Optical planar Bragg grating sensor for real-time detection of benzene, toluene and xylene in solvent vapour

We report on an optical planar Bragg grating sensor functionalized by a comparatively simple method to detect substances such as benzene, toluene and xylene (BTX). The functionalization is performed by allyl substituted γ-cyclodextrin derivatives which are immobilized on the sensor surface by dip coating. Our results prove the capability of this functionalized sensor system to detect lowest concentrations of BTX in solvent vapour in real-time with a sensitivity of 3±0.4 pm/100 ppm for benzene, 8±1 pm/100 ppm for toluene and 32±1 pm/100 ppm for m-xylene. Taking into account the spectral resolution and repeatability of the interrogation system this corresponds to a minimum concentration threshold of 200±25 ppm for benzene, 70±15 ppm for toluene and 20±2 ppm for m-xylene, respectively.