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Plasma treatment of polypropylene (PP) is a well‐established method of improving its surface properties. However, the efficiencies of different plasma discharges are seldom compared. Herein, we discuss the differences in PP treated by three arc‐based commercial plasma jets working in dry air, Plasmatreat rotating plasma jet (PT‐RPJ), AFS PlasmaJet® (AFS‐PJ), and SurfaceTreat gliding arc jet (ST‐GA), and by the low‐temperature RF plasma slit jet (RF‐PSJ) working in argon. The AFS‐PJ has a significantly different reactive species composition dominated by nitrogen oxides. It induced higher thermal loads leading to surface damage. The other arc‐based jets (PT‐RPJ and ST‐GA) created the PP surface with higher oxygen and nitrogen concentration than the low‐temperature RF‐PSJ. It induced a higher adhesion strength measured on PP‐aluminum joints. [ABSTRACT FROM AUTHOR]

Pursuing more efficient nitrogen fixation in the context of the current climate crisis is of prime importance. The Haber‐Bosch process (NH3 production) accounts for at least 2% of the yearly released greenhouse gases. Alternatively, different atmospheric nonthermal discharges have proven their ability to convert nitrogen and oxygen from the air into nitrogen oxides (NO, NO2, and HNO3 hereafter referred as NOx). Among them, dielectric barrier discharges (DBDs) in N2/O2 are very interesting as they are characterized by microdischarges (MDs) developing into filaments under specific conditions (gap length, voltage, frequency, nature of the dielectrics). In this work, we used a sinusoidal voltage at 4, 12, 17.5, and 30 kHz as a key parameter to manipulate the MDs behaviors in an N2/O2 DBD and tailor the chemistry of the discharge. We characterized the MDs distribution by high‐speed camera imaging. Two different nitrogen emission systems, that is, the second positive system (SPS) and the first negative system (FNS), were used to assess the filament temperature and what we define as the delayed‐glow temperature, respectively. The influence of the filament's distribution on the overall discharge temperature has also been evaluated, by using a novel approach allowing the generation of heat distribution maps directly on a thermosensitive paper exposed to the discharge. Finally, the effect of the filaments on ozone (O3) and NOx production has been monitored by in situ Fourier‐transform infrared (FTIR). The DBD can be tuned between homogenously distributed MDs at 4 and 12 kHz to highly localized filaments at 17.5 and 30 kHz. A high filament temperature combined with a cold delayed‐glow is observed at 17.5 kHz while both the filament and the delayed‐glow temperature are high at 30 kHz. Low frequencies lead to heat spreading into the whole discharge volume, while localization of heat along the filament's paths is observed at high frequencies. High‐temperature filaments in the 30 kHz discharge and in the globally heated discharge at low frequencies quickly remove O3 from the discharge and consequently limit the overall NOx production by removing important oxidation pathways. On the contrary, filaments surrounded by cold gas observed at 17.5 kHz allowed to maintain a high concentration of O3 necessary for a faster oxidation of NO and thus increase the HNO3 production, even after 250 s, by avoiding backward reactions. [ABSTRACT FROM AUTHOR]

In this work, immobilization of the often unwanted filaments in dielectric barrier discharges (DBD) is achieved and used for one‐step deposition of patterned coatings. By texturing one of the dielectric surfaces, a discharge containing stationary plasma filaments is ignited in a mix of argon and propargyl methacrylate (PMA) in a reactor operating at atmospheric pressure. From PMA, hydrophobic and hydrophilic chemical and topographical contrasts at sub‐millimeter scale are obtained on silicon and glass substrates. Chemical and physical characterizations of the samples are performed by micrometer‐scale X‐ray photoelectron spectroscopy and infrared imaging and by water contact angle and profilometry, respectively. From the latter and additional information from high‐speed imaging of the plasma phase and electrical measurements, it is suggested that filaments, denser in energetic species, lead to higher deposition rate with higher fragmentation of the precursor, while surface discharges igniting outwards the filaments are leading to smoother and slower deposition. This work opens a new route for a one‐step large‐area chemical and morphological patterning of surfaces at sub‐millimeter scales. Moreover, the possibility to separately deposit coatings from filaments and the surrounding plasma phase can be helpful to better understand the processes occurring during plasma polymerization in filamentary DBD. [ABSTRACT FROM AUTHOR]

