Corantes orgânicos são uma importante classe de poluentes ambientais, sendo que a natureza da interação de tais espécies com ácidos húmicos determina seu comportamento e destino ambiental. Este trabalho investiga abordagens diferentes para a síntese de nanopartículas de ouro-ácido húmico (NPs Au/AH), o desempenho destas partículas como sensores para a determinação de traço de corantes orgânicos e da natureza da sua interação química com ácidos húmicos por técnicas de espectroscopia Raman intensificada por superfície (surface-enhanced Raman scattering, SERS). As nanopartículas de ouro foram obtidas de forma direta em meio aquoso. A síntese foi realizada na presença de ácido húmico em vários valores de pH e na presença e na ausência de citrato de sódio. Nesta abordagem, o ácido húmico apresenta propósitos diferentes. Na síntese das nanopartículas, ele serve como agente redutor e para a estabilização da superfície, impedindo a coalescência das nanopartículas em meio aquoso. Considerando-se a utilização de nanopartículas como substratos SERS-ativos, o ácido húmico serve como uma fase de extração associada com a plataforma SERS, favorecendo a interação dos corantes orgânicos com as nanopartículas metálicas. Esta abordagem pode ser utilizada para aumentar a sensibilidade e seletividade da técnica SERS e evitar a interferência de outras espécies em solução. É também importante mencionar que o ácido húmico dá origem a um espectro Raman muito fraco e, portanto, não interfere de forma significativa na detecção espectroscópica das espécies de interesse. As NPs Au/AH obtidas foram caracterizadas por espectroscopia eletrônica, microscopia eletrônica de varredura e SERS, a fim de estabelecer uma correlação entre a sua morfologia, plasmon superficial, e seu uso potencial como substratos SERS. As NPs Au/AH foram utilizadas como substratos SERS no estudo de corantes têxteis aniônicos e catiônicos. Os espectros Raman, nestes casos, foram atribuídos ao complexo formado pelo ácido húmico e cada uma das espécies de interesse. Os resultados obtidos revelaram uma dependência significativa entre as propriedades morfológicas e eletrônicas das NPs Au/AH com o procedimento de síntese, e também uma interação preferencial entre as nanopartículas e os corantes catiônicos. Conclui-se que as NPs Au/AH podem proporcionar uma abordagem útil para a caracterização espectroscópica de espécies relevantes para o ambiente e sua interação química com os ácidos húmicos, através do uso da espectroscopia Raman intensificada pela superfície / Organic dyes are an important class on environmental pollutants, and the nature of the interaction of such species with humic acid strongly determines their environmental behavior and fate. This work investigates different approaches for the synthesis of humic acid-gold nanoparticles (HA-AuNP), the performance of these particles as sensors for trace determination of organic dyes and the nature of their chemical interaction with humic acids by surface-enhanced Raman scattering (SERS). The Au nanoparticles were obtained by direct fabrication in aqueous media.The synthesis were carried out in the presence of humic acid at various pH values, and in the presence and absence of sodium citrate. In this approach, humic acid serves different purposes. In the synthesis of the nanoparticles, they serve as reducing agent and for surface stabilization, preventing coalescence of the nanoparticles in aqueous media. Considering the use of the nanoparticles as SERSactive substrates, the humic acid serves as an extraction phase associated with the SERS platform, favoring the interaction of the organic dyes with the metallic nanoparticles. This approach can be used to enhance the sensitivity and selectivity of SERS technique and avoid interference from other species in solution. It is also important to mention that the humic acid gives rise to a very weak Raman spectrum, and therefore does not interfere significantly in the spectroscopic detection of the species of interest. The obtained HA-AuNPs were characterized by electronic spectroscopy, scanning electron microscopy and SERS, in order to establish a correlation between their morphology, surface plasmon, and their potential use as SERS platforms. The HA-AuNPs have been applied as SERS substrates for anionic and cationic textile dyes. The recorded Raman spectra are, in these cases, assigned to the complex formed by the humic acid and each of the species of interest. The obtained results revealed a significant dependence on the morphological and electronic properties of the HA-AuNPs with the synthesis procedure, and also a strong interaction between the nanoparticles and cationic dies. We conclude that HA-AuNP may provide a valuable approach for the spectroscopic characterization of environmentally relevant species and their chemical interaction with humic acids, through the use of surface enhanced Raman spectroscopy

