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ABSTRACT: Nano-structured cubic SnO2 crystalines were successfully synthesized through solvothermal route. The obtained products were characterized by X-ray diffraction
(XRD), transmission electron microscopy (TEM) and high resolution TEM (HRTEM). The study showed that, the SnO2 particles were rutile structured and almost uniformly cube shaped crystals in quantum size (3–8 nm). Self-assembly behavior
of the cubic SnO2 quantum dots was also observed. The synthesis process can be defined as an nonhydrolysis (NH) hydroxylation reaction provided
by the amide elimination of carboxylated precursors. The formation of cubic morphology of SnO2 can be ascribed to the mild reaction featured by high nucleation rate and low growth rate, surface energy difference of the
crystallographic facets of SnO2 and the passivation effect of the starting material-dodecylamine which drastically reduced the dipole interation. The selfassembly
of the cubic SnO2 quantum dots was driven by van der Waals force and capillary force.
Key wordsnanocube–quantum dot–crystal growth–tin oxide
Journal of Wuhan University of Technology-Mater Sci Ed 04/2012; 26(2):269-272. · 0.35 Impact Factor
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ABSTRACT: Highly crystalline orthorhombic Bi2WO6 powders were hydrothermally synthesized from aqueous solutions of Na2WO4 · 2H2O and Bi (NO3)3 · 5H2O over a wide range of pH. The effect of pH on morphologies, sizes and properties of the Bi2WO6 crystals was investigated. The band gaps of the as-prepared Bi2WO6 were determined from the onset of the absorption edge of UV-vis diffuse reflectance spectra. The methyl orange photodegradation
was employed as a probe reaction to test the photocatalytic activity of the as-prepared samples under visible light irradiation.
The photocatalytic activities of methyl orange degradation under visible light irradiation are strongly dependent on the pH
used in the synthesis. The highest efficiency is observed at pH=7.
Journal of Wuhan University of Technology-Mater Sci Ed 04/2012; 24(4):533-536. · 0.35 Impact Factor
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ABSTRACT: A simple sonochemical route for the surface coating of titanium dioxide on cadmium sulfide nanocrystal was reported. After
2 h ultrasonic irradiation treatment, the mixture of CdS nanocrystals and tetrabutyl titanate in an aqueous medium yielded
CdS/TiO2 nanocrystals composites with core/shell structure. The thickness of TiO2 layer with smooth interface could be easily controlled via changing the concentration of the precursors and the time of irradiation.
The core/shell nanocrysrals were characterized by X-ray diffraction, transmission electron microscope and UV-vis spectrometry
techniques. The prepared semiconductor composites with particular band structure present appealing properties especially in
photochemical activity.
Journal of Wuhan University of Technology-Mater Sci Ed 04/2012; 24(5):698-701. · 0.35 Impact Factor
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ABSTRACT: Yb(3+)-doped glass and glass ceramic containing ZnO nanocrystals were prepared by the melting-quenching method and subsequent heat treatment. Intense near-IR emission around 1000 nm that originated from the transition of Yb(3+):(2)F(5/2)→(2)F(7/2) was generated as a result of energy transfer from oxygen interstitials in ZnO nanocrystals to Yb(3+) with energy transfer efficiency of about 10%. The quantum yield for the near-IR emission of Yb(3+) under the excitation of 390 nm was about 16.7%. These materials have potential application in achieving high-efficiency Si solar cells via spectrum modification.
Optics Letters 08/2011; 36(15):2767-9. · 3.40 Impact Factor
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ABSTRACT: The Eu2+ and Mn2+ codoped 50SiO2–17Al2O3–23MgF2–10NaF glasses and glass–ceramics were prepared and their luminescence properties were investigated. The red emission intensity of Mn2+ in the Eu2+ and Mn2+ codoped glass was about five times stronger than that in the Mn2+ doped glass, which could be attributed to energy transfer from Eu2+ to Mn2+. The energy transfer mechanism from Eu2+ to Mn2+ in glasses was determined to be a dipole-quadrupole interaction. The luminescence intensity of the glass–ceramics was stronger than that of the glass because some Eu2+ and Mn2+ ions entered lower phonon energy environment of MgF2 nanocrystals in the glass–ceramics.
