Seznam abstraktů 2021: POSTEROVÁ SEKCE B

In this study, a WO3/Cu2O based heterojunction was synthesized via a facile solvothermal method. The as-prepared nanocomposite was characterized by XRD, SEM, and UV-vis spectroscopy. The photocatalytic activity of the as-prepared heterojunction was evaluated by the means of estradiol (E2) and 17α-ethynylestradiol (EE2) hormone degradation under UV LED illumination wavelength at λmax~ 365 nm. The degradation results showed that the prepared photocatalyst was able to achieve considerable photoactivity owing to the intrinsic heterojunction charge transfer mechanism. Photocatalytic degradation rates of 27 and 35 % were achieved for the E2 and EE2 hormones, respectively.

Hydrogenation reactions are one of the main reactions in the chemical industry. Semihydrogenation of carbon-carbon triple bond is a challenge these days. In this work, we have demonstrated a combination of the work of bimetal nanoparticles and plasmonics. Using phenylacetylene as an example, it was shown that plasmon accelerates the hydrogenation process, and a low temperature makes it possible to do this selectively (the C-C triple bond transforms only into the C-C double bond). The catalytic characteristics of Au@Pt nanoparticles in the hemihydrogenation of phenylacetylene can achieve a high conversion of 100% and a high selectivity of 100%.
ACKNOWLEDGEMENTS: This work was supported by the project Internal Grant Agency UCT No A2_FCHT_2021_086

Global warming is becoming the biggest problem nowadays. One of the main factors in its raising is the increase level of CO2 emission and its related high concentration in atmosphere. To reduce the concentration of carbon dioxide, various solutions are proposed, such as biosynthesis of methane, capturing of carbon dioxide in various non-volatile forms and even pumping it into rocks. A more promising way is to develop a closed to zero carbon cycle, in which carbon dioxide will be converted into a convenient fuel such as methanol and re-used in this form. However, converting carbon dioxide to methanol is an energy-intensive process and should be performed with implementation of environmentally friendly approaches, ideally with utilization of renewable (in particular - solar) energy inputs. In this work, we propose a new catalyst based on a composite of porphyrin and metal nanoparticles for the photo-synthesis of methanol from carbon dioxide with utilization of broad-spectrum light source.

In recent years, new iron-nitrogen (Fe-N4) catalysts have become the most promising alternative to rare metals (for example - Pd or Ir), used in fuel cell elements. In this work, we have developed a simple method for the preparation of high-performance electrocatalysts for activation of oxygen reduction hald-reaction (ORR), based on Fe-N4 compounds. The catalytic centres were grafted to reduced graphene oxide (rGO) surface and further coupled photosensibilized by plasmon-active nanostructures. In the first step the graphene oxide was synthesized, and then thermal reduced to rGO. In the next step, the -Ph-SO3H chemical moities were grafted to rGO surface using the diazonium chemistry for further entrapping of Fe complexes. Then the sample was annealed in a nitrogen atmosphere at different temperatures to obtain the optimal distribution of catalytic centres on rGO surface. Successful synthesis was verified using FTIR, XRD, BET and XPS methods. After addition of plasmon-active nanostructures the final hybrid plasmonic structure was tested in model ORR reaction, performed under different conditions. Our study presents a new possibility of the preparation of photo-electrochemical catalysts for ORR activation and creation of Pd or Ir-free duel cell elements.

Plasmons are collective oscillations of the free electrons, excited by external electromagnetic radiation at the metal-dielectric interface. One of main area of plasmon application today is plasmon catalysis of organic reactions, which allows to overcome many of the limitations of conventional catalysts. Commonly plasmon catalysis is performed in traditional organic media, like alcohols or others organic solvent. In these regards it will be especially interesting to combine the plasmon chemistry with alternative trends in organic chemical transformation - utilization of environmental friendly, non-toxic reaction media. Deep Eutectic Solvents (DES) represent new alternative media for applications as a “green” reaction medium in organic synthesis. In contrast to traditional organic solvents, DES is biodegradable, non-toxic and non-flammable. In this work, we investigated the combination of plasmon catalysis and DES systems for the first time on the model plasmon-assisted chemical transformation. Gold nanoparticles were prepared on aluminum oxide microparticles surface. DES was prepared from choline chloride and urea, and embedded with the plamon-active nano/micro particles. Created system was characterized using UV-VIS spectroscopy, as well as TEM, HRTEM, EDX and XPS techniques. The reaction mixture was irradiated with wavelength, corresponded to plasmon absorption in DES and reaction proceeding was monitored as a function of illumination regime. The obtained results showed that irradiation of the reaction mixture with plasmon-active nanoparticles leads to improved efficiency of chemical transformation.
ACKNOWLEDGEMENTS: This work was supported by the project Internal Grant Agency A2_FCHT_2021_090

