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ABSTRACT We present here anticorrosive silica coatings doped with lanthanum ions for the protection of metallic surfaces as an alternative to chromate (VI)-based conversion coatings. The coatings were synthesized by the sol–gel method... more
ABSTRACT We present here anticorrosive silica coatings doped with lanthanum ions for the protection of metallic surfaces as an alternative to chromate (VI)-based conversion coatings. The coatings were synthesized by the sol–gel method starting from silicon alkoxides and two different lanthanum precursors: La (III) acetate hydrate and La (III) isopropoxide. Artificial corrosion tests in acid and alkaline media showed their effectiveness for the corrosion protection of AA2024 aluminum alloy sheets for coating prepared with both precursors. The X-ray absorption Near Edge Structure and X-ray Absorption Fine Structure analysis of the coatings confirmed the key role of lanthanum in the structural properties of the coating determining its anticorrosive properties.
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ABSTRACT We have synthesized ZnO nanoparticles capped with butanethiol, octanethiol, and dodecanethiol. In all of the cases, the capped ZnO nanoparticles exhibit ferromagnetic-like behavior up to room temperature whose intrinsic origin... more
ABSTRACT We have synthesized ZnO nanoparticles capped with butanethiol, octanethiol, and dodecanethiol. In all of the cases, the capped ZnO nanoparticles exhibit ferromagnetic-like behavior up to room temperature whose intrinsic origin has been demonstrated by using both X-ray magnetic circular dichroism (XMCD) and X-ray absorption spectroscopy (XAS) at the Zn K-edge. Using these tools, we have also determined that the occurrence of ferromagnetism does not critically depend on the details of the synthesis but on the formation of a pristine ZnS/ZnO interface. Within this interface, ferromagnetism is favored in those regions where the local order is closer to wurzite-like ZnO than to w-ZnS. The study of ZnS–ZnO films prepared by cosputtering clearly indicates that increasing the disorder of this interface weakens the onset of ferromagnetic behavior.
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... Consequently, the sensors are adequate for an easy and fast monitoring in one step of relative humidity and environmental acidity of engraved historical, artistic and cultural heritage assets and can help to improve the preventive... more
... Consequently, the sensors are adequate for an easy and fast monitoring in one step of relative humidity and environmental acidity of engraved historical, artistic and cultural heritage assets and can help to improve the preventive conservation of this valuable legacy. ...
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With the aim to study the chemical response of selected glass samples to an underwater medium, accelerated ageing tests were undertaken in the laboratory by immersing the samples into a solution, which simulates the average composition of... more
With the aim to study the chemical response of selected glass samples to an underwater medium, accelerated ageing tests were undertaken in the laboratory by immersing the samples into a solution, which simulates the average composition of sea water. Tests were conducted both at low (−15°C) and high (40°C) temperature for several time cycles. The main goal of the research was to study, through different observation and analytical techniques, chemical alteration mechanisms as a function of the glass compositions and experimental conditions (e.g., temperature, time). Results showed that glasses experience a recurrent decay process, which starts at a neutral pH medium with leaching of alkaline ions and concludes at a basic medium, as a consequence of hydrolytic attack, with destruction of glass network and loss of main forming oxides. The research has thus provided outstanding data that will be useful for future conservation and restoration of historical glasses preserved in an underwater medium.
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New sol–gel based sensitive materials able to detect moderate doses of UV, Vis and near IR radiations have been designed, prepared and characterised. These glasslike detectors are respectively composed by four different sols of inorganic... more
New sol–gel based sensitive materials able to detect moderate doses of UV, Vis and near IR radiations have been designed, prepared and characterised. These glasslike detectors are respectively composed by four different sols of inorganic and hybrid organic–inorganic silica matrixes. The sols were prepared from alkoxide (TEOS) and alkylalkoxide (GLYMO) precursors with molar ratios 1:0, 1:1, 1:4 and 0:1, respectively.
