Fiber-optic potassium ion sensor based on a novel color-changing crown ether dye

A novel color-changing anionic crown ether dye, 4'-[2″,4″-di-(2,4-dinitro-6-trifluoromethylphenylamino)-6″-trifluoromethylphenyl]aminobenzo-15-crown-5 (chromogenic aminobenzo-15-crown-5, CAB15C5), was synthesized and applied to a new photochemical material K⁺ sensor. The photochemical K⁺-sensor probe was prepared using the CAB15C5-based poly (vinyl chloride) matrix-membrane set 1 mm apart from the tip of a bifurcated optical fiber with a cylindrical plastic support. This sensor could detect a wide range of K⁺ concentration (10^-6~10^-1 M) at pH 10 by measuring the absorbance change at 520 nm with approximately 1000 times selectivity against Na⁺. The theory of the photochemical K⁺-sensor was discussed on the basis of the cation extraction mechanism using the color-changing crown ether dye (GAB15C5).