellent performances such as compact structure and low land occupation as well as the security stability. However, inside defects caused during manufacture process can lead to partial discharge which might develop into serious insulation failure. Online monitoring method on basis of gas sensors is considered a promising way of detecting partial discharge for alarm ahead of time. Research has found that TiO2 nanotubes sensors show good response to SO2, SOF2, SO2F2, the decomposition components as a result of partial discharge. In order to investigate the gas-sensing mechanism of nitrogen-doped TiO2 prepared via plasma treatment methods to SO2, SOF2, and SO2F2, the adsorption structures of both three gas molecules and anatase TiO2 (101) surface were built, and DFT calculations were then carried out for calculation and analysis of adsorption parameters. Adsorption property comparison of anatase TiO2 (101) surface after nitrogen doping with Au doping and without doping shows that nitrogen doping can obviously enhance the adsorption energy for SO2 and SOF2 adsorption and no charge transfer for SO2F2 adsorption, further explaining the adsorption mechanism and doping influence of different doping elements.

The light transmission and distribution in an optical fiber coated with TiO2 particles.

PubMed

Wang, Wen; Ku, Young

2003-03-01

The light delivery and distribution phenomena along the optical fiber coated with the P-25 TiO(2) particles by dipping was investigated. The surface properties (coverage, roughness and thickness) of the TiO(2) layer coated on the optical fiber were characterized by SEM micrographs. For TiO(2) layer prepared from solutions containing less than 20 wt.% of TiO(2) slurry, the thickness of layer was increased linearly with the TiO(2) slurry content in solutions. The UV light intensity transmitted along a TiO(2)-coated optical fiber decreased more rapidly than that transmitted along a non-coated fiber. Based on the experimental results, the light intensity distribution around a coated optical fiber was modeled to determine the optimum configuration for the design of optical fiber reactors under various operational conditions. Copyright 2002 Elsevier Science Ltd.

Composite WO 3/TiO 2 nanostructures for high electrochromic activity

DOE PAGES

Reyes-Gil, Karla R.; Stephens, Zachary D.; Stavila, Vitalie; ...

2015-01-06

A composite material consisting of TiO 2 nanotubes (NT) with WO 3 electrodeposited on its surface has been fabricated, detached from its Ti substrate, and attached to a fluorine-doped tin oxide (FTO) film on glass for application to electrochromic (EC) reactions. Several adhesion layers were tested, finding that a paste of TiO 2 made from commercially available TiO 2 nanoparticles creates an interface for the TiO 2 NT film to attach to the FTO glass, which is conductive and does not cause solution-phase ions in an electrolyte to bind irreversibly with the material. The effect of NT length and WOmore » 3 concentration on the EC performance were studied. As a result, the composite WO 3/TiO 2 nanostructures showed higher ion storage capacity, better stability, enhanced EC contrast, and longer memory time compared with the pure WO 3 and TiO 2 materials« less

Thermo-Optical Properties of Thin-Film TiO2–Al2O3 Bilayers Fabricated by Atomic Layer Deposition

PubMed Central

Ali, Rizwan; Saleem, Muhammad Rizwan; Pääkkönen, Pertti; Honkanen, Seppo

2015-01-01

We investigate the optical and thermo-optical properties of amorphous TiO2–Al2O3 thin-film bilayers fabricated by atomic layer deposition (ALD). Seven samples of TiO2–Al2O3 bilayers are fabricated by growing Al2O3 films of different thicknesses on the surface of TiO2 films of constant thickness (100 nm). Temperature-induced changes in the optical refractive indices of these thin-film bilayers are measured by a variable angle spectroscopic ellipsometer VASE®. The optical data and the thermo-optic coefficients of the films are retrieved and calculated by applying the Cauchy model and the linear fitting regression algorithm, in order to evaluate the surface porosity model of TiO2 films. The effects of TiO2 surface defects on the films’ thermo-optic properties are reduced and modified by depositing ultra-thin ALD-Al2O3 diffusion barrier layers. Increasing the ALD-Al2O3 thickness from 20 nm to 30 nm results in a sign change of the thermo-optic coefficient of the ALD-TiO2. The thermo-optic coefficients of the 100 nm-thick ALD-TiO2 film and 30 nm-thick ALD-Al2O3 film in a bilayer are (0.048 ± 0.134) × 10−4 °C−1 and (0.680 ± 0.313) × 10−4 °C−1, respectively, at a temperature T = 62 °C.

Fabrication of Semiordered Nanopatterned Diamond-like Carbon and Titania Films for Blood Contacting Applications.

PubMed

Nandakumar, Deepika; Bendavid, Avi; Martin, Philip J; Harris, Kenneth D; Ruys, Andrew J; Lord, Megan S

2016-03-23

Biomaterials with the ability to interface with, but not activate, blood components are essential for a multitude of medical devices. Diamond-like carbon (DLC) and titania (TiO2) have shown promise for these applications; however, both support platelet adhesion and activation. This study explored the fabrication of nanostructured DLC and TiO2 thin film coatings using a block copolymer deposition technique that produced semiordered nanopatterns with low surface roughness (5-8 nm Rrms). These surfaces supported fibrinogen and plasma protein adsorption that predominantly adsorbed between the nanofeatures and reduced the overall surface roughness. The conformation of the adsorbed fibrinogen was altered on the nanopatterned surfaces as compared with the planar surfaces to reveal higher levels of the platelet binding region. Planar DLC and TiO2 coatings supported less platelet adhesion than nanopatterned DLC and TiO2. However, platelets on the nanopatterned DLC coatings were less spread indicating a lower level of platelet activation on the nanostructured DLC coatings compared with the planar DLC coatings. These data indicated that nanostructured DLC coatings may find application in blood contacting medical devices in the future.

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

PubMed Central

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

2013-01-01

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

Photocatalytic oxidation of tabun simulant-diethyl cyanophosphate: FTIR in situ investigation.

PubMed

Kolinko, P A; Kozlov, D V

2008-06-15

Gas phase photocatalytic oxidation of diethyl cyanophosphate vapor in a static reactor using TiO2 and modified TiO2 as the photocatalyst was studied with the FTIR in situ method. The transition metals Pt, Au, and Ag were used for TiO2 modification by the chemical and photochemical deposition methods as well as the mechanical mixture of TiO2 with manganese oxide to improve its adsorption and catalytic activity. Photocatalytic oxidation of diethyl cyanophosphate in a static reactor results in its complete mineralization with carbon dioxide, phosphoric and nitric acids, and water as the major final products. HCN was demonstrated to be the only toxic gaseous intermediate of diethyl cyanophosphate photocatalytic oxidation, formed as a result of diethyl cyanophosphate hydrolysis. Diethylphosphate and acetic and formic acids were registered as the surface intermediates. It was found that cyanhydric acid is oxidized slowly with the use of unmodified TiO2. The formation of surface cyanide complexes with Ag and Au ions could be responsible for the fast removal of HCN from the gas phase and its further photooxidation in the case of using TiO2 with deposited Au and Ag.

Fabrication of A/R-TiO2 composite for enhanced photoelectrochemical performance: Solar hydrogen generation and dye degradation

NASA Astrophysics Data System (ADS)

Mahadik, Mahadeo A.; An, Gil Woo; David, Selvaraj; Choi, Sun Hee; Cho, Min; Jang, Jum Suk

2017-12-01

Anatase/rutile TiO2 nanorods composites were prepared by a facile hydrothermal method followed by dip coating method using titanium isopropoxide in acetic acid and ethanol solvent. The effects of the titanium isopropoxide precursor concentration, on the formation of dip coated anatase/rutile TiO2 nanorods composite were systematically explored. The growth of anatase on rutile TiO2 nanorods can be controlled by varying the titanium isopropoxide concentration. The morphological study reveals that anatase TiO2 nanograins formed on the surface of rutile TiO2 nanorod arrays through dip coating method. Photoelectrochemical analyses showed that the enhancement of the photocatalytic activities of the samples is affected by the anatase nanograins present on the rutile TiO2 nanorods, which can induce the separation of electrons and holes. To interpret the photoelectrochemical behaviors, the prepared photoelectrodes were applied in photoelectrochemical solar hydrogen generation and orange II dye degradation. The optimized photocurrent density of 1.8 mA cm-2 and the 625 μmol hydrogen generation was observed for 10 mM anatase/rutile TiO2 NRs composites. Additionally, 96% removal of the orange II dye was achieved within 5 h during oxidative degradation under solar light irradiation. One of the benefits of high specific surface area and the efficient photogenerated charge transport in the anatase/rutile TiO2 nanorod composite improves the photoelectrochemical hydrogen generation and orange dye degradation compared to the rutile TiO2. Thus, our strategy provides a promising, stable, and low cost alternative to existing photocatalysts and is expected to attract considerable attention for industrial applications.

Heterogeneous Reactivity of NO2 with Photocatalytic Paints: A Possible Source of Nitrous Acid (HONO) in the Indoor Environment

NASA Astrophysics Data System (ADS)

Gligorovski, S.; Bartolomei, V.; Gandolfo, A.; Gomez Alvarez, E.; Kleffmann, J.; Wortham, H.

2014-12-01

There is an increasing concern about the indoor air environment, where we spend most of our time. Common methods of improving indoor air quality include controlling pollution sources, increasing ventilation rates or using air purifiers. Photocatalytic remediation technology was suggested as a new possibility to eliminate indoor air pollutants instead of just diluting or disposing them. In the present study, heterogeneous reactions of NO2 were studied on photocatalytic paints containing different size and quantity of TiO2. The heterogeneous reactions were conducted in a photo reactor under simulated atmospheric conditions. The flat pyrex rectangular plates covered with the paint were inserted into the reactor. These plates have been sprayed with the photocatalytic paints at our industrial partner's (ALLIOS) facilities using a high precision procedure that allowed the application of a thin layer of a given thickness of the paint. This allows a homogeneous coverage of the surface with the paint and an accurate determination of the exact amount of paint exposed to gaseous NO2. We demonstrate that the indoor photocatalytic paints which contain TiO2 can substantially reduce the concentrations of nitrogen dioxide (NO2). We show that the efficiency of nitrogen dioxide (NO2) removal increase with the quantity of TiO2 in the range 0 - 7 %. The geometric uptake coefficients increase from 5 · 10-6 to 1.6 · 10-5 under light irradiation of the paints. On the other hand, during the reactions of NO2 with this paint (7 % of TiO2) nitric oxide (NO) and nitrous acid (HONO) are formed. Nitrous acid (HONO) is an important harmful indoor pollutant and its photolysis leads to the formation of highly reactive OH radicals (Gomez Alvarez et al., 2013). Maximum conversion efficiencies of NO2to HONO and NO of 15 % and 33 % were observed at 30 % RH, respectively. Thus, the quantity of TiO2 embedded in the paint is an important parameter regarding the nitrogen oxides (NOx = NO + NO2) remediation, but may also influence formation of harmful by-products such as HONO, which should be considered for future optimization of photocatalytic paints aimed for indoor applications. Reference: Gómez Alvarez E., Amedro D., Afif C., Gligorovski S., Schoemacker C., Fittschen C., Doussin J.F., Wortham H. Proc. Natl. Acad. Sci. U.S.A, 110(33), 13294-13299, 2013.

