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Proceedings Paper

Detection of low-concentration ammonia using differential laser-induced fluorescence on vapochromic coordination polymers
Author(s): Dawei Yin; Glenn H. Chapman; David Stevens; Bonnie Gray; Daniel Leznoff
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Paper Abstract

The detection of ammonia in parts per millions range has been challenging in sensors research, and is of great importance for industrial applications. In previous literature, Vapochromic Coordination Polymers (VCP) were developed to achieve luminescence upon a targeted gas exposures. We investigate a specific VCP, Zn[Au(CN)2]2,as an ammonia sensing material. Upon high concentration ammonia exposure, the fluorescent peak under near-UV stimulation undergoes a spectral shift from 460nm to 520nm, while the intensity increases by 3~4X. However, at ammonia concentrations < 50ppm, the spectral shift becomes hidden within the overall changing fluorescent spectrum shape. Then simple methods, such as detecting the peak wavelength or subtracting post-exposure from pre-exposure spectrums do not work. We developed further excitation and data processing techniques to detect ammonia at lower concentrations. A low-cost 405nm blue-ray DVD laser diode was used as the excitation source, providing a narrow band-width (4nm) stimulation that is separated from the emission peak. We measured the emission using a portable spectrometer (Photon Control SPM-002), and processed the data by separating the spectrum into two regions; (A) from 425 nm to 460 nm and (B) from 460nm to 500nm. Next, the integrated emissions under both regions were computed, and the value of shorter wavelength region (A) was subtracted from the longer wavelength one (B). When exposed to ammonia, region (A) reduces overall intensity while region (B) increases, resulting a signal starting from negative value and gradually increases to positive values, enabling the detection of 5ppm ammonia in less than 30 seconds gas exposure.

Paper Details

Date Published: 22 February 2018
PDF: 9 pages
Proc. SPIE 10539, Photonic Instrumentation Engineering V, 105390K (22 February 2018); doi: 10.1117/12.2285686
Show Author Affiliations
Dawei Yin, Simon Fraser Univ. (Canada)
Glenn H. Chapman, Simon Fraser Univ. (Canada)
David Stevens, Simon Fraser Univ. (Canada)
Bonnie Gray, Simon Fraser Univ. (Canada)
Daniel Leznoff, Simon Fraser Univ. (Canada)

Published in SPIE Proceedings Vol. 10539:
Photonic Instrumentation Engineering V
Yakov G. Soskind, Editor(s)

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