Elektrostatické zvlákňování polyvinylalkoholu a jeho směsi se stříbrnými nanočástice připravenými biosyntézou

This bachelor thesis focuses on the study of biosynthesized silver nanoparticles and electrospinning process poly(vinyl alcohol) and its mixture with prepared nanoparticles. The theoretical part describes partly the preparation and antibacterial properties of silver nanoparticles and partly the process of electrostatic spinning with focus on preparation of poly(vinyl alcohol) fibrous samples. The experimental part aims at characterization how silver nanoparticles are prepared via phytosynthesis and polymeric nanofibers as well as mixture of polymer with nanoparticles via electrospinning method. For characterization of prepared samples, several methods such as electron microscopy, infrared spectroscopy, ultraviolet visible spectroscopy, X-ray diffraction and dynamic light scattering were used. Silver nanoparticles were successfully synthetized via phytosynthesis. Then, electrostatic spinning of poly(vinyl alcohol) and its mixture with prepared silver nanoparticles was evaluated as successful and repeatable.Bakalářská práce se věnuje studiu biosyntetizovaných stříbrných nanočástic a elektrostatickému zvlákňování čistého polyvinylalkoholu a jeho směsi s připravenými stříbrnými nanočásticemi. Teoretická část je z části věnována přípravě a antibakteriálním vlastnostem stříbrných nanočástic a z části elektrostatickému zvlákňování polymerů se zaměřením na polyvinylalkohol. Experimentální část je zaměřena na charakterizaci připravených stříbrných nanočástic fotosyntézou, zvlákněného polyvinylalkoholu připraveného elektrostatickým zvlákňováním i směsi polymeru a stříbrných nanočástic. K charakterizaci bylo použito několik metod jako: skenovací a transmisní elektronová mikroskopie, infračervená mikroskopie, ultrafialovo-viditelná spektroskopie, rentgenová difrakční analýza a metoda založená na dynamickém rozptylu světla. Nanočástice stříbra byly za pomocí fytosyntézy úspěšně připraveny. Následně elektrostatické zvlákňování polyvinylalkoholu a jeho směsi s připravenými nanočásticemi bylo zhodnoceno jako úspěšné a opakovatelné.9360 - Centrum nanotechnologiívýborn

Kotvení biosyntetizovaných nanočástic stříbra na polykaprolaktonová vlákna pro využití v medicíně

This diploma thesis focuses on the mechanisms involved in the formation of silver nanoparticles by biosynthesis. Here, the electro-spraying method was employed with poly(vinyl alcohol), and this was combined with silver nanoparticles on a poly(ε caprolacton) fibrous material. The theoretical part of the thesis describes the preparation and antibacterial properties of silver nanoparticles and their incorporation in polymeric droplets by electrostatic spraying. These processes were conducted to prove the hypothesis that fibrous materials combined with silver nanoparticles have great possibility for application in medicine and especially in wound dressings. The experimental part then demonstrates how silver nanoparticles are prepared by the chosen organic compound - maleic acid - with concentration gradient. This is followed by the attachment of polymeric droplets, and final mixing of the polymer with nanoparticles on the fibrous matrix by electro-spraying. The analyses used to characterise the prepared silver nanoparticles and fibrous materials include electron microscopy, X-ray diffraction and dynamic light scattering. These confirmed that the silver nanoparticles were successfully synthesised, and they were then subjected to antibacterial and cytotoxicity testing to illustrate their worth in the biomedical field. Finally, the electrostatic spraying of poly(vinyl alcohol) and its mixture with silver nanoparticles for attachment to the prepared poly(ε-caprolacton) fibrous matrix was evaluated. This also proved successful and, most importantly, it produced no cytotoxic effect.Diplomová práce se věnuje studiu mechanismu tvorby stříbrných nanočástic metodou fytosyntézy a elektrostatickému procesu sprejování polyvinyl alkoholu a jeho směsi s připravenými nanočásticemi na polykaprolaktonová vlákna. Teoretická část je z části věnována přípravě a antibakteriálním vlastnostem nanočástic stříbra a částečně elektrostatickému procesu a jeho využití při přípravě antibakteriálních materiálů s potenciálem v medicíně. Experimentální část je zaměřena na popis a charakterizaci nanočástic stříbra, které jsou připraveny pomocí vybrané organické sloučeniny kyseliny maleinové a jejich ukotvení na polykaprolaktonových vláknech za pomoci elektrostatického sprejování směsi polymerního roztoku polyvinyl alkoholu a připravených nanočástic. Pro charakterizaci nanočástic stříbra a vlákenných materiálů bylo použito několik metod, jako je elektronová mikroskopie, rentgenová difrakce, dynamický rozptyl světla, antibakteriální a cytotoxické testování. Nanočástice stříbra byly úspěšně syntetizovány. Připravené vláknité materiály byly vyhodnoceny jako netoxické vůči testovaným buňkám s možnou následnou aplikací v medicíně.9360 - Centrum nanotechnologiívýborn

