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High-resolution non-invasive 3D imaging of paint microstructure by synchrotron-based X-ray laminography

The characterisation of the microstructure and micromechanical behaviour of paint is key to a range of problems related to the conservation or technical art history of paintings. Synchrotron-based X-ray laminography is demonstrated in this paper to image the local sub-surface microstructure in paintings in a non-invasive and non-destructive way. Based on absorption and phase contrast, the method can provide high-resolution 3D maps of the paint stratigraphy, including the substrate, and visualise small features, such as pigment particles, voids, cracks, wood cells, canvas fibres etc. Reconstructions may be indicative of local density or chemical composition due to increased attenuation of X-rays by elements of higher atomic number. The paint layers and their interfaces can be distinguished via variations in morphology or composition. Results of feasibility tests on a painting mockup (oak panel, chalk ground, vermilion and lead white paint) are shown, where lateral and depth resolution of up to a few micrometres is demonstrated. The method is well adapted to study the temporal evolution of the stratigraphy in test specimens and offers an alternative to destructive sampling of original works of art.     

Very Facile Polarity Umpolung and Noncovalent Functionalization of Inorganic Nanoparticles: A Tool Kit for Supramolecular Materials Chemistry

The facile assembly of shell‐by‐shell (SbS)‐coated nanoparticles [TiO₂?PAC₁₆]@shell 1 – 7 (PAC₁₆=hexadecylphosphonic acid), which are soluble in water and can be isolated as stable solids, is reported. In these functional architectures, an umpolung of dispersibility (organic apolar versus water) was accomplished by the noncovalent binding of ligands 1 – 7 to titania nanoparticles [TiO₂?PAC₁₆] containing a first covalent coating with PAC₁₆. Ligands 1 – 7 are amphiphilic and form the outer second shell of [TiO₂?PAC₁₆]@shell 1 – 7 . The tailor‐designed dendritic building blocks 3 – 5 contain negative and positive charges in the same molecule, and ligands 6 and 7 contain a perylenetetracarboxylic acid dimide (PDI) core ( 6 / 7 ) as a photoactive reporter component. In the redox and photoactive system [TiO₂?PAC₁₆]@shell 7 , electronic communication between the inorganic core to the PDI ligands was observed.     

Evaluation of Pd→B Interactions in Diphosphinoborane Complexes and Impact on Inner-Sphere Reductive Elimination

The dative Pd→B interaction in a series of ^RDPB^R’ Pd⁰ and Pd^II complexes (^RDPB^R’=(o-PR₂C₆H₄)₂BR’, diphosphinoborane) was analyzed using XRD, ¹¹B NMR spectroscopy and NBO/NLMO calculations. The borane acceptor discriminates between the oxidation state Pd^II and Pd⁰, stabilizing the latter. Reaction of lithium amides with [(^RDPB^R’)Pd^II(4-NO₂C₆H₄)I] chemoselectively yields the C−N coupling product. DFT modelling indicates no significant impact of Pd^II→B coordination on the inner-sphere reductive elimination rate.     

Synthesis,crystal structure,magnetism, and absorption spectra of A2UX5 Type Halides (A = K,Rb; X = Cl,Br, I)

The ternary uranium(III) halides A₂UX₅ (A = K, Rb; X = Cl, Br, I) have been prepared from the binary components AX and UX₃ in sealed tantalum containers. According to their Guinier X-ray powder patterns, they all crystallize with the K₂PrCl₅/Y₂HfS₅ type of structure. Lattice constants for ambient temperature are reported. Single-crystal structure refinemens were undertaken for K₂UI₅ and Rb₂UCl₅. Magnetic susceptibility data were recorded with a SQUID magnetometer from liquid helium to room temperature. One-dimensional (intrachain) and three-dimensional antiferromagnetic ordering occur at low temperatures dependent upon the U³⁺? U³⁺ distance. Absorption spectra were recorded between 4 000 and 28 000 cm^?1. They show f—f transitions typical for U³⁺ and, depending on the halide, very strong f—d transitions above 14 000 to 15 000 cm^?1, respectively.     

