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Η διπλωματική εργασία που παρουσιάζεται παρακάτω έχει ως σκοπό τη μελέτη του ψυχρού πλάσματος που παράγεται σε ανομοιογενές ηλεκτρικό πεδίο ακίδα – πλάκα, διάκενου 1 cm και αρνητικής πολικότητας σε συνθήκες χαμηλής πίεσης ατμοσφαιρικού αέρα (5 έως 50 mbar). Αρχικά γίνεται μία πρώτη γνωριμία με το πλάσμα και στη συνέχεια παρουσιάζονται στοιχεία θεωρίας των ηλεκτρικών εκκενώσεων. Το πλάσμα είναι προϊόν ηλεκτρικών εκκενώσεων μέσα σε αέρια, τα οποία από μονωτικά υλικά μετατρέπονται σε αγωγούς. Βάσει το βαθμό ιονισμού του, την ηλεκτρονική πυκνότητα και την ηλεκτρονική του θερμοκρασία, διακρίνεται σε ψυχρό, θερμικό και θερμό. Η παραγωγή του εξαρτάται από παράγοντες όπως το σύστημα τροφοδοσίας, η γεωμετρία του αντιδραστήρα και του διακένου όπως επίσης και τα χαρακτηριστικά του αερίου μέσου και βρίσκει εφαρμογές στην παραγωγή Laser, στην παρασκευή όζοντος, στην επεξεργασία υλικών και επιφανειών κτλ. Ακριβώς μετά, αναπτύσσονται στοιχεία θεωρίας των ηλεκτρικών εκκενώσεων όπως η θεωρία του Townsend, ο νόμος του Paschen και η ηλεκτρική εκκένωση χαμηλής πίεσης (Εκκένωση Αίγλης). Στη συνέχεια παρουσιάζεται η πειραματική διάταξη και ο εξοπλισμός που χρησιμοποιήθηκε κατά τη διάρκεια του πειράματος ενώ μετά ακολουθούν οι μετρήσεις (Καμπύλες V-I και παλμογραφήματα του ρεύματος και του φωτοπολλαπλασιαστή). Τέλος, συνοψίζονται χρήσιμα συμπεράσματα από την εργασία όπως ότι οι εκκενώσεις του πειράματος ήταν ευσταθείς για την αντίσταση φόρτου που επιλέξαμε, παρατηρήθηκε γραμμική σχέση της τάσης [V] και της πίεσης [P], εντοπίστηκαν παλμοί Trichel και παρατηρήθηκαν ομοιότητες στη συμπεριφορά με εκκενώσεις θετικής πολικότητας και ομογενούς ηλεκτρικού πεδίου. / The diplomatic work that is presented below has as aim the study of cold plasma that is produced in non-homogeneous electric field spike - plate, gap 1 cm and negative polarity in conditions of low pressure of atmospheric air (5 until 50 mbar). Initially becomes a first acquaintance with plasma and afterwards is presented elements of theory of electric evacuations. The plasma is product of electric evacuations in gases, which from insulator materials are changed in conductors. From his degree of ionization, the electronic density and his electronic temperature, it is distinguished in cold, thermic and hot. His production depends on factors as the system of catering, the geometry of reactor and gap as also and the characteristics of gas of means and find applications in the production Laser, in production of ozone, in the treatment of materials and surfaces etc. Precisely, are afterwards developed elements of theory of electric evacuations as the theory of Townsend, the law of Paschen and the electric evacuation of low pressure (Evacuation of Glamour). Afterwards are presented the experimental provision and the equipment that was used at the duration of experiment while afterwards follow the measurements (curves V-I and oscillator graphs of the current and the photomultiplier). Finally, are summarisen useful conclusions from the work that the evacuations of experiment were valid for the resistance of pressure that we selected, it was observed linear relation of Voltage [V] and Pressure [P], they were located vibrations Trichel and were observed resemblances in the behavior with evacuations of positive polarity and homogenous electric field.

Cold plasma is useful in numerous medical applications, largely because of the highly-reactive chemical species generated in the discharge. The hydroxyl radical (OH) is of these species and has significant biological importance. An atmospheric pressure plasma jet (APPJ) was constructed in the form of a plasma pencil, and relative and absolute measurements were made of OH in both its first excited ground state—OH(A) and OH(X), respectively—using optical emission spectroscopy and cavity ring-down spectroscopy (CRDS). The total number of OH radicals were found to be constant in the plume and within the range given by relative measurements made on similar devices in the literature.

