The catalytic efficiency of Fe-containing nanocomposites based on highly dispersed silica in the reaction of CO2 hydrogenation

Research on Chemical Intermediates - Oxide Ni(80)Fe(20)/SiO2, Co(93)Fe(7)/SiO2, and Ni(19)Co(77)Fe(4)/SiO2 nanocomposites (NCs) were prepared using highly dispersed silica. It was modified by...     

Probing How Counterion Structure and Dynamics Determine Polyelectrolyte Solutions Using EPR Spectroscopy

In this review article, we describe how methods of electron paramagnetic resonance (EPR) spectroscopy were used to investigate polyion–counterion interactions in polyelectrolyte solutions. This subject is usually treated experimentally by light, X-ray, or neutron scattering techniques. It is shown that a large arsenal of EPR spectroscopic methods–from various sophisticated methods of line shape analysis of continuous-wave EPR, via electron spin echo envelope modulation, nanoscale distance measurements through double electron–electron resonance to high-field pulse EPR–can be used to characterize the intrinsically complicated structures formed in polyelectrolyte solutions. We show that even polymer physical models such as scaling relations can be tested in this way. The distinguishing feature with respect to the numerous scattering studies in this area is that EPR techniques are local methods, and by employing spin-carrying (i.e., EPR-active) probe ions, it is possible to examine polyelectrolytes from the counterions’ point of view.     

Coiled molecules in spring loaded devices

A cylindrical capsule containing a coiled alkane incorporates spacers. The alkane lengthens and gauche strain is relieved. The spacer can be removed to reset the system to the original state. The system represents a spring-loaded device that operates reversibly in response to acids and bases.     

Even factor of bridgeless graphs containing two specified edges

An even factor of a graph is a spanning subgraph in which each vertex has a positive even degree. Let G be a bridgeless simple graph with minimum degree at least 3. Jackson and Yoshimoto (2007) showed that G has an even factor containing two arbitrary prescribed edges. They also proved that G has an even factor in which each component has order at least four. Moreover, Xiong, Lu and Han (2009) showed that for each pair of edges e₁ and e₂ of G, there is an even factor containing e₁ and e₂ in which each component containing neither e₁ nor e₂ has order at least four. In this paper we improve this result and prove that G has an even factor containing e₁ and e₂ such that each component has order at least four.     

Infrared and X-ray simultaneous spectroscopy: a novel conceptual beamline design for time resolved experiments

Many physical/chemical processes such as metal–insulator transitions or self-assembly phenomena involve correlated changes of electronic and atomic structure in a wide time range from microseconds to minutes. To investigate these dynamic processes we not only need a highly brilliant photon source in order to achieve high spatial and time resolution but new experimental methods have to be implemented. Here we present a new optical layout for performing simultaneous or concurrent infrared and X-ray measurements. This approach may indeed return unique information for example the interplay between structural changes and chemical processes occurring in the investigated sample. A beamline combining two X-ray and IR beams may really take advantage of the unique synchrotron radiation properties: the high brilliance and the broad spectrum. In this contribution we will describe the conceptual layout and the expected performance of a complex system designed to collect IR and X-ray radiation from the same bending magnet on a third-generation synchrotron radiation ring. If realized, this beamline will enable time-resolved spectroscopy experiments offering new scientific opportunities at the frontiers of science.     

Nanostructure Copper-exchanged ZSM-5 Catalytic Activity for Conversion of Volatile Organic Compounds (Toluene and Ethyl Acetate)

Gas phase catalytic oxidation of ethyl acetate and toluene was examined over copper modified ZSM‐5 catalysts under atmospheric pressure. Nanostructure of ZSM‐5 was characterized by XRD, SEM and TEM techniques. Elemental composition of ZSM‐5 was determined using EDX, ICP‐AES and XPS techniques. Results of catalytic studies showed better catalytic activity of Cu‐ZSM‐5 catalysts than those of parent ZSM‐5 and HZSM‐5, which revealed catalytic role of copper ions in the Cu‐ZSM‐5 catalysts. Effects of some parameters over catalytic conversion of these compounds were also studied. Ethyl acetate showed more reactivity than toluene over the Cu‐ZSM‐5 catalysts. Furthermore, the catalytic activity of Cu‐ZSM‐5 catalysts increased with increasing the copper loadings. The conversion behavior of a binary mixture of ethyl acetate and toluene was different from that of a single form. A promotive and inhibitive behavior was observed for conversion of ethyl acetate and toluene in the binary mixture, respectively. Water vapor as co‐feed had an inhibitive effect on conversion of organic compounds over the Cu‐ZSM‐5 catalysts.     

Network formation involving polyelectrolytes in solution: the role of counterions

The network-forming ability of a small fraction of nanosized trianions of the triarylmethyl class (TAM) with poly(diallyldimethylammonium chloride) (PDADMAC) polyelectrolyte is studied by high-field/high-frequency (94 GHz) electron paramagnetic resonance spectroscopy. These tristar-shaped organic ions are expected to undergo both electrostatic and hydrophobic interactions with PDADMAC chains. The dependence of electron spin echo (ESE)-detected spectra of the TAM spin probe on PDADMAC concentration reveals a heterogeneous distribution of the spin-carrying counterions. One fraction of these ions forms densely packed clusters while another one is highly diluted. On varying the concentration ratio of TAM spin probe/PDADMAC, the mean distance between closest neighbors within clusters of approximately 1.5 nm does not change significantly, while their fraction increases with decreasing polyelectrolyte content. These findings indicate that the nanosized organic TAM trianions induce network formation in solutions of PDADMAC polyelectrolyte. The data are consistent with a zip-like cooperative binding effect of TAM ions, making this spin probe an interesting building block for electrostatic self-assembly.Dedicated to Professor E.W. Fischer on the occasion of his 75th birthday.