吡唑-吡啶铕配合物的合成、结构及荧光效应

以硝酸铕为金属源,2,6-二-[3-(5-苯基-1-氢-吡唑基)]吡啶(L)为配体,在水热反应条件下合成了一种新型配合物Eu(L)(MeOH)(NO₃)₃。 通过元素分析、红外光谱、热重分析、X射线粉末衍射以及X射线单晶衍射方法对该配合物进行了表征。 结构分析表明,配合物的中心金属为九配位,每个中心金属铕原子与L配体中的3个N原子和硝酸根离子和配位甲醇分子上的6个氧原子配位,形成轻微扭曲的三帽三角棱柱体的空间构型。 荧光性能研究发现,该配合物对金属离子铜和镍有较强的荧光猝灭效应。即使在其它竞争金属离子的存在下,配合物仍然可以选择性地检测Cu²⁺,但对选择性的检测Ni²⁺有一定影响。     

面式、经式异构体的钴-氨基硫脲配合物作为催化剂应用于可见光催化分解水产氢（英文）

近年来,作为替代贵金属铂催化剂的铁、钴和镍等非贵金属配合物分子催化剂,由于合成容易、结构调控方便以及具有良好的催化活性等特点,成为均相光催化分解水产氢领域的研究热点.其中,钴配合物具有结构简单、成本低廉、容易合成以及具有理想的氧化还原电位等优势,更是光催化分解水产氢领域的优先研究对象.由于稳定性及溶解度的问题,在已报道的研究工作中,大部分钴配合物测试环境均在有机溶剂或有机溶剂/水混合溶剂中.因此,寻找水溶性良好的钴配合物催化剂成为了目前的均相光催化分解水产氢领域的研究焦点之一.在此之前,氨基硫脲配合物已经广泛用于生物和制药等研究,例如:抗氧化、抗菌以及抗病毒等领域.而在人工光合产氢领域采用氨基硫脲配合物作为催化剂的例子则比较罕见.在该项研究中,我们报道了一对水溶性较好(40 mg mL~(–1),20°C)且具有几何异构特征的八面体钴-氨基硫脲配合物作为光、电催化质子还原产氢的分子催化剂.这对几何异构体分别为:面式异构体[Co(Htsc)_3]Cl_3·3H_2O(C1,Htsc=氨基硫脲配体)和经式异构体[Co(Htsc)_3]Cl_3·4H_2O(C2).我们将几何异构体C1和C2作为水还原分子催化剂,与有机光敏剂荧光素一起构筑了不含贵金属成分的光催化分解水产氢体系.在三乙胺作为牺牲剂及纯水环境中,体系展现出了良好的光催化制氢性能.可见光照15 h后,体系产氢相对于催化剂的TON接近900.对比实验结果表明,具有这对几何异构的C1和C2具有相似的光催化产氢性能,暗示其催化机理的相似性.汞中毒实验结果表明,光催化分解水产氢过程中并没有钴纳米胶体形成,可以确定这是一个均相光催化分解水产氢体系.在纯水环境下,我们将C1和C2与传统的钴配合物(钴肟配合物:[Co(dmgH)_2pyCl](dmg H=丁二酮肟,py=吡啶);联吡啶钴配合物:[Co(bpy)_3Cl_2](bpy=2,2'-联吡啶))的催化活性进行对比.结果表明,催化剂C1和C2展现出了较强的光催化产氢活性.此外,电催化实验表明,在乙腈中且乙酸作为质子源的条件下,C1和C2具有相同的电催化活性,过电位接近640毫伏,催化转化频率(TOF)为每秒210.同时,在pH=7的磷酸盐缓冲溶液中,C1和C2也同样表现出对水分子的电催化产氢性能,过电势为560毫伏.这是当前第一例具有几何异构体的分子催化剂对光、电催化产氢体系影响的工作.     

The optimal fin spacing for three-row flat tube bank fin mounted with vortex generators

To reduce the size and the weight of heat exchangers, vortex generators (VGs) were punched on fin surface to improve the fin heat transfer performance. This paper is focused on the optimal fin spacing for three-row flat tube bank fin mounted with VGs. The results show, for commonly used fin materials and fin thickness, the optimal fin spacing is about 2 mm in industrial application for the configuration of tube bank fin studied.     

Hydrothermal synthesis of hierarchical SnO2 nanomaterials for high-efficiency detection of pesticide residue

Acephate pesticide contamination in agricultural production has caused serious human health problems. Metal oxide semiconductor (MOS) gas sensor can be used as a portable and promising alternative tool for efficiently detection of acephate. In this study, hierarchical assembled SnO₂ nanosphere, SnO₂ hollow nanosphere and SnO₂ nanoflower were synthesized respectively as high efficiency sensing materials to build rapid and selective acephate pesticide residues sensors. The morphologies of different SnO₂ 3D nanostructures were characterized by various material characterization technology. The sensitive performance test results of the 3D SnO₂ nanomaterials towards acephate show that hollow nanosphere SnO₂ based sensor displayed preferable sensitivity, selectivity, and rapid response (9 s) properties toward acephate at the optimal working temperature (300 °C). This SnO₂ hollow nanosphere based gas sensor represents a useful tool for simple and highly effective monitoring of acephate pesticide residues in food and environment. According to the characterization results, particularly Brunauer-Emmett-Teller (BET) and Ultraviolet-Visible Spectroscopy (UV–vis), the obvious and fast response can be attributed to the mesoporous hollow nanosphere structure and appropriate band gap of SnO₂ hollow nanosphere.     

