Gregorio Bottaro

Photocatalytic and antibacterial activity of TiO2 and Au/TiO2 nanosystems

This work focuses on the photocatalytic performances and antibacterial activity of TiO2 and Au/TiO2 nanosystems. While the former are obtained by a sol?gel route, the latter are synthesized by an innovative hybrid RF-sputtering/sol?gel approach, followed by ex situ annealing in air up to 600??C. Important information on nanoparticle size, shape and distribution is obtained by the combined use of glancing incidence x-ray diffraction (GIXRD) and field emission-scanning electron microscopy (FE-SEM). Subsequently, the photocatalytic performances of the obtained nanosystems in the decomposition of the azo-dye Plasmocorinth B and their antibacterial activity in the elimination of Bacillus subtilis are illustrated and discussed in comparison with films obtained from standard Degussa P25 powders. The obtained results show a significant dependence of the functional performances on the systems compositional, structural and morphological properties. In particular, the dispersion of gold nanoparticles on the TiO2 matrix has a beneficial influence on the azo-dye photodegradation, whereas the antimicrobial activity of Au/TiO2 films is retarded with respect to pure TiO2.

A sol–gel approach to nanophasic copper oxide thin films

Abstract Nanostructured copper oxide films were prepared via sol–gel starting from ethanolic solutions of copper (II) acetate [Cu(CH 3 COO) 2 ·H 2 O]. Films were obtained by dip-coating at room temperature in air and were subsequently heat-treated at different temperatures (100–900 °C) in oxidizing (air), inert (N 2 ) or reducing (4% H 2 in N 2 ) atmospheres. The evolution of the oxide coatings under thermal treatment was studied by glancing incidence X-ray diffraction, X-ray photoelectron spectroscopy and X-ray excited Auger electron spectroscopy. Different crystalline phases were observed as a function of the annealing conditions. Depending on both temperature and atmosphere, the film composition resulted single- or multi-phasic. All the layers were nanostructured with an average crystallite size lower than 20 nm. The most relevant results concerning sample composition and microstructure as well as their mutual relations with the synthesis conditions are presented and discussed.

Bismuth oxychloride nanoflakes: Interplay between composition-structure and optical properties

Strongly (001) oriented BiOCl nanoflakes have been prepared at room temperature by the controlled hydrolysis of bismuth chloride in the presence of acetylacetone. The nanoflakes thermally treated in air up to 600 °C have been studied by X-Ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Composition, structure and morphology of the nanoflakes have been correlated to their electronic absorption and luminescence properties. Irrespective of the thermal treatments, the samples are characterized by transmittance higher than 98% in the near-infrared region. In the mildly annealed specimen (≤ 200 °C), the absorption bands in the ultraviolet can be effectively exploited for the selective excitation of the blue (394 nm) and green (520 nm) photoluminescence, the latter being visible only for λ(exc) > 310 nm. Conversely, at higher temperature only the blue emission is observed which, on the basis of the observed trend, can be assigned to emitting centres located in the oxide sheet of the Bi-O-Cl stacks.

Rational Design of Ag/TiO2 Nanosystems by a Combined RF-Sputtering/Sol-Gel Approach

The present work is devoted to the preparation of Ag/TiO(2) nanosystems by an original synthetic strategy, based on the radio-frequency (RF) sputtering of silver particles on titania-based xerogels prepared by the sol-gel (SG) route. This approach takes advantage of the synergy between the microporous xerogel structure and the infiltration power characterizing RF-sputtering, whose combination enables the obtainment of a tailored dispersion of Ag-containing particles into the titania matrix. In addition, the systems chemico-physical features can be tuned further through proper ex situ thermal treatments in air at 400 and 600 degrees C. The synthesized composites are extensively characterized by the joint use of complementary techniques, that is, X-ray photoelectron and X-ray excited Auger electron spectroscopies (XPS, XE-AES), secondary ion mass spectrometry (SIMS), glancing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), electron diffraction (ED), high-angle annular dark field scanning TEM (HAADF-STEM), energy-filtered TEM (EF-TEM) and optical absorption spectroscopy. Finally, the photocatalytic performances of selected samples in the decomposition of the azo-dye Plasmocorinth B are preliminarily investigated. The obtained results highlight the possibility of tailoring the system characteristics over a broad range, directly influencing their eventual functional properties.

Plasma-Enhanced CVD CeO2 Nanocrystalline Thin Films Analyzed by XPS

CeO2 nanocrystalline films were deposited on SiO2 and SiO2/Si(100) substrates by plasma enhanced-chemical vapor deposition (PE-CVD) in Ar–O2 atmospheres. Ce(dpm)4 (dpm = 2,2-6,6-tetramethyl-3,5-heptanedionate) was used as a precursor, which allows a clean conversion into CeO2 due to the presence of Ce–O bonds. The coatings were pale yellow in color, homogeneous and crack-free. In this study, an x-ray photoelectron spectroscopy (XPS) investigation of the principal core levels (O ls, Ce 3d) of CeO2 films was performed. The relative Ce(III)/Ce(IV) amount was estimated by evaluating the ratio of the Ce 3d3/2(u′′′) satellite to the total Ce 3d integral area. The relative content of Ce(III) and Ce(IV) amount can be tailored by controlling the O2 partial pressure and substrate temperature during the depositions. The reported results represent the extension of a recently published article (Ref. 1).

