Plasmon-mediated Energy Conversion in Metal Nanoparticle-doped Hybrid Nanomaterials

Climate change and population growth demand long-term solutions for clean water and energy. Plasmon-active nanomaterials offer a promising route towards improved energetics for efficient chemical separation and light harvesting schemes. Two material platforms featuring highly absorptive plasmonic gold nanoparticles (AuNPs) are advanced herein to maximize photon conversion into thermal or electronic energy. Optical extinction, attributable to diffraction-induced internal reflection, was enhanced up to 1.5-fold in three-dimensional polymer films containing AuNPs at interparticle separations approaching the resonant wavelength. Comprehensive methods developed to characterize heat dissipation following plasmonic absorption was extended beyond conventional optical and heat transfer descriptions, where good agreement was obtained between measured and estimated thermal profiles for AuNP-polymer dispersions. Concurrently, in situ reduction of AuNPs on two-dimensional semiconducting tungsten disulfide (WS2) addressed two current material limitations for efficient light harvesting: low monolayer content and lack of optoelectronic tunability. Order-of-magnitude increases in WS2 monolayer content, enhanced broadband optical extinction, and energetic electron injection were probed using a combination of spectroscopic techniques and continuum electromagnetic descriptions. Together, engineering these plasmon-mediated hybrid nanomaterials to facilitate local exchange of optical, thermal, and electronic energy supports design and implementation into several emerging sustainable water and energy applications

The effect of geometry and surface morphology on the optical properties of metal-dielectric systems

xiii, 133 p. ; ill. (some col.) A print copy of this title is available through the UO Libraries. Search the library catalog for the location and call number.We analyze the effect of geometry and surface morphology on the optical properties of metal-dielectric systems. Using both analytical and numerical modeling, we study how surface curvature affects the propagation of surface plasmon polaritons (SPPs) along a metal-dielectric interface. We provide an intuitive explanation for how the curvature causes the phase front to distort, causing the SPPs to radiate their energy away from the metal-dielectric interface. We quantify the propagation efficiency as functions of the radius of curvature, and show that it depends nonmonotonically on the bend radius. We also show how the surface morphology influences the transmittance and the reflectance of light from disordered metal-dielectric nanocomposite films. The films consist of semicontinuous silver films of various surface coverage that are chemically deposited onto glass substrates. They exhibit a large and broadband reflection asymmetry in the visible spectral range. In order to investigate how the surface morphology affects the asymmetry, we anneal the samples at various temperatures to induce changes in the morphology, and observe changes in the reflection spectra. Our study indicates that the surface roughness and the metal surface coverage are the key geometric parameters affecting the reflection spectra, and reveals that the large asymmetry is due to the different surface roughness light encounters when incident from different side of the film. Additionally, we analyze how thin metal and dielectric layers affect the optical properties of metal-dielectric systems. Using the concept of dispersion engineering, we show that a metal-dielectric-metal microsphere--a metal sphere coated with a thin dielectric shell, followed by a metal shell--support a band of surface plasmon resonances (SPRs) with nearly identical frequencies. A large number of modes belonging to this band can be excited simultaneously by a plane wave, and hence enhancing the absorption cross-section. We also find that the enhanced absorption is accompanied by a plasmon assisted transparency due to an avoided crossing of dominant SPR bands. We demonstrate numerically that both the enhanced absorption and the plasmon assisted transparency are tunable over the entire visible range. We also present an experimental study of light scattering from silica spheres coated with thin semicontinuous silver shells, and attempt to describe their optical response using a modified scaling theory. This dissertation includes previously published co-authored materials.Adviser: Miriam Deutsc

Reflective Coloration from Structural Plasmonic to Disordered Polarizonic

The generation of pigment‐free colors by nanostructures and subwavelength patterns has evolved in the last decade and outperformed the conventional paints in terms of durability, recyclability, and environmental friendliness. The recent progress in the field of structural coloration, particularly reflective coloration, offering a full‐color gamut, has realized high‐resolution printing, not attainable by the pigment paints. Herein, an overview of the various systems able to offer reflective coloration for a variety of optical applications with static and dynamic responses is presented. Specifically, an emphasis is given to recent works of the article's authors on the cooperative action of the disordered particles and dipoles that can generate specular reflective colors. In addition, further developments of reflective color nanosystems are discussed. In the first section, an overview of the recent progress in the field of plasmonic reflective structural coloration is provided. The second part of the article deals with the authors’ latest findings with respect to polarizonic color generation and its implementation in various areas ranging from environmental detection and biosensing to colored solar perfect absorbers. The report is wrapped up with an outlook and summary

