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Chitosan (CS) is largely employed in environmental applications as an adsorbent of anionic dyes, due to the presence in its chemical structure of amine groups that, if protonated, act as adsorbing sites for negatively charged molecules. Efficient adsorption of both cationic and anionic dyes is thus not achievable with a pristine chitosan adsorbent, but it requires the combination of two or more components. Here, we show that simultaneous adsorption of cationic and anionic dyes can be obtained by embedding Linde Type A (LTA) zeolite particles in a crosslinked CS-based aerogel. In order to optimize dye removal ability of the hybrid aerogel, we target the crosslinker concentration so that crosslinking is mainly activated during the thermal treatment after the fast freezing of the CS/LTA mixture. The adsorption of isotherms is obtained for different CS/LTA weight ratios and for different types of anionic and cationic dyes. Irrespective of the formulation, the Langmuir model was found to accurately describe the adsorption isotherms. The optimal tradeoff in the adsorption behavior was obtained with the CS/LTA aerogel (1:1 weight ratio), for which the maximum uptake of indigo carmine (anionic dye) and rhodamine 6G (cationic dye) is 103 and 43 mg g−1, respectively. The behavior observed for the adsorption capacity and energy cannot be rationalized as a pure superposition of the two components, but suggests that reciprocal steric effects, chemical heterogeneity, and molecular interactions between CS and LTA zeolite particles play an important role.

NMR spectroscopy is used in the temperature range 180–350 K to study the local order and transport properties of pure liquid water (bulk and confined) and its solutions with glycerol and methanol at different molar fractions. We focused our interest on the hydrophobic effects (HE), i.e., the competition between hydrophilic and hydrophobic interactions. Nowadays, compared to hydrophilicity, little is known about hydrophobicity. Therefore, the main purpose of this study is to gain new information about hydrophobicity. As the liquid water properties are dominated by polymorphism (two coexisting liquid phases of high and low density) due to hydrogen bond interactions (HB), creating (especially in the supercooled regime) the tetrahedral networking, we focused our interest to the HE of these structures. We measured the relaxation times (T1 and T2) and the self-diffusion (DS). From these times, we took advantage of the NMR property to follow the behaviors of each molecular component (the hydrophilic and hydrophobic groups) separately. In contrast, DS is studied in terms of the Adam–Gibbs model by obtaining the configurational entropy (Sconf) and the specific heat contributions (CP,conf). We find that, for the HE, all of the studied quantities behave differently. For water–glycerol, the HB interaction is dominant for all conditions, water–methanol, two different T-regions above and below 265 K are observable, dominated by hydrophobicity and hydrophilicity, respectively. Below this temperature, where the LDL phase and the HB network develops and grows, with the times and CP,conf change behaviors leading to maxima and minima. Above it, the HB becomes weak and less stable, the HDL dominates, and hydrophobicity determines the solution.

Molecular mechanisms for N2 fixation (solar NH3) and CO2 conversion to C2+ products in enzymatic conversion (nitrogenase), electrocatalysis, metal complexes and plasma catalysis are analyzed and compared. It is evidenced that differently from what is present in thermal and plasma catalysis, the electrocatalytic path requires not only the direct coordination and hydrogenation of undissociated N2 molecules, but it is necessary to realize features present in the nitrogenase mechanism. There is the need for (i) a multi-electron and -proton simultaneous transfer, not as sequential steps, (ii) forming bridging metal hydride species, (iii) generating intermediates stabilized by bridging multiple metal atoms and (iv) the capability of the same sites to be effective both in N2 fixation and in COx reduction to C2+ products. Only iron oxide/hydroxide stabilized at defective sites of nanocarbons was found to have these features. This comparison of the molecular mechanisms in solar NH3 production and CO2 reduction is proposed to be a source of inspiration to develop the next generation electrocatalysts to address the challenging transition to future sustainable energy and chemistry beyond fossil fuels.

Nuclear Magnetic Resonance (NMR) is an analytical technique extensively used in almost every chemical laboratory for structural identification. This technique provides statistically equivalent signals in spite of using spectrometer with different hardware features and is successfully used for the traceability and quantification of analytes in food samples. Nevertheless, to date only a few internationally agreed guidelines have been reported on the use of NMR for quantitative analysis. The main goal of the present study is to provide a methodological pipeline to assess the reproducibility of NMR data produced for a given matrix by spectrometers from different manufacturers, with different magnetic field strengths, age and hardware configurations. The results have been analyzed through a sequence of chemometric tests to generate a community-built calibration system which was used to verify the performance of the spectrometers and the reproducibility of the predicted sample concentrations.

The thermal properties of an extra Virgin Olive Oil (eVOO) depend on its composition and indeed characterize its quality. Many studies have shown that the freezing and melting behaviors of eVOOs can serve for geographical or chemical discrimination. We use Nuclear Magnetic Resonance spectroscopy to study the evolution of the fatty acids bands as a function of temperature during freezing and melting processes. In such a way we can follow separately the variations in the thermal properties of the different molecular groups during these thermodynamic phase transitions. The data indicate that the methyl group which is at the end of every fatty chain displays the major changes during both freezing and melting processes.

