Time-resolved structure investigation with small angle X-ray scattering using scanning techniques

Abstract: Due to the availability of high-brilliance X-rays at synchrotron radiation facilities, small angle X-ray scattering (SAXS) measurements have become feasible for new sample environments, like microfluidics or aerosol systems. The combination of continuous flow methods and SAXS with spatial scanning enables in situ measurements of time-resolved structures at the nanoscale important for reactions kinetics and material synthesis and processing. In this review we present the latest achievements in terms of scanning SAXS along continuous flow mixing devices reducing the limit of time resolution at the microsecond range. This led to the determination of early stages of biological reactions like protein folding, and to gain insight into chemical reaction kinetics like nanoparticles formation. We also describe the coupling of scanning SAXS with aerosol generators, which is the only way to study the mechanisms for the self-assembly and aggregation of nanomaterials via the aerosol route. We finally give a brief outlook, as the potentiality of these techniques has not been fully exploited, leaving the possibility for further improvements in time resolution and sample consumption, for example with the new X-ray sources like Free Electron Lasers.