Plant-derived cis-β-ocimene as a precursor for biocompatible, transparent, thermally-stable dielectric and encapsulating layers for organic electronics

This article presents low-temperature, one-step dry synthesis of optically transparent thermally-stable, biocompatible cis-β-ocimene-based thin films for applications as interlayer dielectric and encapsulating layer for flexible electronic devices, e.g. OLEDs. Morphological analysis of thin films shows uniform, very smooth (R q < 1 nm) and defect-free moderately hydrophilic surfaces. The films are optically transparent, with a refractive index of ∼1.58 at 600 nm, an optical band gap of ∼2.85 eV, and dielectric constant of 3.5-3.6 at 1 kHz. Upon heating, thin films are chemically and optically stable up to at least 200 °C, where thermal stability increases for films manufactured at higher RF power as well as for films deposited away from the plasma glow. Heating of the sample increases the dielectric constant, from 3.7 (25 °C) to 4.7 (120 °C) at 1 kHz for polymer fabricated at 25 W. Polymers are biocompatible with non-adherent THP-1 cells and adherent mouse macrophage cells, including LPS-stimulated macrophages, and maintain their material properties after 48 h of immersion into simulated body fluid. The versatile nature of the films fabricated in this study may be exploited in next-generation consumer electronics and energy technologies

Decontamination-induced modification of bioactivity in essential oil-based plasma polymer coatings

Plasma polymer coatings fabricated from Melaleuca alternifolia essential oil and its derivatives have been previously shown to reduce the extent of microbial adhesion on titanium, polymers, and other implantable materials used in dentistry. Previous studies have shown these coatings to maintain their performance under standard operating conditions; however, when used in e.g., a dental implant, these coatings may inadvertently become subject to in situ cleaning treatments, such as those using an atmospheric pressure plasma jet, a promising tool for the effective in situ removal of biofilms from tissues and implant surfaces. Here, we investigated the effect of such an exposure on the antimicrobial performance of the Melaleuca alternifolia polymer coating. It was found that direct exposure of the polymer coating surface to the jet for periods less than 60 s was sufficient to induce changes in its surface chemistry and topography, affecting its ability to retard subsequent microbial attachment. The exact effect of the jet exposure depended on the chemistry of the polymer coating, the length of plasma treatment, cell type, and incubation conditions. The change in the antimicrobial activity for polymer coatings fabricated at powers of 20–30 W was not statistically significant due to their limited baseline bioactivity. Interestingly, the bioactivity of polymer coatings fabricated at 10 and 15 W against Staphylococcus aureus cells was temporarily improved after the treatment, which could be attributed to the generation of loosely attached bioactive fragments on the treated surface, resulting in an increase in the dose of the bioactive agents being eluted by the surface. Attachment and proliferation of Pseudomonas aeruginosa cells and mixed cultures were less affected by changes in the bioactivity profile of the surface. The sensitivity of the cells to the change imparted by the jet treatment was also found to be dependent on their origin culture, with mature biofilm-derived P. aeruginosa bacterial cells showing a greater ability to colonize the surface when compared to its planktonic broth-grown counterpart. The presence of plasma-generated reactive oxygen and nitrogen species in the culture media was also found to enhance the bioactivity of polymer coatings fabricated at power levels of 10 and 15 W, due to a synergistic effect arising from simultaneous exposure of cells to reactive oxygen and nitrogen species (RONS) and eluted bioactive fragments. These results suggest that it is important to consider the possible implications of inadvertent changes in the properties and performance of plasma polymer coatings as a result of exposure to in situ decontamination, to both prevent suboptimal performance and to exploit possible synergies that may arise for some polymer coating-surface treatment combinations

