Fiber-optic sensors for the estimation of pH within natural biofilms on metals

This paper presents an optical approach to estimate the pH within the biofilms grown on stainless steels-316L in natural aqueous environment. The response time, linear range, hysterisis, reproducibility and long-term stability of fiber-optic sensor have been analyzed using the membrane made of cellulose acetate with congo red and neutral red as pH indicators. The experimental results show the kind of variability in pH from point to point both parallel and perpendicular to the metal surface. The pH ranges from below 3 in localized areas to 8 in the outer portions of the biofilm. Optical response of the biofilm grown metal surface is found to be a consistent measure of the pH within biofilms.