portable sequentially shifted excitation raman spectroscopy as an innovative tool for in situ chemical interrogation of painted surfaces

We present the first validation and application of portable Sequentially Shifted Excitation (SSE) Raman spectroscopy for the survey of painted layers in art

Studying pigments via portable FTIR

When analytical chemistry is called to support a conservation work on a polychrome surface, one of the main issues is the characterization of the palette. When sampling is permitted a laboratory analytical plan is designed. Since some years, the concerns about the correct conservation of the artworks, advised to avoid sampling; consequently the analytical protocols have been integrated with portable techniques. In fact XRF, FORS, Raman constitutes a valid support in individuating the used pigments. These latter have been recently flanked by portable FTIR; in case of the use of FTIR, spectra have been acquired with a non destructive and non invasive sampling method, via the external reflectance technique. Unfortunately bibliography which can provide reference reflectance spectra is lacking. In this paper a first attempt to build a set of reference data of a painting materials is presented. The FT-IR Spectrometer (Alpha-R, Bruker Optik GmbH) has been used sampling a circular area with about 6 mm of diameter and with the following parameters: 7500-375cm-1 spectral range, 4cm-1 spectral resolution, 200 number of scans. More than 50 pigments, provided by Kremer Pigmente GmbH, as pure pigments, were analysed representing a complete palette. Pulverized pigments were deposited in the cavity of an aluminium sample holder for X Ray Diffraction and the spectra were acquired without the need of further pre-treatment of samples. Moreover nearly 20 different organic substances were applied over a glass slide covered with an aluminium foil in order to acquire binder references. A selection of the spectral reflection features are presented in the paper, together with a discussion and the attribution of the more interesting ones. For each of the pigments part of the study, the characterisation has been completed with a micro-Raman spectrum (Senterra, Bruker Optik GmbH; 785 nm and 532 nm laser lines) and an XRD (X Ray Diffraction) analysis (Panalytical X'Pert PRO) in order to better complete and attribute the spectral data coming from portable FTIR

Application of terahertz spectroscopy to time-dependent chemical-physical phenomena

We present here a “proof of concepts” experiment that has been realized to show that time-dependent phenomena can be successfully studied in the terahertz region in a non pump−probe configuration. We have built-up an original analytical setup that has allowed following the evaporation of a deuterated water droplet cast on a CVD diamond substrate simultaneously in the near-middle infrared region and in the terahertz range. We have used a synchrotron light source in the terahertz region and a conventional thermal source in the infrared range. The results demonstrate that it is possible to study time-dependent phenomena simultaneously in the middle and terahertz ranges monitoring the entire chemical-physical process that occurs in the time domain of minutes

Special-Effect and Conventional Pigments in Black Light Art: A Multi-Technique Approach to an In-Situ Investigation

Since their introduction in the early decades of the 20th century, fluorescent pigments have found progressively wider applications in several fields. Their chemical composition has been optimized to obtain the best physical properties, but is not usually disclosed by the manufacturers. Even the other class of luminescent pigments, namely the phosphorescent ones, is now produced industrially. The peculiar optical properties of these pigments have attracted more and more the attention of famous artists since the middle of the last century. The Italian Black Light Art movement exploits the possibility of conveying different aesthetical messages depending on the kind of radiation (UV or visible) with which the artwork is illuminated. In the present work, a non-invasive in-situ investigation based on Raman, fluorescence, and visible-reflectance spectroscopies was performed on a series of Black Light Art paintings exhibited in Milan (Italy) in 2017, succeeding in the identification of the materials used by the artists. In particular, the use of both fluorescent and phosphorescent pigments, alone or combined with conventional synthetic organic pigments, has been recognized

Chemometrics approach to FT-IR hyperspectral imaging analysis of degradation products in artwork cross-section

Ascertain the distribution of materials and that of their degradation products in historical artifacts is crucial to understand their conservation status. Among the different analytical techniques that can be used, FT-IR imaging supplies information on the molecular composition of the material on a micrometric-scale in a nondestructive way (i.e. respecting the physical integrity of the material/object and without inducing visible damage to the object. This is possible by limiting the sampling to very small amounts.) (K.H.A. Janssens, R. van Grieken, Non-destructive microanalysis of cultural heritage materials, Elsevier, 2004). When thin sections of the material are not exploitable for transmission, and when ATR imaging mode is not suitable due to possible damages on the sample surface, FT-IR imaging is performed in reflection mode on thick polished, matrix embedded samples. Even if many efforts have been done in the optimization of the sample preparation, the material's surface quality is a critical issue that can hinder the achievement of good infrared images. Moreover, spectral artifacts due to volume and surface interactions can yield uncertain results in standard data treatment. In this paper we address a multivariate statistical analysis as an alternative and complementary approach to obtain high contrast FT-IR large images from hyperspectral data obtained by reflection μ-FTIR analysis. While applications of Principal Component Analysis (PCA) for chemical mapping is well established, no clustering unsupervised method applied to μ-FTIR data have been reported so far in the field of analytical chemistry for cultural heritage. In order to obtain certain chemical distribution of the stratigraphy materials, in this work the use of Hierarchical Cluster Analysis (HCA), validated with a supervised Principal Component based k-Nearest Neighbor (PCA-kNN) Analysis, has been successfully used for the re-construction of the μ-FTIR image, extracting useful information from the complex data set. A case study (a patina from the Arch of Septimius Severus in the Roman Forum) is presented to validate the model and to show new perspectives for FT-IR imaging in art conservation

Fast infrared detectors for beam diagnostics with synchrotron radiation

Abstract Beam diagnostic is a fundamental constituent of any particle accelerators either dedicated to high-energy physics or to synchrotron radiation experiments. All storage rings emit radiations. Actually they are high brilliant sources of radiation: the synchrotron radiation emission covers from the infrared range to the X-ray domain with a pulsed structure depending on the temporal characteristics of the stored beam. The time structure of the emitted radiation is extremely useful as a tool to perform time-resolved experiments. However, this radiation can be also used for beam diagnostic to determine the beam stability and to measure the dimensions of the e − or e + beam. Because of the temporal structure of the synchrotron radiation to perform diagnostic, we need very fast detectors. Indeed, the detectors required for the diagnostics of the stored particle bunches at third generation synchrotron radiation sources and FEL need response times in the sub-ns and even ps range. To resolve the bunch length and detect bunch instabilities, X-ray and visible photon detectors may be used achieving response times of a few picoseconds. Recently, photon uncooled infrared devices optimized for the mid-IR range realized with HgCdTe semiconductors allowed to obtain sub-nanosecond response times. These devices can be used for fast detection of intense IRSR sources and for beam diagnostic. We present here preliminary experimental data of the pulsed synchrotron radiation emission of DAΦNE, the electron positron collider of the LNF laboratory of the INFN, performed with new uncooled IR detectors with a time resolution of a few hundreds of picoseconds