Helical tube triggered two-stage emission behavior for tetraphenylethene-functionalised hemicyanine dye: Better dispersion stronger fluorescence

ABSTRACT: Aggregation-induced emission (AIE) luminogens have recently received great attention for their wide applications in chemical sensors and biological probes. However, it remains a formidable challenge to render them multi-stage emission in one system. Herein, the emission of a tetraphenylethene (TPE)-functionalised hemicyanine dye (TPEBe-I) is awoken using a poly(m-phenylene diethynylene)-based helical tube (Poly-1) in aqueous buffer solution, although TPEBe-I alone shows an aggregation-caused quenching (ACQ) phenomenon due to the heavy atom effect of iodide. Upon increasing Poly-1, the dyes first dock on Poly-1 surface to form an aggregation complex via electrostatic interaction, and then intercalate into the tubular cavities of Poly-1 with a confined space in the single-molecular form. As the increase of Poly-1, the restriction of intramolecular motions of dyes changes from partial to sufficient, leading to an unusual AIE phenomenon of better dispersion stronger fluorescence. At last, the fluorescence intensity is enhanced by 160-fold. As a result, a two-stage emission behavior in a single system is achieved.