Graphene liquid cell electron microscopy for growth, etching and motional dynamics of colloidal nanoparticles

Abstract

The nanoparticle means a structure comprising atoms or molecules with a particle size of 20 nm or less and it has been considered a key material in fundamental research and bio or catalyst application because of novel physical and chemical properties different from the bulk system. The liquid-phase synthesis is one of the most effective methods to obtain the desired properties of the nanoparticles by precisely controlling structural characteristics, such as the shape, size, or composition of nanoparticles. However, the lack of understanding of the complex inter-particle interactions that occur in liquid environments and the fundamental instability of nanostructures at the nano-scale is a major obstacle to understanding and controlling the particle formation pathway. In this thesis, real-time and high-resolution observation of the fluctuation and dynamic behavior of colloidal nanoparticles occurring in the liquid environment was performed by using graphene liquid cell transmission electron microscopy. Through in-situ liquid phase transmission electron microscopy, the structural fluctuation of the nanoparticles that occur during the particle size change in the liquid phase was investigated, and the origin of the structural instability of the nanoparticle that occurs in the real liquid environment was discussed. In addition, by directly observing the Brownian motion of the particles due to the interaction between the nanoparticles and the graphene liquid cell, the dynamic behavior of the nanoparticles was examined. This study presents a practical method for observing dynamical phenomena occurring at the nanoscale in the liquid environment and improves the fundamental understanding of the colloidal system for structural instability and motional behavior in the liquid phase, thereby contributing to the advancement of basic nanoscience and industry.