Lattice-site engineering in ZnGa₂O₄:Cr³⁺ through Li⁺ doping for dynamic luminescence and advanced optical anti-counterfeiting

Abstract

To develop reliable optical anti-counterfeiting materials, higher requirements are put forward for innovative anti-counterfeiting phosphors, which are hardly observed under natural light but recognizable under specified conditions. Herein, novel multimode...

Regulating the trap distribution of ZnGa2O4:Cr3+ by Li+/Ga3+ doping for upconversion-like trap energy transfer NIR persistent luminescence

“…The results show that only the O orbital levels contribute to the valence band maximum, whereas both the O and Ga orbital levels contribute significantly to the conduction band minimum, consistent with previous reports. 22,30 The calculated bandgap of a perfect ZGO crystal (2.27 eV) is smaller than the experimental value (4.47 eV) (Fig. 6c).…”

“…Referring to the ionic radii, Li + /Ga 3+ ions preferably occupy Zn 2+ sites, but the specific occupations need to be determined by a variety of structural detection methods. 11,22,30…”

“…The diffuse reflectance ( R ∞ ) of ZLGGO was obtained (Fig. S5†) and converted by the Kubelka–Munk function, and it can be used to characterize the band structure in detail: 14,30 F ( R ∞ ) = (1 − R ∞ ) 2 /2 R ∞ and the [ F ( R ∞ ) hν ] 2 verses hν plots were obtained based on the following function:[ F ( R ∞ ) hν ] 2 = A ( hν − E g )where E g and hν are the bandgap energy and incident photon energy, respectively, and A is a constant. The [ F ( R ∞ ) hν ] 2 − hν plot of ZLGGO shown in Fig.…”

“…Referring to the ionic radii, Li + /Ga 3+ ions preferably occupy Zn 2+ sites, but the specific occupations need to be determined by a variety of structural detection methods. 11,22,30 Different configurations were built for formation energy calculation to explore the site preference of Li + /Ga 3+ doping in ZnGa 2 O 4 . There are two conditions for Li/Ga doping in spinel ZnGa 2 O 4 : (1) Li and Ga occupy the tetrahedral sites and (2) Li occupies the octahedral sites and Ga occupies the tetrahedral sites, which are defined as Li4-Ga4 and Li8-Ga4, respectively.…”

“…The diffuse reflectance (R ∞ ) of ZLGGO was obtained (Fig. S5 †) and converted by the Kubelka-Munk function, and it can be used to characterize the band structure in detail: 14,30 FðR…”