Figure 5.

Time-resolved dynamics of nanoparticle clusters. (a) Ensemble of particle clusters formed by 31 nm radius PS monomers features an average fractal dimension D_f close to 2.35. The insets on the top show some pictorial depictions of possible clusters with various fractal dimensions. (b–e) Time-resolved behavior of a representative cluster, characterized in terms of its radius r (b), refractive index difference Δn (c), number of monomers N (d), and fractal dimension D_f (e). While r, Δn, and N greatly vary over time, D_f remains stable in time. The shaded regions represent the estimated standard deviation of the error. The cluster is characterized using a moving window of 20 observations, acquired at a frame rate of 30 frames per second. The fractal dimension of the cluster is estimated based on the scaling of its size and refractive index with the number of monomers, assuming a known monomer with a radius of 31 nm and a refractive index of 1.58.