UNRAVELLING AND GUIDING THE MOLECULAR SELF-ASSEMBLY ON SURFACES An - - PowerPoint PPT Presentation

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UNRAVELLING AND GUIDING THE MOLECULAR SELF-ASSEMBLY ON SURFACES An - - PowerPoint PPT Presentation

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`ONTRAFELEN EN STUREN VAN MOLECULAIRE ZELF-ASSEMBLAGE OP SUBSTRATEN UNRAVELLING AND GUIDING THE MOLECULAR SELF-ASSEMBLY ON SURFACES An Ver Heyen February 2008 Overview Introduction Atomic force microscopy Experiments and

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UNRAVELLING AND GUIDING THE MOLECULAR SELF-ASSEMBLY ON SURFACES

`ONTRAFELEN EN STUREN VAN MOLECULAIRE ZELF-ASSEMBLAGE OP SUBSTRATEN’

An Ver Heyen

February 2008

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Overview

  • Introduction
  • Atomic force microscopy
  • Experiments and results

➡ part 1: dendrimer ➡ part 2: macrocycle

  • Conclusions and perspectives
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Introduction

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Nanoscale world

~1.3×107 m

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Nanoscale world

~1.3×107 m ~20 cm >>> :108

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Nanoscale world

~1.3×107 m ~20 cm >>> :108 few nm >>> :108

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Molecular self-assembly

0D 1D 2D 3D

molecular building blocks

SA

  • Organic molecules as building blocks

aromatic electrostatic hydrophobic van der Waals hydrogen-bond

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Dendrimers

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Dendrimers

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Dendrimers

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Dendrimers second generation polyphenylene dendrimer

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Dendrimers second generation polyphenylene dendrimer

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Dendrimers

HN = O N O O = = = F F F F F

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E' A A E A A E' E E A A A A E I I A A A A A A A A E E E E

Macrocycles

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E' A A E A A E' E E A A A A E I I A A A A A A A A E E E E

Macrocycles

Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl

Polychlorotriphenylmethyl derivatives

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Nanofabrication methods

top-down bottom-up

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Nanofabrication methods

top-down bottom-up 0D 1D 2D 3D

building blocks

SA

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Nanofabrication methods

top-down

guiding methods

stamps, molds, patterns, ... bottom-up 0D 1D 2D 3D

building blocks

SA

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Nanofabrication methods

  • Implementation of self-assembly in existing processes

top-down

guiding methods

stamps, molds, patterns, ... bottom-up 0D 1D 2D 3D

building blocks

SA directed assembly

  • fundamental

research

  • functional

nanotechnologies

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Atomic Force Microscopy

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interaction detection feedback loop

interaction signal z-voltage

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Experiments and results part 1: dendrimer

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molecules in solution

Insight in self-assembly

  • In solution

➡ critical concentration

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molecules in solution air interface substrate interface

Insight in self-assembly

  • Transfer onto a substrate by dropcasting
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molecules in solution substrate interface air interface

Insight in self-assembly

  • Transfer onto a substrate by dropcasting
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Evaporation of solvent fast slow

importance of a (solvent) saturated environment during sample preparation

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Optical viewing system

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Optical viewing system

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Optical viewing system

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Reversibility

➡ fast evaporation

part 1 sample preparation under ambient conditions

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Reversibility

➡ fast evaporation

part 1 sample preparation under ambient conditions

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Reversibility

➡ fast evaporation

part 1 sample preparation under ambient conditions

➡ slow evaporation

part 2 adding solvent in a (solvent) saturated environment

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Reversibility

➡ fast evaporation

part 1 sample preparation under ambient conditions

➡ slow evaporation

part 2 adding solvent in a (solvent) saturated environment

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air interface substrate interface molecules in solution

Insight in self-assembly

  • Transfer onto a substrate by dropcasting
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Solvent mixtures 10% C6F6 20% C6F6 5% C6F6 adding increasing amount of hexafluorobenzene (C6F6) to the dendrimer solution in tetrahydrofuran (THF)

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molecules in solution air interface substrate interface

Insight in self-assembly

  • Transfer onto a substrate by dropcasting
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mica HOPG silicon Substrate effect

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mica HOPG silicon Substrate effect

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mica HOPG silicon Substrate effect

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Silicon covered with a silane layer as substrate

SiCl3-(CH2)11-CN SiCl3-(CH2)2-(CF2)7-CF3 SiCl3-(CH2)15-CH3 SiCl3-(CH2)21-CH3 SiCl3-(CH2)9-CH3

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Insight in self-assembly

  • Solution

➡ critical concentration to obtain aggregates

  • Fibre formation on substrate

➡ saturated environment (slow) / reversible ➡ π-π interactions ➡ formation on silicon, not on silicon

covered with a silane layer

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  • Patterned substrates

Guiding the self-assembly

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  • Patterned substrates

Guiding the self-assembly

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  • Patterned substrates

Guiding the self-assembly

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  • Patterned substrates

Guiding the self-assembly

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  • Patterned substrates

Guiding the self-assembly

SiCl3-(CH2)2-(CF2)7-CF3

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  • Patterned substrates

Guiding the self-assembly

SiCl3-(CH2)2-(CF2)7-CF3

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  • Patterned substrates

Guiding the self-assembly

SiCl3-(CH2)2-(CF2)7-CF3

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Guiding the self-assembly

  • Patterned substrates
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Guiding the self-assembly

  • Patterned substrates
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Guiding the self-assembly

  • Patterned substrates
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Guiding the self-assembly

  • Patterned substrates
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Experiments and results Part 2: macrocycle

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Insight in self-assembly

O O O n O O O n

  • Solution
  • Substrate
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Insight in self-assembly

O O O n O O O n

  • Solution
  • Substrate
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  • Solution in a high magnetic field

➡ magnets on fridge: 10 gauss = 0.001 tesla ➡ experiments: up to 20 tesla (i.e. ×20.000) !

Guiding the self-assembly

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In solution

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In solution

water at 8 ºC (80L/s) to cool the magnet

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In solution

water at 8 ºC (80L/s) to cool the magnet position for cuvette with solution sample holder MF

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In solution

position for cuvette with solution sample holder MF

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In solution

position for cuvette with solution sample holder MF

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In solution

retardation (deg) magnetic field (T)

  • 2
  • 1
  • 3
  • 5
  • 4
  • 6
  • 8
  • 7

2 4 6 8 10 12 14 16 18 20

fit (~1200 nanometre)

data

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Conclusions and perspectives

  • Implementing molecular self-assembly processes in

a combined top-down/bottom-up approach could be a route towards creating nanostructures for the design of efficient functional devices in the nanoscale world.

  • As these results indicate the potential and

challenges of this approach, they open a path for further investigation of other self-assembling systems and combinations with other top-down techniques.

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Acknowledgements

  • promoters
  • Prof. De Schryver
  • Prof. De Feyter
  • Prof. Müllen’s group

(Max-Planck Institute for Polymer Research)

  • Tianshi Qin
  • Roland Bauer
  • Randy de Palma (IMEC)
  • Prof. Höger’s group

(Kekulé-Institut für Organische Chemie und Biochemie)

  • Jeroen Gielen, Peter Christianen (HFML)
  • Prof.

Veciana's group (Institut de Ciència de Materials de Barcelona)

  • Núria Crivillers
  • Alexander

Volodin (Physics department)

  • Cédric Buron, Prof. Jonas (LLN)
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