A modern approach to the diagnosis of artistic heritage makes use of non-destructive techniques which avoid damage to artworks or signs of interaction with the analytical technique used. For this reason, today, the employment of X-rays to study artistic heritage is quite widespread. Computed tomography (CT) Imaging was first used as specialized medical diagnostic tool in the early 1970s. Today, CT scanners have become more common, and non-destructive three-dimensional imaging has found an increasing number of uses in different areas such as materials research, geology, archaeology, and museum conservation. In this work, a new generation of clinical CT (based on the Dual Energy and multi-slice acquisition principle) is used to investigate an Egyptian wooden mummy board with a total acquisition time of 93.23 seconds and a voxel size of 0.078 × 0.078 × 1.5 mm. The use of two distinct techniques of image post-processing, the two-dimensional multi-planar reconstruction (MPR) and the three-dimensional volume rendering technique (VRT) allowed us to: evaluate the state of conservation of the mummy board, determine how the wooden object was implemented, recognize a nineteenth-century intervention of consolidation, and advance the hypothesis that the wooden planks were reused. In particular, we highlight the use of the cardiovascular and pulmonary filter with VRT reconstruction, which allows a virtual elimination of different parts of the mummy board to investigate those areas otherwise accessible only by removing parts of the board and thus damaging the work.

A study of the rotation dynamics of the spin probe TEMPO by electron spin resonance (ESR) spectroscopy in a series of six short- and medium-sized n-alkanes is presented. In addition to the usual crossover effects connected with solid-liquid phase transitions at temperature Tm and the solid-solid transition at Tss, we find a strong correlation between the change in reorientation at the characteristic ESR temperature TfastX1 < Tss and/or Tm with the ratio TfastX1/Tm = 0.76 ± 0.03 and the characteristic dynamic temperature, TX, obtained from the viscosity data. This indicates the presence of local disordered regions in the crystalline structure which is indeed sensitive to dynamic change at the crossover temperature TX ≅ TfastX1.

The aim of this research is the identification of main and common physical-chemical parameters which induce paper degradation. A simple protocol to monitor the quality and molecular structure of ancient papers under natural degradation processes was proposed. Two-dimensional micro-Raman mapping were carried out. Then, point to point, the changes of both the cellulose Raman signature and fluorescence signal intensity were analysed. Modern papers were artificially aged to simulate the natural degradation and a comparison with the trend found for the ancient paper was presented and discussed. Cellulose degradation involves different mechanisms such as dehydration, cleaving of cellulose-glycosidic bonds and glucopyranose rings oxidation, that induce a reduction in the polymerization degree. As shown by the changes of Raman and fluorescence signals and NMR relaxation times, the rate of each processes depends on the initial amount of glycosidic bonds in the cellulose amorphous and crystalline regions, respectively. All these informations are useful both to define procedures to restore old documents and also to preserve the quality of modern papers for a long-term time.

Spectroscopic non-targeted methods are gaining ever-growing importance in quality control and authenticity assessment of food products because of their strong potential for identification of specific features of the products by data-driven classifiers. One of the factors hampering the diffusion of spectroscopic non-targeted methods and data-driven classifiers is the lack of harmonized guidelines for their development and validation. In particular, to date, neither conditions to directly compare spectra recorded by different spectrometers nor studies demonstrating the statistical equivalence of the spectra are available. Among the spectroscopic analytical techniques suitable for the development of non-targeted methods, nuclear magnetic resonance (NMR) offers the unique opportunity to generate statistically equivalent signals. In this paper, the feasibility of NMR spectroscopy to generate statistically equivalent NMR signals from a number of different spectrometers was demonstrated for complex mixtures (aqueous extracts of wheat and flour) by organizing an inter-laboratory comparison involving 36 NMR spectrometers. Univariate statistics along with multivariate analysis were exploited to establish unbiased criteria for assessing the statistical equivalence of the NMR signals. The aspects affecting the signal equivalence were investigated, and possible solutions to reduce the extent of the human error were proposed and applied with satisfactory results. This study furnishes the scientific community with an appropriate and easy procedure to validate non-targeted NMR methods and provides error values to be used as a reference for future studies.

Liquid water is considered to be a peculiar example of glass forming materials because of the possibility of giving rise to amorphous phases with different densities and of the thermodynamic anomalies that characterize its supercooled liquid phase. In the present work, literature data on the density of bulk liquid water are analyzed in a wide temperature-pressure range, also including the glass phases. A careful data analysis, which was performed on different density isobars, made in terms of thermodynamic response functions, like the thermal expansion &alpha, P and the specific heat differences CP&minus, CV, proves, exclusively from the experimental data, the thermodynamic consistence of the liquid-liquid transition hypothesis. The study confirms that supercooled bulk water is a mixture of two liquid &ldquo, phases&rdquo, namely the high density (HDL) and the low density (LDL) liquids that characterize different regions of the water phase diagram. Furthermore, the CP&minus, CV isobars behaviors clearly support the existence of both a liquid&ndash, liquid transition and of a liquid&ndash, liquid critical point.

