Thermoelectric materials are of particular interest in a variety of fields because of their ability to directly convert heat to electricity (and vice versa), however, they struggle to gain widespread adoption because of their low efficiency. A common strategy in the field of thermoelectricity is to introduce material defects into...
High performance polymers and their composites have wide ranging application in advanced and emerging material systems. The macroscale performance of these advanced materials is often defined by interfaces that induce nanoscale changes in the microstructure or molecular conformations (termed the ‘interphase’) of the polymer. Atomic force microscopy (AFM) is an...
Given directives such as the UN Global Goals targeting sustainable development, the research presented herein makes but a small contribution to the advancement of alternative energy technologies. Nevertheless, the present work was largely motivated to address specific points of intrigue within the thermoelectrics community. The general principles demonstrated, however, may...
An extensive set of functional electronic properties depends on the electronic structure. These properties are directly connected to the reciprocal-space representation of electronic structure. However, there is a complementary, real-space perspective that is described by combinations of atomic orbitals. Atomic orbitals are the components of electronic structures, analogous to how...
Structural colors originate from the interaction between the incident light and a surface with periodic submicron structures. They enable the creation of a spectrum of nonfading colors, potentially replacing toxic metal oxides and conjugated organic pigments. However, significant challenges remain, including lack of contrast needed for the complete gamut of...
A series of theories and models are developed and used to investigate the growth of protective oxide films on metal and alloy surfaces for cases in which Wagner's classical model of oxidation does not hold. First, irreversible thermodynamics is applied to formulate a model for the outward growth of rocksalt...
Part I: Design of Photo-Responsive Molecules towards Biomedical ApplicationsThe use of light to control systems provides numerous advantages such as spatiotemporal precision, non-invasive penetration, and precise energy input. Specifically, molecules that undergo photoinduced cleavage, photoremovable protecting groups (PPGs) have emerged as an active area of research due to their broad...
A significant portion of material science research is concerned with understanding theway that defects affect the properties materials. In the field of thermoelectrics introducingor removing point (0D), dislocation (1D), grain boundary (2D), or precipitate (3D) defectsare popular methods for altering a materials thermoelectric efficiency. Herein I discussdifferent studies conducted during...
Transition metal oxides (TMOs) like perovskites are known to be versatile for functional properties such as ferroelectricity, magnetism, optical properties, and high-temperature superconductivity, because of their sensitive coupling between atomic structure and properties. By studying and understanding the fundamental structure-property relationships present in TMOs, it is possible to strategically engineer...
Supervised learning model is one of the most fundamental machine learning models. It can provide powerful capability of prediction by learning complex patterns hidden in many, sometimes thousands, predictors. It can also be used as a building block of other machine learning tasks, like unsupervised learning and reinforcement learning. Such...
Thermoelectric materials have attracted widespread attention in recent decades because of their ability to directly convert thermal energy into electrical energy. Given that waste heat is the primary source of lost energy in the world, the implications of developing better thermoelectric materials are both immediate and far-reaching. Admittedly, large progress...
Dual-phase (DP) steels have been widely applied in automobile industry, and are famous for continuous yielding in their corresponding stress-strain curves. The appearance of yield-point phenomena, or discontinuous yielding, is considered undesirable for DP steels. Herein, we take advantage of the undesirable appearance of yield-point phenomena in DP steels as...
The investigation of ceria-related materials has a long history since 1920s. The first publication on web of science traces back to 1928. Ever since that, more studies come out and surge starting from 1987. This material has attracted extensive attention due to its wide applications in electrochemical devices, catalysis, and...
Biological organisms have the extraordinary ability to form mineral structures with unparalleled control. From curved single crystals to hierarchically structured skeletal parts, biomineralization processes produce materials with properties that are highly optimized for their intended applications. These processing techniques occur at ambient conditions using materials abundant in the environment, and...
Multimetallic nanoparticles represent an important class of electrocatalysts which are critical for many energy and environmental applications including fuel cells, hydrogen production, and greenhouse gas elimination. The properties of these nanoparticles depend on their composition, size, shape, and structure. Therefore, developing new strategies which provide a high level of control...
Tooth enamel, the outermost layer of human teeth, is a complex, hierarchically structured biocomposite. The details of this structure are important in multiple human health contexts, from understanding the progression of dental caries (tooth decay) to understanding the process of amelogenesis (enamel formation) and related developmental defects.While much is known...
The three-dimensional (3D) nanoscale structure of III-As nanowires is correlated with optical and electronic property measurements to deconvolve the contributions of strain, composition, and crystal structure to characteristics of interest for future electronic and optoelectronic devices. Multiple advanced two-dimensional (2D) and 3D characterization techniques are employed such as atom probe...
