Au Nanoclusters Sensitized Black TiO2-x Nanotubes for Enhanced Photodynamic Therapy Driven by Near-Infrared Light.

PubMed

Yang, Dan; Gulzar, Arif; Yang, Guixin; Gai, Shili; He, Fei; Dai, Yunlu; Zhong, Chongna; Yang, Piaoping

2017-12-01

The low reactive oxygen species production capability and the shallow tissue penetration of excited light (UV) are still two barriers in photodynamic therapy (PDT). Here, Au cluster anchored black anatase TiO 2- x nanotubes (abbreviated as Au 25 /B-TiO 2- x NTs) are synthesized by gaseous reduction of anatase TiO 2 NTs and subsequent deposition of noble metal. The Au 25 /B-TiO 2- x NTs with thickness of about 2 nm exhibit excellent PDT performance. The reduction process increased the density of Ti 3+ on the surface of TiO 2 , which effectively depresses the recombination of electron and hole. Furthermore, after modification of Au 25 nanoclusters, the PDT efficiency is further enhanced owing to the changed electrical distribution in the composite, which forms a shallow potential well on the metal-TiO 2 interface to further hamper the recombination of electron and hole. Especially, the reduction of anatase TiO 2 can expend the light response range (UV) of TiO 2 to the visible and even near infrared (NIR) light region with high tissue penetration depth. When excited by NIR light, the nanoplatform shows markedly improved therapeutic efficacy attributed to the photocatalytic synergistic effect, and promotes separation or restrained recombination of electron and hole, which is verified by experimental results in vitro and in vivo. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal degradation of TiO2 nanotubes on titanium

NASA Astrophysics Data System (ADS)

Shivaram, Anish; Bose, Susmita; Bandyopadhyay, Amit

2014-10-01

The objective of this research was to study thermal degradation behavior of TiO2 nanotubes on titanium (Ti). TiO2 nanotubes were grown via anodization method on commercially pure Ti (Cp-Ti) discs using two different electrolytes, 1 vol. % HF in deionized (DI) water and 1 vol. % HF + 0.5 wt. % NH4F + 10 vol. % DI water in ethylene glycol, to obtain nanotubes with two different lengths, 300 nm and 950 nm keeping the nanotube diameter constant at 100 ± 20 nm. As grown TiO2 nanotubes were subjected to heat treatment to understand thermal degradation as a function of both temperature and hold time. The signs of degradation were observed mainly when amorphous nanotubes started to crystallize, however the crystallization temperature varied based on TiO2 nanotubes length and anodizing condition. Overall, 300 nm nanotubes were thermally stable at least up to 400 °C for 12 h, while the 950 nm long nanotubes show signs of degradation from 400 °C for 6 h only. Clearly, length of nanotubes, heat treatment temperature as well as hold times show influence toward degradation kinetics of TiO2 nanotubes on titanium.

High pressure synthesis of amorphous TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Li, Quanjun; Liu, Ran; Wang, Tianyi; Xu, Ke; Dong, Qing; Liu, Bo; Liu, Jing; Liu, Bingbing

2015-09-01

Amorphous TiO2 nanotubes with diameters of 8-10 nm and length of several nanometers were synthesized by high pressure treatment of anatase TiO2 nanotubes. The structural phase transitions of anatase TiO2 nanotubes were investigated by using in-situ high-pressure synchrotron X-ray diffraction (XRD) method. The starting anatase structure is stable up to ˜20GPa, and transforms into a high-density amorphous (HDA) form at higher pressure. Pressure-modified high- to low-density transition was observed in the amorphous form upon decompression. The pressure-induced amorphization and polyamorphism are in good agreement with the previous results in ultrafine TiO2 nanoparticles and nanoribbons. The relationship between the LDA form and α-PbO2 phase was revealed by high-resolution transmission electron microscopy (HRTEM) study. In addition, the bulk modulus (B0 = 158 GPa) of the anatase TiO2 nanotubes is smaller than those of the corresponding bulks and nanoparticles (180-240 GPa). We suggest that the unique open-ended nanotube morphology and nanosize play important roles in the high pressure phase transition of TiO2 nanotubes.

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

An innovative approach to synthesize highly-ordered TiO2 nanotubes.

PubMed

Isimjan, Tayirjan T; Yang, D Q; Rohani, Sohrab; Ray, Ajay K

2011-02-01

An innovative route to prepare highly-ordered and dimensionally controlled TiO2 nanotubes has been proposed using a mild sonication method. The nanotube arrays were prepared by the anodization of titanium in an electrolyte containing 3% NH4F and 5% H2O in glycerol. It is demonstrated that the TiO2 nanostructures has two layers: the top layer is TiO2 nanowire and underneath is well-ordered TiO2 nanotubes. The top layer can easily fall off and form nanowires bundles by implementing a mild sonication after a short annealing time. We found that the dimensions of the TiO2 nanotubes were only dependent on the anodizing condition. The proposed technique may be extended to fabricate reproducible well-ordered TiO2 nanotubes with large area on other metals.

Ternary CNTs@TiO2/CoO Nanotube Composites: Improved Anode Materials for High Performance Lithium Ion Batteries

PubMed Central

Madian, Mahmoud; Ummethala, Raghunandan; Abo El Naga, Ahmed Osama; Ismail, Nahla; Rümmeli, Mark Hermann; Eychmüller, Alexander; Giebeler, Lars

2017-01-01

TiO2 nanotubes (NTs) synthesized by electrochemical anodization are discussed as very promising anodes for lithium ion batteries, owing to their high structural stability, high surface area, safety, and low production cost. However, their poor electronic conductivity and low Li+ ion diffusivity are the main drawbacks that prevent them from achieving high electrochemical performance. Herein, we report the fabrication of a novel ternary carbon nanotubes (CNTs)@TiO2/CoO nanotubes composite by a two-step synthesis method. The preparation includes an initial anodic fabrication of well-ordered TiO2/CoO NTs from a Ti-Co alloy, followed by growing of CNTs horizontally on the top of the oxide films using a simple spray pyrolysis technique. The unique 1D structure of such a hybrid nanostructure with the inclusion of CNTs demonstrates significantly enhanced areal capacity and rate performances compared to pure TiO2 and TiO2/CoO NTs, without CNTs tested under identical conditions. The findings reveal that CNTs provide a highly conductive network that improves Li+ ion diffusivity, promoting a strongly favored lithium insertion into the TiO2/CoO NT framework, and hence resulting in high capacity and an extremely reproducible high rate capability. PMID:28773032

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.

Amorphous and crystalline TiO2 nanotube arrays for enhanced Li-ion intercalation properties.

PubMed

Guan, Dongsheng; Cai, Chuan; Wang, Ying

2011-04-01

We have employed a simple process of anodizing Ti foils to prepare TiO2 nanotube arrays which show enhanced electrochemical properties for applications as Li-ion battery electrode materials. The lengths and pore diameters of TiO2 nanotubes can be finely tuned by varying voltage, electrolyte composition, or anodization time. The as-prepared nanotubes are amorphous and can be converted into anatase nanotubes with heat treatment at 480 degrees C. Rutile crystallites emerge in the anatase nanotube when the annealing temperature is increased to 580 degrees C, resulting in TiO2 nanotubes of mixed phases. The morphological features of nanotubes remain unchanged after annealing. Li-ion insertion performance has been studied for amorphous and crystalline TiO2 nanotube arrays. Amorphous nanotubes with a length of 3.0 microm and an outer diameter of 125 nm deliver a capacity of 91.2 microA h cm(-2) at a current density of 400 microA cm(-2), while those with a length of 25 microm and an outer diameter of 158 nm display a capacity of 533 microA h cm-2. When the 3-microm long nanotubes become crystalline, they deliver lower capacities: the anatase nanotubes and nanotubes of mixed phases show capacities of 53.8 microA h cm-2 and 63.1 microA h cm(-2), respectively at the same current density. The amorphous nanotubes show excellent capacity retention ability over 50 cycles. The cycled nanotubes show little change in morphology compared to the nanotubes before electrochemical cycling. All the TiO2 nanotubes demonstrate higher capacities than amorphous TiO2 compact layer reported in literature. The amorphous TiO2 nanotubes with a length of 1.9 microm exhibit a capacity five times higher than that of TiO2 compact layer even when the nanotube array is cycled at a current density 80 times higher than that for the compact layer. These results suggest that anodic TiO2 nanotube arrays are promising electrode materials for rechargeable Li-ion batteries.

Nanoindentation study of the mechanical behavior of TiO2 nanotube arrays

NASA Astrophysics Data System (ADS)

Xu, Y. N.; Liu, M. N.; Wang, M. C.; Oloyede, A.; Bell, J. M.; Yan, C.

2015-10-01

Titanium dioxide (TiO2) nanotube arrays are attracting increasing attention for use in solar cells, lithium-ion batteries, and biomedical implants. To take full advantage of their unique physical properties, such arrays need to maintain adequate mechanical integrity in applications. However, the mechanical performance of TiO2 nanotube arrays is not well understood. In this work, we investigate the deformation and failure of TiO2 nanotube arrays using the nanoindentation technique. We found that the load-displacement response of the arrays strongly depends on the indentation depth and indenter shape. Substrate-independent elastic modulus and hardness can be obtained when the indentation depth is less than 2.5% of the array height. The deformation mechanisms of TiO2 nanotube arrays by Berkovich and conical indenters are closely associated with the densification of TiO2 nanotubes under compression. A theoretical model for deformation of the arrays under a large-radius conical indenter is also proposed.

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.

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.

Effects of Functionalization of TiO2 Nanotube Array Sensors with Pd Nanoparticles on Their Selectivity

PubMed Central

Park, Sunghoon; Kim, Soohyun; Park, Suyoung; Lee, Wan In; Lee, Chongmu

2014-01-01

This study compared the responses of Pd-functionalized and pristine titanate (TiO2) nanotube arrays to ethanol with those to acetone to determine the effects of functionalization of TiO2 nanotubes with Pd nanoparticles on the sensitivity and selectivity. The responses of pristine and Pd-functionalized TiO2 nanotube arrays to ethanol gas at 200 °C were ∼2877% and ∼21,253%, respectively. On the other hand, the responses of pristine and Pd-functionalized TiO2 nanotube arrays to acetone gas at 250 °C were ∼1636% and 8746% respectively. In the case of ethanol sensing, the response and recovery times of Pd-functionalized TiO2 nanotubes (10.2 and 7.1 s) were obviously shorter than those of pristine TiO2 nanotubes (14.3 and 8.8 s), respectively. In contrast, in the case of acetone sensing the response and recovery times of Pd-functionalized TiO2 nanotubes (42.5 and 19.7 s) were almost the same as those of pristine TiO2 nanotubes (47.2 and 17.9 s). TiO2 nanotube arrays showed the strongest response to ethanol and Pd functionalization was the most effective in improving the response of TiO2 nanotubes to ethanol among six different types of gases: ethanol, acetone, CO, H2, NH3 and NO2. The origin of the superior sensing properties of Pd-functionalized TiO2 nanotubes toward ethanol to acetone is also discussed. PMID:25166499

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.

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.

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

One‐dimensional TiO2 Nanotube Photocatalysts for Solar Water Splitting

PubMed Central

Ge, Mingzheng; Li, Qingsong; Cao, Chunyan; Huang, Jianying; Li, Shuhui; Zhang, Songnan; Chen, Zhong; Zhang, Keqin; Al‐Deyab, Salem S.

2016-01-01

Hydrogen production from water splitting by photo/photoelectron‐catalytic process is a promising route to solve both fossil fuel depletion and environmental pollution at the same time. Titanium dioxide (TiO2) nanotubes have attracted much interest due to their large specific surface area and highly ordered structure, which has led to promising potential applications in photocatalytic degradation, photoreduction of CO2, water splitting, supercapacitors, dye‐sensitized solar cells, lithium‐ion batteries and biomedical devices. Nanotubes can be fabricated via facile hydrothermal method, solvothermal method, template technique and electrochemical anodic oxidation. In this report, we provide a comprehensive review on recent progress of the synthesis and modification of TiO2 nanotubes to be used for photo/photoelectro‐catalytic water splitting. The future development of TiO2 nanotubes is also discussed. PMID:28105391

Formation and evolution of anodic TiO2 nanotube embryos

NASA Astrophysics Data System (ADS)

Jin, Rong; Liao, Maoying; Lin, Tong; Zhang, Shaoyu; Shen, Xiaoping; Song, Ye; Zhu, Xufei

2017-06-01

Anodic TiO2 nanotubes (ATNTs) have been widely investigated for decades due to their interesting nanostructures and various applications. However, the formation mechanism of ATNTs still remains unclear. To date, most of researches focus on the tubular structure but neglect the formation process of initial nanotube embryos. Herein, polyethylene glycol (PEG) is added into the traditional electrolyte to moderate the transformation process from compact layer to porous layer. Based on ‘oxygen bubble mould’ and ‘plastic flow model’ theory, the formation and evolution process of nanotube embryo is clarified firstly. Results validate the effect of ‘oxygen bubble mould’ on the formation of nanotube embryo, which has a great effect on regulating the morphology of ATNT arrays. Besides, nanotubes prepared in electrolytes with PEG show shorter tube length with larger diameter than that prepared in traditional electrolytes. The addition of PEG can also effectively avoid the breakdown phenomenon. Highlights Transformation from compact layer into porous layer is observed in PEG electrolyte. The effect of oxygen bubble mould is first demonstrated and observed. The formation process of TiO2 nanotube embryo is described systematically. TiO2 nanotubes prepared in PEG electrolyte show short length and large diameter.

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.

The effects of nanostructures on the mechanical and tribological properties of TiO2 nanotubes.

PubMed

Yoon, Yeoungchin; Park, Jeongwon

2018-04-20

TiO 2 nanotubes were prepared by anodization on Ti substrates with a diameter variation of 30-100 nm, and the structure of the nanotubes were studied using x-ray diffraction and Raman spectroscopy, which confirmed the structure changes from the anatase phase to the rutile phase of TiO 2 at a diameter below 50 nm. The tribological behaviors of TiO 2 nanotubes were investigated with different diameters. The effectiveness of the rutile phase and the diameter size enhanced the frictional performance of TiO 2 nanotubes.

The effects of nanostructures on the mechanical and tribological properties of TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Yoon, Yeoungchin; Park, Jeongwon

2018-04-01

TiO2 nanotubes were prepared by anodization on Ti substrates with a diameter variation of 30-100 nm, and the structure of the nanotubes were studied using x-ray diffraction and Raman spectroscopy, which confirmed the structure changes from the anatase phase to the rutile phase of TiO2 at a diameter below 50 nm. The tribological behaviors of TiO2 nanotubes were investigated with different diameters. The effectiveness of the rutile phase and the diameter size enhanced the frictional performance of TiO2 nanotubes.

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

NASA Astrophysics Data System (ADS)

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

2016-01-01

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

Synthesis of highly ordered TiO2 nanotube in malonic acid solution by anodization.

PubMed

Ryu, Won Hee; Park, Chan Jin; Kwon, Hyuk Sang

2008-10-01

We synthesized TiO2 nanotube array by anodizing in a solution of malonic acid (HOOCCH2COOH) and NH4F, and analyzed the morphology of the nanotube using scanning electron microscopy (SEM). The morphology of TiO2 nanotube was largely affected by anodizing time, anodizing voltage, and malonic acid concentration. With increasing the anodizing voltage from 5 V to 20 V, the diameter of TiO2 nanotube was increased from about 20 nm to 110 nm and its length from about 10 nm to 700 nm. In addition, the length of TiO2 nanotube was increased with increasing anodizing time up to 6 h at 20 V. We obtained the longest and the most highly ordered nanotube structure when anodizing Ti in a solution of 0.5 wt% NH4F and 1 M malonic acid at 20 V for 6 h.

Self-standing crystalline TiO2 nanotubes/CNTs heterojunction membrane: synthesis and characterization.

PubMed

Hesabi, Zohreh R; Allam, Nageh K; Dahmen, Klaus; Garmestani, Hamid; A El-Sayed, Mostafa

2011-04-01

In the present study, we report for the first time synthesis of TiO(2) nanotubes/CNTs heterojunction membrane. Chemical vapor deposition (CVD) of CNTs at 650 °C in a mixture of H(2)/He atmosphere led to in situ detachment of the anodically fabricated TiO(2) nanotube layers from the Ti substrate underneath. Morphological and structural evolution of TiO(2) nanotubes after CNTs deposition were investigated by field- emission scanning electron microscopy (FESEM), glancing angle X-ray diffraction (GAXRD), and X-ray photoelectron spectroscopy (XPS) analyses. © 2011 American Chemical Society

Efficient silver modification of TiO2 nanotubes with enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Huang, Jing; Ding, Lei; Xi, Yaoning; Shi, Liang; Su, Ge; Gao, Rongjie; Wang, Wei; Dong, Bohua; Cao, Lixin

2018-06-01

In this paper, Ag(CH3NH2)2+, Ag(NH3)2+ and Ag+ with different radii have been used as silver sources to find out the distribution of Ag ions on the H-TNT surface, which is critical to the final performance. The influence of this distribution on visible photocatalytic activity is further studied. The results indicate that, when Ag+ used as silver source with low concentration, these small sized silver ions mainly distribute on interlayer spacing of H-TNT. After heat-treatment and photo-reduction, the generated silver nanoparticles uniformly embed in the anatase TiO2 nanotube walls, and bring large interfacial area between Ag particles and TiO2 nanotubes. The separation effect of photogenerated electron-hole pair in TiO2 is enhanced by Ag particles, and achieves the best at 0.15 g/L, much higher than P25, TiO2/0, Ag-N@TiO2 and Ag-C-N@TiO2. This paper provides new ideas for the modification of TiO2 nanotubes.

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.

Effects of highly ordered TiO2 nanotube substrates on the nucleation of Cu electrodeposits.

PubMed

Ryu, Won Hee; Park, Chan Jin; Kwon, Hyuk Sang

2010-05-01

We investigated the effects of TiO2 nanotube substrates on the nucleation density of Cu during electrodeposition in a solution of CuSO4 and H2SO4 at 50 degrees C compared with those of pure Ti and micro-porous TiO2 substrates. During electrodeposition, the density of Cu nuclei on the TiO2 nanotube substrate increased and the average size of Cu nuclei decreased with increasing anodizing voltage and time for the synthesis of the substrate. In addition, the nucleation density of Cu electrodeposits on the highly ordered TiO2 nanotube substrate was much higher than that on pure Ti and micro-porous TiO2 substrates.

Synthesis of carbon-coated TiO 2 nanotubes for high-power lithium-ion batteries

NASA Astrophysics Data System (ADS)

Park, Sang-Jun; Kim, Young-Jun; Lee, Hyukjae

Carbon-coated TiO 2 nanotubes are prepared by a simple one-step hydrothermal method with an addition of glucose in the starting powder, and are characterized by morphological analysis and electrochemical measurement. A thin carbon coating on the nanotube surface effectively suppresses severe agglomeration of TiO 2 nanotubes during hydrothermal reaction and post calcination. This action results in better ionic and electronic kinetics when applied to lithium-ion batteries. Consequently, carbon-coated TiO 2 nanotubes deliver a remarkable lithium-ion intercalation/deintercalation performance, such as reversible capacities of 286 and 150 mAh g -1 at 250 and 7500 mA g -1, respectively.

Conical islands of TiO2 nanotube arrays in the photoelectrode of dye-sensitized solar cells.

PubMed

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

2015-01-01

Ti conical island structures were fabricated using photolithography and the reactive ion etching method. The resulting conical island structures were anodized in ethylene glycol solution containing 0.25 wt% NH4F and 2 vol% H2O, and conical islands composed of TiO2 nanotubes were successfully formed on the Ti foils. The conical islands composed of TiO2 nanotubes were employed in photoelectrodes for dye-sensitized solar cells (DSCs). DSC photoelectrodes based on planar Ti structures covered with TiO2 nanotubes were also fabricated as a reference. The short-circuit current (J sc) and efficiency of DSCs based on the conical island structures were higher than those of the reference samples. The efficiency of DSCs based on the conical island structures reached up to 1.866%. From electrochemical impedance spectroscopy and open-circuit voltage (V oc) decay measurements, DSCs based on the conical island structures exhibited a lower charge transfer resistance at the counter cathode and a longer electron lifetime at the interface of the photoelectrode and electrolyte compared to the reference samples. The conical island structure was very effective at improving performances of DSCs based on TiO2 nanotubes. Graphical AbstractConical islands of TiO2 nanotube arrays are fabricated by an anodizing process with Ti protruding dots which have a conical shape. The conical islands are applied for use in DSC photoelectrodes. DSCs based on the conical islands of TiO2 nanotube arrays have the potential to achieve higher efficiency levels compared to DSCs based on normal TiO2 nanotubes and TiO2 nanoparticles because the conical islands of TiO2 nanotube arrays enlarge the surface area for dye adsorption.

Acid-assisted hydrothermal synthesis of nanocrystalline TiO2 from titanate nanotubes: influence of acids on the photodegradation of gaseous toluene.

PubMed

Chen, Kunyang; Zhu, Lizhong; Yang, Kun

2015-01-01

In order to efficiently remove volatile organic compounds (VOCs) from indoor air, one-dimensional titanate nanotubes (TiNTs) were hydrothermally treated to prepare TiO2 nanocrystals with different crystalline phases, shapes and sizes. The influences of various acids such as CH3COOH, HNO3, HCl, HF and H2SO4 used in the treatment were separately compared to optimize the performance of the TiO2 nanocrystals. Compared with the strong and corrosive inorganic acids, CH3COOH was not only safer and more environmentally friendly, but also more efficient in promoting the photocatalytic activity of the obtained TiO2. It was observed that the anatase TiO2 synthesized in 15 mol/L CH3COOH solution exhibited the highest photodegradation rate of gaseous toluene (94%), exceeding that of P25 (44%) by a factor of more than two. The improved photocatalytic activity was attributed to the small crystallite size and surface modification by CH3COOH. The influence of relative humidity (20%-80%) on the performance of TiO2 nanocrystals was also studied. The anatase TiO2 synthesized in 15 mol/L CH3COOH solution was more tolerant to moisture than the other TiO2 nanocrystals and P25. Copyright © 2014. Published by Elsevier B.V.

Low-temperature crystallization of anodized TiO2 nanotubes at the solid-gas interface and their photoelectrochemical properties

NASA Astrophysics Data System (ADS)

Liu, Jing; Liu, Zhaoyue; Zhang, Tierui; Zhai, Jin; Jiang, Lei

2013-06-01

TiO2 nanotubular arrays formed by electrochemical anodization have attracted significant attention for photoelectrochemical applications that utilize solar energy. However, the as-anodized TiO2 nanotubes are amorphous, and need to be crystallized by high-temperature thermal annealing. Herein, we describe a low-temperature hydrothermal solid-gas route to crystallize TiO2 nanotubes. In this process, the as-anodized TiO2 hydroxo nanotubes are dehydrated to yield anatase phase via solid-gas interface reaction in an autoclave at a temperature of less than 180 °C. The solid-gas interface reaction alleviates the collapse of as-anodized TiO2 nanotubes during hydrothermal process efficiently. Compared with the common thermal annealing at the same temperature but at atmospheric pressure, the hydrothermal route improves the photocurrent density of TiO2 nanotubes by ~10 times in KOH electrolyte. The duration of the hydrothermal reaction has a substantial effect on the photoelectrochemical properties of TiO2 nanotubes, which is ascribed to the synergetic effect between the crystallization and structural evolution. Electron donors can further suppress the charge recombination in the low-temperature crystallized TiO2 nanotubes and boost the photocurrent density by ~120%.TiO2 nanotubular arrays formed by electrochemical anodization have attracted significant attention for photoelectrochemical applications that utilize solar energy. However, the as-anodized TiO2 nanotubes are amorphous, and need to be crystallized by high-temperature thermal annealing. Herein, we describe a low-temperature hydrothermal solid-gas route to crystallize TiO2 nanotubes. In this process, the as-anodized TiO2 hydroxo nanotubes are dehydrated to yield anatase phase via solid-gas interface reaction in an autoclave at a temperature of less than 180 °C. The solid-gas interface reaction alleviates the collapse of as-anodized TiO2 nanotubes during hydrothermal process efficiently. Compared with the common

Improved attachment of mesenchymal stem cells on super-hydrophobic TiO2 nanotubes.

PubMed

Bauer, Sebastian; Park, Jung; von der Mark, Klaus; Schmuki, Patrik

2008-09-01

Self-organized layers of vertically orientated TiO(2) nanotubes providing defined diameters ranging from 15 up to 100nm were grown on titanium by anodic oxidation. These TiO(2) nanotube layers show super-hydrophilic behavior. After coating TiO(2) nanotube layers with a self-assembled monolayer (octadecylphosphonic acid) they showed a diameter-dependent wetting behavior ranging from hydrophobic (108+/-2 degrees ) up to super-hydrophobic (167+/-2 degrees ). Cell adhesion, spreading and growth of mesenchymal stem cells on the unmodified and modified nanotube layers were investigated and compared. We show that cell adhesion and proliferation are strongly affected in the super-hydrophobic range. Adsorption of extracellular matrix proteins as fibronectin, type I collagen and laminin, as well as bovine serum albumin, on the coated and uncoated surfaces showed a strong influence on wetting behavior and dependence on tube diameter.

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.

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.

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

Electrochemical synthesis of self-organized TiO2 crystalline nanotubes without annealing

NASA Astrophysics Data System (ADS)

Giorgi, Leonardo; Dikonimos, Theodoros; Giorgi, Rossella; Buonocore, Francesco; Faggio, Giuliana; Messina, Giacomo; Lisi, Nicola

2018-03-01

This work demonstrates that upon anodic polarization in an aqueous fluoride-containing electrolyte, TiO2 nanotube array films can be formed with a well-defined crystalline phase, rather than an amorphous one. The crystalline phase was obtained avoiding any high temperature annealing. We studied the formation of nanotubes in an HF/H2O medium and the development of crystalline grains on the nanotube wall, and we found a facile way to achieve crystalline TiO2 nanotube arrays through a one-step anodization. The crystallinity of the film was influenced by the synthesis parameters, and the optimization of the electrolyte composition and anodization conditions (applied voltage and time) were carried out. For comparison purposes, crystalline anatase TiO2 nanotubes were also prepared by thermal treatment of amorphous nanotubes grown in an organic bath (ethylene glycol/NH4F/H2O). The morphology and the crystallinity of the nanotubes were studied by field emission gun-scanning electron microscopy (FEG-SEM) and Raman spectroscopy, whereas the electrochemical and semiconducting properties were analyzed by means of linear sweep voltammetry, impedance spectroscopy, and Mott-Schottky plots. X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) allowed us to determine the surface composition and the electronic structure of the samples and to correlate them with the electrochemical data. The optimal conditions to achieve a crystalline phase with high donor concentration are defined.

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.

Influence of anodization parameters on the morphology of TiO 2 nanotube arrays

NASA Astrophysics Data System (ADS)

Omidvar, Hamid; Goodarzi, Saba; Seif, Ahmad; Azadmehr, Amir R.

2011-07-01

TiO 2 nanotube arrays can be fabricated by electrochemical anodization in organic and inorganic electrolytes. Morphology of these nanotube arrays changes when anodization parameters such as applied voltage, type of electrolyte, time and temperature are varied. Nanotube arrays fabricated by anodization of commercial titanium in electrolytes containing NH 4F solution and either sulfuric or phosphoric acid were studied at room temperature; time of anodization was kept constant. Applied voltage, fluoride ion concentration, and acid concentrations were varied and their influences on TiO 2 nanotubes were investigated. The current density of anodizing was recorded by computer controlled digital multimeter. The surface morphology (top-view) of nanotube arrays were observed by SEM. The nanotube arrays in this study have inner diameters in range of 40-80 nm.

Photoactive layered nanocomposites obtained by direct transferring of anodic TiO2 nanotubes to commodity thermoplastics

NASA Astrophysics Data System (ADS)

Sanz, Ruy; Buccheri, Maria Antonietta; Zimbone, Massimo; Scuderi, Viviana; Amiard, Guillaume; Impellizzeri, Giuliana; Romano, Lucia; Privitera, Vittorio

2017-03-01

TiO2 nanotubes demonstrated to be a versatile nanostructure for biomaterials, clean energy and water remediation applications. However, the cost of titanium and the poor mechanical properties of the nanotubes hinder their adoption at large scale. This work presents a straightforward and scalable method for transferring photoactive anodic TiO2 nanotubes from titanium foils to commodity thermoplastic polymers, polypropylene, polyethylene terephthalate, polycarbonate, and polymethylmetacrylate, allowing the reusing of the remaining titanium. The obtained flexible nanocomposites reach a maximum photonic efficiencies of 0.038% (ISO-10678:2010) representing the 93% of photonic efficiency of TiO2 nanotubes on titanium. In addition, the nanocomposites and TiO2 nanotubes on titanium present similar antibacterial properties under 1 mW cm-2 UV-A, 60% of Escherichia coli survival after 1 h of exposition. The final objective of this work is to point out main concepts and key parameters for a low-cost fabrication of a photoactive nanocomposite material.

Flexible symmetric supercapacitors based on vertical TiO2 and carbon nanotubes

NASA Astrophysics Data System (ADS)

Chien, C. J.; Chang, Pai-Chun; Lu, Jia G.

2010-03-01

Highly conducting and porous carbon nanotubes are widely used as electrodes in double-layer-effect supercapacitors. In this presentation, vertical TiO2 nanotube array is fabricated by anodization process and used as supercapacitor electrode utilizing its compact density, high surface area and porous structure. By spin coating carbon nanotube networks on vertical TiO2 nanotube array as electrodes with 1M H2SO4 electrolyte in between, the specific capacitance can be enhanced by 30% compared to using pure carbon nanotube network alone because of the combination of double layer effect and redox reaction from metal oxide materials. Based on cyclic voltammetry and galvanostatic charge-discharge measurements, this type of hybrid electrode has proven to be suitable for high performance supercapacitor application and maintain desirable cycling stability. The electrochemical impedance spectroscopy technique shows that the electrode has good electrical conductivity. Furthermore, we will discuss the prospect of extending this energy storage approach in flexible electronics.

Structure and dye-sensitized solar cell application of TiO2 nanotube arrays fabricated by the anodic oxidation method

NASA Astrophysics Data System (ADS)

Ok, Seon-Yeong; Cho, Kwon-Koo; Kim, Ki-Won; Ryu, Kwang-Sun

2010-05-01

Well-ordered TiO2 nanotube arrays were fabricated by the potentiostatic anodic oxidation method using pure Ti foil as a working electrode and ethylene glycol solution as an electrolyte with the small addition of NH4F and H2O. The influence of anodization temperature and time on the morphology and formation of TiO2 nanotube arrays was examined. The TiO2 nanotube arrays were applied as a photoelectrode to dye-sensitized solar cells. Regardless of anodizing temperature and time, the average diameter and wall thickness of TiO2 nanotube arrays show a similar value, whereas the length increases with decreasing reaction temperature. The conversion efficiency is very low, which is due to a morphology breaking of the TiO2 nanotube arrays in the manufacturing process of a photoelectrode.

The porous TiO2 nanotubes/Ag3PO4 heterojunction for enhancing sunlight photocatalytic activity

NASA Astrophysics Data System (ADS)

Chi, Chunyan; Pan, Jiaqi; You, Mingzhu; Dong, Zongjun; Zhao, Weijie; Song, Changsheng; Zheng, Yingying; Li, Chaorong

2018-03-01

The porous TiO2 nanotubes/Ag3PO4 heterojunction are synthesized via simple electrospining and chemical co-deposition method. The results of SEM, XRD, TEM and XPS imply that the Ag3PO4 nanoparticles have been introduced on to the surface of TiO2 nanotubes successfully. Compared with the unmodified samples, the photocatalytic activity of the as-prepared porous TiO2 nanotubes/Ag3PO4 heterojunction exhibit a remarkable enhancement by the degradation of methylene blue (MB) under the sunlight. Further, the Z-Scheme structure of the samples and the porous-tubular structure of the TiO2 are considered as the main reasons for the enhancement.

Crystallization of TiO2 Nanotubes by In Situ Heating TEM

PubMed Central

Casu, Alberto; Lamberti, Andrea

2018-01-01

The thermally-induced crystallization of anodically grown TiO2 amorphous nanotubes has been studied so far under ambient pressure conditions by techniques such as differential scanning calorimetry and in situ X-ray diffraction, then looking at the overall response of several thousands of nanotubes in a carpet arrangement. Here we report a study of this phenomenon based on an in situ transmission electron microscopy approach that uses a twofold strategy. First, a group of some tens of TiO2 amorphous nanotubes was heated looking at their electron diffraction pattern change versus temperature, in order to determine both the initial temperature of crystallization and the corresponding crystalline phases. Second, the experiment was repeated on groups of few nanotubes, imaging their structural evolution in the direct space by spherical aberration-corrected high resolution transmission electron microscopy. These studies showed that, differently from what happens under ambient pressure conditions, under the microscope’s high vacuum (p < 10−5 Pa) the crystallization of TiO2 amorphous nanotubes starts from local small seeds of rutile and brookite, which then grow up with the increasing temperature. Besides, the crystallization started at different temperatures, namely 450 and 380 °C, when the in situ heating was performed irradiating the sample with electron beam energy of 120 or 300 keV, respectively. This difference is due to atomic knock-on effects induced by the electron beam with diverse energy. PMID:29342894

Low temperature synthesis of polyaniline-crystalline TiO2-halloysite composite nanotubes with enhanced visible light photocatalytic activity.

PubMed

Li, Cuiping; Wang, Jie; Guo, Hong; Ding, Shujiang

2015-11-15

A series of one-dimensional polyaniline-crystalline TiO2-halloysite composite nanotubes with different mass ratio of polyaniline to TiO2 are facilely prepared by employing the low-temperature synthesis of crystalline TiO2 on halloysite nanotubes. The halloysite nanotubes can adsorb TiO2/polyaniline precursors and induce TiO2 nanocrystals/polyaniline to grow on the support in situ simultaneously. By simply adjusting the acidity of reaction system, PANI-crystalline TiO2-HA composite nanotubes composed of anatase, a mixed phase TiO2 and different PANI redox state are obtained. The XRD and UV-vis results show that the surface polyaniline sensitization has no effect on the crystalline structure of halloysite and TiO2 and the light response of TiO2 is extended to visible-light regions. Photocatalysis test results reveal the photocatalytic activity will be affected by the pH value and the volume ratio of ANI to TTIP. The highest photocatalytic activity is achieved with the composite photocatalysts prepared at pH 0.5 and 1% volume ratio of ANI and TTIP owing to the sensitizing effect of polyaniline and the charge transfer from the photoexcited PANI sensitizer to TiO2. Moreover, the PANI-TiO2-HA composite nanotubes synthesized by one-step at pH 0.5 with 1% volume ratio of ANI to TTIP exhibit higher visible light photocatalytic activity than those synthesized by the two-step. Heterogeneous PANI-TiO2-HA composite nanotubes prepared at pH 0.5 exhibit a higher degradation activity than that prepared at pH 1.5. The redoped experiment proves that the PANI redox state plays the main contribution to the enhanced visible light catalytic degradation efficiency of PANI-TiO2-HA prepared at pH 0.5. Furthermore, the heterogeneous PANI-crystalline TiO2-HA nanotubes have good photocatalytic stability and can be reused four times with only gradual loss of activity under visible light irradiation. Copyright © 2015 Elsevier Inc. All rights reserved.

Plasma-induced synthesis of Pt nanoparticles supported on TiO2 nanotubes for enhanced methanol electro-oxidation

NASA Astrophysics Data System (ADS)

Su, Nan; Hu, Xiulan; Zhang, Jianbo; Huang, Huihong; Cheng, Jiexu; Yu, Jinchen; Ge, Chao

2017-03-01

A Pt/C/TiO2 nanotube composite catalyst was successfully prepared for enhanced methanol electro-oxidation. Pt nanoparticles with a particle size of 2 nm were synthesized by plasma sputtering in water, and anatase TiO2 nanotubes with an inner diameter of approximately 100 nm were prepared by a simple two-step anodization method and annealing process. Field-emission scanning electron microscopy images indicated that the different morphologies of TiO2 synthesized on the surface of Ti foils were dependent on the different anodization parameters. The electrochemical performance of Pt/C/TiO2 catalysts for methanol oxidation showed that TiO2 nanotubes were more suitable for use as Pt nanoparticle support materials than irregular TiO2 short nanorods due to their tubular morphology and better electronic conductivity. X-ray photoelectron spectroscopy characterization showed that the binding energies of the Pt 4f of the Pt/C/TiO2 nanotubes exhibited a slightly positive shift caused by the relatively strong interaction between Pt and the TiO2 nanotubes, which could mitigate the poisoning of the Pt catalyst by COads, and further enhance the electrocatalytic performance. Thus, the as-obtained Pt/C/TiO2 nanotubes composites may become a promising catalyst for methanol electro-oxidation.

