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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.