Fabrication of titania nanotube arrays on curved surface

In this paper, well-ordered titania nanotube arrays were formed on curved surface provided by titanium wire via anodic oxidation. The morphology of the nanotube arrays was observed by scanning electron microscopy (SEM). It was found that within the range of 360°, all the growing orientations of each nanotube keep correspondence with their outer electric fields. That is to say the surface shapes of anode play an important role on morphology of nanotube arrays. Compared with foils, by changing the anode shape, higher aspect ratio can be obtained. The nanotube arrays formed on wires can provide good understanding for the formation mechanism of the nanotube arrays. Furthermore, it can stimulate new thoughts in practical applications due to its ringed shaper.     

A multi-drug delivery system with sequential release using titania nanotube arrays

A multi-drug delivery system with sequential release based on titania nanotube arrays and polymer micelles as drug carriers is presented. Delivery of multiple water insoluble and soluble drugs required for combined local therapy is demonstrated.     

A highly ordered titania nanotube array as a supercapacitor electrode

We report the synthesis of self-organized titania nanotubes and nanocrystalline titania powders employing an alternative and novel approach. Integrating these nanostructures in a binder-free working electrode improved the capacitance up to 911 μF cm(-2), which is around one to two orders of magnitude higher than the conventional electric double layer capacitors.     

Double-sided anodic titania nanotube arrays: a lopsided growth process

In the past decade, the pore diameter of anodic titania nanotubes was reported to be influenced by a number of factors in organic electrolyte, for example, applied potential, working distance, water content, and temperature. All these were closely related to potential drop in the organic electrolyte. In this work, the essential role of electric field originating from the potential drop was directly revealed for the first time using a simple two-electrode anodizing method. Anodic titania nanotube arrays were grown simultaneously at both sides of a titanium foil, with tube length being longer at the front side than that at the back side. This lopsided growth was attributed to the higher ionic flux induced by electric field at the front side. Accordingly, the nanotube length was further tailored to be comparable at both sides by modulating the electric field. These results are promising to be used in parallel configuration dye-sensitized solar cells, water splitting, and gas sensors, as a result of high surface area produced by the double-sided architecture.     

Surface-assisted laser desorption/ionization mass spectrometry on titania nanotube arrays

Titania nanotube arrays (NTA) generated from anodizing processes are tested as the substrate for surface-assisted laser desorption/ionization mass spectrometry (SALDI MS). The background generated from titania NTA is very low, making the approach suitable for the analysis of small molecules. The upper detectable mass is approximately 29 kDa. Homogeneous sample deposition leads to good shot-to-shot reproducibility and suitability for quantitative analysis. Additionally, phosphopeptides can be selectively trapped on the titania NTA substrate, as illustrated by simply depositing a tryptic digest of beta-casein followed by titania NTA SALDI MS analysis. The detection limit for small organics and peptides is in low fmol.     

High density copper nanowire arrays deposition inside ordered titania pores by electrodeposition

Large area and free-standing TiO₂ films was prepared by ultrasonic splitting and a chemical etching step was used to open the closed bottom end of TiO₂ films and yields a high aspect-ratio anodic titanium oxide membrane open at both ends. Ordered Cu nanowire structures were fabricated by a simple electroplating method inside high aspect-ratio anodic titanium oxide membrane. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the X-ray diffraction (XRD) were employed to characterize the resulting samples. Detailed results and the possible mechanism are presented.     

A self-cleaning nonenzymatic glucose detection system based on titania nanotube arrays modified with platinum nanoparticles

In the present work, we show how TiO₂ nanotube layers that are decorated with a Pt-nanoparticle coating can be fabricated and operated as a reusable glucose sensing system. A critical amount of Pt coating is essential not only to provide an effective catalyst for glucose oxidation but also to establish a sufficient conductivity along TiO₂ nanotube walls to allow an efficient amperometric operation of the electrode. On such an electrode the self-cleaning photocatalytic features of TiO₂ can be maintained and used to re-establish poisoned activity of the Pt particles.     

Photocatalytic decompositions of gaseous HCHO and methylene blue with highly ordered TiO_2 nanotube arrays

The highly ordered Ti O_2nanotubes(NTs) were fabricated by the anodic oxidation method.Their morphology,structure and crystalline phase were characterized by scanning electron microscopy(SEM) and X-ray diffractometer(XRD).The effects of morphology,specific surface area,pore structures and photocatalytic activity of the Ti O_2 NTs were investigated.UV–vis spectra analysis showed that its light absorption had been extended to the visible light range.The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic oxidation of gaseous HCHO and MB aqueous solution.The samples had better adhesion strength in the dark and showed a higher photocatalytic activity than nanoparticles.Especially,with ultraviolet light pretreatment,the nanotubes exhibited more stable active for photocatalytic decomposition and the photodecomposition rate remained at high level after 3 cycles of the photocatalysis experiment.Thus,how the number of surface active group ·OH increased and the mechanism for the great improvement for the photocatalytic activity are discussed.     

