Abstract: An optical chemical sensor was developed for the determination of Co2+ based on the reversible fluorescence quenching of 5-tert-butyl-2-methoxy thiacalix[4] arene(Tc4A-OCH3) immobilized on a plasticized polyvinyl chloride(PVC) membrane. The optimum membrane of the sensor is composed of 50 mg of PVC, 100 mg of dioctyl sebacate(DOS) and 2.5 mg of 5-tert-butyl-2-methoxy thiacalix[4] arene. The maximum response of the membrane for Co2+ was obtained in nitric acid solution with pH of 5.6, and the proposed sensor responds linearly in a concentration range of 6.31×10-6～1.26×10-2 mol/L, with a detection limit of 3.11×10-7 mol/L. The sensing membrane has the advantages of high reproducibility, reversibility of the fluorescence signal and good selectivity. Common inorganic ions have no interferences.

Key words: tret-butyl-methoxy thiacalix[4] arene, fluorescence quenching, Optical chemical sensor,, cobalt ion(Ⅱ)