α‐Al₂O₃/Organo‐Modified Silica pH Sensing Film with High Alkali Resistance and Sensitivity

Abstract

In order to develop a stable and sensitive layer for optical pH sensors which can be used in a wide pH range with long service life, we prepared an α-Al 2 O 3 /organo-modified silica pH composite sensing film by a sol-gel method with thymol blue as the indicator and α-Al 2 O 3 as the nano-reinforced filler. The α-Al 2 O 3 nanoparticles enable the pH sensing film to test solutions in the pH range of 1-12, with good reversibility, sensitivity and excellent resistance to strong acids and bases. Its alkaline resistance at pH = 12 is far superior to its silica counterparts, and it can remain stable for over 22 days at pH = 12. This study provides theoretical and experimental support for improving the acid and alkaline resistance of the silica gels. The α-Al 2 O 3 / organo modified pH sensing film is expected to provide stable pH testing in strongly alkaline environment (pH = 12) and have wide application prospects.