UMD Theses and Dissertations
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Item VISUALIZING DYNAMICS DURING CHEMICAL REACTION DRIVEN NON – EQUILIBRIUM COLLOIDAL AND NANOPARTICLE ASSEMBLY(2023) Dissanayake Appuhamillage, Thilini Umesha; Woehl, Taylor; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biological nano and microstructures exist far from thermodynamic equilibrium by continuous consumption of energy that allows them to reconfigure or adapt to changes in the local environment. Utilization of these non-equilibrium structure formation processes in synthetic colloidal particle and nanoparticle (NP) systems is expected to enable unprecedented control over the dynamics of synthetic active soft materials and systems that are beyond the reach of equilibrium self – assembly. In this work we adapted two non – equilibrium structure formation processes observed in biological systems, dissipative assembly and reaction diffusion instability, to generate dynamic colloidal assemblies and self-organized patterns of nanoparticles. First, we investigated how the surface chemistry and interparticle interactions between colloids changed during chemical reaction driven dissipative assembly of polystyrene colloids. A key result was the first, time dependent measurements of the dynamic colloid surface chemistry (surface charge and hydrophobicity) during dissipative assembly. Importantly, we demonstrated that thermodynamic interparticle interaction models typically used for equilibrium self-assembly are effective in describing fuel driven colloid assembly far from equilibrium. The interparticle interaction models demonstrated that electrostatic interactions controlled the concentration of particle aggregates while the strength of hydrophobic interactions determined whether colloids underwent irreversible aggregation or dissipative assembly. Next, using a correlative fluorescence microscopy and liquid phase transmission electron microscopy (LPTEM) method, we demonstrated that aminated polymer capping ligands on metal NPs undergo crosslinking and chain scission reactions as a result of formation of hydroxyl and hydrogen radicals due to electron beam induced radiolysis of water. We demonstrated that a hydroxyl radical scavenger can minimize the electron beam induced reactions in the polymers. Based on this fundamental knowledge, we introduced an instability to an initially homogenous gold NP decorated aminopolysiloxane thin film immersed in water by scanning TEM beam. Radiolysis driven polymer radical reactions of polysiloxane coupled with diffusion of radicals, polymers, and NPs caused the polymer and NP to self-organize into repeating spatial patterns, i.e., Turing patterns, with no template or specific interparticle interactions. Spots, strings and labyrinth patterns that closely resembled Turing skin pigmentation patterns on various animals were obtained by tuning the chemistry of the system. A series of systematic experiments identified that hydroxyl radicals and NPs as critical species driving the formation of the NP patterns. We expect this work could be used as a model system in establishing design rules for nanoscale pattern formation by reaction – diffusion instability.Item Functionalized Nanoparticles for the Controlled Modulation of Cellular Behavior(2023) Pendragon, Katherine Evelyn; Fisher, John; Delehanty, James; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The ability to control cellular behavior at the single-cell level is of great importance for gaining a nuanced understanding of cellular machinery. This dissertation focuses on the development of novel hard nanoparticle (NP) bioconjugate materials, specifically gold nanoparticles (AuNPs) and quantum dots (QDs), for the controlled modulation of cellular behavior. These hard NPs offer advantages such as small size on the order of 1 – 100 nm, high stability, unique optical properties, and the ability to load cargo on a large surface area to volume ratio, making them ideal tools for understanding and controlling cell behavior. In Aim 1, we demonstrate the use of AuNPs to manipulate cellular biological functions, specifically the modulation of membrane potential. We present the conception of anisotropic-shaped AuNPs, known as gold nanoflowers (AuNFs), which exhibit broad absorption extending into the near-infrared region of the spectrum. We demonstrate the effectiveness of utilizing the plasmonic properties AuNFs for inducing plasma membrane depolarization in rat adrenal medulla pheochromocytoma (PC-12) neuron-like cells. Importantly, this is achieved with temporal control and without negatively impacting cellular viability. Aim 2 explores the use of QDs as an optical, trackable scaffold for the multivalent display of growth factors, specifically erythropoietin (EPO), for the enhanced induction of protein expression of aquaporin-4 (AQPN-4) within human astrocytes. This