R-3 Repository :: Browsing by Author "Tour, James M"

Browsing by Author "Tour, James M"

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Atomic metal on graphene for electrochemistry
(2019-04-18) Zhang, Chenhao; Tour, James M
As the limit in downsizing metal morphology is sought, the concept of single-atom catalysts (SACs) has emerged since it maximizes transition metal atom utilization and includes high exposed atom efficiency for a range of reactions. However, the preparation of SACs remains challenging because the high free energy of individual metal atoms leads to metal aggregation, affording nanoclusters or nanoparticles. A strong interaction between metal atoms and the supporting substrate is a desirable approach to anchor and stabilize these atomically dispersed metal sites. Because of its high specific area, large electron mobility and tunable surface chemistry, graphene, a well-defined 2D structure, is a promising substrate to support these single-atomic active sites for electrocatalytic applications. This thesis begins with the investigation of a general synthetic approach towards the atomic dispersion of metal atoms on nitrogen-doped graphene derived from graphene oxide. Herein, a series of atomic transition metal dispersed on nitrogen-doped graphene are synthesized and investigated as efficient electrocatalyst for the oxygen reduction reaction (ORR), CO2 reduction reaction (CO2RR) and nitrogen reduction reaction (NRR). In Chapter 1, single atomic dispersed rutheniums on nitrogen doped graphene are disclosed as efficient catalytic sites for ORR in acidic medium. This reaction is important in proton-exchange membrane fuel cells (PEMFC) that convert chemical energy liberated from the electrochemical reaction between hydrogen and oxygen into electrical energy, which is considered as a possible main source of power for next-generation automobiles. Chapter 2 describes the electrocatalytic performance of atomic iron on nitrogen-doped graphene for direct reduction of CO2 to CO in aqueous solution. Nitrogen-doping were also found to play vital roles in the enhancement of CO conversion. Finally, a preliminary result in Chapter 3 demonstrates that atomic Mo catalytic sites anchoring on a holey nitrogen-doped graphene framework possess an intriguing activity toward electrochemical N2 reduction to NH3 with excellent selectivity under ambient conditions. The holey nitrogen-doped graphene is an efficiency substrate for dispersing and bonding atomic Mo species, which are considered to be the active site for NRR. In general, aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure analysis (XAFS) reveals the existence of nitrogen-coordinated atomic metal moieties embedded on the nitrogen-doped graphene substrate. The electrochemical reaction mechanism on those isolated metal atoms surrounded by nitrogen atoms embedded in nitrogen-doped graphene is further investigated through density functional theory calculations. The nitrogen doped graphene substrate not only provides a stabilizing matrix for the metal atoms, but also impacts the electronic density of the metal atoms due to strong nitrogen-metal interactions, which may lead to their enhanced electrocatalytic activity in ORR, CO2RR and NRR. This work has built a bridge between homogenous and heterogenous catalysts, expanding the possibility of designing and engineering atomic structures of graphene with transition metals toward electrochemical applications.
