Showing papers by "Galen D. Stucky published in 2005"

Sacrificial bonds and hidden length dissipate energy as mineralized fibrils separate during bone fracture.

Abstract: Properties of the organic matrix of bone as well as its function in the microstructure could be the key to the remarkable mechanical properties of bone. Previously, it was found that on the molecular level, calcium-mediated sacrificial bonds increased stiffness and enhanced energy dissipation in bone constituent molecules. Here we present evidence for how this sacrificial bond and hidden length mechanism contributes to the mechanical properties of the bone composite, by investigating the nanoscale arrangement of the bone constituents and their interactions. We find evidence that bone consists of mineralized collagen fibrils and a non-fibrillar organic matrix, which acts as a 'glue' that holds the mineralized fibrils together. We believe that this glue may resist the separation of mineralized collagen fibrils. As in the case of the sacrificial bonds in single molecules, the effectiveness of this mechanism increases with the presence of Ca2+ ions.

Automated Electrochemical Synthesis and Photoelectrochemical Characterization of Zn1-xCoxO Thin Films for Solar Hydrogen Production

Abstract: High-throughput electrochemical methods have been developed for the investigation of Zn1-xCoxO films for photoelectrochemical hydrogen production from water. A library of 120 samples containing 27 different compositions (0 <= x <= 0.068) was synthesized by automated serial electrochemical deposition. High-throughput photoelectrochemical screening revealed improved solar hydrogen production for the cobalt-doped films, with Zn0.956Co0.044O exhibiting a 4-fold improvement over pure ZnO with no external bias. Flat-band potential, bias-dependent photocurrent, and action spectra were also measured automatically with the high-throughput screening system. The 200-nm-thick films were subsequently characterized by numerous techniques, including SEM, XRD, XPS, and UV-vis, which show that the depositions are well-controlled. Zn/Co stoichiometry in the films was controlled by the ratio of the Zn and Co precursors in each deposition bath. All films exhibited the wurtzite structure typical of pure ZnO, and the Co2+ appears to substitute Zn2+, forming a single-phase solid solution. Band gaps of the solid solutions were systematically lower than the 3.2-eV band gap typical of ZnO.

3-D Molecular Assembly of Function in Titania-Based Composite Material Systems

Abstract: Various examples of composite titania-based nanostructured materials exhibiting cooperative functionalities between different active components are presented. The fabrication of these integrated composite materials is based on one-pot supramolecular templating techniques combined with acidic sol−gel chemistry. The defined 3-D nanoscale organization and integration of various functional components results in advanced optoelectronic and photonic applications such as visible light sensitization of mesoporous titania photocatalysts with cadmium sulfide nanocrystals acting as sensitizing integral part of the mesopore wall structure, narrow bandwidth emission from rare earth ion activated nanocrystalline mesoporous titania films, and mirrorless lasing in dye-doped hybrid organic/inorganic mesostructured titania waveguides.

Ag/AgCl-Loaded Ordered Mesoporous Anatase for Photocatalysis

Abstract: Thin films of ordered mesoporous anatase have been prepared using a dip-coating procedure. Silver nanoparticles were introduced into the mesopores using wet impregnation followed by heat treatment....

Structural Analysis of Hybrid Titania-Based Mesostructured Composites

Abstract: High-optical-quality titania-based mesostructured films with cubic or 2D-hexagonal symmetry were fabricated by combining trifluoroacetate (TFA)-modified titanium precursors with amphiphilic triblock poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO−PPO−PEO) copolymers. The distribution, dynamics, and local environments of the TFA-modified titania, PEO, and PPO components of the hybrid were investigated. IR/Raman spectroscopy, in situ small-angle X-ray scattering, and transmission electron microscopy studies indicate that TFA coordinates the titanium center and forms a stable complex that is subsequently organized by the block copolymer species into ordered mesostructures. Solid-state NMR 19F→1H cross-polarization, 13C{1H} two-dimensional heteronuclear correlation, and 1H relaxation techniques were used to determine that PEO is predominantly incorporated within the TFA-modified titania, and that PPO environments encompass both microphase separated regions and interfacial regions composed...

