Crystallization of amorphous anodized TiO2 nanotube arrays.

Herein, we report the preparation and characterizations of the sulfur (S)-doped TiO2 nanotube (TONT) arrays prepared by a sulfurization process of TONT arrays via electrochemical anodization on a Ti substrate with pure TONT arrays. The S-doped TONT arrays were prepared with the annealing temperature from 450 to 550 °C under H2S gas for 10 min, and these reaction conditions corresponded to no modification of the morphological features relative to that of the TONT arrays. Furthermore, the 500 °C annealed S-doped TONT arrays showed enhanced visible light absorption and high electric conductivity, thus resulting in the most improved photocurrent density (2.92 mA cm–2 at 1.0 V vs sat. Ag/AgCl) in the 0.1 M KOH solution as compared with that (0.965 mA cm–2 at 1.0 V vs sat. Ag/AgCl) of TONT arrays. In addition, the incident photon-to-electron conversion efficiency (IPCE) of S-doped TONT arrays exhibited approximately 43% in the UV region, whereas TONT arrays had 32% IPCE in the UV region. In addition, the small ...

Photoactivity of amorphous and crystalline TiO2 nanotube arrays (TNA) films in gas phase CO2 reduction to methane with simultaneous H2 production

The effects of titania nanotubes with embedded silver oxide nanoparticles on bacteria and osteoblasts

1. Introduction Dye-sensitized solar cells (DSSCs) are considered as a new generation of solar cells due to their low cost and high performance [1-4]. DSSCs based on a TiO2 nanoparticle (TiO2 NP) network with air mass (AM) 1.5 solar efficiencies of more than 10% have been demonstrated. However, further enhancement in power conversion efficiency (PCE) has been difficult to achieve partly due to charge recombination and a reduced electron transport rate through the nanocrystalline photoanodes. Metal nanoparticles can contribute to the effective light absorption of solar cells, both by local field enhancement through the localized surface plasmon resonance and by light scattering leading to prolonged optical-path lengths [5]. Many researchers demonstrated that the size of the metal nanoparticles is a key factor for determining the plasmonic phenomena, and especially, light scattering occurs more dominantly than light absorption as the size of the metal nanoparticles increases [6]. In this work, TiO2 nanotubes (TNs) array synthesized by anodization method had a much organized standing nanotubes and tubes with uniform length, thickness, and diameter. The anodic oxidation process was carried out at 30 V, 25°C, 0.3 wt% NH4F + 3 vol% H2O as electrolyte and an anodization time of 1 h. The DSSC with TNs array as working electrode had fill-factor of 77.94%, Voc of 0.69 V, Isc of 6.85 mA/cm2, and 3.68% of efficiency. Since TNs array had roughly 1.2% higher efficiency than randomly stacked TNs, I have decided to further enhance the TNs array with gold nanoparticles. The DSSC with gold-lined TNs array as working electrode had fill-factor of 81.09%, Voc of 0.72 V, Isc of 7.54 mA/cm2, and finally an efficiency of 4.40%. 2. Experimental Once the Ti plate was cleaned thoroughly, apply Teflon® tape at the back of the plate to avoid oxidation on the back of the Ti plate. Clamp the plate with positive (anode) charge. The buffer solution used for the anodization is a mixture of 0.25 wt% NH4F plus 3 vol% H2O in ethyl glycol, stirred for one hour. The optimized voltage, setting temperature, and oxidation time are 30 V, 25°C, and one hour, respectively. After anodization, the Ti plate is immersed in ethanol and place in an ultrasonic bath to remove any excess contaminations, and then dried in room temperature overnight. Synthesize TNs array using optimized parameter setting, after annealing process, dipped the Ti foil into 1 mM of AuCl4 solution for 5 min, rinsed with deionized water, then dipped the foil into 0.15 M NaBH4 solution for another 5 min.To fabricate DSSCs, TiO2 nanotube arrays with or without Au modifications were soaked with N719 dye was added tert-butanol and acetonitrile solution, such mixing ratio 1:1 to prepare a concentration of 5 × 10-4 M dye solution. The DSSCs were finally packed by sealing the dye-coated electrode with a thermally platinized FTO counter electrode through a thin thermal plastic film (Surlyn, 25 ƒÝm, Solaronix). An electrolyte composed of 0.1 M N-methyl benzimidiazoium, 0.6 M 1-propyl-3-methylimidiazolium iodide, 0.05 M I2, 0.1 M guanidinium thiocyanate, and 0.2 M NaI in 3-methoxypropionitrile was introduced into the cell through a pre-drilled hole in the counter electrode. The hole was subsequently sealed with a microscope slip using Surlyn film. 3. Results and Discussion Fig. 1 Gold nanoparticles within TNs array.Fig. 2 I-V characteristic curves of DSSCs with Au nanoparticles by anodic oxidation at different voltage. 4. Conclusions In conclusion, anatase TiO2 nanotube arrays with Au nanoparticles was synthesized by anodic oxidation. At the deposition voltage of 30 V and Au-doped TiO2 nanotube arrays, the η, Jsc, and FF all reached the maximum. Compared with the conventional DSSCs Jsc, Voc, and η are 7.54 mA/cm2, 0.72 V, and 4.4%. Au-doped DSSCs has evident adsorption peak in visible range, indicating that Au-doped TiO2nanotubes are hopeful to become visible light photocatalyst.

