A LONG-RANGE FIBER OPTIC PH SENSOR PREPARED BY DYE-DOPED SOL-GEL IMMOBILIZATION TECHNIQUE

A long-range fiber optic pH sensor based on evanescent wave absorption is presented. The probe is prepared by immobilizing a mixture of thre e pH-sensitive dyes (cresol red, bromophenol blue and chlorophenol red ) on the surface of the fiber core using sol-gel technology. The senso r has a linear and reproducible pH response in the pH range from 4.5 t o 13.0. Due to its long dynamic pH range the sensor is expected to fin d wide applications. (C) 1998 Elsevier Science B.V. All rights reserve d.