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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: A facile method has been developed to encapsulate Fe3O4 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, Cd2+, and thiolglycolic acid (TGA) to an ultrasound-driven synthesis, the Fe3O4 NCs were coated with a thin composite shell. Supersonic treatment plays an important role to prevent the agglomeration of the Fe3O4 NCs in an alkaline condition. The composite shell became thicker due to the deposition of SiO2 monomers, Cd–TGA clusters, Cd2+, and free TGA molecules during reflux. In addition, these composite shell-coated Fe3O4 NCs were assembled in composite fibers which were created by the growth of Cd–TGA clusters and the deposition of SiO2 monomers. The Fe3O4 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 Fe3O4 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. [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 series of rare-earth zirconate RE2Zr2O7 nanocrystals (RE=La, Nd, Eu and Y) were prepared by a simple combustion method. These compounds possess either a pyrochlore structure (P-RE2Zr2O7) or a defect fluorite structure (F-RE2Zr2O7), which depends on the ionic radius of RE3+. The photoluminescence (PL) property of the as-prepared RE2Zr2O7 nanocrystals was studied, and the observed emissions in the UV and visible range were attributed to different transition mechanisms for RE2Zr2O7 with different RE ion. A PL mechanism has been proposed, associated with the transition between the valence band and a mid-gap state related to oxygen vacancies. Divalent Pb ions were introduced into RE2Zr2O7 nanocrystals and the luminescence of the Pb2+-doped samples was also recorded for comparison. The PL property of RE2Zr2O7 was found to be intimately related to their intrinsic defect structure, and PL was thought as a new method to estimate the degree of disorder in the A2B2O7 structure (from pyrochlore structure to defect fluorite structure). [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]

Abstract: Eu3+-doped SrZrO3 nanocrystals with a size of about 10nm were synthesized by a simple sol–gel combustion method, and characterized by X-ray diffraction, transmission electron microscopy and photoluminescence spectroscopy. The nanocrystalline intend to assemble to a porous morphology. Both intrinsic defects related and activator luminescence were observed. The red emission of Eu3+ is intense and the spectra show a minor difference with different excitation wavelengths. [Copyright &y& Elsevier]

Abstract: Strontium zirconate (SrZrO3) nanocrystals with an average size of 19nm were prepared by a simple sol–gel combustion method. The combustion reaction was induced just at 300°C. Under conventional UV excitation, the SrZrO3 nanocrystals showed a strong violet emission at 400nm. The number of luminescent zirconates is small, especially of those with visible emission. The novel luminescence was tentatively attributed to the existence of defect levels. Further study was carried out corresponding the size dependence of the luminescence property. [Copyright &y& Elsevier]

Abstract: CdTe nanocrystals (NCs) were coated with a hybrid SiO2 shell containing CdS-like clusters by a facile reflux. These hybrid SiO2-coated CdTe NCs exhibited tunable photoluminescence (PL) and high fluorescence quantum yields (QYs) up to 70% (the QY of initial CdTe NCs is 24%) due to the CdS-like cluster in the SiO2 shell nearby the CdTe core. The average fluorescence lifetime of the hybrid SiO2-coated NCs and the CdTe NCs are 36 and 25ns, respectively. Because increased fluorescence QYs and slightly blue-shifted PL peak wavelength for these hybrid NCs were observed after the removing of TGA and Cd2+, the hybrid SiO2 shell can sufficiently passivate PL, improve chemical stability, and prevent the surface deterioration of the CdTe NCs. This is crucial for applications in biolabeling and optoelectronic devices. [Copyright &y& Elsevier]

The polyvinylpyrrolidone (PVP) hybrid luminescent micro-/nanofibers doped with the novel hybrid SiO 2 -coated CdTe nanocrystals (HS-CdTe NCs) have been fabricated for the first time via the electrospinning technique. The morphologies and photoluminescence (PL) emissions of HS-CdTe/PVP micro-/nanofibers prepared by doping the HS-CdTe NCs with the different PL peak wavelength (571, 616, and 643 nm) in PVP fibers were investigated by optical and PL microscope. The results revealed that all the HS-CdTe/PVP hybrid fibers showed an ultralong length for several hundreds of micrometers and a relatively uniform diameter of 1000 ∼ 1200 nm. The hybrid fibers displayed a wavelength-tunable PL emission, determining by the PL of doped HS-CdTe NCs. Moreover, similar to the original PL properties of HS-CdTe NCs before the electrospinning, the HS-CdTe/PVP fibers also showed a series of superior PL properties, such as narrow and symmetry PL spectrum, high, and uniform brightness. For comparison purpose, we also prepared three CdTe/PVP hybrid fibers by doping the 553 nm, 600 nm, and 633 nm PL-emitting CdTe NCs respectively in PVP electrospinning fibers. The characterization results showed that, the obtained three CdTe/PVP hybrid fibers had a basically satisfactory micro-/nanofiber morphology with a long length and relatively uniform diameter, but all the fibers exhibited very weak PL emissions. The enormous contrast in PL properties between HS-CdTe/PVP and CdTe/PVP fibers should mainly be ascribed to the different connection modes of ligands with the NCs and the passivation effect of inert hybrid silica shell on HS-CdTe. It is hopeful that the high luminescent HS-CdTe/PVP micro-/nanofibers with the tunable PL peak wavelength would be a good candidate in the optical sensor, light-emitting devices (LEDs), nanometer-scale waveguides, and the other related photonic materials. [ABSTRACT FROM AUTHOR]

Abstract: Strontium stannate (SrSnO3) nanocrystals have been synthesized by using an efficient combustion method for the first time. The corresponding nanorods integrated with nanoparticles are also obtained with the coprecipitation method. X-ray diffraction, transmission electron micrograph and scanning transmission electron micrograph are used to illustrate the crystal structure, phase purity and morphology of the synthesized nanocrystals. The growth mechanisms are investigated in detail. [Copyright &y& Elsevier]