How much chemistry is there in chemical force microscopy?

Chemical force microscopy (CFM) is a name given to the technique whereby chemical specificity is added to atomic force microscopy by deliberate derivatisation of an atomic force microscopy (AFM) probe. The most fundamental question that surrounds the technique is-how much 'chemistry' is added. Put another way, how valid is it to interpret image and adhesion contrast in terms of differences in surface chemistry? In this paper three aspects of this problem are described. In the first, the role of the substrate is discussed. Secondly, a series of experiments concerned with the interactions of pi electron systems is described. These show that it is not possible to interpret CFM solely in terms of electronic, or intermolecular interactions. The third section reviews CFM experiments with chiral surfaces. It is shown that chiral discrimination is not only possible but that the results are in accordance with parallel experiments using high performance liquid chromatography (HPLC). Somewhat surprisingly, CFM experiments are more sensitive to chirality than HPLC.