Surface Of Titania Nanotubes Research Articles

AuCo/TiO2-NTs Anode Catalysts for Direct Borohydride Fuel Cells

Gold-cobalt catalysts deposited on titania nanotubes surface (denoted as AuCo/TiO2-NTs) are studied as possible anode materials for direct borohydride/hydrogen peroxide fuel cells. The morphology and composition of the catalysts is characterized by field emission scanning electron microscopy and by inductively coupled plasma optical emission spectroscopy. The fuel cell measurements are performed at four temperatures, in the 25–55°C range, on a lab-scale direct alkaline NaBH4-H2O2 single fuel cell. Polarization curves are recorded to evaluate the fuel cell performance using each prepared anode catalyst. The peak power density dependence on temperature is in the 87–102 mWcm−2 range for Co/TiO2-NTs catalyst and in the 163–283 mWcm−2 range for the AuCo/TiO2-NTs catalysts with Au loadings ranging from 10 to 60 μgAucm−2. The present results demonstrate that power density is raised by over 150% due to the use of AuCo/TiO2-NTs as anode catalysts.

Stability studies of PbS sensitised TiO2 nanotube arrays for visible light photocatalytic applications by X-ray photoelectron spectroscopy (XPS)

Titania nanotube array sensitised with lead sulphide (PbS) were synthesised using a successive ionic layer adsorption and reaction (SILAR) method. The PbS sensitation gives visible light sensitivity to the titania nanotube arrays. The PbS sensitised titania nanotube were characterised using X-ray diffraction, UV–visible spectroscopy and scanning electron microscopy. The stability of the PbS sensitised titania nanotube were monitored through the X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the titania sensitised with PbS were studied by monitoring the degradation of methylene blue under visible light irradiation. The photocatalytic activity and solar cell efficiency is found to be highly depended on the number of SILAR cycle used for the sensitisation of PbS on titania nanotube. The sample coated for 3 SILAR cycle of PbS shows highest solar cell efficiency and photocatalytic activity under visible light. The photocatalytic activity drastically decreased in the samples after the Ist cycle of photocatalytic reaction. The drastic decrease in the photoactivity is due to the dissolution of PbS nanoparticle on the surface of titania nanotube after the first cycle of photocatalytic reaction. XPS was employed as a tool to probe the dissolution of PbS nanoparticles.

Comparison of platelet adhesion behavior on pure titanium surfaces modified by different techniques

To evaluate the platelet adhesion ability on pure titanium surfaces modified with different techniques. Pure titanium specimens were treated with 5 different surface modification techniques, including machine polish (MP), dual acid-etch (DAE), sand blast-large grit and acid-etch (SLA), micro-arc oxidation (MAO) and anodized titania nanotube (TNT). The surface topographies of specimens were observed by scanning electron microscopy (SEM). Chemical compositions, surface roughness and static water contact angle of specimens were detected by energy dispersive spectrometer (EDS), laser scanning confocal microscope (LSCM) and contact angle analyzer respectively. Platelets were cultured on specimen surfaces for 30 min. The amount and viability of adhered platelets adhered were evaluated. Platelet distribution and morphology were observed by LSCM and SEM. Surface topographies of the five groups of specimens differed significantly. MP, DAE, SLA and MAO surfaces showed micro-scale topographies, while TNT surfaces showed nano-scale topography with nanotubes at the diameter of (80.46 ± 0.35) nm. The surface roughness of MAO was the highest among the 5 groups. TNT surfaces demonstrated the lowest roughness as well as the lowest static water contact angle as 13.55° ± 0.96°. The amount of platelets adhered on TNT surface was the greatest as (300 729 ± 8 325) platelet/µl and the viability was the highest (A450 value 2.14 ± 0.05). Platelet adhered intensively on TNT surfaces, forming pseudopodia, extending and connecting with each other. Surface properties of pure titanium affect platelet adhesion ability. Nano-scale topography can greatly improve platelet adhesion. Increased surface roughness and hydrophilicity can improve platelet adhesion ability.

Polydopamine-induced nanocomposite Ag/CaP coatings on the surface of titania nanotubes for antibacterial and osteointegration functions.

