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Unexpected finding of Egyptian blue emerged in Raphael’s fresco Triumph of Galatea at Villa Farnesina, in Rome. This pigment is the oldest man-made blue, dating back to Egyptians who manufactured it first and whose occurrence was thought to be lost with Romans. Thanks to advanced imaging techniques it has been possible to non-invasively map its distribution throughout the frescoed surface and to obtain a non-invasive imaging stratigraphic analysis indicating whether pure painting layers, mixtures or overlapping occurred. Egyptian blue identification on Raphael’s Galatea is so far the earliest of sixteenth century, and could be the first step towards its tracking in Renaissance, demonstrating that non-invasive techniques are a mandatory step not only for materials identification but also for understanding art history and its dynamics.

In this work the formulation of 20 Johann Faber felt-tip pens commercialized in the 1960s and belonging to and used by the architect and designer Lina Bo Bardi have been investigated by an integrated analytical methodology. Minimally destructive vibrational spectroscopic methods permitted a qualitative interpretation of constituents which could be corroborated and ulteriorly supplemented by more destructive chromatographic techniques. This combined approach constitutes an effective collaboration for an in-depth study chronicling the chemical characterization of the first era of commercially viable felt-tip pen inks by providing for the identification of dyes and separation of their mixtures (triarylmethanes, xanthenes, indigoids, azo dyes, azines), binders (plant gums) and additives (diethylene glycol, phenols/antioxidant, diisoctyl phthalate/plasticizer). The comparison between the early and more recent commercial felt-tip pens has allowed to differentiate dyes, pigments and binders, which may provide a useful reference for future studies on the chemical characterization of historical samples.

Egyptian blue, the oldest man-made blue ever, invented by the Egyptians around 5000 years ago has newly raised to prominence for its very recent finding on Raphael’s Roman fresco the Triumph of Galatea hosted in Villa Farnesina, Rome. This is the first case in the Renaissance after centuries of oblivion. In recent years, due to its peculiar spectroscopic properties, Egyptian blue made itself known for manifold application in numerous and very different fields, far beyond its original purpose. Contrary to its brilliant present, its past remains still obscure, characterized from twists and turns which sporadically let it re-emerge. To track its modifications over centuries and places and piece together its fascinating path which has led it from pyramids to nanoscale applications, a network called BLUENET has been established. It is composed by more than 60 institutions and more than 100 researchers working on this subject and exploiting different aspects of Egyptian blue, from synthesis and its modifications to energetic, medical and forensic applications. A mini-review is given here accounting for the structural properties of such material, its currently applications in medical, forensic, energetics, and the raising questions reawakened by the authors’ finding on the Raphael’s fresco of Villa Farnesina together with their approach to address such issues by establishing a dedicated network composed by researchers from all over the world.

In order to evaluate the effectiveness of cyclododecane (CDD) as a temporary protective coating and consolidating agent for fragile stone materials, this paper focuses on its physicochemical behaviour in terms of its penetration into porous matrices and subsequent sublimation. In particular, a near-infrared spectroscopy (NIR) and NMR in-depth profilometry study has been carried out by monitoring the evaporation/sublimation process of CDD solutions as a function of time. By means of this non-invasive multitechnique approach, the behavior of CDD both on the surface and inside the first millimeters of the stones has been adequately described. It has also been highlighted how the progression of CDD's disappearance within different stones is affected by both substrate porosity and boiling point of the carrier solvent. These results demonstrate the potential of such a method of protocol for non-invasive in situ monitoring of the unconstrained sublimation process of this temporary protective agent. © 2014 Elsevier Masson SAS. All rights reserved.

With the aim of studying the process of blackening of lead white in mural painting, a set of samples from the Cimabue’s paintings at the Assisi Cathedral have been studied by Raman and XRD methods, complemented with related techniques (i.e. reflection FTIR, XRF, SEM-EDS). The investigation highlighted that a complete oxidation of lead white to lead dioxide occurred all over the external paint layer having a thickness of 20–30 microns. This alteration occurred both when lead white was applied alone and when used in mixture with azurite, that appears partially converted to copper chlorine compounds. Chemical mapping by Raman spectroscopy and SEM-EDS allowed a good characterization of the painting technique to be carried out. The secco painting nature shown by the examined samples excludes that the oxidation of lead white occurred as a consequence of the alkaline nature of the fresco mortar. Conversely, a possible role of chlorine compounds has been highlighted.

