The developing nanotechnology are getting increased attention through wide range of industries. A variety of nanofibers can be made for applications in many research and industrial branches as well as civil engineering. One of our aims is to find out more about applicaton of nanofibers in civil enginnering. The possible uses of these electrospun nanofibers are promissing as the surface protective layers. There is a great potencial for utilizing of nanofibers in civil engineering. We measured contact angles on SiO2 nanofibers and biocidal properties. The biocidal properties of SiO2 nanofibers againts mold were evaluated by laboratory test as a percentage of the surface coverage of the fibers by molds. Aspergillus niger was used as a model organism.
Research topic was to investigate preparation of antibacterial (AMB) nanoadditive using alternative nanotechnological procedures and various types of nanocarriers based on SiO2 (e.g. Sipernat 22S, Sipernat 44MS and Sidistar T 120).
Results of so-called standard method used to prepare AMB nanoadditive are compared with results of antimicrobial efficiency of an nanoadditive prepared by a method in which antibacterial nanosol containing Ag is used, or by direct incorporation of AgNO3 into siloxane mixture and subsequent doping of nano-SiO2 on the carrier surface.
Results of Ag-content in different types of powder nanoadditives determined using atomic absorption spectrometry (AAS) and antimicrobial efficiency of the nanoadditive determined according to ASTM E 2149-13a method on Escherichia coli CCM 3954 bacterium are presented in table form.
Besides, images of the nanoadditive surface obtained using SEM method and results obtained by analysis of Ag-content and form of the Ag ion using XPS method (X-ray analysis of atomic structure) are shown.
Results from application of the AMB nanoadditive in PP fibres, PP and PE foils in the form of evaluation of antimicrobial efficiency using AATCC 100: 2015 method on Escherichia coli CCM bacterium are given in final part of the poster.
Results acquired in applying the AMB nanoadditive in PP fibres, PP and PE foils are focusing on fibre, textile and food industry.
Nanofiltration with additional antibacterial effect is still one of the big challenges in applied nanotechnology. Due to bio-fouling have pure nanofilters lower durability and efficiency for filtration. The solution for this problem, are antibacterial filtration membranes, which are designed for high efficiency, because they have large antibacterial activity.
Antibacterial membranes were fabricated using Nanospider technology. Nanospider is modified wire electrospinning, which is used for production of nanofibers in large amount. One-step synthesis was used for preparation of antibacterial membranes. Three types of antibacterial agents were used, 1-dodecyltrimethylammonium bromide (DTAB), benzyltrimethylammonium bromide (BTAB) and chlorhexidine (CHX). These agents were added directly to the polymer solution for electrospinning.
Microstructure of antibacterial membranes was studied by X-ray diffraction analysis. The results of XRD showed that the nanofiber structure is combination of alpha and gamma phase of nylon 6. The phase composition is affected by antibacterial agents, mostly by chlorhexidine. The surface chemistry was determined by X-ray photoelectron spectroscopy. The results showed the presence of antibacterial agents on the nanofibers surface. For better unferstanding of the arrangement of antibacterial molecules, the molecular modeling using Materials Studio and Amber software was used.
Antibacterial activity of membranes was tested by parallel streak method according to standard AATCC: 147-2004. Test organism Staphylococus aureus was used for antibacterial tests. The results showed very good antibacterial activity for CHX and DTAB agents. Modification with BTAB was not active.
Sustainable development is still in the focus of researchers. One of the most important problems to be solved is the fate of waste. In the case of polymer technology, one solution could be the application of compostable polymers, like poly(lactic acid) (PLA). These materials are often comingled with other components, which widens their applicability. In this case, after composting, residual materials can remain, which damage the environment. One solution for this problem is to apply additives and reinforcing materials from natural resources. On the other hand, nowadays several types of nano and micro reinforcing materials are used in polymer composite applications. Besides the generally applied micro sized reinforcements, nanosized materials may have good complementary effect on the properties of the composites. In this study, we investigated the effects of basalt fibre as a natural resource-based micro fibre and untreated natural montmorillonite as a natural nanoparticle on the mechanical and morphological properties of PLA. The results showed that the use of these reinforcements together can improve tensile properties effectively.
Viscose fabric was used as the basis for an acrylic coating with two additives in the form of nanoparticles: zinc oxide and dolomite. These two additives were added in order to create a canvas with higher resistance to acidic environments and higher biological resistance against fungi and microbial growth. At the same time, this canvas has received a new mechanical properties such as higher strength and significant elongation changes depending on the amount of dolomite and also without worsening of abrasion. The canvas has been developed and tested specifically for use in libraries and archives in order to increase the lifespan of stored book collections.
The article deals with an experiment that was carried out on a test spinning device designed for the production of nanofibres by electrostatic spinning from a string. In the experiment, a spinning device was created in the form of a vertical stringed moving electrode. This was rewound between two coils and a polymer solution was continuously delivered to the electrode surface by a special dosing device. The intensity of the electric field and the distance of the Taylor cones. Nozzles from which emerging nanofibers travel to the collector, depend on the different cross sections of the strings used. The aim was to choose the appropriate geometry of the cross-section of the string so that the critical stress would be lower than the standard circular cross section used.
Solid phase microextraction (SPME) has been established as a convenient method of sample preparation in organic analytical chemistry since its introduction by Pawliszyn in the nineties of the 20th century. Recently, first attempts are reported on the preparation of SPME sorbents by electrospun nanofibres, in contrast to routinely applied sol-gel techniques. The intention of using electrospun fibres geometry is to enhance the sorbent sensitivity and capacity. In this work, polyetherimide (PEI) electrospun nanofibres were prepared from PEI 15 % solution in DMF/THF 80:20 using a needle electrospinner and SPME steel core as electrode under 10 kV. Adhesion between steel core and polymeric coating was optimized to obtain thermally stable PEI/PDMS SPME fibre assembly. Final laboratory-made SPME fibres were characterized by SEM and TGA and their analytical performance (in determination of hexachlorocyclohexanes - HCH by headspace-SPME GC/MS) was compared with commercially available SPME fibres.
Wooden buildings are a traditional type of construction that has been gradually replaced by brick and monolithic technology. However, current trends tend to use more renewable materials even include thermal insulation. The construction industry commonly use materials on a plant basis. If heat-humidity mode (especially increased humidity) is disturbed, suitable conditions for the occurrence of microorganisms are created. These organisms are mainly molds, bacteria and algae. Biodegradability of plant based material is a major drawback to using these materials in buildings. Given that condensation occurs in timber construction and materials for plant-based are susceptible to attack by microorganisms, it is necessary to protect these materials prior to their occurrence. The paper describes the study of the possibility of protection of these insulation material against mold by nanofiber textile and solutions doped by silver. The comparison of individual used measures is included.
The nature is continually providing varied resources for creating textile materials for various applications. Although many textile fibers in the nature are provided with the fibrous kind itself, nature additionally offers raw materials that maybe changed and formed into a filament in a way similar to the melt and solution spinning of other textile fibers. Basalt is an igneous rock, which is solidified volcanic lava. In recent years, basalt received attention as a replacement for asbestos fibers. In particular, basalt fibers, have recently gained an increasing attention as possible replacement of the conventional glass or carbon fibers due to their advantages in terms of environmental cost and chemical vs. physical properties.Their properties like mechanical and functional properties are determined in terms of fabric and composites .They can be used as nano particles for various applications.Their properties as nano particles on textiles are also checked.
The problem of urinary tract infections and unpleasant odor is persistent problem for patients who are suffering from urine-incontinent. For the most part, those patients fail to control the discharge of urine and excrement. The risk of bactericidal growth increases since the absorbing materials is always wet and in direct contact with the skin. The urine concentrates in the absorbing articles and gets warm for long time, because if the closeness to the body, which creates a conductive atmosphere for bacterial growth. Such bacteria, especially Proteus bacilli, can break down urea to ammonia, through the secretion of urease enzyme. The ammonia not only produces unpleasant odor but also increases the pH of the medium, which may result in skin damage and diaper rash. An odor-inhibiting and germicidal protective layer composed of electrospun cellulose acetate/lignin/copper II-complex nanofiber composite was implemented to solve such problem. A bidentate Schiff base of aminophenylcholorothiazole derivative was reacted with copper salt to produce germicidal activity. Cellulose acetate/lignin nanofibers were produced via electrospinning in different weight ratios. The presence of lignin in the matric allowed a controlled release of the active ingredients, copper-complex. The morphology of CA/Lig/Cu-complex nanofiber mats were characterized using SEM. In addition, thermal behavior of such fibers were investigated via thermal gravimetric analysis (TGA) as well as differential scanning calorimetry (DSC). Copper complex was loaded to the nanofiber system and its antibacterial activity was assessed against common strain of bacteria, which grow in diapers, such as Staphylococcus aureus and Pseudomonas aeruginosa.
