TiO2 Nanotubes Research Articles

Review on TiO2 nanotubes in dye-sensitized solar cells: electrochemical anodization and hydrothermal method

Review on TiO2 nanotubes in dye-sensitized solar cells: electrochemical anodization and hydrothermal method

AuCu bimetallic nanocluster-modified titania nanotubes for photoelectrochemical water splitting: composition-dependent atomic arrangement and activity.

The photoelectrochemical (PEC) water splitting reaction of bimetallic AuxCu1-x (x = 1, 0.75, 0.5, 0.25 and 0) nanocluster-decorated TiO2 nanotube (TNT) photoanodes was investigated using a solar simulator. A strong enhancement in the anodic photocurrent relative to pristine TNTs was found with clear composition-dependent PEC activity, increasing with the Cu content and peaking at Au0.25Cu0.75. Electron microscopy and X-ray absorption fine structure spectra recorded at both Au and Cu edges identified a clear composition-dependent atomic arrangement of the spherical nanoclusters on anatase TNTs, resulting mostly from a time-dependent restructuring of the original metallic nanoalloys in the ambient environment. With time, Cu segregates from the alloy to form a surface oxide layer surrounding a pure gold metallic core in the gold-rich nanoclusters (x = 0.75 and 0.50) or a face centered tetragonal (fct)-intermetallic Au0.5Cu0.5 nanoalloy in copper-rich (x = 0.25) particles. In pure Cu nanoclusters, a metallic Cu core is stabilized by surrounding Cu2O and CuO. The enhanced PEC activity is attributed to a synergy between Au and Cu that upon segregation produces bifunctional catalytic sites consisting of a metallic Au/AuCu alloy and copper oxide at the surface of the nanoclusters. The photoactivity under solar light illumination is boosted by the plasmonic response of the metal. The ordered structure of the fct-AuCu alloy present in the most active Au0.25Cu0.75 may explain its higher stability and photocatalytic performance. Hence, this work provides insight into the relationship between the atomic-level structure of AuxCu1-x nanoalloys on TNTs and their PEC activity.

Performance of Ti/TiO2-ZIF-67 photoanode under LED irradiation applied to the photoelectrodegradation of the antidepressant venlafaxine (VEN) in municipal wastewater effluent

This work describes the direct deposition of ZIF-67 metal-organic framework (MOF) onto Ti/TiO2 nanotubes forming a photoanode for the degradation of the antidepressant Venlafaxine (VEN). This material combines the excellent characteristics of ZIF-67 MOF in enhancing photocatalytic reduction and oxidation reactions induced by UV LED irradiation, as well as the storage of VEN molecules in its pores. Ti/TiO2-ZIF-67 features an eco-friendly technology for degradation of pharmaceutical micropollutants such as antidepressants. The photoanode was prepared, characterized and applied in the degradation of VEN by photocatalysis (PC), electrocatalysis (EC), photolysis (PL) and PEC processes. PEC process presented the best performance when compared to the others processes in both simulated solutions and real wastewater, achieving 100% and 89% degradation of VEN after 60 and 90 min, with TOC removal rates of 50% and 4%, respectively. The lower mineralization rate suggests that the degradation of VEN in complex matrices such as that of real wastewater produced recalcitrant by-products that are difficult to convert into CO2 and H2O. Zeta potential measurement showed that at pH 6 and 8 there is an effect of attraction of opposite electrostatic charges between the surface of ZIF-67 (positive) and VEN (negative), favoring the degradation of VEN in this pH range. The good performance of the Ti/TiO2-ZIF-67 can be attributed to the formation of the Z-scheme heterojunction between the TiO2 nanotubes and the ZIF-67 MOF which contributed to a lower rate of electron-hole (e-/h+) pairs recombination, favoring VEN degradation mainly to higher generation of •OH radical and less contribution of O2•- superoxide produced by UV irradiation forming some degradation by-products through demethylation and oxidation reactions.

A novel electrochemical biosensor based on TiO2 nanotube array films for highly sensitive detection of exosomes.

