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414 results on '"Kim, Joohoon"'

104. Graphene oxide hybrid with amine‐terminated poly(amidoamine) dendrimers encapsulating Pt nanoparticles for electrochemical oxygen reduction reaction.

Author

Kim, Jiwoong and Kim, Joohoon

Subjects
*OXYGEN reduction, *PLATINUM nanoparticles, *GRAPHENE oxide, *ELECTROLYTIC reduction, *DENDRIMERS, *NANOPARTICLES
Abstract

We synthesized Pt nanoparticles using amine‐terminated poly(amidoamine) dendrimers to hybridize the nanoparticles encapsulated inside dendrimers with graphene oxide (GO) sheets. The resulting Pt–GO hybrid composites revealed improved electrocatalytic activity in oxygen reduction reaction compared with GO sheets. [ABSTRACT FROM AUTHOR]

Published
2022
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105. Electrochemically induced deposition of hydroxyl‐terminated poly(amidoamine) dendrimers encapsulating Pt nanoparticles on indium tin oxide for enhanced electrochemiluminescence.

Author

Kim, Jiwoo and Kim, Joohoon

Subjects
*INDIUM tin oxide, *DENDRIMERS, *ELECTROCHEMILUMINESCENCE, *NANOPARTICLES
Abstract

We reported the electrochemically induced deposition of hydroxyl‐terminated poly(amidoamine) dendrimers encapsulating Pt nanoparticles on the surface of indium tin oxide (ITO). The electrochemical deposition led to significantly high surface coverage of Pt nanoparticles encapsulated inside the dendrimers on ITO surfaces, which allowed enhanced (i.e., ca. 212‐fold) electrochemiluminescence of Ru(bpy)32+/tripropylamine on the modified ITOs compared to unmodified ITO. [ABSTRACT FROM AUTHOR]

Published
2021
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106. Photonic Encryption Platform viaDual-Band Vectorial Metaholograms in the Ultraviolet and Visible

Author

Kim, Joohoon, Jeon, Dongmin, Seong, Junhwa, Badloe, Trevon, Jeon, Nara, Kim, Gyeongtae, Kim, Jaekyung, Baek, Sangwon, Lee, Jong-Lam, and Rho, Junsuk

Abstract

Metasurface-driven optical encryption devices have attracted much attention. Here, we propose a dual-band vectorial metahologram in the visible and ultraviolet (UV) regimes for optical encryption. Nine polarization-encoded vectorial holograms are observed under UV laser illumination, while another independent hologram appears under visible laser illumination. The proposed engineered silicon nitride, which is transparent in UV, is employed to demonstrate the UV hologram. Nine holographic images for different polarization states are encoded using a pixelated metasurface. The dual-band metahologram is experimentally implemented by stacking the individual metasurfaces that operate in the UV and visible. The visible hologram can be decrypted to provide the first key, a polarization state, which is used to decode the password hidden in the UV vectorial hologram through the use of an analyzer. Considering the property of UV to be invisible to the naked eye, the multiple polarization channels of the vectorial hologram, and the dual-band decoupling, the demonstrated dual-band vectorial hologram device could be applied in various high-security and anticounterfeiting applications.

Published
2022
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110. Direct electrochemical detection of individual collisions between magnetic microbead/silver nanoparticle conjugates and a magnetized ultramicroelectrode† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5sc02259b Click here for additional data file

Author

Yoo, Jason J., Kim, Joohoon, and Crooks, Richard M.

Subjects
Chemistry, Physics::Optics
Abstract

Magnetic fields and silver nanoparticles increase the frequency and current signature of collisions between individual particles and electrode surfaces., Here, we report on the electrochemical detection of individual collisions between a conjugate consisting of silver nanoparticles (AgNPs) linked to conductive magnetic microbeads (cMμBs) via DNA hybridization and a magnetized electrode. The important result is that the presence of the magnetic field increases the flux of the conjugate to the electrode surface, and this in turn increases the collision frequency and improves the limit of detection (20 aM). In addition, the magnitude of the charge associated with the collisions is greatly enhanced in the presence of the magnetic field. The integration of DNA into the detection protocol potentially provides a means for using electrochemical collisions for applications in biological and chemical sensing.

Published
2015

135. Filling South Korea's Counterinsurgency Gap: Looking Ahead to Potential Problems Facing South Korea in the Aftermath of North Korea's Collapse

Author

ARMY COMMAND AND GENERAL STAFF COLL FORT LEAVENWORTH KS SCHOOL OF ADVANCED MILITARY STUDIES, Kim, Joohoon, ARMY COMMAND AND GENERAL STAFF COLL FORT LEAVENWORTH KS SCHOOL OF ADVANCED MILITARY STUDIES, and Kim, Joohoon

