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In the field of book heritage, it is important to develop cleaning/disinfecting treatments that can slow down the degradation of paper to prevent evident and irreversible damage. The objectives of the cleaning treatments are to remove external contaminants and oxidation and decomposition products of the paper, but these processes must not modify the unique characteristics of the book heritage resulting in irreversible changes in the structure of the paper. Recently, several innovative cleaning treatments were developed with the aim of being minimally invasive; however, to assess the effect of these treatments on paper, it is necessary to use a diagnostic non-destructive, rapid, and affordable process. In previous work, we used surface scanning Raman spectroscopy to develop a diagnostic protocol able to follow the aging processes of the paper, discriminating between hydrolysis and oxidation. In this paper, we applied this protocol to study the action of different types of treatments (hydrogel and EUV irradiation), evaluating both their effectiveness and impact on paper parameters. The results reported here demonstrate that the developed in operando diagnostic procedure can follow the changes in the paper structure comparing them to the variability due to the intrinsic inhomogeneity of paper, without sample contact in a rapid and effective way.

Lithium fluoride (LiF) film detectors for extreme ultraviolet radiation, soft and hard X-rays, based on the photoluminescence of radiation-induced electronic defects, have been proposed and are currently under further development and investigation. LiF film detectors are versatile and can be integrated in different experimental apparatus and imaging configurations. LiF can be grown in the form of polycrystalline thin films and it is compatible with several substrates. The radiation-induced color center (CCs) photoluminescence (PL) response can be enhanced through the appropriate choice of substrates and multilayer designs, and by tailoring the micro-structural properties of polycrystalline LiF films through the control of the growth conditions. In this work, we present the characterization, through fluorescence and Raman micro-spectroscopy, of LiF films, thermally evaporated on different substrates with thicknesses of up to 1 μm, irradiated with soft X-rays produced by a laser plasma source. The combination of these micro-spectroscopy techniques could represent an advanced method to investigate the role of the polycrystalline film structures in CC formation efficiency at the microscopic level, a fundamental aspect of the development of LiF film radiation-imaging detectors.

In recent years, there has been an open debate on proper sun exposure to reduce the risk of developing skin cancer. The mainly encountered issue is that general guidelines for UV radiation exposure could not be effective for all skin types. The implementation of customized guidelines requires a method by which to measure the UV dose as a result of daily exposure to sunlight, ideally with an inexpensive, easy-to-read sensor. In this work, we present the characterization of nanocomposite hydrogel materials acting as colorimetric sensors upon exposure to UV light. The sensor was prepared using a poly(acrylic acid) (PAA) hydrogel matrix in which TiO2 nanoparticles and methylene blue (MB) were integrated. Raman mapping was used to determine the network structure of the hydrogel and its water distribution. The TiO2 nanoparticles dispersed in the PAA matrix maintain their photoactivity and catalyze a reaction by which methylene blue is converted into leuko-methylene. The conversion causes a discoloration effect that is visible to the naked eye and can therefore be used as an indicator of UV radiation exposure. Moreover, it was possible to tune the discoloration rate to the limit exposure of each skin type, simply by changing the ratio of titanium dioxide to dye. We obtained a response time ranging from 30 min to 1.5 h. Future work will be dedicated to the possibility of scaling up this range and to improve the sensor wearability; however, our study paves the way to the realisation of sensors suitable for public use, which could help us find a solution to the challenge of balancing sufficient UV exposure to prevent Vitamin D deficiency with excessive UV exposure that could ultimately cause skin cancer.

Micro-Raman and luminescence spectroscopy were combined with morphological analysis to study the conservation state of differently degraded paper samples, dated from 1873 to 2021. The aim of the work reported in this paper was to obtain ageing markers based on variations of Raman and fluorescence spectral features. Raman and luminescence spectra were acquired by scanning non-printed areas of books, and Raman and fluorescence maps were built by contrasting spectral parameters point by point, obtaining a micron-scale space resolved imaging of the degradation pattern. Complementary information on paper morphology and surface compactness were obtained by high-resolution scanning electron and atomic force microscopy. The proposed non-destructive procedure is particularly interesting for precious and ancient samples to analyze their degradation processes and to evaluate the performance and effectiveness of restoration treatments.

Radiation-induced color centers locally produced in lithium fluoride (LiF) are successfully used for radiation detectors. LiF detectors for extreme ultraviolet radiation, soft and hard X-rays, based on photoluminescence from aggregate electronic defects, are currently under development for imaging applications with laboratory radiation sources, as well as large-scale facilities. Among the peculiarities of LiF-based detectors, noteworthy ones are their very high intrinsic spatial resolution across a large field of view, wide dynamic range, and versatility. LiF crystals irradiated with a monochromatic 8 keV X-ray beam at KIT synchrotron light source (Karlsruhe, Germany) and with the broadband white beam spectrum of the synchrotron bending magnet have been investigated by optical spectroscopy, laser scanning confocal microscopy in fluorescence mode, and confocal Raman micro-spectroscopy. The 3D reconstruction of the distributions of the color centers induced by the X-rays has been performed with both confocal techniques. The combination of the LiF crystal capability to register volumetric X-ray mapping with the optical sectioning operations of the confocal techniques has allowed performing 3D reconstructions of the X-ray colored volumes and it could provide advanced tools for 3D X-ray detection.

Surface-enhanced Raman spectroscopy (SERS) measurements of some common military explosives were performed with a table-top micro-Raman system integrated with a Serstech R785 miniaturized device, comprising a spectrometer and detector for near-infrared (NIR) laser excitation (785 nm). R785 was tested as the main component of a miniaturized SERS detector, designed for in situ and stand-alone sensing of molecules released at low concentrations, as could happen in the case of traces of explosives found in an illegal bomb factory, where solid microparticles of explosives could be released in the air and then collected on the sensor’s surface, if placed near the factory, as a consequence of bomb preparation. SERS spectra were obtained, exciting samples in picogram quantities on specific substrates, starting from standard commercial solutions. The main vibrational features of each substance were clearly identified also in low quantities. The amount of the sampled substance was determined through the analysis of scanning electron microscope images, while the spectral resolution and the detector sensitivity were sufficiently high to clearly distinguish spectra belonging to different samples with an exposure time of 10 s. A principal component analysis procedure was applied to the experimental data to understand which are the main factors affecting spectra variation across different samples. The score plots for the first three principal components show that the examined explosive materials can be clearly classified on the basis of their SERS spectra.