## 3 Results and Discussion  
Triangular silver nanoplates were successfully prepared by direct chemical reduction at room temperature as reported by [PERSON] [32]. The formation of the nanoplates was simply obtained by the reduction of silver ion to silver from silver nitrate by a reduction agent, namely sodium borohydride. This shape formation was effectively controlled by trisodium citrate and hydrogen peroxide. The triangular nanoplate formation could be roughly observed via color change when sodium borohydride was injected into the colorless solution which contained silver nitrate, trisodium citrate, and hydrogen peroxide. The solution color changed to yellowish after 1 min during the reduction process. The color continued to change for five minutes until the color remained dark blue. The centrifuged silver nanoplate pellet was resuspended and then was characterized to study the optical properties, uniformity of shape, and particle size. The optical properties of the silver nanoplates were studied using the surface plasmon resonance of the particles, which can be probed using the absorbance spectrum. This resonance has a strong dependence on the shape of particles [33]. The resuspended silver nanoplate suspension was characterized by UV-Vis and the optical absorbance spectrum is shown in Figure 1. Based on the absorbance spectrum, it was found that the triangular silver nanoplates exhibited a sharp plasmon band at 333 nm and an intense broad surface plasmon situated at 660 nm along with a shoulder at around 500 nm. Figure 1: Optical absorbance with corresponding mode of plasmon excitation of resuspended triangular silver nanoplate solution. In Figure 1, the corresponding modes of plasmon excitation for each extinction peak of the solution are also provided. The three characteristic peaks correspond to different modes of plasmon excitation of triangular nanoplates [34]. The two dominant bands located at 333 nm and 660 nm are due to the out-of-plane quadrupole resonance and in-plane dipole resonance, respectively. The shoulder at 500 nm is a result of the formation of anisotropic nanoparticles and it is attributed to the in-plane quadrupole resonance of silver nanoplates. These three modes of plasmon excitation agree with the structure of the triangular nanoplate shown in the observed TEM images (Figure 2a). The resuspended triangular silver nanoplate solution was dropped on a cuprum grid surface for TEM characterization. The solution was first dried at room temperature for 10 min prior to imaging. Figure 2a shows an image of triangular nanoplates that was captured with 120 kV. However, it is difficult to observe the triangular shape because the nanoplates have a tendency to stack face-to-face via self-assembly during the evaporation of the solvent in preparing the TEM sample. The uniform thickness of the plates can be seen from this stacking formation and this allowed determination of the plate size. This size measurement was analyzed using iTEM software (Adelaide, Australia), and the average plate thickness is 7 \(\pm\) 2 nm while the average edge length of triangular nanoplates is 26 \(\pm\) 1 nm. The inset figure in Figure 2a shows the captured lattice of nanoplates when imaged by TEM. The perfect lattice was measured at 0.48 nm, which corresponds to the lattice spacing of face-centered cubic (FCC) silver crystal. The growth direction of nanoplates corresponding to this measured lattice spacing is likely to be the \(<\)111\(>\) direction based on the X-ray diffraction (XRD) Bruker XRD D8 Advance; (Selangor, Malaysia) characterization [35]. Given this is the most stable FCC crystal plane, this is the growth direction that would be expected. The average size of triangular nanoplates was also confirmed using dynamic light scattering (DLS) as plotted in Figure 2b.