Gold-coated iron (Fe@Au) nanoparticles: Synthesis, characterization, and magnetic field-induced self-assembly

A unique reverse micelle method has been developed to prepare gold-coated iron (Fe@Au) nanoparticles. XRD, UV/vis, TEM, and magnetic measurements are utilized to characterize the nanocomposites. XRD only gives FCC patterns of gold for the obtained nanoparticles. The absorption band of the Fe@Au colloid shifts to a longer wavelength and broadens relative to that of the pure gold colloid. TEM results show that the average size of Fe@Au nanoparticles is about 10 nm, These nanoparticles are self-assembled into chains on micron scale under a 0.5 T magnetic field. Magnetic measurements show that the particles are superparamagnetic with a blocking temperature (T-B) of 42 K, At 300 K (above T-B), no coercivity (Hc) and remanence (M-r) is observed in the magnetization curve, while at 2K (below T-B) He and M, are observed to be 728 Oe and 4.12 emu/g, respectively, (C) 2001 Academic Press.

Surface photovoltage spectra and photoelectrochemical properties of semiconductor-sensitized nanostructured TiO2 electrodes

Three kinds of TiO2 nanostructured thin films and their CdS-sensitized films, consisting of different sizes of TiO2 nanoparticles prepared with different methods, have been investigated. The surface photovoltage spectra (SPS) measurements indicate that the density of surface states on TiO2 is likely dependent upon the details of prepared methods. TiO2 particles prepared from basic sol have more surface states than that prepared from acidic sol. When the TiO2 thin films prepared using the TiO2 sols were sensitized by CdS particles, the SPS responses relative to the surface states on TiO2 from 350 to 800 nm were decreased. The photoelectrochemical properties of nanostructured TiO2 electrodes suggest that the fewer the surface states and the smaller the particle sizes of TiO2, the larger the photocurrent response. For CdS sensitized TiO2 thin film electrode, it is shown that the semiconductor sensitization is an efficient way to decrease the influence of surface states on the charge separation, and can improve the intensity of photocurrent response. (C) 2001 Elsevier Science B.V. All rights reserved.

Compatibilization of blends of polystyrene and zinc salt of sulfonated polystyrene by poly(styrene-b-4-vinylpyridine) diblock copolymer

The compatibilizing effect and mechanism of poly(styrene-b-4-vinylpyridine) diblock copolymer, P(S-b-4VPy), on the immiscible blend of polystyrene (PS)/zinc salt of sulphonated polystyrene (Zn-SPS) were studied. SEM results show that the domains of the dispersed phase in the blend become finer. DSC experiments reveal that the difference between the two T-g's corresponding to the phases in the blends becomes larger on addition of P(S-b-4VPy), mainly resulting from dissolving of the poly(4-vinylpyridine (P4VPy) block in the Zn-SPS phase. FTIR analysis shows that compatibility of P4VPy and Zn-SPS arises from the stoichiometric coordination of the zinc ions of Zn-SPS and pyridine nitrogens of P4VPy. SAXS analysis indicates the effect of the P(S-b-4VPy) content on the structure of the compatibilized blends. When the content of the block copolymer is lower than 4.1 wt%, the number of ion pairs in an aggregate in the Zn-SPS becomes smaller, and aggregates in ionomer in the blend become less organized with increasing P(S-b-4VPy). When the P(S-b-4VPy) content in the blend is up to 7.4 wt%, a fraction of P(S-b-4VPy) form a separate domain in the blend. (C) 1999 Elsevier Science Ltd. All rights reserved.

Compatibilizing effect of polystyrene-block-poly(4-vinylpyridine) for poly(2,6-dimethyl-1,4-phenyleneoxide) chlorinated polyethylene blends

The compatibilizing effect and mechanism of compatibilization of the diblock copolymer polystyrene-block-poly(4-vinylpyridine) P(S-b-4VPy) on immiscible blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)/chlorinated polyethylene (CPE) were studied by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), mechanical properties and FTIR measurements. The block copolymer was synthesized by sequential anionic polymerization and melt-blended with PPO and CPE. The results show that the P(S-b-4VPy) added acts as an effective compatibilizer, located at the interface between the PPO and the CPE phase, reducing the interfacial tension, and improving the interfacial adhesion. The tensile strength and modulus of all blends increase with P(S-b-4VPy) content, whereas the elongation at break increases for PPO-rich blends, but decreases for CPE-rich blends. The polystyrene block of the diblock copolymer is compatible with PPO, and the poly(4-vinylpyridine) block and CPE are partially miscible.

