The development of multimodal contrast agents for magnetic resonance (MR) optical imaging has attracted considerable attention due to the combination of both high spatial and temporal resolution of MR imaging with the sensitivity of optical imaging. In this work, a form of dual functional nanocomposites SiO2@(Y0.95–xGdxEu0.05)2O3 (x = 0–0.95) with core–shell structures have been synthesized for magnetic resonance and optical imaging. Based on the results of transmission electron microscopy (TEM), (Y0.95–xGdxEu0.05)2O3 nanoshells of around 8 nm were successfully coated onto amorphous SiO2 nanocores (ca. 115 nm in diameter). The XRD patterns indicate that the shell is crystalline after annealing. Under excitation with UV light (250 nm), the Eu3+ ions in the core–shell nanocomposites of SiO2@(Y0.95–xGdxEu0.05)2O3 mainly exhibit their characteristic red emission (612 nm, 5D0–7F2); increasing the content of Gd increased the luminescent intensity of the nanocomposites significantly. The relationship between T1‐weighted MR imaging and the amount of doped Gd (x) was also investigated. It was found that the highest MR imaging signal intensity was obtained at x = 0.45. In vitro fluorescence imaging indicated that the monodisperse nanoparticles of SiO2@(Y0.95–xGdxEu0.05)2O3 were successfully internalized by RAW 264.7 cells and that they show bright intracellular luminescence. Furthermore, this facile precipitation method may be readily extended to the synthesis of SiO2@(Y0.7Yb0.18Er0.02Gd0.1)2O3 nanocomposites, which present both up‐conversion luminescence and MR contrast properties. The nanocomposites investigated in this study have a certain potential to serve as a versatile material for multimodal imaging probes.

Endowing scaffold with antibacterial activity is an effective countermeasure to prevent bacterial infection in bone repair. Silver nanoparticles (Ag NPs) possess broad-spectrum antibacterial efficiency, whereas the agglomeration and burst releasing of Ag NPs hindered their clinic application in bone repair. In this work, Ag NPs were in situ grown on graphene oxide (GO) to construct Ag@GO nanohybrids and then were introduced into polymer scaffold. GO could efficiently load Ag NPs thereby improving their agglomeration in a scaffold, owing to their abundant active groups and large surface areas. Furthermore, GO could realize the sustained release of Ag ions from the scaffold. The results demonstrated the antibacterial scaffold exhibited robust antibacterial performance with an antibacterial rate of 95% against Staphylococcus aureus. On one hand, GO with honeycomb nanostructure and sharp edge could capture and pierce bacteria membrane, which results in physical damage of bacteria. On the other hand, the released Ag NPs from Ag@GO nanohybrids could promote the generation of reactive oxygen species, which causes the inactivation of bacteria. Encouragingly, the antibacterial scaffold also exhibited good cytocompatibility. This work developed an efficient antibacterial material for the scaffold in bone repair.

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