Browsing by Author "Tour, James M."
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Item A scientific machine learning framework to understand flash graphene synthesis(Royal Society of Chemistry, 2023) Sattari, Kianoosh; Eddy, Lucas; Beckham, Jacob L.; Wyss, Kevin M.; Byfield, Richard; Qian, Long; Tour, James M.; Lin, Jian; NanoCarbon Center; Welch Institute for Advanced MaterialsFlash Joule heating (FJH) is a far-from-equilibrium (FFE) processing method for converting low-value carbon-based materials to flash graphene (FG). Despite its promises in scalability and performance, attempts to explore the reaction mechanism have been limited due to the complexities involved in the FFE process. Data-driven machine learning (ML) models effectively account for the complexities, but the model training requires a considerable amount of experimental data. To tackle this challenge, we constructed a scientific ML (SML) framework trained by using both direct processing variables and indirect, physics-informed variables to predict the FG yield. The indirect variables include current-derived features (final current, maximum current, and charge density) predicted from the proxy ML models and reaction temperatures simulated from multi-physics modeling. With the combined indirect features, the final ML model achieves an average R2 score of 0.81 ± 0.05 and an average RMSE of 12.1% ± 2.0% in predicting the FG yield, which is significantly higher than the model trained without them (R2 of 0.73 ± 0.05 and an RMSE of 14.3% ± 2.0%). Feature importance analysis validates the key roles of these indirect features in determining the reaction outcome. These results illustrate the promise of this SML to elucidate FFE material synthesis outcomes, thus paving a new avenue to processing other datasets from the materials systems involving the same or different FFE processes.Item Addressable SiOX memory array with incorporated diodes(2016-07-05) Tour, James M.; Yao, Jun; Lin, Jian; Wang, Gunuk; Palem, Krishna; Rice University; Nanyang Technological University; United States Patent and Trademark OfficeVarious embodiments of the resistive memory cells and arrays discussed herein comprise: (1) a first electrode; (2) a second electrode; (3) resistive memory material; and (4) a diode. The resistive memory material is selected from the group consisting of SiOx, SiOxH, SiOxNy, SiOxNyH, SiOxCz, SiOxCzH, and combinations thereof, wherein each of x, y and z are equal to or greater than 1 and equal to or less than 2. The diode may be any suitable diode, such as n-p diodes, p-n diodes, and Schottky diodes.Item Adsorption of aqueous insensitive munitions compounds by graphene nanoplatelets(Elsevier, 2024) Gurtowski, Luke A.; McLeod, Sheila J.; Zetterholm, Sarah Grace; Allison, Cleveland D.; Griggs, Chris S.; Gramm, Josh; Wyss, Kevin; Tour, James M.; Sanchez, Florence; Rice Advanced Materials Institute; Smalley-Curl InstituteMitigation strategies for potential environmental impacts of insensitive munition (IM) compounds, including 2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), nitroguanidine (NQ), and methylnitroguanidine, (MeNQ) are being considered to enhance sustainability of current or potential IM formulations. Graphene nanoplatelets (GnPs) were investigated for adsorptive removal of each compound. GnPs were characterized to determine surface areas, along with particle size and zeta potential at different pH and ionic strength conditions. Adsorption kinetics and isotherm studies were conducted, comparing results against granular activated carbon (GAC). Ionic strength, pH, and temperature were adjusted to inform impacts on adsorptive behaviors and performance. The results indicated that GnPs adsorbed IM compounds more rapidly than GAC. Additionally, GnPs removed DNAN with greater capacity compared to GAC, likely due to π-π interactions. GnPs removed other compounds via van der Waals forces, while GAC exhibited greater adsorption capacities due to higher surface area. Although negative charges associated with GnPs and dissociated NTO species hindered adsorption, pH and ionic strength did not impact other compounds. Moreover, this study reports the first environmental treatment technique for MeNQ. Overall, these findings suggest that GnPs are a promising treatment technology for IM-laden waters, particularly those with compounds like DNAN where specific interactions enhance removal efficiency.Item