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831.
Hoon‐Je Cho Do‐Hoon Hwang Jong‐Don Lee Nam‐Sung Cho Sang‐Kyu Lee Jonghee Lee Young Kwan Jung Hong‐Ku Shim 《Journal of polymer science. Part A, Polymer chemistry》2008,46(3):979-988
Novel blue‐emitting germanium‐containing poly(p‐phenylenevinylene) (PPV) derivatives with well‐defined conjugation lengths were synthesized via Wittig‐condensation polymerizations. The polymers can be color‐tuned by the introduction of various chromophores into the PPV‐based polymer backbones. The photoluminescence (PL) spectra of the polymers, GePVK (containing carbazole moieties), GeMEH (containing dialkoxybenzene moieties), and GePTH (containing phenothiazine moieties), were found to exhibit blue, greenish blue, and green emissions, respectively. GePTH produces more red‐shifted emission than GeMEH and GEPVK, resulting in green emission, and the solution and solid state PL spectra of GePVK consist of almost blue emission. The electroluminescence spectra of GeMEH and GePTH contain yellowy green and yellow colors, respectively. Interestingly, GePVK exhibits white emission with CIE coordinates of (0.33, 0.37) due to electroplex emission in the light‐emitting diodes. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 979–988, 2008 相似文献
832.
Jeong Ho Ryu Kang Min Kim Sung Wook Mhin Gyeong Seon Park Jong Won Eun Kwang Bo Shim Chang Sung Lim 《Applied Physics A: Materials Science & Processing》2008,92(2):407-412
Pulsed laser ablation in a liquid phase was successfully employed to synthesize a barium molybdate (BaMoO4) nanocolloidal suspension. The nanocolloidal suspension was composed of well-dispersed and horizontally assembled BaMoO4 aggregates. The BaMoO4 aggregates showed predominantly elliptically shaped nanorods with sizes between 100 and 200 nm. The preferential elliptical
growth was rationalized from the viewpoint of the intrinsic structure of BaMoO4. The optical properties of the prepared BaMoO4 colloidal nanoparticles were investigated using Raman spectroscopy, UV–vis spectroscopy and photoluminescence (PL) spectrophotometry.
The optical band gap was estimated by Tauc and Menth’s law. The PL emission feature was decomposed into several individual
Gaussian components, which could be interpreted by a Jahn–Teller splitting effect on the [MoO4]2- tetrahedron of the BaMoO4 colloidal nanoparticles.
PACS 42.62.-b; 82.70.Dd; 78.55.Hx; 81.07.Wx 相似文献
833.
Giseop Kwak Ga Hyoung Lee Shang‐hun Shim Keun‐Byoung Yoon 《Macromolecular rapid communications》2008,29(10):815-820
Light‐guiding core/sheath fibers are fabricated from two different refractive index (RI) polymers by coaxial electrospinning. The morphology and fiber diameter are analyzed with scanning electron and fluorescence microscopies. It is found that the diameter of the core and the thickness of the sheath could be varied from 100 to 400 nm by changing the concentration of the outer solution. The incorporation of a chromophore into the inner material confirmed the uniformity of the core/sheath structure in long segments of the fibers. The boundary is clearly seen: the core diameter and the thickness of the sheath are constant along the fiber axis in fluorescence images. The ejected beam is circular and light‐guided along the fiber axis as in an optical fiber.
834.
Large grain niobium has the potential of simplifying the production sequence and consequently reducing the cost of the superconducting RF cavities for ILC. To investigate the feasibility of fabrication and the possibility to achieve high gradient by large grain cavities, two 1.3GHz cavities were made of China large grain niobium and a series of vertical tests were carried out following several different
surfaces treatment procedures. Two cavities have both reached the high
gradient of more than 43MV/m repeatedly and the maximum accelerating field of 47.9MV/m has been achieved by China large grain niobium. This paper introduces the features of the fabrication and surface treatments on the large grain cavities and presents the preliminary results of the research. 相似文献
835.
Sang Youn Chae Ja Youn Choi Yoolim Kim Dang Le Tri Nguyen Oh‐Shim Joo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(46):16547-16551
Electrochemical and photoelectrochemical CO2 reductions were carried out with Re(bh‐bipy)(CO)3(OH2) cocatalysts in aqueous electrolytes. Competition between hydrogen evolution and CO2 reduction was observed under (photo)electrochemical conditions for both glassy carbon and CuInS2 electrodes. The partial current density for CO generation is limited even though the additional potential is applied. However, electrochemical hydrogen evolution was suppressed under photoelectrochemical conditions, and the selectivity and partial current density for CO were considerably increased when compared to the electrochemical reduction in an identical electrode/electrolyte system. This finding may provide insights into using semiconductor/liquid junctions for solar fuel devices to overcome the limitations of electrolysis systems with an external bias. 相似文献
836.
837.
Eunji Lee In‐Hyeok Park Huiyeong Ju Seulgi Kim Jong Hwa Jung Yoichi Habata Shim Sung Lee 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(33):11418-11422
A one‐pot reaction of the A1/A2‐thiopyridyl pillar[5]arene L with silver(I) trifluoroacetate in the presence of the linear dinitrile guest C8 , [CN(CH2)nCN, n=8], afforded the first example of a two‐dimensional (2D) poly‐pseudo‐rotaxane {[(μ4‐Ag)2( C8 @ L )2(μ ‐C8 )](CF3CO2)2}n. Surprisingly, in this structure the C8 guest not only threads into the pillar[5]arene unit but also crosslinks the 1D coordinative polymeric arrays. The formation of the 2D poly‐pseudo‐rotaxane is driven by an adaptive rearrangement of the components that minimizes the steric clashes not only between the threaded guests but also between the threaded and crosslinked guests where crosslinking occurs. A pathway for the formation of the 2D poly‐pseudo‐rotaxane is proposed. 相似文献
838.
Kyeongchan Noh Minsu Kim Sang-Hyun Lee Hwang-Sik Yun Tae-Hyeon Lim Yeongho Choi Ki-Ju Kim Yiran Jiang Keonwon Beom Minju Kim Young-Gwang Kim Pilwoo Lee Nuri Oh Bong Hoon Kim Chansun Shin Hyun Ho Lee Tae-Sik Yoon Moonsub Shim Seong-Yong Cho 《Current Applied Physics》2019,19(9):998-1005
The aging of ZnO nanoparticles in quantum dot light-emitting diode (QD-LED) structures was studied. Coarsening of as-synthesized ZnO nanoparticles is observed in both solution and thin film structures, which potentially deteriorates the performance of QD-LED devices over time. First, the temperature effect on ZnO coarsening was investigated, and it was revealed that aging of ZnO nanoparticles is faster at higher temperature due to a diffusion-controlled mechanism of nanoparticle coarsening. To observe aggregation of ZnO in the film state, the electron transporting part (ZnO/Al) of the QD-LED structure was prepared. The current density of a ZnO film and an electron-only device (QD/ZnO between two electrodes) was also measured. Resistance of the film increased as a function of aging time, which corresponded with observations of the ZnO film by optical microscopy. Aggregation of ZnO nanoparticles was directly measured by the root-mean-square value using atomic force microscopy. Ethanolamine (EA) stabilizer was added to the ZnO solution to disperse the ZnO nanoparticles without aggregation. The effect of EA on the surface passivation of the ZnO found to suppress pinhole formation, as revealed by scanning electron microscopy observations. Finally, the device lifetime was measured for QD-LEDs with EA-stabilized ZnO to understand the effect of ZnO aging on long-term QD-LED device operation. 相似文献
839.
840.