With the aim of deepening the knowledge on the behavior of cyclododecane (CDD) as a temporary consolidant agent for weathered stones, NMR longitudinal and transverse relaxation decays have been exploited to follow the distribution of cyclododecane solutions into porous matrices. By measuring as function of time the relaxation decay constants of CDD solutions dropped onto porous supports, it has been possible to differentiate the step encompassing the solvent evaporation, which determines the consolidant migration within the matrix, from that governing the consolidant sublimation, which is related to the consolidation effectiveness over time. Copyright © 2014 John Wiley & Sons, Ltd.

In this work Raman spectroscopic techniques have been utilized to characterize the vibrational spectral features of orchil dyed wool samples. Specifically, it is noted by surface enhanced Raman spectroscopy that wool dyed purple with two historically used orchil species (Roccella tinctoria and Lasallia pustulata) show spectral differences possibly owing to their specific dye-precursor constituents. The additional natural dyestuff woad (Isatis tinctoria L.) overdyeing the R. tinctoria orchil dyed wool is a further challenge when distinguishing the mixed dye components given by the co-adsorption of the dyestuffs as permitted by the selection rules of surface enhanced Raman spectroscopy. Furthermore, the effects of dilution of the L. pustulata species in its spectral detection have been assessed along with the evaluation of subsequent lichen extract boiling before dyeing which resulted in the detection of a degraded form of the orchil dye. Proof of concept included the surface enhanced Raman spectroscopy (SERS) investigation of a purple dyed tapestry (XVI century) which permitted an aged orchil dye to be determined. This contribution utilizes SERS as a fast, reproducible and specific method for both orchil dye detection and alteration induced by degradation. Copyright © 2014 John Wiley & Sons, Ltd.

A complete non-invasive characterization by XRF, XRD, near-FTIR and UV–Vis reflectance spectroscopy has been performed on some commercially available violet pigments as well as on pure violet Co-salts also known to be used as pigments. The obtained results show that, after a preliminary elemental characterization, the studied pigments can be easily identified by near-FTIR and UV–Vis spectroscopies since they exhibit peculiar spectral bands in these regions. Among the analyzed samples emerged that the pigment 45350 - “Manganviolett” from Kremer consists of two α- and β-NH4MnP2O7 polymorphs, being α-NH4MnP2O7 the most abundant one; furthermore we found that the pigment R1215D -“Cobalt violet” by Winsor & Newton (no longer available since 2006) displays spectral features that match exactly those of 45820-“Kobaltviolett hell” from Kremer and both are composed by cobalt ammonium phosphate hydrate. Such non-invasive study allowed for the identification of “Manganese Violet” (α-NH4MnP2O7) and anhydrous cobalt phosphate (Co3(PO4)2) on some Boccioni's paintings during MOLAB in situ measurements at the Museo del Novecento (Milano).

The new nitrogen-rich oxide N 3 O has been detected in the gas phase by mass spectrometric experiments. The radical has been assigned a minimum lifetime of 0.7 μs and an open-chain NNNO structure in the quartet state. Structures and energies of the N 3 O + precursor ion and the N 3 O radical have been investigated by ab initio calculations.

We have implemented the polarizable continuum model for solute–solvent interactions into a plane-wave (PW) Car–Parrinello code. A comparison between PW and Gaussian-type orbitals (GTO) basis sets implementations, concerning solvation energies and dipole moments of a number of small systems, is reported. All the computations have been performed using the BPW91 exchange-correlation functional. GTO calculation has been performed using the 6-311G(d,p) basis set for geometry optimizations, and the aug-cc-pVTZ basis for energies and dipole moments. PW calculations were carried out on the Gaussian optimized geometries, up to an energy cutoff of 30 Ry. Excellent agreement between PW and GTO calculations is obtained, with average deviations of solute–solvent interaction energies lower than 0.5 kcal/mol.