Optimizing of the Balanced Scorecard method for management of mining companies with the use of factor analysis

The managers of information age companies cannot rely merely on data derived from past activities of the company and focus on improving existing processes. They need a frame for measuring values that result from strategic goals of the company, a tool, which is focusing on obtaining information about company's current success, as well as finding new driving forces to ensure the future competitiveness of the company. Strategic business performance measurement system the Balanced Scorecard (BSC) is a suitable tool for improving the competitiveness of industrial companies. During its implementation, however, there is a conflict of perception of the importance of individual goals and measurable characteristics in partial perspectives of the BSC and its actual enforcement of the various strategic objectives in companies. The aim of this article is to verify the accuracy of BSC settings in an environment of selected companies in the Moravian-Silesian region with the emphasis placed on mining companies with the help of multidimensional statistics - factor analysis. The research took place in 2015 in cooperation with managers from the Moravian-Silesian Region (MSR), and it was divided into two kinds of research - quantitative and qualitative.Web of Science22444743

Ag-AgCl nanoparticles fixation on electrospun PVA fibres: Technological concept and progress

Polymer-metal based material with unique 3D structure is an attractive substrate for the development of biomedical applications. A novel preparation of the composite from polymer fibres and silver nanoparticles has been designed through: (1) preparation of silver nanoparticles by phytosynthesis and (2) incorporation of these nanoparticles in a fibrous membrane prepared by electrospinning. The nanoparticle biosynthesis was performed in a pure environmental-friendly, easy, static, bottom-up in vitro regime using Tilia sp. leachate. TEM and XRD depict the formation, stabilisation and encapsulation of crystalline silver (14 +/- 9 nm) nanoparticles (NPs) in one simple step with low tendency to aggregate. We achieved successful incorporation in the uniform electrospun 221 +/- 24 nm poly(vinylalcohol) fibres, and this confirms the possibility of its use in the biomedical field. Both SEM with EDX and TEM analysis determined fibre uniformity with the presence of silver NPs, and ICP-AES confirmed the relatively similar metal concentration throughout the triplicate measurement of fibre structures on the 2 x 2 cm area in the following manner: 0.303 +/- 0.018 wt. %, 0.282 +/- 0.017 wt. %, and 0.281 +/- 0.017 wt. %. Our hypothesis is based on previously verified preparation of active silver NPs and the easily prepared PVA electrospun fibres which act as a water soluble matrix. The simple methodology of incorporating biosynthetically prepared NPs in the PVA fibers highlights the effectiveness of this material, with simple release from water-soluble PVA and final activation of the prepared NPs.Web of Science9art. no. 1552

Evaluation of the functionality of bankruptcy models in mining companies

Mining companies are an important part of the national industry of the Czech Republic. Since mining companies are important for the industry, it is necessary to predict their economic development. Moreover, forecasting the economic development of an enterprise in terms of the risk of bankruptcy is an important activity for the financial management of any enterprise. One of the ways to predict economic development and assess the risk of possible bankruptcy is to use bankruptcy models. The aim of this paper is to determine the most appropriate model for predicting the bankruptcy risk of a mining company. The subject of the article is to identify the most suitable bankruptcy models applicable for bankruptcy risk prediction in Czech conditions of mining enterprises and to verify their functionality on real data of mining enterprises. On the basis of a search of expert sources and comparative analysis, it was found that the most suitable models for predicting the development of the enterprise in terms of bankruptcy risk are modified versions of traditional bankruptcy models. The analysis showed that the bankruptcy models are the IN05 Index, Altman's analysis for Czech companies and the modified Taffler's index. The authors' team conducted a thorough analysis during which they verified the functionality of the selected bankruptcy models on real data of mining companies. After a thorough analysis to test the functionality of bankruptcy models on real data from mining companies, the most appropriate model for estimating the evolution of bankruptcy probability risk was identified.Web of Science27376675

