Electrical properties of pyrrole and its copolymers

Kanazawa, K. Keiji; Diaz, A. F.; Krounbi, M.; Street, G. B.

doi:10.1016/0379-6779(81)90027-8

Cited by 162 publications

(35 citation statements)

References 13 publications

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“…Since the electrochemical potential of PY+ /PY is more positive (EO = + 1.30 V vs. SCE) (22) The polypyrrole films produced in this work exhibited excellent electrochemical and optical properties. For example, the cyclic voltammetric behavior of a chemically polymerized polypyrrole film showed a cathodic wave at -0.40 V, which corresponded to the reduction of polypyrrole to its neutral nonconducting state, and an anodic wave at -0.20 V, which corresponded to the reoxidation of polypyrrole to its conducting state (24). The lack of additional faradaic current, which would result from the oxidation and reduction of phosphomolybdic acid in the film, suggested that the Keggin structure of phosphomolybdic acid was not present in the film (25) and implies that MoO2-, or other anions, served as the polypyrrole counterions in the polymerized films.…”

Section: Resultsmentioning

confidence: 99%

A chemically diverse conducting polymer-based "electronic nose".

Freund

Lewis

1995

Proc. Natl. Acad. Sci. U.S.A.

310

188

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We describe a method for generating a variety of chemically diverse broadly responsive low-power vapor sen-sors. The chemical polymerization of pyrrole in the presence of plasticizers has yielded conducting organic polymer films whose resistivities are sensitive to the identity and concentration of various vapors in air. An array of such sensing elements produced a chemically reversible diagnostic pattern of electrical resistance changes upon exposure to different odorants. Principal component analysis has demonstrated that such sensors can identify and quantity different airborne organic solvents and can yield information on the components of gas mixtures.There is considerable interest in developing sensors that act as analogs of the mammalian olfactory system (1, 2). This system is thought to utilize probabilistic repertoires of many different receptors to recognize a single odorant (3, 4). In such a configuration, the burden of recognition is not on highly specific receptors, as in the traditional "lock-and-key" molecular recognition approach to chemical sensing, but lies instead on the distributed pattern processing of the olfactory bulb and the brain (5, 6). We describe herein the construction and characterization of a broadly responsive vapor detection array based on conducting polymer "chemiresistor" elements. Such conducting polymer elements are simply prepared and are readily modified chemically to respond to a broad range of analytes. In addition, these sensors yield a fairly rapid lowpower dc electrical signal in response to the vapor of interest, and their signals are readily integrated with software-or hardware-based neural networks for purposes of analyte identification.Prior attempts to produce a broadly responsive sensor array have exploited heated metal oxide thin film resistors (7-9), polymer sorption layers on the surfaces of acoustic wave resonators (10, 11), arrays of electrochemical detectors (12-14), or conductive polymers (15, 16). Arrays of metal oxide thin film resistors, typically based on SnO2 films that have been coated with various catalysts, yield distinct diagnostic responses for several vapors (7-9). However, due to the lack of understanding of catalyst function, SnO2 arrays do not allow deliberate chemical control of the response of elements in the arrays nor reproducibility of response from array to array. Surface acoustic wave resonators are extremely sensitive to both mass and acoustic impedance changes of the coatings in array elements, but the signal transduction mechanism involves somewhat complicated electronics, requiring frequency measurement to 1 Hz while sustaining a 100-MHz Rayleigh wave in the crystal (10, 11). Electrically conductive organic polymer elements are well-suited for such an array, because swelling of the polymer upon exposure to an analyte will induce changes in the resistivity of the polymer film (17,18). This enables a direct low-power electrical signal readout (the film resistance) to be used as the sensing signal. Some prior work has been pe...

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Section: Resultsmentioning

confidence: 99%

A chemically diverse conducting polymer-based "electronic nose".

Freund

Lewis

1995

Proc. Natl. Acad. Sci. U.S.A.

310

188

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“…This explains the low electrical conductivity of hybrid B compared to that of pristine PPy (40-100 S/cm) grown electrochemically in acetonitrile [16]. The lowered conductivity in the substituted PPy can be due to the loss of planarity or increased chain separation [17]. The position of the substitution also plays a role.…”

Section: Discussionmentioning

confidence: 99%

Sol-Gel Synthesis And Characterization Of Molybdenum Oxide/Polypyrrole Hybrids

Dong

Dunn

1999

MRS Proc.

