Fiber loop ring down (FLRD) spectroscopy is a sensitive spectroscopic technique that is based on absorption and it is convenient for trace chemical detection. Different FLRD systems are being improved in order to increase their sensitivity. In FLRD spectroscopy, detection of a sample is done by measuring of a leaking light at each trip within an optical cavity. Intensity of leaking light has an exponential decay where it is reduced by absorption of sample and scattering of light. In this project, two FLRD set-ups at 1535 nm and 808 nm were designed. In both set-ups, optical fiber and optical fiber couplers are used to form a cavity. At 1535 nm, a FLRD set-up is constructed by utilizing a pulsed laser and used for characterization of thin films, various pure liquids and fluorescein solutions. Two different sensor regions are designed with free space collimators and ferrules for the measurement of thin films and liquids, respectively. The future endeavor of the set-up is improvement for reliability and reproducibility of the system. For visible and NIR regions, a fiber coupled laser with four colors as 642 nm, 785 nm, 808 nm and 852 nm laser is used to design of a FLRD set-up. 808 nm laser is selected to build a prototype of the FLRD system. The construction of a closed loop FLRD set-up is completed and the system is characterized. Ultimate aim in our project is to be able to do trace detection at visible and NIR regions where the chemical sensitivity is higher.

Un spectromètre utilisant la technique CRDS a été développé entre 2.00 et 2.35 µm afin de réaliser la spectroscopie en absorption de molécules d’intérêt atmosphérique et planétologique avec une très grande sensibilité et à haute résolution spectrale. Cette région du spectre correspond à une fenêtre de transparence de la vapeur d’eau et du dioxyde de carbone. Ces fenêtres sont des zones de très faible absorption utilisées pour le sondage des atmosphères terrestre et vénusienne dans lesquelles la vapeur d’eau et le dioxyde de carbone représentent respectivement les absorbants gazeux principaux dans l’infrarouge.La technique CRDS consiste à injecter des photons dans une cavité optique de haute finesse et à mesurer la durée de vie des photons dans cette cavité. Celle-ci est mesurée en interrompant l’injection des photons dans la cavité optique lors du passage en résonance du laser avec l’un des modes longitudinaux. Cette durée de vie dépend de la réflectivité des miroirs et des pertes intra-cavité comme celles induites par un gaz qui absorbe. Mesurer ces pertes en fonction de la longueur d’onde permet d’obtenir le spectre d’absorption du gaz en question. L’extrême réflectivité des miroirs permet d’atteindre dans une cavité d’un peu plus d’1 m de longueur une sensibilité équivalente à celle qui serait obtenue classiquement avec une cellule d’absorption longue de plusieurs milliers de kilomètres.Trois diodes laser DFB émettant autour de 2.35, 2.26 et 2.21 µm ont été utilisées avec ce spectromètre. Grâce à une rétro-action optique provenant d’une cavité externe, certaines de ces diodes ont pu être affinées, ce qui a permis de mieux injecter la cavité haute finesse et ainsi de réduire le niveau de bruit du spectromètre. Parallèlement grâce à une collaboration avec l’Institut d’Electronique (IES, UMR 5214) à Montpellier et la société Innoptics nous avons pu tester le prototype d’un VECSEL (Vertical-External-Cavity Surface-Emitting-Laser). Ce laser a permis de couvrir une gamme spectrale de 80 cm-1, entre 4300 et 4380 cm-1, équivalente à quatre diodes laser DFB. La sensibilité obtenue en routine avec ce spectromètre, correspondant au coefficient minimum détectable, est typiquement de 1×10-10 cm-1. Le chapitre introductif (Chapitre 1) fait le point sur les différentes techniques permettant d’acquérir des spectres en absorption dans la gamme spectrale étudiée et sur les sensibilités atteintes. A notre connaissance l’instrument développé ici est le plus sensible dans cette région du spectre. Le fonctionnement de ce spectromètre CRDS est détaillé dans le chapitre 2.Pour démontrer les performances obtenues avec notre instrument celui-ci a été utilisé pour enregistrer des transitions quadrupolaires donc de très faible intensité. Ainsi la transition S(3) de la bande 1–0 de HD a été enregistrée pour la première fois et son intensité mesurée (S=2.5×10-27 cm/molecule). La sensibilité obtenue en routine a encore pu être améliorée en réalisant