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41.
Qinglin Sai Changtai Xia Han Rao Xiaodong Xu Peng Xu 《Journal of luminescence》2011,131(11):2359-2364
The Mn-, Cr-doped and Mn, Cr-co-doped MgAl2O4 powders have been synthesized via a gel-solid reaction method. Energy transfer from Mn2+ to Cr3+ has been observed for the first time in the co-doped MgAl2O4 phosphors. When excited with blue light with a wavelength of 450 nm at room temperature, both green emission from Mn2+ around 520 nm and red emission from Cr3+ around 675and 693 nm were generated. Moreover, the color of the emission can be modified by controlling the doping concentrations of Mn2+ and Cr3+. Therefore, MgAl2O4: Mn2+, Cr3+ could be used as a single-phased phosphor for white LED with a blue LED chip. The energy transfer in terms of Mn2+ to Cr3+ is determined by means of radiation and reabsorption. 相似文献
42.
Gwan-Hyoung Lee 《Journal of luminescence》2011,131(12):2606-2611
The correlation between the crystal structure and luminescent properties of Eu3+-doped metal tungstate phosphors for white LEDs was investigated. Red-emitting A4−3x(WO4)2:Eux3+ (A=Li, Na, K) and B(4−3x)/2(WO4)2:Eux3+ (B=Mg, Ca, Sr) phosphors were synthesized by solid-state reactions. The findings confirmed that these phosphors exhibited a strong absorption in the near UV to green range, due to the intra-configurational 4f-4f electron transition of Eu3+ ions. The high doping concentration of Eu3+ enhanced the absorption of near UV light and red emission without any detectable concentration quenching. Based on the results of a Rietveld refinement, it was attributed to the unique crystal structure. In the crystal structure of the Eu3+-doped metal tungstate phosphor, the critical energy transfer distance is larger than 5 Å so that exchange interactions between Eu3+ ions would occur with difficulty, even at a high doping concentration. The energy transfer between Eu3+ ions, which causes a decrease in red emission with increasing concentration of Eu3+, appears to be due to electric multi-polar interactions. In addition, the Eu-O distance in the host lattice affected the shape of emission spectrum by splitting of emission peak at the 5D0→7F2 transition of Eu3+. 相似文献
43.
两原子间隔一定距离且两原子跃迁频率接近时,两原子之间可发生能量传递.理论研究了供能原子和受能原子两共振原子的能量传递.求解薛定谔方程得出两原子共振能量传递效率.结果表明,供能原子在真空场中的激发态寿命在能量传递效率中起到十分重要的作用.能量传递效率与两原子间距离的负三次幂的正弦值的平方成正比,在一阶近似条件下,与两原子间距离的6次方成反比.以供能原子处于激发态时为初始时刻,能量从初始时刻随时间由供能原子向受能原子传递,对受能原子的单次能量提取的最大值大约在供能原子寿命的2/3时刻;对受能原子的连续N次能量提取的最大值,每次提取时间大约在供能原子寿命的1/2时刻. 相似文献
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基于荧光共振能量转移的原理,以修饰于核酸适体上的FAM作为能量供体,以氧化石墨烯作为能量受体,构建了荧光适体传感器,分别对不同浓度的胰岛素和多巴胺进行检测.结果表明,胰岛素的线性检测范围为0.05~10μmol/L,多巴胺的线性检测范围为1~500μmol/L,当胰岛素和多巴胺检测浓度相同时,胰岛素检测信号远强于多巴胺.对胰岛素和多巴胺分别进行特异性实验,发现该传感器对胰岛素和多巴胺有较强的特异性.说明基于荧光共振能量转移的核酸适体传感器不仅可实现多种物质的微量检测,还具有较强的选择性,在生物和医药检测领域应用前景广阔. 相似文献
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The theory for a general departure function, f, for laser-irradiated cavities was previously developed to estimate laser energy coupling to an opaque solid target as a function of heat transfer and the cavity shape and size. In this article, a specific form of f is calculated for ultraviolet (UV) laser ablation of copper (Cu) and aluminum (Al) targets. Methods are also given for calculating the geometric factor, a, and experimentally determining the heat transfer parameter, ν, which is shown for this form of f to be the intensity-dependent effective reflectivity of the material. Experimental results for different gauges of laser energy coupling with a solid target are given and compared to calculations of net absorbed energy based on f and the incident laser energy. Using the simplified cavity analysis, the results demonstrate that the experimental values for f fall within the limits predicted by the theory, and that energy coupling can be predicted to within a mean of 2% of experimental gauges. Neglecting the factors in f from calculations of energy coupling can lead to large errors for laser-irradiated cavities, establishing that both cavity shape and heat transfer should be simultaneously considered. In addition, a first-order sensitivity analysis based on f shows that the initial rate of change in material removal strongly increases with reflectivity, which can lead to runaway cavity formation for highly reflective materials. 相似文献
50.
文中主要对回热器中的能流及其能流分量进行了模拟 ,并在此基础上分析了能流及其分量对热声热机的影响 ,为更深地理解热声热机中所发生的能量转换现象 ,更好地设计热声热机提供有价值的依据和参考。 相似文献