Quantum confinement of two-dimensional surface electronic states is a possible avenue for the controllable modification of metal surface electronic structure. The Nazin Lab used scanning tunneling microscopy and spectroscopy (STM/STS) to study the electron confinement within individual ring-shaped cycloparaphenylene (CPP) molecules, prepared by Evan Darzi and Ramesh Jasti, that formed self-assembled films on Ag(111) and Au(111) surfaces. STM imaging and STS mapping revealed the presence of electronic states localized in the interiors of CPP rings, inconsistent with the expected localization of molecular electronic orbitals. Electronic energies of these states showed considerable variations correlated with the molecular shape. These observations are explained by the presence of localized states formed due to confinement of surface electrons by the CPP skeletal framework, which thus acts as a molecular electronic “corral”. These experiments suggest an approach to robust, large-area modification of the surface electronic structure via quantum confinement within molecules forming self-assembled layers.

Benjamen N. Taber, Christian F. Gervasi, Jon M. Mills, Dmitry A. Kislitsyn, Evan R. Darzi, William G. Crowley, Ramesh Jasti, and George V. Nazin published their results, “Quantum Confinement of Surface Electrons by Molecular Nanohoop Corrals”,  in the Journal of Physical Chemistry Letters. The letter was published online on July 26, 2016, and is available at: http://pubs.acs.org/doi/abs/10.1021/acs.jpclett.6b01279.