Persistent Luminescence Phosphor Research Articles

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.

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.

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.

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.

Zn2SiO4: Mn2+, Yb3+ long afterglow materials prepared employing Zn-based coordination polymer as precursor: Properties, Mechanism and Application

An excellent green persistent luminescence (PersL) phosphor Zn2SiO4: Mn2+, Yb3+ was synthesized through a new method via reacting Zn-based coordination polymer particles with SiO2 submicrospheres. The structure properties including the phase purity, structural parameters and crystal structure were investigated in details. Morphological analysis revealed that Zn2SiO4: Mn2+, Yb3+ retained the morphology of SiO2 submicrospheres with diameter ∼200 nm. The PersL of Zn2SiO4: Mn2+ displayed a remarkably enhanced afterglow duration by codoping with Yb3+, in which the duration time prolonged from 5 min to 114 min (∼23 times) as compared with that of Zn2SiO4 host or singly Mn2+ doped. The depths of the traps responsible for PersL were estimated to be in the range of 0.696–1.112 eV, and an additional trap that are deemed to play a role for the improvement was discussed. The prepared phosphors were successfully used for the latent fingerprint visualization and exhibited high accuracy of fingerprint recognition. These findings not only provids a new synthetic approach for PersL materials with designated morphology and dimensions, but also indicates the product may find applications in advanced latent fingerprint identification, information storage and anticounterfeiting technology.

Effect of ambient temperature on optical performances of Eu2+/Ho3+ co-doped Ba2SiO4 phosphors

Persistent luminescence phosphor, as an extraordinary photonic material, is widely used in the many fields ranging from photodynamic therapy to optical data storage. The phosphor is sensitive to the ambient temperature; thus, the ambient temperature of the phosphor is a key in the widespread utilization. Here, the relation between the ambient temperature of Ba2SiO4:Eu2+/Ho3+ phosphor and the optical performances is evaluated. A warm storge condition is preferred before the excitation, while a low-temperature condition is necessary after charging for the high-intense response. The findings could make a suggestion for the preservation condition of the phosphors in the various applications.

Independent dual-responsive luminous composite fibers with controllable full-color emissions

Accumulated ultraviolet (UV) under high temperature is prone to cause photoaging, skin burns, and even induce skin cancers during outdoor activities. Fiber-based wearable sensors with color-tunable luminescent ability are urgently demanded for real-time monitoring of human health conditions to enhance personal awareness of these hazards. To achieve tunable full-color emission, a set of three primary colors (red, green, and blue) of rare-earth doped persistent luminescent phosphors are successfully synthesized. After simply mixing them with particular ratios, a tunable full-color emission system can be realized. Herein, by integrating the thermochromic dyes, photochromic dyes, and luminescent phosphors directly into polyacrylonitrile (PAN) matrix, novel thermo-UV-sensing composite fibers with color-tunable luminescent ability are prepared via the facile wet-spinning process. The obtained fibers can be switched among four different colors with brilliant reversible color changes in response to temperature and UV irradiation both independently and in combination. Besides, the fibers can emit tunable emissions under in full spectral range 365 nm excitation. This work paves the way for as-prepared fibers for diverse applications including energy-free, wearable real-time monitors of the temperature/UV, and high-level information encryption.

Color-tunable persistent luminescence in LiTa3O8 based phosphors for dynamic anticounterfeiting

Rare earth-doped persistent luminescent (PersL) phosphors are excellent candidates for anticounterfeiting due to their superior properties, including various luminescent colors, multifarious luminescent modes, and dynamic emission intensity. For classical PersL phosphors, single-doped phosphor always shows monotonous luminescent color in different emission modes, such as photoluminescence (PL) and PersL, which limits the anticounterfeiting level to a low degree. To optimize the optical properties of phosphors for anticounterfeiting applications, constructing multiactivator-doped phosphors with polychromatic luminescence emissions can be a feasible strategy in practical material development. In this study, a novel multicolor PersL material, Pr3+/Tb3+-doped LiTa3O8, was reported for the first time, where the PersL color of Pr3+ in LiTa3O8 host was red whereas terbium(III) (Tb3+) ions exhibited green PersL color. Two improvement strategies were implemented, including substitution of tin(IV) (Sn4+) and codoping with gadolinium(III) (Gd3+), to enhance PersL properties by regulating distribution of traps. Gd3+ codoping strategy effectively improved PersL intensity while the Sn substitution strategy increased the initial PersL intensity by four-fold and the duration prolonged by 2.5-fold. Based on the results of luminescent properties, a multicolor tunable PersL material, LiTa3O8:0.7 %Pr3+ 1 % Tb3+, was synthesized and conceptually designed into a multimode anticounterfeiting application. Based on this scheme, prototype anticounterfeiting devices were developed, which could display the anticounterfeiting patterns in both dynamic and static states. Thus, this study fabricated a novel PersL material with multicolor light in different luminescent modes, thus deepening the fundamental understanding of PersL materials and diversifying the potential candidates of optical anticounterfeiting materials.

