One-pot preparation and uranyl adsorption properties of hierarchically porous zirconium titanium oxide beads using phase separation processes to vary macropore morphology

A simple and engineering friendly one-step process has been used to prepare zirconium titanium mixed oxide beads with porosity on multiple length scales. In this facile synthesis, the bead diameter and the macroporosity can be conveniently controlled through minor alterations in the synthesis conditions. The precursor solution consisted of poly(acrylonitrile) dissolved in dimethyl sulfoxide to which was added block copolymer Pluronic F127 and metal alkoxides. The millimeter-sized spheres were fabricated with differing macropore dimensions and morphology through dropwise addition of the precursor solution into a gelation bath consisting of water (H(2)O beads) or liquid nitrogen (LN(2) beads). The inorganic beads obtained after calcination (550 °C in air) had surface areas of 140 and 128 m(2) g(-1), respectively, and had varied pore architectures. The H(2)O-derived beads had much larger macropores (5.7 μm) and smaller mesopores (6.3 nm) compared with the LN(2)-derived beads (0.8 μm and 24 nm, respectively). Pluronic F127 was an important addition to the precursor solution, as it resulted in increased surface area, pore volume, and compressive yield point. From nonambient XRD analysis, it was concluded that the zirconium and titanium were homogeneously mixed within the oxide. The beads were analyzed for surface accessibility and adsorption rate by monitoring the uptake of uranyl species from solution. The macropore diameter and morphology greatly impacted surface accessibility. Beads with larger macropores reached adsorption equilibrium much faster than the beads with a more tortuous macropore network.     

Functionalization of Reduced Graphite Oxide Sheets with a Zwitterionic Surfactant

Films of a few layers in thickness of reduced graphite oxide (RGO) sheets functionalized by the zwitterionic surfactant N‐dodecyl‐N,N‐dimethyl‐3‐ammonio‐1‐propanesulfonate (DDPS) are obtained by using the Langmuir–Blodgett method. The quality of the RGO sheets is checked by analyzing the degrees of reduction and defect repair by means of X‐ray photoelectron spectroscopy, atomic force microscopy (AFM), field‐emission scanning electron microscopy (SEM), micro‐Raman spectroscopy, and electrical conductivity measurements. A modified Hummers method is used to obtain highly oxidized graphite oxide (GO) together with a centrifugation‐based method to improve the quality of GO. The GO samples are reduced by hydrazine or vitamin C. Functionalization of RGO with the zwitterionic surfactant improves the degrees of reduction and defect repair of the two reducing agents and significantly increases the electrical conductivity of paperlike films compared with those prepared from unfunctionalized RGO.     

The first regioselective palladium-catalyzed indolization of 2-bromo- or 2-chloroanilines with internal alkynes: a new approach to 2,3-disubstituted indoles

[reaction: see text] The first practical and economical process for synthesis of 2,3-disubstituted indole compounds has been developed with high regioselectivity by palladium-catalyzed indolization of 2-bromo- or chloroanilines and their derivatives with internal alkynes.     

Electrophilicity Scale of Activated Amides: 17O NMR and 15N NMR Chemical Shifts of Acyclic Twisted Amides in N−C(O) Cross-Coupling

The structure and properties of amides are of tremendous interest in organic synthesis and biochemistry. Traditional amides are planar and the carbonyl group non-electrophilic due to n_N→π*_C=O conjugation. In this study, we report electrophilicity scale by exploiting ¹⁷O NMR and ¹⁵N NMR chemical shifts of acyclic twisted and destabilized acyclic amides that have recently received major attention as precursors in N-C(O) cross-coupling by selective oxidative addition as well as precursors in electrophilic activation of N-C(O) bonds. Most crucially, we demonstrate that acyclic twisted amides feature electrophilicity of the carbonyl group that ranges between that of acid anhydrides and acid chlorides. Furthermore, a wide range of electrophilic amides is possible with gradually varying carbonyl electrophilicity by steric and electronic tuning of amide bond properties. Overall, the study quantifies for the first time that steric and electronic destabilization of the amide bond in common acyclic amides renders the amide bond as electrophilic as acid anhydrides and chlorides. These findings should have major implications on the fundamental properties of amide bonds.     

Dark and Photochemical Interactions of Dimethyltetrahydrobenzoangelicin with DNA

A study of dark interaction and photoreaction between 4,6-dimethyltetrahydrobenzoangelicin (THBA) and DNA is described. 4,6-Dimethyltetrahydrobenzoangelicin is a furocoumarin derivative in which 4'and 5'carbons are linked by a four-methylene bridge. In spite of the bulky aliphatic ring, THBA forms a complex with DNA in the dark and, on UVA irradiation, reacts with pyrimidine bases of DNA yielding monoadducts only involving its furan side double bond. Two main photoproducts form: they derive from a C₄-cycloaddition to thymine and cytosine, respectively, and account for 56% and 39% of the total photoreaction yield. Both show cis-syn configuration. Two other isomers, one with thymine and one with cytosine, formed with so much lower yield ( ca 3 and 1%, respectively) that their structure could not be assigned. Furthermore, in spite of its angular structure, THBA induces a small number of crosslinks in DNA.     

