Positive Encapsulation-Induced Emission Control of Aggregation-Induced Emission-Active Anthracenes within Micellar Capsules in Water

Abstract

Whereas aggregation-induced emission (AIE) is a useful tool to develop photofunctional host systems, its guest usability has been largely unexplored within well-defined host compounds so far, mainly owing to the absence of suitable cavities. Here we report the emission control of AIE-active anthracenes upon efficient encapsulation by a terpene-based micellar capsule in 100% water. Encapsulation of monopiperidyl-substituted anthracenes yields a well-defined host-guest composite, with an average diameter of ∼3 nm, displaying green emission with high quantum yield (Φ_F = 53%). The yield is >50 and >10-fold higher than those of the AIE-dye in tetrahydrofuran (THF) and H₂O/THF suspension (Φ_F = 1 and 4%), respectively. This encapsulation-induced emission (EIE) is altered by changing the substituent number/shape on the aromatic framework, leading to up to Φ_F = 65%. Co-encapsulation of the AIE-anthracenes with aggregation-caused quenching (ACQ) dyes (i.e., rubrene) enables strong yellow emission (up to Φ_F = 55%) through high guest-to-guest Förster Resonance Energy Transfer (FRET) and antenna effect (up to 80% and 25, respectively) in the cavity. Furthermore, this strategy realizes strong pure-white emission (Φ_F = 36%; CIE of (0.33, 0.33)) using other AIE-active molecules in water. The photofunctions of AIE-molecules can thus be largely expanded by the present capsule.

Keywords

AIE-active anthracene / co-encapsulation / encapsulation-induced emission / micellar capsule / substituent effect

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