Silanization is the covering of a surface with organo functional chloro or alkoxysilane molecules. Oxide components like the native oxide layer, silicic acids, silica gel, silica nanoparticles, glass and metal oxide surfaces can be silanized, because they contain hydroxyl or silanol groups which attack and displace the alkoxy groups on the silane thus forming a covalent -Si-O-Si- bond. The goal of silanization is to form bonds across the interface between mineral/inorganic components and organic components present in paints, adhesives, etc. or as the anchor for further steps of surface modifications.
Methoxy- and ethoxy groups are usually used as leaving groups. Alkoxysilanes are classified according to their C-terminated organic functionality: Aminosilanes, Glycidoxysilanes, Mercaptosilanes etc. One main issue in using silanization in surface engineering is to minimize the polymerization of the alkoxysilane, especially of APTES.
Silanization protocols for glass slides and silicon oxide substrates usually include acid rinsing steps to activate the surfaces prior to silanization. Han et al. (2006) silanized thin oxide layers with (3-aminopropyl) triethoxysilane. Thicknesses and uniformity of the silane coatings were evaluated by Imaging ellipsometry.
Reference:
Han Y., Mayer D., Offenhäusser A., Ingebrandt S. (2006) Surface activation of thin silicon oxides by wet cleaning and silanization. Thin Solid Films 510, 175 – 180.
Silanization as it is used for silicon surfaces is a widely used method to hydrophobize samples. A very thin layer of organic silane in the fluid phase, known as octadecyltrichlorosilane (OTS), is covalently bonded to the silicon surface at high temperatures. These extremely hydrophobic surfaces are used to prepare phospholipid monolayers on solid supports. In structural studies of OTS monolayers with undulator radiation at highly brilliant synchrotron radiation sources, we have observed severe beam damage. Ellipsometry can be used to locally image the structural degradation at the point where the x-ray beam has penetrated the sample (sample provided by Klaus Giewekemeyer, IRP)
