Spontaneous emission in nanoscopic dielectric particles

We report on theoretical studies of the inhibition of the spontaneous emission process in subwavelength dielectric media. We discuss the modification of the spontaneous emission rate as a function of the size and shape of the medium as well as the position of the emitter in it.     

Komplexe von Nonactin und Monactin mit Natrium-, Kalium-und Ammonium-Ionen

1:1-Complexes between nonactin and monactin, and sodium, potassium, and ammonium thiocyanate are described.     

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...     

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     

Lithium-ion Mobility in Li6B18(Li3N) and Li Vacancy Tuning in the Solid Solution Li6B18(Li3N)1−x(Li2O)x

All-solid-state batteries are promising candidates for safe energy-storage systems due to non-flammable solid electrolytes and the possibility to use metallic lithium as an anode. Thus, there is a challenge to design new solid electrolytes and to understand the principles of ion conduction on an atomic scale. We report on a new concept for compounds with high lithium ion mobility based on a rigid open-framework boron structure. The host–guest structure Li₆B₁₈(Li₃N) comprises large hexagonal pores filled with Li₇N] strands that represent a perfect cutout from the structure of α-Li₃N. Variable-temperature ⁷Li NMR spectroscopy reveals a very high Li mobility in the template phase with a remarkably low activation energy below 19 kJ mol⁻¹ and thus much lower than pristine Li₃N. The formation of the solid solution of Li₆B₁₈(Li₃N) and Li₆B₁₈(Li₂O) over the complete compositional range allows the tuning of lithium defects in the template structure that is not possible for pristine Li₃N and Li₂O.