Described here is the first application of plasma-enhanced chemical vapor deposition (PE-CVD) to thesynthesis of catalytically active materials, prepared by covering Merrifield resin beads with an oxygen-containing fluorocarbon thin film deposited in a hexafluoropropene-O2plasma. Such modified resinscatalyze both the selective epoxidation of trans--methylstyrene and its double oxidative cleavage tobenzaldeyde in organic-water biphasic media at room temperature, using potassium monoperoxysulfate(KHSO5) as the terminal oxidant. Interestingly, the epoxide/benzaldehyde product ratio strictly dependson the conditions adopted for catalyst generation. This, coupled with evidence for the presence of carbonylgroups on the surface of treated resins, point to dioxirane and singlet oxygen (1O2)-mediated oxidations;1O2being produced in the decomposition of KHSO5. Compared to traditional synthetic procedures toobtain similar catalytic active materials, the application of PE-CVD is eco-sustainable and less expensive.Also, the activity of catalysts can be fully restored upon iterative re-treatment of the exhausted resin.

A facile atmospheric pressure cold plasma process is presented to deposit a novel organic-inorganic hydrocarbon polymer/ZnO nanoparticles nanocomposite coating. Specifically, this method involves the utilization of an atmospheric pressure dielectric barrier discharge (DBD) fed with helium and the aerosol of a dispersion of oleate-capped ZnO nanoparticles (NPs) in n-octane. As assessed by X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, the deposited nanocomposite coating combines the chemical features of both the oleate-capped ZnO NPs and the polyethylene-like organic component originated from the plasma polymerization of n-octane. Additionally, scanning electron microscopy (SEM) and transmission scanning electron microscopy (TSEM) confirm the synthesis of hierarchical micro/nanostructured coatings containing quasi-spherical NPs agglomerates.The polyethylene-like polymer covers the NPs agglomerates to different extents and contributes to their immobilization in the three-dimensional network of the coating. The increase of both the deposition time (1-10 min) and the NPs concentration in the dispersion (0.5-5 wt %) has a significant effect on the chemical and morphological structure of the thin films and, in fact, results in the increase the ZnO NPs content, which ultimately leads to superhydrophobic surfaces (advancing and receding water contact angles higher than 160°) with low hysteresis due to the hierarchical multiscale roughness of the coating.

Low pressure plasma technologies have been widely and successfully utilizedfor the production of a large variety of organic-inorganic nanocomposite (NC) thin filmsconsisting of metal or metal oxide nanoparticles embedded in a polymer matrix. Recently,the deposition of this class of coatings has been also accomplished by atmospheric pressurecold plasmas using aerosol-assisted processes in which a dispersion containing preformedinorganic nanoparticles and the liquid precursor of the polymeric component is atomizedand injected in aerosol form in the atmospheric plasma. This short review is aimed atpresenting this approach which is expected to enlarge the range of structures and propertiesof organic-inorganic NC coatings deposited by cold plasma technologies.

The thin film deposition in DBDs fed with Ar/HMDSO/O2 mixtures was studied by comparingthe FT-IR spectra of the deposits with the GC-MS analyses of the exhaust gas. Under theexperimental conditions investigated, oxygen addition does not enhance the activation of themonomer while it highly influences the chemical composition and structure of the depositedcoating as well as the quali-quantitative distribution of by-products in the exhaust. Withoutoxygen addition a coating with high monomer structureretention is obtained and the exhaust containsseveral by-products such as silanes, silanols, and linearand cyclic siloxanes. The dimethylsiloxane unit seemsto be the most important building block of oligomers.Oxygen addition to the feed is responsible for anintense reduction of the organic character of the coatingas well as for a steep decrease, below the quantificationlimit, of the concentration of all by-productsexcept silanols. Some evidences induce to claim thatthe silanol groups contained in the deposits are formedthrough heterogeneous (plasma-surface) reactions.

Atmospheric pressure plasmas are acquiring more interest in biomedical applications where synthetic biodegradable polymers modified to impart cells adhesion properties play a crucial role. This paper shows a new approach for the bio functionalization of such materials: inclusion of a biomolecule during the plasma deposition. A dielectric barrier discharge system was used for the coatings deposition, coupled with an atomizer for the lactic acid/elastin aerosol feeding. ATR-FTIR, XPS, and UV-VIS were used to investigate the chemical composition of the coatings. By properly tuning plasma parameters, a good retention of the monomer chemical structure could be obtained in the coatings, as well as the inclusion of elastin in its structure.

Over the last ten years, expansion of atmospheric pressure plasma solutions for surface treatment of materials has been remarkable, however direct plasma technology for thin film deposition needs still great effort. The objective of this paper is to establish the state of the art on scientific and technologic locks, which have to be opened to consider direct atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) a viable option for industrial application. Basic scientific principles to understand and optimize an AP-PECVD process are summarized. Laboratory reactor configurations are reviewed. Reference points for the design and use of AP-PECVD reactors according to the desired thin film properties are given. Finally, solutions to avoid powder formation and to increase the thin film growth rate are discussed.

