Personne :
Laroche, Gaétan

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Adresse électronique
Date de naissance
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Structures organisationnelles
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Université Laval. Département de génie des mines, de la métallurgie et des matériaux
Identifiant Canadiana

Résultats de recherche

Voici les éléments 1 - 10 sur 50
  • Publication
    Accès libre
    Polycaprolactone (PCL) chains grafting on the surface of cellulose nanocrystals (CNCs) during in situ polymerization of ε-caprolactone at room temperature
    (Materials Sciences and Applications, Vol. 11 (11), 2020, 2020-11-13) Astruc, jérémy; Cousin, Patrice; Laroche, Gaétan; Robert, Mathieu; Elkoun, S. (Saïd)
    This work aimed at investigating the feasibility of surface modification of cellulose nanocrystals (CNCs) using in situ ring opening polymerization of ε-caprolactone (ε-CL) at room temperature. Residues of flax and milkweed (Asclepias syriaca) stem fibers were used as a source of cellulose to obtain and isolate CNCs. The cationic ring opening polymerization (CROP) of the monomer ε-CL was used to covalently graft polycaprolactone (PCL) chains at the CNCs surface. Silver hexafluoroantimonate (AgSbF6) was used in combination with the extracted CNCs to initiate, at room temperature, the polymerization and the grafting reactions with no other stimulus. Fourier-Transform InfraRed (FTIR), X-ray Photoelectron Spectrometry (XPS), UV/visible absorption and Gel Permeation Chromatography (GPC) analyses evidenced the presence of PCL chains covalently grafted at CNCs surface, the formation of Ag(0) particles as well as low or moderate molecular weight free PCL chains.
  • Publication
    Accès libre
    Fourier-Transform infrared spectroscopy of ethyl lactate decomposition and thin-film coating in a filamentary and a glow dielectric barrier discharge
    (Wiley-VCH-Verl., 2021-07-05) Milaniak, Natalia; Laroche, Gaétan; Massines, Françoise
    Glow and filamentary regimes of atmospheric pressure plasma-enhanced chemical vapor deposition in a planar dielectric barrier discharge configuration were compared for thin-film deposition from ethyl lactate (EL). EL decomposition in the plasma phase and thin-film composition were both characterized by Fourier- transform infrared spectroscopy. EL chemical bonds' concentration along the gas flow decreases progressively in the glow dielectric barrier discharge (GDBD), whereas it drastically oscillates in the filamentary dielectric barrier discharge (FDBD), with values higher than that of the initial mixture. EL decomposition route depends on the discharge regime, as the decrease of the concentration of the different investigated bonds is different for an identical amount of energy provided to EL molecules. CO2 is systematically formed reaching concentrations of 25 and 40 ppm, respectively, in FDBD and GDBD.
  • Publication
    Accès libre
    Unveiling the origin of the anti fogging of plasma-coated glass : role of the structure and chemistry of siloxane precursors
    (Elsevier Science, 2020-01-25) Laroche, Gaétan; Rodríguez Durán, Iván
    The application of (super)hydrophilic coatings in sectors of activity concerned by fogging, such as the food industry, the architectural sector, and medicine has attracted enormous attention over the past few years. However, despite this interest, most of the coating deposition techniques used thus far are not suitable for large-scale production because of their multistep nature. In this regard, the use of atmospheric pressure dielectric barrier discharges (AP-DBD) operated under a controlled N2/N2O atmosphere offers a promising alternative to conventional deposition techniques for the fabrication of anti-fogging coatings. Using this one-step coating approach, four siloxane precursors with different structures and different number of Si―H and Si−CH3 groups; namely, 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS), octamethylcyclotetrasiloxane (OMCTS), 1,1,3,3-tetramethyldisiloxane (TMDSO), and hexamethyldisiloxane (HMDSO) were deposited on glass samples. Because of their extreme wetting behavior (WCA < 5°), TMCTS-coated glasses featured an excellent anti-fogging performance, in contrast to OMCTS-, TMDSO-, and HMDSO-coated glasses which were not fogging-resistant (WCA ≈ 80°)). Coupled with hydrophilic functionalities, such as Csingle bondO, Odouble bond Csingle bondO, and Sisingle bondOH groups, the relatively high surface roughness of TMCTS-coated glass, compared with that of OMCTS-, TMDSO-, or HMDSO-coated glass, accounted for its superior visual characteristics when exposed to water vapor at 80 °C. These results allow us to confidently conclude that the cyclic structure of TMCTS in conjunction with the high reactivity of the Si-H bonds is responsible for the observed anti-fogging effect.