une moyenne d’une centaine de spectres sur une gamme spectrale réduite pour atteindre 1×10-11 cm-1. Grâce à cela nous avons pu mesurer la position et l’intensité de la raie quadrupolaire électrique O(14) de la bande 2–0 de N2 qui est très fortement interdite avec une intensité de 1.5×10-30 cm/molecule. Ces mesures font l’objet du chapitre 3 de cette thèse.Les deux derniers chapitres sont dédiés à la caractérisation de l’absorption du CO2, au centre de la fenêtre de transparence, et à celle de la vapeur d’eau. Dans les deux cas, les transitions permises du monomère et la contribution du continuum ont été étudiées. Ce dernier correspond à une absorption variant lentement avec la longueur d’onde. Les sections efficaces du « self-continuum » de la vapeur d’eau ont notamment été mesurées en plusieurs points de la fenêtre de transparence avec une incertitude beaucoup plus faible que les mesures existantes. Elles représentent un jeu de données décisif pour tester les modèles décrivant ce continuum. / A cavity ring down spectrometer has been developed in the 2.00-2.35 µm spectral range to achieve highly sensitive absorption spectroscopy of molecules of atmospheric and planetologic interest and at high spectral resolution. This spectral region corresponds to a transparency window for water vapor and carbon dioxide. Atmospheric windows, where absorption is weak, are used to sound the Earth’s and Venus’ atmospheres where water vapor and carbon dioxide represent the main gaseous absorbers in the infrared, respectively.The CRDS technique consists of injecting photons inside a high finesse optical cavity and measuring the photon’s life time of this cavity. This life-time depends on the mirror reflectivity and on the intra-cavity losses due to the absorbing gas in the cavity. Measuring these losses versus the wavelength allow obtaining the absorption spectrum of the gas. The extreme reflectivity of the mirrors allows reaching, for a 1-meter long cavity, a sensitivity equivalent to the one obtained classically with absorption cells of several thousands of kilometers.Three DFB laser diodes emitting around 2.35, 2.26, 2.21 µm were used with this spectrometer giving access to the 4249-4257, 4422-4442 and 4516-4534 cm-1 interval, respectively. Thanks to optical feedback from an external cavity, two of these diodes were spectrally narrowed leading to a better injection of the high finesse cavity thus reducing the noise level of the spectrometer. In parallel, we tested a VECSEL (Vertical-external-Cavity, Surface Emitting laser) through a collaboration with the Institu d’Electronique (IES, UMR 5214) in Montpellier and the Innoptics firm. This laser source is able to cover a 80 cm-1 spectral range centered at 4340 cm-1, equivalent to four DFB laser diodes. In routine the achieved sensitivity with this spectrometer, corresponding to the minimum detectable coefficient is typically of 1×10-10 cm-1. The introductive chapter (Chapter 1) makes the point on the different techniques allowing absorption spectra recordings in the studied spectral region and on their sensitivity. The experimental set-up, the characteristics and performances by the CRD spectrometer developed in this work are detailed in Chapter 2. To our knowledge this instrument is the most sensitive in the considered spectral region.In Chapter 3, detection of quadrupolar electric transitions of HD and N2 illustrate the level of sensitivity reached: (i) the S(3) transition in the 1-0 band of HD has been recorded for the first time and its intensity measured (S=2.5×10-27 cm/molecule), (ii) the position and intensity of the highly forbidden O(14) quadrupolar electric transition of the 2-0 band of N2 have also been newly determined.The two last chapters are devoted to the characterization of the CO2 absorption, in the centre of the transparency window, and of the water vapor absorption. In both cases, we not only studied the allowed transitions of the monomer, but also the continuum absorption. This latter correspond to a weak background absorption varying slowly with the wave length. The self-continuum cross-sections of the water vapor continuum were measured in many spectral points through the transparency window with a much better accuracy compared to existing measurements. These CRDS data constitute a valuable data set to validate the reference model (MT_CKD) for the continuum which is implemented in most of the atmospheric radiative transfer codes.

