Plasmonic quantum size effects in silver nanoparticles are dominated by interfaces and local environments

When metallic dimensions are reduced to the nanoscale, a phenomenon termed localized surface-plasmon resonance (LSPR) appears due to electron oscillations, resulting in distinct optical properties suited for advanced imaging and sensing technologies. As particles approach the quantum regime with dimensions less than 10 nm in diameter, however, the existing knowledge of their properties becomes quite hazy. The plasmonic character depends on the collective electronic excitation that can be tuned across a large spectral range by adjusting the material's size and shape. Size dependent spectral shifts of the LSPR in small metal nanoparticles are induced by quantum effects, but the existing literature on the subject is quite controversial due to inconsistencies.