Recovery of ammonia from wastewater through chemical precipitation

Journal of Thermal Analysis and Calorimetry - Chemical precipitation is a consolidated technique applied in wastewater treatment to remove and recover phosphorous and ammonium that remain in the...     

Reduced charge transfer exciton recombination in organic semiconductor heterojunctions by molecular doping

We investigate the effect of molecular doping on the recombination of electrons and holes localized at conjugated-polymer-fullerene interfaces. We demonstrate that a low concentration of p-type dopant molecules (<4% weight) reduces the interfacial recombination via charge transfer excitons and results in a favored formation of separated carriers. This is observed by the ultrafast quenching of photoluminescence from charge transfer excitons and the increase in photoinduced polaron density by ~70%. The results are consistent with a reduced formation of emissive charge transfer excitons, induced by state filling of tail states.     

Convergent Versus Divergent Three-Step Synthesis of the First (4-Aminophenoxy)alkanoic Acid–Based Tripodal Melamines

Starting from N-(4-hydroxyphenyl)acetamide (Paracetamol, convergent approach) or from cyanuric chloride in reaction with 4-aminophenol (divergent approach), two synthetic routes toward novel tripodal N-substituted melamines as s-triazine derivatives of (4-aminophenoxy)acetic acid or of 4-(4-aminophenoxy)butyric acid are comparatively defined. The key steps consist of Williamson etherification of N-masked forms of 4-aminophenol and acidic hydrolysis of the N- and/or O-protected (4-aminophenoxy)alkanoic segments.     

Microencapsulation of an acrylate monomer in silica particles by sol–gel process

The sol–gel synthesis strategies combined with the templated growth of organic–inorganic hybrid networks provide access to an immense new area of innovative multi-functional advanced materials. One possible way to prepare such new advanced materials is to encapsulate liquid active agents (such as monomers, dyes, catalysts and hardeners) in microcapsules. Silica microcapsules of tetraethylortosilicate (TEOS) and 3-(trimethoxysilyl)propyl methacrylate (MPTS) were prepared in a precursor-monomer/NH₄OH water microemulsion system. Trimethylolpropane triacrylate (TMPTA)—a trifunctional monomer useful in manufacturing of coatings, inks and adhesives—and a corresponding photoinitiator (DAROCUR 1173) were entrapped inside the obtained microcapsules. MPTS was used to increase compatibility between TMPTA and the sol–gel precursors. As stability agent we added a “home made” product resulted from functionalization of poly (ethylene glycol) methyl ether (MPEG) with (3-isocyanatopropyl) triethoxysilane (NCOTEOS). Were obtained microcapsules containing incorporated monomer and having average particle size in range of 0.5–50 μm. Thermal analysis, morphology study and the increase of the silica microcapsules average diameter, measured by DLS technique confirm the monomer encapsulation.     

Synthesis of N-phenyl β-amino acids via iridium-catalyzed asymmetric hydrogenation using mixed monodentate ligands

The iridium-catalyzed asymmetric hydrogenation of N-phenyl-β-dehydroamino acid derivatives was examined using monodentate phosphoramidite ligands. The highest yields and enantioselectivities were obtained using a mixed ligand approach with PipPhos L1 and achiral triphenylphosphine (full conversion, 70% ee).     

Synthesis of tervalent phosphorus esters in biphasic system using potassium phosphate as unique solid base

The synthesis of tervalent phosphorus esters continues to be a significant area of interest, much of it again directed toward the synthesis of phosphite ligands for metal‐catalyzed reactions. Typically, they were obtained through esterification of the corresponding phosphorus chlorides with the appropriate alcohols in the presence of an amine. In this paper, we present a new method for the synthesis of tervalent phosphorus esters, not yet mentioned in the literature, when potassium phosphate, as a unique base, is used in liquid–solid system. Symmetrical and unsymmetrical phosphites were obtained with good yields (65%–80%) using this method. The compounds were characterized by ³¹P NMR spectroscopy. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:360–364, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20438     

Aggregation and chiroptical behavior of a high molecular weight chirally substituted dialkylpoly(p‐phenyleneethynylene)

The solvent and temperature dependent aggregation of high molecular weight bis[S‐(+)‐3,7‐dimethyloctyl)] substituted poly(p‐phenyleneethynylene) (PPE, 2 ) was examined by absorption, emission and circular dichroism spectroscopy. All herein employed methods strongly support the view that 2 forms ordered aggregates in the solid state and in solvent mixtures. This is the first case in which a chiral high molecular weight PPE displays its aggregation by both optical and chiroptical methods.     

The Raman spectra of different ladder type poly(p-phenylenes) and ladder type oligo(p-phenylenes)

We report on Raman spectra of ladder type oligo(p-phenylenes) of different chain lengths (5LOPP and 7LOPP) and make a comparison to the Raman spectrum of the corresponding polymer, ladder type poly(p-phenylene) (LPPP). For a better understanding of the vibrational behavior of LPPP, several LPPPs with different substituents (methyl, allyl, n-butyl, 1-adamantyl) were investigated. The recorded Raman spectra of these LPPPs show significant changes in the interring CC stretching regions. An experimental analysis of the frequencies, intensities and line-shapes of significant modes is given in dependence on the substituents and chain lengths.     

Materials for polymer electronics applications – semiconducting polymer thin films and nanoparticles

The paper presents two different approaches to nanostructured semiconducting polymer materials: (i) the generation of aqueous semiconducting polymer dispersions (semiconducting polymer nanospheres SPNs) and their processing into dense films and layers, and (ii) the synthesis of novel semiconducting polyfluorene-block-polyaniline (PF-b-PANI) block copolymers composed of conjugated blocks of different redox potentials which form nanosized morphologies in the solid state.