Tailoring molecular weight of the conjugated model polymer MEH-PPV and its structure-property relations

In der vorliegenden Arbeit wurden Struktur-Eigenschaftsbeziehungen des konjugierten Modell-Polymers MEH-PPV untersucht. Dazu wurde F��llungs-fraktionierung eingesetzt, um MEH-PPV mit unterschiedlichem Molekulargewicht (Mw) zu erhalten, insbesondere MEH-PPV mit niedrigem Mw, da dieses f��r optische Wellenleiterbauelemente optimal geeignet ist Wir konnten feststellen, dass die Pr��paration einer ausreichenden Menge von MEH-PPV mit niedrigem Mw und geringer Mw-Verteilung wesentlich von der geeigneten Wahl des L��sungsmittels und der Temperatur w��hrend der Zugabe des F��llungsmittels abh��ngt. Alternativ dazu wurden UV-induzierte Kettenspaltungseffekte untersucht. Wir folgern aus dem Vergleich beider Vorgehensweisen, dass die F��llungsfraktionierung verglichen mit der UV-Behandlung besser geeignet ist zur Herstellung von MEH-PPV mit spezifischem Mw, da das UV-Licht Kettendefekte l��ngs des Polymerr��ckgrats erzeugt. 1H NMR and FTIR Spektroskopie wurden zur Untersuchung dieser Kettendefekte herangezogen. Wir konnten au��erdem beobachten, dass die Wellenl��ngen der Absorptionsmaxima der MEH-PPV Fraktionen mit der Kettenl��nge zunehmen bis die Zahl der Wiederholeinheiten n ��� 110 erreicht ist. Dieser Wert ist signifikant gr����er als fr��her berichtet. rnOptische Eigenschaften von MEH-PPV Wellenleitern wurden untersucht und es konnte gezeigt werden, dass sich die optischen Konstanten ausgezeichnet reproduzieren lassen. Wir haben die Einfl��sse der L��sungsmittel und Temperatur beim Spincoaten auf Schichtdicke, Oberfl��chenrauigkeit, Brechungsindex, Doppelbrechung und Wellenleiter-D��mpfungsverlust untersucht. Wir fanden, dass mit der Erh��hung der Siedetemperatur der L��sungsmittel die Schichtdicke und die Rauigkeit kleiner werden, w��hrend Brechungsindex, Doppelbrechung sowie Wellenleiter-D��mpfungsverluste zunahmen. Wir schlie��en daraus, dass hohe Siedetemperaturen der L��sungsmittel niedrige Verdampfungsraten erzeugen, was die Aggregatbildung w��hrend des Spincoatings beg��nstigt. Hingegen bewirkt eine erh��hte Temperatur w��hrend der Schichtpr��paration eine Erh��hung von Schichtdicke und Rauhigkeit. Jedoch nehmen Brechungsindex und der Doppelbrechung dabei ab.rn F��r die Schichtpr��paration auf Glassubstraten und Quarzglas-Fasern kam das Dip-Coating Verfahren zum Einsatz. Die Schichtdicke der Filme h��ngt ab von Konzentration der L��sung, Transfergeschwindigkeit und Immersionszeit. Mit Tauchbeschichtung haben wir Schichten von MEH-PPV auf Flaschen-Mikroresonatoren aufgebracht zur Untersuchung von rein-optischen Schaltprozessen. Dieses Verfahren erweist sich insbesondere f��r MEH-PPV mit niedrigem Mw als vielversprechend f��r die rein-optische Signalverarbeitung mit gro��er Bandbreite.rn Zus��tzlich wurde auch die Morphologie d��nner Schichten aus anderen PPV-Derivaten mit Hilfe von FTIR Spektroskopie untersucht. Wir konnten herausfinden, dass der Alkyl-Substitutionsgrad einen starken Einfluss auf die mittlere Orientierung der Polymerr��ckgrate in d��nnen Filmen hat.rn

Modeling of complex chemical reactions and macromolecular orientation phenomena in confined geometries

