Two-dimensional diffraction of molecular nanosheet crystallites of titanium oxide

We have examined two-dimensional diffraction features of novel nanosheet cr ystallites of quasi-TiO2. A single crystallite gave a face-centered orthogo nal array of hl diffraction spots representing a 0.38 nm x 0.30 nm periodic ity, which reflects the two-dimensional atomic arrangement in the nanosheet . Diffraction collected from plural crystallites was composed of concentric circles as a result of their random orientation in the TEM grid plane, whi ch were transformed into ovals on tilting the sample stage. Analysis of the "oval-shaped" electron diffraction pattern allowed the direct probing of t he reciprocal lattice geometry and its intensity distribution. The reconstr ucted reciprocal space:is of nested cylinders for multiple nanosheets, and consequently, a set of parallel diffuse rods for one crystallite, being dia gnostic of the two-dimensional crystal. The intensity modulation along the reciprocal rods demonstrates the molecular feature of the nanosheet:and pos sible adsorption of water molecules on it.