In this dissertation, nanostructured materials are examined for electrochemical energy storage devices with high energy and power densities. While previous research on nanostructured materials for energy storage has mostly focused on the effects of reduced dimensionality on diffusion distances, the research presented here demonstrates how nanostructuring can lead to new charge storage mechanisms. The first part of the dissertation describes the low-potential reactivity of V₂O₅ aerogels and how nanostructuring leads to significantly improved reversibility of the charge storage process. The second part details the rapid kinetic response of T-Nb₂O₅ and in addition, how the combination of nanostructure and appropriate crystalline structure leads to a mechanism called intercalation pseudocapacitance. The third part examines how a 2D nanosheet morphology changes both the redox potentials and kinetics of lithium ion storage in TiO₂. These investigations underscore how reducing a material's dimensions and morphology leads to unique electrochemical behavior beyond simple decreasing of diffusion distances, and how such structures could lead to ultimately higher energy and power density electrochemical energy storage devices.

This thesis involves synthesis, derivatization and biomedical applications of mesoporous silica nanoparticles (MSNs) based delivery systems. Chapter 1 introduces the background of MSNs including the advantages of MSNs, modification on MSNs for multifunctionality; formation mechanism, a typical synthesis condition for MCM-41 and following characterizaitons. In chapter 2 & 3, the synthesis and application of target moiety functionalized MSNs for gene therapy in vitro and in vivo are introduced. Chapters 4, & 5 introduce the relevant studies of utilizing MSN based delivery system for the treatment of infectious disease, from a pharmacokinetic study of moxifloxacin delivered by MSNs via different routes, to the enhanced efficacy of MSN based treatment by materials optimizations via inhalation administration route. Chapter 6 discusses the study of a general synthesis method for pore enlargement in various types of MSNs. In Chapter 7, the design and preparation of a thin film consist of ultra large pore-sized mesoporous silica spheres and polymer template macropores is illustrated. Overall, these chapters demonstrate the successful engineering of mesoporous silica nanoparticles and materials optimization and their enhanced performance in biological applications from in vivo tumor shrinkage by gene delivery to antibiotics delivery for enhanced bacterial killing efficacy in mouse model.

