Growth Kinetics of Gold Nanocrystals: A Combined Small‐Angle X‐Ray Scattering and Calorimetric Study

Abstract

The growth of gold nanocrystals prepared by the reduction of tetrachloroauric acid by tetrakis(hydroxymethyl)phosphonium chloride, which allows slow reduction, is investigated by small-angle X-ray scattering and isothermal titration calorimetry in combination with transmission electron microscopy. The growth of the nanocrystals does not follow the diffusion-limited Ostwald ripening but instead follows a sigmoidal rate curve. The activation energy obtained from the temperature-dependent growth study is very small. The heat change associated with the growth is determined for the first time as approximately 10 kcal mol(-1) per 1 nm increase in the nanocrystals' diameter.