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od 2020-09-20

Dr Mariusz Jancelewicz  | 1999-10 <> 2008-12

Doktorant

   CNBM UAM      +48 61-829-5022       marcel@hoth.amu.edu.pl

  0000-0003-2813-1574     25321144800  

Zainteresowania naukowe:
Polimery, dynamika molekularna polimerów w stanie stopionym

Publikacje                          Seminaria


19.

Jenczyk J., Woźniak-Budych M., Jancelewicz M., Jarek M., Jurga S.

Structural and dynamic study of block copolymer - Nanoparticles nanocomposites Nanocomposites based on block copolymer (BCP) and gold nanoparticles (NPs) filler were measured in terms of their structure and polymer chain molecular dynamics. NPs were functionalized in order to gain selective affinity to one specific type of BCP domain. BCP directed NPs assembly was monitored using atomic force microscopy. Thin nanocomposite films were fabricated via spin-coating technique, annealed and subsequently subjected to reactive ion etching in order to expose inorganic NPs location within the BCP matrix. Selective NPs incorporation was confirmed. Furthermore, interesting NPs distribution in quasi-2D crystallites was revealed. Spectroscopic methods (nuclear magnetic resonance and dielectric spectroscopy) enabled investigation of polymer chain reorientations and estimation of the impact of nano-filler on polymer dynamics. Nanocomposite crystallinity was assessed via thermal analysis and supported by spectroscopic techniques.

Polymer, 167, 130-137 (2019)

DOI: 10.1016/j.polymer.2019.01.080   (Pobrane:  2019-03-19)


18.

Pavlenko M., Siuzdak K., Coy L.E., Jancelewicz M., Jurga S., Iatsunskyi I.

Silicon/TiO2 core-shell nanopillar photoanodes for enhanced photoelectrochemical water oxidation Nanostructured Si/TiO2 core-shell nanopillar (NP) photoanodes were synthesized to overcome photodegradation stability of Si and to enhance the efficiency for photoelectrochemical water splitting. The core-shell structures were fabricated by atomic layer deposition of TiO2 onto Si nanopillars synthesized by metal-assisted chemical etching and nanosphere lithography. Scanning electron microscopy, transmission electron microscopy, Raman and reflectance spectroscopies were utilized to characterize fabricated photoanodes. The obtained Si/TiO2 core-shell NP arrays exhibit less than 6% of optical reflectance in UV and visible region, providing good optical absorption. Photoelectrochemical (PEC) water oxidation of fabricated photoanodes was studied. We showed that n-Si/n-TiO2 NP exhibited a larger photocurrent than p-Si/n-TiO2 due to a barrier at the heterojunction. Optimal morphological parameter of Si/TiO2 NP for enhanced PEC water splitting were found. We demonstrated its enhanced PEC performance with a photocurrent density of 1.5 mA/cm2 under simulated solar radiation with intensity of 100 mW/cm2. The relationship between the PEC performance and the electrolyte pH was also discussed. The design of the geometry of Si/TiO2 core-shell NP arrays offers a new approach for preparing stable and highly efficient photoanodes for PEC water splitting.

International Journal of Hydrogen Energy, 42(51), 30076-30085 (2017)

DOI: 10.1016/j.ijhydene.2017.10.033   (Pobrane:  2017-12-21)


17.

Gierszewski M., Glinka A., Gradzka I., Jancelewicz M., Ziółek M.

Effects of post-assembly molecular and atomic passivation of sensitized titania surface: dynamics of electron transfer measured from femtoseconds to seconds The dynamics of electron transfer at the dye-titania and titania-electrolyte interfaces is investigated in two post-sensitization processes: (i) atomic layer deposition of blocking alumina coating and (ii) hierarchical molecular multicapping. To measure the electron transfer dynamics, time-resolved spectroscopic methods (femtosecond transient absorption on the time scale from femtoseconds to nanoseconds and electrochemical impedance spectroscopy on the time scale from milliseconds to seconds) are applied to the complete dye-sensitized solar cells with cobalt-based electrolyte and champion ADEKA-1 dye (with silyl-anchor unit) or its popular carboxyl-anchor analogue, MK-2 dye. Both molecular capping and alumina blocking layers slow down the electron injection process (the average rate constant decreases from 1.1 ps-1 to 0.4 ps-1) and partial sub-nanosecond back electron transfer from titania to the dye (from ca. 10 ns-1 to 5 ns-1). Very small alumina layers (of 0.1 nm thickness) have the highest impact on reducing the rate constants of these electron transfer processes, and for the thicknesses greater than 0.3 nm the rate constants hardly change. In contrast, the electron recombination between titania and electrolyte, occurring on the millisecond time scale, starts to be significantly suppressed for the blocking layers of 0.3 nm or more in thickness (up to ca. 20 times for 0.5 nm thickness with respect to that for untreated sample), improving open circuit voltage and fill factor of the cells. The amplitude of the relative photocurrent (short circuit current per number of absorbed photons) is found to depend almost exclusively on the ultrafast and fast processes taking place in the first nanoseconds after dye excitation. The positive impact of coadsorbents on the solar cells performance for both ADEKA-1 and MK-2 is also studied.

