Synthesis and characterization of luminescent SiO2 @Eu(phen-Si) core-shell nanospheres.

Four core-shell structured nanometre luminescent composites with different kernel sizes and different shell layer thicknesses (SiO2(500) @Eu (phen-Si)(50) , SiO2(500) @Eu (phen-Si)(15) , SiO2(250) @Eu (phen-Si)(5) and SiO2(250) @Eu (phen-Si)(10) ) were made by changing synthesis conditions. Here, initial subscript numbers in parentheses refer to the particle size of the SiO2 core, whereas the final subscript numbers in parentheses refer to shell layer thickness. In these composites, silica spheres of 500 nm or 250 nm were identified as the core. The shell layer was composited of silicon, 1,10-phenanthroline and europium perchlorate, abbreviated as Eu(phen-Si); the chemical formula of phen-Si was phen-N-(CONH (CH2 )Si(OCH2 CH3 )3 )2 . The composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and infrared spectroscopy. The monodispersed spherical SiO2 showed characteristics of a regular microstructure and a smooth surface, as well as the advantage of dispersity, shown by SEM. The Eu(phen-Si) complex was able to self-assemble into monodispersed SiO2 spheres, as seen using TEM. Fluorescence spectra indicated that the four composites had excellent luminescence properties. Furthermore, composites composed of a SiO2 core and a 250 nm kernel size exhibited stronger fluorescence than 500 nm kernel-sized composites. Fluorescence properties were affected by shell thickness: the thicker the shell, the greater the fluorescence intensity. For the four composites, quantum yield values and fluorescence lifetime corresponded to fluorescence emission intensity data as quantum yield values and fluorescence lifetime were higher, and luminescence properties increased.

Preparation, characterization and luminescence properties of core-shell ternary terbium composites SiO2(600)@Tb(MABA-Si)•L.

Two novel core-shell structure ternary terbium composites SiO2(600)@Tb(MABA-Si)·L(L:dipy/phen) nanometre luminescence materials were prepared by ternary terbium complexes Tb(MABA-Si)·L2·(ClO4)3·2H2O shell grafted onto the surface of SiO2 microspheres. And corresponding ternary terbium complexes were synthesized using (CONH(CH2)3Si(OCH2CH3)3)2 (denoted as MABA-Si) as first ligand and L as second ligand coordinated with terbium perchlorate. The as-synthesized products were characterized by means of IR spectra, 1HNMR, element analysis, molar conductivity, SEM and TEM. It was found that the first ligand MABA-Si of terbium ternary complex hydrolysed to generate the Si-OH and the Si-OH condensate with the Si-OH on the surface of SiO2 microspheres; then ligand MABA-Si grafted onto the surface of SiO2 microspheres. The diameter of SiO2 core of SiO2(600)@Tb(MABA-Si)·L was approximately 600 nm. Interestingly, the luminescence properties demonstrate that the two core-shell structure ternary terbium composites SiO2(600)Tb(MABA-Si)·L(dipy/phen) exhibit strong emission intensities, which are 2.49 and 3.35 times higher than that of the corresponding complexes Tb(MABA-Si)·L2·(ClO4)3·2H2O, respectively. Luminescence decay curves show that core-shell structure ternary terbium composites have longer lifetime. Excellent luminescence properties enable the core-shell materials to have potential applications in medicine, industry, luminescent fibres and various biomaterials fields.

Influence of citrate on phase transformation and photoluminescence properties in LaPO4 and LaPO4:Eu.

The hexagonal and monoclinic phase LaPO4 and LaPO4:Eu nanostructures have been controllably synthesized by a citrate-induced hydrothermal process at 100 °C. The crystal growth of LaPO4 nanostructures was investigated, and the phase transformation of nanostructured LaPO4 was systematically studied by varying the citrate concentration, pH value and reaction temperature. When 0.8 mmol of citrate was added into the reaction system, the hexagonal phase LaPO4 transformed into the monoclinic phase. High concentrations of citrate would lead to the formation of hexagonal phase LaPO4. The photoluminescence properties of the monoclinic phase LaPO4:Eu prepared using a citrate-induced process demonstrate that the electric dipole transition (5D0 → 7F2) is stronger than the magnetic dipole transition (5D0 → 7F1), which indicated that Eu3+ is in a site with no inversion center. The strongest emission peak of hexagonal phase LaPO4:Eu comes from 5D0 → 7F1. Furthermore, the citrate-induced hexagonal phase LaPO4:Eu has a stronger emission intensity than the hexagonal phase LaPO4:Eu prepared not using a citrate-induced process.

Synthesis, characterization and luminescence of europium perchlorate with MABA-Si complex and coating structure SiO2 @Eu(MABA-Si) luminescence nanoparticles.

