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Kim, Min Su,Roy, Shrawan,Lee, Jubok,Kim, Byung Gu,Kim, Hyun,Park, Ji-Hoon,Yun, Seok Joon,Han, Gang Hee,Leem, Jae-Young,Kim, Jeongyong American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.42
<P>Monolayer transition-metal dichalcogenides (1L-TMDs) are atomically thin direct band gap semiconductors, from which the emission of light is determined by optical transitions of exciton complexes such as neutral excitons and trions. While the quantum yields of 1L-TMDs are quite low, the ability to control the populations of exciton complexes in 1L-TMDs through various doping processes is an interesting advantage, and provides ample possibilities for engineering the optical properties of these semiconductor monolayers. Here we demonstrate a simple method of controlling the populations of excitons and trions to enhance the light emission of 1L-TMDs by having them form heterostructures with ZnO thin films (TFs). 1Ls of MoS2 or MoSe2 showed up to 17-fold increases in photoluminescence (PL) when they were placed on similar to 50 nm thick ZnO TFs. This enhancement of the PL was due to charge exchanges occurring through the 1L-TMD/ZnO interface. The PL enhancements and changes in the PL spectra of the 1L-TMDs were greater when the 1L-TMD/ZnO heterostructures were subjected to 355 nm wavelength laser excitation than when they were excited with a 514 nm wavelength laser, which we attributed to the onset of energy transfer by photoexcited excitons and/or the additional p-doping by photoexcited holes in ZnO. The p-doping phenomenon and the enhanced light emission of 1L-TMD/ZnO heterostructures were unambiguously visualized in spatially resolved PL and Raman spectral maps. Our approach using the 1L-TMD/ZnO TF heterostructure suggests that a rich variety of options for engineering the optical properties of 1L-TMDs may be made available by carrying out simple and intuitive manipulations of exciton complexes, and these endeavors may yield practical applications for 1L-TMDs in nanophotonic devices.</P>
Complex Nanoparticle of Light-Emitting MEH-PPV with Au: Enhanced Luminescence
Kim, Mi Suk,Park, Dong Hyuk,Cho, Eun Hei,Kim, Kyoung Ho,Park, Q-Han,Song, Hugeun,Kim, Dae-Chul,Kim, Jeongyong,Joo, Jinsoo American Chemical Society 2009 ACS NANO Vol.3 No.6
<P>Complex nanoparticles (NPs) of poly(2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene) (MEH-PPV) NP adsorbed with Au NPs (MEH-PPV/Au NPs) were fabricated through a reprecipitation method. The formation of MEH-PPV/Au NP complexes was confirmed through high-resolution transmission electron microscopy and Fourier transform infrared experiments. The laser confocal microscope photoluminescence (PL) efficiency of the complex MEH-PPV/Au single NP dramatically increased compared with that of the MEH-PPV single NP without Au NPs, which was directly confirmed through color charge-coupled device images. The enhanced PL efficiency of the MEH-PPV/Au NP complex might have originated from the energy transfer effect in a surface plasmon resonance coupling between a MEH-PPV NP and Au NPs. The strong local field enhancement due to nanogaps between Au NPs in the background of a light-emitting MEH-PPV NP might be another origin of the PL enhancement of the NP complex, as supported by finite difference time domain calculations. We also observed the blue shift of the PL peaks of the single MEH-PPV and MEH-PPV/Au NP, compared with the solution PL peaks of those NPs.</P>
Efficacy of reduced-size short tandem repeat PCR analysis for degraded DNA samples
Jeongyong Kim,Hyojeong Kim,Youn‑Hyoung Nam,Ja Hyun Lee,Hyo Sook Kim,Eungsoo Kim 한국유전학회 2021 Genes & Genomics Vol.43 No.7
Background Short tandem repeats (STR) typing is an essential analysis method for human identifcation in forensic feld. When DNAs obtained from the feld as evidences are severely degraded or in too small amounts, STR analysis often shows allele drop-out. Objective To improve STR analysis for degraded DNA or trace DNA, reduced-size STR (rSTR) polymerase chain reaction (PCR) system was devised by selecting relatively large-size STR loci. Methods The rSTR PCR system consisted of 8 loci (amelogenin, SE33, CSF1PO, D7S820, D13S317, D2S1338, TPOX, and FGA). The size of PCR product was reduced by designing new primers in the fanking region. The efciency of this system was verifed against existing kits through concordance study, sensitivity study, efciency study, and casework sample study. Results The size of PCR product in the rSTR PCR system was reduced to be less than 322 bp. The amplicon of each locus was reduced by about 100 bp on average. Results of this rSTR PCR system were confrmed using 146 Korean samples and other commercial kits. The rSTR PCR system was capable of analyzing DNA samples with a minimum amount of DNA of 16 pg and a degradation index of 4.215. Conclusion The rSTR PCR system was more efective than other PCR kits for obtaining genetic profles from a small amount of DNA or degraded DNA. The combination of this new system and other commercial kits is more efective than existing systems. This combination is expected to be helpful for the identifcation of unidentifed bodies and skeletal samples.
