How much chemistry is there in chemical force microscopy?

Chemical force microscopy (CFM) is a name given to the technique whereby ch emical specificity is added to atomic force microscopy by deliberate deriva tisation of an atomic force microscopy (AFM) probe. The most fundamental qu estion that surrounds the technique is-how much 'chemistry' is added. Put a nother way, how valid is it to interpret image and adhesion contrast in ter ms of differences in surface chemistry? In this paper three aspects of this problem are described. In the first, the role of the substrate is discusse d. Secondly, a series of experiments concerned with the interactions of pi electron systems is described. These show that it is not possible to interp ret CFM solely in terms of electronic, or intermolecular interactions. The third section reviews CFM experiments with chiral surfaces. It is shown tha t chiral discrimination is not only possible but that the results are in ac cordance with parallel experiments using high performance liquid chromatogr aphy (HPLC). Somewhat surprisingly, CFM experiments are more sensitive to c hirality than HPLC.