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Additional file 1: Figure S1. Points analysed on the Kiss by the different techniques. Figure S2. Points analysed on the Garden airplane trap by the different techniques. Figure S3. Points analysed on the Entire city by the different techniques. Figure S4. Points analysed on the Zoomorphic couple by the different techniques. Figure S5. Points analysed on the Attirement of the bride by the different techniques. Figure S6. Points analysed on the Antipope by the different techniques. Figure S7.Chroma DI (1050-650, 650-550, 550-450 nm) of the Entire city: the red arrow points at the moon circle, not visible in the RGB image (yellow square). Figure S8. Spectral features of Prussian blue recognized in The Kiss: (a) in-situ Raman spectrum and (b) ER-FTIR spectrum, the absorption at 512 cm-1 is to refer to ν(ZnO). Figure S9. ER-FTIR spectra of three yellow tones in The Kiss which show the presence of silicates. Figure S10. In-situ Raman analysis of the Kiss identifying chrome yellow orange. Figure S11. In-situ Raman analysis of the Zoomorphic couple identifying iron oxide (green peaks) and lead white (blue peak). Figure S12. ER-FTIR reflection spectra showing the presence of alteration products in AP (green lines), KI (black line) ZC (red for the spectrum collected in dark tones, cyan for the one collected on light tones), VS (magenta line), GA (blue line) and EC (orange line). Zinc oxalate (magenta dashed line) was identified by the typical inverted doublet at ≈1364 and ≈1320 cm-1, attributable to the νs(CO) and by the derivative ν(OH) at ≈3400 cm-1 [1]. Instead, Zn metal soaps, probably zinc stearate (dark cyan dashed line), were rec-ognized by the sharp inverted bands at ≈1540 and ≈1395 cm-1 which can be reasonably attributed to the asymmetric and symmetric stretching of the carboxylate group in zinc stearate [2, 3, 4, 5].

Several strategies have been effectively tested in the past to improve the Laser Induced Breakdown Spectroscopy (LIBS) signal for the analysis of liquid samples, involving peculiar experimental configurations, such as Double Pulse LIBS (DP-LIBS). Recently, sample treatment has proven to be a viable and simple way to enhance the performances of LIBS towards the analysis of solutions. Among the various strategies, the most promising and versatile appears to be Thin Film Microextraction (TFME) using carbon-based adsorbents. Another sample pre-treatment procedure, Nanoparticle-Enhanced LIBS (NELIBS), has gained significant interest due to its relative simplicity and effectiveness. This methodology uses a deposition of silver nanoparticles (AgNPs) on the sample to greatly increase the emission of the LIBS plasma. In this work, we investigate for the first time the possibility of combining TFME and NELIBS. We developed TFME supports by depositing an aqueous graphene nano-sheets (aq-GRA) prepared by Pulsed Laser Ablation in Liquid (PLAL) on a glass substrate. The preparation of the supports was optimized with regards to the substrate nature, deposition method, sorbent volume and drying method. Then, the TFME supports were tested for the extraction of Chromium from aqueous solution at different extraction times and analyte concentration. Subsequently, the TFME supports were treated with a deposition of silver nanoparticles (AgNP) to test the feasibility of the NELIBS approach. We observed an enhancement in the emission lines of Cr when the AgNPs were applied, as well as a lower estimated LOD value when compared to plain graphene TFME supports. M. Hidalgo is grateful to Ministerio de Economía, Industria y Competitividad [CTQ2016-79991-R] and Conselleria de Educación, Investigación, Cultura y Deporte (Regional Government of Valencia, Spain) [PROMETEO/2018/087] for the financial support.

Imaging systems are the basic tools of the trade for art historians, conservators, and archaeologists, when they are called to document the results of their work. However, photo cameras and imaging systems are also powerful research tools. These systems, in fact, are inherently portable and give the possibility of acquiring high-resolution, spectrally resolved digital images that can be elaborated exploiting the most advanced algorithms of information science. In this contribution, we will outline the many possibilities opened by the available instrumentation and techniques, to suggest the use of image analysis as the first step of the diagnostic process in Cultural Heritage conservation and study.

The micro-laser induced breakdown spectroscopy (µ-LIBS) technique allows performing fast elemental analyses, without sample preparation and thus making it specifically useful in the analysis of the composition of ancient potsherd. The µ-LIBS instrument is equipped with a microscope and a scanning system allowing to realize small craters (about Ø = 25 µm) in order to obtain detailed hyperspectral surfaces maps (up to a maximum size of one square centimeter). The data are processed by Self-Organizing Maps (SOMs) method to visualize in 2D representations allowing significant information on the technological features of ceramic samples., Estudos de Conservação e Restauro, n. 9 (2018)

This paper presents the study of various Roman materials used in the construction of the Maritime Theatre, one of the main buildings in the Hadrian’s Villa complex, a designated UNESCO World Heritage Site located in Tivoli (Rome, Italy), dating to the first half of the II century A.D. The plaster layers (arriccio and intonachino) and overlying original Roman paintings that form the concave wall of the portico as well as some bedding mortars of the pyramidal stone elements (i.e. cubilia) of the circular masonry have been studied in particular. In addition, the acid volcanic rocks of the cubilia have been investigated, aiming to understand their state of alteration and geological origin. By mineralogical-petrographic microscopy (OM), diffractometry (XRPD), Raman spectroscopy, Point Load Tests (PLT), helium pycnometry, and particle size analysis, the composition and granulometric distribution of the aggregate, type and characteristics of the binder, and various physical-mechanical properties (density, porosity, water absorption, imbibition and saturation indices, mechanical resistance) of mortars and stones were defined. In addition, through digital image analysis of thin sections, the binder/aggregate ratio and some geometric characteristics of the aggregates (e.g. circularity) were determined. The research aims to improve the knowledge of the constructive technologies of the Maritime Theatre through the analysis of its materials.

