Formation Of TiO2 Nanotubes Research Articles

Effects of TiO2 Nanotubes and Reduced Graphene Oxide on Streptococcus mutans and Preosteoblastic Cells at an Early Stage.

The effects of TiO2 nanotube (TNT) and reduced graphene oxide (rGO) deposition onto titanium, which is widely used in dental implants, on Streptococcus mutans (S. mutans) and preosteoblastic cells were evaluated. TNTs were formed through anodic oxidation on pure titanium, and rGO was deposited using an atmospheric plasma generator. The specimens used were divided into a control group of titanium specimens and three experimental groups: Group N (specimens with TNT formation), Group G (rGO-deposited specimens), and Group NG (specimens under rGO deposition after TNT formation). Adhesion of S. mutans to the surface was assessed after 24 h of culture using a crystal violet assay, while adhesion and proliferation of MC3T3-E1 cells, a mouse preosteoblastic cell line, were evaluated after 24 and 72 h through a water-soluble tetrazolium salt assay. TNT formation and rGO deposition on titanium decreased S. mutans adhesion (p < 0.05) and increased MC3T3-E1 cell adhesion and proliferation (p < 0.0083). In Group NG, S. mutans adhesion was the lowest (p < 0.05), while MC3T3-E1 cell proliferation was the highest (p < 0.0083). In this study, TNT formation and rGO deposition on a pure titanium surface inhibited the adhesion of S. mutans at an early stage and increased the initial adhesion and proliferation of preosteoblastic cells.

In situ Pt single-atom trapping on TiO2 nanotubes via ultrasonication: a one-pot approach to produce active electrodes for electrocatalytic H2 evolution

In the present study, we demonstrate a straightforward sonochemical approach for in situ defect formation and Pt single-atoms (SAs) decoration of anodic TiO2 nanotubes (TNTs).

Formation of TiO2 nanotubes and deposition of silver nanoparticle and reduced graphene oxide: Antibacterial and biocompatibility behavior

The biocompatibility of titanium alloys used as implant material is enhanced by TiO2 nanotubes. Particles deposited on TiO2 nanotubes for antibacterial purposes may affect bacterial attachment and biofilm formation differently, thus being effective in preventing formation or development of implant-related infections. To investigate this aspect, TiO2 nanotubes were produced on Ti6Al4V-ELI by anodic oxidation (30 V-1 h, ethylene glycol, 0.5 % NH4F, 5 % H2O). Silver nanoparticles (AgNP) and reduced graphene oxide (rGO) were electrophoretically deposited on nanotube surfaces. The antibacterial activity and biocompatibility of the samples were investigated. 96-h tests with S. aureus revealed that TiO2 NT-AgNP and TiO2 NT-rGO improved antibacterial activity and TiO2 NT-rGO did not cause any morphological damage on bacteria. As a result of biocompatibility tests on L929 fibroblast cells for 72 h with MTT method, none of the samples showed cytotoxicity, instead, AgNP and rGO had a positive effect on cell adhesion and proliferation without giving any adverse effects on cell morphology. This study provides new insights into the effect of nanotube formation and nanoparticle decoration on the Ti6Al4V-ELI surface on interaction of bacterial biofilm and cell. These encouraging findings will contribute to development of AgNP- and rGO-deposited TiO2 NTs to prevent various implant-related health problems. In further studies, TiO2 NT-AgNP can be suggested to reduce bacterial attachment, and TiO2 NT-rGO can be recommended to delay maturation of bacterial biofilm.

Removal of contaminants of emerging concern by photocatalysis with a highly ordered TiO2 nanotubular array catalyst

In this work, the treatment of wastewater polluted with contaminants of emerging concern is evaluated by heterogeneous photocatalysis with TiO2. Titanium plates are anodized by different experimental conditions, and the influence of these conditions on the catalytic performance is evaluated by factorial design of experiments. The formation of TiO2 nanotubes in the anatase form is sought for photocatalysts with high active surface. Thus, electrolyte used in the anodization process (NH4F/H2O in ethylene glycol or H2SO4 in water), potential ramp (2 – 4 V min−1), maximal applied potential (20 – 60 V) and heat treatment are evaluated as influencing factors of the experimental design. The activity of these catalysts is tested by ofloxacin (pharmaceutical compound used as model of contaminant of emerging concern) degradation in wastewater treatment, obtaining the kinetic constant of the process, parameter chosen as response variable of the experimental design. Results show that NH4F/H2O as electrolyte, 2 V min−1, 40 V and a heat treatment are the optimum conditions for the formation of TiO2–anatase nanotubes with a good disposition and arrangement, observing the higher efficiency in the wastewater treatment process. In addition, wastewater treatment conditions are evaluated (UV wavelength, irradiance and initial concentration of ofloxacin), and it is found that UV-B, maximal irradiance and minimal initial concentration of the pollutant are the optimal factors for a higher process efficiency. This is a work that opens the door to the removal of contaminants of emerging concern from wastewater with a technology of low cost, with easy implantation and environmental compatibility, making possible to use only sunlight as a reagent.

