Enhancement of proton mobility and mitigation of methanol crossover in sPEEK fuel cells by an organically modified titania nanofiller

An organically functionalized titania, TiO₂-RSO₃H, was evaluated as filler in sulfonated polyetheretherketone (sPEEK)-based composite membranes for application in high temperature direct methanol fuel cells. The presence of propylsulfonic acid groups covalently bound onto the TiO₂ surface and the nanometric nature of the additive were analyzed by Raman spectroscopy and transmission electron microscopy, respectively. The properties of the sPEEK/TiO₂-RSO₃H composite membranes were compared with those of the pure sPEEK membranes and those of the sPEEK/TiO₂ composite membranes containing pristine titania nanoparticles at same filler content. Water and methanol transport properties were investigated by NMR methods, including relaxation times and self-diffusion coefficients as function of temperature (up to 130 °C), and pressure (from 0 up to 2 kbar). The incorporation of the nanoadditivies in the sPEEK polymer demonstrates considerable effects on the morphology and stiffness of the membranes, as well as on the transport properties and barrier effect to the methanol crossover. In particular, the functionalization by propylsulfonic acid groups promotes a higher reticulation between the polymeric chains, increasing the tortuosity of the methanol diffusional paths, so reducing the molecular diffusion, while the proton mobility increases being favored by the Grotthus-type mechanism. Conductivity measurements point out that the filler surface functionalization avoids the reduction of the overall proton conduction of the electrolyte due to the embedding of the low-conducting TiO₂. Finally, remarkable improvements were found when using the sPEEK/TiO₂-RSO₃H composite membrane as electrolyte in a DMFC, in terms of reduced methanol crossover and higher current and power density delivered.     

Fluorescent Imidazo[1,2-a]pyrimidine Compounds as Biocompatible Organic Photosensitizers that Generate Singlet Oxygen: A Potential Tool for Phototheranostics

Photodynamic therapy has been used to treat a variety of diseases, however, there is continuing search for new biocompatible photosensitizers. Herein, we demonstrate for the first time that imidazo[1,2-a]pyrimidine compounds are able to generate singlet oxygen species and can act as photosensitizers in the intracellular environment. Our results show that this class of compounds absorb and emit in the 400–500 nm region, present low cytotoxicity in the dark, are efficiently uptaken by cells, are fluorescent in intracellular medium, and generate singlet oxygen upon irradiation, killing cancer cells within 2 h at low concentration (2.0 μm ). The imidazo[1,2-a]pyrimidine compounds are a potential new tool for phototheranostics, because they can be simultaneously used for fluorescence imaging and photodynamic therapy.     

Dimensional and elemental characterization of suspended particulate matter in natural waters: quantitative aspects in the integrated ultrafiltration, splitt-flow thin cell and inductively coupled plasma–atomic emission spectrometry approach

The present study investigates the quantitative aspects of an analytical procedure for the trace element characterization of suspended particulate matter (SPM) in natural waters. The procedure consists of the following steps: (1) ultrafiltration (UF) concentration; (2) splitt-flow thin (SPLITT) cell fractionation (SF) into different micronic–submicronic dimensional ranges; and (3) inductively coupled plasma–atomic emission spectrometry (ICP–AES) elemental determination on both the separated fractions and the bulk phase. One specific feature of the UF/SF steps is that they are gentle and thus preserve the complexity of the colloidal features of SPM samples as far as possible. The investigation was performed on a real SPM sample (Po River, Italy). Two SF modes were considered: the so called conventional SPLITT fractionation (CSF) mode and the full feed depletion SPLITT fractionation (FFDSF) mode. These differ in terms of resolution, time (both better in CSF as compared to FFDSF) and operating mode (FFDSF does not require a diluting carrier). Quantitative aspects of the UF step recovery and of the CSF and FFDSF modes were investigated in terms of total mass balance proving that only the FFDSF mode is currently satisfactory for quantitative purposes. Mass balance versus the following elements: Cd, Cr, Cu, Mn, Ni and Pb, was performed using ICP–AES over the 0.2–1.5 and 1.5–20 μm FFDSF SPM fractions, proving that the analytical procedure based on UF/FFDSF/ICP–AES is consistent and useful in the investigation of trace element distribution in different SPM dimensional ranges versus that of the bulk phase. The relevance of aggregation–solubility equilibria concerning colloids of SPM phase is emphasized and further improvement of the procedure is discussed.     

