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Open AccessArticle

Evanescent-Wave Fiber Optic Sensing of the Anionic Dye Uranine Based on Ion Association Extraction

Department of Environmental Biology and Chemistry, Graduate School of Science and Engineering for Research, University of Toyama, Toyama 930-8555, Japan
Department of Applied Chemistry, School of Science and Technology, Meiji University, Kanagawa 214-8571, Japan
Author to whom correspondence should be addressed.
Sensors 2020, 20(10), 2796;
Received: 30 March 2020 / Revised: 1 May 2020 / Accepted: 11 May 2020 / Published: 14 May 2020
(This article belongs to the Special Issue Optical Fiber Sensors and Photonic Devices)
Herein, we propose an evanescent-wave fiber optic sensing technique for the anionic dye uranine based on ion association extraction. The sensor was prepared by removing a section of the cladding from a multimode fiber and hydrophobization of the exposed core surface. Uranine was extracted in association along with hexadecyltrimethylammonium (CTA) ion onto the fiber surface and detected via absorption of the evanescent wave generated on the surface of the exposed fiber core. The effect of CTA+ concentration added for ion association was investigated, revealing that the absorbance of uranine increased with increasing CTA+ concentration. A change in the sensor response as a function of the added uranine concentration was clearly observed. The extraction data were analyzed using a distribution equilibrium model and a Freundlich isotherm. The uranine concentration in the evanescent field of the fiber optic was up to 54 times higher than that in the bulk solution, and the limit of detection (3σ) for uranine was found to be 1.3 nM. View Full-Text
Keywords: evanescent-wave fiber optic sensor; ion association; uranine evanescent-wave fiber optic sensor; ion association; uranine
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MDPI and ACS Style

Okazaki, T.; Watanabe, T.; Kuramitz, H. Evanescent-Wave Fiber Optic Sensing of the Anionic Dye Uranine Based on Ion Association Extraction. Sensors 2020, 20, 2796.

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