Low-threshold interband cascade lasers operating above room temperature

Mid-IR type-II interband cascade lasers were demonstrated in pulsed mode at temperatures up to 325 K and in continuous mode up to 200 K. At 80 K, the threshold current density was 8.9 A/cm² and a continuous wave output power of 140 mW/facet was obtained.     

多组分单体接枝聚丙烯/尼龙6反应共混物结晶行为研究

用多组分熔融接枝的方法将甲基丙烯酸缩水甘油酯 (GMA)和苯乙烯 (St)共同接枝到聚丙烯 (PP)上 ,制得具有较高GMA接枝率的多单体接枝聚丙烯 ,PP g (GMA co St) .将PP g (GMA co St)与尼龙 6 (PA6 )进行共混 ,利用扫描电镜 (SEM) ,差示扫描量热计 (DSC)和广角X射线衍射 (WAXD)对共混物的形态和结晶进行了研究 .在共混过程中 ,PP g (GMA co St)与PA6反应原位生成了PP g PA6 ,有效改善了共混物的相容性 ,分散相尺寸明显减小 .在PP g (GMA co St) PA6为 3 7的体系中 ,PP g (GMA co St)出现分级结晶现象 ,其在较低温度下的结晶属于均相成核结晶 .在PP g (GMA co St) PA6为 7 3的体系中 ,由于PA6相分散细微 ,在通常结晶温度下不结晶 ,而是在低温下均相成核与PP g (GMA co St)同时结晶 .WAXD证实体系中接枝PP ,PA6为分别结晶 ,无共晶或新的晶型产生     

聚酰胺修饰碳糊电极测定槲皮素的研究

用聚酰胺修饰碳糊电极在ｐＨ３６０的Ｂｒｉｔｏｎ－Ｒｏｂｉｎｓｏｎ缓冲溶液中，将槲皮素开路富集一定时间后，从０４５Ｖ（ｖｓ．Ａｇ／ＡｇＣｌ）向阴极化扫描至－０５５Ｖ获得Ｉ－Ｅ曲线。槲皮素的峰电位为０１８Ｖ。峰电流与槲皮素浓度在１０～４００μｍｏｌ／Ｌ范围内呈良好的线性关系。所拟定方法用于芦丁水解产物测定，结果满意。     

聚(丁二酸丁二酯-co-丁二酸丙二酯)的等温结晶行为研究

以1,4-丁二酸、1,4-丁二醇和1,3-丙二醇为原料通过直接熔融缩聚法合成了聚丁二酸丁二酯(PBS),聚丁二酸丙二酯(PPS)和聚(丁二酸丁二酯-co-丁二酸丙二酯)(PBSPS)等脂肪族聚酯.利用1H-NMR,WAXD,DSC和POM等研究了聚酯的结晶结构和结晶动力学过程等结晶行为.PBSPS的结晶晶型与PBS一致,说明只有丁二酸丁二酯(BS)单元结晶而丁二酸丙二酯(PS)单元处于无定形区.聚酯等温结晶后,在升温熔融过程中出现了多重熔融峰.分析表明多重熔融峰主要来自于聚酯升温过程中的熔融-重结晶行为.利用Avrami方程分析了聚酯的等温结晶动力学,Avrami指数n为2.2~2.8,说明聚酯等温结晶时主要以异相成核的三维生长方式进行;随着PS单元的增多,聚酯的表观结晶活化能升高,也就是说BS单元的结晶变得困难.POM观察到聚酯等温结晶时都出现了环带球晶现象,球晶形态会随着结晶温度和化学结构差异而改变.     

