3D‐printed Portable Platform for Mechanized Handling and Injection of Microvolumes Coupled to Electrochemical Detection

We present a low‐cost mechanized system fabricated using fused deposition modelling 3D‐printing technology to manipulate microvolumes and perform injections on an electrochemical cell in wall‐jet configuration. As a proof‐of‐concept, the amperometric detection of paracetamol (model analyte) on a screen‐printed electrode using 0.5 μL aliquots resulted in highly reproducible responses (RSD <3 %). Moreover, handling of microliter aliquots of butylhydroxytoluene (phenolic antioxidant) and 2,2‐diphenyl‐2‐picrylhydrazyl (DPPH) to promote the radical‐scavenging reaction to determine antioxidant capacity by electrochemical detection of residual DPPH was demonstrated (time‐controlled reaction). A final application of the system was devoted to the analysis of cocaine and a common adulterant found in seized samples. The mechanized 3D‐printed analytical platform is capable to execute diverse sample preparation steps on board by handling microliter aliquots and subsequent electrochemical detection. 3D‐printing technology enabled the fabrication of a versatile and low‐cost (<U$200) mechanized system accessible to general chemistry labs.     

Spin currents in rough graphene nanoribbons: universal fluctuations and spin injection

We investigate spin conductance in zigzag graphene nanoribbons and propose a spin injection mechanism based only on graphitic nanostructures. We find that nanoribbons with atomically straight, symmetric edges show zero spin conductance but nonzero spin Hall conductance. Only nanoribbons with asymmetrically shaped edges give rise to a finite spin conductance and can be used for spin injection into graphene. Furthermore, nanoribbons with rough edges exhibit mesoscopic spin conductance fluctuations with a universal value of rmsG_{s} approximately 0.4e/4pi.     

Semiclassical mechanism for the quantum decay in open chaotic systems

We address the decay in open chaotic quantum systems and calculate semiclassical corrections to the classical exponential decay. We confirm random matrix predictions and, going beyond, calculate Ehrenfest time effects. To support our results we perform extensive numerical simulations. Within our approach we show that certain (previously unnoticed) pairs of interfering, correlated classical trajectories are of vital importance. They also provide the dynamical mechanism for related phenomena such as photoionization and photodissociation, for which we compute cross-section correlations. Moreover, these orbits allow us to establish a semiclassical version of the continuity equation.     

Accurate reflectance measurements in the infrared spectral range using an integrating sphere

An integrating sphere is used together with a Fourier transform spectrometer for directional-hemispherical reflectance measurements in the spectral range from 1m to 15m. Comparisons with PTB's fundamental sphere reflectometer around 1m show that the uncertainty of the infrared measurements is ±0.01.     

Investigation of the thermal stability of Ni/C multilayers by X-ray methods

Microstructural properties of Ni/C multilayers prepared by PLD (pulsed laser deposition) have been investigated after heat treatment in vacuum at temperatures in the range of 50°C to 500°C. X-ray diffractometry, X-ray reflectometry, fluorescence EXAFS (extended X-ray absorption fine structure) and HREM (high resolution transmission electron microscopy) have been applied to characterize samples in the initial state and after annealing. The multilayer reflectivity remained unchanged or increased at temperatures below 400°C due to sharpening of the interfaces caused by the formation of -nickel and nickel carbide. The reflectivity decreased at temperatures above 400°C because of the fragmentation of the nickel layers. It can be shown, that both chemical and mechanical driving forces are responsible for the observed modifications of the initial specimen state.     

The fragmentation behavior of differently substituted 2-amino-1,3,4-benzotriazepines

The mass spectra of eighteen 2-amino-1,3,4-benzotriazepines were recorded under electron ionization, and the fragmentation patterns were elucidated by metastable ion analysis and exact mass measurements. The most typical fragmentations were ring contraction reactions with the loss of nitrogen atoms at positions 3 and 4. Extensive rearrangement reactions took place as well. In these the substituted 2-amino group played an important role. Isomeric compounds were easily distinguished.     

Molekülstrukturen von Kupfer(II)- und Eisen(III)-Chlorokomplexen mit di- und monoprotoniertem N-(Pyrid-2-ylmethyl)ethylendiamin-N,N′,N′-triacetat (H2pedta−; Hpedta2−)

Molecular Structures of Copper(II) and Iron(III) Chloro Complexes with di- and monoprotonated N-(pyrid-2-ylmethyl)ethylenediamine-N,N′,N′-triacetate (H₂pedta^?; Hpedta^2?) The molecular structures of two complexes of di- and monoprotonated N-(pyrid-2-ylmethyl)ethylenediamine-N,N′,N′ -triacetate (pedta^3?) with Cu^II and Fe^III as central atoms have been determined by single crystal X-ray diffraction methods. Both complexes have a distorted octahedral coordination with H₂pedta^? and Hpedta^2? as pentadentate ligands and a chloride ion occupying the sixth coordination site. The different oxidation states of the central atoms result in a completely different coordination behaviour of the carboxyl groups. In both complexes one of the ? CH₂? COOH groups is uncoordinated. In the Fe^III complex, the central atom is coordinated by the hydroxylic O atoms of the deprotonated carboxyl groups. Contrary to this in the Cu^II complex, the central atom is coordinated by the carbonylic O atoms. One of the coordinated carboxyl groups is protonated and the other is deprotonated. All protonated carboxyl groups in both complexes form intermolecular hydrogen bonds.     

Synthese von Aryl-bis(trimethylsilyl)-phosphonsäureestern via Tris-trimethylsilylphosphit – Ein Beitrag zur nickel- katalysierten Michaelis-Arbusov-Reaktion

Synthesis of Aryl-bis(trimethylsilyl)-phosphonic Acid Esters via Tris-trimethylsilylphosphite – a Contribution of the Nickel-catalyzed Michaelis-Arbusov Reaction . The preparation of various aryl-bis(trimethylsilyl)-phosphonic acid esters via P(OSiMe₃)₃ or a mixture of HP(O)(OSiMe₃)₂/P(OSiMe₃)₃/Me₃Si? NH? SiMe₃ in presence of nickel compounds are described. The structures are proved by the ³¹P n.m.r. spectra.