Journal of the American Ceramic Society 04/2011; 94(6):1670 - 1674. · 2.27 Impact Factor
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ABSTRACT: The self-assembly of anatase TiO2 nanorods into 1D (ribbon), 2D (smectic, domino, honeycomb) and 3D (lamellar) liquidcrystalline ordered superlattices is a process that depends on the collaboration between evaporation dynamics and directional interactions. Herein, the roles of entropic depletion attractions and energetic dipole-dipole couplings between TiO2 nanorods in self-assembly process are particularly emphasized. Excess oleic acid surfactants act as depletion agents to induce the inter-rod depletion effect, and the origin of electric dipole moment along the longitudinal axes of TiO2 rods is theoretically authenticated by applying the Accelrys Materials Studio as a new strategy combined with Tasker's theory. These nanorod superlattices provided here may have great importance for tailoring new promising structures for photovoltaic application or exploring new inorganic liquid crystal materials.
Current Nanoscience 05/2010; 6(3):262-268. · 1.78 Impact Factor
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ABSTRACT: The Eu2+-doped glasses and glass ceramics containing SrF2 nanocrystals were prepared and their luminescence properties were investigated. The formation of SrF2 nanocrystals in glass ceramics was confirmed by X-ray diffraction and transmission electron microscopy. The melting in a reducing atmosphere and then the crystallization of glass resulted in the reduction of almost all Eu3+ ions to Eu2+ ions in the glass ceramics. The Eu2+-doped glass ceramics containing SrF2 nanocrystals exhibited a much stronger broad blue emission band and a longer lifetime of excited state than the glasses.
Journal of the American Ceramic Society 04/2010; 93(9):2684 - 2688. · 2.27 Impact Factor
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ABSTRACT: We report on the use of 800 nm, 250 kHz femtosecond laser pulses to precipitate Er(3+)-doped CaF(2) crystals inside oxyfluoride glass, which was confirmed with x-ray diffraction analysis. Confocal upconversion luminescence spectra show that the precipitated crystals have greatly enhanced upconversion luminescence intensity in comparison with unmodified glass. We demonstrate the possibility of three-dimensional optical data storage in the glass by the use of the confocal upconversion luminescence imaging.
Optics Letters 11/2009; 34(21):3433-5. · 3.40 Impact Factor
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ABSTRACT: We demonstrated the conversion of near-ultraviolet radiation of 250–350 nm into visible emission of 450–600 nm and near-infrared emission of 970–1100 nm in the Yb <sub>2</sub> O <sub>3</sub> doped transparent 40 SrO- 20 TiO <sub>2</sub>-40 SiO <sub>2</sub> glasses. The observed broad visible emission band centered at 510 nm is associated with silicon-oxygen-related defects in the glassy matrix, and the near-infrared emission originated from the Yb <sup>3+</sup> <sup>2</sup> F <sub>5/2</sub>→<sup>2</sup> F <sub>7/2</sub> transition is due to the energy transfer from silicon-oxygen-related defects to Yb <sup>3+</sup> . The energy transfer process was studied by both the steady state spectra and the time-resolved spectra of Yb <sup>3+</sup> at 15 K. The temperature dependent energy transfer rate was calculated. The Yb <sub>2</sub> O <sub>3</sub> concentration dependent energy transfer efficiency has also been evaluated, and the maximum value is 56% for 12 mol % Yb <sub>2</sub> O <sub>3</sub> doped glass.
Journal of Applied Physics 04/2009; · 2.17 Impact Factor
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ABSTRACT: The Eu2+-doped glass ceramics containing BaF2 nanocrystals were prepared and their luminescence properties were investigated. The excitation spectra of Eu2+-doped glass ceramics showed an excellent overlap with the main emission region of an ultraviolet light-emitting diode (UV-LED) centered at 380 nm. The 450 nm emission of Eu2+ in glass ceramics under the 385 nm excitation was much stronger than that in glass. The Eu2+-doped glass ceramics containing BaF2 nanocrystals may be used as a potential blue-emitting phosphor for UV-LED.
Journal of the American Ceramic Society 03/2009; 92(4):942 - 944. · 2.27 Impact Factor
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ABSTRACT: We demonstrated the conversion of near-ultraviolet radiation of 250-350 nm into visible emission of 450-600 nm and near-infrared emission of 970-1100 nm in the Yb{sub 2}O{sub 3} doped transparent 40SrO-20TiO{sub 2}-40SiO{sub 2} glasses. The observed broad visible emission band centered at 510 nm is associated with silicon-oxygen-related defects in the glassy matrix, and the near-infrared emission originated from the Yb{sup 3+} {sup 2}F{sub 5/2}{yields}{sup 2}F{sub 7/2} transition is due to the energy transfer from silicon-oxygen-related defects to Yb{sup 3+}. The energy transfer process was studied by both the steady state spectra and the time-resolved spectra of Yb{sup 3+} at 15 K. The temperature dependent energy transfer rate was calculated. The Yb{sub 2}O{sub 3} concentration dependent energy transfer efficiency has also been evaluated, and the maximum value is 56% for 12 mol % Yb{sub 2}O{sub 3} doped glass.