Analysis and modelling of single domain core-shell (αFeNi/chromite) nanoparticles emitted during selective laser melting, and their magnetic remanence

Despite recent intense implementation of increasingly eco-friendly additive manufacturing, the properties of nanoparticulate pollutants emitted during Laser Powder Bed Fusion are still not fully understood, and have generally been overlooked. This study aims to fill this gap in current research by providing new insights into distinct metal/oxide core-shell nanoparticles (3–36 nm) that are produced during 3D printing using stainless steel. It also suggests possible ways for the removal of these potentially harmful by-products. Further, this research also provides a newly developed kinetic model that predicts a metal core growth time of below 200 μs and confirms the predicted theory for the formation of these by-products. In the current study it was found that the cores produced during this process are purely metallic and consist of meteoroid phase kamacite (αFeNi). Within this study there was found to be a complete dominance of single-domain cores of kamacite with prevailing particles below the superparamagnetic threshold showing strong magnetic response and remanence. This new knowledge can be used to minimize potential health risks and reduce contamination of raw materials by this nanoparticulate pollutant, which can adversely affect the quality of printed metal parts, the environment, and the health of the operator. These findings also provide a new possibility of targeted efficient production of superparamagnetic core-shell nanoparticles with a metallic kamacite core during laser powder bed fusion of austenitic steel 316L powder, which can be used in the production of sensors.Web of Science400art. no. 13668

Deposition of photocatalytic nanomaterials on fabrics and their use in the degradation of pollutants

