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A series of Ca 9-x M x La(PO 4) 7 :Eu2+ (M = Sr2+, Ba2+) phosphors were synthesized by the high temperature solid-state method, among which Ca 9 La(PO 4) 7 :Eu2+ (CLP:Eu2+) has a spectral emission range of 400–700 nm at the excitation wavelength of 330 nm. By using Sr2+ and Ba2+ to partially replace Ca2+ in the matrix to control the crystal field environment around Eu2+, the half-peak width of the spectrum is widened and the emission center is redshifted about 10 nm. When Ca2+ is replaced by Sr2+, the broadening of the spectrum is caused by the distortion of the lattice, but the difference is that when Ca2+ is replaced by Ba2+, the broadening of the spectrum is caused by the different redshift rates of the three luminous centers. This study provides a new idea to regulate the luminescence of Eu2+ by regulating the matrix composition and inducing potential luminescence centers in the matrix. [Display omitted] • A series of Ca 9-x M x La(PO 4) 7 :Eu2+ (M = Sr2+, Ba2+) were synthesized. • The emitting color can be changed by using Sr2+ and Ba2+ to partially replace Ca2+. • White emitting phosphor shows good temperature stability. [ABSTRACT FROM AUTHOR]

Persistent luminescent materials can continue to emit light after stopping excitation, and their stored energy is gradually released during the decay time after persistent emitting, which makes the color and luminance changes in slow decay and plays an important role in protecting information and combating forgery. When combined with other anti‐counterfeiting technologies to form a multi‐modal and multi‐process anti‐counterfeiting design, it perfectly hides the real information and has a broad application prospect in anti‐counterfeiting logo design. A brief overview of the design of three different persistent luminescence‐based anti‐counterfeiting applications in unimodality to achieve information encryption in the time dimension. The energy stored in the trap is studied to be released by different physical stimuli and applied to stimulus‐like responsive persistent luminescent materials, and the design of persistent luminescence anti‐counterfeiting applications based on many different processes in dual‐modality, obtaining the dynamic anti‐counterfeiting effect of multiple processes in multiple modes. This work reviews the research background of persistent luminescent materials in the field of anti‐counterfeiting in recent years, compares the important breakthrough progress of persistent luminescent materials applied to anti‐counterfeiting research, and finally puts forward the current problems, future challenges, and development directions. [ABSTRACT FROM AUTHOR]

A high resolution absorption spectrum of neutral fluorine(F I) was observed around 800 nm using concentration modulation absorption spectroscopy with a tunable Ti : Sapphire laser. The fluorine atoms were produced by discharging the mixed gases of helium and sulfur hexafluoride (SF 6 ) in a glass tube. Thirty four hyperfine structure ( hfs ) resolved transitions were analyzed to obtain 23 magnetic dipole hfs constants A for 2 p 4 ( 3 P)3 s , 2 p 4 ( 3 P)3 p and 2 p 4 ( 3 P)3 d configurations. The hfs constants in 2 p 4 ( 3 P)3 s and 2 p 4 ( 3 P)3 p configurations were compared with those obtained from experiments and calculations. Fifteen constants in 2 p 4 ( 3 P)3 d configuration were reported - to our knowledge - for the first time. [ABSTRACT FROM AUTHOR]

A series of Tb3+, Eu3+, Tm3+ doped Mg 2 Y 2 Al 2 Si 2 O 12 (MYAS) phosphors were synthesized by high temperature solid-state method. The emission spectra and energy transfer between lanthanide ions in the materials were studied in detail. Under the excitation of near ultraviolet light, the emission spectra of Mg 2 Y 2 Al 2 Si 2 O 12 :Tb3+, Eu3+, Tm3+ phosphors show visible emission peaks of Tb3+, Eu3+, Tm3+, mainly including 1D 2 →3F 4 electron transition (blue light) of Tm3+, 5D 3 →7F J (J =4, 5, 6) and 5D 4 →7F J (J =3, 4, 5, 6) electron transition (green light) of Tb3+ and 5D 0 -7F 1 , 5D 0 -7F 2 and 5D 0 -7F 3 electron transition (red light) of Eu3+. By measuring the emission spectrum, excitation spectrum and fluorescence lifetime of Mg 2 Y 2 Al 2 Si 2 O 12 :Tb3+, Eu3+ and Mg 2 Y 2 Al 2 Si 2 O 12 :Tm3+, Eu3+ phosphors, it is proved that the energy transfer mechanisms between Tb3+-Eu3+ and Tm3+-Eu3+ in the matrix Mg 2 Y 2 Al 2 Si 2 O 12 are dipole-quadrupole interaction and dipole-dipole interaction, respectively. By changing the concentration of Tb3+, Eu3+, Tm3+ in the matrix, phosphors with adjustable colors from green to red and from blue to red can be obtained, importantly, Mg 2 Y 2 Al 2 Si 2 O 12 :0.03Tb3+, yEu3+, 0.05Tm3+ can emit white light with good temperature stability by the energy transfer. • MYAS:Tb3+, Eu3+, Tm3+ can emit white light with the relative ratio of Tb3+, Eu3+ and Tm3+. • There is the efficiently energy transfer from Tb3+ and Tm3+ to Eu3+. • White emitting phosphor shows good temperature stability. [ABSTRACT FROM AUTHOR]

