Chemistry Letters Vol.33, No.2 (2004)
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from 4.9 to 7.4 nm only by varying alkyl chain of fatty acid silver
salts; 4.9 nm (0.4 nm)(C10-Ag), 5.2 nm (0.7 nm)(C12-Ag), 5.5 nm
for only 1 min were similar to those obtained at 413 K for
5 min under MW irradiation. As alkyl chains of alcohols became
longer, average diameter of Ag nanoparticles, which were pre-
pared from C16-Ag at 413 K for 5 min under MW irradiation, de-
creased slightly: 6.4 nm (0.9 nm)(1-pentanol), 6.0 nm (1.1 nm)-
(1-hexanol), 5.4 nm (0.9 nm)(1-heptanol), and 5.3 nm (0.7 nm)-
(1-octanol). The intense peak was observed at 1395 cmꢁ1 in
the FT-IR spectrum of the Ag nanoparticles prepared using
C12-Ag, which should be assigned to the symmetric stretching
vibration of a carboxylate group ꢀs(COOꢁ). This suggests
strongly that silver nanoparticles are capped by fatty acids as
Lee et al. suggested based on the observation of the peak at
1396 cmꢁ1 in the literature.6b
(0.6 nm)(C14-Ag),
6.0 nm
(1.1 nm)(C16-Ag),
5.8 nm
(0.9 nm)(C18-Ag), 7.4 nm (0.9 nm)(C18:1-Ag), and 6.1 nm
(1.0 nm)(C18:2-Ag), where the values in parenthesis are the
standard deviation, compared with 5 nm silver nanoparticles
synthesized by a thermal decomposition of fatty acid silver salts
at 523 K.6a From UV–vis spectrum of Ag nanoparticle prepared
from C16-Ag in hexane solution, an absorption maximum peak
was observed at 418 nm due to the surface plasmon absorption,1a
in good agreement with the reported values.6b
At low temperature (383 K), the size of Ag nanoparticles
prepared for 40 min was similar to those obtained at 413 K for
5 min. At high temperature (430 K), Ag nanoparticles prepared
In our MW-synthesis, silver ion was reduced by alcohol and
converted into silver nanoparticles under the precise size-con-
trol, which were stabilized by surface modification with fatty
acid.
The present study was mainly supported by ‘‘21st Century
Center of Excellence Program.’’ A part of this work was support-
ed by ‘‘Nanotechnology Support Project’’ of the Ministry of
Education, Culture, Sports, Science and Technology (MEXT),
Japan.
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Figure 1. TEM images of Ag nanoparticles prepared in 1-hex-
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Published on the web (Advance View) January 14, 2004; DOI 10.1246/cl.2004.158