Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The WineScan FT120 is widely used in wine laboratories across South Africa. The WineScan FT120 uses Fourier transform infrared (FT-IR) spectroscopy with multivariate data analysis to correlate spectra with chemical compositional data. Ready-to-use, commercially available calibration models for a FT-IR spectroscopy instrument are an advantage for unskilled users and routine analysis. Introducing spirit products to this technology introduced new interferences, which necessitated vastly different calibrations models to compensate for the changes. Accuracy, precision and ruggedness of the reference methods validated during method validation, verified the suitability of the reference methods used to quantify the parameters in question before calibration model building was attempted. Various principal component analysis (PCA) were performed prior to the calibration step with the aim to identify outliers and inspect groupings. PCA models could identify samples with atypical spectra and differentiate between product types. Two tactics regarding data sets for calibration set-up was experimented with, all the products together and calibration models per product. Partial least squares (PLS) regression was used to establish the calibration models for ethanol, density, obscuration and colour. With all the calibration models, the calibration models based on the product specific data sets, achieved better predicting statistics. The best performing ethanol calibration models achieved Residual mean square error of prediction (RMSEP) = 0.038 to 0.106 %v/v and showed significant improvement on previously reported prediction errors by Lachenmeier (2007). The results for the density calibration showed a similar trend, with the product specific calibration models outperforming the calibration model when all samples were included into one calibration model. This study produced novel results for quantification of obscuration (RMSEP = 0.10 and 0.09 in blended brandies and potstill brandies, respectively) and colour (RMSEP < 2.286 gold units) of brandies and whiskies. The correlation coefficients (R²) between true and predicted values, for the four parameters tested, indicated good to excellent precision (0.8 < R² < 1.0). Minimising the variation between the samples of the data set, gave more accurate regression statistics, but this resulted in a lower residual predictive deviation (RPD) value (< 5) that indicated models were not suitable for quantification. Adding more samples per product will add more variability into a data set per product, increase the SD and result in an increase in the RPD. The results pave the way for the development of calibration models for the quantification of other parameters for specific products. Following the groupings of product types, further classifications of brandy brands were investigated. PCA plots showed clear separation between potstill brandies and blended brandies and some degree of clustering between some of the blended brands was observed. Classification of brandies were investigated using the Soft Independent Modeling of Class Analogy (SIMCA) approach resulting in a total correct classification rates between 81.25% and 100% for the various brandy brands. These preliminary results were very promising and highlight the potential of using FT-IR spectroscopy and multivariate classification techniques as a tool for rapid quality control and authentication of brandy brands. Using this work as base for further classification projects, this could be of great benefit to the alcoholic beverage industry of South Africa. Future work will involve the development of a database comprised of more products guaranteed authentic to expand the discriminating options. The results suggest FT-IR spectroscopy could be useful in authentication studies. / AFRIKAANSE OPSOMMING: Die WineScan FT120 is ‘n algemeen gebruikte instrument regoor Suid-Afrika. Die WineScan FT120 gebruik Fourier-transformasie-infrarooi (FT-IR) spektroskopie tesame met multiveranderlike statistiese metodes om spektra te korreleer met chemiese samestellingsdata. Die kommersieël beskikbare kalibrasiemodelle vir die FT-IR spektroskopie-instrument is ‘n voordeel vir onbedrewe gebruikers en roetine ontleding. Blootstelling van spiritusprodukte aan die tegnologie, het nuwe hindernisse bekend gestel en dus is verskillende kalibrasiemodelle genoodsaak om hiervoor te kompenseer. Akkuraatheid, presiesheid en ruheid van die verwysingsmetodes is geëvalueer tydens metodevalidasie. Die verwysingsmetodes is geskik verklaar vir die konstruksie van die kalibrasiemodel met geverifieërde akkurate verwysingsresultate. Verskeie multiveranderlike hoofkomponentanalise (MVK) was uitgevoer voor die kalibrasiestap met die doel om uitskieters te identifiseer en groeperings te inspekteer. MVK modelle kon monsters met atipiese spektra identifiseer en onderskei tussen verskillende produk tipes. Twee taktieke aangaande datastelsamestelling is getoets tydens kalibrasiemodel-opstelling, al die produkte saam en kalibrasiemodelle per produk soos met die MVK aangedui. Parsiële kleinste kwadraat (PKK)- regressie is gebruik vir die opstel van die kalibrasiemodelle vir etanol, digtheid, obskurasie en kleur. Met al die kalibrasiemodelle het die produk spesifieke kalibrasiemodelle beter regressiestatistiek gelewer. Die beste presterende etanol kalibrasiemodelle het ‘n standaardvoorspellingsfout (SVF) = 0.038 tot 0.106 %v/v bereik en het ‘n beduidende verbetering getoon op vorige gerapporteerde studies op spiritusprodukte (Lachenmeier, 2007). Die resultate vir die digtheidskalibrasiemodelle het ‘n eenderse tendens getoon soos die etanol, met die produk spesifieke kalibrasiemodelle wat beter presteer het. Hierdie studie was eerste in sy soort met die kalibrasiemodel vir obskurasie (SVF = 0.10 en 0.09 in gemengde brandewyne en potketel brandewyne, onderskeidelik) en kleur (SVF < 2.286 goud eenhede) van brandewyne en whiskies. Die bepalingskoëffisiënt (R²) vir die vier parameters, dui op goeie tot uitstekende presiesheid (0.8 < R² < 1.0). Vermindering van die variasie tussen die monsters in die datastel, het meer akkurate regressiestatistiek teweeg gebring, maar ‘n laer relatiewe voorspellingsafwyking (RVA) waarde (<5) tot gevolg gehad wat aan dui dat hierdie modelle nie geskik is vir sifting of kwantifisering nie. Die byvoeging van meer monsters per produk sal meer verskeidenheid in die datastel per produk bring, wat dan die standaardafwyking sal laat toeneem en uiteindelik die RVA laat toeneem. Die resultate het die fondasie gelê vir die ontwikkeling van kalibrasiemodelle vir die kwantifisering van ander parameters vir spesifieke produkte. As opvolg tot die groeperings van die produk tipe, waargeneem in die MVK modelle, was klassifikasie van brandewyn handelsmerke ondersoek. MVK modelle het duidelike skeiding gewys tussen potketel en gemengde brandewyne en tot ‘n sekere mate groepering tussen handelsmerke. Klassifikasie van brandewyne was ondersoek met behulp van the Soft Independent Modeling of Class Analogy (SIMCA) met die resultaat van ‘n totale korrekte klassifikasiekoers van tussen 81.25% en 100% vir die verskeie brandewyn handelsmerke. Hierdie voorlopige resultate toon belowend en beklemtoon die potensiaal van FT-IR spektroskopie en chemometrics tegnieke as toerusting vir die vinnige kwaliteitskontrole en egtheid van brandewyn handelsmerke studies. Met hierdie werk as basis vir verdere klassifikasie projekte, kan dit ‘n groot aanwins wees tot die alkoholiese drank industrie van Suid-Afrika. Toekomstige werk sal insluit die ontwikkeling van ‘n databasis saamgestel met meer gewaarborgde egte produkte om die klassifikasie uit te brei.

