Search results for "Tassi"
showing 10 items of 997 documents
Effect of Organic Tin Compounds on Electric Properties of Model Membranes
2006
The objective of the present work was to investigate the effect of selected organic tin compounds and potassium chloride (used as a reference substance) on the trans-membrane electric voltage and electric resistance of model membranes, the latter being nitrocellulose filters impregnated with butylene ester of lauric acid. The increasing KCl concentration (in the measurement chambers) caused a rapid rise of the negative trans-membrane voltage, whose value stabilized afterwards. In the case of (C3H7)3SnCl an abrupt maximum of the negative voltage was observed followed by a monotonic drop to zero. In the case of highest concentrations of this compound the voltages, after having reached zero, c…
Bright Beaches of Nanoscale Potassium Islands on Graphite in STM Imaging
2008
We demonstrate, via scanning tunneling microscopy (STM) measurements performed at 48 K, the existence of "bright beaches" at the edges of K islands (diameter approximately 5-500 nm) on the graphite surface. The enhanced tunneling current is only observed in monolayer-high islands on graphite, and not in islands of similar geometry on top of a K monolayer film. First-principles density functional calculations and STM simulations suggest that this is an STM field effect, which appears as the positive tip attracts donated electrons back to the metallic K islands. The restored charge accumulates preferentially at the island edges.
Ion-Selective Organic Electrochemical Transistors
2014
Ion-selective organic electrochemical transistors with sensitivity to potassium approaching 50 μA dec(-1) are demonstrated. The remarkable sensitivity arises from the use of high transconductance devices, where the conducting polymer is in direct contact with a reference gel electrolyte and integrated with an ion-selective membrane.
Ni alloy nanowires as high efficiency electrode materials for alkaline electrolysers
2021
Abstract The fabrication and characterization of nickel-alloy electrodes for alkaline electrolysers is reported. Three different alloys (Ni–Co, Ni–Zn and Ni–W) at different composition were studied in order to determine the optimum condition. Nanostructured electrodes were obtained by template electrodeposition into a nanoporous membrane, starting from aqueous solution containing the two elements of the alloy at different concentrations. Composition of alloys can be tuned by electrolyte composition and also depends on the difference of the redox potential of elements and on the presence of complexing agents in deposition bath. Electrochemical and electrocatalytic tests, aimed at establishin…
Ion conduction in the KcsA potassium channel analyzed with a minimal kinetic model.
2004
We use a model by Nelson to study the current-voltage and conductance-concentration curves of bacterial potassium channel KcsA without assuming rapid ion translocation. Ion association to the channel filter is rate controlling at low concentrations, but dissociation and transport in the filter can limit conduction at high concentration for ions other than ${\mathrm{K}}^{+}$. The absolute values of the effective rate constants are tentative but the relative changes in these constants needed to qualitatively explain the experiments should be of significance.
Prussian blue@MoS2 layer composites as highly efficient cathodes for sodium- and potassium-ion batteries
2018
Prussian blue (PB) represents a simple, economical, and eco‐friendly system as cathode material for sodium‐ion batteries (SIBs). However, structural problems usually worsen its experimental performance thus motivating the search for alternative synthetic strategies and the formation of composites that compensate these deficiencies. Herein, a straightforward approach for the preparation of PB/MoS2‐based nanocomposites is presented. MoS2 provides a 2D active support for the homogeneous nucleation of porous PB nanocrystals, which feature superior surface areas than those obtained by other methodologies, giving rise to a compact PB shell covering the full flake. The nanocomposite exhibits an ex…
Effect of alkali metal nitrate treatment on the optical properties of CsPbBr3 nanocrystal films
2021
Abstract Colloidal cesium lead bromide (CsPbBr3) perovskite nanocrystals (NCs) are fabricated as densely packed thin films using doctor blade method through a layer-by-layer assembly approach. It is found that the optical properties of the CsPbBr3 NC films are significantly improved after a ligand exchange of oleic acid (OA) and oleylamine (OAm) by sodium and potassium nitrate in ethyl acetate. Ligand-induced surface defects are passivated by the sodium and potassium cations and nitrate, which leads to the improvement in photoluminescence (PL) and life-time properties. Compared with pristine OAm-OA capped CsPbBr3 NC film, Alkali-metal nitrate salts treated films are showing higher PL intens…
Fluoride-induced precipitates on enamel surface and subsurface areas visualised by electron microscopy and confocal laser scanning microscopy
1997
The present study examined the enamel surface after in vitro topical treatments with a neutral 2% NaF solution. For minimising the risk of artefacts, samples were inspected without pre-treatment as fresh, naturally wet specimens by complementary techniques: variable pressure electron microscopy (VP-SEM) and confocal laser scanning microscopy (CLSM). VP-SEM provided information on the surface morphology, whereas CLSM allowed non-destructive visualisation of subsurface areas. Neutral NaF solutions induced globular precipitates on the enamel surfaces. If the globules formed may be described as "calcium fluoride like material", the additional information of this experiment is that, after intera…
Incorporation of potassium halides in the mechanosynthesis of inorganic perovskites: feasibility and limitations of ion-replacement and trap passivat…
2018
Potassium halides (KX; X = I, Br, or Cl) were incorporated as partial replacements of CsBr in the mechanosynthesis of CsPbBr3. This led to partial substitution of both monovalent ions forming mixed Cs1−xKxPbBr3−yXy perovskites. Longer photoluminescence lifetimes were also observed, possibly linked to the formation of a non-perovskite KPb2X5 passivating layer.
Dielectric investigation of sodium potassium niobate ceramic doped 7% of antimony
2012
Abstract Electric properties of sodium potassium niobate ceramic doped antimony (Na0.5K0.5)(Nb0.93Sb0.07)O3 with sintering aid MnO2 (0.5 mol% MnO2) (KNNSbx + 0.5Mn) were investigated in a broad frequency (from 1 Hz to 54 GHz) and temperature (from 110 K to 800 K) ranges. The mean relaxation times calculated from the dielectric permittivity measurements fulfill Arrhenius relationship with dipole activation energy EA = 3409 K (EA/kB = 0.29 eV). The DC conductivity has been extracted from experimental results and the activation energy was calculated EA = 11733.78 K (EA/kB = 1.011 eV).