Adsorption properties of decyl thiocyanate and decanethiol on platinum substrates studied by sum-frequency generation spectroscopy

in Surface Science (2007), 601

Recently, thiocyanate groups were successfully used as precursors for thiolate assemblies. Indeed, they provide a useful alternative to thiol groups for self-assembly on metallic substrates. In order to ... [more ▼]

Recently, thiocyanate groups were successfully used as precursors for thiolate assemblies. Indeed, they provide a useful alternative to thiol groups for self-assembly on metallic substrates. In order to check the adsorption properties and the quality of the thiocyanate-based self-assembled monolayers (SAMs), we use sum-frequency generation spectroscopy (SFG) and apply it to characterize the ad-layers of two similar molecules: decanethiol (DT) and decyl thiocyanate (DTCN) adsorbed on platinum surfaces. By comparing the SFG signals of the methyl and methylene vibration modes, we show that DTCN SAMs are less ordered than DT ones. These effects are related to the SAMs quality which depends on the molecular packing as highlighted by scanning tunnelling microscopy and X-ray photoelectron spectroscopy. [less ▲]

Thiocyanate and thiol self-assembling process on platinum investigated by means of sum-frequency generation

Poster (2005, September)

Sum-frequency generation from surface species in porous silicon

in Phys. Stat. Sol. (a) (2005), 202(8), 1487-1491

For the first time, the sum-frequency generation (SFG) spectra of surface species have been measured in porous silicon (PS) layers. The range of the vibrations 2000–2300 cm–1 for the native species Si–Hx ... [more ▼]

For the first time, the sum-frequency generation (SFG) spectra of surface species have been measured in porous silicon (PS) layers. The range of the vibrations 2000–2300 cm–1 for the native species Si–Hx has been explored. Furthermore for the studied mesoporous materials, it has been found that, as opposed to the infrared absorption, the SFG signal increases with porosity. Finally, the angular dependence and the enhancement of the SFG signal were measured in a one-dimensional PS photonic crystal structure with a defect producing an energy level in the photonic band gap. [less ▲]

Two-color-sum-frequency generation characterization of a protein monolayer adsorbed on a metallic substrate

Poster (2004, June)

Picosecond laser for performance of efficient nonlinear spectroscopy from 10 to 21 mm

in Optics Letters (2004), 29(3), 274-276

Laser tunability from 10 to 21 mm is obtained by use of an optical parametric oscillator based on a KTP crystal followed by a difference-frequency stage with a CdSe crystal. An all-solid-state picosecond ... [more ▼]

Laser tunability from 10 to 21 mm is obtained by use of an optical parametric oscillator based on a KTP crystal followed by a difference-frequency stage with a CdSe crystal. An all-solid-state picosecond Nd:YAG oscillator mode locked by a frequency-doubling nonlinear mirror is used for synchronous pumping. [less ▲]

Potential-dependent structure of the interfacial water on the gold electrode

in Surface Science (2004), 573

Doubly tunable sum frequency generation (SFG) spectra demonstrate that the water molecules at gold/electrolyte interface change their orientation with applied potential. At negative potentials, water ... [more ▼]

Doubly tunable sum frequency generation (SFG) spectra demonstrate that the water molecules at gold/electrolyte interface change their orientation with applied potential. At negative potentials, water molecules in the double layer align with their oxygen atom pointing to the solution. As potential became positive to be close to the potential of zero charge (PZC), the SFG signal decreased, suggesting the OH groups of the water molecule are either in random orientation or parallel to the electrode. As potential became more positive than the PZC, the SFG signal increased again with the oxygen-up orientation as same as in the negative potential region, indicating that water molecules interact with the adsorbed sulfate anions. The peak position of the SFG spectra indicates a relatively disordered state of water molecules at the gold electrode surface, in contrast to the previously observed ice-like structure of water at electrolyte/oxide interfaces. [less ▲]

Molecule orientation in self-assembled monolayers determined by infrared-visible sum-frequency generation spectroscopy

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 ▲]

Study by sum-frequency generation spectroscopy of a model biosensor : the biocytin-avidin complex

Poster (2003, May)

Study by the sum-frequency generation spectroscopy of a model biosensor : The biocytin-avidin complex*

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 ▲]

Two-color sum-frequency generation spectroscopy: a powerful tool for the study of self-assembled monolayers

Poster (2002, July)