Publications by authors named "Czesław Kapusta"

25 Publications

  • Page 1 of 1

Structure, Morphology, Heat Capacity, and Electrical Transport Properties of Ti(Al,Si)C Materials.

Materials (Basel) 2021 Jun 11;14(12). Epub 2021 Jun 11.

Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, Poland.

A study of TiAlSiC ( = 0 to = 1) MAX-phase alloys is reported. The materials were obtained from mixtures of TiAlC and TiSiC powders with hot pressing sintering technique. They were characterised with X-ray diffraction, heat capacity, electrical resistivity, and magnetoresistance measurements. The results show a good quality crystal structure and metallic properties with high residual resistivity. The resistivity weakly varies with Si doping and shows a small, positive magnetoresistance effect. The magnetoresistance exhibits a quadratic dependence on the magnetic field, which indicates a dominant contribution from open electronic orbits. The Debye temperatures and Sommerfeld coefficient values derived from specific heat data show slight variations with Si content, with decreasing tendency for the former and an increase for the latter. Experimental results were supported by band structure calculations whose results are consistent with the experiment concerning specific heat, resistivity, and magnetoresistance measurements. In particular, they reveal that of the s-electrons at the Fermi level, those of Al and Si have prevailing density of states and, thus predominantly contribute to the metallic conductivity. This also shows that the high residual resistivity of the materials studied is an intrinsic effect, not due to defects of the crystal structure.
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http://dx.doi.org/10.3390/ma14123222DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8230697PMC
June 2021

Enhanced Thermal Conductivity of Polyamide-Based Nanocomposites Containing Graphene Oxide Sheets Decorated with Compatible Polymer Brushes.

Materials (Basel) 2021 Feb 5;14(4). Epub 2021 Feb 5.

Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland.

Polyamide-based nanocomposites containing graphene platelets decorated with poly(acrylamide) brushes were prepared and characterized. The brushes were grafted from the surface of graphene oxide (GO), a thermally conductive additive, using atom transfer radical polymerization, which led to the formation of the platelets coated with covalently tethered polymer layers (GO_PAAM), accounting for ca. 31% of the total mass. Polyamide-6 (PA6) nanocomposites containing 1% of GO_PAAM were formed by extrusion followed by injection molding. The thermal conductivity of the nanocomposite was 54% higher than that of PA6 even for such a low content of GO. The result was assigned to strong interfacial interactions between the brushes and PA6 matrix related to hydrogen bonding. Control nanocomposites containing similarly prepared GO decorated with other polymer brushes that are not able to form hydrogen bonds with PA6 revealed no enhancement of the conductivity. Importantly, the nanocomposite containing GO_PAAM also demonstrated larger tensile strength without deteriorating the elongation at break value, which was significantly decreased for the other coated platelets. The proposed approach enhances the interfacial interactions thanks to the covalent tethering of dense polymer brushes on 2D fillers and may be used to improve thermal properties of other polymer-based nanocomposites with simultaneous enhancement of their mechanical properties.
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http://dx.doi.org/10.3390/ma14040751DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7914667PMC
February 2021

Modelling of Effective Thermal Conductivity of Composites Filled with Core-Shell Fillers.

Materials (Basel) 2020 Dec 1;13(23). Epub 2020 Dec 1.

Department of Solid State Physics, Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, 30-059 Krakow, Poland.

An effective model to calculate thermal conductivity of polymer composites using core-shell fillers is presented, wherein a core material of filler grains is covered by a layer of a high-thermal-conductivity (HTC) material. Such fillers can provide a significant increase of the composite thermal conductivity by an addition of a small amount of the HTC material. The model employs the Lewis-Nielsen formula describing filled systems. The effective thermal conductivity of the core-shell filler grains is calculated using the Russel model for porous materials. Modelling results are compared with recent measurements made on composites filled with cellulose microbeads coated with hexagonal boron nitride (h-BN) platelets and good agreement is demonstrated. Comparison with measurements made on epoxy composites, using silver-coated glass spheres as a filler, is also provided. It is demonstrated how the modelling procedure can improve understanding of properties of materials and structures used and mechanisms of thermal conduction within the composite.
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http://dx.doi.org/10.3390/ma13235480DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7731075PMC
December 2020

High-Entropy Perovskites as Multifunctional Metal Oxide Semiconductors: Synthesis and Characterization of (GdNdLaSmY)CoO.

