Demetrios Anglos

In the context of modern Heritage Science (HS) studies, chemical analysis together with contextual information provide valuable insights into the composition and structure, provenance, age, and/or production technology of objects and materials, facilitating also decision-making concerning the selection of appropriate conservation approaches for artifacts and monuments. While powerful laboratory techniques are often employed in such investigations, an increasing demand exists for the use of portable instrumentation that can be deployed at archaeological sites or museums. To address these needs, TriENA, a portable, hybrid instrument, has been developed, which integrates three complementary spectrochemical tools: Laser-Induced Breakdown Spectroscopy (LIBS), LED-Induced Fluorescence (LED-IF), and Diffuse Reflectance (DR) spectroscopy. These techniques facilitate compositional analysis of different types of materials, including metals, alloys and their corrosion products, pottery, pigments in various types of painted objects, or the identification of biodeterioration on stone monuments. In this article, the design concept of TriENA is presented. Detailed technical information concerning the main components of the instrument is provided, and key engineering aspects are discussed. A series of test cases demonstrate that this hybrid spectrometer is a valuable and versatile tool for conservators, heritage scientists, and archaeologists, as it enables rapid, portable, and comprehensive characterization of a wide range of objects, addressing a broad spectrum of analytical challenges.

In this study, we have investigated the relationship between the plasma temperature in remote laser-induced breakdown spectroscopy (LIBS) experiments and the hydrophobic properties of silicone rubber insulators (SIRs). Contact angle and LIBS measurements were conducted on both artificially-aged (accelerated aging) and field-aged SIRs. This study reveals a clear connection between plasma temperature and the properties of aged SIRs on artificially-aged SIR specimens. Specifically, the plasma temperature exhibits a consistent increase with the duration of the accelerated aging test. The hydrophobicity of the artificially-aged SIRs was assessed by performing contact angle measurements, revealing a decrease in the hydrophobicity with increased aging test duration. Furthermore, we extended our investigation to the study of nine field-aged SIRs that had been in use on 150 kV overhead transmission lines for 0 to 21 years. We find that the laser absorption and hardness of the material do not relate to the plasma temperature. In summary, we observe a direct connection of plasma temperature to both contact-angle measurements and operation time of the in-service insulators. These results strongly suggest the potential use of LIBS for remotely evaluating the hydrophobicity and aging degree of silicone rubber insulators, thus assessing their real-time on-site operational quality.

Laser-induced breakdown spectroscopy (LIBS) is a versatile analytical technique that can be used to probe the elemental composition of materials in diverse types of heritage samples, objects or monuments. The main physical principles underlying LIBS are presented along with analytical figures of merit and technical details concerning instrumentation. In practice, LIBS analysis does not require any sample preparation and the technique is nearly non-invasive, offering close to microscopic spatial resolution and the possibility for depth profile analysis. These features are, at present, available in a number of compact or transportable instruments that offer versatility and enable the use of LIBS for the analysis of a broad variety of objects/samples at diverse locations and this can be highly valuable at several stages of archaeological investigations and conservation campaigns. Representative examples are presented indicating how LIBS has been used to obtain compositional information for materials in the context of archaeological science, art history and conservation.

Elemental analysis of biogeochemical archives is an established technique used to study climate in a range of applications, including ocean circulation, glacial/interglacial climates, and anthropogenic climate change. Data from mollusc archives are especially important because of their global abundance and sub-annual resolution. Despite this potential, they are underrepresented among palaeoclimate studies, due to enigmatic physiological influences skewing the elemental record. Understanding the patterns behind these influences will improve data interpretation and lead to the development of new climate proxies. Here, we show for the first time that extensive spatial mapping of multiple mollusc specimens using Laser Induced Breakdown Spectroscopy (LIBS) across a wider region can resolve enigmatic patterns within the elemental record caused by physiological influences. 2D elemental (Mg/Ca) maps of whole limpet shells (Patella caerulea) from across the Mediterranean revealed patterns of variability within individual mollusc records as well as within isochronous parts of specimens. By registering and quantifying these patterns, we established previously uninterpretable correlations with temperature (R² > 0.8, p < 0.01). This outcome redefines the possibilities of accessing sub-annual climate proxies and presents the means to assess annual temperature ranges using oxygen isotope analysis requiring only 2 samples per shell.

Records of past environmental conditions in shell carbonate are usually derived from compositional analysis (i.e. trace elements, stable oxygen, carbon, and nitrogen isotopes) performed along the direction of the shell's growth and thus through time. However, compositional variations within isochronous parts of the shell can distort the environmental record and are difficult to assess without extensively mapping the whole shell. Here we apply Laser Induced Breakdown Spectroscopy (LIBS) to efficiently map the elemental change throughout the growth increments of three mollusc shells (Conomurex fasciatus, Ostrea edulis, Anomalocardia flexuosa). We employ an automated LIBS setup to map the Mg/Ca composition of whole shell sections with over 2000 data points per hour. By assessing the spatial variability of Mg/Ca intensity ratios this method has the potential to mitigate distorted results while increasing the resolution of derived palaeoenvironmental information.