Since the development of batteries by Edison and Volta, energy storage has become an integral part of our technology. As the energy storage devices we manufacture, research and develop new energy storage systems has been standardized. This dissertation present three alternative approaches to developing energy storage devices which could completely change the paradigm by which we manufacture and use energy storage. First, I present my work in developing energy storage devices that can be directly integrated into the back of Silicon photovoltaics. This includes initial proof of concept of direct integration of porous Si supercapacitors followed by investigations into high rate faradaic chemical reactions with porous Si and coated porous Si. These faradaic reactions have the possibility of higher energy storage and power matching the performance of silicon photovoltaics. Second, I demonstrate the feasibility of using scrap metals to make high rate batteries that can be paired with photovoltaics by anodizing scrap steel and brass using simple manufacturing methods compatible with do it yourself manufacturing. Third, I will present my work in developing multifunctional structural supercapacitor composites. I demonstrate the ability to measure in-situ the electrochemical response of solid state electrolyte and supercapacitors. I follow this initial work up with the realization of a structural supercapacitor with the mechanical performance approaching that of commercial structural composites and energy storage performance approaching commercial supercapacitors.

<p> The next generation of rechargeable batteries must have significantly improved gravimetric and volumetric energy densities while maintaining a long cycle life and a low risk of catastrophic failure. Replacing the conventional graphite anode in a lithium ion battery with lithium foil increases the theoretical energy density of the battery by more than 40%. Furthermore, there is significant interest within the scientific community on new cathode chemistries, like sulfur and air, that presume the use of a lithium metal anode to achieve theoretical energy densities as high as 5217 W&dot;h/kg. However, lithium metal is highly unstable toward traditional liquid electrolytes like ethylene carbonate and dimethyl carbonate. The solid electrolyte interphase that forms between lithium metal and these liquid electrolytes is brittle which causes a highly irregular current distribution at the anode, resulting in the formation of lithium metal protrusions. Ionic current concentrates at these protrusions leading to the formation of lithium dendrites that propagate through the electrolyte as the battery is charged, causing it to fail by short-circuit. The rapid release of energy during this short-circuit event can result in catastrophic cell failure. </p><p> Polymer electrolytes are promising alternatives to traditional liquid electrolytes because they form a stable, elastomeric interface with lithium metal. Additionally, polymer electrolytes are significantly less flammable than their liquid electrolyte counterparts. The prototypical polymer electrolyte is poly(ethylene oxide). Unfortunately, when lithium anodes are used with a poly(ethylene oxide) electrolyte, lithium dendrites still form and cause premature battery failure. Theoretically, an electrolyte with a shear modulus twice that of lithium metal could eliminate the formation of lithium dendrites entirely. While a shear modulus of this magnitude is difficult to achieve with polymer electrolytes, we can greatly enhance the modulus of our electrolytes by covalently bonding the rubbery poly(ethylene oxide) to a glassy polystyrene chain. The block copolymer phase separates into a lamellar morphology yielding co-continuous nanoscale domains of poly(ethylene oxide), for ionic conduction, and polystyrene, for mechanical rigidity. On the macroscale, the electrolyte membrane is a tough free-standing film, while on the nanoscale, ions are transported through the liquid-like poly(ethylene oxide) domains. </p><p> Little is known about the formation of lithium dendrites from stiff polymer electrolyte membranes given the experimental challenges associated with imaging lithium metal. The objective of this dissertation is to strengthen our understanding of the influence of the electrolyte modulus on the formation and growth of lithium dendrites from lithium metal anodes. This understanding will help us design electrolytes that have the potential to more fully suppress the formation of dendrites yielding high energy density batteries that operate safely and have a long cycle life. </p><p> Synchrotron hard X-ray microtomography was used to non-destructively image the interior of lithium-polymer-lithium symmetric cells cycled to various stages of life. These experiments showed that in the early stages of lithium dendrite development, the bulk of the dendritic structure was inside of the lithium electrode. Furthermore, impurity particles were found at the base of the lithium dendrites. The portion of the lithium dendrite protruding into the electrolyte increased as the cell approached the end of life. This imaging technique allowed for the first glimpse at the portion of lithium dendrites that resides inside of the lithium electrode. </p><p> After finding a robust technique to study the formation and growth of lithium dendrites, a series of experiments were performed to elucidate the influence of the electrolyte&rsquo;s modulus on the formation of lithium dendrites. Typically, electrochemical cells using a polystyrene &ndash; block&not; &ndash; poly(ethylene oxide) copolymer electrolyte are operated at 90 &deg;C which is above the melting point of poly(ethylene oxide) and below the glass transition temperature of polystyrene. In these experiments, the formation of dendrites in cells operated at temperatures ranging from 90 &deg;C to 120 &deg;C were compared. The glass transition temperature of polystyrene (107 &deg;C) is included in this range resulting in a large change in electrolyte modulus over a relatively small temperature window. The X-ray microtomography experiments showed that as the polymer electrolyte shifted from a glassy state to a rubbery state, the portion of the lithium dendrite buried inside of the lithium metal electrode decreased. These images coupled with electrochemical characterization and rheological measurements shed light on the factors that influence dendrite growth through electrolytes with viscoelastic mechanical properties. (Abstract shortened by ProQuest.)</p>

