A highly efficient approach for metal filling of TiO2 nanotube layers is demonstrated. Electrochemical self‐doping is used to switch selectively the bottom of TiO2 nanotubes into a conductive state. ...Subsequent metal electrodeposition therefore starts at the tube bottom and continues in a homogenous and controllable manner up the tubes. The approach essentially allows to deposit all material classes into TiO2 nanotubes and therefore provides the basis for a large variety of functional TiO2 nanotubes – composite materials.
Self‐organized zirconium titanate nanotube layers (see figure) have been produced by anodizing a Ti–Zr alloy in a fluoride‐containing electrolyte. The diameter of the tubes can be adjusted by the ...anodization voltage and ranges from several tens of nanometers to several hundreds of nanometers. The as‐formed layers are amorphous but can be crystallized to zirconium titanate by an adequate thermal treatment.
Titanium and titanium alloys exhibit a unique combination of strength and biocompatibility, which enables their use in medical applications and accounts for their extensive use as implant materials ...in the last 50 years. Currently, a large amount of research is being carried out in order to determine the optimal surface topography for use in bioapplications, and thus the emphasis is on nanotechnology for biomedical applications. It was recently shown that titanium implants with rough surface topography and free energy increase osteoblast adhesion, maturation and subsequent bone formation. Furthermore, the adhesion of different cell lines to the surface of titanium implants is influenced by the surface characteristics of titanium; namely topography, charge distribution and chemistry. The present review article focuses on the specific nanotopography of titanium, i.e. titanium dioxide (TiO2) nanotubes, using a simple electrochemical anodisation method of the metallic substrate and other processes such as the hydrothermal or sol-gel template. One key advantage of using TiO2 nanotubes in cell interactions is based on the fact that TiO2 nanotube morphology is correlated with cell adhesion, spreading, growth and differentiation of mesenchymal stem cells, which were shown to be maximally induced on smaller diameter nanotubes (15 nm), but hindered on larger diameter (100 nm) tubes, leading to cell death and apoptosis. Research has supported the significance of nanotopography (TiO2 nanotube diameter) in cell adhesion and cell growth, and suggests that the mechanics of focal adhesion formation are similar among different cell types. As such, the present review will focus on perhaps the most spectacular and surprising one-dimensional structures and their unique biomedical applications for increased osseointegration, protein interaction and antibacterial properties.
The anodic formation of nanoporous TiO2 on titanium was investigated in Na2SO4 electrolytes containing low concentrations of NaF (0.1-1 wt.%). It was found that under optimized electrolyte conditions ...and extended polarization, a self-organized nanostructure consisting of porous TiO2 is obtained. The porous structure is arranged in sections of arrays with single pore diameters of typically 100 nm and an average spacing of 150 nm. The pores are open at the top and covered by oxide at the bottom. Compared with earlier work, we show that using a neutral NaF electrolyte significantly thicker porous layers can be obtained than in acidic solutions.
The present paper gives an overview and review on self-organized TiO2 nanotube layers and other transition metal oxide tubular structures grown by controlled anodic oxidation of a metal substrate. We ...describe mechanistic aspects of the tube growth and discuss the electrochemical conditions that need to be fulfilled in order to synthesize these layers. Key properties of these highly ordered, high aspect ratio tubular layers are discussed. In the past few years, a wide range of functional applications of the layers have been explored ranging from photocatalysis, solar energy conversion, electrochromic effects over using the material as a template or catalyst support to applications in the biomedical field. A comprehensive view on state of the art is provided.
We describe a rapid screening technique for determining the optimal characteristics of nanophotocatalysts for the production of H2 on a single surface. Arrays of TiO2 nanotubes (NTs) with a gradient ...in length and diameter were fabricated by bipolar anodization, and a perpendicular gradient of Pt nanoparticles (NPs) was generated by the toposelective decoration of the TiO2 NTs. Photocatalytic hydrogen evolution was locally triggered with a UV laser beam, and the arrays were screened in the x and y directions for spatially resolved kinetic measurements and the mapping of the optimal hydrogen production. By using this technique, we demonstrate the time-efficient and straightforward determination of the tube dimensions and Pt loading for optimized H2 production. The concept holds promise for generally improving the study of many photoreactions as a function of the physicochemical characteristic of nanophotocatalysts, which renders it highly attractive for the optimization of various important chemical processes.
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