Oil Removal Using Diethyl Ether Extracted and Ground Kenaf Core

Lee, Beom Goo,Lee, Hyun Jong,Shin, Dae Yong,Jeong, Yeon Ho,Jin, Cheng Wu,Cho, Dong Ha,Lee, Kang Yol,Kim, Dong Eun,Kang, Wie Soo,Goh, Young Gyun,Hwang, Byung Ho Trans Tech Publications, Ltd. 2008 Materials science forum Vol.569 No.-

<P>Kenaf core was tested for its ability to sorb diesel oil from the pure diesel oil bath and the diesel oil containing water bath after extracting with diethyl ether to remove wax from fiber surface, grinding to disrupt lumen structure and presoaking in water. Oil sorption capacity was the highest as 8.0 g/g in diethyl ether extracted fiber in oil bath, and the lowest as 1.3 g/g in water soaked kenaf core in water bath. Diesel oil sorption capacity was much higher in oil bath than in water bath. In diethyl ether extraction the diesel oil sorption capacity was not changed much in kenaf core, compared to that of control. Also, even after grinding and passing through 20 mesh screen (0.86mm) the diesel oil sorption capacity was almost same. When kenaf core was presoaked in water the oil sorption capacity was decreased to about half of control as 1.3g/g in water bath. Grinding, extracting and water presoaking all contributed to the changes in oil sorption capacity. The results show that if in lignocelluloscic fiber like kenaf core the fiber structure is not disrupted during processing and the intact lumen structure can be kept, the oil sorption capacity may not be affected much by physical and chemical changes.</P>

Autophagic flux induced by graphene oxide has a neuroprotective effect against human prion protein fragments

Jeong, Jae-Kyo,Lee, You-Jin,Jeong, Seung Yol,Jeong, Sooyeon,Lee, Geon-Woong,Park, Sang-Youel DOVE MEDICAL PRESS 2017 INTERNATIONAL JOURNAL OF NANOMEDICINE Vol.12 No.-

<P>Graphene oxide (GO) is a nanomaterial with newly developing biological applications. Autophagy is an intracellular degradation system that has been associated with the progression of neurodegenerative disorders. Although induction of autophagic flux by GO has been reported, the underlying signaling pathway in neurodegenerative disorders and how this is involved in neuroprotection remain obscure. We show that GO itself activates autophagic flux in neuronal cells and confers a neuroprotective effect against prion protein (PrP) (106–126)-mediated neurotoxicity. GO can be detected in SK-N-SH neuronal cells, where it triggers autophagic flux signaling. GO-induced autophagic flux prevented PrP (106–126)-induced neurotoxicity in SK-N-SH cells. Moreover, inactivation of autophagic flux blocked GO-induced neuroprotection against prion-mediated mitochondrial neurotoxicity. This is the first study to demonstrate that GO regulates autophagic flux in neuronal cells, and that activation of autophagic flux signals, induced by GO, plays a neuroprotective role against prion-mediated mitochondrial neurotoxicity. These results suggest that the nanomaterial GO may be used to activate autophagic flux and could be used in neuroprotective strategies for treatment of neurodegenerative disorders, including prion diseases.</P>

Arrays of vertically aligned tubular-structured graphene for flexible field emitters

Jeong, Hee Jin,Kim, Ho Young,Jeong, Hae Deuk,Jeong, Seung Yol,Han, Joong Tark,Lee, Geon-Woong The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.22

