Chemists in France have made heteroditopic ligands and used them to stabilize gold nanoparticles. 

Cédric Mayer and colleagues from the University of Versailles have designed the ligands in a specific way in order to fulfil certain criteria. A 2-mercaptopyridine group at one end of the ligand ensures a strong interaction with the gold surface of the nanoparticle. At the other end, a bidentate or tridentate pendant group is able to generate a variety of metallic complexes. Finally, the groups at each end are connected via a fully conjugated system, which could allow electron transfer. 

The team then found that gold nanoparticles functionalized with these two ligands show exceptional monodispersity in size and shape. They can also be reversibly transferred from water to non aqueous solvents, and they are easy to purify. Consequently, the team successfully used them as nanobuilding blocks for coordination chemistry. 'Ruthenium complexes have been gathered on the surface of the pre-functionalised gold nanoparticles without noticeable alteration of their size or shape,' said Mayer. The presence of a fully conjugated bridge between the ruthenium centre and the metallic nanoparticles makes these systems particularly unique. 

The group hope that the systems presented in their work will offer new perspectives for the synthesis of a variety of nanocomposites with tunable properties in the future. Their next challenge is to find a method to control and adjust the electronic transfer between the metallic nanoparticles and the metallic complexes in their systems. 'Our ultimate goal is to be able to synthesise nanosystems with specific physico-chemical properties for a target application,' said Mayer. 

Jenna Wilson