Upconversion luminescence properties of monodisperse spherical Y2O2S:Yb,Ho nanocrystals

2009 ◽  
Vol 24 (5) ◽  
pp. 1756-1760 ◽  
Author(s):  
Xixian Luo ◽  
Wanghe Cao ◽  
Mingming Xing
Keyword(s):  
Particle Size ◽  
Low Temperature ◽  
Formation Mechanism ◽  
In Vivo Imaging ◽  
Upconversion Luminescence ◽  
Green Emission ◽  
Precipitation Method ◽  
Homogeneous Precipitation ◽  
Homogeneous Precipitation Method

Monodisperse spherical Y2O2S:Yb,Ho nanocrystals with particle size about 50 nm were prepared by a modified homogeneous precipitation method combined with low-temperature sulfurization process. The Y2O2S:Yb,Ho nanocrystals exhibit an intense green emission assigned to the Ho3+ ions 5F4, 5S2 → 4I15/2 transition under 980 nm infrared pump. The upconversion luminescence brightness of Y2O2S:Yb,Ho is 526 Cd/m2 under 4.63 W/cm2 pump density, indicating that the as-prepared Y2O2S:Yb,Ho nanocrystals can meet the requirement of in vivo imaging. The formation mechanism of monodisperse spherical oxysulfide nanoparticles is also discussed.

scholarly journals Synthesis of Y_2O_3 nanophosphors by homogeneous precipitation method using excessive urea for cathodoluminescence and upconversion luminescence bioimaging

2016 ◽  
Vol 6 (3) ◽  
pp. 831 ◽  
Author(s):  
Shoichiro Fukushima ◽  
Taichi Furukawa ◽  
Hirohiko Niioka ◽  
Masayoshi Ichimiya ◽  
Takumi Sannomiya ◽  
...  
Keyword(s):  
Upconversion Luminescence ◽  
Precipitation Method ◽  
Homogeneous Precipitation ◽  
Homogeneous Precipitation Method

Synthesis and characterization of TiO2 nanocrystalline powder prepared by homogeneous precipitation using urea

2003 ◽  
Vol 18 (3) ◽  
pp. 571-577 ◽  
Author(s):  
Dong Seok Seo ◽  
Hwan Kim ◽  
Hang Chul Jung ◽  
Jong Kook Lee
Keyword(s):  
Particle Size ◽  
Particle Shape ◽  
Elevated Temperatures ◽  
Treatment Temperature ◽  
Precipitation Method ◽  
Nanocrystalline Powder ◽  
Homogeneous Precipitation ◽  
Homogeneous Precipitation Method ◽  
Good Crystallinity

TiO2 nanocrystalline powder was synthesized by homogeneous precipitation method using urea, and its characteristics were investigated through comparison with the powder prepared by conventional precipitation using ammonia. The homogeneously precipitated powder was anatase-type TiO2 with a particle size of 4–5 nm and a uniform spherical particle shape. The fact that the transformation from anatase to rutile was prohibited at elevated temperatures in the homogeneously precipitated powder can be useful to prepare anatase-type TiO2 thin films by calcination at high temperatures. With increasing heat-treatment temperature, the particle size of the homogeneously precipitated powder was smaller than that of the conventionally precipitated powder, and the particle shape was more uniform. The homogeneously precipitated powder showed good photocatalytic activity for Ag ion photoadsorption because the powder had both good crystallinity and a large specific surface area of 280 m2/g.

Synthesis of Spherical Zinc Oxide Micro-Flower via an Electric Field-Assisted Homogeneous Precipitation Method

2011 ◽  
Vol 328-330 ◽  
pp. 1541-1544 ◽  
Author(s):  
Xiu Juan Liang ◽  
Xiao Fang Hu ◽  
Xing Xing Weng ◽  
Da Wei Hu ◽  
Hai Xu Ji
Keyword(s):  
Crystal Structure ◽  
Particle Size ◽  
Zinc Oxide ◽  
Electric Field ◽  
Precipitation Method ◽  
Homogeneous Precipitation ◽  
Homogeneous Precipitation Method ◽  
Ft Ir ◽  
Particle Size And Morphology ◽  
Size And Morphology

This paper presents the experimental results on electric field-assisted synthesis of spherical Zinc Oxide (ZnO) micro-flower in an homogeneous precipitation method. The synthesis processes with and without an electric field were compared. The products were characterized via SEM, XRD, TGA and FT-IR spectrum. The results show that the spherical ZnO micro-flower composed of ZnO single crystalline nanoparticles have thickness of about 10nm, width of about 50nm.The SEM results show that the application of an electric field caused the morphology transformation from flake-like to flower-like. It was found that an electric field had an effect on the crystal structure,the particle size and morphology.

