Dextran templating for the synthesis of metallic and metal oxide sponges

Abstract

Silver or gold-containing porous frameworks have been used extensively in catalysis, electrochemistry, heat dissipation and biofiltration. These materials are often prepared by thermal reduction of metal-ion-impregnated porous insoluble supports (such as alumina and pumice), and have surface areas of about 1 m(2) g(-1), which is typically higher than that obtained for pure metal powders or foils prepared electrolytically or by infiltration and thermal decomposition of insoluble cellulose supports. Starch gels have been used in association with zeolite nanoparticles to produce porous inorganic materials with structural hierarchy, but the use of soft sacrificial templates in the synthesis of metallic sponges has not been investigated. Here we demonstrate that self-supporting macroporous frameworks of silver, gold and copper oxide, as well as composites of silver/copper oxide or silver/titania can be routinely prepared by heating metal-salt-containing pastes of the polysaccharide, dextran, to temperatures between 500 and 900 degrees C. Magnetic sponges were similarly prepared by replacing the metal salt precursor with preformed iron oxide (magnetite) nanoparticles. The use of dextran as a sacrificial template for the fabrication of metallic and metal oxide sponges should have significant benefits over existing technologies because the method is facile, inexpensive, environmentally benign, and amenable to scale-up and processing.

Potentials of Exopolysaccharides from Lactic Acid Bacteria

“…Dextrans have also found use in veterinary medicines. Use of dextrans have ramified into paper, metal-plating processes [19] and enhanced oil recovery [20]. They are used as food syrup stabilizers and dough improvers [21].…”

Magnetic Iron Oxide Nanoworms for Tumor Targeting and Imaging

“…The synthetic strategy is inspired by the previous observation that magnetic nanoparticles can become aligned along strands of high-molecularweight dextran. [31] We find that the geometry of the nanoparticles (elongated versus spherical) influences their efficacy both in vitro and in vivo by enhancing their magnetic relaxivity in MRI, increasing their ability to attach to tumor cells in vitro owing to enhanced multivalent interactions between peptide-modified NW and cell receptors, and amplifying their passive accumulation in vivo over spherical nanoparticle controls. The NW synthesis is similar to the typical preparation of magnetic IO nanospheres (NSs), involving the reaction of Fe(II) and Fe(III) salts in the presence of dextran.…”

Activation of dihydrogen on supported and unsupported silver catalysts

“…The preparation yields silver in a sponge-like morphology (cf. [61]) with particle diameters of a few µm, which probably can be rather compared to the granular silver in the work of Mikovsky et al [32] than the silver foil.…”