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利用N-甲基甘氨酸、2,4-二硝基苯甲醛和C60反应,合成分离出了含有两个硝基的新型富勒烯吡咯烷衍生物1,并对其工艺条件进行了研究,探讨了反应物剂量比、温度和时间对产物1产率的影响,得到了合成产物1的最佳工艺条件:反应物剂量比为1∶2∶6、温度为95 ℃、反应时间为40 h,此时产物1产率可达到65.8%(以消耗的C60计)。同时用1H NMR、FT-IR、MS、UV-Vis等光谱手段确定了产物1的分子结构。 相似文献
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La0.7Ca0.3MnO3:xZn0.95Co0.05O (x=0.0,0.05, 0.1, 0.15mol) composites are prepared by a sol-gel process. X- ray diffraction and energy diffraction spectroscopy reveal that there is no evidence of a reaction between the La0.7 Ca0.3 MnO3 (LCMO) and Zn0.95Co0.05 O (ZCO). Magnetization M, Curie temperature Tc and metal-insulator transition temperatures Tp are observed to decrease with increasing ZCO content. Compared with x = 0.0, a great enhancement in the magnetoresistance (MR) is observed at around Tc for x = 0.05, 0.10, 0.15. Based on the tunneling MR and percolation models, this great change of MR is well explained. 相似文献
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The transparent TiO2 thin films coated on fused-SiO2 substrates were prepared by the sol–gel method and spin-coating technique. Effects of calcination temperature on crystal
structure, grain size, surface texture, and light transmittance of the films were investigated. After calcining at 600–1,200 °C,
the thicknesses of the TiO2 films were all around 80 nm and the molecular structures of the films were anatase, even at 1,200 °C. The calcined TiO2 films had the ultraviolet light (wavelength 200–400 nm) transmittances of ≤29% and the visible light (wavelength 400–800 nm)
transmittance of ≥72%. By photocatalytically decomposing the methylene blue (MB) in water, the photocatalytic activities of
the TiO2 thin films were measured and represented using the characteristic time constant (τ) for the MB degradation. While the films
prepared at 1,000 and 1,200 °C photodecomposed about 54 mol% of the MB in water (the corresponding τ ≈ 14.8 h) after exposing to 365-nm UV light for 12 h, the films prepared at 600 and 800 °C had smaller τ (≈9.0 h) and photodecomposed
about 74 mol% of the MB in water at the same testing conditions. 相似文献
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利用化学气相沉积法, 在铜箔上成功制备出形似自然界中刺球花的ZnO纳米花结构. 实验进一步研究了氧气和氩气流量比例分别为1:150, 1:200, 1:250和1:400时对ZnO纳米花结构和性能的影响. 结果表明, ZnO纳米花上的ZnO纳米棒的长径比随氧气氛的减少而减小; 在氧气和氩气流量比例为1:250时制备出的ZnO纳米花尺寸均匀、形貌均一、花型结构最完美. ZnO 纳米花的室温光致发光谱表明, 随着氧气氛的减少, 可见区域的发光从一个波包变成一个宽峰, 且与锌空位相关的缺陷发光峰在减弱, 与氧空位相关的缺陷发光峰在增强. 基于实验结果, 提出了一种在铜箔上制备ZnO纳米花结构的生长模型. 相似文献
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Structure and luminescence of Ca2Si5N8:Eu^2+ phosphor for warm white light-emitting diodes
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We have synthesized Ca 2 Si 5 N 8:Eu 2+ phosphor through a solid-state reaction and investigated its structural and luminescent properties.Our Rietveld refinement of the crystal structure of Ca 1.9 Eu 0.1 Si 5 N 8 reveals that Eu atoms substituting for Ca atoms occupy two crystallographic positions.Between 10 K and 300 K,Ca 2 Si 5 N 8:Eu 2+ phosphor shows a broad red emission band centred at ~1.97 eV-2.01 eV.The gravity centre of the excitation band is located at 3.0 eV-3.31 eV.The centroid shift of the 5d levels of Eu 2+ is determined to be ~1.17 eV,and the red-shift of the lowest absorption band to be ~ 0.54 eV due to the crystal field splitting.We have analysed the temperature dependence of PL by using a configuration coordinate model.The Huang-Rhys parameter S=6.0,the phonon energy ν=52 meV,and the Stokes shift S=0.57 eV are obtained.The emission intensity maximum occurring at ~200 K can be explained by a trapping effect.Both photoluminescence (PL) emission intensity and decay time decrease with temperature increasing beyond 200 K due to the non-radiative process. 相似文献
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