1D and 3D surface-assisted self-organization

In view of the many potential applications for functional hybrid interfaces, the controlled assembly of sophisticated structures on surfaces is a current challenge for chemists. Applications can be foreseen in fields such as molecular electronics, spintronics, sensors, catalysis and even synthesis. Independent of their functional nature, the characterization of nano-objects usually involves their deposition on surfaces. Whereas the formation of 2D networks on a surface corresponds to the association of scaffolds of the same dimensionality, 1D and 3D self-organized materials clearly differ from the 2D nature of the support. Unless necessary, organized 2D networks will not be examined in detail, as this subject has been periodically reviewed elsewhere. In this review, concepts originating from the 2D organization, but leading to the surface-assisted production of organized 1D and 3D self-assemblies will be examined and illustrated by selected recent examples from the literature.Three roles can be played by the surface. First, the surface can simply serve as an inert foundation for the organization of the functional layer, which is controlled by molecule–molecule interactions only. Second, the surface can be considered as a template by adding specific constraints to the assembly of the building blocks, restricting their conformational freedom and thus confining the growth in a surface plane or directing the growth of the nanostructures along specific symmetry axes (epitaxy) or surface defects and heterogeneities (step edges). This case seems the most conceptually advanced and has already led to integration of self-assembled materials into devices by using preferred orientations of the surface to align molecules in given directions, for example between interdigitated electrodes. Third, the surface itself can be a source of constituents, or adatoms, of the assembly and can alter the electronic structure of the building blocks, thus directly participating in the assembly process and final function of the structures. The latter case is more scarcely spread over different explorative works in which the major road maps are the successive growth of layers into three dimensions from a preorganized two dimensional (molecular) adlayer, as well as surface-induced reactions within an organized layer.

► Implementation of self-assembled molecular objects involves surface deposition.
► A surface's role is an inherent part of designing self-assembling building blocks.
► Surface controlled processes are illustrated for 1D and 3D constructions.