Publications by authors named "Chanmin Lee"

6 Publications

  • Page 1 of 1

Morphological Analysis of PSMA/PEI Core-Shell Nanoparticles Synthesized by Soap-Free Emulsion Polymerization.

Nanomaterials (Basel) 2021 Jul 29;11(8). Epub 2021 Jul 29.

Research Institute of Sustainable Manufacturing System, Intelligent Sustainable Materials R&D Group, Korea Institute of Industrial Technology, 89 Yangdaegiro-gil, Ipjang-myeon, Seobuk-gu, Cheonan-si 31056, Korea.

Emulsion polymerization presents the disadvantage that the physical properties of polymer particles are altered by surfactant adsorption. Therefore, in the soap-free emulsion polymerization method, a hydrophilic initiator is utilized while inducing repulsion among particles on the polymer particle surface, resulting in stable polymer particle production. In this study, we developed a methodology wherein spherical and uniform poly(styrene--maleic anhydride) (PSMA)/polyethyleneimine (PEI) core-shell nanoparticles were prepared. Further, their morphology was analyzed. During PSMA polymerization, the addition of up to 30% maleic anhydride (MA) resulted in stable polymerization. In PSMA/PEI nanoparticle fabrication, the number of reactants increased with increased initial monomer feed amounts; consequently, the particle size increased, and as the complete monomer consumption time increased, the particle distribution widened. The styrene (St) copolymer acted as a stabilizer, reducing particle size and narrowing particle distribution. Furthermore, the monomers were more rapidly consumed at high initiator concentrations, irrespective of the initiator used, resulting in increased particle stability and narrowed particle distribution. The shell thickness and particle size were PEI feed ratio dependent, with 0.08 being the optimal PEI-to-MA ratio. The fabricated nanoparticles possess immense potential for application in environmental science and in chemical and health care industries.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/nano11081958DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8402240PMC
July 2021

Colorimetric Visualization Using Polymeric Core-Shell Nanoparticles: Enhanced Sensitivity for Formaldehyde Gas Sensors.

Polymers (Basel) 2020 Apr 25;12(5). Epub 2020 Apr 25.

Research Institute of Sustainable Manufacturing System, Intelligent Sustainable Materials R&D Group, Korea Institute of Industrial Technology, 89 Yangdaegiro-gil, Ipjang-myeon, Seobuk-gu, Cheonan-si, Chungcheongnam-do 31056, Korea.

Although equipment-based gas sensor systems (e.g., high-performance liquid chromatography) have been widely applied for formaldehyde gas detection, pre-treatment and expensive instrumentation are required. To overcome these disadvantages, we developed a colorimetric sensor based on polymer-based core-shell nanoparticles (PCSNPs), which are inexpensive, stable, and exhibit enhanced selectivity. Spherical and uniform poly(styrene-co-maleic anhydride) (PSMA)/polyethyleneimine (PEI) core-shell nanoparticles were prepared and then impregnated with Methyl Red (MR), Bromocresol Purple (BCP), or 4-nitrophenol (4-NP) to construct colorimetric sensors for formaldehyde gas. The intrinsic properties of these dyes were maintained when introduced into the PCSNPs. In the presence of formaldehyde, the MR, BCP, and 4-NP colorimetric sensors changed to yellow, red, and gray, respectively. The colorimetric response was maximized at a PEI/PSMA ratio of four, likely owing to the high content of amine groups. Effective formaldehyde gas detection was achieved at a relative humidity of 30% using the MR colorimetric sensor, which exhibited a large color change (92%) in 1 min. Advantageously, this stable sensor allowed sensitive and rapid naked-eye detection of low formaldehyde concentrations (0.5 ppm). Hence, this approach is promising for real-time formaldehyde gas visualization and can also be adapted to other colorimetric gas sensor systems to improve sensitivity and simplicity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/polym12050998DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7285312PMC
April 2020

Rapid development of dual porous poly(lactic acid) foam using fused deposition modeling (FDM) 3D printing for medical scaffold application.

Mater Sci Eng C Mater Biol Appl 2020 May 27;110:110693. Epub 2020 Jan 27.

Korea Institute of Industrial Technology (KITECH), 89, Yangdaegiro-gil, Ipjang-myeon, Seobuk-gu, Cheonan-si, Chungcheongnam-do 31056, Republic of Korea. Electronic address:

The poor melt property and brittleness of poly(lactic acid) (PLA) cause difficulties in extrusion foaming and decrease product performance in industrial and research fields. In this paper, the rheological properties of PLA resin were improved using an epoxy chain extension reaction, which led to the improvement of pore properties such as morphology and foamability. Reinforced PLA was extruded in a porous filament, and a scaffold was fabricated with design freedom, one-step processing, and dual porosity by extrusion foaming and 3D printing. In addition, in vitro cell culture tests were performed to verify the cell biology assessment and confirm the potential of the scaffold for application as medical scaffolds.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.msec.2020.110693DOI Listing
May 2020

Changes in the Physical Properties of Calcium Alginate Gel Beads Under a Wide Range of Gelation Temperature Conditions.

