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Currently, silicon-based electronic devices dominate our technology landscape, significantly enhancing human life and realizing various technological possibilities. However, we are transitioning into an era where carbon-based organic electronic devices are gaining prominence. This shift was enabled by the groundbreaking discovery that polymers, previously regarded as insulators, can exhibit electrical conductivity. Since then, research has advanced significantly in the development of electronic devices utilizing conductive polymers and organic semiconductors. The semiconductor and conductive properties of these organic materials are heavily influenced by the degree of doping. While research has primarily focused on doping methods using various dopants, challenges related to stability and uniformity have emerged. To address these issues, conjugated polyelectrolytes (CPEs) with self-doping capabilities have been developed. These materials incorporate functional groups directly into the polymer structure, eliminating the need for external dopants. This advancement has enhanced their performance as both active layers and interface layers in organic devices, and their potential applications as biosensors are particularly promising. Despite progress in the field, a comprehensive understanding of complex donor-acceptor (D-A) type CPEs remains limited. This dissertation explores the design and application of D-A type self-doping CPEs. We systematically synthesized various D-A CPEs with different electron acceptor groups and investigated their optical and electronical properties. Our analysis revealed that these properties are predominantly influenced by the molecular structure, with experimental results aligning well with theoretical calculations. A notable finding was the significant variation in self-doping levels between two CPEs with similar energy levels. Simulation-based analysis of the protonation step's Gibbs free energy provided insights into this discrepancy, suggesting that such factors should be considered during the synthesis of self-doped CPEs. Furthermore, we evaluated the performance of these CPEs in organic electrochemical transistors (OECTs), a leading biosensor technology, to assess their practical applications.For OECTs, CPEs are considered ideal materials due to their high electrical and ionic conductivity. However, their efficiency can be limited by issues related to device performance. This study addresses these limitations through precise control of the molecular weight of CPE-BT-K. It was observed that charged CPEs with either excessively low or high molecular weights tend to form poorly ordered structures. This structural irregularity adversely impacts the transistor's performance by affecting the material's charge transfer behavior. Our analysis of CPE-OECT performance demonstrates that CPE-BT-K, with an optimized molecular weight, achieves the highest performance reported for OECTs to date.Beyond OECTs, there has been increasing interest in infrared organic photodetectors due to their broad applicability. However, high dark current remains a significant challenge for these devices. To tackle this issue, we explored the use of CPE-Ph as the interface layer in conjunction with cross-linking techniques. We found that the CPE-Ph thin film, when cross-linked, significantly reduces dark current. This improvement is attributed to effective energy level tuning and the insulating properties provided by GOPS localized on the surface. The resulting organic photodetector, with its ultra-low dark current, showcased exceptional performance and revealed that the activation energy of the dark current closely aligns with the band gap. This breakthrough addresses a major limitation of organic photodetectors, paving the way for enhanced device performance.

The semiconductor industry is growing at a rapid rate. As Moore’s Law drives thedemand for smaller and more efficient microelectronic devices, the need for advancedlithographic techniques and materials becomes paramount. In order to meet this demand,lithography has advanced from using deep ultraviolet (DUV) to extreme ultraviolet (EUV)light for patterning chemically amplified resists (CARs). Yet, overcoming nanoscaleheterogeneities due to material stochastics remains a limiting factor in achieving highprecision patterning. Sequence-defined, bio-inspired polymers, such as polypeptoids, can beemployed to address the stochastic limitations inherent to synthetic polymers. This workexplores polypeptoids as a materials platform for understanding the effects of sequence onpatterning. Seven 10-mer polypeptoid sequences with varying architectures and terminalgroups were synthesized and purified. The materials were characterized using analytical highperformance liquid chromatography–mass spectrometry (HPLC–MS), differential scanningcalorimeter (DSC), and UV-Vis spectrophotometry. Preliminary patterning results provideinsight on the impact of monomer species and sequence on feature sizes, therebydemonstrating the potential of these materials in the semiconductor industry.