<p> Carbon nanotubes (CNTs) are materials with significant potential applications due to their desirable mechanical and electronic properties, which can both vary based on their structure. Electronic applications for CNTs are still few and not widely available, mainly due to the difficulty in the control of fabrication. Carbon nanotubes are grown in batches, but despite many years of research from their first discovery in 1991, there are still many unanswered questions regarding how to control the structure of CNTs. This work attempts to bridge some of the gap between question and answer by focusing on the catalyst particle used in common CNT growth procedures. Ostwald ripening studies on iron nanoparticles are performed in an attempt to link catalyst morphology during growth and CNT chirality (the structure aspect of a nanotube that determines its electrical properties). These results suggest that inert gas dynamics play a critical role on the catalyst morphology during CNT growth. A novel method for CNT catalyst activation by substrate manipulation is presented. Results of this study build upon prior knowledge of the role of the chemistry of the substrate supporting CNT catalysts. By bombarding sapphire, a substrate known to not support CNT growth, with an argon ion beam, the substrate is transformed into an active CNT growth support by modifying both the structure and chemistry of the sapphire surface. Finally, catalyst formation is studied with transmission electron microscopy by depositing an iron gradient film in order to identify a potential critical catalyst size and morphology for CNT growth. A relationship between catalyst size and morphology has been identified that adds evidence to the hypothesis that a catalysts activity is determined by its size and ability to properly reduce.</p>

Nanomaterials have enabled significant breakthroughs in energy storage capabilities. In particular, the use of nanoscale components in lithium-sulfur and lithium-oxygen batteries have generated energy densities 2-3x greater than todayâs lithium-ion batteries. However, a major roadblock to commercially viable applications of nanomaterials is the ability to cost-effectively manufacture electrode-scale films while still maintaining precise control over the nanoscale morphology. In this regard, electrophoretic deposition (EPD) provides a promising tool for large-scale manufacture of nanomaterial systems using conventional liquid processing techniques. During EPD, the use of electrochemical equilibria to stabilize suspensions of nanomaterials eliminates the need for additives and provides a mechanism to control the placement of individual nanostructures on both 2D and 3D substrates through the application of an electric field. The viability of this process for large scale manufacture is demonstrated by integrating EPD electrode fabrication with nanomaterial synthesis processes on a benchtop roll-to-roll platform. Using this approach, lithium-sulfur and lithium-oxygen electrodes are fabricated that demonstrate enhanced mass-specific performance compared with identical material compositions assembled using conventional techniques. For lithium-oxygen batteries, the role that catalyst assembly plays in dictating the performance of the battery is elucidated and improved through EPD. Likewise, for lithium-sulfur batteries, the coating of an elemental sulfur layer is engineered in conjunction with an all-carbon EPD assembled electrode to produce one of highest capacity and most reversible lithium-sulfur cathodes ever reported. Overall, this thesis demonstrates the role of nanomaterial assembly in determining the energy storage performance of electrode-scale films and presents a method to control this assembly that is amenable to large-scale manufacture.

