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The present study aims at the investigation of the changes in water distribution among the organic components of selected honey samples following honey storage at different temperatures. Results, achieved by application of fast field cycling NMR relaxometry, revealed that the organic constituents were homogeneously distributed within the whole samples stored at room temperature. Conversely, after four months of refrigeration at 4°C, the organic systems were included in persistent clusters, as a consequence of the water release due to the larger stability of the intramolecular interactions over the intermolecular ones. The new conformational arrangements of the honey constituents entailed enhancement of honey moisture content. For this reason, it can be suggested that honey refrigeration prior to storage at room temperature may be detrimental for its long-term storage. In fact, higher risk of fermentation may occur once the sample is warmed after the first refrigeration step. [ABSTRACT FROM AUTHOR]

Aqueous salt solutions play an important role in nature because of their effects on environmental biogeochemical processes and on structural properties of biomolecules. Upon dissolution, salts split in ions that are solvated. Water in hydration shells is subjected to molecular motions that can be monitored by 1H T1 NMR relaxometry. This technique allowed the evaluation of the nature of the interactions between water and ions via variable temperature experiments. Examination of relaxometry properties of aqueous solutions at variable salt concentrations allowed acknowledgement of the role played by ions in either structuring or destructuring water aggregates. A mathematical model has been applied on six environmentally relevant salts: NaCl, KCl, CaCl2, CaCO3, NaNO3, and NH4NO3. It was linear only for the concentration dependence of KCl-R1. This model accorded with the one reported in literature where it has been considered valid only for diluted solutions. However, in the present study, the range of linearity for KCl was extended up to the saturation point. The model was modified for NaCl, CaCl2, and CaCO3 by using it as an exponential form in order to account for the nonlinearity of the R1- versus-concentration curves. Nonlinearity was explained by the nonnegligible ion-ion interactions occurring as concentration was increased. Finally, further modification was needed to account for the asymmetric distribution of water around nitrate (in NaNO3 and NH4NO3) and ammonium (in NH4NO3). This study is preliminary to the comprehension of the diffusion mechanisms of ions in water solutions at the equilibrium condition with solid surfaces such as soils and biochar-amended soils. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Purpose: Biochar has unique properties which make it a powerful tool to increase soil fertility and to contribute to the decrease of the amount of atmospheric carbon dioxide through the mechanisms of C sequestration in soils. Chemical and physical biochar characteristics depend upon the technique used for its production and the biomass nature. For this reason, biochar characterization is very important in order to address its use either for agricultural or environmental purposes. Materials and methods: Three different biochars obtained from an industrial gasification process were selected in order to establish their chemical and physical peculiarities for a possible use in agronomical practices. They were obtained by charring residues from the wine-making industry (marc) and from poplar and conifer forests. Routine analyses such as pH measurements, elemental composition, and ash and metal contents were performed together with the evaluation of the cross-polarization magic angle spinning (CPMAS) C NMR spectra of all the biochar samples. Finally, relaxometry properties of water-saturated biochars were retrieved in order to obtain information on pore size distribution. Results and discussion: All the biochars revealed basic pH values due to their large content of alkaline metals. The quality of CPMAS C NMR spectra, which showed the typical signal pattern for charred systems, was not affected by the presence of paramagnetic centers. Although paramagnetism was negligible for the acquisition of solid state spectra, it was effective in some of the relaxometry experiments. For this reason, no useful information could be retrieved about water dynamics in marc char. Conversely, both relaxograms and nuclear magnetic resonance dispersion profiles of poplar and conifer chars indicated that poplar char is richer in small-sized pores, while larger pores appear to be characteristic for the conifer char. Conclusions: This study showed the potential of relaxometry in revealing chemical-physical information on industrially produced biochar. This knowledge is of paramount importance to properly direct biochar agronomical uses. [ABSTRACT FROM AUTHOR]

