• Journal of the Korean Chemical Society
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• v.60 no.2
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• pp.131-136
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• 2016

Copper ion induced photoluminescence (PL) quenching dynamics and recovery of the PL by zinc ions were investigated for CdSe based nanocrystals. When copper ions were added, CdSe quantum dots showed fast and dramatically PL quenching whereas PL of CdSe nanorod gradually decreased. In the presence of zinc ions, the PL of CdSe/CdS (core/shell) nanocrystals that have quenched by copper ions was efficiently recovered. It showed that the PL intensity of nanocrystals increased by 50% in a solution containing 1 μM zinc ions. The PL intensity was increasing with increasing zinc ions, and could be described by Langmuir binding isotherm model. We showcase that the CdSe based nanocrystals can be used as fluorescence turn-on sensor.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.275.1-275.1
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• 2016

반전형 폴리머 태양전지는 그 구조에 의하여 훌륭한 안정성을 가질 뿐만 아니라 roll-to-roll 공정을 통한 대량생산이 가능하여 각광받고 있는 구조이다. 이런 반전형 구조에서, 금속 산화물 나노파티클에 의해 만들어지는 금속 산화물 층은 전자수송층으로서 사용된다. 이 연구에서는 표면개질 물질인 PEIE (Polyethyleneimine-ethoxylate)와 화학적으로 기능화된 산화아연/그래핀 핵/껍질 양자점을 이용하여 전기수송층의 역할을 하는 기능화된 산화아연/그래핀 단분자층을 가지는 태양전지를 제작하였다. 이는 기능화된 산화아연/그래핀 단분자층이 표면개질, 광센서, 전기수송층의 역할을 동시에 수행하는 효과로 인해 제작된 태양전지는 향상된 전자 수집능력을 보였다. 단분자층이 잘 형성되어 있는지 확인하기 위하여 집속 이온 빔 장비를 이용하여 태양전지의 내부 구조를 확인하였으며, density functional theory (DFT)을 이용한 모델링을 통하여 기능화된 산화아연/그래핀 양자점의 전자상태밀도를 분석하였다. 기능화된 산화아연 단분자층에 의한 효과적인 계면 제어 및 전하수송에 의해 약 10.3%의 높은 효율을 가지는 반전형 폴리머 태양전지를 제작할 수 있었다.

• Applied Chemistry for Engineering
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• v.22 no.3
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• pp.328-331
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• 2011

ZnSe quantum dots (QDs) were prepared by employing water-containing Dioctyl sodium sulfosuccinate (AOT) reversed micelles (microemulsions) and the silica-encapsulated ZnSe QDs were obtained by a direct injection of tetraethyl orthosilicate (TEOS) into the microemulsion system. When the QDs were coated by silica, well-defined spherical shapes were formed and the average size of the QDs was near 7 nm. In addition, the photoluminescence (PL) efficiency of the QDs was reduced from 8.0 to 1.1% as they were encapsulated by silica. However, the solid layers of the silica-encapsulated ZnSe QDs on gold surfaces showed the excellent photostability. In particular, they are cadmium free and thus, less toxic. Moreover, the present method does not require a hot reaction temperature or extremely toxic H2Se gas as a Se precursor. Accordingly, the method can be a safer and more economical process for producing silica-encapsulated ZnSe QDs, which may be a potential media for biosensors.

• The Science & Technology
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• no.3 s.406
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• pp.54-61
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• 2003

주입식 조직공학/ 무선센서망/ 글리코믹스/ 그리드 컴퓨팅/ 메카트로닉스/ 나노인쇄 리토그래피/ 분자 영상/ 양자 암호/ 나노태양전지/ 소프트웨어의 보증

• The Journal of the Acoustical Society of Korea
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• v.27 no.3
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• pp.149-153
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• 2008

General underwater target detection methods adopt short-time FFT for estimate target doppler. This paper proposes the efficient target detection method, instead of conventional FFT, using approximate FFT for distributed sensor network target detection, which requires lighter computations. In the proposed method, we decrease computational rate of FFT by the quantization of received signal. For validation of the proposed method, experiment result which is applied to FFT based active sonar detector and real oceanic data is presented.

