Spinel-phase Zn2Ga2.98Ge0.75–xSnxO8:Cr0.023+ (ZGGSO:Cr3+) nanoparticles with various Sn4+ concentrations were prepared by a hydrothermal method in combination with a post-annealing in vacuum at high temperature. For these nanoparticles, the observed near infrared (NIR) persistent luminescence peaked at ∼697 nm and originates from the 2E, 4T2 (4F) → 4A2 transitions of Cr3+ and the afterglow time exceeds 800 min. For both the interior and surface Cr3+ ions in the ZGGSO host, it can be found that the increased energy transfer from Cr3+ to the deep trap (anti-site defects, ) after the substitution of Ge4+ by Sn4+ plays a key role in enhancing the persistent luminescence of the ZGGSO:Cr3+ nanoparticles. Strikingly, this energy transfer process can be controlled through the variations in the crystal field strength and the trap depths. Our results suggest that not only Sn4+ substitution can improve in vivo bioimaging but also the existence of deep traps in ZGGSO:Cr3+ nanoparticles is helpful for retracing in vivo bioimaging at any time.
In this work, Nd 2 (Zr 1- x Sn x ) 3 (MoO 4 ) 9 (0.02 ≤ x ≤ 0.1) (NZSM) ceramics were successfully obtained through conventional solid-state route. Phase analysis, microstructure, and properties were investigated scientifically by XRD , SEM, and network analyzer, respectively. XRD results revealed that all samples with different substitution amounts of Sn 4+ formed the pure phase with R-3c space group. The permittivity was related to the polarizability and the bond of Zr2-O5, the bond of Nd-O2 possessed a positive influence on Q×f . The reduced octahedral distortion and increased bond energy made the temperature coefficient more stable. Infrared reflection spectrum results showed that the permittivity was mainly caused by the absorption of phonon oscillation. The optimum properties ( ε r = 10.34, Q×f = 74,795 GHz, τ f = −13.55 ppm/°C) were obtained when x = 0.02 sintered at 750 °C.
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