• Title/Summary/Keyword: nanodots

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Green Synthesis of Multifunctional Carbon Nanodots and Their Applications as a Smart Nanothermometer and Cr(VI) Ions Sensor

  • Li, Lu;Shao, Congying;Wu, Qian;Wang, Yunjian;Liu, Mingzhu
    • Nano
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    • v.13 no.12
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    • pp.1850147.1-1850147.14
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    • 2018

  • In this work, water-soluble and blue-emitting carbon nanodots (CDs) were synthesized from apple peels for the first time via one-step hydrothermal method. The synthetic route is facile, green, economical and viable. The as-prepared CDs were characterized thoroughly by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman, Fourier transform infrared (FT-IR), X-ray photoelectron (XPS), fluorescence and UV-Vis absorption spectroscopy in terms of their morphology, surface functional groups and optical properties. The results show that these CDs possessed ultrasmall size, good dispersivity, and high tolerance to pH, ionic strength and continuous UV irradiation. Significantly, the CDs had fast and reversible response towards temperature, and the accurate linear relationship between fluorescence intensity and temperature was used to design a novel nanothermometer in a broad temperature range from 5 to $65^{\circ}C$ facilely. In addition, the fluorescence intensity of CDs was observed to be quenched immediately by Cr(VI) ions based on the inner filter effect. A low-cost Cr(VI) ions sensor was proposed employing CDs as fluorescent probe, and it displayed a wide linear range from 0.5 to $200{\mu}M$ with a detection limit of $0.73{\mu}M$. The practicability of the developed Cr(VI) sensor for real water sample assay was also validated with satisfactory recoveries.

  • https://doi.org/10.1142/S1793292018501473 인용

Flux pinning properties of rf-sputtered YBCO films with $BaZrO_3$ doping (스퍼터링법에 의한 $BaZrO_3$도핑 YBCO 박막의 자속고정 특성 연구)

  • Chung, K.C.;Kim, Y.K.;Wang, X.L.;Dou, S.X.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.374-374
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    • 2009

  • We have fabricated pure YBCO films and $BaZrO_3$ doped ones on $CeO_2$ buffered YSZ single crystal substrates using rf-sputtering method. In this work, pure YBCO and 2 vol% BZO doped YBCO target were used to investigate the flux pinning properties of BZO doped YBCO films compared to undoped ones. BZO nanodots within the superconducting materials was known to comprise the self-assembled columnar defects along the c-axis from the bottom of YBCO films up to the top surface, thus can be a very strong pinning sites in the applied magnetic field parallel to them. We will discuss the possibility of growing self-assembled columnar defects in the rf-sputtering method. It is speculated that BZO and YBCO phases can separate and BZO form nanodots surrounded by YBCO epitaxial layers and continuous phase separation and ordering between these two materials, which was well studied in Pulsed Laser Deposition method. For this purpose, some severe experimental conditions such as on-axis sputtering, shorter target-substrate distance, high rf-power, etc was adopted and their results will be presented.

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Morphology Control of ZnO Nanostructures by Surfactants During Hydrothermal Growth (수열합성중 계면활성제를 이용한 ZnO 나노구조 형상 제어)

  • Park, Il-Kyu
    • Journal of Powder Materials
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    • v.23 no.4
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    • pp.270-275
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    • 2016

  • We report on an all-solution-processed hydrothermal method to control the morphology of ZnO nanostructures on Si substrates from three-dimensional hemispherical structures to two-dimensional thin film layers, by controlling the seed layer and the molar contents of surfactants during their primary growth. The size and the density of the seed layer, which is composed of ZnO nanodots, change with variation in the solute concentration. The ZnO nanodots act as heterogeneous nucleation sites for the main ZnO nanostructures. When the seed layer concentration is increased, the ZnO nanostructures change from a hemispherical shape to a thin film structure, formed by densely packed ZnO hemispheres. In addition, the morphology of the ZnO layer is systematically controlled by using trisodium citrate, which acts as a surfactant to enhance the lateral growth of ZnO crystals rather than a preferential one-dimensional growth along the c-direction. X-ray diffraction and energy dispersive X-ray spectroscopy results reveal that the ZnO structure is wurtzite and did not incorporate any impurities from the surfactants used in this study.

  • https://doi.org/10.4150/KPMI.2016.23.4.270 인용 PDF KSCI