37 巻 (2016) 10 号 p. 475-481
Surface charges on nanometer-scale structures in liquids play an essentially important role in various physical, chemical and biochemical phenomena such as ionic adsorptions, microscopic electrode reactions and specific ligand bindings. These molecular-scale interactions are mediated through local electric double layers (EDLs) formed by the counter ions in electrolyte solution. Although static-mode atomic force microscopy (AFM) including colloidal probe AFM is a powerful technique for surface charge density measurements and EDL analysis on a submicron scale in liquids, precise surface charge density analysis with molecular resolution has not been realized because of its limitation of the resolution and the electrical force detection sensitivity. Here recent molecular-scale surface charge measurements of self-assembled micellar structures and biomolecules by three-dimensional (3D) force mapping based on frequency modulation AFM are presented.