Herein we study the different microscopic interactions occurring in wa- ter/methanol solutions at different methanol molar fractions, using NMR spctroscopy. Temperature was found to determine which interaction domi- nates. It was found that the mixing between water and methanol is non-ideal because of the presence of interactions like hydrophobicity and hydrophilic- ity. These results indicate that the competition between hydrophilic and hydrophobic interactions is different in different thermal regions, and that the physical properties of the solution are determined by the character of the solution itself, which in turn depends on the mole fraction of methanol and on the temperature.

The biological activity of proteins depends on their three-dimensional structure, known as the native state. The main force driving the correct folding mechanism is the hydrophobic effect and when this folding kinetics is altered, aggregation phenomena intervene causing the occurrence of illnesses such as Alzheimer and Parkinson’s diseases. The other important effect is performed by water molecules and by their ability to form a complex network of hydrogen bonds whose dynamics influence the mobility of protein amino acids. In this work, we review the recent results obtained by means of spectroscopic techniques, such as Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopies, on hydrated lysozyme. In particular, we explore the Energy Landscape from the thermal region of configurational stability up to that of the irreversible denaturation. The importance of the coupling between the solute and the solvent will be highlighted as well as the different behaviors of hydrophilic and hydrophobic moieties of protein amino acid residues.

The hydrogen bonding ability of both water and methanol, together with the occurrence of hydrophobic interactions, makes their solutions nonideal. This nonideality is reflected in both dynamic and thermodynamic quantities at different extent depending on temperature and concentration. The thermal behavior in terms of transport quantities is investigated for different methanol molar fractions by using the concepts of the Stokes-Einstein relation. Starting from the pure compounds, we compare self-diffusion and viscosity data as a function of the temperature for methanol molar fractions XMeOH = 0.22, 0.5, and 0.7. The results are interpreted within the scenario of the mode coupling theory and show that the Stokes-Einstein relation is violated in a different way depending on the solution concentration.

We performed a statistical analysis of the concentration of mineral elements, by means of inductively coupled plasma mass spectrometry (ICP-MS), in different varieties of garlic from Spain, Tunisia, and Italy. Nubia Red Garlic (Sicily) is one of the most known Italian varieties that belongs to traditional Italian food products (P.A.T.) of the Ministry of Agriculture, Food, and Forestry. The obtained results suggest that the concentrations of the considered elements may serve as geographical indicators for the discrimination of the origin of the different samples. In particular, we found a relatively high content of Selenium in the garlic variety known as Nubia red garlic, and, indeed, it could be used as an anticarcinogenic agent.

Toxic and essential metals content was determined by inductively coupled plasma mass spectrometry in commercial sea urchins samples from the Mediterranean Sea and Pacific Ocean. Results show that Chilean samples have the highest values of Cd, As, Ni, Cr and V; Spanish samples have the maximum Hg content while Sicilian samples have the lowest content of toxic metals. The toxic metal traces were compared with the limits of European Community (EC) No. 1881/2006 for bivalve molluscs. All samples exceed Pb and Cd limit levels; regarding Hg levels, only Sicilian and Sardinian samples have Hg content below the EC limits. The dietary intake of toxic and essential elements was evaluated for an adult. Furthermore, our study highlights a correlation between the toxic elements content and the marine environmental conditions of the places of origin even though only the generic FAO fishing area is specified.

The thermodynamic properties of water are essential for determining the corresponding properties of every biosystem it interacts with. Indeed, the comprehension of hydration mechanisms is fundamental for the understanding and the control of paper degradation pathways induced by natural or artificial aging. In fact, the interactions between water and cellulose at the accessible sites within the fibres' complex structure are responsible for the rupture of hydrogen bonds and the consequent swelling of the cellulose fibres and consumption of the amorphous regions. In this paper we study the hydration process of cellulose in naturally and artificially aged paper samples by measuring the proton spin-lattice (T1) and spin-spin (T2) relaxation times of the macroscopic magnetization through nuclear magnetic resonance (NMR) experiments. The observed behaviour of T1 and T2 is quite complex and strictly dependent on the water content of paper samples. This has been interpreted as due to the occurrence of different mechanisms regulating the water-cellulose interaction within the fibres. Furthermore, we have measured T1 as a function of the artificial aging time comparing the results with those measured on three paper samples dated back to the 15th century. We found that the evolution of T1 in model papers artificially aged is correlated with that of ancient paper, providing therefore a way for estimating the degradation of cellulosic materials in terms of an equivalent time of artificial aging. These results provide fundamental information for industrial applications and for the preservation and restoration of cultural heritage materials based on cellulose such as ancient paper or textiles. © the Owner Societies 2016.