Carbon and Silicon Nanomaterials for Medical Nanotechnology Applications
(2015-05-18) Gizzatov, Ayrat; Wilson, Lon J.; Tour, James M; Vajtai, Robert; Decuzzi, Paolo
This dissertation focuses on the development of sp2-carbon- and silicon-based nanomaterials for medical diagnostics and in vivo magnetic field-guided delivery applications. To realize these applications, especially for the development of new in vivo Magnetic Resonance Imaging (MRI) contrast agents (CAs), high solubility in aqueous media is required. Therefore, this work first details development of a new non-covalent method for the preparation of stable aqueous colloidal solution of surfactant-free sp2-carbon nanostructures, as well as a second rapid covalent functionalization procedure to produce highly-water-dispersible honey-comb carbon nanostructures (ca. 50 mg/mL). Next, highly-water-dispersible graphene nanoribbons and Gd3+ ions were together used to produce a high-performance MRI CA for T1- and T2- weighted imaging. In terms of its relaxivity (r1,2) values, this new CA material outperforms currently-available clinical CAs by up to 16 times for r1 and 21 times for r2. Finally, sub-micrometer discoidal magnetic nanoconstructs have been produced and studied for applications for in vivo magnetic-field-guided delivery into cancerous tumors. The nanoconstructs were produced by confining ultra-small superparamagnetic iron oxide nanoparticles (USPIOs) within mesoporous silicon which produced T2-weighted MRI CA performance 2.5 times greater than for the free USPIOs themselves. Moreover, these nanoconstructs, under the influence of an external magnetic field, collectively cooperated via a new mechanism to amplify accumulation in melanoma tumors of mice. Overall, the results of this dissertation could aid in the rapid translation of these nanotechnologies into the clinic, while, hopefully, also serving as an inspiration for continued research into the field of Medical Nanotechnology.
Carbon Nanomaterials and Their Derivatives for Traumatic Brain Injury and Other Biomedical Applications
(2018-10-23) Mendoza, Kimberly; Tour, James M
Carbon nanomaterials possess unique chemical and functional properties allowing for their applications across a variety of fields including medicine, energy, materials, mechanics and more. Herein, the synthesis of poly(ethylene glycol) hydrophilic carbon clusters (PEG-HCCs) and poly(ethylene glycol) graphene quantum dots (PEG-GQDs), as well as their biomedical applications as antioxidants is described. Although use of antioxidants has been aimed at reducing the presence of reactive oxygen and nitrogen species (ROS and RNS), success in clinical trials has been disappointing. Traumatic brain injury (TBI) is a leading cause of death and disability in the United States, especially when complicated by secondary trauma, such as hemorrhagic hypotension. Oxidative stress is a prominent feature of TBI that can result in loss of cerebral blood flow (CBF) to the brain causing an increased susceptibility to hypotension and intracranial hypertension. The development of PEG-HCCs through the oxidation of single-walled carbon nanotubes (SWCNTs) has shown its capability to quench SO and HO•. PEG-HCCs are soluble, non-toxic potent antioxidants that are stable in biological media. They can be administered through IV and have been tested in a rat model of TBI. Additionally, the application of PEG-HCCs in a mouse Alzheimer’s disease model was also explored. PEG-HCCs have demonstrated the ability to restore CBF to the brain after injury when administered through IV. Additionally, intranasal administration of PEG-HCCs has been shown to reduce amyloid precursor protein (APP) in the brain. PEG-GQDs, similar to PEG-HCCs, was developed as a derivative and cost-effective antioxidant carbon nanomaterial for the treatment of TBI. Using coal as a starting material (bituminous and anthracite) GQDs were characterized and modified with poly(ethylene glycol). Their intrinsic and chemical properties were evaluated also showing the ability to quench superoxide (SO) and hydroxyl radical (HO•). PEG-GQDs were tested in a rat model of TBI and demonstrated the ability to restore CBF to the brain after injury. PEG-GQDs are water-soluble, non-toxic antioxidants that can be administered intravenously. Overall, PEG-HCCs and PEG-GQDs were studied in vitro and in vivo animal models with novel results that bear further investigation. The need for the development of robust therapy to address oxidative stress is necessary to effectively treat and eliminate damage that otherwise results in devastating outcomes for patients on personal, social and societal levels.