• Journal of Sensor Science and Technology
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• v.3 no.3
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• pp.16-21
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• 1994

A 3-terminal pin-type photosensor with gate contrail is fabricated using standard silicon CMOS IC process. The photosensor of a $100{\mu}m{\times}120{\mu}m$ size has dark current less than 1nA and its breakdown voltage is -14V with a depletion capacitance 0.75 pF at -5V reverse bias. Responsivity at 0V gate voltage is 0.25A/W at $0.633{\mu}m$ wavelength, 0.19A/W at $0.805{\mu}m$. Responsivity increases with increasing gate voltage. The integrated circuit of photosensor and CMOS inverter shows $22K{\Omega}$ transimpedance and photocurrent of $90{\mu}A$ switchs the output state of digital inverter without additional amplifier.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.699-704
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• 2006

무선 센서 네트워크는 소형의 무선 센서노드들로 구성된 네트워크이다. 무선으로 구성된 센서 네트워크는 사물과 환경의 변화를 감지하여 싱크로 전송하게 된다. 무선 센서 네트워크에서 센서노드는 무선으로 데이터를 전송할 때 가장 많은 에너지를 소모한다. 한정된 에너지 자원을 효율적으로 사용하기 위해서는 데이터 전송에 이용하는 라디오모듈의 사용을 최소화하여 네트워크 전체의 데이터 전송량을 감소시켜야 한다. 본 논문에서 제안하는 시스템은 에너지 소모를 줄이기 위해 DPCM, 웨이블릿, 양자화, 가변 길이 부호화를 사용하여 전송되는 데이터의 양을 줄여 라디오모듈을 통한 데이터 전송 횟수를 줄였고, 결과적으로 센서 네트워크의 트래픽을 감소시켜 에너지 소모를 줄였다.

• Journal of Powder Materials
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• v.31 no.2
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• pp.169-179
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• 2024

Colloidal quantum dot (QDs) have emerged as a crucial building block for LEDs due to their size-tunable emission wavelength, narrow spectral line width, and high quantum efficiency. Tremendous efforts have been dedicated to improving the performance of quantum dot light-emitting diodes (QLEDs) in the past decade, primarily focusing on optimization of device architectures and synthetic procedures for high quality QDs. However, despite these efforts, the commercialization of QLEDs has yet to be realized due to the absence of suitable large-scale patterning technologies for high-resolution devices., This review will focus on the development trends associated with transfer printing, photolithography, and inkjet printing, and aims to provide a brief overview of the fabricated QLED devices. The advancement of various quantum dot patterning methods will lead to the development of not only QLED devices but also solar cells, quantum communication, and quantum computers.

• Journal of Power System Engineering
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• v.5 no.1
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• pp.73-79
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• 2001

정전기력을 이용하는 마이크로가속도계 센서는 단결성 실리콘 SOI(Silicon On Insulator) 웨이퍼의 기판에 절전재료 적층과 등방성 및 이방성 부식공정으로 제작한다. 마이크로가속도 센서 개발에는 3차원 미소구조체의 제작공정에서 가열 및 냉각공정의 온도구배로 야기되는 포핑업과 같은 열변형 해석이 최적 형상설계에 중요한 요건이다. 본 연구에서는 양자역학적 현상인 턴널링전류 원리로 승용차 에어백의 검침부 역할을 하는 마이크로가속도 센서의 제조공정에서 소착현상을 방지하는 부가 비임과 턴널갭의 FIB 절단가공과 백금 적층공정의 열적 거동을 해석한다. 마이크로머시닝 공정에서 온도의존성을 고려하여 연성해석하고 유한요소법의 상용코드인 MARC K6.1로 분석한 결과를 단결정 실리콘 웨이퍼로 가공하는 마이크로가속도 센서의 최적공정 및 형상설계를 위한 기초자료로 활용될 수 있을 것으로 기대된다.

• Journal of Radiation Industry
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• v.9 no.3
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• pp.143-151
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• 2015

A PET-MR system is particularly useful in diagnosing brain diseases. We have developed a prototype positron emission tomography (PET) system which can be inserted into the bore of a whole-body magnetic resonance imaging (MRI) system that enables us to obtain PET and MRI images simultaneously with a reduced cost. Silicon photomultipliers (SiPM) are appropriated as a PET detector at PET/MR system because detectors have a high gain and are insensitive to magnetic fields. Despite of its improved performance compared to that of PMT-based detectors, there is a problem of the photo-peak channel shift which is due to the increase of the temperature inside the ring detector. This problem will occur decreasing sensitivity of the PET and image distortion. In this paper, I quantitative analyze parameters of the KAIST SiPM depending on temperature by experiments. And I designed cooling methods in consideration of the degradation of sensors for correction of the temperature in the PET gantry. According to this research, we expect that distortive images and degradation of the sensitivity will not be occurred with using the above idea to reduce heat even if the PET system operates for a long time.