Bridging the Pressure and Materials Gaps: High Pressure Sum Frequency Generation Study on Supported Pd Nanoparticles

Dellwig, Thilo; Rupprechter, Günther; Unterhalt, Holger; Freund, Hans‐Joachim

doi:10.1103/physrevlett.85.776

Cited by 161 publications

(156 citation statements)

References 24 publications

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“…The SFG photons are detected at o SFG ¼ o Ir þ o Vis . SFG provides the interface vibrational fingerprint, as illustrated by various works on organic monolayers adsorbed on metals and insulators [3,4]. Today, thanks to the emergence of new optical parametric oscillators (OPOs) tuneable in the visible frequency range [5], SFG is extended to the so-called two-colour sumfrequency generation spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Self-assembled organic and fullerene monolayers characterisation by two-colour SFG spectroscopy: a pathway to meet doubly resonant SFG process

Humbert

CAUDANO

Dreesen

et al. 2004

Applied Surface Science

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Two-colour sum-frequency generation (two-colour SFG) spectroscopy was used to probe both vibrational and electronic properties of 1-dodecanethiol/Ag(1 1 1), Au(1 1 1), and Pt(1 1 1), of 5-[p-(6-mercaptohexoxy)-phenyl]-10,15,20-triphenylporphin/Pt(1 1 1), and of C 60 /Ag(1 1 1). The role of the various physical parameters determining the sum-frequency generation (SFG) intensity equation is highlighted. The enhancement of the non-linear second order susceptibility in the aforementioned interfaces is explained in terms of metal interband transition, molecular electronic transition and of electron-phonon coupling, respectively.

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Section: Introductionmentioning

confidence: 99%

Self-assembled organic and fullerene monolayers characterisation by two-colour SFG spectroscopy: a pathway to meet doubly resonant SFG process

Humbert

CAUDANO

Dreesen

et al. 2004

Applied Surface Science

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“…[2] In the past the in situ investigation of catalyst surfaces was difficult, because the most surface sensitive imaging and spectroscopy techniques were restricted to high vacuum conditions. [3,4] Recent instrumental developments however, have made possible the investigations at elevated pressures using imaging [5][6][7][8][9][10] and spectroscopic [11,12,13] methods, among them X-ray photoelectron spectroscopy (XPS) [14,15,16] that has been shown to be able to operate at pressures of up to 10 mbar. [17,18] Here we present the use of XPS at millibar pressures to determine the chemical species near the surface of a catalyst, including the gas phase reaction products, in situ, i.e.…”

Section: Introductionmentioning

confidence: 99%

Methanol Oxidation on a Copper Catalyst Investigated Using in Situ X-ray Photoelectron Spectroscopy

Bluhm¹,

Hävecker²,

et al. 2004

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The surface and near-surface region of an active catalyst and the adjacent gas-phase reactants were investigated simultaneously under reaction conditions using in situ X-ray photoelectron spectroscopy (XPS). This investigation of methanol oxidation on a copper catalyst showed that there was a linear correlation between the catalytic activity of the sample and the presence of a sub-surface oxygen species that can only be observed in situ. The concentration profile of the sub-surface oxygen species within the first few nanometers below the surface was determined using photon energy-dependent depth-profiling. The chemical composition of the surface and the near-surface region varied strongly with the oxygen-tomethanol ratio in the reactant stream. The experiments show that the pure metal is not an active catalyst for the methanol oxidation reaction, but that a certain amount of oxygen has to be present in the sub-surface region to activate the catalytic reaction. Oxide formation was found to be detrimental to formaldehyde production. Our results demonstrate also that for an understanding of heterogeneous catalysts a characterization of the surface alone may not be sufficient, and that sub-surface characterization is essential.

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“…In vibrational sum-frequency generation (SFG) spectroscopy, one successful attempt of characterization was performed on a cationic surfactant deposited on anionic stabilized AuNPs forming a monolayer on a silicon wafer [4]. Other major works with SFG on nanoparticles are based on catalysis experiments such as in the case of CO molecules adsorbed on Pd or Pt nanoparticles at controlled pressure and temperature [5][6][7]. In this paper, we characterize by SFG, at ambient conditions, thiolate self-assembled monolayers (SAMs) on AuNPs films.…”

Section: Introductionmentioning

confidence: 99%

Self-assembled organic monolayers on gold nanoparticles: A study by sum-frequency generation combined with UV–vis spectroscopy

Humbert

Busson

Abid

et al. 2005

Electrochimica Acta

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We use sum-frequency generation spectroscopy (SFG) in the infrared 2800-3000 cm −1 spectral range and UV-vis spectroscopy (transmission) in the 450-650 nm spectral range in order to characterize vibrational and electronic properties of various interfaces composed of organic monolayers adsorbed on gold nanoparticles (AuNPs) with 19 nm average diameter. SFG signal is observed for AuNPs films deposited on glass substrates using the following silane intermediates: 3-(aminopropyl) triethoxysilane and 3-(mercaptopropyl) trimethoxysilane. The density of AuNPs and their aggregates are measured with a scanning electron microscope. For the samples showing a strong well-defined surface plasmon resonance (SPR), we also observe an enhancement of their non-linear optical properties. Furthermore, the SFG measurements show that 1-dodecanethiol films are rather well ordered on specific AuNPs substrates. In this way, the presence of the SFG signal, which comes from both the bulk electronic s-d interband transition and the vibrational states of the adsorbed molecules, depends on a SPR process. This phenomenon is evidenced on the AuNPs by the incident visible beam located at 532 nm, i.e. near the SPR energy maximum of these interfaces. These results open the door to experiments involving macromolecular and biological materials networks deposited on ultrathin metal electrodes in a controlled electrochemical environment.

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Bridging the Pressure and Materials Gaps: High Pressure Sum Frequency Generation Study on Supported Pd Nanoparticles

Cited by 161 publications

References 24 publications

Self-assembled organic and fullerene monolayers characterisation by two-colour SFG spectroscopy: a pathway to meet doubly resonant SFG process

Self-assembled organic and fullerene monolayers characterisation by two-colour SFG spectroscopy: a pathway to meet doubly resonant SFG process

Methanol Oxidation on a Copper Catalyst Investigated Using in Situ X-ray Photoelectron Spectroscopy

Self-assembled organic monolayers on gold nanoparticles: A study by sum-frequency generation combined with UV–vis spectroscopy

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