High efficiency branched thermal activated delayed fluorescent probe based on cyanogroup for detecting Fe3+ with low limit of detection

A multipolarization branched thermal activated delayed fluorescence sensor BrACCN was designed and synthesized based on cyano-carbazole. The classical molecule structure 4CzCN was used as luminescent nucleus, which was progressively branched for photophysical optimization. On the basis of the thermal activated delayed fluorescence material 4CzCN and 4Cz-CzCN , the molecular modification was optimized to achieve long fluorescence life and high quantum yield . Through research and analysis, the fluorescence quantum yield of the branched probe was 73%, which was 1.5 times higher than that of unbranched 4CzCN . The fluorescence lifetime of the probe BrACCN was doubled up to 3 μs based on the introduction of peripheral Br atoms. Meanwhile, the probe has high selectivity and sensitivity for Fe 3+ ions. In the presence of multiple ions, the probe responded only to Fe 3+ with a complexing mode of 1:1 and the fluorescence was turned off. The probe has a low limit of detection (LOD) of 2.9 × 10 −8 mol/L for Fe 3+ ions. The probe also has a strong AIE characteristic, which is extremely beneficial for the application range of the probe. Moreover, these excellent properties of the probe will offer promising applications in live-cell confocal fluorescence imaging and time-resolved fluorescence imaging. • The PLQY of the encapsulated probe BrACCN is 1.5 times higher than that of unencapsulated. • The optimized TADF molecule structure has a longer fluorescence lifetime up to 3 μs. • The TADF probe can quickly recognize Fe 3+ with a response time of 2 s. • The TADF probe has been proved to be used for detection of domestic drinking water.