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Four glasses in the R2O–CaO–SiO2 (R = Na, K) system, following similar compositions to historical glasses used for production of stained glass windows, were prepared with different CaO/R2O ratio. The samples were submitted to accelerated... more
Four glasses in the R2O–CaO–SiO2 (R = Na, K) system, following similar compositions to historical glasses used for production of stained glass windows, were prepared with different CaO/R2O ratio. The samples were submitted to accelerated weathering test under different temperature and relative humidity conditions, as well as under controlled SO2-polluted atmosphere. The experimental set up was selected to simulate the
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ABSTRACT Pure and quinine doped silica coatings have been prepared over sodalime glasses. The coatings were consolidated at low temperature (range 60–180 °C) preserving optical activity of quinine molecule. We designed a device to test... more
ABSTRACT Pure and quinine doped silica coatings have been prepared over sodalime glasses. The coatings were consolidated at low temperature (range 60–180 °C) preserving optical activity of quinine molecule. We designed a device to test the guiding properties of the coatings. We confirmed with this device that light injected in pure silica coatings is guided over distances of meters while quinine presence induces isotropic photoluminescence. With the combined use of both type of coatings, it is possible to design light guiding devices and illuminate regions in glass elements without electronic circuits.
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ABSTRACT We present here a study of historic glass decay by means of X-ray absorption spectroscopy (XAS). Transition metal cations incorporated in the glass as chromophores exhibit modifications of their oxidising state and chemical... more
ABSTRACT We present here a study of historic glass decay by means of X-ray absorption spectroscopy (XAS). Transition metal cations incorporated in the glass as chromophores exhibit modifications of their oxidising state and chemical environment as the glass suffers a decay process. These modifications can be monitored by measuring X-ray absorption near edge structure, XANES, and extended X-ray absorption fine structure, EXAFS, spectra around a selected atomic species. We apply the technique here to glasses from different periods ranging from 1st century BC to 18th century, demonstrating that XAS provides an advanced tool for qualitative analysis of glass decay. In particular we have found that it is possible to establish a relationship between the oxidation state of Fe and Cu cations and the decay suffered by the glass. In contrast, our results indicate that the Mn oxidizing state is not directly involved in the glass decay of the studied samples.
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The EC BONSAI Project intends to develop multifunctional nanoparticles with tailored optical and/or magnetic properties for visualizing complex cellular structures (in tissues and organs), receptors, tumor cells and masses. In this... more
The EC BONSAI Project intends to develop multifunctional nanoparticles with tailored optical and/or magnetic properties for visualizing complex cellular structures (in tissues and organs), receptors, tumor cells and masses. In this framework, here we will report on recent advances on the preparation of luminescent silicon nanoparticles, magnetic iron oxide nanoparticles and Au nanorods for bio-imaging applications.
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ABSTRACT There is a growing interest by art conservators for laser cleaning of organic materials, such as wooden artworks, paper and textiles, since traditional cleaning with solvents can be a source of further decay and mechanical... more
ABSTRACT There is a growing interest by art conservators for laser cleaning of organic materials, such as wooden artworks, paper and textiles, since traditional cleaning with solvents can be a source of further decay and mechanical cleaning may be too abrasive for sensitive fibers. In this work we present a successful laser cleaning approach for 19th century rattan mats from the Brooklyn Museum collection of African Art, now part of the study collection at the Conservation Center in New York. Tests were carried out using the fundamental (1064nm) and second harmonic (532nm) wavelength of a Q-switched Nd:YAG laser to measure threshold values both for surface damage and color changes for different types of rattan samples. The irradiated substrates were investigated by optical microscopy, scanning electron microscopy and by UV–vis spectroscopy in order to determine the efficiency of laser cleaning and to assess possible deterioration effects that may have occurred as a result of laser irradiation. The study showed that by using the laser emission at 532nm, a wavelength for which photon energy is below the bond dissociation level of the main cellulosic compounds and the water absorption is negligible, it is possible to select a range of laser fluences to remove the black dust layer without damaging the rattan material.
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ABSTRACT Discoveries of room-temperature ferromagnetism (RTFM) in semiconductors hold great promise in future spintronics technologies. Unfortunately, this ferromagnetism remains poorly understood and the debate concerning the nature,... more
ABSTRACT Discoveries of room-temperature ferromagnetism (RTFM) in semiconductors hold great promise in future spintronics technologies. Unfortunately, this ferromagnetism remains poorly understood and the debate concerning the nature, carrier-mediated versus defect-mediated, of this ferromagnetism in semiconducting oxides is still open. Here, by using X-ray absorption (XAS) and X-ray magnetic circular dichroism (XMCD), it is demonstrated that the oxygen ions have a ferromagnetic response in different ZnO-based compounds showing RTFM behavior: ZnO nanoparticles capped with organic molecules and ZnO/ZnS heterostructures. These results demonstrate the intrinsic occurrence of RTFM in these systems, and point out that it is not related to the metallic cation but it relays on the conduction band of the semiconductor.