Atomic Layer Deposition for the Conformal Coating of Nanoporous Materials

Atomic layer deposition (ALD) is ideal for applying precise and conformal coatings over nanoporous materials. We have recently used ALD to coat two nanoporous solids: anodic aluminum oxide (AAO) and silica aerogels. AAO possesses hexagonally ordered pores with diameters d ~ 40 nm and pore length L ~ 70 microns. The AAO membranes were coated by ALD to fabricate catalytic membranes that demonstrate remarkable selectivity in the oxidative dehydrogenation of cyclohexane. Additional AAO membranes coated with ALD Pd films show promise as hydrogen sensors. Silica aerogels have the lowest density and highest surface area of any solid material. Consequently, these materials serve as an excellent substrate to fabricate novel catalytic materials and gas sensors by ALD.