Cold Plasma Deposition Research Articles

Plasma enhanced chemical vapor deposition (PECVD) of SiOx thin films on Portuguese limestone: An experimental study

Plasma Enhanced Chemical Vapor Deposition (PECVD) of SiOx thin films has been applied to the stone surface under laboratory conditions in order to assess its feasibility as an alternative method for stone protection. SiOx thin layers were deposited on oolitic limestone lithologies known to have been used for the construction and restoration of the Batalha Monastery in Portugal surface by PECVD from tetraethoxysilane (TEOS) as the reaction precursor, in capacitively coupled parallel-plate reactor. The thickness, morphologies and chemical properties of the deposited film were characterized by attenuated total reflectance -Fourier transform infrared (ATR-FTIR) spectroscopy and scanning electron microscopy (SEM+EDS). Laboratory simulated decay and natural aging tests were implemented to evaluate the protective effect of the deposited micron-size SiOx thin films. Results suggested that, due to the good barrier effect, SiOx films were able to isolate the stones from aggressive acidic solution, thus reducing possible dissolution-related damage. Natural aging tests proved that SiOx thin films were also able to inhibit to a high extent bio-colonization while, at the same time reducing soiling of the stone appearance. Durability and wetting property of this SiOx thin film were preliminarily assessed. This research tested, for the first time, the feasibility of applying micron-size SiOx film quickly and directly via cold plasma deposition and its versatile protection performance on carbonate stone.

Classical Concept of Semiconductor Heterojunctions in the Approach to Nanohybrid Catalysts.

Recalling the well-established theory of heterojunction formation between two different semiconductors or a semiconductor and a metal can elucidate the remarkable catalytic properties of nanohybrid systems employed in thermal catalysis. Upon the creation of heterojunctions, involved nanoparticles or nanometer-sized thin films, as a result of their dimensions, may become entirely filled with space charges generated from the development of depletion or accumulation regions. This phenomenon dictates the nature of catalytic sites and consequently affects the catalytic activity of such nanohybrids. The following perspective presents this concept and examples of experimental results that substantiate its validity, along with an extremely effective tool, cold plasma deposition, for designing and realizing in a controlled manner the structure of nanohybrids with heterojunctions. This approach will undoubtedly broaden the view of the contemporary "alchemy" of nanocatalysts.

Cold Plasma Deposition of Tobramycin as an Approach to Localized Antibiotic Delivery to Combat Biofilm Formation.

Hospital-acquired infections (HAIs) remain a significant factor in hospitals, with implant surfaces often becoming contaminated by highly resistant strains of bacteria. Recent studies have shown that electrical plasma discharges can reduce bacterial load on surfaces, and this approach may help augment traditional antibiotic treatments. To investigate this, a cold atmospheric plasma was used to deposit tobramycin sulphate onto various surfaces, and the bacterial growth rate of K. pneumoniae in its planktonic and biofilm form was observed to probe the interactions between the plasma discharge and the antibiotic and to determine if there were any synergistic effects on the growth rate. The plasma-deposited tobramycin was still active after passing through the plasma field and being deposited onto titanium or polystyrene. This led to the significant inhibition of K. pneumoniae, with predictable antibiotic dose dependence. Separate studies have shown that the plasma treatment of the biofilm had a weak antimicrobial effect and reduced the amount of biofilm by around 50%. Combining a plasma pre-treatment on exposed biofilm followed by deposited tobramycin application proved to be somewhat effective in further reducing biofilm growth. The plasma discharge pre-treatment produced a further reduction in the biofilm load beyond that expected from just the antibiotic alone. However, the effect was not additive, and the results suggest that a complex interaction between plasma and antibiotic may be at play, with increasing plasma power producing a non-linear effect. This study may contribute to the treatment of infected surgical sites, with the coating of biomaterial surfaces with antibiotics reducing overall antibiotic use through the targeted delivery of therapeutics.

Plasma-Deposited CoO–(Carbon Matrix) Thin-Film Nanocatalysts: The Impact of Nanoscale p-n Heterojunctions on Activity in CO2 Methanation

Addressing the challenges associated with the highly exothermic nature of CO2 methanation, there is considerable interest in innovative catalyst designs on structural metallic supports. One promising solution in this regard involves thin films containing cobalt oxide within a carbon matrix, fabricated using the cold plasma deposition method (PECVD). The objective of this study was to search for a relationship between the molecular structure, nanostructure, and electronic structure of such films and their catalytic activity. The investigations employed various techniques, including X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), X-ray diffraction (XRD), UV-VIS absorption, and catalytic tests in the CO2 methanation process. Three types of films were tested: untreated as-deposited (ad-CoO), thermally post-treated (TT-CoO), and argon plasma post-treated (PT-CoO) films. Among these, TT-CoO exhibited the most favorable catalytic properties, demonstrating a CO2 conversion rate of 83%, CH4 selectivity of 98% at 400 °C, and stability during the catalytic process. This superior performance was attributed to the formation of nanoscale heterojunctions in the TT-CoO film, where p-type CoO nanocrystallites interacted with the n-type carbon matrix. This work provides compelling evidence highlighting the key role of nanoscale heterojunctions in shaping the properties of nanocatalysts in thermal catalysis. These findings suggest promising prospects for designing new catalytic systems by manipulating interactions at the nanoscale.

