The large quadrupole of water molecules

Many quantum mechanical calculations indicate water molecules in the gas and liquid phase have much larger quadrupole moments than any of the common site models of water for computer simulations. Here, comparisons of multipoles from quantum mechanical∕molecular mechanical (QM∕MM) calculations at the MP2∕aug-cc-pVQZ level on a B3LYP∕aug-cc-pVQZ level geometry of a waterlike cluster and from various site models show that the increased square planar quadrupole can be attributed to the p-orbital character perpendicular to the molecular plane of the highest occupied molecular orbital as well as a slight shift of negative charge toward the hydrogens. The common site models do not account for the p-orbital type electron density and fitting partial charges of TIP4P- or TIP5P-type models to the QM∕MM dipole and quadrupole give unreasonable higher moments. Furthermore, six partial charge sites are necessary to account reasonably for the large quadrupole, and polarizable site models will not remedy the problem unless they account for the p-orbital in the gas phase since the QM calculations show it is present there too. On the other hand, multipole models by definition can use the correct multipoles and the electrostatic potential from the QM∕MM multipoles is much closer than that from the site models to the potential from the QM∕MM electron density. Finally, Monte Carlo simulations show that increasing the quadrupole in the soft-sticky dipole-quadrupole-octupole multipole model gives radial distribution functions that are in good agreement with experiment.     

Silver and gold icosahedra: one-pot water-based synthesis and their superior performance in the electrocatalysis for oxygen reduction reactions in alkaline media

Much effort has gone into generating polyhedral noble metal nanostructures because of their superior electrocatalytic activities for fuel cells. Herein, we report uniform, high-yield icosahedral silver and gold nanoparticles by using a facile one-pot, seedless, water-based approach that incorporates polyvinyl pyrrolidone and ammonia. Electrocatalysis of the oxygen-reduction reaction was carried out in alkaline media to evaluate the performance of the icosahedral nanoparticles. They showed excellent stability and much higher electrocatalytic activity than the spherelike nanoparticles; they display a positive shift in reduction peak potential for O(2) of 0.14 and 0.05 V, while the reduction peak currents of the silver and gold icosahedra are 1.5- and 1.6-fold, respectively, better than the spherelike nanoparticles. More importantly, the icosahedral nanoparticles display electrocatalytic activities comparable with commercial Pt/C electrocatalysts. The facile preparation of icosahedral silver and gold nanoparticles and their superior performance in the oxygen reduction reaction render them attractive replacements for Pt as cathode electrocatalysts in alkaline fuel cells.     

Synthesis, structure, and photoluminescence properties of a novel 3D 3d-4f heterometallic polymer: Pr4(H2O)9Cu3.5Cl0.5(Bpdc)6.5(OH)2 · 5H2O (H2Bpdc = 2,2′-bipyridyl-5,5-dicarboxylic acid)

A novel 3D 3d–4f heterometallic polymer Pr₄(H₂O)₉Cu_3.5Cl_0.5(Bpdc)_6.5(OH)₂ · 5H₂O (I) (H₂Bpdc = 2,2′-bipyridyl-5,5′-dicarboxylic acid) has been hydrothermally synthesized by the reaction of CuCl₂ · 2H₂O, PrCl₃, H₂Bpdc, TAA (TAA = 1H-tetrazolyl-1-acetic acid) and glacial acetic acid and characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. Single-crystal structural analysis shows that I displays an interesting heterometallic 3D coordination framework constructed from 2D praseodymium-oxygen layers and [Cu(Bpdc)2]^3? and [CuCl(Bpdc)]^2? pillars. The photofluorescence properties of I have been investigated.     

Effects of deposition of different contents of Ag nanoparticles on thickness and structural,morphological, compositional,optical, and photocatalytic properties of 1D TiO2 nanoarrays

Research on Chemical Intermediates - One-dimensional (1D) TiO2 nanoarrays (NAs) were synthesized by a hydrothermal process, and Ag nanoparticles (NPs) were deposited on the arrays using a...     

Effect of environmental conditions on the sorption of radiocobalt from aqueous solution to treated eggshell as biosorbent

Carbonate hydroxylapatite (CHAP), prepared from eggshell waste, was used to remove ⁶⁰Co(II) from aqueous solutions. The sorption of ⁶⁰Co(II) on CHAP as a function of contact time, pH, ionic strength and foreign ions in the absence and presence of humic acid and fulvic acid under ambient conditions was studied. The sorption of ⁶⁰Co(II) on CHAP was strongly dependent on pH and ionic strength. The thermodynamic parameters (ΔH ⁰, ΔS ⁰, ΔG ⁰) of ⁶⁰Co(II) sorption on CHAP were calculated from the temperature-dependent sorption isotherms, and the results indicated that the sorption process of ⁶⁰Co(II) on CHAP was endothermic and spontaneous. At low pH, the sorption of ⁶⁰Co(II) was dominated by outer-sphere surface complexation and ion exchange with Na⁺/H⁺ on CHAP surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. Experimental results also indicated that CHAP was a suitable low-cost adsorbent for pre-concentration and solidification of ⁶⁰Co(II) from large volumes of aqueous solutions.     