This contribution focuses on an analytical evaluation of the use of cyclododecane (CDD) (C12H24) as a temporary protective coating for non-porous stone materials of cultural heritage interest.

With the aim of characterizing ground preparations of paintings by infrared reflection spectroscopy, the CaSO4–H2O system (gypsum/bassanite/anhydrite) has been re-investigated, evaluating and assigning the SO42- and OH overtone and combination bands, respectively, in the ranges 1900–2700 cm−1 and 5000–6000 cm−1 resulting from reflection and high concentration transmission spectra. The second-order modes have been proven to be highly specific, reliable, and less affected by overlap with bands of organic binders and can hence be exploited for the identification of the sulfate hydration phase using infrared (IR) reflection spectroscopy. Subsequently, the characterization and identification of hydration phases in unknown sulfate-based ground preparations on authentic artworks have been carried out noninvasively by fiber-optic reflection IR spectroscopy and on cross-sections by infrared reflection micro-spectroscopy. The spectroscopic data collected both on standards and artworks have been cross-validated by X-ray diffraction.

The aim of this study is to develop a method for the non-invasive and in situ identification of organic binders in wall paintings by fiber optic mid-FTIR reflectance spectroscopy. The non-invasive point analysis methodology was set-up working on a wide set of wall painting replicas of known composition and using statistical multivariate methods, in particular principal component analysis (PCA), for the interpretation, understanding, and management of data acquired with reflectance mid-FTIR spectroscopy. Results show that PCA can be helpful in managing and preliminary sorting of the large amount of spectra typically collected during non-invasive measurement campaigns and highlight further avenues for research. The developed PCA model was finally applied to the case of a Renaissance wall painting by Perugino assessing it predictability as compared to the interpretation of the single spectrum.

The absorption and emission properties of the two components of the yellow color extracted from weld (Reseda luteola L.), apigenin and luteolin, have been extensively investigated by means of DFT and TDDFT calculations. Our calculations reproduce the absorption spectra of both flavonoids in good agreement with the experimental data and allow us to assign the transitions giving rise to the main spectral features. For apigenin, we have also computed the electronic spectrum of the monodeprotonated species, providing a rationale for the red-shift of the experimental spectrum with increasing pH. The fluorescence emission of both apigenin and luteolin has then been investigated. Excited-state TDDFT geometry optimizations have highlighted an excited-state intramolecular proton transfer (ESIPT) from the 5-hydroxyl to the 4-carbonyl oxygen of the substituted benzopyrone moiety. By computing the potential energy curves at the ground and excited states as a function of an approximate proton transfer coordinate for apigenin, we have been able to trace an ESIPT pathway and thus explain the double emission observed experimentally.

Finite-length models of chiral semiconducting carbon nanotubes based on Clar sextet theory allowed carrying out accurate calculations, performed by application of gradient-corrected density functional theory, on the energetic of sidewall reactions. In particular, we analyzed the addition of atomic fluorine and carbene (CH2) to (6,4) and (6,5) nanotubes, finding excellent convergence of reaction energies with respect to the model length and good agreement with literature data. Our study demonstrates the importance of using models of carbon nanotubes based on chemical considerations to evaluate consistently the electronic and reactive properties of the sidewall.

The structural properties of luteolin, apigenin and of all their possible mono-deprotonated species are studied with ab initio methods in vacuo and in solution. Molecular structures have been optimized by MP2 and DFT using different functionals and basis sets. Harmonic vibrational frequency calculations have been performed on the optimized structures to ensure geometries obtained were real minima. All calculations resulted in non-planar structures except for deprotonation in 4' position at the DFT level. An interesting behavior for the torsional potential between phenyl B ring and the 1,4-benzopyrone skeleton has been detected. Therefore, potential energy profiles along this coordinate have been characterized and analyzed in terms of conjugative and steric interactions through the evaluation of the coefficients fitted with an eight-term Fourier expansion. The frontier molecular orbitals and the HOMO-LUMO gap at the different geometries along this torsion curve have been computed and their changes have been thoroughly analyzed. Finally, structural and electronic changes on deprotonation and frontier molecular orbitals for all mono-deprotonated species have been studied. (C) 2008 Elsevier B.V. All rights reserved.

