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Vanadium dioxide has attracted much interest due to the drastic change of the electrical and optical properties it exhibits during the transition from the semiconductor state to the metallic state, which takes place at a critical temperature of about 68 °C. Much study has been especially devoted to developing advanced fabrication methodologies to improve the performance of VO2 thin films for phase-change applications in optical devices. Films structural and morphological characterisation is normally performed with expensive and time consuming equipment, as x-ray diffractometers, electron microscopes and atomic force microscopes. Here we propose a purely optical approach which combines Polarized Raman Mapping and Phase-Transition by Continuous Wave Optical Excitation (PTCWE) to acquire through two simple measurements structural, morphological and thermal behaviour information on polycrystalline VO2 thin films. The combination of the two techniques allows to reconstruct a complete picture of the properties of the films in a fast and effective manner, and also to unveil an interesting stepped appearance of the hysteresis cycles probably induced by the progressive stabilization of rutile metallic domains embedded in the semiconducting monoclinic matrix. [ABSTRACT FROM AUTHOR]

Alessandro Paolini,1 Giulia Battafarano,1 Valentina D’Oria,1 Francesco Mura,2 Simona Sennato,3 Valentina Mussi,4 Roberta Risoluti,5 Stefano Materazzi,5 Andrea Del Fattore,1 Andrea Masotti1 1Bambino Gesù Children’s Hospital, IRCCS, Research Laboratories, Rome 00146, Italy; 2Center for Nanotechnology for Engineering (CNIS), Sapienza University of Rome, Rome 00185, Italy; 3CNR-ISC UOS Sapienza and Physics Department, Sapienza University of Rome, Rome 00185, Italy; 4National Research Council, Institute for Microelectronics and Microsystems IMM-CNR, Roma 00133, Italy; 5Department of Chemistry, Sapienza University of Rome, Rome 00185, ItalyCorrespondence: Andrea MasottiBambino Gesù Children’s Hospital, IRCCS, Research Laboratories, Gene Expression-Microarrays Laboratory, Viale di San Paolo 15, Rome 00146, ItalyTel +39-06-68592650Fax +39-0668592904Email andrea.masotti@opbg.netBackground: The advent of 3D printing technology allowed the realization of custom devices that can be used not only in the everyday life but also in the nanotechnology and biomedical fields. In nanotechnology, the use of bi-dimensional nanostructures based on carbon nanotubes, generally referred as buckypapers, have received considerable attention for their versatility and potential application in many biomedical fields. Unfortunately, buckypapers are extremely hydrophobic and cannot be used in aqueous media to culture cells.Methods: A polymeric device able to accommodate buckypapers and facilitate cell growth was fabricated by using 3D printing technology. We imparted hydrophilicity to buckypapers by coating them with polyamidoamine (PAMAM) dendrimers.Results: We found that by using novel techniques such as polymer coating the buckypaper hydrophilicity increased, whereas the use of 3D printing technology allowed us to obtain custom devices that have been used to culture cells on buckypapers for many days. We characterized in details the morphology of these structures and studied for the first time the kinetic of cell proliferation. We found that these scaffolds, if properly functionalized, are suitable materials to grow cells for long time and potentially employable in the biomedical field.Conclusion: Although these materials are cytotoxic under certain circumstances, we have found a suitable coating and specific experimental conditions that encourage using buckypapers as novel scaffolds for cell growth and for potential applications in tissue repair and regeneration.Keywords: 3D printing, buckypaper, PAMAM dendrimer, cell proliferation, tissue regeneration, transfection

Among the optical techniques used for exploring the properties of cells and tissues, those based on hyperspectral label-free analysis are particularly interesting due to their non-invasive character and their ability to fast collect a huge number of information on the different sample constituents and their spatial distribution. Here we present results obtained with a novel hyperspectral reflectance confocal microscope of label-free discrimination of cells undergoing apoptosis. Our data, analyzed by means of a powerful statistical method, enable to obtain information on the biological status at a single cell level through the local measurement of reflectivity. Furthermore, an optical model of the local dielectric response gives an additional insight of the parameters linking the optical responsivity to the biological status.

