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하승규,송진동,김수연,Samir Bounouar,Le Si Dang,김종수 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.51
Low-density (∼3.5 × 10^9 cm^(−2)) GaAs quantum dots intended for single photon source application were grown between Al^(0.3)Ga^(0.7)As barriers by using droplet epitaxy. This material system has an emitting wavelength compatible with cost-effective Si-based detectors. Excitation-power-dependent and time-resolved micro-photoluminescence measurements were performed at low temperature (7 K) to characterize the optical properties of the excitonic states, which are attributed to good quantum confinement in the GaAs quantum dots.
Facile synthesis of SnO2eZnO coreeshell nanowires for enhanced ethanol-sensing performance
Dang Thi Thanh Le,Do Dang Trung,Nguyen Duc Chinh,Bui Thi Thanh Binh,Hoang Si Hong,Nguyen Van Duya,Nguyen Duc Hoa,Nguyen Van Hieu 한국물리학회 2013 Current Applied Physics Vol.13 No.8
The design of coreeshell heteronanostructures is powerful tool to control both the gas selectivity and the sensitivity due to their hybrid properties. In this work, the SnO2eZnO coreeshell nanowires (NWs) were fabricated via two-step process comprising the thermal evaporation of the single crystalline SnO2 NWs core and the spray-coating of the grainy polycrystalline ZnO shell for enhanced ethanol sensing performance. The as-obtained products were investigated by X-ray diffraction, scanning electron microscopy,and photoluminescence. The ethanol gas-sensing properties of pristine SnO2 and ZnOeSnO2 core eshell NW sensors were studied and compared. The gas response to 500 ppm ethanol of the coreeshell NW sensor increased to 33.84, which was 12.5-fold higher than that of the pristine SnO2 NW sensor. The selectivity of the coreeshell NW sensor also improved. The response to 100 ppm ethanol was about 14.1,whereas the response to 100 ppm liquefied petroleum gas, NH3, H2, and CO was smaller, and ranged from 2.5 to 5.3. This indicates that the coreeshell heterostructures have great potential for use as gas sensing materials.
GaN Quantum Dots: Physics and Applications
Le si Dang,B. Daudin,C. Adelmann,E. Martinez,E. Monroy,G. Fishman,H. Mariette,J. Simon,J. L. Rouviere,N. Pelekanos,조용훈 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III
Recent works by our group on hexagonal and cubic GaN/AlN quantum dots grown by molecular beam epitaxy are reviewed. It is shown that the growth of GaN on AlN can occur either in a layer-by-layer mode to form quantum wells or in the Stranski-Krastanow mode to form self-assembled quantum dots. High resolution transmission electron microscopy reveals that quantum dots are truncated pyramids (typically 3 nm high and 15 nm wide), nucleating on top of a wetting layer. The existence of internal electric fields of 7 MV/cm in hexagonal quantum dots is evidenced by observations of various physical effects related to the quantum confined Stark effect, {\it e.g.} energy redshift of the interband transition, decrease of its oscillator strength, or enhancement of the exciton interaction with LO phonons. Prospects for UV and near-IR applications, using interband and intersubband transitions of GaN/AlN quantum dots, respectively, will be discussed also in this presentation.
Antiviral Peptide from Pseudomonas chlororaphis O6 against Tobacco Mosaic Virus (TMV)
박주연,Si Young Yang,Young Cheol Kim,김진철,Quang Le Dang,Jeong Jun Kim,In Seon Kim 한국응용생명화학회 2012 Applied Biological Chemistry (Appl Biol Chem) Vol.55 No.1
Although Pseudomonas chlororaphis O6 (O6) is known to be a rhizobacterium capable of inducing systemic resistance against plant virus, its antiviral products from O6remain unknown. In the present study, an antiviral cyclic peptide was identified from the cell-free supernatant of O6. O6 cultures grown on Luria Bertani medium were centrifuged, and the resulting supernatant was extracted with organic solvent, followed by a series of column chromatography and preparative high performance liquid chromatography (HPLC). Bioassay-guided fractionations were involved in the isolation of antiviral products against tobacco mosaic virus (TMV). Time of flight mass spectrometry (TOF-MS) analysis of the isolated product detected (M+H)+ peak at m/z 887.4242 that generated m/z 756.3859,657.3180, 556.2724, 459.2208, 345.1873, and 171.1130 as the main fragment ions. NMR analyses characterized all protons and carbons of the isolated product. Based on the data, the isolated antiviral product was determined to be a cyclic peptide with molecular formula C39H67N9O12S consisting of seven different amino acids. The antiviral peptide exhibited more than 95%disease suppression of TMV at 1,000 μg/mL. O6 may play a role in promoting plant growth.
