Chemical modification of self-assembled silane based monolayers by surface reactions.

In this critical review, we look at how the functionalization of solid substrates by self-assembly processes provides the possibility to tailor their surface properties in a controllable fashion. One class of molecules, which attracted significant attention during the past decades, are silanes self-assembled on hydroxyl terminated substrates, e.g. silicon and glass. These systems are physically and chemically robust and can be applied in various fields of technology, e.g., electronics, sensors, and others. The introduction of chemical functionalities in such monolayers can be generally obtained via two methods. This involves either the use of pre-functionalized molecules, which can be synthesized by different synthetic routes and subsequent self-assembly of these moieties on the surface. The second method utilizes chemical surface reactions for the modification of the monolayer. The latter method offers the possibility to apply a large variety of different organic reaction pathways on surfaces, which allows the introduction of a wide range of terminal end groups on well-defined base monolayers. In contrast to the first approach an important advantage is that the optimization of the reaction conditions for suitable precursor molecules is circumvented. The following review highlights a selection of chemical surface reactions, i.e., nucleophilic substitution, click chemistry and supramolecular modification, which have been used for the functionalization of solid substrates (80 references).