Fluorescent materials have gradually become a hot spot in the field of anti-counterfeiting. Multifunctional phosphors used in anti-counterfeiting designs still have the problems of disordered reading sequences, difficulty in detection, and easy forging. To resolve these problems, we propose a new flexible dual-mode anti-counterfeiting design using a series of phosphors Ca3Al2Ge3O12:Cr3+ (CAG) with deep red persistent luminescence peaking at 722 nm. By adjusting the doping concentration of Cr3+ from 2% to 6%, deep red persistent luminescence with different afterglow intensities and durations can be achieved. By performing a series of thermoluminescence (TL) experiments under different conditions, the defects in materials were comprehensively and systematically analyzed. The defects contributed to the deep and shallow traps; this led to an obvious improvement in its long persistent luminescence (LPL). Such a dual-mode system with flexibility and simplicity properties is a good choice not only for anti-counterfeiting, but also for multi-layer information encryption, and a series of demo experiments based on the digital tube, Moss code, QR code, bar-code, school celebration pattern, and love letter information encryption design were implemented. Their dynamic anti-counterfeiting applications have been demonstrated, which provides a new way to rationally design multi-functional luminescent materials. [ABSTRACT FROM AUTHOR]

Generally, traditional anti-counterfeiting fluorescent materials usually show a single peak under single wavelength excitation, which cannot meet the security of authentication information. Therefore, the simultaneous realization of multicolor, multiexcitation and multimodal luminescence properties remains a fascinating goal, especially in a single host. In this work, the sustained luminescent materials Ca 3 Al 2 Ge 3 O 12 :Yb3+, Er3+ (CAG:Yb3+, Er3+) were obtained, which can exhibit bright red and green luminescence with Er3+ ions under the 490 nm and near-infrared (980 nm) light excitation. The red emission dominates under the 980 nm laser irradiation, and the sample showed excellent photoluminescence (PL) and persistent luminescence (PersL) performance under the 490 nm irradiation, and the afterglow can exceed 6h. The up-conversion mechanism and emission properties of the phosphors were analytically studied, and some fluorescence-safe anti-counterfeiting patterns and multifunctional latent fingerprint (LFP) afterglow time imaging were designed as potential applications for anti-counterfeiting aspects and information storage. [Display omitted] [ABSTRACT FROM AUTHOR]

Generally, traditional anti-counterfeiting fluorescent materials usually show a single peak under single wavelength excitation, which cannot meet the security of authentication information. Therefore, the simultaneous realization of multicolor, multiexcitation and multimodal luminescence properties remains a fascinating goal, especially in a single host. In this work, the sustained luminescent materials Ca 3 Al 2 Ge 3 O 12 :Yb3+, Er3+ (CAG:Yb3+, Er3+) were obtained, which can exhibit bright red and green luminescence with Er3+ ions under the 490 nm and near-infrared (980 nm) light excitation. The red emission dominates under the 980 nm laser irradiation, and the sample showed excellent photoluminescence (PL) and persistent luminescence (PersL) performance under the 490 nm irradiation, and the afterglow can exceed 6h. The up-conversion mechanism and emission properties of the phosphors were analytically studied, and some fluorescence-safe anti-counterfeiting patterns and multifunctional latent fingerprint (LFP) afterglow time imaging were designed as potential applications for anti-counterfeiting aspects and information storage. [Display omitted] [ABSTRACT FROM AUTHOR]

Experimental results of the hyperfine structure ( hfs ) constants of levels of the iodine atom are reported. The absorption spectra of 50 transitions in the near infrared spectral region were observed using concentration modulation technique with a tunable single-mode cw Ti:Sapphire laser. Magnetic dipole hfs constants A and electric quadrupole hfs constants B for 54 levels were determined, out of which for 10 levels were examined for the first time, the constants were confirmed for 44 levels. [ABSTRACT FROM AUTHOR]

