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931.
Hojin Ryu 《Physica B: Condensed Matter》2008,403(18):3195-3198
CaAl2O4:Eu2+ co-doped with varying concentrations of Er3+ was prepared by solid-state reaction method. Prepared materials with 1 mol% Eu2+ and 2-10 mol% of Er3+ were investigated for their photoluminescence properties. Phase, morphology and crystalline structure were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Broad band UV-excited luminescence was observed for CaAl2O4:Eu2+, Er3+ in the blue region (λmax=440 nm) due to transitions from 4f65d1 to the 4f7 configuration of the Eu2+ ion. The Er3+ ion co-doping generates deep traps, which results in longer decay time for phosphorescence. 相似文献
932.
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
933.
Choi Jung-Weon Ryu Hayeon Oh Wonzin Choi Sang-June 《Journal of Radioanalytical and Nuclear Chemistry》2019,320(2):329-336
The effect of Tf2N−, as a common anion in aqueous and ionic liquid (IL) phases, on Cs extraction in the IL system was investigated using C2mimTf2N as an IL and DCH18C6 as an extractant. The “common anion (Tf2N−) effect” operated via the movement of Cs+·Tf2N− from the aqueous phase into the IL phase by extraction in the form of Cs+·extractant·Tf2N−, without any traditional cation exchange. The extraction product was recovered as a precipitate using a small amount of IL, which facilitated precipitation via supersaturation.
相似文献934.
A series of amphiphilic graft copolymers of poly (vinylidene fluoride‐co‐chlorotrifluoroethylene)‐g‐poly(2‐vinyl pyridine), P (VDF‐co‐CTFE)‐g‐P2VP, with different degrees of P2VP grafting (from 26.3 to 45.6 wt%) was synthesized via one‐pot atom transfer radical polymerization (ATRP). The amphiphilic properties of P (VDF‐co‐CTFE)‐g‐P2VP graft copolymers allowed itself to self‐assemble into nanoscale structures. P (VDF‐co‐CTFE)‐g‐P2VP graft copolymers were introduced into neat P (VDF‐co‐CTFE) as additives to form blending membranes. When two different solvents, N‐methyl‐2‐pyrrolidone (NMP) and dimethylformamide (DMF), were used, specific organized crystalline structures were observed only in the NMP systems. P (VDF‐co‐CTFE)‐g‐P2VP played a pivotal role in controlling the morphology and pore structure of membranes. The water flux of the membranes increased from 57.2 to 310.1 L m?2 h?1 bar?1 with an increase in the PVDF‐co‐CTFE‐g‐P2VP loading (from 0 to 30 wt%) due to increased porosity and hydrophilicity. The flux recovery ratio (FRR) increased from 67.03% to 87.18%, and the irreversible fouling (Rir) decreased from 32.97% to 12.82%. Moreover, the pure gas permeance of the membranes with respect to N2 was as high as 6.2 × 104 GPU (1 GPU = 10–6 cm3[STP]/[s cm2 cmHg]), indicating their possible use as a porous polymer support for gas separation applications. 相似文献
935.
We have synthesized an amphiphilic triblock coil-rod-coil molecule consisting of a rigid aromatic building block and poly(ethylene oxide). The coil-rod-coil molecule was observed to assemble into a cylindrical micelle structure in aqueous solution. Notably, addition of a small amount of a rod-coil-rod molecule into the cylindrical micellar solution can induce the anisotropic gelation due to dynamic interconnection of adjacent cylindrical micelles via hydrophobic and pi-pi interactions. Depending on the concentration of the rod-coil-rod molecule, the nematic gel can be reversibly switched into an isotropic solution of cylindrical micelles. 相似文献
936.
Ryu I Kreimerman S Araki F Nishitani S Oderaotoshi Y Minakata S Komatsu M 《Journal of the American Chemical Society》2002,124(15):3812-3813
Cascade reactions of 4-alkenyl iodides, involving a carbonylation-cyclization-carbonylation sequence, were accomplished by a hnu/Pd system. The stereochemical outcomes suggest that radical carbonylation and subsequent acyl radical cyclization may be involved in this reaction. 相似文献
937.
938.
Mee-Yi Ryu E KuokstisC.Q Chen J.W YangG Simin M Asif KhanG.G Sim P.W Yu 《Solid State Communications》2003,126(6):329-332
A comparative combined study of photoluminescence (PL), PL kinetics, stimulated emission (SE) and photoreflectance (PR) properties in InxGa1−xN epilayers is carried out in the composition range 0≤x≤0.19. In-incorporation up to 4% leads to the sufficient longer radiative recombination decay time due to the decrease in non-radiative recombination channels, which are peculiar to GaN, and band-to-band optical transitions predominate the spontaneous PL spectrum. Further In-incorporation (x>4%) leads to the localization of carriers and/or excitons at band-tails in the In-rich areas. Correlation between the position of dominant low-energy PR oscillation due to the main band gap and SE peak position shows that band-to-band transitions are responsible for lasing and dominate the PL spectrum in all highly pumped InxGa1−xN samples. 相似文献
939.
Both electrical and optical activation studies of Si-implanted Al0.18Ga0.82N have been made as a function of anneal time and anneal temperature to obtain maximum possible electrical activation efficiency. Silicon ions were implanted at 200 keV with doses of 5×1014 and 1×1015 cm−2, and the samples were annealed from 1100 to 1250 °C for 5-25 min with a 500 Å thick AlN cap in a nitrogen environment. The electrical activation efficiency and Hall mobility increase with anneal time and anneal temperature. Nearly 100 and 95% electrical activation efficiencies were obtained for Si-implanted Al0.18Ga0.82N with doses of 5×1014 and 1×1015 cm−2 and annealing at 1250 and 1200 °C for 25 min, respectively. The photoluminescence measurements show an excellent implantation damage recovery after annealing at these optimum anneal conditions, showing a strong near band emission. These optical results correlate well with the electrical results. 相似文献
940.
Kimun Ryu 《Journal of Mathematical Analysis and Applications》2003,283(1):46-65
In this paper, we discuss the existence of positive solutions to certain nonlinear elliptic systems representing competitive interaction with self-cross diffusions between two species. The method employed is the fixed point index theory in a positive cone. Sufficient conditions for the existence of positive solutions are provided. 相似文献