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Bystrzejewski M.,University of Warsaw | Karoly Z.,Institute of Materials and Environmental Chemistry | Szepvolgyi J.,Institute of Materials and Environmental Chemistry | Szepvolgyi J.,University of Pannonia | And 2 more authors.
Materials Research Bulletin | Year: 2011

Carbon-encapsulated iron nanoparticles were continuously and selectively synthesised in a thermal plasma jet from ethanol (carbon source) and Fe powders with different grain sizes. The grain size of the Fe powder influenced the size distribution of the as-produced carbon encapsulates. The products obtained from large Fe particles (50-78 μm) were comprised of small encapsulates with diameters between 5 and 10 nm. Larger carbon encapsulates with a broad diameter distribution (10-100 nm) were synthesised from the finest Fe particles (18 μm). It was also found that Fe particle size was the most crucial parameter for determining the encapsulation yield. The encapsulation yield was also influenced by the carbon to iron ratio and the thermal conductivity of the plasma gas. © 2011 Elsevier Ltd. All rights reserved.

Fodor-Kardos A.,Institute of Materials and Environmental Chemistry | Fodor-Kardos A.,University of Pannonia | Toth J.,Institute of Materials and Environmental Chemistry | Toth J.,University of Pannonia | Gyenis J.,University of Pannonia
Powder Technology | Year: 2013

Combined precipitation and spherical agglomeration was carried out in the non-miscible region of ethyl acetate-ethanol-water ternary solvent system. At first, w/o type quasi emulsion was prepared by sequential introduction of aqueous solutions of human serum albumin (HSA), chitosan (CS), and poly(4-styrenesulfonate) (PSS) into an ethyl acetate-ethanol solvent mixture. HSA was used to model a protein type drug, while CS and PSS served as matrix material in the obtained composite particles. PSS also served as chemical precipitation agent for both of the HSA and CS. The solubility of all these substances was reduced by introduction of additional amounts of ethyl acetate-ethanol mixture and/or ethanol as poor solvents. Due to the counter-diffusion of the good and poor solvents between the water rich droplets and the ethyl acetate-ethanol rich continuous phase, the aqueous phase gradually disappeared and partial agglomeration of the precipitated solids and their transfer to the continuous organic phase took place. The paper gives a report on the effect of several process variables on the quality of the obtained microparticles, such as their shape and stability against disintegration. The effects of the composition of the ternary solvent mixture, the route of its variation, the feeding method and composition of the added poor solvents, the stirring rate and the duration of agitation were studied. Spherical agglomeration was carried out in EtOAc-EtOH-H2 O ternary system. The model drug was human serum albumin. The paper describes the effects of the most important process variables. Under given conditions nearly spherical shape agglomerates was achieved. The paper proposes a probable mechanism of formation of the composite microparticle. © 2013 Elsevier B.V.

Feczko T.,University of El Salvador | Feczko T.,Institute of Materials and Environmental Chemistry | Feczko T.,University of Pannonia | Kokol V.,University of El Salvador | Voncina B.,University of El Salvador
Macromolecular Research | Year: 2010

A model fragrance, vanillin, was encapsulated into ethylcellulose using an oil-in-water solvent evaporation method to prepare biodegradable microcapsules that can sustain the release of the model agent and potentially be bound to textile material. This study examined the effect of vanillin and polymer concentrations on the encapsulation efficiency, vanillin content and size of microcapsules. Microcapsules were dip-coated by chitosan, and the coating was crosslinked with non-toxic 1,2,3,4-butanetetracarboxylic acid. The release of vanillin from the uncoated and coated capsules was examined in air at elevated temperature. The experiments showed that ethylcellulose could efficiently sustain the delivery of vanillin, and additional chitosan layer increased the release of the model fragrance. © The Polymer Society of Korea.

Nagy B.,Budapest University of Technology and Economics | Abraham D.,Budapest University of Technology and Economics | Dobos G.,Budapest University of Technology and Economics | Madarasz J.,Budapest University of Technology and Economics | And 4 more authors.
Carbon | Year: 2014