The cooperative motion algorithm was applied on the molecular simulation of complex chemical reactions and macromolecular orientation phenomena in confined geometries. First, we investigated the case of equilibrium step-growth polymerization in lamellae, pores and droplets. In such systems, confinement was quantified as the area/volume ratio. Results showed that, as confinement increases, polymerization becomes slower and the average molecular weight (MW) at equilibrium decreases. This is caused by the sterical hindrance imposed by the walls since chain growth reactions in their close vicinity have less realization possibilities. For reactions inside droplets at surfaces, contact angles usually increased after polymerization to compensate conformation restrictions imposed by confinement upon growing chains. In a second investigation, we considered monodisperse and chemically inert chains and focused on the effect of confinement on chain orientation. Simulations of thin polymer films showed that chains are preferably oriented parallel to the surface. Orientation increases as MW increases or as film thickness d decreases, in qualitative agreement with experiments with low MW polystyrene. It is demonstrated that the orientation of simulated chains results from a size effect, being a function of the ratio between chain end-to-end distance and d. This study was complemented by experiments with thin films of pi-conjugated polymers like MEH-PPV. Anisotropic refractive index measurements were used to analyze chain orientation. With increasing MW, orientation is enhanced. However, for MEH-PPV, orientation does not depend on d even at thicknesses much larger than the chain contour length. This contradiction with simulations was discussed by considering additional causes for orientation, for instance the appearance of nematic-like ordering in polymer films. In another investigation, we simulated droplet evaporation at soluble surfaces and reproduced the formation of wells surrounded by ringlike deposits at the surface, as observed experimentally. In our simulations, swollen substrate particles migrate to the border of the droplet to minimize the contact between solvent and vacuum, which costs the most energy. Deposit formation in the beginning of evaporation results in pinning of the droplet. When polymer chains at the substrate surface have strong uniaxial orientation, the resulting pattern is no longer similar to a ring but to a pair of half-moons. In a final stage, as an extension for the model developed for polymerization in nanoreactors, we studied the effect of geometrical confinement on a hypothetical oscillating reaction following the mechanism of the so called periodically forced Brusselator. It was shown that a reaction which is chaotic in the bulk may be driven to periodicity by confinement and vice-versa, opening new perspectives for chaos control.

Ein neuartiges Interferometer zur Messung magneto-optischer Effekte an L-Absorptionskanten von ferromagnetischen Metallen mit linearpolarisierter Undulatorstrahlung

