Yu Jin Kim

MEDIPOST Biomedical Research Institute, Sŏul, Seoul, South Korea

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Publications (155)453.93 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Antiferroelectric HfxZr1−xO2 (HZO, x=0.1–0.3) films are reported herein as new Si-compatible materials for monolithic devices for pyroelectric energy harvesting, electrocaloric cooling, electrostatic energy storage, and infrared sensing. Hf0.2Zr0.8O2 and Hf0.3Zr0.7O2 films could work as pyroelectric energy harvesters using the Olsen cycle with the harvested energy densities of 11.5 and 5.7 J cm−3 cycle−1, which are ~7.6 and ~3.7 times larger than the largest value ever reported. The electrocaloric effect (ECE) of HZO films was also firstly examined, and the maximum ΔT values of the Hf0.2Zr0.8O2 and Hf0.3Zr0.7O2 films were 13.4 (at 307 K) and 9.8 K (at 448 K), respectively. The wide temperature range for the large ECE of the HZO films was highly promising for the actual cooling cycle with large reversible work values. Moreover, the large capacitance of the HZO films due to the field-induced phase transition between the poled and anti-poled states can be used for electrostatic energy storage and high-charge capacitors. The k2 and Fv values, which are the figures of merit for conventional pyroelectric energy conversion and infrared detection for thermal imaging, of the Hf0.2Zr0.8O2 film were 24.4×10−3 and 32.0×10−2 m2 C−1, respectively, which prove that Hf0.2Zr0.8O2 is also a promising material for these applications.
    Nano Energy 03/2015; 12. · 10.21 Impact Factor
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    ABSTRACT: A novel copolymer, PNDT-BTN, based on naphtho[2,1-b:3,4-b′]dithiophene (NDT) and alkoxy naphthalene, was designed and synthesized by the Pd-catalyzed Stille-coupling method. The copolymer demonstrated good solubility and film-forming ability, along with good thermal stability. PNDT-BTN exhibited a broad absorption (from 300 to 600 nm), centered at 492 nm. HOMO and LUMO energy levels of the polymer were estimated to be −5.56 eV and −3.48 eV, respectively. The polymer solar cell fabricated from the blend of the polymer (donor) and PC71BM (acceptor) exhibited a high power conversion efficiency of 4.29% with a high VOC of 0.98 V. To the best of our knowledge, this is among the highest VOC values of PSCs based on NDT derivatives. This work demonstrates that the replacement of a vinylene group in a conjugated polymer with alkoxy naphthalene moieties is able to significantly lower HOMO energy levels, and therefore, increase the open circuit voltage of solar cells.
    J. Mater. Chem. C. 01/2015;
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    ABSTRACT: The efficacy of tenofovir disoproxil fumarate (TDF) for the treatment of chronic hepatitis B (CHB) patients following prior treatment failure with multiple nucleos(t)ide analogues (NAs) is not well defined, especially in Asian populations. In this study we investigated the efficacy and safety of TDF rescue therapy in CHB patients after multiple NA treatment failure. The study retrospectively analyzed 52 CHB patients who experienced failure with two or more NAs and who were switched to regimens containing TDF. The efficacy and safety assessments included hepatitis B virus (HBV) DNA undetectability, hepatitis B envelop antigen (HBeAg) seroclearance, alanine transaminase (ALT) normalization and changes in serum creatinine and phosphorus levels. The mean HBV DNA level at baseline was 5.4 ± 1.76 log10 IU/mL. At a median duration of 34.5 months of TDF treatment, the cumulative probabilities of achieving complete virological response (CVR) were 25.0%, 51.8%, 74.2%, and 96.7% at 6, 12, 24, and 48 months, respectively. HBeAg seroclearance occurred in seven of 48 patients (14.6%). ALT levels were normalized in 27 of 31 patients (87.1%) with elevated ALT at baseline. Lower levels of HBV DNA at baseline were significantly associated with increased CVR rates (p < 0.001). However, CVR rates did not differ between TDF monotherapy or combination therapy with other NAs, and were not affected by mutations associated with resistance to NAs. No significant adverse events were observed. TDF is an efficient and safe rescue therapy for CHB patients after treatment failure with multiple NAs.
    The Korean Journal of Internal Medicine 01/2015; 30(1):32-41.
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    ABSTRACT: A new push–pull organic semiconductor, DMF-BP-T-MMN, containing a functionalized amine donor and a methylene malononitrile (MMN) acceptor has been designed and synthesized for use in solution-processable small molecule solar cells. This material exhibits superior intramolecular charge transfer from the functionalized amine group to MMN, which produces an electron-rich MMN group that facilitates electron transfer into the active layer constituent phenyl-C71-butyric acid methyl ester in a solar cell. As a result, DMF-BP-T-MMN was found to exhibit excellent p-type semiconductor performance in an optimized organic solar cell: a power conversion efficiency of 3.40% with a high photocurrent density of 8.2 mA cm−2.
