An optoelectrochemical thin-film chlorine sensor employing evanescent fields on planar optical waveguides

Abstract

A new type of optoelectrochemical sensor based on an electrochromic thin-film sensing layer placed on top of a planar waveguide has been developed. The oxidation state of the sensing film is quantitatively measured by the evanescent field of the light transmitted through the waveguide. The functioning of the device has been ascertained which dissolved chlorine, employing an electrochemically resettable film of lutetium biphthalocyanine. Detection of film oxidation has been carried out at 950 nm. This technique appears promising for the detection of residual chlorine, since only changes due to the sensing reaction are monitored. Although the device has not been optimized, a potential sensitivity below 1 ppm has been demonstrated. The integration of modem optical technology and electrochemical techniques for sensing applications appears to be a powerful new approach.