Blends of linear low-density polyethylene and a diblock copolymer of hydrogenated polybutadiene and methyl methacrylate

Blends of linear low-density polyethylene (LLDPE) and a diblock copolymer of hydrogenated polybutadiene and methyl methacrylate [P(HB-b-MMA)] were studied by transimission electron microscope (TEM), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD). At 10 wt% block copolymer content, block copolymer chains exist as spherical micelles and cylindrical micelles in LLDPE matrix. At 50 wt% block copolymer content, block copolymer chains mainly form cylindrical micelles. The core and corona of micelles consist of PMMA and PHB blocks, respectively. DSC results show that the total enthalpy of crystallization of the blends varies linearly with LLDPE weight percent, indicating no interactions in the crystalline phase. In the blends, no distortion of the unit cell is observed in WAXD tests.

Crystallization of micelles and matrix in dilute diblock copolymer/homopolymer solutions

The crystallization, morphology, and crystalline structure of dilute solid solutions of tetrahydrofuran-methyl methacrylate diblock copolymer (PTHF-b-PMMA) in poly(ethylene oxide) (PEO) and PTHF have been studied with differential scanning calorimetry (DSC), X-ray, and optical microscopy. This study provides a new insight into the crystallization behavior of block copolymers. For the dilute PTHF-b-PMMA/PEO system containing only 2 to 7 wt % of PTHF content, crystallization of the PTHF micellar core was detected both on cooling and on heating. Compared the crystallization of the PTHF in the dilute solutions with that in the pure copolymer, it was found that the crystallizability of the PTHF micellar core in the solution is much greater than that of the dispersed PTHF microdomain in the pure copolymer. The stronger crystallizability in the solution was presumably due to a softened PMMA corona formed in the solution of the copolymer with PEG. However, the "soft" micelles formed in the solution (meaning that the glass transition temperatures (T-g) of the micelle is lower than the T-m of the matrix phase) showed almost no effects on the spherulitic morphology of the PEO component, compared with that of the pure PEO sample. In contrast, significant effects of the micelles with a "hard" PMMA core (meaning that the T-g of the core is higher than the T-m of the PTHF homopolymer) on the nucleation, crystalline structure, and spherulitic morphology were observed for the dilute PTHF-b-PMMA/PTHF system. (C) 1998 John Wiley & Sons, Inc.

Compatibilization of blends of polybutadiene and poly(methyl methacrylate) with poly(butadiene-block-methyl methacrylate)

Compatibilization of blends of polybutadiene and poly(methyl methacrylate) with butadiene-methyl methacrylate diblock copolymers has been investigated by transmission electron microscopy. When the diblock copolymers are added to the blends, the size of PB particles decreases and their size distribution gets narrower. In PB/PMMA7.6K blends with P(B-b-MMA)25.2K as a compatibilizer, most of micelles exist in the PMMA phase. However, using P(B-b-MMA)38K as a compatibilizer, the micellar aggregation exists in PB particles besides that existing in the PMMA phase. The core of a micelle in the PMMA phase is about 10 nm. In this article the influences of temperature and homo-PMMA molecular weight on compatibilization were also examined. At a high temperature PB particles in blends tend to agglomerate into bigger particles. When the molecular weight of PMMA is close to that of the corresponding block of the copolymer, the best compatibilization result would be achieved. (C) 1998 John Wiley & Sons, Inc.

THE VISCOSITY BEHAVIOUR OF SEP BLOCK COPOLYMER SOLUTION DURING ITS MICELLIZATION

The viscosities of polystyrene-b-poly (ethylene/propylene) diblock copolymer in mixed solvent of n-octane and benzene were measured. The influences of the constitution of the mixed solvent, temperature and concentration were on the viscosity investigated. During the micellization the solution viscosity increases rapidly. The results are consistent with the study on the micellization by light scattering. The average mass of micelleswas measured and the hydrodynamic radius of gyrations were calculated.

