Two-dimensional diffraction of molecular nanosheet crystallites of titanium oxide

We have examined two-dimensional diffraction features of novel nanosheet crystallites of quasi-TiO2. A single crystallite gave a face-centered orthogonal array of hl diffraction spots representing a 0.38 nm x 0.30 nm periodicity, 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, which were transformed into ovals on tilting the sample stage. Analysis of the "oval-shaped" electron diffraction pattern allowed the direct probing of the reciprocal lattice geometry and its intensity distribution. The reconstructed reciprocal space:is of nested cylinders for multiple nanosheets, and consequently, a set of parallel diffuse rods for one crystallite, being diagnostic of the two-dimensional crystal. The intensity modulation along the reciprocal rods demonstrates the molecular feature of the nanosheet:and possible adsorption of water molecules on it.