Compositional Optimization of Sputtered WO3/MoO3 Films for High Coloration Efficiency

Thin films of mixed MoO3 and WO3 were obtained using reactive magnetron sputtering onto ITO-covered glass, and the optimal composition was determined for the best electrochromic (EC) properties. A combinatorial material synthesis approach was applied throughout the deposition experiments, and the samples represented the full composition range of the binary MoO3/WO3 system. The electrochromic characteristics of the mixed oxide films were determined with simultaneous measurement of layer transmittance and applied electric current through the using organic propylene carbonate electrolyte cells in a conventional three-electrode configuration. Coloration efficiency data evaluated from the primary data plotted against the composition displayed a characteristic maximum at around 60% MoO3. Our combinatorial approach allows the localization of the maximum at 5% accuracy.

Composite ligand shells on gold nanoprisms - an ensemble and single particle study

The attachment of thiolated molecules onto gold surfaces is one of the most extensively used and robust ligand exchange approaches to exploit the nanooptical features of nanoscale and nanostructured plasmonic materials. In this work, the impact of thiol adsorption on the optical properties of wet-chemically synthesized gold nanoprisms is studied both at the ensemble and single particle level to investigate the build-up of more complex ligand layers. Two prototypical ligands with different lengths have been investigated ((16-mercaptohexadecyl)trimethylammonium bromide - MTAB and thiolated polyethylene glycol - mPEG-SH). From ensemble experiments it is found that composite ligand layers are obtained by the sequential addition of the two thiols, and an island-like surface accumulation of the molecules can be anticipated. The single particle experiment derived chemical interface damping and resonance energy changes further support this and show additionally that when the two thiols are used simultaneously, a higher density, intermixed layer is formed. Hence, when working with more than a single type of ligand during surface modification, sequential adsorption is preferred for the combination of accessible essential surface functionalities, whereas for high overall loading the simultaneous use of the different ligand types is favourable.

Investigation of Combinatorial WO3-MoO3 Mixed Layers by Spectroscopic Ellipsometry using Different Optical Models

Reactive (Ar-O₂ plasma) magnetron sputtered WO₃-MoO₃ (nanometer scaled) mixed layers were investigated and mapped by Spectroscopic Ellipsometry (SE). The W- and Mo-targets were placed separately, and 30 × 30 cm glass substrates were slowly moved under the two (W and Mo) separated targets. We used different (oscillator- and Effective Medium Approximation, EMA-based) optical models to obtain the thickness and composition maps of the sample layer relatively quickly and in a cost-effective and contactless way. In addition, we used Rutherford Backscattering Spectrometry to check the SE results. Herein, we compare the “goodness” of different optical models depending upon the sample preparation conditions, for instance, the speed and cycle number of the substrate motion. Finally, we can choose between appropriate optical models (2-Tauc-Lorentz oscillator model vs. the Bruggeman Effective Medium Approximation, BEMA) depending on the process parameters. If one has more than one “molecular layer” in the “sublayers”, BEMA can be used. If one has an atomic mixture, the multiple oscillator model is better (more precise) for this type of layer structure.

Micro-combinatorial sampling of the optical properties of hydrogenated amorphous [Formula: see text] for the entire range of compositions towards a database for optoelectronics

The optical parameters of hydrogenated amorphous a-[Formula: see text]:H layers were measured with focused beam mapping ellipsometry for photon energies from 0.7 to 6.5 eV. The applied single-sample micro-combinatorial technique enables the preparation of a-[Formula: see text]:H with full range composition spread. Linearly variable composition profile was revealed along the 20 mm long gradient part of the sample by Rutherford backscattering spectrometry and elastic recoil detection analysis. The Cody-Lorentz approach was identified as the best method to describe the optical dispersion of the alloy. The effect of incorporated H on the optical absorption is explained by the lowering of the density of localized states in the mobility gap. It is shown that in the low-dispersion near infrared range the refractive index of the a-[Formula: see text] alloy can be comprehended as a linear combination of the optical parameters of the components. The micro-combinatorial sample preparation with mapping ellipsometry is not only suitable for the fabrication of samples with controlled lateral distribution of the concentrations, but also opens new prospects in creating databases of compounds for optical and optoelectonic applications.