Exosomes have emerged as a powerful biomarker for early cancer diagnosis, however, accurately detecting cancer-derived exosomes in biofluids remains a crucial challenge. In this study, we present a novel label-free electrochemical biosensor utilizing titanium dioxide nanotube array films (TiO2NTAs) for the sensitive detection of exosomes in complex biological samples. This innovative biosensor takes advantage of the excellent electrochemical properties of TiO2NTAs and their specific interactions with the phosphate groups of exosomes. The transport of ions and electrons within the exosome-captured TiO2 nanotubes is hindered, leading to a significant alteration in the electrochemical response signal and enabling highly sensitive detection of exosomes. Consequently, the biosensor demonstrates a wide linear detection range from 5×101 to 1×107 particles/μL with a limit of detection of 12.7 particles/μL and 12.6 particles/μL for the exosomes derived from hepatocellular carcinoma and colon cancer cells, respectively. Furthermore, the TiO2NTAs biosensor can successfully distinguish the signal of extracellular vesicles in real human serum samples between 20 hepatocellular carcinoma, 20 colon cancer and 20 healthy persons (p<0.0001). This method had a promising potential in biochemical analysis and clinical cancer diagnosis.

Enzyme-free detection of creatinine as a kidney dysfunction biomarker using TiO2 flow-through membranes.

TiO2 nanotube flow-through membranes (TNTsM) were fabricated via anodization of Ti foil and explored as a biosensing platform for creatinine detection. The electrodes were prepared in different configurations including TNT membrane with top surface up (TNTsMTU/TNPs/FTO), TNT membrane with bottom surface up (TNTsMBU/TNPs/FTO), TNT membrane with top surface up containing nanograss (TNTsMNG/TNPs/FTO), and TNTs/NPs/FTO and TiO2 nanoparticles (TNPs) film on fluorine doped tin oxide (TNPs/FTO). Electrochemical studies depict the higher electrochemical activity (sensitivity ∼19.88 μA μM-1 cm-2) of TNTsMTU/TNPs/FTO towards creatinine compared to other configurations. This exceptional performance of the TNTsMTU/TNPs/FTO electrode results from the flow-through nature of TNTsM and the removal of the bottom oxide barrier layer through etching in H2O2. The underlying layer of TiO2 NPs also contributes to the higher current response of the TNTsMTU/TNPs/FTO. The relevance of the biosensor structural design is demonstrated by the increased amperometric response of TNTsMTU/TNPs/FTO and greater redox peak current in cyclic voltammograms. Furthermore, the higher selectivity, stability, and reproducibility of the electrode can be due to the suitable redox potential, chemical stability, and controlled fabrication process of TNT membranes.

