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Gold Nanoclusters Deposited on SiO2 via Water as Buffer Layer: CO-IRAS and TPD Characterization

Summary: Gold Nanoclusters Deposited on SiO2 via Water as Buffer Layer: CO-IRAS and TPD
Elad Gross and Micha Asscher*
Department of Physical Chemistry, The Hebrew UniVersity of Jerusalem 91904, Israel
Matthew Lundwall and D. Wayne Goodman
Department of Chemistry, Texas A&M UniVersity, College Station, Texas 77842
ReceiVed: July 11, 2007; In Final Form: August 16, 2007
CO adsorption properties on gold clusters were studied by infrared reflection absorption spectroscopy (IRAS)
and temperature-programmed desorption (TPD). Two growth procedures that differ in the final gold clusters
morphology were compared. In the first, the clusters were prepared by direct deposition (DD) of gold atoms
on SiO2/Si(100) substrates. The second growth mode is based on initial evaporation of gold atoms on top of
amorphous solid water as a buffer layer at 100 K that separates the small gold seed clusters from the substrate.
Subsequent annealing to 300 K desorbs the water molecules, resulting in nanocluster growth and their (cold)
deposition on the substrate in a buffer layer assisted growth (BLAG) mechanism. It is demonstrated here for
the first time that one can independently control cluster size and density by repeating the BLAG procedure
as many times as needed. BLAG clusters are more 3D in nature, have larger height to diameter ratio, yet
their interaction with CO is very similar to DD clusters. This is reflected by the practically identical CO
stretch observed on both clusters at 2106 ( 2 cm-1
. The CO stretch frequency was found BLAG clusters size
(2-10 nm) independent. CO molecules that are most strongly bound at the perimeter of the gold clusters do


Source: Asscher, Micha - Institute of Chemistry, Hebrew University of Jerusalem
Goodman, Wayne - Department of Chemistry, Texas A&M University


Collections: Chemistry