Rapport Annuel 2010: Summary on the study of the Tractatus Primus, Secundus, Tertius Instrumentorum Mechanicorum Levini Hulsii, a 17th Century book

Report (2010)

Gold-loaded carbon nanoparticles from poly(vinyl alcohol)-b-poly(acrylonitrile) non-shell-cross-linked micelles

in Chemistry : An Asian Journal (2009), 4(8), 1338-1345

Herein we show that a new amphiphilic poly(vinyl alcohol)-b-poly(acrylonitrile) block copolymer dispersed in water can be easily loaded with gold nanoparticles by addition of chlorauric acid followed by ... [more ▼]

Herein we show that a new amphiphilic poly(vinyl alcohol)-b-poly(acrylonitrile) block copolymer dispersed in water can be easily loaded with gold nanoparticles by addition of chlorauric acid followed by reduction by sodium borohydride. After deposition of the so-loaded micelles onto a silicon wafer, followed by an appropriate thermal treatment, the poly(acrylonitrile) core of the micelles is carbonized, while the poly(vinyl alcohol) shell is completely decomposed and volatilized, leading to gold encapsulated in carbon nanoparticles. The morphology of the micelles is maintained during thermal treatment without requiring shell-cross-linking of the micelles prior to pyrolysis. [less ▲]

About the Acidity-Catalytic Activity Relationship in Ionic Liquids: Application to the Selective Isobutene Dimerization

in Oil & Gas Science and Technology (2009), 64(6), 669

The Brønsted acidity level was evaluated for ionic liquids to which a strong acid has been added. As a first approach, the evaluation method was based on the determination of the Hammett acidity functions ... [more ▼]

The Brønsted acidity level was evaluated for ionic liquids to which a strong acid has been added. As a first approach, the evaluation method was based on the determination of the Hammett acidity functions H0, using UV-Visible spectroscopy. The acidity of protons is mainly determined by their solvation state and consequently, the properties of protons depend on both the nature of the solvent and the nature and concentration of the acid. An apparent acidity scale was defined following this principle. It was found that, for the investigated ionic liquids, the cation does not play a dominant role on the acidity level ([BMIm] ~ [BHIm] ~ [HNEt3]), whereas changing the nature of the anion of the ionic liquid may lead to very different acidities ([SbF6] > [PF6] > [BF4] > [NTf2] > [OTf]). This “acidity scale” was tentatively compared with an “activity scale” obtained for the dimerization of isobutene into isooctenes. The tendencies concerning the cation effect were confirmed ([BMIm] ~ [BuMePyrr] ~ [HNEt3]). The anion effect in only partially validated with a different behaviour for NTf2 type ionic liquids ([NTf2] ~ [SbF6] > [PF6] ~ [BF4] > [OTf]). By an adequate choice of the ionic liquid, selectivity for isobutene dimers can reach 88 wt% (at 70% isobutene conversion) with possible recycling of the catalytic system without loss of activity and selectivity. [less ▲]

A Comparison of the Acidity Levels in Room-Temperature Ionic Liquids

in Journal of the Electrochemical Society (2009), 156(9), 115

The Broensted acidity level was evaluated for several ionic liqs. ([BMIm][BF4], [BMIm][PF6], [BMIm][SbF6], [BMIm][OTf], [BMIm][NTf2], [HNET3][NTf2], and [HBIm][NTf2]) to which a strong acid, such as HNTf2 ... [more ▼]

The Broensted acidity level was evaluated for several ionic liqs. ([BMIm][BF4], [BMIm][PF6], [BMIm][SbF6], [BMIm][OTf], [BMIm][NTf2], [HNET3][NTf2], and [HBIm][NTf2]) to which a strong acid, such as HNTf2 [NTf2=N(CF3SO2)2] and HOTf (OTf=CF3SO3), has been added. The main purpose is to tentatively measure the influence on the resulting acidity of (i) the solvent anion or cation structure and (ii) the added acid nature. The evaluation method is based on the detn. of the Hammett acidity functions H0 using UV/visible spectroscopy. The acidity of protons is mainly detd. by their solvation state, and consequently, the properties of protons depend on both the nature of the solvent and the nature and concn. of the acid. In practice, for the investigated ionic liqs., the cation as well as the added acid nature does not play a dominant role, whereas changing the anion nature may lead to very different acidities. Indeed, for a similar content of added acid, the measured acidity levels are in the order PF6- > BF4- > NTf2- > OTf-. The problems of the influence of impurities on the final acidity and of the dissocg. character of the ionic liq. are addressed. [less ▲]

Application of Raman spectroscopy to forensic fibre cases

in Science & Justice : Journal of the Forensic Science Society (2008), 48(3), 109-117

Five forensic fibre cases in which Raman spectroscopy proved to be a good confirmatory method for microspectrophotometry (MSP) are described. Absorption spectra in the visible range are indeed sometimes ... [more ▼]

Five forensic fibre cases in which Raman spectroscopy proved to be a good confirmatory method for microspectrophotometry (MSP) are described. Absorption spectra in the visible range are indeed sometimes characteristic of a certain dye but this one can be subsequently identified unambiguously by Raman spectroscopy using a spectral library. In other cases the comparison of Raman spectra of reference fibres and suspect fibres led to an improvement of the discrimination power. The Raman measurements have been performed directly on mounted fibres and the spectra showed only little interference from the mounting resin and glass. Raman spectroscopy is therefore a powerful method that can be applied in routine fibre analysis following optical microscopy and MSP measurements. [less ▲]

