Deep-red to NIR mechanoluminescence in centrosymmetric perovskite MgGeO3: Mn2+ for potential dynamic signature anti-counterfeiting

Tunable and enhanced mechanoluminescence in LiYGeO4:Tb3+via Bi3+ → Tb3+ energy transfer

“…The change in ML intensity can be associated with the movement of the trapped charge carriers, where the force and UV irradiation play the roles in releasing and capturing the charge carriers, respectively. 19 As shown in Fig. 5c, the CIE chromaticity coordinates ( x , y ) shift from the blue region to the green region and then to the white region with the increase of Tb 3+ concentration, which shows tunable ML emissions.…”

“…6c and d exhibit two strong bands peaking at 348.9 and 379.5 K. And there is also a weak peak at 459 K, which is ascribed to Bi. 29,31,38 Using the empirical equation: 19 E denotes the trap depth and T m is the temperature of the TL peak, the corresponding trap depths of Li 0.997 YGeO 4 :0.5% Bi 3+ ,1.0% Tb 3+ are determined to be 0.6978 eV and 0.759 eV, respectively. Compared to the TL curve of the host, the peaks at 0.6978 eV and 0.759 eV can be ascribed to (the vacancy of the Li + ion) and Ge i (the Ge ion in the interval), which can be generated from the matrix.…”

“…Notably, PersL has a similar luminescent center and luminescence mechanism to ML, but the excitation source is thermal disturbance instead of the mechanical stimulus. 19…”

“…11,14 Up to now, the emissions of ML phosphors have been proved to range from the ultraviolet to NIR spectral range such as in SrAl 2 O 4 :Ce 3+ (ultraviolet, 375 nm), SrCaSi 2 O 7 :Eu 2+ (blue, 450 nm), Ca 2 Nb 2 O 7 :Pr 3+ (red, 620 nm), MgGeO 3 :Mn 2+ (deep red, 679 nm) and LiGa 5 O 8 :Cr 3+ (NIR, 715 nm), where the rare earth ions are mostly used as the activator ions for ML emissions. [15][16][17][18][19] However, quite a few problems in ML materials have to be solved; for example, weak ML intensity and limited ML regulation methods. 20,21 Due to the strong capacity of light absorption and high photoelectric conversion efficiency, choosing rare earth ions is particularly significant for high intensity ML.…”

Development of NaY9Si6O26:Yb3+ phosphors with high thermal stability for NIR anti-counterfeiting: study of its crystal structure and luminescent properties

“…In recent years, counterfeiting technology of security materials has advanced, making anti-counterfeiting technology an important tool for protecting the legitimate rights of consumers and enterprises. 32,33 It is therefore imperative to develop new materials for advanced anti-counterfeiting security. For this application, it is necessary to develop an NIR-emitting material that is sensitive in the NIR region beyond the existing method of checking security through ultraviolet excitation.…”