Fabrication and Characterization of a Poly (3-Hexylthiophene) Thin Film Micro-sensor for Hypergolic Vapor Detection
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0951-E06-32
Fabrication and Characterization of a Poly (3-Hexylthiophene) Thin Film Micro-Sensor for Hypergolic Vapor Detection Huihua Shu, Jiehui Wan, John Shu, Hong Yang, and Bryan A. Chin Auburn University, Auburn, AL, 36849
ABSTRACT A passive chemiresistor micro-sensor was investigated for the detection of hydrazine compounds. Hydrazine compounds are a highly toxic and carcinogenic species exhibiting toxic effects in humans at very low levels of exposure. Therefore, a sensor capable of detecting ppb levels of hydrazine compounds is required to insure the safety of personnel. The present study describes the fabrication, testing, and characterization of a low-cost, ultrasensitive Poly (3Hexylthiophene) (P3HT) thin film-based micro-sensor for the detection of hydrazine compounds. Standard microelectronic manufacturing techniques were used to form a microsensor composed of a silicon substrate, interdigitated gold electrodes, and P3HT sensing film. Responses of the micro-sensor to hydrazine compounds at different temperatures and concentration levels are reported. When exposed to 25 ppm hydrazine in nitrogen, the sensor’s resistance was measured to change from a few ohms to over 10 Megaohms. The thermal stability of the P3HT micro-sensor and the method to improve thermal stability are also explored. Thermally annealing the P3HT micro-sensor was found to improve thermal stability at high temperatures. Moreover, the sensor exhibits good specificity to hydrazine and does not respond to the presence of NO2 and/or N2O. INTRODUCTION Chemical sensor technologies have emerged as dynamic approaches for identifying and quantitating specific analytes of human and environmental levels of concerns. Due to the growing need for rapid, continuous and multi-component analysis, new sensing methods are emerging that making environmental monitoring much simpler with lower cost [1]. The chemiresistor sensor is one type of chemical sensor representing a conceptually very simple electronic approach to detect chemical species in the gas phase. Changes in the resistance of an organic or inorganic material in response to the target gas molecules provide the main mechanism of detection. Hydrazine, and its two main derivatives monomethylhydrazine (MMH), and unsymmetrical dimethylhydrazine (UDMH) have been used in the guidance of missiles and satellites, water treatment, and a variety of other industrial applications [2]. However, these compounds have been implicated as highly toxic and carcinogenic species, which exhibit toxic effects in humans at very low levels of exposure [3]. As a result of the reactivity and toxicity, the facile detection of these compounds becomes very desirable to ensure a healthy workplace environment for personnel. Several traditional analytical methods utilized for hydrazine detection have been reported including colorimetric and coulometric techniques, mass spectrometric methods, electrochemical detectors, as well as chemiluminescence detectors. However, each of them has one or more disadvantages that limit their a
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