Mo-doped carbon aerogels were obtained in the polycondensation reaction of aqueous resorcinol and formaldehyde by adding Mo-salt at two different stages of the synthesis: (i) to the initial sol; (ii) by incipient wetting impregnation of the supercritically dried polymer gel. Molybdenum added during the polymerization yielded a more compact gel structure with practically no mesoporosity. With post-impregnation, by contrast, mesopores of diameter 3-15 nm were generated. Carbonization appreciably enhanced the microporous character of both samples, but in the mesopore range their pore size distribution was conserved. The Mo-content of the samples was also different: Mo was lost during the solvent exchange before the supercritical drying (i.e., the Mo failed to bind chemically to the polymer matrix). The residual Mo congregated into 25-60 nm bulk clusters of α-Mo2C. In the other carbon aerogel, finely dispersed α-Mo2C and η-Mo3C2 crystals formed, of size 8-20 nm. On the surface of both carbons the Mo formed oxides. In the model test reaction (acetic acid hydroconversion) the catalytic activity of both carbon aerogels was enhanced by molybdenum. The more open pore structure, higher concentration and finer Mo distribution, as well as its chemical form, may all be responsible for the greater conversion and higher value products obtained with the post-impregnated sample. © 2013 Elsevier Ltd. All rights reserved.

Kertesz K.,Institute of Technical Physics and Materials Science | Piszter G.,Institute of Technical Physics and Materials Science | Jakab E.,Institute of Materials and Environmental Chemistry | Balint Zs.,Hungarian Natural History Museum | And 2 more authors.
Materials Science and Engineering C | Year: 2014

The sensing of gasses/vapors in the ambient air is the focus of attention due to the need to monitor our everyday environment. Photonic crystals are sensing materials of the future because of their strong light-manipulating properties. Natural photonic structures are well-suited materials for testing detection principles because they are significantly cheaper than artificial photonic structures and are available in larger sizes. Additionally, natural photonic structures may provide new ideas for developing novel artificial photonic nanoarchitectures with improved properties. In the present paper, we discuss the effects arising from the sensor temperature and the vapor concentration in air during measurements with a photonic crystal-type optical gas sensor. Our results shed light on the sources of discrepancy between simulated and experimental sensing behaviors of photonic crystal-type structures. Through capillary condensation, the vapors will condensate to a liquid state inside the nanocavities. Due to the temperature and radius of curvature dependence of capillary condensation, the measured signals are affected by the sensor temperature as well as by the presence of a nanocavity size distribution. The sensing materials used are natural photonic nanoarchitectures present in the wing scales of blue butterflies. © 2014 Elsevier B.V. All rights reserved.

Kertesz K.,Institute of Technical Physics and Materials Science | Piszter G.,Institute of Technical Physics and Materials Science | Jakab E.,Institute of Materials and Environmental Chemistry | Balint Z.,Hungarian Natural History Museum | And 2 more authors.
Applied Surface Science | Year: 2013

Photonic crystals are periodic dielectric nanocomposites, which have photonic band gaps that forbid the propagation of light within certain frequency ranges. The optical response of such nanoarchitectures on chemical changes in the environment is determined by the spectral change of the reflected light, and depends on the composition of the ambient atmosphere and on the nanostructure characteristics. We carried out reflectance measurements on closely related Blue lycaenid butterfly males possessing so-called "pepper-pot" type photonic nanoarchitecture in their scales covering their dorsal wing surfaces. Experiments were carried out changing the concentration and nature of test vapors while monitoring the spectral variations in time. All the tests were done with the sample temperature set at, and below the room temperature. The spectral changes were found to be linear with the increasing of concentration and the signal amplitude is higher at lower temperatures. The mechanism of reflectance spectra modification is based on capillary condensation of the vapors penetrating in the nanostructure. These structures of natural origin may serve as cheap, environmentally free and biodegradable sensor elements. The study of these nanoarchitectures of biologic origin could be the source of various new bioinspired systems. © 2013 Elsevier B.V.

Garcia-Diez R.,Physikalisch - Technische Bundesanstalt | Gollwitzer C.,Physikalisch - Technische Bundesanstalt | Krumrey M.,Physikalisch - Technische Bundesanstalt | Varga Z.,Institute of Materials and Environmental Chemistry
Langmuir | Year: 2016