Synthesis of Calcium Carbonate from Calcium Chlorine Solution Using Homogeneous Precipitation Method

2005 ◽  
Vol 486-487 ◽  
pp. 542-545 ◽  
Author(s):  
Kyung Nam Kim ◽  
Dae Yong Shin ◽  
Se Gu Son ◽  
Yong Do Kim
Keyword(s):  
Particle Size ◽  
Calcium Carbonate ◽  
Precipitation Method ◽  
Homogeneous Precipitation ◽  
Reaction Conditions ◽  
Homogeneous Precipitation Method ◽  
Reaction Solution ◽  
Particle Size And Morphology ◽  
Size And Morphology ◽  
Hydrolysis Of

Calcium carbonate(CaCO3) was synthesized from aqueous CaCl2 solution, using the homogeneous precipitation technique, which uses the hydrolysis of urea. The effects of reaction conditions on the morphology of CaCO3 were examined at 50-90°C. Particle size of CaCO3 decreases, as the concentrations of urea and [Ca2+] are increased. Calcite is produced more, as the concentration of [Ca2+] is increased. Method to stir the reaction solution affects significantly the particle size and morphology of CaCO3. Uniform needle-like aragonite particles were obtained, when left at 90°C for 4hours without stirring.

scholarly journals Synthesis of ZnO Nanopowders by the Homogeneous Precipitation Method: Use of Taguchi’s Method for Analyzing the Effect of Different Variables

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
R. Herrera-Rivera ◽  
M. de la L. Olvera ◽  
A. Maldonado
Keyword(s):  
Particle Size ◽  
Experimental Design ◽  
Size Variation ◽  
Statistical Technique ◽  
Morphological Properties ◽  
Precipitation Method ◽  
Statistical Experimental Design ◽  
Homogeneous Precipitation ◽  
Taguchi’S Method ◽  
Homogeneous Precipitation Method

In the present work the effect of different factors in the synthesis of ZnO powders by the homogeneous precipitation method is analyzed. A robust statistical technique, Taguchi’s method, was used to reduce the experiments number. The variables studied were precursor, solvent and precipitating agent type, Zn molar concentration, percentage of saturation, speed and time of agitation, and temperature of synthesis. In order to optimize the particle size, an experimental design of 18 trials was proposed, according to L18 Taguchi array. Structural and morphological properties were characterized by X-ray diffraction (XRD) and scanning and transmission electron microscopy techniques (SEM and TEM). The estimated crystallite size in synthesized samples ranged from 32 to 57 nm. The morphologies obtained presented several forms, such as spheres, wires, flowers, bars, and tetrahedrons, with a particle size variation of 35 to 165 nm. In this work it is shown that using a statistical experimental design leads us to a fast and reliable optimization of the synthesis parameters for obtaining small size ZnO nanoparticles, thus optimizing time and human and materials resources.

scholarly journals Low Temperature Synthesis of α-Alumina with a Seeding Technique

ISRN Ceramics ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Kazuhiro Inoue ◽  
Masachika Hama ◽  
Yoshio Kobayashi ◽  
Yusuke Yasuda ◽  
Toshiaki Morita
Keyword(s):  
Particle Size ◽  
Low Temperature ◽  
Room Temperature ◽  
Precipitation Method ◽  
Low Temperature Synthesis ◽  
Particle Content ◽  
Homogeneous Precipitation Method ◽  
Transparent Alumina ◽  
Alumina Gel ◽  
Alumina Sol

This paper reports a method for producing α-Al2O3 at low temperature, which uses a seeding technique. White precipitate of aluminum hydroxide, which was prepared with a homogeneous precipitation method using aluminum nitrate and urea in aqueous solution, was peptized by using acetic acid at room temperature and then transformed to a transparent alumina sol. To the alumina sol α-Al2O3 particles were added as a seed, and then the sol containing α-Al2O3 particles was transformed to an α-Al2O3-seeded alumina gel by drying the sol at room temperature. The nonseeded alumina gel was amorphous or fine crystallites even after being annealed at 600°C and was crystallized to γ-Al2O3 at 700°C. The α-Al2O3 seeding promoted crystallization of alumina gel to α-Al2O3. The promotion of crystallization was made remarkable with a decrease in α-Al2O3 particle size and an increase in α-Al2O3 particle content in weight for the final seeded alumina gel. With an α-Al2O3 particle size of 150 nm and an α-Al2O3 particle content of 5%, the seeded alumina gel was partially crystallized to α-Al2O3 by annealing at a temperature as low as 700°C and mostly at 900°C.

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