| Abstract
| - In this work, gold nanocrystals with various shapes and sizes, including spherical, regular nanoplates, spiralnanoplates, nanowalls, lamellar nanoagglomerates, and spherical nanoagglomerates, were produced at highyield by reacting an aqueous solution of chloroauric acid with the mycelia-free spent medium or the extractof a filamentous fungus, Aspergillus niger. Structural characterizations showed that the plate-like structureswere oriented with {111} planes as the basal plane. The results implicated proteins on the fungal cell wallsand 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 biomoleculesand enzymes served as the substrates and catalysts, respectively. The formation of these highly anisotropicstructures was kinetically controlled, as shown by the dependence of particle shape and size on environmentalvariables such as the temperature and pH of the solution.
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