Persistent Luminescence Phosphor Research Articles

Phosphorescence of beta irradiated Sr4Al14O25:Eu2+,Dy3+ ─ A persistent luminescence phosphor

Phosphorescence of beta irradiated Sr4Al14O25:Eu2+,Dy3+ has been analysed. The persistent luminescence that defines this phosphor is phosphorescence hence the justification for this study. A set of phosphorescence decay curves were measured at various temperatures Tph between 20 and 352 °C following irradiation to 2 Gy. The residual thermoluminescence (R-TL) was recorded at 1 °C/s after the phosphorescence decay. A conventional TL glow curve recorded at the same rate following irradiation to 2 Gy produces two composite glow peaks P1 and P2 at 63 and 252 °C respectively. The decay curves measured between Tph = 28–60 °C and 200–240 °C associated with peaks P1 and P2 respectively give the values of the activation energy of peaks P1 and P2 as 0.59 ± 0.01 and 0.80 ± 0.04 eV. The effective frequency factors associated with the traps are 6.2 × 109 and 6.4 × 105 s−1 respectively. Peaks P1 and P2 are affected by thermal quenching with activation energy W = 0.69 ± 0.06 eV and 0.66 ± 0.03 eV respectively. The R-TL glow curves show two maxima R1 and R2 at ∼72 and 260 °C respectively. Kinetic analysis of R-TL peak R2 shows a Gaussian distribution of trap energy whereas the same analysis on R-TL peak R1 shows a non-Gaussian distribution of trap energy. The mean values of activation energy corresponding to the respective electron traps of R1 and R2 are estimated to be 0.62 ± 0.07 and 1.04 ± 0.06 eV. For peak R2, the Gaussian distribution curve shows the maximum at ∼1.06 eV which indicates that most electron traps corresponding to peak R2 have this trap depth.

Fe3+-activated magnetoplumbite persistent luminescence phosphor by modulating the oxygen vacancy.

Broadband near-infrared (NIR) spectroscopy has gained significant attention due to its versatile application in various fields. In the realm of NIR phosphors, Fe3+ ion is an excellent activator known for its nontoxic and harmless nature. In this study, we prepared an Fe3+-activated SrGa12O19 (SGO) NIR phosphor and analyzed its phase and luminescence properties. Upon excitation at 326 nm, the SGO:Fe3+ phosphor exhibited a broadband emission in the range 700-1000 nm, peaking at 816 nm. The optical band gap of SGO:Fe3+ was evaluated. To enhance the long-lasting phosphorescence, an oxygen vacancy-rich SGO:Fe3+ (VO-SGO:Fe3+) sample was prepared for activation. Interestingly, the increase in the oxygen-vacancy concentration indeed contributed to the activation of persistent luminescence of Fe3+ ions. The VO-SGO:Fe3+ sample has a long duration and high charge storage capacity, allowing it to perform efficiently in various applications. This work provides the foundation for further design of Cr3+-free PersL phosphors with efficient NIR PersL.

X-ray-activated polymerization expanding the frontiers of deep-tissue hydrogel formation

Photo-crosslinking polymerization stands as a fundamental pillar in the domains of chemistry, biology, and medicine. Yet, prevailing strategies heavily rely on ultraviolet/visible (UV/Vis) light to elicit in situ crosslinking. The inherent perils associated with UV radiation, namely the potential for DNA damage, coupled with the limited depth of tissue penetration exhibited by UV/Vis light, severely restrict the scope of photo-crosslinking within living organisms. Although near-infrared light has been explored as an external excitation source, enabling partial mitigation of these constraints, its penetration depth remains insufficient, particularly within bone tissues. In this study, we introduce an approach employing X-ray activation for deep-tissue hydrogel formation, surpassing all previous boundaries. Our approach harnesses a low-dose X-ray-activated persistent luminescent phosphor, triggering on demand in situ photo-crosslinking reactions and enabling the formation of hydrogels in male rats. A breakthrough of our method lies in its capability to penetrate deep even within thick bovine bone, demonstrating unmatched potential for bone penetration. By extending the reach of hydrogel formation within such formidable depths, our study represents an advancement in the field. This application of X-ray-activated polymerization enables precise and safe deep-tissue photo-crosslinking hydrogel formation, with profound implications for a multitude of disciplines.

