Placido Mineo

Thiophene Based Europium β-Diketonate Complexes: Effect of the Ligand Structure on the Emission Quantum Yield

The synthesis and the molecular and photophysical characterization, together with solid state and solution structure analysis, of a series of europium complexes based on β-diketonate ligands are reported. The Eu(III) complex emission, specifically its photoluminescence quantum yield (PL-QY), can be tuned by changing ligands which finely modifies the environment of the metal ion. Steady-state and time-resolved emission spectroscopy and overall PL-QY measurements are reported and related to geometrical features observed in crystal structures of some selected compounds. Moreover, paramagnetic NMR, based on the analogous complexes with other lanthanides, are use to demonstrate that there is a significant structural reorganization upon dissolution, which justifies the observed differences in the emission properties between solid and solution states. The energy of the triplet levels of the ligands and the occurrence of nonradiative deactivation processes clearly account for the luminescence efficiencies of the complexes in the series.

Selective monitoring of parts per million levels of CO by covalently immobilized metal complexes on glass

Optical detection of parts-per-million (ppm) levels of CO by a structurally well-defined monolayer consisting of bimetallic rhodium complexes on glass substrates has been demonstrated.

Very fast CO2 response and hydrophobic properties of novel poly(ionic liquid)s

A series of polymerizable tetraalkylammonium ionic liquids based on [2-(methacryloyloxy)ethyl]dimethylheptyl ammonium cation and bis(trifluoromethylsulfonyl)imide, nonafluoro-1-butanesulfonate, dodecylbenzenesulfonate, heptadecafluorooctanesulfonate, 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecanoate anions, as well as their corresponding homo- and copolymers, have been synthesized and characterized by means of 1H NMR, TG-DTA, DSC, MALDI-TOF, viscosimetry and XPS investigations. Hydrophobic and CO2 sensing properties of the poly(ionic liquid)s have been explored by dynamic contact angle and quartz crystal microbalance measurements. The CO2 sensing behavior of present polymers is very remarkable as they are featured by extremely rapid and completely reversible response without any memory-effect. Best results, in terms of sensitivity, have been obtained for [2-(methacryloyloxy)ethyl]dimethylheptyl ammonium nonafluoro-1-butanesulfonate-based homopolymer. Tensiometric data show good hydrophobic properties with θadv > 90° for all the polymers under study except the one involving 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecanoate anion (θadv = 78.3°); receding contact angles, representative of the most hydrophilic portions of the polymers surface, lie in the range 22–54° and can be further improved by choosing the proper long-chained N-alkyl groups.

Synthesis and Characterization of Uncharged Water-Soluble Star Polymers Containing a Porphyrin Core

Uncharged water-soluble porphyrins were prepared by reaction between tetrakis(p-hydroxy-phenyl)porphyrin and chlorinated poly(ethylen glycol) methyl ethers of different molecular weights. Water-solubility was achieved by binding four poly(ethylene glycol) branches to a porphyrin core to give star polymers with molecular weights in the range 2000-21 000 Da. Structural characterization of these star polymers was performed by means of gel permeation chromatography, NMR spectroscopy, and MALDI-TOF analysis.

A new application of ionic liquids: hydrophobic properties of tetraalkylammonium-based poly(ionic liquid)s

The potential of using poly(ionic liquid)s as a new family of hydrorepellent materials has been explored. Free-radical polymerization of a series of ionic liquids based on the polymerizable cation [2-(methacryloyloxy)ethyl]trimethylammonium and on the hydrophobic anions bis(trifluoromethylsulfonyl)imide, nonafluoro-1-butanesulfonate and dodecylbenzenesulfonate led to the corresponding poly(ionic liquid)s that were characterized by TGA and DSC analysis, SEM, MALDI-TOF and XPS spectroscopy. Contact angle investigations show that the nature of the surface of the poly(ionic liquid)s based on the nonafluoro-1-butanesulfonate and dodecylbenzenesulfonate anions are featured by remarkable hydrophobic properties with advancing contact angles (θadv) lying in the range 113–118°, while to the polymer poly[2-(methacryloyloxy)ethyl]trimethylammonium bis(trifluoromethylsulfonyl)imide is associated poor hydrorepellent activity (θadv = 76°). The tensiometric measurements also experience receding contact angles (θrec) lying in the range 16–20° and a consequent high hysteresis suggesting that, on the outermost layers of the polymers, very high and very low-energy surface portions are present.

Effect of combined changes in delayed extraction time and potential gradient on the mass resolution and ion discrimination in the analysis of polydisperse polymers and polymer blends by delayed extraction matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

Data reported here show that, in the delayed extraction matrix-assisted laser desorption/ionization time-of-flight (DE-MALDI-TOF) mass spectrometric analysis of synthetic polydisperse polymers, different experimental conditions of spectral recording are required to optimize the signal in all the m/z regions of the spectrum. The effect of combined changes in delay time and grid voltage % values on both mass resolution and mass accuracy of DE spectra of a polyethylene glycol sample (PEG(mix), with a well-defined molar distribution of its components) is discussed. The necessity of a compromise between the values of these two parameters is shown. Furthermore, the occurrence of analyte discrimination, which can invalidate the composition analysis especially in the case of polymer blends, is demonstrated. Copyright 1999 John Wiley & Sons, Ltd.