The initial implant-associated infections and post aseptic loosening are the major obstacles for the clinical applications of titanium-based dental and orthopedic implants. To tackle these issues, the implant surface is engineered to possess combined osteointegration and antibacterial properties. Therefore, a mussel-inspired novel nano silver/calcium phosphate (CaP) composite coating was prepared on anodized Ti, in the expectation of its surface maintaining preferable biological performance and possessing long-term antibacterial ability. This approach involves three steps: (i) the anodic oxidation of Ti to enable it to have a TiO2 nanotubular (TNT) surface structure, (ii) the self-polymerization of dopamine on TNT and the reduction of Ag and (iii) the modification of the Ag nanoparticles using polydopamine and further being immersed in SBF for the biomimetic mineralization of CaP. The surface morphology and microstructure of this novel coating was fully characterized. The Ag/CaP coatings displayed obvious antibacterial effects to S. aureus bacteria and relatively good in vitro cytocompatibility to MG63 cells. Compared with the pristine Ti, the cells cultured on the coated Ti showed enhanced ALP activities.

Gold-Metal (Ni, Cu) Deposited on the Titania Nanotubes as Electrocatalysts for Borohydride Oxidation

In the present work the optimization of the preparation of titania nanotube supported Au-Ni and Au-Cu catalysts (denoted as Au(Ni)/TiO2-NTs and Au(Cu)/TiO2-NTs) via the galvanic displacement technique is presented. The catalysts were prepared according the following procedures: i) preparation of TiO2 nanotube arrays by anodization of titanium sheets in an aqueous sulfuric acid solution containing some NH4F; ii) deposition of an electroless Ni or Cu sublayers on the synthesized TiO2 nanotube arrays [1-3] and iii) subsequent immersion of the Ni/TiO2-NTs or Cu/NiTiO2-NTs electrodes into the gold-containing solution for various time periods. The morphology and composition of the catalysts were examined by means of Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, X-ray diffraction and Inductively Coupled Plasma Optical Emission Spectroscopy. The electrochemical behavior and electrocatalytic activity of the fabricated catalysts towards borohydride oxidation were measured by means of cyclic voltammetry. The electroactive area of gold surface created on fabricated catalysts was determined from cyclic voltammograms of Au/TiO2-NTs electrodes recorded in a deaerated 0.5 M H2SO4 solution at a scan rate of 10 mV s-1.The prepared Au(Ni)/TiO2-NTs and Au(Cu)/TiO2-NTs electrodes exhibited a high catalytic efficiency towards the oxidation of borohydride when compared to that of bulk Au electrode. A higher catalytic activity of the prepared Au(Ni)/TiO2-NTs and Au(Cu)/TiO2-NTs catalysts under various conditions may be related to production of smaller gold nanoparticles and their fine and uniform dispersion on the surface.The Au-Ni and Au-Cu catalysts deposited on the titania nanotube surface seem to be a promising anodic material for direct borohydride fuel cells. Acknowledgement This research was funded by a grant (No. ATE-08/2012) from the Research Council of Lithuania.

Nanostructured Gold-Nickel/Titania Nanotubes Electrocatalysts for Hydrazine Oxidation

