Enzyme immobilization is necessary process to improve the bioactivity and stability of the biocatalyst. In this study, glucose oxidase (GOx) enzyme was immobilized on plasma-treated fibrous carbon felt as a textile carrier to produce a heterogeneous catalyst. Genipin, as a naturally occurring crosslinker, that has less cytotoxicity than conventional crosslinkers, was used in the enzyme immobilization process. UV-Vis and FTIR spectra confirmed the crosslinking reaction between genipin and the primary amines of GOx enzyme, by forming blue-pigmented aggregates. GOx relative activity after crosslinking and immobilization on the carbon felt was maintained up to 40%, with stability in performance up to 6 cycles for the plasma treated carbon, while maintaining their bioelectro-activity as shown from cyclic voltammetry scans (CV). The obtained heterogeneous catalysts have been tested for use in sustainable wastewater treatment of Remazol Blue RR (RB) dyestuff by means of Bio-Fenton (BF) and enzymatic Bio-electro-Fenton (BEF) processes. The produced samples resulted in high color removal efficiency, up to 93% discoloration of (RB) for the first use in (BF) process in 3 h. Meanwhile, enzymatic (BEF) process resulted in up to 34% of COD removal, with simultaneous power density generation up to 0.16 +/- 0.01 mu W.cm(-2) at a current density of around 10 +/- 2 mu A.cm(-2) in 12 h. These results highlight the importance of genipin as a bio-based crosslinker for enzymes, and the potential use in both (BF) and (BEF) as sustainable approaches for wastewater treatment and as a step towards zero-energy degradation of organic matter.

ABSTRACTIncreasing wettability of carbon felts is an important strategy to improve their efficiency in bio‐electrochemical applications. Herein, influence of cold remote plasma (N2 + O2) treatment on surface properties of carbon felts with poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) coating was tested, aiming to improve immobilizing of glucose oxidase enzyme (GOx). Spectra of N 1s and O 1s confirmed the integration of carbonyl and ether as well as amide and amine groups on bare carbon fiber surface, while on coated fibers, carbonyl groups were pre‐dominant. S 2p spectra confirmed oxidation of PEDOT:PSS coating with reduction of (S−) compared to (SO3−) group. GOx immobilized on different samples showed highest activity for PEDOT:PSS coating subjected to plasma with 2% O2, maintaining up to 60% after immobilization, and 37% of its activity after six cycles for some samples. Enzymes immobilized on samples without plasma treatment lost their activity after four cycles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48521.

Despite their chemical inertness and poor hydrophilicity, carbon-based materials are widely used in electro-chemical applications due to their robustness, good electrical conductivity and corrosion resistance. The purpose of the work carried was to increase the wettability of nonwoven carbon fiber felts for improved efficiency in bio/electrochemical applications. Virgin Carbon Felt (VCF) was first treated with cold remote plasma (CRP) using a mixture of nitrogen and oxygen (1 or 2%) as plasma gas. Bio-functionalization of the carbon felts with glucose oxidase (GOx) enzyme was then carried using physical adsorption method. FTIR and XPS analysis showed an integration of new oxygenated functional groups (C-O and C=O) as well as amines and amides on the surface of VCF treated by the CRP treatment, which improved the wettability of the samples. Capillary uptake increased from around 0% (for VCF) to nearly 750% with 2% oxygen in plasma gas. GOx enzyme showed higher activity after immobilization at pH 5.5 on the CRP treated samples, maintaining up to 50% of its initial enzymatic activity after six cycles while with the VCF, no enzymatic activity was observed after the fourth cycle. These obtained felts can be used as electrodes in sustainable bioprocesses.

A Cold Remote (N-2 + O-2) Plasma (CRNOP) process was used in order to create new surface properties on various wooden samples. Two applications were studied and optimized using experimental design. The first one involved samples (fir, pine, beech and oak) treated by the CRNOP in order to increase their impregnability evaluated by dynamic wetting and water absorption measurements. In the best conditions, water absorption was increased by 1.8; 1.9; 2.0 and 5.1 for fir, pine, oak and beech, respectively. The second application involved a plasma polymerization of 1,1,3,3, tetramethyldisiloxane induced by the CRNOP in order to create a superhydrophobic coating on beech sample previously treated by the CRNOP. In optimal conditions, a contact angle equal to 160 degrees could be reached. FTIR spectroscopy give evidence for Si-O-Si, Si-O-C and Si(CH3)(n) bands in a polysiloxane structure. (C) 2018 Elsevier B.V. All rights reserved.