ACS Applied Materials & Interfaces, 9(20), 17102-17114 (2017)

DOI: 10.1021/acsami.7b03288


16.

Coy E. Yate L., Kabacińska Z., Jancelewicz M., Jurga S., Iatsunskyi I.

Topographic reconstruction and mechanical analysis of atomic layer deposited Al2O3/TiO2 nanolaminates by nanoindentation A novel method of nanomechanical testing of multilayered Al2O3/TiO2 nanolaminates was implemented by the nanoindentation technique. The indentation data were reconstructed and filtered by a statistical analysis algorithm and presented as a function of the penetration depth of the indenter. Results show the increment of mechanical properties on the laminates as a function of the amorphous interfaces of the individual layers and the effective control of the wear rate of the structures for further applications. The results presented show both important insights on the mechanical behavior of nanolaminates and the further applicability of the reconstruction model for error reduction on mechanical testing of nanolaminate samples. boratory efficiencies of dye-sensitized

Materials & Design, 111, 584-591 (2016)

DOI: 10.1016/j.matdes.2016.09.030   (Pobrane:  2018-04-03)


15.

Skonieczny R., Popielarski P., Bała W., Fabisiak K., Paprocki K., Jancelewicz M., Kowalska M., Szybowicz M.

Effect of annealing temperature on optical and electrical properties of metallophthalocyanine thin films deposited on silicon substrate The cobalt phthalocyanine (CoPc) thin films (300 nm thick) deposited on n-type silicon substrate have been studied using micro-Raman spectroscopy, atomic force spectroscopy (AFM) and I-V measurement. The CoPc thin layers have been deposited at room temperature by the quasi-molecular beam evaporation technique. The micro-Raman spectra of CoPc thin films have been recorded in the spectral range of 1000 cm-1 to 1900 cm-1 using 488 nm excitation wavelength. Moreover, using surface Raman mapping it was possible to obtain information about polymorphic forms distribution (before and after annealing) of metallophthalocyanine (α and β form) from polarized Raman spectra. The I-V characteristics of the Au/CoPc/n-Si/Al Schottky barrier were also investigated. The obtained results showed that influence of the annealing process plays a crucial role in the ordering and electrical conductivity of the molecular structure of CoPc thin films deposited on n-type silicon substrate.

Materials Science-Poland, 34(3), 676-683 (2016)

DOI: 10.1515/msp-2016-0086   (Pobrane:  2020-10-21)


14.

Sobuś J., Gierczyk B., Burdziński G., Jancelewicz M., Polański E., Hagfeldt A. Ziółek M.

Factors affecting the performance of champion silyl-anchor carbazole dye revealed in the femtosecond to second studies of complete ADEKA-1 sensitized solar cells Record laboratory efficiencies of dye-sensitized solar cells have been recently reported using an alkoxysilyl-anchor dye, ADEKA-1 (over 14 %). In this work we use time-resolved techniques to study the impact of key preparation factors (dye synthesis route, addition of co-adsorbent, use of cobalt-based electrolytes of different redox potential, creation of insulating Al2O3 layers and molecule capping passivation of the electrode) on the partial charge separation efficiencies in ADEKA-1 solar cells. We have observed that unwanted fast recombination of electrons from titania to the dye, probably associated with the orientation of the dyes on the titania surface, plays a crucial role in the performance of the cells. This recombination, taking place on the sub-ns and ns time scales, is suppressed in the optimized dye synthesis methods and upon addition of the co-adsorbent. Capping treatment significantly reduces the charge recombination between titania and electrolyte, improving the electron lifetime from tens of ms to hundreds of ms, or even to single seconds. Similar increase in electron lifetime is observed for homogenous Al2O3 over-layers on titania nanoparticles, however, in this case the total solar cells photocurrent is decreased due to smaller electron injection yield from the dye. Our studies should be important for a broader use of very promising silyl-anchor dyes and the further optimization and development of dye-sensitized solar cells.

