Design of pH Sensors in Long-Period Fiber Gratings Using Polymeric Nanocoatings

• Published in: IEEE sensors journal Vol. 7; no. 3; pp. 455 - 463
• Main Authors: Corres, J.M., Matias, I.R., del Villar, I., Arregui, F.J.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.03.2007; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Coupled-mode analysis; electrostatic self-assembly (ESA); Electrostatics; Fiber gratings; Fibers; long-period fiber gratings; Mathematical models; Nanomaterials; nanophotonics; Nanostructure; nanostructured materials; Nonhomogeneous media; Optical fiber sensors; pH sensor; Pigmentation; Polyallylamine hydrochloride; Polymer films; Predictive models; Self-assembly; Sensors; Studies; Transmission line matrix methods; Waveguide theory
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2007.891933

In this paper, two different pH sensors based on the deposition of nanometric scale polymeric films onto the surface of a long-period fiber grating (LPFG) have been studied and compared. An electrostatic self-assembled (ESA) method has been used to create sensitive films with an optimal overlay thickness. Two types of sensors have been designed: The first one is based on polyallylamine hydrochloride (PAH), polyacrylic acid (PAA), and the second one was done incorporating the pigment Prussian blue (PB) in the PAH/PAA matrix. A theoretical model of multilayer cylindrical waveguides based on coupled-mode theory has been used to predict the position of the attenuation bands as a function of the overlay thickness. Both sensors were tested and compared in terms of sensitivity and response time. A faster response was obtained with the introduction of PB particles in the polymeric matrix. Linear sensors in the pH range 4-7 were obtained, showing good repeatability and high sensitivity