Advances in molecular electronics: Synthesis and testing of potential molecular electronic devices(2003) Price, David Wilson, Jr; Tour, James M.New potential molecular electronics devices have been synthesized based on our knowledge of previous systems that have come out of our group. Previous studies and current studies have shown that simple molecular systems demonstrate negative differential resistance (NDR) and memory characteristics. The new systems rely primarily on the redox properties of the compounds to improve upon the solid state properties already observed. Most of these new organic compounds use thiol-based "alligator clips" for attachment to metal surfaces. Some of the compounds, however, contain different "alligator clips," primarily isonitriles, for attachment to metal substrates. It is our hope that these new "alligator clips" will offer lower conductivity barriers (higher current density). Electrochemical tests have been performed in order to evaluate those redox properties and in the hope of using those electrochemical results as a predictive tool to evaluate the usefulness of those compounds. Also, organic structures with polymerizable functionalities have been synthesized in order to cross-link the molecules once they are a part of a self-assembled monolayer (SAM). This has been shown to enable the electrochemical growth of polypyrrole from a SAM in a controllable manner.Item Advances in molecular scale electronics: Synthesis and testing of nanoscale wires and devices(2000) Rawlett, Adam Madison; Tour, James M.Chapter 1 discusses advances in molecular scale electronics. With the miniaturization of transistors on silicon semiconductor chips comes faster processing speeds and more powerful computational power; however, certain size constraints on today's semiconductor industry will soon be realized. Therefore, a new method of computer architecture must be developed. The use of a discrete, highly conjugated organic molecule as a molecular scale wire to conduct an electric current has been demonstrated. We have developed molecular scale gates, from organic molecules, that can be altered "on" and "off" with the use of an electric field. Additionally, we have synthesized and tested nanoscale devices that exhibit negative differential resistance with a valley to peak ratio of over 1000:1 that is 10 times that of current solid-state devices and shown long lasting random access memory. The use of these molecular scale wires and devices should allow us to overcome the miniaturization barrier. Chapter 2 describes a simple bench-top gravity column chromatography method for the purification of C60, C70, and the higher fullerenes < C100. The stationary phase is based on poly(dibromostyrene)/divinylbenzene and the eluent is chlorobenzene. This new stationary phase (1) uses an inexpensive monomer that can be easily polymerized by standard suspension techniques, (2) permits the use of potent fullerene solvents, and (3) can be reused without additional preparation. Chapter 3 discusses the use of phenylene ethynylene oligomers as self assembled monolayer negative tone resist for the manufacture of even smaller semiconductor chips. With current methods of silicon etching with polymer resists, devices with sub-25 run feature size are not obtainable. We have prepared the first self-assembled monolayer that upon irradiation acts as a negative tone resist. In addition, we have synthesized a phenylene-ethynylene substituted trichlorosilane that should crosslink with exposure to irradiation to be a superior resist material. We are currently in the process of evaluating what functionalities are necessary to form negative tone resists at lower doses of energy. This will allow the fabrication of device feature sizes below 8 nm. Chapters 4, 5, and 6 discuss the great utility of substituted phenylene ethynylenes in the areas of cluster and surface binding study, STM patterning, and organic LEDs.Item Alkali-metal anode with alloy coating applied by friction(2024-05-14) Tour, James M.; Salvatierra, Rodrigo Villegas; Luong, Duy Xuan; Rice University; United States Patent and Trademark OfficeAn electrochemical cell with a lithium-metal anode that suppresses dendrite formation and can be fabricated using a simple, inexpensive, and solvent-free process. The anode is coated with a layer of disordered nanomaterial, saturated with lithium ions, that suppresses dendrite formation