Preparation and characterization of transducer layers for opto-electrochemical detection of chlorine in water

Abstract

The control of chlorine content in water is an important issue in water treatment. This paper presents an opto-electrochemical approach to the detection of chlorine in water. In this approach, optical changes of a sensing layer caused by its interaction with chlorine are electrically reversed by using a thin conductive and transparent layer of Indium-Tin-Oxide (ITO) deposited in between an optical substrate and the sensing layer acting as an electrode. The paper deals with the preparation and characterization of sensing layers based on commercially available transducers suitable for the detection of chlorine in water and applicable on ITO-coated planar substrates and/or silica optical fibers. Sensing layers of several absorption and luminescent transducers were applied onto ITO layers deposited on planar glass or fiber-optic substrates by electropolymerization or by the sol-gel method. The best response was observed from o-phenylenediamine and polyluminol layers prepared by electropolymerization. The sensitivity and limit of detection of a polyluminol layers are comparable to hygienic limits for the chlorination of water. The parameters of o-phenylenediamine layers obtained up to now are close to these values. A damaging effect of chlorine in higher concentrations on the sensing layers was observed.