Preparation and characterization of thin transducer layers sensitive to free chlorine in water

The paper deals with preparation and characterization of layers of optical absorption transducers sensitive to free chlorine in water and based on commercially available chemicals. The electrochemical deposition and chemical approach based on the sol–gel method were employed for the immobilization of the transducers onto ITO-coated planar optical substrates. The transducers, namely methylene blue, o-phenylenediamine, Lu (III) acetate pthalocyanine tetrasulfonate tetrasodium salt (Lu-III-complex), murexid, quercetin, 1,2,3-benzenetriazole, benzopurpurine, thionine, bilirubin and its metal complexes, and 3-methyl-4 nitro-1(4-nitrophenyl) 2-pyriazoline-5-one (picrolonic acid), were tested. Transmission spectra, redox potentials, layer thickness and optical responses of the transducer layers to chlorine were investigated. By using sensitive layers based on o-phenylenediamine and methylene blue it was possible to detect chlorine in a minimum concentration of 0.25 ppm. The best results were obtained with the o-phenylenediamine layers prepared electrochemically. Both these transducer layers are useable for detection of chlorine up to concentration ∼ 8 ppm.