Radiation-induced synthesis is based on the irradiation of aqueous solutions of suitable precursors by the ionizing and non-ionizing radiation. Due to the irradiation, solid phase is formed and subsequently processed to the final product. This method can be used to prepare materials of high chemical and phase purity.
Various types of powder materials can be prepared by this method. Nanoparticles of metals and single or double oxides (i.e. perovskites and garnets) are included. Various nanomaterials prepared, especially nanoscintillators, possess high application potential in the fields of optoelectronics and radiation detection. Nanosorbents with high specific surface area can be also prepared (nanomaterials with high specific surface area and the ability to bond various substances), which could find application in filters for the capture radionuclides or other contaminants. Last but not least, nanopowder oxidic (photo)catalysts or metal nanoparticles can be easily prepared and utilized in many other applications.
Irradiation is performed by two methods, as mentioned above. Non-ionizing radiation if produced by low pressure amalgam lamps. Preparation by this method is more time consuming, however, the device can be operated almost unattended. The linear electron accelerator LINAC-4-1200 is used as a source of ionizing radiation. The preparation of nanoparticles by this way can be reduced to units of hours. The materials currently being prepared include synthetic garnets YAG (Y3Al5O12), GGAG (Gd3(Ga, Al)5O12), doped with Ce for scintillation use and then ZnO doped with Ga. A wide range of materials can be produced and the composition can be situationally changed according to the customer’s needs.

Nanostructured ZnS-based materials (nano-ZnS) have aroused considerable interest as technologically important material due to its wide band gap. Higher surface-to-volume ratio and improved photocatalytic properties are associated with particle size reduction and predestine the nano-ZnS to applications for wastewater treatment, solar cells, lithium-ion batteries, optical sensors, etc. This study aims on a comparison of hydrothermal and microwave-assisted co-precipitation syntheses of nano-ZnS and to determine the effect of reaction conditions on nano-ZnS properties. Optimization of the synthesis process was performed in order to achieve the highest photocatalytic activity and the highest yield with a short reaction time. Samples were prepared by mixing ZnCl2 and Na2S solutions with different nZn/nS ratios (1:1, 1.5:1, 2:1) and six different reactions times were tested. Morphology of samples have been investigated using scanning electron microscopy, and to identify the structure and crystalline phase, X-ray powder diffraction analysis was carried out. Samples were also characterized using Fourier-transform infrared spectroscopy and Raman microspectroscopy to confirm the ZnS presence. Photocatalytic activity of the prepared nano-ZnS was investigated by photodegradation of organic azo dye Acid Orange 7. ACKNOWLEDGEMENTS: This work was supported by The Ministry of Education, Youth and Sports of the Czech Republic (project SP2021/106) and has been elaborated in the framework of the grant programme „Support for Science and Research in the Moravia-Silesia Region 2020" (RRC/02/2020), financed from the budget of the Moravian-Silesian Region.

Surface Plasmon Resonance (SPR) of noble metal nanoparticles have attracted increasing attention in recent years as an alternative method for photocatalytic activity increasing, with utilization of visible light spectrum. Optical excitations of the SPR on metallic nanoparticles lead to a several photochemical and photophysical effects, such as enhanced light scattering or absorption, localized photothermal heat generation, and creation of energetic hot electrons and holes that are far from the thermal equilibrium.
SPR-supported metal nanostructures are recently proposed as catalysts for a range of relevant chemical transformations, such as C-C couplings, oxidation-reduction reactions etc. Latest research also shown, that SPR is effective for initiation of azide-alkyne cycloaddition (AAC).
In this study, we investigated the ability to perform the AAC reaction under simultaneous plasmon triggering and external electric field application. The main assumption is based on EF induced splitting of molecular orbitals, with corresponded increase of the probability of plasmon induced hot electron or excited state injection in initial reagents and more effective chemical transformation activation. The kinetic and rate of plasmon-assisted AAC reaction was studied as a function of time and EF intensity. Further evaluation of reaction kinetics demonstrates that the AAC reaction rate can be significantly enhanced in the presence of the electric field.

In the last decade, a plasmon-assistance in chemical transformation triggering was considered as an effective way for simplification of reaction conditions. However, the mechanism of plasmon assistance is still under debate, and several different reaction pathways and reagents activation events are commonly considered. In this work, we propose and alternative system for investigation of plasmon-assistance in organic chemical transformation. We used the plasmon active optical fibers, with the aim to subdivide the impact of plasmon, photon and thermal treatment. As a model compounds, involved in chemical transformation the symmetric and asymmetric iodonium salts were used, able to undergo the homolysis of C - I bonds with formation or reactive radicals’ species, which were immediately grafted to closed noble metal surface. Presence of grafted moieties allows to estimate the efficiency of plasmon catalysis. Obtained results were compared with the results of quantum mechanics calculation performed in TURBOMOL software. The obtained experimental and theoretical data prove that the plasmon is capable of breaking C - I bonds in iodonium salts even through the inner electron(s) excitation.

