The presented diploma thesis is focused on finding conditions suitable for the study of surface reactions, especially Suzuki-Miyaura cross-coupling reaction (SMCR), by the surface- enhanced Raman scattering (SERS) method. The first part of the work deals with the optimization of the conditions of individual reactions using the classical synthetic Schlenk technique. Traditional, published, conditions for SMCR were gradually modified during the work so that the reactions could be performed in aqueous media and at room temperature, i.e., under conditions suitable for SERS spectroscopy. The following catalysts were tested: (i) PEPPSI - the traditional SMCR catalyst; (ii) palladium ions; (iii) Pd colloids; (iv) bimetallic colloids of Pd and plasmonic metal (Ag, Au) in the form of core-shell and alloy; (v) Ag and Au colloids with additions of palladium salt or N- heterocyclic carbenes (NHC-catalysts). Two groups of substrates were used: substrates with functional groups with high affinity for the surfaces of metal nanoparticles (NPs) and substrates without these anchoring functional groups. Substrates without the anchoring functional groups can be expected to enter the SMCR reaction from solution. In the second part of this diploma thesis selected reaction mixtures for SMCR were performed in septum...

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La spectroscopie Raman exaltée de surface (SERS) est largement utilisée comme un outil non-intrusif et sans marquage pour identifier les empreintes spectrales moléculaires dans des applications comme la pharmacologie, la salubrité des aliments, etc. Cette thèse présente un micro-capteur SERS basé sur un guide d'ondes hybride constitué de fentes métalliques (Au/Al) et de rubans diélectriques (Si3N4) et sur une méthode pour promouvoir la capacité de détection SERS en plaçant des nanoparticules métalliques dans la fente du capteur. L'étude théorique du capteur est principalement menée par la méthode des différences finies dans le domaine temps en trois dimensions (3D-FDTD) qui fournit la réponse électromagnétique à large bande des nanostructures métalliques. Les facteurs d'exaltation du capteur sont estimés par l’approximation |E|4. Les expériences sont basées principalement sur la fabrication de fentes métalliques, qui est réalisée par la lithographie à faisceau d'électrons (EBL), et sur la caractérisation de la capacité de détection SERS des capteurs. Les résultats montrent que les signaux Raman donnés par les capteurs SERS sont détectables. Les nanoparticules métalliques, qui sont situées dans le capteur, peuvent améliorer considérablement la capacité de détection SERS. En combinant le capteur SERS avec les éléments photoniques et électroniques, un système de détection SERS entièrement intégré sur une puce peut être développé dans un proche avenir pour des détections SERS portables et stables / Surface-enhanced Raman spectroscopy (SERS) is widely used as a non-intrusive and label-free tool to identify the molecular spectral fingerprints in pharmacology, biology, etc. This thesis presents a SERS sensor based on the hybrid waveguide made of metallic (Au/Al) slots and dielectric (Si3N4) strips and a method to improve the SERS-detection capacity by placing metallic nanoparticles into the sensor’s slot. The theoretical investigation of the sensor is mainly conducted by the 3D finite-difference time-domain method (3D-FDTD) which provides the broadband electromagnetic response of metallic nanostructures. The enhancement factors in the sensor’s slot are estimated based on the |E|4-approximation. The experiments are mainly the fabrication of metallic slots, which is conducted by the electron beam lithography (EBL), and the characterization of the SERS-detection capacity of the sensors. The results show that the Raman signals given out by the SERS sensors are detectable. Metallic nanoparticles, which are located in the sensor’s slot, can improve dramatically the SERS-detection capacity. By combining the SERS sensor with the extended photonic and electronic elements, a fully integrated-on-chip SERS detection system on a chip can be developed in the near future for portable and stable SERS detections

This thesis deals with the study of microbial pigment violacein in the real sample of lyophilized microorganisms. The sample was investigated by using methods of vibrational spectroscopy with focusing on the applicability of surface enhanced and resonance micro-Raman spectroscopy. For this purpose several different systems for enhancing Raman intensity together with the set of excitation lasers emitting in the visible light region were used. The conclusion of this thesis are the recommendations connected with the appropriateness of using each amplifying systems and excitation wavelengths for the successful identification of violacein pigment in the sample. Powered by TCPDF (www.tcpdf.org)

