近红外发光Ag2S-CdS 核壳结构水溶性量子点的合成及光学性质

本文以谷胱甘肽(GSH)作为表面活性剂,采用两步法,先生成Ag2S核,再生长CdS,得到了高质量的Ag2S-CdS核壳结构水溶性量子点。我们用XRD,TEM,HRTEM和EDS研究了产物的结构,形貌和组分,用紫外可见吸收光谱和荧光发射光谱研究了所得量子点的光学性质,同时考察了反应时间,GSH的量,Ag和S源前驱物的含量对量子点光学性质的影响。实验结果表明量子点稳定性好,荧光寿命长,可在710~718 nm近红外区域发光。在核生长过程中,Ag和S源的含量同时影响量子点的发光位置和强度,而GSH量和壳层生长中S源的量几乎只影响近红外发光强度,发光位置保持不变。不同的量子点光学性质可能来源于量子点中组分及表面缺陷的分布。     

Hydrophilic Conjugated Polymers with Large Bandgaps and Deep‐Lying HOMO Levels as an Efficient Cathode Interlayer in Inverted Polymer Solar Cells

Two hydrophilic conjugated polymers, PmP‐NOH and PmP36F‐NOH, with polar diethanol­amine on the side chains and main chain structures of poly(meta‐phenylene) and poly(meta‐phenylene‐alt‐3,6‐fluorene), respectively, are successfully synthesized. The films of PmP‐NOH and PmP36F‐NOH show absorption edges at 340 and 343 nm, respectively. The calculated optical bandgaps of the two polymers are 3.65 and 3.62 eV, respectively, the largest ones so far reported for hydrophilic conjugated polymers. PmP‐NOH and PmP36F‐NOH also possess deep‐lying highest occupied molecular orbital levels of −6.19 and −6.15 eV, respectively. Inserting PmP‐NOH and PmP36F‐NOH as a cathode interlayer in inverted polymer solar cells with a PTB7/PC₇₁BM blend as the active layer, high power conversion efficiencies of 8.58% and 8.33%, respectively, are achieved, demonstrating that the two hydrophilic polymers are excellent interlayers for efficient inverted polymer solar cells.

     

有界平均振幅空间上的乘法算子

有界平均振幅空间的研究在算子理论及全纯空间的研究中具有重要的作用.主要研究了有界平均振幅空间上乘法算子的性质,并且得到了托普里兹算子有界性及紧性的条件.     

超临界CO_2在内螺纹管内换热特性研究

建立了外径为3 mm的内螺纹管三维实体模型,使用Fluent软件研究了在不同的进口雷诺数和操作压力下超临界二氧化碳在水平内螺纹管内的流动与传热特性。研究表明:不同截面局部换热系数和相同流体局部平均温度下的局部换热系数均随着冷却压力的增大而增大;相同流体局部平均温度下的局部换热系数随着进口雷诺数的增加而增大;不同冷却压力和进口雷诺数下,流体局部平均温度越接近超临界二氧化碳的临界点温度,局部换热系数也就越大。     

Towards Long‐Term Photostability of Nickel Hydroxide/BiVO4 Photoanodes for Oxygen Evolution Catalysts via In Situ Catalyst Tuning

Increasing long‐term photostability of BiVO₄ photoelectrode is an important issue for solar water splitting. The NiOOH oxygen evolution catalyst (OEC) has fast water oxidation kinetics compared to the FeOOH OEC. However, it generally shows a lower photoresponse and poor stability because of the more substantial interface recombination at the NiOOH/BiVO₄ junction. Herein, we utilize a plasma etching approach to reduce both interface/surface recombination at NiOOH/BiVO₄ and NiOOH/electrolyte junctions. Further, adding Fe²⁺ into the borate buffer electrolyte alleviates the active but unstable character of etched‐NiOOH/BiVO₄, leading to an outstanding oxygen evolution over 200 h. The improved charge transfer and photostability can be attributed to the active defects and a mixture of NiOOH/NiO/Ni in OEC induced by plasma etching. Metallic Ni acts as the ion source for the in situ generation of the NiFe OEC over long‐term durability.     

长链卟啉金属配合物的合成与性质研究

通过带有12条长链的卟啉配体Meso-5, 10, 15, 20-四[3, 4, 5-三（辛酰氧基）苯基]卟啉（P）,与金属氯化盐（ZnCl₂, CuCl₂, CoCl₂, NiCl₂, CdCl₂, MnCl₂, PdCl₂, PtCl₂）发生配位反应,合成出长链卟啉的8种金属配合物：Zn-P, Cu-P, Co-P, Ni-P, Cd-P, Mn-P, Pd-P, Pt-P,通过UV – Vis, ¹H NMR, IR,HR-MS进行了表征,研究了不同金属卟啉配合物合成的反应条件,并通过荧光光谱、荧光寿命等方法研究了卟啉化合物的发光性质。      

Prediction error criterion for selecting variables in a linear regression model

Several criteria, such as CV, C _p , AIC, CAIC, and MAIC, are used for selecting variables in linear regression models. It might be noted that C _p has been proposed as an estimator of the expected standardized prediction error, although the target risk function of CV might be regarded as the expected prediction error R _PE. On the other hand, the target risk function of AIC, CAIC, and MAIC is the expected log-predictive likelihood. In this paper, we propose a prediction error criterion, PE, which is an estimator of the expected prediction error R _PE. Consequently, it is also a competitor of CV. Results of this study show that PE is an unbiased estimator when the true model is contained in the full model. The property is shown without the assumption of normality. In fact, PE is demonstrated as more faithful for its risk function than CV. The prediction error criterion PE is extended to the multivariate case. Furthermore, using simulations, we examine some peculiarities of all these criteria.     

平面图线性色数的一个上界

如果图G的一个正常染色满足染任意两种颜色的顶点集合导出的子图是一些点不交的路的并,则称这个正常染色为图G的线性染色．图G的线性色数用lc（G）表示,是指G的所有线性染色中所用的最少颜色的个数．证明了：若G是一个最大度△（G）≠5,6的平面图,则lc（G）≤2△（G）．     

Thermal loading induced near-infrared broadband upconversion emission of Sm-doped β-NaYbF4 nano-phosphors

A non-closed hydrothermal synthetic processing is improved to synthesize Sm³⁺ doped β-NaYbF₄ nano-phosphors at 98 °C without any high-temperature and high-pressure treatments as a final step. Novel green, red, and near-infrared broadband (799-873 nm) upconversion emissions of Sm³⁺-doped β-NaYbF₄ nano-phosphors under 980 nm excitation are observed. These UC emissions can be assigned to the Sm³⁺ transitions of ⁴G_J, ⁴F_3/2 and ⁶F_11/2→⁶H_J. The half-width of 873 nm emission band is broadened nearly two-fold through the annealing treatment for nano-phosphors. The upconversion process in Yb³⁺-Sm³⁺ system is discussed based on energy transfer mechanisms.