The ceiling of the GNBs was relatively plane (Figure ). The comparison of the scanning electron microscopy (SEM) images of gold nanourchins and the GNBs indicated that the ceiling of GNB did not exhibit a large convex. This is dissimilar to the convex NRs or nanocubes . We observed that 80 µL of 400 mM L-AA(aq) was ideal for the synthesis of GNBs. The concentration of L-AA(aq) represented a relatively higher condition than the usual experimental condition for synthesizing GNRs, although the GNBs exhibited a uniform shape . The counting of the NPs in the TEM images revealed that the GNB ratio was ~70% under our condition (Figure ). Under low concentrations of L-AA, the GNBs could not be synthesized as the main product; rather, the GNRs were generated (Figures and). A higher concentration of L-AA increased and decreased the ratios of the sphere-shaped-gold-nanoparticles (refered to as GNPs in this paper) and GNB, respectively (Figures and). Based on the experiments discussed above, the amount of L-AA(aq) was fixed at 80 µL. The typical morphological characteristic of each kind of nanomaterial is also shown in Figure .