Electronic structure and optical transitions of Au(20-x)Cu(x) nanoclusters

Remarkable Structural Effect on the Gold-Hydrogen Analogy in Hydrogen-Doped Gold Cluster

In accordance with the well established gold-hydrogen analogy, a hydrogen atom mimics the properties of a gold atom in gold clusters. In a recent study it has been demonstrated that the properties of a hydrogen atom doped small gold cluster (Au₇H) are not in conformity with the aforementioned analogy. In this paper we study the properties of the Au₇H cluster exhaustively to re-examine the validity of the gold-hydrogen analogy in the context of adsorption of CO and O₂ molecules on pristine gold and hydrogen atom doped gold clusters. For this purpose we first determine the most stable structure of the Au₇H cluster by using an ab initio density functional theory based method with generalized gradient approximation (GGA) and Meta-GGA exchange-correlation functionals. We carry out geometry optimization by considering various planar and three-dimensional isomers of the Au₇H cluster as initial geometries. We find that the lowest energy structure of Au₇H is a planar one with C_{2 v} symmetry, and it is very close to the structure of the Au₈ cluster with D_{4 h} symmetry. Furthermore, to examine the validity of the gold-hydrogen analogy we carry out a detailed investigation of the adsorption of CO and O₂ molecules on the most stable as well as various other low energy isomers of the Au₇H cluster. We find that the adsorption energies and the extent of activation of CO and O₂ molecules on the most stable planar isomer of Au₇H are almost the same as those on the parent Au₈ cluster with D_{4 h} symmetry proving the validity of the gold-hydrogen analogy. On the other hand, for the high energy three-dimensional isomers of the Au₇H cluster obtained from the pristine Au₈ cluster with T _d symmetry, we find a significant enhancement in adsorption energy as well as the extent of activation of CO and O₂ molecules as compared to those for the corresponding pristine cluster. Therefore, the high reactivity of the 3D isomer of the Au₇H cluster may be attributed to its existence in a state which is higher in energy than its most stable planar isomer.

Achievement of silver-directed enhanced photophysical properties of gold nanoclusters

Silver-induced enhanced fluorescence of gold nanoclusters through a facile green synthesis.

First-principles investigation of Ag-doped gold nanoclusters

Gold nanoclusters have the tunable optical absorption property, and are promising for cancer cell imaging, photothermal therapy and radiotherapy. First-principle is a very powerful tool for design of novel materials. In the present work, structural properties, band gap engineering and tunable optical properties of Ag-doped gold clusters have been calculated using density functional theory. The electronic structure of a stable Au₂₀ cluster can be modulated by incorporating Ag, and the HOMO–LUMO gap of Au_20−nAg_n clusters is modulated due to the incorporation of Ag electronic states in the HOMO and LUMO. Furthermore, the results of the imaginary part of the dielectric function indicate that the optical transition of gold clusters is concentration-dependent and the optical transition between HOMO and LUMO shifts to the low energy range as the Ag atom increases. These calculated results are helpful for the design of gold cluster-based biomaterials, and will be of interest in the fields of radiation medicine, biophysics and nanoscience.