20 (2014) Scientific papers, Series A
Permanentní URI k tomuto záznamuhttps://hdl.handle.net/10195/75412
Procházet
Článekpeer-reviewedpublished Otevřený přístup Characterization of vanadium sites on vanadium-containing mesoporous silica catalysts and their catalytic behaviour in propane ODH(University of Pardubice, 2014) Drenchev, Nikola; Švadlák, Daniel; Setnička, Michal; Čičmanec, Pavel; Bulánek, RomanParameters that affect the catalytic behaviour of vanadium-containing mesoporous silicas in oxidative dehydrogenation reaction of propane are mainly aggregation state of surface VOx species and reducibility of vanadium species. Type and conditions of synthesis have big impact on the nature of vanadium species and, therefore, influence significantly catalytic properties. Two vanadiumcontaining mesoporous silica catalysts were synthesized by different techniques (including direct synthesis from hydrogel containing vanadium precursor and wet impregnation of SBA-15 mesoporous silica by vanadyl acetylacetonate) and their physico-chemical and catalytic properties were studied and compared. Direct synthesis of vanadosilicate led to catalysts with non-uniform mesoporosity, but exhibiting better spreading of vanadium on the surface resulting in species with lower degree of polymerization compared to impregnated catalyst. It is reflected in higher iso-conversional selectivity of directly synthesized catalyst towards propene.Článekpeer-reviewedpublished Otevřený přístup Synthesis and characterization of magnetic nanoparticles Fe3O4@SiO2 decorated with amino groups(University of Pardubice, 2014) Harmand, Lydie; Bhosale, Dattary; Beneš, Ludvík; Palarčík, Jiří; Kalendová, Andréa; Sedlák, MilošThe oxidation of ferrous sulfate in aqueous medium was used to prepare hydrophilic nanoparticles of Fe3O4 with the hydrodynamic size of 114 ± 59 nm. By means of sol-gel method, the nanoparticles were coated with a layer of amorphous SiO2, which provided the Fe3O4@SiO2 nanoparticles with the size of 188 ± 36 nm. The reaction of Fe3O4@SiO2 with 3-aminopropyltriethoxysilane resulted in attaching of amino groups to the surface of the particles. During the reaction lasting 1 hour, the original size of particles (190 ± 40 nm) remained unchanged, and the total nitrogen content was 2.21 %, and the nitrogen content corresponding to reactive amino groups was 1.22 %. A prolongation of the reaction time up to 3 hours resulted in production of aggregates and increase in the total nitrogen content up to 3.75 %. However, the content of reactive nitrogen increased only negligibly (1.30 %). The spherical shape of the Fe3O4@SiO2–NH2 particles produced and their hydrodynamic size are suitable for applications to catalysis as well as for biomedical applications.Článekpeer-reviewedpublished Otevřený přístup Study of compositional changes of (Ag-)Sb-S thin films after Ar+ ion laser irradiation by means of micro X-ray fluorescence(University of Pardubice, 2014) Gutwirth, Jan; Bezdička, Petr; Wágner, Tomáš; Frumar, MiloslavThin amorphous films from (Ag-)Sb-S system were prepared as potential candidates for new phase-change memory films. Amorphous (Ag-)Sb-S thin films were deposited by thermal evaporation (TE) of Sb33S67 bulk sample followed by optically induced diffusion and dissolution (OIDD) of thermally evaporated Ag thin films. The phase-change recording process was realized via photocrystallization experiments done by Ar+ ion dot laser exposures of prepared films. Morphology of the laser exposed dots was observed by transmission optical microscopy while micro X-ray diffraction (:-XRD) was utilized for determination of crystallinity of the exposed dots. Laser induced changes were quantified by local measurement of optical transmission in dependence on laser exposure time. Compositional changes are determined via micro-X-Ray Fluorescence (:-XRF). The results prove crystallization of laser exposed thin film. Kinetic of this process is described in terms of transmittance change, evolution of X-Ray diffractograms and changes observable by optical microscopy. Moreover, the results do not indicate any significant chemical change in the case of stoichiometric Sb2S3 after laser irradiation while certain migration of silver takes place in sulfur rich Sb-S films doped by Ag.