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Towards an integrated modeling of the plasma-solid interface
Michael Bonitz, Alexey Filinov, Jan-Willem Abraham, Karsten Balzer, Hanno Kählert, Eckhard Pehlke, Franz X. Bronold, Matthias Pamperin, Markus Becker, Dettlef Loffhagen, Holger Fehske
Front. Chem. Sci. Eng.. 2019, 13 (2 ): 201-237.
https://doi.org/10.1007/s11705-019-1793-4
Solids facing a plasma are a common situation in many astrophysical systems and laboratory setups. Moreover, many plasma technology applications rely on the control of the plasma-surface interaction, i.e., of the particle, momentum and energy fluxes across the plasma-solid interface. However, presently often a fundamental understanding of them is missing, so most technological applications are being developed via trial and error. The reason is that the physical processes at the interface of a low-temperature plasma and a solid are extremely complex, involving a large number of elementary processes in the plasma, in the solid as well as fluxes across the interface. An accurate theoretical treatment of these processes is very difficult due to the vastly different system properties on both sides of the interface: Quantum versus classical behavior of electrons in the solid and plasma, respectively; as well as the dramatically differing electron densities, length and time scales. Moreover, often the system is far from equilibrium. In the majority of plasma simulations surface processes are either neglected or treated via phenomenological parameters such as sticking coefficients, sputter rates or secondary electron emission coefficients. However, those parameters are known only in some cases and with very limited accuracy. Similarly, while surface physics simulations have often studied the impact of single ions or neutrals, so far, the influence of a plasma medium and correlations between successive impacts have not been taken into account. Such an approach, necessarily neglects the mutual influences between plasma and solid surface and cannot have predictive power.
In this paper we discuss in some detail the physical processes of the plasma-solid interface which brings us to the necessity of coupled plasma-solid simulations. We briefly summarize relevant theoretical methods from solid state and surface physics that are suitable to contribute to such an approach and identify four methods. The first are mesoscopic simulations such as kinetic Monte Carlo and molecular dynamics that are able to treat complex processes on large scales but neglect electronic effects. The second are quantum kinetic methods based on the quantum Boltzmann equation that give access to a more accurate treatment of surface processes using simplifying models for the solid. The third approach are ab initio simulations of surface process that are based on density functional theory (DFT) and time-dependent DFT. The fourths are nonequilibrium Green functions that able to treat correlation effects in the material and at the interface. The price for the increased quality is a dramatic increase of computational effort and a restriction to short time and length scales. We conclude that, presently, none of the four methods is capable of providing a complete picture of the processes at the interface. Instead, each of them provides complementary information, and we discuss possible combinations.
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Important parameters in plasma jets for the production of RONS in liquids for plasma medicine: A brief review
Anna Khlyustova, Cédric Labay, Zdenko Machala, Maria-Pau Ginebra, Cristina Canal
Front. Chem. Sci. Eng.. 2019, 13 (2 ): 238-252.
https://doi.org/10.1007/s11705-019-1801-8
Reactive oxygen and nitrogen species (RONS) are among the key factors in plasma medicine. They are generated by atmospheric plasmas in biological fluids, living tissues and in a variety of liquids. This ability of plasmas to create a delicate mix of RONS in liquids has been used to design remote or indirect treatments for oncological therapy by treating biological fluids by plasmas and putting them in contact with the tumour. Documented effects include selective cancer cell toxicity, even though the exact mechanisms involved are still under investigation. However, the “right” dose for suitable therapeutical activity is crucial and still under debate. The wide variety of plasma sources hampers comparisons. This review focuses on atmospheric pressure plasma jets as the most studied plasma devices in plasma medicine and compiles the conditions employed to generate RONS in relevant liquids and the concentration ranges obtained. The concentrations of H2 O2 , NO2 − , NO3 − and short-lived oxygen species are compared critically to provide a useful overview for the reader.