Two different dielectric barrier discharge processes are presented, fedwith the aerosol of the organic precursor, todeposit -CHO containing coatings from lactic acid (pdLA) and tetraethylene glycol dimethyl ether (PEO-like) ofpossible interest in biomedical applications as biodegradable and non-fouling polymers, respectively.

Thin films containing carboxylic acid groups are deposited from mixtures of helium, acrylic acid, and ethylene using an atmospheric pressure cold plasma jet in dielectric barrier discharge (DBD) configuration. The influence of the feed gas composition on the properties of the deposits is investigated. As assessed by X-ray photoelectron spectroscopy (XPS), the oxygen atomic concentration of the coatings as well as the percentage of the XPS C1s component ascribed to carboxylic groups (i.e., COOH and COOR moieties) increase with the acrylic acid concentration in the feed gas. On the other hand, ethylene addition enhances the deposition rate, reduces the carboxylic groups content of the coatings, and significantly improves their chemical and morphological stability upon immersion in water for 72h. The surface concentration of COOH groups before and after immersion in water is determined by chemical derivatization in conjunction with XPS.

A new hybrid material (3) consisting of trifluoromethyl ketone (TFMK) moieties, immobilized on silica through an appropriate spacer, was synthesized and characterized. Lacking easily oxidizable functionalities in the spacer chain, this material proved to be an excellent catalyst in heterogeneous epoxidations with potassium caroate (KHSO 5), surpassing other reported catalysts in performance and stability. The efficiency of silica-supported catalyst 3 could be assessed upon carrying out the selective dioxirane-mediated epoxidation of representative alkenes in high yields. The solid catalyst could then be recovered and reused in a number of consecutive oxidation cycles. The synthesis of a new hybrid, which presents trifluoromethyl ketone moieties anchored on silica gel through a short spacer, is reported. Lacking easily oxidizable functionalities in the linker chain, this solid material is an efficient catalyst in dioxirane-mediated heterogeneous epoxidations using potassium caroate.

The influence of N2, O2, air, and water vapor feed gas impurities on the operation of an atmospheric pressure parallel plate DBD fed with helium and argon was investigated. The addition of increasing amounts of these impurities, under fixed excitation frequency and applied voltage, is responsible above certain thresholds of two distinct phenomena, namely the transition from a homogeneous to a filamentary appearance of the discharge and the contraction of the discharge volume. Among the different contaminants N2 shows the highestthreshold limit values, O2 and H2O the lowest ones, while air generally exhibits an intermediate behavior. The effect of feed gas impurities was also studied on the PE-CVD of fluoropolymers from Ar-C3F6 fed filamentary DBDs. Contaminants addition results in a decrease of the input power and of the deposition rate as well as in a change of the film morphology, however it does not influence significantly the chemical composition of thefluoropolymer film, the monomer depletion and the distribution of by-products in the exhaust gas.

A facile atmospheric pressure cold plasma process is presented to deposit a novel organic-inorganic hydrocarbon polymer/ZnO nanoparticles nanocomposite coating. Specifically, this method involves the utilization of an atmospheric pressure dielectric barrier discharge (DBD) fed with helium and the aerosol of a dispersion of oleate-capped ZnO nanoparticles (NPs) in n-octane. As assessed by X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, the deposited nanocomposite coating combines the chemical features of both the oleate-capped ZnO NPs and the polyethylene-like organic component originated from the plasma polymerization of n-octane. Additionally, scanning electron microscopy (SEM) and transmission scanning electron microscopy (TSEM) confirm the synthesis of hierarchical micro/nanostructured coatings containing quasi-spherical NPs agglomerates. The polyethylene-like polymer covers the NPs agglomerates to different extents and contributes to their immobilization in the three-dimensional network of the coating. The increase of both the deposition time (1-10 min) and the NPs concentration in the dispersion (0.5-5 wt %) has a significant effect on the chemical and morphological structure of the thin films and, in fact, results in the increase the ZnO NPs content, which ultimately leads to superhydrophobic surfaces (advancing and receding water contact angles higher than 160) with low hysteresis due to the hierarchical multiscale roughness of the coating. © 2014 American Chemical Society.

This study deals with the investigation by means of gas chromatography-mass spectrometry (GC-MS) of the exhaust gas of an rf low pressure (LP) glow discharge and of an atmospheric pressure (AP) FDBD fed with hexamethyldisiloxane (HMDSO), O2, and Ar. The influence of feed composition on monomer depletion and on the qualitative-quantitative distribution of stable by-products formed by recombination of plasma intermediates is investigated. Without O2 addition to the feed almost comparable values of HMDSO depletion are observed both at low and AP. Oxygen addition does not influence the monomer depletion at LP while it induces a slight decrease of the depletion at AP. Whatever the working pressure, O2 controls the overall chemistry of the plasma, since it influences the concentration of by-products (e.g., silanes, silanols, linear, and cyclic methylsiloxanes). At AP evidences of the importance of methyl abstraction from HMDSO molecule have been obtained, while at LP the prevalence of Si-O bond rupture, of fragmentation, and oligomerization reactions is observed. The comparison of results from the GCMS investigation of the exhaust gas with FT-IR spectra of the deposited coatings allows to enhance hypotheses on the formation of silanols in the gas phase and in the deposit.

