C60空心纳米壳的制备及研究

利用超声技术, 选择间二甲苯溶液和乙腈两种不互溶的溶剂, 首次成功地制备了C60的空心纳米壳. 选择扫描电镜(SEM), 透射电镜(TEM)等对所制得的C60的空心纳米壳的形貌及结构进行表征. C60空心纳米壳的外直径为300～400 nm, 内直径为200～300 nm, 壁厚约100 nm. X射线衍射光谱(XRD)、傅里叶红外光谱检测结果表明其为C60分子组成的单晶结构. 利用电泳方法制备了均匀的C60的空心纳米壳膜电极, 并利用电沉积方法在所制备的C60的空心纳米壳电极表面沉积了金(Au)纳米颗粒. 为进一步沉积其它金属, 研究其在生物传感器及燃料电池方面的应用提供了基础.     

H2和CO在间二甲苯中的溶解度和体积传质系数的研究

使用ＩＬ搅拌釜，在温度８０～１６０℃，压力０．５～５．０ＭＰａ范围内，实测了Ｈ２和ＣＯ在间二甲苯中的溶解度和体积传质系数。结果表明，两者均随温度和压力的升高而增大。实验结果与工于正规溶液理论Ｐｒａｕｓｎｉｔｚ－Ｓｈａｉｒ法计算的气体溶解度比较相符。在相同温度、压力条件下，ＣＯ的溶解度和体积传质系数比Ｈ２大。相同温度、压力下不同液相介质中Ｈ２和ＣＯ的体积传质系数排序如下：（ｋＬａ）ＭＥＦ〉（ｋＬａ）     

Macrocyclic hosts for fullerenes: extreme changes in binding abilities with small structural variations

Exploiting the shape and electronic complementarity of C(60) and C(70) with π-extended derivatives of tetrathiafulvalene (exTTF), we have very recently reported a macrocyclic receptor featuring two exTTF recognizing units which forms 1:1 complexes with C(60) with log K(a) = 6.5 ± 0.5 in chlorobenzene at 298 K. This represents one of the highest binding constants toward C(60) reported to date and a world-record for all-organic receptors. Here, we describe our efforts to fine-tune our macrocyclic bis-exTTF hosts to bind C(60) and/or C(70), through structural variations. On the basis of preliminary molecular modeling, we have explored p-xylene, m-xylene, and 2,6-dimethylnaphthalene as aromatic spacers between the two exTTF fragments and three alkene-terminated chains of different length to achieve macrocycles of different size through ring closing metathesis. Owing to the structural simplicity of our design, all nine receptors could be accessed in a synthetically straightforward manner. A thorough investigation of the binding abilities of these nine receptors toward C(60) and C(70) has been carried out by means of UV-vis titrations. We have found that relatively small variations in the structure of the host lead to very significant changes in affinity toward the fullerene, and in some cases even in the stoichiometry of the associates. Our results highlight the peculiarities of fullerenes as guests in molecular recognition. The extreme stability of these associates in solution and the unique combination of electronic and geometrical reciprocity of exTTF and fullerenes are the main features of this new family of macrocyclic hosts for fullerenes.     

Importance of Debye and Keesom interactions in separating m-xylene and p-xylene in GC-MS analysis utilizing PEG stationary phase

