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Oriented Attachment and Nanorod Formation in Atomic Layer Deposition of TiO2 on Graphene Nanoplatelets

Grillo, Fabio, La Zara, Damiano, Mulder, Paul, Kreutzer, Michiel T., Ruud van Ommen, J.
Journal of physical chemistry 2018 v.122 no.34 pp. 19981-19991
nanocomposites, nanocrystals, nanoparticles, nanorods, physical chemistry, titanium dioxide, transmission electron microscopy
Understanding the spontaneous organization of atoms on well-defined surfaces promises to enable control over the shape and size of supported nanostructures. Atomic layer deposition (ALD) boasts atomic-scale control in the synthesis of thin films and nanoparticles. Yet, the possibility to control the shape of ALD-grown nanostructures remains mostly unexplored. Here, we report on the bottom-up formation of both linear and V-shaped anatase TiO₂ nanorods (NRs) on graphene nanoplatelets during TiCl₄/H₂O ALD carried out at 300 °C. NRs as large as 200 nm form after only five ALD cycles, indicating that diffusional processes rather than layer-by-layer growth are behind the NR formation. In particular, high-resolution transmission electron microscopy reveals that the TiO₂ NRs and graphene nanoplatelets are in rotational alignment as a result of lattice matching. Crucially, we also show that individual nanocrystals can undergo in-plane oriented attachment.