Chitosan Membranes for Optical pH Chemical Sensors

A three-layer membrane for optical pH chemical sensors has been developed consisting of layers of polyester support, chitosan-indicator and polyvinly alcohol-titanium dioxide for reflection. The chitosan membrane was more stable and easier for immobilizing of benzopurprine 4B or fluorescein isothiocyanate than a cellulose membrane on which polyvinyl alcohol with titanium dioxide and calcium carbonate was coated and heated at 140°C in nitrogen atmosphere followed by dissolving of calcium carbonate to form a porous water-resistant membrane for reflection of light. The sensor membrane shows a pH-induced color change than makes it capable of measuring pH in the 3-7 range.