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Red/near infrared (NIR) long persistent phosphors have received extensive attentions in biomedical, food inspection, iris recognition, biological imaging, etc. Herein, a new phosphor, Li2ZnGe3O8:Cr3+, is reported with deep red persistent luminescence peaking at 708 nm. By adjusting the Cr3+ doping concentration, the competitive site occupation at [ZnO6] and [GeO6] polyhedral enables different traps behaviors including trap types, trap concentration and trap depth, which in turn leads to different afterglow duration time from 2 to 20 h. The persistent luminescence mechanisms originated from different trap models have been discussed, and it is found that they can cooperate or inhibit each other, enabling different luminescence depending on time. The dynamic anti‐counterfeiting applications have been demonstrated, which provides a new way to rationally designing for multi‐functional luminescent materials. [ABSTRACT FROM AUTHOR]

Recently, near-infrared phosphors that can be applied in many fields such as night vision, agriculture, and bio-applications have attracted considerable interest in the research field worldwide. Herein, a multi-functional and dual-excited near-infrared phosphor Mg14Ge5O24:Cr3+,Cr4+ which provides two emission bands ranging from 700 nm to 1100 nm and 1100 nm to 1700 nm has been obtained via the traditional high-temperature solid state reaction. The presence of six and four coordination ions in the olivine structure of Mg14Ge5O24 provides a favorable environment for the coexistence of Cr3+ and Cr4+. Under blue light excitation, a super broad emission band ranging from 650 nm to 1100 nm with a full-width at half maximum (FWHM) of 266 nm is assigned to the spin-allowed 4T2 (4F) → 4A2 transition of Cr3+ in a weak crystal-field environment. With the increase in the concentration of Cr ions, more and more Cr4+ preferentially occupies four coordinated Ge4+ sites, and the other broad emission band ranging from 1100 nm to 1600 nm with a FWHM of 256 nm that comes from the 3T2 → 3A2 transition of Cr4+ is observed. The phenomenon of NIR I region excitation and NIR II region emission appears. The transmission experiment of a biological tissue proves that the Mg14Ge5O24:Cr3+,Cr4+ phosphor has potential applications in the field of near-infrared light-emitting diodes for biological detection. [ABSTRACT FROM AUTHOR]

Cr3+-doped Ca 3 Y 2 Ge 3 O 12 broadband near-infrared phosphor was synthesized by the high temperature solidstate reaction method. Under the excitation of 475 nm, the emission peak of Ca 3 Y 2 Ge 3 O 12 :Cr3+ is at 823 nm and the full width at half maximum (FWHM) is 155 nm. The introduction of Ce3+ as a sensitizer leads to the enhancement of CYG:Cr3+ emission intensity. The emission range of CYG:Ce3+, Cr3+ can perfectly cover the frequency doubling absorption band of C–H, O–H and other hydrogen groups. There is an energy transfer process between Ce3+ and Cr3+, and the energy transfer efficiency is as high as 94.21%. According to the near-infrared response to hydrogen group and Lambert-Beer law, the dependence of absorbance Lg(I 0 / I) on sugar content was explored, and then the reliability and accuracy of the method were verified. The results show that the phosphor Ca 3 Y 2 Ge 3 O 12 :Ce3+, Cr3+ phosphor has prospects for a potential application in nondestructive food detection. • There is the energy transfer from Ce3+ to Cr3+. • CYG:Ce3+, Cr3+ has certain application value in nondestructive food detection. • The best excitation wavelength of the sample is 475 nm, which can be effectively excited by the blue light chip, and the FWHM is 155 nm. [ABSTRACT FROM AUTHOR]