Characterization of OCB overlayed with AuAg nanoparticles TEM imaging (Figure ) reveals faceted plasmonic NPs with an average size of 49.2 ± 14.4 nm. The light and dark color bands on the NPs may correspond to stacking faults . Due to the similarity in contrast of silver and gold, these two components are difficult to distinguish with bright-field SEM imaging. In contrast, dark-field SEM with energy dispersive analysis by Xray (EDX) analysis (Figure ) revealed evidence of core-shell particle structures, as well as particles made of homometallic silver or a mix of silver and gold. The nanoparticles containing a mix of silver and gold may be attributed to AuAg alloy, as AuAg alloys are known to have more negative formation energy than their core-shell counterparts, indicating that the alloy phase is more stable .