Quantitative SPLITT fractionation of lagoon sediments

In this work, SPLITT Fractionation (split flow thin cell) is used to sort hydrodynamically sedimented particles coming from the Sacca di Goro, a lagoon-like system close to the Po River delta (Italy). First the possibility of performing quantitative mass separations with a SPLITT cell apparatus was checked on a standard silica sample of known particle size distribution (PSD). Environmental sediment samples and relative SPLITT sub-fractions were subject to Inductive Coupled Plasma--Atomic Emission Spectroscopy (ICP-AES) characterization for the following elements: Al, Fe, Cd, Cr, Cu, Ni, Mn, Pb and Zn. The distribution of these metals by particle size fractions has been investigated. The accuracy of the entire separation procedure has been also evaluated.     

Enantioselective Reactions in a Static Magnetic Field

Shortly after publication, E. Breitmaier, C. Eisenbraun, and G. J. Wolff declared their disassociation from this article owing to apparent manipulation of results by G. Zadel. Also see DOI: 10.1002/anie.199412011 , 10.1002/anie.199414571 , 10.1002/anie.199414581 , 10.1002/anie.199414591 .     

One-pot regioselective synthesis of nitrophenyloxazolinyl styrene oxides by the Darzens reaction of vicarious nucleophilic substitution-formed carbanions of 2-dichloromethyl-4,4-dimethyloxazoline

The vicarious nucleophilic substitution reaction of dichloromethyloxazoline 2 with nitrobenzene has been investigated. Treatment of 2 with t-BuOK followed by the addition of nitrobenzene leads to benzylic carbanions 4 or 9 depending upon the solvent used (DMSO, DMF, or THF). Subsequent treatment of 4 or 9 with aldehydes, in a Darzens-like reaction, furnishes very good yields of nitrophenyl oxazolinyloxiranes 8 and 11. 1,2-Dioxazolinyl-1,2-dinitrophenylethene 7 forms quantitatively when carbanion 4 is allowed to warm to room temperature in the absence of external electrophiles.     

Non-invasive and micro-destructive investigation of the <Emphasis Type="Italic">Domus Aurea</Emphasis> wall painting decorations

The paper reports on the exploitation of an educated multi-technique analytical approach based on a wide non invasive step followed by a focused micro-destructive step, aimed at the minimally invasive identification of the pigments decorating the ceiling of the Gilded Vault of the Domus Aurea in Rome. The combination of elemental analysis with molecular characterization provided by X-ray fluorescence and UV–vis spectroscopies, respectively, allowed for the in situ non-invasive identification of a remarkable number of pigments, namely Egyptian blue, green earth, cinnabar, red ochre and an anthraquinonic lake. The study was completed with the Raman analysis of two bulk samples, in particular, SERS measurements allowed for the speciation of the anthraquinonic pigment. Elemental mapping by scanning electron microscopy-energy dispersive spectrometer combined with micro-fluorimetry on cross-section gave an insight into both the distribution of different blend of pigments and on the nature of the inorganic support of the red dye.     

Development of new chromatographic tools based on A2A adenosine receptor subtype for ligand characterization and screening by FAC-MS

A liquid chromatographic stationary phase containing immobilized membranes from cells expressing A_2A adenosine receptor (A_2AAR) is firstly described. Cellular membranes from CHO cells stably transfected with human A_2AAR vector (A_2A(+)) and from the same cell line transfected with the corresponding empty vector (A_2A(?)) were entrapped on immobilized artificial membrane (IAM) support and packed into 6.6 mm I.D. glass columns to create A_2A(+)-IAM and A_2A(?)-IAM stationary phases. Frontal chromatography experiments on both A_2A(+)-IAM and A_2A(?)-IAM columns demonstrated the presence of a low specific interaction with the receptor. However, immobilized A_2A retained its ability to specifically bind known ligands as demonstrated by the agreement of the calculated K _d values with two different chromatographic protocols in comparison to previously reported data. In order to maximize the specific interaction, the same cellular membranes were immobilized on the inner surface of a silica capillary (40 cm?×?100 μm I.D.) by non-covalent interactions using the avidin–biotin coupling system to create two open tubular columns A_2A(+)-OT and A_2A(?)-OT. The open tubular system was characterized by ranking experiments for affinity studies in mixture useful for the selection of new potential candidates.