Browsing by Author "Kannan, Harikishan"

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    Facile Synthesis Routes for Application-Oriented Modification of Nanomaterials
    (2023-04-20) Kannan, Harikishan; Ajayan, Pulickel M
    Chemical functionalization provides the necessary tools to pick and modulate specific properties while retaining most of the essential characteristics of a material. Hexagonal boron nitride (h-BN) and diamond have been uniquely identified for excellent mechanical characteristics, an ultra-wide bandgap, and a common resistance to not easily succumb to chemical modification. To that extent, the fulcrum of this thesis hinges on chalking out novel pathways that leverage their properties while chemically modifying them through a highly facile, scalable, and economical route with specific end goals. The first half of the thesis accomplishes this through a solvothermal approach using Deep Eutectic Solvents (DES) as medium in which transition metal atoms (Fe, Cu) were controllably and covalently anchored on a defect-rich h-BN. The Fe-hBN nanocomposites were used to comprehensively study the degradation of Perfluorooctanoic Acid (PFOA). On the other hand, the Cu-hBN nanocomposites were evaluated for lubrication studies Detailed bandgap measurements showed charge modulation thus cementing this approach as a sustainable option to modify h-BN. The second half of the thesis explores a facile gas-phase fluorination approach to etch diamond crystals. In light of all the attention diamond has received for its device applications, its use in quantum optics and quantum information processing has gained an increased impetus due to its negatively charged nitrogen-vacancy (NV-) defect centers. This work has upped the ante through a systematic study of correlating the fluorination conditions with the ensuing emission characteristics to form a new stable defect ensemble - Fluorine vacancy (FV) color centers in diamond, through this facile approach. The dichotomy of breaking and forming the C-F bond in the thesis’ first and latter parts respectively, remains central to its vision of modulating nanomaterials via facile chemical functionalization routes towards specific use cases
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    Substitution of copper atoms into defect-rich molybdenum sulfides and their electrocatalytic activity
    (Royal Society of Chemistry, 2021) Wang, Zixing; Kannan, Harikishan; Su, Tonghui; Swaminathan, Jayashree; Shirodkar, Sharmila N.; Hernandez, Francisco C. Robles; Benavides, Hector Calderon; Vajtai, Robert; Yakobson, Boris I.; Meiyazhagan, Ashokkumar; Ajayan, Pulickel M.
    Studies on intercalation or substitution of atoms into layered two-dimensional (2D) materials are rapidly expanding and gaining significant consideration due to their importance in electronics, catalysts, batteries, sensors, etc. In this manuscript, we report a straightforward method to create sulphur (S) deficient molybdenum (Mo) sulfide (MoS2−x) structures and substitute them with zerovalent copper (Cu) atoms using a colloidal synthesis method. The synthesized materials were studied using several techniques to understand the proportion and position of copper atoms and the effect of copper functionalization. Specifically, the impact of change in the ratio of Cu : S and the hydrogen evolution reaction (HER) activity of the derived materials were evaluated. This technique paves the way for the synthesis of various functionalized 2D materials with a significant impact on their physical and chemical behavior making them potential candidates for catalysis and several other applications such as energy storage and the development of numerous functional devices.