There is considerable technical interest in the improvement of battery technology, as it would allow for the enhancement and realization of many different applications, including the continued miniaturization of portable computational devices, plug-in electric vehicles, and intermittent power storage. Lithium metal represents a theoretical limit on the anode energy density...
As demonstrated by efforts in graphene commercialization, scalable synthesis and high-quality material availability are primary limiting factors for the realization of technologies based on two-dimensional (2D) materials. Thus, in considering the fate of emergent 2D materials such as the metal chalcogenides, the challenge of scalable synthesis is a highly relevant...
Self-assembly of colloidal particles at the nano- and microscale has been a powerful tool for producing structures with emergent properties in applications ranging from electro-mechanical systems to photonics and biomedical devices. Great success has been achieved in experiments, where a variety of exotic phases have been discovered and even reconfigurable...
Recent advances in high-performance computing have resulted in massive databases of materials properties calculated with techniques such as ab initio density functional theory. In fact, some of the largest of such databases have calculations of nearly all distinct, ordered, experimentally-reported compounds. This thesis discusses the application of data in one...
There is no group of materials as diverse, complex, and ubiquitous as polymers. From plastic bags, to rubber tires, electronics, food packaging, water filtration and even aerospace applications, the penetration of polymer materials into all aspects of life make them very important materials throughout all engineering fields. However, this breadth...
The advancement of nanotechnology is at least partially dependent on the ability to synthesize and arrange complex nanostructures on a substrate. Nanolithography, or the patterning of materials at the sub-micrometer length-scale, has been traditionally performed using a number of methods such as conventional photolithography, ion-beam etching, and electron-beam lithography. While...
NiTi shape memory alloy (SMA) has drawn a great deal of attention for its various applications in the medical field (orthodontics, cardiovascular stents technology, etc.) and in other engineering fields (aerospace, aircraft, automotive, etc.) as it shows shape memory effect, superelasticity and biocompatibility. The fatigue-related issues, however, are pronounced in...
Physiochemical phenomena in aqueous systems, such as corrosion, catalysis, and energy storage, are driven by the molecular-scale interactions of ionic species with charged solid surfaces. In particular, an electrical double layer (EDL) of ions forms within nanometers of a charged surface. The properties of the EDL have been explored from...
The effect of interfaces in solids on the overall charge transport properties has become a topic of growing importance for energy materials such as thermoelectrics. In some polycrystalline thermoelectric materials, the performance near room temperature is significantly limited due to thermally-activated electrical conductivity near room-temperature, which can be attributed to...
Non-planar and curved architectures of otherwise flat 2D materials present an important paradigm for nanoscale analysis and design of emergent material properties. Atomically-thin transition metal dichalcogenides (TMDs) have emerged at the forefront of the 2D materials field in recent years largely due to their attractive and tunable chemical, optical, and...
Melanin is a functional biopolymer most commonly associated with human skin pigmentation, where it serves as a radiation protection agent, shielding us from the harmful effects of UV radiation. However, melanin is also present in human ears, eyes, hair, and brains, serving a variety of functions. In fact, melanin...
Superconductivity is a fascinating manifestation of quantum mechanics on a macroscopic scale that has led to greater insights of the strongly correlated physics of a large number of interacting electrons ever since its discovery $\sim$ 100 years ago in elemental Hg. The unconventional superconductors that are based on uranium offer...
Exploratory phase stability analysis in Materials Science has two primary goals: (a) Characterizing the evolution of the materials single phase field in composition space to identify solubility and electronic dopability limits and (b) Accelerated prediction of new phases of technological importance. In this thesis we reorganize defect theory --- the...
The era of quantum information science (QIS) can usher revolutionary new capabilities ranging from quantum computation to quantum sensing. At the core of these technologies is the fundamental unit of QIS, the quantum bit or qubit. The power of qubits over their classical counterparts lies in their ability to be...
Two-step, solar thermochemical water splitting using nonstoichiometric oxides has emerged as an attractive approach for large-scale hydrogen production. Perovskite-structured oxides, with their wide tunability, offer the potential for high fuel productivity at moderate operating temperatures. Given the vast chemical space, the materials development effort is carried out here in combination...
Surface patterns that can reconfigure under external stimuli are important for tailoring diverse properties such as surface adhesion, optical transmittance, and wettability depending on the feature size and orientation. Wrinkling a stiff skin layer on a pre-strained elastomer substrate has emerged as a method to create responsive structures without using...
Continuous and coordinated materials discovery efforts have amassed a wealth of knowledge concerning many general classes of materials. The number of known phases of all structure-types, however, is far less than number of possible materials dictated by the elements on the periodic table. Recently, with improved computational abilities and well-developed...
