Surface Studies of Thiolate Adsorbates on Some Metals

The results and discussions in this thesis are based on my studies about selfassembled thiol layers on gold, platinum, silver and copper surfaces. These kinds of layers are two-dimensional, one molecule thick and covalently organized at the surface. They are an easy way to modify surface properties. Self-assembly is today an intensive research field because of the promise it holds for producing new technology at nanoscale, the scale of atoms and molecules. These kinds of films have applications for example, in the fields of physics, biology, engineering, chemistry and computer science. Compared to the extensive literature concerning self-assembled monolayers (SAMs) on gold, little is known about the structure and properties of thiolbased SAMs on other metals. In this thesis I have focused on thiol layers on gold, platinum, silver and copper substrates. These studies can be regarded as a basic study of SAMs. Nevertheless, an understanding of the physical and chemical nature of SAMs allows the correlation between atomic structure and macroscopic properties. The results can be used as a starting point for many practical applications. X-ray photoelectron spectroscopy (XPS) and synchrotron radiation excited high resolution photoelectron spectroscopy (HR-XPS) together with time-offlight secondary ion mass spectrometry (ToF-SIMS) were applied to investigate thin organic films formed by the spontaneous adsorption of molecules on metal surfaces. Photoelectron spectroscopy was the main method used in these studies. In photoelectron spectroscopy, the sample is irradiated with photons and emitted photoelectrons are energy-analyzed. The obtained spectra give information about the atomic composition of the surface and about the chemical state of the detected elements. It is widely used in the study of thin layers and is a very powerful tool for this purpose. Some XPS results were complemented with ToF-SIMS measurements. It provides information on the chemical composition and molecular structure of the samples. Thiol (1-Dodecanethiol, CH3(CH2)11SH) solution was used to create SAMs on metal substrates. Uniform layers were formed on most of the studied metal surfaces. On platinum, surface aligned molecules were also detected in investigations by XPS and ToF-SIMS. The influence of radiation on the layer structure was studied, leading to the conclusion that parts of the hydrocarbon chains break off due to radiation and the rest of the layer is deformed. The results obtained showed differences depending on the substrate material. The influence of oxygen on layer formation was also studied. Thiol molecules were found to replace some of the oxygen from the metal surfaces.

Capillary electrophoresis for monitoring of carboxylic, phenolic and amino acids in bioprocesses

Bioprocess technology is a multidisciplinary industry that combines knowledge of biology and chemistry with process engineering. It is a growing industry because its applications have an important role in the food, pharmaceutical, diagnostics and chemical industries. In addition, the current pressure to decrease our dependence on fossil fuels motivates new, innovative research in the replacement of petrochemical products. Bioprocesses are processes that utilize cells and/or their components in the production of desired products. Bioprocesses are already used to produce fuels and chemicals, especially ethanol and building-block chemicals such as carboxylic acids. In order to enable more efficient, sustainable and economically feasible bioprocesses, the raw materials must be cheap and the bioprocesses must be operated at optimal conditions. It is essential to measure different parameters that provide information about the process conditions and the main critical process parameters including cell density, substrate concentrations and products. In addition to offline analysis methods, online monitoring tools are becoming increasingly important in the optimization of bioprocesses. Capillary electrophoresis (CE) is a versatile analysis technique with no limitations concerning polar solvents, analytes or samples. Its resolution and efficiency are high in optimized methods creating a great potential for rapid detection and quantification. This work demonstrates the potential and possibilities of CE as a versatile bioprocess monitoring tool. As a part of this study a commercial CE device was modified for use as an online analysis tool for automated monitoring. The work describes three offline CE analysis methods for the determination of carboxylic, phenolic and amino acids that are present in bioprocesses, and an online CE analysis method for the monitoring of carboxylic acid production during bioprocesses. The detection methods were indirect and direct UV, and laser-induced frescence. The results of this work can be used for the optimization of bioprocess conditions, for the development of more robust and tolerant microorganisms, and to study the dynamics of bioprocesses.