Disertační práce zkoumala problematikou opakovaného používání filtrů, kdy v průběhu času dochází k nahromadění virů, bakterií a polutantů na jejich površích. To může vést k tomu, že se samotný filtr po takové kontaminaci stane zdrojem infekce nebo toxických látek. Ke zmírnění a případně k úplné eliminaci tohoto znečištění se jako efektivním nástrojem prokázalo být využití fyzikálně-chemického působení nábojů fotokatalytických částic, které jsou fixovány na vláknech filtru. V první části se práce zabývá přípravou a vlastnostmi fotokatalytického grafitického nitridu uhlíku (g-C3N4) z močoviny a melaminu, v jejich objemové formě a po následné aplikaci exfoliačních technik: tepelné, kavitační a mlecí. Fotokatalytická aktivita byla zkoumána při degradaci fenolu za viditelného záření ve spolupráci s Univerzitou v Portu, Portugalsko. Ukázalo se, že objemová forma z močoviny vykazuje vyšší fotokatalytickou aktivitu ve srovnání s objemovou formou z melaminu, nicméně v případě močoviny došlo k vysokému hmotnostnímu úbytku. Mletí se ukázalo jako nevhodné pro g-C3N4 z močoviny, protože způsobilo snížení fotokatalytické aktivity, ale pro melamin je tato technika exfoliace efektivní. Termální exfoliace vedly k nejvyšší fotokatalytické aktivitě, kdy došlo i k největším nárůstům specifického povrchu a materiály současně vykazovaly i nejvyšší hodnoty fluorescence. V následující části se práce zaměřila na přípravu polymerní vlákenné membrány z polyvinyldifluoridu (PVDF) a polyvinylbutyralu (PVB) s deponovanými fotokatalyticky aktivními částicemi g-C3N4. Ty mají prokázanou virucidní a baktericidní aktivitu při vystavení viditelnému záření a současně v testech nevykázaly žádnou cytotoxicitu. Byly připraveny a charakterizovány čisté membrány spolu s membránami, na nichž byly deponovány fotokatalyticky aktivní částice g-C3N4 blend, termální a chemickou metodou. Nejčastěji používaná blend metoda vykazovala nejvyšší plošnou hustotu deponovaných částicAvšak vedla k zapouzdření částic polymerem dovnitř vlákna a ke snížení fotokatalytického působení. Bylo prokázáno, že termální metoda není u polymeru PVDF vhodná díky tepelné stabilitě. Strukturní a chemické vlastnosti PVDF byly modifikovány hydroxidem draselným, což vedlo k navázání částic g-C3N4 na povrch vláken. Tato technika vedla k vyšší plošné hustotě částic než u termální metody a povrchové navázání částic na vlákna umožnilo jejich efektivnější fotokatalytické působení. U PVB membrán bylo navíc dokázáno, pro sérii tří PVB membrán připravených stejnými metodami, že metody přípravy jsou reprodukovatelné. Výsledky této práce ukázaly, že membrány vyrobené z obou polymerů jsou fotokatalyticky efektivní a jsou po regeneraci opakovaně použitelné. Avšak, během analýzy morfologie membrán před a po reakcích (12 hodin) byla prokázána degradace polymerních PVB vláken, zatímco u polymerních membrán z PVDF změny viditelné nebyly. Další částí práce bylo stanovení filtrační účinnosti podle Evropského standardu EN 14683:2019+AC. Odvozený semiempirický matematický model popisuje závislost účinnosti filtrace částic na průřezové rychlosti proudění vzduchu membránou. Modelový matematický tvar byl úspěšně ověřen regresí na experimentálních datech měření čtyř komerčních vlákenných filtrů. Výsledky měření ukázaly konstantní limitní účinnosti při vysokých rychlostech a současně potvrdily modelový předpoklad, že filtry nemohou dosáhnout 100 % účinnosti filtrace kvůli Brownovu pohybu částic ani při nulových rychlostech proudění.This thesis deals with the problem of repeated filter usage when viruses, bacteria, and pollutants accumulate on their surfaces over time. Such accumulation poses the risk of the filter becoming a potential source of infection or toxic substances after such contamination. Using photocatalytic particles adhered to filter fibers is an effective tool to mitigate and eliminate such contamination through physicochemical actions of charges. The first part of this thesis focuses on the preparation and characterization of photocatalytic graphitic carbon nitride (g-C3N4), synthesized from urea and melamine in their bulk forms and followed by exfoliation methods: thermal, ultrasound cavitation, and mill exfoliation. The University of Porto, Portugal, collaborated to assess the photocatalytic efficacy through phenol degradation under visible light. Results indicated that the urea-derived bulk form displayed superior photocatalytic activity over its melamine-derived opposite, although with a notable mass loss. Milling was found to be ineffective from urea precursor; in contrast, for melamine, this exfoliation technique was efficient. Thermal exfoliations resulted in the highest photocatalytic activity and induced the highest increases in specific surface areas and the highest fluorescence values. The thesis then focused on preparing and characterizing polymeric fiber membranes using polyvinylidene fluoride (PVDF) and polyvinyl butyral (PVB), onto which photocatalytic g-C3N4 were deposited. These particles have demonstrated virucidal and bactericidal properties upon exposure to visible light, with no observed toxicity in tests. Membranes were synthesized in their pure form and assessed alongside membranes featuring g-C3N4 particles deposited through blend, thermal, and chemical methods. Among these, the blend method exhibited the highest areal density of deposited particles, nevertheless, it resulted in particle encapsulation within the polymer fiber, decreasing photocatalytic effectiveness. The thermal method is unsuitable for PVDF polymer due to its high thermal stability. PVDF's structural and chemical properties were modified with potassium hydroxide allowing g-C3N4 particles deposition to the fibers surface. This method achieved a higher areal density of particles, and the surface particles binding to the fibers resulted in the highest photocatalytic activity. Moreover, the reproducibility of the preparation methods was successfully confirmed for a series of three PVB membranes prepared using the same techniques. The study revealed that membranes exhibit photocatalytic activity and are reusable. However, morphology before and after reactions (12 hours) highlighted degradation of the polymeric PVB fibers, whereas no changes were observed in the PVDF membranes. Another aspect of the research was assessing filtration efficiency according to European standard EN 14683:2019+AC. A semi-empirical mathematical model describes the dependency between particle filtration efficiency and cross-sectional airflow velocity through the membrane. This mathematical formulation was effectively validated through regression analysis on experimental data obtained from four commercial filters. The measurement indicated consistent limiting efficiencies at high velocities and affirmed the model's assumption that filters cannot attain 100% filtration efficiency due to the Brownian motion of particles, even at zero flow velocities.9360 - Centrum nanotechnologiívyhově