Abstract

South Korea needs to look ahead to problems it may face after North Korea's collapse and prepare to counter any North Korean insurgency that might result from the expansion of conflicts between political power groups. After the death of Kim Jong-il, the political situation in North Korea became increasingly unstable as power transferred to Kim Jong-un. There has been a growing concern about the chaotic aftermath of a regime collapse in the North. The South Korean military has the desire to meet the requirements for an efficient counterinsurgency campaign in order to seize, retain, and exploit the initiative against North Korea's possible insurgents. However, there currently appear to be operational shortfalls in the knowledge, planning, and potential execution of counterinsurgency within the South Korean military. This monograph applies the Capability-Based-Assessment (CBA) process model to distill counterinsurgency requirements for the South Korean military within three of these commodity areas: doctrine, organization, and leadership and education. The CBA model includes a three-phased process: Functional Area Analysis (FAA), Functional Needs Analysis (FNA), and Functional Solutions Analysis (FSA). Doctrinal views highlight the value of operational art and design as a means to balance cost and benefit from the strategic perspectives. Organizational views pursue unity of efforts between armed services and other agencies through a comprehensive governmental counterinsurgency operation. The leadership and educational aspect focuses on the application of mission command related to time sensitivity for adaptive control of insurgents on the Korean Peninsula. Finally, a recommendation made for the successful execution of counterinsurgency operations calls for operational thinking that would enable the South Korean Army to respond quickly and seize the initiative in COIN operations.

Published
2012

136. Current Issues Concerning Korea's Anti-Terrorism Programs

Author

ARMY COMMAND AND GENERAL STAFF COLL FORT LEAVENWORTH KS, Kim, Joohoon, ARMY COMMAND AND GENERAL STAFF COLL FORT LEAVENWORTH KS, and Kim, Joohoon

Abstract

The Korean people are exposed to diverse threats from terrorist organizations at home and abroad despite the government's recently increased efforts to cope with terrorist threats. The 9/11 attacks were an important turning point in terrorism and raised questions concerning the effectiveness of anti-terrorism programs to prevent terrorist attacks. As a result of these attacks, the US and the UK undertook great preventive measures in the field of the legal framework, organization, and leadership. Given that these two countries are now the targets of various terrorist organizations both domestically and abroad, Korea can learn lessons from both countries. Improving anti-terrorism programs could potentially provide Koreans with safety and establish conditions for better stability in the world. Accordingly, the findings of this study include recommendations regarding what's required to improve Korean anti-terrorism programs and efforts., The original document contains color images.

Published
2011

142. Fluorescence Quenching of Dendrimer-Encapsulated CdS Quantum Dots for the Detection of H2O2.

Author

Lim, Hyojung, Kim, Hai Dong, and Kim, Joohoon

Subjects
FLUORESCENCE quenching, DENDRIMERS, LUMINESCENCE quenching, HYDROGEN peroxide, QUANTUM dots, CADMIUM sulfide
Abstract

The article discusses that Fluorescence Quenching of Dendrimer-Encapsulated cadmium sulfide (CdS) Quantum Dots (QDs) can be used for detection of Hydrogen peroxide. It mentions that hydrogen peroxide is present at micromolar range in rainwater, and is a an important byproduct in many chemical reactions. It reflects on the use of dendrimers for synthesis of cadmium sulfide (CdS) Quantum Dots, and discusses the hydrogen peroxide sensitive fluorescence of CdS QDs.

Published
2016
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147. Spontaneous Pt Deposition on Defective Surfaces of In2O3Nanocrystals Confined within Cavities of Hollow Silica Nanoshells: Pt Catalyst-Modified ITO Electrode with Enhanced ECL Performance

Author

Cho, Young Shin, Kim, Soo Min, Ju, Youngwon, Kim, Junghoon, Jeon, Ki-Wan, Cho, Seung Hwan, Kim, Joohoon, and Lee, In Su

Abstract

Although the deposition of metallic domains on a preformed semiconductor nanocrystal provides an effective pathway to access diverse hybrid nanocrystals with synergistic metal/semiconductor heterojunction interface, those reactions that take place on the surface of semiconductor nanoscrystals have not been investigated thoroughly, because of the impediments caused by the surface-capping organic surfactants. By exploiting the interfacial reactions occurring between the solution and nanoparticles confined with the cavities of hollow nanoparticles, we propose a novel nanospace-confined strategy for assessing the innate reactivity of surfaces of inorganic semiconductor nanoparticles. This strategy was adopted to investigate the newly discovered process of spontaneous Pt deposition on In2O3nanocrystals. Through an in-depth examination involving varying key reaction parameters, the Pt deposition process was identified to be templated by the defective In2O3surface via a unique redox process involving the oxygen vacancies in the In2O3lattice, whose density can be controlled by high-temperature annealing. The product of the Pt-deposition reaction inside the hollow silica nanoparticle, bearing In2O3-supported Pt catalysts inside the cavity protected by a porous silica shell, was proved to be an effective nanoreactor system which selectively and sustainably catalyzed the reduction reaction of small-sized aromatic nitro-compounds. Moreover, the surfactant-free and electroless Pt deposition protocol, which was devised based on the surface chemistry of the In2O3nanoparticles, was successfully employed to fabricate Pt-catalyst-modified ITO electrodes with enhanced electrogenerated chemiluminescece (ECL) performance.

Published
2017
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