Electrically insulating plasma polymer/ZnO composite films

In this report, the electrical properties of plasma polymer films functionalized with ZnO nanoparticles were investigated with respect to their potential applications in biomaterials and microelectronics fields. The nanocomposite films were produced using a single-step method that combines simultaneous plasma polymerization of renewable geranium essential oil with thermal decomposition of zinc acetylacetonate Zn(acac)₂. The input power used for the deposition of composites were 10Wand 50W, and the resulting composite structures were abbreviated as Zn/Ge 10Wand Zn/Ge 50W, respectively. The electrical properties of pristine polymers and Zn/polymer composite films were studied in metal-insulator-metal structures. At a quantity of ZnO of around ~1%, it was found that ZnO had a small influence on the capacitance and dielectric constants of thus-fabricated films. The dielectric constant of films with smaller-sized nanoparticles exhibited the highest value, whereas, with the increase in ZnO particle size, the dielectric constant decreases. The conductivity of the composites was calculated to be in the in the range of 10⁻¹⁴-10⁻¹⁵ Ω⁻¹ m⁻¹, significantly greater than that for the pristine polymer, the latter estimated to be in the range of 10⁻¹⁶-10⁻¹⁷ Ω⁻¹ m⁻¹

Plant secondary metabolite-derived polymers: a potential approach to develop antimicrobial films

The persistent issue of bacterial and fungal colonization of artificial implantable materials and the decreasing efficacy of conventional systemic antibiotics used to treat implant-associated infections has led to the development of a wide range of antifouling and antibacterial strategies. This article reviews one such strategy where inherently biologically active renewable resources, i.e., plant secondary metabolites (PSMs) and their naturally occurring combinations (i.e., essential oils) are used for surface functionalization and synthesis of polymer thin films. With a distinct mode of antibacterial activity, broad spectrum of action, and diversity of available chemistries, plant secondary metabolites present an attractive alternative to conventional antibiotics. However, their conversion from liquid to solid phase without a significant loss of activity is not trivial. Using selected examples, this article shows how plasma techniques provide a sufficiently flexible and chemically reactive environment to enable the synthesis of biologically-active polymer coatings from volatile renewable resources

Bactericidal vertically aligned graphene networks derived from renewable precursor

Graphene nanostructures exhibit a wide range of remarkable properties suitable for many applications, including those in the field of biomedical engineering. In this work, plasma-enhanced chemical vapor deposition was utilized at different applied RF power for the fabrication of vertical graphene nanowalls on silicon and quartz substrates from an inherently volatile carbon precursor without the use of any catalyst. AFM confirmed the presence of very sharp exposed graphene edges, with associated high surface roughness. The hydrophobicity of the material increased with the power of deposition, reaching the water contact angle of 123 ˚ for 500 W. Confocal scanning laser microscopy demonstrated that the viability of gram-negative Escherichia coli and gram-positive Staphylococcus aureus cells were 33% and 37% when incubated on graphene samples, respectively, compared to controls (quartz) that showed the viability of 82% and 84%, respectively. SEM verified significant morphological damage to bacterial cell walls by the sharp edges of graphene walls, with cells appearing abnormal and deformed. The presented data clearly contributed to the current understanding of the mechanical-bactericidal mechanism of vertically oriented graphene nanowalls upon direct contact with microorganisms

In-Situ surface modification of terpinen-4-ol plasma polymers for increased antibacterial activity

Surface modification of thin films is often performed to enhance their properties. In this work, in situ modification of Terpinen-4-ol (T4) plasma polymer is carried out via simultaneous surface functionalization and nanoparticle immobilization. Terpinen-4-ol plasma polymers surface were decorated with a layer of ZnO nanoparticles in an oxygen plasma environment immediately after polymer deposition. A combination of hydrophilic modification and ZnO nanoparticle functionalization of the T4 polymer surface led to an enhancement in antibacterial properties by factor of 3 (from 0.75 to 0.25 CFU. mm-2). In addition, ZnO nanoparticle-modified coatings demonstrated improved UV absorbing characteristics in the region of 300-400 nm by 60% relative to unmodified coatings. The ZnO modified coatings were transparent in the visible region of 400-700 nm. The finding points towards the potential use of ZnO nanoparticle-modified T4 plasma polymers as optically transparent UV absorbing coatings

Ways To Optimize SQL Queries To Improve Database Performance In High-Load Systems

