Photocatalytic activity of nanostructured TiO2 coating on glass slides and optical fibers for methylene blue or methyl orange decomposition under different light excitation

• Photocatalytic decompossition of methylene blue or methyl orange catalysed by nanostructured TiO2 coatings on glass slides and silica fibers under different excitation arrangements.
• Nanostructured coatings prepared by sol–gel methods, by using dip-coating and on fibers by a coating die, too.
• Kinetics of the dye decomposition measured and kinetic curves fitted with a 1st order kinetic model as a measure of the coating photocatalytic activity.
• Values of the rate constant of the decomposition controlled by the catalyst amount, type of the dye and by the light intensity in the coating.

The paper presents results of the investigation of photocatalytic activity of coatings of nanoparticles of titania applied on glass slides and silica optical fiber using side excitation of the slides and fibers and direct launching of the excitation light into the fiber input face. Titania nanoparticle coatings were prepared by the alkoxide sol–gel method from titanium isopropoxide and from dispersion of anatase nanoparticles Aeroxide® P25 in water. The dip-coating technique was used for the application of the sols onto slides and fibers and a coating die for the continuous application of a sol during fiber drawing. Kinetics of decomposition of methylene blue and methyl orange solutions in water was employed to characterize the photocatalytic activity of the coatings. The measured kinetic data were fitted by a model of 1st order reaction. The 1st order rate constant related to the catalyst amount, a relative 1st order rate constant, was employed for evaluating the photocatalytic activity. It has been found that coatings fabricated from the nanoparticle dispersion are more active than those obtained by the alkoxide method. In the case of methylene blue, a value of the relative 1st order rate constant of about 1.55 ± 0.13 min−1 g−1 was obtained for coatings on slides and fibers which is practically independent of the excitation way.