results in enhanced cellular water transport within human astrocytes, a critical function in the brain's glymphatic system. We show that EPO-QD-induced augmented AQPN-4 expression does not negatively impact astrocyte viability and augments the rate of water efflux from astrocytes by approximately two-fold compared to cells treated with monomeric EPO, demonstrating the potential of EPO-NP conjugates as research tools and prospective therapeutics for modulating glymphatic system function. Overall, the body of work presented in this dissertation develops new NP tools, namely solid anisotropic AuNFs and growth factor-delivering QDs, for the understanding and control of cell function. These new functional nanomaterials pave the way for the continued development of novel NP-based tools for the precise modulation of cellular physiology.Item RAPID HEATING AND CHEMICAL SPECIATION CHARACTERIZATION FOR COMBUSTION PERFORMANCE ANALYSIS OF METALLIZED, NANOSCALE THERMITES AND PVDF BOUND SOLID PROPELLANT COMPOSITIONS(2021) Rehwoldt, Miles Christian; Rodriguez, Efrain; Zachariah, Michael R; Chemical Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Energetic materials research focuses on performance analysis of cost-effective solid materials which safely, precisely, and efficiently transitions stored chemical potential energy to kinetic energy at a rate throttled through chemical or architectural means. Heterogenous compositions of metal fuels and solid materials with a high storage capacity of condensed oxidizing elements, such as oxygen and/or fluorine, is a class of energetic material of interest given its relatively high reaction enthalpies and adiabatic flame temperatures. In the wake of the earliest instances of metal fuels being used as a high energy additive during World War II, characterizing the reaction mechanisms of micron and nanoparticle aluminum fuels with various oxidizer sources has been a primary subject of research within the solid energetics community. The advent of nanotechnologies within the past two decades brought with it the promise of a prospective revolution within the energetics community to expand the utility and characterization of metallized energetic materials in solid propellants and pyrotechnics. Significant prior research has mapped reactivity advantages, as well as the many short comings of aluminum-based nanoscale energetic formulations. Examples of short comings include difficulties of materials processing, relative increase in native oxide shell thickness, and particle aggregate sintering before primary reaction. The less than flaw-less promises of nanoscale aluminum fuels have thus become the impetus for the development of novel architectural solutions and material formulations to eliminate drawbacks of nanomaterial energetics while maintaining and improving the benefits. This dissertation focuses on further understanding reaction mechanisms and overall combustion behavior of nanoscale solid energetic composite materials and their potential future applications. My research branches out from the heavy research involved in binary, aluminum centric systems by developing generalized intuition of reaction and combustion behaviors through modeling efforts and coupling time-of-flight mass spectrometry to rapid heating techniques and novel modes of product sampling. The studies emphasize reaction mechanisms and microwave sensitivities of under-utilized compositions using metal fuels such as titanium, generalize the understanding of the interaction of fluoropolymer binders with metal fuels and oxidizer particles, and characterize how multi-scale architectural structure-function relations of materials effect ignition properties and energy release rates.Item DEVELOPMENT OF ΒETA-LACTOGLOBULIN BASED PARTICLES AS COLLOIDAL STABILIZERS AND EVALUATION OF THEIR PERFORMANCE ON INTERFACES(2020) ZHANG, JINGLIN; Wang, Qin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Beta-lactoglobulin (Blg) is a major whey protein in bovine milk. The desirable functional properties of Blg make it a versatile material, which has been processed into various types of colloidal systems such as nanoparticles, microgels and emulsions. This dissertation first developed several stable colloidal systems using native Blg molecules or denatured Blg aggregates as stabilizers. The study then elucidated the stabilization mechanism by characterizing Blg microgels adsorption on the interface. Firstly, novel selenium nanoparticles were developed using Blg as a stabilizer. The synthesized Blg-selenium nanoparticles were stable at pH 2.5-3.5 and 6.5-8.5 at 4ºC for 30 days as a result of electrostatic repulsions. Furthermore, the cell toxicity of selenium nanoparticles was significantly lower than that of sodium selenite on both cancerous and non-cancerous cells, implying their potential uses as anti-cancer medicines. The second part of this study was