Maya blue-green pigments found in Calakmul, Mexico: a study by Raman and UV-visible spectroscopy

in Journal Of Raman Spectroscopy (2008), 39(8), 1050-1056

After more than two decades of fieldwork in the Maya archaeological site of Calakmul, Mexico, numerous remnants of blue and green pigments have been reported on wall paintings, as well as on funerary ... [more ▼]

After more than two decades of fieldwork in the Maya archaeological site of Calakmul, Mexico, numerous remnants of blue and green pigments have been reported on wall paintings, as well as on funerary paraphernalia, such as masks, miniatures and vases. The importance of these pigments is linked to the sacred values that Maya people associate with blue and green colours since pre-Columbian times. These hues symbolise water, and are therefore associated with fertility and regeneration. This paper aims to perform a survey of the blue and green pigments used in the Early Classic and Late Classic periods in Calakmul (300-850 A.D.), in order to have a better understanding of their chemical composition and origin. Analyses were performed on microsamples using Raman and UV-visible spectroscopies to evaluate the possibilities that these techniques can offer in future in situ researches on Mesoamerican archaeological materials and objects. With these analyses, we have documented a large blue-green chromatic palette, which includes the earliest Blue Maya and Green Maya known to date, as well as malachite, pseudomalachite and an unknown-up-to-now blue-green mineral pigment, veszelyite, used specifically for ritual objects. The results indicate a careful selection of imported products and the mastering of a complex ancient Maya pictorial tradition. Copyright (c) 2008 John Wiley & Sons, Ltd. [less ▲]

About the Acidity Level in Room Temperature Ionic Liquids

in ECS Transactions (2007), 3(35), 71

The Brønsted acidity level was evaluated for ionic liquids to which a strong acid has been added. The evaluation method is based on the determination of the Hammett acidity functions H0, using UV-Visible ... [more ▼]

The Brønsted acidity level was evaluated for ionic liquids to which a strong acid has been added. The evaluation method is based on the determination of the Hammett acidity functions H0, using UV-Visible spectroscopy. The acidity of protons is mainly determined by their solvation state and consequently, the properties of protons depend on both the nature of the solvent and the nature and concentration of the acid. In practice, it was found that, for the investigated ionic liquids, the cation as well as the added acid nature does not play a dominant role, whereas changing the anion nature may lead to very different acidities. Indeed, for a similar content of added acid, the measured acidity levels are in the order: PF6- > BF4- > NTf2- > OTf-. The problems of the influence of impurities on the final acidity and of the weakly dissociating character of the ionic liquid are addressed. [less ▲]

Combination of electrografting and atom-transfer radical polymerization for making the stainless steel surface antibacterial and protein antiadhesive

in Langmuir (2006), 22(1), 255-262

A two-step "grafting from" method has been successfully carried out, which is based on the electrografting of polyacrylate chains containing an initiator for the atom transfer radical polymerization (ATRP ... [more ▼]

A two-step "grafting from" method has been successfully carried out, which is based on the electrografting of polyacrylate chains containing an initiator for the atom transfer radical polymerization (ATRP) of 2-(tert-butylamino)ethyl methacrylate (TBAEMA) or copolymerization of TBAEMA with either monomethyl ether of poly(ethylene oxide) methacrylate (PEOMA) or acrylic acid (AA) or styrene. The chemisorption of this type of polymer brushes onto stainless steel surfaces has potential in orthopaedic surgery. These films have been characterized by ATR-FTIR, Raman spectroscopy, atomic force microscopy (AFM), and measurement of contact angles of water. The polymer formed in solution by ATRP and that one detached on purpose from the surface have been analyzed by size exclusion chromathography (SEC) and H-1 NMR spectroscopy. The strong adherence of the films onto stainless steel has been assessed by peeling tests. AFM analysis has shown that addition of hydrophilic comonomers to the grafted chains decreases the surface roughness. According to dynamic quartz crystal microbalance experiments, proteins (e.g., fibrinogen) are more effectively repelled whenever copolymer brushes contain neutral hydrophilic (PEOMA) co-units rather than negatively charged groups (PAA salt). Moreover, a 2- to 3-fold decrease in the fibrinogen adsorption is observed when TBAEMA is copolymerized with either PEOMA or AA rather than homopolymerized or copolymerized with styrene. Compared to the bare stainless steel surface, brushes of polyTBAEMA, poly (TBAEMA-co-PEOMA) and poly(TBAEMA-co-AA) decrease the bacteria adhesion by 3 to 4 orders of magnitude as revealed by Gram-positive bacteria S. aureus adhesion tests. [less ▲]

Electrografting of Poly(ethylene glycol) Acrylate : A One-Step Strategy for the Synthesis of Protein-Repellent Surfaces

in Angewandte Chemie (International ed. in English) (2005), 44(34), 5505-5509

Electrografting of acrylate end-capped poly(ethylene glycol) (PEG) is an important technique for the one-step coating of electroconductive substrates by an adherent hydrophilic coating (see figure). This ... [more ▼]

Electrografting of acrylate end-capped poly(ethylene glycol) (PEG) is an important technique for the one-step coating of electroconductive substrates by an adherent hydrophilic coating (see figure). This technique is very efficient for the production of new protein-repellent surfaces. [less ▲]

Semi-crystalline polymer thin films: preparation, processing and peculiar features

Poster (2005, June 01)