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Plasma for cancer treatment: How can RONS penetrate through the cell membrane? Answers from computer modeling
Annemie Bogaerts, Maksudbek Yusupov, Jamoliddin Razzokov, Jonas Van der Paal
Front. Chem. Sci. Eng.. 2019, 13 (2 ): 253-263.
https://doi.org/10.1007/s11705-018-1786-8
Plasma is gaining increasing interest for cancer treatment, but the underlying mechanisms are not yet fully understood. Using computer simulations at the molecular level, we try to gain better insight in how plasma-generated reactive oxygen and nitrogen species (RONS) can penetrate through the cell membrane. Specifically, we compare the permeability of various (hydrophilic and hydrophobic) RONS across both oxidized and non-oxidized cell membranes. We also study pore formation, and how it is hampered by higher concentrations of cholesterol in the cell membrane, and we illustrate the much higher permeability of H2 O2 through aquaporin channels. Both mechanisms may explain the selective cytotoxic effect of plasma towards cancer cells. Finally, we also discuss the synergistic effect of plasma-induced oxidation and electric fields towards pore formation.
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Phosphorene: Current status, challenges and opportunities
Anandarup Goswami, Manoj B. Gawande
Front. Chem. Sci. Eng.. 2019, 13 (2 ): 296-309.
https://doi.org/10.1007/s11705-018-1783-y
The field of 2-dimensional (2D) materials has witnessed a sharp growth since its inception and can majorly be attributed to the substantial technical and scientific developments, leading to significant improvements in their syntheses, characterization and applications. In the list of 2D materials, the relatively newer addition is phosphorene, which ideally consists of a single layer of black phosphorous. Keeping in mind the past, and ongoing research activities, this short account offers a brief overview of the present status and the associated challenges in the field of phosphorene-related research, with special emphasis on their syntheses, properties, applications and future opportunities.
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Carbon-based materials for photodynamic therapy: A mini-review
Di Lu, Ran Tao, Zheng Wang
Front. Chem. Sci. Eng.. 2019, 13 (2 ): 310-323.
https://doi.org/10.1007/s11705-018-1750-7
Carbon-based materials have been extensively applied in photodynamic therapy owing to the unique optical characteristics, good biocompatibility and tunable systematic toxicity. This mini-review mainly focuses on the recent application of carbon-based materials including graphene, carbon nanotube, fullerene, corannulene, carbon dot and mesoporous carbon nanoparticle. The carbon-based materials can perform not only as photosensitizers, but also effective carriers for photosensitizers in photodynamic therapy, and its combined treatment.
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Multifunctional antimicrobial chlorhexidine polymers by remote plasma assisted vacuum deposition
Ana Mora-Boza, Francisco J. Aparicio, María Alcaire, Carmen López-Santos, Juan P. Espinós, Daniel Torres-Lagares, Ana Borrás, Angel Barranco
Front. Chem. Sci. Eng.. 2019, 13 (2 ): 330-339.
https://doi.org/10.1007/s11705-019-1803-6
Novel antibacterial materials for implants and medical instruments are essential to develop practical strategies to stop the spread of healthcare associated infections. This study presents the synthesis of multifunctional antibacterial nanocoatings on polydimethylsiloxane (PDMS) by remote plasma assisted deposition of sublimated chlorhexidine powders at low pressure and room temperature. The obtained materials present effective antibacterial activity against Escherichia coli K12, either by contact killing and antibacterial adhesion or by biocide agents release depending on the synthetic parameters. In addition, these multifunctional coatings allow the endure hydrophilization of the hydrophobic PDMS surface, thereby improving their biocompatibility. Importantly, cell-viability tests conducted on these materials also prove their non-cytotoxicity, opening a way for the integration of this type of functional plasma films in biomedical devices.
