VIRTUAL REALITY FOR HISTORICAL ARCHITECTURE Agnello, F.; Avella, F.; Agnello, S.
International archives of the photogrammetry, remote sensing and spatial information sciences.,
01/2019, Letnik:
XLII-2/W9
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
This article shows a first step in the development of an immersive virtual tour of the Cathedral of Palermo, entering the fields of Digital Cultural Heritage and Edutainment. Its purpose is to help ...people to gain knowledge about the site, highlighting the complex stratifications that have characterized its history.The development of the project has been possible thanks to different phases of work: surveys were initially carried out by laser scanning, then assembled and processed to obtain the 3D model of the current state; at the same time, the model of reconstruction was processed in several phases, based on historical, archival and iconographic sources; both models were, later, subject to post-processing, preparatory to the development of virtual navigation. The tour scenario includes options in order to make it attractive for the player, such as interactive elements, interfaces and animations.
Metal-organic frameworks (MOFs) are an intriguing group of porous materials due to their potential influence on the development of indispensable technologies like luminescent sensors and solid-state ...light devices, luminescent multifunctional nanomaterials. In this research work we explored MIL-53(Al), an exceptional class of MOF that, along with guest adsorption, undergoes structural transitions exhibiting breathing behavior between narrow pore and large pore under temperature and mechanical stress. Therefore, we opted for the time resolved luminescence and FT-Raman spectroscopy to investigate the mechanochromic and thermochromic response of this material under external stimuli. Intriguingly, when subjected to temperature changes, MIL-53(Al) exhibited a ratiometric fluorescence behavior related to the reversible relationship of photoluminescence emission intensity with respect to temperature. Moreover, under higher mechanical stress MIL-53(Al) displayed turn-on behavior in emission intensity, hence offering a thrilling avenue for the application in mechanically deformed-based luminescent sensors and ratiometric fluorescence temperature sensors.
The nucleation and growth mechanism of aluminum oxide (Al2O3) in the early stages of atomic layer deposition (ALD) on monolayer epitaxial graphene (EG) on silicon carbide (4H–SiC) has been ...investigated by atomic force microscopy (AFM), conductive-atomic force microscopy (C-AFM) and Raman spectroscopy. Differently than for other types of graphene, a large and uniform density of nucleation sites was observed in the case of EG and ascribed to the presence of the buffer layer at EG/SiC interface. The deposition process was characterized by Al2O3 island growth in the very early stages, followed by the formation of a continuous Al2O3 film (∼2.4 nm thick) after only 40 ALD cycles due to the islands coalescence, and subsequent layer-by-layer growth. The electrical insulating properties of the deposited ultrathin Al2O3 films were demonstrated by nanoscale current mapping with C-AFM. Raman spectroscopy analyses showed low impact of the ALD process on the defect’s density of EG. The EG strain was also almost unaffected by the deposition in the regime of island growth and coalescence, whereas a significant increase was observed after the formation of a compact Al2O3 film. The obtained results can have important implications for device applications of epitaxial graphene requiring ultra-thin high-k insulators.
Display omitted
In the present investigation we report experimental data regarding the Raman and Infra-Red (IR) absorption activities of commercial silica nanoparticles. We compared the data of the nanoparticles ...with the ones acquired in the same experimental conditions for commercial bulk silica. By this comparison we highlighted that the variability of the spectral features of the matrix related Raman and IR bands in the nanoparticles is above the one observed for the bulk systems before any treatments. Furthermore, by studying nanoparticles with different sizes (diameters from 40 to 7nm) and applying the shell-model we can suggest that the core network of the nanoparticles is close to the one encountered in the bulk materials. By contrast for the surface shell, having a thickness of about 1nm, as suggested by previous investigations, the structure is strongly modified. In fact, from Raman and IR data it appears that the Si–O–Si angle has a lower main value than those encountered in bulk systems and that the ring statistic is shifted towards lower member rings.
► We studied the Raman and IR spectra of different commercial silica nanoparticles. ► The nanoparticles had different sizes (diameters from 40 to 7nm). ► Applying a shell-model we suggest that the core matrix is close some bulk materials. ► In the surface shell (thickness of about 1nm), the structure is strongly modified. ► The Si–O–Si angle has a lower main value and the lower member ring number is larger.
Metal–organic frameworks (MOFs) are getting closer to finally being used in commercial applications. In order to maximize their packing density, mechanical strength, stability in reactive ...environments, and many other properties, the compaction of MOF powders is a fundamental step for the application field of research of these extraordinary materials. In particular, HKUST-1 is among the most promising and studied MOF. Contrary to what reported so far in the literature, here we prove that the tableting of HKUST-1 powders without any damage of the lattice is possible and easy to get. For the first time, this kind of investigation has been performed exploiting its peculiar magnetic properties with the aid of electron paramagnetic resonance spectroscopy. Indeed, they have allowed us to explore in detail all the smallest changes induced in the paramagnetic paddle-wheel units by the application of the mechanical pressure on the material. This original approach has permitted us to unveil the main source of structural instability of HKUST-1 during compaction, that is, the water molecules adsorbed by the powdered sample before tableting and finally to establish a proper compaction protocol. Our conclusions are also fully supported by the results obtained with powder X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, water sorption isotherms, and surface area estimation with the Brunauer–Emmett–Teller method, which prove that the tablet of HKUST-1 obtained by this new protocol actually preserves the crystal structure and porosity of the pristine powders. A morphological characterization has also been conducted with a combined use of optical and atomic force microscopies.
