References of "Dreesen, Laurent"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailSelf-Assembled Film Organization in Fast Microcontact Printing Investigated by Sum Frequency Generation Spectroscopy
Lis, Dan; Peremans, André; Sartenaer, Yannick et al

in Journal of Physical Chemistry C: Nanomaterials, Interfaces, and Hard Matter (2009), 113

The ability of microcontact printing to build highly ordered alkanethiol self-assembled monolayers (SAMs) on Pt substrates within a short time is studied by sum frequency generation (SFG) spectroscopy and ... [more ▼]

The ability of microcontact printing to build highly ordered alkanethiol self-assembled monolayers (SAMs) on Pt substrates within a short time is studied by sum frequency generation (SFG) spectroscopy and contact angle measurements. The deposition of ordered hexadecanethiol and dodecanethiol monolayers onto platinum substrates is achieved in less than 1 s. The film order and the alkane chain orientation are deduced from the SFG fingerprint acquired under different sets of laser polarization. Comparisons between the SAMs prepared by printing or by immersion demonstrate that both methods lead to the same high quality organization. Patterning effects within printed films are also investigated with respect to the layer conformation. Finally, wetting properties of printed layers are correlated with the printing duration, corroborating the spectroscopic results. [less ▲]

Detailed reference viewed: 51 (5 ULg)
Full Text
Peer Reviewed
See detailDielectric Multilayer Films Fabricated by Magnetron Sputtering: How Far Can the Iridescence Be Tuned?
Deparis, Olivier; Rassart, Marie; Vandenbem, Cedric et al

in Plasma Processes and Polymers (2009), 6

Periodic dielectric multilayer structures can generate interferential colours from optically transparent basic materials. Their iridescence property, i.e. the change of colour with the illumination or ... [more ▼]

Periodic dielectric multilayer structures can generate interferential colours from optically transparent basic materials. Their iridescence property, i.e. the change of colour with the illumination or viewing angle, is exploited in the industry to produce structurally coloured coatings and paints. Magnetron sputtering is an efficient technique for producing multilayer films owing to its ability to deposit films on large surfaces with excellent uniformity and reproducibility in both the film thickness and composition. Based on a theoretical model of the optical response, we investigated the iridescence tuning range of the technologically important SiO2/TiO2 material system. Radically different iridescent behaviours were predicted theoretically and demonstrated experimentally by selecting appropriate combinations of period and layer thickness ratio. [less ▲]

Detailed reference viewed: 37 (3 ULg)
Full Text
Peer Reviewed
See detailClose-packed array of gold nanoparticles and Sum Frequency Generation spectroscopy in total internal reflection: A platform for studying biomolecules and biosensors
Tourillon, Gérard; Dreesen, Laurent ULg; Volcke, Cédric et al

in Journal of Materials Science (2009), 44(24), 6805-6810

An approach is introduced for studying the adsorption and recognition mechanisms of biomolecules, without using any markers. We show for the first time, that the Sum Frequency Generation spectroscopy ... [more ▼]

An approach is introduced for studying the adsorption and recognition mechanisms of biomolecules, without using any markers. We show for the first time, that the Sum Frequency Generation spectroscopy performed in the Total Internal Reflection (TIR-SFG) geometry, combined with a regular close-packed array of gold nanoparticles allows to probe with a high sensitivity the changes in conformation and orientation induced by the recognition process of avidin by biocytin. This approach represents a new platform with potential use in biosensors, diagnostics and bioactive layers. [less ▲]

Detailed reference viewed: 70 (4 ULg)
Full Text
Peer Reviewed
See detailDC Magnetron Sputtering Deposition of Titanium Oxide Nanoparticles: Influence of Temperature, Pressure and Deposition Time on the Deposited Layer Morphology, the Wetting and Optical Surface Properties
Dreesen, Laurent ULg; Cecchet, Francesca; Lucas, Stéphane

in Plasma Processes and Polymers (2009), 6

Titanium dioxide nanoparticles were prepared on glass substrates by reactive DC magnetron sputtering. As highlighted by the atomic force microscopy characterization, we were able to control the ... [more ▼]

