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Jiye Fang

Publications and source records attributed to Jiye Fang.

15 recordsLinked to original sources
PubMed2006

Characterization of synthesized titanium oxide nanoclusters by MALDI-TOF mass spectrometry.

Titania represents an important material that has wide applications. The bactericidal efficiency of TiO(2) has been shown to be dependent on the size of the nanoparticles, so it is important to be able to reliably estimate their dimensions. In this study, a stable TiO(2) cluster suspension is produced by the thermal solvent process, and ultrasmall clusters (<1 nm) with different sizes are obtained by size-selection treatment. MALDI-TOF-MS and LDI-TOF-MS are shown to be useful for characterization of these ultrasmall nanoparticles. Peak maxima are found to correlate with nanoparticle size, and the possibility of using these mass spectrometry-based approaches to estimate nanoparticle size is affirmed. The size distributions of TiO(2) nanoparticles obtained from MALDI- and LDI-TOF-MS are in good agreement with parallel TEM observations. Finally, PSD analysis of inorganic nanomaterials is performed and valuable information about the structure of analytes has been obtained.

Mass Spectrometry↗
PubMed2006

Low-temperature anomalies of two-photon absorption in In2O3 nanocrystals incorporated into PMMA matrixes.

By using a method of two-photon absorption, it has been observed that monodisperse In2O3 nanocrystals (NCs) with sizes equal to approximately 14-24 nm show significant increase of two-photon absorption at low temperatures. When T = 40 K, the two-photon absorption coefficients for low-sized samples drastically increase, whereas such enhancement for the samples with averaged sizes above approximately 24 nm is not significant. The nondiagonal tensor components give one-order-less two-photon absorption values. A principal role in the observed dependences is played by interface nanolayers, demonstrating substantial contribution of nanoconfined effects. This phenomenon could only be observed in highly monodisperse NCs. Increase of the size distribution substantially suppresses the two-photon absorption observed. For the relatively large nanocrystals, the effects are comparable with those of the bulklike crystals. At the same time, the drastic increase at low temperatures may indicate a substantial role of the phonon subsystem.

Journal Article↗
PubMed2006

Silica encapsulation of hydrophobically ligated PbSe nanocrystals.

Spherical PbSe@SiO2 nanoparticles have been successfully synthesized within reverse micelles via metal alkoxide hydrolysis and condensation within a microemulsion system. These core-shell nanoparticles were characterized by transmission electron microscopy (TEM), NIR absorption spectroscopy, energy-dispersive X-ray analysis, and TEM electron diffractions. It shows that the obtained core-shell structures have a spherical shape with narrow size distribution (average size approximately 35 nm) and smooth surfaces. The size of the particles and the thickness of the shells can be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of tetraethoxysilane (TEOS) within the microemulsion.

Journal Article↗
PubMed2006

Orbital susceptibilities of PbSe quantum dots.

Different sizes of three-dimensional PbSe quantum dots have been synthesized for the study of orbital magnetic susceptibilities. Two types of orbital susceptibilities have been found, including the Curie susceptibility and finite-size corrections to the Landau susceptibility. The Curie term of a quantum dot manifests itself in the temperature dependence of magnetic susceptibility at low temperatures, while the field dependence of differential susceptibility at high temperatures shows finite-size corrections to the Landau susceptibility. Both of the two kinds of orbital susceptibility, estimated per quantum dot, show linear dependence on the size.

Journal Article↗
PubMed2006

Syntheses of Ag, PbSe, and PbTe nanocrystals and their binary self-assembly exploration at low size-ratio.

Nanocrystals of Ag, PbSe, and PbTe were prepared via a high-temperature organic solution approach, respectively. Using a size-selection technique, the size-distribution of each set of nanocrystals could be fine-tuned and finally monodisperse products were achieved. Superlattice structure of binary self-assemblies in low size-ratio were also explored and characterized by transmission electron microscopy. It is realized that a success of achieving binary self-assembly pattern is greatly dependent on several key factors including particle size-distributions, relative concentrations of both components, as well as the size-ratios between Ag and PbSe (or PbTe) nanocrystals.

Lead↗
PubMed2005

Formation of PbSe nanocrystals: A growth toward nanocubes.

In this paper we report an electron microscopic observation of crystal shape development when PbSe nanocrystals were synthesized using a dynamic injection technique at different temperatures in the presence of oleic acid. A two-step evolution mechanism was proposed, indicating that the shape evolution of PbSe nanocrystals is dependent on the growth time, whereas the crystalline size can be tuned by varying the growth temperature under the studied conditions. It also implies that a higher growth rate in the 111 direction compared to that in the 100 direction results in the formation of nanocubes.

Journal Article↗
PubMed2005

Bismuth telluride hexagonal nanoplatelets and their two-step epitaxial growth.

We report a synthesis of discrete, single-crystal, defect-free, and hexagonal Bi2Te3 nanoplatelets using a high-temperature organic solution approach, and we demonstrate a two-step epitaxial growth of the cylindrical strings of Bi2Te3 nanoplatelets on the surface of the Te rod by packing them along c-axis in a top-bottom-top-bottom sequence. This type of building-up provides additional opportunity for the exploration of novel thermoelectric properties from such quantum-confined materials, in which the boundary scattering of phonons is anticipated to enhance.

