• Bulletin of the Korean Chemical Society
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• 제16권2호
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• pp.126-129
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• 1995

Linear and nonlinear optical properties of CuCl nanocrystals in silica glass have been studied using low temperature absorption, degenerate four wave mixing (DFWM), and time-resolved photoluminescence spectroscopy. Assuming a spherical shape, effective radius of the CuCl quantum dots was estimated to be 2.5 nm, which is obtained from low temperature absorption data. The DFWM experiment was performed in 380-386 nm wavelength region, and the diffracted signal was measured as a function of wavelength with 1.0 nm interval. Time-resolved photoluminescence measurement was also carried out at 77 K to obtain the time response of CuCl nanocrystals. The experimental results on the large third order nonlinear optical of CuCl quantum dots are explained in terms of crystal size and oscillator strength of quantum spheres.

• Bulletin of the Korean Chemical Society
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• 제31권6호
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• pp.1474-1478
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• 2010

An efficient method for labeling individual proteins in live cells is required for investigations into biological mechanisms and cellular processes. Here we describe the preparation of small quantum dots (QDs) that target membrane surface proteins bearing a hexahistidine-tag ($His_6$-tag) via specific binding to an nitrilotriacetic acid complex of nickel(II) ($NTA{\cdot}Ni^{2+}$) on the QD surfaces. We showed that the $NTA{\cdot}Ni^{2+}$-QDs bound to His-tag functionalized beads as a cellular mimic with high specificity and that QDs successfully targeted $His_6$-tagged vesicle-associated membrane proteins (VMAP) on cell surfaces. This strategy provides an efficient approach to monitoring synaptic protein dynamics in spatially restricted and confined biological environments.

• 대한화학회지
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• 제59권2호
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• pp.136-141
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• 2015

We have discovered that quercetin, once coated on the CdSe and CdSe-CdS quantum dots (QDs), becoming highly water soluble. In the present work, we have successfully synthesized CdSe/CdS/N-Acetyl-L-Cysteine(NAC)/Quercetin nano-composites in the aqueous solution. The products were characterized using UV-vis spectroscopy, X-ray powder diffraction, fluorescence spectroscopy, and Fourier transform infrared spectroscopy. The transmission electron microscopy (TEM) tests indicated that our nano-composite products are highly stable with homogeneous particle size and great monodispersity. Quercetin coated nano-composite CdSe/CdS/NAC/Quercetin showed different fluorescence behavior from that of CdSe/CdS/NAC. Most amazingly, the synthesized CdSe/CdS/NAC/Quercetin nano-composite exhibits strong antibacterial activity. The combination of the strong fluorescence and its antibacterial activity makes the quercetin modified quantum dots as a potential candidate for cancer targeted therapy and other cancer treatments.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.191.2-191.2
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• 2015

Details of carrier dynamics in self-assembled quantum dots (QDs) with a particular attention to nonradiative processes are not only interesting for fundamental physics, but it is also relevant to performance of optoelectronic devices and the exploitation of nanocrystals in practical applications. In general, the possible processes in such systems can be considered as radiative relaxation, carrier transfer between dots of different dimensions, Auger nonradiactive scattering, thermal escape from the dot, and trapping in surface and/or defects states. Authors of recent studies have proposed a mechanism for the carrier dynamics of time-resolved photoluminescence CdTe (a type II-VI QDs) systems. This mechanism involves the activation of phonons mediated by electron-phonon interactions. Confinement of both electrons and holes is strongly dependent on the thermal escape process, which can include multi-longitudinal optical phonon absorption resulting from carriers trapped in QD surface defects. Furthermore, the discrete quantized energies in the QD density of states (1S, 2S, 1P, etc.) arise mainly from ${\delta}$-functions in the QDs, which are related to different orbitals. Multiple discrete transitions between well separated energy states may play a critical role in carrier dynamics at low temperature when the thermal escape processes is not available. The decay time in QD structures slightly increases with temperature due to the redistribution of the QDs into discrete levels. Among II-VI QDs, wide-gap CdZnTe QD structures characterized by large excitonic binding energies are of great interest because of their potential use in optoelectronic devices that operate in the green spectral range. Furthermore, CdZnTe layers have emerged as excellent candidates for possible fabrication of ferroelectric non-volatile flash memory. In this study, we investigated the optical properties of CdZnTe/ZnTe QDs on Si substrate grown using molecular beam epitaxy. Time-resolved and temperature-dependent PL measurements were carried out in order to investigate the temperature-dependent carrier dynamics and the activation energy of CdZnTe/ZnTe QDs on Si substrate.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.627-627
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• 2013

