Functionalizing hydrogen-bonded surface networks with self-assembled monolayers Rafael Madueno, Minna T. Räisänen, Chistophe Silien, Manfred Buck Nature 2008, 454, 618. Tobe laboratory Koji Inukai

Contents Introduction Constructing Nanostructures Adsorption Types: vertical and parallel to surface Results and discussion Hybrid Network and its application Summary

Two Strategies for Constructing Nanostructures ・ Top-down Approach 日立製作所（株）資料より ・ Bottom-up Approach Self-Assembly 自己集合 Molecule (0.5~5 nm) Easy to create structure in low nanometer region.

Self-Assembled Molecular Monolayer on Surface Type I; Molecules attaching vertically to substrates by strong substrate-molecule interaction Type II; Molecules lying parallel to substrates Self-assembled molecular monolayers are categorized into two types. ·Chemisorptions (thiol on gold) ·van der Waals interaction (alkane on graphite) Functionalization is easy. Various nanostructures can be constructed.

Tail group - Determine surface properties Head group - Connect to surface Monolayer: Molecules Attaching Vertically to Surface Spacer -Act as physical barrier

Monolayer: Molecules Laying Parallel to Surface substrate moleculesolvent molecule-molecule interaction molecule-solvent interaction solvent-substrate interaction molecule- substrate interaction interactions

Molecular Network Consisted of Hydrogen Bondings Hydrogen bonding Molecular network of trimesic acid Electronegativity O > H electrostatic interactions on graphite at ambient condition trimesic acid Heckl, M. et al. Langmuir 2004, 20, 9403.

Molecular Network Consisted of Hydrogen Bondings Perylenediimide (PDI) Melamine Network model Hydrogen bonding on Ag/Si(111)-  3   3R30°in vacuum Champness, N.; Beton, P. et al. Nature 2003, 424, nm

Purpose of This Work + Creating novel functional surface by combining non-covalent self-assembly of porous network and covalent self-assembly.

Experimantal Scanning tunneling microscopy (STM) ・ STM is an instrument to observe tunneling current. ・ Adsorbed molecules change resistance for tunneling current. ・ We can see these resistance change for tunneling current as contrast changes in an STM image. method: Au (111) substrate is immersed to PDI and melamine solution for 1 min at 371 K. Perylenediimide (PDI) Melamine

Monolayer of a Mixture of Perylenediimide and Melamine on Au(111) in vacuum at ambient condition In contrast to the network in vacuum, the network formed over exteded area. 10 nm 3 nm

Thiol Fabrication on Honeycomb Network on Au intermolecular interaction strong weak

Thiol Fabrication on Honeycomb Network on Au Prolonged exposure to thiol solution Exposure to thiol solution Honeycomb network was displaced by C12SH. Honeycomb network was displaced by BP3SH. Honeycomb network is very stable. Selective adsorption in the pore can be controlled kinetically. 10 nm 5 nm

Deposition of Cu Cation at Thiol Coated Area = Honeycomb network of PDI and melanine is very strong.

Deposition of Cu Cation at Thiol Coated Area = In the pore indicated by white arrows, Cu atom was confined. →Honeycomb network played a role of a diffusion barrier.

Summary The honeycomb network involving three hydrogen bonds demonstrates sufficient stability to act as template in subsequent processes. Formation of four component monolayer by the combination of two different molecule-substrate interactions is achieved. The resulting hybrid system is robust enough to be used for technological applications, such as for sensor devices in nano-sized components.