In recent years, a new and very useful way of introducing external energy into a chemical reaction was proposed, so-called plasmon-assisted catalysis. The high electric field associated with plasmons excitation on metal(s) surface leads to a huge deformation of molecular bonds as well as potential injection of hot electrons into the surrounding dielectric medium, which reduces the reaction activation barriers and simplifies the conditions of chemical transformation. In this work, we present a new method for the controlled plasmon hydrogenation of phenylacetylene to styrene, performed in a microfluidic regime. In particular, we have developed a microfluidic chip filled with plasmon-active particles on the aluminum oxide support, where Al2O3 microparticles act as a carrier onto which Au nanoparticles are grafted using diazonium chemistry. In the next step, a thin Pt layer was deposited on the surface of gold nanoparticles. A phenylacetylene solution and an aqueous NaBH4 solution were fed into the microfluidic chip and illuminated with a wavelength corresponding to the plasmon absorption band. (≈550 nm). In other words, the hydrogenation reaction was performed in a microfluidic regime, under the plasmon assistance. The proposed approach has been shown to hydrogenate phenylacetylene to styrene after several cycles or reaction mixture flowing in the microfluidic chip.

Polymer-electrolyte membrane fuel cells (PEMFCs) belong to promising sources of clean energy in a low-carbon economy. Catalytic Pt-CeOx layers prepared on carbon substrate by magnetron sputtering in an oxygen atmosphere are known for high surface area and well-dispersed catalytically active platinum species. Such catalytic layers exhibit a high level of platinum utilization in hydrogen-powered fuel cells. However, exposure to working conditions of fuel cell causes diffusion of the active metal into the volume, its sintering and agglomeration, thus leading to deactivation of the catalytic layer. Herein we present a study showing structural and chemical changes of Pt-CeOx catalytic layers exposed to simulated fuel cell conditions by transmission electron microscopy (TEM) and near-ambient pressure photoelectron spectroscopy (NAP-XPS). This study clarifies the dynamic character of the prepared catalytic layers in reactive conditions, which is essential for understanding their catalytic activity and durability.

Solid-state batteries (SSBs) are the next step in energy storage technology. SSBs are considered safer and have a large cyclic resource. One of the main problems in developing such batteries is selecting and synthesizing solid-state electrolytes (SSE). In this work, SSE was obtained by the progressive method of atomic layer deposition (ALD), making it possible to make homogeneous coatings with precision control of the thickness. ALD of LixTaOy thin films on silicon and stainless steel substrates using Ta(OEt)5 and LiOtBu was studied. The synthesis temperature was 300 ℃ based on the previous research. Samples were synthesized with different ratios of Li:Ta = 1:2, 1:3, 1:7, and depending on the ratio of metals, the growth rate per supercycle varied from 0.21 to 0.46 nm/supercycle. Determination of thin film thicknesses was carried out using spectral ellipsometry. A scanning electron microscopy was used to determine the conformity and morphology of the coatings. X-ray Photoelectron Spectroscopy was used to determine the elemental composition on the surface and in the volume of SSE. The resulting films are amorphous by X-ray Diffraction. Cyclic voltammetry was used to show no current increase in the cathodic region. The cathodic region cycling at different discharge currents (from 20 to 80 mA) presents a low capacity.

Plasma spraying (PS) is a potentially useful method for depositing the functionally graded electrode materials (anodes, cathodes) for Solid Oxide Fuel Cells (SOFCs). By utilizing deposition from multiphase liquid feedstock’s (suspension, solution, powder, and their combination), new features in electrodes can be implemented that may lead to the improved electrochemical performance of SOFCs at reduced temperature, and also to more efficient process route of the cell components. Herein we report on the preparation and characterization of NiO-YSZ layers for SOFC anode application. As a source of plasma, we utilize a unique hybrid water-argon stabilized plasma torch (WSP-H), which provides an exclusive combination of the plasma properties that primarily allows high coating throughput and also a possibility to control the coating microstructure. We show that the microstructural and chemical characteristics of the anode layers depend on the types of liquid feedstock (ethanol-based and water-based solutions). The ethanol-based feedstock benefits the NiO-YSZ layers by the presence of metallic Ni in its composition, and also by optimal porosity and microstructure, especially when mass ratios of NiO to YSZ are equal in such layers. Apart from potentially sufficient electrochemical performance, such anode layers may also reduce both the manufacturing cost and the initial start-up time of the SOFC system.

During the past few years, perovskite solar cells (PSC) gained enormous attention due to their rapid increase in power conversion efficiency (PCE) above 25 % and low fabrication cost. The perovskite absorber layer along with charge transport layers and their interfaces play a vital role in overall device performance. Currently, SnO2 nanoparticles are considered as an efficient electron transport layer (ETL) owing to stability under ultraviolet (UV) exposure, higher electron mobility than TiO2, and low-temperature annealing preparation. We doped SnO2 nanoparticles with Ti3C2Tx (MXene) nanoflakes to enhance the performance of SnO2 nanoparticle-based ETL. MXenes are two-dimensional (2D) materials that possess metallic conductivity and tunable work function in a wide-range of 1.6-8.0 eV. The 2D Ti3C2Tx (MXene)-doped SnO2 thin films with 22 nm thickness were prepared by spin coating over the indium-doped tin oxide substrate in a doping concentration range of MXene 0-0.2 wt.%. The presence of MXene few-layer nanoflakes was confirmed by scanning electron microscopy. The effect of the MXene doping on the electronic properties was analyzed by the perpendicular conductivity measurements and work function measurements by the Kelvin probe. In addition, the effect of such a MXene-doped SnO2 ETL on the MAPbI3 perovskite growth was analyzed by AFM and XRD. The results demonstrate the positive effect and potential of MXene doping of the SnO2 ETL and thereby on the properties of the PSCs.
ACKNOWLEDGEMENTS: Financial support of the project APVV-19-0465 and VEGA 2/0046/21 is acknowledged.

