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Impact of Annealing Treatment on the Behaviour of Titanium Dioxide Nanotube Layers  [PDF]
Marie Siampiringue, Christophe Massard, Eric Caudron, Yves Sibaud, Mohammed Sarakha, Komla Oscar Awitor
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2016, DOI: 10.4236/jbnb.2016.73015
Abstract: In this work, we study the influence of the annealing treatment on the behaviour of titanium dioxide nanotube layers. The heat treatment protocol is actually the key parameter to induce stable oxide layers and needs to be better understood. Nanotube layers were prepared by electrochemical anodization of Ti foil in 0.4 wt% hydrofluoric acid solution during 20 minutes and then annealed in air atmosphere. In-situ X-ray diffraction analysis, coupled with thermogravimetry, gives us an inside on the oxidation behaviour of titanium dioxide nanotube layers compared to bulk reference samples. Structural studies were performed at 700°C for 12 h in order to follow the time consequences on the oxidation of the material, in sufficient stability conditions. In-situ XRD brought to light that the amorphous oxide layer induced by anodization is responsible for the simultaneous growths of anatase and rutile phase during the first 30 minutes of annealing while the bulk sample oxidation leads to the nucleation of a small amount of anatase TiO2. The initial amorphous oxide layer created by anodization is also responsible for the delay in crystallization compared to the bulk sample. Thermogravimetric analysis exhibits parabolic shape of the mass gain for both anodized and bulk sample; this kinetics is caused by the formation of a rutile external protective layer, as depicted by the associated in-situ XRD diffractograms. We recorded that titanium dioxide nanotube layers exhibit a lower mean mass gain than the bulk, because of the presence of an initial amorphous oxide layer on anodized samples. In-situ XRD results also provide accurate information concerning the sub-layers behavior during the annealing treatment for the bulk and nanostructured layer. Anatase crystallites are mainly localized at the interface oxide layer-metal and the rutile is at the external interface. Sample surface topography was characterized using scanning electron microscopy (SEM).
Photoelectric Properties of Silicon Nanocrystals/P3HT Bulk-Heterojunction Ordered in Titanium Dioxide Nanotube Arrays  [cached]
?vr?ek Vladimir,Turkevych Ivan,Kondo Michio
Nanoscale Research Letters , 2009,
Abstract: A silicon nanocrystals (Si-ncs) conjugated-polymer-based bulk-heterojunction represents a promising approach for low-cost hybrid solar cells. In this contribution, the bulk-heterojunction is based on Si-ncs prepared by electrochemical etching and poly(3-hexylthiophene) (P3HT) polymer. Photoelectric properties in parallel and vertical device-like configuration were investigated. Electronic interaction between the polymer and surfactant-free Si-ncs is achieved. Temperature-dependent photoluminescence and transport properties were studied and the ratio between the photo- and dark-conductivity of 1.7 was achieved at ambient conditions. Furthermore the porous titanium dioxide (TiO2) nanotubes’ template was used for vertical order of photosensitive Si-ncs/P3HT-based blend. The anodization of titanium foil in ethylene glycol-based electrolyte containing fluoride ions and subsequent thermal annealing were used to prepare anatase TiO2nanotube arrays. The arrays with nanotube inner diameter of 90 and 50 nm were used for vertical ordering of the Si-ncs/P3HT bulk-heterojunction.
Multiple Functionality in Nanotube Transistors  [PDF]
F. Leonard,J. Tersoff
Physics , 2002, DOI: 10.1103/PhysRevLett.88.258302
Abstract: Calculations of quantum transport in a carbon nanotube transistor show that such a device offers unique functionality. It can operate as a ballistic field-effect transistor, with excellent characteristics even when scaled to 10 nm dimensions. At larger gate voltages, channel inversion leads to resonant tunneling through an electrostatically defined nanoscale quantum dot. Thus the transistor becomes a gated resonant tunelling device, with negative differential resistance at a tunable threshold. For the dimensions considered here, the device operates in the Coulomb blockade regime, even at room temperature.
Self-Ordered Titanium Dioxide Nanotube Arrays: Anodic Synthesis and Their Photo/Electro-Catalytic Applications  [PDF]
York R. Smith,Rupashree S. Ray,Krista Carlson,Biplab Sarma,Mano Misra
Materials , 2013, DOI: 10.3390/ma6072892
Abstract: Metal oxide nanotubes have become a widely investigated material, more specifically, self-organized titania nanotube arrays synthesized by electrochemical anodization. As a highly investigated material with a wide gamut of applications, the majority of published literature focuses on the solar-based applications of this material. The scope of this review summarizes some of the recent advances made using metal oxide nanotube arrays formed via anodization in solar-based applications. A general methodology for theoretical modeling of titania surfaces in solar applications is also presented.
