Self-organized TiO2 Nanotube Research Articles

Anodic TiO2 Single Nanotubes with Fe3O4 Nanoparticles: Advanced Photocatalytical Applications

Self-organized TiO2 nanotube (TNT) layers, formed by electrochemical anodization of Ti foils, have attracted tremendous scientific and technological attention, due to their remarkable properties such as the tunability of dimensions, their directionality, high surface area, high stability, and the ability to absorb a significant amount of incident light [1,2].The most widely used electrolyte to develop TNT layers is based on ethylene glycol containing small amounts of water and fluoride ions. However, TNT layers prepared in these electrolytes present a double-walled structure. The outer wall consists of almost pure TiO2, and the inner wall consists of TiO2 contaminated with carbon and fluoride species [3,4]. In recent years, the selective etching of the inner nanotube wall of the TNT layer enabled the synthesis of single-wall nanotubes that showed superior photo-electrochemical performance compared to their double-walled counterparts [5,6]. Modification of the etching process by prolonging and optimizing the etching conditions also enabled the synthesis of single-tube TiO2 powders, which offer various new prospects compared to the TNT layers. At first glance, these powders can be effectively decorated with Fe3O4 nanoparticles to act as magnetically guidable photocatalysts, which is exactly what we recently exploited [7,8,9].The presentation will discuss the synthesis of these TiO2 nanotube morphologies and their performance in the photocatalytic degradation of model dye in the liquid phase and model drugs that are unwanted in wastewater. We will demonstrate how photocatalytic performance is influenced by single nanotubes and single nanotubes decorated with Fe3O4 magnetic particles. Experimental details and photocatalytic results will be presented and discussed.

(Invited) One Dimensional Anodic TiO2 Nanotubes for Energy and Catalytic Applications

Self-organized TiO2 nanotube (TNT) layers, prepared by anodization of Ti have in suitable electrolytes, attracted considerable scientific and technological interest, especially due to their wide range of applications including (photo-) catalysis, hydrogen generation and biomedical uses [1,2].The advantages of anodic TNT layers compared to TiO2 nanotubes prepared by other methods (e.g. hydrothermal) are the tunability of dimensions, their directionality, the ability to absorb significant amount of incident light, and the possibility to utilize nanotube interiors and exteriors for decoration or coating with secondary materials [2].The presentation will review the recent advancements in TNT layer synthesis for their use for the photocatalytic degradation of pollutants in the liquid and in the gas phase. This will include the upscaling of TNT layers from the laboratory scale to several dozens of cm2 [3-6], with a strong focus on the anodization of 3D Ti substrates by bipolar electrochemistry, which cannot be directly connected to the potentiostat (such as Ti meshes) [5-6]. The application of these large scale TiO2 nanotube layers in flow-through photocatalytic reactors will be discussed [3-6]. Additionally, the selective etching of double wall TiO2 nanotube layers towards single wall TiO2 nanotube layers [7] and single nanotube powders [8, 9] will be presented, showing the possibility of preparing magnetically guidable single nanotube photocatalysts by a decoration with Fe3O4.The presentation will also summarize recent advancements in the utilization of TNT layers in energy conversion and energy storage applications [10], in particular Li-ion microbatteries. Experimental details and photocatalytic and battery results will be presented and discussed.

TiO2 nanotubes modification by photodeposition with noble metals: Characterization, optimization, photocatalytic activity, and by-products analysis

TiO2 nanotubes modification by photodeposition with noble metals: Characterization, optimization, photocatalytic activity, and by-products analysis

Wettability and adhesion of nanotubes applied to the surface of titanium implants by anodic oxidation.