Supercapacitors have attracted great interest because of their fast, reversible operation and sustainability. However, their energy densities remain below those of batteries. We report reaction of fluorographene with nitrogen source which enables the preparation of a material combining graphene-type sp2 layers with diamond like C-C bonds and nitrogen superdoping (16%). This material with an ultra-high mass density of 2.8 g/cm3, is delivering unprecedented energy densities of 200 Wh/L (at power of 2.6 kW/L) and 143 Wh/L (at power of 52 kW/L). These findings open a route to eco-friendly materials whose properties may enable a transformative improvement in the performance of sustainable supercapacitor components.

Organosilica binders are a promising way to interconnect various nanoparticles in printed coatings for photovoltaic cells and other applications. Post-deposition treatment of printed nanoparticle films with organosilica binders is required to remove the organic moieties and thus achieve the optimal optoelectronic properties of the resulting film. As a result, the polysiloxane binder is converted to almost fully amorphous silica and this process is called mineralization. Atmospheric pressure plasma operating in open air has proven to be the most promising method, as the operating temperature can be kept below 70 °C and the overall treatment time required is in order of minutes. These are significant advantages compared to alternative approaches like thermal sintering, where temperatures required are around 450 °C, or chemical or UV light treatment, where the treatment times extend into the order of hours. To better understand the underlying chemistry in the interaction of the ambient air plasma and the organosilica binder we performed an X-ray photoelectron spectroscopy (XPS) study on the plasma-treated films of silica binder, regularly used with titania nanoparticles. The detailed analysis of core-level spectra of C 1s, O 1s and Si 2p were used to observe the removal of methyl groups from the film and gradual transformation into amorphous silica. The scanning electron microscope revealed significant patterning of the surface by interaction with plasma after exposures longer than 16 seconds.

Concerns surrounding the limited supply of fossil fuels have been the subject of much debate. As of promising solutions, polymers like poly(vinylidene fluoride) (PVDF) have gained attention due to their ability to generate electrical energy from the waste mechanical vibrations. The energy harvesting and vibration sensing potential of PVDF is however limited due to its low content of electroactive β-phase, which has to be increased by indirect post-processing. Recently, a synergistic effect was found in PVDF directly blended with its trifluoroethylene copolymer (PVDF-TrFE) due to strong interfacial polarization. In this study, we aim to further increment the piezoelectric performance of PVDF/PVDF-TrFE blends by incorporating a small amount of BaTiO3 nanocrystals via a facile and scalable processing route. The β-phase content was monitored using FTIR and XRD. Melt rheology experiments showed that co-blending of PVDF-TrFE as well as the addition of BaTiO3 slightly increased melt viscosity and complex modulus. Despite that, rheological data suggested that developed formulations can be processed by conventional techniques intended for a large-scale production. More importantly, PVDF/PVDF-TrFE binary blends supplemented with BaTiO3 are expected to exhibit superior d33 compared to conventional neat blends, which could make them highly promising for modern energy harvesting and sensor-related applications.
ACKNOWLEDGEMENTS: The authors gratefully acknowledge the Czech Science Foundation (grant no. 19-17457S) for the financial support. This work was also supported by the Ministry of Education, Youth and Sports of the Czech Republic - DKRVO (RP/CPS/2020/003) and (RP/CPS/2020/006).

At the present work, MnCo2S4 nanoparticles were successfully synthesised for the first time by rapid and low-cost microwave method and synthesis parameters were optimized in range of 500-1200 Watt microwave power. Microstructure, crystallite, and electrochemical properties of the obtained nanoparticles were characterized by using of x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) measurements. From the 500 to 900 Watt, the grain size of the MnCo2S4 nanoparticles reduced, and crystallite quality improved with increasing the microwave power. After 900 Watt, the grain of the MnCo2S4 nanoparticles to agglomerate and crystallite quality reduced. Therefore, the optimum power of microwave can be selected as 900 Watt. Furthermore, obtained MnCo2S4 nanoparticles obtained under optimum condition were spin-coated on F:SnO glass substrate to investigate its potential as counter electrode (CE) material used in dye-sensitized solar cell (DSSC). Electrochemical analyses suggested that MnCo2S4 possess higher peak current density (Jpc) and lower electron transfer resistance (Rct) than that of platinum (Pt) CE, resulting in higher overall conversion efficiency of a DSSC. Therefore, it can be said that due to low-cost, fast, and environmentally friendliness of microwave method, and excellent electrocatalytic activity of MnCo2S4, the cost/performance of a DSSC can be lowered by employing MnCo2S4 synthesised via microwave method.
ACKNOWLEDGEMENTS: Authors would like to thank the Scientific and Technological Research Council of Turkey (TUBITAK Grant Number 120M101) for the financial support of this research.

