Green Synthesis of Nanoconfined CsPbBr3 Nanocrystals in Nanoporous Silica and Densely Sealed by Silica Gel for Moisture- and Air-Stable Phosphor Applications

High-performance CsPbBr₃ nanocrystal phosphors were prepared using an environmentally friendly and straightforward aqueous one-pot synthesis method at 70 °C. CsPbBr₃ nanocrystals were nucleated and grew in situ within the nanopores of a porous silica (p-SiO₂) support, yielding nanoconfined CsPbBr₃@p-SiO₂ (“@” denotes nanocrystals confined in silica nanopores). The nanocrystals were sealed by a highly cross-linked sodium silica gel (SS), creating a protective layer that enhanced the stability of the resulting CsPbBr₃@p-SiO₂/SS phosphor (“/” denotes an external sealing layer). The effects of the silica sealing precursor and the pH condition during nanoporous support synthesis were systematically examined. The phosphors exhibited strong light absorption in the visible range and emitted high-intensity green fluorescence at 520 nm. The fluorescence emission showed a minimum full width at half-maximum of 24.5 nm, a maximum photoluminescence quantum yield of 96.1%, and an average fluorescence lifetime of up to 40.84 ns. The materials retain long-term ambient stability for ≥180 days under moisture and air exposure. These results highlight how nanoscale confinement and interfacial nanosealing cooperatively stabilize perovskite nanocrystals, positioning CsPbBr₃@p-SiO₂/SS as a robust candidate for advanced phosphor applications.