Li, L., L.-L. Wang, D.D. Johnson, Z. Zhang, S.I. Sanchez, J.H. Kang, R.G. Nuzzo, Q. Wang, A.I. Frenkel, J. Li, J. Ciston, E.A. Stach, and J.C. Yang, “Non-Crystalline-to-Crystalline Transformations in Pt Nanoparticles”, Journal of the American Chemical Society, Vol. 135(35), pp. 13062-13072, 2013. DOI: 10.1021/ja405497p
We show that the non-crystalline-to-crystalline transition of supported Pt nanoparticles (NPs) in the sub-nm to nm size range is statistical in nature, and strongly affected by particle size, support, and adsorbates (here we use H2). Unlike in the bulk, a non-crystalline phase exists and is stable in small NPs, reflecting a general mesoscopic feature. Observations of >3000 particles by high-resolution transmission electron microscopy show a non-crystalline-to-crystalline transition zone that is non-abrupt – there is a size regime where disordered and ordered NPs coexist. The NP size at which this transition occurs is strongly dependent on both the adsorbate and the support, and this effect is general for late 5d transition metals. All results are reconciled via a statistical description of particle-support-adsorbate interactions.
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