Biomedical subjects

NS Lewis

Publications and source records attributed to NS Lewis.

3 recordsLinked to original sources

PubMed2000

Preparation and properties of vapor detector arrays formed from poly(3,4-ethylenedioxy)thiophene-poly(styrene sulfonate)/insulating polymer composites

Poly(3,4-ethylenedioxy)thiophene-poly(styrene sulfonate) (PEDOT-PSS) was used as the conductive component in a matrix of chemically different insulating polymers to form an array of vapor detectors. Such composites produced larger relative differential resistance responses when exposed to polar analytes than did the corresponding carbon black filled polymer composite detectors. However, the PEDOT-PSS composites produced smaller responses than carbon black composites when exposed to nonpolar analytes. The resolving power of a PEDOT-PSS detector array was compared to that of a carbon black composite array for a broadly construed set of organic vapors. The PEDOT-PSS array exhibited better, on average, discrimination between pairs of polar analytes and polar/nonpolar analytes than did the carbon black composite array. The carbon black composite array out-performed the PEDOT-PSS array in discriminating between nonpolar compounds. The addition of PEDOT-PSS composites to an array of carbon black composite detectors therefore can produce improved overall discrimination in a vapor sensor system when used in tasks to differentiate between of a broad set of analyte vapors.

Journal Article↗

PubMed2000

Relationships among resonant frequency changes on a coated quartz crystal microbalance, thickness changes, and resistance responses of polymer-carbon black composite chemiresistors

The relationships among frequency changes on a film-coated quartz crystal microbalance, thickness changes, and dc resistance changes have been investigated for carbon black-insulating polymer composite vapor detectors. Quartz crystal microbalance (QCM) measurements and ellipsometry measurements have been performed simultaneously on polymer films that do not contain carbon black filler to relate the QCM frequency change and the ellipsometrically determined thickness change to the analyte concentration in the vapor phase. In addition, quartz crystal microbalance measurements and dc resistance measurements on carbon black composites of these same polymers have been performed simultaneously to relate the QCM frequency change and dc electrical resistance response to the analyte concentration in the vapor phase. The data indicate that the dc resistance change is directly relatable to the thickness change of the polymers and that a variety of analytes that produce a given thickness change produce a constant resistance change for each member of the test set of polymers investigated in this work.

Journal Article↗

PubMed1996

Rate Constants for Charge Transfer Across Semiconductor-Liquid Interfaces

Interfacial charge-transfer rate constants have been measured for n-type Si electrodes in contact with a series of viologen-based redox couples in methanol through analyses of the behavior of these junctions with respect to their current density versus potential and differential capacitance versus potential properties. The data allow evaluation of the maximum rate constant (and therefore the electronic coupling) for majority carriers in the solid as well as of the dependence of the rate constant on the driving force for transfer of delocalized electrons from the n-Si semiconducting electrode into the localized molecular redox species in the solution phase. The data are in good agreement with existing models of this interfacial electron transfer process and provide insight into the fundamental kinetic events underlying the use of semiconducting photoelectrodes in applications such as solar energy conversion.

Journal Article↗