Tungsten trioxide (WO3) possesses numerous interesting properties. It has gaso-chromic [1] and electrochromic [2] properties, which can be used in gasochromic and electrochromic windows. It means that it changes the color in presence of gas or elec-tric voltage. It is used as a pigment in ceramics and paints. Tungsten oxide is also very good photocatalyst [3] owing to its low bandgap and photo-electrochemical stability.
Among available nanostructures, WO3 fibers possess a high specific area, well de-fined porosity, numerous active catalytic sites, etc.. Electrospinning has been a clas-sical technique to make fibers, including inorganic ones. However, recently also the centrifugal spinning turned out to be a very viable technique for fiber synthesis, able to produce large amount of fibers in a short time, which has positive cost figure and it is very attractive for industry. Even though the average fiber diameter of centrifu-gal spun fibers is a bit larger than for the electrospun ones.
In this work, we prepared WO3 fibers from solutions of different composition by cen-trifugal spinning technique. The prepared fibers were characterized by scanning electron microscope and XRD. Their specific surface and texture was evaluated by BET analysis. The photocatalytic activities of WO3 fibers was evaluated using photo-catalytic decomposition of methylene blue solution (MB; initial concentration = 1x10-5 M) against reference WO3 nanoparticles and electrospun WO3 nanofibers. The presentation will discuss the recent results on synthesis and photocatalytic applica-tions of centrifugal spun WO3 fibers [4,5].
REFERENCES: [1] Zhang, Y et al. Rev. Sci. Instrum., 2016, 87, 125002.; [2] Adhikari, S. et al., Electrochim. Acta 2014, 138, 115-123.; [3] Tong, H. X. et al., J. Cent. South Univ. 2017, 24, 1275-1280.; [4] Hromadko, L. , et al. , Ceramics International, submitted.; [5] Hromadko , L., et al., Czech patent, nr. 308897.

The aim of this work was to determine the effect of plasma on the substrate and on the nanofibers themselves. The PA6 nanofibrous material and the PP carrier were exposed to the effects of dielectric barrier plasma generated in air at atmospheric pressure. Changes in chemical composition, the effect on adhesions to the support substrate and especially the plasma effect on the filtration efficiency of the nanofiber material were studied.
ACKNOWLEDGEMENTS: This work was supported by project No. E01-14 funded by the ELIIT initiative.

This work deals with the use of nanoparticles of palladium and platinum transition metals in a composite with PU nanofibers prepared by needle electrospinning to form a nanofiber membrane based on polyurethane (PU) for CO2 sorption and composite nanofiber membranes PU / nanoPd and PU / nanoPt for hydrogen capture from pyrolysis gases and its reuse reuse. For this purpose, an extensive optimization of the polyurethane spinning technology of polyurethane was performed in order to obtain the necessary morphology and properties of the polymer membrane, respectively parameters, which were subsequently used to facilitate and streamline the final modification. The modification was performed directly in a spun solution of polyurethane and dimethylformamide, to which a specific percentage of chloride salts of Pd and Pt was added, the subsequent post-process reduction in the form of spun membranes was carried out in a solution of hydrazine and distilled water. The resulting samples were characterized by a variety of methods, such as scanning electron microscopy (SEM) and high-resolution scanning electron microscopy (HRSEM), where both morphology itself and fiber and nanoparticle diameters were assessed; energy dispersive spectroscopy (EDS) and X-ray photon (XPS) spectroscopy, in which the presence of nanoparticles of the aforementioned metals has been demonstrated; X-ray diffraction (XRD) analysis, which compared the crystallinity and phase composition of an unmodified, modified membrane in which the presence of modifying metals was confirmed; Zeta potential analysis (ζ), which was used to compare this important parameter indicating the properties of the membranes again in the unmodified, modified state; Sorption tests of the unmodified PU nanofiber membrane showed a significant sorption capacity of the above-mentioned greenhouse gas. Nanofiber membranes PU / nanoPd and PU / nanoPt were successfully prepared, however, their sorption capabilities proved to be insufficient. A secondary but important result of this work is the preparation of a nanobead PU polymer layer.

Nanofibrous materials are currently in transition between laboratory and industrial scaled production. The main factor that hinders transition speed is relatively low productivity compared to widely used technologies such as melt-blown or force-spinning. One possible solution is to use a different technology than a typical direct current electrospinning (DC). It is possible to electrospin solutions using another type of high voltage source - providing alternating current energy (AC). The potential of AC technology lies in increased productivity of the process and the possibility to electrospin solutions containing a high dose of additives (15-30% wt) such as hydroxyapatite, ceramics, or aluminum. When using AC technology, some problems can arise. The main one is the transition of working solution that spins well in small laboratory DC systems or industrial-scale NanospiderTM machines that is also driven by direct current. It is usually required to modify the solution in some manner that will improve the spinnability of the solution in the AC system. In our case, we experienced the problem in the spinnability of PA 6 when using the so-called “overflow electrode” that enables the spinning of polymer for a longer period of time (multiple hours). The initial solution of PA 6 did not produce a nanofibrous layer, only small flakes that were technologically unprocessable. We show that minor modification of solutions using oxoacids can lead to major improvement of the nanofibrous product. The results are presented in the form of SEM images and histograms showing the change in diameters of nanofibers.

