Polythiophene based fluorescence sensors for acids and metal ions

Poly(thiophene-3-yl-acetic acid 8-quinolinyl ester) is a fluorescent material and it shows fluorescence at 540 nm. The fluorescence of poly (thiophene-3-yl-acetic acid 8-quinolinyl ester) has been studied in the presence of acids, metal ions, nucleotides and protein (l-proline). The fluorescence of polymer is quenched by the addition of HCl which could be recovered by the addition of equivalent amount of alkali. The Stern–Volmer quenching coefficient for HCl is calculated and found to be 141 M−1. Moreover quenching depends on concentration of HCl. Similarly, the fluorescence of polymer is quenched by copper, cadmium and lead metal ions and quenching is sensitive to concentrations of metal ions. The Stern–Volmer quenching coefficient is 2.285 × 103 M−1 for Cu2+ ions, 2.287 × 103 M−1 for Cd2+ ions and 3.7 × 104 M−1 for Pb2+ ions. In Al3+, Zn2+, nucleotides and protein (l-proline), the fluorescence is exorbitantly increased.