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.
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.
The shifts of the emission band to longer wavelength (yellow-orange) of the Sr3SiO5:Eu yellow phosphor under the 450–470 nm excitation range have been achieved by adding the codoping element (Ba2+) 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 (Sr2SiO4:Eu yellow phosphor +Ba2+ co-doped Sr3SiO5: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.
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.
Carbon‐protected iron cobalt nanoparticles (FeCo/C NPs) are synthesized using a hydrothermal approach. It is demonstrated that FeCo/C NPs can be used as highly sensitive magnetic resonance and Raman imaging probes. These FeCo/C NPs are then used for targeting tumor cells for combined siRNA and hyperthermia‐based therapy, resulting in the significant inhibition of proliferation and induction of apoptosis in tumor cells.
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