We report for the first time fabrication of self-aligned hexagonally closed-packed titania nanotube arrays of
over 1000 μm in length and aspect ratio ≈10 000 by potentiostatic anodization of titanium. We describe a
process by which such thick nanotube array films can be transformed into self-standing, flat or cylindrical,
mechanically robust, polycrystalline TiO2 membranes of precisely controlled nanoscale porosity. The self-standing membranes are characterized using Brunauer−Emmett−Teller surface area measurements, glancing
angle X-ray diffraction, and transmission electron microscopy. In initial application, such membranes are
used to control the diffusion of phenol red.
Nanotubes for drug release: Titania nanotubes (see image) fabricated by an easy anodization process can be used as drug‐eluting coatings for implantable devices. The release rate of the drugs is controlled by varying the amount of proteins loaded into the nanotubes. Moreover, by changing the nanotube diameter, wall thickness, and length, the release kinetics can be altered for each specific drug to achieve a sustained release.
Abstract-A biosensor application of vertically coupled glass microring resonators with Q ∼ 12 000 is introduced. Using balanced photodetection, very high signal to noise ratios, and thus high sensitivity to refractive index changes (limit of detection of 1.8 × 10
Nanoporous alumina surfaces have a variety of applications in biosensors, biofiltration, and targeted drug delivery. However, the fabrication route to create these nanopores in alumina results in surface defects in the crystal lattice. This results in inherent charge on the porous surface causing biofouling, that is, nonspecific adsorption of biomolecules. Poly(ethylene glycol) (PEG) is known to form biocompatible nonfouling films on silicon surfaces. However, its application to alumina surfaces is very limited and has not been well investigated. In this study, we have covalently attached PEG to nanoporous alumina surfaces to improve their nonfouling properties. A PEG-silane coupling technique was used to modify the surface. Different concentrations of PEG for different immobilization times were used to form PEG films of various grafting densities. X-ray photoelectron spectroscopy (XPS) was used to verify the presence of PEG moieties on the alumina surface. High-resolution C1s spectra show that with an increase in concentration and immobilization time, the grafting density of PEG also increases. Further, a standard overlayer model was used to calculate the thickness of PEG films formed using the XPS intensities of the Al2p peaks. The films formed by this technique are less than 2.5 nm thick, suggesting that such films will not clog the pores which are in the range of 70-80 nm.
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