Am Mainzer Mikrotron MAMI wurde ein neuartiges Interferometer entwickelt und getestet, mit dem magneto-optische Effekte an d��nnen, freitragenden Folien von 3d-��bergangsmetallen wie Eisen, Kobalt oder Nickel an den L_{2,3}-Absorptionskanten (im Spektralbereich der weichen R��ntgenstrahlung) gemessen werden k��nnen. Es handelt sich um eine Weiterentwicklung eines an MAMI erprobten Interferometers, das im wesentlichen aus einer kollinearen Anordnung zweier identischer Undulatoren, zwischen die die d��nne Probefolie eingebracht wird, und einem Gitterspektrometer besteht. Aus den als Funktion des Abstands der Undulatoren beobachtbaren Intensit��tsoszillation lassen sich das Dekrement des Realteils �� und der Absorptionskoeffizient �� des komplexen Brechungsindex bestimmen.rnIm Rahmen der vorliegenden Arbeit wurde die Apparatur derart weiterentwickelt, dass auch die magnetisch zirkulare Doppelbrechung ���� und der magnetisch zirkulare Dichroismus ���� an den L_{2,3}-Absorptionskanten von ��bergangsmetallen gemessen werden k��nnen. Der zweite Undulator wurde um die Elektronenstrahlachse um den Winkel �� = ��107�� drehbar gemacht. Damit dient er auch als Analysator der aus der Folie austretenden elliptisch polarisierten weichen R��ntgenstrahlung, f��r die - wie bei der Faraday-Rotation - die Polarisationsebene gedreht ist. Weiterhin kann die Spaltbreite der 10-poligen Hybrid-Undulatoren mit einer Periodenl��nge von 12 mm und damit der Undulatorparameter ��ber eine Antriebsmechanik kontinuierlich variiert werden, wodurch eine optimale Anpassung der Amplituden der Undulatorstrahlung aus den beiden Undulatoren m��glich wird. Der maximale Undulatorparameter betr��gt K = 1.1. Auch das Spektrometer, das auf einem selbstfokussierenden Gitter mit variierter Liniendichte (im Mittel 1400 Linien / mm) basiert, wurde weiterentwickelt. Als Detektor kommt jetzt eine fensterlose CCD mit 1024 x 1024 Pixeln und einer Pixelgr����e von 13 ��m x 13 ��m zum Einsatz, die im Bildmodus betrieben wird, was die gleichzeitige Messung eines Energieintervalls von ca. 50 eV erm��glicht. Die totale Linienbreite wurde bei einer vertikalen Strahlfleckausdehnung von ��_y = 70 ��m (rms) am Neon 1s-3p ��bergang bei (867.18 ��0.02) eV zu ������ = (0.218 ��0.002) eV (FWHM) gemessen. Das hohe Aufl��sungsverm��gen von 4000 und die M��glichkeit der Eichung gegen den 1s-3p ��bergang von Neon wurden ausgenutzt, um die Energie der Maxima an den Absorptionskanten von Nickel (wei��e Linien) neu zu bestimmen. Die Ergebnisse E_{L_2}=(869.65_{-0.16}^{+0.27}) eV und E_{L_3}=(852.37_{-0.11}^{+0.16}) eV stellen eine Verbesserung fr��herer Messungen dar, die gro��e Streuungen aufwiesen.rnAus systematischen Messungen als Funktion des Abstandes der Undulatoren und des Drehwinkels �� wurden die magnetisch zirkulare Doppelbrechung ���� im Energiebereich 834 eV ��� ���� ��� 885 eV an einer freitragenden, bis zur S��ttigung magnetisierten Nickelfolie der Dicke von (96.4 ��2.7) nm gemessen. Sowohl das Aufl��sungsverm��gen als auch die Genauigkeit der Messungen f��r ���� ��bersteigen bekannte Literaturangaben signifikant, so dass eine bisher nicht bekannte Feinstruktur gefunden werden konnte. Au��erdem wurde der Betrag des magnetisch zirkularen Dichroismus |����| im Bereich des Maximums an der L_3-Absorptionskante mit hoher Genauigkeit gemessen.rn

