Surface plasma resonances in small spherical silver and gold particles

Abstract

With 51 keV electrons surface plasma losses have been investigated on small spherical Ag and Au particles embedded in a medium with dielectric constant %=2.37. The surface loss of particles with radii of about 50/~ is found at 2.99_+ 0.03 eV for silver and 2.34+0.03 eV for gold being in good agreement with calculated values. For larger radii the loss shifts to higher energy values which agrees qualitatively with the theory of Fujimoto and Komaki for the free electron gas. The optical extinction bands of the particles have been raeasured, too. Their maxima are shifted to lower energies, in accordance with Mie's theory, if the particle size increases sufficiently. Comparison of the energy values of the "'electric" extinction bands with those of the surface plasmons shows, that they correspond in theory and experiment, if the particles are small. This confirms, that the optical colloid extinction of Ag and Au may be interpreted as plasma resonance absorption and emission of the particles.

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

“…They found the EELS resonance positions to be systematically blueshifted with respect to the optical extinction-resonance positions. 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.…”

“…The lateral antenna parameters have been chosen to result in resonance positions in the infrared to avoid possible effects of interband transitions in the metal like, e.g., in [3]. Further details are described in [1].…”

“…We should like to argue that, on the basis of the experimental literature, the answer is not really clear. Several decades ago, Kreibig and Zacharias [3] have systematically compared EELS and optical spectra of colloids of gold and silver nanoparticles in the range from about 10 to 100 nm particle diameter. Under these conditions, not only intraband (i.e., free electrons) but also interband transitions in the metal play a significant role.…”

Anomalous Frequency and Temperature Dependence of the Optical Absorption of Small Gold Particles

“…Introduction. -Special surface plasmon modes can be excited optically in small metallic particles [1][2][3][4][5][6][7][8]. Their investigation has become a widely accepted method in small particle physics 49] and has revealed information concerning the transition from the molecular state to the bulky solid.…”

Study Of Signal Transmission through Different Array of Cu, Au and Ag Nanospheres

“…It was the first theoretical description of surface plasmons. In 1970 Uwe Keribig and Peter Zacharias (Kreibig & Zacharias 1970), performed a study in which they compared the electronic and optical responses of gold and silver nanoparticles. For the first time they described the optical properties of metal nanoparticles in terms of surface plasmon.…”