Nanosecond resistive switching in Ag/AgI/PtIr nanojunctions

Nanometer-scale resistive switching devices operated in the metallic conductance regime offer ultimately scalable and widely reconfigurable hardware elements for novel in-memory and neuromorphic computing architectures. Moreover, they exhibit high operation speed at low power arising from the ease of the electric-field-driven redistribution of only a small amount of highly mobile ionic species upon resistive switching. We investigate the memristive behavior of a so-far less explored representative of this class, the Ag/AgI material system in a point contact arrangement established by the conducting PtIr tip of a scanning probe microscope. We demonstrate stable resistive switching duty cycles and investigate the dynamical aspects of non-volatile operation in detail. The high-speed switching capabilities are explored by a custom-designed microwave setup that enables time-resolved studies of subsequent set and reset transitions upon biasing the Ag/AgI/PtIr nanojunctions with sub-nanosecond voltage pulses. Our results demonstrate the potential of Ag-based filamentary memristive nanodevices to serve as the hardware elements in high-speed neuromorphic circuits.

Corrosion Resistance of Nanosized Silicon Carbide-Rich Composite Coatings Produced by Noble Gas Ion Mixing

Ion beam mixing has been used to produce a silicon carbide (SiC)-rich nanolayer for protective coating. Different C/Si/C/Si/C/Si(substrate) multilayer structures (with individual layer thicknesses falling in the range of 10-20 nm) have been irradiated by Ar⁺ and Xe⁺ ions at room temperature in the energy and fluence ranges of 40-120 keV and 1-6 × 10¹⁶ ion/cm², respectively. The effects of ion irradiation, including the in-depth distribution of the SiC produced, was determined by Auger electron spectroscopy depth profiling. The thickness of the SiC-rich region was only some nanometers, and it could be tailored by changing the layer structure and the ion irradiation conditions. The corrosion resistance of the layers was investigated by potentiodynamic electrochemical test in 4 M KOH solution. The measured corrosion resistance of the SiC-rich layers was orders of magnitude better than that of pure silicon, and a correlation was found between the corrosion current density and the effective areal density of the SiC.

Evolution of magnetism on a curved nano-surface

To design custom magnetic nanostructures, it is indispensable to acquire precise knowledge about the systems in the nanoscale range where the magnetism forms. In this paper we present the effect of a curved surface on the evolution of magnetism in ultrathin iron films. Nominally 70 Å thick iron films were deposited in 9 steps on 3 different types of templates: (a) a monolayer of silica spheres with 25 nm diameter, (b) a monolayer of silica spheres with 400 nm diameter and (c) for comparison a flat silicon substrate. In situ iron evaporation took place in an ultrahigh vacuum chamber using the molecular beam epitaxy technique. After the evaporation steps, time differential nuclear forward scattering spectra, grazing incidence small angle X-ray scattering images and X-ray reflectivity curves were recorded. In order to reconstruct and visualize the magnetic moment configuration in the iron cap formed on top of the silica spheres, micromagnetic simulations were performed for all iron thicknesses. We found a great influence of the template topography on the onset of magnetism and on the developed magnetic nanostructure. We observed an individual magnetic behaviour for the 400 nm spheres which was modelled by vortex formation and a collective magnetic structure for the 25 nm spheres where magnetic domains spread over several particles. Depth selective nuclear forward scattering measurements showed that the formation of magnetism begins at the top region of the 400 nm spheres in contrast to the 25 nm particles where the magnetism first appears in the region where the spheres are in contact with each other.

Introducing nanoscaled surface morphology and percolation barrier network into mesoporous silica coatings

The advantages of surface pattern and mesoporous character of silica thin films were combined, while preserving the interconnected pore system or creating laterally separated porous volumes surrounded by nonpermeable compact zones.

Antibacterial properties of Ag–TiO2 composite sol–gel coatings

This study reveals the connection between the silver-doping method, the resulting nature and amount of the silver dopant together with the structural properties and the long-term antibacterial activity of composite coatings.

