Emergent dynamics of light-induced active colloids probed by XPCS

Abstract Self-propelled particulate systems manifest certain collective behavior of living matter, which have been the subject intense research over past decades. One elegant methods for realizing such active motions is by means custom synthesized Janus particles suspended in a catalytic medium that can be triggered upon illumination ultraviolet light. In this work, evolution particle dynamics from passive diffusive to ballistic light was probed multispeckle x-ray photon correlation spectroscopy (XPCS). This technique enables not only studying emergence three dimensions (3D) but also deciphering different contributions overall dynamics. Using combination homodyne and heterodyne analysis, ensemble averaged mean velocity, velocity fluctuations diffusion coefficient were determined thermodynamic limit. Results revealed gradual transition with systematic increase activity. At intermediate region, dominated Gaussian an enhanced relaxation rate weaker wave vector dependence similar superdiffusive behavior. For highest activity, became purely Lorentzian-like distribution fluctuations. Presented results demonstrate aspects investigated 3D broad range Péclet numbers other control parameters XPCS.