Metastability and structural polymorphism in noble metals: The role of composition and metal atom coordination in mono- and bimetallic nanoclusters

Sergio I. Sanchez, Matthew W. Small, Emil S. Bozin, Jian Guo Wen, Jian Min Zuo, Ralph G. Nuzzo

Research output: Contribution to journalArticlepeer-review

Abstract

This study examines structural variations found in the atomic ordering of different transition metal nanoparticles synthesized via a common, kinetically controlled protocol: reduction of an aqueous solution of metal precursor salt(s) with NaBH4 at 273 K in the presence of a capping polymer ligand. These noble metal nanoparticles were characterized at the atomic scale using spherical aberration-corrected scanning transmission electron microscopy (C s-STEM). It was found for monometallic samples that the third row, face-centered-cubic (fcc), transition metal [(3M) - Ir, Pt, and Au] particles exhibited more coherently ordered geometries than their second row, fcc, transition metal [(2M) - Rh, Pd, and Ag] analogues. The former exhibit growth habits favoring crystalline phases with specific facet structures while the latter samples are dominated by more disordered atomic arrangements that include complex systems of facets and twinning. Atomic pair distribution function (PDF) measurements further confirmed these observations, establishing that the 3M clusters exhibit longer ranged ordering than their 2M counterparts. The assembly of intracolumn bimetallic nanoparticles (Au-Ag, Pt-Pd, and Ir-Rh) using the same experimental conditions showed a strong tendency for the 3M atoms to template long-ranged, crystalline growth of 2M metal atoms extending up to over 8 nm beyond the 3M core.

Original languageEnglish (US)
Pages (from-to)1542-1557
Number of pages16
JournalACS Nano
Volume7
Issue number2
DOIs
StatePublished - Feb 26 2013

Keywords

  • aberration corrected electron microscopy
  • atomic structure
  • bimetallic
  • core-shell
  • nanoparticle
  • noble metals
  • pair distribution function

ASJC Scopus subject areas

  • Engineering(all)
  • Materials Science(all)
  • Physics and Astronomy(all)

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