Determination of conditional stability constants for some divalent transition metal ion‐EDTA complexes by electrospray ionization mass spectrometry

Conditional stability constants of coordination complexes comprising divalent transition metals, Cu²⁺, Ni²⁺, Zn²⁺, Co²⁺, and ethylenediaminetetraacetic acid (EDTA) were determined utilizing electrospray ionization mass spectrometry. The deviation of signal response of a reference complex was monitored at addition of a second metal ion. The conditional stability constant for the competing metal was then determined through solution equilibria equations. The method showed to be applicable to a system where Co²⁺ and Zn²⁺ competed for EDTA at pH 5. When Cu²⁺ and Ni²⁺ competed for EDTA, the equilibrium changed over time. This change was shown to be affected in rate and size by the type of organic solvent added. In this work, 30% of either methanol or acetonitrile was used. It was found that if calibration curves are prepared for both metal complexes in solution and the measurements are repeated with sufficient time space, any change in equilibrium of sample solutions will be discovered. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis of Two‐Dimensional Transition‐Metal Phosphates with Highly Ordered Mesoporous Structures for Lithium‐Ion Battery Applications

Materials with ordered mesoporous structures have shown great potential in a wide range of applications. In particular, the combination of mesoporosity, low dimensionality, and well‐defined morphology in nanostructures may exhibit even more attractive features. However, the synthesis of such structures is still challenging in polar solvents. Herein, we report the preparation of ultrathin two‐dimensional (2D) nanoflakes of transition‐metal phosphates, including FePO₄, Mn₃(PO₄)₂, and Co₃(PO₄)₂, with highly ordered mesoporous structures in a nonpolar solvent. The as‐obtained nanoflakes with thicknesses of about 3.7 nm are constructed from a single layer of parallel‐packed pore channels. These uniquely ordered mesoporous 2D nanostructures may originate from the 2D assembly of cylindrical micelles formed by the amphiphilic precursors in the nonpolar solvent. The 2D mesoporous FePO₄ nanoflakes were used as the cathode for a lithium‐ion battery, which exhibits excellent stability and high rate capabilities.     

Catalytic 1,4‐Rhodium(III) Migration Enables 1,3‐Enynes to Function as One‐Carbon Oxidative Annulation Partners in CH Functionalizations

1,3‐Enynes containing allylic hydrogens cis to the alkyne are shown to act as one‐carbon partners, rather than two‐carbon partners, in various rhodium‐catalyzed oxidative annulations. The mechanism of these unexpected transformations is proposed to occur through double C? H activation, involving a hitherto rare example of the 1,4‐migration of a Rh^III species. This phenomenon is general across a variety of substrates, and provides a diverse range of heterocyclic products.     

The Isomerization of Allylrhodium Intermediates in the Rhodium‐Catalyzed Nucleophilic Allylation of Cyclic Imines

Allylrhodium species generated from potassium allyltrifluoroborates can undergo isomerization by 1,4‐rhodium(I) migration to give more complex isomers, which then react with cyclic imines to provide products with up to three new stereochemical elements. High enantioselectivities are obtained using chiral diene–rhodium complexes.     

Fabrication and characterization of TEOS-based silica aerogels prepared using rapid supercritical extraction

Silica aerogels were prepared using the precursor tetraethylorthosilicate (TEOS) via a rapid supercritical extraction (RSCE) method. Multiple consistent batches of monolithic TEOS-based aerogels were fabricated via an 8-h RSCE process. Fabricating TEOS-based aerogels with an RSCE method offers some distinct advantages. One advantage is the relative simplicity of the RSCE approach: liquid precursors are mixed and poured into a metal mold in a hydraulic hot-press, where gelation, aging and extraction of liquid from the pores occur. The precursor recipe employs TEOS, ethanol, water, oxalic acid to catalyze hydrolysis, and ammonia to catalyze the subsequent polycondensation reactions. Another advantage is that reaction of TEOS to form sol gels yields ethanol as a byproduct. A process that releases ethanol, rather than methanol (as in tetramethylorthosilicate (TMOS)-based aerogels) may be more appealing for commercial applications, involving scale-up of the process. The significantly lower cost of TEOS, compared to TMOS, is a considerable advantage. The TEOS-based RSCE aerogels are mesoporous and optically translucent, have bulk densities of 0.099(±0.003) g/cm³ and surface areas of 460(±10) m²/g. Signals observed in infrared and Raman spectra of the aerogels are consistent with Si–O framework bonds. Using scanning electron microscopy imaging, the surface morphology of the aerogel samples was imaged at magnifications up to 150 kX.     

