This work describes some single walled carboxylic carbon nanotubes with outstanding transport properties when assembled in a 3D microarray working like a humidity membrane-sensor and an adjustable moisture regulator. Combined nano-assembly approaches are used to build up a better quality pathway through which assisted-charge and mass transport synchronically takes place. The structure-electrical response relationship is found, while controllable and tunable donor-acceptor interactions established at material interfaces are regarded as key factors for the accomplishment of charge transportation, enhanced electrical responses and adjustable moisture exchange. Raman and infrared spectroscopy provides indications about the fine structural and chemical features of the hybrid-composite membranes, resulting in perfect agreement with related morphology and electrical properties. Enhanced and modular electrical response to changes in the surrounding atmosphere is concerned with doping events, while assisted moisture regulation is discussed in relation to swelling and hopping actions. The electro-activated hybrid-composite membrane proposed in this work can be regarded as an attractive 'sense-to-act' precursor for smart long-distance monitoring systems with capability to adapt itself and provide local comfortable microenvironments.

Single crystals of Zn-doped enstatite (Mg1−xZnx)SiO3 have been synthesized by slow-cooling flux method using two different fluxes. The starting mixtures were first held at a temperature between 1350 and 950 °C and then slowly cooled to the final temperature (600–750 °C) at four different rates. The grown crystals were characterized by binocular microscope, X-ray powder diffraction, scanning electron microscopy with energy-dispersive spectrometry. When LiCO3, MoO3 and V2O5 were used as flux, Zn-doped enstatite crystals up to 3.5 mm in length grew successfully. They were transparent in color and showed the typical prismatic form. Chemical analyses on several Zn-doped enstatite crystals showed that the amount of Zn2+ indicated as ZnO wt% ranges from 3.37 to 10.49 wt%. Further characterization by cathodoluminescence and by µ-Raman spectroscopy allowed us to study the effect of zinc dopant on the chemical/physical characteristics of the doped enstatite.

In this work we present a study of growth and characterization of silver/carbon nanotube (CNT) composites.The composites were prepared with chemical mix techniques and characterized with SEM analysis, X-ray Photoelectron Spectroscopy (XPS) and Photoluminescence (PL) Spectroscopy. The analysis showed that the sample is formed by an uniform network of silver microparticles in direct contact between CNT. SEM images show CNTs overlapping Ag micrometer particles while XPS spectroscopy indicates the presence of chemical bonds between Ag and CNT.Photoluminescence spectra, taken from samples at room temperature, show a yellow-red luminescence signal with two bands centered at about 530 and 670 nm. Moreover, measurements of optical absorbance indicate great difference between the spectra of pure CNT and composites. As well known, pure CNTs have a NIR absorption band at about 1.3 eV, our Ag/CNT composites, instead, show three bands: one in the UV (0.2 eV), one in visible region (1.5-2.9 eV) and a NIR band at about 1.3 eV. These optical results indicate changes in band structures of the Ag/CNT composites compared to pure CNT and Ag particles and open the possibility to use these new materials in optoelectronic devices. (C) 2013 Elsevier Ltd. All rights reserved.

In this work we present a method for preparing carbon nanotubes/titanium dioxide (CNTs/TiO2) composites with a simple metal vaporization technique in ultra high vacuum ambient at high temperature. We obtain a composite with a highly uniform layer of Ti/TiO2 on CNT and measure exactly the ratio between composites with X-ray Photoemission Spectroscopy (XPS). The obtained Ti-TiO2 film has a thickness of about 1.5 micron and it is perfectly super imposed to carbon nanotubes buckypaper without formation of chemical bonds between tubes and Ti at interface. Comparison between TEM images taken from CNT before and after the treatment indicates the absence of deformation and changes in tube structures. The crystallinity of deposed TiO2 was investigated by Fourier Transform Infrared Spectroscopy (FTIR) which indicate the only presence of anatase. Titanium dioxide is produced by bonds between evaporated Ti atoms and oxygen already adsorbed on carbon nanotubes. Moreover the produced film is very stable and we do not observe changes in Ti percentage after several annealing cycles at high temperatures (500 degrees C).Finally cathode-luminescence measurements indicate the formation of TiO2 film without presence of oxygen vacancies defects. (C) 2012 Elsevier B.V. All rights reserved.

In this work we perform a study on growth and characterization of LiF/carbon nanotube (CNT) composites.The composite was prepared with chemical mix techniques and then characterized with SEM analysis, Auger Electron Spectroscopy (AES) and Cathodoluminescence (CL) spectroscopy. The obtained samples, as it can be seen in SEM images, are formed by carbon nanotubes overlapping LiF micrometric crystals. AES spectroscopy shows the presence of chemical bonds between LiF and CNT and a good homogeneity in all the prepared samples.Finally CL studies indicate a UV luminescence signal centered at about 310 nm, with a FWHM of about 60 nm. These results may allow the possible use of this composite as UV emitters or micro-tunable laser devices. (C) 2012 Elsevier Ltd. All rights reserved.

