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Yun, Jin‐,Mun,Yeo, Jun‐,Seok,Kim, Juhwan,Jeong, Hyung‐,Gu,Kim, Dong‐,Yu,Noh, Yong‐,Jin,Kim, Seok‐,Soon,Ku, Bon‐,Cheol,Na, Seok‐,In WILEY‐VCH Verlag 2011 Advanced Materials Vol.23 No.42
<P>Solution‐processable reduced graphene oxide as a hole‐transporting layer for highly efficient and stable organic solar cells is reported on page 4923 by Dong‐Yu Kim, Seok‐In Na, and co‐workers. Introduction of a newly reduced graphene oxide by simple solution processing into solar cells dramatically raises the cell efficiency and cell life‐time. The results will allow full use of chemically reduced graphene and will advance the realization of carbon‐based printable optoelectronic devices. </P>
( Ji Yong Kim ),( Jai Sung Lee ),( Yong Seok Han ),( Jun Hee Lee ),( Inhyu Bae ),( Yeo Min Yoon ),( Sang Mo Kwon ),( Sang Hun Lee ) 한국응용약물학회 2015 Biomolecules & Therapeutics(구 응용약물학회지) Vol.23 No.6
Human mesenchymal stem cells (MSCs) have been used in cell-based therapy to promote revascularization after peripheral or myocardial ischemia. High levels of reactive oxygen species (ROS) are involved in the senescence and apoptosis of MSCs, causing defective neovascularization. Here, we examined the effect of the natural antioxidant lycopene on oxidative stress-induced apoptosis in MSCs. Although H2O2 (200 mM) increased intracellular ROS levels in human MSCs, lycopene (10 μmM) pretreatment suppressed H2O2-induced ROS generation and increased survival. H2O2-induced ROS increased the levels of phosphorylated p38 mitogen activated protein kinase (MAPK), Jun-N-terminal kinase (JNK), ataxia telangiectasia mutated (ATM), and p53, which were inhibited by lycopene pretreatment. Furthermore, lycopene pretreatment decreased the expression of cleaved poly (ADP ribose) polymerase-1 (PARP-1) and caspase-3 and increased the expression of B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax), which were induced by H2O2 treatment. Moreover, lycopene significantly increased manganese superoxide dismutase (MnSOD) expression and decreased cellular ROS levels via the PI3K-Akt pathway. Our findings show that lycopene pretreatment prevents ischemic injury by suppressing apoptosis-associated signal pathway and enhancing anti-oxidant protein, suggesting that lycopene could be developed as a beneficial broad-spectrum agent for the successful MSC transplantation in ischemic diseases.
Kim, Ji Yong,Lee, Jai-Sung,Han, Yong-Seok,Lee, Jun Hee,Bae, Inhyu,Yoon, Yeo Min,Kwon, Sang Mo,Lee, Sang Hun The Korean Society of Applied Pharmacology 2015 Biomolecules & Therapeutics(구 응용약물학회지) Vol.23 No.6
Human mesenchymal stem cells (MSCs) have been used in cell-based therapy to promote revascularization after peripheral or myocardial ischemia. High levels of reactive oxygen species (ROS) are involved in the senescence and apoptosis of MSCs, causing defective neovascularization. Here, we examined the effect of the natural antioxidant lycopene on oxidative stress-induced apoptosis in MSCs. Although $H_2O_2$ ($200{\mu}M$) increased intracellular ROS levels in human MSCs, lycopene ($10{\mu}M$) pretreatment suppressed $H_2O_2$-induced ROS generation and increased survival. $H_2O_2$-induced ROS increased the levels of phosphorylated p38 mitogen activated protein kinase (MAPK), Jun-N-terminal kinase (JNK), ataxia telangiectasia mutated (ATM), and p53, which were inhibited by lycopene pretreatment. Furthermore, lycopene pretreatment decreased the expression of cleaved poly (ADP ribose) polymerase-1 (PARP-1) and caspase-3 and increased the expression of B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax), which were induced by $H_2O_2$ treatment. Moreover, lycopene significantly increased manganese superoxide dismutase (MnSOD) expression and decreased cellular ROS levels via the PI3K-Akt pathway. Our findings show that lycopene pretreatment prevents ischemic injury by suppressing apoptosis-associated signal pathway and enhancing anti-oxidant protein, suggesting that lycopene could be developed as a beneficial broad-spectrum agent for the successful MSC transplantation in ischemic diseases.
