Samuel Shian

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Diatoms are eukaryotic microalgae that produce species-specifically structured cell walls made of SiO(2) (silica). Formation of the intricate silica structures of diatoms is regarded as a paradigm for biomolecule-controlled self-assembly of three-dimensional, nano- to microscale-patterned inorganic materials. Silica formation involves long-chain polyamines(More)
The carbothermal reduction of silica into silicon requires the use of temperatures well above the silicon melting point (> or =2,000 degrees C). Solid silicon has recently been generated directly from silica at much lower temperatures (< or =850 degrees C) via electrochemical reduction in molten salts. However, the silicon products of such electrochemical(More)
Appreciable global efforts are underway to develop processes for fabricating three-dimensional (3-D) nanostructured assemblies for advanced devices. Widespread commercialization of such devices will require: (i) precise 3-D fabrication of chemically tailored structures on a fine scale and (ii) mass production of such structures on a large scale. These(More)
A simple protein-mediated approach for preparing freestanding (silica free) microscale titania structures with morphologies inherited from complex-shaped, three-dimensional (3-D) biosilica templates (diatom frustules) is demonstrated. The silica diatom frustules were exposed in a repetitive alternating fashion to a silica-binding, titania-forming protein(More)
The synthesis of three-dimensional (3-D) assemblies of zirconia nanocrystals via the shape-preserving reactive conversion of biologically reproducible, silica-based microtemplates (diatom microshells) is demonstrated for the first time. Silica diatom microshells were first converted into magnesia replicas via an oxidation–reduction displacement reaction(More)
An externally heated, x-ray transparent reaction chamber has been developed to enable the dynamic high temperature x-ray diffraction (HTXRD) analysis of a gas/solid [TiF(4)(g)/SiO(2)(s)] reaction involving a halide gas reactant formed at elevated temperatures (up to 350 degrees C) from a condensed source (TiF(4) powder) sealed within the chamber. The(More)
Three-dimensional microscale assemblies of fluorine-doped titania nanoparticles were synthesized from silica-based diatom microshells (frustules) via a shape-preserving reactive conversion process (as per the method of Unocic et al.). The nanostructured F-doped titania frustules were found to induce rapid hydrolysis of the organophosphorous esters, methyl(More)
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