ACS Appl Electron Mater 2020 Oct 18;2(10):3211-3220. Epub 2020 Sep 18.

Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, Al. Mickiewicza 30, 30059 Kraków, Poland.

Single-phase multicomponent perovskite-type cobalt oxide containing five cations in equiatomic amounts on the A-site, namely, (GdNdLaSmY)CoO, has been synthesized via the modified coprecipitation hydrothermal method. Using an original approach for heat treatment, which comprises quenching utilizing liquid nitrogen as a cooling medium, a single-phase ceramic with high configuration entropy, crystallizing in an orthorhombic distorted structure was obtained. It reveals the anomalous temperature dependence of the lattice expansion with two weak transitions at approx. 80 and 240 K that are assigned to gradual crossover from the low- via intermediate- to high-spin state of Co. The compound exhibits weak ferromagnetism at ≤ 10 K and signatures of antiferromagnetic correlations in the paramagnetic phase. Ab initio calculations predict a band gap Δ = 1.18 eV in the ground-state electronic structure with the dominant contribution of O_p and Co_d orbitals in the valence and conduction bands, respectively. Electronic transport measurements confirm the negative temperature coefficient of resistivity characteristic to a semiconducting material and reveal a sudden drop in activation energy at ∼ 240 K from ∼ 1 eV in the low-temperature phase to ∼ 0.3 eV at room temperature. The possibility of fine tuning of the semiconducting band gap via a subtle change in A-site stoichiometry is discussed.
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http://dx.doi.org/10.1021/acsaelm.0c00559DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7660934PMC
October 2020

Correlation of magnetic and magnetoresistive properties of nanoporous Co/Pd thin multilayers fabricated on anodized TiO templates.

Sci Rep 2020 Jul 2;10(1):10838. Epub 2020 Jul 2.

Department of Physics, University of Gothenburg, 41296, Gothenburg, Sweden.

In this study, we consider a technological approach to obtain a high perpendicular magnetic anisotropy of the Co/Pd multilayers deposited on nanoporous TiO templates of different types of surface morphology. It is found that the use of templates with homogeneous and smoothed surface relief, formed on silicon wafers, ensures conservation of perpendicular anisotropy of the deposited films inherent in the continuous multilayers. Also, their magnetic hardening with doubling of the coercive field is observed. However, inhomogeneous magnetic ordering is revealed in the porous films due to the occurrence of magnetically soft regions near the pore edges and/or inside the pores. Modeling of the field dependences of magnetization and electrical resistance indicates that coherent rotation is the dominant mechanism of magnetization reversal in the porous system instead of the domain-wall motion typical of the continuous multilayers, while their magnetoresistance is determined by electron-magnon scattering, similarly to the continuous counterpart. The preservation of spin waves in the porous films indicates a high uniformity of the magnetic ordering in the fabricated porous systems due to a sufficiently regular pores array introduced into the films, despite the existence of soft-magnetic regions. The results are promising for the design and fabrication of future spintronic devices.
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http://dx.doi.org/10.1038/s41598-020-67677-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7331621PMC
July 2020

Thin-Film Engineering of Mechanical Fragmentation Properties of Atomic-Layer-Deposited Metal Oxides.

Nanomaterials (Basel) 2020 Mar 19;10(3). Epub 2020 Mar 19.

Empa-Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures, Feuerwerkerstrasse 39, CH-3602 Thun, Switzerland.

Mechanical fracture properties were studied for the common atomic-layer-deposited AlO, ZnO, TiO, ZrO, and YO thin films, and selected multilayer combinations via uniaxial tensile testing and Weibull statistics. The crack onset strains and interfacial shear strains were studied, and for crack onset strain, TiO/AlO and ZrO/AlO bilayer films exhibited the highest values. The films adhered well to the polyimide carrier substrates, as delamination of the films was not observed. For AlO films, higher deposition temperatures resulted in higher crack onset strain and cohesive strain values, which was explained by the temperature dependence of the residual strain. Doping YO with Al or nanolaminating it with AlO enabled control over the crystal size of YO, and provided us with means for improving the mechanical properties of the YO films. Tensile fracture toughness and fracture energy are reported for AlO films grown at 135 °C, 155 °C, and 220 °C. We present thin-film engineering via multilayering and residual-strain control in order to tailor the mechanical properties of thin-film systems for applications requiring mechanical stretchability and flexibility.
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http://dx.doi.org/10.3390/nano10030558DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7153380PMC
March 2020

Hydrophobically Coated Superparamagnetic Iron Oxides Nanoparticles Incorporated into Polymer-Based Nanocapsules Dispersed in Water.

