A stable room-temperature molecular assembly of zwitterionic organic dipoles guided by a Si(111)-7x7 template effect.
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ABSTRACT: In order to address the interplay of hydrogen bonding, dipolar interactions, and metal coordination, we have investigated the two-dimensional mono- and bicomponent self-assembly of three closely related diaminotriazine-based molecular building blocks and a complementary perylenetetracarboxylic diimide by means of scanning tunneling microscopy. The simplest molecular species, bis-diaminotriazine-benzene, only interacts via hydrogen bonds and forms a unique supramolecular pattern on the Au(111) surface. For the two related molecular species, which exhibit in addition to hydrogen bonding also dipolar interactions and metal coordination, the number of distinct supramolecular structures increases dramatically with the number of possible interaction channels. Deposition together with the complementary perylene species, however, always results in a single well-defined supramolecular arrangement of molecules. A detailed analysis of the observed mono- and bicomponent assemblies allows shedding light on the hierarchy of the competing interactions, with important implications for the fabrication of surface-supported supramolecular networks by design.ACS Nano 01/2011; 5(1):457-69. · 12.03 Impact Factor
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ABSTRACT: Carrier doping of MoS2 nanoflakes was achieved by functional self-assembled monolayers (SAMs) with different dipole moments. The effect of SAMs on the charge transfer between the substrates and MoS2 nanoflakes was studied by Raman spectroscopy, field-effect transistors (FET) measurements and Kelvin probe microscope (KFM). Raman data and FET results verified that fluoroalkyltrichlorosilane-SAM with a large positive dipole moment, acting as holes donors, significantly reduced the intrinsic n-doping characteristic of MoS2 nanoflakes, while 3-(Trimethoxysilyl)-1-propanamine-SAMs, acting as electrons donors, enhanced the n-doping characteristic. The additional build-in electric field at the interface between SiO2 substrates and MoS2 nanoflakes induced by SAMs with molecular dipole moments determined the charge transfer process. KFM results clearly demonstrated the charge transfer between MoS2 and SAMs and the obvious interlayer screening effect of the pristine and SAMs-modified MoS2 nanoflakes. However, the KFM results were not fully consistent with the Raman and FET results since the externally absorbed water molecules were shown to partially shield the actual surface potential measurement. By eliminating the contribution of the water molecules, the Fermi level of monolayer MoS2 could be estimated to modulate in a range of more than 0.45-0.47 eV. This work manifests that the work function of MoS2 nanoflakes can be significantly tuned by SAMs by virtue of affecting the electrostatic potential between the substrates and MoS2 nanoflakes.ACS Nano 08/2013; · 12.03 Impact Factor
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ABSTRACT: Supramolecular self-assembly of the organic semiconductor perylene-3,4,9,10-tetracarboxylic diimide (PTCDI) together with Ni atoms on the inert Au(111) surface has been investigated using high-resolution scanning tunneling microscopy under ultrahigh vacuum conditions. We demonstrate that it is possible by tuning the co-adsorption conditions to synthesize three distinct self-assembled Ni-PTCDI nanostructures from zero-dimensional (0-D) nanodots over one-dimensional (1-D) chains to a two-dimensional (2-D) porous network. The subtle interplay among non-covalent interactions responsible for the formation of the observed structures has been revealed from force-field structural modeling and calculations of partial charges, bond orders and binding energies in the structures. A unifying motif for the 1-D chains and the 2-D network is found to be double N-H…O hydrogen bonds between PTCDI molecules, similar to the situation found in surface structures formed from pure PTCDI. Most interestingly, we find that the role of the Ni atoms in forming the observed structures is not to participate in metal-organic coordination bonding. Rather, the Ni adatoms acquire a negative partial charge through interaction with the substrate and the Ni-PTCDI interaction is entirely electrostatic.Nano Research 5(12). · 7.39 Impact Factor
© Wiley-VCH 2007
69451 Weinheim, Germany
Stable room temperature molecular assembly of zwitterionic
organic dipoles guided by Si(111)-7x7 template effect **
Younes Makoudi, Madjid Arab, Frank Palmino, Eric Duverger, Christophe Ramseyer,
Fabien Picaud, and Frédéric Chérioux*
Synthesis of MSPS
[∗] Y. Makoudi, Dr. M. Arab, Dr. F. Palmino, Dr. E. Duverger
and Dr. F. Chérioux
Institut FEMTO-ST/LPMO UMR CNRS 6174
32, Avenue de l’Observatoire, F-25044 Besancon cedex,
Fax: (+) 33 8185 3998
Homepage ((optional)): www.femto-st.fr
Dr. F. Picaud and Prof. Dr. C. Ramseyer
Laboratoire de Physique Moléculaire, UMR CNRS 6624
16 Route de Gray, F-25030 Besancon cedex, FRANCE
[∗∗] This work was supported by the Communauté
d’Agglomération du Pays de Montbéliard. Authors thank Dr.