<p> Nanoparticles on a substrate have numerous applications in nanotechnology, from enhancements to solar cell efficiency to improvements in carbon nanotube growth. Producing nanoparticles in a cheap fashion with some control over size and spacing is difficult to do, but desired. This work presents a novel method for altering the radius and pitch distributions of nickel and gold nanoparticles in a scalable fashion. The introduction of alumina capping layers to thin nickel films during a pulsed laser-induced dewetting process has yielded reductions in the mean and standard deviation of radii and pitch for dewet nanoparticles. Carbon nanotube mats grown on these samples show a much thicker mat for the capped case. The same capping layers have produced an opposite effect of increased nanoparticle size and spacing during a solid state dewetting process of a gold film. These results also show a decrease in the magnitude of the effect as the capping layer thickness increases. Since the subject of research interest for using these nanoparticles has shifted towards producing ordered arrays with size and spacing control, the uncertainty in the values of these distributions needs to be quantified for any form of meaningful comparison to be made between fabrication methods. Presented here is a first step in the uncertainty analysis of such samples via synthetic images producing error distributions.</p>

Since the Nobel Prize awarded discovery that some polymers or “plastics” can be made electronically conducting, the scientific field of organic electronics has arisen. The use of conducting polymers in electronic devices is appealing, because the materials can be processed from a liquid phase, much like ordinary non-conducting plastics. This gives the opportunity to utilize printing technologies and manufacture electronics roll-to-roll on flexible substrates, ultimately at very low costs. Even more intriguing are the possibilities to achieve completely novel functionalities in combination with the inherent compatibility of these materials with biological species. Therefore, organic electronics can be merged with biology and medicine to create organic bioelectronics, i.e. organic electronic devices that interact with biological samples directly or are used for biological applications. This thesis aims at giving a background to the field of organic bioelectronics and focuses on how electrochemical devices may be utilized. An organic electronic wettability switch that can be used for lab-on-a-chip applications and control of cell growth as well as an electrochemical ion pump for cell communication and drug delivery are introduced. Furthermore, the underlying electrochemical structures that are the basis for the above mentioned devices, electrochemical display pixels etc. are discussed in detail. In summary, the work contributes to the understanding of electrochemical polymer electronics and, by presenting new bioelectronic inventions, builds a foundation for future projects and discoveries.

As electronic and optical devices shrink to the nanoscale, accurate methods for characterizing electromagnetic fields generated by sub-wavelength structures become increasingly important. Absorption in poly(methyl methacrylate) (PMMA) via 4th harmonic generation in metallic nanostructures is a way to characterize complex resonance modes. When exposed with a femptosecond Ti:sapphire oscillator, the damaged PMMA surrounding the nanoparticles can be imaged with an scanning electron microscope, creating an electric near-field intensity profile. This occurs without absorbing the fundamental frequency, and provides an accurate visualization of the resonant fields. Localized surface plasmonic near-fields generated by metallic nanorods have been mapped previously with this technique. In this document, nanorods and bowtie antennas are fabricated and the electric near-field intensity imaged with PMMA mapping. We then analyzed this data to determine more about the technique and about what drives the resonance of plasmonic nanoantennas.

