Browsing by Author "Ozden, Sehmus"
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Item 3D Macroporous Solids from Chemically Cross-linked Carbon Nanotubes(Wiley, 2014) Ozden, Sehmus; Narayanan, Tharangattu N.; Tiwary, Chandra S.; Dong, Pei; Hart, Amelia H.C.; Vajtai, Robert; Ajayan, Pulickel M.Suzuki reaction for covalently interconnected 3D carbon nanotube (CNT) architectures is reported. The synthesis of 3D macroscopic solids made of CNTs covalently connected via Suzuki cross-coupling, a well-known carbon-carbon covalent bond forming reaction in organic chemistry, is scalable. The resulting solid has a highly porous, interconnected structure of chemically cross-linked CNTs. Its use for the removal of oil from contaminated water is demonstrated.Item Advanced Three-Dimensional Structural Carbon Nanomaterials(2016-08-17) Ozden, Sehmus; Ajayan, Pulickel M.Carbon nanomaterials, such as carbon nanotubes (CNTs) and graphene, are most intensively investigated carbon allotropes because of their outstanding physical and chemical properties. Recently, it has been realized that threedimensional (3D) carbon-based structures with nanoscale interconnection provide the remarkably improved properties required for critically needed applications. The properties of 3D-CNTs and graphene architectures can be tweaked for various applications. Therefore, 3D carbon-based solids with nanoscale intermolecular junctions present an exciting research area and provide opportunities for fabrication of various 3D-macroscopic architectures with unexpected properties. The creation of nanoengineered 3D-macroscopic structures in a scalable synthetic process still remains a challenge. The fundamental problem is the difficulty in introducing atomic-scale junctions between individual nanoscale structures so that they can be organized as covalently interconnected nanostructured networks with controllable physical characteristics, such as density and porosity. Here, 3D structures have been created using chemical vapor deposition method, solutionbased chemistry technique and welding method via hypervelocity impact method to generate atomic-scale junction between carbon nanostructures. The scalable fabrication of 3D macroscopic scaffolds with different hierarchical interconnected structures and soldering-like junctions between CNTs using chemical vapor deposition (CVD) technique is reported. These intermolecular junctions of CNTs result in a high thermal stability, high electrical conductivity, excellent mechanical properties, as well as excellent structural stability in a concentrated acid, base, and organic solvents. The CNT solids with such tremendous properties represent the next generation of carbon-based materials with a broad range of potential applications; we demonstrate here a couple such utility impact damping, removal oil from contaminated water and as a marker for the oil industry. Additionally, in situ nano-indentation inside a scanning electron microscopy (SEM) were used to determine the mechanical response of individual covalent junction, formed in different configurations such as “X”, “Y” and “” shapes between individual CNTs. Fully atomistic reactive molecular dynamics simulations are used to support the experimental results as well as to study the deformation behavior of junctions. Vertically aligned multiwall carbon nanotube forests (NTF) synthesized by water assisted CVD method and both sides functionalized with different functionalities as hydrophobic and hydrophilic. The produced hygroscopic nanotube forest demonstrate for water harvesting from air. The second approach has been used in this work is solution chemistry to generate crosslinking nanotube structures. The scalable synthesis of 3D macroscopic solids made of covalently connected nanotubes via Suzuki cross-coupling reaction, a well-known carbon-carbon covalent bond forming reaction in organic chemistry. The resulting CNTs solids are made of highly porous, interconnected structures made of chemically crosslinked carbon nanotubes after freeze-drying process. CNTs solids demonstrated one such utility in the removal of oil from contaminated water. In another approach hypervelocity impact method was used to investigate mechanical behavior of CNTs. The hypervelocity impact of CNT bundles against metallic targets resulted their unzipping along the tube axis, which leads to the formation of graphene