Depuis la première observation du phénomène de Diffusion Raman Exaltée de Surface (DRES) en 1974 de nombreuses méthodes ont été développées pour contrôler l'arrangement de nanostructures métalliques sur une surface dans le but d'augmenter le signal de diffusion Raman. La valeur du facteur d'amplification de la DRES résulte principalement de l’accroissement localisé du champ électromagnétique pour des surfaces métalliques nanostructurées. Des études antérieures ont révélé que l'espacement nanométrique entre les nanoparticules constituait des zones de forte exaltation appelées «points chauds». Nous avons développé et breveté une méthode de lithographique assistée par AFM permettant la fabrication de surfaces métalliques. Il a été démontré que cette méthode fournissait une approche relativement simple pour réaliser d’une part des surfaces reproductibles à géométrie contrôlée à l’échelle nanométrique, et d’autre part des surfaces modèles pour étudier l'influence de la géométrie des motifs sur l'effet DRES. Afin d'étudier la relation entre les propriétés optiques et la géométrie de nos systèmes la résonance plasmon localisée de surface (LSPR) et le facteur d'exaltation du champ électrique local ont été simulés par éléments finis. Les zones de forte exaltations ont été localisées sur les nanostructures par microscopie par photoémission d'électrons (PEEM) et l'effet DRES a été démontré en effectuant des mesures Raman avec plusieurs molécules cibles. Les corrélations effectuées entre les résultats de PEEM, les calculs du champ local et les facteurs d’exaltation Raman seront présentées en lien avec les paramètres géométriques des motifs de nanostructures. / Since the first observation of Surface Enhanced Raman Scattering (SERS) in 1974 a variety of methods have been developed to physically control the arrangement of metallic nanostructures onto a surface in order to enhance Raman signals. The magnitude of the SERS enhancement factor is mainly driven by the enhanced local electromagnetic field in nanostructured metal surfaces. Gaps between adjacent nanoparticles give rise to strong enhancement effects, often referred as ‘hot spots’. One way to produce highly efficient SERS substrates is to develop a reproducible system of interacting metal nanostructures capable of high field enhancement.We patented a force-assisted Atomic Force Microscopy lithographic method allowing the fabrication of a metallic substrate. It will be shown that this method also provides a relatively simple approach to realize reproducible patterns with controlled geometry that can be used to study the influence of specific pattern geometry on SERS phenomenon.In order to investigate the relationship between optical properties and pattern geometries, localized surface plasmon resonance (LSPR) and local electric field enhancement are simulated.Whereas electric field enhancement regions (hot spot) have been observed on the top of the nanostructures with PhotoEmission Electron Microscopy (PEEM), SERS effect has been demonstrated by performing Raman measurements using several probe molecules. Correlations between PEEM measurements, Raman exaltation and local field calculations are presented in relation with the geometrical parameters of the nanostructured patterns.

Lithium Ion Batteries (LIBs) are important in today's society, powering cars and mobile devices. LIBs consist of a negative anode commonly made of graphite, and a positive cathode commonly made from transition metal oxides. Between these electrodes are separators and organic solvent based electrolyte. Due to the high potential of LIBs the electrolyte is reduced at the anode. The electrolyte reduction results in the formation of a layer called the Solid Electrolyte Interphase (SEI), which prohibits the further breakdown of the electrolyte. Despite being researched for over50 years, the composition formation of the SEI is still poorly understood. The aim of this project is to develop strategies for efficient identification and classification of various active and intermediate components in the SEI, to, in turn, gain an understanding of the reactions taking place, which will help find routes to stabilize and tailor the composition of the SEI layer for long-term stability and optimal battery performance. For a model gold/li-ion battery electrolyte system, Raman spectra will be obtained using Surface Enhanced Raman Spectroscopy (SERS) in a spectroelectrochemical application where the voltage of the working gold electrode is swept from high to low potentials. Spectra of common components of the SEI as well as similar compounds will be simulated using Density Functional Theory (DFT). The DFT data is also used to calculate the spontaneity of reactions speculated to form the SEI. The simulated data will be validated by comparing it to experimental spectra from pure substances. The spectroelectrochemical SERS results show a clear formation of Li-carbonate at the SERS substrate, as well as the decomposition of the electrolyte into other species, according to the simulated data. It is however shown that there are several issues when modelling spectra, that makes it harder to correlate the simulated spectra with the spectroelectrochemical spectra. These issues include limited knowledge of the structure of the compounds thought to form on the anode surface, and incorrect choices in simulational parameters. To solve these issues, more work is needed in these areas, and the spectroelectrochemical methods used in this thesis needs to be combined with other experimental methods to narrow down the amount of compounds to be modelled. More work is also needed to avoid impurities in the electrolyte. Impurities leads to a thick inorganic layer which prohibits the observation of species in the organic layer.

