Intrinsic Sol−Gel Clad Fiber-Optic Sensors with Time-Resolved Detection

Abstract

Sol-gel clad fiber-optic waveguides are investigated as intrinsic distributed fiber-optic chemical sensors. The porous sol-gel cladding allows diffusion of analytes into the evanescent field region close to the fiber-optic core. Pulsed optical excitation (0.5 ns) and time-resolved emission detection can be used to simultaneously monitor several multiplexed sensor clad regions along a single optical fiber. Time-resolved detection is also demonstrated as a means of resolving both the spatial location and the fluorescence kinetics of intrinsic sensor chromophores along the fiber-optic waveguide. Narrow band excitation and spectrally resolved emission provide additional experimental means for discriminating between specific sensor clad regions. A fluorescein-doped silica xerogel clad pH sensor and an undoped aluminosilica xerogel clad quinone sensor are demonstrated as intrinsic sol-gel clad fiber-optic sensors.Fiber-optic chemical sensors provide an efficient and inexpensive method for selective, in situ, real-time chemical sensing. [1][2][3][4] The active sensor region of a fiber can be either immobilized at the distal end of an optical fiber (extrinsic) 2,5 or distributed along the length of the fiber-optic waveguide (intrinsic). 6,7 Submicrometer sized extensive fiber-optic sensors have also been reported, 8

Applications of the Planar Fiber Optic Chip

“…Potyrailo & Hieftje, 1999) An alternative strategy to increase n clad in the sensing region of a de-clad fiber is the application of a sol-gel cladding containing an analyte sensitive dye. (Browne et al, 1996;Kao et al, 1998;MacCraith et al, 1993;O'Keeffe et al, 1995) A second method to match the V-number between the clad and unclad sensing region of fiber optic sensors is to decrease r in the sensing region through etching the declad fiber. Fluorescent fiber sensors, where the de-clad sensing region has been step-or taper-etched, exhibit a 20 to 50 fold improvement in sensitivity.…”

Linear Combinatorial Synthesis with Fourier Transform Library Analysis

“…As described above, it is an inherent virtue of our one-dimensional chemistry method that with the location of a compound on the linear support, its complete synthetic history is immediately known. Evanescent excitation of fluorophores located in the fiber cladding and subsequent evanescent capture of the fluorescence by light modes in the fiber core were first combined with the OTDR method by Kvasnik et al [47] and Chronister et al [48] The small losses incurred when core modes interact with fluorophores in the cladding allow for the readout of a fiber containing many fluorescent regions (for example in fluorescent fiber sensor arrays). This is also important in assays of combinatorial libraries, particularly when the assay method is not the binding of a fluorophore (where there is no absorption if no positive identification is made) but for assays that rely upon changes in fluorescence intensity, fluorescence emission-wavelength, or fluorescence decay-time.…”

Investigation of dye-doped sol–gels for ammonia gas sensing

“…Many pH dyes have been entrapped in sol-gels for the sensing of pH and acid-base gases including CO 2 and NH 3 [3][4][5][6][7][8][9][10][11][12][13][14]. In general, dye leaching was a major problem for pH sensors based on dyes entrapped in sol-gel.…”