INVESTIGATING THE ROLE OF CRYSTALLINE TiO2 NANOTUBES IN THE PHOTOELECTROCHEMICAL PERFORMANCE OF g-C3N4/TiO2 COMPOSITES

Sunlight driven photoelectrochemical (PEC) water splitting has garnered excessive attention as an eco-friendly technique to produce renewable hydrogen. Designing TiO&lt;sub&gt;2&lt;/sub&gt; based composites have evolved as an efficient strategy to extend the photoactivity of TiO&lt;sub&gt;2&lt;/sub&gt;, inhibit their charge recombination and increase their stability. Owing to its well-matched energy bands, graphitic carbon nitride (g-C&lt;sub&gt;3&lt;/sub&gt;N&lt;sub&gt;4&lt;/sub&gt;) has emerged as an effective counterpart of TiO&lt;sub&gt;2&lt;/sub&gt;. The present work reports the synthesis of gC&lt;sub&gt;3&lt;/sub&gt;N&lt;sub&gt;4&lt;/sub&gt;/ TiO&lt;sub&gt;2&lt;/sub&gt; composites from a three-step process where bulk g-C&lt;sub&gt;3&lt;/sub&gt;N&lt;sub&gt;4&lt;/sub&gt; was electrodeposited on separated TiO&lt;sub&gt;2&lt;/sub&gt; nanotubes from a constantly rotating organic suspension at a voltage of about &amp;#126; 90 V for desired time. To explore the role of crystalline TiO&lt;sub&gt;2&lt;/sub&gt; nanotubes on the composite formation, g-C&lt;sub&gt;3&lt;/sub&gt;N&lt;sub&gt;4&lt;/sub&gt; was similarly electrodeposited on amorphous separated nanotubes etched from Ti Foil to obtain g-C&lt;sub&gt;3&lt;/sub&gt;N&lt;sub&gt;4&lt;/sub&gt;/amorphous TiO&lt;sub&gt;2&lt;/sub&gt; nanotube which was then annealed at 450&amp;deg;C for 3 h. UV-Vis, FTIR, Raman and PL spectra was recorded for virgin TiO&lt;sub&gt;2&lt;/sub&gt; nanotube and g-C&lt;sub&gt;3&lt;/sub&gt;N&lt;sub&gt;4&lt;/sub&gt;/ TiO&lt;sub&gt;2&lt;/sub&gt; nanotube composites formed under varying deposition conditions to investigate their optoelectronic properties comparatively. The photoresponse of the samples was evaluated from photoelectrochemical measurements. All the composites demonstrated good photoactivity and enhanced photoelectrochemical response going upto an order increase than bare TiO&lt;sub&gt;2&lt;/sub&gt;. The microstructural study revealed the effect of crystalline TiO&lt;sub&gt;2&lt;/sub&gt; nanotubes on the composite formation. TiO&lt;sub&gt;2&lt;/sub&gt; nanotube arrays provide a direct pathway for electron transfer and the ease of access of its inner and outer surfaces aid in light scattering more efficiently. Incorporating bulk g-C&lt;sub&gt;3&lt;/sub&gt;N&lt;sub&gt;4&lt;/sub&gt; is appealing as a simple process that decreases the complexity and promotes increased light harvesting.

TiO2 nanotubes grown on Ti and Ti6Al4V alloy spheres by bipolar anodization

TiO2 nanotubes grown on Ti and Ti6Al4V alloy spheres by bipolar anodization

Ultrathin ALD Coatings of Zr and V Oxides on Anodic TiO2 Nanotube Layers: Comparison of the Osteoblast Cell Growth.

The current study investigates and compares the biological effects of ultrathin conformal coatings of zirconium dioxide (ZrO2) and vanadium pentoxide (V2O5) on osteoblastic MG-63 cells grown on TiO2 nanotube layers (TNTs). Coatings were achieved by the atomic layer deposition (ALD) technique. TNTs with average tube diameters of 15, 30, and 100 nm were fabricated on Ti substrates (via electrochemical anodization) and were used as primary substrates for the study. The MG-63 cell growth and proliferation after 48 h of incubation on hybrid TNTs/ZrO2 and TNTs/V2O5 surfaces was evaluated in comparison to the uncoated TNTs of each diameter. The density of viable MG-63 cells was assessed for all the TNT surfaces, along with the cell morphology and the spreading behavior (i.e., the cell length). The ultrathin coatings retained the original morphology of the TNTs but changed the surface chemical composition, wettability, and cell behavior, whose interplay is the subject of the present investigation. These findings offer interesting views on the influence of the composition of biomedical implant surfaces, triggered by ALD ultrathin coatings on them. The outcomes of this work shed light on the assessment of the biocompatibility of the two different ALD coatings.

TiO2 nanotubes incorporated into a glaze-coating ceramic: surface roughness, color, and antibiofilm activity.

