Master of Science / Department of Geology / Brice LaCroix / The Los Burros mining district (LBMD) is located within the Lucia subterrane (Underwood et al., 1995) along the Sur- San Gregorio-San Simeon-Hosgri fault system of California’s Franciscan complex. The LBMD presented an attractive gold prospecting and mining area during the late 19th and early 20th centuries. Recent interest in the area has focused on fault-offset modelling through thermochronology (Underwood et al., 1995, Chapman et al., 2016). However, the mechanism, conditions, and timing of ore formation in the area are poorly constrained due to a lack of academic interest and documentation. This research seeks to arrive at a better understanding of gold emplacement mechanisms in the LBMD through an examination of lithologic and structural controls coupled with source fluid composition and peak P/T constraints. Sampling and mapping of lithologies and structures within the vicinity of the LBMD were conducted during the summer of 2016. Samples were collected for clay-fraction and bulk-rock mineralogy via XRD analyses, petrographic inspection and interpretation, including fluid inclusion microscopy/microthermometry as well as Raman spectroscopy. These analyses were conducted in an endeavor to constrain and explain a previously identified regional thermal anomaly within the vicinity of the LBMD with the intention of characterizing and modelling the impacts of structural controls on gold deposition. The results of this study suggest gold deposition from a gas-poor, metamorphic source-fluid with approximately 300 ppm CH₄, CO₂ density of 0.15 g/cm³, and an average salinity of 1.7 wt % NaCl equivalent. These data, along with peak P/T conditions of ~285°C and 680 bars were inferred using input from illite crystallinity data, fluid inclusion microthermometry, and the application of the Raman spectroscopy of carbonaceous material (RSCM) geothermometer used by Lahfid et al. Gold mobilization from sulfide and carbonaceous-rich sediments through polyphase deformation events led to emplacement along structural and lithologic contacts likely as a syn-orogenic event. Gold emplacement occurred during the reorientation of the regional structure by transpression.

This diploma thesis deals with optimization of analysis process and measuring antibiotics induced changes in E. coli cells via Raman spectroscopy, LTRS and microfluidic systems. Optical micromanipulation by a laser beam allows noncontact and noninvasive manipulation of objects on scale 10^-5–10^-8 m, for example bacterial cells. Microfluidic device consists of microchannels and microchambers in transparent polymer and it is used for isolation, observation and cultivation of bacterial cells. Combination of these methods gives an effective tool for observation, manipulation and analysis of microorganisms. E. coli is a microorganism potentially pathogenic for humans and faster detection of its sensitivity to antibiotic treatment would make the whole process of diagnostics and treatment easier. We performed laser tweezer-Raman spectroscopy and conventional Raman spectroscopy of bacterial cells and cells under antibiotic stress and collected Raman spectra and characteristic areas were compared with literature to establish the reliability and usefulness of this method.

Mechanics of bone is widely studied and researched, mainly for the study of fracture. This has been done mostly on a macro scale. In this work hierarchical nature of bone has been explored to investigate bone mechanics in more detail. Flexural test were done to classify the bones according to their strength and deflection. Raman spectroscopy analysis was done to map the mineralization, collagen crosslinking changes across the thickness of the bone. Nanoindentation was done to map indentation hardness and indentation modulus across femoral cortex of the bone. The results indicate that the composition of the bone changes across the thickness of the femoral cortex. The hypothesis is confirmed as increase in mineralization, carbonate to phosphate ratio and collagen crosslinking shows the effect as increased indentation hardness and modulus and decreased deflection.