An Alternative to Annealing TiO2 Nanotubes for Morphology Preservation: Atmospheric Pressure Plasma Jet Treatment.

PubMed

Seo, Sang-Hee; Uhm, Soo-Hyuk; Kwon, Jae-Sung; Choi, Eun Ha; Kim, Kwang-Mahn; Kim, Kyoung-Nam

2015-03-01

Titanium oxide nanotube layer formed by plasma electrolytic oxidation (PEO) is known to be excellent in biomaterial applications. However, the annealing process which is commonly performed on the TiO2 nanotubes cause defects in the nanotubular structure. The purpose of this work was to apply a non-thermal atmospheric pressure plasma jet on diameter-controlled TiO2 nanotubes to mimic the effects of annealing while maintaining the tubular structure for use as biomaterial. Diameter-controlled nanotube samples fabricated by plasma electrolytic oxidation were dried and prepared under three different conditions: untreated, annealed at 450 °C for 1 h in air with a heating rate of 10 °C/min, and treated with an air-based non-thermal atmospheric pressure plasma jet for 5 minutes. The contact angle measurement was investigated to confirm the enhanced hydrophilicity of the TiO2 nanotubes. The chemical composition of the surface was studied using X-ray photoelectron spectroscopy, and the morphology of TiO2 nanotubes was examined by field emission scanning electron microscopy. For the viability of the cell, the attachment of the osteoblastic cell line MC3T3-E1 was determined using the water-soluble tetrazolium salt assay. We found that there are no morphological changes in the TiO2 nanotubular structure after the plasma treatment. Also, we investigated a change in the chemical composition and enhanced hydrophilicity which result in improved cell behavior. The results of this study indicated that the non-thermal atmospheric pressure plasma jet results in osteoblast functionality that is comparable to annealed samples while maintaining the tubular structure of the TiO2 nanotubes. Therefore, this study concluded that the use of a non-thermal atmospheric pressure plasma jet on nanotube surfaces may replace the annealing process following plasma electrolytic oxidation.

Chemical modification of TiO2 nanotube arrays for label-free optical biosensing applications

NASA Astrophysics Data System (ADS)

Terracciano, Monica; Galstyan, Vardan; Rea, Ilaria; Casalino, Maurizio; De Stefano, Luca; Sbervegleri, Giorgio

2017-10-01

In this study, we have fabricated TiO2 nanotube arrays by the potentiostatic anodic oxidation of Ti foils in fluoride-containing electrolyte and explored them as versatile devices for biosensing applications. TiO2 nanotubes have been chemically modified in order to bind Protein A as a specific target analyte for the optical biosensing. The obtained structures have been characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, water contact angle, fluorescence microscopy, spectroscopic reflectometry and photoluminescence. Investigations show that the prepared TiO2 nanotubes, 2.5 μm long and 75 nm thick, can be easily and efficiently bio-modified, and the obtained structures are strongly photoluminescent, thus suitable for the label-free biosensing applications in the range of μM, due to their peculiar optical properties.

Formation of TiO2 nanotube arrays in KOH added fluoride-ethylene glycol (EG) electrolyte and its photoelectrochemical response

NASA Astrophysics Data System (ADS)

Nyein, Nyein; Lockman, Zainovia; Matsuda, Astunori; Kawamura, Go; Tan, Wai Kian; Oo, Than Zaw

2016-07-01

In this study, highly ordered TiO2 nanotube arrays were prepared by anodic oxidation of titanium foil in fluoride -EG electrolyte containing a small amount of potassium hydroxide, KOH at 60 V for 30 min. This electrolyte resulted in the formation of long nanotubes with an average length of 10 µm and diameter of 170 nm. For comparison, TiO2 nanotubes anodized in H2O added EG electrolyte which produces short nanotubes with an average tube length of 5 µm and diameter of 170 nm. It appears that the addition of KOH into the fluoride EG electrolyte accelerated the formation of the TiO2 nanotubes as it is believed that the chemical dissolution at the tips of the nanotubes is suppressed. Highly ordered TiO2 nanotubes anodized in KOH added EG electrolyte exhibited the photocurrent density of 2 mA/cm2, which is significantly higher than H2O added sample (1.5 mA/cm2).

In situ synthesis of TiO2(B) nanotube/nanoparticle composite anode materials for lithium ion batteries.

PubMed

Liu, Xiang; Sun, Qian; Ng, Alan M C; Djurišić, Aleksandra B; Xie, Maohai; Liao, Changzhong; Shih, Kaimin; Vranješ, Mila; Nedeljković, Jovan M; Deng, Zhaofeng

2015-10-23

Titania nanotubes were prepared by a simple hydrothermal route. Their electrochemical performance has been examined in detail and compared to TiO2(B) nanoparticles, TiO2 anatase and P25 titania nanoparticles. The cycling and rate performance of TiO2 nanotubes is superior to both types of nanoparticles, and it can be further improved by an in situ titanium precursor treatment, which results in the formation of TiO2 nanoparticles on/between the nanotubes. The obtained specific capacity after 200 cycles at 0.2 A g(-1) charge/discharge rate remained above 130 mAh g(-1). The enhanced lithium storage properties of these samples can be attributed to their unique morphology and crystal structure.

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.

MoSe2 modified TiO2 nanotube arrays with superior photoelectrochemical performance

NASA Astrophysics Data System (ADS)

Zhang, Yaping; Zhu, Haifeng; Yu, Lianqing; He, Jiandong; Huang, Chengxing

2018-04-01

TiO2 nanotube arrays (TNTs) are first prepared by anodization Ti foils in ethylene glycol electrolyte. Then, MoSe2 deposites electrochemically on TNTs. The as-synthesized MoSe2/TiO2 composite has a much higher photocurrent density of 1.07 mA cm‑2 at 0 V than pure TNTs of 0.38 mA cm‑2, which suggests that the MoSe2/TiO2 composite film has optimum photoelectrocatalysis properties. The electron transport resistances of the MoSe2/TiO2 decreases to half of pure TiO2, at 295.6 ohm/cm2. Both photocurrent-time and Mott-Schottky plots indicate MoSe2 a p-type semiconductor characteristics. MoSe2/TiO2 composite can achieve a maximum 5 orders of magnitude enhancement in carrier density (4.650 × 1027 cm‑3) than that of pure TiO2 arrays. It can be attributed to p-n heterojunction formed between MoSe2 and TiO2, and the composite can be potentially applied in photoelectrochemical, photocatalysis fields.

Photocathodic Protection of 304 Stainless Steel by Bi2S3/TiO2 Nanotube Films Under Visible Light

NASA Astrophysics Data System (ADS)

Li, Hong; Wang, Xiutong; Wei, Qinyi; Hou, Baorong

2017-01-01

We report the preparation of TiO2 nanotubes coupled with a narrow bandgap semiconductor, i.e., Bi2S3, to improve the photocathodic protection property of TiO2 for metals under visible light. Bi2S3/TiO2 nanotube films were successfully synthesized using the successive ionic layer adsorption and reaction (SILAR) method. The morphology and structure of the composite films were studied by scanning electron microscopy and X-ray diffraction, respectively. UV-visible diffuse reflectance spectra were recorded to analyze the optical absorption property of the composite films. In addition, the influence of Bi2S3 deposition cycles on the photoelectrochemical and photocathodic protection properties of the composite films was also studied. Results revealed that the heterostructure comprised crystalline anatase TiO2 and orthorhombic Bi2S3 and exhibited a high visible light response. The photocurrent density of Bi2S3/TiO2 was significantly higher than that of pure TiO2 under visible light. The sensitization of Bi2S3 enhanced the separation efficiency of the photogenerated charges and photocathodic protection properties of TiO2. The Bi2S3/TiO2 nanotubes prepared by SILAR deposition with 20 cycles exhibited the optimal photogenerated cathodic protection performance on the 304 stainless steel under visible light.

Photocathodic Protection of 304 Stainless Steel by Bi2S3/TiO2 Nanotube Films Under Visible Light.

PubMed

Li, Hong; Wang, Xiutong; Wei, Qinyi; Hou, Baorong

2017-12-01

We report the preparation of TiO 2 nanotubes coupled with a narrow bandgap semiconductor, i.e., Bi 2 S 3 , to improve the photocathodic protection property of TiO 2 for metals under visible light. Bi 2 S 3 /TiO 2 nanotube films were successfully synthesized using the successive ionic layer adsorption and reaction (SILAR) method. The morphology and structure of the composite films were studied by scanning electron microscopy and X-ray diffraction, respectively. UV-visible diffuse reflectance spectra were recorded to analyze the optical absorption property of the composite films. In addition, the influence of Bi 2 S 3 deposition cycles on the photoelectrochemical and photocathodic protection properties of the composite films was also studied. Results revealed that the heterostructure comprised crystalline anatase TiO 2 and orthorhombic Bi 2 S 3 and exhibited a high visible light response. The photocurrent density of Bi 2 S 3 /TiO 2 was significantly higher than that of pure TiO 2 under visible light. The sensitization of Bi 2 S 3 enhanced the separation efficiency of the photogenerated charges and photocathodic protection properties of TiO 2 . The Bi 2 S 3 /TiO 2 nanotubes prepared by SILAR deposition with 20 cycles exhibited the optimal photogenerated cathodic protection performance on the 304 stainless steel under visible light.

Electrochemical oxidation of 4-chlorophenol for wastewater treatment using highly active UV treated TiO2 nanotubes.

PubMed

Tian, Min; Thind, Sapanbir S; Dondapati, Jesse S; Li, Xinyong; Chen, Aicheng

2018-06-07

In the present work, we report on a facile UV treatment approach for enhancing the electrocatalytic activity of TiO 2 nanotubes. The TiO 2 nanotubes were prepared using an anodization oxidation method by applying a voltage of 40 V for 8 h in a DMSO + 2% HF solution, and further treated under UV light irradiation. Compared with Pt and untreated TiO 2 nanotubes, the UV treated electrode exhibited a superior electrocatalytic activity toward the oxidation of 4-chlorophenol (4-ClPh). The effects of current density and temperature on the electrochemical oxidation of the 4-ClPh were also systematically investigated. The high electrocatalytic activity of the UV treated TiO 2 nanotubes was further confirmed by the electrochemical oxidation of other persistent organic pollutants including phenol, 2-, 3-, 4-nitrophenol, and 4-aminophenol. The total organic carbon (TOC) analysis revealed that over 90% 4-ClPh was removed when the UV treated TiO 2 electrode was employed and the rate constant was 16 times faster than that of the untreated TiO 2 electrode; whereas only 60% 4-ClPh was eliminated at the Pt electrode under the same conditions. This dramatically improved electrocatalytic activity might be attributed to the enhanced donor density, conductivity, and high overpotential for oxygen evolution. Our results demonstrated that the application of the UV treatment to the TiO 2 nanotubes enhanced their electrochemical activity and energy consumption efficiency significantly, which is highly desirable for the abatement of persistent organic pollutants. Copyright © 2018 Elsevier Ltd. All rights reserved.

Three-dimensional SnO2@TiO2 double-shell nanotubes on carbon cloth as a flexible anode for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Zhang, Haifeng; Ren, Weina; Cheng, Chuanwei

2015-07-01

In this study, three-dimensional SnO2@TiO2 double-shell nanotubes on carbon cloth are synthesized by a combination of the hydrothermal method for ZnO nanorods and a subsequent SnO2 and TiO2 thin film coating with atomic layer deposition (ALD). The as-prepared SnO2@TiO2 double-shell nanotubes are further tested as a flexible anode for Li ion batteries. The SnO2@TiO2 double-shell nanotubes/carbon cloth electrode exhibited a high initial discharge capacity (e.g. 778.8 mA h g-1 at a high current density of 780 mA g-1) and good cycling performance, which could be attributed to the 3D double-layer nanotube structure. The interior space of the stable TiO2 hollow tube can accommodate the large internal stress caused by volume expansion of SnO2 and protect SnO2 from pulverization and exfoliation.

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.

Scanning electron microscopy of heat treated TiO2 nanotubes arrays obtained by anodic oxidation

NASA Astrophysics Data System (ADS)

Naranjo, D. I.; García-Vergara, S. J.; Blanco, S.

2017-12-01

Scanning electron microscopy was used to investigate the anatase-rutile transformation of self-organized TiO2 nanotubes obtained on titanium foil by anodizing and subsequent heat treatment. The anodizing was carried out at 20V in an 1% v/v HF acid and ethylene glycol:water (50:50) electrolyte at room temperature. The anodized samples were initially pre-heat treated at 450°C for 4 hours to modify the amorphous structure of TiO2 nanotubes into anatase structure. Then, the samples were heated between 600 to 800°C for different times, in order to promote the transformation to rutile structure. The formation of TiO2 nanotubes is evident by SEM images. Notably, when the samples are treated at high temperature, the formation of rutile crystals starts to become evident at the nanotubes located on the originally grain boundaries of the titanium. Thus, the anatase - rutile transformation has a close relationship with the microstructure of the titanium, more exactly with grain boundaries.

Fast fabrication of long TiO2 nanotube array with high photoelectrochemical property on flexible stainless steel.

PubMed

Tao, Jie; Wu, Tao; Gao, Peng

2012-03-01

Oriented highly ordered long TiO2 nanotube array films with nanopore structure and high photoelectrochemical property were fabricated on flexible stainless steel substrate (50 microm) by anodization treatment of titanium thin films in a short time. The samples were characterized by means of field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and photoelectrochemical methods, respectively. The results showed that Ti films deposited at the condition of 0.7 Pa Ar pressure and 96 W sputtering power at room temperature was uniform and dense with good homogeneity and high crystallinity. The voltage and the anodization time both played significant roles in the formation of TiO2 nanopore-nanotube array film. The optimal voltage was 60 V and the anodization time is less than 30 min by anodizing Ti films in ethylene glycerol containing 0.5% (w) NH4F and 3% (w) H2O. The growth rate of TiO2 nanotube array was as high as 340 nm/min. Moreover, the photocurrent-potential curves, photocurrent response curves and electrochemical impedance spectra results indicated that the TiO2 nanotube array film with the nanoporous structure exhibited a better photo-response ability and photoelectrochemical performance than the ordinary TiO2 nanotube array film. The reason is that the nanoporous structure on the surface of the nanotube array can separate the photo electron-hole pairs more efficiently and completely than the tubular structure.

Wire-shaped perovskite solar cell based on TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Wang, Xiaoyan; Kulkarni, Sneha A.; Li, Zhen; Xu, Wenjing; Batabyal, Sudip K.; Zhang, Sam; Cao, Anyuan; Wong, Lydia Helena

2016-05-01

In this work, a wire-shaped perovskite solar cell based on TiO2 nanotube (TNT) arrays is demonstrated for the first time by integrating a perovskite absorber on TNT-coated Ti wire. Anodization was adopted for the conformal growth of TNTs on Ti wire, together with the simultaneous formation of a compact TiO2 layer. A sequential step dipping process is employed to produce a uniform and compact perovskite layer on top of TNTs with conformal coverage as the efficient light absorber. Transparent carbon nanotube film is wrapped around Ti wire as the hole collector and counter electrode. The integrated perovskite solar cell wire by facile fabrication approaches shows a promising future in portable and wearable textile electronics.

Ni-doped TiO2 nanotubes photoanode for enhanced photoelectrochemical water splitting

NASA Astrophysics Data System (ADS)

Dong, Zhenbiao; Ding, Dongyan; Li, Ting; Ning, Congqin

2018-06-01

Photoelectrochemical (PEC) water splitting hydrogen production provides a promising way for sustainable development. In this work, we prepared Ni-doped TiO2 (Ti-Ni-O) nanotubes through anodizing different Ti-Ni alloys and further annealing them at elevated temperatures, and reported their PEC water splitting performance. It was found that Ni doping could improve light absorption and facilitate separation of photo-excited electron-hole pair. The nanotubes fabricated on Ti-1 wt.% Ni alloy and annealed at 550 °C exhibited better PEC water splitting performance than those on Ti-10 wt.% Ni alloy. The photoconversion efficiency was 0.67%, which was 3.35 times the photoconversion efficiency of undoped TiO2. It demonstrated that it was feasible to fabricate high-performance Ti-Ni-O nanotubes on Ti-Ni alloys and used as photoanode for improving PEC water splitting.

Hydrogenated TiO2 nanotube arrays for supercapacitors.

PubMed

Lu, Xihong; Wang, Gongming; Zhai, Teng; Yu, Minghao; Gan, Jiayong; Tong, Yexiang; Li, Yat

2012-03-14

We report a new and general strategy for improving the capacitive properties of TiO(2) materials for supercapacitors, involving the synthesis of hydrogenated TiO(2) nanotube arrays (NTAs). The hydrogenated TiO(2) (denoted as H-TiO(2)) were obtained by calcination of anodized TiO(2) NTAs in hydrogen atmosphere in a range of temperatures between 300 to 600 °C. The H-TiO(2) NTAs prepared at 400 °C yields the largest specific capacitance of 3.24 mF cm(-2) at a scan rate of 100 mV s(-1), which is 40 times higher than the capacitance obtained from air-annealed TiO(2) NTAs at the same conditions. Importantly, H-TiO(2) NTAs also show remarkable rate capability with 68% areal capacitance retained when the scan rate increase from 10 to 1000 mV s(-1), as well as outstanding long-term cycling stability with only 3.1% reduction of initial specific capacitance after 10,000 cycles. The prominent electrochemical capacitive properties of H-TiO(2) are attributed to the enhanced carrier density and increased density of hydroxyl group on TiO(2) surface, as a result of hydrogenation. Furthermore, we demonstrate that H-TiO(2) NTAs is a good scaffold to support MnO(2) nanoparticles. The capacitor electrodes made by electrochemical deposition of MnO(2) nanoparticles on H-TiO(2) NTAs achieve a remarkable specific capacitance of 912 F g(-1) at a scan rate of 10 mV s(-1) (based on the mass of MnO(2)). The ability to improve the capacitive properties of TiO(2) electrode materials should open up new opportunities for high-performance supercapacitors. © 2012 American Chemical Society

Hybrid biocomposites based on titania nanotubes and a hydroxyapatite coating deposited by RF-magnetron sputtering: Surface topography, structure, and mechanical properties

NASA Astrophysics Data System (ADS)

Chernozem, Roman V.; Surmeneva, Maria A.; Krause, Bärbel; Baumbach, Tilo; Ignatov, Viktor P.; Tyurin, Alexander I.; Loza, Kateryna; Epple, Matthias; Surmenev, Roman A.

2017-12-01

In this study, biocomposites based on porous titanium oxide structures and a calcium phosphate (CaP) or hydroxyapatite (HA) coating are described and prepared. Nanotubes (NTs) with different pore dimensions were processed using anodic oxidation of Ti substrates in a NH4F-containing electrolyte solution at anodization voltages of 30 and 60 V with a DC power supply. The external diameters of the nanotubes prepared at 30 V and 60 V were 53 ± 10 and 98 ± 16 nm, respectively. RF-magnetron sputtering of the HA target in a single deposition run was performed to prepare a coating on the surface of TiO2 NTs prepared at 30 and 60 V. The thickness of the CaP coating deposited on the mirror-polished Si substrate in the same deposition run with TiO2 NTs was determined by optical ellipsometry (SE) 95 ± 5 nm. Uncoated and CaP-coated NTs were annealed at 500 °C in air. Afterwards, the presence of TiO2 (anatase) was observed. The scanning electron microscopy (SEM), X-ray diffraction (XRD), photoelectron spectroscopy (XPS) and nanoindentation results revealed the influence that the NT dimensions had on the CaP coating deposition process. The tubular surfaces of the NTs were completely coated with the HA coating when prepared at 30 V, and no homogeneous CaP coating was observed when prepared at 60 V. The XRD patterns show peaks assigned to crystalline HA only for the coated TiO2 NTs prepared at 30 V. High-resolution XPS spectra show binding energies (BE) of Ca 2p, P 2p and O 1s core-levels corresponding to HA and amorphous calcium phosphate on TiO2 NTs prepared at 30 V and 60 V, respectively. Fabrication of TiO2 NTs results in a significant decrease to the elastic modulus and nanohardness compared to the Ti substrate. The porous structure of the NTs causes an increase in the elastic strain to failure of the coating (H/E) and the parameter used to describe the resistance of the material to plastic deformation (H3/E2) at the nanoscale level compared to the Ti substrate. Furthermore

TiO2 nanotubes and mesoporous silica as containers in self-healing epoxy coatings

PubMed Central

Vijayan P., Poornima; Al-Maadeed, Mariam Ali S. A.

2016-01-01

The potential of inorganic nanomaterials as reservoirs for healing agents is presented here. Mesoporous silica (SBA-15) and TiO2 nanotubes (TNTs) were synthesized. Both epoxy-encapsulated TiO2 nanotubes and amine-immobilized mesoporous silica were incorporated into epoxy and subsequently coated on a carbon steel substrate. The encapsulated TiO2 nanotubes was quantitatively estimated using a ‘dead pore ratio’ calculation. The morphology of the composite coating was studied in detail using transmission electron microscopic (TEM) analysis. The self-healing ability of the coating was monitored using electrochemical impedance spectroscopy (EIS); the coating recovered 57% of its anticorrosive property in 5 days. The self-healing of the scratch on the coating was monitored using Scanning Electron Microscopy (SEM). The results confirmed that the epoxy pre-polymer was slowly released into the crack. The released epoxy pre-polymer came into contact with the amine immobilized in mesoporous silica and cross-linked to heal the scratch. PMID:27941829

Polyoxometalate-modified TiO2 nanotube arrays photoanode materials for enhanced dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Liu, Ran; Sun, Zhixia; Zhang, Yuzhuo; Xu, Lin; Li, Na

2017-10-01

In this work, we prepared for the first time the TiO2 nanotube arrays (TNAs) photoanode with polyoxometalate(POMs)-modified TiO2 electron-transport layer for improving the performance of zinc phthalocyanine(ZnPc)-sensitized solar cells. The as-prepared POMs/TNAs/ZnPc composite photoanode exhibited higher photovoltaic performances than the TNAs/ZnPc photoanode, so that the power conversion efficiency of the solar cell device based on the POMs/TNAs/ZnPc photoanode displayed a notable improvement of 45%. These results indicated that the POMs play a key role in reducing charge recombination in phthalocyanine-sensitized solar cells, together with TiO2 nanotube arrays being helpful for electron transport. The mechanism of the performance improvement was demonstrated by the measurements of electrochemical impedance spectra and open-circuit voltage decay curves. Although the resulting performance is still below that of the state-of-the-art dye-sensitized solar cells, this study presents a new insight into improving the power conversion efficiency of phthalocyanine-sensitized solar cells via polyoxometalate-modified TiO2 nanotube arrays photoanode.

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.

Synthesis of stable TiO2 nanotubes: effect of hydrothermal treatment, acid washing and annealing temperature.

PubMed

López Zavala, Miguel Ángel; Lozano Morales, Samuel Alejandro; Ávila-Santos, Manuel

2017-11-01

Effect of hydrothermal treatment, acid washing and annealing temperature on the structure and morphology of TiO 2 nanotubes during the formation process was assessed. X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy analysis were conducted to describe the formation and characterization of the structure and morphology of nanotubes. Hydrothermal treatment of TiO 2 precursor nanoparticles and acid washing are fundamental to form and define the nanotubes structure. Hydrothermal treatment causes a change in the crystallinity of the precursor nanoparticles from anatase phase to a monoclinic phase, which characterizes the TiO 2 nanosheets structure. The acid washing promotes the formation of high purity nanotubes due to Na + is exchanged from the titanate structure to the hydrochloric acid (HCl) solution. The annealing temperature affects the dimensions, structure and the morphology of the nanotubes. Annealing temperatures in the range of 400 °C and 600 °C are optimum to maintain a highly stable tubular morphology of nanotubes. Additionally, nanotubes conserve the physicochemical properties of the precursor Degussa P25 nanoparticles. Temperatures greater than 600 °C alter the morphology of nanotubes from tubular to an irregular structure of nanoparticles, which are bigger than those of the precursor material, i.e., the crystallinity turn from anatase phase to rutile phase inducing the collapse of the nanotubes.

Self-Organized Formation of Short TiO2 Nanotube Arrays By Complete Anodization of Ti Thin Films

NASA Astrophysics Data System (ADS)

Okada, Masahisa; Tajima, Kazuki; Yamada, Yasusei; Yoshimura, Kazuki

We investigate the self-organized growth of short TiO2 nanotubes by complete anodization of Ti thin films deposited on Si substrates in ethylene glycol electrolytes with small addition of NH4F. During the anodization process, real-time inspection of the current transient is performed to anodize the Ti films completely. X-ray photoelectron spectroscopy and scanning electron microscopy are employed to characterize the resulting samples. We find that the length of the formed TiO2 nanotubes is governed by the thickness of Ti thin films independently of the tube diameter. Short TiO2 nanotubes are also found to be stable up to 550 °C in air atmosphere even after crystallization to rutile.

Enhanced photo-assistant electrocatalysis of anodization TiO2 nanotubes via surrounded surface decoration with MoS2 for hydrogen evolution reaction

NASA Astrophysics Data System (ADS)

Tian, Yuanyuan; Song, Ye; Dou, Meiling; Ji, Jing; Wang, Feng

2018-03-01

A highly ordered TiO2 nanotube array covered with MoS2 is fabricated through a facile anodization of a metallic Ti followed by electrochemical deposition approach. The morphologies characterization of v-TiO2@MoS2 indicate that a whole scale of 1D TiO2nanotube uniformly covered with the MoS2 layer inside and outside, and the pathway inside the TiO2nanotube is kept flow-through. The as-synthesized v-TiO2@MoS2 hybrid exhibits higher efficient and stable visible light activities than that of either pure TiO2 nanotubes or nv-TiO2@MoS2 nanostructures. By electrochemical measurements such as linear sweep voltammetry(LSV) and electrochemical impedance spectroscope (EIS) under light illumination or in dark, we find that the v-TiO2@MoS2hybrid shows markedly enhanced photoelectrochemical performance. Furthermore, we compare the electrocatalytic behavior of v-TiO2@MoS2under illumination in H2SO4/Lactic acid within Na2S/NaSO3 solution. The results show that the photo-assistant electrocatalytic activity in acidic environment is much better than in alkaline environment. The highly directional and orthogonal separation of charge carriers between TiO2 nanotubes and MoS2 layer, together with maximally exposed MoS2 edges, light harvesting and junctions formed between TiO2 and MoS2 is supposed to be mainly responsible for the enhanced photo-assistant electrocatalytic activity of v-TiO2@MoS2.

Application of nitrogen-doped TiO2 nano-tubes in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Tran, Vy Anh; Truong, Trieu Thinh; Phan, Thu Anh Pham; Nguyen, Trang Ngoc; Huynh, Tuan Van; Agresti, Antonio; Pescetelli, Sara; Le, Tien Khoa; Di Carlo, Aldo; Lund, Torben; Le, So-Nhu; Nguyen, Phuong Tuyet

2017-03-01

Our research aimed to improve the overall energy conversion efficiency of DSCs by applying nitrogen-doped TiO2 nano-tubes (N-TNT) for the preparation of DSCs photo-anodes. The none-doped TiO2 nano-tubes (TNTs) were synthesized by alkaline hydrothermal treatment of Degussa P25 TiO2 particles in 10 M NaOH. The nano-tubes were N-doped by reflux in various concentrations of NH4NO3. The effects of nitrogen doping on the structure, morphology, and crystallography of N-TNT were analyzed by transmission electron microscopy (TEM), infrared spectroscopy (IR), Raman spectroscopy, and X-ray photoelectron spectra (XPS). DSCs fabricated with doped N-TNT and TNT was characterized by J-V measurements. Results showed that nitrogen doping significantly enhanced the efficiency of N-TNT cells, reaching the optimum value (η = 7.36%) with 2 M nitrogen dopant, compared to η = 4.75% of TNT cells. The high efficiency of the N-TNT cells was attributed to increased current density due to the reduction of dark current in the DSCs.

Atomic Layer Deposition Al2O3 Coatings Significantly Improve Thermal, Chemical, and Mechanical Stability of Anodic TiO2 Nanotube Layers

PubMed Central

2017-01-01

We report on a very significant enhancement of the thermal, chemical, and mechanical stability of self-organized TiO2 nanotubes layers, provided by thin Al2O3 coatings of different thicknesses prepared by atomic layer deposition (ALD). TiO2 nanotube layers coated with Al2O3 coatings exhibit significantly improved thermal stability as illustrated by the preservation of the nanotubular structure upon annealing treatment at high temperatures (870 °C). In addition, a high anatase content is preserved in the nanotube layers against expectation of the total rutile conversion at such a high temperature. Hardness of the resulting nanotube layers is investigated by nanoindentation measurements and shows strongly improved values compared to uncoated counterparts. Finally, it is demonstrated that Al2O3 coatings guarantee unprecedented chemical stability of TiO2 nanotube layers in harsh environments of concentrated H3PO4 solutions. PMID:28291942

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.

TiO2 Nanotubes: Recent Advances in Synthesis and Gas Sensing Properties

PubMed Central

Galstyan, Vardan; Comini, Elisabetta; Faglia, Guido; Sberveglieri, Giorgio

2013-01-01

Synthesis—particularly by electrochemical anodization-, growth mechanism and chemical sensing properties of pure, doped and mixed titania tubular arrays are reviewed. The first part deals on how anodization parameters affect the size, shape and morphology of titania nanotubes. In the second part fabrication of sensing devices based on titania nanotubes is presented, together with their most notable gas sensing performances. Doping largely improves conductivity and enhances gas sensing performances of TiO2 nanotubes. PMID:24184919

All electrochemical process for synthesis of Si coating on TiO2 nanotubes as durable negative electrode material for lithium ion batteries

NASA Astrophysics Data System (ADS)

Nemaga, Abirdu Woreka; Mallet, Jeremy; Michel, Jean; Guery, Claude; Molinari, Michael; Morcrette, Mathieu

2018-07-01

The development of high energy density Li-ion batteries requires to look for electrode materials with high capacity while keeping their stability upon cycling. In this study, amorphous silicon (a-Si) thin film deposited on self-organized TiO2 nanotubes is investigated as negative electrode for Li-ion batteries. Nanostructured composite negative electrodes were fabricated by a two-step cost effective electrochemical process. Firstly, self-organized TiO2 nanotube arrays were synthesised by anodizing of Ti foil. Subsequently, thanks to the use of room temperature ionic liquid, conformal Si layer was electrodeposited on the TiO2 nanotubes to achieve the synthesis of nanostructured a-Si/TiO2 nanotube composite negative electrodes. The influence of the Si loading as well as the crystallinity of the TiO2 nanotubes have been studied in terms of capacity and cyclic stability. For an optimized a-Si loading, it is shown that the amorphous state for the TiO2 nanotubes enables to get stable lithiation and delithiation with a total areal charge capacity of about 0.32 mA h cm-2 with improved capacity retention of about 84% after 50 cycles, while a-Si on crystalline TiO2 nanotubes shows poor cyclic stability independently from the Si loading.

Fabrication of thin film TiO2 nanotube arrays on Co-28Cr-6Mo alloy by anodization.

PubMed

Ni, Jiahua; Frandsen, Christine J; Noh, Kunbae; Johnston, Gary W; He, Guo; Tang, Tingting; Jin, Sungho

2013-04-01

Titanium oxide (TiO2) nanotube arrays were prepared by anodization of Ti/Au/Ti trilayer thin film DC sputtered onto forged and cast Co-28Cr-6Mo alloy substrate at 400 °C. Two different types of deposited film structures (Ti/Au/Ti trilayer and Ti monolayer), and two deposition temperatures (room temperature and 400 °C) were compared in this work. The concentrations of ammonium fluoride (NH4F) and H2O in glycerol electrolyte were varied to study their effect on the formation of TiO2 nanotube arrays on a forged and cast Co-28Cr-6Mo alloy. The results show that Ti/Au/Ti trilayer thin film and elevated temperature sputtered films are favorable for the formation of well-ordered nanotube arrays. The optimized electrolyte concentration for the growth of TiO2 nanotube arrays on forged and cast Co-28Cr-6Mo alloy was obtained. This work contains meaningful results for the application of a TiO2 nanotube coating to a CoCr alloy implant for potential next-generation orthopedic implant surface coatings with improved osseointegrative capabilities. Copyright © 2013 Elsevier B.V. All rights reserved.

Highly efficient and completely flexible fiber-shaped dye-sensitized solar cell based on TiO2 nanotube array

NASA Astrophysics Data System (ADS)

Lv, Zhibin; Yu, Jiefeng; Wu, Hongwei; Shang, Jian; Wang, Dan; Hou, Shaocong; Fu, Yongping; Wu, Kai; Zou, Dechun

2012-02-01

A type of highly efficient completely flexible fiber-shaped solar cell based on TiO2 nanotube array is successfully prepared. Under air mass 1.5G (100 mW cm-2) illumination conditions, the photoelectric conversion efficiency of the solar cell approaches 7%, the highest among all fiber-shaped cells based on TiO2 nanotube arrays and the first completely flexible fiber-shaped DSSC. The fiber-shaped solar cell demonstrates good flexibility, which makes it suitable for modularization using weaving technologies.A type of highly efficient completely flexible fiber-shaped solar cell based on TiO2 nanotube array is successfully prepared. Under air mass 1.5G (100 mW cm-2) illumination conditions, the photoelectric conversion efficiency of the solar cell approaches 7%, the highest among all fiber-shaped cells based on TiO2 nanotube arrays and the first completely flexible fiber-shaped DSSC. The fiber-shaped solar cell demonstrates good flexibility, which makes it suitable for modularization using weaving technologies. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr11532h

Enhanced Photocatalytic Activity of La3+-Doped TiO2 Nanotubes with Full Wave-Band Absorption

NASA Astrophysics Data System (ADS)

Xia, Minghao; Huang, Lingling; Zhang, Yubo; Wang, Yongqian

2018-06-01

TiO2 nanotubes doped with La3+ were synthesized by anodic oxidation method and the photocatalytic activity was detected by photodegrading methylene blue. As-prepared samples improved the absorption of both ultraviolet light and visible light and have a great enhancement on the photocatalytic activity while contrasting with the pristine TiO2 nanotubes. A tentative mechanism for the enhancement of photocatalytic activity with full wave-band absorption is proposed.

Photoelectrocatalytic Synthesis of Hydrogen Peroxide by Molecular Copper-Porphyrin Supported on Titanium Dioxide Nanotubes.

PubMed

Apaydin, Dogukan H; Seelajaroen, Hathaichanok; Pengsakul, Orathip; Thamyongkit, Patchanita; Sariciftci, Niyazi Serdar; Kunze-Liebhäuser, Julia; Portenkirchner, Engelbert

2018-04-24

We report on a self-assembled system comprising a molecular copper-porphyrin photoelectrocatalyst, 5-(4-carboxy-phenyl)-10,15,20-triphenylporphyrinatocopper(II) (CuTPP-COOH), covalently bound to self-organized, anodic titania nanotube arrays (TiO 2 NTs) for photoelectrochemical reduction of oxygen. Visible light irradiation of the porphyrin-covered TiO 2 NTs under cathodic polarization up to -0.3 V vs. Normal hydrogen electrode (NHE) photocatalytically produces H 2 O 2 in pH neutral electrolyte, at room temperature and without need of sacrificial electron donors. The formation of H 2 O 2 upon irradiation is proven and quantified by direct colorimetric detection using 4-nitrophenyl boronic acid ( p -NPBA) as a reactant. This simple approach for the attachment of a small molecular catalyst to TiO 2 NTs may ultimately allow for the preparation of a low-cost H 2 O 2 evolving cathode for efficient photoelectrochemical energy storage under ambient conditions.

Facile fabrication of Si-doped TiO2 nanotubes photoanode for enhanced photoelectrochemical hydrogen generation

NASA Astrophysics Data System (ADS)

Dong, Zhenbiao; Ding, Dongyan; Li, Ting; Ning, Congqin

2018-04-01

Photoelectrochemical (PEC) water splitting based doping modified one dimensional (1D) titanium dioxide (TiO2) nanostructures provide an efficient method for hydrogen generation. Here we first successfully fabricated 1D Si-doped TiO2 (Ti-Si-O) nanotube arrays through anodizing Ti-Si alloys with different Si amount, and reported the PEC properties for water splitting. The Ti-Si-O nanotube arrays fabricated on Ti-5 wt.% Si alloy and annealed at 600 °C possess higher PEC activity, yielding a higher photocurrent density of 0.83 mA/cm2 at 0 V vs. Ag/AgCl. The maximum photoconversion efficiency was 0.54%, which was 2.7 times the photoconversion efficiency of undoped TiO2.

Effects of various applied voltages on physical properties of TiO2 nanotubes by anodization method

NASA Astrophysics Data System (ADS)

Hoseinzadeh, T.; Ghorannevis, Z.; Ghoranneviss, M.; Sari, A. H.; Salem, M. K.

