<title>Characterization of porous Sol-Gel films on fiber optic surface plasmon resonance sensors</title>

Abstract

ABSTRACTFiber optic surface plasmon resonance sensors are used to characterize thin porous Sol-Gel films applied to the sensor surfaces. Techniques for coating the sensors and curing the films are discussed. Experimental and analytical methods are presented for using analysis of wavelength modulated surface plasmon resonance spectra to determine pore volume and refractive index of the films. INTRODUCTION Surface plasmon resonance (SPR) has been investigated as a phenomenon useful in the sensing of refractive index (RI)1. Surface plasmons, or surface plasmon waves (SPWs), describe the optical excitation of charge density waves along theinterface between a metal and a dielectric medium. Optical excitation occurs when incident light is transferred to charge density waves. SPR sensing techniques analyze either the angular or wavelength reflection spectra off the sensor interface asthe reflections change in response to RI changes in the sensed medium. SPR has also been successfully utilized for chemicalsensing. One method involves monitoring the RI of a sample, as is commonly done to determine concentration of sugars oralcohols in a solution2. A second technique involves utilizing a transducing film on the sensor surface. Transducing filmshave been created by binding selective chemistry directly to the metal interface3 or into a porous matrix applied to the sensorsurface4. If a chemical specific reaction occurs that affects either the RI or thickness of the transducing film, the change canbe detected via SPR and correlated to the presence of the analyte.Thin ceramic films produced by the Sol-Gel method are of general interest for use in chemical selective transducing films.