to stabilize a novel water-in-water (W/W) emulsion system using self-assembled Blg microgels. The microstructure and stability of the W/W emulsion were investigated under different environmental conditions. Microgels accumulating at the liquid-liquid interface led to a stable emulsion at pH 3 to 5. When pH was increased above the pI of the microgels, the emulsion was destabilized because the microgels tended to stay in the continuous phase (i.e., dextran) rather than the interface. In addition to electrostatic interactions, interfacial tension and hydrophobic attraction between microgels and two polymer phases were investigated to better understand the driving force for particles’ accumulation at the interface. Lastly, we proposed a new method to study the interfacial properties of Blg microgel. Quartz crystal microbalance with dissipation (QCM-D) was employed to investigate adsorption behavior of Blg microgels on a hydrophobic solid surface, which was hypothesized to mimic the oil-water interface. Coupling with atomic force microscopy (AFM), QCM-D showed the ability to characterize the microgels adsorption efficiency and viscoelasticity of adsorbed layer on the solid surface. The application of QCM-D and AFM enabled us to generate insights into the fundamental behavior of soft particles at a solid-liquid interface.Item BILAYER MEMBRANE ELECTROSTATICS AND CHARGE-REGULATED MEMBRANE-NANOPARTICLE INTERACTIONS(2018) Sinha, Shayandev; Das, Siddhartha; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Nanoparticle (NP) driven targeted drug delivery and NP driven imaging of cells, tumors etc. have been one of the most investigated areas in interfacial and biomedical engineering in recent years involving a massive amount interdisciplinary efforts cutting across disciplines like physics, chemistry, material science, biology, pharmaceutics, and engineering. Drug delivery or imaging with the NPs invariably require the NPs to first adhere to the surface of a cell, which is bound by a cell membrane (also known as plasma membrane or PM). All of these processes occur in an electrolyte medium as the fluids present inside and outside the cell have ions inside them. There have been significant amount of studies on adhesion of nanoparticles but until today, there has been very less number of investigations on the role of the ionic environment on such systems of adhesion. The ions present in the intracellular and the extracellular space produce an electric double layer (EDL) on both sides of the PM. The PM is also a semipermeable membrane i.e it does not let all kinds of ions to pass through it. The moieties that it lets to pass through it is completely dependent on the ion channels present across it and such semi-permeable action dictates the ion distribution around the PM, which in turn would regulate the NP-PM interactions. The main aim of this dissertation is to look into the influence of this ionic environment and the role that it can play on adhesion of NPs. In order to look deeply we first look into the electrostatics of the PMs. We develop a continuum model to investigate the role of the ionic environment or the EDL on the electrostatics present across the membrane. This investigation led us to a very important aspect of membrane electrostatics. We found out charge-inversion (CI) like characteristics on the cytosol side (fluids present inside the cell) of the membrane. There has been no previous reports of such CI like characteristics in either the PM electrostatics or more importantly, in a system consisting of only monovalent electrolyte ions (as is the case we consider). In the next step, we looked into the role of the the surface charge density of the membrane and the concentration of the ions in influencing this PM electrostatics. This led to more interesting results. We found out that for biologically relevant conditions and for standard membrane surface charges, there is a possibility of having the location of CI on the surface of the membrane itself. This is a most remarkable result establishing a positive zeta potential on the surface of the negatively charged PM and we explored the phase-space where such situation of opposite signs of membrane zeta potential and membrane surface charge persists. This electrostatics definitely influences various measurable properties of the membrane. One such very important measurable property of a membrane is the membrane capacitance. It has been widely reported that the ionic environment does not influence the capacitance much. However, with exploration of this phase-space through our continuum simulations we were able to pinpoint a domain where the capacitance can be influenced by as much as 15%. This also stems from the fact that the electrostatics of the system is itself very interesting to study under various conditions. We then move on to explore the effect of this electrostatics on the