Monodispersed Porphyrin Nanocrystal Through Acid-base Neutralization And Micelle Confined Controllable Self-Assembly

Self-assembly is a process that building blocks form ordered structures spontaneously by non-covalent weak interaction, which is an important means to create new substances and new features. Using the self-assembly technique to realize the controlled self-assembly of porphyrin molecules in supramolecular level, and further to realize the specific functions, is a key issue in supramolecular chemistry, nanotechnology, materials chemistry and other fields. How to design and synthesize functional nanomaterials with specific morphologies and properties at the molecular level, through intermolecular non-covalent interactions such as hydrogen bond, coordination bonding, hydrophilic/hydrophobic interactions, electrostatic forces, van der Waals interactions, and so on, is a difficult point in self-assembly area and also the breakthrough point for the development of self-assembly technology. Our group has developed a simple, effective, economic, universal technology for the large-scale preparation of ordered porphyrin nanostructures: acid-alkali neutralization and micelle confined assisted controllable self-assembly, which is a facile new method to realize the controlled self-assembly of porphyrin. This dissertation mainly focuses on the following two aspects:1. By employing the Sodium dodecyl sulfate(SDS) as an emulsifier, and zinc meso-Tetra(4-pyridyl)porphine(ZnTPyP) as self-assembly unit, we successful fabricate the two dimensional porphyrin nanostructure via the formation of ZnTPyP-SDS intermediate and further acid-alkali neutralization process. First of all, the zinc porphyrin powder was dissolved in dilute hydrochloric acid solution with certain concentration and the four pyridyl group at peripheral position of porphyrin protonated simultaneously, forming [ZnTPyPH4]4+ cations which were well dissolved in water and helped to improve the reaction efficiency and large-scale preparation. Then the porphyrin solution was added to the aqueous solution of SDS, forming ZnTPyP-SDS intermediate. The NaOH solution was added into the above solution to adjust the pH value of reaction, in this case, the [ZnTPyPH4]4+ will be deprotonated immediately and precipitated from the solution via confined assembly in SDS micelle. Monodispersed two-dimensional porphyrin nanosheets were obtained by changing the molar ratio of SDS to ZnTPyP and the pH value of the system, which were analyzed by SEM, TEM, AFM and other testing methods. The results showed that monodisperse nanosheets with regular and uniform shape were obtained, and in addition, the higher the concentration of SDS, and the lower the pH, the greater the size of nanosheets and the more regular morphology. We further investigated the assembling mechanism of porphyrin and found that the electrostatic interaction between the anionic emulsifier SDS and the protonated pyridine of zinc porphyrin is the main driving force for the formation of porphyrin nanosheets. The nanosheets were further used for the degradation of organic pollutants methyl orange in visible light, which exhibited superior performance than that of single molecules of porphyrin of equivalent dosage, owing to excellent synergistic effect of porphyrin molecules.2. By employing the Sodium dodecyl sulfate(SDS) as an emulsifier, and zinc meso-Tetra(4-pyridyl) porphine(ZnTPyP) as self-assembly unit, we successfully fabricate the one dimensional porphyrin nanostructure via the formation of [ZnTPyPH4]4+ intermediate and further acid-alkali neutralization process. By adjusting the pH, ZnTPyP concentration, the molar ratio of SDS to porphyrin and other experimental conditions, we realized the controlled assembly of porphyrin with regulated shape and size. The study found that porous monodisperse hexagonal nanorods were obtained in this system. When the concentration of SDS and ZnTPyP were fixed and increased pH, the length and diameter of the hexagonal rods changed from big to small. When the concentration of SDS and pH were fixed and increased the concentration of ZnTPyP, the length and diameter of the hexagonal rods changed from big to small. When the concentration of ZnTPyP and pH were fixed and increased the molar ratio of SDS to ZnTPyP, the diameter of the hexagonal rods become smaller at first and then become larger, the length of the hexagonal rods become longer at first and then become shorter. These results suggest that we successfully realized the controlled adjustment of the self-assembled hexagonal rods, that is, the length of the hexagonal rods could be controlled from 270 nm to 78 nm, and the diameter of the hexagonal rods could be controlled from 210 nm to 15 nm, which provide clue for the future research and control of the self-assembly process.