Particle shape optimization by changing from an isotropic to an anisotropic nanostructure: preparation of highly active and stable supported Pt catalysts in microemulsions

We recently introduced a new method to synthesize an active and stable Pt catalyst, namely thermo-destabilization of microemulsions (see R. Y. Parapat, V. Parwoto, M. Schwarze, B. Zhang, D. S. Su and R. Schomäcker, J. Mater. Chem., 2012, 22 (23), 11605–11614). We are able to produce Pt nanocrystals with a small size (2.5 nm) of an isotropic structure i.e. truncated octahedral and deposit them well on support materials. Although we have obtained good results, the performance of the catalyst still needed to be improved and optimized. We followed the strategy to retain the small size but change the shape to an anisotropic structure of Pt nanocrystals which produces more active sites by means of a weaker reducing agent. We found that our catalysts are more active than those we reported before and even show the potential to be applied in a challenging reaction such as hydrogenation of levulinic acid

Indirect and direct optical transitions in In0.5Ga0.5As/GaP quantum dots

We present a study of self-assembled In0.5Ga0.5As quantum dots on GaP(001) surfaces linking growth parameters with structural, optical, and electronic properties. Quantum dot densities from 5.0 × 107 cm−2 to 1.5 × 1011 cm−2 are achieved. A ripening process during a growth interruption after In0.5Ga0.5As deposition is used to vary the quantum dot size. The main focus of this work lies on the nature of optical transitions which can be switched from low-efficient indirect to high-efficient direct ones through improved strain relief of the quantum dots by different cap layers

Growth and structure of In0.5Ga0.5Sb quantum dots on GaP(001)

Stranski-Krastanov (SK) growth of In0.5Ga0.5Sb quantum dots (QDs) on GaP(001) by metalorganic vapor phase epitaxy is demonstrated. A thin GaAs interlayer prior to QD deposition enables QD nucleation. The impact of a short Sb-flush before supplying InGaSb is investigated. QD growth gets partially suppressed for GaAs interlayer thicknesses below 6 monolayers. QD densities vary from 5 × 109 to 2 × 1011 cm−2 depending on material deposition and Sb-flush time. When In0.5Ga0.5Sb growth is carried out without Sb-flush, the QD density is generally decreased, and up to 60% larger QDs are obtained

The JNK Inhibitor XG-102 Protects against TNBS-Induced Colitis

The c-Jun N-terminal kinase (JNK)-inhibiting peptide D-JNKI-1, syn. XG-102 was tested for its therapeutic potential in acute inflammatory bowel disease (IBD) in mice. Rectal instillation of the chemical irritant trinitrobenzene sulfonic acid (TNBS) provoked a dramatic acute inflammation in the colon of 7–9 weeks old mice. Coincident subcutaneous application of 100 µg/kg XG-102 significantly reduced the loss of body weight, rectal bleeding and diarrhoea. After 72 h, the end of the study, the colon was removed and immuno-histochemically analysed. XG-102 significantly reduced (i) pathological changes such as ulceration or crypt deformation, (ii) immune cell pathology such as infiltration and presence of CD3- and CD68-positive cells, (iii) the production of tumor necrosis factor (TNF)-α in colon tissue cultures from TNBS-treated mice, (iv) expression of Bim, Bax, FasL, p53, and activation of caspase 3, (v) complexation of JNK2 and Bim, and (vi) expression and activation of the JNK substrate and transcription factor c-Jun. A single application of subcutaneous XG-102 was at least as effective or even better depending on the outcome parameter as the daily oral application of sulfasalazine used for treatment of IBD

The influence of heat Treatments on the microstructure and the mechanical properties in Commercial 7020 alloys

The spatial distribution of Al in magnetron sputtered ZnO Al films has been investigated in depth. Two different kinds of inhomogeneities were observed an enrichment in the bulk of the film and an enrichment at the interface to the substrate. This has been correlated to the electrical properties of the films the former inhomogeneities can lead to trap states at the grain boundaries limiting the free carrier mobility. The latter can promote the formation of secondary phases, which leads to an electrical inactivation of the dopant. Furthermore, this effect can contribute to the thickness dependence of the electrical properties of ZnO Al film

A rabies serosurvey of domestic dogs in rural Tanzania: results of a rapid fluorescent focus inhibition test (RFFIT) and a liquid-phase blocking ELISA used in parallel.

