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A series of medium- and long-chain zinc carboxylates was analyzed by ultra-high-field 67Zn NMR, 13C NMR and FTIR spectroscopy. Novel crystal structures for three of these carboxylates are also reported.

In this study a multi-analytical approach has been performed to characterise the constitutive materials of an ancient painted barkcloth or Tapa. Originating from Wallis Island, Polynesia, this cloth likely served utilitarian or ceremonial purposes and is part of the Felice Junck collection at the Pigorini, Muciv museum of Rome. During a recent conservation project, some micro-samples were taken from the support, brown and black painted areas and were investigated using the complementarity of SEM-EDX, FT-IR, Raman/SERS and solid-state 13C NMR and 1H HR-MAS spectroscopy. The combination of these techniques allowed the chemical characterization of the constitutive materials, from distinguishing the lignin and cellulose content of the support to the use of organic materials including condensed tannins (catechin, anthocyanidins, alkaloids), phlobaphene and vegetal anthraquinone based Morinda genus dyes for the decorations. A primary focus was placed on an understanding of its state of conservation where data of alteration products collected, namely metal carboxylates and oxalates can serve to formulate apt restoration efforts for this specific artefact.

Nuclear magnetic resonance spectroscopy has advanced our understanding of cultural heritage objects. Solution NMR, solid state NMR, unilateral NMR, magnetic resonance imaging (MRI) and other MR techniques have been used on a wide variety of materials such as stone, ceramics, paintings, biological remains, paper, wood, textiles, resins, gums, and synthetic materials. This review highlights NMR studies that provide structural and chemical identification, moisture content and distribution, uncovers artistic techniques, determines geographical origins, identifies constituent materials of an object and helps to determine the best cleaning or treatment method for conservation. In addition, physical and chemical transformations and structural modifications due to deterioration of an object can be monitored by NMR methods, and this information provides conservators with clues as to the most appropriate methods of preservation of a unique artifact. With the continued development of NMR pulse sequences, probes and sensors, the sensitivity and utility of NMR spectroscopy in cultural heritage continues to grow.

A multidisciplinary protocol is proposed to monitor the preservation of fresh pumpkin samples (FP) using three commercial polymeric films: A made of biodegradable cellophane from regenerated cellulose pulp, B from corn starch, cassava and eucalyptus, C made of polylactic acid from corn starch, and a polyethylene film used as reference (REF). Chemical, mechanical and microbiological analyses were applied on packaging and fresh and packaged samples at different times. After an 11-day period, NMR spectroscopy results showed a sucrose increase and a malic acid decrease in all the biofilms with respect to FP, fructose, glucose, galactose levels remained quite constant in biofilms B and C, the most abundant amino acids remained quite constant in biofilm A and decreased significantly in biofilm B. From microbiological analyses total microbial count was below the threshold value up to 7 days for samples in all the films, and 11 days for biofilm C. The lactic acid bacteria, and yeasts and molds counts were below the acceptability limit during the 11 days for all packages. In the case of biofilm C, the most promising packaging for microbiological point of view, aroma analysis was also carried out. In this paper, you can find all the analysis performed and all the values found.

San Nicola in Carcere, one of the minor basilicas in the historical center of Rome, was the location of a wide investigation campaign of the water-related deterioration causes, present in the lower sector of the apse and adjacent pillars, affected by water infiltrations, mould and salt efflorescence. The results obtained identify the presence of water content and related effects mainly on the sides of the apsidal wall. This work focuses on the use of five Non-Destructive Techniques (NDT) and intends to show the gains obtained by integrating widely interdisciplinary methods, namely the Infrared Thermography (IRT), the Unilateral Nuclear Magnetic Resonance (Unilateral NMR), the Acoustic Tomography (AT), the Acoustic Imaging (AI) and the Laser-Induced Fluorescence (LIF). All the techniques contribute to the rapid, non-invasive and early identification of the moisture distribution, while some of them (LIF and AI) also address the determination of some moisture effects. The integrated use of different techniques helps to take the multidisciplinary point of view necessary to formulate an effective restoration intervention based on a sound scientific rationale, nonetheless, it allows to experiment a holistic approach, verifying the potential of a wide range of NDTs available within the context of a restoration yard.