Triboelectric layer is based on PVDF nanofiber fabric made by electro spinning. Used fabric contains pure PVDF and structure is chaotic without definition of fibre direction. Sensing structure is made as planar stack with 6 electrodes. Sensing structure is prestressed inside of laser welded stainless steel casing and does not contain electronic component. This sensor was excited by impulse exciter. Result show promising level of output electric charge around 1200 pC/mm. Sensor is possible to use for simple measurement with high impedance probe itself or it could be used for energy harvesting. Goal of project was sensitive sensor for detection slow small movements and also fast high impacts.

This work deals with the optimization of technological parameters of needle electrospinning (polymer concentration in solution, process parameters and environmental parameters - especially air humidity) on the structure, morphology and properties of polyacrylonitrile (PAN) nanofiber membranes. It also includes a comparison with the morphology of layers prepared by needleless electrospinning and one-step modification of membranes prepared under optimized conditions by selected modifiers for use in CO2 capture from waste gases. Amines and organometallic compounds of the MOF type were used as modifiers. The work also deals with the characterization of prepared nanofibrous materials by analytical techniques - SEM + HRSEM, XRD, Zeta potential measurement and air permeability measurement. The adsorption BET isotherm was used to analyze the sorption capacity of the membrane for CO2 adsorption.

For polymer materials surface treatment, cold atmospheric plasma is widely used. Polypropylene (PP) is a famous type of polyolefin used in a wide variety of applications. Although the biaxially oriented polypropylene (BOPP) films have many advantageous properties, their applications have limitations due to the poor adhesion properties resulting from their non-polar nature and low surface energy. In this comparison study, the thin BOPP film was treated by plasma generated by two different atmospheric-pressure plasma sources with different exposure times in seconds. The first one was represented by the diffuse coplanar surface barrier discharge (DCSBD) generated in ambient air at the power of 400 W, and the second one by the plasma jet using argon as the working gas at power 12 W. The surface wettability of BOPP film treated was investigated by measuring the water contact angle (WCA) immediately after treatment, and after 1 and 3 weeks later to study the possible aging behavior. Furthermore, ATR-FTIR for characterization of the plasma-induced chemical groups changes on the surface, the profilometer/roughness gauge for roughness measurement, and SEM for BOPP film surface morphology investigation were used and the results were compared. The best WCA values immediately after treatment were shown for the treatment by plasma jet with 10 s exposure time. However, the most stable treatment was confirmed for DCSBD plasma treatment with the 5 second exposure time. The results of SEM and roughness measurement of the BOPP film surface after DCSBD and plasma jet treatments were very similar.

Flexible electronics are nowadays manufactured on substrates made particularly of plastics and paper. In demand for better optical and chemical properties, glass is also used in its ultra-thin flexible form (UTFG). Digital ink-jet printing is an attractive method for deposition of conductive precursors on flexible substrates, mainly due to its ability to be incorporated into roll-to-roll systems for massive production. Plasma cleaning and activation is proposed here as a dry, efficient, and controllable method for pre-treatment of glass substrate before deposition of conductive inks. Tested plasma sources were chosen with respect to the specific thermomechanical properties of UTFG and requirements of large area printing on flexible substrates. Both diffuse coplanar surface barrier discharge (DCSBD) and industrial corona achieved a significant wetting improvement of UTFG, which results from modification of properties governed by surface nanolayer. Water contact angle (WCA) measurement and X-ray photoelectron spectroscopy revealed strong activation of UTFG surface due to incorporation of oxygen-based polar groups. The ageing of plasma-treated glass, monitored for one week, showed better stability of the DCSBD plasma-treated UTFG surface. We observed the WCA recovery from 7 % to 38 % in respect to the initial value measured on the untreated UTFG (68°). The impact of plasma on the morphology of the glass surface was analysed using atomic force microscopy.
ACKNOWLEDGEMENTS: This research has been supported by the projects LM2018097 funded by the Ministry of Education, Youth and Sports (CEPLANT centre) and project FV40114 funded by the Ministry of Industry and Trade (program TRIO).

The incorporation of metal oxide particles into polymer matrix in many cases leads to improved characteristics of the material: thermal stability, mechanical strength, light absorbing or antibacterial properties etc.
This study aims to develop polyethylene/hematite composites prepared with hematite (α-Fe2O3) particles of different size. Such types of composites have not been yet thoroughly studied but have a potential to reveal improved properties in comparison to the pure polymer. Polyethylene is a material with a broad field of application, primarily as packaging material for food and other products. Hematite is non-toxic, thermally and chemically stable low-cost metal oxide. There is also a demanding task to prepare composites with non-aggregated hematite particles and their fine dispersion in polyethylene matrix.
In this work two types of hematite with well-defined shape and uniform size were used for preparation of the composites: hematite HC1 with cubic particles of average size of 2 μm and HS2 with spherical particles sized of about 100 nm. The mass fraction of hematite in the composites was 0.25, 0.5 and 1 %. Prepared polyethylene/hematite composites were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and diffuse reflectance UV-Vis-NIR spectroscopy. The mechanical properties were also studied. The results show that such composites have improved properties in comparison to a pure polyethylene, especially the composites with hematite HS2 due to its particles of lower size and large surface. Obtained results reveal that such composites may be a promising material for wide range of applications.
ACKNOWLEDGEMENTS: This research was supported by the Croatian Science Foundation (project number IP-2016-06-8254).