    RSC Advances 12/2014; 5(5). · 3.71 Impact Factor
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    ABSTRACT: A new alternating copolymer, CO-BDT–DTBT, designed with the “weak donor/strong acceptor” strategy has been synthesized and characterized. This strategy was tested by constructing a library of polymers employing alkanoyloxy-substituted benzodithiophene (BDT) as the weak donor, and benzothiadiazole (BT) as the strong acceptor. CO-BDT–DTBT has a low HOMO energy level of −5.62 eV, and as a result a BHJ device containing CO-BDT–DTBT blended with PC71BM was found to exhibit a high VOC of 0.88 V. These findings confirm that “weak donor/strong acceptor” polymers are a promising new class of alternating copolymers for polymer solar cell applications.
    Synthetic Metals 12/2014; 198:93–100. · 2.22 Impact Factor
  • Dermatologic Surgery 10/2014; · 1.56 Impact Factor
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    ABSTRACT: Three types of amorphous thienothiophene (TT)-benzothiadiazole (BT) based copolymers (PFTTBT) were synthesized by incorporating alkyl-substituted fluorene moieties as a third component in the polymer backbone. Their optical, electrochemical, morphological and photovoltaic properties were examined by a comparison with those of a crystalline TT-BT derivative (PTTBT14). PTTBT14 was reported to have a high hole mobility (0.26 cm2/Vs) due to the pronounced interchain ordering but poor photovoltaic power conversion efficiency (PCE) of 2.4 ~ 2.6% was reported due to excessively strong self-interactions with poor miscibility with fullerene structures. By incorporating fluorene units, the UV-Vis spectra showed an increased bandgap (~1.9 eV) with the disappearance of the packing-originated shoulder peak, and the valence band decreased compared to crystalline PTTBT14. The amorphous PFTTBT polymers showed substantially improved photovoltaic properties compared to PTTBT14, even though they showed poor hole mobility (~10-6 cm2/Vs) and fill factor. The optimal devices were achieved by blending with excess PC71BM (polymer:PC71BM = 1:4 by weight), showing little improvement in the thermal and additive treatments. Under simulated solar illumination of AM 1.5G, the best PCE of 6.6% was achieved for a PFehTTBT:PC71BM device with an open-circuit voltage of 0.92 V, a short-circuit current of 15.1 mA/cm2 and a fill factor of 0.48. These results suggest that it is useful to disrupt partially the interchain organizations of excessively crystalline polymers, enabling fine-control of intermolecular ordering and the morphological properties (i.e. miscibility with fullerene derivatives, etc.) to utilize the advantages of both crystalline and amorphous materials for further improving PCE of polymer solar cells.
    ACS Applied Materials & Interfaces 10/2014; · 5.90 Impact Factor
  • Dermatologic Surgery 10/2014; · 1.56 Impact Factor
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    ABSTRACT: With increasing annealing temperature (Tanneal), the magnitude of the electric fields for the antiferroelectric-to-ferro-electric (EAF) and ferroelectric-to-antiferroelectric (EFA) transition of a 9.2 nm thick Hf0.3Zr0.7O2 film decreased. The energy storage densities of the Hf0.3Zr0.7O2 films crystallized at 400 °C, 500 °C, and 600 °C were as large as 42.2 J/cm3, 40.4 J/cm3, and 28.3 J/cm3, respectively, at the electric field of 4.35 MV/cm. The maximum dielectric constant of the Hf0.3Zr0.7O2 film crystallized at 600 °C was the largest (∼46) as it had the smallest EAF and EFA, whereas the leakage current density of the film crystallized at 400 °C was the smallest. The 400 °C of Tanneal was the optimum condition for energy storage application. (© 2014 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)
    physica status solidi (RRL) - Rapid Research Letters 10/2014; 9999(10). · 2.39 Impact Factor
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    ABSTRACT: Organic bulk heterojunction photovoltaic devices based on a series of three naphtho[2,1-b:3,4-b′]dithiophene (NDT) derivatives blended with phenyl-C71-butyric acid methyl ester were studied. These three derivatives, which have NDT units with various thiophene-chain lengths, were employed as the donor polymers. The influence of their molecular structures on the correlation between their solar-cell performances and their degree of crystallization was assessed. The grazing-incidence angle X-ray diffraction and atomic force microscopy results showed that the three derivatives exhibit three distinct nanoscale morphologies. We correlated these morphologies with the device physics by determining the J–V characteristics and the hole and electron mobilities of the devices. On the basis of our results, we propose new rules for the design of future generations of NDT-based polymers for use in bulk heterojunction solar cells.
