The isolation of single layers of van der Waals materials has shown that their properties can be significantly different compared to their bulk counterparts. These observations, illustrates the importance of interface interactions for determining the materials properties even in weakly interacting materials and raise the question if materials properties of single layer van der Waals materials can be controlled by appropriate hetero-interfaces. To study interface effects in monolayer systems, surface science techniques, such as photoemission spectroscopy and scanning probe microscopy/spectroscopy, are ideally suited. However, before these characterization methods can be employed, approaches for the synthesis of hetero-van der Waals systems must be developed, preferably in-situ with the characterization methods, i.e. in ultra-high vacuum. Therefore, in this thesis, we explored novel approaches for creating van der Waals heterostructures and characterized fundamental structural and electronic properties of such systems. Specifically, we developed an approach to decouple graphene from a Ir(111) growth substrate by intercalation growth of a 2D-FeO layer, and we investigate van der Waals epitaxy of MoSe2 on graphite and other transition metal dichalcogenide substrates. For the Ir(111)/2D-FeO/graphene heterostructure system, we first demonstrated the growth of 2D-FeO on Ir(111). The FeO monolayer on Ir(111) exhibits a long range moiré structure indicating the locally varying change of the coordination of the Fe atoms with respect to the substrate Ir atoms. This variation also gives rise to modulations in the Fe2+-O2- separation, and thus in the monolayer dipole. We demonstrated that this structure can be intercalated underneath of graphene grown on Ir(111) by chemical vapor deposition. The modulation of the dipole in the 2D-FeO moiré structure consequently gives rise to a modulated charge doping in the graphene. This effect has been studied by C-1s core level broadening. In general, this study demonstrates that modulated substrates can be used to periodically modify 2D materials. Growth of transition metal dichalcogenides (TMDCs) by molecular beam epitaxy (MBE) is a very versatile approach for growing TMDC heterostructures. However, there may be unforeseen challenges in the synthesis of some of these materials. Here we show that in MBE growth of MoSe2, the formation of twin grain boundaries is very abundant. While this is detrimental in our efforts for characterizing interface properties of TMDC heterostructures, however the twin grain boundaries have exciting properties. Since the twin grain boundaries are aligned in an epitaxial film we were able to characterize their properties by angle resolved photoemission spectroscopy (ARPES), which may be the first time a material’s line defects could be studied by this method. We demonstrate that the line defects are metallic and exhibit a parabolic dispersing band. Because of the 1D nature of the metallic lines, embedded in a semiconducting matrix, the electronic structure follows a Tomonaga Luttinger formalism and our studies showed strong evidence of the predicted so-called spin charge separation in such 1D electron systems. Moreover, a metal-to-insulator Peierls transition has been observed in this system by scanning tunneling microscopy as well as in transport measurements. Finally, we have shown that the defect network that forms at the surface also lends itself for decoration with metal clusters. Although unexpected, the formation of grain boundary networks in MoSe2 marks the discovery of a new material with exciting quantum properties.

Friction between nanoscale objects has been a subject of great interest and intense research effort for the last two decades. However, the vast majority of the work done in this area has focused upon the sliding friction between two rigid, atomically smooth surfaces. Thus the parameter most explored has been the corrugation in the atomic potentials and how this affects the force required to slide one object across another. In truth, many nanoscale objects whose translation force is of practical interest are more spherical in nature. We hypothesize that the factors that determine the translation force will be related, not only to the interfacial adhesion, but also to the mechanical properties of the translating object and its underlying surface. The dependence on these quantities of the friction is not known. In this dissertation we have utilized Atomic Force Microscopy and Force Spectroscopy to study the tribological properties of submicron scale polymeric particles to explore how the friction between these submicron spherical objects translating over planar substrates is related to interfacial energy and the mechanical properties for these particles. A technique for modifying the mechanical properties was developed and used to provide a set of samples over which we had control of the elastic modulus without corresponding changes in the chemical bonds. The modified mechanical properties were tested against the Flory-Rehner theory. Lateral force microscopy was used to measure the force required to translate asymmetric, nanoscale particles of controlled size, surface chemistry and moduli. Silicon wafers were used as the substrate. The effects of work of adhesion, elastic modulus of polystyrene microspheres, and contact radius between particle and substrate have been studied for the different modes of particle translation under an external force.

