One-dimensional conducting polymer nanocomposites: Synthesis, properties and applications

We report the use of carbon nanotubes as a sensor for chemical nerve agents. Thin-film transistors constructed from random networks of single-walled carbon nanotubes were used to detect dimethyl methylphosphonate (DMMP), a simulant for the nerve agent sarin. These sensors are reversible and capable of detecting DMMP at sub-ppb concentration levels, and they are intrinsically selective against interferent signals from hydrocarbon vapors and humidity. We provide additional chemical specificity by the use of filters coated with chemoselective polymer films. These results indicate that the electronic detection of sub-ppb concentrations of nerve agents and potentially other chemical warfare agents is possible with simple-to-fabricate carbon nanotube devices.

Nerve agent detection using networks of single-walled carbon nanotubes

The development of a low-cost, sensitive colorimetric sensor array for the detection and identification of volatile organic compounds (VOCs) is reported. Using an array composed of chemoresponsive dyes, enormous discriminatory power is possible in a simple device that can be imaged easily with an ordinary flatbed scanner. Excellent differentiation of closely related organic compounds can be achieved, and a library of 100 VOCs is presented. The array discriminates among VOCs by probing a wide range of intermolecular interactions, including Lewis acid/base, Bronsted acid/base, metal ion coordination, hydrogen bonding, and dipolar interactions. Importantly, by proper choice of dyes and substrate, the array is essentially nonresponsive to changes in humidity.

Colorimetric sensor arrays for volatile organic compounds.

Conducting polymers (CPs) have drawn considerable attention because of their economical importance, good environmental stability and electrical conductivity as well as due to their useful mechanical, optical and electronic properties. Some of the widest applications of conducting polymers include: they are used in electrostatic materials, conducting adhesives, electromagnetic shielding against electromagnetic interference (EMI), artificial nerves, aircraft structures, diodes, and transistors. This review covers some of the potential applications of these nanofibers and nanotubes in sensors, nanodiodes, field effect transistors, field emission and electrochromic displays, super-capacitors and energy storage, actuators, drug delivery, neural interfaces, and protein purification and its future prospects.

Review on Conducting Polymers and Their Applications

We demonstrate a new, versatile class of nanoscale chemical sensors based on single-stranded DNA (ss-DNA) as the chemical recognition site and single-walled carbon nanotube field effect transistors (swCN-FETs) as the electronic read-out component. swCN-FETs with a nanoscale coating of ss-DNA respond to gas odors that do not cause a detectable conductivity change in bare devices. Responses of ss-DNA/swCN-FETs differ in sign and magnitude for different gases and can be tuned by choosing the base sequence of the ss-DNA. ss-DNA/swCN-FET sensors detect a variety of odors, with rapid response and recovery times on the scale of seconds. The sensor surface is self-regenerating: samples maintain a constant response with no need for sensor refreshing through at least 50 gas exposure cycles. This remarkable set of attributes makes sensors based on ss-DNA decorated nanotubes very promising for "electronic nose" and "electronic tongue" applications ranging from homeland security to disease diagnosis.

DNA-decorated carbon nanotubes for chemical sensing.

Arrays of conducting polymer composite vapor detectors have been evaluated for performance in the presence of the nerve agent simulants dimethylmethylphosphonate (DMMP) and diisopropylmethylphosponate (DIMP). Limits of detection for DMMP on unoptimized carbon black/organic polymer composite vapor detectors in laboratory air were estimated to be 0.047−0.24 mg m^(-3). These values are lower than the EC_50 value (where EC_50 is the airborne concentration sufficient to induce severe effects in 50% of those exposed for 30 min) for the nerve agents sarin (methylphosphonofluoridic acid, 1-methylethyl ester) and soman (methylphosphonofluoridic acid, 1,2,2-trimethylpropyl ester), which has been established as ∼0.8 mg m^(-3). Arrays of these vapor detectors were easily able to resolve signatures due to exposures to DMMP from those due to DIMP or due to a variety of other test analytes (including water, methanol, benzene, toluene, diesel fuel, lighter fluid, vinegar, and tetrahydrofuran) in a laboratory air background. In addition, DMMP at 27 mg m^(-3) could be detected and differentiated from the signatures of the other test analytes in the presence of backgrounds of potential interferences, including water, methanol, benzene, toluene, diesel fuel, lighter fluid, vinegar, and tetrahydrofuran, even when these interferents were present in much higher concentrations than that of the DMMP or DIMP being detected.

