Multicolor Persistent Luminescence

Persistent phosphors are very demanding materials nowadays owing to their various applications. The emission wavelength determines the color of the emission. An activator can exhibit different emission colors in different hosts. Several approaches have been carried out to produce multicolor long-lasting phosphors, but their short persistent time and color fading issues restricted them from being used for potential applications. However, the results of the color conversion method are appreciable. This chapter discusses the multicolor persistent luminescence based on the color conversion method. The color conversion method is based on two parameters: phosphorescent light source and color conversion agent. The excitation spectrum of the color conversion agent should be matched with the emission spectrum of the phosphorescent light source. In the color conversion method, long-lasting phosphor (LLP) can be used as a phosphorescent light source, while the organic/ inorganic fluorescent dye can be used as a color conversion agent. The light emitted by LLP is absorbed by the dyes and converted into long-lasting phosphorescence with different colors. The mixture of LLPs and dye-encapsulated mesoporous silica nanoparticles showed multicolor persistent luminescence. Traditional LLPs have large grains with a small surface area, limiting the absorption of dye molecules on the particle surface. Furthermore, high concentrations of dyes can lead to self-quenching, reducing conversion efficiency. Also, some dyes are unstable and prone to bleaching under light exposure. To address these issues, fluorescent dyes are encapsulated into mesoporous silica. Mesoporous silica provides a significant surface area, allowing a larger number of dye molecules to be absorbed by one particle, thus increasing adsorption efficiency. Encapsulation enhances the stability of fluorescent dyes, preventing bleaching in light environments. The encapsulated fluorescent dyes produce characteristic emissions, contributing to improved color conversion efficiency.