The aim of this study was to evaluate the wettability and adhesion of self-organized TiO2 nanotubes formed on the surface of 8 commercially pure titanium (CP-Ti) disks and 12 dental implants (n = 12) by anodization in a glycerol-H2O (50-50 v/v) electrolyte containing NH4F. Two disk specimens were not submitted to anodization (controls). The nanotubes thus obtained had average dimensions of 50 nm in diameter by 900 nm in length. The treated disk specimens were stored for 2, 14 and 35 days (n = 2), and the wettability of their surfaces was evaluated with a goniometer at the end of each storing period. The adhesion of nanotubes to titanium was evaluated by field emission scanning electron microscopy after subjecting the 12 implants to a simulation of clinical stress in two-part synthetic bone blocks. After installing the implants with the application of an insertion torque, the two halves of the block were separated, and the implants were removed. The nanotubes remained adhered to the substrate, with no apparent deformation. The contact angles after 14 days and 35 days were 16.47° and 17.97°, respectively, values significantly higher than that observed at 2 days, which was 9.24° (p < 0.05). It was concluded that the method of anodic oxidation tested promoted the formation of a surface suitable for clinical use, containing nanotubes with levels of wettability and adhesion to titanium compatible with those obtained by other methods found in the literature. The wettability, however, did not prove stable over the tested storage periods.

Photocatalytic TiO2 Nanotube Layers on 3D Substrates Using Bipolar Electrochemistry

Self-organized TiO2 nanotube (TNT) layers have attracted considerable scientific and technological interest over the past almost 20 years, due to their wide range of applications, including (photo-) catalysis, hydrogen generation and biomedical uses [1,2]. The synthesis of these TNT layers is usually carried out by electrochemical anodization of valve Ti metal substrates in various F--containing electrolytes using a conventional 2-electrode set-up with the Ti substrate as anode and a Pt-foil as cathode.By now, the TiO2 nanotube layer modification of Ti substrates is mainly focused on planar substrates, such as Ti foils and 2D Ti meshes, as these substrates can easily be connected to the potentiostat during anodization. However, for the real application in photocatalytic cleaners, 3D Ti substrates, such as 3D meshes or Ti spheres, are of high interest due to their significantly increased surface area compressed in a small volume.To anodize such 3D Ti substrates towards TiO2 nanotube layers, bipolar electrochemistry can be employed instead of using a conventional set-up [3-5]. In such a bipolar set-up, the Ti substrate is not directly connected to the potentiostat but placed in an electrolyte between two so-called feeder electrodes. Due to the electric field between the feeder electrodes, the Ti substrate is polarized and can be anodized if the applied potential between the feeder electrodes is high enough. This method opens the door for the preparation of TNT layers with gradients in dimensions (i.e. diameter and length of the nanotubes) [3-5] as well as for the preparation of TNT layers on Ti substrates, which cannot be directly connected to the potentiostat, e.g. small Ti spheres [6] and complicated 3D printed structures [7].In this presentation, the preparation of TNT layers on small Ti spheres [6] as well as on 3D printed Ti substrates [7] using bipolar electrochemistry will be shown. Their application in liquid and gas phase photocatalysis will be discussed. Furthermore, we will also show the possibility of using closed bipolar electrochemical cells, consisting of two closed half-cells with the Ti substrate as obstacle between the cells for the preparation of TiO2 nanotube layers with different dimensions on the two sides of a classical Ti foil [8].

(Invited) TiO2 Single Nanotubes Decorated with Fe3O4 Nanoparticles for Photocatalytical Environmental Applications