Anticounterfeiting is a highly required technique to protect the product and consumer rights in modern society. The traditional anti-counterfeiting luminescent materials are generally presented as monochromatic emission and fixed excitation modes. Here, rare earth ions (Re3+=Tb3+, Pr3+, Dy3+) doped Ca 3 Al 2 Ge 3 O 12 can produce the novel multi-modal and multi-color long afterglow anti-counterfeit material. When adjusted the Tb3+ concentration, the different trap types, the trap concentrations and trap depths were formed, leading to the different afterglow of Ca 3 Al 2 Ge 3 O 12 :Tb3+ duration from 4 to 24 h. The long afterglow color of Ca 3 Al 2 Ge 3 O 12 :Pr3+ can turn from red to green by the cross-relaxation process with changing the Pr3+ ions concentration. The afterglow color of Ca 3 Al 2 Ge 3 O 12 :Dy3+ can change from blue to cyan due to the different afterglow decay lifetimes of the Dy3+ emission peaks. Based on the above luminous mode Ca 3 Al 2 Ge 3 O 12 :Re3+ (Re3+=Tb3+, Pr3+, Dy3+), developed multiple anti-counterfeiting devices that can be used for passport and fingerprint verification, etc. In addition, under the high-temperature conditions, there will still be an afterglow color display, and the multi-level anti-counterfeiting strategies can be used to solve counterfeiting problems in various fields. • Three different afterglow anti-counterfeiting modes were prepared. • The afterglow time of 4%–5%Tb3+ is about 4–24 h. • 7% Pr3+ shows green, 2% Pr3+ shows orange-red. • The 1%Dy3+ afterglow color changes from blue to cyan over time. [ABSTRACT FROM AUTHOR]

The vibration deterioration of discontinuities with different joint wall material (DDJM) plays a vital role in the seismic behavior of soft and hard interbedded rock slopes under earthquake; however, too little work has been devoted to the subject due to lack of attention. In the present study, the seismic behavior of soft and hard interbedded rock slopes considering the vibration deterioration of DDJM was studied by taking the Shaba slope in China as a study case. A mathematical model quantitatively describing the strength deterioration of DDJM under strong earthquakes was established based on the results of the cyclic shear test, and the deterioration process was implemented by the FISH programming language in numerical software 3DEC. The deformation characteristics and supporting effects of the Shaba slope with the deterioration model were analyzed under seismic loads with different intensities. The results show that the maximum permanent displacements of the Shaba slope without supports obviously rise with the enlargement of seismic loads. Compared with results without considering the vibration deterioration of DDJM, the difference of maximum permanent displacements increases from 15 to 39.7% under seismic loads with intensities from VI to VIII degree. The existing supporting measures on the Shaba slope can not withstand the seismic load with intensities above VI degree and need to be optimized to prevent earthquake-induced disasters in the future. [ABSTRACT FROM AUTHOR]

In this work, a novel yellow-emitting phosphor SrLa2Sc2O7(SLSO):Bi3+ was synthesized by a high temperature solid-state method, with a wide coverage from 400 nm to 800 nm under near-ultraviolet (NUV) excitation and the full width at half maximum (FWHM) of up to 180 nm. The phosphor emits bright yellow light, which is observed using optical microscopy. Alkali metal (Li+, Na+, K+) ions were used as charge compensators to enhance the luminescence intensities of SrLa2Sc2O7:Bi3+. Finally, the yellow SrLa2Sc2O7:Bi3+,Li+ and blue Sr5(PO4)3Cl:Eu2+ phosphors were homogeneously mixed with silica gel and coated on a NUV light emitting diode (LED) at 370 nm to obtain white LEDs with a high color rendering index (Ra = 91.3), a low correlated color temperature (CCT = 4879 K) and color coordinates (0.34, 0.30). This work can provide a good candidate for making white LEDs. [ABSTRACT FROM AUTHOR]

In this work, a new NIR phosphor Ca2GeO4:xCr was developed, whose emission range (1000–1700 nm) is well within NIR-II, with a full width at half maximum (FWHM) of 215 nm. Interestingly, by sintering under an air atmosphere, the Cr3+ ions in the raw material are oxidized to Cr4+, and the near-infrared light emitted by the material is not the usual luminescence of Cr3+ ions located in NIR-I, which can be attributed to the dominant substitution of Cr4+ ions doped into the lattice sites. A pc-LED fabricated with this phosphor can detect different concentrations of ethanol, which demonstrates its good potential for non-destructive testing applications. [ABSTRACT FROM AUTHOR]

