Persistent and Photostimulated Red Emission in CaS:Eu<sup>2+</sup>,Dy<sup>3+</sup> Nanophosphors

Rodríguez, Diana; Sharma, Suchinder K.; Dorenbos, P.; Viana, Bruno; Capobianco, John A.

doi:10.1002/adom.201400562

Cited by 148 publications

(99 citation statements)

References 27 publications

(22 reference statements)

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“…Recently, Rodríguez Burbano et al reported that this material also exhibits OSL under illumination with infrared light [16]. Therefore, the sample was illuminated with 970 nm infrared light after measuring the initial afterglow.…”

Section: Resultsmentioning

confidence: 99%

“…The phase purity of both phosphors was verified by powder X-ray (Cu K

α

) diffraction measurements using a Siemens D5000 diffractometer. Details concerning the synthesis, characterization and structural properties of the CaS:Eu nanophosphor were described by Rodríguez Burbano et al [16]. The phosphors were incorporated into a polymer layer by mixing an appropriate amount of the powders in a 20 wt% solution of kraton FG1901X in 3:1 toluene-to-methyl ethyl ketone, after which the mixture was cast on a circular glass plate with a diameter of 18 mm [42].…”

Section: Methodsmentioning

confidence: 99%

“…It was quickly found that the phosphor exhibits persistent luminescence when it is codoped with other lanthanides [14,15], which possibly paves the way for other applications. Recently it was reported that the persistent luminescence also arises in CaS:Eu if the grain size of the powder is reduced to a few hundred nanometers [16]. The dimensions of the grains in the nano-sized regime, in combination with the spectral location of the emission, provides the phosphor with characteristics for applications such as optical imaging in biomedicine.…”

Section: Introductionmentioning

confidence: 99%

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Counting the Photons: Determining the Absolute Storage Capacity of Persistent Phosphors

et al. 2017

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The performance of a persistent phosphor is often determined by comparing luminance decay curves, expressed in cd/m2. However, these photometric units do not enable a straightforward, objective comparison between different phosphors in terms of the total number of emitted photons, as these units are dependent on the emission spectrum of the phosphor. This may lead to incorrect conclusions regarding the storage capacity of the phosphor. An alternative and convenient technique of characterizing the performance of a phosphor was developed on the basis of the absolute storage capacity of phosphors. In this technique, the phosphor is incorporated in a transparent polymer and the measured afterglow is converted into an absolute number of emitted photons, effectively quantifying the amount of energy that can be stored in the material. This method was applied to the benchmark phosphor SrAl2O4:Eu,Dy and to the nano-sized phosphor CaS:Eu. The results indicated that only a fraction of the Eu ions (around 1.6% in the case of SrAl2O4:Eu,Dy) participated in the energy storage process, which is in line with earlier reports based on X-ray absorption spectroscopy. These findings imply that there is still a significant margin for improving the storage capacity of persistent phosphors.

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Section: Resultsmentioning

confidence: 99%

“…The phase purity of both phosphors was verified by powder X-ray (Cu K

α

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Counting the Photons: Determining the Absolute Storage Capacity of Persistent Phosphors

et al. 2017

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“…Other methods for determining the 5d-CB separation, such as using the charge transfer to a trivalent RE ion, can be more accurate. [ 19,28 ] However, the fi ts to the thermal quenching data give the qualitative indication that the 5d states of SLA are further separated from the CB than those of SMS. The source of SLA's temperature stability seems clear, the 5d states are well separated from the edge of the conduction band.…”

Section: Full Paper Full Paper Full Papermentioning

confidence: 93%

Electronic Structure, Bandgap, and Thermal Quenching of Sr[Mg₃SiN₄]:Eu²⁺ in Comparison to Sr[LiAl₃N₄]:Eu²⁺

