Properties of polypropylene nanocomposites containing silver nanoparticles

Silver/polypropylene (PP) nanocomposites containing silver nanoparticles smaller than 10 nm were prepared using a new synthetic method. AgNO3 crystals were dissolved into hydrophilic domain of polyoxyethylene maleate-based surfactant (PEOM), which gives self-assembly nano-structures. The AgNO3 in the nano-domains of PEOM was reduced by NaBH4 to form nanoparticles. The colloidal solutions with silver nanoparticles were diluted with ethanol and were mixed with PP pellets. Silver nanocomposites were prepared by extrusion compounding process after drying the pellets. Contents of silver nanoparticles dispersed within PP resin were changed from 100 to 1000 ppm. Formation of silver nanoparticles within PP was confirmed by UV-Vis spectroscopy and TEM. Size and distribution of dispersed silver nanoparticles were also measured by TEM. Silver/PP nanocomposites films showed not only improved thermal stability but also increased mechanical properties compared to neat PP film. Tensile properties of PP nanocomposites were largely improved compared with neat PP resin, and elongation increased also by 175% for the nanocomposites containing 1000 ppm silver nanoparticles.     

Electrochemical and SEM properties of Co<Superscript>2+</Superscript> ion in hexagonal mesophase of pluronic lyotropic liquid crystal template

The electrochemical and SEM properties of Co²⁺ ion in hexagonal mesophase of the pluronic lyotropic liquid crystal template are reported. The cyclic voltammetric studies evidenced the occurrence of two slow electron transfer reduction processes. Such a reaction presumably related to the reduction of Co²⁺ ion to Co metal. The hexagonal (H₁) lyotropic liquid crystalline phases of P₈₄ surfactant have been used to template the electrochemical deposition of nanostructured cobalt films as well as its uses as background electrolyte. Electrochemical studies show that these films have very high surface areas, which reveals that the deposited film exhibits promising properties. The electrode parameters of Co(II) ion in hexagonal meso phase of the lyotropic liquid crystal ternary system (pluronic P₈₄/cobalt/p-xylene) is determined using cyclic voltammetry, deduced convolutive voltammetry and chronoamperometry techniques. The morphology of nanostructured deposited films of Co²⁺ ion in pluronic lyotropic liquid crystal template was investigated via scanning electron microscopy (SEM) technique.     

Dielectric properties of GaN nanoparticles

Three kinds of GaN samples (hexagonal coarse-grain powders, hexagonal nanoparticles and cubic nanoparticles) were synthesized by different methods. The room-temperature frequency spectra of the relative dielectric constant and that of the dielectric loss were measured in the frequency range of 100 Hz to 10 MHz. Analysis of these spectra indicates that the grain size of samples has great influence on the dielectric behavior of samples whereas the crystallography symmetry almost has no impact on the relative dielectric constant.     

不同晶型La2O3：Eu3＋纳米棒的制备及发光性质

以阴离子交换树脂为原料,液相反应制备了不同晶型La2O3：Eu3＋纳米棒,通过XRD、SEM、HRTEM和EDS对La2O3：Eu3＋纳米棒进行了分析和表征,结果表明,经650℃焙烧处理后制备的六方La203：Eu3＋纳米棒,直径为40～100nm,长度约2μm;当焙烧温度升高到850℃时,相变为立方相结构;利用D荧光光谱确定La2O3：Eu3＋纳米棒的最佳监测波长和激发波长,观察到在394nm的激发波长下Eu3＋在六方和立方晶型La2O3纳米棒中的主发射峰均为5D0→7F2跃迁,分别位于615nm和625nm处,且Eu3＋在六方相结构中的发光性质优于立方相结构。     

Hexagonal lyotropic liquid crystalline mesophase: change of rod-like micelle sizes with changes in concentrations

In the present work, change of rod-like micelle sizes with change of amphiphile concentration in hexagonal mesophase and the effect of inorganic salt additions on the effective length of these micelles have been studied. The investigations were made by the using of electrical conductivity method in shear flow. The dependence of form factor on the anisometricity parameter of rod-like micelles were determined for investigated lyotropic systems.     

Morphological transition of gold nanostructures induced by continuous ultraviolet irradiation

Gold nanoparticles were synthesized through a continuous UV irradiation method using citric acid as a reducer and protective agent. After a period of continuous UV irradiation, the nanoparticles transformed into two-dimensional (2D) nanonetworks, porous nanoplates and compact nanoplates with hexagonal, triangular or truncated triangular pores through a self-assembly process which was dependent on the citric acid concentration. Selected area electron diffraction (SAED) patterns indicated that both the nanonetworks and the porous nanoplates were single crystalline. The influence of citric acid concentration and irradiation time on the morphological transition of Au nanostructures was investigated. The process of morphological transition was presumably discussed.     

