Modified ZSM-5 zeolite film-integrated fiber optic sensors for ammonia detection

Xiling Tang; Zhong Tang; Seok-Jhin Kim; Junhang Dong

doi:10.1117/12.817887

30 April 2009 Modified ZSM-5 zeolite film-integrated fiber optic sensors for ammonia detection

Xiling Tang, Zhong Tang, Seok-Jhin Kim, Junhang Dong

Proceedings Volume 7312, Advanced Environmental, Chemical, and Biological Sensing Technologies VI; 73120C (2009) https://doi.org/10.1117/12.817887
Event: SPIE Defense, Security, and Sensing, 2009, Orlando, Florida, United States

Abstract

This paper reports the development of surface modified ZSM-5 zeolite thin-film coated long-period fiber grating (LPFG) sensors for in situ detection of ammonia (NH3). The sensor was fabricated by growing MFI-type zeolite thin film (i.e. ZSM-5 with Si/Al ratio of 15) on the optical fiber grating by in situ hydrothermal crystallization. The sensor measures ammonia concentration by monitoring the molecular adsorption-induced shift of LPFG resonant wavelength (λ_R) in near infrared (IR) region. Upon loading the analyte (NH3) molecules, the refractive index of the zeolite film changes in the close vicinity of the fiber index where the LPFG has a large response to achieve high sensitivity. High sensitivity of this sensor also comes from the ability of the nanoporous zeolite to effectively concentrate the target molecules by selective adsorption. The sensor was capable of sensitive detection of ammonia at lower ppm level. The zeolite's internal surface was modified by ion exchange with NH₄+ followed by thermal treatments to enhance the surface acidity. The acidic ZSM-5 (i.e. H-ZSM-5) film exhibited higher sensitivity and improved selectivity for NH₃.

Citation Download Citation

Xiling Tang, Zhong Tang, Seok-Jhin Kim, and Junhang Dong "Modified ZSM-5 zeolite film-integrated fiber optic sensors for ammonia detection", Proc. SPIE 7312, Advanced Environmental, Chemical, and Biological Sensing Technologies VI, 73120C (30 April 2009); https://doi.org/10.1117/12.817887

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