Carbon nanomaterials and their small molecule analogues for biomedical applications
(2017-09-26) Nilewski, Lizanne G.; Tour, James M
Carbon nanomaterials possess unique structural features that give them interesting properties and reactivity for applications in medicine, electronics, materials, catalysis, and more. Herein, the synthesis of PEG-HCCs, PEG-GQDs, and small molecule analogues of these functionalized carbon nanomaterials, as well as their biomedical applications as drug delivery vehicles and antioxidants, are described. PEGylated hydrophilic carbon clusters (PEG-HCCs) are non-toxic water-soluble carbon nanomaterials synthesized by the oxidation of single walled carbon nanotubes (SWCNTs). It is shown that PEG-HCCs can be non-covalently loaded with drugs and covalently modified with various targeting peptides to deliver drugs selectively to glioblastoma cells in vitro and tumors in vivo. It was also found that sensitive imaging of tumors over normal tissue could be achieved by loading the peptide-targeted PEG-HCCs with fluorescent dyes instead of drugs. PEG-HCCs are also powerful antioxidants that are capable of quenching superoxide and hydroxyl radicals. The application of PEG-HCCs as immunomodulators for the treatment of multiple sclerosis (MS) and other T cell-mediated autoimmune disorders like rheumatoid arthritis, was explored. PEG-HCCs were observed to selectively target T cells over other immune cells, and were found to modulate T cell activity by inhibiting proliferation, and they significantly reduced the severity of symptoms in a rat model of MS. In addition to PEG-HCCs, another class of antioxidant carbon nanomaterials, coal-derived graphene quantum dots (GODs) and PEG-GQDs, was developed. These highly oxidized redox active materials were characterized and tested with respect to superoxide and hydroxyl radical activity. PEG-GQDs were also studied in a rat model of traumatic brain injury. It was found that GQDs and PEG-GQDs possess similar characteristics, reactivity, and antioxidant abilities to the HCCs both in cell-free systems and in vivo. Furthermore, perylene diimides (PDIs) and naphthalene diimides (NDIs) were synthesized to mimic the structure and antioxidant activity of the HCCs and GQDs. The PDIs in particular were found to mimic both HCCs and the enzyme SOD by catalyzing the dismutation of superoxide into O2 and H2O2. PDIs were studied with respect to their antioxidant properties, and modified PDIs were also synthesized to modulate their redox properties. Finally, PDIs were studied as antioxidants in in vitro T cell experiments, where it was found they have similar behavior to the PEG-HCCs as potential immunomodulators. Lastly, another class of biologically active targeted molecules was studied for the treatment of cancer. Light-activated nanomachines based on the previous work of the Tour lab were selectively targeted to cancer cells using short peptides, similar to the targeting of PEG-HCCs to tumors. These peptide-targeted nanomachines were shown to associate with their intended target cancer cells over control cells, and once bound to the membranes of target cells, the nanomachines were activated using UV light. This induced MHz rotation of the “motor” moiety and mechanically disrupted the cell membrane leading to cell death. Overall, the PEG-HCCs, PEG-GQDs, PDI/NDI small molecules, and nanomachines were studied in cell-free systems, in vitro, and in vivo with promising results that warrant continued investigation of their mechanism and applications.
Energy Applications of Graphene-Based Nanomaterials and Their Composites
(2018-11-26) Wang, Tuo; Tour, James M
Graphene-based nanomaterials, which contain two-dimensional graphene sheets that consist of sp2-C atoms arranged in a hexagonal lattice, have exceptional electrical conductivity and mechanical properties, thereby showing promise for use in energy-related devices. Two different types of graphene nanomaterials were studied: one-dimensional graphene nanoribbons and three-dimensional graphene foams. The graphene nanoribbons have both abundant edges for chemical functionalization that improves their dispersibility and interfacial interaction with other materials, and high aspect ratio that affords percolation on a specific area at a smaller mass loading. They have been demonstrated to be an excellent choice for making conductive films with deicing and anti-icing capabilities (Chapter 1) and as a conductive additive for dendrite-free Li metal anodes in Li metal batteries and red P anodes in high energy density Li-ion batteries (Chapter 2). It was found that red P was not only a good candidate for anode materials, but a surprisingly powerful tool to improve battery safety by in situ detection of Li dendrites in an ordinary two-electrode battery system. The other graphene nanomaterial, the three-dimensional graphene foams prepared from polyacrylonitrile using the powder metallurgy method, exhibited high electrical conductivity and high mechanical strength that powdered graphene species cannot achieve, which enabled them to reinforce epoxy resin and enhance the electrical conductivity of the epoxy to an unprecedented level (Chapter 3).
