Magnetic-fluorescent nanohybrids of carbon nanotubes coated with Eu, Gd Co-doped LaF3 as a multimodal imaging probe

► Magnetic-fluorescent nanohybrids were designed by a LBL self-assembly technique. ► The nanohybrids consist of lanthanide doped nanocrystals on the surface of MWNTs. ► We circumvented the PL quenching of lanthanide by growth of a SiO2 shell spacer. ► The nanohybrids showed powerful T1 and T2-weighted MRI signal. ► The nanohybrids were promising for multimodal MRI/optical imaging.