Study on electrolyte stability and oxygen reduction reaction mechanisms in the presence of manganese oxide catalysts for aprotic lithium-oxygen batteries

The impact of different manganese oxide electrocatalysts on the oxygen reduction reaction (ORR) in aprotic media was investigated. In the absence of a catalyst on pure carbon powder, the ORR was found to proceed partially by O2 dissociation before reduction. The O adatoms generated during this process have been reported previously to promote the decomposition of aprotic electrolytes. The extent to which this mechanism takes place depends strongly on the potential scan rate applied during the cyclic voltammetry measurements. The presence of manganese oxides has different effects on the reaction mechanism: whereas Mn3O4 and Mn5O8 nanoparticles promote chemical O2 dissociation, mesoporous α-Mn2O3 particles suppress this mechanism in favor of the direct reduction of O2, thus forming the desired final product Li2O2. These results lead to a better understanding of the morphological and structural properties, which ideal catalysts for an application in aprotic Li–air batteries should exhibit

Doping dependent phase fractions in hydrothermally synthesized Mn doped CuFeO2

Using a simple hydrothermal method, CuFe1−xMnxO2 delafossite materials are produced and investigated by means of X-ray diffraction, ultraviolet-visible reflectance measurements, and electron microscopy. Up to nominally x = 0.3, the synthesis yields delafossite material, which generally consists of both the 2H and R3 phase without any impurities. Lattice parameters and the indirect optical band gap of delafossite close to about 1.3 eV decrease upon increasing Mn content, which confirms the successful doping with Mn up to an actual Mn content of x = 0.05. The 2H phase fraction shows a pronounced and peaked dependence on Mn content with a maximum 2H mass fraction of about 27% at nominally x = 0.01, whereas the hexagonal particle morphology and the platelet size of about 500 nm as measured by both scanning and transmission electron microscopy are independent from the latter

Nucleus accumbens activation is linked to salience in social decision making

Aberrant salience may explain hasty decision making and psychotic symptoms in schizophrenia. In healthy individuals, final decisions in probabilistic reasoning tasks are related to Nucleus accumbens (Nacc) activation. However, research investigating the Nacc in social decision making is missing. Our study aimed at investigating the role of the Nacc for social decision making and its link to (aberrant) salience attribution. 47 healthy individuals completed a novel social jumping-to-conclusion (JTC) fMRI-paradigm, showing morphed faces simultaneously expressing fear and happiness. Participants decided on the 'current' emotion after each picture, and on the 'general' emotion of series of faces. Nacc activation was stronger during final decisions than in previous trials without a decision, particularly in fear rather than happiness series. A JTC-bias was associated with higher Nacc activation for last fearful, but not last happy faces. Apparently, mechanisms underlying probabilistic reasoning are also relevant for social decision making. The pattern of Nacc activation suggests salience, not reward, drives the final decision. Based on these findings, we hypothesize that aberrant salience might also explain social-cognitive deficits in schizophrenia.publishe

Emotion recognition in borderline personality disorder : effects of emotional information on negative bias

Background: Borderline Personality Disorder (BPD) is characterized by severe deficits in social interactions, which might be linked to deficits in emotion recognition. Research on emotion recognition abilities in BPD revealed heterogeneous results, ranging from deficits to heightened sensitivity. The most stable findings point to an impairment in the evaluation of neutral facial expressions as neutral, as well as to a negative bias in emotion recognition; that is the tendency to attribute negative emotions to neutral expressions, or in a broader sense to report a more negative emotion category than depicted. However, it remains unclear which contextual factors influence the occurrence of this negative bias. Previous studies suggest that priming by preceding emotional information and also constrained processing time might augment the emotion recognition deficit in BPD.Methods: To test these assumptions, 32 female BPD patients and 31 healthy females, matched for age and education, participated in an emotion recognition study, in which every facial expression was preceded by either a positive, neutral or negative scene. Furthermore, time constraints for processing were varied by presenting the facial expressions with short (100 ms) or long duration (up to 3000 ms) in two separate blocks.Results: BPD patients showed a significant deficit in emotion recognition for neutral and positive facial expression, associated with a significant negative bias. In BPD patients, this emotion recognition deficit was differentially affected by preceding emotional information and time constraints, with a greater influence of emotional information during long face presentations and a greater influence of neutral information during short face presentations.Conclusions: Our results are in line with previous findings supporting the existence of a negative bias in emotion recognition in BPD patients, and provide further insights into biased social perceptions in BPD patients.publishe

