The structural evolution of small copper clusters of up to 15 atoms and the dissociative chemisorption of H2 on the minimum energy clusters are studied systematically using density functional theory. The preferred copper sites for chemisorption are identified and the transition state structures and activation barriers for clusters four to nine atoms are determined and found to be inconsistent with the empirical Bronsted-Evans-Polanyi relationship. The physicochemical properties of the clusters are computed and compared with the bulk and surface values. The results indicate that a phase transition must occur in the going from cluster to bulk.

R-and -Ni(OH) 2 with three-dimensional (3D) nanostructures were synthesized in a water-in-oil reverse micelle/ microemulsion system. The form and shape of Ni(OH) 2 can be readily tuned by adjusting experimental parameters of the reverse micelle/microemulsion system. R-Ni(OH) 2 with dandelion-like nanostructures was obtained in the reverse microemulsion of cetyltrimethylammonium bromide (CTAB)/water/cyclohexane/n-pentanol with a molar ratio of H 2 O to surfactant of 40; -Ni(OH) 2 phase with flower-like nanostructures was formed in the reverse micelles of the same composition with a molar ratio of H 2 O to surfactant of 10. Electrochemical measurements of the as-synthesized R-Ni(OH) 2 phase showed that the 3D R-Ni(OH) 2 nanostructures exhibited superior cycling reversibility and improved capacity compared with commercial Ni(OH) 2 .

The controlled synthesis of SrCO3 nanostructures with different morphologies, such as rodlike, whiskerlike, ellipsoidlike, and spherelike, were successfully achieved by the cationic surfactant-CTAB-microemulsion-mediated solvothermal method. Various comparison experiments showed that fundamental experimental parameters, such as the molar ratio of H2O to CTAB and the concentration of reactants, played important roles in the morphological control of SrCO3 nanostructures. A lower molar ratio of H2O to CTAB favors rodlike products, whereas a higher molar ratio generally leads to the formation of spherical products. A rational mechanism based on fusion, aggregate, and coalescence of microemulsion droplets is proposed for the selective formation of various morphologies. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and field-emission scanning electron microscope (FE-SEM) were used to characterize the products.

Prussian blue analogue Co3[Co(CN)6]2 nanostructures with morphologies of truncated nanocubes (polyhedra), cubes and rods, were synthesized in large quantities by a direct dissociation of the single-source precursor K3[Co(CN)6] in a microemulsion system; the molar ratio of H2O to surfactant and the concentration of K3[Co(CN)6] both played important roles in determining the shape of the product.

Regular, single-crystalline nanocubes of Prussian blue, Fe 4 [Fe(CN) 6 ] 3 , with different sizes were synthesized in large quantities by a direct dissociation of the single-source precursor K 4 Fe(CN) 6 in acidic solution under ultrasonic conditions. The size and size distribution of the cubes strongly depends on the reaction temperature, the concentration of K 4 Fe(CN) 6 aqueous solution, and the ultrasonic condition. The probable mechanism of formation of Prussian blue is discussed.

Here, we investigated the anti-oxidant and anti-melanogenic effects of pomelo peel essential oil (PPEO) from pomelo cv. Guan Xi. The volatile chemical composition of PPEO was analyzed with gas chromatography–mass spectrometry (GC/MS). The most abundant component of PPEO was limonene (55.92%), followed by β-myrcene (31.17%), and β-pinene (3.16%). PPEO showed strong anti-oxidant activities against 2,2-diphenyl-2-picryhydrazyl (DPPH), 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate (ABTS) and superoxide anion free radicals. Based on the B16 melanoma cell system, the effects of PPEO on the viability and morphology of B16 cells and the production of melanin were evaluated. The results revealed that PPEO at concentrations below 50 μg/mL could decrease the melanin content without affecting cell viability and morphology. Intracellular tyrosinase (TYR) activity and Western blot analysis showed that PPEO could down-regulate the expression level of TYR in B16 cells and dose-dependently inhibit TYR activity (by a maximum of 64.54%). In conclusion, PPEO has good anti-oxidant and anti-melanogenic activity, and thus can be widely used as a natural antioxidant in the food, pharmaceutical, and cosmetic industries.

The sequential growth of small copper clusters up to 15 atoms and the dissociative chemisorption of H 2 on the minimum energy clusters are studied systematically using density functional theory under the generalized gradient approximation. We found that small Cu n clusters grow by adopting a triangular growth pathway. The pentagon bipyramid structural arrangements are strongly favored energetically in the growth and the new addition in the cluster occurs preferably at a site where the atom is capable of interacting with more adjacent atoms. To understand the evolution of small copper clusters, we also performed calculations on selected icosahedral clusters ͑for n = 13, 19, 25, 55͒ and fcc-like clusters ͑n = 14, 23, 32, 41͒. By extrapolating/ interpolating the binding energies of triangular clusters, icosahedral clusters, and bulk-like clusters, we found that structural transitions from the triangular growth clusters to the icosahedral and fcc-like clusters occur at approximately n = 16 and n = 32, respectively. Subsequently, we performed extensive calculations on the dissociative chemisorption of H 2 on the minimum energy clusters. The chemisorption likely occurs near the most acute metal site with the two H atoms residing on the edges, which differs significantly from the chemisorption on Cu surfaces that usually takes place at the hollow sites.

Transition state theory is used to estimate rate constants for dissociative chemisorption of H 2 on copper clusters. Activation energies and transition state partition functions are obtained from density functional theory for small clusters of less than 10 atoms. The violation of the Bronsted-Evans-Polanyi relation, which was previously observed for these clusters, is explained in terms of structural relaxation due to the chemisorption process. For large clusters, the impact of chemisorption on the global structure of the clusters is reduced. This restores the validity of the Bronsted-Evans-Polanyi relation and allows an extrapolation scheme for nano-size clusters to be developed.