Článekpeer-reviewedpublished Otevřený přístup Reactions of S-, N-ambident nucleophiles with polarized ethylenes giving pyrimidines and 1,3-thiazines(University of Pardubice, 2014) Tarabová, Denisa; Hanusek, JiříThe review is focused on a diverse use of polarized ethylenes bearing an alkoxy, halogen or amino group in the reaction with S-, N- ambident nucleophiles (thioamides, thioureas, thiosemicarbazides, thiocarbamates, dithiocarbamates) to give pyrimidine and 1,3-thiazine ring. Other possibilities of synthesis of these heterocyclic scaffolds are also reported.Článekpeer-reviewedpublished Otevřený přístup Formation and properties of strontium zinc pyrophosphate(University of Pardubice, 2014) Gorodylova, Nataliia; Dohnalová, Žaneta; Šulcová, PetraIn present research we focused on the synthesis and investigation of properties of double strontium(II) zinc(II) phosphate — SrZnP2O7. Different synthesis approaches, including solid state reaction and coprecipitation, as well as different experimental conditions (initial reagents and homogenisation route) were used for the preparation of SrZnP2O7. The reaction route between the initial reagents was followed using DTA/TG and XRD methods. The obtained powders were characterised by IR spectroscopy and their thermal stability was followed by heating microscopy. Focusing on pigmentary application, specific properties of the samples were evaluated such as particle size distribution, colour parameters, and also preliminary anticorrosion tests were performed.Článekpeer-reviewedpublished Otevřený přístup Thermodynamic model and viscosity of As-Se glasses(University of Pardubice, 2014) Chovanec, Jozef; Shánělová, Jana; Málek, JiříThis work is focused on study of structure and viscosity relationship of As-Se glass melts. The structure was described by the thermodynamic model (or model of association solutions) of Shakhmatkin and Vedishcheva. The system contains five components (As, Se, AsSe, As2Se3, As4Se3) according to the phase diagrams. In this model, we consider only four components because the last one is in linear dependence on the As amounts. For a description of experimental viscosity values, we used the regular Adam & Gibbs, Avramov and Milchev and MYEGA viscosity equations. The thermodynamic model described the structural units in the As-Se undercooled glasses with sufficient precision. The best fit of viscosity data was achieved using the Adam & Gibbs model.Článekpeer-reviewedpublished Otevřený přístup Ball milling: A top down facile approach to synthesize AgInSe2 nanostructures(University of Pardubice, 2014) Pathak, Dinesh; Wágner, Tomáš; Šubrt, Jan; KupčíK, JaroslavA quantum dot solar cell is an emerging field in solar cell research that uses quantum dots as the photovoltaic material. Quantum dots have band gaps that are tunable across a wide range of energy levels by changing the quantum dot size. The embedment of different sized dots within absorbing layer encourages harnessing of the maximum spectrum energy. Also other effects like very high surface to volume ratio, Quantum Transport make them attractive for future devices. For an attempt of AIS quantum dots (QDs), AIS nanoparticles with tetragonally distorted phase were prepared by mechanically alloying the synthesized bulk AIS powder at room temperature in a planetary ball mill under Ar. Nanoparticles are formed with range -10 nm in size. These ball-milled nanoparticles contain different shapes, and the Rietveld analysis of X-ray powder diffraction data reveals their detailed structural features. High resolution transmission electron microscope (HRTEM) images also detect the presence of the tetragonal phase in ball-milled samples. Peak Broadening (FWHM), which is the main characteristics of decrease in size, is observed. XRD data reveals the downscaling of crystallite from 103 nm to 7 nm, also tetragonally distorted structure of the system was not disturbed by milling. The DSC study also reveals the phase evolution and crystallization kinetics. Bulk samples show endo melting peak at 134 °C and 220 °C. Cooling-crystallization complexity of the peak/peaks signifies crystallization from melt was heterogeneous nucleation and crystallization from multiple types of centers. Unlike this, milled samples show two crystallization effects at approx. 