Simona Raneri

Nanocrystalline TiO2 coatings by sol–gel: photocatalytic activity on Pietra di Noto biocalcarenite

Self-cleaning photocatalytic coatings based on TiO2 nanoparticles obtained by sol–gel techniques at two different pH values (1.3–10.6) have been investigated on carbonatic stone. The selected material is the yellowish lithofacies of Palazzolo Formation calcarenite, commonly named Pietra di Noto, widely used in the Baroque monuments of the Noto Valley (Sicily, Italy). SEM–EDS, XRD and Raman investigations were carried out to characterize the TiO2 nanoparticles (mainly nanocrystalline anatase) obtained by the acid and basic nanosols and the corresponding coatings on pietra di Noto. To evaluate the effects of the treatments at two different pH values, changes in the stone color appearance, water absorption by capillarity and the behavior for salt crystallization were measured. The photocatalytic activity of the coatings was evaluated under UV irradiation, by monitoring methyl orange and methylene blue dye degradation as a function of time. The results highlight the compatibility of both treatments with respect to the properties of the calcarenite stone, showing no chromatic changes, no alteration of physical properties, an improvement in the resistance to salts crystallization and the good photocatalytic activity on both dyes. The experimental data suggest that the basic coating has to be preferred for carbonatic stones for its harmlessness and better performances in terms of self-cleaning action and protection against water and salts.Graphical AbstractSelf-cleaning photocatalytic coatings based on TiO2, obtained by sol–gel at two different pH values, are applied on Pietra di Noto carbonatic stone. TiO2 nanoparticles and coatings are characterized by SEM, XRD and Raman. The photocatalytic activity of the coatings is evaluated under UV irradiation, by monitoring methyl orange and methylene blue dye degradation as a function of time. The basic coating is suitable for carbonatic stones for its harmlessness and better performances in terms of self-cleaning action and protection against water and salts.

A multi-technique approach for the determination of the porous structure of building stone

The complete knowledge of the porous structure of rocks is necessarily requested for the prediction of the damages induced by salt crystallization. Nevertheless, the geometric description of the porous structure is usually very difficult because of the variability of the size distribution of voids, ranging from nanometers to millimeters, which generally is not accessible by a single methodology. For this reason, a multi-technique approach was used here: the investigation at sub-micrometric dimensional scale (> 0.004 μm) was carried out by Hg intrusion porosimetry (MIP), whereas the study at the nanoscale required Small Angle Neutron Scattering (SANS) analysis. All the results were interpreted in the framework of a fractal model. The analyses were performed on limestones of different geological formations, cropping out in south-eastern Sicily and largely used as building stones in Baroque monuments of the Noto Valley (belonging to the UNESCO Heritage List).

Technological Analysis of Sicilian Prehistoric Pottery Production through Small Angle Neutron Scattering Technique

The Middle Bronze Age in Sicily (15th-13th century BC) represents a crucial moment in the evolution of Prehistoric pottery production. However, the scarcity of specific petrographic and chemical studies has represented until now a serious interpretative handicap for archaeologists. The recent study of an important Middle Bronze Age pottery complex from the site of Grotte di Marineo (Licodia Eubea, Catania), offers the possibility to add new significant data in this field. The analyses, carried out on a group of diagnostic samples represent 13% of the whole complex. This allowed us to obtain a precise characterization that surpassed the misleading identification based on the simple autoptic exam. In this context, this paper highlights the potentiality of the small angle neutron scattering (SANS) technique as a non-invasive analytical tool for the study of technological aspects, in conjunction with other, more usual, methodologies such as scanning electron microscopy (SEM), in order to better investigate production technology of Middle Bronze Age Sicilian pottery.

Neutron radiography for the characterization of porous structure in degraded building stones

As it is well known, the porous structure of stones can change due to different degradation processes that modify the characteristics of freshly quarried blocks. Their knowledge is fundamental for predicting the behavior of stones and the efficacy of conservative treatments. In this context, neutron radiography is a useful tool not only to visualize the structure of porous materials, but also to evaluate the degree of degradation and surface modifications resulting from weathering processes. Furthermore, since thermal neutrons suffer a strong attenuation by hydrogen, this technique is effective in order to investigate the amount of absorbed water in building materials. In the present work, we report a neutron radiography investigation of limestones cropping out in the South-Eastern Sicily and widely used as building stones in Baroque monuments of the Noto Valley. The analyzed samples have been submitted to cyclic salt crystallization that simulate degradation processes acting in exposed stones of buildings. The obtained results demonstrate the interest of neutron radiography to better understand deterioration processes in limestones and to acquire information useful for restoration projects.

Raman Investigation of Precious Jewelry Collections Preserved in Paolo Orsi Regional Museum (Siracusa, Sicily) Using Portable Equipment.

