Spin-Polarized Photoluminescence in Au25(SC8H9)18 Monolayer-Protected Clusters

Here, the observation of spin-polarized emission for the Au-25(SC8H9)(18) monolayer-protected cluster (MPC) is reported. Variable-temperature variable-field magnetic circular photoluminescence (VTV (H) over right arrow, MCPL) measurements are combined with VT-PL spectroscopy to provide state-resolved characterization of the transient electronic structure and spin-polarized electron-hole recombination dynamics of Au-25(SC8H9)(18). Through analysis of VTV (H) over right arrow;-MCPL measurements, a low energy (1.64 eV) emission peak is assigned to intraband relaxation between core-metal-localized superatom-D to -P orbitals. Two higher energy interband components (1.78 eV, 1.94 eV) are assigned to relaxation from superatom-D orbitals to states localized to the inorganic semirings. For both intraband superatom-based or interband relaxation mechanisms, the extent of spin-polarization, quantified as the degree of circular polarization (DOCP), is determined by state-specific electron-vibration coupling strengths and energy separations of bright and dark electronic fine-structure levels. At low temperatures (<60 K), metal-metal superatom-based intraband transitions dominate the global PL emission. At higher temperatures (>60 K), interband ligand-based emission is dominant. In the low-temperature PL regime, increased sample temperature results in larger global PL intensity. In the high-temperature regime, increased temperature quenches interband radiative recombination. The relative intensity for each PL mechanism is discussed in terms of state-specific electronic-vibrational coupling strengths and related to the total angular momentum, quantified by Lande g-factors.

Automated summary

The study reports on the observation of spin-polarized emission for the Au-25(SC8H9)(18) monolayer-protected cluster. By analyzing variable-temperature variable-field magnetic circular photoluminescence (VTV (H) over right arrow, MCPL) measurements, the degree of spin polarization for different relaxation mechanisms is determined and discussed in terms of relative intensities of different emission mechanisms. Additionally, it is found that the emission characteristics of the Au-25(SC8H9)(18) monolayer-protected cluster vary with temperature.