Grantee Research Project Results
2000 Progress Report: Development of a Miniature Detector for Accurate Identification of Toxic Environmental Contaminants (DATEC)
EPA Grant Number: R826648Title: Development of a Miniature Detector for Accurate Identification of Toxic Environmental Contaminants (DATEC)
Investigators: Tepper, Gary C.
Institution: Virginia Commonwealth University
EPA Project Officer: Aja, Hayley
Project Period: October 1, 1998 through September 30, 2001
Project Period Covered by this Report: October 1, 2000 through September 30, 2001
Project Amount: $302,268
RFA: Exploratory Research - Environmental Chemistry (1998) RFA Text | Recipients Lists
Research Category: Sustainable and Healthy Communities , Land and Waste Management , Air , Safer Chemicals
Objective:
This program is for the development of a new chemical sensor technology that will allow accurate in-situ identification and quantification of volatile organic compounds (VOCs) in the Environment. Specifically, the detector will be small, portable, inexpensive and capable of monitoring the presence of a wide range of atmospheric contaminants.Progress Summary:
We have been applying the technique known as Rapid Expansion of Supercritical Solutions (RESS) to deposit polymer coatings onto microfabricated Surface Acoustic Wave (SAW) transducers. The development and calibration of the RESS apparatus was accomplished in the first year of the project. In the current year, the focus has shifted toward coating development and characterization.
Coatings consisting of siloxane-based polymer particles have been deposited using supercritical CO2 as the RESS solvent. It was determined that the coating morphology depends primarily upon the location at which the phase boundary is crossed during the RESS expansion. For example, if the nucleation begins upstream of the nozzle, large, elongated particles are produced. However, if the nucleation begins near the exit of the nozzle, small, spherical particles are formed. Thus, it is now possible to achieve particular micro and nanometer scale coating morphologies simply by adjusting the expansion conditions.
The mechanical properties of the sensing surfaces have been significantly improved by coupling the RESS deposition process with gas phase and ultraviolet (UV) curing. Solid particles with excellent surface adhesion were developed from hydroxystearate terminated polydimethylsiloxane (PDMS) after reaction with toluene di-isocyanate (TDI). Infrared spectroscopy was used to quantify the degree of network formation. This successful combination of supercritical fluid polymer processing and network formation provides enormous flexibility for tailoring both the morphology and mechanical properties of polymer sensing surfaces. In fact it may now be possible to use a combination of RESS and photocuring to produce imprinted polymer nanoparticles for enhanced chemical selectivity and we are currently investigating this possibility.
Optical and scanning electron microscopy has been used to characterize coating morphologies as a function of RESS expansion parameters, polymer concentration and average molecular weight. The polymer network formation was monitored using infrared spectroscopy. Hydroxyl groups react with isocyanate groups from TDI to form urethane bridges between polymer macromolecules and the degree of crosslinking can be varied by controlling the reaction time.
A new dynamic sensor calibration system was designed, built and tested. The new system provides the ability to test the performance of the polymer-coated, microfabricated sensors under atmospheric conditions by independently controlling important operational parameters including vapor concentration, duty cycle and sensor temperature. The system is being used to investigate the relationship between coating properties and sensor performance. Currently, the sensors exhibits fast, sensitive and reversible response to the target vapors. Next we will characterize the sensitivity and selectivity of the sensor upon exposure to various VOCs.
We have begun the construction of a laboratory prototype unit. The prototype will consist of chemically sensitive polymer particles deposited onto a miniature surface acoustic wave (SAW) transducer and is expected to exhibit sensitive, fast and reversible response to volatile organic compounds in the atmosphere.
Future Activities:
All project tasks are proceeding on schedule. The next activities will focus primarily on establishing a relationship between specific coating properties and sensor performance parameters. This will be followed by an optimization of the sensor performance and on the development of a prototype unit.Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 24 publications | 3 publications in selected types | All 3 journal articles |
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Type | Citation | ||
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Tepper G, Levit N. Polymer deposition from supercritical solutions for sensing applications. Industrial & Engineering Chemistry Research 2000;39(12):4445-4449. |
R826648 (2000) R826648 (2001) R826648 (Final) |
not available |
Supplemental Keywords:
VOC sensor, atmospheric contaminants, environmental monitoring., Scientific Discipline, Air, Toxics, Environmental Chemistry, Chemistry, VOCs, Environmental Monitoring, Engineering, Chemistry, & Physics, thermally stable polymer film, field portable systems, surface acustic wave thermal desorption, spectroscopic studies, portable atmospheric contamination detector, air sampling, chemical composition, field monitoring, spectroscopy, chemical detection techniques, analytical chemistry, DATECProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.