Porous sol gel silica films doped with crystalline NiO nanoparticles for gas sensing applications

A reliable sol gel route to synthesize NiO doped SiO₂ films with different NiO content is here described. The films showed detectable and reversible changes in both optical and electrical properties when exposed to some reducing/oxidizing gaseous species at temperatures in the 250°C–350°C range. A functional characterization protocol has been designed and some of the sensing properties of the materials have been investigated for detecting NO₂, CH₄, CO and H₂. An optical transmittance increase up to 2% has been detected for 1% CO in dry air atmospheres, while relative resistance response (R _R = R _gas/R _air) values up to 4.97 for 850 ppm H₂/air mixtures have been registered for conductometric gas sensing. Films at all NiO molar concentrations in the 10% NiO - 40% range showed an optical response to the target gas, while only 30% and 40% NiO films provided a detectable gas induced resistance change.     

Fabrication and Characterization of Sol-Gel GeO2-SiO2Erbium-Doped Planar Waveguides

GeO2-SiO2 sol-gel planar waveguides doped with Er were deposited by spinning on silica substrates. P2 O5 or Al2O3 were used as co-dopants to improve erbium dissolution in the GeO2-SiO2 matrix. Multilayer amorphous films were obtained at 600 or 700°C.Er ions in the planar waveguide pumped at 980 nm showed fluorescence features around 1530 nm. Narrow fluorescence spectra (20 nm) and long lifetimes (6 ms) were found in P2O5 co-doped samples, whereas Al2O3 co-doping gave wider spectra (50 nm) with slightly lower lifetimes (5 ms). The quenching concentration in the Al2O3 co-doped samples was 0.9 mol% Er.Heat treatments in CCl4 improve the active properties and the addition of Yb enhances the pump absorption efficiency.     

Silver-sensitized erbium-doped ion-exchanged sol–gel waveguides

Ag- and Er-doped glass films have been synthesized with a combined sol–gel and ion-exchange route. The introduction of silver as erbium sensitizer in the film was obtained by ion exchanging Er-doped SiO₂–Al₂O₃–Na₂O sol–gel films. The films were subsequently annealed under controlled atmosphere to induce the migration and aggregation of the metal ions. Films showed different Er³⁺ photoluminescence behaviors depending on silver concentration and aggregation state. The interaction between erbium ions and Ag centers has been investigated and enhancement of the excitation cross section due to the silver sensitizing effect has been demonstrated. The developed synthesis also allowed the realization of erbium-doped channel waveguides by a selective Na–Ag ion-exchange process . PACS 81.20.Fw; 78.55.-m; 42.82.Et     

Preparation and Characterization of Fullerenes Containing Sol-Gel Glass

Transparent materials containing C₆₀ are interesting because of their optical limiting properties. Fullerenes can be incorporated in sol-gel matrices, but their poor solubility in the solvents commonly used in the process and their tendency to form clusters constitutes the main experimental problem. For this reason we have synthesized C₆₀ derivatives with high solubility and having reactive groups that could covalently bond to the inorganic network. By this way and by an optimization of the sol-gel preparation procedure, transparent films and bulks were obtained. Good optical limiting performances were demonstrated by experimental measurements.     

Fabrication of functional nanostructured coatings by a combined sol–gel and plasma-enhanced chemical vapour deposition method

Nanostructures have a wide range of potential applications in industry because they can impart novel mechanical or functional properties to coatings such as abrasion resistance, UV shielding, superhydrophobicity. In this work we present a method for the fabrication of nanostructured coatings with improved mechanical properties, in which sol–gel nanoparticles are deposited on a surface and embedded in a ceramic film by plasma-enhanced chemical vapour deposition. This synthetic strategy is applied to the fabrication of transparent nanostructured antiscratch coatings.     

Surface‐enhanced Raman spectroscopy (SERS) on silver colloids for the identification of ancient textile dyes. Part II: pomegranate and sumac

