Raman spectroscopy records the inelastic scattering of photons originating from striking a sample with monochromatic light. Inelastic, or Raman, scattered photons shift in wavelength due to excitation of the vibrational modes of molecules struck by the incident light. The Raman scattered photons are representative of all of the covalent bonds contained within a sample. Raman spectra taken of biological systems such as proteins, bacterial colonies, and liquid waste, are difficult to interpret due to the complexity of their covalent bond landscape and mixtures of molecules in highly variable concentrations. Rather than deconstructing Raman spectra to attempt assignment of specific bonds and functional groups to wavenumber peaks, here we have developed a chemometric analysis pipeline for quantifying the similarities and differences among a set of Raman spectra. This quantification aids in both classification of samples, and in measuring how samples change over time. The chemometric approach for interpretation of Raman spectra was made freely available in a user-friendly format via a MATLAB add-on called the Raman Data Analysis (RDA) Toolbox. Demonstrations of the RDA Toolbox functionalities on Raman spectra taken of various common biological systems are included, such as determination of protein concentration and monitoring bacterial culture growth. The RDA Toolbox and Raman spectroscopy are also used to initiate research in novel areas. Fast and accurate evaluation of enzyme specific activity is required for engineering enzymes, and results of Raman assays, evaluated in the RDA Toolbox, are successfully correlated to absorbance activity assays of an enzyme WT and mutant library. Further development of this research could alleviate the bottleneck of screening mutant libraries in enzyme engineering projects. The Toolbox is then used in a distinctly different application for evaluating urine and spent dialysate samples from patients with end stage renal disease. Categorization between samples from healthy volunteers and patients is accomplished with close to 100% accuracy, and evidence indicating that Raman spectroscopy can serve as an early diagnostic tool for infections of the peritoneal membrane is presented. / PHD / Raman spectroscopy, unlike other forms of spectroscopy, provides a complete picture of the chemical make-up of a sample. However, Raman spectra of biological samples are very difficult to interpret due to the complex mixture of molecules in living systems. Rather than trying to discern what specific molecules are in a sample, we have developed a method for measuring the similarities and differences among a set of Raman spectra. These measurements help us classify samples and monitor how samples change over time. We made a MATLAB add-on called the Raman Data Analysis (RDA) Toolbox to automate our method for interpreting Raman spectra, and made it available online for anyone to download and use. Raman spectroscopy and the RDA Toolbox are used to measure enzyme reaction speed, and the results compare favorably with a traditional method for measuring enzyme reaction speed. The final part of this dissertation focuses on using Raman spectroscopy and the RDA Toolbox to evaluate the health of patients with end stage renal disease (ESRD) by scanning urine and spent dialysate samples to detect failing kidney function or the onset of infection.

Monocamadas auto-organizadas da 2,2\':6\' ,2\" -terpiridina formadas sobre a superficie do eletrodo de Ag e Cu foram caracterizadas através da técnica SERS (Surface Enhanced Raman Spectroscopy) em experimentos ex situ e in situ. Foram estudadas alterações nas espécies adsorvidas em função da natureza das soluções-mãe e das soluções eletrolíticas utilizadas, tais como, solvente, pH da solução, ânion-suporte e a presença de outro adsorbato orgânico: a 2-mercaptopirimidina (mpy). Para estudar-se a adsorção da tpy foram obtidos padrões espectrais em que a molécula realiza diferentes interações com a vizinhança: