High-quality manganese-doped zinc sulfide quantum rods with tunable dual-color and multiphoton emissions

We report a simple, fast and green phosphine-free colloidal chemistry to synthesize high-quality wurtzite-type Mn-doped ZnS quantum rods (QRs) with tunable diameters (1.6-5.6 nm), high aspect ratios (up to 50), variable Mn doping levels (0.18-1.60%), and high quantum yields (up to 45%). The electron paramagnetic resonance spectra with modeling reveal the successful doping of paramagnetic Mn(2+) ions in the host ZnS QRs. The Mn-doped ZnS QRs demonstrate tunable dual-color (orange and blue) emissions by tuning the doping levels and UV excitation wavelengths. The orange emission with long decay lifetime (3.3 ms) originates from the doped Mn(2+) states, while the blue emission with fast decay lifetime (0.31 ns) is attributed to the QR surface states. The bright two- and three-photon excitation upconversion luminescence from the Mn-doped ZnS QRs have been observed using tunable near-infrared femtosecond laser. Our strategy provides a versatile route to programmably control the optical properties of anisotropic semiconductor nanomaterials, which may create new opportunities for photonic devices and bioimaging applications.     

Thermodynamic and dynamic anomalies in a one-dimensional lattice model of liquid water

We investigate the occurrence of waterlike thermodynamic and dynamic anomalous behavior in a one dimensional lattice gas model. The system thermodynamics is obtained using the transfer matrix technique and anomalies on density and thermodynamic response functions are found. When the hydrogen bond (molecules separated by holes) is more attractive than the van der Waals interaction (molecules in contact) a transition between two fluid structures is found at null temperature and high pressure. This transition is analogous to a 'critical point' and intimately connects the anomalies in density and in thermodynamic response functions. Monte Carlo simulations were performed in the neighborhood of this transition and used to calculate the self diffusion constant, which increases with density as in liquid water.     

Laser microperforated biodegradable microbial polyhydroxyalkanoate substrates for tissue repair strategies: an infrared microspectroscopy study

Flexible and biodegradable film substrates prepared by solvent casting from poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) solutions in chloroform were microperforated by ultraviolet laser ablation and subsequently characterized using infrared (IR) microspectroscopy and imaging techniques and scanning electron microscopy (SEM). Both transmission synchrotron IR microspectroscopy and attenuated total reflectance microspectroscopy measurements demonstrate variations in the polymer at the ablated pore rims, including evidence for changes in chemical structure and crystallinity. SEM results on microperforated PHBHV substrates after cell culture demonstrated that the physical and chemical changes observed in the biomaterial did not hinder cell migration through the pores.     

Belief functions combination without the assumption of independence of the information sources

This paper considers the problem of combining belief functions obtained from not necessarily independent sources of information. It introduces two combination rules for the situation in which no assumption is made about the dependence of the information sources. These two rules are based on cautious combinations of plausibility and commonality functions, respectively. The paper studies the properties of these rules and their connection with Dempster’s rules of conditioning and combination and the minimum rule of possibility theory.     

Strict core fuzzy logics and quasi-witnessed models

In this paper we prove strong completeness of axiomatic extensions of first-order strict core fuzzy logics with the so-called quasi-witnessed axioms with respect to quasi-witnessed models. As a consequence we obtain strong completeness of Product Predicate Logic with respect to quasi-witnessed models, already proven by M.C. Laskowski and S. Malekpour in [19]. Finally we study similar problems for expansions with ??, define ??-quasi-witnessed axioms and prove that any axiomatic extension of a first-order strict core fuzzy logic, expanded with ??, and ??-quasi-witnessed axioms are complete with respect to ??-quasi-witnessed models.     

How linker's modification controls swelling properties of highly flexible iron(III) dicarboxylates MIL-88

A series of organically modified iron(III) terephthalate MIL-88B and iron(III) 4,4'-biphenyl dicarboxylate MIL-88D flexible solids have been synthesized and characterized through a combination of X-ray diffraction, IR spectroscopy, and thermal analysis (MIL stands for Material from Institut Lavoisier). The swelling amplitude of the highly flexible MOFs tuned by introducing functional groups onto the phenyl rings shows a clear dependence on the steric hindrance and on the number of groups per aromatic ring. For instance, while the introduction of four methyl groups per spacer in dried MIL-88B results in a large permanent porosity, introducing two or four methyl groups in MIL-88D allows an easier pore opening in the presence of liquids without drastically decreasing the swelling magnitude. The influence of the degree of saturation of the metal center and the nature of the solvent on the swelling is also discussed. Finally, a computationally assisted structure determination has led to a proposal of plausible structures for the closed (dried) and open forms of modified MIL-88B and MIL-88D and to evaluation of their framework energies subject to the nature of the functional groups.     

