Potentiostatic Preparation of Molecular Adsorbates for Scanning Probe Microscopy

We have described various ways in which molecules can be chemically reacted with a metal substrate in an electrochemistry cell. This, in some cases, allows molecules to be bonded strongly enough to be imaged in scanning probe microscopes (SPM) such as the scanning tunnelling microscope (STM) or the atomic force microscope (AFM). In the case of negatively charged molecules (such as DNA) it is remarkably hard to get them onto an electrode, since most surfaces are intrinsically negatively charged (repelling the molecule). We have discovered a remarkably simple procedure for both getting the molecules onto a substrate and for holding them there. It is based on our proposal that DNA could be attracted to a surface made to be positively charged by potentiostatic control of an electrode using a covering electrolyte (Lindsay and Barris, 1988).