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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)