Wearable protective clothing that can introduce instant recognition of hazards is a significant frontier that has not yet been crossed because of limitations and experimental circumstances. This research work aims to develop highly efficient smart fabrics toward both of protection and selective detection of industrial toxic gases, chemical and biological hazardous materials including different acidic/alkaline vapors and nerve agents. Our main objective is to create fully flexible early warning portable devices with protection ability from wearable chromic smart fabrics able to detect these hazardous chemicals. Novel thermochromic and pH-sensory molecular switch disperse colorants containing a hydrazone recognition unit have been prepared to be immobilized in textile fibers that can function as solid state matrices. The advantages of textile sensors derived from their large surface area and high-quality mechanical and exploitation characteristics such as flexibility, softness, strength, lightness, and capability to permeate gases. Our results indicates that dyed polyolefin fibers exhibit color change from yellow to purple with a fast response time less than 1 second at very low concentrations (ppb level) upon exposure to acidic and alkaline vapors respectively, Protective films are formulated in the nanoscale to function as protective and selective solid-state optical barcodes for qualitative and quantitative probing of different hazardous chemical and biological materials. This information will help first responders to rapidly make decisions regarding evacuation and decontamination of the site containing toxic gas or nerve agent toward the development of a portable chip-based anti-terrorism tool.
The paper deals with the analysis of the equipment for electrospinning from the free layer using wire spinneret. Simulations of the electrostatic field were performed by using the finite element method. Main part of simulations is focused on analyzing the influence of shape of wire on the distribution of electric field around the wire. The influence of design dimensions of spinning machine was observed as well. Next part of simulations deals with influence of the electric voltages among wire, collector and background. According to the simulations the experiments were done. Main part of the experiments was focused on measurement of critical electric voltages. The conclusion compares simulations to results of experiments.
Optical fiber based sensors are well established as superior to other (especially the electrically conductive) types of sensors within the same applications due to their: light weight, flexibility, sensitivity, large surface area, potential for multi-functionality and multiplexing, immunity to interference with electromagnetic fields, resilience to harsh environmental conditions as well as their safe and hazard-free use during biological interaction. Also, as the lightwaves can cross over cavities and gaps, there is no essential need for continuity in the structure; as it is required in electrically conductive materials. Nevertheless, silica glass - and many polymeric - optical fiber sensors have limited stretchability and fail at low strains; which is not suitable for applications that require higher mechanical compliance such as wearable and stretchable electronics. Therefore, this work investigates the possibilities for utilizing structural fibers (the building blocks of fibrous materials) and using them for light wave-guidance, with a study for the intensity modulation under external mechanical-strains. In particular, elastomeric fibers will be used; as they have a relatively high refractive index (thus, allows the total internal reflection of lightwaves), and high mechanical compliance with elastic stretchability up to 100%. The outcomes of this work should lead to novel sensory materials with high stretchability which are essential for many applications such as robotics and wearable devices.
The submicron metal-oxide fibers (SiO2, TiO2, Al2O3, ...) are finding their application in many fields of industry. They are produced most often by thermal sintering of electrospun hybrid fibers consisting of a base polymer and a metal precursor.
In the process called thermal calcination, the polymer/precursor fibers are exposed to high temperatures in the range of 500-1100°C for several hours (2-10 hours). The oxidation and removal of the base polymer and a part of precursor occurs and fibers are transformed to ceramics. However, this high temperature process has a number of technological disadvantages such as the choice of substrate (thermal stability and oxidation resistance), the need of controlled heating rate and long-term temperature increase, low adhesion of the fibers to the substrate and the time and energy intensity of the process.
One of the alternative technology is the application of low-temperature plasma generated in gases with high oxidation activity. Plasma-assisted calcination can be used as replacement or pre-treatment method before thermal calcination.
In our contribution we compare the effect of low-temperature plasma generated in ambient air by Diffuse Coplanar Surface Barrier Discharge on three types of most commonly used polymers - polyvinylpyrrolidone, polyvinyl alcohol and polyacrylonitrile with suitable precursors. Samples were studied in terms of chemical composition (ATR-FTIR, EDX) and surface morphology (SEM). The method was studied as a separate treatment method or pre-treatment before thermal calcination.
Thanks to the high power density of generated plasma and related high density of active particles, a significant removal of the organic part of the hybrid fiber without the damage of the fibrous structure was observed in the first ten minutes. Plasma treatment before sintering decreases the time and temperature needed to complete removal of organics, does not require slow temperature rise, therefore decreases the cost and simplifies the preparation of metal-oxide fibers.
Synthetic polycrystalline diamond films are routinely grown over the world not only for basic research but also for industrial uses in many different fields including optics and photonics. Optically tailored diamond films are usually grown by microwave plasma chemical vapor deposition (MWCVD) reactors. Here we will present two unique MWCVD reactors for diamond films synthesis: i) focused MW plasma with ellipsoidal cavity resonator and ii) pulsed MW plasma with linear antenna arrangement. Both these CVD reactors can be operated in complementary process parameters, i.e. high vs. low pressure (10 kPa vs. 10 Pa), high vs. low substrate temperature (900 °C vs. 250 °C) or small vs. large deposition area (9 cm2 vs. 600 cm2). Moreover, they offer a broad variety of complementary deposition conditions which allow us to grow diamond films of required properties (pure intrinsic vs. containing optically active color centers) on flat, 3D and periodically structured substrates. We will also introduce technological aspects of before-growth (seeding, structuring by optical, electron and microsphere lithography) and after-growth (etching, functionalization) treatments. Optimized treatment and CVD growth procedures result in a new class of optical elements such as diamond coated IR optical elements (diamond coated Au mirrors for the grazing angle reflectance IR spectroscopy, diamond coated Si and Ge attenuated total reflectance prisms), planar high-index-contrast optical waveguides (diamond/SiO2/Si structure), photonic structures for VIS and IR regions and free-standing structured diamond membranes, discs or grids. Selected technological aspects in fabrication of such optically-oriented elements will be highlighted more in detail. This work was supported by the MSMT project No. LD15003 within the frame of the COST Action MP1403 “Nanoscale Quantum Optics” and GACR project No. 16-09692Y.
Plasma polymerisation in atmospheric pressure is an emerging method of creating highly hydrophilic surfaces, with water contact angles below 10°. Unlike low-pressure plasma polymerisation, it is cheaper, faster and can be done inline, but requires larger amounts of precursor. Unlike plasma activation, the increase of wettability does not show an aging effect. In our experiments, we deposited hydrocarbon films from low concentration propane-butane in nitrogen plasma at atmospheric pressure on c-Si 2 cm x 3 cm large, 0.6 mm thick substrates from distance 0.1 mm. We used three different concentrations of propane-butane. Using thermal desorption spectroscopy, we have systematically analysed the thermal stability of all these films. The samples were slowly heated in high vacuum at constant speed to temperatures up to 1000 °C. Thermally desorbed gases from the sample were analysed using a mass spectrometer. The dependences of partial pressures on particle mass and temperature were rendered into colour maps. We have found that the hydrocarbon films are stable up to 500 °C, at higher temperatures films show strong instability and they could have been destroyed. Samples before and after annealing were analysed by means of common
laboratory tests. We have found that the hydrocarbon films remain on the surface in temperatures up to 500 °C, but in higher temperatures, they are destroyed.
Thermal barrier coatings (TBC) represent the most effective system to protect structural components from damage caused by high temperature and corrosive/erosive environments. Bond coat is the essential part of TBC which ensure the adherence of the YSZ top coat. Y, Ta doped NiCrAl compounds bond coat obtained by air plasma spray (APS) and high velocity air fuel (HVAF) have been subjected to increasing temperature thermal treatments (700 – 1 300 oC/5 h). Spurious Y-Ta-O structures have been evidenced which otherwise failed to be observed by conventional XRD/SEM-EDS. The resulted oxides structures have been investigated by High Resolution Electron Microscopy (HRTEM). Scanning Transmission Electron Microscopy (STEM), SAED, EDS, High Annular Angular Dark Field (HAADF) show the oxidation resistance of HVAF vs APS deposited. This microphases which appear at the high temperature represent the nucleation point for thermal grown oxide (TGO). In APS deposited bond coat the TGO was distributed in the whole mass of the bond coat, while in the HVAF deposited bond coat the TGO is pushed toward its outer surface.
