Personne :
Laroche, Gaétan

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Université Laval. Département de génie des mines, de la métallurgie et des matériaux
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  • Publication
    Accès libre
    Rapid nucleation of iron oxide nanoclusters in aqueous solution by plasma electrochemistry
    (ACS Publications, 2015-06-18) Turgeon, Stéphane; Fortin, Marc-André; Laroche, Gaétan; Sarra-Bournet, Christian; Lagueux, Jean; Létourneau, Mathieu; Chevallier, Pascale; Laprise-Pelletier, Myriam; Bouchard, Mathieu
    Progresses in cold atmospheric plasma technologies have made possible the synthesis of nanoparticles in aqueous solutions using plasma electrochemistry principles. In this contribution, a reactor based on microhollow cathodes and operating at atmospheric pressure was developed to synthesize iron-based nanoclusters (nanoparticles). Argon plasma discharges are generated at the tip of the microhollow cathodes, which are placed near the surface of an aqueous solution containing iron salts (FeCl₂ and FeCl₃) and surfactants (biocompatible dextran). Upon reaction at the plasma−liquid interface, reduction processes occur and lead to the nucleation of ultrasmall iron-based nanoclusters (IONCs). The purified IONCs were investigated by XPS and FTIR, which confirmed that the nucleated clusters contain a highly hydrated form of iron oxide, close to the stoichiometric constituents of α-FeOOH (goethite) or Fe₅O₃(OH)₉ (ferrihydrite). Relaxivity values of r₁ = 0.40 mM−¹ s−¹ and r₂/r₁ = 1.35 were measured (at 1.41 T); these are intermediate values between the relaxometric properties of superparamagnetic iron oxide nanoparticles used in medicine (USPIO) and those of ferritin, an endogenous contrast agent. Plasma-synthesized IONCs were injected into the mouse model and provided positive vascular signal enhancement in T₁-w. MRI for a period of 10−20 min. Indications of rapid and strong elimination through the urinary and gastrointestinal tracts were also found. This study is the first to report on the development of a compact reactor suitable for the synthesis of MRI iron-based contrast media solutions, on site and upon demand.
  • Publication
    Accès libre
    Atmospheric pressure cold plasma versus wet-chemical surface treatments for carboxyl functionalization of polylactic acid : a first step toward the immobilization of bioactive molecules
    (Elsevier, 2020-02-08) Laroche, Gaétan; Rodríguez Durán, Iván; Vanslambrouck, Stéphanie; Chevallier, Pascale
    The use of polylactic acid (PLA) has attracted growing interest, particularly in recent years, for biomedical applications because of its mechanical properties, biocompatibility, and biodegradability. Despite this, features such as surface hydrophobicity and the absence of suitable functional groups for covalent immobilization of bioactive molecules, make it challenging to endow PLA-based medical devices with additional features and thus broaden their range of applicability. In the present study, we demonstrate the suitability of atmospheric pressure dielectric barrier discharges operating in the Townsend regime as a promising alternative to other surface treatments, such as diazonium and alkali hydrolytic treatments, for carboxyl functionalization of PLA. Chemical changes in PLA surfaces are evaluated by contact angle measurements and by X-ray photoelectron spectroscopy while physical changes are investigated by scanning electron microscopy and atomic force microscopy. The amount of carboxyl groups generated on PLA surfaces is assessed by toluidine blue O assay and substantiated by grafting, through carboxyl groups, a fluorescent probe containing amino functionalities. All of the surface treatments have proven to be very effective in generating carboxylic groups on the PLA surface. Nevertheless, plasma treatment is shown to not degrade the PLA surface, in sharp contrast with diazonium and alkali hydrolytic treatments.
