Search results for "COMPOUND"

Cobalt Clusters with Cubane-Type Topologies Based on Trivacant Polyoxometalate Ligands.

2016

Four novel cobalt-substituted polyoxometalates having cobalt cores exhibiting cubane or dicubane topologies have been synthesized and characterized by IR, elemental analysis, electrochemistry, UV-vis spectroscopy, X-ray single-crystal analysis, and magnetic studies. The tetracobalt(II)-substituted polyoxometalate [Co4(OH)3(H2O)6(PW9O34)](4-) (1) consists of a trilacunary [B-α-PW9O34](9-) unit which accommodates a cubane-like {Co(II)4O4} core. In the heptacobalt(II,III)-containing polyoxometalates [Co7(OH)6(H2O)6(PW9O34)2](9-) (2), [Co7(OH)6(H2O)4(PW9O34)2]n(9n-) (3), and [Co7(OH)6(H2O)6(P2W15O56)2](15-) (4), dicubane-like {Co(II)6Co(III)O8} cores are encapsulated between two heptadentate [B…

Two-photon absorption of BF2-carrying compounds: insights from theory and experiment

2017

This communication presents a structure–property study of a few novel pyridine-based difluoroborate compounds with a N–BF2–O core, which exhibit outstanding fluorescence properties. To exploit their potential for two-photon bioimaging, relationships between the two-photon action cross section and systematic structural modifications have been investigated and unravelled.

Theoretical study on the decomposition mechanism of bisphenol A polycarbonate induced by the combined effect of humidity and UV irradiation.

2020

Polycarbonate (PC) is a good material for covering and protecting cultural heritage sites because of its durability, mechanical properties, and transparency. When bisphenol A polycarbonate is subjected to weathering conditions this polymer shows several degradation processes depending on the irradiation wavelength, humidity and temperature. In particular, the combined effects of humidity and UV irradiation speed up the PC molecular weight reduction. In this work, the decomposition mechanisms associated to the hydrolysis process are scrutinized and the effects of UV irradiation on the hydrolysis process are evaluated throughout the Density Functional Theory (DFT) approach. It was found that …

Effect of AlR3 (R = Me, Et, iBu) addition on the composition and microstructure of ethylene/1-olefin copolymers made with post-metallocene complexes …

2018

The effect of trialkylaluminum compound (AlR3, where R = Me, Et, iBu) addition on the performance of the [LigZrCl]2(μ-O)/AliBu3/Ph3CB(C6F5)4 and LigTiCl2/AliBu3/Ph3CB(C6F5)4 (Lig = Me2N(CH2)2N(CH2-2-O-3,5-tBu2-C6H2)2) catalysts in ethylene/1-olefin copolymerization was investigated. The presence of AlMe3 in the feed during the copolymerization process catalyzed by the diamine-bis(phenolate) zirconium catalyst greatly increases the amount of incorporated comonomer and leads to microstructural changes, e.g., the formation of blocky and alternating sequences of 1-olefin units. Moreover, the use of AlMe3 limits the reaction yield and decreases the molecular weight of the produced copolymers. Th…

The complementary structural studies of the double metal cyanide type catalysts for the ring opening polymerization of the oxiranes

2016

Determination and Toxicology Studies of Quaternary Ammonium Salts in Solution after Organoclay Processing

2018

Organoclays have potential to be used as additives in various facade paints and other finishing materials. Such new innovative materials must be rigorously tested for them to have no impact on environment. Focus of this study was to develop HPLC – TOF/MS method for determining quaternary ammonium salts in various material washing solutions and to determine organoclay toxicity by performing acute toxicity test on Daphnia magna. From the obtained results, it was possible to conclude that organoclays can be safely used as additives in various materials with low or no impact on environment. We determined that organoclays are significantly less toxic then some quaternary ammonium salts on its ow…

Computational Study of the Effect of Glyoxal–Sulfate Clustering on the Henry’s Law Coefficient of Glyoxal

2014

We have used quantum chemical methods to investigate the molecular mechanism behind the recently reported ( Kampf , C. J. ; Environ. Sci. Technol . 2013 , 47 , 4236 - 4244 ) strong dependence of the Henry's law coefficient of glyoxal (C2O2H2) on the sulfate concentration of the aqueous phase. Although the glyoxal molecule interacts only weakly with sulfate, its hydrated forms (C2O3H4 and C2O4H6) form strong complexes with sulfate, displacing water molecules from the solvation shell and increasing the uptake of glyoxal into sulfate-containing aqueous solutions, including sulfate-containing aerosol particles. This promotes the participation of glyoxal in reactions leading to secondary organic…

A novel comprehensive procedure for estimating greenhouse gas emissions from water resource recovery facilities

2017

The emissions of the major greenhouse gases (GHGs), i.e. carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from water resource recovery facilities (WRRFs) are of increasing concern in the water industry. In order to produce useful and comparable information for monitoring, assessing, and reporting GHG emissions from WRRFs, there is a need for a generally accepted methodology for their quantification. This paper aims at proposing the first protocol for monitoring and accounting for GHG emissions from WRRFs, taking into account both direct and indirect internal emissions and focusing the attention on plant sections known to be primarily responsible for GHG emissions (i.e. oxidation…

Diagenetic stability of non-traditional stable isotope systems (Ca, Sr, Mg, Zn) in teeth – An in-vitro alteration experiment of biogenic apatite in i…

2021

Stable isotope ratios and trace element concentrations of fossil bones and teeth are important geochemical proxies for the reconstruction of diet and past environment in archaeology and palaeontology. However, since diagenesis can significantly alter primary diet-related isotope signatures and elemental compositions, it is important to understand and quantify alteration processes. Here, we present the results of in-vitro alteration experiments of dental tissues from a modern African elephant molar reacted in aqueous solutions at 30 °C and 90 °C for 4 to 63 days. Dental cubes with ≈ 3 mm edge length, comprising both enamel and dentin, were placed into 2 mL of acidic aqueous sol…

Aerosol Chemistry Resolved by Mass Spectrometry: Linking Field Measurements of Cloud Condensation Nuclei Activity to Organic Aerosol Composition.

2016

Aerosol hygroscopic properties were linked to its chemical composition by using complementary online mass spectrometric techniques in a comprehensive chemical characterization study at a rural mountaintop station in central Germany in August 2012. In particular, atmospheric pressure chemical ionization mass spectrometry ((-)APCI-MS) provided measurements of organic acids, organosulfates, and nitrooxy-organosulfates in the particle phase at 1 min time resolution. Offline analysis of filter samples enabled us to determine the molecular composition of signals appearing in the online (-)APCI-MS spectra. Aerosol mass spectrometry (AMS) provided quantitative measurements of total submicrometer or…