In the pursuit of economical and rapid fabrication solutions on the micro and nano scale, polymer replication has proven itself to be a formidable technique, which despite zealous development by the research community, remains full of promise. This thesis explores the potential of elastomers in what is a distinctly multidisciplinary field. The focus is on developing innovative fabrication solutions for planar photonic devices and for nanoscale devices in general. Innovations are derived from treatments of master structures, imprintable substrates and device applications. Major contributions made by this work include fully replicated planar integrated optical devices, nanoscale applications for photolithographic standing wave corrugations (SWC), and a biologically templated, optical fiber based, surface-enhanced Raman scattering (SERS) sensor. The planar devices take the form of dielectric rib waveguides which for the first time, have been integrated with long-period gratings by replication. The heretofore unemployed SWC is used to demonstrate two innovations. The first is a novel demonstration of elastomeric sidewall photolithographic mask, which exploits the capacity of elastomers to cast undercut structures. The second demonstrates that the corrugations themselves in the absence of elastomers, can be employed as shadow masks in a directional flux to produce vertical stacks of straight lines and circles of nanowires and nanoribbons. The thesis then closes by conceptually combining the preceding demonstrations of waveguides and nanostructures. An optical fiber endface is em ployed for the first time as a substrate for patterning by replication, wherein the pattern is a nanostructure derived from a biological template. This replicated nanostructure is used to impart a SERS capability to the optical fiber, demonstrating an ultra-sensitive, integrated photonic device realized at great economy of both time and money, with very real potential for mass fabrication.

Metal nanostructures exhibit a wide variety of interesting physical and chemical properties, which can be tailored by altering their size, morphology, composition, and environment. Gold and silver nanostructures have received considerable attention for many decades because of their widespread use in applications such as catalysis, photonics, electronics, optoelectronics, information storage, chemical and biological sensing, surface plasmon resonance and surface-enhanced Raman scattering (SERS) detection. This thesis is composed of three main parts about the synthesis, characterization and SERS applications of shape-controlled and surface modified noble metal nanoparticles. The first part is related to a simple synthesis of shape controlled solid gold, hollow gold, silver, gold-silver core-shell, hollow gold-silver double-shell nanoparticles by applying aqueous solution chemistry. Nanoparticles obtained were used for SERS detection of dye molecules like brilliant cresyl blue (BCB) and crystal violet (CV) in aqueous system. v The second part involves the synthesis of surface modified silver nanoparticles for the detection of dopamine (DA) molecules. Determination of a dopamine molecule attached to a iron-nitrilotriaceticacid modified silver (Ag-Fe(NTA)) nanoparticles by using surface-enhanced resonance Raman scattering (SERRS) was achieved. The Ag-Fe (NTA) substrate provided reproducibility and excellent sensitivity. Experimental results showed that DA was detected quickly and accurately without any pretreatment in nM levels with excellent discrimination against ascorbic acid (AA) (which was among the lowest value reported in direct SERS detection of DA). In the third part, a lanthanide series ion (Eu3+) containing silver nanoparticle was prepared for constructing a molecular recognition SERS substrate for the first time. The procedure reported herein, provides a simple way of achieving reproducible and sensitive SERS spectroscopy for organophosphates (OPP) detection. The sensing of the target species was confirmed by the appearance of an intense SERS signal of the methyl phosphonic acid (MPA), a model compound for nonvolatile organophosphate nerve agents, which bound to the surface of the Ag-Eu3+ nanostructure. The simplicity and low cost of the overall process makes this procedure a potential candidate for analytical control processes of nerve agents.

Raman spectroscopy offers much better spectral selectivity but its usage has been limited by its poor sensitivity. The discovery of surface-enhanced Raman scattering (SERS) effect, which results in increased sensitivities of up to 108-fold for some compounds, has eliminated this drawback. A new SERS active substrate was developed in this study. Silver nanoparticle-doped polyvinyl alcohol (PVA) coated SERS substrate prepared through chemical and electrochemical reduction of silver particles dispersed in the polymer matrix. Performances of the substrates were evaluated with some biologically important compounds. The specific detection of DNA has gained significance in recent years since increasingly DNA sequences of different organisms are being assigned. Such sequence knowledge can be employed for identification of the genes of microorganisms or diseases. In this study, specific proteasome gene sequences were detected both label free spectrophotometric detection and SERS detection. In label free spectrophotometic detection, proteasome gene probe and complementary target gene sequence were attached to the gold nanoparticles separately. Then, the target and probe oligonucleotide-modified gold solutions were mixed for hybridization and the shift in the surface plasmon absorption band of gold nanoparticles were followed. SERS detection of specific nucleic acid sequences are mainly based on hybridization of DNA targets to complementary probe sequences, which are labelled with SERS active dyes. In this study, to show correlation between circulating proteasome levels and disease state we suggest a Raman spectroscopic technique that uses SERGen probes. This novel approach deals with specific detection of elevated or decreased levels of proteasome genes&rsquo / transcription in patients as an alternative to available enzyme activity measurement methods. First, SERGen probes were prepared using SERS active labels and specific proteasome gene sequences. Then DNA targets to complementary SERGen probe sequences were hybridized and SERS active label peak was followed.

