Advanced functional polymer membranes

An array of aligned carbon nanotubes (CNTs) was incorporated across a polymer film to form a well-ordered nanoporous membrane structure This membrane structure was confirmed by electron microscopy, anisotropic electrical conductivity, gas flow, and ionic transport studies The measured nitrogen permeance was consistent with the flux calculated by Knudsen diffusion through nanometer-scale tubes of the observed microstructure Data on Ru(NH3)6(3+) transport across the membrane in aqueous solution also indicated transport through aligned CNT cores of the observed microstructure The lengths of the nanotubes within the polymer film were reduced by selective electrochemical oxidation, allowing for tunable pore lengths Oxidative trimming processes resulted in carboxylate end groups that were readily functionalized at the entrance to each CNT inner core Membranes with CNT tips that were functionalized with biotin showed a reduction in Ru(NH3)6(3+) flux by a factor of 15 when bound with streptavidin, thereby demonstrating the ability to gate molecular transport through CNT cores for potential applications in chemical separations and sensing

https://science.sciencemag.org/content/sci/303/5654/62.full.pdf

Aligned multiwalled carbon nanotube membranes.

Nanoporous anodic aluminium oxide has been widely used for the development of various functional nanostructures. So far these self-organized pore structures could only be prepared within narrow processing conditions. Here we report a new oxalic-acid-based anodization process for long-range ordered alumina membranes. This process is a new generation of the so-called "hard anodization" approach that has been widely used in industry for high-speed fabrication of mechanically robust, very thick (>100 microm) and low-porosity alumina films since the 1960s. This hard anodization approach establishes a new self-ordering regime with interpore distances, (D(int))=200-300 nm, which have not been achieved by mild anodization processes so far. It offers substantial advantages over conventional anodization processes in terms of processing time, allowing 2,500-3,500% faster oxide growth with improved ordering of the nanopores. Perfectly ordered alumina membranes with high aspect ratios (>1,000) of uniform nanopores with periodically modulated diameters have been realized.

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Fast fabrication of long-range ordered porous alumina membranes by hard anodization

Urchinlike TiO2 spheres with tunable chamber structure were synthesized using a template-free solvothermal method. The unique sphere-in-sphere chamber structure allows multiple reflections of UV light resulting in greatly enhanced photocatalytic activity. This work provided novel structural platforms for novel materials and device applications.

Mesoporous titania spheres with tunable chamber stucture and enhanced photocatalytic activity.

Porous anodic aluminum oxide: anodization and templated synthesis of functional nanostructures.

Synthetic bio-nanotube membranes were developed and used to separate two enantiomers of a chiral drug. These membranes are based on alumina films that have cylindrical pores with monodisperse nanoscopic diameters (for example, 20 nanometers). Silica nanotubes were chemically synthesized within the pores of these films, and an antibody that selectively binds one of the enantiomers of the drug was attached to the inner walls of the silica nanotubes. These membranes selectively transport the enantiomer that specifically binds to the antibody, relative to the enantiomer that has lower affinity for the antibody. The solvent dimethyl sulfoxide was used to tune the antibody binding affinity. The enantiomeric selectivity coefficient increases as the inside diameter of the silica nanotubes decreases.

http://science.sciencemag.org/content/sci/296/5576/2198.full.pdf

Antibody-based bio-nanotube membranes for enantiomeric drug separations.

Tube-shaped nanostructures (nanotubes) have a number of attributes that make them potentially useful for biomedical applications such as drug delivery/detoxification and enzyme immobilization. Template synthesis provides a route for preparing monodisperse nanotubes of nearly any size and composed of nearly any material. We show here that template-synthesized silica nanotubes can be biochemically functionalized such that they act as biocatalysts and highly selective nano-phase extraction agents for bioseparations. For example, nanotubes containing an enantioselective antibody selectively extract the enantiomer of a drug molecule that binds to the antibody, relative to the enantiomer that has no specific interaction with the antibody. Nanotubes containing the enzyme glucose oxidase function as nanophase bioreactors to catalyze the oxidation of glucose.

Hans Söderlund

Papers

Antibody-based bio-nanotube membranes for enantiomeric drug separations.

Smart nanotubes for bioseparations and biocatalysis.