Progress 01/01/13 to 12/31/13
Outputs
Target Audience: scientist/engineer in sensor technology, environmental science, Changes/Problems: The originally proposed optical fiber chemical sensor for monitroing ammonia in air is based on fiber optic spectrometry. The interference of water vapor in air on the sensor's response is a issue. We developed an optical fiber ammonia sensor using a pH-indicating agent doped PVA coating as a transducer in previous work to eliminate water vapor interference problem. That technique works very good. However, PVA is a water soluable polymer. Such a coating could have problem when the sensor is working in a high-humidity environment. The PI developed a new sensor technology during this reporting period by using a PANi membrane coated on the end of an optical fiber as a transducer. A specially designed sensor probe provide opportunity to simultaneously monitor electrical resistance and optical absorbance spectrum of the PANi membrane, and thus provide an opportunity to simultaneously monitor both humidity and trace ammonia in air. An approach has been developed to eliminate water vapor interference on ammonia sensing using the newly developed technology. What opportunities for training and professional development has the project provided? A graduate student has an opportunity to work on this project. The graduate student has been trained to do scientific research involving sensor technologies. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
1. Developed a technology to make a polyaniline (PANi) coated optoeletrode 2. Developed a new sensing technology, which measures electrical resistance and optical absorption signal using a single optoelectrode. 3. Investigated the response of the PANi coated optoelectrode to trace ammonia and water vapor in air, and proved that the sensing technology can simultaneously monitor ammonia and water vapor in air. 4. Developed a technique to eliminate the interference of water vapor in air on fiber optoelectrical sensor for monitoring ammonia in air
Publications
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2013
Citation:
Simultaneous Monitoring of Ammonia and Moisture Using a Single Fiber Optoelectrode as a Transducer
- Type:
Conference Papers and Presentations
Status:
Awaiting Publication
Year Published:
2013
Citation:
Simultaneous monitoring of electrical resistance and optical absorbance signals of a fiber optoelectrode for multiple gas sensing
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Progress 01/01/10 to 12/31/13
Outputs
Target Audience: Scientists/enginners specialized in air quality research related to animal feeding industry. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? This project provided training opportunity for two graduate students (MS). Both successfully finished their study and thesis work. How have the results been disseminated to communities of interest? Scientific conferences and NIFA organized annual symposium. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
In the development of sensor technologies for monitoring trace gas species for air quality monitoring program one must take into consideration of potential interference from cross response to humidity, CO2 and temperature. The concentrations of water vapor, CO2 in air are thousands to millions of times higher than that of trace gases (NH3, H2S, SO2, NOx, CH4) in air. In addition, the concentrations of these species in air are continuous changing with time and location. Temperature is another fact affects the response of most sensors. The air temperature is also in continuous changing with location and time. During this project, we developed three sensor technologies for monitoring trace ammonia in real world air quality monitoring. These technologies are: 1) an optical fiber ammonia sensor having a bromocreasol purple doped sol-gel silica coating on a bent optical fiber probe as a transducer; 2) an optical fiber ammonia sensor having a dual layer (PMMA/CPR) coating on an bent optical fiber probe as a transducer; 3) an fiber opto-electrochemical ammonia sensor having an electrically conductive poly aniline coated on the end of an optical fiber as a transducer. The first two sensor technologies using sensing reagent coated bent optical fiber probes have high sensitivity, achieved detection limit of ammonia in air sample in part-per-billion level. However, it was found that moisture in air also contribute to sensing signal. The problem of moisture has been solved through carefully choosing polymers to immobilize sensing reagents (please see: Y. Huang, L. Wieck and S. Tao, Atmospheric Environment, 66, 1-7 (2013)). Therefore, we developed a sensor technology which can be used to continuously monitoring trace ammonia (in sub-ppm level) in real world air, which is the goal of this seed project. In another development, we developed a new sensor technology, which integrating optical spectroscopy and electrochemistry in one single optical probe. In this sensor technology, an electrically conductive and optically transparent polymer is coated on the end of an optical fiber. The exposure of this coated fiber to trace ammonia in an air sample caused changes of both the coated membrane’s electrical conductivity and optical absorption spectrum. The polymer coating’s electrical resistance signal also responses to moisture in air. However, the change of air moisture level does not cause significant change of the membrane’s optical property. We developed a technique to simultaneously monitor the fiber opto-electrode’s electrical resistance and optical absorption spectrum signals, and therefore, continuously monitor the concentration of trace ammonia and moisture in air sample (please see: S. Shao, Y. Huang and S. Tao, IEEE Sensors Journal, 14, 847-852 (2014)).