Magnesium and its alloys are a material with increasing application potential in many fields (e.g. automotive and aerospace industries). Magnesium alloys can also be used as a sacrificial anode for the cathodic protection of underground steel structure in soil containing humic acids.
AZ31 alloy was corroded in NaCl solution with and without humic acid under conditions of different pH. Corrosion tests were performed using potentiodynamic polarization. The surface of the corrosion products was analyzed by scanning electron microscope with energy dispersive X-ray spectroscopy
to determine the impact on morphology and chemical composition after corrosion. Attention was also paid to the formation of magnesium hydroxide nanoparticles during the corrosion process.

Two-dimensional (2D) molybdenum disulfide (MoS2) belongs to a class of materials called transition metal dichalcogenides (TMDCs). Due to its large surface area, high biocompatibility, non-zero band-gap, structural versatility and mechanical flexibility, MoS2 can be used for next-generation sensing devices for various analyses. In this work, printable high viscosity inks containing MoS2 in various ratios and ethyl cellulose (EC) as a binder were prepared. The effect of different MoS2 concentrations was investigated by measuring inks rheological properties. Structural and chemical properties of electrodes were studied by optical microscopy, SEM/EDX analysis and Raman spectroscopy. In addition, prepared MoS2/EC inks were screen-printed onto fluorine-doped tin oxide (FTO) coated glass substrates to develop working electrodes for electrochemical sensing applications. Finally, differential pulse voltammetry measurements by applying FTO/MoS2 sensors showed that the limit of detection (LOD) for dopamine was below the micromolar level. This work points to the potential of fast, simple and mass printing production of MoS2 sensors to detect further target analytes.

Environmental problems related to the economy based on fossil fuels are of paramount importance. However, transition to renewable energy sources is restrained by the availability of storage technologies. Electrochemistry is a widely recognized prominent tool to achieve this goal by converting renewable energy into the form of chemical bonds accessible further as fuels, such as hydrogen produced by water splitting. Crucial losses in such process are caused by the high overpotentials. To achieve required efficiency of water splitting appropriate catalysts have to be found with the best combination of activity, stability and cost. Nano-structured, two-dimensional materials (2D) are attractive candidates due possessing many of the desired properties and highly tunable characteristics. Employing light allows additional degree of freedom to boost conventional electrocatalysis, in particular plasmon-mediated electrocatalysis. In this study, we combine Au grating with 2D nanoparticles of titanium diboride (TiB2) to perform plasmon-mediated electrocatalysis. Catalytic activity of the obtained system was explored towards water splitting.

This contribution is focused on superabsorbent materials based on polymerization of partially neutralized acrylic acid. Several types of superabsorbents were prepared. They differed by content of anorganic (NPK fertilizer) and organic (lignohumate) nutrients for their release in soil systems. Superabsorbents were characterized from point of view of their swelling capacity in order to evaluate their ability to control water management soil. Gradual release of incorporated nutrient into water was monitored in time and complemented by measuremets of pH and conductivity. It was found that the nutriets were released from superabsorbents for the duration of several days in the dependence on the ty pe of prepared material. In conclusion, simple pot experiments with corn were realized. It was confirmed, that the application of superabsorbents can improve soil properties, water management, nutrient uptake and growth of plants.

In the recent years, access to the fresh water in the world has decreased dramatically. Water is an essential commodity for humans and animals. Around 1,2 billion people have limited access to drinkable water and millions die every year because of sicknesses caused due to the consumption of impure water or lack of water. In the coming years, this problem will only progress because at alarming rates due to an aggressive growth of population, urbanization and droughts. One of the best solutions for saving water is purification and reusing existing water supplies. It is essential to investigate new approaches for water treatment with low energy costs and economic benefits. Membrane filtration is a relatively new approach and has numerous advantages when to compare to other methods. The biggest problem in membrane filtrations is fouling, which causes membrane pore blockages and create a cake layer on membrane surface. This leads to a reduction of filtration efficiency, decreases permeate flux, shortens membranes lifetime and hinders mass transfer through the membranes. Nanofibers are characterized by high porosity, good selectivity, small pore size, low production costs and high filtration efficiency. Thus, making them a promising material for water purification. Fouling can be caused by microorganisms, organic/inorganic matter. The aim of the project is to obtain nanofibrous membranes, which provide high fouling resistance and antibacterial properties for water purification. Moreover, the hydrophilicity of membranes is improved by chemical treatment to provide better fouling resistance as a result of interactions between the polar groups on the membrane surface and chemical groups in organic matter. Ag, ZnO, TiO2 and CuO nanoparticles, known for their antibacterial properties to increase the antibacterial properties of membranes, are attached and bonded to the structure of the membranes. To obtain nanofibrous membranes, which provide maximum efficiency and productivity of water filtration, various combinations of nanofibers and nanoparticles are tested and compared to each other. As a result of this project, the obtained nanofibrous membranes, can find applications in various life branches like food and pharmaceutical industry, wastewater treatment or small and medium water purification systems.

