Transistor polypyrrole

Polypyrrole field effect transistors have been produced by an electrochemical method in which conducting polymer nanostructures are directly grown between metal electrodes with the geometry controlled by hydrophilic/hydropho-... 

Henry S. White, Gregg P. Kittlesen, and Mark S. Wrighton. Chemical deriva-tization of an array of three gold microelectrodes with polypyrrole fabrication of a molecule-based transistor. Journal of the American Chemical Society, 106(18) 5375-5377, 1984. 

Fig. 8.2. Plots of the drain current, /drain as a function of the drain voltage, / llrain, for a polypyrrole-based micro-eletrochemical transistor operated in MeCN containing 0.1 mol dm 3 B114NCIO4. Each curve corresponds to a different value of the gate voltage, /Jgate. As the gate voltage increases from —0.1 V vs. SCE to 0.6 V the resistance of the polypyrrole film decreases. The inset shows the arrangement used to make the measurement. Reproduced with permission from [1]. Copyright 1984 American Chemical Society...

Polypyrrole Apolymer of pyrrole, afive-membered heterocyclic substance with one nitrogen and four carbon atoms and with two double bonds. The polymer can be prepared via electrochemical polymerization. Polymers thus prepared are doped by electrolyte anion and are electrically conductive. Polypyrrole is used in lightweight secondary batteries, as electromagnetic interference shielding, anodic coatings, photoconductors, solar cells, and transistors. 

Kou, C.T., and T.R. Lion. 1996. Characterization of metal-oxide-semiconductor field-effect transistor (MOSFET) for polypyrrole and poly(N-alkylpyrrole)s prepared by electrochemical synthesis. Synth Met 82 167. 

Josowicz, M., and J. Janata. 1986. Suspended gate field effect transistors modified with polypyrrole as alcohol sensor. Anal Chem 58 514. 

Electronic noses The so-called electronic noses consist of chemical gas sensors that are able to monitor changes in the offgas composition of fermentation processes. The different sensors of electronic noses are based on conductive polymers (CP), metal oxide semiconductors (MOS), metal oxide semiconductor field effect transistors (MOSFET), or quartz crystal microbalance (QCM). CP-based sensors use the electrochemical properties of polymers like polypyrrole or polyindole. The absorbance of selected molecules of the off-gas into the polymer film causes changes in the sensors conductivity. MOS sensors possess an electrochemically active surface of metal oxides like tin oxide or copper oxide. The sensitivity... 

Conjugated polymers have been the subject of great interest, both theoretically and experimentally, since the discovery of conductivity in doped polyacetylene in the seventies [1]. Many works have been devoted to their synthesis, characterizations and properties [2]. They have found many apphcations, particularly in the field of optoelectronics, as light-emitting diodes (LEDs), field-effect transistors (FETs), solar cells, etc., due to the semi-conducting behavior of the conjugated backbone [3]. Among them, polythiophenes (PTh) and polypyrroles (PPy) have been extensively studied because of their synthesis versatility and environmental stability [4-6]. Their functionalization permits the combination of their... 

The chemically selective layer can also be deposited inside a narrow gap formed in the gate structure. Thus, the so-called suspended-gate-field-effect transistor (SGFET) can be produced. Besides Pd [111], layers based on polypyrrole, sensitive to hydrogen-bonding gases [112], can be used, in the same way as polypyrrole-nitrotoluene copolymer, selective to aromatic hydrocarbons [113] and Pb phtalocyanine sensitive to NO2 [114]. Discontinuous or perforated Pd-gate FETs can be used for the determination of NH3 [115] or CO [116]. 

There is also interest in using switching films deposited on an array of microelectrodes which when mounted in an electrochemical cell functions like a transistor For this application, an eight gold microelectrode array, 3 jim wide, 140 pm long, 0.12 pm thick, and separated by 1.4 pm, was connected by a coating of electropoly-merized polypyrrole. The electrochemical characteristics of this electrode are analogous to those described with polyaniline and the reader is referred to Sect. 2.1 for details. 

Polypyrrole and polythiophene, both first described in 1963 as electrically conducting materials [la], experienced a renaissance when Diaz and Street gave new attention to the electrochemical oxidation of pyrrole [21], and Gamier to the polythiphene field transistor. Polyphenylene vinylene, polyaniline, polyphenylene sulfide, polycarbazole, polyindole, polypyrene and polyene fulvene are just a few of the large number of electrically conducting polymers with specific properties and interest [22]. 

A pH-sensitive microelectrochemical transistor [288] is based on the pH dependence of the reduction potential of a 4,4 -bipyridine-substituted polypyrrole. At a fixed gate voltage, file source-drain current is pH-dependent, as a result of the reversible protonation of the bipyridinium group. 

Electrochemical transistors have been manufactured in which the gate is constituted by a poly-methylthiophene [398] or polypyrrole [397] film deposited between the source and the drain, the drain current being driven by the electrochemically controlled conductivity of the polymer film. 

The science of chemical sensors is being studied at Manchester University for the use and application of conducting polymers [4]. Derivatives of polyaniline, polythiophene, polypyrrole and poly(phenylene vinylene) doped with various ions have been investigated as chemical sensors for biosensors, volatile organic compounds, polymer field-effect gas-sensitive transistors and optical sensors based on electrochromic properties. 

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