Development of Quantum Dot with High Quantum Yield and Stability

김형모,황도원,정흥수,( Xuan-hung Pham ),함은일,김태한,이동수,전봉현 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

Luminescent semiconductor quantum dots (QDs) have many advantages including a photo-stability, a narrow emission spectrum, high quantum yield (QY) and a signal brightness, compared to a traditional fluorescent dye. For this reason, QDs are widely used to conjugate with many biological materials. However, conventional QDs have some problems in bio-application and we will discuss on one of these problems. After the surface modification of QDs for bio-applications, QY is getting significantly lower. In this study, we describe our QDs with high quantum yield. This QDs show a strong fluorescence character compared to conventional QDs. Besides, our QDs indicate a high stability in a strong pH range. After the surface modification for bio-applications, our QDs were not specifically reduced QY. In comparison with conventional QDs, our QDs were discovered a strong fluorescence as feature in vitro and in vivo.

Water-Soluble Multi-Shell Quantum Dot with Stability High and Quantum Yield

하유나,김형모,함은일,김태용,강은지,전봉현 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

Semiconductor quantum dots (QDs) have many advantages including a high quantum yield (QY), high fluorescent signal, photo-stability and narrow emission spectrum, compared to a traditional fluorescent dye. However, After the surface modification of QDs for bio-applications, QY is getting significantly lower. In this study, we describe the water-soluble multi shell QDs with high quantum yield. This multi-shell QDs show a strong fluorescence signal compared to established single shell QDs. Besides, multi shell QDs indicate a high stability in a strong pH range. After the surface modification for bio-applications, multi-shell QDs maintain slightly reduced QY. In comparison with single shell QDs, multi shell QDs were discovered a strong fluorescence as feature in vitro and in vivo. This water-soluble multi shell QDs, which surface modified possible one, have a great potential for practical bio-imaging.

Axially substituted silicon (IV) tetrapyrazinoporphyrazines: Synthesis, characterization and investigation of photophysicochemical properties

Jung, C.Y.,Park, J.M.,Song, C.J.,Jaung, J.Y. Elsevier [etc.] 2016 Journal of luminescence Vol.170 No.1

<P>A series of silicon tetrapyrazinoporphyrazine (SiPz) complexes, conjugated with various substituents at their axial positions, were synthesized into non-aggregated structures in organic solvents. The UV-vis spectra of the SiPz complexes maintained a strong and sharp Q-band, which is an archetypal characteristic of non-aggregated phthalocyanines (Pcs), in various organic solvents under high concentrations. In addition, the SiPz complexes with axial alkyl groups had high fluorescence quantum yields and singlet oxygen quantum yields. However, the SiPz complexes with axial aniline groups had very low fluorescence quantum yields and singlet oxygen quantum yields due to the quenching ability of the aniline group. (C) 2015 Elsevier B.V. All rights reserved.</P>

남서해역에서 양식되는 방사무늬김(Porphyra yezoensis Ueda)의 Diving-PAM에 의한 광합성 특성

김정배 ( Jeong Bae Kim ),이원찬 ( Won Chan Lee ),김형철 ( Hyung Chul Kim ),최희구 ( Hee Gu Choi ),박정임 ( Jung Im Park ),조윤식 ( Yoon Sik Cho ),박환희 ( Hwan Hee Park ) 한국환경생물학회 2012 환경생물 : 환경생물학회지 Vol.30 No.3

