Growth optimization of single-phase novel colloidal perovskite Cs3Bi2I9 nanocrystals and Cs3Bi2I9@SiO2 core–shell nanocomposites for bio-medical application

Lead-free halide perovskites have gained attention in recent years as viable materials with more distinctive characteristics than conventional semiconductor materials. Lead-free Cs₃Bi₂I₉ colloidal perovskite nanocrystal is chosen to eliminate its single-phase synthesis difficulty and implement the material in bioimaging applications. Nanostructured Cs₃Bi₂I₉ perovskite composites were coated with a thin coating of SiO₂ by an in situ tetraethyl orthosilicate/(3-aminopropyl)trimethoxysilane injection growth method to enhance their stability in aqueous medium and biocompatibility. Single-phase novel Cs₃Bi₂I₉ colloidal perovskite nanocrystal synthesis was successfully developed and optimized by adopting different synthetic conditions with varied experimental parameters. Characterization studies, including X-ray diffractometry and transmission electron microscopy, confirm the hexagonal structure of Cs₃Bi₂I₉ crystals and their cubic morphology. A broad emission peak in the red region was captured for pure and composite perovskite under different excitation wavelengths and was observed using a UV-visible spectrophotometer. Bioimaging of Cs₃Bi₂I₉@SiO₂ composites incorporated with L929 cells was conducted using an inverted fluorescence microscope under blue and green excitation. The results obtained from bioimaging studies indicated that the Cs₃Bi₂I₉@SiO₂ nanocomposites entered the cell field and exhibited an emission under excitation. The non-toxic behavior of the synthesized Cs₃Bi₂I₉@SiO₂ composites was demonstrated using MTT cytotoxicity assay in L929 fibroblast mouse cells, showing better cell compatibility.