Chemistry - A Europen Journal, 22, 1-13 (2016)

DOI: 10.1002/chem.201603059


13.

Idígoras J., Sobuś, J., Jancelewicz M., Azaceta E., Tena-Zaera R., Anta J.A., Ziółek M.

Effect of different photoanode nanostructures on the initial charge separation and electron injection process in dye sensitized solar cells: A photophysical study with indoline dyes Ultrafast and fast charge separation processes were investigated for complete cells based on several ZnO-based photoanode nanostructures and standard TiO2 nanoparticle layers sensitized with the indoline dye coded D358. Different ZnO morphologies (nanoparticles, nanowires, mesoporous), synthesis methods (hydrothermal, gas-phase, electrodeposition in aqueous media and ionic liquid media) and coatings (ZnO-ZnO core-shell, ZnO-TiO2 core-shell) were measured by transient absorption techniques in the time scale from 100 fs to 100 μs and in the visible and near-infrared spectral range. All of ZnO cells show worse electron injection yields with respect to those with standard TiO2 material. Lower refractive index of ZnO than that of TiO2 is suggested to be an additional factor, not considered so far, that can decrease the performance of ZnO-based solar cells. Evidence of the participation of the excited charge transfer state of the dye in the charge separation process is provided here. The lifetime of this state in fully working devices extends from several ps to several tens of ps, which is much longer than the typically postulated electron injection times in all-organic dye-sensitized solar cells. The results here provided, comprising a wide variety of morphologies and preparation methods, point to the universality of the poor performance of ZnO as photoanode material with respect to standard TiO2. © 2015 Elsevier B.V.

Materials Chemistry and Physics, 170(15), 218-228 (2016)

DOI: 10.1016/j.matchemphys.2015.12.042


12.

Pavlenko M., Coy E., Jancelewicz M., Karol Załęski K., Smyntyna V., Jurga S.,Iatsunskyi I.

Enhancement of optical and mechanical properties of Si nanopillars by ALD TiO2 coating The mechanical and optical properties of Si and TiO2-Si nanopillars (NPl) were investigated. Mesoporous silicon NPl arrays were fabricated by metal-assisted chemical etching and nanosphere lithography, and then pillars were covered by TiO2 using the atomic layer deposition technique. We performed scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, reflectance, photoluminescence (PL) spectroscopy and nanoindentation to characterize the as-prepared and annealed TiO2-Si NPl. The main structural and mechanical parameters of TiO2-Si NPl (grain size, strain, critical load, elastic recovery and Young’s module) were calculated. Reflectance and PL spectroscopy were used to study the impact of morphology on optical properties of TiO2-Si NPl before and after annealing. It was established that the nanostructures of TiO2 penetrated inside the porous matrix of Si pillar improve the mechanical properties of TiO2-Si NPl. The results of nanoindentation study have shown that Young’s Modulus of annealed TiO2-Si NPl is about three times higher than for the pure Si NPl.

RSC Advances, 6(99), 97070-97076 (2016)

DOI: 10.1039/c6ra21742g   (Pobrane:  2018-04-03)


11.

Fedorenko V., Iatsunskyi I., Pavlenko M., Jancelewicz M., Coy E., Viter R.

Structural and optical properties of TiO2-Al2O3 nanolaminates produced by atomic layer deposition Structural and optical properties of Al2O3/TiO2 nanolaminates fabricated by atomic layer deposition (ALD) were investigated. We performed Raman spectroscopy, transmission electron microscopy (TEM), X-Ray reflectivity (XRR), UV-Vis spectroscopy, and photoluminescence (PL) spectroscopy to characterize the Al2O3/TiO2 nanolaminates. The main structural and optical parameters of Al2O3/TiO2 nanolaminates were calculated. It was established that with decreasing of the layer thickness, the value of band gap energy increases due to the quantum size effect related to the reduction of the nanograins size. It was also shown that there is an interdiffusion layer at the Al2O3/TiO2 interface which plays a crucial role in explaining the optical properties of Al2O3/TiO2 nanolaminates. Correlation between structural and optical parameters was discussed. © 2015 SPIE.

