An Investigation of the Concentration Dependence and Response to Analyte Mixtures of Carbon Black/Insulating Organic Polymer Composite Vapor Detectors

Abstract

The responses relative to an air background of carbon black/polymer composite vapor detectors have been determined as a function of the concentration of a homologous series of alcohols (n-CnH2n+1OH, 1 < or = n < or = 8), a homologous series of alkanes (n-CnH2n+2, 5 < or = n < or = 10 and n = 12, 14), and a set of diverse solvent vapors. In all cases, the steady-state relative differential resistance responses, delta R/Rb, of the carbon black/polymer composite vapor detectors were well-described by a linear relationship with respect to the analyte partial pressure, at least over the tested concentration range (P/P degree = 0.005-0.03, where P degree is the vapor pressure of the analyte). When two vapors in air were simultaneously presented to the detectors, the delta R/Rb response, relative to an air background, was the sum of the delta R/Rb values obtained when each analyte was exposed separately to the carbon black/polymer composite detectors under study. Similarly, when an analyte was exposed to the detectors on top of a background level of another analyte, the delta R/Rb values of the array of detectors were very close to those obtained when the test analyte was exposed to the detectors only in the presence of background air. The initial training requirements from the array response output data of such detectors are minimized because the delta R/Rb response pattern produced by the analyte of concern can be associated uniquely with that odor, under the conditions explored in this work.

Hildebrand and Hansen solubility parameters from Molecular Dynamics with applications to electronic nose polymer sensors

“…In polymer calculations, the number of monomers in each chain is usually determined such that the total volume of the four chains is at least 6000 Å. 3 Alternatively, a degree of polymerization of 30 suffices to give values comparable to experiment. In such polymer samples, the minimum number of atoms is at least 1000.…”

“…The pattern is unique and unambiguously identifies the compound. 3,23 The experimentally determined changes in relative resistivity, ⌬R/R, of seven polymer sensors upon exposure to 24 solvent vapors were correlated with the calculated Hansen solubility components. The permeability of a given odorant in a polymer is given by 24…”

“…(6) to experimental changes in resistivity 27 are shown in Figure 6 for seven electronic nose polymer sensors and 24 solvents. 3,22 Pearson's correlations between the experimentally determined change in resistivity and the Hansen solubilities are shown for polymer sensors [poly(methylmethacrylate] (PMMA), poly(4-hydroxystyrene) (P4HS), polyethyleneoxide (PEO), polyethylene (PE), poly(ethylenevinyl acetate) (PEVA), polysulfone, and caprolactone) in Table 6. The calculated Hansen solubilities for the seven polymers and 24 solvents are summarized in Table 7.…”

“…The resulting odor signature from the array of broadly crossresponsive detectors is used to classify, and in some cases quantify, the analyte of concern. Vapor detectors based on this experimental principles have been used to produce an "electronic nose" 3 by Caltech scientists. A theoretical method to model the effect of "analytes" a priori on specific polymer sensors could further aid development of these devices.…”

Exploitation of spatiotemporal information and geometric optimization of signal/noise performance using arrays of carbon black-polymer composite vapor detectors

“…We have previously reported that the steady-state DR/R b values for various carbon black-polymer composite chemiresistors are linearly dependent on analyte concentration over a range of analyte/detector combinations and analyte concentrations [31]. The noise measurements reported herein, in conjunction with the previously reported dependence of DR/ R b on the partial pressure of the analyte [30] and the analyte/ polymer sensitivity factors that can be deduced from such plots, allow estimation of the detection limits for various analyte/carbon black composite detector combinations.…”