The quantitative evaluation of the three-dimensional (3D) morphology of porous composite materials is important for understanding mass transport phenomena, which further impact their functionalities and durability. Reactive porous paint materials are composites in nature and widely used in arts and technological applications. In artistic oil paintings, ambient moisture and water and organic solvents used in conservation treatments are known to trigger multiple physical and chemical degradation processes; however, there is no complete physical model that can quantitatively describe their transport in the paint films. In the present study, model oil paints with lead white (2PbCO3·Pb(OH)2) and zinc white (ZnO) pigments, which are frequently found in artistic oil paintings and are associated with the widespread heavy metal soap deterioration, were studied using synchrotron X-ray nano-tomography and unilateral nuclear magnetic resonance. This study aims to establish a relationship among the paints’ compositions, the 3D morphological properties and degradation. This connection is crucial for establishing reliable models that can predict transport properties of solvents used in conservation treatments and of species involved in deterioration reactions, such as soap formation.

Ancient vegetable tanned leathers and parchments are very complex materials in which both different manufacturing and deterioration processes make their study and chemical characterisation difficult. In this research, solid-state nuclear magnetic resonance (NMR) spectroscopy was applied to identify different tannin families (condensed and hydrolysable) in historical leather objects such as bookbindings, wall upholsters, footwear and accessories, and military apparel. Furthermore, leather deterioration with special focus on collagen gelatinisation was investigated. A comparison with Fourier transform infrared (FTIR) spectroscopy and micro-differential scanning calorimetry (micro-DSC) was also performed to support the C-13 CP-MAS NMR findings and to point out the advantages and limitations of solid-state NMR in analysing historical and archaeological leathers. A wide database of NMR and FTIR spectra of commercial tannins compounds was also collected in order to characterise historical and archaeological leathers.

Paintings are complex multi-layered systems made of organic and inorganic materials. Several factors can affect the degradation of paintings, such as environmental conditions, past restoration works and, finally, the type of painting technique and the art materials used over the centuries. The chemical&ndash, physical characterization of paintings is a constant challenge that requires research into and the development of novel analytical methodologies and processes. In recent years, solvents and water-related issues in paintings are attracting more attention, and several studies have been focused on analyzing the interaction between water molecules and the constitutive materials. In this study, recent applications applying different NMR methodologies were shown, highlighting the weakness and the strength of the techniques in analyzing paintings. In particular, the study of water and its diffusive interactions within wall and oil paintings was performed to prove how the portable NMR can be used directly in museums for planning restoration work and to monitor the degradation processes. Furthermore, some preliminary results on the analysis of varnishes and binders, such us linseed oil, shellac, sandarac and colophony resins, were obtained by 1H HR-MAS NMR spectroscopy, highlighting the weakness and strengths of this technique in the field of conservation science.

Heavy metal carboxylate or soap formation is a widespread deterioration problem affecting oil paintings and other works of art bearing oil-based media. Lead soaps are prevalent in traditional oil paintings because lead white was the white pigment most frequently chosen by old masters for the paints and in some cases for the ground preparations, until the development of other white pigments from approximately the middle of the 18th century on, and because of the wide use of lead-tin yellow. In the latter part of the 19th century, lead white began to be replaced by zinc white. The factors that influence soap formation have been the focus of intense study starting in the late 1990s. Since 2014, nuclear magnetic resonance (NMR) studies have contributed a unique perspective on the issue by providing chemical, structural, and dynamic information about the species involved in the process, as well as the effects of environmental conditions such as relative humidity and temperature on the kinetics of the reaction(s). In this review, we explore recent insights into soap formation gained through solid-state NMR and single-sided NMR techniques.