Transition metal oxide (TMO) semiconductors are abundant and inexpensive materials with remarkable electrical and chemical properties suitable for solar energy conversion. Solar power has the potential to deliver energy that is clean, renewable, and sustainable provided that it can be harvested efficiently. Semiconducting TMOs are extensively developed and utilized for this purpose, particularly in the construction of energy-harvesting solar devices. This research focuses on the thin film fabrication and utilization of TMO semiconductors namely, Cu2O, BiVO4, ZnO, TiO2, SnO2, and NiOx for photoelectrochemical (PEC) water splitting and photovoltaic (PV) devices. Chapter I provides a brief introduction to the chemical and electrical properties of semiconducting TMOs and their most common methods of preparation, as well as their broad applications in solar energy conversion.In Chapter II, the fabrication of a direct tandem Cu2O/Mo:BiVO4 PEC solar device is discussed. Here, we present a fabrication scheme that is facile and scalable, using electrochemical deposition for Cu2O and electrophoretic deposition for Mo:BiVO4. We prepared nanoparticles of BiVO4 and successfully doped the material with Mo to improve its electrical conductivity. Thermal annealing converts the Mo:BiVO4 into a semi-transparent material, allowing light to reach the Cu2O layer and partially protect it from corrosion. We show that Cu2O/Mo:BiVO4 on fluorine-doped tin oxide (FTO) substrate works as a photoanode for water oxidation, capable of evolving oxygen at a Faraday efficiency of 92% and achieving a photocurrent of 1.45 mA cm^-2 at 1.23 V vs. RHE under simulated sunlight conditions. The FTO/Cu2O/Mo:BiVO4 exhibited about nine times higher incident photon-to-light conversion efficiency (IPCE) value at 400 nm than the FTO/Mo:BiVO4 film. The FTO/Cu2O/Mo:BiVO4 device is still functional after 15 hours of continuous operation. Using surface photovoltage spectroscopy (SPS) and open circuit potential (OCP) measurements, we show that the Cu2O and Mo:BiVO4 form a p-n heterojunction and work as tandem under applied bias conditions. Chapter III emphasizes the use of SPS for the construction of a Cu2O-based PV cell. Here, we fabricated Cu2O by electrochemical deposition onto FTO, Mo and Ni conductive substrates. We show that Ni gives the highest surface photovoltage for Cu2O among all the substrates, providing up to 1.7 V at 285.75 mW-cm^-2 light intensity using a 405 nm light emitting diode (LED ) lamp. We also electrochemically deposited a ZnO overlayer to extract the electrons from Cu2O, which resulted in about 30% increase in the surface photovoltage. ZnO likely formed a deep depletion layer and removed the defect states in Cu2O as previously seen in the literature, causing the increase in photovoltage. Using SPS, we determined that the 1500-s deposition time for ZnO is optimal. Pre-made silver nanowires and conductive Ag paint were added to complete the final PV device structure. The completed device achieved an OCP value of ~16 mV under simulated 1 sun illumination, however, it still suffers from low conductivity issues. Improving the lateral conductivity in the ZnO electron transport layer (ETL ) layer and selecting metal front contact will be key to achieving a better-performing Cu2O-based PV device.Chapter IV focuses on the thin film fabrication of TiO2, SnO2, and NiOx selective transport layers and their application in the FTO/Cu2O/Mo:BiVO4 PEC device. Using combined spin coating and solution combustion synthesis methods, we optimized the thin film fabrication of these selective contacts at 250 oC. We monitored the reaction progress using infrared spectroscopy, and the conductivity and rectifying behavior of the films were evaluated by PEC measurements. Using SPS, we show that NiOx promotes hole extraction from Cu2O to the surface and remains the same after adding SnO2. Although all elements were detected, we could not confirm the presence of each selective transport layer in the sandwich FTO/Cu2O/NiOx/SnO2/Mo:BiVO4 FTO/TiO2/Cu2O/NiOx/SnO2/Mo:BiVO4 structures due to the thickness and low concentration of these materials in the device. Here, we report 25% and 50% photocurrent enhancements in the FTO/Cu2O/NiOx/SnO2/Mo:BiVO4 and FTO/TiO2/Cu2O/NiOx/SnO2/Mo:BiVO4 sandwich film structures, respectively at 1.23 V vs. reversible hydrogen electrode (RHE ) versus the PEC device structure without any charge selective contact.

In situ transmission electron microscopy enables the study of nanoscale solution state events such as battery electrode deposition and molecular self-assembly. Recent improvements in electron microscope detectors have vastly improved the spatial resolution (pixel count) and temporal resolution (frame rate) of microscopy videos, which has resulted in large, information-rich datasets. The central mission of my PhD has been to use image analysis techniques and algorithms to translate improvements in microscopy signal collection to improvements in materials insight. Towards this, I have developed several novel image analysis algorithms built on deterministic image science methods which extract quantitative information from raw microscopy datasets. I developed an algorithm to quantify materials dynamics captured with in situ microscopy videos and applied this algorithm to quantify the spatiotemporal dynamics of dissipative self-assembly processes (Chapters 1-2). I applied image science to track the presence of an unstable phase captured in time-resolved cryogenic transmission electron microscopy (Chapter 3). And finally, I applied a variety of custom image analysis algorithms to quantify amphiphilic block copolymer morphological transitions such as vesical-to-bilayer transitions, droplet-to-bilayer transitions, and droplet dissolution dynamics (Chapters 4-5). In each case, I demonstrate the power of deterministic image analysis methods for converting raw microscopy datasets into interpretable materials science results.

Acenes and N-heteroacenes have been synthesized and studied for over a century because of their fundamentally interesting materials properties and promise for device applications. Within this context, our laboratory has previously synthesized nitrogen-containing tetrabenzo[de,hi,op,st]pentacenes via an aza-Diels–Alder reaction-based approach, and herein, we expand our methodology to obtain substituted, expanded, functionalized, and dimeric tetrabenzoacenes. Overall, our study adds to the limited number of tetrabenzoacene derivatives reported to date and may open further opportunities for these materials in organic optoelectronics applications.