动态光散射法研究BR的溶胶和凝胶

用动态光散射法(DLS)直接测定了镍系顺丁橡胶(NiBR)在环己烷溶液中溶胶分子的扩散系数D_0和流体力学半径R_h,求得两者与(?)_w的关系分别为:D_0=2.39×10~(-4)(?)_w~(-0.595),R_h=9.979×10~(-10)(?)_w~(0.595);分析了含凝胶的NiBR与钴系BR(CoBR)溶液中粒子的D及R_h的变化,结果看出,微凝胶的粒径比溶胶的粒径大1～2个数量级。

THE THERMODYNAMICS OF MICELLIZATION BY BLOCK COPOLYMER SEP IN ORGANIC SOLVENTS

The thermodynamics of micellization for polystyrene-b-poly(ethylene/propylene) two-Mock copolymer(SEP) in the mixtures of n-octane and benzene with different proportions have been studied in this paper, The critical micelle concentrations(GMC) of micelle solutions at various temperatures were measured by lost angle laser light scattering photometer(LALLS), The results shove that the micellization process of nonpolar copolymer SEP in hydrocarbon solvents ire exothermal, and the entropy change is negative, In contrast, far ordinary surfactants in water, it is the enthalpy contribution to the energy change which is responsible for micellization.

Translocation of assimilates in Undaria and its cultivation in China

Undaria cultivation on a commercial scale began in China only in the last decade. Today, Undaria pinnatifida is the main species under cultivation concentrated in two provinces, Liaoning and Shandong. The annual production in the early nineties was 8000-13 000 tons dry weight, which is two or three times the pre-1980 figures. The raft cultivation method maintaining the alga at the desired depths generally ensures the light saturated rate of photosynthesis on clear days, and enhances production. Under the cultivated condition, the calculated annual primary productivity of this alga is 160 g C m(-2) y(-1). Translocation of C-14-labelled photoassimilates in rapidly growing sporophyte of Undaria pinnatifida was studied in the open sea. Samples from different parts of the blade with counterparts exposed to tracer ((NaHCO3)-C-14) showed that the translocation that occurred mainly from the tip of the blade to the growing region had obvious source-sink relationship. It took 20 minutes to translocate the labelled photoassimilates from the epidermis, via cortex, to the medulla of the midrib, where rates of translocation averaging 42-48 cm h(-1) were observed in the open sea. Production experiments of tip-cutting of the blades showed an increased production of 9%.

Cultivation of the brown alga Hizikia fusiformis (Harvey) Okamura: controlled fertilization and early development of seedlings in raceway tanks in ambient light and temperature

Commercial cultivation of the dioecious brown macroalga Hizikia fusiformis (Harvey) Okamura in East Asia depends on the supply of young seedlings from regenerated holdfasts or from wild population. Recent development of synchronized release of male and female gametes in tumble culture provides a possibility of mass production of young seedlings via sexual reproduction. In this paper, we demonstrate that controlled fertilization can be efficiently realized in ambient light and temperature in a specially designed raceway tank in which the sperm-containing water has been recirculated. The effective fertilization time of eggs by sperm was found to be within six hours. Fast growth and development of the young seedlings relied on the presence of water currents. Velocity tests demonstrated that young seedlings of 2-3 mm in length could withstand a water current of 190 cm s(-1) stop without detachment. Culture experiments at 24 h postfertilization showed that elongation of both the seedlings and their rhizoids were not hampered by high irradiance up to 600 mu mol photons m(-2) stop s(-1) stop. However, growth was slightly retarded if cultured at a temperature of 16 degrees C compared to other culture temperatures of 22, 25 and 29 degrees C. No seedling detachment was observed after transfer of the young seedlings to raft cultivation in the sea after one and 1.5 months post-fertilization, indicating the feasibility of obtaining large quantity of seedlings in such a system.

