(114c) Highly b-Oriented MFI Monolayer Film Synthesized Optical Fiber Chemical Sensor for Analysis of Gas Diffusion

A highly b-Oriented monolayer MFI type zeolite film was synthesized on optical fiber end face and a time-resolved microscopic laser refractometry method is established to measure gas diffusivity behavior in zeolite membrane. The monolayer zeolite film was fabricated by direct in situ hydrothermal crystallization upon the cleaved end face of a standard single-model optical fiber. Effect on thin film thickness and surface coverage was investigated by varying crystallization time and composition of the synthesis solution. The films are characterized with scanning electron microscopy and the thicknesses were able to be controlled from 1μm up to 2μm. The zeolite-fiber integrated optical sensor operates by ultra-sensitive and fast-speed monitoring the optical reflectivity change caused by the sorption of gas molecules. Interference spectrums at varied sorbate concentrations\ under equilibrium conditions were analyzed to determine refractive index as function of concentration. The sorbate uptake curves were obtained by measuring single wavelength laser reflectance as a function of time during non-equilibrium dynamic process of adsorption. Gas diffusivity values at different sorbate concentration were derived from each uptake curves mathematically.