Publications by authors named "Juhyeon Park"

13 Publications

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Fabrication strategies and surface tuning of hierarchical gold nanostructures for electrochemical detection and removal of toxic pollutants.

J Hazard Mater 2021 Jul 14;420:126648. Epub 2021 Jul 14.

Core-Facility Center for Photochemistry & Nanomaterials, Department of Chemistry (BK21 FOUR), Research Institute of Natural Sciences, Gyeongsang National University, Jinju 52828, South Korea. Electronic address:

The intensive research on the synthesis and characterization of gold (Au) nanostructures has been extensively documented over the last decades. These investigations allow the researchers to understand the relationships between the intrinsic properties of Au nanostructures such as particle size, shape, morphology, and composition to synthesize the Au nano/hybrid nanostructures with novel physicochemical properties. By tuning the properties above, these nanostructures are extensively employed to detect and remove trace amounts of toxic pollutants from the environment. This review attempts to document the achievements and current progress in Au-based nanostructures, general synthetic and fabrication strategies and their utilization in electrochemical sensing and environmental remediation applications. Additionally, the applications of Au nanostructures (e.g., as adsorbents, sensing platforms, catalysts, and electrodes) and advancements in the field of electrochemical sensing of different target analytes (e.g., proteins, nucleic acids, heavy metals, small molecules, and antigens) are summarized. The literature survey concludes the existing methods for the detection of toxic contaminants at various concentration levels. Finally, the existing challenges and future research directions on electrochemical sensing and degradation of toxic contaminants using Au nanostructures are defined.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126648DOI Listing
July 2021

Production of copper nanoparticles exhibiting various morphologies via pulsed laser ablation in different solvents and their catalytic activity for reduction of toxic nitroaromatic compounds.

J Hazard Mater 2021 05 28;409:124412. Epub 2020 Oct 28.

Department of Chemistry (BK21 FOUR) and Research Institute of Natural Science, Gyeongsang National University, Jinju 52828, Republic of Korea. Electronic address:

Comparative experiments were conducted to determine the effects of various solvents (i.e., deionized water, methanol, ethanol, 1-propanol, butanol, ethylene glycol, hexane, and acetonitrile) on the final compositions, morphologies, and catalytic activities of copper-based nanoparticles (NPs). The NPs were effectively synthesized by pulsed laser ablation (PLA) using a copper plate as the target. The obtained copper NPs were characterized utilizing various analytical techniques. It was established that the developed methodology allows for the production of NPs with different morphologies and compositions in a safe and simple manner. When laser ablation of a solid copper plate was performed in acetonitrile, the formation of copper(I) cyanide cubes was observed. On the other hand, in deionized water and methanol, spherical and rod-like particles of copper(I) and copper(II) oxide were detected, respectively. The catalytic activity of the prepared copper NPs in the reduction of aromatic nitro compounds, such as 4-nitrophenol and nitrobenzene, was also evaluated. A high k value was determined for the reduction over the copper(II) oxide NPs produced in methanol. Moreover, particles with graphitic carbon (GC) layers exhibited superior catalytic performance in the reduction of a hydrophobic substance, i.e., nitrobenzene, over the reduction of 4-nitrophenol. The enhanced catalytic activity of this catalyst may be due its unique surface morphology and the synergistic effects between the copper nanostructure and the GC layer. Lastly, a detailed reduction pathway mechanism for the catalytic reduction of 4-nitrophenol and nitrobenzene has been proposed.
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http://dx.doi.org/10.1016/j.jhazmat.2020.124412DOI Listing
May 2021

Versatile Cp*Co(III)(LX) Catalyst System for Selective Intramolecular C-H Amidation Reactions.

J Am Chem Soc 2020 07 1;142(28):12324-12332. Epub 2020 Jul 1.

Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea.

Herein, we report the development of a tailored cobalt catalyst system of Cp*Co(III)(LX) toward intramolecular C-H nitrene insertion of azidoformates to afford cyclic carbamates. The cobalt complexes were easy to prepare and bench-stable, thus offering a convenient reaction protocol. The catalytic reactivity was significantly improved by the electronic tuning of the bidentate LX ligands, and the observed regioselectivity was rationalized by the conformational analysis and DFT calculations of the transition states. The superior performance of the newly developed cobalt catalyst system could be broadly applied to both C(sp)-H and C(sp)-H carbamation reactions under mild conditions.
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http://dx.doi.org/10.1021/jacs.0c04448DOI Listing
July 2020

Crystal structure of ,'-bis-[3-(methyl-sulfan-yl)prop-yl]-1,8:4,5-naphthalene-tetra-carb-oxy-lic di-imide.

