OPTICAL PH SENSOR BASED ON THE CHEMICAL MODIFICATION OF A POROUS POLYMER FILM

A new approach to the design and construction of an optical pH sensor has been developed by immobilizing a direct azo dye at a porous cellulosic polymer film. The sensor was fabricated by binding Congo Red to a cellulose acetate film that had previously been subjected to an exhaustive base hydrolysis. Advantageous features of the design include (1) a rapid equilibration time ( less than 1. 3 s), (2) a large dynamic range ( greater than 4 pH units), and (3) ease of fabrication. The rapid response results from the porous structure of the polymeric support, which minimizes barriers to mass transport.