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101.
Summary Thirty standard painting layers were analysed by pyrolysis-gas chromatography/mass spectrometry (Py-GC-MS) and by Py-GC-MS
in the presence of tetramethylammonium hydroxide (pyrolysis/methylation). Painting layers were prepared according to Renaissance
recipes for tempera, employing proteinaceous binders (egg, glue and casein) and six different pigments. Thermal degradation
products of proteins, carbohydrates and lipids were selected for semiquantitative analysis based on single/summed ion monitoring
(SIM) mode. The relative distribution of these products was used to characterise binding media for the purpose of their identification
in painting layers. 相似文献
102.
Mennucci B Caricato M Ingrosso F Cappelli C Cammi R Tomasi J Scalmani G Frisch MJ 《The journal of physical chemistry. B》2008,112(2):414-423
The spectroscopic behavior of 6-propionyl-2-(N,N-dimethyl)aminonaphthalene (PRODAN) is investigated in different environments, ranging from homogeneous solutions of different polarities to diffuse interfaces mimicking membranes. The variety of experimental data as well as computational results present in the literature still do not clarify the nature of the emission process; in particular, it is not well-established whether fluorescence in such a molecule occurs from a planar or from a twisted intramolecular charge transfer state. The first part of the work is thus devoted to better understand how the electronic transition processes occur in homogeneous solvents. The effect of the medium polarity as well as the hydrogen bond formation are studied. In the second part of the paper, a first attempt to interpret the experimental results of PRODAN in unilamellar vesicles is carried out. The complexity of the still-open questions about the photophysics of PRODAN has prompted us to base the study on quantum-mechanical calculations performed at various levels of theory, namely, DFT, TDDFT, CIS, and SAC-CI, and to include the effects of the environment in a self-consistent way. This is achieved by using the integral equation formalism version of the polarizable continuum model (IEFPCM). IEFPCM is a quite versatile approach, being able to treat equilibrium and nonequilibrium solvation in both homogeneous and heterogeneous media. 相似文献
103.
Massimo Brochetta Tania Borsari Andrea Gandini Sandip Porey Arghya Deb Emanuele Casali Arka Chakraborty Prof. Dr. Giuseppe Zanoni Prof. Dr. Debabrata Maiti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(3):750-753
A silver(I) catalyzed regioselective trifluoromethylation of allenes using Langlois's salt (NaOSOCF3) is demonstrated. This transformation enables direct expedient access to α-trifluoromethylated acroleins, which are valuable synthons for a number of pharmaceuticals and agrochemicals containing vinyl-CF3 moieties. Versatility of this trifluoromethylation method has been established with good yield and excellent regioselectivity. Preliminary experiments and computational studies were carried out to elucidate the mechanistic insight of this protocol. 相似文献
104.
Dr. Davide Franchini Dr. Alessandra Forni Dr. Alessandro Genoni Prof. Stefano Pieraccini Dr. Enrico Gandini Prof. Maurizio Sironi 《ChemistryOpen》2020,9(4):445-450
A detailed Valence Bond-Spin Coupled analysis of a series of halogenated molecules is here reported, allowing to get a rigorous ab initio demonstration of the qualitative models previously proposed to explain the origin of halogen bonding. The concepts of σ-hole and negative belt observed around the halogen atoms in the electrostatic potential maps are here interpreted by analysis of the relevant Spin Coupled orbitals. 相似文献
105.
Jacopo Dosso Tommaso Battisti Dr. Benjamin D. Ward Dr. Nicola Demitri Dr. Colan E. Hughes Dr. P. Andrew Williams Prof. Dr. Kenneth D. M. Harris Prof. Dr. Davide Bonifazi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(29):6608-6621
In this work, a comprehensive account of the authors’ synthetic efforts to prepare borazino-doped hexabenzocoronenes by using the Friedel–Crafts-type electrophilic aromatic substitution is reported. Hexafluoro-functionalized aryl borazines, bearing an ortho fluoride leaving group on each of the N- and B-aryl rings, was shown to lead to cascade-type electrophilic aromatic substitution events in the stepwise C−C bond formation, giving higher yields of borazinocoronenes than those obtained with borazine precursors bearing fluoride leaving groups at the ortho positions of the B-aryl substituents. By using this pathway, an unprecedented boroxadizine-doped PAH featuring a gulf-type periphery could be isolated, and its structure proven by single-crystal X-ray diffraction analysis. Mechanistic studies on the stepwise Friedel–Crafts-type cyclization suggest that the mechanism of the planarization reaction proceeds through extension of the π system. To appraise the doping effect of the boroxadizine unit on the optoelectronic properties of topology-equivalent molecular graphenes, the all-carbon and pyrylium PAH analogues, all featuring a gulf-type periphery, were also prepared. As already shown for the borazino-doped hexabenzocoronene, the replacement of the central benzene ring by its B3N2O congener widens the HOMO–LUMO gap and dramatically enhances the fluorescence quantum yield. 相似文献
106.
107.