Many papers dealing with the surface analysis of plasma polymers or plasmamodified polymers report the use of X-ray photoelectron spectroscopy (XPS) to quantify the surface composition. However, most of the time, quantification is performed using software that includes an equation based on the assumption that the sample is homogeneous in composition. However, for plasma-treated samples, this is often not the case. The usual analysis of XPS spectra does not allow the exact quantification in the case of an inhomogeneous sample. In this paper, we show that it is possible to obtain a depth profile of the composition, and a more accurate surface composition by using another mathematical approach for surface quantification, being QUASES Tougaard. [ABSTRACT FROM AUTHOR]

Textile industry is constantly searching for easy and rapid ways to improve the properties of textiles. In this matter, plasma treatments have already proven to be an efficient and green solution, as they proceed in a dry environment and require minimal use of chemicals. To date, most of the work on the subject has been performed with low‐pressure plasmas. Recently, atmospheric plasmas have received increasing interest, especially for industrial applications. Indeed, the possibility to avoid the use of pumping systems makes this technology easily implementable in continuous in‐line processes. For many applications, the treatment aims at modifying the textile surface to increase the overall hydrophilicity. The latter is often probed by the water contact angle, but this does not always reflect the global hydrophilic behavior of the textile as a three‐dimensional material. A complementary study of the wicking properties is important to better reflect the penetration of liquids into the textile, but it is poorly reported in the literature. The present work aims at increasing the water uptake of polyethylene terephthalate (PET) textile by direct or remote plasma treatment, which are the two main trends in this field. For this purpose, a dielectric barrier discharge (DBD) and a radiofrequency plasma torch at atmospheric pressure are used, respectively. Different plasma parameters are varied and their respective effect on the wicking properties of the fabric, assessed by an absorbency test developed ad hoc, are correlated to their surface chemical composition determined by X‐ray photoelectron spectroscopy. These results are compared with the possible changes in wetting of the fiber surface witnessed by water contact angles measured on PET foil samples submitted to the same plasma treatments. Complete wicking of water in PET textile can be obtained after 20 or 10 s of torch treatment with pure Ar plasma or Ar/O2 mixture, respectively. However, a comparable effect is detected, after 30 s of DBD Ar plasma treatment, under the used experimental conditions. Besides, the addition of O2 to the discharge has an opposite effect on the fabric wicking. These results are discussed in terms of the peculiar processes in surface activation and modification of the fabric surface triggered by the two different plasma technologies. [ABSTRACT FROM AUTHOR]

In this study, an atmospheric‐pressure filamentary dielectric barrier discharge plasma is produced over a deionized (DI) water surface to study the physicochemical mechanisms of plasma–liquid surface interactions for NOx synthesis. The gas‐phase plasma diagnostics are performed using optical emission spectroscopy, Fourier‐transform infrared spectroscopy, and by recording voltage–current curves, and liquid‐phase species are analyzed using ion chromatography and UV−visible spectrophotometer. The investigations indicate that the reaction pathways for reactive oxygen and nitrogen species (H2O2, NO2‐, NO3−) formation in DI water depend on different experimental conditions. It is observed that the conversion of nitrites into nitrates is significantly influenced by reactive oxygen species. The energy yield for the total amount of NOx synthesized ranges from 1.3 × 10−4 to 3.4 × 10−3 mol/MJ. [ABSTRACT FROM AUTHOR]

This paper shows that, to a certain extent, remote atmospheric mass spectrometry can be used to identify signature fragments, which are able to predict the final surface chemistry of plasma‐deposited organic hydrophilic or hydrophobic coatings, to propose polymerization mechanisms and to predict coating contamination. Examples are given for the plasma polymerization of anhydrides and organic acids for polar coatings and for the polymerization of fluorinated precursors for hydrophobic coatings. To predict the final surface chemistry of hydrophilic coatings, we show that by tracking the evolution of the CO+ and CO2+ fragments in the plasma phase, one can deduce the relative amount of polar functions on the final coating surface. Similarly, the change in intensities of the various CFx+ fragments during the plasma polymerization of hydrophobic coatings is correlated with the relative amount of such CFx groups in the coating. For the same coatings, when CO2+, COF+, and COF2+ fragments are detected in the gas phase, the final coating will be contaminated. The possibilities, as well as some limits of this approach, are discussed. [ABSTRACT FROM AUTHOR]

