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Investigating molecular size variations in thin film chemical vapor sensors

Citation

Folinsky, Anna Barr (2010) Investigating molecular size variations in thin film chemical vapor sensors. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:05252010-102954788

Abstract

Vapor sensing arrays composed of broadly responsive, chemically sensitive detectors have been explored for many years. They have been used in fields ranging from good quality control, to environmental monitoring and explosives detection, to disease diagnostics. All of these tasks require high sensitivity and fine discrimination ability. As new challenges arise, the ability to understand the performance and improve the availability of array components becomes paramount. This work details progress in gaining greater understanding of certain chemical substrates used in sensor arrays. Specifically, arrays using insulator/carbon black composite sensors have been prepared using either polymer or non-volatile small organic molecules as the insulating, chemically sensitive component. The crystallinity of the small molecules as compared to the polymers was determined to cause the differing formulation requirements between the polymers and the small molecules. Additionally, arrays of sensors composed of varying molecular weights of a given polymer were examined. Very low molecular weights of polystyrene, a high glass transition temperature polymer, exhibited improved behavior and response times compared to higher molecular weights. Finally, arrays composed of varied length carboxylic and dicarboxylic acids were studied. Of these two homologous series, the arrays composed of carboxylic acids provided better discrimination than did those composed of dicarboxylic acids, suggesting the utility of sensor materials containing multiple accessible functional groups. These studies, taken together, suggest several new ways to increase the number of compounds and chemical functionalities available to use in chemical vapor sensors. Increased sensor choice allows construction of more broadly responsive and finely discriminating sensor arrays, thereby increasing the general utility of composite vapor sensor arrays.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:electronic nose; vapor sensors; sensor array; chemical sensing
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Mixed availability, specified at file level
Research Advisor(s):
  • Lewis, Nathan Saul
Thesis Committee:
  • Gray, Harry B. (chair)
  • Stoltz, Brian M.
  • Davis, Mark E.
Defense Date:12 May 2010
Record Number:CaltechTHESIS:05252010-102954788
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:05252010-102954788
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5834
Collection:CaltechTHESIS
Deposited By: Anna Folinsky
Deposited On:03 Jun 2010 17:17
Last Modified:26 Dec 2012 03:26

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PDF (Double sided, color, final thesis version) - Final Version
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PDF (Single sided, color, final thesis version) - Final Version
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PDF (Header pages and Introduction) - Final Version
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PDF (Chapter 2 - Polymers v. Small Molecules) - Final Version
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PDF (Chapter 3 - Polymer Weight Variations) - Final Version
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PDF (Chapter 4 - Small Molecule Weight Variations) - Final Version
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PDF (Appendix - Principal Components Analysis) - Final Version
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