Wood is a hygroscopic, multi-scale and anisotropic natural material composed of pores with different size and differently oriented. In particular, archaeologically excavated wood generally is waterlogged wood with very high moisture content (400%–800%) that need to have a rapid investigation at the microstructural level to obtain the best treatment with preservative agents. Time-dependent diffusion coefficient D(t) quantified by Pulse Field Gradient (PFG) Nuclear Magnetic Resonance (NMR) techniques provides useful information about complex porous media, such as the tortuosity (τ) describing pore connectivity and fluid transport through media, the average-pore size, the anisotropic degree (an). However, diffusion NMR is intrinsically limited since it is an indirect measure of medium microstructure and relies on inferences from models and estimation of relevant diffusion parameters. Therefore, it is necessary to validate the information obtained from NMR diffusion parameters through complementary investigations. In this work, the structures of five waterlogged wood species were studied by PFG of absorbed water. D(t) and τ of water diffusing along and perpendicular to vessels/tracheids main axes together with relaxation times and an were quantified. From these parameters, the pore sizes distribution and the wood microstructure characterization were obtained. Results among wood species were compared, validated and integrated by micro-imaging NMR (μ-MRI), environmental-scanning electron-microscope (ESEM) images, wood dry density and imbibition times measurement of all woods. The work suggests that an vs τ rather than the estimated pore size diversifies and characterize the different wood species. As a consequence diffusion-anisotropy vs tortuosity could be an alternative method to characterize and differentiate wood species of waterlogged wood when high resolution images (μ-MRI and ESEM) are not available. Moreover, the combined use of D(t) and micro-MRI expands the scale of dimensions observable by NMR covering all the interesting length scales of wood.

We report that nanoparticles prepared from appropriately functionalized polythiophenes once administered to live cells can acquire phototransduction properties under illumination, becoming photoactive sites able to absorb visible light and convert it to an electrical signal through cell membrane polarization. Amine-reactive fluorescent nanoparticles with pendant N-succinimidyl-ester groups (NPs-NHS) are prepared from polythiophenes alternating unsubstituted and 3-(2,5-dioxopyrrolidin-1-yl-8-octanoate)-substituted thiophenes by a nanoprecipitation method. By 1H NMR of nanoparticles prepared using THF-d8/D2O (solvent/non-solvent) we demonstrate that the hydrolysis of the N-succinimidyl-ester group to free N-hydroxysuccinimide takes place slowly over several hours. NPs-NHS reactivity towards primary amine groups is tested towards the NH2 of d- and l-enantiomers of tryptophan. We show that the formation of a tryptophan-nanoparticle amidic bond creates a chiral shell displaying opposite CD signals for the nanoparticles bound to d or l enantiomers. The interaction of NPs-NHS with live HEK-293 cells is monitored via LSCM. We show that the NPs-NHS are not internalized but remain docked on the cell membrane. We assume that this is mainly the result of the reaction of the NHS groups in the external layer with NH2 groups present in cell membrane proteins, although the contribution of alternative mechanisms cannot be excluded. To support this assumption LSCM experiments show that nanoparticles of comparable size obtained from poly(3-hexylthiophene), NPs-P3HT, are rapidly internalized by live HEK-293 cells. Finally, using the whole-cell current clamp technique under light illumination we demonstrate that NPs-NHS can polarize the cell membrane upon light irradiation while NPs-P3HT cannot.

Chlorin e6-conjugated keratin nanoparticles were obtained and their effectiveness as carriers for cancer photodynamic therapy was demonstratedin vitro.

This work investigates the preparation of wool keratin sponges by freeze-drying procedure starting form keratin aqueous solutions. The study highlights the correlations between process parameters (protein concentration and freezing rate) and the chemical-physical properties of the final sponges.In particular, as the keratin concentration increases from 1 to 20% wt, the mean pore size and the porosity decrease from 62 to 37 mu m and from 94 to 50% respectively, while the chemical stability in physiological conditions increases, as well as the thermal stability and the elastic modulus. On the other hand, the increase of the freezing rate affects the design of sponges that appear as stacked leaflets structures with oriented pores.Moreover, in order to confer to keratin sponges antioxidant properties, polydopamine (PDA) nanoparticles were used as fillers. To this end, PDA nanoparticles of about 130 nm were successfully dispersed in the sponges, bestowing time-dependent anti-oxidant properties on the scaffolds, with no significant modification of sponges morphological structure as well as reduction of the thermal stability and mechanical behaviour. (C) 2016 Elsevier Ltd. All rights reserved.

