Higher Energy Gap Control of Fluorescence in Conjugated Polymers: Turn-On Amplifying Chemosensor for Hydrogen Sulfide

5 years ago

Higher Energy Gap Control of Fluorescence in Conjugated Polymers: Turn-On Amplifying Chemosensor for Hydrogen Sulfide

Chien-Hung Chiang, Evgueni E. Nesterov, Deepa Pangeni

The significance of conjugated polymers for sensing applications stems from the intrinsic amplification of analyte binding events which is related to the efficient excitation energy migration in the polymers. Within the framework of conventional design of amplifying sensory polymers, interaction with an analyte creates a lower energy gap site within the conjugated backbone which acts as a trap for randomly migrating excitons typically producing a fluorescence quenching effect (turn-off sensors). Herein, we describe an alternative “higher energy gap” paradigm, a general design concept surprisingly overlooked so far. Within this paradigm, reaction with an analyte generates a higher energy gap site in the conjugated backbone. This higher energy gap site diminishes exciton migration length and causes pronounced enhancement of the polymer fluorescence (turn-on response). This effect benefits from the signal amplification and therefore can be used universally to design a wide range of fluorescent sensors. To demonstrate the practical utility of the “higher energy gap” concept, we used it to develop an efficient turn-on amplifying fluorescent sensor for hydrogen sulfide—an important industrial and biomedical analytical target. From a fundamental standpoint, the “higher energy gap” paradigm demonstrates the importance of the through-bond (Dexter-type) mechanism for intramolecular energy transfer in conjugated polymers—still a widely debatable issue.

Publisher URL: http://dx.doi.org/10.1021/acs.macromol.7b01706

DOI: 10.1021/acs.macromol.7b01706