This study evaluated the surface roughness, color change, and antibacterial effect of a ceramic glaze enhanced with TiO2 nanotubes (n-TiO2). n-TiO2 (0, 2, 2.5, and 5 wt%) was added to a ceramic glaze powder, applied to the surface of forty feldspathic ceramic specimens, and sintered. The surface roughness average (Ra) before glaze application (T0) and after glaze crystallization (T1) was measured using a profilometer. The colorimetric alteration was determined by CIEDE2000 (ΔE00) and CIELab (ΔEab), and the whiteness index for dentistry (ΔWID). The antibacterial effect against S. mutans and S. sanguinis was evaluated (CFU/mL). Data were analyzed by two-way repeated-measures ANOVA, followed by the Bonferroni test (α = 0.05). No differences in ΔEab and ΔE00 were observed among groups (p > 0.05), and ΔWID was only affected by 5% n-TiO2. All groups surpassed the perception thresholds of 1.8 (ΔE00) and 2.3 (ΔEab). At T0, no Ra differences were detected among groups (p > 0.05). In T1, Ra decreased (p < 005) compared to T0, but 5% n-TiO2 increased roughness compared to the control group (without n-TiO2). The incorporation of n-TiO2 into the glaze powder did not impair bacteria adhesion, and no differences in biofilm formation were found among the concentrations (p < 0.05). The ceramic covered with a glaze containing 5% n-TiO2 caused minimal interference in the color and roughness with no effect on biofilm formation.

Enhanced photocatalytic H2 generation via in-situ grown CuO-decorated TiO2 nanotubes on Ti-Cu alloys: A synergistic thermo-electrochemical approach

In the present study, we developed a thermo-electrochemical strategy to grow CuO self-decorated TiO2 nanotubes (TiNTs) on Ti-xCu alloys (x = 0, 2, 4, 6, and 8 wt%). The Ti-xCu metastable solid solution alloys were prepared by rapid quenching after solid solution heat treatment. Based on microstructural analyses, unlike all other samples, which consist of the α-Ti phase, the microstructure of the Ti-8Cu sample is biphasic, consisting of α-Ti and the Ti2Cu intermetallic compound. Electrochemical anodization of the Ti-xCu samples results in the in-situ formation of CuO nanoparticles decorating the TiO2 nanotubes on substrates containing Cu. As the Cu concentration increases, the order and integrity of the nanotube arrays gradually decrease while the Cu concentration within the nanotubes increases; however, the Ti-6Cu sample presents a satisfactory structural order and a uniform distribution of Cu. Based on XPS analysis, it has been determined that CuO is the main species decorating the TiNTs. This results in a maximum reduction of the band gap by approximately 0.5 eV for the Ti-6Cu sample compared to the pure Ti sample (3.35 eV), leading to improved absorption of visible light. Furthermore, the CuO species extended the lifetime of charge carriers, as demonstrated by electrochemical impedance spectroscopy. This combination of band gap reduction and enhanced charge carrier separation in Ti-6Cu resulted in a photocatalytic H2 production rate of 35.8 µL/cm2·h, more than ten times higher than the pure Ti sample. These findings hold significant promise for developing efficient and sustainable energy production systems.

Enhancement of biocompatibility of anodic nanotube structures on biomedical Ti-6Al-4V alloy via ultrathin TiO2 coatings.

This work aims to describe the effect of the surface modification of TiO2 nanotube (TNT) layers on Ti-6Al-4V (TiAlV) alloy by ultrathin TiO2 coatings prepared via Atomic Layer Deposition (ALD) on the growth of MG-63 osteoblastic cells. The TNT layers with two distinctly different inner diameters, namely ∼15nm and ∼50nm, were prepared via anodic oxidation of the TiAlV alloy. Flat, i.e., non-anodized, TiAlV alloy foils were used as reference substrates. Additionally, a part of the TNT layers and alloy foils was coated with ultrathin coatings of TiO2 by ALD. The number of TiO2 ALD cycles used was 1 and 5 leading to a nominal TiO2 thickness of ∼0.055 and ∼0.3nm, respectively. The ultrathin TiO2 coating by ALD enabled to optimize the surface hydrophilicity for optimal cell growth. In addition, coatings shaded impurities of V- and F-based species (stemming from the alloy and the anodization electrolyte) that affect the biocompatibility of the tested materials while preserving the original structure and morphology. The evaluation of the biocompatibility before and after TiO2 ALD coating on TiAlV flat surfaces and TNT layers was carried out using MG-63 osteoblastic cells and compared after incubation for up to 96h. The cell growth, adhesion, and proliferation of the MG-63 on TiAlV foils and TNT layers showed significant enhancement after the surface modification by TiO2 ALD.