The use of nanoparticles for disease treatment is an increasingly popular area of research. The potential for multi-functionality allows nanoparticles to be used as transport and delivery vehicles for drugs and as diagnostic aides, among other applications, to address the unmet needs of many disease treatments. One such class of disease is osteoporosis including severe disorders, like Paget’s disease, Osteogenesis Imperfecta and Legg Calve Perthes disease. In this dissertation, we discuss a nanoparticle system consisting of gold nanoparticles surface functionalized with primary amine bisphosphonates, which is a classification of pharmaceuticals that is common in the treatment of osteoporosis. Functionalized nanoparticles allow for greater intracellular concentrations of pharmaceutical, while the properties of the gold nanoparticles provide the ability to track the pharmaceutical and enhance imaging. We have synthesized and characterized bisphosphonate functionalized gold nanoparticles of controlled size of approximately 15 nm, which are suitable for cellular uptake, and functionalized the surface using self-assembly with pamidronate and alendronate. In one major finding of this study, inductively coupled plasma mass spectrometry was used to estimate approximate surface density of the bisphosphonates on the gold nanoparticles. This resulted in concentrations of approximately 0.65 molecules per nm2 (approximately 154 Å2/molecule) for pamidronate functionalized on gold, and approximately 2.6 molecules per nm2 (approximately 39 Å2/molecule) for alendronate functionalized on gold. This allows for more accurate estimates of pharmaceutical concentrations, during in vitro and in vivo studies. Additionally, we investigated the effects of bisphosphonate functionalized gold nanoparticles on the viability and morphology of osteoclast and osteoblast cells in vitro. We found that attaching the bisphosphonates to the surface of the nanoparticles leads to increased apoptotic effects of the bisphosphonates on the osteoclast cells compared to free bisphosphonates. Further, we showed bisphosphonate functionalized gold nanoparticles may have an effect on nuclei morphology that may provide an additional means of modulating bone resorption rather than just through influencing viability. Further we showed that it may be possible to target concentrations that are safe for osteoblasts, which is critical in determining potential treatment concentrations. These viability results bring to light a number of potential considerations into the optimization of potential treatments, such as dosing concentrations. Finally, detailed results are given on effects of bisphosphonate functionalized gold nanoparticles on important behavior and activity of osteoclast and osteoblast cells in vitro. We showed that while using concentrations below the toxicity threshold, some of the normal activity of the cells could be maintained. RANKL and ALP expression in osteoblasts were maintained when removing viability as a variable. Additionally, bone nodule formation was also maintained for osteoblasts and co-cultured in vitro systems. Finally, we showed that the introduction of bone in the in vitro studies adds a new degree of consideration as to the interaction of the bisphosphonates with the hydroxyapatite surface. This strong interaction with bone is an important consideration in further developing potential treatments for osteoporotic disease. This dissertation provides insights into the use of bisphosphonate functionalized gold nanoparticles as a potential treatment and means of study for bone remodeling disorders.