Natural archives such as lake sediments allow us to assess contemporary ecosystem responses to climate and environmental changes in a long-term context beyond the few decades to at most few centuries covered by monitoring or historical data. To achieve a comprehensive view of the changes preserved in sediment records, multi-proxy studies – ideally in high resolution – are necessary. However, this combination of including a range of analyses and high resolution constrains the amount of material available for analyses and increases the analytical costs. Infrared spectroscopic methods are a cost-efficient alternative to conventional methods because they offer a) a simple sample pre-treatment, b) a rapid measurement time, c) the non- or minimal consumption of sample material, and d) the potential to extract quantitative and qualitative information about organic and inorganic sediment components from a single measurement. The main objective of this doctoral thesis was twofold. The first part was to further explore the potential of Fourier transform infrared (FTIR) and visible-near infrared (VNIR) spectroscopy in paleolimnological studies as a) an alternative tool to conventional methods for quantifying biogenic silica (bSi) – a common proxy of paleoproductivity in lakes – in sediments and b) as a tool to infer past lake-water total organic carbon (TOC) levels from sediments. In a methodological study, I developed an independent application of FTIR spectroscopy and PLS modeling for determining bSi in sediments by using synthetic sediment mixtures with known bSi content. In contrast to previous models, this model is independent from conventional wet-chemical techniques, which had thus far been used as the calibration reference, and their inherent measurement uncertainties. The second part of the research was to apply these techniques as part of three multi-proxy studies aiming to a) improve our understanding of long-term element cycling in boreal and arctic landscapes in response to climatic and environmental changes, and b) to assess ongoing changes, particularly in lake-water TOC, on a centennial to millennial time scale. In the first applied study, high-resolution FTIR measurements of the 318-m long sediment record of Lake El’gygytgyn provided a detailed insight into long-term climate variability in the Siberian Arctic over the past 3.6 million years. Highest bSi accumulation occurred during the warm middle Pliocene (3.6-3.3 Ma), followed by a gradual but variable decline, which reflects the first onset of glacial periods and then the finally full establishment of glacial–interglacial cycles during the Quaternary. The second applied study investigated the sediment record of Torneträsk in subarctic northern Sweden also in relation to climate change, but only over the recent post-glacial period (~10 ka). By comparing responses to past climatic and environmental forcings that were recorded in this large-lake system with those recorded in small lakes from its catchment, I determined the significance and magnitude of larger-scale changes across the study region. Three different types of response were identified over the Holocene: i) a gradual response to the early landscape development following deglaciation (~10000-5300 cal yr BP); ii) an abrupt but delayed response following climate cooling during the late Holocene, which occurred c. 1300 cal yr BP – about 1000-2000 years later than in smaller lakes from the area; and iii) an immediate response to the ongoing climate change during the past century. The rapid, recent response in a previously rather insensitive lake-ecosystem emphasizes the unprecedented scale of ongoing climate change in northern Fennoscandia. In the third applied study, VNIR-inferred lake-water TOC concentrations from lakes across central Sweden showed that the ongoing, observed increase in surface water TOC in this region was in fact preceded by a long-term decline beginning already AD 1450-1600. These dynamics coincided with early human land use activities in the form of widespread summer forest grazing and farming that ceased over the past century. The results of this study show the strong impact of past human activities on past as well as ongoing TOC levels in surface waters, which has thus far been underestimated. The research in this thesis demonstrates that infrared spectroscopic methods can be an essential component in high-resolution, multi-proxy studies of past environmental and climate changes.