Synthesis of TiO2 Nanotubes for Improving the Corrosion Resistance Performance of the Titanium Implants

TiO2 nanotubes were successfully synthesized by electrochemical method. A fluoride salt mixture was used as an electrolyte for synthesizing TiO2 nanotubes on titanium substrates. In this work, we have reported the synthesis procedure of TiO2 nanotubes and investigated the corrosion resistance of TiO2 nanotubes coated on the Ti substrate. FE-SEM was used to observe the morphology and determine the size of the TiO2 nanotubes. The phase formation and crystal quality of TiO2 nanotubes were studied by XRD measurements. One-microliter distilled water droplets were used to define the wettability of the TiO2 nanotube surfaces by measuring the contact angle. The corrosion resistance behavior of specimens was analyzed in the simulated body fluid solution (SBF) using potentiodynamic polarization tests for potential application as implants.&#x0D;

Fabrication of Mo-doped TiO2 nanotube arrays photocatalysts: The effect of Mo dopant addition time to an aqueous electrolyte on the structure and photocatalytic activity

Molybdenum-doped TiO2 nanotubes (TNTs) samples were synthesized in two routes by a single-step anodization method for a sustainable photocatalytic process. This study aimed to evaluate the effectiveness of dopant adding time on the photocatalytic activity of TiO2 nanotubes. In the first route, molybdenum dopant with three initial concentrations of 0.02, 0.06, and 0.1 M was added to the electrolyte at the beginning of the anodizing process, while in the second route, molybdenum precursors were added to the electrolyte after 30 min from the beginning of anodization (after the formation of nanotubes). The structural characteristics of Mo-doped TNTs in both routes were compared with non-doped nanotubes using field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. The optical properties and efficiency of electron-hole pairs separation and charge transfer kinetics were evaluated by diffuse reflectance spectroscopy (DRS) and electrochemical impedance spectroscopy (EIS) methods. Moreover, methylene blue (MB) degradation under visible light was performed to investigate the photocatalytic activity. The results indicate that the second route of synthesis causes the formation of well-aligned TNTs while increasing the Mo concentration will destroy the tube structure in some places on the surface and cause the loss of structural order, in the first path. By Mo doping into TiO2 nanotubes, the optical properties are improved and the absorption edge of TiO2 nanotubes was extended to the visible region. The Mo-doped samples in the second route with concentrations of 0.1 M exhibited the highest visible light absorption and charge transfer rate among all the Mo-doped samples. Also, Mo-doped samples had better photocatalytic activity than non-doped samples in MB degradation and the highest photocatalytic efficiency was related to the Mo-doped sample synthesized in the second route with a Mo concentration of 0.1 M.

Effects of sputtering power of Ti films on morphology of TiO2 nanotubes synthesized via anodization process

In this paper, we aimed to find the sputtering power most suitable for fabricating anodized TiO2 nanotubes (TNTs) with high dimensions (diameter and length). TNTs were synthesized via anodization of Ti films deposited on a glass substrate at varying sputtering power from 50 W to 200 W. The properties of Ti films such as crystallinity, residual stress, and roughness were investigated, which affected the morphology of TNTs. Sputtering power levels of 150 W and 200 W were suitable for TNTs formation via the anodization process in NH4F concentrations from 1.0 wt% to 2.5 wt% due to the increased density and crystallinity of Ti films. Boosting the sputtering power to 200 W increases the roughness of the surface, resulting in a decrease in tube diameter and length. Increasing the sputtering power to 200 W also causes the residual stress of the film to be converted from compression to tensile stress, which allows for more TNTs structures to be formed on the film. Nanotubes fabricated on 150 W sputtered films have been proven to be superior to those fabricated at 200 W in every NH4F concentration in terms of length and diameter. Thus, they are more suitable for applications.

Nanofunctionalization of Additively Manufactured Titanium Substrates for Surface-Enhanced Raman Spectroscopy Measurements.

