Self-Assembly of Platinum Nanoparticles of Various Size and Shape

The addition of dodecanethiol to a polydisperse platinum colloidal aqueous solution capped with acrylic acid leads to self-assembled monolayers which not only contain various sizes, but also various shapes of nanoparticles. Assembled monolayers arranged in hcp arrays are achieved for mixed shape samples. In the case of the assembly of cubic nanoparticles, cubic closest packing is achieved when the size difference between the nanoparticles is less than 25% (or between 6 and 8 nm). The ccp array is disrupted when the size difference is between 25 and 60% or there is a mixture of shapes. Finally, size segregation is seen in regions where the size difference is more than 60% with the resultant assembly being hcp no matter what the shape.