No abstract

No abstract

Scientific analyses of ancient glasses have been carried out for many years using elemental chemical analysis. However, it is known that the control of the redox conditions in the glass melt has a strong implication on the final hue of glass because it affects Fe2+/ΣFe. Therefore an increasing number of studies on the redox conditions have been published in recent years by means of synchrotron based X-ray absorption spectroscopy. This is a technique which is not easily accessible and requires dedicated facilities. In this paper we describe an alternative approach by means of optical absorption spectroscopy. We synthesised 10 soda-lime-silica glasses with known redox conditions and iron concentration to calibrate the absorption at 1100 nm as a function of Fe2+ concentration. The linear extinction coefficient was also determined. These glasses were also studied by means of X-ray Absorption Near Edge Structure (XANES) spectroscopy. Electron paramagnetic resonance spectroscopy was additionally used as an ancillary method to verify the quality of our data. Furthermore 28 samples from real archaeological samples were analysed by XANES and optical spectroscopy as a case study. The Fe2+/ΣFe values obtained were compared and demonstrated that the two techniques were in good agreement with each other. Optical spectroscopy can be applied in situ with moderate sample preparation to determine the concentration of Fe2+. To investigate the redox conditions, especially as a first screening approach, this methodology is an important tool to take into consideration before applying more sophisticated techniques such as XANES, which is more elaborate and requires high-tech resources

No abstract

Raman spectroscopy has been used to identify iron-containing glasses. This nondestructive technique offers a fast method to obtain qualitative information about the presence of iron oxides in glass. The effect of the iron content in glass samples is reflected on the topology of the Raman spectra: A strong link between the ratio of the Q 2 /Q 3 vibration units of the silica tetrahedral structure is seen. If matrix effects are taken into account, also (semi)quantitative results can be obtained from the calibration lines. The linear calibration is based on the normalized band intensity at 980 cm −1 (I 980 /I 1090 ) and the iron oxide concentration for similar glasses. In amber and dark colored glasses, an extra peak in the spectrum indicates the presence of a FeS chromophore. Different series of glasses of various origins (ancient and modern/industrial glass) have been considered.

Civilized societies should safeguard their heritage as it plays an important role in community building. Moreover, past technologies often inspire new technology. Authenticity is besides conservation and restoration a key aspect in preserving our past, for example in museums when exposing showpieces. The classification of being authentic relies on an interdisciplinary approach integrating art historical and archaeological research complemented with applied research. In recent decades analytical dating tools are based on determining the raw materials used. However, the traditional applied non-portable, chemical techniques are destructive and time-consuming. Since museums oftentimes only consent to research actions which are completely non-destructive, optical spectroscopy might offer a solution. As a case-study we apply this technique on two stained glass panels for which the 14th century dating is nowadays questioned. With this research we were able to identify how simultaneous mapping of spectral signatures measured with a low cost optical spectrum analyser unveils information regarding the production period. The significance of this research extends beyond the re-dating of these panels to the 19th century as it provides an instant tool enabling immediate answering authenticity questions during the conservation process of stained glass, thereby providing the necessary data for solving deontological questions about heritage preservation.

We propose a semianalytical method to model, in both two and three dimensions (2D and 3D, respectively), the radiation emission of quantum emitters (QEs) interacting with nanopatterned structures. We then investigate the emission from QEs near a hyperbolic metamaterial (HMM) with a metallic cylindrical grating on its top and a poly(methyl methacrylate) substrate embedded with QEs on its bottom. The optimization of the cylindrical grating is carried out first using a 2D model (due to its low computational cost), followed by a performance study based on a 3D model. We show that an appropriate choice of grating parameters (period, height, and fill factor) allows not only the control of the QE emission direction but also the increase of both the Purcell factor and the total power coupled from the HMM into free space. In addition, the proposed method provides a detailed mapping of both the Purcell factor and the radiated power as a function of position, enabling us to understand how the QE location affects its behavior. Furthermore, we demonstrate that the QEs with the highest Purcell factor (viz., perpendicularly polarized ones) contribute more to the power radiated into the far field than previously expected. We also show that, in addition to a high Purcell factor of about 145, perpendicularly polarized QEs radiate up to 2 times more power if placed 10 nm from the HMM as they would in free space.

In the 1st–2nd century AD, glass was made black using strongly reducing conditions. Later, the black appearance was obtained adding an excess of colourant rather than controlling the furnace atmosphere.