Self-organized TiO2 nanotubes arrays, formed by electrochemical anodization of Ti, have attracted tremendous scientific and technological attention, due to their remarkable properties such as the tunability of dimensions, their directionality, high surface area, high stability, and ability to absorb a significant amount of incident light [1,2].The most widely used electrolyte for the synthesis of TiO2 nanotube layers is based on ethylene glycol containing small amounts of water and fluoride ions. However, nanotubes prepared in these electrolytes present a double-walled structure. The outer wall consists of almost pure TiO2, and the inner wall consists of TiO2 contaminated with carbon and fluoride species [3,4]. In recent years, the selective etching of the inner nanotube wall on Ti layer enabled the synthesis of single-wall nanotubes that showed superior photo-electrochemical performance compared to their double-walled counterparts [5]. An extensive etching also enabled the synthesis of single-tube powders, which can be in turn effectively decorated with Fe3O4 nanoparticles to act as magnetically guidable photocatalysts [6,7].The presentation will discuss the synthesis of these nanotube morphologies and their performance in the photocatalytic degradation of model dye in the liquid phase as well as model drugs that are problematic in wastewaters. We will demonstrate how the photocatalytic performance is influenced by the single nanotubes and single nanotubes decorated with Fe3O4 magnetic particles. Experimental details and photocatalytic results will be presented and discussed.

Formation of self-organized TiO2 nanotube arrays and its photoelectrochemical response

Formation of self-organized TiO2 nanotube arrays and its photoelectrochemical response

Facile Synthesis of Ge@TiO2 Nanotube Hybrid Nanostructure Anode Materials for Li-Ion Batteries.

Utilizing nanostructures of Li-alloying anode materials (e.g., Si, Ge, Sn, etc.) has been proposed as a key strategy to improve the electrochemical performance. However, the main challenge lies in the costly and complex nanostructure synthesis processes. Notably, the nanostructure growth processes are mainly supported by Li-inactive templates, which later need to be removed, and the template removal process results in the destruction of the desired nanostructures. In this report, we demonstrated the use of a Li-active, self-organized TiO2 nanotube template to fabricate germanium (Ge)-based nanostructured anodes. This has been achieved as follows: first, TiO2 nanotubes are fabricated via electrochemical anodization of titanium foil. Then, the nanotubes are coated with a Ge film in the second step via electrodeposition. Besides the effective nanostructure growth using a Li-active template, the implemented electrochemical synthesis methods are cost-effective, accessible, and scalable. Furthermore, the electrochemical methods allow the fabrication of nanostructures with well-controlled structures, morphology, and compositions. Accordingly, a Ge-coated TiO2 nanotube (Ge@TiO2) nanocomposite anode has been successfully fabricated, and its electrochemical performance has been tested for Li-ion batteries. The study has shown the important roles of TiO2 nanotube arrays in improving the performance by providing strong mechanical support to buffer the volume expansion and offering a high surface area to enhance Ge-active mass loading. Moreover, the direct contact of the nanotubes with a Ti current collector facilitates one-dimensional (1D) electron transport and avoids the need of adding inactive binders or conductive additives.

Bipolar Anodization for the Synthesis of TiO2 Nanotube Layers: New Concepts and Cell Designs

Self-organized TiO2 nanotube (TNT) layers have attracted considerable scientific and technological interest over the past almost 20 years, due to their wide range of applications, including (photo-) catalysis, hydrogen generation and biomedical uses [1,2]. The synthesis of these TNT layers is usually carried out by electrochemical anodization of valve Ti metal substrates in various F--containing electrolytes using a conventional 2-electrode set-up with the Ti substrate as anode and a Pt-foil as cathode.By now, the TiO2 nanotube layer modification of Ti substrates is mainly focused on planar substrates, such as Ti foils and 2D Ti meshes, as these substrates can easily be connected to the potentiostat during anodization. However, for the real application in photocatalytic cleaners, 3D Ti substrates, such as 3D meshes or Ti spheres, are of high interest due to their significantly increased surface area compressed in a small volume.To anodize such 3D Ti substrates towards TiO2 nanotube layers, bipolar electrochemistry can be employed instead of using a conventional set-up [3-5]. In such a bipolar set-up, the Ti substrate is not directly connected to the potentiostat but placed in an electrolyte between two so-called feeder electrodes. Due to the electric field between the feeder electrodes, the Ti substrate is polarized and can be anodized if the applied potential between the feeder electrodes is high enough. This method opens the door for the preparation of TNT layers with gradients in dimensions (i.e. diameter and length of the nanotubes) [3-5] as well as for the preparation of TNT layers on Ti substrates, which cannot be directly connected to the potentiostat, e.g. small Ti spheres [6] and complicated 3D printed structures [7].In this presentation, the preparation of TNT layers on small Ti spheres [6] as well as on 3D printed Ti substrates [7] using bipolar electrochemistry will be shown. Their application in liquid and gas phase photocatalysis will be discussed. Furthermore, we will also show the possibility of using closed bipolar electrochemical cells, consisting of two closed half-cells with the Ti substrate as obstacle between the cells for the preparation of TiO2 nanotube layers with different dimensions on the two sides of a classical Ti foil [8].