2017-09-01

Three steps anodization process is used to synthesize highly ordered and uniform multilayered titanium oxide (TiO2) nanotubes and effect of different anodization voltages are studied on their physical properties such as structural, morphological and optical. The crystalized structure of the synthesized tubes is investigated by X-ray diffractometer analysis. To study the morphology of the tubes, field emission scanning electron microscopy is used, which showed that the wall thicknesses and the diameters of the tubes are affected by the different anodization voltages. Moreover, optical studies performed by diffuse reflection spectra suggested that band gap of the TiO2 nanotubes are also changed by applying different anodization voltages. In this study using physical investigations, an optimum anodization voltage is obtained to synthesize the uniform crystalized TiO2 nanotubes with suitable diameter, wall thickness and optical properties.

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

NASA Astrophysics Data System (ADS)

Xie, Yi; Heo, Sung Hwan; Yoo, Seung Hwa; Ali, Ghafar; Cho, Sung Oh

2010-03-01

A simple and straightforward approach to prepare TiO2-coated carbon nanotubes (CNTs) is presented. Anatase TiO2 nanoparticles (NPs) with the average size ~8 nm were coated on CNTs from peroxo titanic acid (PTA) precursor even at low temperature of 100 °C. We demonstrate the effects of CNTs/TiO2 molar ratio on the adsorption capability and photocatalytic efficiency under UV-visible irradiation. The samples showed not only good optical absorption in visible range, but also great adsorption capacity for methyl orange (MO) dye molecules. These properties facilitated the great enhancement of photocatalytic activity of TiO2 NPs-coated CNTs photocatalysts. The TiO2 NPs-coated CNTs exhibited 2.45 times higher photocatalytic activity for MO degradation than that of pure TiO2.

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

PubMed Central

2010-01-01

A simple and straightforward approach to prepare TiO2-coated carbon nanotubes (CNTs) is presented. Anatase TiO2 nanoparticles (NPs) with the average size ~8 nm were coated on CNTs from peroxo titanic acid (PTA) precursor even at low temperature of 100 °C. We demonstrate the effects of CNTs/TiO2 molar ratio on the adsorption capability and photocatalytic efficiency under UV–visible irradiation. The samples showed not only good optical absorption in visible range, but also great adsorption capacity for methyl orange (MO) dye molecules. These properties facilitated the great enhancement of photocatalytic activity of TiO2 NPs-coated CNTs photocatalysts. The TiO2 NPs-coated CNTs exhibited 2.45 times higher photocatalytic activity for MO degradation than that of pure TiO2. PMID:20671780

Exploring doxorubicin localization in eluting TiO2 nanotube arrays through fluorescence correlation spectroscopy analysis.

PubMed

De Santo, Ilaria; Sanguigno, Luigi; Causa, Filippo; Monetta, Tullio; Netti, Paolo A

2012-11-07

Drug elution properties of TiO(2) nanotube arrays have been largely investigated by means of solely macroscopic observations. Controversial elution performances have been reported so far and a clear comprehension of these phenomena is still missing as a consequence of a lack of molecular investigation methods. Here we propose a way to discern drug elution properties of nanotubes through the evaluation of drug localization by Fluorescence Correlation Spectroscopy (FCS) analysis. We verified this method upon doxorubicin elution from differently loaded TiO(2) nanotubes. Diverse elution profiles were obtained from nanotubes filled by soaking and wet vacuum impregnation methods. Impregnated nanotubes controlled drug diffusion up to thirty days, while soaked samples completed elution in seven days. FCS analysis of doxorubicin motion in loaded nanotubes clarified that more than 90% of drugs dwell preferentially in inter-nanotube spaces in soaked samples due to decorrelation in a 2D fashion, while a 97% fraction of molecules showed 1D mobility ascribable to displacements along the nanotube vertical axis of wet vacuum impregnated nanotubes. The diverse drug localizations inferred from FCS measurements, together with distinct drug-surface interaction strengths resulting from diverse drug filling techniques, could explain the variability in elution kinetics.

Mechanical degradation of TiO2 nanotubes with and without nanoparticulate silver coating

PubMed Central

Shivaram, Anish; Bose, Susmita; Bandyopadhyay, Amit

2016-01-01

The primary objective of this research was to evaluate the extent of mechanical degradation on TiO2 nanotubes on Ti with and without nano-particulate silver coating using two different lengths of TiO2 nanotubes- 300nm and ~ 1µm, which were fabricated on commercially pure Titanium (cp-Ti) rods using anodization method using two different electrolytic mediums - (1) deionized (DI) water with 1% HF, and (2) ethylene glycol with 1% HF, 0.5 wt%. NH4F and 10% DI water. Nanotubes fabricated rods were implanted into equine cadaver bone to evaluate mechanical damage at the surface. Silver was electrochemically deposited on these nanotubes and using a release study, silver ion concentrations were measured before and after implantation, followed by surface characterization using a Field Emission Scanning Electron Microscope (FESEM). In vitro cell-material interaction study was performed using human fetal osteoblast cells (hFOB) to understand the effect of silver coating using an MTT assay for proliferation and to determine any cytotoxic effect on the cells and to study its biocompatibility. No significant damage due to implantation was observed for nanotubes up to ~1 µm length under current experimental conditions. Cell-materials interaction showed no cytotoxic effects on the cells due to silver coating and anodization of samples. PMID:27017285

Novel UV-Visible Photodetector in Photovoltaic Mode with Fast Response and Ultrahigh Photosensitivity Employing Se/TiO2 Nanotubes Heterojunction.

PubMed

Zheng, Lingxia; Hu, Kai; Teng, Feng; Fang, Xiaosheng

2017-02-01

A feasible strategy for hybrid photodetector by integrating an array of self-ordered TiO 2 nanotubes (NTs) and selenium is demonstrated to break the compromise between the responsivity and response speed. Novel heterojunction between the TiO 2 NTs and Se in combination with the surface trap states at TiO 2 help regulate the electron transport and facilitate the separation of photogenerated electron-hole pairs under photovoltaic mode (at zero bias), leading to a high responsivity of ≈100 mA W -1 at 620 nm light illumination and the ultrashort rise/decay time (1.4/7.8 ms). The implanting of intrinsic p-type Se into TiO 2 NTs broadens the detection range to UV-visible (280-700 nm) with a large detectivity of over 10 12 Jones and a high linear dynamic range of over 80 dB. In addition, a maximum photocurrent of ≈10 7 A is achieved at 450 nm light illumination and an ultrahigh photosensitivity (on/off ratio up to 10 4 ) under zero bias upon UV and visible light illumination is readily achieved. The concept of employing novel heterojunction geometry holds great potential to pave a new way to realize high performance and energy-efficient optoelectronic devices for practical applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transparent anodic TiO2 nanotube arrays on plastic substrates for disposable biosensors and flexible electronics.

PubMed

Farsinezhad, Samira; Mohammadpour, Arash; Dalrymple, Ashley N; Geisinger, Jared; Kar, Piyush; Brett, Michael J; Shankar, Karthik

2013-04-01

Exploitation of anodically formed self-organized TiO2 nanotube arrays in mass-manufactured, disposable biosensors, rollable electrochromic displays and flexible large-area solar cells would greatly benefit from integration with transparent and flexible polymeric substrates. Such integration requires the vacuum deposition of a thin film of titanium on the desired substrate, which is then anodized in suitable media to generate TiO2 nanotube arrays. However the challenges associated with control of Ti film morphology, nanotube array synthesis conditions, and film adhesion and transparency, have necessitated the use of substrate heating during deposition to temperatures of at least 300 degrees C and as high as 500 degrees C to generate highly ordered open-pore nanotube arrays, thus preventing the use of polymeric substrates. We report on a film growth technique that exploits atomic peening to achieve high quality transparent TiO2 nanotube arrays with lengths up to 5.1 microm at room temperature on polyimide substrates without the need for substrate heating or substrate biasing or a Kauffman ion source. The superior optical quality and uniformity of the nanotube arrays was evidenced by the high specular reflectivity and the smooth pattern of periodic interferometric fringes in the transmission spectra of the nanotube arrays, from which the wavelength-dependent effective refractive index was extracted for the air-TiO2 composite medium. A fluorescent immunoassay biosensor constructed using 5.1 microm-long transparent titania nanotube arrays (TTNAs) grown on Kapton substrates detected human cardiac troponin I at a concentration of 0.1 microg ml(-1).

Visible light-harvesting of TiO2 nanotubes array by pulsed laser deposited CdS

NASA Astrophysics Data System (ADS)

Bjelajac, Andjelika; Djokic, Veljko; Petrovic, Rada; Socol, Gabiel; Mihailescu, Ion N.; Florea, Ileana; Ersen, Ovidiu; Janackovic, Djordje

2014-08-01

Titanium dioxide (TiO2) nanotubes arrays, obtained by anodization technique and annealing, were decorated with CdS using pulsed laser deposition method. Their structural, morphological and chemical characterization was carried out by electron microscopy in scanning (SEM) and transmission (TEM) modes, combined with energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS). It was demonstrated that the quantity of deposited CdS can be controlled by varying the number of laser pulses. The chemical mapping of the elements of interest was performed using the energy filtered mode of the electron microscope. The results showed that pulse laser deposition is an adequate technique for deposition of CdS inside and between 100 nm wide TiO2 nanotubes. The diffuse reflectance spectroscopy investigation of selected samples proved that the absorption edge of the prepared CdS/TiO2 nanocomposites is significantly extended to the visible range. The corresponding band gaps were determinated from the Tauc plot of transformed Kubelka-Munk function. The band gap reduction of TiO2 nanotubes by pulsed laser deposition of CdS was put in evidence.

Efficient suppression of nanograss during porous anodic TiO2 nanotubes growth

NASA Astrophysics Data System (ADS)

Gui, Qunfang; Yu, Dongliang; Li, Dongdong; Song, Ye; Zhu, Xufei; Cao, Liu; Zhang, Shaoyu; Ma, Weihua; You, Shiyu

2014-09-01

When Ti foil was anodized in fluoride-containing electrolyte for a long time, undesired etching-induced "nanograss" would inevitably generate on the top of porous anodic TiO2 nanotubes (PATNTs). The nanograss will hinder the ions transport and in turn yield depressed (photo) electrochemical performance. In order to obtain nanograss-free nanotubes, a modified three-step anodization and two-layer nanostructure of PATNTs were designed to avoid the nanograss. The first layer (L1) nanotubes were obtained by the conventional two-step anodization. After washing and drying processes, the third-step anodization was carried out with the presence of L1 nanotubes. The L1 nanotubes, serving as a sacrificed layer, was etched and transformed into nanograss, while the ultralong nanotubes (L2) were maintained underneath the L1. The bi-layer nanostructure of the nanograss/nanotubes (L1/L2) was then ultrasonically rinsed in deionized water to remove the nanograss (L1 layer). Then much longer nanotubes (L2 layer) with intact nanotube mouths could be obtained. Using this novel approach, the ultralong nanotubes without nanograss can be rationally controlled by adjusting the anodizing times of two layers.

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.

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.

Optimizing TiO2 nanotube top geometry for use in dye-sensitized solar cells.

PubMed

Mir, Nooshin; Lee, Kiyoung; Paramasivam, Indhumati; Schmuki, Patrik

2012-09-17

Recombination dynamics: For TiO(2) nanotube-based dye-sensitized solar cells, the efficiency can be drastically enhanced by a synergetic effect that occurs when using nanowire-ended nanotubes in combination with an adequate nanoparticle decoration (see figure). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Incorporating TiO2 nanotubes with a peptide of D-amino K122-4 (D) for enhanced mechanical and photocatalytic properties

NASA Astrophysics Data System (ADS)

Guo, L. Q.; Hu, Y. W.; Yu, B.; Davis, E.; Irvin, R.; Yan, X. G.; Li, D. Y.

2016-02-01

Titanium dioxide (TiO2) nanotubes are promising for a wide variety of potential applications in energy, biomedical and environmental sectors. However, their low mechanical strength and wide band gap limit their widespread technological use. This article reports our recent efforts to increase the mechanical strength of TiO2 nanotubes with lowered band gap by immobilizing a peptide of D-amino K122-4 (D) onto the nanotubes. Topographies and chemical compositions of the peptide-coated and uncoated TiO2 nanotubular arrays were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy (XPS). Properties of the peptide-coated and uncoated TiO2 nanotubular arrays, including hardness, elastic modulus, electron work function and photocurrent, were evaluated using micromechanical probe, Kelvin Probe and electrochemical system. Effect of the peptide on surface conductivity was also investigated through current mapping and I-V curve analysis with conductive atomic force microscopy. It is demonstrated that the peptide coating simultaneously enhances the mechanical strength, photocatalytic and electrical properties of TiO2 nanotubes.

Transparent TiO 2 nanotube array photoelectrodes prepared via two-step anodization

DOE PAGES

Kim, Jin Young; Zhu, Kai; Neale, Nathan R.; ...

2014-04-04

Two-step anodization of transparent TiO 2 nanotube arrays has been demonstrated with aid of a Nb-doped TiO 2 buffer layer deposited between the Ti layer and TCO substrate. Enhanced physical adhesion and electrochemical stability provided by the buffer layer has been found to be important for successful implementation of the two-step anodization process. As a result, with the proposed approach, the morphology and thickness of NT arrays could be controlled very precisely, which in turn, influenced their optical and photoelectrochemical properties.

One-Step Formation of WO3-Loaded TiO2 Nanotubes Composite Film for High Photocatalytic Performance

PubMed Central

Lee, Wai Hong; Lai, Chin Wei; Abd Hamid, Sharifah Bee

2015-01-01

High aspect ratio of WO3-loaded TiO2 nanotube arrays have been successfully synthesized using the electrochemical anodization method in an ethylene glycol electrolyte containing 0.5 wt% ammonium fluoride in a range of applied voltage of 10–40 V for 30 min. The novelty of this research works in the one-step formation of WO3-loaded TiO2 nanotube arrays composite film by using tungsten as the cathode material instead of the conventionally used platinum electrode. As compared with platinum, tungsten metal has lower stability, forming dissolved ions (W6+) in the electrolyte. The W6+ ions then move towards the titanium foil and form a coherent deposit on titanium foil. By controlling the oxidation rate and chemical dissolution rate of TiO2 during the electrochemical anodization, the nanotubular structure of TiO2 film could be achieved. In the present study, nanotube arrays were characterized using FESEM, EDAX, XRD, as well as Raman spectroscopy. Based on the results obtained, nanotube arrays with average pore diameter of up to 74 nm and length of 1.6 µm were produced. EDAX confirmed the presence of tungsten element within the nanotube arrays which varied in content from 1.06 at% to 3.29 at%. The photocatalytic activity of the nanotube arrays was then investigated using methyl orange degradation under TUV 96W UV-B Germicidal light irradiation. The nanotube with the highest aspect ratio, geometric surface area factor and at% of tungsten exhibited the highest photocatalytic activity due to more photo-induced electron-hole pairs generated by the larger surface area and because WO3 improves charge separation, reduces charge carrier recombination and increases charge carrier lifetime via accumulation of electrons and holes in the two different metal oxide semiconductor components.

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

Surface functionalization of TiO2 nanotubes with minocycline and its in vitro biological effects on Schwann cells.

PubMed

A, Lan; Xu, Wenzhou; Zhao, Jinghui; Li, Chunyan; Qi, Manlin; Li, Xue; Wang, Lin; Zhou, Yanmin

2018-06-20

Minocycline has been widely used in central nervous system disease. However, the effect of minocycline on the repairing of nerve fibers around dental implants had not been previously investigated. The aim of the present study was to evaluate the possibility of using minocycline for the repairing of nerve fibers around dental implants by investigating the effect of minocycline on the proliferation of Schwann cells and secretion of neurotrophic factors nerve growth factor and glial cell line-derived neurotrophic factor in vitro. TiO 2 nanotubes were fabricated on the surface of pure titanium via anodization at the voltage of 20, 30, 40 and 50 V. The nanotubes structure were characterized by scanning electron microscopy and examined with an optical contact angle. Then drug loading capability and release behavior were detected in vitro. The TiO 2 nanotubes loaded with different concentration of minocycline were used to produce conditioned media with which to treat the Schwann cells. A cell counting kit-8 assay and cell viability were both selected to study the proliferative effect of the specimens on Schwann cell. Reverse transcription-quantitative PCR and western blot analyses were used to detect the related gene/protein expression of Schwann cells. The results showed that the diameter of TiO 2 nanotubes at different voltage varied from 100 to 200 nm. The results of optical contact angle and releasing profile showed the nanotubes fabricated at the voltage of 30 V met the needs of the carrier of minocycline. In addition, the TiO 2 nanotubes loaded with the concentration of 20 μg/mL minocycline increased Schwann cells proliferation and secretion of neurotrophic factors in vitro. The results suggested that the surface functionalization of TiO 2 nanotubes with minocycline was a promising candidate biomaterial for the peripheral nerve regeneration around dental implants and has potential to be applied in improving the osseoperception of dental implant.

Carbon nanotube TiO2 hybrid films for detecting traces of O2

NASA Astrophysics Data System (ADS)

Llobet, E.; Espinosa, E. H.; Sotter, E.; Ionescu, R.; Vilanova, X.; Torres, J.; Felten, A.; Pireaux, J. J.; Ke, X.; Van Tendeloo, G.; Renaux, F.; Paint, Y.; Hecq, M.; Bittencourt, C.

2008-09-01

Hybrid titania films have been prepared using an adapted sol-gel method for obtaining well-dispersed hydrogen plasma-treated multiwall carbon nanotubes in either pure titania or Nb-doped titania. The drop-coating method has been used to fabricate resistive oxygen sensors based on titania or on titania and carbon nanotube hybrids. Morphology and composition studies have revealed that the dispersion of low amounts of carbon nanotubes within the titania matrix does not significantly alter its crystallization behaviour. The gas sensitivity studies performed on the different samples have shown that the hybrid layers based on titania and carbon nanotubes possess an unprecedented responsiveness towards oxygen (i.e. more than four times higher than that shown by optimized Nb-doped TiO2 films). Furthermore, hybrid sensors containing carbon nanotubes respond at significantly lower operating temperatures than their non-hybrid counterparts. These new hybrid sensors show a strong potential for monitoring traces of oxygen (i.e. <=10 ppm) in a flow of CO2, which is of interest for the beverage industry.

N- and C-Modified TiO2 Nanotube Arrays: Enhanced Photoelectrochemical Properties and Effect of Nanotubes Length on Photoconversion Efficiency

PubMed Central

Mohamed, Ahmed El Ruby; Barghi, Shahzad

2018-01-01

In this investigation, a new, facile, low cost and environmental-friendly method was introduced to fabricate N- and C-modified TiO2 nanotube arrays by immersing the as-anodized TiO2 nanotube arrays (TNTAs) in a urea aqueous solution with mechanical agitation for a short time and keeping the TNTAs immersed in the solution for 6 h at room temperature. Then, the TNTAs were annealed at different temperatures. The produced N-, C-modified TNTAs were characterized using FESEM, EDX, XRD, XPS, UV-Vis diffuse reflectance spectra. Modified optical properties with narrow band gap energy, Eg, of 2.65 eV was obtained after annealing the modified TNTAs at 550 °C. Modified TNTAs showed enhanced photoelectochemical performance. Photoconversion efficiency (PCE) was increased from 4.35% for pristine (unmodified) TNTAs to 5.18% for modified TNTAs, an increase of 19%. Effect of nanotubes length of modified TNTAs on photoelectrochemical performance was also studied. Photocurrent density and PCE were increased by increasing nanotube length with a maximum PCE of 6.38% for nanotube length of 55 µm. This high PCE value was attributed to: band gap reduction due to C- and N-modification of TNTAs surface, increased surface area of long TNTAs compared with short TNTAs, investigated in previous studies. PMID:29597248

Preparation and UV-Vis photodegradation of gaseous benzene by TiO2 nanotube arrays supporting V2O5 nanoparticles

NASA Astrophysics Data System (ADS)

Zhao, Chunxia; Song, Yanbao; Yang, Yunxia; Chen, Wen; Li, Xiaoyu; Wang, Zongsheng

2015-07-01

TiO2-based catalysts effective in visible radiation for eliminating organic pollutants have attracted intense research activity as a future generation photocatalytic material. However, recombination of electron-hole pairs through trapping/de-trapping as well as the disadvantages of recycling and separation/filtration of powders lead to the limitation of powder TiO2 materials. TiO2 nanotube array films supporting vanadium pentoxide nanoparticles (VTNTs) were synthesized by electrophoresis deposition method with the prepared TiO2 nanotube arrays as the cathode and V2O5 sol as the electrolyte. The results indicate that the formation of Ti-O-V bonds and intimate interaction between host-guest interfaces help to enhance the hybrids’ photodegradation activity of gaseous benzene. Importantly, hybrid film catalysts prepared with 0.05 mol/L V2O5 sol for 10 min electrophoresis deposition perform a 98% conversion rate of benzene and 1028.8 mg/m3CO2 production in 80 min under UV-Vis irradiation.

Morphological evolution of TiO2 nanotube arrays with lotus-root-shaped nanostructure

NASA Astrophysics Data System (ADS)

Yu, Dongliang; Song, Ye; Zhu, Xufei; Yang, Ruiquan; Han, Aijun

2013-07-01

TiO2 nanotube arrays (TNAs) with lotus-root-shaped nanostructure have been fabricated by a modified two-step electrochemical anodization method. In the present work, different morphologies formed under different anodizing voltages are investigated in detail by field-emission scanning electron microscope. The results show that the concaves left by the first-step anodization can guide the uniform growth of TNAs in some degree as the second-step anodizing voltage is the same with that in the first step, however, when lower voltages are adopted in the second-step anodization, no guidance can be achieved, and different morphological TNAs with lotus-root-shaped nanostructure are fabricated. And we find that the nanotube diameters are directly proportional to the applied voltage in the second-step anodization. Furthermore, a possible mechanism for the growth of the TiO2 nanotubes with the special morphology is proposed for the first time, which depends on both the oxygen bubble mold and the viscous flow of the barrier oxide from the pore base to the pore wall.

Dye-sensitized solar cells employing doubly or singly open-ended TiO2 nanotube arrays: structural geometry and charge transport.

PubMed

Choi, Jongmin; Song, Seulki; Kang, Gyeongho; Park, Taiho

2014-09-10

We systematically investigated the charge transport properties of doubly or singly open-ended TiO2 nanotube arrays (DNT and SNT, respectively) for their utility as electrodes in dye-sensitized solar cells (DSCs). The SNT or DNT arrays were transferred in a bottom-up (B-up) or top-up (T-up) configuration onto a fluorine-doped tin oxide (FTO) substrate onto which had been deposited a 2 μm thick TiO2 nanoparticle (NP) interlayer. This process yielded four types of DSCs prepared with SNTs (B-up or T-up) or DNT (B-up or T-up). The photovoltaic performances of these DSCs were analyzed by measuring the dependence of the charge transport on the DSC geometry. High resolution scanning electron microscopy techniques were used to characterize the electrode cross sections, and electrochemical impedance spectroscopy was used to characterize the electrical connection at the interface between the NT array and the TiO2 NP interlayer. We examined the effects of decorating the DNT or SNT arrays with small NPs (sNP@DNT and sNP@SNT, respectively) in an effort to increase the extent of dye loading. The DNT arrays decorated with small NPs performed better than the decorated SNT arrays, most likely because the Ti(OH)4 precursor solution flowed freely into the array through the open ends of the NTs in the DNT case but not in the SNT case. The sNP@DNT-based DSC exhibited a better PCE (10%) compared to the sNP@SNT-based DSCs (6.8%) because the electrolyte solution flow was not restricted, direct electron transport though the NT arrays was possible, the electrical connection at the interface between the NT array and the TiO2 NP interlayer was good, and the array provided efficient light harvesting.

Oriented TiO2 nanotubes as a lithium metal storage medium

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

Kim, Jae-Hun; Kang, Hee-Kook; Woo, Sang-Gil

2014-07-01

A new strategy for suppressing dendritic lithium growth in rechargeable lithium metal batteries is introduced, in which TiO2 nanotube (NT) array electrodes prepared by anodization are used as a metallic lithium storage medium. During the first charge process, lithium ions are inserted into the crystal structure of the TiO2 NT arrays, and then, lithium metal is deposited on the surfaces of the NT arrays, i.e., in the NT pores and between NT walls. From the second cycle onward, the TiO2 material is used as lithium ion pathways, which results in the effective current distribution for lithium deposition and prevents disintegrationmore » of the deposited metallic lithium. Compared to a Li(Cu foil)-LiCoO2 cell, the Li(TiO2 NT)-LiCoO2 cell exhibits enhanced cycling efficiency. This new concept will enable other 3D structured negative active materials to be used as lithium metal storage media for lithium metal batteries.« less

Synthesis of TiO2 nanotubes with ZnO nanoparticles to achieve antibacterial properties and stem cell compatibility

NASA Astrophysics Data System (ADS)

Liu, Wenwen; Su, Penglei; Chen, Su; Wang, Na; Ma, Yuanping; Liu, Yiran; Wang, Jinshu; Zhang, Zhenting; Li, Hongyi; Webster, Thomas J.

2014-07-01

To endow titanium (Ti) with antibacterial properties, different concentrations of zinc oxide (ZnO) nanoparticles were decorated on anodized titanium dioxide (TiO2) nanotubes by a simple hydrothermal treatment method. The particle sizes of ZnO, which were evenly distributed and tightly adherent to the walls of the Ti nanotubes, ranged from 20-50 nm. Results from this study showed that Zn was released from the TiO2 nanotubes in a constant, slow, and biologically inspired manner. Importantly, the results showed that the ZnO decorated TiO2 nanotubular samples inhibited Streptococcus mutants and Porphyromonas gingivalis growth compared to control unmodified Ti samples. Specifically, S. mutants and P. gingivalis growth were both reduced 45-85% on the ZnO decorated Ti samples compared to Ti controls after 7 days of culture. When examining the mechanism of action, it has been further found for the first time that the ZnO decorated Ti samples inhibited the expression of Streptococcus mutans bacterial adhesion genes. Lastly, the results showed that the same samples which decreased bacterial growth the most (0.015 M precursor Zn(NO3)2 samples) did not inhibit mesenchymal stem cell growth compared to Ti controls for up to 7 days. In summary, results from this study showed that compared to plain TiO2 nanotubes, TiO2 decorated with 0.015 M ZnO provided unprecedented antibacterial properties while maintaining the stem cell proliferation capacity necessary for enhancing the use of Ti in numerous medical applications, particularly in dentistry.

Synthesis of TiO2 nanotubes with ZnO nanoparticles to achieve antibacterial properties and stem cell compatibility.

PubMed

Liu, Wenwen; Su, Penglei; Chen, Su; Wang, Na; Ma, Yuanping; Liu, Yiran; Wang, Jinshu; Zhang, Zhenting; Li, Hongyi; Webster, Thomas J

2014-08-07

To endow titanium (Ti) with antibacterial properties, different concentrations of zinc oxide (ZnO) nanoparticles were decorated on anodized titanium dioxide (TiO2) nanotubes by a simple hydrothermal treatment method. The particle sizes of ZnO, which were evenly distributed and tightly adherent to the walls of the Ti nanotubes, ranged from 20-50 nm. Results from this study showed that Zn was released from the TiO2 nanotubes in a constant, slow, and biologically inspired manner. Importantly, the results showed that the ZnO decorated TiO2 nanotubular samples inhibited Streptococcus mutants and Porphyromonas gingivalis growth compared to control unmodified Ti samples. Specifically, S. mutants and P. gingivalis growth were both reduced 45-85% on the ZnO decorated Ti samples compared to Ti controls after 7 days of culture. When examining the mechanism of action, it has been further found for the first time that the ZnO decorated Ti samples inhibited the expression of Streptococcus mutans bacterial adhesion genes. Lastly, the results showed that the same samples which decreased bacterial growth the most (0.015 M precursor Zn(NO3)2 samples) did not inhibit mesenchymal stem cell growth compared to Ti controls for up to 7 days. In summary, results from this study showed that compared to plain TiO2 nanotubes, TiO2 decorated with 0.015 M ZnO provided unprecedented antibacterial properties while maintaining the stem cell proliferation capacity necessary for enhancing the use of Ti in numerous medical applications, particularly in dentistry.

Bioactivity of self-organized TiO2 nanotubes used as surface treatment on Ti biomaterials

NASA Astrophysics Data System (ADS)

Souza, M. R.; Reyes, K. M.; Oliveira, N. T. C.; Kuromoto, N. K.; Marino, C. E. B.

2016-03-01

Titanium and its alloys are widely used as implants due to their excellent mechanical properties, corrosion resistance and biocompatibility. TiO2 nanotubes have been studied as surface treatment to increase the specific area and to improve osseointegration. However, the thermodynamic stability and bioactivity of these nanostructures must be evaluated. The objective of this research was to obtain nanotubes oxides on Ti6Al4V alloy and to analyze the electrochemical stability in physiological solution at 37 °C and the bioactive response of the biomaterial. The nanotubes were obtained by potentiostatic anodization. The morphology of the oxides was evaluated by scanning electron microscopy. The chemical characterization was analyzed by energy dispersive spectroscopy and x-ray photoelectron spectroscopy techniques. The electrochemical stability was analyzed by open circuit potential (OCP) and the bioactivity by biomimetic test in a simulated body fluid (SBF) solution. The OCP of the nanotubes oxides was shown to be more noble and stable than the compacted oxides. The biomaterial covered with theses oxides showed sealing by Ca and P after 30 d immersion in artificial blood. And after 15 d of immersion in SBF, the hydroxyapatite could be seen on the non-sealed nanotubes. TiO2 nanotube layers could improve the superficial chemical stability and also the osseointegration process.

SnO2@TiO2 double-shell nanotubes for a lithium ion battery anode with excellent high rate cyclability.

PubMed

Jeun, Jeong-Hoon; Park, Kyu-Young; Kim, Dai-Hong; Kim, Won-Sik; Kim, Hong-Chan; Lee, Byoung-Sun; Kim, Honggu; Yu, Woong-Ryeol; Kang, Kisuk; Hong, Seong-Hyeon

2013-09-21

SnO2@TiO2 double-shell nanotubes have been facilely synthesized by atomic layer deposition (ALD) using electrospun PAN nanofibers as templates. The double-shell nanotubes exhibited excellent high rate cyclability for lithium ion batteries. The retention of hollow structures during cycling was demonstrated.

Sustained release of melatonin from TiO2 nanotubes for modulating osteogenic differentiation of mesenchymal stem cells in vitro.

PubMed

Lai, Min; Jin, Ziyang; Tang, Qiang; Lu, Min

2017-10-01

To control the sustained release of melatonin and modulate the osteogenic differentiation of mesenchymal stem cells (MSCs), melatonin was firstly loaded onto TiO 2 nanotubes by direct dropping method, and then a multilayered film was coated by a spin-assisted layer-by-layer technique, which was composed of chitosan (Chi) and gelatin (Gel). Successful fabrication was characterized by field emission scanning electron microscopy, atomic force microscope, X-ray photoelectron spectroscopy and contact angle measurement, respectively. The efficient sustained release of melatonin was measured by UV-visible-spectrophotometer. After 2 days of culture, well-spread morphology was observed in MSCs grown on the Chi/Gel multilayer-coated melatonin-loaded TiO 2 nanotube substrates as compared to different groups. After 4, 7, 14 and 21 days of culture, the multilayered-coated melatonin-loaded TiO 2 nanotube substrates increased cell proliferation, increased alkaline phosphatase (ALP) and mineralization, increased expression of mRNA levels for runt-related transcription factor 2 (Runx2), ALP, osteopontin (OPN) and osteocalcin (OC), indicative of osteoblastic differentiation. These results demonstrated that Chi/Gel multilayer-coated melatonin-loaded TiO 2 nanotube substrates promoted cell adhesion, spreading, proliferation and differentiation and could provide an alternative fabrication method for titanium-based implants to enhance the osteointegration between bone tissues and implant surfaces.

Structure reconstruction of TiO2-based multi-wall nanotubes: first-principles calculations.

PubMed

Bandura, A V; Evarestov, R A; Lukyanov, S I

2014-07-28

A new method of theoretical modelling of polyhedral single-walled nanotubes based on the consolidation of walls in the rolled-up multi-walled nanotubes is proposed. Molecular mechanics and ab initio quantum mechanics methods are applied to investigate the merging of walls in nanotubes constructed from the different phases of titania. The combination of two methods allows us to simulate the structures which are difficult to find only by ab initio calculations. For nanotube folding we have used (1) the 3-plane fluorite TiO2 layer; (2) the anatase (101) 6-plane layer; (3) the rutile (110) 6-plane layer; and (4) the 6-plane layer with lepidocrocite morphology. The symmetry of the resulting single-walled nanotubes is significantly lower than the symmetry of initial coaxial cylindrical double- or triple-walled nanotubes. These merged nanotubes acquire higher stability in comparison with the initial multi-walled nanotubes. The wall thickness of the merged nanotubes exceeds 1 nm and approaches the corresponding parameter of the experimental patterns. The present investigation demonstrates that the merged nanotubes can integrate the two different crystalline phases in one and the same wall structure.

On Multiple Zagreb Indices of TiO2 Nanotubes.

PubMed

Malik, Mehar Ali; Imran, Muhammad

2015-01-01

The First and Second Zagreb indices were first introduced by I. Gutman and N. Trinajstic in 1972. It is reported that these indices are useful in the study of anti-inflammatory activities of certain chemical instances, and in elsewhere. Recently, the first and second multiple Zagreb indices of a graph were introduced by Ghorbani and Azimi in 2012. In this paper, we calculate the Zagreb indices and the multiplicative versions of the Zagreb indices of an infinite class of Titania nanotubes TiO(2)[m,n].

Highly efficient and completely flexible fiber-shaped dye-sensitized solar cell based on TiO2 nanotube array.

PubMed

Lv, Zhibin; Yu, Jiefeng; Wu, Hongwei; Shang, Jian; Wang, Dan; Hou, Shaocong; Fu, Yongping; Wu, Kai; Zou, Dechun

2012-02-21

A type of highly efficient completely flexible fiber-shaped solar cell based on TiO(2) nanotube array is successfully prepared. Under air mass 1.5G (100 mW cm(-2)) illumination conditions, the photoelectric conversion efficiency of the solar cell approaches 7%, the highest among all fiber-shaped cells based on TiO(2) nanotube arrays and the first completely flexible fiber-shaped DSSC. The fiber-shaped solar cell demonstrates good flexibility, which makes it suitable for modularization using weaving technologies. This journal is © The Royal Society of Chemistry 2012

Preparation of Sb2S3 nanocrystals modified TiO2 dendritic structure with nanotubes for hybrid solar cell

NASA Astrophysics Data System (ADS)

Li, Yingpin; Wei, Yanan; Feng, Kangning; Hao, Yanzhong; Pei, Juan; Sun, Bao

2018-06-01

Array of TiO2 dendritic structure with nanotubes was constructed on transparent conductive fluorine-doped tin oxide glass (FTO) with titanium potassium oxalate as titanium source. Sb2S3 nanocrystals were successfully deposited on the TiO2 substrate via spin-coating method. Furthermore, TiO2/Sb2S3/P3HT/PEDOT:PSS composite film was prepared by successively spin-coating P3HT and PEDOT:PSS on TiO2/Sb2S3. It was demonstrated that the modification of TiO2 dendritic structure with Sb2S3 could enhance the light absorption in the visible region. The champion hybrid solar cell assembled by TiO2/Sb2S3/P3HT/PEDOT:PSS composite film achieved a power conversion efficiency (PCE) of 1.56%.

Carbon-dot-decorated TiO2 nanotube arrays used for photo/voltage-induced organic pollutant degradation and the inactivation of bacteria

NASA Astrophysics Data System (ADS)

Feng, Lingyan; Sun, Hanjun; Ren, Jinsong; Qu, Xiaogang

2016-03-01

Photoluminescent carbon dots (c-dots) have recently attracted growing interest as a new member of the carbon-nanomaterial family. Here, we report for the first time that c-dot-decorated TiO2 nanotube arrays (c-dot/TiNTs) exhibit highly enhanced abilities regarding photo/voltage-induced organic pollutant degradation and bacterial inactivation. By applying UV irradiation (365 nm) or an electrochemical potential over 3 V (versus Ag/AgCl), an organic dye and a herbicide were efficiently degraded. Moreover, the inactivation of Gram-positive S. aureus and Gram-negative E. coli bacteria was realized on a c-dot/TiNT film. The c-dots were able to absorb light efficiently resulting in multiple exciton generation and also a reduction in the recombination of the e-/h+ pair produced in c-dot/TiNT film during photo/voltage-induced degradation. It was also possible to readily regenerate the surface using ultraviolet light irradiation, leaving the whole film structure undamaged and with high reproducibility and stability.

