An easy, low-cost, repeatable seed-mediated growth approach in solvothermal condition has been proposed to synthesize bimagnetic spinel ferrite core-shell heterostructures in the 10-20 nm particle size range. Cobalt ferrite and manganese ferrite nanoparticles (CoFeO and MnFeO) have been coated with isostructural spinel ferrites like maghemite/magnetite, MnFeO, and CoFeO with similar cell parameters to create different heterostructures. The conventional study of the structure, morphology, and composition has been combined with advanced techniques in order to achieve details on the interface at the nanoscale level. Clear evidence of the heterostructure formation have been obtained (i) indirectly by comparing the Fe Mössbauer spectra of the core-shell samples and an ad hoc mechanical mixture and (ii) directly by mapping the nanoparticles' chemical composition by electron energy loss spectroscopy (EELS) and energy-dispersive X-ray spectroscopy (EDX) in the scanning transmission electron microscopy mode (STEM). In addition, chemical-sensitive electron tomography in STEM-EDX mode has been applied in order to obtain detailed 3D images with a sub-nanometer spatial resolution.

The heating abilities of bi-magnetic core–shell nanostructures are studied depending on core size, nature of the shell, and shell thickness.

MCM-41 is proposed to build mesostructured Fe2O3-based sorbents as an alternative to other silica or alumina\ud supports for mid-temperature H2S removal. MCM-41 was synthesized as micrometric (MCM41_M) and\ud nanometric (MCM41_N) particles and impregnated through an efficient two-solvent (hexane–water)\ud procedure to obtain the corresponding gamma-Fe2O3@MCM-41 composites. The active phase is homogeneously\ud dispersed within the 2 nm channels in the form of ultrasmall maghemite nanoparticles assuring a high active\ud phase reactivity. The final micrometric (Fe_MCM41_M) and nanometric (Fe_MCM41_N) composites were\ud tested as sorbents for hydrogen sulphide removal at 300 °C and the results were compared with a reference\ud sorbent (commercial unsupported ZnO) and an analogous silica-based sorbent (Fe_SBA15). MCM-41 based\ud sorbents, having the highest surface areas, showed superior performances that were retained after the first\ud sulphidation cycle. Specifically, the micrometric sorbent (Fe_MCM41_M) showed a higher SRC value than the\ud nanometric one (Fe_MCM41_N), due to the low stability of the nanosized particles over time caused by their\ud high reactivity. Furthermore, the low regeneration temperature (300–350 °C), besides the high removal\ud capacity, renders MCM41-based systems an alternative class of regenerable sorbents for thermally efficient\ud cleaning up processes in Integrated Gasification Combined Cycles (IGCC) systems

An ecofriendly, low-cost, one-pot solvothermal approach has been developed to prepare spherical magnetite nanoparticles with sizes in the 7−12 nm range capped with a dialkylamine. Iron isopropoxide, water vapor, absolute ethanol, oleic acid, and oleylamine were used as iron oxide precursor, hydrolysis agent, solvent and surfactants, respectively. The surfactants' role was investigated and an accurate correlation among the synthetic parameters, the crystallographic phases, and both crystallite and particle size was found. The amounts of oleylamine and oleic acid and the temperature have been revealed to be the key parameters in order to tune particle size and their polydispersity. An in-depth study on the role of each surfactant has pointed out the fundamental role of the amine as a reduction promoter as demonstrated by using different amines and confirmed by Mossbauer measurements. A dual 1 H NMR-Fourier transform infrared spectroscopy approach on selected experiments for the investigation of the capping agents (in the presence of a magnetic phase (Magnetite) or a diamagnetic one (Anatase) prepared in the same synthetic conditions) has been found to be fundamental to clarify the actual nature of the capping agent of the nanoparticles and the reactions involved between the surfactants. New insights on the reaction mechanism confirm the formation of an amide that represents a new cosurfactant for the size and shape regulation and a biocompatible molecular coating of magnetite and anatase nanoparticles.

In this work, the effect of the M41S support pore structure (hexagonal or cubic) and of the wall thickness of the silica mesochannels has been evaluated aimed at achieving more and more efficient and regenerable iron oxidebased sorbents for H 2 S removal at midtemperature. With this purpose, we set up a simple Pluronic-free synthetic strategy capable of producing silica supports with hexagonal (MCM-41) or cubic (MCM-48) pore structure with different wall thicknesses that have been used to fabricate the corresponding sorbents made up of iron oxide nanoparticles homogeneously dispersed into the mesochannels. The combined use of 57 Fe-Mossbauer Spectroscopy and DC magnetometry has allowed for ascertaining the presence of maghemite in the form of ultrasmall nanoparticles in both composites and gives new insights on the influence of the different silica matrices on the active phase features. The performances of the sorbents have been evaluated at midtemperature (300 °C) through three repeated sulfidation and regeneration cycles and then correlated to their microstructure and textural properties.

In this work, industrial waste hexafluorosilicic acid (H 2 SiF 6 or FSA) has been proven to be a low-cost alternative to silicate esters for the synthesis of high-quality MCM-41 (high surface area, high degree of order, narrow pore size distribution, high thermal stability) through a head-to-head comparison between the most common silica precursor, tetraethylorthosilicate (TEOS), and FSA. The effect of different parameters such as temperature, time, hydrothermal treatment, and the presence of ethyl acetate has been explored by studying the textural, structural, and morphological features. On the most promising samples, thermal and hydrothermal stability has been assessed, indicating a higher thermal stability for the FSA-derived sample, due to the thicker walls, and comparable hydrothermal stability. The mother solution treatment has allowed the obtainment of nanostructured fluorite as an additional valuable product and a CTAB-rich ammonia solution for successive synthesis with FSA. Recovery processes for the templating agent entrapped in the MCM-41 mesostructure have also been explored for both FSA-and TEOS-derived samples, showing an easier removal in the case of FSA-MCM-41. Moreover, mesostructured silica derived from FSA has also been proven to be an ideal support to design efficient and regenerable mesostructured iron oxide-based sorbents for H 2 S removal from syngas, showing similar performance to that of the corresponding nanocomposite prepared from TEOS.

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