Since the 20th century, deep space missions flown by NASA have been critical for exploration of the solar system and have provided a wealth of fundamental scientific knowledge. Electrical power for these missions is supplied by radioisotope thermoelectric generators (RTG’s) which produce electricity from a radioactive heat source. This technology has a history of reliable power generation and has flown on missions such as Pioneer, Cassini, New Horizons, and, most notably, Voyager which has been in continuous operation for over 45 years. However, device efficiency is limited due to the poor heat-to-electricity conversion of thermoelectric materials, which is quantified by the dimensionless figure of merit, ZT. Therefore, a longstanding goal in the field is that of developing higher ZT materials to improve RTG specific power.Lanthanum telluride (La3-xTe4) has been identified as a prime candidate for next generation RTG’s owing to its ZT of 1.1 at 1275K. However, poor machinability and susceptibility to oxidation are current bottlenecks for device fabrication. The overarching goal of the work presented in this dissertation is to investigate novel processing strategies for La3-xTe4 to facilitate device fabrication and expand pathways for fundamental study of its thermoelectric performance. The first study (Chapter 2) investigates the La3-xTe4 oxidation mechanism to establish the process by which thermoelectric properties degrade and inform oxide mitigation strategies for synthesis and device fabrication. As-synthesized La3-xTe4 powder contains an amorphous surface oxide at room temperature. At elevated temperature, oxidation progresses with the formation of mobile elemental Te, Te-rich lanthanum telluride phases, and crystalline La2O2Te and glassy La2O3 as the bulk material reacts with oxygen. The oxide phases are non-passivating and thermodynamically stable, requiring multifaceted oxide mitigation strategies. The second study (Chapter 3) demonstrates synthesis of La3-xTe4 films by electrophoretic deposition (EPD) using tetrahydrofuran (THF) as solvent. Uniform La3-xTe4 films 10-15 �m thick with a green density of ~65% are deposited on both planar and non-planar substrates. The versatility and scalability of EPD expands thermoelectric device fabrication capabilities and enables study of La3-xTe4-metal composite geometries that are not attainable with current bulk processing methods. The third study (Chapter 4) utilizes ultrafast high-temperature sintering (UHS) to densify La3-xTe4 films and bulk pellets in as little as 10 seconds. Sample densities >90% can be achieved with well-defined grains on the order of 1-10 �m in size. Rapid densification is proposed to result from the extreme heating rate of UHS which maintains a high driving force for densification and quickly activates diffusion mechanisms that attend fast pore elimination and grain growth. Pressure-less sintering of La3-xTe4 via UHS is a significant achievement and demonstrates that complex pressure sintering techniques are not required for densification. The fourth study (Chapter 5) investigates the thermoelectric properties of UHS La3-xTe4. Bulk UHS La3-xTe4 pellets achieve a peak ZT of 1.06 at 1273K with comparable performance to optimized La3-xTe4 prepared by established methods. Initial power factor measurements up to 573K suggest that the performance of UHS La3-xTe4 EPD films is similar to bulk UHS La3-xTe4, but more accurate thin film measurement techniques are necessary to fully characterize their ZT. Achievement of high performance La3-xTe4 via UHS greatly expands and simplifies processing of the material without sacrificing thermoelectric performance. The results of these four studies significantly enhance processing and future device fabrication of La3-xTe4 for high-temperature thermoelectric applications. The detailed understanding of the La3-xTe4 oxidation mechanism informs oxide mitigation strategies for device design. The novel combination of EPD and UHS forms a simple, high-throughput processing scheme that expands possible device architectures while maintaining established thermoelectric performance. Finally, EPD and UHS can be applied to other thermoelectric materials, thus providing unique and adaptable processing enhancements for the broader thermoelectric community.

The development of the lithium-ion battery has played an indispensable role in shaping the landscape of portable electronics and emerging electric vehicle industry. While its development has been recognized with a Nobel Prize in 2019, battery technology is far from mature. Since its conception, the battery research landscape has only widened with the rise of electric vehicles and wearable devices, each having a different set of requirements. Therefore, the “next-generation” in the context of this dissertation focuses on two different aspects of the battery field. The first aspect considers the development of high energy density batteries and more specifically the move away from capacity-limited intercalation chemistries. Chapter 3 delves into the interfacial challenges posed by lithium metal anodes during the Li plating/stripping reactions while Chapter 4 visits the complex reaction pathways in FeS2 conversion cathodes to understand charge product formation and identify capacity loss mechanisms. While both Li and FeS2 are commercialized as primary battery electrode materials and have the potential to provide high energy density rechargeable batteries, safety and performance issues have limited their use to primary systems. Ultimately, better understanding of the interfaces and reaction pathways can fuel the design of solutions to improve the performance and safety of these systems. The latter part of the dissertation focuses on the other type of “next-generation” battery, namely, that of miniaturized power sources for IoT technologies. With the vision of an on-chip battery integrated into a device, new materials and processes must be developed to integrate the same semiconductor processing techniques used to make the device to make the batteries as well. Chapter 5 details the development of a conformal, photopatternable separator and the integration of the separator onto various battery architectures. The ability to spatially photopattern a porous separator onto three dimensional architectures provides a path towards high power on-chip batteries. In summary this dissertation aims to provide perspective in the different directions and progress towards the next generation of rechargeable batteries. From better fundamental insights on complex electrochemical pathways to application-driven materials design and development, this dissertation highlights a few of the challenges, discoveries, and advancements of a much larger research landscape of “next-generation” batteries.

