高分子基质作用下多孔碳酸钙的仿生合成

依据生物矿化的基本原理,通过仿生合成的方法,以聚丙烯酰胺作为基质合成了一种有机、无机复合的多孔碳酸钙材料.用X射线粉末衍射(XRD)分析、扫描电子显微镜(SEM)、傅里叶变换红外吸收光谱(FT-IR)和电导率测定等手段对所得复合碳酸钙进行了表征,结果发现该多孔CaCO3晶体为方解石型,并且在结晶过程中,聚丙烯酰胺与CaCO3之间存在着相互作用,本文讨论了这种作用的可能机理.     

孪生球状碳酸钙的直接混合沉淀法制备及表征

以醋酸钙和碳酸钠为原料, 柠檬酸三钠为晶形控制剂, 利用液相直接混合沉淀法合成了分散性好、粒度约1.5~3.0 μm、长短轴比约2∶1的孪生球形碳酸钙晶体. 利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、傅里叶红外光谱仪(FTIR)、原子力扫描探针显微镜(ASPM)和粒度分析仪等对样品进行了表征. 结果表明, 在不添加柠檬酸三钠的溶液中得到微米级的立方状碳酸钙晶体, 而添加柠檬酸三钠(质量分数30%~40%)后则得到具有不同表面粗糙度的孪生球状碳酸钙晶体. 同时, 用分形生长理论和成核限制聚集(NLA)模型对孪生球状碳酸钙粒子的形成机理进行了分析.     

二次碳化法制备疏水链状纳米碳酸钙

以柠檬酸和十六酸的氨溶液为表面控制剂, 用二次碳化法制备了疏水链状纳米碳酸钙晶体. 用透射电子显微镜、X射线衍射、红外光谱、热重分析和接触角测试对产品进行了分析. 结果表明, 表面控制剂在反应过程中不但可以控制晶体的成核生长, 还能对碳酸钙表面进行修饰. 在不添加表面控制剂的溶液中得到立方体状表面亲水的纳米碳酸钙晶体; 添加柠檬酸和十六酸的氨溶液后所得纳米碳酸钙晶体为链状表面疏水. 将碳酸钙添加到聚乙烯中, 聚乙烯的初始热分解温度提高, 热力学稳定性增加.     

明胶基质作用下碳酸钙的仿生合成

依据生物矿化的基本原理, 以明胶为基质, 在动态条件下, 仿生合成碳酸钙/明胶复合材料. 扫描电子显微镜和能量分散X射线(SEM-EDAX)分析表明, 明胶基质中形成的碳酸钙完全不同于纯水中形成的碳酸钙, 具有独特的微观结构形态和取向. 明胶浓度不同, 晶体的形态、取向以及主要元素Ca, O和N的含量相差较大.     

均匀大颗粒球形碳酸钙的仿生合成

依据仿生矿化原理,采用难溶性CaSO4作为钙源,以柠檬酸钠为模板剂合成出了均匀大颗粒球形碳酸钙晶体,用X射线粉末衍射(XRD)分析、扫描电子显微镜(SEM)、傅立叶变换红外吸收光谱(FTIR)和热重分析等测试技术对所得碳酸钙样品进行了表征,探讨了其合成机理. 研究表明,柠檬酸钠对碳酸钙的晶形具有调控作用,在柠檬酸钠质量浓度为0.9%的条件下,能合成出大小均匀、分散性好、粒度为10～15 μm的大颗粒球形碳酸钙晶体.     

天然抗氧化剂麦角硫因的合成工艺研究

采用仿生合成法制备麦角硫因。以L-组氨酸(2)为起始原料,经还原胺化、甲基化得直接生物前体L-组氨酸甜菜碱(4);4与L-半胱氨酸、3-巯基丙酸经“一锅法”合成麦角硫因(1),总收率46.95%,其结构经¹H NMR,¹³C NMR和MS(ESI)谱确证,纯度为99.56%(HPLC法)。该路线步骤简短、原料价廉易得、反应条件温和、操作简便、收率较高,适用于百克级麦角硫因的制备。     

