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In sulphide mineral flotation a sufficient hydrophobicity of the mineral surfaces is obtained by the adsorption of collector chemicals at the metal sulphide/aqueous interface. This surface alteration is of fundamental and applied interest. In this thesis, attenuated total reflection infrared spectroscopy has been used to monitor the adsorption kinetics and the orientation of heptyl xanthate when adsorbed onto three solid surfaces - germanium, zinc sulphide and lead sulphide in-situ. The choice of using the ATR technique is because it is very suitable when working with water as solvent, and the choice of germanium as internal reflection element is because of its small penetration depth due to a high refraction index. The Chemical Bath Deposition method has been used to deposit metal sulphides onto germanium internal reflection elements. For determining the adsorption of heptyl xanthate onto lead sulphide a novel method has been tested, and verified as capable in recovering information about surface reactions at a lead sulphide/aqueous interface. In the study of surface reactions the substrate is of vast importance, implying that the chemistry of the surface has to be well characterised. This work has utilized X-ray Photoelectron spectroscopy, and ATR spectroscopy, in the characterisation of the different surfaces. The adsorption kinetics has been followed to adsorption equilibrium at different concentrations. In the case of heptyl xanthate adsorbed at the zinc sulphide/aqueous interface, an adsorption isotherm has been calculated from the equilibrium data. On the assumption that the adsorption step was rate controlling a second order rate equation was derived and adsorption rate data tested according to this equation. In addition, an orientation study of the heptyl xanthate molecule at the different interfaces was performed, which requires polarised infrared light. In the case of heptyl xanthate adorbed onto germanium, both surface excess and a degree of alignment of the alkyl chain from the surface normal has been calculated. / Godkänd; 2004; 20070127 (ysko)

Mass spectrometry, and especially inductively coupled plasma mass spectrometry (ICP-MS), suffers heavily from mass bias, or instrumental mass discrimination. The nett result of this effect is the preferential transmission, most often of heavier ions through the mass spectrometer. Most work regarding this phenomenon in ICP-MS dates back quite far, and has been interpreted in terms of the space-charge effect. This means that Coulombic forces acting on the beam of positively charged particles extracted from the ICP result in greater dissipation of lighter, and hence more mobile ions from the beam axis. In this work the importance of the space-charge effect as a universal explanation for mass bias is challenged by the results of high precision measurements of isotope ratios. Other than considering some commonly known sources of isotope ratio measurement bias, a not previously considered mechanism of isotopic fractionation has been investigated, i.e. diffusion in solution. It was established that, indeed, diffusion does lead to isotopic fractionation in solution, and although this is a long term process, may contribute to the minor isotopic variations observed in certain aquatic environments. Furthermore it was established that spectral interferences of argone oxide ions could be discerned from the ions of iron using high resolution ICP-MS, thus eliminating this potential source of artificial fractionation. Most significant was the discovery that the extent of mass bias varied throughout the volume of the plasma, and was further affected by sample characteristics, such as analyte concentration and acid strength. This identifies the plasma itself as the major source of instrumental mass discrimination. Varying the sampling position, i.e. the point at which ions are extracted from the plasma, not only affected the measured isotope ratios, but also the precision of such measurements. From these results, it is not recommended to measure at the sampling position providing maximum signal, since the variability in the isotope ratio is also at its' maximum there. Instead, the ions should be sampled from a point below the maximum, where the stability of the ratios will be better. / Godkänd; 2004; 20070128 (ysko)

The finite nature of fossil fuels and their effect on the global climate, raised the need to find an alternative source of energy. This source should be environment compatible, cheap and abundant. The light coming from the Sun is a promising alternative. To be fruitful, the solar energy needs to be transformed in storable and transportable energy forms like electricityor fuels. Amongst the most studied techniques dye sensitised devices offer the possibility to be designed for both the scopes: solar-to-electricity and solar-to-fuel conversions. In these applications a photocathode and a photoanode, constructed by mesoporous semisconductor films sensitised with dyes, are placed in series with one another.It follows that the photocurrent generated by one electrode should be sustained by the photocurrent produced by the other electrode. At the moment there is a substantial difference between the conversion efficiencies and the photocurrent produced by photoanodes and photocathodes. In this thesis the reasons for this discrepancy are investigated. The main responsible of the bad performance is identified in the semiconductor normally used in photocathodes, Nickel Oxide (NiO). Electrochemical impedance spectroscopy was used to elucidate the electrical properties of mesoporous NiO films. The study revealed that NiO films are able to carry a large enough current to establish that conductivity is not a limiting factor. The recombination reactions were then accused as the cause of the power losses. A time resolved spectroscopic study revealed that NiO can host two kinds of holes. One of these holes is responsible for a fast dye-NiO recombination (100 ns) and the other one for a slow recombination (10 ms). A cell featuring only the slow dye-NiO recombination would possibly reach high efficiency. The characterisation of the species associated with these two holes was performed by density-of-state assisted spectroelectrochemistry. The holes were found to be trapped by Ni2+ and Ni3+ sites located on the NiO surface forming respectively Ni3+ and Ni4+ states. A study by fs and ns transient absorption spectroscopy revealed that Ni3+ sites can trap a hole in subpicosecond time scale and this hole relaxes into a Ni2+ trap in ns timescale. The control of the Ni2+/Ni3+ratio on the NiO surface was found  to be crucial for a high cell photovoltage. In the thesis these results are discussed and used to propose an explanation and some solutions to the poor performance of NiO-based dye sensitised cells.