  • Publication
    Accès libre
    Influence of a square pulse voltage on argon-ethyl lactate discharges and their plasma-deposited coatings using time-resolved spectroscopy and surface characterization
    (AIP Publishing, 2018-10-15) Laroche, Gaétan; Desjardins, Edouard; Naudé, Nicolas; Meichelboeck, Maximilian; Belinger, Antoine; Laurent, Morgane; Stafford, Luc; Gherardi, Nicolas
    By comparing time-resolved optical emission spectroscopy measurements and the predictions of a collisional-radiative model, the evolutions of electron temperature (Te) and number density of argon metastable atoms [n(Arm)] were determined in argon-ethyl lactate dielectric barrier discharges. The influence of a square pulse power supply on Te, n(Arm), and discharge current is evaluated and correlated with the chemistry and the topography of plasma-deposited coatings. Pulsed discharges were found to have shorter (100 ns) but stronger (1 A) current peaks and higher electron temperatures (0.7 eV) than when using a 35 kHz sinusoidal power supply (2 μs, 30 mA, 0.3 eV). The n(Arm) values seemed to be rather stable around 1011 cm−3 with a sinus power supply. In contrast, with a pulse power supply with long time off (i.e., time without discharge) between each pulse, a progressive increase in n(Arm) from 1011 cm−3 up to 1012–1013 cm−3 was observed. When the time off was reduced, this increase was measured in sync with the current peak. The chemical composition of the coatings was not significantly affected by using a pulse signal, whereas the topography was strongly influenced and led to powder formations when reducing the time off.
  • Publication
    Accès libre
    Transdermal diffusion, spatial distribution and physical state of a potential anticancer drug in mouse skin as studied by diffusion and spectroscopic techniques
    (IOS Press, 2018-05-07) Lefèvre, Thierry; Le, Quoc-Chon; Auger, Michèle; Laroche, Gaétan; C. Gaudreault, René.
    Background:Understanding the efficiency of a transdermal medical drug requires the characterization of its diffusion process, including its diffusion rate, pathways and physical state. Objective:The aim of this work is to develop a strategy to achieve this goal. Methods:FTIR spectroscopic imaging in conjunction with a Franz cell and HPLC measurements were used to examine the transdermal penetration of deuterated tert-butyl phenylchloroethylurea (tBCEU), a molecule with a potential anticancer action. tBCEU has been solubilized in an expedient solvent mixture and its diffusion in hairless mouse skin has been studied. Results:The results indicate that tBCEU diffuses across the skin for more than 10 hours with a rate comparable to selegiline, an officially-approved transdermal drug. IR image analyses reveal that after 10 hours, tBCEU penetrates skin and that its spatial distribution does not correlate with neither the distribution of lipids nor proteins. tBCEU accumulates in cluster domains but overall low concentrations are found in skin. FTIR spectroscopic imaging additionally reveals that tBCEU is in a crystalline form. Conclusions:The results suggest that tBCEU is conveyed through the skin without preferential pathway. FTIR spectroscopic imaging and transdermal diffusion measurements appear as complementary techniques to investigate drug diffusion in skin.
  • Publication
    Accès libre
    Characterization of carbon anode protected by low boron level : an attempt to understand carbon−boron inhibitor mechanism
    (American Chemical Society, 2017-07-19) Ziegler, Donald Paul; Laroche, Gaétan; Lamonier, Jean-François; Darvishi Alamdari, Houshang; Ishak, Ramzi
    Several chemical reactions occur during the electrolysis of alumina in the Hall–Héroult process resulting in a significant overconsumption of the carbon anode. Carbon oxidation with oxygen is one of these reactions. The inhibition of this reaction by the application of protective layers on the anode can be an effective technique to reduce carbon consumption. Boron impregnation was shown to suppress this reaction. In this study, very low boron content has been impregnated on the anode, and several characterization methods have been performed to understand the protection mechanism of such a low boron concentration during the oxidation reaction of anodes. An air reactivity test of boron-impregnated anodes has been performed at temperatures between 400 and 600 °C. The samples were characterized using XPS, Raman spectroscopy, XRD, XRF, porosimetry, and thermogravimetric analysis (TGA). TGA revealed that the total number of interactions between oxygen atoms and carbon active sites was reduced, decreasing the pre-exponential factor. Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) has been employed as a highly sensitive surface characterization method to identify chemical forms of boron on the anode. It has been confirmed that boron blocks active sites of carbon by creating boron–carbon bonds, thus reducing the interaction of carbon active sites with oxygen.