Catalytic oxidation of 1,2-DCBz over V2O5/TiO2-CNTs: effect of CNT diameter and surface functional groups.

PubMed

Du, Cuicui; Wang, Qiulin; Peng, Yaqi; Lu, Shengyong; Ji, Longjie; Ni, Mingjiang

2017-02-01

A series of V 2 O 5 /TiO 2 -carbon nanotube (CNT) catalysts were prepared and tested to decompose gaseous 1,2-dichlorobenzene (1,2-DCBz). Several physicochemical methods, including nitrogen adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and H 2 temperature-programmed reduction (TPR) were employed to characterise their physicochemical properties. To better understand the effect of CNT properties on the reactivity of V 2 O 5 /TiO 2 -CNT catalysts, the 1,2-DCBz residue remaining in the off-gas and on the catalyst surface were both collected and analysed. The results indicate that the outer diameter and the surface functional groups (hydroxide radical and carboxyl) of CNTs significantly influence upon the catalytic activity of CNT-containing V 2 O 5 /TiO 2 catalysts: the CNT outer diameter mainly affects the aggregation of CNTs and the π-π interaction between the benzene ring and CNTs, while the introduction of -OH and -COOH groups by acid treatment can further enlarge specific surface area (SSA) and contribute to a higher average oxidation state of vanadium (V aos ) and supplemental surface chemisorbed oxygen (O ads ). In addition, the enhanced mobility of lattice oxygen (O latt) also improves the oxidation ability of the catalysts.

Visible light guided manipulation of liquid wettability on photoresponsive surfaces

PubMed Central

Kwon, Gibum; Panchanathan, Divya; Mahmoudi, Seyed Reza; Gondal, Mohammed A.; McKinley, Gareth H.; Varanasi, Kripa K.

2017-01-01

Photoresponsive titania surfaces are of great interest due to their unique wettability change upon ultraviolet light illumination. However, their applications are often limited either by the inability to respond to visible light or the need for special treatment to recover the original wettability. Sensitizing TiO2 surfaces with visible light-absorbing materials has been utilized in photovoltaic applications. Here we demonstrate that a dye-sensitized TiO2 surface can selectively change the wettability towards contacting liquids upon visible light illumination due to a photo-induced voltage across the liquid and the underlying surface. The photo-induced wettability change of our surfaces enables external manipulation of liquid droplet motion upon illumination. We show demulsification of surfactant-stabilized brine-in-oil emulsions via coalescence of brine droplets on our dye-sensitized TiO2 surface upon visible light illumination. We anticipate that our surfaces will have a wide range of applications including microfluidic devices with customizable wettability, solar-driven oil–water clean-up and demulsification technologies. PMID:28440292

Density functional theory study of atomic and electronic properties of defects in reduced anatase TiO2 nanocrystals

NASA Astrophysics Data System (ADS)

Morita, Kazuki; Yasuoka, Kenji

2018-03-01

Anatase TiO2 nanocrystals have received considerable attention owing to their promising applications in photocatalysis, photovoltaics, and fuel cells. Although experimental evidence has shown that the performance of nanocrystals can be significantly improved through reduction, the mechanistic basis of this enhancement remains unclear. To shed a light on the chemistry of reduced anatase TiO2 nanocrystals, density functional theory were used to investigate the properties of defects and excess electrons. We demonstrated that oxygen vacancies are stable both on the surface and at the sub-surface of the nanocrystal, while titanium interstitials prefer sub-surface sites. Different defect locations possessed different excess electron structures, which contributed to deep and shallow states in the band gap of the nanocrystals. Furthermore, valence band tailing was observed, resulting in band gap narrowing. The theoretical results presented here deepen our understanding, and show the potential of defects to considerably change the macroscopic properties of anatase TiO2 nanocrystals.

Direct observation of interfacial Au atoms on TiO₂ in three dimensions.

PubMed

Gao, Wenpei; Sivaramakrishnan, Shankar; Wen, Jianguo; Zuo, Jian-Min

2015-04-08

Interfacial atoms, which result from interactions between the metal nanoparticles and support, have a large impact on the physical and chemical properties of nanoparticles. However, they are difficult to observe; the lack of knowledge has been a major obstacle toward unraveling their role in chemical transformations. Here we report conclusive evidence of interfacial Au atoms formed on the rutile (TiO2) (110) surfaces by activation using high-temperature (∼500 °C) annealing in air. Three-dimensional imaging was performed using depth-sectioning enabled by aberration-corrected scanning transmission electron microscopy. Results show that the interface between Au nanocrystals and TiO2 (110) surfaces consists of a single atomic layer with Au atoms embedded inside Ti-O. The number of interfacial Au atoms is estimated from ∼1-8 in an interfacial atomic column. Direct impact of interfacial Au atoms is observed on an enhanced Au-TiO2 interaction and the reduction of surface TiO2; both are critical to Au catalysis.

Modified microwave method for the synthesis of visible light-responsive TiO2/MWCNTs nanocatalysts

PubMed Central

2013-01-01

Recently, TiO2/multi-walled carbon nanotube (MWCNT) hybrid nanocatalysts have been a subject of high interest due to their excellent structures, large surface areas and peculiar optical properties, which enhance their photocatalytic performance. In this work, a modified microwave technique was used to rapidly synthesise a TiO2/MWCNT nanocatalyst with a large surface area. X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller measurements were used to characterise the structure, morphology and the surface area of the sample. The photocatalytic activity of the hybrid nanocatalysts was evaluated through a comparison of the degradation of methylene blue dye under irradiation with ultraviolet and visible light. The results showed that the TiO2/MWCNT hybrid nanocatalysts degraded 34.9% of the methylene blue (MB) under irradiation with ultraviolet light, whereas 96.3% of the MB was degraded under irradiation with visible light. PMID:23919496

Survival of Staphylococcus aureus exposed to UV radiation on the surface of ceramic tiles coated with TiO2.

PubMed

Szczawiński, J; Tomaszewski, H; Jackowska-Tracz, A; Szczawińska, M E

2011-01-01

The aim of this study was to determine and compare the antimicrobial activity of UV radiation of wavelength 253.7 nm (used in typical germicidal lamps) against Staphylococcus aureus on the surfaces of conventionally produced white ceramic wall tiles (matt and shiny) and the same tiles coated with TiO2 using three different methods: RF diode sputtering, atmospheric pressure chemical vapour deposition (APCVD) and spray pyrolysis deposition (SPD). Results clearly indicate that the bactericidal action of UV radiation is much stronger on the surfaces of tiles coated with TiO2 than on the tiles uncovered. The strongest bactericidal effect of UV radiation was found for film prepared by APCVD. Results of experiments for shiny and matt tiles did not differ statistically. The use of ceramic wall tiles coated with TiO2 films in hospitals, veterinary clinics, laboratories, food processing plants and other places where UV radiation is applied for disinfection should greatly improve the efficiency of this treatment.

Comparison of Cluster, Slab, and Analytic Potential Models for the Dimethyl Methylphosphonate (DMMP)/TiO2 (110) Intermolecular Interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Li; Tunega, Daniel; Xu, Lai

2013-08-29

In a previous study (J. Phys. Chem. C 2011, 115, 12403) cluster models for the TiO2 rutile (110) surface and MP2 calculations were used to develop an analytic potential energy function for dimethyl methylphosphonate (DMMP) interacting with this surface. In the work presented here, this analytic potential and MP2 cluster models are compared with DFT "slab" calculations for DMMP interacting with the TiO2 (110) surface and with DFT cluster models for the TiO2 (110) surface. The DFT slab calculations were performed with the PW91 and PBE functionals. The analytic potential gives DMMP/ TiO2 (110) potential energy curves in excellent agreementmore » with those obtained from the slab calculations. The cluster models for the TiO2 (110) surface, used for the MP2 calculations, were extended to DFT calculations with the B3LYP, PW91, and PBE functional. These DFT calculations do not give DMMP/TiO2 (110) interaction energies which agree with those from the DFT slab calculations. Analyses of the wave functions for these cluster models show that they do not accurately represent the HOMO and LUMO for the surface, which should be 2p and 3d orbitals, respectively, and the models also do not give an accurate band gap. The MP2 cluster models do not accurately represent the LUMO and that they give accurate DMMP/TiO2 (110) interaction energies is apparently fortuitous, arising from their highly inaccurate band gaps. Accurate cluster models, consisting of 7, 10, and 15 Ti-atoms and which have the correct HOMO and LUMO properties, are proposed. The work presented here illustrates the care that must be taken in "constructing" cluster models which accurately model surfaces.« less

Photocatalytic activity of TiO2/Nb2O5/PANI and TiO2/Nb2O5/RGO as new nanocomposites for degradation of organic pollutants.

PubMed

Zarrin, Saviz; Heshmatpour, Felora

2018-06-05

In this study, highly active titanium dioxide modified by niobium oxide (Nb 2 O 5 ), polymer (PANI) and reduced graphene oxide (RGO) were successfully prepared. The morphology, structure, surface area and light absorption properties of the present nanocomposites for removal of methylene blue (MB) and methyl orange (MO) were investigated and compared with those of TiO 2 /Nb 2 O 5 and TiO 2 nanoparticles. The characterization techniques such as XRD, FT-IR, UV-vis, SEM, EDX, BET and TEM were employed in order to identify the nanocomposites. Also, photocatalytic properties of TiO 2 /Nb 2 O 5 /PANI and TiO 2 /Nb 2 O 5 /RGO nanocomposites under visible light irradiation were studied. In this way, the obtained results were compared to each other and also compared to TiO 2 /Nb 2 O 5 and TiO 2 nanoparticles. In this context, the chemical oxygen demand (COD) removal follows the photodegradation in observed performance. The results indicate that reduced TiO 2 /Nb 2 O 5 nanocomposite is effectively modified by graphene oxide to give TiO 2 /Nb 2 O 5 /RGO composite. The TiO 2 /Nb 2 O 5 /RGO exhibits significantly higher photocatalytic activity in degradation of organic dyes under visible light rather than that of TiO 2 /Nb 2 O 5 /PANI, TiO 2 /Nb 2 O 5 and pure TiO 2 . Copyright © 2018 Elsevier B.V. All rights reserved.

