Molecule-specific interactions of diatomic adsorbates at metal-liquid interfaces

Abstract

Ultrafast vibrational dynamics of small molecules on platinum (Pt) layers in water are investigated using 2D attenuated total reflectance IR spectroscopy. Isotope combinations of carbon monoxide and cyanide are used to elucidate inter-adsorbate and substrate-adsorbate interactions. Despite observed cross-peaks in the CO spectra, we conclude that the molecules are not vibrationally coupled. Rather, strong substrate-adsorbate interactions evoke rapid (∼2 ps) vibrational relaxation from the adsorbate into the Pt layer, leading to thermal cross-peaks. In the case of CN, vibrational relaxation is significantly slower (∼10 ps) and dominated by adsorbate-solvent interactions, while the coupling to the substrate is negligible.

Characterization of the Platinum–Hydrogen Bond by Surface-Sensitive Time-Resolved Infrared Spectroscopy

“…1c of Ref. 27 ). Such ultra thin metal layers are advantageous for the ultrafast experiments due to their low metal absorption that result in negligible line-shape distortions and reduced scattering.…”

Ultrafast Vibrational Energy Transfer in Catalytic Monolayers at Solid–Liquid Interfaces

“…[24][25][26] Under these circumstances, immobilization of the sample at the interface allows obtaining surface-sensitive signals from solid-liquid interfaces. With this approach, we have recently investigated the ultrafast vibrational dynamics of surface-bound carbon monoxide 17,27 and cyanide 28 as well as self-assembled organic monolayers under various conditions 18,19,29,30 . Figure 1.…”

“…In particular, it has been shown that if molecules are immobilized on a surface, relaxation-induced heat generated in the substrate can give rise to cross-peaks between different adsorbate bands. 28,41 Such signals originate from a response (e.g. a frequency-shift and broadening) of the vibrational lineshape of all adsorbate modes on the surface to the substrate temperature.…”

“…The absence of any long-lived signals in the data clearly rules out temperature effects, presumably since the CO ligands are too far away from the substrate (in contrast to the CO molecules directly bound to a Ptsurface in ref. 28 ).…”

Infrared Spectroscopy as Molecular Probe of the Macroscopic Metal-Liquid Interface

“…A similar method was applied by Mundunkatowa et al [24]. Kraack et al [25,26] demonstrated a surface-enhanced ATR technique, utilizing gold or platinum nanoparticles at the IRE. Aguirre and co-workers [27] presented spectra from the solid-liquid interface in a specially designed microfluidic reactor.…”