Synthesis of LaVO4/TiO2 heterojunction nanotubes by sol-gel coupled with hydrothermal method for photocatalytic air purification.

PubMed

Zou, Xuejun; Li, Xinyong; Zhao, Qidong; Liu, Shaomin

2012-10-01

With the aim of improving the effective utilization of visible light, the LaVO(4)/TiO(2) heterojunction nanotubes were fabricated by sol-gel coupled with hydrothermal method. The photocatalytic ability was demonstrated through catalytic removal of gaseous toluene species. The nanotube samples were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), surface photovoltage (SPV), Raman spectra and N(2) adsorption-desorption measurements. The characterization results showed that the samples with high specific surface areas were of typical nanotubular morphology, which would lead to the high separation and transfer efficiency of photo induced electron-hole pairs. The as-prepared nanotubes exhibited high photocatalytic activity in decomposing toluene species under visible light irradiation with fine photochemical stability. The enhanced photocatalytic performance of LaVO(4)/TiO(2) nanotubes might be attributed to the matching band potentials, the interconnected heterojunction of LaVO(4) versus TiO(2), and the large specific surface areas of nanotubes. Copyright © 2012 Elsevier Inc. All rights reserved.

Ternary composite of TiO2 nanotubes/Ti plates modified by g-C3N4 and SnO2 with enhanced photocatalytic activity for enhancing antibacterial and photocatalytic activity.

PubMed

Faraji, Masoud; Mohaghegh, Neda; Abedini, Amir

2018-01-01

A series of g-C 3 N 4 -SnO 2 /TiO 2 nanotubes/Ti plates were fabricated via simple dipping of TiO 2 nanotubes/Ti in a solution containing SnCl 2 and g-C 3 N 4 nanosheets and finally annealing of the plates. Synthesized plates were characterized by various techniques. The SEM analysis revealed that the g-C 3 N 4 -SnO 2 nanosheets with high physical stability have been successfully deposited onto the surface of TiO 2 nanotubes/Ti plate. Photocatalytic activity was investigated using two probe chemical reactions: oxidative decomposition of acetic acid and oxidation of 2-propanol under irradiation. Antibacterial activities for Escherichia coli (E. coli) bacteria were also investigated in dark and under UV/Vis illuminations. Detailed characterization and results of photocatalytic and antibacterial activity tests revealed that semiconductor coupling significantly affected the photocatalyst properties synthesized and hence their photocatalytic and antibacterial activities. Modification of TiO 2 nanotubes/Ti plates with g-C 3 N 4 -SnO 2 deposits resulted in enhanced photocatalytic activities in both chemical and microbial systems. The g-C 3 N 4 -SnO 2 /TiO 2 nanotubes/Ti plate exhibited the highest photocatalytic and antibacterial activity, probably due to the heterojunction between g-C 3 N 4 -SnO 2 and TiO 2 nanotubes/Ti in the ternary composite plate and thus lower electron/hole recombination rate. Based on the obtained results, a photocatalytic and an antibacterial mechanism for the degradation of E. coli bacteria and chemical pollutants over g-C 3 N 4 -SnO 2 /TiO 2 nanotubes/Ti plate were proposed and discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Electrical characterization of TiO2 nanotubes synthesized through electrochemical anodizing method

NASA Astrophysics Data System (ADS)

Manescu Paltanea, Veronica; Paltanea, Gheorghe; Popovici, Dorina; Jiga, Gabriel

2016-05-01

In the present paper, the electrochemical anodizing method was used for the obtaining of TiO2 nanotube layers, developed on titanium surface. Self-organized titanium nanotubes were obtained when an aqueous solution of 49.5 wt % H2O - 49.5 wt % glycerol - 1 wt % HF was used as electrolyte, the anodizing time being equal to 8 hours and the applied voltage to 25 V. Scanning electron microscopy shows that the one-dimensional nanostructure has a tubular configuration with an inner diameter of approximately 60 nm and an outer diameter of approximately 100 nm. The electrical properties of these materials were analyzed through dielectric spectroscopy method.

Disorder engineering of undoped TiO2 nanotube arrays for highly efficient solar-driven oxygen evolution.

PubMed

Salari, M; Aboutalebi, S H; Aghassi, A; Wagner, P; Mozer, A J; Wallace, G G

2015-02-28

The trade-off between performance and complexity of the device manufacturing process should be balanced to enable the economic harvest of solar energy. Here, we demonstrate a conceptual, yet practical and well-regulated strategy to achieve efficient solar photocatalytic activity in TiO2 through controlled phase transformation and disorder engineering in the surface layers of TiO2 nanotubes. This approach enabled us to fine-tune the bandgap structure of undoped TiO2 according to our needs while simultaneously obtaining robust separation of photo-excited charge carriers. Introduction of specific surface defects also assisted in utilization of the visible part of sunlight to split water molecules for the production of oxygen. The strategy proposed here can serve as a guideline to overcome the practical limitation in the realization of efficient, non-toxic, chemically stable photoelectrochemical systems with high catalytic activity at neutral pH under visible illumination conditions. We also successfully incorporated TiO2 nanotube arrays (TNTAs) with free-based porphyrin affording a pathway with an overall 140% enhanced efficiency, an oxygen evolution rate of 436 μL h(-1) and faradic efficiencies over 100%.

Synthesis and magnetotransport studies of CrO2 films grown on TiO2 nanotube arrays by chemical vapor deposition

NASA Astrophysics Data System (ADS)

Wang, Xiaoling; Zhang, Caiping; Wang, Lu; Lin, Tao; Wen, Gehui

2018-04-01

The CrO2 films have been prepared on the TiO2 nanotube array template via atmospheric pressure chemical vapor deposition method. And the growth procedure was studied. In the beginning of the deposition process, the CrO2 grows on the cross section of the TiO2 nanotubes wall, forms a nanonet-like layer. And the grain size of CrO2 is very small. With the increase of the deposition time, the grain size of CrO2 also increases, and the nanonet-like layer changes into porous film. With the further increase of the deposition time, all the nanotubes are covered by CrO2 grains and the surface structure becomes polycrystalline film. The average grain size on the surface of the CrO2 films deposited for 1 h, 2 h and 5 h is about 190 nm, 300 nm and 470 nm. The X-ray diffraction pattern reveals that the rutile CrO2 film has been synthesized on the TiO2 nanotube array template. The CrO2 films show large magnetoresistance (MR) at low temperature, which should originate from spin-dependent tunneling through grain boundaries between CrO2 grains. And the tunneling mechanism of the CrO2 films can be well described by the fluctuation-induced tunneling (FIT) model. The CrO2 film deposited for 2 h shows insulator behavior from 5 k to 300 K, but the CrO2 film deposited for 5 h shows insulator-metal transition around 140 K. The reason is briefly discussed.

Reagentless Detection of Low-Molecular-Weight Triamterene Using Self-Doped TiO2 Nanotubes.

PubMed

Hudari, Felipe F; Bessegato, Guilherme G; Bedatty Fernandes, Flávio C; Zanoni, Maria V B; Bueno, Paulo R

2018-06-19

TiO 2 nanotube electrodes were self-doped by electrochemical cathodic polarization, potentially converting Ti 4+ into Ti 3+ , and thereby increasing both the normalized conductance and capacitance of the electrodes. One-hundred (from 19.2 ± 0.1 μF cm -2 to 1.9 ± 0.1 mF cm -2 for SD-TNT) and two-fold (from ∼6.2 to ∼14.4 mS cm -2 ) concomitant increases in capacitance and conductance, respectively, were achieved in self-doped TiO 2 nanotubes; this was compared with the results for their undoped counterparts. The increases in the capacitance and conductance indicate that the Ti 3+ states enhance the density of the electronic states; this is attributed to an existing relationship between the conductance and capacitance for nanoscale structures built on macroscopic electrodes. The ratio between the conductance and capacitance was used to detect and quantify, in a reagentless manner, the triamterene (TRT) diuretic by designing an appropriate doping level of TiO 2 nanotubes. The sensitivity was improved when using immittance spectroscopy (Patil et al. Anal. Chem. 2015, 87, 944-950; Bedatty Fernandes et al. Anal. Chem. 2015, 87, 12137-12144) (2.4 × 10 6 % decade -1 ) compared to cyclic voltammetry (5.8 × 10 5 % decade -1 ). Furthermore, a higher linear range from 0.5 to 100 μmol L -1 (5.0 to 100 μmol L -1 for cyclic voltammetry measurements) and a lower limit-of-detection of approximately 0.2 μmol L -1 were achieved by using immittance function methodology (better than the 4.1 μmol L -1 obtained by using cyclic voltammetry).

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

PubMed Central

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

2015-01-01

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

Three-dimensional hot electron photovoltaic device with vertically aligned TiO2 nanotubes.

PubMed

Goddeti, Kalyan C; Lee, Changhwan; Lee, Young Keun; Park, Jeong Young

2018-05-09

Titanium dioxide (TiO 2 ) nanotubes with vertically aligned array structures show substantial advantages in solar cells as an electron transport material that offers a large surface area where charges travel linearly along the nanotubes. Integrating this one-dimensional semiconductor material with plasmonic metals to create a three-dimensional plasmonic nanodiode can influence solar energy conversion by utilizing the generated hot electrons. Here, we devised plasmonic Au/TiO 2 and Ag/TiO 2 nanodiode architectures composed of TiO 2 nanotube arrays for enhanced photon absorption, and for the subsequent generation and capture of hot carriers. The photocurrents and incident photon to current conversion efficiencies (IPCE) were obtained as a function of photon energy for hot electron detection. We observed enhanced photocurrents and IPCE using the Ag/TiO 2 nanodiode. The strong plasmonic peaks of the Au and Ag from the IPCE clearly indicate an enhancement of the hot electron flux resulting from the presence of surface plasmons. The calculated electric fields and the corresponding absorbances of the nanodiode using finite-difference time-domain simulation methods are also in good agreement with the experimental results. These results show a unique strategy of combining a hot electron photovoltaic device with a three-dimensional architecture, which has the clear advantages of maximizing light absorption and a metal-semiconductor interface area.

TiO2 Nanotube Arrays: Fabricated by Soft-Hard Template and the Grain Size Dependence of Field Emission Performance

NASA Astrophysics Data System (ADS)

Yang, Xuxin; Ma, Pei; Qi, Hui; Zhao, Jingxin; Wu, Qiang; You, Jichun; Li, Yongjin

2017-11-01

Highly ordered TiO2 nanotube (TNT) arrays were successfully synthesized by the combination of soft and hard templates. In the fabrication of them, anodic aluminum oxide membranes act as the hard template while the self-assembly of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) complexed with titanium-tetraisopropoxide (TTIP, the precursor of TiO2) provides the soft template to control the grain size of TiO2 nanotubes. Our results indicate that the field emission (FE) performance depends crucially on the grain size of the calcinated TiO2 which is dominated by the PS-b-PEO and its blending ratio with TTIP. The optimized sample (with the TTIP/PEO ratio of 3.87) exhibits excellent FE performances involving both a low turn-on field of 3.3 V/um and a high current density of 7.6 mA/cm2 at 12.7 V/μm. The enhanced FE properties can be attributed to the low effective work function (1.2 eV) resulted from the smaller grain size of TiO2.

Atomic Layer Deposition for Coating of High Aspect Ratio TiO2 Nanotube Layers

PubMed Central

2016-01-01

We present an optimized approach for the deposition of Al2O3 (as a model secondary material) coating into high aspect ratio (≈180) anodic TiO2 nanotube layers using the atomic layer deposition (ALD) process. In order to study the influence of the diffusion of the Al2O3 precursors on the resulting coating thickness, ALD processes with different exposure times (i.e., 0.5, 2, 5, and 10 s) of the trimethylaluminum (TMA) precursor were performed. Uniform coating of the nanotube interiors was achieved with longer exposure times (5 and 10 s), as verified by detailed scanning electron microscopy analysis. Quartz crystal microbalance measurements were used to monitor the deposition process and its particular features due to the tube diameter gradient. Finally, theoretical calculations were performed to calculate the minimum precursor exposure time to attain uniform coating. Theoretical values on the diffusion regime matched with the experimental results and helped to obtain valuable information for further optimization of ALD coating processes. The presented approach provides a straightforward solution toward the development of many novel devices, based on a high surface area interface between TiO2 nanotubes and a secondary material (such as Al2O3). PMID:27643411

Evidence of iridescence in TiO2 nanostructures: An approximation in plane wave expansion method

NASA Astrophysics Data System (ADS)

Quiroz, Heiddy P.; Barrera-Patiño, C. P.; Rey-González, R. R.; Dussan, A.

2016-11-01

Titanium dioxide nanotubes, TiO2 NTs, can be obtained by electrochemical anodization of Titanium sheets. After nanotubes are removed by mechanical stress, residual structures or traces on the surface of titanium sheets can be observed. These traces show iridescent effects. In this paper we carry out both experimental and theoretical study of those interesting and novel optical properties. For the experimental analysis we use angle resolved UV-vis spectroscopy while in the theoretical study is evaluated the photonic spectra using numerical simulations into the frequency-domain and the framework of the wave plane approximation. The iridescent effect is a strong property and independent of the sample. This behavior can be important to design new materials or compounds for several applications such as, cosmetic industry, optoelectronic devices, photocatalysis, sensors, among others.

Improved Osteoblast and Chondrocyte Adhesion and Viability by Surface-Modified Ti6Al4V Alloy with Anodized TiO2 Nanotubes Using a Super-Oxidative Solution

PubMed Central

Beltrán-Partida, Ernesto; Moreno-Ulloa, Aldo; Valdez-Salas, Benjamín; Velasquillo, Cristina; Carrillo, Monica; Escamilla, Alan; Valdez, Ernesto; Villarreal, Francisco

2015-01-01

Titanium (Ti) and its alloys are amongst the most commonly-used biomaterials in orthopedic and dental applications. The Ti-aluminum-vanadium alloy (Ti6Al4V) is widely used as a biomaterial for these applications by virtue of its favorable properties, such as high tensile strength, good biocompatibility and excellent corrosion resistance. TiO2 nanotube (NTs) layers formed by anodization on Ti6Al4V alloy have been shown to improve osteoblast adhesion and function when compared to non-anodized material. In his study, NTs were grown on a Ti6Al4V alloy by anodic oxidation for 5 min using a super-oxidative aqueous solution, and their in vitro biocompatibility was investigated in pig periosteal osteoblasts and cartilage chondrocytes. Scanning electron microscopy (SEM), energy dispersion X-ray analysis (EDX) and atomic force microscopy (AFM) were used to characterize the materials. Cell morphology was analyzed by SEM and AFM. Cell viability was examined by fluorescence microscopy. Cell adhesion was evaluated by nuclei staining and cell number quantification by fluorescence microscopy. The average diameter of the NTs was 80 nm. The results demonstrate improved cell adhesion and viability at Day 1 and Day 3 of cell growth on the nanostructured material as compared to the non-anodized alloy. In conclusion, this study evidences the suitability of NTs grown on Ti6Al4V alloy using a super-oxidative water and a short anodization process to enhance the adhesion and viability of osteoblasts and chondrocytes. The results warrant further investigation for its use as medical implant materials. PMID:28787976

High Electromagnetic Field Enhancement of TiO2 Nanotube Electrodes.

PubMed

Öner, Ibrahim Halil; Querebillo, Christine Joy; David, Christin; Gernert, Ulrich; Walter, Carsten; Driess, Matthias; Leimkühler, Silke; Ly, Khoa Hoang; Weidinger, Inez M

2018-06-11

We present the fabrication of TiO 2 nanotube electrodes with high biocompatibility and extraordinary spectroscopic properties. Intense surface-enhanced resonance Raman signals of the heme unit of the redox enzyme Cytochrome b 5 were observed upon covalent immobilization of the protein matrix on the TiO 2 surface, revealing overall preserved structural integrity and redox behavior. The enhancement factor could be rationally controlled by varying the electrode annealing temperature, reaching a record maximum value of over 70 at 475 °C. For the first time, such high values are reported for non-directly surface-interacting probes, for which the involvement of charge-transfer processes in signal amplification can be excluded. The origin of the surface enhancement is exclusively attributed to enhanced localized electric fields resulting from the specific optical properties of the nanotubular geometry of the electrode. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photoelectrocatalytic degradation of atrazine by boron-fluorine co-doped TiO2 nanotube arrays.

PubMed

Wang, He-Xuan; Zhu, Li-Nan; Guo, Fu-Qiao

2018-06-23

Atrazine, one of the most widespread herbicides in the world, is considered as an environmental estrogen and has potential carcinogenicity. In this study, atrazine was degraded on boron-fluorine co-doped TiO 2 nanotube arrays (B, F-TiO 2 NTAs), which had similar morphology with the pristine TiO 2 NTAs. The structure and morphology of TiO 2 nanotube samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-visible diffuse reflectance spectroscopy (DRS). It showed that the decoration of fluorine and boron made both the absorption in the visible region enhanced and the band edge absorption shifted. The efficiency of atrazine degradation by B, F-TiO 2 NTAs through photoelectrocatalysis was investigated by current, solution pH, and electrolyte concentration, respectively. The atrazine removal rate reached 76% through photoelectrocatalytic reaction by B, F-TiO 2 NTAs, which was 46% higher than that under the photocatalysis process. Moreover, the maximum degradation rate was achieved at pH of 6 in 0.01 M of Na 2 SO 4 electrolyte solution under a current of 0.02 A and visible light for 2 h in the presence of B, F-TiO 2 NTAs. These results showed that B, F-TiO 2 NTAs exhibit remarkable photoelectrocatalytic activity in degradation of atrazine.

Electrocatalytic activity of Pd-loaded Ti/TiO2 nanotubes cathode for TCE reduction in groundwater.

PubMed

Xie, Wenjing; Yuan, Songhu; Mao, Xuhui; Hu, Wei; Liao, Peng; Tong, Man; Alshawabkeh, Akram N

2013-07-01

A novel cathode, Pd loaded Ti/TiO2 nanotubes (Pd-Ti/TiO2NTs), is synthesized for the electrocatalytic reduction of trichloroethylene (TCE) in groundwater. Pd nanoparticles are successfully loaded on TiO2 nanotubes which grow on Ti plate via anodization. Using Pd-Ti/TiO2NTs as the cathode in an undivided electrolytic cell, TCE is efficiently and quantitatively transformed to ethane. Under conditions of 100 mA and pH 7, the removal efficiency of TCE (21 mg/L) is up to 91% within 120 min, following pseudo-first-order kinetics with the rate constant of 0.019 min(-1). Reduction rates increase from 0.007 to 0.019 min(-1) with increasing the current from 20 to 100 mA, slightly decrease in the presence of 10 mM chloride or bicarbonate, and decline with increasing the concentrations of sulfite or sulfide. O2 generated at the anode slightly influences TCE reduction. At low currents, TCE is mainly reduced by direct electron transfer on the Pd-Ti/TiO2NT cathode. However, the contribution of Pd-catalytic hydrodechlorination, an indirect reduction mechanism, becomes significant with increasing the current. Compared with other common cathodes, i.e., Ti-based mixed metal oxides, graphite and Pd/Ti, Pd-Ti/TiO2NTs cathode shows superior performance for TCE reduction. Copyright © 2013 Elsevier Ltd. All rights reserved.

Controllable Synthesis of TiO2@Fe2O3 Core-Shell Nanotube Arrays with Double-Wall Coating as Superb Lithium-Ion Battery Anodes

PubMed Central

Zhong, Yan; Ma, Yifan; Guo, Qiubo; Liu, Jiaqi; Wang, Yadong; Yang, Mei; Xia, Hui

2017-01-01

Highlighted by the safe operation and stable performances, titanium oxides (TiO2) are deemed as promising candidates for next generation lithium-ion batteries (LIBs). However, the pervasively low capacity is casting shadow on desirable electrochemical behaviors and obscuring their practical applications. In this work, we reported a unique template-assisted and two-step atomic layer deposition (ALD) method to achieve TiO2@Fe2O3 core-shell nanotube arrays with hollow interior and double-wall coating. The as-prepared architecture combines both merits of the high specific capacity of Fe2O3 and structural stability of TiO2 backbone. Owing to the nanotubular structural advantages integrating facile strain relaxation as well as rapid ion and electron transport, the TiO2@Fe2O3 nanotube arrays with a high mass loading of Fe2O3 attained desirable capacity of ~520 mA h g−1, exhibiting both good rate capability under uprated current density of 10 A g−1 and especially enhanced cycle stability (~450 mA h g−1 after 600 cycles), outclassing most reported TiO2@metal oxide composites. The results not only provide a new avenue for hybrid core-shell nanotube formation, but also offer an insight for rational design of advanced electrode materials for LIBs. PMID:28098237

Low temperature RF plasma nitriding of self-organized TiO2 nanotubes for effective bandgap reduction

NASA Astrophysics Data System (ADS)

Bonelli, Thiago Scremin; Pereyra, Inés

2018-06-01

Titanium dioxide is a widely studied semiconductor material found in many nanostructured forms, presenting very interesting properties for several applications, particularly photocatalysis. TiO2 nanotubes have a high surface-to-volume ratio and functional electronic properties for light harvesting. Despite these manifold advantages, TiO2 photocatalytic activity is limited to UV radiation due to its large band gap. In this work, TiO2 nanotubes produced by electrochemical anodization were submitted to plasma nitriding processes in a PECVD reactor. The plasma parameters were evaluated to find the best conditions for gap reduction, in order to increase their photocatalytic activity. The pressure and RF power density were varied from 0.66 to 2.66 mbar and 0.22 to 3.51 W/cm2 respectively. The best gap reduction, to 2.80 eV, was achieved using a pressure of 1.33 mbar and 1.75 W/cm2 RF power at 320 °C, during a 2-h process. This leads to a 14% reduction in the band gap value and an increase of 25.3% in methylene blue reduction, doubling the range of solar photons absorption from 5 to 10% of the solar spectrum.

Electrodeposition of hydroxyapatite nanoparticles onto ultra-fine TiO2 nanotube layer by electrochemical reaction in mixed electrolyte.

PubMed

Park, Su-Jung; Jang, Jae-Myung

2011-08-01

Electrochemical depositions of HAp nanoparticles onto Ultra-fine TiO2 nanotube layer were carried out by the electrochemical reaction in mixed electrolyte of 1.6 M (NH4)H2PO4 + 0.8 M NH4F containing 0.15 and 0.25 wt% HAp. The Ca/P ratios of the HAp nanoparticles were evaluated by EDS analysis and their values were 1.53 and 1.66 respectively. The distribution quantity of Ca and P were remained at the middle region of TiO2 nanotube, but the Ti element was mainly stayed at the bottom of barrier layer from the result of line scanning diagram. Especially, adsorbed phosphate ions facilitated nucleation of nanophase calcium phosphate material inside the TiO2 nanotubu layer that resulted in vertical growth of HAp nanoparticles. These surfaces and structures were all effective for biocompatibility from the SBF tests.

A thermal study on the structural changes of bimetallic ZrO2-modified TiO2 nanotubes synthesized using supercritical CO2.

PubMed

Lucky, R A; Charpentier, P A

2009-05-13

In this study the thermal behavior of bimetallic ZrO(2)-TiO(2) (10/90 mol/mol) nanotubes are discussed which were synthesized via a sol-gel process in supercritical carbon dioxide (scCO(2)). The effects of calcination temperature on the morphology, phase structure, mean crystallite size, specific surface area and pore volume of the nanotubes were investigated by using a variety of physiochemical techniques. We report that SEM and TEM images showed that the nanotubular structure was preserved at up to 800 degrees C calcination temperature. When exposed to higher temperatures (900-1000 degrees C) the ZrO(2)-TiO(2) tubes deformed and the crystallites fused together, forming larger crystallites, and a bimetallic ZrTiO(4) species was detected. These results were further examined using TGA, FTIR, XRD and HRTEM analysis. The BET textural properties demonstrated that the presence of a small amount of Zr in the TiO(2) matrix inhibited the grain growth, stabilized the anatase phase and increased the thermal stability.

Gas Sensitivity and Sensing Mechanism Studies on Au-Doped TiO2 Nanotube Arrays for Detecting SF6 Decomposed Components

PubMed Central

Zhang, Xiaoxing; Yu, Lei; Tie, Jing; Dong, Xingchen

2014-01-01

The analysis to SF6 decomposed component gases is an efficient diagnostic approach to detect the partial discharge in gas-insulated switchgear (GIS) for the purpose of accessing the operating state of power equipment. This paper applied the Au-doped TiO2 nanotube array sensor (Au-TiO2 NTAs) to detect SF6 decomposed components. The electrochemical constant potential method was adopted in the Au-TiO2 NTAs' fabrication, and a series of experiments were conducted to test the characteristic SF6 decomposed gases for a thorough investigation of sensing performances. The sensing characteristic curves of intrinsic and Au-doped TiO2 NTAs were compared to study the mechanism of the gas sensing response. The results indicated that the doped Au could change the TiO2 nanotube arrays' performances of gas sensing selectivity in SF6 decomposed components, as well as reducing the working temperature of TiO2 NTAs. PMID:25330053

Influence of Different Defects in Vertically Aligned Carbon Nanotubes on TiO2 Nanoparticle Formation through Atomic Layer Deposition.

PubMed

Acauan, Luiz; Dias, Anna C; Pereira, Marcelo B; Horowitz, Flavio; Bergmann, Carlos P

2016-06-29

The chemical inertness of carbon nanotubes (CNT) requires some degree of "defect engineering" for controlled deposition of metal oxides through atomic layer deposition (ALD). The type, quantity, and distribution of such defects rules the deposition rate and defines the growth behavior. In this work, we employed ALD to grow titanium oxide (TiO2) on vertically aligned carbon nanotubes (VACNT). The effects of nitrogen doping and oxygen plasma pretreatment of the CNT on the morphology and total amount of TiO2 were systematically studied using transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. The induced chemical changes for each functionalization route were identified by X-ray photoelectron and Raman spectroscopies. The TiO2 mass fraction deposited with the same number of cycles for the pristine CNT, nitrogen-doped CNT, and plasma-treated CNT were 8, 47, and 80%, respectively. We demonstrate that TiO2 nucleation is dependent mainly on surface incorporation of heteroatoms and their distribution rather than structural defects that govern the growth behavior. Therefore, selecting the best way to functionalize CNT will allow us to tailor TiO2 distribution and hence fabricate complex heterostructures.

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.

Non-metal doped TiO2 nanotube arrays for high efficiency photocatalytic decomposition of organic species in water

NASA Astrophysics Data System (ADS)

Szkoda, Mariusz; Siuzdak, Katarzyna; Lisowska-Oleksiak, Anna

2016-10-01

Titanium dioxide is a well-known photoactive semiconductor with a variety of possible applications. The procedure of pollutant degradation is mainly performed using TiO2 powder suspension. It can also be exploited an immobilized catalyst on a solid support. Morphology and chemical doping have a great influence on TiO2 activity under illumination. Here we compare photoactivity of titania nanotube arrays doped with non-metal atoms: nitrogen, iodine and boron applied for photodegradation of organic dye - methylene blue and terephtalic acid. The doped samples act as a much better photocatalyst in the degradation process of methylene blue and lead to the formation of much higher amount of hydroxyl radicals (•OH) than undoped TiO2 nanotube arrays. The use of a catalyst active under solar light illumination in the form of thin films on a stable substrate can be scaled up for an industrial application.

Photoinduced deposition of gold nanoparticles on TiO2-WO3 nanotube films as efficient photoanodes for solar water splitting

NASA Astrophysics Data System (ADS)

Momeni, Mohamad Mohsen; Ghayeb, Yousef

2016-06-01

Gold-modified TiO2-WO3 nanotubes with different amounts of gold were obtained by two methods; photoassisted deposition and one-step electrochemical anodizing method. The morphology, crystallinity and elemental composition were studied by FE-SEM, XRD and EDX. The photoelectrochemical performance was examined under Xe light illumination in 1 M NaOH electrolyte. Characterization of the as-prepared TiO2-WO3 samples indicated that sodium tungstate concentration in anodizing solution significantly influenced the morphology and photoelectrochemical activity of fabricated films. Also, photoelectrochemical characterizations show that the photocatalytic activity of Au/TiO2-WO3 nanotubes was improved as compared with that of bare TiO2-WO3 nanotubes. The experimental results showed that the photocatalytic activities of Au/TiO2-WO3 were significantly affected by the amount of Au nanoparticles. The amount of gold nanoparticles was effectively controlled by time of photoreduction of the chloroauric acid solution. These new photoanodes showed enhanced high photocurrent density with good stability and are a highly promising photoanodes for photocatalytic hydrogen production.

TiO2 quantum dots embedded in bamboo-like porous carbon nanotubes as ultra high power and long life anodes for lithium ion batteries

NASA Astrophysics Data System (ADS)

Tang, Yakun; Liu, Lang; Wang, Xingchao; Jia, Dianzeng; Xia, Wei; Zhao, Zongbin; Qiu, Jieshan

2016-07-01

TiO2 quantum dots embedded in bamboo-like porous carbon nanotubes have been constructed through the pyrolysis of sulfonated polymer nanotubes and TiO2 hybrids. The TiO2 quantum dots are formed during the pyrolysis, due to the space confinement within the highly cross-linked copolymer networks. The sulfonation degree of the polymer nanotubes is a critical factor to ensure the formation of the unique interpenetrating structure. The nanocomposites exhibit high reversible capacity of 523 mAh g-1 at 100 mA g-1 after 200 cycles, excellent rate capability and superior long-term cycling stability at high current density, which could attain a high discharge capacity of 189 mAh g-1 at 2000 mA g-1 for up to 2000 cycles. The enhanced electrochemical performance of the nanocomposites benefit from the uniform distribution of TiO2 quantum dots, high electronic conductivity of porous carbons and unique interpenetrating structure, which simultaneously solved the major problems of TiO2 anode facing the pulverization, loss of electrical contact and particle aggregation.

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.

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.

Visible-light-driven photoelectrochemical and photocatalytic performances of Cr-doped SrTiO3/TiO2 heterostructured nanotube arrays.

PubMed

Jiao, Zhengbo; Chen, Tao; Xiong, Jinyan; Wang, Teng; Lu, Gongxuan; Ye, Jinhua; Bi, Yingpu

2013-01-01

Well-aligned TiO2 nanotube arrays have become of increasing significance because of their unique highly ordered array structure, high specific surface area, unidirectional charge transfer and transportation features. However, their poor visible light utilization as well as the high recombination rate of photoexcited electron-hole pairs greatly limited their practical applications. Herein, we demonstrate the fabrication of visible-light-responsive heterostructured Cr-doped SrTiO3/TiO2 nanotube arrays by a simple hydrothermal method, which facilitate efficient charge separation and thus improve the photoelectrochemical as well as photocatalytic performances.

Enhancement in photo-electrochemical efficiency by reducing recombination rate in branched TiO2 nanotube array on functionalizing with ZnO micro crystals

NASA Astrophysics Data System (ADS)

Boda, Muzaffar Ahmad; Ashraf Shah, Mohammad

2018-06-01

In this study, branched TiO2 nanotube array were fabricated through electrochemical anodization process at constant voltage using third generation electrolyte. On account of morphological advantage, these nanotubes shows significant enhancement in photo-electrochemical property than compact or conventional titania nanotube array. However, their photo-electrochemical efficiency intensifies on coating with ZnO micro-crystals. ZnO coated branched TiO2 nanotube array shows a photocurrent density of 27.8 mA cm‑2 which is 1.55 times the photocurrent density (17.2 mA cm‑2) shown by bare branched titania nanotubes. The significant enhancement in photocurrent density shown by the resulting ZnO/TiO2 hybrid structure is attributed to suppression in electron–hole recombination phenomenon by offering smooth pathway to photo generated excitons on account of staggered band edge positions in individual semiconductors.

Electrolyte Concentration Effect of a Photoelectrochemical Cell Consisting of TiO 2 Nanotube Anode

DOE PAGES

Ren, Kai; Gan, Yong X.; Nikolaidis, Efstratios; ...

2013-01-01

The photoelectrochemical responses of a TiO 2 nanotube anode in ethylene glycol (EG), glycerol, ammonia, ethanol, urea, and Na 2 S electrolytes with different concentrations were investigated. The TiO 2 nanotube anode was highly efficient in photoelectrocatalysis in these solutions under UV light illumination. The photocurrent density is obviously affected by the concentration change. Na 2 S generated the highest photocurrent density at 0, 1, and 2 V bias voltages, but its concentration does not significantly affect the photocurrent density. Urea shows high open circuit voltage at proper concentration and low photocurrent at different concentrations. Externally applied bias voltage is alsomore » an important factor that changes the photoelectrochemical reaction process. In view of the open circuit voltage, EG, ammonia, and ethanol fuel cells show the trend that the open circuit voltage (OCV) increases with the increase of the concentration of the solutions. Glycerol has the highest OCV compared with others, and it deceases with the increase in the concentration because of the high viscosity. The OCV of the urea and Na 2 S solutions did not show obvious concentration effect.« less

Distinguishing between deep trapping transients of electrons and holes in TiO2 nanotube arrays using planar microwave resonator sensor.

PubMed

Zarifi, Mohammad H; Wiltshire, Benjamin Daniel; Mahdi, Najia; Shankar, Karthik; Daneshmand, Mojgan

2018-05-16

A large signal DC bias and a small signal microwave bias were simultaneously applied to TiO2 nanotube membranes mounted on a planar microwave resonator. The DC bias modulated the electron concentration in the TiO2 nanotubes, and was varied between 0 and 120 V in this study. Transients immediately following the application and removal of DC bias were measured by monitoring the S-parameters of the resonator as a function of time. The DC bias stimulated Poole-Frenkel type trap-mediated electrical injection of excess carriers into TiO2 nanotubes which resulted in a near constant resonant frequency but a pronounced decrease in the microwave amplitude due to free electron absorption. When ultraviolet illumination and DC bias were both present and then step-wise removed, the resonant frequency shifted due to trapping -mediated change in the dielectric constant of the nanotube membranes. Characteristic lifetimes of 60-80 s, 300-800 s and ~3000 s were present regardless of whether light or bias was applied and are also observed in the presence of a hole scavenger, which we attribute to oxygen adsorption and deep electron traps while another characteristic lifetime > 9000 s was only present when illumination was applied, and is attributed to the presence of hole traps.

Activity of vancomycin release from bioinspired coatings of hydroxyapatite or TiO2 nanotubes.

PubMed

Ionita, Daniela; Bajenaru-Georgescu, Daniela; Totea, Georgeta; Mazare, Anca; Schmuki, Patrik; Demetrescu, Ioana

2017-01-30

Herein we investigate the efficiency of various biomimetic coatings for localized drug delivery, using vancomycin as key therapeutic drug, which is a widely used antibiotic for the treatment of strong infections caused by positive Gram bacteria. We evaluate classical hydroxyapatite and biomimetic hydroxyapatite-collagen coatings obtained by electrochemical deposition as well as TiO 2 nanotubes arrays obtained by electrochemical anodization. Surface morphology, compositional and structural data confirm the incorporation of vancomycin into the layers and drug release profiles for vancomycin evaluate their release ability. Namely, hydroxyapatite coatings lead to a ≈92% vancomycin release after 30h and hydroxyapatite-collagen to 85%, while the TiO 2 nanotubes layers lead to 78% release. The antibacterial effect of such drug loaded coatings is evaluated against S. aureus (Gram-positive bacteria). Our study shows that the vancomycin incorporated hydroxyapatite coatings lead to a faster release, while the nanotubular coatings may lead to longer time release and additionally both types of coatings ensure a good antibacterial inhibition. Copyright © 2016 Elsevier B.V. All rights reserved.

The influence of CdS intermediate layer on CdSe/CdS co-sensitized free-standing TiO2 nanotube solar cells

NASA Astrophysics Data System (ADS)

Ren, Xuefeng; Yu, Libo; Li, Zhen; Song, Hai; Wang, Qingyun

2018-01-01

We build CdSe quantum dots (QDs) sensitized TiO2 NT solar cells (CdSe/TiO2 solar cells) by successive ionic layer adsorption reaction (SILAR) method on free-standing translucent TiO2 nanotube (NT) film. The best power conversion efficiency (PCE) 0.74% is obtained with CdSe/TiO2 NT solar cells, however, it is very low. Hence, we introduced the CdS QDs layer located between CdSe QDs and TiO2 NT to achieve an enhanced photovoltaic performance. The J-V test results indicated that the insert of CdS intermediate layer yield a significant improvement of PCE to 2.52%. Combining experimental and theoretical analysis, we find that the effects caused by a translucent TiO2 nanotube film, a better lattices match between CdS and TiO2, and a new formed stepwise band edges structure not only improve the light harvesting efficiency but also increase the driving force of electrons, leading to the improvement of photovoltaic performance.

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.