Formation mechanism of TiO2 nanotubes and their applications in photoelectrochemical water splitting and supercapacitors.

PubMed

Chen, Bo; Hou, Junbo; Lu, Kathy

2013-05-14

Structural observations of the transition of TiO2 nanopores into nanotubes by increasing the OH(-) concentration in the electrolyte challenge the validity of existing formation mechanisms of anodic TiO2 nanotubes. In this study, dehydration of titanium hydroxide in the cell wall is proposed as the mechanism that leads to the separation of neighboring nanotubes. Based on this understanding, bamboo-type TiO2 nanotubes with large surface area and excellent interconnectivity are achieved by cycling high and low applied potentials. After thermal treatment in a H2 atmosphere, the bamboo-type TiO2 nanotubes show large photoelectrochemical water splitting efficiency and supercapacitors performace.

Quantum chemical elucidation of the mechanism for hydrogenation of TiO2 anatase crystals

NASA Astrophysics Data System (ADS)

Raghunath, P.; Huang, W. F.; Lin, M. C.

2013-04-01

Hydrogenation of TiO2 is relevant to hydrogen storage and water splitting. We have carried out a detailed mechanistic study on TiO2 hydrogenation through H and/or H2 diffusion from the surface into subsurface layers of anatase TiO2 (101) by periodic density functional theory calculations implementing on-site Coulomb interactions (DFT + U). Both H atoms and H2 molecules can migrate from the crystal surface into TiO2 near subsurface layer with 27.8 and 46.2 kcal/mol energy barriers, respectively. The controlling step for the former process is the dissociative adsorption of H2 on the surface which requires 47.8 kcal/mol of energy barrier. Both hydrogen incorporation processes are expected to be equally favorable. The barrier energy for H2 migration from the first layer of the subsurface Osub1 to the 2nd layer of the subsurface oxygen Osub2 requires only 6.6 kcal. The presence of H atoms on the surface and inside the subsurface layer tends to promote both H and H2 penetration into the subsurface layer by reducing their energy barriers, as well as to prevent the escape of the H2 from the cage by increasing its escaping barrier energy. The H2 molecule inside a cage can readily dissociate and form 2HO-species exothermically (ΔH = -31.0 kcal/mol) with only 26.2 kcal/mol barrier. The 2HO-species within the cage may further transform into H2O with a 22.0 kcal/mol barrier and 19.3 kcal/mol exothermicity relative to the caged H2 molecule. H2O formation following the breaking of Ti-O bonds within the cage may result in the formation of O-vacancies and surface disordering as observed experimentally under a high pressure and moderately high temperature condition. According to density of states analysis, the projected density of states of the interstitial H, H2, and H2O appear prominently within the TiO2 band gap; in addition, the former induces a shift of the band gap position notably towards the conduction band. The thermochemistry for formation of the most stable sub-surface species (2HO and H2O) has been predicted. These results satisfactorily account for the photo-catalytic activity enhancement observed experimentally by hydrogenation at high temperatures and high pressures.

Enhanced Charge Collection with Passivation Layers in Perovskite Solar Cells.

PubMed

Lee, Yong Hui; Luo, Jingshan; Son, Min-Kyu; Gao, Peng; Cho, Kyung Taek; Seo, Jiyoun; Zakeeruddin, Shaik M; Grätzel, Michael; Nazeeruddin, Mohammad Khaja

2016-05-01

The Al2 O3 passivation layer is beneficial for mesoporous TiO2 -based perovskite solar cells when it is deposited selectively on the compact TiO2 surface. Such a passivation layer suppressing surface recombination can be formed by thermal decomposition of the perovskite layer during post-annealing. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An ingenious strategy of preparing TiO2/g-C3N4 heterojunction photocatalyst: In situ growth of TiO2 nanocrystals on g-C3N4 nanosheets via impregnation-calcination method

NASA Astrophysics Data System (ADS)

Zhang, Guanghui; Zhang, Tianyong; Li, Bin; Jiang, Shuang; Zhang, Xia; Hai, Li; Chen, Xingwei; Wu, Wubin

2018-03-01

An ingenious method was employed to design and fabricate the TiO2/g-C3N4 heterojunction photocatalysts in this study. The thermal oxidation etching of g-C3N4 nanosheets and the in situ growth of TiO2 nanocrystal on the surface of g-C3N4 nanosheets were completed simultaneously by the calcination process. The g-C3N4 nanosheets played a crucial role in regulating and assembling the structures and morphologies of TiO2. Furthermore, the thickness and content of g-C3N4, and the crystallinity of TiO2 in TiO2/g-C3N4 composites could be regulated and controlled by the calcination temperature. Among the resultant TiO2/g-C3N4 samples, the TiO2/g-C3N4 sample with 41.6 wt% g-C3N4 exhibited the highest photocatalytic activity. It could degrade almost all MO molecules under visible light irradiation within 3 h. Moreover, it displayed higher visible light photocatalytic performance for degrading MO solution than pure g-C3N4 and D-TiO2. The synergistic effect between TiO2 and g-C3N4 makes significant contributions to the enhancement of the visible light photocatalytic activity. In addition, the favorable photocatalytic performance of TiO2/g-C3N4 nanocomposites is also attributed to the porous structures and uniform morphologies, and large surface area. Furthermore, the resultant TiO2/g-C3N4 exhibits excellent photocatalytic stability. Radical trapping experiments indicated that rad O2- and h+ were the main reactive species during the photodegradation process under visible light irradiation. Hopefully, the results can offer new design and strategy for preparing other g-C3N4-based nanocomposites for environmental and energy applications.

Uniform TiO2-SiO2 hollow nanospheres: Synthesis, characterization and enhanced adsorption-photodegradation of azo dyes and phenol

NASA Astrophysics Data System (ADS)

Guo, Na; Liang, Yimai; Lan, Shi; Liu, Lu; Ji, Guijuan; Gan, Shucai; Zou, Haifeng; Xu, Xuechun

2014-06-01

TiO2-SiO2 hollow nanospheres with remarkable enhanced photocatalytic performance have been fabricated by sol-gel method. The hollow sphere possesses both high phototcatalytic activity and adsorption capability. The as-prepared samples were characterized by XRD, SEM, TEM, FTIR, XPS, BJH and TGA/DSC. The experiment results show that, the photocatalyst calcined at 500 °C with Ti/Si ratio of 5:1 (denoted as 5T/S-500) displayed superiorities in both textural and functional properties with the enhanced degradation efficiency on azo dyes (methylene blue, methyl orange) and phenol. The high adsorption capability of organic poisonous contaminants onto 5T/S-500 in aqueous solution demonstrated that the photocatalyst can remove the contaminants from water effectively even without illumination. The TEM and SEM morphologies demonstrated unique hollow and coarse structure of 5T/S-500. Structural analysis showed that Si was doped into the lattice of TiO2 and SiO2 nanoparticles can work as a surface modifier on TiO2. The surface area of 5T/S-500 is 1105 m2/g, 14.5 times as great as that of the pure hollow TiO2 nanosphere, confirms the effect of SiO2 on the improvement of specific surface area. The high photocatalytic activities and high adsorption ability for organic poisonous contaminants demonstrate that the nanocomposite of TiO2-SiO2 is a promising candidate material for future treatment of contaminated water.

Cracking and Exfoliation of TiO2 Film Irradiated with Excimer Laser

NASA Astrophysics Data System (ADS)

Qian, H. X.; Zhou, W.; Zheng, H. Y.

TiO2 film deposited on glass was irradiated in air with single-shot KrF excimer laser pulse. The surface roughened as the result of the laser ablation. It is further noted that single-pulse irradiation with fluence ranging from 400 to 1200 mJ/cm2 gave rise to protrusion of the irradiated surface above the original surface, which is in contrast to usual expectation that irradiated surface is below the unirradiated surface. The surface protrusion is mainly attributed to the effect of surface tension. At the laser fluence of 1000 mJ/cm2, cracks were formed in the irradiated area and severe film exfoliation was observed at the periphery of the irradiated area due to the release of internal stress. With higher laser fluence above 1000 mJ/cm2, patches of film were observed to peel off within the irradiated areas. Hydrodynamic ablation is proposed to account for film exfoliation. The observed phenomenon is useful for further understanding how TiO2 film reacts to strong UV laser irradiation.

Removal of elemental mercury by TiO₂doped with WO₃ and V₂O₅ for their photo- and thermo-catalytic removal mechanisms.

PubMed

Shen, Huazhen; Ie, Iau-Ren; Yuan, Chung-Shin; Hung, Chung-Hsuang; Chen, Wei-Hsiang

2016-03-01

The catalytic removal of Hg(0) was investigated to ascertain whether the catalysts could simultaneously possess both thermo- and photo-catalytic reactivity. The immobilized V2O5/TiO2 and WO3/TiO2 catalysts were synthesized by sol-gel method and then coated on the surface of glass beads for catalytic removal of Hg(0). They were also characterized by SEM, BET, XRD, UV-visible, and XPS analysis, and their catalytic reactivity was tested under 100-160 °C under the near-UV irradiation. The results indicated that V2O5/TiO2 solely possessed the thermo-catalytic reactivity while WO3/TiO2 only had photo-catalytic reactivity. Although the synthesis catalytic reactivity has not been found for these catalysts up to date, but compared with TiO2, the removal efficiencies of Hg(0) at 140 and 160 °C were enhanced; particularly, the efficiency was improved from 20 % at 160 °C by TiO2 to nearly 90 % by WO3/TiO2 under the same operating conditions. The effects of doping amount of V2O5 and WO3 were also investigated, and the results showed that 10 % V2O5 and 5 % WO3/TiO2 were the best immobilized catalysts for thermo- and photo-catalytic reactivity, respectively. The effect of different influent concentrations of Hg(0) was demonstrated that the highest concentration of Hg(0) led to the best removal efficiencies for V2O5/TiO2 and WO3/TiO2 at 140 and 160 °C, because high Hg(0) concentration increased the mass transfer rate of Hg(0) toward the surface of catalysts and drove the reaction to proceed. At last, the effect of single gas component on the removal of Hg(0) was also investigated.

Ultrasonic spray pyrolysis synthesis of reduced graphene oxide/anatase TiO2 composite and its application in the photocatalytic degradation of methylene blue in water.

