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Fig. 11.1
Transmission Electron Microscopy (TEM) images of gold nanoparticles for
a
40 s
b
70 s and their corresponding size distribution for
c
40 s
d
70 s, respectively. (Adopted with kind
permission from Arshi et al.
2011a
)
Microwave irradiation is an efficient and distinct heating method, and has
attracted interest of researchers owing to its unique features such as short reac-
tion time, rapid volumetric heating, energy saving, environmental friendly and
high reaction rate (Ela et al.
2009
; Ahmed et al.
2011a
,
b
). The synthesized gold
nanoparticles were characterized by Transmission Electron Microscopy (TEM) and
UV/Vis spectroscopy. The TEM images (Fig.
11.1
) reflect stable and nearly spheri-
cal nanoparticles with an average diameter of 4.05 nm and 1.05 nm for samples at
40 s and 70 s irradiation time, respectively. Particle size calculated by using ap-
proximately 100 randomly selected individual nanoparticles from TEM micrograph
shows that the size of the nanoparticles for 40 s and 70 s ranges from 1-10 nm (see
Fig.
11.1a
) and 1-2 nm (see Fig.
11.1b
), respectively.
Figure
11.2
shows the UV/Vis absorption spectra of gold nanoparticles. Surface
plasmon resonance peaking at 590 nm for 40 s and 560 nm for 70 s samples respec-
tively, confirms the presence of gold nanoparticles. Generally, the broadness of the
peak is a clear indicator of the size of the nanoparticles. There is a blueshift in the
absorption peak to 560 nm which shows that the particle's size is decreasing as the
heating time exceeds from 40 to 70s (Shahverdi et al.
2007
).