Antireflection technique find many applications including solar cells, light emitting diodes, imaging systems, and so on. A single dielectric coating is an easy and traditional method for antireflection technique. But, it works well for only a narrow range of wavelengths. Texturing or pattering of surfaces is effective to produce antireflection properties for broadbands. In particular, Si rods or pillars in nanometer scale exhibit low reflectivity. For the purpose of antireflection, slanted pillars have advantages over vertical structures.
Wet chemical etching and ion beam etching are the conventional methods for the fabrication of slanted structures. Fabrication of slanted structures by wet chemical etching is based on the orientation-dependent etching of a crystalline substrate in a specific solution. Wet chemical etching is very simple to operate, but the material is limited to crystalline substrates. The range of the structure angles is limited as well. Ion beam etching or focused ion beam etching makes use of ions extracted from an ion source. Ion beam etching can offer arbitrary angles. However, the etching area is limited to the ion beam diameter (a few hundred nanometers at most) and the etch rate is extremely slow. Physical damage of the substrate is also detrimental because a high energy ion beam (up to several tens of keV) bombards the substrate during ion beam etching. Plasma etching has been well developed in microelectronics industries for the past several decades. Plasma etching offers high aspect ratio structures due to its anisotropic etching characteristics. In a conventional etching process, a sheath is formed along the surface of a substrate, irrespective of its angle. Therefore, simply tilting of a sample is not adequate for obtaining slanted etch profiles during conventional plasma etching.
In this study, antireflection properties of Si surfaces were investigated by fabricating slanted Si nanopillars at arbitray angles. Si surfaces having nanopillars at various angles were obtained using slanted plasma etching. The diameter and height of the pillars varied to investigate their effects on reflectance. It was shown that the reflectance of the surface with Si pillars was affected by the aspect ratio as well as the opening area of the pillars.
By combining Combustion Chemical Vapor Deposition (CCVD) and Sol-Gel Technology, flexible transparent gas and migration barrier coatings can be generated on polymer films.
The CCVD (especially the Pyrosil® method) allows the formation of highly compact oxide layers based on silicon under atmospheric pressure. In order to make them more flexible and to reduce the permeability, the use of the Sol-Gel technique is suitable. In this case, hybrid Si and / or Al oxide layers with an inorganic and an organic network can be deposited.
The Oxygen Transmission Rate (OTR) and the Water Vapor Transmission Rate (WVTR) are mainly used as an indicator for the barrier effect against gases. They can be significantly reduced by synergy effects if both coating techniques were combined to create a stacked system of layers.
These systems are only a few hundred nm thick, that’s why they appear optically transparent. This is very important for usability in the packaging and electronics industry. To analyze their topography AFM were used, for the chemical behavior FTIR and for the layer thickness Profilometry or Ellipsometry.
Furthermore, the overall permeability to certain permeates can be regulated by the property of each single layer. This allows the generation of semipermeable membranes and therefore the use in filtration technology.
Release liner papers are used in various self-adhesive applications such as hygiene products, envelopes, bar code labels, packaging tapes, postage stamps, etc. The main function of the release liner is to protect the adhesive layer in the product. It has to stick to the adhesive, but also be easily removed from it. However, a typical problem for silicone based release liners is transfer and migration from the release coating on surfaces they come in contact with. In this work atmospheric pressure plasma was used for pre-treatment of clay coated paper before silicone coating as well as for post-treatment to prepare the release liner with low adhesion. Volume dielectric barrier discharge (DBD), often referred to as “industrial corona”, in roll-to-roll configuration was used for plasma treatment of clay coated paper. The aim was to evaluate the effect of plasma on adhesive properties of silicone layer on paper. Processes of plasma pre- and post-treatment were done in ambient air. The plasma exposure time varied from 0.25 sec up to 5 sec. The input power has been set to the values corresponding to the power density of 2.5 W/cm2. Plasma pre-treated paper was sprayed with silicone oil (0.25 - 0.5 ml/A4 size) using spray gun with subsequent plasma post-treatment. Surface of silicone coated paper was analyzed by water contact angle measurement after coating and 1 and 3 months later. The possible changes in morphology were characterized by scanning electron microscopy, chemical composition by X-ray photoelectron spectroscopy and the adhesion by measuring tape peeling force. The silicone coated paper was characterized by increase of hydrophobicity and decrease of release factor with significant impact of plasma post-treatment.
Progressive electrochemical technologies such as dye-sensitized solar cell, electroanalysis focused or water treatment involve the use of high quality Boron Doped Diamond for highly effective and long service life time electrodes. Enlargement of the electrode specific surface area is of particular interest for these applications. We recently reported simple multilayer process of PECVD diamond coating on a polymer-SiO2 nanofibers mix as promising method to produce stable porous diamond electrodes.
In this work, we report on the optimization of the electrospun SiO2 nanofibres/polymer mix and boron doped diamond coating to address imperfect diamond coverage of the fibers and low electrical conductivity. We studied in particular the effect of the various photoresist mix preparation steps, the implementation of metallic fibers and the diamond deposition conditions on the structural, electrical and electrochemical properties of the porous diamond electrodes. Boron doped diamond (BDD) porous layers have been deposited using a conventional microwave plasma enhanced chemical vapor deposition system. Porous layers have been deposited on various substrates Si, metal (Ti), glass or can be made free standing. The layers were characterized by Raman spectroscopy, Scanning electron microscopy, Van der Pauw method and cyclic voltammetry. Finally, the fabrication method has been implemented on microwave plasma enhanced linear antenna chemical vapor deposition system allowing fabrication of large area (6 inches and higher) porous doped diamond electrodes.
The financial support from the following sources is gratefully acknowledged: Academy of Sciences of the Czech Republic, Czech Science Foundation (GACR) Grant ID: GACR 13-31783S, J. E. Purkyne fellowship awarded to V. Mortet by Academy of Sciences of the Czech Republic and SEM work was supported in part by the MEYS CR FUNBIO CZ.2.16/3.1.00/21568 (SEM purchase), LO1409 and LM2015088 projects (SEM maintenance).
This artice is focused on testing and monitoring of chemical resistance and Subsequent influence on the properties of thin layers based on the methyl silicone resin containing nanoparticles of ZrO2 and SiO2.
Tha aim of this study was the testing of hydrofobity and tribological properties after the chemicals affecting.
For testing were used two emulsion which were designed to protect the metal surfaces. Those two emulsions were applied on to the surfaces of samples made of austhenitic steel and thus prepared samples were immersed to the solutions of NaOH (pH 13) and HCl (2,5). In both cases was the testing time set in the range of 0-360 hours. After the each Expiration of the set time was on each sample tested the hydrofobity and tribological properties with Subsequent comparison of every measured values.
Ultrasonic sprayed Cu2ZnSnS4 (CZTS) were successfully deposited on microscopic glass substrates from an aqueous solution of CuCl2 2H2O, ZnCl2, SnCl2 and thiourea. The deposited films at substrate temperature of 310 °C were heat treated up to 550 °C under N2 gas flows with sulfurization process (under sulfur vapor flow ). The effect of annealing time from 30 to 90 min on optical, structural and morphological properties was investigated using a combination of Raman spectroscopy, scanning electronic microscopy and Ultraviolet visible near infrared absorbance spectroscopy. Raman studies confirm the formation of Kesterite type CZTS with CuS as a secondary component. All the deposited films show an optical absorption coefficient higher than 104 cm-1 and an optical band gap between 1.55 and 1.58 eV. By increasing sintering duration, the optical band gap was slightly influenced while the grain size increased strongly up to 2 µm.
Non-thermal atmospheric pressure plasma jets represent a simple technology for the modification of material nanostructure and surface chemistry. They can be applied to polymers aiming at improved adhesion of further coatings or adhesives, to synthetic polymer textiles for improved wettability and biocompatibility or to clean or activate water. We have investigated three types of atmospheric plasma jets - one industrial device based on gliding arc discharge working in air at 50 Hz and two RF generated plasma jets with argon as working medium. Their gas-phase chemistry was studied by optical emission spectroscopy and plasma-surface interaction was assessed by analysis of modified polypropylene. Besides, we also implement a gas flow model of the industrial device and investigate ozone concentration via the Schönbein method.