Smart windows based on ultraviolet-B persistent luminescence phosphors for bacterial inhibition and food preservation

Herein, ultraviolet B (UVB) persistent luminescence phosphors containing SrAl12O19: Ce3+, Sc3+ nanoparticles were reported. Thermoluminescence (TL) spectrum analysis reveals that the shallow trap induced by Sc3+ co-doping plays an important role in photoluminescence persistent luminescence (PersL) development, while the deep trap dominates the generation of optical stimulated luminescence (OSL). Owing the appearance of deep trap, the OSL is observed under light (700 nm - 900 nm) excitation. UVB luminescence exerts good bactericidal effects on pathogenic bacteria involved in the process of food spoilage. Thus, the smart window with SrAl12O19: Ce3+, Sc3+/PDMS produces UVB PersL to efficiently inactivate Escherichia coli and Staphylococcus aureus. In addition, the presence of the smart window delays the critical point of pork decay, and greatly reduces the time of pork spoilage. It maximizes the convenience of eradicating bacteria and preserving food, thus offering a fresh perspective on the use of UV light for food sterilization and preservation.

Multifunctional near-infrared long persistent luminescence phosphor BaLu2Al2Ga2SiO12:Cr3+, Tb3+ with good thermal stability, promising quantum efficiency, and excellent environmental resistance

Near-infrared (NIR) persistent luminescence (PersL) phosphors have gained significant study attention in bioimaging and biomedical fields due to the advantages of persistent emission and elimination of biological tissue autofluorescence. However, PersL phosphors generally have difficulty in guaranteeing both good thermal stability and external quantum efficiency (EQE), which limits the multi-functional applications of NIR PersL phosphors. Herein, we developed a novel multifunctional NIR PersL phosphor BaLu2Al2Ga2SiO12:Cr3+ (BLAGSO:Cr3+). Interestingly, this NIR phosphor has good thermal stability (99.7 %@150 °C for BLAGSO:0.03Cr3+) and promising EQE (31.08 % for BLAGSO:0.03Cr3+). To further improve its PersL performance, Tb3+ ion which is believed to act as a modulator of matrix defects and enhances the storage capacity of traps for electrons is introduced into BLAGSO:0.03Cr3+ and an optimal PersL duration of more than 48 h is achieved. Meanwhile, BLAGSO:0.03Cr3+, 0.03 Tb3+ also exhibits good photo-stimulated PersL (PSPL) ability, and the quenched PersL can be rejuvenated by external photo-stimulation. The potential uses of BLAGSO:0.03Cr3+, 0.03 Tb3+ in NIR pc-LEDs and bioimaging are explored and demonstrated. This work is anticipated to drive the research of multifunctional NIR PersL phosphors.

Probing the electron trap-depth distribution in Sr4Al14O25:Eu2+,Dy3+

Sr4Al14O25:Eu2+,Dy3+ is a superluminous persistent luminescence phosphor. Owing to its intrinsic and extrinsic point defects, it tends to luminescence incessantly after excitation, in some cases doing so for as long as 20 h. We report analysis for the energy distribution of its electron traps. The study was done using thermoluminescence (TL) measured on a sample irradiated to 2 Gy at 20 °C. A glow curve measured at 1 °C/s shows two glow peaks at 64 °C (labelled as P1) and at 252 °C (P2). The variation of intensity of peak P1 as a function of heating rate is consistent with competing radiative and non-radiative recombination processes. When the heating rate is faster than 1 °C/s, non-radiative recombinations dominate and the luminescence efficiency drops sharply beyond 70 °C. The activation energy for thermal quenching is estimated to be 0.69±0.06 eV. Once corrected for thermal quenching, the glow curves show a secondary peak (P1A) on the high temperature end of P1. The so-called Tm-Tstop method shows that peaks P1 and P2 gradually shift towards high temperature with preheating temperature Tstop. Indeed, the peak position Tm of both peaks increases with irradiation temperature Tirr. Together, these results suggest that peaks P1 and P2 are each composed of closely spaced overlapping peaks. Analysis of the fractional area between a pair of glow curves measured from the sample irradiated at different temperatures (Tirr) shows that the trap distribution associated with peak P2 is Gaussian whereas that associated with peak P1 follows a non-Gaussian distribution. The activation energy of the electron traps responsible for P1 are estimated to be in the range 0.63–0.68 eV. On the other hand, the Gaussian distribution of trap energy levels responsible for peak P2 suggests that most of the traps have an activation energy of ∼1.58 eV.

