Study On Chirality Transfer Of Organic Laser Dyes Based On Distyrylbenzene Skeleton

In recent years,with the research of organic lasers,organic circularly polarized lasers combined organic lasers with circularly polarized emission have become one of the current research hotspots because of their good application prospects in the fields of 3D display,optical communication and study on chiral light-matter interaction.However,organic laser dyes are often difficult to achieve high fluorescence quantum yield and high luminescence asymmetry factor at the same time,which hinders their application as organic circularly polarized laser materials.Due to its high fluorescence quantum yield and amplified spontaneous emission（ASE）behavior,distyrylbenzene（DSB）derivatives have attracted extensive attention in the research of organic micro/nanoscale lasers.Therefore,in this paper,a series of organic fluorescent dye molecules were designed and synthesized with organic laser dye DSB as the molecular skeleton.Using the organic laser dye DSB derivatives with high fluorescence quantum yield,strategies of chirality transfer were designed to realize circularly polarized luminescence with high asymmetry factor,so as to explore its possibility as organic circularly polarized luminescence materials.The specific research contents of this paper included:1.A series of DSB derivative molecules with different substituents were designed and synthesized to prepare micro/nanocrystals and study their optical properties.By introducing different substituents,the solid-state fluorescent emission wavelengths of dye molecules were regulated.Combined with the single crystal data and the characterization of basic photophysical properties,the influence of solid-state molecular stacking modes on optical properties was studied,which provides guidance for the design of laser dye molecules with full-color wavelength and high fluorescence quantum yield.The one-dimensional and two-dimensional micro/nanocrystals samples of the synthesized molecules were prepared by solvent diffusion method and micro-spacing sublimation method.It was found that the edges of these micro/nanocrystals had bright fluorescent emission and good optical waveguide effect.In the micro-spacing sublimation method,micro/nanocrystals with different emission wavelengths were obtained by adjusting the sublimation temperature.It is first reported that the sublimation temperature was used to tuned the emission wavelength of the crystals.2.Protonation of achiral DSB molecules and chiral molecules was used to realize chirality transfer and obtain chiral organic micro/nano structures.DSB derivatives with pyridine unit were designed and synthesized.They were protonated with chiral sulfonic acid in ultrasonic condition.Chiral pyridine sulfonate crystals with red shift of solid emission wavelength were obtained by adjusting the reactant concentration and ultrasonic time.After the achiral DSB derivatives were protonated with chiral acid to form ionic salts,the realization of chiral transfer in ionic salts was verified by characterization of circular dichroism spectroscopy.3.Using fluorescence resonance energy transfer（FRET）co-assembled system to realize chiral transfer,organic circularly polarized luminescence materials with high asymmetry factor were constructed.The green emitting DSB derivative OC5introduced into the chiral cholesteric side chains was used as the donor,the red emitting molecule DSB derivative M-BT with methyl group was used as the short alkyl chain acceptor,and H-BT,the DSB derivative with n-hexyl group,was used as the long alkyl chain acceptor,we obtained co-assembled films with different doping ratios by heating.The ultrafast dynamics of the OC5 film and its doped co-assembled films were characterized by femtosecond transient absorption spectroscopy,which helps to further study the excited states of FRET process in solid phase and to learn the dynamic process involved in energy transfer.Through the characterization of circular dichroism and circularly polarized luminescence spectra,chiral optical properties and chirality transfer mechanism in self-assembly and co-assembly systems of the OC5 film and co-assembled films were studied.Experiments show that chirality amplification was realized by self-assembly.And in co-assembly systems,the chirality transfer,amplification and inversion from chiral donor to achiral acceptor were realized,and the circularly polarized luminescence with the maximum luminescence asymmetry factor of 10^-1 was achieved.Moreover,the handedness of circularly polarized luminescence were regulated by adjusting the length of alkyl chain of achiral acceptor in the co-assembly system for the first time,which provided a design reference for organic circularly polarized luminescence materials.