Long-afterglow Materials Research Articles

Host-Guest Metal-Organic Frameworks-Based Long-Afterglow Luminescence Materials.

Long-afterglow materials have a broad of applications in optoelectronic devices, sensors, medicine and other fields due to their excellent luminescent properties. The host-guest long-afterglow MOFs material combines the advantages of multi-component characteristics and the stability of MOFs, which improves its luminous performance and expands its other properties. This review introduces the classification, synthesis and application of host-guest MOFs materials with long afterglow. Due to their rigid frames and multi-channel characteristics, MOFs can load common guest materials including rare earth metals, organic dyes, carbon dots, etc. The synthesis methods of loading guest materials into MOFs include solvothermal synthesis, post-encapsulation, post-modification, etc. Those long-afterglow host-guest MOFs have a wide range of applications in the fields of sensors, information security and biological imaging.

Implementing All-Weather Photocatalysis of Exhaust Fumes Based on the g-C3N4/TiO2/SrAl2O4: Eu2+, Dy3+ Ternary Composite Coating

This study examines the use of SrAl2O4: Eu2+, Dy3+ long-afterglow materials doped into g-C3N4/TiO2 coatings for photodegradation. The prepared sample was tested for the purification of automotive exhaust fumes, with the optimal mass ratio of g-C3N4/TiO2 and SrAl2O4: Eu2+, Dy3+ determined to be 1:1. Characterization tests, including XRD, FT-IR, XPS, and TG-DSC, were conducted to evaluate the microstructure and properties of the samples. Under poor lighting conditions, g-C3N4/TiO2 reduced CH and NOx by 59 ppm and 13 ppm within 4 h, respectively, while g-C3N4/TiO2/SrAl2O4: Eu2+, Dy3+ decreased CH and NOx by 98ppm and 34ppm, respectively, resulting in a significant improvement in degradation efficiency. The addition of long-afterglow materials significantly improves the efficiency of photocatalysts in purifying exhaust fumes in low-light environments, providing potential value for all-weather exhaust treatment in the future.

Photocatalytic Hydrogen and Oxygen Evolution Performed by a Long-Afterglow Material.

A micron-sized long-afterglow material, Sr2MgSi2O7:Eu,Ce, was utilized to conduct the hydrogen evolution reaction and oxygen evolution reaction, two half-reactions of water splitting, in the presence of sacrificial agents under both light and dark conditions for the first time. The as-synthesized Sr2MgSi2O7:Eu,Ce exhibited higher photocatalytic activity compared to that of the referenced Sr2MgSi2O7:Eu and Sr2MgSi2O7:Ce samples. Herein, in addition to benefiting from the long photogenerated carrier lifetime of long-afterglow materials, the higher photocatalytic activity was attributed to the conjugated electronic structure between Eu and Ce ions. This structure facilitates charge and energy transfer between them, leading to an enhanced photocatalytic efficiency. This research provides a new strategy for designing efficient long-afterglow material photocatalysts through the construction of conjugated electronic structures.

Visible-excitable long-afterglow material with dual-mode emission of delayed fluorescence and room temperature phosphorescence

The BA@Fluo can achieve dual-mode emission of RTP and TADF, and colorful afterglow can be achieved under temperature regulation. Particularly, BA@Fluo was characterized by fluorescence discoloration, and increased quantum yield caused by grinding.

All optical artificial synapses based on long-afterglow material for optical neural network

All optical artificial synapses based on long-afterglow material for optical neural network

Developing single silane-derived delayed fluorescent carbon dots as donors for energy transfer-based aqueous-phase multicolor afterglow application

DF-CDs@SiO2and multicolor CDs@SiO2are applied in advanced information encryption, LEDs, hydrogel-based biosensing, and autofluorescence-free bioimaging.

Pure-organic phosphine oxide luminescent materials

Phosphine-oxide-(PO)-based optoelectronic materials are attracting increasing attention owing to the unique advantages of P = O groups in modulating the molecular configuration, excited-state properties, and intermolecular interactions. P = O groups are also effective for the molecular design of high-performance luminescent materials. In this review, the research progress of pure-organic PO materials for light-emitting applications with high radiation is summarized. After a brief introduction about the luminescent mechanisms and the functions of P = O groups, this review focuses on the material design and structural-property relationships, especially the influences of P = O groups on the material performances, which are divided into three chapters according to the mechanisms of fluorescent (FL), thermally active delayed fluorescent (TADF), and charge-transfer-(CT)-based long-afterglow materials. It was shown that the electron-withdrawing effect and the insulating character of the P = O joint could improve the electrical properties and enhance inter – and intramolecular CT without remarkably changing the emission color, making it almost ‘ideal’ for blue emitters. The steric hindrance of 3D PO molecules further suppressed the quenching effects for emission efficiency improvement. These superiorities guarantee that the pure-organic PO system is one of the best fluorescent materials for diverse applications.

Trap distribution and mechanism for near infrared long-afterglow material AlMgGaO4:Cr3.

Near infrared (NIR) long-afterglow materials have attracted much attention due to their high penetration and low destruction in biological tissues. Here, a series of deep red and near infrared materials, AlMgGaO4:xCr3+, were successfully synthesized by a high temperature solid state method. AlMgGaO4 was selected as the host considering its rich antisite defects, which can effectively capture electrons. The emission spectra of AlMgGaO4:xCr3+ range from 680 nm to 1100 nm, which can be nicely decomposed into four Gaussian bands with peaks centered at 706 nm, 723 nm, 916 nm, and 938 nm, respectively. At low temperature (10 K), the emission spectra show there are four emission peaks: a sharp line (peak 1) and broad emission band (peak 2) come from Cr3+ substituting for the regular octahedron [AlO6], and two broad emission bands (peaks 3 and 4) which originate from the spin-allowed transition 4T2(4F) → 4A2(4F) of Cr3+ in the disordered [GaO6] and [MgO6] octahedra, respectively. Remarkably, after removing the excitation source, it exhibited more than 10 hours of afterglow emission which decreased sharply in the first 30 min and then decreased slowly. With an increase in the Cr3+ concentration, the trap depth became shallower due to the generation of the electronic trap centers . The distribution of trap centers and the mechanism of the persistent luminescence have been carefully analyzed and are also discussed.

