O. Berkesi

University of Szeged, Algyő, Csongrád, Hungary

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Publications (56)95.95 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The identity of the predominating tin(II)-hydroxide complex formed in hyper-alkaline aqueous solution (0.2  CNaOH  12 mol⋅dm-3) has been determined by potentiomet¬ric titrations, Raman, Mössbauer and XANES spectroscopy, supplemented by quantum chemical calculations. Thermodyna¬mic studies using a H2/Pt electrode up to free hydroxide concentrations of 1 mol⋅dm-3 showed the presence of a single monomeric complex with a tin(II):hydroxide ratio of 1:3. This observation together with Raman and Mössbauer spectroscopic measurements supplemented by quantum mechanical calculations proved that the predominating complex is [Sn(OH)3]–, and that the presence of the other possible complex, [SnO(OH)]–, could not be proven with neither experiments nor simulations. The structure of the trihydroxido-stannate(II) complex, [Sn(OH)3]-, was determined by EXAFS and was found to be independent of the applied hydroxide and tin(II) concentrations. The mean Sn-O bond distance is short, 2.078 Å, and in very good agreement with the only structure reported in the solid state. It is also shown that at pH values above 13 the speciation of the predominating trihydroxidostannate(II) complex is not affected by the presence of high concentrations of chloride ions.
    Dalton Transactions 10/2014; · 3.81 Impact Factor
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    ABSTRACT: The plasmonic Ag-TiO2 (with 0.5 wt% Ag) photocatalyst was prepared on P25 TiO2 surface. The presence of AgNPs on the titania was indicated by the UV–vis spectrum, which showed a plasmonic absorbance band in the visible range (λ max = 455 nm). XPS measurements suggested that Ag was in metallic (Ag) and in oxide forms on TiO2. Ag-TiO2 photocatalyst and TiO2 were embedded in [poly(ethyl acrylate-co-methyl methacrylate; p(EA-co-MMA)] copolymer to attain mechanically stable, photocatalytically active nanocomposite films. The photooxidation of ethanol was slower on the photocatalyst/polymer nanocomposites, but it could be significantly improved by irradiating them with UV light. The photoaging was applied as a post-preparation treatment to improve the photocatalytic activity of the nanocomposite films. Changed surface morphology and the partial destruction of the polymer were supported by AFM and FTIR results. Contact angle measurements were used to determine the surface free energies of the prepared and the photoaged nanocomposite films.
    Colloid and Polymer Science 01/2014; 292(1). · 2.16 Impact Factor
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    ABSTRACT: Psoriasis is a T lymphocyte-mediated inflammatory disorder that affects the skin. A number of studies have demonstrated the occurrence of lipid alterations in psoriatic skin, resulting in a highly perturbed stratum corneum (SC). Relatively little attention has been paid to the protein conformation of the SC. In this study, the attenuated total reflection Fourier transform infrared (ATR-FTIR) spectrum of the untreated psoriatic patients' unharmed SC was obtained after tape stripping. We focused on the amide-I band components in order to establish whether there are any protein alterations in the intact areas of psoriatic skin. Fourier self-deconvolution (FSD) of the amide-I band was followed by curve-fitting to generate the underlying components. Integration of band areas provided an estimate of the secondary structure. The results indicated decreases in all amide-I band components, the peak at 1660 cm− 1 revealing the most dramatic change. This peak is characteristic of the turn structure in the protein chain. The decrease is marked in the case of the β-sheet structure at 1630 cm− 1 too. This ATR-FTIR imaging is a rapid and simple noninvasive method, promotes a better understanding of the disease, and would be helpful in following the treatment.
    Microchemical Journal 01/2014; 117:183–186. · 2.88 Impact Factor
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    ABSTRACT: We have prepared multiwalled carbon nanotube (MWCNT)/In2O3 composites using a simple impregnation method. The precursor compound indium(III) chloride (InCl3) was used to cover the surface of MWCNTs and distilled water was used as solvent. The applied mass ratio was 4:1 (In2O3/MWCNT), and during the calcination process different temperatures (300, 350 and 400 °C) were investigated. The produced materials were characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, transmission and scanning electron microscopy, and a thermogravimetric analysis was executed also. The average thickness of the produced surface layer and the average sizes of the In2O3 particles were calculated with the Scherrer formula and the ImageJ-program. The results show that the heat treatment temperature affected the characteristic morphology and the crystal structure of the as-prepared composite. These multiwalled carbon nanotube-based composites are promising candidates as gas sensors and catalyst.