生物可降解聚丁二酸/苯基丁二酸丁二醇酯系列共聚物的合成及其结晶行为

合成了一系列聚丁二酸/苯基丁二酸丁二醇共聚酯(PBSBS),利用DSC、1H-NMR和X射线等测试手段对共聚物组成、热力学性能、结晶性能、等温结晶行为进行了表征和研究.结果表明,含苯基的共聚单元的引入显著改变了聚丁二酸丁二醇酯(PBS)的热力学性能4,利用Hoffman-Week曲线得到的共聚物平衡熔点随共聚组分含量的增加显著降低,玻璃化转变温度则明显升高,结晶熔点符合无规共聚物的Flory方程.此外,利用Avrami方程对均聚物PBS以及共聚物PBSBS-10分别进行了等温结晶行为研究,结果表明共聚使结晶速率降低,PBS和PBSBS-10的Avrami指数分别介于2.8~3.0和2.7~2.9之间,结晶方式为三维生长异相成核,X射线测试结果表明共聚不影响晶体结构.     

四唑及其衍生物的理论研究（6）

对7个肼基四唑衍生物进行了HF／6－31G水平的几何构型全优化及MP2／6－31G／／HF／6－31G水平的总能量计算．结果表明，四唑环基本上取平面构型，肼基不与环共面．键长与重叠布居之间不存在平行关系．环上N1和N4原子荷负电多、利于质子化．1H．肼基四唑的HOMO－LUMO能级差（△E）较2H式的大，中性分子的△E教相应的负离子的大．还计算研究了7个标题物的红外光谱并由此求得了它们的热力学性质．     

Finite iterative algorithm for the symmetric periodic least squares solutions of a class of periodic Sylvester matrix equations

Numerical Algorithms - The present work proposes a finite iterative algorithm to find the least squares solutions of periodic matrix equations over symmetric ξ-periodic matrices. By this...     

Enantioselective Recognition for Carboxylic Acids by Novel Chiral Macrocyclic Polyamides Derived from L-/D-tartaric Acid

The enantioselectivity of chiral macrocyclic polyamides 1–3 derived from L-/D-tartaric acid was investigated by using ¹H NMR. All the macrocycles exhibited certain chiral recognition towards the enantiomers of the racemic carboxylic acids we had chosen. As a chiral solvating agent, the compound 3 has the excellent enantiomeric discriminating ability for mandelic acids and its derivatives, containing an α-OH at the chiral carbon, while the compound 2 has the best enantioselectivity towards dibenzoyltartaric acid. The molar ratio and the association constants of the compound 3 with each of the enantiomers of some guest molecules were determined by using the Job's plots and a nonlinear leastsquares fitting method, respectively. The effect of the structure of the hosts or guests on the enantioselectivity of the compound 1–3 has been explored.     

Highly porous magnetite/graphene nanocomposites for a solid-state electrochemiluminescence sensor on paper-based chips

Graphene-nanosheet-based highly porous magnetite nanocomposites (GN-HPMNs) have been prepared using a simple solvothermal method and used as an immobilization matrix for the fabrication of a solid-state electrochemiluminescence (ECL) sensor on paper-based chips. Highly porous Fe₃O₄ nanocrystal clusters were coated with acrylate and wrapped tightly on the skeleton of graphene nanosheets. The structures and sizes of the GN-HPMNs could be tuned by varying the proportions of the solvents ethylene glycol and diethylene glycol. Then, the relatively highly porous ones with an average diameter of about 65 nm were combined with Nafion to form composite films on an electrode surface for immobilization of Ru(bpy)₃ ²⁺ (bpy is 2,2′-bipyridine). Because of their porosity, negatively charged surface, and cooperative characteristics of magnetic nanomaterials and graphene, under an external magnetic field, the GN-HPMNs ensured effective immobilization, excellent electron transfer, and long-term stability of Ru(bpy)₃ ²⁺ in the composite film. The sensor developed exhibited excellent reproducibility with a relative standard deviation of 0.65 % for 30 continuous cycles. It was found to be much more favorable for detecting compounds containing tertiary amino groups and DNAs with guanine and adenine. A detection limit (signal-to-noise ratio of 3) of 5.0 nM was obtained for tripropylamine. As an application example, 0.5 nM single-nucleotide mismatch could be detected. This was the first attempt to introduce magnetic nanomaterials and an external magnetic field into paper-based chips. The sensor developed has the advantages of high sensitivity, good stability, and wide potential applicability as well as simplicity, low cost, and good disposability.