In der vorliegenden Arbeit werden verschiedene Spektrometer für die Analyse von Gasen bzw. Gasgemischen vorgestellt und deren Design, Aufbau, Charakterisierung und Optimierung beschrieben. Das Resultat der Optimierung und Weiterentwicklungen ist ein spektral breitbandiges Cavity-Ring-Down-Spektrometer (CRD-Spektrometer). Ausgangspunkt der hier vorgestellten Arbeit ist ein Spektrometer auf Basis klassischer Absorptionsspektroskopie in einer Multireflexionszelle. Für dieses Spektrometer wurde als Strahlquelle ein Superkontinuumlaser verwendet. Der Vorteil dieses Spektrometers liegt in seiner Kompaktheit. Mit diesem Spektrometer wurden Absorptionsspektren von mehreren Reingasen und einem Gasgemisch über einen Wellenlängenbereich von 1500 nm – 1700 nm aufgenommen. Der qualitative Vergleich mit zu erwartenden Spektren, welche auf der HITRAN-Datenbank basieren, zeigte eine gute Übereinstimmung. Die quantitative Interpretierbarkeit der Daten war jedoch stark eingeschränkt aufgrund des hohen zufälligen und systematischen Fehlers der Messungen. Als Konsequenz aus der als nicht zufriedenstellend bewerteten quantitativen Interpretierbarkeit der Daten wurde eine alternative Messmethode gesucht, welche eine höhere Sensitivität und Genauigkeit ermöglicht. Die Wahl fiel auf die Cavity-Ring-Down-Spektroskopie, eine resonatorgestützte Variante der Absorptionsspektroskopie. Wesentliche Vorteile dieser Technik sind a) die Unabhängigkeit von Leistungsschwankungen der Strahlquelle, b) ein effektiver Absorptionsweg von bis zu mehreren Kilometern, welcher sich unmittelbar auf die Sensitivität der Messungen auswirkt, c) die Ermittlung absoluter Absorberkonzentrationen, ohne die Notwendigkeit einer Kalibrierung oder den Vergleich mit einer Referenzzelle und d) die Vernachlässigbarkeit von Absorptionen außerhalb des Resonators. Als notwendiger Zwischenschritt auf dem Weg zu einem breitbandigen CRD-Spektrometer wurde zunächst ein monochromatisches CRD-Spektrometer designt, aufgebaut und charakterisiert. Für die effektive Einkopplung von Strahlungsenergie in einen Resonator ist die Anpassung der Strahlparameter an die Mode des Resonators notwendig. Voraussetzung dieser Anpassung ist die Kenntnis der Strahlparameter, welche experimentell ermittelt wurden. Im Laufe des Aufbaus des Spektrometers ergab sich, dass trotz der Modenanpassung die Einkopplung der Strahlungsenergie in den Resonator gestört wurde. Daraufhin wurden systematisch mögliche Ursachen dieser Störung untersucht und das Spektrometer optimiert. Mit diesem optimierten Spektrometer wurden Spektren gemessen, welche sowohl qualitativ als auch quantitativ gut mit den zu erwartenden Spektren übereinstimmen. Als Nachweisgrenze dieses Spektrometers wurde ein Wert für den Absorptionskoeffizienten alpha von 10^-8 cm-1 bestimmt. Mit dem monochromatischen CRD-Spektrometer war es zudem möglich, isotopenspezifische Messungen durchzuführen. Für das breitbandige Spektrometer wurde als Strahlquelle eine ASE-Diode (amplified spontaneous emission) verwendet. Dabei handelt es sich um eine inkohärente Strahlquelle. Mittels Messungen nach dem Prinzip der Cavity-Enhanced-Absorptionsspektroskopie wurde die generelle Funktionalität des resonatorgestützten Spektrometers überprüft. Anschließend wurden die wellenlängenabhängigen Abklingsignale des leeren und des mit einem CO2-Luft-Gemisch gefüllten Resonators gemessen und ebenfalls mit den zu erwartenden Spektren verglichen. Qualitativ stimmen die experimentellen Spektren gut mit den zu erwartenden Spektren überein. Für die quantitative Interpretation der Daten wurde ein spezieller Algorithmus entwickelt, der die spektrale Auflösung des Systems berücksichtigt. Mit dem vorgestellten Spektrometer ist