The aim of this study was to investigate the effect of 3 different surface plasma treatments on the immobilization of β-galactosidase on a fibrous PET nonwoven membrane. Two methods 1. Entrapment in a thin calcium alginate coating and 2. Direct sorption, were used to immobilize the enzyme. The three different plasma treatments for surface activation of PET nonwovens were: 1. Air atmospheric DBD plasma, 2. Cold remote plasma-CRP with 100% N2 and 3.- CRP with a mixture of N2/O2 gases. Plasma treatment of the PET fiber surface increased the quantity of immobilized enzyme using the entrapment method, and the degree of alginate film cross-linking highly influenced the enzyme activity. Highest enzyme activity was reached for the PET treated with air atmospheric plasma and cross-linked with 0.25g/l of CaCl2. With the direct sorption method, greater amounts of enzyme were immobilized as compared to the entrapment method, but a considerable proportion of enzyme lost their catalytic activity. Only with the CRP N2/O2 plasma treatment, up to 90% of sorbed enzyme maintained their activity. Reusability study showed that for the optimized entrapment method, a progressive decrease in activity was observed after each use cycle. With the optimized sorption method using N2/O2 CRP plasma, no decrease in enzyme activity was detected, and the immobilized enzyme could be used over more than 15 cycles.

Polysiloxane films obtained from a cold remote nitrogen plasma polymerization of 1,1,3,3-tetramethyldisiloxane monomer mixed with oxygen show attractive properties and can be used for many applications. These films can also be modified in-situ by the (nitrogen+oxygen) remote plasma. An increase of the atomic oxygen concentration in the plasma leads to carbon removal and to an enhancement of the cross-linking of the Si–O–Si chains. The uppermost layer tends towards a silica structure while the core of the coating remained unchanged. By successive (deposition/plasma treatment) sequences, it was possible to obtain multilayer coatings which were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infra-Red (FTIR) spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and contact angles measurements. The efficiency of such multilayer coatings to protect carbon steel against corrosion in NaCl 0.5M was also investigated from polarization curves and Electrochemical Impedance Spectroscopy (EIS).

Carbon steel (C75) is exposed to highly reactive species such as hydroxyl radicals (OH)-O-center dot created by a gliding arc discharge (GAD) in humid air at atmospheric pressure. The protective properties of carbon steel treated by GAD are studied versus different treatment times (t) and for an immersion in corroding 0.5 M sodium chloride solution during 24 h. Evolutions of corrosion rate are studied using weight loss measurements and electrochemical methods, e.g., electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The results obtained by GAD treatment show that the corrosion rate of steel decreases with the ennoblement of the corrosion potential and the decrease of the corrosion current density. This indicates that the plasma treatment acts as an anodic type inhibitor and suggests the formation of a protective layer. EIS measurements confirm the presence of this film: the charge transfer resistance (R-ct) increases with GAD treatment time, leading to a corrosion inhibition efficiency around 73% for a treatment time equal to 60 min. This confirms the importance of the plasma effect. The gliding arc discharge is a clean and efficient technology for the surface treatment of carbon steel; it improves the anticorrosion properties of steel in aggressive environments, forming a resistant and insulating barrier.

The chemistry of the coating of stainless steel plates and foams with VOx/TiO2 catalyst to be utilised in the oxidative dehydrogenation of propane is described. A primer layer of SiO2 was first deposited by RPECVD, to anchor the active phase, to accommodate the difference of dilatation coefficient with steel and to act as a barrier against diffusion of poisonous steel elements. The coated VOx/TiO2 foams were inserted in a tube that could also be loaded with VOx/TiO2 powders to compare their catalytic performance. Preliminary results showed that the selectivity to propene was higher by 10% on silica-protected (ca. 5 μm thick) VOx/TiO2 foam than in the absence of silica, and higher by more than 20% than VOx/TiO2 powders at any conversion. The better performance was attributed to enhanced heat and mass transfers due to turbulent flow regime and to the high conduction of metallic foam. Hot spots which generate over-oxidation of propene were avoided. The choice of the substrate material, of which depend the mechanical and chemical properties of the active phase coating, and of the reactor configurations vs. the efficiency of heat and mass transfers was also commented.

Two model reactions were used to show the influence of catalytic foams on improving heat transfer. The catalytic performances were compared to those observed when using the same reactors packed with catalytic powder or beads. One reaction was the exothermic oxidative dehydrogenation of propane which was investigated on 7%V2O5/TiO2 coated on stainless steel foam. A silica layer was first deposited on the foam surface by Remote Plasma Enhanced Chemical Vapour Deposition to avoid poisoning of active phase by iron species, to favour the anchoring of TiO2 support and to accommodate the difference of dilatation coefficients. When comparing catalytic foams with powders in the same reactor, the selectivity to propene at isoconversion was higher by 12–45mol% for the same amount and composition (7%V2O5/TiO2) of the active phase and in the same operating conditions (contact time, C3/O2 ratio, temperature range). The other reaction was the endothermic dehydrogenation of methylcyclohexane on 2%Pt/Al2O3 directly coated on foams and on molecular sieve beads. To study the influence of heat and mass transfers, the material (FeCrAlloy or alumina) and porosity (81–97%) of foams were varied. It was found that, even for highly exothermic or endothermic reactions not limited by external transport, the coated foams significantly increased the effective conductivity of catalytic beds, the denser foam leading to higher effective conductivity.

