Synthesis and characterization of Eu(III)-incorporated silica nanoparticles for application to UV-LED (original) (raw)
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Comparison of Eu(NO3)3 and Eu(acac)3 precursors for doping luminescent silica nanoparticles
Journal of Nanoparticle Research, 2009
In this study, we report the comparison between Eu 3?-doped silica nanoparticles synthesized by Stöber method using Eu(NO 3) 3 or Eu(acac) 3 as precursors. The impact of different europium species on the properties of the final silica nanospheres is investigated in details in terms of size, morphology, reachable doping amount, and luminescence efficiency. Moreover, the results obtained for different thermal treatments are presented and discussed. It is shown that the organic complex modify the silica growing process, leading to bigger and irregular nanoparticles (500-800 nm) with respect to the perfectly spherical ones (400 nm) obtained by the nitrate salt, but their luminescence intensity and lifetime is significantly higher when 800-900°C annealing is performed.
Structures and luminescence properties of Eu2+- doped α-sialon phosphors for UV-LED
Journal of Electroceramics, 2008
Eu 2+-doped α-sialon phosphor was synthesized and structures and various luminescence properties were studied. High crystalline Ca 0.8 Al 2.8 Si 9.2 O 1.169 N 14.94 phase was successively obtained for undoped and Eu 2+-doped samples. Eu 2+-doped α-sialon phosphor exhibited wide absorption in ultra violet (UV) and visible range, and high broad emission band peaking at from 570 to 582 nm. The optimum compositions and process conditions was obtained from 0.75 mol% Eu 2+-doped Ca 0.8 Al 2.8 Si 9.2 O 1.169 N 14.94 fired at 1650°C for 2 h in 30% H 2-70% N 2 atm. In addition, fabrication of UV-light emitting diode (LED) lamp using this phosphor was conducted and the optical properties were measured. Relative quantum efficiency of the phosphor and luminous efficiency of the lamp were 83.66% and 35.28 lm/W, respectively. Those results indicated that Eu 2+-doped α-sialon phosphor in this study was a good candidate for UV-LED light source. Keywords Eu 2+. α-Sialon. Phosphor. UV-LED. Structures. Luminescence properties. Process conditions 1 Introductions Recently, white LED was under a rapid development for new light source, which had merits such as a high efficiency, long lifetime and low power consumption [1-3]. In the first generation of white LED, blue-emitting (460 nm) chip packaged with Y 3 Al 5 O 12 :Ce 3+ (YAG) yellow phosphor, namely, blue-LED has been used [2, 3]. However, a low color rendering index (CRI) of blue-LED limited its commercialization as a new light source. Therefore, there were enormous researches for the next generation of white LED consisted of UV-emitting (380×420 nm) chip with red, green, blue (RGB) or red, yellow, green, blue (RYGB) phosphors (UV-LED) [4, 5]. Especially, phosphors excited in UV-range around 400 nm have been rarely reported because most existing oxide phosphors were excited below far from 400 nm. On the other hand in nitride host, higher covalency of nitrogen than that of oxygen makes its excitation band locate in higher wavelength. In addition, larger ligand-field splitting due to nitrogen broadens emission band. Therefore, there have been lots of researches on oxynitride or nitride phosphors in the last few years [6-16]. As an oxynitride phosphor, Eu 2+ doped α-sialon was widely studied as a yellow phosphor [6-14]. Actually, sialon ceramics has been developed for structural engineering applications because of good mechanical and chemical properties such as strength, hardness, thermal shock resistance and wear resistance [17-19]. These ceramics were stabilized by incorporation of Y, Li, Ca or rare earth oxide elements [19]. Krevel et al. reported Ce 3+-and Eu 2+doped M-α-sialon (M = Y, Ca) could be applied for green and yellow phosphors [6]. Ca-α-sialon has the maximum excitation peaks at 254 and 365 nm and the maximum
Journal of Luminescence, 2014
Ordered mesoporous silica nanoparticles (MSNs) were impregnated with different loadings of the luminescent complex tris(dibenzoylmethane) mono(1,10-phenanthroline)europium(III) (Eu(dbm) 3 phen), with the aim of increasing the luminescence by avoiding concentration quenching and having mainly in mind the application as spectral converter for multi-crystalline silicon solar cells. The morphological, structural and luminescence properties of the impregnated silica nanoparticles were characterized by N 2 physisorption, X-ray diffraction, transmission electron microscopy, infrared spectroscopy, UV-visible spectroscopy and photoluminescence excitation and emission measurements. Photostability was tested under 1 sun (1000 W/m 2) illumination for 24 h and the related effects were inspected by UV-visible and photoluminescence spectroscopies. Impregnation of the complex into 50-70 nm MSNs with pore size tailored around 2.9 nm depressed concentration quenching and allowed the use of complex loadings as high as 23 wt%. Sunlight irradiation caused a marked increase in the luminescence intensity.
