Intense fluorescence of Au20

Abstract

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 Au 20 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. Au 20 shows a very rich absorption fine structure reminiscent of well defined molecule-like quantum levels. These levels are resolved since Au 20 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. Published by AIP Publishing. [http://dx

(Meta-)stability and Core–Shell Dynamics of Gold Nanoclusters at Finite Temperature

“…Further MD details are described in the Supporting Information. These settings have been already adopted in refs , , and and were shown to yield observable quantities in good agreement with experiments in the size range between 3 and 20 gold atoms. Gold nanoclusters are strongly influenced by relativistic effects, , as the contraction of the 6s orbital and expansion of the 5d results in a smaller s–d gap and an increased directionality in the Au–Au bonding.…”

Principles of Optical Spectroscopy of Aromatic Alloy Nanomolecules: Au36–xAgx(SPh-tBu)24

“…55 Indeed, recent experimental work demonstrates that mixed Ag−Au MPC systems protected by aromatic ligands can exhibit highly enhanced photoluminescence quantum yield. 56 However, we conjecture that intersystem crossing effects recently investigated for bare Au cluster 57 are likely to be even stronger in aromatic-protected clusters, which severely complicates theoretical analysis so that we defer this study to future work.…”

NWChem: Past, present, and future

“…6, we report the parallel performance of the Gaussian basis set LR-TDDFT module in NWChem. This calculation involved computing 100 excitation energies, requiring 11 Davidson iterations, for the Au 20 molecule surrounded by a matrix of 80 Ne atoms 360 (1840 basis functions) with D 2 symmetry using the B3LYP functional. These calculations were performed on the Cascade supercomputer located at PNNL.…”