Proceedings of SPIE - Electro-Optical Remote Sensing, Photonic Technologies, and Applications IX, ISBN: 9781628418590, 9649, 96490X (2015)

DOI: 10.1117/12.2194295
WWW: ISBN: 9781628418590
ISBN:


10.

Iatsunskyi I., Coy E., Viter R., Nowaczyk G., Jancelewicz M., Baleviciute I., Załęski K., Jurga S.

Study on structural, mechanical and optical properties of Al2O3-TiO2 nanolaminates prepared by atomic layer deposition Structural, optical, and mechanical properties of Al2O3/TiO2 nanolaminates fabricated by atomic layer deposition (ALD) were investigated. We performed transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray reflectivity (XRR), energy dispersive X-ray spectroscopy (EDX), ellipsometry, UV-vis spectroscopy, photoluminescence (PL) spectroscopy, and nanointendation to characterize the Al2O3/TiO2 nanolaminates. The main structural, optical, and mechanical parameters of Al2O3/TiO2 nanolaminates (thickness, grain size, refractive index, extinction coefficient, band gap, hardness, and Young’s module) were calculated. It was established that with decreasing of the layer thickness, the value of band gap energy increases due to the quantum size effect related to the reduction of the nanograins size. On the other hand, the decreasing of nanograins size leads to generation of interface defects and, as a consequence, to the increasing of Urbach energy. It was also shown that there is an interdiffusion layer at the Al2O3-TiO2 interface, which plays a crucial role in explaining mechanical and optical properties of Al2O3/TiO2 nanolaminates. The correlation between structural, optical, and mechanical parameters was discussed.

Journal of Physical Chemistry C, 119(35), 20591-20599 (2015)

DOI: 10.1021/acs.jpcc.5b06745


9.

Iatsunskyi I., Jancelewicz M., Nowaczyk G., Kempiński M., Peplińska B., Jarek M., Załęski K., Jurga S., Smyntyna V.

Atomic layer deposition TiO2 coated porous silicon surface: Structural characterization and morphological features TiO2 thin films were grown on highly-doped p-Si (100) macro- and mesoporous structures by atomic layer deposition (ALD) using TiCl4 and deionized water as precursors at 300 °C. The crystalline structure, chemical composition, and morphology of the deposited films and initial silicon nanostructures were investigated by scanning electron microscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy and X-ray diffraction (XRD). The mean size of TiO2 crystallites was determined by TEM, XRD and Raman spectroscopy. It was shown that the mean crystallite size and the crystallinity of the TiO2 are influenced dramatically by the morphology of the porous silicon, with the mesoporous silicon resulting in a much finer grain size and amorphous structure than the macroporous silicon having a partially crystal anatase phase. A simple model of the ALD layer growth inside the pores was presented.

Thin Solid Films , 589, 303-308 (2015)

DOI: 10.1016/j.tsf.2015.05.056


8.

Iatsunskyi I., Kempinski M., Nowaczyk G., Jancelewicz M., Pavlenko M., Zaleski K., Jurga S.

Structural and XPS studies of PSi/TiO2 nanocomposites prepared by ALD and Ag-assisted chemical etching PSi/TiO2 nanocomposites fabricated by atomic layer deposition (ALD) and metal-assisted chemical etching (MACE) were investigated. The morphology and phase structure of PSi/TiO2 nanocomposites were studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM) with an energy dispersive X-ray spectroscopy (EDX) and Raman spectroscopy. The mean size of TiO2 nanocrystals was determined by TEM and Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) was used to analyze the chemical elemental composition by observing the behavior of the Ti 2p, 0 1s and Si 2p lines. TEM, Raman spectroscopy and XPS binding energy analysis confirmed the formation of TiO2 anatase phase inside the PSi matrix. The XPS valence band analysis was performed in order to investigate the modification of PSi/TiO2 nanocomposites electronic structure. Surface defects states of Ti3+ at PSi/TiO2 nanocomposites were identified by analyzing of XPS valence band spectra.
(C) 2015 Elsevier B.V. All rights reserved.

Applied Surface Science, 347, 777-783 (2015)

DOI: 10.1016/j.apsusc.2015.04.172


7.

