Qiwei Chen

Lattice-Directed Formation of Covalent and Organometallic Molecular Wires by Terminal Alkynes on Ag Surfaces

Surface reactions of 2,5-diethynyl-1,4-bis(phenylethynyl)benzene on Ag(111), Ag(110), and Ag(100) were systematically explored and scrutinized by scanning tunneling microscopy, molecular mechanics simulations, and density functional theory calculations. On Ag(111), Glaser coupling reaction became dominant, yielding one-dimensional molecular wires formed by covalent bonds. On Ag(110) and Ag(100), however, the terminal alkynes reacted with surface metal atoms, leading to one-dimensional organometallic nanostructures. Detailed experimental and theoretical analyses revealed that such a lattice dependence of the terminal alkyne reaction at surfaces originated from the matching degree between the periodicities of the produced molecular wires and the substrate lattice structures.

Unraveling Charge State of Supported Au Single-Atoms during CO Oxidation

Thermally stable Au single-atoms supported by monolayered CuO grown at Cu(110) have been successfully prepared. The charge transfer from the CuO support to single Au atoms is confirmed to play a key role in tuning the activity for CO oxidation. Initially, the negatively charged Au single-atom is active for CO oxidation with its adjacent lattice O atom depleted to generate an O vacancy in the CuO monolayer. Afterward, the Au single-atom is neutralized, preventing further CO reaction. The produced O vacancy can be healed by exposure to O2 at 400 K and accordingly the reaction activity is restored.

Stabilizing surface Ag adatoms into tunable single atom arrays by terminal alkyne assembly

Ordered two-dimensional arrays of silver adatoms with tunable metal atom density stabilized by 1,4-diethynyl-2,5-dimethylbenzene, a terminal alkyne, were prepared on Ag(111) and scrutinized by scanning tunneling microscopy and density functional theory calculations. Stabilization of the adatom arrays was attributed to the substrate-mediated electron localizations of the Ag adatom and terminal alkynyl in the molecule.