  • Publication
    Accès libre
    A new approach for synthesizing plasmonic polymer nanocomposite thin films by combining a gold salt aerosol and an atmospheric pressure low-temperature plasma
    (2021-02-05) Nadal, Elie; Milaniak, Natalia; Laroche, Gaétan; Glenat, Hervé; Massines, Françoise
    The proof of the concept of a new, onestep and safe by design process to synthesize metal-polymer nanocomposites thin films on a large surface is presented. It is based on the injection of an aerosol of a solution of metal (gold) salts dissolved in a polymerizable solvent (isopropanol) into an argon atmospheric pressure dielectric barrier discharge. The main novelty of this method resides in the fact that the nanoparticles are formed in situ, inside the plasma reactor, in the gas phase. Consequently, the nanoparticle synthesis and deposition are concomitant with the solvent polymerization used to produce the matrix, which makes it possible to obtain homogeneous layers of non-agglomerated nanoparticles (NPs) with high NPs density. By toggling between low and high-frequency discharges, gold/polymer nanocomposites with different morphologies and optical properties are synthesized. The effect of the concentration of gold in the aerosol and the gas residence time in the plasma as well as the ratio of high and low-frequency discharge and their repetition rate are presented. The thin films are systematically characterized by AFM and UV–visible spectroscopy to analyze their morphologies along with their plasmonic resonances.
  • Publication
    Accès libre
    Synthesis, characterization, and functionalization of ZnO nanoparticles by N-(trimethoxysilylpropyl) ethylenediamine triacetic acid (TMSEDTA) : investigation of the interactions between Phloroglucinol and ZnO@TMSEDTA
    (King Saud University, 2016-05-14) Barrak, Haythem; Laroche, Gaétan; Saied, Taieb; Chevallier, Pascale; M’nif, Adel; Hamzaoui, Ahmed Hichem
    The use of semiconductor oxides, such as chemical or biological sensors, requires their functionalization with appropriate molecules displaying specific interaction with the substance to be detected. Generally, the support materials used are TiO₂ or SiO₂. In the present work, zinc oxide nanoparticles (ZnO NPs), known for its reactivity and high specific area, were used. The synthesis of nanoscale ZnO was advantageously performed by precipitation at low temperature (60 °C). To our knowledge, it was the first time that this material was synthesized at such a low temperature, therefore lowering production cost. Moreover, the surface functionalization of ZnO was performed with N-(trimethoxysilylpropyl) ethylenediamine triacetic acid (TMSEDTA) in ethanol. This allowed shortening the functionalization reaction duration as compared to previously published literaturein the field. The samples obtained were analyzed by XRD, TEM, DLS, FTIR, TGA and XPS, which all concur with the successful synthesis of ZnO nanoparticles as well as the efficiency of TMSEDTA grafting on ZnO. Then, the interactions of this functionalized material, ZnO@TMSEDTA, with the Phloroglucinol (drug) were evaluated by using cyclic voltammetry measurements in solution. The cyclic voltammograms showed an intense cathodic peak which was correlated to the initial concentration of free Phloroglucinol. This cathodic peak was degraded upon addition of ZnO@TMSEDTA particles due to the drug interactions with free available carboxylic groups on the functionalized NPs. Based on a calibration curve, the drug concentration uptake can be therefore quantified. Thus, these results establish a big step to develop a Phloroglucinol sensor.
  • Publication
    Accès libre
    Characterization of argon dielectric barrier discharges applied to ethyl lactate plasma polymerization
    (Institute of Physics Publishing Ltd, 2017-11-03) Laroche, Gaétan; Desjardins, Edouard; Naudé, Nicolas; Meichelboeck, Maximilian; Laurent, Morgane; Stafford, Luc; Gherardi, Nicolas
    The influence of the input voltage frequency (35 and 150 kHz), interelectrode gap (1 and 2 mm) and precursor concentration (250, 350, and 450 ppm) on the electron temperature (Te), number density of metastable Ar atoms (n(Arm)), and discharge current density (proportional to the electron density ne) is studied in an argon-ethyl lactate dielectric barrier discharge (DBD). An argon-ammonia Penning mixture is also considered as reference. These results are correlated to the chemistry (XPS, IR) and topography (AFM) of the ethyl-lactate-based plasma polymer coatings. Low Te values from 0.3 to 0.5 eV were obtained for all discharges. This observation, in addition to resemblances with the Ar–NH3 mixture, suggested that the ionization kinetics of ethyl lactate-based discharges is driven by Penning reactions. Among the investigated parameters, the dissipated power obtained through changes of the excitation frequency had the largest impact on both the coatings properties and the discharge behavior.