We report pump-probe transient absorption measurements addressing the photocycle of the Germanium lone pair center (GLPC) point defect with an unprecedented time resolution. The GLPC is a model point ...defect with a simple and well-understood electronic structure, highly relevant for several applications. Therefore, a full explanation of its photocycle is fundamental to understand the relaxation mechanisms of such molecular-like systems in solid state. The experiment, carried out exciting the sample resonantly with the ultraviolet (UV) GLPC absorption band peaked at 5.1 eV, gave us the possibility to follow the defect excitation-relaxation dynamics from the femto-picosecond to the nanosecond timescale in the UV-visible range. Moreover, the transient absorption signal was studied as a function of the excitation photon energy and comparative experiments were conducted on highly- and weakly-germanium doped silica glasses. The results offer a comprehensive picture of the relaxation dynamics of GLPC and allow observing the interplay between electronic transitions localized on the defect and those related to bandgap transitions, providing a clear evidence that the role of dopant high concentration is not negligible in the earliest dynamics.
Time dynamics of doping and strain induced in single layer graphene by thermal treatments up to 300°C in vacuum, nitrogen, carbon dioxide and oxygen controlled atmosphere are deeply studied by Raman ...spectroscopy and they are compared with its morphological evolution investigated by Atomic Force Microscopy. The reaction dynamics in oxygen treatments is determined down to a time scale of few minutes as well as that of dedoping process made by water vapor treatment. The interplay of strain modification and doping effects is separated. The strain is clarified to be strongly influenced by the cooling time. The doping removal is dominated by the water vapor, showing that the concentration of molecular water in gas phase governs the process rate. The opportune choice of heating/cooling and atmosphere enables to tune selectively the strain or doping.
Display omitted
1Fabrication route for MAPbI3 directly on substrates over large areas;.2Correlation between the growth parameters and the thickness of the layers.3Characterization of the crystallinity and ...composition of the fabricated material.4Correlation between the optical absorbance and the thickness of the thin films.5Films with thickness of 1.3 µm have absorption ≥99.9% in the whole visible range.
Organometallic perovskites are one of the most investigated materials for high-efficiency thin-film devices to convert solar energy and supply energy. In particular, methylammonium lead iodide has been used to realize thin-film perovskite solar cells, achieving an efficiency higher than 20%. Different fabrication procedures based on the spin-coating technique have been proposed, which do not ensure homogenous morphologies.
In this work, we present a scalable process to fabricate methylammonium lead iodide thin films directly on conductive substrates, consisting of electrodeposition and two subsequent chemical conversions. A thorough investigation of the morphological, structural and compositional properties of the layer is performed after each fabrication step. It is demonstrated that this method allows fine control of the thickness of the layer by tuning the cell parameters during the electrodeposition step. X-ray diffraction patterns and energy-dispersive X-ray analysis indicate the achievement of high-purity methylammonium lead iodide layers. Micro-Raman analyses were used to demonstrate the formation of methylammonium lead iodide. Finally, ultraviolet-visible absorption spectra were acquired to determine the optical band edge of the layer (̴ 1.56 eV) and the absorbance of methylammonium lead iodide as a function of the film thickness. As expected, the material exploits excellent optical properties, achieving an absorption ≥ 99.9% in the entire visible range for a layer thickness of 1.3 µm. The results presented here pave the way for the application of cost-friendly solution-based processes to fabricate high-quality perovskite solar cells.
Doping and stability of monolayer low defect content graphene transferred on a silicon dioxide substrate on silicon are investigated by micro-Raman spectroscopy and atomic force microscopy (AFM) ...during thermal treatments in oxygen and vacuum controlled atmosphere. The exposure to molecular oxygen induces graphene changes as evidenced by a blue-shift of the G and 2D Raman bands, together with the decrease of I 2D/I G intensity ratio, which are consistent with a high p-type doping (∼1013 cm–2) of graphene. The successive thermal treatment in vacuum does not affect the induced doping showing this latter stability. By investigating the temperature range 140–350 °C and the process time evolution, the thermal properties of this doping procedure are characterized, and an activation energy of ∼56 meV is estimated. These results are interpreted on the basis of molecular oxygen induced ∼1013 cm–2 p-type doping of graphene with stability energy >49 meV and postdoping reactivity in ambient atmosphere due to reaction of air molecules with oxygen trapped between graphene and substrate.
PDF
