Beurling-Ahlfors延拓的伸张函数

本文研究了实轴上的保向同胚映照到上半平面的Beurling-Ahlfors延拓的性质.对上半平面及实轴附近的伸张函数分别作了估计,获得了一个最佳估计,改进了已有的结果.     

Effect of Sodium Alginate Concentration on Membrane Strength and Permeating Property of Poly-l-arginine Group Microcapsule

A novel poly-l-arginine microcapsule was prepared due to its nutritional function and pharmacological efficacy. A high-voltage electrostatic droplet generator was used to make uniform microcapsules. The results show that the membrane strength and permeating property are both remarkably affected with the changes of sodium alginate concentration. With the sodium alginate concentration increasing, gel beads sizes increase from 233μtm to 350μtm, release ratio is also higher at the same time, but the membrane strength decreases.     

手性拆分l-脯氨酸分子印迹聚合物的制备及其性能

以壳聚糖(CTS)为功能基体,以L-脯氨酸(L-Pro)为模板分子,采用分子印迹技术,在水溶液中合成了在空间结构和结合位点上与L-脯氨酸匹配的分子印迹聚合物(L-Pro-M IPs)。利用红外、扫描电镜和热失重分析,对相关化合物进行了表征,并对合成机理进行初步探索;通过对pH值、反应时间、交联剂用量的调节,获得最佳的反应条件为:制备壳聚糖-L-脯氨酸复合物的pH=10.7,干复合物1.0 g,交联剂8 mL,室温下反应18 h。结果表明,在水相中,L-Pro-M IPs对L-Pro具有良好的吸附选择性和高效分离特性,分离因子为4.67。     

镍-镧合金的电沉积及其晶化行为与析氢性能

在尿素-溴化钠熔体中电沉积Ni-La合金,考察了合金的沉积行为和阴极电流密度对合金组成和表面形貌的影响。结果表明,镧与镍经过诱导共沉积形成Ni-La合金;随着阴极电流密度的增加,镀层中镧含量先升高后降低（在15 mA·cm^-2条件下达到最高）,镀层表面微粒变大。用热分析技术和X射线衍射研究了Ni89.7La10.3合金的晶化行为,该合金在镀态时呈非晶态结构,在446.1℃热处理后的镀层晶化生成面心立方Ni-La相（Fm3m）。采用电化学技术研究了该镀层的电催化析氢性能,实验证实Ni89.7La10.3合金的电催化析氢性能优于镍。     

Photocatalysis of 4-nitrophenol using zinc phthalocyanine complexes

Photodegradation of 4-nitrophenol (4-Np) in the presence of zinc tetrasulfophthalocyanine (ZnPcS₄), zinc octacarboxyphthalocyanine (ZnPc(COOH)₈) and a sulfonated ZnPc containing a mixture of differently sulfonated derivatives (ZnPcS_mix), as photocatalysts is reported. ZnPcS_mix is the most effective catalyst in terms of a high quantum yield for 4-Np degradation and the stability of the catalyst. However ZnPc(COOH)₈ degrades readily during the catalysis, but it has a higher quantum yield (Φ_4-Np) for 4-Np degradation than the rest of the complexes. The Φ_4-Np values were closely related to the singlet oxygen quantum yields Φ_Δ and hence aggregation. The rate constants for the reaction with 4-Np were k_r = 0.67 × 10⁶ mol⁻¹ dm³ s⁻¹ for ZnPcS_mix and 2.8 × 10⁸ mol⁻¹ dm³ s⁻¹ for ZnPc(COOH)₈.     

PMMA/graphite nanosheets composite and its conducting properties

Graphite nanosheets (NanoG) were prepared by treating the expanded graphite with sonication in aqueous alcohol solution. Nanocomposites of poly(methyl methacrylate) (PMMA) with NanoG were prepared via an in situ polymerization of MMA in the presence of NanoG with the aid of sonication. The nanocomposites were then dispersed with chloroform (CHCl₃) and casted on glass slides to form conducting films. The percolation threshold of PMMA/NanoG conducting films at room temperature was as low as 0.31 vol%, much lower than that of the composites filled with conventional graphite particles. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area diffraction (SAD) and etc. were used to characterize the structure of the graphite nanosheets and the nanocomposites. Results showed that the high-aspect-ratio structure of graphite nanosheets played an important role in forming conducting network in PMMA matrix. The conducting behavior of the composite was interpreted by percolation theory.     