adhesion of NP on the membranes. Most of these adhesive processes occur through the receptor-ligand (R-L) mechanism. Therefore, until and unless a ligand is able to physically influence a receptor and can get bonded to it, the process of adhesion will never begin. The electrostatics can cause a hindrance to this phenomenon. The main reason is the electrostatic osmotic or disjoining pressure, which causes a repulsion between the ligand-bearing NP and the receptor-bearing cell membrane, and forbids the NP to come to significant proximity of the PM for ensuring that the ligands start to interact with the receptors. Through our analysis, we calculated such repulsion and calculated the distance up to which this repulsion remains strong and can overcome the influence of other attractive effects (e.g., van der Waals forces or thermal forces) that drive the NP closer to the PM. We hypothesize that if the length of the ligand-receptor complex is not larger than this distance up to which the electrostatic repulsion effects remain dominant then the process of adhesion will not even begin. Next, we study what is the role of this ionic environment for the case where the NP adhere to the PMs non-specifically. Such non-specific adhesion (NSA) refers to the adhesion of the NP to the PM by actual physical attachment without involving R-L interactions. Understanding such NSA is vital to gauge the side effects of the NP-based drug delivery -- the dug carrying NP will invariably adhere (non-specifically) to the healthy cells causing damages to the healthy cells. Therefore the current practice necessitates uses of those NPs that demonstrate least cytotoxicity post adhesion and internalization in healthy cells. We show that when metallic NPs non-specifically adhere to the PMs, the resulting destruction of the surface charge effects of PMs would lead to a favorable energy change, which in turn drives the NP NSA to even stiffer membranes (e.g., cell membranes rich in cholesterol). Subsequently, we show that one can use biomimetic NPs (namely NPs encapsulated in PM-derived lipid bilayers) to ensure that electrostatic interactions between the biomimetic NPs and the PM can usher in the most coveted scenario where one can simultaneously ensure the promotion of specific adhesion and prevention of NSA. Finally we address the future directions of this work and how this work can start the discussion about the role of other kinds on nanoparticles in drug delivery and therapy.Item HIGH TEMPERATURE NANOMANUFACTURING FOR EMERGING TECHNOLOGIES(2018) Yao, Yonggang; Hu, Liangbing; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)High temperature processing can provide sufficient activation energy for materials’ compositional, structural, and morphological evolutions, and is essential for various kinds of reactions, synthesis, and post-treatment. However, the current high temperature heating sources, mostly furnaces, are far from satisfying for nanomaterials processing owing to their bulky size and limited temperature and ramp range (~1300 K, ~10 K/min). In this thesis, we have focused on the study of electrical triggered Joule heating as a new route for high temperature engineering of nanomaterials toward nanomanufacturing. We developed facile, highly stable and controllable heating strategies for micro/nanoscale high temperature engineering. Ultrahigh temperature annealing (>2500 K) is applied to carbon nanomaterials to address the defects and poor interfacial problems. In the carbon nanofibers (CNFs), the high temperature graphitizes the carbon nanomaterials with significantly improved crystallinity and less defects. Importantly, the rapid heating (~100 K/min) leads to junction welding at fiber intersections. Similarly in carbon nanotubes (CNTs), welded CNTs is achieved by incorporating a thin polymer coating, followed by high temperature annealing to form 3D interconnected structures, defined as an “epitaxial welding” process. Ultrafast thermal shock (~2000 K in 55 ms) is applied to metal salt loaded carbon substrates for in-situ synthesis of ultrasmall, well-dispersed nanoparticles. Metal salts decompose rapidly at high temperatures and nucleate into well-dispersed nanoparticles during the rapid cooling (rate of ~10E5 K/s). By varying the composition in salt mixtures, we synthesized bimetallic, multimetallic and high entropy alloy nanoparticles (HEA-NPs) containing up to 8 different and immiscible elements. The high temperature leads to atomic mixing in the liquid alloy state, while rapid quenching freezes the completely mixed state to form solid solution nanoparticles with a narrow size distribution. This is for the first time HEA-NPs were synthesized, enabled by the unique thermal shock method. We also developed scalable approaches such as employing non-contact radiative heating for large scale substrates (either conductive or non-conductive) and continuous