135 °C and 380 °C. Optical properties were investigated to find band edges, and suggest it around 1.3 eV which is encouraging for photovoltaic applications.Článekpeer-reviewedpublished Otevřený přístup Mitigation of fouling of submerged hollow fiber membrane in microfiltration of TiO2 photocatalyst particles(University of Pardubice, 2014) Kertèsz, Szabolcs; Popović, Svetlana; Cakl, JiříThe subject of investigation is fouling of a polypropylene hollow fiber membrane by TiO2 catalyst particles, and mitigation of fouling during and after microfiltration. To remove or reduce fouling, two techniques were applied: backflushing (BF) and ultrasound (US). The fouling caused by the TiO2 particles is of the low extent, so the fouling resistances are more than twice lower than the resistance of the used membrane. From the flux stepping experiments, it was obtained that the critical flux is 60 l m–2 h–1. For the filtration below the critical flux, it is proved that application of back-flushing is more effective than the US, in removing a fouling cake layer which was already deposited on the membrane surface. Application of the US together with the filtration process was suitable for the prevention of fouling when it was applied from the beginning of the filtration process.Článekpeer-reviewedpublished Otevřený přístup Utilization of hydrosilated silica-based stationary phases for separation of antioxidants(University of Pardubice, 2014) Soukup, Jan; Janás, Petr; Jandera, PavelWe studied the influence of mobile phase composition on the retention of phenolic acids and flavonoid compounds on five different hydrosilated silica-based stationary phases in buffered aqueous acetonitrile. Cogent UDC cholesterolTM, Cogent bidentate C18TM and Cogent Phenyl hydrideTM columns show significant dual reversed-phase/normal-phase retention behaviour, while Cogent Diamond hydrideTM and Cogent Silica-CTM columns provide very low retention in the reversed-phase mode. The effect of the aqueous acetate buffer concentration on retention factors of phenolic acids and flavonoid compounds over the full mobile phase composition range, including both aqueous normal-phase (ANP) and reversed-phase (RP) mechanisms, can be described by a four-parameter equation for dual-retention mechanism. At increasing temperature, the retention factors and peak widths decrease in the aqueous normal-phase range. In agreement with van’t Hoff model, linear ln k versus 1/T plots were observed, showing a single retention mechanism. From among the stationary phases tested, Cogent UDC cholesterolTM column has high temperature stability (up to 100 °C) and provides the most selective and efficient separations of flavones in the ANP mode and Cogent Diamond hydrideTM is the most selective and effective for separation of phenolic acids.Článekpeer-reviewedpublished Otevřený přístup Microwave assisted synthesis, absorption and fluorescence of furopyrrolinone pigments(University of Pardubice, 2014) Aysha, Tarek; Luňák, Stanislav; Hrdina, RadimFuropyrrolinone pigments were synthesized using solvent-free conditions and microwave heating. Soluble derivatives were prepared by N-butylation of pigment precursors. Absorption and fluorescence spectra were studied in DMSO both experimentally and theoretically, using time-dependent density functional theory. N-butylated derivatives show solid-state fluorescence.