An extremely sensitive monoboronic acid based fluorescent sensor for glucose

An extremely sensitive monoboronic acid based fluorescent sensor for glucose was developed. This was carried out by assembling a fluorescent monoboronic acid, 3-aminophenylboronic acid (PBA) indirectly onto gold surface via its electrostatic interaction with cysteine (Cys) that was directly assembled on the gold surface. The formation of self-assembled bilayers (SAB) was confirmed and primarily characterized by cyclic voltammetry and X-ray photoelectron spectra (XPS). The SAB containing PBA was found fluorescent and its fluorescence showed an extremely high sensitivity to the presence of glucose and other monosaccharides such as galactose and fructose with quenching constants at 10⁸ M⁻¹ order of magnitude compared to those at 10² M⁻¹ in bulk solutions. The quenching constants were found to vary in the order of that is different from that in bulk solution which shows the highest binding affinity toward d-fructose and very low sensitivity toward glucose. The reported monoboronic acid based SAB fluorescent sensor showed the highest sensitivity towards glucose with the capacity of detecting saccharides of concentration down to nanomolar level. It was also demonstrated that the fluorescence from PBA/Cys/Au can be easily recovered after each measurement event and therefore also represents a new reusable method for immobilizing reagent in fabricating chemosensors.     

Hydrothermal synthesis and structure of one-dimensional Co(dien)2(VO3)3·(H2O) (dien=diethylenetriamine)

One-dimensional Co(dien)₂(VO₃)₃·(H₂O) was prepared from the hydrothermal reaction of NH₄VO₃, Co₂O₃, diethylenetriamine (dien) and H₂O at 130 °C. The compound crystallizes in the monoclinic system, space group P2₁/c with a=16.1581(6) Å, b=8.7006(3) Å, c=13.9893(4) Å, β=103.1483(11)°, V=1915.13(11) Å³, Z=4, and R₁=0.0268 for 3060 observed reflections. Single crystal X-ray diffraction revealed that the structure is composed of infinite one-dimensional chains formed by corner-sharing VO₄ tetrahedra with Co(dien)³⁺ complex cations and crystallization water molecules occupying the interchain positions, which are held together to a three-dimensional network via extensive hydrogen-bonding interactions. The compound, with a new zig-zag conformation of metavanadate chains, is the first example of vanadium oxides incorporating trivalent transition metal coordination groups. Other characterizations by elemental analysis, IR and thermal analysis are also described.     

New trends of molecular probes based on the fluorophore 4-amino-1,8-naphthalimide

4-Amino-1,8-naphthalimide (ANI) is one of the popular fluorophores for the constructions of various probes. In this review, the major progresses of ANI probes in the past decade have been highlighted and categorized into three trends. The future development of ANI probes has been expected, too.     

含钴(Ⅱ)配阳离子的MoS2基嵌入化合物

本文测量了表面ζ电位随pH值的变化关系，表明MoS₂单分子层表面吸附的是OH^-离子，其等电点在pH=2附近。在pH=5～10范围内，ζ电位在-22到-24 mV之间，较为稳定。在pH=7.2条件下，利用MoS₂单分子层与钴(Ⅱ)配位阳离子基团反应合成了3个嵌入化合物[Co(H₂O)_z]_y/2MoS₂、[Co(bpy)₃]_y/2MoS₂和[Co(phen)₃]_y/2MoS₂。X-射线衍射、元素分析和热重分析研究表明前一个化合物中每10个{MoS₂}单元约嵌入一个水合钴离子，层间距增大了0.893nm，水合钴离子在基体层间按双层错开排列。后两个化合物中每20个{MoS₂}单元约嵌入一个钴有机配阳离子，层间距分别增大了0.953和1.018 nm，配位阳离子则单层排列于MoS₂基体层间，[Co(bpy)₃]²⁺和[Co(phen)₃]²⁺离子中CoN₆配位八面体的三次对称轴近于垂直于MoS₂基体层板。