Nanostructured Spinel Ferrites: Synthesis, Functionalization, Nanomagnetism and Environmental Applications

Nanostructured spinel ferrites have gained a great deal of attention. It comes from the possibility of tuning their magnetic properties by careful manipulation of the synthetic conditions. At the same time, since the nanoparticle (NP) surface is reactive toward many chemical groups, it provides great versatility for further functionalization of the nanosystems. Such characteristics make ferrite nanoparticles excellent candidates for environmental applications. First, the chapter deals with the basics of the synthetic methodologies, functionalization strategies and magnetic properties of nanoparticles, with emphasis on how surface manipulation is reflected in the properties of the materials. Next, we review some of the applications of ferrites as magnetic sorbents for several hazardous substances in aqueous medium and try to systematize the adsorption mechanism as a function of the coating material. Finally, a short summary concerning the main uses of ferrites as magnetic catalysts in oxidation technologies is included

1-(2-Furo­yl)-3-(1-naphth­yl)thio­urea

In the title compound, C16H12N2O2S, the carbonyl­thio­urea group forms dihedral angles of 75.4 (1) and 13.1 (2)°, respectively, with the naphthalene ring system and furan ring. The mol­ecule adopts a trans–cis configuration with respect to the positions of the furoyl and naphthyl groups relative to the S atom across the thio­urea C—N bonds. This geometry is stabilized by an N—H⋯·O intra­molecular hydrogen bond. In the crystal structure, mol­ecules are linked by N—H⋯S hydrogen bonds, forming centrosymmetric dimers which are inter­linked through C—H⋯π inter­actions

CH4 and CO2 Adsorption Study in ZIF-8 and Al-BDC MOFs

CH4 and CO2 adsorption capacity at 25, 50 and 75°C was evaluated in two metal-organic frameworks: Al-BDC and ZIF-8, the later with zeolite topology. Adsorption experiments were carried out under static conditions using a gravimetric suspension balance until 40 bar of pressure. Adsorption isotherms of type I were obtained for both materials showing high adsorption capacity values. ZIF-8 exhibited the higher uptake value for both CH4 and CO2 (4.9 and 8.5 mmol g-1, respectively). The Toth equilibrium model was used to fit experimental isotherms in order to obtain qm (maximum adsorption capacity) and t (related to energetical heterogeneity of the surface). Isosteric heats of adsorption were also calculated by Clausius-Clapeyron equation.Thanks to UNESCO/Keizo Obuchi Research Fellowships Programme (UNESCO/Japan Young Researcher’s Fellowship Program), Cycle 2012, Programa de Becas para la realización de la tesis doctoral en la Universidad de Málaga convocatoria curso 2011-2012 (AUIP-UMA), European project 295156, FP7-PEOPLE-2011-IRSES and MINECO, Spain, Project CTQ2015-68951-C3-3-R and FEDER funds. Dr. Giselle Autié Castro thanks to CNPq-TWAS Postdoctoral Fellowship 2014 and its financial support

Almacenamiento de hidrógeno a alta densidad en nanocavidades

Segunda serie de Seminarios Virtuales sobre Materiales Avanzados (SEVIMAT). Tema; Laboratorios Compartidos. Institución; Instituto Politécnico Nacional (IPN). Coordinador; Patricia Santiago Jacinto. Colaborador; Universidad Nacional Autónoma de México(UNAM). Formato; video/flv.Seminarios Virtuales sobre Materiales Avanzados (SEVIM@T). Conferencia titulada "Almacenamiento de Hidrógeno a Alta Densidad en Nanocavidades” por el Dr. Edilso Reguera del Centro de Investigación en Ciencia y Tecnología Aplicada del IPN

