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Notable effect of water on excess electron attachment to aqueous DNA deoxyribonucleosides
No full textComputations using the combined quantum mechanical/molecular mechanical (QM/MM) method were performed to investigate excess electron attachment to and detachment from aqueous deoxyribonucleosides (dRNs). The QM/MM vertical electron affinities (VEAs) of four dRNs are higher than the values of the corresponding nucleobases by similar to 0.20 eV. The QM/MM diabatic electron affinities (AEAs) are much larger than the calculations of the implicit solvent model. Bulk water induces evident VEA and AEA increases and boosts the vertical detachment energies by over 1.20 eV. It affects excess electron attachment to and detachment from aqueous dRNs and stabilizes the anions. Moreover, the water molecules around deoxyadenosine (dA) anions form intermolecular hydrogen bonds with dA and break the intramolecular hydrogen bond of dA which had been found in the gas structure. In vertical electron attachment, similar to 50% of excess electrons would be delocalized over the water molecules around the dRNs. The anionic structural relaxations cause the transfer of similar to -0.30 e excess electrons from the water molecules to the dRN nucleobases. However, the main excess electrons (similar to -0.76 e) would be localized on dRN nucleobases in the stable anionic structure
Science Fund for Creative Research Groups of the National Natural Science Foundation of China[61421002]
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Location determination of metal nanoparticles relative to a metal-organic framework
No full textMetal nanoparticles (NPs) stabilized by metal-organic frameworks (MOFs) have been intensively studied in recent decades, while investigations on the location of guest metal NPs relative to host MOF particles remain challenging and very rare. In this work, we have developed several characterization techniques, including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) tomography, hyperpolarized Xe-129 NMR spectroscopy and positron annihilation spectroscopy (PAS), which are able to determine the specific location of metal NPs relative to the MOF particle. The fine PdCu NPs confined inside MIL-101 exhibit excellent catalytic activity, absolute selectivity and satisfied recyclability in the aerobic oxidation of benzyl alcohol in pure water. As far as we know, the determination for the location of metal NPs relative to MOF particles and pore structure information of metal NPs/MOF composites by Xe-129 NMR and PAS techniques has not yet been reported