In this work we present the results of photoluminescence study on heterostructures constituted by single walled carbon nanotubes (CNT) and by a semiconductor (zinc sulphide) or an insulator (Lithium fluoride, TiO2 anatase) indicated by X. We observe a very different signal between single components and heterostructures. In particular we observe for all sample a decreasing in luminescence signal respect to X component and a blue shift of about 10-20 nm for some lines. We hypothesize that these effects can be caused by the uniform distribution of X components molecules or crystals with carbon nanotubes. SEM images on our samples show, in fact, a substantial contact between CNT and X component which can modify the energy levels of X component creating new traps or luminescence centers or shifting the existing levels. Furthermore we can note that the FWHM of the Photoluminescence (PL) lines is unchanged between pure X components and composites, indicating the homogeneity of coverage of X components with CNT bundles. Finally we do not observe formation of (C-X) chemical bonds in ZnS/CNT and anatase/CNT composites, while such bonds are observed in LiF/CNT structures.

Luminescence spectra obtained by electron bombardment (cathodoluminescence, CL) on TiO2 (anatase)/carbon nanotubes (CNT) composite, show only one visible band at 498nm, while the spectra taken from pure anatase samples show two bands at 498 and 545nm. We demonstrate that the visible luminescence bands are originated by TiO2 surface defects due to oxygen vacancies, and that this luminescence signal is independent of TiO2 mineral form (anatase or rutile). Moreover we obtain that the 545nm band quenching in TiO2/CNT composites is caused by empty oxygen vacancies (OV) related to oxygen given from oxygen-rich pristine powder of carbon nanotubes. Our conclusions are also supported by X-ray photoelectron spectroscopy (XPS), SEM analysis and energy dispersed X-ray measurements (EDX). Furthermore we can confirm that the NIR TiO2 luminescence emission is linked only to the presence of Ti rutile form as described in several works in literature.

Luminescence spectra obtained by electron bombardment of carbon nanotubes bundles show an UV signal centered at about 380 nm. We show that these transitions are extrinsic to nanotubes, in the sense that they are not linked to any carbon compound or structure, but are caused by the residual catalyst material used in the growth process. A possible role of such luminescence attributable to impurities is also discussed. In fact our luminescence measurements, in association with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and X-ray photoelectron spectroscopy (XPS), permit us to assign these spectral bands to Zn and Al oxides. Our conclusions, supported by data in literature, and the comparison with the quantitative results obtained by LA-ICP-MS spectrometry (which detects ppm) allows us to define cathode-luminescence analysis as a good technique to control cleanness and purity of carbon nanotube samples.

This paper illustrates the results of a multidisciplinary study on two white marble statues placed in the San Bruno Church (Calabria—Southern Italy): the ‘Madonna con Bambino’ and ‘San Bruno’ statues. The study, performed by combining different analytical techniques (LA-ICP-MS, CL, SEM-EDS, OM, FT-IR, isotopic ratios of 18O/16O and 13C/12C by mass spectrometry), aims to give information on the provenance of the marble, the kinds and causes of decay forms that affect the surface of the statues, and the materials used during some undated renovation works. As regards the “San Bruno” statue, three past undocumented restoration samples were analysed. Two of these samples were made with a mixture of gypsum and white pigments, while the other one is a mixture of lime mortar and white pigments, with the addition of diatomaceous earth. A comparison of the obtained data with bibliographic studies concerning pigments allowed the formulation of some hypotheses about the renovation works: they were probably carried out after the early 800s. For both statues several analyses were carried out to characterise some yellow–brown patinas present on their bases. Wax and calcium oxalate are the main components of the patinas on the statues: the former attributable to the use of wax candles, the latter, probably due to the alteration of organic matter, which may have been used during previous restoration phases. The Mn content, the maximum grain size (MGS) of calcite crystals and the isotopic analyses (δ 13C, δ 18O) confirmed that Carrara white marble was used to sculpt the two statues and their bases.

Luminescence spectra obtained by electron bombardment (cathodoluminescence, CL) on bundles of pristine single walled (SWCNT) and multi walled carbon nanotubes (MWCNT) show several common peaks at 1.76, 1.94, 2.06, and 2.22 eV which disappear after beating the samples up to 1300 K. We show that these transitions are extrinsic to nanotubes and originate from nickel oxide impurities, residual catalyst material used in the growth processes. Our conclusions are confirmed by X-ray photoelectron spectroscopy (XPS) and energy dispersed X-ray analysis measurements. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.