Tolhurst

Schmiechen

Pust

et al. 2015

Advanced Optical Materials

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from a lack of emissions in the red-spectral region. Other designs are therefore preferable for high-quality illumination. [ 3 ] If pc-LEDs are to be used in general lighting they must be effi cient, have high color rendering and temperature-stable emission spectra. Two promising designs meeting these requirements are UV and blue LED chips, using three and two phosphors, respectively. Even these designs have encountered challenges, such as the ineffi ciency of the available red phosphors. [ 2 ] The discovery of new, effi cient red phosphors is therefore of the utmost importance. With constantly improving effi ciency and color rendition, along with dropping production costs, pc-LEDs can be expected to replace traditional lighting methods in the near future. [ 4 ] Rare earth (RE)-doped nitride phosphors based on condensed tetrahedral networks, with their tendency to exhibit highly effi cient and stable emissions, are promising candidates for the next generation of phosphors for pc-LEDs. [ 3,4 ] However, not all nitride matrices are equal. The polarizability of the ligands, covalency, and crystal fi eld splitting (CFS) experienced by the RE dopants are all key parameters. [ 4 ] Recently, the promising, red phosphors Sr[Mg 3 SiN 4 ]:Eu 2+ (SMS) and Sr[LiAl 3 N 4 ]:Eu 2+ (SLA) have been reported. [ 5,6 ] These highly condensed nitrides show narrow-band emissions in the red-spectral region. SMS shows λ em = 615 nm with an FWHM of 43 nm, while SLA shows λ em = 650 nm with an FWHM of 50 nm. Narrow emissions in this region are of interest because they are more likely to fall within the sensitivity range of the human eye. Emissions outside of this range, which often occur with a large FWHM in the red-spectral region, lead to wasted energy input and additional heating in the device. This work will focus on characterizing the electronic structure of SMS, which exhibits the narrowest emissions to date for a red-emitting, Eu 2+ -doped phosphor. [ 5 ] A combination of X-ray spectroscopy and density functional theory (DFT) calculations is used in this characterization. The thermal quenching data for the visible, Eu 2+ 5d→4f emissions of SMS and SLA are also modeled and compared. Where SMS shows poor emission stability with increases in temperature, SLA shows exceptional stability. However, SMS emits at a shorter wavelength, which may be more useful for certain applications. Between these phosphors many ideal characteristics for use in pc-LEDs are present. Their comparison (SLA), which shows different, yet exceptional emission characteristics in the red-spectral region. It is found that SMS has an indirect band gap of 3.28 ± 0.20 eV, strong uniformity in the density of states of its nonequivalent nitrogen sites, and an estimated energetic separation between the lowest Eu 2+ 5d state and the conduction band of ≈0.13 eV. The Eu 2+ 5d-conduction band separation in SLA is found to be ≈0.28 eV, which points to why the visible emissions of SLA, and not SMS, show outstanding thermal stability. A bonding scheme explaining the band gap di...

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“…[4] Specifically,aCaS:Ce 3+ phosphor has been documented as an efficient green phosphor for white light-emitting diode (LED) because the absorption of Ce 3+ ion in the CaS lattice is in the blue region of the spectrum which matches well with the emission of aGaN blue LED chip. [4] Specifically,aCaS:Ce 3+ phosphor has been documented as an efficient green phosphor for white light-emitting diode (LED) because the absorption of Ce 3+ ion in the CaS lattice is in the blue region of the spectrum which matches well with the emission of aGaN blue LED chip.…”

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confidence: 98%

A New Class of Blue‐LED‐Excitable NIR‐II Luminescent Nanoprobes Based on Lanthanide‐Doped CaS Nanoparticles

et al. 2019

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Lanthanide (Ln 3+ )-doped luminescent nanoparticles (NPs) with emission in the second near-infrared (NIR-II) biological windowh ave shown great promise but their applications are currently limited by the lowa bsorption efficiency of Ln 3+ owing to the parity-forbidden 4f!4f electronic transition. Herein, we developed as trategy for the controlled synthesis of an ew class of NIR-II luminescent nanoprobes based on Ce 3+ /Er 3+ and Ce 3+ /Nd 3+ co-doped CaS NPs,which can be effectively excited by using alow-cost blue light-emitting diode chip.Through sensitization by the allowed 4f!5d transition of Ce 3+ ,i ntense NIR-II luminescence from Er 3+ and Nd 3+ with quantum yields of 9.3 %a nd 7.7 %w as achieved, respectively.B yc oating them with al ayer of amphiphilic phospholipids,these NPs exhibit excellent stability in water and can be exploited as sensitive NIR-II luminescent nanoprobes for the accurate detection of an important disease biomarker,xanthine,with adetection limit of 32.0 nm.

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Persistent and Photostimulated Red Emission in CaS:Eu²⁺,Dy³⁺ Nanophosphors

Cited by 148 publications

References 27 publications

Counting the Photons: Determining the Absolute Storage Capacity of Persistent Phosphors

Counting the Photons: Determining the Absolute Storage Capacity of Persistent Phosphors

Electronic Structure, Bandgap, and Thermal Quenching of Sr[Mg₃SiN₄]:Eu²⁺ in Comparison to Sr[LiAl₃N₄]:Eu²⁺

A New Class of Blue‐LED‐Excitable NIR‐II Luminescent Nanoprobes Based on Lanthanide‐Doped CaS Nanoparticles

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Persistent and Photostimulated Red Emission in CaS:Eu2+,Dy3+ Nanophosphors

Cited by 148 publications

References 27 publications

Counting the Photons: Determining the Absolute Storage Capacity of Persistent Phosphors

Counting the Photons: Determining the Absolute Storage Capacity of Persistent Phosphors

Electronic Structure, Bandgap, and Thermal Quenching of Sr[Mg3SiN4]:Eu2+ in Comparison to Sr[LiAl3N4]:Eu2+

A New Class of Blue‐LED‐Excitable NIR‐II Luminescent Nanoprobes Based on Lanthanide‐Doped CaS Nanoparticles

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Persistent and Photostimulated Red Emission in CaS:Eu²⁺,Dy³⁺ Nanophosphors

Electronic Structure, Bandgap, and Thermal Quenching of Sr[Mg₃SiN₄]:Eu²⁺ in Comparison to Sr[LiAl₃N₄]:Eu²⁺