Agar is an interesting and versatile biopolymer capable of forming hydrogels useful in different applications. In particular, in the field of Cultural Heritage agar gels are often used as tools for cleaning the surfaces of artifacts. Agar gels are thermoreversible, peelable materials, exhibiting high retention of water and an intrinsic cleaning capability that can be increased and modulated by loading different cleaning agents. Agar gels are able to solubilize and retain dirt, and allow a confined release of the liquid phase, which is especially important when they are applied on water sensitive substrates. A detailed knowledge of the role of water in agar gels and of water/agar interactions is important to fully understand the properties and performances of agar gels as cleaning materials. Here we report the results of a systematic study aimed at exploring the water state and the types of water (i.e. bound non-freezable, bound freezable and freezable bulk-like) in agar hydrogels prepared from four different types of commercial agar powders. The influence of agar concentration on the water behaviour in the hydrogels was also investigated. The total water content, the identification and quantification of the different types of water was carried out by gravimetric, thermogravimetric and calorimetric analyses, while water mobility and localization in the gel network were investigated by unilateral H-1 NMR. Moreover, H-1 NMR depth profiles of agar gels applied on Noto stone specimens were collected to monitor the gel deformation due to water release and to evaluate the ability of the gel in controlling the water release into a porous material. (C) 2018 Elsevier B.V. All rights reserved.

Low-field 1H NMR relaxometry is an important tool used to investigate on the most abundant components of intact foodstuffs based on relaxation parameters and amplitude of the NMR signals. In particular, information on water compartments, diffusion and movement can be obtained by detecting proton signals prevalently ascribable to H2O contained in foodstuffs. The main advantage of this technique is that it does not require any pretreatment of the sample and once developed, standard protocols based on rapid measurements can be easily transferred to quality control applications. An actual breakthrough for the low-field NMR application to food science has certainly been the development of unilateral NMR sensors. These devices present an attractive option for non-invasive assessment of compositional and microstructure of food materials. They are portable and allow easy sample access, which makes them attractive for quality control in industrial environments and directly on sealed packaged foods. A price to pay is the inhomogeneity of the magnetic field, which compromises the sensitivity of these devices. However, recent developments in unilateral magnets design offer larger sensitive volume, higher sensitivity and shorter dead times. In this brief review, we highlight the different uses of unilateral NMR devices in food analysis. Graphical abstract .

Heavy metal carboxylate degradation severely affects thousands of oil paintings. Relative humidity has been reported to accelerate the rate of the reactions. To evaluate its role further, water diffusion and molecular mobility of protons in linseed oil-based lead white paints were studied by unilateral NMR and

Heavy metal carboxylate degradation severely affects thousands of oil paintings. Relative humidity has been reported to accelerate the rate of the reactions. To evaluate its role further, water diffusion and molecular mobility of protons in linseed oil-based lead white paints were studied by unilateral NMR and 1H HRMAS spectroscopy. The results indicate that exposure to high %RH for relatively long times affects the dynamics of the oil paint's mobile fraction and that the effect is more pronounced as the thickness of the film increases. It was found that the paint can absorb appreciable amounts of water and has a porosity of approximately 6 % available for the diffusion of water, for which a regime of restricted diffusion was observed. Furthermore, the presence of bound and free-moving water, due to the possible formation of hydrated ionic-group clusters, supports the hypothesis of a polymeric/ionomeric network, as well as regions of essentially water free to move as in the bulk. The findings allow a better understanding of the role of water as a factor activating the degradation process in linseed oil-based lead white paints.

13C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) and µ-Raman spectroscopy were applied to characterize Sicilian amber samples. The main goal of this work was to supply a complete study of simetite, highlighting discriminating criteria useful to distinguish Sicilian amber from fossil resins from other regions and laying the foundations for building a spectroscopic database of Sicilian amber. With this aim, a private collection of unrefined simetite samples and fossil resins from the Baltic region and Dominican Republic was analyzed. Overall, the obtained spectra permitted simetite to be distinguished from the other resins. In addition, principal component analysis (PCA) was applied to the spectroscopic data, allowing the clustering of simetite samples with respect to the Baltic and Dominican samples and to group the simetite samples in two sets, depending on their maturity. Finally, the analysis of loadings allowed for a better understanding of the spectral features that mainly influenced the discriminating characteristics of the investigated ambers.

