Stable aqueous dispersion of superparamagnetic iron oxide nanoparticles protected by charged chitosan derivatives

This article presents the synthesis and characterization of biocompatible superparamagnetic iron oxide nanoparticles (SPIONs) coated with ultrathin layer of anionic derivative of chitosan. The water-based fabrication involved a two-step procedure. In the first step, the nanoparticles were obtained by co-precipita- tion of ferrous and ferric aqueous salt solutions with ammonia in the presence of cationic derivative of chitosan. In the second step, such prepared materials were subjected to adsorption of oppositely charged chitosan derivative which resulted in the preparation of negatively charged SPIONs. They were found to develop highly stable dispersion in water. The core size of the nanocoated SPIONs, determined using transmis- sion electron microscopy, was measured to be slightly above 10 nm. The coated nanoparticles form aggregates with majority of them having hydrodynamic diameter below 100 nm, as measured by dynamic light scattering. Their composition and properties were studied using FTIR and thermogravimetric analyses. They exhibit magnetic properties typical for superparamagnetic material with a high saturation magnetization value of 123 ± 12 emu g - 1 Fe. Very high value of the measured r 2 relaxivity, 369 ± 3mM - 1 s - 1 , is conducive for the potential application of the obtained SPIONs as prom- ising contrast agents in magnetic resonance imaging

Państwo i społeczeństwo w XXI wieku. Style myślenia politycznego Polaków na progu XXI stulecia. Akcenty retro- i prospektywne

Słowo wstępne: "W kształtowaniu tożsam ości ideowej III R zeczpospolitej uczest­niczą przedstawiciele różnych nurtów ideowych i orientacji politycz­nych. Są wśród nich socjaliści, upom inający się o niezalatw ione kwe­stie społeczne, ludowcy i agraryści, odzyskujący swoje miejsce na wsi z hasłam i „żywią, bronią i gospodarują”, i chrześcijańscy dem okraci, apelujący w stylu „niech każdy robi w swoim kręgu co każe duch boży a całość jakoś się ułoży” oraz nieliczni konserwatyści-zachowawcy, przypominający o zasadniczych wartościach życia publicznego (tra­dycji, rodzinie, religii i własności pryw atnej) a także narodow i dem o­kraci z pakietem uwspółcześnionych „myśli nowoczesnego Polaka”. W ich dążeniach do uspraw nienia państw a i uporządkow ania życia publicznego, jak i wyobrażeniach o sam orządnej III R P uwidaczniają się idee, poglądy i koncepcje, słowem - styl m yślenia politycznego minionych generacji, zwłaszcza pokolenia II Rzeczpospolitej."(...

Magnetostrictive Functional Materials of Tb0.27Dy0.73(Fe1-xAlx)2 Series as Prospective Constituents of Magnetoelectric Composites

Structural, magnetic, and magnetostrictive properties of two-sublattice Tb0.27Dy0.73(Fe1-xAlx)2 polycrystalline intermetallic ferrimagnets (x = 0-0.2 and 1.0) were studied using X-ray powder diffraction, magnetometry, and strain gauge magnetostriction measurements. Temperature dependences of magnetization starting from 80 K were presented, and Curie temperatures were estimated. Coercive force, residual, and saturation magnetizations were determined from the magnetic hysteresis loops at room temperature. Longitudinal, transversal, form and volume magnetostrictions were investigated against the x parameter and the intensity of the magnetic field. The piezomagnetic coefficients were determined and the maximum value at the field below 1 kOe, even enhanced than that in Terfenol-D, was observed for the material TTb0.27Dy0.73(Fe0.9Al0.1)2. It means that this compound is promising for use in magnetoelectric composites

Synthesis and characterization of the superparamagnetic iron oxide nanoparticles modified with cationic chitosan and coated with silica shell

Novel method for synthesis of superparamagnetic iron oxide nanoparticles (SPION) modified with a cationic chitosan (CCh) and coated with a silica shell, SPION-CCh-SiO2 was developed. The process was carried out in two steps. In the first step the chitosan coated SPIONs were obtained by co-precipitation of Fe2+ and Fe3+ with ammonium hydroxide in aqueous solution of CCh. In the second one, the silica shell is formed on their surfaces. The formation of SPION-CCh-SiO2 was achieved by direct decomposition of tetraethoxysilane (TEOS) adsorbed on a surface of SPION-CCh dispersed in aqueous phase under sonication and mechanical stirring at room temperature. The chemical composition and physicochemical properties of the materials were determined using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Light Scattering (DLS) and zeta potential measurements. The morphology of the particles was evaluated by Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). Magnetic properties were confirmed using Atomic Force Microscopy/Magnetic Force Microscopy (AFM/MFM) and magnetization measurements. The resulting products are negatively charged, rounded in shape and exhibit the superparamagnetic properties what implies their potential applications in engineering and biomedicine areas

Temperature Evolution of Composition, Thermal, Electrical and Magnetic Properties of Ti₃C₂T_x-MXene

MXenes are a family of two-dimensional nanomaterials. Titanium carbide MXene (Ti3C2Tx-MXene), reported in 2011, is the first inorganic compound reported among the MXene family. In the present work, we report on the study of the composition and various physical properties of Ti3C2Tx-MXene nanomaterial, as well as their temperature evolution, to consider MXenes for space applications. X-ray diffraction, thermal analysis and mass spectroscopy measurements confirmed the structure and terminating groups of the MXene surface, revealing a predominant single OH layer character. The temperature dependence of the specific heat shows a Debye-like character in the measured range of 2 K–300 K with a linear part below 10 K, characteristic of conduction electrons of metallic materials. The electron density of states (DOS) calculations for Ti3C2OH-MXene reveal a significant DOS value at the Fermi level, with a large slope, confirming its metallic character, which is consistent with the experimental findings. The temperature dependence of electrical resistivity of the MXene samples was tested for a wide temperature range (3 K–350 K) and shows a decrease on lowering temperature with an upturn at low temperatures, where negative magnetoresistance is observed. The magnetoresistance versus field is approximately linear and increases its magnitude with decreasing temperature. The magnetization curves are straight lines with temperature-independent positive slopes, indicating Pauli paramagnetism due to conduction electrons