Functional nano-hydroxyapatite for applications in conservation of stony monuments of cultural heritage

Stone is one of the most durable construction materials used in historic buildings all over the world. However, over time, the stone can be subject to various degradation processes leading to physical and chemical modifications. Although these effects may be limited to the surface and negligible to the structural stability of the affected buildings, they can represent a major problem in decorative elements of artistic value, where any detail should be preserved [1]. The challenge for conservators and material scientists involved in stone conservation has always been to find a way to stop or delay the effects of these degradation processes. The basic principle of the patrimony is that the cultural heritage is an incalculable and integral legacy to our future: observing and knowing the past, will help next generations to better challenge the future. Thus, conservation of stone heritage is always a delicate and complex task, due to the multiple variables that have to be taken into account to identify the problems, and to define the necessary conservation actions and to select materials and best procedures to be used. The variety of factors to be analyzed includes the intrinsic stone properties (from geological features up to mechanical behavior), the state of conservation, the degradation mechanisms and the environmental factors. One of the most promising technology employed for lowering the previously described degradation processes, is that of nanomaterials, nowadays largely applied in the maintenance of the world cultural heritage, with the aim of improving the consolidation and protection treatments of damaged stone materials they are made of [2]. Such nanomaterials display important advantages that could solve many problems found in the traditional interventions, that often showed the serious bias of the lack the vital compatibility with the original substrate and a durable performance: application of nanotechnology in the cultural heritage conservation is characterized by the possibility to design consolidant products strongly compatible with the original stone substrate. Moreover, when particles have dimensions of about 100 nanometers, the material properties change significantly from those at larger scales. The nanoparticles must show: stability and sustained photoactivity; biological and chemical inactivity nontoxicity, as well as antimicrobial properties for lowering ecotoxicological impact on animals and plants [3]; low cost suitability towards visible or near UV light; high conversion efficiency and high quantum yield. In addition, these treatments can also have water repellent properties which favor this self-cleaning action and prevent the generation of damage caused by water. The most commonly used inorganic consolidant agents are the products based on Ca(OH)2 calcium hydroxide nanoparticles [4], due to their compatibility with a large part of the built and sculptural heritage. As well as other hydroxides (Mg(OH)2, Sr(OH)2), metal oxides (TiO2, ZnO), and metal nanoparticles (Au, Ag, Pt)) have been reported in the literature, focusing on their potential as consolidants on different artifacts of cultural heritage [2, 5]. But one of the most challenging nanomaterial is Ca10(PO4)6(OH)2 hydroxyapatite (HAP), already applied in a large variety of technological and biomedical applications, mainly due to its close relationship with mineral component of hard human tissues [6-7], and in cultural heritage conservation used for carbonate stone consolidation [2]. HAP can be applied for the consolidation of limestones, marbles and sandstones with different carbonate contents. This product is not introduced directly into stone material, but it comes from the reaction between phosphate ions from an aqueous solution of diammonium hydrogen phosphate applied to the stone and calcium ions coming from substrate. Among its advantages, HAP has a similar crystal structure and close lattice parameters of CaCO3 calcite, the main constituents of marbles and limestone. Thanks to its low viscous nature, this aqueous consolidant product is able to penetrate deeply into the stone, generating a significant improvement in mechanical properties of the same stone. The HAP has been tested as a protective treatment for marble against acid rain corrosion [8]. The study of compatibility and adaptability requires that the physical and chemical properties of both consolidator products and stone substrate are well known. Such a knowledge plays a very important role for the good outcome of the present project. Materials of interest, synthesized in our labs has been analysed by using: 1) X-ray diffraction (XRD), effective on crystalline materials and able to carry out information on chemical composition, size, shape and atomic structure, 2) small- and/or wide-angle scattering (SAXS/WAXS), powerful tool to investigate the domain of phosphate particles as a function of their optical properties; in the case of SAXS the technique can be applied to HAp nanoparticles characterization; 3) Fourier-Transform Infrared (FTIR) spectroscopy, reliable techniques for investigating hydroxyl anions and variations within anionic and cationic groups in the obtained materials; 4) scanning electron microscopy for checking morphologies of nanonparticles; 5) biological evaluation of the antimicrobial properties of obtained HAp materials, through direct contact and disc diffusion methods versus most common gram + and gram - bacteria present in human or animal biosystems 6) Laser Induced Breakdown Spectroscopy (LIBS), a non-destructive technique able to get quali-quantitative informations on museal artifacts. 1 - Pesce C., Moretto L.M., Orsega E.F., Pesce G.L., Corradi M., Weber J. Effectiveness and Compatibility of a Novel Sustainable Method for Stone Consolidation Based on Di-Ammonium Phosphate and Calcium-Based Nanomaterials. Materials 12 (2019) 3025. 2 - David, M.E., Ion, R.-M., Grigorescu, R.M., Iancu, L., Andrei, E.R. Nanomaterials Used in Conservation and Restoration of Cultural Heritage: An Up-to-Date Overview. Materials 13 (2020) 2064. 3 - Reyes-Estebanez, M., Ortega-Morales, B.O., Chan-Bacab, M., Granados-Echegoyen, C., Camacho-Chab, J.C., Pereanez-Sacarias J.E., Gaylarde C. Antimicrobial engineered nanoparticles in the built cultural heritage context and their ecotoxicological impact on animals and plants: a brief review. Heritage Science 6 (2018) 52. 4 - El Bakkari M, Bindiganavile V, Boluk Y. Facile Synthesis of Calcium Hydroxide Nanoparticles onto TEMPO-Oxidized Cellulose Nanofibers for Heritage Conservation. ACS Omega 4 (2019) 20606-20611. 5 - Dida B., Siliqi D., Baldassarre, F., Karaj D., Hasimi A., Kasemi V., Nika V., Vozga I. "Nanomaterialet per Konservimin e Trashegimise Kulturore", SHLBSH, Tirana (2020), ISBN 978-99943-2-468-2 6 - Rakovan J.R., Pasteris J.D. A technological gem: Materials, Medical, and Environmental Mineralogy of Apatite. Elements 11 (2015) 195-200. 7 - Baldassarre F., Altomare A., Corriero N., Mesto E., Lacalamita M., Bruno G., Sacchetti A., Dida B., Karaj D., Della Ventura G.D., Capitelli, F., Siliqi, D. Crystal Chemistry and Luminescence Properties of Eu-Doped Polycrystalline Hydroxyapatite Synthesized by Chemical Precipitation at Room Temperature. Crystals 10 (202) 250. 8 - Graziani G., Sassoni E., Franzoni E., Scherer G.W. Hydroxyapatite Coatings for Marble Protection: Optimization of Calcite Covering and Acid Resistance. Applied Surface Science 368 (2016) 241-257

