Carbon fiber sensors

Fig. S Scanning electron micrograph of a thin film of polymeric (TMHPP)Ni (a) and the tip of a thermally pointed carbon fiber sensor covered with polymeric (TMHPP)Ni and Nafion...

The detection limit of this sensor is similar to that obtained from the carbon fiber sensor. This sensor provides a convenient way to measure NO release in cell cultures under various conditions. 

Mounier, A. L., Binetruy, C. and Krawczak, R, Multipurpose carbon fiber sensor design for analysis and monitoring of the resin transfer molding of polymer composites , Polymer Composites, 26(5), 717-730, 2005. 

Segawa H., Ohnishi E., Arai Y., Yoshida K., Sensitivity of fiber-optic carbon dioxide sensors utilizing indicator dye, Sens. ActuatB 2003 94 276-281. 

Surface modified NO sensors incorporate an electrode surface that has been modified or treated in some way so as to increase the selectivity of the sensor for NO and promote catalytic oxidation of NO. An early example of such a sensor was presented by Malinski and Taha in 1992 [27], In this publication an —500nm diameter carbon fiber electrode was coated with tetrakis(3-methoxy-4-hydroxyphenyl)porphyrin, via oxidative polymerization, and Nation. This electrode was shown to have a detection limit of — lOnM for NO and great selectivity against common interferences. However, recently it has been shown that this electrode suffers severe interference from H202 [28],... 

X.J. Zhang, L. Cardosa, M. Broderick, H. Fein, and J. Lin, An integrated nitric oxide sensor based on carbon fiber coated with selective membranes. Electroanalysis 12, 1113-1117 (2001). 

J.K. Park, P.H. Tran, J.K.T. Chao, R. Ghodadra, R. Rangarajan, and N.V. Thakor, In vivo nitric oxide sensor using non-conducting polymer-modified carbon fiber. Biosens. Bioelectron. 13, 1187—1195 (1998). 

The major potential application of active carbon fibers is as an adsorbent in environmental control, as outlined in the previous section. However, there is a number of smaller scale, niche applications that seem to be particularly suited to ACF. These emerging applications include the use of ACF in medicine [111 (see also 59,60),112], as capacitors [113-119] and vapor sensors [120], and in refrigeration [121]. The first two of these applications are summarized below. However, there are not many detailed, publicly-available sources describing any of these applications, partly for commercial reasons and partly because the technology is emerging, so any summary is necessarily limited in scope. 

The acid-base properties of polyaniline can be utilized to produce solid-state pH sensors where polyaniline works both as the pH-sensitive material and as the ion-to-electron transducer. An excellent example is the electrodeposition of polyaniline on an ion-beam etched carbon fiber with a tip diameter of ca. 100-500 nm resulting in a solid-state pH nanoelectrode with a linear response (slope ca. — 60mV/pH unit) in the pH range of 2.0-12.5 and a working lifetime of 3 weeks [104]. The response time vary from ca. 10 s (around pH 7) to ca. 2 min (at pH 12.5). 

Some researchers see a bright future for dendrimers in many different industrial, medical, research, and consumer applications. One company that produces dendrimers lists applications in drug delivery systems, gene transfection, biotechnology, sensors for diagnostics and detection systems, carbon fiber coatings, microcontact printing, adhesion, molecular batteries, catalysis, separation systems, lasers, composites, and ultrathin films used in optics. 

Biosensors based on carbon fiber ultramicroelectrodes have been used to determine pyruvate (2) and glucose (3). Glucose sensors using platinum ultramicroelectrodes have also been reported (4), including the entrapment of glucose oxidase in an electropolymerized film of polyaniline (5,6). Ikariyama and co-workers have used platinum ultramicroelectrodes modified with platinum black to construct very sensitive glucose sensors (7-13). 

A self-contained system, which integrated the remote carbon-fiber electrochemical sensor with a voltammetric analyzer and a wireless communication system, was described by Fu et al. [21]. The mobile remote underwater systems were applied for field measurements of explosive residues in marine environments. 

