INSTITUT DE SCIENCE ET D'INGÉNIERIE SUPRAMOLÉCULAIRE

Nanochimie

Description

Niveau: Supérieur, Doctorat, Bac+8
INSTITUT DE SCIENCE ET D'INGÉNIERIE SUPRAMOLÉCULAIRE UNIVERSITÉ LOUIS PASTEUR THÈSE DE DOCTORAT « SELF-ASSEMBLY OF FUNCTIONAL MOLECULES AT SURFACES » Présentée par : GIUSEPPINA PACE Unité de Recherche : UMR N° 7006 Nanochemistry Laboratory (ISIS-ULP) Directeur de Thèse : Professeur SAMORÍ PAOLO

• institut de science et d'ingénierie supramoléculaire


• scanning tunnelin


• sams………… …


• stm


• experimental procedures…………………………………………………………………


• component sam


• individual functional mol

Sujets

• Louis Pasteur University

Informations

• Publié par: profil-zyak-2012
• Nombre de lectures: 61
• Poids de l'ouvrage: 20 Mo

Extrait

INSTITUT DE SCIENCE ET D’INGÉNIERIE SUPRAMOLÉCULAIRE


UNIVERSITÉ LOUIS PASTEUR








THÈSE DE DOCTORAT



« SELF-ASSEMBLY OF FUNCTIONAL MOLECULES AT SURFACES »







Présentée par : GIUSEPPINA PACE








Unité de Recherche : UMR N° 7006 Nanochemistry Laboratory
(ISIS-ULP)



Directeur de Thèse : Professeur SAMORÍ PAOLO


Table of content



Abstract……………………………………………………………………………………... IV


Chapter 1: INTRODUCTION TO THE THESIS

1.1 Molecular electronics…………………………………………………………………… 1
1.1.2 Current research in Molecular Electronics and motivation of this thesis work…... 2
1.2 Overview on Self-Assembled Monolayers (SAMs)……………………………………. 8
1.2.1 SAM formation: a many steps process………………………………………….. 14
References………………………………………………………………………………… 19

Chapter 2: EXPERIMENTAL TECHNIQUES

2.1 Scanning Tunneling Microscopy (STM)……………………………………………….. 22
2.1.2 Imaging molecules adsorbed on solid substrate…………………………………… 29
2.1.3 Origin of the STM image contrast in SAMs……………………………………… 30
2.2 Electrochemistry: Cyclic Voltammetry on SAMs………………………………………. 31
2.3 Infrared (IR) spectroscopy………………………………………………………………. 34
2.3.1 The FT-IR spectrometer…………………………………………………………… 36
2.3.2 FT-IR Reflection Absorption Spectroscopy of Thin Layers………………………..37
2.3.3 Absorbance of a thin anisotropic film on metal substrate…………………………..37
References……………………………………………………………………………………41

Chapter 3: METHODS

3.1 STM Measurements………………………………………………………………………43
3.1.2 Investigations at the solid-liquid interface………………………………………….43
3.2 Cyclic Voltammetry Measurement……………………………………………………….45
I3.3 Ultra-flat substrates……………………………………………………………………… 45
3.3.1 The reconstructed Au (111) surface: Preparation methodologies………………… 46
3.3.1.1 Au(111) preparation procedures……………………………………………… 49
3.3.1.2 Preparation of Template stripped gold……………………………………….... 49
3.3.1.3 Flame annealed gold substrates………………………………………………... 51
3.3.2 High Ordered Pyrolitic Graphite (HOPG)………………………………………… 51
3.4 Self-Assembled Monolayer preparation………………………………………………… 54
References…………………………………………………………………………………... 55

Chapter 4: ISOMERIZATION OF AZOBENZENE CHEMISORBED IN A MONO-
COMPONENT SAM

4.1 Introduction…………………………………………………………………………….. 56
4.1.2 Azobenzenes at surfaces………………………………………………………….. 57
4.2 Characterization of Self-assembled Monolayers (SAMs)……………………………… 60
4.2.1 Cyclic Voltammetry (CV) measurements………………………………………… 61
4.3 STM measurements……………………………………………………………………... 63
4.4 Photoisomerization of AZO’s SAMs……………………………………………………. 70
4.4.1 Photochemical Studies…………………………………………………………….. 70
4.4.2 STM studies……………………………………………………………………….. 73
4.5 Exploiting the photo-mechanical effect in electronic devices………………………… 79
4.6 Summary and Conclusions………………………………………………………………. 82
4.7 Experimental procedures………………………………………………………………….84
References……………………………………………………………………………………85

Appendix to chapter 4……………………………………………………………………… 90
A- 4.1 Solid state structure analysis of an AZO1 precursor………………………………… 90
A- 4.2 UV/Vis spectroscopy and photo-irradiation………………………………………… 91
A- 4.2.1 Photo-isomerization in Solution……………………………………………… 91
A- 4.2.2 Photo-isomerization in SAMs………………………………………………… 93
A- 4.3 Experimental procedures for Photochemical Investigations…………………………. 95
References of the Appendix to chapter 4…………………………………………………… 96


