Silylation from supercritical carbon dioxide: a powerful technique for modification of surfaces

Silylation is one of the most frequently employed surface-functionalization techniques. Silylation of surfaces from supercritical CO2 (scCO2) solutions, which is carried out by exposing the surface to a solution of a silane-based modifying agent dissolved in scCO2, has been attracting increased attention due to its numerous advantages over the conventional silylation techniques which utilize liquid solutions or vapor phase. Besides being a green and environmentally friendly route, silylation using scCO2 provides solvent-free materials after processing, enhanced diffusion and mass-transfer rates, faster reactions, homogenous and uniform surfaces, and control over the properties of the surface. Such advantages have led to many interesting studies on the development of novel scCO2-based silylation technologies in various fields ranging from porous materials to microelectronic processing, and from thin films to nanocomposites. In this article, we give an overview of the fundamental aspects of silylation from scCO2 and summarize the studies in the literature in various fields.