P3.2 - Interrogating Water Content in Organic Solvents by Planar Bragg Grating Sensor
- Event
- SENSOR+TEST Conferences 2009
2009-05-26 - 2009-05-28
Congress Center Nürnberg - Band
- Proceedings SENSOR 2009, Volume II
- Chapter
- P3 - Chemo-/Bio-Sensors
- Author(s)
- S. Belle, S. Scheurich, R. Hellmann - University of Applied Sciences, Aschaffenburg, Germany, S. So, I. Sparrow, G. Emmerson - Stratophase Ltd., Romsey, Great Britain
- Pages
- 323 - 328
- DOI
- 10.5162/sensor09/v2/p3.2
- ISBN
- 978-3-9810993-5-5
- Price
- free
Abstract
We report on a planar Bragg grating evanescent field refractive index sensor capable of monitoring online the water content in organic solvents in the range from 0-100%. The sensor structure consists of a Bragg Grating buried in a planar multilayer silica on silicon structure in which both the waveguide and Bragg grating are introduced by UV radiation. Using this sensor, we have investigated the influence of varying water content on the reflected Bragg wavelength, i.e. effective refractive index, in different solvents. The measurements are accompanied by determining the refractive index and the density of the analyte. Karl Fischer Titration serves as a reference to calibrate our samples. Our results prove the capability of the sensor to measure online the water content up to 100% in the entire range of solvents, with a sensitivity on the order of 138nm/riu, corresponding to a minimum detectable index resolution of 7.3·10E-6 (e.g. in the case of ethanol). For higher refractive index samples the sensitivity increases as the effective index approaches the index of the waveguide of 1.46. Measurements of 2-butanol confirm this dependence. The observed nonlinear dependence of the Bragg wavelength on composition of aqueous solutions is attributed to the physicochemical properties of the solvents due to the presence of hydration shells around the solvent molecules.