T. Mark McCleskey

The large scale synthesis of pure imidazolium and pyrrolidinium ionic liquids

Ionic liquids are being employed in almost all areas of chemistry and materials, yet there are inherent issues which arise if the utmost care is not taken in the preparation and purification of these materials. They are not easily synthesized and purified using the existing methods. We describe a reliable method for producing large quantities of high quality ionic liquids. Additionally, we show that imidazoliums are not ‘special’ due to their ‘inherently fluorescent’ nature, that spectroscopically clean imidazoliums are attainable, and most classes of ionic liquids do exhibit fluorescent backgrounds when extreme care is not taken during their synthesis and purification.

Fluorescence studies of protein thermostability in ionic liquidsElectronic supplementary information (ESI) available: synthesis of [C4mpy][Tf2N]. See http://www.rsc.org/suppdata/cc/b4/b401304m/

Using the single tryptophan residue in the sweet protein monellin as a spectroscopic handle, we show the extreme thermodynamic stabilization offered by an ionic liquid; T(un) approximately 105 degrees C in [C4mpy][Tf2N] compared to 40 degrees C in bulk water.

The bioinorganic chemistry and associated immunology of chronic beryllium disease

Chronic beryllium disease (CBD) is a debilitating, incurable, and often fatal disease that is caused by the inhalation of beryllium particulates. The growing use of beryllium in the modern world, in products ranging from computers to dental prosthetics (390 tons of beryllium in the US in the year 2000) necessitates a molecular based understanding of the disease in order to prevent and cure CBD. We have investigated the molecular basis of CBD at Los Alamos National Laboratory during the past six years, employing a multidisciplinary approach of bioinorganic chemistry and immunology. The results of this work, including speciation, inhalation and dissolution, and immunology will be discussed.

Highly Conductive Films of Layered Ternary Transition‐Metal Nitrides

Film studies: Epitaxial films of BaZrN(2) (see TEM image) and BaHfN(2) are grown by polymer-assisted deposition on SrTiO(3) (STO) substrates. The films are phase-pure, allowing the intrinsic physical properties of the ternary nitrides to be studied. From 5 to 300 K, the films exhibit metallic-like resistivity-temperature behavior, with large residual resistivity ratios.

Noncontact two-color luminescence thermometry based on intramolecular luminophore cyclization within an ionic liquid

A self-referencing optical thermometer based on a reversible, temperature-dependent monomer-excimer interconversion of 1,3-bis(1-pyrenyl)propane dissolved in an ionic liquid and operating in the 25 to 140 degrees C range is reported.

Polymer-assisted chemical solution approach to YVO4:Eu nanoparticle networks

Phosphor YVO4:Eu nanoparticle networks were synthesized using water soluble ethylenediaminetetraacetic acid (EDTA) and polyethyleneimine (PEI) as binding ligands. The morphology, particle size, BET surface area, and photoluminescence of YVO4:Eu processed at different annealing temperatures (500, 600, 700, and 800 °C) and EDTA/PEI mass ratios (1 : 4, 1 : 2.5, 1 : 2, 1 : 1.5, 1 : 1, 2 : 1, and 4 : 1) were determined by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, fluorescence spectrophotometer, and N2 adsorption and desorption. The red emission was observed with increasing the annealing temperature. Importantly, the nanoparticles did not aggregate at high annealing temperatures up to 800 °C. The smallest size of the YVO4:Eu nanoparticles is about 18 nm and the surface area is 35 m2 g−1 with the EDTA/PEI mass ratios of 1 : 1–2.5.

Ultrathin epitaxial superconducting niobium nitride films grown by a chemical solution technique

Ultrathin epitaxial superconducting NbN (18 nm) films, exhibiting a superconducting transition temperature of 14 K and a critical current density as high as 5.2 MA cm(-2) at 5 K under zero magnetic field, were grown on SrTiO(3) (STO) by a chemical solution technique, polymer assisted deposition (PAD).