Organic complexes of Eu3+ supported in functionalized silica gel: highly luminescent material
Journal of Alloys and Compounds, 1994
Eu III ion and its chelates of 1,10-phenantroline (phen), 2,2-bipyridine (bpy), benzoyltrifluoroacetone (bfa) and acetylacetone (acac) were supported on silica gel (SG) and silica gel functionalyzed with propyl imidazole (IPG). The luminescence studies of Eu III showed an increase in the intensity and lifetime of the Eu IIII 5Do--* 7F2 transition in the presense of IPG, when compared with SG. The energy transfer from bfa and phen to the Eu III ion was also detected. In these cases, an increase in the intensity and lifetime of Eu III related to the direct excitation at the metallic ion was observed.
Highly efficient visible light sensitized red emission from europium tris1-(4-biphenoyl)-3-(2-fluoroyl)propanedione complex grafted on silica nanoparticles
Journal of Materials Chemistry, 2010
A novel class of efficient visible light sensitized antenna complexes of Eu 3+ based on the use of a highly conjugated b-diketonate, namely, 1-(4-biphenoyl)-3-(2-fluoroyl)propanedione (HBFPD) and 1,10phenanthroline as an ancillary ligand has been designed, synthesized, characterized and their photophysical properties (PL) investigated. PL measurement results indicated that suitably expanded p-conjugation in the complex molecules makes the excitation band red shift to the visible region and hence the Eu 3+ complexes exhibit intense red emission under blue light excitation (440 nm) with a solidstate quantum yield of 32 AE 3%, which is the highest so far reported in the literature. Further, in the present work, the visible sensitized Eu 3+ complex has been covalently anchored to the ordered mesoporous MCM-41 via the modified HBFPD ligand for the first time to the best of our knowledge. b-Diketonate grafted to the coupling agent 3-(triethoxysilyl)propylisocyanate was used as the precursor for the preparation of mesoporous nanomaterials. MCM-41 consisting of ternary complex Eu(SiBFPD) 3 (phen) covalently bonded to the silica-based network, which was designated as Eu(SiBFPD) 3 (Phen)/MCM-41 (3), was obtained by interacting europium nitrate, SiBFPD-Na and 1,10-phenanthroline into the hybrid material via a ligand-exchange reaction. The designed material was further characterized by powder X-ray diffraction, dynamic light scattering (DLS) technique, thermogravimetric analysis, N 2 adsorption-desorption, SEM, TEM, FT-IR, FT-Raman, 13 C and 29 Si CPMAS NMR and photoluminescence spectroscopic techniques. The hybrid material covalently bonded to MCM-41 exhibits an efficient intramolecular energy transfer process from the silylated bdiketonate to the central Eu 3+ , namely, the ''antenna effect'', which favored a stronger red/orange intensity ratio, longer lifetime, and high thermal stability than the precursor complex.