Polarization insensitive wavelength multicasting of DPSK signal using four-wave mixing in a birefringent photonic crystal fiber

We demonstrate polarization-insensitive wavelength multicasting of differential phase-shift keying (DPSK) signal based on four-wave mixing (FWM) in a highly nonlinear, birefringent photonic crystal fiber (PCF). The 10-Gbit/s RZ-DPSK input signal is copied to 8 wavelength channels through FWM with three optical pumps. The pump wavelengths are unequally spaced to avoid undesirable crosstalk from pump-to-pump beatings. The dependence of conversion efficiency on input signal polarization is suppressed by exploiting the PCF birefringence together with control of the pump polarizations. All pump polarizations are aligned at 45 degrees to the principal axes of the PCF. Open eyes and error-free results are obtained in all the 8 multicast channels for polarization-scrambled RZ-DPSK input signal.     

悬浮固化分散液液微萃取-高效液相色谱法测定水体中邻苯二甲酸酯

建立了悬浮固化分散液液微萃取（SFO-DLLME）结合高效液相色谱（HPLC）快速测定水样中6种邻苯二甲酸酯（PAEs）的分析方法。通过对影响萃取效率因素的优化,确定了最佳萃取条件：十二烷醇萃取剂20 μL、萃取温度60℃、离子强度20 g/L、萃取时间1 min。6种PAEs在2~2000 μg/L范围内呈良好的线性关系,相关系数（r）为0.9995~0.9999,检出限（S/N=3）为0.3~0.6 μg/L。对自来水、湖水、江水、污水、海水、市售塑料瓶装纯净水和矿泉水进行测定,能检测到部分PAEs。对加标水样进行回收率试验（10、100和1000 μg/L）,6种PAEs的回收率为84.9%~94.5%,相对标准偏差为4.1%~6.8%（n=5）。该法环保、简单,可用于实际水样中6种PAEs的检测分析。     

掺杂丙烯酸酯单体合成及泡沫制备技术

 通过丙烯酸、2-甲基丙烯酸、巴豆酸与五氯苯酚的酯化反应实现了3种丙烯酸酯单体的掺杂改性合成,采用核磁共振和质谱测试技术对掺杂丙烯酸酯单体进行了表征。利用掺杂改性后的丙烯酸单体与季戊四醇四丙烯酸酯之间的共聚反应,结合超临界萃取技术,制备出理论密度为50 mg·cm^-3、掺杂氯元素质量百分数平均值最高约为15%的掺杂丙烯酸酯聚合物泡沫。通过测定聚合物凝胶速率,初步探讨了掺杂丙烯酸酯单体与多元丙烯酸酯单体的共聚合反应机理。     

Facile synthesis and electrochemical properties of MnO2/carbon nanotubes

The poor electrical conductivity of MnO2 limits its use as an electrode material. To overcome this limitation, we report an easy and rapid approach to deposit nanosized MnO2 onto multi-wall carbon nanotubes functionalized with hydroxyl groups （MWCNTs-OH） by chemical reduction of KMnO4 with MnSO4 in aqueous solution under ambient conditions. Characterization with XRD and TEM reveals that the obtained MnO2/MWCNTs-OH composite is nanocrystalline and partially covered by Mn02 nanosheets with a thick- ness of 1-3 nm at a MnO2 loading of 20 wt%. Cyclic voltammetry （CV） and galvanostatic charge-discharge measurements reveal that the MnO2/MWCNTs-OH composite with a MnO2 loading of 20 wt% has a relatively high specific capacitance of 234 F/g at a scan rate of 2 mV/s and exhibits good cycling stability. Furthermore, the oxygen reduction reaction （ORR） shows that MnO2/MWCNTs-OH composite may have potential applications as a non-noble metal electrocatalyst in fuel cells and metal-air batteries.     

抛物型方程在变动区域中的Galarkin有限元法及其对Stefan问题的应用

文中叙述了具变系数抛物型方程在变动区域中的有限元半离散格式和全离散θ格式,给出了误差界和稳定性结果,并应用于求解Stefan问题。     

Extremal characterizations of asplund spaces

We prove new characterizations of Asplund spaces through certain extremal principles in nonsmooth analysis and optimization. The latter principles provide necessary conditions for extremal points of set systems in terms of Fréchet normals and -normals.