Highly performing cleaning systems based on hydrogels for buildings and artefacts were studied by unilateral NMR. Specifically, the release and diffusion of water from gellan gum formulations at the gel stone interface were investigated. The study was carried out by applying gel formulations to stone specimens with different porosimetric properties, namely Yellow Tuff of Via Tiberina and Lecce stone. NMR measurements and a suitable processing of data allowed the obtainment of the total open porosity, the average pore size, and the tortuosity of the stones. Properly calibrated H-1 NMR depth profiles with micrometric resolution were used to evaluate the effective volume of absorbed water, the distribution of water in porous stone specimens, and the degree of saturation. The deformation coefficient of the gel after water release was also determined. The obtained results indicated that the performance of the gel depends not only on its physical-chemical properties but also on the porosimetric properties of the stone to which the gel is applied. Therefore, the knowledge of the porosimetric properties of the material is important for selecting a suitable and highly performing gel cleaning system. (C) 2017 Elsevier Inc. All rights reserved.

Unilateral NMR is a powerful tool to evaluate water mobility and diffusion in gels used in a fully non-invasive and nondestructive way. Different types of gel formulations to be used as cleaning systems for wall painting were investigated. Transverse relaxation times measured in gel formulations indicate the presence of water in two environments. The water molecules with a short relaxation time may be involved in hydrogen bonding interactions and/or proton exchange with gel macromolecules, while the molecules with a longer relaxation time are free to move through the network, although self-diffusion measurements demonstrate that their translational motion is increasingly hindered as the average probability of collisions with the gel network increases. The release and diffusion of water at the gel-wall painting interface were investigated. Gellan concentration and application time of the gel may be tuned to modulate the amount and the depth of penetration of the liquid phase through the porous network. Water absorption, distribution and penetration in the support depend not only on the physical-chemical and rheological properties of the gel but also on the properties of the support to which the gel is applied. This study is part of a more extensive research effort aimed at obtaining an analytical protocol for establishing in situ the performance of cleaning systems.

Insights into the diets of early societies can be gained, indirectly, from the cultural evidence of artefacts related to food procurement, preparation and consumption and human skeletal remains. However, more direct evidence for dietary constituents derives from the identification of intact plant and animal remains collected during the excavations but also from the exam of the amorphous remains of foodstuff associated with artefacts. Organic residues adhering to the surface or absorbed into the porous fabric of an unglazed cooking vessel should provide important information both about the usage of the vessel and dietary practices. This contribute deals with the results of a combined analytical research via 1 H- 1 H NMR 2D-TOCSY, ATR FT-IR and SEM-EDX on organic residues on pottery from two Sicilian prehistoric sites of Monte Kronio and Sant'Ippolito. The goal was that to shed new light on the use of certain ceramic shapes and infer some hypothesis about ancient dietary habits.

Consolidation and protection are among the most important treatments usually carried out in conservation of stone artifacts and monuments. In this paper, portable unilateral NMR and conventional techniques were used for investigating new multifunctional treatments based on tetraethoxysilane, silica, and polytetrafluoroethylene nanoparticles. The study was carried out on a very complex and heterogeneous porous stone such as tuff. NMR study allowed to obtain detailed information on the penetration depth of treatments, the hydrophobic effect, and changes in the open porosity caused by treatments. Physical and chemical inhomogeneities between the impregnated layers of tuff and the layers underneath were also detected. The average pores radius and pores interconnection obtained from NMR diffusion measurements were used for the first time to compare effects of different consolidating and/or protective treatments on stone. Because unilateral NMR technique is neither destructive nor invasive, investigation of treatments can be also carried out and optimized directly on buildings and monuments of interest for Cultural Heritage. Copyright © 2014 John Wiley & Sons, Ltd.

A multi-analytical study was carried out on materials, techniques, and state of conservation of a set of detached Nubian mural paintings, originally belonging to the 10th century pictorial cycle of the church of Sonqi Tino, Sudan (70 km south of the Egypt–Sudan border). These paintings represent one of the very few examples of Christian Nubian pictorial cycles preserved from the wide defacement experienced by these artifacts with the building up of the Aswan Dam. Non-invasive NMR depth profiling was used to preliminary study the hydrogen rich layers of the detached mural paintings. By this technique, it was possible to perform a virtual coring with a reconstruction of the complex series of layers that characterize the investigated artifacts. Then, micro-sampling and cross-section examination by SEM-EDX, micro-Raman, micro-FTIR, and 27Al and 29Si MAS NMR, allowed us to shed light on materials and technology exploited by the Medieval Nubian painters, with the identification of pigments and composition of the original primer, obtaining also information on layering of materials used by conservators during the detachment of the paintings and their transfer to a new support. The combination of preliminary non-invasive investigation with a set of micro-invasive analytical techniques allowed us to set up a protocol for a satisfactory decoding of the multilayered complex systems that characterize the detached paintings.