聚对苯二甲酸乙二醇酯/碳酸钙纳米复合材料的制备和表征

以聚乙二醇磷酸酯1000为表面处理剂, 采用碳化法合成了方解石型碳酸钙纳米粒子, 进一步制备了聚对苯二甲酸乙二醇酯/碳酸钙纳米复合材料. 采用透射电子显微镜(TEM)、 X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR), 场发射扫描电子显微镜(FESEM)和热重分析(TGA)对样品进行了分析. 结果表明, 聚乙二醇磷酸酯1000成功地修饰到碳酸钙的表面, 并得到平均直径为60 nm, 形貌为立方体的纳米碳酸钙晶体. 与碳酸钙(空白)样品相比, 表面处理碳酸钙的复合材料表现出更好的分散性和热稳定性. 采用Friedman方法计算了复合材料热分解的活化能. 聚对苯二甲酸乙二醇酯、 聚对苯二甲酸乙二醇酯/空白碳酸钙和聚对苯二甲酸乙二醇酯/表面处理碳酸钙的活化能分别为200.58, 214.86和219.50 kJ/mol, 进一步说明了表面处理碳酸钙更好地改善了聚对苯二甲酸乙二醇酯的热稳定性.     

碳酸钙在聚合物胶束控制下的仿生合成

合成了温敏性的聚(N-异丙基丙烯酰胺)-b-聚(L-谷氨酸)(PNIPAM-b-PLGA)嵌段共聚物,在较高温度下制备了以PNIPAM为核、以PLGA为壳的自组装胶束,研究了胶束对碳酸钙晶体生长的控制作用.使用扫描电镜和X射线衍射表征了碳酸钙晶体的形貌和晶型.当聚合物胶束浓度较高时,得到纤维状的文石;当胶束浓度较低时,...     

柠檬酸钠与碳酸钙晶型和形貌的控制

晶体的晶型和形貌是碳酸钙制备中的关键问题之一。 采用尿素水解均匀沉淀法来控制碳酸钙的晶型和形貌。 利用XRD和SEM等技术手段对CaCO₃晶体的结构和形貌进行了表征。 结果表明,高温条件下(90 ℃)水溶液中得到均匀的针状结构的文石晶体。 添加适量柠檬酸钠后,则得到的是特殊形貌的方解石晶体。 在乙醇/水混合溶剂中,柠檬酸钠对CaCO₃晶体的形貌也有重要影响,通过改变乙醇体积分数,得到了中空绒毛球状的球霰石。     

高分子模板调控不同形貌氧化亚铜的仿生合成

采用聚丙烯酰胺(PAM)为软模板,在CuSO4、Na2SO3体系中调控合成了片状、海胆状、一维线、针状聚集体氧化亚铜晶体。研究了不同浓度Cu2+、不同PAM含量及不同温度对晶体生长的影响。结果表明,PAM促使氧化亚铜异相成核,氧化亚铜形貌随PAM质量分数的变化而变化:当c(Cu2+)=0.5mol.L-1时,PAM质量分数为3.0%(常温引入体系),产物主要为片状晶体;PAM质量分数为1.0%、3.0%时(高温引入体系),分别获得一维线状、海胆状晶体;当Cu2+浓度为0.1 mol.L-1时,体系中高温引入质量分数3.0%的PAM,得到片层状晶体;当Cu2+浓度为0.3、0.4 mol.L-1时,得到针状聚集体氧化亚铜晶体。分别用X射线粉末衍射、冷场发射扫描电子显微镜和激光粒度仪对所制备的产品进行了表征。     

分散聚合法制备微米级核壳复合粒子

在硬脂酸改性纳米CaCO3存在下进行了苯乙烯(St)和丙烯酸正丁酯(nBA)的分散共聚合,制备了平均粒径为1.76 μm、单分散性较好的CaCO3/P(St-co-nBA) 核壳复合粒子。包覆层聚合物P(St-co-nBA)与CaCO3粒子之间存在物理吸附和化学键合作用,使其热分解温度比共聚物P(St-co-nBA)高。 经热二甲苯抽提后复合物中仍有共聚物存在,这部分共聚物与CaCO3通过化学键牢固的结合。 热失重结果表明,CaCO3的稳定包覆率为6.6%。     

