Characterization of fresh and aged natural ingredients used in historical ointments by molecular spectroscopic techniques: IR, Raman and fluorescence

Multi-analytical characterisation of blotting sands on documents from religious orders in Portugal (16th-19th centuries)

Too little is known about areia de escrever, i.e., blotting sands, the intriguing particles sprinkled on freshly written scripts to accelerate the drying time of the ink. Blotting sands constitute a valuable but underestimated historical source. This work investigated the blotting sands used on the account books of the religious houses scattered across continental Portugal and Madeira Island (16th-19th centuries). The sands were mainly composed of different minerals, predominately black sands, but in a few cases, minerals were found mixed with gums, paper cocoons or bone shavings. The combined use of SEM-EDS, µ-Raman and FT-IR techniques uncovered the materials' chemical or mineralogical composition and morphology. This approach, allied with image analysis and statistics complemented with multivariate analysis, allowed us to look for trends between the samples and hypothesise about their provenance. Heavy minerals, such as ilmenite, hematite and almandine, were identified as major components, together with other silicates (e.g. quartz). Samples were dominated by medium-sized grains with shape features indicating texturally mature sediments resulting from a medium-to-long sedimentary transport. Due to shorter geological transport distances, Madeira Island was the exception, with more angular grains. This work allowed us to uncover blotting sands, value them as historical sources, and establish a roadmap for their use in Portugal, aiming to pave the way towards a more global context in Europe.

A review on tragacanth gum: A promising natural polysaccharide in drug delivery and cell therapy

Tragacanth is an abundant natural gum extracted from wounds created in some plants and is dried for use in various applications from industry to biomedicines. It is a cost-effective and easily accessible polysaccharide with desirable biocompatibility and biodegradability, drawing much attention for use in new biomedical applications such as wound healing and tissue engineering. Moreover, this anionic polysaccharide with a highly branched structure has been used as an emulsifier and thickening agent in pharmaceutical applications. In the following, this gum has been interested as an appealing biomaterial for producing engineering tools in drug delivery. Furthermore, the biological properties of tragacanth gum have made it a favorable biomaterial in cell therapies, especially for bone tissue engineering. This review aims to discuss the recent studies on this natural gum as a potential carrier for different drugs and cells.

Multi-Analytical Assessment of Bodied Drying Oil Varnishes and Their Use as Binders in Armour Paints

The characteristics of commercially available refined and bodied linseed and tung oils, used as binders in the production of armour paints after historic recipes, are explored. Employed as anticorrosive paints mainly from the 1920s to 1960s, armour paints are greener alternatives that can be used for protection in industrial heritage conservation. Using a multi-analytical approach, chemical and physical properties of the fresh oils and solid films before and after accelerated ageing (ISO 16474-2:2013) were investigated to better understand which features are beneficial for the technical function of armour paints. Tests included measurements of density, the refractive index, insoluble impurities, alkaline impurities, the water content, the iodine value, the saponification value, the free fatty acid concentration, the acid value, the peroxide value and colour (Lovibond) and cold tests. The characterisation of the fresh oils using molecular analysis with FTIR and GC-MS revealed the complexity of the commercial formulations, for which additions of semi- and non-drying oils were detected. The results show that organic paint binders follow complex chemical reactions (such as oxidation and decrease of unsaturation being variable or swelling following water-immersion tests), with implications for their suitability for use in protection.

Analytical Techniques for the Preservation of Cultural Heritage: Frontiers in Knowledge and Application

Chemistry is considered as the heart of preservation science. The archaeological objects are an organic-inorganic system and need comprehensive techniques to investigate the different materials with a high resolution and accuracy. The characterization process of archaeological materials is a useful guide to develop the right strategy for the conservation and intervention of the objects. In analytical chemistry practice, there are many techniques to employ the characterization process of the artworks: molecular, elemental, imaging, surface, thermal, separation, nuclear, dating, electrochemical, and miscellaneous techniques. It highlights the potential of chemical investigations to present reliable information to the conservators and art historians.

Spectroscopic Methods in the Evaluation of Modified Vegetable Base Oils from Crambe abyssinica

Raw vegetable oil from Crambe abyssinica was subjected to oxidative treatment to enhance its viscosity. The oxidation processes were carried out in the presence of N-hydroxyphthalimide with or without supercritical CO₂ as a solvent. Four spectroscopic techniques (Raman, UV-VIS, FT-IR, NMR) were applied to assess the chemical changes taking place during the oxidation. Raman and NMR spectroscopy proved best in the assessment of the chemical transformations leading to increased viscosity of the modified vegetable oil.