Flash Graphene Synthesis: Optimization, Scaling, and Thermodynamics
(2023-11-09) Eddy, Lucas; Tour, James M
Flash Joule heating has been widely used as an ultrafast, scalable, and versatile synthesis method, most prominently in the synthesis of flash graphene. Traditional methods of graphene synthesis involve purely chemical or thermal means and are far more energy-intensive and far less scalable than flash Joule heating. Herein, we demonstrate kilogram-scale flash graphene synthesis using an automated flash Joule heater. We implement a pulse width modulation system to improve graphene quality and uniformity while scaling up to larger batch sizes. We furthermore report evidence that the flash Joule heating synthesis of graphene is an electrothermal process in which the presence of charge and the resulting electric field inside the graphene precursor facilitates graphene synthesis by lowering the activation energy of the reaction. We present both through experiment and theory the thermodynamic values of the flash Joule heating transition from amorphous carbon feedstocks, to turbostratic graphene, to finally ordered graphene and graphite. We finally compare the energy, environmental, and monetary costs of flash Joule heating to other scalable methods for graphene production via life cycle and technoeconomic assessments.
Flash Joule heating for nanomaterials synthesis, waste upcycling, and hydrogen production
(2023-08-11) Wyss, Kevin Michael; Tour, James M; Weisman, Bruce
Many sustainable technologies, such as chemical recycling of waste plastics or the low-carbon intensity production of clean-burning hydrogen gas, have existed for decades. However, despite current political and societal initiatives to minimize plastic waste or transition to hydrogen energy sources, little global progress has been made in their widescale adoption. Over-complexity or critical shortcomings in the economic viability and scalability of these processes often limit their industrial implementation and overall impact. Similarly, although hailed a 21st century ‘wonder-material’, graphene has followed a related trajectory because of the same limiting factors. Flash Joule heating represents a new strategy that can be adapted to address many applications including plastic recycling or upcycling, low-carbon intensity hydrogen production, and graphene synthesis. Flash Joule heating is scalable, low in process complexity, and affords low-cost, efficient, and environmentally friendly production of high-value nanomaterials. This thesis begins by introducing current industrial graphene production methods and applications in chapter 1. Chapters 2-4 highlight the synthesis, characterization, and application of turbostratic graphene from amorphous carbonaceous feedstocks. In chapter 2, simple flash Joule heating synthesizes graphene from waste materials such as ash resulting from the chemical recycling of plastics. The graphene quality is optimized and characterized, and the value of the produced graphene is demonstrated as a reinforcing additive in various composite applications. In chapter 3, graphene with varying 13C/12C isotopic content is prepared, up to 99% 13C content, which results in unexpected spectroscopic findings. In chapter 4, graphene is formed from mixed waste plastics, with quantified efficiency and tabulated environmental burdens, and compared to current industrial methods, using a perspective life-cycle assessment. Taking inspiration from chemical vapor deposition and different bottom-up reaction strategies, other exciting classes of graphitic carbon nanomaterials can be synthesized using flash Joule heating. Holey and wrinkled graphene with significantly increased surface area is synthesized from mixed waste plastics in chapter 5, and applied in electrocatalytic and energy-storage applications. A similar material can be synthesized in a scalable manner using simple alkaline salt templating, and used for water purification applications, as demonstrated in chapter 6. Carbon nanotubes, nanofibers, and hybrid 1-dimensional and 2-dimensional materials can also synthesized through the in situ formation of catalytic growth nanoparticles, upcycling mixed waste plastic to outperform carbon nanotubes and graphene in composite applications, with significant improvements in environmental impact as compared to current carbon nanotube production methods. Lastly, in chapter 8, production of clean hydrogen gas from waste plastic at zero net-cost is demonstrated, due to the co-production of high-value graphene. Through process optimization, flash Joule heating of plastics, with no added catalyst, the highest yet-published yields of hydrogen gas from plastics is achieved and demonstrated for all common consumer waste plastics. Life-cycle assessment and techno-economic analysis demonstrate that the flash Joule heating hydrogen production strategy releases less CO2 than all current methods excluding electrolysis, while affording extreme cost-competitiveness for hydrogen production. Further, through study of the reaction intermediates and other volatiles coupled with thermodynamic and molecular dynamics simulations, the seed-growth, bottom-up hypothesis of graphene formation during flash Joule heating can be further substantiated.
