Gabriel Maria Ingo

Properties of CuxS thin film based structures: influence on the sensitivity to ammonia at room temperatures

Abstract Surface and electrical properties of thin CuxS films grown on different substrates (polyethylene and micro-porous-Si layer) sensitive to ammonia at room temperature are investigated. The resistance response to ammonia is measured in the CuxS in air with relative humidity from 15 to 100% at temperatures from 290 to 350 K. The surface chemical composition and the morphology are analysed. A honeycombed construction of the CuxS films deposited on a micro-porous Si-layer and proportions between components in the chemical composition are found to correlate with the higher sensitivity to ammonia in air at room temperature.

Superhydrophobic fabrics for oil–water separation through a diamond like carbon (DLC) coating

The recent oil spill in the Gulf of Mexico has already caused, and is continuing to cause, significant global environmental issues and has severely impacted peoples lives and natural resources. The ramifications of oil spill accidents highlight the difficulty of achieving effective oil–water separation, and the consequences of these accidents are harsh and long-term. In this work, we describe a convenient approach to fabricate cotton textiles with a hydrophilic coating, showing both superhydrophobic and superoleophilic properties. The surfaces are successfully prepared by one-step growth of a diamond-like carbon film onto the textiles via plasma-enhanced chemical vapour deposition and exhibit highly controllable, energy-efficient oil–water separation with high separation efficiency. The results have important implications for oil-absorption dynamics while repelling water completely. The present work suggests encouraging applications to marine spilt oil cleanup and other water–oil separation systems.

Surface studies of in vitro biocompatibility of titanium oxide coatings

Titanium oxide coatings are normally used for orthopaedic and dental prostheses. Nevertheless, their chemical, biological and mechanical properties can be still improved by the development of new preparation technologies. In this paper a surface characterisation of the titanium oxide layer, grown on commercial Ti substrates by metal organic chemical vapour deposition (MOCVD) technique, is reported. The biocompatibility of the samples is tested upon in vitro treatment as a function of the exposure time. The surface characterisation of the titanium substrate and the oxide coatings is performed by using different analytical techniques. Surface chemical composition and morphology of the coatings are investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and scanning tunnelling microscopy (STM). Quantitative XPS analysis and surface physical images show a good quality (cleanness, homogeneity, roughness) of the oxide coating deposited by MOCVD and the surface modifications induced by the interaction with osteoblast cells.

Green synthesis of gold-chitosan nanocomposites for caffeic acid sensing.

In this work, colloidal gold nanoparticles (AuNPs) stabilized into a chitosan matrix were prepared using a green route. The synthesis was carried out by reducing Au(III) to Au(0) in an aqueous solution of chitosan and different organic acids (i.e., acetic, malonic, or oxalic acid). We have demonstrated that by varying the nature of the acid it is possible to tune the reduction rate of the gold precursor (HAuCl(4)) and to modify the morphology of the resulting metal nanoparticles. The use of chitosan, a biocompatible and biodegradable polymer with a large number of amino and hydroxyl functional groups, enables the simultaneous synthesis and surface modification of AuNPs in one pot. Because of the excellent film-forming capability of this polymer, AuNPs-chitosan solutions were used to obtain hybrid nanocomposite films that combine highly conductive AuNPs with a large number of organic functional groups. Herein, Au-chitosan nanocomposites are successfully proposed as sensitive and selective electrochemical sensors for the determination of caffeic acid, an antioxidant that has recently attracted much attention because of its benefits to human health. A linear response was obtained over a wide range of concentration from 5.00 × 10(-8) M to 2.00 × 10(-3) M, and the limit of detection (LOD) was estimated to be 2.50 × 10(-8) M. Moreover, further analyses have demonstrated that a high selectivity toward caffeic acid can be achieved without interference from catechin or ascorbic acid (flavonoid and nonphenolic antioxidants, respectively). This novel synthesis approach and the high performances of Au-chitosan hybrid materials in the determination of caffeic acid open up new routes in the design of highly efficient sensors, which are of great interest for the analysis of complex matrices such as wine, soft drinks, and fruit beverages.

XPS investigation on vacuum thermal desorption of UV/ozone treated GaAs(100) surfaces

Abstract In order to prepare suitable surfaces for molecular beam epitaxy (MBE), sacrificial thin oxide layers on HCl etched GaAs(100) surfaces were grown by both air and UV/ozone exposure. Passive films were subsequently removed by vacuum thermal desorption to achieve surfaces that were smooth and clean on an atomic scale. The evolution of the surface chemical composition, as a function of vacuum desorption temperature, has been studied by means of X-ray photoelectron spectroscopy (XPS). XPS results have evidenced for air and UV/ozone exposed GaAs(100) surfaces a relationship between desorption temperature and surface chemical composition; indeed, the oxide removal is temperature dependent and sequentially selective as follows: As2O3. AsO and Ga2O3. Furthermore, XPS results have shown that air-grown films have a chemical composition and thermal desorption behaviour different from UV/ozone treated materials. Indeed, these latter have an As2O3/Ga2O3 and an unoxidized As/Ga ratio close to unity for as grown and thermal treated at 580°C surfaces, respectively. By contrast, air-exposed GaAs(100) materials are Ga2O3-enriched and after vacuum thermal desorption treatments have never a stoichiometric composition(As(GaAs)/Ga(GaAs)= 1). Furthermore UV/ozone treated GaAs(100) surfaces subjected to a vacuum thermal treatment at 580°C, have a troublesome organic contamination level below XPS detectability, whereas from air-exposed surfaces, carbon is not completely thermally removable

Surface characterization of biocompatible hydroxyapatite coatings

The coatings of hydroxyapatite are widely used for orthopaedic and dental prostheses. Nevertheless, their chemical, biological and mechanical properties still can be improved by the development of new preparation technologies. Here we report a surface characterization of hydroxyapatite coatings prepared by different deposition techniques. The layers of hydroxyapatite are grown on commercial titanium substrates by using sol-gel and electrodeposition techniques. The biocompatibility of the samples is tested upon in vitro treatment as a function of the exposure time. Surface chemical composition and morphology of the coatings are studied by means of x-ray photoelectron spectroscopy (XPS), scanning Auger microscopy (SAM) and scanning electron microscopy (SEM). Quantitative XPS analysis and surface chemical and physical images reveal different features (cleanness, homogeneity, roughness) of the coatings and different surface modifications induced by the interaction with osteoblast cells.