Condensed matter physics today stands at the forefront of exploring unusual emergent material properties and exotic phenomena. At UC Berkeley, my research has been driven by a fundamental question: Can we engineer fundamental properties of novel organic quantum materials to address real-world problems? I believe the answer to this question lies at the intersection of various fundamental disciplines. In chemistry, my focus has been developing on-surface reactions that enable the assembly of unprecedented chemical structures, giving access to exotic materials with uncommon electronic structures. These synthetic innovations have been translated into developing organic quantum materials with unique properties in condensed matter physics.In Part 1 of this dissertation, we start with the tight-binding approximation and density functional theory to illustrate the theoretical principles for constructing organic quantum materials (Chapter 1). We then focus on the carbon material system under investigation, examining the quantum confinement effect in Chapter 2, followed by an introduction to the scanning tunneling microscope that we used in this research.In Part 2, we present several successful examples of constructing novel organic quantum materials based on the theoretical and instrumental background from Part 1. To this end, we have developed the low-dimensional N-heterocyclic carbene lattices, utilizing the frontier orbital to engineer one-dimensional to two-dimensional low-workfunction materials (Chapter 4). Additionally, we have employed orbital engineering concepts to construct a Dirac nodal-line semimetal in a dual-square covalent-organic framework (Chapter 5). The final example in Chapter 6 discusses the spontaneous symmetry-breaking Jahn-Teller distortion effect in an unconventional π-conjugated polymer.

The rate of discovery of novel materials has accelerated in recent decades, and the slow step in realizing these materials has long been in synthesis design. Improving our understanding of the sequence of phases formed during reaction, from precursors to target, and how that sequence is affected by the conditions for synthesis would provide researchers with a means to predict the conditions required to reach new desired outcomes. Because of the vast dimensionality in synthesis design space, such a prediction task is suitable for data-driven methods: combining machine learning with real experiment and computational modeling to both generate and test hypotheses that rationalize synthesis pathways. Driving hypothesis generation from data requires a substantial source for historical syntheses; in this thesis, we leverage the availability of synthesis procedures and characterized outcomes from the scientific literature. Text mining of the scientific literature, using natural language processing as well as manual methods, has been extensively employed in materials science over the past decade, with applications ranging from systematic literature review to generating datasets of material properties to studies in synthesis science. Yet, in the sphere of text mining for synthesis science little attention has been paid to distinguishing syntheses by their outcome (e.g., final phase purity, particle morphology). The availability of such experimental outcome information and subsequent analysis would provide researchers with useful data to develop models that hypothesize the effects of specific synthesis features on desired outcomes. By tapping into the available synthesis literature, this recipe-outcome-paired data would be ample. Progress in automatic text mining of the scientific literature is persistent, particularly with the recent rise of generative large language models. However, there still remain pitfalls in the reliable extraction of materials synthesis recipes and linking to outcome, making manual curation of such datastets more attractive in some cases. This thesis highlights both (1) advances made in automatic methods for acquiring inorganic synthesis procedures and outcomes from the literature as well as (2) data-driven insights into synthesis science that are gleaned from synthesis datasets extracted manually from the literature in combination with direct experiment and first principles computations. For (1), we developed robust named entity recognition models for the extraction of synthesis procedure graphs as well as morphological outcomes for nanoparticle synthesis. To demonstrate the application of these methods, we constructed a large-scale text-mined dataset of gold nanoparticle synthesis recipes, which are plentiful in the literature and thus represent a rich source for data-driven synthesis design. Importantly, we include extraction of their morphological outcomes; the inclusion of both input synthesis conditions and the corresponding output makes this dataset valuable for data-driven synthesis science efforts. For task (2), we focus on the extraction of phase purity outcomes for oxide materials. Impurity phases, in the form of remnant precursors or intermediate phases, offer clues into the synthesis pathway traversed in a reaction. BiFeO3 is an important multiferroic material that is frequently synthesized in the literature and has a strong tendency to coincide with competitive impurity phases when synthesized. We thus pivot our focus in chemistry space to BiFeO3 for this second task. For this system, we demonstrate how text-mined datasets of such recipes and outcomes can be used to inform real experiments and computational modeling that rationalize synthesis pathways. In this thesis, we endeavor to improve the role of text mining, automated and manual, in data-driven synthesis science. Our attention on extracting synthesis outcomes in addition to their corresponding procedures helps advance this subfield of materials science and paves the way for future efforts to accelerate both progress in our understanding of synthesis mechanisms for existing materials and the discovery of new compounds.

