Search

Your search keyword '"Nam, Yun-Sik"' showing total 150 results
Start Over Author "Nam, Yun-Sik"
150 results on '"Nam, Yun-Sik"'

23. High-sensitivity NH3 gas sensor using pristine graphene doped with CuO nanoparticles.

Author

Tsymbalenko, Oleksandr, Lee, Soyoung, Lee, Yong-Min, Nam, Yun-Sik, Kim, Byoung Chan, Kim, Jin Young, and Lee, Kang-Bong

Subjects
GAS detectors, SURFACE plasmon resonance, GRAPHENE, COPPER oxide, CHARGE carriers, CHEMICAL vapor deposition, NANOPARTICLES
Abstract

A highly sensitive and selective NH3 gas sensor was developed based on single-layer pristine graphene doped with copper(II) oxide (CuO) nanoparticles of a specific size. High-quality single-layer graphene was grown using chemical vapor deposition. Approximately 15 nm-sized CuO colloidal nanoparticles were fabricated by a microwave-assisted thermal method using copper acetate as the precursor, and dimethylformamide as the reducing and stabilizing agent. Pristine graphene was doped with an aqueous suspension of CuO nanoparticles at a coating speed of 1500 rpm using a simple spin coater. CuO nanoparticle doping induces changes in the electronic properties of graphene; in particular, p-type doping significantly altered graphene resistivity in the presence of NH3 gas. Upon exposure of the pristine graphene surface to NH3 gas, NH3 reacted with O2−/ O−/ O2− species on the graphene surface and released electrons into graphene. This caused a change in the concentration of charge carriers in the valence channel of graphene and an increase in graphene resistivity, facilitating real-time NH3 monitoring with quick response and rapid recovery at 25 ℃ and ~ 55% relative humidity. Our results indicated that graphene doped with ~ 15 nm-sized CuO nanoparticles can sense NH3 gas selectively with a resistivity response of ~ 83%. Moreover, the sensor exhibited good reusability, fast response (~ 19 s), and rapid recovery (~ 277 s) with a detection limit of 0.041 ppm and a relative standard deviation of 0.76%. [ABSTRACT FROM AUTHOR]

Published
2023
Full Text
View/download PDF

33. The phosphorous-doped 2D nanosheet assembled 3D Mn2V2O7microflowers on Ni foam as a binder-free electrode for high energy density asymmetric supercapacitor application

Author

Rajalakshmi, Kanagaraj, Yesuraj, Johnbosco, Muthusamy, Selvaraj, Selvam, N. Clament Sagaya, Nam, Yun Sik, Kim, Kibum, and Xu, Yuanguo

Abstract

In recent times, transition-metal oxides have been recognized as highly promising candidates for supercapacitor applications. Nevertheless, their progress in diverse fields has been hindered by challenges such as poor electrical conductivity and a shortage of active reaction centers. Doping heteroatoms would overcome these drawbacks and enhance the supercapacitor properties in transition metal oxides. Herein, the phosphorous-doped 2D nanosheet assembled 3D Mn2V2O7micro flowers were grown on the Nickel foam using the hydrothermal method and successively phosphatized in a tube furnace, which was utilized as a binder-free supercapacitor electrode. The synthesis process involved varying the concentration of phosphorus (P), resulting in the successful formation of uniform P-decorated Mn2V2O7microflowers. The unique microflower structure and doping P into the Mn2V2O7material enhance the electrochemical properties with a specific capacity of 850C g−1(1545 F g−1) at 1 A g−1in a three-electrode cell. Moreover, the assembled Mn2V2O7–600/NF//AC device delivers a specific capacity of 258C g−1(211 F g−1) at 1 A g−1with a remarkable rate of 47 % at a high current density of 20 Ag −1. The device achieved a maximum energy density of 43.2 Wh kg−1at a power density of 604.7 W kg−1, and it maintained 91 % of initial capacity after 10,000 charge/discharge cycles at 20 A g−1. These results suggest that the P-doping 2D nanosheet assembled 3D Mn2V2O7could be promising electrode materials for supercapacitor applications.

