Browsing by Author "Wang, Chueh-Han"

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Ionic Liquids with Various Constituent Ions To Optimize Non-Enzymatic Electrochemical Detection Properties of Graphene Electrodes
(2019-10-07)
Xie, Jian-De
;
Wang, Chueh-Han
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Patra, Jagabandhu
;
Rath, Purna Chandra
;
Gandomi, Yasser Ashraf
Palladium (Pd) nanoparticles, ionic liquids (ILs), or both are integrated with graphene sheets to serve as an electrochemical sensor for detecting various bio-species. Ascorbic acid (AA), uric acid (UA), and dopamine (DA) are used as the model analytes. To assess the effects of the constituent ions of ILs on sensing properties, various ILs, namely, EMI-SCN, EMI-DCA, BMP-DCA, BMI-PF6, EMI-NTF2, and BMP-NTF2, are investigated. The results demonstrate that the graphene/IL electrode shows superior detection sensitivity compared to those of the graphene/Pd and graphene/Pd/IL electrodes. Interestingly, the IL anions are found to play a crucial role in sensing performance. Angle-resolved X-ray photoelectron spectroscopy reveals that graphene can create an aligned cation/anion orientation in the adsorbed IL film, with the anions preferentially occupying the topmost surface, thus dominating the interaction with analytes. The graphene/EMI-SCN electrode shows the highest sensitivity among the electrodes, 1.49 mu A mu M-1 cm(-2), and a detection limit of 0.11 mu M toward DA. Even with large excesses of AA and UA, the concentration of DA can be effectively detected.
Titanium Carbide (MXene) as a Current Collector for Lithium-Ion Batteries
(2018-10-01)
Wang, Chueh-Han
;
Kurra, Narendra
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Alhabeb, Mohamed
;
Chang, Jeng-Kuei
;
Alshareef, Husam N.
MXenes are a class of two-dimensional (2D) transition-metal carbides and nitrides that are currently at the forefront of 2D materials research. In this study, we demonstrate the use of metallically conductive free-standing films of 2D titanium carbide (MXene) as current-collecting layers (conductivity of similar to 8000 S/cm, sheet resistance of 0.5 Omega/sq) for battery electrode materials. Multilayer Ti3C2Tx (T-x: surface functional groups -O, -OH and -F) is used as an anode material and LiFePO4 as a cathode material on 5 mu m MXene films. Our results show that the capacities and rate performances of electrode materials using Ti3C2Tx MXene current collectors match those of conventional Cu and Al current collectors, but at significantly reduced device weight and thickness. This study opens new avenues for developing MXene-based current collectors for improving volumetric and gravimetric performances of energy-storage devices.