Photo electrocatalytic degradation 2,4-dichlorophenoxyacetic acid in water using NiTiO2-NT/AC-PTFE electrode under ultraviolet and visible irradiation: Electrode fabrication and toxicity test

The degradation of 2,4-Dichlorophenoxyacetic acid (2,4-D) pesticide by photo-electrocatalytic process (PEC) equipped with special NiTiO2-NT/AC-PTFE electrodes was evaluated. The NiTiO2-NT/AC-PTFE electrodes were prepared by electrodepositing method and doping Ni into TiO2 nanotubes. Fabricated electrodes were that Ni doping, increases the removal efficiency of 2,4-D in the UV and visible light range. Characterized using SEM, EDX, and XRD analyses. The results showed that the use of an ultraviolet light source indicated a higher degradation in nickel concentration of 0.5 mg/L compared to 0.25 mg/L. Best results were achieved under the condition of a 90-min timeout, 0.1 A current, electrolyte concentration of 125 mg/L, and UV light source and the pesticide removal efficiency was 90 %. Therefore, the PEC process with the NiTiO2-NT/AC-PTFE electrode is as a relatively high-performance process for degrading 2,4-D from aqueous solutions. The organic byproducts were also identified by GC–MS analysis and toxicity tests were carried out by Chlorella vulgaris. The high concentration of pesticides increases the inhibition of algae growth due to their effects on algae.

Boosting CO2 photoreduction to acetic acid via the van der waals heterostructures of monolayer Nb2O5 modified TiO2 nanotubes

Photoreduction of CO2 to hydrocarbons encounters two significant challenges: low product yields and poor selectivity. Furthermore, the difficulty of C-C coupling reactions hinders the formation of higher-value two-carbon products. This paper presents a strategy to address these challenges by fabricating a van der Waals heterostructure photocatalyst through the surface modification of TiO2 nanotubes (TNTs) with monolayer Nb2O5, denoted as 3 %Nb2O5/TNTs. Compared with TNTs, the acetic acid yield of heterostructures reached 28.4 μmol gcat-1h−1, and the selectivity rose from 48 % to 69 %. The van der Waals heterostructures reduced the photogenerated electron-hole recombination, extending the lifetime of charge carriers. The reduction of resistance and the presence of built-in fields accelerated the migration of charge carriers, thereby showing an enhanced photocatalytic performance. Surface modification of monolayer Nb2O5 promoted the activation adsorption of CO2 to CO2·-, facilitating the following C-C coupling reaction. Furthermore, its surface acidity sites modulated the hydrogenation reactions following C-C coupling, thereby increasing both the yield and selectivity of acetic acid.

Recent Advances in Preparation, Modification, and Application of Free-Standing and Flow-Through Anodic TiO2 Nanotube Membranes.

Free-standing and flow-through anodic TiO2 nanotube (TNT) membranes are gaining attention due to their unique synergy of properties and morphology, making them valuable in diverse research areas such as (photo)catalysis, energy conversion, environmental purification, sensors, and the biomedical field. The well-organized TiO2 nanotubes can be efficiently and cost-effectively produced through anodizing, while further utility of this material can be achieved by creating detached and flow-through membranes. This article reviews the latest advancements in the preparation, modification, and application of free-standing and flow-through anodic TiO2 nanotubes. It offers a comprehensive discussion of the factors influencing the morphology of the oxide and the potential mechanisms behind the electrochemical formation of TiO2 nanotubes. It examines methods for detachment and opening the bottom ends to prepare free-standing and flow-through TNT membranes and posttreatment strategies tailored to different applications. The article also provides an overview of recent applications of these materials in various fields, including hydrogen production, fuel and solar cells, batteries, pollutant diffusion and degradation, biomedical applications, micromotors, and electrochromic devices.

Effect of Chemical Polishing on the Formation of TiO2 Nanotube Arrays Using Ti Mesh as a Raw Material.