ABSTRACT Synthesis and characterization of a new gold-2-mercapto-1-methyl imidazole are reported. This new organic material shows an extraordinary fluorescence activity (superfluorescence) up to 220°C with an unusual quantum yield of 0.2. Both fluorescence and NMR spectroscopy were applied to understand the behavior of the gold-2-mercapto-1-methylimidazole complex. Results suggest that the superfluorescence activity can be attributed to the shrinking of the HOMO-LUMO band gap energy following complexation of the organic imidazole system with gold. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Dissolved organic matter (DOM) is a very important environmental constituent due to its role in controlling factors for soil formation, mineral weathering and pollutant transport in the environment. Prediction of DOM physical–chemical properties is achieved by studying its chemical structure and spatial conformation. In the present study, dissolved organic matter extracted from compost obtained from the organic fraction of urban wastes (DOM-P) has been analysed by FT-IR, CPMAS 13C NMR spectroscopy and 1H T 1 NMR relaxometry with fast field cycling (FFC) setup. While the first two spectroscopic techniques revealed the chemical changes of dissolved organic matter after adsorption either on kaolinite (DOM-K) or montmorillonite (DOM-S), the latter permitted the evaluation of the conformational variations as assessed by longitudinal relaxation time (T 1) distribution at the fixed magnetic field of 500 mT. Alterations of T 1 distributions from DOM-P to DOM-K and DOM-S were attributed to a decreasing molecular complexity following DOM-P adsorption on the clay minerals. This study applied for the first time solid state 1H T 1 NMR relaxometry to dissolved organic matter from compost obtained from the organic fraction of urban wastes and revealed that this technique is very promising for studying environmentally relevant natural organic systems. [Copyright &y& Elsevier]

Abstract: Cross polarization (CP) magic angle spinning (MAS) 13C NMR spectroscopy is a solid state NMR technique widely applied to study the chemical composition of natural organic matter. In high magnetic fields (>7T), fast sample spinning is required in order to reduce the influence of spinning sidebands underlying other chemical shift regions. As the spinning speed increases, the Hartmann–Hahn matching profiles break down into a series of narrow matching bands. In order to account for this instability variable amplitude cross polarization techniques (e.g. VACP, ramp-CP) have been developed. In the present study, we experimentally verified the stability of the Hartmann–Hahn condition under two MAS speeds for different samples with known structure and two different humic acids. For a complete restoration of flat matching profiles, large ramp sizes were needed. The matching profiles of the humic acids showed that both samples needed different ramp sizes to restore flat profiles. A set up based on the matching profiles of the commonly used glycine would have led to an insufficient ramp size for one of the humic acids. For the characterization of natural organic matter, we hence recommend to roughly set the matching conditions with a standard and subsequently optimize the matching conditions on a more complex, preferably representative, sample such as a humic acid. We would suggest to either run an array of different ramp sizes until maximum signal intensity is reached for all chemical shift regions or, in the case of unavailable measurement time, to use a ramp size twice the spinning speed. [Copyright &y& Elsevier]

The 90° pulse calibration is essential in NMR spectroscopy to prevent artefacts in the liquid state or to enhance cross-polarization efficiency in the solid state. We verified pulse-angle (PA) errors due to circuit impedances in solid-state NMR and suggested a possible solution to prevent the inconvenience of PA errors. The classic pulse sequences used to calibrate 1H 90° pulse lengths by direct detection of protons or by cross-polarization were modified in order to replace single 1H pulses with 1H pulse trains. Pulse trains were found to decrease the effect of PA imperfections in the calibration of basic pulses (i.e. 90° and 180°) for a number of organic substrates. The modified sequences are especially important to rapidly obtain pulse calibration of complex and heterogeneous molecular systems such as humic substances, which usually require a long time when using single 1H pulses. [ABSTRACT FROM AUTHOR]