In this study a multi-analytical approach was used to characterize ancient and modern constitutive materials and the stratigraphy of a Sienese wooden painting consisting of four cusps belonging to a lost Polyptych, by Andrea di Bartolo dated back to the late 14th century, repainted in the 16th century and partially restored and cleaned in the 20th century. In order to distinguish the original layers from the other ones, a comparison with the painting Adorazione dei Magi by Bartolo di Fredi (Andrea's father) dated to the 14th century, was performed. The painting Adorazione dei Magi was found to be in a very good state of conservation and provided a model of the artistic technique used in Sienese painting in the 14th century. In situ measurements by portable NMR were performed to investigate the stratigraphy of the paintings in a non-destructive and non-invasive way. By means of this technique, information about all layers constituting the paintings were obtained and used to plan the successive micro-sampling. High resolution NMR spectroscopy was applied on a few samples to characterize binders and organic substances. Specifically, solid state 13C and 31P CPMAS NMR spectroscopy and 1H NMR spectroscopy in solution were applied to characterize original and non-original materials. Other techniques such as ToF-SIMS, HPLC, IR and Raman spectroscopy were also applied.

The effectiveness and the mechanism of copper stain removal from stones by agar gels was systematically studied using marble laboratory specimens, stained and cleaned in well-controlled and reproducible conditions. The same cleaning procedure was also applied on the marble base of Napoleon's statue by A. Canova. The water release from agar gels to stones was investigated by capillarity absorption and unilateral Nuclear Magnetic Resonance. The cleaning by different agar gel formulations (pure and added with chemicals) was studied both on the stone substrate (optical microscopy and colour measurements) and in the gels (inductively coupled plasma-atomic emission spectrometry, electron paramagnetic resonance spectroscopy). Among the considered cleaning systems, the most effective ones for copper removal were agar gels 3% containing additives, with no significant difference among the used additives. However, agar gels with additives host copper in different ways: in gels added with ethylenediamine tetraacetic acid (EDTA), all copper centers are coordinated, while copper centers are also dispersed in water within gels added with ammonium citrate tribasic (TAC). The stain cleaning process of stones probably starts with the diffusion of water at the gel-stone interface, but it finds the driving force in the copper coordination. (C) 2016 Elsevier B.V. All rights reserved.

The use of nanotechnology in conservation is a relatively new concept. Usually, classical cleanup methods take into account the use of other chemicals: On the one hand they help the environment destroying pollutants, but on the other hand they often become new pollutants. Among the new oxidation methods called advanced oxidation processes, heterogeneous photocatalysis has appeared an emerging technology with several economic and environmental advantages. A new sol-gel method of synthesis of TiO2 anatase is reported in this work using lithium and cobalt (II) salts. The activation energy of the doped photocatalyst was analyzed by solid-state UV-Vis spectrophotometer. The mobility of Li ions on TiO2 NPs surface was studied by Li-7 MAS NMR spectroscopy. Use of doped nanotitania is suggested from authors for the removal of pollutants in confined areas containing goods that must be preserved from decomposition and aging phenomena.