Practical synthesis of (2'R)-2'-deoxy-2'-C-methyluridine by highly diastereoselective homogeneous hydrogenation

Diastereoselective hydrogenation of 2'-deoxy-2'-exo-methyleneuridine was carried out under homogeneous conditions using a low loading of a chiral Rh catalyst. This, coupled with improvements in the synthesis of the substrate, allowed the smooth pilot plant preparation of the title compound on >10 kg scale.     

Structural characterization techniques for the analysis of semiconductor strained heterostructures

A combined method for structural characterization of strained epitaxial heterostructures involving different techniques such as Rutherford backscattering spectrometry (RBS), multiple crystal X-ray diffractometry (MCD) and transmission electron microscopy (TEM) is presented. In order to obtain a complete characterization of the analysed structure, three different quantities are measured independently: the epilayer thickness, the density of misfit dislocations which may appear at the interface, and the significant components of the strain tensor, mainly the tetragonal distortion, affecting the epilayer lattice. In this way the thermodynamic state and the mechanisms of plastic deformation of the structures can be fully investigated. In this contribution we present and discuss the experimental results concerning a set of InP/GaAs samples having different layer thicknesses ranging from 5 to 500 nm. The thickness of the samples has been determined by RBS. Measurements of in-plane strain and tetragonal distortion have been performed by MCD and RBS-channelling respectively, finally TEM has been used for determining the defects densities and distribution.     

EPR and kinetic investigation of free cyanide oxidation by photocatalysis and ozonation

Oxidation of free cyanide in aqueous suspensions of three commercial TiO₂ specimens, with different anatase crystal size, has been carried out in a batch photoreactor by simultaneously applying ozonation and photocatalysis. Dissolved ozone participates both in homogeneous and catalytic reactions with cyanide; the extents of these two processes are comparable to that of the photodegradation with oxygen. The reactivity results are well described by the Langmuir-Hinshelwood kinetic model, providing the values of the kinetic and equilibrium adsorption constants for the catalytic and photocatalytic reactions contributing to cyanide oxidation. The cyanide concentration decreases faster with time for catalysts with increasing anatase crystal size, being more marked under UV irradiation. EPR studies on gaseous ozone adsorption on the three samples in the dark have shown stronger ozone interactions with Ti⁴⁺ and O^2? ions of the samples with largest anatase crystal size, leading to the formation of significant signals of Ti³⁺ and _s O^??O₂ radicals than with the anatase with the lowest crystal size, where ozone was mainly adsorbed on water molecular arrangements covering its surface. The hampering of the ozone and/or cyanide adsorption by the water molecular arrangements covering the surface of the catalyst with the lowest crystal size would justify the low cyanide degradation rate observed for this sample.     

Structures of Highly Twisted Amides Relevant to Amide N−C Cross‐Coupling: Evidence for Ground‐State Amide Destabilization

Herein, we show that acyclic amides that have recently enabled a series of elusive transition‐metal‐catalyzed N?C activation/cross‐coupling reactions are highly twisted around the N?C(O) axis by a new destabilization mechanism of the amide bond. A unique effect of the N‐glutarimide substituent, leading to uniformly high twist (ca. 90°) irrespective of the steric effect at the carbon side of the amide bond has been found. This represents the first example of a twisted amide that does not bear significant steric hindrance at the α‐carbon atom. The ¹⁵N NMR data show linear correlations between electron density at nitrogen and amide bond twist. This study strongly supports the concept of amide bond ground‐state twist as a blueprint for activation of amides toward N?C bond cleavage. The new mechanism offers considerable opportunities for organic synthesis and biological processes involving non‐planar amide bonds.     

Poly‐l‐Lactic Acid Nanofiber–Polyamidoamine Hydrogel Composites: Preparation,Properties, and Preliminary Evaluation as Scaffolds for Human Pluripotent Stem Cell Culturing

Electrospun poly‐l ‐lactic acid (PLLA) nanofiber mats carrying surface amine groups, previously introduced by nitrogen atmospheric pressure nonequilibrium plasma, are embedded into aqueous solutions of oligomeric acrylamide‐end capped AGMA1, a biocompatible polyamidoamine with arg‐gly‐asp (RGD)‐reminiscent repeating units. The resultant mixture is finally cured giving PLLA‐AGMA1 hydrogel composites that absorb large amounts of water and, in the swollen state, are translucent, soft, and pliable, yet as strong as the parent PLLA mat. They do not split apart from each other when swollen in water and remain highly flexible and resistant, since the hydrogel portion is covalently grafted onto the PLLA nanofibers via the addition reaction of the surface amine groups to a part of the terminal acrylic double bonds of AGMA1 oligomers. Preliminary tested as scaffolds, the composites prove capable of maintaining short‐term undifferentiated cultures of human pluripotent stem cells in feeder‐free conditions.