Growth of Gracilaria lemaneiformis under different cultivation conditions and its effects on nutrient removal in Chinese coastal waters

Gracilaria lemaneiformis (Bory) Daws has been extensively cultivated as a source of commercial agar and the ecomaterials in Shenao Bay, Guangdong Province, Jiaozhou Bay, Shandong Province and other waters in China. This paper examines the in situ suspended farming of G. lemaneiformis using raft cultivation under different conditions and its effects on nutrient removal in the laboratory. The results showed that cultivated Gracilaria grew well in both Shenao Bay and Jiaozhou Bay. The biomass of Gracilaria increased from 50 to 775 g m(-1) (fresh weight) during 28 days, with special growth rate (SPG) 13.9% d(-1) under horizontal cultivation in Jiaozhou Bay. Light, temperature, nutrient supply, as well as cultivation treatments such as initial density, and depth of suspension seaweed were important to the growth of Gracilaria. The highest biomass production was observed in the horizontal culture condition (0.0 m) and 0.5-1.5 m deep layer in Jiaozhou Bay. However, the highest growth rate in Shenao Bay appeared under the lowest initial stocking density treatment. In the laboratory, the aquarium experiments (fish and seaweed culture systems) demonstrated that Gracilaria was able to remove inorganic nutrients effectively. The concentration of NH4+-N decreased by 85.53% and 69.45%, and the concentration of PO4-P decreased 65.97% and 26.74% in aquaria with Gracilaria after 23 days and 40 days, respectively. The results indicate that Gracilaria has the potential to remove excess nutrient from coastal areas, and the large-scale cultivation of G. lemaneiformis could be effective to control eutrophication in Chinese coastal waters. (c) 2005 Elsevier B.V. All rights reserved.

Effects of organic modifiers on solute retention and electrokinetic migrations in micellar electrokinetic capillary chromatography

Influences of seven organic modifiers, including urea, methanol (MeOH), dioxane (DIO), tetrahydrofuran (THF), acetonitrile (ACN), 1-propanol (1-PrOH) and 2-propanol (2-PrOH), on the solute retention and the electrokinetic migrations in micellar electrokinetic capillary chromatography (MEKC) are investigated with sodium dodecyl sulfate (SDS) micelle as pseudostationary phase. It is observed that in the limited concentration ranges used in the MEKC systems the effect of organic modifier concentration on the retention can be described by the equation logk'=logk'(w)-SC for most binary aqueous-organic buffer, but deviations from this retention equation are observed at ACN and particularly THF as organic modifiers. With parameter S as a measure of the elutropic strength, the elutropic strength of the organic modifiers is found to follow a general order urea micelle in different patterns depending on the buffer composition used, while the addition of the other modifiers leads to a rough linear decrease of the electrophoretic mobility of the SDS micelle. The suppressing strength of THF on the electrophoretic mobility of the SDS micelle is strongly related to the buffer composition, whereas the suppressing strength for the other modifiers follows the sequence urea < MeOH < DIO, 1-PrOH, 2-PrOH. The migration time window is expanded by the use of organic modifiers. Urea and MeOH have the least expanding strength while ACN, DIO, THF, 1-PrOH and 2-PrOH have the highest expanding strength on the migration time window.

Homogeneous time-resolved fluoroimmunoassay of bensulfuron-methyl by using terbium fluorescence energy transfer

A sensitive homogenous time-resolved fluoroimmunoassay (TR-FIA) method for bensulfuron-methyl (BSM) based on fluorescence resonance energy transfer (FRET) from a Tb3+ fluorescent chelate with N,N,N',N'-[2,6-bis(3'-aminomethyl-1'-pyrazoly)-4-phenylpyridine] tetrakis(acetic acid) (BPTA-Tb3+) to organic dye, Cy3 or Cy3.5 has been developed. New method combined the use of BPTA-Tb3+ labeled streptavidin, Cy3 or Cy3.5 labeled anti-BSM monoclonal antibody and biotinylated BSM-BSA conjugate (BSA is bovine serum albumin) for competitive-type immunoassay. After BPTA-Tb3+ labeled streptavidin was reacted with a competitive immune reaction solution containing biotinylated BSM-BSA, BSM sample and Cy3 or Cy3.5 labeled anti-BSM monoclonal antibody, the sensitized and long-lived emission of Cy3 or Cy3.5 derived from FRET was measured, and thus the concentration of BSM in sample was calculated. The present method has the advantages of rapidity, simplicity and high sensitivity since the B/F (bound reagent/free reagent) separation steps and the solid-phase carrier are not necessary. The method gives the detection limit of 2.10 ng ml(-1). The coefficient variations of the method are less than 1.5% and the recoveries are in the range of 95-105% for BSM water sample measurement. (C) 2001 Elsevier Science B.V. All rights reserved.