Progress in the Synthesis and Characterization of Gold Nanoclusters - Gold Clusters, Colloids and Nanoparticles - page 136

Fig. 9 (a) UV-Vis spectra of Au 25 (SC 2 H 4 Ph) 18 in the reduced ( black curve ) form, isolated by
extraction into acetonitrile (in which the oxidized form is insoluble) and of the oxidized ( red
curve ) form prepared by chemical oxidation using Ce IV .(b) Synthetic clusters obtained in single-
phase THF synthesis in the presence ( black curve ) and absence ( red curve ) of Oct 4 N + Br .
Reprinted from [ 90 ] with permission by the American Chemical Society
large-scale production of atomically precise Au nanoclusters protected by thiol
ligands. In another report, Xie and coworkers [ 91 ] reported a fast synthetic strategy
of thiolated Au 25 nanoclusters via protection-deprotection method. Three steps
were involved in the synthesis. In the first step, Au(I)SR complexes with a
protecting layer of cetyltrimethyl ammonium bromide (CTAB) were prepared.
The CTAB-protected Cys-Au I complexes were then reduced by NaBH 4 to
Cys-protected Au nanoclusters, followed by the transfer of clusters from the
aqueous to organic phase. During this step, the protecting CTAB layer could
provide a good steric hindrance and thus control the formation rate of thiolated
Au nanoclusters, resulting in the formation of atomically precise Au 25 nanoclusters
inside the protecting layer. Finally, the protecting CTAB layer was removed from
the surface of Au nanoclusters to bring back the water-soluble Cys-Au 25
nanoclusters. This method provides a facile and highly efficient process for the
production of high-purity Au 25 nanoclusters within only 10 min.
3.12 Au 36 Nanoclusters
In the synthesis of metal nanoclusters, the structure and property of selected
protecting ligand can determine the size, surface properties (e.g., solubility, fluo-
rescence, electronic structure, and chiral signature), and the application of the
resulting clusters. Recently, Dass and coworkers [ 92 ] reported the synthesis of an
aromatic thiol group-capped Au 36 nanoclusters. The Au 36 (SPh) 23 clusters were
produced through a two-stage process. A mixture containing Au 68 and Au 102 as
major species was first prepared according to a modified one-phase method
established previously [ 20 ]. An etching process was conducted in the second