Highly homogeneous, transparent and luminescent SiO2 glassy layers containing a covalently bound tetraazacyclododecane–triacetic acid–Eu(III)–acetophenone complex

The preparation of sol–gel glasses is described wherein highly stable Eu(III) centres are anchored to the silica glass upon acidic hydrolysis and by using tetraethylorthosilicate (TEOS) as a silica source. The complex employed is Eu·1 and is obtained from bipartite ligand 1, which features a DO3A macrocycle as a hosting unit for the Eu(III) centre, a methoxy-acetophenone unit as an antenna chromophore, and an alkyl chain bearing one primary hydroxy group (DO3A is 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid). Eu·1 is linked to the forming silica glass through the –OH groups and a uniform distribution of the luminescent centres is obtained, as indicated by results from secondary ion mass spectrometry in-depth profiling. The luminescent efficiency of the Eu(III) centres in the solid matrix is evaluated to be 10%, which is comparable to that of Eu·1 in water solution and of a convenient reference complex, Eu·2 (2 is a ligand featuring the same hosting and antenna functionalities of 1, wherein the –OH residue is replaced by an unreactive group, a benzoylmethyl residue). A discussion is given of the photophysical properties exhibited by the complexes in the film and in solution.

Transition metal oxide-doped mesostructured silica films

Abstract Mixed metal oxide-doped mesostructured silica films have been prepared by a combination of a ligand-assisted templating (LAT) and solvent evaporation-induced self-assembly (EISA) approach using metal alkoxides as precursors. To overcome the problem of the different hydrolysis and condensation rates of the various alkoxide precursors (silicon alkoxides and transition metal alkoxides), the hydrophilic head group of oligo(ethylene oxide) containing surfactants was coordinated to the M(OR) x groups resulting in metal-containing surfactants. These novel surfactants serve different functions in the EISA process: first, they moderate the hydrolysis and condensation rate of the transition metal alkoxide; second, they allow for a positioning of the transition metal alkoxide within the silica matrix; and third, they act as structure-directing agents. The obtained films are characterized by a high loading of the transition metal oxide species within the silica matrix and a homogeneous distribution throughout the whole film as shown by X-ray photoelectron (XPS) and extended X-ray absorption fine structure (EXAFS) spectroscopy. Several transition metal oxides have been incorporated into the silica matrix such as titania, zirconia and tantalum oxide.

Photophysical properties and tunable colour changes of silica single layers doped with lanthanide(III) complexes

Highly stable Eu(III) and Tb(III) complexes, emitting in the red and green visible regions, respectively, have been anchored onto a single SiO(2) transparent layer, yielding ca. 40 nm thick films; this allows high loading of tailored proportions of the red and green emitters within the films and results in highly uniform and easily colour-tunable luminescent layers.

Structural characterization of sol-gel lanthanum cobaltite thin films

Abstract The present paper is focused on structural, microstructural and compositional studies on nanophasic LaCoO 3 thin films obtained by the sol-gel route. The sample structure and microstructure were investigated by Glancing Incidence X-Ray Diffraction (GIXRD) and X-Ray microdiffraction (MicroXRD), whereas the surface and in-depth chemical composition was studied by X-Ray Photoelectron Spectroscopy (XPS). All the films are structurally homogeneous and not textured. A cubic-to-rhomboedral phase transition was detected after the thermal treatment at 800 °C. Evidence of residual stress was found by GIXRD patterns collected at different incidence angles. After thermal annealing at 1000 °C, only the crystalline La 2 O 3 phase was detected.

Folic Acid-Conjugated Europium Complexes as Luminescent Probes for Selective Targeting of Cancer Cells

We report the synthesis of three optical probes (Eu(3+)⊂1, Eu(3+)⊂2, and Eu(3+)⊂3) having a luminescent Eu complex (signaling unit) bonded in different positions to folic acid (FA), the folate receptor (FR) targeting unit. The structures of the two regioisomers Eu(3+)⊂1 and Eu(3+)⊂2 were assigned by mass spectrometric experiments. The optical properties and stability of these probes were assessed in phosphate-buffered saline, cell culture medium, rat serum, and cellular lysate, and results indicated that they are chemically and photophysically stable. Cytotoxicity was studied with ovarian cancer cells having high (SKOV-3), intermediate (OVCAR-3), low (IGROV-1), or null (A2780) expression of FRs. The internalized probe, evaluated in SKOV-3, IGROV-1, and A2780 cells, was in the order Eu(3+)⊂2 > Eu(3+)⊂1 > Eu(3+)⊂3. No internalization was observed for A2780 cells. Such results, together with those obtained in competition experiments of FA versus Eu(3+)⊂2 and FA or Eu(3+)⊂2 versus (3)H-FA, indicate that internalization is receptor-mediated and that Eu(3+)⊂2 shows high selectivity and specificity for FR.