The research on optical chemical sensing characteristics of the dye-doped sol-gel coating film

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The application to optical pH sensor and optical humidity sensor as an optical chemical sensor based on the fluorescence of a dye-doped sol-gel coating film was considered, and the effect based sample preparation condition of sensing characteristics was examined.1. Dye-doped sol-gel coating film as an optical pH sensor.The fluorescence of coumarin-4-, coumarin-6- and fluoresein-doped sol-gel coating films shows pH dependence so that the molecule may show acid-base equilibrium. Therefore, it has the application possibility to the optical pH sensor. These optical pH sensing characteristics are as follows.(1) It is excellent in respect of response range and response speed for pH of the fluorescence intensity. However, it is lacking for the stability for pH of the fluorescence intensity.(2) The method for using the intensity ratio at two fluorescent wavelengths for the improvement on the stability was done in a coumarin-4-doped sol-gel coating film. As the result, it was proven that the effect by the preparation condition was big, though to some extent improvement was accepted.And, when rhodamine6G is doped together with coumarin6 and fluorescein in sol-gel coating films, its emission showed energy transfer from coumarin6 and fluoresein to rhodamine6G.The fluorescent pH dependence of rhodamine6G by the energy transfer has the application possibility to the optical pH sensor.2. Dye-doped sol-gel coating film as an optical humidity sensor.The fluorescence of coumain-4-, coumarin-6-, fluoresein- and rhodamine6G-doped sol-gel coating films changes by moisture, and there is the application possibility to the optical humidity sensor based on the fluorescence. It was proven that the fluorescent humidity dependence was classified into two of (1) the fluorescence quenching of molecular aggregation and the monomer molecule, and (2) change of the fluorescence by acid-base equilibrium.