Incorporation of Eu3+ in ZnGa2O4:Ni2+ for improved NIR persistent luminescence located in second transparency window

AbstractIt is well known that near‐infrared (NIR) persistent phosphors have rather low absorption coefficients of biological tissues for NIR light. However, recent research shows that the phosphors emitting NIR lights in second NIR (NIR‐II, 1000–1350 nm) and third (NIR‐III, 1500–1800 nm) biological window have advantages over that in NIR‐I (650–900 nm). Although ZnGa2O4:Ni2+ outputs NIR emission and afterglow locatedin NIR‐II, the weak signal significant limits its application. In this work, persistent luminescent phosphors of ZnGa2O4:xNi2+, yEu3+ (x = 0–0.013, y = 0.01–0.06) (termed as ZEGN) were synthesized via a traditional high‐temperature solid‐state reaction, which feature a broad emission band in the NIR‐II window. The phosphors exhibit a broad NIR emission at about 1300 nm after ultraviolet (UV) or orange–red lights excitation, arising from the 3T2(3F) → 3A2(3F) transition of Ni2+. However, incorporation of Eu3+ ions, the NIR emission intensity significantly increases with the increase of Ni2+ ion concentration, reaching the maximum by 18 times at x = 0.005. Removing the light source, the sample still outputs intense NIR afterglow and red afterglow that can last over 500 s. It is noteworthy that the red afterglow of Eu3+ shows a dramatically decrease but the NIR afterglow increases with increasing the Ni2+ ion concentration, because of energy transfer. Under the excitation of 282‐nm UV light, the ZGEN sample exhibits a good thermal stability. The phosphor offers a promising application in biological imaging due to broadband NIR‐II light and afterglow.

Long persistent luminescence and photostimulated luminescence in Y3GaO6:Pr3+ phosphor

Long persistent luminescence (LPL) phosphors have a wide range of potential applications, including multi-color anticounterfeiting and long-term continuous detection of short-wavelength ultra-violet (UV) radiation. However, developing a stable carrier container that can provide ultra-long carrier storage for activators and visible multi-color LPL is a challenging task. In this work, we presented a series of Pr3+-doped Y3GaO6 (YGO) LPL phosphors that take full advantage of the synergistic relationship between the host lattice, emitters, and carrier traps. The host provides a suitable lattice site for rare-earth Pr3+ and offers a broad band gap of 5.69 eV to hold traps with depths ranging from 1.01 to 2.17 eV. We observed LPL that was visible to the naked eye for 6 h after excitation, and strong thermoluminescence (TL) spectra could be detected after the phosphor was placed in darkness for 20 days at room temperature. Additionally, we observed photostimulated luminescence under 980 nm and 808 nm laser irradiation with a power density of 5 W cm-2, indicating that low-energy excitation not only leads to LPL but also accelerates the elimination of previously stored carriers. After investigating the crystal structure and possible defects generated in the materials, we proposed a mechanism for LPL. Our findings demonstrate the potential of Pr3+-doped YGO LPL phosphors for a range of applications, such as multi-color anticounterfeiting and long-term continuous detection of short-wavelength UV radiation.

Color-tunable persistent luminescence phosphor for multimode dynamic anti-counterfeiting

Using a solid-state approach, the persistent luminescence property in sodium yttrium silicate which was single-doped or co-doped by europium or cerium was studied. The orthorhombic structure with the space group P212121 could be indexed to all samples, according to X-ray powder diffraction. The luminescence characteristics of these phosphors, including photoluminescence, luminescence degradation, and temperature-dependent emission, were systematically investigated. Under UV (∼365 nm) irradiation, blue/green emissions with broad bands peaking at 450/510 nm attributed to the characteristic 5d→4f/4f65d→4f7 transitions of Ce3+/Eu2+ could be observed in Na3LuSi3O9:Ce3+ and Na3LuSi3O9:Eu2+, respectively. Moreover, blue and green persistent luminescence was also observed in Ce3+ or Eu2+ single-doped samples. Thermoluminescence curve of Na3LuSi3O9:Eu2+, Ce3+ reveals that Na3LuSi3O9:Ce3+ and Na3LuSi3O9:Eu2+ have similar trap distribution. Tunable persistent luminescence can be realized via ratio control of Ce3+ and Eu2+. A possible afterglow mechanism was presented and discussed. The prepared materials have the potential of multimode dynamic luminescence, because they are highly sensitive to the composition, the excitation wavelength, and the detecting time. The outstanding abilities of Na3LuSi3O9:Ce3+, Eu2+ demonstrate the practical capability of this material for fingerprint identification and anti-counterfeiting.

