Incorporation of NiO into SiO2, TiO2, Al2O3, and Na4.2Ca2.8(Si6O18) Matrices: Medium Effect on the Optical Properties and Catalytic Degradation of Methylene Blue.

The medium effect of the optical and catalytic degradation of methylene blue was studied in the NiO/SiO2, NiO/TiO2, NiO/Al2O3, and NiO/Na4.2Ca2.8(Si6O18) composites, which were prepared by a solid-state method. The new composites were characterized by XRD (X-ray diffraction of powder), SEM/EDS, TEM, and HR-TEM. The size of the NiO nanoparticles obtained from the PSP-4-PVP (polyvinylpyrrolidone) precursors inside the different matrices follow the order of SiO2 > TiO2 > Al2O3. However, NiO nanoparticles obtained from the chitosan precursor does not present an effect on the particle size. It was found that the medium effect of the matrices (SiO2, TiO2, Al2O3, and Na4.2Ca2.8(Si6O18)) on the photocatalytic methylene blue degradation, can be described as a specific interaction of the NiO material acting as a semiconductor with the MxOy materials through a possible p-n junction. The highest catalytic activity was found for the TiO2 and glass composites where a favorable p-n junction was formed. The isolating character of Al2O3 and SiO2 and their non-semiconductor behavior preclude this interaction to form a p-n junction, and thus a lower catalytic activity. NiO/SiO2 and NiO/Na4.2Ca2.8(Si6O18) showed a similar photocatalytic behavior. On the other hand, the effect of the matrix on the optical properties for the NiO/SiO2, NiO/TiO2, NiO/Al2O3, and NiO/Na4.2Ca2.8(Si6O18) composites can be described by the different dielectric constants of the SiO2, TiO2, Al2O3, Na4.2Ca2.8(Si6O18) matrices. The maxima absorption of the composites (λmax) exhibit a direct relationship with the dielectric constants, while their semiconductor bandgap (Eg) present an inverse relationship with the dielectric constants. A direct relationship between λmax and Eg was found from these correlations. The effect of the polymer precursor on the particle size can explain some deviations from this relationship, as the correlation between the particle size and absorption is well known. Finally, the NiO/Na4.2Ca2.8(Si6O18) composite was reported in this work for the first time.

Minimizing the risk of reporting false aromaticity and antiaromaticity in inorganic heterocycles following magnetic criteria.

Although aromaticity is a concept in chemistry, in the last years, special efforts have been carried out in order to propose theoretical strategies to quantify it as a property of molecular rings. Among them, perhaps the computation of nucleus independent chemical shifts (NICSs) is the most commonly used, since it is possible to calculate it in an easy and fast way with most used quantum chemistry software. However, contradicting assignments of aromaticity by NICS and other methods have been reported in the literature, especially in studies concerning inorganic chemistry. In this Article is proposed a new and simple strategy to use the NICS information to assess aromaticity, identifying the point along the axis perpendicular to the molecular plane where the in-plane component of NICS becomes zero; it is called free of in-plane component NICS (FiPC-NICS). This spatial point is proposed as secure to consider NICS as an aromaticity descriptor; this simple proposal is evaluated in borazine and cyclotriphosphazenes. The results are compared with carefully examined aromatic stabilization energies and magnetically induced current-density analysis.

Solid state pathways to complex shape evolution and tunable porosity during metallic crystal growth.

Growing complex metallic crystals, supported high index facet nanocrystal composites and tunable porosity metals, and exploiting factors that influence shape and morphology is crucial in many exciting developments in chemistry, catalysis, biotechnology and nanoscience. Assembly, organization and ordered crystallization of nanostructures into complex shapes requires understanding of the building blocks and their association, and this relationship can define the many physical properties of crystals and their assemblies. Understanding crystal evolution pathways is required for controlled deposition onto surfaces. Here, complex metallic crystals on the nano- and microscale, carbon supported nanoparticles, and spinodal porous noble metals with defined inter-feature distances in 3D, are accomplished in the solid-state for Au, Ag, Pd, and Re. Bottom-up growth and positioning is possible through competitive coarsening of mobile nanoparticles and their site-specific crystallization in a nucleation-dewetted matrix. Shape evolution, density and growth mechanism of complex metallic crystals and porous metals can be imaged during growth.

Polyphosphazenes as tunable and recyclable supports to immobilize alcohol dehydrogenases and lipases: synthesis, catalytic activity, and recycling efficiency.

The polyphosphazene {NP[O(2)C(12)H(7.5)(NH(2))(0.5)]}(n), prepared by reacting {NP[O(2)C(12)H(7.5)(NO(2))(0.5)]} with the Lalancette's reagent, was used for attaching enzymes such as alcohol dehydrogenase (ADH-A) and lipase (CAL-B). The resulting new biocatalysts exhibited great potential as tunable supports for enzymatic reactions in both aqueous and organic media. The material with immobilized ADH-A was as efficient as the commercial enzyme to perform stereoselective bioreductions of ketones in aqueous solutions and could be used for the reduction of various aliphatic and aromatic ketones up to 60 degrees C and recycled several times without significant loss of activity even after three months of storage. The biocatalyst obtained with CAL-B was more efficient than the free enzyme for kinetic resolutions in organic solvents and exhibited a moderately good capability of reutilization.

Consumo de leche "Purita Cereal" (PNAC) en una comunidad rural / Jutake of \"Purita Cereal\" milk (PNAC) in a rural communiter

Con el propósito de conocer la utilización de los productos del PNAC, se cuantificó la ingesta de leche "Purita Cereal"-en 174 niños de 1 a 5 años de edad controlados en el Consultorio Til Til, durante agosto a octubre de 1984. El grupo de lactantes 12-23 meses presentó ingesta inadecuada, en tanto que un consumo más aceptable fue frecuente en el grupo de preescolares. Estas observaciones se relacionan con la tolerancia digestiva y aceptabilidad organoléptica determinadas para la LC en nuestro estudio. Se da énfasis en la necesidad de mantener continuidad en investigaciones sobre utilización de los diferentes alimentos del PNAC, con el fin de colaborar en el desarrollo y marcha del Programa