Thesis advisor: Matthias Waegele / Heterogeneous electrocatalytic reduction is an environmentally friendly method for the conversion of abundant feedstock molecules into valuable products. Examples include the reduction of carbon dioxide to hydrocarbons and the reduction of nitrate to ammonia. Heterogeneous electrocatalysis occurs at the interface between an electrode and an electrolyte. Interfacial properties, such as surface morphology, interfacial electric field, interfacial water structure, and local pH, can substantially influence the activity and selectivity of electrocatalytic reduction processes. However, a comprehensive, molecular-level understanding of how these interfacial properties control electrocatalysis is still largely lacking to date. To develop such an understanding, it is essential to probe the properties of the electrocatalytic interface under operating conditions. This great experimental challenge is further compounded by the fact that the interface often undergoes dynamic changes during catalysis. In this thesis, we took a multimodal approach to characterize the aqueous electrolyte/copper interface during CO2/CO reduction and hydrogen evolution. Copper is the only pure metal that promotes the reduction of CO2/CO to hydrocarbons at significant reaction rates. The hydrogen evolution reaction is the main competing reaction in aqueous electrolytes. It is therefore essential to understand how these reactions are controlled by the properties of the interface. In the first part of this thesis, we employed in-situ surface-enhanced infrared absorption spectroscopy (SEIRAS) and surface-enhanced Raman spectroscopy (SERS) to investigate dynamic changes of the copper electrode surface. We found that the polycrystalline copper electrode surface undergoes a reconstruction process upon adsorption of CO. The formation of nanoscale metal clusters on the electrode manifests itself by the appearance of a new CO stretch band, which arises from a CO sub-population bound to undercoordinated copper atoms. The formation of these clusters is reversible, that is, they disappear upon desorption of CO. This work demonstratesthat a reaction intermediate such as CO can induce dynamic and reversible changes in the surface morphology of a heterogeneous catalyst. Because the changes are reversible, they would escape ex situ measurements. Our findings highlight the need for probing catalytic surfaces under operating conditions. In the second part of this thesis, we focused on how the electrolyte influences electrocatalysis at the aqueous electrolyte/copper electrode interface. Specifically, we explored the mechanisms by which cations of the supporting electrolyte affect the reduction of CO and the hydrogen evolution reaction on copper. With differential electrochemical mass spectrometry (DEMS), we determined to what extent the reduction of CO to ethylene is affected by the identity of the cations of the supporting electrolyte. Ethylene is produced in the presence of methyl4N+ and ethyl4N+ cations, whereas this product is not synthesized in propyl4N+- and butyl4N+-containing electrolytes. With SEIRAS, we found that an intermolecular interaction between surface-adsorbed CO and interfacial water is disrupted in the presence of the two larger cations. This observation suggests that this interaction promotes the hydrogenation of surface-bound CO to ethylene. This work illustrates that weak intermolecular interactions can substantially influence electrocatalytic processes. In a related study, we examined the effect of alkali metal cations of the supporting electrolyte on the hydrogen evolution reaction. We found that, in alkaline conditions, changing the cation from Na+ to Cs+ has no measurable effect on the HER. Because it is well-established that Cs+ promotes the reduction of CO2/CO to hydrocarbons, the results illustrate the changing the alkali cation enables the selective promotion of this pathway under alkaline conditions. Further, we found that in 0.1 M solutions of NaOH and CsOH of the highest commercially available purity grades, trace impurities of iron deposit on the copper electrode during the hydrogen evolution reaction. Because iron is a better catalyst for the hyrogen evolution reaction than copper, the rate of the hydrogen evolution reaction is enhanced by up to a factor of 5. These findings demonstrate that trace impurities of this ubiquitous metal pose a great challenge for the development of selective catalytic processes for CO2/CO reduction. This thesis provides a critical study of how the interfacial properties change under the electrocatalytic reduction of CO2/CO and hydrogen evolution conditions. The properties of both Cu electrode and the electrolyte contribute to the control of the selectivity of these complex electrocatalytic processes. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

In this work, new small deflection magnetic actuators have been proposed, designed, and tested for applications in Surface Enhanced Raman Scattering optical sensors. Despite the fact that SERS sensors have been shown to increase Raman over ten orders of magnitude for molecular detection, several technological challenges have prevented the design of practical sensors, such as making SERS sensors that can efficiently detect a wide variety of molecules. Since the optimum signal-to-noise in SERS occurs at different excitation wavelengths for different molecules, individual metal nanostructures need to be designed and fabricated for each independent chemical species. One possible solution to this problem is to tune the plasmon resonance frequency of the metal nanoparticles to eliminate the need for individually optimized particles. In order to achieve a tunable local dielectric environment, and thus allow for control over the resonance frequency of metal nanoparticles, a new SERS sensor geometry is proposed and a large deflection magnetic actuator is fabricated and tested as a starting point for the design of a small deflection magnetic actuator. Using the newly developed SERS geometry and the optimized fabrication processing techniques, two small deflection magnetic actuator beam structures were designed, fabricated, and tested. These devices utilizes an off-chip electromagnet source able to produce a magnetic force of approximately 14 μN on the on-chip nickel film generating deflections up to 139 nm for the straight beam device and 164 nm for the curved beam device. iii In the process of characterizing the newly developed small deflection magnetic actuator, an integrated magnetic actuator with electrostatic restoration geometry was conceived. This device was designed to meet the specifications of the small deflection magnetic actuator as well as eliminate the need of an off-chip magnetic source and fully integrate the process atop the metal nanoparticle arrays. Using adhesive iron based magnetic strips as the magnetic drive source, circular NiFe beams with 1, 2, 3, and 4 mm diameters were designed and simulated. Calculations predicted maximum achievable actuation of up to 2.5 μm. Processing steps were laid out for a set of integrated devices as a possible predecessor to the newly designed small deflection magnetic actuator.