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Y. Huang, L. Wieck and S. Tao, "Developing and Evaluating Optical Fiber NH3 Sensors for Application in Air Quality Research/Monitoring" Atmospheric Environment, 66, 1-7 (2013).
- Type:
Journal Articles
Status:
Published
Year Published:
2011
Citation:
Y. Huang and S. Tao, "An optical fiber sensor probe using a PMMA/CPR coated bent optical fiber as a transducer for monitoring trace ammonia", Journal of Sensor Technology, 1, 29-35 (2011).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2011
Citation:
Y. Huang and S. Tao, "An Optical Fiber Sensor Probe Using a PMMA/CPR Coated Bent Optical Fiber as a Transducer for Monitoring Trace Ammonia", Abstract of 242nd Amarican Chemical Society National Meeting, Denver, CO,
September, 2011
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2011
Citation:
S. Tao, Y. Huang and L. Wieck, "Optical Fiber Ammonia Sensors for Air Quality Monitoring", Abstract of 242nd Amarican Chemical Society National Meeting, Denver, CO, September, 2011.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
S. Shao, Y. Huang and S. Tao, Simultaneous monitoring of ammonia and moisture using a single fiber optoelectrode as a transducer , IEEE Sensors Journal, 14, 847-852 (2014).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
S. Shao, Y. Huang and S. Tao, Simultaneous monitoring of electrical resistance and optical absorbance signals of a fiber optoelectrode for multiple gas sensing , Proceedings of SPIE-The Intern. Soc. Opt. Eng., in press.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2012
Citation:
Development of ammonia sensors for air quality monitoring
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2013
Citation:
Simultaneous monitoring of ammonia and moisture using a single fiber optoelectrode as a transducer
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Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: Activities: During the reporting period, we focused our research on investigating the properties of polymers used in immobilizing ammonia-indicating reagent and response of the sensors to humidity. Several polymers, including PMMA, sol-gel silica, PVA, have been tested. The responses of the sensors to humidity and ammonia in air have been investigated. An optical microscope has been employed to observe the structure of the reagent-doped polymer coatings. PARTICIPANTS: 1. Dr. Shiquan Tao is the Principle Investigator for this project. Dr. Tao is an assistant professor of chemistry at West Texas A&M University. 2. Mr. Yu Huang is a research assistant for this project. Mr. Huang is a graduate student at West Te3xas A&M University. He graduated from WTAMU in May, 2012 TARGET AUDIENCES: Farmers, scientific community and industry related in air quality research and air quality monitoring product development, federal agency PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Outcomes: It was discovered that PVA can form continuous membranes without any crack on the surface of optical fibers. An optical fiber chemical sensor using a bromocreasol purple doped PVA coating on the surface of an optical fiber still has high sensitivity in monitoring trace ammonia in air. In addition, this sensor does not have cross-response to the change of moisture in air. Impacts: A major issue for using our highly sensitive fiber optic sensor for monitoring trace ammonia in air is the sensors cross response to humidity, which is in continuous changing in real world. Although the moisture cross-response of these sensors can be eliminated by using a moisture sensor and a computer program together with the gas sensor, it makes the sensor system very complicated. A simple sensor which only responses to ammonia is needed. The results from the work of this reporting period provide the method to build such simple sensors.
Publications
- Huang, Y., Wieck, L., Tao, S., 2013. Development and evaluation of optical fiber NH3 sensors for applications in air quality monitoring. Atmospheric Environment, 66, 1-7.
