Uniform N-(2-Aminoethyl)(3-aminopropyl)trimethoxysilane Monolayer Growth in Water

The commonly preferred approach to grow silane self-assembled monolayers (SAMs), using anhydrous solvents while maintaining some absorbed water at the solid substrates, is difficult to control and very often leads to irreproducibility. In the search for a new approach for functional hydrophilic monolayers, we tested water as a solvent for monolayer growth. As a model system, we investigated monolayer growth of N -(2-aminoethyl)(3-aminopropyl)trimethoxysilane (EDA) in water at various silane concentrations and temperatures. The topology and the thickness of the EDA layers were measured by atomic force microscopy and ellipsometry respectively; their molecular properties were studied by using liquid crystals as an optical amplification probe. We found that growth at low silane concentrations and low temperatures resulted in uniform monolayers. This makes our method of considerable interest for the construction of (bio)functionalized surfaces that require the use of aqueous media.