Metallic nanoparticles detected by infrared spectroscopy

Abstract

Small Ni, Cu, Fe, Ag, Pt, Au nanoparticles with average diameters in the nanometer range have been studied by infrared spectroscopy. The Ni, Cu, Fe, Ag, Au nanoparticles were embedded in transparent matrices, AlN or Si3N4, or deposited on Si3N4 in the case of Pt. They were previously characterized by several techniques such as X-ray absorption spectroscopy, grazing incidence small-angle X-ray scattering or transmission electron microscopy. Infrared absorption depending on the metal is detected in the 60 meV to 140 meV energy range. It is interpreted as due to low-energy collective electron excitations related to the 2D confinement occurring at the metal-matrix interface.

Oxygen vibrations and acoustic surface plasmon on Be(0001)

“…23) and Cu(111). 24 Experimental evidence for surface acoustic plasmons has also been reported for metallic nanoparticles 25 and for epitaxial graphene on Pt(111). 26 Since electronic surface states are significantly affected by even small amounts of adsorbates, 27 a question arises as to the influence of adsorbates on acoustic surface plasmons.…”

Low-energy plasmons in quantum-well and surface states of metallic thin films

“…74 It also would be interesting to investigate the influence of the ISP and I and II modes on the optical properties of thin films. Additionally, the lateral confinement (for instance, by formation of islands 75,76 ) of the strongly dispersing acoustic-like modes might have a strong effect on the light absorption in infrared range, as was recently suggested in the case of metallic nanoparticles 77 and demonstrated in the case of Ag bilayer nanodisks 58 and In atomic chains. 75 Varying slab thickness, material, and lateral size would introduce great possibilities in the ability to tune the plasmonic properties of such atomic-scale structures.…”

Interplay between metal nanoparticles and dielectric spacing layers during the growth of Au/Si3N4 multilayers

“…The frequencies j of the oscillators required to fit the experimental spectra are gathered in Table III together with their intensity in arbitrary units and in percentage. 13 A narrowing of the bands located below 1000 cm −1 is observed for the composite films when compared to pure Si 3 N 4 , except for the Si 3 N 4 / Au͑1.6 nm͒ / Si 3 N 4 and Si 3 N 4 / ͓Au͑1.6 nm͒ / Si 3 N 4 ͔ 75 films. [28][29][30] Additional contributions can be seen whatever the sample thickness in the 800-1200 cm −1 range.…”

“…7 Roughness accumulation is a typical example of the decisive role of the structure of the already deposited layers on the growth of those that remain to be deposited. In contrast with the three former techniques which are commonly used, infrared spectroscopy has just proved to be a powerful candidate for the detection of MNPs, 13 in addition to its potential for monitoring phase transitions in solid matrices. 8,9 Alternatively, the growth of a dielectric cap deposited onto a granular metal layer has been shown to be influenced by the presence of the MNPs.…”