Pajzderska A.,Adam Mickiewicz University |
Gonzalez M.A.,Laue Langevin Institute |
Embs J.P.,Paul Scherrer Institute |
Mielcarek J.,Poznan University of Medical Sciences |
And 2 more authors.
RSC Advances | Year: 2017
The dynamics of methyl groups in crystalline and amorphous diazepam were investigated by a combination of molecular dynamics simulations and quasielastic neutron spectroscopy methods. The reorientation of the methyl group with a single correlation time was detected in crystalline diazepam. On the other hand, methyl group rotations in the amorphous sample cannot be represented by a single relaxation time and a distribution of correlation times approximated by a log-normal function is needed to explain both the simulation and neutron results. Additionally, MD simulations showed that the intermolecular part of the interactions due to the different environment around each methyl group is responsible for the distribution of correlation times observed experimentally. © 2017 The Royal Society of Chemistry.
Tarnacka M.,University of Silesia |
Adrjanowicz K.,University of Silesia |
Adrjanowicz K.,NanoBioMedical Center |
Kaminska E.,University of Silesia |
And 11 more authors.
Physical Chemistry Chemical Physics | Year: 2013
Comprehensive molecular dynamics studies of vitrified and cryogrounded itraconazole (Itr) were performed at ambient and elevated pressure. DSC measurements yielded besides melting and glass transition observed during heating and cooling of both samples two further endothermic events at around T = 363 K and T = 346 K. The nature of these transitions was investigated using X-ray diffraction, broadband dielectric spectroscopy and Density Functional Theory calculations. The X-ray measurements indicated that extra ordering in itraconazole is likely to occur. Based on calculations and theory derived by Letz et al.15 the transition observed at T = 363 K was discussed in the context of formation of the nematic mesophase. In fact, additional FTIR measurements revealed that order parameter variation in Itr shows a typical sequence of liquid crystal phases with axially symmetric orientational order; i.e. a nematic phase in the temperature range 361.7 K to 346.5 K and a smectic A phase below 346.5. Moreover, dielectric measurements demonstrated that except for the structural relaxation process, there is also slower mode above the glass transition temperature in both vitrified and cryogrounded samples. We considered the origin of this mode taking into account DFT calculations, rod like shape of itraconazole and distribution of its dipole moment vectors. For the dielectric data collected at elevated pressure, evolution of the steepness index versus pressure was determined. Finally, the pressure coefficient of the glass transition temperature was evaluated to be equal to 190 K GPa -1. © 2013 the Owner Societies.
Kossack W.,University of Leipzig |
Kipnusu W.K.,University of Leipzig |
Dulski M.,University of Silesia |
Adrjanowicz K.,NanoBioMedical Center |
And 6 more authors.
Journal of Chemical Physics | Year: 2014
Fourier Transform Infrared Spectroscopy and Broadband Dielectric Spectroscopy are combined to trace kinetics of mutarotation in L-fucose. After quenching molten samples down to temperatures between T = 313 K and 328 K, the concentrations of two anomeric species change according to a simple exponential time dependence, as seen by an increase in absorbance of specific IR-vibrations. In contrast, the dielectric spectra reveal a slowing down of the structural (α-) relaxation process according to a stretched exponential time dependence (stretching exponent of 1.5 ± 0.2). The rates of change in the IR absorption for α- and β-fucopyranose are (at T = 313 K) nearly one decade faster than that of the intermolecular interactions as measured by the shift of the α-relaxation. This reflects the fact that the α-relaxation monitors the equilibration at a mesoscopic length scale, resulting from fluctuations in the anomeric composition. © 2014 AIP Publishing LLC.
PubMed | NanoBioMedical Center, University of Silesia and Leibniz Institute of Polymer Research
Type: Journal Article | Journal: The Journal of chemical physics | Year: 2015
Pressure-Volume-Temperature (PVT) measurements and broadband dielectric spectroscopy were carried out to investigate molecular dynamics and to test the validity of thermodynamic scaling of two homologous compounds of pharmaceutical activity: itraconazole and ketoconazole in the wide range of thermodynamic conditions. The pressure coefficients of the glass transition temperature (dT(g)/dp) for itraconazole and ketoconazole were determined to be equal to 183 and 228 K/GPa, respectively. However, for itraconazole, the additional transition to the nematic phase was observed and characterized by the pressure coefficient dT(n)/dp = 258 K/GPa. From PVT and dielectric data, we obtained that the liquid-nematic phase transition is governed by the relaxation time since it occurred at constant () = 10(-5) s. Furthermore, we plotted the obtained relaxation times as a function of T(-1)v(-), which has revealed that the validity of thermodynamic scaling with the exponent equals to 3.69 0.04 and 3.64 0.03 for itraconazole and ketoconazole, respectively. Further analysis of the scaling parameter in itraconazole revealed that it unexpectedly decreases with increasing relaxation time, which resulted in dramatic change of the shape of the thermodynamic scaling master curve. While in the case of ketoconazole, it remained the same within entire range of data (within experimental uncertainty). We suppose that in case of itraconazole, this peculiar behavior is related to the liquid crystals properties of itraconazole molecule.