Iatsunskyi I., Pavlenko M., Viter R., Jancelewicz M., Nowaczyk G., Baleviciute I., Załęski K., Jurga S., Ramanavicius A., Smyntyna V.

Tailoring the structural, optical, and photoluminescence properties of porous silicon/TiO2 nanostructures The structural, optical, and photoluminescence properties of porous silicon (PSi)/titanium dioxide (TiO2) nanostructures were investigated. PSi structures consisting of macro- and mesoporous layers were fabricated by metal-assisted chemical etching, and then TiO2 was introduced inside the PSi matrix using the atomic layer deposition technique. We performed scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction, energy dispersive X-ray spectroscopy, Raman spectroscopy, ellipsometry, and photoluminescence (PL) spectroscopy to characterize the prepared and annealed PSi/TiO2 nanostructures. TEM and Raman analyses revealed that TiO2 had a crystalline anatase structure. PL measurements of the PSi/TiO2 composite system showed two broad peaks at approximately 2.4-3 eV (blue PL) and 1.7-1.9 eV (red PL). The mechanisms of the emissions were discussed, and it was found that two main competing recombination mechanisms take place, including radiative recombination through the surface states (surface recombination) and through oxygen vacancies and self-trapped excitons (volume recombination).

Journal of Physical Chemistry C, 119(13), 7164-7171 (2015)

DOI: 10.1021/acs.jpcc.5b01670


6.

Iatsunskyi I., Kempiński M., Jancelewicz M., Załęski K., Jurga S., Smyntyna V.

Structural and XPS characterization of ALD Al2O3 coated porous silicon Al2O3 thin films were grown on highly-doped p-Si (100) macro- and mesoporous structures by atomic layer deposition (ALD) using trimethylaluminum (TMA) and water H2O as precursors at 300 degrees C. The porous silicon (PSi) samples were fabricated utilizing a metal-assisted chemical etching process (MACE). The morphology of the deposited films and initial silicon nanostructures were investigated by means of scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). X-ray photoelectron spectroscopy (XPS) was used to analyze the chemical elemental composition by observing the behavior of the Al 2p, O 1s and C 1s lines. Calculated Auger parameter and binding energy analysis confirmed Al2O3 formation. The measurement of band gap energies of Al2O3 was performed.
(C) 2014 Elsevier Ltd. All rights reserved.

Vacuum, 13, 52-58 (2015)

DOI: 10.1016/j.vacuum.2014.12.015   (Pobrane:  2019-10-15)


5.

Makrocka-Rydzyk M., Wypych A., Dobies M., Jancelewicz M., Jurga S., Cho HY., Gao HF., Matyjaszewski K.

Molecular dynamics in PBA/PEO miktoarm star copolymers Molecular dynamics of miktoarm star copolymers consisting of poly(n-butyl acrylate) PBA and polyethylene oxide (PEO) arms was studied by means of Broadband Dielectric Spectroscopy (BDS) and Nuclear Magnetic Resonance (NMR) methods. The spectroscopic studies were performed for three types of copolymers differing in the composition, namely materials containing 76%, 46% and 16% molar fraction of PBA arms. The local processes, described by the Arrhenius law (e.g. the anisotropic rotation of methyl groups and the anisotropic local motions in the PEO chain), were observed for the studied systems below the glass transition temperature. It was found that the investigated PBA/PEO miktoarm star copolymers are characterized by single glass transition, which may result from similar values of glass transition temperatures of the PBA and PEO polymers. The segmental dynamics in the studied systems was quantitatively described by using the Vogel-Fulcher-Tammann (VFT) relation applied to combined NMR and BDS data. Moreover, above the glass transition temperature the interfacial polarization and conductivity phenomena were detected with the BDS method for all systems under study.
(C) 2013 Elsevier Ltd. All rights reserved.

Polymer, 54(13), 3341-3349 (2013)

DOI: 10.1016/j.polymer.2013.04.004


4.

Jancelewicz M., Fojud Z., Waszkowiak W., Jurga S.

Local mobility in grafted polydimethylsiloxane melts 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.
(C) 2010 Elsevier Ltd All rights reserved

European Polymer Journal, 47(1), 48-51 (2011)

DOI: 10.1016/j.eurpolymj.2010.10.032


3.

Jancelewicz M., Nowaczyk G., Makrocka-Rydzyk M., Wypych A., Fojud Z., Jurga S., Maciejewski H.