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: Activities: In the development of sensor technologies for monitoring trace gas species for air quality monitoring program must take into consideration of potential interference from cross response to humidity, CO2 and temperature. The concentrations of water vapor, CO2 in air are thousands to millions of times higher than that of trace gases (NH3, H2S, SO2, NOx, CH4) in air. In addition, the concentrations of these species in air are continuous changing with time and location. Temperature is another fact affects the response of most sensors. The air temperature is also in continuous changing with location and time. Our work in previous work was focused on investigating the effect of humidity (water vapor concentration) on our fiber optic ammonia sensors. During this reporting period, we focus our work on investigating the effect of CO2 and temperature on the responses of our fiber optic ammonia sensors. Products: The effect of CO2 on two highly sensitive fiber optic ammonia sensors developed from my previous works has been investigated. The change of CO2 concentration in the tested range from 350 ppm to 1500 ppm in air was found not effect the response of the sensors to ammonia in air. It is believed that the polymers (sol-gel silica, PMMA) used to immobilize the sensing reagents (bromocreasol purple, chrlorophenol red) played critical roles in eliminating CO2 interference. The effect of temperature on the response of fiber optic ammonia sensors to trace ammonia in air has been investigated. The ammonia sensors are based on the reactions of gas phase ammonia with sensing reagents in porous polymer membranes (solid phase), and detecting the reaction products with fiber optic spectroscopic techniques. The concentration of reaction products in the polymer membrane phases are in equilibrium with the concentration gas phase ammonia. The change of temperature is expected to change such equilibria, and affect the sensor's responses. Through the research work of this reporting period, the relationship of the fiber optic sensor's response and temperature is quantitatively established. This information will be used in further work to develop a computer program to eliminate the interference of temperature change on fiber optic ammonia sensors. PARTICIPANTS: Dr. Shiquan Tao, Principle Investigator, is an Assistant Professor of Chemistry at West Texas A&M University. He has eight years experience in fiber optic sensor research and development. Dr. Tao's fiber optic sensor research has been focused on highly sensitive active core fiber optic sensors using porous silica optical fibers, liquid core waveguide and hollow core waveguide, highly sensitive gas sensors using sensing agent coated bent optical fiber probes, long-pathlength evanescent wave fiber optic sensors using flexible light-guiding capillary, high-temperature fiber optic gas sensors using nanoparticle-doped semiconductor metal oxide coatings and sol-gel derived porous silica optical fibers. Dr. Tao has also recently developed a new technique for fabricating highly sensitive scintillating optical fibers, which have been successfully tested for detecting gamma-ray. Dr. Tao's present efforts on fiber optic sensor are focused on: 1). highly sensitive fiber optic gas sensors and sensor network technologies for air quality monitoring; 2). laser total internal reflection fluorescence spectrometry using a dual optical fiber structure for single molecular detection, and its applications in quick detecting of food-born pathogens; 3). development of highly sensitive scintillating optical fibers for applications in micro position-emission tomography. Dr. Tao can be reached by e-mail: stao@wtamu.edu; or by phone (806-651-2539 Mr. Yu Huang is a graduate student at the Department of Mathematics, Chemistry & Physics of West Texas A&M University. He started to work on this project from September 2010. Mr. Huang developed the dial-layer PMMA/CPR coating for designing a highly sensitive fiber optic ammonia sensor. Mr. Huang also did experiments investigating the effect of CO2 and temperature on the response of fiber optic ammonia sensors. TARGET AUDIENCES: Target audiences include animal feeding industry, residents near concentrated animal feeding facility, environmental protection agency, science/engineering communities having interesting in air quality monitoring, control. PROJECT MODIFICATIONS: No major change in approach
Impacts
Most chemical sensors for gas sensing are based on the reactions of analytes in gas phase with sensing reagents immobilized in porous polymer membranes or coated as a pure reagent membrane on a substrate. The sensing signals are related to reaction products in the solid phase. The concentration of such a reaction product is usually in equilibrium with analyte gas compound in gas phase, which is the foundation for monitoring the concentration of analyte in the gas phase, such as air in this project. The discovery of temperature change on these chemical equilibria, and the method developed from this work to develop quantitative relationship between temperature and sensor's response is significant for further works on developing similar sensor technologies.
Publications
- 1. Huang, Y., and Tao, S., (2011). An optical fiber sensor probe using a PMMA/CPR coated bent optical fiber as a transducer for monitoring trace ammonia. J. Sens. Technol., 1: 29-35.
- 2. Huang, Y., Wieck, L., and Tao, S., (2011). Developing and Evaluating Optical Fiber NH3 Sensors for Application in Air Quality Research/Monitoring. Atm. Environ., (pending).