  • Publication
    Accès libre
    Time-resolved study of the electron temperature and number density of argon metastable atoms in argon-based dielectric barrier discharges
    (IOP Publishing, 2018-01-24) Desjardins, Edouard; Laroche, Gaétan; Naudé, Nicolas; Durocher-Jean, Antoine; Laurent, Morgane; Gherardi, Nicolas; Stafford, Luc
    A combination of optical emission spectroscopy and collisional-radiative modelling is used to determine the time-resolved electron temperature (assuming Maxwellian electron energy distribution function) and number density of Ar 1s states in atmospheric pressure Ar-based dielectric barrier discharges in presence of either NH₃ or ethyl lactate. In both cases, Te values were higher early in the discharge cycle (around 0.8 eV), decreased down to about 0.35 eV with the rise of the discharge current, and then remained fairly constant during discharge extinction. The opposite behaviour was observed for Ar 1s states, with cycle-averaged values in the 10¹⁷ m−³ range. Based on these findings, a link was established between the discharge ionization kinetics (and thus the electron temperature) and the number density of Ar 1s state.
  • Publication
    Accès libre
    Surface grafting of Fc-binding peptides as a simple platformto immobilize and identify antibodies that selectively capture circulating endothelial progenitor cells
    (2020-09-09) Bashth, Omar S.; Laroche, Gaétan; Elkhodirya, Mohamed A.; Hoesli, Corinne A.
    Antibody surface immobilization is a promising strategy to capture cells of interest from circulating fluids in vitro and in vivo. An application of particular interest in vascular interventions is to capture endothelial progenitor cells (EPCs) on the surface of stents to accelerate endothelialization. The clinical impact of EPC capture stents has been limited by the lack of efficient selective cell capture. Here, we describe a simple method to immobilize a variety of immunoglobulin G antibodies through their fragment crystallizable (Fc) regions via surface-conjugated RRGW peptides for cell capture applications. As an EPC capture model, peripheral blood endothelial colony-forming cells suspended in cell culture medium with up to 70% serum were captured by immobilized anti-CD144, anti-CD34 or anti-CD309 antibodies under laminar flow. The endothelial colony-forming cells were successfully enriched from a mixture with peripheral blood mononuclear cells using surfaces with anti-CD309 but not anti-CD45. This antibody immobilization approach holds great promise to engineer vascular biomaterials with improved EPC capture potential. The ease of immobilizing different antibodies using the same Fc-binding peptide surface grafting chemistry renders this platform suitable to screen antibodies that maximize cell capture efficiency and selectivity.
  • Publication
    Accès libre
    Dynamics of endothelial cell responses to laminar shear stress on surfaces functionalized with fibronectin-derived peptides
    (American Chemical Society, 2018-10-11) Duchesne, Carl; Ruel, Jean; Tremblay, Catherine; Juneau, Pierre-Marc; Beland, Ariane V.; Garnier, Alain; Ling, Si Da; Boulanger, Mariève D.; Laroche, Gaétan; Hoesli, Corinne A.; Gaillet, Bruno
    Surface endothelialization could improve the long-term performance of vascular grafts and stents. We previously demonstrated that aerosol-generated fibronectin-derived peptide micropatterns consisting of GRGDS spots over a WQPPRARI background increase endothelial cell yields in static cultures. We developed a novel fluorophore-tagged RGD peptide (RGD-TAMRA) to visualize cell–surface interactions in real-time. Here, we studied the dynamics of endothelial cell response to laminar flow on these peptide-functionalized surfaces. Endothelial cells were exposed to 22 dyn/cm² wall shear stress while acquiring time-lapse images. Cell surface coverage and cell alignment were quantified by undecimated wavelet transform multivariate image analysis. Similar to gelatin-coated surfaces, surfaces with uniform RGD-TAMRA distribution led to cell retention and rapid cell alignment (∼63% of the final cell alignment was reached within 1.5 h), contrary to the micropatterned surfaces. The RGD-TAMRA peptide is a promising candidate for endothelial cell retention under flow, and the spray-based micropatterned surfaces are more promising for static cultures.
  • Publication
    Accès libre
    Optical emission spectroscopy as a process-monitoring tool in plasma enhanced chemical vapor deposition of amorphous carbon coatings - multivariate statistical modelling
    (Elsevier Science, 2018-03-01) Turgeon, Stéphane; Anooshehpour, Farid; Laroche, Gaétan; Mantovani, D. (Diego); Cloutier, Maxime
    Production of Diamond-Like Carbon (DLC) nanocoatings using plasma enhanced chemical vapor deposition is studied by Optical Emission Spectroscopy (OES) as a plasma diagnostic technique. The objective of the current research is to establish a predictive model of DLC properties using a multivariate analysis method. This model is based on OES data instead of process parameters, which are reactor dependent and accordingly, their effect on the plasma deposition process may vary from one reactor to another. The predictive potential of OES is evaluated using partial least square regression (PLSR) analysis. The results show that OES derived data are capable of replacing some process parameters to predict the DLC properties. The perspective of PLSR modelling and OES application for the development and monitoring of a structurally graded DLC coating is also discussed.