Molecular dynamics in grafted polydimethylsiloxanes Rheological and dielectric behavior of linear PDMS and alkyl-modified PDMS melts has been studied. Molecular dynamics of linear PDMS, being a model of grafted polydimethylsiloxanes studied, has been examined carefully with particular attention paid to its ability to form the semicrystalline phase. Random incorporation of alkyl groups into PDMS chain has been shown to prevent the polymer crystallization. The glass transition temperature of the grafted PDMS changes proportionally to the modifier content. Both techniques allow characterization of the main alpha-relaxation, which is related to the glass transition and exhibits similar behavior in all systems. This relaxation is discussed in terms of the Vogel-Fulcher-Tammann-Hesse (VFTH) approach. The fragility of grafted PDMS materials was found to be higher as compared to the linear polymer. The analysis of the rheological data shows the existence of additional slow relaxation, which has been interpreted as the polymer chain motion.
(C) 2010 Elsevier B.V. All rights reserved.

Journal of Non-Crystalline Solids, 356(11-17), 669-675 (2010)

DOI: 10.1016/j.jnoncrysol.2009.07.036   (Pobrane:  2020-10-21)


2.

Garnczarska M., Bednarski W., Jancelewicz M.

Ability of lupine seeds to germinate and to tolerate desiccation as related to changes in free radicals level and antioxidants in freshly harvested seeds Seeds of yellow lupine (Lupinus Luteus L cv. Juno) were collected throughout their development on the mother plant to determine whether the ability to germinate and to tolerate desiccation is related to the level of free radicals and the changes in the redox state of ascorbate and glutathione as well as the activities of antioxidative enzymes. Electron paramagnetic resonance (EPR)-based analyses showed that development of lupine seed was accompanied by generation of free radicals with g(1) and g(2) values of 2.0049 ± 0.0004 and 2.0029 ± 0.0003, respectively. Free radical level increased significantly 25 DAF and decreased thereafter. The amount of hydrogen peroxide was high in fresh immature seeds and decreased during maturation drying. Ascorbate accumulated in lupine embryos during early seed filling stage whereas glutathione content increased during late seed filling phase. During maturation drying the redox state of both ascorbate and glutathione pools shifted towards the oxidized forms. While superoxide dismutase (SOD, EC 1.15.1.1), and ascorbate peroxidase (APX, EC 1.11.1.11) activities remained high at the early seed filling stage the activities of both dehydroascorbate reductase (DHAR, EC 1.8.5.1) and glutathione reductase (GR, EC 1.6.4.2) and that of catalase (CAT, EC 1.11.1.6) increased before seeds reached physiological maturity and decreased thereafter. The changes of isoform patterns of antioxidative enzymes were observed during seed maturation. Immature lupine seeds tested immediately after harvest acquired the ability to germinate when less than half-filled and reached high tolerance to desiccation just after physiological maturity. The physiological implications of the changes in antioxidative machinery for the acquisition of desiccation tolerance and seeds germinability are discussed.
(C) 2008 Elsevier Masson SAS. All rights reserved.

Plant Physiology and Biochemistry, 47(1), 56-62 (2009)

DOI: 10.1016/j.plaphy.2008.09.003   (Pobrane:  2020-10-25)


1.

Nozirov F., Fojud Z., Jancelewicz M., Nazirov A., Jurga S.

Molecular motion in the biocopolymer sequence of glycolide and lactide studied by solid state NMR This paper reports a nuclear magnetic resonance study of the molecular motion in copolymers derived from glycolide and L-lactide in the solid state. Variation of T-1 relaxation times with temperature reflects a local disorder and the fast segment conformational motions which can be quantified in terms of correlation times predicted by the Bloembergen-Purcell-Pound and Davidson-Cole models. At low temperatures, spin relaxation is dominated by the axial methyl rotation in lactide units described by an asymmetry parameter of the correlation time delta which takes a value of about 0.45 for all systems. Above the devitrification points the trans and gauche isomerization in glycolide segments occurs. In addition to the chemical structure characterization, solid-state magic-angle spinning spectroscopy gives an insight into the role of glycol segments in the chain mobility.

Applied Magnetic Resonance, 34(1-2), 193-203 (2008)

DOI: 10.1007/s00723-008-0102-z   (Pobrane:  2020-10-23)


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