表面改性及原位还原法制备聚酰亚胺/镍纳米复合薄膜

通过对均苯四甲酸二酐-4,4’-二胺基二苯醚(PMDA-4,4’-ODA)型聚酰亚胺(PI)成品薄膜的表层水解处理、并在硫酸镍水溶液中实施离子交换以及随后的乙二醇热还原的方法,制备了聚酰亚胺/镍纳米复合薄膜。通过X射线衍射仪(XRD)、傅立叶变换红外光谱仪(FT-IR),透射电子显微镜(TEM)等方法研究了复合薄膜结构的变化,结果表明,经乙二醇热还原后,水解后的聚酰亚胺表层又重新形成亚胺环结构,并在其内部形成了均匀分散的具有面心立方晶型(FCC)的金属镍粒子,直径约为100 nm~200 nm。     

Pressure-jump X-ray studies of liquid crystal transitions in lipids

In this paper, we give an overview of our studies by static and time-resolved X-ray diffraction of inverse cubic phases and phase transitions in lipids. In [section sign] 1, we briefly discuss the lyotropic phase behaviour of lipids, focusing attention on non-lamellar structures, and their geometric/topological relationship to fusion processes in lipid membranes. Possible pathways for transitions between different cubic phases are also outlined. In [section sign] 2, we discuss the effects of hydrostatic pressure on lipid membranes and lipid phase transitions, and describe how the parameters required to predict the pressure dependence of lipid phase transition temperatures can be conveniently measured. We review some earlier results of inverse bicontinuous cubic phases from our laboratory, showing effects such as pressure-induced formation and swelling. In [section sign] 3, we describe the technique of pressure-jump synchrotron X-ray diffraction. We present results that have been obtained from the lipid system 1:2 dilauroylphosphatidylcholine/lauric acid for cubic-inverse hexagonal, cubic-cubic and lamellar-cubic transitions. The rate of transition was found to increase with the amplitude of the pressure-jump and with increasing temperature. Evidence for intermediate structures occurring transiently during the transitions was also obtained. In [section sign] 4, we describe an IDL-based 'AXcess' software package being developed in our laboratory to permit batch processing and analysis of the large X-ray datasets produced by pressure-jump synchrotron experiments. In [section sign] 5, we present some recent results on the fluid lamellar-Pn3m cubic phase transition of the single-chain lipid 1-monoelaidin, which we have studied both by pressure-jump and temperature-jump X-ray diffraction. Finally, in [section sign] 6, we give a few indicators of future directions of this research. We anticipate that the most useful technical advance will be the development of pressure-jump apparatus on the microsecond time-scale, which will involve the use of a stack of piezoelectric pressure actuators. The pressure-jump technique is not restricted to lipid phase transitions, but can be used to study a wide range of soft matter transitions, ranging from protein unfolding and DNA unwinding and transitions, to phase transitions in thermotropic liquid crystals, surfactants and block copolymers.     

Controlling the phase composition of cadmium sulfide films during pulsed laser deposition

Thin cadmium sulfide films grown by pulsed laser deposition on crystalline and amorphous substrates have been shown to consist of a mixture of a cubic (sphalerite structure) and a hexagonal (wurtzite structure) phase. We have demonstrated the possibility of controlling the percentages of the hexagonal and cubic phases in cadmium sulfide films by varying pulsed laser deposition parameters. Varying the deposition parameters allows one to control the optical and structural parameters and surface morphology of thin cadmium sulfide films.     

Preparation of conductive polypyrrole-palladium composite nanospheres by inverse microemulsion polymerization

Conductive polypyrrole-palladium (PPy-Pd) composite nanospheres of about 50 nm in diameter, containing dispersed Pd metal nanoparticles of about 2-4 nm in size, were prepared in a 1-step oxidative polymerization of pyrrole by Pd(NO3)2. Pyrrole was oxidized by Pd(NO3)2 in an inverse microemulsion polymerization system, yielding PPy nanospheres and elemental Pd nanoparticles simultaneously. Palladium nanoparticles were uniformly dispersed in the nanospheres of PPy chains. The latter also exhibited an enhanced effective conjugation. The chemical composition of the PPy-Pd composite nanospheres was characterized by X-ray photoelectron spectroscopy and FTIR spectroscopy. The crystalline structure of the Pd nanoparticles was deduced from X-ray diffraction patterns. The morphology of the composites was revealed by scanning and transmission electron microscopy.     

