Experimental set-up for time resolved small angle X-ray scattering studies of nanoparticles formation using a free-jet micromixer

Recently we have designed, fabricated and tested a free jet micromixer for time resolved Small Angle X-ray Scattering (SAXS) studies of nanoparticles formation in the < 100 ìs time range. The microjet has a diameter of 25 ìm and a time of first accessible measurement of 75 ìs has been obtained. This result can still be improved. In this communication we present a method to estimate whether a given chemical or biological reaction can be investigated with the micromixer, and to optimize the beam size for the measurement at the chosen SAXS beamline. Moreover, we describe a system based on stereoscopic imaging which allows the alignment of the jet with the x-ray beam with a precision of 20 ìm. The proposed experimental procedures have been successfully employed to observe the formation of calcium carbonate (CaCO3) nanoparticles from the reaction of sodium carbonate (Na2CO3) and calcium chloride (CaCl2). The induction time has been estimated in the order of 200 ìs and the determined radius of the particles is about 15 nm.