马来酸酐(MAH)表面改性纳米碳酸钙粉体的制备及表面性能

通过在两相法制备纳米碳酸钙的过程中添加一定量的马来酸酐(MAH)的方法，在纳米碳酸钙的表面引入羧基、羟基、双键等活性基团对纳米碳酸钙进行表面改性，并通过调节马来酸酐的用量，有效地控制纳米碳酸钙的极性和表面能。接触角实验结果表明，当马来酸酐的加入量为2%时可以获得界面性能最理想的改性纳米碳酸钙。还在此基础上提出了马来酸酐(MAH)对纳米碳酸钙进行表面改性的过程机理，并以SEM，ATR-FTIR和TGA等手段对上述过程机理进行了验证。     

纳米CaCO3改性对医用胶乳制品的影响

纳米CaCO3是20世纪80年代发展起来的一种新型超细固体材料。由于纳米CaCO3的超细微化，其晶体结构和表面电子结构发生变化，产生普通碳酸钙所不具有的量子尺寸效应、小尺寸效应、表面效应和宏观量子效应。也由于纳米CaCO3的超细微化，使其自身存在难以克服的缺点——附聚形成二次结构。如果附聚粒子最终不能被碾碎后分散，就会潜伏下来，成为应力集中点，最终导致改性材料性能的下降，欲充分发挥纳米CaCO3的纳米效应，有必要研究其填充改性的影响因素，从而确立纳米CaCO3填充改性的最佳参数。实验证明：纳米CaCO3表面状态、含量、表面处理剂用量、纳米CaCO3表面活化改性时搅拌时间都对纳米CaCO3填充改性的效果产生影响。     

Photochromism of mixed crystals containing bisthienyl-, bisthiazolyl-, and bisoxazolylethene derivatives

Single crystals composed of two or three different kinds of diarylethenes, having similar geometrical structures but different colors in the closed-ring isomers, 1,2-bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene (1a), 1,2-bis(5-methyl-2-phenyl- 4-thiazolyl)perfluorocyclopentene (2a), and 1,2-bis(5-methyl-2-phenyl-4-oxazolyl)perfluorocyclopentene (3a) have been prepared in an attempt to form single crystals which exhibit different colors, depending on illumination wavelengths. When 1a and 2a are mixed in ethanol and the content of 2a in the feed is higher than that of 1a, only a needle-shaped crystal is obtained. The crystal shape is similar to that of 2a. On the other hand, high content of 1a in the feed leads to formation of a block-shaped crystal, of which the shape is similar to that of 1a. At a feed ratio of 1:1 for 1a and 2a, two types of crystals such as needle- and block-shapes are obtained from the same batch. Mixed crystals composed of three kinds of derivatives 1a/2a/3a have also been prepared. A crystal composed of the three derivatives in the molar ratio of 32 (1a):53 (2a):15 (3a) was obtained. X-ray analysis proved that 1a and 3a are packed in the crystal lattice of 2a. The mixed crystal 1a/2a/3a changed color from colorless to yellow, red, and blue upon irradiation with light of appropriate wavelengths.     

碳酸钙的原位合成及表面改性

利用碳化法, 选用几种常见的改性剂(硬脂酸钠、十八碳醇磷酸酯和油酸)对碳酸钙进行了原位合成及表面改性. 通过活化度、白度、接触角的测定, 对比了其改性效果, 同时通过傅里叶变换红外光谱(FT-IR)、X射线衍射(XRD)、透射电镜(TEM)等测试手段对产品进行表征. FT-IR结果表明, 改性剂与碳酸钙表面是以化学键合和物理吸附方式相结合. 碳酸钙改性后, 其红外υ3特征吸收峰出现约44 cm-1的蓝移现象. 对反应机理进行了初步探讨. 实验结果表明, 当十八碳醇磷酸酯用量达到2%(以碳酸钙的质量分数计)时, 产品活化度达到99.9%, 白度值达到97.3%, 接触角达到了122.25°, 从而为新型无机填料的制备提供了理论依据和合成手段.     

Structural, vibrational and ab initio studies of L-histidine oxalate

Single crystals of L-histidine oxalate were obtained by slow evaporation of an aqueous solution at room temperature. The grown crystals have been subjected to X-ray diffraction (XRD), Infrared, and Raman spectroscopy. The title compound crystallises in the non-centrosymmetric space group P2(1)2(1)2(1,) the crystal cohesion is achieved by relatively strong hydrogen bonds, so that the NH3 groups show significant distortion with respect to the tetrahedral symmetry. Raman and infrared spectra of the title compound were recorded in the frequency range 300-3200 and 400-4000 cm-1, respectively. To obtain a reliable assignment of the observed spectral lines, we have calculated the geometry and the frequencies of the vibrational modes of histidine cation and the oxalate anion using the semi empirical PM3 method.     