Solid state 1H, 31P and 27Al Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) was used in studies of surface species formed on a synthetic fluorapatite in aqueous suspensions at different pH with or without ions or ion complexes of iron or aluminium in the suspension. Different sites related to the PO43- ions at the mineral surface were suggested, POx, POxH and POxH2. Also, three sites formed of Ca2+, H+ and OH- ions at the fluorapatite surface CaOH2+, CaOH and Ca(OH) 2- were suggested. Both single-pulse and cross polarization MAS NMR experiments were used to measure the 1H, 31P and 27Al isotropic chemical shifts. In the 1H to 31P cross polarization experiments the contact time was varied in order to differentiate the resonance liners corresponding to different surface sites from the resonance lines assigned to the PO43- ions in the crystal structure of fluorapatite. In the solid state dipole-dipole recoupling MAS NMR experiments the sequence XY8-DRAMA was used in studies of distances between O,O'- dialkyldithiophosphates adsorbed on synthetic galena (PbS). The sequence was tested experimentally and gave highest double-quantum excitation efficiency of the tested dipole-dipole recoupling sequences tested at the spinning frequency 4.2 kHz. A new sequence IRS-DRAMA was derived analytically and showed high double quantum excitation efficiency in a broad interval of the 31P resonance frequencies at the spinning frequency 2.1 kHz. / Godkänd; 2006; 20061205 (haneit)

In sulphide mineral flotation, a sufficient hydrophobicity of the mineral surfaces is obtained by the adsorption of collector chemicals at the metal sulphide/aqueous interface. This surface alteration is of fundamental and applied interest. In this thesis, attenuated total reflection infrared spectroscopy has been used to monitor the adsorption kinetics and the orientation of heptyl xanthate when adsorbed onto three solid surfaces - germanium, zinc sulphide and lead sulphide in-situ. The Chemical Bath Deposition method has been used to deposit metal sulphides onto germanium internal reflection elements, and verified as capable in synthesizing metal sulphide surfaces for adsorption studies recovering information about surface reactions at metal sulphide/solution interfaces. In the study of surface reactions the substrate is of great importance, implying that the chemistry of the surface has to be well characterised. This work has utilized X-ray photoelectron spectroscopy in the characterisation of the different surfaces. The adsorption kinetics has been followed to monitor the adsorption equilibria at different concentrations. In the case of heptyl xanthate adsorbed at the zinc sulphide/aqueous interface, an adsorption isotherm has been calculated from the equilibrium data. On the assumption that the adsorption step was rate controlling a pseudo-first order equation was derived and adsorption rate data, in all the three studied systems, tested according to this equation. In addition, an orientation study of the heptyl xanthate molecule at the different interfaces was performed, which requires polarised infrared light. Density Functional calculations of a free heptyl xanthate molecule, and a heptyl xanthate molecule adsorbed on a pure Ge(111) were utilized to get more information about the in-situ adsorption of heptyl xanthate on a germanium surface. The important vibration bands were assigned to different vibrations, and the theoretical infrared spectra were compared with the experimentally analyzed spectra. This study shows the strengths of using advanced first-principle Density Functional Theory in the interpretation of real surface adsorption systems. / Godkänd; 2006; 20070314 (evan)

Polymers are of fundamental importance to our society and can befound in many different products. Block copolymers are polymerswhich are divided up into distinct blocks of two or more differentmonomers. Block copolymers with regions of difference in polarityare capable of self assembling into ordered systems. These systemscan be tailored to be used for different purposes such as templatesfor material synthesis or drug delivery vehicles. The objective ofthis study was to investigate how different methods of preparing asample affect the micellar structures for the systems poly(2-ethylhexyl methacrylate) (PEHMA) - quaternized poly(dimethylaminoethyl methacrylate) (qPDMAEMA) and poly(2-ethyl-hexylmethacrylate) (PEHMA)- poly(methacrylic acid)(PMAA). The parametersstudied were choice of cosolvent and order of mixing, i.e. mixingwater with polymer solution or polymer solution with water. Thestability over time of the micellar structures were studied as wellas the Zetapotential and adsorption to model silica surfaces. Theresults showed that using different cosolvents yielded a differencein size but not in micelle stability over time. The investigationalso showed that preparing the sample by adding polymer solution towater, versus adding water to polymer solution, yielded nosignificant difference in polymer size or stability. However as thestudy was done in small volumes the concentration gradient producedduring the two methods may not differ that much and using largersample volumes may produce different results. Using a triblockcopolymer over a diblock copolymer of a corresponding size yieldedvastly different results in size, stability and adsorption. Thetriblock polymer produced smaller more stable aggregates whichadsorbed quickly and the diblock copolymer produced large,polydisperse aggregates which started to aggregate after around 7days and adsorbed slowly.

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