Stabilized Silver Nanoparticles and Nanoclusters Ag<Subscript>n</Subscript> in Humic-Based Bioactive Nanocomposites

Silver-containing nanocomposites synthesized from the compounds of a humic series have been studied using modern physical–chemical methods (EPR, TEM, IR and XRD, etc.). It is shown that the humic substances with different functional groups and isolated from different sources have also different ability of stabilizing the silver nanoparticles. Long-term stable nanoparticles and silver clusters have been found. A multiplet, observed in the EPR spectra of silver-containing nanocomposites, which are obtained from humic substances isolated from therapeutic muds and shales, is assigned to the formed Ag_n nanoclusters. Formation of the silver molecular clusters depends on the kind of humic substances and depth of their decomposition.     

Impact of regulatory trade barriers and controls of the movement of capital and people on international trade of selected Central,Eastern and Southeastern European economies

Central European Journal of Operations Research - Free movement of people, goods, services and capital is one of the cornerstones of the European Union (EU). Although various obstacles to free...     

Generalized Sequential Differential Calculus for Expected-Integral Functionals

Set-Valued and Variational Analysis - Motivated by applications to stochastic programming, we introduce and study the expected-integral functionals, which are mappings given in an integral form...     

Femtosecond Spectroscopy and Nonlinear Optical Properties of aza-BODIPY Derivatives in Solution

The fast relaxation processes in the excited electronic states of functionalized aza-boron-dipyrromethene (aza-BODIPY) derivatives ( 1 – 4 ) were investigated in liquid media at room temperature, including the linear photophysical, photochemical, and nonlinear optical (NLO) properties. Optical gain was revealed for nonfluorescent derivatives 3 and 4 in the near infrared (NIR) spectral range under femtosecond excitation. The values of two-photon absorption (2PA) and excited-state absorption (ESA) cross-sections were obtained for 1–4 in dichloromethane using femtosecond Z-scans, and the role of bromine substituents in the molecular structures of 2 and 4 is discussed. The nature of the excited states involved in electronic transitions of these dyes was investigated using quantum-chemical TD-DFT calculations, and the obtained spectral parameters are in reasonable agreement with the experimental data. Significant 2PA (maxima cross-sections ∼2000 GM), and large ESA cross-sections ∼10⁻²⁰ m² of these new aza-BODIPY derivatives 1–4 along with their measured high photostability reveal their potential for photonic applications in general and optical limiting in particular.     

Optimization of Grignard ring-opening of α-brominated dioxolanes for the preparation of β-hydroxy-protected vinyl ethers by a three-step one-pot procedure

Aliphatic, cyclic, and aromatic benzoate-protected γ-hydroxy enol ethers were prepared from α-brominated dioxolanes by a three-step reaction procedure and a one-pot protocol involving Grignard reagent formation, ring-opening, and final benzoate protection. Additionally, tert-butyldiphenylsilyl, acetate, and 4,4′-dimethoxytrityl were also successfully used as alternative protecting groups.