Selective transport of single protein molecules inside gold nanotubes

Diffusion of single protein molecules inside gold nanotubes was investigated. 3-dimensional imaging was employed to locate the individual molecules inside the nanotubes as a function of time. As expected, larger proteins and smaller pore sizes resulted in smaller diffusion coefficients. Diffusion within PEG-coated gold nanotubes was found to be two orders of magnitude faster than in previously reported, similar sized untreated polycarbonate membrane pores, showing that adsorption was serious in the latter case. We further demonstrate chromatographic selectivity during transport by modifying the inner surface of the gold nanotubes with self-assembled monolayers of derivatized alkyl thiols. These results should be useful for designing membrane separations.