Interfacial Chemistry at the Surfaces of Engineered and Natural Nanomaterials

The central theme of my research seeks to understand the interfacial chemistry of engineered and natural nanomaterials. Manipulation of the surface chemistry of nanostructures is an important tool in tuning their properties for various applications, given that these properties are greatly influenced by the high abundance of defects and dangling bonds on the surface. When an ad-atom, molecule, or periodic solid interacts with the surface of a material, the interaction can be classified as either physisorptive or chemisorptive. Herein, I present three disparate areas of research, which explore interfacial interactions at nanostructured surfaces. Emphasis on the chemisorption and physisorption on engineered nanomaterials is provided in the first and third projects. The first project illustrates that graphene oxide is partially reduced when used as a substrate for the atomic layer deposition (ALD) of amorphous HfOv2. Understanding the interfacial chemistry between graphene oxide and HfOv2 provides new knowledge on designing graphene-based field effect transistors and semiconductor heterostructures for catalysis. In the third project, a novel ex situ doping technique for modulating the metal—insulator transition (TvMIT) of VOv2 has been developed. Initial deposition of the molecular boron precursor 2-allyl-4,4,5,5-tetramethyl-1,3,2-dioxaborolane on the surface of VOv2 nanowires allows for the subsequent incorporation of B atoms in the tetrahedral interstitial sites of VOv2 upon rapid thermal annealing, which results in the stabilization of the rutile phase in greater proximity to room temperature. The diffusive annealing process can be tuned to program the TvMIT of VOv2 for applications such as thermochromic fenestration and the design of memory devices. The second project is focused on natural nanomaterials, wherein the interactions of Ag-Au bimetallic alloy nanoparticles in aquatic media have been investigated. The growth of these alloy nanoparticles is mediated by dissolved organic matter (DOMs) such as fulvic and humic acids, with or without photoillumination from natural sunlight. In the absence of natural sunlight, Ag- and Au-ions are first complexed with Lewis basic groups (carbonyls, carboxyls, thiols) on the DOM; subsequently, alloy formation is facilitated by galvanic replacement. Under visible light irradiation, Ag, Au, and Ag-Au bimetallic alloy nanocrystals are grown via a plasmon-induced mechanism. The study of the interfacial chemistry at the surfaces of these nanomaterials paves way for the rational design of various architectures which can be used for various applications such as catalysis, environmental remediation, and thermochromic fenestration

Design and characterization of surface-enhanced Raman scattering nanoparticles as spectroscopic probes for biological imaging

The development of highly sensitive and chemically specific optical probes has only been marginally realized to date. Surface-enhanced Raman spectroscopy (SERS) is an emerging technique that offers both chemical sensitivity and specificity. This dissertation examines the rational design, synthesis, characterization, and application of SERS-based optical probes designed for biological imaging and chemical sensing experiments. Special attention is paid to both the probe stability and the stability of its chemical signature. Our results indicate that significant care is required to successfully manufacture and use probes that are intended for biological investigation. An inner-filter effect between the extinction of light propagating through a matrix of probes, modeled as a colloidal solution, and surface-enhancement requires precise selection of the laser excitation wavelength and the optical properties of the probe. Metallic nanostructures consisting of noble metals such as gold and silver were investigated as probes because they provide intense surface-enhancement effects and the ability to tune their optical properties as desired. In particular, gold nanostructures are highly desirable because of their biocompatibility and inertness. Surface chemistry modification and characterization of metallic nanostructures were investigated to further our understanding of the requirements needed for preparing highly stable probes. Light scattering simulations were performed to predict the influence of certain geometries, materials, and illumination modalities on the probe's optical properties. This dissertation discusses studies that have investigated the long-term stability nanoprobes, the kinetics of surface ligand exchange, nanoprobe imaging in cellular systems, the properties of reflective substrates, and electron microscopy characterization of metallic nanostructures

Energy Transport and Conversion in Semiconductor Nanocrystal Solids

Solids constructed with single and multicomponent nanocrystal represent an exciting new form of condensed matter, as they can potentially capture not only the quantum features of the individual building blocks but also novel collective properties that arise from coupling of nanocrystal components. In this thesis, measurement and interpretation of temperature-dependent thermopower in semiconductor nanocrystal solids are used to elucidate the Fermi energy level and the density of state distribution. The physical understating of temperature dependence of thermopower is, in turn, utilized to develop a powerful tool with which to monitor doping in PbTe nanocrystal solids with different concentrations of Ag2Te nanocrystal dopants. Combining the temperature-dependent thermopower and electrical conductivity measurements provides a unique electronic spectroscopy tool with which to reveal the carrier distribution and dynamics in semiconductor nanocrystal solids

