Browsing by Author "Dimiev, Ayrat M."

Now showing 1 - 4 of 4
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    Enhanced MRI relaxivity of aquated Gd3+ﾠions by carboxyphenylated water-dispersed graphene nanoribbons
    (Royal Society of Chemistry, 2014) Gizzatov, Ayrat; Keshishian, Vazrik; Guven, Adem; Dimiev, Ayrat M.; Qu, Feifei; Muthupillai, Raja; Decuzzi, Paolo; Bryant, Robert G.; Tour, James M.; Wilson, Lon J.; Richard E. Smalley Institute for Nanoscale Science and Technology
    The present study demonstrates that highly water-dispersed graphene nanoribbons dispersed by carboxyphenylated substituents and conjugated to aquated Gd3+ﾠions can serve as a high-performance contrast agent (CA) for applications inﾠT1- andﾠT2-weighted magnetic resonance imaging (MRI) with relaxivity (r1,2) values outperforming currently-available clinical CAs by up to 16 times forﾠr1ﾠand 21 times forﾠr2.
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    Layer-by-layer removal of graphene
    (2015-04-14) Tour, James M.; Dimiev, Ayrat M.; Kosynkin, Dmitry V.; Rice University; United States Patent and Trademark Office
    The present invention provides methods of selectively removing one or more graphene layers from a graphene material by: (1) applying a metal to a surface of the graphene material; and (2) applying a hydrogen containing solution to the surface of the graphene material that is associated with the metal. The hydrogen containing solution dissolves the metal along with one or more layers of graphene associated with the metal, thereby removing the layer(s) of graphene from the graphene material. In some embodiments, the hydrogen containing solution is an acidic solution, such as hydrochloric acid. In some embodiments, the metal is zinc. In some embodiments, the methods of the present invention are utilized to selectively remove one or more layers of graphene from one or more targeted sites on the surface of a graphene material.
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    Mechanism of Graphene Oxide Formation
    (American Chemical Society, 2014) Dimiev, Ayrat M.; Tour, James M.; Smalley Institute for Nanoscale Science and Technology
    Despite intensive research, the mechanism of graphene oxide (GO) formation remains unclear. The role of interfacial interactions between solid graphite and the liquid reaction medium, and transport of the oxidizing agent into the graphite, has not been well-addressed. In this work, we show that formation of GO from graphite constitutes three distinct independent steps. The reaction can be stopped at each step, and the corresponding intermediate products can be isolated, characterized, and stored under appropriate conditions. The first step is conversion of graphite into a stage-1 graphite intercalation compound (GIC). The second step is conversion of the stage-1 GIC into oxidized graphite, which we define as pristine graphite oxide (PGO). This step involves diffusion of the oxidizing agent into the preoccupied graphite galleries. This rate-determining step makes the entire process diffusive-controlled. The third step is conversion of PGO into conventional GO after exposure to water, which involves hydrolysis of covalent sulfates and loss of all interlayer registry.
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    Oxidatively modified carbon as efficient material for removing radionuclides from water
    (Elsevier, 2017) Khannanov, Artur; Nekljudov, Vadim V.; Gareev, Bulat; Kiiamov, Airat; Tour, James M.; Dimiev, Ayrat M.; NanoCarbon Center
    There is a constant need to develop advantageous materials for removing radioactive waste from aqueous systems. Here we propose a new carbon-based material prepared by oxidative treatment of various natural carbon sources. The as-prepared oxidatively modified carbon (OMC) has an oxygen-rich surface, and retains its particulate granular texture. It has relatively low cost and can be used in traditional filtration columns. The sorption ability of OMC toward several metal cations is demonstrated. It is especially efficient toward Cs+ cations, the species that are among the most difficult to remove from the waters at the Fukushima nuclear plant.