Open AccessIntense fluorescence of Au20
Author(s) -
Chongqi Yu,
W. Harbich,
Luca Sementa,
Luca M. Ghiringhelli,
Edoardo Aprà,
Mauro Stener,
Alessandro Fortunelli,
Harald Brune
Publication year - 2017
Publication title -
the journal of chemical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.071
H-Index - 357
eISSN - 1089-7690
pISSN - 0021-9606
DOI - 10.1063/1.4996687
Subject(s) - fluorescence , homo/lumo , density functional theory , absorption (acoustics) , cluster (spacecraft) , chemistry , crystallography , molecule , photochemistry , materials science , computational chemistry , physics , optics , organic chemistry , computer science , composite material , programming language
Ligand-protected Au clusters are non-bleaching fluorescence markers in bio- and medical applications. Here we show that their fluorescence can be an intrinsic property of the Au cluster itself. We find a very intense and sharp fluorescence peak located at λ=739.2 nm (1.68 eV) for Au20 clusters in a Ne matrix held at 6 K. The fluorescence reflects the Highest Occupied Molecular Orbital-Lowest Unoccupied Molecular Orbital (HOMO-LUMO) diabatic bandgap of the cluster. Au20 shows a very rich absorption fine structure reminiscent of well defined molecule-like quantum levels. These levels are resolved since Au20 has only one stable isomer (tetrahedral); therefore our sample is mono-disperse in cluster size and conformation. Density-functional theory (DFT) and time-dependent DFT calculations clarify the nature of optical absorption and predict both main absorption peaks and intrinsic fluorescence in fair agreement with experiment
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