no estado sólido, em solução, fundida e formando complexos com os íons CU2+ e Ag+. Também foram obtidos padrões para o ânion Cl04- coordenado ao CU2+, possibilitando explicar a adsorção deste ânion à superficie. Os resultados indicam que a tpy adsorve sobre a superficie metálica através de seus átomos de nitrogênio formando complexos de superficie do tipo I e do tipo II, nos quais assume uma conformação cis-cis. A tpy protonada, preferencialmente, perde o próton para adsorver sobre o eletrodo. Em experimentos in situ, quando potenciais mais negativos são aplicados, a tpy adsorve sobre a superfície metálica em uma posição próxima à horizontal através dos elétrons π dos anéis piridínicos. Na presença da mpy a tpy adsorve horizontalmente sobre a superfície do eletrodo, não ocorrendo sua coordenação com o metal. Estudos da adsorção do composto 4\'-(5-mercaptopentil)-2,2\':6\',2\" - terpiridina (tpy-SH) sobre eletrodo de Ag indicam que a molécula adsorve através do átomo de enxofre sem que ocorra interação entre os átomos de nitrogênio da parte tpy e a superficie metálica. Isto foi confirmado pela coordenação do cátion CU2+ com a parte tpy das moléculas tpy-SH adsorvidas, bem como pela intensificação das bandas atribuídas à parte alcano-tiol da molécula devido sua proximidade com a superficie. Os estudos do complexo [Cu(II)tpyH2OCl04]Cl04 mostram que a exposição à radiação excitante produz a perda da coordenação da água ao íon metálico com o ânion Cl04- passando a coordenar por dois átomos de oxigênio. O perfil de excitação deste complexo foi realizado e constatou-se pré-ressonância do sinal Raman com a transição eletrônica da molécula na região entre 300 e 350 nm. Ao ser adsorvido sobre a superficie do eletrodo este complexo sofre redução e a tpy coordena aos átomos metálicos do eletrodo formando um complexo de superficie. / Self-assembly monolayers of 2,2\':6\',2\" - terpyridine (tpy) were grown on Ag and Cu electrode surface and studied ex situ and in situ by SERS (Surface Enhanced Raman Spectroscopy). The nature of the adsorbate species was studied as a function of the mother-sulution changing solvent, pH and supporting-anion. The effect of 2-mercaptopyrimidine (mpy) as co-adsorbate was also investigated. For comparison purposes the Raman spectrum of tpy was obtained as solid, solution, molten and as Ag+ and CU2+ complexes. A supplementary Raman study of CU2+ perchlorates was also performed to facilitate the understanding of the Cl04- adsorption on the metal surface. The results showed that tpy adsorb on the metallic surface through the nitrogen atoms forming two different surface complexes (type I and type II) that have cis-cis conformation. Protonated tpy, preferentially, loses the proton to adsorb on the electrode. In the in situ experiments, when more negative potentials were applied, the observed spectral changes were ascribed to a modification in the adsorption geometry leading to a nearly flat arrangement. In presence of mpy, tpy adsorbs flat on the electrode surface and coordination with the metal is not observed. Studies on the adsorption of the 4\'-(5-mercaptopentyl)-2,2\':6\',2\"-terpyridine (tpy-SH) on Ag electrode showed that the molecule adsorb through the sulfur atom and there is no interaction between the nitrogen atoms of tpy moiety and the metal. This was confirmed by coordination of CU2+ with the tpy moiety of adsorbed tpy-SH molecules and by the enhancement of the alkyl-thiol bands which are close to the surface. Studies of the [Cu(II)tpyH2OCl04]Cl04 complex showed that depending on the energy density used the exciting radiation may cause the release of the coordinated water, leading to a bidentate coordination of the Cl04- anion. The Raman excitation profile for this complex was obtained and pre-resonance enhancement associated with a transition between 300 e 350 nm was observed. When adsorbed on the electrode surface this complex undergoes reduction and the tpy coordinates to the metal atoms forming a surface complex.

