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61.
Branchi B Bergamini G Fiandro L Ceroni P Alvino A Doddi G Vögtle F Klärner FG 《Dalton transactions (Cambridge, England : 2003)》2011,40(6):1356-1364
Complexation of Zn(II) ions by cyclam cored dendrimers appended with four (G0), eight (G1) and 16 naphthyl chromophores (G2) at the periphery have been investigated in CH?CN-CH?Cl? 1?:?1 (v/v) solution by absorption and emission, ESI-mass and 1H NMR spectroscopy. The results obtained can be interpreted by the formation of complexes of 2?:?1 dendrimer to metal stoichiometry, at low metal ion concentration, and 1?:?1 complexes upon further addition of Zn(II) ions, for all the dendrimer generations. Upon addition of a molecular clip C2? consisting of two anthracene sidewalls bridged by a benzene group with two sulfate substituents in the para positions, heteroleptic complexes of general formula [GnZnC] are formed. Interestingly, in these complexes, a very efficient quenching (practically 100%) of the dendrimer naphthyl luminescence and sensitization (ca. 90%) of the clip anthracene emission take place. The complex [G2ZnC] exhibits a very high molar absorption coefficient in the UV spectral region owing to the 16 naphthyl chromophores of the dendrimer and the two anthracene units of the clip (ε = 1.7 × 10? M?1 cm?1 at 263 nm). Furthermore, the excitation energy absorbed by the naphthyl chromophores is efficiently funneled to the two anthracene units of the clip, which emits in the blue spectral region. 相似文献
62.
Muniz-Miranda M Del Rosso T Giorgetti E Margheri G Ghini G Cicchi S 《Analytical and bioanalytical chemistry》2011,400(2):361-367
We investigated the chemisorption of self-assembled monolayers of sulfur-functionalized 4-amino-7-nitrobenzofurazan on gold
and silver nanoisland films (NIFs) by means of surface-enhanced fluorescence (SEF) and surface-enhanced Raman scattering (SERS).
The ligand is a push–pull molecule, where an intramolecular charge transfer occurs between an electron-donor and an electron-acceptor
group, thus exhibiting nonlinear optical properties that are related to both SERS and SEF effects. The presence of different
heteroatoms in the molecule ensures the possibility of chemical interaction with both silver and gold substrates. The SERS
spectra suggest that furazan is bound to silver via lone pairs of the nitrogen atoms, whereas the ligand is linked to gold
via a sulfur atom. Silver NIFs provide more efficient enhancement of both fluorescence and Raman scattering in comparison
with gold NIFs. The present SEF and SERS investigation could provide useful information for foreseeing changes in the nonlinear
responses of this push–pull molecule. 相似文献
63.
We consider the problem of the existence of uniform interpolants in the modal logic K4. We first prove that all ${\square}$ -free formulas have uniform interpolants in this logic. In the general case, we shall prove that given a modal formula ${\phi}$ and a sublanguage L of the language of the formula, we can decide whether ${\phi}$ has a uniform interpolant with respect to L in K4. The ${\square}$ -free case is proved using a reduction to the G?del L?b Logic GL, while in the general case we prove that the question of whether a modal formula has uniform interpolants over transitive frames can be reduced to a decidable expressivity problem on the???-calculus. 相似文献
64.
Giacomo Lenzi 《Mathematical Logic Quarterly》2011,57(5):474-480
We introduce a quite natural Frege‐style set theory, which we call Strong‐Frege‐2 $(\mathsf {SF}_2)$, a sort of simplification of the theory considered in 13 (under the name Strong‐Frege‐3) and 1 (under the name F2). We give a model of a weaker variant of $\mathsf {SF}_2$, called $\mathsf {SF}_2\mathsf {AC}$, where atoms and coatoms are allowed. To construct the model we use an enumeration “almost without repetitions” of the Π11 sets of natural numbers; such an enumeration can be obtained via a classical priority argument much in the style of 5 and 15 . © 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim 相似文献
65.
Angela Cardelli Lucia Ricci Giacomo Ruggeri Silvia Borsacchi Marco Geppi 《European Polymer Journal》2011,(8):1589-1600
A micrometric silica modified with perylene derivative (SiO2–TES) has been prepared by hydrolysis–condensation reactions between silica and N,N’-bis-(3-triethoxysilylpropyl)-perylene-tetracarboxyldiimide (P-TES) and utilized as filler in LLDPE films together with a compatibilizer. Spectroscopic analyses on SiO2–TES confirmed the grafting of P-TES on silica, while its amount was determined by thermogravimetric analysis. Solid state NMR provided information about the structure of silicon atoms involved in the condensation of SiO2 and P-TES that resulted mainly in silicon atoms grafted with bi-dentate anchorages.UV–Vis and fluorescence analyses carried out on P-TES showed the ability of the dye to generate J-type aggregates in apolar solvents. The same analyses on SiO2–TES revealed the presence of both isolated and aggregated dye molecules grafted on silica surface, while on polymeric dispersions of SiO2–TES, they have shown only the presence of P-TES aggregates grafted to silica.Thanks to the direct correlation between optical properties (obtained both by UV–Vis and by fluorescence analyses) and the chemical environment of composites, the luminescent silica SiO2–TES could be used to estimate the filler dispersion extent in different microcomposite polymer materials. 相似文献
66.