<P>Arrays of tubular-structured reduced graphene oxide (RGO) were fabricated by a simple method involving filtration of a solution containing highly dispersed RGO sheets. The length and alignment of the tubular-structured RGO arrays were controlled by the filtration rate and by tuning the interactions between the hydrophobic RGO sheets and the porous walls, rather than the top surfaces, of the polycarbonate filter membrane. As expected, the lengths of the RGO arrays increased with higher filtration rates; however, maximum field emission characteristics were obtained at an intermediate filtration rate because field screening reduced electron emission from the longer-length RGO arrays. ZnO-coated RGO arrays showed excellent emission stability without significant current degradation or fluctuations, even under O<SUB>2</SUB> exposure. The ZnO layer protected the emission site of the RGO arrays from the reactive ion bombardment of oxidative gas species. Moreover, the RGO arrays were highly flexible with preservation of the field emission properties, even at large bending angles. The excellent field emission characteristics of the tubular structured RGO arrays were attributed to the high crystallinity, abundant sharp edges, and the chemical stability of the RGO arrays, as well as the strong interactions between the RGO arrays and the substrate.</P> <P>Graphic Abstract</P><P>High-performance flexible field emission was demonstrated using tubular-structured reduced graphene oxide arrays by a simple method involving filtration of a solution containing highly dispersed RGO sheets. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm31263h'> </P>

Highly Concentrated and Conductive Reduced Graphene Oxide Nanosheets by Monovalent Cation–<i>π</i> Interaction: Toward Printed Electronics

Jeong, Seung Yol,Kim, Sung Hun,Han, Joong Tark,Jeong, Hee Jin,Jeong, Soo Yeon,Lee, Geon‐,Woong WILEY‐VCH Verlag 2012 Advanced Functional Materials Vol.22 No.15

<P><B>Abstract</B></P><P>A novel route to preparing highly concentrated and conductive reduced graphene oxide (RGO) in various solvents by monovalent cation–<I>π</I> interaction. Previously, the hydrophobic properties of high‐quality RGO containing few defects and oxygen moieties have precluded the formation of stable dispersion in various solvents. Cation–<I>π</I> interaction between monovalent cations, such as Na<SUP>+</SUP> or K<SUP>+</SUP>, and six‐membered sp<SUP>2</SUP> carbons on graphene were achieved by simple aging process of graphene oxide (GO) nanosheets dispersed in alkali solvent. The noncovalent binding forces introduced by the cation–<I>π</I> interactions were evident from the chemical shift of the sp<SUP>2</SUP> peak in the solid <SUP>13</SUP>C NMR spectra. Raman spectra and the <I>I</I>‐<I>V</I> characteristics demonstrated the interactions in terms of the presence of <I>n</I>‐type doping effect due to the adsorption of cations with high electron mobility (39 cm<SUP>2</SUP>/Vs). The RGO film prepared without a post‐annealing process displayed superior electrical conductivity of 97,500 S/m at a thickness of 1.7 μm. Moreover, mass production of GO paste with a concentration as high as 20 g/L was achieved by accelerating the cation–<I>π</I> interactions with densification process. This strategy can facilitate the development of large scalable production methods for preparing printed electronics made from high‐quality RGO nanosheets.</P>

Effect of Grinding and Extraction of Lignocellulosic Fiber on Oil Sorption

Lee, Beom Goo,Lee, Hyun Jong,Shin, Dae Yong,Jeong, Yeon Ho,Wu, Jin Chen,Cho, Dong Ha,Lee, Kang Yol,Kim, Dong Eun,Kang, Wie Soo,Goh, Young Gyun Trans Tech Publications, Ltd. 2007 Materials science forum Vol.544 No.-

<P>Cotton, a lignocellulosic fiber and environment friendly natural material, was tested for its ability to sorb diesel oil from the pure diesel oil bath and the diesel oil containing water bath. The fiber was ground to disrupt the lumen structure or extracted with diethyl ether to remove wax from cotton. Diethyl ether is an organic solvent and extracts only extractives in the cell wall. Oil sorption capacity was the highest in control as 30.6 g/g in the pure diesel oil bath, and the lowest in ground cotton as 0.8 g/g in the diesel oil containing water bath. Cotton is mainly composed of hydrophilic components and sorb water more easily than oil. As a result diesel oil sorption capacity was much higher in the oil bath than in the water bath. However, after grinding and passing through 20 mesh screen (0.86 cm), wax is preserved but the lumen structure of cotton, of which the fiber length is about 18 mm, is disrupted by grinding and can not hold oil. Therefore, the diesel oil sorption capacity of cotton was decreased significantly to 5.2 g/g in the pure diesel oil bath, and to 0.8 g/g in the water bath, compared to those of control. And because wax is removed but lumen structure is not destroyed after diethyl ether extraction, the diesel oil sorption capacity decreased slightly to 27.7 g/g in the oil bath and to 7.5 g/g in the water. When cotton was presoaked in water, cotton sank during the presoaking process, and so the oil sorption capacity could not be determined. Grinding, extractingand presoaking all contributed to the changes in oil sorption capacity. The most significant change is attributed to the reduction in the particle size of cotton.</P>

