The Influence of Pd-Atom Substitution on Au25(SC8H9)18 Cluster Photoluminescence

The photoluminescence (PL) of Au-25(SC8H9)(18) and Au24Pd(SC8H9)(18) was investigated using variable-field magnetic circular photoluminescence (VH-MCPL) spectroscopy. The comparison of low-temperature (4.5 K) PL spectra measured for both nanoclusters revealed an approximate to 40 meV blueshift of intraband emission upon Pd substitution. Compared to that for the the Au-25(SC8H9)(18) cluster, the degree of circular-polarization for the Au24Pd(SC8H9)(18) cluster increased for the low energy (<1.65 eV) portion of the PL spectrum, but decreased for the higher energy (>1.65 eV) spectral region. MCPL spectra included three distinct components, underlying the global PL spectrum, for both clusters. Variable-field analysis of each MCPL component revealed an increase in spin-orbit coupling (Lande ' g-factor) magnitudes for radiative transitions of the Pd-substituted cluster with respect to Au-25(SC8H9)(18). Variable-temperature (VT) PL spectroscopy yielded reduced integrated global PL intensity and increased electron-vibrational coupling for Au24Pd(SC8H9)(18), as compared to Au-25(SC8H9)(18). The results indicate that Pd-substitution for Au in Au-25(SC8H9)(18) results in increased angular momenta for metal-metal intraband transitions; the Lande ' g-factor for these transitions increased by approximate to 55% upon substitution, as compared to an approximate 19% increase for ligand-based transitions. The increased angular momentum translates to a 30% increase in electron-phonon coupling constants for intraband transitions, but only a 3% increase for ligand-based transitions. As a result, Pd substitution leads to less efficient metal-metal (intraband) radiative emission for Au24Pd (SC8H9)(18) than for Au-25(SC8H9)(18).

Automated summary

By using VH-MCPL spectroscopy, this study investigated the photoluminescence of Au-25(SC8H9)(18) and Au24Pd(SC8H9)(18), revealing a blueshift and changes in circular polarization upon Pd substitution. Variable-temperature PL spectroscopy showed increased angular momentum for metal-metal intraband transitions due to Pd substitution.