Evidence for Electron Transfer between Graphene and Non-Covalently Bound π-Systems

Hybridizing graphene and molecules possess a high potential for developing materials for new applications. However, new methods to characterize such hybrids must be developed. Herein, the wet-chemical non-covalent functionalization of graphene with cationic π-systems is presented and the interaction between graphene and the molecules is characterized in detail. A series of tricationic benzimidazolium salts with various steric demand and counterions was synthesized, characterized and used for the fabrication of graphene hybrids. Subsequently, the doping effects were studied. The molecules are adsorbed onto graphene and studied by Raman spectroscopy, XPS as well as ToF-SIMS. The charged π-systems show a p-doping effect on the underlying graphene. Consequently, the tricationic molecules are reduced through a partial electron transfer process from graphene, a process which is accompanied by the loss of counterions. DFT calculations support this hypothesis and the strong p-doping could be confirmed in fabricated monolayer graphene/hybrid FET devices. The results are the basis to develop sensor applications, which are based on analyte/molecule interactions and effects on doping.     

Three‐Pronged Attack by Homologous Far‐red/NIR AIEgens to Achieve 1+1+1>3 Synergistic Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) has long been shown to be a powerful therapeutic modality for cancer. However, PDT is undiversified and has become stereotyped in recent years. Exploration of distinctive PDT methods is thus highly in demand but remains a severe challenge. Herein, an unprecedented 1+1+1>3 synergistic strategy is proposed and validated for the first time. Three homologous luminogens with aggregation‐induced emission (AIE) characteristics were rationally designed based on a simple backbone. Through slight structural tuning, these far‐red/near‐infrared AIE luminogens are capable of specifically anchoring to mitochondria, cell membrane, and lysosome, and effectively generating reactive oxygen species (ROS). Notably, biological studies demonstrated combined usage of three AIE photosensitizers gives multiple ROS sources simultaneously derived from several organelles, which gives superior therapeutic effect than that from a single organelle at the same photosensitizers concentration. This strategy is conceptually and operationally simple, providing an innovative approach and renewed awareness of improving therapeutic effect through three‐pronged PDT.     

Aldehyde oxidase assay by capillary electrophoresis: From off‐line,online up to immobilized enzyme reactor

Capillary electrophoresis is a modern separation technique characterized by many benefits, which qualify it also for enzyme assays and the study of enzyme kinetics during drug development. Homogeneous or heterogeneous approaches can be followed for the enzymatic incubation. In this study, an immobilization procedure of aldehyde oxidase on magnetic particles was developed considering their integration with capillary electrophoresis. A number of magnetic nano/microparticle types were tested for this purpose, showing that aldehyde oxidase was most active when immobilized on bare silica magnetic nanoparticles. Primarily, the reusability of the enzyme immobilized on bare silica nanoparticles was tested. Three consecutive incubations with substrate could be performed, but the activity considerably dropped after the first incubation. One reason could be an enzyme detachment from the nanoparticles, but no release was detected neither at 4°C nor at 37°C during 5 h. The drop in enzymatic activity observed in consecutive incubations, could also be due to inactivation of the enzyme over time at given temperature. For the immobilized enzyme stored at 4°C, the activity decreased to 83% after 5 h, in contrast with a steep decrease at 37°C to 37%.     

Modeling of interphase in composite materials: Characterization of epoxy resin/aminosilane system

The system studied here principally is γ-APS + BADGE (γ-aminopropyltriethoxysilane + diglycidyl ether of bisphenol A). The reaction takes place even at −20°C. It is first the epoxy-amine autocatalytic second-order reaction, but we also have a cross-linking reaction which needs more time and higher temperature. The behaviour of this system is the same as γ-APS-PGE (phenylglycidyl ether) system: we can obtain the complete disappearance of OH groups. The thermomechanical properties of the reaction product considerably change with the temperature, moisture and curing time.