Fabio Canepa

Structure and magnetism of Gd2Co2Ga, Gd2Co2Al and Gd14Co3In2.7

The paper reports on the crystal structure determination and magnetic measurements of the Gd2Co2Al, Gd2Co2Ga and Gd14Co3In2.7 phases. Gd2Co2Ga and the new intermetallic compound Gd2Co2Al crystallise in the Pr2Ni2Al structure, while single crystal data show that Gd14Co3In2.7 is closely related to the Lu14Co2In3 phase, but with a different occupation of the Co and In sites. Gd2Co2Al and Gd2Co2Ga order ferromagnetically below 78.2 and 76 K, respectively, and the isothermal magnetisation in the ordered state (5 K) saturates completely to the same value for both compounds (μsat.=6.6 μB/Gd atom). The intermetallic compound Gd14Co3In2.7, on the contrary, is antiferromagnetic below TN=37 K and reveals a metamagnetic transition at μ0H=1.4 Tesla, detected also by AC susceptibility measurements.

Functionalization of Fe3O4 NPs by Silanization: Use of Amine (APTES) and Thiol (MPTMS) Silanes and Their Physical Characterization

In this paper the results concerning the synthesis of magnetite (Fe3O4) nanoparticles (NPs), their functionalization using silane derivatives, such as (3-Aminopropyl)triethoxysilane (APTES) and (3-mercaptopropyl)trimethoxysilane (MPTMS), and their exhaustive morphological and physical characterization by field emission scanning electron microscopy (FE-SEM) with energy dispersion X-ray spectrometer (EDX) analysis, AC magnetic susceptibility, UV-VIS and IR spectroscopy, and thermogravimetric (TGA) analyses are reported. Two different paths were adopted to achieve the desired functionalization: (1) the direct reaction between the functionalized organo-silane molecule and the surface of the magnetite nanoparticle; and (2) the use of an intermediate silica coating. Finally, the occurrence of both the functionalization with amino and thiol groups has been demonstrated by the reaction with ninhydrin and the capture of Au NPs, respectively.

Heat capacity and thermodynamic properties of some Ca silicides

The heat capacities of three Ca compounds, namely CaSi2, Ca3Si4 and Ca14Si19 were measured in the 3–300 K temperature range by adiabatic calorimetry. No thermal anomalies were found in the whole temperature range. In the three Ca silicides, from an analysis of the low temperature data (T<40 K), a power law lower than three in the lattice heat capacity behaviour was observed and tentatively ascribed to the layered structure of the compounds, in agreement with structural informations. From heat capacity data the thermodynamic functions entropy, enthalpy and Gibbs energy were calculated at 298 K.

Magnetic characterization of undoped and 15%F-doped LaFeAsO and SmFeAsO compounds

Abstract In this paper, the magnetic behavior of undoped and 15%F-doped SmFeAsO (Sm-1111) and LaFeAsO (La-1111) samples is presented and discussed. Magnetization measurements are not a simple tool to use for the characterization of the new family of Fe-based superconductors, because magnetic impurities can be easily formed during the preparation procedure and may affect the magnetic signal. In spite of this problem bulk magnetization measurements, properly treated, may give very useful information. In the undoped samples we gathered the main aspects of the physical behavior of the 1111 phase, i.e. the onset of the spin density wave (SDW), the antiferromagnetic ordering at the Sm sublattice and the susceptibility increase with increasing temperature above the SDW temperature, and, in addition, we were able to estimate the Pauli contribution to susceptibility and therein the Wilson ratio both for LaFeAsO and SmFeAsO compounds, and the amplitude of the jump at the SDW temperature. In the doped samples, while the presence of magnetic signals due to impurities is dominating in the normal state, the superconducting behavior may be clearly observed and studied. In particular, in the Sm-1111 superconducting sample the coexistence-competition between superconductivity and antiferromagnetic ordering of the Sm ions was clearly observed.

Enhancement of TiO2 NPs activity by Fe3O4 nano-seeds for removal of organic pollutants in water

The enhancement of the photocatalytic activity of TiO2 nanoparticles (NPs), synthesized in the presence of a very small amount of magnetite (Fe3O4) nanoparticles, is here presented and discussed. From X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses, the crystallinity of TiO2 nanoparticles (NPs) seems to be affected by Fe3O4, acting as nano-seeds to improve the tetragonal TiO2 anatase structure with respect to the amorphous one. Photocatalytic activity data, i.e., the degradation of methylene blue and the Ofloxacin fluoroquinolone emerging pollutant, give evidence that the increased crystalline structure of the NPs, even if correlated to a reduced surface to mass ratio (with respect to commercial TiO2 NPs), enhances the performance of this type of catalyst. The achievement of a relatively well-defined crystal structure at low temperatures (Tmax = 150 °C), preventing the sintering of the TiO2 NPs and, thus, preserving the high density of active sites, seems to be the keystone to understand the obtained results.

