Scalable synthesis of phosphorescent SiO2 nanospheres and their use for angle-dependent and thermoresponsive photonic gels with multimode luminescence

Developing room-temperature phosphorescent (RTP) materials with microscale periodic structures presents a promising prospect for future optical applications but remains challenging due to the complex integration of luminescent and structural components. Herein, we present a strategy for large-scale production of RTP silica nanospheres (RTP SiO₂ NPs) with a low dispersity in size using a modified Stöber method, where organic molecules are embedded in silica networks and subsequently undergo in-situ carbonization, aggregation and crystallization to form phosphorescent carbon dots under high-temperature calcination. These NPs can self-assemble into photonic crystal (PC) structures, enabling the straightforward integration of structural color, fluorescence (FL) and RTP to achieve multimodal luminescent properties. The angle-dependent photonic bandgap (PBG) generated by the physical periodic structure modulates light propagation in RTP PC gels, creating FL and RTP angle-dependent chromatic responses. Temperature-induced refractive index changes between SiO₂ and the liquid matrix further enable dynamic control of light-scattering states, significantly altering transmittance and emission intensities of FL and RTP. This fusion of physical photonic structures with luminescence offers potential approach for constructing advanced multimodal luminescent devices.