Hybrid Locally-excited And Charge-Transfer Blue-emissive Materials And Their Applications In Electro-fluorescence Device And Chemical Warfare Agents Detections

Numerous methods such as the triplet-Triplet Annihilation（TTA）,the thermally-Activated Delayed Fluorescence（TADF）and the hybrid locally-excited and charge-transfer（HLCT）are raised to solve the problem of electro-triplet excitons utilization caused by spin-statistic limit in OLED.Among the above strategies,the HLCT method can simultaneously realize highly efficient photoluminescence and exceeding utilization of electro-excitons,owing to the hybridization of emissive locally-excited（LE）excited state component and triplet-exciton-utilizable charge-transfer（CT）excited state component.Just as such,the HLCT method is especially proper for the molecular design of the relatively scarce blue-emissive materials,because that besides the low efficiency caused by the separated excited state hole and electron wavefunctions,balanced hybridization of LE and CT excited state components can effectively suppress the spectral red-shifting and broadening that are originated from pure CT excited state.More importantly,specific external stimuli can cause the phenomenon of"dehybridization"of HLCT materials,that is,the state-hybridization of LE and CT excited states are broken and then lead to the change of fluorescence phenomenon,so as to realize the fluorescence detection of specific substances,such as Chemical warfare agents（CWAs）.In recent decades,chemical warfare agents are seriously threatening public security and even international security.On-site detection has always been a tough question for the traditional detection method of CWAs such as mass spectroscopy,however,this problem could be solved by applying HLCT materials to the detection of CWAs.The last but not the least,the de-hybridization fluorescence detection mechanism is different from other classical detection mechanisms which rely on a newly generated energy trap state to cause fluorescence quenching,the HLCT molecular probe is a reasonable construction of excited state in nature,and is of many advantages such as higher sensitivity and better selectivity.In this dissertation,we focus on constructing HLCT excited state for the high efficiency blue-emissive fluorescence materials.By using triazole as acceptor and triphenylamine as donor,we designed and synthesized a series of D-A molecules with varying degrees of hybridization,and carried out the theoretical and experimental studies on the relationship between structure and photophysical properties,electroluminescence performance and sensing performance of CWAs analogues.The main contents and conclusions of the dissertation are summarized as follows:（1）We have synthesized a weakly-coupled HLCT molecule（TPA-2CNTAZ）and three strongly-coupled HLCT molecules（TPA-HTAZ,TPA-BTAZ and TPA-CNTAZ）.According to the evaluating of electroluminescent performance of doped devices between two HLCT molecules,on the whole,weakly-coupled HLCT molecules are more likely to deep blue-emissive,but in terms of efficiency and exciton utilization,the better coupled molecules are superior to this weakly-coupled molecule.（2）In the detection process of four fluorescent probes for CWAs analogues,the state-of-the-art ultra-low detection limit(LOD _TPA-HTAZ=0.25 ppb)has been achieved,the response time is less than 2 seconds,and it has good recovery and anti-interference ability,which reflects the advantages of HLCT materials in fluorescence detection.（3）In terms of the molecular construction of the“vertical type”quasi-equivalent HLCT molecules,both TPA-HTAZ and TPA-CNTAZ are based on TPA-BTAZ,and increase the proportion of CT components by changing the twist angle and adding the receptor in the vertical direction,which provides a new structural design idea for reasonably introducing CT components into the excited state.