Sparse and incomplete factorial matrices to screen membrane protein 2D crystallization

Electron crystallography is well suited for studying the structure of membrane proteins in their native lipid bilayer environment. This technique relies on electron cryomicroscopy of two-dimensional (2D) crystals, grown generally by reconstitution of purified membrane proteins into proteoliposomes under conditions favoring the formation of well-ordered lattices. Growing these crystals presents one of the major hurdles in the application of this technique. To identify conditions favoring crystallization a wide range of factors that can lead to a vast matrix of possible reagent combinations must be screened. However, in 2D crystallization these factors have traditionally been surveyed in a relatively limited fashion. To address this problem we carried out a detailed analysis of published 2D crystallization conditions for 12 β-barrel and 138 α-helical membrane proteins. From this analysis we identified the most successful conditions and applied them in the design of new sparse and incomplete factorial matrices to screen membrane protein 2D crystallization. Using these matrices we have run 19 crystallization screens for 16 different membrane proteins totaling over 1300 individual crystallization conditions. Six membrane proteins have yielded diffracting 2D crystals suitable for structure determination, indicating that these new matrices show promise to accelerate the success rate of membrane protein 2D crystallization.

Various nanostructures on macroscopically large areas prepared by tunable ion-swelling

Various nanostructures were fabricated by ion irradiation on large area (100) Si surfaces covered by colloidal Langmuir-Blodgett films as nanolithographic masks. The ordered structure of the Langmuir-Blodgett monolayer composed from spherical Stöber silica particles of 200 nm and 450 nm diameter offer the possibility to form local surface swelling patterns during the ion bombardment step. Utilizing the dependence of the surface morphology on the irradiation parameters the tunability of nanostructuring was studied for 40 keV Ar+ and 500 keV Xe2+ ions. We show that the periodicity of the resulted surface pattern is determined by the size of the masking particles, while the height of nanostructures can be tuned by the ion fluence. The quality of projection of the nanomask contours to the substrate-the contrast of masking-can be set by choosing appropriate ion energy, thereby determining the curvature of the surface pattern. Moreover, deformation of the nanomask due to ion-nanoparticle interactions should be taken into account since these effects can be also utilized for tailoring various structures. The silica masking layers before and after ion irradiation and the resulting Si surface patterns were investigated by field emission scanning electron microscopy and atomic force microscopy analysis.

The Center for Eukaryotic Structural Genomics

The Center for Eukaryotic Structural Genomics (CESG) is a "specialized" or "technology development" center supported by the Protein Structure Initiative (PSI). CESG's mission is to develop improved methods for the high-throughput solution of structures from eukaryotic proteins, with a very strong weighting toward human proteins of biomedical relevance. During the first three years of PSI-2, CESG selected targets representing 601 proteins from Homo sapiens, 33 from mouse, 10 from rat, 139 from Galdieria sulphuraria, 35 from Arabidopsis thaliana, 96 from Cyanidioschyzon merolae, 80 from Plasmodium falciparum, 24 from yeast, and about 25 from other eukaryotes. Notably, 30% of all structures of human proteins solved by the PSI Centers were determined at CESG. Whereas eukaryotic proteins generally are considered to be much more challenging targets than prokaryotic proteins, the technology now in place at CESG yields success rates that are comparable to those of the large production centers that work primarily on prokaryotic proteins. We describe here the technological innovations that underlie CESG's platforms for bioinformatics and laboratory information management, target selection, protein production, and structure determination by X-ray crystallography or NMR spectroscopy.

New bioinformatics resources for metabolomics

We recently developed two databases and a laboratory information system as resources for the metabolomics community. These tools are freely available and are intended to ease data analysis in both MS and NMR based metabolomics studies. The first database is a metabolomics extension to the BioMagResBank (BMRB, http://www.bmrb.wisc.edu), which currently contains experimental spectral data on over 270 pure compounds. Each small molecule entry consists of five or six one- and two-dimensional NMR data sets, along with information about the source of the compound, solution conditions, data collection protocol and the NMR pulse sequences. Users have free access to peak lists, spectra, and original time-domain data. The BMRB database can be queried by name, monoisotopic mass and chemical shift. We are currently developing a deposition tool that will enable people in the community to add their own data to this resource. Our second database, the Madison Metabolomics Consortium Database (MMCD, available from http://mmcd.nmrfam.wisc.edu/), is a hub for information on over 10,000 metabolites. These data were collected from a variety of sites with an emphasis on metabolites found in Arabidopsis. The MMC database supports extensive search functions and allows users to make bulk queries using experimental MS and/or NMR data. In addition to these databases, we have developed a new module for the Sesame laboratory information management system (http://www.sesame.wisc.edu) that captures all of the experimental protocols, background information, and experimental data associated with metabolomics samples. Sesame was designed to help coordinate research efforts in laboratories with high sample throughput and multiple investigators and to track all of the actions that have taken place in a particular study.