From Laser-Induced Graphene to Flash Graphene
(2020-03-20) Luong, Duy X; Tour, James M
Laser-induced graphene (LIG) was recently discovered by one step laser treatment of polyimide with a CO2 laser (10.6 µm wavelength) under ambient atmosphere. Because of the porous structure of LIG with abundant accessible graphene domains, LIG was applied in mircrosupercapacitors, electrochemical catalysts, heat transfer materials and many other applications. In this thesis, in the first chapter, I will begin my work with tailoring the laser induced graphene chemically and morphologically. A new LIG structure named laser-induced graphene Fibers (LIGF) was also discovered as fiber versions of LIG that can be fabricated to millimeter-long scale vertical aligned graphene forests. Further, I will discuss how a controlled environment alters the morphology and doping of LIG that eventually leads to the change from superhydrophobic to superhydrophilic surface. The second chapter will be the laminated object manufacturing technique for the 3D printing of both LIG and LIGF and their potential applications in energy storage and flexible electronics. In the third chapter, I will discuss the method to make LIG composite with a variety of materials. The last chapter will apply the knowledge of laser induced graphene to develop a facile graphene synthesis from a flash Joule heating process that I call flash graphene.
Hybrid Carbon Nanostructures for Li-based Energy Devices
(2018-11-08) Lopez Silva, Gladys Anahi; Tour, James M
In this work, we explored the use of carbon nanostructures as host materials, interlayers, and electrodes for high-performance lithium-sulfur (Li-S) batteries, as well as lithium-ion (Li-ion) capacitors. The adverse effects of CO2 on the environment have driven the transition to a more carbon-neutral society, where batteries and capacitors play a crucial role by making possible self-sustained renewable sources and electric transportation. However, these applications demand the development of devices with higher energy densities or that they can withstand harsh conditions. Herein, the use of nanostructures based on carbon nanotubes, graphene, and graphene nanoribbons to stabilize the sulfur cathode and the lithium metal anode is presented. Also, this thesis describes the use of the same structures to fabricate an all-carbon Li-ion capacitor capable of performing at high pressures. Our results indicate that 3D conductive carbon networks are essential to obtain high capacities and good rate capabilities; however, the cycle stability can only be obtained when the lithium polysulfide diffusion is mitigated. In the case of lithium metal anodes, a lithiated carbon nanotube interface can control the Li+ ion flux and suppress the growth of lithium dendrites. Lastly, pressure can improve the energy and power densities of Li-ion capacitors, but there is a balance where it can also affect the performance. Future research could undertake to explore more carbon materials for the stabilization of sulfur cathodes and lithium metal anodes and to identify the changes that the electrodes experience while performing in harsh conditions.
Laser induced graphene materials and their use in electronic devices
(2022-09-06) Tour, James M; Lin, Jian; Peng, Zhiwei; Kittrell, Wilbur Carter; Rice University; William Marsh Rice University; United States Patent and Trademark Office
In some embodiments, the present disclosure pertains to methods of producing a graphene material by exposing a polymer to a laser source. In some embodiments, the exposing results in formation of a graphene from the polymer. In some embodiments, the methods of the present disclosure also include a step of separating the formed graphene from the polymer to form an isolated graphene. In some embodiments, the methods of the present disclosure also include a step of incorporating the graphene material or the isolated graphene into an electronic device, such as an energy storage device. In some embodiments, the graphene is utilized as at least one of an electrode, current collector or additive in the electronic device. Additional embodiments of the present disclosure pertain to the graphene materials, isolated graphenes, and electronic devices that are formed by the methods of the present disclosure.