Acta Crystallogr E Crystallogr Commun 2019 Jun 31;75(Pt 6):934-938. Epub 2019 May 31.

Department of Chemistry (BK21 plus) and Research Institute of Natural Sciences, Gyeongsang National University, Jinju 52828, Republic of Korea.

The title compound, CHNOS, was synthesized by the reaction of 1,4,5,8-naphthalene-tetra-carb-oxy-lic dianhydride with 3-(methyl-sulfan-yl)propyl-amine. The whole mol-ecule is generated by an inversion operation of the asymmetric unit. This mol-ecule has an form with the terminal methyl-thio-propyl groups above and below the aromatic di-imide plane, where four intra-molecular C-H⋯O and C-H⋯S hydrogen bonds are present and the O⋯H⋯S angle is 100.8°. DFT calculations revealed slight differences between the solid state and gas phase structures. In the crystal, C-H⋯O and C-H⋯S hydrogen bonds link the mol-ecules into chains along the [2 direction. adjacent chains are inter-connected by π-π inter-actions, forming a two-dimensional network parallel to the (001) plane. Each two-dimensional layer is further packed in an sequence along the -axis direction. Hirshfeld surface analysis shows that van der Waals inter-actions make important contributions to the inter-molecular contacts. The most important contacts found in the Hirshfeld surface analysis are H⋯H (44.2%), H⋯O/O⋯H (18.2%), H⋯C/C⋯H (14.4%), and H⋯S/S⋯H (10.2%).
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http://dx.doi.org/10.1107/S2056989019007771DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6658963PMC
June 2019

Defining heatwave thresholds using an inductive machine learning approach.

PLoS One 2018 7;13(11):e0206872. Epub 2018 Nov 7.

School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology, Ulsan, South Korea.

Establishing appropriate heatwave thresholds is important in reducing adverse human health consequences as it enables a more effective heatwave warning system and response plan. This paper defined such thresholds by focusing on the non-linear relationship between heatwave outcomes and meteorological variables as part of an inductive approach. Daily data on emergency department visitors who were diagnosed with heat illnesses and information on 19 meteorological variables were obtained for the years 2011 to 2016 from relevant government agencies. A Multivariate Adaptive Regression Splines (MARS) analysis was performed to explore points (referred to as "knots") where the behaviour of the variables rapidly changed. For all emergency department visitors, two thresholds (a maximum daily temperature ≥ 32.58°C for 2 consecutive days and a heat index ≥ 79.64) were selected based on the dramatic rise of morbidity at these points. Nonetheless, visitors, who included children and outside workers diagnosed in the early summer season, were reported as being sensitive to heatwaves at lower thresholds. The average daytime temperature (from noon to 6 PM) was determined to represent an alternative threshold for heatwaves. The findings have implications for exploring complex heatwave-morbidity relationships and for developing appropriate intervention strategies to prevent and mitigate the health impact of heatwaves.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0206872PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6221332PMC
April 2019

Comparison of the Reactivities and Selectivities of Group 9 [Cp*M ] Catalysts in C-H Functionalization Reactions.

Chem Asian J 2018 May 30;13(9):1089-1102. Epub 2018 Mar 30.

Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.

Pentamethylcyclopentadienyl (Cp*)-based Group 9 metal (Co, Rh, or Ir) catalysts have emerged as powerful tools for C-H functionalization reactions. Whilst a diverse range of organic transformations have been developed by using [Cp*M ] catalysts, they have often exhibited orthogonal reactivities and varied selectivities that depended on the choice of the central metal atom. An understanding of the physicochemical properties of the metals, as well as of their reaction mechanisms, has led to significant expansion of the synthetic scope of C-H functionalization reactions. This Focus Review summarizes and discusses the comparative catalytic reactivities and selectivities of the [Cp*M ] catalysts, with an emphasis on metal-dependent pathway-switching by considering the mechanistic rationale.
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http://dx.doi.org/10.1002/asia.201800204DOI Listing
May 2018

Iterative C-H Functionalization Leading to Multiple Amidations of Anilides.

