Kahng, Se-Jong

Arrays of C60 molecules nested inside single-walled nanotubes represent a class of nanoscale materials having tunable properties. We report electronic measurements of this system made with a scanning tunneling microscope and demonstrate that the encapsulated C60 molecules modify the local electronic structure of the nanotube. Our measurements and calculations also show that a periodic array of C60 molecules gives rise to a hybrid electronic band, which derives its character from both the nanotub

Interchain interactions in arrays of metal–organic hybrid chains were studied using scanning tunneling microscopy and ab initio calculations. The array of hybrid chains having a Ag–anthryl biradical were self-assembled by catalytic scission of Br–C bonds in 9,10-dibromoanthracene on Ag(111). An atomic model for the observed chain structures was proposed. Ag atoms in chains were alternatingly located at hollow sites, making slightly zigzaging structures. Between the hybrid chains, Br atoms locate

The role of hydrogen in the growth of Ge on a $\mathrm{Si}(001)\ensuremath{-}(2\ifmmode\times\else\texttimes\fi{}1)$ surface was studied by scanning tunneling microscopy and medium energy ion scattering spectroscopy. The adsorbed hydrogen was found to (i) increase the number of equilibrium adsorption sites, (ii) lift the diffusion anisotropy, and (iii) lower the diffusivity for Ge adatom, as suggested by the recent first principle calculation. With a dynamically supplied atomic hydrogen flux of

Supramolecular interactions were studied in two planar model systems, 1,5- and 2,6-dibromoanthraquinones, prepared on Au(111) using scanning tunneling microscopy. In both systems, we found rigid triangular structures that consisted of simultaneous halogen bonds and hydrogen bonds, as reported in protein−ligand complexes. We proposed molecular models that were well reproduced by first-principle studies and could be explained by halogen and hydrogen bonds. The distances, angles, and, strengths of

Controlling and sensing spin states of magnetic molecules at the single-molecule level is essential for spintronic molecular device applications. Here, we demonstrate that spin states of Co-porphyrin on Au(111) can be reversibly switched over by binding and unbinding of the NO molecule and can be sensed using scanning tunneling microscopy and spectroscopy (STM and STS). Before NO exposure, Co-porphryin showed a clear zero-bias peak, a signature of Kondo effect in STS, whereas after NO exposures,

Intermolecular structures of porous two-dimensional supramolecular networks are studied using scanning tunnelling microscopy combined with density functional theory calculations. The local configurations of halogen bonds in polymorphic porous supramolecular networks are directly visualized in support of previous bulk crystal studies.

The electronic structures of self-assembled hybrid chains comprising Ag atoms and organic molecules were studied using scanning tunneling microscopy (STM) and spectroscopy (STS) in parallel with density functional theory (DFT). Hybrid chains were prepared by catalytic breaking of Br-C bonds in 4,4″-dibromo-p-terphenyl molecules, followed by spontaneous formation of Ag-C bonds on Ag(111). An atomic model was proposed for the observed hybrid chain structures. Four electronic states were resolved u

Host–guest interactions in porous supramolecular structures have been studied on surfaces using scanning tunneling microscopy, with anticipation of biochemical and sensor applications, but limited to cases of van der Waals interactions and hydrogen bonds. Here, we studied the intermolecular structures of 4,4″-dibromo- p -terphenyl molecules self-caged in porous supramolecular structures with halogen bonds on Ag(111). The caged molecules hopped among six different configurations at higher than 50

Dynamically supplied atomic hydrogen was used for a surfactant growth of Ge on a Si(100) surface. The transition from three-dimensional to two-dimensional growth of Ge was observed as the hydrogen flux was increased to ∼1 ML/s in scanning tunneling microscope images. Layer-by-layer growth was successfully achieved up to 5 ML of Ge in the presence of atomic hydrogen. Observed missing dimer rows, irregular trench structures, and new “pin holes” are believed to be the product of strain relieving me

The role of halogen bonds in self-assembled networks for systems with Br and I ligands has recently been studied with scanning tunneling microscopy (STM), which provides physical insight at the atomic scale. Here, we study the supramolecular interactions of 1,5-dichloroanthraquinone molecules on Au(111), including Cl ligands, by using STM. Two different molecular structures of chevron and square networks are observed, and their molecular models are proposed. Both molecular structures are stabili

The coordination structure between small molecules and metalloporphyrins plays a crucial role in functional reactions such as bio-oxidation and catalytic activation. Their vertical, tilting, and dynamic structures have been actively studied with diffraction and resonance spectroscopy for the past four decades. Contrastingly, real-space visualization beyond simple protrusion and depression is relatively rare. In this paper, high-resolution scanning tunnelling microscopy (STM) images are presented

The molecular spin of Co-tetraphenylporphyrin on metal substrates can be atomically controlled by diatomic molecule adsorption from quantum mechanics prediction.

Axial coordinations of diatomic NO molecules to metalloporphyrins play key roles in dynamic processes of biological functions such as blood pressure control and immune response. Probing such reactions at the single molecule level is essential to understand their physical mechanisms but has been rarely performed. Here we report on our single molecule dissociation experiments of diatomic NO from NO-Co-porphyrin complexes describing its dissociation mechanisms. Under tunneling junctions of scanning