The thermal decomposition products (TDP) generated during fire suppression with 1,1,1,2,2,4,5,5,5 nonafluoro-4-trifluoromethyl pentan-3-one were studied using wet chemistry and FTIR. Small-scale testing was conducted in a 1.28-m3 (45-ft3) enclosure. The effects of fire size, agent discharge time, and agent concentration on TDP are reported. A comparison of the two methods is presented. In terms of magnitude and generation trends, the TDPs were found to be comparable to other in-kind halon alternatives.

This study focuses on various aspects of nanocrystals embedded in a dielectric matrix. In the first part of this work, a new approach with the use of Fourier Transform Infrared spectroscopy (FTIR) in the nanocrystal analysis was developed and presented. Si and Ge nanocrystals embedded in SiO2 matrix were mainly studied. This new approach is based on the analysis of structural variations of SiO2 matrix during the formation of semiconductor nanocrystlas. It is shown that the chemical and structural variations of the host matrix are directly related to the precipitation of nanocrystals in it. This correlation provides valuable information about the presences of nanocrystals in the matrix. In the second part of this work, fabrication of SiC films with and without Si nanocrystals inclusions was studied. With this aim, stoichiometric SiC and Si rich SiC thin films were fabricated by using magnetron co-sputtering and Plasma Enhanced Chemical Vapor Deposition (PECVD) techniques. For SiC films, the structural and optical analyses were performed. For Si rich SiC films, the formation conditions of Si nanocrystals were investigated. Post annealing studies were carried out to track the evolution of the SiC matrix and formation of Si nanocrystals at different temperatures. Chemical and structural properties of the SiC host matrix were investigated with FTIR spectroscopy. Optimum conditions for the fabrication of stoichiometric SiC layers were determined. The crystallography of the nanocrystals was investigated by X-Ray Diffraction (XRD). The variation of the atomic concentrations and bond formations were investigated with X-Ray Photoelectron Spectroscopy (XPS). Raman spectroscopy and Transmission Electron Microscopy (TEM) were used to verify the formation of Si nanocrystals. We have shown that both single and multilayer Si nanocrystals can be fabricated in the amorphous SiC matrix for applications such as light emitting diodes and solar cells.

