Biosynthesis of Silver and Gold Crystals Using Grapefruit Extract

In this paper, biological synthesis of silver and gold crystals using grapefruit extract is reported. On treatment of aqueous solutions of silver nitrate and chloroauric acid with grapefruit extract, the formation of stable silver and gold particles at high concentrations is observed to occur. The silver particles formed are quasi-spherical or irregular with sizes ranging from several hundred nanometers to several microns. The gold quasi-spheres with holes on surfaces and with diameters ranging from 1 to 3 microns are obtained. The formation mechanism of silver and gold crystals is discussed, indicating that the soluble biomolecules such as protein(s) and vitamin C in grapefruit extract may play a crucial role in defining the morphology and/or crystal phase of silver and gold crystals. Keywords: silver, gold, biological synthesis, grapefruit, extract