Siuzdak K.,Szewalski Institute of Fluid Flow Machinery |
Sawczak M.,Szewalski Institute of Fluid Flow Machinery |
Klein M.,Szewalski Institute of Fluid Flow Machinery |
Klein M.,Technical University of Gdansk |
And 3 more authors.
Physical Chemistry Chemical Physics | Year: 2014
We report on the preparation method of nanocrystalline titanium dioxide modified with platinum by using nanosecond laser ablation in liquid (LAL). Titania in the form of anatase crystals has been prepared in a two-stage process. Initially, irradiation by laser beam of a titanium metal plate fixed in a glass container filled with deionized water was conducted. After that, the ablation process was continued, with the use of a platinum target placed in a freshly obtained titania colloid. In this work, characterization of the obtained nanoparticles, based on spectroscopic techniques-Raman, X-ray photoelectron and UV-vis reflectance spectroscopy-is given. High resolution transmission electron microscopy was used to describe particle morphology. On the basis of photocatalytic studies we observed the rate of degradation process of methylene blue (MB) (a model organic pollution) in the presence of Pt modified titania in comparison to pure TiO2-as a reference case. Physical and chemical mechanisms of the formation of platinum modified titania are also discussed here. Stable colloidal suspensions containing Pt modified titanium dioxide crystalline anatase particles show an almost perfect spherical shape with diameters ranging from 5 to 30 nm. The TiO2 nanoparticles decorated with platinum exhibit much higher (up to 30%) photocatalytic activity towards the degradation of MB under UV illumination than pure titania. This journal is © the Partner Organisations 2014.
Sterczynska A.,NanoBioMedical Center |
Sterczynska A.,Adam Mickiewicz University |
Derylo-Marczewska A.,Maria Curie Sklodowska University |
liwinska-Bartkowiak M.,Adam Mickiewicz University |
And 5 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2014
We report the melting behaviour of a dipolar cyclic siloxane liquid: octamethylcyclotetrasiloxane (OMCTS) confined in three mesoporous silica matrices: Al-SBA-15, SBA-15 and CPG glasses, using differential scanning calorimetry and dielectric spectroscopy. We investigate the influence of acid sites on the adsorptive properties of mesoporous silica materials, which were synthesized by applying Pluronic-type polymers as pore-creating agents. Aluminosilicate matrices have been synthesized by direct synthesis procedure using aluminium chloride. These materials characterized by N2sorption measurements, and the small-angle X-ray scattering data exhibit the same hexagonal P6 mm structure with a mean mesopores size of 4.6 nm (Al-SBA-15) and 4.9 nm (SBA-15). The controlled pore glasses used in this experiment have pores of mean diameter of 7.5 nm. For all systems studied, the OMCTS melting point in pores has been found to decrease with decreasing pore diameter. This result is in qualitative agreement with that obtained in molecular simulation where the adsorbate-wall interactions are weak compared to the adsorbate-adsorbate interactions. © 2014 The Author(s).
Ventura J.,University of Barcelona |
Polo M.C.,University of Barcelona |
Ferrater C.,University of Barcelona |
Hernandez S.,University of Barcelona |
And 6 more authors.
Applied Surface Science | Year: 2016
The isovalent susbstitution of Ti4+ by Zr4+ in BaZrxTi1-xO3 modifies the dielectric character of ferroelectric BaTiO3 yielding different behaviours such as relaxor, polar cluster, etc. The dynamic coupling between BaTiO3 polar nanoregions and BaZrO3 nonpolar ones as well as microstrain between them are thought to be behind such a rich phase diagram. However, these short-range compositonal variations are elusive to detect and this topic is thus rarely addressed. We have grown epitaxial thin films of BaZrxTi1-xO3 on (001)-oriented SrTiO3 substrates by pulsed laser deposition sweeping the entire composition range between BaTiO3 and BaZrO3 in increments of 0.1 in x. Several characterization techniques (AFM, TEM, XRD, Raman spectroscopy) were used for this research in order to understand the morphological and structural properties of the deposited films. Ellipsometric measurements allowed the calculation of the band gap energy of the films. This work demonstrates the existence of a heterogeneous distribution in the substitution of titanium by zirconium yielding relaxor and polar cluster nanoregions. © 2015 Elsevier B.V.