In this work, a fast method for obtaining a quantitative elemental mapping of highly inhomogeneous samples by µ-LIBS maps is proposed. The method, transportable and cheap, allows the analysis of large maps through the use of a Self-Organizing Map clustering method coupled to Calibration-Free LIBS for quantification of cluster prototypes. The method proposed has been verified on heterogeneous materials such historical lime mortars but it can be easily applied to a larger class of inhomogeneous materials for very different applications (modern building materials, biological samples, industrial materials, etc.).

In the study of ancient pottery, thin section analysis represents the basic approach to study mineralogical and petrografic features in order to obtain preliminary information about the production technology and origin of archaeological ceramics. However, even if thin section analysis allows investigating the textural and structural characteristics of potteries, peculiar features related to clay paste and temper composition, as well as provenance issues, can be detailed addressed only by quantitative mineralogical and chemical studies. In the realization of thin sections, a negative face is always produced, similar to the thin section itself; these remains can be used for additional analyses, such as high spatial resolution micro-chemical studies using, for example, a micro-laser induced breakdown spectroscopy (LIBS) scanner. LIBS is a spectroscopic technique that, exploiting the laser radiation, is able to bring into the plasma state micrometric portions of the sample, and to analyse its content through the study of the optical emission of the plasma itself. Unlike other techniques, LIBS can detect and quantify also light elements such as aluminium and magnesium. Images produced by the micro-LIBS instrument show the spatial distribution of the chemical elements within a portion of the sample, which may have dimensions from a few hundred microns up to several centimeters. The combination of these images with algorithms derived from image processing techniques may return interesting information and supporting data to in-depth investigate pottery components detected by optical microscopy observations. In this work, we present the results of an experimental study performed on thin-section negatives with different grain size, surface treatments and aggregates, coming from some Neolithic Italian sites, exploring the potential of the LIBS method in microchemical studies of ancient potsherds.

The stone used on the monuments, especially if they come from ancient times (e.g. medieval period), when exposed to the atmosphere, they are frequently affected by weathering and bio-deterioration processes. Thus, these latter produce various chemical and mineralogical transformations of substrate at the interface with the atmospheric agents as function of intrinsic compositional and physical characteristics of the material. Moreover, if there also are ancient treatments on the surface of geomaterials, the investigation field is further complicated. This research aims to analyse the surfaces of different volcanic lithology (basalts, andesite, pyroclastic rocks) used in the medieval Romanesque churches of Sardinia (XI-XIV cent.) having high historical-architectural and cultural relevance. By mineralogical and petrographic analysis (OM) and other different analytical methods (XRPD, colorimetry) the investigations addressed to define: i) petrographic features of volcanic rocks substrate; ii) chemical and mineralogical composition of coatings/crusts and any salt fanoand cryptoefflorescence; iii) compositional and microstratigraphic characterization of ancient treatments (i.e., Ca-oxalate films) on the surface of facades; iv) chromatic modifications of surface with respect to the substrate due to the alteration processes. The results show the incidence of several factors in the alteration process, as function of the occurred time, petrophysical features and composition of geomaterials, their position in the monument structure, exposition to the weathering processes, microclimatic characteristics, environmental conditions.

In the context of scientific visualization, the main challenge is to achieve a good balance between the accurate representation of scientific data (computed or stored in databases) and the visual quality of the virtual experience itself. Traditional scientific software relies on custom tools meant to be used on conventional terminals or software developed with mouse and keyboard in mind. However, the true advantage of Virtual Reality is the enhanced ability of finding connections between apparently heterogeneous information, discovering correlations that would otherwise be harder to detect. In particular, in the field of Digital Humanities, it is increasingly necessary to develop and validate virtual reality tools that are capable of combining various scientific data in a Virtual Reality context with access and consultation of online repositories. This paper reports the main aspects of the implementation of a heterogeneous relational database available online storing 3D models, metadata and chemical analyses related to different sectors of digital humanities. The Virtual Reality software, called PROTEUS, allows the user to shrink himself from the macroscopic world of Digital Humanities, down to the microscopic world of molecular sciences. The web platform is connected to the virtual reconstruction software, which dynamically loads the information available in the online repository within the virtual reality application. This application also provides a detailed explanation of the reconstruction of the 3D models for the various objects, and the chemical analyses. The real advantage of a virtual reality application is the real time interaction with data and 3D models, thus allowing the researcher to understand and manipulate objects, to test hypotheses and to seek meaningful results, visualizing the metadata while changing the parameters of the simulation in a dynamic and interactive way. This is a significant step forward in the democratization of science, by means of an user friendly and immersive access to advanced scientific algorithms, and the integration of the Proxima Molecular Perception library, which allows the automatic perception of structural and topological features of the underlying molecular and supra-molecular systems.