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Single-particle mapping of nonequilibrium nanocrystal transformations

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Science  18 Nov 2016:
Vol. 354, Issue 6314, pp. 874-877
DOI: 10.1126/science.aah4434

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Watching it all fall apart

The control of the shape and size of metal nanoparticles can be very sensitive to the growth conditions of the particles. Ye et al. studied the reverse process: They tracked the dissolution of gold nanoparticles in a redox environment inside a liquid cell within an electron microscope, controlling the particle dissolution with the electron beam. Tracking short-lived particle shapes revealed structures of greater or lesser stability. The findings suggest kinetic routes to particle sizes and shapes that would otherwise be difficult to generate.

Science, this issue p. 874

Abstract

Chemists have developed mechanistic insight into numerous chemical reactions by thoroughly characterizing nonequilibrium species. Although methods to probe these processes are well established for molecules, analogous techniques for understanding intermediate structures in nanomaterials have been lacking. We monitor the shape evolution of individual anisotropic gold nanostructures as they are oxidatively etched in a graphene liquid cell with a controlled redox environment. Short-lived, nonequilibrium nanocrystals are observed, structurally analyzed, and rationalized through Monte Carlo simulations. Understanding these reaction trajectories provides important fundamental insight connecting high-energy nanocrystal morphologies to the development of kinetically stabilized surface features and demonstrates the importance of developing tools capable of probing short-lived nanoscale species at the single-particle level.

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