H2 and O2 photocatalytic production on TiO2 nanotube arrays: Effect of the anodization time on structural features and photoactivity

Enhanced efficiency of dye-sensitized solar cells through TiCl4-treated, nanoporous-layer-covered TiO2 nanotube arrays

Enhanced solar water-splitting performance of TiO2 nanotube arrays by annealing and quenching

Dye-sensitized solar cells (DSSCs) were fabricated using TiO2 nanoparticles (NPs), TiO2 nanotube arrays (NTAs), and surface-modified NTAs with a TiCl4 treatment. The photovoltaic efficiencies of the DSSCs using TiO2 NP, NTA, and TiCl4-treated NTA electrodes are 4.25, 4.74, and 7.47 %, respectively. The highest performance was observed with a TiCl4-treated TiO2 NTA photoanode, although in the case of the latter two electrodes, the amounts of N719 dye adsorbed were similar and 68 % of that of the NP electrode. Electrochemical impedance measurements show that the overall resistance, including the charge–transfer resistance, was smaller with NTA morphologies than with NP morphologies. We suggest that a different electron transfer mechanism along the one-dimensional nanostructure of the TiO2 NTAs contributes to the smaller charge–transfer resistance, resulting in a higher short circuit current (J sc), even at lower dye adsorption. Furthermore, the TiCl4-treated NTAs showed even smaller charge–transfer resistance, resulting in the highest J sc value, because the downward shift in the conduction band edge improves the electron injection efficiency from the excited dye into the TiCl4-treated TiO2 electrodes.

High-ordered anatase TiO2 nanotube array films coated with exposed high-reactive {001} nanofacets were fabricated by a modified hydrothermal method using amorphous anodic TiO2 nanotube arrays (ATONAs) as starting materials. It was found that the reaction between gas phase HF and solid ATONAs played a key role in the transformation process from amorphous to anatase TiO2, and the TiO2 tubular structure kept unchanged during the surface modification with an exposed {001} facets up to 76.5%, which could be attributed to the low reaction temperature of 130 °C. Our study provided a novel route for the facile preparation of {001} facets exposed anatase TiO2.

TiO2 nanotube arrays treated with (NH4)2TiF6 dilute solution for better supercapacitive performances

A comprehensive review on anodic TiO2 nanotube arrays (TNTAs) and their composite photocatalysts for environmental and energy applications: Fundamentals, recent advances and applications

Effect of NaBF4 addition on the anodic synthesis of TiO2 nanotube arrays photocatalyst for production of hydrogen from glycerol–water solution

Large-area noncurling crystallized free-standing TiO2 nanotube (TNT) arrays have been fabricated by a two-step anodization process. These free-standing crystallized TNT arrays can be easily transferred to fluorine-doped tin oxide glass substrates without any crack. Furthermore, the investigation of these crystallized free-standing TNT arrays in dye-sensitized solar cells (DSSCs) was carried out and showed a roughly 100% enhanced conversion efficiency compared with that of the TNT array on a Ti substrate.

Dye-sensitized solar cells (DSSCs) have received worldwide research interest as a promising and competitive candidate for low-cost photovoltaics. Highly-ordered TiO 2 nanotube arrays prepared by electrochemical anodization have been developed as an intriguing photoanode owing to vertical tube alignment for one-dimensional electron transport and available inner and outer tube surface for dye attachment. For nanotubes based DSSCs, one main efficiency limitation factor is the relatively low tube surface area due to accessible large diameter (usually ~ 100 nm).

It has been revealed that the different morphologies of anodized TiO2 nanotubes, especially nanotube diameters, triggered different cell behaviors. However, the influence of TiO2 nanotubes with coexisting multi-size diameters on cell behaviors is seldom reported. In this work, coexisting four-diameter TiO2 nanotube samples, namely, one single substrate with the integration of four different nanotube diameters (60, 150, 250, and 350 nm), were prepared by repeated anodization. The boundaries between two different diameter regions show well-organized structure without obvious difference in height. The adhesion behaviors of MC3T3-E1 cells on the coexisting four-diameter TiO2 nanotube arrays were investigated. The results exhibit a significant difference of cell density between smaller diameters (60 and 150 nm) and larger diameters (250 and 350 nm) within 24 h incubation with the coexistence of different diameters, which is totally different from that on the single-diameter TiO2 nanotube arrays. The coexistence of four different diameters does not change greatly the cell morphologies compared with the single-diameter nanotubes. The findings in this work are expected to offer further understanding of the interaction between cells and materials.