    ChemPhysChem 08/2014; · 3.36 Impact Factor
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    ABSTRACT: Hf0.5Zr0.5O2 films could show excellent ferroelectricity with a large remanent polarization (Pr, > 16 μC/cm2) on TiN and Ir electrodes, but their Pr decreased with the increasing thickness and monoclinic phase portion. The critical thickness for the degradation of the ferroelectricity of Hf0.5Zr0.5O2 films was smaller on the Ir electrode than the TiN electrode. This was due to the formation of larger grains, favorable for the formation of the monoclinic phase, on the Ir electrode than on the TiN electrode. The oxygen supply from IrOx exaggerated the initial growth on the Ir electrode and formed the larger grains.
    Applied Physics Letters 08/2014; 105(7):072902-072902-5. · 3.52 Impact Factor
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    ABSTRACT: We designed and synthesized a dithienobenzodithiophene (DTBDT)-based molecule with a planar molecular geometry, DTBDT-TTPD, for the fabrication of solution-processable organic solar cells (OSCs). DTBDT-TTPD exhibited both a low optical band gap of 1.88 eV and a low-lying highest occupied molecular orbital (HOMO) energy level of –5.61 eV, indicating that DTBDT-TTPD is a promising electron donor for use in OSCs. OSCs prepared with DTBDT-TTPD as the electron donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the electron acceptor were fabricated. An optimized power conversion efficiency of 4.98% with a high short circuit current of 10.6 mA/cm2 was achieved after finely tuning the morphology through an annealing step. These results indicate that DTBDT-TTPD is an effective compound for producing very promising characteristics in small molecule solar cell devices.
    J. Mater. Chem. A. 08/2014;
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    ABSTRACT: Phlebectasia, also known as venous aneurysm, is a rare condition, especially in the upper part of the body. The authors present an unusual case of aneurysm-like dilatation of the periorbital vein with a previous blunt trauma history, along with its corresponding venous anatomy. In addition, the proper diagnostic process is described and the need for prompt removal of periorbital phlebectasia emphasized.
    Journal of Plastic Reconstructive & Aesthetic Surgery 08/2014; · 1.47 Impact Factor
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    ABSTRACT: We report on tuning of the interfacial properties of a highly sensitive organic photodiode by introducing a buffer layer between the anode and the semiconductor layer. The effects of different buffer layers consisting of a self-assembled monolayer (SAM), PEDOT:PSS, and pentacene on the morphology and crystallinity of the upper-deposited bulk heterojunction semiconductor layer are carefully analyzed combined with electrical analysis. The active layer is controlled to be nearly homogeneous and to have low crystallinity by using a SAM or PEDOT:PSS buffer layers, whereas a highly crystalline morphology is realized by using the pentacene buffer layer. When exposed to light pulses, the external quantum efficiency and thus the photocurrent are slightly higher for the PEDOT:PSS-based photodiode; however the dark current is the lowest for the pentacene-based photodiode. We discuss the origin of the high sensitivity (a detectivity of 1.3 × 10(12) Jones and a linear dynamic range of 95 dB) of the pentacene-based photodiode, particularly in terms of the morphology-driven low dark current.
    Physical Chemistry Chemical Physics 07/2014; · 4.20 Impact Factor
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    ABSTRACT: A series of small molecules that contained identical π-spacers (ethyne), a central diketopyrrolopyrrole (DPP) unit, and different aromatic electron-donating end-groups were synthesized and used in organic solar cells (OSCs) to study the effect of electron-donating groups on the device performance. The three compounds, DPP-A-Ph, DPP-A-Na, and DPP-A-An, possessed intense absorption bands that covered a wide range, from 350 to 750 nm, and relatively low HOMO energy levels, from -5.50 to -5.55 eV. DPP-A-An, which contained anthracene end-groups, demonstrated a stronger absorbance and a higher hole mobility than DPP-A-Ph, which contained phenyl groups, and DPP-A-Na, which contained naphthalene units. The power-conversion efficiencies (PCEs) of OSCs based on organic:PC71 BM blends (1:1, w/w) with a processed DIO additive were 3.93 % for DPP-A-An, 3.02 % for DPP-Na, and 2.26 % for DPP-A-Ph. These findings suggest that a DPP core that is functionalized with electron-donating capping groups constitutes a promising new class of solution-processable small molecules for OSC applications.
    Chemistry - An Asian Journal 07/2014; 9(9). · 4.57 Impact Factor
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    ABSTRACT: Combined pulmonary fibrosis and emphysema (CPFE) have different pulmonary function tests (PFTs) and outcomes than idiopathic pulmonary fibrosis (IPF). The intention of this study was to identify unknown differences between CPFE and IPF by a retrospective comparison of clinical data including baseline and annual changes in pulmonary function, comorbidities, laboratory findings, clinical characteristics and cause of hospitalization.