- 3. Huang, Y., and Tao, S., (2011). An Optical Fiber Sensor Probe Using a PMMA/CPR Coated Bent Optical Fiber as a Transducer for Monitoring Trace Ammonia. Abstract of 242nd Amarican Chemical Society National Meeting, Denver, CO, September, 2011.
- 4. Tao, S., Huang, Y., and Wieck, L., Optical Fiber Ammonia Sensors for Air Quality Monitoring. Abstract of 242nd Amarican Chemical Society National Meeting, Denver, CO, September, 2011.
- 5. Tao, S., Huang, Y., and Wieck L., Highly Sensitive Optical Fiber NH3 Sensors for Air Quality Monitoring in Agricultural Environmental Program. Abstract of Pittscon 2012 (pending).
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: Water vapor is a major component of air, and its concentration (usually expressed as relative humidity, RH%) continuously changes with time and location. Therefore, the potential interference caused by RH% change in air samples must be taken into consideration when developing sensor technologies for monitoring air quality, such as monitoring the concentration of CH4, CO, CO2, H2S, NH3, NOx, O2, O3, SO2 in air. In evanescent wave optical fiber chemical sensors, polymers are frequently used to immobilize sensing agents. The property of polymers, interaction of polymer with water vapor, and interaction of water vapor with immobilized reagent could affect the intensity of light guided through an optical fiber coated with a reagent immobilized polymer. In my previous work, I developed a sensitive fiber optic ammonia gas sensor using a bromocreasol purple immobilized sol-gel derived silica coating as a sensing material. The sensor is very sensitive, can be used to monitor ammonia in air samples down to 15 ppbv. The sol-gel derived silica polymer coating absorbs moisture from air, and water content absorbed by the coating depends on RH% in air to which the sensor exposed. The porous polymer coating on the surface of an optical fiber core also scatters evanescent wave (EWS) of light guided inside the fiber, and the EWS is affected by absorbed water content in the porous polymer coating. Therefore, the sensor has cross-response to RH% change. In an effort to reduce/eliminate the interference of RH% on optical fiber chemical sensors for air quality monitoring my first year work for this project was focused on: 1). investigating the effect of RH% change on fiber optic sensor probes having different polymer coatings; 2). developing new methods of coating polymers and sensing agents on surface of bent optical fiber probes for designing sensors. Three polymers, sol-gel derived silica, poly(methyl methacrylate) (PMMA) and polyvinyl alcohol (PVA), and mixture of these polymers (hybrid polymers) have been investigated for immobilizing a pH-indicating agent, bromocresol purple (BCP), for designing evanescent wave based fiber optic ammonia sensors. The pure polymers, hybrid polymers, BCP-immobilized polymers and BCP-immobilized hybrid polymers were coated on bent optical fiber probes using dip-coating methods. The fiber optic evanescent wave spectroscopic responses of these coated probes to RH% change and trace NH3 in air have been investigated. Two methods of coating PMMA and a sensing agent, chlorophenol red (CPR), on surface of bent optical fiber probes have also been investigated. In the first method, CPR dissolved together with PMMA in an acetone solution, which was used as a coating solution in a dip-coating process. In the second method, PMMA in acetone and CPR in acetone were used as coating solutions. PMMA is first coated on the surface of a bent optical fiber probe, and CPR is coated on the surface of the PMMA coating (dual-layer PMMA/CPR coating). The responses of sensor probes made from these two methods to RH% change and trace NH3 in air were investigated. PARTICIPANTS: Dr. Shiquan Tao, Principle Investigator, is an Assistant Professor of Chemistry at West Texas A&M University. He has eight years experience in fiber optic sensor research and development. Dr. Tao's fiber optic sensor research has been focused on highly sensitive active core fiber optic sensors using porous silica optical fibers, liquid core waveguide and hollow core waveguide, highly sensitive gas sensors using sensing agent coated bent optical fiber probes, long-pathlength evanescent wave fiber optic sensors using flexible light-guiding capillary, high-temperature fiber optic gas sensors using nanoparticle-doped semiconductor metal oxide coatings and sol-gel derived porous silica optical fibers. Dr. Tao has also recently developed a new technique for fabricating highly sensitive scintillating optical fibers, which have been successfully tested for detecting gamma-ray. Dr. Tao's present efforts on fiber optic sensor are focused on: 1). highly sensitive fiber optic gas sensors and sensor network technologies for air quality monitoring; 2). laser total internal reflection fluorescence spectrometry using a dual optical fiber structure for single molecular detection, and its applications in quick detecting of food-born pathogens; 3). development of highly sensitive scintillating optical fibers for applications in micro position-emission tomography. Dr. Tao can be reached by e-mail: stao@wtamu.edu; or by phone (806-651-2539). Mr. Yu Huang is a graduate student at the Department of Mathematics, Chemistry & Physics of West Texas A&M University. He started to work on this project from September 2010. Mr. Huang developed the dial-layer PMMA/CPR coating for designing a highly sensitive fiber optic ammonia sensor. Mr. Lucas Wieck was an undergraduate student in the Department of Mathematics, Chemistry & Physics. Mr. Wieck worked on this project from February to May 2010, investigated the effect of polymer coatings on the response of fiber optic sensors to humidity change. TARGET AUDIENCES: Target audiences include animal feeding industry, residents near concentrated animal feeding facility, environmental protection agency, science/engineering communities having interesting in air quality monitoring, control. PROJECT MODIFICATIONS: No major change in approach.
