Coupling of chromophores with exactly opposite luminescence behaviours in mesostructured organosilicas for high-efficiency multicolour emission

Abstract

Aggregation-induced emission (AIE) and aggregation-caused quenching (ACQ) materials are important for various fluorescence-based applications but cannot easily collaborate because of their opposite luminescence behaviours. Here, we demonstrate a strategy to integrate AIE and ACQ chromophores in periodic mesoporous organosilicas (PMOs) for high-efficiency multicolour emission. Tetraphenylethene (TPE)-bridged AIE-PMOs are prepared as hosts to encapsulate ACQ dyes (e.g. RhB), which enables fine-tuning of ACQ@AIE-PMO emissions over the entire visible spectrum in the solid and film states. Significantly, high-quality white light is achieved with CIE coordinates of (0.32, 0.33) and a quantum yield of up to 49.6%. Because of their high stability and solution processability, the ACQ@AIE-PMOs can be applied in solid-state lighting and bioimaging. This design concept opens up new perspectives for developing high-performance luminescent materials by the combination of a wide variety of AIE and ACQ chromophores.

Fig. 1. Schematic illustration of the construction of ACQ@AIE-PMO with tuneable multicolour emission. AIE-PMO nanospheres are prepared by using AIE-active TPE-Si as a precursor, where TPE units are covalently embedded within the framework forming the pore walls; ACQ molecules (such as RhB) are then encapsulated in the mesoporous channels of the AIE-PMO; tuneable multicolour emission of PMO is achieved on the basis of FRET from the AIE-PMO donor to the ACQ acceptor. Note that the TPE-Si precursor is nonemissive in solution but luminesces intensively upon molecular aggregation, while RhB dye is emissive in solution but suffers from aggregation-caused fluorescence quenching.

Fig. 2. (a) Powder XRD patterns of mesostructured AIE-PMOs. (b) SEM image of AIE-PMO3. (c) N₂ adsorption–desorption isotherms of AIE-PMOs and their corresponding pore size distributions. (d) TEM image of AIE-PMO3.

Fig. 3. (a) Fluorescence spectra of AIE-PMOs in the solid state. (b) Fluorescence spectra of RhB@AIE-PMO2 powders with different RhB contents. (c) Corresponding emission colours of RhB@AIE-PMO2 powders (marked by the dots) in the CIE 1931 chromaticity diagram. (d) Fluorescence decay profiles of RhB@AIE-PMO2 with different RhB contents at λ_ex = 365 nm and λ_em = 480 nm.

Fig. 4. (Left) Bright-field and (right) fluorescent images of HeLa cells after incubation with RhB@AIE-PMO2 with different RhB concentrations: (a and b) 0 mol%, (c and d) 0.36 mol%, and (e and f) 1.71 mol%.

Fig. 5. (a) Fluorescence spectra of RhB@AIE-PMO films with different RhB content. (b) Corresponding emission colours of the films (marked by the dots) in the CIE 1931 chromaticity diagram. (c) PMO composite films coated on 10 × 10 cm glass under sunlight (left), blue film on 10 × 10 cm glass (middle) and white-light film on 5 × 5 cm quartz (right) under 365 nm UV irradiation.