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ABSTRACT: We present a facile synthesis of europium-doped gadolinium sulfide (GdS:Eu(3+)) opto-magnetic nanoparticles (NPs) via sonochemistry. Their photoluminescence and strong paramagnetic properties enable these NPs to be utilized as an in vitro cell imaging and in vivo T(1)-weighted MR imaging probe. The GdS:Eu(3+) NPs have a prominent longitudinal (r(1)) relaxivity value, which is a critical parameter for T(1)-weighted MR imaging. Here, we showed not only their strong positive contrast effect to blood vessels and organs of mice, but also blood half-life and biodistribution including clearance from organs, in order to assess the GdS:Eu(3+) NPs as a competent nanocrystal-based T(1) contrast agent. We further showed confocal images of breast cancer cells containing GdS:Eu(3+) NPs to evaluate as a photoluminescence probe. Dual-mode imaging capability obtained from the GdS:Eu(3+) NPs will allow target-oriented cellular imaging as well as the resulting disease-specific MR imaging.
Biomaterials 05/2012; 33(24):5865-74. · 7.40 Impact Factor
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ABSTRACT: We prepared GdS:Eu(3+) by simple thermal decomposition under 1-dodecanethiol. A reduction process was observed from Eu(3+) to Eu(2+) when oleic acid and hexadecylamine were injected into GdS:Eu(3+). Under UV excitation, GdS:Eu(3+) showed an intense orange-red emission and GdS:Eu(2+) showed a broad green band.
Chemical Communications 12/2011; 48(6):904-6. · 6.17 Impact Factor
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ABSTRACT: The graphite encapsulation of metal alloy magnetic nanoparticles has attracted attention for biological applications because of the high magnetization of the encapsulated particles. However, most of the synthetic methods have limitations in terms of scalability and economics because of the demanding synthetic conditions and low yields. Here, we show that well controlled graphite-encapsulated FeCo core-shell nanoparticles can be synthesized by a hydrothermal method, simply by mixing Fe/Co with sucrose as a carbon source. Various Fe/Co metal ratios were used to determine the compositional dependence of the saturation magnetization and relaxivity coefficient. Transmission electron microscopy indicated that the particle sizes were 7 nm. In order to test the capability of graphite-encapsulated FeCo nanoparticles as magnetic resonance imaging (MRI) contrast agents, these nanoparticles were solubilized in water by the nonspecific physical adsorption of sodium dodecylbenzene sulfonate.
Nanotechnology 09/2011; 22(37):375603. · 3.98 Impact Factor
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Small 06/2011; 7(12):1647-52. · 8.35 Impact Factor
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ABSTRACT: Ultrasonic irradiation of core/shell structures was shown to lead to low toxicity and high quantum yields relative to thermal methods for bio-application.
Chemical Communications 12/2008; · 6.17 Impact Factor
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ABSTRACT: Europium-doped calcium sulfide phosphor was synthesized by a co-precipitation method using calcium carbonate and ammonium sulfate as the sources for calcium and sulfide, respectively. Reduction of the precipitated CaSO4 into CaS was carried out at 550°, 750°, 950°, and 1150°C at a flow rate of H2 5 mL/min and N2 95 mL/min. The formation of crystalline CaS phase was evident by the X-ray diffraction analysis of the fired products. The phosphor yielded red emission of wavelength 634 nm for the excitation wavelength of 465 nm. The emission intensity of the phosphors increased with increasing firing temperature from 550° to 950°C, but firing at 1150°C showed a dramatic decline in emission due to thermal quenching. The study of the effect of Eu loading level showed a decrease in emission with an increase in loading, and the optimum loading for maximum emission was found to be 0.5 mol%. And it can be possible to generate white light of light emitting devices by mixing with SrGa2S4:Eu green phosphor and this phosphor on the 460 nm InGaN blue chip.
Journal of the American Ceramic Society 09/2006; 89(11):3413 - 3416. · 2.27 Impact Factor
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ABSTRACT: The shifts of the emission band to longer wavelength (yellow-orange) of the Sr <sub>3</sub> Si O <sub>5</sub>: Eu yellow phosphor under the 450–470 nm excitation range have been achieved by adding the codoping element ( Ba <sup>2+</sup>) in the host. In order to apply to white-light-emitting diodes (LEDs) with warm white and high color rendering index, we have fabricated white LEDs through the integration of the InGaN blue LED chip and the two phosphor blends ( Sr <sub>2</sub> Si O <sub>4</sub>: Eu yellow phosphor + Ba <sup>2+</sup> co-doped Sr <sub>3</sub> Si O <sub>5</sub>: Eu yellow-orange phosphor) into a single package. By employing two phosphors, covering a red region, the white LEDs show a warm white in the range of 2500–5000 K correlated color temperature and a good color rendering of over 85.