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Continuous flow removal of acid fuchsine by dielectric barrier discharge plasma water bed enhanced by activated carbon adsorption
Rusen Zhou, Renwu Zhou, Xianhui Zhang, Kateryna Bazaka, Kostya (Ken) Ostrikov
Front. Chem. Sci. Eng.. 2019, 13 (2 ): 340-349.
https://doi.org/10.1007/s11705-019-1798-z
Continuous processes which allow for large amount of wastewater to be treated to meet drainage standards while reducing treatment time and energy consumption are urgently needed. In this study, a dielectric barrier discharge plasma water bed system was designed and then coupled with granular activated carbon (GAC) adsorption to rapidly remove acid fuchsine (AF) with high efficiency. Effects of feeding gases, treatment time and initial concentration of AF on removal efficiency were investigated. Results showed that compared to the N2 and air plasmas treatments, O2 plasma processing was most effective for AF degradation due to the strong oxidation ability of generated activated species, especially the OH radicals. The addition of GAC significantly enhanced the removal efficiency of AF in aqueous solution and shorten the required time by 50%. The effect was attributed to the ability of porous carbon to trap and concentrate the dye, increasing the time dye molecules were exposed to the plasma discharge zone, and to enhance the production of OH radicals on/in GAC to boost the degradation of dyes by plasma as well as in situ regenerate the exhausted GAC. The study offers a new opportunity for continuous effective remediation of wastewater contaminated with organic dyes using plasma technologies.
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Synthesis of Ag and Cd nanoparticles by nanosecond-pulsed discharge in liquid nitrogen
Mahmoud Trad, Alexandre Nominé, Natalie Tarasenka, Jaafar Ghanbaja, Cédric Noël, Malek Tabbal, Thierry Belmonte
Front. Chem. Sci. Eng.. 2019, 13 (2 ): 360-368.
https://doi.org/10.1007/s11705-019-1802-7
The synthesis of CdO, Ag2 O (5 nm) and Ag (~20‒30 nm) nano-objects is achieved simultaneously by nanosecond-pulsed discharges in liquid nitrogen between one cadmium electrode and one silver electrode. Oxidation occurs when liquid nitrogen is fully evaporated and nanoparticles are in contact with the air. No alloy is formed, whatever the conditions, even though both elements are present simultaneously, as showed by time-resolved optical emission spectroscopy. This lack of reactivity between elements is attributed to the high pressure within the discharge that keeps each metallic vapor around the electrode it comes from. Each element exhibits a specific behavior. Cubic Cd particles, formed at 4 kV, get elongated with filamentary tips when the applied voltage reaches 7 and 10 kV. Cd wires are formed by assembly in liquid nitrogen of Cd nanoparticles driven by dipole assembly, and not by dielectrophoresis. On the contrary, silver spherical particles get assembled into 2D dendritic structures. The anisotropic growth of these structures is assumed to be due to the existence of pressure gradients.
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The synthesis of 6-(tert -butyl)-8-fluoro-2,3-dimethylquinoline carbonate derivatives and their antifungal activity against Pyricularia oryzae
Long Cheng, Ruirui Zhang, Hongke Wu, Xinghai Liu, Tianming Xu
Front. Chem. Sci. Eng.. 2019, 13 (2 ): 369-376.
https://doi.org/10.1007/s11705-018-1734-7
A series of novel 6-(tert -butyl)-8-fluoro-2,3-dimethylquinoline carbonate derivatives were designed and synthesized. Bioassay results showed that some of them exhibited good activity against Pyricularia oryzae (P. oryzae ). It was found that the compound 5q (benzyl (6-(tert -butyl)-8-fluoro-2,3-dimethylquinolin-4-yl) carbonate) possessed good activity against P. oryzae whatever protective activity (10 mg·L− 1 ) or curative activity (25 mg·L− 1 ), which was better than that of control tebufloquin. In addition, the frontier molecular orbit results revealed that the compound held higher activity against P. oryzae when the total energy was low and the ClogP was high, which may provide useful information for further design novel fungicides.
