One-step solvothermal synthesis of single-crystalline TiOF2 nanotubes with high lithium-ion battery performance

Single-crystalline TiOF(2) nanotubes were prepared by a one-step solvothermal method. The nanotubes are rectangular in shape with a length of 2-3?μm, width of 200-300?nm, and wall thickness of 40-60?nm. The formation of TiOF(2) nanotubes is directly driven by the interaction between TiF(4) and oleic acid in octadecane to form the 1D nanorods, and this is followed by a mass diffusion process to form the hollow structures. The synthesis approach can be extended to grow TiOF(2) nanoparticles and nanorods. Compared with TiO(2), which is the more commonly considered anode material in lithium-ion batteries, TiOF(2) has the advantages of a lower Li-intercalation voltage (e.g., to help increase the total voltage of the battery cell) and higher specific capacities. The TiOF(2) nanotubes showed good Li-storage properties with high specific capacities, stable cyclabilities, and good rate capabilities.     

Di- and tetranuclear heterometallic CuII-LnIII complexes (Ln = Gd and Dy): Synthesis, structure and magnetic properties

Four 3d-4f heterometallic complexes, [CuⅡ LnⅢ (bpt) 2 (NO 3 ) 3 (MeOH)] (Ln = Gd, 1; Dy, 2; bptH = 3,5-bis(pyrid-2-yl)-1,2,4- triazole), [CuⅡ 2 LnⅢ 2 (μ-OH) 2 (bpt) 4 Cl 4 (H 2 O) 2 ]·6H 2 O (Ln = Gd, 3; Dy, 4), have been synthesized under solvothermal conditions. X-ray structural analyses reveal that 1 and 2 are isostructural while 3 and 4 are isostructural. In each complex, the copper and gadolinium or dysprosium ions are linked by two triazolate bridges and form a CuⅡ -LnⅢ dinuclear unit. The intramolecular Cu-Ln distances are 4.542, 4.525, 4.545 and 4.538 for 1, 2, 3 and 4, respectively. Two dinuclear CuLn units are bridged by two OH- groups into the zig-zag tetranuclear {CuⅡ 2 LnⅢ 2 } structures with the Ln(Ⅲ) Ln(Ⅲ) distances of 3.742 and 3.684 for 3 and 4, respectively. Magnetic studies show that the antiferromagnetic CuⅡ-LnⅢ interactions occur in 1 (J CuGd = 0.21 cm-1 ) and 2. The antiferromagnetic interaction occurs in complex 3 with J CuGd = 0.82 cm-1 and J GdGd = 0.065 cm-1 , while dominant ferromagnetic interaction occurs in complex 4.     

Preparation of amphiphilic graft copolymer with polyisoprene backbone by combination of anionic polymerization and “click” reaction

A novel graft copolymer consisting of polyisoprene backbone and hydrophilic side chain with carbamic acid ester functional group was prepared via thiol-ene"click"reaction and alcohol-isocyanate reactions.Polyisoprene was synthesized by anionic polymerization using n-butyl lithium as initiator,and the pendant hydroxyl groups were introduced by the thiol-ene reaction of mercaptoethanol with the double bond of 1,2-addition units of PI backbone in the presence of radical initiator azobisisobutyronitrile. Isocyanate end group capped poly(ethylene glycol)(mPEG-NCO) was grafted onto the PI backbone through alcoholisocyanate reaction between the pendant hydroxyl groups and isocyanate group of mPEG-NCO.The structure of the graft copolymer were characterized and confirmed by means of size-exclusion chromatography,~1H NMR and FTIR spectroscopy.     

Application of differential pulse stripping voltammetry and chemometrics for the determination of three antibiotic drugs in food samples

A reliable method for simultaneous determination of three antibiotic drugs(levofloxacin,gatifloxacin and lomefloxacin) by differential pulse stripping voltammetry(DPSV) in Britton-Robinson buffer(pH 7.96) was presented.The method is based on adsorptive accumulation of the antibacterial drugs on a hanging mercury dropping electrode(HMDE),followed by the reduction of the adsorptive species by the technique of DPSV.Optimal conditions,the deposition time of 80 s,the deposition potential of—1250 mV,and the scan rate of 25 mV/s,were obtained.The linear concentration ranges of 0.010-0.080μg/mL were obtained for all these three antibiotic drugs,while the detection limits were 2.38,3.20 and 1.60ng/mL for levofloxacin,gatifloxacin and lomefloxacin,respectively.In this work,chemometrics methods,such as classical least squares(CLS),partial least squares(PLS), principle component regression(PCR) and radial basis function-artificial neural networks(RBF-ANN),were used to quantitatively resolve the overlapping signals.It was found that PCR gave the best results with total relative prediction error(RPE_T) of 7.71%.The proposed method was applied to determine these three drugs in several commercial food samples with spiked method and yielded satisfactory recoveries.     

