Time filter

Source Type

Trunov M.L.,Uzhgorod National University | Lytvyn P.M.,V Lashkaryov Institute Of Semiconductors Nas Ukraine | Nagy P.M.,Research Center for Natural Science | Csik A.,Institute for Nuclear Research | Kokenyesi S.,Debrecen University
Physica Status Solidi (B) Basic Research | Year: 2014

Two types of amorphous functional materials, based on light-sensitive inorganic compounds like Se and As20Se80 chalcogenide glass (ChG) were investigated with the aim to establish the influence of plasmonic fields, excited by the recording light in nanocomposite layers made of these compounds and gold nanoparticles on their photomechanical response. Both these basic materials are characterized by pronounced photoplastic effect and used for real-time optical recording of optoelectronic elements (based mainly on surface relief gratings) due to high photofluidity and polarization-dependent mass-transport. We have established that mass-transport processes in these ChG can be enhanced in the presence of localized plasmonic fields generated by light if the condition of surface plasmon resonance (SPR) is fulfilled. The subjects of special interest are the mass-transport processes at nano-scale stimulated in the nano-composite layers either by uniform or periodically distributed optical fields. It was found that irradiation by light in the presence of SPR really enhanced the efficiency of mass-transport and produced surface nanostructurizations. The variation in the topography follows closely and permanently the underlying near field intensity pattern. Nanostructurization of photosensitive amorphous As20Se80 film by surface plasmon near field irradiation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Khanh N.Q.,Research Center for Natural science | Lukacs I.,Research Center for Natural science | Safran Gy.,Research Center for Natural science | Erdelyi R.,Research Center for Natural science | And 4 more authors.
Materials Letters | Year: 2012

Very high aspect ratio ZnO nanowires have been prepared by a novel nanosphere assisted hydrothermal method. The wires were synthesized on a ZnO seed layer, which was covered by a monolayer of Stöber silica nanoparticles. The so formed nanowires were ca. 30 nm in width and up to 7 μm in length in contrast with the thicker (60 nm) and shorter (0.85 μm) ones grown without nanoparticle film under identical conditions. Larger nanoparticles result in shorter nanowires, but the diameter of the nanowires is not affected by the particle diameter in the investigated size range (240-450 nm). The thin nanowires show superior photoresponse upon exposure to 360 nm UV light compared to those grown without cap layer. © 2012 Elsevier B.V. All rights reserved.


PubMed | University of Aarhus and Research Center for Natural science
Type: | Journal: Scientific reports | Year: 2016

Organic molecules are currently investigated as redox species for aqueous low-cost redox flow batteries (RFBs). The envisioned features of using organic redox species are low cost and increased flexibility with respect to tailoring redox potential and solubility from molecular engineering of side groups on the organic redox-active species. In this paper 33, mainly quinone-based, compounds are studied experimentially in terms of pH dependent redox potential, solubility and stability, combined with single cell battery RFB tests on selected redox pairs. Data shows that both the solubility and redox potential are determined by the position of the side groups and only to a small extent by the number of side groups. Additionally, the chemical stability and possible degradation mechanisms leading to capacity loss over time are discussed. The main challenge for the development of all-organic RFBs is to identify a redox pair for the positive side with sufficiently high stability and redox potential that enables battery cell potentials above 1V.


PubMed | Karlsruhe Institute of Technology, Research Center for Natural science, University of Heidelberg and J. Heyrovsky Institute of Physical Chemistry
Type: Journal Article | Journal: Chemistry (Weinheim an der Bergstrasse, Germany) | Year: 2016

The efficient synthesis of tripodal platforms based on tetraphenylmethane with three acetyl-protected thiol groups in either meta or para positions relative to the central sp(3) carbon for deposition on Au (111) surfaces is reported. These platforms are intended to provide a vertical arrangement of the substituent in position4 of the perpendicular phenyl ring and an electronic coupling to the gold substrate. The self-assembly features of both derivatives are analyzed on Au (111) surfaces by low-temperature ultra-high-vacuum STM, high-resolution X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and reductive voltammetric desorption studies. These experiments indicated that the meta derivative forms a well-ordered monolayer, with most of the anchoring groups bound to the surface, whereas the para derivative forms a multilayer film with physically adsorbed adlayers on the chemisorbed para monolayer. Single-molecule conductance values for both tripodal platforms are obtained through an STM break junction experiment.


