Chemical Structure Effect And Ion Recognition Of Self Aggregation Of Conjugated Dyes

In the process of self aggregation of organic dyes,due to their excellent fluorescence properties,they have attracted great interests of researchers.For example,light-emitting diodes,optical sensors,aiegens nonlinear optical effect nanocrystals for ultra deep in vivo imaging,catalysis and so on.Anions or cations are introduced into aggregation induced fluorescence enhanced organic dye aggregates.Based on the influence of ions on their fluorescence phenomena,they are used as a new fluorescence probes for the imaging analysis of environment related bioactive molecules.Through the analysis of the distribution,transport,change and interaction rules of various active species in cells,tissues and living bodies,the relationship between environment and health.In this thesis,MEH 1～MEH 8 dyes have been invesitgated.In order to further study the effect of hydrogen bond on the aggregation induced fluorescence enhancement（AIEE）,we selected the compounds THY 1～THY 4 including naphthyl and stilbene groups,which is the fragment structure of MEH 1～MEH 8,and its aggregation state was studied.In addition,the influence of specific ions on the fluorescence phenomenon was further explored.（1）The target compounds MEH 1～MEH 8 was added into the mixed system of DMF and H₂O to adjust the mixing ratios of two solvents.After standing for a period of time,under the irradiation of 365 nm ultraviolet lamp,the mixed solution presented obvious blue fluorescence.The concentration of water with the highest fluorescence intensity was selected,and the aggregation process at different time intervals was studied.Through the analysis of ultraviolet absorption spectrum and fluorescence emission spectrum,it was found that these dyes could produce aggregation induced fluorescence enhancement（AIEE）in the mixed system of DMF/H₂O,and the fluorescence intensity gradually increased with the extension of time,and reached a stable state at 12h.Due to the intermolecular interaction（such asπ-π,H-bond）,J-type organic aggregates are formed,which limits the free rotation（RIR）of intramolecular groups and inhibits the formation of non radiation channels.In addition,the morphology and size of the target compound aggregates were characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）and dynamic light scattering（DLS）.The results show that the morphology and size of the aggregates show great difference.（2）For the reference molecules MEH 2,MEH 4,MEH 6 and MEH 8,which also have similar branching spatial structures to MEH 1,MEH 3,MEH 5 and MEH 7,the enhanced fluorescence intensity during aggregation is lower than that of the compounds MEH1,MEH3,MEH5 and MEH7 due to lack of hydrogen bond,However,aggregation induced fluorescence enhancement（AIEE）still occurs.It can be concluded that intermolecular/intramolecular hydrogen bonds play an important role in the formation of aggregates.（3）By the same method and characterization,it was observed that only the mixture of compounds THY 3 produced blue fluorescence,while compounds THY 1,THY 2and THY 4 did not exhibit aggregation induced fluorescence enhancement（AIEE）.Even if there is no AIEE occurred,molecular aggregates can still be generated,which may be caused by the sharp change of polarity of mixed solvents,and theπ-πinteraction between molecules.Owing to strong electron-donating nature of N,N-dimethyl group,THY3 can present AIEE properties.（4）The recognition effect of MEH 5～MEH 8 on various metal ions was discussed.The results showed that the target compounds MEH 5～MEH 8 had a good recognition effect on Fe³⁺ions.The coordination ratio and binding constant of MEH 5～MEH 8 and Fe³⁺were obtained by job’splot method and equation X-ray photoelectron spectroscopy（XPS）showed that Fe³⁺formed a stable complex with MEH 5～MEH 8.Because the N element in MEH 5～MEH 8 contained lone pair electrons,and the 4S orbital of Fe was coordinated,the distance between MEH 5～MEH 8 molecules in DMF system was affected,and then the aggregation state was affected.