Recent research has paid little attention to weakening of discontinuities with different joint wall material (DDJM) induced by wetting and drying cycles. Experimental investigations were conducted to examine the effects of wetting–drying cycles on weakening of three typical types of natural planar DDJM collected from a sliding-prone formation in the Three Gorges reservoir region of China. Deterioration of the corresponding four types of discontinuities with identical joint wall material (DIJM) were also been studied for comparison. The weakening laws of DDJM were revealed from macro- and microperspectives by testing on mineral compositions, microstructures and water absorption rate of joint walls as well as shear strength of discontinuities. The results indicate that the repeated wetting–drying cycles lead to obvious changes in microstructure and increases of macro water absorption rate for the studied joint walls with the changing degree closely related to their clay mineral contents; the peak shear strengths of DDJM gradually decreases with the wetting and drying cycles for a certain normal stress with the weakening rate between that of the DIJM with two joint wall materials of the DDJM, while closer to that of DIJM with the weak half materials of the DDJM; significant correlations have been found between the variation coefficient of rock microstructure of joint walls and the macrodeterioration coefficient of DDJM; the changing rates of multi-scale parameters before and after six wetting–drying cycles vary obviously, indicating the weakening is slowed down after six wetting–drying cycles for the studied discontinuities. Highlights: Effects of wetting-drying cycles on weakening discontinuities with different joint wall material were studied. Deterioration of the discontinuities with identical joint wall material were also been investigated for comparison. The weakening laws were revealed from macro and micro perspectives. Significant correlations have been found between the variation coefficient of microstructure of joint walls and the macro deterioration coefficient. The results could provide a basis to better understand the stability evolution of rock slopes with soft and hard rock interbedded. [ABSTRACT FROM AUTHOR]

A series of bluish-cyan color adjustable phosphors Y2MgAl4SiO12:xEu2+(YMAS) and Y2(Mg1−y,My)Al4SiO12:Eu2+ (M = Zn, Ca, Sr) were synthesized by the solid-state method. The thermal stability can be improved by modifying the cation, especially the thermal stability of Y2MgAl4SiO12:Eu2+ at 150 °C gradually improved to 92.34% of the original luminescence intensity by introducing Sr2+. The white light emitting diode (LED) was fabricated by combining near ultraviolet (NUV) LED chip (370 nm) with a mixture of Y2Mg0.8Sr0.2Al4SiO12:0.01Eu2+ along with green (Ba,Sr)2SiO4:Eu and red CaSiAlN3:Eu in different proportions. A bright warm white LED gives a high color rendering index Ra = 96.4, a low correlated color temperature CCT = 4434 K, and CIE chromaticity coordinates at (0.35, 0.34). The results demonstrate that Y2Mg0.8Sr0.2Al4SiO12:Eu2+ phosphor has potential application in the field of white LEDs. [ABSTRACT FROM AUTHOR]

In this work, in order to meet the application of near-infrared phosphor-converted light emitting diodes (pc-LEDs), an ultra-broadband emission phosphor, LiScGeO4:Cr, was synthesized. Its FWHM reaches 335 nm, and its emission spectrum ranges from 800 nm to 1650 nm, which almost covers the entire near-infrared second window (NIR-II). The broadband emission is thought to be caused by the 4T2 → 4A2 transition of the Cr3+ ion. This transition occurs due to the olivine structure of the crystal, which causes the Cr3+ ions to inhabit a low-symmetric crystal field, and the crystal field strength is very weak. NIR pc-LEDs were fabricated by combining a 460 nm blue LED with this phosphor, which penetrates 4 cm thick beef. The results indicate that there may be a potential application for this phosphor in the field of biological tissue penetration and non-destructive testing. [ABSTRACT FROM AUTHOR]

A series of near-infrared broadband luminescent phosphors LiScGeO 4 :0.007Cr, Er3+ were prepared by the high temperature solid-state method, and the energy transfer from Cr ions to rare earth Er3+ ions was realized. Co-doping of Cr and Er makes up for the luminescence of LiScGeO 4 :Cr at 1531 nm and improves the luminescence intensity at NIR-III biological windows, (1500–1800 nm). By co-doping rare earth ions, the thermal stability is improved, which is beneficial to the application of phosphor-converted light emitting diodes (pc-LED). Finally, the packaged pc-LED penetrates the fingers and leaves, showing its good penetration ability. • Co-doping of Cr and Er makes up for the luminescence of LiScGeO 4 :Cr at 1531 nm and improves the luminescence intensity at NIR-III biological windows. • The material shows a high emission intensity in the whole NIR-II. • The thermal stability of rare earth co-doped phosphors is also significantly improved. • The packaged pc-LED penetrates the fingers and leaves, showing its good penetration ability. [ABSTRACT FROM AUTHOR]