Increasing the effectivity of the antimicrobial surface of carbon quantum dots-based nanocomposite by atmospheric pressure plasma

Among commercial polymer materials, polypropylene (PP) is the most preferred in the world. Low‐density materials such as polymers and polymer composites are increasingly used to produce lighter structures. In the automotive industry, these parts are used for painting. Due to the non‐polar surface chemistry of PP, PP surfaces have low surface energy, which causes weak bonds in coating, painting, and bonding processes. Therefore, various physical and chemical processes are used to increase the surface energy of PP first, and then the surface is prepared with a primer before painting. However, the primer material and surface treatments used have disadvantages such as extra cost, being harmful to the environment, and the use of fossil fuels. Atmospheric pressure plasma (APP) surface treatment has recently become an alternative to traditional methods. In this study, the chemical and physical changes caused by APP surface treatment on PP surfaces were examined, the effects of process parameters were investigated, and the paintability of surfaces with and without primer was investigated.Highlights Primerless painting feasibility per standards is under investigation. Eco‐friendly alternatives to traditional pre‐paint treatments are under study. Polypropylene surface properties' effects on painting are under study. Optimal atmospheric pressure plasma parameters for painting are determined.

ABSTRACTCarbon Fiber Reinforced Polymer (CFRP) is used extensively in aerospace applications. Acceptance of bonded CFRP structures, mainly for aerospace applications, requires a robust surface preparation method with improved process controls to ensure high bond quality. Consistent repeatability is a factor lacking from many surface preparation processes. Atmospheric pressure plasma surface treatment is one of the robust surface preparation processes that have drawn wide attention in recent years. This process is capable of being applied in a production clean room environment that would minimize the risk of contamination and reduce cost. In plasma surface treatment the process parameters are easily controlled, documented providing a repeatable process with a high level of consistency. In this paper, the process parameters for atmospheric pressure plasma surface treatment and their effect on bonding for Out-Of-Autoclave (OOA) CFRP composite panels were fully investigated. A mechanized machine with sensory feedback to plasma treat surfaces was developed to change the process parameters for application on larger panels. By the aid of Design of Experiment (DOE) methodology critical process parameters were identified and a mathematical regression model was developed. The mathematical regression model was used to quantify the effect of process parameters on the bonding strength and the model was optimized to find the optimum settings.

Atmospheric plasma treatment is an effective and economical surface treatment technique. The main advantage of this technique is that the bulk properties of the material remain unchanged while the surface properties and biocompatibility are enhanced. Polymers are used in many biomedical applications; such as implants, because of their variable bulk properties. On the other hand, their surface properties are inadequate which demands certain surface treatments including atmospheric pressure plasma treatment. In biomedical applications, surface treatment is important to promote good cell adhesion, proliferation, and growth. This article aim is to give an overview of different atmospheric pressure plasma treatments of polymer surface, and their influence on cell-material interaction with different cell lines.

This paper investigates the use of atmospheric pressure plasma (APP) treatment for improving the surface hydrophobicity of rayon flock synthetic leather with organosilane precursor (tetramethylsilane (TMS)). Plasma deposition of TMS is regarded as an effective, simple, and low-pollution process. The results show that a highly hydrophobic surface is formulated on the rayon flock synthetic leather. Under a particular combination of treatment parameters, a hydrophobic surface was achieved on the APP-treated sample with a contact angle of 135° while the untreated sample had a contact angle of 0° (i.e., the fabric surface was completely drenched immediately). Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Photoelectron Spectroscopy (XPS) confirmed the deposition of organosilane.

Transparent semiconductor thin films such as indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) are commonly used in optoelectronic devices due to their favorable properties such as high conductivity and transparency and suitable work function [1]. Their use ranges from light-emitting diodes through flat panel displays up to solar cells. In this context, surface stoichiometry plays a crucial role in influencing the final properties of the final device. Therefore, efficient surface treatment has been a topic in research for years, covering a wide range of approaches from wet and dry treatments. Among these possibilities, plasma treatment remains today the most effective. In several studies [2, 3], atmospheric pressure plasma shown an increase of surface energy, decrease the contamination while enhancing the work function of both ITO and FTO. Low temperature, fast processing times, and no special requirements for working gas are the main advantages of this approach.In this study, the authors compare the effects of cold (<100°C) atmospheric pressure plasma on ITO and FTO after air and nitrogen treatment to provide deeper insight into the interaction of discharge with semiconductive materials during treatment. A coplanar dielectric barrier discharge has been used for the surface modification (more information available in [4]). For this configuration both electrodes lay in one plane, and the discharge occurs on the top of the barrier. Chemical changes in the surface were also evaluated as a function of plasma parameters without any pre-treatment of the substrates. For both studied materials, similar trends were observed at fast treatment times (<60s of plasma exposure). The plasma treatment resulted in a decrease of water contact angle from the initial 90° for ITO to 10° after 30 seconds of exposure. For FTO, the initial angle 60° was lowered to 10° after just 5 seconds of exposure, and complete hydrophilicity was obtained after 30 seconds of plasma treatment. An interesting trend in oxygen concentration measured by XPS was observed for ITO but not FTO samples. From a physical point of view, the interaction with the conductive sample affects the orientation of filaments during the surface modification. Additionally, the results suggest that for small working distances, the physical regime can vary from coplanar to volume discharge as shown in Figure 1. All changes were observed with ICCD imaging (Pi-Max 4, Princeton Instruments). Regarding the physical changes over the surface, the plasma treatment resulted in decreased roughness with no significant effect on conductivity.In conclusion, the results obtained in this study can be utilized in the manufacturing process of microelectronic devices and provide a deeper insight into how the treatment process influences discharge parameters.[1] Armstrong et al. https://doi.org/10.1016/j.tsf.2003.08.067[2] Šimor et al. https://doi.org/10.1063/1.1513185[3] Donley et al. https://doi.org/10.1021/la011101t[3] Chaney et al. https://doi.org/10.1016/S0169-4332(03)00617-2 Figure 1

