Incorporation of Mg2+/Si4+ in ZnGa2O4:Cr3+ to Generate Remarkably Improved Near-Infrared Persistent Luminescence

Abstract

Near-infrared emitting nano-sized particles of ZnGa2−x(Mg/Si)xO4:Cr3+ (x = 0–0.15, termed as ZGMSO:Cr3+) with persistent luminescence were prepared by sol-gel processing followed by calcination. The samples were tested by XRD, TEM, STEM, SAED, Raman, XPS, UV-Vis-NIR, TL, PLE/PL spectroscopy, and persistent luminescence decay analysis. Equimolar incorporation of Mg2+ and Si4+ ions did not change the spindle structure of ZnGa2O4 seriously. Most Mg2+ ions are more likely to occupy the sites in octahedron, but Si4+ ions are more likely to occupy the sites in tetrahedron in priority. A broader bandgap, up shift of conduction band minimum, and more anti-defects were found at a higher Mg2+/Si4+ doping concentration. ZGMSO:Cr3+ outputs near-infrared emission with a dominated band at 694 nm (2E → 4A2 transition of Cr3+), which can last longer than 48 h after the stoppage of UV irradiation. Mg2+/Si4+ doping contributes to a better near-infrared persistent luminescence, and the strongest and the longest NIR afterglow was observed at x = 0.05, owing to that the x = 0.05 sample has the deepest defects. The synthesized nanoparticles of ZGMSO:Cr3+ not only output intense NIR afterglow but also can be recharged by the red light of LED several times, indicating that they are the potential nano probes for bio imaging in living animals.

X-ray-activated ultra-long UVA persistent luminescence from a Bi-doped perovskite LaGaO3 for photodynamic activation

“…8 Exploring materials like Zn 3 Ga 2 Ge 2 O 10 :Cr 3+ (NIR, >360 h) and ZnGa 2 O 4 :Cr 3+ (NIR, >48 h) has opened a new research frontier in PersL materials. 9,10 In stark contrast to the evolving progress in the visible and NIR PersL, research in the UV region (200-400 nm) remains relatively sluggish. There is an increasing trend in the research of UV PersL materials, such as rare-earth-doped phosphors Lu 2 GdAl 2 Ga 3 O 12 :Pr 3+ and YPO 4 :Tm 3+ .…”

Near-infrared afterglow enhancement of ZnGa2O4:Cr3+via regulating trap distribution guided by the VRBE diagram

“…8 Monika et al promoted the generation of charge compensation traps in phosphors by doping different concentrations of Li + into ZnGa 2 O 4 :Cr 3+ , and Zhang et al facilitated the formation of anti-defects by doping heterovalent ions Si 4+ /Mg 2+ into ZnGa 2 O 4 :Cr 3+ . 9,10 In summary, trap regulation by doping diverse ions is significant for optimizing the afterglow properties of ZnGa 2 O 4 -based phosphors. Among the common dopant ions, lanthanide ions possess unfilled 4f shell layers which are shielded by the 5s 2 and 5p 6 orbitals, so the electron transitions of lanthanide ions are little affected by the crystal field environment.…”

Color tunability and NIR luminescence in Cr3+/Li+ co-doped ZnGa2O4 phosphor for solid state lighting and NIR LEDs

“…The emission intensity of different phosphor materials have been found to enhance by doping of different impurity ions, such as Li + , Na + , K + , Bi 3+ , Mg 2+ , Ca 2+ etc [20][21][22][23][24][25][26]. The Mg 2+ , Bi 3+ , and Si 4+ ions have been found to increase the near infrared (NIR) persistent luminescence intensity of the Cr 3+ :ZGO phosphor [27,28]. However, Li + ion has been widely used to enhance the emission intensity of different phosphor materials in many cases due to its small ionic size (0.76 Ǻ), which can be easily introduced in different host lattices [14,15,22,23,29].…”