共沉淀法制备参数对(Y，Gd)2O3∶Eu3+纳米粉体性能的影响

采用氨水为沉淀剂,正向滴定共沉淀法制备(Y,Gd)2O3:Eu3+纳米粉体.用XRD、SEM和荧光光度计对粉体的形貌和特性进行了分析.结果表明:稀土溶液的起始浓度0.15 mol·L-1,体系温度0℃,滴定速度2 mL·min-1,静止12 h,添加3%(NH4)2SO4(质量分数)并且在800℃煅烧2 h的条件下,合成出(Y,Cd)2O3:Eu3+纳米粉体近似球形,粒径尺寸约为30～60 nm且分散性良好.添加3%(NH4)2SO4的含量能够改善(Y,Gd)2O3:Eu3+纳米粉体的发光性能,并使发射光谱在5D0→7F2跃迁态上获得最大的相对发光峰值.     

颗粒内部的碘离子对碘溴化银微晶照相性能的影响

本文研究了用连体四角锥碘化银为晶核制备类似于四面体碘溴化银微晶和用六方角锥碘化银为晶核制备片状碘溴化银微晶的方法,并对两种不同微晶的结构,形态和性能进行了比较和分析.     

纳米CuO/Bi2O3粉体的制备及催化性能

以Cu(NO3)2,Bi(NO3)3和CO(NH2)2为原料,用水解法并掺加添加剂直接制备出纳米CuO／Bi203粉体。用FI-IR,XRD和TEM对其组成、粒子大小、表面形貌进行表征。结果表明,CuO／Bi：0,为类球形纳米粉体,粒度均匀,粒径20nm～4nm。实验结果证明CuO／Bi2O3对合成丁炔二醇具有良好的催化活性和选择性。     

碳酸氢镁溶液受热后的产物研究

长期以来 ,化学教材中硬水软化部分 ,对煮沸Mg(HCO3 ) 2 溶液的产物有不同看法。笔者用Mg(OH) 2 与CO2 反应制得Mg(HCO3 ) 2 溶液 ,对煮沸Mg(HCO3 ) 2 溶液所得产物 ,用EDTA配位滴定和热重进行了分析 ,确定其组成为碱式碳酸镁 [3MgCO3 ·Mg(OH) 2 ·3H2 O],并建议在高中教材改革中将该部分进行适当修正     

采用碳化-沉淀法制备纤维状纳米Mg(OH)_2的研究

本文以轻烧白云石粉料为原料,用碳化法制备出碱式碳酸镁,酸化后以氨水为沉淀剂,用化学沉淀法制得Mg(OH)2,用乙二胺对制得的Mg(OH)2进行后处理,制得纤维状纳米Mg(OH)2。用SEM、XRD和TG-DTA对制得的Mg(OH)2进行表征。XRD结果表明重结晶温度180℃以上可以得到具有完整晶体结构的Mg(OH)2。SEM结果显示Mg(OH)2颗粒的尺寸随着乙二胺加入量的增大而增大。当Mg(OH)2的重结晶时间超过21 h后,可以得到直径20~30 nm,长度400~700 nm的纤维状Mg(OH)2。TG-DTA表明Mg(OH)2在318~416℃分解为MgO。     

共沉淀法制备六方相ITO纳米粉体及其光电性能

以金属In、SnCl_4·5H_2O为原料、尿素为沉淀剂,采用共沉淀法加入(NH_4)_2SO_4,制备出六方相ITO纳米粉体。通过XRD、TEM、四探针电阻仪、荧光光谱仪以及XPS,研究了ITO粉体的晶型、颗粒形貌、电性能以及光性能。结果表明:加入(NH_4)_2SO_4后,ITO粉体形貌由类菱面体和类球形混合体转变为类球形;不加(NH_4)_2SO_4时晶型为立方相结构,当(NH_4)_2SO_4与铟的物质的量之比为1∶3.45和1∶1.73时粉体晶型转变为六方相结构,继续添加(NH_4)_2SO_4晶型又转变为立方相结构。立方相ITO粉体的电阻率较低为0.64Ω·cm,六方相ITO粉体在相同激发波长下,发射光强度相对较高。     

