An electroless plating method was used to deposit Au nanotubules within the pores of track-etched polycarbonate template membranes. The effect of nanotubule inside diameter on rate and selectivity of protein transport was investigated for three proteins: lysozyme (Lys), bovine serum albumin (BSA), and β-lactoglobulin A. Transport selectivity increased as the inside diameter of the nanotubules within the membrane decreased, and selectivity coefficients in excess of 20 were observed for the separation of Lys from BSA. Protein adsorption, and hence membrane fouling, was eliminated by chemisorbing a poly(ethylene glycol) thiol to the Au nanotubule membranes.
We have been investigating applications of nanopore membranes in analytical chemistry-specifically in membrane-based bioseparations, in electroanalytical chemistry, and in the development of new approaches to biosensor design. Membranes that have conically shaped pores (as opposed to the more conventional cylindrical shape) may offer some advantages for these applications. We describe here a simple plasma-etch method that converts cylindrical nanopores in track-etched polymeric membranes into conically shaped pores. This method allows for control of the shape of the resulting conical nanopores. For example, the plasma-etched pores may be cylindrical through most of the membrane thickness blossoming into cones at one face of the membrane (trumpet-shaped), or they may be nearly perfect cones. The key advantage of the conical pore shape is a dramatic enhancement in the rate of transport through the membrane, relative to an analogous cylindrical pore membrane. We demonstrate this here by measuring the ionic resistances of the plasma-etched conical pore membranes.
A new electroless plating method was used to deposit palladium nanotubes within the pores of tracketched polycarbonate membranes. The morphology of the deposited palladium nanostructures were characterized with the use of field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectrometry (EDX), and transmission electron microscopy (TEM). The largely expanded surface area and granular nature of the nanotubes make them ideal for applications that require high surface area. One of the applications investigated here is hydrogen sensing. Palladium nanotubes excel in high sensitivity, low detection limit, and fast response times in hydrogen sensing compared to sputtered Pd thin film on glass. The response time ranges from a few seconds to tens of seconds depending on the concentration of hydrogen. The hydrogen sensing behavior can be understood with the Langmuir adsorption isotherm theory at very low hydrogen concentration. The high sensitivity and fast response time in the nanotube imbedded samples imply that the nanostructures create not only larger surface areas but also many more favorable sites for hydrogen adsorption to occur. These new nanostructured sensing elements are superior to the conventional thin film sensors especially in the low hydrogen concentration region.
Gold nanotube membranes are ideal model systems for exploring how pore size affects the rate and selectivity of protein transport in synthetic membranes. This is because these membranes have cylindrical, monodisperse pores (the nanotubes) with diameters that can be varied at will from tens of nanometers down to less than 1 nm. We report here on the effects of nanotube inside diameter, solution pH, and applied transmembrane potential on the rate and selectivity of protein transport in PEG-thiol-treated gold nanotube membranes. The transport properties of four proteins of differing sizes and pI values--lysozyme, bovine serum albumin, carbonic anhydrase, and bovine hemoglobulin--were investigated. In general, membranes containing larger diameter nanotubes showed higher fluxes and lower selectivities than membranes with smaller diameter nanotubes. Transmembrane electrophoresis can be used to augment the diffusive transport selectivity. For example, for proteins that are oppositely charged, a combination of a large transmembrane potential and a large nanotube diameter can be used to optimize both selectivity and flux. In addition to transmembrane potential and nanotube diameter, solution pH value plays an important role in determining the transport selectivity. This is because pH determines the net charge on the protein molecule and this, in turn, determines the importance of the electrophoretic transport term.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.