Journal Article↗
PubMed2005

Study of quasi-monodisperse In2O3 nanocrystals: synthesis and optical determination.

In this communication, we report a successful synthesis of quasi-monodisperse In2O3 nanocrystals with high crystallinity in a high-temperature organic solution. The average size of nanocrystals can be tuned using a dynamic injection technique. TEM and XRD investigations indicate that each nanocrystal is a single crystal. The optical determination implies that the photoluminescence behavior of these In2O3 nanocrystals is different from that of the bulk, probably due to the combination of weak quantum-confinement-effects and the nature of high crystallinity in nanocrystals.

Journal Article↗
PubMed2005

Single crystalline magnetite nanotubes.

We descried a method to synthesize single crystalline Fe3O4 nanotubes by wet-etching the MgO inner cores of MgO/Fe3O4 core-shell nanowires. Homogeneous Fe3O4 nanotubes with controllable length, diameter, and wall thickness have been obtained. Resistivity of the Fe3O4 nanotubes was estimated to be approximately 4 x 10-2 Omega cm at room temperature. Magnetoresistance of approximately 1% was observed at T = 77 K when a magnetic field of B = 0.7 T was applied. The synthetic strategy presented here may be extended to a variety of materials such as YBCO, PZT, and LCMO which should provide ideal candidates for fundamental studies of superconductivity, piezoelectricity, and ferromagnetism in nanoscale structures.

Ferrosoferric Oxide↗
PubMed2005

Polyol-mediated synthesis and photoluminescent properties of Ce3+ and/or Tb3+-doped LaPO4 nanoparticles.

Rare-earth ion (Ce3+, Tb3+) doped LaPO4 nanoparticles were prepared by the polyol method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV-vis absorption spectroscopy, photoluminescence (PL) spectroscopy, and lifetimes. The results of XRD indicate that the as-prepared nanoparticles are well-crystallized at 160 degrees C and assigned to the monoclinic monazite structure of the LaPO4 phase. The obtained LaPO4:Ce3+, Tb3+ nanoparticles are spherical with narrow size distribution and average size of 20 nm. The doped rare-earth ions show their characteristic emission in LaPO4 nanoparticles, i.e., Ce3+ 5d-4f and Tb3+ 5D4-7FJ (J = 6-3) transitions, respectively. The optimum doping concentration for Tb3+ in La(0.8-x)Ce0.2TbxPO4 nanoparticles is determined to be 15 mol% (x = 0.15). The luminescence decay curves of Ce3+ in LaPO4:Ce3+ and LaPO4:Ce3+, Tb3+ nanoparticles present a single-exponential behavior, and the lifetimes (tau) of Ce3+ decrease with increasing Tb3+ concentrations (at the constant Ce3+ concentration) in LaPO4:Ce3+, Tb3+ nanoparticles due to the energy transfer from Ce3+ to Tb3+. The energy-transfer efficiency from Ce3+ to Tb3+ was calculated, which depends on the doping concentrations of Tb3+ if the concentration of Ce3+ is fixed.

Cesium↗
PubMed2004

Perfect orientation ordered in-situ one-dimensional self-assembly of Mn-doped PbSe nanocrystals.

We demonstrate a novel approach for the large-scale, shape-controlled synthesis of one-dimensional (1D) corrugated nanoarrays of Pb(1-x)Mn(x)Se nanocrystals (0.002 < or = x < or = 0.008) through an in-situ self-assembly without using either capping polymer or ionic surfactant. The one-step-prepared 1D nanoarrays exhibit a well-defined morphology, single-crystal orientation, and clean surface without amorphous contamination. The average diameter of the 1D nanoarrays can be controlled and varied from <10 to 80 nm by finely tuning the assembly temperature and the growth time. Four growth models were suggested to explain the in-situ self-assembly processes based on the fundamental building blocks of octahedral nanocrystals by sharing [111] facets.

Journal Article↗
PubMed2004

Shape evolution and self assembly of monodisperse PbTe nanocrystals.

In this communication, we report our recent achievement in synthesis and self-assembly of both spherical and cubic PbTe nanocrystals using a high-temperature solution-phase synthesis approach. The possible mechanism of nanocrystalline evolution from spherical to cubic structure has also been discussed. It is possible to use the highly orientated PbTe nanocrystals as building blocks to achieve thickness-controlled film for further manipulation into thermoelectric devices.

Journal Article↗
PubMed2003

The first synthesis of Pb(1-x)Mn(x)Se nanocrystals.

In this work, Mn-doped PbSe nanocrystals (NCs) have been, for the first time, prepared through a high-temperature organic solution approach. To ensure that all the Mn2+ ions are indeed incorporated into the NCs and not only physically presented at the surface, Mn-Se prebonded precursor was selected, and a ligand-exchange process was also conducted before and after the synthesis, respectively. Various analyses including EDS, ICP, XRD, SQUID, and EPR confirm that the Mn2+ ions have been successfully doped into PbSe NCs.

Journal Article↗
PubMed2003

Morphology control of the produced Ag nanoparticles by soft-template technique.

The morphology of the produced Ag nanoparticle is controlled successfully by UV irradiating the reaction solution of AgAc/ethyl alcohol/1-octadeconal/1-dodecanethiol. With use of a novel solution such as soft template, Ag nanorods with different sizes and different ratios of length to diameter can be obtained by adjusting the concentrations of the solution compositions.

Ethanol↗