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Stress and Surface Tension Analyses of Water on Graphene-Coated Copper Surfaces
Chinh Thanh Nguyen,김보흥 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.4
Graphene-coated materials have recently emerged as promising materials for green renewable energy applications due to the benefits of combining graphene and metals. For these types of composites, the effect of graphene coating on the wettability of metal substrates has attracted much attention from researchers. In this paper, a series of molecular dynamics simulations, in which water droplets are deposited on bare Cu (111) and graphene-coated Cu (111), were conducted to investigate the influences of graphene coating on the wettability of copper. We found that water contact angles gradually increased and converged to the value measured on pure graphite surfaces as the number of graphene layers deposited on the Cu (111) surface increased. The “wetting transparency of graphene was proven to break down as demonstrated by the fact that the water contact angle of mono-layer graphene-coated copper was found to significantly increase as compared to that of bare copper. Density and stress profiles of water droplets were examined to confirm the effect of the number of graphene layers on copper-water interactions. We also examined the surface tensions of water droplets on graphene-coated copper substrates. We found that the liquid-vapor and solid-vapor surface tensions are constant while the solidliquid tension varies with the graphene coating; this leads to the variation in the water droplet contact angles.
Chinh, Nguyen Duc,Hien, Truong Thi,Do Van, Lam,Hieu, Nguyen Minh,Quang, Nguyen Duc,Lee, Seung-Mo,Kim, Chunjoong,Kim, Dojin Elsevier 2019 Sensors and actuators. B, Chemical Vol.281 No.-
<P><B>Abstract</B></P> <P>ZnO thin-films with precisely controlled thicknesses were fabricated by the atomic layer deposition and their <I>NO</I> gas sensing properties were investigated at different temperatures, and in particular, under light irradiation of various energy and intensity at room temperature with and without Au catalyst. The molecular dynamics of <I>NO</I> and <I>O</I> <SUB>2</SUB> during the response and recovery cycles in relation with the <I>NO</I> sensing performance in air environment was elaborated using the energy diagram modelled for adsorption and desorption kinetics of the gas molecules. The blue light irradiation combined with Au catalytic effect greatly enhanced the <I>NO</I> response rate, but delayed the recovery rate in the air environment via molecular dynamic interference from the environmental oxygen. The optimum condition for <I>NO</I> sensing was obtained for the film thickness, light energy and intensity. Critical issues for the stable sensor operation such as concentration dependence, gas selectivity, and humidity effect were also reported.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Gas sensing response/recovery kinetics of NO sensing by ZnO with light irradiation and Au catalytic effect at room temperature. </LI> <LI> Molecular dynamics consideration for adsorption and desorption to explain the detection of ppm level gas concentrations. </LI> <LI> The nano-effect in varying thicknesses of ZnO. </LI> </UL> </P>
Chinh Van Luu,Minh Van Chau,Jung-Joon Lee,Sang-Hun Jung 대한약학회 2006 Archives of Pharmacal Research Vol.29 No.10
For the exploration of pharmacophoric moiety of malloapelta B (1) possessing the inhibitory activity of NF-κB activation, structural variation of α,β-unsaturated carbonyl motif was attempted. 1 was reduced by catalytic hydrogenation, sodium borohydride, and lithium aluminumhydride. Catalytic hydrogenation with 30 psi or 15 psi of H2 gas of 1 generated 8-butyl–5,7- dimethoxy-2,2-dimethylchroman (2) and 1-(5,7-dimethoxy-2,2-dimethylchroman-8-yl)butan-1- one (3), respectively. Reduction with sodium borohydride occurred at the double bond of α,β- unsaturated ketone of 1 to give 1-(5,7-dimethoxy-2,2-dimethyl-2H-chromen-8-yl)butan-1-one (4). Reduction of 1 with lithium aluminumhydride and then quenched with methanol and water produced unexpected products, 1-(5,7-dimethoxy-2,2-dimethyl-2H-chromen-8-yl)-3-methoxy-1- butene (5) and 1-(5,7-dimethoxy-2,2-dimethyl-2H-chromen-8-yl)-3-hydroxy-1-butene (6). These are formed from the isomerization of initial product 9 through the continuous conjugate carbocation intermediate 11. Addition of ethylmagnesium bromide and dimethyl malonate anion to 1 gave the conjugate adducts 7 and 8. Ethylmagesium bromide and sodium borohydride reduction unusually gave the conjugate addition due to steric congestion around carbonyl group of 1. Compound 2 exhibits the reduced inhibitory activity against NF-κB activation and the others do not show the activity. Therefore α,β-unsaturated carbonyl group of 1 should be important for its inhibitory activity.
Chinh, Nguyen Duc,Kim, Chunjoong,Kim, Dojin Elsevier 2019 Journal of Alloys and Compounds Vol.778 No.-
<P><B>Abstract</B></P> <P>A UV-light-activated TiO<SUB>2</SUB> thin film gas sensor composed of nanoparticles is reported for H<SUB>2</SUB>S detection at room temperature. TiO<SUB>2</SUB> nanoparticulate thin films were fabricated by bar coating of a mixture of TiO<SUB>2</SUB> powder and acetic acid. The morphology and structural properties of the films were examined by scanning electron microscopy, X-ray diffraction, photoluminescence spectroscopy, and absorption spectroscopy. The nil response to H<SUB>2</SUB>S was significantly enhanced by UV light irradiation in the response levels and response/recovery kinetics. The effect of the sensor conductance and light intensity towards sensor optimization was discussed. The sensor exhibited high gas selectivity, repeatability, and linearity for practical applications of the sensor, but the interference of humidity on the sensing process needs to be solved. The results exhibited a simple way to detect parts per million concentrations of H<SUB>2</SUB>S at room temperature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nanoparticulate TiO<SUB>2</SUB> thin film was fabricated by a cost-effective method of bar coating. </LI> <LI> H<SUB>2</SUB>S sensing at room temperature under UV irradiation satisfying the sensor. </LI> <LI> Analysis of the response-recovery kinetics under UV irradiation at RT. </LI> </UL> </P>
The Tasting of Korean Fresh Strawberry Matters Significantly for Vietnam Consumers
Thi Chinh Vo,지성태,김태윤 한국농식품정책학회 2023 농업경영정책연구 Vol.50 No.3
Vietnam has become a significant foreign market in Southeast Asia, especially for fresh agricultural products. This study examined Vietnamese consumers’ preferences and willingness to pay (WTP) for 330g packages of fresh Korean strawberries. Using data from 600 participants in Hanoi, key determinants in purchasing decisions were identified as shopping venues, price, and the GAP certification. Results showed a pronounced preference for fruit specialty stores and heightened food safety awareness. The treatment group’s WTP was notably higher (6.4 to 4.3 times) than the control group. Young consumers aged up to 40 with middle to high incomes displayed a higher demand. The findings suggest marketing strategies for Korean exporters targeting the Vietnamese market should emphasize food safety certifications and tasting trials.