Adsorption mechanisms of glucose in aqueous goethite suspensions

The adsorption of glucose and polysaccharides onto solid surfaces is important in several areas of science and engineering including soil chemistry and mineral processing. In this work we have studied the adsorption of D-glucose at the water-goethite (α-FeOOH) interface as a function of pH using batch adsorption measurements and a simultaneous infrared and potentiometric technique. Molecular orbital calculations were also performed in order to support interpretations of the infrared spectroscopic data. Infrared spectroscopy has shown that glucose adsorbs at the water-goethite interface with an intact ring structure and that the β-form is favored relative to the α isomer. The collective spectroscopic and macroscopic results were fully consistent with an adsorption mechanism where glucose interacts with goethite surface sites via hydrogen bonding interactions. Specific infrared peak shifts indicated that glucose primarily acts as a hydrogen bond donor and that it interacts with acceptor sites that become increasingly more prevalent as the surface is deprotonated. These results are in general agreement with the acid/base model for mono- and polysaccharide interactions at metal oxide surfaces, but contradict the inner sphere hypothesis that was proposed based on ex situ spectroscopic measurements.     

Introduction to the special issue Stochastic Financial Economics, Volume 1

Outlined here are the research papers published in Volume 1 of the special issue Stochastic Financial Economics, each considering investor behavior in financial markets.     

Novel Colored Systems of the “Inverted Triphenylmethylium Dye” Type Containing Nitrogen,Phosphorus, Sulfur and Congeneric Donor Centers

Abstract

In the course of a fundamental study relating to the question of color and constitution it was found, that a simple HMO-treatment of the isoconjugate resonance system of triphenylmethylium (TPM) dyes¹ provides a very variegated scenery for imagining some novel dye systems. Thus, for the archetype of all TPM-dyes, crystal violet, the spectroscopically relevant frontier orbitals show above a core of nine bonding MO's with a limiting energy of ß, two nonbonding levels (nb), one slightly bonding (b) and one slightly antibonding (ab) MO, respectively. The occupancy of the frontier orbitals is 6, so that the longest wavelength absorption corresponds to an excitation from a nb-MO to the weakly antibonding MO. One sees at once, that diminuation of the frontier orbital occupancy by 4, leaving only 2 electrons, should generate a new dye system presenting approximatly the same color as crystal violet, since now the longest wavelength absorption would correspond to a transition from the (symmetrically situated) slightly bonding MO to a nb-MO.     

Alignment of low‐dose X‐ray fluorescence tomography images using differential phase contrast

X‐ray fluorescence nanotomography provides unprecedented sensitivity for studies of trace metal distributions in whole biological cells. Dose fractionation, in which one acquires very low dose individual projections and then obtains high statistics reconstructions as signal from a voxel is brought together (Hegerl & Hoppe, 1976), requires accurate alignment of these individual projections so as to correct for rotation stage runout. It is shown here that differential phase contrast at 10.2 keV beam energy offers the potential for accurate cross‐correlation alignment of successive projections, by demonstrating that successive low dose, 3 ms per pixel, images acquired at the same specimen position and rotation angle have a narrower and smoother cross‐correlation function (1.5 pixels FWHM at 300 nm pixel size) than that obtained from zinc fluorescence images (25 pixels FWHM). The differential phase contrast alignment resolution is thus well below the 700 nm × 500 nm beam spot size used in this demonstration, so that dose fractionation should be possible for reduced‐dose, more rapidly acquired, fluorescence nanotomography experiments.     

Redox Switching in Ethenyl‐Bridged Bisphospholes

A 2e^?/2H⁺ redox platform has been implemented in the ethenyl‐bridged bisphosphol‐3‐ol 1 to afford the first phospholes that feature chemically reversible oxidations. Oxidation of the title compounds to the corresponding bisphosphol‐3‐one 2 leads to a change in conjugation topology and a concomitant hypsochromic shift of the lowest‐energy absorption maximum by 100 nm. Electrochemical oxidation proceeds without any detectable intermediates, whereas the deprotonated form of 1 can be observed in an aprotic medium during the reduction of 2 . This dianionic intermediate 3 is characterized by end absorptions that are bathochromically shifted by circa 200 nm compared to those of 2 .     

Formation of N-alkoxyindole framework: intramolecular heterocyclization of 3-alkoxyimino-2-arylalkylnitriles mediated by ferric chloride

A variety of functionalized N-alkoxyindole-3-carbonitrile derivatives are achieved under remarkably mild conditions by applying a FeCl3-mediated intramolecular heterocyclization of 3-alkoxyimino-2-arylalkylnitriles. This novel synthesis allows the N-moiety on the side chain to be annulated to the benzene ring as the final synthetic step, which enables the functionalization of the benzenoid portion of the indole at an early stage of the synthesis.     

Supercritical fluid swelling of liquid crystal films

The influence of liquid and supercritical carbon dioxide and liquid propane on the structural properties of both ionic and nonionic surfactant-based liquid crystal films is discussed in this paper. Swelling of the films, measured using in situ small-angle neutron scattering (SANS), was found to be dependent on the solubility of the propane/carbon dioxide in the micelles of the respective liquid crystals. Additionally, under certain pressure conditions the structural properties of some of the films were observed to change, ultimately leading to a loss of order in the micellar arrays of the liquid crystals.     

Elusive trimethyllanthanum: snapshots of extensive methyl group degradation in la--Al heterobimetallic complexes

Reactions of [La(AlMe4)3] and [Y(AlMe4)3] with PMe3 show that the phosphine can cleave Ln--CH3--Al linkages, separating Me3Al(PMe3). PMe3 (3 mol equiv) reacts with [Y(AlMe4)3] to give [(YMe3)n] contaminated with by-products containing phosphorus and aluminum. The La-based analog, [(LaMe3)n], is not formed selectively from the reaction of [La(AlMe4)3] with PMe3 or Et2O, which rather yields insoluble La/Al heterobimetallic products. Three multi-nuclear La-based clusters were obtained from a reaction of [La(AlMe4)3] with PMe3 (1 equiv) and identified by X-ray structure analyses. Each cluster exhibits extensive methyl group degradation and contains methylene, methine, or carbide moieties. [La4Al8(CH)4(CH2)2(CH3)20(PMe3)] has a [La4(CH)4] cuboid core supported by AlMe3, Me2AlCH2AlMe2, and PMe3 ligands. [La4Al8(C)(CH)2(CH2)2(CH3)22(toluene)] also contains a cuboid core, [La3Al(C)(CH)2(CH2)], which includes one exo cubic lanthanum atom, and is supported by AlMe3, Me3AlCH2AlMe2, (AlMe4)-, and toluene ligands. The lanthanum atoms in [La5Al9(CH)6(CH3)30] are arranged in a trigonal bipyramidal fashion with (CH) functionalities capping each face. The [La5(CH)6]3- core is formally balanced by three AlMe2 + moieties and is additionally supported by six AlMe3 ligands. The unit cell contains two independent La5 clusters, one with pseudo-C3h and the other with pseudo-D3 symmetry, as well as two molecules of the separation co-product Me3Al(PMe3).     

Pd-catalyzed diarylation of aniline--a way to a non-linear bis(terpyridyl) ligand providing increased electronic communication

An amine-linked bis(terpyridyl) ligand, prepared via Pd-catalyzed diarylation of aniline, mediates unusually strong metal-metal interaction in its Ru(2) polypyridyl complex.