Mechanism Of Ce3 Research Articles

Ratiometric fluorescence sensor based on europium-organic frameworks for selective and quantitative detection of cerium ions

BackgroundDue to the unavoidable use of cerium in daily life, the accumulation of cerium in the environment increases health risks for humans. Therefore, it is crucial to develop a chemical sensing technology for the rapid, sensitive, and selective detection of cerium ions. ResultsIn this research work, a novel two-dimensional chain structure of a europium-based metal organic framework (Eu-MOF) [Eu2(tcpa)(Htcpa)2] was synthesized by using 3,4,5,6-tetrachloro-1,2-benzenedicarboxylic acid (H2TCPA) as the ligand and europium nitrate as the metal source. The results of powder X-ray diffraction and thermogravimetric analysis show that the synthesized Eu-MOF has excellent chemical and thermal stability. When the Eu-MOF suspension was excited by ultraviolet light at 292 nm, four fluorescence emissions were observed at 420, 595, 620 and 705 nm. It was particularly interesting that when cerium ions (Ce3+/Ce4+) were added to the Eu-MOF suspension, the fluorescence intensity at 420 nm was enhanced, while the fluorescence at 620 nm was quenched. On this basis, a ratiometric fluorescent sensor for detecting cerium ions was constructed, which has a good linear relationship in the range of 0.05–15 μM and a detection limit of 16 nM. The plausible mechanism of the change in the fluorescence characteristics of Eu-MOF caused by cerium ions was discussed in detail. Through the study of fluorescence lifetime and ultraviolet absorption, it was proven that the mechanism of Ce3+-quenching Eu-MOF fluorescence is the inner filter effect. Photoinduced electron transfer and internal filtering effects lead to fluorescence quenching at 620 nm, while redox reactions lead to fluorescence enhancement of the ligand at 420 nm. SignificanceThe proposed ratiometric fluorescence sensor was successfully employed for the detection of cerium ions in real water samples, confirming that it can be used as an alternative method for the detection of Ce3+ and Ce4+ in environmental samples.

Tunable Luminescence of Ce3+/Eu2+ Activated in Single-Phase Li2BaSiO4 Phosphor via Energy Transfer

A series of Ce3+,Eu2+ co-doped Li2BaSiO4 cyan-green phosphors were synthesized by a high temperature solid phase method. The crystal structure, morphology, luminescent properties and temperature characteristics of the corresponding samples were systematically studied. The main peaks of the emission spectra of Li2BaSiO4:Ce3+,Eu2+ were shifted from 400 nm to 500 nm by adjusting the Ce3+,Eu2+ co-doping concentration. And a series of phosphors with continuous changes from blue to cyan green were obtained, which effectively compensated for the gap between the white LED at 470–510 nm region. The energy transfer efficiency and mechanism of Ce3+,Eu2+ in Li2BaSiO4 were studied by fluorescence lifetime. The highest energy transfer efficiency was 46.01%, and the energy transfer mechanism was determined to be electric dipole-electric dipole transition. Finally, fabricating a white LED device which coated blue, green-yellow, red and as-prepared cyan phosphors on the surface of ultraviolet chip (350 nm), and the device exhibited excellent luminescence characteristics (Ra = 95.2, CCT = 3105 K). The results show that the Li2BaSiO4:Ce3+,Eu2+ phosphor developed can be regard as single-component tunable color luminescent materials under the excitation of near ultraviolet light.

The photoluminescence, thermal properties and tunable color of bright green-emitting Ba3Sc(BO3)3:Ce3+/Tb3+ phosphors via efficient energy transfer

The single-phase Ba3Sc(BO3)3:Ce3+/Tb3+ samples were synthetized via high-temperature solid-state reaction. X-ray diffraction (XRD), Rietveld refinement and transmission electron microscopy (TEM) were used for characterizing the morphology and phase purity of Ba3Sc(BO3)3. The photoluminescence emission (PL) and excitation (PLE) spectra, lifetime decay behavior and thermal stability of the Ba3Sc(BO3)3:Ce3+/Tb3+ phosphors were discussed in detail. Site occupation of Ce3+ ions in Ba2+ and Sc3+ sites were explained through Gaussian fitting and Van Uitert empirical equation. All these properties are closely related to the intrinsic crystallization structure of the Ba3Sc(BO3)3 matrix, which is discussed in detail in this paper. Compared with Ba3Sc(BO3)3:1%Tb3+ sample, the luminous intensity of Tb3+ increased about 3.2 and 4.1 times for Ba3Sc(BO3)3:2%Ce3+,1%Tb3+ monitored at 342 and 313 nm, respectively. Energy transfer (ET) mechanism of Ce3+→Tb3+ were dipole-dipole interactions and quadrupole-quadrupole interactions at Ce3+(1) and Ce3+(2) sites, respectively. The temperature-dependent PL spectra of Ba3Sc(BO3)3: Ce3+,Tb3+ illustrated that this phosphor possesses excellent thermal stability and chromaticity stability. Finally, a white LED device was prepared via the combination of the n-UV chip (365 nm), commercial blue BAM:Eu2+ phosphor, green Ba3Sc(BO3)3:2%Ce3+,6%Tb3+ phosphor and commercial red Sr2Si5N8:Eu2+ phosphor, which showed bright warm-white light. These conclusions proved that the green Ba3Sc(BO3)3:2%Ce3+,6%Tb3+ phosphor is desirable for white LED applications.

