• Elastomers and Composites
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• v.47 no.3
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• pp.238-245
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• 2012

Graphene oxide was synthesized from natural graphite, and its surface was modified using diisocyanatodicyclohexylmethane( $H_{12}MDI$). Isocyanate-graphene sheet(i-RGO) was obtained by reduction of surface modified GO. To select nanofiller having good dispersion with polyurethane, GO, i-RGO, natural graphite and thermal reduced graphite were analyzed, and then i-RGO was selected as a suitable nanofiller. PU/i-RGO nanocomposite was synthesized with various i-RGO contents to estimate effect of reinforcement on nanocomposite. Thermal stability, hardness, contact angle were increased with i-RGO contents due to i-RGO characteristic and crosslink bridge effect. But, tensile strength and elongation were decreased at i-RGO contents more than the 4 wt%. This phenomenon was interpreted by the excess formation of crosslink bridge.

• Journal of Ginseng Research
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• v.46 no.2
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• pp.214-224
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• 2022

Red ginseng oil (RGO), rather than the conventional aqueous extract of red ginseng, has been receiving much attention due to accumulating evidence of its functional and pharmacological potential. In this review, we describe the key extraction technologies, chemical composition, potential health benefits, and safety of RGO. This review emphasizes the proposed molecular mechanisms by which RGO is involved in various bioactivities. RGO is mainly produced using organic solvents or supercritical fluid extraction, with the choice of method greatly affecting the yield and quality of the end products. RGO contains a high unsaturated fatty acid levels along with considerable amounts of lipophilic components such as phytosterols, tocopherols, and polyacetylenes. The beneficial health properties of RGO include cellular defense, antioxidation, anti-inflammation, anti-apoptosis, chemoprevention, hair growth promotion, and skin health improvement. We propose several molecular mechanisms and signaling pathways that underlie the bioactivity of RGO. In addition, RGO is regarded as safe and nontoxic. Further studies on RGO must focus on a deeper understanding of the underlying molecular mechanisms, composition-functionality relationship, and verification of the bioactivities of RGO in clinical models. This review may provide useful information in the development of RGO-based products in nutraceuticals, functional foods, and functional cosmetics.

• Polymer(Korea)
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• v.38 no.4
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• pp.484-490
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• 2014

Reduced graphene oxide (RGO) was fabricated using gelatin as a reductant, and it could be stably dispersed in gelatin solution without aggregation. A series of RGO/gelatin composite films with various RGO contents were prepared by a solution-casting method. The structure and thermal properties of the RGO/gelatin composite films were characterized by UV-vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA). The addition of RGO enhances the degree of crosslinking of gelatin films and decreases the swelling ability of the gelatin films in water, indicating that RGO/gelatin composite films have a better wet stability than gelatin films. The glass transition temperature ($T_g$) of gelatin films is also increased with the incorporation of RGO. The presence of RGO slightly increases the degradation temperature of gelatin films due to the very low content of RGO in the composite films. Since gelatin is a natural and nontoxic biomacromolecule, the RGO/gelatin composite films are expected to have potential applications in the biomedical field.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.752-759
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• 2002

This paper presented a design and a control of a biped walking RGO and walking simulation by this system. The biped walking RGO was distinguished from the other one by which had a very light-weight and a new RGO type with 12-servo motors. The vibration evaluation of the dynamic PLS on the biped walking RGO was used to access by the 3-axis accelerometer with a low frequency vibration for the spinal cord injuries. The gait of a biped walking RGO depended on the constrains of mechanical kinematics and the initial posture. The stability of dynamic walking was investigated by a ZMP (Zero Moment Point) of the biped walking RGO. It was designed according to a human wear type and was able to accomodate itself to a human environments. The joints of each leg were adopted with a good kinematic characteristics. To test of the analysis of joint kinematic properties, we did the strain stress analysis of the dynamic PLS and the analysis study of FEM with a dynamic PLS. It will be expect that the spinal cord injury patients are able to recover effectively with a biped walking RGO.

• Carbon letters
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• v.15 no.1
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• pp.67-70
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• 2014

In this work, nanocomposites of epoxy resin and chemically reduced graphene oxide (RGO) were prepared by thermal curing process. X-ray diffractions confirmed the microstructural properties of RGO. Differential scanning calorimetry was used to evaluate the curing behaviors of RGO/epoxy nanocomposites with different RGO loading amounts. We investigated the effect of RGO loading amounts on the mechanical properties of the epoxy nanocomposites. It was found that the presence of RGO improved both flexural strength and modulus of the epoxy nanocomposites till the RGO loading reached 0.4 wt%, and then decreased. The optimum loading achieved about 24.5 and 25.7% improvements, respectively, compared to the neat-epoxy composites. The observed mechanical reinforcement might be an enhancement of mechanical interlocking between the epoxy matrix and RGO due to the unique planar structures.