Materials (Basel) 2020 Mar 9;13(5). Epub 2020 Mar 9.

Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Mickiewicza Av. 30, 30-059 Krakow, Poland.

This paper reports the characterization of iron oxide magnetic nanoparticles obtained via the thermal decomposition of an organometallic precursor, which were then loaded into nanocapsules prepared via the emulsification process in the presence of an amphiphilic derivative of chitosan. The applied synthetic method led to the formation of a hydrophobic layer on the surface of nanoparticles that enabled their loading in the hydrophobic liquid inside of the polymer-based capsules. The average diameter of nanoparticles was determined to be equal to 15 nm, and they were thoroughly characterized using X-ray diffraction (XRD), magnetometry, and Mössbauer spectroscopy. A core-shell structure consisting of a wüstite core and maghemite-like shell was revealed, resulting in an exchange bias effect and a considerable magnetocrystalline anisotropy at low temperatures and a superparamagnetic behavior at room temperature. Importantly, superparamagnetic behavior was observed for the aqueous dispersion of the nanocapsules loaded with the superparamagnetic nanoparticles, and the dispersion was shown to be very stable (at least 48 weeks). The results were analyzed and discussed with respect to the potential future applications of these nanoparticles and nanocapsules based on biopolymers as platforms designed for the magnetically navigated transport of encapsulated hydrophobic substances.
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http://dx.doi.org/10.3390/ma13051219DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7085046PMC
March 2020

Complex magnetic ordering in nanoporous [Co/Pd]-IrMn multilayers with perpendicular magnetic anisotropy and its impact on magnetization reversal and magnetoresistance.

Phys Chem Chem Phys 2020 Feb 31;22(6):3661-3674. Epub 2020 Jan 31.

Department of Physics, University of Gothenburg, 41296 Göteborg, Sweden.

We have systematically investigated the magnetization reversal characteristics and magnetoresistance of continuous and nanoporous [Co/Pd]-IrMn multilayered thin films with perpendicular magnetic anisotropy at different temperatures (4-300 K). For their nanostructuring, porosity was induced by means of deposition onto templates of anodized titania with small (∼30 nm in diameter) homogeneously distributed pores. The magnetization reversal and magnetoresistance of the porous films were found to be closely related to the splitting of the ferromagnetic material into regions with different magnetic properties, in correlation with the complex morphology of the porous system. Independent magnetization reversal is detected for these regions, and is accompanied by its strong impact on the magnetic order in the capping IrMn layer. Electron-magnon scattering is found to be a dominant mechanism of magnetoresistance, determining its almost linear field dependence in a high magnetic field and contributing to its magnetoresistance behavior, similar to magnetization reversal, in a low magnetic field. Partial rotation of IrMn magnetic moments, consistent with the magnetization reversal of the ferromagnet, is proposed as an explanation for the two-state resistance behavior observed in switching between high-resistive and low-resistive values at the magnetization reversal of the porous system studied.
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http://dx.doi.org/10.1039/c9cp05947dDOI Listing
February 2020

Focused Electron Beam-Induced Deposition and Post-Growth Purification Using the Heteroleptic Ru Complex (η-CH)Ru(CO)Br.

ACS Appl Mater Interfaces 2019 Aug 29;11(31):28164-28171. Epub 2019 Jul 29.

Laboratory for Mechanics of Materials and Nanostructures , Empa-Swiss Federal Laboratories for Materials Science and Technology , Feuerwerkerstrasse 39 , CH-3602 Thun , Switzerland.