Titanium dioxide nanoparticles were prepared on glass substrates by reactive DC magnetron sputtering. As highlighted by the atomic force microscopy characterization, we were able to control the nanoparticles' surface coverage and diameter by varying the deposition time and the total pressure, respectively. The titanium dioxide energy band gap, determined by using ultraviolet-visible, spectroscopy, depends on the total pressure but is quite independent of the deposition temperature. On the contrary, it is blue shifted when the pressure increases. Finally, the contact angles slightly decrease after ultraviolet illumination irrespective of the different deposition parameters, indicating an improvement of the hydrophilic properties of the adsorbed layer. After 21 h in dark, the contact angles are nearly identical to the ones before exposure to UV light: the samples do not keep their hydrophilic behaviour. [less ▲]

Detailed reference viewed: 89 (8 ULg)
Full Text
Peer Reviewed
See detailSynthesis of titanium dioxide nanoparticles by reactive DC magnetron sputtering
Dreesen, Laurent ULg; Colomer, Jean-François; Limage, Hervé et al

in Thin Solid Films (2009), 518

Nanometer-sized titanium dioxide (TiO2) particles were prepared on carbon substrates by reactive direct-current magnetron sputtering. By performing measurements with high resolution electron microscopes ... [more ▼]

Nanometer-sized titanium dioxide (TiO2) particles were prepared on carbon substrates by reactive direct-current magnetron sputtering. By performing measurements with high resolution electron microscopes, the mean nanoparticle diameter and the coverage fraction of the substrate by the nanoparticles (NPs) were measured at 19 nm and 30%, respectively. Moreover, electron diffraction analysis showed that the TiO2 NPs' crystalline structure on the carbon substrate was a mixture of anatase and rutile. Finally,we provided information on the TiO2 initial growth stage: crystalline NPs were formed after deposition of amorphous nanoparticles on the substrate and heating. [less ▲]

Detailed reference viewed: 109 (11 ULg)
Peer Reviewed
See detailDC magnetron sputtering deposition of titanium oxide nanoparticles : influence
Dreesen, Laurent ULg; Cecchet, Francesca; Lucas, Stéphane

Conference (2008, September)

Detailed reference viewed: 20 (4 ULg)
Full Text
Peer Reviewed
See detailOrientation and Order of Self-Assembled p-Benzenedimethanethiol Films on Pt(111) Obtained by Direct Adsorption and via Alkanethiol Displacement
Silien, Christophe; Dreesen, Laurent ULg; Cecchet, Francesca et al

in Journal of Physical Chemistry C: Nanomaterials, Interfaces, and Hard Matter (2007), 111

Self-assembly of p-benzenedimethanethiol (p-BDMT) on Pt(111) has been investigated by high-resolution electron energy loss spectroscopy and sum-frequency generation spectroscopy. The molecules adsorb on ... [more ▼]

Self-assembly of p-benzenedimethanethiol (p-BDMT) on Pt(111) has been investigated by high-resolution electron energy loss spectroscopy and sum-frequency generation spectroscopy. The molecules adsorb on Pt-(111) like on gold, attached through one single thiol, leaving the second thiol moiety unreacted and exposed to the outer surface. Yet, the order of the p-BDMT self-assembled film is poor in comparison to alkanethiol SAMs. Displacement in solution of a preadsorbed pentanethiol (PTT) SAM by p-BDMT molecules proved to be a successful approach to achieve films of higher quality, where the size of the dithiol molecular domains tends toward the size measured for PTT. Nearly complete exchange is accomplished after 42 h. However, no significant exchange is observed when dodecanethiol replaces PTT. Displacing the alkanethiols by benzenethiol leads to the same conclusions, suggesting that the exchange processes are lessened as compared to gold. [less ▲]

Detailed reference viewed: 23 (1 ULg)
Full Text
Peer Reviewed
See detailAdsorption properties of decyl thiocyanate and decanethiol on platinum substrates studied by sum-frequency generation spectroscopy
Sartenaer, Yannick; Dreesen, Laurent ULg; Humbert, Christophe et al