Yellow pyroantimonates PbSb, PbSbSn and PbSbZn were synthesized by solid-state reactions at high temperature and characterized by X-ray diffraction and Raman spectroscopy. The lattice size of cubic pyrochlores increases with Sn and Zn doping and with Pb overstoichiometry, indicating the replacement of Sb5+ by the larger cations. This fact permits the understanding of the corresponding Raman spectral modifications as a consequence of the changes in the local symmetry of the SbO polyhedra, justifying the exploitation of Raman spectroscopy to noninvasively identify structural modifications of pyroantimonate pigments in artworks. Copyright © 2008 John Wiley & Sons, Ltd.

The acid–base chemistry of luteolin, a flavonoid with important pharmacological and dyeing properties, and of the related methyl ether derivatives have been investigated by DFT and MP2 methods, testing different computational setups. We calculate the p K a ’s of all the possible deprotonation sites, for which no experimental assignment could be achieved. The calculated p K a ’s deliver a different acidity order for the two most acidic deprotonation sites between luteolin and its methyl ether derivatives, due to intramolecular hydrogen bonding in luteolin. A lowest pKa of 6.19 is computed for luteolin, in good agreement with available experimental data.

We report a theoretical investigation of β-elimination reactions in systems activated by the pyridine ring. The investigated reaction, the acetohydroxamate-induced β-elimination in protonated N-[2-(2-pyridyl)ethyl]quinuclidinium, offers a unique opportunity to test computational methodologies since detailed kinetic experimental data are available. We calculated the pKas of the acetohydroxamic acid and the substrate and thoroughly characterized the reactive free-energy profile. The reaction proceeds via a stable carbanion intermediate. Except a discrepancy in the reproduction of the pKa of the acetohydroxamic acid, the calculated free-energy profile is in excellent agreement with the experiment, showing the general reliability of the present approach.

Density functional theory calculations have been performed on the main adsorption configurations of pentacene on the Si(100) surface and on the possible pathways for the following C-H bond cleavage. We considered possible candidates for all the orientations of pentacene experimentally observed with STM, i.e., on the top of silicon dimer rows, perpendicular to the dimer rows, diagonal to the dimer rows and between two adjacent dimer rows ("in between"). Our calculations indicate that the most stable adsorption configuration of pentacene on the Si(100) surface is the symmetric perpendicular structure with an adsorption energy of -128.3 kcal mol -1 , with the in between structure 10.5 kcal mol -1 and the symmetric parallel structure 13.0 kcal mol -1 higher in energy. Transition states for the dissociation of C-H and formation of Si-H bonds from the main adsorption configurations of pentacene have been characterized and the corresponding energy barriers estimated. We identified two kinds of adsorbed configurations of pentacene from which the breaking of two C-H bonds can be accessible: one on top of a silicon dimer row with one or both outer benzene rings di-σ- bonded through a [2 + 2] cycloaddition; one with one or more pentacene rings 1,4 di-σ-bonded across two dimer rows, such as the in between structure. The kinetically most favorable reactive channel is that from the in between configuration and involves the separate abstraction of two hydrogen atoms on the sp 3 carbon atoms by the two silicon atoms of the two dimers bearing an unpaired electron, with an energy barrier of 29-30 kcal mol -1 .

The in situ non invasive methods have experienced a significant development in the last decade because they meet specific needs of analytical chemistry in the field of cultural heritage where artworks are rarely moved from their locations, sampling is rarely permitted, and analytes are a wide range of inorganic, organic and organometallic substances in complex and precious matrices. MOLAB, a unique collection of integrated mobile instruments, has greatly contributed to demonstrate that it is now possible to obtain satisfactory results in the study of a variety of heritage objects without sampling or moving them to a laboratory. The current chapter describes an account of these results with particular attention to ancient, modern, and contemporary paintings. Several non-invasive methods by portable equipment, including XRF, mid- and near-FTIR, UV-Vis and Raman spectroscopy, as well as XRD, are discussed in detail along with their impact on our understanding of painting materials and execution techniques. Examples of successful applications are given, both for point analyses and hyperspectral imaging approaches. Lines for future perspectives are finally drawn.