Powerful optical spectroscopic and imaging tools have revolutionized many areas of science and technology. The detection sensitivity and chemical specificity are two major considerations when characterizing an optical technique. The fluorescence spectroscopy and microscopy provide excellent sensitivity down to single molecules. However, its reliance on probing the electronic transition limits the obtainable chemical information. In contrast, vibrational spectroscopy such as Raman scattering provides exquisite chemical specificity about the molecular structure, dynamics, and coupling with the environment. However, Raman scattering is intrinsically weak, and its cross sections are many orders of magnitudes smaller than those of fluorescence. The efforts that trying to bridge these two powerful methods can be traced back to the 1980s. But it was until our attempt in 2019, by carefully tuning the electronic pre-resonance and optimizing the excitation duration, the first successful Raman-featured fluorescence spectroscopy was demonstrated. This hybrid technique was named as stimulated Raman excited fluorescence (SREF). As expected, SREF combines both high sensitivity and exquisite chemical specificity, which enables the first all-far-field single-molecule Raman spectroscopy and imaging. This thesis is trying to provide a comprehensive interpretation of SREF, and at the same time serves as a practical guide for experiments and instrumentation. In chapter 1, the early (unsuccessful) attempts for SREF spectroscopy are reviewed. Additionally, I briefly summarize the basic theory for single- and multi-photon excitation process of a single fluorophore, from which the feasibility of SREF spectroscopy is explained. Chapter 2 is mainly focused on the instrumental details of the first successful SREF spectroscopy, and the basic spectroscopic features of SREF are summarized. The generality of SREF spectroscopy is systematically discussed in Chapter 3, and a rule-of-thumb criterion for successful SREF excitation based on the simple two-beam excitation strategy is proposed. Aimed at background-free SREF microscopy, a three-beam system based on nonlinear fiber optics and lock-in detection is illustrated in Chapter 4. In chapter 5, the first attempt to combine SREF and the stimulated emission depletion (STED) for an all-far-field super-resolution vibrational imaging is proposed. At last, as a simple application of SREF microscopy, SREF-based vibrational Stark spectroscopy on visualizing the electrostatic field at the water-oil interface of microdroplets is discussed(Chapter 6).

In this dissertation, the emerging stimulated Raman scattering (SRS) microscopy in combination with various vibrational tags was extensively used to explore various aspects of biological systems. New techniques as well as new Raman active materials were also developed to facilitate the applications of SRS in biology. Chapter one introduces and comprehensively reviews vibrational tags that have been developed to date in combination with imaging techniques and their applications in biological sciences to investigate metabolism in living organisms. Chapter two studies lipotoxicity, a phenomenon that is well known but poorly understood. The study found phase separation can form on ER membrane in cells treated with long chain fatty acids due to the high transition temptation of their metabolites. It was also found that the phase separation severely disturbs normal distribution of ER membrane proteins because of hydrophobic mismatching. As the result, ER normal structure is disrupted, luminal space is collapsed, and interconnectivity of ER that ensures normal ER functions is lost. Additionally, ER stress sensor IRE1α was found to be activated directly by the formation of phase separation, which triggers apoptosis and ultimately leads to cell death. Chapter three describes the development of a new method termed as metabolic activity phenotyping (MAP) that acquires quantitative measurements of metabolic activities of individual cells, which is essential to understanding questions in diverse fields in biology. To achieve the goal, an automatic system was designed and built that improves the acquisition speed by more than 100 times compared to commercially available instruments. A set of vibrational probes with deuterium labeling was also carefully selected to enable accurate measurement of metabolic flux. Combining the merits of high throughput measurements and vibrational tags, MAP was applied to investigate the metabolic activity differences among various cancer cells, to study the heterogeneity of drug efficacy, and to facilitate breast cancer subtyping. Chapter four describes the development and application of a new class of Raman active nanoparticles, or Rdots. These Rdots were generated by non-covalently incorporating small molecule Raman probe into polymeric nanoparticles. The resulted Rdots are of compact size (~20 nm) and preserve all Raman spectral features of the small molecule probes used. Rdots were compared to other existing Raman active materials including SERS nanoparticles, and Rdots surpass all the other materials in terms of brightness. In addition, Rdots also possess narrow spectral linewidth (< 3 nm), making them ideal for multiplexed imaging. In the study, Rdots were used as immunostaining reporters to visualize cytoskeleton networks and surface markers in cell and tissue samples.