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Detection and classification characteristics of arrays of carbon black/organic polymer composite chemiresistive vapor detectors for the nerve agent simulants dimethylmethylphosphonate and diisopropylmethylphosponate.

Arrays of conducting polymer composite vapor detectors have been evaluated for performance in the presence of the nerve agent simulants dimethylmethylphosphonate (DMMP) and diisopropylmethylphosponate (DIMP). Limits of detection for DMMP on unoptimized carbon black-organic polymer composite vapor detectors in laboratory air were estimated to be 0.047-0.24 mg m-3. These values are lower than the EC50 value for the nerve agents sarin (methylphosphonofluoridic acid, (1-methylethyl) ester) and soman, which have been established as equals 0.8 mg m-3. Arrays of these vapor detectors were easily able to resolve signatures due to exposures to DMMP from those due to DIMP or due to a variety of other test analytes in a laboratory air background. In addition, DMMP at 27 mg m-3 could be detected and differentiated from the signatures of the other test analytes in the presence of backgrounds of potential interferents in the background ambient, including water, methanol, benzene, toluene, diesel fuel, lighter fluid, vinegar and tetrahydrofuran, even when these interferents were present in much higher concentrations than that of the DMMP or DIMP being detected.

Detection and classification characteristics of arrays of carbon black/organic polymer composite chemiresistive vapor detectors for the nerve agent simulants Dimethylmethylphosphonate and Diisopropy

Arrays of polymer films embedded with conductive or resistive material have attracted significant attention as “electronic noses”. Sorption of a vapor into the polymer films causes physical swelling, which leads to a change in the DC electrical resistance of the film. Like the receptors of the mammalian olfactory system, each polymer-based detector responds to more than one analyte and each analyte elicits a response from more than one detector. The DC resistance across the array of detectors is sampled versus time producing a multivariate time-series. Except when rapid response is critical, this multivariate time-series can be converted into a vector representation by focusing on the steady-state behavior and calculating the relative change in resistance in each channel relative to an initial baseline. In this paper, we provide an overview of our efforts to mine useful information from electronic nose data. Four case studies are presented: rapid detection of DNT (dinitrotoluene) vapors at very low concentrations (< 1 part-per-billion), pairwise discrimination between chemically similar analytes (e.g., H2O and D2O; heptane and hexane), prediction of human percepts of odor quality from electronic nose detector responses, and classification of vapors into the appropriate chemical family (e.g., saying methanol is an alcohol without having previously smelled methanol). keywords: electronic nose, scientific datasets, case study/application, pattern recognition, classification, statistical methods ∗1. JPL, M/S 126-347, 4800 Oak Grove Drive, Pasadena, CA 91109, burl@aig.jpl.nasa.gov †2. WUSTL, Campus Box 1134, St. Louis, MO 63130, vaid@wuchem.wustl.edu ‡3. Caltech, M/S 127-72, Pasadena, CA 91125, nslewis@its.caltech.edu 1 Copyright © by SIAM. Unauthorized reproduction of this article is prohibited burlm re 2001/2/17 page 2 ✐ ✐

http://www.siam.org/meetings/sdm01/pdf/sdm01_11.pdf

Alan R. Hopkins

Papers

Detection and classification characteristics of arrays of carbon black/organic polymer composite chemiresistive vapor detectors for the nerve agent simulants dimethylmethylphosphonate and diisopropylmethylphosponate.

Detection and classification characteristics of arrays of carbon black/organic polymer composite chemiresistive vapor detectors for the nerve agent simulants Dimethylmethylphosphonate and Diisopropy

Mining the Detector Responses of a Conducting Polymer Composite-Based Electronic Nose.