Large Area Maskless Photopolymerization (LAMP) is a direct digital manufacturing technology being developed at Georgia Tech to produce ceramic molds for investment casting of turbine airfoils. In LAMP, UV light incident on a spatial light modulator is projected in the form of a structured black and white bitmap image onto a platform supporting slurry comprising a ceramic particle loaded photocurable resin. Curing of the resin is completed rapidly with exposures lasting 20~160ms. Three-dimensional parts are built layer-by-layer by sequentially applying and selectively curing resin layers of 25-100 micron thickness. In LAMP, diacrylate-based ceramic particle-loaded resins with photoinitiators sensitive in the range of spectral characteristics of the UV source form the basis for an ultra-fast photopolymerization reaction. At the start of the reaction, the monomer molecules are separated by van der Waals distance (~10⁴Å). As the reaction proceeds, these monomer molecules form a closely packed network thereby reducing their separation to covalent bond lengths (~ 1 Å). This results in bulk contraction in the cured resin, which accumulates as the part is fabricated layer-by-layer. The degree of shrinkage is a direct measure of the number of covalent bonds formed. Thus, shrinkage in LAMP is characterized by estimating the number of covalent bonds formed during the photopolymerization reaction. Polymerization shrinkage and accompanying stresses developed during photopolymerization of ceramic particle-loaded resins in LAMP can cause deviations from the desired geometry. The extent of deviations depends on the photoinitiator concentration, the filler loading, the degree of monomer conversion, and the operating parameters such as energy dose. An understanding of shrinkage and stresses built up in a part can assist in developing source geometry compensation algorithms and exposure strategies to alleviate these effects. In this thesis, an attempt has been made to understand the curing kinetics of the reaction and its relation to the polymerization shrinkage. Realtime Fourier Transform Infrared Spectroscopy (RTFTIR) is used to determine the conversion of monomers into polymer networks by analyzing the changes in the chemical bonds of the participating species of molecules. The conversion data can further be used to estimate the curing kinetics of the reaction and the relative volumetric shrinkage strain due to polymerization.

Atoms construct the molecules and molecules construct the material substances (with the exceptions as well, e.g.., metals, where atoms directly construct the material substances). Intermolecular interactions play an important role in most of the branches of sciences, ranging from material sciences to biological sciences. Van der Waals interactions are weak intermolecular interactions while hydrogen bonding varies in strength from weak to strong (1 to 40 kcal/mol). The present work focuses on applying some theoretical methods (ab initio and Atoms in Molecules theory) on these interactions to differentiate them with physically meaningful parameters such as hydrogen bond radii and atoms in molecules theory parameters. 1)Defining and calculating H-bond radii have been done using atoms in molecules theory approach which can explain ruling out the presence or absence of an H-bond in an intermolecular interaction. 2) A blue-shift of 200 cm-1 for a weakly bound complex is unprecedented. Our studies on weakly bound complexes showed the blue-shift of 200 cm-1 for H3C•••CIF and shift has been found to be purely from the mixing of normal modes and not because of an interaction. 3)Methane, a symmetric top molecule can act both as H-bond acceptor and donor. The present work shows that methane is rather a better H-bond acceptor than a donor and all the calculated parameters are in favor of this description. 4) Microwave spectrometer is an ultimate tool (at least at present) for structural characterization of the weakly bound complexes accurately. The rotational spectrum of the weakly bound isotopomer weakly bound complexes accurately. The rotational spectrum of the weakly bound isotopomer 13CC5H6•••Ar, which is a symmetric top and gives only “B” rotational constant. Moreover, the A rotational constant of the complex is the same as the rotational constant for 13CC5H6, which has no dipole moment. C2H2 molecule is an astrophysically important molecule as it is present in asymptotic giant branch and T-type stars (Teff<3000K). Due to its various infrared active vibrational modes, C2H2 is one of the most important sources in cool stars. The production of C2H2 infrared spectroscopic data at high temperature is therefore essential to trace back physical characteristics of these objects and to model the radiative transfer in their envelope. The databases such as “HITRAN”, do not have enough data available for stimulating high temperature spectra. Keeping all these objectives in mind, high temperature emission spectrum of acetylene has been recorded around 3µm region of acetylene.

Recently, the high radiance of synchrotron sources was used to enhance FTIR spectrometer performance. However, excessive channel spectra when synchrotron sources are used degrade the quality of retrieved spectral parameters. In the research reported in this thesis, seven different techniques for handling channel spectra were investigated. These techniques were used to reduce channel spectra for a test group of seven samples of CO2 mixed with air recorded using the synchrotron source at the Canadian Light Source. The increases in signal to noise ratio (SNR) of spectra handled with each technique were calculated. SNR results showed that transmission spectra, produced using synthetic background spectra with simulated channel spectra, achieved the highest SNR improvement. However, when the spectra groups were fitted using nonlinear least square fit algorithm, the technique using channel spectra fitting produced the smallest fitting residual. Moreover, the retrieved intensities and air broadening coefficients of 21 spectral lines showed that the spectral fitting technique produced the most accurate values as compared to the HITRAN 2008 database. Although the spectral fitting technique was accurate in retrieving spectral line parameters, applying the technique at wider spectral ranges was less accurate. A modification to the channel spectra fitting technique by performing iterations of channel fitting was introduced to process wider spectral ranges. Carbon dioxide laser band I centred at 961 wavenumber was analyzed using 24 spectra recorded under different experimental conditions. The intensity and air-and self-broadening coefficients were retrieved for 48 spectral lines with average deviations from HITRAN database values of 2.11%, 1.25% and 4.14%, respectively, using the Voigt profile. These average deviations lie within the uncertainty limits listed by the database. The deviation between our results and other results reported in the literature were also examined and it is found to be also within the range of HITRAN uncertainties. The effect of errors in fitting channel spectra parameters was examined and found to be mitigated by the inclusion of channel-free spectra in the multispectral fit. / xiv, 134 leaves : ill. ; 29 cm

