Al–X and Cu–X [X = Li, Na] nano-alloys: a low cost alternative to silver and gold nanoparticles for plasmonic applications

Abstract

We present a systematic study of the electronic and optical properties of the Li and Na doped Al–X and Cu–X (X = Li, Na) nanoalloys in the framework of density functional theory in order to evaluate their potential as low cost plasmonic materials as alternatives to silver and gold. A single atom in the 13 atoms Al and Cu clusters is replaced by the Li and Na atoms in the core and surface positions to form core-doped and surface-doped Al₁₂X and Cu₁₂X bimetallic clusters respectively. Vibrational analysis has ensured the structural stability of the doped clusters. Binding energies and HOMO–LUMO gaps are calculated to predict the electronic stability, as well as the ionization potential and electron affinity of the clusters. Large HOMO–LUMO gaps with small electron affinity of the doped clusters ensured that anions of the Cu₁₂X and Al₁₂X clusters will be very reactive. The optical absorption properties of the undoped and doped clusters are calculated in the framework of TDDFT. It is observed that the Li and Na doping into the Al and Cu clusters yield significant increase in the absorption band-gap in both of the Cu and Al clusters. In particular, the surface doped Al₁₂X clusters exhibit remarkable large bandgap which comprises from 3 eV to 11 eV. Due to their electronic and optical properties, the Al–X and Cu–X doped clusters may be considered as an excellent low cost alternative to silver and gold, which can find its worth in catalytic, opto-electronic and UV-absorption applications.