(a) Schematic illustration of the experimental setup. The distance between particles is denoted by r, the separation from the center of the particle monolayer to the water–oil interface is denoted by z, and the parameter a is the particle radius. (b) Optical microscopic image of silica particles of radius a = 1.0 μ m suspended near a water–decalin interface at an area fraction of n = 0.01. (c) Normalized self-diffusion coefficient D s ( n ) / D 0 as a function of the area fraction n for each of the three samples: S1 (black pentagon), S2 (red dot), and S3 (purple star). The green curves are fits to the following second-order polynomial D s ( n ) / D 0 = α ( 1 − β · n − γ · n 2 ) .