C. Joachim (CEMES, FRANCE) for fruitful discussions
Supporting information for this article is available on the
WWW under http://www.angewandte.org or from the
MSPS molecules have been synthesised in accordance with the method previously described by Nicoud et al.i
The procedure is based on two steps:
1) formation on the zwitterion
2) building of the large dipole
EtOH, Reflux, 10h
4-Picoline was treated at 0 °C with one equivalent of propylsultone, leading to crystalline 4-methyl-(n-
sulfonatopropyl)pyridinium, which was used for the subsequent reaction without further purification. To a
solution of 4-methyl-(n-sulfonatopropyl)pyridinium in 15 mL of anhydrous ethanol was added one equivalent of
the 4-methoxybenzaldehyde and a catalytic amount of pyrrolidine. The mixture was heated under reflux for 10 h
and then cooled to 0 °C. The precipitated product was filtered and washed with ether. The pale yellow solid was
purified by column chromatography (Silica gel, acetone, Rf close to 0.5). The pure MSPS was isolated as an
intense yellow powder after evaporation of the solvent.
1H NMR (300 MHz, CDCl3, 25°C): δ = 1.96 (quint., 3J = 7.3 Hz, 2H), 2.45 (t, 3J = 7.3 Hz,
2H), 3.76 (s, 3H), 4.62 (t, 3J = 7.3 Hz, 2H), 6.85 (d, 3J = 8.7 Hz, 2H), 7.06 (d, 3J = 16.2 Hz,
1H), 7.59 (d, 3J = 8.7 Hz, 2H), 7.69 (d, 3J = 16.2 Hz, 1H), 8.03 (d, 3J = 6.7 Hz, 2H), 8.99 (d,
3J = 6.7 Hz, 2H). MS (ESI): m/z : 333 [M+]; elemental analysis (%) calcd for C17H19NO4S
(333.10): C 61.24, H 5.74, N 4.20; found: C 61.17, H 5.81, N 4.09.
All properties of the isolated molecules are obtained by using the Vienna Ab Initio Simulation Package
(VASP),ii which is a density functional theory (DFT) code with plane wave basis set. Electron–ion interactions
were described using the projector-augmented wave (PAW) method, which was expanded within a plane wave
basis set up to a cutoff energy of 400 eV. Electron exchange and correlation effects were described by the
Perdew–Burke–Ernzerhof (PBE) GGA type exchange-correlation functional.
In order to investigate the molecule-substrate interactions, two pictures showing the DOS isolines evolution for
the entire system at different cut planes centered on the MSPS have been described in the following figures. We
have used Xcrysdeniii for the isolines dos representation.
In this top view, the methoxy group/Si(111)-7x7 interactions are proved by the DOS isolines (bias voltage +2V).
In this top view, the sulfonato/Si(111)-7x7 interactions are proved by the DOS isolines (bias voltage -2V).
These two figures show the template effect of the surface which induces a change conformation of MSPS in
order to lead to the supramolecular self-assembly of three MSPS in a Si(111)-7x7 half-cell.
i Serbutoviez, C.; Nicoud, J.-F.; Fisher, J.; Ledoux, I. & Zyss, J. Chem. Mater. 1994, 6, 1358-1368.
ii (a) Kresse, G. & Furthmüller, J. Phys. Rev. B 1996, 54, 11169-11186. (b) Blöchl, P. E. Phys. Rev. B 1994, 50,
iii (a) Kokalj, A. J. Mol. Graphics Modelling 1999, 17, 176. (b) Kokalj, A. Comput. Mater. 2003, 28, 155.