Luminescent and magnetic properties of multifunctional europium(III) complex based nanocomposite

The luminescent rare earth (RE) complex based multifunctional nanocomposites offer new potential applications of multimodal imaging (magnetic resonance imaging (MRI), fluorescent bioimaging, etc.) that can be associated with therapeutic activities. In this study, we report some results obtained with novel multifunctional Fe₃O₄/Si-amine/Eu(NTA)₃ nanocomposites that are composed of europium(III) complex with 1-(2-naphthoyl)-3,3,3-trifluoroacetone ligands (NTA) (Eu(NTA)₃) and superparamagnetic Fe₃O₄ nanoparticles. These nanocomposites were functionalized with an amine group for biomedicine application. The multifunctional Fe₃O₄/Si-amine/Eu(NTA)₃ nanocomposites exhibit both good magnetic behavior of Fe₃O₄ nanoparticles as a core and strong fluorescent property of europium(III) complex. Their characterizations were analyzed by XRD, SEM, EDX and FTIR spectra. The optical properties were studied in detail by UV-VIS spectra and luminescent emission spectra. The magnetic property was estimated by VMS. The effect of concentrations of luminescent Eu(NTA)₃ complex on luminescent and magnetic properties is discussed.     

Plasmon-enhanced broad-band quantum-cutting of NaBaPO4:Eu2+,Er3+ phosphors with silver nano-particles

NaBaPO₄:Eu²⁺,Er³⁺ phosphors and Ag nano-particles (NPs) were prepared by the solid-state reaction and chemical reduction method, respectively. The fluorescence spectra and decay curves demonstrate the effective energy transfer from Eu²⁺ to Er³⁺ and the existence of three-photon quantum-cutting through two-step cross-relaxation of Er³⁺. The quantum-cutting emission is peaked at 1534 nm with a broad excitation band centered at 352 nm. Plasmon-enhanced quantum-cutting of NaBaPO₄:Eu²⁺,Er³⁺ phosphors was realized by decorating Ag NPs. The largest enhancement factor is 1.395. It is hopeful to improve the photovoltaic conversion efficiency of Ge solar cells by using this phosphor.     

Ln3+ (Ln = Eu,Dy) - doped Sr2CeO4 fine phosphor particles: Wet chemical preparation,energy transfer and tunable luminescence

The Sr₂CeO₄:Ln³⁺ (Ln = Eu, Dy) fine phosphor particles were prepared by a facile wet chemical approach, in which the consecutive hydrothermal-combustion reaction was performed. The doping of Ln³⁺ into Sr₂CeO₄ has little influence on the structure of host, and the as-prepared samples display well-crystallized spherical or elliptical shape with an average particle size at about 100–200 nm. For Eu³⁺ ions-doped Sr₂CeO₄, with the increase of Eu³⁺-doping concentration, the blue light emission band with the maximum at 468 nm originating from a Ce⁴⁺ → O²⁻ charge transfer of the host decreases obviously and the characteristic red light emission of Eu³⁺ (⁵D₀→⁷F₂ transition at 618 nm) is enhanced gradually. Simultaneously, the fluorescent lifetime of the broadband emission of Sr₂CeO₄ decreases with the doping of Eu³⁺, indicating an efficient energy transfer from the host to the doping Eu³⁺ ions. The energy transfer efficiency from the host to Eu³⁺ was investigated in detail, and the emitting color of Sr₂CeO₄:Eu³⁺ can be easily tuned from blue to red by varying the doping concentration of Eu³⁺ ions. Moreover, the luminescence of Dy³⁺-doped Sr₂CeO₄ was also studied. Similar energy transfer phenomenon can be observed, and the incorporation of Dy³⁺ into Sr₂CeO₄ host leads to the characteristic emission of ⁴F_9/2 → ⁶H_15/2 (488 nm, blue light) and ⁴F_9/2 → ⁶H_13/2 (574 nm, yellow light) of Dy³⁺. The Sr₂CeO₄:Ln³⁺ fine particles with tunable luminescence are quite beneficial for its potential applications in the optoelectronic fields.     

A stimuli responsive lanthanide-based hydrogel possessing tunable luminescence by efficient energy transfer pathways

Energy transfer as an important component in light-harvesting antenna systems can mimic effectively natural photosynthesis processes, showing great potential in optoelectronic devices. Herein, we report a responsive polymeric hydrogel based on the combination of excited state intramolecular proton transfer (ESIPT) molecule (Salicylic acid, Sal) and terbium (III) (Tb³⁺), as enabled by external stimuli to construct artificial light-harvesting antenna systems. Benefiting from unique photophysical properties of Sal, the synthesized hydrogel displays a temperature-dependent reversible opaque ? transparent states transition, accompanied with an interesting photoluminescence behavior. Moreover, by further incorporating europium (III) (Eu³⁺) into the hydrogel, we demonstrate well-defined cascades of energy transfer that provides a tunable optical output from the collection of lanthanides by the excitation of a common sensitizer (Sal) upon base vapor stimulation. Efficient energy transfer efficiency from Tb³⁺ to Eu³⁺, as high as 97.8%, was also obtained as established by the time-resolved fluorescence spectroscopy analysis.     

Preparation,luminescence and photofunctional performances of a hybrid layered gadolinium-europium hydroxide

The design and fabrication of rare earth ions incorporated into the inorganic/organic hybrid materials have attracted growing attention for seeking improved optical properties and photofunctional performances.In this paper,a novel hybrid composite based on the layered rare earth hydroxides was successfully prepared by the ion-exchange and intercalation chemical process.The rare earth elements in the composite contain gadolinium(Gd) and europium(Eu) and the molar ratio of Gd to Eu is kept constan...     