2D Enantioselective Disposable Stochastic Sensor for Fast Real-Time Enantioanalysis of Glutamine in Biological Samples

As protein is both a structural component and a metabolic intermediary, amino acids play a crucial function in the body. When it comes to proteins, only the L-configuration of chiral amino acids is found. At the molecular level, symmetry is disrupted; however, the scientific basis for this symmetry breaking is not yet known. Enantioanalysis of chiral compounds such as amino acids plays a very important role in the correct diagnosis of illnesses, such as cancer. The enantiomers of glutamine—a chiral amino acid—were investigated in biological samples using a disposable stochastic sensor. The disposable stochastic sensor based on immobilization of maltodextrin (DE 4.0–7.0) on the surface of a disposable sensor based on graphene decorated with Ag was designed, characterized, and validated for screening tests of whole blood and tissue samples. The stochastic sensor was designed using cold plasma deposition of graphene decorated with Ag on plastic material. The sensor was enantioselective, being able to discriminate between the enantiomers of glutamine. High sensitivities were recorded for both enantiomers, while the limits of determination were 100 fmol L−1 for L-glutamine and 1 fmol L−1 for D-glutamine. High recoveries were determined for the assay of one enantiomer in the presence of the other, despite the ratio between the two enantiomers.

Cold Plasma Synthesis and Testing of NiOX-Based Thin-Film Catalysts for CO2 Methanation

An essential problem in managing CO2 and transforming it into methane as a useful fuel is the quest for adequately efficient and cheap catalysts. Another condition is imposed by the new designs of structured reactors, which require catalysts in the form of the thinnest possible films. The aim of this work was to produce Ni-based thin-film catalysts by the cold plasma deposition method (PECVD) from a volatile metal complex (Ni(CO)4) and to study their structure and catalytic properties in the CO2 methanation process. We tested three basic types of films: as-deposited, calcined in Ar, and calcined in air. The nanostructure and molecular structure of the films were investigated by electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The catalytic activity was evaluated in the methanation process (CO2 + H2), which was performed in a tubular reactor operating in the temperature range of 300–400 °C. The films calcined in air showed the highest activity in this process but behaved unstably. However, their regeneration by recalcination in air restored the initial catalytic activity. An important conclusion emerged from the obtained results, namely that the active phase in the tested films is Ni3+ (most likely in the form of Ni2O3), contrary to the common opinion that this phase is metallic Ni0. In our case, Ni0 quenches the catalytic activity.

Theoretical insight into plasma deposition of laccase bio-coating formation

Development of new techniques for deposition of biologically active coatings in the form of bio-recognition layers in biosensor construction is a current technological challenge. Biosensors are widely applied in environmental protection in determination of hazardous materials, e.g., catechol, hydrochinon or resorcinol. Application of a soft plasma polymerization (SPP) technique by low-energy-density corona discharge has allowed significant simplification of the deposition process of bio-recognition layers. However, the mechanism of the SPP process is by no means fully understood. This paper presents insights into the mechanism of binding laccase enzyme onto graphene oxide (GO) and multi-walled carbon nanotubes (MWCNT) through analysis carried out by density functional theory (DFT) methods and Fourier transform infrared spectroscopy (FTIR). The objective was to examine the mechanism on the basis of binding energies and electrostatic interactions between laccase and carbon nanomaterials as well as enzyme structure after cold plasma deposition. The lowest binding energies have been calculated for the O–N bond between the arginine amino acid of laccase and the hydroxyl group of GO and the C–O bond between the serine molecule of laccase and the carboxyl groups of GO and MWCNT. FTIR and DFT studies showed that the chemical structures of the laccase enzyme and carbon nanomaterials after corona jet plasma treatment are not substantially changed. Preliminary recognition of the mechanism of biosensing layer deposition by the SPP technique opens the way to application of this innovative technique to the construction of other biosensors such as for determination of pollutants in water samples.

