Wisniewska M.,Maria Curie Sklodowska University |
Zarko V.I.,Institute of Surface Chemistry
Journal of Industrial and Engineering Chemistry | Year: 2015
The effects of solution pH, supporting electrolyte presence and solid content on nanosilica suspension stability were examined. The turbidimetry method was applied to monitor the changes in the system stability in the short (about 2h) and long (about 18 days) periods of time. The stability coefficients and aggregate diameters were calculated numerically to estimate colloidal system properties. The sodium chloride presence (as a supporting electrolyte) improves the stability conditions of SiO2 suspension. The greatest effect of solution pH change is observed in the aqueous medium. The most unstable system occurs at pH 10.6 after 18 days. © 2015 The Korean Society of Industrial and Engineering Chemistry.
Pustovit V.N.,CNRS Paul Pascal Research Center |
Pustovit V.N.,Institute of Surface Chemistry |
Shahbazyan T.V.,Jackson State University
Physical Review B - Condensed Matter and Materials Physics | Year: 2011
We develop a unified theory of plasmon-assisted resonance energy transfer (RET) between molecules near a metal nanostructure that maintains energy balance between transfer, dissipation, and radiation. We show that in a wide range of parameters, including in the near field, RET is dominated by plasmon-enhanced radiative transfer (PERT) rather than by a nonradiative transfer mechanism. Our numerical calculations performed for molecules near the Ag nanoparticle indicate that RET magnitude is highly sensitive to molecules' positions. © 2011 American Physical Society.
Wisniewska M.,Maria Curie Sklodowska University |
Terpilowski K.,Maria Curie Sklodowska University |
Chibowski S.,Maria Curie Sklodowska University |
Urban T.,Maria Curie Sklodowska University |
And 2 more authors.
Powder Technology | Year: 2013
The influence of solution pH and polymer molecular weight on the stability of mixed alumina-silica oxide suspension in the absence and presence of polyacrylic acid (PAA) was studied. The composition of the adsorbent was: Al 2O 3 (96%) and SiO 2 (3%). To obtain changes in the stability of the investigated systems as a function of time the turbidimetry method was applied. It was shown that the suspension without the polymer was characterized by the smallest stability at pH 9, whereas at pH 3 and 6 the systems are successively stable. PAA with the molecular weighs 2000 at pH 3 (large deterioration of system stability conditions) and PAA (all molecular weights) at pH 9 (considerable improvement of suspension stability) have a great effect on the alumina-silica stability. The specific conformation of PAA chains on the solid surface which depends on solution pH and polymer molecular weight is responsible for the stabilization-flocculation properties of polyacrylic acid in the colloidal suspension. © 2012 Elsevier B.V.
PubMed | Institute of Surface Chemistry, Maria Curie Sklodowska University and Warsaw University of Technology
Type: Journal Article | Journal: Journal of separation science | Year: 2016
A novel approach is proposed to modify the porous structure and surface properties of the polymers used in solid-phase extraction. The approach involves soaking in water or acetone, followed by freezing in liquid nitrogen (77.4 K) and was employed for two polymeric materials: Amberlite XAD-7 and Amberlite XAD-16. Variations in the surface properties of the adsorbents were justified by the action of acetone and water as solvents affecting the textural and other characteristic of the materials. The initial and treated adsorbents were used in extraction of explosive nitramines from aqueous samples. The performed modifications of the polymer texture allow us to increase the recovery rate as compared with the initial adsorbents. The results were justified by the swelling of fragments of the polymers and by the additional process of sorption of nitramines. The results indicate that polymeric adsorbents can be easily modified by the soaking/freezing process and the materials can be achieved that prove usefulness for the effective separation of explosive nitramines from aqueous samples.
Andriiko A.A.,Kharkiv Polytechnic Institute |
Globa N.I.,8 A Vernadskii Boulrd |
Zul'Figarov A.O.,Kharkiv Polytechnic Institute |
Prisiazhnyi V.D.,8 A Vernadskii Boulrd |
And 2 more authors.
International Journal of Hydrogen Energy | Year: 2013
Discharge-ionization of hydrogen on carbon nanotube (CNT) electrodes in H3PO4 aqueous solution has been investigated and the effect of catalysts (Pt and polynuclear complexes 2Co-Ni with aminoethanol ligands) has been studied. It was found that the most probable mechanism contains the slow step of hydrogen atoms recombination on highly energetically nonuniform surface of CNT when the polarization is low. Increasing the polarization for more than -300 to -350 mV vs silver chloride reference electrode results in the operation of the CNT as a porous gas electrode with linear current-potential dependence. The influence of catalysts consists in the, first, decrease of the ohmic resistance of this electrode and, second, increase of the coulomb efficiency of charge (reduction of H+ ions) to discharge (oxidation of stored H2) from 70 to 80-90%. As follows from the results, the complexes 2Co-Ni can be used instead of Pt in the CNT-based hydrogen storage materials. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Tomaszewski W.,Warsaw University of Technology |
Gun'Ko V.M.,Institute of Surface Chemistry
Journal of Separation Science | Year: 2015
New series of carbon/silica gel nanocomposites, carbosils, prepared by the carbonization of starch bound to silica gel, and carbosils additionally silylated with octadecyldimethylchlorosilane were synthesized. These materials were applied as adsorbents in the solid-phase extraction of explosive nitrate esters and nitroaromatics from aqueous solutions. The adsorption and desorption steps were evaluated separately. It was found that both the molecular properties of explosives (dipole moments, orbital energies, solvation effects) and textural properties influenced by carbon deposits or octadecyl moieties have a large impact on the recovery rates. It was shown that the composites with moderate content of carbon deposits or with the highest amounts of carbon deposits and additionally silylated can be used as materials tailored for extraction of explosives from the aqueous solutions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Gun'Ko V.M.,University of Brighton |
Gun'Ko V.M.,Institute of Surface Chemistry |
Mikhalovska L.I.,University of Brighton |
Savina I.N.,University of Brighton |
And 4 more authors.