so die qualitative und quantitative Interpretation der Spektren möglich. Die Nachweisgrenze des breitbandigen Cavity-Ring-Down-Spektrometers wurde zu einem Wert von alpha = 8x10^-7 cm-1 bestimmt. Der systematischen und der zufällige Fehler der Messungen lagen bei Werten von ca. 1%. Bei diesem Spektrometer handelt es sich um einen Prototyp. Mittels Optimierung des Systems lassen sich sowohl der Wert der Nachweisgrenze als auch die Fehler der Messungen verbessern. / This thesis presents the design, set-up, characterisation and optimization of various spectrometers to be used for the analysis of gases and gas mixtures. The result of this optimization and its further development is a spectrally broadband cavity ring-down spectrometer (CRD spectrometer), which uses an incoherent light source that emits in the near-infrared. The starting point of the development was a spectrometer which is based on classic absorption spectroscopy inside a multipass cell. This spectrometer uses a supercontinuum laser as light source. The advantage of this spectrometer is its compactness. With this spectrometer, the spectra of various gases and a gas mixture were detected in the spectral range of 1500 nm to 1700 nm. The experimentally derived spectra are in good qualitative accordance to expected spectra based on the HITRAN database. Nevertheless, the qualitative interpretation of the data reveals significant systematic and random errors. As a consequence, a different spectroscopic approach was chosen. The method of choice was cavity ring-down spectroscopy. The advantages of this technique are a) the independence from power fluctuations of the light source, b) an effective absorption path length of up to several kilometres, c) absolute measurement of absorber concentration and d) independence of absorption outside of the cavity. As an important intermediate step on the way to the broadband CRD spectrometer, a monochromatic CRD spectrometer was designed, set up and characterised. To effectively couple light into the cavity, the beam parameters have to be matched to the cavity’s mode. Prerequisite of this mode matching is the knowledge of the beam parameters, which were determined experimentally. Despite this mode matching, the coupling of the light into the cavity turned out to be instable. The cause of that disturbance was systematically investigated, which let to an optimization of the system. The spectra measured with this optimized system were in very good qualitative and quantitative agreement with the expected spectra. The limit of detection of this spectrometer was determined to an absorption coefficient alpha of 10^-8 cm-1. Furthermore, isotope-selective measurements were performed. The light source of the broadband CRD spectrometer is an amplified spontaneous emission diode, which is an incoherent light source. The general functionality of the spectrometer was first tested by means of CEAS measurements (cavity enhanced absorption spectroscopy). Afterwards, the wavelength dependent ring-down signals of the empty cavity and the cavity filled with a CO2 air mixture were detected. The qualitative comparison with the expected data shows very good agreement. For the quantitative interpretation of the experimental data, a special algorithm was developed. Thereby the data measured with the presented spectrometer can be interpreted both qualitatively and quantitatively. The limit of detection of the broadband CRD spectrometer was determined to a value of alpha = 8x10^-7 cm-1. The systematic and the random error are in the range of 1 %. The presented spectrometer is a prototype. Therefore the systematic and random error will be improved by further optimization of the spectrometer.

