Optical spectroscopy is the study of the interaction between matter and ultraviolet, visible and near infrared radiation. It has been widely used as a non-invasive method for the study of cultural heritage materials for several decades. In particular, fibers optical reflectance spectroscopy (FORS), introduced in the 1980s, allows acquiring hundreds of reflectance spectra in situ in a short time, an approach particularly suitable for cultural heritage diagnostics. More recently, optical spectroscopy has been applied to ancient paper with the aim of noninvasive evaluation of the state of degradation of ancient artworks and as a preliminary technique for the analysis of inks, pigments and dyes used as graphic signs on paper. The discoloration phenomena of paper substrate is responsible for visual degradation of ancient artworks. It is due to the development of oxidized groups acting as chromophores in its chief component, cellulose. This contribution shows the interpretation of optical reflectance measurements by using theoretical simulations of the chromophores' optical spectra. By using this approach it has been possible to describe and quantify the chromophores affecting Leonardo da Vinci's drawings which, compared with future measurements, will assess its degradation rate. This is a fundamental information in order to plan appropriate conservation strategies for very important work of art on paper.

The nickel complexes (PCN)NiX (PC(H)N = 2-(3-((di-tert-butylphosphino)methyl)phenoxy)benzo[d]thiazole; X = F, Br) containing the unsymmetrical pincer k-tridendate ligand with an oxo-bridged benzothiazole side-arm have been tested as homogeneous catalysts in ethylene oligomerization after preliminary activation by Modified Methylaluminoxane (MMAO). They showed high activity in the process (up to 200 × 10 mol?mol?h), with formation of even-numbered olefins (mainly C-C fractions) as products. The comparison of their performance with the results obtained for more rigid pyrazole-based analogues (PCN)NiX (PC(H)N = 1-[3-[(di-tert-butylphosphino)methyl]phenyl]-1H-pyrazole; X = F, Br) demonstrates a positive effect stemming from the increased ligand flexibility. Moreover, the activation of (PCN)NiX by MMAO was studied by UV-Vis and P NMR spectroscopies combined with time-dependent density functional theory (TD-DFT), revealing the formation of Ni-CH species. Finally, DFT calculations were also performed to explore the mechanism of ethylene oligomerization catalyzed by the methyl analogues (PCN)Ni(CH) and (PCN)Ni(CH).

In this paper, we present the design and synthesis of three organic dyes specially developed for the fabrication of dye-sensitized solar cells for application in greenhouses cladding. The dyes (BTD-DTP1-3) are based on a benzothiadiazole (BTD)-dithienopyrrole (DTP) scaffold, and were assembled by using direct arylation reactions, allowing significant reduction of the number of synthetic and purification steps compared to classic cross-coupling procedures. Thanks to their structural design, the dyes absorb light in the green part of the visible spectrum while allowing good transmittance in the red and blue regions, thus ensuring high compatibility with light absorption by plants. Dye-sensitized solar cells built with the three dyes provided energy conversion efficiencies (ECEs) comparable or even superior to those obtained with the reference Ru-based dye N719, especially when using a thin and semitransparent TiO2 layer (up to 8.77%). The photovoltaic performances are discussed considering the need to reach the best compromise between good ECE values and high levels of weighed transparency against the main plant photoreceptors.

UV-Vis reflectance spectroscopy has been widely used as a non-invasive method for the study of cultural heritage materials for several decades. In particular, FORS, introduced in the 1980s, allows to acquire hundreds of reflectance spectra in situ in a short time, contributing to the identification of artist's materials. More recently, microspectrofluorimetry has also been proposed as a powerful non-invasive method for the identification of dyes and lake pigments that provides high sensitivity and selectivity. In this chapter, the concepts behind these spectroscopic methodologies will be discussed, as well as the instrumentation and measurement modes used. Case studies related with different cultural heritage materials (paintings and manuscripts, textiles, carpets and tapestries, glass, metals, and minerals), which show the usefulness of UV-Vis reflectance spectroscopy and microspectrofluorimetry applied to the study of artworks, will also be presented.

It is well known that energetic demand and environmental pollution are strictly connected; the side products of vehicle and industrial exhausts are considered extremely dangerous for both human and environmental health. In the last years, the possibility to simultaneously photo-degrade water dissolved pollutants by means of ZnO nanostructures and to use their piezoelectric features to enhance the photo-degradation process has been investigated. In the present contribution, an easy and low-cost wet approach to synthetize hexagonal elongated ZnO microstructures in the wurtzite phase was developed. ZnO performances as photo-catalysts, under UV-light irradiation, were confirmed on water dissolved methylene blue dye. Piezoelectric responses of the synthetized ZnO microstructures were evaluated, as well, by depositing them into films onto flexible substrates, and a home-made layout was developed, in order to stimulate the ZnO microstructures deposited on solid supports by means of mechanical stress and UV photons, simultaneously. A relevant increment of the photo-degradation efficiency was observed when the piezopotential was applied, proposing the present approach as a completely eco-friendly tool, able to use renewable energy sources to degrade water solved pollutants.

