Electrochemical detection of trace insulin at carbon-nanotube-modified electrodes

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This digital document is a journal article from Analytica Chimica Acta, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Carbon-nanotube (CNT)-modified glassy-carbon electrodes dramatically accelerate the electrooxidation of insulin to offer an attractive amperometric detection of this important hormone. Hydrodynamic voltammograms indicate a substantial lowering of the detection potential, with oxidation starting above +0.5V (versus Ag/AgCl) and leveling off of the response above +0.7V. The flow-injection amperometric response (at pH 7.4) is highly linear (to at least 1000nM), reproducible (RSD=4.8%;n=30), and fast (peak width of 45s). The high sensitivity (48nA/@mM) and moderate detection potential (+0.8V) lead to a low detection limit of 14nM. Such performance characteristics compare favorably with those of previously reported metal-oxide-modified electrodes for insulin, and indicate great promise for in vivo measurements of insulin release and for monitoring this hormone in chromatographic effluents.

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Nanocomposite Said To Boost Lithium Batteries By 5X

Nanocomposites aim to boost the capacity of lithium ion batteries by five-times by hanging nanometer-sized silicon particles on trees of carbon black that self-assemble into porous micron-sized spheres, which increase an electrode’s surface area with interconnected internal channels.

High-performance lithium ion batteries today use anodes made from carbon (graphite). Silicon has been proposed as a substitute for graphite since it offers a theoretical improvement of 10-times in capacity over graphite, but so far prototypes have proven too unstable for creating lithium batteries with a long lifetime, according to professor Gleb Yushin at the Georgia Institute of Technology.

The problem, according to Yushin, is that silicon particles crack when they are formed at the same granularity of graphite particles—about 15 to 20 microns. The new nanocomposite material solves that problem by hanging 30 nanometer sized silicon particles on trees of carbon black which then self-assemble into porous spheres about 10-to-30 microns in diameter. The resulting electrode remains stable due to the durable carbon-superstructure that prevents cracking, but benefits from the increased surface area afforded by the smaller silicon nanoparticles.

Common chemical vapor deposition processes allow the new hybrid silicon-carbon electrodes to be mass produced economically, according to Yushin. He also claimes that because the tiny silicon nanoparticles are permanently attached to the micron-sized carbon black trees, they avoid the health hazards of processes that require handling of nanoscale particles.

So far Georgia Tech has fabricated experimental anode electrodes, which it is testing for use in standard manufacturing processes for lithium batteries. Their prototype has survived over one hundred recharge cycles without any degradation, leading the researchers to predict they will last for thousands of recharges.

Besides Yushin, other Georgia Tech researchers involved in the project include Alexandre Magasinki, Patrick Dixon, Benjamin Hertzberg and Alexander Alexeev, along with Alexander Kvit from the University of Wisconsin-Madison, Igor Luzinov from Clemson University, and Jorge Ayala from Superior Graphite (Chicago).

Funding was provided by a Small Business Innovation Research (SBIR) grant from the National Aeronautics and Space Administration (NASA) to Superior Graphite and Streamline Nanotechnologies, Inc.

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Electrochemical determination of hydrogen sulfide at carbon nanotube modified electrodes

Product Description
This digital document is a journal article from Analytica Chimica Acta, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Carbon nanotube (CNT) modified glassy carbon electrodes exhibiting a strong and stable electrocatalytic response towards sulfide are described. A substantial (400mV) decrease in the overvoltage of the sulfide oxidation reaction (compared to ordinary carbon electrodes) is observed using the CNT-modified electrode, with oxidation starting at ca. -0.3V (versus Ag/AgCl; pH 7.4). The CNT-coated electrodes thus allow highly sensitive, low potential (+0.1V), stable amperometric sensing. A wide linear dynamic range (1.25-112.5@mM) was achieved with a detection limit of 0.3@mM (9ppb). The enhance sensitivity is coupled to an improved stability. Such ability of carbon nanotubes to promote the sulfide electron-transfer reaction suggests great promise for miniaturized sensors for hydrogen sulfide.

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Electrical detection of deoxyribonucleic acid hybridization based on carbon-nanotubes/nano zirconium dioxide/chitosan-modified electrodes

Product Description
This digital document is a journal article from Analytica Chimica Acta, published by Elsevier in 2007. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
A novel and sensitive electrochemical DNA biosensor based on nanoparticles ZrO”2 and multi-walled carbon nanotubes (MWNTs) for DNA immobilization and enhanced hybridization detection is described. The MWNTs/nano ZrO”2/chitosan-modified glassy carbon electrode (GCE) was fabricated and oligonucleotides were immobilized to the GCE. The hybridization reaction on the electrode was monitored by differential pulse voltammetry (DPV) analysis using electroactive daunomycin as an indicator. Compared with previous DNA sensors with oligonucleotides directly incorporated on carbon electrodes, this carbon nanotube-based assay with its large surface area and good charge-transport characteristics increased DNA attachment quantity and complementary DNA detection sensitivity. The response signal increases linearly with the increase of the logarithm of the target DNA concentration in the range of 1.49×10^-^1^0 to 9.32×10^-^8molL^-^1 with the detection limit of 7.5×10^-^1^1molL^-^1 (S/N=3). The linear regression equation is I=32.62+3.037logC”D”N”A (molL^-^1) with a correlation coefficient value of 0.9842. This is the first application of carbon nanotubes combined with nano ZrO”2 to the fabrication of an electrochemical DNA biosensor with a favorable performance for the rapid detection of specific hybridization.

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Electrocatalytic detection of insulin at RuOx/carbon nanotube-modified carbon electrodes

Product Description
This digital document is a journal article from Analytica Chimica Acta, published by Elsevier in 2007. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
A bilayer surface coating, prepared by electrodepositing ruthenium oxide (RuOx) onto a carbon nanotube (CNT) layer, offers dramatic improvements in the stability and sensitivity of voltammetric and amperometric measurements of insulin compared to the individual (CNT or RuOx) coated electrodes. The enhanced electrocatalytic activity towards insulin is indicated from lowering the potential of the oxidation process (starting around 0.35 versus Ag/AgCl) and the substantially higher sensitivity over the entire potential range. A wide linear dynamic range (10-800nM) was achieved with a detection limit of 1nM. The marked electrocatalytic activity of the RuOx/CNT coating towards insulin is coupled with a greatly enhanced stability. For example, the insulin amperometric response of the RuOx/CNT-coated electrodes is highly stable, with 97% of the initial activity remaining after 60min stirring of 2×10^-^6M solution (compared to significantly faster current diminutions at the RuOx- or CNT-coated surfaces). The results suggest great promise for miniaturized sensors and detectors for monitoring insulin.

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