Chemical sensor based on a long-period fibre grating modified by a functionalized polydimethylsiloxane coating

Abstract

A chemical sensor based on a coated long-period grating has been prepared and characterized. Designer coatings based on polydimethylsiloxane were prepared by the incorporation of diphenylsiloxane and titanium cross-linker in order to provide enhanced sensitivity for a variety of key environmental pollutants and optimal refractive index of the coating. Upon microextraction of the analyte into the polymer matrix, an increase in the refractive index of the coating resulted in a change in the attenuation spectrum of the long-period grating. The grating was interrogated using ring-down detection as a means to amplify the optical loss and to gain stability against misalignment and power fluctuations. Chemical differentiation of cyclohexane and xylene was achieved and a detection limit of 300 ppm of xylene vapour was realized.

Detection of volatile organic compounds with functionalized long-period gratings and micro-ring resonators

“…Here, we implement fiber-loop (CRD) spectroscopy in its phase-shift CRD variant ( Fig 1A) [6]. Details on the optical design have been published elsewhere [2].…”

“…As described previously [2] the PDMS/PDPS co-polymer was synthesized by first using acid catalyzed co-condensation of dichlorodimethyl silane and diphenyldiethoxy silane at a 4:1 ratio, followed by addition of titanium tetraisopropoxide crosslinking agent. The polymer was dissolved in hexane solution, was applied to the sensor devices and annealed for a few hours before use.…”

“…For environmental sensors reversibility of the binding process under ambient conditions is essential, since elaborate recovery of a field deployable sensor is not practical. PDMS has previously demonstrated a large refractive index change upon reversible uptake of m-xylene from air when applied to a longperiod grating sensor [2,3].…”

Detection of lead contamination of water and VOC contamination of air using SOI micro-optical devices

“…For environmental sensors reversibility of the binding process under ambient conditions is essential, since elaborate recovery of a field deployable sensor is not practical. One microextraction film was based on polydimethyl siloxane (PDMS), which has already demonstrated a large refractive index change upon uptake of m-xylene from air when applied to a long-period grating sensor [3,4]. The second microextraction film is based on a tetrasulfide-functionalized mesoporous silicate material which has also been previously applied to a long-period grating and showed a large affinity to lead Pb(II) [5].…”

Fiber loop ringdown glucose sensors: initial tests in human diabetic urines

“…Therefore, FLRD technique has high sensitivity, and it is insensitive to light source fluctuations. Although early studies of the FLRD technique were focused on trace gas detections [6], soon after, the FLRD technique was extended to detection of small volumes of fluids [7], chemical vapors [8], single bio-molecular cell [9], etc. The technique was also further developed for detections of physical quantities, such as pressure [10] and temperature [11].…”