Multimode Dynamic Photoluminescence of Bi³⁺-Activated ZnGa₂O₄ for Optical Information Encryption

Abstract

Optical storage technology for information encryption is a popular means of safeguarding information. Herein, a Bi3+-activated ZnGa2O4 multimode dynamic photoluminescence (PL) material is developed. Upon being irradiated with an ultraviolet lamp at a fixed excitation wavelength of 254 nm, the ZnGa2O4: x% Bi3+ (x = 0.5–5.0) samples exhibit varying degrees of dynamic PL emission due to a distinct Bi3+ doping effect. The mechanism underlying the dynamic PL of ZnGa2O4: Bi3+ associated with Bi3+-activated trap concentration modulation is investigated using thermoluminescence spectra. Additionally, the ZnGa2O4: 5% Bi3+ sample shows a reversible thermally responsive dynamic PL with a color variation from blue to red upon heating from 283 to 393 K. Predesigned procedures based on single-wavelength-mediated photochromic and thermochromic dynamic PL emissions of ZnGa2O4: Bi3+ are designed for rewritable optical data storage and high-level information encryption. Also, an enhanced encryption scheme with a mask encoding technique applying a ZnGa2O4: Bi3+ hybridized polyvinylidene difluoride film is then proposed to increase the security level. Accordingly, this work provides a feasible way to rationally design dynamic PL material offering more creative designs for safeguarding information via encryption.

Modulation of Reactive Hydrogen Adsorbed on Dual-Active Site NiMoO4 Nanocubes for Reduction of Nitrate to Ammonia

“…Similarly, peaks arising from the Ni 2+ and Ni 3+ states can be distinguished from Ni 2p 1/2 with binding energies of 871.1 and 873.2 eV, respectively. In addition, the peaks at binding energies of 860.9 and 879.0 eV are satellite peaks of Ni 2p. − In the XPS spectra of Mo 3d, the peaks with binding energies at 232.4 and 235.7 eV can be attributed to Mo 6+ (Figure c). , In Figure d, the O 1s spectrum can be deconvoluted into three different peaks, of which the peak at 531.38 eV can be attributed to the oxygen vacancies. − It was further proven by the ESR spectra in Figure S7. The aforementioned results demonstrate that the designed NiMoO 4 comprises numerous oxygen vacancies on the surface, which is conducive to providing more active sites and further improving the electrocatalytic performance of NiMoO 4 …”

Prolonged Red Persistent Luminescence in Bi3+ Single-Doped LiGa5O8: Regulating Traps by Site Selective Occupation

“…Moreover, according to the analysis of XPS in Figure S3, only trivalent bismuth ions exist in the LiGa 5 O 8 :1% Bi 3+ sample, so the possibility to achieve the NIR luminescence due to the formation of Bi 2+ ions caused by IVCT is also very low. As observed from the experimental data (Figure b), the PLE spectrum of the LiGa 5 O 8 :1% Bi 3+ sample, monitored at 718 nm, is composed of two peaks located at 257 and 300 nm, which can be denoted as the 1 S 0 → 1 P 1 and 1 S 0 → 3 P 1 transitions of Bi 3+ , respectively. − The broad band peaking at 511 nm corresponds to the excitation of the 1 S 0 → 1 P 1 transition of Bi 3+ . Therefore, the Bi 3+ -dependent emission of LiGa 5 O 8 :Bi 3+ can only be assigned to the 3 P 1 → 1 S 0 transition of Bi 3+ ions …”