Alkaline range pH sensor based on chitosan hydrogel: A novel approach to pH sensing.

Monitoring of pH under extreme alkaline range is still a challenge due to the lack of accuracy and validity. This research developed a novel pH sensor (hydrogel/BTB) based on the transition of bromothymol blue from the hydrogel matrix into the pH-examining sample solution. The hydrogel/BTB sensor was synthesized through the solvent casting of chitosan, citric acid as the crosslinker, and bromothymol blue as a pH-sensitive dye.