The effectiveness of surface‐enhanced Raman spectroscopy (SERS) spectrocsopy on Ag colloids has been successfully demonstrated for the identification of a yellow dye in two ancient wool threads found in the Royal Tumulus of In Aghelachem, Libyan Sahara, belonging to the Garamantian period (2nd–3rd century A.D.). High‐performance liquid chromatography (HPLC) highlighted the presence of ellagic acid in the extracts from the threads, excluding other chromophores. This result, together with the abundance of malic acid detected by gas chromatography‐mass spectrometry (GC‐MS), suggested the possible use of pomegranate rind or sumac berries as source of the yellow dye, both plants being documented in the Fezzan area during the Garamantian period. HPLC analyses and SERS spectra acquired on the extracts of the ancient threads were therefore compared with those obtained from pomegranate and sumac extracts of the corresponding fruits and reference dyed wool samples, allowing us to identify the yellow dye as deriving from pomegranate (Punica granatum L.). SERS spectra of ellagic acid and dyes extracted from pomegranate rind and sumac berries are reported here for the first time. A methodological improvement is also presented, based on the use of NaClO₄ as aggregating agent, that leads to a significant increase of the signal‐to‐noise ratio in the SERS spectra. Copyright © 2010 John Wiley & Sons, Ltd.     

Fundamental and technological aspects of glass studied by nuclear techniques

Abstract

Nuclear techniques (Rutherford back-scattering and nuclear reactions) appear very useful in the near surface analysis of glass. These techniques offer a non-destructive method of analysis, with high depth resolution without radiation effects induced by the ion beam.

In this paper we present some experimental results concerning the analysis of glass surfaces obtained by different treatments. Initially the water vapour attack kinetics was investigated with the ²³Na(ρ, α)²⁰Ne nuclear reaction. Measurements were performed on three different flat glasses obtained by different industrial processes.

Another aspect of particular importance from both scientific and applied viewpoints is the kinetics of the surface reaction and diffusion processes occurring in silicate glasses. In particular the Na⁺?K⁺ interdiffusion has been investigated with the RBS technique at different temperatures in aluminosilicate and borosilicate glasses.

Finally, a technological aspect of great interest is connected to the optical properties modification when glasses are covered with different types of coatings. RBS analysis allows helpful information about elemental composition of the coatings and their depth distribution. In many cases it is possible to obtain the stoichiometric composition and the thickness when atomic density is known.     

Immunoblot as a potential diagnostic tool for myofibrillar myopathies

Myofibrillar myopathies (MFMs) are a group of inherited or sporadic neuromuscular disorders morphologically characterized by foci of myofibril dissolution, disintegration of the Z‐disk, and insoluble protein aggregates within the muscle fibers. The diagnosis is based on muscle biopsy. Light and electron microscopy has a central role in the diagnostic work up, and immunohistochemistry shows abnormal deposition of several proteins including αB‐crystallin, desmin, and myotilin. In contrast, immunoblotting does not have any diagnostic value because it does not highlight differences in the amount of involved proteins. We investigated the pattern and level expression of desmin, αB‐crystallin, myotilin, and ZASP (Z‐band alternatively spliced PDZ motif‐containing protein) in muscle of seven patients with MFMs by immunoblotting after SDS‐PAGE and 2D‐PAGE using two different solubilizing solutions, one radioimmunoprecipitation assay (RIPA) buffer, and the other urea‐containing buffer. Our data demonstrated that urea‐containing buffer improves the solubilization and recovery of desmin, αB‐crystallin, myotilin, and ZASP as compared with RIPA buffer and that the total content of these proteins is increased in muscles of patients. The present results provide evidence that immunoblotting is an additional tool for confirming diagnosis of MFMs.     

Laser damage of glycidoxypropyltrimethoxysilane based hybrid materials

The preparation of solid samples, having specific optical properties, is one of the main goals for the realization of devices in the photonic field. To this end, it is important to attain the best control of the optical properties in the final materials. The sol-gel technique is a powerful synthesis method allowing the preparation of matrices with high stability, mechanical resistance and high optical quality. The use of hybrid organic-inorganic precursors permits samples with different thicknesses, ranging from films of hundreds of nanometers to bulk samples of millimeters, to be obtained. The control of the synthesis protocol and the choice of precursors and catalyst allows the control of the final matrix microstructure, which is related to optical properties, like the laser damage threshold. In this work four different matrices, based on glycidoxypropyltrimethoxysilane and Zr alcoxide, have been prepared through sol-gel synthesis. An interpenetrating organic and inorganic network, controlled by the synthesis protocol, characterizes these matrices. The obtained materials show high resistance to the optical damage and long term stability.     

SiO2 gel-glasses prepared from alkoxide, colloidal and amine-silicate solutions, a comparison

Silica gels were prepared by the alkoxide, collidal and amine-silicate methods. The obtained gels and glasses were characterized by density and Vickers microhardness measurements, thermal analysis and Raman spectroscopy. Differences in physical properties and in the behavior during thermal treatment are discussed and related to the process chemistry and the structure of the products.