In this work we report the results of both theoretical and experimental strain analysis of Silicon waveguides and couplers. Simulations of induced stress and strain distributions on photonic structures (waveguides with 450 × 220 nm cross section) have been performed taking into account a ~375 nm thick Si3N4 straining layer. The Convergent Beam Electron Diffraction (CBED) technique has also been employed to provide locally accurate strain measurements on fabricated silicon rib and coupling structures across the nitride-to-silicon interface, showing a good match between multiphysics simulations and measurements along the rib cross-section, resulting in notable attained strain levels.

The convergent beam electron diffraction (CBED) technique has been applied to determine the lattice strain in Si1-xGex/Si heterostructures and in local isolation structures. Both plan and cross-sections have been investigated by transmission electron microscopy. In the heterostructures, the strain value obtained by CBED along the growth direction epsilon(CBED) is affected by ii relaxation induced by the thinning process in a direction normal to the cross-section plane, being generally smaller than the bulk tetragonal value epsilon(T). This effect can be overcome using the large angle CBED technique on plan sections. In addition, in the heterostructures the Ge concentration has been determined by energy dispersive X-ray spectrometry: allowing the pseudomorphicity of the samples to be evaluated. All the values of strain and Ge concentration thus obtained ale in good agreement with those deduced from Rutherford backscattering spectrometry. In isolation structures, the CBED technique has been applied to determine the distribution of the components of the strain tensor along a line parallel to the pad oxide/substrate interface. The values obtained are in agreement with the predictions of a previously reported simple model.

CdTe and CdS are emerging as the most promising materials for thin film photovoltaics in the quest of the achievement of grid parity. The major challenge for the advancement of grid parity is the achievement of high quality at the same time as low fabrication cost. The present paper reports the results of the new deposition technique, Pulsed Plasma Deposition (PPD), for the growth of the CdTe layers on CdS/ZnO/quartz and quartz substrates. The PPD method allows to deposit at low temperature. The optical band gap of deposited layers is 1.50 eV, in perfect accord with the value reported in the literature for the crystalline cubic phase of the CdTe. The films are highly crystalline with a predominant cubic phase, a random orientation of the grains of the film and have an extremely low surface roughness of 4.6±0.7 nm r.m.s.. The low roughness, compared to traditional thermal deposition methods (close space sublimation and vapour transport) permits the reduction of the active absorber and n-type semiconductor layers resulting in a dramatic reduction of material usage and the relative deposition issues like safety, deposition rate and ultimately cost

CdTe and CdS are emerging as the most promising materials for thin film photovoltaics in the quest of the achievement of grid parity. The major challenge for the advancement of grid parity is the achievement of high quality at the same time as low fabrication cost. The present paper reports the results of the new deposition technique, Pulsed Plasma Deposition (PPD), for the growth of the CdTe layers on CdS/ZnO/quartz and quartz substrates. The PPD method allows to deposit at low temperature. The optical band gap of deposited layers is 1.50 eV, in perfect accord with the value reported in the literature for the crystalline cubic phase of the CdTe. The films are highly crystalline with a predominant cubic phase, a random orientation of the grains of the film and have an extremely low surface roughness of 4.6\pm0.7 nm r.m.s.. The low roughness, compared to traditional thermal deposition methods (close space sublimation and vapour transport) permits the reduction of the active absorber and n-type semiconductor layers resulting in a dramatic reduction of material usage and the relative deposition issues like safety, deposition rate and ultimately cost

In the last fifteen years a significant work on the interpretation of Backscattered Electron (BSE) and Secondary Electron (SE) compositional imaging has been performed. The starting point of the research was represented by the experimental evidence of nanometric resolution of compositional features in BSE and SE imaging at relatively high energy (20–30 keV). The interpretation of these results required a reconsideration of the resolution definition, usually associated to the Full Width Half Maximum (FWHM) of the collected signal and to the local variations of the SE yield. In fact, this approach was not able to justify the experimental results with BSE because an interaction volume of the order of a µm and an exit profile of the BSE signal having a comparable FWHM did not appear compatible with the observed resolution of a few nm. Also the SE images were hard to interpret because the yield is practically independent of the layer composition [1–3].

The difficulty to infiltrate solid-state hole semiconductors within micron-thick porous titania films is one of the major limiting factors for the achievement of efficient solid-state dye-sensitized solar cells. It was already shown that through the ordered interconnected pores of an inverse opal, the large surface area of several microns thick titania film can be easily decorated with a dye and filled with a solid-state hole semiconductor. In this paper, we show that ordered inverse opal mesoporous thick films of TiO2 with these characteristics can be obtained by using a slurry of monodispersed polystyrene spheres and a titania-lactate precursor deposited by the doctor blade technique. The mechanism of formation of the inverse opal is also discussed.

