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See detailSelf-assembled organic and fullerene monolayers characterisation by two-colour SFG spectroscopy: a pathway to meet doubly resonant SFG process
Humbert, C.; Caudano, Y.; Dreesen, Laurent ULg et al

in Applied Surface Science (2004), 237

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 ... [more ▼]

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 C60/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. [less ▲]

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See detailSum-frequency generation spectroscopy applied to model biosensors systems
Dreesen, Laurent ULg; Sartenaer, Y.; Humbert, C. et al

in Thin Solid Films (2004), 464-465

Vibrational information recorded by infrared-visible sum frequency generation spectroscopy was used to study the adsorption of a derivated vitamin (biocytin) on different substrates and its subsequent ... [more ▼]

Vibrational information recorded by infrared-visible sum frequency generation spectroscopy was used to study the adsorption of a derivated vitamin (biocytin) on different substrates and its subsequent reaction with a protein (avidin). No reaction is observed on metallic substrates. When the experiments are carried out with a CaF2 substrate in the total internal reflection configuration, significant changes of the CH and NH vibrations can be related to the specific bonding of avidin to biocytin. [less ▲]

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See detailMolecule orientation in self-assembled monolayers determined by infrared-visible sum-frequency generation spectroscopy
Mani, A. A.; Schultz, Z. D.; Champagne, B. et al

in Applied Surface Science (2004), 237

The molecular orientation in self-assembled monolayers of thiophenol (TP) on Ag(1 1 1) and of para-nitroanilinododecane-thiol (NAT) on Au was investigated by infrared-visible sum-frequency generation ... [more ▼]

The molecular orientation in self-assembled monolayers of thiophenol (TP) on Ag(1 1 1) and of para-nitroanilinododecane-thiol (NAT) on Au was investigated by infrared-visible sum-frequency generation between 500 and 1500 cm-1. Ab initio calculations were performed to determine the interface nonlinear response. The combined experimental and theoretical results reveal that the S–C bond of TP is tilted 37° from the Ag(1 1 1) surface normal, with the aromatic ring plane perpendicular to the surface. On Au, the tilt angle of the NAT molecule stabilizes below 60° at the end of film growth. [less ▲]

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See detailSum-frequency generation characterization of the molecular recognition of avidin by biocytin films adsorbed on metallic substrates
Dreesen, Laurent ULg; Humbert, Christophe; Sartenaer, Yannick et al

Poster (2003, June)

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See detailStudy by sum-frequency generation spectroscopy of a model biosensor : the biocytin-avidin complex
Sartenaer, Yannick; Dreesen, Laurent ULg; Mani, Alaa Adin et al

Poster (2003, May)

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See detailE lectron–phonon couplings at C60 interfaces: a case study by two- color, infrared–visible sum–frequency generation spectroscopy
Caudano, Yves; Silien, C.; Humbert, Christophe et al

in Journal of Electron Spectroscopy & Related Phenomena (2003), 129

We demonstrate the ability of doubly resonant sum–frequency generation (DR-SFG) to investigate electron–phonon couplings at C60 –metal interfaces. Due to its coupling to electronic transitions, the ... [more ▼]

We demonstrate the ability of doubly resonant sum–frequency generation (DR-SFG) to investigate electron–phonon couplings at C60 –metal interfaces. Due to its coupling to electronic transitions, the totally symmetric Ag(2) vibration of C60 exhibits a huge enhancement of its nonlinear response for sum–frequency energies above the molecular electronic gap. We attribute this resonance to the coupling of the pentagonal pinch mode with the tiu lowest unoccupied molecular orbital (LUMO) of C60. [less ▲]

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See detailStudy by the sum-frequency generation spectroscopy of a model biosensor : The biocytin-avidin complex*
Sartenaer, Y.; Dreesen, Laurent ULg; Humbert, Christophe et al

in Physicalia Magazine (2003), 25(3), 221-229

Infrared-visible sum-frequency generation (SFG) spectroscopy is used to study the recognition of a protein (avidin) by a derivated vitamin (biocytin). No interaction is observed when the measurements are ... [more ▼]

Infrared-visible sum-frequency generation (SFG) spectroscopy is used to study the recognition of a protein (avidin) by a derivated vitamin (biocytin). No interaction is observed when the measurements are performed on metallic substrates in the normal co-propagative configuration. When the biocytin layer is deposited on a CaF2 substrate and the SFG measurements are performed in the total internal reflection configuration, drastic modifications in the C-H and N-H spectral ranges attest the molecular recognition of avidin by biocytin. The specificity of the recognition process is confirmed by replacing avidin by other proteins. [less ▲]