The low-temperature atmospheric plasma generated in pure hydrogen by diffuse coplanar surface barrier discharge was used for plasma surface etching of various polymers. Flexible polymer foils were plasma-modified in roll-to-roll configuration. Various polymers, such as polypropylene (PP), polyethylene terephthalate (PET), and polymethylmethacrylate (PMMA) foils were exhibited to the hydrogen plasma etching. Scanning electron microscopy was used to determine the change in the thickness of the samples from the measurement of cross-section images of polymer foils. As shown, the etching rate of tested samples was of the order of ~ 10 - 100 nm/min. Therefore, the presented method is most suitable for precise etching of nanostructures and thin polymeric layers from the top of various substrates. Finally, one particular example of hydrogen-plasma etching at atmospheric pressure is presented. A thin surface polymer (PMMA-based) layer was removed from the upper part of polymer - metallic mesh flexible foil which can be used as a substrate e.g. in photovoltaic applications. Very short exposition times (~ 1s) are enough for etching of thin nano layers of PMMA with a thickness of the order of ~ 10 - 100 nm. Moreover, a selectivity of reduction hydrogen plasma is discussed in the paper.
In this work, we present preparation and photocatalytic activity of highly photoactive zinc oxide nanoparticles deposited on graphene-like carbon nitride (g-C3N4). Prepared material exhibits more than two times larger specific surface area than pure g-C3N4. Material was prepared by sonication of vigorously stirred aqueous solution of zinc acetate and g-C3N4. The supplied energy was high enough to intercalate layered structure of g-C3N4 with zinc acetate. Prepared dispersion was turned into powder material by vacuum freeze drying technique. This technique preserves most of particles specific surface area by conserving chaotic arrangement of given particles in water solution. Prepared powder was further calcinated at 500 °C for one hour. g-C3N4 was exfoliated during calcination and zinc oxide nanoparticles were formed also within remaining layers of g-C3N4. The material was subjected to test of photocatalytic degradation of Rhodamine B at the wavelength of 416 nm. Prepared ZnO/g-C3N4 nanocomposite showed higher photocatalytic activity than standard TiO2 (Degussa, P25).
Features of propane conversion in the presence of (Sm, Eu, Gd) vanadite and (Sm, Eu, Gd) vanadate, both produced via solid-phase synthesis, are studied. It is shown that (Sm, Eu, Gd)VO3 catalyzes mainly the propane cracking process to form methane and ethylene, while (Sm, Eu, Gd)VO4 equally accelerates both cracking and the dehydrogenation of propane. Based on the results from catalytic experiments, energies of activation are calculated for the thermal cracking of propane (124 kJ/mol) and the conversion of propane in the presence of (Sm, Eu, Gd)VO3 and (Sm, Eu, Gd)VO4 occurs at lower activation energies.
In our investigations we prepared two different kinds of oxide coatings aiming for highly active photocatalytic properties and moreover deposition conditions, which could make them useful potentially also for temperature sensitive substrate materials. The first ones are titanium oxide thin films created by PECVD under atmospheric pressure conditions using plasma jet technology in combination with a specially designed precursor aerosol injection system. Experiments were done mainly on glass and silicon wafers for the coating experiments and investigations of the morphology (SEM), layer thickness (profilometry), photocatalytic (decomposition of stearic acid after irradiation) and optical properties (ellipsometry, UV/Vis spectroscopy). The results show the possibility to obtain photocatalytic layers in the range of commercially available products even without an additional substrate heating during the plasma deposition or a thermal post treatment. However, thermal post annealing at 450 °C can further improve this photocatalytic effect.
Secondly, zinc oxide coatings were created by sol-gel technique via dip-coating in combination with a thermal treatment of around 100 °C for 24 h, whereby for both layer types the film thickness was in a range of 50-100 nm. The sol formulations are based on zinc acetate and the solution was catalyzed in an alkaline pH-range. Also these layers show photocatalytic properties already in its as-deposited state, which can be further enhanced either at higher temperatures (450 °C), or preferably by flash lamp annealing (one pulse, millisecond duration). Furthermore, these zinc oxide coatings showed strong antimicrobial properties (towards bacteria and fungi) in first experiments.
The ortho–para conversion plays a very important role in the storage of condensed hydrogen. The spontaneous conversation of o–H2 to p–H2 is slow at low temperature and a nonequilibrium mixture can exist. The energy released on converting normal hydrogen to liquid para–hydrogen is sufficient to vaporize 64% of the original liquid. Therefore the catalysts have been developed that rapidly convert o–H2 to p–H2, thereby facilitating the storage of liquid hydrogen.
Gold nanoparticles, unlike the bulk metal, are able to catalyze many reactions. It was shown that the smaller the particle size, the higher the specific catalytic activity. As the particle size increases the catalytic activity considerably decreases. For reactions involving molecular hydrogen, this size dependence of the catalytic activity is attributed to the structural state of the particle surface.
We set ourselves the task to perform a systematic study of the ortho–para conversion of protium catalyzed by γ-Al2O3-supported gold nanoparticles of various sizes at a temperature of 77 K. Our results unambiguously indicate that nanoparticles, as opposed to the bulk metal, shown a high catalytic activity. It is exhibited that all Au/γ-Al2O3 catalysts with nanoparticles of 4.6-40.1 nm sizes show high catalytic activity in ortho-para conversion reaction. The calculated specific catalytic activity Ksp of ortho–para hydrogen conversion were (3.9±1.2)×1014 mol/cm2∙s for all of the catalysts tested. The conversion of o-protium to p-protium catalyzed by gold nanoparticles does not depend on the nanoparticle size. ACKNOWLEDGEMENTS: The work was funded by RFBR according to the research project № 15-03-02068-a.
Titanium catalysts are important materials for many types of oxidation reactions. Conventionally prepared microporous titanosilicate, namely TS-1, is well-known catalyst used in oxidation reaction with hydrogen peroxide. Since the size restriction of pores in microporous catalysts limits their wide application, large effort has been invested in order to prepare new types of catalysts with expanded surface area and pore size. Such new type of catalyst, mesoporous TS-1, was compared with conventional microporous TS-1 in our study.
Besides the typical reactions, e.g. epoxidations, oxidation of sulfides represents another important branch of application. This type of reaction leads to the preparation of organic sulfoxides and sulfones, which are important chemical intermediates and building blocks of pharmaceutical and agrochemical compounds. Our study is focused on the testing of both types of catalysts, i.e., microporous TS-1 and mesoporous TS-1, in the oxidation of methyl(phenyl)sulfide with 30 % hydrogen peroxide, and the influence of the structure in conversions of reagents and the selectivity to products was described. The samples were studied using BET analysis and X-ray powder diffraction analysis. The morphology of the samples was observed by atomic force microscopy.
Cotton wool was used as a biotemplate for the synthesis of nanostructured ZnO with enhanced visible light photocatalytic activity. Zn(II+) complexes were introduced into the structure of cotton fibers via evaporation of ammonia solution containing dissolved ZnO powder. Thermal decomposition of Zn(II+) impregnated biotemplate at 500 °C, 600 °C and 700 °C provides yellowish ZnO fine powder which retains the morphology of cotton wool fibers. The photocatalytic activities of both starting and biotemplated ZnO powders were evaluated from the time dependency of degradation of Methyl Violet 2B under the UV (λ~ 365 nm) and visible light (λ~ 400 nm and λ~ 425 nm) irradiation. Measurements were carried out online in UV-Vis spectrometer using a homemade cuvette holder housing equipped with an LED diode. The degradation rate constant for biotemplated ZnO under visible light irradiation was 8 times higher than that of the starting ZnO. The significantly enhanced photocatalytic activity of biotemplated ZnO under visible light irradiation can be attributed to the intimate contact of the ZnO crystalline phase with residual carbonaceous species.
