Andrea Atrei

A novel strategy for engineering hydrogels with ferromagnetic nanoparticles as crosslinkers of the polymer chains. Potential applications as a targeted drug delivery system

An efficient strategy is employed for the preparation of magnetic hybrid hydrogels consisting of functionalized CoFe2O4 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.

Structure and composition of the titanium oxide layers formed by low-pressure oxidation of the Ni94Ti6(110) surface

Abstract The structure and composition of the titanium oxide phases obtained by low-pressure oxidation at ca 800 K of the Ni 94 Ti 6 (110) surface have been investigated by a combination of surface sensitive techniques. We found that upon oxygen exposure in these conditions layers of oxide consisting mainly of TiO 2 grow on the alloy surface. The TiO 2 phase formed in the very early stages of oxidation has a quasi-hexagonal unit cell, as shown by low-energy electron diffraction, and its structure has no equivalent in any of the stable phases of TiO 2 . The structure of this ultrathin oxide film consists of a layer of titanium atoms between two atomic planes of oxygen atoms. Upon increasing the oxygen exposure, islands of epitaxial rutile (110) form on the surface, as shown by the X-ray photoelectron diffraction data.

X-ray photoelectron diffraction (XPD) study of the atomic structure of the ultrathin CdS phase deposited on Ag(111) by electrochemical atomic layer epitaxy (ECALE)

Abstract Electrochemical Atomic Layer Epitaxy (ECALE) was used to obtain multi-atomic layers of CdS on a single crystal Ag(111) substrate. Electrochemical stripping measurements indicate that the amount of Cd and S in these films corresponds to the stoichiometric 1:1 ratio. This result was confirmed by X-ray photoelectron spectroscopy (XPS). Measurements performed by X-ray photoelectron diffraction (XPD) permitted the determination of the structure and orientation of the CdS phase. This structure turned out to be the wurtzite lattice with the (0001) plane parallel to the substrate plane and a Cd type termination.

Lepidocrocite-like structure of the TiO2 monolayer grown on Ag(100)

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.

STM study of the nanostructures prepared by deposition of NiO on Ag(001)

Submonolayers of nickel oxide were grown on the Ag(001) surface by evaporation of Ni in the presence of O2 at a pressure of 1 ? 10?6?mbar. In the early stages of deposition, two-dimensional oxide islands with a (2 ? 1) periodicity grow on Ag(001). After annealing at about 500?K, the (2 ? 1) single atomic layer transforms into NiO(001) double layer islands. The 1:1 stoichiometry of the film is not influenced by whether the annealing is carried out in vacuum or in the presence of oxygen. However, the oxide islands exhibit different morphologies depending on the O2 pressure during the annealing process.

Ultrathin nickel oxide films grown on Ag(0 0 1): a study by XPS,LEIS and LEED intensity analysis

The structure of a nickel oxide film 2 ML thick has been investigated by LEED intensity analysis. The NiO film was prepared by evaporating Ni in presence of O2 at a pressure in the 10 � 6 mbar range. The growth of the oxide film was followed by XPS,LEIS and LEED. In the early stages of deposition,the film shows a (2 � 1) superstructure in LEED. After deposition of 2 ML of NiO,a sharp (1 � 1) LEED pattern is observed. The intensity versus electron energy curves of the LEED spots were measured for this NiO(1 � 1) film and analysed by means of the tensor LEED method. A good level of agreement of the experimental LEED intensities with those calculated for a pseudomorphic NiO(0 0 1) film was obtained. We found that oxygen atoms at the oxide–substrate interface are on-top silver atoms. The interlayer distance in the oxide does not differ significantly from that in bulk NiO(0 0 1),within the accuracy of the analysis. An outward displacement (0.05 � 0.05 � of oxygen atoms with respect to nickel atoms was found at the oxide film surface. The interlayer distance at the silver–nickel oxide interface is 2.43 � 0.05 � 2003 Elsevier Science B.V. All rights reserved.

New Formulations of Polysaccharide-Based Hydrogels for Drug Release and Tissue Engineering

Polysaccharide-based hydrogels are very promising materials for a wide range of medical applications, ranging from tissue engineering to controlled drug delivery for local therapy. The most interesting property of this class of materials is the ability to be injected without any alteration of their chemical, mechanical and biological properties, by taking advantage of their thixotropic behavior. It is possible to modulate the rheological and chemical-physical properties of polysaccharide hydrogels by varying the cross-linking agents and exploiting their thixotropic behavior. We present here an overview of our synthetic strategies and applications of innovative polysaccharide-based hydrogels: hyaluronan-based hydrogel and new derivatives of carboxymethylcellulose have been used as matrices in the field of tissue engineering; while guar gum-based hydrogel and hybrid magnetic hydrogels, have been used as promising systems for targeted controlled drug release. Moreover, a new class of materials, interpenetrating hydrogels (IPH), have been obtained by mixing various native thixotropic hydrogels.

Epitaxial growth of TiO2 films with the rutile (110) structure on Ag(100)

Ultrathin films of TiO(2) were grown on Ag(100) by evaporation of titanium in the presence of O(2) at a pressure in the 10(-4) Pa range and annealing at 770 K. The composition of the deposited films was monitored by XPS and LEIS. The morphology at the nanometric scale of the TiO(2) films and their crystallographic structure were investigated by means of STM, LEED and XPD. Above the monolayer coverage (at which the oxide film has a lepidocrocite-like structure), STM images show the formation of multilayer islands with a distribution of heights. XPD results indicate that these oxide islands have the rutile (110) structure and are epitaxially oriented with the sides of the oxide unit cell parallel to those of the substrate unit cell. The results of the DFT calculations justify the 3D growth of rutile (110) on Ag(100). The calculated strain energy required to match the metal substrate can explain the incommensurate growth of the overlayer in the direction of the long side of the oxide unit cell. The results of the calculations indicate that a commensurate growth of rutile (110) may be possible along the short side of the oxide unit cell, taking into account the relatively small strain energy to fit the lattice parameter of the substrate. The DFT calculations predict a considerable increase of the work function upon deposition of titania films on Ag(100), which can be attributed to a charge transfer from the metal to the 3d Ti empty states.

Structure of a non-bulk termination of the clean Pt3Sn(111) surface : a study by low-energy electron diffraction and x-ray photoelectron diffraction

A non-bulk termination with a ( square root 3* square root 3)R30 degrees periodicity was observed on the clean Pt3Sn(111) surface. X-ray photoelectron diffraction and low-energy electron diffraction showed that this phase is a mixed Sn-Pt topmost layer which is enriched in tin with respect to the bulk composition. The data also indicate that the subsurface region is depleted in tin. The structure of the ( square root 3* square root 3)R30 degrees phase is the same as that of the phase observed in the case of tin deposited on the clean Pt(111) surface.

Non-destructive characterisation of fourteenth century painting by means of molecular spectroscopy and unilateral NMR

Abstract The present work was aimed at characterising the materials and assessing the state of conservation of the ‘Adorazione dei Magi’, a wooden panel painted by Bartolo di Fredi in the second half of fourteenth century. To this goal, innovative non-destructive investigation techniques such as portable Raman spectroscopy, visible reflectance spectroscopy and unilateral nuclear magnetic resonance, were used in situ in order to achieve surface and bulk compositional data. The former allowed the identification of the artist’s palette including cinnabar, red ochre, minium, carbon black, lead white, ultramarine blue, malachite and phthalocyanine green, while the latter provided information on the stratigraphic structure and state of conservation of the wooden panel.