Large-Scale Anodic TiO2 Nanotube Layers: Gas Phase Photocatalysis and Virus Killing

Self-organized TiO2 nanotube layers have attracted considerable scientific and technological interest over the past 15 years motivated for their wide range of applications including (photo-) catalysis, hydrogen generation and biomedical uses [1,2]. The synthesis of the 1D TiO2 nanotube layers is carried out by a conventional electrochemical anodization of valve Ti metal sheets in various electrolytes.By now, the synthesis of TiO2 nanotube layers with different nanotube dimensions (diameter, length) and the application of these nanotube layers is well established on the laboratory scale. However, for real applications outside the laboratory scale, such as photocatalysis [3], TiO2 nanotube layers of much larger size are necessary. To date, just a few efforts were carried out to scale up the size of the nanotube layers to more than a few cm2 [3-7] due to the difficulty of controlling the parameters of the anodization process on a larger scale. The main challenge is the huge current received during the anodization of large substrates. This, in turn, leads to an increase in the electrolyte temperature that may result in dielectric breakdown of the growing nanotube layers.In this presentation, the preparation of TiO2 nanotube layers on larger area titanium substrates (dozens of cm2) will be discussed, taking into account the control of the anodization parameters. The TiO2 nanotube layers with different thicknesses and nanotube diameters were employed for gas phase photocatalysis, following the ISO standards [3,8]. In addition, results from antivirotic tests of these layers will be demonstrated. Experimental details and photocatalytic results will be presented and discussed.

Self-organized TiO2 Nanotube Arrays with Controllable Geometric Parameters for Highly Efficient PEC Water Splitting①

Self-organized TiO2 Nanotube Arrays with Controllable Geometric Parameters for Highly Efficient PEC Water Splitting①

A comparative study of two-step anodization with one-step anodization at constant voltage

Two-step anodization has been widely used because it can produce highly self-organized anodic TiO2 nanotubes, but the differences in morphology and current-time curve of one-step anodization and two-step anodization are rarely reported. Here, one-step anodization and two-step anodization were conducted at different voltages. By comparing the FESEM image of anodic TiO2 nanotubes fabricated by one-step anodization and two-step anodization, it was found that the variation of morphology characteristics is same with voltage. The distinction of morphology and current-time curve between one-step anodization and two-step anodization at the same voltage were analyzed: the nanotube average growth rate and porosity of two-step anodization are greater than that of one-step anodization. In the current-time curve, the duration of stage I and stage II in two-step anodization are significantly shorter than one-step anodization. The traditional field-assisted dissolution theory cannot explain the three stages of the current-time curves and their physics meaning under different voltages in the same fluoride electrolyte. Here, the distinction between one-step anodization and two-step anodization was clarified successfully by the theories of ionic current and electronic current and oxygen bubble mould.