Focused electron beam-induced deposition using the heteroleptic complex (η-CH)Ru(CO)Br as a precursor resulted in deposition of material with Ru content of 23 at. %. Transmission electron microscopy images indicated a nanogranular structure of pure Ru nanocrystals, embedded into a matrix containing carbon, oxygen, and bromine. The deposits were purified by annealing in a reactive 98% N/2% H atmosphere at 300 °C, resulting in a reduction of contaminants and an increase of the Ru content to 83 at. %. Although a significant volume loss of 79% was found, the shrinkage was observed mostly for vertical thickness (around 75%). The lateral dimensions decreased much less significantly (around 9%). Deposition results, in conjunction with previous gas-phase and condensed-phase surface studies on the electron-induced reactions of (η-CH)Ru(CO)Br, provide insights into the behavior of allyl, carbonyl, and bromide ligands under identical electron beam irradiation.
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http://dx.doi.org/10.1021/acsami.9b07634DOI Listing
August 2019

Dynamics of Superparamagnetic Iron Oxide Nanoparticles with Various Polymeric Coatings.

Materials (Basel) 2019 Jun 3;12(11). Epub 2019 Jun 3.

AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Department of Solid State Physics, Mickiewicza 30, 30-059 Krakow, Poland.

In this article, the results of a study of the magnetic dynamics of superparamagnetic iron oxide nanoparticles (SPIONs) with chitosan and polyethylene glycol (PEG) coatings are reported. The materials were prepared by the co-precipitation method and characterized by X-ray diffraction, dynamic light scattering and scanning transmission electron microscopy. It was shown that the cores contain maghemite, and their hydrodynamic diameters vary from 49 nm for PEG-coated to 200 nm for chitosan-coated particles. The magnetic dynamics of the nanoparticles in terms of the function of temperature was studied with magnetic susceptometry and Mössbauer spectroscopy. Their superparamagnetic fluctuations frequencies, determined from the fits of Mössbauer spectra, range from tens to hundreds of megahertz at room temperature and mostly decrease in the applied magnetic field. For water suspensions of nanoparticles, maxima are observed in the absorption part of magnetic susceptibility and they shift to higher temperatures with increasing excitation frequency. A step-like decrease of the susceptibility occurs at freezing, and from that, the Brown's and Néel's contributions are extracted and compared for nanoparticles differing in core sizes and types of coating. The results are analyzed and discussed with respect to the tailoring of the dynamic properties of these nanoparticle materials for requirements related to the characteristic frequency ranges of MRI and electromagnetic field hyperthermia.
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http://dx.doi.org/10.3390/ma12111793DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6600702PMC
June 2019

Magnetically Navigated Core-Shell Polymer Capsules as Nanoreactors Loadable at the Oil/Water Interface.

ACS Appl Mater Interfaces 2019 Mar 12;11(11):10905-10913. Epub 2019 Mar 12.

Faculty of Chemistry , Jagiellonian University , Gronostajowa 2 , 30-387 Krakow , Poland.

Polymer core-shell nanocapsules with magnetic nanoparticles embedded in their oil cores were fabricated and applied as nano(photo)reactors. Superparamagnetic iron oxide nanoparticles (SPIONs) coated with oleic acid were first synthesized and characterized structurally, and their magnetic properties were determined. The capsules with chitosan-based shells were then formed in a one-step process by sonication-assisted mixing of (1) an aqueous solution of the hydrophobically derived chitosan and (2) oleic acid containing the dispersed SPIONs. In this way, magnetic capsules with a diameter of approximately 500-600 nm containing encapsulated SPIONs with an average diameter of approximately 20-30 nm were formed as revealed by dynamic light scattering and scanning transmission electron microscopy measurements. The composition and magnetic properties of the formed capsules were also followed using dynamic light scattering, electron microscopies, and magnetic force microscopy. The water-dispersible capsules, thanks to their magnetic properties, were then navigated in a static magnetic field gradient and transferred between the water and oil phases, as evidenced by fluorescence microscopy. In this way, the capsules could be loaded in a controlled way with a hydrophobic reactant, perylene, which was later photooxidized upon transferring the capsules to the aqueous phase. The capsules were shown to serve as robust reloadable nanoreactors/nanocontainers that via magnetic navigation can be transferred between immiscible phases without disruption. These features make them promising reusable systems not only for loading and carrying lipophilic actives, conducting useful reactions in the confined environment of the capsules, but also for magnetically separating and guiding the encapsulated active molecules to the site of action.
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http://dx.doi.org/10.1021/acsami.8b22690DOI Listing
March 2019

Fabrication of Functional Carbon/Magnetic Nanocomposites as A Promising Model of Utilization of Used Crosslinked Polymers.