Journal of Applied Physics. 03/2009; 105(6).
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ABSTRACT: The Ce <sup>3+</sup> and Dy <sup>3+</sup> codoped oxyfluoride glasses and glass ceramics containing LaF <sub>3</sub> nanocrystals have been prepared in the reducing atmosphere. The emission intensity and Commission International de I'Eclairage (CIE) chromaticity coordinates of the Ce <sup>3+</sup> and Dy <sup>3+</sup> codoped glasses significantly changed with concentration ratio of Ce <sup>3+</sup> to Dy <sup>3+</sup> . The emission intensity of both Ce <sup>3+</sup> ions and Dy <sup>3+</sup> ions in the 3.0% Ce <sup>3+</sup> and 3.0% Dy <sup>3+</sup> codoped glass ceramics increased significantly in comparison with that in the glass. The glasses and glass ceramics could emit bright white light by adjusting the concentration ratio of Ce <sup>3+</sup> to Dy <sup>3+</sup> .
Journal of Applied Physics 03/2009; · 2.17 Impact Factor
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ABSTRACT: The spectroscopic properties of Er3+/Yb3+ co-doped 50SiO2–10Al2O3–20ZnF2–20SrF2 glass and glass ceramic containing SrF2 nanocrystals were investigated. The formation of SrF2 nanocrystals in the glass ceramic was confirmed by XRD. The oscillator strengths for several transitions of the Er3+ ions in the glass ceramic have been obtained and the Judd–Ofelt parameters were then determined. The XRD result and Judd–Ofelt parameters suggested that Er3+ and Yb3+ ions had efficiently enriched in the SrF2 nanocrystals in the glass ceramic. The lifetime of excited states has been used to reveal the surroundings of luminescent Er3+ and Yb3+ and energy transfer (ET) mechanism between Er3+ and Yb3+. Much stronger upconversion luminescence and longer lifetime of the Er3+/Yb3+ co-doped glass ceramic were observed in comparison with the Er3+/Yb3+ co-doped glass, which could be ascribed to more efficient ET from Yb3+ to Er3+ due to the enrichment of Yb3+ and Er3+ and the shortening of the distance between lanthanide ions in the precipitated SrF2 nanocrystals.
Journal of Physics D Applied Physics 02/2009; 42(5):055103. · 2.54 Impact Factor
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ABSTRACT: The luminescence behaviors of Er <sup>3+</sup> doped glass ceramics containing Sr <sub>2</sub>R F <sub>7</sub> (R= Y , Gd , La ) nanocrystals were investigated. The formation of Sr <sub>2</sub>R F <sub>7</sub> nanocrystals in the glass ceramics was confirmed by x-ray diffraction and high resolution transmission electron microscopy. Energy dispersive x-ray spectroscopy analysis showed that the Er <sup>3+</sup> ions were efficiently incorporated in Sr <sub>2</sub> GdF <sub>7</sub> nanocrystals. The efficient upconversion luminescence of the Er <sup>3+</sup> in the glass ceramics can be observed. The lifetime of the Er <sup>3+</sup> in the glass ceramics was found to be much longer than that in the glass due to the lower phonon energy of fluoride crystals when Er <sup>3+</sup> entered efficiently fluoride crystals in the glass ceramics.
Journal of Applied Physics 09/2008; · 2.17 Impact Factor
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ABSTRACT: Yb3+/Er3+ and Yb3+/Tm3+ co-doped LaF3 nanoparticles with upconversion luminescence properties were prepared via the co-precipitation method, followed by heat treatment at different temperatures in the range of 180°C to 600°C. We investigated the influence of heat treatment temperatures on the size, morphology, and upconversion luminescence intensity of the nanoparticles. Significant increases of the particle size and upconversion luminescence intensity of the nanoparticles were observed with increasing heat treatment temperature. The upconversion mechanism of the LaF3:Yb3+,Er3+ and LaF3:Yb3+,Tm3+ nanoparticles was also discussed.