Perovskite-type compounds are an important class of materials and there are extensively studied in high-temperature catalytic processes. Dry (carbon dioxide) reforming of methane (DRM) to synthesis gas is one of the most important reactions using such materials as catalysts. In this study, perovskite-type complex oxides GdBO3 (B = Fe, Mn, Co) applied as catalysts for syngas production via dry reforming of methane. These samples were obtained by ceramic technology and were investigated by means of X-ray diffraction, scanning electron microscopy, Mossbauer microscopy, and X-ray photoelectron spectroscopy. Catalytic activities were evaluated at atmospheric pressure in the temperature raised from 773 to 1223 K under continuous flow of reactant gases with a CH4:CO2 = 1:1 ratio. The test samples catalytic activity depends on the oxygen stoichiometry in the complex oxide. Thus, the presence of oxygen vacancies in the perovskite containing cobalt cation in the B-site of the perovskite structure proved to be favorable for DRM. It was on this sample that conversions of CH4 and CO2 were the maximum values of 99 and 97% at 1223 K, respectively, while syngas was obtained with H2/CO molar ratio close to unity. Besides, GdCoO3 showed the high stability in the DRM process: the catalytic performances retained more than 110 h time. The presence of oxygen vacancies is probably due to the crystallographic radius size of the cation introduced into the B-site of the complex oxide. Therefore, the catalytic activities of the investigated samples increased in the order: GdMnO3 < GdFeO3 < GdCoO3.
Zinc oxide (ZnO) nanoparticles are commonly prepared by mixing aqueous solution of zinc salt (acetate, chloride, nitrate, etc.) with sodium hydroxide in a certain ratio. This study is focused on preparation of ZnO nanoparticles by heat-induced decomposition of sodium zinc carbonate (Na2Zn3(CO3)4∙3H2O) clusters synthesized in the first step of this preparation process from zinc chloride and sodium carbonate in water suspension of kaolin. Kaolin KKAF, clay rich in phyllosilicate kaolinite, was used as a microsized (size fraction < 40 µm was used) substrate on which the sodium zinc carbonate clusters were formed. In the second step of the preparation process, such obtained material was thermally treated at 100 – 600 °C in order to obtain ultrafine ZnO nanoparticles anchored to the kaolin. X-ray diffraction analysis revealed that highly crystalline nanoparticles are obtained at a temperature above 400 °C. According to X-ray fluorescence spectroscopy, resulting nanocomposites contain ~ 40 wt.% of ZnO. Morphology of the nanocomposites was observed using transmission electron microscopy and ultrafine ZnO nanoparticles evenly distributed on the kaolinite surface were observed. Preferred growth of ZnO nanoparticles on different kaolinite surfaces was investigated using molecular simulations. All nanocomposites (and pristine ZnO nanoparticles prepared similarly as control samples) were characterized also by UV-VIS diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. Photocatalytic activity (tested by discoloration of Acid Orange 7 aqueous solution) of the nanocomposites was found higher than of pristine ZnO nanoparticles which together with high stability (according to leaching tests) is a good prerequisite for the use of samples in various green applications.
Nitrous oxide is compound damaging the stratospheric ozone layer and contributing to the greenhouse effect. One of the promising methods of photocatalytic decomposition of N2O is semiconductor photocatalysts efficient under UV or visible light irradiation. At present time, most research focuses on photocatalysts containing metallic compounds, such as metal oxides, metal sulfides, etc. A new type of non-metallic polymeric semiconductor material is graphitized carbon nitride (g-C3N4) having high thermal and chemical stability, but also interesting electronic and optical properties. The easy agglomeration and weak adsorption ability of pristine g-C3N4 limit its practical applications. These problems could be solved by phyllosilicate - montmorillonite (MMT) as a suitable photocatalyst carrier.
The aim of the present work was the preparation of photoactive composites of g-C3N4/MMT type. In this work, g-C3N4/ MMT photocatalysts were prepared by thermal polycondensation of the mechanical mixture of melamine and MMT at different temperatures (450°C, 550°C, 600°C, 620°C, 650°C, and 700°C). Using wide range of analytical methods (X-ray diffraction, infrared spectroscopy, diffuse reflectance spectroscopy, and photoluminescence) a significant differences in crystalline structure, morphology, and optical properties between the prepared composites were found. Furthermore, composites prepared at 550-650 °C were tested for the photocatalytic decomposition of N2O. The photocatalytic experiments showed that the activity of all the samples synthesized at 550-650°C was very similar. However, the best photocatalytic activity was exhibited by the sample prepared at 650°C. After 16 h, the total conversion of N2O reached ~ 58 %.
ACKNOWLEDGEMENTS: This work was supported by the Czech Science Foundation (project no. 16-10527S).
Conductometric chemical sensors based on metal oxides semiconductors are highly interesting for researchers due to their simple preparation and operation, low costs of fabrication, large number of potential detections and applications and possibility for miniaturization. Current researches aim to improve their sensitivity, selectivity, stability and speed (i.e. response and recovery rates). Since the interaction between gas molecules and active oxide takes place at its surface, one way to to enhance the effects of surface phenomena would be to increase the surface to volume ratio. This ratio is high for metal oxide nanowires. If they are monocristalline with well defined crystal orientation, the reactions will be controlled and the stability will increase.
The present work investigates SnO2 nanowires synthetized by vapour-liquid-solid (VLS) technique) on alumina substrate using different metal nanoparticles as catalyst for the growth.
We present here the comparative results of the Transmission Electron Microscopy (TEM) investigation of SnO2 nanowires grown from Au and Sn catalysts. Various modes and techniques [High Resolution (Scanning) TEM (HR(S)STEM), Selected Area Electron Diffraction (SAED), Energy Dispersive X-Ray Spectroscopy (EDX)] were used to analyze the morphology, the crystalline structure and the chemical composition of the samples.
This work is the result of an international collaboration in the frame of the CERIC-ERIC consortium.
The laboratory experiment in flow arrangement is designed for the purpose of the detailed study of synergic effect of iron particles support by electric current. This test enables to observe the processes close to the electrodes and its surroundings. The experimental arrangement and its boundary conditions was designed for possible simulation of real processes which going on the sites.
The submitted paper presents the methodology of laboratory tests and selected results under its use. The aim of presented laboratory tests was the detailed defining of physical-chemical properties and electric conditions which can improve the efficiency of chlorinated hydrocarbons (CHCs) reduction process by zero-valent iron nanoparticles (nZVI). Besides the procedure which enables to describe the system behaviour by known water composition (geochemical model) and which can be used for control of the support system by electric current is presented.
The contribution deals with the study of Li behavior in Ni-Li-Ni thin film systems (a part of research on lithium ion battery – LIBs).
The Ni-Li-Ni systems were prepared on Si substrates by Ar+ ion sputtering of Ni and Li. The Li distributions was analyzed by Neutron Depth Profiling (NDP), Ni-Li-Ni compositions by Rutherford Back Scattering (RBS), surface morphology by Atomic Force Microscopy (AFM).
Li as a reactive element requires a thin covering to be protected against atmospheric oxidation. To avoid oxidation of Li, a relatively thick Ni film (ca > 100 nm) should be deposited on the film. For thinner films, oxidation occurs and causes an extensive transition in morphology of Ni - it is due to a Li2O phase with greater spatial demands than as-deposited Li. NDP and AFM showed that for Ni < 100 nm, Li2O penetrates to the surface – in the Ni films ripples and cracks are formed and Li2O is exposed. For thicker Ni coverings, Li remains confined and oxidation does not occur.
The possible oxidation and interdiffusion of Li in Ni-Li-Ni with thick Ni coverings were inspected after annealing at 200 °C. Both NDP and AFM showed a prospective slight change: the Li distributions became broader and the surface morphology of Ni smoother.
The study showed that for very thin LIBs, the Li ions need to be protected against oxidation. In case of Ni (NiO), which is seen as a novel construction material of LIBs, the thickness of Ni should be > 100 nm.
Based on the fast growth of the device performance, there has been an increasing demand for handling the issue of thermal management in electronic equipments. Therefore, it is of great significance to improve the thermal conductivity of thermoplastics, which are commonly used in electronic components. However, the difficulty of graphene dispersion and strong interfacial phonon scattering restrict the heat dissipation performance of graphene/thermoplastic composites, especially in the case of polypropylene (PP) or polyethylene (PE). Here, we propose a single-step and versatile approach to fabricate graphene/ thermoplastic composites with a remarkable thermal conductivity enhancement. The composites were prepared by coating graphene on polymer powder first, followed by hot pressing. As a result, an interconnected graphene framework can be developed in the thermoplastic matrix, leading to significant heat transfer enhancement of the composites. At a 10 wt% graphene content, the thermal conductivity reaches 1.84, 1.53, 1.43, and 1.47 W m1 K1 for PE, PP, PVA (poly(vinyl alcohol)), and PVDF (poly(vinylidene fluoride)) composites, respectively. Our finding provides a path to develop a variety of highly thermally conductive thermoplastic composites for use in heat dissipation and other thermal applications.
