`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 results ➡ part 1: dendrimer ➡ part 2: macrocycle • Conclusions and perspectives
Introduction
Nanoscale world ~ 1.3 × 10 7 m
Nanoscale world :10 8 ~ 1.3 × 10 7 m >>> ~ 20 cm
Nanoscale world :10 8 :10 8 ~ 1.3 × 10 7 m >>> ~ 20 cm >>> few nm
Molecular self-assembly • Organic molecules as building blocks 1D 2D SA 0D 3D aromatic electrostatic hydrophobic van der Waals hydrogen-bond molecular building blocks
Dendrimers
Dendrimers
Dendrimers
Dendrimers second generation polyphenylene dendrimer
Dendrimers second generation polyphenylene dendrimer
Dendrimers O O F HN F F N = = = = O F F
Macrocycles E' A A A A I E E E E A A A A A A A A E E E E I A A A A E'
Macrocycles E' A A A A I E E E E A A A A A A A A E E E E I A A A A E' Polychlorotriphenylmethyl derivatives Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl
Nanofabrication methods bottom-up top-down
Nanofabrication methods 1D 2D 0D 3D SA building blocks bottom-up top-down
Nanofabrication methods 1D 2D 0D 3D SA building blocks bottom-up guiding methods stamps, molds, patterns, ... top-down
Nanofabrication methods • Implementation of self-assembly in existing processes 1D 2D 0D 3D SA building blocks bottom-up • fundamental directed research • functional assembly nanotechnologies guiding methods stamps, molds, patterns, ... top-down
Atomic Force Microscopy
interaction detection interaction signal feedback loop z-voltage
Experiments and results part 1: dendrimer
Insight in self-assembly • In solution ➡ critical concentration molecules in solution
Insight in self-assembly • Transfer onto a substrate by dropcasting air molecules substrate interface in solution interface
Insight in self-assembly • Transfer onto a substrate by dropcasting air molecules substrate interface in solution interface
Evaporation of solvent fast slow importance of a (solvent) saturated environment during sample preparation
Optical viewing system
Optical viewing system
Optical viewing system
Reversibility part 1 sample preparation under ambient conditions ➡ fast evaporation
Reversibility part 1 sample preparation under ambient conditions ➡ fast evaporation
Reversibility part 1 sample preparation under ambient conditions ➡ fast evaporation part 2 adding solvent in a (solvent) saturated environment ➡ slow evaporation
Reversibility part 1 sample preparation under ambient conditions ➡ fast evaporation part 2 adding solvent in a (solvent) saturated environment ➡ slow evaporation
Insight in self-assembly • Transfer onto a substrate by dropcasting air molecules substrate interface in solution interface
Solvent mixtures adding increasing amount of hexafluorobenzene (C 6 F 6 ) to the dendrimer solution in tetrahydrofuran (THF) 5% C 6 F 6 10% C 6 F 6 20% C 6 F 6
Insight in self-assembly • Transfer onto a substrate by dropcasting air molecules substrate interface in solution interface
Substrate effect mica HOPG silicon
Substrate effect mica HOPG silicon
Substrate effect mica HOPG silicon
Silicon covered with a silane layer as substrate SiCl 3 -(CH 2 ) 11 -CN SiCl 3 -(CH 2 ) 2 -(CF 2 ) 7 -CF 3 SiCl 3 -(CH 2 ) 21 -CH 3 SiCl 3 -(CH 2 ) 15 -CH 3 SiCl 3 -(CH 2 ) 9 -CH 3
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
Guiding the self-assembly • Patterned substrates
Guiding the self-assembly • Patterned substrates
Guiding the self-assembly • Patterned substrates
Guiding the self-assembly • Patterned substrates
Guiding the self-assembly • Patterned substrates SiCl 3 -(CH 2 ) 2 -(CF 2 ) 7 -CF 3
Guiding the self-assembly • Patterned substrates SiCl 3 -(CH 2 ) 2 -(CF 2 ) 7 -CF 3
Guiding the self-assembly • Patterned substrates SiCl 3 -(CH 2 ) 2 -(CF 2 ) 7 -CF 3
Guiding the self-assembly • Patterned substrates
Guiding the self-assembly • Patterned substrates
Guiding the self-assembly • Patterned substrates
Guiding the self-assembly • Patterned substrates
Experiments and results Part 2: macrocycle
Insight in self-assembly • Solution • Substrate O n O O O n O O
Insight in self-assembly • Solution • Substrate O n O O O n O O
Guiding the self-assembly • Solution in a high magnetic field ➡ magnets on fridge: 10 gauss = 0.001 tesla ➡ experiments: up to 20 tesla (i.e. × 20.000) !
In solution
In solution water at 8 ºC (80L/s) to cool the magnet
In solution sample holder MF position for cuvette water at 8 ºC (80L/s) with to cool the magnet solution
In solution sample holder MF position for cuvette with solution
In solution sample holder MF position for cuvette with solution
In solution 0 data fit (~1200 nanometre) -1 -2 retardation (deg) -3 -4 -5 -6 -7 -8 0 2 4 6 8 10 12 14 16 20 18 magnetic field (T)
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.
Acknowledgements • promoters - Prof. De Schryver - Prof. De Feyter • Prof. Höger’s group • Prof. • Prof. Müllen’s group Veciana's group (Kekulé-Institut für (Institut de Ciència de (Max-Planck Institute Organische Chemie Materials de Barcelona) for Polymer Research) - Núria Crivillers - Tianshi Qin und Biochemie) - Roland Bauer • Randy de Palma (IMEC) • Alexander Volodin (Physics department) • Cédric Buron, Prof. Jonas (LLN) • Jeroen Gielen, Peter Christianen (HFML)
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