The morphological characteristics, carbon and nitrogen concentrations, stable isotope values and photosynthetic rates of Porphyra yezoensis were studied at the main purple lavers production areas on southwestern coast of Korea. The morphological characteristics of leaf length, leaf width and weight of Porphyra blades were between 11.6~16.3 (average 13.8) cm, 4.6~6.3 (average 5.4) cm, 1.1~2.6 (average 1.86) g DW m-2, respectively. Photosynthetic pigment of Chl a concentration of Porphyra blades was between 2.18~17.77 (average 9.65) mg DW Chl a m-2. Carbon and nitrogen concentrations of Porphyra blades was between 201~317 (average 240) mg DW g-1, 39.8~50.0 (average 43.5) mg DW g-1 and C/N ratio 5.0~6.7 (average 5.5). The range of average δ13C and δ15N values of Porphyra blades was between - 25.6 to - 24.0 (average - 24.7)‰ for δ13C, and 1.3 to 4.1 (average 2.1)‰ for δ15N. Photosynthetic characteristics of seaweeds measured by pulse amplitude modulation (PAM) fluorometry was used as an indicator of photosynthetic activity. We use Diving-PAM fluorometry to examine photosynthetic rates of the seaweeds Porphyra yezoensis at each station. Maximum quantum yield of Porphyra blades was between 0.46~ 0.55 (average 0.52), the variance of the effective PS II maximum quantum yield of the station was broadly similar. Maximum relative electron transport rate (rETRmax) of Porphyra blades was between 4.71~5.84 (average 5.33) μmol electrons m-2 s-1, the changes of maximum relative electron transport rate (rETRmax) of Porphyra yezoensis were similar to those of PS II maximum quantum yield. Photosynthetic efficiency (α) was between 0.027~0.045 (average 0.036). Minimum saturating irradiance (Ek) range was 139~180 (average 156) μmol photons m-2 s-1. Minimum saturating irradiance (Ek) made a difference by station within the area on southwestern coast. Carbon and nitrogen concentrations and photosynthetic rates of Porphyra blades production areas on southwestern coast were broadly similar. The photosynthetic characteristics showed low photosynthetic rates because the low maximum quantum yields and low maximum relative electron transport rate.

Highly Fluorescent and Stable Quantum Dot-Polymer-Layered Double Hydroxide Composites

Cho, Seungho,Kwag, Jungheon,Jeong, Sanghwa,Baek, Yeonggyeong,Kim, Sungjee American Chemical Society 2013 Chemistry of materials Vol.25 No.7

<P>We report a designed strategy for a synthesis of highly luminescent and photostable composites by incorporating quantum dots (QDs) into layered double hydroxide (LDH) matrices without deterioration of a photoluminescence (PL) efficiency of the fluorophores during the entire processes of composite formations. The QDs synthesized in an organic solvent are encapsulated by polymers, poly(maleic acid-alt-octadecene) to transfer them into water without altering the initial surface ligands. The polymer-encapsulated QDs with negative zeta potentials (−29.5 ± 2.2 mV) were electrostatically assembled with positively charged (24.9 ± 0.6 mV) LDH nanosheets to form QD-polymer-LDH composites (PL quantum yield: 74.1%). QD-polymer-LDH composite films are fabricated by a drop-casting of the solution on substrates. The PL properties of the films preserve those of the organic QD solutions. We also demonstrate that the formation of the QD-polymer-LDH composites affords enhanced photostabilities through multiple protections of QD surface by polymers and LDH nanosheets from the environment.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2013/cmatex.2013.25.issue-7/cm3040505/production/images/medium/cm-2012-040505_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm3040505'>ACS Electronic Supporting Info</A></P>

딸기 수경재배 시 ‘베리스타’와 ‘죽향’의 생육과 품질 향상을 위한 적정 양액농도 설정

최수현(Su Hyun Choi),최경이(Gyeong Lee Choi),정호정(Ho Jeong Jeong),김승유(Seung Yu Kim),이성찬(Seong Chan Lee),최효길(Hyo Gil Choi) (사)한국생물환경조절학회 2017 생물환경조절학회지 Vol.26 No.4