IIChapter 5: MIXED SELF-ASSEMBLED MONOLAYERS

5.1 Introduction…………………………………………………………………………… 97
5.2 Patterning of SAMs……………………………………………………………………. 99
5.2.1 Thermodynamic and kinetic factors in the formation of Mixed SAMs…………. 101
5.3 Results and discussion………………………………………………………………… 107
5.3.1 Mono-component SAMs………………………………………………………… 108
5.3.2 Bi-component SAMs…………………………………………………………….. 113
5.3.3 Striped domains and c(4×2) superstructure……………………………………... 123
5.3.4 FTIR characterization……………………………………………………………. 126
5.4 Conclusions…………………………………………………………………………….. 130
5.5 Experimental procedure……………………………………………………………… 131

Appendix to chapter 5……………………………………………………………………….132
References………………………………………………………………………………… 135

Chapter 6: ADSORPTION OF MOLECULAR GRID S ON HOPG SUBSTRATE

6.1 STM at the solid-liquid interface………………………………………………………. 138
6.2 Grid-type metal ion architectures………………………………………………………. 138
6.3 Results and discussions………………………………………………………………… 141
6.3.1 Self-Assembly of the free ligand on HOPG……………………………………… 143
6.3.2 Self-assembly of molecular Co-grid of L1 on HOPG……………………………. 149
References…………………………………………………………………………………. 154

Conclusions and perspectives………………………………………………………………156

List of publications…………………………………………………………………………. 158

Acknowledgements




III




Abstract


This work is aimed at establishing a correlation between molecule-substrate and molecule-
molecule interactions in view of the future implementation of nano-electronic devices based
on unctional molecules.
In particular, we studied the self-assembly behaviour of organic thiols functionalized
molecules holding potential to act as switches on solid substrates. We focused on the
isomerization of azobenzene based Self-Assembled Monolayers (SAMs) on gold substrates. A
fine tuning of interchain interactions within the SAM made it possible to obtain high yield of
isomerization.
We also devised a new method to isolate individual functional molecules in a host SAM.
In the final chapter we present our studies on the self-assembly properties of grid-like
supramolecular architectures.
Sub-molecularly resolved Scanning Tunneling Microscopy studies offered direct insights
into structural and dynamic properties of the monolayers.


IVChapter 1- Introduction



CHAPTER 1


INTRODUCTION TO THE THESIS



1.1 Molecular electronics

Nowadays electronic devices are developed making use of “conventional” inorganic
semiconductors. These semiconductor-based devices are built exploiting the “top-down
iapproach”, but when reaching the nanometer-scale the lithographic and etching
methodologies used to pattern a substrate becomes more challenging. Presently we are
reaching the limit of this miniaturization dictated by both physics laws and the production
costs. This limit can be overcome by taking advantage of the wide opportunities offered by
iimolecular electronics . Pioneers in the field of molecular electronics are Aviram and
Ratner[1] who first proposed donor-acceptor (D- σ-A) molecules as unimolecular rectifiers
i.e., molecular based p-n junctions.
Benefiting from the development in molecular engineering of organic molecules,
various electroactive systems can be designed to generate specific functions. Such versatility,

i Two main approaches are used in nanotechnology: one is a "bottom-up" approach where materials and devices
are built from molecular components which assemble using principles of molecular recognition; the other being
a "top-down" approach large entities are downscaled using nanofabrication tools which unfortunately do not
offer a control down to the atomic level. Importantly, nanotechnology encompasses many disciplines, including
colloidal science, chemistry, applied physics, materials science, and even mechanical and electrical engineering.
ii The first distinguishing concepts in nanotechnology was in "There's Plenty of Room at the Bottom," a talk
given by physicist Richard Feynman at an American Physical Society meeting at Caltech on December 29,
1959. In the course of this, he noted, scaling issues would arise from the changing magnitude of various physical
phenomena: gravity would become less important, surface tension and Van der Waals attraction would become
more important, etc.
- 1 -Chapter 1- Introduction
together with the molecular scale size, is the major advantage of molecular electronics which
relies on the “bottom-up” approach to build devices from single atoms building blocks with a
very high accuracy.
As already mentioned, improvements in computer science require the reduction of the
circuit feature size and the increase of the integration density of the actual semiconductor
based electronics. However, presently the electronic principles exploited in operating devices
are based on the bulk properties of semiconductors and, when reaching dimensions
comparable to the exciton Bohr radius, quantum mechanical effects come into play. This
leads to sensible variation in the principles governing the electronic processes which brings to
severe changes in the device behaviour. Since the shrinking of the device’s size implies to
take into account the quantum phenomena then, it is not