Two dimensional restriction-induced luminescence of tetraphenyl ethylene within the layered double hydroxide ultrathin films and its fluorescence resonance energy transfer

Neutral poly(vinyl carbazole) (PVK) and tetraphenylethylene (TPE) molecules were assembled within the interlayers of layered double hydroxide (LDH) nanosheets to form (TPE@PVK/LDH)(n) ultrathin films (UTFs) by the hydrogen-bonding layer by layer assembly method. These UTFs exhibit well defined blue luminescence of TPE, which implies that the intercalation anchoring of aggregation induced emission (AIE)-type chromophores to the rigid LDH matrix can serve as an alternative mechanism for restricting the rotation of the phenyl rings of TPE. The concentration-fluorescence relationship study implied that the AIE effect of intercalated TPE can be regarded as the 2D restriction-induced photoemission (RIE) effect within the interlayers. Moreover, the 2D Forster/fluorescence resonance energy transfer (FRET) process between PVK and TPE was realized within these UTFs, by which the UTFs exhibit reversible two-state switching of fluorescence emission (violet vs. blue) with the free/restriction states of TPE triggered by the external stimuli (e. g. volatile organic compound (VOC) vapors). Therefore, this 2D assembly of UTFs worked not only as the 2D RIE environment for TPE molecules, but also as a FRET 2D protocol for fluorescence sensing applications.