Článekpeer-reviewedpublished Otevřený přístup Evaluation of structural and charge properties of polyamide nanofiltration membrane(University of Pardubice, 2014) GHERASIM, CRISTINA VERONICA; Mikulášek, Petr; Chýlková, Jaromíra; Krejčová, AnnaNanofiltration (NF) is a highly efficient membrane separation process which has various environmental and industrial applications. Nanofiltration membranes are finely porous membranes with specific interesting features, their characterization being important for understanding of the NF processes and for their prediction for practical use. A polyamide thin-film composite NF membrane (AFC 80) was characterized in the present work by two different techniques: modelling of the rejection of uncharged solutes and modelling of the salt rejection. The interpretation of the data from uncharged solutes rejection experiments by using Donnan steric partitioning pore model (DSPM) allows to determine the structural characteristics of the AFC 80 membrane, i.e., effective pore radius (rp), and thickness to porosity ratio ()x/Ak). The experimental data for sodium chloride rejection were used to calculate the effective fixed charge density (MX) by means of an irreversible thermodynamics model (Spiegler–Kedem model) and of a charge model, namely Teorell–Meyer–Sievers (TMS) model. It was found that the membrane charge depends on the salt concentration in solution, this behaviour being attributed to ion adsorption on the membrane. The dependence of the charge density on NaCl concentration obeys a Freundlich isotherm equation.Článekpeer-reviewedpublished Otevřený přístup Determination of trinitrotoluene at ex-situ prepared bismuth film electrode: An initial study(University of Pardubice, 2014) Sopha, Hanna; Švancara, IvanA bismuth film electrode prepared ex-situ on a glassy carbon powder substrate (BiF-GCPE) was applied to the determination of trinitrotoluene (TNT) in combination with square-wave adsorptive stripping voltammetry. The electroanalytical performance of the BiF-GCPE was studied in Britton-Robinson buffers in the range of pH 4-9, revealing the most favourable stripping signals in mild alkaline solutions (pH 9.0). For calibration, linear responses could be obtained in the concentration range of 0.5-5.0 ppm TNT, when using a deposition time of 60 s (R2 = 0.9999), and within 0.1-1.5 ppm TNT after deposition for 120 s (R2 = 0.9983). The LOD (3F) was estimated to be about 7 ppb (for deposition time of 240 s), and the BiF-GCPE exhibited a very good repeatability (RSD = ±2.3 %; n = 10, ci = 0.5 ppm). Finally, possible determination of TNT in the presence of nitrobenzene was also shown.Článekpeer-reviewedpublished Otevřený přístup Relative quantitation of phosphatidylcholines with interfered masses of protonated and sodiated molecules by matrix-assisted laser desorption/ionization mass spectroscopy(University of Pardubice, 2014) Chagovets, Vitaliy; Holčapek, Michal; Lísa, MiroslavThis work presents a computational method for deconvolution of interfered peaks of protonated and sodiated phosphatidylcholines (PCs) to solve the problem of relative quantitation of these PCs. The method is based on the fact that adducts of PCs with proton and sodium ion give unique characteristic peaks in tandem mass spectra. The intensities of these peaks were used to find out contribution of protonated and sodiated PCs to the formation of interfered peak in full-scan mass spectrum and, further, to correlate peak intensities that correspond to PCs in fullscan mass spectrum with PC’s concentrations. The model was calibrated on synthesized PCs and verified for applicability in the range of Na+ ion concentrations from trace to physiological one.Článekpeer-reviewedpublished Otevřený přístup Role of methods and conditions of preparation of vanadium species supported on lamellar zeolite MCM-36 in their catalytic behaviour in oxidative dehydrogenation of propane(University of Pardubice, 2014) Hidalgo-Carrillo, Jesus; Švadlák, Daniel; Bulánek, Roman; Čičmanec, Pavel; Setnička, Michal; Drenchev, Nikola; Eliášová, PavlaIn this work, we report successful preparation of hierarchical VOx-MCM-36 catalysts. Lamellar pillared zeolitic support (MCM-36) was prepared from layered precursor of MCM-22P zeolite by swelling and pillaring. Vanadium was introduced into MCM-36 support by different methods (including conventional impregnation and ion exchange) by means of different precursors and synthesis conditions. Textural properties of prepared catalysts were characterized by nitrogen adsorption-desorption isotherms, the concentration of vanadium was determined by X-ray fluorescence and vanadium complex speciation was investigated by diffuse reflectance UV-vis spectroscopy, hydrogen temperature programmed reduction (H2 -TPR), electron paramagnetic resonance (EPR) and Fourier transform infrared (FTIR) spectroscopy. Effect of synthesis method and conditions on catalytic behaviour was tested in the oxidative dehydrogenation of propane at 540 °C. The vanadium is present in oxidation state IV, instead of usual oxidation state V, in the cases of the catalyst with low content of vanadium. The best selectivity to propene with 13 % of conversion (43.9 %) was obtained when the acid center was neutralized with potassium cations and the content of vanadium was 2 wt %.