Hydrogen adsorption on zigzag (8,0) boron nitride nanotubes

The chemical adsorption of H atoms on an (8,0) zigzag boron nitride nanotube is studied using the density functional theory with the supercell method. One to four H atoms per 32 B and 32 N are considered. The results show that H atoms prefer to adsorb on the top sites of adjacent B and N atoms to form an armchair chain along the tube axis. An even-odd oscillation behavior of the adsorption energy of H atoms on the tube is found, and the average adsorption energy of even H atoms is obviously bigger than that of odd H atoms. The results can be understood with the frontier orbital theory. Based on this adsorption behavior, several high-symmetric structures of H adsorbed boron nitride nanotubes with 50% and 100% coverages are studied. The pairs of lines' pattern with 50% coverage has the biggest average adsorption energy per H(2) among the chosen configurations, corresponding to approximately 4 wt % hydrogen storage.     

液相色谱-串联质谱法同时测定大黄鱼中20种磺胺类药物残留

建立了一种液相色谱-电喷雾串联质谱同时测定大黄鱼中20种磺胺类药物残留的方法.均质样品先后用乙腈、二氯甲烷提取,合并提取液,取部分提取液经氮吹浓缩.残渣用1 mL流动相溶解,饱和正己烷脱脂净化.采用ZORBAX Eclipse XDB-C8色谱柱,以含0.2%乙酸的水溶液和甲醇(7: 3)为流动相,梯度洗脱,在电喷雾-多反应监测离子模式下,进行定量定性分析.方法的定量限为5 μg/kg;以标准加入法计算回收率,在10～40 μg/kg添加范围内,平均回收率为79.6%～109%;相对标准偏差为3.55%～16.5%.     

Breaking symmetry: spontaneous resolution of a polyoxometalate

A chiral polyoxometalate [Hf(PW11O39)2]10- (1) has been prepared and structurally characterized. It crystallizes in the chiral space group P2(1)2(1)2, as a conglomerate of two enantiomerically pure crystals in the absence of any chiral source. The absolute configuration of 1 was determined from the Flack parameter by X-ray crystallography. The structure of 1 comprises two lacunary [PW11O39]7- units, each functioning as a tetra-dentate ligand sandwiching an 8-coordinate HfIV centre in a distorted square antiprismatic geometry. Optically active crystals of both enantiomers were spectroscopically distinguishable by means of solid state circular dichroism spectroscopy. This hafnium-substituted polyoxometalate (POM), 1, shows that spontaneous chiral resolution, a rare phenomenon, can be operable in POM systems.     

Inorganic electrides

Inorganic electrides are a novel kind of ionic compounds in which the anions are electrons confined in a complex array of cavities or channels and the cations are nanoscale arrays of alkali metal ions that provide charge balance. In electrides the donated electron behaves like a low-density correlated electron gas, whereby the dimensionality of the electron gas and its electronic and magnetic properties are determined by the topology of the cavities in the host matrix. Unlike traditional electrides, in which alkali cations are encapsulated within an organic cage, inorganic electrides are thermally stable. The current inorganic electrides based on alkali metal loaded zeolites can be designed as useful reduced-dimensionality materials. Inorganic electrides are powerful reducing agents, and they are able to reduce small aromatic molecules to the radical anions within the channels of the zeolite.     

Controlling the framework formation of silver(I) coordination polymers with 1,4-bis(phenylthio)butane by varying the solvents,metal-to-ligand ratio,and counteranions

The reactions of 1,4-bis(phenylthio)butane (L) with Ag(I) salts in varied conditions (varying the solvents, metal-to-ligand ratios, and counteranions) lead to the formation of four new two-dimensional (2D) coordination polymers with different network structures: [Ag(2)L(3)(ClO(4))(2)](infinity) 1, [Ag(2)L(3)(ClO(4))(2) x CH(3)OH](infinity) 2, [[AgL(2)](ClO(4))](infinity) 3, and [AgLNO(3)](infinity) 4. All the structures were established by single-crystal X-ray diffraction analysis. Crystal data for 1: triclinic, P-1, a = 11.0253(9) A, b = 11.3455(9) A, c = 11.5231(9) A, alpha = 93.931(2) degrees, beta = 92.689(2) degrees, gamma = 112.9810(10) degrees, Z = 2. 2: triclinic, P-1, a = 11.9147(13) A, b = 16.1534(17) A, c = 16.2259(17) A, alpha = 74.977(2) degrees, beta = 69.030(2) degrees, gamma = 69.986(2) degrees, Z = 2. 3: triclinic, P-1, a = 12.1617(9) A, b = 12.5054(10) A, c = 13.1547(10) A, alpha = 64.3370(10) degrees, beta =85.938 (2) degrees, gamma = 69.3010(10) degrees, Z = 2. 4: monoclinic, P2(1)/c, a = 5.4032(17) A, b = 16.974(6) A, c = 19.489(6) A, beta = 94.234(6) degrees, Z = 4. In all four complexes, each Ag(I) center has a tetracoordination geometry, and the 2D networks consist of fused large macrometallacyclic ring systems. The "hexagonal" 42-membered rings, Ag(6)L(6), observed in 1 and 2 are nearly identical, which could be considered as unique examples of self-sustaining noninterpenetrated frameworks formed with flexible ligands. The repeating rectangular 28-membered macrometallacycle, Ag(4)L(4), is the basis for the network of 3, in which the perchlorate anions occupy the voids to prevent the ring from collapsing. In 4, columns of the fused rectangular 22-membered rings, Ag(4)L(2)(NO(3))(2), are cross-linked through the L ligands to form a unique 2D network consisting of two types of 22-membered repeating units.     