An important aspect of engineering systems for use in extreme environments is understanding the performance of electronic components in radiation environments (e.g., space environments, nuclear reactors, particle accelerators). To accomplish this, experimental and computational modeling approaches are used to understand physical mechanisms that lead to system level failures. When experimentally investigating displacement damage, a common radiation effect, the most important parameter to measure is the particle fluence. An approach that offers benefits over traditional measurement techniques uses the degradation of current gain in silicon bipolar junction transistors as a direct metric for displacement damage in silicon. This thesis covers the bipolar device physics and particle/crystal interactions necessary to understand how displacement damage leads to gain degradation and describes how bipolar devices can be applied as displacement damage sensors to measure particle fluence. The use of bipolar junction transistors as displacement damage sensors in neutron irradiations is demonstrated at lower fluences than previously achieved and first-of-a-kind displacement damage sensor measurements for proton irradiations are provided. The non-ionizing energy loss (NIEL) of each particle is shown to adequately correlate the two particle types, neutrons and protons, across five orders of magnitude of particle fluence using three bipolar junction transistors (2N1486, 2N2484, 2N2222).

Colloidal semiconductor nanocrystals have become one of the most versatile systems for studying the fundamental properties of nanoscale materials and their applications. The ternary I-III-VI2 semiconductors hold particular promise for applications due to their flexible stoichiometry, low toxicity constituent elements, and range of desirable band gap energies (0.5 â 3.5 eV). Furthermore, I-III-VI2 nanocrystals can be isolated in metastable, anisotropic crystal structures not seen in the bulk. This structural anisotropy can be exploited to produce nanostructures with asymmetric morphology and electronic structure, which can enhance their performance in optoelectronic applications. In this dissertation, metastable, anisotropic crystal structures of I-III-VI2 materials are synthesized and their optoelectronic properties are investigated. CuInS2 has been widely explored for use in solar energy capture due to its band gap near the visible spectral region. Here, a direct synthesis to luminescent CuInS2 nanocrystals with the anisotropic wurtzite phase is developed and the mechanism of their formation is identified. A combined experimental and theoretical approach is then used to identify the radiative defect responsible for the luminescence observed. Furthermore, hybrid wurtzite CuInS2-Pt nanocrystals are prepared and their photoelectrical properties characterized to determine the efficacy of this system in photocatalytic applications. The knowledge obtained from the CuInS2 system is then applied to additional I-III-VI2 materials, CuFeS2 and AgFeS2. Wurtzite CuFeS2 is prepared using three distinct synthetic routes and the resultant nanocrystals are compared to each other and the In-containing analogues. Anisotropic, orthorhombic nanocrystals of AgFeS2 are also synthesized and characterized for the first time. The presence of Fe in both these systems leads to the observation of broad multimodal absorbance features at low energy, which can be utilized in thermoelectric and photothermal applications. Experimental measurements and density functional theory calculations indicate that this unique absorbance originates from changes in the composition of the nanocrystals.

Researchers discovered the existence of non-coding RNA while unraveling the secrets of the human genome. Non-coding RNA molecules are never translated into proteins, yet they are highly abundant and serve critical functions within all cells. Imbalances in one class of regulatory non-coding RNA, known as microRNA (miRNA), lead to diseases such as cancer and cardiovascular disease. MiRNA inhibition is a potent therapeutic strategy because single miRNAs can regulate hundreds of different disease-associated genes. Peptide nucleic acids (PNA) are excellent miRNA inhibitors, yet they have no innate ability to reach miRNA targets in the body. This worksâ central hypothesis is that therapeutic anti-miRNA activity can be improved by engineering nanoparticles to increase PNA blood circulation half-life, cellular uptake, and targeted delivery to the cytoplasm of diseased cells. In this thesis, two highly tunable biomaterials (porous silicon and âsmartâ polymers) are combined to form composite nanoparticles that improve the PNA therapeutic delivery. These nanocomposites are shown to be non-toxic, increase PNA blood-circulation half-life from <1 min to 70 min, and improve PNA delivery to its site of action in target cells. This thesis demonstrates how nanotechnology can aid the clinical translation of a promising new class of therapeutics.