The continuously growing complexity of nanodrugs urges for complementary characterization techniques which can elude the current limitations. In this paper, the applicability of continuous contrast variation in small-angle X-ray scattering (SAXS) for the accurate size determination of a complex nanocarrier is demonstrated on the example of PEGylated liposomal doxorubicin (Caelyx). The mean size and average electron density of Caelyx was determined by SAXS using a gradient of aqueous iodixanol (Optiprep), an iso-osmolar suspending medium. The study is focused on the isoscattering point position and the analysis of the Guinier region of the scattering curves recorded at different solvent densities. An average diameter of (69 ± 5) nm and electron density of (346.2 ± 1.2) nm-3 were determined for the liposomal formulation of doxorubicin. The response of the liposomal nanocarrier to increasing solvent osmolality and the structure of the liposome-encapsulated doxorubicin after the osmotic shrinkage of the liposome are evaluated with sucrose contrast variation in SAXS and wide-angle X-ray scattering (WAXS). In the case of using sucrose as contrast agent, a clear osmolality threshold at 670 mOsm kg-1 was observed, above which the liposomal drug carriers start to shrink, though preserving the intraliposomal doxorubicin structure. The average size obtained by this technique is smaller than the value measured by dynamic light scattering (DLS), though this difference is expected due to the hydrodynamic size of the PEG moieties attached to the liposomal surface, which are not probed with solvent contrast variation in SAXS. The advantages and drawbacks of the proposed technique are discussed in comparison to DLS, the most frequently used sizing method in nanomedicine. © 2015 American Chemical Society.

Tuvi-Arad I.,Open University of Israel | Rozgonyi T.,Institute of Materials and Environmental Chemistry | Stirling A.,Institute of Organic Chemistry
Journal of Physical Chemistry A | Year: 2013

Many reactions feature symmetry variation along the reaction path on the potential energy surface. The interconversion of the point group symmetry of the stationary points can be characteristic of these processes. Increasing the temperature, however, leads to the loss of symmetry in its traditional yes-no language. We find that in such cases the instantaneous distance of the molecular structure from its symmetric counterpart is a suitable collective variable that can describe the reaction process. We show that this quantity, the continuous symmetry measure (CSM), has a positive linear relationship with temperature, implying that even highly symmetric molecules should be considered as asymmetric above 0 K. Using ab initio molecular dynamics, we simulate the temperature-induced Cope rearrangements of several fluxional molecules and employ different CSMs to follow the reaction progress. We use this methodology to demonstrate the validity of important concepts governing these reactions: Woodward-Hoffmann rules and TS aromaticity. Statistical analysis of the CSM distributions reveals that ligands connected to the carbon frame have profound effect on the reaction course. In particular, our results show that lower temperatures tend to enhance the differences between the TS-stabilizing effect of the substituents. © 2013 American Chemical Society.

Szabo S.,Institute of Materials and Environmental Chemistry | Bakos I.,Institute of Materials and Environmental Chemistry
International Journal of Corrosion | Year: 2010

With especial regard to hydrogen electrode, the theoretical fundamentals of electrode potential, the most important reference electrodes and the electrode potential measurement have been discussed. In the case of the hydrogen electrode, it have been emphasised that there is no equilibrium between the hydrogen molecule (H and the hydrogen (H+), hydronium (H+) ion in the absence of a suitable catalyst. Taking into account the practical aspects as well, the theorectical basis of working of hydrogen, copper-copper sulphate, mercury-mercurous halide, silver-silver halide, metal-metal oxide, metal-metal sulphate and "Thalamid" electrodes, has been discussed. © 2010 S. Szabó and I. Bakos.

Mestl G.,Clariant | Margitfalvi J.L.,Combitech Nanotech Ltd. | Vegvari L.,Combitech Nanotech Ltd. | Szijjarto G.P.,Institute of Materials and Environmental Chemistry | Tompos A.,Institute of Materials and Environmental Chemistry
Applied Catalysis A: General | Year: 2014

In this study Mo-V-Te-Nb based multi-component catalysts were designed and tested using combinatorial and high-throughput methods. Based on the composition of the M1 matrix phase new compositions were designed containing additional promoters Mn, Ni, W and In. The following promoters were tested too in preliminary experiments and disregarded because of the detrimental effect on acrylic acid yields: Cu, Sb, Fe, Sm, Sn, Bi, Co, and Cr. In addition, citric acid in different ratios was used in the synthesis as a structure-directing agent. An optimization variable has been defined as the molar ratio of a given component to Mo in the synthesis mixture. Consequently, the experimental space had eight variables. The discrete levels of variables are established in such a way that the size of the multi-dimensional experimental space was in the range of 200 000 theoretical experiments. Five generations were designed using an optimization platform consisting of artificial neural networks and holographic optimization algorithm. Altogether 215 catalysts were prepared and tested. The elite list in each generation was created according to the yield of acrylic acid (AA). The yield of AA over the best catalyst after five generations was 59%. On the basis of holographic maps correlations between the composition of the synthesis mixture and yield of AA were visualized. Two catalysts families amongst the good performing catalysts have been distinguished that differ from each other in their low and high V content as referenced to molybdenum. © 2013 Elsevier B.V.

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