Highly ordered arrays of metal/semiconductor core-shell nanoparticles with tunable nanostructures and photoluminescence

Most of the approaches so far in fabricating core-shell nanoparticles (CSNs) are based on wet-chemical methods. It is usually difficult to achieve highly ordered CSN arrays on substrates from such a wet-chemical method. In this work, highly ordered indium oxide coated indium CSNs, with a structure-dependence photoluminescence, are fabricated on Si substrates using a three-step oxidation process. By controlling the three-step oxidation process, the volume ratio of the oxide shell to the whole CSN can be adjusted continuously from 0 to 1, which results in fine-tuning of the intensity and peak-shift of the photoluminescence from the CSNs. Our work is based on a dry oxidation method for fabricating CSNs, which is capable of achieving highly ordered CSN arrays with tunable nanostructures and optical properties.     

Fabrication of highly ordered TiO2 nanotube arrays using an organic electrolyte

Anodization of titanium in a fluorinated dimethyl sulfoxide (DMSO) and ethanol mixture electrolyte is investigated. The prepared anodic film has a highly ordered nanotube-array surface architecture. Using a 20 V anodization potential (vs Pt) nanotube arrays having an inner diameter of 60 nm and 40 nm wall thickness are formed. The overall length of the nanotube arrays is controlled by the duration of the anodization, with nanotubes appearing only after approximately 48 h; a 72 h anodization results in a nanotube array approximately 2.3 mum in length. The photoelectrochemical response of the nanotube-array photoelectrodes is studied using a 1 M KOH solution under both UV and visible (AM 1.5) illumination. Enhanced photocurrent density is observed for samples obtained in the organic electrolyte, with an UV photoconversion efficiency of 10.7%.     

Nanostructured ultrathin catalyst layer with ordered platinum nanotube arrays for polymer electrolyte membrane fuel cells

Fabrication of novel electrode architectures with nanostructured ultrathin catalyst layers is an effective strategy to improve catalyst utilization and enhance mass transport for polymer electrolyte membrane fuel cells (PEMFCs).Herein,we report the design and construction of a nanostructured ultrathin catalyst layer with ordered Pt nanotube arrays,which were obtained by a hard-template strategy based on ZnO,via hydrothermal synthesis and magnetron sputtering for PEMFC application.Because of the crystallographically preferential growth of Pt (111) facets,which was attributed to the structural effects of ZnO nanoarrays on the Pt nanotubes,the catalyst layers exhibit obviously higher electrochemical activity with remarkable enhancement of specific activity and mass transport compared with the state-of-the-art randomly distributed Pt/C catalyst layer.The PEMFC fabricated with the as-prepared catalyst layer composed of optimized Pt nanotubes with an average diameter of 90(±10) nm shows excellent performance with a peak power density of 6.0W/mg~(Pt) at 1 A/cm~2,which is 11.6%greater than that of the conventional Pt/C electrode.     

Highly ordered structures of peptides by using molecular scaffolds

Protein secondary structures such as alpha-helices, beta-sheets, and beta-turns are important in inducing the three-dimensional structure and biological activity of proteins. Designing secondary structure mimics composed of short peptides has attracted much attention not only to gain fundamental insight into the factors affecting protein folding but also to develop pharmacologically useful compounds, artificial receptors, asymmetric catalysts, and new materials. In this tutorial review, we focus on molecular scaffolds employed to induce beta-sheet-like structure in attached peptide chains, thereby creating highly ordered molecular structures, and discuss the versatility of these molecular scaffolds to regulate the attached peptide strands in the appropriate dimensions.     

Flexible fiber-type dye-sensitized solar cells based on highly ordered TiO2 nanotube arrays

A double-sided, transparent conducting and flexible dye-sensitized solar cell (DSSC) was developed. The device comprised two metal electrodes whereby the working electrode consisted of highly ordered titania (TiO₂) nanotube arrays. The maximum conversion efficiency of the DSSC was 5.1% and decreased by 6% under a 90° bending. Surface treatment of the TiO₂ nanotube arrays in niobium isopropoxide solution lifted the conversion efficiency to 6.8%.     