Preparation and characterization of highly dispersed and crystallised ITO nanoparticles

Nanosized ITO particles with perfect crystallinity and dispersibility in the size range of 5-16 nm were prepared by heterogeneous nucleation combined with the coprecipitation method. The effect and mechanism of the calcination temperature on the microstructure, crystal composition and morphology were investigated and discussed. Results indicate that the nanoparticles were hexagonal structure of ITO solid solution (HS) at 500 °C. However, the nanoparticles were well dispersed and mostly had the cubic structure of ITO solid solution (CS) with little HS at 600-900 °C. The pinning effect resulting from the mixed structure of HS and CS on grain boundaries could impede the diffusion of atoms from one surface layer into another compared with the traditional single CS and hence reduce the aggregation of nanoparticles.     

Liquid crystal membranes for serum-compatible diabetes management-assisting subcutaneously implanted amperometric glucose sensors

Membranes formed of thermodynamically stable cubic phase lyotropic liquid crystals (LLCs) could replace the presently used polymeric membranes, applied to reduce the flux of glucose in semicontinuous, subcutaneously implanted, user-replaced, miniature, amperometric glucose sensors, assisting in the management of diabetes. LLC-forming amphiphilic compounds set and toughen spontaneously after mixing with water, without undergoing chemical change. When applied by doctor-blading, they form membranes having three-dimensionally interconnected water channels of uniform diameter, with reproducible glucose transport-characteristics. We find that the best studied cubic phase LLCs, which are formed of monoolein and water, are not useful in their intended application because they are hydrolyzed by serum lipases. Those formed of phytantriol, a liquid at ambient temperature, and water, are not hydrolyzed but change their shape and size in a dehydration and rehydration cycle. Because glucose sensors are sterilized and stored in a sealed package in a dry atmosphere, drying and rehydration must not change the transport characteristics. A third, novel, LLC-forming, amphiphile 1-O-beta-(3,7,11,15-tetramethylhexadecyl)-d-ribopyranoside, I, was synthesized, and its phase diagram was tailored by adding Vitamin E acetate, to form a cubic phase. The phase was stable through the 20 degrees C-90 degrees C temperature range in excess of water and had the desired glucose-transport characteristics. A preferred LLC, II, was formed of water and I containing 7 wt % of Vitamin E acetate. When II was applied to a wired glucose oxidase bioelectrocatalyst, sensors of reproducible glucose-sensitivity were formed. At a 0.1 mm thickness of II, the membrane reduced the glucose flux 5-fold and increased the 90% response-time by less than 2 min. The membrane was mechanically rugged, withstanding the approximately 1 N m(-2) maximal shear stress at 5 mm diameter electrodes rotating at 4000 rpm. The activation energy for glucose permeation through II was reduced to 15.6 kJ/mol, making the sensors's current less temperature-dependent than that of the polymeric-membrane overcoated implantable glucose sensors.     

Detection of hydrogen peroxide at mesoporous platinum microelectrodes

Mesoporous (H(I)-ePt) platinum microelectrodes electrodeposited from the hexagonal (H(I)) lyotropic liquid crystalline phase are shown to be excellent amperometric sensors for the detection of hydrogen peroxide over a wide range of concentrations. Good reproducibility, high precision, and accuracy of measurements are demonstrated. Mesoporous microelectrodes retain the high rates of mass transport typical of conventional microelectrodes, and their high real surface area greatly enhances their catalytic activity. This unique combination of properties overcomes the limitations of previous amperometric hydrogen peroxide sensors and yields outstanding qualitative and quantitative results.     

Molybdenum nitride nanoparticles — high-resolution transmission electron microscopy study

The structure and size of molybdenum nitride nanoparticles were investigated using high-resolution transmission electron microscopy (HRTEM). Typical sizes of the particles were between 3 and 5 nm and they were mostly clustered together. High-resolution lattice imaging shows that the particles are single crystalline in nature and defect free. Two different phases of molybdenum nitride, γ-Mo₂N (cubic) and δ-MoN (hexagonal) were identified. In addition, body centered cubic molybdenum phase was also present. It is anticipated that molybdenum is formed because of insufficient N₂ supply or slow reaction rate. A mixture of γ-Mo₂N and δ-MoN suggests the existence of a temperature gradient in the chamber leading to formation of γ-Mo₂N at lower temperature (500 to 700 °C) and δ-MoN at higher temperature (850 °C).     