This article reports a novel category of coating structure SiO2 @Eu(MABA-Si) luminescence nanoparticles (NPs) consisting of a unique organic shell, composed of perchlorate europium(III) complex, and an inorganic core, composed of silica. The binary complex Eu(MABA-Si)3 ·(ClO4 )3 ·5H2 O was synthesized using HOOCC6 H4 N(CONH(CH2 )3 Si(OCH2 CH3 )3 )2 (MABA-Si) and was used as a ligand. Furthermore, the as-prepared silica NPs were successfully coated with the -Si(OCH2 CH3 )3 group of MABA-Si to form Si-O-Si chemical bonds by means of the hydrolyzation of MABA-Si. The binary complexes were characterized by elemental analysis, molar conductivity and coordination titration analysis. The results indicated that the composition of the binary complex was Eu(MABA-Si)3 ·(ClO4 )3 ·5H2 O. Coating structure SiO2 @Eu(MABA-Si) NPs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and infrared (IR) spectra. Based on the SEM and TEM measurements, the diameter of core-SiO2 particles was ~400 and 600 nm, and the thickness of the cladding layer Eu(MABA-Si) was ~20 nm. In the binary complex Eu(MABA-Si)3 ·(ClO4 )3 ·5H2 O, the fluorescence spectra illustrated that the energy of the ligand MABA-Si transferred to the energy level for the excitation state of europium(III) ion. Coating structure SiO2 @Eu(MABA-Si) NPs exhibited intense red luminescence compared with the binary complex. The fluorescence lifetime and fluorescence quantum efficiency of the binary complex and of the coating structure NPs were also calculated. The way in which the size of core-SiO2 spheres influences the luminescence was also studied. Moreover, the luminescent mechanisms of the complex were studied and explained.

[Hydrothermal synthesis and luminescence properties of CePO4 : Tb flower-like clusters].

Tb(3+)-doped CePO4 flower-like clusters were hydrothermally synthesized without using any template or surfactant by varying the reactant Tb3+ cation concentration. It was observed that the flower-like clusters were composed by nanowires with a diameter of about 80-90 nm and lengths up to 1 microm. The structures, morphologies, sizes and luminescence properties of the products were studied by X-ray powder diffraction (XRD), field-emission scanning electronic microscopy (FE-SEM), and luminescence spectra. With the reactant Ce3+ /Tb3+ molar ratio of 0.850 : 0.150, the uniform flower-like clusters were actually composed of a self-assembly of the oriented nanowires through an Tb(3+)-induced in the excessive PO4(3-). It was found that the reactant Ce3+/Tb3+ molar ratio and phosphoric acid played key roles in the morphology control of the product. A possible formation mechanism for the flower-like morphology was also proposed. The luminescence properties of CePO4 : Tb flower-like cluster were performed, indicating that the strongest emission intensity was reached with 0.850 : 0.150 molar ratios of Ce3+/Tb3+.

[Controlled syntheses and photoluminescence characterization of monoclinic cerium orthophosphate with nanostructure].

The nanostructured CePO4 with monoclinic phase was controllably synthesized through a low temperature hydrothermal route by varying the reactant PO4(3-)/Ce(3+) molar ratio. The structures, morphologies, sizes and luminescence properties of the products were studied by XRD, FE-SEM, DSC-TG and photoluminescence spectra. With the PO4(3-)/Ce(3+) molar ratios increased, the synthesis temperature of as-synthesized monoclinic CePO4 was decreased, and the morphologies underwent the evolution from the rod-like nano-structures to the flower-like nanoclusters. When the PO4(3-)/Ce(3+) molar ratio was lower, CePO4 nanorods were obtained, while the PO4(3-)/Ce(3+) molar ratio was higher, the monoclinic CePO4 flower-like nanoclusters were crystallized. The photoluminescence spectrum showed that the CePO4 nanorods exhibit better photoluminescent property than the CePO4 flower-like nanoclusters. With the cycling use of phosphoric acid, the low-cost preparation of CePO4 could be achieved.

[Influence of La3+ on Eu3+ luminescence of three component complex system of europium-2-thiophene carboxylic acid-phen].

Seven solid complexes of proportional mixed complexes (Eu3+ mixed with La3+) of rare earth perchlorate with the 2-thiophene carboxylic acid and 1.10-phenanthroline were synthesized. By elemental analysis, coordination titration and molar conductance measurement, the composition of the complexes were suggested to be (Eu(1-x)La(x)) x L3 x phen x 1/2H2O (x = 0.000-0.200, L as 2-thiophene carboxylic acid and phen for 1.10-phenanthroline) respectively. The ligands and coordination compounds were studied by means of IR spectra and fluorescence excitation and emission spectra. The molar conductivities in DMF solvent suggested that the complexes are nonelectrolyte. IR spectra studies indicate that the 2-thiophene carboxylic acid ligands bonded with RE(II) through oxygen atoms in carboxyl group and 1.10-phenanthroline ligand is bonded to RE(III) through nitrogen atoms. In the fluorescence spectra it was found that the Eu3+ complex has no symmetrical center. La3+ has a great influence on the luminescence of Eu3+. The fluorescence emission intensity of Eu3+ was enhanced by La3+ and the fluorescence intensity with x = 0.050 is much higher. With La3+ concentration increasing the luminescence of Eu3+ is less intense.

[Synthesis, characterization and fluorescence of Eu3+, Tb3+ complexes with 2-thiophencarboxylic acid and 2,2'-bipyridine].

Two binary complexes of Eu3+ and Tb3+ with 2-thiophene carboxylic acid and two ternary complexes of Eu3+ and Tb3+ with 2-thiophene carboxylic acid(L)-2, 2'-bipyridine were synthesized. By elemental analysis, rare earth coordination titration, and molar conductivities studies, the compositions of the complexes were suggested as REL3 x 2H2O and REL3L' x C2H5OH(RE=Eu, Tb, L = 2-thiophene carboxylic acid, L' = 2, 2'-bipyridine) respectively. The ligands and coordination compounds were studied by means of IR spectra, 1H NMR and fluorescence excitation and emission spectra. IR spectra and 1H NMR studies indicate that 2-thiophene carboxylic acid was bonded with RE(III) through oxygen atoms in the carboxyl group, and 2, 2'-bipyridine ligand was bonded to RE(III) through nitrogen atoms. The fluoresence spectra showed that the fluorescence emission intensity of ternary complexes was stronger than that of the binary complexes.