Marco Di Giovannantonio SIF September 25 th 2015

ISTITUTO DI
STRUTTURA DELLA MATERIA
CNR - ITALY
UNIVERSITA’ DI ROMA
“TOR VERGATA”
ITALY
Surface-confined polymerization on I/Au(111)
in acqueous solution under pH-control
Marco Di Giovannantonio, Tomasz Kosmala, Beatrice Bonanni, Giulia Serrano,
Nicola Zema, Stefano Turchini, Daniele Catone, Klaus Wandelt, Giorgio Contini, Claudio Goletti
Positioning the matter at the nanoscale
[2]
«There’s plenty of room
at the bottom» [1]
[4]
[3]
[1] Feynman, R. P., There's plenty of room at the bottom. Eng. Sci. 1960, 23, 22-36
[2] Eigler, D. M.; Schweizer, E. K., Positioning single atoms with a scanning tunneling microscope. Nature 1990, 344, 524-526.
[3] Crommie, M. F.; Lutz, C. P.; Eigler, D. M., Confinement of Electrons to Quantum Corrals on a Metal Surface. Science 1993, 262, 218-220.
[4] Song, H.; Reed, M. A.; Lee, T., Single Molecule Electronic Devices. Adv. Mater. 2011, 23, 1583-1608.
Marco Di Giovannantonio
SIF
September 25th 2015
There’s plenty of room at the top!
Organic molecules
on surfaces
Molecular self-assembly
Bottom-up
approach
Supramolecular chemistry
Chemistry beyond the molecule
[Yokoyama, T. et al., Selective assembly on a surface of supramolecular aggregates with controlled size and shape. Nature 2001, 413, 619-621]
Marco Di Giovannantonio
SIF
September 25th 2015
Covalent assembly
FROM
TO
non-covalent molecular self-assembly
covalent bonding
polymers
• Improved mechanical stability
• Higher intermolecular electron transport (π-conjugation)
Marco Di Giovannantonio
SIF
September 25th 2015
Surface-confined synthesis
Confinement to a 2D plane
• Long-range order
• Active role of the surface
• 1D or 2D systems
 Tunable geometry and properties
 High flexibility of the method
Marco Di Giovannantonio
SIF
September 25th 2015
Types of surface-confined polymerization
Solid-vacuum
Solid-air
Solid-liquid
Ullmann coupling
Schiff-base coupling
Schiff-base coupling
Dehydrogenation
Dehydration
Oxydative
electropolymerization
Dehydration
Electrochemical
oxydative coupling
Radical addition
Ullmann coupling
Schiff-base coupling
Mixed strategies
Imidization
Ullmann coupling
+ dehydrogenation
Dehydrogenation
+ decarboxylation
Dehydration
+ Ullmann coupling
Marco Di Giovannantonio
SIF
September 25th 2015
At the solid-liquid interface
Schiff-base coupling
Precursors dissolved in tetrahydrofuran (THF)
[Liu, X.-H.; Mo, Y.-P.; Yue, J.-Y.; Zheng, Q.-N.; Yan, H.-J.; Wang, D.; Wan, L.-J., Isomeric Routes to Schiff-Base Single-layered Covalent Organic
Frameworks. Small 2014, 10, 4934-4939]
Marco Di Giovannantonio
SIF
September 25th 2015
Reversibility of the Schiff-base coupling
The reversibility of the reaction
allows the formation of defectfree continuous polymer sheets
[Perepichka, D. F.; Rosei, F., Extending
Polymer Conjugation into the Second
Dimension. Science 2009, 323, 216-217]
[Ciesielski, A.; El Garah, M.; Haar, S.; Kovaříček, P.;
Lehn, J.-M.; Samorì, P., Dynamic covalent chemistry
of bisimines at the solid/liquid interface monitored by
scanning tunnelling microscopy. Nat. Chem. 2014, 6,
1017-1023]
Marco Di Giovannantonio
SIF
September 25th 2015
Motivation
Necessity for:
 Spectroscopic evidence of the polymerization
 Insight into the transition to polymers
 Study on the effect of the surface
Marco Di Giovannantonio
SIF
September 25th 2015
Studied system
Schiff-base coupling
Carbinolamine
Hemiaminal
Aldehyde
Imine
Azomethine
Schiff-base
I/Au(111)
Amine
pH
TPA
NH3
+
NH3+
CHO

NH2
NH2
CHO
ASB
intermediate phase
CHO
NH2
π-conjugated polymer
NH2
CHO
[Di Giovannantonio, M. et al. J. Phys. Chem. C 2015, 119, 19228-19235]
Marco Di Giovannantonio
SIF
September 25th 2015
ASB+TPA in bulk water
pH
pH 1.0
[Di Giovannantonio, M. et al. J. Phys. Chem. C 2015, 119, 19228-19235]
Marco Di Giovannantonio
SIF
September 25th 2015
STM at the I/Au(111)-water interface
40×40 nm2
20×20 nm2
pH 2.1
100×100 nm2
9×9 nm2
STM-tip
Templating effect
of the substrate
pH 3.6
I/Au(111)
120°
TPA
ASB
Internal
Spacing
0.65±0.05 nm
intermediate phase
π-conjugated polymer
?