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

NASA Astrophysics Data System (ADS)

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

2014-03-01

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

Rapid, conformal gas-phase formation of silica (SiO2) nanotubes from water condensates

NASA Astrophysics Data System (ADS)

Bae, Changdeuck; Kim, Hyunchul; Yang, Yunjeong; Yoo, Hyunjun; Montero Moreno, Josep M.; Bachmann, Julien; Nielsch, Kornelius; Shin, Hyunjung

2013-06-01

An innovative atomic layer deposition (ALD) concept, with which nanostructures of water condensates with high aspect ratio at equilibrium in cylindrical nanopores can be transformed uniformly into silica (SiO2) at near room temperature and ambient pressure, has been demonstrated for the first time. As a challenging model system, we first prove the conversion of cylindrical water condensates in porous alumina membranes to silica nanotubes (NTs) by introducing SiCl4 as a metal reactant without involving any catalytic reaction. Surprisingly, the water NTs reproducibly transformed into silica NTs, where the wall thickness of the silica NTs deposited per cycle was found to be limited by the amount of condensed water, and it was on the orders of ten nanometers per cycle (i.e., over 50 times faster than that of conventional ALD). More remarkably, the reactions only took place for 10-20 minutes or less without vacuum-related equipment. The thickness of initially adsorbed water layers in cylindrical nanopores was indirectly estimated from the thickness of formed SiO2 layers. With systematic experimental designs, we tackle the classical Kelvin equation in the nanosized pores, and the role of van der Waals forces in the nanoscale wetting phenomena, which is a long-standing issue lacking experimental insight. Moreover, we show that the present strategy is likely generalized to other oxide systems such as TiO2. Our approach opens up a new avenue for ultra-simple preparation of porous oxides and allows for the room temperature formation of dielectric layers toward organic electronic and photovoltaic applications.An innovative atomic layer deposition (ALD) concept, with which nanostructures of water condensates with high aspect ratio at equilibrium in cylindrical nanopores can be transformed uniformly into silica (SiO2) at near room temperature and ambient pressure, has been demonstrated for the first time. As a challenging model system, we first prove the conversion of

Photoelectric performance of TiO2 nanotube array photoelectrodes sensitized with CdS0.54Se0.46 quantum dots

NASA Astrophysics Data System (ADS)

Gakhar, Ruchi; Smith, York R.; Misra, Mano; Chidambaram, Dev

2015-11-01

The photoelectrochemical performance of CdSSe quantum dots tethered to a framework of vertically oriented titania (TiO2) nanotubes was studied. The TiO2/CdSSe framework demonstrated improved charge transfer due to its unique band edge structure, thus validating the higher photocurrent generation. The composite film led to an 11-fold enhancement in comparison to the control TiO2 film, implying that the ternary quantum dots and the nanotubular structure of TiO2 work in tandem to promote charge separation and favorably impact photoelectrochemical performance. Further, the results also suggest that structural and optoelectronic properties of TiO2 films are significantly affected by the thicknesses of the CdSSe layer.

The effect of crystal structure of TiO2 nanotubes on the formation of calcium phosphate coatings during biomimetic deposition

NASA Astrophysics Data System (ADS)

Liu, Yi; Kim, Sun; McLeod, John A.; Li, Jun; Guo, Xiaoxuan; Sham, Tsun-Kong; Liu, Lijia

2017-02-01

The crystallization process of bioactive calcium phosphate (CaP) species via biomimetic deposition onto anodic TiO2 nanotubes is investigated. The porous surface of nanostructured TiO2 provides an ideal substrate for CaP crystallization. The compositions of CaP coatings are studied using X-ray absorption near-edge structures (XANES) at the Ca K-edge. Using detection modes with different probing depths, both the surface of the CaP coating and the CaP-TiO2 interface are simultaneously analyzed. Calcium phosphate (CaP) species, such as hydroxyapatite (HAp), octacalcium phosphate (Ca8(HPO4)2(PO4)4·5H2O, OCP), brushite (CaHPO4·2H2O, DCPD), and amorphous calcium phosphate (ACP), are found in the CaP coatings. TiO2 nanotubes of amorphous and anatase phases are comparatively studied to determine their effect on the efficiency of CaP formation and the phase transformation among CaP species in prolonged deposition time. It is found the composition of CaP coating has a strong dependency on the crystal structure of TiO2 substrate and the kinetics (deposition time).

Reduction of CO2 to low carbon alcohols on CuO FCs/Fe2O3 NTs catalyst with photoelectric dual catalytic interfaces

NASA Astrophysics Data System (ADS)

Li, Peiqiang; Wang, Huying; Xu, Jinfeng; Jing, Hua; Zhang, Jun; Han, Haixiang; Lu, Fusui

2013-11-01

In this paper, the CuO FCs/Fe2O3 NTs catalyst was obtained after Fe2O3 nanotubes (Fe2O3 NTs) were decorated with CuO flower clusters (CuO FCs) by the pulse electrochemical deposition method. The in situ vertically aligned Fe2O3 NTs were prepared on the ferrous substrate by a potentiostatic anodization method. The SEM result showed the volcano-like Fe2O3 NTs were arranged in order and the CuO FCs constituted of flaky CuO distributed on the Fe2O3 NTs surface uniformly. After CuO FCs were loaded on Fe2O3 NTs, the absorption of visible light was enhanced noticeably, and its band gap narrowed to 1.78 eV from 2.03 eV. The conduction band and valence band locating at -0.73 eV and 1.05 eV, respectively were further obtained. In the PEC reduction of CO2 process, methanol and ethanol were two major products identified by chromatography. Their contents reached 1.00 mmol L-1 cm-2 and 107.38 μmol L-1 cm-2 after 6 h, respectively. This high-efficiency catalyst with photoelectric dual catalytic interfaces has a great guidance and reference significance for CO2 reduction to liquid carbon fuels.In this paper, the CuO FCs/Fe2O3 NTs catalyst was obtained after Fe2O3 nanotubes (Fe2O3 NTs) were decorated with CuO flower clusters (CuO FCs) by the pulse electrochemical deposition method. The in situ vertically aligned Fe2O3 NTs were prepared on the ferrous substrate by a potentiostatic anodization method. The SEM result showed the volcano-like Fe2O3 NTs were arranged in order and the CuO FCs constituted of flaky CuO distributed on the Fe2O3 NTs surface uniformly. After CuO FCs were loaded on Fe2O3 NTs, the absorption of visible light was enhanced noticeably, and its band gap narrowed to 1.78 eV from 2.03 eV. The conduction band and valence band locating at -0.73 eV and 1.05 eV, respectively were further obtained. In the PEC reduction of CO2 process, methanol and ethanol were two major products identified by chromatography. Their contents reached 1.00 mmol L-1 cm-2 and 107.38 μmol L-1

Electronic Properties of SiNTs Under External Electric and Magnetic Fields Using the Tight-Binding Method

NASA Astrophysics Data System (ADS)

Chegel, Raad; Behzad, Somayeh

2014-02-01

We investigated the electronic properties of silicon nanotubes (SiNTs) under external transverse electric fields and axial magnetic fields using the tight-binding approximation. It was found that, after switching on the electric and magnetic fields, band modifications such as distortion of degeneracy, change in energy dispersion and subband spacing, and bandgap size reduction occur. The bandgap of silicon gear-like nanotubes (Si g-NTs) decreases linearly with increasing electric field strength, but the bandgap for silicon hexagonal nanotubes (Si h-NTs) first increases and then decreases (metallic) or first remains constant and then decreases (semiconducting). Our results show that the bandgap of Si h-NTs is very sensitive to both electric and magnetic fields, unlike Si g-NTs, which are more sensitive to electric than magnetic fields.

Electrochemically conductive treatment of TiO2 nanotube arrays in AlCl3 aqueous solution for supercapacitors

NASA Astrophysics Data System (ADS)

Zhong, Wenjie; Sang, Shangbin; Liu, Yingying; Wu, Qiumei; Liu, Kaiyu; Liu, Hongtao

2015-10-01

Highly ordered TiO2 nanotube arrays (NTAs) with excellent stability and large specific surface area make them competitive using as supercapacitor materials. Improving the conductivity of TiO2 is of great concern for the construction of high-performance supercapacitors. In this work, we developed a novel approach to improve the performance of TiO2 materials, involving the fabrication of Al-doped TiO2 NTAs by a simple electrochemical cathodic polarization treatment in AlCl3 aqueous solution. The prepared Al-doped TiO2 NTAs exhibited excellent electrochemical performances, attributing to the remarkably improved electrical conductivity (i.e., from approx. 10 kΩ to 20 Ω). Further analysis showed that Al3+ ions rather than H+ protons doped into TiO2 lattice cause this high conductivity. A MnO2/Al-TiO2 composite was evaluated by cyclic voltammetry, and achieved the specific capacitance of 544 F g-1, and the Ragone plot of the sample showed a high power density but less reduction of energy density. These results indicate that the MnO2/Al-TiO2 NTAs sample could be served as a promising electrode material for high -performance supercapacitors.

Cobalt and Yttrium Modified TiO2 Nanotubes Based Dye-Sensitized Solar Cells for Solar-Energy Conversion

NASA Astrophysics Data System (ADS)

Shabanov, N. S.; Isaev, A. B.; Orudzhev, F. F.; Murliev, E. K.

2018-01-01

The solar-energy conversion in eosin-sensitized solar cells based on cobalt and yttrium modified TiO2 nanotubes has been studied.It is established that the doping with metal ions shifts the absorption edge for Co and Y doped titanium dioxide samples to longer and shorter wavelengths, respectively. The efficiency of solar energy conversion depends on the wide bandgap of the semiconductor anode and reaches a maximum (4.4%) for yttrium-doped TiO2 in comparison to that (4.1%) for pure titanium dioxide.

Nanoscale TiO2 nanotubes govern the biological behavior of human glioma and osteosarcoma cells

PubMed Central

Tian, Ang; Qin, Xiaofei; Wu, Anhua; Zhang, Hangzhou; Xu, Quan; Xing, Deguang; Yang, He; Qiu, Bo; Xue, Xiangxin; Zhang, Dongyong; Dong, Chenbo

2015-01-01

Cells respond to their surroundings through an interactive adhesion process that has direct effects on cell proliferation and migration. This research was designed to investigate the effects of TiO2 nanotubes with different topographies and structures on the biological behavior of cultured cells. The results demonstrated that the nanotube diameter, rather than the crystalline structure of the coatings, was a major factor for the biological behavior of the cultured cells. The optimal diameter of the nanotubes was 20 nm for cell adhesion, migration, and proliferation in both glioma and osteosarcoma cells. The expression levels of vitronectin and phosphor-focal adhesion kinase were affected by the nanotube diameter; therefore, it is proposed that the responses of vitronectin and phosphor-focal adhesion kinase to the nanotube could modulate cell fate. In addition, the geometry and size of the nanotube coating could regulate the degree of expression of acetylated α-tubulin, thus indirectly modulating cell migration behavior. Moreover, the expression levels of apoptosis-associated proteins were influenced by the topography. In conclusion, a nanotube diameter of 20 nm was the critical threshold that upregulated the expression level of Bcl-2 and obviously decreased the expression levels of Bax and caspase-3. This information will be useful for future biomedical and clinical applications. PMID:25848261

TiO2 with controlled nanoring/nanotube hierarchical structure: Multiabsorption oscillating peaks and photoelectrochemical properties

NASA Astrophysics Data System (ADS)

Sang, Lixia; Zhao, Yangbo; Niu, Youchen; Bai, Guangmei

2018-02-01

TiO2 with Nanoring/Nanotube (R/T) hierarchical structure can be prepared by tuning the oxidation time and oxidation voltage in the second step anodization. The resulting multiabsorption oscillating peaks in the visible light region present a strong dependence on the tube length which are derived from the interference of light reflected from the top nanorings and the bottom Ti substrate, and the optical path length in TiO2 R/T hierarchical structure can be estimated as about 2 μm. The tube length of the as-prepared TiO2 photoelectrode affects greatly its saturation photocurrent density, and the different tube-wall thickness can change the photocurrent-saturation potential. Under simulated AM 1.5 irradiation (100 mW/cm2), TiO2 R/T hierarchical structure with tube diameters of 20-40 nm and tube length of about 1.5 μm shows higher photocurrent density and hydrogen production rate at the bias of 0 V (vs. Ag/AgCl). The results from the IPCE plots and I-t curves verify that TiO2 R/T hierarchical structure can exhibit the visible light activity, which is more related to the absorption induced by the defects rather than oscillating peaks. Based on the unique multiple light reflection in TiO2 R/T hierarchical structure, surface treatment will pave a way for the better utilization of oscillating peaks in the visible light region.

Protein interactions with layers of TiO2 nanotube and nanopore arrays: Morphology and surface charge influence.

PubMed

Kulkarni, Mukta; Mazare, Anca; Park, Jung; Gongadze, Ekaterina; Killian, Manuela Sonja; Kralj, Slavko; von der Mark, Klaus; Iglič, Aleš; Schmuki, Patrik

2016-11-01

In the present work we investigate the key factors involved in the interaction of small-sized charged proteins with TiO 2 nanostructures, i.e. albumin (negatively charged), histone (positively charged). We examine anodic nanotubes with specific morphology (simultaneous control over diameter and length, e.g. diameter - 15, 50 or 100nm, length - 250nm up to 10μm) and nanopores. The nanostructures surface area has a direct influence on the amount of bound protein, nonetheless the protein physical properties as electric charge and size (in relation to nanotopography and biomaterial's electric charge) are crucial too. The highest quantity of adsorbed protein is registered for histone, for 100nm diameter nanotubes (10μm length) while higher values are registered for 15nm diameter nanotubes when normalizing protein adsorption to nanostructures' surface unit area (evaluated from dye desorption measurements) - consistent with theoretical considerations. The proteins presence on the nanostructures is evaluated by XPS and ToF-SIMS; additionally, we qualitatively assess their presence along the nanostructures length by ToF-SIMS depth profiles, with decreasing concentration towards the bottom. Surface nanostructuring of titanium biomedical devices with TiO 2 nanotubes was shown to significantly influence the adhesion, proliferation and differentiation of mesenchymal stem cells (and other cells too). A high level of control over the nanoscale topography and over the surface area of such 1D nanostructures enables a direct influence on protein adhesion. Herein, we investigate and show how the nanostructure morphology (nanotube diameter and length) influences the interactions with small-sized charged proteins, using as model proteins bovine serum albumin (negatively charged) and histone (positively charged). We show that the protein charge strongly influences their adhesion to the TiO 2 nanostructures. Protein adhesion is quantified by ELISA measurements and determination of the

Interface architecture determined electrocatalytic activity of Pt on vertically oriented TiO(2) nanotubes.

PubMed

Rettew, Robert E; Allam, Nageh K; Alamgir, Faisal M

2011-02-01

The surface atomic structure and chemical state of Pt is consequential in a variety of surface-intensive devices. Herein we present the direct interrelationship between the growth scheme of Pt films, the resulting atomic and electronic structure of Pt species, and the consequent activity for methanol electro-oxidation in Pt/TiO(2) nanotube hybrid electrodes. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) measurements were performed to relate the observed electrocatalytic activity to the oxidation state and the atomic structure of the deposited Pt species. The atomic structure as well as the oxidation state of the deposited Pt was found to depend on the pretreatment of the TiO(2) nanotube surfaces with electrodeposited Cu. Pt growth through Cu replacement increases Pt dispersion, and a separation of surface Pt atoms beyond a threshold distance from the TiO(2) substrate renders them metallic, rather than cationic. The increased dispersion and the metallic character of Pt results in strongly enhanced electrocatalytic activity toward methanol oxidation. This study points to a general phenomenon whereby the growth scheme and the substrate-to-surface-Pt distance dictates the chemical state of the surface Pt atoms, and thereby, the performance of Pt-based surface-intensive devices.

Polydopamine-Coated TiO2 Nanotubes for Selective Photocatalytic Oxidation of Benzyl Alcohol to Benzaldehyde Under Visible Light.

PubMed

Tripathy, Jyotsna; Loget, Gabriel; Altomare, Marco; Schmuki, Patrik

2016-05-01

TiO2 nanotube arrays grown by anodization were coated with thin layers of polydopamine as visible light sensitizer. The PDA-coated TiO2 scaffolds were used as photocatalyst for selective oxidation of benzyl alcohol under monochromatic irradiation at 473 nm. Benzaldehyde was selectively formed and no by-products could be detected. A maximized reaction yield was obtained in O2-saturated acetonitrile. A mechanism is proposed that implies firstly the charge carrier generation in polydopamine as a consequence of visible light absorption. Secondly, photo-promoted electrons are injected in TiO2 conduction band, and subsequently transferred to dissolved O2 to form O*2- radicals. These radicals react with benzyl alcohol and lead to its selective dehydrogenation oxidation towards benzaldehyde.

Fabrication of transparent TiO2 nanotube-based photoanodes for CdS/CdTe quantum co-sensitized solar cells

NASA Astrophysics Data System (ADS)

Gualdrón-Reyes, A. F.; Cárdenas-Arenas, A.; Martínez, C. A.; Kouznetsov, V. V.; Meléndez, A. M.

2017-01-01

In order to fabricate a solar cell, ordered TiO2 nanotube (TNT) arrays were prepared by double anodization. TNT arrays with variable lengths were obtained by changing the duration of the anodizing process of up to 3h. TNT membranes were transferred to indium tin oxide substrates and attached with a B-TiO2 sol. TNT photoanode with the best photoelectrochemical performance was sensitized with CdS by SILAR method. On other hand, CdTe quantum dots prepared via colloidal synthesis were deposited on TNT photoanodes for 2h, 4h and 6h. In addition, TNT/CdS was loaded with CdTe quantum dots for 4 h. Morphology and chemical modification of TiO2 were characterized by FESEM and XPS, while their photoelectrochemical performance was measured by open-circuit photopotential and photovoltammetry under visible light. TiO2 nanotubes grown during 2.5h showed the highest photocurrent due to presence of Ti3+ donor states by N and F co-doping, increasing the number of photogenerated electrons transported to back collector. TNT/CdS/CdTe photoanode reach the highest conversion efficiency under AM 1.5G simulated solar illumination.

Morphology modulation of SrTiO3/TiO2 heterostructures for enhanced photoelectrochemical performance.

PubMed

Jiao, Zhengbo; Chen, Tao; Yu, Hongchao; Wang, Teng; Lu, Gongxuan; Bi, Yingpu

2014-04-01

Design and fabrication of nanoscale semiconductors with regulatable morphology or structure has attracted tremendous interest due to the dependency relationship between properties and architectures. Two types of SrTiO3/TiO2 nanocomposites with different morphologies and structures have been fabricated by controlling the kinetics of hydrothermal reactions. One is TiO2 nanotube arrays densely wrapped by SrTiO3 film and the other is SrTiO3 nanospheres distributed on the top region of TiO2 nanotube arrays, which has been firstly fabricated. It has been found that the photoelectrochemical performances of these heterostructures are crucially dominated by their architectures. Heterostructured SrTiO3/TiO2 nanotube arrays were fabricated by traditional method in the absence of NaOH and they exhibited higher photoelectrochemical performance than pure TiO2 nanotube arrays. However, the compact SrTiO3 coating film on the sidewalls of TiO2 nanotube arrays could inevitably destroy the tubular structures of TiO2 and thus go against the vectorial transport of electrons. Interestingly, when excess NaOH was added into the growth solution, SrTiO3 nanospheres would be rationally grafted on the top of TiO2 nanotube arrays, which could preserve the tubular structures of TiO2, and thus further improve the photoelectrochemical performance. Copyright © 2013 Elsevier Inc. All rights reserved.

Thin layer of ordered boron-doped TiO2 nanotubes fabricated in a novel type of electrolyte and characterized by remarkably improved photoactivity

NASA Astrophysics Data System (ADS)

Siuzdak, Katarzyna; Szkoda, Mariusz; Lisowska-Oleksiak, Anna; Grochowska, Katarzyna; Karczewski, Jakub; Ryl, Jacek

2015-12-01

This paper reports a novel method of boron doped titania nanotube arrays preparation by electrochemical anodization in electrolyte containing boron precursor - boron trifluoride diethyl etherate (BF3 C4H10O), simultaneously acting as an anodizing agent. A pure, ordered TiO2 nanotubes array, as a reference sample, was also prepared in solution containing a standard etching compound: ammonium fluoride. The doped and pure titania were characterized by scanning electron microscopy, UV-vis spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, photoluminescence emission spectroscopy and by means of electrochemical methods. The B-doping decidedly shifts the absorption edge of TiO2 nanotubes towards the visible light region and significantly inhibits the radiative recombination processes. Despite the fact that the doped sample is characterized by 4.6 lower real surface area when compared to pure titania, it leads to the decomposition of methylene blue in 93%, that is over 2.3 times higher than the degradation efficiency exhibited by the undoped material. The formation rate of hydroxyl radicals (rad OH) upon illumination significantly favours boron doped titania as a photocatalytic material. Moreover, the simple doping of TiO2 nanotubes array results in the enhancement of generated photocurrent from 120 μA/cm2 to 350 μA/cm2 registered for undoped and doped electrode, respectively.

Rapid, conformal gas-phase formation of silica (SiO2) nanotubes from water condensates.

PubMed

Bae, Changdeuck; Kim, Hyunchul; Yang, Yunjeong; Yoo, Hyunjun; Montero Moreno, Josep M; Bachmann, Julien; Nielsch, Kornelius; Shin, Hyunjung

2013-07-07

An innovative atomic layer deposition (ALD) concept, with which nanostructures of water condensates with high aspect ratio at equilibrium in cylindrical nanopores can be transformed uniformly into silica (SiO2) at near room temperature and ambient pressure, has been demonstrated for the first time. As a challenging model system, we first prove the conversion of cylindrical water condensates in porous alumina membranes to silica nanotubes (NTs) by introducing SiCl4 as a metal reactant without involving any catalytic reaction. Surprisingly, the water NTs reproducibly transformed into silica NTs, where the wall thickness of the silica NTs deposited per cycle was found to be limited by the amount of condensed water, and it was on the orders of ten nanometers per cycle (i.e., over 50 times faster than that of conventional ALD). More remarkably, the reactions only took place for 10-20 minutes or less without vacuum-related equipment. The thickness of initially adsorbed water layers in cylindrical nanopores was indirectly estimated from the thickness of formed SiO2 layers. With systematic experimental designs, we tackle the classical Kelvin equation in the nanosized pores, and the role of van der Waals forces in the nanoscale wetting phenomena, which is a long-standing issue lacking experimental insight. Moreover, we show that the present strategy is likely generalized to other oxide systems such as TiO2. Our approach opens up a new avenue for ultra-simple preparation of porous oxides and allows for the room temperature formation of dielectric layers toward organic electronic and photovoltaic applications.

Hydrothermal solid-gas route to TiO2 nanoparticles/nanotube arrays for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Fan, Haowen; Zhang, He; Luo, Xiaolei; Liao, Maoying; Zhu, Xufei; Ma, Jing; Song, Ye

2017-07-01

Although TiO2 nanotube arrays (TNTAs) have shown great promise as supercapacitor materials, their specific capacitances are still not comparable with some typical materials. Here, TiO2 nanoparticles (NPs)/TNTAs hybrid structure has been derived from the anodized TNTAs by a facile hydrothermal solid-gas method (HSGM), which can avoid cracking or curling of the TNTAs from Ti substrate. The obtained NPs/TNTAs hybrid structure can exhibit a ∼4.90 times increase in surface area and a ∼5.49 times increase in areal specific capacitance compared to the TNTAs without HSGM treatment. Besides, the argon-atmosphere annealing can offer improved areal capacitance and cycling stability relative to the air-atmosphere annealing. The hydrothermal vapor pressure is a key factor for controlling microscopic morphologies of TNTAs, the morphology transformations of TNTAs during the HSGM treatment can be accelerated under enhanced vapor pressures. The highest areal capacitance of HSGM-treated TNTAs is up to 76.12 mF cm-2 at 0.5 mA cm-2, well above that of any TiO2 materials reported to date.

Photocatalytic performance of freestanding tetragonal zirconia nanotubes formed in H2O2/NH4F/ethylene glycol electrolyte by anodisation of zirconium

NASA Astrophysics Data System (ADS)

Rozana, Monna; Izza Soaid, Nurul; Kian, Tan Wai; Kawamura, Go; Matsuda, Atsunori; Lockman, Zainovia

2017-04-01

ZrO2 nanotubes (ZrNTs) were produced by anodisation of zirconium foil in H2O2/NH4F/ethylene glycol electrolyte. The as-anodised foils were then soaked in the anodising electrolyte for 12 h. Soaking weakens the adherence of the anodic layer from the substrate resulting in freestanding ZrNTs (FS-ZrNTs). Moreover, the presence of H2O2 in the electrolyte also aids in weakening the adhesion of the film from the foil, as foil anodised in electrolyte without H2O2 has good film adherence. The as-anodised FS-ZrNTs film was amorphous and crystallised to predominantly tetragonal phase upon annealing at >300 °C. Annealing must, however, be done at <500 °C to avoid monoclinic ZrO2 formation and nanotubes disintegration. FS-ZrNTs annealed at 450 °C exhibited the highest photocatalytic ability to degrade methyl orange (MO), whereby 82% MO degradation was observed after 5 h, whereas FS-ZrNTs with a mixture of monoclinic and tetragonal degraded 70% of MO after 5 h.

Augmented Photoelectrochemical Efficiency of ZnO/TiO2 Nanotube Heterostructures

NASA Astrophysics Data System (ADS)

Boda, Muzaffar Ahmad; Shah, Mohammad Ashraf

2017-11-01

ZnO/TiO2 nanotube heterostructures have been fabricated by electrodeposition of ZnO microcrystals over electrochemically anodized TiO2 nanotube arrays. The resulting ZnO/TiO2 nanotube heterostructures showed enhanced photocurrent density of 5.72 mA cm-2, about 1.5 times the value of 3.68 mA cm-2 shown by bare compact TiO2 nanotubes. This enhanced photocurrent density of the ZnO/TiO2 nanotube heterostructures is due to high electron mobility in the ZnO crystals, thereby decreasing the electron-hole recombination process, good interfacial quality between the ZnO and TiO2 structures, and a proposed smooth charge-transfer mechanism due to band bending at the interface. The morphological features of the as-prepared heterostructures were determined by field-emission scanning electron microscopy (FESEM). The crystallinity and phase purity of the samples were confirmed by x-ray diffraction (XRD) analysis. The light absorption properties of the prepared samples were investigated by ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). The photoelectrochemical efficiency of bare and ZnO-modified TiO2 nanotube heterostructures was determined by electrochemical analyzer.

Effects of incorporation of 2.5 and 5 wt% TiO2 nanotubes on fracture toughness, flexural strength, and microhardness of denture base poly methyl methacrylate (PMMA).

PubMed

Abdulrazzaq Naji, Sahar; Behroozibakhsh, Marjan; Jafarzadeh Kashi, Tahereh Sadat; Eslami, Hossein; Masaeli, Reza; Mahgoli, Hosseinali; Tahriri, Mohammadreza; Ghavvami Lahiji, Mehrsima; Rakhshan, Vahid

2018-04-01

The aim of this preliminary study was to investigate, for the first time, the effects of addition of titania nanotubes (n-TiO 2 ) to poly methyl methacrylate (PMMA) on mechanical properties of PMMA denture base. TiO 2 nanotubes were prepared using alkaline hydrothermal process. Obtained nanotubes were assessed using FESEM-EDX, XRD, and FT-IR. For 3 experiments of this study (fracture toughness, three-point bending flexural strength, and Vickers microhardness), 135 specimens were prepared according to ISO 20795-1:2013 (n of each experiment=45). For each experiment, PMMA was mixed with 0% (control), 2.5 wt%, and 5 wt% nanotubes. From each TiO 2 :PMMA ratio, 15 specimens were fabricated for each experiment. Effects of n-TiO 2 addition on 3 mechanical properties were assessed using Pearson, ANOVA, and Tukey tests. SEM images of n-TiO 2 exhibited the presence of elongated tubular structures. The XRD pattern of synthesized n-TiO 2 represented the anatase crystal phase of TiO 2 . Moderate to very strong significant positive correlations were observed between the concentration of n-TiO 2 and each of the 3 physicomechanical properties of PMMA (Pearson's P value ≤.001, correlation coefficient ranging between 0.5 and 0.9). Flexural strength and hardness values of specimens modified with both 2.5 and 5 wt% n-TiO 2 were significantly higher than those of control ( P ≤.001). Fracture toughness of samples reinforced with 5 wt% n-TiO 2 (but not those of 2.5% n-TiO 2 ) was higher than control ( P =.002). Titania nanotubes were successfully introduced for the first time as a means of enhancing the hardness, flexural strength, and fracture toughness of denture base PMMA.

Electrochemical growth behavior, surface properties, and enhanced in vivo bone response of TiO2 nanotubes on microstructured surfaces of blasted, screw-shaped titanium implants

PubMed Central

Sul, Young-Taeg

2010-01-01

TiO2 nanotubes are fabricated on TiO2 grit-blasted, screw-shaped rough titanium (ASTM grade 4) implants (3.75 × 7 mm) using potentiostatic anodization at 20 V in 1 M H3PO4 + 0.4 wt.% HF. The growth behavior and surface properties of the nanotubes are investigated as a function of the reaction time. The results show that vertically aligned nanotubes of ≈700 nm in length, with highly ordered structures of ≈40 nm spacing and ≈15 nm wall thickness may be grown independent of reaction time. The geometrical properties of nanotubes increase with reaction time (mean pore size, pore size distribution [PSD], and porosity ≈90 nm, ≈40–127 nm and 45%, respectively for 30 minutes; ≈107 nm, ≈63–140 nm and 56% for one hour; ≈108 nm, ≈58–150 nm and 60% for three hours). It is found that the fluorinated chemistry of the nanotubes of F-TiO2, TiOF2, and F-Ti-O with F ion incorporation of ≈5 at.%, and their amorphous structure is the same regardless of the reaction time, while the average roughness (Sa) gradually decreases and the developed surface area (Sdr) slightly increases with reaction time. The results of studies on animals show that, despite their low roughness values, after six weeks the fluorinated TiO2 nanotube implants in rabbit femurs demonstrate significantly increased osseointegration strengths (41 vs 29 Ncm; P = 0.008) and new bone formation (57.5% vs 65.5%; P = 0.008) (n = 8), and reveal more frequently direct bone/cell contact at the bone–implant interface by high-resolution scanning electron microscope observations as compared with the blasted, moderately rough implants that have hitherto been widely used for clinically favorable performance. The results of the animal studies constitute significant evidence that the presence of the nanotubes and the resulting fluorinated surface chemistry determine the nature of the bone responses to the implants. The present in vivo results point to potential applications of the TiO2 nanotubes in the

Water Adsorption on Clean and Defective Anatase TiO2 (001) Nanotube Surfaces: A Surface Science Approach.

PubMed

Kenmoe, Stephane; Lisovski, Oleg; Piskunov, Sergei; Bocharov, Dmitry; Zhukovskii, Yuri F; Spohr, Eckhard

2018-05-31

We use ab initio molecular dynamics simulations to study the adsorption of thin water films with 1 and 2 ML coverage on anatase TiO 2 (001) nanotubes. The nanotubes are modeled as 2D slabs, which consist of partially constrained and partially relaxed structural motifs from nanotubes. The effect of anion doping on the adsorption is investigated by substituting O atoms with N and S impurities on the nanotube slab surface. Due to strain-induced curvature effects, water adsorbs molecularly on defect-free surfaces via weak bonds on Ti sites and H bonds to surface oxygens. While the introduction of an S atom weakens the interaction of the surface with water, which adsorbs molecularly, the presence of an N impurity renders the surface more reactive to water, with a proton transfer from the water film and the formation of an NH group at the N site. At 2 ML coverage, a further surface-assisted proton transfer takes place in the water film, resulting in the formation of an OH - group and an NH 2 + cationic site on the surface.

Antibacterial activity and inflammation inhibition of ZnO nanoparticles embedded TiO2 nanotubes.

PubMed

Yao, Shenglian; Feng, Xujia; Lu, Jiaju; Zheng, Yudong; Wang, Xiumei; Volinsky, Alex A; Wang, Lu-Ning

2018-06-15

Titanium (Ti) with nanoscale structure on the surface exhibits excellent biocompatibility and bone integration. Once implanted, the surgical implantation may lead to bacterial infection and inflammatory reaction, which cause the implant failure. In this work, irregular and nanorod-shaped ZnO nanoparticles were doped into TiO 2 nanotubes (TNTs) with inner diameter of about 50 nm by electro-deposition. The antibacterial properties of ZnO incorporated into TiO 2 nanotubes (TNTs/ZnO) were evaluated using Staphylococcus aureus (S. aureus). Zn ions released from the nanoparticles and the morphology could work together, improving antibacterial effectiveness up to 99.3% compared with the TNTs. Macrophages were cultured on the samples to determine their respective anti-inflammatory properties. The proliferation and viability of macrophages were evaluated by the CCK-8 method and Live&Dead stain, and the morphology of the cells was observed by scanning electron microscopy. Results indicated that TNTs/ZnO has a significant inhibitory effect on the proliferation and adhesion of macrophages, which could be used to prevent chronic inflammation and control the inflammatory reaction. Besides, the release of Zn ions from the ZnO nanoparticles is a long-term process, which could be beneficial for bone integration. Results demonstrate that ZnO deposited into TNTs improved the antibacterial effectiveness and weakened the inflammatory reaction of titanium-based implants, which is a promising approach to enhance their bioactivity.

Antibacterial activity and inflammation inhibition of ZnO nanoparticles embedded TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Yao, Shenglian; Feng, Xujia; Lu, Jiaju; Zheng, Yudong; Wang, Xiumei; Volinsky, Alex A.; Wang, Lu-Ning

2018-06-01

Titanium (Ti) with nanoscale structure on the surface exhibits excellent biocompatibility and bone integration. Once implanted, the surgical implantation may lead to bacterial infection and inflammatory reaction, which cause the implant failure. In this work, irregular and nanorod-shaped ZnO nanoparticles were doped into TiO2 nanotubes (TNTs) with inner diameter of about 50 nm by electro-deposition. The antibacterial properties of ZnO incorporated into TiO2 nanotubes (TNTs/ZnO) were evaluated using Staphylococcus aureus (S. aureus). Zn ions released from the nanoparticles and the morphology could work together, improving antibacterial effectiveness up to 99.3% compared with the TNTs. Macrophages were cultured on the samples to determine their respective anti-inflammatory properties. The proliferation and viability of macrophages were evaluated by the CCK-8 method and Live&Dead stain, and the morphology of the cells was observed by scanning electron microscopy. Results indicated that TNTs/ZnO has a significant inhibitory effect on the proliferation and adhesion of macrophages, which could be used to prevent chronic inflammation and control the inflammatory reaction. Besides, the release of Zn ions from the ZnO nanoparticles is a long-term process, which could be beneficial for bone integration. Results demonstrate that ZnO deposited into TNTs improved the antibacterial effectiveness and weakened the inflammatory reaction of titanium-based implants, which is a promising approach to enhance their bioactivity.

Magnetic, electronic, optical, and photocatalytic properties of nonmetal- and halogen-doped anatase TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Fadlallah, M. M.

2017-05-01

The structure stability, magnetic, electronic, optical, and photocatalytic properties of nonmetal (B, C, N, P, and S), and halogen (F, Cl, Br, and I)-doped anatase TiO2 nanotubes (TNTs) have been investigated using spin polarized density functional theory. The N- and F-doped TNTs are the most stable among other doped TNTs. It is found that the magnetic moment of doped TNT is the difference between the number of the valence electrons of the dopant and host anion. All dopants decrease the band gap of TNT. The decrease in the band gap of nonmetal (C, N, P, and S)-doped TNTs, in particular N and P, is larger than that of halogen-doped TNTs due to the created states of the nonmetal dopant in the band gap. There is a good agreement between the calculation results and the experimental observations. Even though C-, N-, and P-doped TNTs have the lowest band gap, they cannot be used as a photocatalysis for water splitting. The B-, S-, and I-doped TiO2 nanotubes are of great potential as candidates for water splitting in the visible light range.

Nanometer Scale Confined Growth of Single-Crystalline Gold Nanowires via Photocatalytic Reduction.

PubMed

Lee, Seonhee; Bae, Changdeuck; Shin, Hyunjung

2018-06-20

Single-crystalline gold nanowires (Au NWs) are directly synthesized by the photocatalytic reduction of an aqueous HAuCl 4 solution inside high-aspect-ratio TiO 2 nanotubes (NTs). Crystalline TiO 2 (anatase) NTs are prepared by the template-assisted atomic layer deposition technique with a subsequent annealing. Under the irradiation of ultraviolet light, photoexcited electrons are formed on the surfaces of TiO 2 NTs and could reduce Au ions to create nuclei without using any surfactant, reducing agent, and/or seed. Once nucleation occurred, high-aspect-ratio Au NWs are grown inside the TiO 2 NTs in a diffusion-controlled manner. As the solution pH increased, the nucleation/growth rate decreased and twin-free (or not observed), single-crystalline Au NWs are formed. At a pH above 6, the nucleation/growth rates increased and Au nanoparticles are observed both inside and outside of the TiO 2 NTs. The confined nanoscale geometries of the interior of the TiO 2 NTs are found to play a key role in the controlled diffusion of Au species and in determining the crystal morphology of the resulting Au NWs.