The interactions of electrons with ions and ions with neutrals are among the most important processes in the chemical evolution of molecules, allowing us to gain a deeper understanding of chemical processes in low-temperature environments in space such as interstellar gas clouds and to obtain feedback for quantum-mechanical calculations. Vari- ous plasma parameters such as kinetic and rotational temperature of ions, their concen- tration, etc. can vary by several orders of magnitude and different diagnostic techniques are used to determine them. Diagnostics such as SA-CRDS and Cryo-CRDS were used in this work. The subject of the study were two molecular ions: N2H+ and N+ 2 from the temperature range of 80-350 K, where we examined their recombination and absorption rate coefficients utilizing the absorption line involving the most populated states. 1

A great deal of attention has been paid to brown carbon aerosol in the troposphere because it can both scatter and absorb solar radiation, thus affecting the Earth’s climate. However, knowledge of the optical and chemical properties of brown carbon aerosol is still limited. In this thesis, we have investigated different aspects of the optical and physicochemical properties of various brown carbon aerosol samples of potential atmospheric importance. First, reactions involving the di-carbonyl species methylglyoxal (MG) have been previously suggested as an important pathway for the production of secondary organic aerosol (SOA) in the atmosphere. Reaction in an aqueous inorganic salt solution, such as ammonium sulfate (AS), leads to the formation of light-absorbing brown carbon (BrC) product. In this thesis work, we employed a variety of experimental approaches to investigate the optical and physicochemical properties of BrC aerosol generated from this AS-MG reaction (BrC (AS/MG)). Optical properties of the dried BrC (AS/MG) aerosol particles were studied by Fourier transform infrared (FTIR) extinction spectroscopy in the mid-infrared region, cavity ring-down spectroscopy (CRDS) at 403 nm in the visible, and by measuring the light scattering phase function and polarization profiles at two different visible wavelengths, 532 and 402 nm. In addition, we used UV−vis spectroscopy to measure the mass absorption coefficient (MAC) of the solution-phase reaction products. The different optical properties were measured as a function of reaction time for a period of up to 22 days. The UV-vis absorption spectra showed a clear increase in measured MAC in the visible and near UV as the solution aged. However, analysis of the light scattering data showed no significant differences between AS and BrC aerosol in the derived refractive indices at either 532 or 402 nm, even for the longest reaction times. The FTIR extinction spectra was modeled in a Mie theory simulation to derive the complex refractive index in the mid-IR range (7000-800 cm−1); the results showed no significant changes in either the real or the imaginary parts of the refractive indices for BrC (AS/MG) aerosol particles when compared to unreacted AS aerosol. From the CRDS extinction data, the optical constants for BrC (AS/MG) particles at 403 nm were also determined through a Mie theory based analysis. The retrieved real index of refraction at 403 nm is n = 1.551 ± 0.005, with an imaginary index value of k = 0.000 ± 0.002; these values do not appear to change significantly with aging time over the course of 22 days and are not markedly different from the AS aerosol values. The small imaginary index value suggests that BrC (AS/MG) aerosol formed from this pathway may not significantly contribute to warming. In addition, CRDS measurements of the BrC (AS/MG) aerosol extinction at 403 nm as a function of particle size show a significant deviation from Mie theory simulations for particles with diameters of ≳500 nm, probably as a result of non-spherical particle shape effects. We also employed atomic force microscopy (AFM)-based IR spectroscopy to investigate the morphology and chemical composition of single SOA particles. AFM analysis of the particle morphology shows that a significant fraction of BrC (AS/MG) particles with diameters of ≳500 nm are non-spherical in shape, consistent with our observed breakdown in the applicability of Mie theory for larger particles. In addition to these measurements, we have characterized additional physicochemical properties of the BrC (AS/MG) aerosol particles including hygroscopic growth using a tandem-differential mobility analyzer. Compared to AS, BrC aerosol particles are found to have lower deliquescence relative humidity (DRH), efflorescence relative humidity (ERH), and hygroscopic growth at the same relative humidity values. Second, we investigated the optical properties of the water soluble products of limonene BrC generated from ozonolysis of d-limonene with further aging by AS. Optical constants for the dried limonene BrC aerosol product were measured at 403 nm by CRDS over the course of 9 days of aging. While the fresh limonene BrC aerosol showed a significant non-zero absorption index, the aged samples showed absorption index values consistent with zero. This result was somewhat unexpected because UV-vis absorption spectra of the bulk reaction solution showed a continued increase in absorption as the solution aged. One possible explanation for this result is that there could be an increase in the fraction of volatile chromophores as the solution ages, that are then removed in the aerosol drying process. Third, we investigated optical properties and chemical compositions of several humic substance (HS) reference samples including humic acid (HA) and fulvic acid (FA) standards by CRDS, UV-vis spectroscopy, elemental analysis, and 13C NMR spectroscopy. Measurements of the optical properties of HS is important in atmospheric science, because it is thought that HS samples have similar optical properties to organic materials, such as HUmic-Like Substances (HULIS), that exist in clouds, fogs, rainwater, and atmospheric aerosol. The humic acid aerosol samples generally showed higher absorption index values than the fulvic acid aerosol samples. We also found a correlation between the absorption index and chemical composition, with the value for k generally increasing with both increasing carbon-to-oxygen atomic ratio and sample aromaticity. In addition, we compared our measured optical constants for the HS aerosol samples with results from previous studies of field collected HULIS. The absorption index values for the fulvic acid aerosol samples give a better match than the humic acid samples when compared to the results from the field collected samples. Overall, these studies provide new details of the optical and physicochemical properties of a class of brown carbon organic aerosol which may have important implications for atmospheric chemistry and climate.