In electron impact gas chromatography (GC)-mass spectrometry analysis of a complex mixture, such as gasoline, two coeluting solutes can be distinguished if each has a unique major ion. The boiling-point difference between m-xylene and p-xylene, which also has identical major ions (mz-1: 91 and 106 Da), is 0.77 degrees C. These cannot be separated even on a crossed-linked polydimethylsiloxane capillary column, which has a minimum of 5000 plates/m. They are separated on a crossed-linked polar polyethylene glycol (PEG) capillary column. GC separation on a stationary phase depends on the relative strengths of solute-solute, stationary phase-stationary phase, and solute-stationary phase interactions. Although the calculated molar electronic polarization and refractivity factor of Lorenz-Lorentz equation for m-xylene and p-xylene are nearly equal because of its greater dipole moment difference (0.30 and 0.02), the calculated orientation polarization of m-xylene is 80 times greater than p-xylene. This implies the dipole reinforcement through inductive polarization by the hydroxyl of PEG stationary phase molecules is greater on m-xylene than p-xylene. In addition, as the permanent dipole moment of m-xylene is 15 times greater than p-xylene, m-xylene has a stronger Keesom interaction with PEG. In order for m-xylene and p-xylene to solvate in PEG, analytes must overcome the PEG-PEG Keesom/hydrogen bonding interaction forces. Physical and chemical parameters indicate that compared with p-xylene, m-xylene has a greater Debye-Keesom interaction tendency with PEG molecules. This is supported by the 0.12-min. retention-time difference between them.     

(Phen)2.5HPW/WO3复合空心微球的制备及光催化性能

通过磷钨酸H3PW12O40(HPW)和邻菲啰啉C12H8N2(Phen)的溶液反应,合成了杂多化合物(C12H8N2)2.5H3PW12O40((Phen)2.5HPW),以WO3空心微球为载体,负载杂多化合物(Phen)2.5HPW,制备了(Phen)2.5HPW/WO3复合空心微球.用等离子体原子发射光谱(ICP...     

Isolating benzenium ion salts

When partnered with carborane anions, arenium ions are remarkably stable. Previously investigated only at subambient temperatures in highly superacidic media, protonated benzene is readily isolated as a crystalline salt, thermally stable to >150 degrees C. Salts of the type [H(arene)][carborane] have been prepared by protonating benzene, toluene, m-xylene, mesitylene, and hexamethylbenzene with the carborane superacid H(CB(11)HR(5)X(6)) (R = H, Me; X = Cl, Br). They have been characterized by elemental analysis, X-ray crystallography, NMR and IR methods. Solid-state (13)C NMR spectra are similar to those observed earlier in solution, indicating that lattice interactions are comparable to solution solvation effects. The acidic proton(s) of the arenium cations interact weakly with the halide substituents of the anion via ion pairing. This is reflected in the dependence of the C-H stretching frequency on the basicity of the carborane anion. Bond lengths in the arenium ions are consistent with predominant cyclohexadienyl cation character, but charge distribution within the cation is less well represented by this resonance form. Structural and vibrational comparison to theory is made for the benzenium ion (C(6)H(7)(+)) with density functional theory at B3LYP/6-31G and B3P86/6-311+G(d,p) levels. The stability of these salts elevates arenium ions from the status of transients (Wheland intermediates) to reagents. They have been used to bracket the solution-phase basicity of C(60) between that of mesitylene and xylene.     

Long TiO2 hollow fibers with mesoporous walls: sol-gel combined electrospun fabrication and photocatalytic properties

Long TiO2 hollow fibers with mesoporous walls have been fabricated with the sol-gel combined two-capillary spinneret electrospinning technique using a triblock copolymer (Pluronic, P123, (H(C2H5O)20(C3H7O)70 (C2H5O)20OH) as a pore-directing agent. The as-prepared hollow fibers were as long as 30 cm with an outer diameter of 0.1-4 microm and wall thickness of 60-500 nm. The diameters and wall thicknesses of the hollow fibers could be tuned by adjusting the electrospinning parameters. The fiber walls were composed of mesopores 6.7 nm in diameter as calculated from the N2 adsorption/desorption isotherm. The high-resolution TEM (HR-TEM) images exhibited that the mesopores were hexagonally aligned with a low order because of the curving of the pores. When comparing with other nanostructured TiO2 materials such as commercial TiO2 nanoparticles (P25, Degussa) and mesoporous TiO2 powders, the hollow fibers exhibited higher photocatalytic activities toward degradation of methylene blue and gaseous formaldehyde.     