Spin dynamics in electrochemically charged CdSe quantum dots

Abstract: We use time-resolved Faraday rotation to measure coherent spin dynamics in colloidal CdSe quantum dots charged in an electrochemical cell at room temperature. Filling of the $1{S}_{\mathrm{e}}$ electron level is demonstrated by the bleaching of the $1{S}_{\mathrm{e}}\ensuremath{-}1{S}_{3∕2}$ absorption peak. One of the two Land\'e $g$ factors observed in uncharged quantum dots disappears upon filling of the $1{S}_{\mathrm{e}}$ electron state. The transverse spin-coherence time, which is over $1\phantom{\rule{0.3em}{0ex}}\mathrm{ns}$ and is limited by inhomogeneous dephasing, also appears to increase with charging voltage. The amplitude of the spin precession signal peaks near the half-filling potential. Its evolution at charging potentials without any observable bleaching of the $1{S}_{\mathrm{e}}\ensuremath{-}1{S}_{3∕2}$ transition suggests that the spin dynamics are influenced by low-energy surface states.

Distribution and Role of Trace Transition Metals in Glycera Worm Jaws Studied with Synchrotron Microbeam Techniques

Abstract: A combination of position-resolved synchrotron microbeam techniques was used to explore the distribution and role of trace transition metals in the jaws of Glycera dibranchiata. The mandibles of this marine sediment worm have recently been found to be reinforced by the copper-based biomineral atacamite [Cu2(OH)3Cl]. Here we show that the system is more complex, containing zinc and iron and unmineralized copper compounds as well. X-ray absorption spectroscopy studies showed that a fraction of copper is present in oxidation state, Cu(I), in contrast to the mineral that exclusively contains Cu(II). X-ray fluorescence imaging revealed traces of copper also in the jaw base devoid of mineral. Traces of iron were found as well, but occurred spatially correlated with the copper mineral, suggesting a substitution of copper atoms by iron in the atacamite mineral. Zinc was evenly dispersed throughout the jaw matrix, quite in analogy to zinc in Nereis jaw, a related worm species, where nonmineralized zinc serves to c...

Synthesis of Au nanoclusters supported upon a TiO2 nanotube array

Abstract: Gold nanoclusters were successfully deposited in the interior of TiO2 nanotubes fabricated as ordered arrays. This approach is a useful fabrication platform for miniature planar fuel cells, gas sensors, and heterogeneous catalysts. A pressure impregnation process was used to inject the titania and Au precursors into mesoporous alumina. After thermal treatment, Au nanoclusters were well-dispersed on the interior walls of nanotubular TiO2. The TiO2 nanotubes were shown by x-ray diffraction to be entirely anatase. Transmission electron microscopy imaging confirmed that 80% of the Au particles were 4.1 nm ± 2.0 nm in diameter. This material exhibited catalytic CO oxidation activity at low temperatures.

New zeotype borophosphates with chiral tetrahedral topology: (H)0.5M1.25(H2O)1.5[BP2O8]·H2O (M = Co(II) and Mn(II))

Abstract: Two new isostructural open-framework zeotype transition metal borophosphate compounds, (H)0.5M1.25(H2O)1.5[BP2O8]·H2O (M = Co(II) and Mn(II)) were synthesized by mild hydrothermal method. The structure of compounds were characterized by single-crystal X-ray diffraction which have ordered, alternating, vertex-sharing BO4, PO4, and (MO4)OM(H2O)2 groups with hexagonal, P 61 2 2 (No 178) space group and unit cell parameters for Co a = 9.4960(6) A, c = 15.6230(13) A, for Mn a = 9.6547(12) A, c = 15.791(3) A, Z = 1 for both of them. TGA/DTA analysis, IR spectroscopy were used for characterization. Magnetic susceptibility measurements for both of the compound indicate strong antiferromagnetic interaction between metal centers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Vesicle array-templated large-area silica surface patterns.

Abstract: Micropatterning has important applications in a wide range of areas, including microelectronics, optics, information displays, and biotechnology. Herein, we describe a vesicle-array templating approach for the generation of surface patterns of micrometer-sized silica features on the surfaces of silica monoliths. The approach makes use of tetraethyl orthosilicate as silica precursor, a poly(ethylene glycol)−block−poly(propylene glycol)−block−poly(ethylene glycol) triblock copolymer, EO2PO16EO2, as surfactants, and water, ethanol, and dimethylformamide as solvents. The morphological shapes of produced silica features are synthetically controlled through varying the sequence of silica precursor hydrolysis, vesicle formation, and silica condensation. Prehydrolysis of the silica precursor, before being mixed with the copolymer, gives hollow convex protrusions. Direct mixing of the silica precursor and the copolymer produces concave depressions. An increase in the amount of water in the mixture solution without...

