Structural influence of the inorganic network in the laser performance of dye-doped hybrid materials

We report a systematic study of the influence on the laser action of Rhodamine 6G (Rh6G) of the composition and structure of new hybrid matrices based on 2-hydroxyethyl methacrylate (HEMA) as organic monomer and different weight proportions of dimethyldiethoxysilane (DEOS) and tetraethoxysilane (TEOS) as inorganic part. We selected mixtures of di- and tetra-functionalized alkoxides trying to decrease, in a controlled way, the rigidity of the three-dimensional network by making use of the flexibility provided by the linear chains acting as a spacer of the inorganic domains. The organization of the molecular units in these nanomaterials was studied through a structural analysis by solid-state NMR. The different reactivity exhibited by di- and tetra-functionalized silanols generates a non-homogeneous tri-dimensional network. Thus, the laser performance in dye-doped hybrid materials is improved when the inorganic phase is composed of a unique alkoxide.This revised version was published online in August 2005 with a corrected cover date.     

Radikalische Copolymerisation von cyclischen Acetalen, die sich vom Acrolein ableiten. 2. Mitt. Alternierende Copolymerisation

Ohne Zusammenfassung     

Radikalische Copolymerisation von Vinylketonen. 1. Mitt. Copolymerisation mit Acrylnitril

Ohne Zusammenfassung     

Synthesis and crystal structure of the first scandium-containing open framework solid

A novel open framework scandium sulfate phosphate is prepared hydrothermally in the presence of the azamacrocycle cyclen (1,4,7,10-tetraazacyclododecane) in which secondary building units of formula Sc7(S,P)12O48 are linked to give a structure with supercages.     

11C-methiodide quinuclidinyl benzilate a muscarinic antagonist for in vivo studies of myocardial muscarinic receptors

A method for labeling MQNB (Methiodide quinuclidinyl benzilate) with carbon-11 using¹¹C-methyl iodide is reported. Injectable labeled product (100 mCi; max. 200 mCi) radiochemically and chemically pure is obtained in a 30 minute synthesis time with a specific activity of 1 Ci/μmol, (max. 2.3 Ci/μmol).     

Capillary electrophoresis-mass spectrometry of proteins at medium pH using bilayer-coated capillaries

The feasibility of using noncovalently bilayer-coated capillaries for capillary electrophoresis-mass spectrometry (CE-MS) of acidic proteins was investigated using background electrolytes (BGEs) of medium pH. The capillary was coated by successively rinsing the capillary with solutions of the oppositely charged polymers polybrene (PB) and poly(vinyl sulfonic acid) (PVS). Volatile BGEs containing ammonium formate and/or N-methyl morpholine were tested at pH 7.5 and 8.5. Overall, these BGEs provided relatively fast protein separations (analysis times of ca. 12 min) and showed high efficiencies (70,000-300,000 plates) when the ionic strength was sufficiently high. Migration-time reproducibilities were very favorable with RSDs of less than 1.0%. Infusion experiments showed satisfactory MS responses for studied proteins dissolved in ammonium formate (pH 8.5), however, high concentrations of N-methyl morpholine appeared to seriously suppress the MS protein signals. Evaluation of the CE-MS system was performed by analyzing a mixture of intact proteins yielding efficient separations and good-quality mass spectra. CE-MS analysis of a reconstituted formulation of the biopharmaceutical recombinant human growth hormone (rhGH) which was stored for a prolonged time, revealed one degradation product which was provisionally identified as desamido rhGH. Based on the MS responses the amount of degradation was estimated to be ca. 25%.     

Photoinitiated homopolymerization and copolymerization of furfuryl methacrylate and N-vinylpyrrolidone

The study of the homo- and copolymerization of furfuryl methacrylate ( F ) and vinylpyrrolidone ( P ) in bulk, initiated by the photoactivation of AIBN at low temperatures (0 and 40°C), is described. The kinetic diagrams for the homopolymerization of F and P were obtained following the evolution of the heat of reaction by DSC, and revealed the autoacceleration and the vitrification effects on the polymerization rate. The influence of oxygen in the photoinitiated polymerization was analyzed by determining the steady-state concentration of oxygen from the kinetic data obtained for polymerizations performed out in the presence and absence of oxygen. The results obtained indicate that P is more sensitive than F to the presence of oxygen in free radical polymerization. The photoinitiated copolymerization process is little affected by the concentration of monomers, giving similar R_p and θ_m values for both systems. However, at low polymerization temperature 0°C non-crosslinked copolymers are obtained, whereas at a temperature of 40°C, the copolymers prepared at conversion higher than 20 mol % become crosslinked as a result of the active participation of the furfuryl ring in the polymerization process at this temperature. © 1996 John Wiley & Sons, Inc.     

185 nm Photoreduction of CO(2) to Methane by Water. Influence of the Presence of a Basic Catalyst

Photolysis of CO(2) at 185 nm using a Hg lamp in the presence of H(2) or H(2)O leads to the formation of CH(4) (after an induction period) and a lesser amount of CO. Using H(2) gas as reducing agent, up to 40% conversion was achieved with almost complete selectivity to methane and energy consumption of 1.55 Gcal/mol. When CO(2) irradiation is carried out in the gas phase in the presence of H(2)O, both reagents can undergo photolysis, and H(2) generation from water is a competing process accompanying the formation of CO and CH(4) (CO(2) conversion 0.67% at 14 h). For the irradiation of CO(2) using H(2)O as reducing agent, basic solids (K(+)-exchanged Y zeolite or hydrotalcites) can increase CO(2) conversion up to 2.21% with total selectivity toward CH(4) and an energy consumption of 4.5 Gcal/mol. This result opens a door in the quest for efficient photocatalysts that could further increase the apparent quantum yield of the process, particularly at longer wavelengths.     

Confinement effects in the hydrogen adsorption on paddle wheel containing metal-organic frameworks

The confinement effects upon hydrogen adsorption in Cu(II)-paddle wheel containing metal-organic frameworks (MOFs) were evaluated and rationalized in terms of the structural properties (cavity types and pore diameters) of PCN-12, HKUST-1, MOF-505, NOTT-103 and NOTT-112. First-principles calculations were employed to identify the strongest adsorption positions at the paddle wheel inorganic building unit (IBU). The adsorption centres due to confinement were located through analysis of 3D occupancy maps obtained from the hydrogen trajectories computed via molecular dynamics simulations. It was found that the confinement enhances the adsorption on the weakest adsorption centres around the IBU in regions close to the narrowest windows and promotes the formation of new adsorption regions into the small cavities. Our results indicate that at low pressure, the high H(2) uptake in these materials is partly due to the presence of small cavities (5.3-8.5 ?) or narrow windows where the long-range contribution to the adsorption becomes important. Conversely, confinement effects in cavities with diameters >12 ? were not observed.