Functional metal oxide nanosystems by a hybrid CVD/Sol-Gel approach

The present contribution is devoted to outlining some recent results from an innovative approach to metal oxide nanosystems. The proposed synthesis pathway is based on three successive steps: i) preparation of a porous xerogel layer (host) via sol\u2013gel (SG); ii) CVD of a guest phase on the above matrix, making it possible to achieve an intimate host/guest intermixing; iii) ex situ thermal treatment under suitable conditions, aimed at tailoring the system properties as a function of the desired application. In particular, the above route has been adopted in two specific cases, LaCoO3 and CeO2\u2013ZrO2 nanostructured thin films, which are acquiring increasing importance in the development of fuel cell technology. The most significant results, obtained by glancing incidence X-ray diffraction (GIXRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), and transmission electron microscopy (TEM), will be critically discussed, emphasizing the achievement of tailored material properties by design

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\u2013600 \ub0C, 1\u20135 h). 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 preparation strategy in tailoring the amount and distribution of Er(III) species in high purity ZnO matrices, resulting in nanosystems endowed with compositional and morphological homogeneity at nanoscale level

Nanoscale ZnS and CdS thin films from single-source molecular precursors

In recent years, a great interest has been focused on II-VI semiconductor films for applications in different technological fields, with particular regard to optics and optoelectronics. In the present work the CVD (Chemical Vapor Deposition) technique was employed for the synthesis of ZnS and CdS nanocrystalline coatings. To this aim, O-isopropyl xanthates [M(O-iPrXan)2; M=Zn, Cd] were synthesised and used as single-source precursors. Film depositions were performed in N2 flow on silica substrates in a low pressure cold-wall CVD apparatus at temperatures between 200 and 450°C. Film crystallinity was studied by Glancing Incidence X-Ray Diffraction (GIXRD), while their chemical composition was analyzed by X-ray Photoelectron (XPS) and X-ray Excited Auger Electron (XE-AES) Spectroscopies. Their surface morphology was analyzed by Atomic Force Microscopy (AFM). Finally, the optical properties were investigated by UV-Vis absorption spectroscopy

Advances in synthetic strategies for metal oxide nanosystems: a non-conventional hybrid CVD/Sol-Gel approach

This paper presents a hybrid molecular approach to the synthesis of metal-oxide nanosystems. The adopted strategy is based on the CVD infiltration of a guest phase in the sponge-like structure of a xerogel host matrix prepared by the Sol-Gel route. Such a combined preparation methodology allows an intimate host-guest intermixing, resulting in chemico-physical properties widely tunable as a function of the synthesis conditions. A further ex-situ annealing can lead to the formation of different kinds of nanosystems with controlled composition, structure and morphology. In order to evidence the peculiar advantages of this method, two selected case studies are presented and discussed, namely CeO2-ZrO2 and LaCoO3 nanostructured thin films. Attention is focused on the system evolution as a function of the processing parameters, highlighting the key issues of the adopted procedure

Sol-gel synthesis and characterization of CuO–based nanosystems

ABSTRACTThis paper is focused on the sol-gel synthesis and characterization of CuO-based nanosystems both in the form of supported films and as guest nanoclusters embedded in a silica matrix. In both cases copper acetate (Cu(CH3COO)2 · H2O) was used as Cu source and, for the CuO :SiO2 nanocomposite systems, tetraethoxysilane (Si(OC2H5)4, TEOS) was adopted as silica precursor. Films were obtained by a dip-coating procedure and subsequently treated in air between 100 and 900°C. The system evolution on thermal annealing was studied by X-ray photoelectron spectroscopy (XPS), Glancing-Incidence X-ray diffraction (GIXRD) and optical absorption. Irrespective of the processing conditions, the formation of tenorite (CuO) crystallites with nanometric dimension was observed. In the nanocomposite samples, copper was homogeneously distributed in the host matrix and stable CuO nanoclusters (φ ≈ 15 nm) were obtained.</jats:p

Hybrid Chemical Vapor Deposition/Sol-Gel Route in the preparation of nanophasic LaCoO3 films

Lanthanum cobaltite (LaCoO3) thin films were synthesized by an innovative route based on the combination of chemical vapor deposition (CVD) and sol-gel (SG) methods. In particular, the approach is based on the sequential deposition of binary oxide systems (Co-O on La-O) and on the ex situ thermal treatment of the final product (T = 400-900 \ub0C, t = 1-8 h), aimed at favoring solid-state reactions for the formation of a ternary La-Co-O nanosystem. To highlight the peculiar effects of these procedures on the characteristics of the final product, both SG and CVD routes were used for the preparation of single-phase La-O and Co-O species. The process resulted in the formation of LaCoO3 nanostructured films with an average crystallite size lower than 20 nm. The required processing conditions were strongly dependent on the specific synthetic pathway: (i) SG of Co-O on CVD La-O; (ii) CVD of Co-O on SG La-O. In this framework, particular attention was focused on the analogies and differences between the two sequences and on a study of the most relevant compositional, structural, and morphological system features

Opto-Microfluidic System for Absorbance Measurements in Lithium Niobate Device Applied to pH Measurements

The aim of Lab-on-a-chip systems is the downscaling of analytical protocols into microfluidic devices, including optical measurements. In this context, the growing interest of the scientific community in opto-microfluidic devices has fueled the development of new materials. Recently, lithium niobate has been presented as a promising material for this scope, thanks to its remarkable optical and physicochemical properties. Here, we present a novel microfluidic device realized starting from a lithium niobate crystal, combining engraved microfluidic channels with integrated and self-aligned optical waveguides. Notably, the proposed microfabrication strategy does not compromise the optical coupling between the waveguides and the microchannel, allowing one to measure the transmitted light through the liquid flowing in the channel. In addition, the device shows a high versatility in terms of the optical properties of the light source, such as wavelength and polarization. Finally, the developed opto-microfluidic system is successfully validated as a probe for real-time pH monitoring of the liquid flowing inside the microchannel, showing a high integrability and fast response

A sol-gel approach to nanophasic copper oxide thin films

Nanostructured copper oxide films were prepared via sol\u2013gel starting from ethanolic solutions of copper (II) acetate wCu(CH3COO)H2Ox.Films were obtained by dip-coating at room temperature in air and were subsequently heat-treated at different temperatures (100\u2013900\ub0C) in oxidizing (air), inert (N2) or reducing (4%H2 in N2) 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-o rmulti-phasic. All the layers were nanostructured with an average crystallite size lower than 20nm.The most relevant results concerning sample composition and microstructure as well as their mutual relations with the synthesis conditions are presented and discussed