Roles of twin defects in the formation of platinum multipod nanocrystals

This paper describes the synthesis of platinum multipods from platinum acetylacetonate in the presence of adamantanecarboxylic acid (ACA), hexadecylamine (HDA), and 1,2-alkanediol. Regular cubes and a range of other shapes can be generated in these reaction mixtures using diphenyl ether as the solvent and at a reaction temperature ranging from 160 to 200 degrees C. The formation of both planar and three-dimensional multipods of platinum can be attributed to the twin defects in the seed crystals. High-resolution transmission electron microscopy (HR-TEM) and electron diffraction (ED) data of platinum multipods show the stacking fault plays a key role in the reduction of symmetry in face-centered cubic metals such as platinum and enables the formation of mono-, bi-, tri-, and multipods of metal nanocrystals. The final shapes of the nanocrystals depend on both the type and number of defects, which can be changed by varying the reaction conditions such as the ACA/HDA molar ratio, the type of diols, the reaction time, and the temperature. High-aspect-ratio multipods of platinum can be generated by using 1,2-dodecanediol. The mechanisms that govern the formation of platinum multipods should be applicable for making other metal multipods.