Controlling the incorporation and release of C60 in nanometer-scale hollow spaces inside single-wall carbon nanohorns

We succeeded in large-scale preparation of single-wall carbon nanohorns (SWNH) encapsulating C60 molecules in a liquid phase at room temperature using a "nano-precipitation" method, that is, complete evaporation of the toluene from a C60-SWNH-toluene mixture. The C60 molecules were found to occupy 6-36% of the hollow space inside the SWNH, depending on the initial quantity of C60. We showed that the C60 in C60@SWNHox was quickly released in toluene, and the release rate decreased by adding ethanol to toluene. Numerical analysis of the release profiles indicated that there were fast and slow release processes. We consider that the incorporation quantity and the release rate of C60 were controllable in/from SWNHs because SWNHs have large diameters, 2-5 nm.     

The preparation and characterization of silver‐loading cellulose acetate hollow fiber membrane for water treatment

Silver‐loading asymmetric cellulose acetate (CA) hollow fiber membrane was spun via the dry jet‐wet spinning technique. The spinning solution was prepared by dissolving AgNO₃ and CA in N,N‐dimethylformamide (DMF). The silver ions were reduced in the spinning dope into silver nano‐particles. The morphology of the resulting hollow fibers was examined using a scanning electron microscope and the silver content in the fiber was measured using an inductively coupled plasma atomic emission spectrometer. The antibacterial activities were evaluated. These hollow fibers had a sponge‐like structure and dense inner and outer surfaces. At a 50 k magnification, the pore on the skin layer was not observable, while the nodule size was smaller than 10 nm. The residual silver content of as‐spun hollow fiber was about 60% of the original silver added in the polymer solution. After immersing in water bath for 180 days, the silver content in the bulk of the hollow fibers decreased to 60% and the silver content on the surface reduced to 10%, yet still showed antibacterial activity against Escherichia coli and Staphylococcus aureus. After permeating with water for 5 days, the silver content in the hollow fibers decreased, and did not show antibacterial activity against E. coli and S. aureus. Thus, silver content must be periodically replenished after permeation. The proper range of AgNO₃ in the spinning solution for CA hollow fiber should be about 100–1000 ppm. Copyright © 2005 John Wiley & Sons, Ltd.     

Template-free synthesis of CdS hollow nanospheres based on an ionic liquid assisted hydrothermal process and their application in photocatalysis

Polycrystalline CdS hollow nanospheres with diameter of about 130 nm have been successfully synthesized in high yield by an ionic liquid (IL) assisted template-free hydrothermal method for the first time. Both the molar ratios of Cd/S precursor in the solution and the reaction temperature play important roles in the formation of the CdS hollow nanospheres. The concentrations of capping agent hexamethylenetetramine (HMT) and polyvinylpyrrolidone (PVP) are also crucial for the morphology and size of the final product. IL was found to be a key component in the formation of CdS hollow structures, because solid spheres were obtained in the absence of IL. A subsequent growth mechanism of hollow interior by localized Ostwald ripening process has been further discussed. Such hollow structures show high photocatalytic ability in the photodegradation of methylene blue.     

(Phen)2.5HPW/WO3复合空心微球的制备及光催化性能

通过磷钨酸H3PW12O40(HPW)和邻菲啰啉C12H8N2(Phen)的溶液反应,合成了杂多化合物(C12H8N2)2.5H3PW12O40((Phen)2.5HPW),以WO3空心微球为载体,负载杂多化合物(Phen)2.5HPW,制备了(Phen)2.5HPW/WO3复合空心微球.用等离子体原子发射光谱(ICP-AES)、元素分析(EA)、热重-差热分析(TG-DTA)、傅里叶变换红外光谱(FTIR)、扫描电子显微镜(SEM)、紫外-可见漫反射吸收光谱(UV-vis DRS)对样品进行了表征.在高压汞灯照射下,研究了杂多化合物(Phen)2.5HPW、WO3空心微球和(Phen)2.5HPW/WO3复合空心微球对甲基橙水溶液的光催化降解活性,结果表明,(Phen)2.5HPW/WO3复合空心微球的光催化活性高于单独的杂多化合物(Phen)2.5HPW和WO3空心微球,催化剂易于回收,光催化性能稳定.     