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See detailProbing a molecular electronic transition by two-colour sum-frequency generation spectroscopy
Humbert, Christophe; Dreesen, Laurent ULg; Nihonyanagi, S. et al

in Applied Surface Science (2003), 212–213

We demonstrate that a new emerging technique, two-colour sum-frequency generation (SFG) spectroscopy, can be used to probe the molecular electronic properties of self-assembled monolayers (SAMs). In the ... [more ▼]

We demonstrate that a new emerging technique, two-colour sum-frequency generation (SFG) spectroscopy, can be used to probe the molecular electronic properties of self-assembled monolayers (SAMs). In the CH spectral range (2800–3200 cm-1), we show that the sum-frequency generation signal of a porphyrin alkanethiol derivative adsorbed on Pt(1 1 1) reaches a maximum intensity at ~435 nm SFG wavelength. This wavelength corresponds to the porphyrin moiety specific p–p*$ molecular electronic transition which is called the Soret or B band. This resonant behaviour is not observed for 1-dodecanethiol SAMs, which are devoid of molecular electronic transition in the investigated visible spectral range. [less ▲]

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See detailTwo-color sum-frequency generation spectroscopy: a powerful tool for the study of self-assembled monolayers
Dreesen, Laurent ULg; Humbert, Christophe; Thiry, Paul et al

Poster (2002, July)

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See detailTwo-color sum-frequency generation spectroscopy: a powerful tool for the study of self-assembled monolayers
Dreesen, Laurent ULg; Humbert, Christophe; Celebi, Michael et al

Poster (2002, June)

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See detailInfluence of the metal electronic properties on the sum-frequency generation spectra of dodecanethiol self-assembled monolayers on Pt (111), Ag (111) and Au (111) single crystals
Dreesen, Laurent ULg; Humbert, Christophe; Celebi, M. et al

in Applied Physics B : Lasers & Optics (2002), 74

Infrared-visible sum-frequency generation (SFG) spectroscopy is performed at different visible wavelengths between 450 and 650 nm in order to investigate the interaction between metallic substrates (Pt ... [more ▼]

Infrared-visible sum-frequency generation (SFG) spectroscopy is performed at different visible wavelengths between 450 and 650 nm in order to investigate the interaction between metallic substrates (Pt, Ag and Au) and 1-dodecanethiol self-assembled monolayers. We show that such measurements provide a means to study the electronic properties of metals as well as the interference phenomena between the SFG signals from the adsorbate and the substrate. The common features of the three interfaces are the vibration modes of the terminal methyl groups. However, these resonances appear as peaks for Pt (111) and as dips in the case of Ag (111). Their shape is not modified when the visible wavelength is tuned between 450 and 650 nm. Moreover, the metal sum-frequency generation contribution is slightly modified in that spectral range. For Au (111) samples, the sum-frequency generation spectrum drastically evolves with the visible wavelength: the peak resonant sum-frequency generation signal at 450 nm becomes rather dip-shaped at 650 nm. The non-linear response of gold is also enhanced when the wavelength associated with the sum-frequency process is close to 480 nm. These results are interpreted on the basis of the metal electronic properties that are responsible for the non-resonant contribution to the SFG signal. [less ▲]

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See detailDevelopment of a two-color picosecond optical parametric oscillator, pumped by a Nd:YAG laser mode locked using a nonlinear mirror, for doubly-resonant sum frequency generation spectroscopy
Mani, A. A.; Dreesen, Laurent ULg; Humbert, C. et al

in Surface Science (2002), 502-503

We step up a doubly-resonant sum frequency generation (DR-SFG) spectrometer based on the use of an all-solid-state flash-lamp-pumped Nd:YAG laser that synchronously pumps two parametric oscillators ... [more ▼]

We step up a doubly-resonant sum frequency generation (DR-SFG) spectrometer based on the use of an all-solid-state flash-lamp-pumped Nd:YAG laser that synchronously pumps two parametric oscillators. Pulses as short as 12 ps FWHM are generated by mode locking a Nd:YAG oscillator using a frequency doubling nonlinear mirror combined with a two-photon absorber. The available pump power is shared between a LiNbO3/AgGaS2 optical parametric oscillator (OPO), tunable from 3800 to 1100cm-1 and a BBO OPO tunable from 410 to 2600 nm. Spectral resolution and pulse are 2 and 3 cm-1 in the infrared and visible spectral ranges, respectively. First DR-SFG spectra of self-assembled monolayers on Au are presented. [less ▲]

