Ilbok Lee

SnO2-graphene nanocomposite free-standing film as anode in lithium-ion batteries

SnO2-reduced graphene oxide nanocomposite in the form of a free-standing film was prepared by simple chemical synthesis. The homogeneous and compact formation of the nanocomposite of SnO2 and reduced graphene oxide was confirmed by various analysis methods. When incorporated as anode in lithium-ion batteries, a high capacity (503 mAh g-1) and very stable cycle life were observed. These favorable properties probably arise from the efficient relaxation of high mechanical stress by the reduced graphene-oxide layers during the lithiation-delithiation process within SnO2.

Mesoporous hollow carbons on graphene and their electrochemical properties

We report the formation of mesoporous hollow carbons with diameters of about 30–40 nm on a graphene (MHCG) surface formed using graphite, the surfactant Pluronic F-127, and porous silica on the graphene as a template to produce a sheet. The specific surface area of the sample produced is 1793.45 m2 g−1, which is hundreds of times larger than that of graphite (31.38 m2 g−1). When applied to supercapacitor electrodes, the MHCG electrode exhibits outstanding maintenance of energy density above 30 W h kg−1 even under 1 kW kg−1 power density, which is attributed to extremely fast electron supply through graphene layers and facile penetration of electrolyte through highly-developed mesopores.

Core-shell type complex gelatin scaffold systems for controlled drug release

Hydrogels are often a favored choice of materials for drug delivery applications. This is due to their excellent bioactive properties such as cell adhesion and proliferation, proteolytic degradation, protein binding, etc. Various hydrogel materials and structures so far have been tested for their efficacy as a scaffold delivery system. Core-shell type hydrogel scaffold system is a structure consisting of a core component in the middle and a shell component completely surrounding the core. Multiple combinations of different crosslinking densities in the core and shell components of the hydrogel scaffolds was constructed and examined. Depending on the ways of combination, our core-shell type hydrogel scaffold structures exhibited different swelling kinetics, degradation rate, encapsulation efficiency and diffusion kinetics. Effects of the crosslinking densities of core and shell components on such factors were evaluated.

Investigation of the Charge-Storage Behavior of Electrochemically Activated Graphene Oxide on Supercapacitor Electrodes in Acidic Electrolyte

AbstractHerein, charge storage behavior of graphene oxide electrode was investigated after its electrochemical activation. X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), galvanostatic chargedischarge method (GCD), and electrochemical impedance spectroscopy (EIS) were employed for this analysis. From XPS analysis, a decrease of atomic ratio of C=C bond was observed after electrochemical activation from 86.94 to 79.64%. Also, enhancement of specific capacitance appeared from 54.1 to 65.7 F g−1 at 20 mV s−1, and rectangular shape in CV became more collapsed in activated grapheme oxide electrode. In the GCD profiles, similarly, difference of resistance values at high and low cut-off potential became larger after activation, indicative of increased polarization. From EIS, detailed resistance components were compared, which reflected that the increased resistance and higher capacitance after activation was probably attributed to larger amount of surface functional groups after activation.