Sunlight-activated long-persistent luminescence in the near-infrared from Cr3+-doped zinc gallogermanates

Abstract

Visible-light persistent phosphors are being widely used as self-sustained night-vision materials because of their sufficiently strong and long afterglow (>10 h) and their ability to be excited by sunlight as well as room light. In contrast, persistent phosphors for near-infrared (NIR) wavelengths are lacking. Here we report a series of Cr(3+)-doped zinc gallogermanate NIR persistent phosphors that exhibit strong emission at 650-1,000 nm, extending beyond the typical 690-750 nm, and with a super-long afterglow of more than 360 h. These new NIR persistent phosphors are all-weather materials that can be rapidly, effectively and repeatedly charged by natural sunlight in almost all kinds of outdoor environment. Seconds to minutes of sunlight activation can result in more than two weeks of persistent NIR light emission. This new series of NIR persistent materials have potential applications in night-vision surveillance, solar energy utilization and in vivo bio-imaging.

In Vivo Repeatedly Charging Near‐Infrared‐Emitting Mesoporous SiO2/ZnGa2O4:Cr3+ Persistent Luminescence Nanocomposites

“…[1,4,7] The PL excitation band from 600 to 650 nm is in the transmission window of biological tissue (600–1100 nm) [12] and thus gives us the opportunity to recharge the energy-exhausted mZGC in deep tissue in situ. Since there is no standard method to accurately evaluate the deep-tissue-imaging ability of PL phosphors, we propose a meat-covering method for comparison according to our previous report on up-conversion imaging (Figure 3A).…”

“…[1–3] The temporal separation of excitation and afterglow properties of these persistent phosphors makes them ideal as in vivo optical imaging contrast reagents. [4–6] Until now, persistent luminescence has relied on short-wavelength excitation (e.g., ultraviolet light) which has rather limited tissue-penetration depth.…”

“…To make such NIR-persistent phosphors bulk crystal requires temperatures >750 °C in traditional solid-state annealing reactions. [1,7,13] Moreover, to convert such bulk crystal into nanoparticles that are sufficiently disperse for biological applications, certain tedious physical treatments such as grinding [2,3,14,15] or laser ablation [16] must be utilized. The afforded products are generally highly heterogeneous and suffer from severe agglomeration.…”

EPR, optical absorption and luminescence studies of Cr3+-doped antimony phosphate glasses

“…4 A 2 (F), R-line) and another intense broad band from 14,500 to 11,100 cm À1 (700-850 nm) centered at 12,790 cm À1 (782 nm) ( 4 T 2 (F) ? 4 A 2 (F)), due to Cr 3+ electronic transitions which depend on the crystal field strength of the host lattice [18,19,37], but also strongly affected by energy transfer from single Cr 3+ ions to pairs [38] and the thermal population of the 4 T 2 (F) level [12,39].…”

X-ray micro-modulated luminescence tomography (XMLT)

“…Unlike conventional nanoparticle probes, LiGa 5 O 8 :Cr 3+ nanoparticles were recently synthesized to facilitate the luminescence energy storage with xray pre-excitation and subsequently stimulated luminescence emission by visible/nearinfrared (NIR) light [17,18]. LiGa 5 O 8 :Cr 3+ nanoparticles are synthesized using a sol-gel method with lithium nitrate, gallium nitrate and chromium nitrate as precursors, followed by calcination and wet mechanical grinding.…”