Powder bed fusion using a laser beam (PBF-LB) is a commonly used additive manufacturing (3D printing) process for the fabrication of various parts from pure metals and their alloys. This work shows for the first time the possibility of using PBF-LB technology for the production of 3D titanium substrates (Ti 3D) for surface-enhanced Raman scattering (SERS) measurements. Thanks to the specific development of the 3D titanium surface and its nanoscale modification by the formation of TiO2 nanotubes with a diameter of ~80 nm by the anodic oxidation process, very efficient SERS substrates were obtained after deposition of silver nanoparticles (0.02 mg/cm2, magnetron sputtering). The average SERS enhancement factor equal to 1.26 × 106 was determined for pyridine (0.05 M + 0.1 M KCl), as a model adsorbate. The estimated enhancement factor is comparable with the data in the literature, and the substrate produced in this way is characterized by the high stability and repeatability of SERS measurements. The combination of the use of a printed metal substrate with nanofunctionalization opens a new path in the design of SERS substrates for applications in analytical chemistry. Methods such as SEM scanning microscopy, photoelectron spectroscopy (XPS) and X-ray diffraction analysis (XRD) were used to determine the morphology, structure and chemical composition of the fabricated materials.

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.

Effects of electrolyte composition on the growth and properties of titanium oxide nanotubes

Titanium oxide nanotubes prepared by anodization are widely used in many fields due to their excellent properties, but the formation mechanism is still under discussion. This paper focuses on the formation of TiO2 nanotubes in different electrolytes. We explored the influence of electrolyte components on anodization process and results through analysing the current–time curves and SEM images. The results showed that the addition of ionizable sodium salt to the electrolyte increased the conductivity of electrolytes, and then promoted the growth of nanotubes with improving the properties. In this paper, we explained the interesting experimental results by the oxygen bubble model theory and double current(ionic current and electronic current) theory.

Controlling anodization time to monitor film thickness, phase composition and crystal orientation during anodic growth of TiO2 nanotubes

Anodic TiO2 nanotube (TNT) films show promises for photon-driven catalytic, electricity storage and chemical processes. The film thickness of anodic TNT is known to affect its performance in optical and electronic applications. Also, factors affecting the morphology and dimensions of anodic TNT films are rather well-known. However, the knowledge on phase transition and composition in the growth of anodic TiO2 from the titanium metal is very limited. In this work, the anodization time is controlled in intervals of 10, 60, 300, 1000, 2000 and 5000 s to investigate its effect on phase composition and transition, and the morphology of the anodic TNT during the growth process. Even though the mechanism of anodic TNT formation is still under debate, the scanning electron microscope results support bottom-up tube growth with evidence of a compact layer. It was also found that the Richards growth model is applicable to correlate growth time and film thickness. Finally, the phase transition, crystal orientation and pore formation during the anodic process are further discussed.

Fast fabrication of small pore anodic titania nanotube arrays under high voltage

Due to their unique structures and physicochemical properties, porous anodic metal oxides including Al2O3, Fe2O3, TiO2, Ta2O5 and so on, prepared by anodization of corresponding metal substrates in appropriate electrolytes have found applications in various fields. Pore diameter plays a significant role in applications of these anodic metal oxides. It is a common knowledge that the pore diameter of porous metal oxides increases with formation voltage despite of a vast variation of anodization parameters and electrolytes used. Here, we demonstrate that the pore diameter and cell size of anodic TiO2 nanotube arrays can decrease dramatically under high voltage accompanied by high current density. Impact factors determining the formation of small pore TiO2 nanotubes under high voltage were discussed. Typically, with the same electrolyte used, the average pore diameter of TiO2 nanotube arrays changes from ca 26 nm at a formation voltage of 10 V to ca 13 nm at 200 V. It is also demonstrated that at high voltage, small pore TiO2 nanotubes could be grown with a rate orders of magnitude faster than those grown in a classic way with low voltage and current density.