Preparation and characterization of high-rate and long-cycle LiFePO4/C nanocomposite as cathode material for lithium-ion battery

Olivine LiFePO₄/C nanocomposite cathode materials with small-sized particles and a unique electrochemical performance were successfully prepared by a simple solid-state reaction using oxalic acid and citric acid as the chelating reagent and carbon source. The structure and electrochemical properties of the samples were investigated. The results show that LiFePO₄/C nanocomposite with oxalic acid (oxalic acid: Fe²⁺= 0.75:1) and a small quantity of citric acid are single phase and deliver initial discharge capacity of 122.1 mAh/g at 1 C with little capacity loss up to 500 cycles at room temperature. The rate capability and cyclability are also outstanding at elevated temperature. When charged/discharged at 60 °C, this materials present excellent initial discharge capacity of 148.8 mAh/g at 1 C, 128.6 mAh/g at 5 C, and 115.0 mAh/g at 10 C, respectively. The extraordinarily high performance of LiFePO₄/C cathode materials can be exploited suitably for practical lithium-ion batteries.     

Structural and theoretical basis for ligand exchange on thiolate monolayer protected gold nanoclusters

Ligand exchange reactions are widely used for imparting new functionality on or integrating nanoparticles into devices. Thiolate-for-thiolate ligand exchange in monolayer protected gold nanoclusters has been used for over a decade; however, a firm structural basis of this reaction has been lacking. Herein, we present the first single-crystal X-ray structure of a partially exchanged Au(102)(p-MBA)(40)(p-BBT)(4) (p-MBA = para-mercaptobenzoic acid, p-BBT = para-bromobenzene thiol) with p-BBT as the incoming ligand. The crystal structure shows that 2 of the 22 symmetry-unique p-MBA ligand sites are partially exchanged to p-BBT under the initial fast kinetics in a 5 min timescale exchange reaction. Each of these ligand-binding sites is bonded to a different solvent-exposed Au atom, suggesting an associative mechanism for the initial ligand exchange. Density functional theory calculations modeling both thiol and thiolate incoming ligands postulate a mechanistic pathway for thiol-based ligand exchange. The discrete modification of a small set of ligand binding sites suggests Au(102)(p-MBA)(44) as a powerful platform for surface chemical engineering.     

超支化聚乙烯亚胺接枝二氧化硅的制备及在聚丙烯改性中的应用

首先利用3-缩水甘油氧基丙基三甲氧基硅烷(简称GPS)作为偶联剂,对纳米SiO2进行表面改性,获得表面含有环氧基的SiO2纳米粒子(SiO2-GPS).利用这些环氧基与超支化聚乙烯亚胺(HPEI)分子中的氨基进行反应,得到SiO2接枝超支化聚乙烯亚胺的纳米粒子(SiO2-GPS-g-HPEI).然后利用SiO2-GPS-g-HPEI与聚丙烯(PP)和PP接枝的马来酸酐(PP-g-MAH)共混、模压,制备PP/SiO2-GPS-g-HPEI/PP-g-MAH复合材料.红外光谱测试和热失重分析(TGA)测试结果表明,SiO2纳米粒子表面依次接枝了GPS和HPEI;扫描电子显微镜(SEM)的测试结果显示,SiO2-GPS-g-HPEI在聚丙烯基体中分散良好,其材料的冲击断裂为韧性断裂;复合材料共混时,扭矩的增加证明了共混物中分散相(SiO2-GPS-g-HPEI)与基体(PP/PP-g-MAH)界面之间存在一定的相互作用.少量SiO2-GPS-g-HPEI加入PP/PP-g-MAH中,冲击强度可增加96.3%,拉伸强度也有较大的提高.     

Sc(P204)3/烷基铝体系催化降冰片烯聚合

以钪的膦酸酯盐Sc(P204)3和烷基铝组成催化体系催化降冰片烯(NBE)聚合,考察了聚合反应条件对单体转化率、产物分子量以及微观结构的影响.当以三乙基铝为助催化剂时,[NBE]/[Sc]=50(摩尔比),[A1]/[Sc]=30(摩尔比),40℃陈化5 min,在甲苯中于60℃聚合7h,单体转化率为98％,所得聚合物可部分溶于有机溶剂;NBE以开环聚合方式为主,开环产物含量为81％ ～88％,其中顺式双键含量为48％ ～58％,分子量2.4×103～ 3.0×103,分子量分布1.9 ～2.2.当以三异丁基铝为助催化剂时,[NBE]/[Sc]=50(摩尔比),[Al]/[Sc] =5(摩尔比),50℃陈化2h,80℃下于甲苯中聚合4h,单体转化率为39％,所得白色聚合产物很难溶于有机溶剂,以开环聚合方式为主,产物中反式双键含量90％.     

含氨基聚芳醚酮/磺化聚芳醚酮砜中高温质子交换复合膜的制备与性能研究

以自制的高磺化度磺化聚芳醚酮砜(SPAEKS)和含有氨基的聚芳醚酮(Am-PAEK)为原料,通过共溶剂涂膜法制备了不同重量比例的Am-PAEK/SPAEKS复合膜.通过高温(160℃)处理使氨基和磺酸基团在复合膜内形成交联,制得交联型复合膜.复合膜的热性能、尺寸稳定性、阻醇性能有所提高,而且交联型复合膜中的Am-PAEK/SPAEKS-C-3质子传导率在120℃时达到了0.0892 S/cm,高于在相同测试条件下SPAEKS膜的0.0654 S/cm和Nafion膜的0.062 S/cm,而其甲醇渗透系数在25℃时达到0.14×10-6cm2/s,低于SPAEKS膜的0.85×10-6cm2/s和Nafion膜的2×10-6cm2/s.实验结果表明,Am-PAEK/SPAEKS交联型复合膜有望在中高温质子交换膜燃料电池中得到应用.