Project management system for structural and functional proteomics: Sesame

A computing infrastructure (Sesame) has been designed to manage and link individual steps in complex projects. Sesame is being developed to support a large-scale structural proteomics pilot project. When complete, the system is expected to manage all steps from target selection to data-bank deposition and report writing. We report here on the design criteria of the Sesame system and on results demonstrating successful achievement of the basic goals of its architecture. The Sesame software package, which follows the client/server paradigm, consists of a framework, which supports secure interactions among the three tiers of the system (the client, server, and database tiers), and application modules that carry out specific tasks. The framework utilizes industry standards. The client tier is written in Java2 and can be accessed anywhere through the Internet. All the development on the server tier is also carried out in Java2 so as to accommodate a wide variety of computer platforms. The database tier employs a commercial database management system. Each Sesame application module consists of a simple user interface in the client tier, corresponding objects in the server tier, and relevant data stored in the centralized database. For security, access to stored data is controlled by access privileges. The system facilitates both local and remote collaborations. Because users interact with the system using Java Web Start or through a web browser, access is limited only by the availability of an Internet connection. We describe several Sesame modules that have been developed to the point where they are being utilized routinely to support steps involved in structural and functional proteomics. This software is available to parties interested in using it and assisting to guide its further development.

Full matrix Analysis of Cross-relaxation Fails in Fractionally Deuterated Molecules

We have analyzed cross-relaxation in fractionally deuterated molecules and showed that the full matrix analysis fails except when the dilution is extreme. This is because the isotopic dilution alters the matrix exponential relationship between the observed spectrum and the cross-relaxation rate constants sought. Consequently, an average of the spectra of various isotopomers differs from the matrix exponential of an average relaxation matrix. We have derived a series expansion that allows the determination of the cross-relaxation rate constants in arbitrarily deuterated molecules.

Solution structures of staphylococcal nuclease from multidimensional, multinuclear NMR: nuclease-H124L and its ternary complex with Ca2+ and thymidine-3',5'-bisphosphate

The solution structures of staphylococcal nuclease (nuclease) H124L and its ternary complex, (nuclease-H124L).pdTp.Ca2+, were determined by ab initio dynamic simulated annealing using 1925 NOE, 119 phi, 20 chi 1 and 112 hydrogen bond constraints for the free protein, and 2003 NOE, 118 phi, 20 chi 1 and 114 hydrogen bond constraints for the ternary complex. In both cases, the final structures display only small deviations from idealized covalent geometry. In structured regions, the overall root-mean-square deviations from mean atomic coordinates are 0.46 (+/- 0.05) A and 0.41 (+/- 0.05) A for the backbone heavy atoms of nuclease and its ternary complex, respectively. The backbone conformations of residues in the loop formed by Arg81-Gly86, which is adjacent to the active site, are more precisely defined in the ternary complex than in unligated nuclease. Also, the protein side chains that show NOEs and evidence for hydrogen bonds to pdTp (Arg35, Lys84, Tyr85, Arg87, Tyr113, and Tyr115) are better defined in the ternary complex. As has been observed previously in the X-ray structures of nuclease-WT, the binding of pdTp causes the backbone of Tyr113 to change from an extended to a left-handed alpha-helical conformation. The NMR structures reported here were compared with available X-ray structures: nuclease-H124L [Truckses et al. (1996) Protein Sci., 5, 1907-1916] and the ternary complex of wild-type staphylococcal nuclease [Loll and Lattman (1989) Proteins Struct. Funct. Genet., 5, 183-201]. Overall, the solution structures of nuclease-H124L are consistent with these crystal structures, but small differences were observed between the structures in the solution and crystal environments. These included differences in the conformations of certain side chains, a reduction in the extent of helix 1 in solution, and many fewer hydrogen bonds involving side chains in solution.

Identification of spin diffusion pathways in proteins by isotope-assisted NMR cross-relaxation network editing

A new isotope-assisted cross-relaxation editing experiment, [1H-13C]DINE-NOESY[1H-15N]HSQC (DINE=Double INEPT Edited), is proposed. It is based on the selective inversion of CH/CH3 or CH2 protons in the middle of the mixing time. The experiment sorts out the spin diffusion paths according to the principal mediators, either the CH/CH3 or the CH2 protons. This is useful in the structure refinement process, as it enables proper alignment of the aliphatic protons in the vicinity of NH protons.