Transition metal dichalcogenides (TMDs) constitute a class of materials wherein transition metals coordinated by bridging chalcogenides form two-dimensional layers that stack via van der Waals (vdW) interactions along the crystallographic c axis. This lamellar structure enables a diverse range of species, including transition metals, to be intercalated into these vdW interfaces. With open-shell intercalants, local magnetic moments can be introduced into the lattice, thereby inducing long-range magnetic order. The versatility of potential intercalants and host lattices has long made this class of materials an appealing choice as tunable platforms for investigating the interplay among composition, structure, and magnetism. More recently, there has been a growing appreciation for the influence of defects and domain structures in these intercalated compounds on exchange interactions and magnetic correlations. This recognition has led to the acknowledgment of complex magnetic phase spaces, highlighting the intricate interplay between structural features and magnetic properties.We design a spin glass with strong spin frustration induced by magnetic disorder by exploiting the distinctive structure of Fe intercalated ZrSe2, where Fe(II) centers are shown to occupy both octahedral and tetrahedral interstitial sites and to distribute between ZrSe2 layers without long-range structural order. Notably, we observe behavior consistent with a magnetically frustrated and multidegenerate ground state in these FexZrSe2 single crystals, which persists above room temperature. Moreover, this magnetic frustration leads to a robust and tunable exchange bias up to 250 K. These results not only offer important insights into the effects of magnetic disorder and frustration in magnetic materials generally, but also highlight as design strategy the idea that a large exchange bias can arise from an inhomogeneous microscopic environment without discernible long-range magnetic order. In addition, these results show that intercalated TMDs like FexZrSe2 hold potential for spintronic technologies that can achieve room temperature applications.Since Fe intercalated ZrSe2 is semiconducting which provides us a knob to tune its physical and chemical properties electrochemically inserting a foreign species (Li+ ions) into their interlayer spacing. We discover substantial enhancement of light transmission and electrical conductivity in thin (∼30 nm) Fe intercalated ZrSe2 nanosheets after Li intercalation due to changes in band structure and the injection of large amounts of free carriers. We also capture the first in situ optical observations of Li intercalation FexZrSe2, shedding light on the dynamics of the intercalation process. The high reversibility of the intercalation process might be attributed to the enhanced stability of the structure induced by the intercalated Fe ion between the host lattice layers. The enhancement of electron transport upon the Li intercalation in the materials lays down a robust groundwork for electrostatic control over spin polarization. We also briefly explore the effect of semiconducting spin glass FexZrSe2 on generating and manipulating spin current in heavy metal, which highlights the potential application of the materials in spintronic technology.Together, we study the interplay among composition, structure, and magnetism of Fe intercalated ZrSe2, explore the impact of electrostatic and electrochemical strategies to manipulate the properties of FexZrSe2, lay down the robust cornerstone for the application of FexZrSe2 in spintronic technology, and inspire the research interest in expanding the knowledge of the magnetic ion intercalated TMDs to diverse 2D heterostructures and twist moiré patterns.

Molecular weaving is the realization of a macroscopic principle on a molecular level. Whereas the concept of interlocking, as observed in chains and fences, can be translated to the molecular level by designing molecularly interlocked molecules (MIMs), the technique of weaving single threads into a pattern is not easily recreated. This can be attributed to the necessity for the formation of extended structures with a high degree of order as weaving fundamentally involves an ordered assembly of single strands into various patterns. Reticular chemistry is uniquely qualified to solve this problem as it involves the design and synthesis of multidimensional, crystalline, and porous extended framework structures by connecting different building blocks through strong bonds. By combining strategies from both MIMs and reticular chemistry, molecular weaving was first realized in 2016 in covalent organic frameworks (COFs) by the Yaghi lab. Because MIMs have been implemented as molecular machines and investigated for their mechanical behavior, the question of the effect of molecular weaving on the overall properties of the material remained unanswered.This dissertation focuses on elucidating the effect of molecularly woven nanocrystals as additives in polymer matrices. The challenge of capturing how molecular weaving influences a material’s properties lies within the small size of the synthesized crystals. As many mechanical engineering techniques are designed to analyze macroscopic samples, the nanometer-sized woven crystals aren’t easily characterized. By utilizing them as fillers in polymers, we are able to study the effect of molecular weaving on a macroscopic scale.Chapter I provides a general introduction into reticular chemistry and its potential to address important problems related to climate change and realize complex concepts such as molecular weaving. I will be discussing the history of reticular chemistry and its materials, followed by a clear definition of this field of chemistry. The chapter concludes with an outlook into the present and future of reticular materials in applications such as molecular weaving.Chapter II introduces the core concept of molecularly woven nanoparticles as additives in different polymers. By leveraging molecular weaving and the inherent porosity of the COF, polymers are able to interact with the pore system by threading through the framework. This leads to the formation of so-called polymer-COF junctions that are able to template polymer entanglement and provide additional pathways for energy dissipation during stress.Chapter III expands upon polymer-COF composites by investigating a molecularly interlocked framework and its effect on the mechanical behavior of the composites. By comparing the behavior of the interlocked COF as an additive both with the woven COF and the demetalated version of itself, more insight into the interactions between polymer matrix and mechanically bonded framework structure can be gained.Chapter IV delves into the scaling of woven COFs and their translation into polymer-COF composites with polycarbonate (PC) and polydimethylsiloxane (PDMS). Additionally, the scaling of a series of mechanically bonded COFs is discussed, and a new pathway to accessing metal-free woven structures is presented.Chapter V discusses the expansion of molecular weaving from three-dimensional (3D) to two-dimensional (2D) COFs. By controlling the angles of the linkers between the tetrahedral weaving nodes, the formation of 2D woven structures can be achieved from generally 3D-directing starting materials.Chapter VI covers an educational research study that introduced a group of high school students to cutting-edge research through an accessible, low-tech synthesis of a water harvesting MOF. Additionally, the participants learned about concepts such as water scarcity and the importance of finding alternate ways to access clean drinking water.Chapter VII serves as a conclusion to the topic of woven COFs and their ability to enhance the mechanical behavior of polymer-COF composites. This chapter also serves as a perspective for future investigations in this field of research.