Yeo, Jun-Seok,Lee, Cheol-Ho,Jang, Dawon,Lee, Sungho,Jo, Seung Mu,Joh, Han-Ik,Kim, Dong-Yu Elsevier 2016 Nano energy Vol.30 No.-
<P><B>Abstract</B></P> <P>Organometal trihalide perovskite solar cells (PeSCs) have recently opened a new era for photovoltaics power sources via the tremendous increase in power conversion efficiency (PCE) in the past five years. The next achievement will occur when scalable and processable PeSCs are realized because of a fundamental understanding of the interfacial characteristics and perovskite crystallization in PeSCs. Here, we report solution-processed planar PeSCs with well-tailored functional graphene, successfully demonstrating excellent module PCEs of 10.0% and 8.1% for rigid and flexible substrates, respectively, with active-area of 10cm<SUP>2</SUP>. Systematic investigations reveal that molecular-doped reduced graphene oxide with fluorine atoms (MFGO) exhibits fast charge-extraction ability and well-aligned energetic interface characteristic due to its intrinsic structure, and MFGO promotes perovskite crystallization and orientation with minimized stoichiometric defects. The solution-processable graphene can function not only as an efficient and stable interlayer but also as an inducer of the crystallization of the perovskite layer in simplified device architectures without a complex process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Interfacial characteristics and crystallinity of active-layer in perovskite solar cells (PeSCs) are tailored by fluorinated reduced graphene oxide (MFGO). </LI> <LI> Comprehensive investigation reveals the multifunctional roles of MFGO as the interfacial layer and crystallinity inducer. </LI> <LI> MFGO-based modules with a 10cm<SUP>2</SUP> active-area exhibit promising PCEs of 10.0% and 8.1% for rigid and flexible substrates, respectively. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
In-depth considerations for better polyelectrolytes as interfacial materials in polymer solar cells
Yeo, Jun-Seok,Kang, Minji,Jung, Yen-Sook,Kang, Rira,Lee, Seung-Hoon,Heo, Youn-Jung,Jin, Sung-Ho,Kim, Dong-Yu,Na, Seok-In Elsevier 2016 Nano energy Vol.21 No.-
<P><B>Abstract</B></P> <P>We perform a comprehensive study to achieve better polyelectrolytes (PEs) as electron-transport layers (ETLs) in polymer solar cells (PSCs). Three well-known PEs – PFN, PEIE, and WPF – are chosen as model systems and investigated with variations in their backbone structures and the state of the amine functionalities on their side chains. Respectively optimized PSCs using the three PEs exhibit different cell-performances, mainly owing to the diode characteristics of built-in potential and recombination strength. To identify how such deviated device-performances correlate with the structural features of PEs, the modulated interfaces of ITO/PEs and PEs/active layer are studied in detail. It is found that conjugated backbones and larger counter-anions on side chains can promote the modulation of ITO work functions (WFs) and that a large amount of protonated amines on PEs is beneficial for junction properties with a subsequent active layer. Additionally, our results indicate that interfacial dipole and electrical doping between the PE and active layer, in addition to WF modulation of the ITO cathode, are important for device efficiency. Accordingly, with the aid of the molecular features of PEIE, PEIE-PSCs exhibit excellent device efficiency and stability compared with PFN- and WPF-PSCs. In the PTB7-th:PC<SUB>71</SUB>BM system, a remarkable power-conversion efficiency of 9.97% is achieved with a single PEIE ETL.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Chemical structure and performance of polyelectrolytes (PEs) in PSCs are correlated. </LI> <LI> Interfacial dipole and doping between PEs and active layer lead to efficient PSCs. </LI> <LI> PEIE-based PSCs have excellent device efficiency and high stability. </LI> <LI> Especially, in the PTB7-th system, encouraging efficiency of 9.97% is achieved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Yeo, Jun-Seok,Lee, Ji-Hoon,Hwang, Seok-Ho Elsevier Science Ltd 2017 Composites Part B, Engineering Vol.130 No.-
<P><B>Abstract</B></P> <P>A pristine lignin and chemically surface modified lignin were used as a low profile additive and reinforcing filler for unsaturated polyester (UPE) resin. The chemical modification for pristine lignin was confirmed by FT-IR and SEM/EDX. Two different styrene/unsaturated polyester/lignin ternary composite series were prepared by using the pristine lignin or allyltrimethoxy silane (VPS)-modified lignin (VPS-lignin) to investigate volume shrinkage behavior and the mechanical properties of the UPE composites according to the lignin filler contents. The tensile and impact properties of the UPE composites showed that VPS-lignin/UPE composites performed better than the pristine lignin/UPE composites due to improved interfacial adhesion between the lignin filler and UPE matrix. However, the results of the volume shrinkage behavior in the UPE composites showed that the pristine lignin was more efficient than the VPS-lignin due to the many micro-voids formed from poor interface adhesion between them.</P>
Yeo, Jun-Seok,Kang, Rira,Lee, Sehyun,Jeon, Ye-Jin,Myoung, NoSoung,Lee, Chang-Lyoul,Kim, Dong-Yu,Yun, Jin-Mun,Seo, You-Hyun,Kim, Seok-Soon,Na, Seok-In Elsevier 2015 Nano energy Vol.12 No.-
<P><B>Abstract</B></P> <P>We demonstrate a simple solution and room-temperature processed reduced graphene oxide (RGO) as a novel hole-transporting material (HTM) to guarantee highly efficient and highly stable CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB> perovskite solar cells (PeSCs). The effects of RGO HTM are systemically investigated in terms of PeSC efficiency, PeSC stability, morphology of perovskite film, recombination dynamics, and charge-transport through CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>/HTM interface. The resultant PeSC with a planar configuration of glass/ITO/RGO/CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>/PC<SUB>61</SUB>BM/bathocuproine (BCP)/Ag exhibits improved device efficiency (maximum PCE of 10.8%) with high reproducibility than those of the reference devices using conventional PEDOT:PSS and GO HTMs. Also, the RGO-based PeSCs show highly desirable device stability in comparison to the PEDOT:PSS PeSCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highly efficient and stable perovskite solar cells are developed using solution and room-temperature processed RGO. </LI> <LI> The resultant PeSC with planar architecture depicts a superior device efficiency (10.8%) to PEDOT:PSS- and GO-based solar cells. </LI> <LI> The use of RGO HTMs with the inherent passivation ability greatly extended the cell-operation time compared to PeSCs with PEDOT:PSS. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>