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<p>  </p> <p>Plastics are the most common polymers used in various industries. However, million tons of plastics are produced and disposed every year around the world, and part of them end up entering the environment and agricultural ecosystems in the form of microplastics. Microplastics have become an environmental and health threat to aquatic species and humans because they are small and can easily reach water bodies for municipal and agricultural uses. Microplastics have been traced in food commodities and products derived from animals and even found in bottles of drinking water. As an approach to permanently remediating microplastics, current microplastic degradation techniques, however, require high energy inputs and thus are generally not cost-efficient. High-voltage atmospheric cold plasma (HVACP) is a low-cost energy-efficient technology to produce highly reactive species that can induce physicochemical changes in polymers. This study, for the first time, used HVACP as a novel remediation strategy for microplastics. HVACP was generated by dielectric barrier discharge at 50 kV using oxygen, nitrogen, or their mixture as working gas. Two types of microplastics, polypropylene (PP) and low-density polyethylene (LDPE), were treated for 30 min, and the effect of 24-h post-treatment was also studied. The properties of HVACP-treated microplastics, including weight, particle size, crystallinity, melting point, carbonyl index (CI), and surface morphology, were comprehensively analyzed. HVACP treatments were found effective in degrading both PP and LDPE microplastics. A larger extent of degradation was observed with PP microplastics treated by O/N mixture plasma, but the nitrogen plasma-treated sample showed a higher degree of oxidation according to its CI. For PE microplastics, oxygen plasma caused more degradation, but post-treatment did not promote further oxidation. The results indicated two potential mechanisms for microplastic degradation by HVACP. LDPE microplastics were degraded by oxidative reactions caused by highly reactive oxygen species, and PP microplastics followed a hydrolytic pathway of degradation as they became more hydrophilic after HVACP treatment. This study proved that HVACP is a promising method for microplastic degradation, and thus has great potential for addressing the severe challenges of microplastics that the food and agriculture sectors are currently facing.</p>

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O colágeno é a proteína mais abundante em mamíferos, sendo o tipo I a forma prevalente. Essa proteína possui propriedades interessantes, como baixa imunogenicidade e toxicidade, biocompatibilidade, além de promover o reconhecimento, adesão e diferenciação celular através de sequências RGD (arginina-glicina-aspartato). Por isso, o colágeno é utilizado na composição de diversos biomateriais. Contudo, após a implantação in vivo, a degradação do material por colagenases endógenas pode ocorrer rapidamente, limitando sua utilização. A funcionalização com plasma frio pode superar essa limitação, sendo capaz de adicionar uniformemente grupos funcionais na superfície de materiais e ser modulada para preservar ou alterar de maneira seletiva as propriedades do material. Este estudo buscou funcionalizar o pericárdio bovino (PB) – composto principalmente por colágeno tipo I – utilizando plasma frio a fim de obter um novo biomaterial. Para isso, amostras de PB foram tratadas com plasma de argônio e CO2 a 2,45GHz e 500 W em um intervalo tempo dede 0s (PBCT) a 240s (PB240) com incrementos de 30s. As amostras foram analisadas por espectroscopia de infravermelho e a validação da análise foi realizada através de modelagem molecular computacional. O material foi caracterizado por microscopia óptica e eletrônica de varredura, ângulo de contato e capacidade higroscópica. A biocompatibilidade do PB tratado foi verificada pela implantação do material na camada subcutânea de camundongos Balb/c durante 3, 7 15 e 30 dias. Os resultados mostraram que as modificações causadas pelo tratamento com plasma foram tempo dependente. Após 120s de tratamento (PB120) houve a adição de grupos éster na forma de ligações crosslink sem alterações à estrutura proteica. Entretanto, após 150s foi observado o início de um processo de etching e degradação do colágeno, acentuado aos 240s. Além disso, o tratamento provocou um aumento na hidrofobicidade da superfície do material. A implantação subcutânea mostrou que não houve perda na biocompatibilidade do nos grupos tratados quando comparado ao controle. Dessa forma, verificou-se que o tratamento com plasma pode ser modulado para modificar o colágeno sem que haja perdas em suas propriedades de interesse. Novos estudos são necessários para a adequação da funcionalização com plasma, direcionando-a para modificações desejadas e aplicações específicas do biomaterial. / Collagen is the most commonly found protein in mammals and Type I is its most prevalent type. This protein shows interesting properties as low immunogenicity and toxicity, biocompatibility, besides the ability to promote cell recognition, differentiation and induce cell attachment through RGD (arginine-glycine-aspartate) sequences. Due to these characteristics, collagen is used in many biomaterials. However, after in vivo implantation, the degradation of the material by endogenous collagenases can occur too soon, impairing its application. Cold plasma functionalization can overcome this limitation; it is able to add evenly new functional groups on materials’ surfaces and can be tailored to preserve or alter selectively the bulk properties of the material. Therefore, this study aimed the functionalization of bovine pericardium (PB) – material composed of collagen type I – using cold plasma in order to obtain a new biomaterial. PB was treated with argon (Ar) and carbon dioxide (CO2), microwave power source 2.45Hz, 500 W. The treatment was carried out from 0 (PBCT) up to 240s (PB240), with a 30s increment. The samples were analysed by FTIR-ATR and the analysis validation was done through computing molecular modelling. The material was characterized by optical microscopy, SEM, contact angle and swelling. PB biocompatibility was assessed through subcutaneous implantation of the material in mice Balb/c for 3, 7, 15 and 30 days. The results indicated the changes caused by plasma treatment were time-dependent. By 120s of treatment (PB120) ester groups were added in the material, forming crosslink bonds without modification within the protein structure while 150s of treatment caused the beginning of an etching process and collagen degradation, which was more distinct at 240s; there was also an increase in the hydrophobicity on the surface of the treated material. The subcutaneous implantation test showed there wasn’t biocompatibility loss of treated PB when compared to control. Therefore, it was verified that plasma treatment can be tailored to modify collagen without impairing its properties of interest. New studies are necessary to suit plasma functionalization according the desired modifications and specific applications of the biomaterial. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

