Ordered Titanium Dioxide Nanotube Research Articles

Electrodeposited Platinum Nanoparticles on Highly Ordered Titanium Dioxide Nanotubes for Photocatalytic Application: Enhancement of Photocatalytic Degradation of Amido Black Dye

Electrodeposited Platinum Nanoparticles on Highly Ordered Titanium Dioxide Nanotubes for Photocatalytic Application: Enhancement of Photocatalytic Degradation of Amido Black Dye

TiO2 nanotubes modified with cobalt oxyphosphide spheres for efficient electrocatalytic hydrogen evolution reaction in alkaline medium

Electronic and surface modulation through coupling between oxygen and phosphorous in cobalt oxyphosphide (CoOP) is identified as an effective approach to enhancing the electrocatalytic hydrogen evolution reaction (HER) in an alkaline medium. This work demonstrates a one-step and safe electrodeposition method to modify the surface of ordered titania nanotubes (TNTs) with CoOP spheres. The effect of electrodeposition charge density, pH of the electrodeposition bath, and presence of citric acid on the electrocatalytic HER performance of CoOP-modified TNTs was investigated. The Ti/TNTs/CoOP electrode requires only 130 mV overpotential to deliver 10 mA cm−2 in a 1.0 M KOH electrolyte. The Tafel slope is estimated to be 72.5 mV dec−1. Both the HER performance and Tafel value of Ti/TNTs/CoOP are superior to CoOP deposited on bare Ti foil (165 mV and 78.4 mV dec−1), FTO (185 mV; 88.1 mV dec−1), and glassy carbon (214 mV; 93 mV dec−1). The electrochemically active surface area (ECSA) and impedance spectroscopy findings revealed that the synergistic coupling between the CoOP and TNTs enhances the surface area and density of accessible active sites while reducing the charge transfer resistance at the electrode/electrolyte interface. Such a synergistic effect is ascribed to the effective electronic interaction between CoOP and TNTs, and the faster electron transfer kinetics because of the unidirectionality of the 1-D TNTs.

INFLUENCE OF ANATASE TITANIUM DIOXIDE NANOTUBE ARRAYS ON HUMIDITY SENSOR SYNTHESIZED BY ELECTROCHEMICAL ANODIZATION

Humidity sensors have become increasingly important and widely used to improve the quality of life and industrial processes. Over the past decades, titanium dioxide (TiO2) has received wide attention in many promising areas such as sensors, solar cells, and photocatalytic. However, TiO2 required high operating conditions such as high temperatures to examine the crystalline stability phase. This study focuses on highly ordered titanium dioxide nanotube arrays (TiO2 NTAs) film synthesized using the electrochemical anodization method. Annealing temperature effect on the fabricated TiO2 NTAs was investigated. An electrolyte solution was prepared by mixing ammonium fluoride (0.3 wt%) and ethylene glycol (25 ml) with deionized water (2 vol%). Titanium (Ti) sheet was anodized at 35 V for 120 minutes. The films were annealed from 350 °C to 550 °C. FESEM images showed the diameter size of TiO2 NTAs film decreases as the annealing temperatures increases. Results had also shown that the average diameter annealed at 450 °C was around ~50.82 nm while the XRD pattern demonstrated TiO2 NTAs exhibiting an anatase phase with a prominent (101) peak recorded for the sample prepared at 450 °C with a high crystallite size of 29.17 nm. The calculated optical band gap annealed at 450 °C (3.24 eV) is comparable with other literature. The current-voltage characteristic of TiO2 NTAs film reported a high current for 450 °C (1.12 x 10-5 A) with a conductivity of 0.048 S.cm-1 and high sensitivity (287.72).