Magnetically guidable single TiO2 nanotube photocatalyst: Structure and photocatalytic properties

The influence of annealing temperature, the crystallinity, textural properties of magnetically guidable anodic TiO 2 nanotubes in form of single tube powders on the photocatalytic decomposition of model organic dye is investigated for the first time. The powders were prepared from self-organized anodic TiO 2 nanotube layers (grown on Ti) by etching in piranha solution, detaching them from the Ti substrate, and annealing in a wide range of temperatures (400–900 °C). The nanotubular shape was preserved up to 800 °C. Powders annealed up to 800 °C did not contain any detectable rutile phase, which is unique among other TiO 2 nanomaterials at this temperature. Part of the obtained TiO 2 ST-NT powders was decorated with Fe 3 O 4 nanoparticles using an oleic acid-based synthesis. The TiO 2 ST-NT and TiO 2 ST-NT@Fe 3 O 4 NPs powders were characterized in terms of morphology, crystallinity, and specific surface area. Finally, all materials were exploited for the photocatalytic decomposition of a model dye. The best photocatalytic performance of TiO 2 ST-NT and TiO 2 ST-NT@Fe 3 O 4 NPs powders were obtained at annealing temperatures of 600 and 700 °C, respectively. The synergy resulting from annealing, crystallite size, and specific surface area enhances the photocatalytic activity of TiO 2 ST-NT and TiO 2 ST-NT@Fe 3 O 4 NPs powders under UV light. This approach goes beyond the classical Kasuga alkaline hydrothermal approach, enabling the preparation of large quantity of TiO 2 nanotubes without any impurities (such as e.g. Na or Ca content resulting from the Kasuga approach).

Bipolar Electrochemistry for the Synthesis of Anodic TiO2 Nanotube Layers

Self-organized TiO2 nanotube (TNT) layers have attracted considerable scientific and technological interest over the past 17 years motivated for their wide range of applications including (photo-) catalysis, hydrogen generation and biomedical uses [1,2]. The synthesis of these TNT layers is carried out by electrochemical anodization of valve Ti metal substrates in various F--containing electrolytes using a conventional 2-electrode set-up with the Ti substrate as anode and a Pt-foil as cathode.Instead of using a conventional set-up, also bipolar electrochemistry can be employed for the anodization of valve metals [3-7]. In this set-up, the Ti substrate is placed in an electrolyte between two so-called feeder electrodes, which are connected to the potentiostat. Due to the electric field between the feeder electrodes, the Ti substrate is polarized. If the applied potential between the feeder electrodes is high enough, redox reactions can be driven on the Ti substrate. This method opens new doors for the preparation of TNT layers with gradients in dimensions (i.e. diameter and length of the nanotubes) [3-5] as well as for the preparation of TNT layers on Ti substrates, which cannot be directly connected to the potentiostat, e.g. Ti spheres [8].In this presentation, the preparation of TNT layers on small Ti spheres [8] as well as on 3D printed Ti substrates [9] using bipolar electrochemistry will be shown and discussed. Furthermore, we will also show the possibility of using closed bipolar electrochemical cells, consisting of two closed half-cells with the Ti substrate as obstacle between the cells [10].

Large-Scale Synthesis of Photocatalytic TiO2 Nanotube Layers

Self-organized TiO2 nanotube layers have attracted considerable scientific and technological interest over the past 15 years motivated for their wide range of applications including (photo-) catalysis, hydrogen generation and biomedical uses [1,2]. The synthesis of the 1D TiO2 nanotube layers is carried out by a conventional electrochemical anodization of valve Ti metal sheets in various electrolytes.By now, the synthesis of TiO2 nanotube layers with different nanotube dimensions (diameter, length) and the application of these nanotube layers is well established on the laboratory scale. However, for real applications outside the laboratory scale, such as photocatalysis [3], TiO2 nanotube layers of much larger size are necessary. To date, just a few efforts were carried out to scale up the size of the nanotube layers to more than a few cm2 [3-7] due to the difficulty of controlling the parameters of the anodization process on a larger scale. The main challenge is the huge current received during the anodization of large substrates. This, in turn, leads to an increase in the electrolyte temperature that may result in dielectric breakdown of the growing nanotube layers.In this presentation, the preparation of TiO2 nanotube layers on larger area titanium substrates (dozens of cm2) will be discussed, taking into account the control of the anodization parameters. The TiO2 nanotube layers with different thicknesses and nanotube diameters were employed for gas phase photocatalysis, following the ISO standards [3,8]. Experimental details and photocatalytic results will be presented and discussed.

