Strontium titanate is seeing increasing interest in fields ranging from thin-film growth to water-splitting catalysis and electronic devices. Although the surface structure and chemistry are of vital importance to many of these applications, theories about the driving forces vary widely 1,2 . We report here a solution to the 3 × 1 SrTiO 3 (110) surface structure obtained through transmission electron diffraction and direct methods, and confirmed through density functional theory calculations and scanning tunnelling microscopy images and simulations, consisting of rings of six or eight cornersharing TiO 4 tetrahedra. Further, by changing the number of tetrahedra per ring, a homologous series of n × 1 (n ≥ 2) surface reconstructions is formed. Calculations show that the lower members of the series (n ≤ 6) are thermodynamically stable and the structures agree with scanning tunnelling microscopy images. Although the surface energy of a crystal is usually thought to determine the structure and stoichiometry, we demonstrate that the opposite can occur. The n × 1 reconstructions are sufficiently close in energy for the stoichiometry in the near-surface region to determine which reconstruction is formed. Our results indicate that the rules of inorganic coordination chemistry apply to oxide surfaces, with concepts such as homologous series and intergrowths as valid at the surface as they are in the bulk.The structure of SrTiO 3 is a cubic close-packed lattice of strontium and oxygen with strontium at the corners and oxygen at the face centres, and titanium at the body centres occupying those octahedral holes that are surrounded only by oxygen. Along the (110) direction SrTiO 3 is polar, composed of alternating layers of SrTiO 4+ and O 2 4− , that is, alternating layers with uncompensated nominal valence charges of 4+/4−. In a fully ionic model, this leads to an unbalanced macroscopic dipole and infinite surface energy. Therefore, we expect a (110) surface to have a nominal excess surface valence of either 2+ or 2− per surface unit cell, as otherwise energetically unfavourable holes in the valence band or electrons in the conduction band would be formed. There has been extensive discussion of the mechanisms of this 'charge compensation' for polar oxide surfaces in the literature (see for instance refs 3-5 and references therein). Various theories, such as a reduction of Coulomb forces 2 or a minimization of 'dangling bonds' 1 , have been described as the driving force behind surface structure formation. An alternative model for oxide surfaces, first proposed for the SrTiO 3 (001) 2 × 1 surface 6 , is that the rules of inorganic coordination chemistry dominate, although, as the (001) surface is not polar, we might question the generality of this model.

Pt/SrTiO3 shows promise as a low temperature hydrocarbon combustion catalyst for automotive applications. In this study, SrTiO3 nanocuboid supports were synthesized using sol-precipitation coupled with hydrothermal synthesis, and platinum was deposited on the nanocuboids with 1, 3, and 5 cycles of atomic layer deposition (ALD). The platinum particles have a highly uniform distribution both before and after reaction testing, and range from 1 to 5 nm in size, depending upon the number of ALD cycles. These materials have a >50 °C lower light-off temperature for propane oxidation than a conventional Pt/Al2O3 catalyst, turn over frequencies up to 3 orders of magnitude higher, and show improved resistance to deactivation. The increased activity is attributed to the stabilization of a Pt/PtO core/shell structure during operating conditions by the strong epitaxy between the Pt and the SrTiO3 support.

Raman spectroscopy was used to demonstrate that the lattice dynamics of SrTiO 3 (STO) nanoparticles strongly depends on their microstructure, which is in turn determined by the synthetic approach employed. First-order Raman modes are observed at room temperature in STO single-crystalline nanocubes with average edge lengths of 60 and 120 nm, obtained via sol-precipitation coupled with hydrothermal synthesis and a molten salt procedure, respectively. First-order Raman scattering arises from local loss of inversion symmetry caused by surface frozen dipoles, oxygen vacancies, and impurities incorporated into the host lattice. The presence of polar domains is suggested by the pronounced Fano asymmetry of the peak corresponding to the TO2 polar phonon, which does not vanish at room temperature. These noncentrosymmetric domains will likely influence the dielectric response of these nanoparticles.