  • Publication
    Accès libre
    Electrode cleanliness impact on the surface treatment of fluoropolymer films for a long-lasting plasma process
    (Elsevier, 2020-09-16) Gélinas, Alex; Laroche, Gaétan; Laurent, Morgane
    A dielectric barrier discharge in a continuous process configuration is used to coat the surface of polymer films. The effect of the growth of a coating layer on top of the uncovered electrode with regards to the physicochemical properties of the film treatment is studied. Plasma electrical parameters such as power density (−2) and voltage (kV) are monitored during a typical cycle, which is comprised between two electrode cleanings. In addition, the surface energy and chemistry are determined at chosen time-points of the process by contact angle measurements with two liquids and X-ray photoelectron spectroscopy (XPS). Based on these analyses, no major modification of the coated polymer physicochemical properties was attributed to the deposition of an organic layer on top of the bare electrodes after the equivalent of 1 h of continuous treatment.
  • 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
    Water drop-surface interactions as the basis for the design of anti-fogging surfaces : theory, practice, and applications trends
    (Elsevier Science, 2018-11-24) Laroche, Gaétan; Rodríguez Durán, Iván
    Glass- and polymer-based materials have become essential in the fabrication of a multitude of elements, including eyeglasses, automobile windshields, bathroom mirrors, greenhouses, and food packages, which unfortunately mist up under typical operating conditions. Far from being an innocuous phenomenon, the formation of minute water drops on the surface is detrimental to their optical properties (e.g., light-transmitting capability) and, in many cases, results in esthetical, hygienic, and safety concerns. In this context, it is therefore not surprising that research in the field of fog-resistant surfaces is gaining in popularity, particularly in recent years, in view of the growing number of studies focusing on this topic. This review addresses the most relevant advances released thus far on anti-fogging surfaces, with a particular focus on coating deposition, surface micro/nanostructuring, and surface functionalization. A brief explanation of how surfaces fog up and the main issues of interest linked to fogging phenomenon, including common problems, anti-fogging strategies, and wetting states are first presented. Anti-fogging mechanisms are then discussed in terms of the morphology of water drops, continuing with a description of the main fabrication techniques toward anti-fogging property. This review concludes with the current and the future perspectives on the utility of anti-fogging surfaces for several applications and some remaining challenges in this field.
  • 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.; 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.
  • Publication
    Accès libre
    Effect of linking arm hydrophilic/hydrophobic nature, length and end-group on the conformation and the RGD accessibility of surface-immobilized fibronectin
    (Elsevier, 2019-10-30) Laroche, Gaétan; Vanslambrouck, Stéphanie; Guay-Bégin, Andrée-Anne; Chevallier, Pascale
    In order to stimulate the cellular response to implant materials, extracellular matrix (ECM) proteins, such as collagen and fibronectin (FN), are immobilized on the implant surface. Amongst all ECM proteins used for biomimetic materials for medical applications, FN is one of the most investigated proteins thanks to its ability to promote cell adhesion and its contribution to important physiological processes. However, its conformation and hence its bioactivity strongly depend on the hydrophilic/hydrophobic nature of the surface as well as on immobilization strategies. This work investigates the effect of these two parameters, as well as the effect of the crosslinker length. FN was grafted onto silicon wafers using eights different linking arms presenting different lengths, hydrophilic/hydrophobic characters and binding sites. The protein was linked through either its amino groups (lysine amino acids) or sulfhydryl functionalities (cysteine amino acids). The grafting of each crosslinker and subsequent FN conjugation onto the surfaces was evidenced by X-ray photoelectron spectroscopy, while the surface hydrophilicity was determined by contact angle measurements. Moreover, atomic force microscopy images revealed that the conformation of surface conjugated FN only depends on the hydrophilicity of the linking arm. The FN conformation was also probed by enzyme-linked immunosorbent assays (ELISA). ELISA data demonstrated that all of the three investigated parameters linking arm parameter (length, hydrophobic/hydrophilic character, and terminal end-group) somewhat influence the RGD accessibility.