Cinzia Maragno

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.

Columnar CeO2 nanostructures for sensor application

CeO2 columnar nanostructures with tailored properties were synthesized by chemical vapour deposition on Si(100) and Al2O3 substrates between 350 and 450 °C and characterized in their structure, composition and morphology by means of a multi-technique approach. Their higher sensitivity in the detection of gaseous ethanol and nitrogen dioxide with respect to continuous CeO2 thin films opens interesting perspectives for the development of nanosized sensor devices.

CVD of Nanosized ZnS and CdS Thin Films from Single-Source Precursors

iPrXan)2 @M 5 Zn,Cd; Oi PrXan 5 S2COCH(CH3) 2] as single-source precursors. Thermal decomposition and fragmentation of M(Oi PrXan)2 compounds were investigated by thermal analyses and mass spectrometry. The sulfide films were thoroughly characterized in their composition, nanostructure, and morphology by means of several analytical techniques. Surface and in-depth chemical composition was studied by X-ray photoelectron spectroscopy, X-ray excited Auger electron spectroscopy, and secondary ion mass spectrometry. Film nanostructure and surface topography were investigated as a function of the synthesis conditions by glancing incidence X-ray diffraction and atomic force microscopy, respectively. Optical absorption properties were also studied. Nanophasic and contaminant-free ZnS and CdS thin films with an average crystallite size lower than 25 nm were obtained. The layers mainly contained the hexagonal ~a! sulfide phase and displayed a smooth and regular surface morphology. In the present work, the influence of synthesis conditions on film characteristics is analyzed and discussed.

Analysis of Nanocrystalline ZnS Thin Films by XPS

Nanocrystalline ZnS thin films were synthesized by chemical vapor deposition (CVD) using Zn(O-iPrXan)2 [O-iPrXan =S2COCH(CH3)2] as a single-source precursor compound. The coatings were deposited on silica substrates in N2 atmosphere at temperatures between 200 and 450 °C and subsequently characterized by glancing-incidence x-ray diffraction (GIXRD), secondary ion mass spectrometry (SIMS), atomic force microscopy (AFM), UV-Vis absorption spectroscopy, x-ray photoelectron (XPS), and x-ray excited auger electron (XE-AES) spectroscopies. This work is dedicated to the XPS and XE-AES characterization of a representative zinc sulfide thin film. Besides the wide scan spectrum, detailed spectra for the Zn 2p3/2, Zn 3p, Zn LMM, S 2p,O 1 s, and C 1s regions and related data are presented and discussed. Both the S/Zn atomic ratio and the evaluation of the Auger parameter point out to the formation of stoichiometric zinc sulfide. Moreover, oxygen and carbon contamination were merely limited to the outermost sample layers.

Silica-supported silver nanoparticles: Tailoring of structure-property relationships

Silica-supported silver nanoparticles were obtained by rf sputtering from Ar plasmas under soft synthesis conditions, with particular attention to the combined influence of rf power and total pressure on the system composition, nanostructure, morphology, and optical properties. In order to attain a thorough insight into the nucleation and growth phenomena of Ag nanoparticles on the silica substrate, several in situ and ex situ characterization techniques were used. In particular, a laser reflection interferometry system was employed for a real-time monitoring of the deposition process, providing useful and complementary information with respect to the other ex situ techniques (x-ray photoelectron spectroscopy and x-ray excited Auger electron spectroscopy, glancing incidence x-ray diffraction, atomic force microscopy, optical-absorption spectroscopy, and transmission electron microscopy). The above investigations evidenced the formation of silver-based nanosystems (average crystallite size ⩽10nm), whose fe...