Bipolar Electrochemistry for the Synthesis of Anodic TiO2 Nanotube Layers

Self-organized TiO2 nanotube (TNT) layers have attracted considerable scientific and technological interest over the past 17 years motivated for their wide range of applications including (photo-) catalysis, hydrogen generation and biomedical uses [1,2]. The synthesis of these TNT layers is carried out by electrochemical anodization of valve Ti metal substrates in various F--containing electrolytes using a conventional 2-electrode set-up with the Ti substrate as anode and a Pt-foil as cathode.Instead of using a conventional set-up, also bipolar electrochemistry can be employed for the anodization of valve metals [3-7]. In this set-up, the Ti substrate is placed in an electrolyte between two so-called feeder electrodes, which are connected to the potentiostat. Due to the electric field between the feeder electrodes, the Ti substrate is polarized. If the applied potential between the feeder electrodes is high enough, redox reactions can be driven on the Ti substrate. This method opens new doors for the preparation of TNT layers with gradients in dimensions (i.e. diameter and length of the nanotubes) [3-5] as well as for the preparation of TNT layers on Ti substrates, which cannot be directly connected to the potentiostat, e.g. Ti spheres [8].In this presentation, the preparation of TNT layers on small Ti spheres [8] as well as on 3D printed Ti substrates [9] using bipolar electrochemistry will be shown and discussed. Furthermore, we will also show the possibility of using closed bipolar electrochemical cells, consisting of two closed half-cells with the Ti substrate as obstacle between the cells [10].

Large-Scale Synthesis of Photocatalytic TiO2 Nanotube Layers

Self-organized TiO2 nanotube layers have attracted considerable scientific and technological interest over the past 15 years motivated for their wide range of applications including (photo-) catalysis, hydrogen generation and biomedical uses [1,2]. The synthesis of the 1D TiO2 nanotube layers is carried out by a conventional electrochemical anodization of valve Ti metal sheets in various electrolytes.By now, the synthesis of TiO2 nanotube layers with different nanotube dimensions (diameter, length) and the application of these nanotube layers is well established on the laboratory scale. However, for real applications outside the laboratory scale, such as photocatalysis [3], TiO2 nanotube layers of much larger size are necessary. To date, just a few efforts were carried out to scale up the size of the nanotube layers to more than a few cm2 [3-7] due to the difficulty of controlling the parameters of the anodization process on a larger scale. The main challenge is the huge current received during the anodization of large substrates. This, in turn, leads to an increase in the electrolyte temperature that may result in dielectric breakdown of the growing nanotube layers.In this presentation, the preparation of TiO2 nanotube layers on larger area titanium substrates (dozens of cm2) will be discussed, taking into account the control of the anodization parameters. The TiO2 nanotube layers with different thicknesses and nanotube diameters were employed for gas phase photocatalysis, following the ISO standards [3,8]. Experimental details and photocatalytic results will be presented and discussed.

Recent Advancements in Morphologies of TiO2 Nanotube Layers and Their Photocatalytic Performance

