Copper Induces a Core Plasmon in Intermetallic Au(144,145)-xCux(SR)60 Nanoclusters.
The electronic structure and optical absorption spectra of intermetallic thiol-stabilized gold-copper clusters, having 144-145 metal atoms and 60 thiols, were studied by ab initio computations. The widely known icosahedral-based cluster model from the work of Lopez-Acevedo et al. (2009) was used, and clusters doped with one to 30 copper atoms were considered. When doped inside the metal core, copper induces dramatic changes in the optical spectrum as compared to the previously studied all-gold Au144(SR)60. An intense broad absorption peak develops in the range 535-587 nm depending on the amount of doping and doping sites. This result agrees very well with recent experiments by the Dass group for Au144-xCux(SR)60 (x ≤ 23). The analysis of the peaks shows a collective plasmon-like dipole oscillation of the electron density in the metal core. Internal charge transfer from copper to gold and an almost perfect alignment of the upper edges of Cu(3d) and Au(5d) bands are observed in the metal core, contributing to the plasmon-like absorption. The calculations also predict energetically preferable doping of the ligand layer by copper, but such clusters are nonplasmonic.
†Department of Physics, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland.
Sami
S
Malola
‡Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States.
Michael J
MJ
Hartmann
†Department of Physics, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland.|§Department of Chemistry, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland.
Hannu
H
Häkkinen
copper; density functional theory; gold; intermetallic cluster; optical absorption