Functionalizing hydrogen-bonded surface networks with self-assembled monolayers

1. Functionalizing hydrogen-bonded surface networks with self-assembled monolayers Rafael Madueno, Minna T. Räisänen, Chistophe Silien, Manfred Buck Nature2008, 454, 618. Tobe laboratory Koji Inukai

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

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

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

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

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

7. Molecular Network Consisted of Hydrogen Bondings Hydrogen bonding Electronegativity O > H electrostatic interactions Molecular network of trimesic acid trimesic acid on graphite at ambient condition Heckl, M. et al. Langmuir2004, 20, 9403.

8. Molecular Network Consisted of Hydrogen Bondings Perylenediimide (PDI) Hydrogen bonding Melamine Network model 3 nm Champness, N.; Beton, P. et al. Nature2003, 424, 1029. on Ag/Si(111)-3  3R30°in vacuum

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

10. Experimantal Melamine Perylenediimide (PDI) method:Au (111) substrate is immersed to PDI and melamine solution for 1 min at 371 K. 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.

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

12. Thiol Fabrication on Honeycomb Network on Au intermolecular interaction strong strong weak

13. Thiol Fabrication on Honeycomb Network on Au 10 nm Exposure to thiol solution 5 nm 5 nm 5 nm Prolonged 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.

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

15. = 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.

16. 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.