SQL statements are used to retrieve information from a database. In most cases, these queries are executed very slowly, the reason for this is the low quality of their writing. For better performance, we need to use faster and more efficient queries. This article shows you how to optimize SQL queries for better performance. The topic of query optimization is very broad, but we will try to cover the most important aspects of this issue. In this paper, I do not focus on in-depth database analysis, but focus on simple hints and tips for setting up queries that can be used to immediately increase productivity

Eco-friendly nanocomposites derived from geranium oil and zinc oxide in one step approach

Nanocomposites offer attractive and cost-effective thin layers with superior properties for antimicrobial, drug delivery and microelectronic applications. This work reports single-step plasmaenabled synthesis of polymer/zinc nanocomposite thin films via co-deposition of renewable geranium essential oil-derived polymer and zinc nanoparticles produced by thermal decomposition of zinc acetylacetonate. The chemical composition, surfaces characteristics and antimicrobial performance of the designed nanocomposite were systematically investigated. XPS survey proved the presence of ZnO in the matrix of formed polymers at 10 W and 50 W. SEM images verified that the average size of a ZnO nanoparticle slightly increased with an increase in the power of deposition, from approximately 60 nm at 10 W to approximately 80 nm at 50 W. Confocal scanning laser microscopy images showed that viability of S. aureus and E. coli cells significantly reduced on surfaces of ZnO/polymer composites compared to pristine polymers. SEM observations further demonstrated that bacterial cells incubated on Zn/Ge 10 W and Zn/Ge 50 W had deteriorated cell walls, compared to pristine polymers and glass control. The release of ZnO nanoparticles from the composite thin films was confirmed using ICP measurements, and can be further controlled by coating the film with a thin polymeric layer. These ecofriendly nanocomposite films could be employed as encapsulation coatings to protect relevant surfaces of medical devices from microbial adhesion and colonization

Comparative study of natural terpenoid precursors in reactive plasmas for thin film deposition

If plasma polymer thin films are to be synthesised from sustainable and natural precursors of chemically heterogeneous composition, it is important to understand the extent to which this composition influences the mechanism of polymerisation. To this end, a well-studied monoterpene alcohol, terpinen-4-ol, has been targeted for a comparative study with the naturally occurring mix of terpenes (viz. Melaleuca alternifolia oil) from which it is commonly distilled. Positive ion mode mass spectra of both terpinen-4-ol and M. alternifolia oil showed a decrease in disparities between the type and abundance of cationic species formed in their respective plasma environments as applied plasma power was increased. Supplementary biological assay revealed the antibacterial action of both terpinen-4-ol and M. alternifolia derived coatings with respect to S. aureus bacteria, whilst cytocompatibility was demonstrated by comparable eukaryotic cell adhesion to both coatings. Elucidating the processes occurring within the reactive plasmas can enhance the economics of plasma polymer deposition by permitting use of the minimum power, time and precursor pre-processing required to control the extent of monomer fragmentation and fabricate a film of the desired thickness and functionality

Formation of Transport and Logistics Complex as a Background of Development of Business Tourism in the Republic of Belarus

В статье рассматривается современное состояние транспортной отрасли Республики Беларусь, ее роль в стимулировании деловой активности и развитии делового туризма в Республике Беларусь. Показано влияние процессов оптимизации транспортно-логистического комплекса на место Беларуси в международных рейтингах. Выявлены проблемы, сдерживающие развитие транспортного рынка, в том числе неравномерное размещение транспортно-логистических комплексов, отсутствие современных предприятий с полным циклом облуживания. Показано, что транспортно-логистические центры играют важную роль в процессах активизации делового туризма.The article considers the current state of the transport industry of the Republic of Belarus, its role in stimulating business activity and developing business tourism in the Republic of Belarus. The influence of optimization processes of the transport and logistics complex on the place of Belarus in international ratings is shown. The problems constraining the development of the transport market, including the uneven distribution of transport and logistics complexes, the lack of modern enterprises with a full service cycle are identified. It is shown that transport and logistics centers play an important role in the process of enhancing business tourism