EMR Data on Mn(III; S=2) Ions in MnTPPCl Complex Modelled by Microscopic Spin Hamiltonian Approach

The electron magnetic resonance data on high-spin (S =2) manganese(III) 3d⁴ ion in tetraphenylporphyrinato chloride complex (MnTPPCl) obtained by high-frequency techniques are reanalysed. Preliminary results of semiempirical modeling of the spin Hamiltonian parameters for Mn(III) in MnTPPCl are presented. The microscopic spin Hamiltonian approach is utilized to predict the zero-field splitting and the Zeeman electronic parameters. It is found that for Mn(III) ions in MnTPPCl matching the experimental spin Hamiltonian parameters and the theoretical ones based on the ligand-field energy levels (Δ_{i}) within the ⁵D multiplet only may not be suitable for this system. Contributions due to the levels arising from the higher-lying ³H multiplet need to be taken into account in order to determine the reasonable values of microscopic parameters describing Mn(III) ions in MnTPPCl

Biomedical Applications of Graphene-Based Structures

Graphene and graphene oxide (GO) structures and their reduced forms, e.g., GO paper and partially or fully reduced three-dimensional (3D) aerogels, are at the forefront of materials design for extensive biomedical applications that allow for the proliferation and differentiation/maturation of cells, drug delivery, and anticancer therapies. Various viability tests that have been conducted in vitro on human cells and in vivo on mice reveal very promising results, which make graphene-based materials suitable for real-life applications. In this review, we will give an overview of the latest studies that utilize graphene-based structures and their composites in biological applications and show how the biomimetic behavior of these materials can be a step forward in bridging the gap between nature and synthetically designed graphene-based nanomaterials

FMR Evidence of Stable Ferromagnetic Correlations at Zigzag Edge States in Graphene

We studied magnetic properties of a composite of paraffin and graphene flakes. Magnetic properties of this composite were investigated by ferromagnetic resonance/electron spin resonance technique. The ferromagnetic resonance signal from graphene suspension in paraffin is broad and shifted from magnetic field corresponding to g ≈ 2 to the low magnetic field. The temperature dependence of the spectra shows that magnetic ordering in the studied system is sensitive to thermal fluctuations. These features are expected for the 1D ferromagnetism and the obtained results are analyzed in the frame of the theoretical predictions concerning magnetic correlations at graphene edges. Therefore, based on our investigation we can conclude the existence of the magnetic edges in graphene and presence of the ferromagnetic correlations between edge spins

Tuning Properties of Partially Reduced Graphene Oxide Fibers upon Calcium Doping

The arrangement of two-dimensional graphene oxide sheets has been shown to influence physico-chemical properties of the final bulk structures. In particular, various graphene oxide microfibers remain of high interest in electronic applications due to their wire-like thin shapes and the ease of hydrothermal fabrication. In this research, we induced the internal ordering of graphene oxide flakes during typical hydrothermal fabrication via doping with Calcium ions (~6 wt.%) from the capillaries. The Ca2+ ions allowed for better graphene oxide flake connections formation during the hydrogelation and further modified the magnetic and electric properties of structures compared to previously studied aerogels. Moreover, we observed the unique pseudo-porous fiber structure and flakes connections perpendicular to the long fiber axis. Pulsed electron paramagnetic resonance (EPR) and conductivity measurements confirmed the denser flake ordering compared to previously studied aerogels. These studies ultimately suggest that doping graphene oxide with Ca2+ (or other) ions during hydrothermal methods could be used to better control the internal architecture and thus tune the properties of the formed structures

Adaptive Modulation Amplitude in 2D Spectral-Spatial EPR Imaging

A study concerning the image quality in Electron Paramagnetic Resonance Imaging (EPRI) in 2D spectral-spatial (2D SSI) experiments is presented. The aim of the measurements is to improve the signal to noise ratio (SNR) of the projections by applying a more consciously selected modulation amplitude parameter. Data is gathered by applying three constant and one adaptive modulation amplitude. The three fixed modulation amplitudes values are leading to undermodulated (0.01 G), partially overmodulated (0.15 G) and fully overmodulated (0.65 G) projections. The study demonstrates the advantages of the adaptive method, which involves selecting different and dependent on cosine function modulation amplitudes for each projection. The study is performed on a phantom containing four tubes of LiPc and TCNQ, characterized by a different peak to peak linewidth and spin concentration

Nanoscale Effects of Radiation (UV, X‑ray, and γ) on Calcite Surfaces: Implications for its Mechanical and Physico-Chemical Properties

Calcite, the most stable polymorph of calcium carbonate (CaCO₃), attracts growing attention due to its wide applications in many fields, such as composite materials, food industry, biomineralization, and dating of archeological and geological objects. Our study shows the influence of UV, X-ray and γ-radiation on the mechanical and physicochemical properties of calcite at the nanoscale. Using nanoindentation technique we observed a clear detriment in the mechanical response (hardness and elastic modulus) of the calcite (104) surface after irradiation, most visible in the case of UV. Changes in mechanical properties were correlated with the accumulation of radiation defects detected using EPR spectroscopy, and information on chemical bonding and composition obtained through XPS analyses. Additionally, the efficiency in generating defects for all three types of radiation was compared, which allowed us to propose a possible mechanism of UV-induced formation of radiation defects in calcite