An experimental study on an innovative contrast agent is presented. This work demonstrates that c... more An experimental study on an innovative contrast agent is presented. This work demonstrates that copper sulfide in the form of small-sized nanoparticles can be exploited in photoacoustic imaging. An advantage of this material is strong light absorption in the near-infrared range, especially in the transparency windows of biological tissues. In order to yield a proper contrast, light absorption must be followed by heat release with high efficiency. Therefore, it is important to evaluate the photochemical conversion efficiency of the material. We applied a method that is strictly related to photoacoustic applications. The nanoparticles were produced according to a well-established synthesis. Subsequently, they were diluted in pure water to obtain an extinction <0.2/cm at 1064 nm. The photoacoustic signals, generated by 1064 nm laser excitation, were analyzed as a function of concentration and incident laser energy below 70 μJ /pulse. The signals were carefully compared with those of...
Madder lake is the most utilized anthraquinone dyestuff in artworks. Its main constituents (aliza... more Madder lake is the most utilized anthraquinone dyestuff in artworks. Its main constituents (alizarin and purpurin, together with other natural dyes) form an organometallic complex (the lake) insoluble in water by precipitation or adsorption of the dye onto an inorganic substrate. Raman spectra of madder lake are strongly affected by fluorescence, making its identification by Raman spectroscopy difficult or impossible. In this work, we prepared different lakes according to historical recipes and characterized them with X-ray diffraction (XRD), IR, and UV-Visible spectroscopies. Additionally, painting mock-ups were prepared and the lakes were extracted with hydrated and ethanol-rich agar gel beads. This work is aimed at showing the advantages and limits for the identification of the madder lake constituents by Raman and SERS (Surface-Enhanced Raman Spectroscopy) methods in the hydrogels used for sample micro-extraction. The main advantage of SERS for madder lake detection is to allow ...
We used Raman spectroscopy combined with multivariate analysis to study noninvasively naturally a... more We used Raman spectroscopy combined with multivariate analysis to study noninvasively naturally and artificially aged samples of silk and wool fibres dyed with turmeric and saffron dyes, following historical recipes. The Raman spectra obtained from all the samples using the two excitation lasers (785 and 1064 nm) showed the characteristic peaks of each dye and fibre. The 1064‐nm macro FT‐Raman offered more information regarding the degradation of the fibre substrate, whereas the μ‐Raman at 785‐nm spectra proved more suitable in the identification of dye characteristic peaks. We also performed colorimetric measurements to evaluate the colour change upon artificial ageing and compared them with the information obtained with Raman spectroscopy. The results suggest saffron has a higher lightfastness than turmeric and that silk fibres suffer higher fading and more evident degradation than wool. Raman spectroscopy informs about the chemical composition of the colourants and fibres and the...
An experimental study on an innovative contrast agent is presented. This work demonstrates that c... more An experimental study on an innovative contrast agent is presented. This work demonstrates that copper sulfide in the form of small-sized nanoparticles can be exploited in photoacoustic imaging. An advantage of this material is strong light absorption in the near-infrared range, especially in the transparency windows of biological tissues. In order to yield a proper contrast, light absorption must be followed by heat release with high efficiency. Therefore, it is important to evaluate the photochemical conversion efficiency of the material. We applied a method that is strictly related to photoacoustic applications. The nanoparticles were produced according to a well-established synthesis. Subsequently, they were diluted in pure water to obtain an extinction <0.2/cm at 1064 nm. The photoacoustic signals, generated by 1064 nm laser excitation, were analyzed as a function of concentration and incident laser energy below 70 μJ /pulse. The signals were carefully compared with those of...
Madder lake is the most utilized anthraquinone dyestuff in artworks. Its main constituents (aliza... more Madder lake is the most utilized anthraquinone dyestuff in artworks. Its main constituents (alizarin and purpurin, together with other natural dyes) form an organometallic complex (the lake) insoluble in water by precipitation or adsorption of the dye onto an inorganic substrate. Raman spectra of madder lake are strongly affected by fluorescence, making its identification by Raman spectroscopy difficult or impossible. In this work, we prepared different lakes according to historical recipes and characterized them with X-ray diffraction (XRD), IR, and UV-Visible spectroscopies. Additionally, painting mock-ups were prepared and the lakes were extracted with hydrated and ethanol-rich agar gel beads. This work is aimed at showing the advantages and limits for the identification of the madder lake constituents by Raman and SERS (Surface-Enhanced Raman Spectroscopy) methods in the hydrogels used for sample micro-extraction. The main advantage of SERS for madder lake detection is to allow ...
We used Raman spectroscopy combined with multivariate analysis to study noninvasively naturally a... more We used Raman spectroscopy combined with multivariate analysis to study noninvasively naturally and artificially aged samples of silk and wool fibres dyed with turmeric and saffron dyes, following historical recipes. The Raman spectra obtained from all the samples using the two excitation lasers (785 and 1064 nm) showed the characteristic peaks of each dye and fibre. The 1064‐nm macro FT‐Raman offered more information regarding the degradation of the fibre substrate, whereas the μ‐Raman at 785‐nm spectra proved more suitable in the identification of dye characteristic peaks. We also performed colorimetric measurements to evaluate the colour change upon artificial ageing and compared them with the information obtained with Raman spectroscopy. The results suggest saffron has a higher lightfastness than turmeric and that silk fibres suffer higher fading and more evident degradation than wool. Raman spectroscopy informs about the chemical composition of the colourants and fibres and the...
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