Li2O-Al2O3-GeO2-P2Os微晶玻璃的微观结构和离子电导率

采用传统熔体冷却法制备了Li3-xAl2-xGex(PO4)3(x=1.1～1.9)体系玻璃,并通过热处理工艺获得了高电导率的微晶玻璃.通过XRD、TEM和交流阻抗等测试方法,研究了该系微晶玻璃的物相组成、微观形貌和锂离子电导率.结果表明:该系统微晶玻璃析出导电主晶相为LiGe2(PO4)3,杂质相为AlPO4和GeO2.当x=1.5时,由于导电主晶相LiGe2(PO4)3晶粒充分长大、分布均匀,所制备微晶玻璃的室温锂离子电导率最高(5.72×10-4 S·cm-1),可以满足全固态锂离子电池对电解质高室温电导率的要求.     

碱式氯化镁5Mg(OH)2·MgCl2·3H2O的制备与表征

以氨水和盐湖盛产的水氯镁石为原料经过两步反应制备碱式氯化镁.第一步,水氯镁石和氨水反应制备氢氧化镁;第二步,利用氢氧化镁和水氯镁石,通过水热反应得到了具有纤维形貌、结晶较好的碱式氯化镁.应用化学分析、XRD、SEM和FIIR等手段对产物进行测试与表征.化学分析结果表明产物组成为5Mg(OH)2·MgCl2·3H2O.将得到的5Mg(OH)2·MgCl2·3H2O和碱式氯化镁系列标准XRD图对照,未有较好的匹配,且结合化学分析和已报道碱式硫酸镁具有5Mg(OH)2·MgSO4·3H2O物相,因而推测其为新物相;SEM图中5Mg(OH)2·MgCl2·3H2O纤维直径约为0.4μm,平均长度大于24 μm,长径比大于60;FTIR图谱中3419 cm-1附近出现了氢键的O-H伸缩振动吸收峰,1635 cm-1附近出现了游离水中H-O-H的弯曲振动吸收峰.水热合成的5Mg(OH)2·MgCl2·3H2O和常压下的产物相比直径较小,晶形更完整,强度更高.     

具有18电子结构的Mg2CoH5纳米晶制备及其储氢性能研究

本文研究了Mg2CoH5纳米晶的制备及其储氢性能。在室温和氩气气氛下,以MgH2和纳米Co为原料,采用球磨法制备了Mg2CoH5纳米晶。对所制备Mg2CoH5的组成、结构和形貌进行了表征,并且对Mg2CoH5的储氢性能进行了研究。实验结果表明,通过该种方法制备了纯度较高(产物纯度为79%)的四方结构Mg2CoH5纳米晶,其形貌呈球形且分布较均匀,最频粒径为80 nm。制备的Mg2CoH5纳米晶具有较低的活化能和较好的吸放氢动力学性能,其放氢的脱附焓和脱附熵分别为-115.0 kJ.mol-1H2和-193.6.1 J.mol-1.K-1H2。再氢化时,在543 K时仅7 min内其吸氢量就达到1.5wt%。     

Mg/Zn/Al类水滑石的热分解和水化性能研究

采用共沉淀法制备了Mg2Al1、Zn2Al1和Mg1Zn1Al1LDHs,利用XRD和SEM表征手段,对它们的热分解及焙烧物在Na2CO3溶液中恢复层状结构的能力进行了对比研究。结果表明,在400～700℃温度范围内,Zn2Al1LDH和Mg2Al1LDH的焙烧物中均出现氧化物相(ZnO和MgO)和尖晶石相(ZnAl2O4和MgAl2O4相);而Mg1Zn1Al1LDH的焙烧物中始终以ZnO相为主,仅在700℃时出现微弱的MgAl2O4相。三种焙烧物恢复层状结构的能力为:Mg1Zn1Al1LDO>Mg2Al1LDO>Zn2Al1LDO,其与焙烧物组成有关。原始LDHs和水化LDHs均呈片状。     

朱砂中汞的生物可接受性及其吸收与排泄

研究了朱砂中汞的生物可接受性及其在体内的吸收与排泄.采用体外消化透析法测定了朱砂中汞的生物可接受性;计算了大鼠灌胃给予临床剂量(50mg/kg)朱砂后汞的药动学参数;测定了给予临床剂量的朱砂后大鼠粪样中汞的排泄量.结果表明,朱砂中汞的溶出率为0.011%,生物可接受率为0.003 3%.大鼠灌胃给予临床剂量的朱砂后,汞的药动学参数为:最高血药浓度(ρmax)为(6.3±1.3)μg/L,达峰时间(tmax)为(1.3±0.4)h,半衰期(t1/2)为(4.2±0.5)h,血药浓度-时间曲线下面积(AUC)为(54.7±8.7)μg.h.L-1.给予朱砂12h后汞在粪便中排泄量最大,96h后在粪样中仍可检测到少量汞.朱砂中汞的生物可接受性较低,在体内吸收少,滞留时间较长,排泄缓慢,长期服用可在体内蓄积,产生毒性.     

