Youngeun Choi

Publications (3)5.27 Total impact

• Article: Silk fibroin particles as templates for mineralization of calcium-deficient hydroxyapatite.

  Youngeun Choi, Se Youn Cho, Doo Jin Park, Hyun Ho Park, Semi Heo, Hyoung-Joon Jin
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  ABSTRACT: Silk fibroin particles prepared by phase separation with polyethylene oxide were coated with calcium-deficient hydroxyapatite (CDHA) crystals under various pH conditions. For different pH values, the growth and the morphology of CDHA crystals on the surface of silk fibroin particles were investigated in detail by zeta potential analysis, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction techniques. Negative charges formed by deprotonation of the functional groups on the surface of silk fibroin particles at high pH lead to an increase of binding affinity between the calcium ions of the CDHA crystals and the functional groups of the silk fibroin particles. Consequently, the generation of many CDHA crystals was promoted to deposit on the surface of silk fibroin particles at a high pH value. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.
  Journal of Biomedical Materials Research Part B Applied Biomaterials 08/2012; 100(8):2029-34. · 2.15 Impact Factor
• Article: Bacterial cellulose nanocrystals-embedded silk nanofibers.

  Doo Jin Park, Youngeun Choi, Semi Heo, Se Youn Cho, Hyung-Joon Jin
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  ABSTRACT: Nanofibrous Bacterial cellulose nanocrystals (BCNs)-embedded silk fibroin were successfully fabricated using electrospinning. The morphology, structure and mechanical properties of the silk fibroin nanofibers were investigated at various BCNs concentrations from 0 to 7 wt%. SEM, TEM and XRD analyses were conducted to confirm the incorporation of the BCNs in the electrospun silk fibroin nanofibers. The average diameter of the silk fibroin/BCNs nanofibers increased from 230 to 430 nm according to the increasing of the BCNs ratio due to the rising solute content. The FT-IR spectra confirmed the conformational transition of the silk fibroin, from a random coil to a beta-sheet structure, which shows the enhanced mechanical properties of silk fibroin based nanofibers even with small amounts of the BCNs. Moreover, it was observed that the Young's modulus of the silk fibroin/BCNs nanofibers unexpectedly increased with the formation of BCNs with a percolation structure at a concentration between 3 and 5 wt%.
  Journal of Nanoscience and Nanotechnology 07/2012; 12(7):6139-44. · 1.56 Impact Factor
• Article: Improved thermal properties of graphene oxide-incorporated poly(methyl methacrylate) microspheres.

  Semi Heo, Se Youn Cho, Do Hyeong Kim, Youngeun Choi, Hyun Ho Park, Hyoung-Joon Jin
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  ABSTRACT: Graphene, a single layer of carbon atoms in a two-dimensional lattice, has attracted considerable attention owing to its unique physical, chemical and mechanical properties. In particular, because of its excellent thermal properties such as high thermal conductivity and good thermal stability, graphene has been regarded as a one of the promising candidates for the reinforcing fillers on the polymer composites field. In this study, we prepared the poly(methyl methacrylate) (PMMA)/graphene oxide (GO) nanocomposite by a simple solution mixing process, and examined the thermal reinforcing effects of GO on a PMMA matrix. Using thermogravimetric analysis, differential scanning calorimeter, and thermal conductivity meter, we investigated the effects of GO on the thermal properties of PMMA/GO nanocomposites. With 3 wt% of GO loading, the glass transition temperature (Tg) of the PMMA/GO nanocomposite were increased by more than 7 degrees C and the thermal conductivity of which also improved 1.8 times compared to pure PMMA.
  Journal of Nanoscience and Nanotechnology 07/2012; 12(7):5990-4. · 1.56 Impact Factor