Search

pH values play an important role in various cell biological processes. Abnormal pH values in living systems are frequently associated with the development of diseases such as cancers, infection, and other diseases. Real-time monitoring of the changes of pH values in vivo will give us the significant indication for these diseases' progression. Within those pH-sensitive imaging probes, aggregation-induced emission (AIE) molecules exhibit great potential in aqueous imaging environment due to their high fluorescence quantum yield and stability. However, the modulation of the AIE probe with pH sensitivity and light-up property face challenges. Here, we introduced a new glycopeptide-modified AIE probe ( TGO ) based on the optimized solid-phase peptide synthesis approach. The response to pH of the peptide: DDDD progression changed hydrophobicity and hydrophilicity, resulting in the change of the amphipathicity balance. When modulating the pH from 5.5 to 8.0, the adverse protonation of the peptide induced assembled nanostructure transformation from nanolamellae to nanomicelles. Meanwhile, the pH-induced charge change in peptides can greatly influence the microenvironment of the AIEgen, resulting in the increase of fluorescence intensity.

The propeller-like conformation of tetraphenylethylene (TPE) with aggregation-induced emission (AIE) effect was partially and completely fixed by intramolecular cyclization for the first time. The immobilization of propeller-like conformation was found to show great advantages in determining the enantiomer purity, identifying the chiral amines. The completely fixed conformers are resolved into M- and P-enantiomer, which showed mirror imaged CD and almost quantitative fluorescence quantum yield. Furthermore, it also showed a mirror and large circularly polarized luminescence dissymmetric factor, depending on the helicity of the enantiomer. The result provides the most direct and persuasive evidence for AIE via the restriction of intramolecular rotation and finds the new insight of the compounds in chiroptical property.

A neutral chiral receptor based on TPE cyclohexylbisurea was synthesized and could discriminate the enantiomers of many different kinds of chiral reagents, including chiral acidic compounds, basic compounds, amino acids, and even neutral alcohols. The (1)H NMR spectra disclosed that the ability of chiral recognition could be ascribed to the multiple hydrogen bonds and CH-π interactions between the TPE urea receptor and the enantiomer of the chiral guest, which led to the selective aggregation of the receptor with one of the two enantiomers. This result exhibited a great potential in enantiomer discernment and high-throughput analysis of enantiomer composition of these chiral analytes by one chiral AIE molecule.

New chiral tetraphenylethylene (TPE) macrocycles bearing optically pure amine groups were synthesized and found to have a discriminating ability between the two enantiomers of not only chiral acidic compounds but also α-amino acids by enantioselective aggregation and aggregation-induced emission (AIE) effects. NMR spectra, including 2D-NOESY, disclosed that the host-guest interaction of the macrocycle receptor played a key role in addition to the acid-base interactions.

The identification of explosives is critical for analyzing the background of terrorism activities and the origin of pollution aroused by the explosives, but it is a challenge to discriminate the explosives with a very similar structure. Herein we report a series of TPE-based macrocycles with an AIE effect for the 0.2-4 ppb level detection of TNT among a number of nitro-aromatic compounds through fluorescence quenching in natural water sources, whereas the contact mode approach using portable paper sensors exhibited a high sensitivity for the detection of TNT at 1.0 × 10(-13) M level. The reliability of the quantitative analysis has been confirmed by HPLC. Our findings demonstrate that the TPE-based macrocycles have great potential as excellent sensors for TNT. Moreover, it was found for the first time that the macrocycles could selectively recognize nitroaromatics explosives bearing methyl group through a CH3-π interactions, and even exhibit a sole selectivity for TNT among the very difficultly differentiating nitroaromatics including trinitrophenol and trinitrobenzene.

A novel imidazolium macrocycle based on bridged tetraphenylethylene (TPE) was synthesized. Because it bears the bridged TPE units, this macrocycle not only displays an aggregation-induced emission (AIE) effect but also exhibits monomer emission, which is very rare in AIE compounds. With aggregation of the macrocycle, the aggregate emission increases while the monomer emission decreases. It was found that this imidazolium macrocycle can form a stable 2:1 complex with C60, which gives rise to quenching of both the aggregate emission and the monomer emission. Unexpectedly, the aggregate emission exhibited a higher quenching efficiency than the monomer emission, probably because one adsorbed C60 molecule could affect more macrocycle molecules in the aggregate.

It was found for the first time that neutral amphiphilc tetraphenylethylene (TPE) derivatives showed an enhanced monomer emission and a decreased aggregate emission when they were included in the cavity of γ-cyclodextrin. This result provided a new insight into the aggregation-induced emission (AIE) effect.