during charging. The dendrite-suppression coating can be applied simply using a dry, abrasive technique in which the lithium-metal anode is alternately abraded to roughen the surface and polished using a polishing powder of a material that alloys with the lithium.Item Amplification of carbon nanotubes via seeded-growth methods(2013-10-22) Smalley, Richard E.; Hauge, Robert H.; Barron, Andrew R.; Tour, James M.; Schmidt, Howard K.; Billups, Edward W.; Dyke, Christopher A.; Moore, Valerie C.; Whitsitt, Elizabeth Anne; Anderson, Robin E.; Colorado Jr., Ramon; Stewart, Michael P.; Ogrin, Douglas C.; Rice University; United States Patent and Trademark OfficeThe present invention is directed towards methods (processes) of providing large quantities of carbon nanotubes (CNTs) of defined diameter and chirality (i.e., precise populations). In such processes, CNT seeds of a pre-selected diameter and chirality are grown to many (e.g., hundreds) times their original length. This is optionally followed by cycling some of the newly grown material back as seed material for regrowth. Thus, the present invention provides for the large-scale production of precise populations of CNTs, the precise composition of such populations capable of being optimized for a particular application (e.g., hydrogen storage). The present invention is also directed to complexes of CNTs and transition metal catalyst precurors, such complexes typically being formed en route to forming CNT seeds.Item Anodes, cathodes, and separators for batteries and methods to make and use same(2024-09-10) Tour, James M.; Salvatierra, Rodrigo Villegas; Silva, Gladys Anahi Lopez; Rice University; United States Patent and Trademark OfficeAnodes, cathodes, and separators for batteries (electrochemical energy storage devices). The anodes are Li metal anodes having lithiated carbon films (Li-MWCNT) (as dendrite suppressors and protective coatings for the Li metal anodes). The cathodes are sulfurized carbon cathodes. The separators are GNR-coated (or modified) separators. The invention includes each of these separately (as well as in combination both with each other and with other anodes, cathodes, and separators) and the methods of making each of these separately (and in combination). The invention further includes a battery that uses at least one of (a) the anode having a lithiated carbon film, (b) the sulfurized carbon cathode, and (c) the GNR-modified separator in the anode/cathode/separator arrangement. For instance, a full battery can include the sulfurized carbon cathode in combination with the Li-MWCNT anode or a full battery can include the sulfurized carbon cathode in combination with other anodes (such as a GCNT-Li anode).Item Antioxidant Carbon Nanoparticles Inhibit Fibroblast-Like Synoviocyte Invasiveness and Reduce Disease Severity in a Rat Model of Rheumatoid Arthritis(MDPI, 2020) Tanner, Mark R.; Huq, Redwan; Sikkema, William K.A.; Nilewski, Lizanne G.; Yosef, Nejla; Schmitt, Cody; Flores-Suarez, Carlos P.; Raugh, Arielle; Laragione, Teresina; Gulko, Pércio S.; Tour, James M.; Beeton, Christine; The NanoCarbon CenterReactive oxygen species have been involved in the pathogenesis of rheumatoid arthritis (RA). Our goal was to determine the effects of selectively scavenging superoxide (O2•−) and hydroxyl radicals with antioxidant nanoparticles, called poly(ethylene glycol)-functionalized hydrophilic carbon clusters (PEG-HCCs), on the pathogenic functions of fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis (RA) and on the progression of an animal model of RA. We used human FLS from patients with RA to determine PEG-HCC internalization and effects on FLS cytotoxicity, invasiveness, proliferation, and production of proteases. We used the pristane-induced arthritis (PIA) rat model of RA to assess the benefits of PEG-HCCs on reducing disease severity. PEG-HCCs were internalized by RA-FLS, reduced their intracellular O2•−, and reduced multiple measures of their pathogenicity in vitro, including proliferation and invasion. In PIA, PEG-HCCs caused a 65% reduction in disease severity, as measured by a standardized scoring system of paw inflammation and caused a significant reduction in bone and tissue damage, and circulating rheumatoid factor. PEG-HCCs did not induce lymphopenia during PIA. Our study demonstrated a role for O2•− and hydroxyl radicals in the pathogenesis of a rat model of RA and showed efficacy