Mechanism Study On Hierarchical Self-assembly Of Cadmium Sulfide Nanoparticles

Nano-materials because of its unique structure and excellent performance gradually by the people's attention.In the past thirty years,nano-materials with various morphologies,sizes,functions and properties have been gradually developed by researchers.The design of nano-materials with different morphologies is one of the research hotspots in nano-material fields.And the study of causes of different morphologies of nanoparticles——the interaction between nanoparticles is a great significance for the synthesis of nanoparticles with different morphologies and different properties.Hierarchical self-assembly of biomolecules is common in nature and necessary for living organisms.Not only the biomolecules,inorganic nanoparticles and biomolecules,but also use hierarchical self-assembly forming various ordered patterns which,however,typically show no characteristic of the who le hierarchy process.The previous researchers achieved inorganic nanoparticles hierarchical self-assembly by using ligand interactions,while achieving hierarchical self-assembly by using the molecular interactions of the nanoparticle themselves is rare.Here,we showed that Cd S nanoparticles can spontaneously form anisotropic strucutures in a hierarchical self-assemblies way.The whole process in particular is: the self-assembly includes first the clustering of primary small Cd S nanoparticles(diameter of them are about 4 nm~6 nm)into large supraparticles(diameter of them are about 25 nm~30 nm)which subsequently organize Cd S supraparticles into hundreds of nanometers long chains or tubules.The mechanism of such hierarchical self-assembly is indicated by our DLVO calculations: the formation of anisotropic structure which is kinetic stable is endorsed by the size increasing in building blocks.The small nanoparticles continue assembly forming the supraparticles.This process is controlled by the thermodynamically control.Then the supraparticles help themselves from the thermodynamically stable state transform to the kintic stable assemble state,these supraparticles are further self-assembled for one-dimensional assembly to form anisotropic one-dimensional nanochains and nanotubes.In this study we find that,nanoparticles due to the addition of different energy barriers to form different directions of the connection.In the whole process,there is cooperative effect with the increase of particle size.Specifically,when the size of nanoparticle was small,the particles were more prone to form three-dimensional assembly.As the assembly proceeded,the radius of the particles increased,When reached a critical point,one-dimensional assembly was more likely to occur.This study provides a insights into understand the self-assembly of complex inorganic nanoparticles,and is rarely mentioned in previous studies.The size induced synergistic effects are considered to be common in hierarchical self-assembly in various inorganic nanoparticles.Our research is an important component in the study of nanoscale intermolecular effects and has great guiding significance for the synthesis of nanomaterials with different morphologies and better properties.