Thermally activated delayed fluorescence fluorescent probe based on triazine as emission core for metal ions detection

A novel thermally activated delayed fluorescence (TADF) sensor PhTRZ-CzOCHO was designed and synthesized with triazine ring as the receptor and carbazole as the donor group. Low temperature dependent photoluminescence spectra shows that PhTRZ-CzOCHO has a small singlet and triplet energy splitting (ΔEST = 0.25 eV), which ensures the efficient reverse intersystem crossing. The intensity of the fluorescence was three times higher after removing oxygen, which also proves the triplet involved TADF process. The photoluminescence quantum yield (PLQY) of PhTRZ-CzOCHO was calculated to be 58%. The delayed fluorescence lifetime of the probe was 0.32 μs. Moreover, the fluorescence titration measurement demonstrates that this TADF probe can recognize most of metal ions due to its strong complexing ability of aldehyde group. The detection limitation of Na+, Mg2+ and Fe3+were calculated to be 7.03 × 10−7 mol/L, 6.7 × 10−7 mol/L and 5.9 × 10−8 mol/L, respectively. To the best of our knowledge, this is the first report of TADF probe to test most of metal ions, which may have potential implications for environmental and biological monitoring.