A "jellyfish" shaped green emitting gallium(III)-containing metallomesogen

The synthesis of the first gallium(III)-based liquid crystal has been achieved grafting around the metal centre two chelating 2-methylquinolin-8-olate anions and one monodentate 3,4,5-tris(hexadecyloxy)benzoyloxy ligand, allowing the resulting complex to be a soft luminescent material with the typical high quantum yield of pentacordinated gallium species.     

Vapochromic behavior of polycarbonate films doped with a luminescent molecular rotor

We report on vapochromic films suitable for detecting volatile organic compounds (VOCs), based on polycarbonate (PC) doped with 4‐(triphenylamino)phthalonitrile (TPAP), a fluorescent molecular rotor sensitive to solvent polarity and viscosity. PC films of variable thickness (from 20 up to 80 µm) and containing small amounts of TPAP (0.05 wt%) were prepared and exposed to a saturated atmosphere of different VOCs. TPAP/PC films showed a gradual decrease and red‐shift of the emission during the exposure to solvents with high polarity index and favorable interaction with the polymer matrix such as THF, CHCl₃, and acetonitrile. In the case of the most interacting solvents (THF and CHCl₃), TPAP/PC films also showed a fluorescence increase at longer exposure times, as a consequence of an irreversible, solvent‐induced crystallization process of the polymeric matrix. The vapochromism of TPAP/PC films is rationalized on the basis of alterations of the rotor intramolecular motion upon solvent uptake by PC and polarity effects of the microenvironment. Interestingly, the fluorescence response of the TPAP/PC films shows a non‐trivial, tuneable dependence on film thickness during the second solvent‐exposure stage. The latter effect is attributed to a variable extent of the crystallization process occurring in the PC films. This observation promptly suggests, in turn, an effective procedure to modulate the spectroscopic response in such functionalized polymeric materials through the precise control of the film thickness. Copyright © 2015 John Wiley & Sons, Ltd.     

Study of beta-cyclodextrin/fluorinated trimethyl ammonium bromide surfactant inclusion complex by fluorinated surfactant ion selective electrode

The construction and performance of a liquid membrane electrode responsive to N-(1,1,2,2-tetrahydroperfluorooctyl)-N,N,N-trimethylammonium bromide (FTABr) and its use for the study of β-cyclodextrin/fluorinated surfactant inclusion complex is described. The electrode is based on the use of tetrahydroperfluorooctyltrimethylammonium-tetraphenylborate ion pair as electro active material in polyvinyl chloride (PVC) matrix plasticized using 2-Nitrophenyl octyl ether (NPOE). The electrode exhibits a fast, stable, reproducible and “Nernstian” response (59 ± 2 mV) for FTABr over the concentration range of 10⁻⁵ to 2 × 10⁻³ mol L⁻¹ at 298 K. The lowest detection limit is 2 × 10⁻⁶ mol L⁻¹ and the response time is around 20-30 s. The validity of the electrode, for detection of fluorinated surfactant ions and hence to carry out electrochemical measurements to study micellization of fluorinated surfactant, is verified by comparing the critical micelle concentration (cmc) value of FTABr obtained by using the electrode, with that obtained by surface tension measurements. Association constant K for β-cyclodextrin/FTABr complex is evaluated from the potentiometric measurements carried out using this electrode and is observed to be ∼1.26 × 10⁵. The results suggest that β-cyclodextrin forms an equimolar association complex with the FTA⁺ surfactant ion.     

Non-ionic amphiphilic homopolymers: synthesis, solution properties, and biochemical validation

A novel type of nonionic amphipols for handling membrane proteins in detergent-free aqueous solutions has been obtained through free-radical homo-telomerization of an acrylamide-based monomer comprising a C(11) alkyl chain and two glucose moieties, using a thiol as transfer reagent. By controlling the thiol/monomer ratio, the number-average molecular weight of the polymers was varied from 8 to 63 kDa. Homopolymeric nonionic amphipols were found to be highly soluble in water and to self-organize, within a large concentration range, into small, compact particles of ~6 nm diameter with a narrow size distribution, regardless of the molecular weight of the polymer. They proved able to trap and stabilize two test membrane proteins, bacteriorhodopsin from Halobium salinarum and the outer membrane protein X of Escherichia coli, under the form of small and well-defined complexes, whose size, composition, and shape were studied by aqueous size-exclusion chromatography, analytical ultracentrifugation, and small-angle neutron scattering. As shown in a companion paper, nonionic amphipols can be used for membrane protein folding, cell-free synthesis, and solution NMR studies (Bazzacco et al. 2012, Biochemistry, DOI: 10.1021/bi201862v).     

Effect of uniaxial strain on the Drude weight of graphene

We study the dependence on the strength and orientation of applied uniaxial strain of the Drude weight in the conductivity of graphene. We find a non-monotonic dependence on strain, which may be related to the proximity to several strain-induced electronic topological transitions. Given the relation between the Drude weight and the long-wavelength plasmon frequency, such a strain dependence can be evidenced by infrared spectroscopy measurements.     

A symmetry result for the p-laplacian equation via the moving planes method

Thsi paper is concerned with a positive solution u of the non–homogeneous p–Laplacian equation in an open, bounded, connected subset Ω of Rⁿ with C² boundary. We assume that u verifies overdetermined boundary conditions and we prove that of us has only one critial point Ω thenΩ is a ball and u is radially symmetric; to prove this result we use the moving planes method introduced by J.Serrien. Using the same technique we also prove that the result is stable in the following sense: the boundary of Ω tends to the boundary of a sphere as the diameter of the critical set u tends to 0.     

The Anti-Plane Shear Problem in Nonlinear Elasticity Revisited

A classical problem in the framework of nonlinear elasticity theory is the characterization of the materials that may sustain a pure state of anti-plane shear in the absence of body forces. This problem has been solved by Knowles and by Hill in the framework of isotropic and incompressible elasticity in the seventies. Here we provide a simpler and shorter proof of these classical results. Moreover, we extend these results to nonlinear elastodynamics and we provide some new special solutions.     

Pairing symmetry of superconducting graphene

The possibility of intrinsic superconductivity in alkali-coated graphene monolayers has been recently suggested theoretically. Here, we derive the possible pairing symmetries of a carbon honeycomb lattice and discuss their phase diagram. We also evaluate the superconducting local density of states (LDOS) around an isolated impurity. This is directly related to scanning tunneling microscopy experiments, and may evidence the occurrence of unconventional superconductivity in graphene.