Analyses of hierarchical structures in vulcanized SBR rubber by using contrast-variation USANS and SANS

The hierarchical structures of poly(styrene-ran-butadiene) (SBR) rubber vulcanized with sulfur in a swollen state were investigated by using the contrast-variation ultra-small-angle neutron scattering (USANS) and small-angle neutron scattering (SANS) techniques. The following three levels of hierarchical structure were found: (i) ZnO clusters surrounded by dense SBR networks of the order of 1000 Å in size, (ii) dense networks of SBR in the size range of 70–100 Å and (iii) a mesh size of the network of the order of 10 Å. In addition to the three kinds of structure, dense networks without ZnO of the order of 1000 Å were also observed. These last networks were formed by ZnO's reaction with sulfur. However, the ZnO clusters disappeared, which is associated with the diffusion of Zn.

Exchange Functionals and Basis Set Comparisons for Theoretical Studies of ZnO Nonoclusters

Catalysts made of nano-scaled metal oxide clusters can push the limits of chemical reactions in the manufacture of paints, cosmetics, and pharmaceuticals. The ZnO clusters can also act as semiconductors with a wide band gap of 3.4 eV at 300 K, and are prospective phoocatalysts in many reactions including H2 production in water splitting reactions. In this project, we studied the structural (geometry) and electronic properties (vertical detachment energy and electron affinity) of ZnO monomers and dimers that form model ZnO clusters, using density functional theory (DFT) with many different exchange functionals and 29 basis sets to optimize their choice. We compared the singlet-triplet energy gaps of small ZnO clusters to find the optimal ZnO cluster size and the best theoretical method to investigate their photocatalytic water splitting activity. Our results show that B3LYP/DGDZVP2 level of exchange functional/basis set theory is the most efficient and fastest of the ones considered. Comparison of the singlet-triplet energy gaps shows that the trimer (ZnO)3, with an energy gap of 58.66 k cal/mol, is approximately equal to the energy of a visible photon at 555 nm and a HOMO-LUMO gap of 4.4 eV, and is the best choice amongst the (ZnO)n clusters of different sizes when the number of monomers n in the clusters ranges from 1 to 6. We used the Gaussian16 software package for all the calculations.

Exchange Functionals and Basis Set Comparisons for Theoretical Studies of ZnO Nonoclusters

Catalysts made of nano-scaled metal oxide clusters can push the limits of chemical reactions in the manufacture of paints, cosmetics, and pharmaceuticals. The ZnO clusters can also act as semiconductors with a wide band gap of 3.4 eV at 300 K, and are prospective phoocatalysts in many reactions including H2 production in water splitting reactions. In this project, we studied the structural (geometry) and electronic properties (vertical detachment energy and electron affinity) of ZnO monomers and dimers that form model ZnO clusters, using density functional theory (DFT) with many different exchange functionals and 29 basis sets to optimize their choice. We compared the singlet-triplet energy gaps of small ZnO clusters to find the optimal ZnO cluster size and the best theoretical method to investigate their photocatalytic water splitting activity. Our results show that B3LYP/DGDZVP2 level of exchange functional/basis set theory is the most efficient and fastest of the ones considered. Comparison of the singlet-triplet energy gaps shows that the trimer (ZnO)3, with an energy gap of 58.66 k cal/mol, is approximately equal to the energy of a visible photon at 555 nm and a HOMO-LUMO gap of 4.4 eV, and is the best choice amongst the (ZnO)n clusters of different sizes when the number of monomers n in the clusters ranges from 1 to 6. We used the Gaussian16 software package for all the calculations.

Confined Synthesis of BiVO4 Nanodots and ZnO Clusters Co-decorated 3DOM TiO2 for Formic Acid Production from Xylan-based Hemicellulose Photorefinery

Biomass photorefinery provides a promising strategy for value-added chemical production from natural feedstocks. Herein, we designed and fabricated three-dimensionally ordered macroporous (3DOM) ternary composite for the photoreforming of hemicellulose and...

Re-Oxidation of ZnO Clusters Grown on HOPG

This article studies the chemical interaction between ZnO and highly oriented pyrolytic graphite for as grown and thermally treated samples. In-situ X-ray photoelectron spectroscopy and ex-situ Raman spectroscopy confirm that graphite is affected by these processes, becoming oxidized and defective only in the presence of ZnO clusters that become recrystallized upon thermal re-oxidation processes performed at 400 °C. By comparing these results with other identical experiments performed with ZnO clusters grown on graphene and even with CoO clusters grown on graphite, the present results show how the interaction of the ZnO clusters with graphitic substrates depend on two factors—firstly, the mode of growth and corresponding morphology, and secondly, the reactivity of the graphitic substrates, either graphene or graphite. The results presented here will help us understand the fundamental interactions in ZnO/graphitic heterostructures and to define their operating limits.