    Tuberculosis and Respiratory Diseases 07/2014; 77(1):18-23.
  • Organic Electronics 07/2014; · 3.68 Impact Factor
  • Advanced Energy Materials 07/2014; · 14.39 Impact Factor
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    ABSTRACT: Vancomycin-resistant enterococci (VRE) are one of the leading causes of nosocomial infection at intensive care unit (ICU). Rapid and sensitive detection of VRE infection is in high demand for timely and suitable antibiotic treatment. Here, we optimized a distinct DNA-based diagnostic technique, loop-mediated isothermal amplification (LAMP) for rapid detection of the presence of vanA gene, a critical component of the gene cluster required for vancomycin resistance. Amplification efficiency was optimal at 62 ˚C and with 2mM MgSO4. The detection limit of the DNA template was 80pg and LAMP amplicons were detected within 40min; thereby suggesting a potential applicability of LAMP as a sensitive and urgent diagnostic method. Furthermore, positive LAMP reaction was directly detected with the naked-eye by monitoring the formation of a white precipitate or the color change induced by hydroxyl naphtol blue (HNB) dye. Finally, 56 clinical isolates were successfully tested for the presence of vanA gene by LAMP, which was determined to be more sensitive than PCR. Together, our results clearly demonstrate the usefulness of LAMP for the diagnosis of VRE infection.
    Journal of Microbiological Methods 06/2014; · 2.10 Impact Factor
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    ABSTRACT: A solution-processed alkylselenophene-substituted benzodithiophene (BDT) small molecule, namely, 3,3′-((4,8-bis(5-(2-ethylhexyl)selenophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)bis(thiophene-5,2-diyl))bis(5-octyl-1-(thiophen-2-yl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione) (BDTSe-TTPD), with broad absorption and suitable energy levels was synthesized. The widely used solvents o-dichlorobenzene (o-DCB), chlorobenzene (CB) or chloroform (CF) were used as the spin-coating solvent, to fabricate efficient photovoltaic devices with BDTSe-TTPD as the donor material and PC71BM as the acceptor. Devices made from a CF solution demonstrated better performance in terms of short-circuit current, fill factor and power conversion efficiency, as compared to the devices made from the o-DCB and CB solutions. Finally, by optimizing the thickness of the active layer, a power conversion efficiency of 4.37% was achieved on devices with an area of 0.09 cm2, under 100 mW cm−2 of simulated AM 1.5 irradiation.
    J. Mater. Chem. C. 06/2014; 2(25).

Publication Stats

454 Citations
453.93 Total Impact Points

Institutions

  • 2014
    • MEDIPOST Biomedical Research Institute
      Sŏul, Seoul, South Korea
  • 2013–2014
    • Pohang University of Science and Technology
      • Department of Chemical Engineering
      Geijitsu, North Gyeongsang, South Korea
    • Hallym University Medical Center
      • Department of Pathology
      Seoul, Seoul, South Korea
  • 2012–2014
    • Seoul National University Bundang Hospital
      • Department of Emergency Medicine
      Sŏul, Seoul, South Korea
  • 2011–2014
    • Seoul National University
      • Department of Materials Science and Engineering
      Sŏul, Seoul, South Korea
  • 2007–2014
    • Yonsei University Hospital
      • Department of Internal Medicine
      Sŏul, Seoul, South Korea
  • 2012–2013
    • Kongju National University
      Gongju, South Chungcheong, South Korea
  • 2011–2013
    • Myongji Hospital
      Kōyō, Gyeonggi Province, South Korea
  • 2009–2013
    • Sungkyunkwan University
      • • Department of Pathology
      • • Department of Pediatrics
      Sŏul, Seoul, South Korea
    • Chungnam National University Hospital
      Sŏul, Seoul, South Korea
  • 2011–2012
    • Korea Research Institute of Bioscience and Biotechnology KRIBB
      • • Functional Metabolite Research Center
      • • Research Center of Integrative Cellunomics
      Anzan, Gyeonggi Province, South Korea
  • 2009–2012
    • Chungbuk National University
      • Department of Food Science and Technology
      Chinch'ŏn, North Chungcheong, South Korea
  • 2008–2012
    • Gachon University
      • Department of Internal Medicine
      Sŏngnam, Gyeonggi Province, South Korea
    • Chungnam National University
      Daiden, Daejeon, South Korea
    • Hallym University
      • College of Medicine
      Seoul, Seoul, South Korea
  • 2007–2008
    • Hanyang University
      • Department of Biomedical Engineering
      Sŏul, Seoul, South Korea
  • 2003–2007
    • Inha University
      • • College of Medicine
      • • Department of Plastic Surgery
      Seoul, Seoul, South Korea
  • 2001–2004
    • Inha University Hospital
      Sinhyeon, South Gyeongsang, South Korea