A Fiber-Optic Sensor for Monitoring Trace Ammonia in High-Temperature Gas Samples With a ${\hbox{CuCl}}_{2}$-Doped Porous Silica Optical Fiber as a Transducer

Abstract

An optical fiber chemical sensor for detecting/monitoring trace ammonia in high-temperature gas streams has been developed. This sensor uses a CuCl 2 -doped porous silica optical fiber, prepared via a previously reported sol-gel process, as a transducer. Trace ammonia in a gas sample diffuses into the porous fiber to react with the doped agent to form a Cu 2+ -ammonia complex. The concentration of the Cu 2+ -ammonia complex inside the porous silica optical fiber is proportional to ammonia concentration in the gas sample, to which the sensing porous silica fiber is exposed. Therefore, ammonia concentration in the gas sample can be detected through detecting the optical absorption signal of the formed Cu 2+ -ammonia complex inside the fiber by using a fiberoptic UV/Vis absorption spectrometric method. This sensor can be used to reversibly monitor trace ammonia in a gas sample at an elevated temperature up to 450 C in the tested range. A detection limit of 0.24 ppmv ammonia in an air gas sample was achieved when the sensor was tested at a temperature of 450 C.Index Terms-Ammonia sensor, chemical sensor, fiber-optic sensor, high-temperature gas sensing, porous silica optical fiber sensor, sol-gel silica fiber.

Bromocresol Green/Mesoporous Silica Adsorbent for Ammonia Gas Sensing via an Optical Sensing Instrument

“…By comparing with related research work using silica materials for the same quantification time of 5 min, we can see that this material can detect NH 3 gas concentrations at least 2 orders lower than those measurable in previous work (145–1,000 ppmv) [ 23 ]. In addition to the lower limit of detection, this linear correlation is also better [ 7 , 15 ]. Moreover, the gas quantification time was only 5 min in this study.…”

“…Optical sensors have attracted much attention because of their accuracy and high sensitivity to low ammonia gas concentrations. Besides, the detection can be achieved without any direct contact between the expensive optical parts and the corrosive ammonia gas samples [ 7 ]. Such features may lead to wide acceptance in real applications, and provide a solution for detecting ammonia at sub-ppmv levels.…”

Simultaneous Monitoring of Ammonia and Moisture Using a Single Fiber Optoelectrode as a Transducer

“…2) integrating a chemical/physical separating element to prevent interfering sample matrix components from contacting with the transducer [4], [10]- [12]. 3) integrating selective chemical/biochemical reactions in the transducer [13]- [16]. For example, in order to selectively monitoring a compound which absorbs light at specific wavelength, a monochromator or an optical band-pass filter can be used to isolate the light of specific wavelength.…”

“…Fiber optic sensors for selective monitoring trace ammonia and hydrogen sulfide in high temperature gas samples have been developed by integrating sensing reagents (CuCl 2 , Cd(NO 3 ) 2 ) into the optical fiber transducer. The sensing reagents selectively and reversibly react with the target compounds and the reaction products were monitored using fiber optical absorption spectrometry [13], [14]. Many biochemical sensors have enzymes in their transducers.…”

An Embedded Passive Resonant Sensor Using Frequency Diversity Technology for High-Temperature Wireless Measurement

“…However, the accuracy, sensitivity, and test range of the sensors are limited, and they cannot be easily employed in hostile environments such as those with radiation and electromagnetic interference [6]- [8]. SAW sensors are used not only for measuring temperature but also for chemical, pressure, humidity, force, and electric measurement by monitoring phase variations.…”