Recent advances in nanotechnology enable the fabrication of tailored materials for a variety of applications e.g. in catalysis or alternative energy. In this contribution, we present a novel process for the creation of uniform nanocavities on the surface of nanoporous materials using atomic layer deposition (ALD) and nanotemplate surface patterning (see Scheme). As nanoporous material, we employed silica SBA-15 owing to its large specific surface area and ordered pore structure. To facilitate the grafting of the calixarene nanotemplate, the surface of SBA-15 was pre-treated with an ALD coating of one monolayer of TiO2 (Ti-SBA-15). The templates were then surrounded by Al2O3 as wall material using further ALD treatment. Template removal was achieved at moderate temperatures (60°C) by reaction with ozone preventing damages to the structure. By this approach a homogeneous distribution of uniform nanocavities of conical shape with 1-2 nm diameter, due to the size and geometry of the calixarene template molecules, was obtained. To elucidate the surface chemistry during nanocavity synthesis, detailed spectroscopic (IR, UV-Vis, and XPS) and microscopic (AFM, TEM) characterization was applied besides thermal analysis. IR and UV-Vis spectra reveal the successful formation of a covalent template-to-substrate binding, which remains unchanged during wall formation but breaks up during ozone treatment. On the other hand, IR spectra confirm that upon grafting the calixarene molecules remain intact. Supporting XPS and TGA measurements give insight into the changing composition of the modified SBA-15 surface and quantification of the amount of grafted template. By using substrates based on planar Si-wafers (SiO2/Si) the process of nanocavity formation could be directly monitored on a monomolecular level through AFM imaging. Our results highlight the use of molecule-templated atomic layer deposition (ALD) for the controlled nanoscale structuring of surfaces enabling novel applications in catalysis or alternative energy.

Nanoscale structuring of surfaces by using atomic layer deposition: Controlled synthesis of nanocavities

256th National Meeting (2018)

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