Laser Induced Graphene Nanomaterials and Applications
(2017-10-16) Luong, Duy Xuan; Tour, James M
Laser-induced graphene (LIG) was recently discovered by one step laser induction of CO2 laser (10.6 µm wavelength) under ambient atmosphere. Because of the porous structure with lots of defect sites, LIG were studied as mircrosupercapacitors, electrochemical catalyst, heat transfer and number of applications are being researched. In this thesis, in the first chapter, I will begin my work with tuning the laser parameters to understand the formation of the LIG structure that was found to be a fluid dynamic that interestingly, is similar to a sneeze. A new LIG structure, another product of this laser induction process which named Laser Induced Graphene Scrolls (LIGS) was also discovered as scrolled version of LIG that can be fabricated to millimeter scale vertical aligned forest. The second chapter will be the laminated object manufacturing technique for the 3D printing of both LIG and LIGS and their potential applications in energy storage and high strength graphene base composite. Lastly, in the third chapter, I will discuss how control environment alter the morphology and doping of LIG that eventually leading to the change from superhydrophobic to superhydrophilics.
Laser-Induced Graphene for Energy application
(2020-08-31) Ren, Muqing; Tour, James M
The rapidly increasing demand for clean energy has stimulated extensive research efforts on the renewable energy technologies, such as fuel cells, hydrogen and oxygen production from water splitting, and rechargeable metal-air batteries. The underlying chemical processes, including the oxygen evolution reaction (OER), hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), generally suffer from sluggish reaction kinetics. Therefore, effective catalysts are necessary to facilitate the reactions. This thesis focuses on the development of laser-induced graphene (LIG) derived materials and catalysts for electrochemical energy storage devices. LIG is a 3D porous graphene material grown on a flexible substrate that is prepared by a one-step laser scribing process on commercial polyimide (PI) film. The LIG derived from PI is highly porous and is easily synthesized under ambient conditions in a scalable process. Chapter 1 discusses the oxidation of LIG by O2 plasma to form oxidized LIG, which boosts its performance in both OER and ORR resulting in an enhanced activity towards rechargeable Li-O2 battery. In Chapter 2, a distinctive re-lasing method was proposed to prepare metal oxide/LIG composites as efficient catalysts for water oxidation (OER). Unlike the conventional methods, such as solvo-/hydro-thermal, thermal pyrolysis or chemical vapor deposition processes, the re-lasing synthesizes the NiFe-based catalysts through a facile laser scribing process without any tedious procedures. Chapter 3 introduces a bifunctional catalyst Co3O4/LIG that was synthesized through a facile re-lasing process, showing OER and ORR activity comparable to noble metal-based catalysts in alkaline electrolyte. Furthermore, the Co3O4/LIG exhibited promising performance in Zn-air and Li-O2 batteries. Chapter 4 discusses ternary metal oxide/graphene hybrid catalysts by combining ORR-active Co/Mn with OER-active Ni and Fe species to promote the bifunctional activity all in an in situ formed LIG flexible film. These hybrid catalysts exhibit high catalytic activity and surpass the performance of precious metal Pt and RuO2 catalysts in Znair batteries and demonstrate applications in flexible Zn-air batteries that would be beneficial for wearable and flexible electronic devices. Chapter 5 discusses the performance of bifunctional OER/ORR catalysts MnNiFe/LIG (M111/LIG and M311/LIG, where the numbers reflect the relative molar ratio of Mn, Ni and Fe species) in Li-O2 and Li-air batteries without the presence of a redox mediator. The underlying mechanism in Li-O2 battery was investigated. Chapter 6 introduces the design of dual polymer gel electrolyte (DPGE). The combination of DPGE with a Mnbased catalyst enhance the performance of quasi-solid-state Li-O2 batteries.