The techniques mostly used to decontaminate air as well as water pollutants have drawbacks in terms of higher costs, require secondary treatment, and some methods are very slow. So, emphasis has been given to water though the use of photocatalysts, which break organic pollutants to water and carbon dioxide and leave no trace of by-products at the end. Photocatalytic remediation aligns with the waste and wastewater industries’ zero waste schemes with lower cost, eco-friendly and sustainable treatment technology. The commonly used photocatalysts such as titanium oxide (TiO2), zinc oxide (ZnO), tungsten oxide (WO3) have band gap of nearly 3.2 eV. The lower energy band-gap of a semiconductor makes it a better photocatalyst. The major drawbacks of photocatalysts are its inefficiency to work under visible light and high photocorrosion which limits its uses. These limitations can be mitigated through dopants and the formation of varying morphologies like nanowires, nanoparticles, nanotubes etc. Several organic pollutants are insoluble in water, which inhibits the pollutant (insoluble) to come in contact with photocatalytic material thus hindering remediation characteristic of a photocatalyst. Binder material used to immobilize the photocatalytic material tends to decompose due to oxidative and reduction reactions around the photocatalyst which causes the loss of photocatalytic material. This investigation displays the advantage of organic remediation in visible radiation using graphene (G) doped TiO2 nanoparticles and nanowires. The nanostructured G-TiO2 nanoparticles and G-TiO2 nanowires were synthesized using sol-gel and hydrothermal methods. The nanostructured materials were characterized using scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR) and particle analyser procedures. The remediation of organic compounds (methyl orange) in water was achieved under visible radiation using graphene doped nanostructured photocatalytic materials. The sol-gel synthesized G-TiO2 nanoparticles has shown complete remediation of methyl orange (MO) in less than four hours, thus displaying enhanced photocatalytic activity achieved through graphene doping on TiO2 nanostructures The dopant and structure introduced in zinc oxide (ZnO) nanomaterials bring foundation for enhanced photocatalytic activity due to lowering of the band gap, and decreasing of photocorrosion through delaying of electron-hole recombination. The challenge to synthesize both nanowire and nanoparticle structures of ZnO doped with graphene (G) are carried out by simple and cost effective hydrothermal as well as super saturation precipitation techniques, respectively. Various nanostructures of ZnO have been synthesized using precipitation and hydrothermal methods are ZnO nanoparticles, G doped ZnO nanoparticles, ZnO nanowires, G doped ZnO nanowires, TiO2 seeded ZnO nanowires and G doped TiO2 seeded ZnO nanowires The synthesized ZnO based nanostructures were characterized using SEM, TEM, XRD, UV-vis, FTIR and particle analyser methods respectively. The standard organic pollutant methyl orange (MO) dye was employed in the water to understand the effective remediation using ZnO nanostructured materials under visible light radiation. The G-ZnO NW structure has shown effective remediation of MO in water in three hours compared to other synthesized nanostructured ZnO materials. The petroleum compounds were photocatalytically remediated from water using G- TiO2 nanoparticles material in visible light radiation. The G-TiO2 nanoparticle was synthesized using sol-gel technique and used on various petroleum-based chemicals (toluene, naphthalene and diesel) were remediated, and samples were analysed using optical and gas chromatography (GC) techniques. The importance of pollutant to come in contact with photocatalyst have been demonstrated by employing surfactant along with G-TiO2 nanoparticles to remediate naphthalene. Earlier studies in this investigation have shown that graphene (G) doping in both titanium oxide (TiO2) and zinc oxide (ZnO), has brought about a reduction in photocorrosion, and an increase in the photocatalytic efficiency for remediation of organics under visible light (λ > 400nm). However, the graphene doped photocatalysts have proven to be hard to coat on a surface, due to the strong hydrophobic nature of graphene. So, attempts have been made to use polyaniline (PANI), a conducting polymer, as a binder material by insitu polymerization of aniline over G-TiO2 nanoparticles (G-TiO2 NP) and G-ZnO nanowires (G-ZnO NW) & characterized using SEM, XRD, UV-vis and FTIR techniques. The photocatalytic, as well as photoelectrochemical catalytic performance of PANI:G-TiO2 NP and PANI:G-ZnO NW, were investigated. The standard MO in water was used for both PANI:G-TiO2 NP and PANI:G-ZnO NW electrodes on conducting substrates. 1:1 PANI:G-TiO2 NP shows an increase of 31% in the remediation of MO in water at potential of +1000 mV, and with the ease in coating PANI:G-TiO2 NP and PANI:G-ZnO NW on various substrates, on top of the visible light remediation allows for the use of these materials and process to be used for practical applications of remediation of organics from water.