Tuning the structure and wetting properties of organic-inorganic nanocomposite coatings prepared by aerosol-assisted atmospheric pressure cold plasma deposition

Dispersions of oleate-capped ZnO nanoparticles (NPs) in binary n-octane/1,7-octadiene solvent mixtures are injected, in aerosol form, in a dielectric barrier discharge to deposit hydrocarbon polymer/ZnO nanoparticles nanocomposite (NC) thin films at atmospheric pressure and room temperature. The chemical composition of the coatings, and in turn their morphology and wettability, can be tuned by simply changing the composition of the starting dispersion. Specifically, the increase of the NPs concentration in the dispersion (0.5–5 wt%) results in a continuous increase of both the ZnO content and deposition rate of the coatings. Moreover, when the concentration of 1,7-octadiene in the solvent mixture is very low (0.5–2 vol%), the incorporation of NPs is further promoted, while at concentrations >2 vol% the growth of the organic component starts to be favored. Overall, results reveal a considerable increase of the root-mean-square (RMS) roughness of the coatings with the ZnO loading. In addition, once the threshold ZnO loading and RMS roughness of 60 wt% and 350 nm are reached, respectively, the coatings are superhydrophobic and exhibit very low water contact angle hysteresis, due to the coexistence of the low surface energy conferred by the hydrocarbon polymer and the hierarchical multiscale surface texture induced by NPs incorporation.

Plasma deposited thin-film sandwich-like bifunctional electrocatalyst for oxygen reduction and evolution reactions

The thin-film sandwich-like system consisting of catalytic films and highly electrically conductive films arranged alternately one on top of the other was prepared using the cold plasma deposition method. The catalytic films were based on cobalt oxide while the electrically conductive carbon–nitrogen films were produced from acrylonitrile. The electrocatalytic activity of the system was tested for both the oxygen reduction reaction (ORR), on O2 gas, and the oxygen evolution reaction (OER), from H2O2. Studies on the molecular structure showed that the catalytic films contained only a fraction of CoO without Co3O4 spinel. It was found that the catalytic activity of the sandwich-like system, for both the ORR and OER, was a several-fold higher compared with a film containing the same amount of the catalyst without the conducting films. It confirms the predictions on the possibility of increasing the catalytic activity by constructing the sandwich-like systems.

Enhancing the water repellency of wood surfaces by atmospheric pressure cold plasma deposition of fluorocarbon film

This study explores the fluorocarbon deposition on wood by atmospheric pressure plasma, with the focus on higher water repellency.

Preparation of Multifunctional Superhydrophobic Nanocomposite Coatings by Aerosol-Assisted Atmospheric Cold Plasma Deposition

Preparation of Multifunctional Superhydrophobic Nanocomposite Coatings by Aerosol-Assisted Atmospheric Cold Plasma Deposition

Correction to Aerosol-Assisted Atmospheric Cold Plasma Deposition and Characterization of Superhydrophobic Organic–Inorganic Nanocomposite Thin Films

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionORIGINAL ARTICLEThis notice is a correctionCorrection to Aerosol-Assisted Atmospheric Cold Plasma Deposition and Characterization of Superhydrophobic Organic–Inorganic Nanocomposite Thin FilmsFiorenza Fanelli*, Anna M. Mastrangelo, and Francesco FracassiCite this: Langmuir 2014, 30, 46, 14111Publication Date (Web):November 12, 2014Publication History Published online12 November 2014Published inissue 25 November 2014https://doi.org/10.1021/la504036fCopyright © 2014 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views324Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (102 KB) Get e-Alerts Get e-Alerts

Aerosol-Assisted Atmospheric Cold Plasma Deposition and Characterization of Superhydrophobic Organic–Inorganic Nanocomposite Thin Films

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.

Fabrication of a Transparent Anti-stain Thin Film Using an Atmospheric Pressure Cold Plasma Deposition System

Recently, outdoor-constructed solar panels have a problem such as power generation efficiency is reduced by the face plate dirt. On the other hand, electronic touch panels have a problem such as deterioration of visibility of the screen by finger grease stain. To solve these problems, we need to fabricate the anti-stain surfaces which have superhydrophobic and oil-repellent abilities without spoiling the transparency of the transparent substrate. In this study, we fabricated lotus leaves like surface on a glass substrate. Firstly, SiO 2 particles of ca. 100 nm diameter were arranged on the glass substrates. Secondly, to obtain the fractal-like structure (ultra-micro-rough structure) on the surface, ZnO thin film having a columnar structure was fabricated on the SiO 2 particles by using an atmospheric pressure cold plasma deposition system. By using these processes, the ZnO columns formed radiantly on the spherical surface of the SiO 2 particles. Furthermore, without spoiling the ultra-micro-rough structure, a transparent anti-stain monolayer with low surface energy was prepared by using a chemical adsorption technique onto the surface. Average value of the water droplet contact angles of the samples fabricated was 151.8 deg. Field emission scanning electron microscope (FE-SEM) observation reviled that this sample has a raspberry structure in which columnar structure has grown radially on the SiO 2 particles.