Yb₁₄MnSb₁₁ is a promising thermoelectric material for high temperature applications with values of the non-dimensional figure of merit ZT peaking at 1.4 above 1200 K. Yb₁₄MnSb₁₁ exhibits low lattice thermal conductivity values and a p-type semimetallic behavior. This compound is a member of a large family of Zintl phases with a "14-1-11" A₁₄MPn₁₁ stoichiometry (Pn = As, Sb, Bi; A = Ca, La, Sr, Yb, Eu; M = Mn, Al, Cd, Ga, In, Nb, Zn). There is significant interest in investigating how substitutions on any of the atomic sites impact the band gap, lattice thermal conductivity and charge carrier concentration and mobility.

High energy ball milling is shown here to be a convenient method of synthesis to prepare Yb₁₄MnSb₁₁ and solid solution systems derived from this compound by substitution of elements. Here compositions in the Yb₁₄Mn_1-xAl_xSb_11-yBi_y, Yb₁₄MnSb_11-yAs_y, Yb_14-xCa_xMnSb₁₁, Yb_14-xLa_xMnSb₁₁ and Yb_14-xNa_xAlSb₁₁ systems are considered. Characterization of the synthesized compositions was done by X-ray diffraction, electron microprobe. High temperature measurements of the electrical and thermal transport properties were carried out up to 1275 K. The experimental results on solid solution samples are compared to that of pure Yb₁₄MnSb₁₁ samples prepared by the same synthesis technique. A single parabolic band degenerate Fermi statistical model was used to estimate various properties such as effective mass. Calculated lattice thermal conductivity in solid solutions was also compared to various models. Though some increase in ZT was calculated below 900K, none of the derivatives studied were calculated to have a averge ZT significantly higher than Yb₁₄MnSb₁₁.

This thesis involves synthesis, derivatization and biomedical applications of mesoporous silica nanopartilces (MSNs) and Fe3O4@SiO2 core/shell nanoparticles. Chapter 1 introduces the development of MSNs including the mesopores formation mechanism, synthesis conditions and their capability to act as stimuli responsive drug delivery platforms. In chapter 2, the synthesis optimization of different kinds of particles and their surface derivatization are introduced. Chapter 3 & 4 give specific examples of successful optimization and in vitro and in vivo application of MSNs enabled with pH-sensitive nanovalves and disulfide snap-tops for delivering the antibiotic moxifloxacin. It is shown that a high release capacity is necessary to reach a high efficacy ratio, compared with free drug. Chapter 5 discusses the uptake and release capacities of Fe3O4@SiO2 core/shell nanoparticles when modified with a pH-sensitive nanovalves, and its thermally cargo release behavior when surrounding temperature increases or an oscillating magnetic field is applied. In Chapter 6, successful distribution of Fe3O4@SiO2 core/shell nanoparticles in biofilms and on-command release of cargo inside biofilms are shown. Overall, these chapters demonstrate the ability of modifying both the outer surface and interior of MSNs, and their capability to act as a biocompatible controlled release platform that is more effective than equivalent amount of free drug.

Recently, ionogels, pseudo-solid-state electrolytes consisting of an ionic liquid electrolyte confined in a mesoporous inorganic matrix, have attracted interest for use as a solid electrolyte in Li+ batteries because of their high ionic conductivity, stability, and solution processability. Here-in, we report adapting the ionogel synthesis route through spin coat processing to obtain thin films. Films down to 600 nanometers were obtained that maintained the properties of the bulk ionogel. By using spin coating to achieve thin films, the ionogel can be processed directly on electrode surfaces as a sol. Thin film ionogels processed on lithium iron phosphate cathodes achieved capacities of 125 mAh g-1 at charge/discharge rates of 2 hours stably over 150 cycles, which corresponds to the highest reported power densities for silica ionogels. The sol-gel process was modified through the addition of a photoacid generator to add UV patternability. The UV crosslinked gel showed comparable properties and cycling to the spin-coated ionogel.

While having high achievable capacities, there have been few studies into deciphering the electrode-ionogel interface. The second section will review our work directed at understanding the interface for solution-processable ionogel electrolytes with various electrode materials. Using XPS, Raman spectroscopy, and electrochemical testing to probe the electrode-ionogel interface, surface reactions were identified as being the source of the interfacial barriers. Our results indicate that the acidity of the sol led to reduction of the transition metal and breakdown of the sol-vent and organic acid, forming an organic surface layer, which impedes Li+ transport. By adjusting the silica gelation route these interfacial reactions can be avoided, leading to stable cycling.

