Ottó Berkesi - Academia.edu (original) (raw)

Papers by Ottó Berkesi

The Journal of Physical Chemistry C

Pharmaceutics

Solvent-free preparation types for cyclodextrin complexation, such as co-grinding, are technologi... more Solvent-free preparation types for cyclodextrin complexation, such as co-grinding, are technologies desired by the industry. However, in-depth analytical evaluation of the process and detailed characterization of intermediate states of the complexes are still lacking in areas. In our work, we aimed to apply the co-grinding technology and characterize the process. Fenofibrate was used as a model drug and dimethyl-β-cyclodextrin as a complexation excipient. The physical mixture of the two substances was ground for 60 min; meanwhile, samples were taken. A solvent product of the same composition was also prepared. The intermediate samples and the final products were characterized with instrumental analytical tools. The XRPD measurements showed a decrease in the crystallinity of the drug and the DSC results showed the appearance of a new crystal form. Correlation analysis of FTIR spectra suggests a three-step complexation process. In vitro dissolution studies were performed to compare th...

In order to mimic copper-containing enzymes, Cu(II)-histidine complexes were grafted onto chlorop... more In order to mimic copper-containing enzymes, Cu(II)-histidine complexes were grafted onto chloropropylated polystyrene resin. The Cu(II)-histidine complexes and the mobile polymer were thought to resemble the active centre and the proteomic skeleton of the enzymes, respectively. The resulting heterogenised complexes were expected to be nearly so active, selective and more durable catalysts that are easier to recycle than their homogeneous counterparts. The intended area of use is oxidation and dismutation reactions. Control for the syntheses was exerted by protecting either the N-terminal or the Cterminal of the covalently grafted L-histidine molecules. However, since the resin was reported to be amino group selective, covalent grafting was performed with the unprotected amino acid as well. During the preparative work generally applied methods of synthetic organic chemistry (alkylation or esterification) were used. The whole procedure was performed in isopropanol to allow appropriate swelling of the host polymer. After deprotecting the immobilised amino acids the complexes were prepared and the emerging structures (just as the full synthetic procedure) were studied by Photoacoustic Infrared Spectroscopy. The photoacoustic spectra revealed that the grafting was successful in each case and the complexes were formed too. However, real control over the preparation could only be proven when the protected amino acids were applied. On the basis of the spectra and chemical reasoning structural features of the immobilised complexes could be described.

A kutatas temaja olyan konjugalt polimereken alapulo osszetett anyagok előallitasa, jellemzese es... more A kutatas temaja olyan konjugalt polimereken alapulo osszetett anyagok előallitasa, jellemzese es alkalmazasi lehetősegeik feltarasa volt, melyek magneses, termoelektromos vagy fotokatalitikus sajatsagokat mutatnak. Megvalositottuk magnetit nanoreszecskek szerves kozegbe tortenő atvitelet, es igazoltuk a magnetit nanoreszecskek feluleten elhelyezkedő hidroxil- es a karbonsavval szubsztitualt tiofenek karboxil-csoportja kozotti kolcsonhatas kemiai jelleget. A magnetit nanoreszecskek feluleten megvalositott adszorpcioja utjan eredmenyesen epitettunk be polipirrol elektrodba B12 vitamint. Megvalositottuk titan-dioxid es szen nanocső kotegeknek vezető polimerekkel tortenő kombinalasat. Kiemelkedő termoelektromos sajatsaggal rendelkező 3-alkiltiofenek polimerjeit atkristalyositva – nemesfemek beepitese reven – nanoszalas kompozitokat alakitottunk ki. A mintakat atfogoan jellemeztuk az anyagtudomany teruleten altalanosan hasznalt technikak (rontgen-diffrakcio, spektroszkopiak, elektronmikroszkop, elektrokemiai nanogravimetria, vezetesmeres) alkalmazasaval. Az irodalomban elsőkent kidolgoztuk az in situ spektroelektrokemiai es impedanciameres szimultan alkalmazhatosagat, kimutattuk es ertelmeztuk a vezetes kialakulasanak az egyes tolteshordozokkal valo – valtozo – korrelaciojat. Felhivtuk a figyelmet az elektronegativ anionok jelenleteben tortenő elektrokemiai polimerizacio veszelyere, es korultekintő alkalmazasanak szuksegessegere. | During the project, conducting polymer based composites – exhibiting magnetic, thermoelectric or photocatalytic properties - have been synthesized. We realised the transfer of magnetic nanoparticles into organic media, and proved the chemical pattern of the interaction between the hydroxyl group on the surface of the magnetic nanoparticles and the carboxyl group of the acid substituted thiophenes. Exploiting the adsorption of vitamin B12 on the magnetite nanoparticles, its successful incorporation into polypyrrole has been achieved. Composites of conducting polymers with nanotube arrays of titanium dioxide and carbon have been also synthesized. Via re-crystallisation of poly(3-alkylthiophenes) – possessing extraordinary good thermoelectric property – nanofils of composites with noble metals have been prepared. The composites have been characterized widely with XRD, SEM – EDX, EQCM, ac conductance, as well as by diffuse reflection mode, UV-VIS absorption and FTIR – ATR mode spectroscopy. For the first time in the literature, we elaborated the application of in situ spectroelectrochemistry and in situ conductance in a hyphenated mode, and elucidated the background of differences in the correlation between the development of the conductance and the optically distinguishable charge carriers. We called the attention to the potential dangers arising during the electro-polymerisation in the presence of electronegative anions, and to the necessity of its careful consideration.

