Signaling Recognition Events with Fluorescent Sensors and Switches.

Recently sulfate radical-based advanced oxidation processes (SR-AOPs) attract increasing attention due to their capability and adaptability in decontamination. The couple of cobalt and peroxymonosulfate (PMS) is an efficient way to produce reactive sulfate radicals. This article reviews the state-of-the-art progress on various heterogeneous cobalt-based catalysts for PMS activation, including cobalt oxides, cobalt-ferrite and supported cobalt by diverse substrates. We summarize the intrinsic properties of these catalysts and their fundamental behaviors in PMS activation, as well as synthetic approaches. In addition, influencing factors and synergistic techniques of Co/PMS systems in organic degradation and possible environmental applications are also discussed. Finally, we propose perspectives on challenges related to cobalt-based catalysts, heterogeneous Co/PMS systems and their potential applications in practical environmental cleanup.

Cobalt-catalyzed sulfate radical-based advanced oxidation: A review on heterogeneous catalysts and applications

As a result of the different degrees of stabilization experienced by the 4f, 5d, and 6s orbitals occurring upon ionization of the neutral metal, the lanthanides (La-Lu, Z ) 57-71) exist almost exclusively in their trivalent state Ln(III) ([Xe]4fn, n ) 0-14) in coordination complexes or supramolecular assemblies.1 Except for some arene compounds involving bulky substituted benzenes or cyclo-octatetraenes,2 covalence plays a minor role in Ln-ligand dative bonds and the nature of the coordination sphere is controlled by a subtle interplay between electrostatic interactions and interligand steric constraints.3 Variable coordination numbers (6 e CN e 12) and geometries are thus observed in lanthanide complexes, leading to limited success in the design of molecular architectures with predetermined structures.3,4 Although rigid or semirigid receptors may help to control the coordination sphere according to the lock-and-key and induced fit concepts,5 detailed studies of lanthanide solvates with water or acetonitrile suggest that trivalent lanthanides display a tendency to adopt nine-coordinate tricapped trigonal prismatic (TTP) arrangements around the metal ion in the solid state. In solution, the picture is a little more subtle:6 in water, for instance, large Ln(III) ions at the beginning of the series (Ln ) La-Nd) adopt TTP geometries, which are gradually transformed into eight-coordinate square antiprismatic (SAP) arrangements for small Ln(III) ions (Ln ) Tb-Lu), equilibria between CN ) 8 and CN ) 9 being observed for Ln ) Nd-Tb.7 The systematic contraction of the ionic radii observed when going from Ln ) La to Lu (often referred to as the lanthanide contraction)8 explains this trend and increases electrostatic bonding for heavier lanthanides, but this variation is so smooth and limited (15% contraction between La and Lu and ≈1% between two successive lanthanides) that selective recognition and incorporation into organized supramolecular architectures remains challenging.5 A rational access to extended polymetallic lanthanide-containing assemblies with predictable and controlled geometries is consequently very limited, and pioneer work in this field has focused on poorly characterized intricate mixtures of complexes in solution which are ‘transformed’ into well-defined solid-state clusters or networks through crystallization processes involving a rich palette of † Institute of Molecular and Biological Chemistry, Lausanne. E-mail: Jean-Claude.Bunzli@epfl.ch. ‡ Department of Inorganic, Analytical and Applied Chemistry, Geneva. E-mail: Claude.Piguet@chiam.unige.ch.

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Lanthanide-containing molecular and supramolecular polymetallic functional assemblies.

The general concept of using the unique phase separation behavior of some surfactant micelle solutions as a means for extractive separation is outlined and described. Next, the specific micellar parameters and phase separation behavior of nonionic and zwitterionic charge-type surfactant solutions are summarized. In addition, the phase behavior of some derivatized B-cyclodextrin solutions is briefly described. The specific applications of such systems and their phase behavior for the extractive preconcentration, separation, and/or purification of metal chelates, biomaterials, and organic compounds are summarized and discussed. The potential use of affinity ligands in conjunction with the cloud-point approach for selective bioextractions is also mentioned. The experimental protocols, advantages, and limitations of the different cloud-point extraction techniques are outlined. The use of zwitterionic as opposed to nonionic surfactant media in such separations is compared and contrasted. In addition, ...

A Critical Review of Surfactant-Mediated Phase Separations (Cloud-Point Extractions): Theory and Applications

The structure and orientation of water molecules at a highly ordered Au(111) electrode surface in perchloric acid have been investigated in-situ as a function of applied potential by means of surface-enhanced infrared absorption spectroscopy. This newly developed infrared spectroscopy technique enables the observation of the electrode/electrolyte interface at a very high sensitivity without interference from the bulk solution. The spectrum of the interfacial water significantly differs from that of bulk water and drastically changes in peak frequencies and band widths around the potential of zero charge (pzc) of the electrode and at about 0.3 V positive from the pzc. The interfacial water molecules are weakly hydrogen-bonded at potentials below the pzc and form a strongly hydrogen-bonded ice-like structure at potentials slightly above the pzc. The ice-like structure is broken at more positive potentials due to the specific adsorption of perchlorate ion, where one OH moiety of water is non-hydrogen-bonded ...

Potential-Dependent Reorientation of Water Molecules at an Electrode/Electrolyte Interface Studied by Surface-Enhanced Infrared Absorption Spectroscopy

Surface-enhanced infrared ATR spectroscopy for in situ studies of electrode/electrolyte interfaces

Real-time monitoring of electrochemical dynamics by submillisecond time-resolved surface-enhanced infrared attenuated-total-reflection spectroscopy

Aqueous perfluorooctanoate (PFOA−) solution of water-miscible organic solvent (SOLV), such as dioxane and acetone, was separated into two immiscible phases reversibly by charge neutralization of PFOA− ion with proton (H+) (pKa value of HPFOA was 1.01, atI = 0.1, 20 °C). The transparent heavier phase, in which HPFOA was concentrated quantitatively, consisted of three components in the molar ratio of HPFOA∶SOLV∶H2O = 1∶4.0∶6.6 for acetone system, and 1∶0.47∶1.9 for dioxane system, respectively. This separation provides a new homogeneous liquid-liquid extraction method, which can be successfully applied to the ultra-high preconcentration of water-soluble porphyrin compounds: 104-fold concentration was achieved within 20 min.

Homogeneous liquid-liquid extraction by pH dependent phase separation with a fluorocarbon ionic surfactant and its application to the preconcentration of porphyrin compounds

Takao Yotsuyanagi

Papers

Surface-enhanced infrared ATR spectroscopy for in situ studies of electrode/electrolyte interfaces

Real-time monitoring of electrochemical dynamics by submillisecond time-resolved surface-enhanced infrared attenuated-total-reflection spectroscopy

Homogeneous liquid-liquid extraction by pH dependent phase separation with a fluorocarbon ionic surfactant and its application to the preconcentration of porphyrin compounds

Separation of 4-(2-pyridylazo)resorcinolato metal chelates by micellar electrokinetic capillary chromatography

Ion-association capillary electrophoresis: New separation mode for equally and highly charged metal chelates