Study on the effect of spinning conditions and surface treatment on the geometry and performance of polymeric hollow-fibre membranes

Hollow-fibre membranes were prepared by the wet-dry spinning technique from polyether sulfone (PES). The effect of spinning conditions such as the flow-rate of the internal coagulant and the flow-rate, composition and temperature of the polymer solution on the geometry and performance of hollow fibres was studied. In particular, five different ratios of pore former/polymer covering the range 0.2–1.0 were investigated while the polymer content was kept constant. Since the viscosity of the spinning dope affects the morphology of the hollow-fibre membrane, hollow fibres were prepared at different temperatures of the spinning dope from 25 to 60°. By scanning electron microscopy (SEM) two layers sandwiching a finger-like cavity structure were observed. Also, the surface on the bore side of the hollow fibre was modified by grafting polyethylene glycol (PEG) with γ-ray irradiation to improve the ultrafiltration performance.     

Silicon dioxide hollow microspheres with porous composite structure: synthesis and characterization

In this paper, a strategy for hollow porous silica microspheres with ideally flower structure is presented. SiO(2)/PAM hybrid composite microspheres with porous were synthesized by the reaction that the porous polyacrylamide (PAM) micro-gels immersed in tetraethoxysilane (TEOS) anhydrous alcohol solution and water in a moist atmosphere, with ammonium hydroxide as a catalyst. The SiO(2) hollow microspheres with porous were obtained after calcination of the composite microspheres at 550 °C for 4 h. The morphology, composition, and crystalline structure of the microspheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo-gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FI-IR), and X-ray diffraction (XRD), N(2) absorption analysis, respectively. The results indicated that the obtained hollow porous SiO(2) microspheres were a perfect flower structure.     

Low-temperature synthesis of alpha-MnO2 hollow urchins and their application in rechargeable Li+ batteries

Novel alpha-MnO2 hollow urchins were synthesized on a large scale by a facile and efficient low-temperature (60 degrees C) mild reduction route, without templates or surfactants in the system. The formation mechanism for the hollow urchins was proved to be the Ostwald ripening process by tracking the crystallization and morphology of the product at different reaction stages. The as-prepared hollow-urchin sample has a high Brunauer-Emmett-Teller surface area of 132 m(2)/g and a mesoporous structure, which were expected to help improve the electrochemical property in Li+ batteries. When the alpha-MnO2 hollow urchins were used as the cathode material in Li batteries, they performed better than the other alpha-MnO2 samples (solid urchins and dispersed nanorods), indicating that the electrochemical performance of the electrode material is sensitive to its morphology. This synthetic procedure is straightforward and inexpensive and thus facilitates mass production of alpha-MnO2 hollow urchins.     

二甲苯、卤代苯在硝酸银溶液中的溶解平衡

具有C＝C双键的许多有机化合物可与银离子形成络合物。L.J.Andrews和R.M.Kcefcr等用在含Ag⁺的芳烃溶液中测定溶解度的方法,计算了某些芳烃与Ag⁺络合物的形成常数^[1]。     

A new simple method to prepare hollow PES microspheres

A new simple method for the formation of hollow polyethersulfone (PES) microspheres was reported in this paper. Coaxial electrospraying equipment and nonsolvent precipitating bath were used to produce hollow microspheres in one step. The properties of the core solution affected the formation of hollow PES microspheres. To form hollow microspheres in one step, the core solution should be removed directly by a nonsolvent. Additionally, the core solution should also be used to occupy the internal space of microspheres and form a supporting layer at the interface between the core solution and the shell solution. The supporting layer formed by the micro-phase that was caused by the phase separation of the core or shell solution was the key factor for the formation of hollow PES microspheres. The performance of hollow microspheres produced by this method was excellent. This method provided a new simple way to form hollow polymer microspheres and can be extended to other polymers to prepare hollow microspheres in one step.     

