We show that dissociative oxygen adsorption on Ag(001) induces below room temperature a missing row $2\sqrt{2}\times \sqrt{2}$ reconstruction of the substrate. As demonstrated by the analysis of the photoelectron diffraction patterns, the oxygen atoms sit thereby in a $c(2\mathrm{}\times 2)$ arrangement in the previous fourfold hollow sites nearly coplanar with the Ag atoms, while rows of substrate atoms are removed along the $\left[100\right]$ directions. Annealing the crystal above 350 K restores the $p(1\mathrm{}\times 1)$ symmetry and the oxygen moves to $0.6\hspace{0.5em}\AA$ above the fourfold hollow site. It becomes then more oxidic in nature, as demonstrated by the shift of the $\mathrm{O}1s$ level from 530.3 eV to 528.3 eV. The phase transition affects also the $\mathrm{O}2s$ and $\mathrm{O}2p$ levels as well as the surface component of $\mathrm{Ag}{3d}_{5/2}.$ The vibrational frequency of the oxygen adatoms against the surface decreases at the phase transition, in accord with the larger adsorption distance. The higher temperature phase is active towards CO and ${\mathrm{C}}_2{\mathrm{H}}_4$ oxidation, while the low-temperature phase is not. When cooling the sample below room temperature the reconstructed phase is restored. The time constant of this process as well as the chemical reactivity of the high-temperature phase are weakly reproducible since they depend on the previous history, i.e., presumably on the subsurface oxygen content of the sample.

Intensity variations of the dimer derived surface shifted Si $2p$ core level from single domain Si(001)-( $2\times 1$) have been measured as a function of azimuthal angle. Comparisons to multiple scattering calculations show that such measurements provide a method for determining the structural origins of surface shifted core levels. In addition, a structural analysis illustrates the sensitivity of this method to the detailed structure around the emitting atoms. In this case, a determination of the surface geometry indicates that the dimer bond is tilted 19.0° with respect to the surface.

In this study, a green and facile thermal reduction of graphene oxide using an eco-friendly system of d-(+)-glucose and NH₄OH for the preparation of reduced graphene oxide was described. The obtained reduced graphene oxide dispersion was characterized by SEM, Dynamic Light Scattering, Raman and X-Ray Photoelectron Spectroscopy. TiO₂ nanoparticles and reduced graphene oxide nanocomposites were successively prepared and used in the preparation of heterogeneous photocatalysts that were characterized by Atomic Force Microscopy and Photoluminescence Spectroscopy and subsequently tested as visible light photocatalysts for the photodegradation of Alizarin Red S in water as target pollutant. Obtained results of photocatalytic tests regarding the visible light photocatalytic degradation of Alizarin Red S demonstrated that the use of reduced graphene oxide in combination with TiO₂ led to a significant improvement for both adsorption of Alizarin Red S on the catalyst surface and photodegradation efficiencies when compared to those obtained with not doped TiO₂.