A humic acid extracted from a volcanic soil was subjected to preparative high-performance size-exclusion chromatography (HPSEC) to reduce its molecular complexity and eleven different size fractions were obtained. Cross-polarization magic-angle spinning 13C NMR (CPMAS 13C NMR) analysis performed with variable contact-time (VCT) pulse sequences showed that the largest molecular-size fractions contained aromatic, alkyl, and carbohydrate-like components. The carbohydrate-like content and the alkyl chain length seemed to decrease with decreasing molecular size. Progressive reduction of aromatic carbon atoms was also observed with decreasing molecular size of the separated fractions. Mathematical treatment of the results from VCT experiments enabled cross polarization ( T CH) and proton spin–lattice relaxation ( % MathType!Translator!2!1!AMS LaTeX.tdl!TeX – AMS-LaTeX! % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX % garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz % aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq % Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq % Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca % WGubWaaSbaaSqaaiaaigdacqaHbpGCaeqaaOWaaeWaaeaacaWGibaa % caGLOaGaayzkaaaaaa!3D70! $$ T_{{1\rho }} {\left( H \right)} $$ ) times to be related to structural differences among the size fractions. The conformational distribution indicated that the eleven size fractions could be allocated to two main groups. The first group, with larger nominal molecular sizes, was characterized by molecular domains with slower local molecular motion. The second group of size fractions, with smaller nominal molecular sizes, was characterized by a larger number of molecular domains with faster local molecular motion. The T CH and % MathType!Translator!2!1!AMS LaTeX.tdl!TeX – AMS-LaTeX! % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX % garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz % aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq % Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq % Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca % WGubWaaSbaaSqaaiaaigdacqaHbpGCaeqaaOWaaeWaaeaacaWGibaa % caGLOaGaayzkaaaaaa!3D70! $$ T_{{1\rho }} {\left( H \right)} $$ values suggested that either condensed or strongly associated aromatic systems were predominant in the size fractions with the largest apparent molecular dimensions. [ABSTRACT FROM AUTHOR]

Reports on the use of high performance size exclusion chromatography to fractionate a humic acid (HA) solution in acetic acid (AcOH). Alteration of the distribution of humic molecular components; Appearance of the untreated HA in the pyrogram after treatment with AcOH; Disruption of the supramolecular structure; Stabilization of the humic molecules by multiple weak interactions in apolar groups.

Air-conditioning (A/C) systems in tropical regions are characterized by significant energy consumption for latent load handling. Decoupling of the latent load from the A/C units can be achieved using a dedicated dehumidification system while the A/C systems handle only the sensible heat at high efficiencies. Desiccants are widely used in industry, and adsorbent materials that exhibit a unique isotherm shape, i.e. "S shape", have been developed extensively. Recently, activated carbons (ACs) have been discussed as effective adsorbents for dehumidification applications. Although pristine ACs are considered to be hydrophobic materials, certain surface treatments initiate surface phenomena that promote water vapour uptake at relative pressures above 0.4 due to microdroplet aggregation. This work reviews and reports the latest developments of sustainable activated carbons for dehumidification using a multiscale approach spanning from the sustainable precursor selection, "green" activation processes and surface functionalization, adsorption thermodynamics, and system-level developments. With the focus on sustainability, we demonstrate that water adsorption and viable adsorption range are gradually improving with the progressing research, and they are reaching operational values required for practical use. The unique adsorption process of water onto ACs is further explained in detail using solvation theory on the microdomains created by the hydrophilic functional groups while providing clarification of thermodynamic properties adopting the specificities of water/activated carbon adsorption pair. The predicted performance of a desiccant dehumidification system utilizing activated carbon is evaluated using the local weather conditions of numerous major cities worldwide. The highest dehumidification performances of activated carbon, as indicated by the unified SDP (specific dehumidification power) value, are reached particularly in cities that suffer from high humidity and temperature the most proving the viability of this cheap and sustainable material. [ABSTRACT FROM AUTHOR]