TiO2@PEI-Grafted-MWCNTs Hybrids Nanocomposites Catalysts for CO2 Photoreduction

PubMed Central

Falcicchio, Aurelia; Fracassi, Francesco; Margiotta, Valerio; Moliterni, Anna

2018-01-01

Anatase (TiO2) and multiwalled carbon nanotubes bearing polyethylenimine (PEI) anchored on their surface were hybridized in different proportions according to a sol-gel method. The resulting nanocomposites (TiO2@PEI-MWCNTs), characterized by BET, XRD, XPS, SEM, and UV techniques, were found efficient catalysts for CO2 photoreduction into formic and acetic acids in water suspension and under visible light irradiation. PEI-grafted nanotubes co-catalysts are believed to act as CO2 activators by forming a carbamate intermediate allowing to accomplish the first example in the literature of polyamines/nanotubes/TiO2 mediated CO2 photoreduction to carboxylic acids. PMID:29461484

Spectroscopic studies of porphyrin functionalized multiwalled carbon nanotubes and their interaction with TiO2 nanoparticles surface

NASA Astrophysics Data System (ADS)

Zannotti, Marco; Giovannetti, Rita; D'Amato, Chiara Anna; Rommozzi, Elena

2016-01-01

UV-vis and fluorescence investigations about the non-covalent interaction, in ethanolic solutions, of multi-wall carbon nanotube (MWCNT) with Coproporphyrin-I, and its Cu(II) and Zn(II) complexes (MCPIs) have been reported. Evidence of binding between MWCNTs and porphyrins was discovered from spectral adsorption decrease with respect to free porphyrins and by the exhibition of photoluminescence quenching with respect to free porphyrins demonstrating that MWCNT@MCPIs are potential donor-acceptor complexes. Equilibrium and kinetic aspects in the interactions with monolayer transparent TiO2 thin films with the obtained MWCNT@MCPIs are clarified showing their effective adsorption by porphyrin links on the TiO2 monolayer support, with respect to not only MWCNTs, according to the Langmuir model and with pseudo-first-order kinetics. Morphological description of the adsorption of MWCNT@MCPIs on TiO2 with scanning electron microscopy has been reported. The obtained experimental evidences describe therefore MWCNT@MCPIs as potential sensitizers in the DSSC (Dye-Sensitized Solar Cell) applications.

Broadband and omnidirectional light harvesting enhancement in photovoltaic devices with aperiodic TiO2 nanotube photonic crystal

NASA Astrophysics Data System (ADS)

Guo, Min; Su, Haijun; Zhang, Jun; Liu, Lin; Fu, Nianqing; Yong, Zehui; Huang, Haitao; Xie, Keyu

2017-03-01

Design of more effective broadband light-trapping elements to improve the light harvesting efficiency under both normal and tilted light for solar cells and other photonic devices is highly desirable. Herein we present a theoretical analysis on the optical properties of a novel TiO2 nanotube aperiodic photonic crystal (NT APC) following an aperiodic sequences and its photocurrent enhancement effect for dye-sensitized solar cells (DSSCs) under various incidence angles. It is found that, compared to regular PC, the designed TiO2 NT APC owns broader reflection region and a desired omnidirectional reflection (ODR) bandgaps, leading to considerable and stable photocurrent enhancement under both normal and oblique light. The effects of the structural parameters of the TiO2 NT APC, including the average lattice constant and the common sequence difference, on the optical properties, ODR bandgaps and absorption magnification of the integrated DSSCs are investigated in detail. Moreover, the angular dependence of photocurrent enhancement and angular compensation effect of such TiO2 NT APCs are also provided to offer a guidance on the optimum structural parameters design under different engineering application conditions.

Mechanical properties of sol–gel derived SiO2 nanotubes

PubMed Central

Antsov, Mikk; Vlassov, Sergei; Dorogin, Leonid M; Vahtrus, Mikk; Zabels, Roberts; Lange, Sven; Lõhmus, Rünno

2014-01-01

Summary The mechanical properties of thick-walled SiO2 nanotubes (NTs) prepared by a sol–gel method while using Ag nanowires (NWs) as templates were measured by using different methods. In situ scanning electron microscopy (SEM) cantilever beam bending tests were carried out by using a nanomanipulator equipped with a force sensor in order to investigate plasticity and flexural response of NTs. Nanoindentation and three point bending tests of NTs were performed by atomic force microscopy (AFM) under ambient conditions. Half-suspended and three-point bending tests were processed in the framework of linear elasticity theory. Finite element method simulations were used to extract Young’s modulus values from the nanoindentation data. Finally, the Young’s moduli of SiO2 NTs measured by different methods were compared and discussed. PMID:25383292

Drug release characteristics of quercetin-loaded TiO2 nanotubes coated with chitosan.

PubMed

Mohan, L; Anandan, C; Rajendran, N

2016-12-01

TiO 2 nanotubes formed by anodic oxidation of Ti-6Al-7Nb were loaded with quercetin (TNTQ) and chitosan was coated on the top of the quercetin (TNTQC) to various thicknesses. Field emission scanning electron microscopy (FESEM), 3D and 2D analyses were used to characterize the samples. The drug release studies of TNTQ and TNTQC were studied in Hanks' solution for 192h. The studies showed that the native oxide on the sample is substituted by self assembled nanotube arrays by anodisation. FESEM images of chitosan-loaded TNT samples showed that filling of chitosan takes place in inter-tubular space and pores. Drug release studies revealed that the release of drug into the local environment during that duration was constant. The local concentration of the drug can be controlled and tuned by controlling the thickness of the chitosan (0.6, 1 and 3μm) to fit into an optimal therapeutic window in order to treat postoperative infections, inflammation and for quick healing with better osseointegration of the titanium implants. Copyright © 2016 Elsevier B.V. All rights reserved.

Tailoring TiO2 Nanotube-Interlaced Graphite Carbon Nitride Nanosheets for Improving Visible-Light-Driven Photocatalytic Performance.

PubMed

Wang, Yang; Liu, Xueqin; Zheng, Cunchuan; Li, Yinchang; Jia, Songru; Li, Zhen; Zhao, Yanli

2018-06-01

Rapid recombination of photoinduced electron-hole pairs is one of the major defects in graphitic carbon nitride (g-C 3 N 4 )-based photocatalysts. To address this issue, perforated ultralong TiO 2 nanotube-interlaced g-C 3 N 4 nanosheets (PGCN/TNTs) are prepared via a template-based process by treating g-C 3 N 4 and TiO 2 nanotubes polymerized hybrids in alkali solution. Shortened migration distance of charge transfer is achieved from perforated PGCN/TNTs on account of cutting redundant g-C 3 N 4 nanosheets, leading to subdued electron-hole recombination. When PGCN/TNTs are employed as photocatalysts for H 2 generation, their in-plane holes and high hydrophilicity accelerate cross-plane diffusion to dramatically promote the photocatalytic reaction in kinetics and supply plentiful catalytic active centers. By having these unique features, PGCN/TNTs exhibit superb visible-light H 2 -generation activity of 1364 µmol h -1 g -1 (λ > 400 nm) and a notable quantum yield of 6.32% at 420 nm, which are much higher than that of bulk g-C 3 N 4 photocatalysts. This study demonstrates an ingenious design to weaken the electron recombination in g-C 3 N 4 for significantly enhancing its photocatalytic capability.

Binding of plasma proteins to titanium dioxide nanotubes with different diameters

PubMed Central

Kulkarni, Mukta; Flašker, Ajda; Lokar, Maruša; Mrak-Poljšak, Katjuša; Mazare, Anca; Artenjak, Andrej; Čučnik, Saša; Kralj, Slavko; Velikonja, Aljaž; Schmuki, Patrik; Kralj-Iglič, Veronika; Sodin-Semrl, Snezna; Iglič, Aleš

2015-01-01

Titanium and titanium alloys are considered to be one of the most applicable materials in medical devices because of their suitable properties, most importantly high corrosion resistance and the specific combination of strength with biocompatibility. In order to improve the biocompatibility of titanium surfaces, the current report initially focuses on specifying the topography of titanium dioxide (TiO2) nanotubes (NTs) by electrochemical anodization. The zeta potential (ζ-potential) of NTs showed a negative value and confirmed the agreement between the measured and theoretically predicted dependence of ζ-potential on salt concentration, whereby the absolute value of ζ-potential diminished with increasing salt concentrations. We investigated binding of various plasma proteins with different sizes and charges using the bicinchoninic acid assay and immunofluorescence microscopy. Results showed effective and comparatively higher protein binding to NTs with 100 nm diameters (compared to 50 or 15 nm). We also showed a dose-dependent effect of serum amyloid A protein binding to NTs. These results and theoretical calculations of total available surface area for binding of proteins indicate that the largest surface area (also considering the NT lengths) is available for 100 nm NTs, with decreasing surface area for 50 and 15 nm NTs. These current investigations will have an impact on increasing the binding ability of biomedical devices in the body leading to increased durability of biomedical devices. PMID:25733829

Fabrication of Cu2O/TiO2 Nanotubes Heterojunction Arrays and Investigation of Their Photoelectrochemical Behaviour

DTIC Science & Technology

2012-11-05

investigate phase transformations in TiO2 NTs after annealing and as a consequence of the functionalization. Electrodeposition was performed in a...deposition Cu2O electrodeposition was performed by polarizing the Ti/TiO2 NTs electrodes at UE = - 0.4 V in the CuSO4 containing bath described in...polarization (UE = - 0.4 V) in the electrodeposition solution (see experimental section). As shown in Fig. 6, in spite of the constant polarizing voltage (i.e

Enhanced photocatalytic activity towards degradation and H2 evolution over one dimensional TiO2@MWCNTs heterojunction

NASA Astrophysics Data System (ADS)

Zhang, Xiao; Cao, Shuang; Wu, Zhijiao; Zhao, Suling; Piao, Lingyu

2017-04-01

With the distinct electronic and optical properties, multiwall carbon nanotubes (MWCNTs) are identified as an outstanding catalyst support, which can effectively improve the performance of the TiO2 photocatalysts. Herein, the unique one dimensional TiO2@MWCNTs nanocomposites have been prepared by a facile hydrothermal method. The TiO2 coating layers are extremely uniform and the thickness is adjustable for different nanocomposites. XPS measurements confirm that intimate electronic interactions are existed between MWCNTs and TiO2 via interfacial Tisbnd Osbnd C bond and the photoluminescence intensity of the TiO2@MWCNTs nanocomposites are effectively quenched compared with pure TiO2, suggesting the fast electron transfer rates. The thickness of TiO2 coating layers of the TiO2@MWCNTs nanocomposites plays a significant role in the photocatalytic degradation of organic pollutants, such as methylene blue (MB) and Rhodamine B (RhB), and photocatalytic H2 evolution from water. Due to the formation of one dimensional heterojunction of TiO2@MWCNTs nanocomposites and the positive synergistic effect between TiO2 and carbon nanotubes, it is found that the photocatalytic activity of the system is significantly improved.

NTS2-selective neurotensin mimetics with tetrahydrofuran amino acids.

PubMed

Simeth, Nadja A; Bause, Manuel; Dobmeier, Michael; Kling, Ralf C; Lachmann, Daniel; Hübner, Harald; Einsiedel, Jürgen; Gmeiner, Peter; König, Burkhard

2017-01-01

Stimulation of the NTS2 neurotensin receptor causes antipsychotic effects and leads to a promotion of the μ-opioid-independent antinociception, which is important in the modulation of tonic pain sensitivity. We report the synthesis and properties of a small library of peptidic agonists based on the active neurotensin fragment NT(8-13). Two tetrahydrofuran amino acid derivatives were synthesized to replace Tyr 11 in NT(8-13). Additionally, Arg 8 , Arg 9 , and Ile 12 of the lead peptide were exchanged by Lys, Lys, and Gly, respectively. The new compounds showed substantial NTS2 binding affinity and up to 1000-fold selectivity over NTS1. The highest selectivity (K i (NTS2): 29nM, K i (NTS1): 35,000nM) was observed for the peptide analog 17R trans . Copyright © 2016 Elsevier Ltd. All rights reserved.

BaTiO3-based nanolayers and nanotubes: first-principles calculations.

PubMed

Evarestov, Robert A; Bandura, Andrei V; Kuruch, Dmitrii D

2013-01-30

The first-principles calculations using hybrid exchange-correlation functional and localized atomic basis set are performed for BaTiO(3) (BTO) nanolayers and nanotubes (NTs) with the structure optimization. Both the cubic and the ferroelectric BTO phases are used for the nanolayers and NTs modeling. It follows from the calculations that nanolayers of the different ferroelectric BTO phases have the practically identical surface energies and are more stable than nanolayers of the cubic phase. Thin nanosheets composed of three or more dense layers of (0 1 0) and (0 1 1[overline]) faces preserve the ferroelectric displacements inherent to the initial bulk phase. The structure and stability of BTO single-wall NTs depends on the original bulk crystal phase and a wall thickness. The majority of the considered NTs with the low formation and strain energies has the mirror plane perpendicular to the tube axis and therefore cannot exhibit ferroelectricity. The NTs folded from (0 1 1[overline]) layers may show antiferroelectric arrangement of Ti-O bonds. Comparison of stability of the BTO-based and SrTiO(3)-based NTs shows that the former are more stable than the latter. Copyright © 2012 Wiley Periodicals, Inc.

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

NASA Astrophysics Data System (ADS)

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

2017-10-01

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

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

NASA Astrophysics Data System (ADS)

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

2015-09-01

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

Fabrication of uniformly dispersed Ag nanoparticles loaded TiO{sub 2} nanotube arrays for enhancing photoelectrochemical and photocatalytic performances under visible light irradiation

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

Yi, Junhui; Zhang, Shengsen; Wang, Hongjuan

2014-12-15

Graphical abstract: Uniformly dispersed Ag nanoparticles (NPs) were successfully loaded on both the outer and inner surface of the TiO{sub 2} nanotube arrays (NTs) through a simple polyol method, which exhibited the enhanced photoelectrochemical and photocatalytic performances under visible-light irradiation due to the more effective separation of photo-generated electron–hole pairs and faster interfacial charge transfer. - Highlights: • Highly dispersed Ag nanoparticles (NPs) are successfully prepared by polyol method. • Ag NPs are uniformly loaded on the surface of the TiO{sub 2} nanotube arrays (NTs). • Ag/TiO{sub 2}-NTs exhibit the enhanced photocatalytic activity under visible-light. • The enhanced photocurrent ismore » explained by electrochemical impedance spectroscopy. - Abstract: Uniformly dispersed Ag nanoparticles (NPs) were successfully loaded on both the outer and inner surface of the TiO{sub 2} nanotube arrays (NTs) through a simple polyol method. The as-prepared Ag/TiO{sub 2}-NTs were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV–vis diffusion reflectance spectroscopy. Photoelectrochemical behaviors were investigated via photocurrent response and electrochemical impedance spectroscopy (EIS). Photocatalytic activity of Ag/TiO{sub 2}-NTs was evaluated by degradation of acid orange II under visible light irradiation. The results showed that photocatalytic efficiency of Ag/TiO{sub 2}-NTs is more than 5 times higher than that of pure TiO{sub 2} NTs. Comparing with the electrochemical deposition method, the photocatalytic activity of Ag/TiO{sub 2}-NTs prepared by polyol method has been obviously increased.« less

Electrical transport properties of individual WS2 nanotubes and their dependence on water and oxygen absorption

NASA Astrophysics Data System (ADS)

Zhang, Chaoying; Ning, Zhiyuan; Liu, Yang; Xu, Tingting; Guo, Yao; Zak, Alla; Zhang, Zhiyong; Wang, Sheng; Tenne, Reshef; Chen, Qing

2012-09-01

The electrical properties of WS2 nanotubes (NTs) were studied through measuring 59 devices. Important electrical parameters, such as the carrier concentration, mobility, and effective barrier height at the contacts, were obtained through fitting experimental non-linear I-V curves using a metal-semiconductor-metal model. The carrier mobility was found to be several orders of magnitude higher than that have been reported previously for WS2 NTs. Water absorption was found to decrease the conductivity and carrier mobility of the NTs, and could be removed when the sample was dried. Oxygen absorption also slightly decreased the conductivity of WS2 NTs.

Reconstruction of TiO2/MnO2-C nanotube/nanoflake core/shell arrays as high-performance supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Xiong, Qinqin; Zheng, Cun; Chi, Hongzhong; Zhang, Jun; Ji, Zhenguo

2017-02-01

Construction of electrodes with fast reaction kinetics is of great importance for achieving advanced supercapacitors. Herein we report a facile combined synthetic strategy with atomic layer deposition (ALD) and electrodeposition to rationally fabricate nanotube/nanoflake core/shell arrays. ALD-TiO2 nanotubes are used as the skeleton core for assembly of electrodeposited MnO2-C nanoflake shells forming a core/shell structure. Highly porous architecture and good electrical conductivity are combined in this unique core/shell structure, resulting in fast ion/electron transfer. In tests of electrochemical performance, the TiO2/MnO2-C core/shell arrays are characterized as cathode for asymmetric supecapacitors and exhibit high specific capacitance (880 F g-1 at 2.5 A g-1), excellent rate properties (735 F g-1 at 30 A g-1) and good long-term cycling stability (94.3% capacitance retention after 20 000 cycles). The proposed electrode construction strategy is favorable for fabrication of other advanced supercapacitor electrodes.

Reconstruction of TiO2/MnO2-C nanotube/nanoflake core/shell arrays as high-performance supercapacitor electrodes.

PubMed

Xiong, Qinqin; Zheng, Cun; Chi, Hongzhong; Zhang, Jun; Ji, Zhenguo

2017-02-03

Construction of electrodes with fast reaction kinetics is of great importance for achieving advanced supercapacitors. Herein we report a facile combined synthetic strategy with atomic layer deposition (ALD) and electrodeposition to rationally fabricate nanotube/nanoflake core/shell arrays. ALD-TiO 2 nanotubes are used as the skeleton core for assembly of electrodeposited MnO 2 -C nanoflake shells forming a core/shell structure. Highly porous architecture and good electrical conductivity are combined in this unique core/shell structure, resulting in fast ion/electron transfer. In tests of electrochemical performance, the TiO 2 /MnO 2 -C core/shell arrays are characterized as cathode for asymmetric supecapacitors and exhibit high specific capacitance (880 F g -1 at 2.5 A g -1 ), excellent rate properties (735 F g -1 at 30 A g -1 ) and good long-term cycling stability (94.3% capacitance retention after 20 000 cycles). The proposed electrode construction strategy is favorable for fabrication of other advanced supercapacitor electrodes.

Enhanced photoelectrochemical degradation of Ibuprofen and generation of hydrogen via BiOI-deposited TiO2 nanotube arrays.

PubMed

Chen, Hanlin; Peng, Yen-Ping; Chen, Ting-Yu; Chen, Ku-Fan; Chang, Ken-Lin; Dang, Zhi; Lu, Gui-Ning; He, Hongping

2018-08-15

This study employed BiOI-deposited TiO 2 nanotube arrays (BiOI-TNTAs) electrode in a photoelectrochemical (PEC) system to oxidize Ibuprofen and generate hydrogen in the anodic and cathodic chamber, respectively. FESEM results revealed the diameter of TiO 2 nanotubes was 90-110nm. According to the XRD analysis, the BiOI-TNTAs were dominated by the anatase phase and tetragonal structure of BiOI. XPS results confirmed the coexistence of BiOI in the BiOI-TNTAs associated with Bi (33.76%) and I (8.81%). UV-vis absorption spectra illustrated BiOI-TNTAs exhibit strong absorptions in the visible light region. The PEC method showed the best degradation efficiency for Ibuprofen is a rate constant of 3.21×10 -2 min -1 . The results of the Nyquist plot revealed the recombination of photogenerated electron-hole pairs was inhibited as the bias potential was applied. Furthermore, the Bode plot demonstrated the lifetime (τ el ) of photoexcited electrons of BiOI-TNTAs was 1.8 and 4.1 times longer than that of BiOI-Ti and TNTAs, respectively. In the cathodic chamber, the amount of hydrogen generation reached 219.94μM/cm 2 after 3h of reaction time. Copyright © 2018 Elsevier B.V. All rights reserved.

Morphological alterations of T24 cells on flat and nanotubular TiO2 surfaces.

PubMed

Imani, Roghayeh; Kabaso, Doron; Erdani Kreft, Mateja; Gongadze, Ekaterina; Penic, Samo; Elersic, Kristina; Kos, Andrej; Veranic, Peter; Zorec, Robert; Iglic, Ales

2012-12-01

To investigate morphological alterations of malignant cancer cells (T24) of urothelial origin seeded on flat titanium (Ti) and nanotubular TiO(2) (titanium dioxide) nanostructures. Using anodization method, TiO(2) surfaces composed of vertically aligned nanotubes of 50-100 nm diameters were produced. The flat Ti surface was used as a reference. The alteration in the morphology of cancer cells was evaluated using scanning electron microscopy (SEM). A computational model, based on the theory of membrane elasticity, was constructed to shed light on the biophysical mechanisms responsible for the observed changes in the contact area of adhesion. Large diameter TiO(2) nanotubes exhibited a significantly smaller contact area of adhesion (P<0.0001) and had more membrane protrusions (eg, microvilli and intercellular membrane nanotubes) than on flat Ti surface. Numerical membrane dynamics simulations revealed that the low adhesion energy per unit area would hinder the cell spreading on the large diameter TiO(2) nanotubular surface, thus explaining the small contact area. The reduction in the cell contact area in the case of large diameter TiO(2) nanotube surface, which does not enable formation of the large enough number of the focal adhesion points, prevents spreading of urothelial cells.

Sustained neurotensin exposure promotes cell surface recruitment of NTS2 receptors

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

Perron, Amelie; Sharif, Nadder; Gendron, Louis

2006-05-12

In this study, we investigated whether persistent agonist stimulation of NTS2 receptors gives rise to down-regulation, in light of reports that their activation induced long-lasting effects. To address this issue, we incubated COS-7 cells expressing the rat NTS2 with neurotensin (NT) for up to 24 h and measured resultant cell surface [{sup 125}I]-NT binding. We found that NTS2-expressing cells retained the same surface receptor density despite efficient internalization mechanisms. This preservation was neither due to NTS2 neosynthesis nor recycling since it was not blocked by cycloheximide or monensin. However, it appeared to involve translocation of spare receptors from internal stores,more » as NT induced NTS2 migration from trans-Golgi network to endosome-like structures. This stimulation-induced regulation of cell surface NTS2 receptors was even more striking in rat spinal cord neurons. Taken together, these results suggest that sustained NTS2 activation promotes recruitment of intracellular receptors to the cell surface, thereby preventing functional desensitization.« less

Heterostructured ZnFe2O4/Fe2TiO5/TiO2 Composite Nanotube Arrays with an Improved Photocatalysis Degradation Efficiency Under Simulated Sunlight Irradiation

NASA Astrophysics Data System (ADS)

Xiong, Kun; Wang, Kunzhou; Chen, Lin; Wang, Xinqing; Fan, Qingbo; Courtois, Jérémie; Liu, Yuliang; Tuo, Xianguo; Yan, Minhao

2018-03-01

To improve the visible light absorption and photocatalytic activity of titanium dioxide nanotube arrays (TONTAs), ZnFe2O4 (ZFO) nanocrystals were perfused into pristine TONTA pipelines using a novel bias voltage-assisted perfusion method. ZFO nanocrystals were well anchored on the inner walls of the pristine TONTAs when the ZFO suspensions (0.025 mg mL-1) were kept under a 60 V bias voltage for 1 h. After annealing at 750 °C for 2 h, the heterostructured ZFO/Fe2TiO5 (FTO)/TiO2 composite nanotube arrays were successfully obtained. Furthermore, Fe3+ was reduced to Fe2+ when solid solution reactions occurred at the interface of ZFO and the pristine TONTAs. Introducing ZFO significantly enhanced the visible light absorption of the ZFO/FTO/TONTAs relative to that of the annealed TONTAs. The coexistence of type I and staggered type II band alignment in the ZFO/FTO/TONTAs facilitated the separation of photogenerated electrons and holes, thereby improving the efficiency of the ZFO/FTO/TONTAs for photocatalytic degradation of methylene blue when irradiated with simulated sunlight. [Figure not available: see fulltext.

Synthesis of Nb doped TiO2 nanotube/reduced graphene oxide heterostructure photocatalyst with high visible light photocatalytic activity

NASA Astrophysics Data System (ADS)

Niu, Xiaoyou; Yan, Weijing; Zhao, Hongli; Yang, Jingkai

2018-05-01

Limited by the narrowed photoresponse range and unsatisfactory recombination of photoinduced electron-hole pairs, the photocatalytic efficiency of TiO2 is still far below what is expected. Here, we initially doped TiO2 nanotubes (TNTS) by transition metal ion Nb, then it is coupled with reduced graphene oxide (rGO) to construct a heterostructure photocatalyst. The defect state presented in TiO2 leading to the formation of localized midgap states (MS) in the bandgap, which regulating the band structure of TiO2 and extending the optical absorption to visible light region. The internal charge transport and transfer behavior analyzed by electrochemical impedance spectroscopy (EIS) reveal that the coupling of rGO with TNTS results in the formation of electron transport channel in the heterostructure, which makes a great contribution to the photoinduced charge separation. As expected, the Nb-TNTS/rGO exhibits a stable and remarkably enhanced photocatalytic activity in the visible-light irradiation degradation of methylene blue (MB), up to ∼5 times with respect to TNTS, which is attributed to the effective inhibition of charge recombination, the reduction of bandgap and higher redox potential, as well as the great adsorptivity.

New Approach to Create TiO2(B)/Carbon Core/Shell Nanotubes: Ideal Structure for Enhanced Lithium Ion Storage.

PubMed

Zhu, Xiaoyi; Yang, Xianfeng; Lv, Chunxiao; Guo, Shaojun; Li, Jianjiang; Zheng, Zhanfeng; Zhu, Huaiyong; Yang, Dongjiang

2016-07-27

To achieve uniform carbon coating on TiO2 nanomaterials, high temperature (>500 °C) annealing treatment is a necessity. However, the annealing treatment inevitably leads to the strong phase transformation from TiO2(B) with high lithium ion storage (LIS) capacity to anatase with low LIS one as well as the damage of nanostructures. Herein, we demonstrate a new approach to create TiO2(B)/carbon core/shell nanotubes (C@TBNTs) using a long-chain silane polymethylhydrosiloxane (PMHS) to bind the TBNTs by forming Si-O-Ti bonds. The key feature of this work is that the introduction of PMHS onto TBNTs can afford TBNTs with very high thermal stability at higher than 700 °C and inhibit the phase transformation from TiO2(B) to anatase. Such a high thermal property of PMHS-TBNTs makes them easily coated with highly graphitic carbon shell via CVD process at 700 °C. The as-prepared C@TBNTs deliver outstanding rate capability and electrochemical stability, i.e., reversible capacity above 250 mAh g(-1) at 10 C and a high specific capacity of 479.2 mAh g(-1) after 1000 cycles at 1 C. As far as we know, the LIS performance of our sample is the highest among the previously reported TiO2(B) anode materials.

Influence of energy band alignment in mixed crystalline TiO2 nanotube arrays: good for photocatalysis, bad for electron transfer

NASA Astrophysics Data System (ADS)

Mohammadpour, Raheleh

2017-12-01

Despite the wide application ranges of TiO2, the precise explanation of the charge transport dynamic through a mixed crystal phase of this semiconductor has remained elusive. Here, in this research, mixed-phase TiO2 nanotube arrays (TNTAs) consisting of anatase and 0-15% rutile phases has been formed through various annealing processes and employed as a photoelectrode of a photovoltaic cell. Wide ranges of optoelectronic experiments have been employed to explore the band alignment position, as well as the depth and density of trap states in TNTAs. Short circuit potential, as well as open circuit potential measurements specified that the band alignment of more than 0.2 eV exists between the anatase and rutile phase Fermi levels, with a higher electron affinity for anatase; this can result in a potential barrier in crystallite interfaces and the deterioration of electron mobility through mixed phase structures. Moreover, a higher density of shallow localized trap states below the conduction band with more depth (133 meV in anatase to 247 meV in 15% rutile phase) and also deep oxygen vacancy traps have been explored upon introducing the rutile phase. Based on our results, employing TiO2 nanotubes as just the electron transport medium in mixed crystalline phases can deteriorate the charge transport mechanism, however, in photocatalytic applications when both electrons and holes are present, a robust charge separation in crystalline anatase/rutile interphases will result in better performances.

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

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.

Cobalt-Doped Black TiO2 Nanotube Array as a Stable Anode for Oxygen Evolution and Electrochemical Wastewater Treatment.

PubMed

Yang, Yang; Kao, Li Cheng; Liu, Yuanyue; Sun, Ke; Yu, Hongtao; Guo, Jinghua; Liou, Sofia Ya Hsuan; Hoffmann, Michael R

2018-05-04

TiO 2 has long been recognized as a stable and reusable photocatalyst for water splitting and pollution control. However, it is an inefficient anode material in the absence of photoactivation due to its low electron conductivity. To overcome this limitation, a series of conductive TiO 2 nanotube array electrodes have been developed. Even though nanotube arrays are effective for electrochemical oxidation initially, deactivation is often observed within a few hours. To overcome the problem of deactivation, we have synthesized cobalt-doped Black-TiO 2 nanotube array (Co-Black NTA) electrodes that are stable for more than 200 h of continuous operation in a NaClO 4 electrolyte at 10 mA cm -2 . Using X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, electron paramagnetic resonance spectroscopy, and DFT simulations, we are able to show that bulk oxygen vacancies (O v ) are the primary source of the enhanced conductivity of Co-Black. Cobalt doping both creates and stabilizes surficial oxygen vacancies, O v , and thus prevents surface passivation. The Co-Black electrodes outperform dimensionally stable IrO 2 anodes (DSA) in the electrolytic oxidation of organic-rich wastewater. Increasing the loading of Co leads to the formation of a CoO x film on top of Co-Black electrode. The CoO x /Co-Black composite electrode was found to have a lower OER overpotential (352 mV) in comparison to a DSA IrO 2 (434 mV) electrode and a stability that is greater than 200 h in a 1.0 M KOH electrolyte at a current density of 10 mA cm -2 .

Cobalt-Doped Black TiO2 Nanotube Array as a Stable Anode for Oxygen Evolution and Electrochemical Wastewater Treatment

PubMed Central

2018-01-01

TiO2 has long been recognized as a stable and reusable photocatalyst for water splitting and pollution control. However, it is an inefficient anode material in the absence of photoactivation due to its low electron conductivity. To overcome this limitation, a series of conductive TiO2 nanotube array electrodes have been developed. Even though nanotube arrays are effective for electrochemical oxidation initially, deactivation is often observed within a few hours. To overcome the problem of deactivation, we have synthesized cobalt-doped Black-TiO2 nanotube array (Co-Black NTA) electrodes that are stable for more than 200 h of continuous operation in a NaClO4 electrolyte at 10 mA cm–2. Using X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, electron paramagnetic resonance spectroscopy, and DFT simulations, we are able to show that bulk oxygen vacancies (Ov) are the primary source of the enhanced conductivity of Co-Black. Cobalt doping both creates and stabilizes surficial oxygen vacancies, Ov, and thus prevents surface passivation. The Co-Black electrodes outperform dimensionally stable IrO2 anodes (DSA) in the electrolytic oxidation of organic-rich wastewater. Increasing the loading of Co leads to the formation of a CoOx film on top of Co-Black electrode. The CoOx/Co-Black composite electrode was found to have a lower OER overpotential (352 mV) in comparison to a DSA IrO2 (434 mV) electrode and a stability that is greater than 200 h in a 1.0 M KOH electrolyte at a current density of 10 mA cm–2. PMID:29755829

Development of electrophoretically deposited hydroxyapatite coatings on anodized nanotubular TiO2 structures: Corrosion and sintering temperature

NASA Astrophysics Data System (ADS)

Goudarzi, Mona; Batmanghelich, Farhad; Afshar, Abdollah; Dolati, Abolghasem; Mortazavi, Golsa

2014-05-01

Hydroxyapatite (HA) coatings in and onto anodized TiO2 nanotube arrays were presented and prepared by electrophoretic deposition technique (EPD). Coatings were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). EPD proved to be an innovative and versatile technique to coat HA on and into nanotubular structures of TiO2 with enhanced adhesion between nanotubes and HA particles provided by mechanical interlocking. After EPD of HA on TiO2 layer, samples were sintered at 400 °C, 600 °C and 800 °C for 2 h in an Ar atmosphere. Effect of EPD processing parameters on thickness of the deposits and rate of deposition was elucidated for HA coatings on the nanotubular TiO2 structures. It was shown that higher applied voltages increase deposition rate and thickness of the coatings. Potentiodynamic polarization measurements proved corrosion protection caused by both HA coating and nanotubular TiO2 structure in simulated body fluid (SBF). Effect of sintering temperature on adhesion strength of HA coatings on TiO2 nanotubes and their composition were also studied.

Photoelectrocatalytic reduction of CO2 into chemicals using Pt-modified reduced graphene oxide combined with Pt-modified TiO2 nanotubes.

PubMed

Cheng, Jun; Zhang, Meng; Wu, Gai; Wang, Xin; Zhou, Junhu; Cen, Kefa

2014-06-17

The photoelectrocatalytic (PEC) reduction of CO2 into high-value chemicals is beneficial in alleviating global warming and advancing a low-carbon economy. In this work, Pt-modified reduced graphene oxide (Pt-RGO) and Pt-modified TiO2 nanotubes (Pt-TNT) were combined as cathode and photoanode catalysts, respectively, to form a PEC reactor for converting CO2 into valuable chemicals. XRD, XPS, TEM, AFM, and SEM were employed to characterize the microstructures of the Pt-RGO and Pt-TNT catalysts. Reduction products, such as C2H5OH and CH3COOH, were obtained from CO2 under band gap illumination and biased voltage. A combined liquid product generation rate (CH3OH, C2H5OH, HCOOH, and CH3COOH) of approximately 600 nmol/(h·cm(2)) was observed. Carbon atom conversion rate reached 1,130 nmol/(h·cm(2)), which were much higher than those achieved using Pt-modified carbon nanotubes and platinum carbon as cathode catalysts.

Double-walled structure of anodic TiO2 nanotubes in H3PO4/NH4F mixed electrolyte

NASA Astrophysics Data System (ADS)

Chen, Siyu; Chen, Ying; Li, Chengyuan; Ouyang, Huijun; Qin, Shuai; Song, Ye

2018-04-01

Normally, the well-ordered anodic TiO2 nanotubes (ATNTs) are obtained in NH4F electrolyte, after annealing, the double-walled structure of nanotubes will appear. Here, after adding H3PO4 into NHF4 electrolyte, we got the double-walled structure of nanotubes by anodizing without annealing, which means the direct existence of anion-contaminated layer in ATNTs. Influence of H3PO4 content on anodizing voltage and morphology of ATNTs were compared in detail. The XRD pattern illustrated that the crystallinity decreases with increasing H3PO4 concentration, and the anion-contaminated layer thickens with the increase of H3PO4 concentration. Meanwhile, the existence of the anion-contaminated layer also proved the limitations of the filed-assisted dissolution theory, while the double-walled structure can be explained by oxygen bubble model and plastic flow model.

Hydroxyapatite electrodeposition on anodized titanium nanotubes for orthopedic applications

NASA Astrophysics Data System (ADS)

Parcharoen, Yardnapar; Kajitvichyanukul, Puangrat; Sirivisoot, Sirinrath; Termsuksawad, Preecha

2014-08-01

Nanotubes modification for orthopedic implants has shown interesting biological performances (such as improving cell adhesion, cell differentiation, and enhancing osseointegration). The purpose of this study is to investigate effect of titanium dioxide (TiO2) nanotube feature on performance of hydroxyapatite-coated titanium (Ti) bone implants. TiO2 nanotubes were prepared by anodization using ammonium fluoride electrolyte (NH4F) with and without modifiers (PEG400 and Glycerol) at various potential forms, and times. After anodization, the nanotubes were subsequently annealed. TiO2 nanotubes were characterized by scanning electron microscope and X-ray diffractometer. The amorphous to anatase transformation due to annealing was observed. Smooth and highly organized TiO2 nanotubes were found when high viscous electrolyte, NH4F in glycerol, was used. Negative voltage (-4 V) during anodization was confirmed to increase nanotube thickness. Length of the TiO2 nanotubes was significantly increased by times. The TiO2 nanotube was electrodeposited with hydroxyapatite (HA) and its adhesion was estimated by adhesive tape test. The result showed that nanotubes with the tube length of 560 nm showed excellent adhesion. The coated HA were tested for biological test by live/dead cell straining. HA coated on TiO2 nanotubes showed higher cells density, higher live cells, and more spreading of MC3T3-E1 cells than that growing on titanium plate surface.