Photocatalytic degradation of azo dyes in aqueous solution by using highly ordered titania nanotube films

Photocatalytic degradation of azo dyes in aqueous solution by using highly ordered titania nanotube films

Achievement and electrochemical responsiveness of advanced boron-doped ultrananocrystalline diamond on highly ordered titanium dioxide nanotubes

Boron-doped ultrananocrystalline diamond grown on titanium dioxide nanotubes without seeding pre-treatment (B-UNCDWS/TDNT/Ti), as a porous composite, was successfully achieved. Innovative approaches concerning the highly ordered TDNT production as well as its singular diamond formation by hot filament chemical vapor deposition (CVD) were explored. The B-UNCD homogeneous cluster progress on the TDNT porous walls as a function of the growth times from 1 to 7 h led to remarkable composite morphologies, keeping the TDNT porosity, where the TiO2 – TiC conversion dominated the renucleation process facilitating the nanometric scale control. Scanning electron microscopy images confirmed the continuous ultrananocrystalline formation as nanoclusters on the TDNT walls with their size evolution as a function of growth time also showing an increase in the CVD diamond ballas clusters. Raman spectra and X-Ray patterns exhibited the diamond characteristics with defined peaks and TiC formation, as expected. The ID(220)/(111) and ID(311)/(111) ratio intensities pointed out the films governed by (220) diamond phase, due to their high renucleation process. Besides, the intensity ratios for both TiC (111) and TiC (200) phases with D(111) peak showed a carbon atoms competition between surface and bulk diffusion on the TiC layer. The electrode reversibility evaluated from cyclic voltammetry curves followed the quasi-reversible criteria for all samples, confirming their promising performance. Mott-Shottky plots are in good agreement with Raman spectra for boron-doped films from 1018 to 1019 B.cm−3 where the highest doped diamond was obtained for the thickest films of 5 and 7 h.

Supercapacitor electrodes based on modified titania nanotube arrays on flexible substrates

Abstract Highly ordered titania nanotube arrays were synthesised on titanium metal foil through electrochemical anodisation. The annealed samples were characterised through scanning electron microscopy and X-ray diffraction analysis. The electrochemical characterisations of the arrays were done through cyclic voltammetry, galvanostatic charge discharge and electrochemical impedance spectroscopy analyses. The titania nanotube arrays exhibited a specific capacitance of 6.8 mF cm–2 at 5 mV s–1 scan rate, which is very much higher than that reported earlier. Pseudocapacitive metal oxides were deposited on these arrays forming composite supercapacitor electrodes and their supercapacitor properties were compared with same deposited on bare titanium foil substrates. Pseudocapacitive metal oxides deposited on these titania nanotube array substrates exhibited improved supercapacitor performance and stability over the same deposited on titanium foil substrates.

A Simple g-C3N4/TNTs Heterojunction for Improving the Photoelectrocatalytic Degradation of Methyl Orange

In this work, highly ordered titanium dioxide nanotube arrays (TNTs) were first prepared by anodic oxidation method. Then, g-C3N4/TNTs heterojunctions were prepared by ultrasonically loading graphitic carbon nitride (g-C3N4) onto the TNTs. The morphology and crystal structure of TNTs and g-C3N4/TNTs were characterized by SEM/TEM and XRD. The photoelectrocatalytic (PEC) degradation of methyl orange (MO) by TNTs and g-C3N4/TNTs was studied in a PEC degradation system. The photocatalytic (PC), electrocatalytic (EC), and PEC degradation properties were compared, and the effect of pollutant concentration on the degradation performance of the catalysts was analyzed. According to the experimental results, the degradation rate of MO with TNTs only reaches 65.1% after 120 min, while the degradation rate of MO with g-C3N4/TNTs reaches 84.6% in the same time. Due to the synergistic effect of light and electricity, the PEC degradation efficiency of the two catalysts is greater than the sum of PC and EC degradation, proving that g-C3N4/TNTs heterojunctions provide excellent PEC performance for the degradation of MO.

