Sol-Gel Derived Sensitive Films for Ammonia Sensors

Abstract

The sol-gel technology allows the preparation of silica thin films ranging in porosity from dense to highly porous films (50%).Porous silica films can function as a matrix that is able to bind the molecules of pH-sensitive indicators and therefore can be utilized as a sensitive film in construction of intensity based fibre or planar optical sensors for ammonia detection.We report the fabrication and characterization of ammonia sensitive, highly porous silica films deposited on soda-lime glass plates and doped with the bromocresole purple, and bromothymol blue molecules.In this paper we present the influence of the substrate withdrawal speed from sol on a thickness and a refractive index of the undoped silica films, as well as spectral absorbance characteristics of the doped films.An influence of ammonia concentration in air and relative humidity on a transmission of produced sensitive films is also presented.