Atomic Force Microscopy Investigation of the Growth of Different Alkylsiloxane Monolayers from Highly Concentrated Solutions

Abstract

The growth of self-assembled monolayers of alkylsiloxanes on silicon surfaces through adsorption of alkyltrichlorosilanes at various concentrations in toluene has been investigated. The influence of high alkylsilane concentrations up to 50 mmol/L on the ordering of the films has been studied. Characterization of the films has been performed with tapping mode atomic force microscopy and ellipsometry. Different alkylsilanes have been used in order to study both the effect of the chain length and the age of the precursor solution on the ordering of the molecules in solution as well as on the substrate surface. For freshly prepared solutions with a high concentration of octadecyltrichlorosilane (OTS, C18), irregular rough films with a maximum surface coverage of 70% have been observed. For C10, C12, and C16 alkylsilanes, comparatively flat films have been obtained under the same conditions. For OTS, such flat films can only be achieved after prolonged aging of the precursor solution. The results are discussed in terms of ordering depending on different experimental parameters.

Functionalization of electropolished titanium surfaces with silane-based self-assembled monolayers and their application in drug delivery

“…5b). An island growth behavior for OTS molecules has been reported to occur on the surface of silica and mica but this did not occur under our experimental conditions at the surface of EP-Ti [33,84,85].…”

“…However, increasing the concentration above 30 mM resulted in a clear shift of these peaks towards higher frequencies representative of a disorganized film. At very high concentrations, the adsorption of the OTS molecules on the substrate during the initial phase of the growth process may be too fast and thus the fast and irregular chemisorption of the OTS molecules may lead to the blockage of surface adsorption sites [33]. Accordingly, the OTS concentration was kept below 30 mM, but not too low in order to keep the kinetics of adsorption reasonably fast [80].…”

Surface modification of cobalt–chromium–tungsten–nickel alloy using octadecyltrichlorosilanes

“…The exact state of mechanism behind the chemical bonding of OTS on a surface is still debatable. The formation of OTS monolayer on a material surface is highly sensitive to several factors, which include (a) the density of surface hydroxyl groups [32]; (b) reaction temperature [29,33]; (c) reaction environment [34,35]; (d) reaction time [34]; (e) solvent used to deposit OTS [35,36]; (f) water content of the solvent [33]; (g) concentration of OTS [35,37]; (h) solution age [38]; (i) roughness of the underlying substrate [39]; and (j) cleaning procedures after SAM deposition [40].…”

Morphology and Amine Accessibility of (3‐Aminopropyl) Triethoxysilane Films on Glass Surfaces

“…Particularly important is the amount of water in the system (Legrange et al ., 1993;McGovern et al ., 1994;Ulman, 1996;Peters et al ., 2002;Foisner et al ., 2003;Wang and Lieberman, 2003) and the nature of the solvent (McGovern et al ., 1994;Fan et al ., 2003;Rozlosnik et al ., 2003). (3-Aminopropyl) triethoxysilane was originally thought to form an ordered monolayer with adjacent silanes bound by Si-O-Si bonds, (Waddell et al ., 1981;Kurth and Bein, 1993;Moon et al ., 1996).…”