This work is focused on the study of self-ordered titania nanotube arrayed electrodes for preparation of efficient nanostructured gold-nickel/titania nanotubes (denoted as Au(Ni)/TiO2-NTs) electrocatalysts for the oxidation of hydrazine in alkaline medium. Titania nanotube arrayed substrate was applied for preparation of catalysts due to its high cation exchange capacity, which provides the possibility of achieving a high loading of active catalyst with an even distribution and high dispersion. The self-ordered TiO2 nanotube arrays were prepared by anodic oxidation of Ti surface in an aqueous sulfuric acid solution containing some NH4F. The average tube diameter was ~100 nm and the thickness of titania layers was ~350 nm. Gold nanoparticles in size of ~10-30 nm were deposited on the surfaces of titania nanotube arrays by partial galvanic displacement of electroless nickel layer that had been previously deposited. The electroless Ni-P layer with the thickness of ~300 nm was deposited on the titania nanotubes surface, which produces a layer of granular nickel particles ~200 nm in size.The morphology, structure and composition of the prepared nanostructured catalysts were examined by field emission scanning electron microscopy, energy dispersive X-ray analysis and inductively coupled optical emission spectroscopy. The electrocatalytic activity of the prepared catalysts was investigated towards the oxidation of hydrazine in alkaline medium by means of cyclic voltammetry and chronoamperometry.Data on the pecularities of various electrodes are compared and discussed on the basis of electrochemical data. The prepared Au(Ni)/TiO2-NTs catalysts with different Au loadings possesses a higher electrocatalytic activity towards the oxidation of hydrazine in alkaline medium as compared to that of TiO2-NTs and Au deposited electrochemically on the TiO2-NTs and seem to be a promising anode materials for direct hydrazine fuel cells. Acknowledgment J. Rakauskas acknowledges support by project "Promotion of Student Scientific Activities" (VP1-3.1-ŠMM-01-V-02-003) from the Research Council of Lithuania. This project is funded by the Republic of Lithuania and European Social Fund under the 2007-2013 Human Resources Development Operational Programme’s priority 3.

ZnO nanoparticle incorporated nanostructured metallic titanium for increased mesenchymal stem cell response and antibacterial activity

Recent trends in titanium implants are towards the development of nanoscale topographies that mimic the nanoscale properties of bone tissue. Although the nanosurface promotes the integration of osteoblast cells, infection related problems can also occur, leading to implant failure. Therefore it is imperative to reduce bacterial adhesion on an implant surface, either with or without the use of drugs/antibacterial agents. Herein, we have investigated two different aspects of Ti surfaces in inhibiting bacterial adhesion and concurrently promoting mammalian cell adhesion. These include (i) the type of nanoscale topography (Titania nanotube (TNT) and Titania nanoleaf (TNL)) and (ii) the presence of an antibacterial agent like zinc oxide nanoparticles (ZnOnp) on Ti nanosurfaces. To address this, periodically arranged TNT (80–120 nm) and non-periodically arranged TNL surfaces were generated by the anodization and hydrothermal techniques respectively, and incorporated with ZnOnp of different concentrations (375 μM, 750 μM, 1.125 mM and 1.5 mM). Interestingly, TNL surfaces decreased the adherence of staphylococcus aureus while increasing the adhesion and viability of human osteosarcoma MG63 cell line and human mesenchymal stem cells, even in the absence of ZnOnp. In contrast, TNT surfaces exhibited an increased bacterial and mammalian cell adhesion. The influence of ZnOnp on these surfaces in altering the bacterial and cell adhesion was found to be concentration dependent, with an optimal range of 375−750 μM. Above 750 μM, although bacterial adhesion was reduced, cellular viability was considerably affected. Thus our study helps us to infer that nanoscale topography by itself or its combination with an optimal concentration of antibacterial ZnOnp would provide a differential cell behavior and thereby a desirable biological response, facilitating the long term success of an implant.

Self-Assembly of Protein-Based Biomaterials Initiated by Titania Nanotubes

Protein-based biomaterials are a promising strategy for creating robust highly selective biocatalysts. The assembled biomaterials must sufficiently retain the near-native structure of proteins and provide molecular access to catalytically active sites. These requirements often exclude the use of conventional assembly techniques, which rely on covalent cross-linking of proteins or entrapment within a scaffold. Here we demonstrate that titania nanotubes can initiate and template the self-assembly of enzymes, such as ribonuclease A, while maintaining their catalytic activity. Initially, the enzymes form multilayer thick ellipsoidal aggregates centered on the nanotube surface; subsequently, these nanosized entities assemble into a micrometer-sized enzyme material that has enhanced enzymatic activity and contains as little as 0.1 wt % TiO2 nanotubes. This phenomenon is uniquely associated with the active anatase (001)-like surface of titania nanotubes and does not occur on other anatase nanomaterials, which contain significantly fewer undercoordinated Ti surface sites. These findings present a nanotechnology-enabled mechanism of biomaterial growth and open a new route for creating stable protein-based biomaterials and biocatalysts without the need for chemical modification.