PubMed

Park, Jeong-Ann; Yang, Boram; Lee, Joongki; Kim, In Gyeom; Kim, Jae-Hyun; Choi, Jae-Woo; Park, Hee-Deung; Nah, In Wook; Lee, Sang-Hyup

2018-01-01

Reduced graphene oxide (RGO)/anatase TiO 2 composite was prepared using a simple one-step technique-ultrasonic spray pyrolysis-in order to inhibit the aggregation of TiO 2 nanoparticles and to improve the photocatalytic performance for degradation of methylene blue (MB). Different proportions (0-5 wt%) of RGO/TiO 2 composites were characterized by scanning electronic microscopy (SEM), dispersive X-ray spectrometry (EDS), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area, X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD), Raman spectroscopy, UV-vis spectroscopy, and electrochemical impedance spectroscopy (EIS) to verify mechanism. From these analysis, TiO 2 nanoparticles are distributed uniformly on the RGO sheets with crumpled shape during ultrasonic spray pyrolysis and surface area is increasing by increasing portion of RGO. Band gap of RGO 5 /TiO 2 (5 wt% of RGO) composite is 2.72 eV and band gap was reduced by increasing portion of RGO in RGO/TiO 2 composites. The RGO 5 /TiO 2 composite was superior to other lower content of RGO/TiO 2 composites with a rapid transport of charge carriers and an effective charge separation. The highest removal efficiency of MB was obtained at the RGO 5 /TiO 2 composite under UVC irradiation, which coincided with the EIS, and the optimal dose of the composite was determined to be 0.5 g/L. The RGO 5 /TiO 2 composite improve the photocatalytic degradation rate of MB over the TiO 2 due to a retardation of electron-hole recombination. The MB adsorption capacity and photocatalytic degradation efficiency were greatly affected by pH changes and increased with increasing pH due to electrostatic interactions and generation of more hydroxyl radicals. The reusability of RGO 5 /TiO 2 composite was examined during 3 cycles. Copyright © 2017 Elsevier Ltd. All rights reserved.

23327Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of flower-like Bi2S3:Eu3+ sub-microspheres.

PubMed

Xu, Bingyu; Wang, Guofeng; Fu, Honggang

2016-03-21

In this paper, TiO2-Bi2S3 and TiO2-Bi2S3:Eu(3+) composite photoanodes were successfully designed, which can not only fully absorb visible light but also transfer the electron from Bi2S3 to TiO2 conduction band due to the narrow band gap and high conduction band of Bi2S3. Compared to pure TiO2 cell, the photoelectric conversion efficiencies of TiO2-Bi2S3 and TiO2-Bi2S3:Eu(3+) composite cells were increased significantly. In addition, the efficiency of TiO2-Bi2S3:Eu(3+) composite cells were higher than that of TiO2-Bi2S3 cell which could be attributed to the larger BET surface area of Bi2S3:Eu(3+). The electron transport and interfacial recombination kinetics were investigated by the electrochemical impedance spectroscopy and intensity-modulated photocurrent/photovoltage spectroscopy. The results indicated that the interfacial resistance of the TiO2-dye|I3(-)/I(-) electrolyte interface of TiO2-Bi2S3:Eu(3+) composite cell was much bigger than that of pure TiO2 cell. In addition, the TiO2-Bi2S3:Eu(3+) cell has longer electron recombination time and longer electron transport time than pure TiO2 cell. The charge collection efficiency of TiO2-Bi2S3:Eu(3+) composite cell was higher than that of pure TiO2 cell.

Interface actions between TiO2 and porous diatomite on the structure and photocatalytic activity of TiO2-diatomite

NASA Astrophysics Data System (ADS)

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.

The chemical bonds effect of anthocyanin and chlorophyll dyes on TiO2 for dye-sensitized solar cell (DSSC)

NASA Astrophysics Data System (ADS)

Ahliha, A. H.; Nurosyid, F.; Supriyanto, A.; Kusumaningsih, T.

2017-11-01

Anthocyanin and chlorophyll dyes have been blended as the photosensitizer of Dye-Sensitized Solar Cell (DSSC). The results study showed the effect of chemical bond dyes on TiO2 and the efficiency of DSSC. Ratio blend of the anthocyanin and chlorophyll dyes are 1:1. The absorbance of dyes and TiO2 were characterized using UV-Vis Spectrophotometer. The chemical bonds contained in TiO2-dyes were characterized using FT-IR spectrophotometer. The efficiency of DSSC was calculated using I-V meter. The absorption spectra of chlorophyll: anthocyanin blend dye solutions and TiO2 films can increase after the dye adsorption. Absorbance characterization of anthocyanin and chlorophyll dye blend solutions showed three peaks at the wavelength of 412 nm; 535.5 nm; and 656.5 nm. Absorbance characterization of spinach before being blend with anthocyanin dyes solutions showed two peaks at the wavelength of 431 nm and 665.5 nm. The absorption spectra of TiO2 films can increase after the dyes adsorption at the wavelength of 400 nm. FT-IR spectra of TiO2 founded the functional groups C-Br, C=C, and O-H. The functional groups founded in anthocyanin: chlorophyll dye blended on the surface of TiO2 are C-Br, C-O, O-H, C-H, C=C, C=O, and O-H. The result showed that the greatest efficiency of 0.0544% at dye red cabbage-spinach. Adsorption blends of anthocyanin and chlorophyll dyes on the surface of TiO2 can be used as the photosensitizer for DSSC.

Effect of low Fe3+ doping on characteristics, sonocatalytic activity and reusability of TiO2 nanotubes catalysts for removal of Rhodamine B from water.

PubMed

Pang, Yean Ling; Abdullah, Ahmad Zuhairi

2012-10-15

Fe-doped titanium dioxide (TiO(2)) nanotubes were prepared using sol-gel followed by hydrothermal methods and characterized using various methods. The sonocatalytic activity was evaluated based on oxidation of Rhodamine B under ultrasonic irradiation. Iron ions (Fe(3+)) might incorporate into the lattice and intercalated in the interlayer spaces of TiO(2) nanotubes. The catalysts showed narrower band gap energies, higher specific surface areas, more active surface oxygen vacancies and significantly improved sonocatalytic activity. The optimum Fe doping at Fe:Ti=0.005 showed the highest sonocatalytic activity and exceeded that of un-doped TiO(2) nanotubes by a factor of 2.3 times. It was believed that Fe(3+) doping induced the formation of new states close to the valence band and conduction bands and accelerated the separation of charge carriers. Leached Fe(3+) could catalyze Fenton-like reaction and led to an increase in the hydroxyl radical (OH) generation. Fe-doped TiO(2) nanotubes could retain high degradation efficiency even after being reused for 4 cycles with minimal loss of Fe from the surface of the catalyst. Copyright © 2012 Elsevier B.V. All rights reserved.

The presence of Ti(II) centers in doped nanoscale TiO2 and TiO2-xNx

NASA Astrophysics Data System (ADS)

Mikulas, Tanya; Fang, Zongtang; Gole, James L.; White, Mark G.; Dixon, David A.

2012-06-01

Unusual trends are observed in the Ti (2s, 2p) XPS spectra of Fe(II) doped TiO2 and TiO2-xNx. The binding energy of Ti (2s, 2p) initially decreases with increasing Fe(II) concentration, as expected, but increases at higher Fe(II) doping levels. Density functional theory is used to analyze the results. The observed VB-XPS and core level XPS spectra are consistent with the facile charge transfer sequence Ti(IV) + Fe(II) → Ti(III) + Fe(III) followed by Ti(III) + Fe(II) → Ti(II) + Fe(III). The formed Ti(II) sites may be relevant to nanoparticle catalysis on TiO2 surfaces.

Degradation of organic dyes using spray deposited nanocrystalline stratified WO3/TiO2 photoelectrodes under sunlight illumination

NASA Astrophysics Data System (ADS)

Hunge, Y. M.; Yadav, A. A.; Mahadik, M. A.; Bulakhe, R. N.; Shim, J. J.; Mathe, V. L.; Bhosale, C. H.

2018-02-01

The need to utilize TiO2 based metal oxide hetero nanostructures for the degradation of environmental pollutants like Rhodamine B and reactive red 152 from the wastewater using stratified WO3/TiO2 catalyst under sunlight illumination. WO3, TiO2 and stratified WO3/TiO2 catalysts were prepared by a spray pyrolysis method. It was found that the stratified WO3/TiO2 heterostructure has high crystallinity, no mixed phase formation occurs, strong optical absorption in the visible region of the solar spectrum, and large surface area. The photocatalytic activity was tested for degradation of Rhodamine B (Rh B) and reactive red 152 in an aqueous medium. TiO2 layer in stratified WO3/TiO2 catalyst helps to extend its absorption spectrum in the solar light region. Rh B and Reactive red 152is eliminated up to 98 and 94% within the 30 and 40 min respectively at optimum experimental condition by stratified WO3/TiO2. Moreover, stratified WO3/TiO2 photoelectrode has good stability and reusability than individual TiO2 and WO3 thin film in the degradation of Rh B and reactive red 152. The photoelectrocatalytic experimental results indicate that stratified WO3/TiO2 photoelectrode is a promising material for dye removal.

Donor defects and small polarons on the TiO2(110) surface

NASA Astrophysics Data System (ADS)

Moses, P. G.; Janotti, A.; Franchini, C.; Kresse, G.; Van de Walle, C. G.

2016-05-01

The role of defects in the chemical activity of the rutile TiO2(110) surface remains a rich topic of research, despite the rutile (110) being one of the most studied surfaces of transition-metal oxides. Here, we present results from hybrid functional calculations that reconcile apparently disparate views on the impact of donor defects, such as oxygen vacancies and hydrogen impurities, on the electronic structure of the (110) rutile surface. We find that the bridging oxygen vacancy and adsorbed or substitutional hydrogen are actually shallow donors, which do not induce gap states. The excess electrons from these donor centers tend to localize in the form of small polarons, which are the factual cause of the deep states ˜1 eV below the conduction band, often observed in photoelectron spectroscopy measurements. Our results offer a new framework for understanding the surface electronic structure of TiO2 and related oxides.