We report time-dependent (TD) and coupled-perturbed (CP) DFT/HF investigations, on the linear and non-linear optical properties of M(II)-complexes of [5-[(4′-dimethylaminophenyl)-ethynyl]-15-[(4″-nitrophenyl)ethynyl]-10,20-diphenylporphyrin], with M = Zn, Cu, Ni. The TD-DFT absorption spectrum is in good agreement with the experimental one, allowing us to identify the transitions mainly responsible of the NLO response. CP-DFT/CP-HF calculations provide similar hyperpolarizability values for the three complexes, suggesting an irrelevant role of the metal center. A sharp hyperpolarizability increase is calculated at an incident laser wavelength of 1.064 μm compared to 1.907 μm, which seems to be responsible for the large differences between Zn, Cu and Ni complexes reported experimentally.

The use of the artificial calcium oxalate treatment providing a protective patina to marble sculptures and a mural facade has been investigated. The longevity of the protective method is controlled at a distance of 3–4 years from its application on two diversely externally exposed Florentine monuments. Micro samples were analysed by optical microscopy (OM), scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX) and MicroRaman spectroscopy to characterize products of deterioration and the efficacy of the applied treatment. Decay is predominately noted at a superficial level and in all cases the calcium oxalate is still present, thus the protective action of the treatment is confirmed and moreover, a consolidant effect is also considered. Both statues present fractures and cavities filled with calcium oxalate residues and various degradation products such as gypsum, lichens and pollution particles. This study contributes to ascertain that artificial calcium oxalate prevents further decay of carbonate materials in urban polluted environments.

The artificial oxalate protection method was analyzed in laboratory experiments in order to achieve an optimum treatment application and concentration giving rise to its most effective protective nature. Spectroscopic (Fourier transform infrared, Micro-Raman and UV-vis colorimetry), microscopic (scanning electron microscope) and contact-angle analyses were carried out to characterize Carrara marble samples before and after application of the treatment to validate its efficiency. The resistance effects against chemical weathering were subsequently observed in a lab-controlled weak acid rain experiment. An acid spray at pH 5.5, representative of normal rain was used to provoke degrade of natural marble, marble treated with the artificial oxalate protective at concentrations of 0.4 and 5% and marble treated with a commercial organic silicon product. Run-off solutions sampled at timely intervals were tested for any change in pH followed by ion chromatography measurements for the presence of calcium ions in solution. The chromatography results of the oxalate treatment applied at a 5% concentration are analogous to an organic commercial product indicating its validity as a method for the conservation of carbonate substrates conferring protection to stone materials against acid environments. (c) 2006 Elsevier B.V. All rights reserved.

Density functional calculations have been performed on possible mechanisms for the hypothetic C-H bond cleavage process of benzene chemisorbed on the Si(100) surface, in order to shed light on the analogous process on larger polycyclic aromatic hydrocarbons. We first identified the minima on the potential energy surface for the benzene adsorption on Si(100) and for the breaking of two C-H bonds, with formation of two Si-H bonds, and then we analyzed possible pathways for the C-H bond cleavage, looking for the transition states connecting the adsorption configurations to the final products of C-H breaking. We identified two adsorbed configurations of benzene from which the breaking of two C-H bonds can be accessible, i.e., the 1,2 tilted di-o bonded configuration on top of a single dimer (T) and the 1,4 di-σ bonded configuration where benzene bridges two dimer rows (BR). The kinetically most favorable reactive channel on the T configuration involves the abstraction of two hydrogen atoms on the sp 3 carbon atoms by the silicon atoms of an adjacent dimer, with an energy barrier of 22.0 kcal mol -1 . Although seemingly low, such an activation energy is not expected to be accessible at temperatures below the onset of benzene desorption from this configuration, which requires 15.9 kcal mol -1 The kinetically most favorable reactive channel on the BR configuration, which has not been experimentally detected for the benzene molecule, involves the rupture of one Si-C bond, passing through an energy barrier of 29.8 kcal mol -1 , and ends with the formation of a Si-H bond and a vertical phenyl unit anchored on a silicon dimer.