Thermal annealing of ordered TiO2 nanotube arrays with water vapor-assisted crystallization under a continuous gas flow for superior photocatalytic performance

Ordered titanium dioxide nanotube arrays fabricated via electrochemical route are considered as a promising material for photocatalytic applications. Due to their amorphous character, a subsequent crystallization step is usually required. In this work, well-aligned nanotube arrays were annealed under flowing gas streams of different compositions (air/steam, air, N2/steam, N2, and O2/steam) in a temperature range from 140 to 543 °C. Under continuous gas flow, the morphology of the crystallized titanium dioxide is strongly affected by the gas atmosphere. When using a dry gas for annealing, the tube structure was almost destroyed after 1 h treatment at 473 °C. In contrast, when annealing the titania nanotube array in a water vapor/gas stream, the tube morphology can be maintained up to 543 °C and 10 h annealing time. Moreover, nanotube arrays crystallized in a flowing gas atmosphere containing water vapor showed a significantly higher photocatalytic activity for phenol degradation under UV irradiation than nanotube arrays crystallized in a dry gas stream. Reasons for this behavior might be the preservation of the tubular structure as well as a lower concentration or density of structural defects in presence of water vapor which leads to an enhanced generation of reactive oxygen species when the arrays are exposed to UV-light.

Preparation and fabrication of NiCo coated TiO2-NTs for hydrogen evolution

ABSTRACT Hydrogen production via water splitting is a very attractive way using effective electrocatalysts. One of the effective electrocatalysts that are used in water splitting is NiCo alloys. In this study, highly ordered titanium dioxide nanotubes (TiO2-NTs) are firstly prepared by electrochemical anodization method in terms of being a substrate material for NiCo coatings. Hydrogen evolution behaviors of three types of NiCo coated TiO2-NTs are investigated in 1 M KOH solution at room temperature. Coated surfaces are characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), and cyclic voltammetry (CV). HER activities of NiCo coated TiO2-NTs are investigated by cathodic current–potential curves, electrochemical impedance spectroscopy (EIS), and electrolysis process. The stability of NiCo-coated TiO2-NTs is also investigated. Results show that TiO2-NTs surface leads to large surface area and high porosity for NiCo nano-particles and thus, HER performance of coatings increases. NiCo-coated TiO2-NTs improves the catalytic HER activity in terms of current density, hydrogen volume, polarization resistance (Rp), and conductivity. Enhanced HER activity can be based on the boosted surface area, conductivity, and more active sites for hydrogen ion adsorption as well as synergistic effects.

Highly Ordered of Anatase Titanium Dioxide Nanotube Arrays at Different Calcination Temperatures via Electrochemical Anodization Method

Highly ordered titanium dioxide nanotube arrays (TNTAs) were fabricated via electrochemical anodization of Ti sheet in electrolyte containing aqueous and nonaqueous electrolyte. The formation of highly ordered TNTAs was varied by calcination temperatures (350, 450, 550oC) for 120 minutes to investigate the effect of calcination temperature on surface morphology, roughness, crystallinity and band gap energy. The field emission scanning electron microscopy revealed that the prepared TNTAs grow uniformly with average diameter in the range of 48.23 to 52.14 nm as the temperature increased from 350 to 550oC. The X-ray diffraction pattern showed the TNTAs exhibit anatase phase with prominent (101) peak recorded for the sample calcined at 450oC. The transformation from anatase to rutile phase appeared after calcination at 450oC. The band gap value (~3.24 eV) was obtained for all calcination temperature sample due to homogeneity of the TNTAs structures.

Nanofibrillated chitosan coated highly ordered titania nanotubes array/graphene nanocomposite with improved biological characters

Designing multifunctional surfaces is key to develop advanced materials for orthopedic applications. In this study, we design a double-layer coating, assembled onto the completely regular titania nanotubes (cRTNT) array. Benefiting from the biological and topological characteristics of chitosan nanofibers (CH) and reduced graphene oxide (RGO) through a unique assembly, the designed material features promoted osteoblast cell viability, prolonged antibiotic release profile, as well as inhibited bacterial biofilm formation. The synergistic effect of RGO and CH on the biological performance of the surface is investigatSed. The unique morphology of the nanofibers leads to the partial coverage of RGO-modified nanotubes, providing an opportunity to access the sublayer properties. Another merit of this coating lies in its morphological similarity to the extracellular matrix (ECM) to boost cellular performance. According to the results of this study, this platform holds promising advantages over the bare and bulk biopolymer-modified TNTs.