Photocatalytic decompositions of gaseous HCHO and methylene blue with highly ordered TiO2 nanotube arrays

The highly ordered Ti O₂nanotubes（NTs） were fabricated by the anodic oxidation method.Their morphology,structure and crystalline phase were characterized by scanning electron microscopy（SEM） and X-ray diffractometer（XRD）.The effects of morphology,specific surface area,pore structures and photocatalytic activity of the Ti O₂ NTs were investigated.UV–vis spectra analysis showed that its light absorption had been extended to the visible light range.The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic oxidation of gaseous HCHO and MB aqueous solution.The samples had better adhesion strength in the dark and showed a higher photocatalytic activity than nanoparticles.Especially,with ultraviolet light pretreatment,the nanotubes exhibited more stable active for photocatalytic decomposition and the photodecomposition rate remained at high level after 3 cycles of the photocatalysis experiment.Thus,how the number of surface active group ·OH increased and the mechanism for the great improvement for the photocatalytic activity are discussed.     

Anodic growth of highly ordered TiO2 nanotube arrays to 134 microm in length

Described is the fabrication of self-aligned highly ordered TiO(2) nanotube arrays by potentiostatic anodization of Ti foil having lengths up to 134 mum, representing well over an order of magnitude increase in length thus far reported. We have achieved the very long nanotube arrays in fluoride ion containing baths in combination with a variety of nonaqueous organic polar electrolytes including dimethyl sulfoxide, formamide, ethylene glycol, and N-methylformamide. Depending on the anodization voltage, pore diameters of the resulting nanotube arrays range from 20 to 150 nm. Our longest nanotube arrays yield a roughness factor of 4750 and length-to-width (outer diameter) aspect ratio of approximately 835. The as-prepared nanotubes are amorphous but crystallize with annealing at elevated temperatures. In initial measurements, 45 mum long nanotube-array samples, 550 degrees C annealed, under UV illumination show a remarkable water photoelectrolysis photoconversion efficiency of 16.25%.     

Highly ordered platinum-nanotube arrays for oxidative determination of trace arsenic(III)

A novel method for the oxidative determination of trace arsenic(III) was investigated on highly ordered platinum-nanotube array electrodes (PtNTAEs). The PtNTAEs with a highly organized structure were fabricated by electrochemical deposition of platinum in a 3-aminopropyltrimethoxysilane-modified porous anodic alumina template (PAA). The morphologies and structures of PtNTAEs were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Electrochemical experiments proved that the PtNTAEs exhibited better performance for As(III) analysis in comparison with platinum nanoparticles-coated GCE (Pt_nano/GCE) or Pt foil electrode. The PtNTAEs showed to provide higher reproducibility and lower detection limit. The relative standard deviation (RSD) was 3.5% for 50 repeated measurements of 20 μM As(III), and the limit of detection (LOD) was 0.1 ppb, which was typically 1–2 orders of magnitude lower than that of Pt_nano/GCE or Pt foil electrode.     

The preparation of highly ordered TiO2 nanotube arrays by an anodization method and their applications

The tubular-shaped nanostructure of TiO(2) is very interesting, and highly ordered arrays of TiO(2) nanotubes (TNTs) can be easily fabricated by anodization of the Ti substrate in specific electrolytes. Here in this feature article, we review synthesis methods for various TNTs including normal, alloy, and architectural forms such as bamboos, lace, and flowers. Specific nanosize architectures such as bamboo and lace types can be regulated by alternating voltage and further anodizing. In order to extend light response of TNTs to visible solar spectra, various dopings of specific elements have been discussed. The normal and modified TNTs are suggested for applications such as dye sensitized solar cells, water splitting, photocatalytic degradation of pollutants, CO(2) reduction, sensors, energy storage devices including Li ion batteries and supercapacitors, and other applications such as flexible substrate and biomaterials.     

Highly interconnected ordered mesoporous carbon-carbon nanotube nanocomposites: Pt-free, highly efficient, and durable counter electrodes for dye-sensitized solar cells

We report the preparation of highly interconnected ordered mesoporous carbon-carbon nanotube nanocomposites which show Pt-like dye-sensitized solar cell (DSSC) efficiency and remarkable long-term durability as DSSC counter electrodes.     

Template-based synthesis of nanorod, nanowire, and nanotube arrays

This review introduces and summarizes the fundamentals and various technical approaches developed for the template-based synthesis of nanorod, nanowire and nanotube arrays. After a brief introduction to various concepts for the growth of nanorods, nanowires and nanobelts, attention will be focused mainly on the most widely used and well established techniques for the template-based growth of nanorod arrays: electrochemical deposition, electrophoretic deposition, filling of templates by capillary force and centrifugation, and chemical conversion. In each section, relevant fundamentals will be first introduced, followed with examples to illustrate the specific details of each technique.