Laser Induced Breakdown Spectroscopy for Elemental Analysis in Environmental, Cultural Heritage and Space Applications: A Review of Methods and Results

Analytical applications of Laser Induced Breakdown Spectroscopy (LIBS), namely optical emission spectroscopy of laser-induced plasmas, have been constantly growing thanks to its intrinsic conceptual simplicity and versatility. Qualitative and quantitative analysis can be performed by LIBS both by drawing calibration lines and by using calibration-free methods and some of its features, so as fast multi-elemental response, micro-destructiveness, instrumentation portability, have rendered it particularly suitable for analytical applications in the field of environmental science, space exploration and cultural heritage. This review reports and discusses LIBS achievements in these areas and results obtained for soils and aqueous samples, meteorites and terrestrial samples simulating extraterrestrial planets, and cultural heritage samples, including buildings and objects of various kinds

Digital geographies and digital surveillance technologies: power and space in the Italian society under control for public health

Social network are shaping relations and socio-economic processes through the automatic production of space that generates new spatialities (Kitchin, Dodge 2011) called cyberplaces (Meek 2011). In fact, digital media are an ever-increasing presence in social movements, political participation and civic engagement. Significant to these debates, digital media and services are becoming increasingly location-based, with more applications providing geographical interfaces and supporting locational data (Elwood, Leszczynski 2013). Since geography information technologies and data available to the public increasingly permeate social movements, bottom-up organizations, citizen groups and the local society, the understanding of different forms of activisms and civic commitment generated by these new spatial media (Crampton, 2009) and the impact produced on affected places is of paramount importance. From softer forms of democracy to participation in real protest movements, these new forms of communication has re-shaped models and practices of mobilization, self-representation and actions. The aim of the proposed paper is based on a collective hub of research, theoretical, empirical and methodological debate. It has the aim of analysing diverse forms, experiences and practices of digital activism and socio-environmental movements, their relations with the territories and their heterogeneous claims and contestations in relation to politics and effects of the environmental crisis and climate change. From a methodological point of view, the examined cyberplaces also called counter-place (Lussault, 2019), will be studied using the discourse analysis and visual methodology, according to an analysis of the semantic web in which digital activism unravels, as well as a visual analysis of counter-places meant as the object of the protest. Whilst the former is useful for understand cultural, social and ideological aspects of a community, the latter help us to understand narrative speaks about a specific place, which produces new spatial forms, its perception and image. The project will investigate the various forms of digital activism and social mobilization related to these topics more in-depth Italy with spots about digital activism for climate change around the world

Assessing Laser Cleaning of a Limestone Monument by Fiber Optics Reflectance Spectroscopy (FORS) and Visible and Near-Infrared (VNIR) Hyperspectral Imaging (HSI)