Acetylcholineesterase and choline oxidase Co-immobilized enzyme (AChE and ChO) on 7 pm diameter carbon-fiber electrode entrapped with polyvinyl alcohol quaternized stil-bazole. Sensor was used as an amperometric detector for ACh. Linear response in the range 0.1-1 mM of ACh. Response time was 5 s. [83]... 

Acetylcholineesterase and choline oxidase Enzyme immobilized over tetra-thiafulvalene tetracyanoquinodi-methane crystals packed into a cavity at the tip of a carbon-fiber electrode. The immobilization matrix consisted of dialdehyde starch/glutaraldehyde, and the sensor was covered with an outer Nafion membrane. The ampero-metric performance of the sensor was studied with the use of FIA system. An applied potential of +100 mV versus SCE (Pt-wire auxiliary electrode) and a carrier flow rate of 1 mL/min. The Ch and ACh biosensors exhibited linear response upto 100 pM and 50 pM, respectively. Response times were 8.2 s. [97]... 

In this paper we consider SHP as a combination of a loop heat pipe (LHP) and ammonia/ (active carbon fiber -I- chemicals) solid sorption cooler. Such system extends the limits of two-phase thermal control and ensures successful mode of electronic components cooling even in very harsh environmental conditions (ambient temperature 40 °C, or more) and ensures a deep cooling of space sensors down to the triple point of the hydrogen. 

In an attempt to improve the selectivity of local dopamine measurements in the complex extracellular matrix of brain fluid, an implantable enzyme-based dopamine microbiosensor has been constructed based on the immobilization of tyrosinase in a thin-film chitosan coating of carbon-fiber disc microelectrodes [357]. o-Dopaquinone, which is the product of the tyrosinase reaction with dopamine, was monitored via its reduction at the modified microelectrode surface. The application of these cathodic tyrosinase dopamine microbiosensors was reported for the continuous real-time in vivo visualization of electrically stimulated dopamine release in the brain of anesthetized laboratory rats. Remarkably, due to the cathodic potential the sensor response was not significantly disturbed by the presence of typical interferences such as ascorbic and uric acid, serotonin, norepinephrine, and epinephrine. 

Suaud-Chagny and Goup (1986) immobilized LDH on a pyrolytic carbon fiber microelectrode by impregnation in an inert protein sheath that was first electrochemically deposited around the active tip of the electrode. The NADH detection was improved by electrochemical treatment of the electrode. The detection limit for pyruvate was lower than 1 pmolA. The sensor was used to estimate pyruvate concentration in rat cerebrospinal fluid. 

Polymers formed from the ROP of [l]ferrocenophanes have been investigated for a variety of uses. Vancso et al. has tested them for nanolithographic and plasma etch-resistant materials.165,166 Pannel and co-workers have reported ferrocenylsilylene polymers for use as tapered optical-fiber sensors in the detection of ammonia and carbon dioxide.167... 

The use of a graphite electrode, particularly glassy carbon, is also relatively limited in microfabricated electrochemical sensors. However, thick-film silk-screened graphite electrodes have been used in chemical sensor development, and the use of carbon fiber in microsensor applications has been reported. The purity of the graphite ink for thick-film silk screening is very critical to the performance of the sensor. 

A more defective form of sp carbon fibers, carbon nanotubules (CNTbs), grown by pyrolytic deposition of carbon into anodized aluminum oxide (AAO) nanochannels, are also used as nanoelectrode arrays for electrochemical sensors. Small graphitic crystallites are deposited on the inner surface of the nanochannels. Since the crystallites do not extend very long (less than micrometers) and are structurally discontinued, the resistance is orders of magnitude higher than CNFs... 

The most recent developments are based on the simultaneous excitation of two fluorescent indicators [52]. This may make possible the realization of a triple one-fiber sensor for oxygen, carbon dioxide and pH (see Section 18.2). 

Although it is generally agreed that fiber sensors will greatly extent the range of instrumentation useful for air pollution studies, there is a certain lack of methods that work with real samples. Most papers describe principles rather than applications. Thus, the sensors developed for sulfur dioxide, hydrogen sulHde, carbon monoxide, and other species (as described in Section 17-2) await their application to practical environmental studies. 

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