An original process based on cold plasma assisted polymerization of tetramethyldisiloxane (TMDSO) in the presence of O-2 was developed to cover substrates showing various shapes (plate and foam). In the frame of catalytic application, this coating has to act as a bonding layer for the deposition of active phase such as VOx/TiO2 well-known for its properties in NOx and volatile organic compounds abatement and in the production of chemical intermediates. Good results were obtained by the deposition of a 5-mu m thick polysiloxane film followed by a thermal treatment under air at 650 degrees C and by a remote nitrogen plasma post treatment. This procedure led to a silica-like layer allowing its coating in an aqueous suspension of TiO2. Such a multilayered material can be obtained homogeneously on the whole surface of a sample showing a 3D open geometry like metallic foam. Characterizations of the different steps of the elaborated multilayer material were performed by Fourier transformed infrared spectroscopy, Raman spectrometry, X-ray photoelectron spectroscopy, and electron probe micro-analyzer. POLYM. ENG. SCI., 51:940-947, 2011. (C) 2011 Society of Plastics Engineers

VOx/TiO2, catalyst of oxidative dehydrogenation of propane, was immobilised on a SiO2 film coating stainless-steel (SS) plates and foams figuring out structured reactors. SiO2 is expected to act as a primer and a barrier against poisoning of VOx/TiO2 catalyst by elements of SS. The adhesive SiO2 layer was first coated on 2D- (plates) and 3D-SS substrates (foams) A good adhesion was obtained after polymerisation by RPECVD (Remote Plasma Enhanced Chemical Vapor Deposition) of a 6 mu m-thick tetramethyldisiloxane polymer layer, followed by calcination (650 degrees C) to obtain the SiO2 layer. A post-treatment in N-2/1.5%O-2 plasma afterglow was necessary to eliminate remaining carbon traces after calcination. The resulting SiO2/SS objects were dip-coated in TiO2-anatase aqueous suspension. Vanadium isopropoxide was grafted on calcined TiO2/SiO2/SS, yielding VOx polyvanadates after calcination at 450 degrees C. The mechanical stability of the VOx/TiO2 catalyst immobilized onto SiO2/SS was examined by scratch test and ultrasonic bath experiment. The successive coated layers were studied by Raman spectroscopy, SEM-EDX, electron probe microanalysis and XPS. A special RPECVD reactor was designed to coat foams instead of plates. For the first time, a thin and homogeneous layer of silica could be deposited through the whole foam. The other steps were applied to obtain VOx/TiO2/SiO2/SS foams. XPS and Raman characteristics of deposits were the same than for coated plates and VOx/TiO2 powders.

Catalytic structured reactors are designed to improve both heat and mass transfers during reactions in the presence of catalytic layers. The know-how acquired in the coating of stainless steel walls by catalytic layers of VOx/TiO2, active in the abatement of volatile organic compounds and in the production of chemical intermediates, was extended to metallic foams. The preferred and original way was to first make a deposit of a silica-like primer by cold plasma assisted polymerization of tetramethyldisiloxane in the presence of oxygen. After mineralisation, this layer was supposed to act as a barrier against poisoning by elements of the metallic substrate, as well as a stabilizer of the catalyst layers. The cells of the foam were homogeneously covered by a 5μm-thick polysiloxane film ending in ca. 1μm thick silica after calcination. After studying the textural properties and zeta potential of aqueous suspensions of TiO2 particles, the silica-coated foams were dipped in a 37 wt.% aqueous suspension of TiO2-anatase. The final VOx/TiO2/SiO2/foams were obtained by grafting polyvanadate specie in sol–gel medium. At every step of coating, the multilayer materials were studied mainly by X-ray Photoelectron Spectroscopy and Electron Probe Micro-Analysis. Moreover the mechanical and chemical stability of the successive coatings was checked.

