Effect of water on silanization of silica by trimethoxysilanes

Water has a big influence on the mechanism of monolayer formation and therefore on the structure of monolayer that can be obtained on a silica surface. Trimethoxysilane in the absence of water can form submonolayers with only one siloxane bond binding functional tails with the surface. We show here that hydrolysis of the remaining methoxy groups on the initial immobilized silane layer by water and followed by another silanization yields enhanced surface density of silanes with improved lateral polymerization and without complications of vertical polymerization. The improved technique allows surface concentration of coumarin dye molecules of 2.7 × 10¹⁴ cm^-2, almost 1.3 times higher than what is possible without water treatment.