A novel long persistent luminescent material CaGeO_(3):Tb^(3+)with photo-stimulation properties

A novel green long afterglow material CaGeO_(3):Tb^(3+)was synthesized by high temperature solid phase method.According to the experimental results,CaGeO_(3):Tb^(3+)is a green long persistent luminescent(LPL)material with excellent performance.CaGeO_(3):Tb^(3+)shows LPL emission peak at 442,490.9,548.7,588.5 and 623.8 nm,corresponding to ^(5)D_(3) to^(7)F_(4)and^(5)D_(4)to^(7)F_(J)(J=6,5,4,3)transitions of Tb^(3+).Its CIE coordinates are(0.27,0.50),indicating that the afterglow emission is close to the light of green region.In addition,after the excitation source is turned off,the afterglow time is longer than 90 min.After an interval of 7 h,the photo-stimulation luminescence(PSL)can be observed by using 980 nm laser cyclic excitation.The thermoluminescence(ThL)results show that there are three types of traps in the material and their depths are 0.666,0.774 and 0.892 eV respectively,which are caused by the doping of Tb^(3+).All the results show that CaGeO_(3):Tb^(3+)is an excellent long afterglow luminescent material.

CaS∶Eu^(2+),Sm^(3+)的制备与表征

采用湿法工艺在还原气氛下制备了CaS∶Eu2+,Sm3+光存储材料。研究了灼烧温度和灼烧时间对样品性能的影响。XRD图谱表明,样品在700℃—1200℃均形成CaS晶格。光谱分析表明,在紫外光(295nm)激发后,用980nm半导体激光照射样品,具有光激励发光现象,发射光谱峰值波长为649nm。

Recent developments and progress of inorganic photo-stimulated phosphors

Photo-stimulated luminescence(PSL) is the process in which trapped charges are released by photons and produce luminescence through recombination. The variegated optical characteristics of photostimulated phosphors(PSPs) have drawn increasing attention and a large body of work encompassing mechanism and application of PSPs has been addressed. The optical data storage capacity resulting from abundant defect states enables PSPs to be applied to information storage. Moreover, PSPs provide potential application for anti-counterfeiting, as color changes due to the tunneling process. Recently, near infrared(NIR) light PSPs have been developed, exhibiting enormous potential for in vivo bio-imaging, as the stable and high noise-signal ratio characteristic of PSL. In this review, we devote to introducing the development and process of PSPs, and the challenge and future advance have also been demonstrated.

Preparation of CaS∶Eu^(2+), Sm^(3+) by Solid Reaction Method and Its Photostimulated Luminescence

The CaS∶Eu^(2+), Sm^(3+) powders were prepared by high-temperature solid method in a reducing atmosphere. The influences of temperature and fired-time on properties of samples were studied. XRD analysis shows that crystal structure of CaS has formed at 700 ℃. Spectrum analysis results show that the samples which were stimulated by 980 nm laser after excited by ultraviolet lamp emit red luminescence peaking at 649 nm.

Simulating the Intensifying Effect of Phosphors on Imaging Plate with UV photons

It is assumed from the energy level that ultraviolet (UV) photons may have intensifying effect on BaFBr∶Eu 2+. In this paper, effect of UV photons (220～290 nm) on the PSL intensity of X-ray irradiated BaFBr∶Eu 2+ was measured and compared to that on the PSL intensity of 220 nm photons irradiated BaFBr∶Eu 2+. It was found that after the excitation of UV photons the PSL intensity of X-ray irradiated samples decreases least at 250 nm and that of 220 nm photons irradiated samples increases most at 250 nm. When the irradiation sources are X-rays and 220 nm photons the excited electrons are photoelectron and thermal-electrons, respectively, and they have different possibility of being captured by electron traps or combined with luminescent centers. And the peak at 250 nm can be explained with the model of electrons tunneling. It is assumed that the electrons excited by 250 nm have the most possibility of tunneling.

Spectral Hole Burning and Photo－Stimulated LuminescenceProcesses in BaF（Cl，Br）：Sm^（2＋）

Before and after X-irradiation, two photon spectral hole burning experiments in BaF (Cl,Br) : Sm2+ were performed by a 560 nm laser light at liquid nitrogen temperature. The results show that spectral hole burning of Sm2+ doped fluoride halide mixed crystals are accompanied by photostimulated luminescence process. This process make hole burning efficiency decreased.

Low-Dose X-Ray Activated Self-luminous Bone Cement with NIR-to-NIR Pseudo-upconverted Persistent Luminescence Sensitized by Nd

X-ray activated near-infrared(NIR)persistent luminescence has promising application in biomedical luminous imaging.However,there are strict medical restrictions on X-ray dosage to avoid radiation disease.There is a need to develop a simple strategy to improve persistent luminescence imaging quality using low-dose X-ray.NIR photo-stimulation can enhance the persistent luminescence intensity by transporting the stored energy from deep traps to shallow ones,so that enhanced upconversion-like NIR-to-NIR persistent luminescence imaging can be conducted after low-dose X-ray excitation.However,existing NIR persistent luminescence phosphors have limited absorption in the NIR.To realize optimized NIR photostimulation,Nd^(3+)is proposed as a potential sensitizer to enhance the absorption of persistent luminescence phosphor to 808 nm light.In this study,ZnGa_(2)O_(4):Sn_(0.1),Cr_(0.003),Nd_(0.01)(ZGSC-Nd)was synthesized with a persistent luminescence peak at~700 nm.After activation with 1 Gy of X-ray,its persistent luminescence attenuated to less than 5%of its original intensity after 2800 s.Interestingly,the nearly vanished persistent luminescence was enhanced 5 times after 808 nm photo-stimulation,which was assigned to Nd absorption.Thus,a pseudo-upconverted persistent luminescence from 808 to 700 nm was realized more efficiently.A Nd-sensitized NIR photo-stimulated persistent luminescence mechanism was proposed.This phenomenon was applied for improved luminous imaging of ZGSC-Nd labeled bone cement after a single low-dose X-ray imaging.This work provides an applicable strategy to realize better persistent luminescence imaging after low-dose X-ray activation and will be significant on designing X-ray activated persistent phosphors for biomedical application.

Effect of trivalent rare earth ions doping on the fluorescence properties of electron trapping materials SrS:Eu^(2+)

Trivalent rare-earth ions （La3＋,Pr3＋,Nd3＋,Sm3＋,Gd3＋,Tb3＋,Dy3＋,Ho3＋,Er3＋,Tm3＋,and Yb3＋） were investigated as the codoped auxiliary sensitizer for the electron trapping materials SrS：Eu2＋ in order to enhance the fluorescence properties.It was found that Sm3＋ and Tb3＋ had the best photoluminescence stimulated luminescence （PSL） effect among the selected trivalent rare-earth ions.All the SrS：Eu2＋ samples doped by different trivalent rare-earth ions could be stimulated by 980 nm laser after being exposed to the conventional sunlight,and they emitted PSL with the peak located at 615 nm.The result also indicated that some co-doped rare earth ions could increase fluorescence intensities of the traditional electron trapping materials SrS：Eu2＋.