Prussian blue is a pigment highly sensitive to electromagnetic radiation, visible light included. This photosensitivity, associated with a complex redox behavior, causes a vulnerability even to Raman lasers, with the possibility of sample alteration or irreversible damage. In this study, we systematically explored the influence of the laser wavelength and laser power on different types of Prussian blue pigments, soluble and insoluble. The use of different laser wavelengths does not influence the position of the characteristic peak, though it affects the signal‐to‐noise ratio. The latter can be improved by increasing the number of accumulations and/or the acquisition time. Furthermore, we evaluated a safe level of Raman laser excitation or “safe zone” with laser power between 0.005 and 0.06 mW, where Raman analysis can be performed without laser‐induced artifacts or damage for the sample. These artifacts may affect the characteristic spectral signature of the two different Prussian blue, leading to a wrong identification of the pigments. Moreover, artifacts can also hide features arisen from fading in objects presenting non‐visible alterations of Prussian blue.

Beside its promising applications in the design of multifunctional materials, batteries and biosensors, the pigment Prussian blue is still studied in heritage science because of its capricious fading behavior due to a complex light-induced redox mechanism. We studied model heritage materials composed of Prussian blue embedded into a cellulosic fiber substrate by means of X-ray absorption near-edge spectroscopy. Significant X-ray radiation damage was observed and characterized. X-ray radiation induced first a reduction of Prussian blue, in a similar way to what visible light does, followed by a complete degradation of the pigment and the formation of iron(III) oxyhydroxide. We took advantage of this X-ray photochemistry to investigate in depth the redox behavior of Prussian blue. We could particularly demonstrate that the rate, extent, and quality of Prussian blue photoreduction can be tuned by modifying the pH and alkali cation content of the cellulosic substrate. The present study represents a step further in the understanding of Prussian blue heritage materials from an electrochemical viewpoint and provides evidence of substrate-mediated photochemistry applicable to a wider class of Prussian blue composite materials.

Extra virgin olive oil (EVOO) is defined as a functional food as it contains numerous phenolic components with well-recognized health-beneficial properties, such as high antioxidant and anti-inflammatory capacity. These characteristics depend on their structural/conformational behavior, which is largely determined by intra- and intermolecular H-bond interactions. While the vibrational dynamics of isolated compounds have been studied in a number of recent investigations, their signal in a real-life sample of EVOO is overwhelmed by the major constituent acids. Here, we provide a full characterization of the vibrational spectroscopic signal from commercially available EVOO samples using Inelastic Neutron Scattering (INS) and Raman spectroscopies. The spectra are dominated by CH2 vibrations, especially at about 750 cm−1 and 1300 cm−1. By comparison with the spectra from hydroxytyrosol and other minor phenolic compounds, we show that the best regions in which to look for the structure–activity information related to the minor polar compounds is at 675 and 1200 cm−1 for hydroxytyrosol, and around 450 cm−1 for all minor polar compounds used as reference, especially if a selectively deuterated sample is available. The regional origin of the EVOO samples investigated appears to be related to the different amount of phenolic esters versus acids as reflected by the relative intensities of the peaks at 1655 and 1747 cm−1.

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