This study reports on green synthesis of titanium and zinc oxide nanoparticles using lemon juice and peel extract, zinc acetate, ethylene glycol and titanium IV isopropoxide as precursors. The prepared TiO2 and ZnO nanoparticles (NPs) were characterized via X-ray Diffraction analysis, UV-vis spectroscopy, Dynamic light scattering, Scanning electron microscopy and EDAX. The prepared samples, TiO2 and ZnO-NPs were further subjected to photocatalytic degradation of estrogenic hormones (Estrone, Estradiol, Ethinyl estradiol, and Estriol) under UV light irradiation at 365 nm and promising photocatalytic activity has been found. All four hormones were significantly degraded owing to the photocatalytic activity combined with a slight contribution of (4% - 11% ) due to hormonal adsorption onto the surface of the photocatalysts. Overall hormonal degradation in the range of 84-93% and approximately 99% was achieved in 60 minutes under UV light irradation by ZnO and TiO2, respectively.

Understanding and timely assessment of chemical balance in the composition of aquatic ecosystems, namely in ponds and lakes, can prevent heavy economic losses in fish production. The phosphorus concentration plays a key role in the prediction of oxygen concentration in water, which is a crucial parameter for fish surviving in ponds. Rapid detection of changes in the phosphate compounds concentration in water, organic sediments, and pond soil, is therefore very important. In this paper, results of running work on a sensitive and efficient method for phosphorus and organophosphates detection in pond water and sediments are presented. We are developing a testing kit for rapid chemical detection based on surface-enhanced Raman scattering (SERS). Although silver colloids can be generally used for highly sensitive SERS detection, organophosphates interact with noble metal substrates only weakly. However, an alumina nanofilm deposited on the surface of a noble metal can solve this problem as it heavily adsorbs the phosphorus compounds and various organophosphates. Here, we developed a combination of these two materials in the form of a core-shell silver-alumina nanopatterned film. In the first step, the silver layer was prepared by physical vapor deposition on a silicon substrate, followed by thermal annealing to form silver nanodots. Subsequently, alumina film was deposited over the silver nanodots using the atomic layer deposition to form the core-shell silver-alumina nanopatterned surface. We prepared Ag/Al2O3 cells varying in thickness from 4 to 10 nm by changing the deposition parameters. The produced Ag/Al2O3 nanofilms show high SERS activity and significant adsorption of phosphate anions on these nanofilms has been confirmed. Employing our Ag/Al2O3 core-shell nanopatterned film, the SERS detection of organophosphates was performed under 532 nm excitation, showing characteristic phosphate bands in a model solution. The method will be further applied for the quantitative detection of organophosphates in real samples.

Industrial development can cause environmental pollution and health problems due to water contamination by hazardous heavy metals, which can be determined using conventional analytical methods such as ICP-MS [1]. A new alternative are the electrochemical analysis based on screen-printed electrodes (SPEs) [2,3], which can be functionalized by modifying the working electrode (WE) using nanomaterials to obtain an enhanced analytical response [3]. In this work, gold-silver nanoboxes (AuAgNBs) were synthesized and characterized, showing nanoprisms with an average diameter of 44.8 ± 0.3 nm. Screen-printed carbon nanofiber electrodes (SPCNFEs) were modified with AuAgNBs by spin coating technique. The modified electrodes (AuAgNBs-SPCNFE) were characterized by means of scanning electron microscopy (SEM) and cyclic voltammetry (CV). Additionally, the analytical response of these modified electrodes was evaluated towards the simultaneous determination of lead(II) and cadmium(II) in acetic acid/acetate buffer pH 4.5 using differential pulse anodic stripping voltammetry (DPASV). The obtained detections limits were 27 µg L-1, and 48 µg L-1, for Pb(II) and Cd(II) respectively.

Hydrogen is a perspective «green» fuel that produces only water when consumed in a fuel cell. The main method for hydrogen production is electrochemical water splitting. However, water electrolysis is a rather energy-consuming process. The alternative method of the overall water splitting is photolysis under light illumination, but the efficiency of this approach remains actually unsolved problem. Thus, the founding of new, photo-catalytically active materials, able to increase the efficiency of photo-induced water splitting is a hot topic of actual research. In recent years, 2D materials have been considered as very promising materials for water splitting potentially allowing the process tuning up to an application-acceptable level. In this work, a hybrid material consisting of plasmon active structures and 2D WO3-CdS composite is created in introduced in water splitting process. Using the proposed design the overall photo-induced water splitting was demonstrated.