Pedone A Prampolini G Monti S Barone V 《Physical chemistry chemical physics : PCCP》2011,13(37):16689-16697
A multi-scale computational protocol, which combines Quantum Mechanics and Molecular Mechanics (QM/MM) calculations with the polarisable continuum model (PCM), has been used to study the tetramethylrhodamine isothiocyanate (TRITC) fluorophore, embedded in three different environments, namely in water, on an amorphous silica surface and covalently encapsulated in a silica nanoparticle (C dot). Absorption and emission spectra have been simulated by using TD-B3LYP/PCM calculations, performed on the TRITC ground and excited state geometries, optimized at the QM/MM level. The results are in good agreement with experimental data confirming the caging effect played by the silica shell on the mobility of the TRITC molecule when covalently encapsulated in silica nanoparticles. This could result in a decrease of the nonradiative decay rate and thus an increase of the quantum yield of the molecule. 相似文献
67.
Barone V Bloino J Monti S Pedone A Prampolini G 《Physical chemistry chemical physics : PCCP》2011,13(6):2160-2166
Classical all-atom molecular dynamics (MD) simulations and quantum mechanical (QM) time-dependent density functional theory (TD-DFT) calculations are employed to study the conformational and photophysical properties of the first emitter excited state of tetramethyl-rhodamine iso-thiocyanate fluorophore in aqueous solution. For this purpose, a specific and accurate force field has been parameterised from QM data to model the fluorophore's first bright excited state. During the MD simulations, the consequences of the π→π* electronic transition on the structure and microsolvation sphere of the dye has been analysed in some detail and compared to the ground state behaviour. Thereafter, fluorescence has been calculated at the TD-DFT level on configurations sampled from the simulated MD trajectories, allowing us to include time dependent solvent effects in the computed emission spectrum. The latter, when compared with the absorption spectrum, reproduces well the experimental Stokes shift, further validating the proposed multilevel computational procedure. 相似文献
68.
Caruso R Gambino GL Scordino M Sabatino L Traulo P Gagliano G 《Natural product communications》2011,6(12):1939-1943
The influence of the wine distillation process on methanol content has been determined by quantitative analysis using gas chromatographic flame ionization (GC-FID) detection. A comparative study between direct injection of diluted wine and injection of distilled wine was performed. The distillation process does not affect methanol quantification in wines in proportions higher than 10%. While quantification performed on distilled samples gives more reliable results, a screening method for wine injection after a 1:5 water dilution could be employed. The proposed technique was found to be a compromise between the time consuming distillation process and direct wine injection. In the studied calibration range, the stability of the volatile compounds in the reference solution is concentration-dependent. The stability is higher in the less concentrated reference solution. To shorten the operation time, a stronger temperature ramp and carrier flow rate was employed. With these conditions, helium consumption and column thermal stress were increased. However, detection limits, calibration limits, and analytical method performances are not affected substantially by changing from normal to forced GC conditions. Statistical data evaluation were made using both ordinary (OLS) and bivariate least squares (BLS) calibration models. Further confirmation was obtained that limit of detection (LOD) values, calculated according to the 3sigma approach, are lower than the respective Hubaux-Vos (H-V) calculation method. H-V LOD depends upon background noise, calibration parameters and the number of reference standard solutions employed in producing the calibration curve. These remarks are confirmed by both calibration models used. 相似文献
69.
70.
A 0/±1 matrix is balanced if it does not contain a square submatrix with exactly two nonzero entries per row and per column
in which the sum of all entries is 2 modulo 4. A 0/1 matrix is balanceable if its nonzero entries can be signed ±1 so that
the resulting matrix is balanced. A signing algorithm due to Camion shows that the problems of recognizing balanced 0/±1 matrices
and balanceable 0/1 matrices are equivalent. Conforti, Cornuéjols, Kapoor and Vušković gave an algorithm to test if a 0/±1
matrix is balanced. Truemper has characterized balanceable 0/1 matrices in terms of forbidden submatrices. In this paper we
give an algorithm that explicitly finds one of these forbidden submatrices or shows that none exists.
Received: October 2004 相似文献