Photoluminescence properties and energy transfer of high thermal stable Na2GdPO4F2:RE (RE = Sm3+, Ce3+, Tb3+) phosphor for solid-state lighting

In this paper, a series of Na2GdPO4F2:Sm3+/Ce3+/Tb3+ phosphors had been synthesized via solid-state reactions and the luminescence properties of the phosphors had been investigated in detail. The Sm3+ ions in the host exhibited intense red emission under 402 nm irradiation and the mechanism for energy migration among Sm3+ ions was determined to be electronic dipole-dipole (d-d) interaction. For Ce3+ and Tb3+ codoped phosphors, the Ce3+→Tb3+ energy transfer took place, making the phosphor has intense green emission at 320 nm excitation. The mechanism for Ce3+→Tb3+ energy transfer had been verified as electronic dipole-quadrupole (d-q) interaction through the luminescence analysis using I–H model. The Na2GdPO4F2:Sm3+ and Na2GdPO4F2:Ce3+,Tb3+ phosphors both possessed pretty good thermal stability, and by coating them on the UV chips, red and green LED devices had been obtained, respectively. Moreover, utilizing the Tb3+ ions as bridges, Ce3+→Tb3+→Sm3+ energy transfer had been observed in NGPF:Ce3+,Tb3+,Sm3+ phosphor. The investigation results on the property of as-prepared samples indicated that Na2GdPO4F2 is a good host for rare earth ion doping and the Na2GdPO4F2:Sm3+ and Na2GdPO4F2:Ce3+,Tb3+ might be potential UV excited red and green phosphors for UV-WLEDs.

Lactic-acid enhanced solvothermal crystallization, color-tunable photoluminescence, and thermal stability of h-LaPO4:Ce3+, Tb3+, Sm3+ nanocrystals

Color-tunable photoluminescence of h-(La0.93−xCe0.05TbxSm0.02)PO4 nanocrystals.

K3YB6O12:Ce3+,Tb3+: A near-ultraviolet-excitable emission-tunable phosphor for white light-emitting diodes

A series of near-ultraviolet-excitable emission-tunable phosphors K3YB6O12:Ce3+,Tb3+ have been successfully prepared via a conventional high-temperature solid-state reaction technique. Their phase structures and luminescence properties were investigated. The green emission of Tb3+ can be largely sensitized by Ce3+ in K3YB6O12 host due to efficient Ce3+ → Tb3+ energy transfer process, which leads to broad and strong excitation band in near-ultraviolet region for K3YB6O12:Ce3+,Tb3+ phosphors. The critical distance, efficiency, and mechanism of Ce3+ → Tb3+ energy transfer are also calculated and determined in term of theoretical formulas. Upon excitation with near-ultraviolet (∼365 nm), the tunable emission-color from blue to green can be realized in the as-prepared phosphors. These results indicate that the K3YB6O12:Ce3+,Tb3+ phosphors might have potential application in near-ultraviolet pumped white light-emitting diodes.