Recently, most studies concerning inorganic CdSe/ZnS quantum dot (QD)-polymer hybrid LEDs have been concentrated on the structure with multiple layers [1,2]. The QD LEDs used almost CdSe materials for color reproduction such as blue, green and red from the light source until current. However, since Cd is one of six substances banned by the Restriction on Hazardous Substances (RoHS) directive and classified into a hazardous substance for utilization and commercialization as well as for use in life, it was reported that the use of CdSe is not suitable to fabricate a photoelectronic device. In this work, we demonstrate a novel, simple and facile technique for the synthesis of ZnO-graphene quasi-core.shell quantum dots utilizing graphene nanodot in order to overcome Cd material including RoHS materials. Also, We investigate the optical and structural properties of the quantum dots using a number of techniques. In result, At the applied bias 10 V, the device produced bluish-white color of the maximum brightness 1118 cd/$m^2$ with CIE coordinates (0.31, 0.26) at the bias 10 V.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.517-518
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• 2006

Optically pumped THz emission has been observed in a wide range of semiconductors, and this process is an important practical source of pulsed THz radiation for time-domain THz spectroscopy and THz imaging. We show that InAs quantum dots on GaAs can be used to significantly enhance THz emission compared with a bare GaAs surface.

• 한국세라믹학회지
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• 제39권5호
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• pp.517-522
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• 2002

본 연구에서는 PVD 공정으로 Si 양자점 형성시 증착조건의 변화가 증착된 양자점 크기와 분포에 미치는 영향을 Monte Carlo법을 응용한 전산모사를 통하여 정량적으로 분석하였다. 전산모사시 PVD 공정에서 일반적으로 제어가 가능한 기판온도, 증착시간, 가스압력과 타겟-기판거리를 공정변수로 선택하였다. 계산 겨로가 증착속도가 0.05 nm/sec이고 기판온도 490${\circ}$, 증착시간 7 sec, 가스압력 3 mTorr, 타겟-기판거리가 8 cm일때 증착 밀도가 $1{\times}10^{12}cm^{-2}$인 Si 양자점 형성이 가능할 것으로 예측되었다.

• 전자통신동향분석
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• 제35권2호
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• pp.79-88
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• 2020

Quantum computing is regarded as one of the revolutionary computing technologies, and has attracted considerable attention in various fields, such as finance, chemistry, and medicine. One of the promising candidates to realize fault tolerant quantum computing is quantum dot qubits, due to their expectation of high scalability. In this study, we briefly introduce the international tendencies for quantum dot quantum computing. First, the current status of quantum dot gate operations is summarized. In most systems, over 99% of single qubit gate operation is realized, and controlled-not and controlled-phase gates as 2-qubit entangling gates are demonstrated in quantum dots. Second, several approaches to expand the number of qubits are introduced, such as 1D and 2D arrays and long-range interaction. Finally, the current quantum dot systems are evaluated for conducting quantum computing in terms of their number of qubits and gate accuracies. Quantum dot quantum computing is expected to implement scalable quantum computing. In the noisy intermediate-scale quantum era, quantum computing will expand its applications, enabling upcoming questions such as a fault-tolerant quantum computing architecture and error correction scheme to be addressed.

• 한국광학회:학술대회논문집
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• 한국광학회 1997년도 Advance Program of 14th optics andquantum Electronics conference, 1997제14 회 광학 및 양자전자 학술 발표회 논문 요약집
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• pp.88-88
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• 1997

• 한국분말재료학회지
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• 제24권1호
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• pp.1-5
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• 2017

We have investigated the washing method of as-synthesized CdSe/ZnS core/shell structure quantum dots (QDs) and the effective surface passivation method of the washed QDs using PMMA. The quantum yield (QY%) of as-synthesized QDs decreases with time, from 79.3% to 21.1%, owing to surface reaction with residual organics. The decreased QY% is restored to the QY% of as-synthesized QDs by washing. However, the QY% of washed QDs also decreases with time, owing to the absence of surface passivation layer. On the other hand, the PMMA-treated QDs maintained a relatively higher QY% after washing than that of the washed QDs that were kept in toluene solution for 30 days. Formation of the PMMA coating layer on CdSe/ZnS QD surface is confirmed by HR-TEM and FT-IR. It is found that the PMMA surface coating, when combined with washing, is useful to be applied in the storage of QDs, owing to its long-term stability.