Persistent luminescent phosphor-in-glass composites based on NaPO3 – Ga2O3 glasses loaded with Sr2MgSi2O7:Eu2+,Dy3+

Phosphor-in-glass (PiG) is a composite material that can combine the chemical stability and more versatile molding and processing of glasses and the singular properties of luminescent polycrystalline materials. Persistent luminescent phosphors have been raising attention due to their long emission times without the need for a steady irradiation source. The association of these polycrystalline materials with transparent glassy hosts leads to the obtainment of robust luminescent bulk materials and expands the possibilities of commercial applications. In this work, the Sr2MgSi2O7:Eu2+,Dy3+ (SMSO) persistent luminescent material was incorporated into a new gallium phosphate glass system with composition 80NaPO3 – 20Ga2O (NaPGa), through the conventional melt-quenching technique and fully characterized from the structural and spectroscopic viewpoints. The composites were prepared using 2, 5, 10, and 20 wt% of SMSO at 900 or 950 °C. It was observed that the higher melting temperature induces the oxidation of Eu2+ ions, which can reduce the persistent luminescent emission. High SMSO concentrations increase the glass melt viscosity, hampering the molding step but optimized samples were successfully obtained as transparent bulk materials with efficient emission in the blue spectral region and promising applications in emergency signaling and as solar cell sensitizers.

A new persistent luminescence phosphor of ZnGa2O4:Ni2+ for the second near-infrared transparency window

Recently, near-infrared (NIR) persistent phosphors become a research hotspot in biomedical application, because of their rather low absorption coefficients of biological tissues for NIR light. Most investigated phosphors emit NIR lights, whose wavelengths are no more than 1000 nm and located in NIR-I biological window. However, the phosphors emitting NIR lights in second (NIR-II, 1000–1350 nm) and third (NIR-III, 1500–1800 nm) biological window have advantages over that in NIR-I one. Here, persistent luminescent phosphors of ZnGa2O4:xNi2+ (x = 0–0.01) were synthesized via a traditional high-temperature solid-state reaction, which feature a broad emission band in the second near-infrared (NIR-II) window. Ni2+ tends to occupy Ga3+ site in ZnGa2O4, which results in the formation of oxygen vacancy. Upon ultraviolet (UV) or orange-red lights excitation, the phosphors exhibit a broad NIR emission at about 1300 nm, arising from the 3T2(3F)→3A2(3F) transition of Ni2+. Removing the light source yields intense NIR afterglow, with the duration longer than 500 s. Strongest NIR emission and best persistent luminescence are found for the x = 0.005 sample, which is excited by 254-nm UV light. The ZnGa2O4:Ni2+ persistent phosphors have potential application in vivo imaging, because of their charming emissions and afterglows with the wavelength locating in NIR-II window.

A building-block strategy for dynamic anti-counterfeiting by using (Ba,Sr)Ga2O4:Sm3+ new red persistent luminescent phosphor as an important component

Long persistent luminescence materials developed to commercial standards are primarily concentrated in the blue and green regions, with only a few in the red region. Red, as one of the three basic colors, can be mixed in various proportions with blue and green to yield various colors. The development of red persistent phosphors has a broader application potential but remains a challenge. A solid-state reaction method was used to synthesize new red persistent luminescent materials of Ba1-xSrxGa2O4:Sm3+ (x = 0–0.09). In BaGa2O4, both Sr2+ and Sm3+ preferentially occupy the Ba2+ site rather than the Ga3+ site. When exposed to UV light at 254 nm, the phosphors emit the characteristic red emission of Sm3+ at wavelengths ranging from 500 nm to 750 nm. After removing the UV light source, an intense red afterglow that lasted more than 1400 s was observed. The red afterglow signal reappears after a heating process. Doping Sr2+ reduces the trap depth and improves the red persistent luminescence significantly. Because the escaped electrons from traps compensate for the emission loss of Sm3+ during the heating process, the red phosphors have unimaginably luminescent thermal stability. Thus, the emission intensity at 200 °C is 1.6 times that at room temperature. The prepared red persistent phosphors show multimode luminescence, with the output signal being time and temperature sensitive, indicating that they are potential luminescent materials for anti-counterfeiting applications. Finally, a building-block strategy for advanced anti-counterfeiting applications of dynamic display information is proposed, with red persistent phosphors serving as an important component combined with upconversion phosphors of NaYF4:Yb3+, Tm3+, and green persistent phosphors of SrAl2O4:Eu2+, Dy3+.

Linear charging-discharging of an ultralong UVA persistent phosphor for advanced optical data storage and wide-wavelength-range detector

Ultraviolet persistent luminescence (UV PersL) phosphor is currently gaining considerable attention due to its promising potential for widespread advanced applications. However, the linear manipulation of electron charging-discharging and the prolongation of persistent time remains a huge challenge. Here, we report a novel Bi3+ doped Mg2GeO4 UVA PersL phosphor via a nonequivalent substitution strategy. The UVA PersL performance of Mg2GeO4:Bi3+ is significantly improved by introducing Li+ ions, yielding a superior UVA PersL property with afterglow lasting time beyond 100 h. The trap distribution management and the captured electron motion dynamics are revealed by the thermoluminescence technique under various external stimuli. Moreover, UVA PersL can be repeatedly rejuvenated by NIR and blue LED stimulation owing to the optically stimulated electrons from different depth traps to shallow traps. Due to the invisibility of UVA light, barcode information stored on the phosphor film can be read by NIR light and then erased by blue light, exhibiting the potential application in optical data storage with good concealment and security. Most remarkable is the electron charging-discharging linear functions of the irradiated power of UV, and blue and NIR light which was never reported, providing a feasible approach for optical power detection in a wide-wavelength-range. This work not only offers a guideline to develop novel high-performance UV PersL materials but also provides a route to effectively manipulate the electrons in the traps toward applications in advanced optical information storage and wide-wavelength-range light detection.