nanoribbons, nanodiamonds and covalently interconnected carbon nanostructures depending on the velocity and impact geometry. This new process can produce chemical-free, high-quality graphene nanoribbons. The experimental results supported by fully atomistic reactive molecular dynamics simulations were used to gain further insights of the pathways and deformation and fracture mechanismsItem Ambient solid-state mechano-chemical reactions between functionalized carbon nanotubes(Nature Publishing Group, 2015) Kabbani, Mohamad A.; Tiwary, Chandra Sekhar; Autreto, Pedro A.S.; Brunetto, Gustavo; Som, Anirban; Krishnadas, K.R.; Ozden, Sehmus; Hackenberg, Ken P.; Gong, Yongi; Galvao, Douglas S.; Vajtai, Robert; Kabbani, Ahmad T.; Pradeep, Thalappil; Ajayan, Pulickel M.Carbon nanotubes can be chemically modified by attaching various functionalities to their surfaces, although harsh chemical treatments can lead to their break-up into graphene nanostructures. On the other hand, direct coupling between functionalities bound on individual nanotubes could lead to, as yet unexplored, spontaneous chemical reactions. Here we report an ambient mechano-chemical reaction between two varieties of nanotubes, carrying predominantly carboxyl and hydroxyl functionalities, respectively, facilitated by simple mechanical grinding of the reactants. The purely solid-state reaction between the chemically differentiated nanotube species produces condensation products and unzipping of nanotubes due to local energy release, as confirmed by spectroscopic measurements, thermal analysis and molecular dynamic simulations.Item Bacteria as Bio-Template for 3D Carbon Nanotube Architectures(Springer Nature, 2017) Ozden, Sehmus; Macwan, Isaac G.; Owuor, Peter S.; Kosolwattana, Suppanat; Autreto, Pedro A.S.; Silwal, Sushila; Vajtai, Robert; Tiwary, Chandra S.; Mohite, Aditya D.; Patra, Prabir K.; Ajayan, Pulickel M.It is one of the most important needs to develop renewable, scalable and multifunctional methods for the fabrication of 3D carbon architectures. Even though a lot of methods have been developed to create porous and mechanically stable 3D scaffolds, the fabrication and control over the synthesis of such architectures still remain a challenge. Here, we used Magnetospirillum magneticum (AMB-1) bacteria as a bio-template to fabricate light-weight 3D solid structure of carbon nanotubes (CNTs) with interconnected porosity. The resulting porous scaffold showed good mechanical stability and large surface area because of the excellent pore interconnection and high porosity. Steered molecular dynamics simulations were used to quantify the interactions between nanotubes and AMB-1 via the cell surface protein MSP-1 and flagellin. The 3D CNTs-AMB1 nanocomposite scaffold is further demonstrated as a potential substrate for electrodes in supercapacitor applications.Item Synthesis and 3D Interconnected Nanostructured h-BN-Based Biocomposites by Low-Temperature Plasma Sintering: Bone Regeneration Applications(American Chemical Society, 2018) Gautam, Chandkiram; Chakravarty, Dibyendu; Gautam, Amarendra; Tiwary, Chandra Sekhar; Woellner, Cristiano Francisco; Mishra, Vijay Kumar; Ahmad, Naseer; Ozden, Sehmus; Jose, Sujin; Biradar, Santoshkumar; Vajtai, Robert; Trivedi, Ritu; Galvao, Douglas S.; Ajayan, Pulickel M.Recent advances and demands in biomedical applications drive a large amount of research to synthesize easily scalable low-density, high-strength, and wear-resistant biomaterials. The chemical inertness with low density combined with high strength makes h-BN one of the promising materials for such application. In this work, three-dimensional hexagonal boron nitride (h-BN) interconnected with boron trioxide (B2O3) was prepared by easily scalable and energy efficient spark plasma sintering (SPS) process. The composite structure shows significant densification (1.6–1.9 g/cm3) and high surface area (0.97–14.5 m2/g) at an extremely low SPS temperature of 250 °C. A high compressive strength of 291 MPa with a reasonably good wear resistance was obtained for the composite structure. The formation of strong covalent bonds between h-BN and B2O3 was formulated and established by molecular dynamics simulation. The composite showed significant effect on cell viability/proliferation. It shows a high mineralized nodule formation over the control, which suggests its use as a possible osteogenic agent in bone formation.