Chemistry Reference
In-Depth Information
Fig. 4
Left
: ESI-QQQ positive-mode spectrum of 1.6 nm diameter hexanethiolate-protected
nanoparticle sample exchanged with [HSC
11
H
22
(CH
2
CH
3
)
3
N
+
][Cl
] (STEA
+
, or T). Six charge
states are detected, from 10
+
to 15
+
, each including both Au
144
L
60
and Au
146
L
59
. The charge
z
is
due to the number of T ligands (STEA
+
). Run in 70:30 MeCN:MeOH (optima grade), with no
added electrolyte. Reprinted with permission from [
2
,
8
]. Copyright 2009 American Chemical
Society.
Right
:(a) ESI mass spectra of Au
144
(SCH
2
CH
2
Ph)
60
nanoparticles. (b) Zoomed-in
spectrum of the 3
+
ion set. (c) Zoomed-in spectrum of the 2+ ion set. In both sets, adducts of
Au
144
(SCH
2
CH
2
Ph)
60
with various numbers of Cs
+
were detected in addition to the plain particle.
Reprinted with permission from [
8
,
46
]. Copyright 2009 American Chemical Society
nanomolecules in minor quantities, which agree with the Au
145-
x
Ag
x
(SR)
59
alloy
composition. An average of 53 silver atom incorporations were found in 1:0.75 Au:
Ag incoming molar ratio and maximum of 60 silver incorporations were found.
Optical spectrum of the Au
144
(SR)
60
is featureless since it lies close to the molecule
to bulk transition point. Incorporation of ~30 silver atoms results in the broad
features at 420 and 550 nm in the UV-visible spectrum. However broad features
at 420 nm were well developed when ~52 silver atoms are incorporated. Optical
features developed upon silver atom incorporation in the case of 144-metal atom
nanomolecule
.
Based on the proposed 3-shell structure of Au
144
(SR)
60
, Dass et al. [
47
] hypoth-
esized that the Ag atoms are selectively incorporated into the 60-atom shell, making
Au
12
,Au
42
, Ag
60
shells with 30 -SR-Au-SR- dimeric motifs. Later, H¨kkinen
group theoretically predicted the incorporation of silver atoms into 60-atom shell to
be the minimum energy isomer [
48
]. Experimentally determined single crystal
X-ray analysis will confirm the total structure and silver atom doping positions in
Au
144
(SR)
60
.
