Photoluminescence Nanoarchitectonics Regulated by Aggregation-Induced Emission and FRET in Aggregates and Langmuir–Blodgett Films of Tetraphenylethylene Derivatives

Photoluminescence regulated by the Förster resonance energy transfer (FRET) process attracts much attention for the development of novel luminescent materials and devices. Here, an efficient FRET system has been designed and constructed with the use of aggregation-induced emission (AIE) units as the energy donor and sulforhodamine B (SRB) as the acceptor in the aggregates, mixed solid powders, and Langmuir-Blodgett (LB) films. Two amphiphilic tetraphenylethene derivatives with octyl chains (C₈TPEs) are synthesized and used as AIEgens, which can form well-organized mixed monolayers with arachidic acid (AA) on the SRB subphase surfaces. Efficient photoinduced energy transfer is observed from AIEgens to SRB in the C₈TPE/SRB powders and C₈TPE-AA/SRB hybrid LB films, with the luminescent colors changing from green through yellow to orange. The differences in their FRET behaviors are interpreted in terms of the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gaps, absorption spectra, and intramolecular charge transfer characteristics by time-dependent density functional theory calculations. It is further revealed that by controlling the SRB concentrations in the subphase, the luminescent emission wavelength for the C₈TPE-AA/SRB hybrid LB films shifts from 490 to 592 nm, that is, from typical AIE to SRB emission. Therefore, this work provides a viable strategy for developing solid-state FRET systems by combining AIEgens' donor with aggregation-caused quenching type acceptors, highlighting their potential in optoelectronic and sensing applications.