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51.
Significance of epoxy network properties for the toughening effect of flaky and fullerene‐like WS2 nanoparticles
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Dietmar Haba Michel Barbezat Santhosh Ayalur‐Karunakaran Sandra Schlögl Andreas J. Brunner Gerald Pinter 《Journal of Polymer Science.Polymer Physics》2016,54(17):1738-1747
This work deals with the toughening effect of flaky WS2 and fullerene‐like WS2 (IF‐WS2) nanoparticles on epoxy with varying network properties. Reducing the amount of curing agent resulted in decreased crosslink density as measured by dynamic‐mechanic analysis and double‐quantum nuclear magnetic resonance spectroscopy. Although that lead to moderate changes in the epoxy's tensile properties, its fracture toughness dropped drastically, probably due to an increased defect fraction. IF‐WS2 could be dispersed significantly more effectively within epoxy resin than flaky WS2, possibly due to its spherical shape, but caused less toughening. IF‐WS2 tended to debond from the epoxy, while flaky WS2 introduced more secondary cracks. Both increased the fracture toughness of the (brittle) substoichiometric, but not that of the (tough) stoichiometric epoxy, possibly due to their interaction with molecular defects. Irrespective of which mechanism resulted in the toughening effect, its effectiveness depended strongly on the epoxy matrix. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1738–1747 相似文献
52.
53.
Degradation of oxalic acid on particulate TiO2, ZnO, CuO, Bi2O3, In2O3, and Nb2O5 under UV‐A light exhibits first‐order kinetics, and the degradation rates increase linearly with the photon flux. All the oxides show sustainable photocatalytic activity, and the photonic efficiencies of degradation of oxalate are very much lower than those of the acid. The ease of degradation of carboxylic acids is the following: formic > oxalic > acetic > citric. Intimate mixtures of two different particulate semiconductors kept under suspension and at continuous motion exhibit higher photocatalytic activity, revealing interparticle charge transfer. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 716–726, 2009 相似文献
54.
V. Thanikachalam A. Arunpandiyan J. Jayabharathi C. Karunakaran P. Ramanathan 《Journal of fluorescence》2014,24(5):1447-1455
The 2-(furan-2-yl)-1-phenyl-1H-phenanthro[9,10-d]imidazole [FPI] has been designed and synthesized as fluorescent sensor for nanoparticulate ZnO. The present work investigates the photoelectron transfer (PET) from FPI to ZnO, Cu-doped ZnO and Ag- doped ZnO nanoparticles using electronic and life time spectral measurements. Broad absorption along with red shift indicates the formation of charge-transfer complex [FPI?Nanoparticles]. The photophysical studies indicate lowering of HOMO and LUMO energy levels of FPI on adsorption on ZnO due to FPI? ZnO interaction. The obtained binding constant implies that the binding of FPI with nanoparticles was influenced by the surface modification of ZnO nanoparticles with Cu and Ag. 相似文献
55.
Chockalingam Karunakaran Premkumar Anilkumar 《Central European Journal of Chemistry》2009,7(3):519-523
Oxidation of iodide ion from an air-saturated solution under natural sunlight (900±50 W m−2) on the surfaces of TiO2, ZnO, Fe2O3, MoO3 and CeO2 enhances by 6 to 12-fold on application of a cathodic bias of −0.2 to −0.3 V (vs NHE) to the semiconductors; light, the semiconductor and dissolved oxygen are essential for iodine generation. The semiconductors
under an anodic bias of +0.2 to +0.3 V (vs NHE) fail to oxidize iodide ion from air-saturated solution under sunlight. Under cathodic bias, semiconductor mixtures like
TiO2-ZnO, TiO2-Fe2O3 and ZnO-Fe2O3 show enhanced photocatalytic activity, indicating improved charge separation in oxide mixtures. The mechanism of photocatalysis
under cathodic bias is discussed.
相似文献
56.
Selectivity in photocatalysis by particulate semiconductors 总被引:1,自引:0,他引:1
Chockalingam Karunakaran Ramamoorthy Dhanalakshmi 《Central European Journal of Chemistry》2009,7(1):134-137
TiO2, Fe2O3, CuO, ZnO, ZnS, Nb2O5, MoO3, CdO, CdS, Sb2O3, CeO2, HgO, Pb2O3, PbO2 and Bi2O3 microparticles exhibit band gap excitation with UV-A light but they are selective to photodegrade phenols. While TiO2 anatase and ZnO photocatalyze the degradation of phenol, o-aminophenol, m-aminophenol, p-aminophenol, o-chlorophenol, m-chlorophenol,
p-chlorophenol, o-nitrophenol, p-nitrophenol, o-cresol, m-cresol, p-cresol, catechol, resorcinol and quinol, MoO3 does not photodegrade any of the fifteen phenols. Fe2O3, CuO, ZnS, Nb2O5, CdO, CdS, Sb2O3, CeO2, HgO, Pb2O3, PbO2 and Bi2O3 are selective in photodegrading the fifteen phenols; however, the phenols get adsorbed over all sixteen particulate semiconductors.