Influence of an Atmospheric Pressure Plasma Surface Treatment on the Interfacial Fracture Toughness on Bonded Composite Joints

This study examined the effects of a He/O2 and He/SF6 atmospheric pressure plasma surface treatment of indium tin oxide (ITO) glass on the ITO surface and electrical characteristics of organic light emitting diodes (OLEDs). The OLEDs composed of ITO glass/2-TNATA/NPD/Alq3/LiF/Al showed better electrical characteristics, such as lower turn-on voltage, higher power efficiency, etc., after the He/O2 or He/SF6 plasma treatment. The He/SF6 treatment resulted in superior electrical characteristics compared with the He/O2 treatment. The electrical improvement as a result of the He/SF6 and He/O2 plasma treatments is related to the decrease in the carbon and Sn4+ concentration on the ITO surface and fluorine doping of the ITO possibly indicating a change in the work function as a result of the treatments.

Antibacterial property of F doped DLC film with plasma treatment

In recent years, biomedical materials have been used in the response to the emergence of medical infections that pose a serious threat to the health and life of patients. The construction of superhydrophobic coatings and antimicrobial coatings is among the most effective strategies to address this type of medical derived infection. Firstly, this paper reviews the preparation methods of superhydrophobic surface coatings and their applications; summarizes the advantages and disadvantages of superhydrophobic surface preparation schemes based on the template method, spraying methods, etching methods, and their respective improvement measures; and focuses on the applications of superhydrophobic surfaces in self-cleaning and antibacterial coatings. Then, the action mechanisms of contact antibacterial coatings, anti-adhesion bacteriostatic coatings, anti-adhesion bactericidal coatings, and intelligent antibacterial coatings are introduced, and their respective characteristics, advantages, and disadvantages are summarized. The application potential of antimicrobial coatings in the field of biomedical materials is highlighted. Finally, the applications of superhydrophobic and antimicrobial coatings in medical devices are discussed in detail, the reasons for their current difficulties in commercial application are analyzed, and the future directions of superhydrophobic coatings and antimicrobial coatings are considered.

The purpose of this study was to investigate the effect of gas species used for low-temperature atmospheric pressure plasma surface treatment, using various gas species and different treatment times, on zirconia surface state and the bond strength between zirconia and dental resin cement. Three groups of zirconia specimens with different surface treatments were prepared as follows: untreated group, alumina sandblasting treatment group, and plasma treatment group. Nitrogen (N2), carbon dioxide (CO2), oxygen (O2), argon (Ar), and air were employed for plasma irradiation. The bond strength between each zirconia specimen and resin cement was compared using a tension test. The effect of the gas species for plasma irradiation on the zirconia surface was investigated using a contact angle meter, an optical interferometer, an X-ray diffractometer, and X-ray photoelectric spectroscopy. Plasma irradiation increased the wettability and decreased the carbon contamination on the zirconia surface, whereas it did not affect the surface topography and crystalline phase. The bond strength varied depending on the gas species and irradiation time. Plasma treatment with N2 gas significantly increased bond strength compared to the untreated group and showed a high bond strength equivalent to that of the sandblasting treatment group. The removal of carbon contamination from the zirconia surface and an increase in the percentage of Zr-O2 on the zirconia surface by plasma irradiation might increase bond strength.

The reaction process model during initial nitridation of Si (111) using atmospheric pressure plasma source was constructed and it was compared to that using a radio frequency plasma source. In atmospheric pressure plasma, emission lines from the N2 second positive system were dominantly observed. By exposing the atmospheric pressure plasma to Si substrate at the temperature ranging from 25to500°C, silicon nitride films with a thickness below 1.8nm were formed. In order to study the nitridation process, the changes in the film thickness against the substrate temperature and nitridation time were systematically studied at a pressure ranging from 50to700Torr. The film thickness increases with increasing the nitridation pressure below 400Torr and it saturates above 500Torr. It was completely regardless of the substrate temperature. From the time dependence of the film thickness at various nitridation pressures, it was revealed that these experimental results were well fitted to a Langmuir-type adsorption model. In the case of nitridation using atmospheric pressure (AP) plasma, molecular species play an important role for nitridation without thermal diffusion. The difference of silicon nitride films fabricated using AP plasma and rf plasma originates from the difference in the active species.