Energy storage technology is one of the most important technological pillars for achieving reduced carbon emissions to decelerate global warming, together with clean energy generation technologies such as solar energy. The development of a low-cost, safe, and high-energy-density energy storage technology is essential for accelerating the electrification of transportation, as well as the widespread adoption of grid energy storage systems.The search for advanced energy storage technologies has increasingly focused on all-solid-state batteries (ASSBs) due to their potential for improved safety and higher energy density. Inorganic lithium superionic conductors are crucial to this emerging technology, offering fast ion transport that rival those of liquid-based systems. However, the challenge lies in finding materials that not only provide superionic conductivity but also meet all practical requirements, underscoring the need for the discovery of novel conductors. The development and identification of new functional materials could significantly transform energy storage technology, particularly as the limitations of current leading technologies are often tied to basic material properties.Understanding the structure-property relationship is at the core of the field of materials science. By understanding how the bulk crystal structure, various defects and microstructures, or local structures within disordered or amorphous systems affect ionic conductivity, the rational design of inorganic lithium superionic conductors can be achieved. In particular, because fast ion transport through the bulk is often a necessary condition in energy storage devices that require a high current of lithium ions, it is essential to understand the structural and chemical features that lead to high bulk ionic conductivities of crystalline materials.This thesis comprehensively investigates the diverse structural and chemical factors that improve ionic conductivity, and the atomistic mechanism by which each factor affects them. Chapter 1 introduces the computational and experimental background for understanding lithium-ion diffusion in inorganic materials as well as some of the chemical factors that can be used to optimize a fast conductor that already has desirable structural features. What often plays a decisive role is the structural feature; the structural features of inorganic crystals dictate whether it can be optimized to a superionic conductor or not. In this dissertation, we decompose the crystal into the framework (i.e., non-lithium cation sites) and lithium-ion diffusion network (i.e., lithium-ion sites), with the former discussed in Chapter 2 and the latter discussed in Chapter 3. In Chapter 4, we investigate structures in which the framework is rotationally mobile and analyze whether the rotational motion of anion groups leads to faster lithium-ion diffusion, also known as the paddlewheel effect. Chapter 5 investigates a remarkable class of ultrafast lithium-ion conductors with van der Waals-bonded frameworks. This chapter demonstrates how the mechanisms of ion transport discussed in Chapters 2, 3, and 4 result in the highest ionic conductivity predicted from computational studies so far. Finally, in Chapter 6, I provide an overview of how the diverse structural and chemical mechanisms of fast lithium-ion diffusion have led to the development of various classes of state-of-the-art superionic conductors by 2024. Here, I attempt to put together a global conceptual framework of various mechanisms that may be used for superionic conductors. Finally, I end with my perspective on future research avenues that may accelerate the discovery and optimization of fast lithium-ion conductors for the accelerated deployment of safer next-generation energy storage technologies.

Moiré superlattices, formed by vertically stacking atomically thin van der Waals layers with a slight interlayer rotation and/or lattice constant difference, are a powerful platform for modulating the physicochemical behavior of two-dimensional solids. While the optical, electronic, and magnetic properties of moiré materials can be intentionally tuned by changing the extent of crystallographic mismatch between constituent layers, structural perturbations such as lattice reconstruction, strain, and disorder also have a substantial impact on observed behavior. Therefore, directly measuring intrinsic structural deformations in moiré superlattices, learning how to dynamically deform moiré structures, and efforts toward correlative structure–property measurements are critical to understanding and controlling the emergent properties of these unique materials. In this dissertation, Chapter 1 first provides an introductory overview of recent developments in the field of two-dimensional materials and how the properties of these materials can be modified, including through construction of moiré superlattices. This discussion is followed by a comprehensive look at the fundamentals of moiré engineering, the role that structural deformations play in affecting moiré properties, and the appeal of a diffraction-based imaging approach for linking the structure of moiré architectures to observed properties and current theoretical models. Chapter 2 then describes the development of Bragg interferometry, a 4D-STEM-based imaging methodology for mapping moiré structures, and the insights afforded by the methodology regarding the spontaneous lattice deformations driving reconstruction in twisted bilayer graphene, the effects of these deformations on flat band formation, and the impact of extrinsic heterostrain on reconstruction-induced strain fields. Chapter 3 explores the extension of Bragg interferometry to transition metal dichalcogenide (TMD) systems, providing evidence of distinct reconstruction mechanisms in twisted bilayer TMDs and heterobilayer TMDs. The compatibility of Bragg interferometry with different heterostructure geometries is also exploited to illuminate the effects of encapsulation layers on in-plane and out-of-plane reconstruction. Chapter 4 demonstrates the application of Bragg interferometry to functional devices for the first time, specifically for mapping the spatial arrangement of polar stacking domains in twisted trilayer WSe2. This information is then complemented by operando dark-field TEM imaging that uncovers a variety of electric field-driven structural responses in different twisted trilayer polytypes. Lastly, Chapter 5 provides a summary of the reported work and an outlook for future endeavours.