The energetics and reaction mechanism of prototypical organometallic reactions have been investigated by combining static and dynamic density functional calculations, based on the Car–Parrinello method. Such an approach allows us to dynamically sample the potential energy surface of the reactive system at finite temperature, providing useful insights into the reaction mechanism and evidencing the presence of reaction intermediates. Applications of this methodology are presented, ranging from the migratory insertions of carbon monoxide and alkyl-isocyanides into different metal–carbon bonds, to the SiH oxidative addition to Pt(PH 3 ) 2 and the acetylene to vinylidene isomerization in the coordination sphere of a transition metal center.

An experimental study via X-ray photoelectron spectroscopy at different takeoff angles of the derivatization of atomically flat, hydrogen terminated, 1 × 1 (1 0 0) Si surfaces with 1-octyne is reported. The major conclusion of the experimental analysis (that a large fraction of the grafted moieties contain unreacted π bonds) is then compared with the results of high-level ab initio modelling with model molecules of the derivatization act.

The intramolecular coupling of the two iminoacyl units in the bis(η 2 -iminoacyl) complexes lcalix[4](OMe) 2 (O) 2 -Zr(η 2 -MeCNBU t ) 2 ]and [(2,6-Bu t 2 C 6 H 3 O)2-Zr(η 2 -MeCNPh) 2 ] to generate the corresponding enediamido species has been investigated by means of both static and dynamic density functional calculations. For both systems we have characterized the stationary points of the potential energy surfaces for the coupling reaction and evaluated the overall energy profile. Car-Parrinello molecular dynamics simulations have been performed to gain insight into the detailed mechanistic features of the iminoacyl coupling and surprisingly show that this reaction occurs through an asynchronous reaction mechanism in which a decoordinated iminoacyl attacks the residual coordinated iminoacyl C-N double bond. A transition state search, performed without any symmetry constraint, led to structures consistent with the proposed mechanism 23.8 and 21.2 kcal mol - 1 above the starting bis-(η 2 -iminoacyl) reagents, in good agreement with experimental activation enthalpies. On the basis of the proposed reaction mechanism we are also able to reproduce the activation energy of the coupling reaction with electron-withdrawing substituents on the iminoacyl moiety. Inspection of the electronic structure changes along the proposed reaction pathway suggests that the iminoacyl coupling process can be described as an intramolecular attack of the decoordinated iminoacyl carbon lone-pair at the coordinated iminoacyl π* orbital, thus reconciling the iminoacyl coupling reaction mechanism with the generally accepted pattern of acyl and iminoacyl reactivity.

Throughout the years, a large number of paintings by Perugino have been investigated using the in situ non-destructive x-ray fluorescence (XRF) technique. Three anomalous characteristics were frequently identified, concerning a brown earth pigment containing zinc, the presence of manganese in some red lakes and the association of the presence of copper and tin with grey-blue regions. In an effort to understand these anomalies better, five micro-samples, taken from selected easel paintings by Perugino at the Galleria Nazionale dell'Umbria and a fresco at the Monastero di Sant'Agnese in Perugia, were studied by micro-Raman spectroscopy and scanning electron microscopy (SEM). Micro-Raman spectroscopy was a useful tool to investigate the molecular nature of such uncommon pigments and SEM provided useful information on the stratigraphy of the paint layers. The brown earth pigments, used by the master in the last period of his production, were definitely confirmed to be characterized by zinc impurities. The manganese contained in red lakes was shown to be due to ground alkaline glass, with a small quantity of manganese and iron, probably added to the oil binder in an attempt to speed up drying. Finally, in the sampled paintings, the grey-blue colour characterized by copper and tin was not present. Copyright (C) 2004 John Wiley Sons, Ltd.

The reaction of acenaphthylene (ACN) with the Si(001) surface has been explored by means of density functional cluster model calculations. We have considered seven reasonable bonding configurations...