The injection of water vapor into ambient 'open air' plasmas for the treatment of polymers represents a promising functionalization route for industrial and medical applications. The present study reports a scientist-independent methodology, based on the ToF-SIMS (time-of-flight secondary ion mass spectrometry) technique coupled with PCA/Wavelet-PCA (principal component analysis), to probe the (sub) surface chemical/structural modifications induced by an atmospheric Ar-D2O post-discharge on low density polyethylene (LDPE) films as a function of two external plasma parameters, namely sample-torch distance and treatment time. The SIMS characterization identifies two different families of samples (type I and II) as a function of time and distance. The highest reactivity of the D2O vapors with the LDPE films is achieved for times of few tens of seconds at a distance of 5 mm from the plasma source. [ABSTRACT FROM AUTHOR]

Allyl methacrylate (AMA), methyl methacrylate (MMA), and propyl isobutyrate (PiB) are plasma deposited at ambient temperature in an atmospheric DBD reactor to assess the effect of precursor carbon double bond unsaturations. The specific plasma deposition rate ( k0) as a function of the Yasuda factor ( Yf) is quantified empirically by: k0 = b (1 − exp(- a Yf/ b)). Fourier transform infrared analysis indicates a loss of carbonyl functionalities with increasing plasma power, and Raman microscopy shows CC double bonds in all plasma films. The methacrylate-like plasma films are found to be heterogeneous with a volatile and a cross-linked fraction observed by thermogravimetric analysis. Differential scanning calorimetry reveals a low glass transition temperature and a characteristic residual reactivity of the coatings. [ABSTRACT FROM AUTHOR]

An organometallic powder (platinum (II) acetylacetonate) is decomposed in the post-discharge of an atmospheric RF plasma torch to deposit Pt nanoparticles on carbon black supports. The resulting nanohybrid materials are characterized by FEG-SEM and XPS techniques to highlight their high content in Pt, their oxidation degree, and the dispersion of the Pt nanoparticles on the substrate. ICP-MS and electrochemical characterizations in a single fuel cell (cyclic voltammetry, dynamic polarization curves) are also performed on electrodes realized by treating the powder mixture overlaid on gas diffusion layers. The comparison of the catalytic activity and the Pt loading with commercially available electrodes shows the great potential of this simple innovative, fast, and robust deposition method. [ABSTRACT FROM AUTHOR]

The atmospheric pressure PECVD deposition and texturization of hydrophobic coatings using liquid fluorinated C6F12 and C6F14 precursors are investigated. The effect of the carrier gas (argon and helium) is discussed in terms of the behavior of the gas phase and of the characteristics of the deposited film. Mass spectrometry measurements indicate that the fragmentation is higher with argon while helium reacts very easily with oxygen impurities leading to the formation of CxFyOz compounds. These observations are consistent with the chemical composition of the films determined by XPS and the variation in the deposition rate. Moreover, the streamers present in the argon discharge affect the morphology of the surface by increasing the roughness, which leads to the increase in the hydrophobicity of the coatings. [ABSTRACT FROM AUTHOR]

This feature article is focused on the application of secondary ion mass spectrometry (time-of-flight SIMS) to the chemical and structural study of plasma-treated organic surfaces and plasma polymer films. After a brief historical perspective and a presentation of the recent developments of SIMS, illustrative case studies involving plasma-treated polymer surfaces and plasma polymers are presented. Beyond surface analysis by static SIMS, we show the potential of molecular depth-profiling by low-energy Cs+ ions and large Arn+ clusters for the in-depth chemical characterization of plasma-modified samples. Together with SIMS data processing by multivariate analysis, molecular depth-profiling could provide a step change for the analysis of films treated or polymerized with plasmas. [ABSTRACT FROM AUTHOR]

This study deals with the development of an original epi-fluorescence-based protocol to evaluate the anti-biofouling character of atmospheric pressure plasma-polymerized poly(ethylene glycol) samples. In this work, fluorescence microscopy is considered as an alternative to XPS for the evaluation of protein adsorption. The full set of samples is tested before and after bovine serum albumin-fluorescein isothiocyanate treatment. It appears that their anti-biofouling property, expressed by the variation of fluorescence intensity, is reduced when the power of the discharge is increased. The reproducibility of the experiments and the relatively high sensitivity of the proposed method are underlined. [ABSTRACT FROM AUTHOR]