Sound recording and reproducing was first obtained by T. A. Edison in 1877 by using the phonograph cylinder. In 1929 a technology to produce phonograph discs based on the coating of a cardboard substrate with a phenol formaldehyde resin, impressed in order to form sound grooves, was introduced in the USA. The commercial name of such discs was Durium and they soon became a cheaper and more easily used substitute of the shellac and bakelite used for traditional record productions. Durium discs were widely used in Europe since the 30's [1]. The Institute for Sound and Audiovisual Heritage (ICBSA) of the Italian Minister of Cultural Heritage (MiBAC) holds a collection of about 1500 Durium discs dated from the 30's to the 50's (Fig. 1). Fig. 1 A Durium disc (diameter 24 cm) labeled "Hit of the week" made in the USA in 1930. The right image shows the cardboard back side. The sound recording lasts 2 minutes and 16 seconds. The Durium discs made by coupling cardboard and plastic material have shown over time strong deformations that make them unreadable with the classic turntables. Therefore a project started aimed at recovering of the sound heritage through the characterization of the constituent materials of the discs and the experimentation of innovative procedures for restoration and digital preservation. Here we report on the non-destructive analysis based on optical, infrared and THz spectroscopies [2,3] for the characterization of the constituent materials of the Durium discs owned by ICBSA. Quantitative information on the morphology of the different layers and grooves have been obtained by microscopic imagining and by an innovative THz imaging approach. Results provided useful information for the planning of the restoration interventions. [1] On this type of disk see also http://hitoftheweek.blogspot.com/ searching 'Hans Koert'. [2] M Missori, D Pawcenis, J Bagniuk, A Mosca Conte, C Violante, MS Maggio, M Peccianti, O Pulci, J ?ojewska, Microchemical Journal 142 (2018) 54-61 [3] M. Peccianti, R. Fastampa, A. Mosca Conte, O. Pulci, C. Violante, J. ?ojewska, M. Clerici, R. Morandotti and M. Missori,Phys. Rev. Applied 7 (2017) 064019-1-064019-7.

During the centuries paper has been the most widely used writing support and therefore paper degradation is a major issue for cultural heritage conservation. The main component of paper is cellulose, one of the most abundant biomaterials on Earth. Cellulose oxidation is mainly responsible for the yellowing of the ancient samples, through the formation of optically active oxidized functional groups (chromophores). This results in severe chromatic deterioration of works of art on paper. In order to investigate the issue we applied several spectroscopic techniques (UV/Vis-IR-THz) interpreted by ab-initio theoretical computational simulations based on Density Functional theory (DFT) and Time-Dependent DFT (TDDFT) methods [1-4]. In this talk, we illustrate the experimental and theoretical methods and show their application to ancient work of art on paper. In particular, we show how to transform UV/Vis reflectance spectra of ancient samples into absorption spectra of cellulose fibers by using an improved version of the Kubelka-Munk theory suitable for strongly absorbing media. The procedure based on experimental and theoretical UV/Vis spectroscopy is particularly promising since it uses non-invasive and non-destructive measurements, which can be performed in-situ, allowing diagnostic analysis of delicate paper artifacts and the monitoring of their restoration interventions. We also present results on the state of degradation of the Leonardo Da Vinci's drawings including the famous self-portrait as well as other famous works of art on paper. [1] A Mosca Conte, O Pulci, MC Misiti, J ?ojewska, L Teodonio, C Violante and M Missori "Visual degradation in Leonardo da Vinci's iconic self-portrait: A nanoscale study" Appl. Phys. Lett.104, 224101-4 (2014). [2] M Peccianti, R Fastampa, AM Conte, O Pulci, C Violante, J ?ojewska, M Clerici, R Morandotti, M Missori "Terahertz absorption by cellulose: Application to ancient paper artifacts" Physical Review Applied 7 (6), 064019 (2017). [3] L Micheli, C Mazzuca, M Missori, L Teodonio, A Mosca Conte, O Pulci, L Arcadipane, S Dominijanni, A Palleschi, G Palleschi, S Iannuccelli, S Sotgiu, "Interdisciplinary approach to develop a disposable real time monitoring tool for the cleaning of graphic artworks. Application on "le Nozze di Psiche", Microchemical Journal 138, 369-378 (2018). [4] M Missori, D Pawcenis, J Bagniuk, A Mosca Conte, C Violante, MS Maggio, M Peccianti, O Pulci, J Lojewska, "Quantitative diagnostics of ancient paper using THz time-domain spectroscopy", Microchemical Journal 142, 54-61 (2018).

