Growth kinetics of platinum nanocrystals prepared by two different methods: Role of the surface

In order to examine the applicability of the diffusion-limited Ostwald ripening model to the growth kinetics of nanocrystals, platinum nanocrystals prepared by two different methods have been investigated by a combined use of small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). One of the methods of synthesis involved the reduction of chloroplatinic acid by sodium citrate while in the other method reduction was carried out in the presence of polyvinylpyrrolidone (PVP) as a capping agent. The growth of platinum nanocrystals prepared by citrate reduction in the absence of any capping agent follows a Ostwald ripening growth with a D3 dependence. In the presence of PVP, the growth of platinum nanocrystals does not completely follow the Ostwald ripening model, making it necessary to include a surface reaction term in the growth equation. Thus, the growth of platinum nanocrystals in the presence of PVP has contributions both from diffusion and surface reaction, exhibiting a D3 + D2 type behavior.

Growth Kinetics of uncapped platinum nanocrystals follows a diffusion-limited Ostwald ripening whereas an additional contribution from surface reaction is needed in the presence of a capping agent.Figure optionsDownload high-quality image (58 K)Download as PowerPoint slideHighlights
► Growth kinetics of platinum nanocrystals was studied by SAXS.
► Observed Ostwald ripening as the growth mechanism in the absence of any capping agent.
► Deviation from Ostwald ripening when PVP was used as the capping agent.
► Role of the surface becomes important in presence of a capping agent.