One-step transfer and integration of multifunctionality in CVD graphene by TiO2/graphene oxide hybrid layer.

Jeong, Hee Jin,Kim, Ho Young,Jeong, Hyun,Han, Joong Tark,Jeong, Seung Yol,Baeg, Kang-Jun,Jeong, Mun Seok,Lee, Geon-Woong Wiley-VCH 2014 Small Vol.10 No.10

<P>We present a straightforward method for simultaneously enhancing the electrical conductivity, environmental stability, and photocatalytic properties of graphene films through one-step transfer of CVD graphene and integration by introducing TiO2/graphene oxide layer. A highly durable and flexible TiO2 layer is successfully used as a supporting layer for graphene transfer instead of the commonly used PMMA. Transferred graphene/TiO2 film is directly used for measuring the carrier transport and optoelectronic properties without an extra TiO2 removal and following deposition steps for multifunctional integration into devices because the thin TiO2 layer is optically transparent and electrically semiconducting. Moreover, the TiO2 layer induces charge screening by electrostatically interacting with the residual oxygen moieties on graphene, which are charge scattering centers, resulting in a reduced current hysteresis. Adsorption of water and other chemical molecules onto the graphene surface is also prevented by the passivating TiO2 layer, resulting in the long term environmental stability of the graphene under high temperature and humidity. In addition, the graphene/TiO2 film shows effectively enhanced photocatalytic properties because of the increase in the transport efficiency of the photogenerated electrons due to the decrease in the injection barrier formed at the interface between the F-doped tin oxide and TiO2 layers.</P>

Comparative Evaluation of a Four-Implant—Supported Polyetherketoneketone Framework Prosthesis: A Three-Dimensional Finite Element Analysis Based on Cone Beam Computed Tomography and Computer-Aided Design

Lee, Ki-Sun,Shin, Sang-Wan,Lee, Sang-Pyo,Kim, Jong-Eun,Kim, Jee-Hwan,Lee, Jeong-Yol QUINTESSENCE PUBLISHING CO LTD 2017 The International journal of prosthodontics Vol.30 No.6

Recruitment and enrollment in a randomized clinical trial of mandibular two-implant overdenture

Lee, Jeong-Yol,Kim, Min-Soo,Kim, Ha-Young,Shin, Sang-Wan The Korean Academy of Prosthodonitics 2013 The Journal of Advanced Prosthodontics Vol.5 No.2

PURPOSE. The purpose of this study was to evaluate the effectiveness of a promotion campaign for subject recruitment and selection, and reasons of withdrawal from a prospective clinical trial of mandibular two-implant supported overdenture. MATERIALS AND METHODS. The subjects of this study were participants in a randomized controlled clinical trial for investigating prognosis of implants and overdentures with attachments. Recruited subjects were classified by gender, age, and participation motives. Withdrawal rate of the participants before and after enrollment were evaluated. RESULTS. 177 patients were recruited and 51 patients were enrolled for the trial. Among them, 40 participants eventually took part in the trial. 116 subjects (65.5%) were recruited by advertisement and 61 (34.5%) were referred by patients of the hospital or local clinics. Regarding recruitment effectiveness, newspaper recruited the largest number of participants. With respect to referral patients, the proportion of our hospital patients was higher (37/61). Subjects in their 70s comprised the largest proportion (22/51). The male to female ratio was similar (25:26). Final withdrawal rate of all subjects were 74.0%. Among the reasons for withdrawal from enrollment (n=126) presence of remaining teeth and lack of motivation were the most common reasons. CONCLUSION. To facilitate recruitment of clinical trial subjects and improve enrollment rate, it is important to obtain a sufficient number of researchers, perform promotion activity with diverse strategies, cooperate with local dentists, increase the research funding, and alleviate subjects' fear against clinical trials by thorough consultation.

