Metallic nanoparticles that can support plasmon resonances are called plasmonic nanoparticles and these are the important building blocks in nanoplasmonic applications. Their surface plasmon resonances (SPR)—collective free electron charge oscillations-provide tunable extinction in the visible to near-infrared range that are dependent on geometric size, shape, and environment. Owing to their highly sensitive resonances, many applications have been proposed, including biosensors [1-3], nanoantennas [4-7], and nonlinear biomarkers [8-11]. Further, their strong and weak SPR coupling property is proposed to be used as a “plasmonic ruler” for detecting DNA folding and unfolding [12] and nanometer-scale plasmonic circuit elements [13-15].