Gold nanotube membranes: Preparation, characterization and application for enantioseparation

Gold nanotube membranes were synthesized using a template-based electroless plating technique. The obtained membranes were characterized with scanning electron microscopy, revealing that gold nanotubes have a circular cross-section but a varying diameter, smaller at the two ends and larger in the middle. The orientation of nanotubes is not perpendicular to the membrane surface, based on which the tortuosity of the nanotubes was thus estimated. The mean inner diameter of the nanotubes was determined by both gas diffusion and water permeation methods. Two approximations (first- and second-order) were proposed to characterize the nanotube profile. The nanotubes with an inner diameter of 1–100 nm were prepared. Human serum albumin, which acts as an enantiomer selector, was immobilized on the inner surface of the nanotube through a reactive thiol. The warfarin enantiomers in mixture were separated with the thus-treated membrane, which was used as the stationary phase of a high-performance liquid chromatograph.