roll-to-roll production. The high temperature engineering on nanomaterials are highly facile, energy-efficient, and reliable toward scalable nanomanufacturing. More exciting results and products are expected for various nanomaterials during/after the unique high temperature engineering.Item Development of Magnetic Nanoparticle-based Enrichment Techniques and Mass Spectrometry Methods for Quantification of the Clinical Biomarker Cardiac Troponin I(2016) Schneck, Nicole; Lee, Sang Bok; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Human cardiac troponin I (cTnI) in serum is a well-known clinical biomarker for cardiac tissue damage and is used for diagnosing myocardial infarction. Unfortunately, commercial cTnI immunoassays from different manufacturers can produce significantly different measurement results for the same sample. In order to improve the comparability of these measurements, clinical cTnI immunoassays need to be standardized. Ultimately, the goal of this work was to develop an isotope dilution-liquid chromatography-mass spectrometry (ID-LC-MS/MS) reference measurement procedure that could be used to assign concentration values to cTnI reference materials. However, given that most serum protein biomarkers are low abundant, enrichment was mandatory to successfully quantify cTnI at clinically significant concentrations (≈ 1-10 ng/mL). As such, the specific aim of this work was to develop enrichment techniques and an ID-LC-MS/MS method to quantify cTnI in patient serum samples. In order to achieved the required LC-MS/MS sensitivity, novel enrichment strategies were investigated to selectively isolate cTnI from serum and plasma. Silica coated magnetic nanoparticles were synthesized and conjugated with antibodies to act as immunoaffinity carriers. Magnetic nanoparticles were selected due to their variable surface modifications, high binding capacity, and the fact that they can be easily isolated using a magnet. After optimizing the enrichment and digestion procedures, isotopically labeled cTnI proteins were used as an internal standard for ID-LC-MS/MS analysis of cTnI to compensate for variations in the sample preparation. Finally, the developed LC-MS/MS-based assay was applied to measure cTnI concentrations in patient plasma samples. Effective enrichment methods proved to be crucial for achieving quantification of cTnI by ID-LC-MS/MS. To this end, a complementary ID-LC-MS/MS method was also developed to evaluate different antibody immobilization strategies and magnetic particle types as part of the method optimization. Overall, this work demonstrates significant improvements in magnetic particle enrichment techniques and LC-MS/MS detection for the analysis of cTnI in patient samples.Item POTENTIAL LOW TOXICITY CROSSLINKER FOR PROTEIN-BASED NANOPARTICLES(2015) XU, RUOYANG; Wang, Qin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Crosslinking is an essential procedure for maintaining the integrity of protein-based nanoparticles, but the application of toxic crosslinkers is usually undesirable. In this study, a tyrosinase-aided crosslinking procedure was developed and compared to a conventional crosslinker (i.e. glutaraldehyde). Nanoparticles were firstly synthesized from sodium caseinate (SC) in both aqueous and alcoholic solvent systems. The particles were crosslinked by tyrosinase (alone or with added natural phenols) or glutaraldehyde and then examined for their integrity under simulated environmental stress, including pH variation and solvent evaporation. Under aqueous condition, SC nanoparticles were not crosslinked sufficiently by tyrosinase or phenols alone, despite the abundance of tyrosine residues in SC. Conversely, satisfying crosslinking was achieved by tyrosinase combined with two natural phenols (catechol or chlorogenic acid, both at 2.5 mol/mol protein), as evidenced by stable particle size and count rate under environmental stress. A higher dose of 7.5 mol/mol protein was required for glutaraldehyde to achieve a comparable efficacy. Upon introduction of alcohol, the efficacies for both glutaraldehyde and tyrosinase-phenol mixtures decreased, but glutaraldehyde required lower dose and exhibited more significant crosslinking for achieving same crosslinking efficiency. However, a considerable number of nanoparticles were detected by scanning electron microscopy with both crosslinkers. Overall, tyrosinase-aided oxidation is a competitive, low-toxicity approach for crosslinking protein nanoparticles.Item FOOD PROTEIN-BASED NANOPARTICLES AS BIOAVAILABILITY ENHANCING ENCAPSULANTS(2015) Teng, Zi; Wang, Qin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Proteins are attractive bioavailability enhancers for poorly absorbed nutraceuticals or drugs, owing to their natural abundance, amphiphilic nature, and desirable biocompatibility. This study systematically investigated the preparation, characterization, and