Surfactants in Solution, 1989

Our investigations of the solubility and micelle formation of Zn(ll) oleate in various organic so... more Our investigations of the solubility and micelle formation of Zn(ll) oleate in various organic solvents led us to the conclusion that besides the monomeric and micellar forms of the soap that have been adequately discussed in the literature an additional form may be present. Besides the concentration of the soap, the nature of the solvent and the temperature influence the amounts of the soap in the different forms. The existence of different association forms of soap molecules and their equilibria in organic solvents has been verified by IR spectroscopy and by other physico-chemical methods, for both Zn(II) oleate and Zn(II) stearate. The new additional form proved to be a non-associated form as it was prepared in a pure state. Vibrational spectroscopic and elemental analysis of this compound showed that its structure is analogous to that of μ4-oxo-hexa-μ-(2-ethy 1 hexanoatoo,o’)-tetrazinc(I I) whose IR spectrum had been recently reported by us. For Zn(II) carboxylates of straight chain acids, this kind of structure has previously been described only for Zn(II) formate and acetate, which are formed under extreme conditions. We have shown that, depending on the circumstances of formation, not only the well known Zn(ll) carboxylate hydrate and anhydrate, but also the tetranuclear-oxo-centered soap and their mixtures can be prepared. The properties of the above-mentioned tetranuclear form of the soap in the pure state and in solution differ essentially from those of the ordinary forms and this fact may be of important theoretical and practical significance.

Inorganica Chimica Acta, 1991

Abstract A new method for producing tetrazinc μ4-oxo-hexa-μ-carboxylates of short straight-chain ... more Abstract A new method for producing tetrazinc μ4-oxo-hexa-μ-carboxylates of short straight-chain carboxylic acids in solution is reported. The complexes with C2–C5 chain have been prepared. Their characteristic IR bands in the mid-IR region are discussed and give a satisfactory identification method for these complexes. The formation process and the influence of the water present in the system have been monitored by FT-IR spectroscopy. A modified mechanism of formation and decomposition, based on an equilibrium and a ‘feedback’ step, is proposed.