The parameters controlling performance of a fiber-reinforced polymer composite are type of matrix and fibers, their amount, aspect ratio, fiber orientation with respect to loading direction, fiber–matrix interface, and processing technique. In the case of carbon fiber reinforcement, fiber–matrix interface has always been a serious concern, because of chemical inertness of carbon fibers toward matrix and hence efforts are continued to enhance the fiber–matrix adhesion. A recent technique of cold remote nitrogen oxygen plasma was employed for surface treatment of carbon fabric (CF) to enhance its chemical reactivity and mechanical interaction toward matrix material. Untreated and plasma treated CF were used as bidirectional reinforcement for developing high performance composites with various specialty polymer matrices such as Polyetherimide, Polyethersulfone, and Polyetheretherketone. Treated CF reinforced composites showed appreciable improvement in most of the mechanical properties, which varied with type of plasma, its dozing and matrix used. X-ray Photoelectron Spectroscopy confirmed improvement in O/C and N/C ratio indicating inclusion of Oxygen and Nitrogen on the surfaces of fibers due to plasma treatment, which was responsible for enhanced adhesion. Similarly, Fourier Transform Infrared–Attenuated Total Reflectance Spectroscopy indicated presence of ether, carboxylic, and carbonyl functional groups on the plasma-treated surface of fibers. Raman spectroscopy indicated slight distortion in graphitic structure of treated CF. Scanning Electron Microscopy also indicated changes in the topography of treated CF, indicating enhanced mechanical interlocking with matrix.

While organic compounds with polymerizable structure are required for conventional way of polymerization, any organic compound can be used for plasma-assisted polymerization process. In this study, polysiloxane thin films were obtained from a Cold Remote Nitrogen Plasma polymerization of 1,1,3,3-tetramethyldisiloxane monomer with and without premixing with oxygen. This reactive medium, far from the discharge, allows to obtain high deposition rate. The films deposited in the present work are characterized by Fourier Transform Infra-red Spectroscopy, X-ray Photoelectron Spectroscopy, Atomic Force Microscopy, Scanning Electron Microscopy and thermo-gravimetric analysis. Their thermo-chemical behaviour is also studied after an in situ plasma assisted post-treatment and after an ex situ thermal post-treatment. A total mineralization of the coating occurs only after a thermal treatment at 600 degrees C and in this case the film structure looks like silica. After the plasma post-treatment, the uppermost layer tends towards a silica structure while the core of the coating remains unchanged. The efficiency of the polysiloxane film as a fire retardant coating for Polyamide-6 nano-composite substrates is evidenced. Fire retardant properties are studied from Limiting Oxygen Index (LOI) tests and cone calorimetry measurements.

Le laboratoire GePIFReM a developpe et concu des enceintes industrielles de traitement de surface de plusieurs m 3 mettant en jeu des plasmas froids d'azote en ecoulement. D'un point de vue industriel, l'utilisation de gaz plasmagenes tels que sont l'oxygene et l'azote est tres interessante. Ces gaz sont bon marches et inoffensifs pour l'environnement.

Modification of polymer surfaces by cold plasma processes is attracting a growing interest. Especially, the use of plasma gases such as N-2, O-2 or air, which are cheap and environmentally safe, is very attractive from an industrial point of view. The lifetime of atomic oxygen being very short, it is very difficult to operate with air or oxygen plasma when wide plasma volume is required. However, it is possible to obtain cold remote nitrogen plasma reaching volume of several m(3) due to the long lifetime of atomic nitrogen because of a re-dissociation mechanism. Moreover, the temperature being close to the ambient makes this plasma very attractive for functionalization and/or coating of polymer surfaces. Several applications of this plasma process are presented in this paper. The incorporation of new chemical functions during the treatment of polymers leads to an increase of their adhesion properties. Several industrial applications (painting, sticking, bonding, foaming and thermo-covering) are presented. The ability of this remote plasma to decompose, to polymerize, or to react with a volatile chemical component is described through three examples involving polymer substrates: (i) the deposition of metallic films; (ii) the synthesis of a nitride film combining hardness and elastic behavior; (iii) the synthesis of an organosilicon film showing interesting barrier properties. Adhesion aspects are investigated for all these examples. (C) Koninklijke Brill NV, Leiden, 2008

This work deals with the chemical grafting of a styrene maleic anhydride copolymer on the surface of a previously hydrolyzed polyethylene terephthalate (PET) film 12μm thick via covalent bond. Two different ways are studied. The first one involves an activation of the hydrolyzed PET by the triethylamine before the grafting step. In the second one, the copolymer reacts with the 4-dimethylaminopyridine in order to form maleinyl pyridinium salt which reacts with alcohol function of the hydrolyzed PET. Characterization and quantification of the grafting are performed by Fourier transform infrared spectroscopy. Factorial experiment designs are used to optimize the process and to estimate experimental parameters effects. The opportunity to associate the chemical process to a cold remote nitrogen plasma one is also examined.