Gd6Co2.2In0.8: an intermetallic compound with complex magnetic behaviour

Abstract Electrical, magnetic and thermodynamic measurements have been performed on the rhombic Gd6Co2.2In0.8 intermetallic phase. The experimental data reveal that two magnetic transitions take place. In the first, at 34 K, the magnetic configuration of the sample changes from an antiferromagnetic type to a ferromagnetic type where, however, antiferromagnetic components, as revealed from magnetoresistivity data, still exist. The second, at 66 K, is the ferro-paramagnetic transition. In the paramagnetic state the low value of the Gd magnetic moment (μeff.=6.8 μB), obtained from AC and DC magnetic measurements, can be explained, in the framework of the RKKY theory, by a strong coupling of the conduction electrons with the localized magnetic moments. With respect to the experimental data, a possible hypothesis about the magnetic structure of the phase at 5 K is presented.

Magnetic properties of R3Co8Sn4 (R=Y, Gd)

Abstract The magnetic properties of the intermetallic phases R3Co8Sn4 (R=Y,xa0Gd) are presented. The two compounds order ferro- (Y) and ferri-magnetically (Gd) with transition temperatures of 61.5 and 102.5 K, respectively. In the paramagnetic region, the Y-compound follows the Curie–Weiss law with μ=0.98xa0μB/Co and θP=62.0xa0K while a more complex behaviour, typical of a ferrimagnetic substance, is observed for Gd3Co8Sn4. The experimental data, analysed in the framework of the molecular field theory, allow to obtain the exchange parameter for the Co–Co (JCo–Co=83kB) and of the Gd–Co (JGd–Co=11kB) interactions.

Magnetism in R3Co8Sn4 compounds (R=Pr, Nd, Sm)

Abstract The magnetic properties of the R 3 Co 8 Sn 4 phases (R=Pr, Nd, Sm) were studied by AC and DC magnetic techniques. The three compounds order magnetically at 17, 37 and 83 K, respectively. Pr 3 Co 8 Sn 4 and Nd 3 Co 8 Sn 4 exhibit a spin reorientation transition under an applied field of 4 T (Pr) and 2 T (Nd), detected also by DC thermomagnetic measurements. The anomalous hysteresis loop of the Sm-phase is discussed in terms of a complete lack in the magnetic coupling of the two ferromagnetic phases: Sm 3 Co 8 Sn 4 and free Co. Dependence of the ferromagnetic transition temperature on Co–Co distances is discussed.

Physical properties of Ce2CoSn2

Abstract A complete physical characterisation, through specific heat, electrical resistivity and magnetization measurements was performed, in a wide temperature range, on the new phase Ce 2 CoSn 2 , which crystallizes in a very large fcc cell with a structure type similar to the Tb 117 Fe 52 Ge 112 one. From the real part of the AC susceptibility data a broad maximum can be observed at 7 K with an inflexion point, in agreement with the maximum observed in the imaginary part of the AC susceptibility, at a lower temperature (around 6 K). We hypothesize that the lower maximum can be attributed to an antiferromagnetic transition while the upper one could be related to the onset of a Kondo regime. The antiferromagnetic order is confirmed by magnetization measurements performed at 2 K in magnetic fields up to 9 Tesla: a metamagnetic transition could be observed around 0.4 Tesla. In the paramagnetic range the inverse of susceptibility follows a modified Curie–Weiss law, with an effective paramagnetic moment μ =2.89 μ B and a paramagnetic Curie temperature slightly positive. The heat capacity results suggest that this phase might be a heavy fermion system, with an electronic specific heat coefficient γ =1.3 J/K 2 mol. The electrical resistivity measurements exhibit a pronounced minimum at about 13 K and below this temperature a logarithmic Kondo-like behaviour is observed.

Sorafenib delivery nanoplatform based on superparamagnetic iron oxide nanoparticles magnetically targets hepatocellular carcinoma

Currently, sorafenib is the only systemic therapy capable of increasing overall survival of hepatocellular carcinoma patients. Unfortunately, its side effects, particularly its overall toxicity, limit the therapeutic response that can be achieved. Superparamagnetic iron oxide nanoparticles (SPIONs) are very attractive for drug delivery because they can be targeted to specific sites in the body through application of a magnetic field, thus improving intratumoral accumulation and reducing adverse effects. Here, nanoformulations based on polyethylene glycol modified phospholipid micelles, loaded with both SPIONs and sorafenib, were successfully prepared and thoroughly investigated by complementary techniques. This nanovector system provided effective drug delivery, had an average hydrodynamic diameter of about 125 nm, had good stability in aqueous medium, and allowed controlled drug loading. Magnetic analysis allowed accurate determination of the amount of SPIONs embedded in each micelle. An in vitro system was designed to test whether the SPION micelles can be efficiently held using a magnetic field under typical flow conditions found in the human liver. Human hepatocellular carcinoma (HepG2) cells were selected as an in vitro system to evaluate tumor cell targeting efficacy of the superparamagnetic micelles loaded with sorafenib. These experiments demonstrated that this delivery platform is able to enhance sorafenib’s antitumor effectiveness by magnetic targeting. The magnetic nanovectors described here represent promising candidates for targeting specific hepatic tumor sites, where selective release of sorafenib can improve its efficacy and safety profile.