Titania nanotube porosity controls dissolution rate of sputter deposited calcium phosphate (CaP) thin film coatings

Calcium phosphate (CaP) coatings are of continuing significant interest due to their ability to directly promote bone cell differentiation. Whereas sputter deposited CaP coatings have much to offer in this regard, in the as-deposited state they are inherently amorphous and readily undergo rapid dissolution. This behaviour severely limits their ability to support bone cell adhesion and the subsequent events of proliferation and/or differentiation without subsequent processing such as thermal annealing. Removal of the need for this additional processing step would significantly increase their utility. This paper reports a study of the use of nano-porous titania substrates to directly control the rate of dissolution of thin amorphous as-deposited CaP sputter coatings. Titania nanotubes with different pore sizes were prepared by electrochemical anodization of titanium foils and sputter coated with CaP. Dissolution studies were performed on the as-deposited CaP layers in cell culture media for periods of up to 21 days. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis confirmed the potential of the nanotubes to prolong the rate of loss of CaP over the entire 21 day period as compared to coatings prepared on flat polished titanium surfaces, which dissolved completely in less than 48 h. The CaP coated titania nanotube surfaces showed high levels of osteoblast attachment and proliferation with no signs of cell death. Alkaline phosphatase (ALP) activity measurements at 21 days indicated that the highest levels of osteoblast differentiation occurred on CaP thin films deposited onto titania nanotubes with an average pore size of 30 ± 7.5 nm and tube length of 1.3 ± 0.2 μm. These results indicate that prolonged availability of the as-deposited sputtered CaP can be provided for by use of a substrate surface comprising titania nanotubes. Moreover, nanotube pore size and tube length affect the rate of CaP dissolution and attendant cell behaviour thereon.

Wettability changes of TiO2 nanotube surfaces

This study examines the effect of environmental and experimental conditions, such astemperature and time, on the wettability properties of titania nanotube (TNT) surfacesfabricated by anodization. The fabricated TNTs are 60–130 nm inner diameter and 7–10 µm height. One-microliter water droplets were used to define the wettability of the TNTsurfaces by measuring the contact angles. A digital image analysis algorithm was developedto obtain contact angles, contact radii and center heights of the droplets on the TNTsurfaces. Bare titanium foil is inherently less hydrophilic with approximately60°–80° contact angle. The as-anodized TNT surfaces are more hydrophilic and annealing furtherincreases this hydrophilic property. Furthermore, it was found that the TNT surfacebecame more hydrophobic when aged in air over a period of three months. It is believedthat the surface wettability can be changed due to alkane contamination and organiccontaminants in an ambient atmosphere. This work can provide guidelines to better specifythe environmental conditions that changes surface properties of TNT surfaces and thereforeaffect their desirable function in specific applications such as orthopedic implants.

Effect of surface defects on biosensing properties of TiO 2 nanotube arrays

In this paper, highly ordered titania nanotube (TNT) arrays fabricated by anodization were annealed at different temperatures in CO to create different concentrations of surface defects. The samples were characterized by SEM, XRD and XPS. The results showed different concentrations of Ti 3+ defects were doped in TNT arrays successfully. Furthermore, after co-immobilized with horseradish peroxidase (HRP) and thionine chloride (Th), TNT arrays was employed as a biosensor to detect hydrogen peroxide (H 2O 2) using an amperometric method. Cyclic voltammetry results and UV–Vis absorption spectra presented that with an increase of Ti 3+ defects concentration, the electron transfer rate and enzyme adsorption amount of TNT arrays were improved largely, which could be ascribed to the creation of hydroxyl groups on TNT surface due to dissociative adsorption of water by Ti 3+ defects. Annealing in CO at 500 °C appeared to be the most favorable condition to achieve desirable nanotube array structure and surface defects density (0.27%), thus the TNT arrays showed the largest adsorption amount of enzyme (9.16 μg/cm 2), faster electron transfer rate (1.34 × 10 −3 cm/s) and the best response sensitivity (88.5 μA/mM l −1).

Nanotechnology in the Surface Treatment of Titanium Implant.