Materials (Basel) 2018 Dec 19;11(12). Epub 2018 Dec 19.

Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, Mickiewicza 30, 30-059 Krakow, Poland.

The utilization of used crosslinked functional polymers (CFP) applied as sorbents or ion-exchangers is a great challenge arising from the need to protect the environment. In this paper we report a very promising way of obtaining carbon/magnetic composites based on metal (Co; Ni; Fe) derivatives of butadiene rubber-based phosphorus-containing polymer, which were treated as the model used CFP. We proposed a facile one-step thermal degradation approach to transform used CFP into carbon/magnetic composites (CMC). The obtained CMCs contained a mixture of metal phosphates and metal phosphides that exhibited strong magnetic properties due to the presence of nanosized metal derivatives with diameters of 100⁻140 nm. Structural and morphological changes of CFP and CMC after thermal degradation were investigated by the FTIR technique, X-ray Diffraction analysis, Scanning Electron Microscope, and Atomic Force Microscope⁻Magnetic Force Microscope. Moreover, thermal degradation kinetics parameters were determined to optimize the efficiency of the process.
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http://dx.doi.org/10.3390/ma11122595DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6316096PMC
December 2018

Selenized polysaccharides - Biosynthesis and structural analysis.

Carbohydr Polym 2018 Oct 15;198:407-417. Epub 2018 Jun 15.

Department of Drug Technology and Pharmaceutical Biotechnology, Medical University of Warsaw, 1 Banacha Str., 02-097 Warszawa, Poland. Electronic address:

The main objective of our research was to analyze the structure of the Se-containing polysaccharides and to examine how the selenium is bound to the polysaccharide molecule. During investigation of the biosynthesis of new immunomodulators, we isolated a selenium (Se)-containing polysaccharide-protein fraction containing proteoglycans of molecular weights of 3.9 × 10 Da and 2.6 × 10 Da, composed of glucose or mannose, nearly 8% of protein and 190 μg Se/g dry weight. X-ray absorption spectroscopy (XAS) data analysis in the near edge region (XANES) confirmed that selenium in the Se-polysaccharides structure is present at the -II oxidation state and that Se is organically bound. The simulation analysis in the EXAFS (extended X-ray absorption fine structure) region suggested that selenium is most likely bound by a glycosidic-link in a β-1,3 or α-1,4-glycosidic bond or substituted for oxygen in a pyranosidic ring. Calculations performed with Gaussian 03 software predicted deformations in the polysaccharide structure caused by the incorporation of the selenium atom including change in bond lengths and torsion angles and, as a result, disappearance of hydrogen bonds in the vicinity of the selenium atoms.
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http://dx.doi.org/10.1016/j.carbpol.2018.06.057DOI Listing
October 2018

Direct Electron Beam Writing of Silver-Based Nanostructures.

ACS Appl Mater Interfaces 2017 Jul 5;9(28):24071-24077. Epub 2017 Jul 5.

Laboratory for Mechanics of Materials and Nanostructures, Empa-Swiss Federal Laboratories for Materials Science and Technology , Feuerwerkerstrasse 39, CH-3602 Thun, Switzerland.

Direct writing utilizing a focused electron beam constitutes an interesting alternative to resist-based techniques, as it allows for precise and flexible growth onto any conductive substrate in a single-step process. One important challenge, however, is the identification of appropriate precursors which allow for deposition of the material of choice, e.g., for envisaged applications in nano-optics. In this regard the coinage metal silver is of particular interest since it shows a relatively high plasma frequency and, thus, excellent plasmonic properties in the visible range. By utilizing the precursor compound AgOMeBu, direct writing of silver-based nanostructures via local electron beam induced deposition could be realized for the first time. Interestingly, the silver deposition was strongly dependent on electron dose; at low doses of 30 nC/μm a dominant formation of pure silver crystals was observed, while at higher electron doses around 10 nC/μm large carbon contents were measured. A scheme for the enhanced silver deposition under low electron fluxes by an electronic activation of precursor dissociation below thermal CVD temperature is proposed and validated using material characterization techniques. Finally, the knowledge gained was employed to fabricate well-defined two-dimensional deposits with maximized silver content approaching 75 at. %, which was achieved by proper adjustment of the deposition parameters. The corresponding deposits consist of plasmonically active silver crystallites and demonstrate a pronounced Raman signal enhancement of the carbonaceous matrix.
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http://dx.doi.org/10.1021/acsami.7b04353DOI Listing
July 2017

Perspective on the phase diagram of cuprate high-temperature superconductors.

