Visualization of Spin Polarized States in Biologically-Produced Ensembles of Ferromagnetic Palladium Nanoparticles

We report visualization of spin polarized states in macroscopic ensembles of biologically-produced ferromagnetic palladium nanoparticles using the Faraday effect-based technique of magneto-optical imaging. The ferromagnetic palladium only exists in the form of nanoparticles. Large quantities of palladium nanoparticles may be synthesized via biomineralization from a Pd2+ solution. The ferromagnetic Pd nanoparticles are formed in the periplasmic space of bacteria during the hydrogen-assisted reduction of Pd2+ ions by hydrogenases. The ferromagnetism in Pd comes from itinerant electrons. A high Curie temperature of ferromagnetic palladium, about 200 degrees centigrade above room temperature, would allow for a range of room-temperature magnetic applications. The processes of the isolation of electron spins in separate nanoparticles, spin hopping, spin transport and spin correlations may even form a basis of quantum computing. So far, measurements of the magnetic properties of Pd nanoparticles (PdNP) have been limited by integral techniques such as SQUID magnetometry, magnetic circular dihroism and muon spin rotation spectroscopy ( SR). In the present study, ferromagnetic Pd nanoparticles are characterized using the technique of magneto-optical imaging. This allows visualization of the spin polarization by the variations in the intensity of polarized light. To perform measurements at relatively low magnetic fields, a spin injection from a colossal magnetoresistive material has been used. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3533

High density heterogenisation of molecular electrocatalysts in a rigid intrinsically microporous polymer host

A water-insoluble Polymer with Intrinsic Microporosity (or PIM, here for the particular case of the Tröger Base system PIM-EA-TB, BET area ca. 103 m2 g−1) is demonstrated to act as a rigid host environment for highly water-insoluble molecular catalysts, here tetraphenylporphyrinato-iron (FeTPP), surrounded by aqueous solution-filled micropores. A PIM-EA-TB film containing catalyst is deposited onto the electrode and immersed for voltammetry (i) with 4-(3-phenyl-propyl)-pyridine to give an organogel, or (ii) bare directly into aqueous solution. The porous host allows processes to be optimised as a function of solution phase, composition, and catalyst loading. Effective electron transfer as well as effective electrocatalysis is reported for aqueous oxygen and peroxide reduction. Given the use of completely water-insoluble catalyst systems, the methodology offers potential for application with a wide range of hitherto unexplored molecular electrocatalysts and catalyst combinations in aqueous media. Keywords: Electrocatalysis, Ion transfer, Peroxide, Oxygen, Fuel cell, Sensin

Intrinsically porous polymer protects catalytic gold particles for enzymeless glucose oxidation

The enzymeless glucose oxidation process readily occurs on nano-gold electrocatalyst at pH 7, but it is highly susceptible to poisoning (competitive binding), for example from protein or chloride. Is it shown here that gold nanoparticle catalyst can be protected against poisoning by a polymer of intrinsic microporosity (PIM-EA-TB with BET surface area 1027 m2 g−1). This PIM material when protonated, achieves a triple catalyst protection effect by (i) size selective repulsion of larger protein molecules (albumins) and (ii) membrane ion selection effects, and (iii) membrane ion activity effects. PIM materials allow “environmental control” to be introduced in electrocatalytic processes

Non-monotonic variation with salt concentration of the second virial coefficient in protein solutions

The osmotic virial coefficient $B_2$ of globular protein solutions is calculated as a function of added salt concentration at fixed pH by computer simulations of the ``primitive model''. The salt and counter-ions as well as a discrete charge pattern on the protein surface are explicitly incorporated. For parameters roughly corresponding to lysozyme, we find that $B_2$ first decreases with added salt concentration up to a threshold concentration, then increases to a maximum, and then decreases again upon further raising the ionic strength. Our studies demonstrate that the existence of a discrete charge pattern on the protein surface profoundly influences the effective interactions and that non-linear Poisson Boltzmann and Derjaguin-Landau-Verwey-Overbeek (DLVO) theory fail for large ionic strength. The observed non-monotonicity of $B_2$ is compared to experiments. Implications for protein crystallization are discussed.Comment: 43 pages, including 17 figure

The structure and reactivity of copper, silver and gold overlayers on W(100)

SIGLEAvailable from British Library Document Supply Centre- DSC:DX83393 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

In situ surface-enhanced raman spectroscopic studies and electrochemical reduction of α-Kensation products at platinum surfaces

The adsorption and hydrogenation of ketopantolactone (KPL) and ethyl pyruvate (EP) on Pt electrodes, measured by surface-enhanced Raman spectroscopy, are compared. In addition, pure samples of self-condensation products of ethyl pyruvate including a dimer (in both linear and cyclized forms) and a lactone have been synthesized. These dimeric and aldol condensation intermediates have previously been proposed by ourselves as playing a crucial role in explaining the significant rate enhancement observed during enantioselective hydrogenation of α-ketoesters at supported platinum catalysts. The adsorption of the linear dimer at platinum leads to cyclization. At hydrogen evolving potentials in dimer-free aqueous sulfuric acid, the dimer may be hydrogenatively desorbed readily from the electrode surface. KPL is found to accumulate at the electrode surface under hydrogen evolving conditions. From comparison with the behavior of EP under similar hydrogenating conditions, it is deduced that self-condensed dimers do not form when EP is being either hydrogenated using gas phase hydrogen or electrocatalytically hydrogenated in aqueous sulfuric acid. In addition, unlike EP, KPL does not form a long-lived half-hydrogenated state surface intermediate, a significant contributory factor in rate enhancement observed when EP is hydrogenated at supported platinum catalysts. Hence, the role of cinchona alkaloids in establishing rate acceleration cannot be ascribed simply to a destabilization of self-condensation products of ethyl pyruvate under reaction conditions. Models to explain the relative degrees of rate acceleration in KPL and EP are discussed