The present review describes our long experience in the application of Mössbauer spectroscopy with a high velocity resolution (a high discretization of the velocity reference signal) in the studies of various nanosized and nanostructured iron-containing materials. The results reviewed discuss investigations of: (I) nanosized iron cores in: (i) extracted ferritin, (ii) ferritin in liver and spleen tissues in normal and pathological cases, (iii) ferritin in bacteria, (iv) pharmaceutical ferritin analogues; (II) nanoparticles developed for magnetic fluids for medical purposes; (III) nanoparticles and nanostructured FINEMET alloys developed for technical purposes. The results obtained demonstrate that the high velocity resolution Mössbauer spectroscopy permits to excavate more information and to extract more spectral components in the complex Mössbauer spectra with overlapped components, in comparison with those obtained by using conventional Mössbauer spectroscopy. This review also shows the advances of Mössbauer spectroscopy with a high velocity resolution in the study of various iron-based nanosized and nanostructured materials since 2005.
Sn-Fe-Ni-Co quaternary alloys, in the composition range of 37-44 at% Sn, 35-39 at% Fe, 6-8 at% Ni and 13-17 at% Co, were prepared by direct current (DC) and pulse plating (PP) electrodeposition. The alloy deposits were characterized by XRD, 57Fe and 119Sn conversion electron Mössbauer spectroscopy, SEM-EDX and magnetization measurements. XRD revealed the amorphous character of the quaternary alloy deposits. The dominant ferromagnetic character of the deposits was shown by magnetization and Mössbauer spectroscopy measurements. Room temperature Mössbauer spectra showed minor paramagnetic phases, where their occurrences (~3-20%) are correlated to the electrodeposition parameters (Jdep from -16 to -23 mA/cm2 for DC, Jpulse from -40 to -75 mA/cm2 for PP), the composition and the saturation magnetization (~52-73 emu/g). A considerable difference was found in the magnetization curves applying parallel or perpendicular orientation of the applied fields, indicating magnetic anisotropy both in DC and pulse plated alloy coatings.
In this work, we describe a low-cost, two-step synthesis of composites of nitrogen-doped carbon quantum dots (NCDs) with γ-Fe2O3 (NCDs/γ-Fe2O3), which is based on a hydrothermal cum co-precipitation method. The product is a fine powder of particles having an average diameter of 9 ± 3 nm. The physical and chemical properties of NCDs/γ-Fe2O3 were studied, as well as the superconducting quantum interference device and Mossbauer analysis of the magnetic properties of these nanocomposites. The interaction of NCDs/γ-Fe2O3 nanocomposites with neuron-like cells was examined, showing efficient uptake and low toxicity. Our research demonstrates the use of the nanocomposites for imaging and for controlling the cellular motility. The NCDs/γ-Fe2O3 nanocomposites are promising because of their biocompatibility, photostability, and potential selective affinity, paving the way for multifunctional biomedical applications.
We have synthesized a novel europium bismuth sulfofluoride, Eu3Bi2S4F4, by solid-state reactions in sealed evacuated quartz ampules. The compound crystallizes in a tetragonal lattice (space group I4/mmm, a = 4.0771(1) Å, c = 32.4330(6) Å, and Z = 2), in which CaF2-type Eu3F4 layers and NaCl-like BiS2 bilayers stack alternately along the crystallographic c axis. There are two crystallographically distinct Eu sites, Eu(1) and Eu(2) at the Wyckoff positions 4e and 2a, respectively. Our bond valence sum calculation, based on the refined structural data, indicates that Eu(1) is essentially divalent, while Eu(2) has an average valence of â¼ +2.64(5). This anomalous Eu valence state is further confirmed and supported, respectively, by Mössbauer and magnetization measurements. The Eu(3+) components donate electrons into the conduction bands that are mainly composed of Bi 6px and 6py states. Consequently, the material itself shows metallic conduction and superconducts at 1.5 K without extrinsic chemical doping.
We present detailed (57)Fe Mössbauer effect spectroscopy (MS) measurements at various temperatures for Ba(Fe(1-x)Ni(x))(2)As(2). The isomer shift values for all samples are in the range of 0.42 ± 0.02 mm s(-1), indicating a typical metallic state of divalent Fe ions. The MS spectra of the magnetic samples (up to x = 0.024) are well reproduced by spin density waves subspectra. Both the magnetic ordering temperatures T(M) and the average magnetic hyperfine fields H(eff), decrease with x. The H(eff) values scale linearly with T(M). For higher x values the samples become superconducting and the MS spectra below and above T(C) are almost identical, indicating that the MS technique are not sensitive enough to the superconducting transition.
Nanosized pure Sn crystals protected by in situ formed carbon synthesized by the thermolysis of allyltriphenyltin in an inert atmosphere under its autogenic pressure in closed reactor showed superconductivity at 3.7 K.
Magnetic nanoparticles consisting of undecanoate-capped magnetite (average diameter approximately 4.5 nm; saturated magnetization, M(s), 38.5 emu g(-1)) are used to control and switch the hydrophobic or hydrophilic properties of the electrode surface. A two-phase system consisting of an aqueous buffer solution and a toluene phase that includes the suspended capped magnetic nanoparticles is used to control the interfacial properties of the electrode surface. The magnetic attraction of the functionalized particles to the electrode by means of an external magnet yields a hydrophobic interface that acts as an insulating layer, prohibiting interfacial electron transfer. The retraction of the magnetic particles from the electrode to the upper toluene phase by means of the external magnet generates a hydrophilic electrode that reveals effective interfacial electron transfer. The electron-transfer resistance and double-layer capacitance of the electrode surface upon the attraction and retraction of the functionalized magnetic particles to and from the electrode, respectively, by means of the external magnet were probed by Faradaic impedance spectroscopy (R(et) = 170 Omega and C(dl) = 40 microF sm(-2) in the hydrophilic state of the electrode and R(et) = 22 k Omega and C(dl) = 0.5 microF sm(-2) in the hydrophobic state of the interface). The magnetoswitchable control of the interface enables magnetic switching of the bioelectrocatalytic oxidation of glucose in the presence of glucose oxidase and ferrocene dicarboxylic acid to "ON" and "OFF" states.