Journal of Experimental Nanoscience 12/2007; 2(4):303-311. · 1.01 Impact Factor
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ABSTRACT: Multicolour colloidal PEI/NaGdF4:Ce3+,Ln3+ (Ln = Tb, Eu, Sm or Dy) nanocrystals were synthesized using a simple one-pot hydrothermal procedure. The nanocrystals consist of well crystallized hexagonal phase and have an elongated spherical shape, with diameters between 25 and 45 nm. Under single-wavelength excitation at 254 nm in the ultraviolet (UV) region, the nanocrystals doped with different lanthanide ions show intense visible (VIS) emissions of different colours. The characteristic luminescence property of the nanocrystals can be attributed to strong absorption of the UV irradiation by the Ce3+, followed by energy transfer to (via Gd3+ sublattice) and emission from the luminescent centres.
Nanotechnology 12/2006; 18(2):025701. · 3.98 Impact Factor
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ABSTRACT: Upconverting materials, which can be efficiently excited by near infrared light and emit strong visible light through a process termed 'upconversion fluorescence', have shown great potential for use in biological labelling and imaging. Some upconverting nanoparticles such as NaYF4 doped with lanthanide ions have been synthesized; however, these nanoparticles are not soluble in water, not biocompatible and do not have functional chemical groups for conjugation of biomolecules, and as a result their bioapplications are very limited unless some surface modifications are performed. Here we report a method for one-pot synthesis of polyethylenimine/NaYF4 nanoparticles doped with lanthanide ions, which are water soluble and biocompatible. The amino groups of polyethylenimine existing on the nanoparticles can be used for attachment of biomolecules. The nanoparticles showed a spherical shape with an average size of about 50 nm. Different lanthanide ions (Yb3+, Er3+ and Tm3+) were doped into the nanoparticles, which showed strong upconversion fluorescence of different colours in aqueous solutions under excitation at 980 nm.
Nanotechnology 11/2006; 17(23):5786. · 3.98 Impact Factor
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ABSTRACT: The Er <sup>3+</sup> doped transparent oxyfluoride glass ceramics containing Sr <sub>2</sub> Gd F <sub>7</sub> nanocrystals were prepared and their spectroscopic properties were discussed. The formation of Sr <sub>2</sub> Gd F <sub>7</sub> nanocrystals in the glass ceramics was confirmed by x-ray diffraction. The split peaks of the upconversion and near infrared emission bands of the Er <sup>3+</sup> doped glass ceramics can be observed. The upconversion luminescence intensity of Er <sup>3+</sup> in the glass ceramics increased significantly with the increasing heat treated temperature. The luminescence decay curves and time-resolved spectra indicated that the lifetime of the <sup>4</sup>S<sub>3/2</sub> state of Er <sup>3+</sup> in the glass ceramic was longer than that in the glass.
Applied Physics Letters 10/2006; · 3.84 Impact Factor
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ABSTRACT: The upconversion luminescence and near infrared luminescence of the Er <sup>3+</sup> ions in transparent oxyfluoride glass ceramics containing Sr F <sub>2</sub> nanocrystals have been investigated. The formation of Sr F <sub>2</sub> nanocrystals in the glass ceramics was confirmed by x-ray diffraction. The oscillator strengths for several transitions of the Er <sup>3+</sup> ions in the glass and glass ceramics have been obtained and then the Judd-Ofelt parameters were determined. The split near infrared emission peaks of the Er <sup>3+</sup> ions in the glass ceramics can be observed because the Er <sup>3+</sup> ions have been incorporated into crystalline environment of the Sr F <sub>2</sub> nanocrystals. The upconversion luminescence intensity of Er <sup>3+</sup> ions in the glass ceramics increased significantly with the increasing crystallization time. The transition mechanisms of the green and red upconversion luminescence have been ascribed to two-photon process and the blue upconversion luminescence to three-photon process.
Journal of Applied Physics 05/2006; · 2.17 Impact Factor
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ABSTRACT: The preparation process and upconversion luminescence of the Er(3+)-doped glass ceramics containing Ba(2)LaF(7) nanocrystals were investigated. The formation of Ba(2)LaF(7) nanocrystals in the glass ceramics was confirmed by X-ray diffraction. Er(3+)-doped glass ceramics containing Ba(2)LaF(7) nanocrystals exhibited highly efficient upconversion luminescence in comparison with glasses. With the increase of heat treatment temperature the upconversion luminescence intensity increased gradually. The composition of glasses was also found to have significant influence on the crystallization process of glass ceramics. The mixture of Ba(2)LaF(7) and La(2)O(3) nanocrystals and the mixture of La(2)F(3) and La(2)O(3) nanocrystals in the glass ceramics could be obtained by controlling different compositions of glasses. The upconversion luminescence intensity also varied significantly with different nanocrystals in the glass ceramics.
The Journal of Physical Chemistry B 04/2006; 110(12):5950-4. · 3.70 Impact Factor
