Aligned Multiwalled Carbon Nanotube Membranes

Abstract

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.

Characterization and evaluation of carbon nanotube Bucky-Paper membranes for direct contact membrane distillation

“…For Knüdsen numbers, K n > 1, the molecule -pore wall collisions dominate leading to Knüdsen type flow: For isoporous membranes with circular pores the permeance is given by [7][8][9][10][11][12][13][14][15][16][17]:…”

“…This has stimulated intense interest in CNT based membranes of various structures [8][9][10][11]. In this work we focus on CNT Bucky-Paper (BP) membranes, which is a paper-like structure of CNTs processed by vacuum filtration [12].…”

Polymeric molecular sieve membranes via in situ cross-linking of non-porous polymer membrane templates

“…Over the past decade, significant progress has been made in molecular sieving materials such as zeolites 2,3 , silica 4 , metal organic frameworks 5 and carbon-based membranes [6][7][8] . However, it is often difficult to both process these materials into membranes and functionalize the micropores, which has limited their gas-separation properties and further hindered the development of this field.…”

Carbon nanotube membranes with ultrahigh specific adsorption capacity for water desalination and purification

“…Recently, carbon nanotubes (CNTs) have emerged as promising nanomaterials in water purification and desalination devices, mainly owing to the advantageous features of fast water transport, large surface area, and ease of functionalization [11][12][13][14][15][16][17][18][19][20] . Water permeability through CNTs interiors could be at least three orders of magnitude higher than that predicted by the Hagen-Poiseuille equation 11,12,15 , thereby significantly reducing the energy consumption in water treatment.…”

“…The most intriguing way of integrating CNTs into water purification and desalination devices is to use vertically aligned CNTs with functionalized open ends that allows water to pass through but rejects salt ions [15][16][17][18][19][20] . However, complex fabrication and the difficulty in obtaining CNTs with subnanometer diameters remain challenges.…”