Biochar is a porous material obtained by biomass thermal degradation in oxygen-starved conditions. It is nowadays applied in many fields. For instance, it is used to synthesize new materials for environmental remediation, catalysis, animal feeding, adsorbent for smells, etc. In the last decades, biochar has been applied also to soils due to its beneficial effects on soil structure, pH, soil organic carbon content, and stability, and, therefore, soil fertility. In addition, this carbonaceous material shows high chemical stability. Once applied to soil it maintains its nature for centuries. Consequently, it can be considered a sink to store atmospheric carbon dioxide in soils, thereby mitigating the effects of global climatic changes. The literature contains plenty of papers dealing with biochar's environmental effects. However, a discrepancy exists between studies dealing with biochar applications and those dealing with the physical-chemistry behind biochar behavior. On the one hand, the impression is that most of the papers where biochar is tested in soils are based on trial-and-error procedures. Sometimes these give positive results, sometimes not. Consequently, it appears that the scientific world is divided into two factions: either supporters or detractors. On the other hand, studies dealing with biochar's physical-chemistry do not appear helpful in settling the factions' problem. This review paper aims at collecting all the information on physical-chemistry of biochar and to use it to explain biochar's role in different fields of application. [ABSTRACT FROM AUTHOR]

• Characteristics of Parmigiano Regg. (PR) cheese from 24 to 84 months were evaluated. • 9Z-octadecenoic acid considerably increased with PR aging. • The reduction of the polymers in the PR has been confirmed with NMR relaxometry. • By NMR relaxometry the water trapped in casein micelles have been recognized. • FFC NMR relaxometry can be a promising technique to monitor PR ripening. It is widely recognized that the longer the ageing, the more valuable Parmigiano Reggiano (PR) cheese becomes, due to the improvement of its sensorial and nutritional properties. Up to now, the evaluation of PR properties has been performed on samples mainly aged up to 40 months. For this reason, this study was aimed at collecting information about the chemical-physical characteristics of PR cheeses after ageing at 24, 48 and 84 months. The basic analyses on water amount, protein content and volatile organic compounds (VOC) revealed that PR ageing is associated to the decomposition of the organic components into smaller units. This drives water molecules closer to the aforementioned units, thereby leading to a reduction of water activity. Moreover, it appears, from VOC investigation, that either the total amount of long chain fatty acids (LCFA) or the sole 9Z-octadecenoic acid considerably increased with PR aging, thereby making these molecular systems good fingerprint to monitor PR ripening. Fast field cycling (FFC) NMR relaxometry revealed different components of the molecular dynamics in the complex PR cheese samples, which were attributed to water trapped in casein micelles, water bound to polar groups in organic components, proteins, and fats. In particular, the reduction of the correlation times associated to the organic components was explained by the molecular size decrement following degradation processes. The ageing-independent component of the motion was assigned to water molecules bound to polar groups in organic moieties. Finally, the ageing-independent contribution to the overall relaxation rate was assigned to water molecules in casein micelles. This study revealed that FFC NMR relaxometry can be a promising technique to monitor the chemical physical changes during Parmigiano Reggiano cheese ripening. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance (NMR) techniques are largely employed in several fields. As an example, NMR spectroscopy is used to provide structural and conformational information on pure systems, while affording quantitative evaluation on the number of nuclei in a given chemical environment. When dealing with relaxation, NMR allows understanding of molecular dynamics, i.e., the time evolution of molecular motions. The analysis of relaxation times conducted on complex liquid–liquid and solid–liquid mixtures is directly related to the nature of the interactions among the components of the mixture. In the present review paper, the peculiarities of low resolution fast field-cycling (FFC) NMR relaxometry in soil science are reported. In particular, the general aspects of the typical FFC NMR relaxometry experiment are firstly provided. Afterwards, a discussion on the main mathematical models to be used to "read" and interpret experimental data on soils is given. Following this, an overview on the main results in soil science is supplied. Finally, new FFC NMR-based hypotheses on nutrient dynamics in soils are described [ABSTRACT FROM AUTHOR]