Excited-State Symmetry Breaking in an Aza-Nanographene Dye

The photophysics of a structurally unique aza-analogue of polycyclic aromatic hydrocarbons characterized by 12 conjugated rings and a curved architecture was studied in detail. The combined experimental and computational investigation reveals that the lowest excited state has charge-transfer character, in spite of the absence of any peripheral electron-withdrawing groups. The exceptionally electron-rich core comprised of two fused pyrrole rings is responsible for it. The observed strong solvatofluorochromism is related to symmetry breaking occurring in the emitting excited state, leading to a significant dipole moment (13.5 D) in the relaxed excited state. The anomalously small fluorescence anisotropy of this molecule, which is qualitatively different from what is observed in standard quadrupolar dyes, is explained as due to the presence of excited states that are close in energy but have different polarization directions.     

Electron beam radiation effects on UHMWPE: an EPR study

Electron paramagnetic resonance (EPR) technique has been employed to detect and characterise a series of different radical species generated in ultra‐high molecular weight polyethylene (UHMWPE) via electron beam irradiation. Three different radical species have been found and assigned on the basis of their EPR spectra and of the related computer simulations. A secondary alkyl species, the prevalent one, is present immediately after irradiation, an allyl species appears only 24 h after irradiation when the alkyl species disappears.The third species, clearly visible at high microwave power only, has been observed for the first time and assigned to a tertiary alkyl carbon radical, whose formation is strictly connected with a Y‐shape crosslink and a migration of the unpaired electron on a carbon atom localised in an adjacent position. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis, Characterization, and Use of Nb(V) /Ce(IV) -Mixed Oxides in the Direct Carboxylation of Ethanol by using Pervaporation Membranes for Water Removal

New catalytic systems based on ceria have been used in the direct carboxylation of ethanol. The catalytic behavior of Al(2) O(3) and Nb(2) O(5) loaded ceria is compared, the latter showing a better performance. A morphological and structural study has been carried out on Nb(2) O(5) /CeO(2) catalysts in order to explain their behavior in catalysis. Pervaporation membranes have been used for water separation. The synthesis of diethylcarbonate (DEC) has been carried out either in a liquid phase (ethanol) pressurized with CO(2) or in supercritical conditions. A set-up has been developed that allows the production of quite pure DEC (>90?%) with recycling of CO(2) and ethanol.     

Synthesis and NLO properties of new trans 2-(thiophen-2-yl)vinyl heteroaromatic iodides

The synthesis and characterisation of new trans 2-(thiophen-2-yl)vinyl pyridinium, imidazolium and quinoilinium iodides is reported together with their solvatochromic shifts and EFISH characterization. 2-{(E)-2-[5'-(dibutylamino)-2,2'-bithien-5-yl]vinyl}-1-methyl pyridinium and quinolinium iodides display high μ.β(vec) values up to 1200 × 10(-48) esu. The promising non-linear optical (NLO) properties of this new family of chromophores, which can be further improved by the design of highly efficient systems exploiting the donor and acceptor properties of both heteroaromatic rings and substituents, make them suitable candidates for second harmonic generation imaging with interesting biological applications.     

A gemini guest triggers the self-assembly of a calixarene capsule in water at neutral pH

A gemini guest having both aromatic units and negative charges induces the self-assembling of a homodimeric capsule when interacting with a positively charged calixarene at pH 7.     

Representation of perfect and local MV-algebras

We describe representation theorems for local and perfect MV-algebras in terms of ultraproducts involving the unit interval [0, 1]. Furthermore, we give a representation of local Abelian ℓ-groups with strong unit as quasi-constant functions on an ultraproduct of the reals. All the above theorems are proved to have a uniform version, depending only on the cardinality of the algebra to be embedded, as well as a definable construction in ZFC.     

Electrochemical characteristics of cathodes based on perovskites modified by ceria

A system consisting of a solid oxide electrolyte of the Ce_0.9Gd_0.1O_{2 − x} (CGO) composition in contact with a two-layer cathode based on a nonstoichiometric composition (La_0.8Sr_0.2)_0.95MnO_{3 ± δ} (LSM1) and a stoichiometric perovskite La_0.8Sr_0.2MnO_{3 ± δ} (LSM2) is prepared by the tape-casting process. It was shown that the best electrochemical characteristics are achieved for a three-layer system LSM2/{CGO-LSM1}/CGO sintered at 1410°C. The use of Ce-modified perovskites La_0.8Sr_0.2MnO_{3 ± δ} and La_0.6Sr_0.6CoO_{3 ± δ} as the collector layer of two-layer electrodes allows the electrochemical characteristics at moderately high temperatures (600–750°C) to be improved.     

Convenient TLC for the detection of a herbal ingredient in a food supplement

This study describes a practical and suitable approach to solve a real problem: the analysis of polyherbal products for which some specifications addressing the composition are lacking (e.g. chemical components). It is reported that an analytical procedure to verify the possible presence in a botanical supplement of a plant is not authorised for use in Italy. No reference of chemical standards for the known components of the plant is commercially available. For this reason and because a rapid response was required, more selective chromatographic techniques such as high-performance liquid chromatography, gas chromatography and liquid chromatography-mass spectrometry were excluded and thin layer chromatography was chosen for applying different experimental procedures. The original English label of the product, which is made by a leading US manufacturer and sold online by American and Italian distributors, lists the same herbal ingredients as the Italian label, but with an addition of Eurycoma longifolia Jack, which is not included in the list of plants admitted in supplements compiled by the Italian Ministry of Health. For greater certainty of the result, a high-performance thin layer chromatography method was then applied. On the basis of the results obtained, it was possible to confirm that E. longifolia Jack was not present in the product.     

EPR study of the relationship between ultra high molecular weight polyethylene structure and radicals formed during irradiation with high energy sources

Three different samples of ultra high molecular weight polyethylene have been irradiated with a high energy source (electron beam), and radicals have been generated. Different radical species have been assigned on the basis of their electron paramagnetic resonance spectra. Electron paramagnetic resonance data have been used also to evaluate the amount of each kind of radical that has been generated on different starting materials. The structure of the polymer (number of double bonds or crystallinity) is strictly connected to the response of the sample itself to the irradiation. A rationalization between these different parameters has been performed in order to evaluate the stability of polymer samples toward high energy irradiation processes. Copyright © 2014 John Wiley & Sons, Ltd.