In an original approach to trace water reactivity upon surface treatment by ambient 'open air' plasma, the H-D exchange processes induced in polyethylene by an Ar-D2O post-discharge are investigated using time-of-flight secondary ion mass spectrometry, both at the surface and along the sample depth. The surface characterization points out the strong influence of the sample-torch distance. The most important chemical modifications, excluding polymer overheating, occur at 5 mm of distance, with 25% of deuterated monomer units at the surface. For the first time, ultra-shallow molecular depth-profiling by Ar noble gas clusters shows the detailed variation of the deuteration of the polymer repeat unit in the topmost surface layer. Our results indicate that the fraction of deuterated monomer units is reduced by a factor >2 over a depth of ∼3 nm. [ABSTRACT FROM AUTHOR]

Low density polyethylene (LDPE) surfaces have been plasma modified to improve their nanostructural and wettability properties. These modifications can significantly improve the deposition of subsequent layers such as films with specific barrier properties. For this purpose, we compare the treatments induced by two atmospheric plasma torches with different configurations (showerhead vs. linear). The modifications of LDPE films in terms of chemical surface composition and surface morphology are evidenced by X-ray photoelectron spectroscopy, water contact angles measurements, and atomic force microscopy. A comparison between the two post-discharge treatments is achieved for several torch-to-substrate distances (gaps), treatment times, and oxygen flow rates in terms of etching rate, roughening rate, diffusion of oxygen into the subsurface and hydrophilicity. By correlating these results with the chemical composition of the post-discharges, we identify and compare the species which are responsible for the chemical surface functionalization, the surface roughening, and etching. [ABSTRACT FROM AUTHOR]

Methyl methacrylate (MMA) is deposited on aluminum substrates using atmospheric dielectric barrier discharge plasma. The thermal properties of plasma deposited MMA (pdMMA) films of 0.5 to 1 μm thickness are evaluated as a function of plasma power and precursor mass feed. Thermogravimetric analysis indicates a low molecular weight fraction in all pdMMA films, which lowers their thermal stability. Differential scanning calorimetry (DSC) is used to quantify the glass transition ( Tg) and residual reactivity of the pdMMA thin films. For all plasma conditions, the Tg remains inferior to conventional PMMA, and ranges from 20 °C in the monomer-deficient domain to 56 °C in the energy-deficient domain. A residual reactivity is measured in the first DSC heating of all pdMMA films, showing an exothermicity up to −160 J g−1. [ABSTRACT FROM AUTHOR]

This work deals with the in-situ mass spectrometric (MS) characterization of gases during the atmospheric pressure plasma-enhanced chemical vapor deposition of propyl isobutyrate (PiB) and allylmethacrylate (AMA). By monitoring the fragments of interest, we are trying to understand the mechanisms involved in the plasma synthesis of acrylate-like coatings. For instance, while CO2+ drastically increases when a PiB/argon plasma is ignited, it decreases in the case of AMA. This trend also appears for other fragments, which leads to the conclusion that while PiB seems to suffer from fragmentation, AMA oligomerizes into the gas phase, resulting in a better protection of the ester functionality. [ABSTRACT FROM AUTHOR]

The in-depth oxygen diffusion into a low density polyethylene film is performed in the post-discharge of an atmospheric plasma torch, supplied in argon as carrier gas and with or without oxygen as reactive gas. The chemical and structural properties of the polymer surface and bulk are studied in terms of plasma parameters (treatment time, power, and reactive gas flow rate). A good correlation between XPS and Fourier transform infrared spectroscopy analyses is demonstrated. The penetration depth of oxygen into the bulk of the polymer is investigated by angle resolved-XPS and time-of-flight SIMS. It is shown that, depending on the plasma conditions, oxygen could penetrate up to 20-40 nm into the low density polyethylene during the atmospheric plasma treatment. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this study, we investigated the atmospheric plasma polymerization of allyl methacrylate (AMA), n-propyl methacrylate ( nPMA), and propyl isobutyrate (PiB), whose chemistry mainly differs by their number of unsaturations. The resulting material is characterized using X-ray photoelectron spectroscopy (XPS) and infrared reflection absorption spectroscopy (IRRAS) while the thickness of the coatings is determined by visible spectroscopic ellipsometry (Vis-SE). The results show that the concentration of ester groups at the surface of the plasma polymers, as well as their deposition rate strongly depends on the surrounding unsaturations present in the precursor. A stabilization of the ester groups and an increase in the deposition rate due to the carbon-carbon double bonds is suggested. [ABSTRACT FROM AUTHOR]

