Spin‐Polarized Photoluminescence in Au25(SC8H9)18 Monolayer‐Protected Clusters. Issue 27 (28th January 2021)

• Record Type: Journal Article
• Authors: Herbert, Patrick J.; Knappenberger, Kenneth L.
• Is Part Of: Small. Volume 17:Issue 27(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-01-28
• Subjects: magneto‐optical spectroscopy -- metal clusters -- spin‐polarized photoluminescence; Nanotechnology -- Periodicals; Nanoparticles -- Periodicals; Microtechnology -- Periodicals; 620.5
• DOI: 10.1002/smll.202004431
• Languages: English
• ISSNs: 1613-6810

Abstract

Abstract: Here, the observation of spin‐polarized emission for the Au25 (SC8 H9 )18 monolayer‐protected cluster (MPC) is reported. Variable‐temperature variable‐field magnetic circular photoluminescence (VTV H ⇀ ‐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 Au25 (SC8 H9 )18 . Through analysis of VTV H ⇀ ‐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 Landé g ‐factors. Abstract : Spin‐polarized photoluminescence is observed for quantum‐confined Au25 (SC8 H9 )18 monolayer‐protected clusters (MPC). Emission mechanisms are determined using variable‐temperature variable‐field magnetic circular photoluminescence spectroscopy. Spin‐polarization amplitudes are correlated to emission by specific nanocluster qauntum states. Atomic‐level nanocluster structure determines electronic fine‐structure energies, electronic‐vibrational coupling, and spin‐orbit coupling parameters, which control the degree of spin polarization for each emission pathway.