Integration of a wet analysis system on a glass chip: determination of Co(ii) as 2-nitroso-1-naphthol chelates by solvent extraction and thermal lens microscopy

The integration of a wet analysis system on a glass chip was demonstrated and determination of Co(II) was performed using this system. The Co(II) was extracted into m-xylene from aqueous solution as 2-nitroso-1-naphthol chelates, and colorimetric determination of the m-xylene phase was applied by a thermal lens microscope. The integration of the chemical operation procedures shown here leads to a considerable reduction in analyzing time. The time for extraction in the integrated system, 10 min, was about tenfold shorter than a conventional system using a separatory funnel and mechanical shaker. Moreover, troublesome operations such as phase separation necessary for the conventional system could be omitted. The determination of Co(II) in the range 2 x 10(-7)-1 x 10(-8) M, which was estimated to be 0.072-1.44 zmol, was achieved.     

Self-assembled photoresponsive amphiphilic diphenylaminofluorene-C60 conjugate vesicles in aqueous solution

Water-soluble oligo(ethylene glycolated) derivatives of two-photon absorptive diphenylaminofluorenocarbonyl-methano[60]fullerene, denoted as C60(>DPAF-EG6), were synthesized with their molecular self-assembly characteristics in H2O studied. The formation of nano- to submicron-sized spherical hollow vesicles with a shell width of 15-20 nm was observed by transmission electron microscopy (TEM) micrographs. This shell width fits approximately with the length of a disordered bilayer-like molecular packing of C60(>DPAF-EG6), arising from strong intermolecular hydrophobic interactions of fullerene cages. Photoinduced intramolecular charge separation followed by charge recombination on the nanosecond time scale, from the DPAF moiety to the C60 cage in the vesicle structure, was detected via transient spectroscopic measurements.     

Development and application of microporous hollow fiber protected liquid-phase microextraction via gaseous diffusion to the determination of phenols in water

A new organic solvent-free microextraction technique termed liquid-gas-liquid microextraction (LGLME) was developed. In this technique, a small amount (6 microl) of aqueous acceptor solution (0.5M NaOH) is introduced into the channel of a 2.65 cm polypropylene hollow fiber. The hollow fiber is then immersed in an aqueous sample donor solution. The aqueous acceptor phase in the channel of the hollow fiber is separated from the sample solution by the hydrophobic microporous hollow fiber wall with air inside its pores. The analytes (phenols) passed through the microporous hollow fiber membrane by gas diffusion and were then trapped by the basic acceptor solution. After extraction, the acceptor solution was withdrawn into a microsyringe and injected into a capillary electrophoresis sample vial for subsequent analysis. Limits of detection of between 0.5 and 10 microg/l for eight phenols could be achieved. The relative standard deviations (n=6) of this technique between 2.7 and 7.6%. The technique also provides good enrichment factors for all the eight analytes.     

Direct determination of chlorophenols in environmental water samples by hollow fiber supported ionic liquid membrane extraction coupled with high-performance liquid chromatography

The 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) ionic liquid was immobilized in the pores of a polypropylene hollow fiber for hollow fiber-protected liquid-phase microextraction. Analytes including 4-chlorophenol (4-CP), 3-chorophenol (3-CP), 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) were extracted into this ionic liquid membrane, and back extracted into 10microL sodium hydroxide acceptor solution in the lumen of the hollow fiber. Then, the acceptor solution was withdrawn into the high-performance liquid chromatography (HPLC) microsyringe connected to the hollow fiber, and directly injected into the HPLC system for analysis. Some parameters that might affect the extraction efficiency were optimized, and low detection limits (0.5microgL(-1) for 4-CP, 3-CP, DCP and 1.0microgL(-1) for TCP) were obtained. Good repeatability was achieved because of the stability of the hollow fiber-supported ionic liquid membrane. The proposed procedure was applied for direct determination of the four chlorophenols in some real water samples including groundwater, river water, wastewater and tap water. All of the four chlorophenols in these water samples were under the limits of determination, and the recoveries were in the range of 70.0-95.7% at 5microgL(-1) spiked level.