Role of the thermal treatment on the microstructure of YAGG nanopowders prepared by urea glass route

Yttrium aluminium gallium garnet (YAGG, Y3Al2Ga3O12) doped with rare-earth ions has drawn large attention owing to its optical properties with applications ranging from persistent luminescent phosphors to nanothermometers. Herein, three different YAGG materials were synthesized via the urea glass route followed by thermal treatment, relatively undoped; doped with Ce3+, Cr3+, and Nd3+; and doped with Ce3+, Cr3+, and Yb3+. The garnet formation was studied in situ upon thermal treatment from 300 to 1000 °C using synchrotron powder diffraction. Our results show that with this method, the onset of formation of the garnet is about 860 °C, with comparable cell parameters for both undoped and doped YAGG. A possible growth mechanism of YAGG is therefore discussed on the basis of observed microstructural parameters such as occupancy, microstrain, and crystallite size.

A new insight into the mechanism of persistent luminescence phosphors SrS: Eu2+, Pr3+

The red persistent luminescence phosphors SrS: , (x = 0∼0.001, y = 0∼0.003) were synthesized by the solid-state reaction method in a weak reducing atmosphere of active carbon. The synthetic parameters, photoluminescence characteristics, and dynamic properties of thermoluminescence of the phosphors were studied systematically. According to the results of photoluminescence spectra of SrS: , , the energy level scheme of the phosphors was confirmed quantitatively. Based on the studies of the scanning electron microscope (SEM), UV-Visible absorbance spectra, afterglow decay curves, thermoluminescence(TL) spectra, and X-ray photoelectron spectroscopy (XPS) spectra, we found that the SrS: , (SSEP) phosphor presented the best persistent luminescence property, which mainly resulted from its outstanding absorbance characteristic, deeper depth of () defects, and fewer defect concentration belonging to the higher-order kinetics. Those comprehensive results deduced that a complex defect ()- should present in the Eu2+ doping phosphors, and the Pr3+ doping will produce defects, which can suppress the formation of () defects and increase their energy depth.

Controlling persistent luminescence in nanocrystalline phosphors.

Persistent luminescent phosphors can store light energy in advance and release it with a long-lasting afterglow emission. With their ability to eliminate in situ excitation and store energy for long periods of time, they are promising for broad applications, including background-free bioimaging, high-resolution radiography, conformal electronics imaging and multilevel encryption. This Review provides an overview of various strategies for trap manipulation in persistent luminescent nanomaterials. We highlight key examples in the design and preparation of nanomaterials with tunable persistent luminescence, particularly in the near-infrared range. In subsequent sections, we cover the most current developments and trends concerning the use of these nanomaterials in biological applications. Moreover, we assess their advantages and disadvantages compared with conventional luminescent materials for biological applications. We also discuss future research directions and challenges, such as insufficient brightness at the single-particle level, and possible solutions to these challenges.

Glass-based composites comprised of CaWO4:Yb3+, Tm3+ crystals and SrAl2O4:Eu2+, Dy3+ phosphors for green afterglow after NIR charging

In this paper, we demonstrated the fabrication of new phosphate-based composites with green persistent luminescence after being charged with near-infrared light using the direct doping method. The composites are composed of a phosphate glass and phosphors. The 75NaPO3 − 25CaF2 and 90NaPO3 − 10NaF (in mol%) were the 2 glasses of investigation. The intense blue up-conversion emission between 450 and 500 nm upon 980 nm pumping is obtained by adding CaWO4: Tm3+, Yb3+ crystals in the glass melt before quenching whereas the green persistent luminescence is from the SrAl2O4:Eu2+,Dy3+ phosphors also added in the glass melt. The green persistent luminescence above 0.3 mcd/m2 is observed for ∼30 min after charging with 980 nm due to energy transfer between the upconverter crystals and the persistent luminescent phosphors. Here, the challenges related to the fabrication of such composites are discussed. While it is important for the blue UC emission to be intense to charge the SrAl2O4:Eu2+,Dy3+ crystals, we demonstrate that the glass matrix should not crystallize upon the addition of the different crystals. Additionally, the composites should remain translucent with limited light scattering for the blue UC emission to charge the persistent luminescent phosphors.

