Facile synthesis of robust free-standing TiO2 nanotubular membranes for biofiltration applications
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Robust monodisperse nanoporous membranes have a wide range of biotechnological applications, but are often difficult or costly to fabricate. Here, a simple technique is reported to produce free-standing TiO2 nanotubular membranes with through-hole morphology. It consists of a three-step anodization procedure carried out at room temperature on a Ti foil. The first anodization (1 h at 80 V) is used to pattern the surface of the metallic foil. Then, the second anodization (24 h at 80 V) produces the array of TiO2 nanotubes that will constitute the final membrane. A higher voltage anodization (3–5 min at 180 V) is finally applied to detach the TiO2 nanotubular layer from the underlying Ti foil. In order to completely remove the barrier layer that obstructs some pores of the membrane, the latter is etched 2 min in a buffered oxide etch solution. The overall process produces 60-μm-thick TiO2 nanotubular membranes with tube openings of 110 nm on one side and 73 nm on the other side. The through-hole morphology of these membranes has been verified by performing diffusion experiments with glucose, insulin, and immunoglobulin G where in differences in diffusion rate are observed based on molecular weight. Such biocompatible TiO2 nanotubular membranes, with controlled pore size and morphology, have broad biotechnological and biomedical applications.
KeywordsTiO2 nanotubes Membranes Multi-step anodization Diffusion of biomolecules Biofiltration
JS and TAD would like to acknowledge financial support from the Juvenile Diabetes Research Foundation. JS is also grateful for a postdoctoral fellowship (2010–2011) from the King Baudouin Foundation (Belgium) and the Belgian American Educational Foundation. All SEM imaging was performed at the Electron Microscope Facility of the San Francisco State University (SFSU).
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