Sub-nanoscale probing of nanojunction using heterogeneous gap-mode Raman spectroscopy.

Symmetric bifunctional molecule-linked nanogap structures have been frequently used in nanoelectronics, it is still challenging to discriminate the phenomenon that happened at both interfacial regions with subnanoscale resolution. Here, we fabricated platinum-silver or silver-platinum heterogeneous nanogap structures using a symmetric isocyanide terminated molecule, and using surface-enhanced Raman spectroscopy, we investigated the electrochemical potential-dependent change in the two distinguishable isocyanide stretching bands in such structures. Counterintuitively, we observed that the isocyanide group at the nanoparticle surface experiences more enhanced effective potential than the one at the plate surface, and this is attributed to the nanoparticle-induced effects rather than the potential drop that conventionally occurred due to molecular resistance. Our study provides a novel strategy allowing the subnanoscale investigation of numerous interfacial phenomena, which could not be achieved via conventional spectroscopic techniques.