相似文献
57.
Chockalingam Karunakaran Premkumar Anilkumar Paramasivan Gomathisankar 《Monatshefte für Chemie / Chemical Monthly》2010,7(3):529-537
Abstract
Ag-doped TiO2 (anatase) samples (mass fraction w Ag = 0.01 and w Ag = 0.02) of 15.9 and 14.5 nm mean particle size and 11.46 and 10.14 m2 g−1 BET surface area were prepared by photodeposition. Doping results in surface plasmon resonance of the metallic silver nanoclusters at around 500 nm, but the absorption edge remains unaltered at 365 nm. Ag-doping remarkably enhances the photooxidation of iodide ion under UV light; iodine formation with Ag/TiO2 with w Ag = 0.01 is 16 times greater than with bare TiO2. The reaction conforms to Langmuir–Hinshelwood kinetics with regard to both I− and O2. Increase of pH slows down iodine formation and sacrificial electron donors arrest the reaction. Pre-sonication of the catalyst slurry hinders the photocatalysis. Generation of iodine is much greater in acetonitrile than in water. Under the experimental conditions, Ag/TiO2 with w Ag = 0.01 is more efficient than Ag/TiO2 with w Ag = 0.02, and the enhanced photocatalysis is likely to be because of suppression of electron–hole pair recombination. Kinetic analysis reveals that increasing the Ag mass fraction from 0.01 to 0.02 enhances the surface pseudo-first-order rate constant but inhibits the adsorption of iodide ion and the oxygen molecule on the illuminated oxide surface. 相似文献58.
PdNi bimetallic nanoparticles coated onto manganite (MN) nanocatalyst was used for ethylene glycol (EG) and glycerol (Gly) electrooxidation in alkaline media. The MN nanorods were prepared by hydrothermal method, and the PdNi was coated on the rods by an in situ reduction method. The prepared nanocomposite was characterized by scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM), Energy dispersive X-ray spectroscopy (EDS), and electrochemical methods. The SEM and TEM images exhibit the formation of nanorods of 10?nm and also show the formation of nanocrystalline PdNi on the walls of the MN nanorods. This study shows that the MN nanorods can be excellent support material and they supply oxygen to the catalyst, by which the catalytic activity is enhanced. The electrooxidation reactions in strong alkaline condition containing various concentrations of EG have been studied. Among the different concentrations, 9?M KOH/6?M EG exhibits the highest activity. PdNi/MN nanocatalyst exhibits better activity even in higher electrolytic concentrations of EG and alkali. 相似文献
59.
R.T. Karunakaran K. Marimuthu S. Surendra Babu S. Arumugam 《Journal of luminescence》2010,130(6):1067-7433
Thermal, structural and optical properties of Dy3+-doped alkali fluoroborate glasses with composition (in mol%), 49B2O3+25XO+25NaF+1Dy2O3 (where X=Li2, Na2, K2, Mg and Ca), have been investigated. Thermal analysis revealed the homogeneous formation of the glasses. The FTIR spectra reveal that the glasses contain BO3, BO4 non-bridging oxygen atoms and strong OH− bonds. From the optical absorption spectra, Judd-Ofelt intensity parameters (Ωλ, λ=2, 4 and 6) have been evaluated and are in turn used to predict radiative properties such as radiative transition probability (A), stimulated emission cross-section () and branching ratios (βR) for the excited levels of Dy3+ ions in alkali fluoroborate glasses. The dependence of the spectral characteristics of Dy3+ ions due to compositional changes has been examined and reported. 相似文献
60.
Chandra Sekhar Prasanth Suneesh C. Karunakaran Albish K. Paul Vesselin Kussovski Vanya Mantareva Danaboyina Ramaiah Leslie Selvaraj Ivan Angelov Latchezar Avramov Krishnankutty Nandakumar Narayanan Subhash 《Photochemistry and photobiology》2014,90(3):628-640
The Gram‐negative Aggregatibacter actinomycetemcomitans and Fusobacterium nucleatum are major causative agents of aggressive periodontal disease. Due to increase in the number of antibiotic‐resistant bacteria, antimicrobial Photodynamic therapy (aPDT) seems to be a plausible alternative. In this work, photosensitization was performed on Gram‐positive and Gram‐negative bacteria in pure culture using new‐age cationic porphyrins, namely mesoimidazolium‐substituted porphyrin derivative ( ImP ) and pyridinium‐substituted porphyrin derivative ( PyP ). The photophysical properties of both the sensitizers including absorption, fluorescence emission, quantum yields of the triplet excited states and singlet oxygen generation efficiencies were evaluated in the context of aPDT application. The studied porphyrins exhibited high ability to accumulate into bacterial cells with complete penetration into early stage biofilms. As compared with ImP, PyP was found to be more effective for photoinactivation of bacterial strains associated with periodontitis, without any signs of dark toxicity, owing to its high photocytotoxicity. 相似文献