Analytical studies of structure and stability of silver nanoparticles in layer-by-layer deposited polyelectrolyte films [Elektronische Ressource] / von Haybat Itani

Itani, Haybat

Informations

• Publié par: ruhr-universitat_bochum
• Publié le: 01 janvier 2010
• Nombre de lectures: 39
• Langue: English
• Poids de l'ouvrage: 12 Mo

Extrait

Analytical Studies of Structure and
Stability of Silver Nanoparticles
in Layer-by-Layer Deposited
Polyelectrolyte Films




Dissertation
zur
Erlangung des Grades
Doktor-Ingenieurin
der
Fakultät für Maschinenbau
der Ruhr-Universität Bochum
von

Haybat Itani
aus Beirut, Lebanon


Bochum (2010)




































Dissertation eingereicht am: 28.04.2010
Tag der mündlichen Prüfung: 02.06.2010
Erster Referent: Prof. Dr. Gunther Eggeler
Zweiter Referent: Prof. Dr. Guido Grundmeier

Doctoral Thesis Haybat Itani

Abstract

The deposition of polymer films with incorporated metal or oxide nanoparticles lead
to new functional properties. Properties such as electronic conductivity, hardness, magnetism,
metal-ion release or optical activity etc. can be adjusted by choosing the right combination of
metal nanocluster/polymer matrix and density of particles in the matrix. The in-situ formation
of Ag-nanoparticles in layer-by-layer (LbL) deposited polyelectrolyte (PE) multilayers is an
effective way to form multifunctional composite films that has many applications like
increase of corrosion resistance, excellent formability and Ag-release for antibacterial
properties. The layer-by-layer electrostatic assembly technique is a rich versatile and
significantly inexpensive approach to the formation of thin films via alternating adsorption of
positively and negatively charged species from aqueous solution.
The system under-study is consisting of embedded Ag-nanoparticles inside a layer-by-
layer polyelectrolyte film composed of poly(acrylic) acid and poly(allylamine) hydrochloride.
+ Incorporation of the nanoparticles is achieved by diffusion of Ag inside the matrix at
different pH-values and various numbers of adsorbed bilayers. The formation of metallic Ag
nanoparticles is realized by reduction in dilute NaBH aqueous solution. The structure of Ag-4
nanoparticles characterised by local distances and coordination shells around the absorbing
atom was investigated by means of X-ray Absorption Spectroscopy (XAS). The analysis of
the near edge structure reflects the fraction composition of the embedded Ag before, during
and after the reduction process and highlights the nanoparticle formation at the carboxylate
sites. The size and the crystallographic properties of the formed nanoparticles were
investigated by means of TEM while the optical properties were monitored in-situ by means
of UV-VIS Spectroscopy. Transport properties through the PE matrix were also investigated
under different post treatment conditions. In-situ Surface Enhanced Raman spectroscopy
(SERS) and Electro-impedance spectroscopy (EIS) were used to detect diffusion under
different conditions like curing at elevated temperatures and with inclusion of Ag-
nanoparticles.
Additionally, LbL Ag-nanoparticles films are interesting arrays of materials that has many
applications in nanoelectronics and optoelectronic devices. Several works used LbL method
to build up layered structure of Ag-nanoparticles, but the nature of attachment is not well
defined up to now. In this work, the effect of the number of layers on the arrangement of Ag-
nanoparticles is investigated by means of single wavelength ellipsomtery (SWE), and high
resolution atomic force microscopy (HR-AFM). The change of the optical properties is also
monitored by means of UV-VIS spectroscopy (UV-VIS).
ii Doctoral Thesis Haybat Itani

Contents

List of Figures......................................................................................................................vi
List of Tables .......................................................................................................................xi

1 Preface............................................................................................................................2
1.1. Motivation and Objectives ..............................................................................................2
1.2. Scope of the Thesis.........................................................................................................5

2 Fundamentals and Theory...............................................................................................7
2.1. Polyelectrolyte Films ......................................................................................................7
2.1.1. Introduction ............................................................................................................7
2.1.2. Weak Polyelectrolytes.............................................................................................8
2.1.2.1. Poly(acrylic) Acid (PAA)....................................................................................9
2.1.2.1.1. Shifts in the titration curve of PAA under different conditions:..........................13
2.1.2.2. Poly(allylamine) Hydrochloride (PAH) .............................................................15
2.1.2.2.1. Polyelectrolyte Complex ...................................................................................17
2.2. Nanoparticles................................................................................................................21
2.2.1. Properties of Nanoparticles ...................................................................................21
2.2.2. Silver Nanoparticles..............................................................................................24
2.3. Metal Nanoparticles in Polyelectrolyte Multilayers.......................................................25
2.3.1. Introduction ..........................................................................................................25
2.3.2. Interface and Bulk Properties of Nanoparticles in Polyelectrolytes as a Hybrid
System 27
2.4. Transport Phenomenon in Polyelectrolyte Films ...........................................................28
2.4.1. Introduction ..........................................................................................................28

3 Ways and Means...........................................................................................................30
3.1. Thin Film Preparation...................................................................................................30
3.1.1. Functionalizing the Substrate by Means of an Adhesion Promoter.........................30
3.1.1.1. 3-Aminopropyl Trimethoxysilane (APTMS) .....................................................30
3.1.1.2. Poly-ethylenimine (PEI)....................................................................................30
3.1.2. Layer by Layer Deposition Method (LbL).............................................................31
3.1.3. Formation of Silver Nanoparticles by Means of NaBH .........................................33 4
3.2. Analytical Approaches..................................................................................................34
3.2.1. Determination of PE Thickness .............................................................................34
3.2.2. Chemical Composition of the Polyelectrolyte Matrix ............................................35
3.2.3. Morphology of the PE Matrix under different Assembly Conditions .....................36
3.2.4. Optical Properties of the Silver/Polyelectrolyte Nanocomposites...........................36
3.2.5. In-situ UV-VIS Spectroscopy and Electrochemical Impedance Spectroscopy........38
3.2.6. In-situ Surface Enhanced Raman Spectroscopy.....................................................39

4 Theory of Experimental Techniques..............................................................................40
4.1. Ellipsometery................................................................................................................40
iii Doctoral Thesis Haybat Itani

4.2. X-ray Absorption Spectroscopy (XAS) .........................................................................46
4.3. UV-VIS Spectroscopy (UV-VIS)..................................................................................48
4.4. Atomic Force Microscopy (AFM).................................................................................50
4.5. Infra-Red Spectroscopy (IR) .........................................................................................51
4.6. Transmission Electron Microscopy (TEM) ...................................................................52
4.7. Surface Enhanced Raman Spectroscopy (SERS)...........................................................53
4.8. Electrochemical Impedance Spectroscopy (EIS) ...........................................................55

5 Results & Discussions: Tailoring of the Film Properties................................................56
5.1. Determination of the Thickness of the PE Matrix..........................................................56
5.1.1 Film Thickness as a Function of the Number of Bilayers at pH=3.5 ......................56
5.1.2 Film Thickness as a Function of the Number of Bilayer