Growth Control and Study of Ultrathin Silver Films for Energy-Saving Coatings

Les couches minces fonctionnelles jouent un rôle prépondérant dans la plupart des secteurs industriels actuels. Ils peuvent aussi bien être une partie intégrante d’un dispositif (cellule solaire, diode électroluminescente, photodétecteur, Laser, capteur thermosolaire, cellule thermoélectrique et bien d’autres), ou bien y amener de nouvelles fonctionnalités (revêtements résistants à la corrosion, l’usure et l’érosion, revêtement antireflet). La montée rapide de cette science est à l’origine d’un développement tout aussi rapide des techniques de dépôt et de synthèse de couches minces. Aujourd’hui, la croissance d’une couche mince avec une précision au nanomètre peut être effectuée par un simple couchage à lame au sein d’un laboratoire de recherche aussi bien que par des techniques d’évaporation dans des chambres à vide industrielles à grande échelle. La facilité d’accès aux techniques de dépôt ainsi que l’envergure des applications scientifiques et technologiques font des couches minces une solution potentielle pour beaucoup d’enjeux technologiques et de sociétés. Certainement, un des plus grands enjeux actuels est le problème de la consommation énergétique à travers le monde et qui peut seulement qu’empirer si aucune solution convenable n’est adoptée. Une approche afin de contrer cette consommation énergétique est de modifier les vitrages architecturaux dans les bâtiments commerciaux et résidentiels en revêtant une fenêtre avec une couche réfléchissante la chaleur afin de réduire de façon drastique les charges de chauffages et de refroidissement. Le recouvrement des fenêtres par de fines couches optiques se fait par des chambres de dépôts montées en ligne, souvent jumelées avec la production du verre flotté. Bien que le maintien et l’installation de ces systèmes de dépôt est d’un grand intérêt et pose de nombreux défis, le travail de recherche présenté dans cette thèse se penche sur le mécanisme de croissance des couches minces d’argent déposé en phase vapeur par assistance plasma pour les filtres à basse émissivité. Le projet est mené en collaboration avec Guardian Industries dans le cadre des vitrages à économies d’énergie. Les couches minces d’argent possèdent des propriétés physiques changeantes dépendamment de leur mécanisme de croissance ainsi que de leur épaisseur. Elles ont tendance à croître en îlots en dessous d’une épaisseur critique et convergent vers une couche réfléchissante la radiation infrarouges. Cette épaisseur critique se nomme le seuil de percolation et dépend fortement de la couche sous-jacente.----------Abstract Functional thin films play a key role in almost all industries today. They can either form an integral part of a device (as heat-reflectors, solar cells, light-emitting diodes, photodetectors, lasers, thermal collectors, thermoelectric cells and many more) or bring additional coating functionalities (such as corrosion, wear and erosion resistance and antireflective coating). The rapid development of thin film science has led to the equally fast growth of thin film deposition techniques. The coating of a surface with precisions in the nanometers can be conducted by simple blade coating in a laboratory setting or large-scale vacuum chambers in heavy industrial environments. Moreover, the rapid rise of thin film science can also be attributed to progresses in characterization techniques. The accessibility of thin film deposition techniques and their wide-ranging scientific and technological applications make thin film science appear as an attractive answer to many industrial and societal challenges. Probably the greatest of these challenges is the energy consumption problem present in large parts of the world and which can only amplify in time if no suitable solutions are adopted. One approach to decrease this energy consumption is to alter glazing units in commercial and residential buildings by coating one side of the window pane with a heat-reflecting layer in order to drastically reduce heating and cooling loads. These glass panes are manufactured by large, in-line vacuum coaters that can be found on the glass production site. Even though the configuration and maintenance of such systems is of great interest and brings important challenges, the research work conducted throughout this thesis is focused in the growth mechanism of very thin silver films inside a low-emissivity stack deposited by plasma-assisted physical vapour deposition, with collaboration with Guardian Industries in the context of energy-saving glazing. Silver thin films have unique varying physical properties attributed to their distinct growth mechanism. They tend to progressively grow as light-absorbing agglomerated clusters below a certain thickness to infrared heat-reflective, continuous films. The main challenge in the context of silver film growth is the inability to obtain heat-reflecting properties below a certain thickness. This thickness is determined by the surface properties of the underlying layer, limiting the possible options available for silver film coating