Development of near-ultraviolet-excitable single-phase white-light-emitting phosphor KBaY(BO3)2:Ce3+,Dy3+ for phosphor-converted white light-emitting-diodes

The development of near-ultraviolet (n-UV)-excitable single-phase white-light-emitting phosphor is highly meaningful for phosphor-converted white light-emitting-diodes (pc-WLEDs) based on n-UV chips. In this work, a series of Dy3+ singly doped and Ce3+, Dy3+ co-doped KBaY(BO3)2 phosphors with different doping concentration of Ce3+/Dy3+ were designed and synthesized via a solid state reaction at high temperature, and their phase structure, photoluminescence properties and potential application in WLEDs were investigated in detail. The prominent sensitization effect of Ce3+ on Dy3+-luminescence based on Ce3+→Dy3+ energy transfer is authenticated by comparatively investigating the photoluminescence excitation and emission spectra of the as-prepared phosphors. The critical distance, efficiency, and mechanism of Ce3+→Dy3+ energy transfer are calculated and determined in term of the theoretical formulas. The n-UV-excitable white light emission is realized in the KBaY(BO3)2:Ce3+,Dy3+ phosphors with the appropriate doping concentration of Ce3+ and Dy3+ ions. A pc-WLEDs device is successfully fabricated by the combination of the single-phase KBaY(BO3)2:Ce3+,Dy3+ phosphor and an n-UV (~365 nm) LED chip. All these properties indicate that the developed single-phase KBaY(BO3)2:Ce3+,Dy3+ phosphor may have potential application prospect for pc-WLEDs.

Luminescence and energy transfer of Ba3P4O13:Ce3+and Ba3P4O13:Ce3+,Tb3+ phosphors

A series of novel Ce3+ singly doped and Ce3+, Tb3+ co-doped Ba3P4O13 phosphors [Ba3P4O13:Ce3+, Ba3P4O13:Ce3+,Tb3+] were synthesized via the high-temperature solid-state reaction method. The photoluminescence properties and energy transfer behavior of the as-prepared phosphors were investigated in detail. The Ba3P4O13:Ce3+ phosphors produced broadband emission ranging from 300 to 400 nm upon UV excitation. The optimal concentration of Ce3+ and critical distance for Ce3+→Ce3+ energy transfer was ascertained by investigating the concentration dependent luminescence properties of Ce3+ in Ba3P4O13 host. The Ce3+→Tb3+ energy transfer phenomenon was proved to exist in the Ba3P4O13:Ce3+,Tb3+ phosphors, which led to the broadband sensitized yellowish-green emission of Ba3P4O13:Ce3+,Tb3+ phosphors upon UV excitation. The efficiency and mechanism of Ce3+→Tb3+ energy transfer was also investigated by theoretical calculation.

Site-occupancy, luminescent properties and energy transfer of a violet-to-red color-tunable phosphor Ca10Li(PO4)7: Ce3+, Mn2+

A series of color-tunable phosphors Ca10Li(PO4)7: Ce3+, Mn2+ were synthesized by high-temperature solid-state reaction. Site occupancy of Ce3+ and Mn2+ in Ca10Li(PO4)7 and corresponding luminescent properties were systemically studied. Rietveld refinement results indicate that the Ce3+ ions are preferred to occupy 7-cooridnated M1 and M3 sites, and Mn2+ ions are mainly occupying distorted octahedral M5 sites, which results in Ce3+ violet emission at 370nm and Mn2+ red emission at 640nm. The intensity of Mn2+ red emission is greatly enhanced through efficient Ce3+-Mn2+ energy transfer (ηET=94%). The critical distance and corresponding mechanism of Ce3+-Mn2+ energy transfer was found to be ~11Å and dipole-quadrupole interaction, respectively. The emitting colors of Ca10Li(PO4)7: Ce3+, Mn2+ phosphors can be tuned from violet through pink to red by adjusting the Ce3+/Mn2+ ratio. The composition-optimized red phosphor Ca10Li(PO4)7: 0.05Ce3+, 0.09Mn2+ exhibits excellent thermal stability at high temperature (~100% at 160°C).

Photoluminescence characterization and energy transfer of color-tunable Li6Y(BO3)3:Ce3+,Tb3+ phosphors

Ce3+ and Tb3+ singly doped and co-doped Li6Y(BO3)3 (LYB) phosphors were synthesized through a solid-state reaction. The phosphors were effectively excited by 350nm, which matched the near-UV emitting InGaN chip. Luminescence spectra and decay lifetime curves of LYB:Ce3+,Tb3+ were measured to prove energy transfer from Ce3+ to Tb3+. Through energy transfer, the intensity of the typical emission peak of Tb3+ at 546nm in LYB:0.05Ce3+,0.03Tb3+ was approximately 1.8 times stronger than that in LYB:0.03Tb3+. The mechanism of Ce3+→Tb3+ energy transfer was a dipole–dipole interaction, and the energy transfer efficiency gradually increased to 29.27% with increasing Tb3+ doping concentration. Furthermore, the emission colors of LYB:Ce3+,Tb3+ varied from blue to green by adjusting the Ce3+/Tb3+ ratio, indicating that the phosphors could be used as blue-to-green emitting phosphors for application in ultraviolet light-emitting diodes.