枪晶石变温拉曼光谱及其固液相微结构研究

枪晶石在传统冶金连铸保护渣中起着十分重要的作用。采用紫外激光光源和电荷耦合器件(CCD)探测器,测定了枪晶石晶体和高温拉曼光谱(温度范围:298~1 723 K),观察了其在变温状态(升温和降温过程)下的特征谱变化。谱图结果显示,枪晶石熔态微结构单元与固态的相比更为多元化,表明熔体状态下多种团簇结构共存。同时,利用枪晶石晶胞结构模型,通过Dmol3密度泛函(DFT)理论计算了其分子振动频率,将其与实验值相结合,确定了特征谱峰的归属,为进一步采用拉曼光谱法原位研究保护渣中枪晶石的结构变化与行为特征提供了重要依据。     

发射光谱研究大气压等离子体射流的气体温度

采用介质阻挡放电等离子体喷枪装置,在大气压下流动氩气中产生了射流等离子体。利用光电倍增管,对射流等离子体进行了时空分辨测量,分析了等离子体喷枪内介质阻挡放电和外部等离子体羽的放电特性。利用高分辨率光谱仪采集等离子体羽处的发射光谱,通过对发射光谱中OH(A2Σ+→X2Π,307.7～308.9nm)及N2+的第一负系(B2Σ+u→X2Π+g,390～391.6nm)谱线拟合得到了射流等离子体的转动温度,拟合得到的转动温度分别为443和450K。在5%的误差范围内,这2种方法得到的结果是一致的。由于在大气压下,转动温度近似等于产生气体放电的气体温度,所以可以确定大气压射流等离子体气体温度。利用该方法研究了不同电压下的气体温度,发现气体温度随着外加电压增加而增大。     

利用Hyperion数据进行环境星HSI红边参数真实性检验

针对我国新发射运行的HJ-1A星HSI数据,利用高光谱分辨率的Hyperion数据进行了HJ-1A星HSI的光谱模拟,提取了红谷位置、红边位置、红边斜率和红边振幅等4个主要的红边参数,对真实与模拟环境星HSI数据的红边参数进行了对比分析,从而以Hyperion数据为参照检验了环境星HSI红边参数的真实性。研究结果显示,环境星HSI与模拟HSI的红边范围光谱反射率平均相关系数为0.946,标准差为0.011,为极显著相关,两种数据在红边范围内的光谱反射率变化高度一致;4个红边参数的相关系数分别为0.414,0.543,0.808和0.802,并且随植被覆盖度的变化呈现出明显的规律性,模拟与真实红边参数差值标准差分别为5.75,1.86,5.7e-4和0.024,认为环境星HSI的红边参数可以较好反映该区域植被变化所造成的红边光谱特征差异。     

Editorial for Special Issue on Frontiers in Optical Bioimaging

<正>Optical bioimaging has become a very important tool in life science because it is noninvasive, of high specificity, capable of performing multi-parameter measurement,     

Development and validation of LC–MS/MS method for amlexanox in rat plasma and its application in preclinical pharmacokinetics

Amlexanox, an anti-inflammatory and anti-allergic agent, has been widely used clinically for the treatment of canker sores, asthma, and allergic rhinitis. Recently, amlexanox has received considerable attention in curing nonalcoholic fatty liver diseases and hepatitis virus infection. Herein, we first established a sensitive high-performance liquid chromatography-tandem mass spectrum (LC–MS/MS) method for the determination of amlexanox in rat plasma. Propranolol was used as the internal standard (IS). Using a simple protein precipitation method, the amlexanox and IS were separated with Capcell Pak C18 column (2.0 × 50 mm, 5 μm) and eluted with water and acetonitrile each containing 0.1% formic acid using gradient elution condition at a flow rate of 0.4 mL·min⁻¹. Amlexanox and IS were detected by a triple quadrupole mass in multiple reactive monitoring (MRM) under the transitions of m/z 299.2 → 281.2 and m/z 259.9 → 116.1 with positive electrospray ionization, respectively. The calibration curves of amlexanox were established with the range of 50 to 2000 ng·mL⁻¹ (r² > 0.99). The validation method consisted of selectivity, accuracy, precision, carryover effect, matrix effect, recovery, dilution effect, and stability. The fully validated method was successfully applied to the pharmacokinetic study of amlexanox in Wistar rats.