Grafting from polymerization was used to synthesize nano-titania/polyurethane (nTiO(2)/polyurethane) composite coatings, where nTiO(2) was chemically attached to the backbone of the polyurethane polymer matrix with a bifunctional monomer, 2,2-bis(hydroxymethyl) propionic acid (DMPA). This bifunctional monomer can coordinate to nTiO(2) through an available -COOH group, with two available hydroxyl groups that can react with diisocyanate terminated pre-polyurethane through step-growth polymerization. The coordination reaction was monitored by FTIR and TGA, with the coordination reaction found to follow first order kinetics. After step-growth polymerization, the polyurethane nanocomposites were found to be stable on standing with excellent distribution of Ti in the polymer matrix without any significant agglomeration compared to simple physical mixtures of nTiO(2) in the polyurethane coatings. The functionalized nTiO(2)-polyurethane composite coatings showed excellent antibacterial activity against gram-negative bacteria Escherichia coli; 99% of E. coli were killed within less than one hour under solar irradiation. Self-cleaning was also demonstrated using stearic acid as a model for 'dirt'.
Hydrogen is the ideal fuel because it contains the most energy per gram of any chemical substance and forms water as the only byproduct of consumption. However, storage still remains a formidable challenge because of the thermodynamic and kinetic issues encountered when binding hydrogen to a carrier. In this study, we demonstrate how the principal binding sites in a new class of hydrogen storage materials based on the Kubas interaction can be tuned by variation of the coordination sphere about the metal to dramatically increase the binding enthalpies and performance, while also avoiding the shortcomings of hydrides and physisorpion materials, which have dominated most research to date. This was accomplished through hydrogenation of chromium alkyl hydrazide gels, synthesized from bis(trimethylsilylmethyl) chromium and hydrazine, to form materials with low-coordinate Cr hydride centers as the principal H(2) binding sites, thus exploiting the fact that metal hydrides form stronger Kubas interactions than the corresponding metal alkyls. This led to up to a 6-fold increase in storage capacity at room temperature. The material with the highest capacity has an excess reversible storage of 3.23 wt % at 298 K and 170 bar without saturation, corresponding to 40.8 kg H(2)/m(3), comparable to the 2015 DOE system goal for volumetric density (40 kg/m(3)) at a safe operating pressure. These materials possess linear isotherms and enthalpies that rise on coverage, retain up to 100% of their adsorption capacities on warming from 77 to 298 K, and have no kinetic barrier to adsorption or desorption. In a practical system, these materials would use pressure instead of temperature as a toggle and can thus be used in compressed gas tanks, currently employed in the majority of hydrogen test vehicles, to dramatically increase the amount of hydrogen stored, and therefore range of any vehicle.
Better than nature! A nickel(II) dithiolene complex [NiII(L2−)(L−.)][PPh4] (1; see figure; L=1,2‐dicarbomethoxyethylene dithiolate) electrocatalyzes hydrogen evolution at the lowest achievable reduction potential (${{{\rm E}{{{\rm {\rm red}}\hfill \atop {\rm {\rm p}}\hfill}}}}$, −0.69 V) in CH3CN and also in aqueous medium (${{{\rm E}{{{\rm {\rm red}}\hfill \atop {\rm {\rm p}}\hfill}}}}$, −0.71 V) to date. Compound 1 shows strikingly similar EPR and reduction potential values to those observed with native Ni‐containing hydrogenases.
Localized surface plasmon resonances in silver and gold nanostructures are engaged to enhance the inelastic Raman scattering and the fluorescence of a phopholipid containing a sulforhodamine 101 acid chloride dye known as Texas Red. The most efficient coupling and enhancement are attained when the excitation laser line is in resonance with both the chromophore and the plasmon absorption of the nanostructure, the case of surface-enhanced resonance Raman scattering, allowing single-molecule detection. The tagged phospholipid was incorporated into a single fatty acid Langmuir monolayer at varying concentrations and transferred onto an evaporated Ag nanoparticle film. Surface-enhanced fluorescence is achieved using shell-isolated silica-coated gold nanoparticles, an emission enhancement named SHINEF.
The surface structures of nickel phosphide (Ni2P) single crystals were studied by scanning tunneling microscopy (STM) and photoemission electron microscopy (PEEM). Atomically resolved 1 x 1 images of the Ni2P(0001) and (1010) surfaces are successfully obtained with STM, whose respective dimensions of (0.59 nm x 0.59 nm) and (0.34 nm x 0.59 nm) match the unit cell lengths. The Ni2P(0001) surface has two possible terminations in which the Ni:P ratios are 3:1 (Ni3P termination) or 3:2 (Ni3P2 termination). In the Ni3P terminated surface the Ni atoms have a square pyramidal structure, and in the Ni3P2 terminated surface the Ni atoms have a tetrahedral structure. Only the P is visible in the STM for Ni2P(0001) and this is explained as being due to the greater extension of the phosphorus p orbitals than the Ni d orbitals at the surface. The surface domain sizes of the Ni3P and Ni3P2 termination structures of Ni2P(0001) are determined to be 500 microm by means of PEEM using a Hg-Xe lamp through a low-pass UV-filter. Evidence is found for dissociative adsorbed hydrogen on the Ni3P termination surface of Ni2P(0001), but not on the Ni3P2 surface, indicating that the square pyramidal sites on the Ni3P surface have high reactivity.
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