Surface Plasmon Enhanced Photocatalysis of Au/Pt-decorated TiO2 Nanopillar Arrays

NASA Astrophysics Data System (ADS)

Shuang, Shuang; Lv, Ruitao; Xie, Zheng; Zhang, Zhengjun

2016-05-01

The low quantum yields and lack of visible light utilization hinder the practical application of TiO2 in high-performance photocatalysis. Herein, we present a design of TiO2 nanopillar arrays (NPAs) decorated with both Au and Pt nanoparticles (NPs) directly synthesized through successive ion layer adsorption and reaction (SILAR) at room temperature. Au/Pt NPs with sizes of ~4 nm are well-dispersed on the TiO2 NPAs as evidenced by electron microscopic analyses. The present design of Au/Pt co-decoration on the TiO2 NPAs shows much higher visible and ultraviolet (UV) light absorption response, which leads to remarkably enhanced photocatalytic activities on both the dye degradation and photoelectrochemical (PEC) performance. Its photocatalytic reaction efficiency is 21 and 13 times higher than that of pure TiO2 sample under UV-vis and visible light, respectively. This great enhancement can be attributed to the synergy of electron-sink function of Pt and surface plasmon resonance (SPR) of Au NPs, which significantly improves charge separation of photoexcited TiO2. Our studies demonstrate that through rational design of composite nanostructures one can harvest visible light through the SPR effect to enhance the photocatalytic activities initiated by UV-light, and thus realize more effectively utilization of the whole solar spectrum for energy conversion.

Visible photoelectrochemical water splitting into H 2 and O 2 in a dye-sensitized photoelectrosynthesis cell

DOE PAGES

Alibabaei, Leila; Sherman, Benjamin D.; Norris, Michael R.; ...

2015-04-27

A hybrid strategy for solar water splitting is exploited here based on a dye-sensitized photoelectrosynthesis cell (DSPEC) with a mesoporous SnO 2/TiO 2 core/shell nanostructured electrode derivatized with a surface-bound Ru(II) polypyridyl-based chromophore–catalyst assembly. The assembly, [(4,4’-(PO 3H 2) 2bpy) 2Ru(4-Mebpy-4’-bimpy)Ru(tpy)(OH 2)] 4+ ([RuaII-RubII-OH 2] 4+, combines both a light absorber and a water oxidation catalyst in a single molecule. It was attached to the TiO 2 shell by phosphonate-surface oxide binding. The oxide-bound assembly was further stabilized on the surface by atomic layer deposition (ALD) of either Al 2O 3 or TiO 2 overlayers. Illumination of the resulting fluorine-dopedmore » tin oxide (FTO)|SnO 2/TiO 2|-[Ru a II-Ru b II-OH 2] 4+(Al 2O 3 or TiO 2) photoanodes in photoelectrochemical cells with a Pt cathode and a small applied bias resulted in visible-light water splitting as shown by direct measurements of both evolved H 2 and O 2. The performance of the resulting DSPECs varies with shell thickness and the nature and extent of the oxide overlayer. Use of the SnO 2/TiO 2 core/shell compared with nanoITO/TiO 2 with the same assembly results in photocurrent enhancements of ~5. In conclusion, systematic variations in shell thickness and ALD overlayer lead to photocurrent densities as high as 1.97 mA/cm 2 with 445-nm, ~90-mW/cm 2 illumination in a phosphate buffer at pH 7.« less

Enhancing the photoelectrochemical response of TiO2 nanotubes through their nanodecoration by pulsed-laser-deposited Ag nanoparticles

NASA Astrophysics Data System (ADS)

Trabelsi, K.; Hajjaji, A.; Gaidi, M.; Bessais, B.; El Khakani, M. A.

2017-08-01

We report on the pulsed laser deposition (PLD) based nanodecoration of titanium dioxide (TiO2) nanotube arrays (NTAs) by Ag nanoparticles (NPs). We focus here on the investigation of the effect of the number of laser ablation pulses (NLP) of the silver target on both the average size of the Ag-NPs and the photoelectrochemical conversion efficiency of the Ag-NP decorated TiO2-NT based photoanodes. By varying the NLP, we were able to not only control the size of the PLD-deposited Ag nanoparticles from 20 to ˜50 nm, but also to increase concomitantly the surface coverage of the TiO2 NTAs by Ag-NPs. The red-shifting of the surface plasmon resonance peak of the PLD-deposited Ag-NPs deposited onto quartz substrates confirmed the increase of their size as the NLP is increased from 500 to 10 000. By investigating the photo-electrochemical properties of Ag-NP decorated TiO2-NTAs, by means of linear sweep cyclic voltammetry under UV-Vis illumination, we found that the generated photocurrent is sensitive to the size of the Ag-NPs and reaches a maximum value at NLP =500 (i.e.,; Ag-NP size of ˜20 nm). For NLP = 500, the photoconversion efficiency of the Ag-NP decorated TiO2-NTAs is shown to reach a maximum of 4.5% (at 0.5 V vs Ag/AgCl). The photocurrent enhancement of Ag-NP decorated TiO2-NTAs is believed to result from the additional light harvesting enabled by the ability of Ag-NPs to absorb visible irradiation caused by various localized surface plasmon resonances, which in turn depend on the size and interdistance of the Ag nanoparticles.

Photocatalytic activity of Ti3+ self-doped dark TiO2 ultrafine nanorods, grey SiO2 nanotwin crystalline, and their composite under visible light

NASA Astrophysics Data System (ADS)

Zhang, Renhui; Yang, Yingchang; Leng, Senlin; Wang, Qing

2018-04-01

Efficient electron-holes separation is of crucial importance for the improvement of photocatalytic activity for photocatalytic reaction. In this work, dark TiO2 (D-TiO2) nanorods, grey SiO2 (G-SiO2) and D-TiO2/G-SiO2 composite with surface defects are synthesized. We report that the efficiency of photo-generated electrons and holes separation is well enhanced by introducing G-SiO2 into D-TiO2 lattice. Using first-principles method, we find that surface defects (O or Si vacancy) can be conducive to improving the optical absorption under visible-light region. Combination of the experimental results, for D-TiO2/G-SiO2 composite, the surface defects of TiO2 nanocrystallines can significantly improve the photocatalytic efficiency.

Rapid fabrication of TiO2@carboxymethyl cellulose coatings capable of shielding UV, antifog and delaying support aging.

PubMed

Li, Xiaozhou; Lv, Junping; Li, Dehuai; Wang, Lin

2017-08-01

Agricultural plastic films capable of shielding UV, filtering visible light and antifog are important to prolong their life and protect safeties of agriculturists and crops. In this work, high stable and small size TiO 2 @polymer nanoparticles (NPs) were prepared by an efficient one-pot microwave synthesis using titanic sulfate as Ti resource, carboxymethyl cellulose sodium (CMC) as complexing agent and stabilizer. The TiO 2 @CMC NPs obtained were then utilized to fabricate poly(ethylene imine) (PEI)/TiO 2 @CMC coatings on the surface of polypropylene films by a layer-by-layer assembly technique. The TiO 2 @CMC NPs show rapid deposition rate because small, spherical and anion-rich TiO 2 @CMC NPs possess large specific surface area and fast diffusion rate. More importantly, property experiments confirm that (PEI/TiO 2 @CMC)*15 coatings can not only effectively shield UV rays, filter visible light and prevent fogging but also delay the aging of their supports. Copyright © 2017 Elsevier Ltd. All rights reserved.

High photocatalytic activity of Fe2O3/TiO2 nanocomposites prepared by photodeposition for degradation of 2,4-dichlorophenoxyacetic acid.

PubMed

Lee, Shu Chin; Lintang, Hendrik O; Yuliati, Leny

2017-01-01

Two series of Fe 2 O 3 /TiO 2 samples were prepared via impregnation and photodeposition methods. The effect of preparation method on the properties and performance of Fe 2 O 3 /TiO 2 for photocatalytic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) under UV light irradiation was examined. The Fe 2 O 3 /TiO 2 nanocomposites prepared by impregnation showed lower activity than the unmodified TiO 2 , mainly due to lower specific surface area caused by heat treatment. On the other hand, the Fe 2 O 3 /TiO 2 nanocomposites prepared by photodeposition showed higher photocatalytic activity than the unmodified TiO 2 . Three times higher photocatalytic activity was obtained on the best photocatalyst, Fe 2 O 3 (0.5)/TiO 2 . The improved activity of TiO 2 after photodeposition of Fe 2 O 3 was contributed to the formation of a heterojunction between the Fe 2 O 3 and TiO 2 nanoparticles that improved charge transfer and suppressed electron-hole recombination. A further investigation on the role of the active species on Fe 2 O 3 /TiO 2 confirmed that the crucial active species were both holes and superoxide radicals. The Fe 2 O 3 (0.5)/TiO 2 sample also showed good stability and reusability, suggesting its potential for water purification applications.

Unravelling Site-Specific Photo-Reactions of Ethanol on Rutile TiO2(110)

PubMed Central

Hansen, Jonas Ø.; Bebensee, Regine; Martinez, Umberto; Porsgaard, Soeren; Lira, Estephania; Wei, Yinying; Lammich, Lutz; Li, Zheshen; Idriss, Hicham; Besenbacher, Flemming; Hammer, Bjørk; Wendt, Stefan

2016-01-01

Finding the active sites of catalysts and photo-catalysts is crucial for an improved fundamental understanding and the development of efficient catalytic systems. Here we have studied the photo-activated dehydrogenation of ethanol on reduced and oxidized rutile TiO2(110) in ultrahigh vacuum conditions. Utilizing scanning tunnelling microscopy, various spectroscopic techniques and theoretical calculations we found that the photo-reaction proceeds most efficiently when the reactants are adsorbed on regular Ti surface sites, whereas species that are strongly adsorbed at surface defects such as O vacancies and step edges show little reaction under reducing conditions. We propose that regular Ti surface sites are the most active sites in photo-reactions on TiO2. PMID:26915303

Experimental and Statistical Analysis of MgO Nanofluids for Thermal Enhancement in a Novel Flat Plate Heat Pipes

NASA Astrophysics Data System (ADS)

Pandiaraj, P.; Gnanavelbabu, A.; Saravanan, P.

Metallic fluids like CuO, Al2O3, ZnO, SiO2 and TiO2 nanofluids were widely used for the development of working fluids in flat plate heat pipes except magnesium oxide (MgO). So, we initiate our idea to use MgO nanofluids in flat plate heat pipe as a working fluid material. MgO nanopowders were synthesized by wet chemical method. Solid state characterizations of synthesized nanopowders were carried out by Ultraviolet Spectroscopy (UV), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) techniques. Synthesized nanopowders were prepared as nanofluids by adding water and as well as water/ethylene glycol as a binary mixture. Thermal conductivity measurements of prepared nanofluids were studied using transient hot-wire apparatus. Response surface methodology based on the Box-Behnken design was implemented to investigate the influence of temperature (30-60∘C), particle fraction (1.5-4.5 vol.%), and solution pH (4-12) of nanofluids as the independent variables. A total of 17 experiments were accomplished for the construction of second-order polynomial equations for target output. All the influential factors, their mutual effects and their quadratic terms were statistically validated by analysis of variance (ANOVA). The optimum stability and thermal conductivity of MgO nanofluids with various temperature, volume fraction and solution pH were predicted and compared with experimental results. The results revealed that increase in particle fraction and pH of MgO nanofluids at certain points would increase thermal conductivity and become stable at nominal temperature.