Článekpeer-reviewedpublished Otevřený přístup Lipidomic analysis of porcine organs using hydrophilic interaction liquid chromatography and mass spectroscopy(University of Pardubice, 2014) Cífková, Eva; Holčapek, Michal; Lísa, MiroslavThe identification and quantitation of all lipids in complex biological tissues is the first step towards the understanding how lipids function in a biological system and the elucidation of the mechanism of lipid-related diseases including obesity, atherosclerosis, cancer, cardiovascular diseases, etc. Our optimized nontargeted method using hydrophilic interaction liquid chromatography (HILIC) coupled to electrospray ionization mass spectrometry (ESI-MS) was used for the characterization of the lipidome, mainly glycerophospholipids and sphingolipids in porcine brain, heart, kidney, liver, lung, spinal cord, spleen and stomach. Individual lipid classes are quantified based on the peak integration of individual lipid classes separated in the HILIC mode multiplied by their response factors and correlated by sphingosylethanolamine (d17:1/12:0) as a single internal standard. Subsequently, relative abundances of deprotonated molecules [M-H]– in negativeion ESI mass spectra are used for determination of lipid species concentration inside individual classes. The approach using [M-H]– ions enables to obtain detailed information about phosphatidylethanolamines and their different forms of fatty acyl linkage on the glycerol skeleton (plasmalogens and ether analogs), phosphatidylinositols and hexosylceramides in studied organs. Our results provide important knowledge about lipid representations in vital porcine organs and can be applied for future metabolic studies on human to investigate serious lipid-related human disorders.Článekpeer-reviewedpublished Otevřený přístup Spectral, electrochemical and calculated properties of quadrupolar chromophores based on tetrafluorobenzene(University of Pardubice, 2014) Pippig, Falko; Mikysek, Tomáš; Ramaiyan, Manikannan; Pytela, Oldřich; Kulhánek, Jiří; Vytřas, Karel; Almonasy, Numan; Bureš, FilipAbsorption/emission and electrochemical properties of four new quadrupolar push-pull-push molecules with central tetrafluorobenzene acceptor and two peripheral N,N-dihexylamino and O-hexyloxy donor groups were investigated. Experimental data were completed with quantum-chemical calculations. The extent of the intramolecular charge-transfer and nonlinear optical properties were elucidated in terms of structure-property relationships. The electronic nature of the appended donor group, length, planarity and composition of the B-linker (combination of 1,4-phenylene, 2,5-thienylene and acetylenic subunits) are the most important factors affecting the linear as well as nonlinear optical properties.Článekpeer-reviewedpublished Otevřený přístup Carbon paste ion-selective electrode for ion-pair formation-based potentiometric titrations of anionic surfactants(University of Pardubice, 2014) Mikysek, Tomáš; Vytřas, KarelIn this contribution, a new carbon paste ion-selective electrode was introduced for ion-pair formation-based potentiometric titrations of anionic surfactants. In the electrode, an extract of hexadecylpyridinium dodecylsulfate in o-nitrophenyl octyl ether was used as both the binder and the electroactive ion-exchanger. Concerning titrants, three cationic compounds were examined: hexadecylpyridinium chloride (CPC), (diisobutylphenoxyethoxyethyl)-dimethyl-benzylammonium chloride (Hyamine 1622, HYA) and 1,3-didecyl-2-methylimid-azolium chloride (Tegotrant A100, TGT). The last one gave potentiometric titration curves with the highest potential breaks (210-260 mV), followed with CPC (90-140 mV) and HYA (40-60 mV). Despite this, the practical use of TGT in control laboratories should economically be considered impossible for its too high price on market. According to the authors’ meaning, the use of CPC as a titrant seems to be the best compromise as the steepness of the corresponding titration breaks is sufficient and its price is acceptable as well.