Generating power by harvesting energy from the ambient environment and biomechanical movements is a concept attracting huge interest. Using the piezoelectricity of ferroelectrics is the most efficient way to harvest electrical energy from mechanical movements. Among perovskites with ferroelectric properties, barium titanate (BaTiO3) and its analogous compounds present the most promising characteristics. In this study, barium titanate (BaTiO3) and barium calcium titanate (Ba1-xCaxTiO3) were synthesized by a two stage solid state reaction. The morphology of the perovskite particles was investigated by Scanning Electron Microscopy (SEM), their elemental distribution was determined by Energy-Dispersive X-ray spectroscopy (EDS) and their crystalline structure was determined by powder X-ray diffraction (XRD). Above a certain content (x) in the structure Ba1-xCaxTiO3 the morphology is drastically influenced and also some changes in the thickness, roughness of the perovskite plate-like shaped particles can be observed. The tetragonality of the perovskites Ba1-xCaxTiO3 varies with respect to the molar ratio Ba:Ca.
ACKNOWLEDGEMENTS: “This work was supported by a grant of the Romanian National Authority for Scientific Research and Innovation, CCCDI-UEFISCDI, project number 49/2016 within PNCDI III - M-ERA NET Program”.
The paper deals with the influence of micro and nanoparticles of dust from the production of glass pans as an addition to geosilicates for the properties of these materials. The basic material were geosilicates based on inorganic bicomponent aluminosilicate binders activated by alkaline activator. For the maturation of geosilicates was chosen a shortened technology using increased temperatures. On the material samles were studied mechanical and thermal properties, especially flexural strength, compressive strength, and changes in structure and properties at increasing temperatures,
ZnTa2O6 and ZnV2O6 nanomaterials were obtained by hydrothermal and co-precipitation synthesis methods. Optical measurements (UV-VIS) were realized for ZnTa2O6 and ZnV2O6 nanomaterials. Using the drop casting method sandwich structures of ZnTa2O6 and ZnV2O6 nanomaterials were deposited on steel electrodes. The morphological characteristics for the obtained layers were investigated before the electrochemical measurements by scanning electron microscopy and optical microscopy. Corrosion tests in NaCl 0.1M solution were performed for the deposited layers on steel electrodes and the tests revealed that the best results were obtained for the sandwich structures using hydrothermally obtained ZnTa2O6 as first layer and ZnTa2O6 obtained by the co-precipitation method as the second layer, i.e. 88.29% inhibition efficiency.
The Ni, Au and Pt nanoparticles were prepared using (Ni(acac)2, HAuCl4 or H2PtCl6) precursors respectively. The precursor was dissolved in oleylamine and injected into preheated mixture of oleylamine and octadecene. The reaction mixture was cooled down to room temperature after time needed for nucleation and growth of nanoparticles. The nanoparticles were separated and purified. The metallic nanoparticles was stabilized in hexane and characterized. The alternative synthesis was reduction using NaBH4 in polar solvent. The precursors of gold or platinum were dissolved in water. The phase transferring agent was used for transfer of side products to organic solvent under intensive stirring. Organic phase was removed and NaBH4 was added. This mixture was stirring again to reduce PtVI into Pt0 or AuIV into Au0. Nanoparticles synthetized via both methods were characterized by Dynamic Light Scattering (DLS), transmission electron microscopy (TEM) in order to determinate average size, size distribution, stability and shape of nanoparticles. Obtained results were discussed from the point of view of the size and stability.
Hydrothermally obtained Mg3Ta208 pseudo-binary nanomaterial from MgO and Ta205 (3:1) precursors was deposited using the pulsed laser deposition (PLD) technique on carbon steel discs. The PLD main processes parameters, i.e the pulse energy and the deposition time were varied in order to determine the combination that ensures the best corrosion inhibition. Morphological investigations were carried out (scanning electron microscopy and atomic force microscopy). The anticorrosive properties of the deposited layers were studied in 0.3M NaCI electrolyte solution. The best anticorrosive protection was observed in the case of the deposited layers on carbon steel disc using the lower energy, i.e. 10mJ for a deposition time of 60s, i.e. 61.94 % inhibition efficiency.
This paper presents some results of the study regarding the corrosion inhibition properties evaluated in HCl environment of drop casting deposited layers on steel, using ZnV2O6 oxide (obtained by hydrothermal and co-precipitation methods) and two Zn–metalloporphyrins, namely: Zn–5-pyridyl-10,15,20-tris(3,4-dimethoxyphenyl)-porphyrin (ZnPyDiMeOPP) and Zn-5(3OH-phenyl)-10,15, 20-tris-(3,4-dimethoxyphenyl)-porphyrin (Zn3OHtris34DiMeOPP).
The open circuit potential measurement and potentyodinamic polarization electrochemical technique with Tafel representation were used to investigate the corrosion protection of mixed sandwich deposited layers.
The performed tests revealed that the best corrosion resistance was obtained in the case of the steel coated with hydrothermally obtained ZnV2O6 oxide as first layer and Zn–5-pyridyl-10,15,20-tris(3,4-dimethoxyphenyl)-porphyrin (ZnPyDiMeOPP) as the second layer, i. e. 70.58 % inhibition efficiency.
ACKNOWLEDGEMENTS: The authors kindly acknowledge the support from UEFISCDI, project PN III No. 107 PED / 03.01.2017 - CorOxiPor: Nanostructured anticorrosive hybrid materials based on pseudo-binary oxides and Zn-metalloporphyrins.
Intensive research in the field of nanotechnology especially development in nanoparticles synthesis and characterization brings new possibilities to combine nanoparticles with traditional materials and enhance material properties in this way. For the preparation of so-called nanocomposites, where the nanoparticles are dispersed in a polymer matrix to enhance its mechanical, barrier or other properties, layered structures are very suitable. Well known are graphene or clay particles, however other layered structures with remarkable properties do exist.
One example are layered organophosphonates which belong to a large group of hybrid organic-inorganic materials. These benefit from the well-defined structure of their inorganic part and the presence of organic moieties which can be modified to obtain desired properties and enhance compatibility with polymers. This work is focused on layered calcium phenylphosphonate (CaPhP), especially on its synthesis, exfoliation into nanosheets and application as a filler in the nanocomposites.
The synthetized compounds were characterized by scanning electron microscopy, atom force microscopy (AFM) and powder X-ray diffraction. Delaminated nanosheets were obtained from them by mechanical exfoliation in ultrasound or by using shear forces. These delaminated particles were measured with dynamic light scattering and AFM. Compatibility with CHS-epoxy 520 polymer matrix was tested, so quality of the particle dispersion and mechanical properties of the composites were also evaluated. Our results suggest that this type of material is suitable for the preparation of epoxy nanocomposites.
Composite nanofiber materials offer advanced properties and functions applicable in many fields, especially in medicine. Nowadays, these materials are mainly fabricated using the DC electrospinning technology with multi-spinnerets electrodes designed for such purpose. For the novel, highly effective AC electrospinning method, spinnerets distance needs to be increased enormously in order to avoid mutual affecting of virtual collectors created around each of the spinnerets. This fact limits the efficient usage of multi spinnerets types of electrodes for production of composite nanofiber materials using the AC electrospinning technology. Here we show, that two independent polymeric solutions can be effectively supplied to a single unique AC electrode and electrospun in order to fabricate bi-component nanofiber structure. This new electrode was designed using a CAD software with relation to the results of electric field distribution analyzed in the Autodesk Simulation Mechanical. The manufactured electrode was experimentally verified for simultaneous AC electrospinning of PVAC and PVB solutions, both with EtOH solvents. SEM scan of fabricated material proved a bi-component structure of the final product. Our results demonstrate the new, experimentally verified technology for simultaneous electrospinning of two independent polymeric solutions from a single electrode and fabricating of composite nanofiber material of advanced mechanical properties. Based on the kind of polymeric solution spun, this represents new possibilities for various applications, e.g. tissue engineering, filtration and others
Silver nanoparticles (AgNPs) represent a nanomaterial, which application is connected with antimicrobial activity.[1] Due to its size, AgNPs are likely to migrate into environment and therefore its immobilization onto solid substrates is recommended. The immobilized particles should be smaller than approx. 50 nm to ensure the antibacterial effect. The particle surface is supposed to be available for the bacterial interaction. They should be bonded to a solid surface via covalent interaction to prevent NPs released. If all of the above mentioned conditions are fulfilled such composite substrate is well protected against bacterial colonization or biofouling.