Dobosz B.,Adam Mickiewicz University |
Krzyminiewski R.,Adam Mickiewicz University |
Koralewski M.,Adam Mickiewicz University |
Halupka-Bryl M.,Adam Mickiewicz University |
Halupka-Bryl M.,Nanobiomedical Center
Journal of Magnetism and Magnetic Materials | Year: 2016
We present ESR measurements of non-interacting magnetic nanoparticle systems. Temperature and orientational dependence of ESR spectra were measured for Fe3O4 nanoparticle coated by dextran or oleic acid, frozen in different magnetic field. Several parameters describing magnetic properties such as g-factor, line width, the anisotropy constant were calculated and discussed. The ESR spectra of investigated nanoparticles were also subjected to Computer Resolution Enhancement Method (CREM). This procedure allows to separate a narrow line on the background of the broad line, which presence in this type of materials was recognized in the recent literature and have been further discussed in the paper. CREM is a valuable tool for monitoring of changes on the surface of magnetic core of nanoparticles. © 2016 Elsevier B.V. All rights reserved.
Rucinska-Sobkowiak R.,Adam Mickiewicz University |
Nowaczyk G.,Adam Mickiewicz University |
Nowaczyk G.,NanoBioMedical Center |
Krzeslowska M.,Adam Mickiewicz University |
And 3 more authors.
Environmental and Experimental Botany | Year: 2013
Water status and diffusion transport were studied in the roots of yellow lupine (Lupinus luteus L., cv. Juno) treated for 48h with two selected concentrations of Pb(NO3)2: 150mgl-1, which inhibited root growth by about 50% (medium stress intensity), as well as 350mgl-1, which almost entirely suppressed root elongation (severe stress intensity). Relative water content (RWC), which characterizes the degree of root water saturation, slightly increased at the lower lead concentration and remained unchanged at the higher lead dose. Ultrastructure analyses under a transmission electron microscope revealed that plasmolysis was not evoked by lead in the apical part of the meristem. Moreover, direct observation of meristem cells using Nomarsky optics indicated enhanced vacuolization in the presence of both lead concentrations. These data suggest that the water status of the roots was not affected by the metal. Due to the fact that proline is involved in the maintenance of turgor in the cells, the metabolism of this amino acid was investigated. In the roots, the activity of enzymes involved in proline synthesis, such as pyrroline-5-carboxylate synthetase (P5CS) and ornithine aminotransferase (OAT), increased at 150mgl-1 Pb2+; nevertheless, proline content was diminished at the lower lead concentration. This effect is likely the result of proline degradation by proline dehydrogenase (PDH), since the activity of this enzyme increased at the lower lead dose. On the other hand, in the presence of 350mgl-1 Pb2+, a low level of proline was correlated with a decrease in the activity of P5CS and OAT, as well as unchanged PDH activity in lupine roots. These data may imply that enzymatic synthesis of proline was strongly damaged by the metal ions. The low level of proline in both experimental variants suggests that proline accumulation is inessential to maintaining the osmotic uptake of water into root cells. NMR spectroscopy showed that exposition of lupine seedlings to lead caused a deceleration in water transport in the roots due to a reduction in the water transfer rate across the membranes (transmembrane transfer) and vacuoles continuum, as well as water diffusion along the root apoplast. Fluorescence staining and immunogold labeling showed the presence of callose strands in cell walls and/or in the vicinity of them. In lead-treated lupine roots, callose was mainly localized in the parenchyma cortex placed lengthwise to the vascular cylinder. Callose deposits in the cell walls may reduce vacuolar transport, as well as increase cell wall resistance to water flow. Deceleration of diffusional water movement to the vascular system, may in turn, influence the rate of long-distance water transport to aerial parts of the plant. © 2012 Elsevier B.V.
Jancelewicz M.,Adam Mickiewicz University |
Jancelewicz M.,NanoBioMedical Center |
Fojud Z.,Adam Mickiewicz University |
Waszkowiak W.,Adam Mickiewicz University |
And 2 more authors.
European Polymer Journal | Year: 2011
Spin-lattice relaxation time constants, T 1, were studied for low-molecular-weight linear and grafted polydimethylsiloxane over a wide temperature and frequency range. Quantitative evaluations of proton T 1 measurements indicated two relaxation processes: anisotropic rotation of methyl groups around the Si-C bond (low temperature process) and motions of the PDMS side-chains connected with the glass transition (high temperature process). Additional analyses of the T 1 relaxation dispersion profiles revealed specific local segment fluctuation times, which are characteristic of the coherent motions in the grafted polymer chains. © 2010 Elsevier Ltd. All rights reserved.