Nat Commun 2016 05 6;7:11413. Epub 2016 May 6.

Institute of Experimental Physics II, University of Leipzig, Faculty of Physics and Earth Sciences, Linnéstrasse 5, Leipzig 04103, Germany.

Universal scaling laws can guide the understanding of new phenomena, and for cuprate high-temperature superconductivity the influential Uemura relation showed, early on, that the maximum critical temperature of superconductivity correlates with the density of the superfluid measured at low temperatures. Here we show that the charge content of the bonding orbitals of copper and oxygen in the ubiquitous CuO2 plane, measured with nuclear magnetic resonance, reproduces this scaling. The charge transfer of the nominal copper hole to planar oxygen sets the maximum critical temperature. A three-dimensional phase diagram in terms of the charge content at copper as well as oxygen is introduced, which has the different cuprate families sorted with respect to their maximum critical temperature. We suggest that the critical temperature could be raised substantially if one were able to synthesize materials that lead to an increased planar oxygen hole content at the expense of that of planar copper.
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http://dx.doi.org/10.1038/ncomms11413DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4859060PMC
May 2016

Correction: Formation of pure Cu nanocrystals upon post-growth annealing of Cu-C material obtained from focused electron beam induced deposition: comparison of different methods.

Beilstein J Nanotechnol 2015 21;6:1935-6. Epub 2015 Sep 21.

Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures, Feuerwerkerstrasse 39, 3602 Thun, Switzerland.

[This corrects the article DOI: 10.3762/bjnano.6.156.].
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http://dx.doi.org/10.3762/bjnano.6.196DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4660905PMC
December 2015

Formation of pure Cu nanocrystals upon post-growth annealing of Cu-C material obtained from focused electron beam induced deposition: comparison of different methods.

Beilstein J Nanotechnol 2015 13;6:1508-17. Epub 2015 Jul 13.

Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures, Feuerwerkerstrasse 39, 3602 Thun, Switzerland.

In this paper we study in detail the post-growth annealing of a copper-containing material deposited with focused electron beam induced deposition (FEBID). The organometallic precursor Cu(II)(hfac)2 was used for deposition and the results were compared to that of compared to earlier experiments with (hfac)Cu(I)(VTMS) and (hfac)Cu(I)(DMB). Transmission electron microscopy revealed the deposition of amorphous material from Cu(II)(hfac)2. In contrast, as-deposited material from (hfac)Cu(I)(VTMS) and (hfac)Cu(I)(DMB) was nano-composite with Cu nanocrystals dispersed in a carbonaceous matrix. After annealing at around 150-200 °C all deposits showed the formation of pure Cu nanocrystals at the outer surface of the initial deposit due to the migration of Cu atoms from the carbonaceous matrix containing the elements carbon, oxygen, and fluorine. Post-irradiation of deposits with 200 keV electrons in a transmission electron microscope favored the formation of Cu nanocrystals within the carbonaceous matrix of freestanding rods and suppressed the formation on their surface. Electrical four-point measurements on FEBID lines from Cu(hfac)2 showed five orders of magnitude improvement in conductivity when being annealed conventionally and by laser-induced heating in the scanning electron microscope chamber.
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http://dx.doi.org/10.3762/bjnano.6.156DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4578412PMC
October 2015

Hydration-switchable charge transfer in the first bimetallic assembly based on the [Ni(cyclam)](3+)--magnetic CN-bridged chain {(H3O)[Ni(III)(cyclam)][Fe(II)(CN)6]·5H2O}n.

Chem Commun (Camb) 2015 Jul;51(57):11485-8

Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland.

An alternating bimetallic {(H3O)[Ni(III)(cyclam)][Fe(II)(CN)6]·5H2O}n chain undergoes reversible dehydration at 40 °C accompanied by electron transfer which leads to Ni(II)-Fe(III) in about 50% of metal centres. The hydrated dark blue form is a paramagnet while the dehydrated yellowish-green form shows ferromagnetic coupling between neighbouring Ni(II) and Fe(III).
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http://dx.doi.org/10.1039/c5cc02805aDOI Listing
July 2015

T-T Dual-modal MRI contrast agents based on superparamagnetic iron oxide nanoparticles with surface attached gadolinium complexes.