최근 국내에서 육성된 딸기 신품종 ‘베리스타’와 ‘죽향’ 의 수경재배 시 생육 단계별 적정한 양액 농도가 품질과 생산성에 미치는 영향을 구명하기 위하여 연구를 수행하였다. 길이 40m, 폭 10m의 플라스틱 온실 내에 높이 1m, 폭 33cm의 수경재배용 베드를 설치하고 원예용상토를 충진한 후 ‘설향’, ‘베리스타’, ‘죽향’ 묘를 정식하였다. 배양액은 네덜란드 PBG 배양액을 사용하였으며, 생육 단계를 생육초기-개화기-수확초기-수확후기로 나누어 처리 2는 ‘설향’ 기준 급액 농도 EC 0.68-1.0-1.2-1.0dS·m<SUP>-1</SUP>, 처리 1은 30% 낮은 농도인 EC 0.68-0.8-0.85-0.7dS·m<SUP>-1</SUP>, 처리 3은 30% 높은 농도인 EC 0.68-1.2-1.55-1.3dS·m<SUP>-1</SUP>으로 급액 하였다. 재배기간 동안 딸기품종별 생육과 수량 등을 조사하였다. ‘베리스타’는 2번 처리구와 3번 처리구 간의 지상부 생육에 차이가 없었으며, ‘베리스타’와 ‘죽향’ 모두 양액 농도가 높을수록 엽색이 짙었으나 양자 효율은 차이가 나지 않았다. ‘죽향’은 급액농도에 따라 3월 이후 생육 후기에 생육 차이가 뚜렷하였고, 3번 처리구에서 가장 생육이 왕성하였다. ‘베리스타’와 ‘죽향’ 모두 과중, 과장, 과폭 및 과실 경도가 3번 처리구에서 유의하게 높은 값을 나타냈다. 수확과의 총 당 함량은 처리 간에 차이가 없었으나 환원당과 비환원당의 조성 비율은 처리별로 다르게 나타났다. 수량을 조사한 결과, ‘베리스타’는 급액 농도가 높아질수록 수확과의 수가 많았으나 수량은 처리별로 큰 차이가 나타나지 않았다. 반면, ‘죽향’은 급액농도 간에 뚜렷한 차이를 보였으며, 3번 처리구에서 가장 수확량이 많았다. 생육 특성과 과실 품질을 종합적으로 고려해 본 결과, ‘베리스타’는 ‘설향’ 표준 급액농도와 동일하게 EC 0.68-1.0-1.2-1.0dS·m<SUP>-1</SUP>로 관리하는 것이 경제적이며, ‘죽향’은 ‘설향’ 기준 급액농도보다 30% 높은 EC 0.68-1.2-1.55-1.3dS·m<SUP>-1</SUP>로 공급해 주는 것이 고품질의 과실을 많이 수확할 수 있는 방법으로 판단된다. This study was conducted to set the optimum nutrient solution concentration by growth stage for new strawberry cultivars ‘Berrystar’ and ‘Jukhyang’(Fragaria × ananassa Duch. cvs. ‘Berrystar’, ‘Jukhyang’) grown through hydroponics to improve the quality and yield. Three different EC levels were applied to the nutrient solution. The treatment levels were 0.7, 1.0 and 1.3 times higher than the nutrient concentration standard for ‘Seolhyang’ based on the ‘Manual for strawberry cultivation’ of Rural Development Administration. Based on the results, there were no significant differences in growth of ‘Berrystar’ by EC level. ‘Jukhyang’ showed the most vigorous growth grown in 1.3 times higher nutrient concentration. While the growth of ‘Berrystar’ and ‘Jukhyang’ grown in higher EC level has leaves with more chlorophyll concentration. However the quantum yield of leaves was not affected by the treatments. On the treatment with 1.3 times higher EC level, the weight, length, width and firmness of ‘Berrystar’ and ’Jukhyang’ were significantly high. The sugar contents of the harvest analyzed by HPLC did not differed particularly, but the percentage composition of reducing sugar and non-reducing sugar were presented differently depending on the treatments. Marketable fruit yield increased as nutrient concentration increases. However, there were no large differences by treatments. Meanwhile, ‘Jukhyang’ showed significant difference by nutrient concentration and had the largest yield for a treatment grown in 1.3 times higher EC level. Based on these results, it is recommended to provide the same nutrient solution concentration level to the nutrient concentration standard of ‘Seolhyang’ for ‘Berrystar’, and the 1.3 times higher level for ‘Jukhyang’.

Enhanced light harvesting with chromium in NaLu_0.70−xGd_0.10F₄:Yb_0.18Er_0.02Cr_x (0≤x≤0.25) upconversion system

Huy, Bui The,Gerelkhuu, Zayakhuu,Chung, Jong Won,Dao, Van-Duong,Ajithkumar, Gangadharan,Lee, Yong-Ill Elsevier 2017 Materials science and engineering B. Advanced Func Vol.223 No.-

<P>Cr3+-doped Nalm(0.70-x)Gd(0.10)F(4):Yb0.18Er0.02Crx nanoparticles were synthesized by one step solvothermal method. The structural, emission properties were studied by XRD, FT-IR, emission spectra. The doping of 15 mol% Cr3+ into NaLu0.70-xGd0.10F4:Yb0.18Er0.02Crx induced cubic-hexagonal phase transition, with a consequent 20 times improvement in the upconversion fluorescence quantum yield. The roles of Cr3+ in the phase transition as well as the mechanism of the multi-photon upconversion process in the material were discussed. The Yb3+-Cr3+ dimer could play the role of as a sensitizer by transferring energy to Er3+. The Cr3+ ions result an asymmetry in the environment surrounding the rare-earth ions, which would favor the hypersensitive transitions. This research may open up a new perspective to prepare high upconversion luminescent materials. (C) 2017 Elsevier B.V. All rights reserved.</P>

