Napthalenediimide derivatives have shown vast applications in the area of chemical sensors for anions due to their special optical and electrical properties. In the current work, NDI derivative having phenyl amine end group (PPD-NDI) has been synthesized by easy and environment friendly methods and tested for sensitivity towards trifluoroacetic acid (TFA), hydrochloric acid (HCl), nitric acid (HNO₃) and sulfuric acid (H₂SO₄) for 1 -65 mMconcen-trations. PPD-NDI shows this special behaviour in the form of a charge transfer band in the range of 500-600 nm in absorption spectra along with color change in the presence of acid. To understand the mechanism of sensitivity, an exclusion method has been applied by analyzing other reference NDI molecules with different end groups and linkers. PPD-NDI shows selective sensitivity for TFA present in low concentration (1 mM) and HCl at all other concentrations. The sensitivity of NDI derivatives can be very helpful in detection of acids in various industrial effluents from cloth, paper, refineries and in smelting industries. We have demonstrated the reversible lab-on paper strip testing experiment for detection of HCl acid by naked eye in low and high concentrations without need of any excitation light source.

Acid Sensor, NDI, Visible Sensor, Lab-on-paper Strip