Electrochemiluminescence resonance energy transfer between quantum dots (QDs) as the donor and Cy5 dye molecules as the acceptor in QD-Cy5 conjugates with biomolecules as the linker

Electrochemiluminescence resonance energy transfer (ECRET) between CdSe/Zns quantum dots (QDs) as the donor and cyanine dye (Cy5) molecules as the acceptor in QD-Cy5 conjugates with DNA or protein as the linker was reported. When a negative potential was applied, the excited-state CdSe/ZnS* was produced in 0.1 mol/L phosphate buffer (pH 7.4) containing 0.1 mol/L K₂S₂O₈ and 0.1 mol/L KNO₃ (PB-K₂S₂O₈). The CdSe/ZnS* went back to the ground-state CdSe/ZnS to emit light at 590 nm or to transfer energy to proximal ground-state Cy5 molecules. The resultant excited-state Cy5 molecules relaxed to their ground state by emitting a light at 675 nm. The ECRET between QDs and Cy5 was used to evaluate interactions between DNAs and to measure conformational changes of DNAs and proteins.     

Unmatched efficiency and selectivity in the epoxidation of olefins with oxo-diperoxomolybdenum(VI) complexes as catalysts and hydrogen peroxide as terminal oxidant

A great variety of olefinic substrates having aromatic, carbocyclic and aliphatic olefins are effectively and selectively oxidized with oxygen-rich molybdenum(VI) complexes, namely [MoO(O₂)₂·2QOH] 1, [MoO(O₂)(QO)₂] 2, [Mo(O)₂(QO)₂] 3, [PPh₄][MoO(O₂)₂(QO)] 4, [PPh₄][Mo(O)₂(O₂)(QO)] 5 and [PPh₄][Mo(O)₃(QO)] 6 (QOH = 8-quinolinol) as catalyst, NaHCO₃ as co-catalyst and H₂O₂ as the terminal oxidant, at room temperature. Catalysts 1 and 4 show unmatched yield, turnover number (TON) and turnover frequency (TOF), and hence shortest reaction time.     

Synthesis of a Novel Core-shell Type Acrylic-polyurethane Hybrid Emulsion Containing Siloxane and Fluorine as well as Water and the Oil Resistances of Cured Film

Aqueous acrylic-polyurethane dispersions have become one of the major types of materials used in coating, paint and adhesive industries, because of excellent properties and environmental advantages1-5. However, some properties for cured film such as water…     

Evaluation of titania as an ion-exchanger and as a ligand-exchanger in HPLC

Summary The chromatographic properties of titania have been compared with those of zirconia and alumina, by comparison of their relative Lewis acidities whenp-substituted benzoic acids were chromatographed with aqueous mobile phases. The retention behavior ofp-substituted benzoic acids on titania was found to be similar to that on zirconia; the slopes of plots of retention factors against solute pK _a were approximately parallel for all pH values and the slopes obtained were similar to the average slope for zirconia. The shapes of solute peaks on titania were more symmetrical than on alumina and zirconia. The effect of calcination temperature on the chromatographic properties of titania was examined by use of titania prepared at different temperatures. The results obtained clearly showed that the preparation temperature affected the chromatographic properties of titania. It seemed, for example, that titania dried at 40°C behaved as a cation-exchanger, titania heated at 200°C behaved as an amphoteric exchanger, and titania calcined at 600°C behaved as an anion-exchanger in the pH range 4.1–6.5 It was found that the control of the preparation temperature enabled us to make effective use of titania.     

