Browsing by Author "Sudeep, Parambath M."

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    Fluorinated h-BN as a magnetic semiconductor
    (American Association for the Advancement of Science, 2017) Radhakrishnan, Sruthi; Das, Deya; Samanta, Atanu; de los Reyes, Carlos A.; Deng, Liangzi; Alemany, Lawrence B.; Weldeghiorghis, Thomas K.; Khabashesku, Valery N.; Kochat, Vidya; Jin, Zehua; Sudeep, Parambath M.; Martí, Angel A.; Chu, Ching-Wu; Roy, Ajit; Tiwary, Chandra Sekhar; Singh, Abhishek K.; Ajayan, Pulickel M.
    We report the fluorination of electrically insulating hexagonal boron nitride (h-BN) and the subsequent modification of its electronic band structure to a wide bandgap semiconductor via introduction of defect levels. The electrophilic nature of fluorine causes changes in the charge distribution around neighboring nitrogen atoms in h-BN, leading to room temperature weak ferromagnetism. The observations are further supported by theoretical calculations considering various possible configurations of fluorinated h-BN structure and their energy states. This unconventional magnetic semiconductor material could spur studies of stable two-dimensional magnetic semiconductors. Although the high thermal and chemical stability of h-BN have found a variety of uses, this chemical functionalization approach expands its functionality to electronic and magnetic devices.
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    Metal-Free Dual Modal Contrast Agents Based on Fluorographene Quantum Dots
    (Wiley, 2016) Radhakrishnan, Sruthi; Samanta, Atanu; Sudeep, Parambath M.; Maldonado, Kiersten L.; Mani, Sendurai A.; Acharya, Ghanashyam; Tiwary, Chandra Sekhar; Singh, Abhishek K.; Ajayan, Pulickel M.
    Fluorographene quantum dots prepared from fluorinated graphene oxide (FGO) show a linear dependence of the magnetization on the applied field. This is further supported by DFT calculations taking into account a few possible systems of functionalized graphene quantum dots. The inherent magnetism, high concentration of fluorine and cyto-compatibility of these quantum dots promise potential application as a dual modal agent for proton and 19F based Magnetic Resonance Imaging which is investigated here. A metal free dual modal contrast agent would bring about a great change in the efficiency and resolution of this widely used imaging tool.
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    Recent Advances in Optical Limiting Properties of Fluorinated Graphene Oxides
    (SPIE, 2013) Chantharasupawong, Panit; Philip, Reji; Narayanan, Narayanan T.; Sudeep, Parambath M.; Mathkar, Akshay; Ajayan, Pulickel M.; Thomas, Jayan
    There is a substantial interest in finding materials with high nonlinear optical (NLO) properties of materials because of its attractive applications in optical limiting for safety protections. In an effort to develop highly performing optical limiting materials, recently we have found that fluorination of graphene oxides leads to improvement in their NLO properties.