Fiber optics reflectance spectroscopy (FORS) and visible and near-infrared (VNIR) hyperspectral imaging (HSI) were applied to assess and control the laser cleaning process of a deeply darkened limestone surface collected from the historic entrance gate of Castello Svevo, Bari, Italy. Both techniques enabled us to verify the different degree of removal of a thick deposit of black crust from the surface of the walls. Results obtained were in good agreement with those of previous studies of the elemental composition achieved by application of laser-induced breakdown spectroscopy (LIBS). Coupling FORS and VNIR-HSI provided important information on the optimal conditions to evaluate the conservation status and determine the more appropriate level of cleaning restoration, thus avoiding over- and/or under-cleaning. Imaging spectroscopy was used to obtain maps of areas featuring the same or different spectral characteristics, so to achieve a sufficient removal of unwanted layers, without modifying the surface underneath, and to increase the efficiency of traditional cleaning techniques. The performance of the combined non-invasive approach used in this work shows promise for further applications to other types of rocks and highlights the potential for in situ assessment of the laser cleaning process based on reflectance spectroscopy

New insights on the Dronino iron meteorite by double-pulse micro-Laser-Induced Breakdown Spectroscopy

Two fragments of an iron meteorite shower named Dronino were characterized by a novel technique, i.e. Double- Pulse micro-Laser Induced Breakdown Spectroscopy (DP-μLIBS) combined with optical microscope. This tech- nique allowed to perform a fast and detailed analysis of the chemical composition of the fragments and permitted to determine their composition, the alteration state differences and the cooling rate of the meteorite. Qualitative analysis indicated the presence of Fe, Ni and Co in both fragments, whereas the elements Al, Ca, Mg, Si and, for the first time Li, were detected only in one fragment and were related to its post-falling alteration and contamination by weathering processes. Quantitative analysis data obtained using the calibration-free (CF) - LIBS method showed a good agreement with those obtained by traditional methods generally applied to meteorite analysis, i.e. Electron Dispersion Spectroscopy - Scanning Electron Microscopy (EDS-SEM), also performed in this study, and Electron Probe Microanalysis (EMPA) (literature data). The local and coupled variability of Ni and Co (in- crease of Ni and decrease of Co) determined for the unaltered portions exhibiting plessite texture, suggested the occurrence of solid state diffusion processes under a slow cooling rate for the Dronino meteorite

Micro-Laser Induced Breakdown Spectroscopy for recognition of chemical zoning of Ti-rich garnets in thin section.

Ti-rich garnets are minerals related to alkali metasomatism and magmatism of carbonatic affinity, which can be found in various undersaturated alkaline igneous rocks. The chemical composition of these minerals depends on the phys- ico-chemical growth conditions under which they formed. Thin sections of these garnets often exhibit colour zonings corresponding to chemical zonings. The innovative approach of double-pulse micro-laser-induced breakdown spectroscopy (DP- μLIBS) technique coupled with optical microscopy can be fruitfully applied to the direct quantitative analysis and character- ization in atmospheric air of the petrographic thin sections [1]. This method shows significant advantages with respect to traditional techniques used to analyze geological samples such as electron-probe microanalysis (EPMA) and scanning elec- tron microscopy-energy dispersive spectrometry (SEM-EDS), including versatility, minimal destructivity, no carbon coating, no waste production, low operating costs, rapidity of analysis and sensitivity to light elements. To validate the analytical performance of this technique, several petrographic thin sections of Ti-rich andradite garnets originated from the volcanic district of Colli Albani, Italy, were investigated. Some of these petrographic thin sections have been previously investigated by EPMA [2-4], and the analyses obtained were used to set-up the one point calibration (OPC) LIBS method in order to de- termine quantitatively the chemical composition of Ti-rich garnets. This method was then applied also to thin sections of garnet not previously investigated by conventional techniques. Several analytical spots were aligned along different direc- tions on the slices. The results obtained show that the samples studied exhibit two different types of chemical zonings. A de- crease of Ti content from core to rim of slices, which reflects the physico-chemical evolution of the growth environment (concentric zoning), and an increase of Ti in the {211} growth sectors, related to growth kinetics [3] (sector zoning). The OPC-LIBS data show a good agreement with the previous EPMA data, suggesting that the DP-μLIBS can be considered a good tool to obtain quick, fast and reliable chemical analyses of petrographic thin sections. [1] Senesi GS, Tempesta G, Manzari P, Agrosì G, (2016) Geostandards and Geoanalytical Research 40(4): 533-541. [2] Agrosì G, Digennaro MA, Scandale E, (2001) Neues Jarhbuch fur Mineralogie Abh 176: 89-107. [3] Agrosì G, Schingaro E, Scordari F, Scandale E, Pedrazzi G, (2002) European Journal of Mineralogy 14: 785-794. [4] Agrosì G, Scandale E, Tempesta G, (2011) Periodico di Mineralogia 80(1): 89-104