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 ▲]

Detailed reference viewed: 33 (2 ULg)
Full Text
Peer Reviewed
See detailDevelopment of an all-solid-state pulsed picosecond laser system for nonlinear spectroscopy
Mani, A. A.; Jazmati, A. K.; Zidan, M. D. et al

in Physical Chemical News (2007), 36

Detailed reference viewed: 38 (1 ULg)
Full Text
Peer Reviewed
See detailSum-frequency generation spectroscopy of DNA monolayers
Sartenaer, Yannick; Tourillon, Gérard; Dreesen, Laurent ULg et al

in Biosensors & Bioelectronics (2007), 22

The anchoring of thiolated single-strandedDNA(HS-ssDNA) monolayers onto platinum substrates was investigated by sum-frequency generation spectroscopy. Different buffer solutions were used for the ... [more ▼]

The anchoring of thiolated single-strandedDNA(HS-ssDNA) monolayers onto platinum substrates was investigated by sum-frequency generation spectroscopy. Different buffer solutions were used for the preparation of the adlayers. Vibrational fingerprints in the 2700–3100 cm−1 spectral range showed the intercalation of Tris/EDTA (TE) buffer molecules within the HS-ssDNA self-assembled monolayer. Buffer contribution to SFG can be quenched either by using SFG inactive molecules like KH2PO4/K2HPO4/NaCl (PBS) or by repeated rinsing of the DNA layer with pure water. Comparing the SFG spectra of HS-ssDNA and mercaptohexanol (MCH), which had been self-assembled onto the same substrate, enabled us to infer ordering of the anchor arms and strong disordering of the DNA strands of HS-ssDNA monolayers self-assembled on platinum. [less ▲]

Detailed reference viewed: 39 (4 ULg)
Full Text
Peer Reviewed
See detailThe interaction between a protein and a ligand molecule studied by linear and non-linear optical spectroscopies
Dreesen, Laurent ULg; Méthivier, C.; Sartenaer, Y. et al

in Physical Chemical News (2007), 36

We use infrared reflection-adsorption (IRRAS) and sum-frequency generation (SFG) spectroscopies to study the interaction between a protein (avidin) and a ligand molecule (biocytin or its thiol derivative ... [more ▼]

We use infrared reflection-adsorption (IRRAS) and sum-frequency generation (SFG) spectroscopies to study the interaction between a protein (avidin) and a ligand molecule (biocytin or its thiol derivative) adsorbed on metals (Au and Ag) and insulators (CaF2 in two separate spectral ranges 2800-3500 cm-1 and 1400-1800 cm-1, respectively. No specific interaction is detected by SFG when the measurements are carried out on metals although IRRAS measurements attest the presence of a protein ad-layer. This is explained by the disordered character of the adsorbed film of avidin which is therefore SFG inactive. When the experiments are performed on an insulating substrate, no change of the biocytin/CaF2 SFG spectrum is detected in the low spectral range (1400-1800 cm-1) after immersion in an avidin solution in contrast with what was clearly demonstrated in the 2800-3500 cm-1 spectral range. Finally, we report, for the first time, the observation by SFG of the CH2 scissor vibration mode at 1465 cm-1. [less ▲]

Detailed reference viewed: 41 (6 ULg)
Full Text
Peer Reviewed
See detailTotal internal reflection sum-frequency generation spectroscopy and dense gold nanoparticles monolayer: a route for probing adsorbed molecules
Tourillon, Gérard; Dreesen, Laurent ULg; Volcke, Cédric et al

in Nanotechnology (2007), 18

We show that sum-frequency generation spectroscopy performed in the total internal reflection configuration (TIR–SFG) combined with a dense gold nanoparticles monolayer allows us to study, with an ... [more ▼]

We show that sum-frequency generation spectroscopy performed in the total internal reflection configuration (TIR–SFG) combined with a dense gold nanoparticles monolayer allows us to study, with an excellent signal to noise ratio and high signal to background ratio, the conformation of adsorbed molecules. Dodecanethiol (DDT) was used as probe molecules in order to assess the potentialities of the approach. An enhancement of more than one order of magnitude of the SFG signals arising from the adsorbed species is observed with the TIR geometry compared to the external reflection one while the SFG non-resonant contribution remains the same for both configurations. Although further work is required to fully understand the origin of the SFG process on nanoparticles, our work opens new possibilities for studying nanostructures. [less ▲]

