Single Particle Plasmon Spectroscopy of Silver Nanowires and Gold Nanorods

Abstract

The excitation of surface plasmons in individual silver nanowires and gold nanorods is investigated by means of high-resolution electron energy loss spectroscopy in a transmission electron microscope. The transverse and longitudinal modes of these nanostructures are resolved, and the size variation of the plasmon peaks is studied. The effect of electromagnetic coupling between closely spaced nanoparticles is also observed. Finally, the relation between energy-loss measurements and optical spectroscopy of nanoparticle plasmon modes is discussed.

Comparison of electron energy-loss and quantitative optical spectroscopy on individual optical gold antennas

“…The blue shift increased in magnitude with increasing particle diameter and reached values exceeding 800 meV for 80 nm diameter silver particles [3]. A blue shift of EELS compared to optics of about the same magnitude was also found in much later theoretical work [4] on prolate gold spheroids. Later experimental work on higher-order plasmonic resonances of silver nanorods did not show a clear correlation between the resonances of measured EELS and measured optical dark-field scattering spectra [5].…”

Surface plasmon modes of a single silver nanorod: an electron energy loss study

“…Only in recent years, thanks primarily to improvements in energy resolution given by the introduction of electron monochromators on commercial transmission electron microscopes (TEMs) [7], has electron energy-loss spectroscopy (EELS) [8] begun to be used routinely as a complementary technique to light-induced SP excitation and analysis; recent publications on the direct mapping of SP resonant modes on metal nanoparticles by EELS include references [9][10][11][12][13][14][15]. The advantages of probing optical excitations with electrons include the possibility of much higher spatial resolution [6] (through the small De Broglie wavelength of the electron beam) and the ability to excite all possible SP modes (both bright and dark modes [16,17]).…”

High-resolution surface plasmon imaging of gold nanoparticles by energy-filtered transmission electron microscopy

“…Here, a high-energy electron beam, with a transversal extension on the sub-nanometer scale, passes in the vicinity or through the nanoparticle, and some electrons lose energy through plasmon excitations, which are subsequently monitored. By raster scanning the beam over the metallic nanoparticle, one obtains information about the photonic local density of states of the metallic nanoparticles [13][14][15][16][17].…”