Self-assembly of platinum nanoparticles and coordination-driven assembly with porphyrin

A one-step photoreduction method was applied to the synthesis of platinum colloids of 15 nm in aqueous solution without the need for organic solvents and templates. The formation process of these Pt nanostructures was studied by means of scanning electron microscopy and UV-visible absorption spectroscopy, and the morphology of the Pt nanoparticles (NPs) was illustrated by transmission electron microscopy. The Pt nanostructures were electrochemically characterized by determining the polarization curve and Tafel plot of the hydrogen evolution reaction. The active and easily accessible surface was demonstrated by the self-assembly of these Pt NPs into perfect dendritic structures on the surface of an indium-tin-oxide thin film after the appropriate addition and evaporation of water, which can be explained by diffusion-limited aggregation theory. Further evidence of the easily accessible surface of Pt NPs, is the coordination interaction between the Pt NPs as prepared and the amine ligand of metalloporphyrin resulting in the appearance of nanospheres. In contrast, the two phenomena were not found in citrate ions-stabilized Pt NPs under the same condition, indicating the Pt NPs synthesized with the photoreduction method have great potential in the fields of nanoelectronics, sensors and catalysis, as the “clean” and active surface might improve electrochemical and catalytic performance. Self-assembly and coordination of the Pt nanoparticles due to the easily accessible surface were verified by the formation of Pt dendrites and metalloporphyrin/Pt nanospheres, which might offer perspective to the design of functional materials.