J Nanopart Res 2014 11;16(11):2678. Epub 2014 Oct 11.

Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow, Poland.

Dual-mode MRI contrast agents consisting of superparamagnetic iron oxide nanoparticle (SPION) cores and gadolinium ions associated with the ionic chitosan protecting layer were synthesized and studied. Gadolinium ions were introduced into the coating layer via direct complex formation on the nanoparticles surface, covalent attachment or electrostatically driven deposition of the preformed Gd complex. The modified SPIONs having hydrodynamic diameters ca. 100 nm form stable, well-defined dispersions in water and have excellent magnetic properties. Physiochemical properties of those new materials were characterized using e.g., FTIR spectroscopy, dynamic light scattering, X-ray fluorescence, TEM, and vibrating sample magnetometry. They behave as superparamagnetics and shorten both T and T proton relaxation times, thus influencing both r and r relaxivity values that reach 53.7 and 375.5 mM s, respectively, at 15 MHz. The obtained materials can be considered as highly effective contrast agents for low-field MRI, particularly useful at permanent magnet-based scanners.
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http://dx.doi.org/10.1007/s11051-014-2678-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4193999PMC
October 2014

Charge transfer phase transition with reversed thermal hysteresis loop in the mixed-valence Fe9[W(CN)8]6·xMeOH cluster.

Chem Commun (Camb) 2014 Apr;50(26):3484-7

Faculty of Chemistry, Jagiellonian Univ., Ingardena 3, 30-060 Kraków, Poland.

A bimetallic pentadecanuclear cyanido-bridged {Fe9[W(CN)8]6 (MeOH)24}·xMeOH cluster of an Fe(II/III)-W(IV/V) mixed valence nature, reveals a reversible single-crystal-to-single-crystal transformation, concomitant with metal-to-metal charge transfer between Fe and W ions. The dominance of (HS)Fe(II)-NC-W(V) units at a high temperature, and (HS)Fe(III)-NC-W(IV) units at a low temperature, leads to an unprecedented reversed thermal hysteresis loop in magnetic measurements.
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http://dx.doi.org/10.1039/c3cc48029aDOI Listing
April 2014

Co-NC-W and Fe-NC-W electron-transfer channels for thermal bistability in trimetallic {Fe6Co3[W(CN)8]6} cyanido-bridged cluster.

Angew Chem Int Ed Engl 2013 Jan 26;52(3):896-900. Epub 2012 Nov 26.

Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland.

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http://dx.doi.org/10.1002/anie.201208023DOI Listing
January 2013

Electrochemical synthesis of magnetic iron oxide nanoparticles with controlled size.

J Nanopart Res 2011 Dec 27;13(12):7167-7176. Epub 2011 Nov 27.

We present a novel and facile method enabling synthesis of iron oxide nanoparticles, which are composed mainly of maghemite according to X-ray diffraction (XRD) and Mössbauer spectroscopy studies. The proposed process is realized by anodic iron polarization in deaerated LiCl solutions containing both water and ethanol. Water seems to play an important role in the synthesis. Morphology of the product was studied by means of transmission electron microscopy and XRD. In the solution containing almost 100% of water a black suspension of round shaped maghemite nanoparticles of 20-40 nm size is obtained. Regulating water concentration allows to control nanoparticle size, which is reduced to 4-6 nm for 5% of water with a possibility to reach intermediate sizes. For 3% or lower water concentration nanoparticles are of a needle-like shape and form a reddish suspension. In this case phase determination is problematic due to a small particle size with the thickness of roughly 3 nm. However, XRD studies indicate the presence of ferrihydrite. Coercivities of the materials are similar to those reported for nanoparticle magnetite powders, whereas the saturation magnetization values are considerably smaller.
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http://dx.doi.org/10.1007/s11051-011-0631-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3236826PMC
December 2011

Iron(II)-octacyanoniobate(IV) ferromagnet with T(C) 43 K.

Dalton Trans 2009 Oct 10(37):7771-7. Epub 2009 Aug 10.

Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060, Kraków, Poland.

