Issue Date: July 30, 2007
Porous Chalcogenide Gels
A new type of porous inorganic gel with semiconducting properties and large surface areas also has the ability to bind heavy metals (Science 2007, 317, 490). Unlike most porous inorganic gels in use, the new materials are not based on silica or other oxides. Mercouri G. Kanatzidis at Northwestern University and colleagues built on a known strategy for organizing inorganic clusters with metal ions around surfactant supports. They linked sulfides or selenides of germanium or tin to platinum ions, but without using a surfactant. For example, clusters such as [Sn2Se6]4- react with Pt2+ in water to form a random, polymeric cross-linked network (shown). Drying the material with supercritical carbon dioxide replaces the water in the pores with air and yields a type of aerogel. The researchers call the materials "chalcogels" because they include chalcogenides (sulfur and selenium.) They tested one chalcogel containing [Ge4S10]4- and found it removed 645 mg/g of Hg2+ from aqueous solution because the heavy-metal ions bind to sulfur. Tests on materials involving less expensive metals than platinum are under way.
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