Web Release Date: October 3,
High-Yield Synthesis of Complex Gold Nanostructures in a Fungal System
and
Singapore-MIT Alliance, National University of Singapore, 4 Engineering Drive 3, Singapore 117576, Department of Chemical Engineering, MIT, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, and Department of Chemical and Biomolecular Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260
Received: July 6, 2007
In Final Form: August 20, 2007
Abstract:
In this work, gold nanocrystals with various shapes and sizes, including spherical, regular nanoplates, spiral nanoplates, nanowalls, lamellar nanoagglomerates, and spherical nanoagglomerates, were produced at high yield by reacting an aqueous solution of chloroauric acid with the mycelia-free spent medium or the extract of a filamentous fungus, Aspergillus niger. Structural characterizations showed that the plate-like structures were oriented with {111} planes as the basal plane. The results implicated proteins on the fungal cell walls and proteins in the fungal extract as the primary biomolecules involved in the synthesis of gold nanocrystals. Reaction in the spent medium, on the other hand, involved an enzymatic process where small biomolecules and enzymes served as the substrates and catalysts, respectively. The formation of these highly anisotropic structures was kinetically controlled, as shown by the dependence of particle shape and size on environmental variables such as the temperature and pH of the solution.
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