Synthesis and Characterization of Ligand-Linked Pt Nanoparticles: Tunable,Three-Dimensional,Porous Networks for Catalytic Hydrogen Sensing

Porous networks of Pt nanoparticles interlinked by bifunctional organic ligands have shown high potential as catalysts in micro-machined hydrogen gas sensors. By varying the ligand among p-phenylenediamine, benzidine, 4,4‘‘-diamino-p-terphenyl, 1,5-diaminonaphthalene, and trans-1,4-diaminocyclohexane, new variants of such networks were synthesized. Inter-particle distances within the networks, determined via transmission electron microscopy tomography, varied from 0.8 to 1.4 nm in accordance with the nominal length of the respective ligand. While stable structures with intact and coordinatively bonded diamines were formed with all ligands, aromatic diamines showed superior thermal stability. The networks exhibited mesoporous structures depending on ligand and synthesis strategy and performed well as catalysts in hydrogen gas microsensors. They demonstrate the possibility of deliberately tuning micro- and mesoporosity and thereby transport properties and steric demands by choice of the right ligand also for other applications in heterogeneous catalysis.     

Cascade Synthesis of Pyrroles from Nitroarenes with Benign Reductants Using a Heterogeneous Cobalt Catalyst

A bifunctional 3d-metal catalyst for the cascade synthesis of diverse pyrroles from nitroarenes is presented. The optimal catalytic system Co/NGr-C@SiO₂-L is obtained by pyrolysis of a cobalt-impregnated composite followed by subsequent selective leaching. In the presence of this material, (transfer) hydrogenation of easily available nitroarenes and subsequent Paal–Knorr/Clauson-Kass condensation provides >40 pyrroles in good to high yields using dihydrogen, formic acid, or a CO/H₂O mixture (WGSR conditions) as reductant. In addition to the favorable step economy, this straightforward domino process does not require any solvents or external co-catalysts. The general synthetic utility of this methodology was demonstrated on a variety of functionalized substrates including the preparation of biologically active and pharmaceutically relevant compounds, for example, (+)-Isamoltane.     

Extreme-field physics in Penning traps

We present two Penning trap experiments concerned with different aspects of the physics of extreme electromagnetic fields, the ARTEMIS experiment designed for bound-electron magnetic moment measurements in the presence of the extremely strong fields close to the nucleus of highly charged ions, and the HILITE experiment, in which well-defined ion targets are to be subjected to high-intensity laser fields.     

Development of cellulose nanowhisker-polyacrylamide copolymer as a highly functional precursor in the synthesis of nanometal particles for conductive textiles

Herein we present extensive studies that were undertaken to develop a new copolymer with distinctive characteristics for utilization in different applications particularly in conductive textiles. The copolymer is based on graft polymerization of cellulose nanowhiskers (CNWs) with acrylamide and therefore nominated CNW-polyacrylamide (PAAm) copolymer. Development of this copolymer comprises preparation of CNWs from purified cotton sliver as per the acid hydrolysis method, followed by copolymerization of the freshly prepared CNWs with AAm at different feeding ratios for the sake of product optimization in the presence of K₂S₂O₈ as initiator. Thus, obtained CNW-PAAm copolymers were characterized by making use of the proper instruments and analysis facilities. Following this, the newly prepared and promising copolymer was selected and used as a precursor in the green synthesis of silver and copper nanoparticles. The crystal nature of CNWs as cellulose I remains unaltered after copolymerization, but the crystallinity decreases. According to thermal gravimetric analysis, the copolymer is much more thermally stable than CNWs. The CNW-PAAm copolymer can be used successfully as a highly functional, effective and adequate precursor for green synthesis of silver and copper nanoparticles as shown by UV-Vis spectral analysis and transmission electron microscopy micrographs. A multi-branched shape and hyperbranched shape-like tree involving silver nanoparticles and the PAAm graft of the copolymer are formed. Furthermore, Cu nanoparticles are chosen as a candidate for conductive fabrics application.     

False theta functions and companions to Capparelli's identities

Capparelli conjectured two modular identities for partitions whose parts satisfy certain gap conditions, which were motivated by the calculation of characters for the standard modules of certain affine Lie algebras and by vertex operator theory. These identities were subsequently proved and refined by Andrews, who related them to Jacobi theta functions, and also by Alladi–Andrews–Gordon, Capparelli and Tamba–Xie. In this paper we prove two new companions to Capparelli's identities, where the evaluations are expressed in terms of Jacobi theta functions and false theta functions.