Renzo Bertoncello

Illuminated manuscripts are, in general, the final products of a wise and complex interaction of different competencies. In particular, each manuscript reflects uses and techniques rooted in the historical and geographical traditions of the area of realization. Defining the characteristics and the materials in these valuable artefacts is an essential element to reconstruct their history and allow a more precise collocation and a possible comparison with other works in similar periods and areas. Non-invasive methods, mainly using portable instruments, offer undoubtedly good support in these studies. Recent analyses of an ancient Persian illuminated manuscript, combining multispectral imaging and spectroscopic measurements made with portable instruments (XRF, FORS, micro-Raman, IR-ATR) on selected points, provided new data for an improved understanding of this rare book. This study details the possibilities offered by combining these non-invasive methods for an in-depth understanding of the techniques and practices behind the realization of Middle Eastern illuminated manuscripts and provided new perspectives for multidisciplinary approaches to research in this field.

Mixed-metal olivine cathode materials are one of the most promising systems in the field of lithium batteries. Their main drawback is their low electronic conductivity, which limits the current rate at which they can be cycled. Herein, the effect on electrochemical properties of vicariant high-valence transition metals (HVTMs) inserted in the olivine crystal structure has been studied. The strategy adopted herein consists of doping a LiFe_1/3Ni_1/15Co_3/5PO₄ cathode by substituting part of the cobalt(II) ions with vanadium(IV), niobium(V), or tantalum(V) HVTMs. The WAXD studies reveal that small HVTMs in molar quantities (HVTM/P = 0.04) are vicariant into the olivine crystal lattice. Single-cell tests show that the Nb-doped cathode has a high-voltage (ca. 4.5 V) and a specific capacity of 149 mA h g⁻¹ (656 mW h g⁻¹). Thus, the insertion of HVTMs in the cathode structure exceptionally improved the electric conductivity of the material and yielded an improved cyclability and rate capability owing to its electro-compensation effect.

Doping hematite with different elements is a common strategy to improve the electrocatalytic activity towards the water oxidation reaction, although the exact effect of these external agents is not yet clearly understood. Using a feasible electrophoretic procedure, we prepared modified hematite films by introducing in the deposition solution Ti(IV) butoxide. Photoelectrochemical performances of all the modified electrodes were superior to the unmodified one, with a 4-fold increase in the photocurrent at 0.65 V vs. SCE in 0.1 M NaOH (pH 13.3) for the 5% Ti-modified electrode, which was the best performing electrode. Subsequent functionalization with an iron-based catalyst led, at the same potential, to a photocurrent of ca. 1.5 mA·cm⁻², one of the highest achieved with materials based on solution processing in the absence of precious elements. AFM, XPS, TEM and XANES analyses revealed the formation of different Ti(IV) oxide phases on the hematite surface, that can reduce surface state recombination and enhance hole injection through local surface field effects, as confirmed by electrochemical impedance analysis.

Potash-lime silica glass was used for window panels in Europe north of the Alps in the medieval era. The high potassium and low silica content of this glass influences its chemical stability. When exposed to atmospheric conditions as well as acidic aqueous solutions, this type of glass can become hazy, foggy and/or flake phenomena can occur, which modify the original appearance of the artworks can occur. For proper conservation it is therefore necessary to understand the mechanisms of corrosion allowing for the selection of better conditions and treatments to slow down or avoid degradation. In previous works the applicability and the protective effect of a sol–gel silica coating on potash-lime-silica glass was tested in aqueous acidic solutions. With this work the previous results are integrated, investigating the protective effect against weathering and accelerated ageing. SEM analyses were performed to monitor the surface of the glass after accelerated ageing, in particular to detect the presence of corrosion products; moreover, ToF–SIMS analysis was performed to visualize the ion distribution as a function of depth and the presence of any changes due to the weathering treatment. The analyses showed that the formation of weathering products on the surface was slowed down significantly compared to the areas of the sample that were not coated with sol–gel. Different results were obtained depending on the glass composition.

Imaging spectroscopy (IS) extends the measurement of one-dimensional UV-VIS-NIR spectroscopy to two-dimensional domain providing material characterization and localization. The technique is gaining importance for the study of cultural heritage but its application is mainly focused on the analysis of pigments in paintings. An IS device has been developed and then applied to the study of chromophores in glassy objects. It consists of a visible imaging spectrograph, mounted on a rotation stage, which captures monochromatic images of the sample within a wavelength range from 420 nm to 850 nm. The system has been used for the characterization and mapping of chromophores of hundreds of coloured glass tesserae of the stained glass windows from the Scrovegni Chapel (Padua, Italy). Two measurement methodologies have been performed: transmission and double-transmission modes. In the first case, lamps used to illuminate the sample and the spectrograph are placed on the opposite side of the window, to acquire directly the signal transmitted from the glass. In the latter case, the lamps and the spectrograph are placed on the same side of the window, that is placed on a white scattering screen. The acquired signal comes from the light of the lamps transmitted through the glass, then diffused back by the opaque white screen and finally transmitted again through the glass. Results are discussed comparing both modalities in terms of signal-to-noise ratio and spectral contrast. Visible spectra acquired allow the clear identification of several chromophores, e.g. Co(II), Cr(III) or Mn(III). The IS device acquires numerous spectra in relatively short time in a non-invasive way. According to the authors knowledge, this is the first time in which visible imaging spectroscopy technique has been applied for the study of stained glass windows. As the results show, it could represent a powerful and innovative tool to map chromophores of this kind of artefact, particularly when integrated with other non-invasive techniques as X-ray fluorescence.

The Grande Albergo Ausonia & Hungaria (Venice Lido, Italy) has an Art Nouveau polychrome ceramic coating on its façade, which was restored in 2007. Soon after the conservation treatment, many tiles of the façade decoration showed coloured alterations putatively attributed to the presence of microbial communities. To confirm the presence of the biological deposit and the stratigraphy of the Hungaria tiles, stereomicroscope, optical and environmental scanning electron microscope observations were made. The characterisation of the microbial community was performed using a PCR–DGGE approach. This study reported the first use of a culture-independent approach to identify the total community present in biodeteriorated artistic tiles. The case study examined here reveals that the coloured alterations on the tiles were mainly due to the presence of cryptoendolithic cyanobacteria. In addition, we proved that the microflora present on the tiles was generally greatly influenced by the environment of the Hungaria hotel. We found several microorganisms related to the alkaline environment, which is in the range of the tile pH, and related to the aquatic environment, the presence of the acrylic resin Paraloid B72® used during the 2007 treatment and the pollutants of the Venice lagoon.