Morphology and Optical Properties of Highly Ordered TiO2 Nanotubes Grown in NH4F/o-H3PO4 Electrolytes in View of Light-Harvesting and Catalytic Applications

Highly ordered titanium dioxide nanotube (TiO2 NT) arrays were grown by electrochemical anodization of titanium in a molten NH4F/o-H3PO4 electrolyte. NTs with various diameters, lengths, wall thick...

Anodization of Highly Ordered Titania Nanotube Prepared with Organic Electrolyte

Ti-6Al-4V as an implant material has bio-inert properties, so it does not support any tissues or bone cells reaction. This study aims to increase the tendency of osteoblast's cell attachment to the surface of implant Ti-6Al-4V by fabricating nanotube structure on the surface by anodization. This study also conducted to study the effect of elements from titanium alloys and organic electrolytes on the mechanism of formation of nanotube structures. The anodization method was chosen because it was easy to do, effective, and inexpensive. The samples were prepared by ground and polished, then washed by ultrasonic. Anodization used organic electrolytes in the form of a mixture of ethylene glycol, 0.5 M NH4F, and 4 w.t% deionized water. The study of the effect of voltage and duration time was carried out to understand the mechanism of nanotube formation, through morphological observation on the surface and cross-section area of nanotubes using SEM and characterization of elements using EDS, diameter, and length of highly ordered nanotubes was observed. The results of the characterization showed that the tube diameter is adjusted by the voltage, while duration time influence the tube length, with a linear relationship, so the widest diameter achieved at 40V 5h, but the longest tube achieved at 30 V 5h. Whereas for 5h duration, the upper part of the tube collapsed and disintegrated. The fluoride ions incorporated at the tube surfaces formed fluoride-titanium oxide cubic agglomerates, and the whole nanotube surface was oxide.

Electrochemical Biosensors with Cross-Linked Hydrogels

Leland C. Clark Jr. and Champ Lyons introduced in 1962 the principle of the first electrochemical biosensor with immobilized glucose oxidase (GOx) [1]. This device was specifically designed and used for fast glucose analysis in blood samples from diabetics. Since then, the biosensor field has experienced important growth. In last few decades, this field has been widely explored in many different environments, such as clinical, biotechnological, food and pharmaceutical. This type of device is object of attention because it allows analysis with high specificity, sensitivity, selectivity and low response time.A key parameter for the proper functioning of electrochemical biosensors is the enzyme immobilization onto the electrochemical interface [2]. Immobilization must be performed in a way that the selected enzyme maintains either structure and spatial orientation. In addition, substrate and product have to be able to diffuse to/from the active site, where the biological reaction takes place. One of the simplest and cost effective immobilization method is the polymer entrapment using natural origin polysaccharides. In that frame, chitosan is currently receiving a great deal of interest because of its intrinsic properties: biocompatible, biodegradable, high abundance, low cost of production and it easily forms hydrogels. However, the poor stability of the hydrogel is of major concern [3] when used as an immobilization strategy in the construction of electrochemical biosensors, since it affects the biosensor lifespan.In the present work, amperometric glucose biosensors based on glucose oxidase (GOx) immobilization onto highly ordered titanium dioxide nanotube arrays (TiO2NTAs) was used to determine the long term stability of the constructed probes. TiO2NTAs were grown by electrochemical anodization of a titanium metal disc in ethylene glycol containing ammonium fluoride (0.3%w/w) and water (2%w/w). The electrochemical synthesis was performed at 30 V for 17 hours. This anodization time yields the maximum sensitivity of the sensor. Higher times result in the nanotube walls collapse. Finally, a thermal annealing was performed at 500 ⁰C for 3 h in air to crystallize TiO2 nanotubes from amorphous to anatase phase.In the sensor architecture chitosan was used as a base material for enzyme immobilization in the hydrogel matrix: Ti/TiO2NTAs/GOx–Chitosan. In order to increase the stability of the immobilization matrix, different crosslinking agents were evaluated onto the chitosan matrix: glutaraldehyde, hypochlorous acid and poly(ethylene glycol) diacrylate. Non-modified chitosan provided a biosensor lifespan around 30 days. In contrast, the used of modified chitosan either increases the long-term stability even the sensitivity of the biosensor.

