Reentrant orbital order and the true ground state of LaSr2Mn2O7

Contrary to conventional wisdom, our purified La 2-2x Sr 1+2x Mn2O7 crystals exhibit CE-type orbital and charge order as the low-temperature ground state for a hole doping level h=0.5. For small deviations from h=0.5, the high-temperature CE phase is replaced at low temperatures by an A-type antiferromagnet without coexistence. Larger deviations result in a lack of CE order at any temperature. Thus, small inhomogeneities in cation or oxygen composition could explain why others commonly see this reentrance with coexistence.     

Simultaneous Raman and fluorescence spectroscopy of single conjugated polymer chains

Simultaneous surface enhanced Raman scattering (SERS) and fluorescence is demonstrated from single conjugated polymer chains. As resonance enhancement of SERS depends on the spectral overlap of the polymer's absorption and the incident laser, resonance Raman and fluorescence effectively probe the absorbing and emitting part of the polymer, respectively. The optical phonon energies change along the polymer chain, providing a window to spatially track excited state relaxation. Whereas a mean spatial redistribution of the excitation is witnessed by a change in vibronic fingerprint following interchromophoric energy transfer, intrachromophoric exciton self-trapping leaves the vibrations unchanged.     

Templated‐Assembly of CsPbBr3 Perovskite Nanocrystals into 2D Photonic Supercrystals with Amplified Spontaneous Emission

Perovskite nanocrystals (NCs) have revolutionized optoelectronic devices because of their versatile optical properties. However, controlling and extending these functionalities often requires a light‐management strategy involving additional processing steps. Herein, we introduce a simple approach to shape perovskite nanocrystals (NC) into photonic architectures that provide light management by directly shaping the active material. Pre‐patterned polydimethylsiloxane (PDMS) templates are used for the template‐induced self‐assembly of 10 nm CsPbBr₃ perovskite NC colloids into large area (1 cm²) 2D photonic crystals with tunable lattice spacing, ranging from 400 nm up to several microns. The photonic crystal arrangement facilitates efficient light coupling to the nanocrystal layer, thereby increasing the electric field intensity within the perovskite film. As a result, CsPbBr₃ 2D photonic crystals show amplified spontaneous emission (ASE) under lower optical excitation fluences in the near‐IR, in contrast to equivalent flat NC films prepared using the same colloidal ink. This improvement is attributed to the enhanced multi‐photon absorption caused by light trapping in the photonic crystal.     

Texture investigations of Mn?Al magnets by neutron time-of-flight diffraction

In the present work the connection between magnetic properties and texture of two samples of the tetragonal Mn Al phase is investigated. The specimens have been prepared by different cold deformation methods to get various texture types. For texture analysis neutron time-of-flight technique has been applied. Some aspects of the mathematical treatment of experimental data has been discussed. The main texture components in the inverse pole figures are inclined with respect to the direction of easy magnetization. Therefore, improved magnetic properties of the material can be expected using more optimal preparation techniques.     

Quantitative analysis of the fibre texture of zirconium by time-of-flight neutron diffraction

Quantitative analysis of the fibre texture of zirconium has been performed by the neutron time-of-flight method. On the pulsed reactor IBR-30 16 diffraction spectra were measured for each of the three deformation states of the sample. Pole figures and inverse pole figures have been determined from the experimental spectra for all deformation states investigated. The development of preferred orientation of the (101 0) lattice plane in the direction of the fibre axis in dependence on increasing deformation has been found.     

Synthesis and properties of alternating copolymers of acrylics and olefins

The free radical copolymerization and terpolymerization of acrylic monomers with olefins in the presence of Lewis acid complexing agent for the acrylic monomer has been investigated. The course of the polyreaction is in agreement with the features of a radical chain growth reaction, and the polymer properties can be varied by changing the composition of the reaction mixture and the reaction conditions. The alternating copolymers are usually amorphous materials, and only the alternating ethylene/acrylonitrile copolymer can be obtained as a material of relatively high crystallinity. The degree of crystallinity can be varied through terpolymerization of complexed acrylonitrile with ethylene/propylene comonomers. The basic features of the polyreaction and the polymer structures as well as some of the physical and material properties of the copolymers have been studied.     

Investigation into the determination of trimethylarsine in natural gas and its partitioning into gas and condensate phases using (cryotrapping)/gas chromatography coupled to inductively coupled plasma mass spectrometry and liquid/solid sorption techniques

Speciation of trialkylated arsenic compunds in natural gas, pressurized and stable condensate samples from the same gas well was performed using (Cryotrapping) Gas Chromatography-Inductively Coupled Plasma Mass Spectrometry. The major species in all phases investigated was found to be trimethylarsine with a highest concentration of 17.8 ng/L (As) in the gas phase and 33.2 μg/L (As) in the stable condensate phase. The highest amount of trimethylarsine (121 μg/L (As)) was found in the pressurized condensate, along with trace amounts of non-identified higher alkylated arsines. Volatile arsenic species in natural gas and its related products cause concern with regards to environment, safety, occupational health and gas processing. Therefore, interest lies in a fast and simple field method for the determination of volatile arsenicals. Here, we use simple liquid and solid sorption techniques, namely absorption in silver nitrate solution and adsorption on silver nitrate impregnated silica gel tubes followed by total arsenic determination as a promising tool for field monitoring of volatile arsenicals in natural gas and gas condensates. Preliminary results obtained for the sorption-based methods show that around 70% of the arsenic is determined with these methods in comparison to volatile arsenic determination using GC-ICP-MS. Furthermore, an inter-laboratory- and inter-method comparison was performed using silver nitrate impregnated silica tubes on 14 different gas samples with concentrations varying from below 1 to 1000 μg As/m³ natural gas. The results obtained from the two laboratories differ in a range of 10 to 60%, but agree within the order of magnitude, which is satisfactory for our purposes.