Design, Synthesis And Performance Study Of Fluorescence Sensor Based On Aggregation Induced Luminescence Effect

Recently, development of fluorescent sensors with high sensitivity and selectivity has attracted wide spread interest. But most of traditionl fluorescent luminogens show "aggregation-induced quenching (ACQ)" effect due to the strong ?-? stacking interactions in the aggregated state, which largely limited their applications in many fields. With the discovery of "aggregation-induced emission" (AIE), the drawback of traditional chromophore was overcome, at the same time, the development of AIE also opened up a new field for fluorescent sensors. In this paper, we designed and synthesized two AIE-active tetraphenylethene (TPE) derivatives to detect mercury ion (?) and homocysteine (Hey):(1) We synthesised a new fluorescent sensor, TPE-Py-Ad, for Hg2+ recognition by introducing adenine in cationic AIE molecule. TPE-Py-Ad exhibited weak emission in DMSO-H2O (1:4, v/v). However, after addition of mercury ion (?), the emission intensity increased sharply. In contrast, the emission spectrum displays negligible influence for other metal ions. Combining the results of 1H NMR titration and SEM images, the excellent sensing behavir of TPE-Py-Ad for Hg2+ is attributed to the ideal coordination between TPE-Py-Ad and Hg2+, which generates aggregate and thus activates the AIE effect of TPE-Py-Ad. We further studied the TPE-Py-Ad for Hg2+ detection in living cells. The experiments results demonstrated that TPE-Py-Ad can target the mitochondria of living cells and its fluorescence can be enhaced in the case of Hg2+, demostrating TPE-Py-Ad can serve as a promsing mitochondria-targeted AIE probe for Hg2+(2) We herein report a new AIE fluorescent sensor for Hey detection by combining ?,?-unsaturated ketone unit with TPE unit. Biothiols can react with ?,?-unsaturated ketone unit through the 1,4-addition reaction route, which results in the disruption of molecular conjugation and thus leads to the change of its fluorescence. Upon addition of Hey, the yellow emission of TPE-Py is switched to blue. However, in the presence of Cys or GSH, the yellow emission of TPE-Py is quenched without the appearance of blue emission. It enables TPE-Py to serve as a highly selective probe for distinguishing Hey over Cys and GSH. Hey is more hydrophobic than Cys and GSH, we hypothesized that the adduct product of TPE-Py and Hey thus possesses poor solubility and forms aggregates in detection media to leads to the intense blue emission for the adduct product of TPE-Py and Hcy. NMR and mass spectra analysis suggests that the biothiols can react with TPE-Py based on the 1,4-addition reaction.