Nitrocellulose is the main component in many types of ammunition, propellants and explosives. The principles of production for nitrocellulose have not changed much since the 19th century when it started being industrially produced for this purpose. The character of the nitrocellulose has a large effect on the end products abilities. The aim of this study was to develop a method that would be able to characterise and distinguish between nitrocellulose from different manufacturers to be able to relate the character of the nitrocellulose to the properties of ammunition, propellants and explosives. Samples were dissolved in acetone and analysed by GC/MS and data were then analysed by multivariable statistics. FTIR was also used to characterise the nitrocellulose. Results from both methods showed very small differences when chromatograms and spectra were analysed. This study shows that GC/MS and FTIR are not suitable for this type of characterisation. The differences between the data were not sufficient to be able to separate the samples from each other. / Nitrocellulosa är den viktigaste komponenten i många typer av ammunition, drivmedel och sprängämnen. Principerna för produktionen av nitrocellulosa har inte förändrats mycket sedan det börjades produceras industriellt för detta ändamål på 1800 talet. Karaktären av nitrocellulosa har en stor inverkan på slutproduktens egenskaper. Syftet med denna studie var att utveckla en metod som skulle kunna karaktärisera och skilja mellan nitrocellulosa från olika tillverkare för att kunna relatera karaktären av nitrocellulosa till egenskaperna hos ammunition, drivmedel och sprängämnen. Proverna löstes i aceton och analyserades med GC/MS och data analyserades med multivariabel statistik. FTIR användes också för att karakterisera nitrocellulosan. Resultaten för båda proverna visade mycket små skillnader när kromatogram och spektra analyserades. Denna studie visar att GC/MS och FTIR inte är lämpliga för denna typ av karaktärisering. Skillnaderna i data var inte tillräckliga för att kunna skilja proverna från varandra.

Deposition of silica shells onto ZnO nanoparticles (NPs) in dimethyl sulfoxide was found to be an efficient tool for terminating the growth of ZnO NPs during thermal treatment and producing stable core–shell ZnO NPs with core sizes of 3.5–5.8 nm. The core–shell ZnO–SiO2 NPs emit two photoluminescence (PL) bands centred at [similar]370 and [similar]550 nm originating from the direct radiative electron–hole recombination and defect-mediated electron–hole recombination, respectively. An increase of the ZnO NP size from 3.5 to 5.8 nm is accompanied by a decrease of the intensity of the defect PL band and growth of its radiative life-time from 0.78 to 1.49 μs. FTIR spectroscopy reveals no size dependence of the FTIR-active spectral features of ZnO–SiO2 NPs in the ZnO core size range of 3.5–5.8 nm, while in the Raman spectra a shift of the LO frequency from 577 cm−1 for the 3.5 nm ZnO core to 573 cm−1 for the 5.8 nm core is observed, which can indicate a larger compressive stress in smaller ZnO cores induced by the SiO2 shell. Simultaneous hydrolysis of zinc(II) acetate and tetraethyl orthosilicate also results in the formation of ZnO–SiO2 NPs with the ZnO core size varying from 3.1 to 3.8 nm. However, unlike the case of the SiO2 shell deposition onto the pre-formed ZnO NPs, individual core–shell NPs are not formed but loosely aggregated constellations of ZnO–SiO2 NPs with a size of 20–30 nm are. The variation of the synthetic procedures in the latter method proposed here allows the size of both the ZnO core and SiO2 host particles to be tuned. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

This paper aims to investigate the embalming process and the Balanites aegyptiaca from two pottery originated in ancient Egypt. The two objects were from Medelhavsmuseet in Stockholm. Samples were collected and analyzed with Fourier transform infrared spectrometry (FTIR) and Gas chromatography/mass spectrometry to identify which components the samples contained. The results show complex mixtures mainly consisting of resin origin from Pinaceae and the vegetable oils from the Balanites aegyptiaca.