Graphene oxide (GO) is a heavily oxidized version of graphene, which is often made by oxidative chemical exfoliation from graphite powders. The reaction decorates the graphene sheets with oxygen-containing functional groups including hydroxyl and epoxide groups on the basal plane, as well as carboxyl groups on the edge, rendering the...
The past decade has seen the rapid progress of deep learning, which becomes a game-changing technique in different data-intensive domains, with the availability of large scale data, cost-effective computing hardware and more advanced learning theory and algorithms. Despite of the rapid progress of deep learning methods in daily-life applications, such...
The successful isolation of graphene marked the advent of two-dimensional (2D) materials. Their atomically thin structures enable unprecedented electrical, optical, and mechanical properties, which have triggered significant research interests in the past decade. For instance, they are promising candidates for the fabrication of flexible electronics, biological sensors, battery electrodes, and...
Thermoelectric devices utilize semiconducting n-type and p-type thermoelectric materials to convert heat into electricity. Despite their promise for deep space power generation or waste heat recovery, most high-performing thermoelectric materials reported in literature are absent in practical applications - partially due to inconsistent synthesis and poor mechanical performance. This work...
As the interest in rational synthesis for solid-state materials accelerates, there is an urgent need to understand the design principles concealed within these reactions. In situ material synthesis provides such an avenue to not only uncover these assembling rules, but also for finding new materials even in seemingly familiar phase...
Part I: Evaluating the relationship between Crosslink Kinetics and Thermodynamics with the hydrogel mechanics. The past two decades have witnessed a surge of applications built upon dynamic covalent chemistry (DCC), both attributed to the scope of developed reactions as well as their modularity.1-3 These reactions have comparable strengths to their...
The ability to control the crystalline ordering and morphology of polymeric nanomaterials is a grand challenge in the field of materials science, which could enable the development of functional materials able to solve long-standing problems in renewable energy and medicine. In this work, we explore a combination of supramolecular chemistry...
Scalable processing of well-defined interfaces is key not only for wider application of two-dimensional (2D) materials in technology but also for improved fundamental understanding. Atomic layer deposition has useful characteristics, especially self-limited growth at low temperatures, that make it well suited for the production of uniform interfaces. Related processes, such...
Nanotechnology research broadly encompasses the exploration of the unique chemical,optical, electronic, or biological properties of materials with dimensions < 1 µm. Inorganic
nanoparticles are one such class of materials, with properties that are exceptionally sensitive to
particle size and structure. This is especially evident in the field of heterogeneous chemical...
This thesis focuses on identifying structure-property-performance relationships in supported nanoparticle catalysts, where an active catalyst material is supported on a high surface area substrate. Identifying these relationships in supported nanoparticle catalysts can be quite challenging, as the complex structure of these catalysts results in numerous potential sources for changes to...
At its core, the purpose of microscopy is to make objects and their underlying structures visible under high magnification. With the remarkable progress of electron microscopy, the sub-micron “high” magnification of light microscopy has been completely refashioned to encompass subatomic length scales. Unfortunately, higher-magnification does little to negate existing interpretability...
Plasmonic nanoparticles have very large absorption cross sections and can concentrate the local density of photon states on the nano scale. When they are coupled to molecules or semiconductor nanocrystals and form different hybrid nanostructures, various light-matter interaction processes can be significantly enhanced or manipulated, including optical responses like fluorescence...
Electrochemical devices play a vital role in the efforts towards a sustainable green future. Solid acid based electrochemical cells, employing super protonic CsH2PO4 (CDP) as the electrolyte component, offer unique application advantages due to their operability at intermediate temperatures 250°C. At these temperatures, one can achieve improved reaction kinetics over...
Nanocarriers are drug delivery vehicles that have at least one dimension at the nanoscale (10-9 m). Engineering the nanocarrier surface is a strategy for targeting drug delivery to specific cell types to enhance efficacy and minimize side effects. A useful analogy is to consider how the chassis of an automotive...
Semiconductor nanocrystals possess unique photophysical properties that make them desirable for many optoelectronic applications such as photovoltaics, LEDs, and quantum computing. When the size of a semiconductor is reduced to below the excitonic Bohr radius of the material, its carriers becomes quantum confined resulting in drastic changes to optical, electronic,...
Materials science has been central to human advancement since time immemorial. There has always been curiosity around studying the processes required to extract materials, examine their structure, and ultimately tailor their properties to meet human needs. Over the last few centuries, the ability to tailor material properties was driven by...
Engineering heat transport in materials is essential for thermal management in a wide range of technologies, from batteries to thermoelectrics. Materials host a wide spectrum of heat-carrying phonons, which vary in their frequency, spatial extent, and degree of plane-wave character. This diversity in phonon properties leads to complex behavior, especially...
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...
Two-dimensional (2D) hybrid halide perovskites have been the response to their exciting but woefully unstable 3D counterparts. These 2D perovskites have been shown to have respectable stabilities as photovoltaic absorbers, yet they lag behind the 3D perovskites in terms of efficiency. With the need to catch up to the efficiencies...
A framework is developed that models point defect diffusion and interaction with pre-existing microstructures during irradiation, including defect-defect interactions and defect sinks. This framework uses a modified diffusion potential that includes not only defect concentration, but also intrinsic stresses from the pre-existing microstructure. Various microstructures are studied in {Fe} by...
The highly flexible nature of 2D materials has led to them becoming fundamental building blocks for achieving novel device physics and potential breakthroughs in practical technologies. 2D layers can be interfaced in a wide array of methods with themselves, other 2D layered materials, or materials of entirely different type or...
Materials that exist as well-defined individual entities at the nanoscale typically have properties that sets them apart from their bulk form. Consequently, there has been much time and effort invested in developing new well-defined nanoscale entities, but few attempts to assemble them into bulk materials. On the other hand, there...
Nanomaterials are increasingly incorporated in modern day life, from the biogenic viruses that cause pandemics and the mineral crystallites embedded alongside collagen in our bones, to the anthropogenic nanomaterials that are small but powerful components of sunscreen and paint, swimming pool algaecides and wound dressings, cancer treatments, bicycle frames, and...
Metallic conductivity and broken inversion symmetry were long thought to be contraindicated properties, under the assumption that long-range Coulombic interactions (screened by free charge carriers) were necessary for coordinated polar displacements. Within the past decade, the discovery of polar metals has prompted a rethinking of the relationship between metallicity and...
This thesis describes the synthesis and photophysical characterization of low-dimensionalmaterials—including thin-film semiconductors, colloidal quantum dots, and molecules—with the
broader motivation of integrating them into mixed-dimensional heterostructures with novel
responses to external stimuli. Due to their high surface area to volume ratio and incomplete
dielectric screening, mixed-dimensional heterostructures have high sensitivity...
Soft materials in nature are formed through programmed self-assembly of biomolecules to create complex architectures and optimized physical properties. It is therefore a key challenge in biomaterials science and engineering to understand the principles that govern the structure and properties of such materials, and the interactions between their different components....
Nanoparticle synthesis is capable of producing particles with any combination of structure, chemistry, size, shape, and surface. All of the different combinations of these physical properties can produce nanoparticles with almost countless materials properties suited for many applications. Given this interest in using nanoparticles in so many different fields, including...
One of the central challenges in solid-state chemistry is synthetic control over structure. Owing to limited reactivity of Pb with transition metals at ambient pressure and high temperature as well as the variety of properties that emerge from the few known binary transition-metal–Pb compounds, this research focuses on accessing and...
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...
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...
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...