442791 Formation Pathways of Pre-Nucleation Species in Aucu Bimetallic Nanoparticle Growth: A First Principles Study

Monday, November 9, 2015
Exhibit Hall 1 (Salt Palace Convention Center)
Peter D. Tancini1, Giannis Mpourmpakis1, Lauren E. Marbella2 and Jill E. Millstone2, (1)Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA, (2)Chemistry, University of Pittsburgh

Using computational chemistry calculations, we simulated the early stage formation of AuCu pre-nucleation complexes, which appear to be important in determining the bimetallic architecture of the formed nanoparticles. The pre-nucleation species growth was simulated through single addition steps of the thiolated metal precursor complexes: AuL, CuL, CuL2, where L= SCH3.  The ΔG of formation was calculated for every single addition reaction steps up to the formation of tetramers. A decrease in the spontaneity of formation was found when the ligand (L) to metal ratio exceeded 1:1, with the most thermodynamically stable structures being the MnLn consisting of equivalent number of metal atoms and thiolate ligands. Most importantly, the Au and Cu metals appear to favorably mix in these complexes. Our computational results are in perfect agreement with MALDI-TOF-MS experiments (Millstone lab at Pitt) identifying pre-nucleation complexes in solution. Important enough, we observed that metal mixing in small nanoparticle alloys may begin before the nucleation process is initiated.

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