Detailed reference viewed: 49 (2 ULg)
Full Text
Peer Reviewed
See detailAdsorption Properties of the Penicillin Derivative DTPA on Gold Substrates
Dreesen, Laurent ULg; Silien, Christophe; Volcke, Cédric et al

in Chemphyschem : A European Journal of Chemical Physics and Physical Chemistry (2007), 8(7), 1071-1076

Despite the large number of articles and patents dealing with penicillin and other b-lactam antibiotics, there have been no reports about the self-assembly of such substances as monolayers on gold ... [more ▼]

Despite the large number of articles and patents dealing with penicillin and other b-lactam antibiotics, there have been no reports about the self-assembly of such substances as monolayers on gold surfaces. The main reason stems from the high reactivity of the b-lactam ring, which hinders the development of molecules possessing this entity together with a metal-anchoring function. Herein, we present the synthesis of a novel molecule, 6-[(R,S)-5-(1,2-dithiolan-3-yl)pentanoyl-amino]-penicillanic acid, which combines the b-lactam ring and a metal-anchoring group. Using spectroscopic tools, we demonstrate the chemisorption of this compound on gold as self-assembled monolayers without any alteration of the penicillin pharmacophore and document its reactivity towards a penicillin-binding protein, BlaR-CTD. Our work is a preliminary step towards the development of new biosensors and well-ordered protein arrays, both based on the high affinity of penicillin for penicillin-binding proteins. [less ▲]

Detailed reference viewed: 86 (22 ULg)
Full Text
Peer Reviewed
See detailHigh energy and short pulses generation by Nd:yttrium aluminum garnet laser mode-locked using frequency-doubling nonlinear mirror
Mani, A. A.; Lis, D.; Grawet, L. et al

in Optics Communications (2007), 276

The generation of laser pulses with energies of >40 mJ at 25 Hz and durations variable from 15 ps to 45 ps using an Nd:yttrium aluminum garnet laser mode-locked with a Stankov nonlinear mirror is ... [more ▼]

The generation of laser pulses with energies of >40 mJ at 25 Hz and durations variable from 15 ps to 45 ps using an Nd:yttrium aluminum garnet laser mode-locked with a Stankov nonlinear mirror is demonstrated. This laser is used to pump an optical parametric generator-amplifier, which is tunable in the visible spectral range. [less ▲]

Detailed reference viewed: 16 (1 ULg)
Full Text
Peer Reviewed
See detailSynthesis and characterization of aromatic self-assembled monolayers containing methylene and ethyleneglycol entities by means of sum-frequency generation spectroscopy
Dreesen, Laurent ULg; Sartenaer, Y.; Peremans, A. et al

in Thin Solid Films (2006), 500

We use infrared-visible sum-frequency generation (SFG) spectroscopy in order to investigate the adsorption properties on Pt(111) of molecules having CH3–C6H4–(O–CH2–CH2)n –O–(CH2)m –SH as general chemical ... [more ▼]

We use infrared-visible sum-frequency generation (SFG) spectroscopy in order to investigate the adsorption properties on Pt(111) of molecules having CH3–C6H4–(O–CH2–CH2)n –O–(CH2)m –SH as general chemical formula. We synthesized three molecules defined by the values m=5 n =4, m =11 n =4, m=11 n =8 and characterized them by Nuclear Magnetic Resonance spectroscopy. Thanks to spectroscopic measurements, we show that these molecules build self-assembled monolayers on Pt(111). First, the weak SFG signals arising from the ad-layer indicate low order and surface coverage of the substrate by these molecules. Next, the vibrational fingerprints of the aforementioned molecules are determined between 2825 and 3125 cm 1 and the observed SFG spectral features are ascribed on the basis of the analysis of shorter and simpler molecules (1- dodecanethiol, 4-methylbenzenethiol and CH3–C6H4–O–(CH2)11–SH) also adsorbed on Pt(111). The occurrence of methylene vibration modes indicates a significant amount of chain defects whatever the n and m numbers are. Finally, the identification of a particular vibration mode, characteristic of the aromatic ring, enables us to qualitatively discuss the effect of the number of methylene and ethylene glycol entities on its orientation. More precisely, higher these numbers, more tilted (with respect to the substrate normal) the aromatic ring plane is. [less ▲]

