Dimeric self-assembling capsules derived from the highly flexible tribenzylamine skeleton

Tris(m-ureidobenzyl)amines dimerize both in solid state and in solution to give molecular capsules which are able to encapsulate small molecules. The self-assembly was confirmed by crystal X-ray analysis and NMR spectroscopy. The X-ray structure showed the encapsulation of one molecule of CH(2)Cl(2). This new type of capsules presents a propeller-like topology and a belt of six hydrogen-bonded ureas. Encapsulation studies in solution and heterodimerization processes are also disclosed.     

Optical characterization of the phosphate glasses containing pair transition ions

The paper deals with optical and electronic properties of the aluminophosphate glasses containing Fe–Mn and Fe–Cr ion pairs in different concentration. The influence of the mixed alkali ions over the electronic properties has been investigated. The optical behavior (optical transmission) of the glass samples has been studied by UV-VIS spectroscopy and the refractive index dependency on wavelength has been discussed. The transmission spectra show features specific for the doping transition ions (TM), revealing different oxidation states of iron (Fe²⁺/Fe³⁺), manganese (Mn²⁺/Mn³⁺) and chromium (Cr³⁺/Cr⁶⁺) in the vitreous network. Mössbauer spectroscopy offers information regarding the TM oxidation states, redox processes and the iron coordination symmetry in the vitreous network. In the case of Fe–Mn doped glasses, the percentage of Fe²⁺ is about 40% and a doubled iron content leads to an increasing of Fe²⁺ percentage up to 53%. The replacing of lithium ions by natrium ions (mixed alkali effect) provides an increasing of the Fe²⁺ percentage up to 56%. The occurrence of the tetrahedral or octahedral symmetry of Fe²⁺ ions bonded by O^2? ions depends on the transition ion nature and Li⁺/Na⁺ ratio. Infrared absorption spectra of the pair transition ions-doped aluminophosphate glasses reveal optical phonons specific for the phosphate glass matrix.     

Complementary use of Fourier transform laser microprobe mass spectrometry and time-of-flight static secondary ion mass spectrometry for the study of the surface adsorption of organic dyes on silicate materials

The adsorption of organic ionic dyes on different pore size engineered silica materials with potential application for industrial wastewater treatment has been investigated using Fourier transform laser microprobe mass spectrometry (FT-LMMS) and time-of-flight secondary ion mass spectrometry (TOF-S-SIMS). The complementary use of the two methods with different information depth allowed data on the subsurface distribution and pore penetration of the adsorbed organic compounds. Macroscopic methods were employed to determine the amount adsorbed on the particles and the specific external surface area. Local MS analysis allows identification of the organic dyes exclusively at the outer particle surface when the pore size is inferior to the size of the adsorbing molecule, or at the surface of the channels inside the material. Specifically, the monolayer information depth of TOF-S-SIMS causes a signal to refer essentially to the adsorbate at the outer particle surface, which is only a fraction of the total adsorption in mesoporous materials, while FT-LMMS allowed detection of the presence of adsorbates at the outer surface as well as inside the subsurface of 10 to 50 nm depending on the material under study. The observed data open perspectives for the molecular monitoring of the adsorption behaviour of different materials at the (sub) microm scale.     

Light collimation and focusing by a thin flat metallic slab

We present experimental and theoretical work showing that a flat metallic slab can collimate and focus light impinging on the slab from a point source. The effect is optimized when the radiation is around the bulk, not at the surface, plasma frequency. Also, the smaller the imaginary part of the permittivity is, the better the collimation. Experiments for Ag in the visible as well as calculations are presented. We also discuss the interesting case of Al, whose imaginary part of permittivity is very small at the plasma frequency in UV radiation. Generalization to other materials and radiations are also discussed.     

