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Filamentous electrodes

Natural template: gold microtubes, molded around filamentous fungi

MARCOS MALTA / UFBANatural template: gold microtubes, molded around filamentous fungiMARCOS MALTA / UFBA

Researchers in the state of Bahia have successfully produced microscopic gold tubes molded around filaments of fungi collected from plants in the Abaeté lagoon, an environmental protection area threatened by urban expansion in Salvador, the Bahian state capital. With permission from the environmental authorities, the team headed by chemist Marcos Malta at the Federal University of Bahia (UFBA) collected stems, leaves, and roots of plants from the Abaeté lagoon and then, in the laboratory, isolated three species of filamentous fungi found growing in the plant matter. The fungi were subsequently cultivated for two months in solutions containing different concentrations of a salt (citrate, used as a nutrient source) and gold nanoparticles. By mechanisms yet unknown, the gold nanoparticles adhered to the outer surface of the fungal cell walls, creating a carapace. After two months, the researchers dried the fungi using a method that preserves their shape, before calcinating away the remaining organic matter. The result were hollow, porous tubes, just a few micrometers long, in the shape of their fungal “templates” (Biomaterials Science, March 2014). The tubes being hollow and porous increases their contact surface, an important feature for electrochemical reactions in which gold is used as a high surface area electrode. “This strategy,” Malta believes, “can reduce the amount of gold needed to produce this type of electrode.”