Optical and electrical conductivity properties of rare earth elements (Sm,Y, La,Er) co-doped CeO2

In this research, un-doped CeO₂ and Ce_0.85La_0.10M_0.05O₂ (M: Sm, Er, Y) compounds were synthesized by hydrothermal method and the multi-functional properties are reported. Oxygen defects were created with the additives of rare earth ions. The electrical and luminescence behaviors of the synthesized compounds were investigated in accord with the types of additives. The synthesized products were characterized by X-ray diffraction (XRD) analysis, Brunauer–Emmett–Teller (BET) measurement, UV–vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and electrochemical impedance spectroscopic (EIS). All synthesized compounds are found to be nano-structured and have cubic phase. The total conductivity of all samples was calculated. Hence, the total conductivity of un-doped CeO₂, Ce_0.85La_0.10Y_0.05O₂, Ce_0.85La_0.10Er_0.05O₂ and Ce_0.85La_0.10Sm_0.05O₂ is found to be 2.07 × 10^?10, 5.70 × 10^?4, 1.0 × 10^?3 and 0.0747 S/cm, respectively. Also, bandgap energy (E_g) of these samples calculated from UV visible absorption spectra is discussed, and the optical results show variation between 3.2 and 2.15 eV. Additionally, the luminescence properties of the compounds were investigated and different emissions occur depending on the additive type. Accordingly, photoluminescent emission spectra of Ce_0.85La_0.10Y_0.05O₂, Ce_0.85La_0.10Er_0.05O₂ and Ce_0.85La_0.10Sm_0.05O₂ phosphors indicate that these phosphors have red, green and orange-red colors, respectively.     

Optical,thermal and luminescence properties of La2O3–Ga2O3–ZrO2 glasses co-doped with Tm3+/Yb3+ prepared by containerless technique

Bulk La₂O₃–Ga₂O₃–ZrO₂ (LGZ) glass and Tm³⁺/Yb³⁺ co-doped LGZ glasses were synthesized successfully using containerless technique. Raman spectra result reveals that the matrix sample possesses the low maximum phonon energy of ～642 cm^?1. The glasses show good compatibility between large Abbe numbers (>31) and high refractive indices (n_d > 1.93). Moreover, transmittance measurements reflect that the glasses have high infrared transmittance of ～81.9%, small OH^– absorption coefficient and long mid-infrared cut-off wavelengths (～7.5 μm). The surface morphology of host glass was characterized by scanning electron microscopy (SEM) micrograph and energy dispersive spectroscopy (EDS) tests reflect that the doped compositions are distributed into the matrix glass homogeneously. The results of thermal analysis show that the glasses have good thermal properties (T_g > 769 °C). Excited by 980 nm laser, an intense 1810 nm fluorescence is obtained originating from the transition: ³F₄ → ³H₆ of Tm³⁺ ion, accompanied by upconversion emission. It can be observed that 1810 nm fluorescence has the highest intensity at 1 mol% Yb₂O₃ and owns broad full width at half-maximum (>245 nm), the luminescence intensity of ³F₄ → ³H₆ transition increases with rising temperature from 300 to 550 K. Furthermore, the value of energy transfer efficiency shows that Yb³⁺ can transfer energy to Tm³⁺ effectively. By fitting the attenuation curves, the lifetimes of 1810 and 474 nm emission can be acquired.     

Growth and optical properties of ytterbium and rare earth ions codoped CaF_2-SrF_2 eutectic solid-solution(RE=Y~(3+),Gd~(3+),La~(3+))

Ytterbium and rare earth ions(RE=Y,Gd,La)codoped CaF₂-SrF₂single crystals(3 at%Yb,6 at%RE:CaF₂-SrF₂)were fabricated by temperature gradient technology(TGT).All the space groups remain the same Fm3m as that of Yb:CaF₂-SrF₂.The lattice parameter a,unit cell volume V,as well as bond length of Ca/Sr-F and F-F increase in the sequence of rare-earth ions radius Y³⁺3+3+.The segregation coefficients of Yb ions are 0.87 in Yb,La:CaF₂-SrF₂and Yb,Gd:CaF₂-SrF₂,which are larger than 0.85 in Yb,Y:CaF₂-SrF₂and 0.80 in Yb:CaF₂-SrF₂.Absorption spectra in the range of 200 and 400 nm were analysed with Yb²⁺contents.The absorption and emission cross-sections in the range of 900-1100 nm were determined together with fluorescence lifetime.The saturation pump density/Sat,minimum pump density/m in and gain cross-section were analysed.Yb,La:CaF₂-SrF₂has a relatively higher optical parameter(δem×t,0.52×10²⁰cm²·ms),lower Isat(3.68 kW/cm²)and^min(0.50 kW/cm²)at 1038 nm indicating the potential application in high power laser.Low phonon energy of CaF₂-SrF₂is 302 cm^-1which is located between those of CaF₂and SrF₂as measured by Raman spectra.It is believed that ytterbium and rare earth ions(RE=Y³⁺,Cd³⁺,La³⁺)codoped CaF₂-SrF₂eutectic solid-solution is promising for high-power and wavelength-tunable solid-state lasers.     

Luminescence Properties of Pyridine Carboxylic Acid-Europium (Ⅲ) Complexes

The luminescent properties of four pyridine carboxylic acid-europium complexes were investigated byinfrared absorption,fluorescence and time-resolved fluorescent spectroscopy.The influences of structure ofcomplex compounds,solvents and pH of the media on the emission intensity and the lifetime are discussed aswell.