Angew Chem Int Ed Engl 2017 04 10;56(15):4256-4260. Epub 2017 Mar 10.

Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.

Polyaminobenzenes were synthesized by the ruthenium-catalyzed iterative C-H amidation of anilides using dioxazolones as an amino source. This strategy could be implemented by the sequential activation of C-H bonds of formerly generated compounds by cascade chelation assistance of newly installed amide groups. Computational studies provided a rationale.
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http://dx.doi.org/10.1002/anie.201701138DOI Listing
April 2017

A Direct Access to 7-Aminoindoles via Iridium-Catalyzed Mild C-H Amidation of N-Pivaloylindoles with Organic Azides.

Org Lett 2016 Apr 29;18(8):1892-5. Epub 2016 Mar 29.

Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 305-701, Korea.

Ir(III)-catalyzed regioselective direct C-7 amidation of indoles in reaction with organic azides has been developed. While its efficiency was varied by the choice of N-directing groups, N-pivaloylindoles were most effective in undergoing the desired amidation at room temperature over a broad range of substrates. The reaction was scalable, and deprotection of the chelation group was also facile.
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http://dx.doi.org/10.1021/acs.orglett.6b00662DOI Listing
April 2016

Comparative Catalytic Activity of Group 9 [Cp*M(III)] Complexes: Cobalt-Catalyzed C-H Amidation of Arenes with Dioxazolones as Amidating Reagents.

Angew Chem Int Ed Engl 2015 Nov 25;54(47):14103-7. Epub 2015 Sep 25.

Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701 (Republic of Korea).

A procedure for the [Cp*Co(III)]-catalyzed direct C-H amidation of arenes with dioxazolone has been developed. This reaction proceeds under straightforward and mild conditions with a broad range of substrates, including anilides. A comparative study on the catalytic activity of Group 9 [{Cp*MCl2}2] complexes revealed the unique efficiency of the cobalt catalyst.
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http://dx.doi.org/10.1002/anie.201505820DOI Listing
November 2015

Boron-Catalyzed Silylative Reduction of Nitriles in Accessing Primary Amines and Imines.

J Org Chem 2015 Jul 8;80(14):7281-7. Epub 2015 Jul 8.

†Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 305-701, Korea.

Silylative reduction of nitriles was studied under transition metal-free conditions by using B(C6F5)3 as a catalyst with hydrosilanes as a reductant. Alkyl and (hetero)aryl nitriles were efficiently converted to primary amines or imines under mild conditions. The choice of silanes was found to determine the selectivity: while a full reduction of nitriles was highly facile, the use of sterically bulky silanes allowed for the partial reduction leading to N-silylimines.
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http://dx.doi.org/10.1021/acs.joc.5b00941DOI Listing
July 2015

Chemoselective Silylative Reduction of Conjugated Nitriles under Metal-Free Catalytic Conditions: β-Silyl Amines and Enamines.

Angew Chem Int Ed Engl 2015 Jun 23;54(23):6832-6. Epub 2015 Apr 23.

Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 305-701 (Korea).

The B(C6F5)3-catalyzed silylative reduction of conjugated nitriles has been developed to afford synthetically valuable β-silyl amines. The reaction is chemoselective and proceeds under mild conditions. Mechanistic elucidation indicates that it proceeds by rapid double hydrosilylation of the conjugated nitrile to an enamine intermediate which is subsequently reduced to the β-silyl amine, thus forming a new C(sp(3))-Si bond. Based on this mechanistic understanding, a preparative route to enamines was also established using bulky silanes.
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http://dx.doi.org/10.1002/anie.201502366DOI Listing
June 2015

Synthesis of phosphoramidates: a facile approach based on the C-N bond formation via Ir-catalyzed direct C-H amidation.

Org Lett 2014 Oct 7;16(20):5466-9. Epub 2014 Oct 7.

Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 305-701, Korea.

A new synthetic route to phosphoramidates by intermolecular C-H amidation is presented. Substrates with assorted directing groups were activated by an iridium-based catalyst system and reacted with a number of phosphoryl azides, executing efficient phosphoramidate synthesis via C-N bond formations.
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http://dx.doi.org/10.1021/ol502722jDOI Listing
October 2014
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