Antiviral Peptide from Pseudomonas chlororaphis O6 against Tobacco Mosaic Virus (TMV)
Park, Ju-Yeon,Yang, Si-Young,Kim, Young-Cheol,Kim, Jin-Cheol,Dang, Quang Le,Kim, Jeong-Jun,Kim, In-Seon The Korean Society for Applied Biological Chemisty 2012 Applied Biological Chemistry (Appl Biol Chem) Vol.55 No.1
Although Pseudomonas chlororaphis O6 (O6) is known to be a rhizobacterium capable of inducing systemic resistance against plant virus, its antiviral products from O6 remain unknown. In the present study, an antiviral cyclic peptide was identified from the cell-free supernatant of O6. O6 cultures grown on Luria Bertani medium were centrifuged, and the resulting supernatant was extracted with organic solvent, followed by a series of column chromatography and preparative high performance liquid chromatography (HPLC). Bioassay-guided fractionations were involved in the isolation of antiviral products against tobacco mosaic virus (TMV). Time of flight mass spectrometry (TOF-MS) analysis of the isolated product detected $(M+H)^+$ peak at m/z 887.4242 that generated m/z 756.3859, 657.3180, 556.2724, 459.2208, 345.1873, and 171.1130 as the main fragment ions. NMR analyses characterized all protons and carbons of the isolated product. Based on the data, the isolated antiviral product was determined to be a cyclic peptide with molecular formula $C_{39}H_{67}N_9O_{12}S$ consisting of seven different amino acids. The antiviral peptide exhibited more than 95% disease suppression of TMV at 1,000 ${\mu}g/mL$. O6 may play a role in promoting plant growth.
Lee, Woojin,Kim, Minwoo,Yang, Hanyi,Kyhm, Kwangseuk,Murayama, Akihiro,Kheng, Kuntheak,Mariette, Henri,Dang, Le Si Optical Society of Korea 2018 Current Optics and Photonics Vol.2 No.6
We have investigated the dimensional nature of center-of-mass exciton confinement states in a CdMnTe/CdTe/CdMnTe heterostructure, where the CdTe well is too wide (144 nm) to confine both electrons and holes but able to confine whole excitons in the center-of-mass coordinate. Fine multiple photoluminescence spectra with a few meV separation were observed at 6 K. From the thickness dependence of the transition rate, they were attributed to even numbered center-of-mass exciton confinement states (N = 2, 4, 6, ${\cdots}$, 18). Dimensionality of the center-of-mass exciton confinement states was also investigated in terms of temperature dependence of radiative decay time. At low temperatures (${\leq}12K$), we found that the ground state excitons are likely localized possibly due to the barrier interface fluctuation, resulting in a constant decay time (~350 ps). With increased temperature (${\geq}12K$), localized excitons are thermally released, giving rise to a linear temperature dependence of radiative decay time as an evidence of two-dimensional nature.
I. C. Robin,C. Tavares,J. Rothman,G. Feuillet,A. H. El-Shaer,A. Bakin,A. Waag,Le Si Dang 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
The structural and the spectroscopic properties of a 2-inch ZnO epilayer grown by using molecular beam epitaxy are investigated. A 500-nm-thick substrate was grown on c-sappire by using a MgO buffer. In spite of the high dislocation density in the epilayer, temperature-dependent photoluminescence measurements show only a small decrease in the luminescence intensity between 4 K and 300 K. Time-resolved photoluminescence measurements reveal a decay time independent of temperature. Cathodoluminescence presents an inhomogeneous emission on a micrometric scale: a stronger emission is measured in small nanometric areas. A tentative explanation of this behavior is proposed.
Self-aligned deterministic coupling of single quantum emitter to nanofocused plasmonic modes
Gong, Su-Hyun,Kim, Je-Hyung,Ko, Young-Ho,Rodriguez, Christophe,Shin, Jonghwa,Lee, Yong-Hee,Dang, Le Si,Zhang, Xiang,Cho, Yong-Hoon National Academy of Sciences 2015 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.112 No.17
<P><B>Significance</B></P><P>Control and optimization of interaction between light and single quantum emitters are a crucial issue for cavity quantum electrodynamics studies and quantum information science. Although considerable efforts have been made, reliable and reproducible coupling between quantum emitter and cavity mode still remains a grand challenge due to the uncertainty of the size, i.e., the emission wavelength, and position of the quantum emitter. Here, we demonstrate an unprecedented approach of the self-aligned deterministic coupling of single quantum dots (QDs) to nanofocused plasmonic modes on an entire wafer. Spatial precision is better than any nanopositioning techniques, and almost all processed QDs exhibit outstanding spontaneous emission rate enhancement. This reliable approach eliminates a major obstacle in the implementation of practical solid-state quantum emitters.</P><P>The quantum plasmonics field has emerged and been growing increasingly, including study of single emitter–light coupling using plasmonic system and scalable quantum plasmonic circuit. This offers opportunity for the quantum control of light with compact device footprint. However, coupling of a single emitter to highly localized plasmonic mode with nanoscale precision remains an important challenge. Today, the spatial overlap between metallic structure and single emitter mostly relies either on chance or on advanced nanopositioning control. Here, we demonstrate deterministic coupling between three-dimensionally nanofocused plasmonic modes and single quantum dots (QDs) without any positioning for single QDs. By depositing a thin silver layer on a site-controlled pyramid QD wafer, three-dimensional plasmonic nanofocusing on each QD at the pyramid apex is geometrically achieved through the silver-coated pyramid facets. Enhancement of the QD spontaneous emission rate as high as 22 ± 16 is measured for all processed QDs emitting over ∼150-meV spectral range. This approach could apply to high fabrication yield on-chip devices for wide application fields, e.g., high-efficiency light-emitting devices and quantum information processing.</P>