Materials and morphologies of the chosen substrates predetermine the functionalization procedure. Three different approaches can be used. Most of the substrates can be functionalized using universal approach to immobilization of AgNPs on solid substrates, where the substrate is modified by a polymer linker and in the second step the particles are generated and immobilized.[2,3] In case when the substrate fabrication can be influenced, it is beneficial to incorporate a polymer linker into the substrate. The particles are then generated/immobilized in a single step. This approach is suitable for membrane filtration materials and some medicinal substrates. The last approach involves first preparation of AgNPs in a form of a powder. These particles can be incorporated into a polymer masterbatch. The particles are then found in the entire volume of the substrate.
ACKNOWLEDGEMENTS: The authors gratefully acknowledge the support by Technology Agency of the Czech Republic, Competence Centers (Project TE01020218) and Competence Centers (Project TE02000006).
REFERENCES: [1] Panacek, Ales; Kolar, Milan; Vecerova, Renata; et al. Biomaterials. 30 (2009) 6333-6340.; [2] Patent CZ303502 (B6) Immobilization method of silver nanoparticles to solid substrates; [3] U.S. Patent No. 9,505,027 B2 "Method Of Immobilization of Silver Nanoparticles On Solid Substrates" from Nat. Phase of PCT/CZ2012/000068.
Nanoscale zero-valent iron (nZVI) materials play a significant role in the field of water treatment technologies. Pyrophoricity, the most significant disadvantage of pristine particles, entails troubles during storage and handling. We present stabilization of 4 samples of nZVI by simple passivation process with ability to control shell thickness from 4 to 10 nm via modification of preparation conditions. We investigate detailed physical-chemical characterization including morphological, structural, and magnetic aspects of core-shell nZVI materials leading to consequently confirmed assumption of ability to control reactivity towards various heavy metals. The reactivity results revealed that not only shell thickness but also its character influence degradation ability of nZVI meaning that cracks and fractures in the thicker shells cause better contact of ZVI with pollutants resulting in faster kinetics and better efficiency. Moreover, the long term stability evaluation confirmed that all materials are stable for at least 1 year from shell and phase composition point of view.
Reactivity and transport properties of metal ions are important both for evaluating and understanding role of humic acids in natural systems and human-driven applications as solving their structural questions. This paper focuses on metal ions diffusion and immobilization in humic hydrogels. Humic acids were purchased from International Humic Substances Society (isolated from different matrices - peat, soil, leonardite, water) and extracted from lignite mined in Czech Republic. Copper(II) ions were chosen as an model example of reactive metal for the diffusion experiments. Previous works showed that transport of metal ions in humic gels were strongly influenced by reactivity of humic acids. Therefore samples isolated from different sources resulted in changes in the content of acidic functional groups and different diffusivity metal ions in prepared hydrogels. The diffusion coefficients of Cu(II) ions, determined in this work, showed the significant dependence on reaction ability of humic hydrogels. Lower amounts of the acidic functional groups caused the increase of the effective diffusion coefficient. In general, diffusion experiments seem to provide valuable method for reactivity mapping studies on humic substances.
Chlorinated ethenes (CEs) are the second most common contaminant worldwide. Remediation procedure combining treatment with nanoscale zerovalent iron (nZVI) and anaerobic microbial degradation supported by electric current belongs to one of the most successful approaches. Here we describe effect of electric current on indigenous microbial degraders of CE in a field study.
Groundwater samples were taken from anode well, four cathode wells and three control wells. Total DNA was isolated by FastDNA Spin Kit for Soil and quantified by Qubit 2.0 fluorometer. Samples were analysed using real-time PCR method. Total bacterial biomass was quantified using 16S rDNA gene. Markers of organohalide respiration included Dehalococcoides sp., Desulfitobacterium spp. and vinyl chloride (VC) reductases vcrA and bvcA. Denitrifying bacteria were tested by nirK marker and sulfate reducing bacteria by apsA2. Representative samples were analysed using NGS method targeted to the V4 region of 16S rDNA gene.
qPCR analysis of the anode well reveal significant decrease in all tested markers connected with an eminent decrease in pH to strongly acidic values. Cathode wells maintained high level of bacterial growth even if there were slight changes in pH. NGS analysis revealed significant changes in bacterial community composition in the anode and cathode wells. In the control wells, a long-term stability in qPCR markers as well as bacterial community composition was observed.
To conclude, electric current caused the decrease in pH in the well with anode leading to decrease in all tested markers. On the other hand, all other wells showed ongoing organohalide respiration important in CEs degradation.
The main goal of this study was to develop and test carriers made of nanofibers to monitor the microbial diversity at a site which is contaminated by BTEX and chlorinated aliphatic hydrocarbons. Nanofibers were chosen due to their very high specific surface area supporting the fixation of microorganisms.
Two different shapes of carriers with three different nanofiber densities (including carrier without nanofibers) were prepared and placed into the contaminated wells. Monitoring lasted for one year with regular monthly sampling. DNA was isolated by FastDNA SPIN Kit for Soil according to manufacturer´s protocol. Qubit 2.0 fluorometer was employed to measure DNA concentration. Extracted DNA was used as a template for real-time PCR amplification. 16S rDNA gene was used as a total bacterial community marker. Specific genes indicating ongoing dehalogenation (Dehalococcoides sp.) and BTEX degradation (catechol 2,3-dioxygenase gene) were also analysed.
Results showed that developed nanofiber carriers are promising tool for long-term monitoring at contaminated sites as providing stable biomass sample and response. Moreover, they are very easy to use and no sample preparation is required prior to analysis. In addition, the long-term stability of nanofiber layer on support thread was confirmed.
An environmental impact of the use of engineered nanoparticles (NPs) is undeniably based on many studies. Considering that NPs eventually end up in wastewater treatment systems, the potential impact of selected NPs as TiO2, SiO2 or ZrO2 on the activated sludge (especially on Microthrix parvicella or Nocardia) was investigated using laboratory-scale batch reactors; short-term (7 days) exposure to 100, 200, 300 mg/L NPs. The change in oxygen uptake rate (through respirometric measurements), the viability of cell (fluorescence microscopy using a live/dead analysis), the morphology of flocks or filaments (based on Gram staining and image analysis) and fluorescence in situ hybridization of the activated sludge compared with the controls were investigated. The shock loads of NPs caused no lethal effects for activated sludge. The presence of NPs in the activated sludge (at a concentration of up to 300 mg/L) paradoxically caused the growth of sludge to be promoted as well as increased sludge activity at the observed time of 7 days for all samples for all monitored parameters. The increase was observed in the range of 0 to 50 %.
Graphitic carbon nitride (g-C3N4) emerges as a frontier of new generation of photocatalysts. It's has photochemical stability, narrow band gap (ca. 2.7 eV) and suitable band energy levels for many reactions including hydrogen evolution, CO2 reduction and photodegradation of organic dyes. Importantly, g-C3N4 can be prepared from low-cost and widely available precursors such as urea, thiourea and melamine. Nonetheless, g-C3N4 also has some intrinsic drawbacks such as low surface area, fast recombination of charge carriers and limited visible light absorption (> 460 nm). A practical approach to resolve some of these issues is to couple g-C3N4 with other materials to create heterojunction photocatalysts. Herein, heterojunction ZnFe2O4/g-C3N4 composite is prepared to improve the photocatalytic activity by suppressing the charge carrier recombination. The magnetic property of ZnFe2O4 allows the separation and collection of the photocatalyst from the reaction mixture for further reuse. The photocatalytic activity of ZnFe2O4/g-C3N4 is demonstrated in photodegradation of organic pollutants using visible light. The reaction kinetics and degradation mechanism are studied in this work. The superior catalytic performance of ZnFe2O4/g-C3N4 photocatalyst exceeds that of pristine g-C3N4 alone. It shows that such composite photocatalyst have potential applications in wastewater treatment.
Recombinant proteins are used throughout biological and biomedical science. High purity of these biomolecules is required especially for in-vivo applications. Affinity chromatography, a specific and effective technique for protein purification, has become increasingly important method in pharmaceutical science, biochemistry or biotechnology. Recombinant proteins are synthesized with appropriate affinity tag which allows their selective purification. For commonly used poly-histidine tag, Immobilized-Metal Affinity Chromatography (IMAC) has been a widely employed purification technique. However, several drawbacks of this method (e. g. utilizing toxic metal ions, insufficient purity of final product etc.) make necessary to develop new materials for an improved isolation of recombinant proteins.
