Facilitating Low-Energy Activation in the Near-Infrared Persistent Luminescent Phosphor Zn_1+xGa_2–2xSn_xO₄:Cr³⁺ via Crystal Field Strength Modulations

Abstract

Cr 3+ -activated persistent luminescent phosphors with a spinel structure are emerging materials in bio-imaging applications for their distinctive features of deep biotissue penetration and rechargeable nearinfrared persistent emission. To realize the long-term and multicycle imaging purpose, reactivation using in situ external light with deep biotissue penetration is an alternative strategy, apart from the efforts on trap modulations for the host lattice. However, recharging with high-energy ultraviolet /visible photons will result in low activation efficiency because of the absorption by biological tissues. Here, we report a low-energy photonrechargeable near-infrared persistent material, with rechargeable efficiency 400 times higher than that of the ZnGa 2 O 4 :Cr 3+ reference material. The crystal field strength and band gap energies can be tailored by control of cation occupancy, contributing the red shift of both the persistent luminescence excitation and emission spectra of the optimized complex spinel samples. The persistent emission red shift is of interest for improved deep tissue penetration for bioimaging, whereas the persistent excitation red shift facilitates the activation of persistent luminescence by low-energy radiation. Furthermore, it demonstrates that increasing the rate of cation site inversion in the spinel can lead to higher storage capacity of charge trapping.

Persistent luminescence of transparent ZnGa2O4:Cr3+ thin films from colloidal nanoparticles of tunable size

“…16,17,18 Because of this property, ZnGaO 4 :Cr persistent nanoparticles and bulk phosphors powders have been widely studied recently. 16,17,19,20,21,22,23 Although several studies have been published about the fabrication of ZnGa 2 O 4 :Cr thin films, 24,25,26,27 none of them mention their persistent luminescence and, consequently, no study about the persistent luminescent properties of ZnGa 2 O 4 :Cr thin films has been reported up to now. Persistent thin films made out of ZnGa 2 O 4 :Cr are attractive as nanosized sensing displays with potential applications in anti-counterfeiting technology.…”

Photochromism and Persistent Luminescence in Ni-Doped ZnGa2O4 Transparent Glass-Ceramics: Toward Optical Memory Applications

“…For instance, the host matrix modification strategy, aiming at red shifting the 4 T 2 → 4 A 2 emission or the co-doping strategy, to induce persistent energy transfer to an emitting ion in the SWIR range, have recently been explored. 45,46 Finally, a last strategy, the replacement of the red emitting Cr 3+ ion by a SWIR emitting ion in the ZnGa 2 O 4 matrix (for instance Co 2+ or Ni 2+ ), has briefly been evocated. 47 This last strategy was chosen in the present work, where the replacement of Cr 3+ by Ni 2+ in ZnGa 2 O 4 :Cr 3+ nanocrystals, is studied optically and is then discussed using both optical and magnetic characterizations.…”

The hydrothermally synthesis of K3AlF6:Cr3+ NIR phosphor and its performance optimization based on phase control

“…[15][16][17][18] One strategy is to employ transition-mental ions, Cr 3+ for instance. [19][20][21] The main hosts for Cr 3+ -doped NIR phosphor are germanate, [22][23][24][25][26][27] silicate, [28][29][30][31][32] phosphate, [33][34][35] and borate. [36][37][38][39] The synthesis of these phosphors requires calcination at a temperature of 800-1600°C, which results in high production costs.…”

“…One strategy is to employ transition‐mental ions, Cr 3+ for instance 19‐21 . The main hosts for Cr 3+ ‐doped NIR phosphor are germanate, 22‐27 silicate, 28‐32 phosphate, 33‐35 and borate 36‐39 .…”