Crystal structure of thiogermanic acid H(4)Ge(4)S(10)

X-ray diffraction analysis reveals the thiogermanic acid H(4)Ge(4)S(10) possesses discrete adamantane-like Ge(4)S(10)(4)(-) complex anions. Each thioanion is composed of four corner shared GeS(2.5)(-) tetrahedral units. Crystals were grown from anhydrous liquid hydrogen sulfide reactions with glassy germanium sulfide at room temperature. The crystal structure was solved and refined from single crystal diffractometer data (Mo Kalpha radiation) obtained at 173 K. H(4)Ge(4)S(10) is triclinic, centrosymmetric space group Ponemacr;, with a = 8.621(4) A, b = 9.899(4) A, c = 10.009(4) A, alpha = 85.963(7) degrees, beta = 64.714(7) degrees, gamma = 89.501(8) degrees, and Z = 2. Average bridging and terminal d(Ge-S) distances are 2.229 and 2.206 A, respectively. Vibrational mode assignments are reported from Raman scattering and IR absorption spectra of polycrystalline samples. The nu(s)(Ge-S-Ge) and nu(s)(Ge-S(-)) stretching modes are observed at 354 and 405 cm(-)(1), respectively.     

Non-covalent reconfigurable microgel colloidosomes with a well-defined bilayer shell

Microgels are extremely interfacially active and are widely used to stabilize emulsions. However, they are commonly used to stabilize oil-in-water emulsions due to their intrinsic hydrophilicity and initially dispersed in water. In addition, there have been no attempts to control microgel structural layers that are formed at the interface and as a result it limits applications of microgel in advanced materials. Here, we show that by introducing octanol into poly(N-isopropylacrylamide-co-methacrylic acid) (PNIPAM-co-MAA) microgels, octanol-swollen microgels can rapidly diffuse from the initially dispersed oil phase onto the water droplet surface. This facilitates the formation of microgel-laden interfacial layers with strong elastic responses and also generates stable inverse water-in-oil Pickering emulsions. These emulsions can be used as templates to produce microgel colloidosomes, herein termed ‘microgelsomes’, with shells that can be fine-tuned from a particle monolayer to a well-defined bilayer. The microgelsomes can then be used to encapsulate and/or anchor nanoparticles, proteins, vitamin C, bio-based nanocrystals or enzymes. Moreover, the programmed release of these substances can be achieved by using ethanol as a trigger to mediate shell permeability. Thus, these reconfigurable microgelsomes with a microgel-bilayer shell can respond to external stimuli and demonstrate tailored properties, which offers novel insights into microgels and promise wider application of Pickering emulsions stabilized by soft colloids.

Inverse W/O Pickering emulsions and reconfigurable microgelsomes with a well-defined bilayer structure are prepared from octanol-swollen PNIPAM-co-MAA microgels and the combination of binary microgels, which promise wider application of soft colloids.     

A new method for the determination of the 34S/32S ratio of water-soluble sulphur in soil

A new method for the determination of the ³⁴S/³²S ratio of water-extractable sulphate in soil is described. Soils are extracted directly with deionized water, which is evaporated down. The remaining residue is then rehydrated and transferred to tin cups containing an adsorbent and mixed with an oxygen donor (V₂O₅). Samples are then analysed using a continuous flow isotope ratio mass spectrometer. The new method requires around 10?g soil per determination, compared to much larger amounts (up to kilograms) of soil required for the previous methods. Sample preparation and subsequent analysis is quick and efficient. The method is demonstrated using a number of soils collected from around the world to provide a range of determined δ³⁴S values. The δ³⁴S values of water-extractable sulphur were broadly similar to those of the soil total sulphur.     

Detailed comparison of the pnicogen bond with chalcogen,halogen, and hydrogen bonds

The characteristics of the pnicogen bond are explored using a variety of quantum chemical techniques. In particular, this interaction is compared with its halogen and chalcogen bond cousins, as well as with the more common H‐bond. In general, these bonds are all of comparable strength. More specifically, they are strengthened by the presence of an electronegative substituent on the electron‐acceptor atom, and each gains strength as one moves down the appropriate column of the periodic table, for example, from N to P to As. These noncovalent bonds owe their stability to a mixture in nearly equal parts of electrostatic attraction and charge transfer, along with a smaller dispersion component. The charge transfer arises from the overlap between the lone pair of the electron donor and a σ* antibond of the acceptor. The angular characteristics of the equilibrium geometry result primarily from a compromise between electrostatic and induction forces. Angular distortions of the H‐bond are typically less energetically demanding than comparable bends of the other noncovalent bonds. © 2012 Wiley Periodicals, Inc.     

High Activity and Selective Fischer–Tropsch Catalysts for Use in a Microchannel Reactor

Each process configuration for practicing the Fischer–Tropsch synthesis places demands particular to that configuration on the catalyst to be used. We discuss how a particular catalyst, prepared by the OMX (organic matrix combustion) method, when used in conjunction with the Velocys microchannel reactor system, results in a very stable, high performance Fischer–Tropsch synthesis system. With the ability to remove heat far more effectively than a conventional reactor system, this microchannel reactor requires a catalyst with much higher volumetric reactive site density. Further, with such a high volumetric reaction rate, mass transfer effects will be important in both the observed activity and selectivity of the operating catalyst. Nevertheless, the catalyst prepared using the OMX method exhibits an apparent turnover frequency which is considerably higher than reported for other catalysts in the literature. In addition to high activity, an economically useful catalyst must exhibit a stable, high selectivity for liquid products and be able to recover near-fresh performance using a regeneration approach which can be carried out with the catalyst in-place. An example of such a stable, multiply regenerated catalyst is given. Finally, further development has focused on a catalyst with even higher C₅₊ selectivity.     

Aerobic Epoxidation of Alkenes Catalysed by Cobalt(II) 1,1,1,5,5,5-Hexafluoroacetylacetonate or Cobalt(II) Benzoylacetonate

The aerobic epoxidation of terminal or electron deficient alkenes with an aldehyde does not proceed with cobalt(II) acetylacetonate but goes to completion with the cobalt(II) benzoylacetonate and cobalt(II) 1,1,1,5,5,5-hexafluoroacetylacetonate complexes.     

Optical studies of dynamic director configurations in ferroelectric liquid crystal devices

An investigation into the transmission spectrum of a ferroelectric liquid crystal device is undertaken. This is done both for an initial static state and during a switching process. Comparisons are made between experimental data and theoretical predictions. The dynamic internal director configurations in the device is shown to be consistent with a simple model during both monopolar and bipolar addressing pulses.