This research focuses on generating, isolating, and characterizing nanophase gold clusters with diameters below two nanometers. In this size regime, the metal cores exhibit electronic and optical properties very different from those of colloidal and bulk gold, arising from quantum size confinement. The unoccupied molecular orbitals of the cores are known to accept electrons, analogous to a capacitor, but with discrete electrochemical potentials. This work describes the novel production of gold clusters with structurally rigid benzenethiolate bound to the surface, rather than typically used alkanethiolates. The Aux(benzenethiolate)y clusters are anionic and charged balanced by tetraoctylammonium cations. They are enriched in ~1.5 nm diameter cores, compared to a dominance of 1.7 nm cores when alkanethiols are used during synthesis. The Aux(benzenethiolate)y clusters are more likely to form bulk crystals and possess enhanced electrochemistry relative to Aux(alkylthiolate)y clusters. They are characterized by x-ray diffraction, carbon and proton NMR, FTIR, optical spectroscopy, mass spectrometry, elemental analysis, and thermogravimetric analysis. The etching of clusters in the presence of hydrogen peroxide and excess benzenethiol to yield smaller 1.1 nm clusters is reported for the first time in this work. These 1.1 nm clusters have a rich optical spectrum with clear electronic transitions at room temperature and orient spontaneously when deposited from solution. This oxidative etching process was applied to alkanethiolate clusters, converting ~2.0 nm polydisperse clusters into smaller clusters. This offers the potential to produce smaller gold clusters with more available charge states and may allow increase the types of thiols that can be bound to the surface of gold monolayer protected clusters (MPCs), known also as quantum dots. The use of the bulky thiol, tert-butylmercaptan to produce 1.5 nm core gold clusters is also reported, indicating sterically hindered alkanethiols can play a role in limiting the size of Aux(alkylthiolate)y clusters. These clusters were characterized by x-ray diffraction, proton NMR, FTIR, optical spectroscopy, and mass spectrometry. The clusters are potentially useful for thiolate exchange reactions to produce new types of Aux(thiolate)y clusters.

Possessing a wide band gap and large break down field, gallium nitride (GaN) is of interest for a host of high power, high frequency applications including next generation cellular base stations, advanced military radar, and WiMAX networks. Much of this interest stems from the continued development of the AlGaN/GaN high electron mobility transistor (HEMT) that is capable of operating at sizable power densities and switching speeds. The same fields responsible for this performance, however, also elicit acute device heating and elastic loads. These induced thermomechanical loads limit both performance and reliability thus necessitating continued improvement in the management and characterization of the coupled environments. In response, this study establishes a new implementation of Raman spectroscopy capable of simultaneously measuring the operational temperature and stress in a HEMT using only the Stokes response. First, the linewidth (FWHM) of the Stokes signal is utilized to quantify the operating temperature of a HEMT independent to the influences of stress. Second, a new method, incorporating the use of the linewidth and peak position in tandem, is developed to estimate the biaxial thermoelastic stress that arises during device operation. With this capability, the HEMT's resultant load is assessed, highlighting the large role of the residual stress on the total mechanical state of the device. Subsequently, this same linewidth is leveraged to identify the distinct effect that electrical carriers have on the thermally relevant decay of longitudinal optical phonon modes. Further investigation of the lattice transport then concludes the study by way of an analytical treatment describing the significant influence of interfacial disorder on the energy transport at GaN/substrate boundaries.

Benzophenone (BP) and substituted BPs constitute a major class of aromatic ketones and are of potential interest in various areas of excited state solution phase photochemistry and photobiology. High triplet state energy, faster rate of intersystem crossing (ISC) and higher triplet state quantum yield enables BP systems as potential photosensitizers via triplet energy transfer mechanism. The short lived triplet state of BP systems are highly reactive and acts as potential electron acceptor and interesting photochemical behavior have been observed for photoinduced electron transfer reactions in various solvent media, in particular for donor-bridgeacceptor (D-B-A) family. Though detailed spectroscopic studies of BP and substituted BP are documented, not much attention are given to its heterocyclic analogue. Substitution of aromatic ring carbon with one or more heteroatom (N and S) results in drastical change in photochemical properties and excited state reactivity. In solution phase and in nanosecond time domain heteroaromatic ketones form the triplet excited state that upon subsequent photoreactions, leads to formation of short lived species viz. radicals, ions and radical ions. Therefore exploring the trends in excited state reactivity with the variation with functional group and ring substitution and solvent medium is of considerable interest. The complete reaction mechanism of a photoreaction can be understood by studying reactivity of various short lived intermediates formed. In solution phase, the reactivity of a certain species or rate of a chemical reaction can be well understood by correlating to its structure. This approach requires accurate reproducible techniques for the excited state structural determination. Wide range of time resolved (TR) spectroscopies spanning over whole electromagnetic spectrum have been developed over decades and successfully applied to study excited state phenomena. In a typical two beam experiment, the pump pulse excites the molecular system to higher electronic state and the probe pulse records the spectrum of intermediate species at variable delay time with respect to the pump. The data from different TR techniques used to be complementary in nature and the combination helps in a deeper understanding of excited state reaction mechanism. Though time resolved absorption (TRA) is the most popular and oldest technique to study the excited state photoreactions, no