Foods 2020 Feb 12;9(2). Epub 2020 Feb 12.

Department of Food Science and Technology, Institute of Seafood Science, Pukyong National University, Busan 48513, Korea.

Until now, most studies using calcium alginate gel (CAG) have been conducted primarily at room temperature (20 °C) without considering gelation temperature. Moreover, the effects of gelation temperature on the physical properties of CAG beads have not been studied in detail. We aimed to study the effect of gelation temperature on the physical properties (diameter, sphericity, and rupture strength) of CAG beads. Response surface methodology was used in this study. The independent variables were sodium alginate concentration (X, 1.2%-3.6%, /), calcium lactate concentration (X, 0.5%-4.5%, /), gelation temperature (X, 5-85 °C), and gelation time (X, 6-30 min). Diameter (Y, mm), sphericity (Y, %), and rupture strength (Y, kPa) were selected as the dependent variables. A decrease in gelation temperature increased the diameter, sphericity and rupture strength of the CAG beads. Additionally, the CAG beads prepared at 5 °C exhibited the highest rupture strength (3976 kPa), lowest calcium content (1.670 mg/g wet), and a regular internal structure. These results indicate that decreasing the gelation temperature slows the calcium diffusion rate in CAG beads, yielding a more regular internal structure and increasing the rupture strength of the beads.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/foods9020180DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7073945PMC
February 2020

Transparent Bendable Secondary Zinc-Air Batteries by Controlled Void Ionic Separators.

Sci Rep 2019 Feb 28;9(1):3175. Epub 2019 Feb 28.

Department of Chemical and Biomolecular Engineering, Yonsei University, 262 Seongsanno, Seodaemun-gu, Seoul, 120-749, South Korea.

First ever transparent bendable secondary zinc-air batteries were fabricated. Transparent stainless-steel mesh was utilized as the current collector for the electrodes due to its reliable mechanical stability and electrical conductivity. After which separate methods were used to apply the active redox species. For the preparation of the anode, zinc was loaded by an electroplating process to the mesh. For the cathode, catalyst ink solution was spray coated with an airbrush for desired dimensions. An alkaline gel electrolyte layer was used for the electrolyte. Microscale domain control of the materials becomes a crucial factor for fabricating transparent batteries. As for the presented cell, anionic exchange polymer layer has been uniquely incorporated on to the cathode mesh as the separator which becomes a key procedure in the fabrication process for obtaining the desired optical properties of the battery. The ionic resin is applied in a fashion where controlled voids exist between the openings of the grid which facilitates light passage while guaranteeing electrical insulation between the electrodes. Further analysis correlates the electrode dimensions to the transparency of the system. Recorded average light transmittance is 48.8% in the visible light region and exhibited a maximum power density of 9.77 mW/cm. The produced battery shows both transparent and flexible properties while maintaining a stable discharge/charge operation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-019-38552-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6395654PMC
February 2019

Oxide-Carbon Nanofibrous Composite Support for a Highly Active and Stable Polymer Electrolyte Membrane Fuel-Cell Catalyst.

ACS Nano 2018 Jul 5;12(7):6819-6829. Epub 2018 Jul 5.

Department of Chemical and Biomolecular Engineering , Yonsei University , Yonsei-ro 50 , Seodaemun-gu, Seoul 03722 , Republic of Korea.

Well-designed electronic configurations and structural properties of electrocatalyst alter the activity, stability, and mass transport for enhanced catalytic reactions. We introduce a nanofibrous oxide-carbon composite by an in situ method of carbon nanofiber (CNF) growth by highly dispersed Ni nanoparticles that are exsoluted from a NiTiO surface. The nanofibrous feature has a 3D web structure with improved mass-transfer properties at the electrode. In addition, the design of the CNF/TiO support allows for complex properties for excellent stability and activity from the TiO oxide support and high electric conductivity through the connected CNF, respectively. Developed CNF/TiO-Pt nanofibrous catalyst displays exemplary oxygen-reduction reaction (ORR) activity with significant improvement of the electrochemical surface area. Moreover, exceptional resistance to carbon corrosion and Pt dissolution is proven by durability-test protocols based on the Department of Energy. These results are well-reflected to the single-cell tests with even-better performance at the kinetic zone compared to the commercial Pt/C under different operation conditions. CNF/TiO-Pt displays an enhanced active state due to the strong synergetic interactions, which decrease the Pt d-band vacancy by electron transfer from the oxide-carbon support. A distinct reaction mechanism is also proposed and eventually demonstrates a promising example of an ORR electrocatalyst design.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsnano.8b02040DOI Listing
July 2018
-->