of PEG-HCCs in treating a rat model of RA.Item Antioxidant Carbon Particles Improve Cerebrovascular Dysfunction Following Traumatic Brain Injury(American Chemical Society, 2012) Bitner, Brittany R.; Marcano, Daniela C.; Berlin, Jacob M.; Fabian, Roderic H.; Cherian, Leela; Culver, James C.; Dickinson, Mary E.; Robertson, Claudia S.; Pautler, Robia G.; Kent, Thomas A.; Tour, James M.; Smalley Institute for Nanoscale Science and TechnologyInjury to the neurovasculature is a feature of brain injury and must be addressed to maximize opportunity for improvement. Cerebrovascular dysfunction, manifested by reduction in cerebral blood flow (CBF), is a key factor that worsens outcome after traumatic brain injury (TBI), most notably under conditions of hypotension. We report here that a new class of antioxidants, poly(ethylene glycol)-functionalized hydrophilic carbon clusters (PEG-HCCs), which are nontoxic carbon particles, rapidly restore CBF in a mild TBI/hypotension/resuscitation rat model when administered during resuscitation--a clinically relevant time point. Along with restoration of CBF, there is a concomitant normalization of superoxide and nitric oxide levels. Given the role of poor CBF in determining outcome, this finding is of major importance for improving patient health under clinically relevant conditions during resuscitative care, and it has direct implications for the current TBI/hypotension war-fighter victims in the Afghanistan and Middle East theaters. The results also have relevancy in other related acute circumstances such as stroke and organ transplantation.Item Application of nanoparticles in downhole detection(2014-12-11) Wang, Lu; Tomson, Mason B.; Bedient, Philip B.; Tour, James M.The revolution of nanotechnology leads to the increasing application of nanoparticles in many industry fields. Nanoparticles, due to the small size, are supposed to transport through subsurface formation without breaking rock structure and thus have received tremendous attention1-12. Nanoparticles also have many unique physical, chemical and optical properties, which are not found in bulk samples with the same chemical composition. Such nanoparticles, therefore, may be attractive as candidates to detect the chemical and physical properties underground, by directly interact with the important targets. Because of the increasing energy demands, it becomes more desirable to develop new technology to detect the downhole conditions. In this paper, nanoparticles possessing functionalized carbon black cores and treated polyvinyl alcohol addends was designed as carrier to deliver probe molecules into the reservoir. When applied in the aqueous environment, nanoparticles tend to interact with the rock surface, which may affect the mobility and stability of the nanoparticles. Deposition of nanoparticles will remove the nanoparticles from the aqueous environment, and therefore understanding the fate and transport of nanoparticles is vitally important for determination of further application strategy. The stability and transport behavior were tested under high temperature, high salinity conditions through a variety of rock formations. A non-radioactive probe molecule, which can be easily detected by mass spectrometry, triphenolamine (TPA), was attached to the nanoparticles surface. When the nanoparticles passed through columns packing with different oil saturation ground rocks, the probe molecules, THA, was selectively released from nanoparticles. This study simulates detection and quantitative analysis of the hydrocarbon content in downhole rock formations, which is vitally needed for oilfield. This technology also shows the potential to be used for DNAPL detection in ground water remediation field. Crude oil is classified as “sour” when it contains total sulfur content greater than 0.5%. Among these sulfur species, H2S is the one of main impurities in sour crude. The sour crude is toxic and corrosive to the materials of construction in pipelines and other holding and transportation vessels. Since the sulfur amount in a sample of crude depends on where it was found, if the concentration of the sulfur species in the subsurface could be accurately monitored, then geologists might be able to evaluate the quality of the crude before large scale extraction ensues. A H2S-sensitive molecule was selected to be attached to nanoparticles surface and the detection ability of H2S concentration