http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Dimensionality Control of Self-Assembled Azobenzene Derivatives on a Gold Surface
Kim, Hyo Won,Jung, Jaehoon,Han, Mina,Ku, JiYeon,Kuk, Young,Kim, Yousoo American Chemical Society 2019 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.123 No.14
<P>Well-defined nanostructures constructed with functional molecules provide a feasible route to realize molecular nanotechnology. Synthesis of selectively interacting molecules is essential to develop nanostructures with desired functionalities and dimensions. Substantial efforts have been devoted to achieve finely controlled supramolecular structures on surfaces using various interactions such as van der Waals (vdW), dipolar, hydrogen boning, and metal-ligand interactions. Yet, controlling the dimensions of a supramolecular assembly by changing the strength of the intermolecular vdW interactions, in particular through attaching alkyl chains of different lengths, has not been reported so far. Here, we present the dimensionality control of self-assembled azobenzene derivatives, from one-dimensional chain to two-dimensional island, on an Au(111) surface by exploiting vdW interactions assisted by hydrogen bonding. The designed azobenzene derivatives have alkoxy groups with different chain lengths (6, 8, and 10 carbons). Depending on the alkyl chain length, the molecules self-assemble into two different stacking structures, which determine the dimensionality of the superstructures. Furthermore, we demonstrate that the reconstructed herringbone structures of the substrate determine the stacking structure and growth direction at the elbow of the Au(111) surface. Our results provide a new perspective for engineering well-defined nanostructures with functional molecules as well as deeper insights into the mechanism of molecular self-assembly on surfaces.</P> [FIG OMISSION]</BR>
One-Dimensional Molecular Zippers
Kim, Hyo Won,Jung, Jaehoon,Han, Mina,Lim, Seongjoon,Tamada, Kaoru,Hara, Masahiko,Kawai, Maki,Kim, Yousoo,Kuk, Young American Chemical Society 2011 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.133 No.24
<P>We synthesized an azobenzene derivative to demonstrate a one-dimensional molecular zipper. The formation and underlying mechanism of the molecular zipper formed by combined hydrogen-bonding and van der Waals interactions between adjacent molecules were investigated on a Au(111) surface using scanning tunneling microscopy and density functional theory calculations.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2011/jacsat.2011.133.issue-24/ja2031486/production/images/medium/ja-2011-031486_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja2031486'>ACS Electronic Supporting Info</A></P>
Direct Pathway to Molecular Photodissociation on Metal Surfaces Using Visible Light
Kazuma, Emiko,Jung, Jaehoon,Ueba, Hiromu,Trenary, Michael,Kim, Yousoo American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.8
<P>We demonstrate molecular photodissociation on single-crystalline metal substrates, driven by visible-light irradiation. The visible-light-induced photodissociation on metal substrates has long been thought to never occur, either because visible-light energy is much smaller than the optical energy gap between the frontier electronic states of the molecule or because the molecular excited states have short lifetimes due to the strong hybridization between the adsorbate molecular orbitals (MOs) and metal substrate. The S-S bond in dimethyl disulfide adsorbed on both Cu(111) and Ag(111) surfaces was dissociated through direct electronic excitation from the HOMO-derived MO (the nonbonding lone-pair type orbitals on the S atoms (n(s)))to the LUMOderived MO (the antibonding orbital localized on the S-S bond (sigma*(ss))) by irradiation with visible light. A combination of scanning tunneling microscopy and density functional theory calculations revealed that visible-light-induced photodissociation becomes possible due to the interfacial electronic structures constructed by the hybridization between molecular orbitals and the metal substrate states. The molecule metal hybridization decreases the gap between the HOMO-and LUMO-derived MOs into the visible-light energy region and forms LUMO-derived MOs that have less overlap with the metal substrate, which results in longer excited-state lifetimes.</P>
Real-space and real-time observation of a plasmon-induced chemical reaction of a single molecule
Kazuma, Emiko,Jung, Jaehoon,Ueba, Hiromu,Trenary, Michael,Kim, Yousoo American Association for the Advancement of Scienc 2018 Science Vol.360 No.6388
<P>Plasmon-induced chemical reactions of molecules adsorbed on metal nanostructures are attracting increased attention for photocatalytic reactions. However, the mechanism remains controversial because of the difficulty of direct observation of the chemical reactions in the plasmonic field, which is strongly localized near the metal surface. We used a scanning tunneling microscope (STM) to achieve real-space and real-time observation of a plasmon-induced chemical reaction at the single-molecule level. A single dimethyl disulfide molecule on silver and copper surfaces was dissociated by the optically excited plasmon at the STM junction. The STM study combined with theoretical calculations shows that this plasmon-induced chemical reaction occurred by a direct intramolecular excitation mechanism.</P>
Shimizu, Tomoko K.,Jung, Jaehoon,Otani, Tetsuya,Han, Young-Kyu,Kawai, Maki,Kim, Yousoo American Chemical Society 2012 ACS NANO Vol.6 No.3
<P>A two-dimensional fluorinated fullerene (C<SUB>60</SUB>F<SUB>36</SUB>) superstructure has been successfully formed on Au(111) and was investigated using scanning tunneling microscopy (STM) and density functional theory calculations. Although there exist three isomers (<I>C</I><SUB>3</SUB>, <I>C</I><SUB>1</SUB>, and <I>T</I>) in our molecular source, STM images of the molecules in the well-ordered region all appear identical, with 3-fold symmetry. This observation together with the differences in the calculated lowest unoccupied molecular orbital (LUMO) distribution among the three isomers suggests that a well-ordered monolayer consists of only the <I>C</I><SUB>3</SUB> isomer. Because of the strong electron-accepting ability of C<SUB>60</SUB>F<SUB>36</SUB>, the adsorption orientation can be explained by localized distribution of its LUMO, where partial electron transfer from Au(111) occurs. Intermolecular C–F···π electrostatic interactions are the other important factor in the formation of the superstructure, which determines the lateral orientation of C<SUB>60</SUB>F<SUB>36</SUB> molecules on Au(111). On the basis of scanning tunneling spectra obtained inside the superstructure, we found that the LUMO is located at 1.0 eV above the Fermi level (<I>E</I><SUB>F</SUB>), while the highest occupied molecular orbital (HOMO) is at 4.6 eV below the <I>E</I><SUB>F</SUB>. This large energy gap with the very deep HOMO as well as uniform electronic structure in the molecular layer implies a potential for application of C<SUB>60</SUB>F<SUB>36</SUB> to an electron transport layer in organic electronic devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-3/nn300064x/production/images/medium/nn-2012-00064x_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn300064x'>ACS Electronic Supporting Info</A></P>