Giomer is a relatively new class of restorative material with aesthetics, handling and physical properties of composite resins, and benefits of glass ionomers: high radiopacity, antiplaque effect, fluoride release, and recharge. To verify the superior properties of Giomers, in this study, a deep morphological characterization has been performed with an in vitro comparative study among a Giomer (Beautifil® II by Shofu Dental Corporation, Osaka, Japan), a Compomer (Dyract Extra by Dentsply, Caulk, Germany), glass ionomer cement (Ketac fil plus by 3M ESPE), and a composite resin (Tetric Evoceram by Ivoclar). In particular, mechanical and optical properties and ageing effects have been compared to investigate materials similarities and differences. Indentation tests, UV-Visible spectroscopy, Raman spectroscopy, and weight loss after storage in saliva or sugary drink have been carried out to analyze materials behavior in real conditions. The results confirm the high quality of Giomer material and indicate possible improvements in their usage. [ABSTRACT FROM AUTHOR]

We apply photo-acoustic (PA) technique to examine plasmonic properties of 2D periodic arrays of nanoholes etched in gold/chromium layer upon a glass substrate. The pitch of these arrays lies in the near IR, and this, under appropriate wave vector matching conditions in the visible region, allows for the excitation of surface plasmon polaritons (SPP) guided along a dielectric – metal surface. SPP offered new approaches in light guiding and local field intensity enhancement, but their detection is often difficult due to the problematic discrimination of their contribution from the overall scattering. Here PA measures the energy absorbed due to the non-radiative decay of SPPs. We report on the absorption enhancement by presenting the spatial mapping of absorption under the incidence angles and wavelength that correspond to the efficient excitation of SPPs. Moreover, a comparison with optical transmission measurements is carried out, underlining the applicability and sensitivity of PA technique. [ABSTRACT FROM AUTHOR]

We investigated 30 kV Ga + ions treatments on (0001) single crystal ZnO in order to assess the potentiality of ion beam based device fabrication on such material. A multi-technique approach combining atomic force microscopy, Raman and energy dispersive X-Ray spectroscopies, and transmission electron microscopy was used to study morphological and structural properties of ZnO upon varying the ion dose. At low doses a shallow defective layer develops showing an increasing defect density as the dose is increased. At higher dose a thinner defective layer with an amorphous layer on top is produced. The ion beam damaged layer on high resistivity ZnO shows enhanced conductivity. KOH based etching removed selectively the damaged ZnO and was found to dissolve rapidly the Ga-rich amorphous layer. The defective layer has an etch rate which depends on the ion dose, and even for prolonged etching processes it was not completely removed. However, conductivity measurements on ion beam fabricated pillars showed that the residual defects do not give a detectable electrical response. These findings indicate that electronic devices and micro-structures with pristine electrical properties of the ZnO crystal can be reliably fabricated by focused ion beam, provided the damaged surface layer is removed by proper etching procedures. [ABSTRACT FROM AUTHOR]

This paper presents the first results of the running project HY-LAP (HYbrid LAP-joints) carried out at the Dipartimento di Meccanica of the Politecnico di Milano in collaboration with MUSP and the University of Parma. Thin plates of aluminium 6022T4 have been joined by means of ultrasonic welding, structural adhesives and a combination of them; the applied experimental procedures (i.e. specimens preparation) have been described and the obtained joints have been characterized in terms of morphology and tensile-shear strength. Results are particularly effective in order to evaluate the relevance of the various phenomena influencing the hybrid joining technique, allowing a deep understanding of the process and the possibility to keep it under control. [ABSTRACT FROM AUTHOR]

Design and manufacturing issues are here studied about the production of hollow structures made of an outer high resistance skin and a metal foam filler. These structures can be very useful as reinforcements against lateral impacts of vehicles. In car bodies, at the waistline or door height, the available space is very limited. Compact bars with light weight, high energy absorption efficiency and limited maximum deflection (i.e. high maximum load) are required. The skin of the proposed structure provides strength and stiffness and can be assembled to the vehicle body. The foam core provides energy absorption properties. The combination of non conventional technologies (hydroforming and metal foams) allows for the production of lightweight, high performance components, particularly suited for flexural resistance in terms of amount of energy absorbed for a given maximum load. A performance indicator y is proposed with the aim of comparing the performance of side impact absorbers with different cross sections and made of different materials. The tube hydroforming process is investigated as a suitable way for performance improvement of metal foam filled structures in side impacts, particularly for non-constant section bars. [ABSTRACT FROM AUTHOR]

Abstract: Planar active waveguides were produced in lithium fluoride crystals by implantation with 1.5MeV He+ ions at several doses. The colored samples have been characterized by optical absorption, photoluminescence and m-line spectroscopy. By comparing the measured guided-mode effective indices with the ones calculated by means of the Chandler–Lama approach, the depth profile of refractive index was derived, showing that there are two competitive physical mechanisms, associated with different processes of energy deposition along the ion track, responsible for positive and negative modifications of the refractive index in the irradiated volume. [Copyright &y& Elsevier]

