Working with Prof. Martin Gruebele at the University of Illinois, we showed that it is possible to capture nanometer resolution images of electronically excited PbS quantum dots, using a combination of single molecule absorption and scanning tunneling microscopy (SMA-STM). Usually STM can only image ground state electron density. Transient or steady-state absorption spectroscopy can access specific excited states, but without the spatial information STM provides. Using the two techniques in tandem allows spatial resolution of excited state density. This gives researchers a powerful diagnostic tool for understanding excited states of quantum dots that can help design nanomaterials for photovoltaics, LEDs, and many other technologically important uses. This work is now available online and can be found here.