CONTROLLED GROWTH OF CDS QUANTUM DOTS

The role of 3-mercaptopropionic acid as a surface anchoring group and the reaction temperature for the controlled growth of CdS crystals was investigated from a one-step aqueous synthesis carried out both at room temperature and using a hydrothermal route. The thiol group of 3-mercaptopropionic acid forms a relatively strong bond with the cadmium atoms found at the particle surface reducing the crystal growth rate. This leads to the formation of monodisperse crystals of about 2 nm diameter. For a low thermal activation, at room temperature, for instance, the crystal growth is mainly determined by the nucleation process without evidence of a large contribution from Ostwald ripening. When the thermal activation competes with the binding energy for the thiol group to the cadmium atom, the surface shell becomes unstable and the crystals growth involves the coarsening mechanism. Under hydrothermal conditions the radius (r ) for the obtained crystals follows a linear dependence for r 3 versus t (reaction time). The crystal growing process is halted when the colloidal suspension is cooled. An appropriate control for the time and temperature of heating allows crystals of a tailored size to be obtained. The obtained colloidal suspensions of CdS nanocrystals were characterized from optical absorption, high-resolution transmission electron microscopy, and photoluminescence data

ADSORPTION AND SEPARATION OF LIGHT ALKANE HYDROCARBONS BY POROUS HEXACYANOCOBALTATES (III)

The adsorption and separation of light n-alkane hydrocarbons (propane, butane, pentane, hexane and heptane) by zinc and cadmium hexacyanocobaltates (III) were studied from inverse gas chromatographic data. These two solids are representative of the porous frameworks found for transition metals hexacyanometallates. For cadmium, the porous framework is related to the presence of systematic vacancies for the building block, [Co(CN)6], while for Zn it is a consequence of a tetrahedral coordination for the Zn atom. These linear light hydrocarbons (paraffins) are effectively separated by these two porous frameworks. The involved differential adsorption heats and the related separation coefficients were estimated from the recorded chromatographic data. No significant differences for the separation ability of light n-alkane hydrocarbons by the evaluatedmaterials were observe

MATERIALS FOR HYDROGEN STORAGE IN NANOCAVITIES: DESIGN CRITERIA

The adsorption potential for a given adsorbate depends of both, material surface and adsorbate properties. In this contribution the possible guest-host interactions for H2 within a cavity or on a surface are discussed considering the molecule physical properties. Five different interactions contribute to the adsorption forces for this molecule: 1) quadrupole moment interaction with the local electric field gradient; 1) electron cloud polarization by a charge center; 3) dispersive forces (van der Waals); 4) quadrupole moment versus quadrupole moment between neighboring H2 molecules, and, 5) H2 coordination to a metal center. The relative importance of these five interactions for the hydrogen storage in nanocavities is discussed from experimental evidences in order to extract materials design criteria for molecular hydrogen storage

Refinamiento estructural en hexacianoferratos: Fenómenos térmicamente inducidos y propiedades magnéticas asociadas

El libro contiene el refinamiento estructural de quince hexacianoferratos (II,III), donde doce estructuras cristalinas se reportan por primera vez. Además, se analiza la distorsión ortorrómbica que aparece en algunas de las estructuras debido a la influencia de los cationes de compensación de carga presentes en las mismas. También se analiza el efecto del tratamiento térmico sobre la estructura y las propiedades magnéticas de los hexacianoferratos (III) de M2+ (M=Zn, Ni, Mn y Cu) y de los hexacianoferrato (III) de Co2+; reportándose una transferencia interna de carga del Co2+ hacia el FeIII que provoca la formación de una solución sólida con estados de valencia mixta. Como parte del estudio, también se analiza el papel que juega el agua estructural en el comportamiento magnético de los materiales.Fil: Martinez Garcia, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; ArgentinaFil: Reguera Ruíz, Edilso. No especifíca

Lattice Gas Model for H2 Adsorption in Nanoporous Zinc Hexacyanometallates

Zinc hexacyanometallates Zn3A2[M(CN)6]2 with different exchangeable alkaline cations A+ and framework transition metals M constitute an excellent model system to study H2 adsorption in nanoporous solids. A lattice gas approach, based on experimental data and simple considerations on the position and energies of adsorption sites, is proposed. Coverage and adsorption enthalpies are calculated and compared with experimental results. The interplay of three necessary conditions for H2 storage in porous solidssfree volume to accommodate guest molecules, charge centers to bind them, and fast diffusion during adsorption or desorptionsis discussed