This paper deals with the GC-MS investigation of the exhaust gas of atmospheric pressure PE-CVD processes inorganosilicon- and fluorocarbon-containing dielectric barrier discharges. The extent of unreacted monomer andthe quali-quantitative distribution of by-products have been investigated as a function of the feed composition.The results confirm that GC-MS is a powerful indirect diagnostic technique of the plasma phase since it allowsto hypothesize some of the reactive moieties formed in the plasma and to clarify some aspects of the depositionmechanism.

his work describes the plasma-enhanced chemical vapor deposition of thin films at atmospheric pressure using dielectric barrier discharges fed with argon, oxygen and different methyldisiloxanes, i.e., hexamethyldisiloxane, pentamethyldisiloxane, and 1,1,3,3-tetramethyldisiloxane. The influence of the methyldisiloxane chemical structure and of the oxygen/methyldisiloxane feed ratio is investigated in order to provide insights into the organosilicon plasma chemistry at atmospheric pressure. As expected the FT-IR and XPS analyses show thatthe carbon content of the coatings depends on the number of methyl groups in the precursor molecule; in the case of coatings obtained with PMDSO and TMDSO carbon removal seems to be further enhanced by the presence of Si-H bonds. Gaschromatography-mass spectrometry analyses of the exhaust gas allow to assess the precursor depletion and to perform the quali-quantitative determination of by-products (e.g., silanes, siloxanes, silanols) formed by plasma activation. The results are exploited to rise hypotheses on the contribution of the different reaction pathways on the deposition mechanism.

In this paper, we describe the deposition of PEO-like coatings using dielectric barrier discharges (DBDs) fed with aerosols of the TEGDME organic precursor in helium. By properly tuning plasma parameters such as aerosol/carrier flow ratio, frequency of the electric field applied and input power, the deposition process could be modulated to obtain coatings with variable PEO character, from 50% (cell adhesive) to 70% (nonfouling), which are interesting for surface modification of biomaterials and biomedical devices.

A general method for the preparation of superhydrophobic organic-inorganic nanocomposite coatings by atmospheric pressure cold plasma is presented. The method consists of a single-step room-temperature aerosol-assisted deposition process in which the aerosol of a dispersion of oleate-capped ZnO nanoparticles in liquid hydrocarbon precursors (i.e., a mixture of n-octane and 1,7-octadiene) is injected in a dielectric barrier discharge. The plasma-deposited hydrocarbon polymer/ZnO nanoparticles nanocomposite coatings show multifunctional behavior and specifically combine the photocatalytic properties of ZnO with superhydrophobicity; the latter results from the synergistic effect of the hierarchical multiscale surface texture due to the incorporation of nanoparticles and the low surface energy organic component formed via plasma polymerization of the hydrocarbon precursors.

Nowadays, atmospheric pressure cold plasmas, particularly in dielectric barrier discharge (DBD)configuration, attract significant interest in the field of surface processing of materials.Fluorocarbon containing DBDs have also been studied, but the state of the art in this field is atits early stages, especially if compared to low pressure plasmas, which have been widely andsuccessfully employed for the etching of inorganic and organic materials, for the deposition offluoropolymers as well as for the treatment of synthetic and natural polymers. This contribution willprovide an overview of our recent studies on fluorocarbon containing DBDs and will presentresults on the deposition of fluoropolymers concerning the tuning of the chemical composition ofthe deposits, the etching-deposition competition and the influence of feed gas contaminants (i.e.air and water vapour).

Thin films are deposited on open-cell polyurethane (PU) foams using an atmospheric pressure dielectric barrier discharge (DBD) fed with helium and hexafluoropropene (C3F6). During deposition processes, a foam substrate is sandwiched between the dielectric-covered electrodes of a parallel plate DBD reactor, so that the discharge can ignite also inside its three-dimensional (3D) interconnected porous structure. This affords the deposition of a fluorocarbon coating on both the exterior and interior of the foam. Scanning electron microscopy (SEM) observations allow estimating the thickness of the coating deposited on the foam struts, while X-ray photoelectron spectroscopy (XPS) analyses show moderate changes in surface chemical composition moving from the outer to the inner surfaces of the plasma-treated foams under all explored experimental conditions.

Cold plasma processes for surface engineering of biomaterials and biomedical devices are traditionallyperformed at low pressure; more and more, though, surface modification plasma processes at atmospheric pressure are also gaining popularity. This short review is aimed to list briefly atmospheric pressure plasma processes reported, in the last decade, for adapting the surface of materials to the best interactions with cells, bacteria and biomolecules.