Zeolite Thin Film-coated Long Period Fiber Grating Sensor for Measuring Trace Organic Vapors
A zeolite thin film-coated long period fiber grating (LPFG) sensor was developed and tested for direct measurement of trace organic vapors with straightforward operation. The sensor was fabricated by growing pure silica MFI-type zeolite (i.e. silicalite) thin film on the optical fiber grating by in situ hydrothermal crystallization. The sensor measures chemical vapor concentration by monitoring the molecular adsorption-induced shift of LPFG resonant wavelength (λR) in near infrared (IR) region. Upon loading analyte molecules, the zeolite's refractive index changes in the close vicinity of the fiber index where the λR responds with extremely high sensitivity. Because the silicalite is hydrophobic and preferentially adsorbs organic molecules, the zeolite-LPFG sensor is capable of quantifying organic vapor concentrations in lower ppm or ppb ranges without sample pre-concentration and rigorous control of operating conditions. The sensor had a much faster response speed for isopropanol than for toluene as the former has a smaller molecular kinetic size and greater diffusivity in the zeolite pores than the latter.
J. Zhang et al., "Zeolite Thin Film-coated Long Period Fiber Grating Sensor for Measuring Trace Organic Vapors," Sensors and Actuators B: Chemical, Elsevier, Jan 2009.
The definitive version is available at http://dx.doi.org/10.1016/j.snb.2008.09.033
Electrical and Computer Engineering
National Energy Technology Laboratory
United States. Department of Energy
Keywords and Phrases
Long Period Fiber Grating; Optical Sensor; Trace Measurement; Optical detectors; Zeolites
Article - Journal
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