Studying the Use of Photocatalytic Coatings to Increase Building/Structure Sustainability and Cleanliness at NASA Stennis Space Center

NASA Technical Reports Server (NTRS)

Underwood, Lauren

2013-01-01

TiO2 coated surfaces demonstrated both visually through photographic representation, and quantitatively, through reflectance measurements that they improved upon the current state of cleanliness upon the surfaces that they were applied to. TiO2 has the potential to both maintain and increase building s sustainability and the overall appearance of cleanliness TiO2 coated slides degraded soot under UV light compared to soot samples on plain uncoated slides under the same conditions Degradation of soot by photocatalysis was far more apparent than degradation of soot by UV light alone This demonstration provides the foundation for a laboratory model that could be used to simulate real world applications for photocatalytic materials Additional research is required to better understand the full potential of TiO2

Efficient Photocatalytic Bilirubin Removal over the Biocompatible Core/Shell P25/g-C3N4 Heterojunctions with Metal-free Exposed Surfaces under Moderate Green Light Irradiation

NASA Astrophysics Data System (ADS)

Kang, Shifei; Qin, Hengfei; Zhang, Lu; Huang, Yongkui; Bai, Xia; Li, Xi; Sun, Di; Wang, Yangang; Cui, Lifeng

2017-03-01

Highly-monodispersed g-C3N4/TiO2 hybrids with a core/shell structure were synthesized from a simple room temperature impregnation method, in which g-C3N4 was coated through self-assembly on the commercially available Degussa P25 TiO2 nanoparticles. Structural and surface characterizations showed that the presence of g-C3N4 notably affected the light absorption characteristics of TiO2. The g-C3N4/TiO2 heterojunctions with metal-free exposed surfaces were directly used as biocompatible photocatalysts for simulated jaundice phototherapy under low-power green-light irradiation. The photocatalytic activity and stability of g-C3N4/TiO2 were enhanced relative to pure P25 or g-C3N4, which could be ascribed to the effective Z-scheme separation of photo-induced charge carriers in g-C3N4/TiO2 heterojunction. The photoactivity was maximized in the 4 wt.% g-C3N4-coated P25, as the bilirubin removal rate under green light irradiation was more than 5-fold higher than that under the clinically-used blue light without any photocatalyst. This study approves the future applications of the photocatalyst-assisted bilirubin removal in jaundice treatment under moderate green light which is more tolerable by humans.

Self-assembled mesoporous TiO2/carbon nanotube composite with a three-dimensional conducting nanonetwork as a high-rate anode material for lithium-ion battery

NASA Astrophysics Data System (ADS)

Wang, Jie; Ran, Ran; Tade, Moses O.; Shao, Zongping

2014-05-01

Mesoporous three-dimensional (3D) TiO2/carbon nanotube conductive hybrid nanostructures can be successfully developed using polyethylene oxide (PEO) to modify the surfaces of carbon nanotubes (CNTs). During the synthesis process, PEO acts as not only "bridges" to connect the TiO2 nanoparticles to the CNT surfaces but also as "hosts" to accommodate and stabilize the in situ generated TiO2 particles. As the electrodes for lithium-ion batteries, such mesoporous 3D TiO2/CNT hybrids, demonstrate high Li storage capacity, superior rate performance and excellent long-term cycling stability. They exhibit a reversible specific capacity of 203 mA h g-1 at 100 mA g-1 and a stable capacity retention of 91 mA h g-1 at 8000 mA g-1 (47.6 C) over 100 cycles; they also retain approximately 90% (71 mA h g-1) of their initial discharge capacity after 900 cycles at an extremely high rate of 15,000 mA g-1 (89 C). This facile synthetic strategy to construct mesoporous 3D TiO2/CNT conductive hybrids provides a convenient route that efficiently assembles various inorganic oxide components on the CNTs' surfaces and enables the formation of heterogeneous nanostructures with novel functionalities. In particular, utilizing a conductive 3D CNT network can serve as a promising strategy for developing high-performance electrodes for Li secondary batteries and supercapacitors.

Efficient Photocatalytic Bilirubin Removal over the Biocompatible Core/Shell P25/g-C3N4 Heterojunctions with Metal-free Exposed Surfaces under Moderate Green Light Irradiation

PubMed Central

Kang, Shifei; Qin, Hengfei; Zhang, Lu; Huang, Yongkui; Bai, Xia; Li, Xi; Sun, Di; Wang, Yangang; Cui, Lifeng

2017-01-01

Highly-monodispersed g-C3N4/TiO2 hybrids with a core/shell structure were synthesized from a simple room temperature impregnation method, in which g-C3N4 was coated through self-assembly on the commercially available Degussa P25 TiO2 nanoparticles. Structural and surface characterizations showed that the presence of g-C3N4 notably affected the light absorption characteristics of TiO2. The g-C3N4/TiO2 heterojunctions with metal-free exposed surfaces were directly used as biocompatible photocatalysts for simulated jaundice phototherapy under low-power green-light irradiation. The photocatalytic activity and stability of g-C3N4/TiO2 were enhanced relative to pure P25 or g-C3N4, which could be ascribed to the effective Z-scheme separation of photo-induced charge carriers in g-C3N4/TiO2 heterojunction. The photoactivity was maximized in the 4 wt.% g-C3N4-coated P25, as the bilirubin removal rate under green light irradiation was more than 5-fold higher than that under the clinically-used blue light without any photocatalyst. This study approves the future applications of the photocatalyst-assisted bilirubin removal in jaundice treatment under moderate green light which is more tolerable by humans. PMID:28287189

Whiter, brighter, and more stable cellulose paper coated with TiO2 /SiO2 core/shell nanoparticles using a layer-by-layer approach.

PubMed

Cheng, Fei; Lorch, Mark; Sajedin, Seyed Mani; Kelly, Stephen M; Kornherr, Andreas

2013-08-01

To inhibit the photocatalytic degradation of organic material supports induced by small titania (TiO2 ) nanoparticles, four kinds of TiO2 nanoparticles, that is, commercial P25-TiO2 , commercial rutile phase TiO2 , rutile TiO2 nanorods and rutile TiO2 spheres, prepared from TiCl4 , were coated with a thin, but dense, coating of silica (SiO2 ) using a conventional sol-gel technique to form TiO2 /SiO2 core/shell nanoparticles. These core/shell particles were deposited and fixed as a very thin coating onto the surface of cellulose paper samples by a wet-chemistry polyelectrolyte layer-by-layer approach. The TiO2 /SiO2 nanocoated paper samples exhibit higher whiteness and brightness and greater stability to UV-bleaching than comparable samples of blank paper. There are many potential applications for this green chemistry approach to protect cellulosic fibres from UV-bleaching in sunlight and to improve their whiteness and brightness. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Increased osteoblast and decreased Staphylococcus epidermidis functions on nanophase ZnO and TiO2.

PubMed

Colon, Gabriel; Ward, Brian C; Webster, Thomas J

2006-09-01

Many engineers and surgeons trace implant failure to poor osseointegration (or the bonding of an orthopedic implant to juxtaposed bone) and/or bacteria infection. By using novel nanotopographies, researchers have shown that nanostructured ceramics, carbon fibers, polymers, metals, and composites enhance osteoblast adhesion and calcium/phosphate mineral deposition. However, the function of bacteria on materials with nanostructured surfaces remains largely uninvestigated. This is despite the fact that during normal surgical insertion of an orthopedic implant, bacteria from the patient's own skin and/or mucosa enters the wound site. These bacteria (namely, Staphylococcus epidermidis) irreversibly adhere to an implant surface while various physiological stresses induce alterations in the bacterial growth rate leading to biofilm formation. Because of their integral role in determining the success of orthopedic implants, the objective of this in vitro study was to examine the functions of (i) S. epidermidis and (ii) osteoblasts (or bone-forming cells) on ZnO and titania (TiO(2)), which possess nanostructured compared to microstructured surface features. ZnO is a well-known antimicrobial agent and TiO(2) readily forms on titanium once implanted. Results of this study provided the first evidence of decreased S. epidermidis adhesion on ZnO and TiO(2) with nanostructured when compared with microstructured surface features. Moreover, compared with microphase formulations, results of this study showed increased osteoblast adhesion, alkaline phosphatase activity, and calcium mineral deposition on nanophase ZnO and TiO(2). In this manner, this study suggests that nanophase ZnO and TiO(2) may reduce S. epidermidis adhesion and increase osteoblast functions necessary to promote the efficacy of orthopedic implants.

Enhanced photochemical catalysis of TiO2 inverse opals by modification with ZnO or Fe2O3 using ALD and the hydrothermal method

NASA Astrophysics Data System (ADS)

Liu, Jiatong; Sun, Cuifeng; Fu, Ming; Long, Jie; He, Dawei; Wang, Yongsheng

2018-02-01

The development of porous materials exhibiting photon regulation abilities for improved photoelectrochemical catalysis performance is always one of the important goals of solar energy harvesting. In this study, methods to improve the photocatalytic activity of TiO2 inverse opals were discussed. TiO2 inverse opals were prepared by atomic layer deposition (ALD) using colloidal crystal templates. In addition, TiO2 inverse opal heterostructures were fabricated using colloidal heterocrystals by repeated vertical deposition using different colloidal spheres. The hydrothermal method and ALD were used to prepare ZnO- or Fe2O3-modified TiO2 inverse opals on the internal surfaces of the TiO2 porous structures. Although the photonic reflection band was not significantly varied by oxide modification, the presence of Fe2O3 in the TiO2 inverse opals enhanced their visible absorption. The conformally modified oxides on the TiO2 inverse opals could also form energy barriers and avoid the recombination of electrons and holes. The fabrication of the TiO2 photonic crystal heterostructures and modification with ZnO or Fe2O3 can enhance the photocatalytic activity of TiO2 inverse opals.

Quantification of the effect of 4-tert-butylpyridine addition to I-/I3- redox electrolytes in dye-sensitized nanostructured TiO2 solar cells.