CaWO4:Yb3+,Tm3+ Crystals and SrAl2O4:Eu2+,Dy3+ Phosphors in Glass-Based Composites for Green Afterglow after NIR Excitation

Here, we present the preparation of composites with green persistent luminescence using melting process. The composites are phosphate glass (75NaPO3-25CaF2 and 90NaPO3-10NaF (in mol%)) with embedded phosphors: CaWO4: Yb3+, Tm3+ crystals with blue upconversion and SrAl2O4:Eu2+,Dy3+ with green persistent luminescence. Green persistent luminescence above 0.3 mcd/m2 can be seen for ~ 30 minutes after charging with 980 nm due to energy transfer between the blue upconverter crystals and the persistent luminescent phosphors. Challenges related to the fabrication of such composites are discussed.

Photoluminescence study of rare earth ions doped Sr2CeO4 phosphor prepared via conventional solid-state reaction method

The lanthanide ions either in their divalent or trivalent charge state form a very important class of luminescence activators in phosphors and single crystals. Doping these lanthanide ions in different host lattices are widely utilized in many areas for example the 5d-4f emission of Ce3+ used in scintillators for γ-ray detection, cathode ray tubes and electroluminescence phosphors. The photon cascade emission from 4f2 levels of Pr3+ used for developing high quantum efficiency phosphors excited by means of a Xe discharge in the vacuum-UV. The narrow line 4f3 transition in Nd3+ is used in laser crystals. The Sm3+ emission used as an electron trap and in information storage properties like optical memory applications, X-ray imaging phosphor applications. The famous 5D0-7Fj 4f6 redline emission of Eu3+ and the blue to red 5d-4f emission of Eu2+ are used in display and lighting phosphors. The 4f8 line emission of Tb3+ is used in tricolor tube lighting. The Dy3+ emission plays an important role in the persistent luminescence phosphors. Er3+, Tm3+ used to investigate for possible photon cascade emission phosphor applications. This is brief and still incomplete summary illustrates the diversity of applications involving the luminescence of lanthanide ions.

Investigation on the luminescence properties and mechanism of a novel Pr3+-based red persistent luminescence phosphor Cd3Ga2Ge3O12:Pr3+

In this work, an red-emitting persistent phosphor Cd3Ga2Ge3O12:Pr3+ was designed and successfully developed. This material presents superior luminescent properties, which could be a promising choice for AC-LEDs, bio-imaging and other fields.

Blue-light activated green emitting BaY2Al2Ga2SiO12:Ce3+,Bi3+: efficient persistent luminescence phosphors for AC-LEDs

An efficient blue-light excited green-emitting persistent luminescence phosphor, BaY2Al2Ga2SiO12:Ce3+,Bi3+, is designed and synthesized to effectively compensate for the flicker effect of AC-LEDs.

Sunlight-activated Eu3+-doped CaNaSb2O6F yellow-orange long-persistence luminescence material

A novel sunlight-activated persistent luminescence phosphor CaNaSb2O6F:Eu3+ with strong yellow-orange PL/PersL is synthesized, and it can be recharged rapidly and effectively in various natural conditions using natural sunlight.

Dual-emissive persistent luminescent phosphors for multi-mode anti-counterfeiting and ratiometric luminescent aptasensors

The developed dual-emissive persistent luminescent phosphors exhibit unique luminescence properties and have been designed for multi-responsive anti-counterfeiting and ratiometric luminescent aptasensors.

UV-A,B,C Emitting Persistent Luminescent Materials

The nearly dormant field of persistent luminescence has gained fresh impetus after the discovery of strontium aluminate persistent luminescence phosphor in 1996. Several efforts have been put in to prepare efficient, long decay, persistent luminescent materials which can be used for different applications. The most explored among all are the materials which emit in the visible wavelength region, 400-650 nm, of the electromagnetic spectrum. However, since 2014, the wavelength range is extended further above 650 nm for biological applications due to easily distinguishable signal between luminescent probe and the auto-fluorescence. Recently, UV-emitting persistent materials have gained interest among researchers' due to their possible application in information storage, phototherapy and photocatalysis. In the present review, we summarize these recent developments on the UV-emitting persistent luminescent materials to motivate young minds working in the field of luminescent materials.