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Electrical property measurements of metallized flagella-templated silica nanotube networks
Jo, Wonjin,Darmawan, Marten,Kim, Jihoon,Ahn, Chi Won,Byun, Doyoung,Baik, Seung Hyun,Kim, Min Jun IOP Pub 2013 Nanotechnology Vol.24 No.13
<P>We present an improvement in the electrical properties of silica nanotubes by coating metal nanoparticles on their surfaces. The silica nanotubes are formed from bacterial flagella bio-templates having a tubular structure. Successive depositions of metal nanoparticles on the silica nanotubes are performed through easily functionalized silica surfaces. The results show uniform metal nanoparticle sizes and a high surface area coverage. By incorporating gold, palladium and iron oxide nanoparticles, the metallized silica nanotubes gain electrical properties with the potential to create unique nanoelectronic materials. In this study, the metallized silica nanotubes with network structures are aligned and their electrical behaviors are investigated in both dry and wet conditions. The metallized silica nanotubes are found to be electrically conductive along the network structures. The current–voltage characteristics show remarkably improved electrical conductivities depending on the type of metal nanoparticle loading and nanotube network concentration.</P>
Development of flagella bio-templated nanomaterials for electronics
Jo Wonjin,Cheang U Kei,Kim Min Jun 나노기술연구협의회 2014 Nano Convergence Vol.1 No.10
Bacterial flagella with their unique structural properties have proven to be promising bio-templates and can be exploited for the creation of nanomaterial with very high aspect ratio and surface area. Their chemically modifiable surfaces allow the flagella be modified to possess electrical/electronic properties. Their extraordinary physical properties along with the many possibilities for manipulation make them ideal systems to study for the purpose of developing nanoelectronics. First, this article reviews the characteristics of bacterial flagella and their utilization as biologically inspired templates. Next, the use of bio-templates for electronic systems such as dye-sensitized solar cell and lithium ion battery is discussed. Finally, we show the future directions for the use of flagella biotemplatednanomaterials for applications in electrical engineering fields.
Fabrication of tunable silica-mineralized nanotubes using flagella as bio-templates
Jo, Wonjin,Freedman, Kevin J,Yi, Dong Kee,Kim, Min Jun IOP Pub 2012 Nanotechnology Vol.23 No.5
<P>Bacterial flagella are particularly attractive bio-templates for nanotubes due to their tubular structures and small inner and outer diameters. In this work, flagella isolated from Salmonella typhimurium were used as templates for silica-mineralized nanotubes. The process involved pretreatment of flagella with aminopropyltriethoxysilane (APTES), followed by the addition of tetraethoxysilane (TEOS). By controlling the concentration of TEOS and the reaction time, we developed a simple and precise method for creating silica-mineralized flagella nanotubes (SMFNs) with various thicknesses of the silica layer. It is demonstrated that flagella can be utilized for the fabrication of SMFNs with tunable thickness. A thicker silica layer was obtained as the concentration ratio of TEOS and reaction time was increased. The present experimental evidence has shown the feasibility of using such fabrication techniques to manufacture nanotubes without genetic modification of flagella which retain the original morphology.</P>
( Wonjin Park ),( Yi-yong Baek ),( Joohwan Kim ),( Dong Hyun Jo ),( Seunghwan Choi ),( Jin Hyoung Kim ),( Taesam Kim ),( Suji Kim ),( Minsik Park ),( Ji Yoon Kim ),( Moo-ho Won ),( Kwon-soo Ha ),( Jeo 한국응용약물학회 2019 Biomolecules & Therapeutics(구 응용약물학회지) Vol.27 No.5
Vascular endothelial growth factor (VEGF) plays a pivotal role in pathologic ocular neovascularization and vascular leakage via activation of VEGF receptor 2 (VEGFR2). This study was undertaken to evaluate the therapeutic mechanisms and effects of the tetrapeptide Arg-Leu-Tyr-Glu (RLYE), a VEGFR2 inhibitor, in the development of vascular permeability and choroidal neovascularization (CNV). In cultured human retinal microvascular endothelial cells (HRMECs), treatment with RLYE blocked VEGF-Ainduced phosphorylation of VEGFR2, Akt, ERK, and endothelial nitric oxide synthase (eNOS), leading to suppression of VEGFA- mediated hyper-production of NO. Treatment with RLYE also inhibited VEGF-A-stimulated angiogenic processes (migration, proliferation, and tube formation) and the hyperpermeability of HRMECs, in addition to attenuating VEGF-A-induced angiogenesis and vascular permeability in mice. The anti-vascular permeability activity of RLYE was correlated with enhanced stability and positioning of the junction proteins VE-cadherin, β-catenin, claudin-5, and ZO-1, critical components of the cortical actin ring structure and retinal endothelial barrier, at the boundary between HRMECs stimulated with VEGF-A. Furthermore, intravitreally injected RLYE bound to retinal microvascular endothelium and inhibited laser-induced CNV in mice. These findings suggest that RLYE has potential as a therapeutic drug for the treatment of CNV by preventing VEGFR2-mediated vascular leakage and angiogenesis.