Journal of Raman Spectroscopy, 2009

Mid infrared, far-infrared and Raman spectroscopic studies, combined with force field analyses, w... more 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 H 2 O and NH 3 to be determined as weak residual bands. The [Pt(OH 2) 6 ] 2+ and [cis-Pt(NH 3) 2 (OH 2) 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(OH 2) 6 ] 2+. The results are consistent with a description of the [Pt(OH 2) 6 ] 2+ and [Pd(OH 2) 6 ] 2+ aqua ions in C 4v symmetry, and with the [cis-Pt(NH 3) 2 (OH 2) 4 ] 2+ complex in the C s point group, and also in qualitative agreement with the structures devised from previous extended X-ray absorption fine structure (EXAFS) measurements.

Spectrochimica Acta Part A: Molecular Spectroscopy, 1992

The complex [Zn40(00CC(CH)) ] 3 3 6 contains a tetrahedral oxo-centred metal cluster unit. Struct... more The complex [Zn40(00CC(CH)) ] 3 3 6 contains a tetrahedral oxo-centred metal cluster unit. Structures of this type have been characterised by X-ray diffraction, and in some cases exact tetrahedral symmetry has been found. However, crystal structures of high symmetry can conceal molecular structures of lower symmetry, averaged by static or dynamic disorder. The symmetry of this complex has therefore been checked over a short time-frame, in solution, by using vibrational spectroscopy with isotopic substitution. The antisymmetric vibration of the central oxide ion (t2 symmetry in the Td point group) has been located unambiguously and shown to be free of splitting by any symmetry lowering, and moreover to be essentially purely localised about the central oxygen.

Journal of Molecular Structure, 2015

ABSTRACT The conformational as well as the structure-forming properties of E-3-(x-pyridyl)propeno... more ABSTRACT The conformational as well as the structure-forming properties of E-3-(x-pyridyl)propenoic acids (x = 2, 3 or 4) have been studied with a combination of computational and spectroscopic methods. IR spectroscopy revealed that in the solid state the zwitterionic species predominate, while NMR measurements showed that dimers, kept together by strong CO⋯HO hydrogen bonds, were formed in a dipolar aprotic solvent (DMSO). In concentrated solution, extended aggregation occurred through the cooperative effect of (aromatic) CH⋯N weak hydrogen bonds. Conformational search was performed at the HF/6-31G(d,p) level of theory. Comparison with experimental values as well as benchmarking calculations at several different levels of theory to probe the performance of the methods, B3LYP/6-31G++(d,p) method was found to be able to provide reasonable geometries as well as quantitative formation energies for the dimers and the tetramers, too.

Nanostructured Carbon for Advanced Applications, 2001

Raman bands measured in various forms of carbon have a dominant contribution from that frequency ... more Raman bands measured in various forms of carbon have a dominant contribution from that frequency range which is related to disorder, the D band in crystalline graphite. The origin of this band will be discussed with the hope to get a better understanding of the less ordered carbon phases. The consequences of the size effect of nanoscopic particles will be discussed in the reciprocal space with regard to the broadening of spectral lines, e.g., Raman lines. Such broadening helps to analyse amorphous carbon forms.

Vibrational Spectroscopy, 1995

The temperature-induced formation of an intermediate modification (the precursor of the tetranucl... more The temperature-induced formation of an intermediate modification (the precursor of the tetranuclear oxo complex) of straight-chain zinc carboxylates (even numbered between C6 and C18) was studied by means of temperature-dependent Fourier transform infrared spectroscopy and differential scanning calorimetry. The formation of this intermediate modification required only low interaction between the alkyl chains, which could be caused by temperature, solvent or