Synthesis and Applications of Carbon Materials
(2018-03-05) Metzger, Andrew; Tour, James M
The synthesis and applications of carbon-containing materials is discussed. Carbon materials discussed range from conductive polymer-coated minerals to polymer-functionalized graphene nanoribbons to graphene quantum dots. Applications range from wellbore reinforcement to conductive drilling fluids to lanthanide sensitization. In the first chapter, the preparation and use of polyaniline-coated barite as a weighting agent in conductive drilling fluids is discussed. In the second chapter, microwave-assisted curing of thermosets accelerated by functionalized graphene nanoribbon is discussed. In the third chapter, the synthesis of graphene quantum dots via nitric acid oxidation of coal is discussed. In the fourth chapter, the sensitization of lanthanides by graphene quantum dots is discussed.
Synthesis and Applications of Flash Graphene and Flash Joule Heating
(2022-11-30) Advincula, Paul Benedict Andrade; Tour, James M
Going into the 21st century, increasing greenhouse gas emissions, growing landfills of waste plastic and rubber, and rising demand for building materials have combined to create one of our greatest environmental challenges. Anthropogenic greenhouse gas emissions are one of the primary drivers of climate change, stemming from a variety of human activities, including burning fossil fuels for heat and energy, storing waste in landfills, and production of industrial materials. Rubber and plastic waste are generally landfilled or incinerated for energy, leading to worldwide contamination and further emission of greenhouse gases. Additionally, urbanization and industrialization across the globe has led to increased demand for industrial materials such as epoxies and cementitious materials. In this work, flash Joule heating (FJH) is shown to be an effective technology for reducing greenhouse gas emissions, upcycling waste materials, and improving common building materials through conversion of carbon materials into flash graphene (tFG/FG) and its subsequent application. Chapter 1 discusses the initial approach to optimizing the FJH process for conversion of waste rubber and rubber tire-derived carbon black into FG materials and their subsequent use as an additive to cementitious materials. Chapter 2 focuses on the use of FJH to obtain hybrid FG/carbon nanotube (CNT) morphologies from pristine single-walled CNT (SWCNT) and their ability to improve the mechanical properties of epoxies. Chapter 3 demonstrates the efficacy of FG made from waste plastic (WPFG) and metallurgical coke (MCFG) as an additive to lubricants to improve their tribological properties. Chapter 4 discusses the ultra-high loading utilization of MCFG as a reinforcing and filling additive in epoxy composites and the reduction in environmental impacts that can result from its use. Chapter 5 demonstrates how a combination of molten carbonate electrolysis and FJH can be used to convert gaseous CO2 into a carbon-negative, reinforcing FG additive to vinyl ester (VE). Chapter 6 provides some preliminary work on replacing fine aggregates in concrete with FG aggregates (FGA) to lighten and strengthen concrete. Chapter 7 discusses the valorization of asphaltene into FG (AFG) and its subsequent effect on the mechanical, thermal, and anti-rust properties of composites.
