Universal scaling of correlated diffusion of colloidal particles near a liquid-liquid interface

In this letter, we investigate the correlated diffusion of colloidal particles in quasi two-dimensional monolayer near an oil-water interface for different distance between the interface and the particle monolayer z. It is found that there is a transition in the behavior of the correlated diffusion from the bulk dominated to the interface dominated with decreasing z or increasing inter-particle separation r. With a scaling method proposed by us, the correlated diffusion can be scaled onto a master curve which captures the characters of this transition. The scale factors and the master curve allow the calculation of the distance z, which are in agreement with the one-particle measurements.