Im Hochvakuum durch thermisches Verdampfen erzeugte polykristalline Schichten aus den organischen Molekülen: Kupferphthalocyanin (CuPc), N,N'-Dimethyl-Perylendicarboximid (MPP) und Fulleren (C60), werden mittels Transmissions- und Reflexionsspektroskopie auf ihre optischen Eigenschaften hin untersucht und die optischen Konstanten bestimmt. Durch die Abscheidung auf Spaltstrukturen und in Mehrschichtform kann das elektrische Gleichstromverhalten dieser Substanzen in Abhängigkeit von Beleuchtung und Probentemperatur analysiert werden. Die durch die Einbettung von Metallclustern (Gold, Kupfer, Silber) hervorgerufenen Veränderungen besonders im optischen, aber auch im elektrischen Verhalten, werden durch den Vergleich der Meßergebnisse mit ungestörten Proben erhalten. Die Untersuchung der Morphologie mittels TEM-Aufnahmen zeigt, daß die Clusterabmessungen und -formen in Abhängigkeit von der gewählten Materialkombination stark variieren können. Ramanmessungen an Mischsystemen zeigen, neben der für Silber erwarteten Erhöhung des molekularen Signals, auch Kupfer- und Goldeinlagerungen SERS-Effekte. Beim Einbau von Metallclustern in organische Einschichtsolarzellen konnte deren Wirkungsgrad bei Beleuchtung mit einem Sonnensimulator (AM2) bis zu einem Faktor ca. 3 erhöht werden.

No description available.

<p>Detection of pathogens, toxins, hazardous chemicals, and allergens in the food industry with reliable, sensitive, efficient, and rapid results has increased the demand to develop innovative diagnostic tools. Surface-enhanced Raman spectroscopy (SERS) sensors have demonstrated to detect a wide variety of analytes using nanomaterials like metal nanoparticles. Concerns of synthetic materials that can affect the environment with disposal of sensors have opened the possibility of fabricating SERS sensors with biodegradable materials. Fabrication of electrospun nanofibers from natural polymeric materials such as soy protein isolate can be used as a SERS platform. In the first part of this research, the characteristics of SPI solutions blended with NaOH and polyethylene oxide (PEO) such as PEO Mw, zeta potential and viscosity as well operating parameters such as voltage (15, 20, and 27 kV) were studied to evaluate the best solutions for a nanofibrous SERS platform. Characteristics of electrospun nanofibers, such as surface wettability, fiber diameters, and morphology using SEM, helped determine the most feasible fibers for decoration with noble metal nanoparticles. Fibers fabricated with 12 wt% SPI + 5 wt% PEO (0.1 MDa) + 1 wt% NaOH solution showed the smallest fiber diameter and highest water contact angle measurements. Glutaraldehyde (GLA) was added as a crosslinker to partly increase nanofibers hydrophobicity. These nanofibers were decorated with Au-nanostars and Au@Ag-NPs suspended in 90% butanol and in water. Partly hydrophobic nanofibers decorated with Au-nanostars and Au@Ag-NPs in butanol showed the most feasible results for a SERS platform due to smallest fiber diameter and higher water contact angle. In the second part of this research, decorated SPI nanofibers were evaluated to study its feasibility as a SERS platform for detecting bisphenol A (BPA), a toxic chemical present in food packaging materials. However, SERS spectra were difficult to obtain due to CCD overflow (excessive number of photons) at all laser powers on SPI nanofiber mats. Optimizing other Raman spectroscopy parameters such as the exposure time and the number of averages could enhance the SERS measurements. The fabricated SPI nanofibers in this research showed that hydrophilic and partly hydrophobic nanofibers mats could be used for decoration with metal nanoparticles by suspending the nanoparticles in a hydrophobic solvent. Hydrophilic nanofiber mats with nanoparticles in a hydrophobic solvent open a new strategy for developing another type of SERS platform.</p>

