| Self-assembly is a process in which the building blocks are assembled into ordered stuctures,generating new properties and functions.Nanocomposites assembled by inorganic nano-materials and organic molecules are a new type of materials that have important application potential in catalysis,photoelectric photothermal and other fields.At present,a variety of nanocomposites constructed by well-designed building blocks via various interactions(electrostatic force,metal coordination,hydrogen bonding,etc.)have been reported.However,the study of using van der Waals interactions to prepare the co-assemblies and is relatively rare and needs further development.Hence,we designed and synthesized a series of asymmetric perylene diimide(PDIs)molecules,and successfully assembled these PDIs with Au nanoparticles(Au NPs)by van der Waals interaction.Then the photo-thermal and catalytic properties of as-prepared nanocomposite materials were investigated,which provides theoretical guidance for designing other new nanocomposite materials.The research contents are as follows:(1)Synthesis of assembly motif PDIs molecules and Au NPs:A series of asymmetric PDIs molecules were designed,synthesized and characterized by changing the substitution sites and substituted groups.The results of DFT calculation preliminarily showed that there were some differences in the intermolecular arrangement of PDIs with different structures.As the properties of nanoparticle superlattice structure was influenced by the size and spacing of nanoparticles,Au NPs with different sizes and thiol ligands were synthesized by changing the mass of reducing agent and the type of thiol ligands,and their TEM images and size distribution statistics were carried out.(2)Three-dimensional assemblies of PDIs molecule and Au NPs and their photothermal properties:Although the structures of PDIs molecules with o/m/p-methoxyphenyl were slightly different,the morphology and structure of their assemblies obtained by emulsion confined selfassembly were similar.The co-assembly of PDIs molecules and Au NPs was obtained by emulsion confined assembly.It was found that the superstructure of nanoparticles would fold with the structure of the co-assembly,and the mass ratio mPDI/mAu,the length of alkyl chain on the surface of Au NPs and the size of Au NPs would affect the ratio of folded structure.The coassembly process was explained as follows:when PDIs and Au NPs were co-assembled in the emulsion droplets,the volatilization of the internal phase of the emulsion droplets would enhance the Van der Waals interaction between the alkyl chain of PDIs molecule and the alkyl chain of Au NPs ligands,thus leading to the cooperative co-assembly;The size of emulsion droplets was decreasing continuously,which provided extra force for the co-assembled structure to fold.The results of light-induced water evaporation showed that this porous nanocomposite had good photothermal conversion efficiency due to its strong light absorption.(3)PDIs molecule-mediated construction of Au NPs one-dimensional assemblies and their catalytic properties:Although the structures of PDIs molecules connected with o/m/pmethylphenylethyl were similar,different supramolecular assemblies(one-dimensional nanofibers,spiral nanoribbons,and two-dimensional nanoplates)were formed by self-assembly through poor solvent diffusion,which showed that tiny structural changes had great influence on the structure of supramolecular assemblies.The structural information of these supramolecular assemblies further led to the assembly of Au NPs into long-term ordered superstructures(one-dimensional superlattice chain,double helix superstructure and twodimensional superlattice sheet).The van der Waals interaction between alkyl chains of supramolecular assemblies and alkyl chains on the surface of Au NPs played a vital role in the process of co-assembly.The catalytic properties of these different superstructures varied widely,which was explained by molecular dynamics simulation. |
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