Development of a pH sensor in range 7–11 using 9H-fluorene and its application in real samples

A Schiff base L was synthesized by condensing through 2-fluorene carboxaldehyde and 2, 4-dinitrophenyl hydrazine in ethanol presence of Conc. H2SO4. The sensor L is demonstrated as a ratiometric sensor for pH sensing. The sensor was found to have an absorbance of 412 nm. When this sensor interacts with OH– ion, a prominent red shift was observed at 510 nm. This change was observed through a color change from yellow to pink. As the sensor responds to the presence of hydroxide ions, it can be used as a pH sensor to sense basicity. This sensor can also be used as in real-sample analysis to test the alkalinity of water sample, the test kit using filter paper was prepared and demonstrated.