This work deals with the plasma-deposition of allyl methacrylate (AMA) and acrylic acid (AA) on metallic substrates. The plasma setup used is an atmospheric pressure radio frequency (RF) torch. Infrared reflection absorption spectroscopy (IRRAS) and X-ray photoelectron spectroscopy (XPS) are used as characterization tools. In addition, spectroscopic ellipsometry (SE) has been used to control the thickness and calculate the corresponding deposition rates. Whereas the surface chemistry of plasma deposited AMA does not seem to be influenced by the plasma power, acrylic acid based coatings are strongly degraded with the increasing power. AMA seems to allow an efficient polymerization, while at the same time is particularly resistant to plasma induced fragmentation in the range of power used. [ABSTRACT FROM AUTHOR]

2,2,4,4,6,8,8-Heptamethylnonane (HMN), a saturated branched hydrocarbon precursor, is deposited by means of atmospheric plasma DBD. Hydrophobic coatings starting from this precursor which is liquid at room temperature can be obtained. The degree of polymerization of the coating seems to be dependent on the amount of provided precursor. The coatings were characterized by FTIR, TOF-SIMS, WCA, SE, and XPS. [ABSTRACT FROM AUTHOR]

An easy procedure to build up membrane-electrode assemblies for applications dedicated to miniaturized PEMFC using H2 or CH3OH by a two-steps atmospheric plasma process is reported. Firstly, catalyst nanoparticles are grafted on carbon substrates by spraying a Pt colloidal solution in the post-discharge of an RF atmospheric plasma torch. In the second step, the resulting decorated electrodes are covered by plasma synthesized polymeric membranes in the discharge of a DBD. The sulfonated polystyrene membranes are synthesized by injecting simultaneously styrene and trifluoromethanesulfonic acid monomers, in the presence of a carrier gas (Ar or He). The membranes are chemically characterized by XPS, ToF-SIMS, and FTIR (IRRAS) and their deposition rate is investigated by SEM. [ABSTRACT FROM AUTHOR]

The texturization of poly(tetrafluoroethylene) (PTFE) surfaces is achieved at atmospheric pressure by using the post-discharge of a radio-frequency plasma torch supplied in helium and oxygen gases. The surface properties are characterized by contact angle measurement, X-ray photoelectron spectroscopy and atomic force microscopy. We show that the plasma treatment increases the surface hydrophobicity (with water contact angles increasing from 115 to 155°) only by modifying the PTFE surface morphology and not the stoichiometry. Measurements of sample mass losses correlated to the ejection of CF2 fragments from the PTFE surface evidenced an etching mechanism at atmospheric pressure. [ABSTRACT FROM AUTHOR]

Allyl methacrylate (AMA) was deposited on aluminium using atmospheric dielectric barrier discharge plasma. AMA posseses two CC bonds which have very different reactivities and the efficiency of the plasma on polymerising the two different kinds of double bonds was evaluated. The Fourier transform infrared spectra and the nuclear magnetic resonance spectra of the plasma coatings were compared with those of conventionally synthesised poly(AMA). The influence of the monomer feed on the ester, the vinyl and the allyl functionalities of the coatings were investigated. Plasma coatings showed lower concentration of non-reacted allyl groups than conventional poly(AMA) suggesting a more cross-linked network. Pull-off adhesion tests were performed after the deposition of the a topcoat to evaluate the potential use of the AMA based coatings as adhesion promoter. [ABSTRACT FROM AUTHOR]

The method developed for fundamental understanding of energetic exchanges between monomer molecules and argon carrier gas in a dielectric barrier discharge (DBD) has previously proven merit. In this seventh article related to this methodology, research has been extended to a new family of precursors: anhydrides. Monomers (typically ‰) were mixed with 10 slm of Ar in a 20 kHz, 8 kV (peak‐to‐peak) DBD corresponding to an energy per cycle of 1600 μJ for pure Ar. For each of the investigated monomers Em, the energy absorbed per molecule was plotted as a function of precursor flow rate. The influence of chemical structure (C/O ratio, unsaturation) has been investigated and compared with previous data for other types of precursors. Thin plasma polymer coatings were deposited; in addition to measuring deposition rates, we also present relationships between Em values, spectro‐ellipsometric and FTIR measurements. [ABSTRACT FROM AUTHOR]