Polymers have revolutionized modern life, finding countless applications due to their low production cost, tunable material properties, and long-term stability. However, this ubiquity and durability present global sustainability challenges necessitating the development of next-generation polymers capable of closed-loop recycling. Currently, sorting and recycling most consumer plastic products is not economically feasible due to the complexity of plastic types, resulting in only 5% of plastics in the United States being recycled. Promising strategies to enhance our recycling capabilities and transform plastics into a sustainable commodity include improving the blending of different polymers, incorporating degradable comonomers, and upcycling unwanted plastic products.To further explore polymer blending, Chapter 2 and Appendix A discussed improving polymer blending by developing polymers end-functionalized with complementary quadruple hydrogen-bonding end groups for improved miscibility. 2-ureido-4[1H]-pyrimidinone (UPy) and 2,7-diamido-1,8-naphthyridine (Napy) functionalized polymers reduced macrophase separation through the formation of the UPy-Napy heterocomplex in solution and thin film studies. This approach enables the creation of challenging silicone-based blends, benefiting both industrial applications and fundamental research.To expand upon the utility of degradable comonomers, Chapter 3 and Appendix B presented a platform to access vinyl-based α,ω-dithiol oligomers by degradation of copolymers derived from α-lipoic acid or ethyl lipoate with various vinyl comonomers. Structurally diverse polymeric α,ω-dithiols are synthesized by incorporating and then reducing disulfide bonds within the vinyl polymer backbone, demonstrating controllable molecular weights and tunable glass-transition temperatures (Tg). The utility of these α,ω-dithiol oligomers is highlighted for use as building blocks or crosslinkers in efficiently photocrosslinked networks.Further expansion of these α,ω-dithiol polymers for facile access to customizable random multiblock copolymers (MBC) was discussed in Chapter 4 and Appendix C. By oxidizing the thiols of low and high Tg dithiol polymers, a diverse range of random MBCs with high molecular weights and modulated mechanical properties were synthesized. This approach enabled precise control over MBC block molecular weight, tunable composition, and added chemical degradability. The versatility and scalability of this approach paves the way for future studies on telechelic thiol vinyl-based polymers and random MBCs.

This dissertation demonstrates the utility of high-resolution microscopy methods to visualize the biomimetic crystallization mechanisms that dictate protein localization and spatial distribution pattern outcomes. Biomineralization is the intricate biochemical process through which living organisms create hierarchically structured organic-inorganic composites that offer crucial biological functionalities like catalysis, storage, and protection. Biomineralization processes have inspired the biomimetic crystallization of protein-based metal-organic framework biocomposites (p@MOFs) to form biohybrid materials for potential applications in biomedicine and biocatalysis. A critical knowledge gap in our understanding of p@MOF structure-function relationships is how the precise spatial localization and distribution patterns of the proteins embedded within the MOF crystals affect their overall properties. Furthermore, the spatiotemporal tracking of protein molecules during the biomimetic crystallization process has yet to be fully elucidated, which is essential for designing synthetic procedures to target specific structures and functions. Chapter 1 outlines fundamental concepts of classical and non-classical crystallization, focusing on techniques used to decipher the key parameters governing crystal nucleation and growth in biomolecule-directed and biomimetic systems. In Chapter 2, the naturally occurring iron oxide mineral core of the protein horse spleen ferritin (Fn) is leveraged as a contrast agent to directly observe individual proteins during the crystallization pathways and outcomes of p@MOFs using transmission electron microscopy (TEM) methods. Chapter 2 illustrates how the 3D mapping of proteins in the crystallization of p@MOFs using advanced TEM techniques can be utilized to analyze protein spatial distribution and aggregation outcomes quantitatively. In Chapter 3, different electron microscopy modalities such as cryogenic TEM (cryo-TEM), cryo-electron tomography (cryo-ET), and liquid phase TEM (LP-TEM) are explored to understand further how proteins influence both classical and nonclassical crystallization pathways. The collective work in Chapters 2 and 3 demonstrates that adjusting the MOF precursor ratios and protein concentrations alters how proteins are arranged, localized, and aggregated within MOF crystals. Furthermore, this localization is intimately tied to the underlying crystal formation mechanism. This work gives essential insights into the influence proteins have on the crystallization pathways of MOFs, serving as a potential roadmap for designing highly controlled advanced materials capable of improving protein immobilization, performance, and delivery. Finally, Chapters 4 and 5 describe the effects of incorporating proximal Lewis acids and electric fields in CO2 activation. Chapter 4 outlines how oriented electric fields have been used to investigate their impact on catalytic activity in synthetic and biological systems. Chapter 5 illustrates heterobimetallic complexes with incorporated alkali cations close to a redox-active transition metal center for CO2 activation and reduction. This work examines how positioned proximal cations can be used in synthetic systems to enhance catalytic performance.

Biology provides many sources of inspiration for synthetic and multi-functional nanomaterials. Naturally evolved proteins possess a range of unique functions and self-assembly behavior. Their flexible design, potential for stimuli responsiveness, and the ability for some proteins to undergo electron transport functions as part of metabolic processes make proteins ideal building blocks of bioelectronic interfaces. In biosensor and electrocatalysis applications, bioelectronic materials are designed to interconvert biological signals or processes into electronic signals and vice versa. Some examples of electronically conductive microbial protein materials motivate the use of peptides and proteins for responsive bioelectronic interfaces. In this work, we designed a peptide fiber structure that exhibits stimuli-responsive self-assembly and the capacity to transport electrical current over micrometer long distances. Hierarchically ordered nanofibers of α-helical coiled-coil peptides were assembled using a pH responsive structure ordering motif comprising of two neighboring lysine residues. Cryo-EM structures of these assemblies reveal a novel organization of α-helical peptides in a cross coiled coil arrangement that exhibits electrical conductivity. Both solid-state and solution-based electrochemical characterization show that these fibers are conductive. Single-fiber conductive AFM determined that the solid-state electrical conductivity is on a similar order of magnitude with conductive cytochrome filaments from bacteria. Solution deposited fiber films approximately doubled the electroactive surface area of the electrode, confirming their conductivity in aqueous environments. Furthermore, these fibers can be used as scaffolds for redox enzyme immobilization for electrochemical biosensing. Progress towards immobilized enzymatic devices will be discussed. This work further expands the field of stimuli-responsive and multifunctional nanomaterials by using peptide assemblies as structural supports for future implementation in bioelectronic and bioelectrochemical materials.

