7th Drug hypersensitivity meeting: part two

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Unlocking Phase Diagrams for Molybdenum and Tungsten Nanoclusters and Prediction of their Formation Constants

Understanding and controlling aqueous speciation of metal oxides are key for the discovery and development of novel materials, and challenge both experimental and computational approaches. Here we present a computational method, called POMSimulator, which is able to predict speciation phase diagrams (Conc. vs pH) for multi-species chemical equilibria in solution, and which we apply to molybdenum and tungsten isopolyoxoanions (IPAs). Starting from the MO4 monomers, and considering dimers, trimers, and larger species, the chemical reaction networks involved in the formation of [H32Mo36O128]8- and [W12O42]12- are sampled in an automatic manner. This information is used for setting up ~105 speciation models, and from there, we generate the speciation phase diagrams, which show an insightful picture of the behavior of IPAs in aqueous solution. Furthermore, we predict the values for 107 formation constants for a diversity of molybdenum and tungsten molecular oxides. Among these species, we could include several pentagonal shaped species and very reactive tungsten intermediates as well. Last but not least, the calibration employed for correcting the DFT Gibbs energies is remarkably similar for both metals, which suggests that a general rule might exist for correcting computed free energies for other metals.<br /

Molecular-Metal-Oxide-nanoelectronicS (M-MOS): Achieving the Molecular Limit

Nowadays interest in electronic, magnetic and optical materials based on inorganic, organic, hybrid and nano-materials is increasing significantly. The EPSRC funded M-MOS Programme Grant provides an exciting opportunity for research in the field of molecular electronics based on hybrid nano-materials. Its main aim is to establish a link between the variability, scalability and reliability of a non-volatile flash-memory cell, in which the charge-storing components constitute of a layer of polyoxometalates molecular clusters (POMs). POMs are metal-oxide inorganic molecules formed by early transition metal ions and oxo ligands [1]. Importantly, they can undergo multiple times reversible reduction/oxidation, which makes them attractive candidates for multi-bit storage for flash memory cells. The use of redox-active molecules to form the floating gate (FG) could offer several very important advantages over the conventional polysilicon FG [2]. However, the latter concept has not been proven so far and the on-going effort in modelling and simulations of flash-cell transistors with a POM-based floating gate plays a pivotal role for the sustainability of any farther experiment effort in this direction. In this work we use a plethora of modelling techniques embodied in a custom-built Simulation Domain Bridge, connecting the quantum chemical and mesoscopic device modelling, that illustrates the proposed advantages of POMs in the non-volatile molecular memories. Our ultimate goal is to provide informed guidance for both chemical synthesis and device design and fabrication, with the knowledge derived from device modelling and simulation and computational chemistry calculations

Molecular-Metal-Oxide-nanoelectronicS (M-MOS): Achieving the Molecular Limit

Nowadays interest in electronic, magnetic and optical materials based on inorganic, organic, hybrid and nano-materials is increasing significantly. The EPSRC funded M-MOS Programme Grant provides an exciting opportunity for research in the field of molecular electronics based on hybrid nano-materials. Its main aim is to establish a link between the variability, scalability and reliability of a non-volatile flash-memory cell, in which the charge-storing components constitute of a layer of polyoxometalates molecular clusters (POMs). POMs are metal-oxide inorganic molecules formed by early transition metal ions and oxo ligands [1]. Importantly, they can undergo multiple times reversible reduction/oxidation, which makes them attractive candidates for multi-bit storage for flash memory cells. The use of redox-active molecules to form the floating gate (FG) could offer several very important advantages over the conventional polysilicon FG [2]. However, the latter concept has not been proven so far and the on-going effort in modelling and simulations of flash-cell transistors with a POM-based floating gate plays a pivotal role for the sustainability of any farther experiment effort in this direction. In this work we use a plethora of modelling techniques embodied in a custom-built Simulation Domain Bridge, connecting the quantum chemical and mesoscopic device modelling, that illustrates the proposed advantages of POMs in the non-volatile molecular memories. Our ultimate goal is to provide informed guidance for both chemical synthesis and device design and fabrication, with the knowledge derived from device modelling and simulation and computational chemistry calculations

Connecting theory with experiment to understand the initial nucleation steps of heteropolyoxometalate clusters

A complimentary combination of Density Functional Theory (DFT) methodology and Electrospray Ionization-Mass Spectrometry (ESI-MS) has been utilized to increase our limited understanding of the first nucleation steps in the formation of the [XM(12)O(40)](n-) Keggin polyoxometalates (POMs) (where addenda metal atom M = W or Mo, and the heteroatom X = P or As). We postulate that the first key steps of nucleation into discrete, high nuclearity heteropolyanions proceed via the formation of isodinuclear species (e. g. [M(2)O(7)](2-)), which undergo successive steps of protonation and water condensation to form a heterotrinuclear fragment, which acts as a template for the constituent parts required for subsequent aggregation and formation of the plenary Keggin heteropolyanion. The stability of calculated structures of the numerous postulated intermediates has been analysed and discussed in detail, and these results complemented using experimental mass spectrometry, using an assembly (reaction solution analysis) and disassembly (fragmentation of single crystals) approach. Overall, no significant differences between the Keggin POMs were found when changing the addenda metal atom (W or Mo) or the heteroatom (P or As); although small differences among the lowest-energy structures were detected

Polyoxometalate {W18O56XO6} clusters with embedded redox-active main-group templates as localized inner-cluster radicals

Non-mixed-valent reduced polyoxometalates, namely {W18O56XO6} Dawson-like clusters (X=IVII or TeVI) with a localized redox active template have been synthesized and redox properties compared with the pure tungsten control (that is, X=WVI). Upon one-electron reduction, the electron localizes on the main-group element, giving IVI or TeV, respectively. These clusters have potential as a new type of electron-transfer reagent

Equity trading in an era of globalising interdependencies

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