Optical pH sensor based on chemical modification of polymer film

A new low-cost pH sensor developed by immobilizing a direct indicator dye to porous and transparent acetylcellulose film. This sensor was fabricated by binding α-Naphthyl Red and Alizarine Yellow GG to a cellulose acetate film that had previously been subjected to an exhaustive base hydrolysis. The membranes have good durability (>12 months) and a short response time (<5 s). The method is easy to perform and uses acetylcellulose as a carrier. The reagents used for the activity of the cellulose support are inexpensive, nontoxic, and widely available. The Alizarine Yellow GG sensor can be used for direct determination of pH in alkaline media without any alkaline error.