手性胺酰胺型液相色谱手性固定相的制备及几种氨基酸衍生物的拆分

用(R)-1-苯基2-对甲基苯基乙基胺(PTE)与L-异亮氨酸制得含两个手性中心的手性选择剂,以琥珀酸酐作为连接臂,将手性选择剂键合到氨基丙基硅胶上制得手性固定相。以正己烷-异丙醇为流动相,利用该固定相对氨基酸衍生物进行高效液相色谱手性拆分,并考察了流动相中异丙醇含量对手性拆分的影响。结果表明,该手性固定相对所分析的氨基酸衍生物大部分都具有一定的拆分能力。当异丙醇含量为1%时,亮氨酸与苯丙氨酸的苯甲酰甲酯衍生物获得基线分离。当异丙醇含量为20%时,亮氨酸、缬氨酸、丙氨酸、谷氨酸的3,5-二硝基苯甲酰甲酯衍生物获得基线分离。     

Immobilization of hemoglobin on SBA-15 applied to the electrocatalytic reduction of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

The direct electron transfer between hemoglobin (Hb) and an electrode was realized by first immobilizing the protein onto SBA-15.The results of the immobilization showed that the adsorption was pH-dependent with a maximum adsorption near the isoelectric point of the protein, and SBA-15 with a larger pore diameter showed greater adsorption capacity for Hb. UV–vis spectroscopy and nitrogen adsorption analysis indicated that Hb was adsorbed within the channel of SBA-15 and no significant denaturation occurred to the protein. The Hb/SBA-15 composite obtained was used for the fabrication of a Hb biosensor to detect hydrogen peroxide. A pair of well-defined redox peaks at −0.337 and −0.370 V on the Hb/SBA-15 composite modified glassy carbon electrode was observed, and the electrode reactions showed a surface-controlled process with a single proton transfer at a scan rate range from 20 to 1,000 mV/s. The sensor showed a fast amperometric response, a low detection limit (2.3 × 10⁻⁹ M) and good stability for the detection of H₂O₂. The electrochemical results indicated that the immobilized Hb still retained its biological activity.     

形态结构和光电特性对纳米TiO2光催化性能的影响

采用sol-gel法制备了系列纳米TiO2光催化剂,运用X射线衍射、BET比表面测定、紫外漫反射吸收光谱和表面光电压谱等手段对催化剂进行表征,并以乙烯作为光催化反应的指标反应分子,研究了TiO2纳米晶的性质对于光催化活性的影响.随着焙烧温度的升高,TiO2的晶粒逐渐增大,比表面积下降,晶相由锐钛矿向金红石转变,其吸收带边与光伏响应阈值向长波方向移动,氧化－还原能力降低,降解乙烯的转化率迅速下降.     

主链含硅聚芳酯的合成及气体透过性能的研究

以双［对－酰氯苯基］二甲基硅烷和酚酞、四溴酚酞以及双酚Ａ为原料，合成了三种主链含硅聚芳酯，并对聚合物相关的物理性质进行了表征，制成了均质透明的薄膜．采用低真空法测定这些聚合物对Ｈ２、Ｏ２、Ｎ２、ＣＯ２、ＣＨ４的气体透过速率，并计算出气体透过系数、扩散系数、溶解系数、分离系数．从气体透过性能与聚合物分子结构关系的角度，按照气体透过的溶解－扩散机制，对聚合物的气体透过性能进行了研究，而且着重讨论了聚合物的堆积密度对气体扩散系数的影响，以及聚合物主链中极性链段的百分含量对气体溶解系数和溶解选择性的影响。