High-resolution scanning tunneling microscopy and dI/dV map studies of peptidenucleic acid and fluorescein isothiocyanate

We used scanning tunneling microscopy (STM) to spatially map the local density of states of individual PNA molecules labeled with fluorescein isothiocyanate (FITC) on a Cu(1 1 1) surface. From the observed bias voltage dependences of the topographic height and the dI/dV map of FITC and individual PNA molecules, we confirmed that FITC and PNA have different electrical properties. We clearly differentiated the FITC and PNA molecules by mapping the density of states feature. This study shows that STM with the dI/dV map method is useful in FITC mapping.