structural information and the poor spectral resolution of the broad and overlapping absorption bands are the limitations towards predicting the reactive intermediates with accuracy. However time resolved resonance Raman (TR3) spectroscopy is a very sensitive technique to obtain vibrational structural information of short lived intermediates. The position and intensity of highly resolved Raman bands provide information about the structural and kinetics parameters respectively. From a set of Raman spectra along various delay time, structure of multiple intermediates evolved for parallel photoreactions can be predicted accurately. We have employed TRA, TR3 and density functional theoretical (DFT) calculation to address few fundamental questions about effect of solvent and ring substitution on the excited state structure and energetics of heterocyclic ketones, hence the reactivity. Comparing the experimental findings with the theoretical output not only makes the data more accurate but also several additional conclusions can be drawn that could not be performed only with the experimental modality. In chapter 1 of the thesis, we have presented a general summary of photophysical phenomena and measured properties and parameters of heterocyclic ketones. Typical photoreactions involving various related aromatic ketones obtained from literature are discussed. This is followed by a brief account of theory of resonance Raman spectroscopy and density functional theoretical calculation. The objectives of the present investigation are highlighted. The detailed assembly of experimental techniques employed for present investigation is discussed in chapter 2. The lasers, spectrometers, collection optics, detection systems and data collection and analysis procedures are briefly illustrated for individual set up. The theory of methods of DFT calculations is also discussed. The effect of substitution of N atom in the aromatic rings on excited state structure and reactivity (hydrogen abstraction reaction) for isomeric (2, 3, 4) benzoylpyridines (BzPy) in various solvents is studied using the above experimental and theoretical methodologies and is presented in Chapter 3. In neutral solvents viz. acetonitrile and carbon tetrachloride the photogenerated lowest triplet state (T1) is observed to be formed that follow monoexponetial decay. In the presence of hydrogen donating solvents like methanol and isopropanol the triplet state is found to undergo hydrogen abstraction reaction to form a ketyl radical and solvent radical. The lifetime and absorption and Raman features of triplet state and ketyl radicals are entirely different from each other and lack any overlapping characteristics. The observed enhanced reactivity of BzPy in comparison to BP is believed to be because of the introduction of the N hetero atom in one of the phenyl ring. From the theoretical data, it was clear that more planarity is attained in case of BzPy as compared to BP and contributes to the enhanced reactivity. The spin density calculation shows that one third of the spin is localized in the phenyl ring in case of BP. The total spin density on Phenyl ring is 0.62 and on carbonyl group is 1.45. In case of BzPy the spin density on phenyl ring is 0.45 and on carbonyl group is 1.59. This indicates that in the excited state the spin is localized more on the carbonyl group. Also from charge density calculation using DFT it is clear that in the triplet state of BzPy the oxygen atom of C=O group is more positive than in case of BP which makes it more electrophilic. Among the three isomeric BzPy the trend in charge density is dependent on the position of nitrogen and found to be in the order of 2-BzPy>3-BzPy>4-BzPy. This can be explained on the basis of -I and –M effect of N atom and the extent depends on its position. So the trend for case of photoreduction follows the order 2-BzPy>3-BzPy>4-BzPy. The hydrogen abstraction reaction used to be considerably fast that produces a substrate ketyl radical and solvent radical (donor radical). These radicals further can dimerise to form various photoproducts viz. Pinacols or can form a stable complex between them. The fate of the radicals formed as a result of hydrogen abstraction of 4-BzPy and the accurate characterization of the adduct is explained in Chapter 4. In the present case the cross coupling reaction of the radicals is observed at longer delay time to form a light absorbing transient (LAT) which is the dominant pathway over other parallel reactions. The exact position of the donor radical in the complex is predicted by correlating the experimental Raman bands and theoretically obtained structural parameters and vibrational frequency. The adduct formed as a result of cross coupling reaction was identified as p-LAT, 2-[4-(hydroxylpyridylmethylene)cyclohexa-2,5dienyl]propan-2-ol. In case of benzoylthiophenes (BzTh), the effect of substitution of S atom on the excited state structure and reactivity towards various hydrogen donors viz. phenol and indole in different solvents are presented in Chapter 5. The difference in rate and mechanism of photoreaction for both the hydrogen donors are compared. For TPK the T1 state is of ππ* character and the T2 state is of nπ* character as is confirmed by flash photolysis and low temperature phosphorescence spectra in EPA matrix. The CO bond length for the triplet state species is more than that of ground state. In case of the ππ* triplet prominent structural changes in thienyl ring are observed and the phenyl ring remains much unaltered. The reaction of the triplet state species with phenol in two different solvents shows a relatively faster rate of reaction. If only ππ* triplet has been taking part in reaction, it might have resulted in slow reaction rate. Because the reaction rate is fairly high, It is concluded that not only ππ* triplet is involved in reaction but there is a contribution from the little higher energy T2 state having nπ* character. The reactivity trends towards hydrogen transfer reaction for three isomeric dithienyl ketones with respect to the position of heteroatoms in the ring are presented in Chapter 6. Energetically close lying (ππ* and nπ*) triplet states are observed to undergo state switching with the change in position of heteroatom in the ring and thus define the characteristics of the triplet state and plays important role in predicting the reactivity trend. Brief summary of the present investigation along with important possible extensions of the present work in described in Chapter 7.