Magnetism and hyperfine interactions in the hexagonal polymorph of delafossite CuFeO 2

peer reviewedThe magnetic susceptibility of and hyperfine interactions in the hexagonal 2H polymorph of delafossite CuFeO2 were investigated by SQUID magnetometry and Mössbauer spectroscopy, respectively, at low temperatures. The hydrothermally synthesized 2H-CuFeO2 sample contained a 10 vol-% α-Fe2O3 impurity detected by X-ray diffraction, whose contribution to the susceptibility and hyperfine interactions were easily distinguishable from the major 2H-CuFeO2 one. Morphology and indirect optical band gap investigated by scanning electron microscopy and diffuse reflectance measurements showed well expected results for a hydrothermally synthesized delafossite sample. The magnetic susceptibility of 2H-CuFeO2 revealed a first antiferromagnetic like transitions at 16 K and a second transition at 13.5 K or 10 K depending on measurement protocol, which points towards modified exchange interactions as compared to the 3R polymorph. Complementary Mössbauer measurements revealed complicated spectral shapes at low temperatures indicating rather complex magnetic structures and magnetic relaxations above 20 K

Magnetism and hyperfine interactions in the hexagonal polymorph of delafossite CuFeO 2

The magnetic susceptibility of and hyperfine interactions in the hexagonal 2H polymorph of delafossite CuFeO were investigated by SQUID magnetometry and Mössbauer spectroscopy, respectively, at low temperatures. The hydrothermally synthesized 2H-CuFeO sample contained a 10 vol-% -FeO impurity detected by X-ray diffraction, whose contribution to the susceptibility and hyperfine interactions were easily distinguishable from the major 2H-CuFeO one. Morphology and indirect optical band gap investigated by scanning electron microscopy and diffuse reflectance measurements showed well expected results for a hydrothermally synthesized delafossite sample. The magnetic susceptibility of 2H-CuFeO revealed a first antiferromagnetic like transitions at 16 K and a second transition at 13.5 K or 10 K depending on measurement protocol, which points towards modified exchange interactions as compared to the 3R polymorph. Complementary Mössbauer measurements revealed complicated spectral shapes at low temperatures indicating rather complex magnetic structures and magnetic relaxations above 20 K

Manganese oxide phases and morphologies: A study on calcination temperature and atmospheric dependence

Manganese oxides are one of the most important groups of materials in energy storage science. In order to fully leverage their application potential, precise control of their properties such as particle size, surface area and Mnx+ oxidation state is required. Here, Mn3O4 and Mn5O8 nanoparticles as well as mesoporous α-Mn2O3 particles were synthesized by calcination of Mn(II) glycolate nanoparticles obtained through an economical route based on a polyol synthesis. The preparation of the different manganese oxides via one route facilitates assigning actual structure–property relationships. The oxidation process related to the different MnOx species was observed by in situ X-ray diffraction (XRD) measurements showing time- and temperature-dependent phase transformations occurring during oxidation of the Mn(II) glycolate precursor to α-Mn2O3 via Mn3O4 and Mn5O8 in O2 atmosphere. Detailed structural and morphological investigations using transmission electron microscopy (TEM) and powder XRD revealed the dependence of the lattice constants and particle sizes of the MnOx species on the calcination temperature and the presence of an oxidizing or neutral atmosphere. Furthermore, to demonstrate the application potential of the synthesized MnOx species, we studied their catalytic activity for the oxygen reduction reaction in aprotic media. Linear sweep voltammetry revealed the best performance for the mesoporous α-Mn2O3 species

Synthesis of lead chalcogenide nanocrystals and study of charge transfer in blends of PbSe nanocrystals and poly(3-hexylthiophene)

Nearly monodisperse lead chalcogenide (PbE, E = S, Se, or Te) semiconductor quantum dots of controllable shape have been produced via a novel synthesis which includes the occurrence of in situ formed Pb-0 particles. Tunable size and shape are achieved through appropriate choice of the precursor type and the stabilizer. As precursor, we use, on the one hand, lead oxide or lead acetate, on the other hand, tellurium, selenium, or sulfur powder dissolved in trioctylphosphine (TOP), tributylphosphine (TBP), or 1-octadecene (ODE). Oleic acid (OA) and various amines, as well as TOP and TBP are used for stabilization. With respect to possible application in hybrid solar cells, the surface of as-synthesized spherical PbSe nanocrystals was investigated by nuclear magnetic resonance (NMR), mass spectrometry (MS) and thermogravimetric analysis (TGA). As an important result, it was found that the surface is not mostly covered by oleic acid after synthesis, but by a phosphorus compound. We also applied a ligand exchange procedure with hexylamine and found evidence for the successful attachment of hexylamine to the nanocrystal surface. Additionally, charge separation between these nanoparticles and the conjugated polymer poly(3-hexylthiophene) (P3HT) is studied by electron spin resonance and photoinduced absorption spectroscopy. The spectra obtained suggest that charges can be produced successfully by photoinduced charge transfer