PubMed

Boschloo, Gerrit; Häggman, Leif; Hagfeldt, Anders

2006-07-06

Addition of 4-tert-butylpyridine (4TBP) to redox electrolytes used in dye-sensitized TiO2 solar cells has a large effect on their performance. In an electrolyte containing 0.7 M LiI and 0.05 M I2 in 3-methoxypropionitrile, addition of 0.5 M 4TBP gave an increase of the open-circuit potential of 260 mV. Using charge extraction and electron lifetime measurements, this increases could be attributed to a shift of the TiO2 band edge toward negative potentials (responsible for 60% of the voltage increase) and to an increase of the electron lifetime (40%). At a lower 4TBP concentration the shift of the band edge was similar, but the effect on the electron lifetime was less pronounced. The working mechanism of 4TBP can be summarized as follows: (1) 4TBP affects the surface charge of TiO2 by decreasing the amount of adsorbed protons and/or Li+ ions. (2) It decreases the recombination of electrons in TiO2 with triiodide in the electrolyte by preventing triiodide access to the TiO2 surface and/or by complexation with iodine in the electrolyte.

Surface modification of titania powder P25 with phosphate and phosphonic acids--effect on thermal stability and photocatalytic activity.

PubMed

Djafer, Lahcène; Ayral, André; Boury, Bruno; Laine, Richard M

2013-03-01

Phosphorus is frequently reported as a doping element for TiO(2) as photocatalyst; however, the previously reported methods used to prepare P-doped TiO(2) do not allow control over the location of the phosphorus either in the bulk or at the surface or both. In this study, we report on the surface modification of Evonik P25 with phosphonic (H(3)PO(3)) and octylphosphonic acid [C(8)H(17)-PO(OH)(2)], done to limit the introduction of phosphorus only to the photocatalyst surface. The effect of this element on the thermal behavior and photocatalytic properties is reported through characterization using elemental analyses, solid state (31)P NMR, X-ray powder diffraction, N(2) porosimetry, dilatometry, etc. Thus, the objective of the work reported here is to focus on the role(s) that phosphorus plays only at TiO(2) crystallite surfaces. For comparison, other samples were treated with phosphoric acid. Copyright © 2012 Elsevier Inc. All rights reserved.

Improved metal-insulator-transition characteristics of ultrathin VO2 epitaxial films by optimized surface preparation of rutile TiO2 substrates

NASA Astrophysics Data System (ADS)

Martens, Koen; Aetukuri, Nagaphani; Jeong, Jaewoo; Samant, Mahesh G.; Parkin, Stuart S. P.

2014-02-01

Key to the growth of epitaxial, atomically thin films is the preparation of the substrates on which they are deposited. Here, we report the growth of atomically smooth, ultrathin films of VO2 (001), only ˜2 nm thick, which exhibit pronounced metal-insulator transitions, with a change in resistivity of ˜500 times, at a temperature that is close to that of films five times thicker. These films were prepared by pulsed laser deposition on single crystalline TiO2(001) substrates that were treated by dipping in acetone, HCl and HF in successive order, followed by an anneal at 700-750 °C in flowing oxygen. This pretreatment removes surface contaminants, TiO2 defects, and provides a terraced, atomically smooth surface.

Effects of Helium Ion Irradiation on Properties of Crystalline and Amorphous Multiphase Ceramic Coatings

NASA Astrophysics Data System (ADS)

Chen, Yong; Hu, Liangbin; Qiu, Changjun; He, Bin; Wang, Zhongchang

2017-08-01

The Al2O3-TiO2 crystalline and amorphous multiphase ceramic coatings were prepared on a martensitic steel by laser in situ reaction technique and impose irradiation with 200 keV He ions at different doses. The helium ion irradiation goes 1.55 μm deep from the surface of coating, and the displacement per atom (dpa) for the Al2O3-TiO2 coating is 20.0. When the irradiation fluency is 5 × 1017 ions/cm2, defects are identified in crystalline areas and there form interfacial areas in the coating. These crystal defects tend to migrate and converge at the interfaces. Moreover, helium ion irradiation is found to exert no effect on surface chemical composition and phase constitution of the coatings, while surface mechanical properties for the coatings after irradiation differ from those before irradiation. Further nano-indentation experiments reveal that surface nano-hardness of the Al2O3-TiO2 multiphase coatings decreases as the helium ions irradiation flux increases. Such Al2O3-TiO2 crystalline and amorphous multiphase ceramic coatings exhibit the strongest resistance against helium ion irradiation which shall be applied as candidate structural materials for accelerator-driven sub-critical system to handle the nuclear waste under extreme conditions.

Simulation and experiment on the catalytic degradation of high-concentration SF6 on TiO2 surface under UV light

NASA Astrophysics Data System (ADS)

Zhang, Ying; Li, Yalong; Cui, Zhaolun; Chen, Dachang; Zhang, Xiaoxing

2018-05-01

The high-temperature effect gas SF6 is used in the power industry, and its emissions are increasing daily. Therefore, the degradation of SF6 is particularly important. In this work, SF6 with a high concentration of 2% was degraded using the catalytic principle of TiO2 under UV light at normal temperature and pressure. Experimental results proved that this method can effectively degrade SF6. Moreover, the addition of TiO2 can effectively increase the degradation rate of SF6. The degradation of eight pieces of TiO2 with a unit area of 3 cm2 was 8.98% after 3 h of catalysis. FTIR spectral analysis showed that the main degradation products were SO2F2, SiF4, SF4, and SO2. Adding H2O can further increase the degradation rate, which can reach 27.22% in 3 h. The main degradation products were SO2F2, SiF4, SF4, SiH4, HF, and SO2. Finally, simulations verified the catalytic decomposition of SF6 on the surface of TiO2.

Atomic layer deposition of nano-TiO2 thin films with enhanced biocompatibility and antimicrobial activity for orthopedic implants

PubMed Central

Liu, Luting; Bhatia, Ritwik; Webster, Thomas J

2017-01-01

Titanium (Ti) and its alloys have been extensively used as implant materials in orthopedic applications. Nevertheless, implants may fail due to a lack of osseointegration and/or infection. The aim of this in vitro study was to endow an implant surface with favorable biological properties by the dual modification of surface chemistry and nanostructured topography. The application of a nanostructured titanium dioxide (TiO2) coating on Ti-based implants has been proposed as a potential way to enhance tissue-implant interactions while inhibiting bacterial colonization simultaneously due to its chemical stability, biocompatibility, and antimicrobial properties. In this paper, temperature-controlled atomic layer deposition (ALD) was introduced for the first time to provide unique nanostructured TiO2 coatings on Ti substrates. The effect of nano-TiO2 coatings with different morphology and structure on human osteoblast and fibroblast functions and bacterial activities was investigated. In vitro results indicated that the TiO2 coating stimulated osteoblast adhesion and proliferation while suppressing fibroblast adhesion and proliferation compared to uncoated materials. In addition, the introduction of nano-TiO2 coatings was shown to inhibit gram-positive bacteria (Staphylococcus aureus), gram-negative bacteria (Escherichia coli), and antibiotic-resistant bacteria (methicillin-resistant Staphylococcus aureus), all without resorting to the use of antibiotics. Our results suggest that the increase in nanoscale roughness and greater surface hydrophilicity (surface energy) together could contribute to increased protein adsorption selectively, which may affect the cellular and bacterial activities. It was found that ALD-grown TiO2-coated samples with a moderate surface energy at 38.79 mJ/m2 showed relatively promising antibacterial properties and desirable cellular functions. The ALD technique provides a novel and effective strategy to produce TiO2 coatings with delicate control of surface nanotopography and surface energy to enhance the interfacial biocompatibility and mitigate bacterial infection, and could potentially be used for improving numerous orthopedic implants. PMID:29263665

Analysis of Ti valence states in resistive switching regions of a rutile TiO2‑ x four-terminal memristive device

NASA Astrophysics Data System (ADS)

Yamaguchi, Kengo; Takeuchi, Shotaro; Tohei, Tetsuya; Ikarashi, Nobuyuki; Sakai, Akira

2018-06-01

We have performed Ti valence state analysis of our four-terminal rutile TiO2‑ x single-crystal memristors using scanning transmission electron microscopy–electron energy loss spectroscopy (STEM–EELS). Analysis of Ti-L2,3 edge EELS spectra revealed that the electrocolored region formed by the application of voltage includes a valence state reflecting highly reduced TiO2‑ x due to the accumulation of oxygen vacancies. Such a valence state mainly exists within ∼50 nm from the crystal surface and extends along specific crystal directions. These electrically reduced surface layers are considered to directly contribute to the resistive switching (RS) in the four-terminal device. The present results add new insights into the microscopic mechanisms of the RS phenomena and should contribute to further development and improvements of TiO2‑ x based memristive devices.

Silver nanoparticles-incorporated Nb2O5 surface passivation layer for efficiency enhancement in dye-sensitized solar cells.

PubMed

Suresh, S; Unni, Gautam E; Satyanarayana, M; Sreekumaran Nair, A; Mahadevan Pillai, V P

2018-08-15

Guiding and capturing photons at the nanoscale by means of metal nanoparticles and interfacial engineering for preventing back-electron transfer are well documented techniques for performance enhancement in excitonic solar cells. Drifting from the conventional route, we propose a simple one-step process to integrate both metal nanoparticles and surface passivation layer in the porous photoanode matrix of a dye-sensitized solar cell. Silver nanoparticles and Nb 2 O 5 surface passivation layer are simultaneously deposited on the surface of a highly porous nanocrystalline TiO 2 photoanode, facilitating an absorption enhancement in the 465 nm and 570 nm wavelength region and a reduction in back-electron transfer in the fabricated dye-sensitized solar cells together. The TiO 2 photoanodes were prepared by spray pyrolysis deposition method from a colloidal solution of TiO 2 nanoparticles. An impressive 43% enhancement in device performance was accomplished in photoanodes having an Ag-incorporated Nb 2 O 5 passivation layer as against a cell without Ag nanoparticles. By introducing this idea, we were able to record two benefits - the metal nanoparticles function as the absorption enhancement agent, and the Nb 2 O 5 layer as surface passivation for TiO 2 nanoparticles and as an energy barrier layer for preventing back-electron transfer - in a single step. Copyright © 2018 Elsevier Inc. All rights reserved.

Hierarchical FeTiO3-TiO2 hollow spheres for efficient simulated sunlight-driven water oxidation.

