Deep hole trap level of nitrogen-doped ZnSe grown by metalorganic vapor phase epitaxy

We investigated the hole trap level of nitrogen-doped ZnSe grown by a metalorganic vapor phase epitaxy method. The deep level transient spectroscopy (DLTS) signal and the C-V profile were measured to obtain the trap level, the capture cross section and the trap concentration. A deep hole trap level of about 1 eV from a valence band (labeled TLIS) was extracted from the tail of the DLTS peak. The distributions of the capture cross section and the trap level of the samples for different growth conditions were drawn in a figure to investigate the validity of the resolution of the DLTS signal. The origin of TLIS is thought to be in relation to the ionized acceptor or the charged acceptor-like localized defects.     

Temperature and pressure dependence of NMR frequencies in ferromagnetic Heusler alloys containing cobalt and manganese

The ⁵⁹Co and ⁵⁵Mn NMR frequencies ν in Co₂MnZ (Z = Si, Ge, Sn and Ga) were measured as a function of temperature T and pressure P by the cw method. The ν/ν_4.2 value decreased faster for ⁵⁹Co than for ⁵⁵Mn with increasing T/T_C especially in Co₂MnGa, for which ∂ν/∂P was positive at 0°C in contrast to the results in other alloys.     

Reagent‐Controlled α‐Selective Dehydrative Glycosylation of 2,6‐Dideoxy‐ and 2,3,6‐Trideoxy Sugars

We have found that activating either 2,3‐bis(2,3,4‐trimethoxyphenyl)cyclopropenone or 2,3‐bis(2,3,4‐trimethoxyphenyl)cyclopropene‐1‐thione with oxalyl bromide results in the formation of a species that promotes the glycosylation between 2,6‐dideoxy‐sugar hemiacetals and glycosyl acceptors in good yield and high α‐selectivity. Both reactions are mild and tolerate a number of sensitive functional groups including highly acid‐labile 2,3,6‐trideoxy‐sugar linkages.     

Enantioselective Nanoporous Carbon Based on Chiral Ionic Liquids

One of the greatest challenges in modern chemical processing is to achieve enantiospecific control in chemical reactions using chiral media such as chiral mesoporous materials. Herein, we describe a novel and effective synthetic pathway for the preparation of enantioselective nanoporous carbon, based on chiral ionic liquids (CILs). CILs of phenylalanine (CIL(Phe)) are used as precursors for the carbonization of chiral mesoporous carbon. We employ circular dichroism spectroscopy, isothermal titration calorimetry (ITC), and chronoamperometry in order to demonstrate the chiral nature of the mesoporous carbon. The approach presented in this paper is highly significant for the development of a new type of chiral porous materials for enantioselective chemistry. In addition, it contributes significantly to our understanding of the structure and nature of chiral nanoporous materials and surfaces.     

Nature of the magnetic order in the charge-ordered cuprate La1.48Nd0.4Sr0.12CuO4

Using polarized neutron scattering we establish that the magnetic order in La(1.48)Nd(0.4)Sr(0.12)CuO(4) is either (i) one dimensionally modulated and collinear, consistent with the stripe model or (ii) two dimensionally modulated with a novel noncollinear structure. The measurements rule out a number of alternative models characterized by 2D electronic order or 1D helical spin order. The low-energy spin excitations are found to be primarily transversely polarized relative to the stripe ordered state, consistent with conventional spin waves.     

Magnetic-field-induced spin excitations and renormalized spin gap of the underdoped La1.895Sr0.105CuO4 superconductor

High-resolution neutron inelastic scattering experiments in applied magnetic fields have been performed on La1.895Sr0.105CuO4 (LSCO). In zero field, the temperature dependence of the low-energy peak intensity at the incommensurate momentum transfer QIC=(0.5,0.5+/-delta,0),(0.5+/-delta,0.5,0) exhibits an anomaly at the superconducting Tc which broadens and shifts to lower temperature upon the application of a magnetic field along the c axis. A field-induced enhancement of the spectral weight is observed, but only at finite energy transfers and in an intermediate temperature range. These observations establish the opening of a strongly downward renormalized spin gap in the underdoped regime of LSCO. This behavior contrasts with the observed doping dependence of most electronic energy features.     

Ortho‐Stabilized 18F‐Azido Click Agents and their Application in PET Imaging with Single‐Stranded DNA Aptamers

Azido ¹⁸F‐arenes are important and versatile building blocks for the radiolabeling of biomolecules via Huisgen cycloaddition (“click chemistry”) for positron emission tomography (PET). However, routine access to such clickable agents is challenged by inefficient and/or poorly defined multistep radiochemical approaches. A high‐yielding direct radiofluorination for azido ¹⁸F‐arenes was achieved through the development of an ortho‐oxygen‐stabilized iodonium derivative (OID). This OID strategy addresses an unmet need for a reliable azido ¹⁸F‐arene clickable agent for bioconjugation reactions. A ssDNA aptamer was radiolabeled with this agent and visualized in a xenograft mouse model of human colon cancer by PET, which demonstrates that this OID approach is a convenient and highly efficient way of labeling and tracking biomolecules.     

'Liquid litmus': chemosensory pH-responsive photonic ionic liquids

We report on the founding member of a unique class of luminescent ionic liquids integrating a photoacidic anion that responds to the presence of both condensed- and gas-phase basicity; the analytical response is ratiometric in nature, visible to the naked eye, and offers fascinating prospects in smart photofluids, liquid logic gates, electronic noses, and sensory inks.     

Fluorescence energy transfer efficiency in labeled yeast cytochrome c: a rapid screen for ion biocompatibility in aqueous ionic liquids

A fluorescence energy transfer "de-quenching" assay was implemented to follow the equilibrium unfolding behaviour of site-specific tetramethylrhodamine-labelled yeast cytochrome c in aqueous ionic liquid solutions; additionally, this approach offers the prospect of naked eye screening for biocompatible ion combinations in hydrated ionic liquids.