An x-ray photoelectron spectra and atomic force microscopy characterization of silica substrates engineered with a covalently assembled siloxane monolayer

Silica substrates were functionalized with a covalent 4-ClCH(2)C(6)H(4)SiCl(3) monolayer. Additional covalent bonding of appropriate functional molecules to the silylated substrates was further achieved. The surface chemical characterization was carried out by angle resolved x-ray photoelectron measurements. Moreover, surface morphological characterizations were performed by atomic force microscopy measurements. Present results provide step by step information on the covalently linked monolayer during the synthetic procedure.

A NEW PROCEDURE FOR QUANTITATIVE CORRECTION OF MATRIX-ASSISTED LASER DESORPTION/IONIZATION TIME-OF-FLIGHT MASS SPECTROMETRIC RESPONSE

A simple procedure for the correction of the decreasing detection response in a Matrix-assisted laser desorption/Ionization time-of-flight (MALDI-TOF) mass spectrum with increasing ion mass is reported. On the basis of the experimental MALDI-TOF mass spectrum of a mixture of four polymethylmethacrylate (PMMA) standards (molecular masses in the range 4–100 kDa), present in equal molar abundance, an equation describing the MALDI-TOF response has been derived. This equation has been used to correct any subsequently recorded MALDI spectrum. As an example, the procedure has been applied here to normalize the MALDI-TOF mass spectrum of a 1,20-di(bisphenoxy-A)eicosane based copolyformal (I) containing porphyrin units in the main chain. # 1998 John Wiley & Sons, Ltd.

Production of filmable medium-chain-length polyhydroxyalkanoates produced from glycerol by Pseudomonas mediterranea

Glycerol is an effective carbon source for the production of scl- and mcl-polyhydroxyalkanoates (PHAs) by Pseudomonas spp. P. mediterranea 9.1 (CFBP 5447) synthesizes an amorphous mcl-PHA when grown on crude glycerol, whereas on both reagent grade (RG) and partially refined (PR) glycerol, it produces two very similar distinctive mcl-PHAs with the unusual property of producing, with the appropriate treatment, a transparent film. Mcl-PHAs recovered after biomass extraction have an average molecular weight of approximately 56,000/63,000 Da. The monomer composition and physicochemical properties of such mcl-PHAs suggest their potential application as a softener of biopolymeric blends for food packaging and medical devices.

Supramolecular Assemblies Based on Complexes of Nonionic Amphiphilic Cyclodextrins and a meso-Tetra(4-sulfonatophenyl)porphine Tributyltin(IV) Derivative: Potential Nanotherapeutics against Melanoma

Amphiphilic cyclodextrin (ACyD) provides water-soluble and adaptable nanovectors by modulating the balance between the hydrophobic and hydrophilic chains at both CyD sides. This work aimed to design nanoassemblies based on nonionic and hydrophilic ACyD (SC6OH) for the delivery of a poor-water-soluble organotin(IV)-porphyrin derivative [(Bu3Sn)4TPPS] to melanoma cancer cells. To characterize the porphyrin derivatives under simulated physiological conditions, a speciation was performed using complementary techniques. In aqueous solution (≤ 20 μM), (Bu3Sn)4TPPS primarily exists as a monomer (2 in Figure 1), as suggested by the low static anisotropy (ρ ≈ 0.02) with a negligible formation of porphyrin supramolecular aggregates. MALDI-TOF spectra indicate the presence of moieties (i.e., [(Bu3Sn)3TPPS](-)) that are derivatives of the monomeric species. Spectrofluorimetry coupled with potentiometric measurements primarily assesses the presence of the hydrolytic [(Bu3Sn)4TPPS (OH)4](4-) species under physiological conditions. Nanoassemblies of (Bu3Sn)4TPPS/SC6OH were prepared by dispersion of organic films in PBS at pH 7.4 and were investigated using a combination of spectroscopic and morphological techniques. The UV-vis and emission fluorescence spectra of the (Bu3Sn)4TPPS/SC6OH reveal shifts in the peculiar bands of the organotin(IV)-porphyrin derivative due to its interaction with the ACyD supramolecular assemblies in aqueous solution. The mean size was within the range of 100-120 nm. The ξ-potential was negative (-16 mV) for the (Bu3Sn)4TPPS/SC6OH nanoassemblies, with an entrapment efficiency of approximately 67%. The intracellular delivery, cytotoxicity, nuclear morphology and cell growth kinetics were evaluated via fluorescence microscopy on A375 human melanoma cells. The delivery of (Bu3Sn)4TPPS by ACyD with respect to free (Bu3Sn)4TPPS increases the internalization efficiency and cytotoxicity to induce apoptotic cell death and, at lower concentrations, changes the cellular morphology and prevents cell proliferation.