Browsing by Author "Hahm, Myung Gwan"

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    Charge-transfer-based Gas Sensing Using Atomic-layer MoS2
    (Nature Publishing Group, 2015) Cho, Byungjin; Hahm, Myung Gwan; Choi, Minseok; Yoon, Jongwon; Kim, Ah Ra; Lee, Young-Joo; Park, Sung-Gyu; Kwon, Jung-Dae; Kim, Chang Su; Song, Myungkwan; Jeong, Yongsoo; Nam, Kee-Seok; Lee, Sangchul; Yoo, Tae Jin; Kang, Chang Goo; Lee, Byoung Hun; Ko, Heung Cho; Ajayan, Pulickel M.; Kim, Dong-Ho
    Two-dimensional (2D) molybdenum disulphide (MoS2) atomic layers have a strong potential to be used as 2D electronic sensor components. However, intrinsic synthesis challenges have made this task difficult. In addition, the detection mechanisms for gas molecules are not fully understood. Here, we report a high-performance gas sensor constructed using atomic-layered MoS2ﾠsynthesised by chemical vapour deposition (CVD). A highly sensitive and selective gas sensor based on the CVD-synthesised MoS2was developed.ﾠIn situﾠphotoluminescence characterisation revealed the charge transfer mechanism between the gas molecules and MoS2, which was validated by theoretical calculations. First-principles density functional theory calculations indicated that NO2ﾠand NH3ﾠmolecules have negative adsorption energies (i.e., the adsorption processes are exothermic). Thus, NO2ﾠand NH3ﾠmolecules are likely to adsorb onto the surface of the MoS2. Theﾠin situﾠPL characterisation of the changes in the peaks corresponding to charged trions and neutral excitons via gas adsorption processes was used to elucidate the mechanisms of charge transfer between the MoS2ﾠand the gas molecules.
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    Transparent, flexible supercapacitors from nano-engineered carbon films
    (Nature Publishing Group, 2012) Jung, Hyun Young; Karimi, Majid B.; Hahm, Myung Gwan; Ajayan, Pulickel M.; Jung, Yung Joon
    Here we construct mechanically flexible and optically transparent thin film solid state supercapacitors by assembling nano-engineered carbon electrodes, prepared in porous templates, with morphology of interconnected arrays of complex shapes and porosity. The highly textured graphitic films act as electrode and current collector and integrated with solid polymer electrolyte, function as thin film supercapacitors. The nanostructured electrode morphology and the conformal electrolyte packaging provide enough energy and power density for the devices in addition to excellent mechanical flexibility and optical transparency, making it a unique design in various power delivery applications.