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We report the comparison of a series of 2D molecular crystals formed from the intermediates of the dehalogenation reaction of iodoethane versus various fluorinated iodoalkanes on Cu(111). High-resolution scanning tunneling microscopy enables us to distinguish the alkyl groups from the iodine atoms, and we find that the ethyl groups and iodine atoms formed from the dissociation of ethyl iodide are well mixed. However, fluorination of the alkyl tail changes this behavior and leads to local segregation of the two species on the surface. We postulate that the low-polarizability and relatively large dipole moment of the fluorinated species drive the ordered assemblies of the fluorinated alkyl species on the surface and discuss this in the context of how solvophobicity can drive the clustering of fluorinated groups and, hence, phase separation.

 

The migration of species across interfaces can crucially affect the performance of heterogeneous catalysts. A key concept in using bimetallic catalysts for hydrogenation is that the active metal supplies hydrogen atoms to the host metal, where selective hydrogenation can then occur. Herein, we demonstrate that, following dihydrogen dissociation on palladium islands, hydrogen atoms migrate from palladium to silver, to which they are generally less strongly bound. This migration is driven by the population of weakly bound states on the palladium at high hydrogen atom coverages which are nearly isoenergetic with binding sites on the silver. The rate of hydrogen atom migration depends on the palladium−silver interface length, with smaller palladium islands more efficiently supplying hydrogen atoms to the silver. This study demonstrates that hydrogen atoms can migrate from a more strongly binding metal to a more weakly binding surface under special conditions, such as high dihydrogen pressure.

 

Chiral surfaces are of growing interest for enantioselective adsorption and reactions. While metal surfaces can be prepared with a wide range of chiral surface orientations, chiral oxide surface preparation is much more challenging. Herein, we demonstrate that the chirality of a metal surface can be used to direct the homochiral growth of a thin film chiral oxide. Specifically, we study the chiral ‘29’ copper oxide, formed by oxidizing a Cu(111) single crystal at 650 K. Surface structure spread single crystals which expose a continuous distribution of surface orientations as a function of position on the crystal, enabled us to systematically investigate the mechanism of chirality transfer between metal and oxide with high-resolution scanning tunneling microscopy. We discovered that the local underlying metal facet directs the orientation and chirality of the oxide overlayer. Importantly, single homochiral domains of the ‘29’ oxide were found in areas where the Cu step edges that templated growth were ≤20 nm apart. We used this information to select a Cu(239 241 246) oriented single crystal and demonstrate that a ‘29’ oxide surface can be grown in homochiral domains by templating from the subtle chirality of the underlying metal crystal. This work demonstrates how a small degree of chirality induced by very slight misorientation of a metal surface (~1 sites/ 20 nm2) can be amplified by oxidation to yield a homochiral oxide with a regular array of chiral oxide pores (~75 sites/ 20 nm2). This offers a general approach for making chiral oxide surfaces via oxidation of an appropriately miscut metal surface.