• Journal of Ginseng Research
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• v.41 no.4
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• pp.595-601
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• 2017

Background: Red ginseng oil (RGO) is produced by supercritical $CO_2$ extraction of secondary products derived from Korean Red Ginseng extract. As the use of RGO has increased, product safety concerns have become more important. Methods: In the present study, the subacute oral toxicity and bacterial reverse mutagenicity of RGO were evaluated. Sprague-Dawley rats were orally administered with RGO for 28 d by gavage. Daily RGO dose concentrations were 0 mg/kg body weight (bw), 500 mg/kg bw, 1,000 mg/kg bw, or 2,000 mg/kg bw per day. Bacterial reverse mutation tests included five bacterial strains (Escherichia coli WP2 and Salmonella typhimurium TA98, TA100, TA1535, and TA1537), which were used in the presence or absence of metabolic activation. The plated incorporation method for mutation test was used with RGO concentrations ranging from $312.5{\mu}g$ to $5,000{\mu}g$ per plate. Results: The subacute oral toxicity test results did not reveal any marked changes in clinical characteristics. There were no toxicological changes related to RGO administration in hematological and serum biochemical characteristics in either control or treatment animals. Furthermore, no gross or histopathological changes related to RGO treatment were observed. The bacterial reverse mutation test results did not reveal, at any RGO concentration level and in all bacterial strains, any increase in the number of revertant colonies in the RGO treatment group compared to that in the negative control group. Conclusion: The no-observed-adverse-effect level of RGO is greater than 2,000 mg/kg bw and RGO did not induce genotoxicity related to bacterial reverse mutations.

• Advances in nano research
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• v.5 no.3
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• pp.231-244
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• 2017

Graphene oxide (GO) was prepared by modified Hummer's method to produce reduced graphene oxide (RGO) following standard thermal and chemical reduction processes. Prepared RGO colloids were utilized to fabricate RGO films over glass and FTO coated glass substrates through drop-coating. A systematic study was performed to evaluate the effect of reduction degree on the optical and electrical properties of the RGO film. We demonstrate that both the reduction process (thermal and chemical) produce RGO films of similar optical and electrical behaviors. However, the RGO films fabricated using chemically reduced GO colloid render better performance in dye sensitized solar cells (DSSCs), when they are used as counter electrodes (CEs). It has been demonstrated that RGO films of optimum thicknesses fabricated using RGO colloids prepared using lower concentration of hydrazine reducer have better catalytic performance in DSSCs due to a better catalytic interaction with redox couple. The better catalytic performance of the RGO films fabricated at optimal hydrazine concentration is associated to their higher available surface area and lower grain boundaries.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.1
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• pp.10-18
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• 2003

This paper presented a design and control of a biped walking RGO(robotic gait orthosis) and its simulation. The biped walking RGO was distinguished from the other one by which had a very light-weight and a new RGO system will be made of 12-servo motors and 12-controllers. The vibration evaluation of the dynamic PLS(posterior leaf splint) on the biped walking RGO was used to access by the 3-axis accelerometer with a low frequency vibration of less than 30 Hz. The galt of the biped walking RGO depends on the constrains of mechanical kinematics and the initial posture. The stability of dynamic walking was investigated by analyzing the ZMP (zero moment point) of the biped walking RGO. It was designed according to the human wear type and was able to accomodate itself to the environments of S.C.I. Patients. The Joints of each leg were adopted with a good kinematic characteristics. To analyse joint kinematic properties. we made the strain stress analysis of the dynamic PLS and the analysis study of FEM with a dynamic PLS.

• Journal of the Semiconductor & Display Technology
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• v.20 no.1
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• pp.54-58
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• 2021

The RGO with controllable oxygen functional groups is a novel material as the active layer of resistive switching memory through a reduction process. We designed a nanoscale conductive channel induced by local oxygen ion diffusion in an Au / RGO+GQD / Al resistive switching memory structure. A strong electric field was locally generated around the Al metal channel generated in BIL, and the local formation of a direct conductive low-dimensional channel in the complex RGO graphene quantum dot region was confirmed. The resistive memory design of the complex RGO graphene quantum dot structure can be applied as an effective structure for charge transport, and it has been shown that the resistive switching mechanism based on the movement of oxygen and metal ions is a fundamental alternative to understanding and application of next-generation intelligent semiconductor systems.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.159-159
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• 2013

넓은 비표면적과 높은 전기전도성을 갖는 표면에 관능기가 도입된 RGO(reduced graphite oxide)를 modified Hummers method 와 thermal exfoliation 을 통해하여 합성하였으며 합성된 RGO를 PtSn alloy 촉매의 담지체로 도입하여 impregnation method를 통해 PtSn/RGO 시리즈 촉매를 합성하였다. XRD, SEM, TEM, XPS 분석을 통해 촉매의 특성을 분석하였고 methanol electrooxidation 활성을 확인하였다.