We have synthesized the octacyanoniobate-based cyano-bridged 3D ferromagnet {[Fe(II)(H(2)O)(2)](2)[Nb(IV)(CN)(8)].4H(2)O}(n) and characterized structurally, spectroscopically (XANES/EXAFS, IR, UV-Vis, Resonance Raman, (57)Fe Mössbauer spectroscopy) and magnetically. crystallizes in the tetragonal system, space group I4/m, a = 11.989(5) A, c = 13.237(5) A, V = 1902.6(13) A(3). 3D coordination architecture comprises two types of Nb(IV)-C-N-Fe(II)(HS) (HS = high spin) linkages with Fe-N-C angles of 154.5 degrees and 167.5 degrees . The XANES/EXAFS spectra at Fe:K and Nb:K lines confirm the presence of Nb(IV)-C-N-Fe(II) linkages. Magnetic measurements reveal ferromagnetic ordering below T(c) = 43 K with some non-collinearity of Nb(IV) (S = 1/2) and Fe(II) (S = 2) magnetic moments. The molecular field model simulation reproduces well the M(T) curve and T(c) value with one average exchange coupling constant J(FeNb) = + 8.1 cm(-1).
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http://dx.doi.org/10.1039/b908486jDOI Listing
October 2009

Cobalt(II) octacyanotungstate(V) organic-inorganic hybrid ferromagnetic materials with pyrazine and 4,4'-bipyridine.

Dalton Trans 2006 Jun 31(23):2801-9. Epub 2006 Jan 31.

Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060, Kraków, Poland.

Two new ferromagnetic organic-inorganic hybrid materials [Co(II)3(H2O)6(pyz)3[W(V)(CN)8]2].3.5H2O (1) and [Co(II)3(H2O)4(4,4'-bpy)3[W(V)(CN)8]2].1.5(4,4'-bpy).6H2O (2) have been synthesised and characterised. The structure of the compounds have been investigated combining EXAFS (extended X-ray absorption fine structure), ES-MS (electrospray mass spectrometry), IR (infrared spectroscopy), UV-VIS electronic spectroscopy and TGA (thermogravimetric analysis) coupled with QMS (quadrupole mass spectrometer) experiments. The studies reveal that both compounds consist of Co(II)-NC-W(V) and Co(II)-L-Co(II) linkages (L = pyrazine (1) or 4,4-bipyridine (2)). Both networks are created by cyano-bridged Co(II)3W(V)2 chains joined by organic linkers into a 2D architecture. A difference of cobalt coordination numbers in both compounds derived from EXAFS study is consistent with the ES-MS conclusion. The ac magnetic characterisation exhibits the transition to the ferromagnetic phase at T(C) = 26 K (1) and to the spin glass-like phase at T(G) = 16 K (2). The frequency dependent chi'(T) and chi''(T) signals indicate the presence of some disorder in spin alignment below ordering temperatures. Both networks are also characterised a by magnetic hysteresis loop of coercive field H(c) = 750 Oe (1) and 1200 Oe (2) at T = 4.2 K.
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http://dx.doi.org/10.1039/b516004aDOI Listing
June 2006

Ca(2.5)Sr(0.5)GaMn2O8: diamagnetic Ga in control of the structural and electronic properties of a bilayered manganate.

J Am Chem Soc 2004 Oct;126(39):12517-27

Inorganic Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QR, United Kingdom.

The temperature dependence of the crystal structure and electronic properties of brownmillerite-like Ca(2.5)Sr(0.5)GaMn(2)O(8) has been studied by neutron powder diffraction and muSR spectroscopy. The results show that short-range 2D magnetic order begins to develop within the perovskite-like bilayers of MnO(6) octahedra approximately 50 K above the 3D Néel temperature of approximately 150 K. The bilayers show a structural response to the onset of magnetism throughout this temperature range whereas the GaO(4) layers that separate the bilayers only respond below the 3D ordering temperature. XANES spectroscopy shows that the sample contains Mn(3+) and Mn(4+) cations in a 1:1 ratio, and the behavior in the region of the Néel transition is interpreted as a local charge ordering. Electron diffraction and high-resolution electron microscopy have been used to show that the local microstructure is more complex than the average structure revealed by neutron diffraction, and that microdomains exist in which the GaO(4) tetrahedra show different orientations. It is argued that the bonding requirements of diamagnetic gallium control the electronic behavior within the perovskite-like bilayers.
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http://dx.doi.org/10.1021/ja0465000DOI Listing
October 2004
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