Remarkable enhancement of photoluminescence and persistent luminescence of NIR emitting ZnGa2O4:Cr3+ nanoparticles

Abstract

Persistent luminescence nanoparticles (NPs) with bright emission and long lifetimes are in high demand owing to their applications in storage media, display devices, bioimaging, security, etc. As a well-known persistent luminescence material, presently available ZnGa₂O₄:Cr³⁺ (ZGOC) does not fully serve its purpose with its existing photoluminescence and persistent luminescence properties, particularly for in vivo bioimaging and long-term optical signaling. To improve its persistent luminescence and make it more commercially viable, in this work, we have hydrothermally synthesized ZGOC NPs by fine-tuning their nucleation kinetics and crystal size through (i) controlled urea precipitation, (ii) adjusting the Zn/Ga precursor ratio, and (iii) the addition of ammonium nitrate. Deep red emitting ZGOC NPs with high PL and PerL are realized, and even compared with their counterparts synthesized using precipitants NaOH and NH₃. The feasibility of our ZGOC NPs for bioimaging application was further studied by incubating them successfully in mouse embryonic fibroblast cells (NIH 3T3). Overall, high PL and PerL intensities and long lifetimes are achieved for ZGOC NPs by the simple approach of controlled nucleation and crystal engineering, which provides a new pathway to design high quality luminescent materials for multifunctional applications in the areas of health, energy, security and environment.