Applied Physics Letters 02/2006; · 3.84 Impact Factor
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ABSTRACT: Large increases in the efficiency of the
yellow phosphor under the
excitation range have been achieved by adding the co-doping element (
and
) in the host. In order to apply to white light-emitting diodes (LEDs), we have synthesized a
co-doped
yellow phosphor and investigated an attempt to develop white LEDs by combining it with an InGaN blue LED chip
. Two distinct emission bands from the InGaN-based LED and the
co-doped
phosphor are clearly observed at 460 and at
, respectively. These two emission bands combine to give a spectrum that appears white to the naked eye.
Journal of The Electrochemical Society. 07/2005; 152(8):H121-H123.
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ABSTRACT: In order to develop yellow phosphors that emit efficiently under the 450–470 nm excitation range, combinatorial chemistry was used based on silicate materials and investigated in an attempt to develop white light-emitting diodes (LEDs) by combining it with an InGaN blue LED chip (460 nm). Quaternary and ternary combinatorial libraries were developed to synthesize, process, and screen for silicate materials. Our combinatorial chemistry system consists of solution-based combinatorial synthesis and characterization, enabling the swift scanning of luminance. As a consequence of the combinatorial approach, several candidates were found to show high luminance under the 450–470 nm excitation range.
Applied Physics Letters 07/2005; 87(3):031108-031108-3. · 3.84 Impact Factor
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ABSTRACT: In order to develop a yellow phosphor that emits efficiently under the 450–470 nm excitation range, we have synthesized a Eu2+-activated Sr3SiO5 yellow phosphor and attempted to develop white light-emitting diodes (LEDs) by combining them with a InGaN blue LED chip (460 nm). Two distinct emission bands from the InGaN-based LED and the Sr3SiO5:Eu phosphor are clearly observed at 460 nm and at 570 nm, respectively. These two emission bands combine to give a spectrum that appears white to the naked eye. Our results showed that InGaN (460 nm chip)-based Sr3SiO5:Eu exhibits a better luminous efficiency than that of the industrially available product InGaN (460 nm chip)-based YAG:Ce. © 2004 American Institute of Physics.
Applied Physics Letters 03/2004; 84(10):1647-1649. · 3.84 Impact Factor
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ABSTRACT: We have studied the photoluminescence properties of
in mullite. The 0.005 mol
-activated
mullite shows a single broad-band emission character and an emission band at about 435 nm. The emission band shifts slightly
to a longer wavelength with an increase in
concentration because the distance between
ions decreases and the probability of energy transfer among
ions increases with increased
concentration. However,
mullite shows two emission centers, an
- and an
-site, which peak at 420 and 482 nm. Also, we investigated the compositional dependence of the luminescence properties of
the
ions based on the different Al/Si ratios. © 2003 The Electrochemical Society. All rights reserved.
Journal of The Electrochemical Society. 09/2003; 150(10):H246-H249.
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Journal of Materials Science Letters 09/2003; 22(19):1351-1353.
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ABSTRACT: We have synthesized a Eu2+-activated Sr2SiO4 yellow phosphor and investigated an attempt to develop white light-emitting diodes (LEDs) by combining it with a GaN blue LED chip. Two distinct emission bands from the GaN-based LED and the Sr2SiO4:Eu phosphor are clearly observed at 400 nm and at around 550 nm, respectively. These two emission bands combine to give a spectrum that appears white to the naked eye. Our results showed that GaN (400-nm chip)-based Sr2SiO4:Eu exhibits a better luminous efficiency than that of the industrially available product InGaN (460-nm chip)-based YAG:Ce. © 2003 American Institute of Physics.
Applied Physics Letters 02/2003; 82(5):683-685. · 3.84 Impact Factor
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ABSTRACT: phosphor was synthesized by a modified combinatorial chemistry method, which was based on the polymeric complex using citric
acid and ethylene glycol. Different particle growth tendencies were observed both above and below 900°C. The luminescent properties
of
phosphor were investigated by photoluminescence. The rising phenomena in the initial part of the
site decay curves are elucidated from the rate equation of the excited populations of the
and
site, respectively. To clarify more precisely the distinction of the site symmetry between
and
sites, the decay behavior is analyzed using the direct quenching scheme. © 2002 The Electrochemical Society. All rights reserved.
Journal of The Electrochemical Society. 12/2002; 150(1):H27-H31.
