Electronic and chemical properties of liquids and solutions [Elektronische Ressource] / vorgelegt von Monika Blum

Monissimo

Sujets

• Physik

Informations

• Publié par: julius-maximilians-universitat_wurzburg
• Publié le: 01 janvier 2009
• Nombre de lectures: 55
• Langue: English
• Poids de l'ouvrage: 15 Mo

Extrait

Electronic and Chemical Properties
of Liquids and Solutions





Dissertation zur Erlangung des
naturwissenschaftlichen Doktorgrades
der Julius-Maximilians-Universität Würzburg






vorgelegt von
Monika Blum
aus Aschaffenburg



Würzburg 2009
Eingereicht am: 9. November 2009
Bei der Fakultät für Physik und Astronomie

1. Gutachter: Prof. Dr. E. Umbach
2. Gutachter: Prof. Dr. K. Fauth
der Dissertation


1. Prüfer: Prof. Dr. E. Umbach
2. Prüfer: Prof. Dr. K. Fauth
3. Prüfer: PD Dr. R. Fink
im Promotionskolloquium


Tag des Promotionskolloquiums: 17. Dezember 2009

Doktorurkunde ausgehändigt am: …
CONTENTS



1 Introduction ...................................................................................................... 1
2 Spectroscopic Methods..................................................................................... 3
2.1 X-ray Absorption Spectroscopy.................................................................... 3
2.2 X-ray Emission Spectroscopy....................................................................... 6
2.2.1 Resonant Inelastic X-ray Scattering ....................................................... 7
2.2.2 RIXS Dynamics ...................................................................................... 9
2.2.3 Raman Shift .......................................................................................... 11
2.2.4 Two-Dimensional RIXS Map............................................................... 11
2.4 X-ray Spectroscopy of Molecules .............................................................. 13
3 Instrumentation............................................................................................ 17
3.1 Membranes ................................................................................................. 17
3.2 Flow-Through Liquid Cell.......................................................................... 19
3.3 Further Developments of the Liquid Cell – an Outlook............................. 23
3.4 The SALSA Endstation – Home of the Flow-Through Liquid Cell........... 25
3.4.1 The SALSA Chamber........................................................................... 25
3.4.2 The X-ray Spectrometer........................................................................ 26
3.5 The Beamline.............................................................................................. 28
4 Sodium Hydroxide and Sodium Deuteroxide in Aqueous Solution........... 31
4.1 Aqueous Solutions of NaOH and NaOD .................................................... 32
4.1.1 The XAS Spectra – Isotope Effect and Concentration Dependence .... 32
4.1.2 The Non-Resonant O K Edge XES Spectra
– Concentration Dependence................................................................ 33
4.1.3 The RIXS Maps – the Electronic Structure of the Hydroxide and
Deuteroxide Ions................................................................................... 34
4.2 Solid NaOH – an Investigation................................................................... 39
4.3 Summary..................................................................................................... 42
I
5 Studies of Amino Acids in a Liquid Environment....................................... 45
5.1 The Smallest Amino Acid: Glycine ............................................................ 49
5.1.1 The Nitrogen K Edge Absorption – a Comparison between Solid State,
Solution, and Gas Phase........................................................................ 51
5.1.2 The Nitrogen K Edge Emission of Glycine – Impact of Different
pH-Values ............................................................................................. 53
5.1.3 The Nitrogen K RIXS Map of the pH 6 Solution ................................. 58
5.1.4 A Glance at the Carbon K and the Oxygen K Edge of Glycine............ 59
5.1.5 Summary ............................................................................................... 65
5.2 An Amino Acid with Two Amine Groups: Lysine..................................... 66
5.3 Summary and Outlook ................................................................................ 70
6 Simple Alcohols and Acids ............................................................................. 73
6.1 Methanol ..................................................................................................... 73
6.1.1 The O K Edge of Methanol .................................................................. 74
6.1.2 The C K Edge of Methanol................................................................... 76
6.2 Acetic Acid ................................................................................................. 79
6.2.1 The O K Edge of Acetic Acid – a RIXS Map Study............................ 80
6.2.2 The C K Edge of Acetic Acid............................................................... 83
6.3 Summary 84
Summary ..................................................................................................................... 87
Zusammenfassung ...................................................................................................... 89
Appendix...................................................................................................................... 91
Bibliography................................................................................................................ 97
Own publications 115
Curriculum Vitae 117
Acknowledgment 119
II CHAPTER I
Introduction



Liquids and solutions seem to be “easy” substances which surround us in our daily
life, including drinks, cleaning chemicals, and medicine.
Therefore, at first sight, one would think that liquids and solutions probably are
well-known “chemicals”. This is probably true, but not on an atomic scale! Indeed, the
geometric structure of liquids and solutions has been investigated by neutron and x-ray
scattering as well as infrared spectroscopy [e.g., Har05, Wer04] but much less is
known about their electronic structure. Since it is the intermittent bonding between
molecules that gives aqueous solutions their peculiar characteristics, the electronic
structure plays a crucial role in understanding the properties of the liquid state. In
particular the dynamical aspects, e.g., the continuous forming and breaking of bonds
within the hydrogen bond network, govern the microscopic and macroscopic behavior
of liquids and solutions. Thus, a detailed investigation of the electronic structure of
liquids is important to understand chemical and biological processes in aqueous
environments. Soft x-ray techniques are an excellent choice to perform such
investigations because they probe the local partial density of states.
This thesis focuses on the investigations of the electronic and chemical
properties of liquids and solutions, which is still a very young field of research but also
very important. In particular, understanding biological molecules in their natural
environment, i.e., in aqueous solution, is crucial to understand biological processes,
e.g. in bio-medicine. One example for such processes is the mechanism of the selective
permeation of ions through channels in cell membranes [Hil92, Bez08]. Among the
biological molecules, amino acids in solutions play an important role since they are the
building blocks of peptides and proteins.
One main obstacle for investigating liquids and solutions with soft x-rays is that
very sophisticated experimental setups are needed for these measurements. Such setups
are not commercially available. The measurements presented in this thesis were
performed in the new synchrotron endstation SALSA (Solid And Liquid Spectroscopic
Analysis) which is dedicated to the studies of biologically relevant systems in their
natural environment [Blu09]. This endstation was developed and commissioned within
the framework of this thesis. In particular, a novel flow-through liquid cell was
developed.
- 1 -
The new setup was used to investigate different liquids and solutions. For
experiments on solutions, a detailed knowledge of the pure solvent is essential.
Therefore, concentration dependent measurements of sodium hydroxide (NaOH) and
sodium deuteroxide (NaOD) were performed. NaOH was used as a solvent to change
the pH-values of the amino acids, which form the center of this thesis. To achieve a
basic knowledge of the electronic structure of amino acids and their pH-value
dependency the simplest amino acid glycine and a small amino acid lysine were
investigated. With the measurements of a simple alcohol and a simple acid, namely
methanol and acetic acid, two common liquids used in daily life are a further topic.
The thesis is organized as follows: in Chapter 2 an overlook of the applied
measurement techniques (photon-in-photon-out) is provided, and the approach of the
RIXS map is introduced. The necessary experimental equipment with the newly
designed flow-through liquid cell and the SALSA endstation are explained in Chapter <