Probing surface plasmons in individual Ag nanoparticles in the ultra-violet spectralregime

Abstract

Previous investigations of surface plasmons in Ag largely focused on their excitations in thevisible spectral regime. Using scanning transmission electron microscopy with anelectron beam of 0.2 nm in conjunction with electron energy-loss spectroscopy, wespectrally and spatially probe the surface plasmons in individual Ag nanoparticles (∼30 nm), grown on Si, in the ultra-violet spectral regime. The nanomaterialsshow respective sharp and broad surface-plasmon resonances at∼3.5 eV(∼355 nm)and ∼7.0 eV (∼177 nm), and the correlated spectral calculations established their multipolar characteristics.The near-field distributions of the surface plasmons on the nanoparticles were alsomapped out, revealing the predominant dipolar nature of the 3.5 eV excitation withobvious near-field enhancements at one end of the nano-object. The unveilednear-field enhancements have potential applications in plasmonics and molecularsensing.