Despite the weak interaction between electrons and atomic vibrations (phonons) in the one-atom thick crystal of carbon called graphene, the scattering of electrons off phonons limits coherent electron transport in pristine devices over mesoscopic length scales. The future of graphene as a replacement to silicon and other materials in advanced electronic devices will depend on the success of controlling and optimizing electronic transport. In this dissertation, we explore the electron-phonon interaction via Raman scattering, elucidating the effects of filling and emptying charge states on the phonons in both the metallic state and when levels are quantized by an applied perpendicular magnetic field. In zero magnetic field, the phonon energy shifts due to electronic screening by charge carriers. Previously, a logarithmic divergence of the phonon energy was predicted as a function of the charge carrier density. For the first time, we observe signatures of this logarithmic divergence at liquid He temperatures after vacuum annealing on single layers. We also measure the electron-phonon coupling strength, Fermi velocity, and broadening of electronic quantum levels from Raman scattering and correlate these parameters to electronic transport. In a strong perpendicular magnetic field, the energy bands split into discrete Landau levels. Here, we observe kinks and splitting of the optical phonon energy, even when the Landau level transitions are far from resonant with the phonons. We discover that the kinks are attributed to charge filling of Landau levels, as understood from a linearized model based on electron-phonon interactions. Moreover, we show that material parameters determined without magnetic fields also describe phonon behavior in high magnetic fields.

No description available.

Electrolyte interactions with ligand functionalized gold nanoparticles (AuNPs) have broad implication to a wide range of applications in nanoparticle research field. Among a wide range of electrolytes, halides, nitrates, borohydrides, and sulfides are used to study the AuNP interfacial interactions. Although there are many studies on AuNP interactions with anionic species (halides, nitrates, borohydrides, and sulphides), there is limited information on AuNP interactions with metallic cations. Therefore, studying the nanoparticle interfacial interactions with both anionic and metallic cation species is highly important. The research reported here is focused on deepening the understanding of electrolyte interactions with ligand functionalized AuNPs in aqueous solutions. The stability of citrate-residues on AuNPs against ligand displacement has been controversial. In the first study, we demonstrated the direct experimental evidence for the simultaneous adsorption of both citrate-residues and solution impurities onto citrate-reduced AuNPs by using AuNPs synthesized with deuterated citrate in combination with the surface-enhanced Raman spectroscopic (SERS) analysis. The citrate-residues can be readily displaced from AuNPs by a wide range of specific and non-specific ligands including organosulfur and electrolytes. In the second study, we investigated the charge state and the mechanism of silver ion binding onto organothiol functionalized AuNPs. Mechanistic study reveals that silver binding onto AuNPs proceeds predominantly through reactive pathways with proton generations providing the first direct experimental evidence that Ag+ can disrupt the Au-S binding and enhance the mobility of the organothiols on AuNPs. Ligand displacement from AuNPs is important in a wide range of applications. Complete and non-destructive removal of ligands from AuNPs is important and challenging due to the strong Au-S binding and the steric hindrance imposed by ligand overlayer on AuNPs. In the final study, we investigated hydrogen sulphide (HS-), an anionic thiol as an effective ligand to induce complete and non-destructive removal of ligands from aggregated AuNPs. The new insights and methodologies presented in this dissertation are important for studying the electrolyte interfacial interactions with ligand functionalized AuNPs which have a broad impact on nanoparticle surface chemistry.

An integrated fiber optical Raman sensor was designed for real-time, non –intrusive detection of liquid and gaseous mixtures at high pressure and high flow rates. The integrated sensor employs a high-power solid-state pumped Nd:YAG frequency doubled (532nm) laser (3W), a modified In Photonics Raman probe which has built-in Raman signal filter optics, and two high-resolution spectrometers and photomultiplier tubes (PMT) with selected bandpass filters to collect both N2 and O2 Raman signals. The detection unit was also integrated with Lab View software interfaced PMT modules for fast data acquisition.

No description available.