Thermochemical growth of Mn-doped CdS nanoparticles and study of luminescence evolution

We report a new method of growing Mn-doped CdS (CdS:Mn) nanoparticles in an aqueous solution at boiling temperature. The idea is to use precursors that react only at high temperature, in order to gain crystalline luminescent nanoparticles. CdSO(4), Mn(NO(3))(2) and Na(2)S(2)O(3) were used as the precursors, and thioglycerol was employed as the capping agent and also the reaction catalyst. Na(2)S(2)O(3) is thermally sensitive and it releases S(2-) ions upon heating. The CdS:Mn nanoparticles obtained are about 4?nm in size and show both cubic and hexagonal crystalline phases with a ratio of 35% to 65%. The luminescence of nanoparticles contains a peak at 580?nm, which is related to Mn(2+) ions. Prolonged reaction time results in a decrease of the Mn luminescence peak to about 35% of the maximum value. We discuss the possible causes of the Mn peak reduction and attribute it to preferential dissolution of Mn ions into the solution due to shape reconfiguration of the nanoparticles.     

CdSe band-splitting on thermal annealed films

Semiconducting polycrystalline CdSe thin films were prepared on glass substrates by chemical bath at 65 °C. As-deposited films grew in the metastable cubic sphalerite (S) crystalline structure with good stoichiometry. Upon thermal annealing (TA) in Ar+Se₂ atmosphere at different temperatures in the range 200–500 °C, the gradual phase transformation from cubic modification to hexagonal wurtzite (W) stable phase could be observed. From optical absorption measurements the fundamental energy band gap (E_g) and the second electronic transition (E_g+ΔE_g) were calculated for as-deposited and thermal annealed films. For TA350 °C, S-phase dominates the crystalline structure and only the spin orbit (ΔE_so) contribution to ΔE_g is present. Above 350 °C, the W-phase dominates and the energy splitting (ΔE_cf), owed to crystal field contribution and originated by the loss of lattice symmetry, should be added to ΔE_so in order to complete ΔE_g in the W-phase. The values ΔE_so=0.389±0.011 eV and ΔE_cf=0.048±0.018 eV were found from our analysis, and T_c=350 °C was here defined as the critical point of the phase transformation.     

On the choice of hexagonal boron nitride for high pressure phase transformation using the catalyst solvent process

The degree of three-dimensional ordering, particle-size distribution and purity of two types of hexagonal boron nitride have been studied with a view to establish any possible correlation between these characteristics with the conversion of hexagonal form to cubic phase at high pressure and high temperature using magnesium as the catalyst solvent. The crystalline phases formed at high pressure and high temperature have been studied and the dependence of degree of graphitization of boron nitride and purity on the cubic boron nitride conversion discussed.     

Synthesis of ZnO nanoparticles and their ink-jetting behavior

Zinc oxide (ZnO) nanoparticles were synthesized by ultrasonically-assisted solution process without using any surfactants. The as-synthesized spherical ZnO nanoparticles with diameter of 20 +/- 5 nm possessed crystalline nature with wurtzite hexagonal phase and showed a blue-shifted near band-edge ultra-violet absorption at -340 nm due to quantum confinement effect of ZnO nanoparticles. The as-synthesized ZnO nanoparticles were further formulated as an ink for ink-jet printing application. Jetting and writing of various line patterns on Si and ITO substrates were demonstrated using the as-formulated ZnO ink. UV-treated substrates showed an improvement in the fixation of ink on substrate due to decreased contact angle with controlled surface wettability.     

Phase and morphology controlled synthesis of high-quality ZnS nanocrystals

Through a facile solvothermal method, the controlled preparation of ZnS nanocrystals with different phases and morphologies was achieved only by changing the organic additives. By adding the surfactant of sodium dodecyl benzene sulfonate (SDBS) into the reaction, the cubic heart-like ZnS nanoparticles with uniform size were obtained in a large scale. While, with the assistance of the biomolecule of alginic acid, the pure phase of hexagonal ZnS nanospheres assembled from small ZnS nanoparticles were synthesized. The optical properties of the obtained ZnS nanocrystals were investigated by ultraviolet-visible (UV-vis) absorption and photoluminescence (PL) spectra. The quantum confinement effect could be observed clearly in ZnS nanoparticles.