Holczer E.,Research Center for Natural science | Holczer E.,Budapest University of Technology and Economics | Fekete Z.,Research Center for Natural science | Fekete Z.,Budapest University of Technology and Economics | Furjes P.,Research Center for Natural science
Materials Science Forum | Year: 2013

The material aspects of a polymer based microfluidic structure were characterised considering the compatibility of the system with bioanalytical applications. The polydimethylsiloxane (PDMS) based channel system is to be integrated in a full polymer photonic biosensor device developed within the European Union project P3SENS (FP7-ICT4-248304). This work is intended to define a modified material composition, which is appropriate to improve both the wettability and the non-specific protein binding characteristics of the PDMS significantly. Triton X-100 (Sigma-Aldrich) surfactant was added to the raw PDMS before polymerisation. The influence of the tenside was studied considering the polymerisation reaction, the surface characteristics and the functional applicability. To test the hydrodynamic behaviour and non-specific protein adsorption on the surfaces, phosphate buffered saline (PBS) solution and fluorescent labelled human serum albumin (HSA) was applied in a microfluidic capillary system. © (2013) Trans Tech Publications, Switzerland.


Terejanszky P.,Budapest University of Technology and Economics | Makra I.,Budapest University of Technology and Economics | Furjes P.,Research Center for Natural science | Gyurcsanyi R.E.,Budapest University of Technology and Economics
Analytical Chemistry | Year: 2014

The feasibility of using quartz nanopipets as simple and cost-effective Coulter counters for calibration-less quantitation and sizing of nanoparticles by resistive pulsing sensing (RPS) was investigated. A refined theory was implemented to calculate the size distribution of nanoparticles based on the amplitude of resistive pulses caused by their translocation through nanopipets of known geometry. The RPS provided diameters of monodisperse latex nanoparticles agreed within the experimental error with those measured by using scanning electron microscopy (SEM), dynamic light scattering (DLS), and nanoparticle tracking analysis (NTA). The nanopipet-based counter, by detecting individual nanoparticles, could resolve with similar resolution as SEM mixtures of monodisperse nanoparticles having partially overlapping size distributions, which could not be discriminated by DLS or NTA. Furthermore, by calculating the hydrodynamic resistance of the nanopipets and consequently the volume flow through the tip enabled for the first time the calibration-less determination of nanoparticle concentrations with nanopipets. The calibration-less methodology is applied to sizing and quantitation of inactivated poliovirus of ∼26 nm diameter, which is the smallest size spherical shape virus ever measured by resistive pulse sensing. © 2014 American Chemical Society.


Ysacco C.,Aix - Marseille University | Karoui H.,Aix - Marseille University | Casano G.,Aix - Marseille University | Le Moigne F.,Aix - Marseille University | And 6 more authors.
Applied Magnetic Resonance | Year: 2012

We have prepared a series of dinitroxides and we investigated their properties as polarizing agents for solid-state nuclear magnetic resonance/dynamic nuclear polarization applications at 100 K, 9.34 T (263 GHz electron paramagnetic resonance and 400 MHz 1H nuclear magnetic resonance). Our results show that a rigid structure with an orthogonal relative orientation of electron g tensors and the appropriate orientation of the two N - O. bonds are required to obtain maximum polarization enhancements. In addition, with dinitroxides exhibiting a long T 1e, the saturation of the irradiated electron spin packet is favored leading to more efficient dynamic nuclear polarization. © 2012 Springer-Verlag.


Aresta M.,CIRCC | Dibenedetto A.,CIRCC | Dibenedetto A.,University of Bari | Angelini A.,CIRCC | And 2 more authors.
Topics in Catalysis | Year: 2015

Dialkylcarbonates, (RO)2CO, can be prepared from alcohols and CO2. Such reaction is clean (water is the co-product) but thermodynamically disfavored. In principle, the reaction mechanism of formation of carbonates requires the acid-base activation of alcohols. Existing data support that the first step is the formation of the alkoxo group RO- that reacts with CO2 to give the hemicarbonate moiety ROC(O)O-. The latter converts into the relevant carbonate (RO)2CO following different pathways depending on the catalyst used. DFT calculations have been used in a few cases to support the reaction mechanism. Transition states relevant to various mechanistic scenarios have been identified. The results indicated that the relative energies of these transition states depend on the nature of the alkyl group and the molecularity of the reactive step. Organic catalysts, homogeneous-, heterogenized- and heterogeneous-metal systems are discussed in this paper and the known relevant mechanisms compared. Water represents a serious limitation to equilibrium shift to the right and can affect the catalysts. Techniques used to remove water are also discussed. © 2014 Springer Science+Business Media New York.


