Single particle imaging requires identical objects successively exposed to powerful, coherent X-ray pulses and 'snapshots' collected at unknown object orientations. To determine the orientations of individual low-signal diffraction patterns and subsequently, to reconstruct the 3D full-pattern diffraction volume requires more signal than currently available. To circumvent this difficulty, the X-MOTION (Exploring nanoscale motion and molecular alignment using ultrafast coherent diffraction) project gathered experimentalists and theoreticians from France, Germany and the United States. These project partners have expertise in ultrafast coherent imaging techniques, nanoscale fabrication, polymer chemistry and X-ray spectroscopy. The synergy between these domains was essential to overcome the issue of single particle orientation using azobenzene-derived polymers (AZOs) and also improve the diffracted signal. AZOs were chosen because their orientation can be manipulated and controlled using ultraviolet light, enabling them to maintain the alignment of particles. The researchers first analysed the azobenzene molecule properties to determine whether or not it is suitable to power and actuate single nanorods to isolate molecules-of-interest (for example, proteins). They used various advanced techniques to study the isomerisation (change in alignment) of azobenzene-nanoparticle complexes. Specifically, the use of ultrafast coherent X-ray diffraction in a pump-probe scheme to follow in real time the isomerisation-induced alignment was tested using diiodobenzonitrile, a simple molecule that is similar in some ways to azobenzene. The results demonstrated that it was possible to measure the diffraction, alignment and structure of the molecule. X-MOTION has pioneered a new approach that will provide unparalleled information about the structure and dynamics of complex nanoparticles. This X-ray imaging technique is expected to have wide-ranging applications, including the time-resolved investigation of large 'electron-opaque' objects and key biological processes.
X-ray, single particle imaging, X-MOTION, azobenzene, ultrafast coherent X-ray diffraction