Effect of span length on the fit of zirconia framework fabricated using CAD/CAM system

Lee, Jeong-Yol,Choi, Sang-Jin,Kim, Min-Soo,Kim, Ha-Young,Kim, Young-Soo,Shin, Sang-Wan The Korean Academy of Prosthodonitics 2013 The Journal of Advanced Prosthodontics Vol.5 No.2

PURPOSE. The purpose of this study was to evaluate the effect of the span length on the fit of zirconia framework fabricated using CAD/CAM system. MATERIALS AND METHODS. Abutments for single, 4-unit and 6-unit fixed partial prostheses were fabricated. Ten zirconia frameworks were fabricated for each group. The marginal and internal gap were presented by means of replica technique and measured by measuring microscope ($AXIO^{(R)}$, Carl Zeiss, Rochester, NY) and software (I-$solution^{(R)}$, IMT i-solution Inc., Vancouver, BC, Canada). The results were statistically analyzed by multivariate analysis test and Dunnett T3 test for post hoc test (${\alpha}$=.05). RESULTS. There were statistically significant differences at 2, 4, 7, 8 points (mesio-distal section) and b, d, e, f, g (labio-lingual section). In some marginal reference points of 6-unit group (P<.05), the marginal gap were larger than 120 ${\mu}m$. CONCLUSION. Span length of zirconia core may have an influence on marginal and internal fit. Within the limitation of this study, the increase of span length of zirconia framework of 6 or more-unit fixed partial denture may decrease the marginal and internal fit.

Highly efficient polymer light-emitting diodes using graphene oxide-modified flexible single-walled carbon nanotube electrodes

Lee, Bo Ram,Kim, Jun Suk,Nam, Yun Seok,Jeong, Hee Jin,Jeong, Seung Yol,Lee, Geon-Woong,Han, Joong Tark,Song, Myoung Hoon The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.40

<P>We present flexible polymer light-emitting diodes (FPLEDs) using graphene oxide-modified single-walled carbon nanotube (GO-SWCNT) films as an anode on polyethylene terephthalate (PET) substrates. The electrode of GO-SWCNTs used in this study shows quite a low sheet resistance of ∼75 Ω per square at 65% (at 550 nm) optical transparency with resistance to bending fatigue. The small-sized GO nanosheets onto the SWCNT network films are significantly effective in reducing the sheet resistance and the surface porosity of the SWCNT network films without sacrificing the transmittance. Moreover, the top layer of the large-sized GO nanosheets are crucial for high device efficiency to reduce the roughness of the SWCNT surface and enhance the wettability with PEDOT:PSS. The optimized FPLED using a GO-SWCNT electrode shows a maximum luminous efficiency of 5.0 cd A<SUP>−1</SUP> (at 9.2 V), power efficiency of 2.4 lm W<SUP>−1</SUP> (at 5.6 V), external quantum efficiency 1.9% (at 9.0 V) and turn-on voltage (2.0 V), which is comparable to conventional PLEDs using an indium-tin-oxide (ITO) electrode (a maximum luminous efficiency of 6.2 cd A<SUP>−1</SUP> (at 9.4 V), power efficiency of 2.6 lm W<SUP>−1</SUP> (at 5.8 V), external quantum efficiency 2.3% (at 9.0 V) and turn-on voltage (2.0 V)). This result confirms that a GO-SWCNT electrode can be efficiently used to replace ITO for flexible optoelectronic devices.</P> <P>Graphic Abstract</P><P>We present flexible polymer light-emitting diodes (FPLEDs) using graphene oxide-modified single-walled carbon nanotube (GO-SWCNT) films as an anode on polyethylene terephthalate (PET) substrates. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm34700h'> </P>