Synthesis and Monitoring of Nanocars Bearing Different Wheel Types
(2016-02-12) Chu, Pinlei Edmund; Tour, James M
Our group has developed different nanomachines over the years, while some of them are designed to perform in solution phase, a group of molecules termed nanocars were designed to specifically operate on solid surfaces. In this work, wheels, designed to yield better surface and molecule interaction for our studies is synthesized. In the past we have used mainly C60 fullerene wheels for our nanocars molecules. But after we decided to integrate a light activated motor into the nanocars, the fullerene wheels had to be phased out since the fullerene is known to quench the light energy used to actuate the motor. Our group then primarily utilized the p-carborane wheel as it does not show the same quenching effect with the motors. To improve the mobility and diffusion constant of the nanocars, a new generation of wheels was developed, featuring adamantane. A four-wheeled and a three-wheeled fluorescent nanocar was synthesized and monitored, showing enhanced performance to the p-carborane wheeled analogue, which we attribute to the lower surface/wheel interactions. The adamantane wheels were then used to synthesize two nanocars with both a fluorescent 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) core and a MHz frequency light-activated unidirectional rotary motor, one molecule that is angular and expected to operate in circles and one that is straight and expected to primarily move in a single direction. Preliminary experiments have been conducted and show promising results. While the BODIPY core does quench some of the energy that was supposed to be directed to the motor, the motor still accelerates the nanocar to increase the diffusion constant. The same principle was used to synthesize a molecule with BODIPY core and motor (but without wheels) that could operate in solution. Finally, a two-wheeled nanocar was synthesized with a water soluble extension that could fit into cyclodextrin (CD) cavities and serve as wheels. This nanocar is expected to have very high surface interaction and could be used as to modify surface interactions and the resulting mobility and diffusion constants of nanocars on surfaces.
Synthesis, Structure and Properties of Various Carbon Nanomaterials
(2017-07-24) Li, Yilun; Tour, James M
Carbon nanomaterials can have a unique place in the field of nanotechnology thanks to their exceptional electrical, optical, chemical, and mechanical properties, and thus they have become promising for a diverse array of applications. More importantly, the properties of a specific carbon nanomaterial are often determined by the structure of the material itself, which further traces back to its synthesis. Accordingly, it is of great interest and importance to understand the relationship between the synthesis, structure, and properties of the carbon nanomaterials. My thesis begins with the chemical vapor deposition (CVD) synthesis and investigation of various graphene/nanotube (NT) hybrid structures in Chapter 1, including rebar graphene from functionalized boron nitride nanotubes (BNNTs), growing carbon nanotubes (CNTs) from both sides of graphene, and the selective growth and transfer of seamless three-dimensional (3D) graphene/CNT hybrids. Then, Chapter 2 discusses the fabrication of laser-induced graphene (LIG) materials in controlled atmospheres. Next, Chapter 3 describes the 3D printed graphene foams. Finally, Chapter 4 introduces biochar as a renewable source for high-performance CO2 porous carbon sorbent.
Ultrashort Single-walled Carbon Nanotubes: A Platform for Medical Imaging and Therapy
(2015-04-21) Law, Justin Jonathan; Wilson, Lon J.; Tour, James M; Wong, Michael S; Curley, Steven A
Ultra-short single-walled carbon nanotubes (US-tubes) have been used to encapsulate various metal ions and small molecules for both diagnostic and therapeutic applications. Of the US-tube derivatives, one of the best characterized is the gadonanotube (GNT). GNTs are remarkable due to their greatly enhanced relaxivity, which is up to 40 times larger than current clinically available gadolinium based contrast. The work in this thesis explores the mechanisms contributing to this phenomenon. This is accomplished by using a series of closely related chelating ligands to explore the role of the coordination environment on the loading, retention, and relaxivity of gadolinium ions within the US-tubes. Further, the chelation system is applied to the positron emitting radioisotope ⁶⁴Cu and concurrent loading with gadolinium ions to produce bimodal imaging agents is discussed. In order to assess the viability of US-tubes as a platform for delivering medically relevant molecules, the biocompatibility of the US-tubes is explored. The cellular uptake and subcellular localization of the US-tubes is determined by Raman mapping and differences in US-tube aggregation and cellular response are analyzed. A strategy for enhancing water solubility of US-tube derivatives while retaining encapsulated ions is discussed. Finally, the heating properties of US-tubes in an external radiofrequency field are assessed to determine potential therapeutic applications.

Browsing by Author "Tour, James M"

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