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See detailIR-visible sum-frequency vibrational spectroscopy of Biphenyl-3 methylene thiol monolayer on gold and silver: effect of the visible wavelength on the SFG spectrum
Humbert, Christophe; Dreesen, Laurent ULg; Mani, A. A. et al

in Surface Science (2002), 502-503

We measured IR-visible sum-frequency generation spectra of CH3-(C6H4)2-(CH2)3-S-H (Biphenyl-3) self-assembled monolayers on a silver and a gold substrate. For the latter substrate, we observed different ... [more ▼]

We measured IR-visible sum-frequency generation spectra of CH3-(C6H4)2-(CH2)3-S-H (Biphenyl-3) self-assembled monolayers on a silver and a gold substrate. For the latter substrate, we observed different interference patterns between the resonant signal of the CH vibration and the non-resonant contribution of the substrate as a function of the visible beam wavelength. The non-linear response of the gold substrate is enhanced around 480 nm corresponding to the s-d interband transition. Such effect is not observed for the silver substrate the interband transition of which is located out of the investigated visible spectral range of 450-700 nm. [less ▲]

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See detailEtude par spectroscopie de génération de la fréquence somme de l'interface méthanol-platine
Vidal, F.; Busson, B.; Six, C. et al

in J. Phys. IV France (2002), 12

La spectroscopie vibrationnelle non-linéaire par génération de la fréquence somme est une sonde particulièrement adaptée à l'étude des interfaces entre milieux denses. Cette technique a été appliquée à l ... [more ▼]

La spectroscopie vibrationnelle non-linéaire par génération de la fréquence somme est une sonde particulièrement adaptée à l'étude des interfaces entre milieux denses. Cette technique a été appliquée à l'étude de l'interface électrochimique monocristal de platine/solution acide de méthanol, système qui constitue un modèle de pile à combustible, dispositif où l'énergie chimique est directement convertie en énergie électrique. Les propriétés vibrationnelles dépendent fortement de l'orientation cristallographique de l'électrode de platine. [less ▲]

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See detailStudy of the metal-adsorbate interactions using SFG spectroscopy at different visible wavelengths
Dreesen, Laurent ULg; Humbert, Christophe; Celebi, Michael et al

Conference (2001, October)

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See detailSum-frequency generation characterisation of the water/polyethylene glycol interface
Dreesen, Laurent ULg; Humbert, Christophe; Hollander, Philippe et al

Poster (2001, June)

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See detailSum-frequency generation characterisation of the water/polyethylene glycol interface
Dreesen, Laurent ULg; Humbert, Christophe; Hollander, Philippe et al

Poster (2001, May)

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See detailStudy of the water/poly(ethylene glycol) interface by IR-visible sum-frequency generation spectroscopy
Dreesen, Laurent ULg; Humbert, C.; Hollander, P. et al

in Chemical Physics Letters (2001), 333

We used infrared-visible sum-frequency generation spectroscopy to investigate the vibrational properties of the water/poly(ethylene glycol) interface in the 2800-3800 cm-1 spectral range. The vibrational ... [more ▼]

We used infrared-visible sum-frequency generation spectroscopy to investigate the vibrational properties of the water/poly(ethylene glycol) interface in the 2800-3800 cm-1 spectral range. The vibrational fingerprint of the interface differs significantly from the one associated with the aire/poly(ethylene glycol) interface. It is shown that the poly(ethylene glycol) molecular arrangement, originally relatively well-ordered, becomes disorganised in the presence of water. Moreover, a new OH band is identified demonstrating the strong interaction of water with the polymer. [less ▲]

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See detailPumping picosecond optical parametric oscillators by a pulsed Nd:YAG laser mode locked using a nonlinear mirror
Mani, A. A.; Dreesen, Laurent ULg; Hollander, Ph. et al

in Applied Physics Letters (2001), 79(13), 1945-1947

We report on the performances of the mode locking of a flash-lamp-pumped Nd:YAG laser using a frequency-doubling nonlinear mirror combined with a two-photon absorber. Pulse lengths from 12 to 8 ps are ... [more ▼]

We report on the performances of the mode locking of a flash-lamp-pumped Nd:YAG laser using a frequency-doubling nonlinear mirror combined with a two-photon absorber. Pulse lengths from 12 to 8 ps are generated. We show that the flat shape of the pulse-train envelope generated by the oscillator is adapted for the synchronous pumping of optical parametric oscillators and we demonstrate the efficient generation of an infrared beam tunable from 3800 to 1100 cm-1 with bandwidth of 2 cm-1 in one single conversion stage in LiNbO3 or AgGaS2. The "all-solid-state" laser system enables surface sum-frequency generation spectroscopy to be performed with high sensitivity and high resolution. [less ▲]

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See detailSum-frequency generation characterisation of methanol, pentadecanoïc acid and water interfaces
Humbert, Christophe; Dreesen, Laurent ULg; Hollander, Philippe et al

Poster (2000, May)

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