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RISS 인기검색어
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- 저자 : ( Kezhi Li ) (검색결과 5 건)
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Molybdenum Trioxide Dihydrate-Graphene Composite for Electrochemical Detection of Thiourea Molecule
Xinmeng Zhang,Kezhi Li,Hejun Li,Jinhua Lu,Leilei Zhang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.3
A novel electrochemical sensing platform was constructed based on a facile self-assembly procedure synthetic laminar molybdenum trioxide dihydrate (MoO3 · 2H2O)-graphene composite. Field emission scanning electron microscopy (FESEM), X-ray spectroscopy, X-ray diffraction (XRD) and Raman spectroscopy were employed to characterize the morphology and composition of the MoO3 · 2H2O-graphene composite. As a model molecule, thiourea was utilized to investigate the electrochemical behaviors of the MoO3 · 2H2O-graphene composite modified glass carbon electrode. The results show that the composite modified electrode has higher electron transfer rate than that of graphene modified electrode and bare glass carbon electrode meanwhile the peak currents of it has a good linear relationship with thiourea concentrations in the range of 2.40 X 10-3 − 19.3 X 10-3 M (R = 0.998) with detection limit of 4.99 µM (S/N = 3). This novel electrochemical sensor exhibits a higher absorption capacity (3.87 X 10-8 mol/cm2 ), a good reproducibility (1.41% relative standard deviation (RSD)), excellent anti-interference and a high stability. These excellent electrochemical properties of the MoO3 · 2H2O-graphene composite are attributed to the loose and porous structure and the synergistic effects between graphene and MoO3 · 2H2O, which make this composite material hold great potential applications for electrochemical sensor.
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One-Step Solvothermal Synthesis of Tetranitro-Cobalt Phthalocyanine/Reduced Graphene Oxide Composite
Lijuan Zhang,Hejun Li,QIANGANG FU,Zhanwei Xu,Kezhi Li,Jianfeng Wei 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.3
Tetranitro-cobalt phthalocyanine/reduced graphene oxide (TNCoPc/RGO) composite was prepared using ethylene glycol as reducing agent and precursor. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the composite. The electrochemical performance of the composite was examined by cyclic voltammetry and rotating disk electrode. The SEM observation and UV-Vis absorption spectrophotometer reveal that TNCoPc nanoparticles are closely contacted with RGO. The results show that the composite has a larger peak current and a higher current density than TNCoPc for oxygen reduction in an alkaline medium. This work offers a simple and environmental route for the synthesis of metal phthalocyanine (MPc)/RGO, which is adaptable to a wide range of applications in fuel cells.
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ZHEN SUN,Hejun Li,Kezhi Li,QIANGANG FU 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2014 NANO Vol.9 No.6
Graphene platelets with a large scale have been synthesized by reduction of graphene oxide (GO)in aqueous solution of hydrazine hydrate under microwave irradiation (MWI). Microstructure ofthe graphene was characterized by X-ray di®raction (XRD), Raman spectroscopy, atomic forcemicroscopy (AFM) and transmission electron microscopy (TEM) together with the selected areaelectron di®raction (SAED). The electrochemical properties were evaluated by the analysis ofcyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 1 M Na 2 SO 4aqueous solution. The results show that the as-prepared materials consist of crumpled, few-layer( ? 3 nm) thick and electronically conductive graphitic sheets. The supercapacitors fabricatedusing this material possess a low equivalent series resistance (ESR) value ? 1.6 ? and a highspeci¯c capacitance of 285 F ? g ? 1 . In addition, the graphene reduced under a diverse duration ofMWI displays a di®erent interlayer spacing, extent of reduction, level of graphitization andspeci¯c capacitances. The duration of MWI and the treatment methods strongly a®ect the mi-crostructure of graphene, and then dominate its electrochemical properties.
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( Peng Liu ),( Gaochao Xu ),( Kun Yang ),( Kezhi Wang ),( Yang Li ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.12
Mobile Edge Computing (MEC) and Wireless Power Transfer (WPT) are both recognized as promising techniques, one is for solving the resource insufficient of mobile devices and the other is for powering the mobile device. Naturally, by integrating the two techniques, task will be capable of being executed by the harvested energy which makes it possible that less intrinsic energy consumption for task execution. However, this innovative integration is facing several challenges inevitably. In this paper, we aim at prolonging the battery life of mobile device for which we need to maximize the harvested energy and minimize the consumed energy simultaneously, which is formulated as residual energy maximization (REM) problem where the offloading ratio, energy harvesting time, CPU frequency and transmission power of mobile device are all considered as key factors. To this end, we jointly optimize the offloading ratio, energy harvesting time, CPU frequency and transmission power of mobile device to solve the REM problem. Furthermore, we propose an efficient convex optimization and sequential unconstrained minimization technique based combining method to solve the formulated multi-constrained nonlinear optimization problem. The result shows that our joint optimization outperforms the single optimization on REM problem. Besides, the proposed algorithm is more efficiency.
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Energy-Aware Preferential Attachment Model for Wireless Sensor Networks with Improved Survivability
( Rufei Ma ),( Erwu Liu ),( Rui Wang ),( Zhengqing Zhang ),( Kezhi Li ),( Chi Liu ),( Ping Wang ),( Tao Zhou ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.7
Recent years have witnessed a dramatic increase in topology research of wireless sensor networks (WSNs) where both energy consumption and survivability need careful consideration. To balance energy consumption and ensure survivability against both random failures and deliberate attacks, we resort to complex network theory and propose an energy-aware preferential attachment (EPA) model to generate a robust topology for WSNs. In the proposed model, by taking the transmission range and energy consumption of the sensor nodes into account, we combine the characters of Erdos -Renyi (ER) model and Barabasi-Albert (BA) model in this new model and introduce tunable coefficients for balancing connectivity, energy consumption, and survivability. The correctness of our theoretic analysis is verified by simulation results. We find that the topology of WSNs built by EPA model is asymptotically power-law and can have different characters in connectivity, energy consumption, and survivability by using different coefficients. This model can significantly improve energy efficiency as well as enhance network survivability by changing coefficients according to the requirement of the real environment where WSNs deployed and therefore lead to a crucial improvement of network performance.
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