A review on the application of vibrational spectroscopy to the chemistry of nuts

Nuts are highly appreciated due to their nutritional relevance and flavour, being the source of many desirable and healthy compounds as polyunsaturated fatty acids and antioxidants. Their characterization became the target of many studies in the last years through conventional analytical techniques as chromatographic ones. Due to the limitations associated to these techniques, as time, cost and environmental concerns, spectroscopic techniques have been increasingly pointed as reliable alternatives. Either applied to raw materials quality control or to more complex process, as industrial in-line monitoring, spectroscopic techniques, namely vibrational spectroscopy, are gathering strong acceptance. This paper presents a review on the application of vibrational spectroscopy, infrared and Raman, to nuts characterization. Estimates of several qualitative and quantitative parameters, origin authentication and/or adulteration in almonds, peanuts, pine nuts, hazelnuts, walnuts, Brazil nuts, cashews, chestnuts and pistachios will be covered. Advantages and limitations of these techniques and future trends will also be discussed.

A Photoluminescence Study of the Changes Induced in the Zinc White Pigment by Formation of Zinc Complexes

It is known that oil paintings containing zinc white are subject to rapid degradation. This is caused by the interaction between the active groups of binder and the metal ions of the pigment, which gives rise to the formation of new zinc complexes (metal soaps). Ongoing studies on zinc white paints have been limited to the chemical mechanisms that lead to the formation of zinc complexes. On the contrary, little is known of the photo-physical changes induced in the zinc oxide crystal structure following this interaction. Time-resolved photoluminescence spectroscopy has been applied to follow modifications in the luminescent zinc white pigment when mixed with binder. Significant changes in trap state photoluminescence emissions have been detected: the enhancement of a blue emission combined with a change of the decay kinetic of the well-known green emission. Complementary data from molecular analysis of paints using Fourier transform infrared spectroscopy confirms the formation of zinc carboxylates and corroborates the mechanism for zinc complexes formation. We support the hypothesis that zinc ions migrate into binder creating novel vacancies, affecting the photoluminescence intensity and lifetime properties of zinc oxide. Here, we further demonstrate the advantages of a time-resolved photoluminescence approach for studying defects in semiconductor pigments.

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

In this work, a portable-Raman device (excitation wavelength 1064nm) 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 wheel moved 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, from those slower due to resins photo-degradation processes.

Vibrational Spectroscopies and Chemometry for Nondestructive Identification and Differentiation of Painting Binders

A comprehensive dataset of vibrational spectra of different natural organic binding media is presented and discussed. The binding media were applied on a glass substrate and analyzed after three months of natural ageing. The combination of Raman and FT-NIR spectroscopies allows for an improved identification of these materials as Raman technique is more informative about the skeletal vibrations, while FT-NIR spectroscopy is more sensitive to the substituents and polar groups. The experimental results are initially discussed in the framework of current spectral assignment. Then, multivariate analysis (PCA) is applied leading to differentiation among the samples. The two major principal components allow for a complete separation of the different classes of organic materials. Further differentiation within the same class is possible thanks to the secondary components. The loadings obtained from PCA are discussed on the basis of the spectral assignment leading to clear understanding of the physical basis of this differentiation process.

Portable Raman, DRIFTS, and XRF Analysis to Diagnose the Conservation State of Two Wall Painting Panels from Pompeii Deposited in the Naples National Archaeological Museum (Italy)

This work presents a methodology that combines spectroscopic speciation, performed through portable Raman spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and energy dispersive X-ray fluorescence spectrometry (ED-XRF) working in situ, and thermodynamic speciation to diagnose the environmental impacts, induced by past and current events, on two wall painting panels (Nos. 9103 and 9255) extracted more than 150 years ago from the walls of a Pompeian house (Marcus Lucretius House, Regio IX, Insula 3, House 5/24) and deposited in the Naples National Archaeological Museum (MANN). The results show a severe chemical attack of the acid gases that can be explained only by the action of H2S during and just after the eruption of the Vesuvius volcano, that expelled a high concentration of sulfur gases. This fact can be considered as the most important process impacting the wall painting panels deposited in the museum, while the rain-wash processes and the colonization of microorganisms have not been observed in contrast to the impacts shown by the wall paintings left outside in the archaeological site of Pompeii. Moreover, the systematic presence of lead traces and strontium in both wall paintings suggests their presence as impurities of the calcite mortars (intonacco) or calcite binder of these particular fresco Pompeian murals.

Simultaneous encapsulation and stabilization of Aloe vera extract on cotton fabric for wound dressing application

Utilization of some herbal products in wound dressing for rapid healing with no side effects is a highly interesting task.

Assessment of in-depth degradation of artificially aged triterpenoid paint varnishes using nonlinear microscopy techniques

The present work investigates the applicability of nonlinear imaging microscopy for the precise assessment of degradation of the outer protective layers of painted artworks as a function of depth due to aging. Two fresh and artificially aged triterpenoid varnishes, dammar and mastic, were tested. Nonlinear imaging techniques have been employed as a new diagnostic tool for determination of the exact thickness of the affected region due to artificial aging of the natural varnishes. The measured thicknesses differ from the calculated mean penetration depths of the samples. These nondestructive, high resolution modalities are valuable analytical tools for aging studies and they have the potential to provide unique in-depth information. Single photon laser induced fluorescence measurements and Raman spectroscopy were used for the integrated investigation and analysis of aging effects in varnishes.