Impacts
The bent optical fiber sensor probes with pure PVA and PMMA coatings do not response to RH% change and trace NH3 in air. A bent optical fiber probe coated with pure sol-gel derived porous silica coating shows strong response to RH% change and a small response to trace ammonia in air (0.2 dB for 50 ppm NH3). The mechanism of the response is enhanced EWS when water vapor or NH3 gas are absorbed into the porous material. When BCP is used as a NH3 indicator, the bent optical fiber probe having a BCP-doped PMMA coating shows a small response, and the optical fiber probe having a BCP-doped porous silica coating shows a strong response (1.7 dB) when air's RH% changed from 20% to 85%. However, a bent optical fiber probe having a BCP-doped PVA coating does not response to RH% change in the tested range from 20% to 85%. All the probes having BCP-doped polymer coatings response to trace NH3 in air samples. The response sensitivity is as follows: BCP-porous silica>>BCP-PVA>BCP-PMMA. The sensitivity of a BCP-PVA coated optical fiber probe is about 10% that of a BCP-porous silica coated sensor probe. Bent optical fiber probes having hybrid PVA/porous silica polymer coatings response to RH% change, but the sensitivity decreases with the increase of PVA ratio in the hybrid polymer. Bent optical fiber probes having BCP-doped hybrid PVA/porous silica coatings also response to trace NH3 in air samples. The sensitivity of the response decreases with the increase of PVA ratio in the hybrid polymer. Based on the test results, a bent optical fiber probe having a BCP-doped PVA coating can be used for monitoring trace NH3 in air in the concentration range from 4 ppm to 100 ppm without cross response to RH% change. All the bent optical fiber probes coated with PMMA and CPR using the two coating methods responses to trace NH3 in air. The sensitivity of the probe having a dual-layer PMMA/CPR coating is about 70-times higher than that of the probe having a CPR-immobilized PMMA coating. The response time of the sensor probe having a dual-layer PMMA/CPR coating is about 4 minute, while the response time to the probe having a CPR-immobilized PMMA coating is longer than 8 minutes. The optical fiber probes having a CPR-immobilized PMMA coating shows a small enhanced EWS response to RH% change (0.2 dB when RH% changed from 14% to 85%). The sensor probe having a dual-layer PMMA/CPR coating does not show enhanced EWS response when air sample's RH% changed from 14% to 85%. However, the reagent (CPR) reacts with water when RH% increases. This reaction causes an absorbance signal, which interfere the sensor's response to NH3 in air. The optical fiber sensor probe having a dual-layer PMMA/CPR coating has been investigated for continuous monitoring trace NH3 in an air sample. This sensor is completely reversible, can detect NH3 in air samples down to 2 ppbv, which makes it useful for monitoring trace NH3 in background air when it is needed to investigate NH3 transportation from an animal feedlot to surrounding air. The results from this year's work provided a direction for designing highly sensitive fiber optic NH3 sensors having no humidity cross response for air quality monitoring.
Publications
- No publications reported this period
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