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching data sources, "".,""" qathering and maintaining the data needed, and completing and reviewing the collection of information. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)Bruce S. Dunn Department of Materials Science and Engineering University of California, Los Angeles Los Angeles, CA 90095 SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)Office of Naval Research 800 North Quincy Street Arlington, VA 22217 PERFORMING ORGANIZATION REPORT NUMBERTechnical Report #13 SPONSOR/MONITOR'S ACRONYM(S)11. SPONSORING/MONITORING AGENCY REPORT NUMBER DISTRIBUTION AVAILABILITY STATEMENTReproduction in whole, or in part, is permitted for any purpose of the United States Government. This document has been approved for public release and sale; its distribution is unlimited. SUPPLEMENTARY NOTES Published in: Proceedings of the MRS Symposium on Organic/Inorganic Hybrid Materials ABSTRACTMonolithic molybdenum oxide/polypyrrole hybrid aerogels and xerogels were successfully synthesized through sol-gel methods. The PPy formed appears to be ß-substituted. A 100 fold increase in electrical conductivity was observed for the hybrids (4 x 10" 3 S/cm) as compared to the pristine Mo0 3 gels (2 x 10' 5 S/cm). An initial increase in Li + intercalation capacity is also observed for the hybrid. The electrical conductivity and Li* intercalation depend greatly on the concentration of Mo-tricholoro alkoxide precursor and sol aging conditions. The hybrid aerogels have a density of 0.5 g/cc and a surface area of 120 m 2 /g. The as-formed gels are amorphous and crystallize to the orthorhombic Mo0 3 phase at 375°C. Reproduction in whole, or in part, is permitted for any purpose of the United States Government.This document has been approved for public release and sale; its distribution is unlimited. SOL-GEL SYNTHESIS AND CHARACTERIZATION OF MOLYBDENUM OXIDE/POLYPYRROLE HYBRIDSW. DONG*, B. DUNN MSE Department, University of California, Los Angeles, CA 90095, *jahn@seas.ucla.edu ABSTRACTMonolithic Mo oxide/polypyrrole hybrid aerogels and xerogels were successfully synthesized through sol-gel methods. The PPy formed appears to be ß-substituted. A 100 fold increase in electrical conductivity was observed for the hybrids (4x 10" 3 S/cm) as compared to the pristine M0O3 gels (2x 10" 5 S/cm). An initial increase in Li + intercalation capacity is also observed for the hybrid. The electrical conductivity and Li + intercalation depend greatly on the concentration of Motrichloro alkoxide precursor and sol aging conditions. The hybrid aerogels have a density of 0.5 g/cc and a surface area of 120 m 2 /g. The as-formed gels are amorphous and crystallize to the orthorhombic Mo0 3 phase at 375°C.

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“…43 The lack of additional faradaic current, which would result from the oxidation and reduction of phosphomolybdic acid in the film, suggested that the Keggin structure of phosphomolybdic acid was not present in the film anions44 and implies that MOO:-, or other anions, served as the poly(pyrro1e) counterions in the polymerized films. The optical spectra of these films were also in accord with expectations for poly(pyrrole), with the processed film displaying an absorption band at 4.0 eV.45946…”

Section: Properties Of the Poly(pyrro1e) Filmsmentioning

confidence: 99%

Array-based vapor sensing using chemically sensitive, polymer composite resistors

Lonergan

Freund

Severin

et al. 1997

1997 IEEE Aerospace Conference

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(8 18) 395-6335 ABS TRACTWe describe herein the construction of simple, low-power, broadly responsive vapor sensors. Insulating polymer-conductor composites have been shown to swell reversibly upon exposure to vapors. Thin films of polymer composites have been deposited across two metallic leads, with swelling-induced resistance changes of the films signaling the presence of vapors. To identify and classify vapors, arrays of such vapor-sensing elements have been constructed, with each element containing either carbon black or poly(pyrro1e) as the conducting phase mixed with one of several different organic polymers as the insulating phase. A convenient chemical polymerization of poly(pyrro1e) which allows a high degree of processibility is also described. The differing gas-solid partition coefficients for the various polymers of the sensor array produce a pattern of resistance changes that can be used to classify vapors and vapor mixtures. This type of sensor array has been shown to resolve common organic solvents, including molecules of different classes (such as aromatics from alcohols) as well as those within a particular class (such as benzene from toluene and methanol from ethanol). The response of an individual composite to varying concentrations of solvent is shown to be consistent with the predictions of percolation theory. Accordingly, significant increases in the signals of array elements have been observed for carbon black-polymer composites that were operated near their percolation thresholds. *Present address: Department of Chemistry, University of Oregon-Ehgene Present address: Department of Chemistry, Lehigh University, 6 East Packer Avenue, Bethlehem, PA 18015-3172 'Author to whom correspondence should be addressed. ** I . INTRODUC'TIONConventional approaches to chemical sensors have traditionally malde use of a "lock-andkey" design, wherein a specific receptor is synthesized in order to bind strongly and highly selectively to the analyte of interest. A related approach involves exploiting a general physicochemical effect selectively toward a single analyte, such as the use of the ionic effect in the construction of a pH electrode.With both of these approaches, selectivity is achieved through precise chemical design of the receptor site. Such approaches are appropriate when a specific target compound is 583 to be identified in the presence of controlled backgrounds and interferences. However, this type of approach requires the synthesis of a separate, highly selective sensor for each analyte to be detected. In addition, this type of approach is not particularly useful for analyzing, classifying, or assigning human value judgments to the composition of complex vapor mixtures such as perfumes, beers, foods, mixtures of solvents, etc.An alternative approach to chemical sensing is closer conceptually to a design widely proposed for the mammalian sense of In such an approach, the strict "lock-and-key" design criterion of traditional sensing devices is abandoned. Instead, in this alternative sensor a...

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Electrical properties of pyrrole and its copolymers

Cited by 162 publications

References 13 publications

A chemically diverse conducting polymer-based "electronic nose".

A chemically diverse conducting polymer-based "electronic nose".

Sol-Gel Synthesis And Characterization Of Molybdenum Oxide/Polypyrrole Hybrids

Array-based vapor sensing using chemically sensitive, polymer composite resistors

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