Tunable multicolor and white luminescence in Tb3+/Dy3+/Mn2+ doped CePO4 via energy transfer

In this paper, a series of Tb3+/Dy3+/Mn2+ doped CePO4 downconversion nanophosphors (DCNPs) were prepared by a one-pot hydrothermal process. The obtained DCNPs presented monoclinic and hexagonal phase structure with wire-like shape. The photoluminescence (PL) properties and the energy transfer (ET) mechanism of these DCNPs were investigated in detail. The ET mechanism of Ce3+/Tb3+ in CePO4 host was calculated by means of concentration quenching and spectral overlapping, and calculation results revealed that dipole–dipole interactions should be more responsible. The maximum value of ET efficiency was measured to 87.4% for Tb3+ doped CePO4 system. In addition, owing to the efficient ET between Ce3+ and Tb3+/Dy3+/Mn2+, these as-prepared DCNPs exhibit tunable multi-color output under ultra-violet (UV) light excitation. More importantly, the intense cold and warm white emissions can be realized by singly doping 2%Dy3+ and 20%Mn2+ in CePO4 host under UV irradiation, respectively. The corresponding CIE 1931 coordinates were calculated to be (0.30, 0.30) and (0.30, 0.32), respectively, which are closed to the standard white emission (0.33, 0.33). These findings demonstrate the efficient white light emission by singly doped Dy3+ or Mn2+ in CePO4 system for the first time, which is different from commonly used co-doped or tri-doped system. The multicolor tuning and white emission make these Tb3+/Dy3+/Mn2+ doped CePO4 DCNPs potential phosphors in the fields of displays, lighting, and field-emission devices.

Luminescence property of Ce3+-Tb3+-Sm3+ co-doped borosilicate glass under various ultraviolet excitations

Ce3+-Tb3+-Sm3+ co-doped white light emitting borosilicate glasses were fabricated by high-temperature melting technique. In this paper, the excitation spectra and the emission spectra of Ce3+, Tb3+ and Sm3+ ions-doped and co-doped samples were measured and the energy transfer mechanism of Ce3+, Tb3+, and Sm3+ were studied by analyzing the fluorescence lifetime of single-doped and co-doped samples. The color coordinate, rendering index, and color temperature of the emission spectra can be adjusted by changing the excitation wavelength of ultraviolet LED. Finally, we have obtained the white light which fits for life, study, and work.

Inhibiting effect of cerium ions on corrosion of 3003 aluminum alloy in ethylene glycol–water solutions

In this study, the inhibiting effect of cerium ions (Ce3+) on corrosion of 3003 aluminum alloy (AA3003) in ethylene glycol–water solutions was investigated using a rotating cylinder electrode, simulating the hydrodynamic condition of the automotive cooling system. Electrochemical measurements and surface characterization were conducted to study the inhibiting mechanism of Ce3+ on the Al alloy corrosion. It is found that Ce3+ serves as a cathodic inhibitor, and inhibits effectively corrosion of AA3003 in the flowing ethylene glycol–water solutions. The inhibiting effect of Ce3+ is resulted from the formation and deposit of Ce oxide and/or Ce hydroxide on the electrode surface. With the immersion time, the Ce deposit layer increases its thickness to cover the second phase particles, eliminating the galvanic coupling effect between the second phase particles and Al alloy substrate.

Structure and Morphology of Sol-Gel Nanocrystalline TiO<sub>2</sub> Films Coated on Glass Substrates

The Ce3+-doped and undoped nanocrystalline TiO2 films were prepared on glass substrates surface by sol-gel dip coating technique. The crystal structure and surface morphology of TiO2 films were characterized by means of X-ray diffractometer (XRD), transmission electron microscopy (TEM) and atomic force microscope (AFM). The results indicated that the Ce3+-doped TiO2 films were solely composed of the anatase phase whereas in the undoped films small amount of the rutile phase of TiO2 were present. The average crystallite size of the undoped TiO2 films was about 30nm and was decreased with Ce3+-doping in the TiO2 films. Moreover, the grains distributed more uniform and the surface roughness was smaller in the Ce3+-doped TiO2 films than in the undoped one. The action mechanism of Ce3+-doping inhibits the crystallization of the rutile phase and decreases the anatase granularity of TiO2 films is associated with its physicochemical properties, as well as ionic diffusion and valance change of Ce3+ to Ce4+ in the sintering process.