In Situ Microscope Measurements of the Formation of Nanometer-Sized Gold Particles at the Dodecane/Water Interface through the Direct Reduction of Aqueous Tetrachloroaurate(III) by Hydrophobic dl-α-Tocopherol in the Presence of 1,10-Phenanthroline

Abstract

The contact of a dodecane solution of hydrophobic dl-α-tocopherol with an aqueous solution of tetrachloroaurate(III) resulted in the direct reduction of tetrachloroaurate(III) and the formation of gold particles at the dodecane/water interface. Without other additives, the gold particles were unfavorably aggregated with each other and chains of gold particles were formed. In the present study, a chemical preventing the aggregation was sought. Fourteen types of chemicals were individually added to the two-phase system, and then the size, shape, and movements of the gold particles formed at the dodecane/water interface were observed through an optical microscope using bright-field illumination, using dark-field illumination, or with scattered laser light under total internal reflection conditions. Of the 14 chemicals, 1,10-phenanthroline (phen) effectively prevented the aggregation of gold particles at the interface. The gold particles formed in the presence of phen under the optimized conditions were recovered on a coverslip, and their size and shape were recorded using an atomic force microscope. Almost all of the recovered gold particles were not higher than 50 nm and this meant that nanometer-sized gold particles were formed.