As a unique form of TiO2, TiO2 nanotube arrays (TiO2NTAs) have been widely used. TiO2NTAs are usually prepared by Ti foil, with little research reporting its preparation by Ti mesh. In this paper, TiO2NTAs are prepared on a Ti mesh surface via an anodic oxidation method in the F-containing electrolyte. The optimal parameters for the synthesis of TiO2NTAs are as follows: the solvent is ethylene glycol and water; the electrolyte is NH4F (0.175 mol/L); the voltage is 20 V; and the anodic oxidation time is 40 min without chemical polishing. However, there is a strange phenomenon where the nanotube arrays grow only at the intersection of Ti wires, which may be caused by chemical polishing, and the other areas, where TiO2NTAs cannot be observed on the surface of Ti mesh, are covered by a dense TiO2 film. New impurities (the hydrate of TiO2 or other products) introduced by chemical polishing and attaching to the surface of the Ti mesh reduce the current of anodic oxidation and further inhibit the growth of TiO2 nanotubes. Hence, under laboratory conditions, for commercially well-preserved Ti mesh, there is no necessity for chemical polishing. The formation of TiO2NTAs includes growth and crystallization processes. For the growth process, F- ions corrode the dense TiO2 film on the surface of Ti mesh to form soluble complexes ([TiF6]2-), and the tiny pores remain on the surface of Ti mesh. Given the basic photoelectrochemical measurements, TiO2NTAs without chemical polishing have better properties.

Fabrication of NiCo2O4 deposited self-doped TiO2 nanotubes as binder-free supercapacitor electrode

Fabrication of NiCo2O4 deposited self-doped TiO2 nanotubes as binder-free supercapacitor electrode

Preliminary Studi of Dye-Sensitized Solar Cell Photoelectrochemical for CO2 Conversion to Methanol Using CuO-modified Dark TiO2 Nanotubes Array as Cathode

The increased atmospheric carbon dioxide (CO2) levels can lead to climate change and adversely affect human health. Therefore, it is necessary to develop a method to capture CO2 and convert it into a more valuable substance, such as methanol. In this study, we established a tandem system involving dye-sensitized solar cells and photoelectrochemical (DSSC-PEC), which included the PEC zone using CuO/dark TiO2 nanotube array (CuO/dTNA) as the dark cathode where CO2 reduction takes place, and Co-Pi/blue TiO2 nanotube array (Co-Pi/bTNA) as the counter photoanode. For the DSSC zone, N719/TNA was used as the photoanode, I-/I3- electrolyte, and Pt/FTO as the cathode. The tandem system was constructed by connecting the PEC cathode to the DSSC photoanode and the PEC photoanode to the DSSC cathode using silver wire. Under solely visible light induction and water containing sodium bicarbonate electrolyte saturated with CO2, the proposed devise produced methanol at 1.292 μmol/hour. Keyword: Carbon dioxide, copper oxide, dark TiO2 nanotube, DSSC-PEC

Biophotoelectrocatalytic detoxification of Bisphenol A using Bismuth-doped TiO2 Nanotubes photoanode coupled with Laccase-immobilized cathode

Photoelectrocatalytic (PEC) technology has been demonstrated to be an effective method for environmental remediation, but its efficiency in detoxifying persistent pollutants such as bisphenol A (BPA) requires further enhancement. Herein, an enzyme-coupled PEC system for detoxification of BPA was proposed by integrating a Bismuth-doped TiO2 Nanotubes (Bi-TiO2 NTs) photoanode and laccase-immobilized cathode. The results reveal that the doping of Bi into TiO2 enhances the visible light absorption and reduces the recombination of photogenerated electron-hole pairs when exposed to simulated solar irradiation. When the laccase-immobilized cathode was incorporated into the PEC device, the resulting biophotoelectrocatalytic system exhibited excellent degradation performance for BPA, owing to the synergistic effect between enzymatic catalysis and photoelectrocatalysis. A potential degradation pathway for BPA was established through the analysis of intermediate products, and subsequent phytotoxicity assessments revealed a significant reduction in the toxicity of the laccase-coupled PEC-degraded BPA solution. This study highlights that coupling a laccase-immobilized cathode with Bi-doped TiO2 NTs photoanodes serves as an effective method for the detoxification of persistent pollutants.