Tissue engineering has been enhanced by advance in biomaterial nature, surface structure and design. In this paper, I report specifically vertically aligned titania (TiO_2) nanotube surface structuring for optimization of titanium implants utilizing nanotechnology. The formation, mechanism, characteristics of titania nanotubes are explained and emerging critical role in tissue engineering and regenerative medicine is reviewed. The main focus of this paper is on the unique 3 dimensional tubular shaped nanostructure of titania and its effects on creating epochal impacts on cell behavior. Particularly, I discuss how different cells cultured on titania nanotube are adhered, proliferated, differentiated and showed phenotypic functionality compared to those cultured on flat titanium. As a matter of fact, the presence of titania nanotube surface structuring on titanium for dental applications had an important effect improving the proliferation and mineralization of osteoblasts in vitro, and enhancing the bone bonding strength with rabbit tibia over conventional titanium implants in vivo. The nano-features of titania nanotubular structure are expected to be advantageous in regulating many positive cell and tissue responses for various tissue engineering and regenerative medicine applications.

Pt nanoparticles on titania nanotubes prepared by vapor-phase impregnation–decomposition method

Platinum (Pt) nanoparticles were prepared on titania nanotubes (TNTs) by vapor-phase impregnation–decomposition method using platinum acetylacetonate as precursor. TNTs and Pt precursor were mixed in 3:1 weight ratio before vapor-phase impregnation. The mixed powders were heated at 453 K for 10 min to evaporate the precursor in a horizontal tube quartz reactor at a total pressure of 66.6 kPa. Then, the impregnated TNTs were moved to a higher temperature zone (673 K) inside the tube reactor to achieve the precursor decomposition. HAADF-STEM observations, AAS and XPS results revealed that this method allows the formation of uniformly distributed Pt nanoparticles on the surface of TNTs with a narrow distribution of particle size (2.1 nm mean size). Pt nanoparticles remain mainly as Pt 0 oxidation state with a Pt 0/Pt 2+ atomic ratio of 3.9.

Tailoring the surface functionalities of titania nanotube arrays

Nanotubular titanium oxide (TiO 2) produced by self-ordering processes using electrochemical anodization have been extensively explored in recent years as a new biomaterial for implants, drug delivery systems, cell growth, biosensors, immunoisolations, bioartificial organs and tissue engineering. Chemical inertness is the main weakness of this material when placed in contact with biological systems and surface modification is a possible solution of this problem. The aim of this study is to develop a flexible and facile method for surface modification of TiO 2 nanotubes to tailor new interfacial properties important in many biomedical applications. TiO 2 nanotubes were prepared by electrochemical anodization of titanium foil using ethylene glycol: NH 4F electrolyte (2% water and 0.3% NH 4F). Plasma surface modification using allylamine (AA) as a precursor has been applied to generate a thin and chemically reactive polymer (AAPP) film rich in amine groups on top of the TiO 2 nanotube surface. This initial polymer film was used for further surface functionalization by attachment of desired molecules. Two modification techniques were used to demonstrate the flexibility for building of new functionalities on titania nanotube surface: electrostatic adsorption of poly(sodium styrenesulfonate) (PSS) as an example of layer-by-layer assembly (LbL), and covalent coupling of poly(ethylene glycol) (PEG) as an example of creating a protein-resistant surface. These approaches for tailoring the surface chemistry and wettability of TiO 2 nanotubes offer considerable prospects for advancing their interfacial properties to improve existing and develop new functional biomaterials for diverse biomedical applications.

Active anatase (0 0 1)-like surface of hydrothermally synthesized titania nanotubes

Using 31P and 13C NMR with DFT calculations we demonstrate the exposed surface of titania nanotubes (TiNTs) is a stable, unterminated anatase (0 0 1)-like surface and is catalytically active under ambient conditions. We find that methanol dissociatively adsorbs on the surface of TiNTs agreeing with the predicted activity of surface dissociation of organic molecules on the crystalline (0 0 1)-anatase surface. We further examined the catalytic activity of anatase power, TiNT, and nanosheets in catalytic hydrolysis of S-[2-(diisopropylamino)ethyl]- O-ethyl methylphosphonothioate (VX) via 31P NMR and demonstrate that titanate-like nanosheets are inactive in the reaction owing to their hydroxylated (0 0 1) surface.

