Browsing by Author "Galvao, Douglas S."

Now showing 1 - 4 of 4
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    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.
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    Development of a schwarzite-based moving bed 3D printed water treatment system for nanoplastic remediation
    (Royal Society of Chemistry, 2021) Gupta, Bramha; Ambekar, Rushikesh S.; Tromer, Raphael M.; Ghosal, Partha Sarathi; Sinha, Rupal; Majumder, Abhradeep; Kumbhakar, Partha; Ajayan, P. M.; Galvao, Douglas S.; Gupta, Ashok Kumar; Tiwary, Chandra Sekhar; Smalley-Curl Institute
    The impact of micro and nanoplastic debris on our aquatic ecosystem is among the most prominent environmental challenges we face today. In addition, nanoplastics create significant concern for environmentalists because of their toxicity and difficulty in separation and removal. Here we report the development of a 3D printed moving bed water filter (M-3DPWF), which can perform as an efficient nanoplastic scavenger. The enhanced separation of the nanoplastics happens due to the creation of a charged filter material that traps the more surface charged nanoparticles selectively. Synthetic contaminated water from polycarbonate waste has been tested with the filter, and enhanced nanoplastic removal has been achieved. The proposed filtration mechanism of surface-charge based water cleaning is further validated using density function theory (semi-empirical) based simulation. The filter has also shown good structural and mechanical stability in both static and dynamic water conditions. The field suitability of the novel treatment system has also been confirmed using water from various sources, such as sea, river, and pond. Our results suggest that the newly developed water filter can be used for the removal of floating nanoparticles in water as a robust advanced treatment system.
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    Fluorinated Multi-Walled Carbon Nanotubes Coated Separator Mitigates Polysulfide Shuttle in Lithium-Sulfur Batteries
    (MDPI, 2023) Salpekar, Devashish; Dong, Changxin; Oliveira, Eliezer F.; Khabashesku, Valery N.; Gao, Guanhui; Ojha, Ved; Vajtai, Robert; Galvao, Douglas S.; Babu, Ganguli; Ajayan, Pulickel M.
    Li-S batteries still suffer from two of the major challenges: polysulfide shuttle and low inherent conductivity of sulfur. Here, we report a facile way to develop a bifunctional separator coated with fluorinated multiwalled carbon nanotubes. Mild fluorination does not affect the inherent graphitic structure of carbon nanotubes as shown by transmission electron microscopy. Fluorinated carbon nanotubes show an improved capacity retention by trapping/repelling lithium polysulfides at the cathode, while simultaneously acting as the “second current collector”. Moreover, reduced charge-transfer resistance and enhanced electrochemical performance at the cathode-separator interface result in a high gravimetric capacity of around 670 mAh g−1 at 4C. Unique chemical interactions between fluorine and carbon at the separator and the polysulfides, studied using DFT calculations, establish a new direction of utilizing highly electronegative fluorine moieties and absorption-based porous carbons for mitigation of polysulfide shuttle in Li-S batteries.
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    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.