Nuclear Magnetic Resonance (NMR) can be successfully applied to a wide number of organic, inorganic, and hybrid materials regarding cultural heritage. High-resolution solid-state NMR provides information on the structure of materials, and portable NMR devices allow non-destructive and non-invasive in situ investigation of variably sized objects. This result is possible by combining open magnets and surface radiofrequency coils to generate a sensitive volume external to the sensor and inside the object under investigation. In this paper we focus on the application of NMR to investigate inorganic porous materials such as pottery, plasters, and stones from cultural heritage sites. 27 Al MAS and 3QMAS, and 29 Si MAS high-resolution solid-state NMR along with spectral deconvolution allowed for the investigation of the chemical structure of ancient pottery. Portable unilateral NMR was used to investigate, in a non-invasive and non-destructive way, the porous structure of pottery. The effect of protective-consolidating treatments on plaster was carefully investigated by 1 H NMR depth profiles that allowed for scanning with micrometric resolution of plaster specimens. Changes occurring in the total open porosity after treatments were also evaluated. NMR diffusion measurements provided information on the restricted geometry of the porous structure of two types of biocalcarenite and tuff. A suitable processing of collected data enabled us to define the average pore radius and pores’ interconnection in these materials.

Consolidation and protection are among the most important treatments usually carried out in conservation of stone artifacts and monuments. In this paper, portable unilateral NMR and conventional techniques were used for investigating new multifunctional treatments based on tetraethoxysilane, silica, and polytetrafluoroethylene nanoparticles. The study was carried out on a very complex and heterogeneous porous stone such as tuff. NMR study allowed to obtain detailed information on the penetration depth of treatments, the hydrophobic effect, and changes in the open porosity caused by treatments. Physical and chemical inhomogeneities between the impregnated layers of tuff and the layers underneath were also detected. The average pores radius and pores interconnection obtained from NMR diffusion measurements were used for the first time to compare effects of different consolidating and/or protective treatments on stone. Because unilateral NMR technique is neither destructive nor invasive, investigation of treatments can be also carried out and optimized directly on buildings and monuments of interest for Cultural Heritage.

NMR stratigraphy was used to investigate in situ, non-destructively and non-invasively, the stratigraphy of hydrogen-rich layers of an ancient Nubian detached mural painting. Because of the detachment procedure, a complex multi-layered artefact was obtained, where, besides layers of the original mural painting, also the materials used during the procedure all became constitutive parts of the artefact. NMR measurements in situ enabled monitoring of the state of conservation of the artefact and planning of minimum representative sampling to validate results obtained in situ by solid state NMR analysis of the samples. This analysis enabled chemical characterization of all organic materials. Use of reference compounds and prepared specimens assisted data interpretation. Keywords NMR stra

Portable unilateral NMR was used to quantitatively map in a fully noninvasive way the moisture distribution in an ancient deteriorated wall painting before and after an intervention to reduce the capillary raise of water through the wall. Maps obtained at a depth of 0.5 cm clearly showed the path of the capillary raise and indicated that, after the intervention, the moisture level was reduced. Maps obtained by measuring the first layers of the wall painting were affected by the critical environmental conditions of the second hypogeous level of St. Clement Basilica, Rome, and by the presence of salts efflorescence and encrustations on the surface of the wall painting. The morphology and the elemental composition of salts investigated by SEM-EDS indicated that efflorescences and encrustations were mostly constituted of gypsum and calcite. The presence of these salts is explained with the presence of high concentration of carbon dioxide and sulphur-rich particles due to pollution which, along with the high-moisture level and the extremely feeble air circulation, cause recarbonation and sulphation processes on the plaster surface.

A multi-technique approach was employed to study a decorated Egyptian wooden sarcophagus (XXV-XXVI dynasty, Third Intermediate Period), belonging to the Museo del Vicino Oriente of the Sapienza University of Rome. Portable non-invasive unilateral NMR was applied to evaluate the conservation state of the sarcophagus. Moreover, using unilateral NMR, a non-invasive analytical protocol was established to detect the presence of organic substances on the surface and/or embedded in the wooden matrix. This protocol allowed for an educated sampling campaign aimed at further investigating the state of degradation of the wood and the presence of organic substances by (13)C cross polarization magic angle spinning (CPMAS) NMR spectroscopy. The composition of the painted layer was analysed by optical microscopy (OM), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Raman and surface enhanced (resonance) Raman spectroscopy (SERS/SERRS), infrared and GC-MS techniques, evidencing original components such as clay minerals, Egyptian green, indigo, natural gums, and also highlighting restoration pigments and alteration compounds. The identification of the wood, of great value for the reconstruction of the history of the artwork, was achieved by means of optical microscopy.