Friday, April 25, 2008
Amperometric glucose biosensor based on boron-doped CNTs modified electrode
Glassy carbon (GC) electrode modified with B-doped carbon nanotubes (BCNTs) shows high electrocatalytic activity for the oxidation of H2O2 due to the large amount of edge sites and oxygen-rich groups located at the defective sites induced by boron doping.
A glucose biosensor based on the GC/BCNTs/Poly(o-aminophenol)-Glucose oxidase electrode exhibits the good characteristics for the glucose determination: such as high sensitivity (171.2 nA mM-1), low detection limit (3.6 microM), wide linear range (up to 8 mM), short response time (within 6 s), satisfactory anti-interference ability and good stability. The apparent Michaelis-Menten constant of the immobilized glucose oxidase is 15.19 mM. These imply that the BCNTs have potential application in constructing enzyme based amperometric biosensors.
Source: Talanta (2008), article in press
A glucose biosensor based on the GC/BCNTs/Poly(o-aminophenol)-Glucose oxidase electrode exhibits the good characteristics for the glucose determination: such as high sensitivity (171.2 nA mM-1), low detection limit (3.6 microM), wide linear range (up to 8 mM), short response time (within 6 s), satisfactory anti-interference ability and good stability. The apparent Michaelis-Menten constant of the immobilized glucose oxidase is 15.19 mM. These imply that the BCNTs have potential application in constructing enzyme based amperometric biosensors.
Source: Talanta (2008), article in press
SWCNTs induce indirect cytotoxicity by medium depletion in A549 lung cells
The ability of two types of single walled carbon nanotubes, namely Arc Discharge (AD) and HiPco® single walled carbon nanotubes, to induce an indirect cytotoxicity in A549 lung cells by means of medium depletion was investigated. The nanotubes were dispersed in a commercial cell culture medium and subsequently removed by centrifugation and filtration. Spectroscopic analysis confirmed the removal of the nanotubes and showed differing degrees of alteration of the composition of the medium upon the removal of the nanotubes. The ability to induce an indirect cytotoxic effect by altering the medium was evaluated using two endpoints, namely the Alamar Blue (AB) and the Clonogenic assay.
Exposure of the A549 cells to the depleted medium which had previously contained carbonaceous nanoparticles, revealed significant cytotoxicity for both endpoints employed. The results presented demonstrate that single walled carbon nanotubes can induce an indirect cytotoxicity by alteration of cell culture medium (in which they have previously been dispersed) which potentially results in a false positive toxic effect being observed in cytotoxicity studies.
Source: Toxicology Letters (2008), accepted manuscript
Exposure of the A549 cells to the depleted medium which had previously contained carbonaceous nanoparticles, revealed significant cytotoxicity for both endpoints employed. The results presented demonstrate that single walled carbon nanotubes can induce an indirect cytotoxicity by alteration of cell culture medium (in which they have previously been dispersed) which potentially results in a false positive toxic effect being observed in cytotoxicity studies.
Source: Toxicology Letters (2008), accepted manuscript
New carbon nanotube composite discovered at Fujitsu Laboratories
Researchers observed that graphene layers grew on the top of vertically aligned carbon nanotubes produced by CVD method. As a result, the high electric conductivity of carbon nanotubes could function well with the two-dimensional conductivity of graphene layers. Fujitsu aims to use the new structure in transistors.
Potential application of carbon nanotubes in biosensing devices
A promising method for assembling carbon nanotubes (CNTs) and poly(diallyldimethylammonium chloride) protected Prussian blue nanoparticles (P-PB) to form three-dimensional (3D) nanostructured films is proposed. The electrostatic interaction, combined with layer-by-layer self-assembly (LBL), between negatively charged CNTs and positively charged P-PB is strong enough to drive the formation of the 3D nanostructured films. Thus, prepared multilayer films were characterized by ultraviolet–visible–near-infrared spectroscopy (UV–vis–NIR), scanning electron microscopy (SEM) and cyclic voltammetry (CV). Regular growth of the mutilayer films is monitored by UV–vis–NIR and CV. SEM provides the morphology of the multilayer films. The 3D multilayer films exhibit good electrocatalytic activity for the reduction of H2O2. This is a very general and powerful technique for the assembling 3D nanostructured films containing carbon nanotubes and nanoparticles. This assembling method introduces opportunities for the incorporation of various functionalities into nanotube devices, which, in turn, opens up the possibility of building more complex multicomponent nanostructures with potential application, such as biosensing devices.
Source: Colloids and Surfaces A: Physicochem. Eng. Aspects 317 (2008) 394–399
Source: Colloids and Surfaces A: Physicochem. Eng. Aspects 317 (2008) 394–399
SWCNT mats and their performance as electromechanical actuators
Carbon nanotube mats (buckypapers) were prepared from three commercial grades of single-walled carbon nanotubes (SWCNTs) and by two processing variants (i.e. filtration of centrifuged and uncentrifuged dispersions). Material properties such as Young's modulus, tensile strength, electrical conductivity, electrical capacitance, specific surface area and morphology were investigated and put in relation to the in-plane actuation performance in an aqueous electrolyte (1M NaCl). A dynamic mechanical analyzer was adapted for actuation strain measurements on the samples under various tensile prestress levels.
The researchers showed that the critical issues affecting the performance of buckypaper actuators are the purity, the dispersibility and the morphology of the underlying SWCNT material. The best overall performance was obtained for mats manufactured from well-dispersed, high-purity material, where centrifugation was used to eliminate nanotube agglomerates, yielding an entangled fibrous structure. Thus, dense buckypapers with bulk Young's moduli of up to 2.5 GPa and specific electrical capacitances of up to 35 F/g could be produced and actuated under an effective prestress level of up to 5 MPa with a reversible actuation strain between 0.040 (free-strain) and 0.018% (5 MPa tensile prestress).Source: Carbon (2008), article in press.
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