Enhanced Understanding of Persistent Luminescence in Submicron Particles of SrAl2O4:Eu2+,Dy3+

Monday, 2 October 2017: 14:10
Chesapeake 11 (Gaylord National Resort and Convention Center)


Bioanalytical applications such as in vivo imaging and point-of-care diagnostics have taken a special interest into the use of persistent luminescence phosphors. Their notable long luminescent decays and environmentally benign materials make them excellent candidates for testing platforms like lateral flow assays (LFAs). However, LFAs require particle sizes that range from 250 nm to 500 nm for adequate spontaneous flow without being subject to gravitational sedimentation or clogging of the assay due to large particle agglomerates. Synthesis methods to produce submicron particle sizes of these materials are widely studied and have shown successful reduction in size. Nevertheless, the shortfall of many of these methods is a lack of understanding on how reduction in particle size affects optical properties, namely a potential significant loss of the characteristic long lifetimes. Here, commercially purchased SrAl2O4:Eu2+,Dy3+ was wet milled followed by a series of centrifugal sedimentation steps to produce nearly monodispersed particles in the diameter (D) range of D ≤ 150 nm to 1000 nm. A detailed analysis of luminescent behavior as a function of particle size was studied on particles before milling, after milling and as a function of particle size. Furthermore, SrAl2O4:Eu2+,Dy3+ is widely known to decompose when exposed to an aqueous environment thus, making it necessary to encapsulate the particles in silica when being used in any bioanalytical testing format. Therefore, analysis of optical properties was also conducted on the varying particle sizes after being encapsulated in silica and compared to optically neutral 500 nm nanospheres exposed to the same optical characterization condition. This investigation gives valuable insight into the effects of post processing to achieve the necessary submicron particles required by bioanalytical applications, while also establishing a more robust understanding of how size impacts the unique characteristics of persistent luminescent phosphors.