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In this thesis, Till Cremer investigates the bulk properties of ionic liquids (IL), the IL/vacuum interface and the IL/solid interface. For these studies the author primarily uses angle-resolved X-ray photoelectron spectroscopy under ultrahigh vacuum conditions. ILs represent a class of materials with unique physico-chemical properties. Many applications take advantage of the extremely low vapor pressure of aprotic ILs to fabricate permanent, non-volatile liquid coatings on solid materials. The author focuses on issues related to thin IL coatings, in particular concerning new catalytic concepts such as the supported ionic liquid phase (SILP) and solid catalyst with ionic liquid layer (SCILL) systems. Till Cremer presents a number of fundamental contributions to the new field of "Ionic Liquid Surface and Interface Science". Highlights are his results concerning anion/cation-interactions and the growth of ultrathin layers of ionic liquids on various substrates in the context of supported ionic liquid catalysis. His results have significantly contributed to the present level of understanding in the field and accordingly he is author and coauthor of ten publications on the topic in high-ranked journals.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction and Motivation

Ionic liquids (ILs) are a new class of materials, which have attracted vast scientific and industrial interest over the last decade.

Till Cremer

Chapter 2. Fundamentals and Techniques

Photoelectron spectroscopy makes use of the photoelectric effect, which was discovered in 1887 by Hertz and explained by Einstein in 1905 [1]. When a material is irradiated with light whose energy hν exceeds the material’s work function (usually a few electron volts, depending on the sample material), electrons are ejected from the material.

Till Cremer

Chapter 3. Pure Ionic Liquid Systems

In this chapter macroscopically thick IL films were investigated with regards to their bulk electronic structure and their surface composition. The (AR) XP spectra of ten [C

8

C

1

Im]

+

-based ILs were analysed while the anion was systematically varied. In Sect. 3.1 the bulk electronic structure and ion–ion interactions are examined, whereas Sect. 3.2 deals with the surface structure of these systems.

Till Cremer

Chapter 4. Ionic Liquid/Metal Interfaces

The previous chapter addressed both bulk- (Sect. 4.3.1) and surface-related (Sect. 4.3.2) IL properties. The IL/solid interface is the third main subject investigated in this thesis. Compared to the previous aspects of IL research, the IL/solid interface is the least explored, as reflected by the small number of fundamental studies available.

Till Cremer

Chapter 5. The Ionic Liquid/Glass Interface and the Nanolab Concept

The interface between ILs and silica is of great interest to the SCILL and, in particular, to the SILP concept introduced earlier. In these catalytic materials silica is used as a structural support for the IL/catalyst coatings due to its high surface area and porous structure. The interaction between the IL and the silica surface determines a number of performance-relevant properties such as wetting behaviour and IL growth characteristics, which are highly dependent on the chemical nature of both support material and IL. For these systems, the desired properties of the resulting IL films on the support material are such that a thin, uniform IL film is formed, thereby yielding the highest-possible surface area and short diffusion pathways through the IL.

Till Cremer

Chapter 6. Summary and Outlook

In this thesis, ionic liquid (IL) bulk properties, the IL/vacuum interface and the IL/solid interface were investigated, primarily using angle-resolved X-ray photoelectron spectroscopy (ARXPS) under ultrahigh vacuum (UHV) conditions. ILs represents a class of materials with unique physico-chemical properties leading to a myriad of potential applications. Many of these take advantage of the extremely low vapour pressure, in particular of aprotic ILs, to fabricate permanent, non-volatile liquid coatings of solid materials. The research carried out herein focused on issues related to thin IL coatings, in particular concerning new catalytic concepts such as the supported ionic liquid phase (SILP) and solid catalyst with ionic liquid layer (SCILL) systems.

Till Cremer

Backmatter

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