Self-organized TiO2 nanotubes arrays, formed by electrochemical anodization of Ti, have attracted tremendous scientific and technological attention, due to their remarkable properties such as the tunability of dimensions, their directionality, high surface area, low density, and ability to absorb significant amount of incident light [1,2].The most widely used electrolyte for the synthesis of TiO2 nanotube layers is based on ethylene glycol containing small amounts of water and fluoride ions. However, nanotubes prepared in these electrolytes present a double-walled structure, with the outer wall consisting of almost pure TiO2 and the inner wall consisting of TiO2 contaminated with carbon and fluoride species [3,4]. In the recent years, the selective etching of the inner nanotube wall on Ti layer enabled synthesis of single-wall nanotubes that showed a superior photo-electrochemical performance compared to their double-walled counterparts [5]. An extensive etching enabled also the synthesis of single tube powders, which could be effectively decorated with Fe3O4 nanoparticles to act as magnetically guidable photocatalyst [6,7].The presentation will focus on the influence of all these nanotube morphologies on the photocatalytic degradation in the liquid phase. In particular, we will discuss, how the annealing temperature of single nanotubes influences their photocatalytic performance [7] and how the wall thickness of the single wall nanotubes can be optimized for the best performance [8]. Experimental details and photocatalytic results will be presented and discussed.

Constructing quantum dots sensitized TiO2 nanotube p-n heterojunction for photoelectrochemical hydrogen generation

PEC devices are fabricated using 1D TiO 2 nanotubes and sensitized with QDs through a simple and low-cost solution-based process. Furthermore, an optimized nanoscale p-n heterojunction is employed using CuSe treatment to enhance the carrier dynamics. Finally, A detailed investigation is conducted on each parameter that affecting the PEC device performance. • Self-organized TiO 2 NTs/QDs photoanodes are fabricated for PEC water splitting. • Surface engineering through p-n heterojunction improves the device performance. • KPFM is used to investigate the surface potential enhancement of the photoanode. • PEC device performance is investigated by changing NTs length. Photoelectrochemical (PEC) water splitting is a promising approach to convert solar radiation into hydrogen (H 2 ) as a clean fuel. The PEC device performance depends on the light harvesting efficiency of the photoanode and the carrier dynamics (i.e. separation/transport rate) at the photoanode/electrolyte interface. Herein, we report a photoanode architecture consisting of self-organized TiO 2 nanotubes (NTs) sensitized by CdS/CdSe quantum dots (QDs) and treated with a Cu-based solution to create a p-n heterojunction. Our results demonstrate that the TiO 2 NTs/QDs PEC device yields a photocurrent density of 4.18 mA.cm −2 at 0.5 V vs RHE, which is 51 times higher than the device based on TiO 2 NTs only (i.e., 0.08 mA.cm −2 ) and 7 times compared to TiO 2 /QDs nanoparticles (NPs) (i.e. 0.45 mA.cm −2 ) under one sun illumination. The p-type CuSe coating over the TiO 2 /QDs NTs photoanodes forms a p-n heterojunction that improves the carrier dynamics. The resulting PEC device shows a 13% improvement in the photocurrent density. In addition, employing longer TiO 2 NTs improves the device's stability. Our results offer a simple and scalable method for the design and optimization of the photoanodes to enhance the performance of PEC and other optoelectronic devices.

Self-organized TiO2 nanotubes on Ti-Nb-Fe alloys for biomedical applications: Synthesis and characterization

Titanium-based biomaterials with a self-organized titanium oxide (TiO2) surface have received considerable attention in recent years owing to enhanced cellular response and bactericidal behavior promoted by the nanostructured surface. The aim of this study was to investigate the effect of Fe addition on the formation and crystallization of TiO2 nanotubes on Ti-30Nb-xFe substrates and the effect of TiO2 crystallinity on biological behavior. Self-ordered TiO2 nanotubes were prepared by anodization of Ti-30Nb-xFe (x = 0, 3, and 5 wt%) alloys using an aqueous 0.3% HF (vol.%) electrolyte. The nanotube morphology, structure, and composition as a function of the annealing temperature were characterized using FE-SEM, XRD and XPS. The crystallization of nanotubes to the rutile phase occurred at similar temperatures for samples with or without Fe addition, and a mixture of anatase and rutile was observed at 675 °C. The cell viability profile on different surfaces was investigated by MTT and adhesion assays, which revealed improved in vitro response to the crystalline nanotubes.