    physica status solidi (b) 12/2013; 60:266–272. · 1.49 Impact Factor
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    ABSTRACT: One of the aims of our long-term research is the identification of metal ion-ligand coordination sites in bioinspired metal ion-C- or N-protected amino acid (histidine, tyrosine, cysteine or cystine) complexes immobilised on the surface of chloropropylated silica gel or Merrifield resin. In an attempt to reach this goal, structurally related, but much simpler complexes have been prepared and their metal ion-ligand vibrations were determined from their low-frequency IR spectra. The central ions were Mn(II), Co(II), Ni(II) or Cu(II) and the ligands (imidazole, isopropylamine, monosodium malonate) were chosen to possess only one-type of potential donor group. The low-frequency IR spectra were taken of the complexes for each ion-ligand combination and the typical metal ion-functional group vibration bands were selected and identified. The usefulness of the obtained assignments is demonstrated on exemplary immobilised metal ion-protected amino acid complexes.
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 11/2013; 122C:257-259. · 1.98 Impact Factor
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    ABSTRACT: The investigation of free films is an essential part of the preformulation studies, because it is necessary to know, weather the given formulation is suitable to coat the corpus or not. As preformulation, the relationships between surface properties, and the structure of ethylcellulose free films containing different amount of plasticizer were studied. The structure analysis, and the incorporation of the plasticizer was performed with the use of FT-IR analysis. The results showed that the films are suitable to produce diffusion coatings.
    Microchemical Journal 01/2013; 110:36-39. · 2.88 Impact Factor
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    ABSTRACT: An exact wavelength separation of the spectrum cannot be accomplished when utilizing common ultraviolet (UV) light sources, so the dependence of photodegradation on wavelength cannot be done directly. The photodegradation of wood resulted in by laser irradiation on various wavelengths can be studied by comparing the changes in the DRIFT spectra of various wood materials. The analysis of the difference spectrum is a widely used method to investigate the changes in the infrared spectrum. As this procedure cannot be used to compare the changes quantitatively, a new indicator was introduced, termed Band Damage Index (BDI). The BDI and the results obtained by its analysis are going to be discussed.
    Journal of photochemistry and photobiology. B, Biology 04/2012; 112:43-7. · 3.11 Impact Factor
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    ABSTRACT: The ionic motion in connection with the redox transformation of poly(3,4-ethylenedioxythiophene) (PEDOT) conjugated polymer have been studied by both experimental-electrochemical (electrochemical quartz crystal nanobalance, EQCN) and spectroscopic (infrared spectroscopy, IR-ATR)-and theoretical methods. The observations have been completed by direct, semiquantitative analytical data, provided by energy dispersive X-ray (EDX) microanalysis. The EQCN results suggested an anomalous behavior, since only cationic movements have been observed for films deposited from chloride solutions. Chloride ions were proved to be immobile also when bulky tetrabutylammonium (Bu(4)N(+)) cations were substituted with even larger (hexadecyltrimethylammonium) cations. Since PEDOT films synthesized in the presence of other spherical, not too large anions-such as perchlorate and tetrafluoroborate-endowed mixed ion exchange behavior together with the Bu(4)N(+) cation, the possibility of a special interaction between chloride and the polymeric chain has been assumed. Semiempirical and DFT calculations indicated that chloride ions interact with the α carbon atoms of the thiophene rings of the oxidized EDOT oligomers, creating sp(3) type perturbations in the polymer chain. FTIR-ATR spectra evidenced the appearance of C-Cl bonds. Elementary analysis, performed by EDX spectroscopy with eight polymer samples at different doping levels clearly showed the permanent presence of constant amount of chlorine, independently of the oxidation state of the PEDOT layer. Finally, the presented observations call attention to the fact that unique dopant-polymer interactions during the electrochemical polymerization are of prime importance, being able to rule over conventions for the charge compensation of conjugated polymers, often solely based on steric parameters.