Metal-organic frameworks (MOFs) present a diverse platform for designing high-performance materials with applications spanning drug delivery, catalysis, sensing, and separation. MOF polymorphism has been widely studied from the perspective of which synthetic factors, such as ligand-to-metal ratio, solvent, and temperature, can be used to control the final polymorph formation. However, limited studies on the nucleation mechanism of multi-polymorph MOFs have been performed. This dissertation aims to highlight the study and understanding of metal-organic framework polymorphs and how to observe and control polymorph formation. Advanced microscopy, scattering and spectroscopy techniques such as cryogenic transmission electron microscopy (cryoTEM), scanning electron microscopy (SEM), powder x-ray diffraction (PXRD), and electrospray ionization mass spectrometry (ESI-MS) are employed to conduct these studies. Here we study the formation of a model zeolitic imidazole framework-8 (ZIF-8) and the mechanism that drives the formation of the two most observed polymorphs, sodalite (SOD) and diamondoid (dia). To understand the mechanism and factors that affect polymorph formation, the prenucleation clusters were studied mainly through in-situ WAXS and ESI-MS, uncovering the role of prenucleation cluster size on the polymorph formation. In a follow up study, we investigate the effect of confinement through reaction vessel size on the nucleation and growth of ZIF-8. This study is of importance for studies involving analytical techniques where the experimental reaction volume varies from the bulk reaction. In addition, we study the encapsulation of bovine serum albumin (BSA) in ZIF-8 frameworks and the effect of supramolecular modification with cyclodextrin on the encapsulation efficiency. To further the studies with cyclodextrin, cyclodextrin-based MOFs are studied to understand their encapsulation efficiency and structure. In summary, this work provides insights into the field of MOF nucleation and growth through a lens of polymorph control and lays the foundation for the development of new MOFs.

Next generation backside imager photodiodes are presently being developed for use in hard x-ray detection and imaging at the National Ignition Facility (NIF) at Lawrence Livermore National Lab (LLNL). NIFs mission is to establish nuclear fusion capabilities, and accurate high-speed diagnostics play a critical role in advancing research. Replacing current silicon-based photodiodes with germanium-based technology allows for utilization of germanium’s improved intrinsic semiconductor properties to create diodes that are thinner and faster. Creating a photodiode with optimized speed and detection limits requires the backside imager geometry in which the substrate is removed, and the bottom of the wafer is used for photon collection. Established silicon etching techniques cannot be applied to germanium due to different fundamental chemical properties thus the selective removal of a germanium substrate is a yet unsolved processing problem.This research project has investigated the use of intentional doping of germanium layers to control and effectively accelerate or arrest electrochemical etching. Research activities were separated into three sections: development of a system and methodology for investigating the electrolytic etch process for germanium, identification of a suitable etchant system, and demonstration of etch selectivity within the determined system. The major result of this PhD project is that under anodic etching conditions with an applied bias of -2V, high-purity intrinsic germanium etches marginally whereas etching of highly boron-doped germanium is accelerated by at least 3 orders of magnitude. A potential processing methodology is proposed that will enable manufacturing of germanium-based photodiodes for future backside imaging devices.

Magnetic nanomaterials have attracted significant attention due to their unique properties that allow for remote, reversible, and rapid tuning under external magnetic fields. Integrating magnetic nanostructures and polymers creates multifunctional materials with advanced properties. These composite nanostructures combine the magnetic responsiveness of magnetic nanoparticles with the colloidal stability and stimulus responsiveness of polymers. This dissertation focuses on magnetic nanostructure-polymer integration for advanced functionalities.In the first part, we studied the heating performance of magnetic nanoparticles for thawing cryopreserved biological samples. By optimizing nanoparticle size and surface polymer coating, we achieved a balance between heating efficiency, colloidal stability, and biocompatibility. These integrated nanomaterials were successfully applied as the first nanowarming case for thawing cryopreserved porcine iliac arteries. In the second part, we delve into polymer-mediated colloidal stability and introduce swellable polymer-coated superparamagnetic nanoparticles for controlled assembly into one-dimensional photonic superstructures. The resorcinol-formaldehyde (RF) polymer coating provides steric hindrance to balance magnetic dipole interactions during the assembly of photonic nanochains. Adjusting the swelling behavior of RF polymers allows modulation of interparticle spacing and diffraction wavelength, creating dynamically tunable responsive optical materials in non-aqueous environments.In the third part, we further explore the assembly behavior of magnetic nanomaterials and their enhanced functions by integrating responsive polymers. Functionalization of magnetic nanorods with polyaniline coatings creates dual-responsive chiral superstructures that exhibit both magnetic and pH responsiveness, allowing dynamic tuning of their chiroptical properties. This dual responsiveness enables the development of advanced chiroptical switches and reconfigurable information encryption systems, showcasing potential applications in optical devices and information security.In the fourth part, we explore a novel multi-responsive plasmonic coupling system that integrates responsive polymer layers with plasmonic metal nanostructures through a space-confined seeded-growth method. The hybrid nanostructures, leveraging the unique responsive swelling behavior of functional polymers, allow dynamic tuning of interparticle distance of plasmonic nanoparticles and their plasmonic coupling properties via external stimuli. This integration expands the possibilities for developing innovative materials with tailorable optical properties, suitable for applications such as anticounterfeiting and adaptive optical materials.

