Papers by Keyword: Nanocrystal

Abstract: The influence of urinary macromolecule chondroitin sulfate A (C₄S) on Zeta potential, aggregation and sedimentation of calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) nanocrystallites with a diameter of about 50 nm were investigated using nanoparticle size Zeta potential analyzer and transmission electron microscope. C₄S could increase the absolute value of Zeta potential on surface of nanoCOM and nanoCOD crystallites by adsorbing on crystal surface, it led an increase of the electrostatic repulsion force between the crystallites, so the aggregation and sedimentation of these crystallites were inhibited, and the stability of the suspension of nanoCOM and nanoCOD was improved. In conclusion, C₄S could inhibit the formation of CaOxa stones。

Abstract: ZnS nanocrystals were prepared via chemical precipitation method and characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) and photoluminescence (PL) spectra. The results indicated that the ZnS nanocrystals have cubic zinc blende structure and diameter is 3.68 nm as demonstrated by XRD. The morphology of nanocrystals is spherical measured by TEM which shows the similar particle size. The photoluminescence spectrum peaking at about 424 nm was due mostly to the trap-state emission, and a satellite peak at 480nm ascribed to the dangling bond of S in the surface of ZnS nanocrystals. The emission intensity of ZnS was enhanced after ultraviolet irradiation, the enhancement of the Photoluminescence intensity was due to the elimination of the surface defects after ultraviolet irradiation, for the growth of the coated shell on ZnS nonacrystals, the Photoluminescence intensity was increased as ultraviolet irradiation time growth, finally tends to be stable for the surface state of nanocrystals steady.

Abstract: The amorphousization of Zr₆₅Nb₃₅ alloy was performed. The Zr-Nb based alloys contained Al and Co elements were fabricated by arc-melting and melt-spinning methods. The superconducting property of the Zr_(65-x)Nb_35-xAl_x (x = 0~15 at%) and Zr_(65-x)Nb₂₀Al₁₅Co_x alloys (x = 3~10 at%) was investigated by magnetic susceptibility measurements. The Zr_(65-x)Nb₂₀Al₁₅Co_x metallic glasses (x = 6~10 at%) with superconducting nanocrystalline particles dispersed in an amorphous matrix exhibited a superconductivity below about 3.5 K. The addition of Co element led drastically to the amorphousization of the superconducting Zr₆₅Nb₂₀Al₁₅ alloy.

Abstract: Silicon nanocrystals (SiNCs) have unique optical and electronic properties that are advantageous for semiconductor device applications and here their application to solar cell is presented. Free-standing, narrow size distribution SiNCs were synthesized by non-thermal plasma using silicon tetrachloride (SiCl4) successfully. Blended solution of as-produced SiNCs and P3HT, or Poly(3-hexylthiophene-2,5-diyl), was spin-casted to form bulk heterojunction solar cell devices. As the weight fraction of SiNCs increased up to 50 wt%, the short circuit current and the power conversion efficiency dramatically increased, while the open circuit voltage and the fill factor do not change significantly. The improved performance is attributable to increased probability of exciton dissociation at acceptor SiNCs and donor P3HT interface.

Abstract: Ag₂Se nanocrystal was successfully prepared by ultrasonic synthesis in water and ethanol systems at an ambient pressure. The powder of selenium was used as the selenium ion source. The size of the nanocrystals is in the scope of 10-20nm. The products were characterized by some means including X-ray Powder Diffraction (XRD) and Transmission Electron Microscopy (TEM) which was used to study the thermostability of the product. The result of the experiments indicated that the concentration of the reactant, the pH of the solution, the react temperature and the surfactant had some important influence on the formation and the size of the Ag₂Se nanoparticles. The method we reported here is proved to be a new and an easy way to prepare the nanocrystals of metal chalcogenide.

Abstract: In this paper, α-Fe₂O₃ nanocrystals have been synthesized, using FeCl₃, oleic acid, ethanol and NaOH as raw materials by a hydrothermal method at 180°C for 10h. The samples were characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) for the information of crystal category, form and size. The results showed the materials are nanocubes and side-length about 20 nm. Moreover, the properties of α-Fe₂O₃ nanocrystals as anode materials for Li-ion batteries had been studied. The first-discharge capacity is 1280 mAh g^-1, which made this material maybe one of the candidates for the negative materials.

Abstract: Nanocrystals of stable, tetragonal tin dioxide have been synthesized using microwave processing, and the effect of microwave heating on the structural phase transformations of the tin compounds involved has been examined. The results are used to determine microwave heating parameters that ensure strong bonding of nanocrystals to the surface of polypropylene nonwoven.

Abstract: Transparent luminescent TiO₂/polymer nanocomposites were obtained through the combined use of copolymerization of a novel titanium ion containing monomer with a liquidsolid reaction. The titanium ions are covalently introduced into polymer chains and transformed into TiO₂ nanocrystals directly in the solid-state polymer matrices. That allows the generation of high-quality anatase TiO₂ nanocrystals with a narrow size distribution in the polymer matrices. The luminescence of the TiO₂ nanocrystals is dominated by band-edge luminescence at room temperature.

Abstract: Thin-film samples of the lithium ionic conductor Li₂SiO₃ (LSO) were deposited on an A-plane sapphire substrate via the pulsed laser deposition (PLD) method, and the irreversible temperature dependence of the ionic conductivity in the thin-film samples was studied. Via transmission electron microscopy (TEM) observations of annealed LSO thin-film, it was found that the as-prepared LSO thin-film was amorphous over the temperature range T 490 K, and that nanocrystals existed in the annealed LSO thin-film in the temperature range T 550 K. Further more, it was clarified the irreversible temperature dependence of the ionic conductivity is due to the generation of nanocrystals.

Abstract: The electrical properties of nanocomposite SiO₂(Si) films containing Si nanoclusters have been investigated. The films were formed by oxide assisted growth that included ion plasma sputtering (IPS) of Si target and following high temperature annealing. It was determined that electrical conductivity of the films correspond to the mechanism of hopping conductivity with variable hopping length through the traps near the Fermi level (Mott mechanism) due to the large number of silicon dangling bonds in the dielectric matrix. The peculiarities of charge capture in nanocomposite SiO₂(Si) films for their application as the medium for charge storage in memory cells have been investigated by C-V method. The good charge storage possibility of SiO₂(Si) films formed by IPS deposition with followed temperature annealing has been observed. The negative differential capacitance has been revealed in conditions of semiconductor surface accumulation. The physical model for explanation of the negative differential capacitance of MIS structures with nanocomposite SiO₂(Si) films as the dielectric has been proposed. The model is based on the parallel conjunction of the oxide capacitance and nanocrystals capacitance.