Ultra-thin gates for the transport of phenol from supported liquid membranes to permanent surface modified membranes

Abstract We report on the development of membranes with an ultra-thin hydrophobic layer that can be used to support a liquid membrane or serve as a selective gate without further modification when the pore size is small enough. We use a thin layer of gold deposited on commercially available alumina supports to generate a layer on the surface that can be readily modified with thiols to control the hydrophobicity. Transport of 2,4,6-trichlorophenol (TCP) was attained with thiol-modified gold-coated alumina membranes sealed with dodecane. The flux rates through these membranes are five times faster than control experiments through unmodified membranes and show complete selectivity. This provides strong evidence that the flux rates are high enough to be limited by simple diffusion through the alumina support. We have also demonstrated that it is possible to make ultra-thin gates with the alkyl chain itself serving as the hydrophobic barrier. With a 17 carbon chain thiol attached to the membrane in the absence of dodecane, quantitative transport is observed with the same high flux rates observed for the dodecane-treated membranes. Fixing the hydrophobic barrier to the surface should allow for more stable membranes.

Epitaxial Ternary Nitride Thin Films Prepared by a Chemical Solution Method

It is indispensable to use thin films for many technological applications. This is the first report of epitaxial growth of ternary nitride AMN2 films. Epitaxial tetragonal SrTiN2 films have been successfully prepared by a chemical solution approach, polymer-assisted deposition. The structural, electrical, and optical properties of the films are also investigated.

Amorphous Silica Nanoparticles Embedded in Epitaxial SrTiO3 and CoFe2O4 Matrices

Silica (SiO2)–metal oxide composites have a wide range of potential applications in many fields such as catalysis, sensors, optics, magnetism, and electronics. For example, SiO2 or mesoporous SiO2 are often used as insulating matrices or supports for metal oxide nanoparticles for catalytic and sensor applications. The addition of SiO2 can enhance the coercivity of CoFe2O4 (CFO) in SiO2-CFO powders or CFO thin films grown on silicon or silica substrates. Furthermore, SiO2 can enhance the magnetoresistance in SiO2– La0.7Sr0.3MnO3 composites. [14] SiO2 not only affects the magnetic properties of magnetic materials but also modifies the electrical properties of oxides. For instance, SiO2 has been used to enhance the dielectric constants of ZrSiO4 and HfSiO4. [15] In addition, SiO2–ZrO2, SiO2–HfO2, and SiO2– SrTiO3 (STO) composites have been investigated as possible replacements for SiO2 as the gate dielectric materials in standard complementary metal-oxide-semiconductor (CMOS) transistors. It should be noted that most efforts in this field have involved incorporating SiO2 into metal oxide powders or metal oxide polycrystalline films. The composites are commonly prepared by the sol–gel method using tetraethoxysilane (TEOS, Si(OC2H5)4) as the silica source. Herein we report SiO2 nanoparticles with grain sizes as small as 10 nm embedded in epitaxial STO and CFOmatrices prepared by a solution approach involving polymer-assisted deposition (PAD). The water-soluble polymer controls the desired viscosity and binds the metal ions to prevent premature precipitation, which results in a homogeneous distribution of the metal ions in solution and the formation of uniform metal oxide thin films. Solutions of different metals can be mixed to control the stoichiometry when preparing complex metal oxides. We found that SiO2 nanoparticles bind to polyethyleneimine (PEI) polymer presumably by a surfactant-like interaction of the polymer with the surface of the nanoparticles. The ease of forming the soluble SiO2 nanoparticle solution makes it very attractive as a precursor to SiO2-metal oxide composite films. Herein we have selected STO and CFO to explore this unique synthetic route to nanocomposite materials. As compared to LAO (pseudo-cubic with a lattice constant a of 0.3789 nm), STO is cubic with a= 0.3905 nm, while CFO possesses a face-centered-cubic inverse spinel structure with a= 0.838 nm (a/2= 0.419 nm). Such small lattice mismatches make it possible to grow both STO and CFO epitaxially on LAO substrates. An analysis of the X-ray diffraction (XRD) q–2q scans indicates that only STO and CFO (001) peaks are present, with no peaks attributable to silica, thereby indicating that silica retains its amorphous nature in the composite films. Figure 1 displays the f-scans