The presented affinity carrier is based on self-organized anodic TiO2 nanotubes decorated homogenously with magnetic Fe3O4 nanoparticles. This material solves the main drawbacks of conventional IMAC materials described above. His-tagged recombinant proteins can be isolated from cell lysates using this new affinity carrier under optimized separation conditions. An increased isolation specificity for His-tagged recombinant proteins was achieved, which results in higher purity of product of interest as compared to a conventional IMAC system (1). Furthermore, its magnetic properties, non-toxicity, recycling ability or easy decontamination are other important benefits which make presented material competitive to well-established materials.
ACKNOWLEDGEMENTS: This work was supported by TACR GAMA TG02010058 with the part 01/021 - TG361021 and by the Ministry of Education, Youth and Sports of the Czech Republic (projects nr. LM2015082 and CZ.02.1.01/0.0/0.0/16_013/0001829).
REFERENCES: [1] Kupcik, R.; Rehulka, P.; Bilkova, Z.; Sopha, H.; Macak, J. M.; ACS Applied Materials & Interfaces 2017, 9(34), 28233–28242.
The recognition of heterocyclic amines and their possible capture from polluted waters by porphyrins represents an ecological challenge. A novel metalloporphyrin bearing a pyridine functional group, Zn (II)-4-pyridyl-tris-(4-phenoxyphenyl) porphyrin (Zn-PyPPP), with high steric hindrance, whose base ligand was synthesized and characterized in our group, was used for a comparative study in order to investigate how the substituent –CH3 group of 1-methyilimidazole would influence the access of the free nitrogen atom to the Zinc atom of the porphyrin, in comparison to pyridine, despite the fact that the whole molecule is smaller than the six-membered cyclic compound. As expected, the performance is lower by using 1-methylimidazole.The formed complexes were also morphologically studied by means of AFM measurements.
Boron doped diamond (BDD) electrodes become attractive sensors in electrochemical detection of a variety of contaminants (e.g. heavy metal traces). BDD electrodes have an extremely high chemical stability, a wide potential window in aqueous media with a low background current, low detection limits for a broad spectrum of analytes (mid to low ppb range) and a stable surface state. Moreover, BDD represents an attractive electrode material for the wastewater cleaning from pollutants (decomposition of organic compounds in reactions with reactive oxygen species or removal of heavy metals by electrowinning).
Here we study electrochemical detection of stand-alone metal ions (Cd2+, Pb2+, Cu2+) and their mixtures using BDD electrodes which are compared with glassy carbon electrodes in sense of reproducibility and sensitivity. It was observed that standard cyclic voltammetry was not sensitive enough to detect 0.1 mM Cd2+ in 0.1 M HCl with carbon based electrodes, however by using differential pulse voltammetry we were able to detect the contaminants even at such low concentrations. We show that for a complex solution consisting of more contaminants (Cd2+, Pb2+ and Cu2+) the BDD electrodes are suitable to recognize each of the contaminants, however their detection limits are influenced by overlapping of their voltammetric peaks or by splitting of the original voltammetric peaks, which is assigned to underpotential deposition of metals on the BDD electrode. Moreover, influence of matrix solution (pure water, spiked tap water, real wastewater sample) to detection limits will be discussed too.
In addition, we demonstrate the applicability of BDD electrodes for the decomposition of methyl orange (as a case study contaminant) with reactive oxygen species. During treatment process the temperature, pH and chemical oxygen demand was monitored and evaluated. The efficiency of decomposition was studied in terms of a BDD film surface morphology (flat/rough surface, patterned surface). The reaction pathway of the electrocatalytic degradation of methyl orange is also discussed. Long-term suitability of diamond electrodes for water purification will be also discussed.
This work is the output of the project cofinanced by European Union „Physics at your service“, number of project: CZ.07.1.02/0.0/0.0/16_023/0000115.
Radioactive waste contains large amount of radionuclides. It is produced by nuclear power generation or other nuclear applications. The radionuclides are unstable nuclides which generate emitting ionizing radiation and they are used in wide spectrum of application. A radioactive isotopes of cesium (Cs-137, half-life time 30 years) and strontium (Sr-90, half-life time 28 years) belong to the main fission products existing in the radioactive wastes produced in nuclear power plant and they are considered to be very dangerous to human health and environment. The safe handling of the radioactive waste is recently one of the main problems. Processes such as ultrafiltration, ion exchange, sorption, evaporation, chemical precipitation are frequently used for the radioactive waste treatment.
In this work, new nanomaterial based on titanium dioxide was investigated as potential inorganic sorbent for the sorption of hazardous radionuclides such as Cs-134, Sr-85 and Eu-152-154. The factors affecting the adsorption of selected radionuclides, such as contact time and pH were evaluated. Furthermore X-ray diffraction (XRD), scanning electron microscopy (SEM) measurements were used in order to assess the physicochemical properties of the prepared nanomaterial.
The results showed that about 92-100% of radionuclides were efficiently adsorbed onto titanium dioxide nanomaterial. Based on the results obtained, it can be concluded that the new nanomaterial is an economic and efficient sorbent for removal of environmental hazardous Cs(I), Sr(II), and Eu(III) radioanuclides from aqueous solutions.
Acknowledgements: This work was partially supported by the Technology Agency of the Czech Republic, project TH02020110.
Nowadays 'green' synthesis of gold nanoparticles (Au NPs), utilizing organic compounds as a reducing and stabilizing agents (e.g. plant extracts, biodegradable polymers), is gaining considerable attention. This approach of nanoparticle synthesis gives the opportunity to avoid often expensive and harmful substances for the environment. In this paper, Au NPs were synthesized, for the first time, by two natural materials - tarragon plant extract and PHB-chitosan polymer conjugate. The analysis of gold nanoparticles was provided by UV–Vis spectroscopy and scanning electron microscopy (SEM). Moreover, the stability of Au NPs was determined by zeta potential analysis whereas their size by differential centrifugal sedimentation (DCS) technique. It was found that the mean size of Au NP's was 7 and 30 nm for the particles reduced with PHB-chitosan polymer conjugate and tarragon plant extract, respectively. Furthermore, the catalytic properties of thus synthesized nanoparticles were compared toward 4-nitrophenol reduction. It was determined that at the optimal conditions the pseudo first-order kinetic rate constant was 0.739 and 0.294 min-1 for the processes involving Au NPs synthesized by PHB-chitosan polymer conjugate and tarragon plant extract, respectively.
Recently, naturally occurring biopolymers have attracted the attention as potential adsorbents for the removal of water contaminants. In this work, we present the development of microcrystalline cellulose (MCC)-based nanogel grafted with acrylamide and acrylic acid in the presence of methylene bisacrylamide and potassium persulphate as a crosslinking agent and initiator, respectively. World-class facilities such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), surface analysis, field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM) and zeta sizer were used to characterize the synthesized MCC based nanogel. The prepared nanogel was applied to remove reactive red 195 (RR195) dye and Cd (II) from aqueous medium at different operational conditions. The adsorption experiments showed that the feed concentration of monomers has a significant effect on the removal of RR195 which peaked (93 % removal) after 10 minutes of contact time at pH 2 and a dose of 1.5 g/L. On contrary, the feed concentration has insignificant effect on the removal of Cd (II) which peaked (97 % removal) after 30 minutes of contact time at pH 6 and a dose of 0.5 g/L. The adsorption equilibrium data of RR195 and Cd (II) was best described by Freundlich and Langmuir, respectively. Conclusively, the prepared MCC based nanogels were proved as promising adsorbents for the removal of organic pollutants as well as heavy metals.
In this work, activated carbon (AC) web was prepared by using waste acrylic fibers followed by physical activation under the layer of charcoal in high temperature furnace. The carbonization of acrylic fibrous waste was performed at different temperatures (800 ◦C, 1000 ◦C and 1200 ◦C) with heating rate of 300 ◦C hr-1and at different holding time. At 1200 ◦C, the heating rate of 300 ◦C hr-1 and no holding time provided better results of surface area as compared to carbonization at 800 ◦C and 1000 ◦C. The activated carbon web AC prepared at 1200 ◦C was used for removal of Acid Red 27 dye from aqueous media by varying different parameters like initial concentration of dye, stirring speed, adsorbent dosage and at and pH. The results were evaluated by using non-linear forms of Langmuir and Freundlich isotherms. The Freundlich isotherm was found to describe the results more effectively because of non-homogenous surface of activated carbon web. Further, the kinetics of adsorption was examined by using linear and non-linear forms of pseudo 1st order and pseudo 2nd order.