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Keywords:

  • palladium;
  • microcrystals;
  • nanocrystals;
  • transmission electron microscopy;
  • thermal annealing

As-grown platelets formed from tris-(dibenzylideneacetone) dipalladium(0) [Pd2(dba)3] precursor in the presence of Pd17 RNA are investigated before and after thermal annealing. Results show that as-grown platelets are disordered crystals of Pd2(dba)3 containing 1−2 nm Pd clusters and platelets grown in the absence of RNA are morphologically and structurally similar to those formed with RNA. The initially formed crystals are so sensitive to environmental variables that the degree of crystallinity can not be determined accurately by electron diffraction. X-ray crystallography on as-grown platelets gives a crystal structure consistent with Pd2(dba)3, but reveals a composition of ≈Pd1.07(dba)3, indicating one Pd atom in Pd2(dba)3 is lost from the structure. Both electron beam and thermally induced decomposition of as-grown Pd2(dba)3 platelets having a hexagonal habit on the micrometer scale produces elemental Pd platelets having a hexagonal habit on the nanometer scale. These hexagonal platelets are composed of a partially sparse form of Pd2(dba)3 that is initially crystalline but rapidly degrades due to the loss of Pd atoms from organic ligand cages. Once released, Pd atoms aggregate to form Pd clusters, which grow and transform into well-formed Pd nanocrystals under electron-beam irradiation or through thermal annealing.