Functional dextran-based hydrogels

Dextran-based polymers are versatile hydrophilic materials, which can provide functionalized surfaces in various areas including biological and medical applications. Functional, responsive, dextran based hydrogels are crosslinked, dextran based polymers allowing the modulation of response towards external stimuli. The controlled modulation of hydrogel properties towards specific applications and the detailed characterization of the optical, mechanical, and chemical properties are of strong interest in science and further applications. Especially, the structural characteristics of swollen hydrogel matrices and the characterization of their variations upon environmental changes are challenging. Depending on their properties hydrogels are applied as actuators, biosensors, in drug delivery, tissue engineering, or for medical coatings. However, the field of possible applications still shows potential to be expanded. rnSurface attached hydrogel films with a thickness of several micrometers can serve as waveguiding matrix for leaky optical waveguide modes. On the basis of highly swelling and waveguiding dextran based hydrogel films an optical biosensor concept was developed. The synthesis of a dextran based hydrogel matrix, its functionalization to modulate its response towards external stimuli, and the characterization of the swollen hydrogel films were main interests within this biosensor project. A second focus was the optimization of the hydrogel characteristics for cell growth with the aim of creating scaffolds for bone regeneration. Matrix modification towards successful cell growth experiments with endothelial cells and osteoblasts was achieved.rnA photo crosslinkable, carboxymethylated dextran based hydrogel (PCMD) was synthesized and characterized in terms of swelling behaviour and structural properties. Further functionalization was carried out before and after crosslinking. This functionalization aimed towards external manipulation of the swelling degree and the charge of the hydrogel matrix important for biosensor experiments as well as for cell adhesion. The modulation of functionalized PCMD hydrogel responses to pH, ion concentration, electrochemical switching, or a magnetic force was investigated. rnThe PCMD hydrogel films were optically characterized by combining surface plasmon resonance (SPR) and optical waveguide mode spectroscopy (OWS). This technique allows a detailed analysis of the refractive index profile perpendicular to the substrate surface by applying the Wentzel Kramers Brillouin (WKB) approximation. rnIn order to perform biosensor experiments, analyte capturing units such as proteins or antibodies were covalently coupled to the crosslinked hydrogel backbone by applying active ester chemistry. Consequently, target analytes could be located inside the waveguiding matrix. By using labeled analytes, fluorescence enhancement was achieved by fluorescence excitation with the electromagnetic field in the center of the optical waveguide modes. The fluorescence excited by the evanescent electromagnetic field of the surface plasmon was 2 3 orders of magnitude lower. Furthermore, the signal to noise ratio was improved by the fluorescence excitation with leaky optical waveguide modes.rnThe applicability of the PCMD hydrogel sensor matrix for clinically relevant samples was proofed in a cooperation project for the detection of PSA in serum with long range surface plasmon spectroscopy (LRSP) and fluorescence excitation by LRSP (LR SPFS). rn

New biosensor applications of surface plasmon and hydrogel optical waveguide spectroscopy

Rapid and sensitive detection of chemical and biological analytes becomes increasingly important in areas such as medical diagnostics, food control and environmental monitoring. Optical biosensors based on surface plasmon resonance (SPR) and optical waveguide spectroscopy have been extensively pushed forward in these fields. In this study, we combine SPR, surface plasmon-enhanced fluorescence spectroscopy (SPFS) and optical waveguide spectroscopy with hydrogel thin film for highly sensitive detection of molecular analytes.rnrnA novel biosensor based on SPFS which was advanced through the excitation of long range surface plasmons (LRSPs) is reported in this study. LRSPs are special surface plasmon waves propagating along thin metal films with orders of magnitude higher electromagnetic field intensity and lower damping than conventional SPs. Therefore, their excitation on the sensor surface provides further increased fluorescence signal. An inhibition immunoassay based on LRSP-enhanced fluorescence spectroscopy (LRSP-FS) was developed for the detection of aflatoxin M1 (AFM1) in milk. The biosensor allowed for the detection of AFM1 in milk at concentrations as low as 0.6 pg mL-1, which is about two orders of magnitude lower than the maximum AFM1 residue level in milk stipulated by the European Commission legislation.rnrnIn addition, LRSPs probe the medium adjacent to the metallic surface with more extended evanescent field than regular SPs. Therefore, three-dimensional binding matrices with up to micrometer thickness have been proposed for the immobilization of biomolecular recognition elements with large surface density that allows to exploit the whole evanescent field of LRSP. A photocrosslinkable carboxymethyl dextran (PCDM) hydrogel thin film is used as a binding matrix, and it is applied for the detection of free prostate specific antigen (f-PSA) based on the LRSP-FS and sandwich immunoassay. We show that this approach allows for the detection of f-PSA at low femto-molar range, which is approximately four orders of magnitude lower than that for direct detection of f-PSA based on the monitoring of binding-induced refractive index changes.rnrnHowever, a three dimensional hydrogel binding matrix with micrometer thickness can also serve as an optical waveguide. Based on the measurement of binding-induced refractive index changes, a hydrogel optical waveguide spectroscopy (HOWS) is reported for a label-free biosensor. This biosensor is implemented by using a SPR optical setup in which a carboxylated poly(N-isoproprylacrylamide) (PNIPAAm) hydrogel film is attached on a metallic surface and modified by protein catcher molecules. Compared to regular SPR biosensor with thiol self-assembled monolayer (SAM), HOWS provides an order of magnitude improved resolution in the refractive index measurements and enlarged binding capacity owing to its low damping and large swelling ratio, respectively. A model immunoassay experiment revealed that HOWS allowed detection of IgG molecules with a 10 pM limit of detection (LOD) that was five-fold lower than that achieved for SPR with thiol SAM. For the high capacity hydrogel matrix, the affinity binding was mass transport limited.rnrnThe mass transport of target molecules to the sensor surface can play as critical a role as the chemical reaction itself. In order to overcome the diffusion-limited mass transfer, magnetic iron oxide nanoparticles were employed. The magnetic nanoparticles (MNPs) can serve both as labels providing enhancement of the refractive index changes, and ���vehicles��� for rapidly delivering the analytes from sample solution to an SPR sensor surface with a gradient magnetic field. A model sandwich assay for the detection of �� human chorionic gonadotropin (��hCG) has been utilized on a gold sensor surface with metallic diffraction grating structure supporting the excitation of SPs. Various detection formats including a) direct detection, b) sandwich assay, c) MNPs immunoassay without and d) with applied magnetic field were compared. The results show that the highly-sensitive MNPs immunoassay improves the LOD on the detection of ��hCG by a factor of 5 orders of magnitude with respect to the direct detection.rn

