Development of an efficient and thermally controlled Raman system for fast and safe molecular characterization of paint layers

An innovative high-efficiency Raman system (exc. wav. 1064 nm) for safe molecular characterization of paint layers and other photosensitive materials has been developed and successfully tested. It was equipped with a novel optical probe, which has been designed and built in order to perform Raman scattering measurements on a relatively large spot at laser intensities lower than the typical ones of the commercial instruments. Original optical solutions were implemented in order to achieve such improved efficiency. Furthermore, the instrument was also equipped with an active thermal control line allowing to prevent alterations of the material under study and to optimize the measurement cycles by means of suitable modulations of the laser power. Comparative tests using the novel analytical tool and an alternative setup based on a commercial Raman probe were carried out on a set of pure pigments and oil paint layers, which allowed assessing the significantly higher efficiency and reliability of the former with respect to the latter

Temperature-controlled portable Raman spectroscopy of photothermally sensitive pigments

In this work, an innovative NIR Raman device (excitation wavelength at 1064 nm) was developed in order to avoid thermal stress and consequent chemical alterations of the materials analyzed. In particular, we devised and tested for the first time a sensored Raman probe allowing for temperature-controlled measurements based on a thermoelectric sensor providing the feedback signal for suitably modulating the output power of the laser source and then limiting undesired heating effects within the irradiated volume. The experimentation was carried out on cinnabar, lead white and indigo pigments frequently used during the past centuries, which presents pronounced photothermal instability. The results achievedin a set of instrumental and analytical tests using different measurement control parameters allowed demonstrating the effectiveness and reliability of the present approach for preventing thermal alterations effects during Raman spectroscopy and speeding the measurements, as well as for monitoring spectral variations associated with the crystals anharmonicity over large temperature ranges. These features alongwith the portability of the novel device can make in situ Raman characterisation of valuable paintedsurfaces including photosensitive materials very safe and efficie

Detection of the Glass Transition of Polymers Used in Art and Art-Conservation Using Raman Spectroscopy

In this work, Raman spectroscopy was employed for the detection of the glass transition temperatures (Tg) of some thermoplastic polymers and natural terpenoid resins. In particular, our attention was focused on evaluating the Tg of polystyrene and colophony. The measurements returned Tg values in accordance with those reported in the literature obtained using the DSC technique, thus confirming the reliability of the approach proposed herein. Further studies will be focused on the evaluation of Tg temperature changes depending on materials treatments and ageing

Reply: Choice of ART programme for serodiscordant couples with an HIV-infected male partner

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Optical Absorption Spectroscopy for Quality Assessment of Extra Virgin Olive Oil

Space scienc

Automated characterization of varnishes photo-degradation using portable T-controlled Raman spectroscopy

In this work, a portable-Raman device (excitationwavelength 1064 nm)was employed for the first time for continuously monitoring the complex molecular dynamics of terpenoid resins (dammar, mastic, colophony, sandarac and shellac), which occur during their ageing under artificial light exposure. The instrumentation was equipped with a pyroelectric sensor allowing for temperature control of the sample's irradiated surface while the acquisition of spectra occurs by setting fixed maximum temperature and total radiant exposure. Resins were dropped into special pits over a dedicated rotating wheelmoved by a USB motor. The rotation allowed samples sliding between the positions designated for the acquisition of the Raman spectra and that for artificial ageing. Samples were exposed to artificial light for 45-days and almost 400 spectra for each resin sample were collected. The exposure to artificial light led to significant changes allowing the characterization of the alteration process. The automated acquisition of a large number of spectra overtime during light-exposure has given the possibility to distinguish fast dynamics,mainly associated to solvent evaporation, fromthose slower due to resins photo-degradation processes

Near-infrared spectroscopy and pattern-recognition processing for classifying wines of two Italian provinces

This paper presents an experiment making use of the near-infrared spectrum for distinguishing the wines produced in two close provinces of Abruzzo region of Italy. A collection of 32 wines was considered, 18 of which were produced in the province of Chieti, while the other 14 were from the province of Teramo. A conventional dual-beam spectrophotometer was used for absorption measurements in the 1300-1900 nm spectroscopic range. Principal Component Analysis was used for explorative analysis. Score maps in the PC1-PC2 or PC2-PC3 spaces were obtained, which successfully grouped the wine samples in two distinct clusters, corresponding to Chieti and Teramo provinces, respectively. A modelling of dual-band spectroscopy was also proposed, making use of two LEDs for illumination and a PIN detector instead of the spectrometer. These data were processed using Linear Discriminant Analysis which demonstrated satisfactory classification result

Light scattering measurements for quantifying biological cell concentration: an optimization of opto-geometric parameters

An experimental study was carried out, aimed at optimizing the optical/geometrical configuration for measuring the concentration of biological cells by means of static light scattering measurements. A LED-based optoelectronic setup making use of optical fibers was experimented, as the precursor of a low-cost device to be integrated in instrumentation for cytometry. Two biological sample types were considered as test samples of the most popular analyses – cervical cells and urine, respectively. The most suitable wavelengths and detecting angles were identified, and calibration curves were calculated