Description and Role of Bimetallic Prenucleation Species in the Formation of Small Nanoparticle Alloys

Abstract

We report the identification, description, and role of multinuclear metal-thiolate complexes in aqueous Au-Cu nanoparticle syntheses. The structure of these species was characterized by nuclear magnetic resonance spectroscopy, mass spectrometry, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy techniques. The observed structures were found to be in good agreement with thermodynamic growth trends predicted by first-principles calculations. The presence of metal-thiolate complexes is then shown to be critical for the formation of alloyed Au-Cu architectures in the small nanoparticle regime (diameter ∼2 nm). In the absence of mixed metal-thiolate precursors, nanoparticles form with a Cu-S shell and a Au-rich interior. Taken together, these results demonstrate that prenucleation species, which are discrete molecular precursors distinct from both initial reagents and final particle products, may provide an important new synthetic route to control final metal nanoparticle composition and composition architectures.

Synthesis of Colloidal Metal Nanocrystals: A Comprehensive Review on the Reductants

“…In exploring the capability of amide‐based organic compounds as reductants, some studies have reported the use of N , N ‐dimethylacetamide (DMAc) in the synthesis of highly dispersed Ag spheroidal nanocrystals in a surfactant‐free system, in which DMAc served as a solvent, and a stabilizer, in addition to a reductant . However, in contrast to DMF, the exact mechanism involved in the oxidation of DMAc is yet to be explored.…”

Molecular “surgery” on a 23-gold-atom nanoparticle

“…5 (see the Supplementary Materials for computational details). The growth and doping reaction steps involving the addition of M 1 (SR) species ( M = Au or Ag) have been referenced to the energies of the thermodynamically very stable tetramer species [ M 4 (SR) 4 ] that have been both computationally ( 39 ) and experimentally ( 40 ) observed in thiolated group XI metal complexes (this reference selection does not affect the relative thermodynamic stability of the species and results in accurate reaction energy calculations; see table S4). First, we observe that for the [Au 23 (SR) 16 ] − and [Au 22 Ag(SR) 16 ] − clusters, Ag doping reactions are exothermic and slightly preferred over growth reactions to form [Au 25− x Ag x (SR) 18 ] − nanoclusters.…”

“…Tetramers [ M 4 (SR 4 )] were used as a common reference for the growth and doping reactions for the M 1 (SR) complexes ( M = Au or Ag) because these tetramers have been previously shown to be highly thermodynamically stable ( 39 ) and similar in structure to the surface staple motifs of the clusters. Moreover, these tetramers have been experimentally observed as prenucleation species in thiolated group XI bimetallic solutions ( 40 ). …”

In Situ Single‐Nanoparticle Spectroscopy Study of Bimetallic Nanostructure Formation

“…Bimetallic compositions often exhibit properties unique from those of the component metals [1,2] either due to geometric strain or the so-called "ligand" environment effect resulting from the formation of heteroatom bonds.I no ther cases,b imetallic compositions allow the synergy between the two metals to be exploited. Bimetallic compositions often exhibit properties unique from those of the component metals [1,2] either due to geometric strain or the so-called "ligand" environment effect resulting from the formation of heteroatom bonds.I no ther cases,b imetallic compositions allow the synergy between the two metals to be exploited.…”

“…While transition-metal nanoparticles (NPs) have been quite popular in heterogeneous catalysis,there is agrowing interest in NPs with bimetallic composition. Bimetallic compositions often exhibit properties unique from those of the component metals [1,2] either due to geometric strain or the so-called "ligand" environment effect resulting from the formation of heteroatom bonds.I no ther cases,b imetallic compositions allow the synergy between the two metals to be exploited. Galvanic exchange (GE) is ap opular method for preparing bimetallic nanostructures with high specific surface area.…”