PubMed

Han, Taoran; Chen, Yajie; Tian, Guohui; Wang, Jian-Qiang; Ren, Zhiyu; Zhou, Wei; Fu, Honggang

2015-10-14

Oxygen generation is the key step for the photocatalytic overall water splitting and considered to be kinetically more challenging than hydrogen generation. Here, an effective water oxidation catalyst of hierarchical FeTiO3-TiO2 hollow spheres are prepared via a two-step sequential solvothermal processes and followed by thermal treatment. The existence of an effective heterointerface and built-in electric field in the surface space charge region in FeTiO3-TiO2 hollow spheres plays a positive role in promoting the separation of photoinduced electron-hole pairs. Surface photovoltage, transient-state photovoltage, fluorescence and electrochemical characterization are used to investigate the transfer process of photoinduced charge carriers. The photogenerated charge carriers in the hierarchical FeTiO3-TiO2 hollow spheres with a proper molar ratio display much higher separation efficiency and longer lifetime than those in the FeTiO3 alone. Moreover, it is suggested that the hierarchical porous hollow structure can contribute to the enhancement of light utilization, surface active sites and material transportation through the framework walls. This specific synergy significantly contributes to the remarkable improvement of the photocatalytic water oxidation activity of the hierarchical FeTiO3-TiO2 hollow spheres under simulated sunlight (AM1.5).

Preparation and characterization of TiO2 and Si-doped octacalcium phosphate composite coatings on zirconia ceramics (Y-TZP) for dental implant applications

NASA Astrophysics Data System (ADS)

Bao, Lei; Liu, Jingxiao; Shi, Fei; Jiang, Yanyan; Liu, Guishan

2014-01-01

In order to prevent the low temperature degradation and improve the bioactivity of zirconia ceramic implants, TiO2 and Si-doped octacalcium phosphate composite coating was prepared on zirconia substrate. The preventive effect on low temperature degradation and surface morphology of the TiO2 layer were studied. Meanwhile, the structure and property changes of the bioactive coating after doping Si were discussed. The results indicate that the dense TiO2 layer, in spite of some microcracks, inhibited the direct contact of the water vapor with the sample's surface and thus prevented the low temperature degradation of zirconia substrates. The acceleration aging test shows that the ratio of the monoclinic phase transition decreased from 10% for the original zirconia substrate to 4% for the TiO2-coated substrate. As to the Si-doped octacalcium phosphate coating prepared by biomimetic method, the main phase composition of the coating was octacalcium phosphate. The morphology of the coating was lamellar-like, and the surface was uniform and continuous with no cracks being observed. It is suggested that Si was added into the coating both through substituting for PO43- and doping as NaSiO3.

Influence of Zr doping on structure and morphology of TiO2 nanorods prepared using hydrothermal method

NASA Astrophysics Data System (ADS)

Muslimin, Masliana; Jumali, Mohammad Hafizuddin; Tee, Tan Sin; Beng, Lee Hock; Hui, Tan Chun; Chin, Yap Chi

2018-04-01

The aim of this work is to investigate the effect of Zr doping on TiO2 nanostructure. TiO2 nanorods thin films with different Zr-doping concentrations (6 × 10-3 M, 13 × 10-3 M and 25 × 10-3 M) were successfully prepared using a simple hydrothermal method. The structural and morphological properties of the samples were evaluated using XRD and FESEM respectively. The XRD results revealed that the TiO2 in all samples stabilized as rutile phase. The FESEM micrographs confirmed that TiO2 exist as square like nanorods with blunt tips. Although the crystallographic nature remains unchanged, the introduction of Zr has altered the surface density, structure and morphology of TiO2 which subsequently will have significant effect on its properties.

Efficient photocatalytic degradation of tetrabromodiphenyl ethers and simultaneous hydrogen production by TiO2-Cu2O composite films in N2 atmosphere: Influencing factors, kinetics and mechanism.

PubMed

Hu, Zhe; Wang, Xi; Dong, Haitai; Li, Shangyi; Li, Xukai; Li, Laisheng

2017-10-15

TiO 2 -Cu 2 O photocatalyst composite film with a heterostructure was synthesized on a copper substrate for 2,2',4,4'-tetrabromodiphenyl ether (BDE47) reduction. First, Cu 2 O film was synthesized by the electrochemical deposition method, and then TiO 2 was coated on the surface of the Cu 2 O film. The morphology, surface chemical composition and optical characteristics of TiO 2 -Cu 2 O film were characterized. The degradation efficiency of BDE47 and hydrogen production by TiO 2 -Cu 2 O films was higher than those by pure TiO 2 or Cu 2 O films. The highest BDE47 degradation efficiency of 90% and hydrogen production of 12.7mmolL liq -1 after 150min were achieved by 67%TiO 2 -Cu 2 O films. The influencing factors were investigated in terms of film component, solvent condition, and initial pH. A kinetics study demonstrated that BDE47 degradation followed a pseudo-first-order model. Photocatalytic apparent reaction rate constant of BDE47 by TiO 2 -Cu 2 O films was 0.0070min -1 , which was 3.3 times of that by directly photolysis process. During photocatalytic debrmination process, the photogenerated holes were reserved in the valance band of Cu 2 O to oxidize methanol. Meanwhile, the partial photogenerated electrons transferred to the conduction band of TiO 2 and directly eliminated the ortho-Br of BDE47 and yielded BDE28 and BDE15. The other partial photogenerated electrons reduced protons (H + ) to form atomic hydrogen (H°), which could substitute the para-Br of BDE47 and generated BDE17 and produce hydrogen. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis of nano-TiO2/diatomite composite and its photocatalytic degradation of gaseous formaldehyde

NASA Astrophysics Data System (ADS)

Zhang, Guangxin; Sun, Zhiming; Duan, Yongwei; Ma, Ruixin; Zheng, Shuilin

2017-08-01

The TiO2/diatomite composite was synthesized through a mild hydrolysis of titanyl sulfate. The prepared composite was characterized by X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis diffused reflectance spectroscopy. The results demonstrate that the anatase TiO2 nanopartilces anchored on the surface of diatomite with Ti-O-Si bonds between diatomite and TiO2. The photodegradation of gaseous formaldehyde under UV irradiation by the TiO2/diatomite composite was studied under various operating conditions, including relative humidity, illumination intensity and catalyst amount, which have significant influence on the degradation process. The TiO2/diatomite composite exhibited better photocatalytic activity than pure TiO2, which could be attributed to the favorable nanoparticles dispersibility and strong formaldehyde adsorption capacity. In addition, the composite exhibited outstanding reusability over five cycles. The TiO2/diatomite composite shows great promising application foreground in formaldehyde degradation.

Atomically precise lateral modulation of a two-dimensional electron liquid in anatase TiO 2 thin films

DOE PAGES

Wang, Zhiming; Zhong, Z.; Walker, S. McKeown; ...

2017-03-10

Engineering the electronic band structure of two-dimensional electron liquids (2DELs) confined at the surface or interface of transition metal oxides is key to unlocking their full potential. Here we describe a new approach to tailoring the electronic structure of an oxide surface 2DEL demonstrating the lateral modulation of electronic states with atomic scale precision on an unprecedented length scale comparable to the Fermi wavelength. To this end, we use pulsed laser deposition to grow anatase TiO 2 films terminated by a (1 x 4) in-plane surface reconstruction. Employing photo-stimulated chemical surface doping we induce 2DELs with tunable carrier densities thatmore » are confined within a few TiO 2 layers below the surface. Subsequent in situ angle resolved photoemission experiments demonstrate that the (1 x 4) surface reconstruction provides a periodic lateral perturbation of the electron liquid. Furthermore, this causes strong backfolding of the electronic bands, opening of unidirectional gaps and a saddle point singularity in the density of states near the chemical potential.« less

Quantum Mechanical Determination of Potential Energy Surfaces for TiO and H2O

NASA Technical Reports Server (NTRS)

Langhoff, Stephen R.

1996-01-01

We discuss current ab initio methods for determining potential energy surfaces, in relation to the TiO and H2O molecules, both of which make important contributions to the opacity of oxygen-rich stars. For the TiO molecule we discuss the determination of the radiative lifetimes of the excited states and band oscillator strengths for both the triplet and singlet band systems. While the theoretical radiative lifetimes for TiO agree well with recent measurements, the band oscillator strengths differ significantly from those currently employed in opacity calculations. For the H2O molecule we discuss the current results for the potential energy and dipole moment ground state surfaces generated at NASA Ames. We show that it is necessary to account for such effects as core-valence Correlation energy to generate a PES of near spectroscopic accuracy. We also describe how we solve the ro-vibrational problem to obtain the line positions and intensities that are needed for opacity sampling.

Enhanced visible-light-driven photocatalytic H2-production activity of CdS-loaded TiO2 microspheres with exposed (001) facets

NASA Astrophysics Data System (ADS)

Gao, Bifen; Yuan, Xia; Lu, Penghui; Lin, Bizhou; Chen, Yilin

2015-12-01

CdS-loaded TiO2 microspheres with highly exposed (001) facets were prepared by hydrothermal treatment of a TiF4-HCl-H2O mixed solution followed by a chemical bath deposition of CdS onto TiO2 microspheres. The crystal structure, surficial micro-structure and photo-absorption property of the samples were characterized by XRD, FE-SEM, TEM and UV-vis diffuse reflectance spectroscopy, etc. The as-prepared samples exhibited superior visible-light-driven photocatalytic H2-production activity from lactic acid aqueous solution in comparison with CdS-sensitized TiO2 nanoparticles, whose surface was dominated by (101) facets. Photoelectrochemical measurement confirmed that (001) facet is beneficial for the transfer of photo-generated electron from CdS to TiO2 microsphere, which led to the unexpected high photocatalytic activity of CdS-loaded TiO2 microspheres.

Synthesis, characterization, antibacterial activity in dark and in vitro cytocompatibility of Ag-incorporated TiO2 microspheres with high specific surface area.

PubMed

Weng, Shengxin; Zhao, Xu; Liu, Guomin; Guan, Yuefeng; Wu, Fanglong; Luo, Yungang

2018-04-23

Postoperative infection associated with medical implants is a devastating complication of orthopedic surgery. Considering the difficulties for the diagnosis and treatment of infection, coating the implant material with antibacterial substances is a promising protocol by which to avoid such an adverse reaction. Nanoparticles (NPs) constructed of anatase microspheres, one form of titanium dioxide (TiO 2 ), with a high specific surface area are fabricated in this study in a facile one-step process using homogeneous precipitation at 90 °C under atmospheric pressure using titanium sulfate (Ti[SO 4 ] 2 ) and urea as the titanium source and precipitant, respectively. The molar ratio of silver (Ag) to TiO 2 can be changed by varying the amount of silver nitrate (AgNO 3 ). The high specific surface area of the TiO 2 microspheres combined with Ag particles (Ag/TiO 2 ) exhibit excellent antibacterial properties against both Staphylococcus aureus and Escherichia coli. In addition, the Ag/TiO 2 material in this work possesses satisfactory biological performance on MC3T3-E1 cells. The high specific surface area of Ag/TiO 2 together with good antibacterial properties and cytocompatibility provide promising applications in dentistry, orthopedics, and other fields of medicine that use biomedical devices.