Fabrication of 3D MoS2-TiO2@PAN electro-spun membrane for efficient and recyclable photocatalytic degradation of organic dyes

In this work, molybdenum disulfide-titanium dioxide (MoS2-TiO2) nanohybrids were decorated on polyacrylonitrile (PAN) electrospun membrane to fabricate a highly efficient and recyclable 3D composite for photocatalytic degradation of organic pollutants. It was found that the high surface area of MoS2 nanosheets facilitated the formation of TiO2 nanotubes, which further promoted the exfoliation of MoS2 nanosheets. In addition, the matched band gaps between MoS2 nanosheets and TiO2 nanotubes brought MoS2-TiO2@PAN membrane excellent photocatalytic degradation performance of five organic dyes. The best degradation efficiency of the as-prepared MoS2-TiO2@PAN membrane was 97.73%. Based on these results, we presented the photocatalytic degradation mechanism of MoS2-TiO2@PAN membrane. Our strategy for fabricating efficient and recyclable 3D MoS2-TiO2@PAN membrane is facile, cost-efficient and eco-friendly, which will be a promising method for the photocatalytic degradation of organic dyes.

Synthesis of Titanium Dioxide Nanotubes with Different N-Containing Ligands via Hydrothermal Method

Titanium dioxide (TiO2) nanotubes (TNT) were successfully synthesized using different N-containing ligands via hydrothermal method. Methylamine, ethylenediamine and diethylenetriamine with different Ti/ligand molar ratios (1:1, 1:3, 1:5 and 1:8) were prepared. As-synthesized TiO2 without N-containing ligands were also prepared for comparison purpose. The X-Ray Diffraction patterns confirmed the presence of anatase phase of TiO2 in all the synthesized samples whereas the presence of sodium titanate was only detected in the samples containing N-containing ligands. The Transmission Electron Microscopy images also showed that the N-containing ligands promoted the formation of nanotubes in the anatase TiO2. Based on the Tauc Plot, the band gap energy of anatase TiO2 was shifted with the addition of methylamine, ethylenediamine and diethylenetriamine. The photoluminescence spectra also showed that with the addition of sufficient amount of N-containing ligands, the intensity of photoluminescence spectrum decreased, suggesting formation of more nanotube and reduction of electron hole recombination rate. The photocatalytic performance of all synthesized samples was determined through photodegradation of Congo red under UV light for 6 hours. The results suggested that among the synthesized materials, the sample which contained diethylenetriamine with molar ratio of 5 gave the highest photocatalytic activity of 76.71% which could be attributed to successful formation of nanotube, its higher surface rate reaction and low electron hole recombination. Diethylenetriamine showed higher efficiency in assisting the formation of TiO2 nanotubes compared to methylamine and ethylenediamine.

The growth of anti-friction and wear-resistance TiO2 nanotube arrays driven by residual stress

Ti-based materials have attracted considerable attention for potential applications in biomedicine due to their excellent chemical inertness, biocompatibility and corrosion resistance. However, the poor friction properties of oxide films (e.g. TiO2) on Ti-based materials significantly deteriorate their service life. Here, the effect of residual stress improves the frictional properties of TiO2 nanotubes were studied. The results show that the residual stresses at the surface of the non-peened sample and the samples peened by steel balls with diameters of 4 and 6 mm are 10.17, 49.97 and 65.31 MPa, respectively. The increase in residual stress improves the growth rate of the TiO2 nanotubes. Meanwhile, with increasing residual stress, the friction coefficient and the wear rates decreases. It is noteworthy that a bridge between theoretical calculations and the experimental testing of surface residual stress is established. The results suggest that the surface with 10% biaxial compression can represent the surface state after shot peening with a 6 mm diameter steel ball. In addition, shot peening could increase the film formation rate of the Ti13Nb13Zr surface and effectively promote the formation of TiO2 nanotubes. Our findings show how the friction performance of TiO2 can be improved by using the residual stress on the surface and provide insights for the rational design of high-performance TiO2 biomedical materials.

Facile fabrication of nanotubular heterostructure for enhanced photoelectrochemical performance

A key challenge in photoelectrochemical water-splitting is the development of photoanodes with improved chemically active and optically efficient. While various nanostructures in heterogeneous materials have been investigated as a potential electrode, existing structures/compositions are still insufficient to meet such demand. Here, we report a scalable strategy to fabricate photoanodes with a nanotubular structure using CdS–TiO2 heterogeneous composite as a model system. Precisely, a ~5 μm thick nanotubular CdS–TiO2 heterostructure is developed on fluorine-doped tin oxide glass by hydrothermal etching and successive ionic layer deposition process. An electron microscopy analysis confirms that the formation of TiO2 nanotubes in the preferential etching direction of [001] as well as uniform coating of the CdS light-absorber layer. We note that the CdS coated on TiO2 nanotubes shows a photocurrent density of 6.9 mA/cm2 at 1.23 VRHE, which is ~2 times higher than that of CdS- nanorod TiO2 heterostructured photoanode. The elemental and optical analysis reveals that the structural modification and sufficient CdS deposition captures a wide range of light absorption from 300 to 550 nm. Our results suggest that an effective fabrication method is applicable for electrodes in numerous energy conversion devices, providing an increase in surface area, light absorption, and chemical stability.