Článekpeer-reviewedpublished Otevřený přístup Synthesis and characterization of push-pull molecules bearing tetrafluorobenzene central acceptor modified with two peripheral hexyloxy and dihexylamino donors(University of Pardubice, 2014) Ramaiyan, Manikannan; Kulhánek, Jiří; Bureš, FilipStarting from 1,4-diiodotetrafluorobenzene or 1,4-bis(5-bromothiophene-2- yl)tetra-fluorobenzene, four new push-pull molecules were synthesized via twofold cross-coupling reactions. Suzuki-Miyaura and Sonogashira reactions were employed to gain access to target molecules. The central tetrafluorobenzene acceptor unit was modified by two peripheral N,N-dihexylamino and Ohexyloxy groups with different donating ability to generate quadrupolar D-π-A- π-D system with tailored intramolecular charge-transfer. The length, planarity and composition of the π-linker between the acceptor and donors was modified by combination of 1,4-phenylene, 2,5-thienylene and acetylenic subunits in order to finely tune the linear as well as nonlinear optical properties.Článekpeer-reviewedpublished Otevřený přístup On approximation of thermodynamic driving force in deeply undercooled melts(University of Pardubice, 2014) Pillai, Suresh K.S.; Málek, JiříThe difference in Gibbs free energy between liquid and solid phases, usually expressed by authors as )G, appears in several theoretical formulations on nucleation and crystal growth. Approximations for )G are used extensively to gain an insight into the solidification phenomenon when thermophysical parameters are not known. In this work, the most commonly used models are applied to four bulk metallic glasses at temperatures starting from that of glass transition. An arithmetic mean of Thomson–Spaepen and Hoffman’s approximations yield significant improvements over new models incorporating nonlinear relationships involving undercoolings.Článekpeer-reviewedpublished Otevřený přístup Quality evaluation of monoclonal antibodies suitable for immunomagnetic purification of native tau protein(University of Pardubice, 2014) Jankovičová, Barbora; Hromádková, Lenka; Kupčík, Rudolf; Kašparová, Jitka; Řípová, Daniela; Bílková, ZuzanaTau protein plays a crucial role in the neuronal cytoskeleton stabilization. Under the pathological conditions, it can be abnormally phosphorylated which leads to the aggregation and formation of neurofibrillary tangles representing pathological hallmark of Alzheimer’s disease (AD). For its association with neurodegenerative diseases, tau protein is intensively studied in various diagnostic and therapeutic applications. Since there is no standard of tau protein involving essential post-translational modifications, it is often necessary to purify it directly from cerebrospinal fluid (CSF) or blood of healthy or AD clinical signs exhibiting organism. The immunomagnetic purification based on the isolation of the target protein using a specific antibody bound to a magnetic carrier is the most effective tool for this purpose. High quality antibodies are the main prerequisite of successful purification, but many commercial antibodies do not comply with the challenging requirements for the immunosorbent preparation. In this work, we compared four different anti-tau monoclonal antibodies currently available on the market (clones HT7, BT2, 8F10, 7E5). The evaluation criteria were set along the intended use for the preparation of specific magnetic immunosorbent subsequently applicable for the native tau protein purification. We evaluated the characteristics declared by producers as specificity, purity and homogeneity. We also tested the binding affinity and IgG stability during the covalent immobilization to the surface of magnetic microparticles and during the immunoprecipitation of intact tau protein or tryptic tau fragments. The results are summarized and discussed here.