In recent years, aggregation-induced emission enhancement (AIEE) molecules have shown great potential for applications in the fields of bio-detection, imaging, optoelectronic devices, and chemical sensing. Based on our previous studies, we investigated the fluorescence properties of six flavonoids and confirmed that compounds1–3have good aggregation-induced emission enhancement (AIEE) properties through a series of spectroscopic experiments. Compounds with AIEE properties have addressed the limitation imposed by the aggregation-caused quenching (ACQ) of classic organic dyes owing to their strong fluorescence emission and high quantum yield. Based on their excellent fluorescence properties, we evaluated their performance in the cell and we found that they could label mitochondria specifically by comparing their Pearson correlation coefficients (R) with Mito Tracker Red and Lyso-Tracker Red. This suggests their future application in mitochondrial imaging. Furthermore, studies of uptake and distribution characterization in 48 hpf zebrafish larvae revealed their potential for monitoring real-time drug behavior. The uptake of compounds by larvae varies significantly across different time cycles (between uptake and utilization in the tissue). This observation has important implications for the development of visualization techniques for pharmacokinetic processes and can enable real-time feedback. More interestingly, according to the data presented, tested compounds aggregated in the liver and intestine of 168 hpf larvae. This finding suggests that they could potentially be used for monitoring and diagnosing liver and intestinal diseases.Keywords:AIEE;flavones;mitochondria;zebrafish;uptake;distribution
The excited-state intramolecular proton transfer (ESPT intra ) process in flavonoids has attracted considerable attention due to its fundamental role in their photophysics. This study systematically investigates the photophysical properties of 5-methoxyflavone (5MF), a flavonoid derivative incapable of ESPT intra . It was demonstrated that intermolecular hydrogen bonding with protic solvents effectively suppress the non-radiative ππ∗-nπ∗ internal conversion in 5MF, leading to significant fluorescence enhancement. In highly acidic aqueous solutions (pH < 3.3), an excited-state intermolecular proton transfer (ESPT inter ) process takes place, generating protonated 5MF (5MFH + ) and resulting in fluorescence quenching. Notably, when incorporated in acidic poly(vinyl alcohol) (PVA) films, the excited-state protonated species 5MFH + exhibits intense fluorescence with a long fluorescence lifetime of 8.4 ns, owing to the suppression of non-radiative decay pathways by the rigid polymer network. Additionally, the dense hydroxyl groups in the PVA matrix also enhance the emission of neutral 5MF. These results highlight the potential of both 5MF and 5MFH + as efficient luminescent chromophores for the design of optical materials based on hydrogen-bonding polymer systems.
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