Further, we changed the molar concentration of the surfactant mixtures from 0.5-fold to 2-fold in stages and monitored the changes in the UV/VIS/NIR spectra and morphology of the nanoparticles (Figures and). The 1-fold sample represents the original concentration for GNB synthesis. By increasing the concentration, the short-wavelength peak of the spectra reduced and shifted to the longer side. The characteristic long-wavelength peak was turned for observation at the surfactant concentration of over 0.8fold; it shifted toward a longer wavelength as the concentration increased. The peak ratio of the short and long wavelengths was >1 until the surfactant concentration reached 1, and the peak intensity reversed under higher concentration conditions. The changes in the nanomaterial shape also corresponded to the spectra changes (Figures and). The GNB shapes were observed well under the one-fold conditions; higher and lower concentrations exhibited lower efficiencies for producing GNBs (Figure ). These data indicated that the concentration of BDAC would affect the morphology of nanomaterials.