We have developed a novel H2S-sensitive film by immobilizing thionine in a silica matrix by means of the solgel process. The film is stable, reversible, and sensitive to dissolved H2S to as low as parts-per-billion levels. The photochemical instability of thionine in basic solution has been improved dramatically by use of this immobilization technique and silica substrate. Based on the developed new films, sensors for monitoring H2S may be prepared either by a fiber-optic approach or by integrated optical circuit techniques.
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