Thin films of polythiophene: Linear and nonlinear optical characterization

Wir haben die linearen und nichtlinearen optischen Eigenschaften von d��nnen Schichten und planaren Wellenleitern aus mehreren konjugierten Polymeren (MEH-PPV und P3AT) und Polymeren mit ���-Elektronen Systemen in der Seitenkette (PVK und PS) untersucht und verglichen. PVK und PS haben relativ kleine Werte des nichtlinearen Brechungsindex n2 bei 532 nm, n��mlich (1,2 �� 0,5)���10-14 cm2/W und (2,6 �� 0,5) ���10-14 cm2/W.rnWir haben die linearen optischen Konstanten von mehreren P3ATs untersucht, insbesondere den Einfluss der Regioregularit��t und Kettenl��nge der Alkylsubstituenten. Wir haben das am besten geeignete Polymere f��r Wellenleiter Anwendungen identifiziert, welches P3BT-ra genannt ist. Wir haben die linearen optischen Eigenschaften d��nner Schichten des P3BT-ra untersucht, die mit Spincoating aus verschiedenen L��sungsmitteln mit unterschiedlichen Siedetemperaturen pr��parieret wurden. Wir haben festgestellt, dass P3BT-ra Filme aus Toluol-L��sungen die am besten geeigneten Wellenleiter f��r die intensit��tsabh��ngigen Prismen-Kopplungs Experimente sind, weil diese geringe Wellenleiterd��mpfungsverluste bei ���= 1064 nm haben. rnWir haben die Dispersionen des Wellenleiterd��mfungsverlustes ���gw, des nichtlinearen Brechungsindex n2 und des nichtlinearen Absorptionskoeffizienten ���2 von Wellenleitern aus P3BT-ra im Bereich von 700 - 1500 nm gemessen. Wir haben gro��e Werte des nichtlinearen Brechungsindex bis 1,5x10-13 cm2/W bei 1150 nm beobachtet. Wir haben gefunden, dass die G��tenkriterien (���figures of merit���) f��r rein optische Schalter im Wellenl��ngebereich 1050 - 1200 nm erf��llt sind. Dieser Bereich entspricht dem niederenergetischen Ausl��ufer der Zwei-Photonen-Absorption. Die G��tekriterien von P3BT-ra geh��ren zu den besten der bisher bekannten Werte von konjugierten Polymeren.rnWir haben gefunden, dass P3BT-ra ein vielversprechender Kandidat f��r integriert-optische Schalter ist, weil es eine gute Kombination aus gro��er Nichtlinearit��t dritter Ordnung, geringen Wellenleiterd��mpfungverlusten und ausreichender Photostabilit��t zeigt. rnWir haben einen Vergleich der gemessenen Dispersion von ���gw, n2 und ���2 mit der Theorie durchgef��hrt. Durch Kurvenanpassung der Dispersion von ���gw haben wir gefunden, dass Rayleigh-Streuung der dominierende D��mpfungsmechanismus in MEH-PPV und P3BT-ra Wellenleitern ist. Ein quantenmechanischer Ansatz wurde zur Berechnung der nichtlinearen Suszeptibilit��t dritter Ordnung ���(3) verwendet, um die gemessenen Spektren von n2 und ���2 von P3BT-ra und MEH-PPV zu simulieren. Dies kann erkl��ren, dass s��ttigbare Absorption und Zwei-Photonen Absorption die haupts��chlichen Effekte sind, welche die Dispersion von n2 und ���2 verursachen. rn

