| Colloids,or colloidal dispersions,are prevalent in nature and play an essential role in various aspects of daily life and production.In this thesis,we begin by introducing the fundamental concepts and properties of soft matter and colloids,along with Brownian motion and correlated motion.The second section presents the basic equations of fluid mechanics,including the Navier-Stokes equation,Langevin equation,Fokker-Planck equation,and related theories of correlated diffusion.The relationship between structure and dynamics is a topic of widespread interest,and investigating the correlated diffusion-structure entropy of colloidal particle monolayers can provide insight into the relationship between the structure of twodimensional systems and hydrodynamic interactions between particles.In recent years,the study of structural entropy-diffusion scale law has become a frontier hotspot in the field of condensed matter physics.However,most of this research has been theoretical or simulated,with few experimental results.Moreover,most discussions of the diffusion-structure relationship have focused on particle self-diffusion,with little attention given to inter-particle correlated diffusion.In the third section of the thesis,we examine the correlated diffusion behavior of colloidal particles at smooth solid interfaces using optical microscopy and multi-particle tracking techniques.We also explore the relationship between correlated diffusion and structural entropy,with a particular focus on the impact of area fraction.The influence of the structural entropy of the system on the hydrodynamic interactions between the particles and the physical mechanism behind is analyzed.The experimental results show that the correlated diffusion between particles at the smooth solid interface does not change significantly with the change of area fraction in the selected range of area fractions.The absolute value of the structural entropy increases with increasing area fraction,and the structural entropy of the same particle size colloidal system in this experiment is mainly determined by the area fraction of the colloidal particles.Therefore,the change of structural entropy did not have a significant effect on the decay law of inter-particle correlated diffusion in the range of area fraction change in this experiment.The study contributes to the understanding of the kinetic properties and structural distribution of membrane proteins.It is also expected to provide a reference for the design of surface materials for specific functions.Fluid interfaces are everywhere,the dynamic behavior of colloidal particles at the fluid interface is quite different from that inside the fluid.The dynamics of interaction and diffusion of colloidal particles at interfaces has been one of the hot topics of research in soft matter physics,colloid physics,and biophysics.However,most of the interfaces used in the studies of the dynamics of colloidal particles at interfaces are mostly smooth interfaces,while in practice there are more rough and non-smooth interfaces,so it is valuable to discuss the effect of non-smooth interfaces on particle dynamics.In Chapter 4,we construct a nonsmooth interface using a periodic lattice substrate formed by a colloidal monolayer of fixed same particle size.By discussing the correlated diffusion of colloidal monolayers on the periodic lattice substrate,it is found that a transverse negative correlation appears among the colloidal particles diffusing on the lattice substrate,that is,when a reference particle moves in one direction,other particles at a specific distance in the transverse direction move in the opposite direction.It is speculated that this phenomenon may be caused by the flow field.In order to clarify the reason for the appearance of the transverse negative correlation,the flow field of particle motion on the lattice substrate was simulated with COMSOL,and it was found that the motion of particles on the periodic lattice structure led to the appearance of vortex flow.The vortex flow leads to the transverse negative correlation,thus confirming our speculation.This work is different from the previously found laws and contributes to the understanding of the dynamical behavior of particles near non-smooth surfaces,as well as to the understanding that non-smooth interfaces lead to the formation of peculiar flow fields and that peculiar flow fields affect the hydrodynamic interactions between particles. |
