Applications Of Fluorescent Probes With Amphiphilic Structure In Organized Molecular Assemblies

Molecular assemblies are defined as a kind of stable non-optically active system which isformed by surfactant molecules aggregating in solution. Fluorescent probe technique supplieda method which can detect its physical and chemical processes and give the correspondinginformations on molecular level through determined the photophysical and photochemicalproperties of materials. Fluorescence parameters (e.g. excitation and emission wavelength,fluorescence intensity, fluorescence lifetime, fluorescence anisotropy, etc.) of fluorescenceprobes are depended on the nature of the micro-environments. However, traditionalfluorescence probes can not characterize the microenvironment of the aggregates effectivelyin some systems due to their insolubility in water and uncertainty in location. Therefore, aseries of water-soluble surfactant fluorescent probes which synthesized by connecting afluorophore to a resonable amphiphilic structure can be used to detect microenvironmentinformations of assemblies. Through this modification, this kind of fluorescence probes notonly retains sensitivity of fluorophore to the micro-environment, but reflects the microscopicinformations as a result of its good solubility in water and participation in the process of theformation of aggregates which fixed fluorophore in the position of the aggregates.Based on this consideration above-mentioned, in this dissertation, pyrene was chosen todesign and synthesize a novel surfactant-like cationic surfactant, PSC-DTAB, which exhibitsensitivity for micro-polarity. In addition, photophysical behaviors of novel surfactant-likenon-ionic surfactants labeled with NBD fluorophore,2-NBD-ch,3-NBD-ch and4-NBD-ch,were investgated, and their applications in formation and transition of aggregates were alsoexplored. Main conclusions are listed below:(1) The non-ionic surfactants fluorescent probes labeled with NBD，n-NBD-ch，havecharacterized its typical structure of ICT. Compared with π→π*electronic transition of4-NBD-ch,2-NBD-ch and3-NBD-ch showed significant double fluorescence characteristicsbecause of their π→π*and n→π*electronic transitions.(2) It is found that2-NBD-ch and3-NBD-ch behave polarity-and viscosity-dependence properties like NBD fragment in their structure. It was shown that emission maximawavelength of540nm are red-shifted in different polarity environment and I430/I540valueschanged with polarity in certain environment, REES and fluorescence anisotropy increasedalong with the increase in viscosity, while4-NBD-ch retained part of these properties. Theseeffective microscopic informations of probes can be a basis in the applictions in formationsand transitions of amphiphilic molecular aggregates.(3) It is demonstrated that2-NBD-ch and3-NBD-ch can be used to detect the micelle’sformation of typical anionic, cationic and non-ionic surfactants conveniently by the maximumemission wavelength and I430/I540value.4-NBD-ch, by contrast, could not be measured CMCof classic surfactants due to its low solubility in water.(4) The changes on maximum emission wavelength, fluorescence intensity of maximumemission wavelength, REES and fluorescence anisotropy of2-NBD-ch,3-NBD-ch and4-NBD-ch can all reflect the difference of different organized aggregates efficiently.2-NBD-ch and3-NBD-ch did not exhibit any advantages over4-NBD-ch.(5) Compared with traditional fluorescence probes, such as pyrene and DPH, n-NBD-chfluorescence probe can more effectively reflect the changes in the aggregate, and n-NBD-chmade up for the defect of ionic fluorescent probes, which synthesized in our lab previously,cannot determine cationic surfactant owing to electrostatic interactions.