One Step Ultrasound Extraction and Purification Method for the Gas Chromatographic Analysis of Hydrocarbons from Marine Sediments: Application to the Monitoring of Italian Coasts

In this study, we describe the development of an ultrasound-assisted method for the simultaneous extraction and purification of hydrocarbons from marine sediments and then its application to the gas chromatographic analysis for the estimation of the biogenic anthropogenic and petrogenic sources of hydrocarbons present in marine sediments. The extraction of hydrocarbons and their simultaneous purification from other organic compounds present in sediments was performed by sonication of a three phase system consisting of sediment, hexane and a HCl medium at pH 2. This method allowed accurate recoveries of the hydrocarbon content in samples. In the following GC-FID analysis, we examined the hydrocarbon distribution in four different areas of the Italian seas determining the pristane to phytane ratio, the total odd n-alkanes to even n-alkanes ratio (carbon preference index), the low molecular weight to high molecular weight ratio, perylene content and the presence of the so called unresolved complex mixture; according to recent studies, these parameters support the identification of the biogenic, anthropogenic and petrogenic hydrocarbon sources present in environmental samples. GC chromatograms were then re-examined by means of two different statistical multivariate methods: two-dimensional mapping (2DMAP) and independent component analysis (ICA). 2DMAP showed the presence of a significant heterogeneity in the hydrocarbon composition of different areas and within samples of a same area. ICA confirmed the general heterogeneity evidenced by 2DMAP allowing in addition to characterise the hydrocarbon composition of one of the investigated areas.

     

Tuning of the spin distribution between ligand- and metal-based spin: electron paramagnetic resonance of mixed-ligand molybdenum tris(dithiolene) complex anions

Electron paramagnetic resonance spectra of homoleptic and mixed-ligand molybdenum tris(dithiolene) complex anions [Mo(tfd)(m)(bdt)(n)](-) (n + m = 3; bdt = S(2)C(6)H(4); tfd = S(2)C(2)(CF(3))(2)) reveal that the spin density has mixed metal-ligand character with more ligand-based spin for [Mo(tfd)(3)](-) and a higher degree of metal-based spin for [Mo(bdt)(3)](-): the magnitude of the isotropic (95,97)Mo hyperfine interaction increases continuously, by a factor of 2.5, on going from the former to the latter. The mixed complexes fall in between, and the metal character of the spin increases with the bdt content. The experiments were corroborated by density functional theory computations, which reproduce this steady increase in metal-based character.     

Modeling the geometric, electronic, and redox properties of iron(III)-containing amphiphiles with asymmetric [NN'O] headgroups

Two iron(III)-containing amphiphiles 1 and 2 have been synthesized with the [NN'O] ligands HL(tBu-ODA) (2-((octadecyl(pyridin-2-ylmethyl)amino)methyl)-4,6-di-tert-butylphenol) and HL(I-ODA) (2-((octadecyl(pyridin-2-ylmethyl)amino)methyl)-4,6-diiodophenol), respectively. Compound 1 is monometallic, whereas EXAFS data suggest that 2 is a mixture of mono- and bimetallic species. The archetypical [Fe(III)(L(NN'O))(2)](+) complexes 3-9 have been isolated and characterized in order to understand the geometric, electronic, and redox properties of the amphiphiles. Preference for a monometallic or bimetallic nuclearity is dependent on (i) the nature of the solvent used for synthesis and (ii) the type of the substituent in the phenol moiety. In methanol, the tert-butyl-, methoxy-, and chloro-substituted 3, 4, and 5 are monometallic species, whereas the bromo- and iodo-substituted 6 and 7 form bimetallic complexes taking advantage of stabilizing methoxo bridges generated by solvent deprotonation. In dichloromethane, the bromo- and iodo-substituted 8 and 9 are monometallic species; however, these species favor meridional coordination in opposition to the facial coordination observed for the tert-butyl- and methoxy-substituted compounds. Molecular structures for species 5, 7, 8, and 9 have been solved by X-ray diffraction. Furthermore, the electronic spectrum of the amphiphile 1 was expected to be similar to those of facial/cis archetypes with similar substituents, but close resemblance was observed with the profile for those meridional/cis species, suggesting a similar coordination mode. This trend is discussed based on DFT calculations, where preference for the meridional/cis coordination mode appears related to the presence of tertiary amine nitrogen on the ligand, as when a long alkyl chain is attached to the [NN'O] headgroup.     

Stereoselective synthesis of tetracyclic indolines via gold-catalyzed cascade cyclization reactions

A reliable synthetic route to fused polycyclic indolines is documented by the development of a stereoselective gold catalyzed cascade cyclization of indole propargylic alcohols.