Plasmonic nanostructures with tunable localized surface plasmon resonance (LSPR) have attracted much attention due to their broad applications in chemical sensing, photothermal therapy, and colorimetric detection. Because LSPR is related to particle morphology, controlling their size and shape is crucial for tailoring and tuning their optical resonance properties. Compared with conventional synthesis methods, space-confined seed-mediated growth is more reproducible and scalable and offers more opportunities to design hybrid and thermodynamically unstable structures. This dissertation discusses the seed-mediated growth of various plasmonic nanostructures within polymer confinement and explores their applications for colorimetric devices.We first investigate the confined seeded growth process of plasmonic nanostructures, which involves the deposition of various metal atoms, including Au, Ag, and Pt, onto the pre-formed seeds confined within polymer nanoshells. The key parameters affecting the growth are systematically studied, including the surfactants, reductants, and some kinetics factors. Different metals are found to exhibit diverse behaviors during the seeded growth process, producing plasmonic-polymeric hybrid nanostructures with different chemical and physical properties. In particular, we highlight the seeded growth of Pt within the confined space, which has not been achieved previously. These plasmonic nanostructures are promising building blocks for designing various colorimetric devices.The seeded growth process is coupled with a plasmonic decoupling mechanism to design a colorimetric pressure sensor that can respond to applied pressure with instant color changes. The sensor consists of a thin film of stacked uniform nanoshells of resorcinol formaldehyde resin, with their inner surfaces functionalized with Ag nanoparticles. Upon compression, the flexible polymer nanoshells expand laterally, inducing plasmonic decoupling between neighboring Ag nanoparticles and a subsequent blueshift. The initial color of the sensor is determined by the extent of plasmonic coupling, which can be controlled by tuning the interparticle distance through a seeded growth process. The sensing range can be conveniently customized by controlling the polymer shell thickness or incorporating the hybrid nanoshells into various polymer matrices. We further demonstrate that the controlled growth of plasmonic nanoparticles within polymer nanoshells offers an excellent opportunity for tuning their refractive index. Such tunability is employed to design novel colloidal photonic crystal films. Theoretical simulations coupled with experimental observations confirm the strong interaction between Au and resorcinol formaldehyde, which results in a notable decrease in the refractive index and a subsequent blueshift in the photonic bandgap. The photonic crystal films fabricated using such nanoshells exhibit brilliant structural colors, which can be conveniently controlled by the amount of Au loading through the seeded growth process. The tuning range of diffraction colors can be tailored by adjusting the diameter and thickness of the polymer nanoshells. This high spectral tunability enables the design of unique colorimetric refractive index sensors capable of distinguishing various polar solvents. Plasmonic nanoparticles can efficiently convert light of their resonance wavelength into heat. This photothermal effect is utilized to induce photoresponsive expansion of hollow polymer nanoshells, resulting in a color response in two-dimensional (2D) arrays assembled on a substrate using these nanoshells. When exposed to light, the liquid inside the polymer shells vaporizes quickly, creating high pressure that causes the shells to expand. The expansion can be controlled by adjusting light intensity, shell thickness, and void size. This expansion allows the nanoshells to reposition themselves, improving the order of the 2D arrays and, consequently, the optical diffraction. Additionally, the expansion causes a redshift in the structural color, enabling the development of a light-responsive writing technique.

This thesis explores magnetization dynamics in materials to help design future low-power electromagnetic devices. In this thesis, we explore materials for multiferroic composites that can couple electricity and magnetism through voltage, rather than current, allowing for the possibility of low power control of magnetism. We study both thin film systems and explore the effect of nanostructure on strain-mediated composites, which utilize a ferroelectric material that exhibits a strain response to an applied voltage, coupled to a magnetostrictive material, which changes magnetization in response to the strain produced by the ferroelectric. In the first part of the thesis, yttrium iron garnet (YIG) is studied as a model system for low loss magnetic materials – a necessary requirement for high-frequency multiferroic devices. YIG is an ideal magnetic material for high-frequency devices, as it exhibits narrow magnetic resonances, but pure YIG has low magnetostriction. Using sol-gel chemistry, we were able to survey a range of cerium- and ruthenium-doped YIG compositions, which have both been shown to increase YIG’s magnetostriction to useful levels in bulk crystals. Homogeneously doped materials were synthesized and characterized, but the polycrystalline nature of the films led to significant magnetic losses at high frequency.In the second part of the thesis, we explore three-dimensionally coupled porous multiferroic composites. These composites were synthesized by first using block-copolymer templating to create a nanoporous magnetostrictive framework. Atomic layer deposition (ALD) was then used to partially coat the inner surface of the pores with a thin layer of ferroelectric material, the thickness of which could be varied to change the extent of residual porosity. We found that composites with larger residual porosities exhibited a larger magnetoelectric coupling, due to the mechanical flexibility of the pores, which enabled larger strains. We first studied ferroelectric lead zirconate titanate (PZT) in magnetostrictive cobalt ferrite (CFO), and observed modest increases in magnetoelectric coupling with increasing porosity. We hypothesized that this was due to the weaker ferroelectricity observed in extremely thin PZT films. Upon switching the ferroelectric to bismuth ferrite (BFO), we find that large (