Center for Functional Nanomaterials Seminar

One of the key challenges in molecular machines and devices is the reproducible assembly of functional units in an addressable arrangement. By combining concepts of supra-molecular chemistry [1] and surface science, increasingly complex functional layers have been manufactured and explored. Site specific molecular interaction is the generic origin of molecular self assembly [2] and distinctively different mechanisms have been identified: Selective chemical bonding [3], conformational bi-stability [4], and 2D phase behaviour [5] produce distinctly different functional layers. Binary molecular systems which involve longer range dipole forces and entropic mobility provide the basis for an increased periodicity [5]. In conjunction with a conformational mechanism the spacing between individual supramolecular units has very recently been increased to 7.2 nm [6]. Beyond supra-molecular assembly, extended networks have been created by a thermally activated chemical reaction [7] and have been used as a template for supra-molecular organisation of ad molecules [8], and for the confinement of coupled quantum dots from delocalised substrate electronic states [9]. A single chain covalent polymer has also been formed [10]. Ultimately, adressable supra-molecular rotor-stator systems [11,12], in particular a supra-molecular rotational switch [12] have been described. Molecular layers on insulator thin films [13] and on ferromagnetic substrates [14] have been characterised for their electronic and magnetic coupling. Notably also tunable porous networks [15] and supramolecular macroscycles [16] have been described, as well as self assembling arrays of C60 / Phthalocyanine systems [17].