UV‐Free Microfluidic Particle Fabrication at Low Temperature Using ARGET‐ATRP as the Initiator System

A new way to fabricate monodisperse polymer particles in a microfluidic device without UV‐light and without the need for high temperatures is described in this article. By applying an activator regeneration by electron transfer ‐ atom transfer radical polymerization (ARGET‐ATRP) initiator system in a co‐capillary microfluidic setup and by separating the monomer mixture in an initiator and a catalyst phase, a fast polymerization of the droplets at low temperature without premature curing and thus clogging of the capillaries can be achieved. The influence of the flow rates on the particle sizes and their polydispersity as well as the controlled character of the polymerization are investigated. The particle size is well adjustable, but the reaction is not controlled due to the high radical concentration needed for rapid polymerization. In addition, particles with incorporated UV‐dyes are produced as a proof of concept at low temperature.

     

Selective reagent ionisation‐time of flight‐mass spectrometry: a rapid technology for the novel analysis of blends of new psychoactive substances

In this study we demonstrate the potential of selective reagent ionisation‐time of flight‐mass spectrometry for the rapid and selective identification of a popular new psychoactive substance blend called ‘synthacaine’, a mixture that is supposed to imitate the sensory and intoxicating effects of cocaine. Reactions with H₃O⁺ result in protonated parent molecules which can be tentatively assigned to benzocaine and methiopropamine. However, by comparing the product ion branching ratios obtained at two reduced electric field values (90 and 170 Td) for two reagent ions (H₃O⁺ and NO⁺) to those of the pure chemicals, we show that identification is possible with a much higher level of confidence then when relying solely on the m/z of protonated parent molecules. A rapid and highly selective analytical identification of the constituents of a recreational drug is particularly crucial to medical personnel for the prompt medical treatment of overdoses, toxic effects or allergic reactions. Copyright © 2015 John Wiley & Sons, Ltd.     

Asymmetric Hydroalkoxylation of Non‐Activated Alkenes: Titanium‐Catalyzed Cycloisomerization of Allylphenols at High Temperatures

The asymmetric catalytic addition of alcohols (phenols) to non‐activated alkenes has been realized through the cycloisomerization of 2‐allylphenols to 2‐methyl‐2,3‐dihydrobenzofurans (2‐methylcoumarans). The reaction was catalyzed by a chiral titanium–carboxylate complex at uncommonly high temperatures for asymmetric catalytic reactions. The catalyst was generated by mixing titanium isopropoxide, the chiral ligand (aS)‐1‐(2‐methoxy‐1‐naphthyl)‐2‐naphthoic acid or its derivatives, and a co‐catalytic amount of water in a ratio of 1:1:1 (5 mol % each). This homogeneous thermal catalysis (HOT‐CAT) gave various (S)‐2‐methylcoumarans with yields of up to 90 % and in up to 85 % ee at 240 °C, and in 87 % ee at 220 °C.     

Porous and Shape‐Anisotropic Single Crystals of the Semiconductor Perovskite CH3NH3PbI3 from a Single‐Source Precursor

Significant progress in solar‐cell research is currently made by the development of metal–organic perovskites (MOPs) owing to their superior properties, such as high absorption coefficients and effective transport of photogenerated charges. As for other semiconductors, it is expected that the properties of MOPs may be significantly improved by a defined nanostructure. However, their chemical sensitivity (e.g., towards hydrolysis) prohibits the application of methods already known for the synthesis of other nanomaterials. A new and general method for the synthesis of various (CH₃NH₃)PbI₃ nanostructures from a novel single‐source precursor is presented. Nanoporous MOP single crystals are obtained by a crystal‐to‐crystal transformation that is accompanied by spinodal demixing of the triethylene glycol containing precursor structure. Selective binding of a capping agent can be used to tune the particle shape of the MOP nanocrystals.     

Fabrication of solid‐state nanopores and its perspectives

Nanofluidics is becoming an extensively developing technique in the field of bioanalytical chemistry. Nanoscale hole embed in an insulating membrane is employed in a vast variety of sensing platforms and applications. Although, biological nanopores have several attractive characteristics, in this paper, we focused on the solid‐state nanopores due to their advantages as high stability, possibility of diameter control, and ease of surface functionalizing. A detection method, based on the translocation of analyzed molecules through nanochannels under applied voltage bias and resistive pulse sensing, is well established. Nevertheless, it seems that the new detection methods like measuring of transverse electron tunneling using nanogap electrodes or optical detection can offer significant additional advantages. The aim of this review is not to cite all related articles, but highlight the steps, which in our opinion, meant important progresses in solid‐state nanopore analysis.