Tailored synthesis of ZnO:Er(III) nanosystems by a hybrid rf-sputtering/sol-gel route

The rational design of rare-earth doped materials represents one of the major goals of current research in the field of optoelectronics. In this study, ZnO:Er(III) nanosystems were synthesized by means of a hybrid rf-sputtering/sol-gel (SG) route, consisting of the erbium (guest) rf-sputtering on porous zinc oxide xerogels (host) obtained by the SG method, followed by ex situ thermal treatments in air (300–600°C, 1–5h). Particular attention was focused on tailoring the erbium content and distribution in the resulting systems by optimization of the processing conditions. The structural, morphological, and compositional characteristics and their interplay with the synthesis procedure were investigated by glancing incidence x-ray diffraction, x-ray photoelectron spectroscopy, x-ray excited Auger electron spectroscopy, secondary ion mass spectrometry, UV-visible-near IR absorption spectroscopy, and atomic force microscopy. The obtained results highlight the advantages and versatility of the adopted preparatio...

TiO2 Thin Films by Chemical Vapor Deposition: An XPS Characterization

As a part of a comprehensive research work on ZnO-TiO2 nanosystems synthesized by Chemical Vapor Deposition (CVD), we initially devoted our attention to the preparation and characterization of nanocrystalline TiO2 thin films. Specifically, the coatings were obtained by CVD on Si(100) substrates starting from Ti(OiPr)2(dpm)2 (OiPr=iso-propoxy; dpm=2,2,6,6-tetramethyl-3,5-heptanedionate), under a dry O2 atmosphere. The obtained samples were characterized by complementary techniques, namely Glancing Incidence X-ray Diffraction (GIXRD), X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM), for a thorough investigation of their microstructure, chemical composition and morphology. The present contribution is devoted to the XPS analysis of a TiO2 thin film obtained at 450 °C. Besides the wide scan spectrum, detailed spectra for the Ti 2p, O ls and C 1s regions and related data are presented and discussed.

Nanostructured Cadmium Sulfide Thin Films by XPS

Nanostructured cadmium sulfide thin films were deposited on SiO2 by a cold-wall low-pressure CVD reaction system starting from the single-source precursor Cd(O-iPrXan)2 [O-iPrXan = S2COCH(CH3)2]. Deposition experiments were carried out in an inert nitrogen atmosphere in optimized pressure/gas flow conditions. The obtained films were analyzed by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) for a detailed determination of their microstructure, chemical composition, and surface morphology, while UV-Vis measurements were carried out in order to investigate their optical properties. Irrespective of the preparative conditions, all the films displayed the typical absorption spectrum of CdS, with an energy gap value Eg ≈ 2.5 eV. AFM analyses showed that flat, uniform, and crack-free layers were obtained under all the adopted synthetic conditions. This result is of interest in view of potential applications in optoelectronic devices like solar cells, where a sm...

Optical and electrical properties of nanostructured LaCoO3 thin films

Nanostructured lanthanum cobaltite thin films have been grown on silica substrates by hybrid chemical vapor deposition/sol-gel approaches. The refractive index and the extinction coefficient of the specimens have been determined in the spectral range of 0.75–6.5 eV by spectroscopic ellipsometry. The conductivity of the films as a function of temperature has been also investigated, highlighting the different electrical behavior of LaCoO3 nanosystems as a function of the adopted synthetic strategy.

LaCoO3 Nanosystems by a Hybrid CVD/Sol-Gel Route: An XPS Investigation

Lanthanum cobaltite (LaCoO3) nanosystems were synthesised by an innovative combined use of the chemical vapor deposition (CVD) and sol-gel (SG) routes. In particular, a lanthanum oxyfluoride based layer was deposited by CVD on CoOx(OH)y SG substrates (xerogel). The subsequent thermal treatment in air, between 400 and 900 °C, was aimed at promoting the solid-state reaction between La-O and Co-O based layers, resulting in the complete formation of LaCoO3. The obtained samples were analyzed by glancing incidence x-ray diffraction (GIXRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), secondary ion mass spectrometry (SIMS), x-ray photoelectron (XPS) and x-ray excited Auger electron (XE-AES) spectroscopies, for a detailed determination of their microstructure, chemical composition, and surface morphology. The present work focuses on the XPS and XE-AES analysis of a selected lanthanum cobaltite (LaCoO3) thin film, annealed at 700 °C for 2 h. Besides the wide scan spectrum, detailed spec...