Effect of the electrolyte chemical nature on the formation and characteristics of TiO2 nanotubes synthesized by anodic oxidation using a Ti cathode

The aim of this work is to show the effect of the electrolyte chemical nature on the formation of self-organized TiO2 nanotubes (TNT) arrays synthesized via anodic oxidation, when using a Ti cathode. The synthesis was performed in situ in a potentiostatic cell provided with an anode and a cathode (both Ti substrates pretreated) under constant hydrodynamic conditions and different anodizing times, temperatures and electrical potentials. Ti electrodes were immersed in 300 mL of each of an inorganic and organic electrolyte. Then, a thermal treatment varying the temperature and the heating rate in each case was applied to convert the amorphous TiO2 to crystalline TiO2. TNT were characterized by field-emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and atomic force microscopy (AFM). FESEM showed the formation of nanotubular structures perpendicular to Ti substrate with average inner diameters of 84 and 57 nm for TNT synthesized in the electrolytes with different nature tested (inorganic and organic), and labeled hereafter as TNT-I and TNT-O, respectively. EDS spectra from different zones of the substrate confirmed the presence of Ti (~ 34.2%) and O (~ 66%) on the surface of the TNT. The anatase (~ 86%) and rutile (~ 14%) crystalline phases were detected via XRD in both cases. AFM provided information about the topographic profile of TNT and the roughness of the substrates. Thus, the use of a semiconductor cathode allowed the successful synthesis of the TNT and the electrolyte chemical nature was found to influence its morphology, dimensions and formation mechanism.

Electrochemical evaluation of IrO2–Ta2O5-MWCNT-coated anodes with different pretreatments of titanium substrate

Mixed metal oxide coatings of IrO2–Ta2O5 modified with multiwalled carbon nanotubes (MWCNTs) were applied on Ti anodes by thermal decomposition method. Effects of nanoporosities film formation and rough structures were examined on the electrocatalytic activity and stability of the anodes. In this respect, the electrochemical response of samples subjected to different pretreatments, including the formation of TiO2 nanotubes by anodizing and etching in 20% oxalic acid, was investigated by cyclic voltammetry, potentiodynamic polarization, galvanostatic, and impedance spectroscopy. IrO2–Ta2O5-MWCNT coating on the etched and anodized substrate formed a compact morphology with fewer cracks. Microstructural examination of coatings showed that the distribution of active IrO2 particles was changed by anodizing pretreatment. The charge transfer resistance of dimensionally stable electrode with anodizing surface preparation was approx. 32% lower than the etched sample due to the porous nature of the Ti/coating interface. The addition of MWCNT to IrO2–Ta2O5 coating on the etched Ti anode extended its service life by ~ 70%, while the formation of TiO2 nanotubes as the result of anodizing surface pretreatment reduced the electrode stability.

The role of barrier layer temperature in the formation of long and small-diameter TiO2 nanotube arrays

Small-diameter TiO2 nanotubes (TNTs) are fabricated at a fast growth rate by developing an effective anodization method in an organic electrolyte. Two different temperatures are applied to both sides of sample in order to increase the current density during the anodization process. Here, we use a high temperature for the backside of the sample (direct heating of the barrier oxide layer) in order to increase the current density while keeping the electrolyte at a low temperature to decrease the chemical etching at top of the TNT arrays. Increasing the backside temperature up to 55 °C leads to the formation of longest TNTs with an average diameter of about 17 nm at high-speed TNT growth of about 2000 nm/h under 20 V. Based on the high-field theory and accurate estimation of the barrier layer (BL) temperature, the incremental effect of increasing the BL temperature on the anodization current is also investigated.

Anodization of electrodeposited titanium films towards TiO2 nanotube layers

Ti films electrodeposited on Ni foils from molten salts were anodized towards TiO2 nanotube formation for the first time. The resulting TiO2 nanotube (TNT) layers were compared with TNT layers prepared under identical conditions on Ti foils by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) measurements, X-ray photoelectron spectroscopy (XPS), and photocurrent measurements. No significant differences were found between the TNT layers prepared on the two different substrates. Electrodeposited Ti films prepared in this way could thus be a viable option for anodization purposes.