Advanced wireless soft electronics integrate a wireless power transfer circuit and a small battery. It is skin-compliant, and lightweight accommodating the complex motion of the body. These unique features of the device provide a continuous physiological measurement without discomfort and spatial constraints. Using the device, we can observe and track...
As the pursuit for higher performance and lower cost photovoltaics, and for new applications of optoelectronic devices moves beyond crystalline silicon, there are many unique opportunities for materials research into hybrid organic-inorganic, and organic semiconductors. This dissertation focuses on both hybrid organic-inorganic materials and organic materials for optoelectronic applications. In...
Electrochemical cell devices are increasingly being sought for energy conversion and storage applications due to their high efficiencies and their potential for operating free of greenhouse gas (GHG) emissions. Solid Acid Electrochemical Cells (SAECs), which most commonly employ CsH2PO4 (CDP) as the electrolyte component, are uniquely suited to meet the...
Discrete molecules, linear and branched polymers, and disordered cross-linked networks are well studied objects of chemical synthesis. However, two-dimensional polymers (2DPs) have been long missing from this continuum of molecular architectures, both in chemical synthesis and in Nature. Recently, new polymerization strategies and characterization methods have enabled the unambiguous realization...
Mixed-dimensional heterojunctions between two-dimensional (2D) materials and organic semiconductors is a rapidly growing field. This is motivated by the promise of leveraging the extraordinary properties of 2D materials with the synthetic tunability and reconfigurability of organic electronics, allowing the realization of new physics or devices that are not possible in...
Ordered arrays of metallic nanoparticles (NPs) are a promising platform for technological applications and fundamental investigations due to their ability to excite surface lattice resonances (SLRs). SLRs can support extremely high local electric fields that have been used to realize exotic physical phenomena. The open cavity architecture lends itself to...
Complex microstructures are ubiquitous in nature. The evolution of these microstructures alters their morphology and topology and thus very often dictates material properties, such as mechanical, electronic, thermal, and magnetic properties. Thus, in order to predict and control material properties, it is essential to have robust and efficient techniques to...
The crystal structure of chalcogenides can vary from simple, ubiquitous structures of rock salt and zinc blende to unique structure types from the intricate packing of complex anionic building blocks. Exploratory synthesis and structural studies of novel chalcogenides containing these complex anions will augment the understanding of bonding in chalcogenides....
The idea that structure determines the properties of a material is a powerful concept in chemistry and in all fields in which chemistry is important, including engineering, medicine, and materials science. My research aims to better understand the structure-property relationships of a class of materials known as metal–organic frameworks (MOFs)....
Increasingly high global energy consumption demands effective approaches to high energy efficiency and, at the same time, paths to reduced release of carbon dioxide, a primary greenhouse gas behind global climate change. Friction reduction is a vital aspect towards making energy systems more efficient and one of the most crucial...
Advancements in the understanding and synthesis of transition metal compounds have allowed materials engineers to design functional materials with a range of properties, such as ferroelectricity, non-linear optical activity, colossal magnetoresistance, and superconductivity. Conventional routes to tune and design functional materials includes chemical cation substitution and heterostructuring of oxide thin...
This dissertation explores the fundamental science of flexoelectricity and its implications using a combined experimental and theoretical approach. I begin by introducing the flexoelectric effect and formalizing the basics of strain gradients, polarization, and flexoelectric coefficients. Next, I describe the development of a flexoelectric characterization system based upon three-point bending...
Over the last few years, there has been a transition away from traditional engineering materials to new advanced materials that exhibit complex architectures with improved mechanical properties. Most of the inspiration for these new materials comes from nature, where organisms have evolved an immense variety of macro and nanoscale shapes...
Thermoelectric (TE) materials has been drawn broad attention given that it can enable direct conversion between thermal and electrical energies, hence is treated as a vital candidate for clean power generation as well as waste heat recycling. However, the energy conversion efficiency of TE devices used nowadays is still very...
The demand for low cost, unconventional electronics requires new materials with unique characteristics that the traditionally used silicon-based technologies cannot provide. Metal oxide semiconductors, such has amorphous indium gallium zinc oxide (a-IGZO), have made impressive strides as alternatives to amorphous silicon for electronics applications. However, to achieve the full potential...
This dissertation explores ways to utilize physical parameters at the nanoscale interface to control the properties of mixed-dimensional heterojunctions (MDHJs). MDHJs combine the desirable properties of different classes of low-dimensional nanomaterials (materials that are quantum confined in at least one dimension). While MDHJs have achieved superlative performance for a variety...