Detailed reference viewed: 29 (1 ULg)
Full Text
Peer Reviewed
See detailComparative study of decyl thiocyanate and decanethiol self-assembled monolayers on gold substrates
Dreesen, Laurent ULg; Volcke, C.; Sartenaer, Y. et al

in Surface Science (2006), 600

In a recent paper Ciszek et al. [J.W. Ciszek, M.P. Stewart, J.M. Tour, J. Am. Chem. Soc. 126 2004) 13172] showed that organic thiocyanates may be an interesting alternative to the use of thiols for ... [more ▼]

In a recent paper Ciszek et al. [J.W. Ciszek, M.P. Stewart, J.M. Tour, J. Am. Chem. Soc. 126 2004) 13172] showed that organic thiocyanates may be an interesting alternative to the use of thiols for thiolate assemblies. We use scanning tunnelling microscopy (STM), infrared reflection absorption and sum-frequency generation spectroscopies (IRRAS and SFG) in order to study the adsorption properties of decyl thiocyanates (DTCN) and compare them to the decanethiol (DT) ones. Firstly, IRRAS measurements show that DTCN molecules form self-assembled monolayers (SAMs) on gold via a thiolate link with the metallic substrate. Secondly, the DTCN SAM on gold is less ordered than the DT one as highlighted by SFG spectroscopy. Indeed, the intensities of the methyl vibration modes vanish while the methylene ones increase when DTCN molecules are adsorbed on the substrate instead of DT. We explain the differences in SAMs quality on the basis of STM measurements which reveal differences in molecular order and packing. [less ▲]

Detailed reference viewed: 37 (1 ULg)
Full Text
Peer Reviewed
See detailMolecular conformation and electronic properties of protoporphyrin-IX self-assembled monolayers adsorbed on a Pt(111) surface
Humbert, C.; Volcke, C.; Sartenaer, Y. et al

in Surface Science (2006), 600

Monolayers of protoporphyrin-IX molecules are prepared on a Pt(111) surface by a self-assembly process in order to manufacture organic devices with controlled electronic properties. Scanning tunnelling ... [more ▼]

Monolayers of protoporphyrin-IX molecules are prepared on a Pt(111) surface by a self-assembly process in order to manufacture organic devices with controlled electronic properties. Scanning tunnelling microscopy (STM) and two-colour sum-frequency generation (2C-SFG) are performed ex situ in ambient air, in order to characterize their molecular conformation and electronic properties at the monolayer level, respectively. STM measurements performed with functionalized gold tips reveal a high covering rate of the metal surface. 2C-SFG measurements highlight CH stretching modes of vinyl substituted groups (R-CH=CH2) in the 2800–3200 cm-1 infrared spectral range and particular electronic features in the visible spectral range, i.e. a Soret band red shift and band separation compared to the liquid phase. Moreover, similar measurements are performed on Zn(II)Protoporphyrin-IX and 5-[p-(6-mercaptohexoxy)-phenyl]-10,15,20-triphenylporphin films for comparison. These results suggest a film conformation with the molecules having different tilt angles with respect to the substrate normal, depending on the ion metal presence or the chain length bonded to the porphyrin moiety. [less ▲]

Detailed reference viewed: 75 (3 ULg)
Full Text
Peer Reviewed
See detailOn the Protoporphyrin Monolayers Conformation
Humbert, Christophe; Dreesen, Laurent ULg; Sartenaer, Yannick et al

in Chemphyschem : A European Journal of Chemical Physics and Physical Chemistry (2006), 7

Detailed reference viewed: 27 (4 ULg)