The Investigation Of The Properties And Applications Of Amphiphilic Naphthalimide Derivatives

Naphthalimide (NDI) derivatives are important molecular building blocks that are currently being investigated for use in a variety of photoelectric organic materials because of their outstanding ICT electronic structure and desirable photophysical properties, such as high fluorescence quantum yields, large Stokes shift, appropriate absorption and emission wavelength. They have been widely used in solar energy conversion, organic light-emitting diodes (OLEDs), biological inhibitor, biological fluorescent probes, ionic fluorescent probes and so on. In recent years, these dyes have generated more and more attention because of their outstanding luminescence and photophysical properties, and gradually become a research hotspot. Among the investigations on surfactants, self-assemblies are crucial, which make surfactants play important roles in life, information, energy, material, etc.This dissertation focuses on naphthalimide fluorescent dyes and surfactants. The amphiphilic naphthalimide fluorescent dyes were designed and synthesized through the introduction of amphiphilic structures into naphthalimide derivatives. The aggregation behaviors of these amphiphilic dyes in water were investigated. Meanwhile, the optical properties of these amphiphilic dyes were studied and their applications in colloid and surface science were explored. The main work of this thesis includes:In chapter1, the synthesis, basic properties and applications of these naphthalimide derivatives have been reviewed. The knowledge about surfactants and their self-assemble properties were briefly summarized. The research progress of amphiphilic dye was selected as the focus.In chapter2, three naphthalimide fluorescent surfactants comprising hydrophobic alkyl chains of different length at the imide nitrogen ([C8ndi]Ⅰ,[C10ndi]Ⅰ and [C12ndi]Ⅰ) were designed and synthesized. The hydrophilic headgroups of these surfactants are the same, piperazine quaternary ammonium salt. They can self-assemble to form spherical micelles in water and the hydrocarbon chains affects the micelle formation, similar to conventional ionic surfactants. The increase of the hydrocarbon chain is beneficial to the micelle formation, and thus the values of CMC become small. The micelle formation process for [C8ndi]I and [C10ndi]I is enthalpy-driven throughout the whole temperature range investigated. Compared with conventional quaternary ammonium surfactants, naphthalimide fluorescent surfactant has a smaller CMC and higher surface activity, which can be attributed to the strong π-π interactions created by the introduced naphthalimide groups. Due to the incorporation of the fluorescent naphthalimide moiety, the naphthalimide fluorescent surfactants show bright yellow color and present strong fluorescence property. The micellization process and the CMC values of [Cnndi]I can be determined by the absorption and fluorescence spectra when there is no any probe. The obtained results are consistent with the traditional methods and reliable.In chapter3, five naphthalimide-based cationic surfactant dyes (1a,1b,1c,2b and3b) were designed and synthesized for the purpose of detecting the anionic surfactants with both absorbance and fluorescence changes, lb and lc are corresponding to [C8ndi]I and [C12ndi]I described in chapter2while the other three are newly synthesized. The optical properties of these five fluorescent cationic surfactants in water and CH2Cl2were characterized. The absorption and fluorescence spectra are directly related to the hydrocarbon chain length, the distance between positive charge center and chromophore and the position of the positive charge center. The cationic hydrophilic headgroups endow these fluorescent cationic surfactant with a strong electrostatic interaction with anionic surfactant headgroup. Meanwhile, the n-alkyl hydrophobic chains endow these dyes with a comparatively strong hydrophobic interaction with anionic surfactants. These two interactions promote the formation of probe-anionic surfactant complex which seriously affects the optical properties of solution. These fluorescent cationic surfactants have unique selectivity to anionic surfactant and can be used as anionic surfactant probes. lb is demonstrated to be the best probe for anionic surfactant due to its moderate hydrocarbon chain length and proper position of positive charge center. Along with the increase of anionic surfactant concentration (below CMC), the absorbance and fluorescence intensity of probe solution show "on-off-on" change. The detection of anionic surfactants can be realized according to the shifts of maximum absorption and fluorescence peaks and the changes of absorbance and fluorescence quantum yield.1b is useful for the quantitative determination of SDS concentrations, especial for SDS concentrations in the range of0.05to1.9mM.In chapter4, base on the investigation in chapter3,1b was chosen and applied as a colorimetric and fluorometric probe for detecting the micellization of anionic surfactants. According to the surface tension and electrical conductivity results, the presence of lb dose not affect the CMC values of anionic surfactants. The ICT electronic structure of1b endows the absorption and fluorescence spectra with a high sensitivity towards solvent polarity. Therefore, the critical micellization concentration of anionic surfactants can be conveniently determined by the change on absorption and fluorescence spectra of lb and the results are in accordance with those of the standard methods. The probe displays highly sensitive and selective spectroscopic responses accompanied with distinctive color change (from colorless to light-green). One can choose any spectroscopic parameter, such as position or intensity of the absorption and emission peaks, to monitor the micelle formation process of anionic surfactants.In chapter5, an amphiphilic dye containing perylene (PDI) and naphthalimide (NDI) groups was designed and synthesized. The photoinduced intramolecular energy and electron transfer processes in the PDI-NDI were investigated. Due to the strong hydrophobic interaction and π-π interaction, PDI-NDI molecules are easily to self-assemble into spherical aggregates in water.