Mo and N Co-Doped Titanium Dioxide Nanotube Arrays with Enhanced Visible Light Photocatalytic Activity  [PDF]
Min Zhang,Juan Wu,Jian Hou,Jianjun Yang
Physics , 2014, DOI: 10.1166/sam.2013.1488
Abstract: Molybdenum and nitrogen co-doped $TiO_2$ nanotube arrays (TNAs) were prepared by anodizing in association with hydrothermal treatment. As-prepared Mo and N co-doped TNAs were characterized by field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and ultraviolet-visible light diffuse reflection spectroscopy. Besides, the photocatalytic activity of Mo and N co-doped TNAs for the degradation of methylene blue (denoted as MB) under visible light irradiation was evaluated. It was found that N in co-doped TNAs coexists in the forms of N-Ti-O and N-O-Ti, while Mo exists as $Mo^{6+}$ by substituting Ti in the lattice of $TiO_2$. In the meantime, Mo and N co-doping extends the absorption of TNAs into the whole visible light region and results in remarkably enhanced photocatalytic activity for the degradation of MB under visible light irradiation. This could be attributed to the synergetic effect between Mo-doping and N-doping. Namely, Mo and N passivated co-doping produces new states in TNAs, thereby narrowing the bandgap and decreasing the recombination rate of electrons and holes. As a result, the visible light absorption and photocatalytic activity of TNAs is greatly increased. Furthermore, Mo ions with multiple valences in all co-doped samples could act as trapping sites to effectively decrease the recombination rate of electrons and holes, which also contribute to improved photocatalytic activity of Mo and N co-doped TNAs. Keywords: TiO2 Nanotube Arrays, Mo, N, Co-Doping, Photocatalytic Activity.
Simulated exposure of titanium dioxide memristors to ion beams
Marjanovi? Nada S.,Vujisi? Milo? Lj.,Stankovi? Koviljka ?.,Despotovi? Dejan
Nuclear Technology and Radiation Protection , 2010, DOI: 10.2298/ntrp1002120m
Abstract: The effects of exposing titanium dioxide memristors to ion beams are investigated through Monte Carlo simulation of particle transport. A model assuming ohmic electronic conduction and linear ionic drift in the memristor is utilized. The memristor is composed of a double-layer titanium dioxide thin film between two platinum electrodes. Obtained results suggest that a significant generation of oxygen ion/oxygen vacancy pairs in the oxide is to be expected along ion tracks. These can influence the device’s operation by lowering the resistance of the stoichiometric oxide region and the mobility of the vacancies. Changes induced by ion irradiation affect the current-voltage characteristic and state retention ability of the memristor. If the displaced oxygen ions reach the platinum electrodes, they can form the O2 gas and cause a permanent disruption of memristor functionality.
Fabrication and photoluminiscent properties of titanium oxide nanotube arrays
Fang, Dong;Huang, Kelong;Liu, Shuqin;Huang, Jianhan;
Journal of the Brazilian Chemical Society , 2008, DOI: 10.1590/S0103-50532008000600002
Abstract: an array of vertically aligned titanium oxide nanotubes was successfully grown on the surface of a titanium substrate by the anodization technique. the nanotubes were characterized by scanning electron microscopy (sem), powder x-ray diffractometry (xrd), raman spectroscopy and photoluminescence spectroscopy (pl). the results indicate that the size of the titanium oxide nanotube is greatly dependent on the applied voltage, and its photoluminescence properties are strongly influenced by the crystal structure. in addition, it is shown that quantum size effects are present in the optical properties of tio2 nanotubes.
in the Surface of Titanium Dioxide: Generation, Properties and Photocatalytic Application
Liang-Bin Xiong,Jia-Lin Li,Bo Yang,Ying Yu
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/831524
Abstract: Titanium dioxide (TiO2) is the most investigated crystalline oxide in the surface science of metal oxides. Its physical and chemical properties are dominantly determined by its surface condition. Ti3
Hydrothermal Synthesis of Nitrogen-Doped Titanium Dioxide and Evaluation of Its Visible Light Photocatalytic Activity
Junjie Qian,Guanjun Cui,Mingjun Jing,Yan Wang,Min Zhang,Jianjun Yang
International Journal of Photoenergy , 2012, DOI: 10.1155/2012/198497
Abstract: Nitrogen-doped titanium dioxide (N-doped TiO2) photocatalyst was synthesized from nanotube titanic acid (denoted as NTA; molecular formula H2Ti2O5?H2O ) precursor via a hydrothermal route in ammonia solution. As-synthesized N-doped TiO2 catalysts were characterized by means of X-ray diffraction, transmission electron microscopy, diffuse reflectance spectrometry, X-ray photoelectron spectroscopy, electron spin resonance spectrometry and Fourier transform infrared spectrometry. It was found that nanotube ammonium titanate (NAT) was produced as an intermediate during the preparation of N-doped TiO2 from NTA, as evidenced by the N1s X-ray photoelectron spectroscopic peak of NH4
Effect of Heating Rate on the Morphology of Nano Titanium Dioxide  [PDF]
LIU Bo, KONG Wei, YE Bo, YU Zhong-Ping, WANG Hua, QIAN Guo-Dong, WANG Zhi-Yu
无机材料学报 , 2010, DOI: 10.3724/sp.j.1077.2010.00906
Abstract: Different shapes of nano titanium dioxide including sphere, rod and irregular-shaped polyhedron were prepared by solvothermal process at heating rates of 240 0min, 90 0min, 40 0min and 20 0min using tetrabutyl titanate as Ti source, oleic acid as solvent, dodecylamine as auxiliary agent. TEM, HRTEM and XRD were adopted to characterize the phase composition morphology and phase structure of the final products. The micro-morphology and growth mechanisms of the titanium dioxide nanocrystals prepared at different heating rates were studied based on the TEM, HRTEM and XRD analyses£ The results show that spherical, rod-like, and irregular polyhedral points of titanium dioxide nanocrystals could be synthesized by strictly controlling the heating rate. The growth rate of along the (001) direction of nanocrystal shows a first upward and then downward trend with the decline of the heating rate.
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