The measured room-temperature absorption spectra of LiF crystals implanted with 1.5 MeV He + ions at different ion doses are presented. The application of a theoretical model allowed us to give an estimation of the band intensities associated with various kinds of electronic defects and to study their dependence on the ion dose. The model also considers the contribution due to nanometric lithium colloids, whose formation starts in the dose range at which the production of colour centres saturates. [ABSTRACT FROM AUTHOR]

We present results on simultaneous nanostructuring and optical activation of lithium fluoride crystals by 800 eV off-normal Ar+ sputtering at different ion doses. The samples were studied by atomic force microscopy and optical spectroscopy. After ion irradiation smoothening of the initial random roughness is achieved and well-defined self-organized ripple structures appear, having a mean periodicity of 30 nm and a mean height of 3 nm. The simultaneous optical activation of the irradiated samples is due to the stable formation of electronic defects with intense photoluminescence in the visible spectral range. [ABSTRACT FROM AUTHOR]

The depth refractive index profiles of broadband visible-emitting planar waveguides produced in LiF crystals with 1.5- and 2-MeV He[sup +] ions at different doses have been derived from mode analysis. They show that there are two competitive mechanisms responsible for positive and negative modifications of the refractive index in the irradiated volume associated with different processes of energy deposition of the incident ions, so as to induce a complex coloration profile along the penetration direction, which is strongly dependent on the irradiation dose. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Erythrocytes (RBCs) constitute a very interesting class of cells both for their physiological function and for a variety of peculiarities. Due to their exceptionally strong relationship with the environment, the morphology and nanoscale characteristics of these cells can reveal their biochemical status and structural integrity. Among the possible subjects of investigations, the RBCs' ageing is of the utmost importance. This is a fundamental phenomenon that, in physiological conditions, triggers the cell turnover and ensures the blood homeostasis. With these premises, in recent years, we have presented an atomic force microscopy–based methodology to characterize the patterns of RBC ageing from the morphological point of view. In the present work, we used an ageing protocol more similar to the physiological conditions and we used differential scanning calorimetry and atomic force microscopy to probe the cross correlation between important structural and functional proteins. We also assessed the role played by fundamental structural and membrane proteins in the development of the most relevant morphological intermediates observed along the ageing. Furthermore, we coupled the morphological ageing patterns to the (bio)chemical alterations detected by Raman spectroscopy. This allowed identifying the chronology of the ageing morphologies and the metabolic pathways most involved in their development. As a whole, the present study provides the base to correlate specific molecular alterations to the development of structural anomalies, and these latter to the functional status of blood cells. We characterized the pattern of erythrocytes' ageing in starvation conditions through an experimental approach that combined atomic force microscopy (AFM), differential scanning calorimetry (DSC), and Raman spectro‐microscopy. Moreover, by using a DSC‐based procedure consisting in the warming and chilling of the samples at specific temperature capable to induce unfolding of specific cytoskeletal proteins, we were able to understand the role of selected molecular components in the development of structural anomalies and in the induction of specific ageing‐related morphologies. [ABSTRACT FROM AUTHOR]

We report on the formation of Zn nanoparticles induced by Ga + focused ion beam on single crystal ZnO. The irradiated materials have been studied as a function of the ion dose by means of atomic force microscopy, scanning electron microscopy, Raman spectroscopy and transmission electron microscopy, evidencing the presence of Zn nanoparticles with size of the order of 5–30 nm. The nanoparticles are found to be embedded in a shallow amorphous ZnO matrix few tens of nanometers thick. Results reveal that ion beam induced Zn clustering occurs producing crystalline particles with the same hexagonal lattice and orientation of the substrate, and could explain the alteration of optical and electrical properties found for FIB fabricated and processed ZnO based devices. [ABSTRACT FROM AUTHOR]

Lithium fluoride (LiF) crystals and films treated with ionizing radiation are promising materials to realize light emitting devices in the visible spectral range. We studied the ion dose dependence of the concentration of F2 and F3+ active defects, both absorbing at about 450 nm and separately emitting in the visible range, in He+ implanted LiF crystals. Quantitative information was deduced from transmission measurements by using a specially developed theoretical model to fit them, and was compared with the results obtained from photoluminescence spectra. Their qualitative agreement confirms the validity of our theoretical approach, which provides a simple and versatile tool of investigation of these peculiar active defects. [Copyright &y& Elsevier]