This work is a part of a large scientific project aimed at highlighting the potential of portable Raman equipment in characterizing jewelry materials preserved in museums, carried out in collaboration with gemologists and archeologists. In detail, we report the results of a measurement campaign performed for the study of gems and jewels preserved in the well-known Medagliere section at the Paolo Orsi Regional Museum of Siracusa (Sicily). The studied materials consist of exquisite examples of engraved loose gems and really rare examples of Hellenistic–Roman jewels, mainly coming from relevant Sicilian archaeological sites. Portable Raman measurements have been carried out using two instruments equipped with different excitation wavelengths. The obtained results have allowed for a complete characterization of the studied gemological materials, also suggesting sometimes misclassification for some valuable objects and gems.

Mortars and plasters from the Bruttii - Roman city of Tauriana (Palmi - RC) - preliminary data

In this work we present the results of the analysis of twelve plaster and mortar samples taken from the siteof Tauriana (Palmi – RC), an important Bruttii - Roman city. Two different construction phases of thecity are investigated referred to Bruttii (IV - I B.C.) and Roman (I B.C. - IV A.D.) presences. The studiedmaterials were collected from different architectonical structures and characterized by means of opticalmicroscopy (OM) and SEM/EDS. The study allowed to obtain interesting information about theevolutions in this chronological lap of production technology of plasters and mortars used in the differentarchitectural structures. Furthermore the petrographic observations allowed to determine the provenanceof raw materials.

Archeometric investigation on wall paintings from the most ancient Hellenistic hypogeum found in Sicily (C.da Apaforte-Licata (AG))

In the present work, an analytical study of paintings from an ancient hypogeum, dated back to 4th–3rd cent B.C. and located in Licata (Sicily, Southern Italy) has been carried out. A selection of representative red, yellow and white wall colored plasters have been sampled and analyzed in non-destructive and micro-destructive way to identify the pigmenting agents, preparation layers and study the deterioration processes. In particular, the quantitative analysis of the chemical composition of the different layers (pigments, preparation layers, deteriorated parts) has been obtained through scanning electron microscopy coupled with energy-dispersive spectrometry (SEM–EDS), while micro-Raman spectroscopy have been performed to investigate the molecular nature of the coloring agents used in the pigment layer. Finally, preliminary macroscopic and thin section analyses (OM) have been carried out with the aim to characterize plaster features and degradation processes. The obtained results, together with previous data on Hellenistic art in Sicily, may be helpful to create a database about the evolution of mural painting in Sicily as well as identify raw materials, pigment agents and painting techniques used in local plasters manufacture.

Mobility of men versus mobility of goods: archaeometric characterization of Middle Bronze Age pottery in Malta and Sicily (15th-13th century BC)

The aim of this paper is to offer the first petrographic and chemical characterization of Middle Bronze Age pottery of Malta (Borġ in-Nadur, half of 15th – early 12th century BC) to discriminate, in the multitude of Borġ in-Nadurvessels found in coeval sites of south-eastern and central-western Sicily, between imports and imitations and to precisely define their provenance.The present research may provide new data in order to shed light on the long standing issue about ‘mobility of men’ and ‘mobility of goods’ between the two insular contexts. A significant amount of Borġ in-Nadurpottery from Malta and Sicily have been sampled and subjected to petrographic exam on thin sections; moreover, chemical analyses of major and trace elements were performed by X-ray fluorescence spectrometry.The research is part of an interdisciplinary project, aimed to create a database of petrographic and chemical data of Borġ in-Nadurtype pottery found in Sicily and in the Maltese archipelago, launched by the University of Catania and Arcadia University in partnership with Heritage Malta and the Superintendence of Cultural Heritage of Malta.

Measuring weathering and nanoparticle coating impact on surface roughness of natural stones

ABSTRACT The surface texture of a stone represents a sensitive parameter in evaluating its conservation state. In monuments and sculptures, in fact, external agents continuously alter the appearance of stones, determining peculiar weathering patterns and modifying properties such as retention of water and particles, interaction with light, color, and finishing. The application of protective coatings also determines changes in surface appearance of a stone, usually evaluated and monitored by color change tests. Surface metrology methods offer the possibility to quantify these changes, evaluating the impact of external agents (natural, i.e. weathering, and artificially, i.e. protective coatings) on natural stones. In this research, we demonstrate the potential of surface areal measurements in describing the evolution of weathering processes and the effects of protective treatments on porous stone materials. The obtained results suggest that the extent of the modifications is related to the scale of observation (small- vs. large-scale undulations, i.e. roughness and waviness, respectively), with an overall increase of surface roughness as the weathering proceeds. Unexpectedly, coatings based on nanoparticle dispersions increase the topographic height parameters, due to the absence of a homogeneous film.

Multi-scale laboratory routine in the efficacy assessment of conservative products for natural stones

Graphical abstract