Energy Transfer from the Aminophthalate Dianion to Fluorescein

Energy transfer from the excited aminophthalate dianion species to fluorescein at pH 8.32 (Tris-HCl buffer) was studied. The excited aminophthalate dianion species was obtained either by excitation with UV radiation (330 nm), with fluorescence emission, or by the well-known chemical reaction luminol-hydrogen peroxide in an alkaline medium, with chemiluminescent emission, both with _max at 425 nm. The influence of Co²⁺ and Mg²⁺ on fluorescence and chemiluminescence (CL) was studied. It was found that at low concentrations (10^–7–10^–9 M), these ions do not modify the fluorescein fluorescence, however, the CL is strong affected. The effect of the concentration of these elements, which exert an influence on CL even at a high dilution (nanomolar concentration), was determined. In the case of Co²⁺ the prooxidant character is stronger than in the case of Mg²⁺, and therefore the CL enhancer effect is higher. Compared to the system without catalyst, their presence ensures stronger, prolonged, and stable light emission. The emission spectra, in the presence of fluorescein, show two bands with maxima at 425 and 520 nm, the second one being specific to fluorescein emission. The intensity of aminophthalate dianion luminescence is lower and the duration shorter in the presence of fluorescein. The influence of Co²⁺ and Mg²⁺ catalyst and fluorescein concentration on the energy transfer process was studied. The efficiency of the energy transfer process for these two situations (fluorescence and CL) was compared. An attempt was made to replace hydrogen peroxide with superoxide anion (solubilized by means of crown ether) and its effect upon the energy transfer process was observed.     

On the luminescence of luminol in DMSO in the presence of potassium superoxide-18-crown-6-ether and fluorescein

Luminol solution in DMSO in the presence of [18C6…K]⁺ O₂⁻ supramolecular complex (achieved from KO₂ and 18-Crown-6 (18C6)-ether) is chemiluminescent, and its intensity depends on the complex concentration. Using fluorescein (Fl) as an energy acceptor in this system, the luminescence energy transfer process from chemically excited species, aminophtalate dianion, to Fl could be evidenced. On the basis of Förster theory, the critical energy transfer distance, for both fluorescence and chemiluminescence, has been determined. The values are comparable: 22.41 Å (for chemiluminescence) and 20.88 Å (for fluorescence).     

Plasma Modification of Surface Wettability and Morphology for Optimization of the Interactions Involved in Blood Constituents Spreading on Some Novel Copolyimide Films

Novel copolyimides (cPIs) based on 3,3??,4,4??-benzophenonetetracarboxylic dianhydride, 4,4??-diaminodiphenylmethane (DDM) and 1,6-diaminohexane (DAH) were synthesized. Their surface wettability was improved by plasma enhancement of polar component contribution to surface tension from 10 to 50?%. Interfacial energy reduction up to 2.07?C2.95?mN/m was depicted in spreading work values that reveal the manner in which cPIs interact with blood constituents. The results showed that by increasing of the aliphatic DAH content in the polymer chain, the rejection of platelets is higher, prohibiting thrombosis and favoring cohesion with plasma proteins. The different water sorptions of the samples were evaluated by considering their morphologies and chemical affinities to water. When DAH prevails to DDM, water sorption capacity is lowered from 6.36 to 4.96?%?db, presumably due to a higher chain packing efficiency. Atomic force microscopy data revealed that surface roughness is <8?nm for all polymers, even after plasma treatment, preventing clot formation.     

Millimetre-wave spectrum of anti-13C1 and 13C2 isotopologues of ethanol

The rotational spectra of the two monosubstituted ¹³C isotopologues of the anti conformer of ethanol have been measured between 80–800 GHz using three different spectrometers at the Cologne Laboratory Astrophysics group. The dataset was constrained for fitting with a standard Watson-S reduction Hamiltonian by rejecting transitions from high-lying states showing significant perturbation with the gauche states and by averaging some small methyl torsional splits. This treatment is compatible with the needs for a first astrophysical research for which an appropriate set of predictions is given.