    The Journal of Physical Chemistry B 04/2012; 116(18):5491-500. · 3.61 Impact Factor
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    ABSTRACT: The steps of formation of an inclusion complex produced by the co-grinding of gemfibrozil and dimethyl-β-cyclodextrin were investigated by differential scanning calorimetry (DSC), X-ray powder diffractometry (XRPD) and Fourier transform infrared (FTIR) spectroscopy with curve-fitting analysis. The endothermic peak at 59.25°C reflecting the melting of gemfibrozil progressively disappeared from the DSC curves of the products on increase of the duration of co-grinding. The crystallinity of the samples too gradually decreased, and after 35min of co-grinding the product was totally amorphous. Up to this co-grinding time, XRPD and FTIR investigations indicated a linear correlation between the cyclodextrin complexation and the co-grinding time. After co-grinding for 30min, the ratio of complex formation did not increase. These studies demonstrated that co-grinding is a suitable method for the complexation of gemfibrozil with dimethyl-β-cyclodextrin. XRPD analysis revealed the amorphous state of the gemfibrozil-dimethyl-β-cyclodextrin product. FTIR spectroscopy with curve-fitting analysis may be useful as a semiquantitative analytical method for discriminating the molecular and amorphous states of gemfibrozil.
    Journal of pharmaceutical and biomedical analysis 08/2011; 57:62-7. · 2.45 Impact Factor
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    ABSTRACT: The compatibility of aceclofenac with various tableting excipients was investigated by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). The excipients applied in the direct pressing retard tablets were Carbopol 940, hydroxypropyl-methyl-cellulose, microcrystalline cellulose, Aerosil 200 and magnesium stearate. The ingredients alone and their 1:1 (w/w) binary mixtures were investigated before and after accelerated storage. An interaction was observed only between aceclofenac and magnesium stearate. The DSC and FT-IR examinations indicated formation of the magnesium salt of aceclofenac. For the other mixtures, there was no incompatibility between the components. KeywordsCompatibility–Aceclofenac–Magnesium stearate–DSC–FT-IR
    Journal of Thermal Analysis and Calorimetry 01/2011; 104(1):265-271. · 1.98 Impact Factor
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    ABSTRACT: Potential metal-organic-framework precursors, Zn(4)O complexes with various alicyclic or aromatic carboxylate ligands, were prepared, in many cases quantitatively, from ZnO and the relevant carboxylic acids in the presence of trace amounts of water. The complexes obtained were characterized with various classical (titration) and instrumental (IR and NMR spectroscopies) methods and molecular modeling (PM3 and PM6 semiempirical quantum chemical methods and HF/6-31G** ab initio calculations). Structural peculiarities reflected in the success or failure in the synthesis could be rationalized with the combination of IR and NMR spectroscopies and molecular modeling.
    Inorganic Chemistry 05/2010; 49(10):4620-5. · 4.59 Impact Factor
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    ABSTRACT: The aim of this work was to investigate the skin penetration enhancer effect of a sucrose ester (SE) in an Ibuprofen (IBU) containing hydrogel and to examine its influence on the special lipid bilayer of the stratum corneum (SC). ATR-FTIR spectroscopic measurements were performed combined with tape stripping method on hairless mice in vivo. A SE containing gel was compared to another gel without SE. It was found that the preparations caused only minimal modifications in the lipid and the protein structure, promoting the skin hydration and therefore also the penetration of IBU. Although the degree of moisturization and penetration were more intense in the case of the SE containing gel treatment, it did not cause greater alterations in the SC structure than the gel without SE. It has been proven that SE acts as an effective and non-irritating hydration and penetration enhancer for IBU through skin.
    Pharmaceutical Development and Technology 01/2010; 17(1):125-8. · 1.33 Impact Factor
  • C. Janaky, B. Endrodi, O. Berkesi, C. Visy
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    ABSTRACT: Conducting polymers are getting more and more interest as both supporting matrixes and electrocatalysts in the oxygen reduction reaction (ORR). A polypyrrole-magnetite nanocomposite layer has been synthesized by using potassium tetraoxalate as the conducting electrolyte. FT-IR measurements proved that chemical modification of the iron oxide by a reaction between the nanoparticles and the salt-leading to an iron oxalate layer on their surface-endows a negative charge to the particles, which leads to their penetration into the polymeric film as a part of the charge compensation. The new hybrid material showed significant photoelectrocatalytic behavior in the ORR. The ratio observed between the stabilized stationary currents under and without illumination is 2.0 for this hybrid. Separate studies on the electrochemical decomposition of H2O2 also indicated an enhanced catalytic activity of the polypyrrole/magnetite hybrid compared with the neat polymer. The results may open new opportunities in the next generation of solar fuel cell applications.
    Journal of Physical Chemistry C. 01/2010; 114(45):19338-19344.
