J. Phys. Chem. C 2010, 114, 741–745
741
Surfactant-free Synthesis of Ultrasmall Gold Nanoclusters Samantha M. Reilly,† Thomas Krick,‡ and Amala Dass*,† Department of Chemistry and Biochemistry, UniVersity of Mississippi, UniVersity, Mississippi 38677, and Department of Biochemistry, Molecular Biology and Biophysics, UniVersity of Minnesota, St. Paul, Minnesota 55108 ReceiVed: July 17, 2009; ReVised Manuscript ReceiVed: NoVember 25, 2009
The role of surfactant (most often tetraoctylammonium bromide) in the two-phase Brust gold nanocluster synthesis (Brust, M.; Walker, M.; Bethell, D.; Schiffrin, D. J.; Whyman, R. J. Chem. Soc., Chem. Commun. 1994, 801) has been unclear. The results of the surfactant-free synthesis of gold nanoclusters in methylene chloride employing NaBH4 as a reducing agent with the usual synthetic conditions such as excess thiol:gold ratio (>3) and ice-cold reaction temperature are reported. A nanocluster mixture, ∼5% yield with Au(I)SR byproducts, was obtained. The isolated Au nanoclusters were characterized by mass spectrometry, UV-visible, and nuclear magnetic resonance spectroscopy. MALDI-TOF mass spectrometry reveals the presence of mixtures of nanoclusters in the Au16-Au31 size range. Discrete features in the UV-visible spectrum suggested the presence of small
