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| <p>X-RAY DIFFRACTION PATTERNS OF SINGLE AU NANOPARTICLES, M. R. Miller1, P. Ho2, R. Santra*2,3, Northwestern University1, Evanston, IL 60201, Argonne National Laboratory2, Chemical Sciences and Engineering Division, Argonne, IL 60439, University of Chicago3, Department of Physics, Chicago, IL 60637, rsantra@anl.gov </p> | |
| <p>X-ray diffraction is a critical technique for structural determination of fixed macromolecular crystals, relying on lattice periodicity to induce constructive interference of photon scattering amplitudes at angles satisfying the Bragg condition. This study investigates the transition of this technique to the imaging of a single gold (Au) nanoparticle aligned within an optical trap. A rectangular prismatic Au nanoparticle of 107 atoms is probed by a 20 keV hard x-ray pulse of 106 photons and (10 μm)2 cross section to match the specifications of existing third-generation synchrotron radiation sources. The resulting diffraction pattern is considered in the small and wide angle regimes to demonstrate the applicability of this technique on all structurally relevant length scales. The response of diffraction patterns to variations in particle aspect ratio and alignment angle with respect to an incident x-ray pulse are demonstrated. Wide angle scattering resolves Ångstrom length scales and indicates lattice alignment sensitivity through the intermittent appearance of Bragg diffraction peaks, while small angle scattering responds to nanometer-scale alterations through the evolution of the intense scattering boundary surrounding the forward peak. Small angle scattering accounts for twenty detectable photons per x-ray pulse at optimal alignment and is present throughout all alignment angles, whereas wide angle scattering collects a maximum of four photons within narrow alignment intervals. X-ray diffraction in the small angle region is thus the best strategy for measurement of the time-evolution of dynamic particle systems with use of the stated x-ray source parameters. Adjustment of the x-ray beam cross section or number of photons per pulse may permit particle structure retrieval from either angular range of a diffraction pattern generated from one x-ray pulse, suggesting x-ray diffraction as a viable tool for analyses of nanoparticle dynamics and interparticle interactions.</p> | |
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