Investigating energy partitioning during photosynthesis using an expanded quantum yield convention

Ahn, T.K.,Avenson, T.J.,Peers, G.,Li, Z.,Dall'Osto, L.,Bassi, R.,Niyogi, K.K.,Fleming, G.R. Elsevier Science Publishers [etc.] 2009 Chemical physics Vol.357 No.1

In higher plants, regulation of excess absorbed light is essential for their survival and fitness, as it enables avoidance of a build up of singlet oxygen and other reactive oxygen species. Regulation processes (known as non-photochemical quenching; NPQ) can be monitored by steady-state fluorescence on intact plant leaves. Pulse amplitude modulated (PAM) measurements of chlorophyll a fluorescence have been used for over 20 years to evaluate the amount of NPQ and photochemistry (PC). Recently, a quantum yield representation of NPQ (Φ<SUB>NPQ</SUB>), which incorporates a variable fraction of open reaction centers, was proposed by Hendrickson et al. [L. Hendrickson, R.T. Furbank, W.S. Chow, Photosynth. Res. 82 (2004) 73]. In this work we extend the quantum yield approach to describe the yields of reversible energy-dependent quenching (Φ<SUB>qE</SUB>), state transitions to balance PC between photosystems II and I (Φ<SUB>qT</SUB>), and photoinhibition quenching associated with damaged reaction centers (Φ<SUB>qI</SUB>). We showed the additivity of the various quantum yield components of NPQ through experiments on wild-type and npq1 strains of Arabidopsis thaliana. The quantum yield approach enables comparison of Φ<SUB>qE</SUB> with data from a variety of techniques used to investigate the mechanism of qE. We showed that Φ<SUB>qE</SUB> for a series of A. thaliana genotypes scales linearly with the magnitude of zeaxanthin cation formation, suggesting that charge-transfer quenching is largely responsible for qE in plants.

The facile synthesis of tunable heteroatom-doped graphene quantum dots for high quantum yield

이기수,장정식 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.1

Sulfur-Nitrogen co-doped graphene quantum dots (S,N-GQD) are synthesized through one-pot carbonization processing of citric acid under the sulfuric acid and dimethylformamide (DMF) condition at low temperature (<160°C). Sulfuric acid as a sulfur dopant catalyzes the dehydration of citric acid. DMF is a nitrogen source and also serves as a quenching solvent to retard the growth of graphene quantum dots to graphene oxide. Incorporated sulfur and nitrogen induce new surface states, which could facilitate more radiative recombination of exciton. In conclusion, the prepared S,N-GQDs exhibit an excellent fluorescence quantum yield (61%), approximately 7 times higher than that of pristine GQDs (9%), with long photoluminescence life time (τ =7.6 ns). Furthermore, this simple and large-scale synthesis of highly fluorescent GQD gives promise for applications in biosensors and optoelectronic devices.

미세유체반응기를 이용한 core/shell 연속 합성 시스템을 이용한 CdSe/ZnS 양자점 합성 및 분석

홍명환,주소영,강이승,이찬기,Hong, Myung Hwan,Joo, So Young,Kang, Lee-Seung,Lee, Chan Gi 한국분말야금학회 2018 한국분말재료학회지 (KPMI) Vol.25 No.2

Core/shell CdSe/ZnS quantum dots (QDs) are synthesized by a microfluidic reactor-assisted continuous reactor system. Photoluminescence and absorbance of synthesized CdSe/ZnS core/shell QDs are investigated by fluorescence spectrophotometry and online UV-Vis spectrometry. Three reaction conditions, namely; the shell coating reaction temperature, the shell coating reaction time, and the ZnS/CdSe precursor volume ratio, are combined in the synthesis process. The quantum yield of the synthesized CdSe QDs is determined for each condition. CdSe/ZnS QDs with a higher quantum yield are obtained compared to the discontinuous microfluidic reactor synthesis system. The maximum quantum efficiency is 98.3% when the reaction temperature, reaction time, and ZnS/CdSe ratio are $270^{\circ}C$, 10 s, and 0.05, respectively. Obtained results indicate that a continuous synthesis of the Core/shell CdSe/ZnS QDs with a high quantum efficiency could be achieved by isolating the reaction from the external environment.