Controlling Atomic Layer Deposition of TiO₂ in Aerogels through Surface Functionalization

This report demonstrates a chemical functionalization method for controlling TiO 2 ALD in low-density nanoporous materials, i.e., aerogels. Functionalization of silica aerogel with trimethylsilane is shown to inhibit TiO 2 growth on the aerogel via ALD. A proposed mechanism for the deactivation effect is the blocking of surface functional groups, such as hydroxyl (OH) moieties, which serve as chemisorption sites for the ALD precursors and hence are essential for nucleating the deposition process. Subsequent modification of the aerogel functionalization through the selective removal of hydrocarbon groups via heat or plasma treatment reactivates the aerogel towards deposition, thereby resulting in TiO 2 growth. The results presented here demonstrate the use of ALD as a selective tool for creating novel nanoporous materials.