Tunneling Dendrimers. Enhancing Charge Transport through Insulating Layer Using Redox Molecular Objects
Résumé
Charge transport through an insulating layer was probed using ferrocenyl-terminated dendrimers and scanning electrochemical microscopy. Experiments show that the passage through the layer is considerably enhanced when the transferred charges are brought globally to the surface by the ferrocenyl dendrimer instead of a single ferrocene molecule. This result shows that charge tunneling through an insulator could be promoted by a purely molecular nano-object. S everal recent studies have highlighted that the charge transfer through an insulating layer from a molecule present in solution to a substrate could be restored by attaching a few nanoparticles 1−4 and even a single nanoparticle on the outside of an insulating layer. 5,6 Theoretical analyses have provided some explanations to understand the origins of this phenomenon. 7,8 A higher density of state in a metallic nanoparticle enhances the electron tunneling across the insulating layer and thus the global kinetics of electron transfer. In other words, tunneling from a nanoparticle to a substrate is much more probable than tunneling from single molecules. Beside the fundamental consequences of this observation, it has already opened a route to the developments of novel analytical methods, whereby a nano-particle deposited on an insulating layer behaves as a functional nanoelectrode. 5,6