Published
2024
Full Text
View/download PDF

39. Glutathione Functionalized Gold Nanoparticles for Colorimetric Detection of Didecyldimethylammonium Chloride

Author

Lee Kang‐Bong, Kim Kyung Min, Nah In Wook, Nam Yun‐Sik, and Lee Yeonhee

Subjects
Materials science, 010401 analytical chemistry, Biomedical Engineering, Bioengineering, 02 engineering and technology, General Chemistry, Glutathione, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, 0104 chemical sciences, chemistry.chemical_compound, chemistry, Colloidal gold, General Materials Science, 0210 nano-technology, Didecyldimethylammonium chloride, Nuclear chemistry
Published
2016

49. Rapid-Response and Highly Sensitive Boronate Derivative-Based Fluorescence Probe for Detecting H2O2 in Living Cells.

Author

Selvaraj, Muthusamy, Rajalakshmi, Kanagaraj, Nam, Yun-Sik, Lee, Yeonhee, Kim, Byoung Chan, Pai, Sung Jin, Han, Sang Soo, and Lee, Kang-Bong

Subjects
FLUORESCENCE, BORONIC esters, REACTIVE oxygen species, ENVIRONMENTAL sampling, FUNCTIONAL groups, PEROXIDES
Abstract

Intracellular H2O2 monitoring is important and has driven researchers to pursue advancements for the rapid identification of H2O2, since H2O2 is short-lived in cell lines. An arylboronate derivative has been investigated as a chemospecific fluorescence recognition agent for H2O2. Triphenylimidazoleoxadiazolephenyl (TPIOP) boronate was contrived as a novel candidate for the rapid and sensitive recognition of H2O2. The probe was conjugated using the TPIOP functional group acting as an excellent fluorescent enhancer. The TPIOP group stimulated the polarization of C–B bond due to its extended π-conjugation, which included heteroatoms, and induced the production of rapid signal because of the highly polar C–B bond along with the corresponding boronate unit. While H2O2 reacts with TPIOP boronate, its nucleophilic addition to the boron generates a charged tetrahedral boronate complex, and then the C–B bond migrates toward one of the electrophilic peroxide oxygen atoms. The resulting boronate ester is then hydrolyzed by water into a phenol, which significantly enhances fluorescence through aggregation-induced emission. The TPIOP boronate probe responded to H2O2 rapidly, within 2 min, and exhibited high sensitivity with a limit of detection of 8 nM and a 1000-fold selectivity in the presence of other reactive oxygen species. Therefore, the developed TPIOP boronate chemodosimeter was successfully utilized to visualize and quantify intracellular H2O2 from human breast cancer (MCF-7) cells, as well as gaseous and aqueous H2O2 from environmental samples using Whatman paper strips coated with TPIOP boronate. [ABSTRACT FROM AUTHOR]

Published
2019
Full Text
View/download PDF

50. Multifunctional Sensors for Successive Detection of Endogenous ONOO–and Mitochondrial Viscosity: Discriminating Normal to Cancer Models

Author

Shen, Jian, Rajalakshmi, Kanagaraj, Muthusamy, Selvaraj, Ahn, Dae-Hwan, Song, Jong-Won, Choi, Ki Young, Xi, Chunyan, Dai, Jindong, Zhou, Zhipeng, Kannan, Palanisamy, Nam, Yun-Sik, and Zhu, Dongwei

Abstract

Diagnosing cancer in its early stages can play an important role in prolonging the lifespan of patients, which demands the use of powerful tools to detect biomarkers accurately. However, since most fluorescent probes described for cancer diagnosis are limited to recognizing a single molecule, achieving the high accuracy criteria remains difficult. Here, sensor 1is constructed for the sequential detection of D, ONOO–, and viscosity. Initially, sensor 1detected Dand underwent an intramolecular charge transfer mechanism, resulting in the formation of 2and fluorescence quenching at 587 nm. Subsequently, the intermediate (2) monitored ONOO–and reproduced sensor 1reversibly with fluorescence enhancement at 496 nm, showing concentration-related quantitative analysis. Similar sensing processes were observed in monitoring ONOO–and viscosity by synthetically developed sensor 2. The proposed mechanisms of sensors 1and 2are verified through various characterizations (1H NMR, HR-MS, and HPLC) and DFT calculations. Investigations on endogenous ONOO–and mitochondrial viscosity in cancer (HeLa) and normal (NCM460) cells were conducted to distinguish cancerous cells from normal cells. We anticipated that sensor 2could effectively serve as a reliable bioanalytical reagent for cancer diagnosis at an earlier stage through sequential detection of two cancer markers, ONOO–and mitochondrial viscosity, in living cells. Importantly, sensor 2has been employed for imaging ONOO–in normal and liver injury mouse models and tissues, achieving outstanding results.

Published
2024
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results