광학적 pH 센서를 위한 지시염료가 고정된 필름의 광학적 특성 연구

Abstract

The optical characteristics of cresol red, phenol red, and neutral red immobilized in the thin film were investigated with absorbance measurement in order to find a sensing part of a fiber-optic pH sensor. Sol-Gel method with tetramethyl orthosilicate as a precursor was used to immobilize the pH indicators in the thin film. The absorbance spectra were measured when pH indicators were immobilizedin the film and were dissolved in the buffer solution. Experimental results showed that the absorbance spectra could be changed whenthe pH indicator is immobilized in the thin film. As compared with other pH indicators, the neutral red exhibited similar absorbancespectra regardless of physical conditions and was sensitive over whole pH range between 4 and 11. In addition, the absorbance ratioof base peak to acid peak tended to increase in proportion to the increase in pH. Experimental results indicate that the neutral red is a good pH indicator for fabrication of a sensing part of the fiber-optic pH sensor.