Templated growth of platinum nanowheels using the inhomogeneous reaction environment of bicelles.

Novel platinum nanowheels were synthesized by the reduction of aqueous platinum complex with ascorbic acid in the presence of disk-like bicelles. The platinum nanowheels possess thickened centers and flared edges that are connected by dendritic platinum nanosheets. This structural complexity can be attributed to the inhomogeneous micro-environment of the templating bicelles consisting of a central bi-layer region and a high curvature rim. The formation mechanism of the nanowheels was investigated by imaging nanostructures at different stages of the reaction. The templating bicelles were also imaged by TEM with the aid of negative staining. The variation of reaction parameters including platinum concentration, temperature, and total concentration of surfactants (CTAB + FC7) led to other types of platinum nanostructures, such as circular dendritic nanosheets with a tunable diameter and rectangular dendritic nanosheets. Interestingly, under irradiation by a TEM electron beam, the dendritic nanosheet portion of the nanowheels transforms into a metastable holey sheet. In addition, the platinum nanowheels have an electrochemical active surface area comparable to that of ETEK platinum black and thus are expected to have potential applications in catalysis.