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    ABSTRACT: In order to find highly active and selective oxygen-transfer catalysts with appreciable durability, Cu(II)–histidine complexes were covalently grafted onto a chlorinated polystyrene resin as copper-containing enzyme mimics. The Cu(II)-histidine complexes and the mobile polymer were to resemble the active center and the proteomic skeleton of the enzymes, respectively. The resulting heterogenized complexes were expected to be nearly so active and more durable catalysts that are easier to recycle than their homogeneous counterparts. The substances were tested in a superoxide radical anion dismutation reaction. Control for the syntheses was exerted by protecting either the N-terminal or the C-terminal of the covalently grafted l-histidine molecules. During the preparative work generally applied methods of synthetic organic chemistry (alkylation or esterification) were used. Various anchored complexes were prepared and characterized by classical analytical methods, different forms of spectroscopy as well as molecular modeling. The covalently grafted complexes having the protected amino acids as ligands displayed remarkably high activities in the superoxide dismutase (SOD) test reaction.
    Catalysis Letters 03/2009; 127(3):239-247. · 2.24 Impact Factor
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    ABSTRACT: The aim of this study was to evaluate the interaction between the film-forming sodium alginate and lactose monohydrate. This combination is used in the co-spray-drying technique for microencapsulation, but no respect on the structure of the film formed has not been published previously. From mechanical tests, positronium lifetime measurements and FT-IR studies on free films containing different ratios of film-former and lactose, we concluded that the mechanical strength of the sodium alginate film decreased with the increasing proportion of lactose. The free volume in the polymer matrix decreased to a minimum as the lactose content was progressively increased to 40%, but subsequently increased at higher lactose contents. The explanation of this phenomenon is the filling of the holes with the sugar. As lactose became predominant component, the structure of the polymer network weakened. These conclusions were supported by the FT-IR findings. The present results permit a clear explanation of the previously reported favourable effects of this film-forming combination on the dissolution of the active agent from the microcapsules.
    Carbohydrate Polymers. 01/2009;
  • C. Janaky, C. Visy, O. Berkesi, E. Tombacz
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    ABSTRACT: Polythiophene- magnetite composite layers have been prepared through the electropolymerization of 3-thiophene-acetic-acid in the presence of Fe3O4 nanoparticles in nitrobenzene. Stabilization of magnetite in this organic medium could be achieved by the reaction between surface -OH groups of the narroparticles and the -COOH function of the monomers. Fourier transformed infrared spectroscopic (FT-IR) measurements evidenced the chemisorption of the monomer on the Surface of the narroparticles. By modifying the amount of iron-oxide in the polymerization solution, the inorganic material content of the layer could be increased up to 80 m/m%. Electrochemical results, including data obtained by electrochemical quartz crystal microbalance (EQCM), proved that the presence of Fe3O4 did not influence the redox properties of the polymeric film. In the presence of magnetite, an extraordinary microstructure can be detected, where the self-assembling magnetic component strongly determines the morphology of the composite, leading to band formation of similar to 1 mu m width. This new modified electrode, incorporating such a large amount of Fe3O4 may be used in magnetic electrocatalysis.
    Journal of Physical Chemistry C. 01/2009; 113(4):1352-1358.
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    ABSTRACT: Ablation of a silicone oil, Dow Corning's DC-705 with laser pulses of sub-ps duration in high vacuum is a novel approach to fabrication of Si-doped carbon nanocomposite films. Gently focused, temporally clean 700 fs pulses @ 248 nm of a hybrid dye/excimer laser system produce power densities of the order of 1011–1012 W cm−2 on the target surface. The evolution of the chemical structure of film material is followed by comparing Fourier Transformed Infrared and X-ray Photoelectron spectra of films deposited at temperatures between room temperature and 250 °C. Despite the low thermal budget technique, in the spectrum of films deposited at room temperature the fingerprint of the silicone oil can clearly be identified. With increasing substrate temperature the contribution of the features characteristic of the oil gradually diminishes, but does not completely disappear even at 250 °C. This result is intriguing since the chance of oil droplets to survive in their original liquid form on the hot surface should be minimal. The results of the X-ray Photoelectron Spectroscopy suggest that the chemical structure of the film material resembles that of the oil. Both reflection mode optical microscopy and low magnification Scanning Electron Microscopy reveal that the films are inhomogeneous: areas of lateral dimensions ranging from a few to tens of micrometers, characterized by different contrasts can be identified. On the other hand, surface mapping by Scanning Electron and Atomic Force Microscopy unambiguously proves that all films possess a solid surface consisting of nanoparticles of less than 100 nm dimension, without the presence of any drop of oil. Possible explanations of the puzzling results can be that the films are polymers consisting mainly of the molecules of the target material, or composites of solid C:Si nanoparticles and oil residues.Graphical abstract
    Solid State Sciences. 01/2009; 11(10):1783-1787.