Soft Matter | Year: 2010
Porosity over a broad range (typically 0.001-300 μm in diameter) of tissue scaffolds provides appropriate conditions for diffusion and adsorption of small molecules and macromolecules, migration of cells through the scaffold, and adequate cell proliferative capacity. Characterisation of pores over this large range poses a problem especially when analysing soft polymer hydrogels, as no one methodology can adequately cover the entire range. This work describes a combined technique used for evaluation of the porous structure of a collagen hydrogel (dermal substitute Integra®) on the basis of NMR-cryoporometry (sensitive to nanopores) and confocal laser scanning microscopy (CLSM) imaging (sensitive to macropores). Thermodesorption of water, diffusion of proteins through a collagen membrane, migration and growth of normal primary human skin fibroblasts, and the interaction kinetics of 3T3 mouse fibroblast cells (using a quartz crystal microbalance) with collagen were analysed with respect to the porous structure of the material. The contribution to the total porosity of pores with a diameter of less than 100 nm is low, at approximately 3-5%, a figure estimated using the methods described above. However, these pores are the main contributor to the specific surface area (S ≈ 120 m2 g -1) as larger diameter macropores, with diameters of 20-200 μm, have a much lower surface area at S ≈ 0.4 m2 g-1 relative to their large pore volume V = 14.4 cm3 g-1. © 2010 The Royal Society of Chemistry.
PubMed | Institute of Surface Chemistry and Warsaw University of Technology
Type: Journal Article | Journal: Journal of separation science | Year: 2015
New series of carbon/silica gel nanocomposites, carbosils, prepared by the carbonization of starch bound to silica gel, and carbosils additionally silylated with octadecyldimethylchlorosilane were synthesized. These materials were applied as adsorbents in the solid-phase extraction of explosive nitrate esters and nitroaromatics from aqueous solutions. The adsorption and desorption steps were evaluated separately. It was found that both the molecular properties of explosives (dipole moments, orbital energies, solvation effects) and textural properties influenced by carbon deposits or octadecyl moieties have a large impact on the recovery rates. It was shown that the composites with moderate content of carbon deposits or with the highest amounts of carbon deposits and additionally silylated can be used as materials tailored for extraction of explosives from the aqueous solutions.
Chernii V.Ya.,Vernadskii Institute of General and Inorganic Chemistry |
Bon V.V.,Vernadskii Institute of General and Inorganic Chemistry |
Tretyakova I.N.,Vernadskii Institute of General and Inorganic Chemistry |
Severinovskaya O.V.,Institute of Surface Chemistry |
Volkov S.V.,Vernadskii Institute of General and Inorganic Chemistry
Dyes and Pigments | Year: 2012
Novel phthalocyanine complexes of zirconium (IV) and hafnium (IV) containing dibenzoylmethane groups as out-of-plane ligands were synthesized and characterized by elemental analyses, GALDI mass spectrometry, IR, 1H NMR, UV-vis and fluorescence spectroscopy. The structures of the complexes were determined by single-crystal X-Ray diffraction. The synthesized compounds are isomorphous, with their central atoms exhibiting (ZrN 4O 4 and HfN 4O 4) square-antiprism coordination geometry, which consists of four nitrogen atoms from the phthalocyanine macrocycle and four oxygen atoms from the two bidentate dibenzoylmethane ligands. GALDI mass spectrometry studies have shown that hafnium phthalocyanine forms adducts with masses higher than the mass of the molecular ion, indicating a high ability of this complex to self-associate in the gas phase. The spectral-luminescent properties of the compounds in different solvents were studied. The splitting of the Q-band observed in the absorption spectra is related to the lowering of complexes symmetry due to the incorporation of two rigid ligands to the central metal atom of the macrocycle. Study of the absorption spectra of phthalocyanines over a wide concentration range does not reveal any indications for the formation of aggregates. Fluorescence quantum yield values of the complexes were determined by a comparative method in toluene and DMSO. © 2012 Elsevier Ltd. All rights reserved.
Klonos P.,National Technical University of Athens |
Sulym I.Ya.,Institute of Surface Chemistry |
Borysenko M.V.,Institute of Surface Chemistry |
Gun'ko V.M.,Institute of Surface Chemistry |
And 3 more authors.
Polymer (United Kingdom) | Year: 2015
Effects of two types of silica particles, with different characteristics of porosity, on segmental mobility of poly(dimethylsiloxane), PDMS, in core-shell nanocomposites with two contents of polymer, 40 and 80 wt%, were studied by employing thermal (DSC) and dielectric (DRS, TSDC) techniques, under different annealing procedures. Filler morphology and polymer-particle interactions were found to affect PDMS crystallinity and segmental mobility. The dielectric techniques allowed the detection of four contributions to the segmental dynamics associated with the glass transition arising, in the order of decreasing mobility, from confined polymer chains in the pores of silica gel (αp relaxation), from the bulk (unaffected) amorphous polymer fraction (α relaxation), from polymer chains restricted between condensed crystal regions (αc) and from semibound polymer in an interfacial layer close to the nanoparticle surface (α′). For the core-shell nanocomposites with high PDMS content (80 wt%) the interfacial α′ relaxation process is found to have similar characteristics with that in conventional PDMS/silica nanocomposites, for lower PDMS content (40 wt%), however, the interfacial relaxation process exhibits distinct differences. The experimental findings are discussed in terms of models proposed for the description of conformations of polymers adsorbed onto a solid surface. © 2014 Elsevier Ltd. All rights reserved.