was tested. The experimental results show that the fluorescent enhancement of the H2S-sensitive addends correlates to the H2S content.Item Applications of functional carbon nanomaterials from hydrogen storage to drug delivery(2010) Leonard, Ashley Dawn; Tour, James M.This dissertation describes the modification and functionalization of single-walled carbon nanotubes (SWCNTs). These SWCNTs were then investigated for their use in medical applications and for the storage of hydrogen. A technique was developed that leads to highly customized, individually suspended aqueous solutions of SWCNTs. These newly generated water-soluble SWCNTs were then functionalized further in water, thereby permitting the second functionalization addends to be chemically sensitive functional groups, for example drugs, that would not withstand the strongly acidic conditions of the first functionalization. The radical scavenging properties of nanovectors derived from SWCNTs were investigated and it was found that even the poorest SWCNT nanovector studied was nearly 40 times more effective at scavenging radicals than dendrite-fullerene DF-1, which has been shown to be a radioprotective to zebrafish via an antioxidant niechanism. This was used as the base to investigate using SWCNTs as protectors and mitigators of radiation exposure. SWCNTs were then explored for their use as drug delivery agents, in particular, the water insoluble chemotherapy drug, paclitaxel. SWCNTs showed promising in vivo and in vitro efficacy in the delivery of paclitaxel. Toxicity and biodistribution studies of the SWCNTs as drug delivery agents were performed in vivo using SWCNTs functionalized with radiolabeled indium. It was found that SWCNTs could be used for hydrogen storage by chemically crosslinking 3-dimensional frameworks of SWCNT fibers. These frameworks were shown to physisorb twice as much hydrogen, at low pressures, with respect to their surface areas, than typical macroporous carbon materials. This makes these SWCNT frameworks attractive materials for the development of a hydrogen vehicle fuel tank.Item Atomic cobalt on nitrogen-doped graphene for hydrogen generation(Nature Publishing Group, 2015) Fei, Huilong; Dong, Juncai; Arellano-Jiménez, M. Josefina; Ye, Gonglan; Kim, Nam Dong; Samuel, Errol L.G.; Peng, Zhiwei; Zhu, Zhuan; Qin, Fan; Bao, Jiming; Yacaman, Miguel Jose; Ajayan, Pulickel M.; Chen, Dongliang; Tour, James M.Reduction of water to hydrogen through electrocatalysis holds great promise for clean energy, but its large-scale application relies on the development of inexpensive and efficient catalysts to replace precious platinum catalysts. Here we report an electrocatalyst for hydrogen generation based on very small amounts of cobalt dispersed as individual atoms on nitrogen-doped graphene. This catalyst is robust and highly active in aqueous media with very low overpotentials (30 mV). A variety of analytical techniques and electrochemical measurements suggest that the catalytically active sites are associated with the metal centres coordinated to nitrogen. This unusual atomic constitution of supported metals is suggestive of a new approach to preparing extremely efficient single-atom catalysts.Item Atomic H-Induced Mo2C Hybrid as an Active and Stable Bifunctional Electrocatalyst(American Chemical Society, 2017) Fan, Xiujun; Liu, Yuanyue; Peng, Zhiwei; Zhang, Zhenhua; Zhou, Haiqing; Zhang, Xianming; Yakobson, Boris I.; Goddard, William A. III; Guo, Xia; Hauge, Robert H.; Tour, James M.; NanoCarbon CenterMo2C nanocrystals (NCs) anchored on vertically aligned graphene nanoribbons (VA-GNR) as hybrid nanoelectrocatalysts (Mo2C–GNR) are synthesized through the direct carbonization of metallic Mo with atomic H treatment. The growth mechanism of Mo2C NCs with atomic H treatment is discussed. The Mo2C–GNR hybrid exhibits highly active and durable electrocatalytic performance for the hydrogen-evolution reaction (HER) and oxygen-reduction reaction (ORR). For HER, in an acidic solution the Mo2C–GNR has an onset potential of 39 mV and a Tafel slope of 65 mV dec–1, and in a basic solution Mo2C–GNR has an onset potential of 53 mV, and Tafel slope of 54 mV dec–1. It is stable in both acidic and basic media. Mo2C–GNR is a high-activity ORR catalyst with a high peak current density of 2.01 mA cm–2, an onset potential of 0.93 V that is more positive vs reversible hydrogen electrode (RHE), a high electron