A cationic porphyrin-based self-assembled film for mercury ion detection

Abstract A cationic 5,15-( p -(9,9-bis(6-trimethylammoniumhexyl)fluorenylethynyl)phenyl)porphyrin tetrabromide was synthesized and the self-assembled films were used for Hg 2+ detection in aqueous media. The detection response is based on fluorescence quenching of the porphyrin molecule upon coordination with Hg 2+ . The detection shows high selectivity for Hg 2+ over Cu 2+ , Zn 2+ , Pb 2+ , Cd 2+ , Mn 2+ , Ni 2+ , Co 2+ and Ca 2+ . A linear response toward Hg 2+ in a concentration range of 1 × 10 −10 –1 × 10 −6  M was observed for the film with a detection limit of 0.1 nM. The cationic porphyrin film shows higher stability and significant improvement in detection sensitivity, as compared to other porphyrin-based sensors. The amphiphilic cationic nature of the porphyrin synthesized also allows for the direct deposition of a porphyrin layer on a bare glass surface through self-assembly.