This thesis studies frequency-shifted interferometry (FSI), a useful and versatile technique for fiber-optic sensing. I first present FSI theory by describing practical FSI configurations and discussing the parameters that affect system performance. Then, I demonstrate the capabilities of FSI in fiber-optic sensor multiplexing and high sensitivity chemical analysis. We implemented a cryogenic liquid level sensing system in which an array of 3 fiber Bragg grating (FBG) based sensors was interrogated by FSI. Despite sensors' spectral overlap, FSI is able to separate sensor signals according to their spatial locations and to measure their spectra, from which whether a sensor is in liquid or air can be unambiguously determined. I showed that a broadband source paired with a fast tunable filter can be used in FSI systems as the light source. An array of 9 spectrally overlapping FBGs was successfully measured by such a system, indicating the potential of system cost reduction as well as measurement speed improvement. I invented the the FSI-CRD technique, a highly sensitive FSI-based fiber cavity ring-down (CRD) method capable of deducing minuscule loss change in a fiber cavity from the intensity decay rate of continuous-wave light circulating in the cavity. As a proof-of-principle experiment, I successfully measured the fiber bend loss introduced in the fiber cavity with FSI-CRD, which was found to be 0.172 dB/m at a bend radius of 12.5 mm. We then applied FSI-CRD to evanescent-field sensing. We incorporated fiber tapers as the sensor head in the system and measured the concentration of 1-octyne solutions. A minimum detectable 1-octyne concentration of 0.29% was achieved with measurement sensitivity of 0.0094 dB/% 1-octyne. The same system also accurately detected the concentration change of sodium chloride (NaCl) and glucose solutions. Refractive index sensitivity of 1 dB/RIU with a measurement error of 1*10^-4 dB was attined for NaCl solutions. Finally, I proposed a theoretical model to study the polarization effects in FSI systems. Preliminary results show that the model can already explain the experimental observations. It not only provides insight into how to improve system performance but also suggests potential new applications of the technique.

This thesis studies frequency-shifted interferometry (FSI), a useful and versatile technique for fiber-optic sensing. I first present FSI theory by describing practical FSI configurations and discussing the parameters that affect system performance. Then, I demonstrate the capabilities of FSI in fiber-optic sensor multiplexing and high sensitivity chemical analysis. We implemented a cryogenic liquid level sensing system in which an array of 3 fiber Bragg grating (FBG) based sensors was interrogated by FSI. Despite sensors' spectral overlap, FSI is able to separate sensor signals according to their spatial locations and to measure their spectra, from which whether a sensor is in liquid or air can be unambiguously determined. I showed that a broadband source paired with a fast tunable filter can be used in FSI systems as the light source. An array of 9 spectrally overlapping FBGs was successfully measured by such a system, indicating the potential of system cost reduction as well as measurement speed improvement. I invented the the FSI-CRD technique, a highly sensitive FSI-based fiber cavity ring-down (CRD) method capable of deducing minuscule loss change in a fiber cavity from the intensity decay rate of continuous-wave light circulating in the cavity. As a proof-of-principle experiment, I successfully measured the fiber bend loss introduced in the fiber cavity with FSI-CRD, which was found to be 0.172 dB/m at a bend radius of 12.5 mm. We then applied FSI-CRD to evanescent-field sensing. We incorporated fiber tapers as the sensor head in the system and measured the concentration of 1-octyne solutions. A minimum detectable 1-octyne concentration of 0.29% was achieved with measurement sensitivity of 0.0094 dB/% 1-octyne. The same system also accurately detected the concentration change of sodium chloride (NaCl) and glucose solutions. Refractive index sensitivity of 1 dB/RIU with a measurement error of 1*10^-4 dB was attined for NaCl solutions. Finally, I proposed a theoretical model to study the polarization effects in FSI systems. Preliminary results show that the model can already explain the experimental observations. It not only provides insight into how to improve system performance but also suggests potential new applications of the technique.