Microchemical study of the black gloss on red-and black-figured Attic vases

The microchemistry of the black gloss decoration layer on black- and red-figured Attic vases (6th to 4th century BC) has been studied by means of selected-area x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS). The results show that the Attic black gloss is obtained from an illitic clay, enriched in iron oxide particles, that is applied on the vase body and fired in an oxidizing-reducing-oxidizing cycle at a top temperature of ∼950°C, Furthermore, the results disclose the presence in the black gloss of iron grains with a complex structure, constituted by discrete areas of single phases with Fe 3+ , Fe 2+ and Fe°. These particles are finely dispersed in a vitreous Al-K- and Fe-enriched silicate where also Fe-C and C-C carbon atoms are present. The information about the raw materials and the firing process shows that the production of Attic vases is important for the history of the art as well as of the ceramic technology.

Ancient mercury-based plating methods: combined use of surface analytical techniques for the study of manufacturing process and degradation phenomena.

Fire gilding and silvering are age-old mercury-based processes used to coat thesurface of less precious substrates with thin layers of gold or silver. In ancient times, these methods were used to produce and decorate different types of artefacts, such as jewels, statues, amulets, and commonly-used objects. Gilders performed these processes not only to decorate objects but also to simulate the appearance of gold or silver, sometimes fraudulently. From a technological point of view, the aim of these workmen over 2000 years ago was to make the precious metal coatings as thin and adherent as possible. This was in order to save expensive metals and to improve the resistance to the wear caused by continued use and circulation. Without knowledge about the chemical-physical processes, the ancient crafts-men systematically manipulated these metals to create functional and decorative artistic objects. The mercury-based methods were also fraudulently used in ancient times to produce objects such as jewels and coins that looked like they were made of silver or gold but actually had a less precious core. These coins were minted by counterfeiters but also by the official issuing authorities. The latter was probably because of a lack of precious metals, reflecting periods of severe economic conditions. In this Account, we discuss some representative cases of gold- and silver-coatedobjects, focusing on unique and valuable Roman and Dark Ages period works of art, such as the St. Ambrogios altar (825 AD), and commonly used objects. We carried out the investigations using surface analytical methods, such as selected area X-ray photoelectron spectroscopy and scanning electron microscopy combined with energy-dispersive spectroscopy. We used these methods to investigate the surface and subsurface chemical features of these important examples of art and technology, interpreting some aspects of the manufacturing methods and of disclosing degradation agents and mechanisms. These findings may contribute to cultural heritage preservation, thus extending the applicability of the surface analytical techniques.

Flame retardant properties of plasma pre-treated/diamond-like carbon (DLC) coated cotton fabrics

Textiles with superior anti-flammability properties combined with minimal environmental impact are extremely necessary to reduce fire-related issues. In this regard, diamond-like carbon (DLC) coatings on cotton fabrics may represent promising candidates as potential flame-retardant (FR) materials. Herein, superhydrophobic and fire-resistant cotton fabrics were fabricated through a two-step plasma strategy by alternately exposing substrates to H2 and O2 plasma pre-treatments and subsequent DLC deposition. Fourier transform-infrared spectroscopy analysis has revealed that different plasma pre-treatments can impose surface modifications on the chemical structure of cotton, especially in carboxylic and hydroxyl groups, leading to a radical alteration of surface roughness and of the crystalline cellulosic external structure. These changes deeply influenced the growth of DLC thin films and the surface properties of cotton fabric because of the combination of a hierarchical structure and surface chemistry as verified using field emission gun-scanning electron microscopy and water contact angle measurements. The effects of both specific gases used in the pre-treatment step and duration of pre-treatment were analysed and compared using thermogravimetric analyses. The H2-pre-treated DLC cottons exhibited good potential as an FR material, showing improved thermal stability in respect to untreated cotton, as evidenced by increased ignition times. Moreover, vertical burning tests have demonstrated that DLC-cotton systems exhibit enhanced flammability resistance.

β-Cyclodextrin-grafted on multiwalled carbon nanotubes as versatile nanoplatform for entrapment of guanine-based drugs

The design of β-cyclodextrin/multiwalled carbon nanotubes hybrid (β-CD-MWCNT) as nanoplatform for the entrapment and delivery of guanine based drugs is described here. The functionalized carbon nanomaterials have been characterized by XPS spectroscopy, electron microscopy (FEG-SEM and TEM), AFM, TGA, and FT-IR to achieve insights on structure, morphology and chemical composition. The drug binding abilities of nanocarrier towards the guanine (G) and Acyclovir (Acy) were proved by UV-vis and DSC experiments. Host-guest equilibrium association constants and drug loading have been evaluated for G/β-CD-MWCNT and Acy/β-CD-MWCNT complexes. The release studies showed a sustained delivery of Acy without initial burst effect confirming a strong interaction of drug with the nanoplatform sites. The preliminary antiviral data indicated that the Acyclovir loaded into the β-CD-MWCNT platform interferes with HSV-1 replication and the antireplicative effect was higher than the free drug.