Single molecule force spectroscopy

Molecular-scale forces has a pivotal role in biological, chemical and physical processes. Single molecule force spectroscopy refers to the study of these forces as well as the mechanical properties of single molecules under applied forces. The term has appeared more than two decades ago in the field of biochemistry, however the recent advances of atomic force microscopy (AFM) operated at low temperature have brought such studies down to the atomic level hence opening new exciting perspectives. At this ultimate level, the intrinsic properties of individual organic species are now quantified by measuring force and conductance informations at the sub-molecular level. Not only restricted to the mechanics of the adsorbates, these techniques are nowadays employed to reveal their chemical structures, their electronic characteristics as well as their optical properties. This chapter reviews proto-typical experiments revealing the fundamental properties of single molecules using advanced spectroscopic techniques at low temperature. First, we will discuss the requirements of such spectroscopic experiments as well as the “essence” of the physical quantities extracted from them. Section 11.3 will respectively show the capability of this approach in the elucidation of the structure of single molecules, the mechanical properties, their internal mechanical behavior under various manipulation processes. Section 11.4 will be dedicated to the study of their electronic and optical properties down to the sub-molecular scale. Finally, Sect. 11.5 will discuss the future prospects.