Laboratory study on the optical properties of absorbing atmospheric aerosols and field applications

The interaction between aerosols and sun light plays an important role in the radiative balance of Earth���s atmosphere. This interaction is obtained by measuring the removal (extinction), redistribution (scattering), and transformation into heat (absorption) of light by the aerosols; i.e. their optical properties. Knowledge of these properties is crucial for our understanding of the atmospheric system. rn Light absorption by aerosols is a major contributor to the direct and indirect effects on our climate system, and an accurate and sensitive measurement method is crucial to further our understanding. A homebuilt photoacoustic sensor (PAS), measuring at a 532nm wavelength, was fully characterized and its functionality validated for measurements of absorbing aerosols. The optical absorption cross-sections of absorbing polystyrene latex spheres, to be used as a standard for aerosol absorption measurements, were measured and compared to literature values. Additionally, a calibration method using absorbing aerosol of known complex refractive index was presented.rn A new approach to retrieve the effective broadband refractive indices (mbroad,eff) of aerosol particles by a white light aerosol spectrometer (WELAS) optical particle counter (OPC) was achieved. Using a tandem differential mobility analyzer (DMA)-OPC system, the nbroad,eff are obtained for both laboratory and field applications. This method was tested in the laboratory using substances with a wide range of optical properties and it was used in ambient measurements to retrieve the nbroad,eff of biomass burning aerosols in a nationwide burning event in Israel. The retrieved effective broadband refractive indices for laboratory generated scattering aerosols were: ammonium sulfate (AS), glutaric acid (GA), and sodium chloride, all within 4% of literature values. For absorbing substances, nigrosine and various mixtures of nigrosine with AS and GA were measured, as well as a lightly absorbing substance, Suwannee river fulvic acid (SRFA). For the ambient measurements, the calibration curves generated from this method were to follow the optical evolution of biomass burning (BB) aerosols. A decrease in the overall aerosol absorption and scattering for aged aerosols during the day after the fires compared to the smoldering phase of the fires was found. rn The connection between light extinction of aerosols, their chemical composition and hygroscopicity for particles with different degrees of absorption was studied. The extinction cross-section (��ext) at 532nm for different mobility diameters was measured at 80% and 90% relative humidity (RH), and at an RH<10%. The ratio of the humidified aerosols to the dry ones, fRHext(%RH,Dry), is presented. For purely scattering aerosols, fRHext(%RH,Dry) is inversely proportional with size; this dependence was suppressed for lightly absorbing ones. In addition, the validity of the mixing rules for water soluble absorbing aerosols is explored. The difference between the derived and calculated real parts of the complex RIs were less than 5.3% for all substances, wavelengths, and RHs. The obtained imaginary parts for the retrieved and calculated RIs were in good agreement with each other, and well within the measurement errors of retrieval from pulsed CRD spectroscopy measurements. Finally, a core-shell structure model is also used to explore the differences between the models, for substances with low growth factors, under these hydration conditions. It was found that at 80% RH and for size parameters less than 2.5, there is less than a 5 % difference between the extinction efficiencies calculated with both models. This difference is within measurement errors; hence, there is no significant difference between the models in this case. However, for greater size parameters the difference can be up to 10%. For 90% RH the differences below a size parameter of 2.5 were up to 7%.rn Finally, the fully characterized PAS together with a cavity ring down spectrometer (CRD), were used to study the optical properties of soot and secondary organic aerosol (SOA) during the SOOT-11 project in the AIDA chamber in Karlsruhe, Germany. The fresh fractal-like soot particles were allowed to coagulate for 28 hours before stepwise coating them with SOA. The single scattering albedo for fresh fractal-like soot was measured to be 0.2 (��0.03), and after allowing the soot to coagulate for 28 hours and coating it with SOA, it increased to 0.71(��0.01). An absorption enhancement of the coated soot of up to 1.71 (��0.03) times from the non-coated coagulated soot was directly measured with the PAS. Monodisperse measurements of SOA and soot coated with SOA were performed to derive the complex refractive index (m) of both aerosols. A complex refractive index of m = 1.471(��0.008) + i0.0(��0.002) for the SOA-��O3 was retrieved. For the compact coagulated soot a preliminary complex refractive index of m = 2.04(+0.21/-0.14) + i0.34(+0.18/-0.06) with 10nm(+4/-6) coating thickness was retrieved.rn These detail properties can be use by modelers to decrease uncertainties in assessing climatic impacts of the different species and to improve weather forecasting.rn