Ti/TiO2ntas/RuO2 Probe for Amperometric Detection of Hypochlorite in Solution

Tool to help provide a healthy environment. Disinfection is a process that is designed to kill actively growing and vegetative microbial microorganisms to a certain level. Generally, there are two methods of disinfection: chemical and physical1. The physical agents of disinfection that have been used include ultraviolet light (UV), electron beam, gamma-ray irradiation, sonication, and heat. Considering the chemical methods, there is a great variety of compounds such as chlorine, ozone, the metals copper and silver, phenolic compounds, quaternary ammonium salts, alcohols and hydrogen peroxide among others. Historically, the most widely used chemical disinfection procedure is chlorination because of its low cost, ease of application, and ability to inactivate a wide variety of pathogenic microorganisms.Hypochlorite ion (ClO-) is widely used in daily life applications such as household bleach, disinfection of drinking water and cooling-water treatment among others. Nevertheless, it has been reported that the abnormal production or the excessive intake of ClO- can lead to numerous diseases, including cardiovascular disorders, neuron degeneration, arthritis or even cancer2. Hence, it is of utmost importance to develop rapid and sensitive methods for the determination of ClO-. So far, iodometric titration and colorimetric methods based on the reaction of ClO- with organic reagents have been widely used so as to determine hypochlorite concentration. These methodologies usually require tedious procedures.In the present work, we propose the design of an amperometric sensor for fast hypochlorite analysis. The architecture of the sensor is a RuO2 coating onto a highly ordered titanium dioxide nanotube array (Ti/TiO2NTAs/RuO2). TiO2NTAs were grown by electrochemical anodization of a titanium metal disc in ethylene glycol containing ammonium fluoride (0.3%w/w) and water (2%w/w). The electrochemical synthesis was performed at 30V. Afterwards, RuO2 was deposited layer by layer onto the TiO2NTAs substrate and a final annealing process was performed at 500 oC in order to fix it to the nanostructure.The fundamental analytical parameters (linear range, limit of detection and sensitivity) of the probe were characterized in the presence of hypochlorite. The sensor working potential was also optimized and then fixed at 0.6 V. Finally, the hypochlorite content of different samples was measured using the sensor and compared with the DPD-method value (Standard Methods: 4500-Cl G)3. The proposed amperometric sensor offers an alternative tool to the classical DPD-method, with higher sensitivity, lower limit of quantification and analysis time.

Modelling of simultaneously obtained small and wide angle synchrotron-radiation scattering depth profiles of ordered titania nanotube thin films

Thin-films of vertically aligned titanium dioxide nanotubes are key constituents of charge transfer layers in 3rd generation photovoltaics. The beneficial charge transport primarily occurs due to the favourable microstructural features, i.e. the large effective surface-to-volume ratio. Here measuring methods are selected which are sensitive to microstructural features: Simultaneous Grazing Incidence Small and Wide Angle X-Ray Scattering (GISWAXS) and Scanning Electron Microscopy (SEM). Further, a model is developed for the simulation and explanation of the GISWAXS experimental data. Titanium nanotube arrays were investigated, which were previously successfully produced by electrochemical anodization of titanium thin film evaporated onto a zinc-oxide coated glass substrate. The developed model was shown to be appropriate to describe the obtained samples, which consist of arrays of single nanotubes with a diameter of 40–80 nm, and a titanium dioxide layer with a porosity of 30–50%. Within this work, we presented simultaneous GISWAXS as a comparable tool to SEM for the fast and successful study of the average nanotubes’ diameters in nanotubes arrays.

