Selective Fluorescence Quenching in Cationic Fluorene-Thiophene Diblock Copolymers for Ratiometric Sensing of Anions

• Published in: Macromolecular rapid communications. 2013-05, Vol.34 (9), p.717-722
• Main Authors: Fonseca, Sofia M., Galvão, Rita P., Burrows, Hugh D., Gutacker, Andrea, Scherf, Ullrich, Bazan, Guillermo C.
• Format: Article
• Language: English
• Subjects: anion sensing; Anions; Anions - chemistry; Cationic; cationic conjugated polyelectrolytes; Cations - chemistry; Copolymers; Deoxyribonucleic acid; Detection; diblock copolymers; DNA - chemistry; DNA, Single-Stranded - chemistry; Fluorenes - chemistry; Fluorescence; Halides; Polymers - chemistry; Quenching; ratiometric fluorescence sensing; sensors; Surface-Active Agents - chemistry; Thiophenes - chemistry
• ISSN: 1022-1336; 1521-3927
• DOI: 10.1002/marc.201200734

The cationic, all‐conjugated AB diblock copolymer poly[9,9‐bis(2‐ethylhexyl)fluorene]‐b‐poly[3‐(6‐trimethylammoniumhexyl) thiophene] bromide (PF2/6‐b‐P3TMAHT) shows dual fluorescence from the poly(fluorene) (PF) and poly(thiophene) (PT) blocks. A comparison of fluorescence quenching of the cationic PT block fluorescence with unquenched PF block provides a sensitive ratiometric method for anion sensing. The application to analysis of halide ions, single‐ and double‐stranded DNA is demonstrated. High selectivity is observed with halide ions, with the strongest quenching being seen with iodide. The quenching with DNA can be used for nucleic acid quantification at sub‐μM concentrations. Selective quenching of the cationic polythiophene block fluorescence in the cationic, all conjugated diblock copolymer poly[9,9‐bis(2 ethylhexyl)fluorene]‐b‐poly[3‐(6‐trimethylammoniumhexyl) thiophene] bromide provides a sensitive ratiometric method for anion sensing. This is demonstrated with both halide ions and DNA. Applications to DNA quantification at sub‐micromolar levels are discussed.