The first thermal cycling experiments of ionic self-assembled multilayer (ISAM) films have been reported examining their survivability through repeated thermal cycles from -20° C to 120° C in ambient atmospheric conditions. The films were constructed from alternating layers of Nile Blue A and gold nanoparticles which provided a strong absorbance in the optical wavelength range. No degradation of the optical characteristics of the ISAM films was observed [1]. Techniques for measuring the capacitance and resistivity of various ISAM films have also been developed allowing for a more complete electrical characterization of ISAM films. Capacitance measurements enabled a calculation of the dielectric function and breakdown field strength of the ISAM films. The capacitance measurement technique was verified by measuring the dielectric function of a spin-coated thin film PMMA, which has a well characterized dielectric function [2]. Surface-enhanced Raman spectroscopy (SERS) has been studied as a possible detection method for malignant melanoma revealing spectral differences in blood sera from healthy horses and horses with malignant melanoma. A SERS microscope system was constructed with the capability of resolving the Raman signal from biologically important molecules such as beta-carotene and blood sera. The resulting Raman signals from sera collected from horses with malignant melanoma were found to have additional peaks not found in the Raman signals obtained from sera collected from healthy horses. A systematic analysis of the combination of absorbance and fluorescence signals of blood sera collected from populations of healthy dogs and dogs with cancer has resulted in a rapid and cost-effective method for monitoring protein concentrations that could possibly be used as part of a cancer screening process. This method was developed using the absorbance and fluorescence signals from known serum proteins, the combinations of which were used to match the absorbance and fluorescence signals of blood sera allowing for an accurate determination of protein concentrations in blood sera [3]. Finally, a novel method for measuring the melting point of DNA in solution using capacitance measurements is presented. This method allows for the determination of the melting temperature as well as the melting entropy and melting enthalpy of DNA strands. Two different short strands of DNA, 5'-CAAAATAGACGCTTACGCAACGAAAAC-3' along with its complement and 5'-GGAAGAGACGGAGGA-3' along with its complement were used to validate the technique as the characteristics of these strands could be modeled using theoretical methods. This experimental technique allows for the precise determination of the melting characteristics of DNA strands and can be used to evaluate the usefulness of theoretical models in calculating the melting point for particular strands of DNA. Additionally, a micro-fluidic device has been proposed that will allow for a rapid and cost-effective determination of the melting characteristics of DNA [4]. / Ph. D.

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

Raman spectroscopy is a powerful tool in the field of biomedicine for disease diagnosis owing to its potential to provide the molecular fingerprint of biological samples. However due to the inherent weak nature of the Raman process, there is a constant quest for enhancing the sensitivity of this technique for enhanced diagnostic efficiency. This thesis focuses on achieving this goal by integrating advanced methods with Raman spectroscopy. Firstly this thesis explores the applicability of a laser based fluorescence suppression technique – Wavelength Modulated Raman Spectroscopy (WMRS) - for suppressing the broad luminescence background which often obscure the Raman peaks. The WMRS technique was optimized for its applications in single cell studies and tissue studies for enhanced sensing without compromising the throughput. It has been demonstrated that the optimized parameter would help to chemically profile single cell within 6 s. A two fold enhancement in SNR of Raman bands was demonstrated when WMRS was implemented in fiber Raman based systems for tissue analysis. The suitability of WMRS on highly sensitive single molecule detection techniques such as Surface Enhanced Raman Spectroscopy (SERS) and Surface Enhanced Resonance Raman Spectroscopy (SERRS) was also explored. Further this optimized technique was successfully used to address an important biological problem in the field of immunology. This involved label-free identification of major immune cell subsets from human blood. Later part of this thesis explores a multimodal approach where Raman spectroscopy was combined with Optical Coherence Tomography (OCT) for enhanced diagnostic sensitivity (>10%). This approach was used to successfully discriminate between ex-vivo adenocarcinoma tissues and normal colon tissues. Finally this thesis explores the design and implementation of a specialized fiber Raman probe that is compatible with surgical environments. This probe was originally developed to be compatible with Magnetic Resonance Imaging (MRI) environment. It has the potential to be used for performing minimally invasive optical biopsy during interventional MRI procedures.