Carbon monoxide annealed TiO2nanotube array electrodes for efficient biosensor applications

Highly ordered titania nanotube (TNT) arrays fabricated by anodic oxidation of titanium foil followed with O2 and CO annealing were employed as matrices for the immobilization of horseradish peroxidase (HRP) and thionine chloride (Th) for biosensor application. The influence of annealing gases on TNT crystallinity, morphology, surface chemistry, and electrochemical properties were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), photoelectron spectroscopy (XPS), and cyclic voltammetry. The results showed that TNT arrays annealed in CO consisted of Ti3+ defects with carbon-doping and exhibited well defined quasi-reversible cyclic voltammetric peaks, indicating enhanced electron transfer and electrical conductivity. When immobilized with HRP and Th, the TNT electrodes were used to sense hydrogen peroxide (H2O2) as investigated by means of UV-Vis absorption spectroscopy, cyclic voltammetry, and amperometry. The results indicated that the biosensor based on a TNT array electrode annealed in CO possessed greatly enhanced properties compared to the as-grown and the O2-annealed TNT array electrodes. The improved biosensor properties of the TiO2nanotube arrays were ascribed to the carbon-doping and the formation of Ti3+ defects.

Decontamination of sulfur mustard and sarin on titania nanotubes

AbstractDecontamination reactions of sulfur mustard and sarin were studied on the surface of titania nanotubes and the data were compared with that of bulk titania. Before the reaction studies, titania nanotube samples were made by using hydrothermal method and were characterized by scanning electron microscopy, N2 BET, X‐ray diffractometry, and thermogravimetry. Soon after that, titania nanotube samples were exposed to sulfur mustard and sarin separately at room temperature (30°C) and the reactions were monitored by gas chromatography, whereas the reaction products were characterized by GC‐MS. The data explore the role of hydrolysis reactions and surface reactions for the decontamination of both sulfur mustard and sarin. © 2008 American Institute of Chemical Engineers AIChE J, 2008

Surface coatings for improvement of bone cell materials and antimicrobial activities of Ti implants

Ti surface was modified to simultaneously improve bone cell materials and antimicrobial activities. Titanium surface was first anodized in sodium fluoride and sulfuric acid electrolytic solution to form titania nanotube on the surface to improve the biocompatibility of the surface. Silver was electrodeposited on the titania nanotube surface at 5 V. Silver added titania nanotube surface was tested for compatibility with bone-cell materials interactions using human osteoblast bone cells. The antibacterial effect was studied using Pseudomonas aeruginosa. Our results show that silver-treated titania nanotube surface may provide antibacterial properties to prevent implants against postoperative infections without interference to the attachment and proliferation of bone tissue on titanium, which is commonly used in dental and orthopedic surgical procedures.

Evolution of titania nanotubes-supported WO x species by in situ thermo-Raman spectroscopy, X-ray diffraction and high resolution transmission electron microscopy

Structural evolution of WO x species on the surface of titania nanotubes was followed by in situ thermo-Raman spectroscopy. A total of 15 wt% of W atoms were loaded on the surface of a hydroxylated titania nanotubes by impregnation with ammonium metatungstate solution and then, the sample was thermally treated in a Linkam cell at different temperatures in nitrogen flow. The band characteristic of the W O bond was observed at 962 cm −1 in the dried sample, which vanished between 300 and 700 °C, and reappear again after annealing at 800 °C, along with a broad band centered at 935 cm −1, attributed to the v 1 vibration of W O in tetrahedral coordination. At 900 and 1000 °C, the broad band decomposed into four bands at 923, 934, 940 and 950 cm −1, corresponding to the symmetric and asymmetric vibration of W O bonds in Na 2WO 4 and Na 2W 2O 7 phases as determined by X-ray diffraction and High resolution transmission electron microscopy (HRTEM). The structure of the nanotubular support was kept at temperatures below 450 °C, thereafter, it transformed into anatase being stabilized at temperatures as high as 900 °C. At 1000 °C, anatase phase partially converted into rutile. After annealing at 1000 °C, a core–shell model material was obtained, with a shell of ca. 5 nm thickness, composed of sodium tungstate nanoclusters, and a core composed mainly of rutile TiO 2 phase.