Rod-shaped plasmonic sensors

Plasmonic nanoparticles exhibit strong light scattering efficiency due to the oscillations of their conductive electrons (plasmon), which are excited by light. For rod-shaped nanoparticles, the resonance position is highly tunable by the aspect ratio (length/width) and the sensitivity to changes in the refractive index in the local environment depends on their diameter, hence, their volume. Therefore, rod-shaped nanoparticles are highly suitable as plasmonic sensors.rnWithin this thesis, I study the formation of gold nanorods and nanorods from a gold-copper alloy using a combination of small-angle X-ray scattering and optical extinction spectroscopy. The latter represents one of the first metal alloy nanoparticle synthesis protocols for producing rod-shaped single crystalline gold-copper (AuxCu(1-x)) alloyed nanoparticles. I find that both length and width independently follow an exponential growth behavior with different time-constants, which intrinsically leads to a switch between positive and negative aspect ratio growth during the course of the synthesis. In a parameter study, I find linear relations for the rate constants as a function of [HAuCl4]/[CTAB] ratio and [HAuCl4]/[seed] ratio. Furthermore, I find a correlation of final aspect ratio and ratio of rate constants for length and width growth rate for different [AgNO3]/[HAuCl4] ratios. I identify ascorbic acid as the yield limiting species in the reaction by the use of spectroscopic monitoring and TEM. Finally, I present the use of plasmonic nanorods that absorb light at 1064nm as contrast agents for photoacoustic imaging (BMBF project Polysound). rnIn the physics part, I present my automated dark-field microscope that is capable of collecting spectra in the range of 450nm to 1750 nm. I show the characteristics of that setup for the spectra acquisition in the UV-VIS range and how I use this information to simulate measurements. I show the major noise sources of the measurements and ways to reduce the noise and how the combination of setup charactersitics and simulations of sensitivity and sensing volume can be used to select appropriate gold rods for single unlabeled protein detection. Using my setup, I show how to estimate the size of gold nano-rods directly from the plasmon linewidth measured from optical single particle spectra. Then, I use this information to reduce the distribution (between particles) of the measured plasmonic sensitivity S by 30% by correcting for the systematic error introduced from the variation in particle size. I investigate the single particle scattering of bowtie structures ��� structures consisting of two (mostly) equilateral triangles pointing one tip at each other. I simulate the spectra of the structures considering the oblique illumination angle in my setup, which leads to additional plasmon modes in the spectra. The simulations agree well with the measurements form a qualitative point of view.rn