Highly efficient TiO2-based microreactor for photocatalytic applications.

PubMed

Krivec, Matic; Žagar, Kristina; Suhadolnik, Luka; Čeh, Miran; Dražić, Goran

2013-09-25

A photocatalytic, TiO2-based microreactor is designed and fabricated on a metal-titanium foil. The microchannel is mechanically engraved in the substrate foil, and a double-layered TiO2 anatase film is immobilized on its inner walls with a two-step synthesis, which included anodization and a hydrothermal treatment. X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirm the presence of an approximately 10-μm-thick layer of titania nanotubes and anatase nanoparticles. The SEM and transmission electron microscopy (TEM) of the cross sections show a dense interface between the titanium substrate and the TiO2 nanotubes. An additional layer of TiO2-anatase nanoparticles on the top of the film provides a large, photocatalytic surface area. The metal-titanium substrate with a functionalized serpentine channel is sealed with UV-transparent Plexiglas, and four 0.8-mW UV LEDs combined with a power controller on a small printed-circuit board are fixed over the substrate. The photocatalytic activity and the kinetic properties for the degradation of caffeine are provided, and the longer-term stability of the TiO2 film is evaluated. The results show that after 6 months of use and 3600 working cycles the microreactor still exhibits 60% of its initial efficiency.

Polyaniline nanotubes coated with TiO2&γ-Fe2O3@graphene oxide as a novel and effective visible light photocatalyst for removal of rhodamine B from water

NASA Astrophysics Data System (ADS)

Ghavami, Monireh; Kassaee, Mohammad Zaman; Mohammadi, Reza; Koohi, Maryam; Haerizadeh, Bibi Narjes

2014-12-01

Synthesis of polyaniline-nanotubes (PANI-NT), in the presence of TiO2 and γ-Fe2O3 functionalized graphene oxide (GO), gives a green and magnetically recyclable photocatalyst, TiO2&γ-Fe2O3@GO/PANI-NT. The later orchestrates 94% photocatalytic efficiency in removal of rhodamine B (RB) from water, under simulated solar light irradiation. This is far higher than the 36% observed in the presence of TiO2&γ-Fe2O3@GO alone, where PANI-NT is excluded from the structure. Morphology, composition, and structural properties of our economically sound photocatalyst are characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy, thermo-gravimetric, transmission electron microscopy, inductively coupled plasma, RAMAN and Fourier-transform infrared spectroscopy.

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.

One-dimensional TiO2 nanomaterials: preparation and catalytic applications.

PubMed

Wu, Yu; Yu, Jie; Liu, Hong-Mei; Xu, Bo-Qing

2010-10-01

This work reports on the syntheses of one-dimensional (1D) H2Ti3O7 materials (nanotubes, nanowires and their mixtures) by autoclaving anatase titania (Raw-TiO2) in NaOH-containing ethanol-water solutions, followed by washing with acid solution. The synthesized nanosized materials were characterized using XRD, TEM/HRTEM, BET and TG techniques. The autoclaving temperature (120-180 degrees C) and ethanol-to-water ratio (V(EtOH)/V(H2O) = 0/60 approximately 30/30) were shown to be critical to the morphology of H2Ti3O7 product. The obtained H2Ti3O7 nanostructures were calcined at 400-900 degrees C to prepare 1D-TiO2 nanomaterials. H2Ti3O7 nanotubes were converted to anatase nanorods while H2Ti3O7 nanowires to TiO2(B) nanowires after the calcination at 400 degrees C. The calcination at higher temperatures led to gradual decomposition of the wires to rods and phase transformation from TiO2(B) to anatase then to rutile. Photocatalytic degradation of methyl orange was conducted to compare the photocatalytic activity of these 1D materials. These 1D materials were used as new support to prepare Au/TiO2 catalysts for CO oxidation at 0 degrees C and 1,3-butadiene hydrogenation at 120 degrees C. For the CO oxidation reaction, Au particles supported on anatase nanorods derived from the H2Ti3O7 nanotubes (Au/W-180-400) were 1.6 times active that in Au/P25-TiO2, 4 times that in Au/Raw-TiO2, and 8 times that on TiO2(B) nanowires derived from the H2Ti3O7 nanotubes (Au/M-180-400). For the hydrogenation of 1,3-butadiene, however, the activity of Au particles in Au/M-180-400 was 3 times higher than those in Au/W-180-400 but similar to those in Au/P25-TiO2. These results demonstrate that the potential of 1D-TiO2 nanomaterials in catalysis is versatile.

Mechanical properties investigation on single-wall ZrO2 nanotubes: A finite element method with equivalent Poisson's ratio for chemical bonds

NASA Astrophysics Data System (ADS)

Yang, Xiao; Li, Huijian; Hu, Minzheng; Liu, Zeliang; Wärnå, John; Cao, Yuying; Ahuja, Rajeev; Luo, Wei

2018-04-01

A method to obtain the equivalent Poisson's ratio in chemical bonds as classical beams with finite element method was proposed from experimental data. The UFF (Universal Force Field) method was employed to calculate the elastic force constants of Zrsbnd O bonds. By applying the equivalent Poisson's ratio, the mechanical properties of single-wall ZrNTs (ZrO2 nanotubes) were investigated by finite element analysis. The nanotubes' Young's modulus (Y), Poisson's ratio (ν) of ZrNTs as function of diameters, length and chirality have been discussed, respectively. We found that the Young's modulus of single-wall ZrNTs is calculated to be between 350 and 420 GPa.

A Novel of Buton Asphalt and Methylene Blue as Dye-Sensitized Solar Cell using TiO2/Ti Nanotubes Electrode

NASA Astrophysics Data System (ADS)

Nurhidayani; Muzakkar, M. Z.; Maulidiyah; Wibowo, D.; Nurdin, M.

2017-11-01

A study of TiO2/Ti nanotubes arrays (NTAs) based on Dye-Sensitized Solar Cell (DSSC) used Asphalt Buton (Asbuton) extract and methylene blue (MB) as a photosensitizer dye has been conducted. The aim of this research is that the Asbuton extract and Methylene Blue (MB) performance as a dye on DSSC solar cells is able to obtain the voltage-currents produced by visible light irradiation. Electrode TiO2/Ti NTAs have been successfully synthesized by anodizing methods, then characterized by using XRD showed that the anatase crystals formed. Subsequently, the morphology showed that the nanotubes formed which has coated by Asbuton extract. The DSSC system was formed by a sandwich structure and tested by using Multimeter Digital with Potentiostat instrument. The characteristics of current (I) and potential (V) versus time indicated that the Asbuton was obtained in a high-performance in 30s of 14,000µV 0.844µA, meanwhile MB dyes were 8,000µV0.573µA. Based on this research, the Asbuton extract from Buton Island-Southeast Sulawesi-Indonesia was potential for natural dyes in DSSC system.

Formation of anodic TiO2 nanotube arrays in NaOH added fluoride-ethylene glycol electrolyte for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Nyein, Nyein; Tan, Wai Kian; Kawamura, Go; Matsuda, Atsunori; Lockman, Zainovia

2017-07-01

TiO2 nanotube (TNT) arrays were formed by anodizing titanium foil in fluoride-ethylene glycol (EG) electrolyte added to it either water (H2O) or sodium hydroxide (NaOH) as oxidant. In NaOH added fluoride-EG electrolyte, 10 µm long TNT arrays were formed compared to 5 μm long nanotubes in H2O added fluoride-EG electrolyte. When NaOH was added to EG, the electrolyte pH was 9. As the pH of the electrolyte was rather high, surface etching of the nanotubes was reduced resulting in tubes with longer length. Moreover, the addition of NaOH into fluoride-EG resulted in the crystallization of anatase in the as-made TNT arrays. Annealing obviously improved the crystallinity of the oxide. The TNT arrays were then used as a photoanode in a dye-sensitized solar cell (DSSC). A photoconversion efficiency of 2.4 % was recorded with photocurrent of 6.9 mA/cm2.

Are TiO2 nanotubes worth using in photocatalytic purification of air and water?

PubMed

Pichat, Pierre

2014-09-19

Titanium dioxide nanotubes (TNT) have mainly been used in dye sensitized solar cells, essentially because of a higher transport rate of electrons from the adsorbed photo-excited dye to the Ti electrode onto which TNT instead of TiO2 nanoparticles (TNP) are attached. The dimension ranges and the two main synthesis methods of TNT are briefly indicated here. Not surprisingly, the particular and regular texture of TNT was also expected to improve the photocatalytic efficacy for pollutant removal in air and water with respect to TNP. In this short review, the validity of this expectation is checked using the regrettably small number of literature comparisons between TNT and commercialized TNP referring to films of similar thickness and layers or slurries containing an equal TiO2 mass. Although the irradiated geometrical area differed for each study, it was identical for each comparison considered here. For the removal of toluene (methylbenzene) or acetaldehyde (ethanal) in air, the average ratio of the efficacy of TNT over that of TiO2 P25 was about 1.5, and for the removal of dyes in water, it was around 1. This lack of major improvement with TNT compared to TNP could partially be due to TNT texture disorders as seems to be suggested by the better average performance of anodic oxidation-prepared TNT. It could also come from the fact that the properties influencing the efficacy are more numerous, their interrelations more complex and their effects more important for pollutant removal than for dye sensitized solar cells and photoelectrocatalysis where the electron transport rate is the crucial parameter.

Selection of a novel peptide aptamer with high affinity for TiO2-nanoparticle through a direct electroporation with TiO2-binding phage complexes.

PubMed

Inoue, Ippei; Ishikawa, Yasuaki; Uraoka, Yukiharu; Yamashita, Ichiro; Yasueda, Hisashi

2016-11-01

We have developed an easy and rapid screening method of peptide aptamers with high affinity for a target material TiO 2 using M13 phage-display and panning procedure. In a selection step, the phage-substrate complexes and Escherichia coli cells were directly applied by electric pulse for electroporation, without separating the objective phages from the TiO 2 nanoparticles. Using this simple and rapid method, we obtained a novel peptide aptamer (named ST-1 with the sequence AYPQKFNNNFMS) with highly strong binding activity for TiO 2 . A cage-shaped protein fused with both ST-1 and an available carbon nanotube-affinity peptide was designed and produced in E. coli. The multi-functional supraprotein could efficiently mineralize a titanium-compound around the surface of single-wall carbon nanotubes (SWNTs), indicating that the ST-1 is valuable in the fabrication of nano-composite materials with titanium-compounds. The structural analysis of ST-1 variants indicated the importance of the N-terminal region (as a motif of AXPQKX 6 S) of the aptamer in the TiO 2 -binding activity. Copyright © 2016 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Homogeneous growth of TiO2-based nanotubes on nitrogen-doped reduced graphene oxide and its enhanced performance as a Li-ion battery anode.

PubMed

Mehraeen, Shayan; Taşdemir, Adnan; Gürsel, Selmiye Alkan; Yürüm, Alp

2018-06-22

The pursuit of a promising replacement candidate for graphite as a Li-ion battery anode, which can satisfy both engineering criteria and market needs has been the target of researchers for more than two decades. In this work, we have investigated the synergistic effect of nitrogen-doped reduced graphene oxide (NrGO) and nanotubular TiO 2 to achieve high rate capabilities with high discharge capacities through a simple, one-step and scalable method. First, nanotubes of hydrogen titanate were hydrothermally grown on the surface of NrGO sheets, and then converted to a mixed phase of TiO 2 -B and anatase (TB) by thermal annealing. Specific surface area, thermal gravimetric, structural and morphological characterizations were performed on the synthesized product. Electrochemical properties were investigated by cyclic voltammetry and cyclic charge/discharge tests. The prepared anode showed high discharge capacity of 150 mAh g -1 at 1 C current rate after 50 cycles. The promising capacity of synthesized NrGO-TB was attributed to the unique and novel microstructure of NrGO-TB in which long nanotubes of TiO 2 have been grown on the surface of NrGO sheets. Such architecture synergistically reduces the solid-state diffusion distance of Li + and increases the electronic conductivity of the anode.

Homogeneous growth of TiO2-based nanotubes on nitrogen-doped reduced graphene oxide and its enhanced performance as a Li-ion battery anode

NASA Astrophysics Data System (ADS)

Mehraeen, Shayan; Taşdemir, Adnan; Alkan Gürsel, Selmiye; Yürüm, Alp

2018-06-01

The pursuit of a promising replacement candidate for graphite as a Li-ion battery anode, which can satisfy both engineering criteria and market needs has been the target of researchers for more than two decades. In this work, we have investigated the synergistic effect of nitrogen-doped reduced graphene oxide (NrGO) and nanotubular TiO2 to achieve high rate capabilities with high discharge capacities through a simple, one-step and scalable method. First, nanotubes of hydrogen titanate were hydrothermally grown on the surface of NrGO sheets, and then converted to a mixed phase of TiO2-B and anatase (TB) by thermal annealing. Specific surface area, thermal gravimetric, structural and morphological characterizations were performed on the synthesized product. Electrochemical properties were investigated by cyclic voltammetry and cyclic charge/discharge tests. The prepared anode showed high discharge capacity of 150 mAh g‑1 at 1 C current rate after 50 cycles. The promising capacity of synthesized NrGO-TB was attributed to the unique and novel microstructure of NrGO-TB in which long nanotubes of TiO2 have been grown on the surface of NrGO sheets. Such architecture synergistically reduces the solid-state diffusion distance of Li+ and increases the electronic conductivity of the anode.

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

NASA Astrophysics Data System (ADS)

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

2014-02-01

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

Effects of hydrogenated TiO2 nanotube arrays on protein adsorption and compatibility with osteoblast-like cells.

PubMed

Lu, Ran; Wang, Caiyun; Wang, Xin; Wang, Yuji; Wang, Na; Chou, Joshua; Li, Tao; Zhang, Zhenting; Ling, Yunhan; Chen, Su

2018-01-01

Modified titanium (Ti) substrates with titanium dioxide (TiO 2 ) nanotubes have broad usage as implant surface treatments and as drug delivery systems. To improve drug-loading capacity and accelerate bone integration with titanium, in this study, we hydrogenated anodized titanium dioxide nanotubes (TNTs) by a thermal treatment. Three groups were examined, namely: hydrogenated TNTs (H 2 -TNTs, test), unmodified TNTs (air-TNTs, control), and Ti substrates (Ti, control). Our results showed that oxygen vacancies were present in all the nanotubes. The quantity of -OH groups greatly increased after hydrogenation. Furthermore, the protein adsorption and loading capacity of the H 2 -TNTs were considerably enhanced as compared with the properties of the air-TNTs ( P <0.05). Additionally, time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to investigate the interactions of TNTs with proteins. During the protein-loading process, the H 2 -TNTs not only enabled rapid protein adsorption, but also decreased the rate of protein elution compared with that of the air-TNTs. We found that the H 2 -TNTs exhibited better biocompatibility than the air-TNT and Ti groups. Both cell adhesion activity and alkaline phosphatase activity were significantly improved toward MG-63 human osteoblast-like cells as compared with the control groups ( P <0.05). We conclude that hydrogenated TNTs could greatly improve the loading capacity of bioactive molecules and MG-63 cell proliferation.

Effects of proton irradiation on structural and electrochemical charge storage properties of TiO 2 nanotube electrodes for lithium-ion batteries

DOE PAGES

Smith, Kassiopeia A.; Savva, Andreas I.; Deng, Changjian; ...

2017-03-23

The effects of proton irradiation on nanostructured metal oxides have been investigated. Recent studies suggest that the presence of structural defects (e.g. vacancies and interstitials) in metal oxides may enhance the material's electrochemical charge storage capacity. A new approach to introduce defects in electrode materials is to use ion irradiation as it can produce a supersaturation of point defects in the target material. In this work we report the effect of low-energy proton irradiation on amorphous TiO 2 nanotube electrodes at both room temperature and high temperature (250 °C). Upon room temperature irradiation the nanotubes demonstrate an irradiation-induced phase transformationmore » to a mixture of amorphous, anatase, and rutile domains while showing a 35% reduction in capacity compared to anatase TiO 2. On the other hand, the high temperature proton irradiation induced a disordered rutile phase within the nanotubes as characterized by Raman spectroscopy and transmission electron microscopy, which displays an improved capacity by 20% at ~240 mA h g –1 as well as improved rate capability compared to an unirradiated anatase sample. Voltammetric sweep data were used to determine the contributions from diffusion-limited intercalation and capacitive processes and it was found that the electrodes after irradiation had more contributions from diffusion in lithium charge storage. Finally, our work suggests that tailoring the defect generation through ion irradiation within metal oxide electrodes could present a new avenue for designing advanced electrode materials.« less

Effects of proton irradiation on structural and electrochemical charge storage properties of TiO 2 nanotube electrodes for lithium-ion batteries

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

Smith, Kassiopeia A.; Savva, Andreas I.; Deng, Changjian

The effects of proton irradiation on nanostructured metal oxides have been investigated. Recent studies suggest that the presence of structural defects (e.g. vacancies and interstitials) in metal oxides may enhance the material's electrochemical charge storage capacity. A new approach to introduce defects in electrode materials is to use ion irradiation as it can produce a supersaturation of point defects in the target material. In this work we report the effect of low-energy proton irradiation on amorphous TiO 2 nanotube electrodes at both room temperature and high temperature (250 °C). Upon room temperature irradiation the nanotubes demonstrate an irradiation-induced phase transformationmore » to a mixture of amorphous, anatase, and rutile domains while showing a 35% reduction in capacity compared to anatase TiO 2. On the other hand, the high temperature proton irradiation induced a disordered rutile phase within the nanotubes as characterized by Raman spectroscopy and transmission electron microscopy, which displays an improved capacity by 20% at ~240 mA h g –1 as well as improved rate capability compared to an unirradiated anatase sample. Voltammetric sweep data were used to determine the contributions from diffusion-limited intercalation and capacitive processes and it was found that the electrodes after irradiation had more contributions from diffusion in lithium charge storage. Finally, our work suggests that tailoring the defect generation through ion irradiation within metal oxide electrodes could present a new avenue for designing advanced electrode materials.« less

Dispersions of geometric TiO2 nanomaterials and their toxicity to RPMI 2650 nasal epithelial cells

NASA Astrophysics Data System (ADS)

Tilly, Trevor B.; Kerr, Lei L.; Braydich-Stolle, Laura K.; Schlager, John J.; Hussain, Saber M.

2014-11-01

Titanium dioxide (TiO2) based nanofilaments—nanotube, nanowire, nanorod—have gained interest for industrial, electrical, and as of recent, medical applications due to their superior performance over TiO2 nanoparticles. Safety assessment of these nanomaterials is critical to protect workers, patients, and bystanders as these technologies become widely implemented. Additionally, TiO2 based nanofilaments can easily be inhaled by humans and their high aspect ratio, much like asbestos fibers, may make them toxic in the respiratory system. The tendency of TiO2 nanofilaments to aggregate makes evaluating their nanotoxicity difficult and the results controversial, because incomplete dispersion results in larger particle sizes that are no longer in the nano dimensional size range. TiO2 nanofilaments are aggregated and difficult to disperse homogeneously in solution by conventional methods, such as sonication and vortexing. In this study, a microfluidic device was utilized to produce stable, homogeneous dosing solutions necessary for in vitro toxicity evaluation by eliminating any toxicity caused by aggregated TiO2 nanomaterials. The toxicity results could then be directly correlated to the TiO2 nanostructure itself. The toxicity of four TiO2 nanogeometries—nanotube, nanowire, nanorod, and nanoparticle—were assessed in RPMI 2650 human nasal epithelial cells at representative day, week, and month in vitro exposure dosages of 10, 50, 100 μg/ml, respectively. All TiO2 based nanomaterials dispersed by the microfluidic method were nontoxic to RPMI 2650 cells at the concentrations tested, whereas higher concentrations of 100 μg/ml of nanowires and nanotubes dispersed by sonication reduced viability up to 27 %, indicating that in vitro toxicity results may be controlled by the dispersion of dosing solutions.

Structural transformation and enhanced gas sensing characteristics of TiO2 nanostructures induced by annealing

NASA Astrophysics Data System (ADS)

Tshabalala, Zamaswazi P.; Motaung, David E.; Swart, Hendrik C.

2018-04-01

The improved sensitivity and selectivity, and admirable stability are fundamental features required for the current age gas sensing devices to appease future humanity and environmental requirements. Therefore, herein, we report on the room temperature gas sensing behaviour of TiO2 nanotubes with significance response and sensitivity towards 60 ppm NO2 gas. Improved sensitivity of 29.44 ppm-1 and admirable selectivity towards NO2, among other gases ensuring adequate safety in monitoring NO2 in automobile and food industries. The improved sensitivity of TiO2 nanotubes was attributed to larger surface area provided by the hollow nanotubes resulting to improved gas adsorption and the relatively high concentration of oxygen vacancies.

Structural and electronic properties of chiral single-wall copper nanotubes

NASA Astrophysics Data System (ADS)

Duan, YingNi; Zhang, JianMin; Xu, KeWei

2014-04-01

The structural, energetic and electronic properties of chiral ( n, m) (3⩽ n⩽6, n/2⩽ m⩽ n) single-wall copper nanotubes (CuNTs) have been investigated by using projector-augmented wave method based on density-functional theory. The (4, 3) CuNT is energetically stable and should be observed experimentally in both free-standing and tip-suspended conditions, whereas the (5, 5) and (6, 4) CuNTs should be observed in free-standing and tip-suspended conditions, respectively. The number of conductance channels in the CuNTs does not always correspond to the number of atomic strands comprising the nanotube. Charge density contours show that there is an enhanced interatomic interaction in CuNTs compared with Cu bulk. Current transporting states display different periods and chirality, the combined effects of which lead to weaker chiral currents on CuNTs.

Engineering of highly ordered TiO2 nanopore arrays by anodization

NASA Astrophysics Data System (ADS)

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

2016-07-01

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

Betavoltaic Enhancement Using Defect-Engineered TiO2 Nanotube Arrays through Electrochemical Reduction in Organic Electrolytes.

PubMed

Ma, Yang; Wang, Na; Chen, Jiang; Chen, Changsong; San, Haisheng; Chen, Jige; Cheng, Zhengdong

2018-06-19

Utilizing high-energy beta particles emitted from radioisotopes for long-lifetime betavoltaic cells is a great challenge due to low energy conversion efficiency. Here, we report a betavoltaic cell fabricated using TiO 2 nanotube arrays (TNTAs) electrochemically reduced in ethylene glycol electrolyte (EGECR-TNTAs) for the enhancement of the betavoltaic effect. The electrochemical reduction of TNTAs using high cathodic bias in organic electrolytes is indeed a facile and effective strategy to induce in situ self-doping of oxygen vacancy (OV) and Ti 3+ defects. The black EGECR-TNTAs are highly stable with a significantly narrower band gap and higher electrical conductivity as well as UV-vis-NIR light absorption. A 20 mCi of 63 Ni betavoltaic cell based on the reduced TNTAs exhibits a maximum ECE of 3.79% with open-circuit voltage of 1.04 V, short-circuit current density of 117.5 nA cm -2 , and a maximum power density of 39.2 nW cm -2 . The betavoltaic enhancement can be attributed to the enhanced charge carrier transport and separation as well as multiple exciton generation of electron-hole pairs due the generation of OV and Ti 3+ interstitial bands below the conductive band of TiO 2.

Hierarchical Oriented Anatase TiO2 Nanostructure arrays on Flexible Substrate for Efficient Dye-sensitized Solar Cells

PubMed Central

Wu, Wu-Qiang; Rao, Hua-Shang; Xu, Yang-Fan; Wang, Yu-Fen; Su, Cheng-Yong; Kuang, Dai-Bin

2013-01-01

The vertically oriented anatase single crystalline TiO2 nanostructure arrays (TNAs) consisting of TiO2 truncated octahedrons with exposed {001} facets or hierarchical TiO2 nanotubes (HNTs) consisting of numerous nanocrystals on Ti-foil substrate were synthesized via a two-step hydrothermal growth process. The first step hydrothermal reaction of Ti foil and NaOH leads to the formation of H-titanate nanowire arrays, which is further performed the second step hydrothermal reaction to obtain the oriented anatase single crystalline TiO2 nanostructures such as TiO2 nanoarrays assembly with truncated octahedral TiO2 nanocrystals in the presence of NH4F aqueous or hierarchical TiO2 nanotubes with walls made of nanocrystals in the presence of pure water. Subsequently, these TiO2 nanostructures were utilized to produce dye-sensitized solar cells in a backside illumination pattern, yielding a significant high power conversion efficiency (PCE) of 4.66% (TNAs, JSC = 7.46 mA cm−2, VOC = 839 mV, FF = 0.75) and 5.84% (HNTs, JSC = 10.02 mA cm−2, VOC = 817 mV, FF = 0.72), respectively. PMID:23715529

Heterojunctions of mixed phase TiO2 nanotubes with Cu, CuPt, and Pt nanoparticles: interfacial band alignment and visible light photoelectrochemical activity

NASA Astrophysics Data System (ADS)

Kar, Piyush; Zhang, Yun; Mahdi, Najia; Thakur, Ujwal K.; Wiltshire, Benjamin D.; Kisslinger, Ryan; Shankar, Karthik

2018-01-01

Anodically formed, vertically oriented, self-organized cylindrical TiO2 nanotube arrays composed of the anatase phase undergo an interesting morphological and phase transition upon flame annealing to square-shaped nanotubes composed of both anatase and rutile phases. This is the first report on heterojunctions consisting of metal nanoparticles (NPs) deposited on square-shaped TiO2 nanotube arrays (STNAs) with mixed rutile and anatase phase content. A simple photochemical deposition process was used to form Cu, CuPt, and Pt NPs on the STNAs, and an enhancement in the visible light photoelectrochemical water splitting performance for the NP-decorated STNAs was observed over the bare STNAs. Under narrow band illumination by visible photons at 410 nm and 505 nm, Cu NP-decorated STNAs performed the best, producing photocurrents 80% higher and 50 times higher than bare STNAs, respectively. Probing the energy level structure at the NP-STNA interface using ultraviolet photoelectron spectroscopy revealed Schottky barrier formation in the NP-decorated STNAs, which assists in separating the photogenerated charge carriers, as also confirmed by longer charge carrier lifetimes in NP-decorated STNAs. While all the NP-decorated STNAs showed enhanced visible light absorption compared to the bare STNAs, only the Cu NPs exhibited a clear plasmonic behavior with an extinction cross section that peaked at 550 nm.

Heterojunctions of mixed phase TiO2 nanotubes with Cu, CuPt, and Pt nanoparticles: interfacial band alignment and visible light photoelectrochemical activity.

PubMed

Kar, Piyush; Zhang, Yun; Mahdi, Najia; Thakur, Ujwal K; Wiltshire, Benjamin D; Kisslinger, Ryan; Shankar, Karthik

2018-01-05

Anodically formed, vertically oriented, self-organized cylindrical TiO 2 nanotube arrays composed of the anatase phase undergo an interesting morphological and phase transition upon flame annealing to square-shaped nanotubes composed of both anatase and rutile phases. This is the first report on heterojunctions consisting of metal nanoparticles (NPs) deposited on square-shaped TiO 2 nanotube arrays (STNAs) with mixed rutile and anatase phase content. A simple photochemical deposition process was used to form Cu, CuPt, and Pt NPs on the STNAs, and an enhancement in the visible light photoelectrochemical water splitting performance for the NP-decorated STNAs was observed over the bare STNAs. Under narrow band illumination by visible photons at 410 nm and 505 nm, Cu NP-decorated STNAs performed the best, producing photocurrents 80% higher and 50 times higher than bare STNAs, respectively. Probing the energy level structure at the NP-STNA interface using ultraviolet photoelectron spectroscopy revealed Schottky barrier formation in the NP-decorated STNAs, which assists in separating the photogenerated charge carriers, as also confirmed by longer charge carrier lifetimes in NP-decorated STNAs. While all the NP-decorated STNAs showed enhanced visible light absorption compared to the bare STNAs, only the Cu NPs exhibited a clear plasmonic behavior with an extinction cross section that peaked at 550 nm.

Electrochemical preparation of vertically aligned, hollow CdSe nanotubes and their p-n junction hybrids with electrodeposited Cu2O

NASA Astrophysics Data System (ADS)

Debgupta, Joyashish; Devarapalli, Ramireddy; Rahman, Shakeelur; Shelke, Manjusha V.; Pillai, Vijayamohanan K.

2014-07-01

Vertically aligned, hollow nanotubes of CdSe are grown on fluorine doped tin oxide (FTO) coated glass substrates by ZnO nanowire template-assisted electrodeposition technique, followed by selective removal of the ZnO core using NH4OH. A detailed mechanism of nucleation and anisotropic growth kinetics of nanotubes have been studied by a combination of characterization tools such as chronoamperometry, SEM and TEM. Interestingly, ``as grown'' CdSe nanotubes (CdSe NTs) on FTO coated glass plates behave as n-type semiconductors exhibiting an excellent photo-response (with a generated photocurrent density value of ~470 μA cm-2) while in contact with p-type Cu2O (p-type semiconductor, grown separately on FTO plates) because of the formation of a n-p heterojunction (type II). The observed photoresponse is 3 times higher than that of a similar device prepared with electrodeposited CdSe films (not nanotubes) and Cu2O on FTO. This has been attributed to the hollow 1-D nature of CdSe NTs, which provides enhanced inner and outer surface areas for better absorption of light and also assists faster transport of photogenerated charge carriers.Vertically aligned, hollow nanotubes of CdSe are grown on fluorine doped tin oxide (FTO) coated glass substrates by ZnO nanowire template-assisted electrodeposition technique, followed by selective removal of the ZnO core using NH4OH. A detailed mechanism of nucleation and anisotropic growth kinetics of nanotubes have been studied by a combination of characterization tools such as chronoamperometry, SEM and TEM. Interestingly, ``as grown'' CdSe nanotubes (CdSe NTs) on FTO coated glass plates behave as n-type semiconductors exhibiting an excellent photo-response (with a generated photocurrent density value of ~470 μA cm-2) while in contact with p-type Cu2O (p-type semiconductor, grown separately on FTO plates) because of the formation of a n-p heterojunction (type II). The observed photoresponse is 3 times higher than that of a similar

Linear Optical Response of Silicon Nanotubes Under Axial Magnetic Field

NASA Astrophysics Data System (ADS)

Chegel, Raad; Behzad, Somayeh

2013-01-01

We investigated the optical properties of silicon nanotubes (SiNTs) in the low energy region, E < 0.5 eV, and middle energy region, 1.8 eV < E < 2 eV. The dependence of optical matrix elements and linear susceptibility on radius and magnetic field, in terms of one-dimensional (1-d) wavevector and subband index, is calculated using the tight-binding approximation. It is found that, on increasing the nanotube diameter, the low-energy peaks show red-shift and their intensities are decreased. Also, we found that in the middle energy region all tubes have two distinct peaks, where the energy position of the second peak is approximately constant and independent of the nanotube diameter. Comparing the band structure of these tubes in different magnetic fields, several differences are clearly seen, such as splitting of degenerate bands, creation of additional band-edge states, and bandgap modification. It is found that applying the magnetic field leads to a phase transition in zigzag silicon hexagonal nanotubes (Si h-NTs), unlike in zigzag silicon gear-like nanotubes (Si g-NTs), which remain semiconducting in any magnetic field. We found that the axial magnetic field has two effects on the linear susceptibility spectrum, namely broadening and splitting. The axial magnetic field leads to the creation of a peak with energy less than 0.2 eV in metallic Si h-NTs, whereas in the absence of a magnetic field such a transition is not allowed.

Boosted surface acidity in TiO2 and Al2O3-TiO2 nanotubes as catalytic supports

NASA Astrophysics Data System (ADS)

Camposeco, R.; Castillo, S.; Mejía-Centeno, Isidro; Navarrete, J.; Nava, N.

2015-11-01

In this study, titanate nanotubes (NT) and titanate nanotubes with alumina (NT-Al) were studied as solid acid catalytic supports to show the relationship between the kind of acidity and catalytic activity. The supports were characterized by XRD, TEM, FTIR, XPS, and tested in the SCR-NO with NH3. It was found that the amount of Brönsted acid sites was maintained and the Lewis acid sites were significantly affected by the addition of alumina (1, 3, 5 and 10 wt.%); such acidity was higher than that of the titanate nanotubes (NT) by two-fold. To confirm the formation of titanate nanotubes and titanate nanotubes with alumina, transmission electron microscopy (TEM) was used. X-ray diffraction (XRD) revealed the formation of the H2Ti4O9·H2O phase. All NT and NT-Al supports presented catalytic activity to remove NO with NH3 under lean conditions, confirming the presence of an important amount of Brönsted and Lewis acid sites in both NT and NT-Al supports.

Photocatalytic oxidation of propylene on La and N codoped TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Liu, Jinfeng; Li, Haiyan; Zong, Lanlan; Li, Qiuye; Wang, Xiaodong; Zhang, Min; Yang, Jianjun

2015-02-01

Lanthanum- and nitrogen-codoped TiO2 photocatalysts was synthesized using orthorhombic nanotubes titanic acid as the precursor by a simple impregnation and subsequent calcination method. The morphology, phase structure, and properties of La- and N-codoped TiO2 were well characterized by transmission electron microscopy, X-ray diffraction, Raman spectra, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectra. The La-/N-codoped TiO2 showed excellent photoactivity of propylene oxidation compared with the single-doped TiO2 and La-/N-codoped P25 TiO2 nanoparticles under visible light irradiation. The origin of the enhancement of the visible light-responsive photocatalytic activity was discussed in detail.

Cr(VI) removal on visible light active TiO2 nanotube arrays

NASA Astrophysics Data System (ADS)

Bashirom, Nurulhuda; Zulkifli, Muhammad Afiq; Subagja, Subagja; Kian, Tan Wai; Matsuda, Atsunori; Lockman, Zainovia

2018-05-01

Self-organized TiO2 nanotube (TNT) arrays were fabricated by anodic oxidation of titanium foil in three different fluoride electrolytes: ethylene glycol (EG), glycerol, and sodium sulfate (Na2SO4) at different voltage and anodization time. In these electrolytes, the TNTs were produced in ˜ 2 µm long, but at the different diameter. The size of inner diameter can be arranged from the largest to the smallest value in the order of glycerol > EG > Na2SO4. Crystallization of the TNTs by annealing was led to the formation of anatase-TiO2. The sample can be activated under natural sunlight for reduction of hexavalent chromium, Cr(VI) into trivalent chromium, Cr(III). The reduction was thought to occur via synergistic reactions between adsorption and photoreduction. The result demonstrates 100 % of Cr(VI) removal efficiency over the TNTs grown in EG after 120 min. Whereas, only 48 % and 45 % of Cr(VI) can be removed over the TNTs fabricated in glycerol and Na2SO4, respectively. High photocatalytic activity of the TNTs-EG can be attributed to high crystallinity of anatase phase, enhanced Cr(VI) adsorption, and less electron-hole recombination due to smoother tube walls.

Photo-Catalytic Properties of TiO2 Supported on MWCNTs, SBA-15 and Silica-Coated MWCNTs Nanocomposites.

PubMed

Ramoraswi, Nteseng O; Ndungu, Patrick G

2015-12-01

Mesoporous silica, specifically SBA-15, acid-treated multi-walled carbon nanotubes and a hybrid nanocomposite of SBA-15 coated onto the sidewalls acid-treated multi-walled carbon nanotubes (CNTs) were prepared and used as supports for anatase TiO2. Sol-gel methods were adapted for the synthesis of selected supports and for coating the materials with selected wt% loading of titania. Physical and chemical properties of the supports and catalyst composite materials were investigated by powder X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis, scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), UV-vis diffuse reflectance spectroscopy and fluorescence spectroscopy. The photo-activity of the catalyst composites were evaluated on the decolorisation of methylene blue as a model pollutant. Coating CNTs with SBA-15 improved the thermal stability and textural properties of the nanotubes. All supported titania composites had high surface areas (207-301 m(2)/g), altered band gap energies and reduced TiO2 crystallite sizes. The TiO2/SBA-CNT composite showed enhanced photo-catalytic properties and activity than the TiO2/SBA-15 and TiO2/CNT composites. In addition, an interesting observation was noted with the TiO2/SBA-15 nanocomposites, which had a significantly greater photo-catalytic activity than the TiO2/CNT nanocomposites in spite of the high electron-hole recombination phenomena observed with the photoluminescence results. Discussions in terms of morphological, textural and physical-chemical aspects to account for the result are presented.

