Editorial for the special issue on nanostructure based sensors for gas sensing: From devices to systems

The development of solid state gas sensors based on microtransducers and nanostructured sensing materials is the key point in the design of new portable measurement systems with sensing and identification performances comparable with those of most sophisticated analytical techniques. In such a context, a lot of effort must be spent of course in the development of the sensing material, but also in the choice of the transducer mechanism and structure, in the electrical characterization of the sensor prototypes, as well as in the design of suitable measurement setups. [...]

Modified POF Sensor for Gaseous Hydrogen Fluoride Monitoring in the Presence of Ionizing Radiations

This paper describes the development of a sensor designed to detect low concentrations of hydrogen fluoride (HF) in gas mixtures. The sensor employs a plastic optical fiber (POF) covered with a thin layer of glass- like material. HF attacks the glass and alters the fiber transmission capability so that the detection simply requires a LED and a photodiode. The coated POF is obtained by means of low-pressure plasma-enhanced chemical vapor deposition that allows the glass-like film to be deposited at low temperature without damaging the fiber core. The developed sensor will be installed in the recirculation gas system of the resistive plate chamber muon detector of the Compact Muon Solenoid experiment at the Large Hadron Collider accelerator of the European Organization for Nuclear Research (CERN

Sodium lactate solutions characterization using Electrochemical Impedance Spectroscopy

Lactate is an important metabolite in human body and, among possible medical applications, it can be used to monitor physical activity. Actually, its concentration represents a clear indication whether optimal training intensity is kept or if muscles are under anaerobic conditions. Routine procedures to measure lactate concentration during physical activity are represented by invasive measurements, which require blood sampling from the patient or the athlete. So, a great advantage would be derived by the possibility to monitor this analyte using non-invasive techniques. Considering the possibility to measure lactate in human sweat during sport activities, this paper presents the characterization of saline aqueous solutions containing sodium lactate by means of Electrochemical Impedance Spectroscopy (EIS). Measurements were performed using a two-electrode electrochemical cell and acquired spectra were analyzed also by means of equivalent electrical circuit (EEC) modeling. Results show an effect due to lactate concentration on solution impedance in the high-frequency region of spectrum, where a change in solution resistance is measured. At the same time, no changes in the measured capacitance were found. Future work will study the electrochemical behavior of lactate solutions also at higher frequencies to further investigate the possible use of EIS for lactate levels monitoring during sport activities

Raman spectroscopic characterization of corrosion products of archaeological iron

Raman spectroscopy is a versatile analytical technique which allows the detection of different molecules analysing the vibrational modes. As a matter of facts, the vibrational frequencies are typical of a specific chemical bond or of a structural symmetry. In this study, the Raman technique is used for the determination of iron corrosion products, mainly oxides and hydroxides. Metallic artefacts buried in soil are affected, in dependence of their electrochemical nobility, by corrosion phenomena of various entities, which partially modify their chemical composition and their structure. The process may occur both during burial time and after the extraction from the archaeological site, implying the potential loss of information about the metallurgical technology and structure of the object. The study of the corrosion phenomena allows to propose tailored strategies for the restoration and conservation of the artefacts, especially in view of the storage of the artefacts in a museum. This study validates the use of the Raman technique for this purpose, showing its efficiency in the identification of the iron corrosion products in favourable conditions for the analysis of Cultural Heritage artefacts, as the possibility of performing in situ analysis without the need of a previous sample preparation

Provenance, manufacturing and corrosion behavior of Ancient Hellenistic coins from Egypt

Some copper alloy coins of the Ptolemaic period from a private collection, providing valuable evidence for both archaeometric as well as materials science and corrosion studies, have been investigated. The coins were found in the ancient city of Bubastis, known as Tell Basta, in the Nile Delta, Egypt. The coins have been examined by optical microscopy for their metallurgical structure, analysed by X-ray fluorescence and Electron Dispersion Spectroscopy for their composition, and by X-ray diffraction for the characterisation of their corrosion products. An attempt has been made to remove part of their corrosion products by mild chemical cleaning procedures. In some areas the coins are heavily corroded by chlorides, however most of the inscriptions on the coins themselves are still decipherable. Assumptions are made on the coins provenance, the production period, the manufacturing technique and the burial environmental conditions