Jeong, Seongpil,Shin, Bongsu,Jo, Wonjin,Kim, Ho-Young,Moon, Myoung-Woon,Lee, Seockheon Elsevier 2016 Desalination Vol.399 No.-
<P><B>Abstract</B></P> <P>Recently, various nanotechnologies have been utilized with regard to membrane modification due to their high activities and the low cost of the nanomaterials involved. In order to enhance the hydrophobicity of the membrane surface for membrane distillation applications by decreasing the surface energy, a radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) process is suggested with surface nanostructuring and a subsequent hydrophobic coating step. In this research, a commercial PVDF membrane was modified by plasma treatments with the two different gases of O<SUB>2</SUB> and CF<SUB>4</SUB>. The water contact angles of the active layers increased from 73 to 117 and 101° and the fluxes of the treated membranes increased to 63 and 27.9% as compared to a virgin PVDF membrane when the feed used was D.I. water by the O<SUB>2</SUB> and CF<SUB>4</SUB> plasma modifications, respectively. Defluorination at the long exposure time (120min) of the plasma treatment and increase of the overall hydrophobicity (the decrease of the contact angle hysteresis) by the HMDSO coating were the reasons of the flux variations for the plasma modified membranes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The PVDF membranes were modified by plasma treatments with O<SUB>2</SUB> and CF<SUB>4</SUB> gases. </LI> <LI> The modified membrane have an enhanced flux and hydrophobicity after the plasma treatment. </LI> <LI> The pore-size and porosity at the membrane surface increased after the plasma treatment. </LI> <LI> The hairy structure was formed at the membrane surface by the HMDSO coating. </LI> <LI> The O<SUB>2</SUB> plasma treatment with HMDSO coating increased the receding contact angle. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Surface Treatment of Air Gap Membrane Distillation (AGMD) Condensation Plates
Rachel Ananda Harianto,Rio Aryapratama,Seockheon Lee,Wonjin Jo,Heon Ju Lee 한국진공학회(ASCT) 2014 Applied Science and Convergence Technology Vol.23 No.5
Air Gap Membrane Distillation (AGMD) is one of several technologies that can be used to solve problems fresh water availability. AGMD exhibits several advantages, including low conductive heat loss and higher thermal efficiency, due to the presence of an air gap between the membrane and condensation wall. A previous study by Bhardwaj found that the condensation surface properties (materials and contact angle) affected the total collected fresh water in the solar distillation process. However, the process condition differences between solar distillation and AGMD might result in different condensation phenomena. In contrast, N. Miljkovic showed that a hydrophobic surface has higher condensation heat transfer. Moreover, to the best of our knowledge, there is no study that investigates the effect of condensation surface properties in AGMD to overall process performance (i.e. flux and thermal efficiency). Thus, in this study, we treated the AGMD condensation surface to make it hydrophobic or hydrophilic. The condensation surface could be made hydrophilic by immersing and boiling plate in deionized (DI) water, which caused the formation of hydrophilic aluminum hydroxide (AlOOH) nanostructures. Afterwards, the treated plate was coated using hexamethyldisiloxane (HMDSO) through plasma-enhanced chemical vapor deposition (PECVD). The result indicated that condensation surface properties do not affect the permeate flux or thermal efficiency significantly. In general, the permeate flux and thermal efficiency for the treated plates were lower than those of the non-treated plate (pristine). However, at a 1 mm and 3 mm air gap, the treated plate outperformed the non-treated plate (pristine) in terms of permeate flux. Therefore, although surface wettability effect was not significant, it still provided a little influence.
이경민(Kyungmin Lee),강진석(Jinsuk Kang),조원진(Wonjin Jo),표순찬(Soonchan Pyo) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
ECU control parameters were optimized on engine test bench to improve the fuel economy of passenger diesel vehicle. Optimization was performed with model based optimization technique of MATLAB<SUP>®</SUP>. The vehicle NEDC test result with newly optimized ECU dataset showed that the reduction amount of fuel consumption, NOx, and PM were 3.4%, 15%, and 23% respectively. NEDC cycle optimization strategy was setup according to engine load conditions.