Synthesis of mesoporous metal oxides and their characterization combining small-angle scattering

173 Pages·2009·5.69 MB·English

by  Mascotto, Simone

Justus-Liebig-Universit¨at Gießen
Synthesis of mesoporous metal
oxides and their characterization
combining small-angle scattering
and gas physisorption methods
Simone Mascotto

Synthesis of mesoporous metal
oxides and their characterization
combining small-angle scattering
and gas physisorption methods
Dissertation
zur Erlangung des akademischen Grades
”doctor rerum naturalium”
(Dr. rer. nat.)
in der Wissenschaftsdisziplin ”Physikalische Chemie”
eingereicht an der
Naturwissenschaftlichen Fakult¨at
Justus-Liebig-Universit¨at Gießen
von
Simone Mascotto
Gießen, im Oktober 2009

When I was a small boy, I used to walk that section of London around the British
Museum; and one day, I came across a shop, which had a notice over the window,
which said ”Philosophical Instruments”. Even as a boy I knew something about
Philosophy, but I couldn´t imagine what ”Philosophical Instruments” could be. So I
went up to the window, and there displayed, were chronometers, slide rules, scales
and all kind of what we now call ”Scientific Instruments”. Because Science used to be
called Natural Philosophy. Because as Aristotle says: ”The beginning of Philosophy is
wonder. Philosophy is man´s expression of curiosity about everything, his attempt to
make sense of world primarily through his intellect”, that he says is faculty for
thinking. And thinking, of course, is a word used in many ways and is a very weighed
word for most people, but I use the word thinking in a very precise way. By thinking,
as distinct from feeling or emoting or sensing, I mean the manipulation of symbols
whether they´d be words, whether they´d be numbers or whether they´d be other
such signs let´s say triangles, squares, circles, astrological signs or whatever.
Alan W. Watts - Speech about Thinking

Contents
Introduction 1
1 Physical methods 5
1.1 Gas physisorption . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1.1 General aspects . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1.2 Determination of the porous features . . . . . . . . . . . . 7
1.2 Small-angle x-ray scattering (SAXS) . . . . . . . . . . . . . . . . 11
1.2.1 Principles of scattering theory . . . . . . . . . . . . . . . . 11
1.2.2 Ordered systems . . . . . . . . . . . . . . . . . . . . . . . 16
1.2.3 Disordered systems . . . . . . . . . . . . . . . . . . . . . . 18
1.2.4 2D low-angle transmission SAXS . . . . . . . . . . . . . . 21
1.3 In-situ SAXS/SANS-physisorption . . . . . . . . . . . . . . . . . . 23
1.4 Wide-angle x-ray scattering (WAXS) . . . . . . . . . . . . . . . . 25
1.5 Electron microscopy . . . . . . . . . . . . . . . . . . . . . . . . . 26
1.6 Atomic force microscopy (AFM) . . . . . . . . . . . . . . . . . . . 27
2 Synthesis of mesoporous metal oxides using new amphiphilic
block copolymers 29
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.2 Nanocasting by liquid crystal templating of block copolymers . . . 32
2.3 Synthesis and characterization . . . . . . . . . . . . . . . . . . . . 34
2.3.1 Nanocasted SiO powders . . . . . . . . . . . . . . . . . . 35
2
2.3.2 Hierarchical SiO systems . . . . . . . . . . . . . . . . . . 41
2
2.3.3 SiO Films . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
2
2.3.4 TiO Films . . . . . . . . . . . . . . . . . . . . . . . . . . 54
2
2.4 Mesoporous TiO thin films as photovoltaic devices . . . . . . . . 62
2
2.4.1 Current state of research . . . . . . . . . . . . . . . . . . . 62
VII
2.4.2 Characteristics of the photovoltaic cell . . . . . . . . . . . 65
2.4.3 Testing of dye sensitized solar cells . . . . . . . . . . . . . 65
2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
3 Microporosity determination of hierarchical mesoporous SiO by
2
in-situ SANS 69
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
3.2 Physisorption analysis . . . . . . . . . . . . . . . . . . . . . . . . 72
3.3 In-situ SANS data . . . . . . . . . . . . . . . . . . . . . . . . . . 74
3.4 Analysis of the in-situ SANS data by the CLD concept . . . . . . 76
3.5 Analysis of the Bragg peak intensity . . . . . . . . . . . . . . . . 81
3.6 General aspects of pore filling behavior . . . . . . . . . . . . . . . 84
3.7 Self-aggregation study of block copolymers by micropore analysis 85
3.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
4 Vapor physisorption on hierarchical SiO by in-situ SAXS/SANS 89
2
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
4.2 Vapor physisorption analyses . . . . . . . . . . . . . . . . . . . . . 90
4.3 Adsorption in-situ SAXS/SANS data . . . . . . . . . . . . . . . . 92
4.4 Desorption in-situ SANS data . . . . . . . . . . . . . . . . . . . . 96
4.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
5 Vapor physisorption on PMO by in-situ SAXS/SANS 103
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.2 Materials investigated . . . . . . . . . . . . . . . . . . . . . . . . 106
5.3 Vapor physisorption analyses . . . . . . . . . . . . . . . . . . . . . 107
5.4 In-situ SAXS/SANS data . . . . . . . . . . . . . . . . . . . . . . 110
5.5 Analysis of the in-situ SAXS curves . . . . . . . . . . . . . . . . . 112
5.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
Conclusion 119
A Appendix 123
A.1 Synthesis strategies . . . . . . . . . . . . . . . . . . . . . . . . . . 123
A.1.1 Nanocasted silica powders . . . . . . . . . . . . . . . . . . 123
A.1.2 Nanocasted hierarchical silica powders . . . . . . . . . . . 123
VIII
A.1.3 Mesoporous silica films . . . . . . . . . . . . . . . . . . . . 123
A.1.4 Mesoporous titania films . . . . . . . . . . . . . . . . . . . 124
A.1.5 Preparation of the DSSC devices . . . . . . . . . . . . . . 125
A.2 Analytical methods . . . . . . . . . . . . . . . . . . . . . . . . . . 127
A.3 In-situ SAXS/SANS-physisorption . . . . . . . . . . . . . . . . . . 128
A.3.1 In-situ SAXS-physisorption . . . . . . . . . . . . . . . . . 128
A.3.2 In-situ SANS-physisorption . . . . . . . . . . . . . . . . . 129
A.4 Mathematical appendix . . . . . . . . . . . . . . . . . . . . . . . . 131
A.4.1 Expressions of F(s) and S(s) for hard-spheres system in
the PY model . . . . . . . . . . . . . . . . . . . . . . . . . 131
A.4.2 Expressions of F(s) and S(s) for hard-discs system in the
PY model . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
⌣
A.4.3 Calculation of the φ from the Bragg peak intensity . . 133
micro
A.5 Discussions on micropore analysis . . . . . . . . . . . . . . . . . . 134
A.5.1 Monolayer formation of adsorbate in hierarchical SiO . . . 134
2
A.5.2 Volume fraction calculation by means of the Bragg peak
analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
A.6 Additional physisorption analyses . . . . . . . . . . . . . . . . . . 137
A.6.1 N physisorption on different batch of PIB-IL . . . . . . . 137
2
A.6.2 Langmuir plot of CH Br physisorption on PMOs . . . . . 138
2 2
A.7 List of Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
Acronyms and Abbreviations 139
Symbols 141
List of Publications 143
Acknowledgment 145
Bibliography 147
List of Figures 162
List of Tables 163
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