[Di Giovannantonio, M. et al. J. Phys. Chem. C 2015, 119, 19228-19235]
Marco Di Giovannantonio
SIF
September 25th 2015
XPS at the I/Au(111) surface
CiPo @ SR Source «Elettra»
(Trieste, Italy)
Hanging meniscus method
N 1s
Intensity (arb. units)
TPA
ASB
intermediate phase
π-conjugated polymer
N 1s
[Di Giovannantonio, M. et al. J. Phys. Chem. C 2015, 119, 19228-19235]
Marco Di Giovannantonio
SIF
September 25th 2015
Surface-enhanced polymerization
Densification at the surface
Hydrophobic surface
Competition solvation/adsorption
Surface-enhanced polymerization
allows to use roll-to-roll methods
π-conjugated polymer
production when the
reaction in solution is
forbidden
Larger amount of
polymers on the surface
even at higher pH
[Di Giovannantonio, M. et al. J. Phys. Chem. C 2015, 119, 19228-19235]
Marco Di Giovannantonio
SIF
September 25th 2015
Concluding remarks and perspectives
Spectroscopic evidence of surface-confined polymerization
Insight into the reaction path
Surface-enhanced reaction
Future studies
• 2D polymers
• Surface-polymerization on insulators and semiconductors
Marco Di Giovannantonio
SIF
September 25th 2015
Acknowledgements
Istituto di Struttura della Materia (ISM) CNR, Roma,
Italy
G. Contini
N. Zema
S. Turchini
D. Catone
Università degli Studi di Roma
“Tor Vergata”, Italy
C. Goletti
B. Bonanni
G. Serrano
F. De Matteis
University of Bonn, Germany
K. Wandelt
T. Kosmala
S. Breuer
Università degli Studi di Pavia, Italy
D. Pasini
Marco Di Giovannantonio
SIF
September 25th 2015
Thank you
for your attention
ASB in bulk water
pH
50%
pKa
Dissociation of an acid
𝐻𝐴
𝐴− + 𝐻 +
Henderson-Hasselbalch equation
𝐴−
𝑝𝐻 = 𝑝𝐾𝑎 + 𝑙𝑜𝑔10
𝐻𝐴
Marco Di Giovannantonio
SIF
𝑝𝐻 = −𝑙𝑜𝑔10 𝐻+
𝑝𝐾𝑎 = −𝑙𝑜𝑔10 𝐾𝑎
𝐴− 𝐻+
𝐾𝑎 =
𝐻𝐴
September 25th 2015
Precipitate at pH>4
Marco Di Giovannantonio
SIF
September 25th 2015
XPS at the I/Au(111) surface
CiPo @ SR Source «Elettra»
(Trieste, Italy)
Hanging meniscus method
Intensity (arb. units)
ON SURFACE
N 1s
Binding Energy (eV)
IN SOLUTION
Competition
adsorption/solvation
Marco Di Giovannantonio
I/Au(111)
H2 O
SIF
H2 O
H2 O
H2 O H2 O
September 25th 2015
Additional XPS results
Air stability of the conjugated polymers. N 1s XPS
spectrum for I/Au(111) immersed in the solution
containing ASB and TPA at pH 4.0 (black curve). The as
measured sample has been then brought out of the
vacuum chamber, exposed to air for 30 minutes,
transferred back in vacuum and measured again (red
curve). No significant changes are observed in the
spectrum, demonstrating the robustness of the polymeric
layer in air. Data are presented after Shirley background
subtraction.
O 1s XPS spectra for I/Au(111) immersed in the solution
containing ASB and TPA at pH 1.7 and 4.0 or ASB at pH 1.0
(red, blue and black curves, respectively). The baseline of
each curve has been vertically shifted. The blue curve has BE
position (about 532.8 eV) and intensity similar to the
spectrum obtained without TPA (black curve), demonstrating
that the oxygen observed at pH 4.0 is mainly related to
contaminations adsorbed on the I/Au(111) surface. The signal
at pH 1.7 (red curve), instead, presents a chemical shift
toward higher BE and increased intensity, witnessing that the
component centered at about 533.6 eV can be attributed to
oxygen atoms in the aldehyde functionalities of intact TPA
and in the intermediate state of the Schiff-base coupling
(Scheme 1) (analogous BE shift has been observed when
molecular oxygen is adsorbed on gold nanoparticles
compared to oxygen adsorbed on carbon atoms of HOPG).
Marco Di Giovannantonio
SIF
September 25th 2015
Additional XPS results
Marco Di Giovannantonio
SIF
September 25th 2015
XPS at the I/Au(111) surface
N 1s
Marco Di Giovannantonio
Hanging meniscus method
SIF
September 25th 2015
Au(111) and I/Au(111)
LEED (a, c) and STM (b, d) images of (a) bare Au(111) surface prepared in UHV by repeated sputtering and annealing
cycles (Ep=63eV); (b) bare Au(111) surface prepared under argon flux by flame annealing (74×74 nm2, Vb=-300 mV,
It=1 nA, imaged in Ar atmosphere); (c) I/Au(111) surface prepared from the UHV cleaned gold (Ep=57eV); (d)
I/Au(111) surface prepared from the flame annealed gold (5.8×5.8 nm2, Vb=-33 mV, It=1 nA, imaged in 1 mM KI).
Herringbone appearance typical for 22 × 3 reconstruction is visible in STM image of the bare Au(111) surface (b)
prepared by flame annealing as well as extra spots surrounding the primary spots of the hexagonal gold bulk surface are
present in the LEED pattern of the bare Au(111) surface (a) prepared in UHV. Iodine 3 × 3 𝑅30 superstructure is
visible in both (d) in situ STM image and ex situ LEED pattern (c).
Marco Di Giovannantonio
SIF
September 25th 2015