Photo-Catalytic Properties of TiO2 Supported on MWCNTs, SBA-15 and Silica-Coated MWCNTs Nanocomposites

NASA Astrophysics Data System (ADS)

Ramoraswi, Nteseng O.; Ndungu, Patrick G.

2015-10-01

Mesoporous silica, specifically SBA-15, acid-treated multi-walled carbon nanotubes and a hybrid nanocomposite of SBA-15 coated onto the sidewalls acid-treated multi-walled carbon nanotubes (CNTs) were prepared and used as supports for anatase TiO2. Sol-gel methods were adapted for the synthesis of selected supports and for coating the materials with selected wt% loading of titania. Physical and chemical properties of the supports and catalyst composite materials were investigated by powder X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis, scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), UV-vis diffuse reflectance spectroscopy and fluorescence spectroscopy. The photo-activity of the catalyst composites were evaluated on the decolorisation of methylene blue as a model pollutant. Coating CNTs with SBA-15 improved the thermal stability and textural properties of the nanotubes. All supported titania composites had high surface areas (207-301 m2/g), altered band gap energies and reduced TiO2 crystallite sizes. The TiO2/SBA-CNT composite showed enhanced photo-catalytic properties and activity than the TiO2/SBA-15 and TiO2/CNT composites. In addition, an interesting observation was noted with the TiO2/SBA-15 nanocomposites, which had a significantly greater photo-catalytic activity than the TiO2/CNT nanocomposites in spite of the high electron-hole recombination phenomena observed with the photoluminescence results. Discussions in terms of morphological, textural and physical-chemical aspects to account for the result are presented.

Recent advances on smart TiO2 nanotube platforms for sustainable drug delivery applications.

PubMed

Wang, Qun; Huang, Jian-Ying; Li, Hua-Qiong; Zhao, Allan Zi-Jian; Wang, Yi; Zhang, Ke-Qin; Sun, Hong-Tao; Lai, Yue-Kun

To address the limitations of traditional drug delivery, TiO 2 nanotubes (TNTs) are recognized as a promising material for localized drug delivery systems. With regard to the excellent biocompatibility and physicochemical properties, TNTs prepared by a facile electrochemical anodizing process have been used to fabricate new drug-releasing implants for localized drug delivery. This review discusses the development of TNTs applied in localized drug delivery systems, focusing on several approaches to control drug release, including the regulation of the dimensions of TNTs, modification of internal chemical characteristics, adjusting pore openings by biopolymer coatings, and employing polymeric micelles as drug nanocarriers. Furthermore, rational strategies on external conditions-triggered stimuli-responsive drug release for localized drug delivery systems are highlighted. Finally, the review concludes with the recent advances on TNTs for controlled drug delivery and corresponding prospects in the future.

Recent advances on smart TiO2 nanotube platforms for sustainable drug delivery applications

PubMed Central

Wang, Qun; Huang, Jian-Ying; Li, Hua-Qiong; Zhao, Allan Zi-Jian; Wang, Yi; Zhang, Ke-Qin; Sun, Hong-Tao; Lai, Yue-Kun

2017-01-01

To address the limitations of traditional drug delivery, TiO2 nanotubes (TNTs) are recognized as a promising material for localized drug delivery systems. With regard to the excellent biocompatibility and physicochemical properties, TNTs prepared by a facile electrochemical anodizing process have been used to fabricate new drug-releasing implants for localized drug delivery. This review discusses the development of TNTs applied in localized drug delivery systems, focusing on several approaches to control drug release, including the regulation of the dimensions of TNTs, modification of internal chemical characteristics, adjusting pore openings by biopolymer coatings, and employing polymeric micelles as drug nanocarriers. Furthermore, rational strategies on external conditions-triggered stimuli-responsive drug release for localized drug delivery systems are highlighted. Finally, the review concludes with the recent advances on TNTs for controlled drug delivery and corresponding prospects in the future. PMID:28053530

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

Photo-reduced Cu/CuO nanoclusters on TiO2 nanotube arrays as highly efficient and reusable catalyst

NASA Astrophysics Data System (ADS)

Jin, Zhao; Liu, Chang; Qi, Kun; Cui, Xiaoqiang

2017-01-01

Non-noble metal nanoparticles are becoming more and more important in catalysis recently. Cu/CuO nanoclusters on highly ordered TiO2 nanotube arrays are successfully developed by a surfactant-free photoreduction method. This non-noble metal Cu/CuO-TiO2 catalyst exhibits excellent catalytic activity and stability for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with the presence of sodium borohydride (NaBH4). The rate constant of this low-cost Cu/CuO based catalyst is even higher than that of the noble metal nanoparticles decorated on the same TiO2 substrate. The conversion efficiency remains almost unchanged after 7 cycles of recycling. The recycle process of this Cu/CuO-TiO2 catalyst supported by Ti foil is very simple and convenient compared with that of the common powder catalysts. This catalyst also exhibited great catalytic activity to other organic dyes, such as methylene blue (MB), rhodamine B (RhB) and methyl orange (MO). This highly efficient, low-cost and easily reusable Cu/CuO-TiO2 catalyst is expected to be of great potential in catalysis in the future.

α-Fe2O3 nanotubes-reduced graphene oxide composites as synergistic electrochemical capacitor materials.

PubMed

Lee, K K; Deng, S; Fan, H M; Mhaisalkar, S; Tan, H R; Tok, E S; Loh, K P; Chin, W S; Sow, C H

2012-04-28

We present a facile approach for the fabrication of a nanocomposite comprising α-Fe(2)O(3) nanotubes (NTs) anchored on reduced graphene oxide (rGO) for electrochemical capacitors (ECs). The hollow tubular structure of the α-Fe(2)O(3) NTs presents a high surface area for reaction, while the incorporation of rGO provides an efficient two-dimensional conductive pathway to allow fast, reversible redox reaction. As a result, the nanocomposite materials exhibit a specific capacitance which is remarkably higher (~7 times) than α-Fe(2)O(3) NTs alone. In addition, the nanocomposites show excellent cycling life and large negative potential window. These findings suggest that such nanocomposites are a promising candidate as negative electrodes in asymmetrical capacitors with neutral electrolytes. This journal is © The Royal Society of Chemistry 2012

Formation of chelating agent driven anodized TiO2 nanotubular membrane and its photovoltaic application

NASA Astrophysics Data System (ADS)

Banerjee, Subarna; Misra, Mano; Mohapatra, Susanta K.; Howard, Cameron; Mohapatra, Srikanta K.; Kamilla, Sushanta K.

2010-04-01

Titania (TiO2) nanotubular arrays provide an exciting material for dye sensitizing solar cells (DSSC) because of their large surface area, lower recombination losses, and fast charge transport properties along the nanotubes. In this paper, design of a next generation DSSC using a TiO2 nanotubular membrane is discussed. A single step, green process is developed to produce stable large area, free-standing TiO2 nanotubular films (in a short time, 30-60 min) by anodizing Ti using an organic electrolyte, containing disodium salt of ethylene diaminetetraacetic acid (Na2[H2EDTA]) as complexing agent, and subsequent drying. Transparent, crack-free TiO2 films, 20-41 µm thick containing ordered hexagonal TiO2 nanotubes are achieved by this process. Films having a geometrical area up to 16.5 cm2 with pore openings of 182 nm have been obtained. These films have been etched to form membranes which provide an exciting prospect for front side illuminated DSSC with good mass and photon transport properties as well as wettability. A photovoltaic efficiency of 2.7% is achieved using a front side illuminated DSSC compared to 1.77% using back side illumination.

Formation of chelating agent driven anodized TiO(2) nanotubular membrane and its photovoltaic application.

PubMed

Banerjee, Subarna; Misra, Mano; Mohapatra, Susanta K; Howard, Cameron; Mohapatra, Srikanta K; Kamilla, Sushanta K

2010-04-09

Titania (TiO(2)) nanotubular arrays provide an exciting material for dye sensitizing solar cells (DSSC) because of their large surface area, lower recombination losses, and fast charge transport properties along the nanotubes. In this paper, design of a next generation DSSC using a TiO(2) nanotubular membrane is discussed. A single step, green process is developed to produce stable large area, free-standing TiO(2) nanotubular films (in a short time, 30-60 min) by anodizing Ti using an organic electrolyte, containing disodium salt of ethylene diaminetetraacetic acid (Na(2)[H(2)EDTA]) as complexing agent, and subsequent drying. Transparent, crack-free TiO(2) films, 20-41 microm thick containing ordered hexagonal TiO(2) nanotubes are achieved by this process. Films having a geometrical area up to 16.5 cm(2) with pore openings of 182 nm have been obtained. These films have been etched to form membranes which provide an exciting prospect for front side illuminated DSSC with good mass and photon transport properties as well as wettability. A photovoltaic efficiency of 2.7% is achieved using a front side illuminated DSSC compared to 1.77% using back side illumination.

Hybrid micro/nano-topography of a TiO2 nanotube-coated commercial zirconia femoral knee implant promotes bone cell adhesion in vitro.

PubMed

Frandsen, Christine J; Noh, Kunbae; Brammer, Karla S; Johnston, Gary; Jin, Sungho

2013-07-01

Various approaches have been studied to engineer the implant surface to enhance bone in-growth properties, particularly using micro- and nano-topography. In this study, the behavior of osteoblast (bone) cells was analyzed in response to a titanium oxide (TiO2) nanotube-coated commercial zirconia femoral knee implant consisting of a combined surface structure of a micro-roughened surface with the nanotube coating. The osteoblast cells demonstrated high degrees of adhesion and integration into the surface of the nanotube-coated implant material, indicating preferential cell behavior on this surface when compared to the bare implant. The results of this brief study provide sufficient evidence to encourage future studies. The development of such hierarchical micro- and nano-topographical features, as demonstrated in this work, can provide insightful designs for advanced bone-inducing material coatings on ceramic orthopedic implant surfaces. Copyright © 2013 Elsevier B.V. All rights reserved.

Protein Corona Prevents TiO2 Phototoxicity.

PubMed

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

2015-01-01

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

Gas Transport Properties of Polybenzimidazole and Poly(Phenylene Oxide) Mixed Matrix Membranes Incorporated with PDA-Functionalised Titanate Nanotubes

NASA Astrophysics Data System (ADS)

Giel, V.; Perchacz, M.; Kredatusová, J.; Pientka, Z.

2017-01-01

Functionalised titanate nanotubes (TiNTs) were incorporated to poly(5,5-bisbenzimidazole-2,2-diyl-1,3-phenylene) (PBI) or poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) for improving the interfacial compatibility between the polymer matrix and inorganic material and for altering the gas separation performance of the neat polymer membranes. Functionalisation consisted in oxidative polymerisation of dopamine-hydrochloride on the surface of non-functionalised TiNTs. Transmission electron microscopy (TEM) confirmed that a thin polydopamine (PDA) layer was created on the surface of TiNTs. 1.5, 3, 6, and 9 wt.% of PDA-functionalised TiNTs (PDA-TiNTs) were dispersed to each type of polymer matrix to create so-called mixed matrix membranes (MMMs). Infrared spectroscopy confirmed that -OH and -NH groups exist on the surface of PDA-TiNTs and that the nanotubes interact via H-bonding with PBI but not with PPO. The distribution of PDA-TiNTs in the MMMs was to some extent uniform as scanning electron microscope (SEM) studies showed. Beyond, PDA-TiNTs exhibit positive effect on gas transport properties, resulting in increased selectivities of MMMs. The addition of nanotubes caused a decrease in permeabilities but an increase in selectivities. It is shown that 9 wt.% of PDA-TiNTs in PBI gave a rise to CO2/N2 and CO2/CH4 selectivities of 112 and 63 %, respectively. In case of PPO-PDA-TiNT MMMs, CO2/N2 and CO2/CH4 selectivity increased about 25 and 17 %, respectively. Sorption measurement showed that the presence of PDA-TiNTs in PBI caused an increase in CO2 sorption, whereas the influence on other gases is less noticeable.

Photocatalysis-assisted water filtration: using TiO2-coated vertically aligned multi-walled carbon nanotube array for removal of Escherichia coli O157:H7.

PubMed

Oza, Goldie; Pandey, Sunil; Gupta, Arvind; Shinde, Sachin; Mewada, Ashmi; Jagadale, Pravin; Sharon, Maheshwar; Sharon, Madhuri

2013-10-01

A porous ceramic was coated with vertically aligned multi-walled carbon nanotubes (MWCNTs) by spray pyrolysis. Titanium dioxide (TiO2) nanoparticles were then coated onto this densely aligned MWCNT. The presence of TiO2/MWCNT interfacial arrays was confirmed by X-ray diffraction (XRD), scanning electron microscope-energy dispersive analysis of X-ray (SEM-EDAX) and transmission electron microscope (TEM). This is a novel report in which water loaded with a most dreadful enterohemorrhagic pathogenic strain of Escherichia coli O157:H7 was filtered through TiO2/MWCNT coated porous ceramic filter and then analysed. Bacterial removal performance was found to be significantly lower in control i.e. plain porous ceramic (P<0.05) as compared to TiO2/MWCNT coated ceramic. The photocatalytic killing rate constant for TiO2-ceramic and MWCNT/TiO2-ceramic under fluorescent light was found be 1.45×10(-2) min(-1) and 2.23×10(-2) min(-1) respectively. Further, when I-V characteristics were performed for TiO2/MWCNT composite, it was corroborated that the current under light irradiation is comparatively higher than that in dark, thus proving it to be photocatalytically efficient system. The enhanced photocatalysis may be a contribution of increased surface area and charge transfer rate as a consequence of aligned MWCNT network. © 2013 Elsevier B.V. All rights reserved.

Highly sensitive chemiluminescence immunoassay on chitosan membrane modified paper platform using TiO2 nanoparticles/multiwalled carbon nanotubes as label.

PubMed

Li, Weiping; Ge, Shenguang; Wang, Shoumei; Yan, Mei; Ge, Lei; Yu, Jinghua

2013-01-01

A highly sensitive chemiluminescence (CL) immunoassay was incorporated into a low-cost microfluidic paper-based analytical device (μ-PAD) to fabricate a facile paper-based CL immunodevice (denoted as μ-PCLI). This μ-PCLI was constructed by covalently immobilizing capture antibody on a chitosan membrane modified μ-PADs, which was developed by simple wax printing methodology. TiO2 nanoparticles coated multiwalled carbon nanotubes (TiO2/MWCNTs) were synthesized as an amplification catalyst tag to label signal antibody (Ab2). After sandwich-type immunoreactions, the TiO2/MWCNTs were captured on the surface of μ-PADs to catalyze the luminol-p-iodophenol-H2O2 CL system, which produced an enhanced CL emission. Using prostate-specific antigen as a model analyte, the approach provided a good linear response range from 0.001 to 20 ng/mL with a low detection limit of 0.8 pg/mL under optimal conditions. This μ-PCLI showed good reproducibility, selectivity and stability. The assay results of prostate-specific antigen in clinical serum samples were in good agreement with that obtained by commercially used electrochemiluminescence methods at the Cancer Research Center of Shandong Tumor Hospital (Jinan, Shandong Province, China). This μ-PCLI could be very useful to realize highly sensitive, qualitative point-of-care testing in developing or developed countries. Copyright © 2013 John Wiley & Sons, Ltd.

Enhanced light trapping and high charge transmission capacities of novel structures for efficient photoelectrochemical water splitting.

PubMed

Mu, Jianglong; Miao, Hui; Liu, Enzhou; Feng, Juan; Teng, Feng; Zhang, Dekai; Kou, Yumeng; Jin, Yanping; Fan, Jun; Hu, Xiaoyun

2018-06-13

Excellent PEC efficiency, good reusability and the super stability of trap-like SnS2/TiO2 nanotube arrays (NTs)-based photoanodes are reported. Specifically, the SnS2/TiO2-180 °C (ST-180) photoanode exhibited the highest photocurrent density (1.05 mA cm-2) and an optimal η (0.73%) at 0.5 V (vs. SCE) under simulated light irradiation (AM 1.5G), which are 4.6 and 3.8 times higher than those of pure TiO2 NTs (0.23 mA cm-2 and 0.19%). The IPCE values of ST-180 can reach 21.5% (365 nm) and 13.8% (420 nm), which are much higher than those of pure TiO2 NTs (10.6% at 365 nm and 0.8% at 420 nm). The APCE values of the pure TiO2 NTs photoelectrode are 12.8% (365 nm) and 1.1% (420 nm), while the ST-180 values are 22.3% and 14.2%, respectively. Furthermore, the generation rates of H2 and O2 for the ST-180 photoanode are 47.2 and 23.1 μmol cm-2 h-1 at 0.5 V under AM 1.5G, corresponding to faradaic efficiencies of around 80.1% and 78.3%, respectively. In short, the high-efficiency PEC water splitting performance of this SnS2/TiO2 photoanode results from the enhanced light harvesting ability of the trap-like SnS2 structure, accelerated carrier transportation properties of TiO2 NTs, and effective carrier separation of the type-II heterojunction structure. This work may offer a combinatorial strategy for the preparation of heterojunction structures with high PEC performance and can be a model structure for similar photoanode materials.

Approaching Piezoelectric Response of Pb-Piezoelectrics in Hydrothermally Synthesized Bi0.5(Na1- xK x)0.5TiO3 Nanotubes.

PubMed

Ghasemian, Mohammad Bagher; Rawal, Aditya; Liu, Yun; Wang, Danyang

2018-06-20

A large piezoelectric coefficient of 76 pm/V along the diameter direction, approaching that of lead-based piezoelectrics, is observed in hydrothermally synthesized Pb-free Bi 0.5 (Na 0.8 K 0.2 ) 0.5 TiO 3 nanotubes. The 30-50 nm diameter nanotubes are formed through a scrolling and wrapping mechanism without the need of a surfactant or template. A molar ratio of KOH/NaOH = 0.5 for the mineralizers yields the Na/K ratio of ∼0.8:0.2, corresponding to an orthorhombic-tetragonal (O-T) phase boundary composition. X-ray diffraction patterns along with transmission electron microscopy analysis ascertain the coexistence of orthorhombic and tetragonal phases with (110) and (001) orientations along the nanotube length direction, respectively. 23 Na NMR spectroscopy confirms the higher degree of disorder in Bi 0.5 (Na 1- x K x ) 0.5 TiO 3 nanotubes with O-T phase coexistence. These findings present a significant advance toward the application of Pb-free piezoelectric materials.

Synthesis, Adsorptive, and Photocatalytic Properties of Carbon Nanotubes/TiO2 Nanocomposite Photocatalysts

NASA Astrophysics Data System (ADS)

Shao, Xiankun; Nie, Shibin; Shao, Liangzhi; Zhang, Baoshan; Li, Benxia

2017-12-01

The carbon nanotubes/TiO2 (CNTs/TiO2) composite photocatalysts composed of TiO2 nanoparticles and multiwalled carbon nanotubes (CNTs) were prepared by a facile hydrothermal method. The photocatalysts were characterized by a range of analytical techniques including X-ray powder diffraction, field emission scanning electron microscope, thermal gravimetric analysis and UV-Vis optical absorption spectra, etc. The amount of TiO2 nanoparticles growing on CNTs could be tuned by adjusting the dosage of precursor in the reaction solution. Both the adsorptivity and photocatalytic activities of pure CNTs, pure TiO2, and the CNTs/TiO2 nanocomposites were tested by the removal of methylene blue from water in dark and under a simulated sunlight, respectively. By comparison, the improved photocatalytic activity of the CNTs/TiO2 nanocomposite is mainly due to that the CNTs can disperse the active component of TiO2 nanoparticles, provide a larger the specific surface area, as well as act as an electron sink to accelerate the separation of the photogenerated charges.

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.

Novel Nanotechnology of TiO2 Improves Physical-Chemical and Biological Properties of Glass Ionomer Cement

PubMed Central

Cibim, Daniela Dellosso; Saito, Miki Taketomi; Giovani, Priscila Alves; Borges, Ana Flávia Sanches; Pecorari, Vanessa Gallego Arias; Gomes, Orisson Ponce; Nociti-Junior, Francisco Humberto

2017-01-01

The aim of this study was to assess the performance of glass ionomer cement (GIC) added with TiO2 nanotubes. TiO2 nanotubes [3%, 5%, and 7% (w/w)] were incorporated into GIC's (Ketac Molar EasyMix™) powder component, whereas unblended powder was used as control. Physical-chemical-biological analysis included energy dispersive spectroscopy (EDS), surface roughness (SR), Knoop hardness (SH), fluoride-releasing analysis, cytotoxicity, cell morphology, and extracellular matrix (ECM) composition. Parametric or nonparametric ANOVA were used for statistical comparisons (α ≤ 0.05). Data analysis revealed that EDS only detected Ti at the 5% and 7% groups and that GIC's physical-chemical properties were significantly improved by the addition of 5% TiO2 as compared to 3% and GIC alone. Furthermore, regardless of TiO2 concentration, no significant effect was found on SR, whereas GIC-containing 7% TiO2 presented decreased SH values. Fluoride release lasted longer for the 5% and 7% TiO2 groups, and cell morphology/spreading and ECM composition were found to be positively affected by TiO2 at 5%. In conclusion, in the current study, nanotechnology incorporated in GIC affected ECM composition and was important for the superior microhardness and fluoride release, suggesting its potential for higher stress-bearing site restorations. PMID:28611845

Influence of immersion cycles during n-β-Bi2O3 sensitization on the photoelectrochemical behaviour of N-F-codoped TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Hoyos, Lina J.; Rivera, Diego F.; Gualdrón-Reyes, Andrés F.; Ospina, Rogelio; Rodríguez-Pereira, Jhonatan; Ropero-Vega, Jose L.; Niño-Gómez, Martha E.

2017-11-01

Sensitization of TiO2 nanotube (TNT)-based photoanodes with narrow-band gap semiconductors is an important alternative to improving the photoelectrochemical properties of the material. However, the interaction between the sensitizer and TNT is not understood deeply enough to relate charge carrier transport into the composite photoanode with its photoactivity. In this contribution, we studied the photoelectrochemical behaviour of N-F-self codoped TiO2 nanotubes (N-F-TNTs) that were grown by anodization of titanium plates and sensitized with β-Bi2O3 by immersing the TNTs into a Bi2O3 sol solution by dip-coating. The number of immersion cycles was varied. The as-fabricated photoanodes were characterized by FESEM, GIXRD, DRS and XPS, while their photoelectrochemical and semiconducting properties were investigated by photovoltammetry, electrochemical impedance spectroscopy and Mott-Schottky analysis in 0.1 M HClO4. The photoelectrocatalytic activity of the composite photoanodes was evaluated for glycerol oxidation under acidic and alkaline conditions. The N-F-TNTs exhibit a well-oriented structure after β-Bi2O3 deposition. The presence of substitutions of both N and F, identified by XPS, indicates the self-doping of the TNTs during anodization. The visible-light harvesting of the N-F-TNT photoanode was enhanced after three -immersion cycles during β-Bi2O3 sensitization, establishing an adequate n-n heterojunction at the N-F-TNT/Bi2O3 interface. In addition, bismuth migration from the sensitizer to the TNT lattice was promoted during thermal treatment, forming Bi-N-F-tridoping of TNT (Bi-N-F-TNT). The suitable band alignment between TNT and β-Bi2O3 and incorporation of the Bi3+ energy levels into TiO2 facilitate charge carrier separation and electron transport throughout the cell. Nevertheless, increasing the number of immersion cycles over three creates an excess of Bi3+ species at the N-F-TNT/β-Bi2O3 interface, producing an energetic barrier that hinders electron

Effective approach to strengthening TiO2 nanotube arrays by using double or triple reinforcements

NASA Astrophysics Data System (ADS)

Sun, Mengwei; Yu, Dongliang; Lu, Linfeng; Ma, Weihua; Song, Ye; Zhu, Xufei

2015-08-01

Porous anodic TiO2 nanotube arrays (TNTAs) are fragile and also susceptible to be damaged during physical manipulation. Few studies have involved the improvement of the poor interfacial adhesion of TNTAs to the Ti substrate. Here, the poor adhesion of TNTAs was dramatically improved by appending an additional compact layer (ACL) formed at the interface between TNTAs and the Ti substrate. The adhesion of TNTAs with single-ACL increased with the increase of the ACL thickness. Furthermore, the reinforced TNTAs with double-ACL and triple-ACL have been successfully developed for the first time. The experimental results indicated that the critical load of the TNTAs with triple-ACL is roughly 5.8 times higher than that of the untreated TNTAs. The present results may be helpful to assemble less brittle and large area TNTAs for extensive applications.

n/p-Type changeable semiconductor TiO2 prepared from NTA

NASA Astrophysics Data System (ADS)

Li, Qiuye; Wang, Xiaodong; Jin, Zhensheng; Yang, Dagang; Zhang, Shunli; Guo, Xinyong; Yang, Jianjun; Zhang, Zhijun

2007-10-01

A novel kind of nano-sized TiO2 (anatase) was obtained by high-temperature (400-700°C) dehydration of nanotube titanic acid (H2Ti2O4(OH)2, NTA). The high-temperature (400-700°C) dehydrated nanotube titanic acids (HD-NTAs) with a unique defect structure exhibited a p-type semiconductor behavior under visible-light irradiation (λ≥420 nm, E photon=2.95 eV), whereas exhibited an n-type semiconductor behavior irradiated with UV light (λ=365 nm, E photon=3.40 eV).

Electrochemical preparation of vertically aligned, hollow CdSe nanotubes and their p-n junction hybrids with electrodeposited Cu2O.

PubMed

Debgupta, Joyashish; Devarapalli, Ramireddy; Rahman, Shakeelur; Shelke, Manjusha V; Pillai, Vijayamohanan K

2014-08-07

Vertically aligned, hollow nanotubes of CdSe are grown on fluorine doped tin oxide (FTO) coated glass substrates by ZnO nanowire template-assisted electrodeposition technique, followed by selective removal of the ZnO core using NH4OH. A detailed mechanism of nucleation and anisotropic growth kinetics of nanotubes have been studied by a combination of characterization tools such as chronoamperometry, SEM and TEM. Interestingly, "as grown" CdSe nanotubes (CdSe NTs) on FTO coated glass plates behave as n-type semiconductors exhibiting an excellent photo-response (with a generated photocurrent density value of ∼ 470 μA cm(-2)) while in contact with p-type Cu2O (p-type semiconductor, grown separately on FTO plates) because of the formation of a n-p heterojunction (type II). The observed photoresponse is 3 times higher than that of a similar device prepared with electrodeposited CdSe films (not nanotubes) and Cu2O on FTO. This has been attributed to the hollow 1-D nature of CdSe NTs, which provides enhanced inner and outer surface areas for better absorption of light and also assists faster transport of photogenerated charge carriers.

Stability and thermal behavior of molybdenum disulfide nanotubes: Nonequilibrium molecular dynamics simulation using REBO potential

NASA Astrophysics Data System (ADS)

Ahadi, Zohreh; Shadman Lakmehsari, Muhammad; Kumar Singh, Sandeep; Davoodi, Jamal

2017-12-01

This study is an attempt to perform equilibrium molecular dynamics and non-equilibrium molecular dynamics (NEMD) to evaluate the stability and thermal behavior of molybdenum disulfide nanotubes (MoS2NTs) by reactive empirical bond order potential. The stability of nanotubes, cohesive energy, isobaric heat capacity, and enthalpies of fusion in armchair and zigzag structures with different radii were calculated. The observed results illustrate that SWMoS2NTs, which have larger diameters, are more stable with more negative energy than the smaller ones. Moreover, it was found that the melting point is increased with an increase in the nanotube's radius. During the melting process, the structural transformation of nanotubes was investigated using a mean-square displacement and radial distribution function diagrams. Afterwards, using a NEMD simulation, the thermal conductivity of nanotubes with various diameters was calculated at a constant nanotube length. The obtained results show that the thermal conductivity coefficient increases with increasing nanotube diameters when the nanotube length is constant.

Design of titania nanotube structures by focused laser beam direct writing

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

Enachi, Mihai; Stevens-Kalceff, Marion A.; Sarua, Andrei

In this work, we report on electrochemical fabrication of titania films consisting of nanotubes (NTs) and their treatment by focused laser beam. The results of sample characterization by optical and scanning electron microscopy, cathodoluminescence imaging, and Raman scattering scanning spectroscopy are compared to those inherent to specimens subjected to thermal treatment in a furnace. The obtained data demonstrate possibilities for controlling crystallographic structure of TiO{sub 2} NTs by focused laser beam direct writing. These findings open new prospects for the design and fabrication of spatial architectures based on titania nanotubes.

Fatigue resistance, electrochemical corrosion and biological response of Ti-15Mo with surface modified by amorphous TiO2 nanotubes layer.

PubMed

Campanelli, Leonardo C; Oliveira, Nilson T C; da Silva, Paulo Sergio C P; Bolfarini, Claudemiro; Palmieri, Annalisa; Cura, Francesca; Carinci, Francesco; Motheo, Artur J

2018-03-04

The objective of this work was a systemic evaluation of the anodizing treatment in a β-type Ti-15Mo alloy to grow a TiO 2 nanostructured layer for osseointegration improvement. The technical viability of the surface modification was assessed based on the resistance to mechanical fatigue, electrochemical corrosion, and biological response. By using an organic solution of NH 4 F in ethylene glycol, a well-organized array of 90 nm diameter nanotubes was obtained with a potential of 40 V for 6 h, while undefined nanotubes of 25 nm diameter were formed with a potential of 20 V for 1 h. Nevertheless, the production of the 90 nm diameter nanotubes was followed by micrometer pits that significantly reduced the fatigue performance. The undefined nanotubes of 25 nm diameter, besides the greater cell viability and improved osteoblastic cell differentiation in comparison to the as-polished surface, were not deleterious to the fatigue and corrosion properties. This result strengthens the necessity of an overall evaluation of the anodizing treatment, particularly the fatigue resistance, before suggesting it for the design of implants. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc.

Synthesis of silicon nanotubes with cobalt silicide ends using anodized aluminum oxide template.

PubMed

Zhang, Zhang; Liu, Lifeng; Shimizu, Tomohiro; Senz, Stephan; Gösele, Ulrich

2010-02-05

Silicon nanotubes (SiNTs) are compatible with Si-based semiconductor technology. In particular, the small diameters and controllable structure of such nanotubes are remaining challenges. Here we describe a method to fabricate SiNTs intrinsically connected with cobalt silicide ends based on highly ordered anodic aluminum oxide (AAO) templates. Size and growth direction of the SiNTs can be well controlled via the templates. The growth of SiNTs is catalyzed by the Co nanoparticles reduced on the pore walls of the AAO after annealing, with a controllable thickness at a given growth temperature and time. Simultaneously, cobalt silicide forms on the bottom side of the SiNTs.

Designing nanostructured one-dimensional TiO2 nanotube and TiO2 nanoparticle multilayer composite film as photoanode in dye-sensitized solar cells to increase the charge collection efficiency

NASA Astrophysics Data System (ADS)

Akilavasan, Jeganathan; Al-Jassim, Maufick; Bandara, Jayasundera

2015-01-01

A photoanode consisting of hydrothermally synthesized TiO2 nanotubes (TNT) and TiO2 nanoparticles (TNP) was designed for efficient charge collection in dye-sensitized solar cells. TNT and TNP films were fabricated on a conductive glass substrate by using electrophoretic deposition and doctor-blade methods, respectively. The TNP, TNT, and TNT/TNP bi-layer electrodes exhibit solar cell efficiencies of 5.3, 7.4, and 9.2%, respectively. Solar cell performance results indicate a higher short-circuit current density (Jsc) for the TNT/TNP bi-layer electrode when compared to a TNT or TNP electrode alone. The open-circuit voltages (Voc) of TNT/TNP and TNT electrodes are comparable while the Voc of TNP electrode is inferior to that of the TNT/TNP electrode. Fill factors of TNT/TNP, TNT, and TNP electrodes also exhibit similar behaviors. The enhanced efficiency of the TNT/TNP bi-layer electrode is found to be mainly due to the enhancement of charge collection efficiency, which is confirmed by the charge transport parameters measured by electrochemical impedance spectroscopy (EIS). EIS analyses also revealed that the TNT/TNP incurs smaller charge transport resistances and longer electron life times when compared to those of TNT or TNP electrodes alone. It was demonstrated that the TNT/TNP bi-layer electrode can possess the advantages of both rapid electron transport rate and a high light scattering effect.

Air-gating and chemical-gating in transistors and sensing devices made from hollow TiO2 semiconductor nanotubes

NASA Astrophysics Data System (ADS)

Alivov, Yahya; Funke, Hans; Nagpal, Prashant

2015-07-01

Rapid miniaturization of electronic devices down to the nanoscale, according to Moore’s law, has led to some undesirable effects like high leakage current in transistors, which can offset additional benefits from scaling down. Development of three-dimensional transistors, by spatial extension in the third dimension, has allowed higher contact area with a gate electrode and better control over conductivity in the semiconductor channel. However, these devices do not utilize the large surface area and interfaces for new electronic functionality. Here, we demonstrate air gating and chemical gating in hollow semiconductor nanotube devices and highlight the potential for development of novel transistors that can be modulated using channel bias, gate voltage, chemical composition, and concentration. Using chemical gating, we reversibly altered the conductivity of nanoscaled semiconductor nanotubes (10-500 nm TiO2 nanotubes) by six orders of magnitude, with a tunable rectification factor (ON/OFF ratio) ranging from 1-106. While demonstrated air- and chemical-gating speeds were slow here (˜seconds) due to the mechanical-evacuation rate and size of our chamber, the small nanoscale volume of these hollow semiconductors can enable much higher switching speeds, limited by the rate of adsorption/desorption of molecules at semiconductor interfaces. These chemical-gating effects are completely reversible, additive between different chemical compositions, and can enable semiconductor nanoelectronic devices for ‘chemical transistors’, ‘chemical diodes’, and very high-efficiency sensing applications.

Single-step preparation of TiO2/MWCNT Nanohybrid materials by laser pyrolysis and application to efficient photovoltaic energy conversion.

PubMed

Wang, Jin; Lin, Yaochen; Pinault, Mathieu; Filoramo, Arianna; Fabert, Marc; Ratier, Bernard; Bouclé, Johann; Herlin-Boime, Nathalie

2015-01-14

This paper presents the continuous-flowand single-step synthesis of a TiO2/MWCNT (multiwall carbon nanotubes) nanohybrid material. The synthesis method allows achieving high coverage and intimate interface between the TiO2particles and MWCNTs, together with a highly homogeneous distribution of nanotubes within the oxide. Such materials used as active layer in theporous photoelectrode of solid-state dye-sensitized solar cells leads to a substantial performance improvement (20%) as compared to reference devices.

Preparation, characterization and photocatalytic activities of TiO2-SrTiO3 composites

NASA Astrophysics Data System (ADS)

Wang, Yan; Zhu, Lianjie; Gao, Fubo; Xie, Hanjie

2017-01-01

Series of TiO2-SrTiO3 composites were synthesized by hydrothermal method, using TiO2 nanotube array as a precursor and Sr(OH)2 as a Sr source material. TiO2-SrTiO3 products with various composition were obtained by simply changing the reaction time. The as-synthesized products were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The optical properties were studied by means of UV-Vis absorption spectroscopy and photoluminescence (PL) spectra. Their photocatalytic activities were assessed by photodegradation of rhodamine B (RhB) solution and the photocatalytic reaction mechanism was discussed. The TiO2-SrTiO3 composites obtained at 2 h exhibits the highest activity for photodegradation of RhB.

Study on physicochemical properties of functionalized-MWNTs with 3-aminopropyltriethoxysilane loaded TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Ahmad, Amirah; Razali, Mohd Hasmizam; Amin, Khairul Anuar Mat

2017-09-01

One of the exciting developments in science today is the design and synthesis of carbon nanotubes (CNTs) that possess novel properties and not exhibited by other individual organic and inorganic materials. CNTs are prepared using a chemical vapor deposition method with acetylene and synthesized mesoporous Ni-MCM41 as the carbon source and catalyst, respectively, and are then functionalized using 3-aminopropyltriethoxysilane (APTES) through the co-condensation method and loaded with commercial TiO2. Mesoporous Ni-MCM41 catalyst is first synthesized by hydrothermal method using sodium metasilicate as silica source and cetyltrimethylammonium bromide (CTABr) as a template. Results of Raman spectroscopy confirm that the synthesized carbon nanotubes are multi-walled. The type IV nitrogen adsorption-desorption isotherm and narrow pore size distribution proved that the functionalized-MWNTs loaded TiO2 is in mesopore range. Field Emission Scanning Electron Microscopy reveals that good dispersions of TiO2 nanoparticles onto functionalized-MWNTs with hair-like structure in between 3-8 nm. BET results indicate that functionalized-MWNTs loaded TiO2 possessed high surface area thus has considerable potential as an adsorbent and photocatalyst in environmental applications.