UV-Vis reflectance spectroscopy has been widely used as a non-invasive method for the study of cultural heritage materials for several decades. In particular, FORS, introduced in the 1980s, allows to acquire hundreds of reflectance spectra in situ in a short time, contributing to the identification of artist's materials. More recently, microspectrofluorimetry has also been proposed as a powerful non-invasive method for the identification of dyes and lake pigments that provides high sensitivity and selectivity. In this chapter, the concepts behind these spectroscopic methodologies will be discussed, as well as the instrumentation and measurement modes used. Case studies related with different cultural heritage materials (paintings and manuscripts, textiles, carpets and tapestries, glass, metals, and minerals), which show the usefulness of UV-Vis reflectance spectroscopy and microspectrofluorimetry applied to the study of artworks, will also be presented.

Solution chemistry of transition metal complexes can be very complicated and difficult to study. The establishment of equilibria depends on the nature of the specific metal ion, its kinetic lability, the thermodynamic stability of the complexes, its oxidation state, the coordinating capability of the solvent where the complexes are dissolved, etc. In fact, while solid complexes represent a "frozen image" of a changing situation, solution chemistry represents a mutating system which can be influenced by a series of factors. A case study to describe the solution chemistry of transition metal ions is represented by vanadium. The solution chemistry of its most important oxidation states, +IV and +V, has been widely investigated because two specific spectroscopic techniques are available: 51V NMR (Nuclear Magnetic Resonance) for V(V) and EPR (Electron Paramagnetic Resonance or ESR, Electron Spin Resonance) for V(IV). In fact, V(V) has no unpaired electrons and can be studied with NMR, while V(IV) has a 3d1 electronic configuration which makes it suitable for EPR spectroscopy. These two techniques permitted the detailed investigation of the solution chemistry of these two oxidation states of the metal and the obtained information is complementary because the two techniques have different limitations. When a specific vanadium complex is dissolved in solution different equiibria can take place: i) redox reactions with interconversion between the two oxidation states; ii) ligand exchange, depending on the thermodynamic stability of the complexes; iii) hydrolysis reactions, with eventual polymerization and/or precipitation of hydroxydes; iv) equilibria between different geometries of the complexes; v) eventual exchange reactions with coordinating solvents. Solution chemistry of vanadium complexes will be discussed in comparison with other transition metal ions. The conclusions drawn for vanadium complexes will be extended to other metal ions which have similar features, while for those which significantly differ from it, the possible scenarios will be depicted.

In this article, we present studies concerning the efficiency enhancement of dye-sensitized solar cells (DSSC) containing cocktails of organic donor-?-acceptor (D-?-A) dyes (L0 and L1) and a squaraine sensitizer (SQ2) by means of the localized surface plasmon resonance (LSPR) effect induced by gold nanorods (GNRs) embedded within the semiconductor layer. In view of the potential application of DSSC devices for building integration, dye cocktails were selected to maximize transparency in the 500-600 nm region, where human eye sensitivity has its peak. Thus, the chosen organic dyes and the squaraine sensitizer had absorption maxima in the 380-410 nm region and above 660 nm, respectively. Thanks to their specific asymmetry, GNRs with a 3:1 aspect ratio could enhance organic dye absorption due to their transverse resonance component as well as squaraine absorption in the far-red/near-infrared (NIR) spectral range due to their longitudinal resonance component; furthermore, they were sequentially coated with thin layers of SiO2 and TiO2 in order to make them robust enough to withstand thermal film sintering and minimize charge recombination during the photovoltaic operation. Whereas incorporation of GNRs in the photoanode did not improve the efficiency of cells prepared with the L0/SQ2 dye combination, a significant increase of 23% (from 3.50% to 4.32%), comparable to that observed for Ru-sensitizer N719, was observed in the case of the L1/SQ2 dye cocktail.

A set of new copolymers is here reported in which the repeating units are connected each other through Cu(II) metal centers. The coordination link is based on the bis-chelating properties of salicylaldiminate groups of two different monomers. Due to their chemical structure, the two monomers afford, respectively, flexible and rigid repeating units in the metallocopolymers constitution upon coordination to copper centers. All the copolymers were soluble and easily processable. As shown by XRD analysis, rigid units' rich copolymers adopt a ribbon-like structure in solid state in which highly planar strands of polymer stack thanks to ?-? interactions, similarly to the polymer composed exclusively by rigid units. This behavior can be justified assuming the existence of a partial block character in copolymer constitution where long sequences of rigid units are alternated to sequences of flexible units. This assumption is supported also by DSC and UV-Vis analysis. © 2014 Wiley Periodicals, Inc.