Karoui H.,Aix - Marseille University | Nsanzumuhire C.,Aix - Marseille University | Le Moigne F.,Aix - Marseille University | Hardy M.,Aix - Marseille University | And 5 more authors.
Chemistry - A European Journal | Year: 2014

The 5-diethoxyphosphonyl-5-methyl-1-pyrroline N-oxide superoxide spin adduct (DEPMPO-OOH) is much more persistent (about 15 times) than the 5,5-dimethyl-1-pyrroline N-oxide superoxide spin adduct (DMPO-OOH). The diethoxyphosphonyl group is bulkier than the methyl group and its electron-withdrawing effect is much stronger. These two factors could play a role in explaining the different half-lifetimes of DMPO-OOH and DEPMPO-OOH. The trifluoromethyl and the diethoxyphosphonyl groups show similar electron-withdrawing effects but have different sizes. We have thus synthesized and studied 5-methyl-5-trifluoromethyl-1-pyrroline N-oxide (5-TFDMPO), a new trifluoromethyl analogue of DMPO, to compare its spin-trapping performance with those of DMPO and DEPMPO. 5-TFDMPO was prepared in a five-step sequence by means of the Zn/AcOH reductive cyclization of 5,5,5-trifluoro-4-methyl-4- nitropentanal, and the geometry of the molecule was estimated by using DFT calculations. The spin-trapping properties were investigated both in toluene and in aqueous buffer solutions for oxygen-, sulfur-, and carbon-centered radicals. All the spin adducts exhibit slightly different fluorine hyperfine coupling constants, thereby suggesting a hindered rotation of the trifluoromethyl group, which was confirmed by variable-temperature EPR studies and DFT calculations. In phosphate buffer at pH-7.4, the half-life of 5-TFDMPO-OOH is about three times shorter than for DEPMPO-OOH and five times longer than for DMPO-OOH. Our results suggest that the stabilization of the superoxide adducts comes from a delicate balance between steric, electronic, and hydrogen-bonding effects that involve the β group, the hydroperoxyl moiety, and the nitroxide. New pieces to the puzzle! A new fluorinated 5,5-dimethyl-1-pyrroline N-oxide (DMPO)-based spin trap (5-TFDMPO; see figure) was synthesized and studied by EPR/spin-trapping techniques. The properties of the new spin trap are reported for various radicals. The role of the trifluoromethyl group on the spin-trapping properties of the superoxide radical is discussed on the basis of a comparison with other spin traps. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Illes E.,University of Szeged | Tombacz E.,University of Szeged | Szekeres M.,University of Szeged | Toth I.Y.,University of Szeged | And 2 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2015

Fabrication of PEG coating on magnetite nanoparticles (MNPs) is one of the most favoured ways to ensure biocompatibility. Surface modification of magnetite by an own-prepared comb-like PEG-copolymer (PEGA-AA) was compared with two commercially available ones (carboxy-PEG (PEG-C) and phosphate-PEG (PEG-P)). ATR FT-IR data revealed that all polymers form complexes on the surface of MNPs. Electrophoresis and dynamic light scattering (DLS) experiments showed that both the type and quantity of the polymers' anchoring groups influence the aggregation of coated nanomagnets. PEG-C shell does not provide excess negative charges, so magnetite particles became aggregated. However PEG-P and PEGA-AA gradually modify the surface: neutralizing the originally positively charged MNPs below loading 0.5 mmol/g, while above it a polyanionic layer forms on nanomagnets dispersing them in salty media at pH ~6.5. The PEGA-AA comb-like copolymer is more efficient for MNPs PEGylation due to the uniform distribution of carboxylates and PEG chains along the carbon skeleton. © 2014 Elsevier B.V.

Loading Research Center for Natural science collaborators
Loading Research Center for Natural science collaborators