Effect of composition electrolyte on the morphology and photocatalytic activity of anodized titanium nanoporous

The morphology of titanium dioxide and titanium dioxide-tungsten trioxide nanocomposite films fabricated by anodizing in a glycerol solution containing 0.13 M NH4F and different quantity of Na2WO4 was investigated as a function of sodium tungstate concentrations. The effects of sodium tungstate concentration on the surface morphology were observed by scanning electron microscopy (SEM). It was clearly seen that highly ordered titanium dioxide nanotube array films were formed in an anodizing solution free of tungsten. With a gradual increase in the sodium tungstate concentration, these nanotube structures changed to nanohoneycombs, nanoporous and compact films without porosity. These findings indicate that the composition of anodizing bath is very important factor in determining the surface and structure of anodized films. UV-Visible spectroscopy data show that the band gap decrease with increasing sodium tungstate from 3.23 eV for bare titanium dioxide to 2.78 eV for titanium dioxide-tungsten trioxide nanocomposites. Photo catalytic activity of samples was evaluated by measuring the degradation of methylene blue dye under visible light irradiation. Results revealed that nanocomposite films have excellent photo catalytic performance.

Titanium Dioxide Nanotubes as Model Systems for Electrosorption Studies.

Highly ordered titanium dioxide nanotubes (TiO2 NTs) were fabricated through anodization and tested for their applicability as model electrodes in electrosorption studies. The crystalline structure of the TiO2 NTs was changed without modifying the nanostructure of the surface. Electrosorption capacity, charging rate, and electrochemical active surface area of TiO2 NTs with two different crystalline structures, anatase and amorphous, were investigated via chronoamperometry, cyclic voltammetry, and electrochemical impedance spectroscopy. The highest electrosorption capacities and charging rates were obtained for the anatase TiO2 NTs, largely because anatase TiO2 has a reported higher electrical conductivity and a crystalline structure that can potentially accommodate small ions within. Both electrosorption capacity and charging rate for the ions studied in this work follow the order of Cs+ > Na+ > Li+, regardless of the crystalline structure of the TiO2 NTs. This order reflects the increasing size of the hydrated ion radii of these monovalent ions. Additionally, larger effective electrochemical active surface areas are required for larger ions and lower conductivities. These findings point towards the fact that smaller hydrated-ions experience less steric hindrance and a larger comparative electrostatic force, enabling them to be more effectively electrosorbed.

Ordered titania nanotubes layer selectively annealed by laser beam for high contrast electrochromic switching

The phase conversion from amorphous into crystalline one in the selected area of as-anodized titania nanotubes was achieved via laser treatment. The optimized processing parameters enable fast, one-minute crystallization of titania within an area limited by a shadow mask and without any morphology damage of ordered TiO2 tubular film. The laser annealed titania nanotubes could be easily overgrown by a conducting polymer without any additional activation procedure. The organic matrix infiltrated down to the titanium substrates as was revealed on the basis of depth profile of elemental composition recorded using X-ray photoelectron spectroscopy technique performed under the etching mode. Obtained inorganic-organic composite exhibits a doubling of its colour depending on the applied potential and high contrast electrochromic properties were verified.

Enhancement of Capacitive Performance in Titania Nanotubes Modified by an Electrochemical Reduction Method

Highly ordered titania nanotubes (TNTs) were synthesised by an electrochemical anodization method for supercapacitor applications. However, the capacitive performance of the TNTs was relatively low and comparable to the conventional capacitor. Therefore, in order to improve the capacitive performance of the TNTs, a fast and facile electrochemical reduction method was applied to modify the TNTs (R-TNTs) by introducing oxygen vacancies into the lattice. X-ray photoelectron spectroscopy (XPS) data confirmed the presence of oxygen vacancies in the R-TNTs lattice upon the reduction of Ti4+ to Ti3+. Electrochemical reduction parameters such as applied voltage and reduction time were varied to optimize the best conditions for the modification process. The electrochemical performance of the samples was analyzed in a three-electrode configuration cell. The cyclic voltammogram recorded at 200 mV s−1 showed a perfect square-shaped voltammogram indicating the excellent electrochemical performance of R-TNTs prepared at 5 V for 30 s. The total area of the R-TNTs voltammogram was 3 times larger than the unmodified TNTs. A specific capacitance of 11.12 mF cm−2 at a current density of 20 μA cm−2 was obtained from constant current charge-discharge measurements, which was approximately 57 times higher than that of unmodified TNTs. R-TNTs also displayed outstanding cycle stability with 99% capacity retention after 1000 cycles.