An anthracene-containing poly(arylene-ethynylene)-alt-poly(arylene-vinylene) (PAE-PAV) of general constitutional unit (PhCCAnthrCCPhCHCHAnthrCHCH)(n) bearing two 2-ethylhexyloxy solubilizing side chains on each phenylene (Ph) unit has been synthesized and characterized. The basic electrochemical characterization was done, showing the existence of two non-reversible oxidation and one reversible reduction peaks. The optical properties, the real and imaginary part of the dielectric function, were probed using spectroscopic ellipsometry (SE). The vibrational structure of the undoped/doped polymer was investigated using Fourier transformed infrared spectroscopy. A strong change in the polaronic absorption was observed during the doping, which after modeling revealed the existence of two separated transitions. The optical changes upon doping were additionally recorded using the SE technique. Similar to the results from FT-IR spectroscopy, two new in-the-gap absorptions were found. Moreover, the electrical conductivity as well as the mobility of positive carriers were measured. In the undoped state, the conductivity of the polymer was found to be below the detection limit (<S cm(-1)), after doping the conductivity increased to 0.69 S cm(-1). (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 338-346

The sooting structure of premixed fuel-rich atmospheric pressure benzene flames burning at the same C/O molar ratio=0.8 was studied in different temperature conditions (T max=1720K and 1810K) by changing the cold gas velocity. Compositional profiles of gaseous and condensed phases, measured by probe sampling and chemical analysis, indicated that pyrolytic routes leading to higher soot formation are more favoured in the lower temperature conditions.The structural analysis of condensed phases, including condensed species and soot, has been carried out by using FT-IR and UV-Visible spectroscopy sensitive to the hydrogen bonding and carbon network, respectively.The very low hydrogenated character, as evaluated by FT-IR and elemental analysis, and the high aromatic/graphitic nature of the benzene soot, as shown by a detailed examination of UV-Visible spectral parameters, confirmed the effect of benzene fuel on the internal structure of soot particles already in the early stages of particle inception.

Several methods have been developed to assess the radical scavenging activity. Among them, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) spectrophotometric method is one of the most widely applied and is appreciated for its reliability. In this study, a comparison of two spectroscopic methods (electron paramagnetic resonance (EPR) and ultraviolet-visible (UV-Vis) spectroscopy) was performed analysing the spectroscopic features of DPPH in mixed ethanol/water solution and the free radical scavenging properties of myrtle leaves extracts and citrus juices. When DPPH was dissolved in mixed solvents, EPR enabled to identify the aggregation phenomena that occur when high amounts of water were employed. On the contrary, UV-Vis revealed only small differences in the absorption maximum among solutions with increasing water contents, without detecting aggregation. EC50 values of myrtle leaf extracts and citrus juices calculated from UV-Vis data were lower than those calculated with EPR. In myrtle extracts, the DPPH depletion measured by UV-Vis was not concentration dependent, revealing the interference in the analysis of the decomposition products of the antioxidants, which absorb at 517 nm. EPR spectroscopy was proven to be most reliable with all types of matrix since it is not dependent on the chemical composition of the extract.

In surface-enhanced Raman scattering (SERS) technique the preparation of metal substrates containing minimum hindrance from impurities is an important issue. The synthesis of silver nanoparticles (Ag NPs) active as SERS substrates and having the above-mentioned advantage, were obtained by electron beam irradiation of Ag+ aqueous solutions. Ag+ ions were reduced by free radicals radiolytically generated in solution without the addition of chemical reductants or stabilizing agents. The metal colloids were characterised by UV-Vis spectroscopy and scanning electron microscopy, monitoring the nanoparticles' growth process that depends on the irradiation dose and the initial AgNO3 concentration. Nanoparticles of long-time stability and with different size and shape, included silver nanocubes, were synthesised by varying the irradiation dose. Different tests on the SERS activity of Ag NPs obtained by electron beam irradiation were performed by using benzenethiol as a probing molecule, achieving a good magnification of the adsorbate Raman bands.

The use of biodegradable polymer films for mulching is a topic of great interest both from the environmental point of view and for the intrinsic properties that the above films, when appropriately designed, might have. In the present article we report on a synthetic approach that, starting from existing biodegradable polymers, leads to a new material characterized by a time-controlled biodegradation. The idea that subsides is to bridge polyvinyl alcohol (PVOH) chains through polycaprolactone (PCL) crosslinks. In such a way, PVOH looses its water sensitivity and can stand on the ground for the time needed for the mulching to occur, while the PCL crosslinks, being sensitive to (slow) fungal attack, will undergo cleavage, followed by the complete bio-assimilation of the residual PVOH chains. The number of crosslinks introduced can control time of biodegradation. The polymers are characterized in their intrinsic chemical-physical properties, while a preliminary evaluation of their efficiency as mulches is obtained through the analysis of their thermal behavior when deposited on an irrigated soil. The results are also compared with a model approach able to predict the thermal behavior of a film in specific environmental conditions. (C) 2002 Wiley Periodicals, Inc.