An efficient strategy is employed for the preparation of magnetic hybrid hydrogels consisting of functionalized CoFe 2 O 4 magnetic nanoparticles covalently bound to a carboxymethylcellulose (CMC) polymer. The method involves the formation of an amide bond between the carboxylic groups of CMC and the amine groups of functionalized nanoparticles, which work as the crosslinking agents of the polymer chains. The hybrid hydrogels were chemically and morphologically characterized. The rheological properties of the hydrogels were also investigated with the aim to verify their behavior under an applied mechanical stress. The hybrid hydrogel turns out to be thixotropic. Thanks to the presence of magnetic nanoparticles, the hydrogel is capable of responding to an external magnetic field. Preliminary data show the possibility of loading the hydrogel with a dye, which can be considered as a drug model, to squeeze it through a syringe and to drive the material by the application of an external magnetic field.

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Titanium oxide ultrathin films were grown on Ag(100) by evaporation of titanium in an O(2) atmosphere. The growth of the oxide films was monitored by means of XPS. The Ti2p XPS spectra indicate the formation of films with a TiO(2) stoichiometry in the whole range of coverages studied here. The STM results show that titania films appear to grow as islands of uniform thickness up to the completion of the first layer. Up to the formation of one complete monolayer, a (5 × 1) LEED pattern is observed. This pattern can be interpreted as a coincidence mesh and the lattice parameters of the oxide layer are very close to those of TiO(2) films with a lepidocrocite-like structure. However, the STM images show a long-range coincidence between the periodicity of the oxide film and that of the substrate along the short side of the oxide unit cell revealing that this lattice parameter is not exactly equal to that of the substrate. Above the monolayer coverage, additional spots become visible in the LEED pattern which can be interpreted in terms of the unit cell of rutile (110). The structural determination was carried out for the monolayer of titania by means of XPD and LEED intensity analysis. The results of these investigations demonstrate that the titania monolayer has a lepidocrocite-like structure. The DFT calculations carried out for the titania monolayer show the higher stability of the lepidocrocite structure with respect to other structures derived from crystallographic planes of bulk TiO(2) phases. Moreover, these calculations allow us to determine the oxide-substrate interface energy as well as to clarify the effect of the strain on the stability of the oxide layer.

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Ultrathin nickel oxide films were grown on the Ag(001) surface by evaporation of Ni in an O2 atmosphere. The growth mechanism, composition, and structure of the NiO layers formed in the early stages of deposition have been investigated by LEIS, XPS, XPD, and LEED. We found that at O2 pressures in the 10-7− 10-6 mbar range and sample temperatures between room temperature and 373 K, a nickel oxide layer forms showing a (2 × 1) LEED pattern. This is a phase of monatomic thickness which gradually covers the substrate surface upon increasing the surface coverage. LEIS and XPS data show that before the (2 × 1) layer is completed NiO(001) islands start to nucleate. The substrate surface is completely covered by NiO(001) for coverages higher than 2 ML. When NiO is deposited with the sample held at 453 K, we found that in the early stages of deposition metallic Ni is present in the subsurface region of the substrate. Upon further NiO deposition the oxide becomes the prevalent species on the surface. Under these conditions, the (2 × 1) phase is not observed. We found that the (2 × 1) phase is not stable upon annealing at 473−600 K and transforms into NiO(001). LEIS and XPD results indicate the formation of NiO islands 2 ML thick upon annealing. The structure of the (2 × 1) phase has been investigated by LEED intensity analysis (tensor LEED method). The best agreement with the experimental data is obtained for a structural model similar to the (111) surface of NiO. The effects of surface temperature and O2 pressure on nickel oxide growth are discussed in terms of the low sticking probability of O2 on Ag(001) and of the interaction between nickel and silver.

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