Photoelectrochemical properties of Single walled and Double walled TiO2 nanotubes

Titanium dioxide (TiO2) is one of the most studied materials to be applied in various filed due to its high environmental compatibility and corrosion resistance [1-2]. Among the nanostructures of TiO2 is including nanoparticles, nanorods, nanoplates, and nanotubes, nanotubular TiO2 acquires not only a high surface area but also rapid charge carrier transfer, providing higher efficiency for photocatalytic application such as, the degradation of organic contaminants and hydrogen production. Although various methods have been investigated to fabricate TiO2 nanotubes, the anodization technique is favored with its straightforward control over structure and direct growth on Ti substrates[3]. However, conventional anodic TiO2 nanotubes exhibit surface irregularities and double-walled structure consisting of carbon-rich inner and TiO2 out layer[4]. The inner layer of TiO2 nanotubes diminishes the photoelectrochemical efficiency owing to the carbon contamination.In this study, double walled TiO2 nanotubes were synthesized by anodization with an applied voltage of 60 V for various periods. A piranha solution was utilized to eliminate the inner layer for double walled TiO2 nanotubes, achieving a single-walled TiO2 nanotube configuration. The morphological properties, crystallinity, and surface resistance of both single and double-walled TiO2 nanotubes were evaluated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Electrochemical Impedance Spectroscopy (EIS). In addition, the photoelectrochemical efficiencies of all TiO2 nanotubes were evaluated employing linear sweep voltammetry (LSV) and Incident photon-to-current efficiency (IPCE) measurements. As a result, the single-walled TiO2 nanotubes, produced under the specific conditions of 60 V for 7 min, showed the highest photoelectrochemical efficiencies at LSV and IPCE. The higher photoelectrochemical properties of the single walled nanotube are attributed to the enhancenment of surfave chage dynamics and environmental reactions as eliminating the inner layer.[1] Fujishima A, Honda K, Electrochemical photolysis of water at semiconductor electrode. Nature 238 (1972) 37-38[2]Lee K, Mazare A, Schmuki P, One-dimensional titanium dioxide nanomaterials: nanotubes, Chem. Rev, 114 (2014) 9385–9454,[3] Yoo JE, Lee K, Altomare M, Selli E, Schmuki P, Self-organized arrays of single-metal catalyst particles in TiO2 cavities: a highly efficient photocatalytic system, Angew. Chem., Int. Ed, 52 (2013) 1002[4] Liu N, Mirabolghasemia H, Lee K, Albua SP, Tighineanua A, Altomareab M, Schmuki P, Anodic TiO2 nanotubes: double walled vs. single walled. Faraday Discuss, 164 (2013) 107-116.

Fabrication of Patterned TiO2 Nanotube Layers Utilizing 3D Printer Platform and Their Electrochromic Properties

An anodization method can easily fabricate nanostructured oxide layers by controlling electrochemical parameters such as the types of electrolyte solutions, the electrolyte composition, applied voltage/current, temperature and pH. In the anodization process, it is common to form an oxide on the surface of a metal substrate with an area of several to several hundred cm2. However, several approaches have been attempted to form oxide layers on a local area or manufacture a certain oxide layer pattern using the anodization process. For this purpose, partial oxidation can be achieved through the masks and patterned metal substrates can be employed for local anodization. However, these methods are disadvantageous in process-complexity and time-consumption. Therefore, this study realizes complicated patterns composed of anodized TiO2 nanostructures using a 3D printer and apply them to the electrochromic displays. A commercial 3D printer was modified to enable a direct anodization and TiO2 nanotube was anodized on the Ti substrate with the desired pattern designed by a digital code (G-code). High speed anodization was performed at a speed of 1 mm/s. Furthermore, the surface of the patterned TiO2 nanotube was modified by adsorption of the viologen molecules and the electrochromic properties of the viologen-anchored TiO2 (V-TiO2) nanotube layers were investigated.