Permeation of a Single-Layer SiO₂ Membrane and Chemistry in Confined Space

Well-ordered, ultrathin silica films grown on metal substrates are composed of layers of corner-sharing [SiO4] tetrahedra (silicatene). Yet unrealized in practice as unsupported material, the double-layer silicatene could constitute the thinnest silica membrane ever fabricated. We addressed here the permeability of such a membrane by using a metal substrate as a gas detector. Permeation of CO and D2 was examined by infrared reflection absorption spectroscopy and temperature-programmed desorption. The results reveal a complex response of such systems upon gas exposures which involves gas transport through amorphous silica pores as well as chemisorption and diffusion across the metal surface underneath the silicatene. Such a hybrid system, which would combine a robust molecular-sieve membrane and a chemically active metal underneath, could become interesting materials for technological applications, in particular, in catalysis and sensor