Die vorliegende Dissertation beschäftigt sich mit der Herstellung und Charakterisierung einzelner Edelmetallnanopartikel-Cluster für die oberflächenverstärkte Raman-Streuung (engl. surface-enhanced Raman scattering; SERS). In Clustern treten stark lokalisierte Regionen mit sehr hohen Feldverstärkungen auf (engl. hot spots), die den SERS-Effekt extrem verstärken. In der Regel werden Metallnanopartikel in kolloidaler Suspension untersucht, so dass nur Aussagen über das gesamte Kolloid und nicht über einzelne Cluster getroffen werden können. Für die Identifizierung von Struktur-Eigenschafts-Korrelationen wurden in dieser Arbeit daher einzelne Cluster optisch und elektronenmikroskopisch charakterisiert. Der erste Teil der vorliegenden Arbeit beschreibt neue Ansätze zur Trennung von glasverkapselten SERS-Nanopartikel-Clustern mit Hilfe der Dichtegradientenzentrifugation sowie die Etablierung einer modifizierten Synthesevorschrift zur Herstellung von monodispersen Silbernanopartikeln. Der zweite Teil beschäftigt sich mit der optischen Charakterisierung einzelner SERS-Cluster und den dafür notwendigen experimentellen Umbauten eines bestehenden Versuchsaufbaus. Anschließend wird die oberflächenverstärkte Raman-Streuung von SERS-Clustern in Abhängigkeit der Polarisation gemessen und die lokalisierte Oberflächenplasmonenresonanz (engl. localized surface plasmon resonance; LSPR) von Nano- und Mikrostrukturen bestimmt.

No description available.

The propagation of contaminants in the environment continues to threaten public health and safety. Conventional analytical techniques for environmental detection require centralized facilities and intensive resources for operation. An effective implementation of a wide network of field deployable point-of-use (POU) sensors can potentially enable real-time monitoring of water quality parameters and inform decision making on public health outbreaks. The use of nanotechnology and field-deployable analytical tools can potentially advance the development of POU sensors for future field application. In this dissertation, we developed environmental sensing techniques that utilize nanocomposites made of low-cost, biocompatible, and sustainable nanomaterials combined with Raman spectroscopy. First, a technology pre-assessment was performed that included a comprehensive evaluation of cellulose-derived nanocomposites and nanobiotechnology enabled techniques for their sustainable long-term environmental application. Furthermore, to contribute to the better understanding of the potential environmental implications of nanomaterial production and application, life cycle assessment (LCA) was used to evaluate the environmental impacts of six iron precursors and seven iron oxide nanoparticle synthesis methods. Secondly, in the technology development step, gold (Au) and iron oxide (Fe3O4) nanoparticles were incorporated onto bacterial cellulose nanocrystals and nanoscale magnetite were synthesized. As proof-of-concept environmental applications, the Au@Fe3O4@BCNCs were applied for the magnetic separation and surface-enhanced Raman scattering (SERS) detection of malachite green isothiocyanate (MGITC), and nanoscale magnetite were applied for phosphate (PO43-) removal and recovery from synthetic urine matrices. Finally, in the technological application step, three environmental sensing applications are presented that use nanomaterial-based sensor platforms and/or Raman spectroscopic techniques. The first application involved using Lectin-modified BCNCs coupled SERS and machine learning for discrimination of bacterial strains. The second application presents a simple Raman-stable isotope labeling approach for the study of viral infection of bacteria. The third application involved use of SERS pH nanoprobes for measuring pH in droplets of complex matrices (e.g., DMEM cell culture media, human saliva). / Doctor of Philosophy / The current generation of analytical tools for environmental detection rely upon centralized facilities and intensive resources for operation. The combination of nanotechnology and field deployable analytical tools can aid in the development of point-of-use (POU) sensors for field monitoring of environmental contaminants. In this dissertation, we combined low-cost, biocompatible, and sustainable nanomaterials with Raman spectroscopy-based techniques to develop potentially field-deployable environmental sensing techniques. First, a technology pre-assessment was performed which involved a comprehensive evaluation of cellulose-derived nanocomposites and nanobiotechnology enabled techniques for their sustainable long-term environmental application. Furthermore, life cycle assessment (LCA) was used to evaluate the environmental impacts of iron oxide nanoparticle synthesis methods to better understand environmental impacts of nanoparticle production. Secondly, in the technology development step, we developed the nanocomposites: Au and Fe3O4 nanoparticles incorporated bacterial cellulose nanocrystals and nanoscale magnetite. As proof-of-concept environmental applications, the Au@Fe3O4@BCNCs were used for the detection of malachite green isothiocyanate (MGITC), and the nanoscale magnetite were used for phosphate (PO43-) removal and recovery from synthetic urine. Finally, in the technological application step, (1) selective detection of bacteria was performed using lectin-modified BCNCs as SERS biosensors coupled with SERS and machine learning. (2) Viral infection of bacteria was evaluated using Raman spectroscopy and Deuterium isotope labeling, and (3) pH in micro-droplets of DMEM cell culture media and human saliva were observed using SERS pH nanoprobes.