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    ABSTRACT: A tricyclic, piperidine derivative of antihistamines, loratadine, which belongs in class II of the Biopharmaceutical Classification System, was investigated. It is an ionizable drug, whose solubility depends on the gastrointestinal pH, and the bioavailability is therefore very variable. The aim of this work was to enhance the dissolution and make the solubility of loratadine independent of pH. Inclusion complexes were prepared between loratadine and dimethyl-β-cyclodextrin in two different molar ratios by three techniques (physical mixing, kneading and spray-drying). The formation and physicochemical properties of the inclusion complexes were investigated by means of dissolution tests, thermal analysis and Fourier Transform Infrared spectroscopy. The instrumental examinations proved the presence of partial or total complexes depending on the preparation method and molar ratio, which resulted in better dissolution. For some compositions and preparation methods, the application of this cyclodextrin made the solubility of loratadine independent of pH.
    Journal of Inclusion Phenomena 01/2009; 64(3):249-254. · 1.40 Impact Factor
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    ABSTRACT: Mid infrared, far-infrared and Raman spectroscopic studies, combined with force field analyses, were performed for the hydrated platinum(II) and palladium(II) ions and cis-diammineplatinum(II) complex in acidic aqueous solutions. Simplified Density Functional Theory (DFT) calculations were made for the equatorial plane of the platinum complexes. Careful subtraction of solvent spectra allowed a number of ‘internal’ modes of coordinated H2O and NH3 to be determined as weak residual bands. The [Pt(OH2)6]2+ and [cis-Pt(NH3)2(OH2)4]2+ complexes were found to be six-coordinated with four ligands strongly bound in an equatorial plane. The assignments of the vibrational modes in the equatorial plane could be performed on the basis of the experimental observations and by comparison with metal–ligand vibrations of square-planar complexes, aided by normal coordinate calculations. For the weakly coordinated axial aqua ligands, the low wavenumber range and the polarizibility properties allowed the assignments of the bands at about 365 and 325 cm−1 to the stretching modes of one short and one longer Pt— O* bound to axial aqua ligands, respectively. A similar picture with even less strongly bound axial water molecules emerges from Raman spectroscopy data for the hydrated palladium(II) ion, [Pd(OH2)6]2+. The results are consistent with a description of the [Pt(OH2)6]2+ and [Pd(OH2)6]2+ aqua ions in C4v symmetry, and with the [cis-Pt(NH3)2(OH2)4]2+ complex in the Cs point group, and also in qualitative agreement with the structures devised from previous extended X-ray absorption fine structure (EXAFS) measurements. Copyright © 2008 John Wiley & Sons, Ltd.
    Journal of Raman Spectroscopy 12/2008; 40(5):481 - 490. · 2.68 Impact Factor
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    ABSTRACT: The majority of active pharmaceutical ingredients are poorly soluble in water. The rate-determining step of absorption is the dissolution of these drugs. Inclusion complexation with cyclodextrin derivatives can lead to improved aqueous solubility and bioavailability of pharmacons due to the formation of co-crystals through hydrogen-bonding between the components. Inclusion complexes of loratadine were prepared by a convenient new method involving microwave irradiation and the products were compared with those of a conventional preparation method. Dissolution studies demonstrated that the solubility and rate of dissolution of loratadine increased in both of the methods used. The interactions between the components were investigated by thermal analysis and Fourier Transform Infrared studies. The microwave treatment did not cause any chemical changes in the loratadine molecule.
    Journal of Pharmaceutical and Biomedical Analysis 08/2008; 48(3):1020-3. · 2.95 Impact Factor

Publication Stats

280 Citations
95.95 Total Impact Points

Institutions

  • 1995–2014
    • University of Szeged
      • • Department of Physical Chemistry and Materials Science
      • • Department of Pharmaceutical Technology
      • • Institute of Chemistry
      Algyő, Csongrád, Hungary
  • 1997
    • University of Pannonia, Veszprém
      • Department of Analytical Chemistry
      Veszprém, Veszprem megye, Hungary
  • 1992
    • University of East Anglia
      Norwich, England, United Kingdom
  • 1991–1992
    • Hungarian Academy of Sciences
      Budapeŝto, Budapest, Hungary
    • University of Bristol
      • School of Chemistry
      Bristol, England, United Kingdom