Search results for "physical chemistry"
showing 10 items of 1199 documents
Chemi- and Bioluminescence of Cyclic Peroxides
2018
Bioluminescence is a phenomenon that has fascinated mankind for centuries. Today the phenomenon and its sibling, chemiluminescence, have impacted society with a number of useful applications in fields like analytical chemistry and medicine, just to mention two. In this review, a molecular-orbital perspective is adopted to explain the chemistry behind chemiexcitation in both chemi- and bioluminescence. First, the uncatalyzed thermal dissociation of 1,2-dioxetane is presented and analyzed to explain, for example, the preference for triplet excited product states and increased yield with larger nonreactive substituents. The catalyzed fragmentation reaction and related details are then exemplif…
Upconversion luminescence of a transparent glass ceramics with hexagonal Na(Gd,Lu)F4 nanocrystals
2017
Novel Er3+ doped transparent glass ceramics containing hexagonal Na(Gd,Lu)F4 nanocrystals were prepared from oxyfluoride glasses. The distribution of rare earth ions in the crystalline and glassy phase has been analyzed by X-ray diffraction and erbium luminescence decay kinetics measurement. A strong deviation of rare earth ion content in fluoride nanocrystals in comparison to the base glass has been observed. Preferential incorporation of Gd3+ over Lu3+ ions in the fluoride lattice leads to the stabilization of hexagonal Na(Gd,Lu)F4 structure and prevents the formation of cubic fluorite type solid solutions. A considerable enhancement of upconversion luminescence correlates with the format…
Electron paramagnetic resonance and photoluminescence investigation of europium local structure in oxyfluoride glass ceramics containing SrF2 nanocry…
2017
Different compositions of europium doped aluminosilicate oxyfluoride glass ceramics prepared in air atmosphere have been studied by electron paramagnetic resonance (EPR) and optical spectroscopy methods. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements show presence of homogenously distributed SrF2 nanocrystals after the heat treatment of the precursor glass. Efficient Eu3+ incorporation in the high symmetry environment of glass ceramics is observed from the photoluminescence spectra. EPR spectra indicate Eu3+ → Eu2+ reduction upon precipitation of crystalline phases in the glass matrix. For composition abundant with Eu2+ in the glassy state such behaviour is …
Oxidation Enhances Human Serum Albumin Thermal Stability and Changes the Routes of Amyloid Fibril Formation
2014
Oxidative damages are linked to several aging-related diseases and are among the chemical pathways determining protein degradation. Specifically, interplay of oxidative stress and protein aggregation is recognized to have a link to the loss of cellular function in pathologies like Alzheimer's and Parkinson's diseases. Interaction between protein and reactive oxygen species may indeed induce small changes in protein structure and lead to the inhibition/modification of protein aggregation process, potentially determining the formation of species with different inherent toxicity. Understanding the temperate relationship between these events can be of utmost importance in unraveling the molecul…
On Complex Formation between 5-Fluorouracil and β-Cyclodextrin in Solution and in the Solid State: IR Markers and Detection of Short-Lived Complexes …
2020
In this work, the nuclear magnetic resonance (NMR) and IR spectroscopic markers of the complexation between 5-fluorouracil (5-FU) and &beta
Linus Pauling’s Breakthrough to the Theory of Aromatic Compounds and Hückel’s Reaction
2009
In the mid-1930s Wheland and Pauling set out to find a quantum theoretical basis for Ingold’s general electronic theory of organic reactions. A brief outline of Ingold’s main concepts will provide the necessary background for an evaluation of their contribution and Huckel’s discussion of it.
NMR Study of Multiferroic Iron Niobate Perovskites
2015
NMR Study of Multiferroic Iron Niobate Perovskites K. Kou°il, V. Chlan, H. t¥pankova, R. ezni£ek, V.V. Laguta and I.P. Raevski Charles University in Prague, Faculty of Mathematics and Physics, V Hole2ovi£kach 2, 180 00 Prague 8, Czech Republic Institute of Physics AS CR, Cukrovarnicka 10, 162 00 Prague 6, Czech Republic Institute of Physics, Southern Federal University, Rostov on Don 344090, Russia We present Nb, Pb and Ba NMR study of multiferroic lead iron niobate and barium iron niobate ceramics. We ascribe development of NMR spectra on cooling below room temperature to magnetism of ferric ions close to resonating nuclei and introduce a framework capable of describing key features of t…
Azide, water and adipate as bridging ligands for Cu(II): Synthesis, structure and magnetism of (μ4-adipato-κ-O)(μ-aqua)(μ-azido-κN1,N1)copper(II) mon…
2016
The Distinguished Scientist Fellowship Program (DSFP) at King Saud University is gratefully acknowledged. The authors are grateful to the Algerian MESRS (Ministère de l’Enseignement Supérieur et de la Recherche Scientifique), the Université Ferhat Abbas Sétif 1, the KSU DSFP program and the Spanish MINECO (CTQ2014-52758-P and MAT2014-56143-R) and the Generalitat Valenciana (PrometeoII/2014/076) for financial support. The synthesis, characterization, single crystal structure and magnetic properties of the compound [(CuN3(OH2))2(adp)]n (1) are presented, in which adp stands for the adipate(2-) anion. This compound consists of layers containing chains of six-coordinated Cu(II) ions; the chains…
Polymeric micelles as a new generation of anti-oxidant carriers
2017
A promising strategy to immobilize a natural stabilizer in polymeric films is presented. Par-Ticularly, nevadensin (N, a natural basil flavonoid) molecules have been encapsulated in Pluronic F-127 micelles [F127, a triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)] and the obtained nanoparticles have been introduced in poly(ethylene glycol), PEG [otherwise known as poly(ethylene oxide), PEO]. In order to verify the effectiveness of the micelles as anti-oxidant carriers, PEG-based films have been subjected to artificial weathering. The encapsulation of anti-oxidant molecules allows the enhancement of N solubility in PEG, leading to advanced materials with enh…
Twentieth colloquium on high resolution molecular spectroscopy - Dijon, 3 to 7 September 2007 - Foreword
2008
International audience