Zugl.: Bielefeld, Univ., Diss., 2008

In dieser Arbeit sollte eine Derivatisierungsmethode entwickelt werden, die die duale Quantifizierung funktioneller Gruppen an Oberflächen mittels Röntgenphotoelektronenspektroskopie (XPS) und Fluoreszenz ermöglicht. Verschiedene Farbstoffe, die robuste Fluoreszenzeigenschaften mit hohen Fluorgehalten für XPS kombinieren, wurden auf ihre selektive Reaktion mit Aminogruppen getestet und der Prototyp einer tiefergehenden Analyse auf einer Oberfläche unterzogen. Durch Fluoreszenzlöschung konnten die Möglichkeiten der bimodalen Analyse nur begrenzt abgeschätzt werden, obwohl in XPS und Fluoreszenz intensive Signale gemessen wurden. Die Herstellung der Modelloberflächen mittels Gasphasenabscheidung von Silanen konnte durch Kontaktwinkelmessungen schrittweise optimiert werden. Die Kombination zweier Monoalkoxysilane ermöglichte die Herstellung von Oberflächen mit variabler Funktionalgruppendichte. Nach Reaktion mit dem dualen Marker ließen sich die Messungen aus XPS und Fluoreszenz mindestens über eine Größenordnung korrelieren. Durch Synchrotron-XPS (SR-XPS) und Röntgenfluoreszenz unter Totalreflektion (TXRF) konnte eine absolute und rückführbare Quantifizierung erzielt werden. Weitere Modelloberflächen auf Basis von Trialkoxysilanen zeigten, dass bei anwendungsnahen Proben Fluoreszenzlöschung auftritt. Diese konnte in einem gewissen Maße mittels Fluoreszenzlebensdauer berechnet werden. Darüberhinaus konnte mit der Photometrie eine unabhängige Methode gefunden werden, die die Quantifizierung des Farbstoffs an der Oberfläche in hoher Präzision ermöglicht und mit Hilfe der XPS auch der funtionellen Gruppen. Die Cavity Ring-Down Spektroskopie (CRDS) wurde als Laserbasierte Methode zur empfindlichen und ortsaufgelösten Messung der Absorption auf transparenten Substraten untersucht und erste vielversprechende Ergebnisse gewonnen. Weiterhin wurde ein modulares Farbstoffsystem entwickelt, das sowohl Variation der spektralen als auch der Bindungseigenschaften erlaubt. / This work aimed on the development of dual-mode labelling method that combines X-ray photoelectron spectroscopy (XPS) with fluorescence measurements for surface functional group quantification. Label dyes combining robust fluorescence properties with high fluorine contents were investigated towards their selective reaction with surface amino groups and the lead candidate subjected to detailed analysis on a surface. Fluorescence quenching precluded a detailed investigation of the capabilities of dual-mode labelling, despite providing sufficient signal in XPS and fluorescence scanning. The fabrication of surfaces using vapour deposition (VD) of silanes in toluene was optimized under aid of contact angle measurements. Binary mixtures of mono-alkoxy silanes were used to prepare surfaces with variable functional group density. Treatment with the label dye showed that XPS and fluorescence provide a linear overlap in signal generation over at least one order of magnitude. The combination of synchrotron radiation XPS (SR-XPS) and total reflection X-ray fluorescence spectroscopy (TXRF) provided an absolute and traceable quantification . Different model surfaces based on trialkoxy silanes showed strong fluorescence quenching. A fluorescence lifetime based correction was developed to account for such quenching effects. Additionally, the application of spectrophotometry provided a independent method of quantification for the surface bound dye and in combination with information obtained from XPS, to determine the surface functional group density. With cavity ring-down spectroscopy (CRDS), a laser based technique for highly sensitive and spatially resolved absorption measurements on transparent substrates could be developed and applied in a proof-of-concept. A modular system for the fabrication of label dyes with adjustable spectral properties and different binding sites was investigated using prototype candidates to prove the general applicability of such systems.

Universiẗat, Diss., 2004--Heidelberg.