The Difference between Plasmon Excitations in Chemically Heterogeneous Gold and Silver Atomic Clusters

TL;DR

This paper explores how adding small amounts of Pd or Pt to gold and silver atomic clusters changes their plasmon peaks, revealing how these changes are linked to electron energy levels and orbital symmetry.

Contribution

The study provides new insights into how plasmon peak evolution in doped atomic clusters is influenced by electron energy positions and orbital symmetry.

Findings

Pd doping in Au arrays caused a significant blueshift in plasmon peaks, while Pt doping caused a slight red shift.

Pt doping in Ag arrays led to a substantial red shift in plasmon peaks, whereas Pd doping caused little shift.

Electron transfer analysis showed a strong correlation between excitation energy and electron transfer from doping atoms.

Abstract

Weak doping can broaden, shift, and quench plasmon peaks in nanoparticles, but the mechanistic intricacies of the diverse responses to doping remain unclear. In this study, we used the time-dependent density functional theory (TD-DFT) to compute the excitation properties of transition-metal Pd- or Pt-doped gold and silver atomic arrays and investigate the evolution characteristics and response mechanisms of their plasmon peaks. The results demonstrated that the Pd or Pt doping of the off-centered 10 × 2 atomic arrays broadened or shifted the plasmon peaks to varying degrees. In particular, for Pd-doped 10 × 2 Au atomic arrays, the broadened plasmon peak significantly blueshifted, whereas a slight red shift was observed for Pt-doped arrays. For the 10 × 2 Ag atomic arrays, Pd doping caused almost no shift in the plasmon peak, whereas Pt doping caused a substantial red shift in the broadened plasmon peak. The analysis revealed that the diversity in these doping responses was related to the energy positions of the d electrons in the gold and silver atomic clusters and the positions of the doping atomic orbitals in the energy bands. The introduction of doping atoms altered the symmetry and gap size of the occupied and unoccupied orbitals, so multiple modes of single-particle transitions were involved in the excitation. An electron transfer analysis indicated a close correlation between excitation energy and the electron transfer of doping atoms. Finally, the differences in the symmetrically centered 11 × 2 doped atomic array were discussed using electron transfer analysis to validate the reliability of this analytical method. These findings elucidate the microscopic mechanisms of the evolution of plasmon peaks in doped atomic clusters and provide new insights into the rational control and application of plasmons in low-dimensional nanostructures.

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