A madeira maciça é um compósito polimérico natural que pode sofrer tratamentos para atender a diversas especificações técnicas. Uma característica da madeira é a sua higroscopicidade. A madeira úmida é vulnerável ao ataque de térmitas e fungos, além de perder estabilidade dimensional. Os tratamentos mais usados são a impregnação e/ou o revestimento com tintas e vernizes. Uma técnica promissora para o revestimento de madeira maciça é o plasma frio ou descarga luminescente. Neste trabalho produziu-se plasmas frios através de descargas elétricas luminescentes em gases rarefeitos. Os precursores gasosos usados foram o etileno, acetileno, 1-buteno, e vapor de metil metacrilato e de acetato de vinila. A superfície de madeira maciça tratada por estes plasmas ficaram hidrofóbicas, sendo que os melhores resultados foram alcançados usando 1-buteno como gás precursor. Apesar do tratamento promover repelência à água, a superfície tratada continuou permeável ao vapor d\'água. Com o emprego de uma mistura gasosa formada por vapor de TEOS e O2, foi possível constatar a ineficiência da descarga luminescente capacitiva em revestir o interior de orifícios em madeira. A deposição de filmes finos a partir de plasmas de 1-buteno foi caracterizada, tendo apresentado propriedades distintas do polímero convencional. O filme depositado por plasma apresentou hidrofobicidade, resistência química, insolubilidade em solventes comuns, e resistência contra teste acelerado de intemperismo. A espectroscopia de infravermelho e a análise elementar também revelaram diferenças entre os filmes convencional e depositado por plasma. As reações químicas no plasma podem ser controladas através de ajustes na potência transferida ao reator, pressão da câmara, vazão dos gases, e tempo de exposição à descarga. Com o uso de plasmas menos energéticos é possível produzir filmes poliméricos com estruturas menos entrecruzadas. Duas técnicas distintas foram testadas neste trabalho: o plasma capacitivo e o jato de plasma. Ambas as técnicas são promissoras em função do baixo nível de vácuo necessário, baixas freqüências, pequeno consumo de energia, ausência de poluição e solventes, e o uso de reagentes disponíveis em escala industrial. / Solid wood is a natural polymer composite that can be subjected to a wide variety of treatments to make it suitable for specific technical applications. The greatest disadvantage of solid wood is its hygroscopicity. Moist wood is vulnerable to attack by fungi and termites, and loses its dimensional stability. The most widely used treatments for solid wood are impregnation and coating with paint and varnish. A promising future technique for solid wood surface coating is a plasma treatment in a glow discharge. Cold plasmas were produced by electrical glow discharges in a gas medium at reduced pressure. The precursor gases used were ethylene, acetylene, 1-butene, and vapor of vinyl acetate. The treatment caused the solid softwood surface to become hydrophobic; 1-butene-plasma produced the best results. Although the surface plasma treatment resulted in water repellence, permeability to water vapor remained. Using a mixture of tetraethyl orthosilicate vapor (TEOS) and oxygen (O2) it was possible to investigate the inability of the glow discharge to coat the surface of wood orifices. Deposition of non-conventional polymeric thin films were observed on solid wood substrate after injecting a 1-butene-argon gas mixture into a glow discharge chamber. The deposited film showed water repellence, chemical resistance, insolubility in most common organic solvents and some protection against weathering. Infrared analyses revealed differences between conventional and plasma polymerized 1-butene. Plasma chemistry can be controlled by external conditions of plasma, such as input power, gas flow rate, pressure, and the time of exposure. Using low energetic plasmas the deposited film can be polymer like with a less crosslinked structure. Two different techniques - known capacitive coupled plasma and plasma jet - were tested in this study. Both these techniques appear promising in view of the low vacum level and low frequency, low power supply required, the lack of pollutants and solventes, and the use of industrial chemicals.

The thesis deals with the influence of cold plasma,as a stress factor, on content and fluorescence of chlorrophylls of oilseed rape. Theoretical part deals with characteristic oilseeds rape, fluorescence, photosynthetic pigments and the effects of cold plasma on on physiology of plants. The theoretical part continues in experimental mesurement. The eperiment was done in laboratory conditions. The own of eperiment was to discover the influence of cold plasma on the amount of chlorophylls and fluorescence of chlorophylls. The rape seads were treated with cold plasma for the duration of various time interval. The thesis considersif the plants, which were sprouted from treated seeds, show higher values of physiological activities as compared with plants germinated from conventional seed.