RPHPLC determination of L- and D-cystine and cysteine as cysteic acid

Summary In the quantitative analysis of cystine and cysteine, before hydrolysis the compounds are often oxidized to cysteic acid with performic acid. The applicability of this process to the quantification of the enantiomers of cystine and cysteine has been examined. An RPHPLC analytical method was developed for determination of the amount of cysteic acid enantiomers and the rate of conversion during oxidation from cystine and cysteine into cysteic acid was determined. Racemization of L-cysteine was not significant during oxidation with performic acid and the process can, therefore, be applied before hydrolysis during quantification of enantiomers of these compounds. Presented at Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 1–3, 1999     

Polymer-supported palladium and rhodium species as hydrogenation catalysts

The synthesis of new copolymers containing amino and heterocyclic ligands and their use for anchoring Pd and Rh species is described. The supported catalysts are effective for the hydrogenation of alkenes, dienes, alkynes, and nitrobenzene under very mild conditions. The catalysts have been characterized by chemical analysis, particle size measurement, IR, and x-ray photoelectron spectroscopy. Relative reactivities and the effects of substrate structure, solvents, catalyst loading, anchoring ligands, metal species, and particle size on the rates of hydrogenation have been determined using a wide variety of substrates. The kinetics of hydrogenation have been analyzed using concepts suitable under slurry reaction conditions. Comparisons between different oxidation states of the same metal and between different metal species have also been made. The recycling efficiencies of the catalysts have been determined and found to be very good. © 1997 John Wiley & Sons, Inc.     

Polymer-supported palladium and platinum species as hydrogenation catalysts

The synthesis of new hydrogel copolymers and their use for anchoring Pd and Pt species is described. The supported catalysts are effective for the reduction of alkenes, dienes, alkynes, and nitroaromatics under mild conditions. The catalysts have been characterized by chemical analysis, particle size measurement, IR, TGA, and x-ray photoelectron spectra. Relative reactivities and the effects of substrate structure, solvents, catalyst loading, particle size of the catalysts, and partial pressure of hydrogen have been determined. The kinetics of hydrogenation have been analyzed using concepts useful under slurry reaction conditions. The recycling efficiencies of the catalysts and product analysis to establish selectivities have been assessed. © 1992 John Wiley & Sons, Inc.     

Aluminate and Magnesiate Complexes as Propagating Species in the Anionic Polymerization of Styrene and Dienes

The influence of MgR₂ and AlR₃ additives on alkyllithium initiators in the anionic polymerization of butadiene has been investigated in non polar solvents. A strong decrease of the diene polymerization rate in the presence of the two Lewis acids was observed, similarly to that observed in the retarded anionic polymerisation of styrene. With n,s-Bu₂Mg, the percentage of 1,2 vinyl units increases with the [Mg]/[Li] ratio. This behavior is specific to magnesium derivatives bearing secondary alkyl groups and likely results from the additional complexation of lithium species by free dialkylmagnesium and/or a 1,4- to 1,2- chain end isomerization process during chain exchanges between polybutadienyl active chains and dormant ones attached to magnesium species. These reversible exchanges also lead to the formation of one supplementary chain by initial dialkyl magnesium which acts as reversible chain transfer agent. On the contrary with the R₃Al/RLi systems the number of chains is only determined by the concentration of initial alkyllithium and no modification of the polybutadiene microstructure compared to lithium initiators (1,4 units = 80%) is noticed. Dialkyl magnesiate complexes with alkali metal derivatives (i.e. alkoxide) are also able to influence the stereochemistry of the styrene insertion during the propagation reaction. Polystyrenes with different tacticities ranging from predominantly isotactic (85% triad iso) to syndiotactic (80% triad syndio) can be obtained with these initiators.     

超顺磁性纳米颗粒为催化剂载体的研究*

如何结合催化剂的制备找到一条新的催化剂分离与回收途径,已成为均相催化剂以及近十年快速发展的纳米催化剂研究中的一项重要内容。近年来,基于超顺磁性纳米颗粒作为催化剂载体来制备新型纳米催化剂的工作因此受到广泛关注。利用超顺磁性纳米颗粒所提供的磁学特性进行磁分离,不仅有效地解决了分离与重复使用问题,而且因其尺度处于纳米级,保持了以上催化剂的高活性、高选择性等动力学优点。本文从超顺磁性纳米载体的制备、催化剂的制备与活性评价等角度对近几年的研究工作进行综述,并对其发展前景进行展望。