Study of Colloidal Gold Synthesis Using Turkevich Method

摘要

The synthesis of colloidal gold or Au‐nanoparticles (Au‐NPs) by reduction of chloroauric acid (HAuCl_4) with sodium citrate was done using Turkevich method. We prepare HAuCl_4 solution by dissolving gold wires (99.99%) into aqua regia solution. To initiate the Au‐NPs synthesis 0.17 ml of 1 % chloroauric acid solution was heated to the boiling point and then 10 ml of 1 % sodium citrate was added to the boiling solution with a constant stirring in order to maintain a homogenous solution. A color of faint gray was observed in the solution approximately one minute and in a period of 2-3 minutes later, it further darkened to deep wine and red color. It showed that the gold solution has reduced to Au‐NPs. The effect of process temperature on the size of Au‐NPs prepared by sodium citrate reduction has also been investigated. With increasing temperature of Au‐NPs synthesis, smaller‐size Au‐NPs were obtained. The higher temperatures shorten the time needed to achieve activation energy for reduction process. The resulting Au‐NPs has been characterized by scanning Electron Microscope (SEM), showing the size of Au‐NPs average diameter is ～20-27 nm. The resulting colloidal gold will be used as catalyst for Si nanowires growth using VLS method.