Persistent luminescent nanomaterials, such as SrAl2O4:Eu2+, Dy3+, have gained significant attention due to their ability to emit light after excitation, making them suitable for various optoelectronic and display applications. However, their thermal stability and luminescent efficiency are highly dependent on synthesis conditions. This study investigates the thermally stable properties of SrAl2O4:Eu2+, Dy3+ nanoparticles (NPs) for the development of efficient luminous nanomaterials, focusing on how synthesis temperature influences their structural and optical characteristics. The NPs were synthesized at varying temperatures (500°C to 1000°C) and analyzed using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, UV-Vis spectroscopy, and scanning electron microscopy (SEM). Their luminescent properties under UV excitation were also evaluated. The NPs exhibited a monoclinic phase, with minor impurities at 500°C and 600°C. Higher synthesis temperatures shifted absorption edges to shorter wavelengths, with the band gap increasing up to 500°C but decreasing at 1000°C. SEM revealed irregular morphologies with pores and cracks, while crystal growth at elevated temperatures enhanced green emission, peaking at 700°C. Beyond 700°C, luminescence declined due to secondary phase formation and rare-earth ion oxidation. Due to their strong green emission and stability, these phosphors could be used in glow-in-the-dark signage, emergency exit indicators, and traffic signs, offering long-lasting visibility without external power sources. Optimized synthesis at 700°C ensures high performance, making them viable for commercial luminescent displays.