The 1st International Electronic Conference on Pharmaceutics, 2020

Recent scientific publications have already demonstrated that co-grinding appears to be an effici... more Recent scientific publications have already demonstrated that co-grinding appears to be an efficient, solvent-free technique for preparing cyclodextrin (CD) complexes and improving physicochemical properties (solubility, stability, etc.) of active ingredients. The improvement of solubility and dissolution rate could enhance the biopharmaceutical properties of the active ingredients in pharmaceutical products. In this study terbinafine hydrochloride (TER), an antifungal BCS II drug was chosen as a model drug. The aim of this study was the follow-through of inclusion complex preparation by co-grinding, using several analytical methods. TER and two amorphous cyclodextrin derivatives (hydroxypropyl-β-cyclodextrin (HPBCD); heptakis-(2,6-di-O-methyl)-β-cyclodextrin (DIMEB)) were used for the preparation of products. Products were analyzed by differential scanning calorimetry (DSC), X-ray powder diffractometry (XRPD), hot-humidity stage X-ray powder diffractometry (HOT-XRPD), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FT-IR). Dissolution studies of TER and products were also performed out. DSC and XRPD studies suggested that the crystallinity of products gradually decreased by the increasing grinding time, and after 75 min of co-grinding the products were completely amorphous. HOT-XRPD studies revealed that the amorphous product containing HPBCD did not change with increasing temperature. However, in the same process, the DIMEB-containing product recrystallized in a new crystalline phase. Raman and FT-IR spectroscopy confirmed the molecular interactions between the components. Dissolution studies showed that the dissolution rate of complexes improved, and the solubility of TER increased in both simulated gastric and intestinal fluid, depending on the pH of the dissolution medium.

Acta Silvatica & Lignaria Hungarica, 2005

We investigated energy dependence of the effect of UV-laser irradiation on the DRIFT spectra of s... more We investigated energy dependence of the effect of UV-laser irradiation on the DRIFT spectra of softwood samples. Changes in the spectra of softwoods have been studied with 248.5 nm wavelength of UV-laser radiation. To monitor the energy dependence, different number of laser impulses were directed towards the sample's surface. The dependence on energy of different bands can be listed into four groups. Broad absorption bands, which belong to the same chemical groups located at various positions, do not show consistent changes due to the absorption of different energy dozes. The intensity of OH bands for the treated samples can be higher or lower depending on the amount of radiation energy. In the CHn and in the band of non-conjugated carbonyl groups only absorption increase can be observed. Bands resulting from only one chemical component, and containing no other absorption maxima around them, uniformly decreased. The regions where the band of a chemical component lies next to an...

Journal of Coating Science and Technology, 2014

Two different preparation methods were developed to cover successfully multi-walled carbon nanotu... more Two different preparation methods were developed to cover successfully multi-walled carbon nanotubes (MWCNT) with tin-dioxide (SnO2) nanoparticles using SnCl2 2H2O as precursor under different solvent conditions. The applied mass ratios of the components were 1:4, 1:8, 1:16, 1:32 and 1:64, respectively. As-prepared tin-dioxide coverages were characterized by TEM, SEM, SEM-EDX, Raman microscopy, BET and X-ray diffraction techniques. Photocatalytic efficiencies of selected composites were investigated in a self-made photoreactor, equipped with UV-A fluorescence lamps. Photocatalytic degradation of phenol solution was followed by using HPLC. Observations revealed that using hydrothermal method we can easily control the layer of SnO2 nanoparticles on the surface of MWCNTs. Using various solvents SnO2 nanoparticles with different morphologies formed. The nanocomposites have low photocatalytic efficiencies under conditions used generally (when >300 nm).

Carbon, 2013

ABSTRACT We have prepared multiwalled carbon nanotube (MWCNT)/In2O3 composites using a simple imp... more 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.

Introduction Our best knowledge this is the first occasion when this type of UV-laser used to stu... more Introduction Our best knowledge this is the first occasion when this type of UV-laser used to study the photodegradation of lignin. In our method exactly o ne wavelength is emitted by the laser in contrast the traditional methods where beside the w id range of UV light considerable amount of visible light and infrared radiation are also em itted. So the result of irradiation by UV-laser must be more identical than the other irradiations, where the results are influenced by other different effects. The effect of irradiation by light of different wav elength were studied in the case of thermomechanical pulp by Kimura et al. (1994). It w as established that the aromatic ring structure in lignin and the C-O and C-H bonds in th e wood carbohydrates decreased much more rapidly at shorter irradiation wavelengths for b th unbleached and bleached samples. Recently, Barta et al.(1998) reported the photodegr adation of eight wood species by using of Excimer UV-laser. The changes reported in th...