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71.
In the past year, emission-tunable crystals based on the rare-earth (RE) ions as luminescent center have been frequently reported for use in UV and blue converted white LEDs, but so far tuning the non-RE Bi3+ related emissions through the crystal field modulation is still not discovered in the perovskite crystals. In this work, we design and report a type of Bi3+ doped La2(Znx,Mg1-x)TiO6 (0 ≤ x ≤ 1) perovskite solid solutions, which enable showing the tunable Bi3+ excitation and emission positions. The XRD results show that gradual substitution of smaller Mg2+ ions with larger Zn2+ ions can lead to the blue-shifting of X-ray diffraction (XRD) position, revealing the expansion of cell lattice. Together with structural analysis, our refined XRD and time-resolved spectral results reveal that there is only one type of La site available for Bi3+ substitution. With this regular crystal lattice change, the crystal field strength around Bi3+ ions is found to vary regularly, allowing to realization of the excitation and emission spectral tuning, i.e., the Bi3+ excitation and emission positions as the Mg ions are replaced by the Zn ions can tune from 348?nm to 392?nm and from 405?nm to 433?nm, respectively. This Bi3+ spectral tuning peak after calculated by the dielectric chemical bond theory features a linear relationship with the crystal field strength and, thus, is ascribed to the crystal field modulation. On basis of the La2(Zn0.4,Mg0.6)TiO6 blue, SrGa2S4:Eu2+ green and Y2O3:Eu3+ red phosphors, a UV converted warm white LED device with desirable color rendering index (CRI) of 78, correlated color temperature (CCT) of 3650 K and good luminous efficacy of 118.13?lm/W, is fabricated. This work provides new insights into using the crystal-field modulation to discover more Bi3+ emission-tunable crystals for white LEDs in the future. 相似文献
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建立了利用填充柱测定液化石油气中二甲醚含量的气相色谱方法。采用水浴完全气化样品,气体进样六通阀进样,热导池检测器检测。定量标准曲线的相关系数大于0.999,最低检测限(S/N=3)为0.8%(V/V),该方法简便快速,已成功地应用于液化石油气样品的测定。 相似文献
75.
Microwave plasma chemical vapor deposition (MPCVD) has gained increasing attention as a feasible and effective way to produce large, high-quality, single-crystal diamonds. However, the growth of polycrystalline diamond on the periphery of the seed crystal and the cracking generated by the internal stress during the growing process lead to significant decline of the quality and integrity of the CVD diamond, thus increasing the difficulty of synthesizing large diamond layers. Although optimized growth parameters and refined substrate holders have been employed by some researchers to improve the periphery quality of CVD diamond layers, more research needs to be done in this area. In this study, we used a specially designed substrate holder with a circular recess, in which the seed crystal was placed. By designing substrate holders with different recess depths and a seed crystal with different side-surface crystallographic orientations, we aimed to determine the influence of the recess depths and the crystallographic orientation of seed sides on the growth quality according to polarizing microscope, laser Raman spectroscopy, UV fluorescence imaging, and photoluminescence (PL) mapping measurements. The results demonstrate that as the recess depth increases, the amount of polycrystalline diamonds and the internal stress on the periphery are controlled effectively. The crystalline quality is improved, and the growth rate is decreased. In addition, compared to the periphery with {100} seed sides, the periphery with {110} seed sides displays better crystalline quality, lower internal stress, and fewer polycrystalline diamonds after growth, which is probably due to the intrinsic nature of the growth steps propagating on the {100} diamond surface and the effect of nitrogen atoms on the growing process in the diamond lattice. 相似文献
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为阐明烫漂方式对热风干燥苹果片品质特性的影响,采用热水、蒸汽和微波对苹果片进行烫漂处理,测定苹果片在烫漂和干燥过程中的色泽、多酚及其抗氧化活性的变化情况。结果表明,热水烫漂苹果片的干燥时间最短,为270 min;不同烫漂方式对苹果片褐变有显著影响(P<0.05),其中热水烫漂的苹果片色泽变化最小,微波烫漂的苹果片色泽最差;与鲜样相比,烫漂方式对苹果片还原糖含量影响较小;干燥过程中微波烫漂的苹果片中产生的5-羟甲基糠醛含量最高,蒸汽烫漂次之,热水烫漂最低;苹果片经热水烫漂和干燥后维生素C损失率分别为34%和52%,而蒸汽烫漂和微波烫漂的苹果片中维生素C损失率较小;热水烫漂的苹果脆片总酚含量最高,达到11.82 mg GAE/g DW;苹果片经烫漂处理后游离多酚和结合多酚单体无显著性变化(P>0.05),但干燥后,所有样品中结合多酚单体含量均显著提高(P<0.05)而游离多酚单体的含量无显著性变化(P>0.05),表明3种烫漂方式都有利于多酚单体的保留;多酚抗氧化能力实验表明烫漂和干燥后苹果片中结合多酚抗氧化活性有显著性变化(P<0.05),其中热水烫漂的苹果... 相似文献
79.
Application of Headspace Solid-Phase Microextraction and Multivariate Analysis for the Differentiation Between Edible Oils and Waste Cooking Oil 总被引:2,自引:0,他引:2
Waste cooking oil (WCO) can be recovered and processed into animal feed additives and bio-oils after purification. Unfortunately, edible oils (EOs) were adulterated with refining and purificating WCO, especially in China. Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) analysis has been applied for the determination of the characteristic volatile profile of pure EOs (sunflower oil, rapeseed oil, and olive oil), WCO, and their mixture. Coupling the HS-SPME/GC-MS analysis data with multivariate analysis (MVA) techniques, such as principal components analysis (PCA) and cluster analysis, it has been possible to classify EOs and WCO on the basis of different volatile compounds. Fresh EOs were characterized by a low number of volatile compounds, while WCO and its mixture are characterized by a prevalence of hexanal, (E)-2-heptenal, hexanoic acid, (E,E)-2,4-decadienal, p-allylanisole esdragol, dihydroanethole, anethole, eugenol, and curcumene. PCA showed similarities in clustering of the data obtained by GC-MS. MVA facilitates comparison of chromatographic profiles of volatile compounds characteristic for various EOs, WCO, and the different oil mixture for monitoring oil quality. MVA has been successfully applied to the analysis of adulterated EOs by the addition of cheaper WCO. 相似文献
80.
采用半互穿网络技术和原位自由基聚合将生物相容性和吸水性优良的丝胶蛋白(SS)引入聚异丙基丙烯酰胺-硅酸镁锂(Poly(NIPAm-LMSH))纳米复合凝胶网络,制得高溶胀度和快速响应的SS/Poly(NIPAm-LMSH)纳米复合凝胶,研究了丝胶含量对纳米复合凝胶的孔洞形态、溶胀动力学、结晶结构、相容性和稳定性的影响。结果表明:冷冻干燥后的SS/Poly(NIPAm-LMSH)水凝胶呈多孔结构,孔洞尺寸为20~30 μm,孔壁薄,为1~4 μm,且随丝胶含量增加而由多面体结构变为狭长形的层状结构。相比于溶胀平衡的纯纳米复合凝胶,丝胶的引入显著提高了其溶胀度,溶胀初期属于Non-Fickian扩散,37 ℃ 10 min内即可失去90%的水。丝胶在凝胶中具有良好的相容性,SS/Poly(NIPAm-LMSH)纳米复合凝胶的 Tg为141~144 ℃,最大热分解温度为365~373 ℃,质量残留率随丝胶含量的增加而增大。 相似文献