transfer number n (∼3.90), and long-term stability.Item Autonomous Single-Molecule Manipulation Based on Reinforcement Learning(American Chemical Society, 2023) Ramsauer, Bernhard; Simpson, Grant J.; Cartus, Johannes J.; Jeindl, Andreas; García-López, Victor; Tour, James M.; Grill, Leonhard; Hofmann, Oliver T.; Smalley-Curl Institute; NanoCarbon CenterBuilding nanostructures one-by-one requires precise control of single molecules over many manipulation steps. The ideal scenario for machine learning algorithms is complex, repetitive, and time-consuming. Here, we show a reinforcement learning algorithm that learns how to control a single dipolar molecule in the electric field of a scanning tunneling microscope. Using about 2250 iterations to train, the algorithm learned to manipulate the molecule toward specific positions on the surface. Simultaneously, it generates physical insights into the movement as well as orientation of the molecule, based on the position where the electric field is applied relative to the molecule. This reveals that molecular movement is strongly inhibited in some directions, and the torque is not symmetric around the dipole moment.Item Bandgap engineering of carbon quantum dots(2018-10-02) Tour, James M.; Ye, Ruquan; Metzger, Andrew; Stavinoha, Macy; Zheng, Yonghao; Rice University; United States Patent and Trademark OfficeEmbodiments of the present disclosure pertain to scalable methods of producing carbon quantum dots with desired bandgaps by the following steps: exposing a carbon source to an oxidant at a reaction temperature, where the exposing results in the formation of the carbon quantum dots; and selecting a desired size of the formed carbon quantum dots. In some embodiments, the selecting occurs by at least one of separating the desired size of the formed carbon quantum dots from other formed carbon quantum dots; selecting the reaction temperature that produces the desired size of the formed carbon quantum dots; and combinations of such steps. The desired size of carbon quantum dots can include a size range. The methods of the present disclosure can also include a step of purifying the formed carbon quantum dots prior to selecting a desired size.Item Battery metal recycling by flash Joule heating(AAAS, 2023) Chen, Weiyin; Chen, Jinhang; Bets, Ksenia V.; Salvatierra, Rodrigo V.; Wyss, Kevin M.; Gao, Guanhui; Choi, Chi Hun; Deng, Bing; Wang, Xin; Li, John Tianci; Kittrell, Carter; La, Nghi; Eddy, Lucas; Scotland, Phelecia; Cheng, Yi; Xu, Shichen; Li, Bowen; Tomson, Mason B.; Han, Yimo; Yakobson, Boris I.; Tour, James M.; Welch Institute for Advanced Materials; NanoCarbon Center; Applied Physics Program; Smalley-Curl InstituteThe staggering accumulation of end-of-life lithium-ion batteries (LIBs) and the growing scarcity of battery metal sources have triggered an urgent call for an effective recycling strategy. However, it is challenging to reclaim these metals with both high efficiency and low environmental footprint. We use here a pulsed dc flash Joule heating (FJH) strategy that heats the black mass, the combined anode and cathode, to >2100 kelvin within seconds, leading to ~1000-fold increase in subsequent leaching kinetics. There are high recovery yields of all the battery metals, regardless of their chemistries, using even diluted acids like 0.01 M HCl, thereby lessening the secondary waste stream. The ultrafast high temperature achieves thermal decomposition of the passivated solid electrolyte interphase and valence state reduction of the hard-to-dissolve metal compounds while mitigating diffusional loss of volatile metals. Life cycle analysis versus present recycling methods shows that FJH significantly reduces the environmental footprint of spent LIB processing while turning it into an economically attractive process.Item Biocompatibility of reduced graphene oxide nanoscaffolds following acute spinal cord injury in rats(Surgical Neurology International, 2016) Palejwala, Ali H.; Fridley, Jared S.; Mata, Javier A.; Samuel, Errol L.G.; Luerssen, Thomas G.; Perlaky, Laszlo; Kent, Thomas A.; Tour, James M.; Jea, AndrewBackground: Graphene has unique electrical, physical, and chemical properties that may have great potential as a bioscaffold for neuronal regeneration after spinal cord injury. These nanoscaffolds have previously been shown to be biocompatible in vitro; in the present study, we wished to evaluate its biocompatibility