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Safety evaluation of microbial pesticide (HaNPV) based on PCR method
Miao Zhao, Shufei Li, Qinghong Zhou, Dianming Zhou, Ning He, Zhiyong Qian
Front. Chem. Sci. Eng.. 2019, 13 (2 ): 377-384.
https://doi.org/10.1007/s11705-018-1777-9
Microbial pesticides can prevent and control diseases and pests of crops, and has become one of the important measures to ensure food and environmental safety. However, the potential harm of microbial pesticides to humans and animals is a serious concern at home and abroad. In this paper, we have investigated the infectivity and pathogenicity of a representative of viral microbial pesticides, helicoverpa armigera nuclear polyhedrosis virus (HaNPV), by specific and highly sensitive polymerase chain reaction technology. The results show that HaNPV can be gradually cleared in a short time after getting into blood of experimental rats, and does not infect other tissues or organs of animals; also indicate that the test subjects are not infectious to experimental rats after intravenous injection of HaNPV. Our method has good specificity and repeatability, and could provide an important reference for establishment of infectivity and pathogenicity detection methods for viral microbial pesticides in future.
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A free-standing superhydrophobic film for highly efficient removal of water from turbine oil
Fan Shu, Meng Wang, Jinbo Pang, Ping Yu
Front. Chem. Sci. Eng.. 2019, 13 (2 ): 393-399.
https://doi.org/10.1007/s11705-018-1754-3
A free-standing superhydrophobic film is prepared by sequentially dip-coating a commercially available filter paper with nano SiO2 suspension, epoxy emulsion, and octyltrimethoxysilane solution. A surface with micro- or nano-roughness is formed because SiO2 nanoparticles are uniformly and firmly adhered on the backbone of the filter paper by the cured epoxy resin. Furthermore, the surface energy is significantly reduced because of introducing octytrimethoxysilane. Such a surface structure makes the prepared film a superhydrophobic material. Due to its free-standing nature, this superhydrophobic film can be used to remove water from turbine oil by filtration. The efficiency of water removal is high (up to 94.1%), and the filtration process is driven solely by gravity without extra energy consumption. Because of the facile fabrication process and the high efficiency of water removal, this free-standing superhydrophobic film may find application in power industry.
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Effect of adding a smart potassium ion-responsive copolymer into polysulfone support membrane on the performance of thin-film composite nanofiltration membrane
Meibo He, Zhuang Liu, Tong Li, Chen Chen, Baicang Liu, John C. Crittenden
Front. Chem. Sci. Eng.. 2019, 13 (2 ): 400-414.
https://doi.org/10.1007/s11705-018-1757-0
Thin-film composite (TFC) nanofiltration (NF) membranes were fabricated via the interfacial polymerization of piperazine (PIP) and 1,3,5-benzenetricarbonyl trichloride on polysulfone (PSf) support membranes blended with K+ -responsive poly(N -isopropylacryamide-co-acryloylamidobenzo-15-crown-5) (P(NIPAM-co-AAB15 C5 )). Membranes were characterized by attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscope, scanning electron microscope, contact angle, and filtration tests. The results showed that: (1) Under K+ -free conditions, the blended P(NIPAM-co-AAB15 C5 )/PSf supports had porous and hydrophilic surfaces, thereby producing NF membranes with smooth surfaces and low MgSO4 rejections; (2) With K+ in the PIP solution, the surface roughness and water permeability of the resultant NF membrane were increased due to the K+ -induced transition of low-content P(NIPAM-co-AAB15 C5 ) from hydrophilic to hydrophobic; (3) After a curing treatment at 95 °C, the improved NF membrane achieved an even higher pure water permeability of 10.97 L·m−2 ·h−1 ·bar−1 under 200 psi. Overall, this study provides a novel method to improve the performance of NF membranes and helps understand the influence of supports on TFC membranes.
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