title: Kinetic behavior of polymer-coated long-period-grating fiber-optic sensors.
abstract: A new method of analysis employing the time-dependent response of long-period-grating (LPG) fiber-optic sensors is introduced. The current kinetic approach allows analysis of the time-dependent wavelength shift of the sensor, in contrast to previous studies, in which the LPG sensing element has been operated in an equilibrium mode and modeled with Langmuir adsorption behavior. A detailed kinetic model presented is based on diffusion of the analyte through the outer protective membrane coating into the affinity coating, which is bound to the fiber cladding. A simpler phenomenological approach presented is based on measurement of the slope of the time-dependent response of the LPG sensor. We demonstrate the principles of the kinetic methods by employing a commercial Cu+2 sensor with a carboxymethylcellulose sensing element. The detailed mathematical model fits the time-dependent behavior well and provides a means of calibrating the concentration-dependent time response. In the current approach, copper concentrations below parts per 10(6) are reliably analyzed. The kinetic model allows early-time measurement for low concentrations of the analyte, where equilibration times are long. This kinetic model should be generally applicable to other affinity-coated LPG fiber-optic sensors.
authors.affiliation: Contribution from Innovative Scientific Solutions, Inc, Dayton, Ohio 45440, USA.
authors.forename: Justyna
authors.initials: J
authors.lastname: Widera
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Bunker
authors.forename: Gilbert E
authors.initials: GE
authors.lastname: Pacey
authors.forename: Viswanath R
authors.initials: VR
authors.lastname: Katta
authors.forename: Michael S
authors.initials: MS
authors.lastname: Brown
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Elster
authors.forename: Mark E
authors.initials: ME
authors.lastname: Jones
authors.forename: James R
authors.initials: JR
authors.lastname: Gord
authors.forename: Steven W
authors.initials: SW
authors.lastname: Buckner