Eu^2+-activated silicon-oxynitride Ca_3Si_2O_4N_2: a green-emitting phosphor for white LEDs
Optics Express, 2011
The green-emitting phosphor Ca 3 Si 2 O 4 N 2 :Eu 2+ was synthesized using a solid-state reaction. The luminescence properties, diffuse reflection spectrum, and thermal quenching were firstly studied, and a white lightemitting diode (wLED) was fabricated using the Eu 2+ -activated Ca 3 Si 2 O 4 N 2 phosphor. Eu 2+ -doped Ca 3 Si 2 O 4 N 2 exhibited a broad green emission band centered between 510 and 550 nm depending on the concentration of Eu 2+ . The optimal doping concentration of Eu 2+ in Ca 3 Si 2 O 4 N 2 was 1 mol%. The energy transfer between Eu 2+ ions proceeds by an electric multipolar interaction mechanism, with a critical transfer distance of approximately 30.08 Å. A wLED with an color-rendering index R a of 88.25 at a correlated color temperature of 6029 K was obtained by combining a GaN-based n-UV LED (380 nm) with the blue-emitting BaMgAl 10 O 17 :Eu 2+ , green-emitting Ca 3 Si 2 O 4 N 2 :Eu 2+ , and red-emitting CaAlSiN 3 :Eu 2+ phosphors. The results present Ca 3 Si 2 O 4 N 2 :Eu 2+ as an attractive candidate for use as a conversion phosphor for wLED applications.
Applied Physics B, 2012
The absolute majority of phosphors are composed of a host lattice and some percentage of an activator. At higher activator concentrations the concentration quenching occurs. However, there are phosphors in which only minor quenching of the emission occurs with increasing of the activator content. Based on the existence of two different valence states of the Eu ion (2+ and 3+), two approaches for the development of "concentrated phosphors", i.e. light emitting materials in which the activator ion is a main part of the crystal lattice, are discussed. In both approaches, reduced energy migration leading to the luminescence quenching is considered as a main condition to reach a high quantum efficiency of a concentrated phosphor. Two kinds of phosphors-Eu 2+ -doped alumosilicate and Eu 3+ -doped oxyfluoride-are used as an experimental basis for this discussion. Starting from the stoichiometric Ca 1−x Eu 2+
J. Mater. Chem., 2010
A novel class of efficient visible light sensitized antenna complexes of Eu 3+ based on the use of a highly conjugated b-diketonate, namely, 1-(4-biphenoyl)-3-(2-fluoroyl)propanedione (HBFPD) and 1,10phenanthroline as an ancillary ligand has been designed, synthesized, characterized and their photophysical properties (PL) investigated. PL measurement results indicated that suitably expanded p-conjugation in the complex molecules makes the excitation band red shift to the visible region and hence the Eu 3+ complexes exhibit intense red emission under blue light excitation (440 nm) with a solidstate quantum yield of 32 AE 3%, which is the highest so far reported in the literature. Further, in the present work, the visible sensitized Eu 3+ complex has been covalently anchored to the ordered mesoporous MCM-41 via the modified HBFPD ligand for the first time to the best of our knowledge. b-Diketonate grafted to the coupling agent 3-(triethoxysilyl)propylisocyanate was used as the precursor for the preparation of mesoporous nanomaterials. MCM-41 consisting of ternary complex Eu(SiBFPD) 3 (phen) covalently bonded to the silica-based network, which was designated as Eu(SiBFPD) 3 (Phen)/MCM-41 (3), was obtained by interacting europium nitrate, SiBFPD-Na and 1,10-phenanthroline into the hybrid material via a ligand-exchange reaction. The designed material was further characterized by powder X-ray diffraction, dynamic light scattering (DLS) technique, thermogravimetric analysis, N 2 adsorption-desorption, SEM, TEM, FT-IR, FT-Raman, 13 C and 29 Si CPMAS NMR and photoluminescence spectroscopic techniques. The hybrid material covalently bonded to MCM-41 exhibits an efficient intramolecular energy transfer process from the silylated bdiketonate to the central Eu 3+ , namely, the ''antenna effect'', which favored a stronger red/orange intensity ratio, longer lifetime, and high thermal stability than the precursor complex.