Patrizia N. Hanieh Jacopo Forte Chiara Di Meo Maria Grazia Ammendolia Elena Del Favero Laura Cant Federica Rinaldi Carlotta Marianecci Maria Carafa 《Molecules (Basel, Switzerland)》2021,26(11)
Hyaluronic acid (HA) is one of the most used biopolymers in the development of drug delivery systems, due to its biocompatibility, biodegradability, non-immunogenicity and intrinsic-targeting properties. HA specifically binds to CD44; this property combined to the EPR effect could provide an option for reinforced active tumor targeting by nanocarriers, improving drug uptake by the cancer cells via the HA-CD44 receptor-mediated endocytosis pathway. Moreover, HA can be easily chemically modified to tailor its physico-chemical properties in view of specific applications. The derivatization with cholesterol confers to HA an amphiphilic character, and then the ability of anchoring to niosomes. HA-Chol was then used to coat Span® or Tween® niosomes providing them with an intrinsic targeting shell. The nanocarrier physico-chemical properties were analyzed in terms of hydrodynamic diameter, ζ-potential, and bilayer structural features to evaluate the difference between naked and HA-coated niosomes. Niosomes stability was evaluated over time and in bovine serum. Moreover, interaction properties of HA-coated nanovesicles with model membranes, namely liposomes, were studied, to obtain insights on their interaction behavior with biological membranes in future experiments. The obtained coated systems showed good chemical physical features and represent a good opportunity to carry out active targeting strategies. 相似文献
108.
Dr. Amol P. Amrute Jacopo De Bellis Dr. Michael Felderhoff Prof. Dr. Ferdi Schüth 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(23):6819-6847
The mechanochemical synthesis of nanomaterials for catalytic applications is a growing research field due to its simplicity, scalability, and eco-friendliness. Besides, it provides materials with distinct features, such as nanocrystallinity, high defect concentration, and close interaction of the components in a system, which are, in most cases, unattainable by conventional routes. Consequently, this research field has recently become highly popular, particularly for the preparation of catalytic materials for various applications, ranging from chemical production over energy conversion catalysis to environmental protection. In this Review, recent studies on mechanochemistry for the synthesis of catalytic materials are discussed. Emphasis is placed on the straightforwardness of the mechanochemical route—in contrast to more conventional synthesis—in fabricating the materials, which otherwise often require harsh conditions. Distinct material properties achieved by mechanochemistry are related to their improved catalytic performance. 相似文献
109.
Direct immersion solid‐phase microextraction with gas chromatography and mass spectrometry for the determination of specific biomarkers of human sweat in melted snow 下载免费PDF全文
Federico Dallo Rossano Piazza Jacopo Gabrieli Jean‐Jacques Filippi Nicolas Baldovini Carlo Barbante 《Journal of separation science》2016,39(7):1300-1309
To provide a reliable tool for investigating diffusion processes of the specific components of the human odor 3‐hydroxy‐3‐methylhexanoic acid and 3‐methyl‐3‐sulfanylhexan‐1‐ol through the snowpack, we developed and optimized an analytical method based on direct immersion solid‐phase microextraction followed by gas chromatography with mass spectrometry. Direct immersion solid‐phase microextraction was performed using polyacrylate fibers placed in aqueous solutions containing 3‐hydroxy‐3‐methylhexanoic acid and 3‐methyl‐3‐sulfanylhexan‐1‐ol. After optimization, absorption times of 120 min provided a good balance to shorten the analysis time and to obtain suitable amounts of extractable analytes. The extraction efficiency was improved by increasing the ionic strength of the solution. Although the absolute extraction efficiency ranged between 10 and 12% for 3‐hydroxy‐3‐methylhexanoic acid and 2–3% for 3‐methyl‐3‐sulfanylhexan‐1‐ol, this method was suitable for analyzing 3‐hydroxy‐3‐methylhexanoic acid and 3‐methyl‐3‐sulfanylhexan‐1‐ol concentrations of at least 0.04 and 0.20 ng/mL, respectively. The precision of the direct immersion solid‐phase microextraction method ranged between 8 and 16%. The variability within a batch of six fibers was 10–18%. The accuracy of the method provided values of 88–95 and 86–101% for 3‐hydroxy‐3‐methylhexanoic acid and 3‐methyl‐3‐sulfanylhexan‐1‐ol, respectively. The limit of detection (and quantification) was 0.01 ng/mL (0.04 ng/mL) for 3‐hydroxy‐3‐methylhexanoic acid and 0.06 ng/mL (0.20 ng/mL) for 3‐methyl‐3‐sulfanylhexan‐1‐ol. The signal versus concentration was linear for both compounds (r2 = 0.973–0.979). The stability of these two compounds showed that 3‐hydroxy‐3‐methylhexanoic acid was more stable in water than 3‐methyl‐3‐sulfanylhexan‐1‐ol. We applied the method to environmental samples in correspondence with an olfactory target buried previously. 相似文献
110.
Dr. Ivana Radivojevic Jovanovic Dr. Colleen M. B. Gallagher Ramsey Salcedo Hossam Elshendidi Dr. Jacopo Samson Dr. Charles M. Drain Dr. Donna McGregor Dr. Wayne W. Lukens Jr. Dr. Benjamin P. Burton-Pye Dr. Lynn C. Francesconi 《欧洲无机化学杂志》2023,26(1):e202200507
Technetium-99 is a prevalent fission product from nuclear waste. The long half-life (211,000 yr) and environmental mobility of pertechnetate (TcO4−) render Tc particularly challenging to isolate and stabilize. Here we present two approaches for development of potential wasteforms using titanium dioxide, TiO2. Approach 1 is a low temperature chemical synthesis of TiO2 doped with Tc(IV) from TcO4− intended to mimic the Tc waste stream from the UREX family of separations and removes 98.5 % of the Tc, mainly present as edge-shared Tc(IV) pairs. Approach 2 utilizes TiO2 to photocatalytically reduce TcO4− to Tc(IV) stabilized on the surface of or within the TiO2 lattice. The %Tc removed from solution and adsorbed to TiO2 is pH dependent, with the maximum Tc(IV) adsorbed at pH 3–4 as either TcO2 or edge-sharing Tc(IV) octahedra. The Tc(IV)-TiO2 composites materials formed by both approaches are suitable for consolidation into a dense wasteform by Hot Isostatic Pressing (HIPing). 相似文献