Point-of-care diagnostics have grown in demand as a reliable resource for bioanalytical technologies due to their ease of use and inexpensive manufacturing. To improve these technologies, researchers are expanding beyond traditional gold or latex nanoparticles and fluors, which are used alternative optical reporters, by developing a new class of reporters based on persistent luminescent inorganic nanophosphors. The appeal of nanophosphors is that their signature long luminescent lifetimes, which in some cases exceed 10 hours, limit the need for complex optical hardware. Additionally, these materials have the advantage of being environmentally benign while also exhibiting low cytotoxicity. However, the synthesis of persistent luminescent phosphors traditionally employ high temperature solid state methods, which tends to generate large particles and agglomerates (>15 μm). Most point-of-care diagnostic formats, such as immonochromographic lateral flow assays (LFAs), necessitate particle sizes that are submicron; therefore, alternative soft chemical synthetic routes that are conducive to forming significantly smaller particles are required. Unfortunately, many of the reported routes lead to impure products, as is the case with monoclinic SrAl₂O₄:Eu²⁺,Dy³⁺ where the presence of the hexagonal phase polymorph and Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ are common. Consequently, the need to employ synthesis routes to limit these phase formations, while reducing particle size is essential. Here, two soft chemical routes, a reverse-micelle combined with microwave assisted heating and a sol-gel method are investigated to establish new alternative synthesis routes addressing these concerns. It can be shown that both methods produce phase pure products that maintain the necessary optical properties while also reducing the particle size of the persistent luminescent phosphors allowing application in a working LFA.