During a serosurvey of domestic dogs in Tanzania, a rapid fluorescent focus inhibition test (RFFIT) and a liquid-phase blocking ELISA (LPBE) were used to measure rabies antibodies in vaccinated and unvaccinated dogs. Post-vaccination titres measured by LPBE correlated closely with those found by RFFIT. Of 567 unvaccinated dogs tested using the LPBE, 42 (7.4%) were seropositive, with titres exceeding 32. Of this group, 233 dogs were tested using the RFFIT and 115 (49.4%) were seropositive, with titres exceeding 0.5 IU/ml. Two lines of evidence pointed to the greater specificity of the LPBE when measuring rabies antibodies induced by natural infections: (a) no seropositive dogs were detected among the 162 unvaccinated dogs from the rabies-free island of Pemba, Tanzania, when using LPBE, whereas 15/145 (10.3%) dogs of the same group were seropositive using RFFIT; (b) among Tanzanian dogs there was a close association between the location of rabies cases and location of seropositive dogs when using LPBE, but not when using RFFIT. These results suggest that LPBE may be of value in rabies seroepidemiological studies and could be developed as a reference technique for the detection of rabies antibody in domestic dogs

Correction: Particle shape optimization by changing from an isotropic to an anisotropic nanostructure: Preparation of highly active and stable supported Pt catalysts in microemulsions

Correction for ‘Particle shape optimization by changing from an isotropic to an anisotropic nanostructure: preparation of highly active and stable supported Pt catalysts in microemulsions’ by Riny Y. Parapat et al., Nanoscale, 2013, 5, 796–805

Optical properties of silver nanocube surfaces obtained by silane immobilization

Silver nanocubes were synthesized by the polyol method and immobilized on a surface in a simple approach using an aminopropyltriethoxysilane (APTES). The optical and structural properties of the polyvinylpyrrolidone (PVP) stabilized nanocubes were investigated in solution and on glass surfaces. The SERS enhancement factors at two excitation wavelengths for crystal violet were compared with electric fields arising in different nano¬particle configurations using finite-difference time-domain simulations. They are in agreement with the preferred face-to-face orientation in the nanoaggregates on the surfaces. The facile immobilization enables on-demand preparation and use of the nanocubes in real analytical applications

Concave curvature facets benefit oxygen electroreduction catalysis on octahedral shaped PtNi nanocatalysts

Studies that demonstrated enhanced electrocatalytic oxygen reduction activities of octahedral PtNi nanocatalysts have routinely motivated and explained their data by the structure-sensitivity of PtNi alloy surfaces in general, more specifically by the favourable performance of the annealed Pt3Ni(111) single crystal surface with a monoatomic Pt skin, in particular. In this contribution, we challenge this view and show that imperfect Ni-enriched {111} nanofacets with concave Pt curvature catalytically outperform flat, well-alloyed, locally ordered {111} and {100} nanofacets in cuboctahedral nanoparticles. To achieve this, we investigate the geometric, compositional, and morphological structure on the ensemble and on the individual particle level of PtNi alloy nano-octahedra. In particular, we track the correlations of these parameters after thermal annealing and link them to their catalytic activity. The level of local compositional and structural disorder appears to be a reliable descriptor and predictor for ORR activity – at least within a family of catalysts. After annealing up to 300 °C, concave Pt {111} facets, with partially flat Ni facets, remained most prevalent, resulting in nanoparticles with pronounced elemental anisotropy. At higher annealing temperature, concave Pt morphologies gave way to cuboctahedra with healed flat {111} and {100} alloy facets. The imperfect concave nano-octahedral catalysts with enhanced local disorder invariably outperformed more ordered particles, yet lagged behind in morphological stability. Faceted PtNi nano-cuboctahedra emerging at 400 °C ultimately offered the most reasonable balance between moderately high activity and good morphological stability. This is why we propose these cuboctahedral shaped Pt alloy nanoparticles as promising PEM cathode fuel cell catalyst of choice. While the present results do not invalidate the exceptional oxygen reduction activity of perfect Pt3Ni(111) “skin” single crystal surfaces, they shed new light on the decade old puzzle about structure–activity relationships of PtNi octahedral nanocrystals