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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. Source

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. Source

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. Source

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. Source

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. Source

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