Two-photon photoluminescence and bio-imaging application of monodispersed perovskite-in-silica nanocrystals with high biocompatibility

[Display omitted] •The application of CsPbBr3@SiO2 NCs in two-photon bioimaging was studied for the first time.•CsPbBr3@SiO2 NCs show strong two-photon photoluminescence and good biocompatibility.•SiO2 shell with optimal thickness can control leakage of Pb2+ and enhance photoluminescence. Developing two-photon photoluminescence bio-probes with high-biocompatibility is still a challenge. In this work, single CsPbBr3 perovskite NCs were encapsulated into a silica nanoshell to prevent leakage of Pb2+ ion out of the shell, and their two- and one-photon photoluminescence property, as well as the application potential for bio-imaging, were investigated by detailed optical characterization and two-photon cell imaging experiment. It turns out that the core–shell NCs show good two-photon absorption property under the excitation of an 800 nm femtosecond laser and emit green light peaked at 526 nm. The survival rate of human hepatocellular carcinomas (HepG2) cells maintains 96.21% after incubating with the core–shell NCs (16 μg/mL) for 24 h without adding protective ligands, demonstrating the excellent biocompatibility of the nanoprobes. Based on the excellent biocompatibility and good two-photon absorption property of the perovskite-in-silica nanoprobes, fluorescence imaging of HepG2 cells was demonstrated under 800 nm femtosecond laser illumination. The cumulative fluorescence intensity of the two-photon fluorescence images was five times higher than the control group. This work demonstrates the good two-photon photoluminescence property of well-controlled core–shell perovskite-in-silica NCs and provides a new insight for the promising applications in bio-imaging.