The high ionic conductivity of ionogels shown in Chapter 3, in comparison to other solid electrolytes, and its solution processability opens the possibility for incorporation into multidimensional cell designs. The last portion of my dissertation will explore using the ionogel electrolyte to form a 2.5D cell consisting of a 3D LiFePO4 cathode and 2D Li metal anode. The electrolyte is shown to penetrate uniformly throughout the 3D electrode array and into each individual post. High areal capacities (1.1 mAh cm-2) were achieved at 1 mA cm-2 with a stable capacity retention at 0.5 mA cm-2 over 50 cycles. The 2.5D cell is comparable or better than current 3D batteries in literature.

Increased demand for battery power due to technological advancement requires more efficient, safer battery systems to be developed. Ionogels, which confine liquid electrolyte interspersed in a nanoporous inorganic matrix, have generated interest due to their ionic conductivity, stability, and capability of providing a solid structure while allowing liquid behavior at the nanoscale. Herein, the results for impedance and microstructure data are reported for ionogels that were processed with varying volumetric amounts of ionic liquid electrolyte (ILE). The gels were created using a standard gelation method, and their conductivities were on the same order of magnitude as the neat ILE. While their room-temperature conductivity was half of the neat ILE at 0.282 mS/cm, the conductivity closed the gap to 70 percent of the ILE at 10.6 mS/cm at 80 �C. The activation energy of the most conductive sample, 0.25 eV, is not much higher than the neat ILE at 0.2 eV. The microstructure data obtained using BET and BJH was in agreement with the reference for a simpler ionogel, but the large pore size of the tested samples was too large to obtain an accurate average pore size. The quantity adsorbed for the current work was also less than a third of the reference, which also indicates its larger pore structure.

Lithium ion batteries as a power source are the most commonly used in the electronic devices and electric vehicles (EV) for grid-energy storage. Anode materials with high specific capacity for lithium ion batteries have been developed in recent years. SnO2 has also been considered as a promising candidate to serve as the anode material for lithium ion batteries due to its high theoretical capacity. But the volume expansion effect results in the degradation of active material and limits the complete realization of theoretical capacity. Graphene has recently become one of the most promising matrices for high-capacity anode materials, due to good electrical conductivity, outstanding mechanical flexibility and high theoretical capacity. In this paper, the nanocomposites of SnO2 and graphene as anode materials for lithium ion batteries were facilely synthesized through hydrothermal method. The design of SnO2/graphene nanocomposites could significantly improve the electrochemical performance by increasing electrical conductivity and buffering volume expansion. It is noteworthy that the quality and structural design of graphene is very important to improve the electrochemical performance for SnO2-based materials. Therefore, on the one hand, a new method to prepare highly dispersible edge-selectively oxidized graphene was reported in this paper. On the other hand, we designed a novel three-dimensional graphene named flower-like graphene tube. Furthermore, characterization and electrochemical performance of these materials were also studied by various technologies.

Invar metal matrix composites, incorporating amorphous silica ranging from 0-50vol%, were produced with the intention of processing the composites using additive manufacturing. These composites were aimed to have a lower density and CTE than that of pure Invar. Densities ranging from 7.44 g/cm3 (92% of theoretical) to 4.79 g/cm3 (93% of theoretical) were attained for pure Invar and the 50/50 composite respectively when sintered at 1250oC for 5 hours. These high temperatures were necessary to sinter the silica-rich regions of the composite however at temperatures exceeding 1200oC, the phase separation of iron silicate was observed on the surface of 90/10 vol% samples. X-ray diffraction also found the amorphous silica would devitrify to cristobalite and tridymite during sintering. These crystalline forms of silica have a larger CTE than Invar, which resulted in a CTE increase with the addition of silica in the composites.