A new polythiophene derivative-based fluorescent sensor for Co2+, Cu2+, Cd2+, and its complex with Cu2+ for sensing homocysteine and glutathione

Abstract

A new polythiophene derivative poly{3-[2-(2-dimethylamino-ethylamino)ethoxy]-4-methyl-thiophene} (PTMA), carrying well defined tridentate N/O-containing ligand, was prepared and its function as fluorescent sensor for heavy metal ions and amino acids in aqueous solutions was evaluated. A dramatically fluorescence decrease of the polymer by the addition of Co2+, Cu2+ and Cd2+ was observed in MeCN/Tris–HCl solution. Particularly, Cd2+ induced a marked bathochromic shift on the maximum absorption of PTMA solution from 420nm to 472nm, which was helpful to differentiate Cd2+ from Co2+ and Cu2+. In addition, the optimized sensor exhibited an excellent selectivity toward Cu2+ in THF/Tris–HCl solution with a fluorescence “turn off” mode. By employing this two solutions, Co2+, Cu2+ and Cd2+ were recognized and distinguished successfully from each other with detection limit of 2.5, 2.0 and 83nM, respectively. Subsequent research revealed that the Cu2+-quenched fluorescence in THF/Tris–HCl solution could be recovered by homocysteine (HCy) and glutathione (GSH) with fluorescence enhancement of 11.5 and 7.7 fold, providing a turn-on fluorescence sensor for neutral amino acids. What is more, Cd2+, Cu2+, Co2+ and amino acids were detectable by naked eyes through evident color changes ether with UV-irradiation or under sunlight.