Environmental monitoring solution for cultural heritage

Environmental monitoring is crucial factor in the safeguard and conservation of the cultural heritage. Unsuitable environmental conditions can easily accelerate the degradation of several materials and, as consequence, damage the stored artifacts. Moreover, environmental conditions can easily change in an unpredictable way and, therefore, the employment of an environmental monitoring system is mandatory in almost all locations, including museums, storage rooms and outdoor exhibitions. This paper tries to explain the main constraints required for environmental monitoring in the cultural heritage field. Moreover, a novel distributed monitoring system, developed at Politecnico di Torino, is described and compared to several solutions that are commercially available. The proposed solution demonstrated excellent characteristics which satisfy the requirements of environmental monitoring in the cultural heritage at a very competitive cost

Vanillin-Based Photocurable Anticorrosion Coatings Reinforced with Nanoclays

This study investigates the chemical-physical properties and anticorrosion effectiveness of UV-cured coatings produced using epoxidized vanillin (DGEVA) as biobased precursor, then reinforced by the addition of nanoclay. After optimizing the UV-curing parameters of three different formulations by Fourier transform infrared spectroscopy (FTIR), the thermo-mechanical properties of the coatings are assessed by differential scanning calorimetric analysis (DSC), dynamic thermal mechanical analysis (DTMA), and pencil hardness. The coatings are applied on mild steel substrates and then their barrier properties are investigated by electrochemical impedance spectroscopy measurements, immersing the samples in 3.5 wt% NaCl aerated solutions. The results show the good corrosion protective effectiveness of the biobased coatings. The nanoclay addition has a beneficial effect, as it hinders the diffusion of the aggressive ions from the electrolyte solution to the metal substrate. The reported findings demonstrate the possibility of using biobased precursors and UV-curing technology to reduce the environmental impact of the coating industry.A photocurable epoxy composite is realized using epoxidized vanillin (DGEVA) as a biobased precursor, and functionalized nanoclay as filler. The coating shows good thermo-mechanical properties, high chemical resistance, and satisfactory corrosion protection effectiveness in aggressive environments containing chlorides. imag

A low-cost automatic acquisition system for photogrammetry

Photogrammetry is a non-destructive technique commonly employed in the cultural heritage field for reconstructing a 3D virtual replica of an artifact by simply taking several photos of the artifact itself from different points of view. The 3D model can be used either for documenting the artifact or for preserving its geometrical information and appearance. Moreover, by using a digital 3D model is extremely easy sharing information with the public and researchers without physically moving the artifact, and this represents a unique opportunity which cannot be achieved with traditional methods. Unfortunately most systems already present on the market are complex and costly both due to their hardware and software. This paper presents a novel acquisition system which is extremely cheap and can be easily arranged in any conservation laboratory. The solution is based on a simple acquisition system designed with the aim of providing researchers with a user-friendly and low-cost platform for the reconstruction of an artifact 3D model. The proposed system can be virtually interfaced to every commercial camera and can be integrated with several 3D reconstruction software. As an example, the authors employed a free open-source software referred to as Meshroom

Assessment of material-atmosphere interactions during scanning laser cleaning of archaeological bronze alloys: A Roman coin case study

The main goal of this research was to assess the presence of possible reoxidation phenomena during laser cleaning procedures carried out on Cu-based archaeological artefacts. Previous studies conducted on archaeological and artificial corrosion layers, highlighted that the laser ablation procedures (removal of unwanted materials) do not change the composition of the corrosion layers and that detectable re-oxidation phenomena occur on laser-treated surfaces for intense laser conditions, not applicable on Cultural Heritage artefacts. A novel approach, recently developed on Material Science field by these Authors, is here applied in the Conservation Science field: the use of a traceable isotope combined with Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) on an archaeological bronze coin. This approach, applied for the first time on an archaeological artefact, allows assessing the presence of possible re-oxidation phenomena that might occur on object surfaces during optimised cleaning procedures

Properties of potential eco-friendly gas replacements for particle detectors in high-energy physics

Gas detectors for elementary particles require F-based gases for optimal performance. Recent regulations demand the use of environmentally unfriendly F-based gases to be limited or banned. This work studies properties of potential eco-friendly gas replacements by computing the physical and chemical parameters relevant for use as detector media, and suggests candidates to be considered for experimental investigation