Automated Electrochemical Synthesis and Photoelectrochemical Characterization of Zn1‐xCoxO Thin Films for Solar Hydrogen Production.

Abstract: High-throughput electrochemical methods have been developed for the investigation of Zn1-xCoxO films for photoelectrochemical hydrogen production from water. A library of 120 samples containing 27 different compositions (0 <= x <= 0.068) was synthesized by automated serial electrochemical deposition. High-throughput photoelectrochemical screening revealed improved solar hydrogen production for the cobalt-doped films, with Zn0.956Co0.044O exhibiting a 4-fold improvement over pure ZnO with no external bias. Flat-band potential, bias-dependent photocurrent, and action spectra were also measured automatically with the high-throughput screening system. The 200-nm-thick films were subsequently characterized by numerous techniques, including SEM, XRD, XPS, and UV-vis, which show that the depositions are well-controlled. Zn/Co stoichiometry in the films was controlled by the ratio of the Zn and Co precursors in each deposition bath. All films exhibited the wurtzite structure typical of pure ZnO, and the Co2+ appears to substitute Zn2+, forming a single-phase solid solution. Band gaps of the solid solutions were systematically lower than the 3.2-eV band gap typical of ZnO.

Hydrogen cyano fullerene containing proton conducting membranes

Abstract: The components of and a proton conducting membrane (PCM) produced from a host polymer and an attached or physically blended in hydrogen cyano fullerene proton-source agent, with the physical blending of the host polymer and hydrogen cyano fullerene further promoted by a poly(ethylene oxide) attached fullerene mixing agent

3-D Molecular Assembly of Function in Titania-Based Composite Material Systems

Abstract: Various examples of composite titania-based nanostructured materials exhibiting cooperative functionalities between different active components are presented. The fabrication of these integrated composite materials is based on one-pot supramolecular templating techniques combined with acidic sol−gel chemistry. The defined 3-D nanoscale organization and integration of various functional components results in advanced optoelectronic and photonic applications such as visible light sensitization of mesoporous titania photocatalysts with cadmium sulfide nanocrystals acting as sensitizing integral part of the mesopore wall structure, narrow bandwidth emission from rare earth ion activated nanocrystalline mesoporous titania films, and mirrorless lasing in dye-doped hybrid organic/inorganic mesostructured titania waveguides.

Hydrophilic polymer-oxide-phosphoric acid compositions for proton conducting membranes

Abstract: An organic-inorganic hydrophilic polymer-oxide hybrid proton conducting membrane (PCM) is produced from a host organic polymer, a filler inorganic oxide, and a proton-source with a pKa less than about 5. Usually, the subject invention comprises PCMs containing host polymer-x-strong acid-y-filler oxide, wherein x is between about 1 and 10 (with “x” as the molar ration of acid anion to polymer repeat unit) and y ≤ about 50% (with “y” the weight percentage of filler oxide in the composite).

Hydro cyano and cyano fullerene derivatives

Abstract: The components of and a proton conducting membrane (PCM) produced from a host polymer and an attached or physically blended in hydrogen cyano fullerene proton-source agent, with the physical blending of the host polymer and hydrogen cyano fullerene further promoted by a poly(ethylene oxide) attached fullerene mixing agent.

The Jaws of Nereis: Microstructure and Mechanical Properties

Abstract: The jaws of the marine worm Nereis sp. are made of protein fibers and are reinforced by zinc. Here we study a transverse section through the jaw using optical microscopy and nanoindentation. Optical microscopy images demonstrate a complex microstructure which includes channels that extend throughout the jaw. We suggest that these channels may be related to jaw remodeling. The mechanical results reveal spatial variations in both indentation hardness and reduced modulus. Specifically, the toothed side of the jaw (used for grasping food) is harder than the remainder of the jaw and the very exterior surface is hardest.