No description available.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23030号 / 理博第4707号 / 新制||理||1675(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 谷村 吉隆, 教授 渡邊 一也, 教授 林 重彦 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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)

Surface- and tip-enhanced resonant Raman scattering (resonant SERS and TERS) by optical phonons in a monolayer of CdSe quantum dots (QDs) is demonstrated. The SERS enhancement was achieved by employing plasmonically active substrates consisting of gold arrays with varying nanocluster diameters prepared by electron-beam lithography. The magnitude of the SERS enhancement depends on the localized surface plasmon resonance (LSPR) energy, which is determined by the structural parameters. The LSPR positions as a function of nanocluster diameter were experimentally determined from spectroscopic micro-ellipsometry, and compared to numerical simulations showing good qualitative agreement. The monolayer of CdSe QDs was deposited by the Langmuir–Blodgett-based technique on the SERS substrates. By tuning the excitation energy close to the band gap of the CdSe QDs and to the LSPR energy, resonant SERS by longitudinal optical (LO) phonons of CdSe QDs was realized. A SERS enhancement factor of 2 × 10³ was achieved. This allowed the detection of higher order LO modes of CdSe QDs, evidencing the high crystalline quality of QDs. The dependence of LO phonon mode intensity on the size of Au nanoclusters reveals a resonant character, suggesting that the electromagnetic mechanism of the SERS enhancement is dominant. Finally, the resonant TERS spectrum from CdSe QDs was obtained using electrochemically etched gold tips providing an enhancement on the order of 10⁴. This is an important step towards the detection of the phonon spectrum from a single QD. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Surface- and tip-enhanced resonant Raman scattering (resonant SERS and TERS) by optical phonons in a monolayer of CdSe quantum dots (QDs) is demonstrated. The SERS enhancement was achieved by employing plasmonically active substrates consisting of gold arrays with varying nanocluster diameters prepared by electron-beam lithography. The magnitude of the SERS enhancement depends on the localized surface plasmon resonance (LSPR) energy, which is determined by the structural parameters. The LSPR positions as a function of nanocluster diameter were experimentally determined from spectroscopic micro-ellipsometry, and compared to numerical simulations showing good qualitative agreement. The monolayer of CdSe QDs was deposited by the Langmuir–Blodgett-based technique on the SERS substrates. By tuning the excitation energy close to the band gap of the CdSe QDs and to the LSPR energy, resonant SERS by longitudinal optical (LO) phonons of CdSe QDs was realized. A SERS enhancement factor of 2 × 10³ was achieved. This allowed the detection of higher order LO modes of CdSe QDs, evidencing the high crystalline quality of QDs. The dependence of LO phonon mode intensity on the size of Au nanoclusters reveals a resonant character, suggesting that the electromagnetic mechanism of the SERS enhancement is dominant. Finally, the resonant TERS spectrum from CdSe QDs was obtained using electrochemically etched gold tips providing an enhancement on the order of 10⁴. This is an important step towards the detection of the phonon spectrum from a single QD. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.