Silver-loaded poly(vinyl alcohol)/polycaprolactone polymer scaffold as a biocompatible antibacterial system

Abstract A chronic nonhealing wound poses a significant risk for infection and subsequent health complications, potentially endangering the patient‘s well-being. Therefore, effective wound dressings must meet several crucial criteria, including: (1) eliminating bacterial pathogen growth within the wound, (2) forming a barrier against airborne microbes, (3) promoting cell proliferation, (4) facilitating tissue repair. In this study, we synthesized 8 ± 3 nm Ag NP with maleic acid and incorporated them into an electrospun polycaprolactone (PCL) matrix with 1.6 and 3.4 µm fiber sizes. The Ag NPs were anchored to the matrix via electrospraying water-soluble poly(vinyl) alcohol (PVA), reducing the average sphere size from 750 to 610 nm in the presence of Ag NPs. Increasing the electrospraying time of Ag NP-treated PVA spheres demonstrated a more pronounced antibacterial effect. The resultant silver-based material exhibited 100% inhibition of gram-negative Escherichia coli and gram-positive Staphylococcus aureus growth within 6 h while showing non-cytotoxic effects on the Vero cell line. We mainly discuss the preparation method aspects of the membrane, its antibacterial properties, and cytotoxicity, suggesting that combining these processes holds promise for various medical applications

The effects of nature-inspired synthesis on silver nanoparticle generation

A wide range of methods can be used for nature-inspired metallic nanoparticle (NP) synthesis. These syntheses, however, are ongoing in the presence of diverse mixtures of different chemical compounds, and all or only a few of these contribute to resultant particle properties. Herein, the linden (Tilia sp.) inflorescence leachate and pure citric and protocatechuic acids were chosen for Ag-AgCl nanoparticle (NP) synthesis, and the resultant particles were then compared. We focused on the following four issues: (1) preparation of Ag-AgCl NPs using the Tilia sp.-based phytosynthetic protocol, (2) analytical determination of the common phenolic, nonphenolic, and inorganic profiles of three Tilia sp. types from different harvesting locations, (3) preparation of Ag-AgCl NPs using a mixture of citric and protocatechuic acids based on chromatographic evaluation, and (4) comparison of Tilia-based and organic acid-based syntheses. Our research confirms that the Tilia organic and inorganic profiles in biomasses are influenced by the harvesting location, and the three sites influenced both the morphology and final NP size. Our processing method was uniform, and this enabled great Ag-AgCl NP reproducibility for each specific biomass. We were then able to prove that the simplified organic acid-based synthesis produced even smaller NPs than Tilia-based synthesis. These findings provide better understanding of the significant influence on NP final properties resulting from other organic acids contained in the linden.Web of Science7

Crucial cytotoxic and antimicrobial activity changes driven by amount of doped silver in biocompatible carbon nitride nanosheets

The use of Ag-modified nanomaterials continues to attract attention in biological contamination control, their potential cytotoxicity is often overlooked. Herein, biocompatible carbon nitride is modified with 1 and 5 wt.% Ag and effects of different nanomaterial dose and Ag content on antimicrobial activity and cytotoxicity is studied. Pure Ag nanoparticles and AgNO3 is tested for comparison, together with ten bacterial strains including panresistant Pseudomonas aeruginosa. Cytotoxicity is then investigated in three adherent and two suspension human cell lines, and results confirm that cancer adherent cell lines are the most immune lines and human cervical adenocarcinoma cells (HeLa) are more resilient than human lung adenocarcinoma cells (A549). The HeLa remains over 90 % viable even after 24-h treatment with the highest concentration of 5%Ag/g-C3N4 (300 mg L-1) while A549 sustained viability only up to 100 mg L-1. Higher concentrations then induce cytotoxicity and A549 cell viability decreases. Our results show the importance of complementary testing of cytotoxicity by LIVE/DEAD assay using flow cytometry with more different human cell lines, which might be less immune to tested nanomaterials than HeLa and A549. Combined controls of new antibacterial agent activity tests then provide increased knowledge of their biocompatibility.Web of Science202art. no. 11168