Pd nanoparticle aging and its implications in the suzuki cross-coupling reaction

Examination of the catalysts recovered in the N,N-dihexylcarbodiimide-palladium nanoparticle composite catalyzed Suzuki cross-coupling reactions revealed that the metal nanoparticles transformed gradually from spherical-shape to larger needle-shaped crystals. Two types of Ostwald ripening processes were observed. One involves rapid aggregation of the incipient nanoparticle catalyst (2-5 nm) into blackberry-like assemblies (100-200 nm), which is accompanied with the much slower dissolution of small crystals or amorphous nanoparticles and the formation of larger needle-shaped crystals. The observed structural changes provided new insights into the durability of the polymer nanoparticle composite catalyst.     

Oxorhenium(V) complexes with the non-sulfur-containing amino acid histidine

Equivalent amounts of ReOX(3)(OPPh(3))(Me(2)S) (where X = Cl, Br) and L-histidine (L-hisH) in acetonitrile yield ReOX(2)(L-his), in which the amino acid monoanion is N,N,O-tridentate. X-ray diffraction work on both compounds shows that the three donors occupy a face in a distorted octahedron and the carboxylate oxygen is coordinated trans to the Re=O bond. The 2:1 complex [ReO(L-his)(2)]I is obtained by reacting 2 equiv of L-histidine with ReO(2)I(PPh(3))(2) in methanol in the presence of NaOCH(3). (1)H NMR spectroscopy indicates that these complexes contain one N,N,O-tridentate histidine anion coordinated as above and one N,N-bidentate histidine anion, whose carboxylate group is free. By refluxing ReOX(2)(L-his) in methanol, the carboxylic groups esterify and two octahedral units condense into an oxo-bridged dinuclear complex [ReOX(2)(L-hisMe)](2)O containing N,N-bidentate histidine methyl ester. The O=Re-O-Re=O backbone is approximately linear, and the two ReOX(2)(L-hisMe) units are related by a 2-fold axis through the central oxygen. Crystals of [ReOBr(2)(L-hisMe)](2)O consist of an ordered phase containing two of the possible diastereoisomers in a 1:1 ratio. (1)H NMR spectra of these crystals include two sets of signals, consistent with the presence of two isomers with C(2) symmetry, and the spectra of the nonrecrystallized material confirm that these are the only two isomers formed.     

<Emphasis Type="Italic">In situ</Emphasis> synthesis and modification of calcium carbonate nanoparticles via a bobbling method

Modified calcium carbonate (CaCO₃) nanoparticles with cubic- and spindle-like configuration were synthesized in situ by the typical bobbling (gas-liquid-solid) method. The modifiers, such as sodium stearate, octadecyl dihydrogen phosphate (ODP) and oleic acid (OA), were used to obtain hydrophobic nanoparticles. The different modification effects of the modifiers were investigated by measuring the active ratio, whiteness and the contact angle. Moreover, transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetry analysis (TGA analysis) were employed to characterize the obtained products. A preliminary reaction mechanism was discussed. According to the results, the active ratio of CaCO₃ modified by ODP was ca. 99.9% and the value of whiteness was 97.3% when the dosage of modifiers reached 2%. The contact angle was 122.25° for the CaCO₃ modified in the presence of sodium stearate, ODP and OA. When modified CaCO₃ was filled into PVC, the mechanical properties of products were improved greatly such as rupture intensity, pull intensity and fuse temperature. The compatibility and affinity between the modified CaCO₃ nanoparticles and the organic matrixes were greatly improved. Supported by the National Natural Science Foundation of China (Grant No. 50372025)     

模拟生物矿化过程原位合成活性纳米碳酸钙

生物矿化是一种广泛而复杂的固液之间、有机物和无机物间的物理化学过程．以少量有机质为模板,进行分子操作,高度有序地组合成无机材料．有机基质能作为构造支持的惰性底质或矿物沉淀的局限空间和核化作用的表面,确定矿物质点的形态大小、空间排列、结晶取向和同质多晶类型,并与生物晶体一起确定生物矿物硬体的机械性质．