Synthesis of antibacterial composite coating containing nanocapsules in an atmospheric pressure plasma

NASA spacecrafts are composed of a variety of conductive and non-conductive materials. For this reason, it is important to study sterilization efficacy of DBD plasma on varying substrates which are conductive, non-conductive, in wet conditions, and in dry conditions. In the experimental setup, “wet” bacteria designates that it is suspended in a 10 µl drop of water and when allowed to dry for 30 minutes, it is designated as “dry”. The bacteria chosen for these experiments are Escherichia coli and Deinococcus radiodurans. Initial results demonstrate an 8-log reduction in wet E. coli deposited on stainless steel after 30 seconds of plasma treatment; a 4-log reduction in dry E. coli deposited on a polyethylene substrate after 30 seconds of plasma treatment; and a 4-log reduction of wet D. radiodurans which was deposited on stainless steel after 15 seconds of plasma treatment. The results will allow NASA researchers to better design spacecraft for higher sterilization efficacy.

Plasma nanosciences and technologies have been leading all industries with bringing about innovations in green and life fields. The non-equilibrium chemical reactions induced by the synergetic effect of ions and radicals in the plasma processing has enabled to realize the isotropic etching with a high aspect ratio, the synthesis of functional nanomaterials through the plasma assisted self-organization and the surface chemical modification and so on in low pressure plasmas. In precise etching processes, the critical size dimension for the nanoscale pattering will be below 1nm and then the control of radical based on reactions on the side wall in the fine pattern with a nanoscale in size is of crucial importance. Additionally, the precise control of radicals is also strongly demanded in nanomaterial plasma processing. Carbon nanomaterials such as nanotubes, nanographenes and nanowalls attracted much attentions. They were synthesized by the plasma assisted self-organization, which was controlled by ions and/or radicals. Recently, the atmospheric pressure plasma and the in-liquid plasma have been developed. These plasmas have been successfully applied not only to the nanomaterial processing in the green innovation but also to the medical and agriculture fields in the life innovation. In these extremely complicated reactions, spatiotemporal controlling of radicals is a key point. Therefore, the measurement of behaviors of radicals in plasma nanoprocesses and thus the control of radicals on the basis of measured results has become important. We have been synthesizing a carbon nanowall, which is a two dimensional grapheme layers are standing vertically on the substrate, by the radical-controlled plasma processing. The structural control of carbon nanowalls was successfully performed by the radical injection to the plasma. Varieties of morphologies of carbon nanowalls were synthesized by controlling radicals and applied to fuel cell devices, catalysis devices and bio template and so on. Furthermore, ultrahigh density plasmas in the atmospheric pressure and in the liquid produce high density radicals. We have synthesized nanographenes by using the in-liquid plasma with alcohols. These nanographenes were also applied to the fuel cell devices. The atmospheric pressure plasma has been exposed to various kinds of cancer cells resulting in killing them. We found that ovarian cancer cells were successfully killed selectively against normal cells by the atmospheric pressure plasma and/or the plasma activated medium. In the case of synthesis of the plasma activated medium, controlling of densities of O radicals together with N and NO radicals exposed to the liquid medium was important to produce the optimum chemical species in the medium, which will be effective to kill cancers in vitro and in vivo. The systematical control of radicals in the nanoscale space at the gas and the liquid phase is a key issue to develop the plasma medicine, too. Therefore, we have stressed on the importance of development of an autonomous control plasma manufacturing system in order to accelerate green and life innovations. This system has multi-monitors to detect chemical reactions in the gas, the surface and interface between the gas and liquid, and in the liquid. On the basis of integration of measured results, it will make the precise control of species, especially radicals in the low pressure, atmospheric pressure and in-liquid plasmas. In this article, cutting edge plasma nanoprocesses with the radical-control in the plasma nanoprocesses for the synthesis of nanocarbons in the green innovation and with that in the plasma medical treatment of cancers in the life innovation are introduced and the future vision for the next generation’s plasma nanoprocessing will be presented.

Atmospheric pressure plasma with dielectric barrier discharge is used to improve the adhesion of novel composite carbon fiber reinforced low melting poly (aryl ether ketone) (CF/LMPAEK) to aerospace coatings under ambient and gas flow (Ar‐O2). The surface activation is evaluated by contact angle measurement and X‐ray photoelectron spectroscopy (XPS). Different atmospheres are used to prevent aging of the treated surface. The water contact angle is considerably reduced after plasma treatment, and the formation of oxygen and nitrogen polar groups is confirmed by XPS analysis. Plasma treatment improves the adhesion of CF/LMPAEK to the topcoat on the primer coating system to the traditional abrasion treatment level. This effect even is intensified with Ar‐O2 plasma. The topcoat alone presents a higher adherence, which provides a reduced coating usage option.