in an in vivo spinal cord injury model. Methods: Graphene nanoscaffolds were prepared by the mild chemical reduction of graphene oxide. Twenty Wistar rats (19 male and 1 female) underwent hemispinal cord transection at approximately the T2 level. To bridge the lesion, graphene nanoscaffolds with a hydrogel were implanted immediately after spinal cord transection. Control animals were treated with hydrogel matrix alone. Histologic evaluation was performed 3 months after the spinal cord transection to assess in vivo biocompatibility of graphene and to measure the ingrowth of tissue elements adjacent to the graphene nanoscaffold. Results: The graphene nanoscaffolds adhered well to the spinal cord tissue. There was no area of pseudocyst around the scaffolds suggestive of cytotoxicity. Instead, histological evaluation showed an ingrowth of connective tissue elements, blood vessels, neurofilaments, and Schwann cells around the graphene nanoscaffolds. Conclusions: Graphene is a nanomaterial that is biocompatible with neurons and may have significant biomedical application. It may provide a scaffold for the ingrowth of regenerating axons after spinal cord injury.Item Bulk separation of carbon nanotubes by bandgap(2011-05-10) Tour, James M.; Dyke, Christopher A.; Flatt, Austen K.; Rice University; United States Patent and Trademark OfficeThe present invention is directed to methods of separating carbon nanotubes (CNTs) by their electronic type (e.g., metallic, semi-metallic, and semiconducting). Perhaps most generally, in some embodiments, the present invention is directed to methods of separating CNTs by bandgap, wherein such separation is effected by interacting the CNTs with a surface such that the surface interacts differentially with the CNTs on the basis of their bandgap, or lack thereof. In some embodiments, such methods can allow for such separations to be carried out in bulk quantities.Item Carbon Based Nanomaterials for Electrochemical Energy Storage Applications(2015-04-22) Li, Lei; Tour, James M.; Ajayan, Pulickel; Martí, Angel A.Ever-growing energy needs, limited energy resources, and the need to decrease soaring greenhouse gas emissions have brought about an urgent demand on the pursuit of energy alternatives, includ¬ing both renewable energy sources and sustainable storage technologies. Electrochemical capacitors (ECs) and reversible lithium ion batteries (LIBs) are two promising energy storage technologies that are well positioned to satisfy this need in a green energy future. However, their large-scale deployment has been significantly hindered by several major technological barriers, such as high cost, intrinsically poor safety characteristic, limited life, and low energy density and/or power density. One promising solution is to develop advanced electrodes materials for these devices. In this thesis, various nanomaterials and nanostructures have been developed to improve the electrochemical performance of ECs and LIBs. My thesis begins with the introduction of energy storage systems of ECs and LIBs in Chapter 1. Chapter 2 to 4 discuss the synthesis of nitrogen-doped carbonized cotton, brush-like structured nanocomposites of polyaniline nanorods-graphene nanoribbons, laser induced graphene-MnO2, and laser induced graphene-polyaniline and their applications in ECs. All of them demonstrated excellent performance in energy storage, showing high potential applications as electrode materials in ECs. Chapter 5 to 8 discuss a graphene wrapping strategy designed to synthesize graphene-metal oxide/sulfide-graphene nanoribbons, including graphene-MnO2-GNRs, graphene-NiO-rGONRs, graphene-Fe3O4-GNRs, and graphene-FeS-GNRs. This sandwich structure mitigated the pulverization of these anode materials from their conversion reactions during extended cycling, leading to a large improvement in the cycling stability of anodes in LIBs. To address the volume change of SnO2-based anode materials, a facile and cost-effective approach was developed to prepare a thin layer SnO2 on reduced graphene oxide nanoribbons. Chapter 9 discusses how this nanocomposite demonstrated excellent cycling stability with high capacity. For LIBs cathode materials, a hierarchical polyaniline matrix was designed to reduce the dissolution of the intermediate lithium polysulfide into the electrolyte as shown in Chapter 10. This material showed great improvement in cycling stability with high capacity.