The typical shape of the nanoparticles was spherical. Figure 6 shows a transmission electron microscopy
(TEM) image of the nanoparticles, and Fig. 7 shows the size distribution of the nanoparticles
measured from the TEM image obtained at the aqueous HAuCl4 solution concentration of 0.60 mM.
The average diameter was 10.5 ± 3.6 nm. This average diameter varied with preparation conditions. The
result of the energy-dispersive X-ray (EDX) analysis indicated that the nanoparticles were composed of
gold. The IR adsorption spectra revealed that the height of the gold-plasmon peak at 540 nm increased
with the discharge time. This also confirmed the synthesis of gold nanoparticles by SPP.