Water is the essential part of every organism and it is also a vital constituent of healthy living and diet. Unfortunately water contamination over the past decade has increased dramatically leading to various diseases. As technology advances, we are detecting many pollutants at smaller levels of concentrations. Arsenic (As) is one of those major pollutants, and Arsenic poisoning is a condition caused due to excess levels of arsenic in the body. The main basis for Arsenic poisoning is from ground water which naturally contains high concentrations of arsenic. A case study from 2007 states that over 137 million people in 70 countries were affected by arsenic poisoning from drinking water [1]. This thesis work is motivated by this study and investigates the fabrication, characterization, and testing of Opuntia ficus-indica mucilage nanofiber membranes formed using a mucilage, polystyrene (PS) and iron oxide (Fe2O3) solution by an electrospinning process. Cactus mucilage is a jelly-like substance, which is extracted from the cactus pad, and is an inexpensive, biodegradable and biocompatible material. It is also an abundant material available in nature. Polystyrene is a synthetic aromatic polymer prepared from monomer styrene. Polystyrene is further dissolved using D-Limonene as a solvent. D-Limonene is a non-toxic solvent and is a citrus extract of orange peelings. In an effort to enhance adsorption capacity for the mucilage nanofiber membranes, iron oxide nanopowder is incorporated into the polymeric solution. A mucilage and polystyrene-iron oxide solution is mixed in different ratios and electrospun to obtain nanofibers. The fibers will be characterized by certain techniques such as Scanning electron microscopy (SEM), contact angle measurements, viscosity and Fourier transform infrared spectroscopy (FTIR). The fibers obtained from mucilage and PS-Fe2O3 will be further tested under Atomic fluorescence spectrometry (AFS) for testing the removal of arsenic from water. Also, a life cycle analysis (LCA) is conducted to evaluate the environmental impacts of the fabrication of the membranes by using SimaPro® software.

There is a high prevalence in malnutrition among traumatic brain injury (TBI) due to the hypermetabolism and hypercatabolism which develop post injury. Traumatic brain injury patients are different, even among themselves, in their energy requirements and response to nutritional therapy. This implies that there are other factors that affect the energy intake of these patients and enhance the incidence of malnutrition. This dissertation study examines the nutritional status of TBI patients upon admission to the intensive care unit (ICU) and during their hospital stay to describe baseline status, detect changes in nutritional status over 7 days, and identify the factors affecting the adequacy of energy intake and the change in nutritional status as a consequence. Anthropometric measurements, biomedical measurements, measures of severity of illness, daily health status, level of brain injury severity, and other data were collected from the medical records of 50 patients, who were ≥ 18 years old, mechanically ventilated in the first 24 hours of ICU admission, and had a Glasgow Coma Scale score between 3-12. These data were used to examine the previous relationships. Although there was no statistically significant change found in body mass index and weight, there was a significant change detected in other nutritional markers, including hemoglobin, albumin, and total lymphocyte levels over the 7 days of ICU and hospital stay. No significant relationship was found between the adequacy of energy intake and total prescribed energy, severity of illness, level of brain injury severity, daily health status, patient age, intracranial pressure, or time of feeding initiation. Findings may be used to develop and test interventions to improve nutritional status during the acute phase of TBI. This will lay a foundation for health care providers, including nurses, to establish standards for practice and nutrition protocols to assure optimal nutrition assessment and intervention in a timely manner.

Permanent magnets are classified as hard magnetic materials with the main purpose of generating flux for applications such as electric motors, turbines, and hard drives. High coercivity, magnetic remanence, and saturation values with high stability are some of the requirements for permanent magnets. Rare-earth magnets including neodymium and samarium based magnets are known to have superior magnetic properties due to their high magnetocrystalline anisotropy. However, due to the price of rare-earth materials development of alternate permanent magnets composed of inexpensive materials is an ongoing process. Previously cobalt carbide (CoxC) have shown promise as a potential rare-earth free magnet alternative with magnetic properties comparable to that of hexaferrite materials. Unfortunately, CoxC magnets have a low magnetic saturation (50 emu g-1) which drastically lowers its energy product. Alternatively, iron carbide has a rather high bulk magnetization value of 140 emu g-1 and is composed of naturally abundant materials. The sole issue of iron carbide is that it is considered an intermediate magnet with properties between those of a hard and a soft magnetic material. The main focus of this work is the enhancement of the hard magnetic properties of iron carbide through size effect, shape anisotropy, magnetocrystalline anisotropy and exchange anisotropy. First a wet synthesis method was developed which utilized hexadecyltrimethylammonium chloride to control particle size, shape, and crystal structure to manipulate the magnetic properties of iron carbide. With this method a semi-hard 50 nm orthorhombic Fe3C phase and a magnetically soft single crystal hexagonal Fe7C3 structure with texture-induced magnetic properties were developed. The properties for both materials were further enhanced through formation of exchange bias Fe3C/CoO nanoaggregates and spring exchange coupling of the ferromagnetically hard and soft phases of Fe7C3/SrFe12O19. A 33% increase in coercivity was observed at room temperature for the antiferro/ferromagnetic Fe3C/CoO in comparison to the bare Fe3C. While iron carbide enhanced the magnetic saturation and remanence of strontium ferrite. This work concludes that with further development of iron carbide nanocomposites they may be employed as future alternative permanent magnets.