Fabrication of Transparent Antifouling Thin Films with Fractal Structure by Atmospheric Pressure Cold Plasma Deposition

Antifouling surface with both superhydrophobicity and oil-repellency has been fabricated on glass substrate by forming fractal microstructure(s). The fractal microstructure was constituted by transparent silica particles of 100 nm diameter and transparent zinc-oxide columns grown on silica particles by atmospheric pressure cold plasma deposition. The sample surface was coated with a chemically adsorbed monomolecular layer. We found that one sample has the superhydrophobic ability with a water droplet contact angle of more than 150°, while another sample has a high transmittance of more than 85% in a wavelength range from 400 to 800 nm.

Photoelectrochemical properties of hierarchical nanocomposite structure: Carbon nanofibers/TiO 2/ZnO thin films

The basic objective of this work is related to the research on the design of hierarchic multilayer systems with the assumed final functionality utilized for microelectronics and photovoltaics. We report on photoelectrochemical functionality of the multilayer system consisting of carbon nanofibers (CNFs)/photoactive anatase TiO 2/conductive ZnO thin films. The CNFs’ layers were obtained by annealing the polyacrylonitrile (PAN) web deposited by the electrospinning method. Titanium dioxide and zinc oxide layers were deposited by means of a hollow cathode cold plasma deposition system. Raman spectra confirmed carbon nanofibers, crystalline TiO 2 and ZnO forming individual layers as well as the final multilayer assembly. A mixture of various Zn x Ti y O z phases was also observed. These structures were produced due to the reactions between the highly energetic zinc ions generated in the plasma environment and the TiO 2 layer. The same phenomenon is probably responsible for the doping of TiO 2 by carbon atoms originating from CNFs and leading to a significant decrease of the photocatalytic activity.

Cold plasma functionalized TeraHertz BioMEMS for enzyme reaction analysis

In this paper, we describe the development, functionalization and functionality testing of a TeraHertz (THz) Bio-MicroElectroMechanical System (BioMEMS) dedicated to enzyme reaction analysis. The microdevice was fabricated by mixing clean room microfabrication with cold plasma deposition. The first is used to build the microfluidic circuits and the THz sensor, while the later serves for the polymerization of allylamine using a homemade glow discharge plasma reactor for a subsequent immobilization of enzymatic biocatalysts. Thermal stability of the deposited plasma polymer has been investigated by infrared spectroscopy. Fluorescent detection confirmed the efficiency of the immobilization and the enzyme hydrolysis into the BioMEMS microchannels. For the first time, the progression of the hydrolysis reaction over time was monitored by the THz sensor connected to a vectorial network analyzer. Preliminary results showed that sub-THz transmission measurements are able to discriminate different solid films, various aqueous media and exhibit specific transmission behavior for the enzyme hydrolysis reaction in the spectral range 0.06–0.11 THz.

Capillary microchannel fabrication using plasma polymerized TMDS for fluidic MEMS technology

This paper reports the first use of cold plasma deposition of polymerizable monomers for the fast, cost-effective and easy fabrication of buried air microchannels. A new method named ‘plasma polymerization on sacrificial layer’ (PPSL) is presented. It consists in the direct polymerization of tetramethyldisiloxane (TMDS) on a photopatterned sacrificial layer. Channels are formed with only one lithographic mask and without any etching or bonding process. The use of polymerized TMDS allows rapid creation of capillarity-driven flow systems with the channel width ranging from 4 to 700 µm without pillars. Channels are characterized and successfully tested. Capillary forces draw water, as well as aqueous solution into the channel from the inlet reservoir to the outlet one, avoiding the need of microfluidic connectors with the surrounding environment. Filling of the capillaries is very fast. It reaches the initial velocity of 4.4 cm s−1 with the geometries and water used here. In addition, PPSL easily allows the building of transparent channel networks directly on processed electrochemical or electromagnetic components. An example of one such integrated fluidic microelectromechanical system (MEMS) is described.

New inorganic electret materials for miniaturized microphones

Electret microphones made with the methods of silicon technology require electret materials other than the conventional polymers. Up to now, amorphous SiO2 has proven its good electret characteristics, and SiO2-electret microphones have already been developed as prototypes. In this paper, new manufacturing methods for SiO2, namely cold plasma deposition and the sol–gel process, are presented. The charge storage behavior, which could be improved by heat treatment or chemical surface modification, was investigated by isothermal and thermally stimulated discharge measurements and the results were compared to the discharge characteristic of thermally wet grown SiO2 electrets. In addition, the chemical composition of the electret surface was investigated by the ESCA method, which revealed the stoichiometry of the differently manufactured and treated SiO2.