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CdSe cores with rod (an aspect ratio of 1.8, d-5 nm) and spherical (an aspect ratio of 1, d-5 nm) morphologies were fabricated by two kinds of organic approaches through adjusting growth processes. Because of large difference of size and morphology, two kinds of cores revealed different absorption spectra. However, these cores exhibited almost same photoluminescence (PL) spectra with a red-emitting PL peak of around 625 nm. This is ascribed that they have a similar size in diameter. A graded Cd(x)Zn1-xS shell of larger band gap was grown around CdSe rods and spheres using oleic acid as a capping agent. Based on the growth kinetics of CdS and ZnS, interfacial segregation was created to preferentially deposit CdS near the core, providing relaxation of the strain at the core/shell interface. For spherical CdSe cores, the homogeneous deposition of the Cd(x)Zn1-xS shell created spherical core/shell nanocrystals (NCs) with a size of 7.1 nm in diameter. In the case of using CdSe cores with rod morphology, the anisotropic aggregation behaviors of CdS monomers on CdSe rods led to the size (approximately 10 nm in diameter) of spherical CdSe/Cd(x)Zn1-xS core/shell NCs with a small difference to the length of the CdSe rod (approximately 8.9 nm). The resulting spherical core/shell NCs created by the rod and spherical cores exhibited almost same PL peak wavelength (652 and 653 nm for using rod and spherical cores, respectively), high PL efficiency up to 50%, and narrow PL spectra (36 and 28 nm of full with at half maximum of PL spectra for the core/shell NCs with CdSe spheres and rods, respectively). These core/shell NCs provide an opportunity for the study of the evolution of PL properties as the shape of semiconductor NCs.

A facile method has been developed to encapsulate Fe(3)O(4) nanocrystals (NCs) in morphology-tunable fibers (belt-like, solid, and tubal) by using a sonochemistry driven synthesis and a subsequent reflux procedure. By adapting the use of tetraethyl orthosilicate, ammonia, Cd(2+), and thiolglycolic acid (TGA) to an ultrasound-driven synthesis, the Fe(3)O(4) NCs were coated with a thin composite shell. Supersonic treatment plays an important role to prevent the agglomeration of the Fe(3)O(4) NCs in an alkaline condition. The composite shell became thicker due to the deposition of SiO(2) monomers, Cd-TGA clusters, Cd(2+), and free TGA molecules during reflux. In addition, these composite shell-coated Fe(3)O(4) NCs were assembled in composite fibers which were created by the growth of Cd-TGA clusters and the deposition of SiO(2) monomers. The Fe(3)O(4) NCs mono-dispersed in fibers revealed superparamagnetic behavior. The magnetic saturation value of tubal fibers is lower than those of belt-like and solid fibers. These fibers with Fe(3)O(4) NCs would be utilizable for further application. The strategy described here should give a useful enlightenment for the design and fabrication of morphology-tunable fibers with functional NCs., (Copyright 2010 Elsevier Inc. All rights reserved.)

Abstract: Comparing with the other metal chalcogenide semiconductors, copper selenide has still not been well researched in nanoscience and nanotechnology, probably due to the difficulty in the controllable synthesis of its various phase. In the present work, Cu2−δ Se and CuSe were synthesized open to air through a green paraffin-acetate method. The morphology study indicated that the copper selenide mainly showed hexagonal nanoplates/nanowires or only hexagonal nanoplates. The SDBS-modified sample exhibited good dispersivity in water. The phase, composition (δ value) and morphology of the products could be controlled by adjusting the reaction parameters. Stability, redox and the effective Cu/Se ratio were thought as the major factors that determine the phase of the final products, and a concentration-limited growth mechanism was proposed to explain the formation of the various morphologies. The optical properties of the copper selenide were characterized by UV–visible diffuse reflectance spectroscopy (UV-DRS). [ABSTRACT FROM AUTHOR]

Abstract: Eu3+ doped yttrium zirconate ((Y1−x Eu x )2Zr2O7) nanocrystals were synthesized by a simple sol–gel combustion method, and characterized by X-ray diffractometry (XRD), transmission electron microscopy (TEM), UV–vis absorption and photoluminescence (PL) spectroscopy. Photoluminescence spectra of (Y1−x Eu x )2Zr2O7 (x =0.005–0.15) show multi-peaks corresponding to the f–f transitions 5 D 0–7 F J (J =1, 2, 3, 4 and 5) of Eu3+. Both the 5 D 0–7 F 1 magnetic dipole transition and the 5 D 0–7 F 2 electric dipole transition are intense and the 5 D 0–7 F 2 emissions split into several peaks depending on the doping concentration. The fine structure of the PL spectra is related to host lattice and the local situation around Eu3+. [Copyright &y& Elsevier]

Abstract: A facile and energy saving sol–gel combustion method has been used to prepare La2Zr2O7 nanocrystallines. The pyrochlore La2Zr2O7 nanocrystals have been obtained at a relatively low temperature with the grain size ranging from 45 to 70nm. Eu3+ and Dy3+ have been introduced into the La2Zr2O7 crystal structure, respectively, and the intense photoluminescence was observed. The relative intensity of electric dipole transition and magnetic dipole transition is considered for luminescence emission both of Eu3+ and Dy3+. The dependence of luminescence intensity on dopant concentration and the effect of Dy3+ co-doping on Eu3+ luminescence are also discussed. [Copyright &y& Elsevier]

CeO 2 nanostructures with various morphologies were prepared through controlling preparation conditions via a hydrothermal method without any surfactants and templates. Cerium acetate, cerium chloride and cerium nitrate were used as cerium precursors to investigate the influence of anions on the growth process of CeO 2 nanostructures. The morphology evolution of CeO 2 and Ce(OH) 3 nanostructures indicates that the anions play an important role for the growth kinetics of resulting samples. Cl − and Ac − ions promoted the formation of one dementional (1D) CeO 2 nanostructures such as nanowires, nanorods and nano hexagonal prisms, while the oxidizing anion NO 3 - facilitated the synthesis of CeO 2 nanocubes. The hydrothermal reaction temperature is another key to govern the morphologies of CeO 2 nanostructures. The formation process of the nanostructures was explored and the possible growth mechanism was discussed. The variety of CeO 2 nanostructures represented inequable catalytic performance for CO oxidation. Because of different surface areas and structures, CeO 2 nanowires revealed the best catalysis performance while that of the nanocubes is the worst. [ABSTRACT FROM AUTHOR]

Abstract: The silver nanorods and nanowires have been synthesized by a facile aqueous solution process using tri-sodium citrate as reducing agent in the presence of anionic surfactant dodecyl benzene sulfonic acid sodium (DBS). The products were characterized by the techniques of X-ray diffraction (XRD) and transmission electron microscopy (TEM). Experimental results indicated that the concentrations of the reactants AgNO3 and tri-sodium citrate, in addition to the surfactant DBS should be interdependent in the formation of the silver nanorods and nanowires. The optical properties were investigated and the prepared nanostructures displayed a very strong absorption band at the room temperature. [Copyright &y& Elsevier]