The understanding of molecular effects in nanoscale environments is becoming increasingly relevant for various emerging fields. These include spectroscopy for molecular identification as well as in finding molecules for energy harvesting. Theoretical quantum chemistry has been increasingly useful to address these phenomena to yield an understanding of these effects. In the first part of this dissertation, we study the chemical effect of surface-enhanced Raman scattering (SERS). We use quantum chemistry simulations to study the metal-molecule interactions present in these systems. We find that the excitations that provide a chemical enhancement contain a mixed contribution from the metal and the molecule. Moreover, using atomistic studies we propose an additional source of enhancement, where a transition metal dopant surface could provide an additional enhancement. We also develop methods to study the electrostatic effects of molecules in metallic environments. We study the importance of image-charge effects, as well as field-bias to molecules interacting with perfect conductors. The atomistic modeling and the electrostatic approximation enable us to study the effects of the metal interacting with the molecule in a complementary fashion, which provides a better understanding of the complex effects present in SERS. In the second part of this dissertation, we present the Harvard Clean Energy project, a high-throughput approach for a large-scale computational screening and design of organic photovoltaic materials. We create molecular libraries to search for candidates structures and use quantum chemistry, machine learning and cheminformatics methods to characterize these systems and find structure-property relations. The scale of this study requires an equally large computational resource. We rely on distributed volunteer computing to obtain these properties. In the third part of this dissertation we present our work related to the acceleration of electronic structure methods using graphics processing units. This hardware represents a change of paradigm with respect to the typical CPU device architectures. We accelerate the resolution-of-the-identity Moller-Plesset second-order perturbation theory algorithm using graphics cards. We also provide detailed tools to address memory and single-precision issues that these cards often present.

No description available.

The effective diagnosis of leukemia subtypes requires the detection of multiple cell surface markers. Current methods of detection use mostly fluorophores, which are limited by their large spectral bandwidths, photobleaching, and incompatibility with histological stains used for morphological assessments. Antibody-conjugated Surface enhanced Raman scattering (SERS) nanoparticles is an alternative tool that overcomes these limitations. A current drawback of SERS is the lack of available tools to analyze the bioconjugation of antibodies to nanoparticles following EDC/sulfo-NHS cross-linking, which produces inconsistent results and determines the efficacy of SERS probe targeting. This study uses the flow cytometry approach to evaluate SERS particles by incorporating FITC and DyLight650 secondary antibodies. Flow cytometry was also used to assess targeting of particles to markers on LY10 cells and CLL cells and to detect SERS signals by inserting a 710 BP 10nm FWHM filter specific for MGITC.

The effective diagnosis of leukemia subtypes requires the detection of multiple cell surface markers. Current methods of detection use mostly fluorophores, which are limited by their large spectral bandwidths, photobleaching, and incompatibility with histological stains used for morphological assessments. Antibody-conjugated Surface enhanced Raman scattering (SERS) nanoparticles is an alternative tool that overcomes these limitations. A current drawback of SERS is the lack of available tools to analyze the bioconjugation of antibodies to nanoparticles following EDC/sulfo-NHS cross-linking, which produces inconsistent results and determines the efficacy of SERS probe targeting. This study uses the flow cytometry approach to evaluate SERS particles by incorporating FITC and DyLight650 secondary antibodies. Flow cytometry was also used to assess targeting of particles to markers on LY10 cells and CLL cells and to detect SERS signals by inserting a 710 BP 10nm FWHM filter specific for MGITC.

Many biological processes, pathogens, and pharmaceuticals act upon, cellular membranes. Accordingly, cell membrane mimics are attractive targets for biosensing, with research, pathology, and pharmacology applications. Lipid bilayers represent a versatile sensor functionalization platform providing antifouling properties, and many receptor integration options, uniquely including transmembrane proteins. Bilayer-coated sensors enable the kinetic characterization of membrane/analyte interactions. Addressed theoretically and experimentally is the self-assembly of model membranes on plasmonic sensors. Two categories of plasmonic sensors are studied in two parts. Part I aims to deposit raft-forming bilayers on planar nanoaperture arrays suitable for multiplexing and device integration. By vesicle fusion, planar bilayers are self-assembled on thiol-acid modified flame-annealed gold without the need for specific lipid head-group requirements. Identification of coexisting lipid phases is accomplished by AFM imaging and force spectroscopy mapping. These methods are successfully extended to metallic, plasmon-active nanohole arrays, nanoslit arrays and annular aperture arrays, with coexisting phases observed among the holes. Vis-NIR transmission spectra of the arrays are measured before and after deposition, indicating bilayer detection. Finally, the extraction of membrane proteins from cell cultures and incorporation into model supported bilayers is demonstrated. These natural membrane proteins potentially act as lipid-bound surface receptors. Part II aims to encapsulate in model lipid bilayers, metallic nanoparticles, which are used as probes in surface enhanced Raman spectroscopy. Three strategies of encapsulating particles, and incorporating Raman-active dyes are demonstrated, each using a different dye: malachite green, rhodamine-PE, and Tryptophan. Dye incorporation is verified by SERS and the bilayer is visualized and measured by TEM, with support from DLS and UV-Vis spectroscopy. In both parts, lipid-coated sensors are successfully fabricated and characterized. These results represent important and novel solutions to the functionalization of plasmonic surfaces with biologically relevant cell membrane mimics.

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...