The objective of this thesis was to investigate whether the addition of carbon nanofibers had an effect on the splitting tensile strength of Hydro-Stone gypsum concrete. The carbon nanofibers used were single-walled carbon nanotubes (SWNT), buckminsterfullerene (C60), and graphene oxide (GO). Evidence of the nanofibers interacting with gypsum crystals in a connective manner was identified in both 1 mm thick concrete discs and concrete columns possessing a height of 2 in and a diameter of 1 in. Before imaging, the columns were subjected to a splitting tensile strength test. The results illustrate that while there is a general decrease in strength with an increase in nanofibers for the nanotubes and graphene oxide, the addition of C60 did not noticeably effect the strength. This trend is consistent with trends determined by previous studies.

Multifunctional nanocomposites are promising for a variety of applications ranging from microwave devices to biomedicine. High demand exists for magnetically tunable nanocomposite materials. My thesis focuses on synthesis and characterization of novel nanomaterials such as polymer nanocomposites (PNCs) and multi-walled carbon nanotubes (MWCNTs) with magnetic nanoparticle (NP) fillers. Magnetite (Fe3O4) and cobalt ferrite (CoFe2O4) NPs with controlled shape, size, and crystallinity were successfully synthesized and used as PNC fillers in a commercial polymer provided by the Rogers Corporation and poly(vinylidene fluoride). Magnetic and microwave experiments were conducted under frequencies of 1-6 GHz in the presence of transverse external magnetic fields of up to 4.5 kOe. Experiments confirm strong magnetic field dependence across all samples. When incorporated in to a cavity resonator device, tangent losses were reduced, quality factor increased by 5.6 times, and tunability of the resonance frequency was demonstrated, regardless of NP-loading. Work on PNC materials revealed the importance of NP interactions in confined spaces and motivated the study of confinement effects of magnetic NPs in more controlled environments, such as MWCNTs with varying diameters. MWCNTs were synthesized with diameters of 60 nm, 100 nm, 250 nm, and 450 nm to contain magnetic NP fillers (~10 nm) consisting of ferrites of the form MFe2O4, where M = Co2+, Ni2+, or Fe2+. All confined samples exhibit superparamagnetic-like behavior with stronger magnetic response with respect to increasing MWCNT diameter up to 250 nm due to the enhancement of interparticle interactions. This thesis provides the first systematic study of this class of nanocomposites, which paves the way to inclusion of novel nanostructured materials in real-world applications.

Metal oxides are of interest not only because of their huge abundance but also for their many applications such as for electrocatalysts, gas sensors, diodes, solar cells and lithium ion batteries (LIBs). Nano-sized metal oxides are especially desirable since they have larger surface-to-volume ratios advantageous for catalytic properties, and can display size and shape confinement properties such as magnetism. Thus, it is very important to explore the synthetic methods for these materials. It is essential, therefore, to understand the reaction mechanisms to create these materials, both on the nanoscale, and in real-time, to have design control of materials with desired morphologies and functions. This dissertation covers both the design of new syntheses for nanomaterials, as well as real-time methods to understand their synthetic reaction mechanisms. It will focus on two parts: first, the synthesis of 1-dimension (1-D) featured nanomaterials, including manganese-containing spinel nanowires, and tin dioxide and zinc oxide-based negative nanowire arrays; and second, a mechanistic study of the synthetic reactions of nanomaterials using in situ transmission electron microscopy (TEM). The work presented here demonstrates unique synthetic routes to single crystalline “positive” and “negative” metal oxide nanowires, and introduces a new mechanism for the formation of single-crystalline hollow nanorods.