application of protein-based nanoparticles as effective nutraceutical/drug carriers. Soy protein, one of the most widely utilized proteins, was firstly employed for preparing nanoparticles. The particle formation involved partial unfolding of protein molecules, limited aggregation in the presence of the antisolvent, crosslinking via chemical bonds, and refolding of the constituent monomers. Satisfactory encapsulation efficiency (EE) and time-dependent release of curcumin, a chemopreventive compound, were observed. The nanoparticles were further subjected to conjugation with folic acid, a cancer cell-targeting ligand. A pronounced increase in the accumulation in tumor cells such as Caco-2 was achieved upon folic acid conjugation, which demonstrated the potential of this technique for the targeted delivery of anti-cancer drugs. To overcome the rapid digestion of soy protein nanoparticles in the gastrointestinal tract, carboxymethyl chitosan was employed as a second coating layer by a simple ionic gelation method. The formed particles exhibited satisfactory EE for vitamin D3 and controlled releasing profile in vitro. Beta lactoglobulin (BLG) as another protein of interest is a major component of whey protein, serving as a natural carrier for lipophilic nutrients. Our study suggested that the interaction between BLG and curcumin could be promoted by tuning the antisolvent content. A loading capacity (LC) and EE of up to 11% and 98% respectively could be achieved under the optimal conditions. Moreover, nanoparticles prepared with cationic beta-lactoglobulin (CBLG) were able to transport most of the encapsulated drug intact through the gastrointestinal (GI) tract owing to its desirable particle integrity. Other advantages of CBLG-based systems included superior mucoadhesion, permeation across the small intestine epithelia, and cellular uptake. Finally, as CBLG molecules/nanoparticles absorbed the negatively charged serum proteins in the cell culturing medium, their surface properties, cytotoxicity, and cellular uptake were significantly altered. This series of studies not only demonstrated the efficiency and versatility of protein-based nanoparticles as bioavailability enhancers but also shed some light on the mechanisms for the encapsulation, transport, and delivery of nutraceuticals or drugs.Item Bimetallic Nanoparticles for Advanced Energy Conversion Technologies(2015) Sims, Christopher; Eichhorn, Bryan W; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The increased demand for a more sustainable energy infrastructure has spurred the development of innovative energy conversion processes and devices, such as the proton exchange membrane fuel cell (PEMFC). PEMFCs are highly regarded as a clean alternative energy technology for various applications, such as motor vehicles or power generators. Factors limiting their commercial viability include the poisoning of the hydrogen oxidation reaction (HOR) electrocatalyst at the anode by carbon monoxide (CO), an impurity in the H2 fuel feedstocks derived from hydrocarbons, and the high expense and inefficiency of the oxygen reduction reaction (ORR) electrocatalyst at the cathode. The research described in this dissertation entails the synthesis and characterization of new bimetallic nanoparticle (NP) catalysts with controlled sizes, compositions, and architectures. By varying the NPs' compositions, structures, and electronic environments, we aimed to elucidate the physical and chemical relationships that govern their ability to catalyze chemical reactions pertinent to PEMFC operation. The ongoing research and development of these NP-based catalytic systems is essential to realizing the viability of this energy conversion technology. We describe the development of a simple method for synthesizing monometallic and bimetallic NPs supported on various reduced graphene oxide (rGO) supports. Electrochemical studies illustrate how the chemical nature of the rGO support impacts the catalytic behavior of the NP catalysts through unique metal-support interactions that differ depending on the elemental composition of the NP substrate. In another study, we present the synthesis and characterization of CoxPty NPs with alloy and intermetallic architectures and describe how their inherent characteristics impact their catalytic activities for electrochemical reactions. CoxPty NPs with alloy architectures were found to have improved CO tolerance compared to their intermetallic counterparts, while the performance of the CoxPty NPs for ORR catalysis was shown to be highly dependent on the NPs' crystal structure. Finally, we present the synthesis and characterization of various bimetallic core-shell NPs. Preliminary data for CO oxidation and PrOx catalysis demonstrated how subsurface metals modify the electronic structure of Ni and enhances its catalytic performance for CO oxidation and the PrOx reaction.