Round-the-Clock Photocatalytic Hydrogen Production with High Efficiency by a Long-Afterglow Material.

Long afterglow materials can store and release light energy after illumination. A brick-like, micrometer-sized Sr2 MgSi2 O7 :Eu2+ ,Dy3+ long-afterglow material is used for hydrogen production by the photocatalytic reforming of methanol under round-the-clock conditions for the first time, achieving a solar-to-hydrogen (STH) conversion efficiency of 5.18 %. This material is one of the most efficient photocatalysts and provides the possibility of practical use on a large scale. Its remarkable photocatalytic activity is attributed to its unique carrier migration path and large number of lattice defects. These findings expand the application scope of long afterglow materials and provide a new strategy to design efficient photocatalysts by constructing trap levels that can prolong carrier lifetimes.

Long-afterglow metal-organic frameworks: reversible guest-induced phosphorescence tunability.

Luminescent metal-organic frameworks (MOFs) have received much attention due to their wide structural tunability and potential application in light-emitting diodes, biological imaging and chemical sensors. However, successful examples of long-persistent afterglow MOFs are still quite limited to date. In this work, we report that two types of Zn-terephthalate (TPA) MOFs (namely [Zn(TPA)(DMF)] (1-DMF) and MOF-5) could exhibit an obvious room-temperature afterglow emission with a time-resolved luminescence lifetime as high as 0.47 seconds. The phosphorescence-based afterglow was also highly sensitive to the temperature, and the reversible emission intensity could be recycled under high/low temperatures. Moreover, both 1-DMF and MOF-5 showed highly tunable afterglow phosphorescence colors (from cyan to yellow and from green to red, respectively) upon treatment with pyridine solution. The fluorescence/phosphorescence emission color of MOF-5 can be reversibly switched due to the addition and removal of a pyridine guest to and from the host nanochannel, as shown in both experimental and computational studies. Therefore, this work not only shows a facile method to develop MOF-based long-afterglow materials at room temperature, but also presents a strategy to tune their phosphorescence in a wide range based on host-guest interactions.

Luminescence decay evaluation of long-afterglow phosphors

In the current study, the phosphorescence decays of the long-afterglow materials of SrAl2O4:Eu, Dy, Sr4Al14O25:Eu, Dy, Sr2MgSi2O7:Eu, Dy, and ZnS:Cu, Co have been measured over long time (15h to 16h). The evaluation methods of luminescence decay are analyzed and summarized. The existing formulas are in accordance with the experimental decay data in the initial fast decay stage. However, the deviation is much larger and the accuracy is much lower in the slow decay stage. Therefore, the existing formulas cannot be used to accurately describe the luminescence decay of the samples with much longer afterglow time (>80min). Moreover, certain formulas do not match the actual decay situation of long-afterglow luminescence. We suggest our solutions for this problem.

Afterglow performance enhancement and mechanism studies on Y2O2S:Eu,Mg,Ti prepared via cold isostatic pressing

Abstract A Y 2 O 2 S:Eu,Mg,Ti material was prepared via a modified sulphide-fusion route. Compared with the traditional solid-state reaction method, the obtained Y 2 O 2 S:Eu,Mg,Ti showed smaller, more uniform particles with higher brightness. The afterglow mechanism study indicated that the long-afterglow material is process-dependent and that its performance is determined by recipe, preparation technology and process used. The luminescence centres of Y 2 O 2 S:Ti; Y 2 O 2 S:Eu,Ti and Y 2 O 2 S:Eu,Mg,Ti are Ti 4+ ions, Ti 4+ + Eu 3+ ions and Ti 4+ + Eu 3+ ions, respectively. The afterglow decay curve cannot be fitted using the exponential equation or first-, second-, third-order exponential decay multiple equations beyond 30 min. The afterglow luminescence of the materials resulted from Ti-related defects that make up two new trap levels. Ti doping created numerous harmful companying defects that decrease luminescence efficiency. Doping of Mg 2+ ions facilitated the introduction of Ti 4+ ions into the Y 2 O 2 S lattice to effectively modulate the depth and concentration of the trap. Doping of Mg 2+ –Ti 4+ ion pairs reduced the number of harmful defects through the formation of a compensation-type hetero-valent substitution solid solution that greatly enhance the afterglow performance. Cold isostatic pressing promoted the entry of Ti ions into the Y 2 O 2 S crystal lattice and eliminated defects, such as preferred orientation. In addition, cold isostatic pressing reduced the E 2 to 0.9 eV, which is beneficial to the long afterglow of the resulting material at room temperature.

Effect of oxygen vacancies on the red phosphorescence of Sr_2SnO_4:Sm^3+ phosphor

We reported the synthesis of a novel red long-afterglow material Sr(2)SnO(4):Sm(3+). Comparing with the air-sintered sample, a significant enhancement in both the fluorescence and phosphorescence for the vacuum-sintered sample was observed. This improvement could be attributed to the increase of oxygen vacancies which act as the sensitizer and the electron traps for the effective energy transfer from Sr(2)SnO(4) host to Sm(3+). The defects act as traps were investigated with thermoluminescence. For the presence of deep stable traps able to immobilize the energy permanently at room temperature, the Sr(2)SnO(4):Sm(3+) could be considered as a potential storage phosphor as well.