Hyojeong Kim,Yoonjung Cho,Jeongyong Kim,Ja Hyun Lee,Hyo Sook Kim,Eungsoo Kim 대한의생명과학회 2020 Biomedical Science Letters Vol.26 No.4
Since its introduction in the forensic field, quantitative PCR (qPCR) has played an essential role in DNA analysis. Quality of DNA should be evaluated before short tandem repeat (STR) profiling to obtain reliable results and reduce unnecessary costs. To this end, various human DNA quantification kits have been developed. Among these kits, the PowerQunat<SUP>®</SUP> System was designed not only to determine the total amount of human DNA and human male DNA from a forensic evidence item, but also to offer data about degradation of DNA samples. However, a crucial limitation of the PowerQunat<SUP>®</SUP> System is its high cost. Therefore, to minimize the cost of DNA quantification, we evaluated kit performance using a reduced volume of reagents (1/2-volume) using DNA samples of varying types and concentrations. Our results demonstrated that the low-volume method has almost comparable performance to the manufacturer"s method for human DNA quantification, human male DNA quantification, and DNA degradation index. Furthermore, using a reduced volume of regents, it is possible to run 2 times more reactions per kit. We expect the proposed low-volume method to cut costs in half for laboratories dealing with large numbers of DNA samples.
Magnetic field-dependent ordinary Hall effect and thermopower of VO2 thin films
Jeongyong Choi,Bong-Jun Kim,Giwan Seo,Hyun-Tak Kim,Sunglae Cho,Yong Wook Lee 한국물리학회 2016 Current Applied Physics Vol.16 No.3
We investigated the magnetic field-dependent Hall effect and the thermopower in VO2 thin films at various temperatures by using physical property measurement systems. From the ordinary Hall effect measured at 300e370 K, it was found that the Hall voltage decreased with increasing magnetic field, attributed to the weakening of strong electron correlation, and dominant charge carriers were changed implying the existence of mixed phases near the critical temperature of VO2. A gradual thermopower increase and its sign inversion with increasing temperature gradient were observed at 320e350 K, which seems to stem from percolation processes during the phase transition in VO2.
Kim, Jeongyong,Song, Hugeun,Park, Inho,Carlisle, Christine R.,Bonin, Keith,Guthold, Martin Wiley Subscription Services, Inc., A Wiley Company 2011 Microscopy research and technique Vol.74 No.3
<P><B>Abstract</B></P><P>Deep ultraviolet (DUV) microscopy is a fluorescence microscopy technique to image unlabeled proteins via the native fluorescence of some of their amino acids. We constructed a DUV fluorescence microscope, capable of 280 nm wavelength excitation by modifying an inverted optical microscope. Moreover, we integrated a nanomanipulator‐controlled micropipette into this instrument for precise delivery of picoliter amounts of fluid to selected regions of the sample. In proof‐of‐principle experiments, we used this instrument to study, in situ, the effect of a denaturing agent on the autofluorescence intensity of single, unlabeled, electrospun fibrinogen nanofibers. Autofluorescence emission from the nanofibers was excited at 280 nm and detected at ∼350 nm. A denaturant solution was discretely applied to small, select sections of the nanofibers and a clear local reduction in autofluorescence intensity was observed. This reduction is attributed to the dissolution of the fibers and the unfolding of proteins in the fibers. Microsc. Res. Tech., 2010. © 2010 Wiley‐Liss, Inc.</P>
Electrically driven lasing in light-emitting devices composed of n-ZnO and p-Si nanowires
Kim, Kwangeun,Moon, Taeho,Kim, Jeongyong,Kim, Sangsig IOP Pub 2011 Nanotechnology Vol.22 No.24
<P>Electrically driven lasing was demonstrated in light-emitting devices composed of n-ZnO and p-Si nanowires (NWs). The ZnO NWs were synthesized by thermal chemical vapor deposition and the Si NWs were formed by crystallographic wet etching of a Si wafer. The p–n heterojunction devices were constructed using the NWs by the direct transfer and dielectrophoresis methods. At an excitation current of 2 µA, the electroluminescence spectrum showed lasing behavior, and this phenomenon was explained by the ZnO-nanostructure-related cavity property. </P>