Surface enhanced Raman spectroscopy (SERS) is highly promising analytical technique for trace detection of analytes. It is particularly well suited for environmental analyses due to its high sensitivity, specificity, ease of operation and rapidity. The detection and characterization of environmental contaminants, using SERS is highly related to the uniformity, activity and reproducibility of the SERS substrate. In this thesis, SERS substrates were produced by gold nanoparticle formation on wax patterned chromatography paper. In situ reduction of hydrogen tetrachloroaurate (gold precursor) by trisodium citrate dihydrate (reducing agent) was used to produce gold nanoparticles within a paper matrix. These gold nanoparticle based SERS substrates were analyzed by FE-SEM, UV-Vis and Raman spectroscopy. This work discusses the SERS signal enhancements for Raman active MGITC dye for a series of substrates prepared by in situ reduction of gold salt and pre-produced gold nanoparticles. UV-Vis analysis was performed to understand the effect of different molar ratio (reducing agent to gold precursor) and reaction time on the size and shape of the localized surface plasmon resonance (LSPR) band that dictates the SERS enhancements. It was concluded that lower molar ratio (1:1 and 2:1) of citrate-to gold produced better SERS signal enhancements and broader LSPR band. Therefore, use of lower molar ratio (MR) was recommended for paper-based substrates using in situ-based reduction approach. / Master of Science

Existing methods for pathogen/pollutant detection or wound infection monitoring employ high-cost instruments that could only be operated by trained personnel, and costly device-based detection requires a time-consuming field-to-lab process. This expensive process with multiple prerequisites prolongs the time that patients must wait for a diagnosis. Therefore, improved methods for point-of-care biosensing are necessary. In this study, we aimed to develop a direct, easy-to-use, portable, low cost, highly sensitive and selective sensor platform with the goal of pollutant detection and wound infection/cancer migration monitoring. This study has two main parts, including microfluidic, electrical, and optical sensing platforms. The first part, including chapters 2, 3, and 4, focuses on Bisphenol A (BPA) lateral flow assay (LFA) detection; the second part, including chapter 5 focuses on the electrical sensing platform fabrication for one of the markers of inflammation, matrix metalloproteinases-9 (MMP-9), monitoring/detection. In chapters 2, 3, and 4, we found that the few lateral flow assays (LFAs) established for detecting the endocrine-disrupting chemical BPA have employed citrate-stabilized gold nanoparticles (GNPs), which have inevitable limitations and instability issues. To address these limitations, in chapter 2, a more stable and more sensitive biosensor is developed by designing strategies for modifying the surfaces of GNPs with polyethylene glycol and then testing their effectiveness and sensitivity toward BPA in an LFA. In chapter 3, we describe the development of a new range-extended bisphenol A (BPA) detection method that uses a surface enhanced Raman scattering lateral flow assay (SERS-LFA) binary system. In chapter 4, we examine advanced bisphenol A (BPA) lateral flow assays (LFAs) that use multiple nanosystems. The assays include three nanosystems, namely, gold nanostars, gold nanocubes, and gold nanorods, which are rarely applied in LFAs, compared with general gold nanoparticles. The developed LFAs show different performances in the detection of BPA. In chapter 5, a stable electrical sensing platform is developed for MMP-9 detection.