21st Century Nanostructured Materials

Nanostructured materials (NMs) are attracting interest as low-dimensional materials in the high-tech era of the 21st century. Recently, nanomaterials have experienced breakthroughs in synthesis and industrial and biomedical applications. This book presents recent achievements related to NMs such as graphene, carbon nanotubes, plasmonic materials, metal nanowires, metal oxides, nanoparticles, metamaterials, nanofibers, and nanocomposites, along with their physical and chemical aspects. Additionally, the book discusses the potential uses of these nanomaterials in photodetectors, transistors, quantum technology, chemical sensors, energy storage, silk fibroin, composites, drug delivery, tissue engineering, and sustainable agriculture and environmental applications

Nanotechnology: An Untapped Resource for Food Packaging

Food commodities are packaged and hygienically transported to protect and preserve them from any un-acceptable alteration in quality, before reaching the end-consumer. Food packaging continues to evolve along-with the innovations in material science and technology, as well as in light of consumer's demand. Presently, the modern consumers of competitive economies demands for food with natural quality, assured safety, minimal processing, extended shelf-life and ready-to-eat concept. Innovative packaging systems, not only ascertains transit preservation and effective distribution, but also facilitates communication at the consumer levels. The technological advances in the domain of food packaging in twenty-first century are mainly chaired by nanotechnology, the science of nano-materials. Nanotechnology manipulates and creates nanometer scale materials, of commercial and scientific relevance. Introduction of nanotechnology in food packaging sector has significantly addressed the food quality, safety and stability concerns. Besides, nanotechnology based packaging intimate's consumers about the real time quality of food product. Additionally, nanotechnology has been explored for controlled release of preservatives/antimicrobials, extending the product shelf life within the package. The promising reports for nanotechnology interventions in food packaging have established this as an independent priority research area. Nanoparticles based food packages offer improved barrier and mechanical properties, along with food preservation and have gained welcoming response from market and end users. In contrary, recent advances and up-liftment in this area have raised various ethical, environmental and safety concerns. Policies and regulation regarding nanoparticles incorporation in food packaging are being reviewed. This review presents the existing knowledge, recent advances, concerns and future applications of nanotechnology in food packaging sector

Integration of micro nano and bio technologies with layer -by -layer self -assembly

In the past decade, layer-by-layer (LbL) nanoassembly has been used as a tool for immobilization and surface modification of materials with applications in biology and physical sciences. Often, in such applications, LbL assembly is integrated with various techniques to form functional surface coatings and immobilized matrices. In this work, integration of LbL with microfabrication and microfluidics, and tissue engineering are explored. In an effort to integrate microfabrication with LbL nanoassembly, microchannels were fabricated using soft-lithography and the surface of these channels was used for the immobilization of materials using LbL and laminar flow patterning. Synthesis of poly(dimethyldiallyl ammonium chloride)/poly(styrene sulfonate) and poly(dimethyldiallyl ammonium chloride)/bovine serum albumin microstrips is demonstrated with the laminar flow microfluidic reactor. Resulting micropatterns are 8-10 μm wide, separated with few micron gaps. The width of these microstrips as well as their position in the microchannel is controlled by varying the flow rate, time of interaction and concentration of the individual components, which is verified by numerical simulation. Spatially resolved pH sensitivity was observed by modifying the surface of the channel with a pH sensitive dye. In order to investigate the integration of LbL assembly with tissue engineering, glass substrates were coated with nanoparticle/polyelectrolyte layers, and two different cell types were used to test the applicability of these coatings for the surface modification of medical implants. Titanium dioxide (TiO 2), silicon dioxide, halloysite and montmorillonite nanoparticles were assembled with oppositely charged polyelectrolytes. In-vitro cytotoxicity tests of the nanoparticle substrates on human dermal firbroblasts (HDFs) showed that the nanoparticle surfaces do not have toxic effects on the cells. HDFs retained their phenotype on the nanoparticle coatings, by synthesizing type-I collagen. These cells also showed active proliferation on the nanoparticle substrates. Cells attached on TiO2 substrates showed faster rate of spreading compared with the other types of nanoparticle coatings. Mesenchymal stem cells (MSCs) were used as a second cell type to support and elaborate on the results obtained with the HDFs. Increasing surface roughness was observed with increasing number of layers of TiO2. Tests with a higher number of layers of TiO2, showed an increased attachment, proliferation and faster spreading of the MSCs on a larger number of layers of TiO2