Molecular Tips for “Intermolecular Tunneling Microscopy”

We describe herein the concept, principle, and experimental results of molecular tips for chemically selective scanning tunneling microscopy. It has been shown that molecular tips allow chemically selective imaging to recognize particular functional groups or chemical species on the basis of the hydrogen bond, metal coordination, and charge-transfer interactions between the sample and tip molecules. The selectivity can be tailored upon designing functional groups of the tip molecules. Furthermore, the molecular tips were successfully applied to differentiate nucleobases. This technique may be coined "intermolecular tunneling microscopy" from its principle, and is of general significance for novel molecular imaging of chemical identities on membrane and solid surfaces.