We consider the effects of different boundaries on the visibility of a specimen detail providing a compositional contrast in scanning electron microscopy, operating with backscattered electrons or secondary electrons. An object characterized by a gradual variation in composition, an As-doped region in Si, is investigated. The different boundaries in the cross-sectioned specimen correspond to the absence or presence of a poly-Si layer on top of the implanted region, deposited after the annealing treatment. It is shown that the interpretation model used for image formation is of paramount relevance for understanding the experimental results, indicating that the boundaries of the doped region are important in hindering or enhancing its visibility. The relevance of experimental parameters such as electron energy and probe dimension is also reported.

Experimental and theoretical results on image contrast of semiconductor multi-layers in scanning electron microscopy investigation are reported. Two imaging modes have been considered: backscattered electron imaging of bulk specimen and scanning transmission imaging of thinned specimens. The following main results have been reached. The image resolution of the multi-layers is, in both cases, defined by the probe size. The contrast, governed by density and atomic number differences, is affected by the size of the interaction volume in backscattered electron imaging and by the beam broadening in scanning transmission. Operating in the scanning transmission mode, the contrast of bright field images can be easily related to local variation in atomic number and density of the specimen while the dark field image contrast is strongly affected by electron beam energy, detector collection angles and specimen thickness. All these factors are able to produce contrast reversals that are difficult to explain without the support of a suitable simulation code.

A scanning electron microscope is used in transmission mode. The image is formed with secondary electrons, collected by the standard detector, resulting from the conversion of transmitted electrons on a circular disk, covered with MgO smoke, located below the thinned specimen, and centered on the optical axis. Operating in this mode, bright-field images of As dopant profiles in Si, having a peak concentrations of 5 and 2.5 at. % and a spatial extension of about 40 nm, have been observed in cross sectioned specimens. The description of the dopant profiles has a resolution of 6 nm as defined by the spot size of the microscope, equipped with a LaB6 tip, and operating at 30 keV.

With the aim of using some well established techniques in the planar tecnology of silicon for the fabrication of high-Tc grain boundary based junctions, we investigated a process suitable for the realisation of step-edge on R-plane sapphire substrates. Step-edges were prepared by exposing a photolitographically defined area to Ar+ ion implantation. The damaged area was selectively removed by different wet etching processes. With this technique we were able to produce 150 nm height steps, 30°-45° slope. The surface roughness on both sides of the step was the same as that of the virgin sustrate. The influences of dose, angle of implant, etch rate and related main feature of the process are discussed.

The LACBED technique has been applied to the determination of the tetragonal distortion in Si1-xGex/Si heterostructures, which are of great interest in the device technology. The strain determination has been performed on plan sections in an analytical electron microscope. The agreement between this strain value and the tetragonal distortion is influenced mainly by the local sample flatness and the acceleration voltage.

In this work the applicability of NIST electromigration test patterns when used to test ''bamboo'' metal lines is discussed, Wafer level tests on passivated and nonpassivated samples employing the Al-1%Si/TiN/Ti metallization scheme were performed, Straight metal lines 1000 mu m long and 0.9 mu m or 1,4 mu m wide were tested at two different current densities, j = 3 MA/cm(2) and j = 4.5 MA/cm(2), keeping the stress temperature at T 230 degrees C, The failures occurred mainly in the end segment areas and hindered the evaluation of the electromigration resistance of the test lines, In order to avoid this problems, completely different test patterns containing a number of geometrical variations should be defined.

The effects of process-induced crystal defects in silicon power devices have been investigated by comparing their electrical activity and structural properties. Fz P-doped silicon has been subjected to boron diffusion and subsequent oxidation during prolonged heat treatments. The induced defects have been analyzed before and after the oxidation process. Their electrical activity has been explored by electron beam induced current (EBIC) method, and related to the structural properties as observed by transmission electron microscopy (TEM). TEM analysis has shown the presence of extended dislocation networks in both sets of samples as well as of polyhedral shaped precipitates, whose shape and distribution depend upon the thermal treatment. The nature of the precipitates has been investigated by electron energy loss spectroscopy (EELS) which revealed the presence of oxygen. The comparison between the EBIC and TEM results indicates that the observed electrical activity of the dislocations is significantly influenced by the oxygen precipitates.

Thin film Si1-xGex alloys have been grown on silicon by molecular beam epitaxy with nominal composition, x, between 10 and 20 at %. These heterostructures have several applications in band-engineering and in the field of device structures. Film thicknesses, germanium atomic fractions and tetragonal distortion were determined by three different techniques, i.e. Rutherford Backscattering Spectrometry-Channeling, Analytical Electron Microscopy and Double Crystal X-ray Diffractometry. The good agreement found between the various analytical results demonstrates that each technique is capable of a high level of accuracy and consistency. These characterization methods are therefore powerful tools for the precise control of the epitaxial layer growth parameters for the fabbrication of different device structures.