Grantee Research Project Results
Final 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 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:
The objective of this research project was to develop a new chemical sensor technology that would allow identification and quantification of volatile organic compounds (VOCs) in the environment. Special requirements were that the detector must be small, portable, inexpensive, and capable of monitoring the presence of a wide range of atmospheric contaminants.A new generation of miniature chemical sensors consisting of a transducer, such as a Surface Acoustic Wave (SAW) and Surface Plasmon Resonance (SPR) device, interfaced with an appropriate chemically sensitive coating have the potential to provide near spectroscopic capabilities in a portable instrument. Currently employed polymer deposition techniques such as air-brushing are based on the use of liquid solvents. Because of solvent residue, the resultant polymer coatings are generally of a poor quality and hardly reproducible from device to device. Coating techniques that provide a higher degree of control over the coating quality?such as self-assembly, plasma polymerization, or MAPLE?are limited to a narrow group of polymers, exhibit very slow deposition rate, and/or require additional resources such as vacuum pumps or lasers. Our work was focused on the development of a new chemical sensor based on chemically sensitive polymer coatings produced from supercritical fluid technology. Specific goals of this research included: development of a new miniature chemical sensor based on advanced polymer coatings produced from supercritical fluid technology; development of novel particulate coatings with increased sensitivity from polymers with low permeability; and improvement of the performance, quality, and reproducibility of portable sensors.
Summary/Accomplishments (Outputs/Outcomes):
Rapid Expansion of Supercritical Solutions (RESS) is shown to be a powerful and robust deposition technique for advanced chemical sensor development. RESS is a spray-on technique that eliminates the use of liquid solvents. Due to the sudden change in solubility upon supercritical fluid expansion, the polymer is completely separated from the solvent prior to surface deposition. Therefore, the films and particulate coatings produced from RESS are of the highest quality and do not contain macroscopic defects due to solvent residue. Nano-size droplets or particles can be achieved by controlling the nucleation and growth rates. One of the goals of this project was to optimize RESS conditions to meet the specialized requirements of coatings for miniature chemical sensors. A qualitative approach was developed for choosing RESS parameters to obtain polymer precipitates in the form of uniform films or small particles suitable as sensing surfaces. RESS is shown to be a robust spray-on technique capable of high deposition rates of well-adhered coatings of both films and particles. A wide variety of polymers were deposited from different supercritical fluids, and the resulting chemical sensors were characterized and exhibited a fast, sensitive, and reversible response.The most important achievement of this work is the successful application of nano-scale particulate coatings to sensor technology. It has been reported that continuous uniform bulk films are optimal for miniature SAW-based chemical sensors. Our work demonstrates the advantages of nano-scale particulate coatings. Increasing the surface-to-volume ratio improves the sensor sensitivity and response time in comparison to bulk films of the same mass loading, especially in the case of polymers with low permeability. The main reason for this is that the adsorption step of the polymer-analyte interaction is increased as the surface area is increased, and the permeation length within the coating is reduced while the volume is decreased. Therefore, the impact of the polymer permeability on the overall response is minimized. At the same time, nano-scale particulate coatings still can be considered as a continuous acoustic media. We have shown that there is no degradation in the SAW sensor performance for particle sizes compared to the distance between interdigital electrodes generating the acoustic waves.
This work demonstrates that many glassy and crystalline polymers, though not previously considered suitable as sensor coatings because of low vapor permeability but exhibiting favorable selectivity to certain analyte molecules, can be interfaced successfully with miniature sensors using supercritical fluid technology. In this work, additional processing steps such as cross-linking, polymerization, and chemical treatment also were successfully combined with the RESS deposition technique to enhance the sensitivity and chemical selectivity of the resultant coatings.
Journal Articles on this Report : 3 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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Levit N, Pestov D, Tepper G. High surface area polymer coatings for SAW-based chemical sensor applications. Sensors and Actuators B-Chemical 2002;82(2-3):241-249. |
R826648 (2001) R826648 (Final) |
not available |
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Pestov D, Levit N, Kessick R, Tepper G. Photosensitive 2,5-distyrylpyrazine particles produced from rapid expansion of supercritical solutions. Polymer 2003;44 (11):3177-3183. |
R826648 (2001) R826648 (Final) |
not available |
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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, air pollution, VOCs, portable sensor, environmental monitoring., Scientific Discipline, Air, Toxics, Environmental Chemistry, Chemistry, VOCs, Environmental Monitoring, Engineering, 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, DATECRelevant Websites:
http://www.electrochem.org/meetings/past/200/abstracts/symposia/g1/0928.pdf
Progress 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.