Single-walled Carbon Nanotube Membranes Research Articles

Facile Synthesis of Platinum Nanoflower Monolayer on Single-Walled Carbon Nanotube Membrane

not Available.

Covalent Binding of Single-Walled Carbon Nanotubes to Polyamide Membranes for Antimicrobial Surface Properties

We propose an innovative approach to impart nanomaterial-specific properties to the surface of thin-film composite membranes. Specifically, biocidal properties were obtained by covalently binding single-walled carbon nanotubes (SWNTs) to the membrane surface. The SWNTs were first modified by purification and ozonolysis to increase their sidewall functionalities, maximize cytotoxic properties, and achieve dispersion in aqueous solution. A tailored reaction protocol was developed to exploit the inherent moieties of hand-cast polyamide membrane surfaces and create covalent amide bonds with the functionalized SWNTs. The reaction is entirely aqueous-based and entails activation of the carboxylate groups of both the membrane and the nanomaterials to maximize reaction with ethylenediamine. The presence of SWNTs was verified after sonication of the membranes, confirming the strength of the bond between the SWNTs and the membrane surface. Characterization of the SWNT-functionalized surfaces demonstrated the attainment of membranes with novel properties that continued to exhibit high performance in water separation processes. The presence of surface-bound antimicrobial SWNTs was confirmed by experiments using E. coli cells that demonstrated an enhanced bacterial cytotoxicity for the SWNT-coated membranes. The SWNT membranes were observed to achieve up to 60% inactivation of bacteria attached to the membrane within 1 h of contact time. Our results suggest the potential of covalently bonded SWNTs to delay the onset of membrane biofouling during operation.

Fabrication and gas transport properties of SWNT/polyacrylic nanocomposite membranes

We demonstrate a comprehensive method for the fabrication and characterization of nanocomposite membranes containing vertically aligned single-walled carbon nanotubes. Preparation involves hydrodynamic self-assembly of carbon nanotubes, followed by encapsulation of the oriented CNTs in an in situ polymerized polyacrylic matrix. The top surface of the polymer film is removed by plasma etching to expose the carbon nanotube tips, leading to fast gas transport rates. Because the preparation method is potentially scalable to industrial-size membranes, it offers an attractive approach in the fabrication of single walled carbon nanotube membrane platforms.

Facile Synthesis of a Platinum Nanoflower Monolayer on a Single-Walled Carbon Nanotube Membrane and Its Application in Glucose Detection

Platinum nanomaterials have shown to be highly attractive due to their superior catalytic ability with high utilization efficiency. Electrodeposition is a flexible technique to produce nanostructures with controllable morphology and high purity. In this study, platinum nanoparticles with tunable structure were synthesized on a single-walled carbon nanotube membrane via cyclic voltammetry. Specifically, a Pt nanoflower monolayer consisting of numerous petal-like nanosheets with a high specific surface area was obtained under the optimized condition. The Pt nanosheet grew anisotropically along the ⟨111⟩ direction and showed a typical face-centered cubic crystal structure. Moreover, the as-prepared free-standing Pt nanoflower membrane exhibited excellent catalytic ability toward amperometric detection of glucose at neutral pH with a low detection limit and a wide linear range.

Aligned dense single-walled carbon nanotube beams and cantilevers for nanoelectromechanical systems applications

A processable approach to fabricate suspended and aligned single-walled carbon nanotube (SWNT) beams and cantilevers is presented in this article. Suspended dense SWNT membranes were aligned and deposited by a controlled dielectrophoresis process. A gallium focused ion beam at 30 keV and 50 pA with an optimized dose bombarded the SWNT membranes to prepare them for suspended nanoscale beams and cantilevers. To demonstrate the application of this process to nanoelectromechanical systems (NEMS), an SWNT switch was realized with a pull-in voltage of ∼7.8 V. Accordingly, the fabrication process of SWNT beams and cantilevers is believed to be very promising for prototyping of many NEMS devices such as switches, resonators, and biosensors.

Intrinsic Ion Selectivity of Narrow Hydrophobic Pores

We show that narrow hydrophobic pores have an intrinsic ion selectivity by using single-walled carbon nanotube membranes as a model. We examined pores of radius 3.4-6.1 A, and conducted molecular dynamics simulations to show that Na+, K+, and Cl- face different free energy barriers when entering hydrophobic pores. Most of the differences result from the different dehydration energies of the ions; however, changes in the solvation shell structure in the confined nanotube interior and van der Waals interactions in the small tubes can both play a role. Molecular dynamics simulations conducted under hydrostatic pressure show that carbon nanotube membranes can act as ion sieves, with the pore radius and pressure determining which ions will permeate through the membrane. This work suggests that the intrinsic ion selectivity of biological pores of differing radii might also play a role in determining their selectivity, in addition to the more common explanations based on electrostatic effects. In addition, "hydrophobic gating" can arise in continuous water-filled pores.

Precise cutting of single-walled carbon nanotubes

We precisely cut single-walled carbon nanotubes (SWNTs) to create short nanotubes with controlledlength and open ends using an ultra-microtome and magnetically aligned SWNT membranes. At−60 °C, multiple layers of SWNT membranes were stacked and frozen together, and then cut atlengths of 50 and 200 nm, respectively. Transmission electron microscopy (TEM) andRaman characterizations clearly indicated that nanotubes were mechanically chopped tocreate open ends without notable sidewall damage. Atomic force microscopy (AFM)characterization and statistical analysis showed that the length distributions of the cutSWNTs can be controlled. Short SWNTs are very promising for applications inbiomolecular transportation, field emission, field effect transistor and nanocomposites.

Adsorption and diffusion of carbon dioxide and nitrogen through single-walled carbon nanotube membranes

We have used atomically detailed simulations to examine the adsorption and transport diffusion of CO2 and N2 in single-walled carbon nanotubes at room temperature as a function of nanotube diameter. Linear and spherical models for CO2 are compared, showing that representing this species as spherical has only a slight impact in the computed diffusion coefficients. Our results support previous predictions that transport diffusivities of molecules inside carbon nanotubes are extremely rapid when compared with other porous materials. By examining carbon nanotubes as large as the (40,40) nanotube, we are able to compare the transport rates predicted by our calculations with recent experimental measurements. The predicted transport rates are in reasonable agreement with experimental observations.

Evaluation of the gauge factor for membranes assembled by single-walled carbon nanotubes

Samples of single-walled carbon nanotubes (SWCNTs) organized in the form of thin membranes have been investigated in order to correlate the mechanical deformation and conductivity behavior of such nanosized material. The nanotubes gauge factor of piezoresistivity has been evaluated by comparing the electrical responses induced by the deformation in SWCNT membranes and in Si substrates with the same electrical characteristics. The gauge factor of the SWCNT–Si systems was found to be a factor 2.3–2.5 larger than that of the Si substrates. We have also observed that temperature slightly enhances the piezoresistive response of the SWCNT.